IMPROVEMENTS IN AND RELATING TO MEANS FOR GENERATING INTERNAL AND EXTERNAL INVOLUTE AND NON-INVOLUTE GEARS

摘要

1,219,081. Gear grinding. PRECISION KINEMATICS (GEARS & MECHANISM) Ltd. 1 Feb., 1968 [17 Jan., 1967], No. 2377/67. Heading B3K. A gear generating machine for generating internal or external spur or helical gears of involute or modified involute tooth form has a bed 1 with a rotary work-table 2 at one end and a stanchion 15 adjustable in centre distance CD towards and away from the work-table, an outrigger slide 16 vertically slidable on the stanchion and a set of three concentric cylindrical individually and conjointly reciprocable and rotatable ram slides 20, 21, 22 mounted in the slide 16, the ram slipe 22 carrying at its lower end means supporting a formed grinding wheel 24. The work-table 2 together with the gear 4 upon which teeth are to be finish ground is rotated by a worm-wheel 6 and worm 7 driven from a motor 10 and during grinding the three ram slides 20, 21, 22 are rotated together in meshing relation to the rotation of the gear 4 through a worm 17 and worm-wheel 18 also driven from motor 10. Ram slide 20 together with ram slides 21, 22 is also reciprocated continuously during grinding by means of fluidoperated piston and cylinder 27, 28. Differential spline couplings 53a, 53b and 54a, 54b provide for the connection and disconnection of the three ram slides under the action of springs 62, 63 and of fluid-operated piston and cylinder units 51, 56, and 52, 55 so as to allow indexing of the grinding head during the non- grinding cycle time. The rotation of ram slides 21, 22 relatively to each other and to ram slide 20 for indexing purposes is effected by motors 42 and 49 and gearing 46, 47 and 44, 45 under programme control means. In order to machine helical teeth an additional rotational motion has to be superimposed on (or subtracted from) the rotation of the ram slide 20 and this is effected by means of racks 19 secured to and reciprocable with the slide 20 the racks 19 having inclined teeth in mesh with corresponding teeth of racks 35 secured to further racks 34 which mesh with gears 33 which themselves mesh with an internal gear 36 secured to the worm-wheel 18. In a modified form shown on the left-hand side of Fig. 2 the single gear 33 is replaced by a pair of parallel mounted gears 37, 38 with lead-change gears 40 therebetween the arrangement being such that with one set of racks 19 varying helix angles of the gear teeth may be obtained by changing the gears 40. The grinding wheel 24 is adjustable to the desired helix angle and means 61 are provided for form-dressing and truing and wear compensating the grinding wheel. In an alternative the spline couplings are placed at the upper ends of the ram slides or may be replaced by differentially acting optical or electrical gratings and cone or flat-faced friction clutches.