GB474992A - - Google Patents

Abstract

474,992. Electric control systems. LINDE AIR PRODUCTS CO. May 29, 1936, No. 15172. Convention date, June 15, 1935. [Class 40 (i)] [Also in Group XL] In a system for reproducing, cutting, or welding in accordance with a predetermined pattern or outline, a photo-electric tracer follows automatically the outline and simultaneously controls the movements of a tool. As shown in Fig. 1, the pattern to be reproduced is placed upon a bed M beneath a photo-electric tracer T comprising a beam of light from a source 51 focused upon the outline of the pattern and adapted to be reflected on to a photoelectric cell P which controls, through an amplifier R, a motor G which determines through gearing 34, 35, the direction of movement of a wheel W which frictionally engages the bed M. The photo-electric apparatus, together with the motor G and the reproducing tool B, is supported on a carriage 18 mounted on runners 17 for movement relative to a carriage 20 also mounted on runners 15 for transverse movement on the bed M. The wheel W is rotated through gearing from a motor 24 in order to drive the apparatus along the bed at uniform speed. The light transmitting apparatus 42, is provided at its lower end with a detachable lens and is held in adjustable spaced relation to the bed M by guide rollers 46 to allow for proper focusing. In operation the tracer is focused upon the outline of the pattern and the output of the photo-electric cell controls the motor G so that the direction of movement of the wheel W which is rotated by the motor 24 is altered so as to maintain the tracer on the outline. Consequently, the tool B co-operating with the work-piece C, is operated in accordance with the outline. Fig. 4 shows the circuit diagram of the system. The output of the cell operates a relay 55 the armature 105 of which is held in neutral position against the action of a spring 100 under the influence of normal current flow in the coil 55. Normally the tracer is focused so that the edge of the outline falls half way across the image, and when, in operation, the tracer departs from the normal position one or other of the A.C. relays 59, 61 is operated to cause rotation of the motor G in the appropriate direction to restore the normal relative position between the tracer and the outline. If the tracer leaves the outline completely one or other of the relays 58, 62 also is operated to short circuit a resistance 87 and speed up the motor. The outline to be reproduced may be drawn on the bed M or a templet may be used. In a modification, an opaque templet is provided on a transparent part of the bed. In this case the light source may be arranged beneath the bed.