Patent GB-803205-A (GB)
Title: Improvements in or relating to apparatus for the exact control of the position of moving objects, and more particularly for the exact control of the movement of machine tool carriages
IPC: B23B39/04
Filed: 1956-04-27
Abstract: 803,205. Drilling; machine-tool details. LINDNER G.m.b.H., H. April 27, 1956 [April 29, 1955], No. 13069/56. Class 83 (3). [Also in Group XL (b)] A machine-tool carriage is controlled photo-electrically so that in its movement to an adjustable desired-position, it is slowed down shortly before that position is reached and then stopped exactly at that position. Table 1 carries a scale 56 composed of gaps 57 in front of openable-diaphragms 59. The light-ray from a fixed-source 60, falling through an open gap 57<SP>1</SP>, illuminates fixed photocells 67, 68 via diaphragms 63, 64, and fixed prisms 65, 66. The photo-cells are connected as arms of a bridge-circuit a, b, c, d, and amplifier valves 73, 74 are connected as shown in diagonal c, d. In operation, assuming that the table is to be moved to a new setting, a key 31 is depressed, thus actuating a clutch electromagnet 18 and contactor 23; rapidtraverse results until an opened measuring-gap 57<SP>1</SP> comes into the light-path. Photo-cell 67 receives illumination, and the bridge-unbalance causes a relay 75 to operate, which actuates a tripping-magnet 44, thus releasing key 31 ; disconnects voltage from contact 31<SP>2</SP> by opening contact 75<SP>3</SP> to ensure against unintended reconnection, and holds connected-contactor 23 over contact 75<SP>2</SP>. Clutch-magnet 18 is deenergized as contact 31<SP>1</SP> opens, and clutch 13 changes over to wheel 12, thus initiating slowfeed. When table 1 reaches its setting, both photo-cells are equally illuminated, the bridge is balanced, relay 75 drops out, contactor 23 is disconnected as contact 75<SP>2</SP> opens, the motor is de-energized as contacts 23<SP>1</SP>, 23<SP>2</SP> open, a motorbrake 26 is applied as contact 23<SP>3</SP> opens, the table stops and the circuit returns to its original condition. For movement of the table to the right, key 32 is depressed and a similar sequence of circuit-operations takes place but with contactor 24 and relay 76 replacing 23 and 75 respectively; motor 6 runs in reverse as the field-windings 7, 8 are connected crosswise with brushes 21, 22. If the table overshoots its setting it is brought back in slow-speed automatically, e.g. if previously relay 75 were connected, the overshoot causes bridge-unbalance to energize relay 76 and motor 6 consequently reverses. Key 36, when operated, releases a locking-bar 34, thus interrupting any rapidtraverse of the table. The scale may be formed with tapered gap-edges (Fig. 2, not shown) ; or as tapered-edge diaphragms with intervening transparent material (Fig. 3, not shown) ; or as a glass-scale carrying measuring-lines, in a supporting-frame having window-apertures closed by diaphragms (Figs. 4 and 5, not shown). In an application of the control-arrangements to a co-ordinate drilling-machine (Fig. 6, not shown), one measuring-scale is provided for longitudinal movement of the upper carriage carrying the work-table and moving on a lower carriage which has a second measuring-scale and transverse motion. Contactors 23, 24 may be replaced by two contactors controlling clockwise and anti-clockwise rotation of spindle 4 with two electromagnetic clutches and interposed reversing-gears. Brakes acting on the carriage may be provided additionally.