GB2046720A

GB2046720A - Screw Closure Cap for a Container

Info

Publication number: GB2046720A
Application number: GB8011425A
Authority: GB
Original assignee: WIEDMER PLASTIKFORM W
Current assignee: WIEDMER PLASTIKFORM W
Priority date: 1979-04-03
Filing date: 1980-04-03
Publication date: 1980-11-19
Also published as: DE3008838A1; FR2453086A1; LU82315A1; DE3008838C2; BE882587A; DE8006293U1; CH635795A5; NL8001835A; FR2453086B1; DK144480A; AT385013B; ATA126180A; GB2046720B

Abstract

A screw closure cap is provided which has a projecting sealing lip 10, adjacent to which there is a depression 11. On fitting the cap to the container the sealing lip is bent into the depression and forms a seal with the mouth of the container, Figure 2 (not shown). The arrangement is preferably such that the seal is formed which completely seals the entire mouth surface of the container. A particular use is as a cap for beverage bottles with a content producing a gas pressure, e.g. mineral water bottles. <IMAGE>

Description

SPECIFICATION Screw Closure Cap for a Container This invention relates to a screw closure cap made from elastic material, and designed to be fitted about the neck of a container.

A problem of non-metallic screw closures is that, despite the elasticity of the material, they must ensure an adequate seal, particularly if the container is under a high internal pressure due to the heating of its content, e.g. during transportation on an open vehicle in sunlight. Due to the fact that said pressure exerts a great axial force on the closure its internal thread preferably cooperates with the container external thread over its entire length. Containers with screw closures and particularly beverage containers have, however, a very short thread due to the standardization approved for metallic closures many decades ago and which is still used as the basis for all screw closure caps today. It is not possible to modify this due to the vast number of bottles in circulation.Thus, despite the fact that the closure is made from a softer material than metal it must be adapted to the container.

Most plastic closures have sealing members which, despite the space constricted by the thread, cooperate with the outside of the container or then with the inside of its mouth.

Sealing members which act on the annular mouth surface of the container are rarely encountered, because the part of the closure acting on this surface, namely the cap is raised from said surface due to the pressure of the container content, so that the seal is normally made problematical. However, proposals in this direction have already been made. On one known closure concentric, thin sealing strips are provided which terminate with a sharp edge. These strips are inclined to the closure axis and have a height which is greater than the lateral spacing of adjacent sealing strips. This ratio between the height and the spacing is intended to provide a scale-like superimposition of the sealing strips and consequently a good sealing action.

However, this is not necessarily the case. In fact the scale-like superimposition has the opposite to the intended effect and the upper sealing strip is at least partly raised from the mouth surface by the underlying tip of the adjacent sealing strip and consequently, despite its long thin shape, its own tip no longer engages with a sufficient pressure on the mouth surface. If due to the pressure in the container the cap is slightly raised, although the sealing strip maintains its contact with the mouth surface it is obviously no longer sufficient to bring about a perfect seal.

A further difficulty is also encountered. As has been stated hereinbefore the closures must be matched to the container thread. The particular consequence of this is that the distance from the bottom of the cap to the start of the inner thread at the free end of the thread head portion must be constant due to the standardization. The closure fitted by an automatic closure machine is rotated until the said bottom engages on the mouth surface, whereupon rotation immediately stops (a slip clutch absorbs this impact-like stopping). This has many effects. Firstly the closure engages with a rotary movement and on abrasive action on the mouth surface of the container. However, such an abrasive movement with the following high fitting pressure is very disadvantageous for long, thin sealing lips which are to engage on one another, due to the frictional and compressive forces which occur.It can damage the sealing lips and cause a loss of sealing action. There is secondly a risk that the long, thin sealing lips are too elastic and consequently bend together too much, even if their shape and arrangement in the engaged state must theoretically ensure maintenance of said normal spacing. However, with too strong bending together the closure is screwed more strongly onto the container than the container thread permits. The closure thread then is supported on the cylindrical part of the container neck, so that the free end of the closure is expanded. The opposite occurs when the sealing lips are too strong, i.e. the closure is not screwed over the entire thread length. In both cases there is a loss of cooperation between the two threads and consequently an increased risk of the closure jumping off the container.

According to one aspect of the present invention, there is provided a screw closure cap for fitting about the neck of a container to close the same, which cap is made from an elastic material and includes an inwardly facing threaded region, wherein (a) that part of the cap which in use is to rest on the edge or rim of the mouth of the container is provided with a deformable annular sealing lip which, when the cap is separate from the container, (i) projects into a space which, when the cap is in use, will be occupied by the neck of the container, and (ii) is inclined with respect to the plane of that portion of the cap which, in use, overlies the mouth of the container; and (b) there is provided in the said portion of the cap a depression adjacent to the sealing lip, the depression being shaped and located so as to receive the sealing lip when the lip is deformed on fitting the cap to the container.

According to another aspect of the present invention, there is provided a screw closure or cap, for a container, made from an elastic material and with an internal thread, as well as a cap on whose side which is to rest on the mouth surface of the container neck is arranged an annular sealing lip which projects in an inclined manner from the plane of said side, wherein in said side and adjacent to the sealing lip a depression is provided and serves to receive the bending sealing lip on fitting the closure.

The invention also provides a combination of a cap as just defined and a container.

Preferably, the depression is arranged radially inwardly (with respect to the screw axis of the cap) of the sealing lip. The sealing lip is advantageously inclined with respect to the screw axis of the cap. Preferably, the shape and width of the depression are such that, on fitting the cap to the container, that side of the sealing lip remote from the depression is pushed or deformed into the plane containing the rest of that part of the cap which is to rest on the edge or rim of the mouth of the container. Also, in the preferred embodiments, the annular sealing lip and the surface from which it depends are such that there is formed a sealing surface for covering the complete width of the edge or rim of the mouth of the container when the cap is fitted to the container.

Advantageously, in the area adjacent to the sealing lip root the depression is shaped in such a way that, with the sealing lip bent back into the depression, an annular pocket is formed in the said area which pocket, in use, can serve to receive any gas pressure produced by the container contents. With such a structure, the sealing lip and the said area adjacent to its root can be formed such that any gas escaping from the container into the said pocket acts on the sealing lip to compress it more tightly onto the edge or rim of the mouth of the container.

The cap of this invention is well suited for use with beverage bottles, e.g. for mineral water.

For a better understanding of the invention, and to show how the same may be carried into effect reference will now be made, by way of example, to the accompanying drawing, in which: Figure 1 shows part of a preferred embodiment of the cap in cross-section; and Figure 2 shows the same part of the cap as Figure 1 but with the cap screwed down.

The cap, which is made from elastic material preferably a synthetic plastics material, is symmetrical about the screw axis 12. The cap has a capping portion 1, a threaded part 2 projecting downwardly therefrom with an internal screw thread 3, and a downwardly projecting inner part 4. As seen from Figure 2, the latter is inserted into the mouth of a bottle 5, where it provides a first seal. Bottle 5 is provided with the conventional standardized external thread 6 which cooperates with the internal thread 3 of the cap. 7 is the annular mouth surface of the bottle onto which the cap is fitted when placed on the bottle by, for example, an automatic bottle capping machine.

The bottom portion 8 of capping portion 1 located between threaded part 2 and inner part 4, includes (going radially inwards from the inner limit of threaded portion 2) a planar ring surface 9 to which are connected an annular sealing lip 10 and a corresponding depression 11. As shown in Figure 1, sealing lip 10 is inclined downwards towards the central screw axis 12 and projects downwards out of the general plane of the bottom 8 of capping portion 1, which is the same as the plane formed by the annular surface 9.

Bottom surface 1 Oa adjacent to surface 9 ends in a tip 1 Ob. Top surface 1 Oc forms one side of depression 11. From its root 1 Od, the width of the sealing lip 10 decreases and it is consequently wedge-shaped, so that although it becomes relatively rigid it can still bend in an elastic manner, as will be described hereinafter.

As is apparent from Figure 2 the closure cap is screwed down until the annular surface 9 engages on the mouth surface 7. This distance between the latter and the end 6a of the external thread 6 is standardized and is the same for all bottles. Thus, the internal thread 3 of the closure must be positioned so that on placing the annular surface 9 on the mouth surface 7 its entire length cooperates with the external thread 6 of bottle 5 in order to be able to take up the pressure produced by the bottle content, particularly on heating it and which presses vertically upwards on the central part of cap 1, in the area within the central part 4. It is therefore also necessary to fix the distance of annular surface 9 from the deepest point 3a of internal thread 3 in Fig. 2.If it were greater the internal thread 3 would pass beyond end 6a of external thread 6, i.e. point 3a would finally be positioned in cylindrical part Sc below the thread which, as shown in Fig. 2, has a larger diameter. Thus, the closure would be expanded, which would also be disadvantageous for the cooperation between the two threads.

Thus, the projecting sealing lip 10 in Fig. 1 must not impede the mounting of sealing surface 9 on mouth surface 7. Consequently not only must it he bent over, but during the bending over must be able to pass back into the plane of annular surface 9 or bottom 8. This is achieved by the said depression 11, which must therefore have a width and depth such that on bending over, sealing lip 10 can completely disappear into it, as shown in Fig. 2. Thus, substantially the entire length of bottom surface 1 0a engages flat with mouth surface 7, with the exception of a small area at the transition between annular surface 9 and bottom surface 1 Oa. Without depression 11 the sealing lip 10 would rest only on mouth surface 7, so that the sealing action would be limited to the length of bottom surface 1 Oa.As a result of the elastic bending of the sealing lip into the depression, said bottom surface 10a engages with a particularly high pressure on mouth surface 7.

In certain cases this pressure can be even higher. In Fig. 2 due to the rounded transition between top surface 1 Oc of the sealing lip close to its root 1 Od and the depression wall facing said side a cavity or pocket 13 is formed on bending sealing lip 10. It can be closed or can have a close connection with the part of depression not filled by the lip. In the case of a high gas pressure gas can travel past the part 4 engaging on the inside of the bottle mouth and then reach the pocket 13, either via the aforementioned close connection or by creating it by expansion (it must be remembered that between the two walls of the depression there is only a limited reciprocal contact pressure if there is contact between the walls, even on bending over the sealing lip). This increased pressure now acts on the top surface 1 Oc of the sealing lip and thus aids its resilient action. As a result the contact pressure of bottom surface 1 Oa on mouth surface 7 is still further increased (gas pressure plus spring tension of sealing lip).

Tests have shown that sealing lip 10, together with annular surface 9, is able to exert a very considerable sealing action, thereby further drastically reducing, in the case of machine-filled bottles, the proportion of bottles which are not tightly sealed compared with the use of other closures.

Portion 14 of cap 1 located between depression 11 and the central part can either be located in the plane of bottom 8 and/or annular surface 9 (indicated by dotted line) or somewhat above it (to save material) without thereby measurably reducing the sealing action.

Claims

1. A screw closure or cap, for a container, made from an elastic material and with an internal thread, as well as a cap on whose side which is to rest on the mouth surface of the container neck is arranged an annular sealing lip which projects in an inclined manner from the plane of said side, wherein in said side and adjacent to the sealing lip a depression is provided and serves to receive the bending sealing lip on fitting the closure.

2. A screw closure cap for fitting about the neck of a container to close the same, which cap is made from an elastic material and includes an inwardly facing threaded region, wherein (a) that part of the cap which in use is to rest on the edge or rim of the mouth of the container is provided with a deformable annular sealing lip which, when the cap is separate from the container, (i) projects into a space which, when the cap is in use, will be occupied by the neck of the container, and (ii) is inclined with respect to the plane of that portion of the cap which, in use overlies the mouth of the container; and (b) there is provided in the said portion of the cap a depression adjacent to the sealing lip, the depression being shaped and located so as to receive the sealing lip when the lip is deformed on fitting the cap to the container.

3. A cap as claimed in claim 1 or 2, wherein the depression is arranged radially inwardly (with respect to the screw axis of the cap) of the sealing lip.

4. A cap as claimed in claim 1, 2 or 3, wherein the sealing lip is inclined with respect to the screw axis of the cap.

5. A cap as claimed in claim 1, 2, 3 or 4, wherein the shape and width of the depression are such that on fitting the cap to the container, that side of the sealing lip remote from the depression is pushed or deformed into the plane containing the rest of that part of the cap which is to rest on the edge or rim of the mouth of the container.

6. A cap as claimed in claim 5, wherein the annular sealing lip and the surface from which it depends are such that there is formed a sealing surface for covering the complete width of the edge or rim of the mouth of the container when the cap is fitted to the container.

7. A cap as claimed in any preceding claim, wherein the sealing lip tapers in a wedge-shaped manner from its root towards its tip.

8. A cap as claimed in any preceding claim, wherein in the area adjacent to the sealing lip root the depression is shaped in such a way that, with the sealing lip bent back into the depression, an annular pocket is formed in the said area which pocket, in use, can serve to receive any gas pressure produced by the container contents.

9. A cap as claimed in claim 8, wherein the sealing lip and the said area adjacent to its root are formed such that any gas escaping from the container into the said pocket acts on the sealing lip to compress it more tightly onto the edge or rim of the mouth of the container.

10. A screw closure cap as claimed in claim 1 or 2, and substantially as hereinbefore described.

11. A screw closure cap substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawing.

12. A combination of a cap as claimed in any preceding claim and a container to which the cap can be fitted.