GB1373126A - Hydraulic circuits - Google Patents

Abstract

1373126 Injection mould closing devices PLAST-UND ELASTVERARBEITUNGSMASCHINEN -KOMBINAT KARL - MARXSTADT VEB 29 Dec 1971 60401/71 Heading B5A In an injection moulding machine hydraulic pressure is applied to a plurality of parallelconnected mould-closing cylinders 1 through non- return valves 2 connected to a common inlet pressure line 2a and is removed from the cylinders 1 through non-return valves 3 connected to a common outlet line 3a in which an adjustable pressure relaxing valve 13 is connected in parallel with a pressure limiting valve 14 acting as safety valve for all the mould-closing cylinders 1. A return line 15 from the valve 13 is connected to the inlet pressure line 2a between a pre-controlled pressure reducing valve 7 and a multi-way valve 6 in the line 2a, the multi-way valve 6 controlling the application and relaxation of pressure in the line 2a. In order to obtain different pressures in the cylinders 1, e.g. for two-stage mould closing, the valve 7 has a precontrol line in which further pressure limiting valves 9, 10 are disposed which can be brought into circuit by way of a further multi-way valve 8. The invention prevents the equalizing of pressure between the cylinders 1 which permits tilting of one mould-art relative to the other. A high-pressure pump 4 supplies the mould closing pressure and a low-pressure pump 11 is connected to the pressure relaxing valve 13. This valve 13 comprises two releasable non- return valves 13a, 13b and a throttle valve 13c. The machine may be used for normal injectionmoulding or for injection-stamping.