Patent GB-557646-A (GB)
Title: Improved method and machine for producing gears
IPC: B23F1/06
Filed: 1942-05-26
Abstract: 557,646. Gear-cutting. GLEASON WORKS. May 26, 1942, No. 7145. Convention date, July 9. 1941. [Class 83 (iii)] In a method of and machine for cutting particularly rough-cut straight bevels a disc milling- cutter is rotated and fed lengthwise of the stationary gear teeth once per revolution of the cutter which is gradually fed to depth and then withdrawn while the blank is indexed. The cutter, Fig. 6, is provided with double sided blades of arcuate profile arranged round its entire periphery. Since the cutter rotates once during the feed travel along the teeth, different blades cut at different points along the tooth space. All the blades have the same radius of curvature r but the centres of curvature are differently spaced along the line 27. Thus the edge 20 which operates at the small end of the blank has its centre at 24, the edge 21 which operates midway along the teeth has its centre at 25, and the edge 22 which operates at the large end of the gear has its centre at 26. The other side edges are similar. For cutting a blank B the cutter C, Fig. 3, is mounted so that its centre y is displaced from its centre of rotation x. Thus while the cutter rotates about centre x from the position shown in Fig. 3 to that shown in Fig. 5 the teeth will move along the tooth space from the small end to the large end. But to compensate for the varying distance between the cutter centre y and the root surface 30 either the cutter or the blank must have a simple harmonic motion in a direction perpendicular to this root surface. Thus during the first 90 degrees of rotation of the cutter from the Fig. 3 position the cutter will move towards the work and this must be compensated by separation of the work and cutter. Similarly during the next 180 degrees of rotation there must be an approach movement between the work and cutter. In the actual machine the cutter makes several traverses across the blank before the full depth position shown in Figs. 3 and 5 is reached and cuts on both its forward and return passages while rotating always in the same direction. The depth feed is independent of the above described harmonic motion required to maintain the cutter at constant depth. When full depth is attained the cutter is withdrawn during the half revolution following after the cutter reaches the Fig. 5 position. In the machine embodiment the harmonic motion is imparted to the cutter-carrying slide 45, Fig. 7, which moves on parallel ways 41. The work slide 50 moves on parallel ways 43, 44 and carries an adjustable plate 51. By adjusting this plate along the inclined upper surface of slide 50 the height of the work spindle may be raised or lowered and the work spindle may be offset if required to cut hypoid gears. Adjustment laterally of the slide 50 is for setting the work to the required cone distance. The work head 52 is angularly adjustable on the plate 51 to set the work to the required root angle. The cutter spindle 46, Fig. 8, carries an eccentric plate 65 carrying an adjustable keyed plate 66 which has a boss 69 entering a bore of the cutter which is secured by a bolt 78. The plate 66 is adjusted to vary the eccentricity of the cutter by screws 74, 75 the setting being indicated by a scale and after adjustment the cutter is clamped to the head by bolts 76. The inserted blades are secured to the cutter body by bolts 72. Preferably successive blades cut on opposite sides. The plate 66 is journalled by needle bearings 80 in an arm 83 which bears on an abutment block 90, Fig. 9, carried by a lever arm 92 pivoted at 93. The lever arm carries an adjustable block bearing on a plate 104 mounted on a lever 105 operated by the feed cam 110 which makes one revolution for every tooth cut, and imparts adjustable depth feed to the cutter. A spring 116 and lever 115 holds the arm 83 against its abutment and the roller 107 against its cam. For any position of the feed cam the abutment 90 is fixed so that the plate 66 causes slide 45 with the cutter spindle to reciprocate on the ways 41 thus causing the cutter centre y to move parallel to the root line of the tooth. As the abutment 90 is advanced by the feed cam during operation the depth feed movement is superposed and the cutter fed to depth. The cutter spindle is driven through the gear train shown in Fig. 15 from the motor 135, the gearing including a splined connection 146 to permit the lateral cutter-spindle movement. A branch from the shaft 143 of this train is connected through change gears 157 and worm gears 162 to the depth feed cam 110. Indexing of the blank is effected from a separate motor 170 the shaft 171 of which is connected through change gearing 201 and worm gears 205 to the work spindle which is held stationary during cutting. The driven worm-wheel 173 of the train carries a ratchet wheel 175 connectible to shaft 177 by a pawl 181 mounted on a stop plate 178. The pawl is urged to engaged position by a plunger 180 and is held out of engagement during cutting by a dog 184 which engages lug 186 and which together with a second dog 188 serves to prevent rotation of the stop plate in either direction. When indexing is to be effected, the dog 184 is moved against a spring plunger 189 by means of a solenoid 195 and pull rod 192, the solenoid being momentarily energized in timed relation with the movement of the feed cam 110 by a switch 196, Fig. 15, operated by a cam 197 on the cam shaft. This occurs when the cutter is withdrawn from the work after completion of a tooth. The dog 184 thereupon releases the pawl 181 which engages its ratchet and connects the motor to the indexing train 201 to index the work. When the stop plate has completed a revolution the dog 184 disengages the pawl and relocks the stop plate thus completing the indexing cycle. A cam 210, Fig. 15, may operate a stop mechanism which cuts out the motors 135, 170 after the predetermined number of teeth have been cut and stops the machine. The work head may be withdrawn for reloading the spindle, moved to working position, clamped and the work chucked by hydraulic mechanism controlled by a valve operated by a hand lever 215, Fig. 7. The invention is applicable to finishing as well as roughing. In some cases ordinary disc milling cutters may be employed. If the abutment block 104 has a concave shape the cutter centre will describe a curved path such as 223, Fig. 20, so that it will cut more deeply at the ends of the teeth, and a crowned form of tooth is obtained. Mating gears cut in this way have a localized tooth bearing. Specifications 514,572 and 528,055 are referred to.