Plastics injection moulding process - with material introduced into mould maintained at excess pressure by prior injection of air

摘要

Injection moulding process to produce articles of expanding or non -expanding plastic materials involves (a) creating an overpressure inside the mould by the forded inlet of air and (b) then injecting plastic material into the so pressurised mould while the air escapes from the mould in volumes corresponding to those of the injected material, for maintaining a constant overpressure inside the mould.