EP0123964B1 - Process and device for the electrostatic spraying of powder particles onto a surface - Google Patents

Process and device for the electrostatic spraying of powder particles onto a surface Download PDF

Info

Publication number
EP0123964B1
EP0123964B1 EP84103847A EP84103847A EP0123964B1 EP 0123964 B1 EP0123964 B1 EP 0123964B1 EP 84103847 A EP84103847 A EP 84103847A EP 84103847 A EP84103847 A EP 84103847A EP 0123964 B1 EP0123964 B1 EP 0123964B1
Authority
EP
European Patent Office
Prior art keywords
electrode
powder mixture
carrying gas
control air
gas stream
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
Application number
EP84103847A
Other languages
German (de)
French (fr)
Other versions
EP0123964A1 (en
Inventor
Wolfgang Kirchner
Otto Gebhardt
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Kopperschmidt-Muller GmbH and Co KG
Original Assignee
Kopperschmidt-Muller GmbH and Co KG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Kopperschmidt-Muller GmbH and Co KG filed Critical Kopperschmidt-Muller GmbH and Co KG
Priority to AT84103847T priority Critical patent/ATE24848T1/en
Publication of EP0123964A1 publication Critical patent/EP0123964A1/en
Application granted granted Critical
Publication of EP0123964B1 publication Critical patent/EP0123964B1/en
Expired legal-status Critical Current

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • 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
    • B05B7/02—Spray pistols; Apparatus for discharge
    • B05B7/08—Spray pistols; Apparatus for discharge with separate outlet orifices, e.g. to form parallel jets, i.e. the axis of the jets being parallel, to form intersecting jets, i.e. the axis of the jets converging but not necessarily intersecting at a point
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B1/00—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means
    • B05B1/26—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means with means for mechanically breaking-up or deflecting the jet after discharge, e.g. with fixed deflectors; Breaking-up the discharged liquid or other fluent material by impinging jets
    • B05B1/262—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means with means for mechanically breaking-up or deflecting the jet after discharge, e.g. with fixed deflectors; Breaking-up the discharged liquid or other fluent material by impinging jets with fixed deflectors
    • B05B1/265—Nozzles, spray heads or other outlets, with or without auxiliary devices such as valves, heating means with means for mechanically breaking-up or deflecting the jet after discharge, e.g. with fixed deflectors; Breaking-up the discharged liquid or other fluent material by impinging jets with fixed deflectors the liquid or other fluent material being symmetrically deflected about the axis of the nozzle
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
    • B05B5/025—Discharge apparatus, e.g. electrostatic spray guns
    • B05B5/03—Discharge apparatus, e.g. electrostatic spray guns characterised by the use of gas, e.g. electrostatically assisted pneumatic spraying
    • B05B5/032—Discharge apparatus, e.g. electrostatic spray guns characterised by the use of gas, e.g. electrostatically assisted pneumatic spraying for spraying particulate materials

Definitions

  • the invention relates to a method for electrostatically spraying powder particles supplied in a conveying gas stream onto a surface to be coated with the features specified in the preamble of patent claim 1 and to a device for carrying out the method according to the preamble of claim 3.
  • the conveying gas powder mixture is guided past a deflection device, from which an air stream emerges radially.
  • the powder cloud can be shaped by regulating the radial air flow.
  • an electrode is provided inside the tube by means of the conveying gas powder mixture.
  • the invention has for its object to provide a method or device with which the spray cloud is better shaped and the powder particles are ionized in such a way that a more uniform coating of the workpiece surface can be achieved.
  • the ionized gas stream is fed separately from the control air stream, which is used to expand the conveying gas / powder mixture. Since the control air flow can be regulated in terms of pressure and quantity, the desired shape of the spray cloud can be set in a simple and advantageous manner.
  • the conveying gas / powder mixture is ionized by the ionized gas stream which is introduced into the conveying gas / powder mixture downstream of the control air flow.
  • the ionized gas flow is thus introduced into the conveying gas / powder mixture in a region of reduced flow velocity, namely downstream of the control air flow used for expansion and braking, so that the duration of action for ion accumulation on the powder particles is extended.
  • the arrangement of the electrode prevents a direct field effect on the surface to be coated.
  • the effect of the electric field emanating from the electrode on the surface to be coated is reduced.
  • the field line concentration of edges and protrusions of the surface to be coated is avoided, so that a more uniform coating can be achieved.
  • the ionized gas flow is also independent of the control air flow and is therefore optimally adjustable.
  • a direct charging of the conveying gas-powder mixture is also provided.
  • the electrostatic charging of the powder particles can be changed and optimally adjusted by regulating the direct charging and regulating the ionized gas flow.
  • Direct charging can be controlled either by changing the voltage applied to the electrode or by means of weakening the electric field. The easiest way to charge the ionized gas flow is to regulate the gas volume.
  • the housing of a spray device 10 is designated 11 and has a longitudinal bore 12, in which a tube 14 is arranged, which is extended beyond the front end face 15 of the housing 11 and consists of an electrically insulating material.
  • the conveying gas powder mixture is introduced on the rear side of the spray device, not shown, in a known manner into the annular channel 18 formed between the housing bore 12 and the pipe 14 and leaves the channel at the outlet nozzle 19 in a substantially axially directed flow.
  • an insert body 20 is arranged, which engages over the end of a further tube 21 arranged within the tube 14.
  • a gas stream is introduced, which is given a swirl by one or more helical grooves 23 on the outer circumference of the insert body 20 and then flows through an annular channel 24 between the insert body 20 and the tube 14.
  • the gas flow radially emerges from the annular channel 24 through a radial gap between the front end face 25 of the tube 14 and a radial shoulder 26 on the insert body out.
  • the insert body 20 is aligned with the outer diameter of the tube 14 and forms a front end extension of the tube within the cross section specified by the tube 14.
  • the control air emerging from the gap 25, 26 serves to brake and expand the conveying gas / powder mixture emerging from the outlet nozzle 19.
  • the desired shape of the powder cloud can be set very precisely by appropriate dimensioning of the control air.
  • a valve (not shown) in the control air supply line is used to measure the control air.
  • Another gas flow passes through a longitudinal bore 26 of the inner tube 21 and through a blind bore 29 and a plurality of radial bore 30 into a recess 31 in the end face of the insert body 20.
  • the end face 32 is hollow-conical.
  • a disc-shaped electrode 34 and an insulating material disc 35 are arranged in the recess 31 thus formed.
  • the electrode 34 is provided with a base 33 which is fastened in the insert body 20 by means of an insulating sleeve 36.
  • the base 33 carries an external thread, not shown, which is screwed to an internal thread, also not shown, of the sleeve 36, so that the width of the annular gap 38 formed between the end face 32 and the outer edge of the electrode 34 or the insulating material disc 35 can be adjusted exactly.
  • a supply line 39 for the electrical high voltage is led forward through the longitudinal bore 28 of the inner tube 21 and fastened to the base 33 at 40 in the bore 29.
  • the electrode 34 is a so-called semiconductor electrode, so it has a relatively high ohmic resistance.
  • the electrical resistance of the semiconductor electrode is so great that a shock discharge, that is to say a short circuit, is not possible on the outer edge of the disk-shaped electrode.
  • the diameter of the insulating material disk 35 is larger than that of the electrode 34, but smaller than the front diameter of the insert body 20. This greatly reduces the field strength and the field line concentration, which emanate from the outer edge of the electrode 34, and the undesired field effect between the electrode and Avoid edges or protrusions on the workpiece surface to be coated.
  • the gas stream emerging through the radial openings 30 is ionized by the high electrical potential of the electrode and strikes the conveying gas / powder mixture deflected by the control air emerging from the gap 25, 26 approximately in Range of the lowest flow speed, namely after its deceleration by the control air.
  • the powder particles entrained in the conveying gas stream are mixed uniformly with the highly ionized gas stream, the powder particles being electrostatically charged, which essentially takes place by the accumulation of gas ions.
  • the charging of the powder particles is favored by the ion accumulation from the gas stream and also by the residence time of the powder particles in the area of high ion concentration. According to the invention, a very uniform spray pattern of the powder cloud can be formed in this way, which leads to a uniform coating of the surface of an earthed workpiece.
  • the electrode 34 is also arranged so that it does not come into contact with the powder stream.
  • the strength of the charging of the powder particles can be optimized by regulating the gas flow through a valve, not shown.
  • the shape and charging of the spray cloud can be optimized by regulating the control air and the ionized gas flow.
  • a ring electrode 42 made of semiconducting material can be used, which is connected to high voltage in a manner not shown.
  • the ring electrode 42 faces the channel 18.
  • the ring electrode 42 serves for additional electrical charging of the conveying gas powder mixture.
  • a sleeve 43 made of insulating material is also axially displaceable, by means of which the effect of the electric field generated by the electrode 42 on the workpiece surface to be coated can be increased or decreased.
  • the voltage applied to the electrode 42 can also be changed. In this way, the precipitation effect of the field forces, which result on the one hand from the ionized gas stream and on the other hand from the additional electrode 42, can be coordinated with one another.
  • FIG. 2 shows a modified embodiment, in which the conveying gas-powder mixture flowing axially on the outer surface of the tube 14 is also expanded by the control air radially emerging from the gap between the surfaces 25 and 26.
  • a gas stream is guided through a longitudinal bore 26 of the inner tube 21 into a bore 46 in a nozzle body 47 and emerges evenly distributed through radial bores 4ß.
  • the gas flow is directed through the hollow cone-shaped end face 32 of the insert 20 approximately radially outward and directed onto the conveying gas powder mixture. This gas flow is ionized by a needle electrode 44 which extends into the bore 46 of the nozzle body 47.

Landscapes

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

Description

Die Erfindung betrifft ein Verfahren zum elektrostatischen Aufsprühen von in einem Fördergasstrom zugeführten Pulverteilchen auf eine zu beschichtende Oberfläche mit den im Oberbegriff des Patentanspruchs 1 angegebenen Merkmalen sowie eine Vorrichtung zum Durchführen des Verfahrens gemäß Oberbegriff des Anspruches 3.The invention relates to a method for electrostatically spraying powder particles supplied in a conveying gas stream onto a surface to be coated with the features specified in the preamble of patent claim 1 and to a device for carrying out the method according to the preamble of claim 3.

Bei einer derartigen Sprühvorrichtung (DE-A-2312 363) wird das Fördergas-Pulvergemisch an einer Ablenkeinrichtung vorbeigeführt, aus der ein Luftstrom radial austritt. Durch Regulieren des radialen Luftstroms läßt sich die Pulverwolke Formen. Zum lonisieren des Pulvers ist eine innerhalb des Rohres im Wege des Fördergas-Pulvergemisches angeordnete Elektrode vorgesehen.In such a spray device (DE-A-2312 363), the conveying gas powder mixture is guided past a deflection device, from which an air stream emerges radially. The powder cloud can be shaped by regulating the radial air flow. To ionize the powder, an electrode is provided inside the tube by means of the conveying gas powder mixture.

Es ist auch bekannt (DE-A- 24 46 022), von dem zur Zerstäubung dienenden Luftstrom einen Teilluftstrom abzuzweigen und den Teilstrom beim Vorüberführen an mindestens einer Nadelelektrode zu ionisieren und außen auf den austretenden Sprühstrahl zu richten. Dabei ragt die Nadelelektrode frei nach außen und ist der zu beschichtenden Oberfläche zugekehrt.It is also known (DE-A-24 46 022) to branch off a partial air stream from the atomizing air stream and to ionize the partial stream as it passes by at least one needle electrode and to direct it outside onto the emerging spray jet. The needle electrode protrudes freely and faces the surface to be coated.

Bei einer Sprühvorrichtung für Naßlack ist es bekannt (US-A- 3 049 092), die Zerstäuberluft an einem stirnseitig vorgesehenen Prallkörper radial umzulenken und den austretenden Luftstrom zum Zerstäuben des aus einem Ringspalt axial austretenden Naßlackes zu verwenden. Dabei ist der Zerstäuberluftstrom mit Rücksicht auf eine vollständige Zerstäubung des Lackes nur in engen Grenzen regelbar. Die Ionisierung erfolgt durch eine Korona-Entladung im Bereich der Außenkante des Prallkörpers, wobei die Hochspannung dem gesamten Sprükopf zugeführt wird.In the case of a spray device for wet paint, it is known (US Pat. No. 3,049,092) to radially deflect the atomizing air on a baffle provided on the end face and to use the emerging air flow to atomize the wet paint emerging axially from an annular gap. The atomizing air flow can only be regulated within narrow limits with a view to complete atomization of the paint. The ionization takes place by means of a corona discharge in the area of the outer edge of the impact body, the high voltage being supplied to the entire spray head.

Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren bzw. Vorrichtung anzugeben, mit dem die Sprühwolke besser geformt und die Pulverteilchen in einer Weise ionisiert werden, daß eine gleichmäßigere Beschichtung der Werkstückoberfläche erzielt werden kann.The invention has for its object to provide a method or device with which the spray cloud is better shaped and the powder particles are ionized in such a way that a more uniform coating of the workpiece surface can be achieved.

Diese Aufgabe ist erfindungsgemäß mit den im kennzeichnenden Teil des Patentanspruchs 1 bzw. des Patentanspruches 3 angegebenen Merkmalen gelöst.This object is achieved with the features specified in the characterizing part of claim 1 and claim 3.

Erfindungsgemäß erfolgt die Zuführung des ionisierten Gasstroms getrennt von dem Steuerluftstrom, der zum Aufweiten des Fördergas-Pulvergemisches dient. Da der Steuerluftstrom für sich dem Druck und der Menge nach regelbar ist, läßt sich die gewünschte Form der Sprühwolke in einfacher und vorteilhafter Weise einstellen. Die Ionisierung des Fördergas-Pulvergemisches erfolgt durch den ionisierten Gasstrom, der stromab des Steuerluftstroms in das Fördergas- Pulvergemisch eingeleitet wird. Damit wird der ionisierte Gasstrom in das Fördergas-- pulvergemisch in einem Bereich verminderter Strömungsgeschwindigkeit eingeleitet, nämlich stromab des zum Aufweiten und Abbremsen dienenden Steuerluftstroms, so daß die Einwirkungsdauer zur lonenanlagerung an die pulverteilchen verlängert wird.According to the invention, the ionized gas stream is fed separately from the control air stream, which is used to expand the conveying gas / powder mixture. Since the control air flow can be regulated in terms of pressure and quantity, the desired shape of the spray cloud can be set in a simple and advantageous manner. The conveying gas / powder mixture is ionized by the ionized gas stream which is introduced into the conveying gas / powder mixture downstream of the control air flow. The ionized gas flow is thus introduced into the conveying gas / powder mixture in a region of reduced flow velocity, namely downstream of the control air flow used for expansion and braking, so that the duration of action for ion accumulation on the powder particles is extended.

Durch die Anordnung der Elektrode wird eine direkte Feldeinwirkung auf die zu beschichtende Fläche vermieden. Die Wirkung des von der Elektrode ausgehenden elektrischen Feldes auf die zu beschichtende Fläche wird vermindert. Insbesondere wird die Feldlinienkonzentration von Kanten und Vorsprüngen der zu beschichtenden Oberfläche vermieden, so daß sich eine gleichmäßigere Beschichtung erzielen läßt. Der ionisierte Gasstrom ist außerdem von dem Steuerluftstrom unabhängig und daher für sich optimal einstellbar.The arrangement of the electrode prevents a direct field effect on the surface to be coated. The effect of the electric field emanating from the electrode on the surface to be coated is reduced. In particular, the field line concentration of edges and protrusions of the surface to be coated is avoided, so that a more uniform coating can be achieved. The ionized gas flow is also independent of the control air flow and is therefore optimally adjustable.

Gemäß Patentanspruch 2 ist ergänzend zur elektrostatischen Aufladung durch den ionisierten Gasstrom auch eine unmittelbare Aufladung des Fördergas-Pulvergemisches vorgesehen. Erfindungsgemäß kann die elektrostatische Aufladung der Pulverteilchen durch Regelung der direkten Aufladung und durch Regelung des ionisierten Gasstroms verändert und optimal eingestellt werden. Die Regelung der direkten Aufladung kann entweder durch Änderung der an die Elektrode angelegten Spannung oder durch Mittel zum Abschwächen des elektrischen Feldes erfolgen. Die Aufladung durch den ionisierten Gasstrom läßt sich am einfachsten durch Regelung des Gasvolumens erzielen.According to claim 2, in addition to the electrostatic charging by the ionized gas stream, a direct charging of the conveying gas-powder mixture is also provided. According to the invention, the electrostatic charging of the powder particles can be changed and optimally adjusted by regulating the direct charging and regulating the ionized gas flow. Direct charging can be controlled either by changing the voltage applied to the electrode or by means of weakening the electric field. The easiest way to charge the ionized gas flow is to regulate the gas volume.

Die Erfindung ist nachstehend anhand der Zeichnung näher erläutert. Es zeigt:

  • Figur 1 einen Schnitt durch das Vorderteil einer Sprühvorrichtung,
  • Figur 2 einen Schnitt durch das Vorderteil in geänderter Ausführungsform.
The invention is explained below with reference to the drawing. It shows:
  • FIG. 1 shows a section through the front part of a spray device,
  • Figure 2 shows a section through the front part in a modified embodiment.

In Figur 1 ist das Gehäuse einer Sprühvorrichtung 10 mit 11 bezeichnet und weist eine Längsbohruhg 12 auf, in der ein Rohr 14 angeordnet ist, das über die vordere Stirnfläche 15 des Gehäuses 11 hinaus verlängert ist und aus elektrisch isolierendem Werkstoff besteht.In Figure 1, the housing of a spray device 10 is designated 11 and has a longitudinal bore 12, in which a tube 14 is arranged, which is extended beyond the front end face 15 of the housing 11 and consists of an electrically insulating material.

Das Fördergas-Pulvergemisch wird auf der nicht dargestellten Rückseite der Sprühvorrichtung in bekannter Weise in den zwischen der Gehäusebohrung 12 und dem Rohr 14 gebildeten ringförmigen Kanal 18 eingeleitet und verläßt den Kanal an der Austrittsdüse 19 in einem im wesentlichen axial gerichteten Strom.The conveying gas powder mixture is introduced on the rear side of the spray device, not shown, in a known manner into the annular channel 18 formed between the housing bore 12 and the pipe 14 and leaves the channel at the outlet nozzle 19 in a substantially axially directed flow.

Am vorderen Ende des Rohres 14 ist ein Einsatzkörper 20 angeordnet, der das Ende eines innerhalb des Rohres 14 angeordneten weiteren Rohres 21 übergreift. In dem Ringspalt 22 zwischen den beiden Rohren 14 und 21 wird ein Gasstrom herangeführt, dem durch eine oder mehrere schraubenförmige Nuten 23 am Außenumfang des Einsatzkörpers 20 ein Drall erteilt wird und anschließend einen Ringkanal 24 zwischen dem Einsatzkörper 20 und dem Rohr 14 durchströmt. Aus dem Ringkanal 24 tritt der Gasstrom durch einen radialen Spalt zwischen der vorderen Stirnfläche 25 des Rohres 14 und einer radialen Schulter 26 am Einsatzkörper radial aus. Der Einsatzkörper 20 fluchtet mit dem äußeren Durchmesser des Rohres 14 und bildet eine vordere stirnseitige Verlängerung des Rohres innerhalb des durch das Rohr 14 vorgegebenen Querschnitts.At the front end of the tube 14, an insert body 20 is arranged, which engages over the end of a further tube 21 arranged within the tube 14. In the annular gap 22 between the two tubes 14 and 21, a gas stream is introduced, which is given a swirl by one or more helical grooves 23 on the outer circumference of the insert body 20 and then flows through an annular channel 24 between the insert body 20 and the tube 14. The gas flow radially emerges from the annular channel 24 through a radial gap between the front end face 25 of the tube 14 and a radial shoulder 26 on the insert body out. The insert body 20 is aligned with the outer diameter of the tube 14 and forms a front end extension of the tube within the cross section specified by the tube 14.

Die aus dem Spalt 25, 26 austretende Steuerluft dient zum Abbremsen und Aufweiten des aus der Austrittsdüse 19 austretenden Fördergas-Pulvergemisches. Durch entsprechende Bemessung der Steuerluft kann die gewünschte Form der Pulverwolke sehr genau eingestellt werden. Zur Bemessung der Steuerluft dient ein nicht dargestelltes Ventil in der Zuleitung der Steuerluft.The control air emerging from the gap 25, 26 serves to brake and expand the conveying gas / powder mixture emerging from the outlet nozzle 19. The desired shape of the powder cloud can be set very precisely by appropriate dimensioning of the control air. A valve (not shown) in the control air supply line is used to measure the control air.

Ein weiterer Gasstrom tritt durch eine Längsbohrung 26 des inneren Rohres 21 und durch eine Sackbohrung 29 und mehrere radiale Bohrung 30 in eine Ausnehmung 31 in der Stirnseite des Einsatzkörpers 20. Die Stirnfläche 32 ist hohlkegelförmig. In der so gebildeten Ausnehmung 31 sind eine scheibenförmige Elektrode 34 und eine Isolierstoffscheibe 35 angeordnet. Die Elektrode 34 ist mit einem Sockel 33 versehen, der in dem Einsatzkörper 20 mittels einer Isolierstoffhülse 36 befestigt ist. Vorzugsweise trägt der Sockel 33 ein nicht dargestelltes Außengewinde, das mit einem ebenfalls nicht dargestellten Innengewinde der Hülse 36 verschraubt ist, so daß die Breite des zwischen der Stirnfläche 32 und der Außenkante der Elektrode 34 bzw. der Isolierstoffscheibe 35 gebildeten Ringspalts 38 genau einstellbar ist.Eine Zuleitung 39 für die elektrische Hochspannung ist durch die Langsbohrung 28 des inneren Rohres 21 nach vorne geführt und am Sockel 33 bei 40 in der Bohrung 29 befestigt.Another gas flow passes through a longitudinal bore 26 of the inner tube 21 and through a blind bore 29 and a plurality of radial bore 30 into a recess 31 in the end face of the insert body 20. The end face 32 is hollow-conical. A disc-shaped electrode 34 and an insulating material disc 35 are arranged in the recess 31 thus formed. The electrode 34 is provided with a base 33 which is fastened in the insert body 20 by means of an insulating sleeve 36. Preferably, the base 33 carries an external thread, not shown, which is screwed to an internal thread, also not shown, of the sleeve 36, so that the width of the annular gap 38 formed between the end face 32 and the outer edge of the electrode 34 or the insulating material disc 35 can be adjusted exactly. A supply line 39 for the electrical high voltage is led forward through the longitudinal bore 28 of the inner tube 21 and fastened to the base 33 at 40 in the bore 29.

Die Elektrode 34 ist eine sogenannte Halbleiterelektrode, weist also einen verhältnismäßig hohen Ohmschen Widerstand auf. Der elektrische Widerstand der Halbleiterelektrode ist so groß, daß an der Außenkante der scheibenförmigen Elektrode eine Stoßentladung, also ein Kurzschluß nicht möglich ist.The electrode 34 is a so-called semiconductor electrode, so it has a relatively high ohmic resistance. The electrical resistance of the semiconductor electrode is so great that a shock discharge, that is to say a short circuit, is not possible on the outer edge of the disk-shaped electrode.

Der Durchmesser der Isolierstoffscheibe 35 ist größer als der der Elektrode 34, aber kleiner als der vordere Durchmesser des Einsatzkörpers 20. Dadurch werden die Feldstärke und die Feldlinienkonzentration, die von der Außenkante der Elektrode 34 ausgehen, stark vermindert und die unerwünschte Feldwirkung zwischen der Elektrode und Kanten oder Vorsprüngen der zu beschichtenden Werkstückoberfläche vermieden.The diameter of the insulating material disk 35 is larger than that of the electrode 34, but smaller than the front diameter of the insert body 20. This greatly reduces the field strength and the field line concentration, which emanate from the outer edge of the electrode 34, and the undesired field effect between the electrode and Avoid edges or protrusions on the workpiece surface to be coated.

Beim Durchströmen des Ringspaltes 36 zwischen der Elektrode 34 und der Stirnfläche 32 wird der durch die radialen Öffnungen 30 austretende Gasstrom von dem hohen elektrischen Potential der Elektrode ionisiert und trifft auf das durch die aus dem Spalt 25, 26 austretende Steuerluft abgelenkte Fördergas- Pulvergemisch etwa im Bereich der geringsten Strömungsgeschwindigkeit, nämlich nach dessen Abbremsung durch die Steuerluft. Dabei werden die im Fördergasstrom mitgeführten Pulverteilchen mit dem hochionisierten Gasstrom gleichmäßig durchmischt, wobei die Pulverteilchen elektrostatisch aufgeladen werden, was im wesentlichen durch Anlagern von Gasionen erfolgt. Die Aufladung der Pulverteilchen wird durch die lonenanlagerung aus dem Gasstrom und auch durch die Verweildauer der Pulverteilchen im Bereich hoher Ionenkonzentration begünstigt. Erfindungsgemäß läßt sich auf diese Weise ein sehr gleichmäßiges Sprühmuster der Pulverwolke ausbilden, die zu einer gleichmäßigen Beschichtung der Oberfläche eines geerdeten Werkstücks führt. Auch ist die Elektrode 34 so angeordnet, daß sie mit dem Pulverstrom nicht in Berührung kommt.When flowing through the annular gap 36 between the electrode 34 and the end face 32, the gas stream emerging through the radial openings 30 is ionized by the high electrical potential of the electrode and strikes the conveying gas / powder mixture deflected by the control air emerging from the gap 25, 26 approximately in Range of the lowest flow speed, namely after its deceleration by the control air. The powder particles entrained in the conveying gas stream are mixed uniformly with the highly ionized gas stream, the powder particles being electrostatically charged, which essentially takes place by the accumulation of gas ions. The charging of the powder particles is favored by the ion accumulation from the gas stream and also by the residence time of the powder particles in the area of high ion concentration. According to the invention, a very uniform spray pattern of the powder cloud can be formed in this way, which leads to a uniform coating of the surface of an earthed workpiece. The electrode 34 is also arranged so that it does not come into contact with the powder stream.

Die Stärke der Aufladung der Pulverteilchen kann durch Regulieren des Gasstromes durch ein nicht dargestelltes Ventil optimiert werden. Erfindungsgemäß läßt sich durch Regulieren der Steuerluft und des ionisierten Gasstroms Form und Aufladung der Sprühwolke optimieren.The strength of the charging of the powder particles can be optimized by regulating the gas flow through a valve, not shown. According to the invention, the shape and charging of the spray cloud can be optimized by regulating the control air and the ionized gas flow.

An der Stirnfläche 15 des Gehäuses 11 kann eine Ringelektrode 42 aus halbleitendem Material eingesetzt sein, die auf nicht dargestellte Weise mit Hochspannung verbunden ist. Die Ringelektrode 42 ist dem Kanal 18 zugekehrt. Die Ringelektrode 42 dient zur zusätzlichen elektrischen Aufladung des Fördergas-Pulvergemisches. Auf dem Gehäuse 11 ist ferner eine Hülse 43 aus Isolierstoff axial verschiebbar, durch die die Wirkung des von der Elektrode 42 erzeugten elektrischen Feldes auf die zu beschichtende Werkstückoberfläche vergrößert bzw. verkleinert werden kann. Auch die an die Elektrode 42 angelegte Spannung kann verändert werden. Auf diese Weise läßt sich die Niederschlagswirkung der Feldkräfte, die einerseits von dem ionisierten Gasstrom und andererseits von der zusätzlichen Elektrode 42 herrühren, aufeinander abstimmen.On the end face 15 of the housing 11, a ring electrode 42 made of semiconducting material can be used, which is connected to high voltage in a manner not shown. The ring electrode 42 faces the channel 18. The ring electrode 42 serves for additional electrical charging of the conveying gas powder mixture. On the housing 11, a sleeve 43 made of insulating material is also axially displaceable, by means of which the effect of the electric field generated by the electrode 42 on the workpiece surface to be coated can be increased or decreased. The voltage applied to the electrode 42 can also be changed. In this way, the precipitation effect of the field forces, which result on the one hand from the ionized gas stream and on the other hand from the additional electrode 42, can be coordinated with one another.

In Figur 2 ist eine abgeänderte Ausführungsform dargestellt, bei der ebenfalls das an der Außenfläche des Rohres 14 axial strömende Fördergas-Pulvergemisch durch die aus dem Spalt zwischen den Flächen 25 und 26 radial austretende Steuerluft aufgeweitet wird. Ein Gasstrom wird durch eine Längsbohrung 26 des inneren Rohres 21 in eine Bohrung 46 in einem Düsenkörper 47 geführt und tritt durch radiale Bohrungen 4ß gleichmäßig verteilt aus. Der Gasstrom wird durch die hohlkegelförmige Stirnfläche 32 des Einsatzes 20 etwa radial nach außen gelenkt und auf das Fördergaspulvergemisch gerichtet. Die Ionisierung dieses Gasstroms erfolgt durch eine Nadelelektrode 44, welche in die Bohrung 46 des Düsenkörpers 47 reicht.FIG. 2 shows a modified embodiment, in which the conveying gas-powder mixture flowing axially on the outer surface of the tube 14 is also expanded by the control air radially emerging from the gap between the surfaces 25 and 26. A gas stream is guided through a longitudinal bore 26 of the inner tube 21 into a bore 46 in a nozzle body 47 and emerges evenly distributed through radial bores 4ß. The gas flow is directed through the hollow cone-shaped end face 32 of the insert 20 approximately radially outward and directed onto the conveying gas powder mixture. This gas flow is ionized by a needle electrode 44 which extends into the bore 46 of the nozzle body 47.

Claims (12)

1. A method for electrostatic powder coating by spraying powder particles entrained in a carrying gas stream upon a surface to be coated, using a spray device, in particular a spray gun, in which method the powder is dispersed by carrying gas and the carrying gas powder mixture discharged from an outlet nozzle in an axial direction is expanded by control air introduced into the carrying gas powder mixture through a radial gap in an approximately radial direction, and the carrying gas powder mixture is ionized, characterized in that a gas stream controllable independently of the carrying gas and/or the control air is fed through a separate passage and is ionized before being discharged and is introduced in an approximately radial direction in an area of reduced flow velocity of the expanded carrying gas powder mixture.
2. The method of claim 1, characterized in that the carrying gas powder mixture is electrostatically charged before the ionized gas stream is fed thereinto, the electrostatic charge and the ionization of the carrying gas powder mixture being matched to each other by controlling the ionized gas stream.
3. An apparatus (10) comprising a tube (14) extending forwards beyond an outlet nozzle (19) for discharging a carrying gas powder mixture, which tube includes an annular passage (24) for feeding control air, a radial gap (25, 26) between the forward end of the tube and an insert member (20) closing said end of the tube, the control air for expanding the carrying gas powder mixture being discharged from said annular gap, and an electrode (34,44) for ionizing the carrying gas powder mixture, characterized in that the electrode is located in a passage (28) provided for separately feeding a gas stream and that the ionized gas stream is introduced in an approximately radial direction into the carrying gas powder mixture downstream of said gap (25, 26) provided for the control air.
4. The apparatus of claim 3, characterized in that the electrode is comprised by a needle electrode (44) disposed in said passage (28) within an annular passage (24) for the control air.
5. The apparatus of claim 3, characterized in that at one end face of the tube comprising the annular passage (24) for control air and the passage for the ionizing gas stream there is disposed a disc-shaped electrode (34).
6. The apparatus of claims 3 and 5, characterized in that the disc-shaped electrode (34) is disposed at the end face (32) of the insert member (20) and has a diameter that is smaller than the diameter of said end face, the front side of said disc-shaped electrode being shielded by an insulating disc (35), and in that a plurality of radial openings (30) for feeding a gas stream extends from a radial longitudinal bore (29) within said insert member (20) to a radially extending annular gap (31) provided between said insert member (20) and said electrode (34), the gas stream ionized on said electrode is fed into the carrying gas powder mixture in a substantially radial direction in the area where the gas stream is expanded by the control air.
7. The apparatus according to any of claims 3 to 6, characterized in that a recess is formed by hollow coneshaped end faces (32) of said insert member (20).
8. The apparatus of any of claims 3 to 7, characterized in that said tube (14) and a portion of the insert member (20) extending beyond the end of said tube (14) are of similar cross-section.
9. The apparatus of any of claims 3 to 8, characterized in that said insert member (20) is provided with helical grooves (23) in the area of the annular passage (22, 24) for the control air.
10. The apparatus of any of claims 3 to 9, characterized in that an annular electrode (42) is provided in the area of said outlet nozzle (19) for ionizing the carrying gas powder mixture discharged from said outlet nozzle (19).
11. The apparatus of claim 10, characterized in that said annular electrode (42) is disposed at the inner periphery of the open end of said outlet nozzle (19) and in that a sleeve (43) of insulating material is displaceably mounted on the outer periphery.
12. The apparatus of claims 6 and 7, characterized in that the electrode (34) and the insulating disc (35) are disposed within the annular recess of said end face (32) of said insert member (20).
EP84103847A 1983-04-07 1984-04-06 Process and device for the electrostatic spraying of powder particles onto a surface Expired EP0123964B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT84103847T ATE24848T1 (en) 1983-04-07 1984-04-06 METHOD AND DEVICE FOR ELECTROSTATIC SPRAYING OF POWDER PARTICLES ONTO A SURFACE TO BE COATED.

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
DE3312509 1983-04-07
DE3312509 1983-04-07
DE19843412694 DE3412694A1 (en) 1983-04-07 1984-04-04 METHOD AND DEVICE FOR ELECTROSTATICALLY SPRAYING ON POWDER PARTICLES ON A SURFACE TO BE COATED
DE3412694 1984-04-04

Publications (2)

Publication Number Publication Date
EP0123964A1 EP0123964A1 (en) 1984-11-07
EP0123964B1 true EP0123964B1 (en) 1987-01-14

Family

ID=25809785

Family Applications (2)

Application Number Title Priority Date Filing Date
EP84901348A Pending EP0144335A1 (en) 1983-04-07 1984-04-06 Method and plant for electrostatically spraying pulverulent particles on a surface to be coated
EP84103847A Expired EP0123964B1 (en) 1983-04-07 1984-04-06 Process and device for the electrostatic spraying of powder particles onto a surface

Family Applications Before (1)

Application Number Title Priority Date Filing Date
EP84901348A Pending EP0144335A1 (en) 1983-04-07 1984-04-06 Method and plant for electrostatically spraying pulverulent particles on a surface to be coated

Country Status (7)

Country Link
US (1) US4735360A (en)
EP (2) EP0144335A1 (en)
BR (1) BR8406511A (en)
DE (2) DE3412694A1 (en)
DK (1) DK159592C (en)
FI (1) FI76262C (en)
WO (1) WO1984003846A1 (en)

Families Citing this family (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU580147B2 (en) * 1985-04-18 1989-01-05 Nordson Corporation Particle spray gun
JPH0675692B2 (en) * 1985-05-16 1994-09-28 小野田セメント株式会社 Electrostatic powder coating method and coating equipment
US4819879A (en) * 1985-10-25 1989-04-11 Nordson Corporation Particle spray gun
DE3601081A1 (en) * 1986-01-16 1987-07-23 Kopperschmidt Mueller & Co ELECTROSTATIC SPRAY GUN, ESPECIALLY FOR POWDER
DE3608415A1 (en) * 1986-03-13 1987-09-24 Gema Ransburg Ag ELECTROSTATIC SPRAYING DEVICE FOR COATING POWDER
DE3608426C3 (en) * 1986-03-13 1994-11-24 Gema Volstatic Ag Electrostatic spraying device for coating powder
EP0236794B1 (en) * 1986-03-13 1991-01-02 ITW Gema AG Electrostatic spray device for coating powder
DD271611A3 (en) * 1987-10-27 1989-09-13 Verkehrswesen Hochschule SPRAY GUN WITH ELECTRIC KINETIC POWDER RECHARGE
JPH04327570A (en) * 1991-02-12 1992-11-17 Hoechst Ag Alkyl ether carboxylic acid tauride
DE19502522A1 (en) * 1995-01-27 1996-08-01 Gema Volstatic Ag Spraying device for coating material
US6003785A (en) * 1997-05-27 1999-12-21 Sames Electrostatic, Inc. Composite material bell cup
US6004625A (en) * 1997-06-16 1999-12-21 Ibick Corporation Method for adhering particles to an object by supplying air ions
IL145464A0 (en) * 2001-09-16 2002-06-30 Pc Composites Ltd Electrostatic coater and method for forming prepregs therewith
DE10319916A1 (en) 2003-05-05 2004-11-25 Itw Gema Ag Spraying device for coating material, in particular coating powder
DE102011055660B4 (en) 2011-11-23 2013-09-05 P+S Pulverbeschichtungs- Und Staubfilteranlagen Gmbh Method for applying powder by means of a powder spray gun and powder spray gun for carrying out the method
US20160368008A1 (en) * 2015-01-12 2016-12-22 Ben-Why Liao Spray head structure slidably assembled with a nut
CN107262320B (en) * 2017-06-26 2023-08-29 中信戴卡股份有限公司 Automatic powder cleaning system for mixed-wire type hub bolt hole and combined powder cleaning gun

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2312363A1 (en) * 1972-03-13 1973-09-27 Atlas Copco Ab ELECTROSTATIC POWDER SPRAY GUN

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3049092A (en) * 1959-07-24 1962-08-14 Interplanetary Res & Dev Corp Apparatus for the electrostatic coating of articles
NL133488C (en) * 1966-04-28
DE1284883B (en) * 1967-10-17 1968-12-05 Mueller Ernst Fa Method and device for the production of coatings from finely divided, liquid or solid substances
US3759151A (en) * 1971-09-21 1973-09-18 R Metz Inspection camera
JPS5145143A (en) * 1974-10-16 1976-04-17 Ransburg Japan Ltd Funshapataanno choseiga kanona funtaitosoyofunshanozuru
ES468633A1 (en) * 1978-04-07 1978-12-01 Rosal Vila Juan Devices for covering objects with electrostatic dust
SE438966B (en) * 1978-12-04 1985-05-28 Gema Ransburg Ag SPRAY DEVICE FOR POWDER WITH SPRAY GAS SPECIFICALLY INTRODUCED IN THE NOZZLE OPENING
US4341347A (en) * 1980-05-05 1982-07-27 S. C. Johnson & Son, Inc. Electrostatic spraying of liquids
US4380320A (en) * 1981-02-25 1983-04-19 Nordson Corporation Electrostatic powder spray gun nozzle

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2312363A1 (en) * 1972-03-13 1973-09-27 Atlas Copco Ab ELECTROSTATIC POWDER SPRAY GUN

Also Published As

Publication number Publication date
FI76262B (en) 1988-06-30
FI844560A0 (en) 1984-11-21
DK548484D0 (en) 1984-11-19
WO1984003846A1 (en) 1984-10-11
DK159592B (en) 1990-11-05
FI844560L (en) 1984-11-21
BR8406511A (en) 1985-03-12
DE3461991D1 (en) 1987-02-19
EP0123964A1 (en) 1984-11-07
FI76262C (en) 1988-10-10
DE3412694A1 (en) 1984-10-11
EP0144335A1 (en) 1985-06-19
US4735360A (en) 1988-04-05
DK548484A (en) 1984-11-19
DK159592C (en) 1991-04-15

Similar Documents

Publication Publication Date Title
EP0123964B1 (en) Process and device for the electrostatic spraying of powder particles onto a surface
DE2852038C2 (en) Device for the electrostatic spraying and application of a liquid coating material
DE2908723A1 (en) METHOD AND DEVICE FOR ELECTROSTATIC SPRAYING A LIQUID
DE2539627A1 (en) ELECTROSTATIC SPRAY GUN
DE1777329A1 (en) Device for electrostatic coating of objects
DE2422597A1 (en) SPRAY DEVICE
EP0808663A2 (en) Electrostatic spraying apparatus
DE2541927A1 (en) POWDER SPRAY NOZZLE WITH JET ADJUSTMENT
EP0314049A2 (en) Powder spray gun with electrocinetic charging
DE2549974A1 (en) DEVICE FOR DUSTING FLOWABLE MEDIA, SUCH AS COLORS, VARNISHES, ETC.
DE19602802A1 (en) Electrostatic ionization system
EP0037910B1 (en) Method and apparatus for spraying powder
EP0283747B1 (en) Electrostatic spray gun
EP0163118B1 (en) Spray gun for the coating of objects with powder
EP0230624B2 (en) Electrostatic spray gun especially for powdered material
DD232595A3 (en) DEVICE FOR ELECTROKINETIC CHARGING OF POWDER-FUSED SUBSTANCES
DE2005830A1 (en) Method and device for spraying liquid
DE2237717C3 (en) Spray gun operated with pressure medium, e.g. paint spray gun
DE2121986C3 (en) Electrostatic spray gun
DE3310983A1 (en) METHOD AND DEVICE FOR SPRAYING POWDER ON ITEMS, IN PARTICULAR FOR ELECTROSTATICALLY SPRAYING ON THE POWDER FOR PRODUCING COLOR APPLICATIONS ON THE ITEMS
DE2555547C3 (en) Device for the electrostatic application or spraying of material particles
DE3329880A1 (en) METHOD FOR SPRAY COATING WITHOUT AIR AND SPRAY GUN FOR COATING WITHOUT AIR
DE2264386C2 (en) Powder spray system - which enables a quickk change of powder colour
DE2749400C3 (en) Electrostatic spray device with protective gas jacket
DD134841B1 (en) Apparatus for electrokinetic coating with powdered and fibrous particles

Legal Events

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

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Designated state(s): IT

17P Request for examination filed

Effective date: 19850302

RBV Designated contracting states (corrected)

Designated state(s): VE BU DE

XX Miscellaneous (additional remarks)

Free format text: VERBUNDEN MIT 84901348.7/0144335 (EUROPAEISCHE ANMELDENUMMER/VEROEFFENTLICHUNGSNUMMER) DURCH ENTSCHEIDUNG VOM 10.03.86.

17Q First examination report despatched

Effective date: 19860407

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): AT BE CH DE FR GB IT LI NL SE

REF Corresponds to:

Ref document number: 24848

Country of ref document: AT

Date of ref document: 19870115

Kind code of ref document: T

XX Miscellaneous (additional remarks)

Free format text: VERBUNDEN MIT 84901348.7/0144335 (EUROPAEISCHE ANMELDENUMMER/VEROEFFENTLICHUNGSNUMMER) DURCH ENTSCHEIDUNG VOM 10.03.86.

REF Corresponds to:

Ref document number: 3461991

Country of ref document: DE

Date of ref document: 19870219

ET Fr: translation filed
ITF It: translation for a ep patent filed

Owner name: MODIANO & ASSOCIATI S.R.L.

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

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

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

26N No opposition filed
ITTA It: last paid annual fee
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 19940421

Year of fee payment: 11

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

Ref country code: SE

Payment date: 19940426

Year of fee payment: 11

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

Ref country code: DE

Payment date: 19940427

Year of fee payment: 11

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

Ref country code: CH

Payment date: 19940429

Year of fee payment: 11

Ref country code: AT

Payment date: 19940429

Year of fee payment: 11

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

Ref country code: NL

Payment date: 19940430

Year of fee payment: 11

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

Ref country code: BE

Payment date: 19940516

Year of fee payment: 11

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

Ref country code: FR

Payment date: 19940517

Year of fee payment: 11

EAL Se: european patent in force in sweden

Ref document number: 84103847.4

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

Ref country code: GB

Effective date: 19950406

Ref country code: AT

Effective date: 19950406

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

Ref country code: SE

Effective date: 19950407

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

Ref country code: LI

Effective date: 19950430

Ref country code: CH

Effective date: 19950430

Ref country code: BE

Effective date: 19950430

BERE Be: lapsed

Owner name: KOPPERSCHMIDT-MUELLER G.M.B.H. & CO K.G.

Effective date: 19950430

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

Ref country code: NL

Effective date: 19951101

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 19950406

REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

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

Ref country code: FR

Effective date: 19951229

NLV4 Nl: lapsed or anulled due to non-payment of the annual fee

Effective date: 19951101

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

Ref country code: DE

Effective date: 19960103

EUG Se: european patent has lapsed

Ref document number: 84103847.4

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST