GB1284946A - Oil pressure controlling device for high inertia loads - Google Patents

Abstract

1284946 Hydraulic motor control circuits KAWASAKI JUKOGYO K K 11 Aug 1969 [14 Aug 1968] 40127/69 Heading F1P A hydraulic motor MF representing a highinertia load is driven by a pump P via a direction control valve V and a spool valve assembly 1 which opens the return passage from the motor MF to the tank T when pressure fluid is applied to it. A relief valve assembly 3 is arranged to bypass pressure fluid to the return passage to prevent excess pressure build-up during stating and stopping of the motor MF. When the valve V is moved to direct pressure, fluid to the port A, in the spool valve 2, the fluid passes through passages 14, 14' and bores 60 in the spool valve 2 to the central passage 18 in the spool 4. Valve 7 is moved to the left against a weak spring 8 and fluid flows via passages 16, 63 to the annular chamber 31 in the relief valve 3 and thence to the motor MF. Pressure fluid from the port A v in the spool valve 2 also passes via passage 29 to the chamber 52 and then via radial bore in the spool 4 and a check valve into the chamber 27. The spool 4 is consequently moved to the right and the return passage 63' from the motor MF is then connected via passage 17 and groove 21 in the spool 4 to the passage 15 and port B, back to the tank T. If on starting the motor MF the pressure in the conduit 63 exceeds a predetermined pressure fluid flows through nozzle 41 into the relief valve 3 through radial bores 64 to move the valve seat cylinder 39 to the right and consequently unseat the valve 33 to allow the fluid to enter the by-pass 45. Both valves 33, 34 are then forced outwardly to allow flow of fluid through radial bores 64' nozzles 42 and annular recess 32 back to the return conduit 63'. Pressure fluid in the by-pass 45 also flows through restricted orifices 40, 40' in the valves 33, 34 and axial bores in the rods 36 to spaces 48 in the end caps 38 to force the members 37 inwardly to further compress the springs 43, 43'. When the control valve V is moved to stop the motor the spool valve 2 is again centralized thereby shutting off the return passage to the tank T. Pressure build up in the return line 63' causes the valve seat cylinder 39 to move to the left and unseat valve 34 and then valve 33 to allow fluid to return to the motor MF. During steady running conditions the valve seat cylinder 39 returns to its central position to enable both valves 33, 34 to seat and thereby close the by-pass port 45.