EP0913203B1 - Method and apparatus for powder coating with purging air supply - Google Patents

Method and apparatus for powder coating with purging air supply Download PDF

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Publication number
EP0913203B1
EP0913203B1 EP98115238A EP98115238A EP0913203B1 EP 0913203 B1 EP0913203 B1 EP 0913203B1 EP 98115238 A EP98115238 A EP 98115238A EP 98115238 A EP98115238 A EP 98115238A EP 0913203 B1 EP0913203 B1 EP 0913203B1
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EP
European Patent Office
Prior art keywords
powder
air
spray
injector
spray coating
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
EP98115238A
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German (de)
French (fr)
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EP0913203A1 (en
Inventor
Felix Mauchle
Heinz HÖFLER
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Gema Switzerland GmbH
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Gema Switzerland GmbH
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/14—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas designed for spraying particulate materials
    • B05B7/1404—Arrangements for supplying particulate material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/14—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas designed for spraying particulate materials
    • B05B7/1404—Arrangements for supplying particulate material
    • B05B7/1472—Powder extracted from a powder container in a direction substantially opposite to gravity by a suction device dipped into the powder
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/14—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas designed for spraying particulate materials
    • B05B7/1481—Spray pistols or apparatus for discharging particulate material
    • B05B7/1486—Spray pistols or apparatus for discharging particulate material for spraying particulate material in dry state

Definitions

  • the invention relates to a method and an apparatus for Powder spray coating objects according to claim 1.
  • a method and a device of this type are known from EP 0 204 437 A2 known.
  • the powder delivery is in each case interrupted by interrupting a conveying air flow.
  • a front half of the gun is in this purge air initiated while the conveying air supply is interrupted.
  • a method and a Device known in which to interrupt the Powder feed is also interrupted by a conveying air flow and also the air-powder flow path through a valve is interrupted.
  • Spray air can flow in downstream of the valves the air-powder path are introduced and then flows through this to a spray device and through it.
  • a powder coating system in which a conveying air flow in a negative pressure area Injector creates a negative pressure and thereby powder sucked out of a container and into a powder line promotes. Downstream of the vacuum area is the Conveying air powder flow Additional air through a Auxiliary air inlet supplied to in the powder line to achieve a predetermined total amount of air. Further is from European patent specification 0 412 289 B1 an electrostatic powder coating system with an injector, which conveying air and Additional air is supplied. The additional air can be used as Control air in the vacuum area of the injector be promoted.
  • the German patent application DE 44 19 987 A1 shows one Injector conveyor for coating powder with a suction pipe, which is connected to the vacuum area of the Injector is connected and down in extends a powder container so that from this Powder is sucked into the vacuum area.
  • the from End section of the vacuum region facing away from the vacuum Suction pipe is supplied to compensating air Compensate for fluctuations in suction pressure.
  • the US patent 3 746 254 shows the powder container also above, instead of below, the vacuum area of the injector so that its Powder suction opening above the vacuum area located.
  • EP 0 769 327 A2 a powder coating device is known, where the injector is at the bottom of a Tube, which is in a powder container is submersible to convey powder from it.
  • the present invention includes all of the foregoing Embodiments and is not specific Embodiment limited.
  • Powder line usually a hose
  • the Spray device from time to time from deposited To clean powder particles. This is necessary to get one uncontrolled leakage of deposited, old Avoid powder particles, as these can disrupt the coated surface of an object.
  • the powder hose and the Spray device is normally supplied to the compressed air Injector and connected by the injector and the Powder hose through the spray device blown.
  • a disadvantage of this known type of flushing is in that the purge air is not just for spraying flows, but also in the injector on others to him splits connected lines.
  • the object of the invention is to be achieved large series of objects with very good To coat coating quality without the Series production of these objects for cleaning work or adjustment work of the spray coating device is disturbed or must be interrupted.
  • Through the Invention are also intended, for example, in car bodies series production with such good surface quality can be coated like this by the Coating with liquid paint is known.
  • the aim is thus, the highest demands on the Powder coating quality to meet regarding Adherence to the object, closedness of the powder layer after burning it onto the object, extreme Uniformity and smoothness of the coating.
  • the method and the device for this are said to be very have high reliability in continuous operation.
  • the powder spray coating device shown in Fig. 1 contains a spray device 2, which a Sprayer 4 for spraying coating powder Exhibits objects 6, for example car bodies, which on a transport device 8 in the direction an arrow 10 in continuous operation across the spray element 4 are shown at the front so that they are in the spray coating area of the spray organ 4 reach.
  • Objects 6 have one between them small distance or a gap 12.
  • the sprayer 4 1 can be a spray nozzle or a Be a body of revolution, for example a rotating one Spray bell.
  • the spray element 4 is with or several high-voltage electrodes 14 for electrostatic charging of the powder.
  • the Electrode 114 can protrude from a carrier tube 16, from which air flows over the electrode 14, so no powder particles are deposited on it.
  • the High voltage for the electrode 14 can be from one High voltage generator are generated, which in the Spray device 2 or be arranged externally can.
  • the spray element 4 is located on the downstream End of a powder channel 18 of the spray device 2, whose upstream beginning 20 via a Powder line 22 to the powder outlet 24 of an injector 26 is connected.
  • the powder outlet 24 is located Delivery air inlet 28 axially opposite, which via a Conveying air line 30, in which there is a pressure regulator 32 is located, and a manifold 34 to a pressure source 36 is connected.
  • An injector channel 38 has adjacent to the supply air inlet 28 one Vacuum area 40 with an enlarged diameter and then a smaller one in cross section Powder outlet channel 42.
  • the vacuum region 40 of the injector 26 opens out Control air inlet 50, which via a control air line 52, which contains a pressure regulator 54, and the Distributor 34 connected to the compressed air source 36 is.
  • control air inlet 50 which via a control air line 52, which contains a pressure regulator 54, and the Distributor 34 connected to the compressed air source 36 is.
  • An additional air inlet opens into the powder outlet channel 42 56, which via an additional air line 58, which may include a pressure regulator 60 and the manifold 34 connected to the pressure source 36.
  • the additional air together with the conveying air gives one Total amount of air in the powder line 22 Pulsations of the powder flow and larger ones Powder deposits prevented.
  • the Additional air of the additional air line 58 could also be used with the Control air of the control air line 52 the total amount of air be influenced, which is unfavorable because the Control air the vacuum effect in the vacuum area 40 and thus also the conveying effect of the conveying air of the Conveying air line 30 affects, so that the conveying air would also have to be changed if the control air to compensate for changes in air volume in the Powder line 22 would be used.
  • the control air of the control air line 52 only to release the negative pressure in the Vacuum area 40 used to thereby the Switch off powder feed, not just reduce it.
  • the conveying air of the conveying air line 30 and the additional air of the additional air line 58 unchanged the injector 26 and the powder line 22 fed while an object gap 12 in front of Sprayer 4 is located.
  • the powder delivery switched on again by the control air of the Control air line 52 is turned off. Switching on and switching off depending on the Conveying speed and the size of the objects 6 is done automatically by a processor-controlled electronic control device 62.
  • the controller 62 is preferably programmed such that that powder production is not only in the object gap 12 is switched off, but shortly before the end of the straight coated object 6, so that the entire im Powder path existing powder still on this object is applied without producing coating defects. This has the further advantage that the loss powder that does not adhere to objects 6, is reduced.
  • the intake pipe 26 is on its from the injector 26 facing away lower end portion 64 with a Equalization air inlet 66 through which Compressed air as compensation air in the intake pipe 46 is promoted to arise in the intake pipe 36 Compensate or dampen pressure fluctuations.
  • the Compensation air inlet 66 is via a compensation air line 68, in which there is a pressure regulator 70 can, to the distributor 34 of the compressed air source 36 connected.
  • the balance air is both during the powder feed as well during Powder feed breaks with constant pressure and constant air rate supplied.
  • Purge air device 72 with at least one purge air inlet 73 provided.
  • the purge air inlet 73 is located preferably at a point from where the Flow resistance for this purge air in the air-powder path, which through the powder line 22, the Spray device 2 and the injector 26 is formed in Direction downstream until through the spray device 2 is smaller than upstream to through the Injector 26 through. This ensures that the Purge air only in the direction of the spray element 4 and out this flows towards the objects 6, however not in the opposite direction to the injector 26 out.
  • the purge air inlet 73 wherein in modified embodiment also several such Places or purge air inlets can be provided, between half the length of the powder line 22 and the Sprayer 4.
  • the powder path in the Spray device 2 can be formed from a similar material be to build up deposits of powder particles to reduce.
  • the sprayer 4 even if it is off the same material must be with purge air inside be cleaned because the powder particles don't just stick to slide along the inner surfaces of the spray element 4, but also hit these inner surfaces across.
  • Preferred embodiments therefore consist in the at least one purge air inlet 73 on one Purge air supply point between half the length of the Powder line 22 or on a length of 75% downstream of the powder line 22, or immediately on Powder inlet 20 of the spray device 2, or 2 of the drawings in the Spray device 2 with a short distance upstream of to arrange the spray element 4 so that the purge air unthrottled on the inner surfaces of the spray element 4 strikes and any powder particles present there rinses.
  • 1 is the Powder line 22 a hose, which on a more than half the length upstream Hose part 22-1 and one much less than that half hose length making up a short hose part 22-2 is divided.
  • the two hose parts 22-1 and 22-2 are through the purge air inlet 73, which is one has annular slot nozzle 74 with each other connected.
  • the purge air flows from the slot nozzle 74 through the downstream hose section 22-2 and thereafter by the spray device 2 without part of it Purge air in the opposite direction to the injector 26 flows.
  • the purging air is not switched on during powder conveyance, but when powder conveyance is switched off either at each object gap 12 or only at one of several object gaps 12 in front of the spray element 4.
  • the purge air is not supplied as a continuous stream of compressed air, but in the form of at least one, or preferably at least two, three or four, briefly successive bursts of compressed air or compressed air pulses.
  • the purge air inlet 73 is connected to the compressed air source 36 or its distributor 34 via a compressed air line 76, in which a pressure regulator 78, a pressure meter 80 and a changeover valve 82 are located one after the other in the direction of flow.
  • the changeover valve 82 is preferably an electromagnetic or pneumatic two / two-way valve which is controlled by the electronic control device 62.
  • the purge air inlet 73 is provided with a non-return valve 84, which can be a filter material for filtering powder particles and / or a check valve which only opens in the direction of flow of the purge air to the purge air inlet 73, but closes at a fluid pressure acting in the opposite direction.
  • the compressed air serving as purge air is supplied to the purge air inlet 73 preferably in an amount in the range from 15-40 Nm 3 / h and a pressure up to a maximum of 6 bar, preferably up to 5 bar.
  • the pressure of the purge air can be adjusted accordingly on its regulator 78.
  • the purge air can be switched on either if all air connections of the injector 26 are switched off or according to the preferred embodiment during all air connections or at least the conveying air of the Injector 26 remain switched on.
  • flow in the preferred embodiment by the spray organ 4 while an object to be coated 6 opposite, conveying air of the conveying air line 30, Auxiliary air of the auxiliary air line 58 and compensation air the balance air line 68; however if there is an object gap 12 is opposite the spray element 4 and the Powder feed through control air supply Control air line 52 is switched off, then flow through the spray organ 4, the conveying air Conveying air line 30, control air of the control air line 52, additional air of the additional air line 58, compensating air the compensation air line 68 and, during the Cleaning phase, also purge air of the purge air inlet 73.
  • the Purge air already switched on when on End section of a coated object 6 still in Spray area of the spray organ 4 is so that all powder used for the coating process becomes.
  • the powder layer on the object 6 thereby receives no other layer thickness or other change if the powder feed also shortly before the end of the just coated object 6 is turned off by the control air of the control air line 52 is switched on and is thus promoted to the vacuum region 40.
  • the temporal coordination of the different types of air is carried out by the electronic control device 62.
  • the purge air inlet 73 at least one annular slot nozzle 74 around the air-powder path so make it a big one Purge air volume can be supplied without a particularly high pressure is required.
  • the 2 has the purge air inlet 73rd instead, a plurality of holes 75, which in the air-powder path and this ring-shaped surround.
  • the ring slot nozzle 74 of FIG. 1 and the purge air bores 75 of FIG. 2 are preferably under one An angle of approximately 45 degrees in the flow direction of the Air powder flow arranged obliquely.

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  • Application Of Or Painting With Fluid Materials (AREA)
  • Nozzles (AREA)
  • Electrostatic Spraying Apparatus (AREA)
  • Coating Apparatus (AREA)

Abstract

The arrangement has a powder spray device (2), an injector (26) for pneumatic powder delivery to the spray device and a powder line (22) connecting an injector powder outlet to a spray device powder inlet. The injector, powder line and spray device form an air-powder path with at least one flushing air inlet (73) at a flushing air delivery point, from where the flow resistance downstream to the spray device is smaller than upstream to the injector. The inlet is connected via an automatically switchable blocking element to a compressed air source to drive flushing air from the inlet through the air-powder path out of the spray device. An independent claim is also included for a method of using the arrangement.

Description

Die Erfindung betrifft ein Verfahren und eine Vorrichtung zum Pulver-Sprühbeschichten von Objekten gemäß Patentanspruch 1.The invention relates to a method and an apparatus for Powder spray coating objects according to claim 1.

Ein Verfahren und eine Vorrichtung dieser Art sind aus der EP 0 204 437 A2 bekannt. Hierbei wird die Pulverförderung jeweils durch Unterbrechen eines Förderluftstromes unterbrochen. Zum Spülen einer vorderen Pistolenhälfte wird in diese Spülluft eingeleitet, während die Förderluftzufuhr unterbrochen ist. Ferner ist aus der US 4,302,481 ein Verfahren und eine Vorrichtung bekannt, bei welcher zur Unterbrechung der Pulverförderung ebenfalls ein Förderluftstrom unterbrochen wird und außerdem der Luft-Pulver-Strömungsweg durch ein Ventil unterbrochen wird. Sprühluft kann stromabwärts der Ventile in den Luft-Pulver-Weg eingebracht werden und strömt dann durch diesen zu einer Sprühvorrichtung und durch diese hindurch. A method and a device of this type are known from EP 0 204 437 A2 known. Here the powder delivery is in each case interrupted by interrupting a conveying air flow. To the Flushing a front half of the gun is in this purge air initiated while the conveying air supply is interrupted. Furthermore, from US 4,302,481 a method and a Device known in which to interrupt the Powder feed is also interrupted by a conveying air flow and also the air-powder flow path through a valve is interrupted. Spray air can flow in downstream of the valves the air-powder path are introduced and then flows through this to a spray device and through it.

Aus der europäischen Patentanmeldung EP 0 718 043 A1 ist eine Pulverbeschichtungsanlage bekannt, bei welcher ein Förderluftstrom in einem Unterdruckbereich eines Injektors einen Unterdruck erzeugt und dadurch Pulver aus einem Behälter ansaugt und in eine Pulverleitung fördert. Stromabwärts des Unterdruckbereiches wird dem Förderluft-Pulver-Strom Zusatzluft über einen Zusatzlufteinlaß zugeführt, um in der Pulverleitung eine vorbestimmte Gesamtluftmenge zu erreichen. Ferner ist aus der europäischen Patentschrift 0 412 289 B1 eine elektrostatische Pulverbeschichtungsanlage mit einem Injektor bekannt, welchem Förderluft und Zusatzluft zugeführt wird. Die Zusatzluft kann als Steuerluft in den Unterdruckbereich des Injektors gefördert werden. Die deutsche Patent-Offenlegungsschrift DE 44 19 987 A1 zeigt eine Injektor-Fördereinrichtung für Beschichtungspulver mit einem Saugrohr, welches an den Unterdruckbereich des Injektors angeschlossen ist und sich nach unten in einen Pulverbehälter erstreckt, so daß aus diesem Pulver in den Unterdruckbereich gesaugt wird. Dem vom Unterdruckbereich abgewandten Endabschnitt des Saugrohres wird Ausgleichsluft zugeführt, um Schwankungen des Saugdruckes auszugleichen. Wie die US-Patentschrift 3 746 254 zeigt, kann der Pulverbehälter auch oberhalb, statt unterhalb, des Unterdruckbereiches des Injektors angeordnet sein, so daß sich seine Pulveransaugöffnung über dem Unterdruckbereich befindet. Aus der europäischen Patentanmeldung EP 0 769 327 A2 ist eine Pulverbeschichtungsvorrichtung bekannt, bei welcher sich der Injektor am unteren Ende eines Rohres befindet, welches in einen Pulverbehälter eintauchbar ist, um daraus Pulver zu fördern.From European patent application EP 0 718 043 A1 a powder coating system is known in which a conveying air flow in a negative pressure area Injector creates a negative pressure and thereby powder sucked out of a container and into a powder line promotes. Downstream of the vacuum area is the Conveying air powder flow Additional air through a Auxiliary air inlet supplied to in the powder line to achieve a predetermined total amount of air. Further is from European patent specification 0 412 289 B1 an electrostatic powder coating system with an injector, which conveying air and Additional air is supplied. The additional air can be used as Control air in the vacuum area of the injector be promoted. The German patent application DE 44 19 987 A1 shows one Injector conveyor for coating powder with a suction pipe, which is connected to the vacuum area of the Injector is connected and down in extends a powder container so that from this Powder is sucked into the vacuum area. The from End section of the vacuum region facing away from the vacuum Suction pipe is supplied to compensating air Compensate for fluctuations in suction pressure. Like the US patent 3 746 254 shows the powder container also above, instead of below, the vacuum area of the injector so that its Powder suction opening above the vacuum area located. From European patent application EP 0 769 327 A2 a powder coating device is known, where the injector is at the bottom of a Tube, which is in a powder container is submersible to convey powder from it.

Vorliegende Erfindung umfaßt alle vorgenannten Ausführungsformen und ist nicht auf eine bestimmte Ausführungsform beschränkt.The present invention includes all of the foregoing Embodiments and is not specific Embodiment limited.

Bei Pulverbeschichtungsanlagen ist es bekannt, die Pulverleitung, normalerweise ein Schlauch, und die Sprühvorrichtung von Zeit zu Zeit von abgelagerten Pulverpartikeln zu reinigen. Dies ist notwendig, um ein unkontrolliertes Austreten von abgelagerten, alten Pulverpartikeln zu vermeiden, da diese zu Störungen der beschichteten Oberfläche eines Objektes führen würden. Zum Spülen des Pulverschlauches und der Sprühvorrichtung wird normalerweise Druckluft an den Injektor angeschlossen und durch den Injektor und den Pulverschlauch hindurch durch die Sprühvorrichtung geblasen. Ein Nachteil dieser bekannten Spülart besteht darin, daß die Spülluft nicht nur zur Sprühvorrichtung strömt, sondern sich auch im Injektor auf andere an ihn angeschlossene Leitungen aufteilt. Ein weiterer Nachteil besteht bei den bekannten Systemen darin, daß für den Reinigungsvorgang mit Spülluft der Pulverbeschichtungsvorgang abgeschaltet werden muß und anschließend die Förderluft und gegebenenfalls verwendete Zusatzluft neu auf die gewünschten Druckverhältnisse und die gewünschte Fördermenge Pulver eingestellt werden müssen. Pulverablagerungen im Pulverschlauch können zwar stark reduziert werden, in dem der Schlauch aus einem dafür geeigneten Material hergestellt wird, jedoch ist bei großen Längen des Pulverschlauches die Summe der abgelagerten Pulverpartikel immer noch relativ hoch.In powder coating systems, it is known that Powder line, usually a hose, and the Spray device from time to time from deposited To clean powder particles. This is necessary to get one uncontrolled leakage of deposited, old Avoid powder particles, as these can disrupt the coated surface of an object. For rinsing the powder hose and the Spray device is normally supplied to the compressed air Injector and connected by the injector and the Powder hose through the spray device blown. A disadvantage of this known type of flushing is in that the purge air is not just for spraying flows, but also in the injector on others to him splits connected lines. Another The disadvantage of the known systems is that for the cleaning process with purge air Powder coating process must be switched off and then the conveying air and if necessary additional air used to the desired Pressure ratios and the desired powder delivery rate must be set. Powder deposits in the Powder hose can be greatly reduced in which the hose from a suitable material is produced, however, for long lengths of Powder hose the sum of the deposited Powder particles still relatively high.

Durch die Erfindung soll die Aufgabe gelöst werden, große Serien von Objekten mit sehr guter Beschichtungsqualität zu beschichten, ohne daß die Serienproduktion dieser Objekte für Reinigungsarbeiten oder Einstellarbeiten der Sprühbeschichtungsvorrichtung gestört wird oder unterbrochen werden muß. Durch die Erfindung sollen beispielsweise auch Autokarosserien in der Serienproduktion mit so guter Oberflächenqualität beschichtet werden können, wie dies von der Beschichtung mit Flüssiglack bekannt ist. Das Ziel ist somit, höchste Ansprüche an die Pulverbeschichtungsqualität zu erfüllen hinsichtlich Haftung am Objekt, Geschlossenheit der Pulverschicht nach ihrem Aufbrennen auf das Objekt, extreme Gleichmäßigkeit und Glattheit der Beschichtung. Das Verfahren und die Vorrichtung hierfür sollen eine sehr hohe Zuverlässigkeit im Dauerbetrieb haben. The object of the invention is to be achieved large series of objects with very good To coat coating quality without the Series production of these objects for cleaning work or adjustment work of the spray coating device is disturbed or must be interrupted. Through the Invention are also intended, for example, in car bodies series production with such good surface quality can be coated like this by the Coating with liquid paint is known. The aim is thus, the highest demands on the Powder coating quality to meet regarding Adherence to the object, closedness of the powder layer after burning it onto the object, extreme Uniformity and smoothness of the coating. The The method and the device for this are said to be very have high reliability in continuous operation.

Diese Aufgabe wird gemäß der Erfindung durch die Merkmale von Anspruch 1 gelöst.This object is achieved according to the invention by Features of claim 1 solved.

Weitere Merkmale der Erfindung sind in den Unteransprüchen enthalten.Further features of the invention are in the Subclaims included.

Die Erfindung wird im folgenden mit Bezug auf die Zeichnungen anhand von bevorzugten Ausführungsformen als Beispiel beschrieben.The invention is described below with reference to the Drawings based on preferred embodiments described as an example.

In den Zeichnungen zeigen

Fig. 1
schematisch und unmaßstäblich eine Pulver-Sprühbeschichtungsvorrichtung gemäß der Erfindung,
Fig. 2
einen Teil einer weiteren Ausführungsform einer Pulver-Sprühbeschichtungsvorrichtung nach der Erfindung, deren fehlender Teil identisch mit dem betreffenden Teil von Fig. 1 ist.
Show in the drawings
Fig. 1
schematically and not to scale a powder spray coating device according to the invention,
Fig. 2
a part of a further embodiment of a powder spray coating device according to the invention, the missing part of which is identical to the relevant part of FIG. 1.

Die in Fig. 1 dargestellte Pulver-Sprühbeschichtungsvorrichtung enthält eine Sprühvorrichtung 2, welche ein Sprühorgan 4 zum Sprühen von Beschichtungspulver auf Objekte 6 aufweist, beispielsweise Autokarosserien, welche an einer Transportvorrichtung 8 in Richtung eines Pfeiles 10 im Dauerbetrieb quer zum Sprühorgan 4 an dessen Vorderseite vorgeführt werden, so daß sie in den Sprühbeschichtungsbereich des Sprühorgans 4 gelangen. Die Objekte 6 haben zwischen sich einen kleinen Abstand oder eine Lücke 12. Das Sprühorgan 4 kann entsprechend Fig. 1 eine Sprühdüse oder ein Rotationskörper sein, beispielsweise eine rotierende Sprüh-Glocke. Das Sprühorgan 4 ist mit einer oder mehreren Hochspannungs-Elektroden 14 zur elektrostatischen Aufladung des Pulvers versehen. Die Elektrode 114 kann aus einem Trägerrohr 16 herausragen, aus welchem Luft über die Elektrode 14 strömt, damit sich an ihr keine Pulverpartikel ablagern. Die Hochspannung für die Elektrode 14 kann von einem Hochspannungserzeuger erzeugt werden, welcher in der Sprühvorrichtung 2 oder extern von ihr angeordnet sein kann. Das Sprühorgan 4 befindet sich am stromabwärtigen Ende eines Pulverkanals 18 der Sprühvorrichtung 2, dessen stromaufwärtiger Anfang 20 über eine Pulverleitung 22 an den Pulverauslaß 24 eines Injektors 26 angeschlossen ist. Dem Pulverauslaß 24 liegt ein Förderlufteinlaß 28 axial gegenüber, welcher über eine Förderluftleitung 30, in welcher sich ein Druckregler 32 befindet, und einen Verteiler 34 an eine Druckquelle 36 angeschlossen ist. Ein Injektorkanal 38 hat benachbart zum Förderlufteinlaß 28 einen Unterdruckbereich 40 mit erweitertem Durchmesser und dann einen im Querschnitt wieder kleineren Pulverauslaßkanal 42. Vom Unterdruckbereich 40 führt über eine Pulvereinlaßöffnung 44 ein Pulveransaugrohr 46 in einen Pulverbehälter 48, so daß der Förderluftstrom der Förderluftleitung 30 im Unterdruckbereich 40 einen Unterdruck oder Vakuum erzeugt und dadurch aus dem Pulverbehälter 48 Pulver ansaugt und über die Pulverleitung 22 zur Sprühvorrichtung 2 fördert, welche das Pulver in Form einer Sprühwolke oder eines Sprühkegels auf die Objekte 6 sprüht.The powder spray coating device shown in Fig. 1 contains a spray device 2, which a Sprayer 4 for spraying coating powder Exhibits objects 6, for example car bodies, which on a transport device 8 in the direction an arrow 10 in continuous operation across the spray element 4 are shown at the front so that they are in the spray coating area of the spray organ 4 reach. Objects 6 have one between them small distance or a gap 12. The sprayer 4 1 can be a spray nozzle or a Be a body of revolution, for example a rotating one Spray bell. The spray element 4 is with or several high-voltage electrodes 14 for electrostatic charging of the powder. The Electrode 114 can protrude from a carrier tube 16, from which air flows over the electrode 14, so no powder particles are deposited on it. The High voltage for the electrode 14 can be from one High voltage generator are generated, which in the Spray device 2 or be arranged externally can. The spray element 4 is located on the downstream End of a powder channel 18 of the spray device 2, whose upstream beginning 20 via a Powder line 22 to the powder outlet 24 of an injector 26 is connected. The powder outlet 24 is located Delivery air inlet 28 axially opposite, which via a Conveying air line 30, in which there is a pressure regulator 32 is located, and a manifold 34 to a pressure source 36 is connected. An injector channel 38 has adjacent to the supply air inlet 28 one Vacuum area 40 with an enlarged diameter and then a smaller one in cross section Powder outlet channel 42. From the negative pressure area 40 leads a powder suction pipe via a powder inlet opening 44 46 in a powder container 48, so that the Conveying air flow of the conveying air line 30 in Vacuum area 40 a vacuum or vacuum generated and thereby 48 powder from the powder container sucks and via the powder line 22 to Spray device 2 promotes the powder in the form a spray cloud or spray cone on the objects 6 sprays.

In den Unterdruckbereich 40 des Injektors 26 mündet ein Steuerlufteinlaß 50, welcher über eine Steuerluftleitung 52, die einen Druckregler 54 enthält, und den Verteiler 34 an die Druckluftquelle 36 angeschlossen ist. Durch Einleiten von Steuerluft in den Unterdruckbereich 40 kann dessen Unterdruck oder Vakuum soweit reduziert oder aufgehoben werden, daß die Pulverförderung aus dem Behälter 48 unterbrochen wird, wenn die Förderluft der Förderluftleitung 32 mit unveränderter Strömungsrate durch den Injektor 26 strömt.The vacuum region 40 of the injector 26 opens out Control air inlet 50, which via a control air line 52, which contains a pressure regulator 54, and the Distributor 34 connected to the compressed air source 36 is. By introducing control air into the Vacuum area 40 can be its vacuum or vacuum reduced or abolished to the extent that the Powder feed from the container 48 is interrupted, if the conveying air of the conveying air line 32 with unchanged flow rate through the injector 26 flows.

In den Pulverauslaßkanal 42 mündet ein Zusatzlufteinlaß 56, welcher über eine Zusatzluftleitung 58, welche einen Druckregler 60 enthalten kann, und den Verteiler 34 an die Druckquelle 36 angeschlossen. Die Zusatzluft ergibt zusammen mit der Förderluft eine Gesamtluftmenge, welche in der Pulverleitung 22 Pulsationen des Pulverstromes und größere Pulverablagerungen verhindert. Anstatt mit der Zusatzluft der Zusatzluftleitung 58 könnte auch mit der Steuerluft der Steuerluftleitung 52 die Gesamtluftmenge beeinflußt werden, was aber ungünstig ist, weil die Steuerluft die Unterdruckwirkung im Unterdruckbereich 40 und damit auch die Förderwirkung der Förderluft der Förderluftleitung 30 beeinflußt, so daß die Förderluft ebenfalls geändert werden müßte, wenn die Steuerluft zum Ausgleich von Luftmengenänderungen in der Pulverleitung 22 verwendet werden würde. Deshalb wird gemäß der Erfindung die Steuerluft der Steuerluftleitung 52 nur zum Aufheben des Unterdruckes im Unterdruckbereich 40 verwendet, um dadurch die Pulverförderung abzuschalten, nicht nur zu reduzieren. Während dieser Unterbrechung der Pulverförderung wird gemäß der Erfindung die Förderluft der Förderluftleitung 30 und die Zusatzluft der Zusatzluftleitung 58 unverändert dem Injektor 26 und der Pulverleitung 22 zugeführt, während sich eine Objektlücke 12 vor dem Sprühorgan 4 befindet. Wenn dann das nächste Objekt 6 vor dem Sprühorgan 4 ist, wird die Pulverförderung wieder eingeschaltet, indem die Steuerluft der Steuerluftleitung 52 abgeschaltet wird. Das Einschalten und Abschalten in Abhängigkeit von der Fördergeschwindigkeit und der Größe der Objekte 6 erfolgt automatisch durch eine prozessorgesteuerte elektronische Steuereinrichtung 62. Dadurch werden folgende Vorteile erreicht: Beim Abschalten der Pulverförderung wird noch das restliche Pulver aus dem Pulver-Luft-Weg (38, 42, 22, 2) herausgefördert und durch das Sprühorgan 4 versprüht. Dadurch ergibt sich beim erneuten Einschalten der Pulverförderung kein Pulverstoß, und damit auch keine Beschichtungsfehler auf dem nächsten zu beschichtenden Objekt 6. Vorzugsweise ist die Steuerung 62 derart programmiert, daß die Pulverförderung nicht erst in der Objektlücke 12 abgeschaltet wird, sondern kurz vor Ende des gerade beschichteten Objektes 6, so daß das gesamte im Pulverweg vorhandene Pulver noch auf dieses Objekt aufgetragen wird, ohne Beschichtungsfehler zu erzeugen. Damit wird der weitere Vorteil erzielt, daß der Verlust an Pulver, welches nicht auf den Objekten 6 haftet, reduziert wird.An additional air inlet opens into the powder outlet channel 42 56, which via an additional air line 58, which may include a pressure regulator 60 and the manifold 34 connected to the pressure source 36. The additional air together with the conveying air gives one Total amount of air in the powder line 22 Pulsations of the powder flow and larger ones Powder deposits prevented. Instead of with the Additional air of the additional air line 58 could also be used with the Control air of the control air line 52 the total amount of air be influenced, which is unfavorable because the Control air the vacuum effect in the vacuum area 40 and thus also the conveying effect of the conveying air of the Conveying air line 30 affects, so that the conveying air would also have to be changed if the control air to compensate for changes in air volume in the Powder line 22 would be used. That is why according to the invention, the control air of the control air line 52 only to release the negative pressure in the Vacuum area 40 used to thereby the Switch off powder feed, not just reduce it. During this interruption of powder delivery according to the invention, the conveying air of the conveying air line 30 and the additional air of the additional air line 58 unchanged the injector 26 and the powder line 22 fed while an object gap 12 in front of Sprayer 4 is located. Then when the next object 6 is in front of the spray organ 4, the powder delivery switched on again by the control air of the Control air line 52 is turned off. Switching on and switching off depending on the Conveying speed and the size of the objects 6 is done automatically by a processor-controlled electronic control device 62. This will achieved the following advantages: The remaining powder from the Powder-air path (38, 42, 22, 2) conveyed out and sprayed by the spray organ 4. This results in when switching on the powder feed again none Powder burst, and therefore no coating defects on the next object to be coated 6. The controller 62 is preferably programmed such that that powder production is not only in the object gap 12 is switched off, but shortly before the end of the straight coated object 6, so that the entire im Powder path existing powder still on this object is applied without producing coating defects. This has the further advantage that the loss powder that does not adhere to objects 6, is reduced.

Das Ansaugrohr 26 ist an seinem vom Injektor 26 abgewandten unteren Endabschnitt 64 mit einem Ausgleichsluft-Einlaß 66 versehen, durch welchen Druckluft als Ausgleichsluft in das Ansaugrohr 46 gefördert wird, um im Ansaugrohr 36 entstehende Druckschwankungen zu kompensieren oder zu dämpfen. Der Ausgleichsluft-Einlaß 66 ist über eine Ausgleichsluft-Leitung 68, in welcher sich ein Druckregler 70 befinden kann, an den Verteiler 34 der Druckluftquelle 36 angeschlossen. Die Ausgleichsluft wird sowohl während der Pulverförderung als auch während Pulverförderungspausen mit konstantem Druck und gleichbleibender Luftrate zugeführt.The intake pipe 26 is on its from the injector 26 facing away lower end portion 64 with a Equalization air inlet 66 through which Compressed air as compensation air in the intake pipe 46 is promoted to arise in the intake pipe 36 Compensate or dampen pressure fluctuations. The Compensation air inlet 66 is via a compensation air line 68, in which there is a pressure regulator 70 can, to the distributor 34 of the compressed air source 36 connected. The balance air is both during the powder feed as well during Powder feed breaks with constant pressure and constant air rate supplied.

Um die Sprühvorrichtung 2 und gewünschtenfalls auch die Pulverleitung 22 sauber zu halten, ist eine Spülluftvorrichtung 72 mit mindestens einem Spülluft-Einlaß 73 vorgesehen. Der Spülluft-Einlaß 73 liegt vorzugsweise an einer Stelle, von wo aus der Strömungswiderstand für diese Spülluft im Luft-Pulver-Weg, welcher durch die Pulverleitung 22, die Sprühvorrichtung 2 und den Injektor 26 gebildet ist, in Richtung stromabwärts bis durch die Sprühvorrichtung 2 hindurch kleiner ist als stromaufwärts bis durch den Injektor 26 hindurch. Dadurch wird erreicht,daß die Spülluft nur in Richtung zum Sprühorgan 4 und aus diesem in Richtung zu den Objekten 6 hin strömt, jedoch nicht in entgegengesetzter Richtung zum Injektor 26 hin. Demzufolge liegt der Spüllufteinlaß 73, wobei in abgewandelter Ausführungsform auch mehrere solche Stellen oder Spüllufteinlässe vorgesehen sein können, zwischen der halben Länge der Pulverleitung 22 und dem Sprühorgan 4. Je besser das Material der Pulverleitung 22, normalerweise ein Schlauch, dazu geeignet ist, Pulverablagerungen in ihr zu verhindern, desto weiter kann der Spüllufteinlaß 73 stromabwärts in Richtung zum Sprühorgan 4 verlagert werden. Der Pulverweg in der Sprühvorrichtung 2 kann aus ähnlichem Material gebildet sein, um Ablagerungen von Pulverpartikeln zu reduzieren. Jedoch das Sprühorgan 4, selbst wenn es aus dem gleichen Material besteht, muß mit Spülluft innen gereinigt werden, weil die Pulverpartikel nicht nur an den Innenflächen des Sprühorgans 4 entlanggleiten, sondern auch quer auf diese Innenflächen auftreffen. Bevorzugte Ausführungsformen bestehen deshalb darin, den mindestens einen Spüllufteinlaß 73 an einer Spülluft-Zufuhrstelle zwischen der halben Länge der Pulverleitung 22 oder auf einer Länge von 75% stromabwärts der Pulverleitung 22, oder unmittelbar am Pulvereinlaß 20 der Sprühvorrichtung 2, oder entsprechend Fig. 2 der Zeichnungen in der Sprühvorrichtung 2 mit kurzem Abstand stromaufwärts von dem Sprühorgan 4 anzuordnen, so daß die Spülluft ungedrosselt auf die Innenflächen des Sprühorgans 4 auftrifft und dort eventuell vorhandene Pulverpartikel wegspült.To the spray device 2 and, if desired, also Keeping the powder line 22 clean is one Purge air device 72 with at least one purge air inlet 73 provided. The purge air inlet 73 is located preferably at a point from where the Flow resistance for this purge air in the air-powder path, which through the powder line 22, the Spray device 2 and the injector 26 is formed in Direction downstream until through the spray device 2 is smaller than upstream to through the Injector 26 through. This ensures that the Purge air only in the direction of the spray element 4 and out this flows towards the objects 6, however not in the opposite direction to the injector 26 out. Accordingly, the purge air inlet 73, wherein in modified embodiment also several such Places or purge air inlets can be provided, between half the length of the powder line 22 and the Sprayer 4. The better the material of the powder line 22, usually a hose, is suitable To prevent powder deposits in it, the further can the purge air inlet 73 downstream toward Sprayer 4 are moved. The powder path in the Spray device 2 can be formed from a similar material be to build up deposits of powder particles to reduce. However, the sprayer 4, even if it is off the same material must be with purge air inside be cleaned because the powder particles don't just stick to slide along the inner surfaces of the spray element 4, but also hit these inner surfaces across. Preferred embodiments therefore consist in the at least one purge air inlet 73 on one Purge air supply point between half the length of the Powder line 22 or on a length of 75% downstream of the powder line 22, or immediately on Powder inlet 20 of the spray device 2, or 2 of the drawings in the Spray device 2 with a short distance upstream of to arrange the spray element 4 so that the purge air unthrottled on the inner surfaces of the spray element 4 strikes and any powder particles present there rinses.

Bei der Ausführungsform nach Fig. 1 ist die Pulverleitung 22 ein Schlauch, welcher auf einen mehr als die halbe Länge ausmachenden stromaufwärtigen Schlauchteil 22-1 und einen wesentlich weniger als die halbe Schlauchlänge ausmachenden kurzen Schlauchteil 22-2 aufgeteilt ist. Die beiden Schlauchteile 22-1 und 22-2 sind durch den Spülluft-Einlaß 73, welcher eine ringförmige Schlitzdüse 74 aufweist, miteinander verbunden. Die Spülluft strömt von der Schlitzdüse 74 durch den stromabwärtigen Schlauchteil 22-2 und danach durch die Sprühvorrichtung 2, ohne daß ein Teil dieser Spülluft in entgegengesetzter Richtung zum Injektor 26 strömt.1 is the Powder line 22 a hose, which on a more than half the length upstream Hose part 22-1 and one much less than that half hose length making up a short hose part 22-2 is divided. The two hose parts 22-1 and 22-2 are through the purge air inlet 73, which is one has annular slot nozzle 74 with each other connected. The purge air flows from the slot nozzle 74 through the downstream hose section 22-2 and thereafter by the spray device 2 without part of it Purge air in the opposite direction to the injector 26 flows.

Die Spülluft wird nicht während der Pulverförderung, sondern bei abgeschalteter Pulverförderung entweder bei jeder Objekt-Lücke 12 oder jeweils nur bei einer von mehreren Objekt-Lücken 12 vor dem Sprühorgan 4 eingeschaltet. Gemäß einer bevorzugten Ausführungsform wird die Spülluft nicht als Dauer-Druckluftstrom zugeführt, sondern in Form von mindestens einem oder vorzugsweise mindestens zwei, drei oder vier kurzzeitig aufeinanderfolgenden Druckluftstößen oder Druckluftpulsen. Zur Erzeugung dieser stoßartigen Druckluftpulse ist der Spülluft-Einlaß 73 über eine Druckluftleitung 76, in welcher sich in Strömungsrichtung nacheinander ein Druckregler 78, ein Druckmesser 80 und ein Umschaltventil 82 befinden, an die Druckluftquelle 36 oder deren Verteiler 34 angeschlossen. Das Umschaltventil 82 ist vorzugsweise ein elektromagnetisches oder pneumatisches Zwei/Zwei-Wegeventil, welches von der elektronischen Steuereinrichtung 62 gesteuert wird. Der Spülluft-Einlaß 73 ist mit einer Rückflußsperre 84 versehen, welches ein Filtermaterial zum Filtern von Pulverpartikeln und/oder ein Rückschlagventil sein kann, welches nur in Strömungsrichtung der Spülluft zum Spülluft-Einlaß 73 hin öffnet, jedoch bei einem in Gegenrichtung wirkenden Fluiddruck schließt. Die als Spülluft dienende Druckluft wird dem Spülluft-Einlaß 73 vorzugsweise in einer Menge im Bereich von 15-40 Nm3/h und einem Druck bis maximal 6 bar, vorzugsweise bis 5 bar zugeführt. Entsprechend ist der Druck der Spülluft an ihrem Regler 78 einstellbar.The purging air is not switched on during powder conveyance, but when powder conveyance is switched off either at each object gap 12 or only at one of several object gaps 12 in front of the spray element 4. According to a preferred embodiment, the purge air is not supplied as a continuous stream of compressed air, but in the form of at least one, or preferably at least two, three or four, briefly successive bursts of compressed air or compressed air pulses. To generate these impulsive compressed air pulses, the purge air inlet 73 is connected to the compressed air source 36 or its distributor 34 via a compressed air line 76, in which a pressure regulator 78, a pressure meter 80 and a changeover valve 82 are located one after the other in the direction of flow. The changeover valve 82 is preferably an electromagnetic or pneumatic two / two-way valve which is controlled by the electronic control device 62. The purge air inlet 73 is provided with a non-return valve 84, which can be a filter material for filtering powder particles and / or a check valve which only opens in the direction of flow of the purge air to the purge air inlet 73, but closes at a fluid pressure acting in the opposite direction. The compressed air serving as purge air is supplied to the purge air inlet 73 preferably in an amount in the range from 15-40 Nm 3 / h and a pressure up to a maximum of 6 bar, preferably up to 5 bar. The pressure of the purge air can be adjusted accordingly on its regulator 78.

Die Spülluft kann eingeschaltet werden entweder wenn alle Luftanschlüsse des Injektors 26 ausgeschaltet sind oder gemäß der bevorzugten Ausführungsform während alle Luftanschlüsse oder mindestens die Förderluft des Injektors 26 eingeschaltet bleiben. Dadurch strömen bei der bevorzugten Ausführungsform durch das Sprühorgan 4, während ihm ein zu beschichtendes Objekt 6 gegenüberliegt, Förderluft der Förderluftleitung 30, Zusatzluft der Zusatzluftleitung 58 und Ausgleichsluft der Ausgleichsluftleitung 68; wenn jedoch eine Objekt-Lücke 12 dem Sprühorgan 4 gegenüberliegt und die Pulverförderung durch Steuerluftzufuhr der Steuerluftleitung 52 abgeschaltet ist, dann strömen durch das Sprühorgan 4 die Förderluft der Förderluftleitung 30, Steuerluft der Steuerluftleitung 52, Zusatzluft der Zusatzluftleitung 58, Ausgleichsluft der Ausgleichsluftleitung 68 und, während der Reinigungsphase, auch Spülluft des Spülluft-Einlasses 73. Gemäß einer besonderen Ausführungsform wird die Spülluft bereits dann eingeschaltet, wenn sich ein Endabschnitt eines beschichteten Objektes 6 noch im Sprühbereich des Sprühorgans 4 befindet, damit das gesamte Pulver für den Beschichtungsvorgang verwendet wird. Die Pulverschicht auf dem Objekt 6 erhält dadurch keine andere Schichtdicke oder andere Veränderung, wenn die Pulverförderung ebenfalls kurz vor dem Ende des gerade beschichteten Objekts 6 abgeschaltet wird, indem die Steuerluft der Steuerluftleitung 52 eingeschaltet und damit in den Unterdruckbereich 40 gefördert wird. Die zeitliche Koordination der verschiedenen Luftarten erfolgt durch die elektronische Steuereinrichtung 62.The purge air can be switched on either if all air connections of the injector 26 are switched off or according to the preferred embodiment during all air connections or at least the conveying air of the Injector 26 remain switched on. Thereby flow in the preferred embodiment by the spray organ 4, while an object to be coated 6 opposite, conveying air of the conveying air line 30, Auxiliary air of the auxiliary air line 58 and compensation air the balance air line 68; however if there is an object gap 12 is opposite the spray element 4 and the Powder feed through control air supply Control air line 52 is switched off, then flow through the spray organ 4, the conveying air Conveying air line 30, control air of the control air line 52, additional air of the additional air line 58, compensating air the compensation air line 68 and, during the Cleaning phase, also purge air of the purge air inlet 73. According to a particular embodiment, the Purge air already switched on when on End section of a coated object 6 still in Spray area of the spray organ 4 is so that all powder used for the coating process becomes. The powder layer on the object 6 thereby receives no other layer thickness or other change if the powder feed also shortly before the end of the just coated object 6 is turned off by the control air of the control air line 52 is switched on and is thus promoted to the vacuum region 40. The temporal coordination of the different types of air is carried out by the electronic control device 62.

Bei der Ausführungsform nach Fig. 1 hat der Spülluft-Einlaß 73 mindestens eine ringförmige Schlitzdüse 74 um den Luft-Pulver-Weg herum, damit diesem eine große Spülluftmenge zugeführt werden kann, ohne daß dafür ein besonders hoher Druck erforderlich ist. Bei der Ausführungsform nach Fig. 2 hat der Spülluft-Einlaß 73 stattdessen eine Vielzahl von Bohrungen 75, welche in den Luft-Pulver-Weg münden und diesen ringförmig umgeben. Mit dieser Ausführungsform wird eine ähnliche Wirkung wie mit einer ringförmigen Schlitzdüse erzielt, jedoch mit einem etwas größeren Strömungswiderstand. Die Ringschlitzdüse 74 von Fig. 1 und die Spülluft-Bohrungen 75 von Fig. 2 sind vorzugsweise unter einem Winkel von ungefähr 45 Grad in Strömungsrichtung des Luft-Pulverstromes schräg angeordnet.In the embodiment of Fig. 1, the purge air inlet 73 at least one annular slot nozzle 74 around the air-powder path so make it a big one Purge air volume can be supplied without a particularly high pressure is required. In the 2 has the purge air inlet 73rd instead, a plurality of holes 75, which in the air-powder path and this ring-shaped surround. With this embodiment, a similar one Effect as achieved with an annular slot nozzle, however with a slightly larger flow resistance. The ring slot nozzle 74 of FIG. 1 and the purge air bores 75 of FIG. 2 are preferably under one An angle of approximately 45 degrees in the flow direction of the Air powder flow arranged obliquely.

Claims (18)

  1. Powder spray coating apparatus containing
    a spray apparatus (2) which has a spray member (4) for spraying the powder onto an object (6) to be coated;
    an injector (26) for pneumatic powder transport from a powder receptacle (48) to the spray apparatus (2), wherein the injector (26) has a partial-pressure zone (40) with a transporting air inlet (28), a powder inlet (44) and a powder outlet (24, 42);
    a powder pipe (22) which connects the powder outlet (24) of the injector (26) to a powder inlet (20) of the spray apparatus (2), so that the injector, the powder pipe and the spray apparatus together form an air-powder path, wherein the air-powder path at at least one scavenging air delivery point is provided with at least one scavenging air inlet (73) which is connected via an automatically switchable shut-off member (82) to a compressed air source (78, 36) to drive compressed scavenging air from the scavenging air inlet (73) through the air-powder path out of the spray apparatus (2) while powder transport is switched off;
    a control device (62) for the control of powder transport and of the shut-off member (82) for the scavenging air as a function of the transport of objects to be coated;
    characterised in that the scavenging air delivery point lies at a location from where the flow resistance for compressed scavenging air downstream to a point through the spray apparatus (2) is lower than upstream to a point through the injector (26); in that the control device (62) is designed to interrupt powder transport by introducing controlling air through a controlling air inlet (50) into the partial-pressure zone (40) and so by reducing the partial pressure, so that then the controlling air is conducted together with the transporting air, but without drawing in powder at the powder inlet (44), and together with the scavenging air through the spray member (4) of the spray apparatus (2).
  2. Powder spray coating apparatus according to claim 1, characterised in that the at least one scavenging air inlet (73) lies between half the length of the powder pipe (22) and the spray member (4) of the spray apparatus (2).
  3. Powder spray coating apparatus according to claim 1, characterised in that the at least one scavenging air inlet (73) lies in the air-powder path between 75% of the length of the powder pipe (22) downstream of the injector (26), and the spray member (4).
  4. Powder spray coating apparatus according to claim 1, characterised in that the at least one scavenging air inlet (73) is arranged at the powder inlet (20) of the spray apparatus (2).
  5. Powder spray coating apparatus according to claim 1, characterised in that the at least one scavenging air inlet (73) is arranged in the spray apparatus (2) upstream of the spray member (4), so that the compressed scavenging air flows without 'substantial flow resistance directly onto the inner surfaces of the spray member (4) and scavenges them.
  6. Powder spray coating apparatus according to any of the preceding claims, characterised in that the scavenging air inlet (73) opens out in a ring from all sides into the powder-air path.
  7. Powder spray coating apparatus according to claim 6, characterised in that the scavenging air inlet (73) has at least one annular slot nozzle (74).
  8. Powder spray coating apparatus according to claim 6, characterised in that the scavenging air inlet (73) has a plurality of nozzle bores (75) which open out into the air-powder path and surround it in a ring.
  9. Powder spray coating apparatus according to any of the preceding claims, characterised in that the scavenging air inlet (73) is provided with a non-return valve (84) which automatically opens in case of fluid pressure in the direction of flow of scavenging air and closes in the opposite direction.
  10. Powder spray coating apparatus according to any of the preceding claims, characterised in that the quantity of scavenging air is 15 to 40 Nm3/h.
  11. Powder spray coating apparatus according to any of the preceding claims, characterised in that the scavenging air is delivered to the air-powder path at a pressure within the range of 2 and 6 bars.
  12. Powder spray coating apparatus according to any of the preceding claims, characterised in that the compressed scavenging air which is conducted into the air-powder path is pulsed compressed air, at least two compressed scavenging air pulses being conducted into the air-powder path per scavenging operation.
  13. Powder spray coating apparatus according to claim 12, characterised in that compressed air pulses have a length from 0.5 to 3 seconds.
  14. Powder spray coating apparatus according to claim 12 or 13, characterised in that the time gaps between the pulses of the pulsed compressed scavenging air are 0.5 to 3 seconds.
  15. Powder spray coating apparatus according to any of the preceding claims, characterised in that the control device (62) is a computer-controlled electronic control device.
  16. Powder spray coating apparatus according to any of the preceding claims, characterised in that the injector is provided with an additional compressed air connection (56, 58, 60) at a point located downstream of its partial-pressure zone (40) for the transport of additional air into the upstream initial portion of the powder pipe (22) in addition to the transporting air (30).
  17. Powder spray coating apparatus according to any of the preceding claims, characterised in that a powder intake pipe (46) which is connected to the partial-pressure zone (40) of the injector is provided, on its end section (64) facing away from the injector (26), with an air inlet (66) for compressed equalising air, for equalising pressure fluctuations in this powder intake pipe.
  18. Use of an apparatus according to any of the preceding claims for carrying out a method for the powder spray coating of objects (6) with the following characteristics:
    pneumatic transport of the powder from a receptacle (48) via an injector (26) and a powder pipe (22) to a spray apparatus (2), wherein a transporting air stream (30) is conducted through the injector (26) which generates a partial pressure in a partial-pressure zone (40) of the injector and so draws in powder from the receptacle and transports it through the powder pipe to the spray apparatus;
    automatic transport of the objects (6) one after the other through the spray coating zone of the spray apparatus (2);
    interruption of powder transport in the object gaps (12) between successive objects (6);
    characterised in that
    during interruption of powder transport, when an object gap (12) is located in the spray coating zone of the spray apparatus (2), the transporting air stream is maintained,
    in that, for interruption of powder transport, a quantity of controlling air (52) required for this is conducted into the partial-pressure zone (40) of the injector (26), reducing the partial pressure to such an extent that powder transport is interrupted,
    in that, during interruption of powder transport, the air-powder path between the injector (26) and a spray member (4) of the spray apparatus (2) is automatically scavenged with compressed scavenging air at least in its downstream section;
    and in that at the end of an object gap (12) powder transport is automatically switched back on by switching off the controlling air or reducing it accordingly;
    in that all the above-mentioned steps are controlled by a computer-controlled control device (62), so that they proceed automatically, coordinated with each other.
EP98115238A 1997-11-03 1998-08-13 Method and apparatus for powder coating with purging air supply Expired - Lifetime EP0913203B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19748375 1997-11-03
DE19748375A DE19748375A1 (en) 1997-11-03 1997-11-03 Method and device for powder spray coating

Publications (2)

Publication Number Publication Date
EP0913203A1 EP0913203A1 (en) 1999-05-06
EP0913203B1 true EP0913203B1 (en) 2004-03-17

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EP98115238A Expired - Lifetime EP0913203B1 (en) 1997-11-03 1998-08-13 Method and apparatus for powder coating with purging air supply

Country Status (5)

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US (1) US6217654B1 (en)
EP (1) EP0913203B1 (en)
JP (1) JPH11207214A (en)
AT (1) ATE261777T1 (en)
DE (2) DE19748375A1 (en)

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US6915966B2 (en) 2003-01-29 2005-07-12 Specialty Minerals (Michigan) Inc. Apparatus for the gunning of a refractory material and nozzles for same
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Also Published As

Publication number Publication date
JPH11207214A (en) 1999-08-03
US6217654B1 (en) 2001-04-17
DE19748375A1 (en) 1999-05-06
EP0913203A1 (en) 1999-05-06
DE59810986D1 (en) 2004-04-22
ATE261777T1 (en) 2004-04-15

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