Patent GB-1026191-A (GB)
Title: Line-following apparatus
Inventor: ASHLEY WALTER ROY
IPC: G06F3/00
Filed: 1961-01-10
Abstract: 1,026,191. Television. BRITISH OXYGEN CO. Ltd. April 10, 1962 [Jan. 10, 1961], No. 1019/61. Heading H4F. [Also in Division G3] In the line following apparatus a cutting burner of a flame cutting machine is caused to follow the outline of a pattern in the form of a line drawing or edge of a template 10 in response to the output of a television camera 11 focused on the line drawing. The output of the camera is applied to a cathode-ray tube 12 through a line 13 and camera synchronizing signals are applied through a line 19 to time bases 14, 15. The cathode-ray tube modulation is such that the image appears white on a dark background. The time bases 14, 15 provide short triangular pulses so that only a small part of the line drawing to be followed is reproduced on the cathode-ray tube. The timing of the pulses is varied by time delay circuits 16, 17 so that successive line images of parts of the line can be reproduced on the cathoderay tube. Photo-electric cells 18 are disposed at 90 degrees to a predetermined vertical orientation of the line image, which lies between the cells 18 and, deviation of the line causes a variation between the outputs of the cells 18. A decade counter 20 receives the outputs of the cells and is adapted to count a hundred for a 90-degree rotation, " clockwise " rotation causing the counter to advance and vice versa. The store in the counter at any time represents the angle 5 to which a tube raster has been rotated and modifies the output of an electronic sine-cosine potentiometer 21 into which are fed the outputs of the delay circuits 16, 17, and the potentiometer provides outputs 23- 26 which through switches 33, 34 controlled by the counter 20 are selectively combined in adder circuits 27, 30 to energize the vertical plates 32 and horizontal plates 29, respectively, to rotate the tube raster and restore the vertical orientation of the line image. Outputs 23, 24 of the potentiometer are fed through rectifiers 35, 36 to apply to gates 37, 38 direct current signals which are proportional to the sine and cosine of the angle 5. The gates are opened by a pulse generator 39, the repetition rate of which is manually controlled to determine the operating speeds of a machine part which is caused to move along a path corresponding to the line drawing being scanned by the camera. The pulses from the gates are fed to diode energy storage counters 40, 41 the outputs of which control the delay circuits 17, 16 so that the timing of pulses from the time bases 14, 15 are continuously varied and consecutive line images of successive incremental parts of the line drawing are reproduced on the face of the cathode-ray tube 12, the visual effect being of a line to be followed being drawn across the face of the tube, its apparent speed of movement being manually controlled, simultaneously with a corresponding control of a machine part, by the pulse generator 39. The outputs 44, 45 represent the x and y co-ordinates of the instantaneous position of the incremental part of the line drawing, represented by the line image, in relation to the line drawing as a whole and are utilized as position representing signals for controlling movement of the machine part. It is stated the output signals can also be derived from the delay circuits 16, 17. In a modification, Fig. 2 (not shown), the sine and cosine signals are resolved into " tens " and " units " signal by diode switches.