Patent GB-535918-A (GB)
Title: Method and apparatus for gear generation
IPC: B23F5/16
Filed: 1940-04-05
Abstract: 535,918. Toothed wheels. FELLOWS GEAR SHAPER CO. April 5, 1940, No. 6201. Convention date, April 5, 1939. [Class 80 (i)] [Also in Group XXII] In a method of and apparatus for generating either cylindrical or face gears and similar toothed articles the cylindrical gear member and the face gear member are rotated together in unison in offset relation, Fig 4, one of the members having cutting teeth and serving to generate the conjugate teeth of the other member by a cutting action produced by the relative slipping between the cutter and gear teeth. caused by the offset relation of the axes. When an involute pinion 20 is rotated in unison with a plastic face gear with an intersecting axis it will mould conjugate straight teeth of which the flanks have greater inclination at the outer than the inner circumference. When, as shown in Fig. 4, the pinion axis is offset by a distance y from the axis of face gear 22a the moulded teeth are tangential to a circle of radius y and the teeth as before are of straight section in planes normal to their length and of gradually increasing slope towards the outer diameter. A helical generating pinion operating in an offset position will similarly generate helical face gear teeth. In Fig. 6, if C represents a circle of the face gear and e, f a corresponding transverse plane of the pinion then the offset of the axis represented by the distance g, f may be represented by the angular displacement B. If V1 represents the length of action on the face gear and V2 the length of action on the pinion, then V3 represents the slip between the pinion and gear teeth and is equal to V2 tan B. This slip is used according to the invention for cutting either the pinion from a face gear cutter or the face gear from a pinion. For cutting face gears the end surface of the pinion has cutting teeth and the tooth faces are relieved to provide clearance. The cutter is then fed axially across the face of the gear. Preferably a number of traverses across the gear are made, depth feed being applied between the traverses. When helical cutters are employed they are given a helical twisting movement during the traverse in addition to the indexing rotation. A helical cutter 26a may be arranged in an offset position Fig. 11, to generate straight radial teeth. For generating cylindrical gears a face gear cutter 28, Fig. 18, is employed the teeth being relieved along the edge 30 to provideclearance. Helical gears may be generated by added rotation related to the feed movement or by the converse arrangement to that shown in Fig. 11. By inclining the direction of feed to the pinion axis tapered teeth may be generated. In a machine for carrying out the invention the pinion member 32 is supported on a spindle 33 and the face gear member 28 is mounted on a spindle 35 carried by a head 36 movable along an angularly adjustable table 38 which is itself supported on a movable table 39. The offset is determined by the vertical adjustment of the knee 40. By adjustment round the pivot 41, the face gear member may be cut with taper teeth to provide side clearance and top rake as is required to produce the cutter member shown in Fig. 18. The cutters used may have either integral or detachable teeth. The latter may be mounted in a head 48 having radial guideways formed with slots 50. Cutter elements each with two teeth 53 are secured by bolts 54 passing through the slots 50. The individual teeth are non-radial, being parallel to a radius such as s, t, the head flange 49 being dished to provide the required top and side clearance. In a modification the inserted teeth may be skewed to cut a straight spur gear in the manner shown in Fig. 4. The cutters are sharpened by grinding the end faces and are then reset to their original position by adjustment along the slots 50. U.S.A. Specification 676,226 is referred to.