Patent GB-522780-A (GB)
Title: Improved process and machine for cutting straight or helical teeth on cylindrical gearwheel blanks
IPC: B23F17/00
Filed: 1938-11-16
Abstract: 522,780. Gear-cutting. CAPELLE, J. J. Nov. 16, 1938, Nos. 33305 and 33306. Convention dates, Nov. 16, 1937 and Nov. 15, 1938. [Class 83 (iii)] Spur or helical wheels are generated by means of a rack tooth cutter, which is reciprocated in an inclined path across the continuously rotating blank, the resultant of the blank rotation and the tool reciprocation being such as to give the required straight or helical tooth line, and the generating movement being obtained by a slow tangential movement of the tool combined with a corresponding additional rotation of the blank which is completely finished at the end of a single generating- movement. The tool may be considered as located in a pitch plane P which moves with uniform velocity V and reciprocates along a path AB which is such that the resultant tool path along the moving plane P is a sinusoidal curve having straight line portions T spaced apart by a distance p representing the pitch or a multiple of the pitch of the gear to be cut. The required movement along the line AB is obtained by a rectilinear movement along the line x, x<SP>1</SP> and a small movement of the same frequency along a perpendicular axis Oy, the latter axis being inclined at an angle y to the direction of the velocity V. The generating movement is superposed on the above described cutting movement and consisting of a slow movement v along the pitch plane P and a corresponding additional rotary movement of the blank. For cutting helical gears the tool carriage is set over at the helical angle in addition to the inclination y required for spur gears and for cutting conjugate helical wheels the carriage is inclined in one direction for one wheel and in the opposite direction for the other. With the same adjustments gears of different pitches may be cut by using the appropriate tools, these pitches being submultiples of the largest possible pitch. In one form of construction, Fig. 3, the blank 2 is continuously rotated on a fixed support 3 and the tool head 5 moves along guides 4 tangentially of the blank on its generating movement v. The head is inclined to the horizontal at the required angle y and carries a reciprocating tool slide 7 which moves along axis x, x<SP>1</SP> and is mounted on a slide 6 to which movement on guides 20 in the perpendicular direction Oy is imparted. The tool 8 is angularly adjustable and its leading face is set parallel to the plane of the blank. In a modification the tangential movement v is imparted to the blank carriage 3 instead of to the tool. The blank carriage is moved along guides 9 by a screw spindle 10, Fig. 6 and carries a rotary table 11 by which rotary movement is imparted to the blank by worm gearing 12 driven from the pulley 43 on a driving shaft 30 through gearing 44, shaft 17 and change gears 16. The tool support 4 is movable to and from the blank axis along ways 18 and carries a head 5 adjustable around a central shaft 19 driven by gears 28 from the shaft 30. The front part of the head 5 carries slideways 20, 20, for the head 6 on which the reciprocating tool slide 7 is mounted. The motions of the slides 6, 7 which are of the same frequency are both derived from the shaft 19. A cam 24 on this shaft operates an arm 23 to rock a shaft 21<SP>1</SP> carrying a crank which through a rod 22 rocks a cylinder 21 pivoted at 35. A piston in this cylinder carries a pivoted rod 34 adjustably connected to the head 6 at 45 to impart the small movement along axis Oy. The shaft 19 is also connected through rod 27, rock shaft 26<SP>1</SP>, adjustable arm 26 and finger 25 to the tool slide 7 which is thus reciprocated along the line x x<SP>1</SP>. The tool 8 is set so that its acting face is horizontal and is relieved on its upward strokes. The required correction of the blank rotation in accordance with the generating movement v of the blank carriage is effected by means of differential gearing 39.