GB2174684A

GB2174684A - Tamper evident closure

Info

Publication number: GB2174684A
Application number: GB08610419A
Authority: GB
Inventors: Michael Heinz Verter
Original assignee: GV Engineering Pty Ltd
Current assignee: GV Engineering Pty Ltd
Priority date: 1985-04-29
Filing date: 1986-04-29
Publication date: 1986-11-12
Also published as: FR2581037A1; GB8610419D0; DE3614508A1

Abstract

A thermoplastic closure for fitment to a container, the closure (1) having a top wall (2), and a threaded annular side wall (3) downwardly depending from said top wall, bridges (5) adjacent a first location upon the bottom of said side wall and adjacent a second location upon the bottom of the side wall diametrically opposed to said first location; such bridges locating a tamper evident band (4) beneath and spaced from said side wall and incorporating a first radially inwardly directed protrusion (6) on the inside of the band centred at approximately ninety degrees from a bridge and a second radially inwardly directed protrusion (6) diametrically opposed to said first protrusion, the protrusions in use adapted to lock under a bead (7) on a container finish; one or more predetermined frangible points in either a bridge or the band or both. <IMAGE>

Description

SPECIFICATION Tamper evident closure The present invention relates to tamper evident closures for containers and in particular such closures when manufactured from thermoplastic material and threaded.

A number of tamper evident threaded closures are presently available most of which include a band or skirt depending from the lower portion of the cap or main body of the closure. Such band or skirt being adapted to come in to a locking engagement with a bead or recess on a container finish after application of the closure and, upon removal of the closure, remain in such locking engagement with the container finish and severed from the cap or main body of the closure. Such products usually incorporate a series of vertical bridges adapted to secure the band to the main body of the cap during application but which fracture upon removal of the cap.Alternatively the bridges may be designed so as to remain in tact if the band itself is provided with a weakened zone or zones intended to fracture upon removal of the cap and consequent radial expansion of the band to clear the container finish. In the lastmentioned example the fractured band is removed with the main body of the closure and does not remain upon the container.

In order that difficulty may not be experienced in applying tamper evident closures as lastmentioned to a container it is necessary that the tamper evident band be capable of passing over the container finish (including externally threaded portions and any beaded portion) without the band or bridges breaking yet of course during the reverse operation the band or the bridges must break. In order to achieve this result the pilfer band is traditionally fabricated from thermoplastic material lighter than the main body of the cap and of sufficient diameter so as to clear the container finish upon application. After application of the closure the closure/container unit is then subjected to heat which results in shrinking of the tamper evident band but of course not the thicker main body of the closure, traditionally fabricated from the same material.

Numerous difficulties have been encountered with closures incorporating traditional tamper evident bands as abovementioned and in particular it has been found out that the application of heat after application of the closure to a container is expensive insofar as such operation dictates that the bottler must purchase capital equipment to effect the heat shrinking operation and and furthermore the energy requirements of such process are significant. Difficulties are also encountered in the quality control of such existing tamper evident closures insofar as it is necessary to fabricate same to a specification such that no damage will occur during application of the closure yet the relevant parts of the bridges or band must unfailingly break or tear during removal of the closure.Where a multiplicity of frangible bridges are incorporated to secure the band to the main body of the cap it has also been found out that high injection pressures are necessary in order to ensure that the thermoplastic material is adequately distributed within the mould and fills the cavities intended to form such delicate bridges.

The present invention seeks to ameliorate one or more of the lastmentioned disadvantages with the prior art or at least provide the market with a choice.

According to the present invention there is provided a thermoplastic closure for fitment to a container said closure having a top wall, a threaded annular side wall downwardly depending from said top wall, bridges adjacent a first location upon the bottom of said side wall and adjacent a second location upon the bottom of the side wall diametrically opposed to said first location; such bridges locating a tamper evident band beneath and spaced from said side wall and incorporating a first radially inwardly directed protrusion on the inside of the band centred at approximately ninety degrees from a bridge and a second radially inwardly directed protrusion diametrically opposd to said first protrusion, the protrusions in use adapted to lock under a bead on a container finish; one or more pre-determined frangible points on either a bridge or the band or both.

One embodiment of the present invention will now be described with reference to the accomanying drawings in which: Figure 1 is a side elevation of a closure in accordance with the present invention; Figure 2 is a bottom plan view of the closure of Fig. 1; Figure 3 is a part section through line A-A' of Fig. 2; and Figure 4 depicts the closure of Fig. 1 during its removal from a container.

According to Fig. 1 there is provided a closure comprising a cap 1 having top wall 2 and side wall 3. The cap is additionally provided with a tamper evident band 4 secured to the lower portion of the cap side wall by bridges 5. It may be seen from Fig. 2 that the bridges 5 are located at approximately 180 degrees from each other around the periphery of the band. Fig. 2 additionally discloses two opposed inwardly directed protrusions 6 centred at 180 degrees from each other around the band and each protrusion extending for an arc of approximately ninety degrees.

Whilst the protrusions stiffen the tamper evident band the portions of the band adjacent the bridges are still relatively flexible assisting the band to deform to an oval type shape whereby the protrusion may clear a container finish during application of the closure. During removal of the closure from a container however the protrusions will lock under the container finish at 7. As may best be seen from Fig. 4 hereof the upward axial movement caused by unscrewing the closure rrsults in the bridges 5 pulling the tamper band 4 axially upwards at an area adjacent the lower extremity of such bridges whereas the inwardly directed protrusions prevent upward axial movement of the band at areas 8.No such obstruction is present adjacent the bridges and the resulting deformation of the pilfer band from its original configuration serves to pull the band radially inwards adjacent the midlength of protrusions 6 thereby enhancing their locking action. Further removal of the cap from the position depicted in Fig. 4 will result in the breaking of at least one of bridge members 5 thereby facilitating removal of the cap, the broken bridge of bridges evidencing such removal.

One advantage of the abovementioned embodiment is that the use of two relatively thick bridges as opposed to a multiplicity of more delicate bridges extending for 360 degrees around the closure, enables lower injection pressures to be used during the moulding process. The relatively stronger bridges additionally reduce the risk of damage to the closure during its removal from a mould as well as during application of the closure to a container.

It should be appreciated that various configurations are possible for a tamper evident closure, apart from that abovementioned, without departing from the scope and intendment of the present invention. For example the present invention may employ more than two bridges provided the absence of bridges at two opposing areas of the tamper band enable the band to move independently of the cap adjacent such areas therefore allowing the deformation of the band necessary to enhance the locking action of the protrusions and to ensure ease of application of the closure to a container. One bridge or one series of bridges may additionally be of a stronger specification than the opposing bridge or series of bridges particularly if the tamper band is required to remain with the cap after removal of the closure as may be the case with returnable containers.In such an embodiment the band itself may be provided with one or more vertical weaknesses in order that it may eventually fracture and remain with the cap rather than on the container.

In one embodiment (not depicted) now being tested four bridges are being utilised, one pair of bridges on one side of the band and another pair approximately 180 degrees removed therefrom. It has been found that such a configuration may be preferable to a single bridge on each side of the band as it provides more support for the pilfer band during the application of the cap to the container. It has been found that a pair of bridges spaced from each other by approximately five millimetres is particularly advantageous.

The protrusions themselves may additionally differ from the configuration above described with reference to the drawings herein as of course the locking action of the protrusions can be achieved where the protrusions extend for less than ninety degrees around the internal periphery of the band or alternatively more than ninety degrees.

It is envisaged that the invention may still operate where each of two protrusions extends for as much as 170 degrees however in such embodiments the presence of the protrusion for most of the circumference of the pilfer band increased difficulties in the application of caps to containers and consequently protrusions extending for ninety degrees or less are considered more advantageous.

It should be obvious to those skilled in the art that a multiplicity of protrusions, or, what is the same thing, one protrusion with a number of discontinuities may function for the purposes of this invention as one continuous protrusion. Consequently the term "protrusion" where used herein is hereby defined to include such embodiments. A multiplicity of protrusions for example or alternatively a protrusion with a discontinuity may be useful where a band is designed to have a vertical weakness in an area where a protrusion may otherwise be required.

It has been found that a protrusion having a veed configuration (in section) with an included angle of approximately sixty degrees and a slightly radiused nose is appropriate for most bottle finishes and this configuration may be viewed best at 6 in Fig. 3. It should be appreciated however that provided the protrusion is sufficient to ensure an interference fit with the relevant portion of the container finish then a variety of configurations may be appropriate.

Claims

1. A thermoplastic closure for fitment to a container, the closure having a top wall, and a threaded annular side wall downwardly depending from said top wall, bridges adjacent a first location upon the bottom of said side wall and adjacent a second location upon the bottom of the side wall diametrically opposed to said first location; such bridges locating a tamper evident band beneath and spaced from said side wall and incorporating a first radially inwardly directed protrusion on the inside of the band centred at approximately ninety degrees from a bridge and a second radially inwardly directed protrusion diametrically opposed to said first protrusion, the protrusions in use adapted to lock under a bead on a container finish; one or more pre-determined frangible points in either a bridge or the band or both.

2. A closure in accordance with claim 1 wherein there are two continuous radially inwardly directed protrusions each extending around the circumference of the pilfer band for between 30 and 100 degrees.

3. A closure in accordance with claim 1 wherein the inwardly directed protrusions are of a veed configuration when viewed in radial section having an included angle of between 45 and 70 degrees and having a radiused nose.

4. A closure in accordance with any one of the preceding claims having four frangible bridges arranged into paired sets each pair being approximately 180 degrees removed from the opposing pair and each pair being removed from the other bridge comprising the pair by betweena 3 and 7 millimetres.

5. A closure in accordance with any one of the preceding claims having frangible bridges the frangible bridge at the first location being weaker than the frangible bridge or bridges at the second location in order to assist in removal of the pilfer band with the main body of the closure.

6. A closure in accordance with any one of the preceding claims wherein the pilfer band is provides with one or more vertical weakness in order that upon removal of the closure the band may fracture before one or more of the bridges fractures thereby ensuring removal of the pilfer band from a container along with the main body of the closure.

7. A closure substantially as hereinbefore described with reference to the accompanying drawings.