Bottles and jars – Closures – Shrinkable closure – fastener – or seal
Patent
1984-07-26
1986-01-14
Norton, Donald F.
Bottles and jars
Closures
Shrinkable closure, fastener, or seal
215252, B65D 4154
Patent
active
045641129
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a closure cap for a container, the cap being of the type which is provided with a heat-shrinkable guarantee strip and is produced integrally with the guarantee strip from thermoplastic material in an injection molding process, wherein the guarantee strip is connected to the lower edge of the closure cap by way of a plurality of rupturable connecting web portions and is intended at least partially to embrace the neck of the container and can be brought into engagement therewith by heat-shrinking, and wherein the wall thickness of the guarantee strip has a reinforcement portion in the region between each two rupturable connecting web portions and the individual reinforcement portions are interrupted and spaced apart by portions of smaller wall thickness.
A closure cap of the kind indicated above is described for example in the European patent publication No. 34,997, published on Sept. 2, 1981. In accordance with that specification, the guarantee strip is provided on the inward side with a chord-like reinforcement, the purpose of which is to enhance the flow behaviour of the thermolastic material in the injection moulding operation. In addition, the reinforcement is intended to facilitate the operation of shrinking the guarantee strip on to the neck of the container by means of the effect of heat.
It has now been found that the dimensions of the reinforcement on the inward side of the guarantee strip can only lie within a restricted range as in that respect the dimensions and the configuration of the neck of the container must be taken into account. In addition, problems still occur when removing the closure cap from a moulding tool which opens in an axial direction, but those problems are not directly related to the reinforcement on the guarantee strip. More specifically, when stripping the closure cap from the inner tool portion, the guarantee strip is subjected to forces which act in the opposite direction to the direction of ejection from the mould and which pull the guarantee strip downwardly. As a result of that, undesirable stretching occurs at the connecting web portions which form the desired rupture locations, as the thermoplastic material is still relatively hot and stretchy after the injection moulding operation. On being removed from the mould, the guarantee strip may be deformed in particular in the region between two desired-rupture connecting web portions, in such a way that it is no longer capable of being brought into proper engagement with the neck of the container.
The object of the present invention is therefore to provide a closure cap of the kind set forth in the opening part of this specification, wherein the thickened portion on the guarantee strip can be better dimensioned in accordance with the requirements involved, and wherein in addition the operation of removing the cap from the injection moulding tool can be carried out without damaging or causing deformation of the guarantee strip.
In accordance with the invention, that object is achieved by a screw cap which includes the features that the reinforcement portions are arranged on the outward side of the guarantee strip, and the cross-sections of the reinforcement portions increase toward the lower edge of the guarantee strip.
By virtue of the reinforcement portion being disposed on the outward side of the guarantee strip, the reinforcement portion can be made of larger dimensions, as required, than would be possible in the case of a reinforcement portion disposed on the inward side of the guarantee strip. As will be described in detail hereinafter, the reinforcement portion also serves as an aid to stripping the cap out of the injection moulding tool, insofar as the guarantee strip itself is retained in the tool by the reinforcement portion upon relative movement of the internal mandrel. The fact that the cross-section of the reinforcement portion increases towards the lower end of the guarantee strip provides that the guarantee strip bears against the tool when the cap is stripped from the internal mand
Crown Obrist AG
Hinds William R.
Norton Donald F.
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