GB239835A - Improvements in gears and methods and apparatus for cutting the same - Google Patents

Abstract

239,835. B÷ttcher, P. May 26, 1925, [Convention date]. Gear-cutting.-In a system of toothed gearing of the herringbone type, applicable to both spur and bevel gears, the longitudinal curve of the teeth has a radius of curvature which gradually increases from the median plane of the wheel towards the end faces. In Fig. 4, which compares the new tooth with the usual double-helical form,. the tooth curves are cyclic curves of approximately parabolic form, but in modifications, hyperbolic or elliptical tooth curves may be adopted. The profile of the sides of the teeth is. in all cases formed according to the usual rolling- generating method, the spur gears being based on a straight sided rack form and the bevel gears on a straight sided crown wheel. In order to cut gears according to the invention, a tool carrier 5 is provided with four cutting tools 8 - - 11 having straight flanks and corresponding in profile to half teeth of the basic rack. the tools beings arranged in diametrically-opposed pairs. A mainshaft 1 driven from a pulley 2 is journaled in a frame 4 and carries a crank-pin 3 rotatably mounted in the tool carrier. A wheel 6 on the carrier engages an internal gear on an extension of the frame 4 so that in operation the carrier has a planetary movement and the resultant path of the cutting edges is as shown in Fig. 9. The ratio of the pitch circle diameters of the wheels 6 and 7 is 4 : 5. Other methods based on combined reciprocating and circular movements or on combinations of circular movements may be used to give the required cutting path to the tools or, alternatively, templets may be employed for this purpose. Instead of the tools moving continuously in one direction, a tool may be oscillated along the required curve to cut the teeth by planing.