Patent GB-310306-A (GB)
Title: Improvements in gear tooth finishing machine
IPC: B23F19/06
Filed: 1928-01-23
Abstract: 310,306. Marks, E. C. R., (Pratt & Whitney Co.). Jan. 23, 1928. Gear-cutting; tools.-In a machine for finishing gear teeth the blank is carried on a fixed oscillatory spindle provided with indexing means and the tools are mounted on a slide which is reciprocated by generating cam-mechanism to move the tools in the plane of the blank, so as to take a shaving cut over the flanks of the teeth in the manner described in Specification 249,938. The hollow sleeve 12 surrounding the work spindle 30 is oscillated by means of an arm 13 connected by a rod 14 to an adjustable crankdisc 16 on a shaft 17. The crank-disc has peripheral teeth and is driven from a motor 18 through gearing 19, clutch 23, and pinion 21. The clutch 23 is operated by a lever 29 and coacts with a friction brake 24 so that when the lever 29 is operated to disengage the clutch, the brake engages a fixed surface to bring the machine quickly to rest. The blank W is secured in a collet chuck 31 and its spindle carries a cam 32 having two oppositely disposed surfaces such that the intercepts between the cam surfaces on lines tangential to the involute base circle are all equal in length. The tool slide 35 is provided with adjustable opposed heads 36 having rollers 37 engaging the cam 32, the slide being thus operated in timed relation with the oscillating work spindle. The tool-holding heads 38 are adjustable on the slide and are provided with straight-edged tools 40 which engage the teeth near the extreme oscillated positions of the work-spindle. The blank is indexed during the mid point of the oscillation in one direction so that all the teeth are cut when the blank has completed one revolution. Preferably the blank is rotated through four revolutions to complete the teeth and the tools are fed at the completion of each revolution. The feed mechanism comprises stepped cams 42 mounted on shafts 41 and engaging screws on the heads 38. The cam shafts are intergeared and are rotated intermittently at each rotation of the blank by the engagement of a wheel 47 with a tooth 48 on an arm 49. The arm is normally swung away from the path of the gear 47., A crank 50 on the main shaft 17 operates a ratchet wheel 54 having the same number of teeth as the blank and secured on a shaft 55 carrying a notched disc 56 co-operating with a lever 58 on the vertical support of the arm 49. Thus, on completion of a revolution of the blank, the lever 58 drops into its notch and moves the arm 49 and tooth 48 into the path of the wheel 47 to impart feed to the tools. The gear W is positioned with respect to the tools by means of a plunger 61 adapted to engage the gear teeth. This plunger is normally held down by a spring 62 and is raised when required by means of a hand lever 68 connected to a lever 69. Interlocking means are provided to ensure that the plunger is not raised while the machine is operating. The main operating-lever 29 is connected to a link 70. When the positioning plunger is in position, a bar 71 connected to the lever 69 extends into the path of the lever 29 which therefore cannot be operated and when the main clutch is engaged the link 70 is in the path of the bar 71 so that the plunger can. not be raised. In order to effect the indexing in one direction of motion of the spindle, the indexing and locking cams are mounted on a swinging frame 75, operated by a cam 76. The spindle 30 carries an index-plate 84 one notch being engaged by a locking-bolt 86 on a plate 87. The locking-bolt is withdrawn bv a cam groove 90 on a plate 91 freely rotatable on the sleeve 12, this plate being operated by a rack bar 92, actuated by a cam 83 on the frame 75. The plate 87 is mounted on an arm 88 which also carries a rotatable arm 95 carrying a pivoted indexing pawl 96, the indexing being effected by moving the arm 95 relatively to the sleeve 12 while the pawl is engaged in a notch. A lever 98 pivoted at 99 to the plate 88 is connected through a link 101 to a pivoted arm 102. In operation, after withdrawal of the locking bolt, the lever 98 is rocked by a cam 97; the pawl 96 is thus first engaged with the indexing wheel and then the plate 95 is moved to impart the required indexing movement. The pawl 96 may be positively held in a notch during the indexing movement by means of a cam 97a and roller 96a. To stop the machine on completion of a gear blank, the shaft 55 carries a pinion 117 engaging a gear 118 on a shaft 119 carrying a cam disc 120. After the required number of revolutions of the work-spindle the disc 120 moves a spring bolt 122 to release a lever 124 and cause the main lever 29 to be moved to inoperative position. To facilitate setting-up, the machine may be manually operated from a hand wheel 135 connected by chain gearing to the shaft 17. Blanks of different diameters may be accommodated by varying the thickness of the'member 34 which supports the slide 35.