Improvements in or relating to drives for gear grinding machines

1,015,662. Gear grinding; machine tool details. NATIONAL RESEARCH DEVELOPMENT CORPORATION. March 7, 1962 [March 9, 1961], No. 8718/61. Headings B3B and B3K. A gear manufacturing machine comprises a worktable 2, Fig. 1, rotatable by an hydraulic motor 5, through a worm and wheel 16, 17, a grinding-wheel 3, rotatable by an electric motor 4, and a comparator 11, for comparing signals generated by the motors and controlling the speed of motor 5. The rotation of a radial optical grating 7 fixed to the shaft of motor 4 is detected by a photo-electric sensing head 8 and a further grating 9 on table 2 is detected by a similar head 10. Pulses from heads 8 and 10 are fed to comparator 11, the former pulses passing via an electronic gear-box 12, which corrects the pulses so that these are nominally the same as pulses from head 10. If the signals are out of step, an error signal passes through an amplifier 14 to a servo valve 14a to control the speed of motor 5, the frequency of the error being recorded at 15. A face cam 18 on table 2 co-operates with a follower 24 connected to worm 16, to rotate the latter, and correct for errors in the worm, and wheel drive. Grinding wheel 3, Figs. 2, 3, is adjustably mounted in a vertically movable slideway 26 carried on a horizontally movable slide 26a. Vertical movement of the wheel past work 1 is produced by a wedge 32 driven at an even speed by means 33, which co-operates with a block 29. To produce helical gears, wedge 32, Fig. 4, carries a bar 41 connected to a slide 37, the latter being connected to sensing head 10 by a steel tape 35. Bar 41 is set relative to wedge 32 according to the helix to be produced, and as the wedge moves, head 10 is rotated. To produce gears having either hand helices two such slides 37 connected to a continuous tape are provided. A light 48 actuated by a cam 49 flashes each time wheel 3 rotates, to produce a stroboscopic effect for checking the engagements of the wheel and gear. Two interconnected heads 10 may be provided, the resultant signal obtained being the average of the readings and in a modification the rotational speed of the work is constant and the movement of the grinding- wheel across the work is adjustable.