METHOD OF MAKING A CAN

Abstract

The present invention relates to can-type containers, closed at one end by a flexible bottom attached to the can by means of a crimping ring which is a welded ring.

Claims

1. A method of manufacturing a can comprising, placing a bottom at one end of a body of the can, the bottom being attached to the body of the can through a retaining ring crimped to the one end of the body of the can, wherein the retaining ring is a welded ring and the bottom is formed from a flexible sheet.

2. The method of claim 1 wherein the welded ring has been obtained by welding a metal strip followed by folding the strip to form a groove.

3. The method of claim 1, wherein the welded ring also has a flat spot directed inwardly of the ring.

4. The method of claim 1, wherein the flexible sheet has a pre-cut portion consisting of a partial incision of the flexible sheet, maintaining the air impermeability.

5. The method of claim 1, according to wherein the flexible sheet comprises at least one gas-tight layer.

6. The method of claim 5, wherein the gas-tight layer is covered on at least one side by a plastic layer.

7. The method of claim 5, wherein the gas-tight layer is covered by a plastic layer on each side.

8. The method of claim 1, wherein the end of the body of the can is circular in shape.

9. The method of claim 1, wherein the end of the body of the can the is rectangular or square in shape.

10. The method of claim 1, wherein the end of the body of the can is oval in shape.

11. A method of applying a bottom to a can body comprising: (a) providing a can body with a bottom attached to an end, (b) providing a flexible sheet (c) cutting the flexible sheet to obtain a cut-out element of a same shape as the end of the can body and with a perimeter slightly larger than a perimeter of the end of the can body, (d) affixing the cut-out element to the end of the can body, (e) crimping the cut-out element to the end of the can body by crimping with a retaining ring, the retaining ring being a welded ring.

12. The method of claim 11, wherein the flexible sheet forms a gas-tight layer.

13. The method of claim 11, wherein the flexible sheet forms a gas-tight metal layer having a plastic layer on each side of the gas-tight metal layer.

14. The method of claim 1, which is carried out continuously.

15. A can having a metal body and at least one end of the metal body closed by a bottom comprising a flexible foil, wherein the flexible foil is held on the metal body by a ring crimped on the metal body, wherein the ring is a welded ring.

16. The can of claim 15, wherein the flexible foil is attached to the crimped ring.

17. The can according to claim 15, wherein the flexible foil is clamped between the metal body and the crimping ring.

18. A method for making the can of claim 15 comprising securing a flexible foil to the bottom of the can by crimping a welded ring onto the bottom of the can.

19. The method of claim 18, wherein the flexible foil forms a gas tight layer.

20. The method of claim 18, wherein the flexible foil is directly attached to the welded ring.

21. The method of claim 18, wherein the flexible foil is trapped between the can wall and the crimping ring and is secured after crimping.

Description

DESCRIPTION OF THE FIGURES

[0164] FIG. 1: A welded holding ring (1) before shaping. The weld line (11) obtained when closing the ring is also indicated.

[0165] FIG. 2: A cross-sectional view of a welded retaining ring (1) for use in crimping onto a container body. The groove (12) intended to be introduced on the end of the container body is shown, as well as the flat (13) which is directed towards the inside of the welded ring.

[0166] FIG. 3: top view of a circular welded ring according to the invention. The weld line (11) and the flattened area (13) are visible.

[0167] FIG. 4: diagram of the process of closing a can (3) according to the invention by means of a flexible bottom (2) which will be fixed by crimping between the body (3) of the can and the holding ring (1). The weld line (11) can be seen.

[0168] FIG. 5: top view of a closed can, with the presence of an opening tab (22) and a fragility line (21) to allow the breaking of the flexible bottom.

EXAMPLES

[0169] The examples below and figures describe an embodiment for cylindrical shaped cans. In these embodiments, the rings are circular. In the case of cans with a non-circular end (rectangular, oval or other), the shape of the ring is identical to that of the end.

Example 1. Manufacture of a Crimping Ring for a 4/4 can

[0170] A welded ring is made for crimping on a 4/4 can. This can has a diameter of 99 mm.

[0171] A strip is cut from a steel sheet with a width of about 9 to 11 mm and a length of 99-101 mm, with a thickness of 0.20 to 0.24, in particular 0.21 to 0.23 mm.

[0172] This steel strip is folded and its ends are welded. An industrial welding machine such as the one sold by Soudronic (Bergdietikon, Switzerland) can be used. The result is a welded ring, similar to the one described in FIG. 1, with a useful diameter of 99 mm for the hemmed area.

[0173] The ring is then shaped into the form shown in FIGS. 2 and 3. Thus, the ring is bent into an inverted U shape to form a groove (12), and a flat (13) is also formed. Devices known in the art, such as a curler mill, can be used. Steel with a suitable malleability (steel grade adapted to the can radius) is used in order to allow the formation of the folds (of the groove) necessary for the crimping.

[0174] The welded ring (1) is thus composed successively (from the outside to the inside) of a hem (121) (hemming zone), a cup (122) (hem return) and a flat (13). The hem (121) and the hem return (122) have a development of about 6 to 7 mm and form the groove (12). The flat has an effective width of about 3 to 4 mm. A steel strip with an effective width of approximately 9 to 11 mm will therefore form a welded ring for a can with a diameter of 99 mm.

Example 2. Crimping of a Non-Peelable Flexible Bottom on a 4/4 can

[0175] The step of crimping a flexible bottom (2) onto a can body (3) is shown in FIG. 4. A flexible bottom (2) is provided, which may have been cut from a film reel and has the same shape as the can body (3) and the crimping ring (1), but slightly larger dimensions (in this case, a diameter). The ring (1) is lowered onto the end of the body (3) so as to trap the bottom (2) between the ring (1) and the body (3), then the crimping is carried out by pressing on the two hems (121) and (122) forming a groove (12). The presence of the flat (13) helps to tighten the flexible bottom (2) during the assembly stage.

[0176] These steps can be carried out continuously using the same machines as those used to crimp conventional rigid bottoms.

Example 3. Crimping of a Flexible Peelable Bottom on a 4/4 can

[0177] A ring (1) as obtained according to example 1 is used. A peelable bottom is attached to this ring according to the methods known in the art for attaching peelable bottoms to rings obtained by cutting out material. The ring with the peelable bottom is then assembled on the body of a can by crimping according to the methods known in the art.

[0178] After crimping, the container can be sterilized and then a partial incision (described as (21) in FIG. 5) can be made on the flexible bottom (maintaining air impermeability which maintains the quality and integrity of the product contained in the can) to create a break line and facilitate opening, for example, via a tab or grip ring (22) which the user can pull on to induce the break and open the container.