GB1260753A - A fluid-pressure control system for dual motors - Google Patents

Abstract

1,260,753. Fluid-pressure servomotor systems. CATERPILLAR TRACTOR CO. Feb. 19, 1969 [May 22, 1968], No.8903/69. Heading G3P. A pair of hydraulic motors 13, 14 controlling a single implement are operated simultaneously by a system comprising a separate main source 16, 17 of fluid under pressure for each motor, a separate control valve 22, 28 between each fluid source and its motor, actuator means 33 connected between the control valves, and means 136, 143 associated with the actuator means and both control valves for positioning the latter to provide equal fluid-flows to both motors. In the preferred embodiment, the motors 13, 14 lift and lower the bucket of an articulated bucket loader while a further pair of motors 11, 12 controlled by valves 21, 27 coupled by linkage 77, 81 to each other and to an actuator 31 regulate the tilting of the bucket. Manuallyoperated valves 37 and 38 control the actuators 31 and 33, respectively, and have passages 73, 87 and 131, 157 to provide a follow-up so that the valve positions determine the speeds of the lift and tilt motors, equal pressures being maintained between the motors of each pair by cross conduits 52, 53 and 54, 56. When the pump 16 is not running and the valve 38 is moved to the position for retracting the lift motors, a valve 169 is moved by a spring to connect a conduit 168 to drain through conduits 171 and 158. A valve 164 is now lifted by the pressure of the fluid beneath the motor pistons to allow them to retract. The inlets to the control valves 21, 22 and 27, 28 are arranged to give operating priority to the tilt motors and are provided with check valves 84, 153 which open when return lines 151, 152 are closed by movement of the valve spools.