Patent GB-706080-A (GB)
Title: Method and machine for cutting gears
IPC: B23F5/12
Filed: 1952-05-07
Abstract: 706,080. Gear-cutting; gear-grinding. GLEASON WORKS. May 7, 1952 [May 25, 1951], No. 11568/52. Class 83 (3). [Also in Group XXIII] A method ot cutting a gear comprises turning the gear 21 about its axis and in time therewith pivoting a cutting tool 22 about an axis which extends in the region of the cut and within the imaginary surface embracing the tops of the gear teeth. In cutting a plain spur gear, the tool 22 is pivoted about an axis 26 lying on the base cylinder 25. It is shown in the Specification that the tool must be turned through # radians while the work is turned through #-sine # radians. The work is indexed either by one or more teeth after each stroke of the tool, or by one tooth after one tooth surface has been finished. When cutting bevel gears, the tool 22, Fig. 4, is pivoted about an axis 26 lying on the base cone and, while the tool turns through # radians, the work is turned through approximately (#-sin#) sec y radians, where y is the pitch angle. The tool is fed continuously or on its non-cutting strokes. The method requires fewer cutting strokes than conventional methods and results in a surface finish as shown in Fig. 6. For rough-cutting, the tooth spaces may first be roughed out to the shape shown in dotted lines in Fig. 8 and the tool then fed inwardly or outwardly by uniform increments so that the curved tip 34 performs the rough cutting. The cutting-edge 23<SP>1</SP> may be relieved by inclining it to the direction of movement 22'. In a machine for carrying out the method, the work is carried on a rotatable support 41 and the tool is mounted for reciprocation on a carrier 42 rotatable about the axis 26. For simplicity, no means are shown for advancing the tool radially or relieving it but the tool is reciprocated at a constant or varying velocity by a crank 43 rotated by a motor through a shaft 52. The carrier 42 is also rotated by the motor 48 through change gears 55, reversing means 59 and worm gear 60, 61. To correlate the work and cutter movements, the work is rotated by the shaft 52 through change gears 97, axially-fast shafts 89 91 and gearing 92, 93 and the motion is modified by a barrel cam 72 rotated through the shaft 58 carrying the worm 60, change gearing 63 and the geared shafts 66, 68. The change gears 97 determine the helical or spiral angle of the teeth and index the work. The cam 72 controls a follower 74 mounted on a slide 75 which carries an angularly-adjustable slotted plate 82 engaged by a pin 81 on a transverse slide 79. The slide 79 carries a rotatable sleeve 88 engaging the oppositely threaded shafts 89, 91. Thus, rotation of the cam 72 and the consequent movement of the sleeve 88 imposes an additional rotary motion on the shaft 91 relative to the shaft 89. By inclining the plate 82 in the opposite direction the motion may be subtracted instead of added. For gears of opposite helical or spiral angle, a reversing pinion is inserted in the gears 97. By modifying the gearing, the track of the barrel cam may extend around the cam through several turns. The change gears 55 determine the number of cuts for each tooth, i.e. they determine the surface finish. When one side of each tooth has been cut, a tool of opposite hand is installed, the rotation of the worm 60 is reversed by the means 59, the plate 82 is inclined in the opposite direction and the roller 74 reset along the cam 72. Modifications of tooth profile.-The pressure angle or tooth bearing may be modified by a displacement of the pivot 26. The profile curvature may be modified by adjusting the plate 83, and/ or by altering the phase relationship between the rotation of the shafts 58 and 66. Spherical involute, octoid or straight profiles may be produced. Tools.-The tool may be a planing, milling or grinding tool having the profile illustrated in Fig. 1.