| 摘要 |
652,199. Lifting-jacks. WILD & CO., Ltd., M. B., and BOUCHER, J. W. Dec. 23, 1948, No. 33168. [Class 78 (iii)] [Also in Group XXIV] In a screw jack, clamping means in engagement with the screw is adapted to co-operate with a part formed on or secured to the nut so that in the event of relative free axial movement of the nut and screw consequent upon stripping of the thread of the nut, the clamping means becomes wedged between the screw and the said part, thereby rendering the jack inoperative. Fig. 1 shows the application to a jack comprising a nut b axially movable along a screw a rotated by gear-wheels h. A member d engaging the screw is located in a socket c formed in the nut and is held in position by a cover e and secured against rotation by pegs g. In the event of stripping of the threads of the nut b, the nut slips axially to a small extent relatively to the screw whereby the member d becomes wedged between the socket and screw so as to stop rotation of the screw. The member d comprises two parts held together by a spring f. Fig. 2 shows the application to a jack comprising an axially-movable but non-rotatable screw a and a nut b rotated by gear-wheels h. The socket c is secured to the nut by bolts i and the member d is connected to the socket by a peg g. |
