WO1998016436A1

WO1998016436A1 - Tamper evident closure

Info

Publication number: WO1998016436A1
Application number: PCT/AU1997/000694
Authority: WO
Inventors: Michael Verter
Original assignee: GV Engineering Pty Ltd
Current assignee: GV Engineering Pty Ltd
Priority date: 1996-10-15
Filing date: 1997-10-15
Publication date: 1998-04-23
Anticipated expiration: 1999-04-15
Also published as: AUPO297196A0; NZ335185A

Abstract

A thermoplastic closure of the type having an internally threaded skirt (2) depending from an upper sealing disk (1) and an annular tamper band (6) affixed to the closure adjacent the lower extremity of the skirt by frangible joining means (5). Radially inwardly directed teeth (7) on the tamper band interact with an annular externally directed bead (17) on a container neck and also with radially outwardly directed teeth (12) on the neck located beneath the bead. The interaction between the teeth (7) on the tamper band and the teeth (12) on the container are such that upon running up of the closure onto the container the teeth readily ride over each other thereby facilitating the closure being fully run up onto the container. The interaction of the teeth upon unscrewing of the closure from the container prevent rotation of the closure relative to the container thereby ensuring that further attempted relative rotation between the closure and the container fractures the frangible joining means between the tamper band and the closure. The profiles of the teeth (7) on the tamper band and the bead (17) on the container are such that the teeth (7) readily ride over the bead (17) during axial motion of the closure relative to the container in the direction necessary to run the closure up onto the container but the profiles interfere with each other upon attempted removal of the closure from the container such that after fracture of the frangible joining means due to rotational movement the tamper band cannot move axially upwardly relative to the conainer but rather remains captive thereabout.

Description

TAMPER EVIDENT CLOSURE

The present invention relates to a tamper evident closure and in particular to an internally threaded plastic closure having an annular tamper band frangibly connected thereto.

For a number of years it has been common to provide food containers and indeed many other containers with tamper evident closures in order that the state of the tamper evident feature associated with the closure clearly indicates whether or not a container has been opened subsequent to its initial sealing.

There are many tamper evident closures presently on the market and one common variant of such closure involves a thermoplastic internally threaded closure having an annular tamper band therebeneath. The tamper band is typically connected to the lower portion of a skirt integral with the closure and is typically provided with internally directed teeth adapted to lock against externally directed teeth on a container during the unscrewing operation (although not during the initial running up of the closure onto the container). The interference of the two sets of teeth during the unscrewing operation causes fracture of the membrane or bridges joining the skirt of the closure to the annular tamper evident band thereby permanently separating the two components and evidencing the opening of the container. Unfortunately the abovementioned type of annular tamper band is usually a nuisance after initial removal of the closure as it is not restrained on the container or the closure. Inversion of the container therefore results in the dropping of the tamper band into the product being dispensed or in many cases pollution of the environment.

It is accordingly an object of the present invention to provide a closure system incorporating an annular tamper band wherein the tamper band is adapted to be restrained on the container at all times.

According to the present invention there is provided a thermoplastic closure of the type having an internally threaded skirt depending from an upper sealing disk; an annular tamper band affixed to the closure adjacent the lower extremity of the skirt by frangible joining means; two or more radially inwardly directed protrusions on the tamper band; the protrusions being adapted to interact with an axial motion control protrusion on a container neck and rotational motion control protrusions on a container neck; the interaction between the protrusions on the tamper band and the rotational motion control protrusions on the container being such that upon running up of the closure onto the container the protrusions readily ride over each other thereby facilitating the closure being folly run up onto the container; the interaction of the protrusions upon unscrewing of the closure from the container however preventing greater than one-half turn rotation of the closure relative to the container thereby ensuring that further attempted relative rotation between the closure and the container fractures the frangible joining means between the tamper band and the closure; the profiles of the protrusions on the tamper band and the axial motion control protrusion on the container being such that the protrusions readily ride over each other during axial motion of the closure relative to the container in the direction necessary to run the closure up onto the container but the profiles interfere with each other upon attempted removal of the closure from the container such that after fracture of the frangible joining means due to rotational movement the tamper band cannot move axially upwardly relative to the container but rather remains captive thereabout.

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

Figure 1 is a perspective view of a closure in accordance with the present invention;

Figure 2 is a part side elevation of a container in accordance with the present invention; and Figure 3 is a part section through A- A' of the closure of figure 1 and B- B' of the container of figure 2.

According to the embodiment of figure 1 there is disclosed a thermoplastic closure 1 having an annular skirt portion 2 depending therefrom; the skirt portion 2 containing internal threads 3.

The lower edge 4 of skirt 2 contains frangible web portions 5 for the purpose of joining the skirt 2 to annular tamper band 6. Annular tamper band 6 is provided with four sets of internally directed teeth 7 approximately ninety degrees removed from each other about the internal circumference of the tamper band.

It will be observed that teeth 7 are all angled in one direction in order that one side thereof presents a ramp portion 8 whereas the opposite side thereof presents an undercut face 9. It will also be observed that the teeth are chamfered along their lower edges 10 adjacent their radially innermost extremities 11.

Teeth 7 are intended to interact with teeth 12 extending radially outwardly from the lower portion of the neck 13 of container 14 as is best viewed from figure 2. The orientation of complementary teeth 7 and 12 is such that during the running up of the closure and attached tamper band onto the container for the first time teeth 7 and 12 do not lock against each other but merely ride over each other due to ramped surfaces 8 and 15 overriding each other.

The placement of four sets of teeth 7 on the tamper band and four teeth (only two shown) on the container neck at approximately ninety degree spacings ensures that within one-quarter turn of the closure relative to the container at the commencement of unscrewing the closure from the container the teeth 7 and 12 will lock against each other, undercut to undercut, and will not permit further relative rotation of the tamper band relative to the container.

Further unscrewing of the closure relative to the container after the lastmentioned interference of teeth 7 with teeth 12 will cause frangible web portions 5 to break due to the shear forces occasioned by a rotating skirt and a stationary tamper band.

It will be noted that in addition to threaded portion 16 the container neck 13 is also provided with an annular externally directed bead 17 extending for three hundred and sixty degrees about the container neck and in this embodiment such bead also serves to brace the top of teeth 12. This bead 17 is provided with an upper ramped surface 18 but a substantially horizontal surface 19 therebeneath forming an included angle of ninety degrees or less with the vertical container neck therebeneath. The profile of bead 17 occasioned by surfaces 18 and 19 is intended to permit teeth 7 to be urged down ramped portion 18 over the bead during the initial running up of the closure and tamper band onto the container. The chamfered surface 10 of the teeth 7 also assists this motion despite the fact that the inner extremities 11 of teeth 7 extend radially inwardly to a position radially inward of the radially outermost extremity 20 of bead 17.

Once the teeth 7 underlie bead 18 as depicted in figure 3 the upper surfaces 21 of teeth 7 and surface 19 of the bead are such that upward axial movement of the tamper band relative to the container is restrained and removal of the tamper band from the container is resisted by the interference of said tooth surfaces.

It will be observed that the upper surfaces 21 of teeth 7 lie beneath the upper extremity 22 of the tamper band in order that the radially outermost extremity 20 of bead 17 may be accommodated beneath the lower edge 4 of the skirt 2 and above the upper surface 21 of the teeth. In order that the sliding claws utilised in the moulding of the closure and tamper band may be removed the fact that the teeth do not extend for the foil depth of the tamper band gives rise to the stepped appearance of the tamper band apparent from figure I and the windows 23 above each set of teeth 7.

Experimentation has shown that whilst it may be possible to utilise one or more inwardly directed protrusions on the tamper band together with bead 17 in the absence of teeth 12 in order to achieve separation of the tamper band from the closure during the relative axial movement between container and closure (occasioned by the unscrewing operation) when closures are of relatively small diameter (say thirty millimetres or less) such configurations tend not to be reliable in relation to closures of larger diameter and in particular closures of above forty-five millimetres in diameter. With closures of over forty-five millimetres diameter and particularly those of approximately seventy millimetres diameter it has been found that there is usually sufficient elasticity in the closure, tamper band and internally directed protrusion such that the tamper band protrusion or protrusions may be worked up over the bead on the container without separation of the tamper evident band from the closure thereby defeating the tamper evident feature.

The purpose of bead 17 and the profile of surfaces 21 and 10 associated with teeth 7 of the present invention is not to achieve severance of the tamper band from the container due to tension in the frangible web portions 5 but rather fracture of frangible web portions 5 is occasioned by shear forces occasioned due to interaction of teeth 7 with teeth 12 during rotation of the closure relative to the container. Bead 17 merely retains the tamper band on the container in order to prevent pollution of the environment or the contents being dispensed from the container. It should be appreciated that alternate embodiments apart from those above described may be devised without departing from the scope and intendment of the present invention. For example the profile, number and location of teeth 7 and 12 may be revised from the configuration depicted.

Claims

The claims defining the invention are as follows:

1. A thermoplastic closure of the type having an internally threaded skirt depending from an upper sealing disk; an annular tamper band affixed to the closure adjacent the lower extremity of the skirt by frangible joining means; two or more radially inwardly directed protrusions on the tamper band; the protrusions being adapted to interact with an axial motion control protrusion on a container neck and rotational motion control protrusions on a container neck; the interaction between the protrusions on the tamper band and the rotational motion control protrusions on the container being such that upon running up of the closure onto the container the protrusions readily ride over each other thereby facilitating the closure being folly run up onto the container; the interaction of the protrusions upon unscrewing of the closure from the container however preventing greater than one-half turn rotation of the closure relative to the container thereby ensuring that further attempted relative rotation between the closure and the container fractures the frangible joining means between the tamper band and the closure; the profiles of the protrusions on the tamper band and the axial motion control protrusion on the container being such that the protrusions readily ride over each other during axial motion of the closure relative to the container in the direction necessary to run the closure up onto the container but the profiles interfere with each other upon attempted removal of the closure from the container such that after fracture of the frangible joining means due to rotational movement the tamper band cannot move axially upwardly relative to the container but rather remains captive thereabout.

2. A thermoplastic closure system incorporating the thermoplastic closure of claim 1 hereof in conjunction with a container having an annular externally directed axial motion control protrusion about the neck portion thereof with an upper surface extending downwardly from its radially innermost portions towards its radially outermost portions so as to provide a ramp over which the inwardly directed protrusions on the tamper band may pass during the running up of a closure onto a container; the underside of the annular protrusion on the container neck not being ramped but rather being profiled such as to prevent the inwardly directed protrusions on the tamper band riding over the axial motion control protrusion on the container during unscrewing of the closure and associated tamper band.

3. A closure in accordance with claim 1 hereof wherein the inwardly directed protrusions on the tamper band comprise inwardly directed teeth exhibiting a chamfer along their lower sides extending radially inwardly and upwardly in order to assist the lower surface of the teeth to ride over the axial motion control protrusion on a container during the running up of the closure onto the container.

4. A thermoplastic closure in accordance with claim 1 hereof wherein there are provided four sets of radially inwardly directed container engaging protrusions each set containing two or more protrusions and each set of protrusions being removed from each adjacent set by approximately ninety degrees such that no more than ninety degrees rotation of the closure is necessary in order that the inwardly directed protrusions engage an externally directed radial motion control protrusion on the container neck.

5. A closure system in accordance with claim 2 hereof wherein the radial motion control protrusions on the container neck comprise two or more vertically orientated teeth extending downwardly along the container neck from a position adjacent the underside of the axial motion control protrusion.

6. A closure system in accordance with claim 2 hereof wherein the upper extremities of the inwardly directed radial motion control protrusions on the tamper band lie beneath the upper extremity of the tamper band and the annular externally directed axial motion control protrusion on the container neck lies above the upper extremities of the inwardly directed protrusions on the tamper band but below the lower extremity of the closure skirt when the closure is in the closed position on the container prior to initial opening.

AMENDED CLAIMS

[received by the International Bureau on 14 January 1998 ( 14.01 .98) ; original claim 1 replaced by amended claim 1 ; remaining claims unchanged (2 pages) ]

The claims defining the invention are as follows:

1. A thermoplastic closure of the type having an internally threaded skirt depending from an upper sealing disk; an annular tamper band affixed to the closure adjacent the lower extremity of the skirt by frangible joining means; two or more radially inwardly directed protrusions on the tamper band; the protrusions being adapted to interact with an axial motion control protrusion on a container neck and rotational motion control protrusions on a container neck; the interaction between the protrusions on the tamper band and the rotational motion control protrusions on the container being such that upon running up of the closure onto the container the protrusions readily ride over each other thereby facilitating the closure being folly run up onto the container; the interaction of the protrusions upon unscrewing of the closure from the container however preventing greater than one-half turn rotation of the closure relative to the container thereby ensuring that further attempted relative rotation between the closure and the container fractures the frangible joining means between the tamper band and the closure; the profiles of the protrusions on the tamper band and the axial motion control protrusion on the container being such that the protrusions readily ride over each other during axial motion of the closure relative to the container in the direction necessary to run the closure up onto the container but the profiles interfere with each other upon attempted removal of the closure from the container such that after fracture of the frangible joining means due to rotational movement the tamper band cannot move axially upwardly relative to the container but rather remains captive thereabout; the upper extremities of the inwardly directed protrusions on the tamper band lying below and spaced from the upper extremities of the tamper band with the annular upper surface of the tamper band being stepped down above each inwardly directed protrusion or group of inwardly directed protrusions so as to leave a void thereabove thereby facilitating unrestricted removal of the closure and tamper band from the core of a mould. 2. A thermoplastic closure system incorporating the thermoplastic closure of claim 1 hereof in conjunction with a container having an annular externally directed axial motion control protrusion about the neck portion thereof with an upper surface extending downwardly from its radially innermost portions towards its radially outermost portions so as to provide a ramp oλ'er which the inwardly directed protrusions on the tamper band may pass during the running up of a closure onto a container; the underside of the annular protrusion on the container neck not being ramped but rather being profiled such as to prevent the inwardly directed protrusions on the tamper band riding over the axial motion control protrusion on the container during unscrewing of the closure and associated tamper band.