Patent GB-760322-A (GB)
Title: Control device for a machine tool
IPC: B23Q5/52
Filed: 1953-03-20
Abstract: 760,322. Machine-tool details. HIJMANS, E. March 20, 1953 [March 25, 1952], No. 7797/53. Class 83 (3). [Also in Group XL (b)] A control device for a machine tool, to limit the feed movement of a tool or work carrier, comprises a switching device, a selector device controlling the switching device and actuating means for the switching device, the actuating means consisting of a stationary source of light adapted to excite a stationary photoelectric cell constituting the switching device, the excitation being controlled by one of a number of symbols on a movable record which is driven by one of the machine carriers and which has its symbols arranged in rows parallel to its direction of movement, means also being provided which, under control of the selector device, makes a desired row of symbols operative. Control devices 2, 3, Fig. 1, for the transverse and longitudinal movements respectively of the tool are each secured to the part of the feed motion which is to be controlled. A screw 1, Fig. 2, secured to a stationary part of the machine passes through the upper part of a control device and engages a pinion 13 secured to a shaft 10. Thus, as the control device moves with its support, e.g. the lathe carriage, the pinion moves over the threads of the screw 1 similar to a rack, and the pinion is thus rotated. The screw 1 would in this case be arranged parallel to the main lathe guideways, but a similar screw for the transverse slide and its control would be arranged transversely of the bed. A gear-wheel 16 is secured to shaft 10 and drives a gear-wheel 19 which drives the shaft 21 by ratchet means in one direction of rotation. A gear 22 fixed to shaft 21 is in mesh with a gear 17 also connected by ratchet gear to the shaft 10. A similar arrangement is incorporated for driving shafts 12, 23, from a pinion on the former which also engages the screw 1. Friction clutches 24 on shafts 21, 23, drive spools 6, 5, which constitute the end spools for a length of film 4. The latter passes over further spools 7, 8, on the shafts 12, 10 and the film is fed through a gate 11. The purpose of the gearing and friction clutches -is to ensure that the film is moved in either direction through the gate without backlash. A spiral spring 9 connects the spool 8 to a sleeve 14 keyed to the shaft 10 to keep the film taut. A source of light and a condenser are carried in the casing 25 above the gate 11 and the film is provided with perforations arranged in eleven rows at predetermined intervals in the longitudinal direction of the film. A screen plate 27 is arranged below an objective 26 which magnifies the image of the perforation. The screen plate contains eleven slits in two groups of five and six, the light passing through the slits in one group falling on a photo-cell 29 via a mirror 31 and that passing through the second group falling on photo-cell 30 via the mirror 32. At given values of the amount of light falling on the photo-cells the feed motion or other function of the machine may be stopped. Each of the slits in the screen plate may be closed by an obturating flap moved by a relay controlled by a switch-drum (not shown), which may thus pre-select a particular sequence of machine operations. The perforations in the film in each row give a particular working sequence to the parts controlled, e.g. the tool in a lathe, or two rows may be combined to give the required control sequence. Specification 719,240 is referred to.