Method for making bowl-shaped packaging containers using sheet metal

Abstract

This invention provides a method for manufacturing bowl-shaped packaging containers using thin metal sheets, belonging to the field of processing technology. It solves the problem of the high difficulty in processing the decorative layer of existing bowl-shaped packaging containers. The method for manufacturing bowl-shaped packaging containers using thin metal sheets follows these steps: First, cutting the sheet; second, using a cold extrusion die to cold extrude the circular sheet into a container blank; third, using a cold extrusion die to cold extrude the container blank into a container preform; fourth, using a cold extrusion die to cold extrude the container preform into a container final form; fifth, removing the excess flat portion from the container preform to obtain the finished packaging container. This method for manufacturing bowl-shaped packaging containers using thin metal sheets is suitable not only for pre-processing coatings and decorative layers onto the surface of thin metal sheets before cold extrusion plastic deformation, but also for pre-cold extrusion plastic deformation of thin metal sheets into finished packaging containers before processing coatings and decorative layers.

Description

Technical Field

[0001] This invention belongs to the field of work technology and relates to a stamping process, particularly a method for making bowl-shaped packaging containers using thin metal sheets. Background Technology

[0002] Packaging containers generally refer to the collective name of packaging equipment, materials, and other auxiliary materials used according to certain technical specifications during the commodity circulation process to protect goods, facilitate storage, facilitate transportation, promote sales, prevent environmental pollution, and prevent safety accidents. Packaging containers can be categorized by shape (bags, boxes, bottles, cans, etc.) and by manufacturing material (plastics, metals, cardboard, wood, etc.). In daily life, packaging containers made of thin metal sheets are more common, such as aluminum cans for cola and beer, and tin cans for luncheon meat.

[0003] A bowl is a utensil for holding food, typically round with a wide mouth and a narrow base. Making packaging containers for foods like porridge and rice into a bowl shape better suits everyday eating habits and enhances the consumer experience. Therefore, those skilled in the art desire to propose a bowl-shaped packaging container made from thin metal sheets.

[0004] Chinese patent literature has disclosed a container forming apparatus, a container forming method, a container, and a method for packaging instant food using the container (application publication number CN112654486A). The container is bowl-shaped, and its bottom and side portions are formed by thermoforming. The inner surface of the container must have a coating that protects against metal and the contents, while the outer surface usually has a decorative layer. The aforementioned method of forming containers using thermoforming means that the coating and decorative layer must be applied after forming. For bowl-shaped packaging containers with complex shapes or curved surfaces, this increases the difficulty of processing the coating and decorative layer, reducing processing costs and the yield rate. Summary of the Invention

[0005] This invention proposes a method for manufacturing bowl-shaped packaging containers using thin metal sheets. The technical problem this invention aims to solve is how to propose another method for manufacturing bowl-shaped packaging containers using thin metal sheets, in which the coating and decorative layer processing can be carried out before or after the packaging container is formed.

[0006] The technical problem to be solved by the present invention can be achieved by the following technical solution: a method for making a bowl-shaped packaging container using a thin metal sheet, characterized in that the bowl-shaped packaging container includes a bottom, an rim, and a side wall connecting the bottom and the rim, the side wall being inclined relative to the bottom, and the rim being used for sealing connection with the container lid; this method is carried out in the following sequence of steps;

[0007] The first step is cutting; the thin metal sheet is cut into multiple circular pieces;

[0008] The second step is blank pressing; the circular sheet is cold-extruded and deformed into a container blank using a cold extrusion die. The inner area of ​​the circular sheet is plastically deformed into a cylindrical blank, and the outer area of ​​the circular sheet is plastically deformed into an annular flat plate connected to the edge of the blank.

[0009] The third step is sidewall preforming; the container blank is cold extruded and deformed into a container preform using a cold extrusion die; the container preform has a preformed sidewall that matches the shape of the finished packaging container, and the sidewall of the blank is plastically deformed into a preformed sidewall.

[0010] The fourth step is container precision forming; the container preform is cold-extruded and deformed into a container precision forming part using a cold extrusion die; the container precision forming part has the same bottom, rim, and sidewalls as the finished packaging container, and also has an extra flat plate connected to the rim; the inner ring area of ​​the preformed sidewalls and annular flat plate of the container preform is plastically deformed into the sidewalls and rim of the finished packaging container, and the width of the annular flat plate is reduced.

[0011] Step 5: Trim the edges; remove the excess flat portion from the preformed container to obtain the finished packaging container.

[0012] Compared to existing technologies, this bowl-shaped packaging container is formed using a cold extrusion plastic deformation method. The coating and decorative layers processed before the packaging container is formed will not be damaged by heat; that is, the coating and decorative layers are processed on both surfaces of the metal sheet. There is no stretching during the cold extrusion plastic deformation process, and the thickness of the metal sheet remains constant, thus preventing stretching damage to the coating and decorative layers processed before the packaging container is formed. The sidewalls of the bowl-shaped packaging container are formed by cold extrusion plastic deformation in three stages, reducing the amount of plastic deformation per stage, thereby reducing the possibility of cracking, improving product qualification rate, and improving product dimensional consistency. The cylindrical preform is suitable for cold extrusion deformation into sidewalls of different shapes, improving the versatility of the preform. In summary, the method of using metal sheets to make bowl-shaped packaging containers is suitable not only for processing the coating and decorative layers onto the surface of the metal sheet before cold extrusion plastic deformation, but also for cold extruding the metal sheet into the finished packaging container first, and then processing the coating and decorative layers.

[0013] Preferably, the outer edge of the bottom is a planar contact section, the central region of the bottom is higher than the planar contact section, and the planar contact section is connected to the central region in sequence through a reinforcing section with a radial cross section of V-shape and an inclined connecting section.

[0014] Preferably, the opening portion includes a vertical section and a horizontal section, which are connected by an arc transition section; the vertical section of the opening portion and the side wall portion are connected by a tapered section or an arc surface.

[0015] The aforementioned bowl-shaped packaging container structure not only facilitates forming during cold extrusion but also improves the strength of the bowl-shaped packaging container, especially reducing the possibility of damage to coatings and decorative layers made on thin metal sheets during cold press forming.

[0016] Preferably, the bottom wall and side wall of the blank, as well as the side wall and the annular flat plate portion of the blank, are transitioned by a circular arc surface.

[0017] Preferably, the height of the blank is h1, and the height of the finished bowl-shaped packaging container is h2, where h1 > 0.8h2.

[0018] Preferably, the diameter φb1 of the blank is located between the diameter of the upper end of the side wall of the finished bowl-shaped packaging container and the diameter of the bottom, and the bottom wall diameter φc1 of the blank is greater than the bottom wall diameter φc2 of the finished bowl-shaped packaging container.

[0019] Preferably, the height of the preformed sidewall is greater than the height of the sidewall of the blank.

[0020] Preferably, the bottom wall diameter of the container preform is the same as the bottom wall diameter of the finished bowl-shaped packaging container.

[0021] The aforementioned structure and values ​​of the preform not only facilitate forming during cold extrusion, but also reduce the likelihood of damage to coatings and decorative layers made on thin metal sheets during cold press forming. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the manufacturing process of this bowl-shaped packaging container.

[0023] Figure 2 This is a schematic diagram of the cross-sectional structure of the billet.

[0024] Figure 3 This is a schematic diagram comparing the cross-sectional structure of the blank and the cross-sectional structure of the container preform.

[0025] Figure 4 This is a schematic diagram comparing the cross-sectional structure of the container preform and the container precision-formed part.

[0026] Figure 5 This is a schematic diagram comparing the cross-sectional view of the precision-formed container part with the cross-sectional view of the finished container.

[0027] In the figure, 1. Bowl-shaped packaging container; 1a. Bottom; 1a1. Planar contact section; 1a2. Central area; 1a3. Reinforcing section; 1a4. Connecting section; 1b. Edge; 1b1. Vertical section; 1b2. Horizontal section; 1c. Side wall; 2. Circular piece; 3. Container blank; 3a. Blank body; 3b. Annular flat plate; 4. Container preform; 4a. Preformed side wall; 5. Container finished part; 5a. Excess flat plate. Detailed Implementation

[0028] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0029] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0030] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0031] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0032] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0033] like Figure 1 and Figure 5 As shown, the bowl-shaped packaging container 1 is generally conical in shape, with the diameter of the opening being larger than the diameter of the bottom. The bowl-shaped packaging container 1 includes a bottom 1a, an rim 1b, and a side wall 1c. The bottom 1a and the rim 1b are connected by the side wall 1c, and there is a smooth arc transition between the bottom 1a and the side wall 1c.

[0034] The outer edge of the bottom 1a is a planar contact section 1a1. The central region 1a2 of the bottom 1a is higher than the planar contact section 1a1. The planar contact section 1a1 is connected to the central region 1a2 in sequence through a reinforcing section 1a3 with a radial cross section of V and an inclined connecting section 1a4. This structure not only reduces the contact area between the bowl-shaped packaging container 1 and the plane and improves the stability of the bowl-shaped packaging container 1, but also increases the strength of the bottom 1a and prevents the central region 1a2 of the bottom 1a from sinking after the contents of the bowl-shaped packaging container 1 are filled.

[0035] The side wall portion 1c is inclined relative to the bottom 1a. The accompanying drawings show that the side wall portion 1c has two arc surfaces. The shape of the side wall portion 1c can be adjusted according to the actual situation.

[0036] The rim 1b is used for a sealing connection with the container lid; the rim 1b includes an upright section 1b1 and a horizontal section 1b2, which are connected by an arc transition section; the upright section 1b1 is not necessarily vertical, but can also be inclined; this rim 1b not only facilitates processing and forming, but is also suitable for matching with lids of many different structures. The accompanying drawings show that the upright section 1b1 and the side wall 1c of the rim 1b are transitioned by a tapered section, but depending on the actual situation, the transition between the upright section 1b1 and the side wall 1c can also be a curved surface.

[0037] A method for manufacturing the above-mentioned bowl-shaped packaging container 1 using a thin metal sheet is carried out in the following sequence of steps;

[0038] The first step is cutting. Cutting involves cutting a large sheet or roll of thin metal into multiple circular pieces. The thin metal sheet is made of aluminum or iron.

[0039] The second step is blank pressing. Blank pressing involves cold-extruded the disc 2 into a container blank 3 using a cold extrusion die. The container blank 3 includes a cylindrical blank 3a and an annular flat plate 3b connected to the edge of the blank 3a. The disc 2 is referred to from the inside out as the central region 1a2, the middle region, and the outer region. During the cold extrusion deformation process, the central region 1a2 of the disc 2 corresponds to the bottom wall of the blank 3a, the outer region of the disc 2 is plastically deformed into the annular flat plate 3b, and the middle region of the disc 2 is plastically deformed into the side wall of the blank 3a. The bottom wall and side wall of the blank 3a, as well as the side wall of the blank 3a and the annular flat plate 3b, are all transitioned by curved surfaces. This not only facilitates forming but also avoids creases and improves the aesthetics of the bowl-shaped packaging container 1.

[0040] During plastic deformation, the metal flows, and the wall thickness of the container blank 3 remains constant relative to the thickness of the metal sheet. Therefore, a suitable size of circular piece 2 can be selected based on the side surface area of ​​the finished bowl-shaped packaging container 1. For example, if the side surface area of ​​the finished bowl-shaped packaging container 1 is 185 cm², a circular piece 2 with a diameter of 158 mm can be selected. During plastic deformation, the outer edge of the annular flat plate portion 3b is wavy, which is an objective fact. The area of ​​the circular piece 2 is slightly larger than the side surface area of ​​the finished bowl-shaped packaging container 1, which leaves a small margin and avoids material shortage at the rim 1b.

[0041] The average outer diameter of the outer edge line of the annular plate portion 3b is necessarily smaller than the diameter of the circular piece 2. For example, if the outer diameter φa1 of the annular plate portion 3b is 120mm, the larger the outer diameter of the annular plate portion 3b, the smaller the height h1 of the blank 3a. The height of the bowl-shaped packaging container 1 is h2, and preferably, the height h1 of the blank 3a is greater than 0.8h2. The diameter φb1 of the blank 3a is located between the upper port diameter of the side wall portion 1c of the finished bowl-shaped packaging container 1 and the diameter of the bottom 1a. Preferably, the diameter φb1 of the blank 3a is only slightly smaller than the upper port diameter φb2 of the side wall portion 1c of the finished bowl-shaped packaging container 1. The bottom wall diameter φc1 of the blank 3a is greater than the bottom wall diameter φc2 of the finished bowl-shaped packaging container 1. In general, the above values ​​of the blank 3a ensure the area required to form the side wall portion 1c of the finished bowl-shaped packaging container 1.

[0042] In actual production, by optimizing the structure of the cold extrusion die, the first and second steps can be performed at the same workstation.

[0043] The third step is sidewall preforming. Sidewall preforming involves cold-extruded the container blank 3 into a preformed container part 4 using a cold extrusion die. The preformed container part 4 has a preformed sidewall 4a that matches the shape of the sidewall portion 1c in the finished packaging container. Specifically, the attached drawings show that the sidewall portion 1c has two arc-shaped surfaces; therefore, the preformed sidewall 4a also has two arc-shaped surfaces, differing mainly in size and slightly in height. During this process, the sidewall of the blank 3a undergoes plastic deformation into the preformed sidewall 4a, and the height of the preformed sidewall 4a is greater than the sidewall height of the blank 3a. The bottom diameter of the preformed container part 4 is approximately the same as the bottom diameter of the finished bowl-shaped packaging container 1. During plastic deformation, the metal flows, and the thickness of the preformed container part 4 relative to the metal sheet remains constant.

[0044] The fourth step is container precision forming. The container preform 4 is cold-extruded and deformed into the container precision form 5 using a cold extrusion die. The container precision form 5 has the same bottom 1a, rim 1b, and sidewall 1c as the finished packaging container. The container precision form 5 also has a redundant flat plate 5a connected to the rim 1b. Specifically, the bottom wall of the container preform 4 is plastically deformed into the bottom 1a of the finished packaging container; the preformed sidewall 4a and the inner ring area of ​​the annular flat plate 3b of the container preform 4 are plastically deformed into the sidewall 1c and rim 1b of the finished packaging container; during this process, the width of the annular flat plate 3b decreases; part of the annular flat plate 3b becomes the flat section 1b2 of the rim 1b, and the remainder is the redundant flat plate 5a, also known as excess material. During the plastic deformation process, the metal flows, and the thickness of the container precision form 5 relative to the metal sheet remains unchanged.

[0045] The fifth step is trimming. Trimming involves removing the excess flat portion 5a of the annular flat portion 3b in the container preform 4, that is, using a punching method to remove the excess material of the annular flat portion 3b, to obtain the finished packaging container.

Claims

1. A method of making a bowl-shaped packaging container from a sheet of metal, characterized in that, The bowl-shaped packaging container comprises a bottom, a rim and a sidewall connecting the bottom and the rim, the sidewall is inclined relative to the bottom, the sidewall has two circular arc surfaces, the bottom and the sidewall are smoothly connected by a circular arc, the rim is used for sealing connection with a container cover, the rim comprises a vertical segment and a horizontal segment, the vertical segment and the horizontal segment are connected by a circular arc transition segment, the vertical segment of the rim and the sidewall are connected by a tapered segment or a circular arc surface; The method for manufacturing the bowl-shaped packaging container by using a metal sheet is performed in the following order: Step 1: cutting; the metal sheet is cut into multiple circular pieces; Step 2: blank pressing; the circular piece is cold extruded into a container initial blank by using a cold extrusion die, the wall thickness of the container initial blank remains unchanged relative to the thickness of the metal sheet; The inner region of the circular piece is plastically deformed into a cylindrical blank body, the center region of the circular piece corresponds to the bottom wall of the blank body, the middle region of the circular piece is plastically deformed into the sidewall of the blank body, and the peripheral region of the circular piece is plastically deformed into an annular flat plate part connected to the rim of the blank body, the bottom wall and the sidewall of the blank body and the sidewall and the annular flat plate part of the blank body are connected by a circular arc surface; Step 3: sidewall preforming; the container initial blank is cold extruded into a container preformed part by using a cold extrusion die, the container preformed part remains unchanged relative to the thickness of the metal sheet; The container preformed part has a preformed sidewall matched with the shape of the finished packaging container, the sidewall of the blank body is plastically deformed into the preformed sidewall, the preformed sidewall has two circular arc surfaces, the height of the preformed sidewall is greater than the height of the sidewall of the blank body, and the bottom wall diameter of the container preformed part is the same as the bottom wall diameter of the finished bowl-shaped packaging container; Step 4: container fine forming; the container preformed part is cold extruded into a container fine formed part by using a cold extrusion die, the container fine formed part remains unchanged relative to the thickness of the metal sheet; The container fine formed part has the same bottom, rim and sidewall as the finished packaging container, and further has a surplus flat plate part connected to the rim; the bottom wall of the container preformed part is plastically deformed into the bottom of the finished packaging container, the preformed sidewall of the container preformed part and the inner ring region of the annular flat plate part are plastically deformed into the sidewall and the rim of the finished packaging container, and the width of the annular flat plate part is reduced; Step 5: edge cutting; the surplus flat plate part of the container preformed part is cut off to obtain the finished packaging container; In the cold extrusion plastic deformation process of steps 2 to 4, the metal sheet is not stretched, the thickness of the metal sheet remains unchanged, and the coating and the decorative layer will not be stretched and damaged.

2. The method of manufacturing a bowl-shaped packaging container from a sheet of metal according to claim 1, characterized in that, The outer edge of the bottom of the bowl-shaped packaging container is a flat contact segment, the center region of the bottom is higher than the flat contact segment, and the flat contact segment is connected to the center region through a radial cross-section V-shaped reinforcing segment and an inclined connecting segment in sequence.

3. The method of making a bowl-shaped packaging container from a sheet of metal according to claim 1, wherein, The height of the blank body is h1, and the height of the finished bowl-shaped packaging container is h2, h1>0.8h2.

4. The method of manufacturing a bowl-shaped packaging container from a sheet of metal according to claim 3, characterized in that, The diameter φb1 of the blank body is between the diameter of the upper end of the sidewall of the finished bowl-shaped packaging container and the diameter of the bottom, and the bottom wall diameter φc1 of the blank body is greater than the bottom wall diameter φc2 of the finished bowl-shaped packaging container.

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