EP0899020B1 - Method for detecting the presence of a workpiece in an electrostatic coating installation and electrostatic coating installation - Google Patents

Method for detecting the presence of a workpiece in an electrostatic coating installation and electrostatic coating installation Download PDF

Info

Publication number
EP0899020B1
EP0899020B1 EP98113602A EP98113602A EP0899020B1 EP 0899020 B1 EP0899020 B1 EP 0899020B1 EP 98113602 A EP98113602 A EP 98113602A EP 98113602 A EP98113602 A EP 98113602A EP 0899020 B1 EP0899020 B1 EP 0899020B1
Authority
EP
European Patent Office
Prior art keywords
coating
workpiece
spray
current
high voltage
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP98113602A
Other languages
German (de)
French (fr)
Other versions
EP0899020A1 (en
Inventor
Kurt Seitz
Markus Hasler
Horst Dr. Adams
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Wagner International AG
Original Assignee
Wagner International AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Wagner International AG filed Critical Wagner International AG
Publication of EP0899020A1 publication Critical patent/EP0899020A1/en
Application granted granted Critical
Publication of EP0899020B1 publication Critical patent/EP0899020B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B12/00—Arrangements for controlling delivery; Arrangements for controlling the spray area
    • B05B12/08—Arrangements for controlling delivery; Arrangements for controlling the spray area responsive to condition of liquid or other fluent material to be discharged, of ambient medium or of target ; responsive to condition of spray devices or of supply means, e.g. pipes, pumps or their drive means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
    • B05B5/025—Discharge apparatus, e.g. electrostatic spray guns
    • B05B5/053—Arrangements for supplying power, e.g. charging power
    • B05B5/0531—Power generators
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B12/00—Arrangements for controlling delivery; Arrangements for controlling the spray area
    • B05B12/08—Arrangements for controlling delivery; Arrangements for controlling the spray area responsive to condition of liquid or other fluent material to be discharged, of ambient medium or of target ; responsive to condition of spray devices or of supply means, e.g. pipes, pumps or their drive means
    • B05B12/12—Arrangements for controlling delivery; Arrangements for controlling the spray area responsive to condition of liquid or other fluent material to be discharged, of ambient medium or of target ; responsive to condition of spray devices or of supply means, e.g. pipes, pumps or their drive means responsive to conditions of ambient medium or target, e.g. humidity, temperature position or movement of the target relative to the spray apparatus
    • B05B12/122—Arrangements for controlling delivery; Arrangements for controlling the spray area responsive to condition of liquid or other fluent material to be discharged, of ambient medium or of target ; responsive to condition of spray devices or of supply means, e.g. pipes, pumps or their drive means responsive to conditions of ambient medium or target, e.g. humidity, temperature position or movement of the target relative to the spray apparatus responsive to presence or shape of target

Definitions

  • the invention relates to a method for recognizing Workpieces in an electrostatic coating system and an electrostatic coating system in which this procedure can be used.
  • the current status of the sensors (e.g. funding cycle of the Workpiece, fill level of the storage container etc.) become cyclical captured by the central unit, the necessary reactions the associated actuators are calculated, and corresponding control commands are sent to the actuators forwarded.
  • the workpiece To ensure an even and sufficient coating thickness the workpiece and to ensure the efficiency of powder application to optimize the vertical stroke of the coating equipment as well as controlled powder delivery. additionally becomes the distance between the coating device and the workpiece set in the spray direction to avoid that if the distance is too short, blow off the powder again will or electrostatic craters form or that in the opposite case, the efficiency of the powder coating deteriorates and e.g. the penetration into cavities decreases.
  • Parts recognition is used, for example, in paint shops Realization of a gap control used. Thereby in Workpiece gaps the promotion and thus the application of Powder paint or wet paint interrupted. This reduces the consumption of coating materials, the amount of waste Wet coatings and the recirculated portion of powder coatings.
  • the basic structure of a gap control of the stand the technique is shown in Figure 9.
  • a workpiece conveyor 902 transports workpieces 904 through a coating booth 901 in the shown Direction.
  • a Device for recognizing a workpiece 904 is required. This consists of a light barrier 906 or 906 ', 908, where light is sent from light transmitter 906 or 906 'and from Receiver 908 is received and corresponding signals be forwarded to a controller 912.
  • the light barrier is primarily outside the coating booth 901.
  • the controller 912 needs an additional one Signal proportional to the speed of the conveyor Is 902.
  • This signal now comes directly from one Conveyor system control 915, or it comes with a special Device 913 for measuring the conveying speed determined.
  • This speed measuring device generates a signal proportional to the conveying speed and conducts it to the controller 912.
  • the controller 912 determines from the Speed information and the signal from the light barrier 806, 908 the time it takes the workpiece 904 to get to sprayer 905.
  • the light barrier 906, 908 "informs" the controller 912 also from the end of a workpiece. Now you have one Means the insertion of a workpiece 904 into the Detects cabin 901, determines its length and delays it, depending on the speed of the conveyor 902, the material feed 910, 911 can switch on and off.
  • the coating devices are in the state Technology further a position control device and Movement control device provided, which is also the information about the start, end and speed of the workpiece need.
  • the position control device controls the Distances of the coating devices to the workpieces.
  • the Motion control device controls the vertical stroke of the coating devices.
  • the coating system requires a great deal of computing effort, coordinated with the several coating devices so on and off, up and down as well as before and to move back that optimal coating result is obtained.
  • the U.S. Patent 4,324,812 describes a powder coating installation in which the spray stream is detected in order depending on the spray flow, the powder mass flow to a coating workpiece is given to control.
  • the patent is based on the knowledge that that smaller areas to be coated concentrate the electric field, so that a higher electricity is drawn while larger areas draw less electricity. It follows, that smaller areas are coated more than larger areas. To counteract this is in the U.S. Patent provided that with a decrease in the spray flow the powder mass flow is increased, while with an increase in the spray flow the Powder mass flow is reduced. A method or device for parts recognition and identification is not described in this document.
  • the invention has for its object a method for Detection of a workpiece in an electrostatic coating system and to specify a new coating system, where the hardware and software expenditure for the Part recognition and identification reduced and control can be simplified.
  • the invention takes advantage of the fact that in an electrostatic Coating device a high voltage electrode or spray electrode, electrostatic charges to the environment emits an electrical spray current from the Generate high voltage electrode through the air to earth, and regardless of whether at the same time by the coating device delivered a coating material to the workpiece will or not. If an electrically conductive, grounded Workpiece passed in front of the coating device the electrical spray current flows from the high voltage electrode through the workpiece to earth.
  • Spray flow As the workpiece approaches the spray gun, it increases Spray flow continuously (see Figure 2). Is located now the spray electrode at the same height as the workpiece, the spray flow changes only insignificantly. The Increasing the spray current is used for part recognition. Measurements have shown that the total current of the through the electrode flows mostly from the distance between Spray electrode and workpiece is determined, as well as by the set high voltage.
  • the measurement of the spray current can therefore be used as a means of detection of a workpiece used in front of the coating device become. According to the invention, depending on the size of the Spray current controlled the operation of the coating device.
  • optical workpiece recognition that is customary in the prior art can be completely omitted.
  • the new method for parts recognition according to the invention enables e.g. a gap control much easier too realize than in the state of the art by directly on site, a workpiece is recognized on the coating gun and depending on the presence of a workpiece and release of the coating material is activated. With the new system there is no external "gap control" needed.
  • this distance should be constant his. However, since there are many workpieces with it lengthways changing contours, and the spray gun one The vertical stroke passes, the distance changes. Dependent the distance can now be measured from the measured spray current between the workpiece and the coating device in the spray direction determined and kept constant.
  • the parts recognition can also be used to determine the speed of a workpiece can be used. Because in practice usually three and more guns in a row horizontally the same distance, the conveying speed be derived. Because once chosen Constant speed over a longer period of time remains, can be relatively imprecise from several successive Measurements by statistical methods the conveyor speed can be calculated more precisely.
  • the speed information can then be used for control and Synchronization of the vertical stroke of the coating devices be used.
  • the invention creates with the method for the detection of Workpieces using the spray currents of the electrostatic Coating equipment a reliable, fast and inexpensive Means for the registration and identification of the coating workpieces, which are those in the prior art usual part recognition and identification devices can completely replace. Furthermore, the invention has the Advantage that the presence of a workpiece in front of each Coating devices running during operation can be checked and not, as in the prior art, only on the basis of a single measurement when the Workpiece in the coating booth is predicted. at an unscheduled standstill of workpiece conveying thereby e.g. the powder supply can be blocked immediately.
  • the invention enables extensive decentralization the coating system because every coating device independently recognizes whether a workpiece is available, and depending on the spray flow its powder delivery and its Can control the distance to the workpiece.
  • FIG. 1 shows a powder coating system according to the invention.
  • This powder coating system is more detailed in the German patent application "control system of a coating system" the same applicant, with the same filing date described. To the disclosure of this patent application and in particular the explanation of the network structure there reference is expressly made.
  • Fig. 1 there are several (five) coating modules each a digital control device 60, an injector 64 and a spray gun 66 shown over a gun bus 62 are connected. Information necessary for the operation about the operating conditions of the coating system receive the control units 60 via an internal bus 80.
  • the multiple coating modules are via the internal bus 80 also with each other and with a central control unit 82 and connected to other components of the system. Additional modules that can be connected to the internal bus are z. B. a powder level control module 88, a position control module 90 and a motion control module 92.
  • modules that have a external bus 100 also with the central control unit 82 are connected; these also include a powder center 102 a powder storage container 104, a layer thickness measuring and Control device 107, 108 and an air quantity control device 109 for a powder recovery system 110, 114 and others
  • LON local area network.
  • the individual components that act as LON nodes configured, can register themselves in the system, other system components recognize themselves on this adjust and communicate with them. You can use the information about the respective operating conditions of the coating system, which you receive via bus 80 or 100 and use.
  • FIG Powder coating system As follows. A workpiece 200 approaches the coating booth 120. At the high voltage electrodes the spray guns 66-1, 66-2, ..., 66-n there is a high voltage of about 100 kV, so that an electrical Spray current from the respective electrodes through the Air flows to earth. This spray stream is as long as no grounded workpiece in front of the respective spray gun located, very small (so-called zero current).
  • Figure 2 shows the relationship between the electrical Spray current and the distance between the coating device 66 and the workpiece 200 or the time.
  • the y axis shows the current, on the x-axis are the distance in cm and the Time represented in seconds, with a constant conveying speed of 10 cm / s is assumed.
  • the freely selectable switch-on threshold is set to 25% of ⁇ I s in this example.
  • the switch-on condition is thus recognized at time t3 and the control unit 60 sends a switch-on command to the injector 64 via the gun bus 62.
  • the injector 64 contains two air quantity regulators for setting the conveying air and metering air for the coating device. This switches on the powder feed. If the workpiece 200 now comes to the coating gun 66, it is coated. In the time interval t 4 to t 5 , the workpiece runs past the gun. In the case described, the length of the workpiece is 20 cm. From time t 5 , the workpiece 200 now moves away from the spray gun 66 and the spray current drops. At time t 6 the workpiece is 10 cm away from the spray gun, again a preselected switching threshold (here 50% of ⁇ I s ) is crossed and the powder feed is switched off via the LON bus 92.
  • a preselected switching threshold here 50% of ⁇ I s
  • the measured spray current can also be used to set the distance used between workpiece 200 and spray gun 66 become.
  • FIG. 3 shows a possible configuration of the position control module shown.
  • Position control becomes common referred to as Z-axis control.
  • Such controls are known, but so far the coating devices are moving on a permanently programmed track. With the new method, the adaptation to the workpiece contour takes place automatically.
  • the high voltage generator integrated in the spray gun 66 generates a spray current from the electrode 17 to the workpiece 200.
  • This spray current is generated by a high-voltage module 300 measured and forwarded to a distance controller 302.
  • This controller tries to regulate a given spray current. Is e.g. the spray flow is less than specified, so controller 302 sends a correction signal to a displacement axis controller 304 transmitted. This in turn causes a servo motor 306 and a gun mount 308 to push the gun 66 closer to the workpiece 200.
  • the Controller 302 is in practice as a "software part" of the High voltage module 300 realized.
  • the regulator mentioned is preferably not a standard PI or PID controller, but a so-called intelligent controller.
  • the conveying speed of the workpiece can be from the times can be determined to which the spray streams of a first and a second spray gun 66-1 and 66-2 a predetermined one Threshold, and depending on the determined times and the known distance between the first and the second spray gun the speed of the workpiece is calculated.
  • Figure 4 shows in principle the arrangement of 3 guns.
  • a conveyor system brings different workpieces 200 in the shown direction in the coating booth 120.
  • a workpiece 200 now moves to the first coating gun 66-1.
  • a first high voltage module 400-1 registers one Increase in spray flow.
  • a real-time clock built into the module registers the exact time of detection and sends the start time of the measurement to a second high-voltage module 400-2.
  • the workpiece now moves to the second Coating gun 66-2 and releases one there again Start time with the help of a real-time clock.
  • This The start value of the second measurement is immediately via the bus system 402 sent to the third high voltage module.
  • the start time the second measurement is also the stop time the first measurement.
  • the speed is between the start and stop time of the workpiece is calculated and sent to any one via bus 402 sent to other bus subscriber 404 who is responsible for his Function must know the speed of the conveyor system.
  • the workpiece 200 now moves on to the third gun 66-3, the second stop time is triggered. From the second time difference (start time No. 2 and stop time No. 2) and the known distance B becomes the second measured speed value determined and transferred to bus 402.
  • This third measurement will be the most accurate because there are inaccuracies in the timing and in the Workpiece detection has less impact the longer the Measuring distance and the measuring time are. Because with every workpiece New speed can be determined from several measurements the average speed of the conveyor system can be calculated.
  • the information about the workpiece speed can Control and synchronization of the spray gun stroke be used.
  • the material deposit on the workpiece is similar in terms of the layer thickness of a Gaussian distribution, therefore can the width of the coating limit is not precisely specified become.
  • FIG. 5a it can be seen that the spray gun (2) that area of Workpiece coated, that of the spray gun (1) not could be coated. By blurring the spray zones in the case of FIG. 5a, the material distribution becomes optimal. Not so in the unsynchronized case of FIG. 5b. There the second gun (2) mainly coats the same Area that gun (1) previously coated. moreover there are intermediate zones that have not been coated.
  • Each coating module can thus both the fact that a workpiece 200 is approaching, as is the type, in particular Size and shape of the workpiece 200, the speed of the workpiece and the distance from the workpiece to the spray gun to capture. This information is put on the bus 100, 80 and are immediately at the other components of the powder coating system to disposal.
  • a high-voltage generation unit usually consists of a high-voltage control module with oscillator, output stage and control unit and a high-voltage generator in the gun, consisting of a high-voltage transformer, multiplier cascade and protective resistors. It has a U / I characteristic curve that determines the electrical behavior of the overall unit. If the total internal resistance were an ohmic resistance, the U / I characteristic curve would be a straight line with the key points: short-circuit current and open circuit voltage. See curve A in Figure 6. In practice, the internal resistance is divided into many, cumulative, complex internal resistances and ohmic components. The resulting characteristic curve is shown in FIG. 6 as curve B.
  • the actual load resistance of a coating unit is the air between the spray electrode and the workpiece and has a purely ohmic character.
  • this ohmic resistance depends on the shape of the workpiece, its size, surface quality, the shape of the spray electrode, the air quality, temperature, pressure, moisture content and the distance between the electrode and the workpiece and also on the high-voltage generator.
  • the shape of the real U / I characteristic curve B is the same for every combination of control unit and high-voltage generator.
  • FIG. 7 shows a family of curves formed from several different voltage settings or, more precisely, different output stage supply voltage settings.
  • the values U 0x in FIG. 7 correspond to the open circuit voltages, which are proportional to the respectively selected supply voltages.
  • the curved characteristic curve is represented by a kink.
  • AP 1 corresponds to a very large distance between the workpiece and the spray electrode, whereby the workpiece is always grounded. The distance is so large that the load carriers moving in the air do not reach the workpiece, but, for example, the gun holder. In practice, point AP 1 represents the maximum high voltage and the minimum current. (Point U 01 can only be reached in the laboratory under certain conditions.) If the distance between the workpiece and the electrode is reduced, the working point moves along curve B 1 to AP 2 . At this point a considerable part of the load is already flowing off the workpiece. If the distance from the workpiece to the electrode is reduced further to the point of contact, the working point moves further via AP 3 to AP 4 (short circuit).
  • the shape of the U / I characteristic is stored in the high-voltage module.
  • the high-voltage module also knows the relationship between supply voltage and U 0 .
  • the high-voltage module thus knows the entire actual family of curves from FIG. 7, including all the curves not shown in between.
  • the high-voltage module calculates the current open-circuit voltage U 0a from the linear relationship between the supply voltage of the high-voltage generator (which is measured) and U 0 .
  • the associated U / I characteristic data are retrieved from the memory.
  • the measured spray current I sm is used by the computer to determine the current working point AP a . This also determines the current electrode voltage U a .
  • a current measuring circuit is shown.
  • the circuit the figure comprises a control device 10, two coupling capacitors 11, 37, a transformer 13 with a primary coil 14 and a secondary coil 15 connected via a bridge 12 are connected, a high-voltage cascade 16, an electrode 17 with an electrode resistor and a resistor 18, which are connected to one another in the manner shown in FIG are. Furthermore, there is a low pass indicated at 22 as well as a current-voltage converter designated 25. Also shown in Figure 8 is one to be coated Workpiece 19.
  • the low pass comprises a first low pass coil 21 which is on the Side of the bridge 12 with the primary coil 14 and one Capacitor 23 is connected to earth 9, and a second Low-pass coil 26, which the current-voltage converter 25 with the connection point 35 of the first low-pass coil 21 and capacitor 23 connects.
  • a resistor 24 connected to the capacitor 23 in series.
  • the current-voltage converter 25 has an operational amplifier 27, whose output is via a feedback resistor 28 is connected to its inverting input.
  • the second low-pass coil 26 is also on the inverting Input 38 of operational amplifier 27 connected, and the non-inverting input 39 of the operational amplifier 27 is connected to earth 9.
  • a filter network 29 from two resistors 30 and 31 and two capacitors 32 and 33 and an output amplifier 34 are arranged, which in the manner shown in Figure 8 with each other are connected.
  • the circuit of Figure 8 operates as follows. If one Workpiece 19 is in front of the electrode 17 and electrical Charge is transferred to the workpiece 19 flows in Spray current over air particles (ions) and powder particles for Workpiece and back to earth to the control unit. This Spray current flows through the operational amplifier 27 Low pass 22 and via the transformer bridge 12 into the high-voltage cascade 16 back.
  • the current-voltage converter 25 is constructed and dimensioned so that at the exit of the Operational amplifier 27 sets a voltage that is proportional to the electrical spray current from the electrode 19 to earth 9.
  • the voltage at the output 36 of this measuring circuit can on the be evaluated as described above.

Description

Die Erfindung betrifft ein Verfahren zum Erkennen von Werkstücken in einer elektrostatischen Beschichtungsanlage sowie eine elektrostatische Beschichtungsanlage, bei der dieses Verfahren angewendet werden kann.The invention relates to a method for recognizing Workpieces in an electrostatic coating system and an electrostatic coating system in which this procedure can be used.

Herkömmliche automatische Beschichtungsanlagen werden über speicherprogrammierbare Steuerungen (SPS) gesteuert. Hierfür ist eine zentrale Recheneinheit vorgesehen, von der aus eine Vielzahl von elektrischen und pneumatischen Leitungen zu Sensoren und Stellgliedern (oder Aktoren) der Anlage gehen.Conventional automatic coating systems are over programmable logic controllers (PLC) controlled. Therefor a central processing unit is provided from which a variety of electrical and pneumatic lines go to sensors and actuators (or actuators) of the system.

Die aktuellen Zustände der Sensoren (z.B. Fördertakt des Werkstücks, Füllstand der Vorratsbehälter etc.) werden zyklisch von der Zentraleinheit erfaßt, die notwendigen Reaktionen der zugehörigen Stellglieder werden jeweils errechnet, und entsprechende Steuerbefehle werden an die Stellglieder weitergeleitet.The current status of the sensors (e.g. funding cycle of the Workpiece, fill level of the storage container etc.) become cyclical captured by the central unit, the necessary reactions the associated actuators are calculated, and corresponding control commands are sent to the actuators forwarded.

Bei den üblichen elektrostatischen Pulverbeschichtungsanlagen läuft ein Werkstück in horizontaler Richtung durch eine Beschichtungskabine, in deren Seitenwand vertikale Schlitze vorgesehen sind. Durch diese Schlitze geben elektrostatische Beschichtungspistolen Beschichtungspulver in die Beschichtungskabine ab. Während das Werkstück durch die Beschichtungskabine geführt wird, bewegen sich die hintereinander angeordneten, mehreren Beschichtungspistolen in vertikaler Richtung auf und ab, wobei das Werkstück durch die Werkstückbewegung in der Horizontalen und der Vertikalen mit mehreren aneinander angrenzenden oder sich teilweise überdeckenden sinusförmigen Pulverschwaden beschichtet wird.With the usual electrostatic powder coating systems runs a workpiece in a horizontal direction Coating booth with vertical slots in the side wall are provided. Pass through these slots electrostatic Coating guns coating powder in the coating booth from. While the workpiece is through the coating booth is led, they move one after the other arranged, several coating guns in a vertical Direction up and down, with the workpiece moving through the workpiece in the horizontal and vertical with several adjacent or partially overlapping sinusoidal powder vapor is coated.

Um eine gleichmäßige und ausreichende Beschichtungsdicke auf dem Werkstück zu erhalten und um den Wirkungsgrad beim Pulverauftrag zu optimieren, werden der Vertikalhub der Beschichtungsgeräte sowie die Pulverabgabe gesteuert. Zusätzlich wird der Abstand zwischen Beschichtungsgerät und Werkstück in der Sprührichtung eingestellt, um zu vermeiden, daß bei einem zu geringen Abstand das Pulver wieder abgeblasen wird oder sich elektrostatische Krater bilden bzw. daß sich im umgekehrten Fall der Wirkungsgrad der Pulverbeschichtung verschlechtert und z.B das Eindringvermögen in Hohlräume abnimmt.To ensure an even and sufficient coating thickness the workpiece and to ensure the efficiency of powder application to optimize the vertical stroke of the coating equipment as well as controlled powder delivery. additionally becomes the distance between the coating device and the workpiece set in the spray direction to avoid that if the distance is too short, blow off the powder again will or electrostatic craters form or that in the opposite case, the efficiency of the powder coating deteriorates and e.g. the penetration into cavities decreases.

Zu diesem Zweck haben bekannte Pulverbeschichtungsanlagen eine Teileerkennungs- und Identifikationseinrichtung sowie eine Zeitgebereinrichtung.Known powder coating systems have been used for this purpose a parts recognition and identification device and a timer device.

Die Teileerkennung wird zum Beispiel in Lackieranlagen zur Realisierung einer Lückensteuerung verwendet. Dabei wird in Werkstücklücken die Förderung und somit das Auftragen von Pulverlack oder Naßlack unterbrochen. Dadurch reduziert sich der Verbrauch an Beschichtungsstoffen, die Abfallmenge bei Naßlacken und der rezirkulierte Anteil bei Pulverlacken. Der prinzipielle Aufbau einer Lückensteuerung des Standes der Technik ist in Figur 9 gezeigt.Parts recognition is used, for example, in paint shops Realization of a gap control used. Thereby in Workpiece gaps the promotion and thus the application of Powder paint or wet paint interrupted. This reduces the consumption of coating materials, the amount of waste Wet coatings and the recirculated portion of powder coatings. The basic structure of a gap control of the stand the technique is shown in Figure 9.

Eine Werkstückfördervorrichtung 902 transportiert Werkstücke 904 durch eine Beschichtungskabine 901 in der gezeigten Richtung. Zur Realisierung der Lückensteuerung wird eine Vorrichtung zur Erkennung eines Werkstücks 904 benötigt. Diese besteht aus einer Lichtschranke 906 oder 906', 908, wobei Licht vom Lichtsender 906 oder 906' gesendet und vom Empfänger 908 empfangen wird, und wobei entsprechende Signale an eine Steuerung 912 weitergeleitet werden.A workpiece conveyor 902 transports workpieces 904 through a coating booth 901 in the shown Direction. To implement gap control, a Device for recognizing a workpiece 904 is required. This consists of a light barrier 906 or 906 ', 908, where light is sent from light transmitter 906 or 906 'and from Receiver 908 is received and corresponding signals be forwarded to a controller 912.

Die Lichtschranke liegt vornehmlich außerhalb der Beschichtungskabine 901. Für die zeitverzögerte Steuerung der Materialförderung benötigt die Steuerung 912 ein zusätzliches Signal, das proportional zur Geschwindigkeit der Fördervorrichtung 902 ist. Dieses Signal kommt nun direkt von einer Fördersystem-Steuerung 915, oder es wird mit einer speziellen Einrichtung 913 zur Messung der Fördergeschwindigkeit ermittelt. Diese Geschwindigkeitsmessvorrichtung erzeugt ein zur Fördergeschwindigkeit proportionales Signal und leitet es zur Steuerung 912. Die Steuerung 912 bestimmt aus der Geschwindigkeitsinformation und dem Signal von der Lichtschranke 806, 908 die Zeit, die das Werkstück 904 benötigt, um bis zur Sprühvorrichtung 905 zu gelangen.The light barrier is primarily outside the coating booth 901. For the delayed control of material handling the controller 912 needs an additional one Signal proportional to the speed of the conveyor Is 902. This signal now comes directly from one Conveyor system control 915, or it comes with a special Device 913 for measuring the conveying speed determined. This speed measuring device generates a signal proportional to the conveying speed and conducts it to the controller 912. The controller 912 determines from the Speed information and the signal from the light barrier 806, 908 the time it takes the workpiece 904 to get to sprayer 905.

Die Lichtschranke 906, 908 "informiert" die Steuerung 912 auch von dem Ende eines Werkstücks. Damit hat man nun eine Einrichtung die das Einfahren eines Werkstücks 904 in die Kabine 901 erkennt, dessen Länge ermittelt und zeitverzögert, abhängig von der Geschwindigkeit des Förderers 902, die Materialförderung 910, 911 ein- und ausschalten kann.The light barrier 906, 908 "informs" the controller 912 also from the end of a workpiece. Now you have one Means the insertion of a workpiece 904 into the Detects cabin 901, determines its length and delays it, depending on the speed of the conveyor 902, the material feed 910, 911 can switch on and off.

Zur Steuerung der Beschichtungsgeräte sind im Stand der Technik weiterhin eine Positionssteuereinrichtung und eine Bewegungssteuereinrichtung vorgesehen, die ebenfalls die Information über Anfang, Ende und Geschwindigkeit des Werkstücks benötigen. Die Positionssteuereinrichtung steuert die Abstände der Beschichtungsgeräte zu den Werkstücken. Die Bewegungssteuereinrichtung steuert den Vertikalhub der Beschichtungsgeräte.To control the coating devices are in the state Technology further a position control device and Movement control device provided, which is also the information about the start, end and speed of the workpiece need. The position control device controls the Distances of the coating devices to the workpieces. The Motion control device controls the vertical stroke of the coating devices.

Die Beschichtungsanlage erfordert einen großen Rechenaufwand, um die mehreren Beschichtungsgeräte aufeinander abgestimmt so ein- und auszuschalten, auf und ab sowie vor und zurück zu bewegen, daß ein optimales Beschichtungsergebnis erhalten wird.The coating system requires a great deal of computing effort, coordinated with the several coating devices so on and off, up and down as well as before and to move back that optimal coating result is obtained.

Ferner ist für die Teileerkennung und -identifikation eine relativ komplexe und teure optische Erfassungsvorrichtung notwendig.Furthermore, for parts recognition and identification relatively complex and expensive optical detection device necessary.

Das U.S. Patent 4,324,812 beschreibt eine Pulverbeschichtungsanlage, bei welcher der Sprühstrom erfaßt wird, um abhängig von dem Sprühstrom den Pulvermassestrom, der an ein zu beschichtendes Werkstück abgegeben wird, zu steuern. Dem Patent liegt die Erkenntnis zugrunde, daß kleinere zu beschichtende Flächen das elektrische Feld konzentrieren, so daß ein höherer Strom gezogen wird, während größere Flächen weniger Strom ziehen. Daraus folgt, daß kleinere Flächen stärker beschichtet werden als größere Flächen. Um dem entgegenzuwirken, ist in dem genannten U.S. Patent vorgesehen, daß bei einer Abnahme des Sprühstroms der Pulvermassestrom erhöht wird, während bei einer Zunahme des Sprühstroms der Pulvermassestrom gesenkt wird. Ein Verfahren oder eine Vorrichtung zur Teileerkennung und -identifikation ist in dieser Druckschrift nicht beschrieben.The U.S. Patent 4,324,812 describes a powder coating installation in which the spray stream is detected in order depending on the spray flow, the powder mass flow to a coating workpiece is given to control. The patent is based on the knowledge that that smaller areas to be coated concentrate the electric field, so that a higher electricity is drawn while larger areas draw less electricity. It follows, that smaller areas are coated more than larger areas. To counteract this is in the U.S. Patent provided that with a decrease in the spray flow the powder mass flow is increased, while with an increase in the spray flow the Powder mass flow is reduced. A method or device for parts recognition and identification is not described in this document.

Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren zum Erkennen eines Werkstücks in einer elektrostatischen Beschichtungsanlage und eine neue Beschichtungsanlage anzugeben, bei denen der Hardware- und Softwareaufwand für die Teileerkennung und -identifikation verringert und die Steuerung vereinfacht werden kann.The invention has for its object a method for Detection of a workpiece in an electrostatic coating system and to specify a new coating system, where the hardware and software expenditure for the Part recognition and identification reduced and control can be simplified.

Diese Aufgabe wird durch ein Verfahren mit den Merkmalen des Anspruchs 1 sowie eine Beschichtungsanlage mit den Merkmalen von Anspruch 7 gelöst. This object is achieved by a method having the features of claim 1 and Coating system with the features of claim 7 solved.

Die Erfindung nutzt die Tatsache aus, daß in einem elektrostatischen Beschichtungsgerät eine Hochspannungselektrode oder Sprühelektrode, elektrostatische Ladungen an die Umgebung abgibt, welche einen elektrischen Sprühstrom von der Hochspannungselektrode durch die Luft zur Erde erzeugen, und zwar unabhängig davon, ob gleichzeitig von dem Beschichtungsgerät ein Beschichtungsmaterial an das Werkstück abgegeben wird oder nicht. Wenn ein elektrisch leitendes, geerdetes Werkstück vor dem Beschichtungsgerät vorbeigeführt wird, fließt der elektrische Sprühstrom von der Hochspannungselektrode durch das Werkstück zur Erde.The invention takes advantage of the fact that in an electrostatic Coating device a high voltage electrode or spray electrode, electrostatic charges to the environment emits an electrical spray current from the Generate high voltage electrode through the air to earth, and regardless of whether at the same time by the coating device delivered a coating material to the workpiece will or not. If an electrically conductive, grounded Workpiece passed in front of the coating device the electrical spray current flows from the high voltage electrode through the workpiece to earth.

Beim Annähern des Werkstücks an die Sprühpistole steigt der Sprühstrom kontinuierlich an (siehe Figur 2). Befindet sich nun die Sprühelektrode auf gleicher Höhe wie das Werkstück, so ändert sich der Sprühstrom nur noch unwesentlich. Die Erhöhung des Sprühstroms wird für die Teileerkennung ausgenutzt. Messungen haben belegt, daß der Gesamtstrom der durch die Elektrode fließt zum größten Teil vom Abstand zwischen Sprühelektrode und Werkstück bestimmt wird, sowie von der eingestellten Hochspannung.As the workpiece approaches the spray gun, it increases Spray flow continuously (see Figure 2). Is located now the spray electrode at the same height as the workpiece, the spray flow changes only insignificantly. The Increasing the spray current is used for part recognition. Measurements have shown that the total current of the through the electrode flows mostly from the distance between Spray electrode and workpiece is determined, as well as by the set high voltage.

Die Messung des Sprühstroms kann daher als Mittel zur Erkennung eines Werkstücks vor dem Beschichtungsgerät verwendet werden. Gemäß der Erfindung wird abhängig von der Größe des Sprühstroms der Betrieb des Beschichtungsgerätes gesteuert.The measurement of the spray current can therefore be used as a means of detection of a workpiece used in front of the coating device become. According to the invention, depending on the size of the Spray current controlled the operation of the coating device.

Die im Stand der Technik übliche optische Werkstückerkennung kann dadurch ganz entfallen.The optical workpiece recognition that is customary in the prior art can be completely omitted.

Durch Definieren geeigneter Schwellwerte kann erkannt werden, ob sich das Werkstück an das Beschichtungsgerät annähert, sich vor diesem befindet oder ob es sich entfernt und ob es den richtigen Abstand zur Sprühelektrode hat.By defining suitable threshold values, it can be recognized whether the workpiece approaches the coating device, is in front of it or whether it is moving away and whether it is at the correct distance from the spray electrode.

Das neue Verfahren zur Teileerkennung gemäß der Erfindung, ermöglicht es, z.B. eine Lückensteuerung viel einfacher zu realisieren als im Stand der Technik, indem direkt vor Ort, an der Beschichtungspistole ein Werkstück erkannt wird und abhängig von dem Vorhandensein eines Werkstücks die Förderung und Abgabe des Beschichtungsmaterials aktiviert wird. Bei dem neuen System wird somit keine externe "Lückensteuerung" benötigt.The new method for parts recognition according to the invention, enables e.g. a gap control much easier too realize than in the state of the art by directly on site, a workpiece is recognized on the coating gun and depending on the presence of a workpiece and release of the coating material is activated. With the new system there is no external "gap control" needed.

Wie bereits erwähnt, ist für die Größe des Sprühstroms neben der Hochspannungsvorwahl vor allem der Abstand von Werkstück und Elektrode maßgebend.As already mentioned, is for the size of the spray current the high voltage preselection, especially the distance from the workpiece and electrode decisive.

Für eine optimale Beschichtung sollte dieser Abstand konstant sein. Da es jedoch viele Werkstücke mit sich in Längsrichtung ändernden Konturen gibt, und die Sprühpistole einen Vertikalhub durchläuft, ändert sich dabei der Abstand. Abhängig von dem gemessenen Sprühstrom kann nun der Abstand zwischen dem Werkstück und dem Beschichtungsgerät in Sprührichtung ermittelt und konstant gehalten werden.For an optimal coating, this distance should be constant his. However, since there are many workpieces with it lengthways changing contours, and the spray gun one The vertical stroke passes, the distance changes. Dependent the distance can now be measured from the measured spray current between the workpiece and the coating device in the spray direction determined and kept constant.

Die Teileerkennung kann auch zur Ermittlung der Geschwindigkeit eines Werkstücks herangezogen werden. Da in der Praxis meistens drei und mehr Pistolen horizontal hintereinander in gleichem Abstand angeordnet sind, kann daraus die Fördergeschwindigkeit hergeleitet werden. Da eine einmal gewählte Geschwindigkeit über einen längeren Zeitraum konstant bleibt, kann aus mehreren aufeinander folgenden relativ ungenauen Messungen durch statistische Methoden die Fördergeschwindigkeit genauer berechnet werden.The parts recognition can also be used to determine the speed of a workpiece can be used. Because in practice usually three and more guns in a row horizontally the same distance, the conveying speed be derived. Because once chosen Constant speed over a longer period of time remains, can be relatively imprecise from several successive Measurements by statistical methods the conveyor speed can be calculated more precisely.

Die Geschwindigkeitsinformation kann dann zur Steuerung und Synchronisierung des Vertikalhubs der Beschichtungsgeräte verwendet werden.The speed information can then be used for control and Synchronization of the vertical stroke of the coating devices be used.

Die Erfindung schafft mit dem Verfahren zur Erkennung von Werkstücken mit Hilfe der Sprühströme der elektrostatischen Beschichtungsgeräte ein zuverlässiges, schnelles und kostengünstiges Mittel für die Erfassung und Identifikation der zu beschichtenden Werkstücke, das die im Stand der Technik üblichen Teileerkennungs- und Identifikationseinrichtungen vollständig ersetzten kann. Ferner hat die Erfindung den Vorteil, daß die Anwesenheit eines Werkstücks vor den jeweiligen Beschichtungsgeräten während des Betriebs laufend überprüft werden kann und nicht, wie im Stand der Technik, nur aufgrund einer einmaligen Messung beim Eintritt des Werkstücks in die Beschichtungskabine vorausgesagt wird. Bei einem außerplanmäßige Stillstand der Werkstückförderung kann dadurch z.B. sofort die Pulverabgabe gesperrt werden. Weiterhin ermöglicht die Erfindung eine weitgehende Dezentralisierung der Beschichtungsanlage, weil jedes Beschichtungsgerät selbständig erkennt, ob ein Werkstück vorhanden ist, und abhängig vom Sprühstrom seine Pulverabgabe und seinen Abstand zum Werkstück steuern kann.The invention creates with the method for the detection of Workpieces using the spray currents of the electrostatic Coating equipment a reliable, fast and inexpensive Means for the registration and identification of the coating workpieces, which are those in the prior art usual part recognition and identification devices can completely replace. Furthermore, the invention has the Advantage that the presence of a workpiece in front of each Coating devices running during operation can be checked and not, as in the prior art, only on the basis of a single measurement when the Workpiece in the coating booth is predicted. at an unscheduled standstill of workpiece conveying thereby e.g. the powder supply can be blocked immediately. Farther the invention enables extensive decentralization the coating system because every coating device independently recognizes whether a workpiece is available, and depending on the spray flow its powder delivery and its Can control the distance to the workpiece.

Die Erfindung ist im folgenden anhand des Beispiels einer elektrostatischen Pulverbeschichtungsanlage mit Bezug auf die Zeichnungen näher erläutert. In den Figuren zeigen:

Fig. 1
eine elektrostatische Pulverbeschichtungsanlage gemäß der vorliegenden Erfindung;
Fig. 2
ein Diagramm des Sprühstrom abhängig von dem Abstand zwischen einer Sprühelektrode und einem Werkstück;
Fig.3
eine schematische Darstellung zur Erläuterung der Abstandseinstellung zwischen Werkstück und Sprühpistole gemäß der Erfindung;
Fig. 4
eine schematische Darstellung zur Erläuterung des Verfahrens zur Ermittlung der Geschwindigkeit eines Werkstücks gemäß der Erfindung;
Fig. 5a, 5b
zwei Diagramme unterschiedlicher Wellenlinien aus Beschichtungsmaterial, die mit zwei synchronisierten bzw. zwei nicht synchronisierten Beschichtungsgeräten erhalten werden;
Fig. 6
eine ideale und eine real U/I-Kennlinie einer Hochspannungselektrode eines Beschichtungsgerätes;
Fig. 7
eine Kurvenschar aus U/I-Kennlinien für unterschiedliche Versorgungsspannungen des Hochspannungserzeugers eines Beschichtungsgerätes;
Fig. 8
eine Einrichtung zur Erfassung des elektrischen Sprühstroms; und
Fig. 9
eine Beschichtungsanlage nach dem Stand der Technik mit einer Lückensteuerung;
The invention is explained below using the example of an electrostatic powder coating system with reference to the drawings. The figures show:
Fig. 1
an electrostatic powder coating system according to the present invention;
Fig. 2
a diagram of the spray current depending on the distance between a spray electrode and a workpiece;
Figure 3
is a schematic representation for explaining the distance setting between the workpiece and spray gun according to the invention;
Fig. 4
a schematic representation for explaining the method for determining the speed of a workpiece according to the invention;
5a, 5b
two diagrams of different wavy lines from coating material, which are obtained with two synchronized or two non-synchronized coating devices;
Fig. 6
an ideal and a real U / I characteristic of a high-voltage electrode of a coating device;
Fig. 7
a family of curves of U / I characteristics for different supply voltages of the high-voltage generator of a coating device;
Fig. 8
a device for detecting the electrical spray current; and
Fig. 9
a coating system according to the prior art with a gap control;

Figur 1 zeigt eine Pulverbeschichtungsanlage gemäß der Erfindung. Diese Pulverbeschichtungsanlage ist ausführlicher in der deutschen Patentanmeldung "Steuersystem einer Beschichtungsanlage" derselben Anmelderin, mit demselben Anmeldetag beschrieben. Auf die Offenbarung dieser Patentanmeldung und insbesondere die dortige Erläuterung der Netzwerkstruktur wird ausdrücklich Bezug genommen.Figure 1 shows a powder coating system according to the invention. This powder coating system is more detailed in the German patent application "control system of a coating system" the same applicant, with the same filing date described. To the disclosure of this patent application and in particular the explanation of the network structure there reference is expressly made.

In Fig. 1 sind mehrere (fünf) Beschichtungsmodule aus jeweils einem digitalen Steuergerät 60, einem Injektor 64 und einer Sprühpistole 66 dargestellt, die über einen Pistolenbus 62 verbunden sind. Für den Betrieb notwendige Informationen über die Betriebszustände der Beschichtungsanlage erhalten die Steuergeräte 60 über einen internen Bus 80.In Fig. 1 there are several (five) coating modules each a digital control device 60, an injector 64 and a spray gun 66 shown over a gun bus 62 are connected. Information necessary for the operation about the operating conditions of the coating system receive the control units 60 via an internal bus 80.

Über den internen Bus 80 sind die mehreren Beschichtungsmodule ferner miteinander und mit einer zentralen Steuereinheit 82 sowie mit weiteren Komponenten des Systems verbunden. Zusätzliche, an den internen Bus anschließbaren Module sind z. B. ein Pulverpegelsteuermodul 88, ein Positionssteuermodul 90 und ein Bewegungssteuermodul 92.The multiple coating modules are via the internal bus 80 also with each other and with a central control unit 82 and connected to other components of the system. Additional modules that can be connected to the internal bus are z. B. a powder level control module 88, a position control module 90 and a motion control module 92.

Es sind noch weitere Baugruppen vorgesehen, die über einen externen Bus 100 ebenfalls mit der zentralen Steuereinheit 82 verbunden sind; diese umfassen ein Pulverzentrum 102 mit einem Pulvervorratsbehälter 104, eine Schichtdickenmeß- und Regeleinrichtung 107, 108 und eine Luftmengenregeleinrichtung 109 für ein Pulverrückgewinnungssystem 110, 114 u.a.There are also other modules that have a external bus 100 also with the central control unit 82 are connected; these also include a powder center 102 a powder storage container 104, a layer thickness measuring and Control device 107, 108 and an air quantity control device 109 for a powder recovery system 110, 114 and others

Die Busse 62, 80, 100 sind vorzugsweise Lon-Busse (LON = local area network). Die einzelnen Komponenten, die als LON-Knoten konfiguriert sind, können sich im System selbst anmelden, andere Systemkomponenten erkennen, sich auf diese einstellen und mit diesen kommunizieren. Sie können die Information über die jeweiligen Betriebszustände der Beschichtungsanlage, die sie über den Bus 80 oder 100 erhalten, auswerten und nutzen.The buses 62, 80, 100 are preferably Lon buses (LON = local area network). The individual components that act as LON nodes configured, can register themselves in the system, other system components recognize themselves on this adjust and communicate with them. You can use the information about the respective operating conditions of the coating system, which you receive via bus 80 or 100 and use.

In groben Zügen läuft der Betrieb in der in Figur 1 gezeigten Pulverbeschichtungsanlage wie folgt ab. Ein Werkstück 200 nähert sich der Beschichtungskabine 120. An den Hochspannungselektroden der Sprühpistolen 66-1, 66-2, ..., 66-n liegt eine Hochspannung von etwa 100 kV an, so daß ein elektrischer Sprühstrom von den jeweiligen Elektroden durch die Luft zu Erde fließt. Dieser Sprühstrom ist, solange sich kein geerdetes Werkstück vor der jeweiligen Sprühpistole befindet, sehr klein (sog. Nullstrom).Broadly speaking, the operation is as shown in FIG Powder coating system as follows. A workpiece 200 approaches the coating booth 120. At the high voltage electrodes the spray guns 66-1, 66-2, ..., 66-n there is a high voltage of about 100 kV, so that an electrical Spray current from the respective electrodes through the Air flows to earth. This spray stream is as long as no grounded workpiece in front of the respective spray gun located, very small (so-called zero current).

Figur 2 zeigt den Zusammenhang zwischen dem elektrischen Sprühstrom und dem Abstand zwischen dem Beschichtungsgerät 66 und dem Werkstück 200 bzw. der Zeit. Die y-Achse zeigt den Strom, auf der x-Achse sind der Abstand in cm und die Zeit in Sekunden dargestellt, wobei eine konstanten Fördergeschwindigkeit von 10 cm/s angenommen wird.Figure 2 shows the relationship between the electrical Spray current and the distance between the coating device 66 and the workpiece 200 or the time. The y axis shows the current, on the x-axis are the distance in cm and the Time represented in seconds, with a constant conveying speed of 10 cm / s is assumed.

Zum Zeitpunkt t1 ist das Werkstück noch sehr weit von der Sprühpistole 66 entfernt. Es fließt ein Sprühstrom I1 zur nächstgelegenen Erde, dieser Sprühstrom wird laufend gemessen und mit vorhergegangenen Meßwerten verglichen. Bis zum Zeitpunkt t2 ändert sich der Strom unwesentlich. Ab demAt time t 1 , the workpiece is still very far away from spray gun 66. A spray current I 1 flows to the nearest earth, this spray current is measured continuously and compared with previous measured values. The current changes insignificantly up to time t 2 . From the

Zeitpunkt t2 beginnt nun der Strom zu steigen. Vom zuvor beschichteten Werkstück kann bereits der ungefähre Endwert I2 bekannt sein. Zum Zeitpunkt t3 ist das Werkstück noch ca. 20 cm von der Sprühpistole entfernt. Die frei wählbare Einschaltschwelle wird in diesem Beispiel auf 25% von ΔIs gesetzt.At time t 2 , the current begins to rise. The approximate final value I 2 of the previously coated workpiece can already be known. At time t 3 , the workpiece is still approx. 20 cm from the spray gun. The freely selectable switch-on threshold is set to 25% of ΔI s in this example.

Zum Zeitpunkt t3 wird somit die Einschaltbedingung erkannt und das Steuergerät 60 schickt über den Pistolenbus 62 einen Einschaltbefehl an den Injektor 64. Der Injektor 64 enthält zwei Luftmengenregler zur Einstellung von Förderluft und Dosierluft für das Beschichtungsgerät. Damit wird die Pulverförderung eingeschaltet. Kommt nun das Werkstück 200 zur Beschichtungspistole 66, so wird es beschichtet. Im Zeitintervall t4 bis t5 läuft das Werkstück an der Pistole vorbei. Im beschriebenen Fall ist die Länge des Werkstücks 20 cm. Ab dem Zeitpunkt t5 entfernt sich nun das Werkstück 200 von der Sprühpistole 66 und der Sprühstrom sinkt. Zum Zeitpunkt t6 ist das Werkstück 10 cm von der Sprühpistole entfernt, wiederum wird eine vorgewählte Schaltschwelle (hier 50% von ΔIs) überquert und über den LON-Bus 92 wird die Pulverförderung abgeschaltet.The switch-on condition is thus recognized at time t3 and the control unit 60 sends a switch-on command to the injector 64 via the gun bus 62. The injector 64 contains two air quantity regulators for setting the conveying air and metering air for the coating device. This switches on the powder feed. If the workpiece 200 now comes to the coating gun 66, it is coated. In the time interval t 4 to t 5 , the workpiece runs past the gun. In the case described, the length of the workpiece is 20 cm. From time t 5 , the workpiece 200 now moves away from the spray gun 66 and the spray current drops. At time t 6 the workpiece is 10 cm away from the spray gun, again a preselected switching threshold (here 50% of ΔI s ) is crossed and the powder feed is switched off via the LON bus 92.

Der gemessene Sprühstrom kann auch zur Einstellung des Abstandes zwischen Werkstück 200 und Sprühpistole 66 verwendet werden.The measured spray current can also be used to set the distance used between workpiece 200 and spray gun 66 become.

In Figur 3 ist eine mögliche Konfiguration des Positionssteuermoduls dargestellt. Die Positionssteuerung wird häufig als Z-Achsensteuerung bezeichnet. Solche Steuerungen sind bekannt, doch bewegen sich die Beschichtungsgeräte bisher auf einer fest einprogrammierten Bahn. Bei der neuen Methode, erfolgt die Anpassung an die Werkstückkontur automatisch.FIG. 3 shows a possible configuration of the position control module shown. Position control becomes common referred to as Z-axis control. Such controls are known, but so far the coating devices are moving on a permanently programmed track. With the new method, the adaptation to the workpiece contour takes place automatically.

Der in der Sprühpistole 66 integrierte Hochspannungserzeuger erzeugt einen Sprühstrom von der Elektrode 17 zum Werkstück 200. Dieser Sprühstrom wird von einem Hochspannungsmodul 300 gemessen und an einen Abstandsregler 302 weitergeleitet. Dieser Regler versucht einen vorgegebenen Sprühstrom einzuregeln. Ist z.B. der Sprühstrom kleiner als vorgegeben, so wird vom Regler 302 ein Korrektursignal an eine Verschiebeachsensteuerung 304 übertragen. Diese wiederum veranlaßt einen Servomotor 306 eine Pistolenhalterung 308 und mit ihr die Pistole 66 näher an das Werkstück 200 zu schieben.The high voltage generator integrated in the spray gun 66 generates a spray current from the electrode 17 to the workpiece 200. This spray current is generated by a high-voltage module 300 measured and forwarded to a distance controller 302. This controller tries to regulate a given spray current. Is e.g. the spray flow is less than specified, so controller 302 sends a correction signal to a displacement axis controller 304 transmitted. This in turn causes a servo motor 306 and a gun mount 308 to push the gun 66 closer to the workpiece 200.

Dieser Regelvorgang muß relativ schnell vor sich gehen. Durch die Auf- und Abbewegung der ganzen Einheit mit Hilfe eines Hubgeräts 310, wird die Elektrode 17 entlang der gestrichelten Linie 312 bewegt. Dadurch wird die Pistole immer in einem korrekten Abstand zum Werkstück 200 gehalten. Der Regler 302 ist in der Praxis als ein "Softwareteil" des Hochspannungsmoduls 300 realisiert. Der erwähnte Regler ist vorzugsweise kein Standard PI oder PID Regler, sondern ein sogenannter intelligenter Regler.This control process must be done relatively quickly. By moving the whole unit up and down with help of a lifting device 310, the electrode 17 is drawn along the dashed line Line 312 moves. This will keep the gun going held at a correct distance from workpiece 200. The Controller 302 is in practice as a "software part" of the High voltage module 300 realized. The regulator mentioned is preferably not a standard PI or PID controller, but a so-called intelligent controller.

Die Fördergeschwindigkeit des Werstücks kann aus den Zeitpunkten ermittelt werden, zu denen die Sprühströme einer ersten und einer zweiten Sprühpistole 66-1 und 66-2 einen vorgegebenen Schwellwert überschreiten, und abhängig von den ermittelten Zeitpunkten und dem bekannten Abstand zwischen der ersten und der zweiten Sprühpistole wird die Geschwindigkeit des Werkstückes berechnet.The conveying speed of the workpiece can be from the times can be determined to which the spray streams of a first and a second spray gun 66-1 and 66-2 a predetermined one Threshold, and depending on the determined times and the known distance between the first and the second spray gun the speed of the workpiece is calculated.

Figur 4 zeigt prinzipiell die Anordnung von 3 Pistolen.Figure 4 shows in principle the arrangement of 3 guns.

Ein Fördersystem bringt verschiedene Werkstücke 200 in der gezeigten Richtung in die Beschichtungskabine 120. Ein Werkstück 200 bewegt sich nun zur ersten Beschichtungspistole 66-1. Ein erstes Hochspannungsmodul 400-1 registriert einen Anstieg des Sprühstroms. Eine im Modul eingebaute Echtzeituhr registriert den genauen Zeitpunkt der Erkennung und sendet den Startzeitpunkt der Messung an ein zweites Hochspannungsmodul 400-2. Das Werkstück bewegt sich nun zur zweiten Beschichtungspistole 66-2 und löst dort wiederum einen Startzeitpunkt mit Hilfe einer Echtzeituhr aus. Dieser Startwert der zweiten Messung wird sogleich über das Bus-System 402 zum dritten Hochspannungsmodul gesendet. Der Startzeitpunkt der zweiten Messung ist zugleich der Stoppzeitpunkt der ersten Messung. Mit Hilfe des bekannten Abstandes A zwischen erster und zweiter Pistole und der Zeitdifferenz zwischen Start- und Stoppzeitpunkt wird die Geschwindigkeit des Werkstücks berechnet und über den Bus 402 an einen beliebigen anderen Busteilnehmer 404 gesendet, der für seine Funktion die Geschwindigkeit des Fördersystems kennen muß.A conveyor system brings different workpieces 200 in the shown direction in the coating booth 120. A workpiece 200 now moves to the first coating gun 66-1. A first high voltage module 400-1 registers one Increase in spray flow. A real-time clock built into the module registers the exact time of detection and sends the start time of the measurement to a second high-voltage module 400-2. The workpiece now moves to the second Coating gun 66-2 and releases one there again Start time with the help of a real-time clock. This The start value of the second measurement is immediately via the bus system 402 sent to the third high voltage module. The start time the second measurement is also the stop time the first measurement. With the help of the known distance A between the first and second gun and the time difference The speed is between the start and stop time of the workpiece is calculated and sent to any one via bus 402 sent to other bus subscriber 404 who is responsible for his Function must know the speed of the conveyor system.

Bewegt sich nun das Werkstück 200 weiter zur dritten Pistole 66-3, so wird der zweite Stoppzeitpunkt ausgelöst. Aus der zweiten Zeitdifferenz (Startzeitpunkt Nr.2 und Stoppzeitpunkt Nr.2) und dem bekannten Abstand B wird der zweite Geschwindigkeits-Meßwert ermittelt und an den Bus 402 übergeben.The workpiece 200 now moves on to the third gun 66-3, the second stop time is triggered. From the second time difference (start time No. 2 and stop time No. 2) and the known distance B becomes the second measured speed value determined and transferred to bus 402.

Auch läßt sich zur Kontrolle und/oder zum Runden aus dem ersten Startzeitpunkt und dem zweiten Stoppzeitpunkt, sowie der Strecke A + B ein dritter Geschwindigkeitsmeßwert errechnen. Dieser dritte Meßwerte wird der genaueste sein, weil sich Ungenauigkeiten in der Zeitmessung und in der Werkstückerkennung um so weniger auswirken, je länger die Meßstrecke und die Meßzeit sind. Da bei jedem Werkstück die Geschwindigkeit neu ermittelt wird, kann aus mehreren Messungen die durchschnittliche Geschwindigkeit des Förder systems errechnet werden.You can also check and / or round from the first Start time and the second stop time, as well calculate a third speed measurement along the route A + B. This third measurement will be the most accurate because there are inaccuracies in the timing and in the Workpiece detection has less impact the longer the Measuring distance and the measuring time are. Because with every workpiece New speed can be determined from several measurements the average speed of the conveyor system can be calculated.

Die Information über die Werkstückgeschwindigkeit kann zur Steuerung und Synchronisation der Hubbewegung der Sprühpistolen verwendet werden.The information about the workpiece speed can Control and synchronization of the spray gun stroke be used.

Für den einfachsten Fall wird angenommen, daß zwei Beschichtungspistolen horizontal nebeneinander angeordnet sind. Diese beiden Beschichtungspistolen sind im Abstand A angeordnet (Figuren 5a und 5b). In the simplest case, it is assumed that two coating guns are arranged horizontally next to each other. These two coating guns are arranged at a distance A. (Figures 5a and 5b).

Diese beiden Beschichtungspistolen sind auf einem sogenannten Hubgerät 306 (Figur 3) befestigt. Das Hubgerät bewegt die Pistolen senkrecht auf und ab, und zwar mit einer konstanten Geschwindigkeit von unten nach oben, und mit der gleichen Geschwindigkeit von oben nach unten. In den Umkehrpunkten wird jeweils so schnell wie möglich die Geschwindigkeitsrichtung umgeschaltet. Bei einem rechteckigen Werkstück das kontinuierlich in die Beschichtungskabine hineinfährt wird dadurch die ganze Fläche gleichmäßig beschichtet, sofern die Geschwindigkeit der Fördereinrichtung und des Hubgeräts "synchronisiert" sind. Zum besseren Verständnis sind in Figur 5a und 5b verschiedene Fälle dargestellt.These two coating guns are on a so-called Lifting device 306 (Figure 3) attached. The lifting device moves the guns up and down vertically, with one constant speed from the bottom up, and with the same speed from top to bottom. In the reversal points becomes the speed direction as quickly as possible switched. With a rectangular one Work piece that continuously into the coating booth the entire surface is coated evenly, provided the speed of the conveyor and the lifting device are "synchronized". For better understanding different cases are shown in FIGS. 5a and 5b.

Der Materialniederschlag auf dem Werkstück ähnelt bezüglich der Schichtdicke einer Gausschen Verteilung, deshalb kann die Beschichtungsgrenze in der Breite nicht genau angegeben werden. Jedoch ist im synchronisierten Fall (Figur 5a) ersichtlich, daß die Sprühpistole (2) denjenigen Bereich des Werkstücks beschichtet, der von der Sprühpistole (1) nicht beschichtet werden konnte. Durch die Verwischung der Sprühzonen wird im Fall der Figur 5a die Materialverteilung optimal. Nicht so im nicht synchronisierten Fall der Figur 5b. Dort beschichtet die zweite Pistole (2) vorwiegend den gleichen Bereich, den zuvor Pistole (1) beschichtet hat. Zudem gibt es Zwischenzonen die nicht beschichtet wurden.The material deposit on the workpiece is similar in terms of the layer thickness of a Gaussian distribution, therefore can the width of the coating limit is not precisely specified become. However, in the synchronized case (FIG. 5a) it can be seen that the spray gun (2) that area of Workpiece coated, that of the spray gun (1) not could be coated. By blurring the spray zones in the case of FIG. 5a, the material distribution becomes optimal. Not so in the unsynchronized case of FIG. 5b. There the second gun (2) mainly coats the same Area that gun (1) previously coated. moreover there are intermediate zones that have not been coated.

Werden mehr als zwei Pistolen nebeneinander angeordnet, so git es mehrere Konstellationen, bei denen eine optimale Abdeckung erreicht wird.If more than two pistols are arranged side by side, so there are several constellations where optimal coverage is achieved.

Jedes Beschichtungsmodul kann somit sowohl die Tatsache, daß ein Werkstück 200 sich annähert, als auch die Art, insbesondere Größe und Form des Werkstücks 200, die Geschwindigkeit des Werkstücks und den Abstand von Werkstück zu Sprühpistole erfassen. Diese Informationen werden auf den Bus 100, 80 gegeben und stehen sofort bei den anderen Komponenten der Pulverbeschichtungsanlage zur Verfügung.Each coating module can thus both the fact that a workpiece 200 is approaching, as is the type, in particular Size and shape of the workpiece 200, the speed of the workpiece and the distance from the workpiece to the spray gun to capture. This information is put on the bus 100, 80 and are immediately at the other components of the powder coating system to disposal.

Zum Verständnis der Sprühstrommessung sei folgendes vorausgeschickt.To understand the spray current measurement, the following should be said.

Im allgemeinen ist die Erzeugung einer Hochspannung in einem elektrostatischen Beschichtungsgerät bekannt. In der DE-A-42 32 026 wird beschrieben, wie eine Schaltung aufgebaut ist, die exakt reproduzierbare Strom/Spannungskennlinien produziert. Diese exakt reproduzierbaren Kennlinien sind eine Grundlagen des erfindungsgemäßen Verfahrens.Generally the generation of high voltage is in one electrostatic coating device known. In DE-A-42 32 026 describes how a circuit is constructed, which produces exactly reproducible current / voltage characteristics. These exactly reproducible characteristics are one Basics of the method according to the invention.

Eine Hochspannungserzeugungseinheit besteht in der Regel aus einem Hochspannungssteuermodul mit Oszillator, Endstufe und Steuereinheit und einem Hochspannungserzeuger in der Pistole, bestehend aus Hochspannungstransformator, Vervielfacherkaskade und Schutzwiderständen. Sie besitzt eine U/I-Kennlinie, die das elektrische Verhalten der Gesamteinheit bestimmt. Wäre der Gesamtinnenwiderstand ein ohmscher Widerstand, so wäre die U/I-Kennlinie eine Gerade, mit den Eckpunkten: Kurzschlußstrom und Leerlaufspannung. Siehe dazu Kurve A in Figur 6. In der Praxis ist der Innenwiderstand aufgeteilt in viele, sich summierende komplexe Innenwiderstände und ohmsche Anteile. Die daraus resultierende Kennlinie ist in Figur 6 als Kurve B dargestellt. Der eigentliche Lastwiderstand einer Beschichtungseinheit ist die Luft zwischen Sprühelektrode und Werkstück und besitzt rein ohmschen Charakter. Jedoch ist dieser ohmsche Widerstand abhängig von der Form des Werkstücks, dessen Größe, Oberflächenbeschaffenheit, der Form der Sprühelektrode, der Luftbeschaffenheit, Temperatur, Druck, Feuchtgehalt sowie dem Abstand zwischen Elektrode und Werkstück und zudem vom Hochspannungserzeuger. A high-voltage generation unit usually consists of a high-voltage control module with oscillator, output stage and control unit and a high-voltage generator in the gun, consisting of a high-voltage transformer, multiplier cascade and protective resistors. It has a U / I characteristic curve that determines the electrical behavior of the overall unit. If the total internal resistance were an ohmic resistance, the U / I characteristic curve would be a straight line with the key points: short-circuit current and open circuit voltage. See curve A in Figure 6. In practice, the internal resistance is divided into many, cumulative, complex internal resistances and ohmic components. The resulting characteristic curve is shown in FIG. 6 as curve B. The actual load resistance of a coating unit is the air between the spray electrode and the workpiece and has a purely ohmic character. However, this ohmic resistance depends on the shape of the workpiece, its size, surface quality, the shape of the spray electrode, the air quality, temperature, pressure, moisture content and the distance between the electrode and the workpiece and also on the high-voltage generator.

Die Form der realen U/I-Kennlinie B ist mit einer geeigneten Ansteuerung bei jeder Kombination aus Steuereinheit und Hochspannungserzeuger die Gleiche.With a suitable control, the shape of the real U / I characteristic curve B is the same for every combination of control unit and high-voltage generator.

Figur 7 zeigt eine Kurvenschar, gebildet aus mehreren unterschiedlichen Spannungseinstellungen oder, genauer gesagt, unterschiedlichen Endstufen-Versorgungsspannungseinstellungen. Dabei entsprechen in Figur 7 die Werte U0x den Leerlaufspannungen, die zu den jeweils gewählten Versorgungsspannungen proportional sind. (Der Einfachheit halber wird die gekrümmte Kennlinie durch einen Knick dargestellt.)FIG. 7 shows a family of curves formed from several different voltage settings or, more precisely, different output stage supply voltage settings. In this case, the values U 0x in FIG. 7 correspond to the open circuit voltages, which are proportional to the respectively selected supply voltages. (For the sake of simplicity, the curved characteristic curve is represented by a kink.)

Nehmen wir z.B. die Kurve B1 mit ihren Eckpunkten U01 und Ik1. Darauf sind nun vier mögliche Arbeitspunkte dargestellt. AP1 entspricht einem sehr großen Abstand zwischen Werkstück und Sprühelektrode, wobei das Werkstück immer geerdet ist. Der Abstand ist so groß, daß die in der Luft bewegten Ladungsträger gar nicht zum Werkstück, sondern z.B. zum Pistolenhalter gelangen. Der Punkt AP1 stellt somit in der Praxis die maximale Hochspannung und den minimalen Strom dar. (Der Punkt U01 kann nur im Labor unter gewissen Bedingungen erreicht werden.) Wird nun der Abstand zwischen Werkstück und Elektrode verringert, so bewegt sich der Arbeitspunkt entlang der Kurve B1 auf AP2 zu. Bei diesem Punkt fließt bereits ein beachtlicher Teil der Ladung über das Werkstück ab. Verringert man nun den Abstand von Werkstück zu Elektrode weiter bis zur Berührung, so wandert der Arbeitspunkt weiter über AP3 bis zu AP4 (Kurzschluß).For example, take curve B 1 with its corner points U 01 and I k1 . Four possible working points are now shown on it. AP 1 corresponds to a very large distance between the workpiece and the spray electrode, whereby the workpiece is always grounded. The distance is so large that the load carriers moving in the air do not reach the workpiece, but, for example, the gun holder. In practice, point AP 1 represents the maximum high voltage and the minimum current. (Point U 01 can only be reached in the laboratory under certain conditions.) If the distance between the workpiece and the electrode is reduced, the working point moves along curve B 1 to AP 2 . At this point a considerable part of the load is already flowing off the workpiece. If the distance from the workpiece to the electrode is reduced further to the point of contact, the working point moves further via AP 3 to AP 4 (short circuit).

Wollte man nun eine Spannungsmessung durchführen, so müßte in dem Hochspannungserzeuger ein Spannungsteiler eingebaut werden, der eine kleine, der Hochspannung proportionale Spannung liefert. Dieser Spannungsteiler muß für hohe Spannung bis 100 KV dimensioniert werden und ist somit groß und voluminös.If you wanted to carry out a voltage measurement, you would have to a voltage divider is installed in the high-voltage generator be a small one, proportional to the high voltage Delivers tension. This voltage divider must be for high voltage are dimensioned up to 100 KV and is therefore large and voluminous.

Günstiger ist dagegen die Messung des Sprühstroms, die unten noch erläutert ist.The measurement of the spray current, on the other hand, is cheaper is still explained.

Die Form der U/I-Kennlinie ist im Hochspannungsmodul abgespeichert. Zudem kennt das Hochspannungsmodul den Zusammenhang zwischen Versorgungsspannung und U0. Damit ist dem Hochspannungsmodul die gesamte tatsächliche Kurvenschar von Figur 7, auch mit allen nicht gezeichneten, dazwischenliegenden Kurven, bekannt.The shape of the U / I characteristic is stored in the high-voltage module. The high-voltage module also knows the relationship between supply voltage and U 0 . The high-voltage module thus knows the entire actual family of curves from FIG. 7, including all the curves not shown in between.

Aus dem linearen Zusammenhang der Versorgungsspannung des Hochspannungserzeugers (die gemessen wird) und U0 errechnet das Hochspannungsmodul die aktuelle Leerlaufspannung U0a. Die dazugehörenden U/I Kennliniendaten werden aus dem Speicher abgerufen. Der gemessene Sprühstrom Ism wird vom Rechner zur Bestimmung des aktuellen Arbeitspunktes APa benutzt. Dadurch ist auch die aktuelle Elektrodenspannung Ua bestimmt .The high-voltage module calculates the current open-circuit voltage U 0a from the linear relationship between the supply voltage of the high-voltage generator (which is measured) and U 0 . The associated U / I characteristic data are retrieved from the memory. The measured spray current I sm is used by the computer to determine the current working point AP a . This also determines the current electrode voltage U a .

Für die vorstehend erläuterte Werkstückerkennung genügt die Kenntnis der jeweils zu verwendenden Kennlinie und des gemessenen Sprühstroms. Häufig ist es jedoch wünschenswert, neben dem Sprühstrom auch die aktuelle Elektrodenspannung Ua anzuzeigen.For the workpiece detection explained above, knowledge of the characteristic curve to be used and the measured spray current is sufficient. However, it is often desirable to display the current electrode voltage U a in addition to the spray current.

In Figur 8 ist eine Strommeßschaltung gezeigt. Die Schaltung der Figur umfaßt eine Steuereinrichtung 10, zwei Koppelkondensatoren 11, 37, einen Transformator 13 mit einer Primärspule 14 und einer Sekundärspule 15, die über eine Brücke 12 verbunden sind, eine Hochspannungskaskade 16, eine Elektrode 17 mit einem Elektrodenwiderstand und einen Widerstand 18, welche auf die in Figur 8 gezeigte Weise miteinander verbunden sind. Weiterhin ist ein mit 22 bezeichneter Tiefpaß sowie ein mit 25 bezeichneter Strom-Spannungs-Wandler vorgesehen. Ebenfalls in Figur 8 gezeigt ist ein zu beschichtendes Werkstück 19.In Figure 8, a current measuring circuit is shown. The circuit the figure comprises a control device 10, two coupling capacitors 11, 37, a transformer 13 with a primary coil 14 and a secondary coil 15 connected via a bridge 12 are connected, a high-voltage cascade 16, an electrode 17 with an electrode resistor and a resistor 18, which are connected to one another in the manner shown in FIG are. Furthermore, there is a low pass indicated at 22 as well as a current-voltage converter designated 25. Also shown in Figure 8 is one to be coated Workpiece 19.

Der Tiefpaß umfaßt eine erste Tiefpaß-Spule 21, die auf der Seite der Brücke 12 mit der Primärspule 14 und über einen Kondensator 23 mit Erde 9 verbunden ist, und eine zweite Tiefpaß-Spule 26, welche den Strom-Spannungs-Wandler 25 mit dem Verbindungspunkt 35 von erster Tiefpaß-Spule 21 und Kondensator 23 verbindet. Zusätzlich ist noch ein Widerstand 24 zu dem Kondensator 23 in Reihe geschaltet.The low pass comprises a first low pass coil 21 which is on the Side of the bridge 12 with the primary coil 14 and one Capacitor 23 is connected to earth 9, and a second Low-pass coil 26, which the current-voltage converter 25 with the connection point 35 of the first low-pass coil 21 and capacitor 23 connects. In addition there is a resistor 24 connected to the capacitor 23 in series.

Der Strom-Spannungs-Wandler 25 weist einen Operationsverstärker 27 auf, dessen Ausgang über einen Rückkopplungswiderstand 28 mit seinem invertierenden Eingang verbunden ist. Die zweite Tiefpaß-Spule 26 ist ebenfalls an den invertierenden Eingang 38 des Operationsverstärkers 27 angeschlossen, und der nicht-invertierende Eingang 39 des Operationsverstärkers 27 ist mit Erde 9 verbunden.The current-voltage converter 25 has an operational amplifier 27, whose output is via a feedback resistor 28 is connected to its inverting input. The second low-pass coil 26 is also on the inverting Input 38 of operational amplifier 27 connected, and the non-inverting input 39 of the operational amplifier 27 is connected to earth 9.

Am Ausgang des Strom-Spannungs-Wandlers 25 ist ein Filternetzwerk 29 aus zwei Widerständen 30 und 31 und zwei Kondensatoren 32 und 33 sowie ein Ausgangsverstärker 34 angeordnet, welche auf die in Figur 8 gezeigte Weise miteinander verbunden sind.At the output of the current-voltage converter 25 is a filter network 29 from two resistors 30 and 31 and two capacitors 32 and 33 and an output amplifier 34 are arranged, which in the manner shown in Figure 8 with each other are connected.

Die Schaltung der Figur 8 arbeitet wie folgt. Wenn sich ein Werkstück 19 vor der Elektrode 17 befindet und elektrische Ladung auf das Werkstück 19 übertragen wird, fließt ein Sprühstrom über Luftpartikel (Ionen) und Pulverteilchen zum Werkstück und über Erde zurück zum Steuergerät. Dieser Sprühstrom fließt durch den Operationsverstärker 27, den Tiefpaß 22 und über die Transformatorbrücke 12 in die Hochspannungskaskade 16 zurück. Der Strom-Spannungs-Wandler 25 ist so aufgebaut und dimensioniert, daß sich am Ausgang des Operationsverstärkers 27 eine Spannung einstellt, die proportional zu dem elektrischen Sprühstrom von der Elektrode 19 zu Erde 9 ist.The circuit of Figure 8 operates as follows. If one Workpiece 19 is in front of the electrode 17 and electrical Charge is transferred to the workpiece 19 flows in Spray current over air particles (ions) and powder particles for Workpiece and back to earth to the control unit. This Spray current flows through the operational amplifier 27 Low pass 22 and via the transformer bridge 12 into the high-voltage cascade 16 back. The current-voltage converter 25 is constructed and dimensioned so that at the exit of the Operational amplifier 27 sets a voltage that is proportional to the electrical spray current from the electrode 19 to earth 9.

Die Spannung am Ausgang 36 dieser Meßschaltung kann auf die oben beschriebene Weise ausgewertet werden.The voltage at the output 36 of this measuring circuit can on the be evaluated as described above.

Die in der vorstehenden Beschreibung, den Ansprüchen und der Zeichnung offenbarten Merkmale können sowohl einzeln als auch in beliebiger Kombination für die Realisierung der Erfindung in den verschiedenen Ausgestaltungen von Bedeutung sein.The in the above description, the claims and the Features disclosed can be drawn individually as well also in any combination for the implementation of the invention of importance in the various configurations his.

Claims (12)

  1. A method of detecting workpieces in an electrostatic coating system, comprising at least one electrostatic coating device (66) which applies a high voltage to a high voltage electrode (17), in which
    a spray current containing electrical charges for charging particles of a coating material to be sprayed is generated by the high voltage electrode,
    an electrically conductive workpiece (19; 200) to be coated is passed by the at least one coating device, and
    the spray current of the high voltage electrode (17) is determined, characterized in that
    the spray current is compared to a first threshold value and, if the spray current exceeds the first threshold value, it is detected that the workpiece (19; 200) approaches the coating device (66).
  2. A method according to claim 1, characterized in that depending on the magnitude of the determined spray current at least one function of the coating system is controlled, in particular at least one of the discharge of the coating material and the movement of the or each coating device (66) in at least one of the vertical and horizontal directions.
  3. A method according to claim 1 or 3, characterized in that the coating device (66) starts discharging the coating material when the spray current exceeds the first threshold value and stops the discharge when the spray current falls below a second threshold value.
  4. A method according to one of the preceding claims, characterized in that depending on the spray current the distance between the workpiece (19; 200) and the high voltage electrode (66) in the spray direction is detected and adjusted.
  5. A method according to one of the preceding claims, characterized in that at least two coating devices (66) are provided, that the times (t1, t2) are detected at which the spray currents of a first and a second coating device exceed a predetermined threshold value, that a time difference (t2-t1) is calculated therefrom and that depending on the time difference and the spacing between the first and the second coating devices (66) the speed of the workpiece (19; 200) is determined.
  6. A method according to one of the preceding claims, characterized in that a plurality of U/I characteristic curves for the or each coating device (66) are stored, that an associated U/I characteristic line is selected in accordance with the supply voltage of a high voltage generator (12-16) for the high voltage electrode (17), that the spray current (I 17-9) is measured and that a working point on the U/I characteristic curve is determined in accordance with the spray current and the actual high voltage at the electrode is determined thereby.
  7. An electrostatic coating system comprising at least one coating device (66), including a high voltage electrode (17) which discharges electrical charges including a spray current for charging particles of a coating material to be sprayed, wherein the or each coating device (66) has assigned thereto a measuring device (22, 25) for measuring the spray current, and an evaluating device (60), characterized in that the evaluating device (60) is configured to compare the measured spray current with a first threshold value and, if the spray current exceeds the first threshold value, to determine that the workpiece (19, 200) approaches the coating device (66).
  8. A coating system according to claim 7, characterized in that each of the at least one coating device (66) has assigned thereto a digital control device (60) for controlling the operation of the coating device in accordance with the measured spray current, and that the coating device and the control device are connected to one another via a bus structure (62).
  9. A coating system according to claim 8, characterized in that a plurality of coating devices (66) exist, each of which is connected to their digital control devices (60) via a gun bus (62), and which form network nodes, and that the digital control devices (60) are connected to further components of the coating system via a coating bus (80), wherein the network nodes are LON nodes.
  10. A coating system according to one of claims 7 to 9, characterized by a high voltage generator (13, 16) in each of the at least one control device (66), which comprises a transformer (13) having a primary coil (14) and a secondary coil (15), which are connected to one another via a bridge (12), wherein the primary coil can be loaded with an alternating control voltage, and wherein the measuring device includes a low pass filter (22), which is connected between the primary coil and ground, and a current/voltage converter (25), which is connected to the low pass filter.
  11. A coating system according to claim 10, characterized in that the low pass filter (22) comprises two coils (21, 26) wherein the first coil is connected to the primary coil (14) and via a capacitor (23) to ground (9), and wherein the current/voltage converter (25) is a current-controlled voltage source (27, 28), which is connected via the second coil (26) to the connection point (35) of the first coil (21) and the capacitor (23).
  12. A coating system according to one of claims 8 to 11, characterized in that each of the at least one coating device (66) has associated thereto a storage device for storing a plurality of U/I characteristic curves for different supply voltages of the high voltage electrode (17), a device (60) for detecting the current supply voltage and an evaluation device (60), in order to select a U/I characteristic curve depending on the supply voltage and to determine a working point on the U/I characteristic curve depending on the spray current, said working point being used for the detection of the actual high voltage at the electrode.
EP98113602A 1997-09-01 1998-07-21 Method for detecting the presence of a workpiece in an electrostatic coating installation and electrostatic coating installation Expired - Lifetime EP0899020B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19738142A DE19738142C1 (en) 1997-09-01 1997-09-01 Electrostatic coating system and method for detecting and coating workpieces in an electrostatic coating system
DE19738142 1997-09-01

Publications (2)

Publication Number Publication Date
EP0899020A1 EP0899020A1 (en) 1999-03-03
EP0899020B1 true EP0899020B1 (en) 2004-09-29

Family

ID=7840843

Family Applications (1)

Application Number Title Priority Date Filing Date
EP98113602A Expired - Lifetime EP0899020B1 (en) 1997-09-01 1998-07-21 Method for detecting the presence of a workpiece in an electrostatic coating installation and electrostatic coating installation

Country Status (4)

Country Link
US (1) US6068877A (en)
EP (1) EP0899020B1 (en)
JP (1) JPH11156247A (en)
DE (2) DE19738142C1 (en)

Families Citing this family (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH04347437A (en) * 1991-05-23 1992-12-02 Matsushita Seiko Co Ltd Controller of air conditioner
DE19926926A1 (en) * 1999-06-14 2000-12-21 Itw Gema Ag Spray coating device
CA2461377A1 (en) * 2001-10-18 2003-05-15 Nordson Corporation Spray gun with variable load line control
US6755339B2 (en) * 2002-06-21 2004-06-29 Delphi Technologies, Inc. Fluxing apparatus for applying powdered flux
DE102006032645B4 (en) * 2006-07-13 2008-06-12 J. Wagner Ag Device for detecting the profile of a workpiece to be coated with powder or wet paint
JP5352799B2 (en) * 2008-04-01 2013-11-27 旭サナック株式会社 Corona charging device
JP5623931B2 (en) * 2011-02-08 2014-11-12 旭サナック株式会社 Electrostatic coating equipment
JP5731219B2 (en) * 2011-02-08 2015-06-10 旭サナック株式会社 Electrostatic coating equipment
JP5731218B2 (en) * 2011-02-08 2015-06-10 旭サナック株式会社 Electrostatic coating equipment
JP6100807B2 (en) * 2015-01-09 2017-03-22 トヨタ自動車株式会社 Electrostatic coating apparatus and its conductivity inspection method
JP2016221518A (en) * 2016-08-26 2016-12-28 アピックヤマダ株式会社 Conductive film formation device and method of the same
DE102019006501A1 (en) * 2019-09-16 2021-03-18 Zasso Group Ag Dielectric drift analyzer
CN114789102B (en) * 2022-05-23 2024-03-26 佛山市德珼尔科技有限公司 Intelligent curved surface spraying production method

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2966880A (en) * 1956-11-23 1961-01-03 Daimler Benz Ag Control arrangement for electrostatic spray installation
US3851618A (en) * 1974-01-14 1974-12-03 Ransburg Corp Electrostatic coating apparatus
DE2849295C2 (en) * 1978-11-14 1985-04-04 Ransburg-Gema AG, St.Gallen Spray coating device for coating objects
DE3014114C2 (en) * 1980-04-12 1982-04-29 Gema AG Apparatebau, 9015 St. Gallen Device for the automatic coating of objects with a spray device
SE8100726L (en) * 1980-05-29 1981-11-30 Ransburg Corp HIGH VOLTAGE DEVICE
US4324812A (en) * 1980-05-29 1982-04-13 Ransburg Corporation Method for controlling the flow of coating material
DE3822835A1 (en) * 1988-07-06 1990-03-08 Josef Schucker Process and arrangement for coating workpiece surfaces
DE4232026C2 (en) * 1992-09-24 1996-10-24 Wagner Int Electrostatic coating gun and method for generating a high voltage
DE4406046C2 (en) * 1994-02-24 1997-11-20 Wagner Int Device and method for measuring a powder mass flow
DE19502390C2 (en) * 1995-01-26 1997-09-25 S & S Metallsuchgeraete & Recy Method and device for applying lubricants to strip material
DE19650112C1 (en) * 1996-12-03 1998-05-20 Wagner Int Device and method for measuring a powder mass flow
DE19738141C2 (en) * 1997-09-01 2003-06-05 Wagner Int Control system of a coating system with a LON bus structure

Also Published As

Publication number Publication date
EP0899020A1 (en) 1999-03-03
DE59812017D1 (en) 2004-11-04
DE19738142C1 (en) 1999-05-20
US6068877A (en) 2000-05-30
JPH11156247A (en) 1999-06-15

Similar Documents

Publication Publication Date Title
EP0899020B1 (en) Method for detecting the presence of a workpiece in an electrostatic coating installation and electrostatic coating installation
EP0037911B1 (en) Apparatus for the automatic coating of articles
DE1287532B (en) Device for determining the high voltage resistance of pieces of material
DE2713249C2 (en) Method and device for coating a substrate by means of powdery material by electrostatic means
EP0452375A1 (en) Automatic goods transport device with transport elements driven by a linear motor.
EP0899019B1 (en) Workpiece related method for controlling an electrostatic coating installation and electrostatic coating installation
EP0283936B1 (en) Process for controlling an electrostatic coating installation
EP0185311B1 (en) Method and apparatus for controlling an electrostatic coating system
EP2496364A1 (en) Coating method and coating system having dynamic adaptation of the atomizer rotational speed and the high voltage
EP0132659B1 (en) Regulating arrangement for an electrofilter
EP1060795B1 (en) Control for an electrostatic spray coating apparatus
EP0899022B1 (en) Method for controlling the exhaust system of an electrostatic powder coating installation and electrostatic powder coating installation
EP0734778A2 (en) Electrostatic spray coating device
DE19717353A1 (en) Powder coating system with several coating units arranged vertically
DE3737774C2 (en)
EP2051345B1 (en) Electrode device
EP3335288A1 (en) Control circuit for protecting against spark discharge
DE102011122056A1 (en) Equipment for coating objects
DE3445851C2 (en)
WO2004101164A1 (en) Coating method, powder spraying nozzle, and coating booth
DE19511254A1 (en) Electrostatic spray coating device
DE102011004037A1 (en) Oscillator for a powder spray coating device
DE4409739A1 (en) Capacitance change detection method for monitoring capacitor-like object
DE2003768A1 (en) Vehicle registration method
DE3606749A1 (en) Method for processing a measurement value present as a frequency

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): CH DE FR GB IT LI

AX Request for extension of the european patent

Free format text: AL;LT;LV;MK;RO;SI

17P Request for examination filed

Effective date: 19990804

AKX Designation fees paid

Free format text: CH DE FR GB IT LI

17Q First examination report despatched

Effective date: 20030210

GRAP Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOSNIGR1

GRAS Grant fee paid

Free format text: ORIGINAL CODE: EPIDOSNIGR3

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): CH DE FR GB IT LI

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20040929

REG Reference to a national code

Ref country code: GB

Ref legal event code: FG4D

Free format text: NOT ENGLISH

REG Reference to a national code

Ref country code: CH

Ref legal event code: EP

REG Reference to a national code

Ref country code: CH

Ref legal event code: NV

Representative=s name: ISLER & PEDRAZZINI AG

REF Corresponds to:

Ref document number: 59812017

Country of ref document: DE

Date of ref document: 20041104

Kind code of ref document: P

GBV Gb: ep patent (uk) treated as always having been void in accordance with gb section 77(7)/1977 [no translation filed]

Effective date: 20040929

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

ET Fr: translation filed
26N No opposition filed

Effective date: 20050630

REG Reference to a national code

Ref country code: CH

Ref legal event code: PCAR

Free format text: ISLER & PEDRAZZINI AG;POSTFACH 1772;8027 ZUERICH (CH)

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 20080718

Year of fee payment: 11

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

Effective date: 20100331

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20090731

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: CH

Payment date: 20100714

Year of fee payment: 13

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 20100726

Year of fee payment: 13

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20090721

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: IT

Payment date: 20100714

Year of fee payment: 13

PGRI Patent reinstated in contracting state [announced from national office to epo]

Ref country code: IT

Effective date: 20110616

REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LI

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20110731

Ref country code: CH

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20110731

Ref country code: DE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20120201

REG Reference to a national code

Ref country code: DE

Ref legal event code: R119

Ref document number: 59812017

Country of ref document: DE

Effective date: 20120201

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20110721