GB1282947A - Improvements in hydraulic motor control devices - Google Patents

Abstract

1282947 Hydraulic motor control circuit ROBERT BOSCH GmbH 19 Dec 1969 [20 Dec 1968] 61881/69 Heading F1P Opposite sides of a double-acting hydraulic piston 35, Fig. 1, suitable for actuating the control lever 42 of a fuel injection pump 13 may be connected by ducts 44, 45 to a drain duct 46 according to which of two selenoid pilot valves 14, 15 are energized and opposite ends of the hydraulic cylinder are connected by lines 37, 41 to load ports 23, 24 of a closed centre three-land spool valve 11 and also to chambers 25, 26 of opposite ends of the spool 16 which chambers are also connected by restricted lines 29, 31 to the supply, inlet 22 of the valve 11 whereby the spool is displaceable from its neutral position shown in the pressure difference developed between said chambers 25, 26 when either of the pilot valves 14, 15 is energized thereby connecting one side of the piston to drain. The pilot valves also control a by-pass line 47 connecting opposite ends of the hydraulic cylinder together so that with valve 11 in neutral and valves 14, 15 unenergized the piston 35 may be moved mechanically to any desired position. In the piston position shown, energization of say valve 14 opens line 44 and hence chamber 25 to drain and results in spool 16 being moved to the left and supply of pressure fluid to cylinder chamber 39 which thus moves piston 35 to the left until when it passes beyond line 44 the piston stops. If with valve 11 in neutral and valves 14, 15 unenergized the piston is at the left hand end of the cylinder and then valve 14 is energized cylinder space 39 and chamber 36 are connected to drain 46 so that spool 16 moves to the right resulting in rightward movement of piston 36 until is passes beyond line 44 after which it is arrested. In a modification a pilot valve 62 Fig. 2 of the stepping type connects a selected return line 63 to 66 say 65 of the hydraulic cylinder to drain 68 whereupon spool 16 is moved to the right and piston 67 moves to the right until it blocks line 65 when the piston is arrested.