Patent GB-287237-A (GB)
Title: Improvements in or relating to gear cutting machines
IPC: B23F5/14
Filed: 1926-12-17
Abstract: 287,237. Jury, F. W. Dec. 17, 1926. Gear-cutting; tools.-In a machine for cutting gears, particularly double helical spur gears, two cutters are reciprocated from opposite sides of the blank or blanks by means of a, pair of cranks arranged at 90‹ or by similar mechanism, whereby the timing of the cutting strokes is spaced unevenly with respect to the complete cycle, indexing being effected while both cutters are clear of the blank. The work W is carried on a mandrel which supported between the centres 82, 83 of a headstock 2, and tailstock 3 which are arranged on a bed 1 and may be traversed thereon by means of handwheels 4, 5 respectively. The cutter head 6 is adjustable perpendicularly to the work axis by a hand-wheel 7 and carries a driving-motor 9 which drives a worm 12 driving a worm wheel 13 on a cross shaft 14. The latter is connected by worm gearing, Fig. 4, to crank shafts 18, 19 provided with adjustable crank discs by which the rack cutters are reciprocated. The cutters are mounted in a vertical slide 29 which may be operated by screw gearing 31, and carries upper and lower guides 41, 42 respectively for the angularly-arranged slides 43 provided with cutter heads 46 to which the rack cutters 44, 45 are p voted. The cutters are provided with teeth of gradually increasing height as indicated in Fig. 1, and are fed upwardly tangentially of the blank to generate the tooth profiles. All the teeth on the blank are completed after a single upward movement of the cutters, during which time the blank, which is indexed between successive cutting cycles, performs several revolutions. In order to allow the indexing movement, the cranks which reciprocate the cutters are arranged at 90‹ and the cutters are swung away from the work on the non-cutting strokes. In this way both cutters are clear of the work for approximately a quarter revolution of the cranks while indexing takes place. The cutter slides are secured to blocks 48 moving in inclined guides in the slide 29 and carrying crank pin guides 50 which extend vertically so as to permit vertical movement of the slide 29. In order to withdraw the cutters on the non-cutting strokes each cutter is connected by links 52, with a ball joint 53 carried by a split friction block 54 mounted in the upper guide 41. Thus, as the cutter moves towards the centre of the work the drag of the friction block pulls the cutter against an abutment 47 into the cutting position while on the return stroke the cutter is swung about its pivot away from the work. During the cutting operation the work is held stationary. The indexing movement is imparted to the work through gearing from the shaft 19 which includes a train 22 - - 27 and bevel gearing 58 arranged to impart continuous rotation to a shaft 59, which through Geneva mechanism 60 imparts intermittent movement to a shaft 67. The movement of this shaft is transmitted through a differential gear M to a shaft 72 connected through change gears 75, shaft 77 and gearing 78 to the headstockspindle 80 carrying the work-driver. The upward generating movement of the plate 29 is effected from the shaft 77 which is connected through spur gearing 85 with a shaft 87. The latter drives a shaft 90 through constant-mesh changespeed gearing 88 controlled by a sliding key actuated from a handle 106 through rack and sector gearing. The shaft 90 drives through change gears 91, shaft 93, and gearing 39 - - 32, the screw 31 operating the slide 29 for the generating movement. Rotation of the blank in unison with the tangential generating movement is superposed on the blank indexing movement by means of gearing from the shaft 90 which is arranged to rotate the casing of the differential gear 68. In order to provide means for quick rotation of the screw 31 an auxiliary motor 10 may be connected by chain gearing to a shaft 109, carrying stationary gears 110, 111. The gear 86 on the shaft 87 may be moved into engagement with the gear 110, which imparts the high speed movement to the slide 29 and corresponding movement to the work spindle to main the correct relative positions. The work may also be rotated independently at high speed from the auxiliary motor by means of a. sliding gear 112 on the shaft 77 which may be moved to disengage a clutch 115 which normally connects the indexing change gears to the shaft 77. The gear 112 is then engaged with the pinion 111 on the high speed shaft. For this movement, which may be employed for the final trimming up of a completed blank, the gear 86 is moved to a neutral position. The gears 86, 112 are operated from levers 113, 114.