Patent GB-261704-A (GB)
Title: Improved method of and apparatus for producing gears
IPC: B23F5/12
Filed: 1926-06-11
Abstract: 261,704. Gleason Works, (Assignees of Candee, A. H., and Johanson, M. H.). Nov. 23, 1925, [Convention date]. Gear-cutting.-Toothed gears having longitudinally curved teeth are produced by a process. wherein the tool is reciprocated in a straight line oblique to the blank axis while imparting continuous rotary movement to the blank, no supplementary indexing-mechanism being employed. In the case of tapered gears of either bevel or hypoid form the path of the tool is offset from the blank cone apex. An additional relative movement between the tool and the blank may also be employed in order to produce a tooth form of single curvature, and to maintain the clearance of the tool approximately constant during the cutting. In the application to bevel gears the basic crown-wheel tooth form produced by reciprocating the tool from a crank r in a line offset the centre X of the wheel is shown at A, Fig. 1. In order to avoid the double curvature of this tooth line an additional relative movement, preferably at twice the frequency of the tool movement is superposed by means of an eccentric F. The effect of this movement combined with the straight line movement of the tool is shown at B and when this curve is combined with the curve A a tooth form C which has a single curvature results. The supplementary harmonic motion is combined with the generating movement of the tool cradle as shown in Fig. 2. The tool T is reciprocated in its offset path by a crank disc M and the blank I rotates continuously and uniformly on its axis. The generating movement is imparted to the tool cradle by means of a worm W on a splined shaft Q driven by gearing V and the supplementary harmonic movement is obtained by reciprocating the worm shaft Q by means of the eccentric F. In the machine embodiment a tool cradle 10 provided with the toolcarrying head 11 is mounted in bearings in a rigid frame 8 and the tool T is reciprocated from a motor 12 through a bevel-driven shaft 14 which through further bevel gearing drives the adjustable crank member 26. The latter is connected by a rod 30 with the tool-head slide 29 to which the head 11 is secured by bolts 36 and adjustment of the head along its slide may be effected from a shaft 38 after loosening the securing bolts. In order to vary the offset of the tool, the tool head guides are located on an arm 42 which is adjustable about a centre Y (Fig. 6) by means of gearing from a shaft 45 which rotates a spur gear engaging a curved rack 53 secured to the cradle. The tool is mounted on a clapper 64 pivoted at 55 to a support 56 which is adjustable to vary the tool clearance in an arcuate seating 58 having a scale 58<1>. The machine is provided with two work heads the support 6 being adapted for mounting gears and the support 7 for pinions. The latter is removed when gears are to be cut. The gear head is fitted with an extension 61 journaled in a bearing and the pinion head has a similar extension 60 which bears in the extension 61. Both heads are angularly adjustable by means of shafts carrying pinions which engage a circular rack 65 secured to the feed rail 66. The heads are slidable on their supports and clamped in adjusted position in T slots 78, this adjustment serving to position the blank cone apex on the axis of the cradle 10. The continuous rotation of the blank is effected from the shaft 14 through bevel gearing 80, differential gearing 83, bevel gearing 86, Fig. 4. further bevel gearing, change gears 99, shaft 100, and worm gearing 107. The shaft 100 may be arranged to drive either the pinion blank spindle or the gear blank spindle, a detaenable connecting member being provided on each blank head. The rotation of a shaft 89 is used to actuate the cutting-oil pump 92 while from a gear 90 in the blank driving train, a lubricating oil pump 94 is operated. The shaft 106 carrying the blank driving worm, Fig. 15, carries a cam 109 which acts through a rocker and push rod 111 to pump oil from a reservoir 112 to lubricate the blank drive mechanism. The suction and delivery of the pump are controlled by ball valves and this pump is auxiliary to the lubricating pump 94. The generating rolling movement is imparted to the cradle 10 by means of a wormwheel 118, Fig. 4, which is driven from the bevel gearing 86 of the blank driving train through shaft 119, change gears 120, shaft 122, reversing bevel gearing 124 controlled by a splined clutch 127, shaft 125, change gears 128, worm gearing 131, shaft 132, worm gearing 138 and further worm gearing 140. The shaft 132 is only rotated when a clutch member 133 is engaged with teeth on the worm wheel 131 and this clutch member carries spur teeth 136 arranged to transmit rotary movement to the blank to compensate for the cradle roll. This is effected as indicated in Fig. 4 through spur gearing 155, bevel gearing 159, 161, change gears 164, shaft 165, and spur gears 167, connected to the casing of the differential gearing 83 of the blank driving train. The added harmonic motion obtained from the eccentric is imparted to the tool cradle and is operated from the shaft 14 through the bevel gearing 80, differential gear 143, shaft 145, bevel gearing 148, shaft 147 and eccentric sleeve 149 which engages in a block and reciprocates the worm shaft 139 of the cradle drive. In order to impart compensating movement to the eccentric drive for the roll of the cradle, a bevel gear 154 keyed to the cradle is arranged to rotate the casing of the differential gear 143 in the eccentric drive. A clutch is provided to permit hand setting of the cradle without moving the blank. A quick return drive for the cradle is also provided. This is operated through a clutch member which controls the bevel gear drive of a shaft 176 which through further bevel gearing 178, shaft 179, and reversing bevel gearing 182 may drive the shaft 132. The quick return movement of the cradle is transmitted through the differential gearing to maintain the blank in correct relation with the tool cradle. A safety device is provided to prevent the simultaneous engagement of the clutches controlling the fast and slow movements of the cradle. For roughing out the gears a depth feed of the blank to the cutters is employed. This motion is derived from the shaft 176, Fig. 4, which through change gears 198, shaft 200, bevel gearing 201, crank 204, connecting rod 205 and pawl mechanism, operates a ratchet wheel 208, and through further worm gearing and clutch mechanism, this motion is transmitted to a shaft 214 which drives a segment 220 secured to the feed rail 65. The ratchet mechanism is provided with an adjustable guard plate to vary the amount of the feed. For quickly withdrawing the blank from cutting position or for quickly returning it to cutting position a rapid feed mechanism is actuated from the shaft 176 through gears 196 shaft 228, reversing gear 234 controlled by a clutch 238, and further bevel and worm gearing to the shaft 214. A clutch 217 may be employed to engage selectively either the fast or slow feeds. For finish-cutting, the clutch 217 is left in a neutral position and no feed movement is transmitted. A safety device is provided to limit the amount of feed. In order to withdraw the tool from the work on the idle stroke, the crank member 26 is provided with a cam slot 35 which reciprocates a rod 257 having spring connection with a sleeve 260, Fig. 56, carrying a pair of racks which mesh with pinions connected through universal joints, telescopic shaft 268, shaft 271, Fig. 60, and bevel gearing to a rack 276, Fig. 62. The rack 276 actuates a segmental spur gear 277 carrying a pin 278 on a block sliding in a groove in the clapper block and thus swing the block about the pivot 55. The arrangement is such that the tool may be arranged to cut on either stroke. A toggle member 282 co-operates with a recess in the clapper block to engage a projection 284 on the block with a lug 285 to lock the tool in the cutting position. The invention is applicable to the production of other types of gears such as cylindrical or hypoid gears whether generated or non-generated. The single tool may also be replaced by a plurality of tools or by a tool which straddles a tooth so as to cut both sides of a tooth simultaneously. Either straightsided or curved-profile cutters may be employed and instead of a planing-tool, a suitable grinding- tool may be employed.