Patent attributes
An electromagnetic operation-type automatic pressure-adjusting valve outputting an air pressure corresponding to an amount of electric power is connected in an air flow path connecting a pressure chamber of a single-acting main cylinder and an air source. A controller is configured to obtain a relationship between a position of a piston and an air pressure from a relationship between the position of the piston of the main cylinder and a spring force of a return spring, and a relationship between the air pressure supplied to the pressure chamber and an acting force applied to the piston by the air pressure. When a target position of a movement of the piston is inputted to the controller, the controller is operated to move the piston toward the target position and to stop the piston at the position by means of controlling the amount of electric power for the automatic pressure-adjusting valve so that an air pressure corresponding to the target position is outputted.
