Method for manufacturing a paper food container, manufacturing mold for a paper food container

Abstract

The application provides a paper food container manufacturing method and a paper food container manufacturing mold. The method comprises the following steps: folding paper to form a container body of a food container, the container body being open at an upper end and having a bottom wall and a peripheral wall adjacent to the bottom wall, at least one seam line being formed on the bottom wall or the peripheral wall, the seam line being located at a seam formed by at least two layers of sheet paper; then, placing the container body on a lower mold, placing a gas-tight film above the lower mold, the gas-tight film being located above a part of the container body; driving an upper mold to move downward, so that the gas-tight film is clamped between the upper mold and the container body; heating the upper mold, so that the gas-tight film is tightly attached to a part of the bottom wall and / or the peripheral wall of the container body and forms a gas-tight film layer. The mold is applied to the manufacturing method to manufacture the paper food container. The paper food container manufactured by the method has a low plastic content, can ensure gas tightness, and meets environmental protection requirements.

Description

Technical Field

[0001] This invention relates to the technical field of disposable tableware manufacturing, specifically, to a method for manufacturing paper food containers made of paper and the mold used in this method. Background Technology

[0002] Traditional disposable food containers are mostly made of plastic. Because plastic food containers are not easily degraded and cause plastic pollution, disposable food containers made of environmentally friendly materials such as paper are becoming increasingly popular.

[0003] Typically, disposable food containers made of paper are formed by folding a flat sheet of kraft paper or cardboard. The fold creates a seam, which becomes a channel for airflow. Gas inside the food container can leak to the outside through the seam, and gas outside can also flow into the inside of the food container through the seam, resulting in poor airtightness of the food container.

[0004] To solve the problem of airtightness of food containers, it is usually necessary to cover the surface of the food container with an airtight film layer. Multi-layer composite films are used, and the film layer is made of materials such as PP, PE, PET, PA, EVOH and other materials with a very thin film layer. The airtight film layer is attached to the inner surface of the food container by traditional vacuum forming, especially at the seams, to seal the seams and reduce the flow of gas inside and outside the food container.

[0005] However, because the airtight membrane layer is made of materials such as PP, PE, PET, PA, and EVOH, rather than environmentally friendly materials like paper, a thicker membrane layer results in a higher plastic content in the food container. For example, if the weight of the membrane layer exceeds 20% of the total weight of the food container, it does not meet environmental requirements. For instance, according to EU law, if the plastic content of a food container exceeds 10%, the user must tear off the plastic airtight membrane layer when discarding the container, and the membrane layer and the paper container body must be recycled separately. Clearly, a heavy airtight membrane layer not only fails to meet environmental requirements but also causes significant inconvenience to users.

[0006] Furthermore, before applying the airtight film layer to the inner surface of a food container using traditional vacuum forming methods, a large sheet of thick plastic film (typically over 0.02 mm thick) with a certain degree of rigidity must first be heated and softened. This softened film is then laid on the food container, and finally, vacuum forming is used to adhere it to the food container. However, this process consumes a significant amount of energy and takes a long time to heat the plastic film, increasing the production time of the food containers and resulting in higher production costs.

[0007] Furthermore, traditional thermoforming methods for forming plastic film on food containers require thermoforming equipment. This equipment typically includes a lower mold and an upper mold. The food container to be coated is placed on the lower mold. During thermoforming, a vacuum is created in the lower mold to adhere the plastic film to the food container. Then, heat is used to press the softened plastic film onto the inner wall of the food container. Therefore, this type of thermoforming equipment requires a vacuum system, has many components, and results in high production costs. Summary of the Invention

[0008] The first objective of this invention is to provide a method for manufacturing paper food containers that has low production costs, low energy consumption, and short production time.

[0009] A second objective of this invention is to provide a mold for manufacturing food containers with good sealing performance and low plastic density.

[0010] To achieve the first objective of this invention, the method for manufacturing a paper food container provided by this invention includes folding paper to form a container body, the container body being open at the top and having a bottom wall and a peripheral wall adjacent to the bottom wall. At least one seam line is formed on the bottom wall or the peripheral wall, the seam line being located at the seam formed by the overlapping of at least two layers of sheet paper, and the outer edge of the seam line forming an edge seam position. Then, the container body is placed on a lower mold, and an airtight film is placed above the lower mold, the airtight film being located above a portion of the container body. The upper mold is driven to move downward, so that the airtight film is clamped between the upper mold and the container body. The upper mold is heated, so that the airtight film is tightly adhered to a portion of the bottom wall and / or peripheral wall of the container body to form an airtight film layer, and all edge seam positions are covered with the airtight film layer, while at least a portion of the bottom wall and / or peripheral wall is not covered with the airtight film layer.

[0011] As can be seen from the above scheme, when making food containers, the container body is placed in the lower mold and an airtight film is laid on top. The upper mold then uses heat pressing to attach the airtight film to a portion of the inner wall of the container body. Since the airtight film layer is not formed by vacuum forming, it does not need to be heated. A relatively soft airtight film can be directly laid on the container body. The production time of the food container is short, and the energy consumption is also low.

[0012] Food containers made using the above method effectively improve airtightness by sealing the edge seams with an airtight membrane layer, thus preventing air leakage at these seams. Furthermore, since the airtight membrane layer only covers a portion of the bottom and / or perimeter walls, and not all edge seams, the coverage area is smaller. This is especially beneficial for flat bottom walls, reducing the overall area and weight of the airtight membrane layer. This lower proportion of the airtight membrane layer's weight to the total container weight meets environmental performance requirements. Users also do not need to remove the airtight membrane layer after use, making it convenient.

[0013] A preferred solution is to place two or more airtight membranes above the lower mold, with each airtight membrane covering a portion of the edge seam.

[0014] Therefore, the airtight membrane layer formed on the food container is not formed by a single piece of airtight membrane, but by multiple airtight membranes covering a portion of the food container. This ensures that the inner wall of the food container is not entirely covered by the airtight membrane layer, thereby reducing the plastic content of the food container.

[0015] A further option is that the airtight membrane has an adhesive portion and a clamping portion, with a fracture portion formed between the adhesive portion and the clamping portion, and the fracture portion having discontinuously distributed fracture through holes.

[0016] As can be seen, by setting a fracture part on the airtight membrane, when the upper mold moves downward, the airtight membrane will break along the fracture part and adhere to the inner wall of the food container under the action of the upper mold, making the processing of the food container very convenient.

[0017] A further solution is to use tensioning elements to tension both ends of the clamping part when placing the airtight membrane above the lower mold, so that the fitting part is located above the container body.

[0018] It is evident that by tensioning the airtight membrane with tensioning components, it can be ensured that the airtight membrane is positioned in the designated location during the production process, thereby achieving the positioning between the airtight membrane and the food container and improving the pass rate of the food container.

[0019] A further option is that the tensioning element includes a winding device for winding the airtight membrane; or the tensioning element includes a clamping element for holding the airtight membrane.

[0020] Therefore, it can be seen that the airtight membrane can be fed and received by the winding device, and automated production can be achieved.

[0021] To achieve the second objective of the present invention, the present invention provides a mold for manufacturing paper food containers, comprising a lower mold with an open upper end, forming a mold cavity in which a container body formed by folding paper can be placed; an upper mold is disposed above the lower mold, and the upper mold moves toward or away from the lower mold; and the upper mold is provided with a base plate, and at least one protrusion is formed on the base plate toward the lower mold, the protrusion extending into the mold cavity of the lower mold, and causing an airtight membrane to be clamped between the protrusion and the container body. After the upper mold is heated, the airtight membrane is tightly attached to a portion of the bottom wall and / or peripheral wall of the container body to form an airtight membrane layer, and at least a portion of the bottom wall and / or peripheral wall is not covered by the airtight membrane layer.

[0022] As can be seen from the above scheme, when using the mold to manufacture food containers, the airtight film layer of the food container is formed on the inner wall of the container body by hot pressing. Since vacuum forming is not required, the production equipment does not need to be equipped with a vacuuming device, nor does it need to heat and soften the airtight film before vacuum forming. Therefore, the production time of the food container is short and the energy consumption is low. Since the produced food container is not covered with the airtight film layer on the entire bottom and side walls, the plastic content is relatively low, and the airtight film layer does not need to be torn off and discarded after use.

[0023] A preferred embodiment is that there are two or more bumps, with a gap between adjacent bumps.

[0024] Therefore, it can be seen that no airtight membrane layer is formed in the gap between two adjacent protrusions of the food container. On the one hand, this can reduce the volume of the protrusions, reduce the material used in the lower mold, and reduce the production cost of the mold. On the other hand, the area of ​​the airtight membrane layer of the food container is small and the plastic content is low, which meets the requirements of environmental protection.

[0025] A further design involves providing a stepped portion at the lower end of the bump, with the upper surface of the stepped portion higher than the lower surface of the bump in the normal direction of the substrate.

[0026] As can be seen, the shape of the protrusions can be flexibly set according to the shape of the food container to ensure that the airtight membrane layer can fit tightly against the inner wall of the food container.

[0027] A further solution is to have a flange support portion located around the periphery of the mold cavity in the lower mold, and the base plate of the upper mold can press the flange portion of the container body onto the flange support portion.

[0028] By placing the airtight membrane on the flange of the food container and then hot-pressing it, the flange of the food container is also covered with the airtight membrane layer, which can improve the food container's resistance to deformation.

[0029] A further approach is to incorporate heating devices within the upper and / or lower molds. Since heating the upper and / or lower molds is necessary when hot-pressing the airtight membrane layer onto the container body, directly placing the heating devices within the upper and / or lower molds improves their heating efficiency, allowing for rapid heating of the upper mold. Furthermore, it avoids the need for external heating devices, which would occupy a larger volume and facilitates miniaturization of the production equipment. Attached Figure Description

[0030] Figure 1 This is a first-view structural diagram of a food container manufactured using an embodiment of the paper food container manufacturing method of the present invention.

[0031] Figure 2 This is a second-view structural diagram of a food container manufactured using an embodiment of the paper food container manufacturing method of the present invention.

[0032] Figure 3 This is a structural diagram of kraft paper unfolded according to an embodiment of a method for manufacturing paper food containers.

[0033] Figure 4 yes Figure 3 A magnified view of a portion of the image.

[0034] Figure 5 This is a third-view structural diagram of a food container manufactured using an embodiment of the paper food container manufacturing method of the present invention.

[0035] Figure 6 This is a fourth-view structural diagram of a food container manufactured using an embodiment of the paper food container manufacturing method of the present invention.

[0036] Figure 7 This is a cross-sectional view of a food container manufactured using an embodiment of the paper food container manufacturing method of the present invention.

[0037] Figure 8 This is a structural diagram of the mold embodiment for manufacturing the paper food container of the present invention and the airtight membrane from a first-view perspective.

[0038] Figure 9 This is a structural diagram of the mold embodiment for manufacturing the paper food container of the present invention and the airtight membrane from a second perspective.

[0039] Figure 10 This is a structural diagram of the lower mold in an embodiment of the mold for manufacturing the paper food container of the present invention.

[0040] Figure 11 This is a structural diagram of the upper mold from a first-view perspective in an embodiment of the mold for manufacturing the paper food container of the present invention.

[0041] Figure 12 This is a structural diagram of the upper mold from a second perspective in an embodiment of the mold for manufacturing the paper food container of the present invention.

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0043] The method for manufacturing paper food containers of the present invention first uses environmentally friendly materials such as paper to make the container body of the food container, and then forms an airtight film layer on the container body by hot pressing. The airtight film layer does not cover the entire inner wall of the food container, but only covers a part of the area, thereby reducing the weight of the airtight film layer to the total weight of the entire food container.

[0044] See Figure 1 and Figure 2 The food container 10 made using the paper food container manufacturing method of the present invention has a container body 11, which is formed by folding a single piece of kraft paper. The shape of the kraft paper before folding is as follows: Figure 3 As shown. The container body 11 has a flat bottom wall 12, on which peripheral walls are formed. In this embodiment, the container body 11 has eight peripheral walls, as shown. Figure 1 As shown, in a clockwise direction, the peripheral walls are 21, 22, 23, 24, 25, 26, 27, and 28, wherein peripheral wall 21 is adjacent to peripheral walls 22 and 28, peripheral wall 22 is adjacent to peripheral walls 21 and 23, and so on. Furthermore, the lower edge of each peripheral wall 21, 22, 23, 24, 25, 26, 27, and 28 is adjacent to the bottom wall 12.

[0045] The container body 11 is an open container at the top, meaning that the end of the container body 11 away from the bottom wall 12 is open and does not have a sealing component. In use, the user places food into the container body and then seals the open end of the container body 11 with a sealing film or similar material. When the user needs to remove the food, they must first tear the sealing film or similar material from the open end of the container body 11.

[0046] See Figure 3The container body 11 is formed by folding a whole piece of kraft paper. Preferably, the surface of the kraft paper is coated with a waterproof coating, such as a plant fiber waterproof coating on one surface of the kraft paper. These waterproof coatings give the kraft paper a certain degree of waterproof performance.

[0047] Multiple fold lines are provided on the kraft paper, such as fold line 401, which is located between the bottom wall 12 and the peripheral wall 21. Folding the kraft paper along fold line 401 forms the bottom wall 12 and the peripheral wall 21 of the container body 11. Similarly, folding along fold line 402 forms the peripheral wall 22 of the container body, and folding along fold line 403 forms the peripheral wall 23 of the container body 11. It can be seen that since the bottom wall 12 of the container body 11 and each of the peripheral walls 21, 22, 23, 24, 25, 26, 27, and 28 are all formed by folding, no seam lines are formed between the bottom wall 12 and each of the peripheral walls 21, 22, 23, 24, 25, 26, 27, and 28, and the bottom wall 12 itself does not have any seam lines. Therefore, the bottom wall 12 itself has good sealing performance.

[0048] A folded portion is formed at one corner of the kraft paper 40. The folded portion includes a sheet 41, which, after being folded, forms the peripheral wall 26 of the container body 11. Additionally, folding tabs 42 and 44 are respectively provided on both sides of the sheet 41. A sheet 43 is also provided on one side of the folding tab 42, which, after being folded, forms the peripheral wall 27. When the kraft paper 40 is folded, the folding tab 42 is folded between the sheet 41 and the sheet 43, that is, onto the folded container body 11. The folding tab 42 is held between the sheet 41 and the sheet 43, as shown below. Figure 5 As shown.

[0049] Thus, a seam is formed at the connection between the sheet 41 and the folded sheet 42, such as Figure 6 As shown, a seam line 31 will be formed between peripheral wall 26 and peripheral wall 27. Seam line 31 is a gap formed by folding the sheet 41 and the folded sheet 42 together; that is, a seam line will be formed where two or more sheets of paper material overlap. Seam line 31 extends from bottom wall 12 to the upper edge of peripheral wall 27. (See attached image.) Figure 4An opening 49 is formed between sheet 43 and the adjacent sheet 48. Therefore, the position of the seam line 31 near this opening 49 is prone to air leakage. This position is the outer edge end of the seam line 31, that is, the position near the edge of the sheet paper, and is called the edge seam. Due to the existence of the edge seam, the air inside the container body 11 can pass through the edge seam and communicate with the outside air. Correspondingly, a seam line 32 is also formed between the peripheral walls 25 and 26. In this embodiment, all seam lines are formed on the peripheral walls, no seam lines are formed on the bottom wall 12, and no seam lines are formed between the peripheral walls and the bottom wall.

[0050] Because airflow occurs between the inside and outside of the container body 11 at the edge seams, this embodiment requires covering the container body 11 with an airtight membrane layer. This airtight membrane layer covers all the edge seams to ensure the food container 10's airtightness. In this embodiment, the airtight membrane layer is a thin film covering a localized area of ​​the bottom wall 12 and / or the peripheral wall. For example, this film is a plastic film made of materials such as PP, PE, PET, PA, or EVOH, or a biodegradable film. The biodegradable film can be PLA, PBS, PVOH, or PCL, and the airtight membrane layer should be a food-grade film to meet food safety requirements.

[0051] like Figure 2 As shown, the airtight membrane layers 60 and 62 are only adsorbed onto a portion of the bottom wall 12, such as at both ends along the length of the bottom wall 12. Therefore, at one end of the airtight membrane layer 60, it extends to the fold line between the bottom wall 12 and the peripheral wall 27, and at the other end, it forms an edge 61 on the bottom wall 12. Correspondingly, at one end of the airtight membrane layer 62, it extends to the fold line between the bottom wall 12 and the peripheral wall 23, and at the other end, it forms an edge 63 on the bottom wall 12. The area between edge 61 and edge 63 is not covered by the airtight membrane layer; that is, the bottom wall 12 is not covered by the airtight membrane layer in the area between edge 61 and edge 63.

[0052] Thus, the airtight membrane layer does not cover the entire bottom wall 12, but only a portion of it. Preferably, the area covered by the airtight membrane layer on the bottom wall 12 does not exceed 50% of the area of ​​the bottom wall 12, and further, the area covered by the airtight membrane layer on the bottom wall 12 does not exceed 10% of the area of ​​the bottom wall 12. Since there are no seams or edge seams on the bottom wall 12, and the kraft paper 40 itself has good airtightness, even if a large area on the bottom wall 12 is not covered by the airtight membrane layer, it will not affect the overall sealing performance of the food container 10.

[0053] Since all edge seams are formed on the peripheral wall, in this embodiment, the airtight membrane layer covers all peripheral walls, ensuring that all edge seams are covered. The excellent sealing performance of the airtight membrane layer prevents air leakage between the inside and outside of the food container 10, ensuring the sealing performance of the food container 10. Preferably, the weight of the airtight membrane layer accounts for less than 12% of the total weight of the food container 10; further, the weight of the airtight membrane layer accounts for less than 5% of the total weight of the food container 10. This results in a very small weight for the airtight membrane layer, which meets environmental protection requirements and also eliminates the need for users to remove the airtight membrane layer after use, making the food container 10 more convenient to use.

[0054] In other embodiments, the airtight membrane layer may cover only a portion of the peripheral wall, rather than covering the entire peripheral wall. This further reduces the area of ​​the airtight membrane layer, resulting in a lower weight. Of course, to ensure that the airtight membrane layer effectively seals all edge seams, a certain distance must be maintained between the edges of the airtight membrane layer and the edge seams; for example, the distance between the edges of the airtight membrane layer and the edge seams should be no less than 5 millimeters.

[0055] During the use of food container 10, users often hold the surrounding wall. Since the paper surrounding wall is relatively soft, it is easy for the surrounding wall to deform severely when the user holds it. If the user holds it with great force, it may cause the surrounding wall to break and the entire food container 10 to break, affecting the use of food container 10.

[0056] To enhance the strength of the peripheral wall, a flange 51 is provided at the upper edge of the peripheral wall, see [reference]. Figure 7 The flange 51 is formed on the peripheral wall 27 near the open end, that is, on the upper edge of the peripheral wall 27 away from the bottom wall 12. The flange 51 extends radially outward from the upper edge of the peripheral wall 27, that is, it flanges outward. See also Figure 3 A flange 46 is provided at one end of the sheet body 43 away from the bottom wall 12. There is a fold line 406 between the flange 46 and the sheet body 43. After the flange 46 and the sheet body 43 are folded along the fold line 406, the flange 46 will form a flanged part 51.

[0057] In this embodiment, each peripheral wall has a flanged portion connected to its upper edge. Therefore, flanged portions are arranged around the entire upper edge of the peripheral wall, that is, around the open end of the food container 10. Furthermore, the flanged portions are also covered with an airtight film layer. Preferably, the airtight film layer is formed on the flanged portions by hot pressing. In this way, the hardness of the flanged portions is enhanced by the hot-pressed airtight film layer, thereby enhancing the strength of the peripheral wall and making it less likely for the peripheral wall to collapse or break when the user holds it.

[0058] In addition, a folded edge portion 52 is provided at the free end of the flange portion 51, such as... Figure 7 As shown, one end of the folded edge 52 is connected to the flanged edge 51, and the free end of the folded edge 52 extends towards the bottom wall 12. In this embodiment, the folded edge 52 extends in a direction substantially perpendicular to the bottom wall 12. See also Figure 3 An extension piece 47 is provided at the end of the flange piece 46 away from the piece body 43. There is a fold 407 between the flange piece 46 and the extension piece 47. After the extension piece 47 and the flange piece 46 are folded along the fold 407, the extension piece 47 will form a folded edge portion 52.

[0059] In addition, an airtight film layer can also be covered on the folded edge 52. Preferably, the airtight film layer is formed on the folded edge 52 by hot pressing. The airtight film layer formed by hot pressing can improve the strength of the folded edge 52, thereby increasing the deformation resistance of the folded edge 52. Since the folded edge 52 is connected to the upper edge of the peripheral wall 27, this design can further improve the strength of the peripheral wall 27. Even if the user holds the peripheral wall 27, it is not easy for the peripheral wall to collapse, so that the food container 10 can maintain its original shape.

[0060] When making a food container, the first step is to make the main body 11 of the food container. First, fold a whole sheet of kraft paper, for example, and cut out a shape like... Figure 3 The kraft paper shown may have a waterproof coating on its surface. Then, it is folded to form the container body 11. It should be noted that the folded container body 11 does not have a flange or folded edge; these are formed after the airtight film layer has been hot-pressed. Next, the container body 11 is placed in a mold, and the mold forms an airtight film layer on the container body 11 through hot pressing.

[0061] See Figure 8 and Figure 9 The mold includes an upper mold 60 and a lower mold 80. The upper mold 60 can move up and down relative to the lower mold 80, meaning it can move closer to or further away from the lower mold 80. When the upper mold 60 moves upward, a gap is formed between the upper mold 60 and the lower mold 80, facilitating the placement of the container body 11 into the lower mold 80, or the removal of a food container with a heat-pressed airtight film layer from the lower mold 80. Additionally, airtight films 91 and 92 are also placed between the upper mold 60 and the lower mold 80.

[0062] See Figure 10The lower mold 80 has a cavity 81, the shape of which is the same as the outer contour of the container body 11. Therefore, when the container body 11 is placed in the cavity 81, the outer surface of the container body 11 can fit against the inner surface of the cavity 81. In addition, the lower mold 80 is also provided with a flange support 83, which surrounds the cavity 81. When the container body 11 is placed in the cavity 81, the flange 52 of the food container is located on the flange support 83.

[0063] See Figure 11 and Figure 12 The upper mold 60 has a base plate 61. At the lower end of the base plate 61, facing the lower mold 80, two protrusions 62 and 63 are provided, with a gap 84 between them. When the upper mold 60 moves downward, the two protrusions 62 and 63 can extend into the mold cavity 81 of the lower mold 80. Furthermore, the shape of each protrusion 62 and 63 at both ends of the upper mold 60 in the length and width directions matches the shape of the mold cavity 81, but a very small gap is formed between each protrusion 62 and 63 and the mold cavity 81. This gap is used to accommodate the container body 11 and the airtight membranes 91 and 92.

[0064] According to the shape of the food container to be manufactured, each protrusion 62, 63 has a step 71 at its lower end. In the normal direction of the substrate 61, the upper end face 72 of the step 71 is higher than the lower end face 70 of the protrusion 62, 63. The lower end face 70 of the protrusion 62, 63 is the end face of the protrusion 62, 63 closest to the bottom wall of the mold cavity 81. Preferably, the shape of the step 71 perfectly matches the shape of the bottom wall of the container body 11. Providing the step 71 allows the airtight membranes 91, 92 to be pressed and tightly adhered to the bottom wall of the container body 11, preventing gaps from forming between the airtight membrane layer and the bottom wall of the container body 11.

[0065] After the container body 11 is placed into the mold cavity 81 of the lower mold 80, the peripheral wall and bottom wall of the container body 11 are attached to the inner surface of the mold cavity 81. Then, two airtight membranes 91 and 92 are placed above the lower mold 81. Figure 8 As shown. Since the container body 11 is also placed inside the mold cavity 81, the two airtight membranes 91 and 92 are also located above the container body 11. Preferably, there is a gap between the two airtight membranes 91 and 92, so the two airtight membranes 91 and 92 do not completely cover the entire container body 11. Since the airtight membranes 91 and 92 are formed by hot pressing on the peripheral and bottom walls of the container body 11 to form an airtight membrane layer, each airtight membrane needs to cover a portion of the edge seams on the container body 11. Furthermore, the two airtight membranes 91 and 92 need to cover all the edge seams on the container body 11 to ensure that the formed airtight membrane layer can cover all the edge seams of the food container.

[0066] Taking the airtight membrane 91 as an example, the airtight membrane 91 has a fitting portion 94 and a clamping portion 93. A fracture portion 95 is formed between the fitting portion 94 and the clamping portion 93. The fracture portion 95 has discontinuously distributed fracture through holes, for example, the fracture portion 95 includes multiple strip-shaped through holes, which can be circular or elongated. The two ends of the clamping portion 93 are tensioned by tensioning members. In this way, before the upper mold 60 moves downward, the airtight membrane 91 always remains in a tensioned state, that is, it remains as if... Figure 8 The state shown is as follows. The position of the airtight membrane 91 can be adjusted by the tensioning member, so that the airtight membrane 91 can be precisely positioned above the container body 11, thereby ensuring that the airtight membrane layer after hot pressing is just attached to the designated position of the container body 11.

[0067] Preferably, the tensioning element includes a winding device, and both ends of the airtight membrane 91 are wound by the winding device. For example, the airtight membrane 91 is a long strip of membrane that is wound up by the winding device. In use, the winding device is used for feeding and unloading, thereby achieving automated production. In other embodiments, the tensioning element may also include clamping elements that clamp both ends of the airtight membrane 91 along its length. The shape of the airtight membrane 92 is the same as that of the airtight membrane 91, and will not be described again.

[0068] After the airtight membranes 91 and 92 are placed above the container body 11, the upper mold 60 is driven to move downward. Preferably, the upper mold 60 is driven by a cylinder or motor or other drive mechanism. When the protrusions 62 and 63 of the upper mold 60 abut against the airtight membranes 91 and 92, under the pressure of the protrusions 62 and 63, the airtight membranes 91 and 92 will break along the fracture portion 95, so that the fitting portion 94 is clamped between the protrusions 62 and 63 and the inner wall of the container body 11, while the clamping portion 93 is still tensioned by the tensioning member.

[0069] Preferably, the airtight membranes 91 and 92, in addition to covering the peripheral and bottom walls of the container body 11, should also cover the flanged and folded edges of the container body 11, so that both the flanged and folded edges are covered with an airtight membrane layer. Therefore, when the upper mold 60 moves downwards, the substrate 61 of the upper mold 60 needs to press the flanged portion of the container body 11 onto the flanged support portion 83, so that the bonding portion 94 also covers the corresponding areas of the flanged and folded edges.

[0070] Then, the upper mold 60 begins to heat. Preferably, at least one of the upper mold 60 or the lower mold 80 is provided with a heating device. Further, heating wires are respectively provided in the two protrusions 62 and 63. The heating temperature and heating time of the upper mold 60 can be determined according to factors such as the material of the container body 11, the material and thickness of the airtight membranes 91 and 92, and the area of ​​the bonding portion 94. After the upper mold 60 is heated, the bonding portion 94 will be tightly bonded to the peripheral wall, bottom wall, flange, and folded edge of the container body 11, thereby forming an airtight membrane layer on the peripheral wall, bottom wall, flange, and folded edge of the container body 11. After heating for a period of time, the upper mold 60 will move upward so as to remove the semi-finished food container covered with the airtight membrane layer from the lower mold 80.

[0071] Next, the semi-finished food container covered with the airtight film layer is moved to the next station. A mold for creating the flanges and folds is used to press the semi-finished food container covered with the airtight film layer, thereby forming flanges and folds on the upper edge of the peripheral wall. At this point, the food container is complete. Because the airtight film layer has a certain degree of toughness, the formation of the flanges and folds does not damage the airtight film layer. Furthermore, since the areas corresponding to the flanges and folds are pre-covered with the airtight film layer, both the flanges and folds are covered with the airtight film layer.

[0072] The food container manufactured using the method of this invention forms an airtight membrane layer on a localized area of ​​the bottom wall and / or peripheral wall, rather than on the entire bottom wall and / or peripheral wall. This reduces the area of ​​the airtight membrane layer and thus reduces its weight as a percentage of the overall weight of the food container. On the one hand, this reduces the amount of airtight membrane layer used, making the food container more environmentally friendly. On the other hand, while meeting the requirements for environmental performance and recycling, it avoids the inconvenience caused to users who need to tear off the airtight membrane layer after using the food container.

[0073] Furthermore, the food container manufacturing process does not use vacuum forming, but rather a thermoforming process, eliminating the need for vacuum equipment and reducing the size of the production equipment. Also, because the airtight membrane is bonded to the container body via thermoforming, there are no requirements on the thickness of the membrane, preventing damage during vacuuming due to insufficient membrane thickness. Therefore, a very thin membrane layer can be used, effectively reducing the plastic content of the food container. In addition, the airtight membrane is not heated to soften it during manufacturing, eliminating the waiting time for softening and improving production efficiency while reducing energy consumption in the food container production process.

[0074] Finally, it should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. Methods for making paper food containers, including: The container body is formed by folding paper to form a food container. The upper end of the container body is open, and the container body has a bottom wall and a peripheral wall adjacent to the bottom wall. At least one seam line is formed on the peripheral wall. The seam line is located at the seam formed by the overlapping of at least two layers of sheet paper. The outer edge of the seam line forms an edge seam. Its features are: The container body is placed on the lower mold, and an airtight membrane is placed on top of the lower mold, with the airtight membrane located above a portion of the container body. The upper mold is driven to move downward, so that the airtight membrane is clamped between the upper mold and the container body. The upper mold is heated, so that the airtight membrane is tightly attached to a part of the bottom wall and / or the peripheral wall of the container body and forms an airtight membrane layer, and all the edge seams are covered with the airtight membrane layer, while at least a part of the bottom wall and / or the peripheral wall is not covered with the airtight membrane layer.

2. The method for manufacturing a paper food container according to claim 1, characterized in that: The number of airtight membranes placed above the lower mold is two or more, and each airtight membrane covers a portion of the edge seam.

3. The method for manufacturing a paper food container according to claim 1 or 2, characterized in that: The airtight membrane has an adhesive portion and a clamping portion, and a fracture portion is formed between the adhesive portion and the clamping portion. The fracture portion has discontinuously distributed fracture through holes.

4. The method for manufacturing a paper food container according to claim 3, characterized in that: When the airtight membrane is placed above the lower mold, the two ends of the clamping part are tensioned using a tensioning member so that the fitting part is located above the container body.

5. The method for manufacturing a paper food container according to claim 4, characterized in that: The tensioning element includes a winding device for winding the airtight membrane; or The tensioning element includes a clamping element that holds the airtight membrane.

6. Molds for making paper food containers, including: The lower mold has an open upper end and forms a mold cavity, into which the container body of the food container, formed by folding paper, can be placed; An upper mold is provided above the lower mold, and the upper mold moves toward or away from the lower mold. Its features are: The upper mold is provided with a base plate, and the base plate has at least one protrusion formed in the direction of the lower mold. The protrusion extends into the mold cavity of the lower mold, and the airtight membrane is clamped between the protrusion and the container body. After the upper mold is heated, the airtight membrane is tightly attached to a part of the bottom wall and / or peripheral wall of the container body to form an airtight membrane layer, and all edge seams are covered with the airtight membrane layer, while at least a part of the bottom wall and / or peripheral wall is not covered with the airtight membrane layer.

7. The mold for making paper food containers according to claim 6, characterized in that: The number of the bumps is two or more, and there is a gap between two adjacent bumps.

8. The mold for manufacturing paper food containers according to claim 7, characterized in that: The lower end of the bump is provided with a stepped portion, and in the normal direction of the substrate, the upper end surface of the stepped portion is higher than the lower end surface of the bump.

9. The mold for manufacturing paper food containers according to any one of claims 6 to 8, characterized in that: The lower mold has a flange support portion located around the periphery of the mold cavity, and the base plate of the upper mold can press the flange portion of the container body onto the flange support portion.

10. The mold for manufacturing paper food containers according to any one of claims 6 to 8, characterized in that: A heating device is provided inside the upper mold and / or the lower mold.

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