Patent GB-675652-A (GB)
Title: Improvements in and relating to machines for moulding plastic materials
IPC: B29C45/70
Filed: 1947-04-29
Abstract: 675,652. Injection-moulding machines. CROWN MACHINE & TOOL CO. April 29, 1947 [Nov. 15, 1946], No. 11425/47. Class 87(ii) Ari extrusion machine for moulding plastic materials, particularly thermoplastics is provided with a plasticizing chamber incorporating a fixed spreader, through which the moulding material passes prior to its introduction into the injection chamber. Fig. 1 shows the machine as a whole, comprising a hopper 2 from which cold granular moulding material is forced by a plunger into a plasticizing chamber located below the hopper, the plasticized material flowing into an injection cylinder and being expelled therefrom by a plunger 50 into a mould held closed between platens 96, 98, Hydraulic mechanism is used to bring about the various movements, and electronic timing gear controls the timing of these movements. Feed hopper.-The hopper has a transverse internal casing 15, Fig. 8. in which reciprocates a crosshead 14 carrying a plunger 12 to expel cold granular material into a passage 6 of the plasticizer. The plunger 12 has helical grooves to effect oscillation of an agitator 24 during reciprocation of the plunger so maintaining free the ports 10 in the plunger cylinder 8. A cooling jacket 44 surrounds the hopper outlet. Plasticizing chamber.-The granular material fed by the plunger 12, Fig. 5, passes into enlarged passages in the plasticizing chamber 32, around a spreader 37 the walls of the passages being heated by hot oil circulated through an inlet 34 and jacket spaces 36, 38, 40 to an outlet 42. Injection cylinder. The plasticized material flows through a port 48 into an injection cylinder when the port is uncovered by a plunger 50 reciprocating in the cylinder. The charge drawn into the cylinder is then expelled through a throat 66, 72 when a port in a reciprocation gate 78 aligns therewith, and passes through the injection nozzle 74. Mould actuation. The mould halves 86, Fig. 16, are forced into engagement with each other and to seat on the injection nozzle 74 by a platen 96, Fig. 4, against the resistance of a platen 98 having spring-loaded guide pins 102. The platens are slidably mounted on tie-rods 60 which couple the injection unit with the gear for actuating and locking the platen 96 in the mould-closed position. The platen 96 is adjustably coupled by screw gear to a member 106 which is guided on the rods 60 and coupled to a crosshead on the actuating ram 120, Fig. 13, by links 110, 114, the common pivot of each pair of links 110, 114 carying a shoe 130. The links 110 have bearing surfaces 126 which engage fixed pins 128 during the advance of the ram 120, until the shoes 130 engage the pins 128 whereupon further advance of the ram 120 rotates the shoes into the locking position shown in Fig. 11, in which position the ram 120 is relieved of the mould thrust this being taken entirely by the pins 128. A three-section electronic timer is provided; the first section controlling the length of time that pressure is applied by the injection plunger 50 to the injected material, the second section controlling the interval before the moulds opens and the third section controlling the period during which the mould remains open for the removal of the mould articles. During this period the plunger 12 operates and replaces material used in the injection. Each section of the timer is variable independently within a given range and the timer is adapted both for fully automatic control of all operations or for semi-automatic action under partial control of the operator by a selector switch which is movable to different positions according to whether entire manual control, semi-automatic control, or fully automatic control is desired.