Patent GB-729273-A (GB)
Title: Improvements relating to a machine and method for generating bevel and hypoid gears
IPC: B23F9/10
Filed: 1953-07-06
Abstract: 729,273. Grinding gears. GLEASON WORKS. July 6, 1953 [July 12, 1952], No. 18742/53. Class 60. [Also in Group XXII] A method of generating a tapered gear by relative motions of the work and a grinding or milling tool about the axis of the work and about the axis of the imaginary gear represented by the tool consists in moving the tool relatively to the work in one direction depthwise of the teeth being cut as the generation proceeds towards approximately the midpoint of the tooth and then moving the tool in the opposite direction. The gear G is adjustable by means of slideways 27, 29 and 32 to position it correctly in relation to a face-mill T or face hob, the gear being either intermittently indexed or continuously rotated. The cutter having alternate outside and inside cutting edges lying on two concentric circles or on a single circle is mounted for a slight degree of axial movement. If a taper hob is used, it is carried in a support mounted for slight axial movement on the cradle 21. Fig. 9 shows a conventional drive for a machine using a face hob T<SP>1</SP>. Generation takes place in one direction of roll, the clutch 68 is then set in neutral and a separate motor returns the cradle to its initial position. If a taper hob is used, extra gearing is necessary to impart motion from the shaft 54 to the angularly related cutter spindle. If a face-mill is used, the differential gearing 56, 57, 58 and gearing 73-76 is omitted as the cutter does not need to rotate in time with the work or cradle; an indexing mechanism is provided between the shaft 60 and the work-drive 61; and a separate reversing mechanism is provided between the main shaft 49 and the shaft 60, there being no need to reverse the cutter drive. Spindle mounting.-The shaft 24, Fig. 2, carrying a face-mill cutter is mounted by roller bearings 78 in a cup 81 which is rotatable by means of an arm 88 engaging the cup through clutch teeth 89. The cup is formed with a helical front face 83 held against a similar surface 85, rollers 84 being interposed, by a spring 87. Clutch teeth 90 allow for the axial movements without bottoming. The arm 88 engages a roller 92 mounted on a slide 94 adjustable about the cradle axis 22 on a fixed member 97. The effect of the movement of the cutter is to relieve the tooth profiles and to crown the teeth by removing extra material from either side of a mean line 102, Fig. 10. By adjusting the roller 92 and arm 88, the mean line 102 may be offset or additional material may be left on either side of the mean line. In the latter case, the cutter is moved towards the work as the generating motion approaches the mean position. The modification applied to the teeth is, in any case, asymmetrical. This is compensated for automatically, if both gear and pinion are cut in the same way, due to the opposite hand of the tooth spiral. If such asymmetry, however, is desired, one member of a pair may be cut with no, or less, axial movement of the cutter. Instead of milling-cutters, grinding tools may be used. Specification 544,556, [Group XXII], is referred to.