GB1038822A - Improvements in or relating to hydraulic systems - Google Patents

Abstract

1,038,822. Hydraulic apparatus. NORMALAIR Ltd. May 5, 1965 [May 8, 1964], No. 19248/64. Heading F1P. A pressure compensating device in a telemotor circuit comprising a double-acting manually operated master cylinder 1 connected by lines 3, 4 to a double-acting slave cylinder 2 comprises a main piston 11 having a central enlarged portion and an auxiliary sleeve piston 12, slidable on one end of piston 11 and the two pistons together with a stepped cylinder 13 provide a chamber 17 connected by a line 27 to a constant pressure or reference source, a vent chamber 16 and chambers 14, 15 connected by 7, 8 to opposite ends of the slave cylinder; the area of end faces of piston 11 bounding chambers 14, 15 being equal and the area of the opposite end 31 of piston 11 being slightly less than the area of end 30 of piston 12. Assuming the circuit to be fully pressurized and freed of air, normal operation of the master and slave cylinders produces no displacement of pistons 11, 12, An increase in working pressure e.g. due to a temperature rise results in displacement of both pistons 11, 12 until the pressure in chambers 14, 15 is reduced to that of the reference pressure in chamber 17. A fall in working pressure in chambers 14, 15 results in opposite displacement at the main piston 11, the sleeve piston 12 being held by a stop 21 whereby the apparatus may continue to function though the working pressure may be reduced to half the reference pressure.