GB621738A - Improvements in or relating to means for cutting internally projecting gear teeth - Google Patents

Abstract

621,738. Grinding and polishing. PARSONS MARINE STEAM TURBINE CO., Ltd., COOK, S. M., and DOUGLAS, L. M. Sept. 14, 1945, No. 23787. [Class 60] [Also in Group XXII] A machine for producing a hob for cutting internal gear teeth of concave involute form comprises a slide rest with cross slides, as provided in the usual relieving lathes, with which is associated a tool holder carried on a further saddle in a circular guide, said saddle being given an intermittent rotary motion, proportional to the rotation of the work, between cuts on successive hob teeth, the arrangement being such that the relieving motion is towards the centre of the radius about which the relieving tool is rotated. The hob 1 is mounted in the lathe on a mandrel 2 and the tool 7, Fig. 6, which may be a profile tool, as shown, or a profile grinder, is carried on a transversely movable slide 8. This slide is carried by a rotatable saddle 10 carried in circular guides 11 in a saddle 12, also transversely movable along guides on the saddle 14. The relieving motion is obtained through gearing 40, Fig. 4, from the headstock drive, and a central shaft 41 drives through slidable bevel gears and pinions 43, 44, Fig. 7, a vertical spindle 46 driving, through gearing, a cam 48 for reciprocating the slide 8 against a spring not shown. One wheel 44 is mounted for adjustment in an arcuate slot so that the relieving drive may be brought into mesh again if the slide 12 is adjusted transversely. The arcuate form of the cutter is obtained' by a stepwise rotation of the tool holder through the rotatable saddle 10, this may take place about a centre on the work axis or a different centre according to the adjustment given to the saddle 12. The stepwise rotation is such that it takes place rapidly while the cutter moves through the flutes or gaps between successive cutter teeth and is obtained by a toothed gear drive 18 from the headstock spindle to a shaft 20, Fig. 4, further gearing 21, 22, a spring coupling 33, notched plate 32, spring-pressed plunger 34 and cam member 36, also mounted on shaft 20. The spring 33 is wound up during cutting of a tooth and then cam member 36 releases the plate 32 which drives through further gear trains 23-30, a worm wheel 19 which rotates the saddle 10. The gearing may be changed to allow for variations in the number of flutes and to vary the amount of angular movement of the tool during each step.