| 摘要 |
1,245,926. Screw-and-nut mechanism. PLESSEY CO. Ltd. 20 Sept., 1968 [29 Sept., 1967], No. 44571/67. Heading F2Q. A mechanism for moving a member 6 axially comprises a motor-driven shaft 8 having a screw-threaded portion 10 on which a nut member 11, rotatably secured to the member 6, is mounted, the nut member 11 being driven in the same direction as the screw 10, but at a slightly different speed, by means of toothed gearing 9, 16, 17 and counter shafts 15. In a modification, shown in Fig. 2, a motor 30 drives a shaft 28 carrying gears 26, 27 meshing gears 20, 23 which respectively rotate with a nut and spindle. A combined brake and clutch device 31 has one position in which both gears 26, 27 are clutched to shaft 28, and another position in which gear 26 is uncoupled from the shaft and braked against rotation, thereby providing high speed operation of the output member. The gears 23, 27 may be accommodated in a pump housing thus forming a gear pump in a linear actuator for the opening and closing of a valve. |
