Patent GB-379637-A (GB)
Title: Improved method of producing gears
IPC: B23F1/06
Filed: 1932-03-09
Abstract: 379,637. Toothed wheels. GLEASON WORKS, 1000, University Street, Rochester, New York, U.S.A.-(Assignees of Wildhaber, E. ; 1110, East 21st Street, Brooklyn, New York, U.S.A.) March 9, 1932, No. 7091. Convention date, March 23, 1931. [Class 80 (i).] In generating tapered gears having inclined or curved teeth which are adapted to coact with a non-generated mating gear, the rolling movement required for generation is effected about an axis angularly disposed to the blank axis and offset from the blank apex, such axis being that of a gear other than the mating gear. In producing curved tooth gears by means of a face milling cutter the non-generated member G of a mating pair is cut by means of a cutter 10 of straight sided rack tooth section the respective axes 13, 14 of the cutter and blank being so inclined as to cut teeth T of the correct taper and the cutter being fed to depth without generating movement. The cutter may be either an annular cutter, in which case the blank is indexed after cutting each tooth or it may be a bobbing cutter of the face mill type which cuts all the teeth during continuous timed rotation of the blank and cutter. If the generated member of the pair is formed by a cutter which accurately represents the mating gear G, the area of contact between the teeth of the pair when running to mesh extends diagonally across the mating tooth surfaces. According to the invention the generated member of the pair, usually the pinion, is generated conjugate to a gear other than its mating gear, the difference being such as to enable the gear pair to engage without the bias bearing " mentioned above. Thus in figure 4 the pinion H of a hypoid pair is generated conjugate to a gear G<1> having a different cone radius from that of the mating gear so that the axis 22 of the gear G<1> is different from that, 14, of the mating gear. The offset y of the axis of the gear G<1> from the pinion axis 25 is also different from the offset x of the mating gear. The axes 14, 22 are preferably inclined at the same angle to the pinion axis 25. The imaginary generating gear G<1> is represented by a face milling cutter 23 the cutter and blank being rolled together during the generation of the teeth as though rhe blank were rolling on the gear G<1>. The tolling movement may be imparted to either the blank or the cutter or partly to the blank and partly to the cutter. The invention may also be applied to bevel gear pairs consisting of a non-generated and a generated gear. The choice of the generating gear G<1> may be determined either mathematically or experimentally. In the latter case a tool C, Fig. 8, is chosen which will produce tooth surfaces of the required curvature to mate with the non-generated gear and this tool is positioned so that a mean point O on the pitch line of its tooth surface will contact with a corresponding point in the mating tooth surface of the pinion. During the generation the tool is rolled about some such axis as 45 or 46 on the line O, 14, and after completion of the pinion it is run with its mate gear and the gears inspected to ascertain whether the position of the axis 45 or 46 was correctly chosen. If the chosen position is incorrect another trial may be made. If further modification of the tooth profile is desired in order to reduce the area of contact, the axis 45 or 46 may be further displaced along a line 49 or 49<1>, parallel to the tooth normal N. In some cases the opposite sides of the pinion teeth may be cut conjugate to different generating gears. Thus the convex sides of the pinion teeth may be cut with a tool having inside edges of less radius than the radius of the tool edges which cut the mating surfaces of the gear the axis of the generating gear being at 45, while for the concave sides the tool edges have a greater radius than the tool edges which cut the mating surface of the gear and the axis of the generating gear is located at a point 46. The invention is also applicable to the cutting of other types of bevel and hypoid gears and different types of tool may be employed. Specification 251,952, [Class 80 (i), Gearing, Belt &c.], is referred to.