Patent GB-382963-A (GB)
Title: Improvements in machines for cutting helical gears
IPC: B23F5/16
Filed: 1931-08-06
Abstract: 382,963. Gear-cutting. SYKES, W. E., 33, Gates Circle, Buffalo, New York, U.S.A. Aug. 6, 1931, No. 22314. Convention date, Aug. 6. [Class 83 (iii).] A gear cutting machine of the type having a pinion cutter mounted on a spindle which is reciprocated substantially axially of the blank has cam means acting through a sliding member having inclined surfaces for moving the cutter support up to the work for the cutting strokes and withdrawing it therefrom for the return strokes. The machine base 10 is provided with a work supporting bed 11 which slides transversely on ways 15, 16 and carries a tailstock 17 supporting one end of a work arbor 18 on which the blank 19 is mounted. The other end of the arbor is secured to a faceplate 20 mounted on a hollow shaft 21. The bed of the cutter carriage carries a reciprocating carriage 23 moving along longitudinal guides and reciprocated by a crank pin 26 on a shaft 27 driven by gearing 28, from a shaft 30 connected by belt gearing 32 from the driving pulley 33 of an electric motor. The eccentricity of the crank pin 26 is adjustable by means of a screw 27e, Fig. 7A, a wedge member 26g being provided to lock the parts in adjusted position. The shaft 27 is connected through gearing to a vertical shaft 41 extending into a gear box 14 and further gearing 42, Fig. 5, from the shaft 41 drives through a toothed clutch 44 and friction clutch 45, a shaft 46. The clutch 44 is controlled by a yoke 84 which may be operated from a handle 88. The shaft 46 is connected through a train including shafts 49, 52, and change gears 54, to a shaft 56 carrying a worm 58 driving a worm wheel on the shaft 21, thus imparting continuous rotary generating movement to the blank. The shaft 49 also carries a bevel gear 60 connected through a gear train to a pair of shafts 66, 67, Fig. 8, driving worm gears 70, 71 respectively, this drive serving to impart corresponding continuous generating movement to the cutters. A bevel gear 72 continuously driven from the bevel wheel 43 drives through a gear train and a shaft 76 a shaft 80 controlling the cutter relieving movement. In a modification, Fig. 5A, the clutch 44 is held in engagement by the pressure of a spring 83c and the clutch yoke is interconnected with a cut-out switch 84c associated with the main electric motor. In this form the clutch teeth are so shaped that when a predetermined working load is exceeded the clutch is disengaged against the spring pressure and the switch is operated to stop the motor. The pinion cutters 89, 90 are mounted on cutter shafts 91, 92 respectively, Fig. 7, the shaft 91 being hollow and the shaft 92 extending therethrough. The cutter shafts are journalled in supports 93, 96 which are slidably secured to carriers 97, 98 for movement transversely of the cutter axes. The carriers are themselves longitudinally adjustable on the carriage 23. The cutter shaft 92 is secured to a spindle 95 which may be reversed in its bearings to vary the distance between the cutters. Each cutter carrier is provided with spaced extensions 100 movable in a guide 99 on the carriage 23. A rotatable nut 101 mounted between the extensions co-operates with a stationary screw 104 secured to the carriage, the nut having spiral teeth 102 engaging teeth on a shaft 107 which may be rotated from a squared end to adjust the corresponding cutter carrier. Clamping in the adjusted position is effected by U-shaped clamping bars 109, 110, Fig. 13, which may be drawn together by means of bolts 117. Each cutter-support has a rearward extension 120 slidable in a guideway 121 in the corresponding carrier, this sliding movement serving to relieve the cutters from the work on the return strokes. The movement towards the blank is limited by a stop 97a. A vertical member 122 has extensions 123, 124 engaging in inclined guideways 125, 126 so that movement of the member 122 in its guideways causes the cutter support to be moved towards or away from the blank. In some cases it is preferable to withdraw the cutters along a line inclined to a plane containing the blank and cutter axis. Thus, in Fig. 27 the guide 120c is inclined so that the withdrawal movement is effected in a correspondingly inclined direction. The upper part of the extension 123 carries an adjustable plunger coacting with a cam 134 mounted on the shaft 80. A spring 138 consists in maintaining the plunger in contact with the cam. In order to ensure positive action a resilient strap 132a may be looped over the cutter relieving cam. The two relieving cams are so arranged that as one cutter commences its cut the other is relieved from the blank. The relief action in the direction X, Fig. 26, is so arranged that in conjunction with the return movement Y of the cutters, a resultant movement Z of the blank away from the blank is produced. The cutter shafts are secured respectively to helical guides 142, 143, Fig. 8, the former being hollow to permit the passage of the shaft 92. Each guide is provided with a pair of diametrically opposed helical grooves 144, 146, the grooves in the two guides being of opposite bands. Each groove receives a guide nut composed of a stationary and a movable part. The guides are slidable in sleeves 150, 151 secured to the worm wheels 70, 71 producing the generating movement. The worm wheels are supported in a frame 156 having guides in which it may be adjusted transversely. An oscillatable member 159 enclosing the bearing sleeves of the worm wheels is provided with a lower extension engaging an eccentric on an adjustable rod 168, and also with an upper extension 171 coacting with a cam 172 on the shaft 76. By adjustment of the corresponding pivot 166 the normal position of each cutter spindle relative to the blank may be transversely adjusted. The cam 172 acts synchronously with the cams on the shaft 80 to swing the frame 156 and thus the bearings of the helical guides are moved simultaneously with the cutter spindle bearings for the relieving movement. The stationary part of each guide nut is rigidly secured to the corresponding sleeve 150 and the movable part is adjusted to take up wear by a screw. The work bed 11 may be adjusted manually by means of a hand-wheel 186 on a shaft 187 whose inner end is threaded on a nut 189 secured to an auxiliary bed. The two beds may be secured together by a bolt 197 and the auxiliary bed may be held stationary on the base by a further bolt. After adjustment and fixing of the auxiliary bed, the main work bed may be automatically moved by the engagement of a roller 199 with a cam 201 mounted on a shaft 202 driven from a pinion 208, Fig. 16, engaging a gear 211 on a shaft carrying a gear 215 engaging a mutilated gear 216 secured to the generating gear 59. The gear 216 is integral with a bevel gear ring 218 and ratchet teeth 219. The bevel gear teeth are cut away opposite the teeth 221, and the remaining teeth are adapted to move through notches 223 cut in the periphery of a mask plate 224. A bell crank 214 has one arm carrying a projection engaging cams 209, 210 on the shaft 202. Another arm of the bell crank carries a roller 231 coacting with a cutout switch 35 controlling the main driving motor, while a third arm 237 gives a visible indication of the bell crank position. The journal box 240 carrying the worm 58 may be raised or lowered by an eccentric stud to disengage the worm to permit manual turning of the wheel 59 by means of a hand-wheel 261 geared to the bevel ring 218. The degree of mesh between the worm and worm wheel may also be adjusted to compensate for wear. Similar adjustments are provided for the worm gearing associated with the cutter generating movement. A modified arrangement of disengageable worm gearing wherein the worm may be quickly withdrawn axially from its housing is described. In operation, the cutters are reciprocated and are at the same time oscillated angularly by the helical guides to cut a helical tooth. On the return strokes the cutters are relieved from the blank by the cams 134, 136, and the housing 156 of the generating gearing associated with the cutters is also withdrawn by the cams 172, 174, so that no lateral strains are placed on the cutter shafts. The clutch 44 is engaged to impart continuous rotary generating movement to both cutters and blank. The blank may be fed into cutting position by the hand-wheel 186 and subsequently the nut on the bolt 197 is slacked off and the automatic in-feed produced by the cam 201. At each complete rotation of the blank, the teeth on the wheel 216 rotate the wheel 215 a quarter of a turn and the shaft 202 one-eighth of a turn so that the full depth feed produced by the cam 201 is effected after eight intermittent feed movements during which time the blank rotates eight revolutions. Other gear ratios may be adopted according to the nature of the work. On completion of the blank, a lug 229 on the cam 209 engages the arm of the bell crank 214 to rock the latter and operate the switch 35 to stop the motor. At the same time the blank is withdrawn from the cutters by the cam 201.