Patent GB-548863-A (GB)
Title: Machine for and method of grinding gears, splines and similar forms
IPC: B23F23/12
Filed: 1940-10-23
Abstract: 548,863. Grinding. ROSS, W. F. Oct. 23, 1940, No. 15587. Convention date, Oct. 30, 1939. [Class 60] [Also in Group XXII) Toothed gears splines and similar parts are generated by means of an abrasive hob which is trued by means of a dressing-wheel the profile of which is maintained by a trueing-diamond under the control of pantograph mechanism. The frame has chambers 21, 22 extending laterally from the forward part thereof, the chamber 22 serving as a coolant reservoir from which coolant is pumped by a motor 23. The grinding-wheel 24 which is of hob-like form is mounted on a spindle 25, Fig. 16, carried by a manually adjustable slide 26. A dressing- wheel 29 is mounted on the spindle of a motor 31, the wheel and motor being angularlyadjustable in arcuate ways 34. The motor support also carries a pantograph table 35 which is adustable by a screw 36 and is carried on compound slides 40, 43. During gear grinding operations, the wheel 24 is driven at high speed from the motor 50 but for dressing the grinding wheel it is driven alternatively in opposite directions at low speed from an auxiliary motor 51. The motor 50 drives the grinding- wheel through change speed gearing, shaft 57 clutch and belt gearing 60. The change speed gearing gives a countershaft speed of 2600 r.p.m. further variation being obtained by altering the belt pulleys 59, 61. The work 99 is mounted on an arbor carried between head and tail stocks 97, 98 mounted on a slidable work table 95 carried by a turntable 96 mounted in a head 70. The head 70 is normally held in a withdrawn position on a saddle 74 by means of a weight. The saddle is itself axially adjustable from a hand wheel 79 through worm gearing 82 and rack-and-pinion gearing 83. The trunnion 86 of the turntable 96 is adjustable by worm gearing 89 and locked by screw-operated wedge devices 91, 92 coacting with a ring 94. A fine axial adjustment of the work-head saddle 74 is obtained from a hand wheel 101 which acts through gearing 102-105 on a feed screw 106 running in a nut 109. In addition to these coarse and fine adjustments the trunnion head 70 may be controlled by the coaction of a fixed cam 110 on the bearing sleeve 107, Fig. 7, with a cam 111 operated by a rack 112 operated by hand levers 114. A shaft 116 driven from the main grindling spindle is connected through a clutch 119 with a shaft 120 geared to a shaft which is connected to a vertical constant speed shaft 128 in the trunnion head this shaft being driven at the same speed as the grinding spindle and being geared through a shaft 136 to the outer member 137 of a rapid return friction clutch, Fig. 8. Further gearing from the shaft 136 including change wheels operates a cross shaft 146 driving a dog clutch member 149, Fig. 8. The table feed shaft 151 extends centrally through the trunnion 86 and carries a splined clutch member 152 which is integral with the inner member 160 of the quick return clutch. The shaft 151 is geared to the table feed screw 156 by bevel gearing 154. The extent of the table feed is controlled by stops 158, 159 coacting with a lever 161. At the end of the operative upward feed of the work table the lever 161 is operated to actuate a collar on the trunnion 86. This collar is connected through lever mechanism and a push rod 170, Fig. 9, to a detent 173 which when operated releases the rack bar 112 whereupon the weight causes the cam 113 to rotate so as to withdraw the trunnion head with the work from the grinding wheel. At the same time the clutch operating lever is operated to shift the clutch 152 to neutral position and stop the rotation of the work. To effect downward return movement of the work table the rack 112 is further moved by one of the hand levers 114, the rack then acting through gearing to engage the rapid return friction clutch. At the end of the return motion a clutch is automatically disengaged to stop the work table. To restart the upward table feed the rack 112 is oppositely moved, causing the cam mechanism 110 to return the table to the working position and re-engaging the forward drive clutch 149. The work rotation is effected from a gear 134 on the constant speed shaft 128. This gear is connected through gear 196, single tooth clutch 198, 199, shaft 200, change gears 204, shaft 205, and gears 206, 207 to one wheel 208 of a differential, Fig. 8. The normal motion is transmitted to the hollow shaft 215 geared to a shaft 218, Fig. 14, carrying a sliding gear 219 connected through gearing 226, 227 and 231 to the headstock spindle 221. In order to provide a finer range of work speed than that obtainable from the change gearing in the work driving train a second differential gear 232, Fig. 11, is fitted in the driving train of the worm 211 which rotates the casing of the main differential. The shaft 205 is geared to a shaft 241, Fig. 11, which is connected through change gears 245 to a shaft 234 which through the casing 232 drives the worm 211 so modifying the work spindle speed. To provide for grinding helical gears the added rotation of the work in unison with the table feed is obtained from the work table feed shaft 151, the sliding clutch member on which carries a pinion 246 geared through reduction gearing and a helix change speed train 275, 279 to the shaft 233 connected to one side of the second differential. In the cutting of taper tooth gears the work table is fed towards the grinding wheel during the operative traverse in unison with the table feed. For this purpose the table feed shaft is geared to a spur wheel 286 engaging a rack 287, the rack being connected by further gearing to a worm 295, Fig. 8, driving the trunnion head feed nut thus moving the trunnion head to or from the grinding wheel in unison with the work feed. The single tooth clutch 198 in the work driving train serves to maintain the correct angular relation between tool and work. This clutch is automatically disengaged when the work table feed is stopped. To eliminate torque flutter a friction brake is provided on the work spindle, the brake parts 378, 380 being pressed into contact by adjustable springs 381. The brake surfaces are lubricated by oil contained in a sump 389, Fig. 14, and circulated to a pipe 397 by a pump driven by a cam 396 in the spindle driving train. The grinding wheel has a section normal to the thread which represents the basic rack of the gear being produced. The thread is first roughly chased on a lathe and then dressed by a dressing wheel of complementary section such section being produced by a pantograph. For dressing the grinding wheel the latter is driven at low speed in alternately opposite directions by a gear train from the motor 51 while the dressing-wheel is driven by a high speed motor 31 and is set to the required helix angle on the guide 32. During dressing the dressing-wheel is traversed along the grinding wheel, withdrawn at the end of the traverse, then returned and advanced to the dressing position for another cycle being advanced as required to increase the depth of cut by the screw 41. A gear train driven by a shaft 116 is connected by a change gear train to the feed screw 45 of the dressing slide the nut on the screw carrying a projection which effects automatic reversal of the drive at opposite ends of the traverse. During reversal a cam plate operates a pinion geared to a rack on a transverse slide 47 of the dressing wheel support so as to effect the alternate in-feed and withdrawal movements of the dressing-wheel. The pantograph for forming the dressing-wheel comprises a fixed pivot 370 and the system of levers shown in Fig. 3A giving a ten-to-one reduction between the pattern 375 and the profile to be formed on the work by a diamond tool 373. To ensure even wear the grinding wheel is periodically adjusted axially by the screw 28 and to compensate for this the work is adjusted angularly relatively to the spindle 221.