GB760601A - Improvements in or relating to screw vices, jacks and the like screw operated devices - Google Patents

Abstract

760,601. Vices. SANDERS, H. B., and SANDERS, B. W. Dec. 10, 1954 [Dec. 17, 1953; June 4, 1954], Nos. 35225/53 and 16666/54. Class 61 [Also in Group XXIV] Screw and nut mechanism applied to a vice comprises an operating spindle 19 provided with screwed portions 13, 18 of different pitches co-operating respectively with a nut 12 on the fixed base 11 of the vice and a nut 20 which is rotatably carried in a cross member 22 secured to the movable member 15. The nut 20 is coupled to the spindle 19 by a torsion spring 26 and on the initial approach movement of the movable jaw 14 to the fixed jaw 10 it rotates with the spindle 19 so that the rate of movement depends upon the pitch of screw portion 13 alone. When resistance to the movement of the jaw 14 is encountered, as when gripping a workpiece, the shoulder 25 of nut 20 is held frictionally by the cross member 22. Relative movement between. the spindle 19 and nut 20 then takes place by the spring 26 being wound up and the spindle advances axially through the nut 20. The movement imparted to member 15 and the movable jaw 14 is at a rate depending upon the difference between the pitches of screws 13 and 18 providing a high mechanical, advantage. On reverse rotation of spindle 19 to release the vice jaws the tensioned spring 26 returns the hut 20 to its original position. In a modified arrangement the nut 20 is initially free from rotational restraint but is adapted upon load to engage a serrated shoulder thereon, with a fixed serrated surface to effect the final. tightening action. In an-. other modification a sleeve is rotatable on the spindle 19 and has an external thread engaging an internal thread on the cross member 22. In this case the helical spring is arranged between the cross member and. the sleeve.