Patent GB-279046-A (GB)
Title: New or improved apparatus for profiling gear teeth
IPC: B23F5/02
Filed: 1927-09-07
Abstract: 279,046. Lees-Bradner Co., (Assignees of Schurr, C. H.). Oct. 15, 1926, [Convention date]. Gear-cutting.-In a method of generating gear teeth wherein the work is rolled relatively to the tool by means of a master gear engaging a master rack, the rolling movement is continued after the operation to carry the master gear into engagement with a second rack which is reciprocated to impart indexing movement to the blank before the master gear is rolled back onto the master rack. The hollow work-spindle 27 is carried on a slide 4 which is reciprocated on guides 3 by means of a rod 5 connected to a slide 7 actuated by a cam 10, mounted on a shaft 12 driven from the power shaft 21 through worm gearing 20, shaft 16, change gears 18, shaft 15, and worm gearing 14. The work-spindle is mounted in conical bearings 28, 29 in a member 24 secured to a housing 23 by bolts 30, and is adjusted by a nut 33 and bearing washer 34. The work arbor 41 carrying the blank 42 fits into a tapered bore 40 in the front end of the work-spindle while the master gear 45 is mounted on an arbor fitting in the rear of the spindle, the two arbors being connected together and drawn firmly into the spindle by means of a rod 47 threaded into the arbor 41. During the reciprocation of the slide 4 the master gear engages a rack 50 to roll the blank relatively to the face of the grinding-wheel 53. In operation, the blank rolls on a fixed rack portion 61 from the position shown in Fig. 5 to the position shown in broken lines on the left of the figure and is then returned so that the grinding-wheel is twice passed over the tooth profile. The backward movement is prolonged to carry the master gear into engagement with a movable rack portion 60 which constitutes the indexing device. This rack portion 60 is connected by a lug 67 to a circular rack 70 which is reciprocated by a gear train operated from the shaft 15' and comprising worm gearing 88, shaft 86, cam 82, rack rod 79, pinion 77, shaft 76, bevel gearing 74, and pinion 73. The arrangement is such that during the grinding operation, the last tooth of the master rack is in alignment with the first tooth 69 of the indexing-rack. After the master gear has rolled onto the indexing-rack the latter is moved through one pitch to index the blank which is then rolled back onto the master rack before the return of the indexing-rack. In order to take up back-lash between the teeth of the master gear and its rack during the generating operation, a third rack portion 62 having teeth in alignment with those of the master rack is urged by the pressure of an adjustable spring 106 so as always to keep one set of tooth faces of the master gear in close engagement with the corresponding faces of the rack. The housing 65 of the indexing-mechanism is adjustable in a horizontal transverse direction by means of bolts 91 and adjusting screw 95 in the bracket 90. This bracket is itself vertically adjustable on ways 93. By suitably shaping the cam 10 the action of the machine may be modified so that different speeds may be employed at different parts of the cycle. The indexing movement may also be varied by means of the cam 82 and if desired the blank may be indexed more than one pitch at each movement. In a modification, indexing may be effected at each end of the rolling movement while the master gear is in the extreme positions shown in Fig. 11, the teeth being profiled by a single passage of the grinding-wheel. In this case the indexing-rack may have teeth 120, 121 arranged at either side of the master rack. The invention is also applicable to cases wherein the work-spindle oscillates about a centre and moves in a curvilinear path, the master rack also being curvilinear and the indexing section being oscillated about a centre to effect indexing. In another modification the rack may be moved relatively to a stationary gear axis.