GB1459496A - Plastic moulding machine - Google Patents

Abstract

1459496 Injection moulding foamed plastics EX-CELL-O CORP 4 Feb 1974 4997/74 Heading B5A Means for foaming and moulding a plastics material comprises a pressure tight supply hopper 26 into which granular plastics material and a gas under pressure are introduced, the hopper 26 being connected in pressure tight manner to a plasticizing chamber 17 wherein the material is converted to a plasticized foamed material with the gas entrained therein as bubbles. A plasticizing screw 18 delivers the material at low pressure through outlets 36, 37 and a distribution network 41-49, Fig. 3, to a plurality of injection assemblies as 54, 54A, 54B, 54C. Each injection assembly comprises an injection chamber 63, Fig. 4, which is connected through a discharge orifice 82, passage 83, Fig. 6, and injection nozzle 88 to a mould (13, 15), Fig. 1 (not shown). A check valve 52 prevents return flow to the plasticizing chamber. As the chamber 63 fills up, an injection ram 71 therein is pushed upwardly until it actuates a switch 78 whereby a valve V B is opened and pressure fluid supplied to a cylinder 74. Since at this point an injection valve 56 is closed, downward movement of ram 71 will close a check valve 52 and prevent further filling of chamber 63. Other injection chambers are filled to a level depending on the setting of the corresponding switch 78. When all the injection units in use have been filled the valves 56 are automatically opened and injection is effected. A single injection unit may be associated with a single mould M, Fig. 3, or two injection units with a single mould M1. Alternatively a single mould M2 with either single or multiple cavities may be associated with all four injection units of a single injection assembly 54C. A still larger mould may be associated with two or more (even all eight) of the injection assemblies shown in, Fig. 3. An opening 28, Fig. 2, is provided for introducing gas under pressure into the hopper 26 and the same or an additional opening 29 may be used for evacuating the hopper. Granular plastics material may be supplied from an upper hopper 30 by opening a valve 31. The mould halves are held together by sprue in opposed recesses 92, 93, Fig. 7, in the mould halves, the sprue being supplied at the same time as the mould cavity or separately from a different source.