Plastic article or earthenware shaping or treating: apparatus – Female mold and charger to supply fluent stock under... – With product ejector
Patent
1995-09-14
1997-09-02
Tentoni, Leo B.
Plastic article or earthenware shaping or treating: apparatus
Female mold and charger to supply fluent stock under...
With product ejector
425441, 425444, 425575, 425589, B29C 4540, B29C 4564
Patent
active
056629524
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an injection mould with a pre-opening jack.
BACKGROUND OF THE INVENTION
An injection mould of this type is disclosed in PATENT ABSTRACTS OF JAPAN, Vol. 13, No. 41 (M-791) (3389), 30 Jan. 1989. In this known mould the mould sections which are moved relative to one another to break a sprue are driven apart by spring force. After these mould sections have moved a limited distance apart, the actual mould is opened to release the product. In order to ensure that the sprue of the product is broken before release starts and to guarantee the sequence of this movement, it is necessary to use relatively heavy springs to guarantee breakage of the sprue. Even if relatively heavy springs of this type are used it is still not always guaranteed that breakage takes place.
This relatively large spring force has to be overcome again when closing the mould before the start of a new injection cycle. This implies that any safety measures fitted which serve to stop the closing movement of the mould if undesired articles are present between the mould sections, or in the case of other irregularities, must have a minimum response force which is equal to the spring pressure to be overcome.
In practice this means that moulds of this type can not be provided with a blocking protection which functions realistically. Consequently it is necessary to fit complex cover constructions around the mould, the movement of the various sections of the mould being interrupted as soon as such a cover is opened. This is a circuitous and undesirable construction with which, moreover, it is not possible to prevent damage occurring to the product and/or mould during the closing movement if, for example, injection moulding residues are in the wrong place. The use of a cover is merely a safety precaution for operators and does not protect the mould and/or the products to be injected. The aim of the invention is to overcome these disadvantages.
SUMMARY OF THE INVENTION
The insight on which the invention is based is not to carry out the breaking movement of the sprue relative to the product using spring force, which, in turn, has to be overcome when the mould is closed, but with the aid of jack means. Said jack means, which are operated by means of a fluid, are pressurised to break the sprue. With this arrangement any desired force can be chosen. The further opening movement of the mould takes place only after the sprue has been broken off. The pressure on said jack means can be released when the mould is closed, so that hardly any force has to be overcome in order to place said jack means in the starting position. If desired, spring means or further jack means can be present to move the jack means back into the starting position thereof after the pressure thereon has been released. In this way it is possible, using an injection mould according to the invention, during closing to measure, in a very sensitive manner, the resistance which has to be overcome by the closing mechanism. If said resistance exceeds a relatively low value, the closing operation can be stopped immediately. This implies that, if residual product or other components are present in the closing path of the injection mould, the closing movement can be suspended without damage being caused to any component.
It is pointed out that French Patent 1,553,114 disclosed an injection mould in which the injection head is arranged so that it is movable backwards and forwards. The sprue is broken with the aid of air pressure, which is applied between two adjoining mould section. Leakage will occur as soon as any movement takes place between said two mould sections, with the consequence that very large amounts of air are required to break the sprue, this being associated with highly undesirable side effects.
In the case of the construction according to said French patent publication, the product is blown towards the injection nozzle. This, like the movable construction of the injection nozzle, results in increased susceptibility to malfun
REFERENCES:
patent: 4085178 (1978-04-01), McNeely et al.
Abstract of Japan 59-179310 (Published Oct. 11, 1984).
Abstract of Japan 63-251215 (Published Oct. 18, 1988).
Den Uyl Hendrik
Teijgeler Johannes
Tentoni Leo B.
TPP Axxicon B.V.
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