초록 ▼

The invention provides a process and apparatus for producing an injection moulding of plastics material. The process comprises introducing the plastics material in the form of a molten stream into a mould space, measuring a quantity of a non-plastics fluid by filling a chamber with the fluid and hol

The invention provides a process and apparatus for producing an injection moulding of plastics material. The process comprises introducing the plastics material in the form of a molten stream into a mould space, measuring a quantity of a non-plastics fluid by filling a chamber with the fluid and holding the fluid in the chamber under pressure, said measured quantity being sufficient to achieve an intended weight reduction in the resultant injection moulding and to create a required internal pressure in the moulding to be formed, injecting the fluid into the stream of plastics material, injection of the fluid commencing as soon as the stream of plastics material has passed the position at which the fluid is injected and the fluid creating a fluid containing cavity or core in the plastics material continuing to inject the pressurized fluid at a controlled rate whereby the fluid containing cavity or core extends with the plastics material as the plastics material continues to flow through the mould space, and after the supply of plastics material is terminated maintaining a pressure within the fluid containing cavity or core to hold the plastics material positively against the mould surfaces as the plastics material solidifies and cools until the moulding can itself sustain the form dictated by the mould surfaces.

대표청구항 ▼

A process of producing an injection moulded plastic article, comprising the steps of: determining a quantity of non-plastic fluid sufficient to achieve an intended weight reduction in the article being produced as well as required internal pressure in the article being produced; increasing the volum

A process of producing an injection moulded plastic article, comprising the steps of: determining a quantity of non-plastic fluid sufficient to achieve an intended weight reduction in the article being produced as well as required internal pressure in the article being produced; increasing the volume of a variable volume chamber to hold the determined quantity of non-plastic fluid; measuring said quantity of the non-plastic fluid by filling said variable volume chamber with the non-plastic fluid at a pressure determined in relation to the increased chamber volume; introducing plastic material in the form of a stream into a mould space; pressurizing the non-plastic fluid to a pressure sufficient to initiate the creation of at least one cavity of non-plastic fluid in the stream of plastic material when the non-plastic fluid is introduced into contact with the plastic material; reducing the volume of said variable volume chamber at a controlled rate to introduce the non-plastic fluid into the stream of plastic material so as to initiate the formation of the cavity of non-plastic fluid within the stream of plastic material; continuing to control the rate of reduction of the variable volume chamber to pressurize the non-plastic fluid after the cavity is initiated, maintaining a non-interrupted flow of the non-plastic fluid at a pressure higher than that of the stream of plastic material yet not so high as to cause a rupture in the plastic material defining the cavity formed therein, terminating the introduction of plastic material; continuing to apply pressure to the plastic material through the pressurized non-plastic fluid until the plastic material has spread completely throughout said mould space and the plastic material is positively held against the surface of said mould space; and continuing to apply a pressure to the plastic material through the pressurized non-plastic fluid within the cavity while the plastic material solidifies and cools until the article can itself sustain the form dictated by the interior surface of the mould. An injection molded article produced by the process of claim 1.