GB1394005A - Hydraulic press - Google Patents

Abstract

1394005 Injection mould closing devices; hydraulic presses KOEHRING CO 19 March 1973 [22 March 1972] 13038/73 Headings B5A and B5F Two-stage closing of an hydraulic press is effected by a main ram 18 in a cylinder 20 and a stationary booster ram 28 extending into a bore or cylinder 29 within the main ram, fluid being supplied under gravity from a reservoir 50 to the cylinder 20 during the rapid low pressure closing movement of the ram 18. The invention is applied to an injection moulding machine having a mould 14, 15 and an injection assembly 11. Rapid closing movement is effected by applying fluid pressure to the end wall of cylinder 29, and final high pressure clamping by applying fluid pressure to the remaining annular area on the rear end of ram 18. Fluid flow to and from the main and booster ram assemblies is controlled by a valve 34 comprising a prefill valve piston 45 slidable within a valve housing 35. A bevelled portion 47 of valve piston 45 seats against a valve seat 76 to close off communication between the reservoir 50 and cylinder 20 via a pipe 72 and opening 73. Operation.-With the parts in the positions shown, pressure from a line 94 is applied to pin valves 66 and through a valve 81 to a chamber 54 in valve housing 35. Valve piston 45 is held open because of the larger pressurized area of piston 45 than pins 66. By moving a valve 80 to the left in Fig. 1 pressure fluid is supplied through line 88 and passages 60, 61 to cause ram 18 to advance rapidly. Prefill fluid flows under gravity from reservoir 50 into region 22 of main ram cylinder 20. When main ram 18 nears the end of its stroke it trips a switch (not shown) which operates the solenoid of valve 81 to move this valve upwardly. This depressurizes chamber 54 and allows pins 66 to move valve piston 45 toward closed position. As pins 66 advance, pressure fluid flows through passages 60, 62, past grooved regions 67 of the pins 66, and through a region 55 (Fig. 3, not shown) and an annular passage 49 to the main ram 18 to cause final clamping pressure.