GB535898A - Improvements in or relating to hydraulic presses - Google Patents

Abstract

535,898. Injection moulding machines; hydraulic presses. ERNST, W. Oct. 20 1939, No. 28342. Convention date, May 5. [Class 37 (ii)] [Also in Group XXIX] In an hydraulic press an initial, rapid movement is imparted to the ram by pressure fluid admitted through a stationary plunger extending into an inner chamber in the ram and, after a pro-determined travel of the ram, the pressure fluid is admitted to the main area thereof through passages in this ram. As shown in Fig. 1, applied to an injection moulding machine, a main ram 58 carrying a mould member 59 is mounted in a cylinder through the end of which is adjustably threaded a plunger 84 having an enlarged end 86 engaging an inner bore 68 in the ram. Passages 71 connecting the rear end of the ram with the bore 68 allow pressure fluid, admitted through a bore 87 in the plunger 84, to pass to the main ram area. Pressure fluid from a tank 37 is supplied by a pump 12 through a valve chamber 15 to a line 80 supplying the bore 87 and also a line 55 connected to pistons 49 carrying a cushioning die 46. During advance of the ram 58 fluid is admitted to the space behind the ram from the tank 37 by a pipe 91 and check valve 99. After clamping the mould parts, material from a hopper 28 is injected through a nozzle 27 by a plunger 24 connected to a piston 23 actuated by pressure fluid supplied by a pump 11 through a valve member 14 and line 34. After the moulding operation the valve 14 is operated to connect line 34 to the tank via line 36 and pressure is admitted to the plunger side of the piston 23 through line 35 to retract the plunger, the extent of retraction being limited by a valved byepass 45. The main ram 58 is retracted by movement of the valve 15 to admit pressure fluid to the line 78, retraction being limited by byepass ports 74, 75 ; fluid displaced from behind the rams passes through pipe 91 to an exhaust. conduit 93 normally closed by a check valve which is lifted by pressure fluid passing from line 78 to a line 113. To vary the extent of retraction of the ram for thick and thin dies, additional ports containing ball check valves 145, 146 and controlled by screws are provided. A modified press is described in which the ram is disposed vertically, pressure fluid being contained in a surge tank above the ram cylinder.