Patent GB-754931-A (GB)
Title: Improvements in or relating to a gear-hobbing machine
IPC: B23F5/22
Filed: 1952-03-18
Abstract: 754,931. Gear-hobbing; centres, drivers and carriers; tailstocks. MICHIGAN TOOL CO. March 18, 1952 [March 28, 1951], No. 6960/52. Class 83 (3). A gear-hobbing machine comprises a screwelement 502, Fig. 20, rotatable on the rotatable and reciprocable spindle carrying the hob 32, means 552 for rotating the screw-element and axially-fast nut means 498, 500 for engaging the screw-element. The hob-spindle is mounted in an angularly-adjustable hob-carrier 24, Fig. 20. The hob-driving mechanism includes a worm 368, Fig. 16, on the axis of the hob-carrier and a worm-wheel 370 movable with the carrier. The hob-carrier is mounted on a slide 22, Figs. 1 and 20, which is moved to-and-from the work by a fluid-pressure-operated piston 44. The length of travel is constant but the limits are determined by a nut 52 having abutment surfaces at each end and adjusted by a hand wheel 80 and worm 84. The slide is clamped during hobbing by levers 109 operated through cams 112 by fluid-pressure means 120. The hob-carrier is adjusted angularly by turning, with a wrench, a worm 154, Fig. 20, engaging a worm-wheel 152 on the axis of the carrier. The carrier is then clamped by bolts in slots 132, 144. Headstocks; tailstocks; centres and drivers.- The work 30, Figs. 1 and 12, is clamped between the tailstock 158 and the headstock 212. The tailstock is adjustable on a table 160 by T-bolts and contains a live centre 194, Fig. 9, which is advanced by fluid-pressure means 200, the piston-rod of which has a quickly-detachable T-slot connection 208. The headstock-spindle 254 is rotated by a worm 238, split to take up backlash, and carries a work-driving device 268. The latter has teeth 270 to engage similar teeth on the spindle nose. The spindle is reciprocated by fluid-pressure pistons 288, 290, attached thereto through a yoke 292, to traverse the work past the hob. Helical gears. A compensatory rotation is imparted to the work by means 308 comprising cam surfaces 316, 318, Fig. 14, which co-operate with an engaging-member made in two parts 310A, 310B, to enable play to be taken up. The cam surfaces are formed according to the helix angle of the gear to be cut and impose a rotational movement on the work additional to that of the worm-wheel 238, as the work-spindle is advanced. In a modification, the travel of the gear is compensated by an adjustable sine-bar 600, Fig. 24, which carries a rack-bar 612 to impart rotation to a gear 618, fast with the work-spindle, as the latter is advanced. The hob 32 and the work 30 are rotated by a common motor 334, Fig. 16, driving the wormwheel 238 and the hob-shaft 380. Axial-feed spindles.-The hob is secured on its spindle by a draw-shaft 482 and the upper end of the spindle is mounted in a screwed sleeve 502 engaged by nuts 498, 500 provided with spacers 524, 526, 528 for taking up backlash. The nut 500 is rotated by a motor 552 to advance the hob a small amount, say <SP>1</SP>/ 1000  th inch, after each operation, to distribute wear, until a stop on the spindle engages a switch 570, Fig. 1, to cut off the motor. To raise the hob rapidly to its initial position, a hand-gear-lever 563 is moved which causes the motor to rotate the sleeve 502 by a worm-wheel on an extension 548 until a further stop on the spindle cuts off the motor. The hob-drive includes a fly-wheel 442. Operation. In operation, the blank 30 is mounted, the slide 22 is advanced against the nut 52, and clamped, the headstock is actuated to feed the blank across the hob, the hob is lowered a slight amount, the clamps released, the slide 22 withdrawn, and the machine then stopped with the blank in its initial position. Specification 754,950 is referred to.