Patent GB-576261-A (GB)
Title: Improvements in gear grinding machines
IPC: B23F23/12
Filed: 1944-05-04
Abstract: 576,261. Trueing grinding wheels. GLEASON WORKS. May 4, 1944, No. 8462. Convention date, Oct. 20, 1943. [Class 60] [Also in Groups XXII and XXXVII] In a machine for producing toothed gears by cutting or grinding, the tool and work are separated periodically and means are provided for automatically shifting, at each separation, a depth controlling device for determining the penetration of the tool into the work so that the tool will re-engage the work at an increased penetration after each separation. The machine also has automatic means for dressing the grinding wheel after some of the separations from the work, and for-determining the extent of the dressing operation. As applied to a machine for-generating spiral and hypoid bevel gears as described in Specification 544,892, the machine shown in Fig. 1 is of the same general arrangement and has an annular grind- . ing wheel W mounted in a swinging carrier in a head 52. Trueing rotating grinding wheels.-The means for dressing the grinding wheel W may be as described in Specification 577,090 and comprises outer and inner tools carried by the arms 1092, 1095, Figs. 4 and 5, respectively, and a tip dressing tool carried by the arm 1146. These arms are mounted for oscillation during dressing by fluid plungers and are carried by brackets 1075, 1152 capable of being swung into and out of dressing position and mounted on a ring 1035 angularly adjustable on a flange 721, Fig. 3, secured to the tool carrier 28. The wheel W is advanced axially before each dressing operation to determine the amount of stock tobe removed, as described in Specification 577,090, and this is effected by a fluid plunger oscillating a lever 1269, Fig. 16, which carries a pawl held by a spring against a ratchet 1272 keyed to a shaft 1270. Bevel gearing 70, 71, to actuate the screw 72 which advances the spindle sleeve 27, and the extent of each advance is controlled by a rod 740, Fig. 16, which may be adjusted axially to cause its lower end to engage one or other of teeth 745 attached to shaft 1270 and thus determine the angle through which the shaft may be rotated at each oscillation of the pawl. To prevent the wheel W from being advanced beyond a safe limit, a screwed sleeve 746 pinned to the shaft 1270 moves a non-rotatable nut 750 axially at each rotation of the shaft and eventually the nut engages a sleeve 751 to move it against a spring and cause a shroud thereon to mask the ratchet. Operation.-The machine automatically per. forms generating cycles on the continuously rotating work, the grinding wheel penetrating deeper at each complete revolution of the work. These cycles continue until it is necessary for the wheel to be dressed, whereupon a button 631, previously positioned on the plate 560, engages a switch 635 in assuming its new indexed station to stop motor 90 and the generating mechanism and start motor 640 to drive the dressing mechanism. This rotates cams which operate valves 700, 701, valve 700 being first operated to actuate the plungers which swing the arms 1092, 1095 and 1146 into operative position and also being effective to rotate ratchet 1272 and advance the wheel axially. Valve 701 then actuates plungers to swing the dressing tools across the wheel and is next reversed to return the tools. The rate of this return, and hence the degree of finish imparted to the wheel, is determined by a valve 772 which throttles the exhaust from the dressing plungers. If a button wipes past the switch 635 in assuming its next indexed position, valve 772 is not actuated and the dressing tools return at a rapid rate for rough dressing but before the final finish-grinding generating cycle, a button remains opposite the switch and valve 772 is actuated to slow down the return.dressing operation and impart a fine finish to the wheel. Whilst dressing is being performed by fluid pressure, switch 663 is opened by a cam to stop motor 640 which is re-started on completion of the dressing operation, to rotate the cams actuating valves 700, 701 and return the dressing mechanism to inoperative position. These cams then actuate a switch 655 to start the generating motor 90 and a switch 666 to stop motor 640 and another series of generating cycles takes place with further dressings of the wheel after predetermined numbers of cycles, and after the final finishing operation on the work, a button 820 on stop plate 560 trips a switch 502 to stop motors 80 and 90.