Patent GB-321251-A (GB)
Title: Improvements in machine for grinding gears
IPC: B23F23/12
Filed: 1928-08-20
Abstract: 321,251. Dehn, F. B., (Hanson, E. A.). Aug. 20, 1928. Gear-cutting. - In a method of grinding toothed gears by means of an abrasive screw which is rotated in timed relation with the blank and acts in the manner of a hob, the abrasive screw is moved longitudinally during operation to distribute the wear thereon, while the gear blank is also fed axially until the teeth are completely formed. A slide 11 moving on ways 10 carries an adjustable supplemental slide 11<1> having an arcuate guide 12 on which slides a member 13 carrying the bearing 14 for the spindle b of the grinding hob c. The member 13 may be angularly adjusted according to the inclination of the threads on the grinding hob and, in the case uf spiral gears, the angle of the teeth to be cut in the blank. The hob is moved axially during the operation in order to distribute the wear over a number of threads, compensating movement being applied to the gear train for rotating the work. On completion of the operation, the hob is withdrawn from the work by means of a cam 15 acting on the slide 11, and the work-spindle is quickly returned. The work carriage 21 which is adjustable on ways 20 by means of a screw 24 has a bearing portion 22 carrying a sleeve 23 in which the work-spindle d is slidably mounted. During operation the work-spindle is raised to carry the gear blank e past the hob by means of a cam 30 mounted on a spindle 55 and acting through an adjustable lever 33. The machine is driven from a pulley 40 on the hob spindle b which carries a worm 41 driving a shaft 43 which is connected through telescopic shaft 48, gears 46, shaft 45, change gears 50, 51 and bevel gearing 52 to a shaft 27 which drives the workspindle through worm gearing 26. The gears 50 change the work spindle speed according to the pitch of the gears to be cut while the gears 51 serve to modify the work rotation for cutting spiral gears, or to compensate for axial movement of the hob or for changing the angular setting of the hob due to wear of the hob caused by repeated trueing operations. The cams 15 and 30 are mounted on a shaft 55 which is driven from the shaft 45 through worm-gearing 60, shaft 58, and worm gearing. The hob is shifted axially during the operation by means of a screw driven from the shaft 43 by worm gearing 63, and clutch 66. On completion of the grinding, ,the hob is axially withdrawn by manually turning the squared end 67 of the screw. In order :to true the grinding hob, the bed a carries a longitudinal slide 75 movable by a screw 76 and carrying a cross slide 77 fitted with a top slide 78. The latter carries a turntable having on its upper face a slide 80 carrying the diamond trueing tool 82. The slide 80 is adjusted according to the angle of the sides of the hob thread and the trueing diamond is traversed along the hob bv driving the screw 76 from the shaft 45 through spiral gears 85, shaft 86, reversing gearing 90-94, clutch 89, shaft 87, and change gears 88. After each traverse, the diamond tool slide 80 is slightly advanced in the direction of the sides of the hob thread, successive cuts being thus taken until the whole thread flank has been trued. The reversing mechanism is operated automatically by dogs 96 on the slide 75, or the reversing clutch may be set in a neutral position by means of a handle 97. On the return strokes of the trueing slide, the diamond is withdrawn from the hob by means of a cam acting on the cross slide 77 through lever mechanism, the cam being mounted on a shaft 101, driven in timed relation with the reversing mechanism by change gearing 110 connected to the shaft 45. When one face of the hob thread has been operated on, the slide 80 is re-set and the other face trued in a similar way. In a modification, Fig. 8, grinding hobs having curved profiles may be trued by means of a diamond carried on a slide 80<a> controlled by cams 125, the slide being held against the cams by springs 127.