Patent GB-516480-A (GB)
Title: Improvements in and relating to machine tools particularly gear generating machines
IPC: B23F5/16
Filed: 1938-06-28
Abstract: 516,480. Gear-cutting &c. MILLER, E. W., and FELLOWS GEAR SHAPER CO. June 28, 1938, No. 19109. [Class 83 (iii)] A gear generating or other machine tool has power actuated means for separating the tool and work holders when the work is to be changed and returning them to an operative position wherein the said power means is automatically disengaged while a depth feed mechanism produces a further advance movement to effect the cutting operation. The cutter spindle 1 carrying a pinion-cutter 2 is reciprocated by a segmental lever 5' having teeth engaging a circular rack 6 on the cutter spindle and operated'from a motor 10 through belt gearing 11 crank shaft 13 and connecting rod 15. Generating movement is imparted to the cutter spindle by worm gearing 16 and for cutting helical gears the usual helical guides 18, 19 are provided for imparting the required twist to the cutter during' its reciprocation. The work spindle 3 is rotated in unison by worm gearing 21 driven by the gear train shown in Fig. 1 from the shaft 13, this train including a telescoping and swinging shaft 22. The ,cutter carriage 25 is movable on a transverse guide 95 on a slide 27 guided on a .rib on the base 26. A screw 30 runs' in a nut 31 which is rotatable in the slide 27, the screw being normally stationary but being rotatable through gears 33, 36, driven from a motor 35 which exerts a constant torque on the gear 33 so as to engage a stop pin 38 against a pivoted abutment lever 39. When a solenoid 44 is energized, the lever 39 is in the position shown in Fig. 11 but when the solenoid circuit is broken, a spring 43 moves the abutment lever and the motor 35 then drives the screw 31 which is held axially by its bearing 32 so that the slide 27 and the bed are moved to or from the work axis. This movement serves for withdrawing the tool from the work for loading and unloading. In order to impart gradual depth feed to the cutter during operation, a depth feed cam 57 driven by a branch train from the work-spindle drive operates a bell crank lever 54 connected through a link 50 to a pivoted link 46 having teeth engaging teeth on the bearing 32 which is thus moved bodily to move the screw 31 and slide 27. A pneumatic or hydraulic cylinder 68 maintains the arm 56 on the depth feed cam 57 and sustains the reaction of the screw 31. The cam is such that the work is rotated for at least a full revolution after full depth is attained. After completion of the operation the motor 35 is energized to withdraw the cutter carriage completely. When the cutter has been fed to depth, the slide 27 is clamped to the bed by means of a gib 73. A stud 74, Fig. 5, secured to the slide 27 is bored to receive the eccentric part 77 of a pin 76 journalled to a clamping block 75. An arm 78 connects the pin to a solenoid 80 which when energized rotates the pin 76 and forces the block 75 upwards to clamp the slide. A spring disengages the clamp. The cutter spindle is mounted in a holder 83 carried on trunnions 84 which permit swinging movement of the holder to relieve the cutter on the return strokes. A relieving cam 85 on the shaft 13 acts through lever mechanism 87, Fig. 1, on a link 90 connected to the spindle holder by pins 91. The pins pass into holes in bushings 93 fitted in the carriage 25, the holes being shaped as shown in Fig. 8 so that the pins engage against the seating surface 94 during cutting but may be moved back on the relieved return strokes. The direction of the relief may be varied by setting over the carriage 25 along the guide 95 by means of a screw 96 so that the relief which is in a direction parallel to the line e d, Fig. 12, is inclined at an angle of about 7 degrees to the line c d joining the tool and work centres. The complete withdrawal of the cutter carriage may also be made in an inclined direction and for this purpose the screw 96 is automatically operated during carriage withdrawal by a change-gear train, Fig. 2, driven from the wheel 33 on the screw 30. The main motor 10 is controlled by a switch 104, Fig. 13, and the motor 35 by a reversing switch 105. A limit switch 106 is worked by a dog 107 on the slide 27 when the desired carriage withdrawal has been made. The solenoid 44 is actuated to move the stop 39 into position at the desired point in the approach movement by a switch 108. The cutter position at the start of the feed is accurately determined by rotating the nut 31 by a gear train operated from the handle 123, Fig. 2. When the shift motor 35 is reversed the solenoid circuit 44 is broken by a switch 110 and the stop lever 39 is withdrawn. The bed-clamping solenoid 80 is energized and de-energized at the required times by switches operated by pins 112, 114 on the depth feed cam. In order to adapt the machine for cutting external gears the lever 56 carries a second arm 125 whose roller engages the opposite side of the feed cam. The direction of fluid pressure in the cylinder 68 is reversed and the feed then takes place in the opposite direction. The seats for the stop bar 91 are also reversed by means of gears 128. The relieving cam 85 may also be displaced through 180 degrees or alternatively the cutter may be reversed to cut on its up-stroke.