GB237252A - Improvements in worm gear - Google Patents

Abstract

237,252. Siegwart, H. July 17, 1924, [Convention date]. Variable-speed toothed gearing.-Worm-wheel teeth are movable towards the wheel axis and are pressed outwards by spring action; worms for engagement therewith may vary in height from end to end. Application to motor vehicles, elevators, cranes, machine tools, tramways, textile and printing machinery, and power transmission generally is referred to. In the variable-speed gear shown in Figs. 1, 2 and 5, the worm-wheel 10 carries roller teeth 13 turning on pins 14 pressed radially outwards by a central spring 20, or by individual springs, and engages alternatively with worms 7, 8, 9 slidable on the driving-shaft 1 with a loose sleeve 3 pivoted to a lever 4 on a slidable and rotatable control shaft 5. A lug 24 on the sleeve 3 co-operates with a slotted change-speed gate. A pin 21 projects from each worm tooth through a slot in the wheel into the path of a bar 23 secured to the shaft 5. so that as the shaft 5 is rotated to release the lug 24, the bar 23 forces in the wormwheel teeth adjacent to the worm and allows sliding of the worms to change the gear. Multithread worms may be employed. In a modification, the form ends are gradually tapered or reduced so as to merge into the body of the worm shaft, and when the gear is to be changed the worm is so rotated that the worm end is adjacent to the worm-wheel. In further modifications, the worm shaft is swung about axes in or parallel to the plane of the worm-wheel to disengage the gearing-parts before the sliding movement of the worms takes place. Fig. 16 shows a form in which the worm-wheel 84 is shifted along its shaft 85 during gear change by a lever 86 on the slidable and rotatable operating- shaft 89, which carries a lever 90 connected to a ring 91 carrying lugs 92 engaging a gate. In the modification shown in Fig. 17, any one of a series 93 .. 98 of loose worms formed with clutch ends 102 may be brought by rotation around a centre 99 into register with a wormwheel 106 and the clutching end 103 of a driving- shaft 104. As shown in Fig. 8, the worm-wheel may be formed in two loose parts 30, 31 provided with inclined teeth and inter-connected by ballended levers 34 passing through a plate 35 secured to the shaft 32; the teeth are thus adapted to set themselves to the inclination of the worm. Fig. 21, shows a construction adapted to produce a reduction ratio twice as great as the number of teeth in the worm-wheel. A series of spaced worms 124 .. 127 of half the pitch of the worm-wheel teeth are so formed that in one complete convolution each worm merges from the shaft, rises to a maximum height and falls again to the shaft level. The starts of the successive worms are spaced 180‹. During the drive, the worm-wheel teeth are pressed in succession into the body of the wheel by engagement with the tops of the worms. In a modified form the teeth of the worm-wheel are staggered.