Food packaging containers

Abstract

To provide a food packaging container that is easily releasable after molding.SOLUTION: A container 1 formed of a bent sheet material S has a bottom part 3, and a wall part 4 erected from the bottom part 3. The wall part 4 has a release surface 5 being a bag-shaped inner periphery. The release surface 5 has a closed tip end part 51 being an end in an erected direction Rd of the wall part 4, an opening 52 being an end on the opposite side in the erected direction Rd in relation to the tip end part 51, and a side face part 53 between the tip end part 51 and the opening 52. The side face part 53 is provided with a vertical rib 8 being protruded or recessed in relation to an inner space A the release surface 5 faces, and extending in the erected direction Rd.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a food packaging container for packaging foods such as sandwiches and other prepared dishes. [Background technology]

[0002] Food packaging containers formed by vacuum forming a synthetic resin sheet material are known. For example, this type of container is formed by vacuum-adhering the sheet material to a predetermined mold while heating it, forming it to follow the shape of the mold, and then releasing (demolding) the container from the mold. Vacuum forming also allows for the molding of containers of various shapes, as long as they are demoldable. For example, as shown in Patent Document 1, a container is known that has walls that stand upright from the four corners of a rectangular bottom. The inside of the walls is a flat demolding surface formed as a bag-shaped inner periphery. The demolding surface is released from the mold, forming the wall of the desired shape. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-155466 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to promote demolding, pressurized air or the like is sometimes supplied toward the gap between the release surface and the mold. However, when the flat release surface and the mold are tightly attached to each other, it is difficult to form a gap sufficient for air to enter between the release surface and the mold, which results in insufficient demolding, resulting in defects such as defective products and reduced yields.

[0005] The present invention aims to solve the above problems and to provide a food packaging container that can be easily released from the mold after molding. [Means for solving the problem]

[0006] The present invention provides a food packaging container formed from a bent sheet material, which comprises a bottom and a wall portion erected from the bottom, the wall portion having a release surface which is a bag-shaped inner circumference, the release surface having a closed tip portion which is the end of the wall portion in the erection direction, an open opening portion which is the end opposite the tip portion in the erection direction, and a side portion between the tip portion and the open portion, and the side portion is provided with a vertical rib which is convex or concave with respect to the internal space facing the release surface and extends along the erection direction.

[0007] A vacuum forming mold such as a metal mold is fitted into the internal space inside the wall and is in close contact with the release surface. During release, the vacuum forming mold moves relative to the wall in a direction away from the wall, and as a result, moves as if being pulled out through the open section. For example, if the contact surface between the release surface and the vacuum forming mold is flat over its entirety, the pressurized air supplied for release will disperse, making it difficult for gaps that trigger release to occur.

[0008] In contrast, the food packaging container according to the present invention has vertical ribs on the side of the release surface, which are convex or concave relative to the interior space and extend along the vertical direction of the wall. After molding, the convex or concave shape of the vertical ribs disrupts the flatness of the contact surface between the vacuum forming mold and the release surface, making gaps more likely to form. When pressurized air is supplied from the open end toward the vertical ribs in this state, the pressurized air penetrates the contact surface of the vertical ribs and forms gaps for release. This gap then serves as a trigger for the pressurized air to penetrate the entire contact surface, facilitating release. As a result, the food packaging container described above facilitates release from the mold.

[0009] In the food packaging container, a plurality of vertical ribs may be provided, and at least some of the vertical ribs may be convex relative to the internal space. After molding, the convex shape of the vertical ribs disrupts the flatness of the contact surface between the vacuum forming mold and the release surface, making it easier to create gaps and release the container from the mold.

[0010] In the above-mentioned food packaging container, the wall portion has an outer peripheral surface opposite to the release surface, the vertical ribs are convex and protrude toward the internal space, and the outer peripheral surface may be provided with concave ribs that are recessed to overlap the vertical ribs and extend along the vertical direction. Since the vertical ribs of the upper food packaging container can be placed over the concave ribs of the lower food packaging container, multiple food packaging containers can be stacked and stored in a compact state.

[0011] In the food packaging container, the wall has a standing wall provided along at least a part of the periphery of the bottom, and the release surface, which is the inner periphery of the standing wall, has an inner release surface on the bottom side and an outer release surface facing the inner release surface and provided on the outside farther from the bottom than the inner release surface, and the vertical ribs may be provided on the outer release surface. The vertical ribs make it easier for gaps to occur at the contact surface between the outer release surface and the vacuum forming mold, making it easier to release the mold.

[0012] In the food packaging container described above, the release surface may have a reference surface that extends along the shape of the periphery of the bottom, and the vertical ribs may be convex, protruding from the reference surface toward the internal space, with the amount of protrusion of the vertical ribs gradually decreasing from the open end side to the tip end side. By increasing the amount of protrusion of the vertical ribs on the open end side, the area where gaps are formed that promote the initial entry of pressurized air is widened. On the other hand, the amount of protrusion at the tip end is reduced, allowing the internal space on the tip end side of the vertical wall to be reduced.

[0013] In the above-mentioned food packaging container, the wall portion has an outer peripheral surface opposite the release surface, the vertical ribs are concave with respect to the internal space, and the outer peripheral surface may be provided with convex ribs that protrude to overlap the vertical ribs and extend along the vertical direction. Since the vertical ribs of the upper food packaging container can be placed over the convex ribs of the lower food packaging container, multiple food packaging containers can be stacked and stored in a compact state.

[0014] In the food packaging container, the peripheral edge of the bottom may have a curved, bent corner, and the upright wall may be provided along the corner. This makes it easier to release the container from the mold even from the upright wall provided along the corner.

[0015] In the above-mentioned food packaging container, the bottom may have a plurality of opposing corners, and the upright wall portions may be provided along each corner. After molding, the food packaging container hardens while shrinking relative to the vacuum forming mold. For example, if the food packaging container has a polygonal shape with a plurality of opposing corners, the food packaging container may shrink in the opposing direction of the corners, hindering release from the mold. However, by providing vertical ribs on the upright wall portions provided along the corners, the possibility of hindering release from the mold can be reduced. [Effects of the Invention]

[0016] The food packaging container according to the present invention can be easily released from the mold after molding. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a side view of a food packaging container according to one embodiment of the present invention. [Figure 2] FIG. 1 is a plan view of a food packaging container. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. [Figure 4] FIG. 2 is an enlarged plan view showing the vertical wall portion of the food packaging container. [Figure 5] FIG. 5 is a cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5. [Figure 7] FIG. 2 is a perspective view showing the state in which the lid is attached to the food packaging container. [Figure 8] FIG. 10 is a cross-sectional view showing a first modified embodiment of a longitudinal rib. [Figure 9] FIG. 10 is a cross-sectional view showing a second modified embodiment of the longitudinal rib. [Figure 10]Other variations of the longitudinal rib are shown, where (a) is a plan view showing a third variation, (b) is a plan view showing a fourth variation, (c) is a plan view showing a fifth variation, and (d) is a cross-sectional view showing a sixth variation. [Figure 11] Other variations of the longitudinal rib are shown, with (a) being a schematic plan view showing the seventh variation, (b) being a schematic plan view showing the eighth variation, and (c) being a schematic plan view showing the ninth variation. [Figure 12] FIG. 1 shows a process for manufacturing a food packaging container, where (a) shows the process of vacuum-forming a sheet material, and (b) shows the process of releasing the sheet material on which the food packaging container has been formed from the mold. [Figure 13] 1A and 1B are diagrams showing the process of releasing the sheet material from the mold, where FIG. 1A is a cross-sectional view of the food packaging container and the mold, and FIG. 1B is a cross-sectional view taken along line bb in FIG. 1A. [Figure 14] 10A and 10B are diagrams showing the process of releasing the sheet material from the mold in the first modified form of the vertical rib, where (a) is a cross-sectional view of the food packaging container and the mold, and (b) is a cross-sectional view along line bb in (a). [Figure 15] FIG. 10 is an explanatory diagram showing a state in which one container is being removed from among a plurality of overlapping containers. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, a food packaging container according to one embodiment of the present invention will be described with reference to the drawings. However, the food packaging container of the present invention is not limited to this embodiment.

[0019] As shown in Figures 1 and 7, a food packaging container (hereinafter referred to as "container") 1 of this embodiment is a container for storing food F such as a sandwich, and a food package 10 is formed by attaching a lid 2. In Figure 1, the lid 2 attached to the container 1 is shown by a two-dot chain line. In this embodiment, the container 1 and the lid 2 are separate bodies, and the food package 10 is formed by attaching the lid 2 to the container 1, but the lid 2 may also be integrally formed with the container 1 via a hinge or the like.

[0020] The container 1 is formed from a bent sheet material S (see FIG. 12), and has one surface (front side) that contacts and holds the food F, and an opposite surface (back side). The container 1 is formed by vacuum forming the sheet material S, and the back side is the surface that is in close contact with a mold 102 (an example of a vacuum forming mold) and is also the surface that is released (de-molded) from the mold 102. In the following description, the side containing the food F is referred to as the upper side, and the opposite side is referred to as the lower side, based on the assumption that the container 1 containing the food F is placed and stabilized on a horizontal surface such as a table.

[0021] The container 1 has a bottom 3 and a wall 4 extending upright from the bottom 3. The bottom 3 is a portion on which food F is placed. The wall 4 is provided along the periphery 3a of the bottom 3 so as to surround the bottom 3, and is a portion that abuts against the food F from the side to hold the food F in a predetermined position. In the following description, the extending direction Rd of the wall 4 (see FIG. 5) refers to the direction moving upward away from the bottom 3, with the bottom 3 as the reference point.

[0022] 2, the shape of the bottom 3 when viewed from above, i.e., when viewed in plan, can be appropriately determined to match the shape of the food F to be placed on it. In this embodiment, a substantially square shape with curved corners 3b in plan view is illustrated. However, the shape of the bottom 3 may also be rectangular, polygonal such as triangular or pentagonal, or curved such as circular or elliptical.

[0023] Legs 3c protruding from the rear surface side are provided at corners 3b of the bottom 3 (see FIG. 3). In addition, the bottom 3 is appropriately provided with reinforcing ribs 3d.

[0024] As shown in Figure 3, the wall 4 has a mountain-like shape that is bent so as to protrude upward, and the back side of the wall 4 is bag-shaped. During vacuum molding, a mold 102 (see Figure 12) is placed on the back side of the wall 4. When the mold 102 is released, an internal space A is formed on the back side of the wall 4. The inner periphery of the bag-shaped part that faces the internal space A is a release surface 5 that has a shape that follows the shape of the mold 102.

[0025] As shown in FIGS. 1 and 3, the wall 4 includes an inner wall 41 that is bent and erected from the bottom 3, an outer wall 42 that is provided to face the inner wall 41, and an upper wall 43 that is provided between the inner wall 41 and the outer wall 42. The inner wall 41 is provided continuously around the entire periphery 3a of the bottom 3. The inner wall 41 includes a lower inner wall portion 41a that is connected to the periphery 3a of the bottom 3, and an upper inner wall portion 41b that is connected to the upper wall portion 43. The inner area surrounded by the upper inner wall portion 41b is larger than the inner area surrounded by the lower inner wall portion 41a. The inner wall 41 is tapered from the lower inner wall portion 41a to the upper inner wall portion 41b so that the inner area expands.

[0026] Like the inner wall portion 41, the outer wall portion 42 is provided without interruption around the entire periphery of the bottom portion 3. The outer wall portion 42 includes an upper outer wall portion 42a connected to the upper wall portion 43, and a lower outer wall portion 42b that is provided at the lower end of the upper outer wall portion 42a and protrudes outward. Between the upper outer wall portion 42a and the lower outer wall portion 42b of the outer wall portion 42, there are provided a lid locking portion 42c that fits onto the inner periphery of the lid body 2 to hold the lid body 2, and a lid seat portion 42d that abuts against a flange portion 21 (see FIG. 1) provided on the outer edge of the lid body 2 to support the lid body 2.

[0027] As shown in FIGS. 1 and 2, the upper wall portion 43 includes a plurality of standing wall portions 6 and a connecting wall portion 7 that connects the standing wall portions 6. The standing wall portions 6 are provided so as to protrude further upward than the connecting wall portions 7. The plurality of standing wall portions 6 according to this embodiment are arranged on diagonal lines of the quadrilateral bottom portion 3 and are provided so as to follow each of the plurality of corner portions 3b of the bottom portion 3. In other words, the plurality of standing wall portions 6 are arranged so as to face each other across the bottom portion 3. The connecting wall portions 7 and the standing wall portions 6, for example, abut against the inner periphery of the lid body 2 so as to fit into the lid body 2, thereby supporting the lid body 2. Furthermore, the standing wall portions 6 protrude taller than the connecting wall portions 7, and laterally support and stably hold food F placed on the bottom portion 3.

[0028] Next, the standing wall portion 6 will be described with reference to Figures 4 and 5. The multiple standing wall portions 6 basically have the same shape and structure, and one standing wall portion 6 will be described as a representative. The standing wall portion 6 is bent so as to form a mountain shape that is taller than the connecting wall portion 7 (see Figure 3). The standing wall portion 6 is roughly inverted V-shaped in cross section, and includes an inner wall portion 61 connected to the inner wall portion 41, an outer wall portion 62 connected to the outer wall portion 42, and an upper end wall portion 63 connected to the upper portion of the inner wall portion 61 and the upper portion of the outer wall portion 62. The inner wall portion 61 and the outer wall portion 62 are inclined so that the distance between them is smaller at the upper portion than at the lower portion.

[0029] The inner periphery of the standing wall portion 6 is part of the release surface 5. The release surface 5 of the standing wall portion 6 has a tip portion 51 which is the end (upper end) of the wall portion 4 in the standing direction Rd, and an open portion 52 which is the end (lower end) on the opposite side of the tip portion 51 in the standing direction Rd. The tip portion 51 closes the internal space A, and the open portion 52 opens the internal space A. The tip portion 51 substantially corresponds to the inner periphery of the upper end wall portion 63.

[0030] The release surface 5 of the standing wall portion 6 has a side portion 53 located between the tip portion 51 and the open portion 52. The side portion 53 has a vertical rib 8 provided thereon. The vertical rib 8 extends along the standing direction Rd. The side portion 53 has an inner release surface 53a which is the inner periphery of the inner wall portion 61, and an outer release surface 53b which is the inner periphery of the outer wall portion 62. The inner release surface 53a is the release surface 5 on the bottom 3 side, and the outer release surface 53b can also be described as a release surface 5 that faces the inner release surface 53a and is provided outwardly, farther from the bottom 3 than the inner release surface 53a.

[0031] 6 is a cross-sectional view of the standing wall portion 6 cut along a plane intersecting (for example, perpendicular to) the standing direction Rd of the standing wall portion 6. The standing direction Rd of the standing wall portion 6 essentially means the standing direction Rd of the wall portion 4. As shown in FIG. 6, the inner release surface 53a is curved to follow the peripheral edge 3a of the bottom portion 3. The outer release surface 53b has a reference surface 53x that is curved to follow the shape of the inner release surface 53a. Since the reference surface 53x follows the shape of the inner release surface 53a, it can be said that the reference surface 53x extends along the shape of the peripheral edge 3a of the bottom portion 3, similar to the inner release surface 53a.

[0032] The vertical ribs 8 according to this embodiment are provided on the outer release surface 53b, and are provided so as to be convex with respect to the internal space A in a cross-sectional view. The convex shape of the vertical ribs 8 means that they are provided so as to protrude toward the internal space A beyond the reference plane 53x of the outer release surface 53b. Furthermore, the vertical ribs 8 according to this embodiment protrude toward the internal space A while being curved, but they may also have a shape that protrudes toward the internal space A by being bent.

[0033] The vertical ribs 8 (see FIG. 5) according to this embodiment are provided continuously without interruption from the open portion 52 to the tip portion 51 of the release surface 5. The upper ends of the vertical ribs 8 may reach the tip portion 51 or may be slightly spaced apart from the tip portion 51.

[0034] As described above, the vertical ribs 8 protrude toward the internal space A. The degree of this protrusion can be described as the protrusion amount D of the vertical ribs 8. The protrusion amount D of the vertical ribs 8 can be determined at each position along the erection direction Rd of the vertical wall portion 6. For example, when the vertical wall portion 6 is viewed in a cross section perpendicular to the erection direction Rd (see FIG. 6 ), a virtual reference plane 53y is first imagined, where the reference plane 53x of the outer release surface 53b extends to the vertical rib 8. Next, the position on the vertical rib 8 on the cross section that is farthest from the virtual reference plane 53y is identified. The distance from this position to the virtual reference plane 53y is the protrusion amount D of the vertical rib 8. The protrusion amount D of the vertical rib 8 is greatest on the open portion 52 side and smallest on the tip end portion 51 side. The protrusion amount D of the vertical rib 8 gradually decreases from the open portion 52 side to the tip end portion 51 side.

[0035] The outer wall portion 62 of the standing wall portion 6 has an outer peripheral surface 62a that is opposite to the outer release surface 53b. The outer peripheral surface 62a is provided with recessed ribs 62b that are recessed so as to overlap the vertical ribs 8. The recessed ribs 62b, like the vertical ribs 8, extend along the standing direction Rd.

[0036] In the above-described embodiment, the height H of the standing wall portion 6 is, for example, 10 mm to 15 mm. The outer wall portion 62 and the inner wall portion 61 are inclined with respect to a virtual plane perpendicular to the bottom portion 3. For example, the inclination angle α between a reference plane that is parallel to the bottom portion 3 and passes through the opening and the outer release surface 53b of the outer wall portion 62 is, for example, 70° to 85°. The inclination angle β between the reference plane and the inner release surface 53a of the inner wall portion 61 is, for example, 70° to 85°. The protrusion amount D of the vertical rib 8 is maximum on the open portion 52 side, and this maximum value is, for example, 0.4 mm to 1.0 mm. When viewed in cross section, the vertical rib 8 is arc-shaped, and the radius of curvature of the vertical rib 8 is, for example, 0.5 mm to 2.0 mm.

[0037] Here, modified forms of the vertical rib 8 will be described. FIG. 8 is a cross-sectional view showing a first modified form of the vertical rib 8. As shown in FIG. 8, the vertical rib 8A according to the first modified form is provided on the outer release surface 53b, and is provided so as to be concave with respect to the internal space A in a cross-sectional view. The concave shape of the vertical rib 8 means a shape that protrudes toward the opposite side of the internal space A from the reference surface 53x. In other words, the concave shape of the vertical rib 8 can also be described as a shape that protrudes in the direction in which the internal space A expands. The concave shape of the vertical rib 8 may be a curved or bent shape.

[0038] The degree to which the vertical rib 8A is recessed relative to the internal space A can be described as the recess depth Dp of the vertical rib 8A. Similar to the protrusion amount D, the recess depth Dp can be determined at each position along the erection direction Rd of the vertical wall portion 6. For example, when the vertical wall portion 6 is viewed in a cross section perpendicular to the erection direction Rd (see FIG. 8), a virtual reference plane 53y is first imagined, where the reference plane 53x of the outer release surface 53b extends to the vertical rib 8. Next, the position on the vertical rib 8A on the cross section farthest from the virtual reference plane 53y is identified. The distance from this position to the virtual reference plane 53y is the recess depth Dp of the vertical rib 8A. The recess depth Dp of the vertical rib 8A is greatest on the open portion 52 side and smallest on the tip end 51 side. The recess depth Dp of the vertical rib 8A gradually decreases from the open portion 52 side to the tip end 51 side.

[0039] The maximum value of the recess depth Dp on the side of the open portion 52 is, for example, 0.4 mm to 1.0 mm. When viewed in cross section, the longitudinal rib 8A is arc-shaped, and the radius of curvature of the longitudinal rib 8 is, for example, 0.5 mm to 2.0 mm.

[0040] The outer wall portion 62 of the standing wall portion 6 has an outer peripheral surface 62a that is on the opposite side to the outer release surface 53b. The outer peripheral surface 62a is provided with a protruding rib 62c that protrudes so as to overlap the vertical rib 8A. The protruding rib 62c extends along the standing direction Rd, similar to the vertical rib 8A.

[0041] FIG. 9 is a cross-sectional view showing a second modified embodiment of the vertical rib 8. As shown in FIG. 9, the inner release surface 53a has a reference surface 53z that extends along the shape of the peripheral edge 3a of the bottom 3. The vertical rib 8B according to the second modified embodiment is provided on the inner release surface 53a and is provided so as to be convex with respect to the internal space A in a cross-sectional view. That is, the vertical rib 8B is provided so as to protrude further into the internal space A than the reference surface 53z of the inner release surface 53a. Note that the vertical rib 8 provided on the inner release surface 53a may be concave with respect to the internal space A. That is, the vertical rib 8 may be provided so as to protrude further toward the opposite side of the internal space A than the reference surface 53z of the inner release surface 53a.

[0042] 10(a) to 10(c) are plan views showing various modified forms of the vertical rib 8. Note that, because Fig. 10(a) to 10(c) are plan views, they do not directly show the release surface 5, which is the back surface, but for convenience, the vertical ribs 8C, 8D, and 8E are shown by solid lines.

[0043] As shown in FIG. 10(a), a plurality of vertical ribs 8C according to the third modified embodiment are provided on the outer release surface 53b. In the third modified embodiment, a plurality of vertical ribs 8 are provided in a row along the peripheral edge 3a of the bottom 3. The vertical ribs 8 may have the same shape and dimensions, or may have different shapes and dimensions. Note that, although the vertical ribs 8C according to the third modified embodiment are exemplified as being convexly protruding from the outer release surface 53b toward the internal space A, they may also be concave, or may be provided on the inner release surface 53a.

[0044] As shown in (b) of Fig. 10, the vertical ribs 8D according to the fourth modified embodiment are provided on the outer release surface 53b. In the fourth modified embodiment, the vertical ribs 8D are provided with a length in the standing direction Rd that is shorter than that of the vertical ribs 8 according to the above-described embodiment. For example, the vertical ribs 8D are provided so as to extend to a midpoint between the opening 52 and the tip end 51. Note that, although the vertical ribs 8D according to the fourth modified embodiment are exemplified as being convexly protruding from the outer release surface 53b toward the internal space A, they may be concavely formed, or may be provided on the inner release surface 53a.

[0045] 10(c), the vertical ribs 8E according to the fifth modified embodiment are provided on the outer release surface 53b. The vertical ribs 8E according to the fifth modified embodiment do not have a shape in which the protrusion amount D gradually decreases from the open portion 52 side to the tip end 51 side, but have a shape in which the same shape continues from the open portion 52 side to the tip end 51 side. Note that, although the vertical ribs 8E according to the fifth modified embodiment are exemplified as protruding from the outer release surface 53b toward the internal space A in a convex shape, they may also be concave, or may be provided on the inner release surface 53a.

[0046] 10(d) is a cross-sectional view showing a sixth modified embodiment of the standing wall portion 6 and the vertical rib 8. The vertical rib 8F according to the sixth modified embodiment is provided on the outer release surface 53b. The vertical rib 8F does not extend continuously from the open portion 52 side to the tip portion 51 side, but has a stepped shape along the way. Note that, although the vertical rib 8F is shown as protruding from the outer release surface 53b toward the internal space A in a convex shape, it may also be concave, or may be provided on the inner release surface 53a.

[0047] 11(a) to 11(c) are plan views schematically showing each modified form of the standing wall portion 6 and the bottom portion 3. Note that, because FIG. 11(a) to 11(c) are plan views, they do not directly show the release surface 5, which is the back surface, but for convenience, the vertical ribs 8 are shown by solid lines. As shown in FIG. 11(a) to 11(c), the container 1 according to each modified form is provided with standing wall portions 6A, 6B, 6C so as to surround the entire periphery of the bottom portions 3A, 3B, 3C, for example.

[0048] As shown in Fig. 11(a), the container 1 according to the seventh modified embodiment has a bottom 3A that is substantially rectangular in plan view, and the longitudinal ribs 8 are provided at the corners 3b and approximately the centers of the long sides of the bottom 3A. As shown in Fig. 11(b), the container 1 according to the eighth modified embodiment has a bottom 3B that is substantially triangular in plan view, and the longitudinal ribs 8 are provided at positions along the corners 3b of the bottom 3B. As shown in Fig. 11(c), the container 1 according to the ninth modified embodiment has a bottom 3C that is elliptical in plan view, and the longitudinal ribs 8 are provided at multiple positions along the periphery 3a of the bottom 3C.

[0049] Next, the function and effect of the container 1 provided with the vertical ribs 8 will be described while explaining a manufacturing method of the container 1 with reference to Figures 12 and 13. The container 1 is made of a synthetic resin sheet material S, and is manufactured by vacuum forming using a mold 102. The synthetic resin from which the container 1 is made can be polystyrene, polypropylene, or polyester, depending on the application, and high impact polystyrene (HIPS), which has excellent impact resistance, is preferably used to stably hold food F. Alloys of these resins or laminates of these resins may also be used.

[0050] First, the molding machine 100 will be described. The molding machine 100 is equipped with a mold 102 (an example of a vacuum forming mold) for molding the sheet material S into a desired shape. Note that in Fig. 12 and Fig. 13(a), the back side of the container 1 is shown facing upward and the front side facing downward.

[0051] The molding machine 100 includes, for example, a heating platen 103 (heating section) that heats the sheet material S, a mold 102 arranged opposite the heating platen 103 across the conveying path of the sheet material S, a movable device 104 (mold moving section) that moves the mold 102 to move the mold 102 toward or away from the sheet material S, and a conveying device (sheet conveying section) that conveys the sheet material S. In addition, as ancillary equipment of the molding machine 100 or as equipment separate from the molding machine 100, there is provided equipment that communicates with the cavity 102a of the mold 102 to draw air and supply (compress) pressurized air into the cavity 102a.

[0052] The manufacturing method using this molding machine 100 is a method called hot plate molding, which is an example of vacuum molding. The molding machine 100 has a mold 102 and a hot plate 103 arranged opposite each other with a conveyance path for the sheet material S in between. A conveying device conveys the unprocessed portion of the sheet material S to a predetermined position. This predetermined position is a position between the mold 102 and the hot plate 103. At the predetermined position, the back surface of the sheet material S faces the cavity 102a of the mold 102.

[0053] Next, the movable device 104 is driven to move the mold 102 so that it approaches the sheet material S and abuts against the sheet material S with the cavity 102a facing the sheet material S. The sheet material S is heated by the heating platen 103 from the surface opposite to the surface facing the cavity 102a, and is softened to an extent that it can be molded.

[0054] Next, the molding process is performed. In the molding process, the heated sheet material S is sucked into the cavity 102a. As a result, the sheet material S comes into contact with the cavity 102a and deforms to fit the shape of the cavity 102a, becoming a molded product. In this molding process, the temperature of the mold 102 is lower than that of the heated sheet material S. As a result, when the sheet material S comes into contact with the cavity 102a, the molded product shrinks. Note that the molded product is actually made into a container 1 by cutting and separating it from the sheet material S, but in the following explanation, for convenience of explanation, the molded product before separation will also be described as a container 1.

[0055] Next, a demolding step is performed to remove the container 1 from the mold 102. Fig. 12(b) shows the demolding step. Fig. 13(a) is an enlarged cross-sectional view of the standing wall portion 6 and the mold 102, showing the state in which pressurized air P is being supplied in the demolding step. Fig. 13(b) is a cross-sectional view taken along line bb in Fig. 13(a), showing the portion T to which the pressurized air P is supplied surrounded by a two-dot chain line.

[0056] In the above molding process, the contact surface between the mold 102 and the container 1 becomes the mold release surface 5. In the mold 102, for example, the protrusion 102b forming the standing wall portion 6 is fitted into the internal space A inside the standing wall portion 6 and is in close contact with the mold release surface 5. In the mold release process, the protrusion 102b moves relative to the standing wall portion 6, for example, in a direction away from the standing wall portion 6, and as a result, moves as if pulled out of the opening 52 and is released from the mold.

[0057] During demolding, in order to promote separation of the mold 102 and the release surface 5, which are in close contact with each other, pressurized air P is supplied targeting the contact surface between the mold 102 and the release surface 5. Here, if the contact surface between the release surface 5 and the mold 102 is flat over the entire surface and is continuously connected, for example, the pressurized air P supplied for demolding will disperse without entering the gaps at the contact surface, making it difficult for gaps that trigger demolding to occur.

[0058] In particular, the standing wall portion 6 is thinner than other portions of the wall portion 4, and therefore the gap that occurs in the internal space A facing the demolding surface 5 is also very narrow. As a result, there is a possibility that the container 1 will shrink during demolding and pinch the mold 102. As a result, when a thin wall portion 4 such as the standing wall portion 6 is formed by vacuum molding the sheet material S, demolding failure is likely to occur even if pressurized air P is supplied.

[0059] In contrast, in the container 1 according to the above embodiment, vertical ribs 8 are provided on the side surface 53 of the release surface 5. After vacuum molding, the flat continuity of the contact surface between the mold 102 and the release surface 5 is interrupted by the convex shape of the vertical ribs 8, making it easy for gaps to form (see FIG. 13(a)). In this state, when pressurized air P is supplied toward the vertical ribs 8 from the open portion 52 side, the pressurized air P enters the contact surface of the vertical ribs 8 and forms gaps Sp for release. This gap Sp then triggers the pressurized air to enter the entire contact surface, facilitating release. As a result, the container 1 makes it easy to release from the mold.

[0060] The container 1 according to the other modified embodiments also achieves the same effect. For example, Fig. 14(a) shows the first modified embodiment, and is an enlarged cross-sectional view of the vertical wall portion 6 provided with the vertical rib 8A and the mold 102 (protrusion portion 102b), showing the state in which pressurized air P is supplied in the demolding process. Fig. 14(b) is a cross-sectional view taken along line bb in Fig. 14(a), showing the area Ta to which the pressurized air P is supplied surrounded by a two-dot chain line.

[0061] In the first modified embodiment, pressurized air P is also supplied to the contact surface between the mold 102 and the release surface 5 to promote separation between the mold 102 and the release surface 5, which are in close contact with each other. In the container 1 according to the first modified embodiment, after vacuum molding, the flat continuity of the contact surface between the mold 102 and the release surface 5 is interrupted by the concave shape of the vertical ribs 8A, making it easy for gaps to form. In this state, when pressurized air P is supplied toward the vertical ribs 8A from the open portion 52 side, the pressurized air P enters the contact surface of the vertical ribs 8A and forms gaps Sp for release. This gap Sp then triggers the pressurized air to enter the entire contact surface, promoting release. As a result, the container 1 equipped with the vertical ribs 8A facilitates release from the mold.

[0062] The container 1 according to the other modified embodiments also achieves the same advantageous effects. That is, the container 1 according to the other modified embodiments is provided with longitudinal ribs 8B to 8F, and after vacuum molding, the flat continuity of the contact surface between the mold 102 and the release surface 5 is interrupted by the convex or concave shape of the longitudinal ribs 8B to 8F, making it easy for gaps to form. In this state, when pressurized air P is supplied toward the longitudinal ribs 8B to 8F, the pressurized air P enters the contact surface of the longitudinal ribs 8B to 8F and forms gaps Sp for release. Then, the gaps Sp act as a trigger for the pressurized air to enter the entire contact surface, facilitating release. As a result, the container 1 provided with the longitudinal ribs 8B to 8F facilitates release from the mold.

[0063] The container 1 according to the embodiment includes a plurality of vertical wall portions 6, and vertical ribs 8 are provided on each of the vertical wall portions 6. In the present embodiment, all of the plurality of vertical ribs 8 are convex with respect to the internal space A that faces the release surface 5. However, some of the plurality of vertical ribs 8 may be convex with respect to the internal space A, and the rest may be concave.

[0064] Furthermore, in the container 1 according to the embodiment, the concave ribs 62b are provided so as to overlap the vertical ribs 8. Therefore, for example, the vertical ribs 8 of the upper container 1 can be placed over the concave ribs 62b of the lower container 1 (see FIG. 15). As a result, multiple containers 1 can be stacked and stored in a compact state. Furthermore, when the vertical ribs 8 are placed over the concave ribs 62b, a small gap is likely to be formed between the concave ribs 62b and the vertical ribs 8. As a result, when removing one container 1 from multiple stacked containers 1, it can be easily and effortlessly removed. Note that, as shown in FIG. 8, the container 1 having the vertical ribs 8A according to the first modified embodiment also achieves the same effect. That is, in the container 1 having the vertical ribs 8A, the vertical ribs 8A of the upper container 1 can be placed over the convex ribs 62c of the lower container 1. As a result, multiple containers 1 can be stacked and stored in a compact state. Furthermore, when the protruding rib 62c is covered with the vertical rib 8, a small gap is likely to be formed between the protruding rib 62c and the vertical rib 8A. As a result, when removing one container 1 from a plurality of stacked containers 1, it can be removed easily and without strain.

[0065] Furthermore, in the container 1 according to the embodiment, the protrusion amount D of the vertical rib 8 gradually decreases from the open portion 52 side toward the tip portion 51 side. By increasing the protrusion amount D of the vertical rib 8 on the open portion 52 side, the area where gaps are formed that encourage the initial entry of pressurized air becomes larger. Note that the recess depth Dp of the vertical rib 8A according to the first modified embodiment gradually decreases from the open portion 52 side toward the tip portion 51 side. By increasing the recess depth Dp of the vertical rib 8A on the open portion 52 side, the area where gaps are formed that encourage the initial entry of pressurized air becomes larger.

[0066] Furthermore, the upright wall portions 6 of the container 1 are provided along the corners 3b of the bottom 3, and since the upright wall portions 6 are provided with vertical ribs 8, the upright wall portions 6 along the corners 3b are also easily demolded. In particular, the bottom 3 according to this embodiment has a plurality of corners 3b arranged opposite each other, and the upright wall portions 6 are provided along each corner 3b. After molding, the container 1 hardens while shrinking relative to the mold 102. For example, if the container 1 has a polygonal shape and a plurality of opposing corners 3b, there is a possibility that the container 1 will shrink in the direction of the corners 3b, hindering demolding. However, by providing the vertical ribs 8 on the plurality of upright wall portions 6 along the corners 3b, the possibility of hindering demolding can be reduced.

[0067] The present invention is not limited to the above-described embodiment. For example, the vertical wall portion may be provided directly on the bottom portion. Furthermore, the vertical ribs may have a mixed shape that is convex or concave relative to the internal space. [Explanation of symbols]

[0068] 1...container (food packaging container), 3, 3A to 3C...bottom, 3a...periphery, 3b...corner, 4...wall, 5...release surface, 6, 6A to 6C...standing wall, 51...tip, 52...opening, 53...side, 8, 8A to 8F...vertical rib, 53a...inner release surface, 53b...outer release surface, 53x...reference surface, A...internal space, D...protrusion amount, 62a...outer peripheral surface, 62b...concave rib, 62c...convex rib, P...compressed air, Rd...standing direction, S...sheet material, Sp...gap.

Claims

1. A food packaging container formed from a bent sheet material, The bottom and a wall portion erected from the bottom portion, The wall portion has a release surface that is a bag-shaped inner periphery, the release surface comprises a closed tip portion which is an end of the wall portion in the standing direction, an open portion which is an end opposite to the tip portion in the standing direction, and a side portion which is between the tip portion and the open portion, The side surface portion is provided with a vertical rib that is convex or concave with respect to an internal space that the release surface faces, The vertical rib extends from the open portion to the tip portion along the upright direction.

2. The longitudinal ribs are provided in plurality, The food packaging container according to claim 1 , wherein at least some of the plurality of longitudinal ribs are convex with respect to the internal space.

3. The wall portion has an outer peripheral surface opposite the release surface, The longitudinal rib has a convex shape that protrudes toward the internal space, 3. The food packaging container according to claim 1, wherein the outer peripheral surface is provided with recessed ribs that are recessed to overlap the longitudinal ribs and extend along the vertical direction.

4. The wall portion has a standing wall portion provided along at least a part of the periphery of the bottom portion, and the release surface which is the inner periphery of the standing wall portion has an inner release surface which is on the bottom portion side, and an outer release surface which faces the inner release surface and is provided on the outside farther from the bottom portion than the inner release surface, The food packaging container according to any one of claims 1 to 3, wherein the vertical ribs are provided on the outer release surface.

5. A food packaging container formed from a bent sheet material, The bottom and a wall portion erected from the bottom portion, The wall portion has a release surface that is a bag-shaped inner periphery, the release surface comprises a closed tip portion which is an end of the wall portion in the standing direction, an open portion which is an end opposite to the tip portion in the standing direction, and a side portion which is between the tip portion and the open portion, The side surface portion is provided with a vertical rib that is convex or concave with respect to an internal space that the release surface faces and extends along the erection direction, The wall portion has a standing wall portion provided along at least a part of the periphery of the bottom portion, and the release surface which is the inner periphery of the standing wall portion has an inner release surface which is on the bottom portion side, and an outer release surface which faces the inner release surface and is provided on the outside farther from the bottom portion than the inner release surface, The longitudinal rib is provided on the outer release surface, the release surface of the upright wall portion has a reference surface extending along the shape of the periphery of the bottom portion, The vertical rib has a convex shape that protrudes from the reference surface toward the internal space, The amount of protrusion of the vertical rib gradually decreases from the opening to the tip.

6. The wall portion has an outer peripheral surface opposite the release surface, The longitudinal rib is recessed relative to the internal space, 3. The food packaging container according to claim 1, wherein the outer peripheral surface is provided with a convex rib that projects so as to overlap the vertical rib and extends along the vertical direction.

7. The peripheral edge of the bottom portion has curved corners, 6. The food packaging container according to claim 4, wherein the upright wall portion is provided along the corner portion.

8. The bottom portion has a plurality of the corner portions arranged opposite to each other, The food packaging container according to claim 7 , wherein the upright wall portions are provided along each of the corners.

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