Abstract: In the present invention, sensors for cylinder control are connected to a main cylinder which has an internal cylinder chamber which is partitioned by a piston into two chambers, and they detect the operational state of the piston. There are provided accumulators connected to one of said two chambers by connecting conduits and whose interiors are pressurized by hydraulic fluid which is expelled from said one chamber, and also stop signal generation mechanisms which generate signals to stop the driving of said main cylinder by pressure differential between said accumulators and said connecting conduits generated at the instant that increase of pressure from said one chamber stops.

Abstract: A second pressure intensifying cylinder subchamber is employed for moving a pressure intensifying piston toward the other side, and the necessity for a control valve with a throttle is thereby eliminated. The pressure intensifying piston is incorporated integrally into a fluid cylinder, and, hence, the fluid cylinder can be installed in an even narrow space. A main cylinder chamber communicates with a pressure intensifying cylinder chamber in the interior of the fluid cylinder, and it is therefore possible to prevent such a situation that a high-pressure fluid sprouts out. A structure of the fluid cylinder is thus simplified enough to reduce the costs, and the safety is improved.

Abstract: A space (32) is formed between an inner end of a fitting hole (31) formed in a piston (21) and a piston rod (22) and is positioned radially inside a sealing member (24). By circulating a cooling fluid through the space, the majority of heat which is transmitted to the piston rod (22) can be absorbed, preventing transmission of heat to the sealing member. The temperature of the sealing member is kept lower and its deterioration can be inhibited.

Abstract: A cylinder apparatus capable of effectively restraining a loss of energy with a simple structure at a low cost. When a piston 16 of a main cylinder 11 cuts off a communication between a subchamber 20 and a supply/exhaust passage 32, a pressure of the subchamber 20 is pushed by the piston 16 and thereby increased. However, an exhaust fluid from the subchamber 20 having the increased pressure is fed to a subcylinder 62. A piston 48 is moved while controlling a velocity by a flow rate control valve 70 in synchronization with the piston 16. This arrangement eliminates a necessity for a special position detector, etc.. The structure is therefore simplified, and the cost decreases. Simultaneously, the energy can be effectively utilized because of employing the exhaust fluid.