Plastic article or earthenware shaping or treating: apparatus – Female mold and charger to supply fluent stock under... – With means to heat or cool
Patent
1992-09-08
1994-06-28
Heitbrink, Tim
Plastic article or earthenware shaping or treating: apparatus
Female mold and charger to supply fluent stock under...
With means to heat or cool
264107, 264334, 425556, 425562, 425810, B29C 4520
Patent
active
053241908
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Injection moulds exist which are equipped for manufacturing disc-shaped articles with a central hole. Examples of this are compact discs, VLPs, laser discs and other information carriers. Such known moulds are of the two-part type and bound in closed position a disc-shaped mould cavity. After the injection moulding treatment the central hole is removed from the formed article by means of a punching process.
The drawback to this known art is that in this way valuable plastic is lost and that the quality of the hole is greatly dependent on the accuracy with which the punching process is performed, in particular the moment during the manufacturing cycle at which the actual punching takes place.
SUMMARY OF THE INVENTION
In order to always obtain disc-shaped articles with a central hole of excellent and fully controllable quality without loss of material, the invention provides an injection mould for manufacturing disc-shaped plastic articles with a. central hole, which mould comprises: of first displacing means; which they together partially bound a mould cavity corresponding to the shape of an article for manufacture, and an open second position in which a formed article can be taken out;
a third mould part which in the closed position of the first and second mould parts extends through the mould cavity defined thereby and in the region of this mould cavity has a shape corresponding to the shape of the central hole, which third mould part is coaxially displaceable by means of second displacing means by means of a guide sleeve forming part of the first mould part between a first position, in which it partially forms a bounding of the mould cavity and a retracted second position; outside end to the injection nozzle of an injection moulding device and at the other side debouches with an injection inlet into the region of the mould cavity in the first position of the first and the second mould parts and the first position of the third mould part, and in the second position of the third mould part debouches blind against the inner wall of the guide sleeve; and
heating means for keeping plastic present in the channel in the plastic state.
To ensure that the zone around the central hole does not shrink fixedly during cooling round the third mould part use can be made of an embodiment having the characteristic that the third mould part has a releasing form in the region of the mould cavity during moving of the third mould part from the first to the second position.
Existing moulds have an ejector for ejecting the central sprue of a formed article after it has been punched out. Use can be made of this existing configuration within the framework of the invention. For this purpose the invention provides a mould of the said type having the feature that the second displacing means comprise an ejector extending through the second mould part.
A very good quality of the plastic article is assured with an embodiment in which the injection inlet comprises a number of peripherally ordered injection inlet openings.
A completely homogenous inflow pattern of the heated plastic into the moulded cavity is assured with an embodiment with the feature that the injection inlet is embodied as an injection inlet opening extending around the entire periphery of the third mould part.
It is important to ensure that in the retracted, non-operational state of the third mould part the plastic present in the channel does not cool. To that end the device preferably displays the characteristic that the third mould part comprises a first heating element.
For the best possible flow pattern and a homogenous heating of the plastic in the third mould part the special feature can be added that the third mould part is elongate in its moving direction, that the channel extends in lengthwise direction and has the form of a cylinder jacket over a portion of considerable length to the injection inlet, and that the first heating element is situated inside this cylinder jacket.
Easy manufacture of the third mould part is ensured
REFERENCES:
patent: 2777164 (1957-01-01), Strahm
patent: 4340353 (1982-07-01), Mayer
patent: 4900560 (1990-02-01), Trakas
patent: 4938681 (1990-07-01), Gellert
patent: 4961884 (1990-10-01), Watanabe et al.
Hackh's Chemical Dictionary, 1969, p. 663.
GPT Axxicon B.V.
Heitbrink Tim
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