Injection moulding apparatus

Apparatus for producing an injection moulding of plastics material comprising means for introducing a supply of plastics material, passage means for communicating the supply means to a mould space, and means for introducing a pressurized gas into the plastics material filling the mould space whereby the gas creates a gas containing cavity in the plastics material and for thereafter relieving the gas pressure within the gas containing cavity before the mould is opened, said gas supply/pressure relieving means comprising a valve port opening directly into the mould space, a valve member for closing the port, a first passageway in said valve member for supplying pressurized gas to the mould space whilst the valve member is in a valve port closed position to create the cavity, and a non-return valve situated in an outlet end of the first passageway such that neither plastics material nor pressurized gas can pass back through the first passageway, and after a moulding operation has been finished, the supply of pressurized gas can be terminated and pressurized gas in the cavity in the moulding can be vented through a second passageway to the atmosphere due to movement of the valve member to a valve port open position, said first and second passageways converging at the valve port.