| 摘要 |
Improved fluid-operated valve actuator means for rotating a valve shaft in opposite directions through a given angle (preferably, 90 DEG in the case of a quarter-turn valve). The invention is characterized by the provision of cam means connected with the output shaft and arranged in a chamber between a pair of freely movable operating pistons. When one end of the chamber is pressurized, the corresponding piston applies an operating force to the cam to rotate the cam and the output shaft through the given angle. In one embodiment, reversing valve means are provided for reversing the ends of the chamber that are pressurized and vented, respectively. In a second embodiment, one end of the chamber is alternately pressurized and vented, respectively, to achieve the desired rotation of the output shaft, the other end of the piston being enlarged to define a pressure fluid reservoir operable to return the output shaft to its initial position. In a third embodiment, spring means assist in returning the output shaft to its initial position. |
