GB2235184A

GB2235184A - Composite cap assembly

Info

Publication number: GB2235184A
Application number: GB8918549A
Authority: GB
Inventors: Henryk Dudzik
Original assignee: Lawson Mardon USA Inc
Current assignee: Amcor Specialty Cartons Americas LLC
Priority date: 1989-08-15
Filing date: 1989-08-15
Publication date: 1991-02-27
Anticipated expiration: 2009-08-15
Also published as: GB8918549D0; GB2235184B

Abstract

In a composite cap assembly comprising a skirt 13 with a substantially gas-impermeable sheet over member 125 secured in contact with the inner surface of the top 12 and peripheral sealing means for sealing within the cap, the cap has an annular projection 115 spaced radially inwardly of the skirt and overlying the cover member 125, the projection 115 being supported by fingers 126 extending from the skirt. The cover member is preferably fused to the cap top and to the projection 115 and fingers 126. <IMAGE>

Description

COMPOSITE CAP ASSEMBLY AND MOULD THEREFOR.

This invention relates to a composite cap assembly and mould therefor.

It has been well known for many years to close jars with a sealing gasket, a cover disc and a ring screw-engaged on the jar and having a flange to consolidate the disc, gasket and jar rim.

GB-A-1477902 discloses such an arrangement having a metal cover disc, a plastisol gasket and a moulded plastics ring.

EP-A-0269920 discloses a similar arrangement using a cover disc made of tin plate or a composite material.

EP-A-0272431 also discloses a similar arrangement with a metal or "barrier plastic" cover disc.

The purpose of this type of assembly is to provide an enclosure which is gas-impermeable, so that the contents cannot spoil. Such assemblies are used particularly for food.

The combination of a metal disc closing a glass jar provides a good gas-impermeable enclosure, although the arrangement is expensive and the metal may corrode. The use of a composite barrier material, e.g. a metal foil and plastics laminate avoids the corrosion problem, but the problem of expense remains.

It is known to produce a composite cap assembly comprising a unitary moulding having a closed top and threaded skirt, with a sealing liner on the inside surface of the top of the cap. EP-A-0094026 discloses such a construction with a flowed-in liner, mechanically held in a peripheral channel adjacent the top. This arrangement provides a cheap cap, but does not provide the gasimpermeable properties necessary for long storage of food.

Recently a composite cap assembly has been proposed which does have these gas-impermeable properties. US-A4774134 discloses a laminated cover disc, made of metal foil with a plastisol on one face and a polyolefin on the opposite face. The disc is insert-moulded in an injection moulded cap.

The cap is moulded from a polyolefin, which fuses with the polyolefin layer of the laminate to adhere the cover disc to the inner surface of the top of the cap. A plastisol gasket is flowed-in around the edge of the cover disc and is adhered to the plastisol coating on the disc.

There are some problems with this arrangement. The peripheral edge of the cover disc is intended to be mechanically held within a groove, defined by the moulding material surrounding the edge, during the moulding step. This is only possible, however, where a thick and rigid laminate is used. Otherwise, the force of the injection of moulding material will cause the peripheral margin to bend and the gasket will be secured only by adhesion to the laminate.

The use of a thick laminate adds substantially to the expense of the cap.

The present invention provides a composite cap assembly, and a mould for such a cap assembly, in which a thin cheap off-the-shelf barrier material may be used for the cover.

The present invention provides a composite cap assembly comprising a cap having a top and a skirt with a substantially gas-impermeable sheet cover member secured in contact with the inner surface of the top, and peripheral sealing means for sealing within the cap1 wherein the cap has an integrally moulded annular projection spaced radially inwardly of the skirt and which overlies the cover member, the projection being supported by integrally moulded fingers extending from the skirt and overlying the cover member.

The cover material is preferably a sheet of polyolefin metallised on one side and the cap is moulded from polyolefin, so that the polyolefin surface of the cover adheres to the inside surface of the top of the cap. The metallic coating may be protected by a plastics layer.

In the preferred embodiment, a polyolefin surface of the cover may be adhered, during the moulding step, to the overlying projection and fingers. This adhesion may be an alternative to the adhesion to the top of the cap, or the protective plastics layer may be a polyolefin, so that the cover is adhered to both the top of the cap and the projection and fingers.

The mould for the preferred embodiment has a groove for forming the projection and a plurality of lands spaced around the groove with moulding material feed channels between the lands. The cover may be positioned on the core so as to overlie the groove, the lands and the feed channels. The cover is thereby supported in its planar state and deformation during the moulding step is avoided.

The injection nozzle will normally be positioned centrally relative to the core and the cover. This may damage the cover adjacent the nozzle. To prevent this, the core may have a small well or domed projection opposite to the nozzle which assist in dissipation of the hot moulding material.

Reference is now made to the accompanying drawings, wherein Figure 1 is a sectional view on the line I--I of Figure 2 of a cap according to the invention; Figure 2 is a sectional view on the line II--II of Figure 1; Figure 3 is a perspective view of a mould core of a mould according to the invention; Figure 4 is a diagrammatic sectional view of the mould; and Figure 5 is a view similar to Figure 1 of a modified cap.

Referring to Figures 1 and 2 of the drawings1 the cap 111 is an injection moulding, e.g. of polypropylene and is formed with a top 12, a skirt 13 and screw threads 14, and the whole of the inner surface 116 of the top of the cap is covered by a disc-shaped cover 125 to provide a gasimpermeable barrier. Radial fingers 126 project inwardly from the skirt 13 and terminate in an annular projection, or ring 115. The fingers and ring both overlie and contact the cover 125.

The ring has an outer surface 118 angled towards the skirt and the skirt has the oppositely angled surface 19 defining a channel to receive a gasket 20. The gasket is flowed-in and is keyed by the fingers 126. The fingers may have a slight taper to aid the keying function. Alternatively a gasket may be push-fitted into the channel.

The cover is insert-moulded by being positioned on the core of the injection mould. The cover is held in place by the ring and the fingers, so that it is not essential for the cover to adhere to the inner surface 116 of the top of the cap. It is preferred, however, that the cover has a polypropylene (or other polyolefin) layer which is fused to the fingers and the ring during moulding. The cover may comprise metallised polypropylene with a polypropylene protective layer so that the cover fuses additionally to the inner surface 116 of the top of the cap.

Reference is now made to Figures 3 and 4 which show a mould for producing a cap.

The mould includes a cylindrical core 30 having a planar, circular end surface 31 provided with a small, shallow, central, concave well 32. Adjacent the end surface 31 is a peripheral groove 39 surrounded by a multiplicity of blocks 34 spaced around the groove. Each block defines a land 35 which is co-planar with the end surface 31. Narrow spaces between the blocks define feed channels 36 for moulding material to pass from the periphery 37 of the core to the groove 39. The bottom of each feed channel is spaced from the planar end surface 31 a distance smaller than the bottom of the groove 39 is spaced from the end surface 31.

The mould has an outer member 40 including an injection nozzle 41 located centrally of the planar end surface 31 of the core.

The cover 125 is placed on the end surface 31 of the core so as to extend over the groove 39 to the periphery 37.

The peripheral margin of the cover is supported by the lands 35. The mould is then closed and the cap is moulded about the cover. The groove 39 forms the ring 115 and the feed channels 36 form the fingers 126. The groove and channels are sufficiently narrow to prevent deformation of the cover into the groove and channels.

There is slight deformation of the cover into the well 32, which is located opposite the nozzle 41. This prevents damage to the cover at that position, which could lead to a break in the barrier.

In a modification of the cap, shown in Figure 5, the gasket is dispensed with and the ring 115 is designed as a resilient sealing ring. The ring may seal on the top of the rim of a container or may seal on the inner peripheral wall in the mouth of the container. Seals of this type are well known. The ring may, for example, be designed as described and illustrated in GB-1583024.

Claims

1. A composite cap assembly comprising a cap having a top and a skirt with a substantially gas-impermeable sheet cover member secured in contact with the inner surface of the top, and peripheral sealing means for sealing within the cap, wherein the cap has an integrally moulded annular projection spaced radially inwardly of the skirt and which overlies the cover member, the projection being supported by integrally moulded fingers extending from the skirt and overlying the cover member.

2. An assembly according to Claim 1, wherein the cover member is a laminate including a barrier layer and a surface layer which is adhered to the projection.

3. An assembly according to Claim 2, wherein the cover member has a surface layer which is adhered to the inner surface of the top.

4. An assembly according to Claim 3, wherein said surface layers comprise polypropylene.

5. An assembly according to any preceding claim wherein the projection is resilient and defines the sealing means.

6. An assembly according to any one of Claims 1 to 4, wherein the projection defines a channel with the skirt and the sealing means comprises a resilient gasket mechanically held in the channel.

7. An injection mould for use in producing a composite cap assembly according to Claim 1, the mould comprising a core and an outer mould member between which the top and the skirt of the cap may be moulded with the cover member seated on the core, the core having an annular groove for moulding the projection, a plurality of lands spaced around the groove for supporting the periphery of the cover member and feed channels between the lands from the periphery of the core to the groove, for forming the fingers extending from the skirt to the projection.

8. An injection mould according to Claim 7, wherein the outer mould member has means substantially centrally positioned relative to the core for injecting moulding material and the core has a central projection or well opposite to said means.

9. An injection mould according to Claim 7, substantially as herein described with reference to the accompanying drawings.

10. A composite cap assembly according to Claim 1, substantially as herein described with reference to the accompanying drawings.