Patent GB-793831-A (GB)
Title: Improvements relating to methods and machines for generating tooth surfaces of gearsand like toothed parts
IPC: B23F9/10
Filed: 1956-01-18
Abstract: 793,831. Gear-cutting; gear-grinding. GLEASON WORKS. Jan. 18, 1956 [Jan. 19, 1955], No. 1711/56. Class 83 (3). A method of gear-tooth surface-generation consists in rotating the work-gear G about its axis 27 while relatively rotating the work-axis and the cutting or grinding-path of a tool C about an axis 12 inclined to the work-axis, and, in time with said rotations, relatively translating said work-axis and tool-path in a direction (vertically), at a constant angle to the work-axis and to the axis of relative rotation. The facemill cutter C is mounted eccentrically in a drum 13 adjustable in a cradle 11 having an axis 12. The cradle may be tiltable. The work-gear G is mounted on a head 25 adjustable vertically on a column 23 adjustable axially of the gear on a slide 19. The slide 19 is angularly-adjustable on a base 17 adjustable axially of the cradle-axis. The cutter C is rotated by a motor 31 through change-gears 34. The motor 31 also drives the generating-motions through generating-cycle speed-change-gears 43, a shaft 45, and a drum 48 which contains means to alternately clutch it to oppositely rotating gears 49, 51. A gear 52 on the drum rotates the cradle 11 about its axis 12 through a shaft 55, a clutch 114 and a worm 57. The rate of rotation of the cradle may be modified as described in Specification 543,408 by reciprocating the worm axially through gears 60, roll-modification change-gears 61 and an adjustable eccentric 59. The work-spindle 26 is rotated from the shaft 55, through ratio-ofroll change-gears 64 (determining the ratio of cradle - rotation/work -spindlerotation), differential-gearing 66-69, and index-change-gears 81. The work-base 17 is withdrawn after a generating roll by a cam rotated by the shaft 45 and worm-gearing 85, 86. A gear 89 on the shaft 45 rotates a Geneva-mechanism 87 which, while the work is withdrawn, is engaged to rotate the differential-gearing 69 and advance the workgear by one or more pitches, as is also described in Specification 543,408. During generating rotation of the work, the head 25 can also be moved on the column 23 by a screw 101 engaging a nut of the circulating-ball-bearing type and rotated from the drum 48 through ratio-changegears 105. When generating bevel and hypoid gears, one of the gears 105 is removed and the screw 101 is locked when the head 25 has been adjusted. When generating cylindrical gears, the clutch 114 is disengaged, the cradle 11 is locked, the appropriate gears 105 are installed, the slide 19 is swung round until the gear-axis is perpendicular to that of the cutter, and the gear is then rotated and moved vertically so that the cutter, representing a rack, cuts symmetrical or helical-type curved teeth 115, 115<SP>1</SP> on the blank as illustrated in Figs. 4 and 5. In a modification, the index-mechanism 88 and the differential are eliminated and the work rotates continuously as in Specification 544,892. In a further modification, the machine operates with a face-hob, each group of cutters comprising an outside and an inside cutting blade. In another modification, the cutter cradle 200, Fig. 11, is mounted in a slide 202 adjustable vertically on a column 203 adjustable axially of the cutter. The work-head 208 is adjustable axially on a swinging base 211. Alternatively, all the generating motions may be applied to the gear G, Fig. 12, and the cutter C be adjustable on slideways 217, 219 for initial positioning or feed. The gear G is then mounted in a head 228 angularly adjustable on vertically-movable slide 227 on a slide 226 adjustable radially of the work cradle 223. In yet another modification, the machine is generally as described in Specification 772,237 and has a cradle carrying twin intermeshing cutters C<SP>11</SP>, Fig. 13, adjustable axially, laterally and angularly to represent a spur or helical rack or a straight or skew bevel crown gear. The work-spindle 311 is adjustable vertically on a column 313 adjustable horizontally and angularly. Planing. The cutter may be replaced by one or more reciprocating-tools or disc-cutters to cut straight teeth or conventional helical teeth. For bevel and hypoid gears having a long conedistance, all the motions are used. The effect of moving the work vertically is to convert the imaginary generating gear G1, Fig. 6, obtained by rolling the cutter C about a fixedcradle-axis 12, into an imaginary gear G2 having its centre at 118 as the cradle axis moves relatively from 12c to 12d. The mean radius 117-118 may thus be varied to infinity. This combined movement results in some bias and curvature change, but the effects are approximately compensated by generating gear-and-pinion in the same way. Alternatively, the cradle-roll may be modified by the eccentric 59 as in Specifications 543,408 and 544,556. Theoretically correct gears may be obtained by moving the work-driving-worm 82 axially by a device such as that for moving the worm 57, and by forming the eccentrics as cams. Specification 772,238 also is referred to.