Abstract: An electric linear actuator includes an output shaft which is non-rotatable but displaceable in an axial direction and which has one end thereof coupled to a driven device; a cylindrical member arranged coaxially with the output shaft and rotatably about the output shaft, and driven by an electric motor for rotation; and a feed screw mechanism arranged between the output shaft and the cylindrical member for converting a rotating motion of the cylindrical member to a linear motion of the output shaft. The feed screw mechanism has a male spiral groove formed in the outer peripheral surface of the output shaft; a nut cylinder secured on the inner peripheral side of the cylindrical member and formed with a plurality of circular holes; and a plurality of balls accommodated in the circular holes and engaged with the male spiral groove.

Abstract: A circuit breaker actuating device comprising valve means interposed between a high pressure section of an operation fluid and a low pressure section thereof to preclude communication therebetween and adapted to cause a variation in pressure to occur either in a high pressure source or low pressure source when actuated to establish communication between the high pressure section and the low pressure section, so as to thereby actuate piston means and cause a circuit breaker to perform a current interrupting operation.