GB2295143A

GB2295143A - Tamper evident closure device

Info

Publication number: GB2295143A
Application number: GB9504262A
Authority: GB
Inventors: Christopher Neil Mcnaughton
Original assignee: MASSMOULD HOLDINGS
Current assignee: MASSMOULD HOLDINGS
Priority date: 1995-03-03
Filing date: 1995-03-03
Publication date: 1996-05-22
Anticipated expiration: 2015-03-03
Also published as: DE69613719T2; DE69603521T2; EP0882656A1; EP0729894A2; GB9504262D0; EP0729894A3; GB2295143B; EP0729894B1; DE69603521D1; EP0882656B1; DE69613719D1

Description

1 CLOSURE DEVICE 2295143 The present invention relates to a closure device

and, in particular, to a closure device adapted for screw-threaded or like engagement with a plastics container such as those used for milk/juice packaging or of other food and non-food products commonly sold in supermarkets. More particularly, the invention is concerned with the provision of an improved tamper-evident arrangement for such a closure device.

Closures having tamper-evident means are well known and serve to reassure would-be purchasers of goods that the contents of a bottle or similar container have not been subject to tampering after filling.

One form of known device comprises a tamper-evident ring which is attached to the downward ly-depend ing skirt of a closure by frangible bridges that sever on the first occasion that the closure is unscrewed. In this known device, the tamper-evident ring is of greater diameter than the closure itself, with the result that manipulation of the closure is hampered by the radially outwardly projecting tamper-evident ring. Sometimes this projection causes minor injuries to users' fingers. Nevertheless, this type of arrangement currently enjoys widespread use by stores retailing milk and non-carbonated fruit drinks in polyethylene containers.

Another drawback of this known design is that the tamperevident ring is not held captive on the container neck once separated from the closure. As a result, there is a tendency for the tamper-evident ring to fall into drinks when the container is tilted, especially when the volume of drink remaining in the container reaches a low level. This problem has led to increasing customer dissatisfaction.

In general, the types of container for which the present invention is intended will be produced by blow-moulding polyethylene, although other materials and moulding processes can be used.

2 Mass produced blow moulded containers, particularly when manufactured to a lightweight design in polyethylene, tend to exhibit a less well-defined neck finish than other containers. This means that, for a closure to function consistently correctly, it must be capable of accommodating a wide spread of neck finish tolerances.

Although other materials and container manufacturing processes can be used, particularly for non-food applications, it is unlikely that the present level of customer dissatisfaction will persuade high volume users of lightweight polyethylene containers to switch to alternative types, especially in view of the low cost, low weight and compatibility which they exhibit with the products with which they come into contact. This is particularly true for the dairy and non-carbonated drinks industries.

It is theref ore an object of the present invention to provide a closure device which is adapted to accommodate a wide range of tolerances in container neck finishes and which addresses the other problems outlined above.

The invention is a plastics closure adapted for releasable engagement with a container, said closure comprising a cap having a skirt portion depending therefrom, said skirt portion having formations on a circumferential inner surface thereof for complementary engagement with corresponding formations on a container, and further comprising a tamperevident ring attached to the skirt portion by a plurality of frangible bridges, wherein at least a portion of the tamper-evident ring has an undercut profile dimensioned to engage projection means on a container during removal of the closure such that separation of the tamperevident ring from the closure is effected.

The advantage conferred by the undercut profile is that it serves to concentrate frictional forces between the projection means on the container neck portion and the tamper- evident ring. This means that the tamper-evident ring effectively bites into the projection means during the action 3 of removal of the closure for the first time. As a result, the tamper- evident ring is prevented f rom riding over the projection means. This arrangement is particularly effective to ensure retention of the tamper- evident ring, even where wide tolerances occur in the neck finishes of the containers to which the closure is applied. It represents a significant improvement over known closures which present a bluff surface or chamfered surface to the retaining projection means on the container.

Preferably, the undercut defines an angle 0 relative to the general plane of the closure, which angle lies in the range from 5 to 250. A most preferred value for 0 is 150. Angles falling outside this range are less effective in achieving the objects of the invention. If the angle is too shallow, the tamper-evident ring does not engage the retaining projection with a sufficiently positive action and the tendency for the tamperevident ring to ride over the retaining projection increases. If the angle is too steep, the undercut profile resembles a flap and has an excessive degree of flexibility. Such flexibility is detrimental to the object of the invention because it enables the undercut profile to be bent over by the retaining projection. Again, the likelihood of the tamper-evident ring riding over the retaining portion is increased.

The portion of the tamper-evident ring on which the undercut profile is provided may be a continuous bead. However, in an especially preferred form of the invention, the undercut profile is formed as a series of radially inwardly projecting nibs provided on the inner circumference of the tamper-evident ring. Such an arrangement offers the advantage over the continuous bead variant that it makes the tamperevident ring more flexible and hence better suited for push-on application when the closure is first fitted. This is particularly advantageous in high speed bottling plant.

4 Where first application by screw-f itting is contemplated, the bottom rim of the skirt portion and the top rim of the tamper-evident ring may be provided with complementary formations which interengage when the closure is subjected to a compressive force as it is screwed onto a container. The complementary formations may be in the form of a series of projections and recesses. In such an arrangement, the frangible bridges flex under the compressive force, causing the separation between the skirt portion and the tamper- evident ring to decrease so that the complementary formations interengage. During the screwing-on process, the skirt portion and the tamper-evident ring effectively behave as a single unit, thereby avoiding stretching of the frangible bridges.

The complementary formations may be configured such that positive engagement between them is facilitated in the forward or screwing-on sense of rotation but inhibited in the reverse or removal sense of rotation. This may be achieved, for example, by providing non-symmetrical driving teeth on one of the components. These are oriented such that they have steeply-pitched trailing surfaces which are engageable against respective bluff surfaces formed in recesses provided on the other component. The teeth have gently- pitched leading surfaces which, in the reverse sense of rotation, engage with similarly-inclined surfaces provided on the recesses, so that there is a tendency for the components to slide over each other and rotate relative to one another. This relative rotation leads to rupture of the frangible bridges when the closure is removed for the first time.

Advantageously, the radially inwardly projecting nibs have a ratchet configuration when viewed from above or below. The leading edge of the nib, when judged in relation to a screwing-on action, has a shallow chamfered surface. The angle of the chamfer is, typically, between 10 and 300. The trailing edge has a much steeper profile and may be substantially radial. This ratchet configuration of the nibs is intended to facilitate installation of the closure on a container for the first time in cases where the container is provided with ratchet dogs on its neck surface beyond the tamper-evident ring projection means.

The tamper-evident ring may be provided with a chamfer in the axial direction to facilitate installation of the closure by push-fitting rather than screw-fitting. In this particular arrangement, the tamper- evident ring has a surface which converges radially inwardly from the free end of the tamper-evident ring. In industrial scale bottling plant, a push-fit closure offers the advantages of being able to increase line speeds and reduce operational complexity because the need for torque-sensing clutch mechanisms to determine when a closure has been screw-tightened sufficiently is avoided.

In another particularly preferred form of the invention, the frangible bridges are attached to the closure and tamperevident ring, respectively, such that they extend in a nonaxial direction from the bottom rim of the closure skirt to the radially innermost extremity of the tamper-evident ring. This means that the frangible bridges form a series of links which converge towards the centre axis of the closure in the direction from the bottom rim of the skirt towards the tamperevident ring.

The advantage of this arrangement is that, when the tamper-evident ring stretches radially outwardly to ride over the retaining projection means on a container during installation of the closure, the frangible bridges are also able to flex in the radially outward direction with minimal stretch or stress due to the additional length which results from their non-axial disposition. This arrangement therefore provides a mechanism whereby the frangible bridges may be formed with increased length relative to conventional bridges, without the disadvantage of making them too long so that their frangibility is compromised. This is particularly important on shallow closures such as those used on milk and non- 6 carbonated fruit drinks containers. Shallow closures have a limited screw- thread engagement and it is unlikely that a tamper-evident ring which is attached to a closure skirt by longer axial bridges would be capable of sufficient thread engagement to enable good separation to take place between the closure skirt and the tamper-evident ring when the closure is removed for the first time.

Typically, the bridges are inclined at an angle of between 15 and 300 to the central axis of the closure. The most preferred angular range is from 20 to 250, with an angle of 220 being especially preferred. Observance of these angles is important to ensure that the closure can be ejected readily from the mould during manufacture. This is an essential point to be borne in mind for components which need to be jumped is from an undercut feature on a mould core. If the angle is too shallow, then severe dragging of the nibs occur, rendering them ineffective. If it is too steep, there is a risk that the frangible bridges will be so excessively long that their extension to breaking point cannot occur within the available travel provided by the threads.

In another preferred variation, the frangible bridges are of non-uniform cross-section, being narrower adjacent the closure skirt. This means that, upon severance, the tails of the bridges remain attached to the tamperevident ring and the closure itself presents a relatively clean bottom rim. Although of seemingly minor importance, this is another factor which influences customer satisfaction.

Preferably, the outer diameter of the tamper-evident ring is the same as the outer diameter of the closure skirt. This provides a greater gripping area on the sides of the closure skirt because it is not inhibited by a so-called "external" tamper-evident ring. Such an arrangement is more comfortable for the user.

7 The invention will now be described by way of example only with reference to the drawings, in which:

Figure 1 is a side sectional partial view of a preferred embodiment of the present invention; Figure 2 is a top plan part view of the tamper-evident ring of Figure 2, showing the ratchet configuration of the nibs and complementary ratchet dogs on a drinks container neck; Figure 3 is a side sectional view of a preferred form of tamper-evident ring, showing the undercut profile of the radial ly- inwardly projecting nibs.

Figure 4 is a side sectional partial view of another embodiment of the invention, showing the skirt portion and the tamper-evident ring with complementary driving formations, and Figure 5 is a similar view to Figure 4 showing the complementary formations in the engaged condition.

Referring now to Figure 1, reference numeral 10 denotes a closure for use on a container such as a milk or other type of bottle containing food or non-food products. The closure itself is moulded from polypropylene and is shown here in enlarged form for ease of reference, the typical diameter for such closures being 38 mm.

Closure 10 comprises a cap 11 having an internal closure plug 12 for sealing engagement with the lip of a container (not shown) during use, and a downwardly depending skirt 13. The skirt 13 has an internal screw thread 14 for engagement with a complementary external screw thread on the neck of the container, and is provided on its outer surface with a gripping portion 15 having a knurled or serrated finish to enable a good grip to be obtained by the user when unscrewing or replacing the closure 10.

8 A tamper-evident ring 30 is attached at the bottom rim 16 of the closure 10 by a plurality of frangible bridges 20. The outer periphery of the tamper-evident ring 30 is substantially co-extensive with that of the skirt 13 so that the gripping portion 15 remains unhindered by radiallyoutwardly projecting features.

The tamper-evident ring 30 is formed on its radially inner surface with a series of nibs 31, each of which is provided with an upward ly-d i rected projection on its radially innermost portion to define an undercut formation 32. This undercut formation 32 serves to engage the underside of a retaining projection (51, see ghost outline in Figure 3) provided on the neck of the container.

During the action of first unscrewing the closure 10, the engagement of the undercut portion 32 against the retaining projection of the container causes axial movement of the tamper-evident ring 30 to be arrested. The closure skirt 13 is able to continue its axial movement by virtue of mutual engagement between the screw threads 14 of the skirt 13 and the external screw threads (not shown) of the container. As a result, the frangible bridges 20 are caused to stretch beyond their breaking points, which breaking points are reached before complete disengagement of the respective screw threads. Although separated from the closure skirt 13, the tamper-evident ring 30 is held captive on the container, behind the retaining projection.

Referring now to Figure 2, this shows a top plan view of the tamperevident ring 30 discussed above with reference to Figure 1. This view shows the ratchet profile of the radial ly- inwardly projecting nibs 31. When judged in relation to the screwing-on direction, as represented by arrow A in the Figure, the leading edge 33 of each nib has a shallow chamfered surface. By contrast, the trailing edge 34 presents a much steeper profile, being substantially radial. The nibs are adapted to cooperate with complementary ratchet dogs 52 formed on the outer periphery of the neck 50 of a container.

9 Typically, the tamper-evident ring 30 has nibs 31 formed at 200 intervals around its periphery. Not all of the nibs have an associated frangible bridge 20 as this would greatly increase the force required to unscrew the closure 10 and 5 effect separation thereof from the tamper-evident ring 30. Conveniently, a frangible bridge 20 is formed at every third nib 31, so that a total of 6 frangible bridges 20 is provided on the complete closure 10. These are shown in cross-section on the Figure.

When the closure 10 is first screwed on to a container neck, the leading edges 33 of the nibs 31 are able to ride over the ratchet dogs 52 formed on the neck because the leading edges 53 of the ratchet dogs 52 are also gently chamfered. However, rotation in the opposite sense, i.e. to unscrew the closure, causes the trailing edges of the ratchet dogs 54 to butt against the trailing edges 34 of the nibs 31, thereby resisting rotation of the tamper-evident ring 30 relative to the container neck 50. Rotation of the closure skirt 13 is, however, still possible against the resistive force of the frangible bridges 20, thereby causing them to elongate.

The elongation of the frangible bridges 20 during removal of the closure 10 for the first time is therefore caused by a combination of two factors: Firstly, axial movement of the tamper-evident ring 30 is prevented by engagement of the undercut portion 32 of the nibs 31 against the retaining projection on the container neck and, secondly, rotational movement of the tamper-evident ring 30 is prevented by abutment of the trailing edges 34 of the nibs 31 against the ratchet dogs 52.

Returning once again to Figure 1, the nibs 31 are also formed with a chamfer 35 in the axial sense. This arrangement allows the closure to be installed on a container neck for the first time by push-fitting rather than screw-fitting.

Referring now to Figure 3, this shows a side sectional part view of the closure skirt 13 and tamper-evident ring 13 of Figures I and 2, joined together by a frangible bridge 20.

Here it is clearly shown that the frangible bridge 20 is inclined at angle a to the rotational axis of the closure by virtue of the fact that the lowermost extremity 22 of the bridge 20 is attached to the rad ia 1 lyinnermost part 32 of the nib 31. This inclination is helpful in enabling the bridge to ride over the retaining projection 51 of a container 50 when the closure is first installed. The additional length of the bridge 20, relative to a prior art bridge having an axis parallel to the rotational axis of the closure, enables it to flex in the direction of the arrow C without extension to breaking point.

The preferred value for the angle of inclination a of the bridges 20 is between 15 and 300, more preferably between 20 and 250. The most preferred angle, as shown in the present example, is 220.

The view of Figure 3 also shows the non-uniform section of the bridge 20. At the upper end 21, adjacent the bottom rim 16 of the skirt 13, the bridge 20 is slightly narrower than at the lower end 22 adjacent nib 31. As a result, when the bridge 20 is stretched to breaking point, the preferred fracture point is in the vicinity of the narrow section at the upper end 21. The advantage of this arrangement is that the skirt 13 presents a relatively clean bottom rim 16 after separation from the tamper-evident ring 30. The severed tails of the frangible bridges 20 remain attached to the tamper evident ring 30 which is held captive on the container neck.

This Figure also shows detail of the configuration of the undercut portion 32 of the nib 31. Preferably, the angle 0 of the undercut lies in the range from 10 to 200, a preferred value being 150.

11 Referring now to Figures 4 and 5, these views show another embodiment of the closure depicted in Figures 1 to 3. In the Figures, like reference numerals are used to denote features common to both embodiments and it is therefore unnecessary to describe in detail those features of the Figure 4 and 5 embodiment which have already been discussed above.

In Figure 4, the bottom rim 16 of the closure skirt portion 13 is provided with a plurality of recesses 46 which are formed with a steeply- pitched trailing surface 47 and a shallow-pitched leading surface 49. Intervening root surface 48 lies substantially parallel to the bottom rim 16 of the skirt portion 13.

The tamper-evident ring 30 is formed with a series of projections 36 around its top rim. These projections 36 are configured to complement the recesses 46 formed in the bottom rim 16 of the skirt portion 13. They each have a steeplypitched trailing surface 37, a shallow-pitched leading surface 39 and an intervening crown surface 38 which is substantially parallel to the top rim of the tamper-evident ring 30.

The terms "leading surface" and "trailing surface" are used here for convenience and should be interpreted with reference to the act of screwing the closure onto a container, indicated by rotation in the sense of arrow B in Figure 5.

Figure 4 depicts this embodiment of the closure in a relaxed condition, either prior to fitting to a container, or after fitting to a container for the first time. In the relaxed condition, the frangible bridges 20 hold the skirt portion 13 and the tamper-evident ring 30 in spaced-apart relationship. The gap between these components is larger than the distance by which the crowns 38 of projections 36 protrude beyond the top rim of the tamper-evident ring 30.

In Figure 5, the closure is depicted in a compressed condition in which the gap between the skirt portion 13 and the tamper-evident ring 30 is decreased as a result of flexure of the frangible bridges 20. This occurs when the closure is applied to a container for the first time.

12 In the compressed condition, the projections 36 on the tamper-evident ring 30 protrude into the recesses 46 on the bottom rim 16 of the skirt portion 13.

When the closure is rotated in the sense of arrow B, the steeply-pitched trailing edges 37 of the projections 36 engage with the steeply-pitched trailing edges 47 of the recesses 46.

This engagement resists relative rotation between the skirt portion 13 and the tamper-evident ring 30, enabling the closure to be screwed onto a container as a unitary assembly without risk of rupturing the frangible bridges 20.

When the closure is rotated in the opposite direction, i.e. for unscrewing, there is less likely to be an applied compressive force acting to reduce the gap between the skirt portion 13 and the tamper-evident ring 30. However, in the event that there is slight compression, the leading edges 39 of the projections 36 engage against leading edges 49 of recesses 46. Both sets of leading edges have shallow pitch, so the resistance to relative rotation between the skirt portion 13 and the tamper-evident ring 30 is easily overcome.

Such relative rotation causes the frangible bridges 20 to elongate until they become stretched beyond breaking point, thereby effecting separation of the tamper-evident ring 30 from the skirt portion 13.

Although the invention has been described above with reference to particular examples, it will be understood by persons skilled in the art that the invention can be applied to a wide variety of containers and that various modifications are possible without departing from the scope of the claims which follow.

13

Claims

1. A plastics closure adapted for releasable engagement with a container, said closure comprising a cap having a skirt portion depending therefrom, said skirt portion having formations on a circumferential inner surface thereof for complementary engagement with corresponding formations on a container, and further comprising a tamper-evident ring attached to the skirt portion by a plurality of frangible bridges, wherein at least a portion of the tamper-evident ring has an undercut profile dimensioned to engage projection means on a container during removal of the closure such that separation of the tamper-evident ring from the closure is effected.

2. A closure as claimed in claim 1 wherein the undercut defines an angle 0 relative to the general plane of the closure, which angle lies in the range from 5 to 250.

3. A closure as claimed in claim 2 wherein the angle 0 is 150.

4. A closure as claimed in any preceding claim wherein the portion of the tamper-evident ring which has the undercut profile is a series of radially inwardly projecting nibs formed on the inner circumference of the tamper-evident ring.

5. A closure as claimed in claim 4 wherein the nibs have a ratchet configuration when viewed from above or below and wherein the leading edge of each nib, when judged in relation to a screwing-on action of the closure, has a shallow chamfered surface.

14

6. A closure as claimed in any preceding claim wherein the tamper-evident ring has a chamfer in the axial direction, converging radially inwardly from the free end of the tamperevident ring.

7. A closure as claimed in any preceding claim wherein the frangible bridges are attached to the closure and tamperevident ring, respectively, such that they extend in a nonaxial direction from the bottom rim of the closure skirt to the radially innermost extremity of the tamper-evident ring.

8. A closure as claimed in claim 7 wherein the frangible bridges are inclined at an angle of between 15 and 300 to the central axis of the closure.

9. A closure as claimed in claim 8 wherein the angle of inclination of the frangible bridges is between 20 and 250.

10. A closure as claimed in claim 9 wherein the angle of inclination of the frangible bridges is 150.

11. A closure as claimed in any preceding claim wherein the frangible bridges are non-uniform in cross-section, having a narrower cross-section in the region thereof adjacent the closure skirt.

12. A closure as claimed in any preceding claim wherein the outer diameter of the tamper-evident ring is substantially the same as the outer diameter of the closure skirt.

13. A closure as claimed in any preceding claim wherein the bottom rim of the skirt portion and the top rim of the tamperevident ring are provided with complementary formations which are interengageable so as to resist relative rotation between the skirt portion and the tamper-evident ring when the closure is first applied to a container.

14. A plastics closure substantially as described herein with reference to Figures 1 to 3 or Figures 4 and 5 of the drawings.

0 '' Ito a 0, Amendments to the claims have been filed as follows 1. A plastics closure adapted for releasable engagement with a container, said closure comprising a cap having a skirt portion depending therefrom, said skirt portion having formations on a circumferential inner surface thereof for complementary engagement with corresponding formations on a container, and further comprising a tamper-evident ring attached to the skirt portion by a plurality of frangible bridges, wherein at least a portion of the upper surface of the inner periphery of the tamper-evident ring is provided with shelf means having an acute-angled vertical cross- section, said shelf means comprising an inclined top surface rising from a root portion joined to said upper surface of the inner periphery of the tamper-evident ring to a tip portion displaced radially inwardly from said root portion, and a radiallyinwardly facing surface extending divergently from said tip portion of the inclined top surface of the shelf means to the inner periphery of the tamper-evident ring, said shelf means being dimensioned to engage the underside of projection means on a container during removal of the closure from said container such that separation of the tamper-evident ring from the skirt is effected.

2. A closure as claimed in claim 1 wherein the shelf means defines an angle 0 relative to the general plane of the closure, which angle lies in the range from 5 to 250.

3. A closure as claimed in claim 2 wherein the angle 0 is 150.

4. A closure as claimed in any preceding claim wherein the portion of the tamper-evident ring which has the shelf means is a series of radially inwardly projecting nibs formed on the inner circumference of the tamperevident ring.