GB2101104A - Closure for containers - Google Patents

Abstract

A plug-type closure for the mouth of a composite container 2 having an inwardly curled edge is flexible, being for example formed by thermo-forming in relatively thin- plastics. It has an external bead 22 which interferes heavily with the inward curl so that the closure fits very firmly to resist accidental removal. Two recesses 10 extend into the closure from its topside. When fingers are inserted into the recesses and squeezed together, the closure deforms, this deformation being assisted by indents 28 which locally reduce the stiffness of its peripheral portion, in such a way that there is a tendency for the peripheral closure portion to be disengaged from the curled container rim in a localised area. By imposing this deformation and simultaneously applying a closure-removing force by means of the fingers, progressive removal of the closure from the container can be achieved without difficulty. <IMAGE>

Description

SPECIFICATION Closures for containers This invention relates to closures for containers.

The invention has particular, but not exclusive, application to closing the mouths of cylindrical paper-board composite or tinplate containers such as are used for containing dry products against moisture and against the entry of oxygen. Commonly, closures for such containers are removed and replaced many times during the use of the contents of the container, and therefore it is desirable that their removal should be quite easy for the user.

On the other hand, it is desirable for the closure when fitted to the container to be very secure, so that the possibility of it being accidentally removed in the course of rough handling, which is especially likely to occur in the case of relatively large containers containing a substantial weight of product, is minimised.

One type of closure which has been used in the above circumstances is a lever lid end which comprises a metal rin secured around the end of the container and specially formed so as to accept a flanged metal plug-type closure which is a tight push fit into the ring.

This provides a secure closure, but it requires an implement to open it and is relatively expensive, requiring the manufacture of two metal components and their attachment to the container body.

A main object of the present invention is to provide a closure for the mouth of the container which is a secure fit in the container mouth but is relatively easy for a user to remove by hand.

The invention provides a closure for the mouth of a container, in the form of a flexible plug which is provided with finger engageable means so arranged that finger pressure applied thereto causes a deformation of the plug which deformation, with the plug push fitted into a container mouth, tends to disengage a portion of the plug periphery from the container mouth to assist or achieve removal of the closure from the container.

Preferably, the finger engageable means also forms a grippable portion by which the closure can be manually pulled away from the container mouth to complete the disengagement.

Depending upon how tightly the closure fits into the container mouth, which is a matter of detailed design, the tendency to disengage a portion of the plug periphery from the container mouth due to plug deformation may actually be sufficient to cause disengagement of that portion, or it may be insufficient for that purpose but nevertheless sufficient to substantially reduce the pulling force required in the closure-removing direction to cause actual disengagement of that periphery portion from the container mouth. In practice, in the various particular embodiments which will be described below, the latter is the case.The closures require a very substantial force to remove them when no deformation is applied to them, but this is very substantially reduced once finger pressure has been applied in the appropriate manner to cause some closure deformation and a consequent encouragement of closure disengagement at a localised portion of the closure periphery.

In those embodiments, the finger engageable means is so arranged that finger pressure applied thereto causes the plug to bend about a diameter or chord thereof.

Further, they incorporate means for concentrating the bending effect, as it affects the periphery of the plug, at periphery portions which lie at both ends of said diameter or chord. It will be appreciated that in principle concentration of the bending effect at only one end of such diameter or chord would be effective, but by achieving it at both ends the user is saved from having to decide which way round the closure should be when he tries to remove it. By concentrating the bending effect at a particular periphery portion, or portions, a greater tendency towards disengagement of the closure is achieved, for any given amount of finger pressure applied to deform the closure.

Preferably, the closure is provided with one or two recesses which extend into it from its outer side and an internal surface of the or each recess constitutes the finger engageable means. In some embodiments, there are two recesses and a finger and thumb are inserted into them, following which squeezing the recesses towards each other causes the desired plug deformation. In another embodiment, there is a single recess arranged so that one or more fingers can be inserted into it and a gripping movement of the hand will then cause the desired deformation.

When the finger engageable means is in the form of recesses, obstruction of these by a tamper-proofing element such as a paper or thermoplastics label extending across the or each recess provides a means of detecting whether or not any attempt has been made to remove the closure by the normal means.

When this feature is provided in conjunction with the closure being a very firm fit in the container mouth, and also being designed so that there is no significant gap for insertion of a closure removing implement between the container body and the closure, then an effective tamper-proof closing of a container can be achieved, since it will not readily be possible to remove the closure without damaging at least the tamper-proofing element or elements across the recess or recesses.

In the embodiments which will be de scribed, the entire closure is formed as a unit by thermo-forming from sheet plastics material, such as polypropylene. This enables very economical manufacture of a one-piece container closure.

In order that the invention may be more clearly understood, some embodiments thereof will now be described, by way of example only with reference to the accompanying drawings in which: Figure 1 shows a first closure in accordance with the invention, in end elevation on the left and in local cross-section on the right; Figure 2 shows a plan view of the closure of Fig. 1 taken from the top, from which it can be seen that the closure is symmetrical about a diameter line; Figure 2A is a cross-section taken on line IIA-IIA of Fig. 2; Figures 3 and 4 are simplified diagrams to assist in explaining how the closure operates; Figure 5 shows the closure of Figs. 1 and 2 in a deformed condition; Figure 6 shows part of a second type of closure in accordance with the invention;; Figure 7 shows a third type of closure in accordance with the invention, taken in crosssection on a diametral plane about which it is symmetrical; Figure 8 shows a top plan view of the closure of Fig. 7; and Figure 9 shows in local cross-section a fourth type of closure in accordance with the invention.

Fig. 1 shows part of a container body 2 which is cylindrical and is made from wound cardboard, in known fashion. At the mouth of the container body the wall edge is inwardly curled as indicated at 4. Typically, the diameter of the curl may be 5mm, approximately four times the thickness of the wall material, and the curl may extend through approximately 120 . Closures in accordance with the invention are intended particularly, but not exclusively for use with such wound cardboard container bodies with an inwardly curled top edge but it will be apparent that they may be designed for use with other container bodies. The particular embodiments described are well suited for use with metal container bodies having an inwardly curled top edge.

The closure shown in Figs. 1, 2 and 2A is thermoformed in one piece from plastics material which is very much thinner than the diameter of the closure, for example 800 micron thick polypropylene. It could alterna tiveiy be injection moulded from plastics material.

The periphery of the plug comprises a wall generally indicated at 6 which extends generally in the direction of insertion and removal of the closure in the container mouth i.e.

generally perpendicular to the plane of the closure as a whole. The central region of the closure comprises a panel 8 which lies in a plane close to the upper limit of the periphery wall 6 as can be seen at the right-hand side od Fig. 1. The panel 8 is formed with two elongated and substantially parallel recesses 10 which extend into the closure from its outer or upper side.The central panel 8 is linked to the periphery wall 6 by an annular portion generally indicated at 1 2 which extends downwardly from the edge 1 4 of the panel and then outwardly to join the lower edge of the periphery wall 6, whereby the wall 6 and the annular portion 1 2 together form an annular trough 1 6 on the outside of the closure and a complementary annular protrusion 1 8 on the inside thereof.

The curl 4 around the mouth of the container body provides around the mouth, internally, a shoulder 20 facing into the container.

The peripheral wall 6 of the closure is formed with an external bead 22 which provides an external shoulder 24 adapted to snap behind the shoulder 20 on the curl when the closure is forced into the mouth of the container. The external diameter of the bead 22 is made sufficiently greater than the internal diameter of the curl 4, for this to provide a very firm fitting of the closure and hence good protection against sifting or leakage of a powder product packed in the container and a reasonable degree of protection against flavour loss.

The generally downwardly facing side of the bead 22, below the shoulder 24, and the continuation of the wall 6 below that, form a portion of decreasing diameter which serves as a lead-in to assist insertion of the closure in the container mouth.

The upper edge of the peripheral wall 6 is formed as a generally radially extending flange 26 for limiting the insertion of the container into the closure mouth. The flange 26 curves smoothly into the remainder of the peripheral wall 6 on a contour which very closely matches the internal contour of the curl 4, so that a close fit is obtained. The wall 6 above the peak of the bead 22 has the same cross-section along the whole of its length, so that this close fit is present around the whole of the closure to provide high resistance to escape of contents along the container-closure interface.

The edge of the flange 26 is formed so that, when the closure has been fitted, it closely engages the top of the curl to avoid providing any significant gap for insertion of a closure removing implement such as a fingernail or tooi.

The intended manner of removing the closure from the container body will be explained in detail below and involves inserting the fingers into the recesses 10. Preferably, these recesses are obstructed by a tamper-proofing element such as a paper or thermoplastics label 27 adhered to the central panel and covering the recesses 10, as shown on the right-hand side of Fig. 1. This, in conjunction with the firm fitting of the closure and the absence of a gap between the flange 26 and the top of the curl, provides quite a high degree of tamper-proofing because it is very difficult to remove the closure from the container without breaking the label 27 to insert fingers in the recesses 10 so as to remove the closure.

A further feature of the closure is that at each end of the central diameter it is provided with an indented deformation 28 of generally rectangular cross-section which extends into the annular protrusion 18, from the inside or underside of the closure. For a purpose which will become apparent, this locally reduces the stiffness of the peripheral region of the closure which, owing to its construction, is relatively stiff even though the closure as a whole is flexible.

In order to remove the closure from the container mouth, fingers, such as a thumb and forefinger, are inserted into the recesses 10 and the inwardly located surfaces 30 are squeezed towards each other. The general effect that this tends to have upon the form of the closure is illustrated in a simplified manner in Figs. 3 and 4 where the closure is shown as a disc 32 of flexible and compressible material approximating in overall shape to that of the closure, and the finger-engageable surfaces 30 are shown as flat finger tabs 30' protruding from its underside. When the tabs 30' are squeezed together in the direction of arrows A, the disc 32 bends about a diameter perpendicular to the plane of Fig. 3 and corresponding to the diameter on which the indentations 28 lie in Fig. 2.In Fig. 3, the central cross-section of the disc is shown cross-hatched while the parallel curved lines 34 indicated the peripheral wall of the disc as seen in end elevation. The same applies to Fig. 4. It can be seen from the two Figs.

taken together that the squeezing pressure applied to surfaces 30' in the direction of arrows A causes the disc to be deformed into a generally saddle shape. In the course of this deformation, the left and right extremities of the disc as seen in Fig. 4, which correspond to the peripheral portions of the closure of Fig. 2 in the vicinity of the indentations 28, move both inwardly and upwardly as indicated by the arrows B.

When fingers are used to squeeze together the receses 10 of the closure in Figs. 1 and 2 it tends to deform very much in the manner just described with reference to Figs. 3 and 4, and it will be appreciated that, when the closure is fitted in a container mouth, this form of deformation tends to disengage the bead 24 from the curl 4 at the peripheral portions in the vicinity of the indentations 28.

In fact, these indentations serve to concentrate the bending of the closure peripheral portion in the vicinity where they are located, so that instead of the closure being smoothly curved as shown in Fig. 3, its curvature is concentrated in the portion C of the periphery as shown in Fig. 5. Consequently the ten dency to disengage the bead 22 from the curl 4 is concentrated very much in the regions of the indentations 28.In a practical construc tion of the embodiment shown in Figs. 1 and 2, this disengagement tendency is not suffici ent in itself to cause disengagement but when the fingers are used to apply a pulling force in the plug removal direction, simultaneously with the squeezing force which causes defor mation, and especially when this pulling force is applied preferentially to the vicinity of one or other of the indentations 28, then it is quite easy to achieve actual disengagement of the bead 24 in the vicinity of that indentation and disengagement of the entire closure fol lows easily and progressively as the pulling force is maintained.It is noticeable in practice that the two indentations 28 in conjunction with the part of the central panel 8 which lies between the recesses 10, and the two inner walls 30 of those recesses, form a fairly rigid beam extending across the diameter of the closure which, when the closure has been deformed as described, is quite resistant to being bent. This tends to concentrate pulling force applied to the closure also in the regions of the identations 28 in addition to the con centration of the disengagement force caused by closure deformation at those points. The combined effect makes closure removal very easy when the above technique is adopted, even though removal of the closure by a straight pulling force without closure deforma tion is very difficult.

Fig. 6 shows part of a further embodiment of the invention. In this embodiment, the central panel 8 has the same form, with two elongated recesses 10, as in the embodiment of Figs. 1 and 2 but it lies in the same plane as the lower limit of the peripheral wall 6 and joins directly to the lower edge of that wall at a corner indicated at 36. In relation to the peripheral wall 6, therefore, it corresponds in position to the base of the trough 1 6 in Fig.

1. The peripheral wall 6 itself the same form as in the first embodiment.

In order to achieve a concentration of bend ing in this embodiment, at the same positions as achieved by the indentations 28 in the embodiment of Figs. 1 and 2, two indenta tions (only one shown) 38 are provided which extend into the peripheral wall 6 almost up to the peak of the bead 22 and also into the adjoining part of the central panel 8, so as to locally reduce the stiffness of the peripheral region of the closure in relation to the squeez ing force imposed by the user.

In principle, it is not essential to provide for concentration of the bending at a localised portion of the rim. In particular, with the type of construction shown in Fig. 6 where the central panel 8 lies in the plane of the lower limit of the peripheral wall 6, the deformation of the closure which can be achieved by finger pressure within the recesses 10 is particularly pronounced, and the closure can be formed so that even when it is a sufficiently firm fit for many practical purposes, nevertheless reasonably easy closure removal can be achieved by normal deformation of the type illustrated in Figs. 3 and 4, without the need to provide the recesses 38 to concentrate it.

However, the normal deformation effect is not sufficient to enable easy removal of a closure as shown in Figs. 1 and 2 with its central panel 8 at or close to the upper limit of the peripheral wall 6, unless the closure is formed so as to be a quite light interference fit in the container mouth, which for most purposes would not be fully satisfactory.

It should be appreciated that the central panel 8 may be positioned at any level relative to the peripheral wall 6 by suitably modifying the design of the annular portion 1 2 which links them together, or even eliminating it as shown in Fig. 6. Experiments suggest that the pulling force required to remove the closure may be smallest if the central panel is located at an intermediate position relative to the peripheral wall. It is accordingly proposed, for a further embodiment, that the central panel is raised above the bottom of the trough 1 6 (Fig. 1) by half the height of the peripheral wall.

In the embodiment shown in Figs. 7 and 8, the peripheral wall 6 of the closure has the same construction as in the embodiment of Figs. 1 and 2 but the central panel 8 is different, consisting of an uninterrupted flat portion 40 which is formed with a single recess 42 adjacent to the peripheral wall 6 on one side. The recess 42 lies on one side of a chord, rather than a diameter, of the closure, at the ends of which chord are located generally triangular recesses 44 which serve to reduce the stiffness of the peripheral portion of the closure where they are located, in simiiar manner to the indentations 28 and 38 already referred to.The closure is removed by inserting two or three fingers into the recess 42, with the palm of the hand resting against the side of the closure, and the container, opposite to that recess, and then by a gripping action of the hand pressing the internal wall surface 46 of the recess in the direction of the arrow D. This causes a similar type of deformation to that already explained with reference to Figs. 3 and 4, except that the downward bending occurs primarily about, and is concentrated at, the chord line on which the indentations 44 are located.Consequently initial disengagement of the closure from the curl is achieved at one or other of the peripheral portions adjacent to one of the indentations 44 and completion of closure removal is achieved by applying a lifting or pulling force with the fingers to the interior of recess 42 in addition to the squeezing force applied in the direction of arrow D.

Fig. 9 shows a local cross-section through a further embodiment in which central panel 8 joins directly to the lower limit of peripheral wall 6 and is formed with a central protrusion 48 which stops short of the peripheral wall at each end, being spaced from it by narrow bridge portions of the central panel. This protrusion is, in plan view, of approximately rectangular shape and preferably indentations of the kind shown at 38 in Fig. 6 would be provided in the peripheral wall 6 and central panel 8 at the ends of the protrusion. Deformation of the closure in the manner already explained is then achieved by applying finger pressure in the direction of arrows E to the opposed major sides of protrusion 48 which serves also as a handle by which a pulling force can be simultaneously applied so as to complete removal of the closure from the container.

Although the curled rim 4 of a wound cardboard container is relatively stiff, nevertheless it has some degree of flexibility and it is believed that this flexibility assists in enabling the closure to be deformed by a modest amount of finger pressure while at the same time the curled rim is sufficiently unyielding so as no to be able to maintain full engagement with the closure as the latter is being deformed. Otherwise, the desired local disengagement followed by progresive removal would not occur, and it would be correspondingly more difficult for the user to open the container. Closures in accordance with the invention may be made to fit the inwardly curled rim (or other inwardly projecting formation) of a metal container body, which rim would be stiffer than that of a wound cardboard body. This makes deformation of the closure by finger pressure more difficult so that a greater squeezing force has to be applied in order to achieve a given level of tendency to disengage at a localised portion of the closure periphery. However, because of the greater stiffness of the container curl, the magnitude of the interference between container and closure required to avoid accidental or unauthorised removal can be reduced, and the deformation and pulling forces need therefore not exceed acceptable levels.

Claims (30)

1. A closure for the mouth of a container, in the form of a flexible plug which is provided with finger engageable means so arranged that finger pressure applied thereto causes a deformation of the plug which deformation, with the plug push fitted into a container mouth, tends to disengage a portion of the plug periphery from the container mouth to assist or achieve removal of the closure from the container.

2. A closure as claimed in claim 1, wherein said finger engageable means also forms a grippable portion by which the closure can be manually pulled away from the container mouth to complete the disengagement.

3. A closure as claimed in claim 1 or claim 2, wherein the finger engageable means is so arranged that finger pressure applied thereto causes the plug to bend about a diameter or chord thereof.

4. A closure as claimed in claim 3, comprising means for concentrating said bending effect, as it affects the periphery of the plug, at a portion of the periphery which lies at an end of said diameter or chord.

A closure as claimed in claim 4, wherein said means concentrates the peripheral bending effect at periphery portions lying at both ends of said diameter or chord.

6. A closure as claimed in any one of claims 3 to 5, wherein the finger engageable means comprises portions located on opposite sides of said diameter or chord which when squeezed towards each other by opposed finger pressures cause said bending.

7. A closure as claimed in any one of claims 3 to 5, wherein said finger engageable means comprises a portion located to one side of said diameter or chord which when pressed in a direction towards the other side thereof by finger pressure causes said bending.

8. A closure as claimed in claim 6 or claim 7, wherein the or each said portion is an internal surface of a recess extending into the closure from its outer side.

9. A closure as claimed in claim 8, wherein finger access to the or each recess is obstructed by a tamper-proofing element extending across it.

1 0. A closure as claimed in claim 9, wherein the tamper-proofing element is a paper or thermoplastics label.

11. A closure as claimed in any preceding claim, the periphery of which is formed with a retaining feature to firmly hold the closure within the mouth of a container.

1 2. A closure as claimed in claim 11 for a container the mouth of which has around it an inwardly extending formation, the closure having around its periphery an external shoulder adapted to engage behind said formation when the closure is fitted into the container mouth.

1 3. A closure as claimed in any preceding claim, having around its periphery a generally radially extending flange for limiting its insertion into the container mouth.

14. A closure as claimed in any preceding claim, which is of material which is thin relative to the plug diameter.

1 5. A closure as claimed in claim 14, in which said material is a plastics material.

1 6. A closure as claimed in claim 15, which has been thermoformed from sheet plastics material.

1 7. A closure as claimed in claim 1 5 or claim 16, wherein the plastics material is polypropylene.

1 8. A closure as claimed in any one of claims 1 4 to 17, wherein the periphery of the plug comprises a wall of said thin material which extends generally in the direction of closure insertion and removal, and the central region of the plug comprises a panel of said thin material.

19. A closure as claimed in claim 18, wherein said panel lies in a plane at or close to the upper limit of said wall.

20. A closure as claimed in claim 18, wherein said panel lies in a plane intermediate the upper and lower limits of said wall.

21. A closure as claimed in in claim 1 9 or claim 20, wherein said panel is linked to said wall by an annular portion of said thin material which extends downwardly from the edge of the panel and outwardly to the lower edge of the wall, whereby said wall and annular portion together form an annular trough on the outside of the closure and a complementary annular protrusion on the inside thereof.

22. A closure as claimed in claim 21 when dependent on claim 4 or claim 5, wherein the or each concentrating means comprises an indent extending into said annular protrustion from the inside of the closure, which locally reduces the stiffness of the peripheral region of the closure with respect to said deformation thereof.

23. A closure as claimed in claim 18, wherein said panel lies substantially in the same plane as the lower limit of said wall and joins directly thereto.

24. A closure as claimed in claim 23 when dependent on claim 4 or claim 5, wheren the or each concentrating means comprises an indent extending into said wall and the adjoining part of said panel from the inside of the closure, which locally reduces the stiffness of the peripheral region of the closure with respect to said deformation thereof.

25. A closure as claimed in any preceding claim, in combination with and fitted into the mouth of a container body.

26. The combination of claim 25, wherein the container body is a wound cardboard body having an inward curl which defines the container mouth.

27. The combination of claim 26, wherein the closure periphery has a continuous shoulder engaging behind the curl to firmly secure it.

28. The combination of either one of claims 26 and 27, wherein the closure periphery has an insertion limiting flange which closely engages the curl to avoid providing any significant gap for insertion of a closure removing implement.

29. The combination of claim 25 in which no significant gap for insertion of a closure removing implement exists between the container body and the closure.

30. A closure substantially as hereinbefore described with reference to any of the accompanying drawings.