Thermoplastic articles having smooth edges and optionally peelable surfaces.

Abstract

To provide shaped thermoplastic articles having smooth peripheries.SOLUTION: The disclosure relates to shaped thermoplastic articles having smooth peripheries. Many thermoplastic articles have sharp edges formed upon molding or cutting the article from a feedstock sheet. Such sharp edges can damage thin plastic films or skin which they contact, and smoothing the edges is desirable. Described herein are methods of forming a smooth periphery for such sharp-edged articles by rolling over the sharp edge. The smoothing operation is performed by forming a deflectable flange including a bend region separated from the potentially sharp peripheral edge by a spacer, deflecting a portion of the deflectable flange, and softening at least one bent portion of the deflectable flange to yield a smooth periphery upon cooling. A liner sheet may be attached to the feedstock sheet prior to, during, or after forming and can be peelable therefrom.SELECTED DRAWING: Figure 8K

Description

Technical Field

[0005] , , , ,

[0004]

[0001]

[0002] The present disclosure generally relates to the field of forming shaped thermoplastic articles.

Background Art

[0002]

[0003] Forming articles from thermoplastic materials is well known. A variety of methods (e.g., thermoforming, casting, molding, and rotational molding) can be used to impart a shape to a softened or melted molten thermoplastic material or a pre-formed thermoplastic sheet.

[0003]

[0004] Trimming waste material from one or more edges of a shaped article is a common finishing technique, but sharp edges remain, which can wound the skin or tear or cut materials in contact with the edges. A common use of shaped thermoplastic materials is to form containers that can be sealed with a thin plastic film, such as trays, balls, or containers intended to contain food and intended to be sealed with a transparent plastic film. Another common use is to contain an item and seal the item from moisture or other materials that may come into contact with the container. Sealing such containers typically involves extending or stretching a film across a compartment formed within the container and sealing the film around the perimeter of the compartment, which perimeter is often positioned adjacent to the trimmed edge of the article containing the compartment. If the edge is sharp, it can cut or break the film, preventing the sealing process.

[0004]

[0005] Three well-known sealing techniques are commonly used to seal food and ingredients to form containers for commercial transport, storage, display, and sale. These are referred to herein as OW, VSP, and MAP techniques. All of these techniques combine a container with a thin plastic film. Due to the fragility of such films and the need to minimize or eliminate tearing or ripping of the film portion that often serves to define the sealed compartment (together with the container), it is important to minimize the chances that the container may tear, rip, or fray its film or the film near the container. In addition to the plastic films used to seal such containers, plastic films are also used to transport containers such as “mother bags” (i.e., typically thin plastic bags) used to contain the packaging of multiple containerized products during transport, and plastic shopping bags used by consumers to carry goods purchased from retail stores. This can be achieved by reducing or eliminating sharp or rough edges of the container in locations on the container where such edges are likely to come into contact with the film during packaging, storage, transport, or display.

[0005]

[0006] Overwrapping (OW) technology involves placing food or other items on one or more surfaces of an article, then sealing the film itself (e.g., by heating the overlapping portion of the film), and finally wrapping or encasing the formed article (e.g., a thermoformed tray, sheet, ball, or multi-compartment container) in a thin (often transparent) plastic film. In such OW technology, sharp or rough edges of the formed article can cause the film to cut, fray, or tear, potentially allowing material to pass through the film and obstruct one or more of its intended uses. Traditionally, OW technology has been primarily used with foam trays or containers without sharp edges. Many local government recycling programs exclude or marginalize foam plastics, and such materials are therefore increasingly unpopular with consumers. Since thermoformable materials tend to be widely accepted in recycling programs, it would be desirable to be able to create thermoformable plastic containers suitable for use with multiple wrapping technologies, including OW technology.

[0006]

[0007] Vacuum sealing packaging (VSP) technology involves adhering a thin (often transparent) plastic film to the surface of a molded article that carries food (e.g., or alternatively, a moisture-sensitive object) on the surface of the molded article. When VSP technology is used to place the item to be packaged on the surface of the molded article or within a cavity in the molded article, the film is positioned so that the item is interposed between the molded article and the film, and air (or any other gas that may be present) is removed from the spacer between the film and the molded article (optionally working together to apply positive pressure to the outside of one or both of the film and the molded article) so that the film is in close proximity to the surface of the molded article and / or the item, and the film is sealed over the surface of the molded article over a desired area (usually completely surrounding the item) (e.g., by thermal induction bonding or electrostatic bonding using the intervening adhesive), and any excess film can be trimmed from the desired area. The seal can resist airflow to maintain a state of exhaust of gases from inside the sealed container. The resulting VSP sealing packaging typically has a topology that mimics the shape of the surface of the molded article on which the item is placed.

[0007]

[0008] MAP is an abbreviation for modified atmosphere packaging, and refers to a sealing technique in which a flexible (often transparent) film is sealed around a substantially rigidly formed article (e.g., using heat or adhesive). When the formed article is closed in any other way (i.e., there are no openings other than those sealed by the film), the gas present in the container can be controlled when the film seals the article. Thus, if the article and film are sealed in the presence of a selected atmosphere (e.g., a gas such as one that is oxygen-free or a gas selected to improve fruit ripening), the selected atmosphere can be maintained within the sealed MAP packaging during subsequent storage, transport, and display of the packaging.

[0008]

[0009] As is well known in the art, shaped articles used in OW, VSP, and MAP sealing processes tend to have different industry-recognized geometric shapes and characteristics among the three molds. Therefore, shaped articles that are useful for one mold of the sealing process are often not very suitable for one or both of the other.

[0009]

[0010] For example, containers used for OW sealing tend to be rectangular, tray- or sheet-shaped, with smooth, blunt edges and rounded corners. The absence of sharp, rough, or pointed edges or corners helps reduce the likelihood that the film used to wrap the container will tear or rip during wrapping. OW containers often have a flat section (for example, on the "bottom" of the container relative to its intended display configuration), and the film wrapped over the flat section can be biased to seal the film itself (for example, when heat is applied to the overlapping film section to ensure a sufficient seal), thus enclosing the container and any items on or inside it.

[0010]

[0011] Containers used for VSP sealing tend to have surfaces or edges (sometimes within recesses) that are adapted to receive the sealing film, as they are fitted to carry the item being sealed between the film and the container and have no sharp points, protrusions, or edges. The absence of such features reduces the likelihood of the film tearing or ripping as it is pulled towards the surface. Unlike OW containers, VSP containers may have sharp edges, corners, or protrusions, at least on parts other than the surface that receives the film, because these parts do not need to come into contact with the film during sealing. However, such sharp parts can still damage the sealing film, especially when multiple VSP sealed packages are stored, transported, or displayed in close proximity to each other, as sharp parts of one container may damage the film of another container (or film or tissue near the container).

[0011]

[0012] Containers used for MAP sealing tend to have a plane (e.g., a broad, flat rim) surrounding the opening to be sealed, by attaching a sheet of film to the opening, sealing the film to the surface (often substantially irreversibly), and then trimming the film around the periphery of the seal. Such containers must be configured so that the film can be attached to the surface without substantial risk of tearing or ripping before and during sealing, and to facilitate trimming of the film from the sealed container. However, since the film typically only comes into contact with a limited portion of the MAP container during the sealing process, MAP containers can or often have sharp, pointed, or rough features in locations that do not participate in the sealing process.

[0012]

[0013] It should be advantageous if the sharp edges of the molded thermoplastic article can be moved in a manner that reduces the risk of injuring or damaging the sealing film. It should be even more advantageous if such individual molded articles can be used with multiple known sealing techniques, such as two or more of the OW, VSP, and MAP techniques. It should be advantageous even in the absence of sealing if the thermoformed article has reduced sharpness and tendency to cause damage and injury. The subject matter disclosed herein addresses this drawback of conventional molded thermoplastic articles.

[0013]

[0014] It is recognized that it is desirable to reduce the appearance of sharp edges on the edges of the overwrapping tray. For example, Nelson et al. (U.S. Patent Application Publication 2015 / 0001127) disclosed a packaging tray formed by thermoforming a film sheet to produce a precursor tray having a U-shaped flange around its periphery, a U-shaped opening end facing the sealing surface, and a peripheral edge of the tray projecting outwards. Nelson's tray is made by cutting a precursor tray from a sheet of thermoformable material such that the peripheral edge extending outwards has an end that is positioned at the end of the U-shaped outer (relative to the tray body) arm. Nelson then compresses the outer arm inwards toward the tray body, leaving a smoother corrugated portion of the U-shaped flange around the periphery of the tray, while the peripheral edge, which may still be sharp, extends toward the sealing surface. In this way, Nelson et al. produce a tray said to be suitable for overwrapping, and the overwrapping film is intended to bias the outer arm of the U-shaped flange toward or toward the inner arm. However, Nelson's trays remain unsuitable for all OW applications and generally remain unsuitable for use with VSP and MAP technologies because the trays retain sharp edges in positions that could cut the film (for example, the peripheral edges of Nelson's trays appear to be in contact with both the film overwrapping and the film overwrapping the adjacent tray in Nelson's Figure 13A). Trays without sharp peripheral edges or sharp corrugations that the film can access (this is also possessed by Nelson's trays; see item 124 in Nelson's Figure 12A) should be preferred for use with each of these sealing technologies. Trays used for VSP and / or MAP packaging should preferably lack both sharp peripheral edges (see peripheral edge 120 in Nelson's Figure 12A) and any relatively sharp corrugations (see item 124 in Nelson's Figure 12A) of the material from which the tray is formed, because such edges and corrugations could snag, tear, or rip the film during or after the sealing process.

[0014]

[0015] The subject matter disclosed herein includes thermoformed articles that are suitable for sealing by multiple technologies.

[0015]

[0016] Furthermore, thermoformed beverage cups with a smooth, rotated rim are also known. Such cups are created by thermoforming a cup having a flange around the periphery of the cup's opening, the flange including a peripheral rim that may be sharp at the distal flange end inside the cup. The flanged cups are stacked in a nesting manner, their flange portions are heated, and then passed through a rotating screw of a helical rim to generate a rotated rim. Such a technique is only useful when rotating a rim surrounding a circular orifice and is therefore impractical when creating a molded article with a rotated rim surrounding a non-circular opening. Also, beverage cups with a rotated rim are not designed to facilitate wrapping or sealing with a thin plastic film. [Overview of the project]

[0016]

[0017] This disclosure relates to a method for moving sharp edges away from the periphery of an article made from a thermoplastic material, in which case the sharp edges may damage surfaces that would otherwise come into contact with the periphery of the article. This disclosure also relates to articles processed according to these methods and to apparatus for performing such processing.

[0017]

[0018] This disclosure relates to a method for forming a smooth edge (i.e., a smooth perimeter) on an article made from a thermoplastic material. The method includes the step of forming a deflectable flange on the edge of the body of the article. The deflectable flange includes the outer edge of the thermoplastic material on a peripheral flange that optionally extends peripherally from the deflectable flange at the peripheral end of the deflectable flange. In one embodiment, the peripheral flange is connected to a spacer by an elbow and extends peripherally beyond the spacer by the distance of the peripheral flange. The distance of the peripheral flange can be selected to produce a desired degree of deflection when the peripheral flange strikes a surface. In one embodiment, the distance of the peripheral flange is selected to be zero (i.e., the peripheral edge is located where the elbow would otherwise be). The spacer is connected to the body by a bending region, which defines the angle between the spacer and the body (this can be acute or obtuse, preferably nearly right). The deflectable flange is biased into the cavity defined by the upper body, for example, because the distance between the elbow and the cavity is smaller than the distance of the peripheral flange, the deflectable flange is deflected in the bending region upon impact with a portion of the cavity on the peripheral flange. Sufficient heat is applied to the bending portion of the deflectable flange (here the bending region) to soften the thermoplastic material in the bending region. The upper body and the article are separated, so that the bending region remains deflected when cooled, resulting in a smooth edge (i.e., periphery) on the article.

[0018]

[0019] This method can be used to form a smooth edge around the entire periphery of an article. To this end, a deflectable flange is formed around the entire edge of the article, and the interior of the cavity is configured to simultaneously collide with the deflectable flange around the entire edge of the article when the deflectable flange is biased internally. In the resulting article, the peripheral edge is effectively "hidden" (e.g., the peripheral edge is behind the deflected peripheral flange or deflected away from the periphery of the article) so that materials in contact with the periphery of the article (e.g., thin plastic film or animal tissue) tend to come into contact with the peripheral edge of the thermoplastic material from which the article is made.

[0019]

[0020] The disclosure also relates to a method for forming a sealed compartment. This method includes the steps of: thermoforming a thermoplastic sheet to form an article having a concave compartment surrounded by a substantially flat sealing surface; cutting the article from the sheet circumferentially with respect to the sealing surface; forming a smooth edge around the entire periphery of the article as described herein; and then sealing an upper sheet to the sealing surface to form a sealed compartment. In one embodiment of this method, the upper sheet is trimmed around the sealing surface after the upper sheet has been sealed to the sealing surface. In another embodiment, the upper sheet is heat-sealed to the sealing surface.

[0020]

[0021] The disclosure further relates to a method for forming a sealed compartment. The method includes the steps of: thermoforming a thermoplastic sheet to form an article having a concave compartment surrounded by a substantially flat sealing surface; cutting the article from the sheet circumferentially with respect to the sealing surface; forming a smooth edge around the entire periphery of the article as described above; and then wrapping and sealing a flexible plastic film around the article to form a sealed compartment.

[0021]

[0022] In some embodiments of the methods described herein, after biasing the deflectable flange into the cavity and before separating the upper body from the article, the ram may be biased inward, in close opposition to the interior, so that the face of the ram strikes the bending region and further deflects the deflectable flange, for example, in the bending region. The face may be, for example, substantially planar. The face may also be substantially perpendicular to the interior portion that strikes the peripheral flange. The face can define an obtuse angle with the interior portion that strikes the peripheral flange. The face may have a concave contour with respect to the interior. When the ram is heated, biasing the ram against the deflectable flange can cause the portion of the deflectable flange in contact with the ram to bend, further deflecting the peripheral edge of the thermoplastic sheet away from the periphery of the formed article.

[0022]

[0023] In non-heated embodiments, the disclosure relates to a method for forming a smooth edge on an article made of a plastic material (e.g., a thin plastic material backed with a deflectable metal layer). The method involves forming a deflectable flange on the edge of a body, the deflectable flange including the peripheral edge of the thermoplastic material at the peripheral end of the peripheral flange. In one embodiment, the peripheral flange is connected to a spacer by an elbow and extends periphery beyond the spacer by a distance of the peripheral flange (which is virtually zero if the peripheral flange is absent). The spacer is then connected to the body or extension by a bending region. The bending region defines an angle between the spacer and the body (which can be acute or obtuse, preferably nearly right or slightly obtuse). The deflectable flange can be biased into the interior of a cavity defined by the upper body, such that the distance between the spacer and the interior is less than the distance of the peripheral flange or it strikes a shaped ram surface that deflects the deflectable flange inward. The deflectable flange is thereby deflected by the bending region or the like upon impact. Sufficient pressure is applied to irreversibly bend the plastic material. The upper body and the article are separated, so that the deflectable flange remains deflected when pressure is released, resulting in a smooth edge on the article. [Brief explanation of the drawing]

[0023] [Figure 1A] This shows a cross-sectional view of a thermoplastic article 100 having a deflectable flange 160 formed on its edge. [Figure 1B] The thermoplastic article 100 is shown inserted inside the upper body 200, and the upper body 200 is shown as a fractured section (indicated by coarse lines). [Figure 1C] The result of inserting the ram 300 (only the fractured portion is shown as indicated by the rough lines) into the upper body 200 behind the thermoplastic article 100 (i.e., when the ram 300 is inserted into the structure shown in Figure 1B) is shown. [Figure 2A-2D]FIG. 2A shows the upper body 200 disposed on the ram 300. FIG. 2B shows the upper body 200 engaged with the ram 300. FIG. 2C is a cutaway view of the engaged upper body 200 and ram 300 shown in FIG. 2B, showing that a portion of the ram 300 fits within the upper body 200 and is proximate and opposed to the inner surface of the recess within the upper body 200. FIG. 2D is a detail of the cross-section shown in FIG. 2C, showing the proximate opposition between the ram 300 and the interior of the upper body 200. [Figure 3A] A finger is visible inside the tray, and a smoothed corner is visible to the left of the finger. [Figure 3B] Another view of the smoothed corner of the tray, similarly created, seen from under the rim of the tray. [Figure 3C] A view of the smoothed corner, with the finger pointing to the smoothed area formed by the bending, softening, and cooling of the bend region of the deflectable flange. [Figure 4] A cross-sectional view taken through the storage container article 100 formed using the method described herein. [Figure 5A] [[ID=…]]A cross-sectional view taken through the storage container article 100 formed using the method described herein. [Figure 5B] A cross-sectional view taken through the storage container article 100 formed using the method described herein. [Figure 5C] A cross-sectional view taken through the storage container article 100 formed using the method described herein. [Figure 6A] A deflectable flange formed within a tray-shaped article thermoformed from a sheet of thermoplastic material is shown. [Figure 6B] A deflectable flange formed within a tray-shaped article thermoformed from a sheet of thermoplastic material is shown. [Figure 6C] A deflectable flange formed within a tray-shaped article thermoformed from a sheet of thermoplastic material is shown. [Figure 6D] A view from below of a rounded rectangular tray having a "rotated" edge around its entire perimeter. [Figure 6E] The first is a perspective view of three identical trays, each having a “rotated” rim as described herein, the degree to which the rim is “rotated” differs among the three. [Figure 7A] This embodiment shows an article 100 formed from a thermoplastic sheet seated on a horizontal plane (horizontal solid line) having a smoothed peripheral edge as described herein. [Figure 7B] This embodiment shows an article 100 formed from a thermoplastic sheet seated on a horizontal plane (horizontal solid line) having a smoothed peripheral edge as described herein. [Figure 7C] This embodiment shows an article 100 formed from a thermoplastic sheet seated on a horizontal plane (horizontal solid line) having a smoothed peripheral edge as described herein. [Figure 8A] The deflection and rotation of the deflectable flange 160, including its sharp peripheral edge 110, are demonstrated using the ram 300 as described herein. [Figure 8Ai] This is a copy of Figure 8A, used to identify the offset angle OA. [Figure 8B] Figure 8A shows the effect of further biasing the item 100 depicted on the ram 300. [Figure 8Bi] This is a copy of Figure 8B, used to identify the offset angle OA. [Figure 8C] Figure 8B shows the effect of continuing to bias the item 100 depicted in the heated ram 300. [Figure 8Ci] This is a copy of Figure 8C, which identifies the offset angle OA. [Figure 8D] This specification indicates the use of one or more objects to assist in deflection and rotation on a deflectable flange as described herein. [Figure 8Di] Figure 8D depicts an article that acts as object 401, shaped like a rounded rectangular tray T with an interior and a plug P with a shape and dimensions that fits inside it, in order to reduce or prevent inward deflection of the side walls of the tray T during rotation of the deflectable flange of the tray T. [Figure 8Dii] This shows the plug inserted inside the tray. [Figure 8E] The figure continuously depicts the effect of further biasing the formed object 100 relative to the ram 300 in the direction indicated by the white arrow in the figure. [Figure 8F] The figure continuously depicts the effect of further biasing the formed object 100 relative to the ram 300 in the direction indicated by the white arrow in the figure. [Figure 8G] The figure continuously depicts the effect of further biasing the formed object 100 relative to the ram 300 in the direction indicated by the white arrow in the figure. [Figure 8H] The figure continuously depicts the effect of further biasing the formed object 100 relative to the ram 300 in the direction indicated by the white arrow in the figure. [Figure 8J] The figure continuously depicts the effect of further biasing the formed object 100 relative to the ram 300 in the direction indicated by the white arrow in the figure. [Figure 8K] The figure continuously depicts the effect of further biasing the formed object 100 relative to the ram 300 in the direction indicated by the white arrow in the figure. [Figure 9A] This is a cross-sectional view of one edge of article 100 showing the form of its deflectable flange 160 before the rotational operation described herein, including the characteristic that a potentially sharp or rough peripheral edge 110 is accessible to contact a film used to seal the article or another nearby film or object. [Figure 9B] Figures 8A to 8C show a cross-sectional view of one edge of an article 100 having a peripheral edge 110 that rotates by the technique shown. [Figure 9C] Figure 9B shows cross-sectional views of the edges of the three articles 100, which are stacked in a nested manner. [Figure 9D] This is an image of a prior art thermoformed plastic tray having stacked protrusions (the lower corner extensions of the rim, towards which a finger is pointing in the image). [Figure 9E]This specification demonstrates that two trays having rotated edges, as described herein, can be stacked in a manner that allows them to be separated into a smaller volume than prior art trays having stacking protrusions can. [Figure 9F] The image shows three nested stacked trays, each having a rotated edge on its left side and a stacked extension 180 formed within its corner to increase the separation between the straight edges of the stacked trays. [Figure 10A] This is an image of a ram 300 having an item 100 shaped like a rounded rectangular tray with a rim, which is supported by it. [Figure 10B] This is part of the upper surface 302 of the ram 300. [Figure 10C] Figure 10B shows a schematic cross-sectional view of the Ram 300, including the marker letters A to E. [Figure 11A] This is a cross-sectional view of one edge of an article comprising a relatively thick thermoformable substrate sheet 101 and a relatively thin flexible liner sheet 500 attached to its surface, showing the configuration of the deflectable flange 160 of the article before the rotational operation described herein, with its potentially sharp or rough peripheral edge 110 in an accessible position. [Figure 11B] This is a cross-sectional view of the same edge of the article after that peripheral edge has been rotated as described herein. [Figure 11C] The sheet of the cover 600 contacts the liner sheet 500 at the deflectable flange extension 50, while the peripheral edge 610 of the cover is positioned beyond the periphery of the article. [Modes for carrying out the invention]

[0024]

[0024] Figure 1 consists of Figures 1A, 1B and 1C, and illustrates the basic operation of the structures and methods described herein. Parallel lines " / / " indicate that the positions where structures, dimensions, and proportions may optionally exist have been omitted for clarity.

[0025]

[0025] Figure 1A shows a cross-sectional view of a thermoplastic article 100 having a deflectable flange 160 formed on its edge. In this embodiment, the deflectable flange 160 includes an extension 50, a bend region 150, a spacer 140, and a peripheral flange 120. The extension 50 connects the formed body 10 of the article 100 to the bend region 150 of the deflectable flange 160. The spacer 140 can (and preferably) be interposed between the bend region 150 and the peripheral flange 120. The peripheral flange 120 is connected to the spacer 140 by an elbow 130, which in this embodiment is shown as a right-angle bend. The bend region 150 connects to the extension 50 and the spacer 140 at approximately a right angle (the angle shown in A). The peripheral flange 120 terminates at the peripheral edge 110 of the thermoplastic material (shown in this figure by a thick solid line) forming the article 100.

[0026]

[0026] Figure 1B shows a thermoplastic article 100 inserted inside the upper body 200, where the upper body 200 is shown as a fractured section (indicated by rough lines). In this embodiment, the deflectable flange 160 is damaged as the peripheral edge 110 of the peripheral flange 120 collides with the inner surface 202 of the upper body 200, causing the deflectable flange 160 to bend at one or more points B within the bending region 150.

[0027]

[0027] Figure 1C shows the result of inserting the ram 300 (only the fracture portion is shown as indicated by the rough lines) into the upper body 200 behind the thermoplastic article 100 (i.e., when the ram 300 is inserted into the structure shown in Figure 1B). The ram 300 is in close proximity to the inner surface 202 of the upper body 200, and the peripheral edge 110 of the peripheral flange 120 collides with the upper surface 302 of the ram 300, causing the deflection of the deflectable flange 160 to become even greater, resulting in a rounded periphery of the article 100 at a point within the bending region 150 where bending is induced.

[0028]

[0028] Figure 2, consisting of Figures 2A, 2B, 2C and 2D, shows a matched upper body 200 and ram 300 for deflecting one or more deflectable flanges 160 formed on the periphery of a molded thermoplastic article having the form of a rectangular tray with rounded corners. Figure 2A shows the upper body 200 positioned on the ram 300, and Figure 2B shows the upper body 200 engaged with the ram 300. Figure 2C is a cutaway of the engaged upper body 200 and ram 300 shown in Figure 2B, showing that a portion of the ram 300 fits inside the upper body 200 and is in close proximity to the inner surface of a recess inside the upper body 200. Figure 2D is a detail of the cross-section shown in Figure 2C, showing the close proximity between the ram 300 and the interior of the upper body 200. In Figure 2D, the inclined shape of the upper surface 302 of the ram 300 is evident.

[0029]

[0029] Figure 3 consists of Figures 3A, 3B, and 3C, which are images of the smoothed periphery and corners of a transparent, molded thermoplastic article having the form of a rectangular tray with rounded corners. The article was smoothed using an upper body 200 and ram 300 similar to the upper body 200 and ram 300 shown in Figure 2. In Figure 3A, a finger is seen inside the tray, and the smoothed corner is seen to the left of the finger. A stacked projection is also visible where the finger is placed, and this stacked projection is part of the corner of the tray, which extends more extensively around the periphery than the corner below the finger. The smoothed straight side wall of the tray extends from the smoothed corner (downwards in the drawing). Wrinkles in the periphery flange are seen below the smoothed corner, and the deflection of the periphery flange can be seen behind the left corner in the drawing, below the smoothed straight edge. Figure 3B is another view of a similarly constructed smoothed corner of a tray, seen from below the rim of the tray. The protruding extension at the corner below the rim is a laminated projection. Figure 3C is a view of the smoothed corner, with a finger pointing to the smoothed area formed by bending, softening, bending, and cooling the bending region of the deflectable flange. The relatively sharp edges of the thermoplastic material forming the tray are bent below the corner as shown in Figures 3A and 3B, so that this smoothed area can be biased against a thin plastic film, for example, without easily tearing it.

[0030]

[0030] Figure 4 shows a cross-sectional view taken through a storage container article 100 formed using the method described herein (parallel lines " / / " indicate that locations where structures, dimensions, and proportions may optionally exist have been omitted for clarity). In the figure, the article 100 has deflectable flanges 160 formed on each of the sides of the container shown in the figure. A single upper body 200 extends throughout the container, including the periphery on both sides where the deflectable flanges 160 are located. A single ram 300 (only two parts are shown in the figure) is inserted behind the article 100 into the cavity within the upper body 200. The peripheral edges 110 of the thermoplastic sheet forming the article 100 penetrate above the upper surface 302 of the ram 300 at each deflectable flange 160, causing the deflectable flanges 160 to deflect inward toward the body of the article 100 by bending at one or more portions of the bending region 150 of each deflectable flange 160. By applying a sufficient amount of heat to soften the thermoplastic sheet, the deflectable flange 160 maintains substantially the shape shown in this figure, and the peripheral edge 110 of the thermoplastic sheet is positioned off-periphery (i.e., within the periphery of article 100, occurring at the position shown in this figure), resulting in a smooth periphery for the formed container as the softened portion cools.

[0031]

[0031] Figure 5 consists of Figures 5A, 5B and 5C, each of which shows a cross-sectional view cut through a storage container article 100 formed using the method described herein (parallel lines " / / " indicate that locations where structures, dimensions and proportions may optionally exist have been omitted for clarity). In the figure, the article 100 has deflectable flanges 160 formed on each side of the container shown in the figure. Each deflectable flange 160 is deflected inward by the upper surface 302 of a single ram 300 (only two parts are shown in this figure) penetrating above it. The peripheral edge 110 of the thermoplastic sheet forming the article 100 penetrates above the upper surface 302 of the ram 300 at each deflectable flange 160, causing the deflectable flange 160 to bend inward toward the body of the article 100 by bending in one or more parts of the bending region 150 of each deflectable flange 160. By applying a sufficient amount of heat to soften the thermoplastic sheet, the deflectable flange 160 maintains substantially the shape shown in this figure, and the peripheral edge 110 of the thermoplastic sheet is positioned off-peripherally (i.e., within the periphery of article 100, occurring at the position shown in this figure), resulting in a smooth periphery to the formed container as the softened portion cools. In this embodiment, two parts of the ram 300 are shown with different contours (one flat and one curved) to illustrate the difference in deflection that can be induced by different contours. Figures 5A, 5B, and 5C show different distances between the elbow and the peripheral edge, which are greater in Figure 5A than in Figure 5B and zero in Figure 5C.

[0032]

[0032] Figures 6A, 6B, 6C, 6D, and 6E show deflectable flanges formed within tray-shaped articles thermoformed from a sheet of thermoplastic material. In Figures 6A and 6B, a finger is touching the sharp edge where the tray is cut from the sheet (i.e., the peripheral edge 110 around the peripheral flange 120). In these figures, the deflectable flange is still not softened, deflected, or cooled, so the sharp edge remains positioned around the periphery of the tray. In comparison, the sharp edge is deflected inward, away from the periphery of the tray shown in Figure 3, and within the tray shown at the bottom of Figure 6C. The tray shown at the top of Figure 6C is identical to the tray shown at the bottom, except that the top tray does not have its deflectable flange that has been "rotated" as the bottom tray has. Figure 6D is a view from below of a rounded rectangular tray with a "rotated" edge around its entire periphery. It can be seen that there are no sharp edges around or near the edges of this tray. Figure 6E is a perspective view of three identical trays, each having a “rotated” edge as described herein, with the degree of “rotation” of the edge differing among the three. The tray labeled "1" has a peripheral edge that is only slightly "rotated" (i.e., a portion of the deflectable flange, including the peripheral edge 110, is deflected inward by approximately 45 degrees from the plane of the rest of the spacer 140, and most of the spacer 140 remains substantially flat within this tray). The tray labeled "2" has a peripheral edge that is more completely "rotated" (i.e., the peripheral edge 110 is almost invisible, and the peripheral edge 110 is "wrapped" behind the remaining visible portion of the spacer 140). On the tray labeled "3", the deflectable flange is rotated even further, and the peripheral edge 110 is invisible. The greater rotation of the deflectable flange on tray "3" than on tray "2" is detectable because the shorter portion of the spacer 140 that remains visible on tray "3" than on tray "2" (and the visible portions of the spacer 140 on trays "2" and "3" are shorter than the visible portion of the spacer 140 on tray "1").Therefore, the three trays shown in Figure 6E can be considered to represent individual degrees of "rotation" of the deflectable flanges.

[0033]

[0033] Figures 7A, 7B, and 7C show an embodiment in which an article 100 (parallel lines " / / " indicate omitted for clarity the location where the structure, dimensions, and proportions may optionally exist) formed from a thermoplastic sheet seated on a horizontal plane (horizontal solid line) has its periphery edge smoothed as described herein. In this embodiment, each of the two deflectable flanges 160 of the article is deflected inward by lowering the upper body 200 (two parts are shown in this cross section) over the article 100 in the direction indicated by the white arrows. In Figure 7A, the outwardly flared portion of the upper body 200 is in contact with the periphery flange 120 of the article 100 as the upper body 200 is lowered over the article toward the horizontal plane, and the deflectable flange begins to deflect in the area marked "B". In Figure 7B, the upper body 200 is lowered to the horizontal plane, and the peripheral edge 110 and peripheral flange 120 of the article 100 are partially deflected inward toward the body 10 of the article 100. In Figure 7C, the ram 300 is inserted behind the article 100 into the cavity within the upper body 200 in the direction indicated by the white arrow, further deflecting the peripheral flange 120 (and the flange 160 which can deflect together with them) through the bending of the thermoplastic sheet forming the article in the region marked "B".

[0034]

[0034] Figure 8 consists of Figures 8A, 8Ai, 8B, 8Bi, 8C, 8Ci, 8D, 8Di, 8Dii, 8E, 8F, 8G, 8H, 8J, and 8K, and shows the deflection and rotation of a deflectable flange 160, including its sharp peripheral edge 110, using a ram 300 as described herein. Each of Figures 8A-8C, 8E-8G, and 8H-8K is a cross-sectional view including only one edge of the article, and the same deflection and rotation of an edge can be simply performed on multiple edges of the article (e.g., all edges) by using multiple rams or one ram that contacts all edges to be treated in this manner. Figures 8Ai, 8Bi, and 8Ci are copies of Figures 8A, 8B, and 8C, each identifying the offset angle OA.

[0035]

[0035] Figures 8A, 8B, and 8C, as can be seen by comparing them with the portion of the article that appears in the left portion of each figure, continuously depict the effect of further biasing the formed article 100 against the ram 300 in the direction indicated by the white arrows in each figure. In the embodiments shown in Figures 8A to 8C, the deflectable flange 160 lacks an elbow and peripheral flanges. The initial form of the formed article (after the ram has struck it beforehand) is the form shown in Figure 9A.

[0036]

[0036] In Figure 8A, the article is biased to the ram such that its deflectable flange 160 contacts the upper surface 302 of the ram at its peripheral edge. The deflectable flange 160 deflects from its previously contacted position to resist the movement it encounters as it contacts the inclined portion of the upper surface 302. In the figure, the peripheral edge 110 of the deflectable flange transitions to the curved contour of the inclined portion of the upper surface, and a portion of the spacer leans against the upper surface in close proximity to the ram, causing the ram to heat up and transfer heat to it.

[0037]

[0037] Figure 8B shows the effect of further biasing the article 100 depicted in Figure 8A to the ram 300. As the ram 300 shown in Figure 8B is heated, the ram 300 softens the material from which the deflectable flange 160 is created in the portion where the deflectable flange approaches or contacts the upper surface 302 of the heated ram 300. Due to the shape of the upper surface 302, the deflectable flange 160 arrives at a position where it cannot advance any further by simply sliding along the surface of the upper surface. As the article 100 (including the deflectable flange 160) is biased in the direction indicated by the white arrow, and as the material from which the deflectable flange is constructed is softened by the heated ram 300, the deflectable flange deforms (at position B) to follow the contour of the upper surface 302 of the ram as the deflectable flange advances against the ram.

[0038]

[0038] Figure 8C shows the effect of continuing to bias the article 100 depicted in Figure 8B against the heated ram 300. As the article (including the deflectable flange 160) is biased in the direction indicated by the white arrow, the deflectable flange continues to bend where it has softened due to contact with the heated ram (i.e., position B). As the deflectable flange continues to move relative to the ram, the peripheral edge 110 of the deflectable flange eventually reaches the edge of the upper surface 302 of the ram. A portion of the deflectable flange, including the peripheral edge, remains softened for a certain period of time (the duration of which depends on the operating conditions in an expected manner). If the peripheral end comes into contact with a portion of the article 100 while it is softened, the peripheral end can thereby be deflected (for example, upward as proposed in the embodiment shown in Figure 8C). The deflection of a portion of the peripheral flange away from contact with the upper surface may also be influenced by the contour of the upper surface 302, including, for example, a "spiral" or "helical" shape as shown in Figure 8C.

[0039]

[0039] Figure 8D shows the use of one or more objects to assist in deflection and rotation on the deflectable flange as described herein. Object 401 (referred to as a plug elsewhere herein) is positioned within the internal compartment of the formed article 100 and contacts the internal surface of the formed article 100 while the deflectable flange 160 is impacting the ram 300 to reduce or prevent inward deflection of the internal surface during operation. Object 403 in this embodiment applies downward pressure (white arrow) to the extension 50 of the deflectable flange 160 so that the deflectable flange 160 impacts the upper surface 302 of the ram 300. In this embodiment, object 402 is in firm contact with objects 401 and 403. The filled arrows illustrate the force pressed against the article 100 when downward pressure is applied. Figure 8Di depicts an article shaped as object 401 in Figure 8D, which reduces or prevents inward deflection of the side walls of the tray T during rotation of the deflectable flange of the tray T, and a plug P that fits inside it, with the shape and dimensions being such that the tray T has a rounded interior. Figure 8Dii shows the plug inserted inside the tray.

[0040]

[0040] Figures 8E, 8F, and 8G (similar to Figures 8A, 8B, and 8C) sequentially illustrate the effect of further biasing the formed article 100 with respect to the ram 300 in the direction indicated by the white arrows in each figure. In the embodiments shown in Figures 8E to 8G, the deflectable flange 160 includes the peripheral flange 120 at the peripheral end of the spacer 140. In these figures, it can be seen that the peripheral flange 120 deflects to such an extent that the deflectable flange 160 becomes indistinguishable from the spacer 140 during the bending of the deflectable flange 160.

[0041]

[0041] Figures 8H, 8J, and 8K (similar to Figures 8A, 8B, and 8C, with Figure 8I intentionally omitted) sequentially illustrate the effect of further biasing the formed article 100 against the ram 300 in the direction indicated by the white arrows in each figure. In the embodiments shown in Figures 8H to 8K, the deflectable flange 160 includes a peripheral flange 120 at the peripheral end of the spacer 140. In these figures, it can be seen that the peripheral flange 120 deflects during the bending of the deflectable flange 160 to such an extent that the deflectable flange 160 bends completely over the spacer 140, forming a "hook" structure. In Figure 8J, B shows that by bending, a portion of the deflectable flange 160 extends over the indicated portion of the upper surface 302 of the ram 300.

[0042]

[0042] Figure 9 consists of Figures 9A, 9B, 9C, 9D, 9E and 9F, and illustrates an advantageous feature of one embodiment of an article manufactured as disclosed herein.

[0043]

[0043] Figure 9A is a cross-sectional view of one edge of article 100 showing the form of its deflectable flange 160 before the rotational operation described herein, and includes the feature that the potentially sharp or rough peripheral edge 110 is accessible to contact a film used to seal the article or another nearby film or object. Figure 9B is a cross-sectional view of one edge of article 100 having the peripheral edge 110 rotated by the technique shown in Figures 8A to 8C. Compared to the article engaged with the ram shown in Figure 8C, the deflectable flange 160 of the article "springs back" in the peripheral direction following engagement and disengagement from the ram. Because the plastic material from which the article is constructed is flexible, the rotated edge shown in Figure 9B exhibits "elasticity" when biased in a direction perpendicular to the plane of the figure, such as in the direction indicated by the white arrow.

[0044]

[0044] Figure 9C is a cross-sectional view of the edges of the three articles 100 shown in Figure 9B, where the articles are stacked in a nesting manner. Since each article has the same shape (for example, a tray similar to the one shown at the bottom of Figure 6C), each article can be nested and, together with the other, can be biased until its rotated edge contacts the tray above and / or below it. Figure 9C shows three such stacked nested trays, and the white arrows indicate the positions where the nested trays can be separated using a standard nesting tool. For example, a finger or screw can engage the area between the trays at these positions, and the finger or screw can be manipulated to separate the trays from each other for individual use (with each normal nesting procedure).

[0045]

[0045] Figure 9D is an image of a prior art thermoformed plastic tray having stacking protrusions (corner extensions below the rim, towards which a finger is pointing in the image). The stacking protrusions serve to maintain a controlled separation distance between the stacked trays, as shown in the left portion of Figure 9E (which is an image of two of these prior art trays stacked on top of each other, with the distance between the trays limited by the stacking protrusions). The right portion of Figure 9E shows two nested trays stacked on top of each other, having a rotated rim (as schematically shown in Figure 9C with three trays). The boundary between the trays is seen between the rims of the two stacked trays. Figure 9E shows that two trays having a rotated rim as described herein can be stacked in a manner that allows them to separate into a smaller volume than a prior art tray having stacking protrusions can. Figure 9F shows three nested stacked trays having a rotated rim on its left side and stacking extensions 180 formed within its corners to increase the separation between the straight edges of the stacked trays. It can be seen that the three stacked trays having the stacking extension 180 have a greater separation distance (larger square bracket on the left side of the figure) than the three identical stacked trays without the stacking extension (smaller square bracket on the right side of the figure).

[0046]

[0046] Figure 10 consists of Figures 10A, 10B and 10C. Figure 10A is an image of a ram 300 having a molded article 100 in the form of a rounded rectangular tray with a rim, which is supported by it. In the lower right portion of the image, the upper surface 302 can be seen, on which a second article can be placed, but is not currently supporting an article. In the upper part of the figure, with the article 100 supported by the ram 300, it can be seen that the extension 50 connects the spacer 140 and the peripheral flange 120 of the deflectable flange to the body 10 of the article 100. The spacer 140 and peripheral flange 120 are supported by the upper surface of the ram 300 in the upper part of the figure, and its upper surface (similar to the upper surface 302 in the lower right of the figure) is therefore not directly visible. "10B" shows a portion of the ram 300 shown in Figure 10B (with the molded article 100 removed). In Figure 10B, a portion of the upper surface 302 of the ram 300 is visible. The dashed line 10C-10C in Figure 10B indicates the approximate location of the cross-section depicted in Figure 10C, and the letters A-E are included as markers to help better understand the surface configuration of the ram 300 by comparing Figure 10B and Figure 10C. Figure 10C is a schematic cross-sectional view of the ram 300 shown in Figure 10B, including the marker letters A-E.

[0047]

[0047] Figure 11, consisting of Figures 11A, 11B, and 11C, shows the features of one embodiment of a molded article having a peelable liner sheet attached to the surface of the article.

[0048]

[0048] Figure 11A is a cross-sectional view of one edge of an article comprising a relatively thick thermoformable substrate sheet 101 and a relatively thin flexible liner sheet 500 attached to its surface, showing the form of the deflectable flange 160 of the article before the rotational operation described herein, including its potentially sharp or rough peripheral edge 110 in an accessible position. Figure 11B is a cross-sectional view of the same edge of the article after its peripheral edge has been rotated as described herein. The peripheral edge 111 of the substrate sheet 101 is rotated sufficiently to "return toward" the body of the article, and the peripheral edge 511 of the liner sheet 500 is pulled away (or peeled away) from the peripheral edge 111 of the substrate sheet in this figure. In Figure 11C, the sheet of the cover 600 is in contact with the liner sheet 500 at the extension 50 of the deflectable flange, while the peripheral edge 610 of the cover is positioned beyond the periphery of the article. The cover 600 and the liner sheet 500 can be attached to each other by interposing an adhesive between them, or by pressing them together at the positions indicated by the white arrows (for example, while applying enough heat to bond or melt them together). When attached to the liner sheet 500 in this manner, the cover 600 can be removed from the substrate sheet 101 of the article together with the liner sheet 500 by the liner sheet 500 gripping the liner sheet at or near its peripheral edge 511, and peeling the liner sheet 500 away from the substrate sheet 101 (while the cover 600 remains attached).

[0049] Detailed explanation

[0049] The subject matter disclosed herein relates to the formation of a molded thermoplastic article, and more particularly to an article in which one or more edges of the article are formed such that the peripheral edge of the thermoplastic sheet forming the article is bent away from the surface of the article, preferably away from the periphery of the article, so that a fragile material (e.g., skin or a thin flexible plastic sheet) applied to the surface or periphery does not come into contact with the edge of the sheet. Such a sheet edge can be sharp, and therefore, when the edge is cut or torn, damage to a fragile material in contact with the surface or periphery can be prevented by oriented the edge away from the surface and / or periphery of the article. The subject matter disclosed herein is specifically used in forming or wrapping a container that is sealed with a fragile plastic film applied to the surface of the container. In a preferred embodiment disclosed herein, the peripheral edge of the thermoplastic sheet on which the article is formed is bent away from the periphery of the article, insofar as the resulting article is suitable for use in any or all OW, VSP and MAP sealing techniques. The molded articles described herein are, in practice, considered to be a first type of packaging that can be sealed using all three of these techniques. Preferably, thermoformable and moldable plastics tend to be widely accepted in recycling programs, and articles made from them are easier to recycle than, for example, foamed plastic articles.

[0050]

[0050] In short, the basic method described herein for forming a molded thermoplastic article having a smooth edge is to form a deflectable flange around the periphery of the article. The deflectable flange includes a potentially sharp or rough peripheral edge of the thermoplastic material on which the article is formed. The deflectable flange is softened in one or more portions such that the peripheral edge is directed away from the periphery of the article when the deflectable flange deflects toward the body of the article (preferably "conceals" the peripheral edge, body, or both between the deflected and extended portions of the deflectable flange). The temperature rises to above the glass transition temperature of the material on which the flange is formed, preferably below the melting point of the material. By cooling the softened and deflected deflectable flange below its glass transition temperature (i.e., re-hardening), the peripheral edge is "locked" in place, reducing the possibility that materials in contact with the periphery of the article (e.g., skin or film) may be damaged by the sharpness or roughness of the peripheral edge.

[0051]

[0051] There is a deflectable flange formed around the periphery that can be “rotated” around the periphery (and specifically the curved edges and corners of the periphery) to produce a smooth periphery. In the aforementioned tray which includes an external flange (for example, a tray which includes a periphery similar to the one shown in Figure 1A, but without the bend region 150, spacer 140, elbow portion 130 and periphery flange 120, and has a periphery edge 110 around the extension portion 50), bending or rotating the external flange is possible along a straight edge, but bending or rotating the curved edges and corners of such an external flange cannot be done without buckling or creasing of the material within the flange, resulting in an undesirable non-smooth edge. There is a smooth bend region 150 and spacer 140 of the deflectable flange described herein which can deflect away from the periphery of the article without the periphery edge 110 buckling or creasing in this manner, resulting in a smooth periphery. As can be seen from Figures 1, 4, 5, 7, and 8, the bending, curving, and bending of the deflectable flange can also affect any one or more extensions 50, bending regions 150, spacers 140, elbows 130, peripheral flanges 120, and peripheral edges 110. Regardless of which of these elements is bent or deflected to achieve the desired effect, the resulting arrangement, which may have sharp peripheral edges 110 away from the periphery of the article, preferably not easily accessible from the outside of the article around its periphery, results in an article with a smooth periphery suitable for contact with fragile films, tissues, or other surfaces.

[0052]

[0052] In one embodiment, the deflectable flange includes a peripheral flange that extends circumferentially from the article and is attached to the spacer portion by an elbow in the thermoplastic material forming the article (e.g., bent at 90 degrees or through some other offset angle such as an angle of 60 to 120 degrees). The body of the article is attached to the spacer by a bending region, the bending region defining an angle (angle A in Figure 1A, preferably nearly right) between the spacer and a portion of the body adjacent to the bending region (i.e., this portion is usually an extension that serves to connect the body to the bending region). The deflectable flange is inserted into the cavity of the body (e.g., upper body 200 or ram 300) such that the peripheral flange collides with the wall of the cavity, thereby deflecting the deflectable flange toward the body of the article. During such deflection, enough heat is applied to the bending region to soften or melt the thermoplastic material in the bending region, so that the deflectable flange remains deflected toward the body as the bending region cools. Optionally, a ram can be inserted into the cavity after the deflectable flange, and the surface of the ram in contact with the deflected peripheral flange can further induce deflection of the deflectable flange, and further move the peripheral edge of the article away from the periphery of the article during cooling. In this way, the smooth "rotated" edge of the thermoplastic material forms the outermost periphery of the article, while the peripheral edge of the thermoplastic material remains within the outermost periphery of the article, in which case its sharp edge is less likely to damage fragile material in contact with the outermost periphery of the article.

[0053]

[0053] In another embodiment, the deflectable flange contacts a ram that modulates the deflectable flange so that the sharp edge of the thermoplastic sheet is deflected away from the periphery of the article. Before, during, or after such modification, one or more portions of the deflectable flange (e.g., a bending region, a spacer, an elbow, a peripheral flange, any portion in contact with the ram, or a combination thereof) are heated sufficiently to soften the thermoplastic material, and the deflectable flange is then cooled to “fix” the deflection. Depending on the angle of deflection, the peripheral edge of the thermoplastic material may also achieve a J-shaped, U-shaped, or helical form (i.e., any shape that results in a substantially smooth peripheral edge), and the peripheral edge may, while softened, simply bend away from the periphery of the article, bend in the nearly opposite direction to the periphery, or “rotate” by deflecting the deflectable flange at a sufficiently narrow radius, so that it is not likely to damage any skin or film present around the article.

[0054]

[0054] Next, the individual elements and aspects of the formed articles and the methods for creating them will be described in more detail.

[0055]

[0055] Shaped article

[0056] The methods described herein are considered applicable to articles of a wide range of shapes and sizes, particularly articles that have sharp edges when manufactured by conventional methods. The motivation for creating molded thermoplastic articles with smooth edges arose, in part, from the desire to create general storage trays (e.g., plastic trays used for storing foods such as raw or frozen meat, fruits, or vegetables) with sufficiently blunt (not sharp) edges that would allow the tray to be wrapped in or in contact with a thin plastic film such as polyvinylidene chloride film and polyethylene film without the film being cut or torn by the edges of the tray under normal use conditions. However, with the development of the methods described herein, it was recognized that smooth, rounded edges are desirable in a variety of other situations, such as preventing skin injury to persons handling trays and other molded articles, and preventing damage to the film sealing one tray by the sharp edges of a second sealed tray (e.g., in a transport container containing multiple sealed trays).

[0056]

[0057] For example, a common method for creating molded items such as meat trays is by thermoforming a sheet of thermoplastic material. In the thermoforming process, a portion of a long sheet of thermoplastic material is heated to a temperature at which the thermoplastic material softens and can be molded. The softened thermoplastic material is pressed against the surface of one or more molds (often using negative air pressure to ensure that the opposite side of the softened thermoplastic film is pressed tightly against the mold surface). As the film cools (e.g., when it comes into contact with the mold surface), the thermoplastic material hardens and becomes less easily deformable, causing the thermoplastic film to reach and maintain the shape pressed by the molding process. Multiple castings are often created from the same item within a single sheet of film in the thermoforming process, and individual items are removed from the film by cutting the film around the item (e.g., die-cutting). This process tends to result in sharp edges at the cut end of the film, including sharp edges surrounding all or part of the item's periphery (i.e., where the item was cut from the film).

[0057]

[0058] Furthermore, for example, thermoplastic material can be melted in an extruder and injected into a mold cavity that defines the shape of the molded article. After cooling, the mold can be opened and the molded article can be removed. In the molding process, thermoplastic material often appears in undesirable places on the finished article, such as "casting," which occurs when molten thermoplastic material flows between the molded plates or through a port supplied into a closed mold. These undesirable parts may be sharp themselves, and sharp edges may remain when these undesirable parts are cut from the molded article.

[0058]

[0059] The size and shape of the articles described herein are not important. Generally, the molded articles are expected to be handled or to come into contact with one or more fragile materials at their peripheral edges. The edge smoothing process described herein can remove one or more sharp edges from thermoplastic articles, which typically have such sharp edges regardless of how the article is manufactured.

[0059]

[0060] How to smooth

[0061] The periphery of a thermoplastic article, specifically an article formed from a bent or molded sheet of thermoplastic material, can be smoothed by a process that includes forming a deflectable flange near the periphery of the edge to be smoothed, deflecting the bent portion of the flange to move the edge away from the periphery of the article, softening the bent portion at least while the flange is in the deflected position, and re-hardening the bent portion while the flange is in the deflected position. This process is shown in Figure 1. A portion of the deflectable flange 160 that can be softened and bent may be a portion of the deflectable flange distal to the bent region 150 or preferably distal to the bent region 150 but proximal to the peripheral edge 110. For example, by softening the spacer 140, its periphery, including the elbow portion 130, the peripheral flange 120 (if these two elements exist) and the peripheral edge 110, can be bent sufficiently inward (i.e., toward the body 10 of the article 100) so that the peripheral edge 110 moves away from the periphery of the article.

[0060]

[0062] Preferably, at least a portion of the spacer 140 is softened and sufficiently bent so that the peripheral edge 110 is "rotated" so that the peripheral edge 110 is positioned so that it does not come into contact with the peripheral edge 110 even when a film wrapping or covering an article is taut and stretched. More preferably, the deflectable flange 160 is rotated sufficiently so that the peripheral edge 110 is obscured by the spacer 140 or the bent region 150 so that the peripheral edge 110 is not visible when the article 100 is viewed horizontally from its periphery (i.e., from its peripheral side). Again preferably, the deflectable flange 160 is rotated sufficiently so that the peripheral edge 110 "facing" the bottom surface of the body 10 or a portion of the deflectable flange 160, meaning that the plane of the deflectable flange intersects with the body 10, including the bottom surface 161 of the deflectable flange 160 (see, for example, Figure 1B), in the portion including its peripheral edge 110. When the plane of the deflectable flange does not face the body 10 (see, for example, offset angle OA in Figure 8Bi) or the bottom surface 161 of the deflectable flange 160 (see, for example, offset angle OA in Figure 8Ci) at its edge, including the peripheral edge 110, the peripheral edge should be offset or rotated sufficiently away from the periphery of the article 100 (see, for example, offset angle OA in Figure 8Ai) so that the peripheral edge 110 is obscured by one or more portions of the deflectable flange 160.

[0061]

[0063] Figure 1A shows a thermoplastic article 100 having a body 10 (which has an irregular shape in this figure) and a deflectable flange connected to the body 10. The deflectable flange includes a peripheral flange 120, which includes a peripheral edge 110 of a thermoplastic sheet, and the article 100 is formed from the thermoplastic sheet. The deflectable flange also includes a bend region 150 interposed between the body 10 and the peripheral flange 120 of the article 100. The bend region 150 is separated from the body 10 by an extension 50, which in this embodiment is simply a flat portion of the thermoplastic sheet. The peripheral flange 120 is similarly separated from the bend region by a flat portion of the thermoplastic sheet designated as a spacer 140 in this embodiment. The peripheral flange 120 is connected to the remainder of the deflectable flange by an elbow 130, which in this embodiment is a right-angled portion of the thermoplastic sheet.

[0062]

[0064] Figure 1A is a cross-sectional view of such an article 100, where the solid black line represents a cross-sectional view of the thermoplastic sheet forming the article 100. Since there is no portion of the article 100 extending further to the right (in this figure), the peripheral edge 110 forms the periphery of the article 100, and the other portions of the spacer 140 and peripheral flange 120 are closer to the body 10 than the peripheral edge 110 of the sheet. Therefore, if an object is biased to the right side of the article 100 (in Figure 1A), the object tends to come into contact with the peripheral edge 110, and the sharpness of that peripheral edge 110 may affect the object by cutting, damaging, or otherwise injuring it.

[0063]

[0065] In Figure 1B, the thermoplastic article 100 is inserted into the internal cavity of the upper body 200. The inner surface 202 of the upper body collides with the peripheral flange 120, deflecting the peripheral flange 120 inward toward the body 10 of the article 100 (i.e., away from the periphery). In this embodiment, both the peripheral edge 110 of the thermoplastic sheet on which the article 100 is formed and most of the periphery of the bending region 150 are positioned substantially equal to the periphery from the body 10. Preferably, the deflectable flange 160 is deflected much more sufficiently inward so that the peripheral edge 110 of the thermoplastic sheet is contained within the internal cavity of the upper body 200. In this embodiment, the spacer 140 is essentially rigid, and substantially all bending occurs within the bending region 150. If enough heat is applied to the bending region 150 (near the location identified as "B" in Figure 1B) to soften the thermoplastic sheet, and the sheet is subsequently cooled sufficiently (preferably below its glass transition temperature), the deflectable flange 160 will maintain the configuration shown in Figure 1B even after the upper body 200 has separated from the article 100 (i.e., the peripheral edge 110 has struck the inner surface 202 of the upper body 200, thus deflecting in relation to its initial form shown in Figure 1A). In this deflected form, the peripheral edge 110 does not extend periphery beyond the rounded bending region 150, and the resulting article is more suitable for sealing with a thin plastic film attached to the extension 50 and bending region 150 than the original pre-deformed article shown in Figure 1A (i.e., due to the potentially sharp protrusion of the peripheral edge 110 beyond the periphery of the bending region 150, the peripheral edge 110 at that location may easily snag, fray, or cut the film).

[0064]

[0066] Figure 1C shows an optional but preferred step in which the ram 300 is inserted behind the article 100 into a cavity within the upper body 200 (i.e., sandwiching at least a deflectable flange 160 between the upper body 200 and the ram 300). This step further deflects the deflectable flange 160 toward the body 10 of the article 100 (relative to the embodiment shown in Figure 1B), thereby moving the (potentially sharp) peripheral edge 110 of the thermoplastic sheet further away from the periphery of the article (i.e., further away from the inner surface 202 of the upper body 200). While the bent region 150 of the deflectable flange 160 is in the configuration shown in Figure 1C, the bent region 150 is heated sufficiently to at least soften it, and then the bent region 150 is cooled below its glass transition temperature to "solidify" the deflectable flange in the shown configuration. In this configuration, the sharp peripheral edge 110 of the sheet forming the article is “pushed” under the other parts of the deflectable flange 160 (if present, e.g., the bending region 150 and extension 50), and as a result is less likely to come into contact with objects that come into contact with the periphery of the article (and less likely to tear, cut, or damage materials that come into contact with the periphery of the article). For example, if a thin plastic film is attached to the extension 50 and bending region 150, the film is less likely to snag, fray, or cut by the potentially sharp peripheral edge 110 in this embodiment than in the embodiment shown in Figure 1B. From this improvement (i.e., greater deflection in Figure 1C than in Figures 1B and 1A), the more the peripheral edge 110 is deflected away from the periphery of the part of the article to which the sealing film is attached, the less likely the film is to be damaged at the edge.

[0065]

[0067] The ram 300 and the upper body 200 serve the purpose of deflecting the deflectable flange by impacting the deflectable flange on or against the deflectable flange. These two items are therefore essentially interchangeable, and each can be used alone or in combination of two or more rams and upper bodies. In this disclosure, the term “ram” is used to refer to the body that impacts the deflectable flange by being applied in one direction or in the opposite direction from the portion of the deflectable flange furthest from the body of the formed article. Similarly, the term “upper body” is used to refer to the body that impacts the deflectable flange by being applied in an substantially opposite direction or in the opposite direction (see Figures 1C and 4).

[0066]

[0068] In the example shown in Figure 1C, a portion of the ram 300 that strikes the peripheral flange 120 of the deflectable flange 160 has a wedge-shaped cross-section while the article is packed into the cavity within the upper body 200. Such a ram can be useful for directing the peripheral flange 120 and peripheral edge 110 in the opposite direction to the periphery, as the ram advances internally from the peripheral edge 110 toward the bending region 150, causing the peripheral flange 120 and peripheral edge 110 to deflect in the opposite direction to the periphery. However, these portions of the ram 300 do not have to be wedge-shaped. When the ram 300 is inserted behind the article 100 in the upper body 200, substantially any shape of ram 300 can be used to deflect the peripheral flange 120 and peripheral edge 110 in the opposite direction to the periphery, such as being blunt or rounded (with its upper surface 302 being convex or concave) or any combination thereof, as shown in Figure 5.

[0067]

[0069] Figure 8 shows an alternative method for rotating or otherwise shaping the edges of the article. As seen in Figure 8A, in this embodiment, the deflectable flange 160 has no elbow or peripheral flange, and instead includes only a spacer portion that terminates at the peripheral edge 110 of the thermoplastic sheet. This deflectable flange is biased against the upper surface 302 of the heated ram (in the direction indicated by the white arrow in Figure 8, regardless of how such biasing is achieved, such as by moving either or both of the article 100 or the ram 300). When the direction of movement of the deflectable flange is close to and parallel to the shape of the upper surface (i.e., as in Figure 8A), relatively little of the deflectable flange may be in contact with the upper surface, and relatively little heat may be transferred from the ram to the deflectable flange. However, as shown in Figure 8B, as the relative motion between the article and the ram increases or brings the contact surface between the upper surface of the ram and the deflectable flange larger, the contact / approaching contact surface area can be larger, and as a result, more heat flows from the ram to the deflectable flange. Sufficient heat flow softens the thermoplastic material, and the deflectable flange takes on the form of the upper surface. As shown in Figure 8C, as the relative motion between the article and the ram increases further, larger portions of the deflectable flange soften and deflect. Similar to the embodiment shown in Figure 1B, in this embodiment, heat suitable for bending the deflectable flange is applied (at multiple locations B in Figures 8B and 8C), but the bending region 150 does not bend much or at all and is not heated, except for a slight possibility that, as shown in Figure 8C, most of the periphery of the bending region 150 approaches the heated ram 300, in order to "rotate" a portion of the deflectable flange including the peripheral edge. For the processes described herein, it is not of much importance, as long as the desired result is obtained, which portion of the deflectable flange is softened and bent, and the potentially sharp peripheral edge 110 is deflected away from the periphery of the article and isolated (as in Figure 8C) to a place where it is very unlikely to come into contact with any fragile film or tissue, preferably in contact with the periphery of the formed article.The deflectable flange allows a portion of the deflectable flange to remain soft, so that a single smooth movement can gradually advance multiple individual flanges or a combination of these flanges into contact with or approach the ram.

[0068]

[0070] When the thermoplastic material moves and ceases contact with the ram (by engaging and disengaging the two, or by a portion of the deflectable flange moving beyond the upper surface of the ram as shown in Figure 8C), the thermoplastic material can cool, and the deflection induced therein is maintained during cooling. As shown in Figures 9B and 9E, the engagement and disengagement of the article with the ram causes the edge of the article to rotate, and the rotated edge has a smooth periphery, making it suitable for handling and / or contact with brittle plastic films. In all possible edge configurations, there is no degree of deflection of the peripheral edge 110 that can be clearly identified as a “minimum” amount of deflection to adequately prevent contact between the edge and fragile tissue or film; however, nevertheless, if the bend of the deflectable flange is sufficiently bent so that the peripheral edge “directs” toward any part of the deflectable flange (e.g., including extensions, bends, spacers, or bent sections) (i.e., planes in contact with a thermoplastic sheet extending through and at the peripheral edge intersect), then it can generally be said that the configuration should generally isolate the peripheral edge to adequately prevent contact between the edge and fragile tissue or film at or near the periphery of the article (see, for example, Figures 8C, 8G, and 9B). Alternatively, the deflectable flange can deflect sufficiently so that the peripheral edge 110 is close to and opposed to the side wall of the recess (see, for example, Figures 8C, 8K, and 9B), or closer to the extension 50 than the bend furthest from the extension (as in Figures 8B, 8D, 8F, and 8J) in order to achieve such isolation. Preferably, the peripheral edge 110 is "contained within" a section defined by either the rotated portion of the deflectable flange and the side wall of the recess (including, for example, as shown in Figure 8K) or a portion of the deflectable flange around the entire periphery of the article, so as to be substantially free of sharp edges that could damage fragile tissue and plastic film near the article.In another embodiment, a tray with a flat bottom has a substantially flat peripheral rim, the plane of the rim being essentially parallel to the bottom surface (as in standard MAP trays and other trays), and with respect to such a flat bottom tray, a rotated peripheral edge is preferably rotated sufficiently so that the peripheral edge "returns toward" the tray cavity (i.e., parallel to the two planes but oriented toward the tray cavity) or further away (for example, rotated sufficiently so that the peripheral edge turns toward the bottom surface of the extension of the rim or toward the bottom surface of the bend).

[0069]

[0071] In Figures 8A–8C, the deflectable flange is depicted without the elbow portion 130 and peripheral edge portion 120 shown in Figure 1A for the sake of simplicity in the illustration. While it is possible to produce deflectable flanges without the elbow portion and peripheral edge portion (for example, by mechanically or laser cutting the deflectable flange with the spacer 140 shown in Figure 1), such production can be difficult and costly and is therefore practically limited to large-scale production operations. For this reason, molded articles 100, such as articles intended for use as packaging for trays for processed foods described herein, often have both the elbow portion and peripheral edge portion shown in Figure 1A. Nevertheless, molded articles bearing the elbow portion and peripheral edge portion can be processed using the methods and apparatus described herein, as shown in Figures 8E–8K.

[0070]

[0072] Figures 8E to 8G illustrate the processing of a fabricated article 100 having a deflectable flange 160 including both the peripheral flange 120 and the elbow portion 130 as described herein, as well as the processing depicted in these figures which is generally similar to the processing shown in Figures 8A to 8C. In Figure 8E, the peripheral edge of the deflectable flange 120 is in direct contact with the upper surface 302 of the ram 300. The ram is heated so that the peripheral edge comes into contact with the ram and is directly conducted to the peripheral edge by radiation from a nearby, opposing position on the spacer 140. By controlling the heat flowing from the ram of article 100 at the position shown in Figure 8E and the residence time, the operator can, specifically, soften a portion of the deflectable flange including its peripheral edge and a portion of the spacer near that peripheral edge. Softening these portions facilitates the bending of the deflectable flange in the softened portion, such as by further biasing the article to the ram, so the curved portion of the upper surface induces bending when driven to the curved portion of the upper surface, with more of the deflectable flange's periphery than less of the periphery (which transmits the force applied to the article), as shown in Figure 8F. By further biasing the article to the ram, as shown in Figure 8G, a portion of the deflectable flange that is in contact with the upper surface of the ram slides across that upper surface. When the material is driven beyond the position where it is in contact with the upper surface, the material may remain softened for a short period (making it more easily bent), or the material may cool and be simply deflectable (rather than bendable or moldable). Whether cooled by the movement of the ram through the heated part of the ram, or by removing the article from the ram in contact with it (or by directing cold air towards the formed part, by using a cooled plug element within the body of the article, or by applying cooling by other means), the deflectable flange is cooled below its glass transition temperature, thereby "setting" or "fixing" the shape of the material at the point of the transition.Therefore, by forming the deflectable flange so that it has the form shown in Figure 8G, and by cooling the deflectable flange below its glass transition temperature, (the bend region 150 is smooth, and the spacer 140 including its peripheral edge 110 is modified to have a form without rough or sharp edges around the article, so the edges of the article can be made smooth.

[0071]

[0073] As shown in Figure 8F, the peripheral flange 120 can be partially deflected during the fabrication of the deflectable flange, so that in the finished article, the peripheral edge "facing" the body or the bottom surface of the deflectable flange. As shown in Figure 8G, the fabrication of the deflectable flange may, in some cases, result in the disappearance of the elbow that intervened between the peripheral flange and the remaining spacer. This may occur because the material in the peripheral flange "melts" into the spacer, or simply because the offset angle of the elbow becomes approximately 180 degrees. As seen in Figure 8J, for example, the peripheral flange 120 can be deflected in a direction in which the peripheral flange 120 remains separated from the remaining spacer, but can form a hook-like structure. Since such a structure can position a peripheral edge that may be sharp or rough around the periphery or near the periphery of the article, it is preferable that the deflectable flange be sufficiently deflected so that any such hook-like structure is contained within the rotated edge (relative to the periphery of the article), as shown in Figure 8K.

[0072]

[0074] In the methods shown in Figures 1 and 8, the walls of the fabricated article may bend inward when the upper body 200, the ram 300, or both collide with the deflectable flange 160. For example, the compression induced in the deflectable flange upon collision with the flange of the side wall of the upper body (compared to the position of the spacer 140 in Figures 1A and 1B) induces an inward force in the extension 50 (i.e., away from the side wall of the upper body and toward the fabricated body 10 of the article 100), and this force is transmitted to the fabricated body, potentially causing a portion of the body to bend or deform. Similarly, collision of the ram with the peripheral flange portion 120 of the deflectable flange will also induce an inward force in the extension, thereby toward the fabricated body. Furthermore, for example, the inward force applied to the deflectable flange in the embodiments shown in Figures 7 and 8 can also be transmitted to the fabricated body of the article. The transmission of force from the deflectable flange to the fabricated body may be undesirable for at least two reasons. Firstly, the deflection of the formed body may alter the orientation of the deflectable flange and the bent portion as described herein, making it difficult to control the final shape of the article (and its edges). Secondly, the force transmitted from the deflectable flange to the body generally does not drive the deflectable flange toward the ram and / or upper body, and the force does not bend and deflect the deflectable flange as described herein to at least the intended degree. Therefore, it is desirable to limit the transmission of force from the deflectable flange, the deflection of the formed body by such force, or both, so that the force is directed toward the deflection of the deflectable flange.

[0073]

[0075] Substantial devices or methods can be used to prevent or reduce the transmission of force from the deflectable flange to the body, to reduce or prevent the deflection of the formed body, or both. An example of such a device and its use is shown in Figure 8D. Figure 8D shows the formation of a deflectable flange 160 within a formed article 100 by applying a downward force (white arrow) as shown in Figure 8B. In contrast to Figure 8B, the formed article shown in Figure 8D is joined with three objects 401, 402, and 403. In the cross-section shown here, the three objects are solids, each having a rounded square contour (e.g., a rounded metal rod). Object 401 contacts a portion of the formed article 100 when an inward force (smaller horizontal filled arrow) is applied as the deflectable flange 160 collides with the upper surface 302 of the ram 300 due to the downward force. Object 403 abuts against the extension 50 of the deflectable flange and transmits a downward force to the deflectable flange. Object 402 connects to objects 401 and 402 (rigidly in this example, but not necessarily). One or more of the three objects can be cooled so that heat (e.g., from the heated ram 300) does not soften the plastic in its body or extension.

[0074]

[0076] In Figure 8D, when a downward force (white arrow) is applied to object 403, the force is transmitted to the deflectable flange. The deflectable flange counteracts the downward force by colliding with the ram 300. This force could, in the absence of object 401, be transmitted through the deflectable flange (i.e., through the extension 50) to the formed body of article 100. However, because object 401 is present and held in place to sufficiently prevent deflection of the portion of article it abuts, the downward force applied to the deflectable flange cannot be dissipated by the deflection of the formed body (i.e., object 401 prevents such deflection in the direction indicated by the small horizontal black arrow in Figure 8D), and instead the downward force is pressed along the deflectable flange in the direction indicated by the large black arrow in Figure 8D. This force drives the deflectable flange (specifically its peripheral edge, and, if present, the peripheral flange and the portion of the spacer closest to the peripheral edge) to the ram 300, inducing deflection of the deflectable flange, alignment of a portion of the deflectable flange with the upper surface 302 of the ram (especially when the amount of heat provided by the ram is sufficient to soften those portions), and movement of the deflectable flange across the surface of the ram. As shown in the drawings, the contour of the upper surface of the ram is thereby imparted to most of the periphery of the deflectable flange, causing the curvature of those portions to be smoothed (assuming the top of the ram has a smooth contour), and the peripheral edge of the deflectable flange to move toward the body of the article (or, for example, to "curl" back over the body as shown in Figure 8C).

[0075]

[0077] The shape, size, arrangement, and fasteners (if any) of objects 401, 402, and 403 are not important. Similarly, all three objects do not necessarily have to be used together, and one, two, or all three can be used. In one embodiment, the three objects are fixed together to form a “lid” or “plug” for a container similar to the one shown in Figure 6, so that part of the lid / plug corresponding to object 401 can substantially fill the interior of the container (i.e., press against all walls, including the four long straight walls of the container in particular, see plug P in Figures 8Di and 8Dii, for example), part of the lid / plug corresponding to object 403 can form a ring that can be attached to the entire rim of the container surrounding its interior, and part of the lid / plug corresponding to object 402 can be any material or mechanism that comes into contact with them. For example, such a lid / plug can be formed from a single piece of material (e.g., a “plug” that fills the entire interior and overlaps the rim surrounding the interior). One or more objects can be cooled (in the flange portion that can deflect to a location other than the desired location) to reduce heating of the formed article and thereby prevent undesirable deformation of the formed article during processing.

[0076]

[0078] In general, object 401 is merely a block to prevent both sides of the formed article from bending during the deflection of the deflectable flange. Such an object may fill substantially the entire interior of the formed article (e.g., the entire interior of the container shown in Figure 6D). Alternatively, one or more objects 401 may be used to support parts of the formed article that are otherwise more easily deflected (e.g., the long, straight sides of the container shown in Figure 6D).

[0077]

[0079] Object 403 can be any object that can bias a deflectable flange to a ram. Multiple objects can be used to bias the deflectable flange to one or more rams at various locations on the article, or a single object 403 can be used that contacts the article with all or near portions of the deflectable flange. In one embodiment, object 403 is the upper body 200 described herein, such as in a form that completely encloses the rim of a container, such as the container shown in Figure 6D. Object 403 may be a frame designed to fit tightly to the entire rim of a container enclosing an internal concave compartment of a chamber, such that the deflectable flange completely enclosing its rim is simultaneously biased to a ram in the manner described herein. In one embodiment, object 403 can be intentionally cooled (for example, by directing a cooling fluid such as cooling water, cooling oil, or ambient air towards or through the object, if the object is made from a good conductor of heat such as metal) to reduce, stop, or prevent heating of the body of the article formed during processing (as shown in Figure 8D). Object 403 may be connected to, rigid to, or movable so as to apply force to the deflectable flange of the article formed by object 403, while the bending-resistant object 401 can apply force to the inside of the formed article.

[0078]

[0080] Object 402, if present, may be an object that connects object 403 to a force source, an object that holds object 401 in place within a recess of article 100 formed during the deflection of the deflectable flange 160, or a combination thereof.

[0079]

[0081] As shown in Figures 9C and 9E, an additional advantage of the rotated edges formed by this process is that they can be used in place of conventional stacking protrusions (i.e., a thermoformed portion of an article, formed along its contour to limit the degree to which it approaches another article, can be nested within another otherwise identically formed article). To perform their desired anti-nesting function, such known stacking protrusions must be narrower at their upper ends than at their lower ends (see Figure 9D as an example) to prevent stacking protrusions of adjacent trays from nesting. This "narrower at the top" configuration represents a known difficulty in demolding trays during thermoforming, as the narrower "upper" portion of the protrusion must be spread or deformed over the larger "bottom" portion of the mold of the protrusion to remove the thermoformed tray from the mold. The rotated (i.e., made as described herein) edges depicted in Figures 8 and 9 avoid this difficulty while still preventing improper close nesting of adjacent trays. The trays having rotated edges described herein can be separated using conventional nesting disassembly tools (e.g., screw and finger-based machines for separating adjacent nested / stacked trays), enabling more densely packed tray packaging than possible using trays having formed stacking protrusions, as shown in Figure 9E.

[0080]

[0082] Figure 9F shows an optional embodiment of the rotated edge described herein, which also affects the stacking characteristics of the formed articles having the rotated edge. On the right side of Figure 9F are shown three stacked trays having the rotated edge described herein, where the rotated edge is substantially uniform (including height) around the entire perimeter of the tray. On the left side of Figure 9F are shown three other stacked trays, which also have the rotated edge described herein around the entire perimeter. However, in contrast to the trays on the right side of the figure, the rotated edges of the trays on the left are not uniform around their entire perimeter. As shown in the figure, the smaller portion of the deflectable flange rotates at the corners of these trays compared to the portion of the deflectable flange that rotates along the rest of the edge. As a result, the trays have rounded stacked extensions 180 at their corners. Similar to the stacked trays shown on the right in Figure 9F, the tray on the left in the figure is nested between them, and is lowered until the lower surface of the rotated edge of the tray is in contact with and seated against the upper surface of the rotated edge of the second tray nested between them. However, because the stacking extension 180 of the left tray in the figure is higher than most of the rest of the rotated edge of those trays, the left tray is nested such that the lower surface of the stacking extension 180 is seated on top of the upper surface of the rotated edge of the tray below it, and most of the lower surface of the rotated edge of the upper tray remains in contact with the tray below it, creating a gap between the nested trays (compare the gap indicated by the large square bracket on the left in Figure 9F with the recess indicated by the small square bracket on the right in Figure 9F). When the formed article 100 is given a rotated edge including a laminate extension 180 as described herein, the degree and method of deflection of the deflectable flange should nevertheless be selected to position the peripheral edge 110 on the laminate extension 180 such that the deflectable flange is less likely to come into contact with the film or other material around the article 100 as described herein.

[0081]

[0083] Another advantage of the “rotated edges” depicted in Figures 8 and 9 is the mechanical strength they impart to articles formed by such edge configurations. Thin plastic films tend to be very flexible, and articles formed from such films may have “very thin” edges that deform easily during handling or operation (e.g., while sealing or wrapping with film). For the same reason that hollow tubes or round materials tend to be stronger and stiffer than flat sheets of material of the same shape and thickness, the curved or rotated edges described herein impart greater edge strength and rigidity to the formed articles described herein than to the corresponding articles without such edges. This edge strength and rigidity makes it possible to form a lid on the formed articles described herein, or to engage a separately made lid with the formed articles described herein. Thus, in addition to the fact that the formed articles can be sealed with film using OW, VSP, or MAP techniques, the improved edge strength of the formed articles described herein allows the articles to be sealed with snap-on / snap-off type lids or other conventional sealing techniques. Furthermore, the strength and rigidity of the edges imparted to the molded article also prevent deflection induced by tension in the film used to withstand stresses applied by (or as required for) handling the container, such as in the case of wrapping or sealing the article (for example, the so-called "bow knot" phenomenon of a concave article closing over its concave surface when wrapped or sealed), and in the case of nesting tools used to separate individual containers from a stack of nested containers.

[0082]

[0084] As described above, the strength and rigidity of the edges of articles formed as described herein (e.g., trays for wrapping or sealing with thin film) are derived from the geometry and materials present at the edges of the articles. These geometry and materials are then derived from the geometry and materials selected for use in the deflectable flanges described herein. Many of the following properties are expected to be immediately apparent to those skilled in the art, but these properties are discussed in the context of selecting geometry and materials to affect the strength and rigidity of the edges. One such property is the thickness of the thermoplastic material used to form the edges. All other things being equal, thicker polymer sheets tend to be more difficult to bend or deform than thinner polymer sheets, and as a result, the strength and rigidity of the edges of articles described herein can be increased by utilizing a thicker thermoplastic material, i.e., by thermoforming a thicker initial sheet, or by thickening the thermoplastic material during rotation of the edges (e.g., by compressing the sheet in-plane while it is softened, or simply by holding the sheet in a softened state for a longer period of time). Furthermore, the radius of curvature of the bending region of the formed article can also affect the strength and rigidity of the edge, with smaller radii generally resulting in greater edge strength and rigidity. The degree to which the peripheral edge 110 and adjacent parts (e.g., spacer 120) of the deflectable flange bend or rotate can also affect the strength and rigidity of the edge. For example, rotating the edge to essentially a perfect circle (i.e., rotating the edge about 360 degrees so that the peripheral edge 110 contacts the bottom surface 161 of the spacer 120) results in substantially greater strength and rigidity than an edge rotated about 180 degrees (e.g., as shown in Figure 9B). The strength and rigidity of the edge can also be increased by increasing the width of the region of the extension 50 surrounding the recess or by forming side walls of the recess to withstand deflection (see, for example, the “ribs” formed within the side walls of the container shown in Figures 6C and 6D).

[0083]

[0085] In one example, a standard-sized tray suitable for MAP sealing was constructed as described herein (i.e., by giving it a curved edge) and compared to a similar tray made of the same material but without a curved edge. The strength and stiffness of the edges of the two trays were measured by evaluating the compressive force required to achieve a 1 / 4-inch deflection when each tray was compressed at the midpoint of the opposing long edges of the tray. Demonstrating an example that substantially strengthens the edge, it was found that the tray with the curved edge described herein was required (approximately 5.5 pounds of force was required for the tray with the curved edge, and approximately 2.3 pounds of force was required for the tray with the non-curved edge). While it is not practical to describe all possible combinations of configurations, dimensions, and material choices that result in the desired edge strength or stiffness, those skilled in the art can use the information provided herein to design edges of articles with a wide range of strength and stiffness superior to that of articles without the deflected edge described herein. The strength and rigidity of the edges of the articles described herein are important for resisting the compressive forces that occur when sealing packaging, when pressurizing or vacuuming the inside of recesses during packaging, and in combination thereof. Therefore, the effect of reinforcing these edges represents a significant improvement in packaging functionality.

[0084]

[0086] Important to these methods is that the potentially sharp peripheral edges 110 of the thermoplastic sheet forming the article 100 should be deflected away from the periphery of the article and positioned by heating, softening, and cooling the portion of the sheet that is bent while the sheet is deflected (this typically involves substantially only the portion of the deflectable flange). The heated, bent, and cooled portion preferably includes at least the bent region 150 of the deflectable flange 160, because that region is designed for a smooth bend and brings a smooth periphery to the container. Other portions of the deflectable flange (e.g., extension 50, spacer 140, elbow 130 and / or peripheral flange 120) can also be softened, bent, and hardened (or alternatively) to contribute to the smoothness of the periphery of the article.

[0085]

[0087] Alternatively, any of these portions of the deflectable flange 160 can be simply bent without heating, provided that sufficient bending force is applied so that the thermoplastic material bends irreversibly (rather than simply deflecting reversibly when the pressure is removed) at the bending point. However, bending methods based on softening without heating tend to leave relatively sharp (or at least not very smooth) edges where the bend is imparted, so such methods are undesirable unless care is taken to ensure smoothness of such bends (for example, by bending the material around a rounded "formed" member). The deflectable flange 160 disclosed herein provides a convenient structure for doing this.

[0086]

[0088] Deflectable flange 160

[0089] The deflectable flange includes a bend region 150, a peripheral edge 110, and a spacer 140 intervening between the two. The bend region forms an angle of less than 180 degrees between the body 10 and the spacer 140, where it functions as a flexible "hinge" from which the spacer region can move relative to the body. The angle formed by the bend region (i.e., the angle designated A in Figure 1A) is preferably about 90 degrees (i.e., nearly a right angle, meaning 75 to 105 degrees, more preferably 85 to 100 degrees, even more preferably 87 to 93 degrees, and most preferably about 92 degrees). When this angle is less than 90 degrees, it may be difficult to remove the thermoformed article from the mold in which it was thermoformed (i.e., the portion closest to the extension between the spacer and the body can be wider than the width between the body and the spacer closer to the peripheral edge, meaning the thermoformed article "gripping" the mold and having to be pulled or expanded to move the article out of the mold). Therefore, the angle formed by the bending region is preferably 90 degrees or greater (e.g., 91, 92, 93, 94, or 95 degrees) to facilitate separation of the thermoformed article and the mold, although the angle can be smaller if the body of the article is, for example, away from the periphery. The availability of angles of 110, 115, 120, 125, 130, or 135 degrees is less desirable, but such articles may require both upper bodies 200 to be applied to reduce the angle to close to 90 degrees before the deflectable flanges collide with the ram 300. As this angle increases, the amount of thermoplastic material present at the outer corners of the thermoformed precursor article (e.g., the four corners of the tray shown in Figures 6A and 6B) increases and may interfere with bending (i.e., "rotation"). This thermoplastic material can be accommodated, for example, by allowing a spacer to "bend" on the ram (or incorporate the space into the upper surface of the ram) in the section where the material is exposed.

[0087]

[0090] When the spacer moves sufficiently, the bending region forms the periphery of the article (i.e., when the spacer bends "below" the joint of the body, regardless of gravity-related orientation). Thus, the bending region typically forms the smooth periphery of the article desired in one embodiment. Nevertheless, in this embodiment, the spacer forms part of the periphery of the article (typically the "bottom" of the periphery relative to the article 100, with the bottom 161 of the deflectable flange 160 contained within the curvature of the rotated edge). For this reason, any part of the spacer that can come reasonably close to a film or other material pressed against the outside of the article (e.g., its bottom periphery) (which may include the elbow portion 130 and the periphery flange 120) should preferably be similarly smooth.

[0088]

[0091] In the formation of articles with smooth perimeters described herein, the deflection of the spacer (and / or other portion) of the deflectable flange induces bending within the bending region, within the spacer, or both. The angled shape of the bending region controls both the location of the bending and the smoothness of the resulting edge. As shown in Figures 1 and 8, the corners of the bending region are not formed as acute angles (i.e., bilinear), but instead as flat portions (e.g., extension 50 and spacer 140) positioned obliquely to each other, and the curved portions (defined by a radius of curvature such as 1, 2, or 3 millimeters or more) may be advantageous when connecting the flat portions. Bending curved corners tends to result in smoother edges that are less likely to damage the film than bending acute angles. As shown in Figures 1, 4, 5, 7, and 8, the boundary between the bending region 150 and spacer 140 may be substantially indistinguishable in practice, and bending of spacer 140 at least in its extent closest to the bending region 150 is expected in the shown embodiments. In particular, bending multiple portions, including most of the periphery of the spacer 140, as shown in Figure 8, is preferable to impart a smooth periphery to the article prepared as described herein.

[0089]

[0092] In one embodiment (shown in Figure 1), the deflectable flange 160 includes at least three parts: a bending region 150, a peripheral flange 120, and an elbow portion 130 positioned between them. The bending region 150 is optionally connected to the remainder of the article 100 by an extension portion 50. The peripheral flange 120 is connected to the bending region 150 by the elbow portion 130, and optionally a spacer 140 is interposed between the bending region 150 and the elbow portion 130. A prototype deflectable flange 160 having these parts is shown in Figure 1A (attached to the body 10 of the article 100).

[0090]

[0093] In this embodiment, the bending region 150 is positioned opposite the periphery (closer to the body 10) of at least the majority of the periphery of the periphery flange 120. The function of the bending region 150 is to deflect when the periphery flange 120 is deflected inward (i.e., away from the periphery, such as by pressing the periphery of the article against a solid). Since the periphery edge 110 of the thermoplastic sheet is not located within the bending region but on the periphery flange 120, the deflection of the bending region provides a smooth surface. The angle formed by the bending region (for example, approximately 90 degrees on the bending region 150 shown in Figure 1A) is not critical and can be selected for ease of manufacturing. The angle can be, for example, obtuse, right, or acute. When this angle is acute, removing the thermoformed (pre-rotated) article from its thermoforming mold can be difficult (because the periphery of the spacer must deflect to remove the article from the mold), and acute angles are undesirable for that reason (even if such articles can still be manufactured). The radius of curvature of the flexion region 150 is not important, but is preferably substantially larger than the radius of curvature of the elbow portion 130.

[0091]

[0094] The bending region 150 preferably has a smooth curved shape, as shown in Figure 1A, with a substantial radius of curvature (e.g., 0.5 mm to several millimeters or more), so that the inward deflection of the deflectable flange 160 results in a smooth periphery for the article. However, it is important that the bending region 150 is not simply sharp or pointed; a non-sharp fold, for example, may suffice. A fragile material in contact with a smooth periphery, such as a thin plastic film or animal hide, is far less susceptible to damage than the same fragile material in contact with the peripheral edge 110 of the thermoplastic sheet.

[0092]

[0095] The bent region 150 can be connected to the remainder of the article 100 by the extension 50. The extension 50 can be discretely distinguished from the bent region 150 (e.g., a flat region is distinguished from the curved bent region 150), or it can be substantially indistinguishable (e.g., a slightly curved region is not easily distinguishable from the curvature of the bent region 150). The dimensions of the extension are not important, and its dimensions can range from where it does not exist (i.e., the bent region 150 begins at the edge of the main body 10 of the article 100) to a fraction of a millimeter to several millimeters or more. One function of the extension 50 is to separate the bent region 150 from the rest of the article 100 (where, in some embodiments, heat is applied to soften the sheet) where potential thermal deformation is undesirable. Another function of the extension 50 may be to provide a functional surface to the article 100, such as an adjacent surface of the bending region 150, where a thin plastic film can be attached to or fused to the article 100 (for example, to cover a cavity formed within the article adjacent to the deflectable flange 160, of which the extension 50 is part) (the plastic film can be pressed against the bending region 150 with little risk of damaging the film). The extension 50 may also perform structural functions, such as providing support or rigidity to the cross section of the article (for example, by forming a relatively rigid "rim" around a cavity in the container to restrain the flexibility of the container while it is sealed). Furthermore, another function of the extension 50 is that it can provide space that can be occupied when the deflectable flange 160 is deflected in the opposite direction around its periphery. Since the extension 50 and the peripheral flange 120 are positioned on opposing sides of the bending region 150, the peripheral flange 120 (and spacer 140) can approach or even contact the extension 50 by sufficiently bending the bending region 150 (for example, when the article 100 is inserted into the upper body 200 and the ram 300 is inserted behind the article), the spacer 140, or both, or the lower part of the extension 50 can be rounded or deflected between the periphery of the article and the side wall of the article's body (see Figure 6E).

[0093]

[0096] For example, in one important embodiment shown in Figures 3A, 3B, and 6E, bending the bending region 150, the spacer 140, or both, and then cooling and hardening them results in an article with a gap between the side wall of the article body and the closest approach (i.e., proximity range) of the bending portion of the deflectable flange. The size and location of this gap can be selected by the selection of the shape of the body, the arrangement of the rams 300, the shape of the upper surface 302 of the rams 300, or a combination thereof. The gap can be selected to extend entirely around the periphery of the article, for example, so that the article has a fully rotated edge around its periphery, and the gap can be adapted to fit into a predetermined shape (e.g., a MAP sealing device designed to engage with a standard-sized tray, e.g., an industry standard #3 tray, etc.). The size and location of this gap are not critical and can be selected to have a width and location that closely resembles, for example, the width and location of the flat portion of the extension 50 (e.g., a flat sealing surface supported on the extension) or its fragment. For example, when the extension 50 bears a flat sealing surface on its upper surface (opposite the concave surface), the rotated edge can be formed to leave a gap on the lower surface of the extension 50, the lower surface of the extension 50 being parallel and having a width of half or three-quarters of the width of the sealing surface on the opposing surface. Alternatively, the process of rotating or deflecting the article and its edge can be selected to result in a gap of substantially constant width (e.g., a gap of 1 / 8, 1 / 4, or 1 / 2 inch) around the entire perimeter of the side wall of the concave surface on the bottom surface of the extension 50.

[0094]

[0097] The molded articles described herein can be manufactured to match the shape, size, dimensions, color and any other characteristics of trays used generally or specifically with particular fixtures. For example, many “industry standard” trays are known, such as MAP trays commonly referred to simply as “No. 2,” “No. 3,” “No. 4,” and “No. 11,” and these MAP trays maintain dimensions and shapes that are essentially kept uniform throughout the industry. The conformity of the molded articles described herein to match the size, shape, dimensions, color and other characteristics of industry standard fixtures is generally known to those skilled in the art.

[0095]

[0098] In Figure 1A, the peripheral flange 120 includes the (potentially sharp) peripheral edge 110 of the thermoplastic sheet forming the article. Because the peripheral flange 120 extends peripherally beyond the bending region 150, when the article is inserted into the cavity of the upper body 200 as shown in Figure 1B, the peripheral flange 120 abuts against the inner surface 202 of the upper body 200. The peripheral flange 120 extends from the elbow 130 to its peripheral edge 110 and, if present, from the bending region 150 or spacer 140 in the direction of the offset angle defined by the elbow 130. The function of the peripheral flange 120 is to engage with (i.e., abut against or be abutted by) the inner surface 202 of the upper body 200 when the article is inserted into the cavity of the upper body 200, thereby deflecting the deflectable flange 160 inward (opposite to the periphery). In addition to moving the peripheral edge 110 of the sheet away from the periphery and bending or flexing the deflectable flange 160 within its bending region 150, this deflection also positions the peripheral flange 120 further away from the periphery when the ram 300 is inserted into the cavity behind the article 100. When the ram 300 is inserted in this manner, it collides with the peripheral flange 120, and as the ram moves further into the cavity, the deflectable flange 160 bends or flexes further within its bending region 150, and the peripheral edge 110 is further deflected away from the periphery.

[0096]

[0099] The length of the peripheral flange 120 (from the elbow to the peripheral edge) is not critical and should be chosen to facilitate the engagement of the ram 300 and to facilitate the movement of the peripheral flange 120 by the ram 300 as the ram advances inside the upper body 200. The length of the peripheral flange 120 is often influenced, at least in part, by its ability to cut the article from the material forming the article. The elbow 130 can, to some extent, function to position the thermoplastic sheet where it can be cut, which is advantageous for releasing the formed article from the precursor sheet. Since the peripheral edge 110 formed by such a cut is the source of sharpness or roughness around the article before the deflectable flange 160 is "rotated", it may be advantageous to cut the sheet as close to the elbow 130 as possible (i.e., make the peripheral flange 120 as small as possible) to reduce the amount of thermoplastic material that has to be moved in order to move the sharpness or roughness of the peripheral edge 110 from the periphery of the article. For example, as shown in Figure 8H, a larger peripheral flange also reduces (and increases) the contact between the upper surfaces of the ram that strike the deflectable flange, and therefore reduces the heat transferred from the ram to the peripheral portion of the deflectable flange. Since the methods described herein rely on heating those portions to a temperature above the glass transition temperature of the peripheral flange, deflecting those portions to a desired shape, and then cooling those portions to a temperature below that, a larger peripheral flange increases the heat input and / or time required for such processing, and is therefore undesirable.

[0097]

[0100] The elbow portion 130 intervenes between the bending region 150 and the surrounding flange 120, and its function is to connect the bending region 150 and the surrounding flange 120 and transmit forces between them. That is, a compressive force applied to the surrounding flange 120 by an impact on it by the upper body 200 or ram 300 is converted into a torsional force applied to the bending region 150 through the elbow portion 130 (and the spacer 140, if present). This conversion from compressive force to torsional force ensures that when a force is applied to the surrounding flange 120, the bending region 150, the spacer 140, or both will bend. Therefore, by applying force to the peripheral flange 120 by the upper body 200 and / or ram 300, the peripheral edge 110 is deflected away from the periphery (i.e., the potentially sharp edge is moved away from the periphery of the article), and the bending region 150, the spacer 140, or both are bent (i.e., the smooth periphery formed by the bent thermoplastic sheet is brought to the periphery of the article), resulting in an article with a smooth periphery even if the article was formed by a process in an intermediate step that brings a sharp peripheral edge. In fact, the force applied to the peripheral flange 120 by the elbow causes the deflectable flange 160 to "rotate" around the periphery of the article, effectively "hiding" the sharp edge of the thermoplastic sheet from the material around the periphery of the article.

[0098]

[0101] Spacer 140 can be interposed between the flexed region 150 and the elbow portion 130. Spacer 140 can be discretely distinguished from the flexed region 150 (e.g., a flat region is distinguishable from the curved flexed region 150), or substantially indistinguishable (e.g., a slightly curved region is not easily distinguishable from the curvature of the flexed region 150). The dimensions of the extension region are not important, and its dimensions can range from nonexistent (i.e., the flexed region 150 begins at the elbow portion 130) to a fraction of a millimeter to several millimeters or more. If present, one function of spacer 140 is to act as a "lever" due to the force applied to the elbow portion 130 transmitted to the flexed region 150 (e.g., by a collision between the peripheral flange 120 and one or both of the upper body 200 and the ram 300). If present, another function of spacer 140 is to position the peripheral flange 120 so as to properly engage one or both of the upper body 200 and the ram 300. If present, yet another function of the spacer 140 is to increase the distance by which the potentially sharp peripheral edge 110 of the thermoplastic sheet can be moved away from the periphery of the article when bending the bending region 150. All other things being, the longer the spacer 140, the further the potentially sharp edge will be from the periphery of the article when the article is manufactured as described herein. A deflectable flange including the spacer 140 but lacking the elbow portion 130 and peripheral flange 120 can be used, for example, as shown in Figures 8A–8D.

[0099]

[0102] The longer spacer 140 facilitates the formation of one or more portions of the “rotated edge” that are higher than the other “rotated” portions of the edge, resulting in a structure that is beneficial as a stacking protrusion (for example, to facilitate selectable spacing between the rotated edges of articles stacked in adjacent nests). In one embodiment, the size of the spacer and the compressive force applied to the spacer (i.e., the force transmitted to the spacer from the extended region balanced by the resistive force applied to the spacer for the reason of impacting the ram) can cause the spacer to bend outward (i.e., periphery away from the body of the article), forming a smooth ridge that forms the outer circumference of the article when cooled.

[0100]

[0103] Whether the bending region 150, the spacer 140, or both bend in the operations described herein, and whether the material that was originally part of the bending region 150, the spacer 140, or both ultimately forms the outer perimeter of the article described herein, it is important that the outer perimeter is free from (or preferably little to no, substantially free from) sharp, pointed, rough, or abrasive edges that could damage thin plastic films, human tissue, or other fragile materials that may come into contact with the outer perimeter.

[0101]

[0104] thermoplastic

[0105] The methods and articles described herein can be carried out and produced using substantially any thermoplastic material. Importantly, the material can be softened by heating and re-hardened upon cooling, at least within the deflectable flange 160 described herein. Substantially all thermoplastics exhibit properties at temperatures higher than which they become soft and bendable or workable, and lower than which they become more rigid and maintain their shape. The thermoplastics desirable for the articles and methods described herein maintain their shape under the general conditions of the expected end use of the container. It is also desirable to use thermoplastics that can be softened under conditions readily achievable in the manufacturing environment. Examples of suitable thermoplastics include polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and polyvinyl chloride (PVC). Other suitable thermoplastics are obvious to those skilled in the art, and substantially any of them can be used. Flexible plastics with deflectable materials, such as metal foil attached to their surface, may also be beneficial.

[0102]

[0106] A thermoplastic article comprises a thermoplastic material and includes at least a portion of an article on which the deflectable flange 160 described herein is formed or present. The identity of the thermoplastic material is not important, nor is the presence or absence of a non-thermoplastic material. If a non-thermoplastic material is present (for example, in a thermoplastic sheet laminated with a metal foil or cardboard layer), the stiffness imparted to the article by the thermoplastic material in its unsoftened and unmelted state is preferably sufficient to define the shape of the article, even when the non-thermoplastic material is bent. The article may include one or more peelable layers, such as those described in concurrently pending U.S. Patent Application Publication 13 / 415,781. When one or more peelable layers are present, whether those layers "rotate" around the peripheral edge of the fabricated article (rather than peeling the edges of the peelable layers from the underlying substrate) is not substantially important. For both aesthetic reasons and to promote sealing, it may be preferable that any peelable layers remain adhered. When a peelable layer is present and adhesion should be promoted, the working temperature should be selected to be suitable for deflecting the deflectable flange as described herein, and also suitable for working on the substrate of the fabricated article and the peelable layer without delaminating the peelable layer.

[0103]

[0107] In key embodiments, the thermoplastic material selected to create the molded article is optically transparent (i.e., transparent, preferably with a transmittance through it greater than 50% of light of wavelengths visible to humans, preferably without substantial distortion). Transparent packaging materials are preferred for many products sold directly to consumers (e.g., meat and fish, vegetables and cooked food). Transparent packaging materials allow direct visual inspection of the contents of the packaging before purchase. Prior to this disclosure, it was difficult or impossible to manufacture molded articles (e.g., trays for containing food) that were both optically transparent and suitable for film sealing using all three OW, VSP, and MAP technologies. OW sealing was generally used with trays with blunt edges, and the bluntness (i.e., not sharp) of the edges was achieved by using foamed plastic materials such as Styrofoam. Trays made from transparent materials were generally unsuitable for OW sealing with at least thin, brittle plastic films. VSP and MAP trays are typically made from polypropylene materials, which are rarely optically transparent, if present.

[0104]

[0108] Various optically transparent plastics can be used for optically transparent molded articles as described herein. For example, PET, PVC, and polycarbonate are suitable. The molded article should be optically transparent at least in the recesses in which contents are intended to be stored, and preferably transparent through all deflectable flanges adjacent to any bends 160 and any parts that are bent during the operations described herein. For this reason, transparent thermoplastic trays, such as trays made from PET or PVC, are preferably used, and any heating or bending conditions applied to these trays during manufacturing are preferably selected so as not to induce the development of opacity in the material (for example, by heating it to a temperature higher than the temperature at which the tray softens before bending).

[0105]

[0109] Upper body 200

[0110] The upper body 200 performs a number of functions. Overall, its function is to contain the deflectable flange 160 described herein within a cavity in the upper body 200 while heat is applied to one or more portions of its bending region 150. This containment function prevents (or induces) undesirable deformation of the deflectable flange 160 or any part thereof during the periphery smoothing operation described herein. Furthermore, the shape of the internal cavity in the upper body 200 can also influence the shape of the deflectable flange when bending it, particularly when softening it. For example, in Figure 1B, the upper body 200 includes a cavity with a right-angle interior that presses a portion of the bending region 150 into it, and the right-angle shape of this portion of the cavity tends to conform the bending region 150 to the right-angle shape, particularly when the bending region 150 is softened. The heat source may be, for example, a portion of the upper body 200 that is applied to the upper body 200 to conduct heat. Furthermore, when the deflectable flange 160 is inserted into its cavity, the upper body 200 collides with the surrounding flange 120 of the deflectable flange 160. When the ram 300 is used, the upper body 200 also serves to prevent the deflectable flange 160 from being pushed out of the cavity, and the upper body 200 can also limit the deflection of the bending region 150 when the deflectable flange 160 is compressed by the ram 300.

[0106]

[0111] The material constituting the upper body is not critical; otherwise, the material should be suitable to withstand the manufacturing conditions described herein. That is, the material should not melt or degrade at the temperatures used in the process. A wide range of metal, ceramic, stone, and polymer materials can be used.

[0107]

[0112] It is important to select the shape of the upper body 200 such that collisions between the interior of the cavity within the upper body 200 and the peripheral flange 120 occur when the article 100 described herein is inserted into the cavity within the upper body. The upper body can have a shape sufficient to collide with multiple peripheral flanges 120 simultaneously on the article, or with most or all of a single peripheral flange 120 occurring on the article (e.g., a collision occurring around the entire peripheral edge of the article). As shown in Figure 2, the upper body 200 can be formed from a solid block of material, the material covering the entire surface of the article while colliding with the peripheral flange 120 occurring on one or more parts of the article. The upper body 200 depicted in Figure 2 is, for example, designed to collide with a single peripheral flange 120, the single peripheral flange 120 extending completely around the periphery of an article having the shape of a rectangular tray-shaped container with rounded corners.

[0108]

[0113] The bent region 150 of the article described herein is typically located within a cavity of the upper body 200 when heat is applied to the bent region 150. Therefore, the upper body should be configured in a manner that facilitates the application of such heat. The upper body 200 may, for example, include a heat source (e.g., an electrically operated heating plate or rod) applied to or fluidly connected to it. Alternatively, the upper body 200 may include one or more ports through which a heated fluid (e.g., a heated gas or liquid) can pass from the source into the cavity within. The method chosen for delivering heat to the bent region 150 (and / or other parts of the peripheral flange, such as the spacer 140, elbow portion 130, and peripheral flange 120) is not critical, and any variety of well-known heat delivery methods and apparatus can be used. If the upper body 200 is capable of conducting heat and is cooled, the heat present in the deflectable flange 160 during its molding can flow to the upper body 200, and this heat flow can, for example, cool the deflectable flange 160 at its deflected position when it is compressed between the upper body 200 and the ram 300, thereby curing it.

[0109]

[0114] For example, as shown in Figures 5 and 8, the deflectable flange can be deflected using only the ram 300, with or without the use of the upper body 200. The upper body can be used both to partially deflect the deflectable flange and to apply force to the article to cause the deflectable flange to collide with the ram. When the upper body 200 is not used, some alternative means must be used to apply force to the article to cause a collision between the ram and the deflectable flange. For example, in Figure 8D, this alternative means is simply depicted as object 403 (optionally working with object 402). The orientation of the parts relative to gravity is not important, and the only requirement is that the “downward” force (white arrow in Figure 8D) biases the deflectable flange 160 towards the ram 300, causing a collision between the two. It is also not important whether the force applied to the article and / or the ram is applied to cause such a collision. The important point is that the impact of the deflectable flange 160 on the ram 300 (and / or upper body 200 as needed) induces the deflection of the peripheral edge 110 of the deflectable flange to a position where it cannot easily approach the periphery of the article. Thus, in one embodiment, the upper body 200 may be a simple plane that can be added to a flat portion of the article (e.g., the extension 50 of the deflectable flange 160 shown in Figure 8D) to drive the deflectable flange toward and ultimately toward the ram.

[0110]

[0115] Ram 300

[0116] The primary function of the ram 300 is to induce deflection within the deflectable flange. The ram can be used with or without the corresponding upper body 200, which can play a role in containing and controlling the article when it comes into contact with the ram. The method and mechanism used to impart relative motion between the article and the ram are not critical. When the upper body is utilized, the ram is used to apply a compressive force to the peripheral flange 120 of the deflectable flange 160 when the article is placed within the upper body 200. This compressive force tends to drive the peripheral flange 120 upward and in the opposite direction to the periphery toward the bend region 150 and extension 50, if present, thereby moving the potentially sharp peripheral edge 110 of the thermoplastic sheet away from the periphery of the thus formed article. Therefore, the design of the ram 300 is not particularly critical as long as such a compressive force is applied. As shown in Figures 1C and 4, a ram 300 having an inclined upper surface 302 tends to orient the peripheral flange 120 in a direction along the inclination when the ram 300 compresses the peripheral flange 120. Therefore, when compression occurs, it may be advantageous to shape the upper surface 302 of the ram 300 in a configuration that deflects or "pushes" the peripheral flange 120 and / or peripheral edge 110 in the opposite direction from the periphery.

[0111]

[0117] Like the upper body 200, the material used to create the ram 300 is not critical. Metals, ceramics, stone, and polymer materials capable of withstanding the operating temperature and pressure can be readily and appropriately selected by those skilled in the art. If the ram 300 is capable of conducting and cooling heat, the heat present within the deflectable flange 160 during its formation can flow into the ram 300, and this heat flow can, for example, cool the deflectable flange 160 at its deflected position when it is compressed between the upper body 200 and the ram 300, thereby curing it. Heat can also be provided to one or more portions of the deflectable flange by the ram 300 in conventional ways, such as by using a heated ram or by incorporating a heating element into or on the ram.

[0112]

[0118] In one embodiment shown in Figure 2, a single ram 300 can be configured to simultaneously strike substantially all of the peripheral flanges 120 of the article. The ram 300 depicted in Figure 2 is designed, for example, to strike and apply compressive force to a single peripheral flange 120, which extends entirely around the periphery of an article having the shape of a rectangular tray-type container with rounded corners.

[0113]

[0119] In the alternative embodiment shown in Figure 5, the deflectable flange 160 of the article is heated to soften and then struck against a ram 300 that lacks the upper body 200 of the type described herein. The absence of the upper body 200 may cause distortion or deflection of the softened portion of the deflectable flange 160 if at least other parts (e.g., the extension 50 or a portion of the body 10 of the article 100 adjacent to the deflectable flange 160) are not rigid enough to prevent such distortion or deflection. However, if such rigidity is present or the final product can withstand such distortion or deflection, the method described herein can be used without the upper body 200.

[0114]

[0120] Figure 5 also illustrates the significance of the peripheral flange length (measured from the elbow to the peripheral edge). The peripheral edge contacts the ram. The force exerted by the ram's surface 302 on the peripheral edge induces a deflection of the deflectable flange 160 toward the body 10 of the article 100. When the deflectable flange 160 includes a peripheral edge 120 that is offset by a 90-degree elbow 130 from the spacer portion 140, as shown in Figures 5A and 5B, the length of the peripheral flange affects the degree of deflection of the deflectable flange. Comparing Figure 5C (a deflectable flange with a peripheral flange "length" of zero, i.e., a deflectable flange without a peripheral flange) with Figure 5B, it can be seen that the presence of the peripheral flange induces a greater deflection of the deflectable flange in the shown configuration. Furthermore, looking at Figure 5A, increasing the length of the peripheral flange increases the degree of deflection induced by the ram. Therefore, while the elbow and surrounding flanges are optional and not present, their presence can increase deflection and enhance the achievable "rotational" effect.

[0115]

[0121] Figure 10 illustrates one embodiment of the ram 300 described herein for rotating the edge of a formed article having a deflectable flange 160. Figure 10A illustrates the ram 300 having at least two positions for accommodating an article 100 having a deflectable flange as described herein. The top of the figure shows the position for bearing the article 100. The position that does not bear an article is partially shown in the lower right of the figure, where the upper surface 302 that would bear an article when present is exposed. In the figure, the position for bearing an article has the same upper surface 302, but is obscured by the spacer 140 and peripheral flange 120 of the article 100 it bears. The figure also shows how far the extension 50 separates the body 10 of the article from the spacer and from the ram, providing a gap (visible through the transparent material forming the extension) that allows the spacer and peripheral flange to deflect, bend, or round.

[0116]

[0122] Figures 10B and 10C show in detail the upper surface 302 of the ram 300, which includes a curve (around D in Figure 10C) that deflects the peripheral edge 110 of the deflectable flange when the upper surface is biased at a softened temperature. Figure 10B is a magnified image of the upper surface, and Figure 10C is a cross-sectional view showing the approximate shape of the upper surface. During operation, the ram is used by the peripheral edge 110 of the deflectable flange colliding with the upper surface 302 at one of the positions between B and D (from the "downward" direction indicated by the white arrow in Figure 10C), and then applying a further downward force to further drive the peripheral portion of the deflectable flange against the ram. This further force induces the peripheral edge to slide, rub, or jump over the upper surface, inducing the deflectable flange to deflect inward (i.e., towards the body of the article located closer to position E than any of A-D in this embodiment). When a deflectable flange is heated above its softening point (i.e., glass transition temperature), this deflection results in loss of elasticity, and when the deflectable flange is subsequently cooled to a temperature below its softening point, this deflection is reflected in the shape of the deflectable flange.

[0117]

[0123] The curve of the upper surface 302 of the ram 300 between positions C and E in Figure 10C induces rotation or rounding of the softened portion of the deflectable flange, and the degree of induced curvature is controlled by the extent to which the deflectable flange collides with the ram. Thus, for example, if the deflectable flange collides only slightly with the upper surface after softening, only the majority of the periphery of the deflectable flange may collide; if the softened portion of the deflectable flange collides within the range of position D, the peripheral edge will collide almost toward the body; and if the softened portion of the deflectable flange collides and spreads beyond position D (for example, as shown in Figures 8G and 8K), the peripheral edge of the deflectable flange will effectively "rotate" (i.e., the plane of the deflectable flange spreads at its peripheral edge so as to intersect with the bottom surface 161 of the deflectable flange). Depending on the material from which the deflectable flange is created, the deflectable flange may substantially maintain its shape as it cools to a "rotated" configuration (for example, PET and PVC materials do not tend to sink or sag when gravity acts on them in a softened state, while PE and PP materials can substantially bend under gravity only when softened). Even if this is not the case, such bending is acceptable as long as the sagging or sinking peripheral edge of the deflectable flange does not expose the peripheral edge at the periphery of the article (for example, when the rotated edge has rotated sufficiently, any sagging occurs in the internal space of the rotation).

[0118]

[0124] sealing film

[0125] An important advantage of articles having periphery treated in the manner described herein is that such treatment provides articles suitable for sealing with a thin plastic film. Sealing articles with a thin plastic film is a well-known process, and many suitable films are known (e.g., thin single or multilayer films made from materials such as polyethylene or polyvinylidene chloride, optionally containing polymer layers that inhibit the passage of wet or certain gases). Articles can be sealed with a plastic film, for example, by completely enclosing the article in the film and sealing the film itself. Alternatively, articles can be sealed by sealing the film around the periphery of a recess, compartment or other orifice defined by the article, and then, if necessary, trimming the portion of the film beyond that periphery. All techniques for sealing articles with a thin plastic film are considered to involve at least intermittent contact between the periphery of the article and the film used for sealing.

[0119]

[0126] Therefore, it is advantageous that articles sealed with a thin plastic film do not have sharp, pointed, rough, jagged, or rough structures, at least in areas of the article that come into contact with the film, or at least substantially so. It is particularly important that there are no surfaces of the article that will inevitably come into contact with the sealing film in such configurations, and it is highly desirable that these structures are not present on any surfaces of the article that may come into contact with the sealing film, whether during the sealing process or during further packaging, transport, unpacking, or retail display of the film-sealed article. Even more preferably, articles wrapped in a thin film do not have such structures on any surfaces where there is a substantial possibility of contact between the surface and the film during any of these processes. Ideally, articles do not have such surfaces at any location where it is reasonably expected that the film used for sealing will come into contact with the surface location during these processes.

[0120]

[0127] It is well known that a variety of thin plastic films are useful for sealing containers, and substantially any of these films can be used to seal the molded articles (or their compartments) described herein. The selection of sealing films (and materials for creating molded articles compatible with such sealing films) is well known in the art, and substantially any known combination of materials can be adapted for use with the molded articles described herein. For example, when a sealing film is to be removablely sealed around a molded article described herein (e.g., an overwrapping film that seals itself but not the wrapped article), the material used to create the molded article should be selected so as not to fuse with the film under the sealing conditions used by the molded article. Conversely, when a sealing film is to be substantially permanently sealed around a molded article (e.g., around a compartment defined by the article), the material used to create the article should be selected to facilitate the formation of a substantially permanent seal under the conditions of actual processing. Similarly, combinations of sealing and container materials and operating conditions that result in a container sealed with a material from which it can be peeled off are also well known and can be used.

[0121]

[0128] A highly desirable embodiment of the articles described herein is an article formed into a tray created by thermoforming (and thus having a potentially sharp peripheral edge before the edge rotation process described herein) such that the peripheral edge is sufficiently deflected around the entire periphery of the tray below the extension and behind the spacer and bending region of the deflectable flange relative to the deflectable flange, so that the peripheral edge cannot be touched by a person's fingertips rubbing along the gap between the deflected peripheral flange and the body of the tray, even if the fingertips rub along this gap around the entire periphery of the tray. Such a tray would not bear sharp, pointed, rough, jagged or rough edges at any location where contact with the sealing film is reasonably foreseeable, regardless of whether OW, VSP, or MAP technology is used in the sealing process. A tray suitable for use with all these sealing technologies is highly desirable and is considered to have been unavailable prior to the disclosure of the subject matter described herein.

[0122]

[0129] Many plastic films used for sealing articles are flexible and do not heat-cur beyond the normal temperature range used during sealing and subsequent handling. Flexible films used for sealing surfaces can sometimes be difficult to remove from the sealing surface in a single piece. For example, a flexible film used to seal around the flat perimeter of a tray may tear or rip when a portion of the film is pulled away from the tray, and the user may need to remove the film in multiple paths or in many strips or pieces. Such difficulties can be particularly severe in situations where the sealing surface is extensive, such as in VSP sealing packaging, where the sealing film may adhere to or melt over a relatively large area of ​​the tray on which the item is sealed between the film and the tray. The techniques described herein can be used to reduce or overcome these difficulties as follows:

[0123]

[0130] A molded article as described herein (for example, an article molded on a tray having a smooth perimeter) can be sealed with a thermosetting (i.e., thermoformable) film to bring the article to be applied to the smooth perimeter of the molded article, as the thermoformable sealing film is heated above its glass transition temperature to soften it. A thermoformable film, heated above the glass transition temperature of the material from which the film is made and then cooled below that temperature, will maintain any form the film has (e.g., the form applied to it) when the temperature drops below its glass transition temperature. Thus, if the thermoplastic film is formed "around" the smooth perimeter of an article as described herein (i.e., stretching more than about 90 degrees around the perimeter), the film is held to the article not only by any attraction or adhesion that may exist between the film and the surface of the article, but also by mechanical forces that form a structure similar to a "snap-off" lid (i.e., the film's resistance to deflection around the smooth perimeter).

[0124]

[0131] Even though a softened thin plastic film may be extremely delicate (e.g., easily damaged by sharp, pointed, rough, jagged, or rough surfaces), the smooth periphery of the molded article described herein can be added to such delicate films. In one example, an article molded in the form of a tray with a smooth periphery can be VSP sealed to enclose the article between the softened thermoplastic sealing film and the tray, with little or no gas contained within the sealed portion. Furthermore, the smooth periphery of the article described herein can be achieved by drawing, pressing, or forming the softened film around the smooth periphery, i.e., not only the top of the periphery (i.e., analogous to the extension 50 of the article edge depicted in Figure 9B) but also around the bent region 150 of the deflectable flange and along the spacer 140 and any bent or rounded portion thereof (such as on or around the rounded bottom surface 145 of the spacer depicted in Figure 9B), and then setting the temperature of the sealing film below its glass transition temperature. Such a sealing form a relatively rigid “lid,” and even if the film does not adhere to or melt with the article where it intersects with the article, the frictional force or shape of the “lid” (for example, the “lid” rotated around the rounded bottom surface 145 of the spacer shown in Figure 9B so that it needs to stretch or expand to engage and disengage the lid from the rotated peripheral flange 160) can hold the sealing film in place on the article. Furthermore, since a softened thermosetting film can be substantially thicker than a thin, flexible sealing film, and therefore stronger and / or more rigid, the thermosetting sealing film can form a sealing or “lid” that is more likely to be removable in a single piece.

[0125]

[0132] In one embodiment of a manufactured article described herein, for example, the article is a tray having food placed on it, and a thermosetting film is draped over the food and the periphery of the tray while the film is softened, and the gas between the film and the tray is drawn out to form a VSP-type seal (the film approaches the surface of the food and the tray on which the food is placed), and the film drapes (from above to the periphery bottom or around the bottom surface), optionally seals or melts onto the tray, trims around the periphery bottom of the tray, and cools. In the finished tray, the “lid” formed when the film cools must “unsnap” the tray by stretching the edge of the lid around the periphery of the tray, but once this operation is performed, the entire lid can be removed from the tray in a single piece.

[0126]

[0133] In another embodiment, the molded article described herein is sealed (after its smooth outer perimeter is formed) using a thermoformable plastic film that extends at least 90 degrees around the opposing smooth peripheral sides of the article (i.e., the opposing ends of a rounded rectangular tray) across a compartment defined by the article. The film is heated above its glass transition temperature and cooled below that temperature while being stretched around the opposing smooth peripheral sides. If necessary, vacuum or gas displacement may be applied to the compartment during such sealing. The resulting article has a thermosetting film cover that must be stretched (or “snap-fastened”) around at least one peripheral side of the article to remove the film from the article (in addition to any other sealing that may exist between the film and the article).

[0127]

[0134] The molded articles described herein can be used in ways in which previously known trays would not be feasible. Typically, containers are used that are specifically designed and manufactured for each of the various sealing techniques described herein (e.g., OW, VSP, and MAP techniques) to seal containers with thin plastic films. That is, food trays designed for OW sealing are generally considered unsuitable for VSP and MAP over-wrapping (e.g., because they lack a suitable surface for sealing in VSP and / or MAP techniques). Similarly, the sharp edges of many containers designed for use with VSP and MAP sealing techniques make them unsuitable for over-wrapping with brittle polymer films. The molded articles described herein can be used to create molded articles that are suitable for use as containers for sealing by any of the OW, VSP, and MAP techniques. Since the molded articles are thermoformed, the surface of a container suitable for VSP and / or MAP sealing can be incorporated into the shape of the article. Any edges of a manufactured article that may pose a risk of tearing the sealing film (or, otherwise, the entire edge of the manufactured article) using the methods described herein can be made to have a smooth shape, for example, by forming a rotated edge or by smoothing the shape of the mold used to thermoform the precursor article. Thus, unlike conventionally known trays, the manufactured articles described herein can be used with substantially any film sealing technology.

[0128]

[0135] Another advantageous use of the molded articles described herein relates to the smoothness of their edges. The articles can be used substantially in any environment where it is desirable or necessary for a solid object to present a smooth edge. For example, instruments used in surgical procedures are typically packaged in resealable containers (for reusability and sterilization during use), which are opened by a person wearing fragile surgical gloves during medical surgery. Thermoformed articles (e.g., packaging that opens with a so-called "shell" snap of a known design) can be made as described herein, and these articles are made by first having a deflectable flange at a location where it is cut from the web of thermoformed material at any point, and then rotating the deflectable flange to produce the smooth edge described herein. Articles made in this manner present a smooth edge to the user and reduce the likelihood of surgical gloves tearing when opening such packaging during surgery. Similarly, thermoformed packaging of known designs used to facilitate handling, deter theft, or achieve other purposes can be adapted to incorporate the advantages of the edge-smoothing techniques described herein (for example, by including deflectable flanges in their designs and rotating them).

[0129]

[0136] System for forming articles

[0137] As described above, precursors of the shaped articles described herein can be formed by standard thermoforming methods using standard thermoforming equipment. For this purpose, thermoforming dies are used to create precursor articles by pressing the desired form of the finished article onto a thermoplastic sheet, except in cases where the deflectable flange described herein is included in the peripheral edge where a smooth periphery should be formed. Once the precursor article is cut from the web of the thermoplastic sheet, the edge smoothing operation described herein can be performed by impacting the deflectable flange against a ram (optionally using the upper body).

[0130]

[0138] Recent thermoformed precursor articles tend to emerge from the thermoforming machine at a temperature close to (but lower than) the glass transition temperature of the thermoplastic material. By having the deflectable flange and ram collide immediately after the precursor article is removed from the thermoforming machine, the amount of thermal energy that must be supplied to one or more portions of the deflectable flange in order to achieve the desired deflection (or “rotated” edge effect) of the deflectable flange as described herein can be reduced. For this purpose, it may be desirable to combine the thermoforming machine, ram and collision mechanism into a single system or a single piece of equipment. Such a system or piece of equipment should include i) a thermoforming machine module capable of forming a precursor article, ii) a cutter for cutting the precursor article from a thermoplastic sheet or the thermoplastic sheet or roll on which it was formed, iii) a ram, and iv) a mechanism for positioning the precursor article relative to the ram (i.e., so that the deflectable flange portion is aligned with the corresponding ram portion) and for colliding the precursor article and the ram together. The heat required during the operation of deflecting the deflectable flange described herein can be provided by a ram, by a cutter (e.g., using a heated cutting blade to heat the peripheral edge and adjacent peripheral portions of the deflectable flange to a temperature above the softening temperature of the thermoplastic material), by a separate heater (e.g., a radiant heating element positioned close to and opposite the ram when the ram engages with the deflectable flange), or by a combination thereof. The precise selection, orientation, order, and structure of these pieces of the apparatus are not critical and can be selected by those skilled in the art, taking into account the requirements and processing steps described herein. The system or apparatus may also include a plug described herein for insertion into a gap in the precursor article before the deflectable flange strikes the ram. [Examples]

[0131]

[0139] Examples

[0140] Next, the subject matter of this disclosure will be described with reference to the following examples. These examples are provided for illustrative purposes only, and the subject matter is not limited to these examples, but rather encompasses all variations that are evident as a result of the teachings provided herein.

[0132]

[0141] Example 1

[0142] Figures 6A and 6B show thermoplastic trays that have been thermoformed from a flat sheet of thermoplastic material and then cut from the sheet. The sharp edges formed by the cutting process are shown in each of these figures, with a finger touching the sharp edge. After the smoothing process described herein has been performed on these trays, the appearance of the trays is substantially shown in Figure 3, in which the sharp edges are "rotated" to face the smooth areas formed by bending and heating at least the bending regions of the tray body and deflectable flanges, and cooling the sharp edges to give the tray a smooth outer circumference, so that the tray does not collide with either the thin plastic attached to the rim of the tray or the thin plastic film tightly wrapped around the entire perimeter of the tray.

[0133]

[0143] Example 2

[0144] This embodiment is provided to illustrate the formation and sealing of articles formed as described herein. This embodiment describes the formation, filling and sealing of a container for containing slices of fresh fish.

[0134]

[0145] The shaped articles for receiving fish are formed by conventional thermoforming methods. A thermoformable material in sheet form (e.g., PET) is heated above its glass transition temperature and biased into a mold using conventional thermoforming techniques (using either a male or female mold, with or without positive and / or negative pressure to bias a portion of the sheet into a portion of the mold). Such thermoforming results in a tray-shaped container having a rounded rectangular overall shape and containing a concave interior for receiving fish slices. The rounded rectangular overall shape of the container is defined by a deflectable flange surrounding the interior around its entire periphery. The deflectable flange has the configuration shown in Figure 1A, and the tray has a shape similar to the tray shown in Figure 6D when the thermoformed tray is cut from the sheet at the peripheral edge 110 of the deflectable flange 160. The die-cutting machine used to cut the tray from the sheet is heated so that the peripheral edge of the tray is heated to or near its glass transition temperature.

[0135]

[0146] A plug having a shape that substantially fills the interior of the tray in the portion adjacent to the extension 50 of the deflectable flange 160 is inserted into the interior (as roughly shown in Figure 8Dii). The tray filled with the plug is then inserted into the ram 300 (as roughly shown in the upper position in Figure 10A, except that the plug is not present in Figure 10A) so that the peripheral edge 110, the spacer 140, or both, are in contact with the upper surface 302 of the ram 300 with substantially all portions of the deflectable flange. A downward pressure (see Figure 10A, the force is applied from the top to the bottom of the image) is applied to the extension 50 of the deflectable flange 160 around the entire periphery of the interior, driving the spacer 140 and / or the peripheral edge 110 portions of the deflectable flange 160 against the ram. The deflectable flange is driven relative to the ram to a position similar to the one shown in the cross-sectional view of Figure 8H, and the part is held in this position for a sufficient period of time by at least a portion of the deflectable flange indicated by "B" in Figure 8J, so that the part reaches a temperature higher than its glass transition temperature by heat conducted or radiated from the ram. The deflectable flange is then further biased to the ram (by the force applied to the extension 50) so that its peripheral edge 110 slides, rubs, or jumps over the inner surface 302 of the ram 300, causing the deflectable flange to advance to around the position shown in Figure 8J. If necessary, the deflectable flange can advance further to the position shown in Figure 8K, and any additional portion of the deflectable flange may reach a temperature higher than its glass transition temperature when interrupted at an optional interval. Also, if necessary, a coolant such as ambient air may be injected to lower the temperature of the deflectable flange at the injection point (e.g., at the position occupied by element 120 in Figure 8K) to prevent further irreversible deflection of such portion. The deflectable flange is sufficiently biased to the ram so that its peripheral edges cannot easily come into contact with the film or other materials present around the tray.

[0136]

[0147] The force biasing the deflectable flange to the ram is interrupted, the article is removed from the ram it is in contact with, and thereby the material of the deflectable flange cools below its glass transition temperature and maintains its shape without any applied force. At this point, an article has been formed into the desired tray shape, and the tray has a smooth perimeter. The tray can be immediately used to package fish slices, or more typically, the tray can be stacked with other such trays and transported to a fish processor.

[0137]

[0148] Whether the tray is used immediately after formation or recovered by unpacking the trays from the stack, the fish slices can be placed in the internal compartments of the tray together with any other materials (e.g., sauces, absorbent pads, vegetables, or condiments) to be packaged with them in preparation for sealing. Any number of known sealing techniques can be used to seal the container and the fish.

[0138]

[0149] The tray can be simply wrapped in a thin plastic film (the film extends around the smoothly curved bend regions 150 and / or spacers 140 of a deflectable flange 160 across the opening of the compartments between extensions 50 on the opposing sides of the compartments), and the ends of the film can be sealed to a portion of the film covering the tray by, for example, applying a heated pad to the ends, after which the film shrinks with heat, resulting in a visually pleasing taut film surface. Since the tray has no sharp or rough edges around its periphery, the wrapping film will not tear during sealing, and such edges will not tear, snag, or rip other sealed packaging during transport. Containers containing wrapped fish can be packaged (for example, in a box together with other such containers or in a plastic bag containing both selected gas or liquid phases and other such containers) and transported to wholesalers, retailers or consumers.

[0139]

[0150] Rather than sealing the packaging with an outer wrapper that seals the outer wrapper itself, the container may be sealed after filling with a film that seals the compartments with an extension 50 around the perimeter of the compartments, instead of wrapping the tray. Such a seal can be produced simply by sealing the film to the extension 50 (using any one or a combination of heat, pressure, and adhesive), preferably by trimming the film around the perimeter of the seal (for example, by trimming the film over a range approximately around the perimeter of the container). If necessary, any open ends of the film seal can be shrunk using heat. Vacuum can be applied to remove gas from inside the compartments before sealing and to pull the film into the contents of the compartments, and a selected gas or mixture of gases can be injected before sealing, optionally.

[0140]

[0151] Example 3

[0152] MAP tray with a peelable surface and a rotating edge.

[0153] One embodiment of a thermoplastic article described herein has proven to have particular practicality and is clearly described in this embodiment. This embodiment is an article having any shape of a standard tray-shaped container in the industry, colloquially referred to by those skilled in the art as a "MAP tray." Such a tray has a concave internal space for holding or containing articles (e.g., a collection of plant parts such as fish, chicken or other meat slices, vegetables, mushrooms or fruits such as cherries). The rim completely encloses the concave internal space so that when the MAP tray is placed on a horizontal surface (MAP trays tend to have a flat bottom to facilitate stable placement on horizontal or inclined surfaces), the material in the concave internal space does not generally flow, spill, or roll over the rim and thereby not escape from the concave internal space. Extending (usually completely) around the opening of the concave internal space at the top of the rim is a flat sealing surface. During use, a thin plastic film (i.e., a sealing film) covers or spreads across the opening of a concave internal space and is then sealed to the flat sealing surface of the tray (e.g., using heat, adhesive, or mechanical impact force). As described above, sharp or rough peripheral edges of the material from which the MAP tray is made may cut, snag, tear, or rip such a sealing film (e.g., the film is attached to the first MAP tray or to a second MAP tray, such as a tray transported together with the first tray).

[0141]

[0154] In the embodiments described herein, the MAP tray is created (e.g., by thermoforming) by producing a precursor tray having the desired bottom, rim, and concave internal space configuration of the desired MAP tray, and the desired MAP tray bears the deflectable flange described herein at the top of the rim at all locations where a flat sealing surface is desired. Typically, the MAP tray has a flat sealing surface that completely encloses the opening of the concave internal space, and the precursor tray corresponding to such a MAP tray should bear the deflectable flange around the entire perimeter around the opening of the concave internal space. The deflectable flange of the precursor tray is then bent, deflected, or rotated as disclosed herein to yield the smooth edge described herein. The extension of the deflectable flange is selected to be large enough to yield a flat sealing surface with desired dimensions (e.g., at least 1 / 4 inch wide around the entire perimeter, measured radially from the center of the MAP tray) that follows the smoothing of the edge of the precursor tray.

[0142]

[0155] Importantly, in the embodiments described in this example, the thermoformable sheet used to form the precursor tray has a peelable layer (i.e., a “liner sheet”) attached to the precursor tray, such as along one side of the thermoformable sheet. The liner sheet can be attached to the thermoformable sheet before the precursor tray is formed (e.g., by laminating two sheets before thermoforming), during the formation of the precursor tray (e.g., by biasing one or both of the two sheets together simultaneously while thermoforming), or (less preferably) after the precursor tray is formed. The liner sheet preferably covers the entire surface of the thermoformable sheet, such as a surface defining the concave interior of the precursor tray. Multiple liner sheets can be adjacent to each other, overlap, or (more preferably) bonded to the thermoformable sheet in a “laminated” configuration, such as when a first liner sheet covers a surface of the thermoformable sheet, a second liner sheet covers the exposed surface of the first liner sheet (i.e., the side opposite to the surface bonded to the thermoformable sheet), and optionally additional liner sheets cover the exposed surfaces of the previous liner sheets.

[0143]

[0156] In another embodiment, one or more liner sheets are attached to a thermoformable sheet after being thermoformed to produce a precursor tray. In this embodiment, the sheet material intended to be attached to the tray is heated to at least its softening point and attached to the surface of the tray (e.g., the surface of the MAP tray defining its concave and surrounding rim), and any gas or other fluid between the surface of the tray and the liner sheet is drawn out (e.g., by applying a vacuum to the space between the tray and the liner sheet). The softened liner sheet is then drawn to the surface of the tray and can adhere to the surface of the tray (due to the nature of the opposing polymer surfaces or by an adhesive applied to one or both opposing surfaces). Upon cooling, the liner sheet has the form of the surface of the tray to which the liner sheet was attached and drawn, and adheres to the surface of the tray. If the liner sheet extends beyond the perimeter of the tray, the liner sheet can be trimmed by any known method (e.g., by “punching” the portion of the liner attached to the tray from a larger sheet of liner material using a die-cutting machine shaped to the perimeter of the tray, or by running a blade along the edge of the tray). Furthermore, the trimming operation may leave tabs of the liner sheet that are not adhered to the tray (for example, to facilitate peeling the liner from the tray). This operation can be repeated two or more times to add additional liner sheets to the tray. When multiple liner sheets are added to the tray, the liner sheets can completely overlap, partially overlap, or not overlap at all (i.e., the liner sheets can be attached to different parts of the tray). In a useful embodiment, multiple liner sheets are attached to the tray in this manner, and each of the multiple liners completely covers the same side of the tray except for the tabs corresponding to each sheet, and the tabs are cut in a manner that allows the tabs to be distinguished from one another, so that the desired liner can be peeled off using the corresponding tabs.For example, a rounded rectangular tray with three liners may have tabs at the corners of the tray for the bottommost liner sheet (i.e., adjacent to the thermoformable sheet), a tab at the midpoint of the longest side of the tray for the topmost liner sheet, and a tab at the midpoint of the shortest side of the tray for the middle liner sheet.

[0144]

[0157] For trays with rotated edges as described herein (and more broadly, articles with rotated edges), liner sheets can be added before or after performing the rotational edge operation described herein on the thermoformable article. That is, one or more liner sheets can be attached to the surface of the article before the edge rotation (including, if necessary, the deflectable flange portion thereof), and the deflectable flange (including the added liner) can then be bent and rotated as described herein. Alternatively, the article can be thermoformed (e.g., including the deflectable flange described herein), its edge can be rotated, and the liner added to one or more surfaces after the edge rotation operation is completed. In one embodiment, for example, a thermoformable sheet is formed by a thermoforming process within individual trays having the deflectable flange described herein around the entire perimeter of the tray. The formed trays can then undergo an edge rotation process to produce stackable trays with smooth perimeter edges. The smooth-edged trays can be stacked and stored. The stacked trays can be unstitched to yield individual smooth-edged trays, which can then be fed into the VSP workshop, where a continuous roll of liner sheet material is fed. In the workshop, the liner sheet material is softened and drawn into the interior of the smooth-edged trays by drawing gas from between the softened liner material and the formed tray. The liner material can be cooled, yielding smooth-edged trays with a portion of the continuous sheet of liner material bonded to its inner surface. After being drawn to the tray surface (i.e., during or after the operation), the liner sheet material can be cut around the perimeter of the tray to yield individual smooth-edged trays with liner sheets bonded to it (leaving a "relaxed" piece of liner material released from the tray to optionally act as a tab for later peeling off the liner). The operation can be repeated as many times as necessary to add additional liner sheets to the tray.

[0145]

[0158] The apparatus and methods used to add the liner sheet to the surface of a pre-formed tray are not critical. Any apparatus and methods capable of substantially softening the liner sheet, aligning it with the surface of the pre-formed tray, and drawing gas or other fluid between the tray and the liner sheet can be utilized. For example, a standard VSP workshop includes equipment for holding the pre-formed tray in a fixed position, softening the polymer sheet near the tray, attaching the softened polymer sheet to the surface of the pre-formed tray (e.g., the upper rim surface of a tray with a rim surrounding its concave interior), and drawing gas from the space defined by the tray, the softened sheet, and their intersection. In a standard VSP workshop, this arrangement is typically used to soften a sheet of lid material, attach it to the tray, make the lid flush with the surface of the tray and any material supported on or within the tray, and to draw gas from the space between the lid and the tray in order to seal the lid to the tray. The same apparatus setup can be used to add a liner to the tray (instead of a lid), but sealing equipment is not required (but can be used if necessary). In this configuration, the tray is empty (no material is carried in or on it), so the softened liner sheet is attracted flush with the surface of the tray when the gas is withdrawn. Careful selection of the tray material, liner sheet material and (if necessary) barrier composition results in a tray from which the liner attached to the tray can be peeled off as needed.

[0146]

[0159] The material used to create the liner sheet is not critical, but it is preferably a flexible plastic material. The liner sheet does not need to be made from thermoformable plastic, but it is possible. Alternatively, the liner sheet can be made from non-thermoformable plastic that exhibits sufficient flexibility to conform to the shape of the thermoformable sheet. The liner sheet can be made from the same or different material as the thermoformable sheet. For example, a relatively thick thermoformable sheet of PET can be used as a substrate, and a relatively thin sheet of PE can be bonded to the surface of the PET sheet (after or preferably before thermoforming the PET sheet to create the fabricated article). Since PE and PET exhibit similar shrinkage rates, temperature-dependent delamination between the two sheets is limited. When a PE sheet is attached to the surface of a PET sheet defining a recess (e.g., inside a MAP or VSP tray), it may be possible to peel and separate the PE and PET sheets without draining the contents of the recess from the PE liner sheet. Furthermore, if the cover is attached to the surrounding liner sheet, it may be possible to separate the liner from the PET substrate sheet without losing the sealing material between the liner and the cover sheet.

[0147]

[0160] Figure 11 shows a cross-sectional view of a portion of a tray as described herein. The tray is formed from a relatively thick thermoformable substrate sheet 101 (e.g., a thick PET sheet), and a relatively thin liner sheet 500 (e.g., a thin PE sheet) is bonded to one surface of the substrate sheet 101. Figure 11A shows a deflectable flange 160 at one periphery of the tray, and the peripheral edge 110 of the bonded sheet is offset away from the body of the article by an extension 50 of the deflectable flange 160 (the portion beyond " / / " is not shown). Thus, Figure 11A shows how the periphery of this tray should appear after the substrate sheet 101 has been thermoformed and the liner sheet 500 has been attached to one surface thereto (either before, during, or after thermoforming), and before the peripheral edge 110 has been rotated as described herein. Figure 11B shows the same portion of the tray after such an edge rotation. In Figure 11B, the substrate sheet 101 has been rotated sufficiently so that its peripheral edge 111 is returned to the body of the article. The liner sheet 500 remains flush with the surface of the substrate sheet 101 in all areas except near its peripheral edge 501, where the liner sheet 500 peels or rotates away from the peripheral edge 111 of the substrate sheet 101. Such peeling or rotation may result, for example, from friction between the ram and the liner sheet 500 during the edge rotation operation, or the peeling / rotation may be intentionally initiated by rubbing the peripheral edge 501 of the liner sheet 500 away from the peripheral edge 111 of the substrate sheet 101 using a fingernail, tool, or a friction treatment step. Having a partially peeled peripheral edge 501 may impair the appearance of the liner sheet 500 or the article, but the partially peeled edge facilitates further peeling of the liner sheet from the article. Figure 11C illustrates that the cover 600 can be attached to the liner sheet 500 in an extended area 50 that extends around the periphery of the MAP or VSP tray (for example, by placing, electrostatically charging, or by adhesive, or by sealing or bonding together by the application of pressure and / or heat).If the cover 600 is attached to the liner sheet 500 rather than the substrate sheet 101, the cover 600 and the liner sheet 500 can be separated from the substrate sheet 101 without optionally cutting the attachment between the cover 600 and the liner sheet 500. If the molded article has, for example, the form of a MAP tray on the back of the liner sheet 500 with its recess and sealing surface (i.e., the surface of the extension 50), and the cover 600 is sealed to the liner sheet 500 with the sealing surface covering the entire periphery of the recess, the liner and cover (and any contents sealed between them) can be peeled off from the remainder of the MAP tray.

[0148]

[0161] A precursor tray, having one or more liner sheets attached thereto, may then undergo the edge-smoothing process described herein, and the deflectable flange may be bent, deflected, or rounded to give the finished MAP tray a smooth peripheral edge. The finished MAP tray has a peelable liner attached to a thermoformable sheet, from which the liner can be peeled off. A lid material may be attached to the liner or thermoformable sheet, or may wrap the finished MAP tray. In one embodiment, the lid is sufficiently elastically bonded to the liner around the entire periphery of the sealing surface (thus defining a compartment between the liner and the lid), so that the liner can be peeled from the thermoformable sheet without damaging the compartment. In this embodiment, the liner, lid, and anything contained within the compartment can be separated from the molded thermoformable sheet of the MAP tray (which can, for example, be recycled) before accessing the contents of the compartment. Alternatively, the contents of the compartment can be accessed before peeling the liner from the molded thermoformable sheet of the MAP tray, and the liner (and any remaining lids) can then be peeled off therefrom.

[0149]

[0162] If the liner covers the surface of a thermoformable sheet before the precursor tray is formed, the liner may detach from all or part of its peripheral edges during the formation of the precursor tray. Similarly, even if the liner remains peelably attached to the entire surface of the thermoformable sheet after the precursor tray has been formed, the liner may detach from all or part of its peripheral edges during the edge smoothing process described herein. Such detachment (peeling) may be undesirable (for example, if the liner is intended to remain visually undetectable), and if so, it can be reduced or prevented by other methods known to those skilled in the art, or a combination thereof, by increasing the strength with which the liner is bonded to the thermoformable sheet, by increasing the flexibility or stretchability of the liner's thermoplastic, and by reducing the "sharpness" (i.e., radius of curvature) of the deflection made to form the precursor tray. On the other hand, detaching a portion of the liner from the thermoplastic sheet may be desirable, particularly at its peripheral edges (for example, to provide a freely graspable portion of the liner that can be used to further peel the liner from the thermoplastic sheet when the user so desires). Such peeling can be enhanced or induced by other methods known to those skilled in the art, or by a combination thereof, such as reducing the strength with which the liner is bonded to a thermoformable sheet, thereby reducing the flexibility or thermoplastic stretchability of the liner, thereby increasing the "sharpness" (i.e., radius of curvature) of the deflection made to form the precursor tray, by abrading or rubbing the peripheral edges of the MAP tray, for example.

[0150]

[0163] Example 4

[0164] Subject matter copied from U.S. Patent Application Publication 13 / 415,781

[0165] As stated above, U.S. Patent Publication No. 13 / 415,781 (currently filed as U.S. Patent No. 9,302,842), which was concurrently pending with U.S. Provisional Patent Application No. 62 / 212,367, is incorporated herein by reference. This disclosure expressly contains all subject matter that may be “basic materials” as appropriately considered as provided for in 37 §1.57(d) of the Code of Federal Rules, and the following portions of U.S. Patent Publication No. 13 / 415,781 are incorporated herein by reference as they appear in the original text. In the incorporated subject matter below, “liner” as referred to in the incorporated subject matter is analogous to “peelable layer” as previously referred to in this disclosure, “lid” or “lid stock” as referred to in the incorporated subject matter is analogous to “lid” as previously referred to in this disclosure, and “substrate” as referred to in the incorporated subject matter is analogous to “formed article” or “formed thermoplastic article” as previously referred to in this disclosure. Any other similarities between the incorporated subject matter and the subject matter previously referred to in this disclosure are likely to be apparent from the relevant context.

[0151]

[0166] The following text is incorporated into this embodiment exactly as it appeared in the original U.S. Patent Application Publication No. 13 / 415,781.

[0152]

[0167] This disclosure relates to a container comprising at least one thermoformable compartment, created by layering at least one polymer sheet on the surface of a substrate. The sheet is bonded to the compartment or storage compartment, in which a liquid or another material can be isolated from the outside of the compartment or storage compartment. The compartment or storage compartment can be bonded by the substrate so that the material within the compartment or storage compartment is in contact with the substrate, or the compartment or storage compartment can be bonded by a second (optionally perforated) sheet so that the material within the compartment is contained between a first sheet and a second sheet. The sheets can be peelably adhered or bonded to the surface of the substrate, either to each other or to both, so that the container can be partially or entirely disassembled. In key embodiments, the sheet bonded to the compartment or storage compartment can be separated from the substrate without damaging the compartment or storage compartment.

[0153]

[0168] Thermoformable polymer sheet

[0169] Each of the substrates and liner sheets described herein may be a thermoformable sheet. The identification and composition of the thermoformable polymer sheet used in the articles and methods described herein is not important. Those skilled in the art will recognize that substantially any thermoformable polymer sheet can be used. Examples of suitable thermoformable polymer materials include polyethylene terephthalate, polyester, polyethylene (e.g., high-density polyethylene and high-molecular-weight polyethylene), polypropylene, polyvinyl chloride, polystyrene, nylon, copolymers thereof, and combinations thereof. Plant-based polymers such as polylactic acid (also known as "lactic acid polymer" and PLA) can also be used. Polymers used in contact with food should, of course, be selected for suitability.

[0154]

[0170] Examples of suitable thermoformable polymer materials for use as substrates include polyethylene terephthalate (e.g., RPET, amorphous PET, and PETG), polyester, polyethylene (e.g., high-density polyethylene and high-molecular-weight polyethylene), polypropylene, polyvinyl chloride, polystyrene, nylon, copolymers thereof, and combinations thereof. Plant-derived polymers such as polylactic acid (also known as "lactic acid polymer" and PLA) can also be used.

[0155]

[0171] Those skilled in the art can select a combination of materials suitable for virtually any application by considering thermoformable polymer materials or properties such as shrinkage rate, crystallinity, thermal deflection temperature, tear strength, stretch ratio, thickness, stiffness, melting temperature, thermal conductivity, and polymer main chain orientation. The selection of materials can also be guided by properties that do not necessarily directly affect the thermoformability of the material, such as price, color, opacity, recycled content, environmental impact, surface energy, chemical resistance, and surface gloss.

[0156]

[0172] When selecting an appropriate material, a person skilled in the art should consider at least two sets of conditions: the environmental conditions the finished molded article will experience and the conditions the material will experience during the thermoforming process. For example, the material should be selected such that, once molded into its desired final shape during the thermoforming process, it exhibits the desired color, shape, strength, rigidity, and release properties. Furthermore, the material should be selected in conjunction with thermoforming conditions so that the material can be assembled and molded into its desired final shape using thermoforming conditions available to a person skilled in the art.

[0157]

[0173] For deep-walled containers (i.e., containers where substantially spreading a laminate of flat substrates or liners is necessary to form the container), a substrate blank, cast, folded, or otherwise formed to have a near-final shape of the container, can be used to reduce the risk of the substrate rupturing due to overstretching. For example, when a metal foil substrate is used, the metal foil substrate can be folded and compressed from a flat sheet of foil to form a blank with a shape close to the final container before a polymer liner sheet is attached to it. Under conditions where the liner sheet can be thermoformed, the final shape of the container can be achieved by thermoforming the liner sheet onto the blank in a thermoforming press.

[0158]

[0174] Special consideration should be given to the selection of substrate materials for containers intended to contain food (especially for human consumption). If the substrate material contains or may contain any substances harmful to health (e.g., recycled substrate material), the substrate should only be used in conjunction with a liner sheet (and / or a barrier sheet or composition interposed between the substrate sheet and the liner sheet) to sufficiently reduce the expected migration of the substrate from the substrate to the compartment under the expected conditions of use. The selection of appropriate materials is known to those skilled in the art.

[0159]

[0175] substrate

[0176] The identification and composition of the substrate are not important. Those skilled in the art will understand that substantially any formable material can be used, such as metals and thermoformable polymers (which are preferred substrates). The substrate sheets described herein do not need to be thicker, more rigid, or more opaque than any other sheets used to create the articles described herein. However, in many embodiments, it is desirable that the substrate contributes significantly to the rigidity, strength, and shape of the article, and that other components contribute relatively little to these properties.

[0160]

[0177] For example, in a container or tray for containing meat or vegetable pieces, the substrate may be substantially the only container that holds the container / tray together when separated from other components. Liner sheets that may serve to prevent direct contact between the meat or vegetable pieces and the substrate, and lids that may serve to hold such pieces in recesses of the container / tray, may not retain their shape when cut or peeled from the substrate, and lids may contribute to the overall shape and rigidity of a filled container / tray only in the point of sealing the meat or vegetable pieces inside or covering the container / tray.

[0161]

[0178] In embodiments where the recyclability of the substrate is an important attribute, the substrate should be made of recyclable material and should constitute the majority (based on volume or weight) of the material used to form the article. Any non-recyclable or difficult-to-recycle liner or capping material portion of such article should preferably be reduced or minimized (compared to the amount used in conventionally known similar articles) to maximize the proportion of recyclable material in the article and reduce the proportion that must be landfilled, incinerated, or disposed of in another environmentally undesirable manner.

[0162]

[0179] liner

[0180] Liner sheets should be susceptible to the effects of reversible attachment to the substrate and attachment to the cover (whether reversible or not). Furthermore, the liner material should be selected for its physical and chemical compatibility with the materials expected to be contained within the compartment. While the liner can be made from the same material as the substrate (e.g., a thinner sheet of the substrate material), this is preferable. If the substrate and liner are made of the same material, a barrier composition must typically be interposed between the substrate and liner to prevent melting of the two sheets during the thermoforming operation. If the substrate and liner are not made of the same material, the materials, surface treatment, and thermoforming conditions should be selected so that the materials bond in a peelable manner under thermoforming conditions, or, if not, a suitable peelable adhesive should be interposed between the sheets.

[0163]

[0181] In key embodiments of the containers described herein, the liner can preferably be peeled away from the substrate without substantially tearing or spreading. The liner should be attached to the substrate in a peelable manner. Peelable adhesion can be achieved by any and all methods known in the art. For example, peelable adhesion can be intervened between the liner and the substrate, or a liner facing a polymer that peelably adheres to the surface of the substrate can be used (for example, when the two surfaces are pressed together).

[0164]

[0182] The identification and composition of the liner polymer sheets used in the articles and methods described herein are not important. Those skilled in the art will recognize that substantially any peelable polymer material can be used. Examples of suitable materials include polyethylene, polypropylene, polyethylene terephthalate, nylon, polyvinyl chloride, copolymers thereof, and combinations thereof. Plant-based polymers such as polylactic acid (also known as "lactic acid polymer" and PLA) can also be used.

[0165]

[0183] Since food containers must exhibit numerous properties, the use of laminated polymer materials is common in food containers, and such laminations may be used as liner sheets in containers described herein. Such laminations should include polymer layers that exhibit desired properties (e.g., tensile strength, vapor resistance / odor resistance, moisture resistance, flexibility, absence of food-incompatible components, and at least no barrier layers intervening between such components and compartments) and sufficient adhesive or tie layers to bond the layers together in a peelable sheet. The outermost polymer layer has additional importance in that (considering any materials intervening between the liner and the substrate) the substrate side of the liner sheet must be compatible with the reversible fasteners on that side of the substrate, and (considering any adhesives or other materials intervening between the liner and the lid) the lid side of the liner sheet must be compatible with the fasteners to the lid.

[0166]

[0184] The peelable liner sheet preferably has sufficient structural integrity so that it does not tear or stretch excessively when subjected to the force required to peel the sheet from the surface to which it is adhered. For example, when a tray having a peelable liner layer is constructed as described herein, the peelable sheet preferably peels off from the substrate as a single, integral sheet (i.e., without holes or tears) without severing the compartments defined by the liner and the lid. A peelable sheet that tears, stretches, or rips is acceptable in embodiments where it is not necessary to contain liquid within the peelable sheet.

[0167]

[0185] Liner sheets are preferably thin and highly flexible. Sheets thicker than 8 mils are undesirable because they may be difficult to peel off. Liner sheets can be made from substantially any polymer material and by substantially any sheet-forming process. For example, a suitable polymer sheet can be made from a polymer material suitable for blow molding, die molding, injection molding, or extrusion molding, or by a combination of some of these processes. When made from a thermoformable material, the liner sheet is preferably thermoformed simultaneously with the substrate to which the sheet is bonded. When made from a non-thermoformable material, the peelable sheet should be able to maintain structural integrity of the sheet under thermoforming conditions that allow the substrate sheet to which the sheet is bonded to be thermoformable.

[0168]

[0186] Liner sheets can be selected that are rigid (i.e., retain their shape after being removed) or substantially impervious (e.g., blow-molded polymer sheets, such as those used for trash can liners and garbage bags).

[0169]

[0187] The peelability of individual liner sheets can be derived from surface attraction between the liner sheet and the underlying surface. Alternatively, an adhesive intervenes between the sheet and the surface, and the peelability of the sheet derives primarily from the adhesive force exerted by the adhesive on the sheet and the surface. The adhesive can be selected (for example, based on the chemical identity or surface treatment of the liner sheet or the surface to which it adheres) so that it preferably remains adhered to the liner sheet or the surface (less preferably if the surface is the surface of a polymer to be recycled) when the liner sheet is peeled off. For example, when the function of the liner sheet is to expose a substrate surface free of adhesive and other contaminants, the adhesive can be selected to adhere more strongly (i.e., more viscously) to the liner sheet so that it adheres to both the liner sheet and the surface, and is removed along the liner sheet from the substrate when peeled off.

[0170]

[0188] The difference in tackiness between two polymer sheets, which is the degree to which an adhesive bonds opposing surfaces, can be controlled in numerous ways, including coating one or more portions of one surface with a composition that prevents the adhesive from bonding to the surface. However, preferably, the difference in tackiness between which the adhesive bonds is controlled by selecting or treating the polymer sheets so that their opposing surfaces exhibit a difference in surface energy. When the difference in surface energy between the two surfaces is relatively large, at least 5 dynes per centimeter, the adhesive will bond to one surface with much greater tackiness than the other. As the difference in surface energy between the two surfaces increases beyond 5 dynes per centimeter, the likelihood that all the adhesive will remain on one sheet when the two sheets are separated increases. A difference in the bonded surfaces of the two sheets of 5 to 14 dynes per centimeter is considered appropriate.

[0171]

[0189] Even if the surface energy difference between the two surfaces is less than 5 dynes per centimeter, it may still be possible to separate two surfaces with an adhesive intervening between them. In this situation, the adhesive may adhere to each of the two surfaces with nearly equal tackiness, and the adhesive may adhere to both surfaces (in varying amounts) after the two surfaces have separated from each other. In many applications, it is desirable to have almost all or all of the adhesive adhering to only one surface of a polymer sheet (usually one of which is peeled away from the rest of the sheet or substrate). For such applications, the two surfaces in contact by the adhesive should preferably have a surface energy difference of at least 5 dynes per centimeter.

[0172]

[0190] The amount of force required to separate the liner sheet from the surface beneath it is not critical, but preferably small enough to prevent the sheet from tearing and stretching substantially when peeled manually from the surface. The amount of separating force required is a feature of the liner sheet, the substrate surface beneath it, and any barrier composition or adhesive material selected for them. In practice, the tackiness of the adhesive between the liner sheet and the underlying surface should be selected such that the sheet can be peeled away from the surface using ordinary human strength, but is not so tacky that the person peeling the sheet from the surface must tear or rip it. Many variables (e.g., the angle at which the sheet is pulled from the surface, whether a fingernail touches the sheet surface, the speed at which the sheet is peeled, the temperature of the fabricated article when peeled) can affect the peelability of the sheet, and those skilled in the art will recognize that the materials described herein include all materials that are operable under ambient conditions corresponding to the expected use of the material and the fabricated article.

[0173]

[0191] Since an objective measure of the force required to peel the sheet from the substrate surface is desirable, a standardized peel strength test can be used. An example of a suitable test is ASTM D3330 / D3330M, which is a standardized test for peeling the adhesive of pressure-sensitive tape. Modifications to this procedure can also be used (e.g., substituting a sheet of substrate material for the standard steel sheet in ASTM D3330 / D3330M, and selecting a peel angle appropriate to the intended use of the fabricated article being tested). In each case, the characteristics of the fabricated article or lamination should be selected so that the force required to peel the liner sheet from the substrate surface is within the limits of ordinary human strength.

[0174]

[0192] Various surface treatments and raw materials for polymer sheets can be used to influence their surface energy. In one embodiment, the substrate and liner sheet are made from the same material. Unless treated differently, two sides of a polymer sheet generally have the same surface energy. Therefore, in a container containing a substrate and liner sheet of the same material, it is important that two sides of the same polymer sheet are treated differently so that each of the two sides has a different surface energy value. Such a sheet is preferably treated so that the surface energy of the two sides differs by at least 5 dynes per centimeter. Many compositions and methods for influencing the surface energy of a polymer sheet are known to those skilled in the art, and substantially any of these methods can be utilized. Such methods include conventional surface finishing techniques such as grinding and polishing, quenching and annealing processes, and corona treatment, as well as plasma contact techniques such as atmospheric, chemical, and flame plasma techniques. Compositions for influencing the surface energy of a polymer sheet surface are also well known and include compounds that can come into contact with or react with the surface to modify its chemical or physical properties (which affect its surface energy).

[0175]

[0193] An example of a suitable surface treatment is a known process known as corona treatment or corona discharge treatment, where corona discharge treatment is applied to the surface with high frequency, high voltage discharge. Corona treatment increases the surface energy of the polymer surface. When applied to one side of a polymer sheet having two otherwise identical sides, corona treatment increases the surface energy of that side relative to the opposite side of the sheet. The power applied to the corona treatment can be controlled to substantially limit the treatment to one side of the sheet. At very high power, the treatment can increase the surface energy of both sides of the same sheet, which would not result in a polymer sheet with different surface energies on its two sides if no other surface treatment were present. If a polymer sheet is corona treated when the sheet is formed or close to it, the effect of the treatment in increasing the surface energy can last for weeks, months, or even years. If the sheet is corona treated days, weeks, or later after the sheet has been formed, the effect of the treatment in increasing the surface energy may be more transient (e.g., lasting only a few days or weeks). Polymer sheets that are corona-treated when they are formed or very close to it can be used in the containers described herein. Alternatively, polymer sheets may be “bump-treated” (i.e., corona-treated regardless of how long after the sheet has been formed) immediately before creating the laminations and articles described herein.

[0176]

[0194] Furthermore, the liner sheet can be attached without the assistance of a lid, preferably a mechanical device that continuously biases the liner and lid toward each other (i.e., "bonded" without continuous external pressure applied to the liner and lid). Preferably, the liner and lid adhere or melt toward each other under the conditions used to contact the lid and liner. For example, if the opposing liner and lid surfaces are made from the same polymer, the two sheets can be brought to melt when biased toward each other at a temperature sufficient to melt the surfaces (e.g., the melting temperature of a common polymer). Alternatively, an adhesive can be intervened between the liner and lid to form a seal insofar as the adhesive bondes both opposing surfaces together.

[0177]

[0195] The seal between the liner and the lid can be peeled (i.e., the tensile strength of the seal can be less than the tensile strength of the weaker of the two polymer sheets), but this is not necessary. When it is desirable to contain liquid within the compartment (or remove liquid from the compartment), the seal should have sufficient strength (i.e., rigidity and / or elasticity) so that it does not break during the expected normal handling of the container. The seal between the liner and the lid can also be essentially irreversible (i.e., the tensile strength of the seal can be greater than the tensile strength of the weaker of the two polymer sheets), in which case opening the compartment is usually achieved by breaking one or both of the liner and the lid rather than by separating the liner and the lid along the seal.

[0178]

[0196] The material used as the liner should be selected to exhibit sufficient barrier properties to exclude from the interior of the compartment any material expected to be present on the substrate surface of the liner under normal use conditions of the container, taking into account any material present in the substrate and any adhesives, barrier compositions, additional polymer sheets, or other components intervening between the liner and the lid. Selecting a material based on its barrier properties is a convention in the art that provides knowledge of materials whose movement should be avoided.

[0179]

[0197] In a preferred embodiment, the liner material is peelably bonded to the substrate and is in close proximity to the substrate surface, so that it may be difficult for a normal auditor to tell that the liner is present, except for selected areas where a tab or folded portion of the liner is present to facilitate peeling it off. In another embodiment, the material or properties (e.g., color) of the substrate and liner are selected to clearly differentiate whether the liner and substrate are bonded. For example, a white liner may be attached to the surface of a black substrate so that the presence of the liner is obvious. The liner, substrate, or both may also carry markings (e.g., stripes, arrows, or the words "Peel Here") that highlight a portion of the container from which the liner can be initiated to peel off the substrate.

[0180]

[0198] Furthermore, the liner should be selected to have sufficient barrier properties to maintain the desired conditions within the compartment, taking into account the barrier properties of the substrate at the point where the liner and substrate are laminated. Food containers are generally intended to maintain a desired atmosphere (i.e., gas content and / or humidity), the presence or absence of compounds within the compartment, or other physical or chemical properties within the compartment containing food ingredients. For example, food ingredients that are relatively susceptible to discoloration or deterioration in the presence of oxygen in the atmosphere may be packaged in an atmosphere where oxygen is substantially depleted, such as an atmosphere of nitrogen, argon, carbon dioxide, or carbon monoxide. Such packaging techniques are generally called gas-substituted packaging, or MAP techniques.

[0181]

[0199] For containers intended for use in combination with desired compartmentalization conditions, a liner material should be selected that can maintain those conditions under the expected conditions of the container's use. Such selections are within the realm of knowledge to those skilled in the art.

[0182]

[0200] For example, meat and poultry products can be packaged in a container in which the substrate is made from PET material (e.g., amorphous PET or PETG), and the liner and lid are each made of a laminated polymer material. In this example, the liner may have substrate sides made of ULDPE or LLDPE, a nylon sheet to impart tensile strength to the liner, an EVOH or PVOH sheet to prevent moisture and vapor from passing through the liner, and a lid side made of the same material as the liner sides of the lid (i.e., to promote thermal fusion of the liner and lid when heat is applied to the opposing surfaces). The lid in this example may have the same layers as the liner. In one embodiment, the liner and lid are identical (for example, in cross-section, the two sheets have the same composition such that only in a reversible configuration the "upper" of one sheet contacts the "upper" of the other), for example, in one embodiment, a portion of the liner is laminated to a convex surface of the substrate, and a second portion of the liner can fold across the opening of the convex surface to form a flap that can seal itself (i.e., the liner and lid are part of the same sheet of polymer or laminate).

[0183]

[0201] In embodiments where a rapidly cooled polymer sheet is used to enhance adhesion, it may be preferable that the directly cooled surface of the sheet (e.g., the surface exposed to water in a water-cooled blow extrusion process, the surface facing a cooled metal surface in an injection molding process, or the surface in contact with a cooled extrusion die) is attached to the sheet to be bonded. Therefore, for example, in an article where a rapidly cooled, relatively thin liner sheet having an EVOH layer sandwiched between two LLDPE layers is bonded to a normal (i.e., unquenched) relatively thick PET substrate sheet, the LLDPE surface of the liner sheet to which the coolant was applied to induce rapid cooling is preferably the surface attached to the PET substrate. In this example, the liner sheet can be laminated onto the PET substrate sheet using a low-temperature nip roller, and the resulting laminate can be thermoformed and then cut to produce a shaped article, such as a tray from which the liner can be peeled off. In this example, if the PET sheet is also rapidly cooled, the directly cooled surface of the PET could be attached to any surface of the liner sheet, just as the directly cooled surface of the liner sheet could be attached to any surface of the substrate sheet. Enhanced adhesion can be achieved by lamination, where both opposing surfaces of adjacent sheets are directly cooled surfaces of a rapidly cooled polymer sheet. By selecting and arranging the directly cooled surfaces of the laminated sheets, those skilled in the art can obtain and select from a variety of beneficial configurations.

[0184]

[0202] Because containers can be subjected to a wide range of ambient conditions, they should be constructed using liner materials that have approximately the same coefficient of thermal expansion ("shrinkage rate") as the substrate.

[0185]

[0203] lid

[0204] The identification of the material to be used as a cover is not important other than that the cover should be able to be attached to the liner and should exhibit all the properties required for the desired application (e.g., tensile strength, barrier properties, ability to bear print or adhesive labels, and surface appearance). The cover material may be the same as or different from the liner material.

[0186]

[0205] In one embodiment, the container is supplied in the form of a kit including a molded substrate (e.g., a tray or a ball) having a liner peelably laminated on its surface and individual lid materials supplied either as a roll or piece of lid material having a size and shape corresponding to a portion of the molded substrate to be attached to the liner with the lid.

[0187]

[0206] In another embodiment, the container is supplied in the form of a molded substrate (e.g., a ball or tray) having a liner peelably laminated on its surface, and the lid exists as an extension of the liner, molded and positioned so that the extension can break through the liner and fold over a portion of the substrate and attach to the liner (e.g., a "ball with a flap", the flap having a size and shape that sufficiently covers the shape of the ball with sufficient overlap along its periphery so that a seal can be formed between the flap and the portion of the liner that the periphery of the ball is covered by, the flap is sized and positioned so that the flap can fold over the orifice of the ball and contact the liner around its periphery to facilitate such a seal around the entire periphery).

[0188]

[0207] In another embodiment, the container is supplied in the form of an unformed (i.e., substantially flat or planar) piece of substrate material having a piece of liner material facing the substrate material (with or without an additional polymer layer, adhesive, barrier composition, or other material intervening between the pieces). The substrate and liner can be thermoformed simultaneously, and the lid is then attached to the liner. In yet another embodiment, the liner and lid are attached to each other (forming a compartment and optionally enclosing an article) before the liner and substrate are reversibly attached.

[0189]

[0208] Adhesion of polymer sheets

[0209] As disclosed herein, various layers (sheets) of polymer materials are intended to be combined to form laminated containers and other articles, although the layers / sheets are still intended to be separable from one another (e.g., peeled apart using ordinary human strength) in many embodiments. Adhesives described herein can be used to assemble such laminated structures. However, in some applications (e.g., food containers), it is preferable that the laminated structure be created in a manner that results in a laminated article in which the layers remain relatively securely related to each other until the layers are peeled apart by the user, without the intervention of adhesives between the layers. Disclosed herein are polymer sheets that peelably adhere to the surface of other polymers without the use of intervening adhesives, as well as methods for creating and using such sheets.

[0190]

[0210] Dissimilar polymer sheets (e.g., barefoot PE and PET sheets) generally do not adhere to each other without differences in electrostatic charge, and it is known that intervening wetting agents, sealants, or adhesives, co-extrusion of polymer layers, the inclusion of additives in one or both sheets to enhance adhesion, or heating one or both polymer sheets above their melting point while biasing them together are used. While these methods can be used to bond polymer sheets, their usefulness is limited to the creation of some of the laminated articles described herein.

[0191]

[0211] For example, due to government regulations, good manufacturing standards, and the additional cost of intervening agents (e.g., adhesives) between adjacent polymer sheets, many chemicals are not used in food packaging materials, and food containers preferably do not contain unnecessary components. For this reason, it is preferable to create containers that do not contain adhesives, wetting agents, or other chemical agents intervened between polymer layers. Some of the articles described herein may be used to contain food, and contact between food and adhesives or other agents between layers (direct or indirect contact, such as the movement of such agents across or around polymer layers) may cause contamination and regulatory concerns. In at least some embodiments, the food containers (and other containers) described herein preferably do not contain adhesives or other materials intervened between peelable polymer layers, and instead incorporate adhesive polymer sheets as described in this chapter.

[0192]

[0212] Furthermore, methods for peelably bonding polymer sheets to each other may impose manufacturing limitations that make such methods difficult to use on a large scale. For example, some PE films can be peelably bonded to PET substrates if the PE is heated above its melting point and compressed against the PET. Thus, for example, a 2-mil PE sheet can be peelably bonded to a 20-mil PET substrate by laminating two sheets and passing them through a high-temperature nip roller that induces the melting of the PE. However, such a process may limit the rate at which the high-temperature nip can transfer heat to the PE film, thereby resulting in a relatively slow processing speed and making commercial-scale production difficult. Similarly, it may be difficult to reliably deliver adhesives and wetting agents between two polymer sheets at high processing speeds. Articles made using bondable polymer sheets can generally be manufactured at higher line speeds because these process limitations do not exist.

[0193]

[0213] The intervention of adhesives, wetting agents, or other materials between polymer sheets can also reduce the recyclability of "webbing" (i.e., laminated polymer material trimmed or extruded from articles manufactured during the manufacturing process) that is produced as a byproduct of the thermoforming manufacturing process. Since the laminated polymer sheets of webbing can be separated from each other without any adhesives or other chemicals adhering to any of the sheets, the resulting separated sheets can be recycled or reused more easily than sheets from similar processes that utilize such chemicals.

[0194]

[0214] It has been discovered that the laminated articles described herein can be made using polymer sheets that can be peelably bonded to each other without the use of intervening adhesives or wetting agents and without applying heat before thermoforming. Polymer sheets that peelably bond to other polymers include sheets in which the surface of the sheet that bonds to the other polymer is rapidly cooled, such as by rapidly cooling a liquid in a blow molding process or by rapidly cooling a liquid (or liquid-cooled metal surface) in a sheet injection molding process. Such sheets can be peelably bonded to the other polymer by biasing the sheet toward the other polymer with the rapidly cooled surface facing the other polymer, such as by using a low-temperature nip-roller process. The rapidly cooled surface may be the surface of a thin liner sheet biased toward the surface of a relatively thick substrate sheet. Alternatively, the surface of a relatively thick substrate sheet can be rapidly cooled and biased toward the surface of a relatively thin liner sheet. In either configuration, the two surfaces are bonded by biasing the rapidly cooled surface toward the other, particularly when the two surfaces are coherently biased together over a large area, such as by compressing the two sheets toward each other between a roller and another surface such as a second roller. In fact, both opposing surfaces can be cooled rapidly.

[0195]

[0215] The properties of a rapidly cooled polymer sheet surface that produces peelable adhesion are considered to include its tackiness, deformability, and cohesiveness. In this regard, "tackiness" refers to the presentation of a slightly viscous tactile sensation, such as a feeling of releaseable adhesion to the fingertip when a finger is pressed against the surface perpendicular to the surface and then withdrawn in the same direction. "Tackiness" also refers to the presentation of friction, which can be measured by the coefficient of static friction that can be measured when the rapidly cooled polymer surface is attached to a substrate surface. Relatively tacky materials will present a higher coefficient of static friction when stationary against the substrate surface than less tacky materials when stationary against the same surface. "Deformability" refers to the ability of a rapidly cooled polymer surface to deviate from its original form and more closely resemble the form of the polymer surface being biased. "Cohesiveness" refers to the ability of a rapidly cooled polymer surface to retain substantially a single polymer substance (i.e., without tearing or shattering) when biased against the polymer surface.

[0196]

[0216] The materials described in this chapter are referred to as “rapidly cooled” polymer sheets, but the benefits of these materials do not necessarily depend on the quenching period. Rather, the benefits are the combination of properties (i.e., tackiness, deformability, and cohesiveness) presented by the rapidly cooled polymer sheet surface that make the material useful. Those skilled in the art should recognize that the surface and volume properties of polymer sheets can be mimicked by rapid cooling through the use of methods and reaction conditions that do not depend solely on the duration of polymer annealing. For example, the annealing of polymer chains and their distribution between amorphous and crystalline regions can be influenced by wettability, temperature, the presence of solvents, the presence of nucleating agents (or nucleating inhibitors) and other factors known in the art. Without being bound by any specific theory of operation, reducing the degree and range of crystallinity on the surface of the polymer sheet is considered an important factor in increasing the tackiness of the polymer surface, and methods and reaction conditions that tend to reduce the degree and / or range of crystallinity are preferred. While still not bound by any specific theory of operation, relatively low density is considered another desirable property induced by rapid cooling on the polymer surface, but it remains unclear whether the relatively low density is the cause of tackiness, coincides with tackiness, or both. Relatively low density coincides with polymer structures that have less order (e.g., less crystallinity) for most polymers. Furthermore, phase transitions in polymer phases with different densities can contribute to adhesion within polymers that may undergo such phase transitions (e.g., when compressed between rollers during lamination).

[0197]

[0217] Regardless of whether or not an adhesive was used in the bonding process, the degree of adhesive effectively maintained between the liner sheet and the opposing substrate sheet is preferably sufficient, so that the liner and substrate can be thermally formed by lamination within a fabricated article without substantially peeling the liner from the substrate. More preferably, the degree of adhesive is sufficient so that the article can not only be formed without substantial peeling, but can also be used for its intended final use without substantially unintended peeling. Depending on the application and use of the article, a greater or lesser degree of adhesive may be desirable for applications and articles where it is intended that there be liner layers that can be peeled off individually, specifically between adjacent liner sheets.

[0198]

[0218] For example, in a food container described herein having a thick, rigid substrate with a peelable liner attached thereto, the liner has a lid stock material bonded around its periphery to form a peelable leak-proof “pocket,” and the liner preferably adheres to the substrate to a sufficient degree so that the liner and substrate can be laminated and thermoformed into the shape of a tray without the liner peeling substantially away from the substrate (except for intentionally formed tabs, e.g., tabs included to facilitate peeling the liner from the substrate). More preferably, the food can be placed on a lid stock that is heat-sealed to the liner around the tray and food (e.g., under vacuum to remove gas from between the liner and the lid stock) to form a leak-proof food-containing pocket bonded to the tray, and the degree of adhesion between the liner and the substrate is sufficient so that these operations can be performed without substantially peeling the liner from the substrate. Even more preferably, the adhesion is such that the liner does not substantially peel away from the substrate even when the packaged food is subjected to handling and storage conditions that are typical of the wholesale and retail sale of food, until such peeling is intentionally initiated by individual desire to consume the food.

[0199]

[0219] The coefficient of friction and other properties of two bonded polymer sheets are typically evaluated empirically, and it is desirable that the magnitude and combination of properties are important, as the selected article or application tends to be functionally defined rather than numerically. Therefore, a person skilled in the art who intends to manufacture and use the articles described herein will often select materials empirically determined through reasonable trial and error, taking into account what is taught in this disclosure, to present properties sufficient to achieve the desired objectives.

[0200]

[0220] While not bound by any specific theory of operation, relatively rapid cooling of polymers tends to maintain the amorphous structure of polymer chains relative to each other and reduce the crystallization of polymer chains, while slower cooling promotes crystalline morphology and other ordered polymer structures. Relatively disordered polymer chain morphology is thought to increase the ability of polymer chains to bond with the surfaces they come into contact with (more than ordered morphology) because the chemical moieties on the chain that exhibit binding ability do not bond to other chains of the same polymer and therefore remain available to bond to parts at the surface. It is also thought that relatively disordered polymer chain morphology increases the ability of polymer chains to slip when biased to such surfaces (more than ordered morphology). Therefore, it is thought that rapidly cooled polymer materials can more closely match opposing surfaces and, even materials composed of the same polymer, can represent a greater / higher concentration of surface-binding parts than materials that can be cooled more slowly. In contrast, slow-cooled polymers can rearrange themselves to assume a more stable configuration of chains in terms of form and energy, thereby reducing the "adhesion potential" of such slow-cooled polymers to the surface they are biased towards.

[0201]

[0221] It is well known that the degree of crystallinity affects the barrier properties of polymer sheets in a relatively predictable manner. For example, the oxygen permeability of nylon and EVOH films tends to decrease as the degree of crystallinity increases. Therefore, the selection of polymers for liners and substrate sheets (and layers within sheets) should take their properties into consideration. For example, an EVOH layer in a liner sheet formed by sandwiching an EVOH layer between two LLDPE layers may have higher oxygen permeability when the sheet is formed by liquid-cooled blow extrusion than when a sheet with layers of the same dimensions and composition is formed by a normal (air) blow extrusion process. In such cases, the thickness of the EVOH layer in a liquid-cooled blow extruded liner sheet may need to be increased if the sheet should exhibit the same oxygen barrier properties as a sheet formed by (air) blow extrusion. Such modifications to known polymer sheet designs are within the realm of knowledge to those skilled in the art, although empirical trial may be necessary.

[0202]

[0222] The tackiness and deformability of rapidly cooled polymers are thought to be related in that as the deformability of a polymer increases, the tackiness required for peelable adhesion to the polymer surface decreases. Similarly, as the tackiness of a polymer increases, the tackiness required for peelable adhesion to the polymer surface decreases. Those skilled in the art will understand that the composition, properties, and manufacturing methods of polymers are often adjusted through reasonable empirical trials, and such trials are well known to such people.

[0203]

[0223] The adhesive force between the cooled polymer surface and the polymer surface to which it adheres should be sufficient to maintain adhesion during the manufacture of the articles described herein and during their normal (pre-peeled) use. The adhesion between the cooled polymer surface and the polymer surface should not be so strong that the two polymers cannot be separated by a user of ordinary human strength, nor so strong that either polymer breaks before it can be peeled from the other. As an example, in retail food containers where a rapidly cooled polymer sheet is used as a liner for the substrate, the liner should adhere to the substrate sufficiently so that it adheres and remains attached to the container as it is made, transported to a food processor for filling, and used to contain food through processing, transport, and wholesale and retail sales.

[0204]

[0224] A disadvantage of insufficient adhesion between liner sheets and substrate sheets is that if the sheets are not pressed uniformly against each other, air pockets may be created between the sheets during lamination. The formation of such air pockets can be induced when the laminated sheets are very sharply "pinched," that is, when the laminated sheets are deflected from a planar shape and the radius of curvature of the deflection is too small. When laminated sheets with air pockets between them are thermoformed, the heat of thermoforming can cause the air in the pockets to expand, potentially preventing adhesion between the parts of the sheets that were intended to be bonded. The materials and processes used to create the fabricated laminated articles described herein should therefore be selected to reduce the occurrence of air pockets. Two important ways in which the occurrence of air pockets can be reduced are by laminating the sheets flush with each other (i.e., in planes that are substantially wrinkle-free and facing each other, such as by passing them through high-temperature or low-temperature rollers), and by reducing the curvature angle of any deflection the laminated sheets experience. As a guideline, many thermoforming and plastic sheet lamination processes can be carried out without laying the sheets around any corners with a radius of curvature of less than 2 inches, and the selection of materials that adhere flush to each other and remain laminated when bent around corners with a radius of curvature of 2 inches or more, with no air pockets between the sheets, should be suitable for producing the articles described herein.

[0205]

[0225] Such containers can be sold in kit form, which includes a substrate having a rapidly cooled surface and a polymer liner sheet bonded to it by a sealing material adapted to bond with the liner sheet (by adhesion, bonding, or melting). Using such a kit, food processors, retailers, or others can place articles (e.g., food ingredients) on or inside the container on a surface that seals the articles within a compartment by the articles coming into contact with the liner and bonding the lid stock to the liner around the articles.

[0206]

[0226] The materials used to create the adhesive polymer sheets described herein are not important other than that they should be able to exhibit the properties described herein. For example, PE and other polyolefins are considered suitable materials that can be rapidly cooled and exhibit the properties described herein when cooled in this manner during their manufacture. A well-adhered polymer sheet is created, for example, by rapidly cooling a rapidly cooled polymer surface that exhibits peelable adhesion to a smooth PET substrate when PE and ULDPE polymers are compressed and biased together using a low-temperature nip roller and then thermoformed.

[0207]

[0227] A multilayer film having a rapidly cooled surface can be used as an adhesive polymer sheet, as long as a rapidly cooled polymer is present on at least one surface of the sheet. A sheet having rapidly cooled polymers on both sides is suitable and can be manufactured, for example, by bonding two sheets back-to-back, each having a rapidly cooled polymer surface on its front. Such a double-faced sheet can be used to delaminate two polymer substrates together by pressing a laminate having two substrates with a double-faced sheet interposed between them.

[0208]

[0228] The properties of the surface to which the adhesive polymer sheet adheres are not important. However, such a surface should be relatively smooth to facilitate the bonding between the sheet in close proximity and between the rapidly cooled polymer layer and the substrate. Polymer substrates (e.g., PET, PETG, and polystyrene) are considered suitable, and other polymers are equally likely.

[0209]

[0229] The method for producing the adhesive polymer sheets described herein is not critical and is considered far less important than the fact that the adhesive polymer surface is rapidly cooled from a molten state during its production. The preferred method of production is by a liquid-cooled blow extrusion process. Equipment for performing liquid-cooled blow film extrusion is available from at least two manufacturers: Windmoeller & Hoelscher Corporation (Lincoln, Rhode Island, USA, particularly AQUAREX brand liquid-cooled blow film extruders) and Brampton Engineering (Brampton, Ontario, Canada, particularly AQUAFROST brand liquid-cooled blow film extruders). Various film injection molding systems can also be used, provided that they are made from a polymer capable of exhibiting the properties described herein when at least one surface of the film is rapidly cooled, and that surface is rapidly cooled.

[0210]

[0230] Rather than rapidly cooling the entire polymer sheet, only one or more portions of such a sheet can be rapidly cooled. For example, a molten polymer extruded material can be layered on top of an existing film and then rapidly cooled (for example, by immersing the film supporting the molten surface in a liquid, or by pressing the molten surface against a liquid-cooled metal surface, such as a liquid-cooled die connected to a metal roller or extruder with circulating cold water). Furthermore, for example, a polymer sheet can be formed by conventional methods, and its surface is not rapidly cooled. The surface of the sheet can then be melted (whether or not other parts of the sheet are melted), and the melted surface is rapidly cooled.

[0211]

[0231] In one embodiment, a lamination of polymer sheets suitable for thermoforming into a molded article having a peelable surface (e.g., a food container) is created by laminating at least two polymer sheets, wherein at least one of the opposing surfaces of the two adjacent sheets has a rapidly cooled surface having the properties described herein. During lamination (e.g., by the laminated sheets passing between low-temperature nip rollers or other compression devices), the sheets adhere to each other in a peelable manner. Three or more sheets can be peelably laminated in this method, provided that at least one surface between each pair of adjacent sheets has a rapidly cooled surface having the properties described herein. Naturally, laminations of multiple sheets can also be created, with some adjacent sheets being peelable due to the presence of rapidly cooled surfaces having the properties described herein, and others being peelable due to the presence of a peelable adhesive intervening between them.

[0212]

[0232] In another embodiment, multiple identical sheets are layered on a substrate and are individually peelable from the structure because at least one surface of each pair of adjacent sheets has a rapidly cooled surface having the properties described herein. Thus, a recycled PET substrate can be covered with multiple laminated sheets of a two-layer film, each sheet of the two-layer film having a rapidly cooled ULDPE layer associated with an unused PET layer. The rapidly cooled ULDPE layer of a sheet adjacent to the substrate adheres peelably to the substrate, revealing the unused PET layer on its opposite surface. A second sheet is laminated on which the ULDPE layer of the sheet adheres peelably to the unused PET layer of the first sheet, and the second sheet has its unused PET layer set away from the substrate. Additional layers can be laminated thereon, and the laminations can be thermoformed, with the thickness of the lamination being substantially limited only by the operating characteristics of the thermoforming machine and the thermoformability of the polymer in the lamination. Similarly, the first polymer sheet (adjacent to the substrate) may have rapidly cooled ULDPE associated with both sides of the PET sheet such that the sheet adheres peelably to the substrate on one side, and a rapidly cooled ULDPE layer is present on the other side that can adhere peelably to the unused PET layer of the PET-ULDPE bilayer sheet. Additional bilayer sheets may be laminated thereon, each substantially facing the substrate with its PET side.

[0213]

[0233] Container creation

[0234] The articles described herein can be produced using known thermoforming apparatus and conditions. Naturally, the apparatus and conditions should be selected based on the identification and characteristics of the material to be processed. The selection of appropriate thermoforming conditions based on the identification of the material to be processed is known to those skilled in the art.

[0214]

[0235] The container is formed by reversibly attaching a liner to a substrate and by attaching a lid to the liner to form a compartment for containing the material.

[0215]

[0236] The substrate can be formed into the desired shape before or after the liner is removably attached to it. However, it may be convenient to attach the liner to the substrate simultaneously (or nearly simultaneously) to form one or both the liner and the substrate, at least for a thermoformed container. Preferably, the substrate has a substantially greater thickness than the liner (for example, a 10, 20, or 50 mil substrate can be bonded to a 1, 2, or 5 mil liner). Preferably, both the liner and the substrate are thermoformable, preferably under general thermoforming conditions.

[0216]

[0237] In one embodiment, the substrate, liner, and lid are subjected to thermoforming conditions simultaneously, and the reversible attachment of the liner and substrate, as well as the attachment of the liner and lid, occur substantially simultaneously during the thermoforming operation. Containing articles within the compartment of a container produced by this method requires either the compartment remaining open after the thermoforming operation, or intervention between the liner and lid during thermoforming so that the articles are contained within the compartment following thermoforming.

[0217]

[0238] One or more tabs may intervene between the substrate and the liner, between the liner and the cover, or both. If the tabs extend beyond the edges of the two sheets, they can be used to facilitate the separation of the first sheet after thermoforming or sealing. The tabs may be attached to either sheet or not to either sheet.

[0218]

[0239] In one embodiment, the tab is relatively firmly bonded to the lower surface of the liner sheet placed on the substrate. The tab is either peelably bonded to or not bonded to the substrate below so that the liner sheet placed on top can grasp the tab from the substrate below and peel off by pulling the sheet placed on top by the tab. The tab can be formed, for example, by folding a piece of liner (e.g., a corner) onto itself.

[0219]

[0240] In the second embodiment, the tab is either peelably adhered to or not adhered to the liner sheet on top so that the liner sheet on top can be peeled off the surface by scraping the edge of the liner sheet on top (for example, with a fingernail or edge tool such as the tip of a fork) and then grasping the partially peeled portion of the liner sheet and pulling the partially peeled portion towards the surface, thereby manually peeling the rest of the liner sheet on top from the surface.

[0220]

[0241] Loose laminations of polymer sheets can be thermoformed using the materials and methods described herein, but it may be convenient to bond the substrate and liner sheets to each other before thermoforming (for example, to facilitate the assembly, storage, transport, handling, manufacturing, and alignment of the sheets). The means used to bond the sheets to each other are not important, but preferably do not affect the properties of the sheets in the area of ​​the sheet to be thermoformed. For example, sheets can be bonded together by using an adhesive applied to the common edge of the first and second sheets, by melting the common edge of the sheets, by stapling the sheets together, by bonding the sheets together using an adhesive applied between the sheets in the area between the formed portion of the sheet and the area between the sheets, or by other means such as providing a continuous (i.e., much longer than the width) roll of substrate sheets with liner sheets bonded toward or opposite to it.

[0221]

[0242] The configuration consists of an easily removable lid stock, a liner, and a circuit board.

[0243] The advantages of food trays and other containers having peelable liners (e.g., recyclability) are described elsewhere in this specification, as are the advantages of other containers further comprising trays and lid stock material attached to the top liner to form sealed compartments. It may be advantageous to create containers from which the liner and lid stock can be removed without damaging the compartments. The ease with which compartments can be removed from the container substrate without damage may affect the desirability of the container to the user performing such removal. Such containers may be displayed in the place of sale of the goods contained therein, and in this case the appearance of the container is also important. Described in this chapter are substrate, liner and lid stock configurations that can present these characteristics.

[0222]

[0244] In this configuration, the lid stock and liner adhere to each other more visibly than the liner would adhere to the surface beneath it, preferably along the periphery of the container, at least in part of the container. Furthermore, the relatively viscous bonding zone should preferably occur along at least one edge of the liner sheet so that the compartment formed between the liner and the lid stock can be easily and intact peeled away from the surface beneath the liner by grasping and peeling the lid stock away. Because the lid stock adheres relatively viscously to the liner at the edge of the liner, lifting the lid stock toward the liner initiates the peeling of the liner from the substrate when lifting and separating it from the substrate at the edge of the liner. This configuration facilitates the manufacture of containers from thermoformable laminates described herein by adding a lid stock to those of conventional methods, etc.

[0223]

[0245] In one structure, a relatively thick substrate (e.g., PET with a thickness of 20-40 mils) has a single relatively thin liner (e.g., 1-6 mils thick) bonded to it. In this embodiment, the thin liner is a homopolymer sheet, such as a polyethylene sheet, that is peelably bonded to the substrate over substantially the entire surface of the substrate. The substrate and the bonded liner have a shape including a recess with a rim surrounding it (e.g., formed by thermoforming a laminated sheet), the rim being substantially planar, preferably so that a flat sheet in contact with the rim around the periphery of the recess seals the recess. A lid stock material (e.g., a homopolymer or laminated polymer sheet with a thickness of 1-10 mils) is preferably taut so that it is in contact with the liner around the rim of the recess and has a substantially flat shape within the periphery of the recess. The lid stock is bonded or fused to the liner at least one portion of the rim, preferably bonded or fused around the entire periphery of the recess. If the liner and the lid stock in contact with it are made from substantially the same material (to the extent necessary for identification will be understood by those skilled in the art), the liner and lid stock can be fused by heating each above the melting temperature of the material, bringing them into contact (these terms are used in the field of plastic packaging, preferably by biasing them toward each other, such as by forming a high-impact seal or a low-impact seal), and then cooling the material below its melting temperature. The liner adheres or melts to the lid stock at at least one edge of the liner / substrate lamination. The adhesion or melt is sufficiently elastic that the liner peels away from the substrate when the lid stock is pulled away from the substrate. The resulting packaging is useful for enclosing an article (e.g., a food article or a liquid-sensitive compartment) within a compartment formed between the lid stock and the liner while the liner is engaged with the substrate, and for peeling the compartment away from the substrate without necessarily destroying the compartment (e.g., by peeling the lid stock from where it adheres or melts to the edge of the liner / substrate lamination).Optionally, the container may include a zippered, resealable opening located either within the lid stock or between the lid stock and the liner to facilitate access to and re-close the compartment between the lid stock and the liner.

[0224]

[0246] In alternative embodiments, the container comprises two or more liners, such as an embodiment of a compartment containing a fluid storage area formed between a perforated liner and a non-perforated liner, and at least one liner is bonded or melted to the lid stock. For example, the container may have a substrate formed to include a recess, and a non-perforated liner peelably bonded to the substrate in at least a portion thereof defining the recess, the perforated liner melting (optionally bonded) with the non-perforated liner around the rim of the recess, and the lid stock melting or melting with the perforated liner around the rim of the recess, including to the edge of the perforated liner. When the lid stock peels away from the substrate, at least the perforated liner (and optionally the non-perforated liner, such as if melted with the perforated liner) is pulled away from the recess, taking with any objects in the compartment between the lid stock and the perforated liner that cannot be mated through the perforation. If the non-perforated liner is not peeled off from the substrate at the same time, the material that can pass through the perforation (e.g., liquid) can be separated from other materials in the compartment and may remain associated with the substrate (and can subsequently be separated from the object by discharge or pouring, or by peeling the non-perforated liner from the substrate). For example, if the non-perforated liner is melted with the perforated liner around the rim, it can be peeled off from the compartment, which may contain materials larger or smaller than the perforation, by peeling the lid stock from the container without separating the lid stock and the liner from each other. Therefore, for example, such a container can be used to contain meat slices in the recesses of the container, liquid seeping out by the meat can be moved into a fluid storage area between the perforated liner and the non-perforated liner, the meat can be removed from the substrate into a sealed compartment, and any seeping liquid can be removed either simultaneously (by peeling off the lid stock and the non-perforated liner from the substrate at the same time) or after the compartment has been removed (by first peeling off the lid stock and associated compartment, and then peeling off the non-perforated liner from the substrate).

[0225]

[0247] In various embodiments, one or more liners and lid stocks may be multiple laminated polymer sheets, such as sheets having various polymer laminations that impart properties such as barrier properties, tensile strength, adhesiveness, melting ability with opposing polymer surfaces, bonding ability with adjacent laminations, or other characteristics. Alternatively, the liners and lid stocks may be homopolymer sheets.

[0226]

[0248] The substrate may have multiple recesses, each of which may be covered with the same liner sheet or a different liner. Some or all of the recesses may have a single lid stock attached to them. Similarly, multiple lid stock pieces (composed of the same or different materials) can be fixed around or across a single recess (for example, two closely spaced lid stock pieces with parallel edges can be fixed across a recess to obtain a compartment that is closed except for the cuts defined by the edges of the lid stock pieces). To facilitate manufacturing, filling and assembly, it is preferable to manufacture the container in two pieces, namely a first piece containing a substrate and all liners peelably bonded thereto (preferably in a shape including any recesses formed by thermoforming a laminate of the substrate and liner), and a second piece containing the lid stock, then fill the container with the desired items (e.g., electronic components or chicken parts in the recesses), and then seal the lid stock onto the molded and filled liner and substrate piece. The first piece may contain a plurality of separable containers, each having a recess, which can be separated by cutting or tearing the first piece after sealing the lid stock into it.

[0227]

[0249] The container types described in this chapter may be particularly advantageous when the container is formed and fabricated in a manner that facilitates the peeling of at least one liner from the substrate when peeling the lid stock from the substrate. This can be achieved by bonding or melting the liner and lid stock at the edge of the liner so that peeling the lid stock past the bonded / melted edge initiates the peeling of the liner from the underlying surface (i.e., from the substrate or from another liner intervening between the substrate and the bonded / melted liner to the lid stock). Such bonding / melting can be achieved by bonding or melting the liner and lid stock before bonding the liner. However, such manufacturing methods may be difficult to implement and may prevent packaging the item between the liner and the lid stock. More typically, the liner bonded to the substrate is manufactured separately from the lid stock, and the lid stock and liner are bonded or melted after packaging the item in the compartment formed between the liner and the lid stock.

[0228]

[0250] The liner edge can be bonded or melted to the lid stock by bringing the liner edge into contact with the lid stock during the bonding / melting process. For ease of manufacturing, edge reinforcement, and aesthetic reasons, thermoformed containers often have curved or bent edges. Bonding the lid stock to the edge is typically not particularly relevant to prior art containers. Instead, the lid stock is usually trimmed near the container edge after being attached, and the lid stock edge is optionally heated to round or shrink around the container edge to fit more closely to it. In the configurations described in this chapter, it is important that the liner edge bonded to the substrate is relatively ductile (compared to the tackiness of the liner bonding to the substrate) so that the liner can be peeled away from the substrate when the lid stock is peeled off from it. To facilitate the bonding of the liner edge to the lid stock, the liner edge should be in close proximity to the lid stock when bonding the liner to the lid stock (by bonding, adhering, melting, or otherwise). Such close-range confrontation can be achieved by virtually any method known in the art.

[0229]

[0251] One way to bring the edge of the liner and the lid stock material into close proximity during bonding between them is to bias the lid stock and the liner together into a form in which the lid stock and the portion of the liner in contact with it are bonded by the liner edge being held against the lid stock during the application of ambient conditions (e.g., temperature, radiation, pressure, adhesive provision). As an example, a liner having a surface that bonds to the lid stock made of the same material as the surface that bonds to the liner of the lid stock material can be bonded to the lid stock material by bringing the two surfaces into contact at a temperature above the melting point of the common material.

[0230]

[0252] When the location where the peeling force applied to the lid stock material is transmitted to the liner bonded to the lid stock is known, it is preferable that the liner and lid stock be maintained in that location through close opposition between them during bonding. Similarly, the locations where such close opposition is maintained during bonding between the liner and lid stock can be indicated on the finished container so that the container user can select those locations as suitable locations for peeling.

[0231]

[0253] Barrier composition

[0254] The specifications and compositions of barrier compositions that can intervene between polymer sheets used in articles, as well as methods such as those described herein, are not important. Those skilled in the art will recognize that substantially any material can be used as a barrier composition between two polymers, as long as the material substantially prevents the melting of two polymers under conditions that allow at least one polymer to be thermoformed. A wide range of such compositions are known for this purpose. Barrier compositions used to create articles molded for use with food should, of course, be selected to be compatible with the food ingredients.

[0232]

[0255] Examples of suitable barrier compositions include various liquids containing adhesives (e.g., peelable adhesives such as pressure-sensitive adhesives), known polymer release agents, polymer films or paper films interposed between polymer layers, and low-tack silicone oils.

[0233]

[0256] A composition intervened between two surfaces (between a first polymer sheet and a second polymer sheet or between two second polymer sheets, as described herein) can act as a barrier composition between the two surfaces if the composition covers at least one of the two surfaces under thermoforming conditions, thereby preventing contact between the surfaces and melting of the two surfaces under thermoforming conditions.

[0234]

[0257] A barrier composition prevents the melting of opposing polymer surfaces only when it intervenes between surfaces under thermoforming conditions. For this reason, the barrier composition must intervene between surfaces over all areas where inter-surface melting is undesirable. This can be achieved in various ways, including the use of liquid and solid barrier compositions. When a laminate is to be thermoformed to create multiple molded objects that are melted on at least one part (e.g., a laminate of meat trays melted on only a single fragile extension of the tray at one corner) rather than on some parts, the barrier composition intervenes between polymer sheets in areas where melting is undesirable, but not in areas where melting is desirable.

[0235]

[0258] The liquid barrier composition should be selected such that it completely covers (i.e., wets) at least one surface over the entire area where melting is undesirable. This can be achieved by selecting a liquid barrier composition (i.e., a composition that is liquid at least under thermoforming conditions, regardless of whether it is liquid at the point of contact with the surface) that has a surface tension much greater than the surface energy of the surface in contact with the liquid (i.e., at least 2 dynes per centimeter, preferably at least 10 dynes per centimeter). This difference in surface energy should ensure that the liquid barrier composition completely wets (i.e., covers) the surface area where melting is undesirable. Preferably, the liquid barrier composition has a surface tension much greater than the surface energies of both surfaces so that the liquid does not move between the surfaces at the point when the two surfaces are tightly biased toward each other.

[0236]

[0259] The solid barrier composition (e.g., a polymer sheet) should be selected so that the solid covers the entire area where melting is undesirable. The identification of the solid is not critical unless it prevents a portion of the polymer sheet to be thermoformed from reaching the conditions for thermoformation. The solid barrier composition can prevent surface melting and / or, for various reasons sufficient to provide a suitable material as a solid barrier composition, it may not melt on one or both surfaces. While some solids can be predicted to act as suitable barrier compositions, others may require empirical testing (e.g., thermoforming two sheets of polymer with a solid intervened between them) to determine their suitability. In any case, the selection of a suitable solid barrier composition is known to those skilled in the art.

[0237]

[0260] Another type of barrier composition that can be used is one that is incorporated as an additive into one or both of the polymer sheets. These compositions melt and "bloom" on the polymer surface when heated, pressed, stretched, or otherwise manipulated. If such a composition is included in one or both of the polymer sheets such that it blooms on the surface of at least one sheet under thermoforming conditions and prevents contact between the polymer sheets themselves, the composition can be used as a barrier composition in the articles and methods described herein. A wide range of compositions exhibiting such blooming behavior are known in the art.

[0238]

[0261] glue

[0262] The identification and composition of adhesives that can intervene between polymer sheets used in articles and methods as described herein are not important. Those skilled in the art will understand that substantially any material can be used as an adhesive between two polymers, as long as the material reversibly bonds the two polymer layers and does not require a force greater than what can actually be applied to the polymer layers by a person with ordinary force to separate them. A wide range of such compositions are known for this purpose. For articles that come into contact with food as described herein, any adhesive used should be selected to be compatible with the food ingredients.

[0239]

[0263] When an adhesive is used between two polymer sheets, the adhesive can be used to cover substantially the entire contact surface area between the two sheets (to "flood coat" the sheets). The adhesive can be removed from a portion of the contact surface area because it can melt (in the absence of other barrier compositions) or because it leaves unbonded portions to facilitate delamination.

[0240]

[0264] The adhesive used between the peelable polymer sheet and the underlying surface is preferably peelable, meaning that the polymer sheet can be peeled from the surface by a person with normal force, preferably without tearing or substantially stretching the sheet. Preferably, an adhesive having a covering weight of about 0.6 to 15 ounces per inch is used to bond the peelable sheet to the underlying surface.

[0241]

[0265] A wide range of suitable adhesives are known in the art and can be used as described herein. Pressure-sensitive adhesives are among the suitable adhesives that can be used. Similarly, adhesives that adhere to one of two bonding surfaces are suitable (when one surface peels away from the other) and are preferred in certain embodiments. For example, if an adhesive adheres to a polymer sheet to which the sheet is more easily peeled than the surface to which the adhesive adheres, the adhesive tends to remain on the sheet when the sheet peels away from the surface.

[0242]

[0266] Various compositions and surface treatments can be used to reduce the force required to pull the adhesive from the surface, and such compositions and treatments can be used to adjust the adhesion of the adhesive to the surfaces described herein.

[0243]

[0267] Specific examples of adhesives that can be used in the articles described herein include polysiloxane adhesives, rubber cements, and acrylic adhesives (for example, the MULTI-LOK brand family of water-based pressure-sensitive acrylic adhesives manufactured by National Adhesives of Bridgewater in New Jersey, USA).

[0244]

[0268] Thermoforming apparatus and conditions

[0269] The articles described herein can be produced using known thermoforming apparatus and conditions. Naturally, the apparatus and conditions should be selected based on the identification and characteristics of the material to be processed. The selection of appropriate thermoforming conditions based on the identification of the material to be processed is known to those skilled in the art.

[0245]

[0270] printing

[0271] Text, images, or other graphic materials can be printed on one or more surfaces of one or more polymer sheets as described herein. A wide range of materials and methods can be used to print such materials onto the surface of polymer sheets. An inherent difficulty in printing on polymer materials is that the print can easily shift from the polymer surface due to heat, light, or mechanical friction, thereby reducing print quality. Furthermore, contact between the material used for printing and other materials within the area may be undesirable.

[0246]

[0272] The adhesiveness for binding a printed matter to a polymer sheet can be affected by surface treatment of the polymer sheet before printing on the sheet, as described herein with respect to the adhesive. For example, corona treatment and plasma discharge techniques can increase the surface energy of the polymer surface, making it more likely to be affected by a stronger bond by the printed matter. Similarly, surface treatment (e.g., corona treatment) of the polymer surface having the printed matter thereon can increase the surface energy of the surface (including the portion where the printed matter is visible). Preferably, the surface energy of one surface of two polymer sheets to be adhered or joined within the article described herein is increased or decreased such that when the two sheets are separated from each other, most or all of the printed matter remains attached to one of the two sheets at the contact surface of the two sheets.

[0247]

[0273] Products formed by the preparation of inks, binders, materials and surfaces used to prepare the surface that receives the printing may include products that are undesirable for food products. Thus, when the articles described herein are to be used for either carrying out printing and containing or contacting food products, care should be taken either to select printing and surface preparation materials suitable for use in food containers (i.e., safe for consumption or insoluble in food), or to create a barrier between the food and any such materials (i.e., prevent the materials from migrating into the food).

[0248]

[0274] For example, in a food container consisting of a thick thermoformable substrate with a thin, peelable liner sheet peelably adhered to the substrate, substantially any material that does not move through the liner sheet under normal food packaging and storage conditions can be used for printing on the substrate or for preparing the surface of the substrate for printing. In at least some of the containers where the liner intervenes between the substrate and the food stored inside the container, the presence of the liner prevents or inhibits substantial movement of such components from the surface of the substrate into the food. Thus, even inks that are unsuitable for inclusion in food and that would normally dissolve in food can be used for printing on the substrate of a food container, as long as a liner sheet through which the ink cannot move under normal conditions intervenes between the food inside the container and the surface to which the ink is applied (regardless of whether other materials intervene between the ink and the food). If the text or image printed on the substrate should be visible through the liner, the liner should be sufficiently transparent or translucent to be so visible.

[0249]

[0275] One embodiment of a food container described herein (referred to as a “two-sided printed container”) is a generally flat tray or dish that bears printing suitable for food, visible from both sides of the container, even when the materials used in the printing process are unsuitable for contact with food. This embodiment includes both a substrate sheet (e.g., a relatively thick thermoformable material such as unused PET or RPET) and a relatively thin liner sheet (e.g., a transparent, one-piece PE sheet or a transparent or translucent multilayer sheet with layers of EVOH sandwiched between PE layers). Intervening between the substrate sheet and the liner sheet is a generally opaque printed sheet that bears text, diagrams, images, or other visual markings on one or both sides thereof.

[0250]

[0276] In a two-sided printed container, identification of the printed sheet should be fixed and installed between the liner and the substrate sheet (i.e., it can be melted, adhered, or joined with both the substrate sheet and the liner sheet, or it is sufficient to hold the printed sheet in place without compromising the structural integrity of the container with sufficient perforations to bond between the substrate and the liner sheet). In its assembled state, the two-sided printed container has a liner sheet on the surface that bears food, the liner sheet overlaps the printed sheet (such that the print on the printed sheet is preferably visible through the liner sheet), and the printed sheet overlaps the substrate (such that the print on the printed sheet is preferably visible through the substrate). In this assembled state, the substrate can provide bulk physical properties (e.g., rigidity and shape), the printed sheet can provide the desired appearance, and the liner sheet can prevent any undesirable substances present on or in the printed sheet or substrate sheet from migrating into the food that contacts the liner on the side of the liner opposite the surfaces facing the printed sheet and substrate sheet).

[0251]

[0277] As with other lined containers described herein, two-sided printed containers can be combined with lid stock material to close one or more orifices or spacers of the container. The lid stock can be peelably bonded or joined to one or more parts of the container, melted with one or more parts of the container, or a combination thereof. For food storage applications, a food-compatible lid stock is preferably sealed around the periphery of an area or cavity defined by a food-compatible liner material, which can be peelably or tackily attached to a base material. For example, a lid stock material having a surface made from the same material as the liner sheet (e.g., ULDPE) can melt with the liner sheet when the two surfaces face each other at a temperature sufficient to melt the material. The lid stock may have printing on it, and the printing may be performed before attaching the lid stock to the container (e.g., attaching a pre-printed packaging design), such attachment (e.g., affixing a "packaged" or "expired" date) and after sealing the container, or a combination thereof. Decals, stickers, price tags, cardboard tubes, and other known product packaging components can also be added during or after packaging.

[0252]

[0278] In certain embodiments of the two-sided printed container, the liner sheet and the substrate sheet are substantially transparent, and the printed sheet is substantially opaque and printed on both sides. In addition, one side of the printed sheet has a material on its surface that adheres to the liner sheet more visibly than the printed sheet would bond to the substrate of the finished container (i.e., the liner and printed sheet can be peeled off together from the substrate sheet). For example, the side of the printed sheet facing the liner sheet can be made from the same material as the opposing side of the liner sheet (e.g., each side may be the same PE) so that it melts when the two sheets are thermoformed or when they pass through a high-temperature nip roller that transfers enough heat to melt the opposing sides. Alternatively, a single container can be made by thermoforming a liner sheet, a printed sheet, and a substrate sheet. The opposing surfaces of the liner sheet and the printed sheet are made from the same material, and the opposing surfaces of the printed sheet and the substrate sheet are also made from the same material (though not necessarily the same as the opposing surfaces of the liner sheet and the printed sheet). Therefore, when the three sheets are thermoformed, the liner sheet melts with the printed sheet, and the printed sheet melts with the substrate sheet, resulting in a single container.

[0253]

[0279] In a two-sided printed container, printing on the side of the printed sheet facing the liner sheet may include, for example, recycling instructions, instructions for removing the printed sheet and liner sheet from the substrate sheet, instructions or diagrams for positioning the food contained on the container before sealing, and recipes or cooking instructions for the food contained. Printing on the side of the printed sheet facing the substrate sheet may include, for example, nutritional information, contact information of the food manufacturer or packager, recipes or cooking instructions for the food contained, instructions for disassembling the container and recycling one or more of its parts, trademark or trade dress materials and design or graphic materials.

[0254]

[0280] Meat trays and other molded articles

[0281] In one embodiment, the subject matter disclosed herein includes a meat tray comprising at least a substrate sheet and a liner sheet that are thermoformed simultaneously from the tray. As used herein, the term “thermoformed” is intended to encompass a variety of methods for shaping thermoplastic sheets or laminated sheets by heating the sheet and applying different pressures to opposing sides of the sheet to match the shape of the welded surface.

[0255]

[0282] While the subject matter of this disclosure is often described in terms of preferred embodiments of simultaneously thermoformable substrates and liner sheets, it will be understood after reading this disclosure that the subject matter also includes simultaneously forming the substrate and a single liner sheet, as well as forming the liner sheet and substrate by other means, such as die-cutting, injection molding, or blow molding. The substrate sheet is preferably a thermoformable plastic, but may be composed of other materials, such as metal.

[0256]

[0283] In one known thermoforming method, known as vacuum forming, a sheet is positioned adjacent to a female (or, less commonly, male) forming section, and vacuum is applied to pull the sheet towards the mold surface. The male mold section may be pressed against the sheet on the opposite side of the sheet from the female mold section to help conform the sheet to the shape of the female mold section. However, when the male mold is used to help form the shaped articles described herein, care must be taken not to prevent the separation of the substrate and the liner sheet and, as a result, the formation of the storage section.

[0257]

[0284] In preferred embodiments of the subject disclosed herein, a lamination comprising flat sheets of thin (e.g., 1 to 7 mils) plastic ("liner sheets") is positioned on the surface of a flat substrate sheet of greater thickness (e.g., 10 to 40 mils) to form a meat tray. Additional liner / substrate sheet laminations may be layered on top of the first lamination, with barrier compositions intervening between the laminations to prevent them from melting.

[0258]

[0285] The sheets can be supplied in either sheet form or roll form. For convenience of transport, storage, and thermoforming, laminated sheets may be supplied to the thermoforming machine in the form of continuous rolls, with barrier compositions interposed between the layers of the rolls. The rolls can be fed continuously through the thermoforming machine, and the length of each tray sheet is indexed and then thermoformed into a certain shape, namely a meat tray. The length and width of the rolls can be as needed. For example, a master pad roll may be 5 to 60 inches wide.

[0259]

[0286] The laminated sheets are thermoformed as a single unit into the shape of a desired article, for example, a meat tray having a liner sheet on top of the concave interior of a meat tray. During cooling, the tray maintains its thermoformed structure due to the thickness and rigidity of the substrate sheets, and the structure of the liner sheets can be set by thermoforming or supported by the presence of adhesive between the sheets.

[0260]

[0287] The meat tray is used in the same way as conventional trays, which should use a regular meat tray without a liner. However, unlike the prior art meat trays described above, there is no need to place or attempt to place a "diaper" or other absorbent liner inside the tray. After use, the top liner sheet can be simply peeled off to release any seepage isolated in the storage area between the substrate and the liner sheet or between multiple bonded liner sheets.

[0261]

[0288] The mold and the tray system thermoformed therefrom can be of various shapes. Generally, the resulting tray has a top-opening internal cavity with a floor and continuous side walls. The molded article may include rigid, flat, or other molded parts, similar to conventional meat trays and other food containers. The molded article may also have separate compartments for containing discrete food portions, and each compartment may have one or more storage compartments communicating with the storage compartments inside the compartment or in other compartments, as necessary.

[0262]

[0289] Use of container

[0290] The containers described herein can be used to isolate articles contained within a compartment. An important intended use of the containers described herein (particularly layered storage containers) is to contain food products such as pieces of meat, poultry, or seafood that tend to release liquid (to "purge" the liquid, sometimes referred to as "purging"), otherwise contaminating the container, and contaminated containers are usually not suitable for recycling.

[0263]

[0291] Containers for disposing of food products often contain absorbent material to absorb purging. Even with absorbent material present, containers can become so soiled that consumers do not want to recycle them, and many local authorities prohibit such items from being included in recycling flows. Even without absorbent material attached to the container, consumers may rather discard the entire container than attempt to sort and clean its various parts due to the uncleanliness of the absorbent material, especially considering the soiling that would otherwise require such cleaning. Food packaging waste constitutes a substantial portion of the current solid waste flow that ends up in landfills.

[0264]

[0292] Food products contained in the containers described herein are disposed of in much the same way as conventionally known containers. However, once the food products are removed from the container, the lid and liner can be peeled off the substrate and discarded, resulting in a substantially clean substrate suitable for inclusion in the recycling process. By recycling the substrate and discarding only the relatively thin liner and lid layers, the volume and weight of material sent to the waste disposal site can be substantially reduced. Moreover, consumers are increasingly seeking products with minimal non-recyclable packaging.

[0265]

[0293] The food containers described herein are typically used with a preformed substrate having a liner sheet removably adhered to its surface. Preferably, the substrate has a configuration that includes a recess (e.g., a bowl or a high-walled tray) for containing foodstuffs. The liner covers the recess. After the foodstuffs are placed on or in the substrate, a lid material is attached to the liner material to form a closed compartment surrounding the foodstuffs (e.g., by adhering or melting a lid and the liner around the edge of the bowl or the wall of the substrate).

[0266]

[0294] A variety of liner and lid items have been used with prototype containers having substrates formed from amorphous PET or PETG. The identified suitable materials include at least the following laminated polymer sheets, namely,

[0295] a multilayer sheet consisting of LLDPE - tie layer - EVOH - tie layer - LLDPE,

[0296] a multilayer sheet consisting of (a mixture of ULDPE and LLDPE) - tie layer - EVOH - tie layer - LLDPE,

[0297] a multilayer sheet consisting of LLDPE - tie layer - EVOH - tie layer - PETG,

[0298] a multilayer sheet consisting of (a mixture of ULDPE and LLDPE) - tie layer - EVOH - tie layer - PETG, and

[0299] a high performance barrier film of the ICE (trademark, Bemis Europe, Soignies, Belgium) brand.

[0267]

[0300] The disclosures of all patents, patent applications, and patent application publications cited herein are hereby incorporated by reference in their entirety.

[0268]

[0301] Although the subject matter has been disclosed with reference to specific embodiments, it will be apparent to those skilled in the art that other embodiments and variations can be devised without departing from the true spirit and scope of the subject matter described herein. The appended claims cover all such embodiments and equivalent variations.

Claims

1. An article formed from a thermoformable sheet having a peripheral edge, The thermoformable sheet has sufficient rigidity to define the shape of the article. The article includes a body, which has an extension that extends periphery away from the body, The aforementioned extension is The peripheral edge of the thermoformable sheet, A bending region including a curved portion, intervening between the contact point between the main body and the extension and the peripheral edge, A peripheral flange intervened between the peripheral edge and the bending region, the peripheral flange being connected to the bending region by the elbow portion, It includes a bent portion intervened between the peripheral edge and the contact point, The bent portion has the shape of a rounded rectangular tray and a smooth periphery, and is sufficiently bent so that the peripheral edge of the thermoformable sheet is moved away from the periphery of the article. The main body has the shape of a tray, The shape of the tray has a concave compartment formed therein and does not include any conventional stacking protrusions. The extension completely encloses the concave section in its periphery, forms a rotated edge around the entire periphery, and forms a rounded layered extension at at least one position on the periphery of the article, thereby the article having a smooth periphery.

2. The article according to claim 1, wherein the extension includes a spacer interposed between the peripheral edge and the bending region.

3. The article according to claim 2, wherein the bending region connects the spacer and a part of the extension between the contact point and the bending region at a 90-degree angle.

4. The article according to claim 1, wherein the curvature of the bending region and the bending portion causes the peripheral edge to move sufficiently so that the peripheral edge cannot be perceived by a person running a finger along the periphery of the article.

5. The article according to claim 1, wherein it is optically transparent.

6. A method for creating a shaped article, The thermoplastic material is formed into a shape including a body having the shape of a rounded rectangular tray, having a concave compartment with an opening and a deflectable flange around the entire periphery of the opening, wherein the deflectable flange includes a spacer that forms the peripheral edge of the thermoplastic material, the spacer is connected to the body at an angle of 75 degrees or more but less than 105 degrees by an extension that extends peripherically away from the body and a bent region that interconnects the spacer and the extension, the spacer includes a peripheral flange at the peripheral edge of the deflectable flange and an elbow that connects the peripheral flange to the remainder of the spacer at an angle other than 180 degrees, the bent region has a smooth contour and interconnects the spacer to the extension at approximately a right angle, The method involves causing a ram to collide with the spacer in order to deflect the spacer toward the extension, thereby reducing the magnitude of the angle between the spacer and the extension with respect to its pre-collision position because at least one portion of the deflectable flange is bent, and the bent portion is selected from the group consisting of the extension, the bent region, and the spacer. The bent portion is heated to at least the glass transition temperature of the thermoplastic material, This includes engaging and disengaging the ram from the spacer, so that the bent portion remains deflected from its pre-collision position even when the collision is interrupted to obtain the body with a smooth periphery, The main body has the shape of a tray, The shape of the tray has a concave compartment formed therein and does not include any conventional stacking protrusions. A method wherein the extension completely encloses the concave section in the periphery, forms a rotated edge around the entire periphery, and forms a rounded stacked extension at at least one position on the periphery of the article.

7. The method according to claim 6, wherein the bending region is connected to the extension at an angle of 75 degrees or more but less than 105 degrees.

8. The method according to claim 6, wherein the ram collides with the spacer such that it moves away from the periphery of the molded article and sufficiently deflects the peripheral edge, so that the flexible film that tautly wraps the molded article does not come into contact with the peripheral edge after the bent portion has cooled.

9. An article formed from a thermoformable sheet having a peripheral edge, The thermoformable sheet has sufficient rigidity to define the shape of the article. The article includes a body having the shape of a container with a rounded rectangular tray shape and a non-circular concave compartment formed therein, The main body completely encloses the periphery of the concave section and has an extension that extends periphery away from the main body, The aforementioned extension is The peripheral edge of the thermoformable sheet, A bending region including a curved portion, intervening between the contact point between the main body and the extension and the peripheral edge, It includes a bent portion intervened between the peripheral edge and the contact point, The bent portion has a smooth periphery and is sufficiently bent so that the peripheral edge of the thermoformable sheet is moved away from the periphery of the article. The main body has a tray shape that does not include any conventional stacking protrusions, The extension completely encloses the concave section in its periphery, forms a rotated edge around the entire periphery, and forms a rounded layered extension at at least one position on the periphery of the article, thereby the article having a smooth periphery.

10. The article according to claim 9, wherein the extension includes a spacer interposed between the peripheral edge and the bending region.

11. The article according to claim 10, wherein the bending region connects the spacer and a part of the extension between the contact point and the bending region at a 90-degree angle.

12. The article according to claim 9, wherein the curvature of the bending region and the bending portion causes the peripheral edge to move sufficiently so that the peripheral edge cannot be perceived by a person running a finger along the periphery of the article.

13. The article according to claim 9, which is optically transparent.

14. A method for creating a molded article having a body with a smooth periphery, The thermoplastic material is formed into a body having the shape of a container having the shape of a rounded rectangular tray and having a non-circular concave compartment formed therein, wherein the body has a deflectable flange that completely surrounds the periphery of the concave compartment, the deflectable flange includes a spacer that forms the peripheral edge of the thermoplastic material, the spacer is connected to the body by an extension that extends peripherically away from the body and a bent region that interconnects the spacer and the extension, the bent region having a smooth contour and interconnecting the spacer with the extension at approximately a right angle, The method involves causing a ram to collide with the spacer in order to deflect the spacer toward the extension, thereby reducing the magnitude of the angle between the spacer and the extension with respect to its pre-collision position because at least one portion of the deflectable flange is bent, and the bent portion is selected from the group consisting of the extension, the bent region, and the spacer. The bent portion is heated to at least the glass transition temperature of the thermoplastic material, This includes engaging and disengaging the ram from the spacer, so that the bent portion remains deflected from its pre-collision position even when the collision is interrupted to obtain the body with a smooth periphery, The main body has the shape of a tray, The shape of the tray has a concave compartment formed therein and does not include any conventional stacking protrusions. A method wherein the extension completely encloses the concave section in the periphery, forms a rotated edge around the entire periphery, and forms a rounded stacked extension at at least one position on the periphery of the article.

15. The method according to claim 14, wherein the bending region is connected to the extension at an angle of 75 degrees or more but less than 105 degrees.

16. The method according to claim 14, wherein the ram collides with the spacer such that the peripheral edge is sufficiently deflected away from the periphery of the molded article, so that the flexible film that tautly wraps the molded article does not come into contact with the peripheral edge after the bent portion has cooled.

Images