GB270669A - - Google Patents

Abstract

270,669. Gleason Works, (Assignees of Wildhaber, E.). May 10, 1926, [Convention date]. Gear-cutting.-Each member of a pair of hypoid gears is produced by a rolling generating process, the larger member being produced in the same manner as are spiral bevel gears by a rolling motion between the blank and a tool which represents a basic crown gear whose axis intersects the blank axis, and the pinion being generated by a rolling motion consisting of the rotation of the blank on its axis and a simultaneous relative movement between the tool and blank about an axis offset from the blank axis and representing the axis of a basic gear engaging the blank. The basic gear in generating the pinion is preferably a true crown gear, while for the gear member of the pair the basic gear may be a nominal crown gear, having a plane top surface. Figs. 1 and 2 show a hypoid gear 10 and pinion 11 having longitudinally-curved teeth, the axes 14, 15 being preferably at right-angles. The invention is also applicable to gears in which one member of the pair has straight teeth either radial or skew. The gear is generated as shown in Fig. 3 by means of a rotary milling cutter or grinding wheel 22. The tool represents a basic crown wheel 21 whose axis 26 intersects the blank axis 25 and during generating the blank rotates on its axis while the tool and blank are also moved relatively about the axis 26. A pair of adjacent toooth faces mav be finished simultaneously and the blank then indexed. In generating the pinion 30, Fig. 5, the cutter 31 represents a true crown wheel 36 whose axis 35 about which the tool and blank are relatively rolled does not intersect the blank axis. The operation may be carried out in the machine described in Specification 263,798. One, set of tooth-faces of the pinion is preferably first generated and the tool and blank are then reset to cut the opposite faces. The gears are so proportioned that the line of action extends substantially in the direction of the pinion axis projected into the common tangent plane to the pitch surfaces of the gear and pinion. A method of calculating the proportions of the gear and pinion in order to fulfil these conditions is described in the Specification. The gear may also be produced by hobbing with a face hob or taper hob or by planing. The crown gear used in generating the pinion is preferably so selected that the pinion produced will mesh correctly with its mating gear along the pitch lines of the two gears. The method of designing this crown gear and the effect of varying the offset of the crown gear axis from the pinion axis is described in the Specification.