GB758135A - An improved speed setting device for machine tools - Google Patents

Abstract

758,135. Electric control systems. RUHRSTAHL AKT.-GES. May 12, 1954 [May 12, 1953; April 13, 1954], No. 13907/54. Class 40(1) [Also in Groups XXII and XL(b)] A machine tool comprises means 8-10 for adjusting the driving means 5 associated with a tool holder 3, the individual tools 15 I-V being available in a storage device 13 such that the adjustment takes place when a tool 15 II is extracted from the storage device and prior to fitting it into the tool holder. In a drilling machine, the spindle is carried on a sliding head 1 and is rotated by a motor 2 through the variable speed gearing 5. The gearing 5 is adjusted by a motor 4 rotating bevel gears 6, 7, the latter engaging a threaded shaft 8 having the rack portion 9 engaging the pinion 10 on the shaft 11 connected to the gearing 5. The setting is indicated on a dial. The gearing may be replaced by stepped gears controlled either by a circular hydraulic valve or by electromagnetic clutches. Each tool 15 in a compartment 14 in the bin 13 is associated with a potentiometer 18 set according to the speed required. When a tool is extracted, a switch 16 is closed and a relay 22 supplies current to rotate the motor 4 in one direction or another until a contact 19 carried on the spindle 8 has been moved to a position of balance in a bridge circuit comprising the potentiometers 18, 20. In a modification, the potentiometer 20 is replaced by a generator driven by the drill spindle. In a further modification, an additional fixed-tapping potentiometer is provided so that, when a tool is extracted from the chuck, or when the tool is withdrawn from the work, or when the drill motor is stopped, the potentiometer 20 is immediately moved to a central position. The time for the next speed change to be effected is thus reduced. Additional sets of potentiometers may be provided for adjusting the feed or drill pressure. In another modification, the tools 36, Figs. 5 and 6, are carried in clips 38 and supported by brackets 50 in a drum rotated by a handwheel 34 to bring them successively into a position where they can be extracted. When a tool is extracted, the arms of the clip 38 move inwardly to close a switch 39 thus operating a solenoid 47 to lock the drum by a catch 41 and to energize a setting circuit according to which of a series of switches 48 is operated by a cam 49. In a final modification, the tools 58, Fig. 7, are carried in containers on a chain 55. When the tool required is extracted from the top of a casing 51, a photoelectric device 60, 61 operates means 65, 66 to lock the chain and to render operative speed adjusting means which have been selected by the actuation of an appropriate switch by a cam disc on a shaft 53.