Bottles and jars – Closures – Shrinkable closure – fastener – or seal
Patent
1986-06-06
1987-10-13
Norton, Donald F.
Bottles and jars
Closures
Shrinkable closure, fastener, or seal
215252, B65D 4134
Patent
active
046992847
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a synthetic closure for a container, with a guarantee ring which is connected to the closure by means of strips in order to indicate the first opening of the container.
Guarantee rings are used in increasing numbers. Their manufacture is carried out together with the closure, of a container. i.e. the guarantee ring and the strips are connected to each other and are made in one piece by means of injection moulding. To this effect, an inner and an outer mould, so-called plungers, are used. The inner or lower plunger is withdrawn after injection whereupon the completely injected and to some extent cooled but still partially plastic closure is ejected upwardly from the outer or upper plunger. The withdrawal of the lower plunger and the extraction of the upper one causes friction between the closure and the plunger walls which the closure must support in order to come out of the mould without damage.
At this point it is essential to briefly refer to the function of the strips. Their purpose is to indicate at the closure which, after having cooled completely, has been placed onto a container, the first opening of the latter, i.e. the first removal of the closure since they are torn apart at the smallest rotation of the closure because the guarantee ring does not rotate. To this effect the strips must therefore be made weaker with regard to the closure and the guarantee ring. Thus they must have a reduced width and thickness.
The problem of the friction referred to earlier herein is a further consideration. If the friction is too great, the strips will have been damaged when the closure is removed from the mould, during the so-called extraction step. This must be avoided. It is noted that a slow removal or extraction step might overcome this problem. However, such a procedure is impractical due to the necessity of obtaining a very high number of closures in a short time. The extraction step must therefore be carried out in the quickest manner possible.
According to the invention, this problem is, solved by the suitable shaping of the closure such that the inner wall of the gurarantee ring enlarges steadily in diameter from the strips toward its free end while the outer wall at least at the limit of the strips, runs in an arc up to a location on which the full wall thickness of the guarantee ring is attained.
The extraction step is thus substantially faciliated by this sort of shape and the danger of damaging the stips is avoided. The conical shape of the guarantee ring is provided by a lower plunger that is shaped as a truncated cone. If the latter now moves downwards, exactly within the rotational axis of the closure just moulded, it can easily be seen that no friction occurs save for an initial static friction at the beginning of the extraction. A gap is immediately formed between plunger and closure thanks to the conical shape so that the motion of the plunger is carried out without friction. This is contrary to the commonly cylindrical plungers and likewise guarantee rings on which, due to the constant diameter, a sliding friction occurs over the entire height.
It appears that the ejection of the closure together with its conical guarantee ring which is carried out upwards out of the upper plunger, causes some difficulties. This is due to the free end of the guarantee ring which has a greater diameter than the upper end which borders the strips. The guarantee ring must therefore be essentially forced through a funnel so that a sliding friction occurs. However, it must be remembered that the lower plunger has already moved from its initial position as already mentioned and that the closure itself is still in a plastic state and thus can be deformed. It can therefore compress itself into the free space that was previously taken up by the lower plunger but resumes its initial shape after having passed through. This passage of the guarantee ring through the upper plunger is also facilitated by the shape of the outer wall of the guarantee ring; the arc-like shaping of said wall enables a g
REFERENCES:
patent: 4415094 (1983-11-01), Baunsfelt
Norton Donald F.
Walter Wiedmer AG Plastikform
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