IES80427B2 - A tamper indicating closure - Google Patents

Abstract

A screw threaded closure 4 has a frangibly connected tamper evident ring with an inwardly directed lip 10 for resiliently fitting over a container neck clipbead 12, such that when the closure is fully tightened onto a container neck, a portion of the ring other than the lip contacts the clipbead and exerts a radial force thereon. The frangible connections may be short tapering tabs (9 fig 8) with a semi-circular cross-section. The closure may comprise cooperating teeth (24, 25 fig 10) so that the closure can be screwed onto a container neck without breaking the frangible connections. The radial force prevents the ring from "kicking" to one side during removal.

Description

Introduction The present invention relates to a tamper indicating closure and in particular to a tamper indicating closure for a container of the type having a bored cylindrical externally threaded neck portion with an annular clipbead inward of the threaded portion and having a recess behind it, the closure being of the type comprising a cap surmounting an outer threaded portion connected by an inner weakened frangible portion to an inner tamper ring and said tamper ring having an inwardly directed lip for engagement over the clipbead and within the recess.

A particularly well known form of such tamper indicating closure has a frangible portion which comprises a series of short tabs interconnecting the main body portion and the tamper ring and in which the remainder of the frangible portion between the main body portion and the tamper ring is cut away to form a series of intermittent slits along the one circumference. Unfortunately with this well known form of closure, it is possible to manipulate the closure by moving it relative to the longitudinal axis of the neck to remove the closure and tamper ring without breaking the tabs thereby negating the tamper evidence. This can be done accidentally let alone deliberately.

Extrusion blow-moulding is the most common method for forming containers and bottles. Unfortunately, extrusion blow-moulding has certain disadvantages which cause problems in trying to provide a reliable tamper indicating closure. Firstly, by it's very nature, extrusion blowmoulding is not done to very tight tolerances and further, there is an inability to form sharp corners or undercuts. - 2 Unfortunately, many closure designs commonly available rely quite heavily on the accurate engagement between closure and container. Further, they require a positive engagement of the tamper ring under the clipbead. Unfortunately, this is dependent on the degree of sharpness of the clipbead. One example of a tamper indicating closure is described in European Patent Specification No. 589254 which will only work with a clipbead having a relatively sharp corner and thus it appears that the successful operation of this invention requires that the container be manufactured by the more expensive injection blowing process. Many closures get over some of the problems of having to have an inwardly directed lip on the tamper ring which is relatively substantial as this requires complex moulds by forming the tamper ring by a series of inwardly projecting spacedapart lugs so as to give sufficient flexibility to the closure when it is being applied to the container. European Patent Specification 219946 is an example of this construction in that the tamper ring is provided with a plurality of spaced-apart individual lugs in the inner surface to cooperate with the externally projecting clipbead.

UK Patent Specification No. 2295143 endeavours to address this problem whereby as the outer threaded portion is pushed towards the inner tamper ring, the two interengage so as to allow them to be screwed onto the container. This obviously prevents the tabs being sheared but does not prevent bulging or axial movement of the tabs outward by this movement together of the outer threaded portion and the inner tamper ring.

US Patent Specification No. 5090788 addresses the problem of the force required to apply the closure to the container. Unfortunately it requires a secondary post forming operation. This specification provides, on the tamper ring, another ring or a series of lugs connected to the tamper ring by a hinge so as to further engage under the clipbead. These pivot out of the way on application and then engage beneath the clipbead when the closure is being unscrewed.

A further problem with closures when the frangible portion comprises a series of short tags interconnected in the main body portion and the tamper ring is that there is a balance required between making the tabs so weak that they break when the cap is first applied or making them so strong that they fail to break on opening. This problem is exacerbated by the weakening effect of the tab when the closure is first applied as the tamper ring experiences resistance on the neck portion of the container as it is being placed in position. This then closes the gap between the outer threaded portion and the tamper ring and thus tends to crush the tab. This bulging or axial movement referred to above is clearly illustrated in US Patent Specification No. 4550843. The problem with this is that this can cause product rejection during the capping process.

It is has been discovered that it is vital to keep the tamper ring at 90° to this longitudinal axis and not to allow it kick to one side during removal.

Statements of Invention According to the invention, there is provided a tamper indicating closure for a container of the type having a bored cylindrical externally threaded neck portion with an annular clipbead inward of the threaded portion and having a recess behind it, the closure being of the type comprising a cap surmounting an outer threaded portion connected by a weakened frangible portion to an inner tamper ring and said tamper ring having an annular surface terminating in an inwardly directed lip for engagement over the clipbead and within the recess, characterised in that the portion of the tamper ring between the inwardly directed lip and the clipbead exerts a radial force inwards on the clipbead with its annular surface against the clipbead. The advantage of the radial inward force on the clipbead is that the tamper ring cannot be kicked sideways or cocked, as it were, when being unscrewed and thus the weakened frangible portion will be broken when the closure is unscrewed, the tamper ring being securely anchored on the container.

In a further embodiment of the invention, the weakened frangible portion comprises a series of short spaced-apart tabs interconnecting the outer portion and the tamper ring across an annular gap, the cross-sectional area of the tab decreasing from where it connects to one of the outer portion and the tamper ring to where it connects with the other. The great advantage of having this tapered design as it where, is that it is relatively strong in compression and will thus resist crushing and stress weakening as the closure is placed in position while it still has a weakened portion which, in sheer and tension, breaks easily when the closure is twisted. It also has the great advantage of allowing a clean break between the withdrawn portion and the tamper ring. This is particularly suitable where co-operating teeth are used as there is no interference with said teeth when the closure is re-applied.

In one embodiment of the invention, the smallest crosssectional area of the tab is where it connects to the outer portion. The advantage of this is that the failure occurs on the withdrawn portion of the closure and thus there is no jagged edge to cause the user any discomfort or injury. It is very desirable that what is, in effect, the whole of the closure as far as the consumer or user is concerned is cosmetically clean and free from projecting tab remnants .

Ideally, the tab has a back wall forming an extension of the bore of the closure and a front semi-circular wall in cross-section. This is particularly advantageous as it allows for a number of small tabs to be provided using only simple side cores in a mould when formed by injection moulding.

Additionally, support lugs are provided connected to only one of the outer portion and the tamper ring and project into the annular gap. Again, this advantageously limits the crushing effect on the tab by weakening the tab as the outer portion and the tamper ring are forced together on application of the closure. The lugs provide added support and resist the tendency of the tabs to bulge outwards .

Preferably, the support lugs are connected to the tamper ring. Again, this leads to a smooth underneath part for the withdrawn portion of the closure.

In one embodiment of the invention, there are cooperating teeth between the outer portion and the tamper ring, which, when the closure is rotated in a closing direction, will engage to prevent the tabs breaking and, when rotated in the opposite direction, allow the tabs to break and wherein the spacing between the outermost portion of a tooth and the opposite portion of the closure is less than the depth of the rest of the annular gap. This cooperates in, what is a well known way of voiding sheer of the tabs, the advantage of the support lugs as hereinbefore described.

In one embodiment of the invention, the bore diameter is 98.5% of the outer diameter with a tolerance ± 0.85%. Since one is using plastics materials, this is one of the easiest ways of providing this inward force. This is efficient for securing the tamper ring in position in that the tamper ring is not alone a force fit on the clipbead but also is in a position whereby any attempt to unscrew the closure will almost certainly break the frangible portion. Preferably the tolerance is ± 0.6%.

Ideally the inwardly directed lip forms a continuous ring. This strengthens the tamper ring and provides a relatively robust closure.

Preferably, the threaded portion is a tight fit on the neck portion. This again ensures that on unscrewing of the closure, the tamper ring cannot kick or pivot away from the neck of the closure. However, in many instances this is not possible in manufacture because of the need to provide the wide tolerances to allow the tamper rings to slip over the clipbeads. However, because, with the present invention, the tabs are well protected, it is possible to provide tighter tolerances for the threads.

In one embodiment of the invention, the closure is so dimensioned that the distance between the interior of the cap and the inwardly directed lip is just sufficient to allow the lip to engage over the clipbead to lie within the recess. All this does is further assist in ensuring that there is no play between the tamper ring and the outer threaded portion of the closure to allow any relative movement therebetween. In conventional closures particularly with those that have relatively large clipbeads, there would not be sufficient clearance to allow application of the closure. Further, the invention provides the use of any of these closures in combination with a container which is manufactured from an extrusion blow-moulded plastics material. A great advantage of using extrusion blow-moulding for the container is it's relative cheapness.

Detailed Description of the Invention The invention will be more clearly understood from the following description of an embodiment thereof given by way of example only with reference to the accompanying drawings in which:Fig. 1 is an exploded side view of a closure according to the invention about to be screwed on to the neck portion of a container; Fig. 2 is a part sectional view of the closure on a container being screwed down onto the neck of the container; Fig. 3 is a view similar to Fig. 2 showing the closure fully screwed down onto the neck of the container; Fig. 4 is a view similar to Figs. 2 and 3 showing the closure being removed from the container; Fig. 5 is a view similar to Fig. 1 showing the closure totally removed from the container; Fig. 6 is an enlarged view of portion of Fig. 1; Fig. 7 is a sectional view in the direction of the arrows VII-VII of Fig. 6; Fig. 8 is a sectional view in the direction of the arrows VIII-VIII of Fig. 6; Fig. 9 is a view similar to Fig. 1 of an alternative construction of closure according to the invention; Fig. 10 is an enlarged detail of the circled portion indicated by the reference letter W in Fig. 9; Fig. 11 is another detailed view of the portion circled in Fig. 9 and indicated by the reference letter W; Fig. 12 is a sectional view showing the closure of Fig. 9 partially screwed onto the neck of a container; Fig. 13 is an enlarged view of the portion circled in Fig. 9 and identified by the reference letter Q; Fig. 14 is a cross-sectional view in the direction of the arrows XIV-XIV of Fig. 13; Fig. 15 is a cross-sectional view in the direction of the arrows XV-XV of Fig. 13; Fig. 16 is an enlarged view of portion of an alternative construction of closure according to the invention; and Fig. 17 is an enlarged view again showing portion of a still further alternative construction of closure according to the invention.

Referring to the drawings and initially to Figs. 1 to 8 thereof there is provided a tamper indicating closure indicated generally by the reference numeral 1 for a container, not shown, having a bored cylindrical outwardly threaded neck portion indicated by the reference numeral 2. The tamper indicating closure 1 has an outer portion 3 terminating in a cap 4 and having internal threads 5 and is connected by a weakened frangible annular portion indicated by the reference numeral 6 to a tamper ring 7. The frangible portion 6 is formed by a series of alternate slits forming an annular gap 8 and tabs 9. The tamper ring 7 has an annular surface 15 and an inwardly directed lip 10.

The neck portion 2 has threads 11 connecting with a clipbead 12 through a radiused lead in surface 13. Behind the clipbead 12 is a recess 14 for reception of the lip 10 as will be described hereinafter. The internal bore of the tamper ring 7 is less than the external diameter of the clipbead 12 and the threads 5 and 11 are a close fit on each other. Further, the closure 1 is so dimensioned that the distance between the outermost internal neck bore closing portion of the cap 4 and the inwardly directed lip 10 is just sufficient to allow the lip 10 to engage over the clipbead 12 to lie within the recess 14. The dimension X as indicated in Fig. 3 is thus kept to a minimum but is not critical.

It will be noted from Figs. 6 to 8 that the tabs 9 do not project across the whole of the depth of the gap 8 and are further thinner adjacent the outer portion 3 than the tamper ring 7 having a reducing cross-sectional area from top to bottom. It will be noted that each tab 9 has a back wall forming an extension of the bore of the closure and a front semi-circular wall in cross section.

In use, the closure 1 is screwed onto the neck portion 2 in the normal manner until the lip 10 begins to engage the radiused lead in surface 13 and is pushed up over the clipbead 12. As the lip 10 is forced over the clipbead 12 it slips behind the clipbead 12 into the recess 14 as shown in Fig. 3. Then the tamper ring 7 engages tight against the clipbead 12 because the internal bore of the tamper ring 7 is less than the external diameter of the clipbead 12 thus forming an interference fit thereon and exerts a positive radial force inwards. When the closure 1 is unscrewed from the neck portion 2 the annular surface of the tamper ring 7 is held tight against the clipbead 12 because of this positive radial inwards force and the frangible portion 6 breaks easily.

It will be noted from Fig. 5 that because the tabs 9 are thinner adjacent the outer portion 3, they fracture where they meet the outer portion 3 and thus, the tabs 9 remain attached to the tamper ring 7. Further, the tapered design produces a number of beneficial effects. It is relatively strong in compression resisting crushing and strength weakening, while at the same time, a clearly defined line of fracture is identified as it where. It is further weak in sheer and tension and it would break easily at it's weakest point. Further, it will afford a clean break leaving the main body of the closure as it where, i.e. the parts that people withdraw, having a cosmetically clean underneath surface which is free from projecting tab or tab remnants. The particular shape of the tab, what one would almost say was a conical design, allows a number of small tabs to be provided using only simple cores in a mould. It also ensures that the outer edge of the whole of the removed portion of the closure is relatively smooth.

Referring now to Figs. 9 to 15 inclusive there is illustrated an alternative construction of tamper indicating closure indicated generally by the reference numeral 20. In these drawings, parts similar to those described with reference to the previous drawings are identified by the same reference numerals. In this embodiment there is provided a frangible portion indicated generally by the reference numeral 21. The frangible portion 21 comprises a plurality of tabs 22 interconnecting the outer threaded portion 3 and the tamper ring 7. There is provided slits interconnecting each tab 22 which form an annular gap 23, the slits are extended to project in a generally longitudinal direction with respect to the closure longitudinal axis and the remainder of the slit is inclined to the axis to form cooperating teeth identified by the reference numerals 24 and 25 on the outer portion 3 of the closure 20 and tamper ring 7 respectively. It will be noted that the spacing between the outermost portion of the tooth 25 and the opposite part of the outer portion 3 is less than the rest of the annular gap 23.

Fig. 10 shows the teeth 24 and 25 in the normal position when the closure 20 is in the position illustrated in Fig. 9. As the closure 20 is screwed down onto the neck portion 2 because of the fact that the lip 10 will begin to bear against the radiused lead in surface 13, a certain pressure will be put onto the frangible portion 21. If the pressure is sufficient, the tabs 22 will begin to distort and the outer portion 3 will rotate somewhat relative to the tamper ring 7 until the teeth 24 and 25 engage. Further, the gap identified by the letter A will be quickly closed so that the tabs 22 further protect it from crushing. It will be appreciated that if the closure 20 is unscrewed from the neck portion 2 that the closure 20 will operate in the same way as the closure 1 and the tamper ring 7 will be fast on the clipbead 12 and the teeth 24 and 25 will smoothly disengage causing the tabs 22 to break as before.

It will be noted from Figs. 13 to 15, that the construction of tab 22 is different to that of the tab 9 of the previous embodiment in that the thinnest portion and thus the weakest portion of the tab 22 lies adjacent the tamper ring 7. Thus when the frangible portion 21 is broken, the tabs 22 will be withdrawn with the outer portion 3 and not left on the tamper ring 7 as with the previous embodiment.

It will be appreciated that this embodiment in which the weakened frangible portion is so shaped that on a closing rotation of the closure, the frangible portion distorts to allow the outer threaded portion locate the tamper ring before the frangible portion breaks to rotate together and an opening rotation to disengage to permit the frangible portion to break is not required for every application but merely for those closing operations or machines where the closing torque is relatively severe.

Referring now to Fig. 16, there is illustrated portion of an alternative construction of closure indicated generally by the reference numeral 30 which is of substantially the same construction as that closure illustrated in Figs. 1 to 8. In this embodiment, in addition to the tabs 9, there are provided support lugs 31 on the outer portion of the tamper ring 7 which project into the annular gap 8. On closing of the closure, as the tamper ring 7 meets resistance on the externally threaded neck portion of the container, the gap 8 will be reduced and the tabs 9 will begin to distort. However, the support lugs 31 will now engage with the outer portion 3 preventing further crushing or bulging of the tabs 9. It will be appreciated that the support lugs could be also placed on the outer portion 3 or there could be some support lugs on both the outer portion 3 and the tamper ring 7.

Referring to Fig. 17, there is illustrated portion of an alternative construction of closure, indicated generally by the reference numeral 40 which is substantially similar in construction to the closure described with reference to Figs. 9 to 15 inclusive. In this embodiment, there are provided tabs 41 in which the smallest cross-sectional area of the tabs is where it connects with the outer portion 3. In this embodiment, there is provided a series of recesses 42 in the outer portion 3 and projecting teeth 43 on the tamper ring 7. It will be noted that the spacing between the outermost portion of the teeth 43 and the interior of the recess 42 as identified by the letter B is less than the depth of the rest of the annular gap 23.

It has been found in practice that the manufacturing tolerances for the closure and specifically the bore or internal diameter ID of the tamper ring 7 is critical. For example, with a relatively common size of container neck with a nominal bead outside diameter 0D of the order of 30 mm the ID of the tamper ring varies between 29.8 to 29.3 mm i.e. + 0.25 mm about a nominal ID of 29.55.

In general a nominal ID for the tamper ring expressed in terms of the nominal 0D of the bead is of the order of 0.985 bead 0D + 0.0060 bead 0D to ± 0.0085 bead 0D or expressed as a percentage 98.5% ± 0.6% or ± 0.85%.

The present invention is particularly suitable for use with containers formed by extrusion blow-moulding. The closure according to the present invention is injection moulded and will accommodate a wide range of container neck sizes and eliminates the need for very sharp undercut corner radiuses on the neck clipbead. This makes the mould easier to manufacture and the cap can be easily ejected from the mould unlike some current constructions.

It will be noted that the present invention utilises a continuously inwardly projecting tamper ring with a relatively small undercut and critically is dimensioned so that the internal diameter of the vertical face of the tamper ring must be considerably stretched over the clipbead so that, even after application, a significant inward radial force is exerted. One of the great advantages of a small undercut on the tamper ring is that it eases the application of a cap on a bottling line. Utilisation of the natural lasting effect of the material of the tamper ring, this enables a wide range of neck clipbead tolerances to be accommodated. It should also be noted that the stretch fit, as it where, of the tamper ring limits rotation sufficiently to aid breaking of tab on first removal of cap and in many instances, does not require the use of the teeth for elaborate ratchet arrangement as described herein, although in certain other situations, this may be useful. Further, it will be seen how the present invention has ensured that the tabs are relatively strong in compression and weak in sheer so that they will easily break when a cap is twisted while, under compression, they resist crushing and bulging which, if inwards, can further increase the torsional force required for application. Similarly, what is in effect a small upstand or downstand provided by the support lugs, is advantageous in further limiting the crushing effect or tab weakening as described before. It will be appreciated that this feature may be used in conjunction with all the embodiments.

It is envisaged that the closure will be made of any suitable elastic or deformable material and that indeed the common plastics such as polypropylene (PP) and high density polyethylene (HDPE) that are used in the construction of such closures are very suitable. - 15 The invention is not limited to the embodiments hereinbefore described which may be varied within the scope of the claims.

Claims (5)

1. A tamper indicating closure for a container of the type having a bored cylindrical externally threaded neck portion with an annular clipbead inward of the threaded portion and having a recess behind it, the closure being of the type comprising a cap surmounting an outer threaded portion connected by a weakened frangible portion to an inner tamper ring and said tamper ring having an annular surface terminating in an inwardly directed lip for engagement over the clipbead and within the recess, characterised in that the portion of the tamper ring between the inwardly directed lip and the clipbead has an internal bore diameter which is 98% of the outer diameter of the clipbead with a tolerance of + 1.35% so that it exerts a radial force inwards on the clipbead with its annular surface against the clipbead and in which the weakened frangible portion is formed from a series of short spaced-apart tabs interconnecting the outer portion and the tamper ring across an annular gap, the cross-sectional area of the tab decreasing from where it connects to one of the outer portion and the tamper ring to where it connects with the other.

2. A closure as claimed in claim 1, in which support lugs are provided connected to only one of the outer portion and the tamper ring and project into the annular gap.

3. A closure as claimed in any preceding claim in which there are co-operating teeth between the outer portion and the tamper ring, which, when the closure is rotated in a closing direction, will engage to prevent the tabs breaking and, when rotated in the opposite direction, allow the tabs to break and wherein the spacing between the outermost portion of a tooth and the opposite portion of the closure is less than the depth of the rest of the annular gap. 5

4. A closure as claimed in any preceding claim, in which the inwardly directed lip forms a continuous ring.

5. A closure substantially as described herein with reference to and as illustrated in the accompanying drawings .