GB727166A - Hypoid gear cutting - Google Patents

Abstract

727,166. Gearing-cutting. FIAT SOC. PER AZIONI, and INGRANAGGI MAMMANO SOC. PER AZIONI. Sept. 26, 1952 [Sept. 29, 1951], No. 24235/52. Class 83 (3). Relates to a method of manufacturing curved toothed hypoid gears with offset orthogonal axes by the continuous generating process employing a face-mill cutter Q which simultaneously cuts both flanks of each tooth space, the axis of the tool being kept parallel with the general axis g-g of the machine and being rotated about the latter at a constant radial distance. The wheel is cut as an ordinary curved tooth bevel gear with its axis inclined at an angle α<SP>1</SP> to the basic plane of the machine and its apex V<SP>1</SP> on the general axis, and the pinion is cut by displacing the apex V<SP>2</SP> of its pitch cone on the same plane with its axis inclined at an angle α<SP>2</SP> to the said plane, the angles α<SP>1</SP> and α<SP>2</SP> being given by the formulµ:- and the angles # and # being defined in terms of k, the ratio of the angular speeds, Z 1 and Z 2 ; the numbers of teeth; and the angle between the contact generatrices V 1 P, V 2 P and the difference in spiral angles of the teeth. The tool has three sets of cutters each set including some roughing and two finishing cutters, so that the blank rotates through three tooth spaces while the tool rotates through one revolution. In Fig. 3, U represents the tool axis normal to the plane of the Figure and UP the cutter radius. If the flat wheel, centred at V1 and represented by the plane of the drawing, and the tool are counter-rotated, the tooth curve SPS is an elongated epicycloid arc, otherwise it is an elongated hypocycloid arc. The method of calculating the smallest practical pitch radius of the wheel is given in the Specification. A single motor 1 rotates the tool Q through gearing 4, 5, the tool drum through gearing G, 7, 8, L, S, and the vertically-adjustable workpiece I through gearing G, 7, 11, 12, 14 and a splined shaft W. For any particular calculation, a slight modification generally needs to be made in view of the fact that the requisite ratio q of the gears G cannot be exactly obtained. The nearest ratio is therefore used and the calculations re-made on that basis. The settings for the tools for cutting both the pinion and the gear are the same. The ratio k is preferably as near unity as possible in order to minimize slip.