Patent GB-375876-A (GB)
Title: Gear generating machine
IPC: B23F5/16
Filed: 1931-03-19
Abstract: 375,876. Gear-cutting. MILLER, E. W., 9, Elm Street, and FELLOWS GEAR SHAPER CO., both in Springfield, Vermont, U.S.A. March 19, 1931, No. 8443. [Class 83 (iii).] Tools.-A machine for making spur gears, pinion-cutters, worms, screws, sprocket wheels or clutch members in which cutting is performed by a reciprocating tool of the pinioncutter type has means for imparting slight angular movements in opposite directions to the cutter so that only one side of its cutting edge is operative at any one instant. A main shaft 1 driven from an electric motor 7 through a belt 6 carries a crank-disc 8 which through a connecting-rod 9, lever 10, segmental teeth 12, and circular rack 13, reciprocates the spindle 14 of a pinion-cutter 15. The blank 16 to be generated is mounted on a vertical spindle 17, the blank and cutter spindles being rotated simultaneously in timed relation to generate the teeth. The rotary movement of the cutterspindle is derived from a worm 18 on the main shaft through worm wheel 19, spur gearing 20, 21, shaft 22, spiral gearing 24, shaft 25, bevel gearing 27, and worm gearing 29, 30. The shaft 22 also drives the work-spindle through change gearing 32, shaft 34, bevel gearing 35, shaft 37, bevel gearing 38, and worm gearing 42. Depth feed mechanism may also be provided. In order to compensate for the reduced thickness of the backed-off cutter teeth caused by repeated sharpening, additional timed oscillating movement of variable amplitude is imparted to the cutter. Thus in Figs. 10, 11 (in which the normal generating movements are not considered) the cutter on one working stroke acts only on the side a of the operative teeth, Fig. 10. For the return stroke, Fig. 11, the cutter is moved angularly so that all the cutting faces are clear of the blank. On the next working stroke, the cutter acts only on the side b of the operative teeth and on the next return stroke the cutter is again entirely clear of the blank. This cycle is then repeated. Preferably the teeth of the cutter when new are slightly narrower than normal and the amount of the oscillatory movement above described required to produce correct teeth on the blank gradually increases as the cutter teeth are further narrowed by sharpening. For imparting the additional movement to the cutter spindle, the worm 29 is moved endwise at the required times by means of a cam 57 on a shaft 58 driven from the main shaft 1 through belt 66, and further gearing. This cam acts through a lever 51 pivoted at 52 on a sleeve 47 which through a thrust bearing 50 imparts end movement to the worm 29. The lever is held up to the cam by a spring. The high portion cd of the cam corresponds to the working stroke in the position shown in Fig. 10. This is followed by a drop de to swing the cutter for the return movement, Fig. 11, a second drop fg which corresponds to the cutter swing required before the next cutting stroke when the cutter teeth have been ground to their least width, a rise hi to clear the cutter for the second return stroke of a cycle and a further rise jc to the original position for another cutting stroke. Only a part of the available drop fg is normally used, this being determined by a stop screw 67 which limits the approach of the roll 56 to the cam axis and is provided with a graduated head 69. In order to clear the tops of the cutter teeth from the work on the return strokes the work is slightly withdrawn. For this purpose the work spindle is carried in a sleeve 72 secured to a member which is pivoted to a lever 76. This lever is pivoted to the frame at 77 and is moved against a spring by a push rod 79 operated from a cam 83 on the main shaft through a bell-crank lever 80. The cam is arranged to hold the work-spindle sleeve against a seating 73 during the cut and to allow the spring to effect withdrawal movement on the return strokes. The auxiliary swinging movements may be applied to the work instead of to the cutter, and the invention is applicable to the cutting of helical gears. For cutting worms and screws the work and cutters are rotated together in the manner of a worm and worm wheel in mesh and alternate oscillations are imparted to the cutter, or the work is reciprocated, to produce the side trimming effect. In another modification the cutter is reciprocated in a helical path and is also oscillated for the side trimming, a gradual additional generating feed being employed.