| 摘要 |
A ball nut is sleeved upon a worm via one or more, preferably two, groups of antifriction balls capable of rolling along internal and external screw threads on the ball nut and the worm. Two crosscuts are formed across the internal thread on the ball nut in axially spaced, diametrically opposite positions thereon, each for intercommunicating two neighboring turns of the helical groove therein. Each crosscut is concaved to provide a bypass for one group of balls around the thread on the worm. Thus each group of balls recirculate along one turn of the helical groove in the ball nut, making it possible for the worm to travel axially in response to the rotation of the ball nut. The converter further includes an antifriction bearing having an outer ring surrounding the ball nut via rolling elements confined therebetween, with the ball nut serving as the inner ring of the bearing. There are also disclosed herein feed mechanisms incorporating one and two such rotary-to-linear converters respectively. In either case the ball nut is gear-driven by an electric motor to cause relative endwise movement of the worm together with an object to be fed. |
