DE2159377C3 - System for coating the surface of a sequence of objects that can be moved relative to the system - Google Patents

Description

The invention relates to an installation for coating the surfaces of a sequence relative to the installation movable objects according to the preamble of claim 1.

In the mass production of automobiles, the automobile bodies are usually used carried at intervals on a conveyor and coated in such a way that they pass through a spray system are promoted, are arranged in the spray guns in a suitable manner so that Spray jets of paint are directed onto the sides and roofs of the bodies. The guns are like that arranged that when the bodies are moved through the system, the guns across the! conveying direction the bodies are moved. The guns should expediently be switched on and off when they reach the limits of the surface to be coated during each transverse movement, as well as on Beginning and end of the area in the conveying direction.

Systems for carrying out such a coating are for use on objects from known shape and size, which move in a known sequence along the conveyor, known.

so from DE-OS 14 27 605 a generic system is known There is a device for Application of coating material to the surfaces to be coated transversely to the conveying direction the objects to be coated are moved in strokes.

H Detect scanning devices designed as light barriers the size and shape of the body and each serve to control a specific program of the coating device. This program, in which the location and the

: o The length of the coating process is fixed, must be set up beforehand for each body type. Likewise, the position of the light barriers must be adapted to the variety of body types in order to identify the respective type.

2i The invention is based on the object of a To create a system of the generic type, which enables the coating of a sequence of objects, even if these arrive at a coating station in random order and even if the sizes

μ and shapes of the surfaces to be coated are not known before the objects reach the coating system.

This object is achieved by the subject matter of the present claim 1. In the inventive The system creates a separate coating program for each object that arrives at the coating station created again, whereby it does not matter what size and shape the object to be coated, as long as one

■ to maximum size, which is essentially determined by the size of the Plant is given. is adhered to. The television camera scans the respective object line by line and delivers a digital value according to the number of lines and also an image signal. The altitude of the Coating apparatus with respect to a base is digitally sensed. A detector device processes this The image signal supplied by the television camera and, if it coincides, gives the digital signal from the aforementioned Values at certain altitudes send a signal to a

ίο Control device for actuating the coating device.

The scanning field of the television camera perpendicular to the direction of movement of the objects is just as large as the Length of the strokes of the coating device. Because of the format of conventional television cameras is in the direction of movement of the objects very wide field scanned. However, it is sufficient and more advantageous for the system to work more precisely, the scanning field of the television camera in the direction of movement of the objects is slightly larger than the width a coating stroke, with means for selecting a window of limited width of the scanning field are provided. These devices are connected upstream of the detector device and include

^ 5 sen a delay device that responds to the horizontal sync pulses the television camera responds, and a pulse generator. By means of the adjustable delay device can be the position of the window

set within the scanning field, while using the adjustable pulse generator, the width of the Window is preheated.

The system according to the invention can independently working coating devices have, each of which is assigned a television camera several spray guns assigned to a coating device can be controlled.

The structure and mode of operation of the invention will be explained with reference to an embodiment shown in FIGS. 1-3 shown and explained. It shows

F i g. 1 is a side view in a schematic representation a loading system for spray painting vehicle bodies;

F i g. 2 is a view along line 2-2 in FIG. 1 and

F i g. 3 shows a block diagram of the electrical control for use with the coating system according to FIG. 1 and 2.

In this exemplary embodiment, a sequence of vehicle bodies 11 is continuously conveyed on a conveyor 12 past a coating station 13 at which paint is sprayed onto the vehicle bodies. Two spray guns 14 and 15 are provided on opposite sides of the conveyor path for coating the sides of the vehicle and are collectively movable up and down vertical supports 16 and 17 so that vertical paint strokes are obtained as the vehicle bodies pass. The spray guns 14 and 15 are moved up and down in a fixed path by devices 10, which may for example be pneumatic devices, with limit switches 8 and 9 being provided at the ends of the path. This solid path begins below the lower edge of the vehicle body and ends above the height of the highest vehicle body to be coated. When the spray guns move up and down, the supply of paint and compressed air to the guns 14 and 15 is controlled by the use of a television camera 18 so that spray paint is applied to the surface areas of the structures to be coated and the spray paint supply to the guns is switched off, as soon as the guns reach the edge of the vehicle body. Another downwardly directed spray gun 19 is arranged horizontally on a carrier 20 which extends transversely to the path of the conveyor and is used to coat the roofs of the vehicle superstructures. A downward facing television camera 21 controls the spray paint supply to the gun 19 in exactly the same way as the camera 18 controls the paint supply to the guns 14 and 15. The manner in which the camera 18 controls the supply to one of the spray guns 14 and 15 is described below in connection with FIG. 2, the operation of the camera 21 being of course essentially the same. The camera 18 is positioned in a stationary position on one side of the conveyor track so as to point to the sides of the successive vehicle structures as they arrive at the coating station. The vertical field of view of the television camera is such that it covers the full height of the vehicle superstructure and extends just beyond the limits of the spray gun path. The horizontal field of view is larger than the vertical field of view, since in a conventional television picture frame the ratio of width to height is 4: 3. The horizontal field of view therefore extends a substantial amount of the length of the vehicle body and covers a width much greater than the stroke width of the spray gun (ie the width of each spray painting stroke on the vehicle body). The camera is used to form an image of the area covered by the movement of the spray gun (which includes the surface to be coated) and the supply to the gun at any given moment depending on what the

looks in camera, steer. The camera's field of view must therefore be able to be subdivided and the separate zones of the field of view must be identified in this way can be that these separate zones with the area which each covered by the spray gun can be correlated. That. Video signal coming from a divided zone of the field of view is derived can be used to determine whether in that part of the Field of view that the camera sees, a surface is to be coated or not and accordingly the Switch the spray paint supply on or off. First, consider the subdivision in the vertical direction. the The spray gun is coupled to a digitizer 30 which is shown in FIG. 3 is shown which is a pulse supplies for each movement unit of the spray gun. The arrangement is such that there are a total of 100 Gives impulses for full movement of the gun from one end of its path to the other. To this Way shows the signal on the output lines 31 of the digitizer 30 the respective vertical Position the spray gun with an accuracy of 1%. The height of the field of view is in the television camera divided, of course, by the scan lines which scan the image from top to bottom. When using

ij of a 625 interlaced system each field consists of 312 lines. A horizontal sync pulse is generated for each line and this Pulses are fed from the camera on line 33 to a “divided by three” element 32. This groups the line pulses into 104 groups and when the arrangement is made so that the vertical The camera's field of view is 4% larger than the spray gun trajectory, the spray gun trajectory will be 100 Groups covered, each group of 3 pulses corresponding to the same vertical unit of distance like a pulse from digitizer 30. The output of gate 32 becomes a register which is formed by two "divided by ten" links 34 and 35. The outputs of the members 34 and 35 on lines 36 count the pulse groups from element 32 and a limit value indicator 37 is used in addition, the number of pulse groups on lines 36 increases with the number of pulses on lines 31 to compare. Both numbers are in binary form. If the numbers on lines 36 and 31 are the same, then shows this indicates that the camera and spray gun are synchronized in the vertical direction at this moment and that the video signal from the camera is relevant to the zone which the spray gun is facing is. The limit indicator or comparator 37 then delivers a marking pulse on the line 38. If 100 pulse groups have been counted by members 34 and 35, a flip-flop 40 is sent on line 39 which in turn controls a gate 41, which is fed into the output line 38 of the limit value indicator 37 is switched. This pulse on the line 39 has the effect that the gate 41 after counting 100 Pulse groups is closed, so that for the

Pulse groups between 100 and 104 no marking pulse can be delivered. This will make the Excess of 4% of the field of view of the camera is rendered ineffective. At the end of each field, a vertical sync pulse to each of members 32, 34, 35 and 40 from the camera on line 42 supplied, whereby the counted number is cleared from the members and from the reset member 40, so that the Gate 41 is opened in preparation for counting the next 100 pulse groups. It follows from this, that the vertical field of view of the camera is divided into 100 numbered strips and the working field the spray gun is similarly divided into 100 numbered strips. The numbers for the two Sizes are compared with each other and every time they are equal, a marking pulse is applied to the Line 38 molded. Because of the scanning speed in a television camera, the spray gun can be longitudinal their path are not moved in the time it takes to scan an image of the camera. the The arrangement is therefore made so that the camera 200 images during a movement of the spray gun longitudinally their path scans. As a result, the camera receives two for every pulse from digitizer 30 scans complete images so that the comparison circuit 37 has two marker pulses for each strip in the vertical direction emits.

The duration of each marker pulse is the same and is approximately equal to the duration of three horizontal sync pulses from the camera, since the comparison circuit 37 on lines 36 supplied Number changes every three sync pulses on line 33. The marker pulses are sent to a gate 43 which is opened by each marking pulse for the duration of this pulse only.

The synchronization of the camera signals with the position of the spray gun in a horizontal direction is described in more detail below. Because the horizontal field of view of the camera is much wider than that Stroke width of the spray gun, the signals from the camera must be similar to a narrow window Width can be restricted as the stroke width of the spray gun, which is placed at one point in the field of view is. which corresponds to the position of the spray gun in a horizontal direction. To achieve this, become horizontal sync pulses. which determine the position of the left end of the field of vision from the Camera along the line 33 of a monostable circuit 44 fed, which the duration of the pulses extends to the required position in the field of vision for the left edge of the window. The exit from the monostable circuit 44 is fed to a further monostable circuit 45, which pulses generated, which are hereinafter referred to as window pulses, which the position and the width of the window determine in the field of vision. The time of occurrence in each scan line of the leading edge of the Window pulse determines the position of the window in the field of vision and the duration of the window pulse determines the width of the window. The pulse stretching achieved by the one-shot circuit 44 is adjustable so that the window can be easily adjusted to synchronize with the spray gun, after the camera and spray gun have been set up. The width of the window can be similar Way can be adjusted in adaptation to the spray gun arrangement in that the monostable circuit 45 is adjusted. The video signal from the camera.

which represents the image seen during the scan sequence is on line 46 a Gate 47 is supplied, which is controlled by the window pulses from the monostable circuit 45. on In this way, the video signal is blanked for most of the horizontal field of view and that Video signal is only passed through gate 47 for the duration of each window pulse, whichever, as mentioned, is chosen so that it corresponds to the vertical band

ι ο corresponds to the length of which the spray gun is working.

To decide whether or not spray paint should be fed to the spray gun, this is done by the Gate 47 passed the video signal to a detector, which by detector units 48 and 49 is formed of high or low level and is coupled to a NOR gate 50. the Detector units 48 and 49 examine the contrast, or level of illumination, indicated by the video signal and when the signal has a level which corresponds to the contrast level of the object to be coated corresponds to, a pulse called an object pulse is passed through the NOR gate 50. The object pulse is then compared in time with the marking pulses by the gate 43, see above

> 3 that if an object and marking pulse are simultaneous occur, the gate 43 emits an action pulse to trigger an electronic switch and thereby to start the coating outlet device. As in Fig. 3 shows the output of the

jo gate 43 is fed to a flip-flop 51, which in turn a thyristor switching device 52 controls. The paint outlet control device 53, which is a pneumatic Valve or solenoid valve, is powered by an AC power supply 54 through the thyristor switch 52

si actuated. A zero voltage detector 55 is between the AC power and switch 52 switched to ensure switching at zero voltages he follows.

There is a connection via a line 56 between the digitizing device 30 and the flip-flop 51 provided so that. when the flip-flop 51 has been opened by a pulse from the gate 43. this is closed again by the next pulse from the digitizer. This means that the Color lacquer emerges separately for each stripe in the vertical direction corresponding to an impulse from the Device 30 is controlled. After a strip has been coated, another action impulse has to go through the gate 43 pass through to another

ίο bring about paint application. That way everyone will separate strip that represents 1% of the length of movement of the spray gun separately rated to see whether to add color or not. In practice, mechanical and pneumatic inertia integrates the

υ Instructions to the exit control device 53. so that a smooth and even response is obtained.

In this way, paint is applied to the area of the surface to be coated, but is

ö »the feed to the spray gun outside of this area; switched off. Because of the maximum error of 1% when assessing the position of the spray gun, it works little paint color lost.

From this it follows. that. if the TV camera the

t-5 objects to be coated over the entire length of the web The spray gun at the coating station scans an accurate control over the coated areas without any prior knowledge of the size or shape of the ar

The objects arriving at the coating station can still be reached by their arrival sequence. In addition to the The television camera is used to locate the upper and lower limits of the vehicle bodies to be coated similarly the front and rear edges of the superstructures in the longitudinal direction of movement of the conveyor and prevents paint spraying and the up and down movement of the Spray guns in the spaces between adjacent superstructures on the conveyor.

The television camera can also be used to display color indicia on a vehicle body to recognize when approaching the coating station and thereby the selection of correct color of the paint supply to the spray gun

steer.

Although the foregoing description is directed to the exit control device 53 which the Controls the paint supply to the spray gun, this normally also includes the control of the supply of Compressed air, which is used to carry out the spraying process.

The invention is of course not limited to the details of the preceding example. For example It is not absolutely necessary to use spray guns in the coating process. Furthermore can the invention, although it is particularly suitable for coating vehicle bodies, also for Coating surfaces of other objects can be used.

For this purpose 2 sheets of drawings

Claims (4)

Patent claims: 1. System for coating the surfaces of a sequence of objects movable relative to the system with a device for applying coating material to the surfaces to be coated and a device for moving this device transversely to the conveying direction of the objects and with scanning means for controlling the coating device by combining
a device (30) for digitally detecting the height of the coating device (14; 15; 19) in relation to a base, a television camera (18; 21) for scanning the object to be coated (11) with the Number of lines! a digital value corresponding to the altitude of the scanning beam with respect to the base (Line 36) delivers, a downstream device (37) for determining the coincidence of the altitudes determined by these digital values and
a detector device (48-50) for differentiating the image signal supplied by the television camera, and a control device (43; 51-53) for actuating the coating device (14; 15; 19) with an input for the coincidence signal and an input for the detector signal. 2. System according to claim 1, characterized in that the scanning field of the television camera (18; 21) across the direction of movement of the objects (U) as large as the length of the strokes of the Coating device (14; 19) and in the direction of movement of the objects (11) larger than is the width of a coating stroke, means (44; 45) for selecting a window of limited width of the scanning field are provided. 3. Plant according to claim 2, characterized in that these devices (44; 45) of the detector device (48-50) are connected upstream and a delay device (44) which responds to the horizontal sync pulses (Line 33) of the television camera (18; 21) responds, and a pulse generator (45) includes. 4. Plant according to one of the preceding claims, characterized in that more than a coating device (14; 15; 19) and more than one television camera (18; 21) are provided.