Abstract: When a prime mover (1) is driven, a controller (25) outputs an open-drive signal for bringing an opening/shutting valve (23) into an open position and, upon a control lever (68, etc.) being operated, a hydraulic fluid is supplied from an auxiliary hydraulic pump (7) through pressure reducing valves to driving sectors of directional control valves (8 to 16) for shifting them. A flow rate and a direction of flow of the hydraulic fluid from main hydraulic pumps (3, 4) are thereby adjusted so that actuators (57A, 57B, 57C, 56A, 54) can be each operated at a speed depending on the amount by which the control lever is operated. When one of the actuators (57A, 57B, 57C, 56A, 54) is to be driven when the prime mover (1) is not driven, an open command is selected in a selection command device (24), whereupon the controller (25) outputs the open-drive signal, causing the opening/shutting valve (23) to open a line interconnecting the accumulator (21) and the pressure reducing valve (17), etc.

Abstract: A hand apparatus of a robot which is less likely to be damaged and can offer a reliable and effective gripping of a workpiece. The hand apparatus comprises a main frame which is mounted to a wrist member through a plurality of damper couplings. Pivotally mounted to the main frame are a pair of four-point-articulated link arms each having two arms extending parallel to each other. A sub-frame having a finger mounted thereon for pivotal movement in every direction is pivotally mounted to the leading end of the respective link arms. A pair of hydraulic cylinders are provided for moving the link arms in a gripping operation.