GB496631A - Improvements in thread milling machines - Google Patents

Abstract

496,631. Thread - milling machines. PLOTTNER, W., and HILLE-WERKE AKT.- GES. April 13, 1938, No. 11421. [Class 83 (iii)] A planetary-type thread-milling machine wherein an annular ring cutter is moved axially through the pitch of the thread during the planetary movement has the cutter spindle mounted eccentrically in an inner sleeve which is itself eccentrically mounted in an outer sleeve, relative movement between the sleeves to determine the depth of cut being permitted by resilient means and co-operating projections on the two sleeves. The milling-spindle 2, driven by a belt pulley 5, is mounted eccentrically in an inner bush 3 which is itself mounted eccentrically in an outer bush 4 which is rotated to give the planetary movement of the cutter round the work by worm gearing 7 driven from a motor through belt pulleys, and bevel gearing. Another worm 15 driven from this train drives a wheel 16 rotatable on the outer bush and carrying a hollow ring 17 having a cam projection 18. The inner bush carries a ring 19 adjustably secured by screws 20, 21 which are loosened when the inner bush is to be rotated to adjust the diameter of the planetary movement. The ring carries a cam 22, and is constrained by springs 25, 26 so as to engage a projection 29 on the ring 19 with a projection 30 on the bush 4. The rotation of the inner bush to the work diameter is effected from a hand operated spindle 33 through worm gearing 36 and disengageable spur gears 32, 31. After completion of the cut, the cutter is withdrawn from the work by automatic relative rotation between the inner and outer bushes. Normally the inner bush is entrained by the springs to rotate with the outer bush but at a predetermined point, after the cutter has rotated a full 360‹ round the work the projection 22 on ring 19 overtakes and engage a projection 18 on the rotating ring 17 and thus prevents the bush 3 from rotating with the outer bush 4. This relative movement between the bushes serves to withdraw the cutter from the work. The relative forward movement of the outer bush after engagement of the parts 22, 18 tensions the springs 25, 26 and separates the abutments 29, 30. After an interval, owing to the eccentric rotation of rings 17, 19 the abutments 18, 22 come out of engagement and the relative positions of the bushes are restored by the springs which cause re-engagement of the abutments 29, 30.