GB817191A - Improvements in or relating to plastic injection moulding machines - Google Patents

Abstract

817,191. Injection moulding machines for plastic cups &c. CROWN MACHINE & TOOL CO. Sept. 21, 1956 [Sept. 23, 1955], No. 29020/56. Class 87(2). An injection moulding machine for, e.g. plastic cups, comprises a platen with a number of separate moulding cavities from which the moulded articles may be ejected in unison, one injection nozzle for each cavity each nozzle having a separate injection unit supplied from a common preplasticizer and each nozzle being arranged on a frame which also supports the platen. The machine has fixed platens 18, 20, 22, 26, 32 and movable cavity and core platens 28, 30 respectively. Hydraulic cylinders 16 on the fixed platen 18 actuate rams 38 connected to injection cylinders 40 with nozzles 42 having reciprocating valves 66 controlling the supply of plastic material from the injection cylinders 40. The cavity platen 28 is movable away from the platen 26, by hydraulic rams 48, to break the injection " pips " from the nozzles 42 which form part of the base of cavities 44 formed in inserts 72 having water channels 74. The core platen 30, actuated by a hydraulic cylinder and ram 34, has, Fig. 4, two core structures 75 each comprising a core element 82 secured to the platen 30 by plates 84, 88. The core element 82 has in insert 92, with water channels 96 connected to a water inlet 100 and outlet 104 in the plate 88, an air piston 140, in a cylinder 142 with grooves 150 in its circumference, connected by studs 156 to an ejector ring 114, and a rod 120, in the insert 92, having at one end a frusto-conical seating 126 forming an air valve and at the other end extending into but not abutting against a boss 138 on the air piston 140. In operation, after the plastic cup has been moulded and its injection " pip " broken, air is admitted to the air cylinder 142, through a connection 146 in the plate 84, causing the piston 140 and hence the ring 114 to move to the left (in relation to Fig. 4) to abut against the rim of the moulded cup to partly free it from the core 82, and at the same time air is admitted through the grooves 150, previously sealed by the piston 140, to the still closed air valve 126, further movement of the piston 140 causes the base of the boss 138 to abut against the rod 120, to move the rod and thus the bottom of the moulded cup and at the same time to emit air from the valve 126 and blow the cup off the core element 82.