Container closures

Abstract

An easy opening container member such as a can end, especially for a container containing pressurised products, comprises a wall having an orifice closed by a plug which is an integral part of a plastic pull tab; the free end of the plug is upset to form a rivet head which secures the pull tab to the wall and closes the orifice, whilst a layer of metal foil covers and is bonded to the back of the wall and the rivet head, preferably by a heat sealable adhesive. In manufacture of the container member, the plug is inserted and the foil laid on, and pressure, with heat if necessary, is applied so as to form the rivet head and bond the foil layer to the other components in one operation.

Description

BACKGROUND OF THE INVENTION

This invention relates to containers and container members of the kind wherein pulling a pull tab causes an orifice of the container or container member to be uncovered. It also includes within its scope a container including a said container member and a method of making said container member or container. Containers of the above kind are often called "easy opening" containers.

DESCRIPTION OF THE PRIOR ART

Known containers of the above kind include those which are commonly called "easy opening" containers, and which fall generally into four main types, in all of which uncovering of the orifice actually opens the container ready for the contents thereof to be removed.

In one said type, the container has a metal end wall having an integral removable portion defined by a score line, a metal pull tab being secured to the removable portion and adapted to break the score line by direct contact when the pull tab is pulled sharply upwards to engage, by lever action, a nose portion thereof with the score line. The orifice does not exist until the score line is broken. This type of closure requires the removable portion to be large enough for the pull tab to be attachable securely thereto, for example by soldering or by means of a "rivet" formed integrally with the removable portion and engaging in a hole in the pull tab. It is not suitable where a small orifice is required, e.g., a circular hole for pouring liquids from the container.

In another known type of easy-opening container, the container wall has just such a small hole, pre-formed in the wall and closed by a removable rubber bung. This is not generally satisfactory because it is difficult to provide a satisfactory seal, especially where the contents of the container are to be pressurised.

A third known type of easy-opening container utilises a strip of metal, which may be foil or thicker than foil, or of plastics material, bonded peelably to the outside of the container wall so as to obscure a pre-formed orifice therein. This form of closure is again not suitable for use with pressurised liquids.

A fourth known type of easy-opening container consists of a number of variations that have been proposed for improving on the sealing integrity of the third type mentioned above. For example, U.S. Pat. No. 2,870,935 (Houghtelling) describes a flat plastic strip, to serve as a pull tab, laid flat on top of a metal can end panel to cover a hole in the can end panel, a film of the same plastic material being applied on the underside of the strip to fill the hole and form a key securing the strip to the end panel. This suffers from the disadvantage that retention of the pull tab on the end panel, and sealing integrity, depend entirely on the ability of the material of the film to become and remain bonded securely to the strip over the area of the hole and also to the metal surrounding the hole. This is difficult to achieve in practice especially in mass production.

Another container of the same general type is described in U.S. Pat. No. 3,241,708 (Ronci), and has a can panel designed so that when opened there shall be a relatively large opening therein. For this purpose, part of the end panel itself consists of a separate somewhat flat member of plastic fitting in the said opening which is formed in the metal with a sharp downwardly directed edge. The flat plastic member has an integral pull tab, and is secured to the metal of the end panel simply by means of a layer of plastic film applied across the underside of both parts of the end panel and bonded thereto. The film layer also provides a measure of sealing, but this arrangement suffers from the disadvantage that the sharp edge of the metal, which is necessary for breaking the plastic film, when the pull tab is lifted, deforms the film abruptly and provides a potentially dangerous source of weakness which means that effective sealing in large quantities of cans can never be guaranteed. It also suffers from the disadvantage that the flat member must be accurately made to fit in the aperture so that on the one hand it is not loose and, on the other hand, it is not too tight so as to tend by its own resilience to spring out of the aperture. This again would be difficult to guarantee in mass production. Such a container is also likely to be somewhat expensive, and aesthetically unpleasing, especially since the flat member is rather thick and bulky.

Yet another example of this fourth general type of easy-opening end is described in British Patent Specification No. 1,059,406, and comprises a rigid, soft metal plug, again made flat and forming part of the end panel itself, the remainder of the end panel being of metal and having a relatively large aperture into which the plug is recessed, the plug being swaged to the edge of the aperture to secure it therein. Sealing is effected by an adhesive sealing compound applied to the underside of the end panel around the aperture and overlapping the underside of the swaged plug. A separate pull tab is secured to the soft metal plug, which is intended to deform out of the aperture when the pull tab is lifted. This type of can end is expensive to produce and unsuitable for small pouring orifices such as those for which the present invention is intended.

British Patent Specification No. 1,195,619 describes yet another easy-opening can end of the same general type, and involves the securing of projecting plugs of a plastic pull tab, in holes formed in a metal can end panel, by means of a layer of adhesive applied over the back of the end panel and over the plug. A layer of foil is laid over the adhesive. In this arrangement, the pull tab merely rests in the holes and is secured only by the adhesive, albeit reinforced by the foil, and sealing integrity relies entirely on the foil and adhesive, there being no particular seal between the plug itself and the hole. Furthermore, the can end panel is formed around each hole with a bead having a sharp cutting edge which is required for rupturing the adhesive and foil when the pull tab is lifted, and a thin portion of adhesive is provided to define a zone of weakness to permit such rupture. This further endangers the sealing integrity and pressure-retaining ability of the container, especially under mass production conditions. Again, in this connection the holes and the pull tab must be made very accurately to ensure reasonable quality of the can end, and this would tend to make such an end relatively expensive.

The said fourth type of known easy-opening container, as exemplified above, can be summarised as one having an end member in which a layer of suitable sealing compound is applied to the rear or inner surface of the end panel or container wall so as to overlap the periphery of an opening in the wall, whereby to bond to the wall the pull tab or strip which closes the opening.

The known examples discussed above are, among other disadvantages, either expensive, and/or unsuitable for small orifices, or do not exhibit satisfactory sealing qualities, especially when made in mass production for retaining pressurised products such as carbonated beverages. It is noted especially that the pull tabs are not secured positively by an integral portion thereof to the end panels, thus always giving rise to the possibility of accidental fracture causing the pull tab to break away, causing leakage or inability to open the container or both.

OBJECTS OF THE INVENTION

The following are among the objects of the present invention (not necessarily in order of importance) in the provision of an easy-opening container member which:

is adapted to close a small orifice in a container wall;

provides improved sealing integrity;

is suitable for containing pressurised liquids;

provides a seal not only between the container wall and an element integral with the pull tab but also further sealing behind the container wall;

has the pull tab positively secured to the container wall by an element integral therewith;

has the orifice filled by an element of the pull tab without requiring accurate manufacture to ensure satisfactory pressure-retention and sealing qualities;

is strong against accidental rupture or other accident such as to break off the pull tab or destroy the seal;

does not have any sharp metal edge or other feature deliberately creating a weakness such as to endanger the seal;

requires only a simple flat panel for insertion of the pull tab therein;

uses only a minimum amount of material compatible with other objects;

is simple and inexpensive to manufacture; and is suitable for mass production with satisfactory consistency of quality.

SUMMARY OF THE INVENTION

The invention provides a container member, or a container including such a member, wherein the said container member comprises a wall in which an orifice is formed, the orifice being closed by a plug portion formed integrally with a plastic pull tab. The member consisting of plug portion and pull tab is referred to herein and in the claims as a closure. The plug portion extends through the orifice and projects behind the container wall, and its free end is in the form of a rivet head having a flange overlying the back face of the wall (i.e. the face opposite that overlain by the pull tab) so as to secure the pull tab positively to the container wall by means of its integral plug portion. A layer of metal foil overlies, and is sealingly bonded to at least part of the back face of the wall and also to the rivet head.

In another aspect, the invention provides a method of making such a container member, wherein the plug is inserted through the orifice; the foil is applied over the back face of the wall; and pressure, with heat if necessary, is applied so as in a single operation to upset the material of the free end of the plug portion (and so form the rivet head) and also to bond the foil to the container wall and to the rivet head.

Seals are thus provided, not only between the plug portion itself, including the flange, and the wall around the orifice, but also by the foil being bonded over the edge of the rivet head.

Preferably, the foil layer is sealingly bonded to said wall by an adhesive layer. It may also be bonded to the rivet head by the adhesive layer.

The container wall may be of metal, though it may be of a suitable plastic material. Use of an adhesive layer will be necessary at least where the wall is of metal.

Use of heat for the upsetting and bonding operation is preferable, in that heat is transmitted through the foil to said free end, and by applying pressure to upset the free end so heated.

The adhesive, where used, is preferably a heat sealable adhesive, the step of upsetting the free end of the plug portion being effected by applying heat to the foil so that heat is transmitted through the foil to said free end and to said adhesive, and by applying pressure to upset the free end so heated and to press the foil layer, adhesive layer and wall firmly together. Thus application of heat and pressure causes the foil, the wall and the closure to become firmly sealed together with the adhesive, in the same operation as the formation of the rivet head.

The adhesive layer may be applied so that it overlaps the orifice, so that subsequently the rivet head as well as the wall is bonded by adhesive to the foil.

In one form of the method according to the present invention, the adhesive layer is applied to the foil and the foil and adhesive layers are therefore applied together to the container wall, either before or after the closure plug portion is introduced into the orifice. Alternatively the adhesive layer may be applied to the container wall, so that when the foil layer is applied it is applied to the adhesive layer already on the wall.

The adhesive layer may be applied to the wall before or after the closure plug portion is introduced into the orifice. It will, however, be understood that if the adhesive is applied to the wall before the introduction of the plug portion to the orifice, there will be no adhesive between the rivet head subsequently formed and that part of the foil layer which covers the rivet head, unless adhesive is applied separately to the free end of the closure plug portion. This may be done before or after introduction of the plug portion into the orifice. If adhesive is applied to the wall after such introduction, it can be applied over the free end of the plug portion at the same time.

It is essential that the rivet head be bonded to the foil layer, either by the use of adhesive between them, or by choosing the closure material so that, when heat is applied to upset the material of the plug portion of the closure, this material becomes bonded directly to the metal foil. In the latter case it is not necessary that the adhesive layer shall extend over the rivet head; in such a case the adhesive, if applied directly to the wall, will not also be applied to the free end of the plug portion; and if applied to the foil, the adhesive will be applied leaving a cricular area of the foil uncovered by adhesive, this circular area corresponding approximately to the orifice in the container wall when the foil carrying the adhesive layer is applied to the wall.

Where the adhesive layer does extend over the free end of the plug portion of the closure, the application of heat will melt or soften the adhesive and at the same time soften the material of the plug portion. There may therefore be some fusion or mixing of the plug portion material with the adhesive, thus creating a particularly strong bond, and, especially in the region of the outer periphery of the rivet head, a good seal.

The foil layer may be of aluminium or iron or any other metal compatible with the intended contents of the container. A layer of protective material such as a lacquer of known kind may be applied over the exposed surface of the foil, or over the container end wall surface after the foil has been applied thereto and the application of heat completed.

It will be realised that, in a container member according to this invention, the closure may be of such a material and so dimensioned that the rivet head flange will become severed from the remainder of the plug portion when the tab portion is pulled outwardly. However, the closure may instead be made so that the flange is sufficiently narrow and flexible to be deformed and forced up and out of the orifice without becoming severed from the remainder of the plug portion. In either case, the foil layer is ruptured around approximately the periphery of the rivet head when the closure is pulled upwards, by virtue of the bond between the closure and the foil. Thus removal of the closure also makes a hole through the foil layer, so bringing the interior of the container into communication with the outside atmosphere.

It will also be understood that, while it is perferable that the rivet head shall sealingly close the orifice in the practice of the present invention, it may in some cases be unnecessary to provide a seal in this way provided the seal provided by the foil and adhesive layers is sufficient.

Other objects and advantages of the invention will be apparent from the description, given by way of example only, of an embodiment of the invention.

IN THE DRAWINGS

FIG. 1 is a top plan view of a can end provided with a closure incorporating features of the invention, FIGS. 2 to 5 being sectional views on a larger scale taken on line II--II in FIG. 1;

FIG. 2 shows components of the can end before assembly;

FIG. 3 shows a stage in the assembly of the can end;

FIG. 4 shows the can end at the end of the assembly process;

FIG. 5 shows the can end being opened; and

FIG. 6 shows a can including the can end.

With reference to the drawings, a container comprises a generally cylindrical metal beer can, FIG. 6, having a cylindrical body 1 and a separate container member consisting of a can end 11 secured in conventional manner to the can body 1 by a peripheral seam 12. The can end 11 includes a metal end panel or container wall 13 through which there is a relatively small circular pouring hole or orifice 14.

The hole 14 is closed by a one-piece closure 15 having an elongate generally flat tab portion 16, one end of which is typically formed into a finger ring 17, and which overlies the top face 84 of the wall 13. A plug portion 18, integral with the tab portion 16, extends transversely to the plane 19 of the latter at the end thereof remote from the finger ring. The plug portion 18 is cylindrical to conform with the shape of the hole 14, and its length and diameter are such that it can be inserted easily but not too loosely into the hole 14 with its free end 20 projecting behind the wall 13.

The closure 15 is preferably of resilient plastics material, for example polypropylene.

In the method of making the container member or can end 11, the components shown in FIG. 2 are assembled together in the following manner. A sheet or strip 80 of alumimium foil, to one surface of which a layer of heat-sealable adhesive 81 has been previously applied, is applied over at least part of the inner surface 82 of the end panel 13, (i.e., the surface or face opposite the face 84), so as to overlap the hole 14 with the adhesive layer 81 between the foil 80 and the panel 13, as shown in FIG. 3. The hole 14 is then closed by inserting the plug portion 18 of the closure in the hole 14. A heated pressure member or mould tool 83, FIG. 4, is now brought into contact with the foil 80, applying heat to the foil so that heat is transmitted through the foil to the plug portion 18. The pressure member is conventionally constructed and arranged in a conventional press of any suitable, well-known kind.

The member 13 is held by suitable means, not shown, such as a clamp of conventional construction, so that the pressure member 83 can apply pressure to it as well as heat. This simultaneous application of heat and pressure upsets the free end 20 of the plug portion and so forms a rivet head 22 which closes the hole 14 and secures the closure 15 to the end panel 13. At the same time the adhesive layer 81 is activated to bond the foil layer 80 to the end panel 13 and to the rivet head 22.

The pressure member 83 is then withdrawn and the completed can end 11 is subsequently attached to the can body. The completed can end in this example is as shown in FIG. 4, the foil layer 80 being sealingly secured by the adhesive layer 81 over the surface 82, overlying the rivet head 22 and being sealingly bonded to it.

The plug portion 18 is deformed by the upsetting operation so that the rivet head 22 has a flange 23 extending from and around the shank 24 which constitutes the remainder of the plug portion, so as to overlie the wall 13 around the hole 14 and sealingly close the lower end of the hole. Some adhesive from the layer 81 may, during the application of heat and pressure by the mould tool 83, find its way between the flange 23 and wall 13, so improving the seal still further.

To open the container, an outward tensile force, as indicated at A in FIG. 5, is applied to the tab portion 16, by pulling up on the finger ring 17 in a direction such as to tend to dislodge the plug portion 18 from the hole 14. This, in this example, causes a circumferential fracture to occur as indicated at 25, whereby the flange 23 is severed from the shank 24 so that the latter is dislodged outwardly. At the same time, the foil and adhesive layers 80, 81 are ruptured adjacent the flange 23 as shown in FIG. 5, so that the closure 15, without the flange 23 but with a portion of the foil still attached to it, can then be lifted off to expose the open hole 14.

It is to be understood that the mode of rupture of the foil and adhesive layers, and of the rivet head if the latter is ruptured, is by shear action entirely or predominantly. Some slight cutting action may be provided by the raw edge of the hole 14, but such cutting is only incidental, shearing being in effect the means by which the seal is broken to release the closure.

The adhesive layer 81, if provided, may be applied, by coating or spraying or by overlaying a sheet of the adhesive material on the surface 82 before the foil layer 80 is applied and preferably before the plug portion 18 is inserted.

Although the present invention is suitable for containers for pressurised liquids, it will be understood that it can be used with containers for containing any product, liquid or otherwise, pressurised, vacuum-packed or otherwise, which is compatible chemically with the material of the closure and where the size of the dispensing or venting orifice closed by the closure is required to be relatively small.

Claims

I claim:

1. An easy opening container member comprising a wall having a dispensing opening therein, a closure of plastics material including a plug portion of an outline corresponding to the outline of said dispensing opening and an integral elongated tab portion, said plug portion extending through said dispensing opening with said tab portion overlying an outer surface of said wall and tightly engaging said wall around said dispensing opening, said plug portion terminating in a rivet head in the form of a radially extending integral flange in molded engagement with an inner surface of said wall and retaining said plug portion in place, a layer of heat sealable adhesive over said rivet head and surrounding adjacent portions of said wall inner surface, and a layer of metal foil underlying said rivet head and said surrounding adjacent portions of said wall and bonded thereto by said adhesive, said adhesive layer and said metal foil layer being molded in the area of said rivet head to define a receptacle for said rivet head, and said rivet head being molded in accordance with the molding of said layers.

2. A container member according to claim 1, constituting an end member wherein the said wall has peripheral means for securing the end member to a container body.

3. A method of making a container member, comprising the steps of inserting, through an orifice of a container member wall, a plug portion of a closure of plastics material comprising an elongate tab portion having said plug portion integral therewith and projecting transversely therefrom, so that said tab portion overlies one face of said wall, applying a layer of metal foil over at least a part of the opposite face of said wall defining said orifice, and, after said foil layer has been so applied and the plug portion so inserted, molding said foil layer and simultaneously upsetting the free end of the plug portion to form a rivet head formed in accordance with said molded foil layer and having a flange overlying said opposite face adjacent the orifice whereby to close the orifice and secure the closure to said wall, and bonding the foil layer to said opposite face and to the rivet head.

4. A method according to claim 3, wherein the step of upsetting the free end of the plug portion is effected by applying heat to the foil so that heat is transmitted through the foil to said free end, and by applying pressure to upset the free end so heated.

5. A method according to claim 4, wherein said heat and pressure are applied simultaneously.

6. A method according to claim 3, wherein the step of applying the foil layer include applying said layer with a layer of adhesive between the foil and said wall for bonding the foil layer to said wall.

7. A method according to claim 6, wherein the adhesive is a heat sealable adhesive, the step of upsetting the free end of the plug portion being effected by applying heat to the foil so that heat is transmitted through the foil to said free end and to said adhesive, and by applying pressure to upset the free end so heated and to press the foil layer, adhesive layer and wall firmly together.

8. A method according to claim 6, wherein the step of applying the foil layer comprises applying the foil layer with said adhesive layer overlapping said orifice for subsequently bonding the foil layer to the rivet head.

9. A method according to claim 6, wherein the adhesive layer is applied over the foil layer before the foil layer is applied over said wall.