GB495944A - Improvements in or relating to the manufacture of gears - Google Patents

Abstract

495,944. Toothed wheels and pinions. GLEASON WORKS. April 14, 1938, No. 11603. Convention date, Sept. 17, 1937. [Class 80 (i)] [Also in Group XXII] Both members of a bevel gear pair may be form cut without rolling generating movements by a rotary cutter which has a number of radial blades with concave arcuate side cutting edges arranged part way round the periphery with a gap between the first and last blades to permit indexing the work without withdrawal of the cutter. Both sides of the blank teeth may be finished simultaneously or each side may be finished separately. During roughing the cutter rotates about a fixed axis 56 and the blank 20 is positioned so that a radial line passing through the centre of the tooth space is perpendicular to the cutter axis. For the finishing cuts the sides are of arcuate profile, Fig. 2 showing the profile 31 of the blade which finishes the large end of a bevel gear tooth and 33, Fig. 3, showing the profile of the blade which finishes the small end. The centres of curvature of the various blades which cut at intermediate points along the tooth are shown at 39-41. The profiles have a common tangent preferably at a point 50 at or near the blade tips and for finishing the side 23, a radius 51 passing through point 50 is located perpendicular to the outer axis. Similarly for finishing the side 24, a number of finishing blades with circular profiles of different radii are provided and the blank is positioned so that a radius through the point 57 at the tip of profile 24 is perpendicular to the cutter axis. During the finishing stage, the cutter is fed relatively along the teeth to the point 56<1>, the differently curved profiles of the finishing cutters coming into action at different points along the teeth as this feed progresses. The tooth bearing of a pair cut in the above manner may be controlled by varying the inclination of the lines of centres 35... 37, Fig. 3, as described in U.S.A. Specification 1,733,326. Where both sides of the teeth are to be cut simultaneously, the gear member 60 is cut by a cutter having a centre at 71. There is no relative feed along the teeth and the blades have constant profile curvature. Each blade may have opposite cutting edges or alternate blades may cut on opposite sides of the gap. The gear is thus form cut with a concave root line. When the pinion 65 is to be cut, Fig. 6, there is a relative feed movement about an axis 95 such that the distance 95, 96 is about equal to the cutter radius 71 ... 98. In this way the pinion has a convex root line which matches the concave root line of the gear. In another modification, the gear and pinion may both be cut simultaneously on both sides with rectilinear longitudinal feed of the cutter along the teeth. The invention may also be applied to the cutting of spur and helical gears. In the latter case, the feed of the finishing blades is along the helical teeth.