EP0559608B1 - Process and device for controlling the emission current in a powder coating installation - Google Patents

Process and device for controlling the emission current in a powder coating installation Download PDF

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Publication number
EP0559608B1
EP0559608B1 EP93810109A EP93810109A EP0559608B1 EP 0559608 B1 EP0559608 B1 EP 0559608B1 EP 93810109 A EP93810109 A EP 93810109A EP 93810109 A EP93810109 A EP 93810109A EP 0559608 B1 EP0559608 B1 EP 0559608B1
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EP
European Patent Office
Prior art keywords
powder particles
spraying
workpiece
powder
current
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EP93810109A
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German (de)
French (fr)
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EP0559608A3 (en
EP0559608A2 (en
Inventor
Walo Steiger
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Frei Siegfried
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Frei Siegfried
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C23C4/12—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the method of spraying
    • 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
    • B05B5/08—Plant for applying liquids or other fluent materials to objects
    • B05B5/10—Arrangements for supplying power, e.g. charging power
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/02—Processes for applying liquids or other fluent materials performed by spraying
    • B05D1/04—Processes for applying liquids or other fluent materials performed by spraying involving the use of an electrostatic field
    • B05D1/06—Applying particulate materials
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C24/00—Coating starting from inorganic powder

Definitions

  • the application relates to a method for monitoring the spray current in an electrostatically operating powder coating system according to the preamble of claim 1.
  • the application also relates to a device for monitoring the spray current in an electrostatically operating powder coating system according to the preamble of claim 3.
  • the technology of electrostatic powder coating is increasingly used. So that powder particles can be applied to the surface of the workpiece, the powder particles must be charged electrostatically (cf., for example, EP-A-0 382 503). This usually happens in that the powder particles transported in an air stream are guided past the tip or tips of electrodes which are connected to a high voltage source. The powder particles charged in this way are then carried by the transport air stream to the surface of the workpiece to be coated and, because they are charged in the opposite direction or connected to the earth, attracted and deposited thereon. So that the workpieces can be coated properly, their conveying elements, e.g.
  • suspension hooks, clamping jaws, etc. are made bright and connected to the ground by a connecting line.
  • the suspension hooks, clamps, etc. must be cleaned at short intervals so that powder deposits do not result in insulation and prevent the charge carried by the powder particles from flowing away. If there is no proper discharge (earthing), the adhesion of the charged particles to the workpiece decreases rapidly, and a perfect coating can no longer take place.
  • the quality of the coating depends not only on the flawless discharge of the charge carried by the powder particles from the workpiece, but also on the flawless charging of the powder particles by the electrodes. The charge also deteriorates if powder particles accumulate on the electrode, form an insulation jacket and the charge of the other powder particles is thereby deteriorated.
  • the object of the present invention is to provide a method and a device with which the charging of the powder particles and thus the quality of the coating can be continuously monitored.
  • a spray space or area 5 and a feed line 7 for powder particles 17 are visible.
  • the spray head 1 is connected at its end on the left side to a welding machine.
  • a can body 11 is guided through a transport device, for example a pair of transport belts 13, in the direction of arrow A from left to right at a constant speed past the spray chamber 5.
  • Magnets 15 can be arranged below the transport belts 13, which hold the can body 3 pressed against the transport belts.
  • Powder particles 17, carried by transport air are conveyed through the feed line 7 into the spray chamber 5 at an angle to the surface of the can body by a powder processing system (not shown). As a result of their kinetic energy, which they received from the transport air, the powder particles 17 move through the spray chamber 5 to the can body 3. When the spray chamber 5 is crossed, the powder particles 17 are positively charged by the electrode or electrodes 9.
  • the can body 3 is connected by a contact bracket 19 and a connecting line 21 with the ground 23, which has negative polarity.
  • An ammeter 25 is used in the connecting line 21, which measures the current flowing from the can body 3 via the contact bracket 19.
  • the powder particles 17 are electrostatically drawn onto the fuselage 3 and held there. After the impact of the powder particles 17, their charge flows at least partially over the can body 3.
  • the quantity of powder particles fed through the supply line 7 per unit of time must be constant and on the other hand the voltage at the electrode 9 or the spray current generated by the electrode 9 must also remain constant.
  • the amount of powder particles delivered per unit of time can be measured outside the spray head 1. It is not the subject of this invention. The measurement of the spray current, on the other hand, must be scanned within the application range of the particles 17.
  • a measurement of the voltage at the electrode 9 may not suffice, since, for example, deposits of powder particles on the tip of the electrode falsify the result.
  • the invention takes advantage of the fact that the electrical charge which is carried by the powder particles 17 charged in the spray chamber 5 must be removed after striking the wall of the fuselage 3. This takes place through the contact bracket 19 and the connecting line 21 to the ground 23. The current flowing out there is proportional to the spray current through which the powder particles 17 in the spray chamber 5 have been charged. Contamination of the electrode tip of the electrode 9 can consequently be determined by a decrease in the derived current, because the contamination of the electrode 9 reduces the charge on the powder particles 17 flying past it with increasing contamination.
  • an open coating system for coating workpieces 103 is shown.
  • the workpieces 103 are guided past a spray head 101, which is held by a robot or by an operator, with a transport carriage 127 which rolls on the rail 131 on the ceiling 131.
  • the spray head 101 in the form of a conventional powder spray gun is connected to the powder feed device by a feed line 107 and to a high-voltage source by an electrical connection line 119.
  • the high-voltage source also represents the positive pole in this exemplary embodiment.
  • Suspension hooks 133 which on the one hand carry the workpieces 103 and on the other hand establish an electrically conductive connection to the earth 123, are fastened to the transport carriage 127 by an insulator 128, insulated from the transport carriage 127.
  • the suspension hooks 133 come into contact with a contact strip 135 during the spraying process.
  • the contact strip 135 is connected to the earth 123 via the line 119.
  • the connection between the transport carriage 127 and the rail 129 is electrically insulated .
  • a current measuring device 125 is inserted into the line, with which the charge flowing off the workpiece 103 via the suspension hook 133 and the contact strip 135 can be measured.
  • the electrostatic charge could of course be derived from the workpiece 103 by a direct connection to the measuring device 125.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Electrostatic Spraying Apparatus (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)

Description

Gegenstand der Anmeldung ist ein Verfahren zur Ueberwachung des Sprühstromes in einer elektrostatisch arbeitenden Pulverbeschichtungsanlage gemäss Oberbegriff des Anspruches 1.
Gegenstand der Anmeldung ist weiter eine Vorrichtung zur Ueberwachung des Sprühstromes in einer elektrostatisch arbeitenden Pulverbeschichtungsanlage gemäss Oberbegriff des Anspruches 3.The application relates to a method for monitoring the spray current in an electrostatically operating powder coating system according to the preamble of claim 1.
The application also relates to a device for monitoring the spray current in an electrostatically operating powder coating system according to the preamble of claim 3.

In der industriellen Fertigung für die Beschichtung von Werkstücken aus Metall wird immer häufiger zur Technologie der elektrostatischen Pulverbeschichtung gegriffen. Damit ein Auftrag von Pulverteilchen auf die Oberfläche des Werkstückes erfolgen kann, müssen die Pulverteilchen elektrostatisch aufgeladen werden (vgl. z.B. EP-A-0 382 503). Dies geschieht meist dadurch, dass die in einem Luftstrom transportierten Pulverteilchen an der oder den Spitzen von Elektroden vorbeigeführt werden, welche mit einer Hochspannungsquelle verbunden sind. Die auf diese Weise aufgeladenen Pulverteilchen werden vom Transportluftstrom danach an die Oberfläche des zu beschichtenden Werkstückes herangetragen und von diesem, weil entgegengesetzt geladen bzw. mit der Erde verbunden, angezogen und darauf abgelagert. Damit eine einwandfreie Beschichtung der Werkstücke erfolgen kann, sind dessen Förderelemente, z.B. Aufhängehaken, Klemmbacken, etc., blank ausgeführt und durch eine Verbindungsleitung mit der Erde verbunden. Die Aufhängehaken, Klammern, etc., müssen in kurzen Abständen gereinigt werden, damit durch Pulverablagerungen keine Isolation entsteht und dadurch der Abfluss der von den Pulverteilchen getragenen Ladung verunmöglicht wird. Erfolgt keine einwandfreie Ableitung (Erdung), so nimmt die Haftung der geladenen Teilchen auf dem Werkstück rapid ab, und es kann keine einwandfreie Beschichtung mehr erfolgen.
Die Qualität der Beschichtung hängt nicht nur von der einwandfreien Ableitung der von den Pulverteilchen herangetragenen Ladung vom Werkstück ab, sondern auch von der einwandfreien Aufladung der Pulverteilchen durch die Elektroden. Eine Verschlechterung der Aufladung tritt auch dann ein, wenn sich auf der Elektrode Pulverteilchen ansammeln, einen Isolationsmantel bilden und dadurch die Aufladung der übrigen Pulverteilchen verschlechtert wird. Die Kontrolle des sogenannten Sprühstromes, d.h. der Ladekapazität der Elektroden lässt sich im Betrieb beim Beschichten bisher nur sehr schlecht bewerkstelligen. Optische Ueberwachungseinrichtungen können deshalb nur schlecht genügen, weil sie durch die elektrisch geladenen Pulverteilchen sehr schnell verschmutzt werden. Z.B. bei der Beschichtung der Schweissnähte an Dosenrümpfen kommt erschwerend hinzu, dass die ganze Beschichtungsvorrichtung innerhalb eines geschlossenen, von aussen unzugänglichen, engen Raumes stattfindet. Auch ist es dort eine Kontrolle der beschichteten Werkstücke, d.h. der Dosenrümpfe, nur sehr schwierig zu erreichen, weil die Beschichtung von aussen nicht sichtbar ist.In industrial manufacturing for the coating of metal workpieces, the technology of electrostatic powder coating is increasingly used. So that powder particles can be applied to the surface of the workpiece, the powder particles must be charged electrostatically (cf., for example, EP-A-0 382 503). This usually happens in that the powder particles transported in an air stream are guided past the tip or tips of electrodes which are connected to a high voltage source. The powder particles charged in this way are then carried by the transport air stream to the surface of the workpiece to be coated and, because they are charged in the opposite direction or connected to the earth, attracted and deposited thereon. So that the workpieces can be coated properly, their conveying elements, e.g. suspension hooks, clamping jaws, etc., are made bright and connected to the ground by a connecting line. The suspension hooks, clamps, etc. must be cleaned at short intervals so that powder deposits do not result in insulation and prevent the charge carried by the powder particles from flowing away. If there is no proper discharge (earthing), the adhesion of the charged particles to the workpiece decreases rapidly, and a perfect coating can no longer take place.
The quality of the coating depends not only on the flawless discharge of the charge carried by the powder particles from the workpiece, but also on the flawless charging of the powder particles by the electrodes. The charge also deteriorates if powder particles accumulate on the electrode, form an insulation jacket and the charge of the other powder particles is thereby deteriorated. The control of the so-called spray current, ie the charging capacity of the electrodes, has hitherto been very difficult to achieve in operation during coating. Optical monitoring devices can therefore only suffice with difficulty because they are soiled very quickly by the electrically charged powder particles. For example, when coating the weld seams on the body of the can, it is made more difficult that the entire coating device takes place within a closed, narrow space that is inaccessible from the outside. It is also very difficult to check the coated workpieces there, ie the can bodies, because the coating is not visible from the outside.

Die Aufgabe der vorliegenden Erfindung besteht darin, ein Verfahren und eine Vorrichtung zu schaffen, mit welchem bzw. welcher die Aufladung der Pulverteilchen und damit die Qualität der Beschichtung kontinuierlich überwacht werden kann.The object of the present invention is to provide a method and a device with which the charging of the powder particles and thus the quality of the coating can be continuously monitored.

Gelöst wird diese Aufgabe durch ein Verfahren gemäss den kennzeichnenden Merkmalen des Anspruches 1 sowie durch eine Vorrichtung gemäss den kennzeichnenden Merkmalen des Anspruches 3.This object is achieved by a method according to the characterizing features of claim 1 and by a device according to the characterizing features of claim 3.

Ueberraschenderweise gelingt es durch Messung des vom Fördermittel bzw. vom Werkstück abfliessenden Entladestromes den Sprühstrom zwischen der Elektrode und dem Werkstuck exakt zu bestimmen. Es genügt, zwischen dem Werkstück und der Erde ein den abfliessenden Strom messendes Element einzusetzen und die gemessenen Werte anzuzeigen und/oder zur Ausgabe eines Alarmes oder zur Steuerung des Sprühstromes heranzuziehen, wenn ein Sollwert unterschritten wird.Surprisingly, it is possible to exactly determine the spray current between the electrode and the workpiece by measuring the discharge current flowing from the conveying means or from the workpiece. It is sufficient to have an element measuring the current flowing between the workpiece and the earth to be used and to display the measured values and / or to use them to output an alarm or to control the spray current if a setpoint is undershot.

Anhand zweier illustrierter Ausführungsbeispiele für ein offenes und für ein geschlossenes System wird die Erfindung näher erläutert. Es zeigen:

Figur 1
einen Ausschnitt aus einer Pulverbeschichtungsanlage für Dosenrümpfe und
Figur 2
einen Ausschnitt aus einer Beschichtungsanlage für hängend transportierte Werkstücke.
The invention is explained in more detail with the aid of two illustrated exemplary embodiments for an open and for a closed system. Show it:
Figure 1
a section of a powder coating system for can bodies and
Figure 2
a section of a coating system for hanging workpieces.

Im ausschnittsweise dargestellten Sprühkopf 1 einer Pulverbeschichtungsvorrichtung für die Beschichtung von Dosenrümpfen 3, welche zuvor auf einer nicht dargestellten Dosenschweissmaschine aus Blechplatten hergestellt worden sind, ist ein Sprühraum oder -bereich 5 und eine Zuführleitung 7 für Pulverpartikel 17 sichtbar. In den Sprühraum 5 ragt das Ende einer Elektrode 9, die mit dem positiven Pol einer nicht dargestellten Hochspannungsquelle verbunden ist. Der Sprühkopf 1 ist mit seinem Ende auf der linken Seite mit Schweissmaschine verbunden. Ein Dosenrumpf 11 wird durch eine Transportvorrichtung, z.B. ein Transportriemenpaar 13, in Richtung des Pfeiles A von links nach rechts mit konstanter Geschwindigkeit am Sprühraum 5 vorbeigeführt. Unterhalb der Transportriemen 13 können Magnete 15 angeordnet sein, welche den Dosenrumpf 3 an die Transportriemen angepresst halten. Durch die Zuführleitung 7 werden von einer Pulveraufbereitungsanlage (nicht dargestellt), getragen durch Transportluft, Pulverpartikel 17 in einem Winkel zur Oberfläche des Dosenrumpfes in den Sprühraum 5 hineingefördert. Infolge ihrer kinetischen Energie, die sie von der Transportluft erhalten haben, bewegen sich die Pulverpartikel 17 durch den Sprühraum 5 hindurch zum Dosenrumpf 3. Beim Durchqueren des Sprühraumes 5 werden die Pulverpartikel 17 durch die Elektrode oder Elektroden 9 positiv aufgeladen. Der Dosenrumpf 3 steht durch einen Kontaktbügel 19 und eine Verbindungsleitung 21 in Verbindung mit der Erdung 23, welche negative Polarität aufweist. In der Verbindungsleitung 21 ist ein Ampèremeter 25 eingesetzt, das den vom Dosenrumpf 3 über den Kontaktbügel 19 abfliessenden Strom misst.
Infolge der gegensätzlichen Ladungen der Pulverpartikel 17 und der zu beschichtenden Wand des Rumpfes 3 werden die Pulverpartikel 17 elektrostatisch an den Rumpf 3 herangezogen und dort festgehalten.
Nach dem Auftreffen der Pulverpartikel 17 fliesst deren Ladung über dem Dosenrumpf 3 mindestens teilweise ab.
Für eine Beschichtung mit gleichbleibender Auftragsmenge pro Zeit- und Flächeneinheit muss zum einen die durch die Zuführleitung 7 pro Zeiteinheit eingespeisten Pulverpartikelmenge konstant sein und zum anderen muss auch die Spannung an der Elektrode 9 bzw. der von der Elektrode 9 erzeugte Sprühstrom konstant bleiben. Die Messung der pro Zeiteinheit geförderten Pulverpartikelmenge kann ausserhalb des Sprühkopfes 1 erfolgen. Sie ist nicht Gegenstand dieser Erfindung. Die Messung des Sprühstromes hingegen muss innerhalb des Auftragsbereiches der Partikel 17 abgetastet werden. Eine Messung der Spannung an der Elektrode 9 kann nicht genügen, da z.B. durch Ablagerungen von Pulverpartikeln auf der Spitze der Elektrode eine Verfälschung des Resultates eintritt.
Die Erfindung macht sich die Tatsache zunutze, dass die elektrische Ladung, welche durch die im Sprühraum 5 aufgeladenen Pulverpartikel 17 mit sich tragen, nach dem Auftreffen auf der Wandung des Rumpfes 3 abgeführt werden muss. Dies geschieht durch den Kontaktbügel 19 und die Verbindungsleitung 21 zur Erdung 23. Der dort abfliessende Strom ist proportional zum Sprühstrom, durch welchen die Pulverpartikel 17 im Sprühraum 5 aufgeladen worden sind. Eine Verschmutzung der Elektrodenspitze der Elektrode 9 kann demzufolge durch ein Absinken des abgeleiteten Stromes festgestellt werden, weil durch die Verschmutzung der Elektrode 9 die Aufladung der an ihr vorbeifliegenden Pulverpartikel 17 mit zunehmender Verschmutzung verringert wird.In the spray head 1 of a powder coating device for the coating of can bodies 3, which was previously produced on a can welding machine (not shown) from sheet metal plates, a spray space or area 5 and a feed line 7 for powder particles 17 are visible. The end of an electrode 9, which is connected to the positive pole of a high-voltage source, not shown, projects into the spray chamber 5. The spray head 1 is connected at its end on the left side to a welding machine. A can body 11 is guided through a transport device, for example a pair of transport belts 13, in the direction of arrow A from left to right at a constant speed past the spray chamber 5. Magnets 15 can be arranged below the transport belts 13, which hold the can body 3 pressed against the transport belts. Powder particles 17, carried by transport air, are conveyed through the feed line 7 into the spray chamber 5 at an angle to the surface of the can body by a powder processing system (not shown). As a result of their kinetic energy, which they received from the transport air, the powder particles 17 move through the spray chamber 5 to the can body 3. When the spray chamber 5 is crossed, the powder particles 17 are positively charged by the electrode or electrodes 9. The can body 3 is connected by a contact bracket 19 and a connecting line 21 with the ground 23, which has negative polarity. An ammeter 25 is used in the connecting line 21, which measures the current flowing from the can body 3 via the contact bracket 19.
As a result of the opposite charges of the powder particles 17 and the wall of the fuselage 3 to be coated, the powder particles 17 are electrostatically drawn onto the fuselage 3 and held there.
After the impact of the powder particles 17, their charge flows at least partially over the can body 3.
For a coating with a constant application quantity per unit of time and area, on the one hand the quantity of powder particles fed through the supply line 7 per unit of time must be constant and on the other hand the voltage at the electrode 9 or the spray current generated by the electrode 9 must also remain constant. The amount of powder particles delivered per unit of time can be measured outside the spray head 1. It is not the subject of this invention. The measurement of the spray current, on the other hand, must be scanned within the application range of the particles 17. A measurement of the voltage at the electrode 9 may not suffice, since, for example, deposits of powder particles on the tip of the electrode falsify the result.
The invention takes advantage of the fact that the electrical charge which is carried by the powder particles 17 charged in the spray chamber 5 must be removed after striking the wall of the fuselage 3. This takes place through the contact bracket 19 and the connecting line 21 to the ground 23. The current flowing out there is proportional to the spray current through which the powder particles 17 in the spray chamber 5 have been charged. Contamination of the electrode tip of the electrode 9 can consequently be determined by a decrease in the derived current, because the contamination of the electrode 9 reduces the charge on the powder particles 17 flying past it with increasing contamination.

Im Ausführungsbeispiel der Erfindung nach Figur 2 wird eine offene Beschichtungsanlage für die Beschichtung von Werkstücken 103 dargestellt.In the exemplary embodiment of the invention according to FIG. 2, an open coating system for coating workpieces 103 is shown.

Die Werkstücke 103 werden mit einem Transportwagen 127, der auf einer Schiene 129 an der Decke 131 rollt, an einem Sprühkopf 101, der von einem Roboter oder von einer Bedienungsperson gehalten wird, vorbeigeführt. Der Sprühkopf 101 in Gestalt einer herkömmlichen Pulversprühpistole ist durch eine Zuführleitung 107 mit der Pulverspeisevorrichtung und durch eine elektrische Verbindungsleitung 119 mit einer Hochspannungsquelle verbunden. Die Hochspannungsquelle stellt auch in diesem Ausführungsbeispiel den positiven Pol dar. An dem Transportwagen 127 sind durch einen Isolator 128 elektrisch isoliert vom Transportwagen 127 Aufhängehaken 133 befestigt, welche zum einen die Werkstücke 103 tragen und zum anderen eine elektrisch leitende Verbindung zur Erde 123 herstellen. Damit eine einwandfreie Erdung während des Beschichtungsvorganges erfolgt, gelangen die Aufhängehaken 133 während des Sprühvorganges in Kontakt mit einer Kontaktleiste 135. Die Kontaktleiste 135 steht über die Leitung 119 in Verbindung mit der Erde 123. Die Verbindung der Transportwagen 127 mit der Schiene 129 ist elektrisch isoliert. In die Leitung ist ein Strommessgerät 125 eingesetzt, mit welchem die vom Werkstück 103 über den Aufhängehaken 133 und die Kontaktleiste 135 abfliessende Ladung gemessen werden kann. Alternativ könnte selbstverständlich die Ableitung der elektrostatischen Ladung vom Werkstück 103 durch eine direkte Verbindung zum Messgerät 125 erfolgen.The workpieces 103 are guided past a spray head 101, which is held by a robot or by an operator, with a transport carriage 127 which rolls on the rail 131 on the ceiling 131. The spray head 101 in the form of a conventional powder spray gun is connected to the powder feed device by a feed line 107 and to a high-voltage source by an electrical connection line 119. The high-voltage source also represents the positive pole in this exemplary embodiment. Suspension hooks 133, which on the one hand carry the workpieces 103 and on the other hand establish an electrically conductive connection to the earth 123, are fastened to the transport carriage 127 by an insulator 128, insulated from the transport carriage 127. So that proper earthing takes place during the coating process, the suspension hooks 133 come into contact with a contact strip 135 during the spraying process. The contact strip 135 is connected to the earth 123 via the line 119. The connection between the transport carriage 127 and the rail 129 is electrically insulated . A current measuring device 125 is inserted into the line, with which the charge flowing off the workpiece 103 via the suspension hook 133 and the contact strip 135 can be measured. Alternatively, the electrostatic charge could of course be derived from the workpiece 103 by a direct connection to the measuring device 125.

Claims (4)

  1. Method of monitoring the flow of spraying in an electrostatically operating powder coating system, in which system powder, which is conveyed by a conveyor gas, is charged in a spraying chamber by an electrode, and the electrostatically charged powder particles are applied to a workpiece connected to earth and deposited on said workpiece in an electrostatically adhesive manner, characterised in that the current (I), flowing from the workpiece (3, 103) to the earth (23, 123), is measured.
  2. Method according to claim 1, characterised in that changes in the current (I) are indicated and/or used to control the flow of spraying.
  3. Apparatus for monitoring the flow of spraying in an electrostatically operating powder coating system, having a spraying region at the end of a conveyor line for the powder particles and an electrode, which is disposed in the spraying region, for charging the powder particles, having a conveyor means for conducting workpieces past the spraying region and an electrically conductive connection line which connects the conveyor means to the earth and which is intended for conducting away the electrostatic charge of the charged powder particles applied to the workpiece, characterised in that a measuring instrument (25, 125), which is suitable for measuring the escaping current (Ia), is inserted in the connection line (21, 121).
  4. Apparatus according to claim 2, characterised in that an ammeter is used as the measuring instrument (25, 125).
EP93810109A 1992-03-06 1993-02-19 Process and device for controlling the emission current in a powder coating installation Expired - Lifetime EP0559608B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH73192 1992-03-06
CH731/92 1992-03-06

Publications (3)

Publication Number Publication Date
EP0559608A2 EP0559608A2 (en) 1993-09-08
EP0559608A3 EP0559608A3 (en) 1993-10-27
EP0559608B1 true EP0559608B1 (en) 1995-12-27

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EP93810109A Expired - Lifetime EP0559608B1 (en) 1992-03-06 1993-02-19 Process and device for controlling the emission current in a powder coating installation

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EP (1) EP0559608B1 (en)
DE (1) DE59301228D1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1060795A2 (en) 1999-06-14 2000-12-20 ITW Gema AG Spray coating apparatus
EP1112801A2 (en) * 1999-12-30 2001-07-04 Frei AG Method for continuously monitoring the powder mixture onto a welding seal of can bodies, and apparatus therefore

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GB1487325A (en) * 1973-11-21 1977-09-28 Ici Ltd Electrostatic deposition of particles
US4291640A (en) * 1977-09-09 1981-09-29 The Continental Group, Inc. Powder coating apparatus for two-piece cans
JPS6138870A (en) * 1984-07-30 1986-02-24 Dowa Teppun Kogyo Kk Continuous mechanical plating and mixture powder therefor
US4987001A (en) * 1989-02-09 1991-01-22 Nordson Corporation Method and apparatus for coating the interior surface of hollow, tubular articles

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1060795A2 (en) 1999-06-14 2000-12-20 ITW Gema AG Spray coating apparatus
DE19926926A1 (en) * 1999-06-14 2000-12-21 Itw Gema Ag Spray coating device
US6537378B1 (en) 1999-06-14 2003-03-25 Itw Gema Ag Spray-coating apparatus
US6656536B2 (en) 1999-06-14 2003-12-02 Itw Gema Ag Method of controlling spray current and voltage in electrostatic coating apparatus
EP1112801A2 (en) * 1999-12-30 2001-07-04 Frei AG Method for continuously monitoring the powder mixture onto a welding seal of can bodies, and apparatus therefore

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EP0559608A3 (en) 1993-10-27
DE59301228D1 (en) 1996-02-08
EP0559608A2 (en) 1993-09-08

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