Patent GB-559416-A (GB)
Title: Machine for generating face gears with teeth unequally distant from the axis
IPC: B23F15/06
Filed: 1943-01-28
Abstract: 559,416. Gear-cutting. FELLOWS GEAR SHAPER CO. Jan. 28, 1943, No. 1484. Convention date, Jan. 7, 1942. [Class 83 (iii)] In a machine for generating face gears with teeth at non-uniform distances from the gear axis the generating motions between the cutter and gear have a relative speed ratio which is varied during operation in proportion to the difference in distance of different points on the tooth line from the gear axis. In cutting a face gear h having spirally-arranged teeth t adapted to coact with a spur or helical pinion the teeth are preferably cut on a raised rib r, but in some cases the tooth tops may be flush with the face of the gear by cutting the tooth spaces below the plane of such face. In one machine embodiment, a ribbed blank W is mounted on a spindle 15 carried in a slide 12 which is reciprocated vertically by a cam 30 and the teeth are generated by a reciprocating pinioncutter C which has a tooth-generating rotation in timed relation to rotation of the blank while at the same time the blank is gradually lowered to follow the spiral from the inner to the outer part thereof. Alternatively the spiral may be followed from the outside inwards. The blank spindle 15 carries a master gear 17 engaged by a spur pinion 18 which determines the blank rotation. The rotation of the pinion 18, the generating rotation of the cutter and the rotation of cam 30 are all derived from a motor 25 which drives a shaft 26 connected through universal shaft 48 and bevel gears 50 to a shaft 27 connected through worm gears 22, 21 to the spindles of the cutter and pinion 18 respectively. The cam is driven through worm gearing 32. If the teeth are to be cut in a closed non-circular circuit the cam is arranged to impart the desired up and down movement to the work. The cutter is reciprocated by a segment 34 engaging circular rack teeth 35 and actuated from the motor 25 or a separate motor. The cutter-spindle can swing about the worm 22 and relief is imparted on the non-cutting strokes by a spring on withdrawal of a rod 41 actuated from a cam 39. The cutter-spindle saddle is supported on a carriage 42 which is reciprocated to feed the cutter to depth by a feed cam 43 acting through a segment 45. The speeds of the cutter and pinion 18 are not necessarily identical, since a larger or smaller pinion 18 may be employed if the worm gearing 21 is adjusted to give the correct generating rotation to the work. Change gears may be fitted for this purpose. During the rapid reciprocation of the cutter, the work and cutter are rotated at the correct generating speeds and at the same time the blank is lowered by the cam 30 so that the pinion 18 is maintained in engagement with the master teeth. The angular velocity of the work changes as the cutter moves radially of the blank and this factor is taken into account in designing the cam. In a modification, Fig. 5, the shaft 15 and the cam are rotated at a constant speed ratio, both being driven from the shaft 58 connected to a motor 55 through infinitely-variable gearing comprising expanding pulleys 77, 78, connected by a V belt 76. A torque motor 69 tends to rotate the master pinion shaft 19 and cutter spindle 24 through worm gearing 20, 23 but the pinion 18 can rotate only so fast as is permitted by the independently driven master gear. The cutter is reciprocated by a motor 75, the driving mechanism and the cutter relief on the non-cutting strokes being as described in Specification 516,480. Since the cutter would normally rotate faster when cutting on the outer parts of the blank it would make fewer strokes per revolution at such parts. To compensate for this the variable speed gearing driving the work is changed by a cam 88 acting through a rod 90 and lever mechanism on the expanding pulleys 77, 78, so that the work is driven at a slower angular velocity when the outer parts of the spiral are being cut. Alternatively, gearing between the motor 75 and the cutter spindle may modify the rate of reciprocation of the cutter according to the radial position of the cutter on the blank. In a further modification, Fig. 7, the master gear and pinion are dispensed with and the lineal rotational cutter speed equalized with that of the work at different distances from its axis by means synchronized from the work movement. The work-spindle is as before moved vertically by a cam 30. A driven shaft 91 is connected to the work-spindle by gearing 98 and to the spindle of the cam 30 by gearing including change gears 102. The cutter is rotated by a torque motor 108 through gears 114, 116, 119, the speed of rotation being determined from the work-spindle speed by a train including gears 120, shaft 122, change gears 123, worm gears 125, and screw 127 running in a member 131 which is reciprocated, in time with the work-spindle movement, by a branch train from the worm shaft 104. This train drives a worm 140 on a shaft 136 which rotates an arm 135 connected by pin-andslot 133 to the member 131 controlling the permissive rotational movement of the cutter. The boundary surfaces of guide 132 may be cam surfaces designed in accordance with the non- circular tooth line required on the blank. When the teeth are to be of helical form the required twisting movement is imparted to the cutterspindle by the usual helical guides. In another modification, when the lines of teeth are widely spaced, a generating hob similar to that described in Specification 552,600 may be used instead of a reciprocating pinion cutter.