Abstract: Apparatus for confirming the clamping conditions of a clamping device which is used to clamp workpieces of different sizes. Signals corresponding to the kind of workpiece being clamped are derived from the flow rate of pressurized fluid used to drive the actuator of the clamping device. These signals are used to confirm the clamping conditions and also the kind, and the presence or absence, of the workpiece.

Abstract: A workpiece clamping device with which workpieces of different sizes can be accommodated without having to make extensive system modifications each time the workpiece is changed and with which clamping operations can be performed with a high efficiency. An operating fluid flow-rate detector is provided in a hydraulic circuit between a hydraulic fluid source and a plurality of operating cylinders which drive clamping pawls to detect the flow rate and amount of the hydraulic fluid therethrough. The clamping position is sensed in accordance with the detected flow rate and amount.