Patent GB-590691-A (GB)
Title: Improvements in or relating to gear cutting machines for spur and screw gears
IPC: B23F5/14
Filed: 1944-07-04
Abstract: 590,691. Gear-cutting. AEPPLI, A. July 4, 1944, No. 12760. Convention date, June 21, 1943. [Class 83 (iii)] In planing spur or helical gear-wheels by means of a rack cutter wherein the work is rotated continuously without indexing so as to produce a continuous generating motion with the. cutter entering different tooth spaces at each stroke, the cutter is moved at uniform velocity during its working stroke by a cam which performs a complete revolution for each reciprocating cycle. For generating spur gears, the cutter 54, Fig. 20, reciprocates with an inclined slide St along a path A so that during the working stroke the resultant relatively to the rotating work B is along R, parallel to the teeth C, but the return stroke is made at a greater speed along the resultant R1 with the cutter withdrawn from the work. For generating helical gears, the cutter 54, Fig. 21, reciprocates along a path A parallel to the work axis so that the resultant R during cutting will be along the required helical angle #, the return stroke being again more rapid and having a resultant R1. The leading face of the cutter is always perpendicular to the teeth being cut, as shown. The cutter slide St is adjustably secured to a ram S, Fig. 5, which may be reciprocated by, involute cams A, B, acting respectively on rollers CA, CB on the slide. The involute A is derived from a small rolling circle a and B from a larger rolling circle b so that the cam A will move the slide slowly during the cutting stroke whilst rotating through a large angle alpha, but cam B will perform the same stroke during a rotation through a smaller angle #, thus returning the slide at a higher speed. The cams A, B may be replaced by a face cam having an archemedian spiral track therein or by a cylindrical cam having a helical groove or opposed helical faces, the return stroke being in each case at a higher speed than the cutting stroke. The length of stroke may be varied by changing the cams or by causing the ram to act on the slide St through a lever with an adjustable fulcrum or through rack-and-pinion gearing incorporating change wheels or through a rack-and-pinion and change wheels driving a rotatable screw engaging a nut on the slide, and the momentum of the ram &c. at each end of the stroke is absorbed by springs. In a machine embodiment of the invention, an electric motor 82, Fig. 1, drives, through belt and spur change gearing 38, 40, a shaft 41 carrying the ram-actuating cams which is also connected by gearing 44 to a shaft 46 which rotates the work table 2 through reverse gearing 47, change wheels 10, a differential gear 7 and a worm 5. The table is mounted on a slide 3 which is given a slow longitudinal generating motion, in unison with the rotation of the work, by a screw M driven from the motor 82 through a belt 37, worm gearing 35, change speed reversing gearing 29, 32, a single speed reversing gear 23 and gearing 18, 20, the gear 20 being connected by modulus adjusting change gears 15 to the spider of the differential gear 7. The reversing gear 23 is for producing a right- or left-hand rolling motion at equal speeds and the reversing gear 29, 32 for returning the table 3 to starting position at a higher speed on completion of a gear cutting operation. The table 3 is carried by a transverse slide 78 fed to and from the cutter by a screw 61 which may be rotated by hand or, through a clutch 62, by worm, change and bevel gears from the feed shaft 34. This shaft may be driven directly from the shaft 46 or made integral therewith to preserve a constant ratio between the rate of reciprocation of the cutter and the speed of rotation of the work. The cutter slide St and the ram reciprocate in guides 81 carried by a head which is rotatably adjustable about the axis of shaft 41 to give the required inclination to the cutting stroke, and the rectilinear component of the rolling motion may be given to the cutter slide instead of to the table 3. The Specification as open to inspection under Sect. 91 states also that the tool 54 may be replaced by a grinding disc having the profile of a basic rack tooth. This subject-matter does not appear in the Specification as accepted. Cutter-releasing tool boxes.-The cutter box 53, Fig. 1, is relieved on the return strokes by a rotary cam 52 driven by gearing 51 from the cutter-reciprocating shaft 41, the box tilting about an axis which is parallel to the leading face of the cutter.