Plastic and nonmetallic article shaping or treating: processes – With step of making mold or mold shaping – per se – Utilizing surface to be reproduced as an impression pattern
Patent
1983-12-21
1985-08-20
Lowe, James
Plastic and nonmetallic article shaping or treating: processes
With step of making mold or mold shaping, per se
Utilizing surface to be reproduced as an impression pattern
249134, 264226, 264338, B29C 102, B28B 734
Patent
active
045363641
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a mould part which is intended to be brought together with at least one other mould part, to form a mould cavity for shaping plastics articles and objects. The present invention also relates to a method in the manufacture of such a mould part, and to a method in the manufacture of shaped, plastics articles and objects while using said mould part.
BACKGROUND ART
Such objects as the hulls of boats, cisterns, car-body components, and other similar objects are being made to an ever increasing extent from fibre-reinforced plastics materials, and particularly from polyester resin reinforced with glass-fibre. The normal method of manufacture is one in which the fibre-reinforcement and the plastics material are placed in layers on a mould, whereupon the plastics material is pressed into the fibre-reinforcement with the aid of a roller, or corresponding device for moistening the reinforcement throughout and for removing air inclusions. In an alternative method, plastics material containing chopped reinforcing fibres is injected, under high pressure, directly into the mould cavity, until a layer of the desired thickness is obtained.
Both of these methods represent serious health hazards especially when using polyester resins which contain harmful styrenes, these styrenes being released during the moulding process, to mix with the air in the workshop. Attempts have been made to overcome this problem, by installing powerful ventilating systems. Among other things, this has proved to be relatively expensive, since in addition to the costs involved in the actual ventilating apparatus, heating costs are also increased. In addition to costs, such systems create irritating noise and raise the level of draughts in the workshop.
In order to solve these problems, and in an effort to increase output, attempts have been made to manufacture products of the aforementioned kind in closed moulds from which gases can be readily removed, so as not to contaminate the air in the workshop. In the case of moulded shells, the moulds comprise a female mould-section and a male mould-section, the latter being brought into the female mould-section to a position in which the distance between the male and female sections of the moulds correspond to the desired thickness of the objects being produced. In one method of procedure, the plastics material is poured into the female mould-section and there subjected to pressure, in conjunction with the insertion of the male section of the mould. Alternatively, a sub-pressure can be created in the female mould-section and the plastics material drawn into the mould cavity as a result thereof, or the plastics material can be forced into the mould cavity by application of an external overpressure.
In order to obtain male and female mould-sections of satisfactory rigidity, surface fineness, and wear durability, the sections must be made of steel. Steel moulds, however, are excessively expensive when intended for manufacture in small series or for the manufacture of large objects, such as the hulls of canoes or dinghies.
OBJECT OF THE INVENTION
The main object of the present invention is to provide moulds and methods of manufacture which can be applied in the rational, closed manufacture of reinforced plastics articles and objects, including small-series manufacture and the manufacture of large objects, while avoiding the aforementioned disadvantages.
BRIEF SUMMARY OF THE INVENTION
This object is achieved in accordance with the invention by using composite moulds which include a rigid support part made of an inexpensive material and having a surface shaped to correspond to the shape of the objects to be moulded, and by detachably arranging on said surface a mould shell having an extremely fine surface which serves as the moulding surface.
The mould shell can either be bonded to the support part, using a plastics bonding agent, in a manner to be readily separated therefrom, or can be held to said support section by, for example, suction or by means of
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patent: 3065511 (1959-11-01), Leitzel
patent: 3683722 (1972-08-01), Pears
patent: 3770690 (1973-11-01), Oswitch
patent: 3773879 (1973-11-01), Munsil et al.
patent: 3959871 (1976-06-01), Reback
patent: 4231982 (1980-11-01), Jansson
Fertig Mary Lynn
Lowe James
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