IE990682A1 - A tamper evident cap - Google Patents

Abstract

A tamper evident plastics cap (1) for a discharge valve on a pressurised fuel gas bottle has a cylindrical side wall (2) terminating in a domed top wall (3) at an upper end of the side wall (2). A circumferential ridge (7) is provided on an inner face of the side wall (2) for snap engagement within a complementary circumferential groove on an outer wall of the gas bottle discharge valve to retain the cap (1) on the gas bottle. The side wall (2) incorporates a tear-away strip which extends upwardly from a bottom edge of the side wall (2) and can be torn away for gripping a ring pull (5). A tamper evident skirt (6) is mounted at the bottom edge of the side wall (2). The skirt (6) will readily break away from the side wall (2) in the event of attempted removal of the cap (1) from the gas bottle discharge valve. <Figure 3>

Description

A tamper evident cap” Introduction This invention relates to a tamper evident cap for a discharge valve on a pressurised fuel gas bottle.

In a previously filed patent application, Publication No. GB 2301348, we disclosed a tamper evident cap for fuel gas bottle valve. The cap has a cylindrical side wall closed at one end by a top wall with a retaining ring on an inside face of the side wall for snap engagement within a complementary circumferential recess in an exterior of the gas bottle valve. A tear-away strip in the side wall can be torn away to release the cap for removal of the cap.

Other examples of tamper indicating caps generally are given in Patent Specification Nos. GB 2182915, GB 2097768, EP 0364857 and US 4712705.

The present invention is particularly concerned with the application of this type ; of tamper indicating cap to relatively small valve bodies - such that the cap typically has a nominal internal 'diameter in the order of ibout 20 mm for example. These small caps, because of heir size, are more easily removed by unauthorised personnel without damaging the tear-away strip. They can le manually gripped and worked off the valve, if necessary prising a screwdriver between the bottom edge of the side wall and the valve. he present invention is directed towards overcoming this iroblem. i tatements of Invention According to the invention there is provided a tamper - 2 evident plastics cap for a discharge valve on a pressurised fuel gas bottle, the cap comprising a generally cylindrical side wall terminating in a domed top wall at an upper end of the side wall, the outer surface of the side wall and the top wall being of smooth construction, retaining means on the side wall for securing the cap in engagement with the discharge valve of the pressurised fuel gas bottle, the retaining means comprising a circumferential ridge within the cap on an inner face of the side wall, the circumferential ridge projecting inwardly on the inner face of the side wall for snap engagement in a complementary circumferential groove on an outer wall of the discharge valve of the pressurised fuel gas bottle, the cap side wall incorporating a tearaway strip extending upwardly from a bottom edge of the side wall, the tear-away strip being defined by a pair of spaced-apart grooves in the side wall extending upwardly from a bottom edge of the side wall and extending over portion of the domed top wall, the tear-away strip having an outwardly extending pull tab at a bottom end of the tear-away strip, and a tamper evident skirt provided at a bottom of a side wall and extending downwardly therefrom.

Advantageously the domed construction of the top wall and the smoothness of the side wall and top wall makes the cap very difficult to grip, again inhibiting unauthorised removal of the cap. Also, advantageously, any attempt to prise the cap off the valve, by for example engaging a screwdriver with the bottom edge of the cap, will break the skirt to give evidence that the cap has been interfered with.

In a particularly preferred embodiment, the tamper evident skirt has a number of circumferentially spaced-apart grooves, each groove extending between a bottom and a top of the skirt in which the wall thickness of the skirt is - 3 reduced defining a number of castellations interconnected by thin frangible membranes at the grooves. Thus the skirt will readily break at one or more of the grooves in the event of attempted unauthorised removal of the cap to give tamper indication.

In a further embodiment, an internally bevelled transition portion is provided between a top of the skirt and the bottom of the side wall, an inner face of the side wall of the cap at the bottom of the side wall tapering outwardly to meet the top of the skirt. This conveniently allows the smooth engagement of the inner face of the side wall with the valve when pushing a cap onto the valve.

Instead of the slots the upper rim of the skirt may itself be attached to the bottom edge of the side wall by a thin membrane such that any attempt to interfere with the skirt will break it away from the side wall.

Preferably, the retaining ridge and/or the cap side wall are of a plastics material which is sufficiently resilient to allow resilient deformation for engagement of the retaining ridge within the complementary groove in the valve such that the cap can be pressed onto the valve.

To aid in removal of the tear-away strip, preferably a ring pull is provided at a bottom end of the tear-away strip.

Detailed Description of the Invention The invention will be more clearly understood by the following description of some embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which: - 4 Fig. 1 is a perspective view of a tamper evident cap according to the invention; Fig. 2 is a plan view of the cap; Fig. 3 is a sectional elevational view of the cap; and Fig. 4 is an elevational view of the cap shown mounted on a valve of a pressurised gas bottle which is indicated in broken outline.

Referring to the drawings there is illustrated a tamper evident cap according to the invention indicated generally by the reference numeral 1. The cap 1 has a generally cylindrical side wall 2 terminating in a generally hemispherical domed top wall 3 at an upper end of the side wall 2. A tear-away strip 4 is incorporated in the side wall 2 and has an associated ring pull 5 for parting the strip 4 from the side wall 2. Also a tamper evident skirt 6 is provided at a bottom of a side wall 2. Within the cap 3 on an inner face of the side wall 2 is a circumferential retaining ridge 7 which projects inwardly on an inside face 8 of the side wall 2 for snap engagement with a complementary circumferential groove (not shown) on an outer wall of a valve 10 of a pressurised fuel gas bottle.

The tamper evident skirt 6 extends downwardly from a bottom of the side wall 2. A number of weakened portions are provided in the skirt 6 formed by circumferentially spaced-apart vertical grooves 11 in which the wall thickness of the skirt 6 is reduced. The grooves 11 extend between a bottom and a top of the skirt 6 and essentially divide the skirt 6 into a number of castellations 12 interconnected by thin frangible membranes 13 at the grooves 11. - 5 An internally bevelled transition portion 14 is provided between a top of the skirt 6 and the bottom of the side wall 2. Thus, the inside face 8 of the side wall 2 tapers outwardly and downwardly to meet the top of the skirt 6.

The tear-away strip 4 is defined by a pair of spaced-apart grooves or slots 15, 16 which extend upwardly from a bottom edge of the skirt 6 through the side wall 2. The slots 15, 16 provide areas where the thickness of the side wall 2 is reduced sufficiently so that upon engagement of the ring pull 5 the strip 4 can be torn upwardly so that the cap 1 can be released from the valve 10. It will be noted that the slots 15, 16 extend up the side wall and partially across the domed top wall 3. Thus the strip 4 can be torn away while at the same time remaining attached to the top wall 3 for convenient disposal.

It will be noted that the outer surface of the side wall 2 and top 3 are smooth. This feature and in addition the domed construction of the top wall 3 make it very difficult for someone to grip the outside of the cap for unauthorised removal.

In use, a pressurised gas bottle is filled and then the cap 1 is pressed into engagement with the valve 10. This can be done in a single movement pressing the cap 1 downwardly. The cap 1 is of plastics material which is sufficiently resilient such that the side wall 2 and ridge 7 deform so that the cap 1 can be pressed downwardly over the valve until the ridge 7 snaps into engagement with a complementary groove on an outer side wall of the valve 10. The cap 1 is then locked in position on the valve 10 and can only be removed by releasing the tear-away strip 4 which gives evidence of tampering. Any attempt to prise the cap 1 upwardly off the valve 10 by for example - 6 engaging a screwdriver with a bottom edge of the skirt 6 will damage the skirt 6 breaking the skirt 6 at one or more of the slots 11 to give evidence of tampering.

It will be noted that the depth of the ridge 7 is such as to allow the cap 1 be pressed into engagement with the valve 10 but once the ridge 7 is engaged with the complementary groove on the valve 10 the cap 1 cannot be pulled off the valve 10 without releasing the tear-away strip 4. It will also be noted that the ridge 7 is interrupted at positions corresponding to the slots 15, 16 on the inside wall 8.

The ring puli 5 provides a secure grip for removal of the tear-away strip.

The invention is not limited to the embodiments hereinbefore described which may be varied in both construction and detail within the scope of the appended claims.

Claims (6)

1. A tamper evident plastics cap for a discharge valve on a pressurised fuel gas bottle, the cap comprising a generally cylindrical side wall terminating in a domed top wall at an upper end of the side wall, the outer surface of the side wall and the top wall being of smooth construction, retaining means on the side wall for securing the cap in engagement with the discharge valve of the pressurised fuel gas bottle, the retaining means comprising a circumferential ridge within the cap on an inner face of the side wall, the circumferential ridge projecting inwardly on the inner face of the side wall for snap engagement in a complementary circumferential groove on an outer wall of the discharge valve of the pressurised fuel gas bottle, the cap side wall incorporating a tear-away strip extending upwardly from a bottom edge of the side wall, the tear-away strip being defined by a pair of spaced-apart grooves in the side wall extending upwardly from a bottom edge of the side wall and extending over portion of the domed top wall, the tear-away strip having an outwardly extending pull tab at a bottom end of the tear-away strip, and a tamper evident skirt provided at a bottom of a side wall and extending downwardly therefrom.

2. A tamper evident plastics cap as claimed in claim 1, wherein the tamper evident skirt has a number of circumferentially spaced-apart grooves, each groove extending between a bottom and a top of the skirt in which the wall thickness of the skirt is reduced defining a number of castellations interconnected by thin frangible membranes at the grooves. - 8

3. A tamper evident plastics cap as claimed in claim 2, wherein an internally bevelled transition portion is provided between a top of the skirt and the bottom of the side wall, an inner face of the side wall of the cap at the bottom of the side wall tapering outwardly to meet the top of the skirt.

4. A tamper evident cap as claimed in claim 1, wherein a top of the tamper evident skirt is attached to the bottom edge of the side wall by a thin frangible membrane.

5. A tamper evident cap as claimed in claim 1, wherein the retaining ridge and/or the cap side wall are of a plastics material which is sufficiently resilient to allow resilient deformation for engagement of the retaining ridge within the complementary groove in the valve such that the cap can be pressed onto the valve.

6. A tamper evident cap as claimed in any preceding claim, wherein a ring pull is provided at a bottom end of the tear-away strip. Ί. A tamper evident plastics cap for a discharge valve on a pressurised fuel gas bottle substantially as hereinbefore described with reference to the accompanying drawings.