Patent GB-536997-A (GB)
Title: Generative gear cutting machines
IPC: B23F5/06
Filed: 1940-03-14
Abstract: 536,997. Gear cutting or grinding. FELLOWS GEAR SHAPER CO. March 14, 1940, No. 4826. Convention date, March 16, 1939. [Class 83 (iii)] In a machine for generating the profiles of gear teeth or like articles the work is rolled past a fixed cutting or grinding tool, and is mounted on a carriage reciprocated by a cam bearing against a fixed abutment, the work and cam spindles being spaced apart in the direction of the carriage movement and having a driving connection by which they are simultaneously actuated. The machine frame has a recessed base 21 fitted with uprights 24, 25, supporting a cross-beam 26. The tool, shown as a grinding wheel having a plane operating face is carried in a head 32 adjustably secured to the cross beam. A carriage 28 moving over the table 27 carries preferably parallel cam and work spindles 33, 29, respectively. The spindle 33 carries a holder for the adjustable involute cam 35 which bears on the adjustably fixed abutment 37. The cam holder is connected by a link 39 to a crank disc 41 driven from a motor 42 through belt gearing 43, and worm gearing 49 thus oscillating the cam and traversing the carriage the return being effected by a weight 52. In order to impart corresponding rotary movement to the work, the cam shaft carries a toothed sector 57 engaging a circular rack part 58a of a member 58 provided with a screw portion 58b engaging a gear 59 on the work-spindle. By rotating the member 58 the work spindle is rotated for indexing without affecting the cam spindle 33. Power for the indexing movement is derived from a torque motor 66 which acts through gearing 68, shaft 70 and gears 72 on an extension of member 58. The motor shaft is also geared to a shaft 78 carrying an index plate 77 engaged by a stop plunger which normally holds the indexing motor stationary but which may be released to allow the revolution of plate 77 to give the indexing movement, which may be varied by change gears. The locking pin 76 is released by the carriage 28 at the end of the withdrawal stroke when the work is clear of the tool. At this point a projection 86 on the cam shaft engages a collar 90 to shift an arm 87 connected by linkage, Fig. 10, to a pusher block 97 having a face concentric with the index plate. A spring-pressed pivoted arm 98 engaging the pusher face carries a pawl 104 actuating an arm on a shaft 106 connected by rack and pinion to the index plunger. When the pusher is moved forward the parts are moved to the Fig. 13 position, withdrawing the plunger and allowing the index plate to rotate through one revolution. A gear segment 113, Fig. 10 is driven from manually-operated gearing 118 and worm gear 114 to advance the stop plunger angularly and so rotate the work to increase the depth of cut. The bracket 100 is locked when the desired depth is reached. Before the locking bolt engages the index plate the latter is braked to lessen the shock by a shoe 125 spring pressed against a drum 124 on the torque motor. A cam 135, Fig. 5, normally holds the brake disengaged but just before the stopping of the index plate a depression in the cam allows the brake to engage its drum. The grinding-wheel is adjustable laterally, angularly and axially. The tool-head 32 carries a spindle 139 driven through a belt 170 from a motor 140. The head moves parallel to the grinding face in guides 141, 142 formed on a base resting through rolls 145 on the arcuate upper surface of a ledge 146 on the cross-beam. The base also has an axial arcuate flange by which it may be secured to the cross-beam by clamps 148 so that when the clamps are loosened the head may be angularly adjusted to place the grinding face in any position between the vertical and about 25 degrees the inclination being measured by a scale 150. Lateral adjustments of the grinding-spindle are effected from a hand wheel 151 through shaft 155 and rack-andpinion gearing 157. Axial adjustment is effected in conjunction with a trueing tool 158 carried by a pivoted arm 159. The grinding-spindle is for this purpose mounted in a sleeve 160 which is moved axially by a screw engaging a tapped hole in the casing 161. The forward and rear ends of the spindle are carried in tapered bearings 172, 173, the rear bearing being movable to take up wear. A thrust bearing 174 is forced outwardly by springs 175 and holds a shoulder 176 on the spindle against a thrust washer 177. Lubricant such as kerosene is contained in a chamber 178 and passes through a filter 179 to an oil channel 181 and finally to a basin 182 whence it is circulated by a pump 184 driven by a belt 185. A member 187 co-acts with the wheel centre 188 to exclude dust. The abutment 37 is carried.on a plate 194 which may be angularly adjusted about a pivot 195 on a slideplate 196, by hand-operated worm gearing 202. Adjustment of the slide 196 in the direction of movement of the carriage 28 may be effected by a screw. The work arbor 29 passes with clearance through a quill 212 in which it is centred by a collet 213, Fig. 2, a nut 214 being loosened to adjust the arbor 29 to the required axial position. The free end of the arbor is carried on a dead centre 215 in a bushing 216 concentric with the quill. The gearing 58b, 59 and the quill bearings are enclosed in a housing 220 and protected by a flexible rubber bushing adjacent the work. For finishing helical gears the work-spindle axis and the carriage path are set to the required inclination. For this purpose table 27 is rotatable on the bed 23 in concentric curved guides and the crank shaft and its driving gear is suspended from the table. The adjustment is effected by worm gearing from a shaft 227 and is indicated by a scale 228. The pulley 44 of the driving mechanism is co-axial with the table. The rolling circle of the mechanism may be varied from 1 inch to 12 inches. A single involute cam 36, Fig. 20, may be used with the abutment 37 and wheel 31 to generate the curve b with a base circle B or with abutment 37a and a wheel 31a it will generate curve c with a base circle C. Other settings within or outside these limits may also be used.