To integrally form an apparatus and a device, reduce size, and simplify a mounting and a handling method by a method wherein a concentric and single wall cylinder tube is arranged on the outside of the cylinder tube and a space between the two cylinder tubes forms a pneumatic - hydraulic converter.

A pneumatic-hydraulic cylinder is constituted by a cylinder tube 1, a cylinder tube 2 is concentric to and positioned outside the cylinder tube 1, and these two cylinder tubes constitutes a pneumatic - hydraulic converter in cooperation with a free piston 5. The effective volume thereof, i.e. the volume of a cylinder chamber 6 is set to be larger than that of the pneumatic - hydraulic cylinder. A feed and exhaust port 10 to the pneumatic - hydraulic cylinder and a feed and exhaust port 11 to the pneumatic - hydraulic converter are formed in a rod cover 7 and a connection passage 12 between the pneumatic - hydraulic converter and the pneumatic - hydraulic cylinder is formed in a heat cover 8. This constitution reduces size, simplifies a mounting and a handling method, and facilitates incorporation of an apparatus, having a demanded function, in the middle of the connection passage 12.