GB536183A - Improvements in or relating to gearing for steering mechanically propelled vehicles and for other purposes - Google Patents

Abstract

536,183. Worm gearing. BISHOP, R., and JOHNSTON, R. H. Nov. 3, 1939, No. 29343. [Class 80 (i)] Relates to gearing particularly applicable to the steering of motor vehicles and of the kind comprising a cylindrical worm engaging a sector mounted on a rocker shaft and having laterally projecting teeth adapted to be engaged successively by the worm. In Specification 502.035 gearing of this kind is described in which the worm has only substantially a single turn of land preferably generated as described in Specification 223,963, [Class 80 (iii)]. According to the invention, the worm has less than a single turn of land and yet has sufficient worm groove between the adjacent ends of the thread to ensure the transfer of the drive from one tooth of the follower to the next. A steering shaft 1 carries a worm 2 co-operating with teeth 11, 12 on the follower 3 carried by a rock-shaft 4. The complete land of the worm 8 extends from 13 to 14 which is less than 360 degrees. The starting ends of the flanks overlap. Thus, the starting point 15 of the flank which finishes at 16 is spaced approximately 20 degrees from the starting point 17 of the other flank which finishes at 18, consequently the ends 15, 17 overlap. The finishing end of a flank terminates 20 degrees short of the starting point of the other flank. The portions of the worm from the point 16 to the end 10 and from the point 18 to the end 9 are formed with outer faces 19. 20 which are in planes at right angles to the worm axis and the ends 9, 10 are at right angles to these faces. The worm has a complete, i.e. non- mutilated, land extending for approximately 340 degrees, i.e. from 13 to 14, the end parts being tapered by the formation of the faces 19, 20.