Systems and methods for forming a double-domed container

Abstract

A bottom forming system for a metal container includes an assembly of domes that forms a double dome at the bottom of the container during the forming process. The dome assembly includes a first dome and a second dome that is movable relative to the first. A method for forming the bottom of a metal container comprises forming a first dome profile at the bottom of the container using the first and second domes of the assembly. The method also includes forming a second dome profile at the bottom of the container by displacing the second dome relative to the first.

Description

Systems and methods for forming a double-domed container Cross-reference to related application This application claims the benefit of U.S. provisional application No. 63 / 250,806 filed on September 30, 2021. Field of invention This application relates to systems and methods for forming containers with specific shapes and, more specifically, to systems and methods for forming metal containers with specific shapes from metals such as aluminum or aluminum alloys. Background Many containers, such as food and beverage cans, fire extinguishers, gasoline drums, oil filter housings, draft regulator housings, and many other types of items, are made from metallic materials such as aluminum, aluminum alloys, stainless steel, brass, low-carbon steel, and other suitable materials. The process of forming the container from the metallic material typically includes a series of operations, such as deep drawing and wall smoothing, a forming process, such as a sequence of steps for tapering the entire body or other mechanical forming processes, and other operations as needed to shape a metal blank into a container of the desired shape.Metal containers designed to hold pressurized contents (e.g., carbonated beverages) often incorporate a dome that extends upward from the bottom wall of the container to resist deformation under pressure. However, existing dome geometries have a lower limit for the thickness of the container wall metal; in other words, domes with a metal thickness below a certain limit will fail or deform under pressure. WO 89 / 07021 A1 relates to a can bottom forming assembly for forming the bottom wall of a can body. A body-making punch pushes the can bottom wall first against an outer forming ring, then against an intermediate forming ring, and finally against a dome die. JP H04-253533 A relates to a method for forming a seamless can bottom in which a radius portion of a seamless can preform has a cylindrical body and a flat bottom connected to the body via a radius. The inner and outer surfaces are pressed, respectively, by a punch with a ring-shaped bottom and a prestressed clamping ring; simultaneously, the lower outer surface is pressed by a doming die to form a portion of the inner wall inclined obliquely downward and inward.After forming a protruding annular portion with an inner wall connected to the outer wall by a base, and a concave center panel in an arc-shaped cross-section, the outer wall is clamped between the ring-shaped portion and the clamping ring, and the base is formed. The center panel, the inner wall portion, and the outer wall portion are moved relative to each other in the axial direction to move away from the front of the ring-shaped portion, thereby reducing the lateral width of the floor portion of the annular protrusion. JP H03-5033 A relates to a method for forming the bottom of a one-piece molded can, comprising forming a concave center panel.A peripheral portion of the central panel at the bottom has a pressure surface whose shape corresponds to the peripheral portion of the central panel to be formed, and is formed into the peripheral portion by being pressed by at least one pair of opposing pressure elements. Then, while the peripheral portion is pressed between the pressure elements, a part of the central panel within the peripheral portion is pressed into the can by a central die having a spherical pressure surface, and the bottom portion is formed into a spherical shape.WO 02 / 45882 A1 relates to a method for producing a metal container from a strip or sheet of low-carbon steel coated on at least one surface with a coherent laminated coating of a thermoplastic polymeric material. The method includes one or more redrawing steps that reduce the thickness of the side walls by means of a draw / stretch operation, and a partial reverse redrawing step to produce an initial inner chamber whose depth is achieved by reducing its height. The initial inner chamber is redesigned to produce two chambers of different diameters and depths. The diameter of the initial chamber is reduced by the redesign operation, and upon insertion into the base, the final chamber is reshaped with a new internal diameter and depth, achieved by reducing the height of the container.WO 2013 / 017485 A1 relates to a method for manufacturing a metal can body in which two or more drawing operations are used to reduce the thickness of the central portion of a cup base before drawing the side wall of the cup to form a can body. By using two or more drawing operations, it was found that it was possible to control the thickness of the base without significantly reducing the pressure performance of the finished can. Compendium The embodiments covered by this patent are defined by the claims below, not by this summary. This summary is a high-level overview of various embodiments and introduces some of the concepts further described in the Detailed Description section below. This summary is not intended to identify the key or essential features of the claimed subject matter, nor is it intended to be used in isolation to delimit the scope of the claimed subject matter. The subject matter should be understood by reference to the appropriate portions of the complete specification of this patent, to any or all of the drawings, and to each claim. The set of conical molds for a bottom forming system according to the invention is defined in claim 1 and the dependent claims thereon, and includes a first dome and a second dome. The first dome includes a first surface that engages with the base of a metal container during the base forming process. The second dome includes a second surface that engages with the base of the metal container during the base forming process. The second dome is movable relative to the first. The bottom forming system for manufacturing a metal container according to the invention is defined in claim 5 and the claims thereon, and includes a doming assembly that forms a double dome at the bottom of the metal container during the bottom forming process. The double dome formed at the bottom of the metal container includes a first dome with a first dome profile and a second dome with a second dome profile. The method for forming the bottom of a metal container according to the invention is defined in claim 10 and the claims derived therefrom, and includes forming a first dome profile on the bottom of the metal container using a first former and a second former from a set of formers. The method consists of forming a second dome profile on the bottom of the metal container by moving the second dome-forming machine relative to the first. Various implementations described herein may include additional systems, methods, features, and advantages, which may not necessarily be expressly disclosed herein but will be apparent to a person skilled in the art upon examination of the following detailed description and accompanying drawings. It is intended that all such systems, methods, features, and advantages be included in this disclosure and protected by the appended claims. Brief description of the drawings The specification refers to the following attached figures, in which the use of similar reference numbers in different figures is intended to illustrate similar or analogous components. Figure 1 illustrates a bottom forming system with a set of domes according to different embodiments. Figure 2 is a top view of the first dome of the set of domes in Figure 1. FIG.3 is a plan view of the dome assembly of FIG.1. FIG.4 is a side view of the dome assembly of FIG.1 with the dome assembly in a first configuration. FIG.5 is a side view of the dome assembly of FIG.1 with the dome assembly in a second configuration. FIG. 6 illustrates the bottom forming system of FIG. 1 during a first phase of the bottom forming process according to some embodiments. FIG.7 shows the bottom forming system of FIG.1 during a second phase of the bottom forming process. Figure 8 shows an example of the bottom of a double-domed metal container according to some embodiments. Figure 9 illustrates an example of the base of a double-domed metal container, according to different embodiments. Detailed description The subject matter of the embodiments is described herein in detail to comply with legal requirements, but this description is not necessarily intended to limit the scope of the claims. The claimed subject matter may be embodied in other ways, may include different elements or stages, and may be used in conjunction with other existing or future technologies. This description should not be construed as implying a particular order or arrangement among various stages or elements except where the order of the arrangement or the individual stages of the elements are explicitly described. Directional references such as "up," "down," "top," "bottom," "left," "right," "front," and "back," among others, are intended to refer to the orientation as illustrated and described in the figure(s) to which the components and directions refer.Although the systems and methods described in this document can be used with any metal, they can be especially useful with aluminum or aluminum alloys. This document describes systems and methods for forming the bottom of a metal container. According to the invention, the systems and methods described herein form a metal container with a double dome. According to the invention, a dome assembly includes a first dome and a second dome that can be selectively moved relative to the first dome. During the first phase of the bottom forming process, the first and second domes together create a dome profile and are attached to the bottom of a metal container to form a first dome profile. During a second phase of the bottom forming process, the second dome is displaced relative to the first to further shape the bottom of the metal container, which can modify the geometry of the first dome profile and create a second dome profile, so that the metal container has a double dome. The geometry of the double dome can withstand and improve the dome's reverse pressure resistance compared to traditional domes. Furthermore, the double dome allows for cans to be manufactured from thinner metal than traditional domed cans while still withstanding reverse dome pressure. The ability to use thinner metal can, in turn, allow for lighter cans (e.g., due to less material), potentially reducing costs for can manufacturers. In certain aspects, the systems and methods described herein can increase the dome's depth / height compared to traditional domes, modify the dome profile geometry compared to traditional domes, increase strain hardening and residual stress, and / or improve the container's dome inversion pressure.The systems and methods described in this document may offer other diverse advantages and benefits, and the benefits mentioned above should not be considered limiting. Figures 1-7 illustrate a bottom forming system 100 for forming a metal container according to various embodiments. The bottom forming system 100 can be used to shape, at least partially, various metal containers as desired, including, but not limited to, beverage containers. The bottom forming system 100 generally includes a dome assembly 102 for shaping the bottom 104 of a metal container. The bottom forming system 100 may also include a retainer 106 and a punch 108, which can assist in shaping the bottom 104 during the bottom forming process. The dome assembly 102 includes at least a first dome 110 and a second dome 112. According to the invention, and as best illustrated in FIG. 2, the first dome 110 is a sleeve having a central opening 114. In these embodiments, the second dome 112 is an insert for the first dome 110 and is at least partially located within the central opening 114 when the dome assembly 102 is assembled. The first dome 110 is illustrated surrounding the second dome 112. In some embodiments, the dome assembly 102 may include more than two domes, such as three domes. In embodiments with more than two domes, one or more of them may be movable with respect to a first dome and / or with respect to each other. As best illustrated in FIGS. 2-5, the first dome 110 includes a first surface 116, and the second dome 112 includes a second surface 118. In the illustrated configuration, the first surface 116 and the second surface 118 have a nonlinear curvature. However, the first surface 116 and the second surface 118 can have various shapes or profiles, as desired, to form dome profiles on the bottom of a metal container during the bottom forming process. By way of non-limiting example, in other embodiments, the curvature of the first surface 116 and / or the second surface 118 can be increased or decreased compared to that illustrated in FIGS. 1-7. During the bottom forming process, the first surface 116 and the second surface 118 are selectively coupled to the bottom 104 to form the bottom 104. According to the invention, the second dome 112 is selectively movable with respect to the first dome 110. In certain aspects, the second dome 112 is axially movable with respect to the first dome 110, although in other embodiments the second dome 112 may include an additional movement with respect to the first dome 110. According to the invention, the second dome 112 can be positioned within the central opening 114 of the first dome 110, and the second dome 112 is movable within the central opening 114. Various mechanisms, devices, or elements may be used to make the second dome 112 movable with respect to the first dome, including, but not limited to, various mechanical systems, pneumatic systems, hydraulic systems, magnetic systems, combinations thereof, and / or other devices or systems as desired. Referring to Figures 4 and 5, the dome assembly 102 according to the invention includes at least a first configuration and a second configuration of the first dome 110 and the second dome 112. The movement of the second dome 112 relative to the first dome 110 allows the dome assembly 102 to be adjusted to adopt either the first or the second configuration. In some embodiments, in the first configuration, the second dome 112 may be in a first position relative to the first dome 110, and in the second configuration, the second dome 112 may be in a second position relative to the first dome 110, displaced from the first position. According to the invention, and as explained in detail below, the second dome 112 is in the first position during a first stage of the bottom forming process and is in the second position during a second stage of the bottom forming process. FIG. 4 shows the dome assembly 102 in the first configuration, in which the second dome 112 is in the first position with respect to the first dome 110. As illustrated in FIG. 4, in the first position, the second surface 118 can be continuous or flush with the first surface 116 such that the first surface 116 and the second surface 118 together form a first dome profile. Figure 5 shows the dome assembly 102 in the second configuration, in which the second dome 112 is in the second position relative to the first dome 110. As illustrated in Figure 5, in the second position, the second dome 112 is moved relative to the first dome 110 such that the second surface 118 is no longer continuous with or flush with the first surface 116. In particular, a side surface 120 of the second dome 112 can optionally extend over the first surface 116. The second surface 118, offset from the first surface 116, forms a second dome profile. In Figure 5, the offset position of the second dome 112 relative to the first dome 110 has been exaggerated for clarity, but during a background forming process, the second dome 112 does not need to be moved or offset to the extent shown in Figure 5. As mentioned, in addition to the dome assembly 102, the bottom forming system 100 may optionally include the retainer 106 and the punch 108. In certain embodiments, the retainer 106 includes a receiving zone 122, and the doming assembly 102 can be positioned and moved within the receiving zone 122 during the bottom forming process. The punch 108 and retainer 106 can be used to further shape the bottom 104 of the metal container during the bottom forming process. However, the illustrated punch 108 and retainer 106 should not be considered limiting, and in other embodiments, punches and / or retainers with different shapes, profiles, characteristics, etc., may be used as desired. In other embodiments, the bottom forming system 100 may include fewer or additional elements, as desired. The following describes in detail a bottom forming process that uses the bottom forming system 100. Referring to FIG. 1, prior to bottom forming, the bottom 104 of a metal container can be supported against the dome assembly 102, optionally using the retainer 106 and / or the punch 108. In some embodiments, the punch 108 can move the bottom part 104 to engage with the retainer 106 before forming with the dome assembly 102. As shown in FIG. 6, during the first phase of the bottom forming process, the dome assembly 102 is coupled to the bottom 104 while the dome assembly is in its initial configuration. In certain embodiments, the dome assembly 102 is coupled to the base 104 by moving the dome assembly 102, by moving the base 104 (for example, using punch 108), or by a combination of both actions. As illustrated in FIG. 6, the dome assembly 102 in its initial configuration forms a first dome on the bottom 104, which has the first dome profile. Optionally, in the first stage of the bottom forming process, punch 108 can be advanced further into the retainer 106 to further shape the bottom 104. Referring to FIG. 7, during a second stage of the background forming process, the second dome 112 moves relative to the first dome 110 so that the dome assembly 102 is in the second configuration. The movement of the second dome 112 relative to the first dome 110 raises and reshapes the base 104 to include a second dome, so that the base 104 has a double dome (i.e., it includes a first dome 126, formed during the first stage, and a second dome 128, formed during the second stage). Optionally, and as illustrated in FIG. 7, the second dome 112 moving to the second position reshapes the lower part 104 in such a way that at least a portion of the lower part 104 does not come into contact with the first surface 116 or the second surface 118, and a space 124 can be formed at least partially between the dome assembly 102 and a portion of the lower part 104.In certain respects, the movement of the second dome 112 against the base 104 to raise the base 104 will increase the maximum height / depth of the dome, change the geometry of the dome profile on the base 104, and increase strain hardening and residual stress in the base 104. In certain respects, the movement of the second dome 112 in the second phase of the bottom forming process may improve the dome's inversion pressure, which may allow the use of thinner metals for the bottom 104 compared to traditional bottom forming processes. Figures 8 and 9 show two non-limiting examples of metal container bottoms formed with the dome assemblies described herein. The bottoms shown in Figures 8 and 9 are presented as examples, and other bottoms can have different profiles as desired, depending on the dome assembly used. Figure 8 illustrates a non-limiting example of a bottom 804 of a metal container formed by a dome assembly that may be similar to dome assembly 102 and includes a first dome and a second dome. The bottom 804 includes an end 838 having a first dome 826 and a second dome 828. As shown in the illustration, the first dome 826 has a first dome depth 830 and the second dome 828 has a second dome depth 832. In the illustrated configuration, the depth of the first dome 830 is 4.1605 mm (0.1638 in) and the depth of the second dome 832 is 10.922 mm (0.430 in). In certain embodiments, the second dome depth 832 is the maximum depth of the double dome. In the illustrated embodiment, the second dome 828 also includes a diameter 834 and a radius of curvature 836.In the illustrated embodiment, the diameter 834 is 39.370 mm (1.550 in) and the radius of curvature 836 is 1.270 mm (0.050 in). In other embodiments, the depth of the first dome 830, the depth of the second dome 832, the diameter 834, and the radius of curvature 836 may take on other values ​​as desired and depending on the set of domes. Figure 9 shows a non-limiting example of a bottom 904 of a metal vessel formed by a set of domes, which may be similar to the dome set 102 and includes a first dome and a second dome. The bottom 904 includes an end 938 having a first dome 926 and a second dome 928. As shown in this example, the first dome 926 has a first dome depth 930, and the second dome 928 has a second dome depth 932. In the illustrated configuration, the depth of the first dome 930 is 6.223 mm (0.245 in.), and the depth of the second dome 932 is 11.252 mm (0.443 in.). In certain embodiments, the second dome depth 932 is the maximum depth of the double dome. In the illustrated embodiment, the second dome 928 also has a diameter 934 and a radius of curvature 936.In the illustrated embodiment, the diameter 934 is 33.020 mm (1.300 in) and the radius of curvature 936 is 1.270 mm (0.050 in). In other embodiments, the depth of the first dome 930, the depth of the second dome 932, the diameter 934, and the radius of curvature 936 may take other values ​​as desired and depending on the set of domes.

Claims

1. A dome assembly (102) for a bottom forming system (100), the dome assembly (102) comprising: a first dome (110) comprising a first surface (116) configured to engage with the bottom (104) of a metal container during a bottom forming process; and a second dome (112) comprising a second surface (118) designed to engage with the bottom (104) of the metal container during the bottom forming process, wherein the second dome (112) is movable with respect to the first dome (110), wherein the first dome (110) is a sleeve and the second dome (112) is a movable insert within the sleeve, characterized in that the first dome (110) and the second dome (112) are configured to jointly form a first dome (126) on the bottom (104) of a metal container during a first stage of the bottom forming process,and that the second dome (112) is configured to form a second dome (128) at the bottom (104) of the metal container during a second stage of the bottom forming process.

2. The dome assembly (102) of claim 1, wherein the second dome (112) is movable within the first dome (110).

3. The dome assembly (102) of claim 1 or 2, wherein the second dome (112) is axially movable with respect to the first dome (110).

4. The dome assembly (102) of any one of claims 1 to 3, wherein the dome assembly (102) can be positioned in a first configuration and a second configuration, wherein, in the first configuration, the first surface (116) is continuous with the second surface (118) and together they form a first dome profile, and wherein, in the second configuration,The second surface (118) is offset from the first surface (116), and the second surface (116) forms a second dome profile.

5. A bottom forming system (100) for forming a metal container, wherein the bottom forming system (100) comprises the dome assembly (102) according to claim 1, configured to form a double dome at the bottom (104) of the metal container during a bottom forming process, comprising a first dome (126) with a first dome profile and a second dome (128) with a second dome profile.

6. The bottom forming system (100) of claim 5, wherein the second dome (112) is selectively movable with respect to the first dome (110).

7. The bottom forming system (100) according to claim 5 or 6,wherein the second dome (112) is axially movable with respect to the first dome (110).

8. The bottom forming system (100) of any of claims 5-7, wherein the first dome (110) comprises a first surface (116) and the second dome (112) comprises a second surface (118), wherein the second dome (112) is movable with respect to the first dome (110) such that, in a first position of the second dome (112) with respect to the first dome (110), the first surface (116) is continuous with the second surface (118), and, in a second position of the second dome (112) with respect to the first dome (110), the second surface (118) is offset with respect to the first surface (116).

9. The bottom forming system (100) of any one of claims 5-8, further comprising: a punch (108); and a retainer (106) comprising a receiving area for a metal container,and wherein the dome assembly (102) is movable within the receiving area.

10. A method for forming the bottom (104) of a metal container, comprising: forming a first dome profile on the bottom (104) of the metal container using a first dome (110) and a second dome (112) from a set of domes (102); and forming a secondary dome profile at the bottom (104) of the metal container by displacing the second dome (112) with respect to the first dome (110), wherein forming the first dome profile comprises axially moving the first dome (110) and the second dome (112) together in a first direction to engage with the bottom (104) of the metal container, and wherein forming the second dome profile comprises moving the second dome (112) with respect to the first dome (110) in the first direction, and wherein the first dome (110) is a sleeve and the second dome (112) is an insert within the sleeve,and wherein forming the second dome profile comprises moving the second dome (112) while the second dome (112) is at least partially inside the sleeve.

11. The method of claim 10, wherein forming the second dome profile comprises axially moving the second dome (112) with respect to the first dome (110).

12. The method of claim 10 or 11, wherein forming the first dome profile comprises using a punch (108) to further form the first dome profile on the bottom (104) of the metal container.

13. The method of any one of claims 10-12, wherein forming the first dome profile comprises coupling a first surface (116) of the first dome (110) and a second surface (118) of the second dome (112) with the bottom (104) of the metal container.

14. The method of claim 13,wherein the formation of the second dome profile comprises moving the second dome (112) with respect to the first dome (110) so that at least a portion of the bottom (104) of the metal container does not come into contact with the first surface (116) or the second surface (118).

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