| 摘要 |
960,358. Screw jacks. JOYCE-CRIDLAND CO. March 15, 1963 [March 23, 1962], No. 10274/63. Heading B8J. A screw jack including a drive nut meshing with a jack screw is provided with means for indicating wear of the drive nut and provision is made for supporting a load safely when operation of the jack is impossible due to wear. Fig. 2 shows a jack when first assembled, the indicator means comprising an auxiliary nut 42 engaging a jack screw 16 and spaced above a drive nut 14. The top surface of the auxiliary nut 42 projects a slight distance above the top of a cap 18 and indicates that the drive nut 14 is unworn. The two nuts are connected by a ring 44 having tongues 50 which project into a pair of slots provided in the hub portion 28 of the drive nut. Pins 46 project through aligned apertures in the ring and the auxiliary nut. Accordingly there is substantially no relative rotation between the nuts. As the threads of the drive nut become worn, the jack screw 16 lowers carrying the auxiliary nut 42 with it. Fig. 3 shows the relative positions of the parts after prolonged use, the top of auxiliary nut 42 being coplanar with the housing cap 18 and indicating to a user that further operation of the jack is undesirable without replacement of the drive nut 14. The tongues 50 of the ring 44 have moved further into the slots in the drive nut. In Fig. 4 the threads of the drive nut have become so worn as to be incapable of supporting the screw 16. The auxiliary nut has dropped further and rests on the drive nut. Thereafter, if the auxiliary nut is rotated in an effort to rotate the jack screw, the pins 46 are sheared and operation of the jack is impossible although the jack screw and the load are safely supported. |
