GB610369A - Improvements in machines for grinding the flanks of threads, chiefly in worms - Google Patents

Abstract

610,369. Thread-grinding machines. MORT, G. N. M. April 1, 1946, No. 9977. Convention date, Aug. 14, 1945. [Class 60] A machine for grinding flanks on worms and screw-threads, of the kind wherein a variable lead action is obtained by means of a slide coupled to the work-holder and movable in a rotatably adjustable slide-way by means actuated in co-ordination with the rotation of the work-holder is characterised by the provision of a change-speed gear coupling the said means to the rotatable work-holder, whereby a continuous range of pitches can be obtained without the use of a lead screw or removable gears. A motor 1, Fig. 2, rotates, through gears 3, 4, a work-spindle 2 and a bevel gear 5 which latter rotates, through change-speed gears 6, a shaft 9 carrying a pinion 10 meshing with a rack 11 movable transversely on a work-slide 17. The rack 11 is pivoted at 12 to a slider 13 movable in a slideway 14 of an angularly adjustable plate 15 mounted on the machine bed. A transverse movement of the rack 11 and the movement of the stub 13 in the fixed slideway 14 causes the required longitudinal movement of the work slide 17. An arrangement for indexing the work in the grinding of multi-thread screws includes two half-spindles 35, 36, Fig. 16, driven normally at the same speed, by worm gears 38, 39 and planet pinions 40, 41, sun gears 42, 43 being held fast. The rotary indexing motion is given to the half-spindle 36 by rotation of the sun wheel 43 by a worm 45 driven from a motor constantly under load, the worm 45 being locked during normal operation by a lever 46 on a shaft 52 engaging a cam 47, not shown, on the worm shaft. The lever 46 may be disengaged from the cam by rod-and-tappet mechanism, Fig. 15, (not shown). Also keyed to the shaft 52 is a lever 49 engaging one of a series of cams 50 driven at the same speed as the shaft 36. The cam 50 has as many notches as there are threads to be ground and when the lever 49 engages one of these, the lever 46 is pressed by a spring 51 (not shown), to engage the cam 47 and stop the rotary indexing motion. An arrangement for dressing the grinding wheel 32 includes, mounted on the work slide 17, a driven spindle 18, Fig. 3, rotating a member 20, running in a bearing 22, which can be swung about a pivot 24 to bring the dressing device into an inoperative position. The member 20 carries a pivoted plate 25, adjustable to give the correct helix angle, carrying another plate 26 pivoted in a vertical plane, to give the correct pressure angle. A sleeve 30 carrying a diamond tool 31 is reciprocated on a slideway in the plate 26 by a motor 29 carried on the member 20, so that as the spindle 18 and thus the member 20 rotates and the slide 17 is given a translational movement, the tool 31 is reciprocated across the grinding wheel 32 tn dress it to the desired outline.