GB720478A - Improvements in or relating to electrically driven feed mechanism for machine tools - Google Patents

Abstract

720,478. Control of two motors. WOLLENHAUPT, J., and MAECKER, K. Nov. 5, 1951 [Nov. 6, 1950; April 14, 1951], No. 25878/51. Class 38 (3) [Also in Group XXII] Relates to an electrically-controlled and selfcontained feed mechanism for machine tools in which a worm wheel 1 is loosely mounted on the feed spindle and engages a shaft mounting a planet wheel geared to a high-speed motor for withdrawing the too] from the work. Another planet wheel is rigidly coupled with the first and engages a gear wheel on the feed spindle. The worm wheel 1 also engages a worm 10 carried by a hollow shaft 11 in which is rotatably mounted a shaft 12 driven through gearing by a slow-speed forward feed motor. The shaft 12 carries a helical gear 16 which engages in the hollow of the shaft 11 and transmits the drive from the feed motor to the worm wheel 1. When a part carried by the tool-holder meets a mechanical stop which is positioned in accordance with a required depth of feed (or the torque of the feed motor is increased in any other manner), the gear 16 moves out of the worm shaft and turns an arm 20 which actuates switching means for stopping the forward feed and starting the quick return movement of the tool. As shown, the arm 20 carries a transverse lever 21 which engages switch-pins 24, 25 of the limit switches 26, 27. The switch-pins operate against adjustable springs 28, 30, supported on plates 29, 31, which are adapted to engage a plate 33 associated with spring 32. In a modification, Figs. 5-7 (not shown), the shaft 12 carries a bevel wheel which drives, through two planet wheels, another bevel wheel on the shaft 11. The planet wheels are mounted on a connecting shaft, and the ends of the shaft bear against two spring-biased ramps, the inclined surfaces of which engage the pins of the limit switches. The high-speed motor may have an electromagnetic brake which slips when the torque, transmitted by the feed motor, after the latter has been switched off, exceeds a predetermined value. The switching means may be associated with a timing mechanism which commences operation when the force due to the springs which regulate the action of the limit switches is exceeded. At the end of the set period the high-speed return movement of the tool is initiated.