Patent GB-181437-A (GB)
Title: Improvements in machines for cutting bevel and mitre gears
IPC: B23F1/04
Filed: 1921-03-05
Abstract: 181,437. Greenwood, E. P., and Greenwood, E. March 5, 1921. Gear-cutting.-A machine for shaping bevel and mitre gears comprises two tools each adapted to cut one side of a tooth and carried by pivoted tool - carrying levers controlled to shape the tooth profile by means of a tapered former or templet cam. The ram 3 of the machine is fitted at the front with guideways accommodating a vertical slide 5 slotted to receive the head of a vertically adjustable bolt 6 on which is mounted a bush carrying blocks engaging slots in tool-carrying levers 7, 8. By adjusting the positions of the blocks in their levers gears of different pitches may be cut. The lower ends of the levers carry clapper boxes in which the cutters 7a, 8<a> are secured while the upper ends carry rollers 12, 13 spring-pressed against a tapered templet cam 14. The latter is provided with faces 1 by means of which the tools are gradually opened to give the required tooth contour and returned at the end of a cutting operation. The cam is supported in bearings on a bracket 17 sliding in vertical guides 1<1>, and is driven from a shaft 37 through worm gearing 32 and chain gearing 29. In order to feed the tools to the required depth, a cam 18 secured to the cam 14 operates a lever on a shaft 21 journaled in the bracket 17 and carrying a sector engaging a fixed rack 23. A block 24 on the slide 5 engages an horizontal guideway in a swinging member 25 pivoted at 26 to the bracket 17 and anchored to a fixed stud 27 in alignment with the cone apex of the blank. The rotation of the cam 18 thus traverses the bracket 17 and this motion is transmitted through the swinging member 25 to the tool-slide 5. To avoid damage to the completed tooth, the cam 18 is timed to withdraw the tools from the work before the cam 14 permits them to close towards each other. The blank 40 is mounted on a mandrel 39 carried in bearings on an angularly adjustable disc 41 attached to a plate slidable by a screw 43 along a bed 45. The bed is vertically adjustable through the gearing shown in Fig. 1 from a square-ended shaft 50. Indexing of the blank is effected by worm gearing 60 driven from a pulley 68 through a clutch 66 notched discs 67, and change gears 70. The indexing is controlled by the movements of the swinging slide 25 which operates an arm 62 connected by lever mechanism to the clutch 66, and the notches in the discs 67 co-operate with pivoted stop levers, the arrangement being such that either one, two, or three revolutions may be given to the shaft 69 and the clutch 66 then automatically disengaged. In a modification, to avoid undue wear of the cam 14, the rollers 12, 13 bear on inclined tracks formed in members surrounding the cam and having longitudinal wearing-strips bearing from end to ehd of the cam. In a further modification, Fig. 7, the tools are carried in holders 74, 75 pivoted to the clapper boxes and having extensions 74<1>, 75<1> connected by pins to links 76, 77 adjustably pivoted together at 78 and pivoted at their lower ends to the cam-controlled levers 7, 8. By adjusting the various pivot points in this mechanism, teeth of different profiles may be produced from a single templet cam.