This invention relates to push-in closures of the easy- opening type, and more p-articularly to tamper-evident closures of this type. Background of the Invention

Push-in easy-opening closures of the fully sheared type have now been in commercial production for over a decade. The two currently available types of push-in easy-opening closures are described in our United States Patent No. 4,267,938, in which Figure 1 shows a push-in easy-open can end designated Presto 1, while later figures show various forms of can end designated Presto 2.

One of the primary difficulties with a fully sheared push-in easy-opening closure is that it may be susceptible to inadvertent or surrep itious opening of the can during commercial handling or while the product is on the supermarket shelves for sale. Accidental opening of the small closure or tab by means of rough or careless handling of a can may result in the small tab in particular being partially opened to allow escape of gas or contents. However, the small tab will usually reseal in such circumstances so that the end purchaser may not be aware that such opening has occurred. Of more concern is the surreptitious opening while the can is on display in a supermarket, usually by children, who shake the can and slightly open the small tab by means of a tooth to enable some of the contents to be consumed, whereupon the can is replaced on the supermarket shelf. Summary of Invention and Object

It is an object of the present invention to provide a means by which the above described types of opening may be made more difficult, and more importantly, may be made visible, or otherwise evident, such as by leakage of the contents, to the purchaser.

In one form, the invention provides a push-in easy- opening closure in a sheet metal container member, comprising an opening in the container member, an integral

closure member for the opening formed by at least partially severing the container member, said closure member being in overlapping and underlying relationship with the free edge portion of said container- member defining said opening, and sealant means applied to the region of the edge of the closure member and the free edge portion of said container member on the inside of said container member, characterised in that the free edge portion of said closure member is formed with at least one latch member dimensioned to engages the free edge portion of said container member defining said opening to increase the push-in force required to open said closure member to a level which ensures that said sealant is fully broken whenever said closure member is opened, said latch means further preventing said closure member resealing after opening.

In one preferred arrangement, the or each latch member comprises a narrow element of said free edge portion of said closure member which slightly overlies the free edge portion of the container member defining said opening. In this form of the invention, the latch member must be displaced past said free edge portion of said container member defining said opening during the opening process. Since the latch member is slightly larger in effective diameter than the opening, the closure member is unable to return to the closed position after it has been opened.

Alternatively, the or each latch member comprises a narrow portion of the free edge portion of the closure member which is reduced in effective diameter to approximately the same diameter as said opening, and is displaced into the same plane as the plane of the free edge portion of the container member defining said opening where it binds against said free edge portion to increase the force required to open the closure. Since the binding force is released when the closure is opened, the free edge portion of the container member defining the opening will reduce slightly in diameter to prevent the closure member being repositioned in its closured position after opening.

In a particularly preferred form of each of the above

embodiments, the closure member is integrally connected to the container member by means of a narrow neck of metal defining a hinge connection for the closure member. The closure member is preferably formed with two angularly spaced latch members of either of the above types, each position at about 90° to 140° from the centre of the narrow neck of metal. In the case of small closure members, and some large closure members, only one latch member need be provided and it is preferably positioned directly opposite the hinge connection.

It is a concern of some beverage manufacturers that foreign substances may be introduced into the container through the push-in closure without being able to be visibly detected. It is therefore another object of the present invention to provide a modified closure design which inhibits the insertion of foreign objects into the container through the push-in easy-opening closure member.

In another form, the invention provides a push-in easy- opening closure in a sheet metal container member comprising an opening in the container member, an integral closure member for the opening formed by partially severing the container member, said closure member being in overlapping and underlying relationship to the free edge portion of said container member defining said opening, sealant means applied to the closure member and said free edge portion of said container member defining said opening on the inside of said container, said closure member being formed with a central upstanding portion and an outwardly extending rim portion which underlies said free edge portion of said container member, said upstanding portion being dimensioned so as to be in close proximity to said free edge portion of said container member to thereby restrict the entry of foreign objects through said closure without visibly opening said closure.

The upstanding portion preferably has sides which are as close to perpendicular to the rim as may be practically achieved. This further increases the difficulty in inserting an object between the closure member and the free edge

portion surrounding the opening.

In a particularly preferred form of this aspect of the invention, the first defined aspect of the invention is also included to further increase the likelihood that tampering with the closure member will be detected.

Two preferred forms of the above aspects of the invention will now be described with reference to the accompanying drawings in which:

Figure 1 is a fragmentary plan view of a can end having push-in easy-opening closure member of the Presto 1 type modified in accordance with one preferred form of the invention ;

Figure 2 is a perspective view of the pouring closure of Figure 1 ;

Figures 3 and 4 are sectional elevations taken along the lines 3-3 and 4-4 respectively in Figure 1 ;

Figures 5 to 7 are views corresponding to Figures 1, 2 and 4 showing a modified form of the invention, and

Figures 8 and 9 are views similar to Figures 5 and 7 showing a modified form of the embodiment of Figures 5 and 7.

Referring firstly to Figures 1 to 4 of the drawings, the closure member embodying the invention will be seen to comprise a generally circular pouring opening 1 and a smaller pressure releasing/venting opening la formed in a can end 2 by partially severing the sheet metal to form closure members 3 and 3a which are integrally connected to the can end 2 by means of narrow necks of metal 4 and 4a defining a hinge means for each closure member 3 and 5. An upstanding semi-circular bead B partly surrounds the pressure releasing closure 3a to protect it against inadvertent opening during handling. Since the closure members 3 and 3a are essentially the same in construction, only the pouring closure 3 will be further described below.

The closure members 4 and 5 formed ith an upstanding domed portion 5 surrounded by an outwardly extending rim 6. The rim 6 is disposed in overlapping and underlying relationship with a free edge portion 7 of the can end

around said opening 1 achieved by flattening a dome formed in said free edge portion 7 in the manner described in greater detail in our Australian Patent No. AU-B ,33044/71 (444,068). If desired, the .closure member 3 may additionally be coined at the rim 6, prior to the flattening operation, o increase the diameter of the closure member 3 and increase the amount of overlap provided. The top of the dome 5 may also be cointed to further increase the diameter of the closure member 3 is increased. In accordance with usual practice, the overlapping regions are covered by a suitable sealant S to hermetically seal the closure members 3 and 3a with respect to the openings 1 and la.

To enable inadvertent or surreptitious opening of the closure member to be readily detected, and to reduce undetectable access to the contents of the container by thin probes, the rim 6 of the closure is formed with two latch members 8 and 9 which overlap and overly the free edge portion 7 of the can end 2 at positions displaced about 120° from the centre of the hinge 4 in either direction. It will be appreciated that the latch members 8 and 9 may be located at other positions, such as at 90° from the centre of the hinge 4, or a single latch member may be located opposite the hinge 4.

In addition to the above, the diameter of the domed portion 5 is increased so that its side wall is as close as possible to the free edge portion 7 of the can end 2 and so that the side wall is as close as possible to perpendicular to the rim 6 thereby increasing the height of the dome 5 compared with earlier versions of the Presto 1 closure. In the present embodiment, the height of the dome 5 is of the order of 1.30 mm while the gap between the side wall of the dome 5 and the free edge portion 7 is only of the order of 0.5 mm, and may be as small as 0.25 mm. By virtue of the closeness of the side wall of the dome 5 to the free edge portion 7, its increased height and the steepness of the wall angle, great difficulty would be experienced in inserting even a small thin probe between the closure member 3 and the free edge portion 7 without significantly opening

the closure member 3, and once opening occurs, the latch members 8 and 9 prevent reclosing so that opening is visually apparent.

The latches 8 and 9 are formed during or immediately after the sheet metal severing operation in which the closure member 3 and the opening 1 are initially defined. The closure member 3 is displaced below the free edge portion 7 prior to the flattening of the free edge portion 7 to reduce the diameter of the opening 1, while the latches 8 and 9, being upwardly inclined with respect to the remaining portion of the rim 6, as shown in Figure 4, are disposed in overlying relationship to the free edge portion 7 after flattening .

The amount of overlap between the latch members 8 and 9 and the free edge portion 7 shown in Figure 4 is exaggerated for clarity, but is selected to be sufficient to increase the opening force required to be approximately equal to the force required to rupture the sealant S which is applied to the inner face of the can end 2 in the region of the rim 6 and free edge portions 7. Since the latch members 8 and 9 are larger in effective diameter than the opening 1, the closure member 3 is not able to return to the fully closed position after opening. In this way, opening of the closure member 3 may be readily detected visually and the contents of the can will be more likely to leak from the can to provide further evidence of tampering.

In the embodiment shown in Figures 5 to 7 of the drawings, the construction of the closure is essentially the same as in the preceding embodiment, with the exception that the latch members 8' and 9' are positioned in abutting relationship with the free edge portion 7 of the can end 2, in the manner shown most clearly in Figure 8 of the drawings. Since the rim 6 is usually in overlapping underlying relationship with the free edge portion 7, the latch members 8' and 9' forcibly engage the free edge portion 7 so that the force required to open the closure member 3 is increased sufficiently to ensure that closure member 3 will be fully opened by the application of the

necessary push-in force. Accordingly, opening of the closure member 3 will be much more visible than in the past, and the contents of the can will tend to leak from the can as further evidence of its opening. In Figures 6 and 7, the height of the latch means 8' and 9' has been exaggerated for clarity .

The embodiment of Figures 5 to 7 is presently preferred as it performs acceptably in practice and is not as noticeably different from a standard Presto 1 construction as the embodiment of Figures 1 to 4. However, in this embodiment, the flattening of the free edge portion 7 to produce the necessary overlap can result in displacement of the closure 3, caused by the flattening of the hinge region 4, causing unacceptable binding of the latch means 8' and 9'. To reduce this effect, the radial sever lines L defining the hinge 4 (and the hinge 4a) are extended as shown in broken outline in Figures 1 and 2, to allow this part of the metal to absorb some of the free metal resulting from the flattening operation, and reducing the displacement of the closure 3 to acceptable levels.

In the embodiment shown in Figures 8 and 9 of the drawings, the closures 3 and 3a (not shown) are each formed with additional abutments 10, which are similar in appearance to the latch means 8' and 9' but are not fully formed to engage the free edge portion 7, as shown most clearly in Figure 9 of the drawings. The purpose of the abutments 10 is to further deter the insertion of small thin probes, which must be angularly inserted at the periphery of the opening 3 in a sliding motion around the periphery. The abutments 10 and the latches 8' and 9' prevent this sliding motion and further deter such activities .

While only one tye of closure member 3 has been shown in the accompanying drawings, it will be appreciated that latch members can be formed in each of the closure members according to the Presto 2 design, although it will be appreciated that the smaller pressure releasing closure member of the Presto 2 design would in such a case cease to

have the pressure resealing property described in greater detail in the Australian and United States patent referred t.o„ a„ 1bove