Patent GB-638437-A (GB)
Title: Improvements in or relating to gear-cutting
IPC: B23F5/14
Filed: 1947-08-12
Abstract: 638,437. Gear-cutting. LEUTHOLD, B. Aug. 12, 1947, No. 22409. [Class 83 (iii)] Relates to a gear-cutting machine, convertible to cut either involute gears or racks, comprising a reciprocable multi-tooth rack-cutter 31, a rotary work-table 34 operatively associated therewith, first and second drive-transmitting means 43, 44 and 46, 47 adjustable to cause either rotary or traverse motion of the table 34 when cutting gears or traverse and cross-feed motion when cutting racks, and drive-control means A, B, also adjustable for either gears or racks. In such a machine, the drive and control means, when adjusted for cutting gears, move the table 34 with intermittent combined rotary and forward traverse cutting movements followed bv reverse traverse without rotation for the indexing phase, and, when adjusted for cutting racks, move the table with intermittent cross-feed movements towards the cutter 31 followed by combined reverse traverse and cross-feed movements from the cutter for the indexing phase. For cutting spur-gears, the blank 32, mounted on a slide 35, Figs. 1 and 3, is traversed past the reciprocating rack-cutter 31 by a screw 13 and is simultaneously rotated by a worm 40, the screw and worm being rotated by a shaft 54. The shaft 54, Fig. 14, is rotated either by a ratchet-wheel 64 advanced by a pawl 63 actuated by a lever connected to the cutter-slide 33, or by an oppositely-rotated, continuously-driven, pulley 69. The ratchet 64 and pulley 69 also rotate a cam-drum 42 which controls the sequence of operations of the machine. After a number of teeth have been cut, according to the length of the cutter, a cam 76 on the drum 42 operates a clutch 70 which is held, by a spring-toggle, to engage a gear 72. A cam 79 then moves the levers 80 to engage the pulley 69 with the gear 72, thus rotating the drum 42 at a faster rate through gears 73, 74 and reversing the rotation of the shaft 54 via gears 73, 74, 66, 65. This latter reversal returns the blank to its initial position. During this return, the blank is not rotated, the drive to the worm 40, via shafts 10 and 11, Figs. 1 and 7, being interrupted by a cam 1 disengaging a clutch 8 via levers 2, 4 and 28, the clutch lever A being in the position II. The second traverse of the blank is initiated by the cam 79 disengaging the pulley 69, a second cam 76 reversing the clutch 70 and the cam 1 releasing the lever 2 to allow the clutch 8 to be re-engaged by a spring. To adjust the slide 35 with respect to the cutter, it is moved by a manually-rotated nut 53 engaging a screw 14 secured to the bed. For rack-cutting, the blank 51, Fig. 4, is mounted on the slide 35, the clutch lever A, Fig. 7, being moved to position I to invalidate the lever 2 and the drive from the shaft 54 being rearranged so that the screw 14 is rotated by the shaft 52 and nut 53 and the screw 13 is rotated by the shaft 10. In addition, a lever B, Fig. 10, is moved to position I to render operative a catch 55 which is pulled by a spring 56 to retain the clutch 8 in a disengaged position and thus cut off the drive to the shaft 10 and hence the screw 13. Rotation of the shaft 54, due to the ratchet 64, now rotates the screw 14 to advance the rack blank into the cutter. When the rack is fed to depth, the cams 76 and 79 act to reverse the shaft 54 and, almost simultaneously, a snail cam 26, mounted on the shaft 54 and inoperative in the reverse direction, turns a bell-crank 24 to release the clutch 8. Thus the blank is moved away from and across the cutter. This movement continues until a cam 15, Fig. 7, moves a lever 16 and hence levers 19, 21 and 28 to disengage the clutch 8, allowing the catch 55 to be re-engaged. A second in-feed of the blank then commences. A few only of the cutter teeth are usually arranged to cut, the other teeth playing in finished spaces until the first teeth become worn. For cutting helical gears or inclined teeth on the racks, the cutter-slide head is set over at the required angle. Specification 109,256, [Class 83 (iii)], is referred to in the Provisional Specification.