GB1374424A - Coating apparatus - Google Patents

Abstract

1374424 Spraying car bodies CARRIER DRYSYS Ltd 29 Oct 1971 [30 Nov 1970] 56747/70 Heading B2L [Also in Division G1] Apparatus for spraying car bodies comprises a series of spray guns 15, 19 which move transversely to the direction of the conveyor 12 and television cameras 18, 21 which scan the passing car bodies to control the discharge of spray so that the spray guns only operate when the body is in the correct position to be sprayed by the gun as it passes. The camera 21 controls the horizontally moving spray gun and the camera 18 the vertically moving guns. The circuit relating to camera 18 and gun 15 is shown in Fig. 3. The gun on its complete movement produces 100 pulses by means of a coating unit digitising device 30 and these pulses are fed to a digital comparator 37. Horizontal synchronising pulses, one for each line of the frame, are fed from a 625 line T.V; camera along a line 33 and it is arranged that two hundred frames are transmitted during one complete movement of the gun. A divide by three unit 32 cuts the number of pulses into 104 groups of three pulses each and two divide by ten units 34, 35 are used to feed the obtained pulses to a digital comparator 37 where they are compared to the output of the spray gun movement. When one hundred groups of pulses have been counted a pulse along line 39 causes a flip flop 40 to close gate 41 and the last four groups of pulses are ignored. When the numbers of pulses from both sources are the same then a stroke pulse is sent along line 38 to a gate 43 and indicates that the camera and spray gun are in vertical synchronism. At the end of each frame a vertical synchronism pulse clears the units 32, 33, 35 and 40. Horizontal synchronising pulses are fed to a monostable pulse stretcher 44 and an adjustable monostable pulse generator 45 provides the timing and duration of a window pulse which is fed to a gate 47. This pulse allows only part of the video signal through so that a vertical strip is taken from the available picture format. High and low level contrast detectors 48, 49 produce an object pulse at gate 43 dependent upon the amount of contrast in the observed strip which signifies the presence of an object adjacent the gun. The gate 43 produces an action pulse which controls the supply of coating material to the gun through a flip flop switch 51. A line 56 direct from the digilising device 30 to the flip flop 51 resets the flip flop as the gun moves one micromental step so that the requirement of actuation of the spray device is assessed for each of the hundred steps in the complete movement of the gun but mechanical inertia in the system ensures that when the object is being coated the spraying is continuous whilst the object is in position. A zero volt detector is connected between the A.C. supply and the thyristor control 52 to ensure that switching occurs at voltage zeros.