GB2206872A

GB2206872A - Can closure

Info

Publication number: GB2206872A
Application number: GB08714029A
Authority: GB
Inventors: Frank Gourlay Thompson
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-06-16
Filing date: 1987-06-16
Publication date: 1989-01-18
Also published as: GB8714029D0

Abstract

A method of makings closure for a can comprises the steps of screw-threading the can wall 11; screwing onto the can wall a co-operatively screw-threaded collar 13 which bears frictionally against the can wall to form a seal against any subsequent passage of air between the co-operating threads and into the can; locating a lid 15 on or in the end of the collar; and seaming the lid to the collar. The can is opened by unscrewing the closure. <IMAGE>

Description

SEAMED-LID CANS Background to the Invention The invention relates to seamed-lid cans.

Lidded cans in which the can lid is seamed to the end periphery of the can wall are well-known as a general class.

Typical though not limiting examples are a can of baked beans and a can of pet food. Once seamed into the can wall, the lid of such a can forms in effect an integral part of the can.

The strength of the seam is such that the lid of a seamedlid can must, in practical terms, be removed by cutting the lid or the can wall. The lid is not intended to be removed by unfastening the seam. Simple hand-operated can openers have been available for many years and are universally used to open all but the "ring-pull" kinds of seamed-lid can.

Without such a can opener, and in any case other than the case of a ring-pull can, the user cannot easily get at the can contents. Screw-lid cans and containers generally are far more easily accessible than seamed-lid cans. But seamedlid cans are so widely used because the seam-seal provides a much better seal than does the fit between the co-operating screw threads of the screw-lid can.

The invention seeks to combine the sealing efficiency of the seamed-lid can with the ease of lid removal of the screwlid can.

Summary of the Invention The invention provides a method of lidding a seamed-lid can, comprising the steps of forming a flange at or adjacent the periphery of that end of the can wall which is to be lidded; screw-threading the can wall adjacent the flange; screwing onto the can wall a co-operatively screw-threaded collar formed with a flange which bears frictionally against the can wall flange to form a seal against any subsequent passage of air between the co-operating threads and into the can; locating the can lid on or in the end of the collar; and seaming the lid to the collar.

The combination of the frictional seal between the two flanges, and the seamed seal between the can lid and the collar, enhances the air-tightness of such a can in comparison with the conventional screw-lid can. At the same time, the lid of a can embodying the invention can be removed by unscrewing it rather than having to cut the lid from the can wall with a can opener.

One of the flanges, preferably the can wall flange, may be beaded. A beaded flange is inherently stronger than an unbeaded one. The two flanges can then be screwed together all the more tightly to give a correspondingly more nearly airtight seal.

In the case just outlined, the relative strengths of the two flanges may be such that as the one bears against the other, the bead deforms. The two flanges can then progressively be tightened one against the other without fear of deforming the deformable flange to such an extent that the seal is rendered useless. Instead, the progressively deforming bead gives ample warning that the flange-seal being created is reaching the limit of tightening that it will stand.

Where the bead deforms as just outlined, it preferably deforms against the can wall or against the collar wall as the case may be. As the lip of the bead contacts the wall, the increased resistance to deformation can be sensed, and the tightening of the two flanges against one another can cease.

The invention includes within its scope a can, lidded by a method in accordance with any of the inventive methods just defined.

Brief Description of the Drawings The accompanying drawings show at least one way in which the invention may be put into practise. It is currently the best way known to the applicant. It is only one example of forms which the invention might take within its broadest aspect.

In these drawings: Figure 1 shows in diagrammatic cross-section the initially open end wall region of a can which is to be lidded, together with a collar which screws onto the can wall; Figure 2 shows the collar screwed tightly against the can wall before the can lid is seamed onto the end of the collar; and Figures 3 and 4 show successive stages in the seaming of the lid onto the end of the collar.

Description of the Preferred Embodiment The initially open end of a circular-cylindrical metal can wall is referenced 11 in Figure 1. It has a flange 12 formed continuously around its periphery. The flange 12 is an inturned flange and is beaded as shown.

A circular-cylindrical metal collar 13 is also formed with an inturned flange, referenced 14, but this flange is not beaded. The collar 13 is a metal collar, and is screw-threaded internally below the flange to co-operate with correspondingly formed external threads in the flanged end region of the can wall 11.

Figure 1 shows the collar 13 initially screwed onto the open end of the can wall 11. As the collar travels along the can wall, the collar flange 14 bears frictionally against the can wall flange 12.

As Figure 2 shows, continued rotation of the collar 13 along the can wall once the two flanges 12, 14 have begun to bear frictionally against one another, causes the bead 12 to deform.

The bead deforms until, as illustrated in Figure 2, it contacts the can wall 11.

The relative strengths of the two flanges 12 and 14 are such that, whilst the beaded flange 12 deforms until it contacts the can wall 11, the flange 14 does not deform to any substantial extent. The result is the formation of an essentially airtight seal, between the two flanges, against any subsequent passage of air between the co-operating threads and into the can.

A circular metal can lid 15 with a continuously beaded periphery is located on the end of the collar 13, as shown in Figure 3; and the beaded periphery of this lid is then seamed to the collar in known manner. The combination of the seal between the two flanges 12 and 14, and the seam-seal between the lid 15 and the collar, substantially prevents the passage of air into the now completely closed can. The other end of the can is assumed to have been seam-lidded by conventional means.

To open the can without using a conventional car; opener, the collar 13 needs to be unscrewed. To facilitate this, the wall of the collar which overlaps the can wall 11 may carry a finger-press portion which, when pressed, weakens the can wall 11. The technology needed to achieve this is within the capabilities of the intended addressee of this specification.

Claims

CLAIMS:

1. A method of lidding a seamed-lid can, comprising the steps of screw-threading the can wall adjacent that end of the can wall which is to be lidded; screwing onto the can wall a co-operatively screw-threaded collar which bears frictionally against the can wall to form a seal against any subsequent passage of air between the co-operating threads and into the can; locating the can lid on or in the end of the collar; and seaming the lid to the collar.

2. A method of lidding a seamed-lid can, comprising the steps of forming a flange at or adjacent the periphery of that end of the can wall which is to be lidded; screwthreading the can wall adjacent the flange; screwing onto the can wall a co-operatively screw-threaded collar formed with a flange which bears frictionally against the can wall flange to form a seal against any subsequent passage of air between the co-operating threads and into the can; locating the can lid on or in the end of the collar; and seaming the lid to the collar.

3. A method according to claim 2, in which one of the flanges is beaded.

4. A method according to claim 3 in which the beaded flange is the can wall flange.

5. A method according to claim 3 or claim 4 in which the relative strengths of the two flanges are such that as the one bears against the other, the bead deforms.

6. A method according to claim 5 in which the bead deforms against the can wall or against the collar wall as the case may be.

7. A method according to any of claims 2 to 6 in which the, or at least one of the, flanges is an inturned flange.

8. A method of lidding a can, substantially as described herein with reference to the accompanying drawings.

9. A can, lidded by a method in accordance with any preceding claim.