GB208177A - Improvements in hobbing machines for cutting the teeth of gear wheels - Google Patents

Abstract

208,177. Taylor, H. E. June 2, 1922. Gear-cutting. - A machine is provided for hobbing bevel and other gear wheels with curved teeth having as their basis a crown wheel wherein the normal cross-section of each tooth and tooth space is uniform from end to end of the teeth, each tooth extending along the crown wheel in a curve of involute form. The blank G is mounted on a spindle F<2> carried by a table angularly adjustable on guides CC, the spindle being driven by worm gearing F<5>, shafts and bevel gearing F<10>, F<11>, and a differential gear P adapted to compensate for the rolling motion of the blank produced during the generating of the involute tooth profile. The bevel P<5>, Fig. 3, is driven through a worm wheel P<3>, change-speed gears N<2>, worm P<1>, shaft F<13> and further change-speed gears M<2> from the hob driving shaft L<2>, and the differential pinions P<6> which drive the shaft F" are journaled on pins secured to the shaft F<13>. The hob B, Fig. 2, is carried by a carriage D angularly adjustable on trunnions D<3> which are axially adjustable in a head A rotatable on a bearing A<2>. The hob spindle, which carries a fly-wheel E<12>, is rotated by means of gears E<3>, bevel pinions E<5>, K, and shafts E<6>, H, a differential gear L being provided to compensate for the rotary movements imparted' to the head through a worm drive P<2>, Fig. 3, change wheels N and the worm P<1>. In operation, the blank is arranged with the apex of its pitch cone in the axis 00 of the bearing A<2> and the side of the cone engaged by the hob, together with the acting side of the hob, is set perpendicular to this axis. The hob axis is offset from the axis 00 by an amount equal to the radius of the base circle from which the longitudinal involute curvature of the teeth is desired. The blank and hob are then rotated in intermeshing relationship and simultaneously the head is slowly rotated about the axis 00, the cutting of the blank being completed when the hob has been swung from one end of the teeth to the other. A multispeed driving gear or a variable-speed electromotor may be embodied in the machine. If it is desired to produce one size of gear only, the parts of the machine may have a fixed relationship. Milling-cutters.-The hob may be of truncated conical form or of cylindrical form with teeth of constant pitch from end to end, or it may be in the form of a gashed spur gear. The teeth may be increased progressively in height from one end of the hob to the other to produce gear teeth of varying depth.