Patent GB-884741-A (GB)
IPC: B23F19/00
Filed: 1958-12-24
Abstract: 884,741. Gear-cutting. GLEASON WORKS. Dec. 24, 1958 [Dec. 30, 1957], No. 41663/58. Class 83 (3). A method of cutting a non-generated spiral bevel or hypoid gear G with a rotary tool C consists in relatively feeding the tool and gear in the direction of the tool axis, the rate of feed being varied to produce tooth surfaces which are helocoids of varying lead. The work G is indexable on a head 29 adjustable about a vertical axis 33 on a slide 32 adjustable on a carriage 35 which can be moved to-and-from working position. The cutter is axially movable on a slide 24 adjustable along inclined ways on an adjustable slide 21. It is rotated by a motor 37, Fig. 3, through an electromagnetic clutch brake unit 38 and speed-change gears 43, against the resistance of a backlash-preventing hydraulic pump 56. The spindle 26 is guided in its axial movement by a key 53 engaging ball-bearings 54, the movement being controlled by a bracket 62 carrying a cylindrical member 75 urged against a sliding follower 76 by springs 71 acting through levers 67. The follower 76 is connected by a ball-joint 77 to a slide bar 78 which is reciprocated ten times for each rotation of the cutter. The stroke of the cutter movement is varied by adjustment of a circular slide 88 by a worm 93 against graduations on the bracket 62 and a dial 95. The relationship between the axial movement and the rotary movement of the cutter may be varied continuously during cutting by oscillating the member 75 on the slide 88 by a double-acting hydraulic piston 105, Fig. 6, having rack teeth engaging teeth on the member. The movement is limited by micrometrically adjusted stops 113, 114 embracing a projection 112 on the member. The slide bar 78 is moved horizontally by the cam 81 on roller bearings in a vertically movable slide 123, Fig. 8. The slide 123 is moved by a bell-crank 137 acted upon by two fluid-operated pistons movable between limits adjusted by micrometric devices. Movement of the slide alters the relative positions of the member 75 and its follower 76. Both of the adjustments which affect the relationship of the member 75 and the follower 76 to the spindle movements result in modification to the size and location of the tooth bearing areas on the work gear. In particular, angular adjustment of the member 75 increases the length of the bearing area, movement of the slide 123 affects its location, and angular adjustment of the slide 88 controls its magnitude. If the member 75 is positioned centrally, the cutter is not moved axially and the gear is simply form-cut. The work gear is initially adjusted so that the cutter teeth 159, Fig. 13, rotate about an axis 27<SP>1</SP> perpendicular to the root plane of the gear instead of about an axis 27<SP>11</SP> perpendicular to the face plane of the gear as in Specification 750,034. The tooth bearing is controlled by a cam 183 acting through a bell-crank lever 184 and a valve 182 to supply fluid alternately to move the member 75 and slide 123 in one direction or the other. The cam 183 shown is effective only while the last four blades are cutting. The machine may be adjusted to modify the tooth bearing on one side only of each tooth, or to cut helicoidal surfaces of constant axial lead as in Specification 750,034, or of varying axial lead. Clutches 61, 80 permit relative adjustments between the cams 81, 183 and the cutter. Cutters.-The cutter has eight blades IVIII, Fig. 15, and two gaps IX, X to allow indexing of the work by a cam coaxial with the cam 183 or by means as described in Specification 818,887. Blades I, III, V and VII are inside-cutting blades having their edges progressively offset as shown in Fig. 17. Similarly, the blades II, IV, VI and VIII are outsidecutting blades, the last two blades VII and VIII being finishing blades. Fig. 19 shows the path 177 of a point 178 on the blade VII and of a point 179 on the blade VIII as the blades are fed to depth while cutting from the small to the large end of a tooth space. The cutter blades have helicoidal surfaces 194, 195, 196, are located by pins secured in notches 193 in the cutter body, and are secured in a V-groove 191 by screws 192. The pressure angles X, Y, Figs. 17 and 18, are 10 and 30 degrees respectively, the clearance angles V, W, Fig. 19, are both 6 degrees and the side clearance angle is 2 to 70 degrees. Specifications 818,888, 884,744 and 884,745 also are referred to.