WO1995028334A1

WO1995028334A1 - Tamper evident closure

Info

Publication number: WO1995028334A1
Application number: PCT/AU1995/000212
Authority: WO
Inventors: Michael Verter
Original assignee: G V Engineering Pty Ltd
Priority date: 1994-04-15
Filing date: 1995-04-13
Publication date: 1995-10-26
Also published as: AUPM505594A0

Abstract

A thermoplastic closure (1) having an annular internally threaded skirt (2) portion; one or more portions of the skirt beneath the internally threaded portion being configured as a flap (7) capable of folding radially outwardly with respect to the skirt about a vertical hinge (12); container engaging means (4) extending towards the container from a position on the flap adjacent its leading edge (with reference to the unscrewing operation) and being adapted to interact with a trigger (9) on or near the neck of the container; the configuration of the container engaging means and trigger means facilitating ratchet-like interaction between the two components whereby they override each other during the running up of the closure onto the container but during unscrewing of the closure from the container the two components interfere with each other so as to impede unscrewing of the closure; one or more frangible joints (13) joining the leading edge of the flap to the closure skirt such frangible joints being adapted to fracture after the container engaging means and trigger means have engaged each other during the unscrewing operation; the flap being adapted to fold radially outwardly about its vertical hinge after said fracture.

Description

TAMPER EVIDENT CLOSURE

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 of the container is evidenced by the breaking of some part of the 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 sldrt. 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 of the 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 of the 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 having an annular internally threaded skirt portion; one or more portions of the skirt beneath the internally threaded portion being configured as a flap capable of folding radially outwardly with respect to the skirt about a vertical binge; container engaging means extending towards the container from a position on the flap adjacent its leading edge (with reference to the unscrewing operation) and being adapted to interact with a trigger on or near the neck of the container; the configuration of the container engaging means and trigger means facilitating ratchet-like interaction between the two components whereby they override each other during the running up of the closure onto the container but during unscrewing of the closure from the container the two components interfere with each other so as to impede unscrewing of the closure; one or more frangible joints joining the leading edge of the flap to the closure skirt such frangible joints being adapted to fracture after the container engaging means and trigger means have engaged each other during the unscrewing operation; the flap being adapted to fold radially outwardly about its vertical binge after said fracture.

One embodiment of the present invention will now be described with reference to the accompanying drawings in which:

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

Figure II is a bottom plan view of the closure of Figure I;

Figure III is a section through A- A' of the closure of Figure I in place upon a container;

Figure IN is a section through the closure and container of Figure HI during the opening operation;

Figure N is an enlarged perspective view of the embodiment depicted in Figure I; and Figure VI is a perspective view of a cap in accordance with the present invention differing from those depicted in Figures I-N hereof.

The embodiment of the present invention depicted in Figures I-IN hereof discloses a closure 1 having an internally threaded portion (not shown) extending down the mid portion of the annular skirt 2 but terminating above lower extremity 3 of annular skirt 2.

As best viewed from Figure H the lower extremity 3 of skirt 2 is provided with two radially inwardly directed teeth 4. The teeth are of a ramp-like configuration such that the leading edges 5 of the teeth are formed as undercuts whereas the opposing and trailing sides 6 of the teeth are of a less steep ramp-like configuration forming an obtuse angle with the adjacent internal surfaces of the skirt 2. The term "leading" as used throughout this document is defined relative to the unscrewing direction of travel of the closure. The term undercut where used herein with reference to the leading faces and/or edges of teeth 4 and more generally protrusions shall mean that the leading face of such protrusions forms an acute angle with a tangent to the skirt in front of the tooth/protrusion with reference to the direction of travel during unscrewing of the closure.

It will be observed that teeth 4 are mounted at the leading edge of flap portions 7 of lower extremity 3 of annular skirt 2; the flap portions being defined by an L shaped cut-away portion 8 of the skirt wall. The L shaped cut-away portion 8 is spanned by bridges 13 at its vertical portion.

As will best be viewed from Figure HI internally directed teeth 4 are adapted to interact with radially externally directed teeth 9 on container neck 10. It will be appreciated that teeth 9 are configured in a similar manner to teeth 4 except that they face the opposite direction. The configuration is such that the undercut face of teeth 9 will interfere with the opposing undercuts 5 on teeth 4 thereby

preventing relative motion between the closure and the container during the unscrewing operation. Conversely during the screwing of the closure onto the container it will be appreciated that the gentle ramp-like portions of teeth 4 and 9 will readily ride over each other thereby peπnitting relative motion.

Once teeth 4 and 9 have come into an undercut to undercut interference relationship with each other during the unscrewing of the closure from the container further unscrewing of the container causes bridges 13 at the leading edge of the flap to fracture. This fracturing allows flap 7 to move radially outwardly with respect to the container neck 10 which movement removes teeth 4 from an interfering relationship with teeth 9 thereby permitting further unscrewing of the closure. The radially outward movement of flap 7 from the main wall of skirt 2 additionally visually evidences the opening of the container. Two weakened hinge portions 12 for each flap 7 define and guide the radially outward movement of flap 7 after opening and cause the flap to adopt a bi-fold configuration which enhances and maintains the radial projection of the flap after opening so as to increase its visual impact. Although it is desirable that hinge portions 12 be weakened as compared to the remainder of the skirt it should be appreciated that the deformable nature of thermoplastic materials from which closures and skirts are normally fabricated may allow a flap to "hinge" irrespective of whether or not a specific weakened "hinge" point existed. The word "hinge" where used herein should therefore be read as encompassing the ability of a flap to bend radially outward whether or not a specific weakened hinge point is provided.

It has been found that with caps manufactured from polyethylene or polypropylene it is desirable that the vertical hinge portions 12 are of reduced thickness as compared with the remainder of the closure walls and in this regard 0.2-0.25 mm in thickness has been found to be ideal although 0.1-0.35 mm in thickness would probably suffice. If the weakened portions are made too thin then there is a danger that they may tear away from the skirt thereby failing to impart the very obvious radially protruding winged appearance to the cap which is essential in order that the best visual evidence of container opening is obtained. If the hinged portions are fabricated from too thick a thermoplastic material then despite frangible bridges breaking and opening of the closure the elastic limit of the thermoplastic material in the hinges may not be exceeded and the flap may return to a position similar to that which it maintains prior to opening again with the result that insufficient visual evidence of opening is present.

It will be noted from the embodiment depicted herewith that four teeth 9 are provided on the container neck whereas two teeth 4 are provided on the closure skirt. The number of teeth may of course be varied without departing from the scope and intendment of the present invention and although it is considered that two flaps and two teeth on each of the container and the closure are desirable the

invention would work with only one flap and one tooth on each of the container and the closure.

It is considered that bi-fold flaps which extend for between ten and twenty degrees of the circumference of the closure are of the greatest utility.

Other embodiments of the present invention may be devised apart from the embodiment above described and for example the lower portion of the skirt wall which defines the flap may not be directly beneath the main body of the skirt wall which carries the internal thread. An alternative embodiment wherein the skirt is stepped radially outwardly at its lower extremity is depicted in Figure VI.

Claims

CLAIMSThe claims defining the invention are as follows:

1. A closure system including a thermoplastic closure having an annular internally threaded skirt portion; one or more portions of the skirt below the internally threaded portion being configured as a flap capable of folding radially outwardly with respect to the skirt about a first vertical binge; container engaging means extending towards the container from a position on the flap adjacent its leading edge and being adapted to interact with a trigger on or near the neck of the container; the configuration of the container engaging means and trigger means facilitating ratchet-like interaction between the two components whereby they override each other during the running up of the closure onto the container but during unscrewing of the closure from the container the two components interfere with each other so as to impede unscrewing of the closure; one or more frangible joints adjacent the leading edge of the flap joining the flap to the closure skirt such frangible joints being adapted to fracture after the container engaging means and trigger means have engaged each other during the unscrewing operation; the flap being adapted to fold radially outwardly about its vertical hinge after said fracture.

2. A closure system in accordance with claim 1 wherein the one or more frangible joints adjacent the leading edge of the flap are in front of the leading edge of the flap.

» JBSTITUTΞ SHEET (Rule 26)

3. A closure system in accordance with claim 1 wherein the flap is provided with a weakened second vertical hinge portion intermediate its leading edge and the first hinge so that upon fracture of the frangible joint the flap may extend outwardly from the skirt in a bi-fold manner with the hinge closest to the frangible joint or joints radially outwardly removed from the closure skirt.

4. A closure system in accordance with claim 1 wherein the flap is provided with a weakened second vertical hinge portion intermediate its leading edge and the first hinge so that upon fracture of the frangible joint the flap may extend outwardly from the skirt in a bi-fold manner with the hinge closest to the frangible joint or joints radially outwardly removed from the closure skirt; both the first vertical hinge and second vertical hinge being formed of appropriate thermoplastic material such that after opening of the closure the elastic properties of the hinge portions are exceeded thereby causing the hinges to permanently hold the flap in its radially extended position with respect to the closure.

5. A closure system in accordance with claim 1 wherein the container engaging means is an inwardly directed ramp-shaped protrusion having an undercut at its leading edge.

6. A system in accordance with claim 1 hereof wherein the trigger means on the closure comprise one or more ramp-shaped protrusions having an undercut adjacent the leading edge thereof adapted to engage the leading edge of the container engaging means during the unscrewing operation.

7. A system in accordance with claim 1 hereof wherein there are two or more trigger means on the neck of the container.

8. A system in accordance with claim 1 hereof wherein there are provided two flaps spaced at approximately one hundred and eighty degrees from each other.

9. A system in accordance with claim 1 hereof wherein the portion of the closure skirt carrying the flaps is the lowermost portion of the skirt.

10. A system in accordance with claim 1 hereof wherein the lowermost portion of the skirt including the flap means is offset radially outwardly with respect to the main body of the skirt of the closure.

11. A thermoplastic closure having an annular internally threaded skirt portion; one or more portions of the skirt beneath the internally threaded portion being configured as a flap capable of folding radially outwardly with respect to the skirt about a vertical hinge; container engaging means extending towards the container from a position on the flap adjacent its leading edge and being adapted to interact with a trigger on or near the neck of the container; one or more frangible joints adjacent the leading edge of the flap joining the leading edge of the flap to the closure skirt.

12. A closure in accordance with claim 9 hereof wherein each flap extends for between ten and twenty degrees of the circumference of the closure.

JOUSTIT-JTE SHEET (Rule 26)