GB1583024A - Cap for closing container - Google Patents

Description

(54) CAP FOR CLOSING CONTAINER (71) We, MARDON ILLINGWORTH LIMITED a British Company of Forest Works, Sutton-in-Ashfield, Notts. NC17 5LH, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - This invention relates to a cap for closing a screw-threaded glass container.

The necks of screw-threaded glass containers are manufactured with a large tolerance. Hence, there may be appreciable differences in diameter between the necks of containers having identical nominal dimensions.

Moulded plastics caps for such containers are, in contrast, manufactured to very close tolerances. Consequently, the caps must be manufactured in such a size and of a material having sufficient resilience such that the caps will fit all the containers they are intended to fit despite the above mentioned differences in diameter of the container necks.

Sealing of such caps is commonly provided by a wad of resilient fluid-resistant material placed inside the cap. The manufacture of such caps is therefore complicated and rendered more expensive by an additional step (the provision and insertion of the wad). Furthermore, in use, it is sometimes found that a wad adheres to the upper face of the container neck when the cap is unscrewed, or falls out, or otherwise loses its sealing properties through continued opening and closing of the container.

It is found that moulded plastics caps, when used without wads, have a tendency to "back off", i.e. unscrew themselves, when left for a period of time. Furthermore, it is difficult to get good sealing with a wadless cap.

It is an object of the present invention to provide a wadless cap which overcomes at least one of the above disadvantages.

According to a first aspect of the present invention there is provided a cap of resilient moulded material for closing a glass - con- tainer having a screw-threaded neck portion, the cap having an outer depending skirt provided on its inner face with a screw thread adapted to co-operate with the screw thread on the neck portion of the container, parallel to the outer skirt an integral inner depending skirt means having a convex outer surface adapted to contact the inner face of the neck portion of the bottle, and, depending from the cap between the inner skirt means and the outer skirt, an annular sealing member arranged to contact the top surface of the neck portion of the container when the cap is screwed onto the container, the separation between the outer surface of the inner skirt means and the inner surface of the outer skirt being such that, on screwing the cap onto the neck portion of the container, the inner skirt means is resiliently flexed radially inwards with respect to the outer skirt to exert, in combination with the outer skirt, a clamping force directed perpendicularly to the inner face of the neck portion of the container.

According to a second aspect of the present invention there is provided the combination of a threaded glass container with a cap according to the first aspect.

The invention will now be described by way of example only, with reference to the accompanying drawings in which, Figure 1 is a vertical cross-section through a portion of the cap of Figure 2, taken along line I-I, Figure 2 is a base plan view of the whole of the cap of Figure 1, and Figure 3 is a vertical cross-section through a similar portion of a similar cap to that shown in Figures 1 and 2.

Referring to Figures 1 and 2 there is shown a cap 10 moulded in one piece from a resilient polypropylene marketed under the name of "Lacqtene P" (Registered Trade Mark) by ATO Chimie, having a density of 0.905 g/cm3, a strength at the yield point of 360 kg/cm2, and a flexural modulus of 16,000 kgm2.

The cap 10 is provided with a top panel 11 from which depend an outer skirt 12, an annular inner skirt 13 parallel to the outer skirt, and an annular sealing member 14 located between the inner and outer skirts.

The outer skirt 12 is provided on its inner face with a screwthread 15.

The inner skirt 13 has a convex outer surface (i.e. the surface facing skirt 12) and a concave inner surface, the lower section of the skirt tapering and being directed radially slightly inwards. Such a shape, as shown in cross-section in Figure 1, may for convenience be termed "banana shaped".

The separation between the outer convex surface of the inner skirt and the inner threaded face of the outer skirt is such that when the cap is screwed onto the threaded neck of a glass bottle or similar glass container (shown in chain line 16 in Figure 1) the wall of the neck flexes the inner skirt inwardly apart from the outer skirt, so that the convex surface of the inner skirt in combination with the outer skirt (which is more rigid by virtue of its greater thickness and strengthening effect of its screw thread 15) exerts a clamping action directed perpendicularly to the inner face of the neck of the bottle 16 and resists the tendency of the cap to back off.

The sealing member 14 is a tapering web depending from the panel 11 at an acute angle and directed radially inwardly of the cap. When the cap is screwed onto the bottle 16 the web 14 is deformed against the top surface 17 of the bottle neck and effects a seal between the cap and the bottle. There is also a sealing effect between the inner surface and the inner face of the bottle neck.

Figure 3 is similar in most respects to Figure 1, identical features including the banana shaped inner skirt each being given the same number, except that the sealing member depending from the panel 11 of the cap between the inner and the outer skirt is provided by an annular protuberance 18 of approximately equilateral triangular cross-section with its apex pointing vertically downwards. This also, by virtue of the resilience of the polypropylene, provides a seal between bottle and cap.

The inner skirt need not be continuous; it may be provided by two or more separate annular segments.

The inner surface of the inner skirt need not be concave; it may be planar, but the inner skirt must be capable of flexing inwards under the action of the bottle neck being screwed in.

Moulded materials other than polypropylene may be used provided they have the necessary qualities of resilience and flexibility.

WHAT WE CLAIM IS: - 1. A cap of resilient moulded material for closing a glass container having a screwthreaded neck portion, the cap having an outer depending skirt provided on its inner face with a screw thread adapted to cooperate with the screw thread on the neck portion of the container, parallel to the outer skirt an integral inner depending skirt means having a convex outer surface adapted to contact the inner face of the neck portion of the bottle, and, depending from the cap between the inner skirt means and the outer skirt, an annular sealing member arranged to contact the top surface of the neck portion of the container when the cap is screwed onto the container, the separattion between the outer surface of the inner skirt means and the inner surface of the outer skirt being such that, on screwing the cap onto the neck portion of the container, the inner skirt means is resiliently flexed radially inwards with respect to the outer skirt to exert, in combination with the outer skirt, a clamping force directed perpendicularly to the inner face of the neck portion of the container.

2. A cap as claimed in claim 1 wherein the sealing member depends inwardly at an acute angle from the cap and tapers whereby resilient sealing deformation of the sealing member against the container is effected when the cap is screwed onto the container.

3. A cap as claimed in claim 1 or 2 wherein the inner surface of the inner skirt means is concave and the skirt tapers towards its lower extremity.

4. A cap as claimed in any preceding claim wherein the inner skirt means is a continuous annular skirt.

5. A cap as claimed in any preceding claim wherein the material is a thermoplastic resin.

6. A cap as claimed in claim 5 wherein the resin is polypropylene.

7. The combination of a threaded glass container with a cap as claimed in any pre

Claims (1)

1. ceding claim.

   8. A cap for closing a g!ass container having a screw-threaded neck portion, as herein described with reference to Figure