Abstract: A valve and valve actuator utilizing a disconnected piston design that separates under conditions of excessive actuator internal pressure to prevent overloading and damaging the threaded connection between the valve stem and actuator piston is disclosed. The hydraulically actuated valve actuator comprises a spring housing including a bonnet for coupling the spring housing to a valve. The spring housing includes an upper head and a packing gland that are sealingly attached to the spring housing to form an interior pressure chamber. The interior pressure chamber has a pressure responsive actuator piston disposed therein with a coil spring designed to move the actuator piston from a normally open to a fail closed position. The pressure responsive actuator piston includes a piston and a spring retainer nut that are separable after closing of the valve to prevent ambient pressure acting within the pressure chamber on the pressure responsive actuator piston from overloading the valve stem.

Abstract: A valve and valve actuator utilizing a disconnected piston design that separates under conditions of excessive actuator internal pressure to prevent overloading and damaging the threaded connection between the valve stem and actuator piston is disclosed. The hydraulically actuated valve actuator comprises a spring housing including a bonnet for coupling the spring housing to a valve. The spring housing includes an upper head and a packing gland that are sealingly attached to the spring housing to form an interior pressure chamber. The interior pressure chamber has a pressure responsive actuator piston disposed therein with a coil spring designed to move the actuator piston from a normally open to a fail closed position. The pressure responsive actuator piston includes a piston and a spring retainer nut that are separable after closing of the valve to prevent ambient pressure acting within the pressure chamber on the pressure responsive actuator piston from overloading the valve stem.

Abstract: A compound linkage arm assembly for providing a substantial force to initially extend an arm assembly from a sonde without increasing the driving force in the opening mechanism. A linear drive mechanism initially acts upon a linkage within an arm assembly of the tool. The links unseat and force the arm away from the tool without much force from the drive mechanism. Once the arm is moved away from the tool by the full extension of the links, push rods act directly upon the arm to contact the bore hole wall. The advantage of this arrangement is that the linear drive mechanism is not required to exert a great amount of lateral force upon the arm to obtain the initial extension. The links acting between the arm and the sonde body provide the lateral force necessary to extend the arm.