EP0412289A2 - Electrostatic spray device - Google Patents

Electrostatic spray device Download PDF

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Publication number
EP0412289A2
EP0412289A2 EP90112723A EP90112723A EP0412289A2 EP 0412289 A2 EP0412289 A2 EP 0412289A2 EP 90112723 A EP90112723 A EP 90112723A EP 90112723 A EP90112723 A EP 90112723A EP 0412289 A2 EP0412289 A2 EP 0412289A2
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EP
European Patent Office
Prior art keywords
gas
powder
pressure
air
injector
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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.)
Granted
Application number
EP90112723A
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German (de)
French (fr)
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EP0412289A3 (en
EP0412289B1 (en
Inventor
Karl Buschor
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Gema Switzerland GmbH
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Gema Switzerland GmbH
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Application filed by Gema Switzerland GmbH filed Critical Gema Switzerland GmbH
Priority to AT90112723T priority Critical patent/ATE96343T1/en
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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
    • 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
    • B05B12/00—Arrangements for controlling delivery; Arrangements for controlling the spray area
    • B05B12/08—Arrangements for controlling delivery; Arrangements for controlling the spray area responsive to condition of liquid or other fluent material to be discharged, of ambient medium or of target ; responsive to condition of spray devices or of supply means, e.g. pipes, pumps or their drive means
    • B05B12/085—Arrangements for controlling delivery; Arrangements for controlling the spray area responsive to condition of liquid or other fluent material to be discharged, of ambient medium or of target ; responsive to condition of spray devices or of supply means, e.g. pipes, pumps or their drive means responsive to flow or pressure of liquid or other fluent material to be discharged
    • 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
    • B05B5/16—Arrangements for supplying liquids or other fluent material
    • B05B5/1683—Arrangements for supplying liquids or other fluent material specially adapted for particulate materials
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/8158—With indicator, register, recorder, alarm or inspection means
    • Y10T137/8175—Plural

Definitions

  • the invention relates to an electrostatic powder coating device according to the preamble of claim 1.
  • spray devices which, in addition to the powder-gas flow, is supplied with cleaning gas which flows over electrodes for electrostatically charging the coating powder and thereby cleans these electrodes and keeps them free from contamination due to powder deposits.
  • the high voltage for the electrodes can be generated in a known manner by a high voltage generator contained in the spraying device or by an external high voltage generator.
  • the high voltage of the high voltage generator creates an electrostatic field between the electrodes and an object to be coated, which is grounded, along which the particles of the coating powder fly from the spray device to the object.
  • the air speed in the fluid lines that is to say in particular in the powder delivery hoses, must be 10 to 15 m / sec.
  • the powder delivery becomes uneven; there is a pulsation of the powder-air mixture, which propagates on the spray device until the powder emerges.
  • the electrostatic application of the coating powder to the object to be coated is very badly affected because there is then a risk that the powder already deposited on the object again is blown away.
  • the amount of powder supplied to the spraying device is increased or decreased.
  • a practical value for the amount of powder supplied per unit of time is 300 g / min. If the quantity of powder supplied per unit of time has to be reduced, the pressure of the conveying air supplied to the injector is first reduced. This also reduces the flow rate of the conveying air in the fluid lines. However, the total air volume must neither become too low nor exceed a maximum value. To compensate for this reduction in air volume, i.e. by at least 10 mm / sec. To reach air speed while maintaining the reduced powder output, more dosing air is fed to the injector.
  • the known function of the injectors is as follows:
  • the conveying air creates a negative pressure in the injector, through which coating powder is sucked out of a powder container, captured by the conveying air and fed to the spraying device through fluid lines.
  • the amount of coating powder delivered per unit of time can be adjusted by changing the pressure and thus also the amount of conveying air. Since the delivery rate depends on the size of the negative pressure generated by the delivery air in the injector, the delivery rate can also be regulated in the case of constant or variable delivery air in that the vacuum range of Injector dosing air is introduced, thereby changing the size of the negative pressure according to the desired flow rate of powder.
  • the powder flow rate is not only dependent on the amount of conveying air, but on the difference between the conveying air minus the metering air.
  • the total amount of air which the coating powder transports must remain constant for a given coating process for the reasons mentioned at the beginning.
  • the operator observes the coating powder cloud directed at the object to be coated and uses this visual observation to set the pressures of the conveying air and the metering air.
  • diagrams are created by the manufacturer of the coating device and supplied with the powder coating device. This allows the operator to set the pressure setting device for the conveying air and the pressure setting device for the metering air so that their pressure values are within a range indicated on the diagrams.
  • the diagrams are rarely or never observed by the operators, which means that incorrect settings are often used.
  • the object of the invention is to facilitate the correct setting of the conveying air quantity and the metering air quantity to optimal values.
  • a first flow meter which provides an indication which is dependent on the total amount of gas flowing per unit of time which transports the coating powder from the injector to the spraying device.
  • This first flow measuring device is preferably arranged in the gas supply line which supplies the conveying gas and the metering gas.
  • This gas flow meter is preferably a so-called variable area flow meter.
  • a float hovers in it in a gas stream flowing from bottom to top. The height of the float depends on the strength of the gas flow and is therefore a measure of the amount of gas flowing through the float flow meter per unit of time. Markings can be attached to the flow meter, which are matched to the gas flow rate.
  • the optimal amount of the total gas depends on several factors, in addition here the diameter and the length of the fluid lines be mentioned.
  • a further application of the inventive concept consists in the use of a second flow meter in an additional gas line, via which additional gas can be fed to the spraying device separately from the coating powder stream.
  • the additional gas can be used for cleaning parts of the spray device, for example for cleaning electrodes, as shown in DE-PS 36 08 426 and 36 08 415, or for generating a gas wall lying in the flow path of the coating powder stream, as is shown in FIG DE-PS 36 08 426 is shown, or are used to generate gas flows which prevent deposition of coating powder on certain outer surfaces of the spraying device, as is known from DE-OS 25 09 851.
  • the pressure of the additional gas is set with a third pressure setting device as a function of the internal cross-sectional sizes and as a function of the lengths of the fluid lines and as a function of other coating criteria.
  • the internal cross-sectional sizes and lengths as well as other criteria can change depending on the use of the powder coating device, as a result of which the pressure of the additional gas must also be changed. At the same time, however, it is often necessary for the quantity of additional gas supplied per unit of time to be kept constant at a predetermined optimal value.
  • the additional gas is also preferably air.
  • the invention also has the advantage that the values can be reproduced in a simple manner. Reproducible here means that when the conveying air and / or dosing air and / or additional air is adjusted, the original conditions and the total air volume can be set again later.
  • the electrostatic powder coating device contains an injector 2, which works on the principle of the Venturi nozzle, also known as a water jet pump.
  • a feed gas line 4 is connected to the injector 2, in which there is a first pressure setting device 6 in the form of an adjustable pressure regulator for setting the pressure of the feed air and a feed gas manometer 8 which visually indicates the pressure of the feed air.
  • the conveying air generates a negative pressure in the vacuum region 10 of the pressure gauge 2 in a known manner and thereby sucks coating powder from a powder container 12, which is then fed from the conveying air to a spray device 16 via a powder supply line 14, normally a hose.
  • the spray device 16 contains electrodes for electrostatically charging the coating powder in a known manner and atomizes the coating powder 18 in the form of a powder cloud onto an object 20 to be coated.
  • the electrodes 22 in the spray device 16 are only shown schematically.
  • the sprayer 16 may take the form of a hand-held gun or an automatic sprayer.
  • a metering gas line 24 is connected to the injector 2, in which there is a flow restrictor 25 and upstream thereof a second pressure setting device 26 in the form of an adjustable pressure regulator and a second manometer 28 for setting and visually displaying the metering gas pressure.
  • the pressure gauges 8 and 28 must therefore be arranged downstream of the two pressure regulators 6 and 26.
  • the dosing air can flow from the dosing gas line 24 into the negative pressure area 10 of the injector 2.
  • the injector 2 delivers most of the coating powder when no dosing air is supplied. The more dosing air is supplied, the lower the vacuum in the vacuum region 10 and the less coating powder is conveyed. Coating powder and conveying gas as well as no or a certain amount of metering gas thus flows in the powder feed line 14.
  • the pressure gauges 8 and 28 are each provided with a scale 29 and 30, which are calibrated in pressure and / or pressure flow quantity per unit of time, for example in Nm 3 / h.
  • the inputs 32 and 34 of the two pressure setting devices 6 and 26 are connected to the output section 36 of a gas supply line 38, the input section 40 of which is connected to the output 42 of an electromagnetically actuated on-off valve 44 (referred to as a directional valve in DIN standards).
  • the two sections 36 and 40 are connected to one another via a first flow measuring device 46, which in the embodiment shown is a vertically arranged variable area flow meter.
  • This consists of a substantially vertically arranged measuring tube 48 and a float 50 arranged therein, which is held in suspension by the gas flowing vertically upwards through it to the outlet section 36, depending on the gas flow rate, at a certain height position.
  • This means that the height position of the float 50 is a measure of the amount of gas flowing through the measuring tube 48 per unit of time.
  • a scale or mark 52 on the measuring tube 48 an operator can see whether the amount of gas supplied per unit of time has the desired value.
  • This amount of gas is the total amount of conveying air and metering air which flows via the injector 2 to the spray device 16.
  • the operator can easily observe this by observing the height position of the float 50 that the total air volume of conveying air and dosing air maintains the desired value or is set to a desired new value.
  • the invention also allows a less qualified operator to easily adjust the pressures and flow rates optimally by observing the pressure gauges 8 and 28 and observing the float 50 relative to the scale or marking 52.
  • the inlet side 54 of the valve 44 is connected to a compressed gas source, preferably a compressed air source 58, via a third pressure regulator 56.
  • a fluid line 62 branches off from the connecting line 60 between the adjustable third pressure regulator 56 and the valve 44, which contains an adjustable fourth pressure regulator 64 and is connected with its downstream end 66 to the powder container 12 for coating powder in a fluidized state in a known manner to keep.
  • an additional gas line 70 for supplying additional gas separately from the coating powder to the spray device 16, which supplies the spray device 16 with additional gas for cleaning the electrodes 22.
  • the cleaning of the electrodes by additional gas is known from DE-PS 36 08 415 and 36 08 426.
  • the additional gas in the spray device 16 can be used to generate a gas flow which deflects the powder flow are used, as is known from DE-PS 36 08 426.
  • the additional gas can also be used to prevent coating powder from outside surfaces of the spray device 16, as is known from DE-OS 25 09 851.
  • the additional gas line 70 there is an adjustable fifth pressure regulator 72 and a second flow measuring device 74, which can be designed in the same way as the first flow measuring device 46 and through which the additional air flow flows from bottom to top and, depending on the flow rate, a float present in a measuring tube 48 50 holds relative to a scale or mark 52 at a certain height position.
  • the measuring tubes 48 of the two flow meters 46 and 74 must therefore be transparent at least on one side so that the float 50 is visible from the outside.
  • the measuring tubes 48 are preferably made entirely of a transparent plastic material.
  • the measuring tubes according to the drawing preferably have a slightly larger truncated cone-shaped inner diameter in the flow direction from bottom to top.
  • adjustable pressure regulators 6, 26, 56, 64 and 72 can also be used.
  • the electrostatic powder coating device according to the invention can be adjusted manually by an operator.
  • the invention also makes it possible to automatically control the pressure setting devices 6, 26 and 72 by means of a microcomputer as a function of target values and as a function of measured values of the two flow measuring devices 46 and 74.

Landscapes

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

Abstract

In the feed gas line (4) and in the metering gas line (24) of an injector (2), there is in each case a pressure-adjustment device (6,26) which can be adjusted with respect to the initial pressure. A gas flow meter (46) indicates the entire quantity of feed air and metering air flowing per time unit. As a result, the pressures of the feed air and of the metering air can be varied and, nevertheless, the entire quantity of gas in the powder/gas stream can be kept at a desired value in a simple manner. <IMAGE>

Description

Die Erfindung betrifft eine elektrostatische Pulverbeschichtungseinrichtung gemäß dem Ober­begriff von Anspruch 1.The invention relates to an electrostatic powder coating device according to the preamble of claim 1.

Eine solche elektrostatische Pulverbeschichtungs­einrichtung ist aus der Praxis bekannt. Bei ihr sind Druckregler als Druckeinstellgeräte vorgesehen. Anstelle von Druckreglern könnten jedoch auch ein­stellbare Hähne oder einstellbare Strömungsdrosseln verwendet werden. Injektoren zur pneumatischen Förderung von Beschichtungspulver sind aus der DE-PS 1 266 685 ( US-PS 3 504 945) bekannt. Sprüh­vorrichtungen können die Form von manuell betätig­baren Pistolen oder von automatisch gesteuerten Sprühgeräten haben. Je nach dem gewünschten Sprüh­verfahren kann die Sprühvorrichtung verschieden ausgebildet sein, wie z.B. die CH-PS 429 517 (=US-­PS 3 521 815), DE-PS 36 08 415 (=US-PS 4 802 625) und DE-PS 36 08 426 (= US-PS 4 788 933) zeigen. In den beiden zuletzt genannten Schriften sind Sprüh­vorrichtungen dargestellt, welchen zusätzlich zum Pulver-Gas-Strom Reinigungsgas zugeführt wird, welches über Elektroden zum elektrostatischen Aufladen des Beschichtungspulvers strömt und da­durch diese Elektroden reinigt und von Verunreini­gungen durch Pulverablagerungen freihält. Die Hochspannung für die Elektroden kann in bekannter Weise durch einen in der Sprühvorrichtung ent­haltenen Hochspannungserzeuger oder durch einen externen Hochspannungserzeuger erzeugt werden. Die Hochspannung des Hochspannungserzeugers erzeugt zwischen den Elektroden und einem zu beschichtenden Objekt, welches geerdet ist, ein elektrostatisches Feld, entlang welchem die Partikel des Beschichtungspulvers von der Sprüh­vorrichtung zum Objekt fliegen.Such an electrostatic powder coating device is known in practice. Pressure regulators are provided as pressure setting devices. Instead of pressure regulators, however, adjustable taps or adjustable flow restrictors could also be used. Injectors for the pneumatic conveying of coating powder are known from DE-PS 1 266 685 (US-PS 3 504 945). Spray devices can take the form of manually operated guns or automatically controlled sprayers. Depending on the desired spraying method, the spraying device can be designed differently, such as, for example, CH-PS 429 517 (= US-PS 3 521 815), DE-PS 36 08 415 (= US-PS 4 802 625) and DE-PS 36 08 426 (= U.S. Patent 4,788,933) show. In the In the latter two documents, spray devices are shown, which, in addition to the powder-gas flow, is supplied with cleaning gas which flows over electrodes for electrostatically charging the coating powder and thereby cleans these electrodes and keeps them free from contamination due to powder deposits. The high voltage for the electrodes can be generated in a known manner by a high voltage generator contained in the spraying device or by an external high voltage generator. The high voltage of the high voltage generator creates an electrostatic field between the electrodes and an object to be coated, which is grounded, along which the particles of the coating powder fly from the spray device to the object.

Um einen konstanten Förderstrom des Pulver-Luft-­Gemisches zu erreichen, muß die Luftgeschwindig­keit in den Fluidleitungen, also insbesondere in den Pulverförderschäuchen, 10 bis 15 m/sec betragen. Bei einer niedrigeren Luftgeschwindig­keit in der Fluidleitung wird die Pulverförderung ungleichmäßig; es entsteht eine Pulsation des Pulver-Luft-Gemisches, welche sich bis zum Pulveraustritt an der Sprühvorrichtung fort­pflanzt. Bei höherer Luftgeschwindigkeit wird das elektrostatische Auftragen des Beschichtungs­pulvers auf das zu beschichtende Objekt sehr stark beeinträchtigt,weil dann die Gefahr besteht, daß das schon auf dem Objekt abgeschiedene Pulver wieder weggeblasen wird.In order to achieve a constant flow rate of the powder-air mixture, the air speed in the fluid lines, that is to say in particular in the powder delivery hoses, must be 10 to 15 m / sec. At a lower air velocity in the fluid line, the powder delivery becomes uneven; there is a pulsation of the powder-air mixture, which propagates on the spray device until the powder emerges. At higher air speeds, the electrostatic application of the coating powder to the object to be coated is very badly affected because there is then a risk that the powder already deposited on the object again is blown away.

Je nach den Erfordernissen des Beschichtungs­vorganges wird die der Sprühvorrichtung zu­geführte Pulvermenge erhöht oder erniedrigt. Ein Praxiswert für die pro Zeiteinheit zuge­führte Pulvermenge ist 300 g/min. Wenn die pro Zeiteinheit zugeführte Pulvermenge redu­ziert werden muß, so wird als erstes der Druck der zum Injektor zugeführten Förderluft reduziert. Damit wird auch die Durchflußgeschwindigkeit der Förderluft in den Fluidleitungen reduziert. Je­doch darf die Gesamtluftmenge weder zu niedrig werden noch einen Höchstwert überschreiten. Um diese Luftmengenreduktion auszugleichen, also um w ieder mindestens auf 10 mm/sec. Luftgeschwindig­keit zu gelangen, unter Beibehaltung des reduzierten Pulverausstoßes, wird dem Injektor mehr Dosier­luft zugeführt. Die bekannte Funktion der Injektoren ist folgende:
Die Förderluft erzeugt im Injektor einen Unter­druck, durch welchen Beschichtungspulver aus einem Pulverbehälter angesaugt, von der Förderluft erfaßt und durch Fluidleitungen der Sprühvorrichtung zugeführt wird. Durch Verändern des Druckes und damit auch der Menge der Förder­luft kann die pro Zeiteinheit geförderte Menge von Beschichtungspulver eingestellt werden. Da die Förderleistung von der Größe des von der Förder­luft erzeugten Unterdruckes im Injektor abhängig ist, kann bei konstanter oder variabler Förder­luft die Förderleistung auch dadurch geregelt werden, daß in den Unterdruckbereich des Injektors Dosierluft eingeleitet wird, um dadurch die Größe des Unterdrucks entsprechend der gewünschten Fördermenge von Pulver zu verändern. Dies bedeutet, daß die Pulverfördermenge nicht allein von der Förderluftmenge abhängig ist, sondern von der Differenz von Förderluft minus Dosierluft. Die Gesamtluftmenge, welche das Beschichtungspulver transportiert, muß jedoch aus den eingangs genannten Gründen für einen be­stimmten Beschichtungsvorgang konstant bleiben.Depending on the requirements of the coating process, the amount of powder supplied to the spraying device is increased or decreased. A practical value for the amount of powder supplied per unit of time is 300 g / min. If the quantity of powder supplied per unit of time has to be reduced, the pressure of the conveying air supplied to the injector is first reduced. This also reduces the flow rate of the conveying air in the fluid lines. However, the total air volume must neither become too low nor exceed a maximum value. To compensate for this reduction in air volume, i.e. by at least 10 mm / sec. To reach air speed while maintaining the reduced powder output, more dosing air is fed to the injector. The known function of the injectors is as follows:
The conveying air creates a negative pressure in the injector, through which coating powder is sucked out of a powder container, captured by the conveying air and fed to the spraying device through fluid lines. The amount of coating powder delivered per unit of time can be adjusted by changing the pressure and thus also the amount of conveying air. Since the delivery rate depends on the size of the negative pressure generated by the delivery air in the injector, the delivery rate can also be regulated in the case of constant or variable delivery air in that the vacuum range of Injector dosing air is introduced, thereby changing the size of the negative pressure according to the desired flow rate of powder. This means that the powder flow rate is not only dependent on the amount of conveying air, but on the difference between the conveying air minus the metering air. However, the total amount of air which the coating powder transports must remain constant for a given coating process for the reasons mentioned at the beginning.

In der Praxis beobachtet die Bedienungsperson die auf das zu beschichtende Objekt gerichtete Beschichtungspulverwolke und stellt anhand dieser visuellen Beobachtung die Drücke der Förderluft und der Dosierluft ein. Damit die Einstellungen im richtigen Maß erfolgen, werden vom Hersteller der Beschichtungseinrichtung Diagramme erstellt und der Pulverbeschichtungseinrichtung mitgeliefert. Dadurch kann die Bedienungsperson das Druckein­stellgerät für die Förderluft und das Druckein­stellgerät für die Dosierluft so einstellen, daß deren Druckwerte innerhalb eines auf den Diagrammen angegebenen Bereiches liegen. Die Diagramme werden aber von den Bedienungspersonen selten oder nie beachtet, was bewirkt, daß oft mit Fehleinstellungen gearbeitet wird.In practice, the operator observes the coating powder cloud directed at the object to be coated and uses this visual observation to set the pressures of the conveying air and the metering air. To ensure that the settings are correct, diagrams are created by the manufacturer of the coating device and supplied with the powder coating device. This allows the operator to set the pressure setting device for the conveying air and the pressure setting device for the metering air so that their pressure values are within a range indicated on the diagrams. However, the diagrams are rarely or never observed by the operators, which means that incorrect settings are often used.

Durch die Erfindung soll die Aufgabe gelöst werden, die richtige Einstellung der Förderluft­menge und der Dosierluftmenge auf optimale Werte zu erleichtern.The object of the invention is to facilitate the correct setting of the conveying air quantity and the metering air quantity to optimal values.

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

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

Gemäß der Erfindung ist ein erstes Durchfluß­meßgerät vorgesehen, welches eine Anzeige liefert, die von der gesamten pro Zeiteinheit strömenden Gasmenge abhängig ist, welche das Beschichtungs­pulver vom Injektor zur Sprühvorrichtung trans­portiert. Dieses erste Durchflußmeßgerät ist vorzugsweise in der Gasversorgungsleitung ange­ordnet, welche das Fördergas und das Dosiergas liefert. Dieses Gas-Durchflußmeßgerät ist vorzugs­weise ein sogenannter Schwebekörper-Durchfluß­messer. In ihm schwebt ein Schwebekörper in einem von unten nach oben strömenden Gasstrom. Die Höhenlage des Schwebekörpers hängt von der Stärke des Gasstromes ab und ist deshalb ein Maß für die pro Zeiteinheit durch den Schwebekörper-Durchfluß­messer hindurchströmenden Gasmenge. Am Durchfluß­messer können Markierungen angebracht sein,welche auf die Gas-Durchflußmenge abgestimmt sind. Dadurch kann die Bedienungsperson, wenn sie den Fördergasdruck und/oder den Dosiergasdruck verändert, am Schwebe­körper-Durchflußmesser darauf achten, daß sich der Schwebekörper bei oder innerhalb von bestimmten Markierungen befindet, welche der optimalen Gesamtgas­menge von Fördergas und Dosiergas entspricht, welche zusammen mit dem Beschichtungspulver vom Injektor zur Sprühvorrichtung strömt. Wie eingangs erwähnt wurde, ist die optimale Menge des gesamten Gases von mehreren Faktoren abhängig, wobei hier zusätzlich noch der Durchmesser und die Länge der Fluidleitungen erwähnt werden.According to the invention, a first flow meter is provided which provides an indication which is dependent on the total amount of gas flowing per unit of time which transports the coating powder from the injector to the spraying device. This first flow measuring device is preferably arranged in the gas supply line which supplies the conveying gas and the metering gas. This gas flow meter is preferably a so-called variable area flow meter. A float hovers in it in a gas stream flowing from bottom to top. The height of the float depends on the strength of the gas flow and is therefore a measure of the amount of gas flowing through the float flow meter per unit of time. Markings can be attached to the flow meter, which are matched to the gas flow rate. This allows the operator, when changing the feed gas pressure and / or the dosing gas pressure, to make sure on the float flow meter that the float is at or within certain markings, which corresponds to the optimal total gas quantity of feed gas and dosing gas, which together with the coating powder flows from the injector to the spray device. As mentioned at the beginning, the optimal amount of the total gas depends on several factors, in addition here the diameter and the length of the fluid lines be mentioned.

Eine weitere Anwendung des Erfindungsgedankens be­steht in der Verwendung eines zweiten Durchflußmeßge­rätes in einer Zusatzgasleitung, über welche der Sprühvorrichtung getrennt vom Beschichtungspulver­strom Zusatzgas zugeführt werden kann. Das Zusatzgas kann zur Reinigung von Teilen der Sprühvorrichtung, beispielsweise zum Reinigen von Elektroden dienen, wie dies in den DE-PS 36 08 426 und 36 08 415 gezeigt ist, oder zur Erzeugung einer im Strömungsweg des Be­schichtungspulverstromes liegenden Gaswand dienen, wie dies in der genannten DE-PS 36 08 426 gezeigt ist, oder zur Erzeugung von Gasströmen dienen, welche eine Ablagerung von Beschichtungspulver auf bestimm­ten Außenflächen der Sprühvorrichtung verhindern, wie dies aus der DE-OS 25 09 851 bekannt ist. Der Druck des Zusatzgases wird mit einem dritten Druckeinstell­gerät in Abhängigkeit von den Innenquerschnittsgrößen und in Abhängigkeit von den Längen der Fluidleitungen sowie in Abhängigkeit von anderen Beschichtungskrite­rien eingestellt.A further application of the inventive concept consists in the use of a second flow meter in an additional gas line, via which additional gas can be fed to the spraying device separately from the coating powder stream. The additional gas can be used for cleaning parts of the spray device, for example for cleaning electrodes, as shown in DE-PS 36 08 426 and 36 08 415, or for generating a gas wall lying in the flow path of the coating powder stream, as is shown in FIG DE-PS 36 08 426 is shown, or are used to generate gas flows which prevent deposition of coating powder on certain outer surfaces of the spraying device, as is known from DE-OS 25 09 851. The pressure of the additional gas is set with a third pressure setting device as a function of the internal cross-sectional sizes and as a function of the lengths of the fluid lines and as a function of other coating criteria.

Die Innenquerschnittsgrößen und Längen sowie anderen Kriterien können sich je nach Verwendung der Pulverbeschichtungseinrichtung ändern, wodurch dann auch der Druck des Zusatzgases geändert werden muß. Gleichzeitig ist es aber häufig erforderlich, daß die pro Zeiteinheit zugeführte Menge von Zusatzgas auf einem vorbestimmten optimalen Wert konstant gehalten wird. Durch Verwendung des zweiten Durchflußmeßgerätes kann die Bedienungsperson Änderungen der Zusatzgas-Mengen erkennen und sie kann die Druckeinstellung am dritten Druckeinstell­gerät so vornehmen, daß die optimale Zusatz-Gasmenge beibehalten wird. Auch das Zusatzgas ist vorzugs­weise Luft.The internal cross-sectional sizes and lengths as well as other criteria can change depending on the use of the powder coating device, as a result of which the pressure of the additional gas must also be changed. At the same time, however, it is often necessary for the quantity of additional gas supplied per unit of time to be kept constant at a predetermined optimal value. By using the second flow meter, the operator can recognize changes in the additional gas quantities and can adjust the pressure on the third pressure setting device in such a way that the optimum additional gas quantity is maintained. The additional gas is also preferably air.

Die Erfindung hat zussätzlich zum Vorteil einer erleichterten Einstellung der optimalen Werte auch den Vorteil, daß die Werte auf einfache Weise reproduzierbar sind. Reproduzierbar bedeutet hierbei, daßbei Verstellung der Förderluft und/oder Dosierluft und/oder Zusatzluft die ursprünglichen Verhältnisse und die Gesamtluftmenge später wieder eingestellt werden können.In addition to the advantage of facilitating the setting of the optimal values, the invention also has the advantage that the values can be reproduced in a simple manner. Reproducible here means that when the conveying air and / or dosing air and / or additional air is adjusted, the original conditions and the total air volume can be set again later.

Die Erfindung wird im folgenden mit Bezug auf die Zeichnung beschrieben.

  • Fig.1 zeigt unmaßstäblich und schematisch eine bevorzugte Ausführungsform einer elektro­statischen Pulverbeschichtungs­einrichtung nach der Erfindung.
The invention is described below with reference to the drawing.
  • 1 shows, to scale and schematically, a preferred embodiment of an electrostatic powder coating device according to the invention.

Die elektrostatische Pulverbeschichtungsein­richtung nach der Erfindung enthält einen Injektor 2, welcher nach dem Prinzip der Venturi-Düse, auch bekannt als Wasserstrahlpumpe, arbeitet. An den Injektor 2 ist eine Fördergasleitung 4 angeschlossen, in welcher sich ein erstes Druck­einstellgerät 6 in Form eines einstellbaren Druckreglers zur Einstellung des Druckes der Förderluft und ein Fördergasmanometer 8 befindet, welches den Druck der Förderluft optisch anzeigt. Die Förderluft erzeugt im Unterdruckbereich 10 des Manometers 2 in bekannter Weise einen Unterdruck und saugt dadurch aus einem Pulverbehälter 12 Beschichtungspulver, welches dann von der Förderluft über eine Pulver­zufuhrleitung 14, normalerweise ein Schlauch, einer Sprühvorrichtung 16 zugeführt wird. Die Sprühvorrichtung 16 enthält in bekannter Weise Elektroden zur elektrostatischen Aufladung des Beschichtungspulvers und zerstäubt das Be­schichtungspulver 18 in Form einer Pulverwolke auf ein zu beschichtendes Objekt 20. Die Elek­troden 22 in der Sprühvorrichtung 16 sind nur schematisch dargestellt. Die Sprühvorrichtung 16 kann die Form einer von Hand bedienbaren Pistole oder eines automatischen Sprühgerätes haben.The electrostatic powder coating device according to the invention contains an injector 2, which works on the principle of the Venturi nozzle, also known as a water jet pump. A feed gas line 4 is connected to the injector 2, in which there is a first pressure setting device 6 in the form of an adjustable pressure regulator for setting the pressure of the feed air and a feed gas manometer 8 which visually indicates the pressure of the feed air. The conveying air generates a negative pressure in the vacuum region 10 of the pressure gauge 2 in a known manner and thereby sucks coating powder from a powder container 12, which is then fed from the conveying air to a spray device 16 via a powder supply line 14, normally a hose. The spray device 16 contains electrodes for electrostatically charging the coating powder in a known manner and atomizes the coating powder 18 in the form of a powder cloud onto an object 20 to be coated. The electrodes 22 in the spray device 16 are only shown schematically. The sprayer 16 may take the form of a hand-held gun or an automatic sprayer.

Ferner ist an den Injektor 2 eine Dosier­gasleitung 24 angeschlossen, in welcher sich eine Strömungsdrossel 25 und stromauf davon ein zweites Druckeinstellgerät 26 in Form eines ein­stellbaren Druckreglers und ein zweites Mano­meter 28 zur Einstellung und visuellen Anzeige des Dosiergasdruckes befinden. Die Manometer 8 und 28 müssen also jeweils stromabwärts von den beiden Druckreglern 6 und 26 angeordnet sein. Die Dosierluft kann von der Dosiergas­leitung 24 in den Unterdruckbereich 10 des Injektors 2 strömen.Der Injektor 2 fördert dann am meisten Beschichtungspulver, wenn keine Dosierluft zugeführt wird. Je mehr Dosierluft zu­geführt wird, desto geringer ist der Unterdruck im Unterdruckbereich 10 und desto weniger Be­schichtungspulver wird gefördert. In der Pulver­zuleitung 14 strömt also Beschichtungspulver und Fördergas sowie keine oder eine bestimmte Menge Dosiergas. Die Manometer 8 und 28 sind jeweils mit einer Skala 29 und 30 versehen, welche in Druck und/oder Druckflußmenge pro Zeiteinheit, z.B. in Nm³/h, geeicht sind. Die Eingänge 32 und 34 der beiden Druckeinstell­geräte 6 und 26 sind an den Ausgangs­abschnitt 36 einer Gaszufuhrleitung 38 angeschlossen, deren Eingangsabschnitt 40 an den Ausgang 42 eines elektromagnetisch betätigbaren Ein-Aus-Ventils 44 (in DIN-Normen als Wegeventil bezeichnet) angeschlossen ist. Die beiden Abschnitte 36 und 40 sind über ein erstes Durchflußmeßgerät 46 miteinander verbunden, welches bei der dargestellten Ausführungsform ein vertikal angeordneter Schwebekörper-Durchflußmesser ist. Dieser besteht aus einem im wesentlichen vertikal angeordneten Meßrohr 48 und einem darin angeordneten Schwebekörper 50, welcher von dem vom Eingangsab­schnitt 40 vertikal nach oben durch ihn hindurch zum Ausgangsabschnitt 36 strömenden Gas je nach Gasstromstärke auf einer bestimmten Höhen­position im Schwebezustand gehalten wird. Dies bedeutet, daß die Höhenposition des Schwebekörpers 50 ein Maß für die pro Zeiteinheit durch das Meßrohr 48 hindurchströmende Gasmenge ist. An der Höhenposition des Schwebekörpers 50 relativ zu einer Skala oder Markierung 52 auf dem Meßrohr 48 kann eine Bedienungsperson erkennen, ob die pro Zeiteinheit zugeführte Gasmenge den gewünschten Wert hat. Diese Gasmenge ist die Gesamtmenge aus Förderluft und Dosierluft, welche über den Injektor 2 zur Sprüh­vorrichtung 16 strömt. Wenn eine Bedienungsperson den ersten Druckregler 6 für Förderluft und/oder den zweiten Druckregler 26 für Dosierluft auf andere Druckwerte einstellt, welche ihr von den Manometern 8 und 28 angezeigt werden, dann kann die Bedienungs­person durch Beobachtung der Höhenposition des Schwebekörpers 50 auf einfache Weise darauf achten, daß die Gesamtluftmenge von Förderluft und Dosierluft den gewünschten Wert beibehält oder auf einen gewünschten neuen Wert eingestellt wird.Furthermore, a metering gas line 24 is connected to the injector 2, in which there is a flow restrictor 25 and upstream thereof a second pressure setting device 26 in the form of an adjustable pressure regulator and a second manometer 28 for setting and visually displaying the metering gas pressure. The pressure gauges 8 and 28 must therefore be arranged downstream of the two pressure regulators 6 and 26. The dosing air can flow from the dosing gas line 24 into the negative pressure area 10 of the injector 2. The injector 2 delivers most of the coating powder when no dosing air is supplied. The more dosing air is supplied, the lower the vacuum in the vacuum region 10 and the less coating powder is conveyed. Coating powder and conveying gas as well as no or a certain amount of metering gas thus flows in the powder feed line 14. The pressure gauges 8 and 28 are each provided with a scale 29 and 30, which are calibrated in pressure and / or pressure flow quantity per unit of time, for example in Nm 3 / h. The inputs 32 and 34 of the two pressure setting devices 6 and 26 are connected to the output section 36 of a gas supply line 38, the input section 40 of which is connected to the output 42 of an electromagnetically actuated on-off valve 44 (referred to as a directional valve in DIN standards). The two sections 36 and 40 are connected to one another via a first flow measuring device 46, which in the embodiment shown is a vertically arranged variable area flow meter. This consists of a substantially vertically arranged measuring tube 48 and a float 50 arranged therein, which is held in suspension by the gas flowing vertically upwards through it to the outlet section 36, depending on the gas flow rate, at a certain height position. This means that the height position of the float 50 is a measure of the amount of gas flowing through the measuring tube 48 per unit of time. At the height position of the float 50 relative to a scale or mark 52 on the measuring tube 48, an operator can see whether the amount of gas supplied per unit of time has the desired value. This amount of gas is the total amount of conveying air and metering air which flows via the injector 2 to the spray device 16. If an operator sets the first pressure regulator 6 for conveying air and / or the second pressure regulator 26 for metering air to other pressure values, which are indicated to them by the pressure gauges 8 and 28, then the operator can easily observe this by observing the height position of the float 50 that the total air volume of conveying air and dosing air maintains the desired value or is set to a desired new value.

Durch die Erfindung kann auch eine weniger qualifizierte Bedieungsperson auf einfache Weise durch Beobachtung der Manometer 8 und 28 und Beobachtung des Schwebekörpers 50 relativ zur Skala oder Markierung 52 die Drücke und Strömungsmengen optimal einstellen.The invention also allows a less qualified operator to easily adjust the pressures and flow rates optimally by observing the pressure gauges 8 and 28 and observing the float 50 relative to the scale or marking 52.

Die Eingangsseite 54 des Ventils 44 ist über einen dritten Druckregler 56 an eine Druck­gasquelle, vorzugsweise eine Druckluft­quelle 58angeschlossen. Von der Verbindungs­leitung 60 zwischen dem einstellbaren dritten Druckregler 56 und dem Ventil 44 zweigt eine Fluidleitung 62 ab, welche einen einstell­baren vierten Druckregler 64 enthält und mit ihrem stromabwärtigen Ende 66 an den Pulver­behälter 12 angeschlossen ist, um darin in bekannter Weise Beschichtungspulver in einem fluidisierten Zustand zu halten.The inlet side 54 of the valve 44 is connected to a compressed gas source, preferably a compressed air source 58, via a third pressure regulator 56. A fluid line 62 branches off from the connecting line 60 between the adjustable third pressure regulator 56 and the valve 44, which contains an adjustable fourth pressure regulator 64 and is connected with its downstream end 66 to the powder container 12 for coating powder in a fluidized state in a known manner to keep.

An den Ausgang 42 des Ventils 44 ist auch eine Zusatzgasleitung 70 zur Zufuhr von Zusatzgas getrennt vom Beschichtungspulver zur Sprüh­vorrichtung 16 angeschlossen, welche der Sprühvorrichtung 16 Zusatzgas zum Reinigen der Elektroden 22 zuführt. Das Reinigen der Elektroden durch Zusatzgas ist aus den DE-PS 36 08 415 und 36 08 426 bekannt. Ferner kann das Zusatzgas in der Sprühvorrichtung 16 zur Erzeugung eines den Pulverstrom ablenkenden Gasstromes verwendet werden, wie dies aus der DE-PS 36 08 426 bekannt ist. Darüberhinaus kann das Zusatzgas auch dazu verwendet werden, Beschichtungspulver von Außenflächen der Sprühvorrichtung 16 abzuhalten, wie dies aus der DE-OS 25 09 851 bekannt ist. In der Zusatzgasleitung 70 befindet sich ein einstellbarer fünfter Druckregler 72 und ein zweites Durchflußmeßgerät 74, welches in gleicher Weise wie das erste Durchflußmeßgerät 46 ausgebildet sein kann und von unten nach oben vom Zusatzluftstrom durchströmt wird und dabei je nach Strömungsstärke einen in einem Meßrohr 48 vor­handenen Schwebekörper 50 relativ zu einer Skala oder Markierung 52 auf einer bestimmten Höhen­position hält . Die Meßrohre 48 der beiden Durchflußmeßgeräte 46 und 74 müssen also zumindest auf einer Seite durchsichtig sein, damit der Schwebekörper 50 von außen sichtbar ist. Vorzugs­weise bestehen die Meßrohre 48 insgesamt aus einem durchsichtigen Kunststoffmaterial. Ferner haben die Meßrohre gemäß der Zeichnung vorzugsweise einen in Strömungsrichtung von unten nach oben kegelstumpfförmig geringfügig größer werdenden Innendurchmesser.At the outlet 42 of the valve 44 there is also connected an additional gas line 70 for supplying additional gas separately from the coating powder to the spray device 16, which supplies the spray device 16 with additional gas for cleaning the electrodes 22. The cleaning of the electrodes by additional gas is known from DE-PS 36 08 415 and 36 08 426. Furthermore, the additional gas in the spray device 16 can be used to generate a gas flow which deflects the powder flow are used, as is known from DE-PS 36 08 426. In addition, the additional gas can also be used to prevent coating powder from outside surfaces of the spray device 16, as is known from DE-OS 25 09 851. In the additional gas line 70 there is an adjustable fifth pressure regulator 72 and a second flow measuring device 74, which can be designed in the same way as the first flow measuring device 46 and through which the additional air flow flows from bottom to top and, depending on the flow rate, a float present in a measuring tube 48 50 holds relative to a scale or mark 52 at a certain height position. The measuring tubes 48 of the two flow meters 46 and 74 must therefore be transparent at least on one side so that the float 50 is visible from the outside. The measuring tubes 48 are preferably made entirely of a transparent plastic material. Furthermore, the measuring tubes according to the drawing preferably have a slightly larger truncated cone-shaped inner diameter in the flow direction from bottom to top.

Anstelle der einstellbaren Druckregler 6, 26, 56,64 und 72 können auch einstellbare Strömungsdrosseln oder Hähne verwendet werden.Instead of the adjustable pressure regulators 6, 26, 56, 64 and 72, adjustable flow restrictors or taps can also be used.

Die elektrostatische Pulverbeschichtungs­einrichtung nach der Erfindung kann von einer Bedienungsperson von Hand eingestellt werden. Jedoch ist es durch die Erfindung auch möglich, die Druckeinstellgeräte 6,26 und 72 in Abhängig­keit von Sollwerten und in Abhängigkeit von Meß­werten der beiden Durchflußmeßgeräte 46 und 74 durch einen Mikrocomputer automatisch zu steuern.The electrostatic powder coating device according to the invention can be adjusted manually by an operator. However, the invention also makes it possible to automatically control the pressure setting devices 6, 26 and 72 by means of a microcomputer as a function of target values and as a function of measured values of the two flow measuring devices 46 and 74.

Claims (5)

1. Elektrostatische Pulverbeschichtungseinrichtung,
- mit einem Injektor (2) zur pneumatischen Förderung von Beschichtungspulver von einem Pulverbehälter (12) zu einer Sprühvor­richtung (16),
- mit einer an den Injektor (2) angeschlossenen Fördergasleitung (4), welche mit einem einstellbaren ersten Druckeinstellgerät (6) versehen ist,
- mit einer an den Injektor (2) angeschlossenen Dosiergasleitung (24), welche mit einem ein­stellbaren zweiten Druckeinstellgerät (26) versehen ist,
- und mit einer Gaszufuhrleitung (38) zur Zufuhr von Gas zu den beiden Druckeinstellgeräten (6, 26),
dadurch gekennzeichnet
- daß ein erstes Durchflußmeßgerät (46) vor­gesehen ist, welches eine Anzeige (50,52) liefert, die von der gesamten Gasdruchfluß­menge abhängig ist, welche pro Zeiteinheit zusammen mit dem Beschichtungspulver vom Injektor (2) zur Sprühvorrichtung (16) strömt.1. electrostatic powder coating device,
- With an injector (2) for the pneumatic conveying of coating powder from a powder container (12) to a spray device (16),
with a conveying gas line (4) connected to the injector (2), which is provided with an adjustable first pressure setting device (6),
with a metering gas line (24) connected to the injector (2), which is provided with an adjustable second pressure setting device (26),
- And with a gas supply line (38) for supplying gas to the two pressure setting devices (6, 26),
characterized
- That a first flow meter (46) is provided, which provides an indicator (50, 52) which is dependent on the total gas flow rate, which flows together with the coating powder from the injector (2) to the spray device (16) per unit time. 2. Pulverbeschichtungseinrichtung nach Anspruch 1,
dadurch gekennzeichnet,
daß die Gaszufuhrleitung (38) mit dem ersten Durchflußmeßgerät (46) versehen ist, und daß dieses eine Anzeige (50,52) liefert, die von der gesamten pro Zeiteinheit zugeführten Gasdurchflußmenge bestehend aus "Fördergas der Fördergasleitung (4) plus Dosiergas der Dosiergasleitung (24)" abhängig ist.2. Powder coating device according to claim 1,
characterized by
that the gas supply line (38) is provided with the first flow measuring device (46) and that this provides an indicator (50, 52) which shows the total gas flow rate supplied per unit of time consisting of "conveying gas from the conveying gas line (4) plus metering gas from the metering gas line ( 24) "is dependent. 3. Pulverbeschichtungseinrichtung nach Anspruch 1 oder 2,
dadurch gekennzeichnet,
daß eine Zusatzgasleitung (70) vorgesehen ist, über welche der Sprühvorrichtung (16) Zusatz­gas getrennt vom Beschichtungspulver zuführbar ist, und daß sich in der Zusatzgasleitung (70) ein drittes Druckeinstellgerät (72) und ein zweites Durchflußmeßgerät (74) befindet.3. Powder coating device according to claim 1 or 2,
characterized by
that an additional gas line (70) is provided, via which the spray device (16) additional gas can be supplied separately from the coating powder, and that in the additional gas line (70) there is a third pressure setting device (72) and a second flow meter (74). 4. Pulverbeschichtungseinrichtung nach einem der Ansprüche 1 bis 3,
dadurch gekennzeichnet,
daß mindestens eines der beiden Durchfluß­meßgeräte (46,74) ein Schwebekörper-Durchfluß­meßgerät mit einem im Gasstrom schwebenden Schwebe­körper (50) ist, dessen von der Strömungsstärke abhängige Position ein Maß für die Pro Zeiteinheit hindurchströmende Gasmenge liefert.4. Powder coating device according to one of claims 1 to 3,
characterized by
that at least one of the two flowmeters (46, 74) is a variable area flowmeter with a floating body (50) suspended in the gas stream, the position of which depends on the flow rate and provides a measure of the amount of gas flowing through per unit time. 5. Pulverbeschichtungseinrichtung nach einem der Ansprüche 1 bis 4,
dadurch gekennzeichnet,
daß mindestens eines der bezüglich ihres Ausgangsdruckes einstellbaren Druckeinstell­geräte (6,26,72) ein einstellbarer Druck­regler ist.5. Powder coating device according to one of claims 1 to 4,
characterized by
that at least one of the pressure setting devices (6, 26, 72) which is adjustable with regard to its outlet pressure is an adjustable pressure regulator.
EP90112723A 1989-08-11 1990-07-04 Electrostatic spray device Expired - Lifetime EP0412289B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT90112723T ATE96343T1 (en) 1989-08-11 1990-07-04 ELECTROSTATIC POWDER COATING EQUIPMENT.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3926624A DE3926624A1 (en) 1989-08-11 1989-08-11 ELECTROSTATIC POWDER COATING DEVICE
DE3926624 1989-08-11

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EP0412289A2 true EP0412289A2 (en) 1991-02-13
EP0412289A3 EP0412289A3 (en) 1991-10-02
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US (1) US5131350A (en)
EP (1) EP0412289B1 (en)
AT (1) ATE96343T1 (en)
CA (1) CA2020348A1 (en)
DE (3) DE8915968U1 (en)
ES (1) ES2046602T3 (en)

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Also Published As

Publication number Publication date
ES2046602T3 (en) 1994-02-01
DE3926624A1 (en) 1991-02-14
CA2020348A1 (en) 1991-02-12
EP0412289A3 (en) 1991-10-02
DE8915968U1 (en) 1992-12-17
US5131350A (en) 1992-07-21
ATE96343T1 (en) 1993-11-15
EP0412289B1 (en) 1993-10-27
DE59003206D1 (en) 1993-12-02

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