| 摘要 |
In a force limiting device for an actuator rod having a valve actuator rod 76 coupled to a piston 66 slidable in a cylinder 64, one side of the piston being loaded by high pressure gas in a chamber 46 and the other side of the piston supplied with or exhausted of hydraulic fluid, the force applied to the actuator rod 76 when the valve has been moved by the hydraulic fluid from its closed position to an open stop position is arranged to be less than the initial valve opening force. The piston includes an interior cylindrical bore 70 which slidably receives a piston head 82 integral with the actuator rod 76. Atmospheric pressure communicates with the bore 70 through a passage 98 to act on the larger side 106 of the piston head, the smaller side 84 being in communication with the cylinder 64 through a clearance space around the rod 76. During valve opening the hydraulic fluid produces a force on the piston head 82 due to the pressure acting on the large area of the piston 66 but when the piston 66 forcibly abuts a piston stop 110 the hydraulic fluid becomes effective primarily only on the smaller piston head side 84 thereby limiting the maximum tensile force on the actuator rod when the valve reaches its fully open stop position. <IMAGE> |
