Patent GB-321443-A (GB)
Title: Improvement in method of and machine for cutting gears
IPC: B23F21/12
Filed: 1928-08-08
Abstract: 321,443. Withers, J. S., (Scurlock Gear Corporation). Aug. 8, 1928. Gear-cutting; milling-cutters. -In a method of cutting spiral bevel gars, a gear blank 26 and a toothed cutter 13 are rotated simultaneously at predetermined speeds and the cutter is fed along a generator of the root cone of the blank, Fig. 19, the cutter being arranged so that successive teeth of the cutter move into successive tooth spaces of the blank and travel substantially in the longitudinal direction of the blank tooth spaces. The base 10 carries a power shaft 15 provided with a clutch 72 operated from a handle 70 and drives, through change gears 16a, a main shaft 17 which is connected through gears 19, 20 with the work spindle 21, mounted in a headstock 14. The work 26 is carried on an arbor 22 which is expanded to grip the work by means of a headed rod 25 which is moved longitudinally by means of a handle 28, acting through lever mechanism 29. The front bearing of the work-spindle is of conical form and wear may be taken up by means of adjusting nuts. The base carries a swivelling frame 11 carrying the cutter spindle 43 which is driven from the shaft 17 through gearing, Fig. 20, comprising shafts 30, 31 a vertical shaft 12 whose axis forms the pivotal axis of the frame 11, reversing bevel gearing 34, shaft 33, change gearing 39 and worm gearing 41. The centre lines of the cutter teeth are tangential to a circle concentric with the cutter axis and the teeth are also inclined longitudinally to correspond with the spiral angle of the teeth to be cut. In order to complete the teeth at a single operation the cutter is fed across the face of the blank during the cutting. For this purpose the swivel frame is adjusted by a scale according to the cone angle of the blank and secured by bolts 38, and the cutter is mounted on a slide 46 which is held against guides 45 by means of plates 48. The cutter-slide feed-screw 57 is driven from the shaft 33 through a vertical shaft 52, feed change gears 54, and worm gearing 55. The feed-screw may also be driven direct from the shaft 52 by means of spiral gears 67 in order to give a quick return movement to the cutter slide, the feed and return movements being controlled by a clutch 60 operated by a hand lever 75 mounted on a shaft 83. When the hand lever is operated, a rod 77 moves a stop rod 78 from a stop 79 on the cutter slide and a spring 76 is compressed. Return movement of the clutch lever is prevented by a finger 80 coacting with a weighted latch lever 81. This gives the feed movement to the cutter slide. A hand lever 85 carries a projection engaging a slot in a bolt 87 whose end projects into a groove 88 in a slide 89 carrying a rod 90. Operation of the lever 85 removes the bolt from the slide which is then moved down by a spring 91, causing the rod 90 to engage a bell-crank 92 which disengages the latch lever of the clutch 60 and causes the spring 76 to push the clutch over to reverse the feed. When the cutter reaches its original position, the stop 79 engages the rod 78 to shift the clutch 60 to a neutral position and stop the feed. In order to withdraw the gear blank from the path of the cutter on the return movement, the slide 89 is provided with an inclined projection 98 engaging a slot in a sleeve 100, Fig. 16, surrounding the screw 101 which is rotated from its end 104 to adjust the headstock. A scale 103 is provided for this adjustment. Thus when the slide 89 is moved to reverse the cutter movement, the screw 101 is shifted bodily to carry the work headstock 14 away from the cutter. For automatic operation of the cutter-slide reversal the cutter-slide may carry a projection 110 engaging a gear segment to slide a rack 112, which through a lever 113 causes the withdrawal of the bolt 87. A handle 95 is provided for manually restoring the slide 89 to its upper position. For cutting right-hand spiral gears a modified cutter, which is traversed' in the opposite direction, is employed. The shaft 15 drives by means of a belt 74 an oil-pump which delivers oil to the work through a hose 73a.