To reduce the size of a device by transmitting thrust force of energizing mechanism through a clutch member which partially is fitted to a piston rod of an air cylinder so as to eliminate movement of the energizing mechanism in a fast forwarding process.

A semicircle clutch member 2 to transmit thrust force of the energizing mechanism is partially fitted to the outer face of a piston rod 1, in the case the energizing mechanism is not operated, the device keeps the state in which friction force is not generated between both while pressing a rod end block 7 of air cylinder with springs 5, 6. When requiring energizing, thrust force is applied to the energizing piston 10 by supplying air to a pressurizing port C and pressurizing the inside of a pressurizing chamber (a). The thrust force gives rotating moment to the clutch member 2 and friction force is generated between the clutch member 2 and piston rod 1, thus, the device is constituted so that the high thrust of the energizing piston 1 is imparted to the piston rod.