GB2097366A

GB2097366A - Bottle and like container closures

Info

Publication number: GB2097366A
Application number: GB8110344A
Authority: GB
Original assignee: SMITHS CONTAINERS Ltd
Current assignee: SMITHS CONTAINERS Ltd
Priority date: 1981-04-02
Filing date: 1981-04-02
Publication date: 1982-11-03
Also published as: GB2097366B

Abstract

A screw-on, pilfer-proof container closure comprises a cap with internal screw threads 24 and a tear-off band 28 adjacent its rim, which tear-off band is formed internally around its circumference with a plurality of ratchet formations 32 for co-operating with complementary ratchet formations formed around the neck of the container below its screw threads, permitting turning of the cap during screwing it on but preventing its unscrewing. The ratchet serrations 32 on the cap are screw-threadably engageable with the screw threads on the container neck, by provision of a helical groove 34. <IMAGE>

Description

SPECIFICATION Bottle and like container closures This invention reiates to a screw cap form of closure for containers such as bottles, and in particular of pilfer-proof type (i.e. it is necessary to break a portion of the cap before the cap can be removed for the first time).

A plastics material screw cap is known wherein the tamper-proof portion comprises an enlarged diameter tear-off band adjacent the rim of the cap and formed internally with some dogs which project generally inwardly at an incline, which dogs are relatively few in number (say 12) and substantially spaced apart around the circumference of this band. When the cap is first applied to its container, the dogs ride over complementary ratchet formations provided in a circumferential zone around the container neck, below the screw threads of the neck, and the dogs and complementary ratchet formations of the neck prevent subsequent turning of the closure cap in the unscrewing or removal direction.For removing the cap, its tear-off band is formed with an outwards projection which may be grasped by hand for tearing the band from around the cap (the band being connected to the remainder of the cap along a line of weakness), thus destroying the ratchet-type interlock provided by the dogs. At the same time, removal of the tear-off band provides a clear visual indication if the closure is tampered with prior to its intended first removal.

The tear-off band with dogs in this known closure is necessarily of an enlarged diameter so that its dogs can be formed so as to clear the threads on the container neck when the cap is being first applied. The result is however that the cap is not of an optimum profile from the point of view of visual appearance or of ease of application and also there is some possibility for prising the tear-off band to disengage the dogs and enable unscrewing of the cap without tearing away the band. Also, because the dogs are few in number and substantially spaced apart, the cap may in fact be unscrewed through a significant angle before the dogs lock-up to prevent further unscrewing, and this may undesirably partially open the closure.

In accordance with this invention, there is provided a container closure, comprising a cap with internal screw threads for screwing onto the container, the cap being provided with a tear-off band adjacent its rim, which band is arranged for tearing from the cap and is formed internally around its circumference with a plurality of ratchet formations for co-operating with a plurality of complementary ratchet formations formed around the circumference of the neck of the container below its screw threads, permitting turning of the cap to its tightened-close position but then preventing unscrewing of the cap, the ratchet formations on the cap being screw-threadably engageable with the screw threads on the neck of the container.

With this arrangement, the tear-off band does not need to have an outer diameter greater than that of the main body of the cap, and indeed it is slightly smaller in an embodiment to be described herein. Thus the cap may exhibit a neat appearance with minimal chance of damage and minimal possibility for prising or springing it off. In the embodiment to be described, a helical groove is formed through the ratchet formations to receive the screw threads of the container neck.

In the embodiment to be described herein, there is a large multiplicity of ratchet formations at ciose-spacing on the tear-off band, providing a positive interlock with the correspondingly-spaced formations (which are albeit fewer in number) on the container neck, and insignificant turning of the cap is possible before the ratchet formations lock up against further turning.

Conventional screw caps, lacking the tear-off band and being of appropriate size, may be fitted to the container in place of the intended cap with tear-off ratchet band: the ratchet zone on the container however remains unobtrusive in this event. However, the ratchet zone on the container can clearly be seen to provide a positive indication of a broken or absent seal in cases where a security closure by the cap with tear-off ratchet band is required.

Said embodiment of this invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a side view of a neck portion only of a plastics bottle or like container; Figure 2 is a section on the line A-A of Figure 1; Figure 3 is a side view of a cap for the container of Figures 1 and 2; Figure 4 is a vertical section through the cap; and Figure is a bottom view of the cap.

Referring to Figures 1 and 2, the neck of a plastics container such as a bottle is shown and comprises a cylindrical portion 10 extending downwards from a rim 1 2 and provided with 1) turns of screw-threading 1 4. Below the screwthreading a circumferential zone 1 6 is provided and formed with a multiplicity of ratchet formations 1 8 in an annulus. The roots between the ratchets are on a circumference slightly larger in diameter than the diameter of the cylindrical screw-threaded portion 10: the crests of the ratchets are on a circumference of the same diameter as that of the crests of the screw threads.The container is designed to be moulded of plastics (e.g. high density polyethylene) in a mould housing two parts which meet on a plane identified by the line P-P in Figure 2, and which are separated by relative movement perpendicular to that plane to enable ejection of the moulded bottle. The ratchet formations and the screw threads are interrupted as shown over a zone extending either side of the mould part line. To each side of the part line, 13 ratchet formations are provided at 10 spacings, the crest of the first being 200 from the mould part line as shown.

Referring to Figures 3, 4 and 5, there is shown a cap injection moulded of, for example, medium density polythene, and for screwing onto the neck shown in Figures 1 and 2 effect closure of the container. The cap comprises a cylindrical tubular portion 20 depending from the top 22 and formed internally with a 141 turns continuous screw thread 24. The cylindrical tubular portion 20 is dimensioned to provide a small clearance between itself and the thread 14 of the container. A short cylindrical tubular portion 26 depends from the top 22 internally of the cap, and is provided externally at its rim with a chamfer for cooperating with the inside rim of the container neck.

A tear-off band 28 is disposed at the rim of the cap and is connected to the main cylindrical tubular portion 20 by an annular membrane 29, internally reduced in thickness, which provides a line of weakness enabling the tearing-off of the band 28 when its outwards hooked projection 30 is grasped by hand and pulled in the opposite circumferential direction to that in which itself it projects: an axially extending groove 31 provides a line of weakness to cause the band itself to tear first before it is then torn along the circumferential line 29. The tear-off band has an outer diameter somewhat smaller than that of the main tubular portion 20, and an inner diameter slightly less than that of the portion 20, but still providing a clearance relative to the thread 14 of the container neck.The tear-off band is formed around its inner surface with a multiplicity (36 in the example shown) of equally spaced ratchet formations 32 complementary with those on the container neck. The ratchet formations 32 extend from the rim of the cap to closely adjacent the upper margin of the band 28, but they are interrupted by a helical groove 34 (the outer diameter of which equals the inner diameter of the tear-off band). This groove 34 corresponds in width and pitch to the screw threads of the container neck, and is so positioned axially relative to threads 24 that, in applying the cap to the container neck, first the groove 34 engages with the threads of the neck and then, still turning the cap continuously and evenly, the thread 24 engages with the container neck threads.Then, as the cap is tightened on the container neck, the ratchet formations 32 of the tear-off band 28 ride over the ratchet formations 1 8 of the container neck to provide a lock preventing turning of the cap in the opposite direction. It is then necessary to tear away the band 28 before the cap may be removed.

The cap is designed to be injection moulded in a mould cavity defined by two mould parts separable by relative movement parallel to the axis of the cap. The upper and lower surfaces of the ratchet formations 32 and the opposite sides of the groove 34 are so chamfered as shown to facilitate removal of the cap from the internal mould part by the jump-off ejection technique. The polythene material provides good flexibility aiding the ejection in this mode.

Although the cap is a nominal 40 mm diameter size, the invention is applicable to a wide range of different sizes.

It is to be noted that the closure achieves an overall locking force (against unscrewing), at least as high as the prior art closure with dogs mentioned earlier in this specification.

Claims

1. A container closure, comprising a cap with internal screw threads for screwing onto the container, the cap being provided with a tear-off band adjacent its rim, which band is arranged for tearing from the cap and is formed internally around its circumference with a plurality of ratchet formations for co-operating with a plurality of complementary ratchet formations formed around the circumference of the neck of the container below its screw threads permitting turning of the cap to its tightened-close position but then preventing unscrewing of the cap, the ratchet formations on the cap being screw-threadably engageable with the screw threads on the neck of the container.

2. A container closure as claimed in claim 1, in which the tear-off band has an outer diameter no greater than that of the main body of the cap.

3. A container closure as claimed in claim 1 or 2, comprising a helical groove formed through the ratchet formations of the cap, to receive the screw threads of the container neck.

4. A container closure substantially as herein described with reference to Figures 3 to 5 of the accompanying drawings.

5. A container having a neck provided externally with screw threads for engagement by internal screw threads of a closure cap, and a plurality of ratchet formations formed around its circumference below its external screw threads, for engagement with a plurality of complementary ratchet formations formed internally of the closure cap adjacent its rim and arranged for permitting turning of the cap to its tightened-close position but then preventing unscrewing of the cap, the crests of the ratchet formations on said neck lying on a circle having a diameter no greater than the diameter of the cylinder circumscribing the screw threads of said neck.

6. A container having a neck substantially as herein described with reference to Figures 1 and 2 of the accompanying drawings.

7. A container as claimed in claim 5 or 6, provided with a closure cap as claimed in any Pne of claims 1 to 4, the ratchet formations on the container neck and closure cap being sufficiently closely spaced to permit insignificant turning of the cap in the cap-removal direction.