Bottles and jars – Closures – Frangible member or portion
Patent
1985-10-03
1987-05-12
Norton, Donald F.
Bottles and jars
Closures
Frangible member or portion
B65D 4134
Patent
active
046642790
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a closure cap of plastic material of the type comprising a female screw thread for closing a mouth of a container having a male screw thread, wherein at its lower edge the cap has a guarantee strip which can be torn off and which is provided on the inside with at least one retaining element which, when the cap is screwed on, engages under an annular projection at the mouth of the container. Closure caps of that kind, with what is referred to as a mechanical guarantee strip, have already been known and conventional for some time. In contrast to shrinkable guarantee strips, mechanical guarantee strips have the advantage that they automatically latch into place when the screw cap is screwed on and that there is no need for additional processing stations such as for example heat shrink tunnels and the like. After the retaining element has latched into place when the closure cap is completely screwed on, the closure cap can only be unscrewed again by destroying the guarantee strip, thus indicating that a container has been opened for the first time.
Difficulties arise in relation to mechanical guarantee strips on the one hand due to the somewhat complicated cross-sectional configuration, when removing the component from the injection moulding tool. On the other hand however it is also necessary to ensure that the mechanical guarantee strip is not damaged at the very time at which the closure cap is being fitted on to the mouth of the container. Therefore, the mechanical guarantee strip must be capable of expanding to a certain degree, when the cap is screwed on, without such expandability having the result, when the closure cap is unscrewed, that the retaining element slides over the annular projection without the guarantee strip being torn away.
GB-A-2 022 063 discloses a closure cap with a mechanical guarantee strip, wherein the retaining element is a bead which extends around the guarantee strip on the inside thereof and which is extended downwardly in a somewhat inclined configuration on one side. The peripheral bead suffers from the disadvantage that it substantially increases the wall thickness of the guarantee strip so that the guarantee strip suffers from over-stretching at the critical location. Such over-stretching can have the result that the bead no longer engages to a sufficient depth beneath the annular projection so that it may be possible for the closure cap to be unscrewed, without the guarantee strip being torn off.
German utility model No. 79 08 673 proposed a very similar principle. In accordance with an alternative embodiment, the bead extends only over a part of the periphery of the guarantee strip. There is no retaining element on the remaining portion. That construction may not be satisfactory insofar as, due to the portion without a retaining element, there is once again the danger that the closure cap can be unscrewed without the guarantee strip being torn off.
A mechanical guarantee strip which is provided on the inside with barb-like means was disclosed in German laid-open application (DE-OS) No. 23 56 007. In that arrangement, the diameter of the guarantee strip is larger than the diameter of the actual closure cap and the guarantee strip is supported with reinforcing ribs against the outside wall of the closure cap. The barb-like means which are proposed in that arrangement can be removed from the injection moulding mould only because the guarantee strip and the side wall of the closure cap are not aligned with each other. In the case of a conventional closure cap for drink bottles, the barb means could not be removed from the mould.
An object of the invention is therefore that of eliminating the above-indicated disadvantages and in particular providing a closure cap of the kind set forth in the opening part of this specification, in which the guarantee strip can be easily fitted on to the mouth of a container, without the danger of being overstretched or the guarantee strip being torn off, while when the closure cap is unscrewed for the first time the guar
Bartl Franz T.
Geisinger Klaus
Obrist Albert
Crown Obrist AG
Hinds William R.
Norton Donald F.
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