Patent GB-826677-A (GB)
Title: Apparatus for terminating the relative movement in a given direction between work and tool in a machine tool
IPC: B23Q5/52
Filed: 1956-05-23
Abstract: 826,677. Lathes; machine-tool details; punching. HUMANS, E. May 23, 1956 [May 31, 1955], No. 16013/56. Classes 83 (3) and 83 (4). Apparatus for terminating at a predetermined position the relative movement in a given direction between work and tool in a turning, drilling, punching, &c., machine, comprises a member carrying a scale, the units of which can be activated individually, and a member for scanning the units and terminating the movement, one of the members being driven by the work or toolholder and the other being fixed. In a lathe, the saddle 2 is traversed by a motor 1, at a speed determined by the setting of control knobs 9<SP>1</SP> controlling magnetic couplings, for a distance determined by a gauging unit 7a associated with a rack 7 attached to the saddle. (The control knobs 9<SP>1</SP> also operate the cross-slide.) The rack 7 meshes with a gear 8 to rotate a disc 11 carrying brushes 12-15 co-operating with rows of contacts 17-19 in a stationary disc 16. The disc 11 rotates once for a saddle traverse of one decimetre, and there are 100 " millimetre " contacts in the row 17, and 10 " centimetre " contacts in the row 19. The row 17, (19), is swept by the brush 12, (15), which is connected to the brush 13, (14), sweeping over a continuous contact ring 20, (21). A set of ten " decimetre " contacts are carried on a further fixed disc 22 which co-operates with a brush on a disc 23, rotating once for every ten revolutions of the disc 11. A fine adjustment to tenths of a millimetre is provided by photo-electric devices 39, 41, one for each direction of rotation, mounted on a carrier 30 which is movable axially by a screw 32 driven by a motor rotating a worm 34 through a slip coupling. The photo-electric device co-operates with an opaque film carrying oblique translucent stripes, and is positioned by advancing a disc 36 through a ratchet device 41<SP>1</SP> to bring one of ten studs 37 to a position where it engages a contact 38 on the carrier 30, to limit the movement and switch off the motor. Ten further studs on the disc 36 are adjustable to provide compensation for tool wear. In operation, a number of dimensions are set up by rows of knobs on a panel 4, each row consisting of four knobs 42-45 controlling stepping switches for decimetres, centimetres, millimetres and tenths of millimetres. A knob 46 selects the row to be operative. The tool is positioned and fed under the control of the knobs 9, and the operation is terminated automatically. The motor 1 may be slowed down for the final millimetre of travel by arranging for the stripe before the last to actuate the photo-electric device to slow down the motor, and the last stripe to stop the motor. In making the apparatus, the rack 7 is made by machining the requisite number of decimetre lengths simultaneously, and placing them endto-end. The film 27 is marked with stripes by positioning the tool at 1 millimetre intervals and exposing the film via a diaphragm. The film is then developed. As each decimetre section is identical, the inaccuracies in the mechanical parts are automatically compensated for the whole length of the rack. In a modification, the photo-electric device is replaced by a brush cooperating with conducting strips or by a magnetic tape and scanner.