Patent GB-379837-A (GB)
Title: A method of and apparatus for lapping gears
IPC: B23F19/04
Filed: 1931-08-17
Abstract: 379,837. Lapping toothed gears. JACKSON L. MELLERSH-, 28, Southampton Buildings, London.-(1, National Broach & Machine Co. ; 11457, Shoemaker Avenue, Detroit, Michigan, U.S.A.) Aug. 17, 1931, No. 23157. [Class 60.] In a method of lapping straight or helical spur gears, a gear to be finished is run in mesh with a lapping tool having teeth of conjugate form to the gear, the axes of the gear and lap being non-parallel and non-intersecting and the lap teeth having a spiral angle different from that of the blank teeth. Thus in Fig. 1 a straight-toothed gear blank D may be mounted on an arbor C, Fig. 3, in a bracket L mounted on the angularly-adjustable table B of a universal milling machine, while the lap 1 having spiral teeth is mounted on an arbor H driven by the usual gearing K. During the operation, the table may be moved in the direction of the lap axis by means of the table feed screw operated by a handle G, this movement being somewhat less in amplitude than the face width of the lap. Reciprocating movement is also imparted to gear in the direction of its axis by means of the handle F, the extent of this movement being preferably somewhat greater than the face width of the gear. The gear dips into a tank N containing abrasive compound during the running and the table is vertically adjusted from time to time until the desired amount of metal has been removed. The lap may be of cast iron, and its teeth are preferably somewhat larger than those of a mating gear, so that there is contact during the operation of points 1, 2, Fig. 5, on opposite sides of a lap tooth. By this means pressure is developed between the contacting faces to produce the desired abrading action. In a modification, Fig. 6, the lap I is mounted on an arbor H<1> journalled in a carriage H2, while the gear blank D is carried on an arbor mounted on a carriage L<1> reciprocating on a vertically-adjustable crosshead L<2>. The column M which carries the crosshead is angularly adjustable on segmental ways M<2> about a vertical axis passing through the axis of the arbor H. The arbor H is driven from a motor N<2>, Fig. 7, through reduction gearing N<3> and belt N. In order to reciprocate the gear blank axially, the carriage L<1> is provided with a rack engaging a pinion O<1> on a shaft 0<2> which is connected by links 0<3>, 0<4> to an adjustable crank 05 on a shaft 0<6> driven through wormreducing gearing from the shaft N<1>. The contacting surfaces of the gear and lap are pressed together with a predetermined pressure by retarding the rotation of the gear by a hydraulic brake. For this purpose the arbor L carries one wheel of a gear pump P which discharges against the adjustable resistance of a spring- loaded valve. In operation the motor N2 is driven first in one direction to lap one set of tooth faces and is then reversed to lap the opposite faces. To facilitate the correction of indexing errors the lap preferably has one tooth more or less than the gear or than any multiple of the number of teeth on the gear. The lap may be replaced by a hardened wheel which finishes the teeth by a burnishing action.