Plastic injection molding machines

987,095. Injection moulding. BRITISH UNITED SHOE MACHINERY CO. Ltd. May 8, 1961 [May 19, 1960], No. 18076/61. Heading B5A. An injection-moulding machine comprises a mould cavity defined by movable members 10, 12, 14 and fed with moulding material by an injection head 22 through a passage 28 provided with a cut-off valve which is operated by a solenoid 30 and a spring 38, the solenoid being de-energized to close the valve by a microswitch in a cut-off device being opened when the mould cavity is full and moulding materialflows into a recess 87. The cut-off device is lodged in a housing 47 and comprises a set of bellows coupled to the micro-switch and connected with a source of compressed-air through a pipe 52, a junction-box 50 and a pipe 48. The compressed-air escapes to the atmosphere through a pipe 54 and conduits 80, 86 until moulding material fills the mould cavity and recess 87, as shown. When the flow of air through conduits 80, 86 is interrupted by the material filling recess 87 the compressed-air inflates the bellows in the cut-off device and causes the micro-switch to open. Specification 930,840 is referred to.