Method for producing a sheet metal cover
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-06-22
- Publication Date
- 2026-03-11
AI Technical Summary
Tin lids produced from deep-drawn cup-like metal containers with differently coated sides pose issues when used as flanged sheet metal lids, as the coatings may not be equally suitable for food contact and environmental exposure, leading to potential problems in packaging.
A method involving the separation of the cup base from the cup wall to form a collar, which is then expanded to create a flange-like edge, allowing the lid to be inverted and clamped between tool parts, forming a flanged connection, and optionally featuring a circumferential limiting collar for enhanced sealing, while ensuring the inside and outside coatings are appropriately suited for their respective roles.
This method enables the production of tin lids that avoid previous disadvantages by ensuring the coatings are optimally utilized, providing a suitable interface for food contact and environmental resistance, and allowing the lid to be securely connected to the packaging frame.
Smart Images
Figure EP2023066993_26122024_PF_FP_ABST
Abstract
Description
[0001] Method for producing a sheet metal lid
[0002] Field of the invention
[0003] The invention relates to a method for producing a sheet metal lid and to a sheet metal lid produced by the method according to the preambles of the independent patent claims.
[0004] background
[0005] Metal lids for food packaging, such as cans, are typically punched out of sheet metal strips or formed from the severed bottom ends of deep-drawn cup-like metal containers, the remaining part of which can subsequently also form the body of the finished filled packaging.
[0006] If metal lids are to be attached to the body of the packaging by means of a flange, it is advisable to design them as a flat bowl with a flanged edge, which can be inserted with the base of the bowl into one end of the body and then connected to it by flanging.
[0007] Severed bottom ends of deep-drawn cup-like metal containers are already bowl-shaped, so that they only need to be provided with a suitable flanged edge in order to be used as a flanged sheet metal lid for a suitable frame.
[0008] However, with sheet materials coated differently on both sides, which is often found in food packaging, there is the disadvantage that when the severed bottom end of a deep-drawn, cup-like metal container is used as a flanged sheet lid for a packaging body formed from the remaining part of the metal container, the outside of the base of the previous metal container forms the inside of the packaging. If the coatings on both sides of the sheet are not equally suitable for contact with food and the environmental influences to which the finished packaging may be exposed, problems can be expected.
[0009] Description of the invention
[0010] The task therefore arises to provide technical solutions which do not have the aforementioned disadvantages of the state of the art or at least partially avoid them.
[0011] This problem is solved by the subject-matter of the independent patent claims.
[0012] According to these, a first aspect of the invention relates to a method for producing a metal lid, in particular for use as a base for a food can.
[0013] In a first step, a deep-drawn cup-like container is produced with a cup opening, a closed cup bottom and a circumferential cup wall extending between the cup bottom and the cup opening.
[0014] The cup base and part of the cup wall are separated from this container in such a way that the separated part of the cup wall forms a collar of uniform height surrounding the cup base.
[0015] This collar is widened in a first forming operation at its end facing away from the cup bottom, such that this end forms a flange-like edge around a cup formed by the cup bottom and the lower end of the collar.
[0016] The flange-like edge thus obtained is then clamped between tool parts and in this state the cup is turned through from the underside of the cup in such a way that an inverted cup is created, the inside of which is formed by the outside of the previous cup.
[0017] The method according to the invention makes it possible to avoid the disadvantages of the prior art described at the outset.
[0018] In a preferred embodiment of the method, the flange-like edge is deformed during clamping.
[0019] In this way, for example, a circumferential limiting collar can be formed around the flange-like edge, which advantageously protrudes from the flange-like edge on the side facing away from the bowl. Such an edge can serve to form a flanged joint when the sheet metal lid is used as intended.
[0020] The collar is preferably widened by clamping the cup base between tool parts, and then inserting the collar, with its end facing away from the cup base, into a guide gap formed between tool parts and thereby widening it. This procedure has proven particularly suitable.
[0021] It is preferred that the collar be shaped when inserted into the gap such that the flange-like edge formed by its end facing away from the cup base is surrounded by a circumferential limiting collar, which advantageously protrudes from the flange-like edge on the side facing away from the bowl. Such an edge can serve to form a flanged joint when the sheet metal lid is used as intended.
[0022] Preferably, the circumferential limiting collar is formed substantially cylindrically.
[0023] In a further preferred embodiment of the method according to the invention, the limiting collar is drawn radially inward at its free end. This facilitates subsequent rolling of the collar to create a flanged connection.
[0024] This drawing in of the collar can be carried out, for example, by a rolling process or by a pressing process, as shown in the exemplary embodiment in the figures.
[0025] The inverted cup created during the inversion preferably has an outer diameter that substantially corresponds to the inner diameter of the original deep-drawn cup-like container. This makes it possible to use the remaining separated part of the original deep-drawn cup-like container as a can body, which, after being filled with a product, is closed with the sheet metal lid according to the invention.
[0026] In a further preferred embodiment of the method, the cup-like container produced is provided on the inside with a first coating, e.g. a coating suitable for foodstuffs, and is provided on the outside with a second coating which is different from the first coating, e.g. an abrasion-resistant and corrosion-resistant coating.
[0027] It is also preferred that the produced deep-drawn cup-like container has a substantially cylindrical cup interior and / or that it is made from a sheet metal blank made of sheet steel or aluminum. Such containers have proven particularly suitable.
[0028] A second aspect of the invention relates to a sheet metal lid produced by the method according to the first aspect of the invention. Brief description of the drawings
[0029] Further embodiments, advantages, and applications of the invention will become apparent from the dependent claims and from the following description with reference to the figures. Figures 1a to 1e show perspective views and sectional representations of various intermediate products in the manufacture of a sheet metal lid according to the invention;
[0030] Fig. 1 f shows a sectional view of the finished sheet metal cover produced from the intermediate products according to Figures 1a to 1e; Figures 2a to 2c show sectional views through the forming tools during a first forming operation in three different stages of progress; Figures 3a to 3c show sectional views through the forming tools during a second forming operation in three different stages of progress; and Figures 4a to 4c show sectional views through the forming tools during a third forming operation in three different stages of progress.
[0031] Ways of carrying out the invention
[0032] Figures 1a to 1e show perspective top views (Figures 1a and 1b) and sections (Figures 1c, 1d and 1e) of the various intermediate products in the inventive production of the sheet metal lid 1 according to the invention, which is shown in a side view in Fig. 1f.
[0033] Fig. 1a shows the deep-drawn cup-like container 2, which is provided as a starting product for the inventive production of the sheet metal lid 1. This has a cup opening 3, a closed cup bottom 4 and a circumferential cup wall 5 extending between the cup bottom 4 and the cup opening 3.
[0034] Fig. 1b shows the state after the cup bottom 4 with a part of the cup wall 5 has been separated from the container 2 in such a way that the part of the cup wall which has also been separated forms a collar 6 of uniform height surrounding the cup bottom.
[0035] Fig. 1c shows the cup bottom 4 separated from the cup upper part with the circumferential collar 6 formed by a part of the previous cup wall 5.
[0036] Fig. 1d shows the cup bottom 4 separated from the cup upper part with the circumferential collar 6 formed by a part of the previous cup wall 5 after the expansion of the collar 6 according to the first forming operation shown in Figures 2a to 2c.
[0037] As can be seen, the widened end of the collar 6 facing away from the cup bottom 4 now forms a flange-like edge 7 around a bowl formed by the cup bottom 4 and the lower end of the collar 6. The flange-like edge 7 is surrounded by a circumferential, cylindrically shaped limiting collar 10, which projects upwards from the flange-like edge 7 on the side facing away from the bowl.
[0038] Fig. 1e shows the bowl surrounded by a flange-like edge 7 with a circumferential cylindrical limiting collar 10 after the bowl has been turned through from the underside of the bowl according to Fig. 1d in a second forming operation such that an inverted bowl is produced, the inside of which is formed by the outside of the previous bowl. This second forming operation is shown in Figs. 3a to 3c. In this state, a sheet metal cover according to the invention according to claim 14 already exists.
[0039] Fig. I f shows the finished sheet metal cover 1, which differs from the sheet metal cover shown in Fig. 1e only in that in a third forming operation, which is shown in Figures 4a to 4c, the limiting collar 10 was drawn radially inwards at its free end.
[0040] As already mentioned, the first forming operation, in which the cup bottom 4 separated from the cup upper part with the circumferential collar 6 formed by a part of the previous cup wall 5 is brought into the shape shown in Fig. 1d according to Fig. 1c, is shown in Figs. 2a to 2c by means of sectional views through the forming tools at three different stages of progress.
[0041] As can be seen, the cup base 4 is clamped between a first tool part 8 and a second tool part 9 (Fig. 2a). A guide gap 13 is then formed between a third tool part 11 and a fourth tool part 12 (Fig. 2b), and the collar 6 is subsequently pushed into the guide gap 13 with its end facing away from the cup base 4, wherein it is widened in such a way that the widened end of the collar 6 facing away from the cup base 4 forms a flange-like edge 7 around a cup formed by the cup base 4 and the lower end of the collar 6, and the flange-like edge 7 is surrounded by a circumferential, cylindrical limiting collar 10 which projects upwards from the flange-like edge 7 on the side facing away from the cup (Fig. 2c).
[0042] The second forming operation, in which the intermediate product resulting from the first forming operation is brought into the shape shown in Fig. Id according to Fig. I f, is shown in Figures 3a to 3c using sectional views through the forming tools at three different stages of progress.
[0043] As can be seen, the flange-like edge 7 is clamped between a fifth tool part 14 and a sixth tool part 15 (Figures 3a and 3b), and in this state the cup is then turned through from the underside of the cup with a seventh tool part 16, in such a way that an inverted cup is created, the inside of which is formed by the outside of the previous cup (Fig. 3c).
[0044] The inverted bowl produced during the inversion has an outer diameter which essentially corresponds to the inner diameter of the original deep-drawn cup-like container 2.
[0045] After carrying out the first and second forming operations, the method according to the invention is already carried out according to claim 1.
[0046] The third forming operation, in which the intermediate product resulting from the second forming operation is brought into the shape shown in Fig. 1e according to Fig. 1e, is shown in Figures 4a to 4c using sectional views through the forming tools at three different stages of progress.
[0047] As can be seen, the flange-like edge 7 is clamped between an eighth tool part 17 and a ninth tool part 18 (Figures 4a and 4b), and in this state the limiting collar 10 is then drawn radially inwards at its free end by means of a tenth tool part 19, so that an inwardly directed "curl" 20 is created. This takes place here in the pressing process.
[0048] While preferred embodiments of the invention are described in the present application, it is to be clearly understood that the invention is not limited thereto and may be embodied in other ways within the scope of the following claims.
Claims
Patent claims 1. A method for producing a sheet metal lid (1), comprising the steps of: a) producing a deep-drawn cup-like container (2) with a cup opening (3), a closed cup base (4) and a circumferential cup wall (5) extending between the cup base and the cup opening; b) separating the cup base (4) together with a part of the cup wall (5) from the container (2) in such a way that the part of the cup wall that is also separated forms a collar (6) of uniform height that runs around the cup base; c) widening the collar (6) at its end facing away from the cup base (4) in such a way that this end forms a flange-like edge (7) around a cup formed by the cup base (4) and the lower end of the collar (6); d) clamping the flange-like edge (7) between tool parts (14, 15);and in this state e) inverting the bowl from the underside of the bowl in such a way that an inverted bowl is formed, the inside of which is formed by the outside of the previous bowl.; 2. Method according to claim 1, wherein the flange-like edge (7) is deformed during clamping.
3. Method according to claim 2, wherein the flange-like edge (7) is deformed during clamping in such a way that a circumferential limiting collar (10) is formed around the flange-like edge (7), which stands up from the flange-like edge (7) in particular on the side facing away from the bowl.
4. Method according to one of the preceding claims, wherein the cup base (4) is clamped between tool parts (8, 9) to widen the collar (6) and then the collar (6) is pushed with its end facing away from the cup base (4) into a gap (13) formed between tool parts (11, 12) and is widened in the process.
5. Method according to claim 4, wherein the collar (6) is shaped when inserted into the gap (13) in such a way that the flange-like edge (7) formed by its end facing away from the cup base (4) is surrounded by a circumferential limiting collar (10) which stands up from the flange-like edge (7) in particular on the side facing away from the cup.
6. The method according to claim 5, wherein the collar (6) is shaped when inserted into the gap (13) such that the limiting collar (10) is cylindrical.
7. Method according to claim 3 and / or according to one of claims 5 to 6, wherein the limiting collar (10) is retracted radially inwards at its free end.
8. The method according to claim 7, wherein the drawing-in is carried out by means of a rolling process.
9. The method according to claim 7, wherein the drawing-in is carried out by means of a pressing process.
10. Method according to one of the preceding claims, wherein the inverted cup produced during the inversion has an outer diameter which substantially corresponds to the inner diameter of the original deep-drawn cup-like container (2).
11. A method according to any one of the preceding claims, wherein the cup-like container produced (2) is provided on the inside with a first coating and on the outside with a second coating, these coatings being different.
12. Method according to one of the preceding claims, wherein the produced deep-drawn cup-like container (2) has a substantially cylindrical cup interior.
13. A method according to any one of the preceding claims, wherein the deep-drawn cup-like container (2) is made from a sheet metal blank made of steel or aluminium sheet.
14. Sheet metal lid (1) produced by the method according to one of the preceding claims.