The present invention relates to a tamper evident closure and in particular to a closure and a system for use in relation to a container having an externally threaded neck.

In recent times it has become desirable to design closures such that once a product is enclosed by a manufacturer within a container any subsequent opening ofthe container is evidenced by the breaking of some part ofthe closure or attachment thereto.

Many commercially successful tamper evident closures have been designed and where screw threaded containers are involved the most popular designs usually involve a cap having a tamper evident band suspended beneath its skirt. Although such designs have been relatively successful there are problems associated with the unintentional breaking of the small bridges which attach the band to the skirt ofthe closure which breakage often occurs during the screwing on of the closure rather than the unscrewing of the closure. In some existing

designs the tamper evident band becomes a nuisance once it breaks away from

the closure as it either falls into the product being dispensed or falls away to create a litter/pollution problem or alternatively just gets in the way. In other

designs the tamper evident feature does not provide sufficient visual evidence

that a container has been opened as a closure may be resealed and only a very close inspection will reveal that the container has been tampered with.

It is accordingly the object ofthe present invention to overcome one or more of the deficiencies associated with existing taper evident closures for screw threaded containers or at least to provide the market with an alternative.

According to the present invention there is provided a thermoplastic closure of the type having an annular internally threaded skirt; an annular skirt extension permanently attached to the skirt adjacent the skirt's lower extremity; one or more discrete arcuate sectors of the skirt extension being configured as flaps permanently affixed to the main body of the skirt extension at a first end being the trailing end during the unscrewing operation and frangibly connected to the main body of the extension at a second end being the leading end of the flap

during the unscrewing operation; container engaging means extending towards the container from each flap adjacent its second end; hinge means on each flap intermediate its first end and the container engaging means; the container engaging means being adapted to override trigger means adjacent a container neck during the running up of the closure onto the container but to lock against

the trigger means during the unscrewing operation; such locking causing the

frangible connection between the main body of the skirt extension and the

second end of the flap to fracture; and thereafter causing the container engaging

means and second end of the flap to fold inwardly about the hinge means to a tamper evident position lying against the radially inner surface of the non-folded portion of the flap; the configuration of the container engaging means and flaps ensuring that once the second end ofthe flap and container engaging means have folded back as above described then subsequent unscrewing and running up of

the closure onto the container will not cause the leading edge of the flap and

associated container engaging means to move substantially out of their tamper evident position or to resume their original position.

Figure I is a side elevation of a closure in accordance with the present invention;

Figure II is a partial section through A- A' of the closure of figure I and a

complementary container prior to closure opening;

Figure III is a partial section through A- A' of the closure of figure I and a complementary container during closure opening;

Figure IV is a partial section through A-A' ofthe closure of figure I and a complementary container after closure opening;

Figure V is a perspective view ofthe closure of figure I prior to opening.

Figure VI is a perspective view ofthe closure of figure I after opening.

Figure VII is a perspective view of an alternate embodiment ofthe present invention;

Figure VIII is a perspective view ofthe closure of figure VII after opening.

Two embodiments ofthe present invention will now be described with reference

to the accompanying drawings.

According to the embodiment of figures I to VI inclusive there is provided a closure having a top 1 and an annular internally threaded (not shown) skirt portion 2 which is knurled on the outside. Immediately below the skirt portion 2 and of substantially the same external diameter in plan view is a skirt extension 3.

In many embodiments the intersection between the skirt and skirt extension may

be virtually indistinguishable although the skirt extension should occur beneath the internally threaded portion ofthe skirt.

Skirt extension 3 incorporates a flap 4 being permanently affixed to the skirt

extension 3 at a first end 5 which corresponds to the trailing end of the flap

during the unscrewing operation. The second and leading end 6 of the flap is

attached to the skirt extension by frangible bridges 7. The second end ofthe flap is additionally provided with a container engaging tooth 8 adapted to interact with tooth 9 provided on the neck 10 (partially shown) of a container (not shown).

The flap 4 of the embodiment of figure I is distinguished (inter alia) from the skirt extension 3 of which it initially forms a part by cuts 18 and 19 one above

and one below the flap. In the case of other embodiments such as that depicted in

figures VII and VIII hereof the lowermost cut is not necessary as the bottom of the flap also comprises the bottom ofthe skirt extension.

It will be noted from figure III that during the unscrewing operation the radially innermost and leading edge of tooth 8 abuts an undercut 9 A on tooth 9. Further unscrewing ofthe closure results in fracture of bridge 7 as depicted in figure III

and a movement of flap 4 radially outwardly (as is best viewed from figure III) with respect to the skirt extension 3 and skirt 2 with the flap eventually folding back on itself about hinge 11. As the unscrewing motion continues the leading edge 6 ofthe flap together with tooth 8 folds back at approximately one hundred and eighty degrees from their original position until they contact the inner

surface of that portion of the flap between the hinge 11 and the first end of the

flap 5.

It will be appreciated that reversal of the rotation of the closure from that

direction depicted in figure III such that the closure is again being screwed onto the container results in presentation of a ramp like surface 8A associated with tooth 8 and second flap end 6 being presented to ramp like surface 12 on tooth 9. These two ramp like profiles will override each other and therefore help

prevent the second end 6 ofthe flap and container engaging tooth 8 folding back out of their tamper evident position depicted in figures IV and VI. It should be appreciated that the position depicted in figures IV and VI is a tamper evident

position having regard to the hole 13 left in the skirt extension at a position between bridge 7 and hinge 11.

It is also desirable that the thickness of material at hinge point 11 is such that after folding hinge 11 will not possess sufficient memory in order to urge a non-

folded portion of the flap between first end 5 and hinge 11 once again radially outwardly after opening ofthe cap thereby failing to maintain the tamper evident position. Conversely the non-folded portion of the flap between first end 5 and hinge 11 should ideally be fabricated of a material and in such a thickness that it

does possess memory characteristics adapted to ensure that after being flexed radially outwardly during the opening operation it seeks to return to its original position substantially aligned with skirt extension 3 in plan view.

In order to further enhance the tendency of the leading edge 6 of the flap to remain folded back at about one hundred and eighty degrees from its original position after opening the leading edge of the flap in the embodiment of figures I- VI inclusive is provided with tab 20. This tab extends upwardly from the leading edge 6 of the flap (the folding portion) and is adapted to at first move radially outwardly during the unscrewing ofthe closure and the folding about the hinge but then to move radially inwardly and come to rest adjacent an outer surface 21 of the skirt extension 3 which acts as a stop preventing the memory

associated with a non-folding portion of the flap urging the tab any further in a

radially inward direction. It will be appreciated from figure VI that tab 20 in conjunction with the memory associated with a non-folding portion of the flap and stop portion 21 of skirt extension 3 serves to maintain the leading edge 6 of the flap and tooth 8 in the tamper evident position.

It is possible to design a closure in accordance with the present invention utilising a skirt extension radially outwardly displaced from the bottom of the skirt such that the second end 6 of the flap and container engaging tooth 8 are positively locked into their tamper evidencing position after opening. Such a configuration is depicted in figures VII and VIII hereof and it will be appreciated that these embodiments rely upon the fact that the lower edge 15 of the skirt 2 extends downwardly to a location below the upper extremity of the skirt

extension 3 and more particularly below the upper extremities of the second end

6 of the flap 4 and the container engaging tooth 8. It should also be noted from

figure VIII that the portion of the flap between first end 5 and hinge 11 which does not fold back about the hinge 11 possesses sufficient resilience and memory such that it tends to reassume its original position as part of the annular skirt extension after temporarily flexing radially outwardly to permit the folding back

of its second end 6 and associated container engaging means 8 into the position

depicted in figure VIII. During the folding of the flap about the hinge 11 the

hinge 11 moves for a considerable distance radially outwardly as depicted in figure III before again moving radially inwardly when the folded portion of the flap lies against the inside ofthe non-folded portion ofthe flap in the final tamper evident position depicted at figure IV. Whilst it is desirable that the non-folded portion of the flap returns to a position as close as possible to its original position aligned with the annular skirt extension it will not be able to completely reassume this position due to the necessity of accommodating the folded portion ofthe flap between the non-folded portion and the container.

In order to assist the container engaging tooth 8 to override tooth 9 on the container during the original running up ofthe closure onto the container portion 16 ofthe skirt extension 3 on the opposite side of frangible bridge or bridges 7 to the flap 4 is configured as a tongue separated from the main body of the skirt

extension and/or cap by cut 17. Cuts 18 and 19 also extend into a corresponding

position in the embodiment of figures I- VI for the same reason.

Examples of the closure in accordance with the present invention which have

been manufactured to date utilise two flaps radially separated by about one hundred and eighty degrees each provided with one tooth comprising the container engaging means. It is envisaged that the containers for use in conjunction with closures of the present invention may be provided with

approximately six to twelve radially spaced trigger means in order that the

tamper evident feature ofthe closure may be triggered by a limited movement of the closure.

It will be appreciated that alternate embodiments apart from those two above described may be devised and are intended to fall within the scope and intendment ofthe present invention.