| 摘要 |
<p>A quick-and-slow speed screw drive mechanism is composed of a supporting seat, a half nut (with inner threads less than half turn), an upand-down sleeve (with up-and-down plate), a screw, a locking device, a spring and a pawl. The screw passes through the supporting holes of supporting seat and the holes of half nut and up-and-down sleeve 3 with the seat, integrating them as a whole. On the outer surface of half nut, guide surfaces are provided to match with the guide surfaces of supporting seat, cam profile is also provided to interact with the inner acting plane of up-and -down plate. When the screw rotates, through a pawl device, the up-and -down sleeve is brought to rotate with the screw, under the action of cam, the half nut is forced to make up-and-down movement, thus realizing the engagement and disengagement between the screw and the half nut, and enabling the screw to move axially with slow or quick speed.</p> |
