689,037. Gear - grinding. GLEASON WORKS. Oct. 11, 1949 [Oct. 23, 1948], No. 26109/49. Class 83 (iii). [Also in Groups XXIII, XXXV and XXXVII] A machine for grinding gears comprises work and tool supports, a cam 200, Fig. 8, for controlling the depth of engagement of the grind. ing tool and the work, and means for rotating the cam step-by-step. The machine, which is for grinding spiral bevel and hypoid gears, comprises a tool-mounting in which the cradle 35, Fig. 4, drum 40, eccentric head 45, and carrier 50 are formed and adjusted as described in Specification 680,104. Mounted in the carrier 50 on an axially reciprocable sleeve-bearing 51 is an electric motor 55 supplied through a commutator 63 and to the shaft of which the grinding-wheel W is secured. Also mounted on the carrier, is a dressing mechanism 280 which may comprise a single-arm diamond dresser travelling round the full wheel profile and which is held against oscillating with the cradle 35 by a turn-buckle pivoted at 290 and anchored to the machine frame. Advance of the sleeve 51, for dressing the wheel, is controlled by a piston 73, Fig. 5, in a cylinder 70, Fig. 4, the piston actuating, on its forward stroke, a ratchet mechanism 79, 77 which rotates a screw engaged with a nut 85 secured to the sleeve. An adjustable stepped member 90 determines the amount of advance and hence the amount of stock removed. A button 96 on the nut actuates a switch 98 either to light a warning lamp indicating when the wheel is worn to its working limit, or to stop the machine. The dressing-mechanism is actuated by a piston 295, Fig. 23, whose movement is regulated by throttle valves 320, 321, the latter being selected for dressing at a slow rate before the final grind. Work-mounting. The work is mounted for angular, vertical and axial adjustment and is driven as described in Specification 680,104. The work can thus be fed in a direction bisecting the angle between opposite sides of the wheel to ensure equal wear of the wheel. The generating- mechanism, including the barrel-cam, is also as described in that Specification. Thus, a lever 136, Fig. 8, is controlled by a track on the barrel cam, to move the work to and from the wheel by the lever 165 connected to the sliding work-base, dwell portions on the cam being provided for the grinding and indexing positions. The hydraulic piston 160 moves the work-base to and from work-loading position. For eliminating bias bearing when both sides of a tooth space of both mating tapered gear and pinion are ground simultaneously, the work is moved in time with the cradle 35. To this end, a gear 192 has a screwed connection with the piston 160 and is rotated by a gear 170 which is attached to the cradle and drives, through reversing change-gears 179,182, a gear 187 which can be clutched to its shaft. The gear 179 may, however, be omitted and no additional motion transmitted. For feeding the work into the wheel when a series of rough-grinding passes are to be made, e.g. when grinding from a solid blank, a number of cams 200, Fig. 16, are provided, which coact with a follower 208 operatively connected with the sliding workbase, the appropriate cam being selected by a hand-operated yoke. Each cam 200 has a dwell portion to enable finish-grinding to be carried out at the same depth as the final roughgrind. The cam-shaft 204 is rotated step-bystep by a hydraulic piston 225, Fig. 17, which oscillates a member carrying a pawl 232 to advance a ratchet-wheel 233, the wheel being held in position by a spring-pressed pawl 239, Fig. 23, which can be released by a hydraulic piston 243. As the shaft 204 rotates, it advances a toothed re-set piston 250, Fig. 23, engaging a pinion 253 on the shaft 204. Gauging-devices.-The initial position of the piston 250 and hence of the work-slide, is determined by a screw 254, which also determines the number of step-by-step advances to be made. A peripheral scale on the sleeve carrying the ratchet 233 allows the screw 254 to be set accurately to gauge the total feed of any given cam 200. The step-by-step feed, the dressing movements, the rate of dressing, and movements of the work to-and-from loading position are controlled respectively by lobed cams 262, Figs. 10 and 14, which are carried on a drum 263 and move levers contacting hydraulic valves 260, 300, 330 and 340, Fig. 23. The drum 263 is rotated intermittently by a piston 350, Figs. 10 and 23, formed with a rack and actuating a ratchet-wheel 356. The wheel 356 is held by a pawl releasable by a piston 365 to allow a re-setting piston 375 to return the drum 263 to its initial position. The piston 350 is controlled by a solenoid-actuated valve 370. Limit switches 560, 562 ensure that the cams 200 and the drum 263 are re-set before grinding commences. Manual operation. For setting-up purposes, manually-operated valves 412, 416 and 452 are moved to prevent automatic operation and to open switches 490 ... 492 allowing the motor 55, a motor 380 driving a hydraulic pump 381, and a main motor (corresponding to the electric motor of Specification 680,104) to be controlled by stop-and-start push-buttons (see Group XXXVII). Automatic operation. A selector switch is moved to automatic position and the valves 412, 416, 452 are closed so that the motor 380 may be started by a push-button and the work chucked by a piston 397 operated by a manually-operated valve 396. The grinding-wheel motor 55 is then started by a push-button. This also causes movement of the piston 350 to advance the drum 263 and hence the cam 296, Fig. 14, by one step to actuate the valve 300 and re-set the dressing piston 295. At its upper limit the piston 295 actuates a valve 310 to move the piston 73 and advance the motor 55. Meanwhile, movement of the drum 263 and ratchet 356 opens a switch 565, Fig. 23, to cause the return of the piston 350. The piston 350 is again advanced by actuation of a switch 638 by the piston 73 and the drum 263 advances to release valve 300, thus causing the return of piston 295 to dress the wheel. The valve 310 is released to re-set the piston 73. Return of the piston 295 also actuates a switch 635 to advance a cam 346 on the drum 263 to move the valve 340 and advance the piston 160 and the workbase to operative position. The movement of the piston 160 actuates switches 636, 637 to again move the piston 350, and a cam 345 then moves the valve 340 to actuate a switch 610 and the main motor is started. Grinding generation and indexing then ensue under the control of the barrel-cam as in the said Specification. When a grinding pass has been completed an automaticstop switch, pre-set to the number of teeth on the work, advances the drum 263 and a surface 278 to move the piston 225 and rotate the operative cam 200 to allow the piston 160 to apply feed to the work-base. Movement of the piston 225 also actuates a switch 258 to advance the drum 263 and re-set the piston itself. A stop-switch, momentarily actuated automatically after each complete indexing movement, then re-starts the main motor and a further grinding pass is made. After four passes controlled by the surfaces 278, a second surface 296 and associated surfaces 345 cause withdrawal of the work and a dressing of the wheel. Before the final pass, a third dressing takes place, the piston 295 being moved at a slower rate under control of the throttle-valve 320, made operative by a surface 337. Finishgrinding may take place without further feed by omitting the last surface 278 or providing a dwell on the cam 200. After finish-grinding, the automatic stop-switch stops the main motor and the drum 263 is advanced to return the work-base to loading-position. At the end of the withdrawal the switch 636 is closed to advance the drum 263 and actuate the limit switch 535, Fig. 10, thus stopping the motor 55 and operating a warning light. On de-chucking the work by the valve 396, pawls 239, 358 are released and the wheels 233, 356 re-set. The pump motor 380 runs continuously until stopped manually. When possible, the workbase is not withdrawn to its loading position for dressing. The modified cam surfaces for the drum 263, when the wheel is trued in its advanced position, are fully described. Specification 689,086 also is referred to.