GB1384180A - Electro-hydraulic control device - Google Patents

Abstract

1384180 Hydraulic control circuits ROBERT BOSCH GmbH 2 Jan 1973 [5 Feb 1972] 269/73 Heading F1P In a control circuit in which a valve 41, Fig. 1, is moved by a pilot control device 12, fluid-flows from a reservoir 23 through a supply line 18, lines 26, the valve 41 and back to the reservoir through return lines 19, 21 when valve 41 is in the neutral position shown, and also charges an accumulator 31 through a line 28 and a reducing valve 33. The accumulator is connected to the pilot control device through a line 36. In operation, if a solenoid valve 51 is closed to isolate the pilot control device 12 from the accumulator 31 fluidflows round the lines 26, 22 without restriction. If-valves 51, 53 are actuated, chambers 48, 49 of the pilot control device are connected to the accumulator 31 by line 36, and slide valve 41 is moved to the right, making connections to the load. At the same time the accumulator is charged through a non-return valve 32 and the pressure reducing valve 33, as soon as the accumulator pressure drops below that at which the reducing valve 33 is set and pressure in circuit 26 is higher. To move the valve 41 to the left, solenoid valves 51, 52 are actuated so that pressure from the accumulator is supplied to the chamber 48. Fig. 2 shows an alternative circuit for controlling the pressure in the accumulator 31. If the latter is fully charged, pressure in chamber 74 will retain valve-member 73 against a spring 72 in a position in which a control duct 69 is open. Fluid therefore flows from circuit 26 through duct 69 to duct 21 and the pressure drop at throttle 71 pushes hollow member 64 against spring 66 into an operative position and the circuit 26 is opened with the band 67. If accumulator pressure drops below the minimum control pressure, valve-member 72 will close control duct 69 and pressure drop at throttle 71 is eliminated. This closes the circuit 26 so that the pressure therein is sufficient to charge the accumulator again. Screw 68 provides adjustment of the position of member 64. Fig. 3 shows an alternative construction of valve 61 which produces a constant pressure drop at the throttle 71 whatever the flow in the circuit 26, Fig. 4 (not shown), illustrates a slightly different arrangement of valve 61.