EP0283747A2 - Electrostatic spray gun - Google Patents

Electrostatic spray gun Download PDF

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Publication number
EP0283747A2
EP0283747A2 EP88102711A EP88102711A EP0283747A2 EP 0283747 A2 EP0283747 A2 EP 0283747A2 EP 88102711 A EP88102711 A EP 88102711A EP 88102711 A EP88102711 A EP 88102711A EP 0283747 A2 EP0283747 A2 EP 0283747A2
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EP
European Patent Office
Prior art keywords
outlet opening
spray gun
electrostatic spray
guide body
gun according
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.)
Granted
Application number
EP88102711A
Other languages
German (de)
French (fr)
Other versions
EP0283747A3 (en
EP0283747B1 (en
Inventor
Wolfgang Kuhn
Karsten Jüterbock
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.)
Graco Verfahrenstechnik GmbH
Original Assignee
Kopperschmidt-Muller GmbH and Co KG
Boellhoff Verbindungstechnik GmbH
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Publication date
Application filed by Kopperschmidt-Muller GmbH and Co KG, Boellhoff Verbindungstechnik GmbH filed Critical Kopperschmidt-Muller GmbH and Co KG
Priority to AT88102711T priority Critical patent/ATE67692T1/en
Publication of EP0283747A2 publication Critical patent/EP0283747A2/en
Publication of EP0283747A3 publication Critical patent/EP0283747A3/en
Application granted granted Critical
Publication of EP0283747B1 publication Critical patent/EP0283747B1/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
    • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
    • B05B5/025—Discharge apparatus, e.g. electrostatic spray guns
    • B05B5/053—Arrangements for supplying power, e.g. charging power
    • B05B5/0533—Electrodes specially adapted therefor; Arrangements of electrodes
    • 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

Definitions

  • the invention relates to an electrostatic spray gun with a spray head made of electrically insulating material, which carries a material outlet opening and at least one high-voltage electrode, with the aid of which the material is charged after it has emerged.
  • the spray head has a flat end face in which a nozzle bore is provided centrally as a material outlet opening and a number of nozzle bores are provided as an atomizing air outlet opening on a circle arranged concentrically therewith.
  • a nozzle bore is provided centrally as a material outlet opening and a number of nozzle bores are provided as an atomizing air outlet opening on a circle arranged concentrically therewith.
  • On opposite sides are two horns, in which there are auxiliary air outlet openings, which direct auxiliary air from both sides to improve the atomization or to form the emerging material.
  • auxiliary air outlet openings In at least one auxiliary air outlet opening or in its immediate vicinity there are one or more high-voltage electrodes which protrude by several millimeters from the surface of the spray head, which is made of an electrically insulating material.
  • auxiliary air or secondary air drawn in from auxiliary air is ionized at these electrodes.
  • the charge is given off to material droplets so that they can follow the course of the electrostatic field lines as they continue to fly.
  • the point of impact of the ionized air on the material is determined by the main function (atomization or shaping).
  • An electrostatic spray gun is also already known (US Pat. No. 3,764,068), in which a total of six high-voltage electrodes are arranged approximately uniformly distributed on a circle which extends around an annular material outlet opening and an annular atomizing air outlet opening which concentrically surrounds this .
  • the electrodes are located near the outer circumference of the slightly profiled end face and protrude considerably beyond this end face. They are hollow so that an auxiliary liquid, possibly in a mixture with air, can be fed through them. Droplets of the auxiliary liquid are ionized and fed to the emerging product. These electrodes are very vulnerable to accidental contact.
  • the invention has for its object to provide an electrostatic spray gun of the type described above, in which a better charging of the spray jet is possible.
  • This object is achieved in that from the end face of the spray head protrudes approximately concentrically to the material outlet opening, tapering forward guide body and that the at least one high-voltage electrode is arranged in the region of the base of the guide body.
  • the tips of the high-voltage electrodes are located in a groove formed by the end face extending from the circumference of the spray head and the guide body.
  • the fillet lies in the area of the flow of the secondary air sucked in by the exiting material. This strikes the exiting material in a section determined by the guide body. Due to the shape and arrangement of the guide body, the impact section can be selected so that the material is optimally charged. For better charging also contributes to the fact that the guide body made of insulating material acts in the first phase as a dielectric insulator between the individual electrodes and the emerging material with a low electrical potential.
  • the electrodes in the fillet are well protected against accidental contact. The radially relatively far inner arrangement of the electrodes also increases the security against sparking when approaching grounded components in comparison to electrodes arranged radially further out.
  • the safety against contact is further improved if the high-voltage electrodes do not protrude or only insignificantly over the end face of the spray head.
  • the protrusion should be at most 6 mm and preferably be less than 1 mm. Even with almost hidden electrode tips, there is sufficient charge due to the large number of electrodes.
  • the junction of the ionized air and the leaked material can be influenced not only by the outer shape of the guide body, but also by the fact that the guide body has a central recess and the material outlet opening is at a distance from the front end of the guide body. This increases the distance between the outlet opening and the impact zone.
  • the guide body is shaped in such a way that a tangent drawn from the electrode tip and touching the guide body intersects the axis of the material outlet opening at a point at which the product begins to break down into droplets. In this area the charge transfer is particularly intensive.
  • an atomizing air outlet opening concentrically surrounding the material outlet opening should lie within the basic diameter of the guide body.
  • the electrodes are then swept by the secondary air drawn in by the atomizing air.
  • horns with auxiliary air outlet openings are provided on opposite sides of the material outlet opening, which direct auxiliary air at the emerging product. Irrespective of the ionization, this results in an atomization aid or beam shaping.
  • At least some of the high-voltage electrodes be arranged offset in the circumferential direction from the horns. Sufficient secondary air is supplied regardless of the auxiliary air so that the material jet is charged as strongly as possible.
  • auxiliary air outlet openings can be directed such that their axes intersect the plane of symmetry between the horns between the material outlet opening and the intersection of the tangents with the axis of the material outlet opening. This measure also contributes to the fact that the concentrated electrostatic field is only effective in the spray where it begins to break down into droplets.
  • a particularly preferred application is the processing of a material with medium to high electrical conductivity, such as water-soluble lacquers or release agents.
  • a material with medium to high electrical conductivity such as water-soluble lacquers or release agents.
  • the electrode arrangement described can be used both for guns with air atomization and for those with hydrostatic atomization ("airless method”). If auxiliary air is used, it can be used for air atomization to shape the spray jet and for hydrostatic atomization aid as an atomization aid in the airless / air process ("airless-plus").
  • the body 1 of a spray gun has a spray head 2, which consists of an insert 2 ⁇ made of electrically insulating material and a union nut 3 connecting it to the body 1.
  • a spray head 2 which consists of an insert 2 ⁇ made of electrically insulating material and a union nut 3 connecting it to the body 1.
  • a nozzle body 4 In the center of the spray head 2 there is a nozzle body 4 with a slot as the material outlet opening 5.
  • a sealing disk 6 and an insert 7 are arranged behind it, which carries a valve seat 8 and encloses a valve rod 9.
  • a sloping shoulder 10 of the body 1 holds the series connection of the nozzle body 4, the sealing disk 6 and the insert 7 in place.
  • the spray head 2 has an end face 11, from which a guide body 12 with a conical surface 13 protrudes in the middle and which extends to the circumference of the spray head 2.
  • the nozzle body 4 is located at the front end of the guide body 12.
  • Each electrode 14 is connected to a distributor ring 16 via a line 15. This is in contact with a high-voltage connection 19 having a protective resistor 18.
  • the material outlet opening 5 emits a spray jet 21.
  • the outlet opening for example up to the distance a, there is still a coherent veil. Behind it breaks up into many small droplets.
  • the material emerging at high speed entrains air so that secondary air flows along the end face 11 and the cone face 13 according to the arrow 22.
  • This air is ionized by the high voltage electrodes 14. It follows the flow drive and the electrostatic field.
  • the guide body 12 has a certain influence on this field.
  • the tangents 23 starting from the electrode tips and touching the guide body 12 meet the axis of the outlet opening at a distance b, that is, where the material begins to break down into droplets. Since the predominant part of the air only hits the spray jet 21 in this area, good droplet charging is ensured. This applies in particular because the ionization takes place from all sides, that is to say concentrically.
  • reference numerals increased by 100 are used for corresponding parts. It is essentially different that the guide body 112 has a surface 113 with a smaller cone angle and that there is a central recess 124 in the interior of the guide body, that is to say the nozzle body 104 is set back a bit to the rear. Both lead to the fact that the ionized air only hits the spray jet 121 at a greater distance from the outlet opening, as is again illustrated by the tangents 123 starting from the electrode tips and touching the guide body 112; here the point of intersection with the axis of the outlet opening 105 is at a distance c from this outlet opening.
  • FIG. 3 shows how the electrodes 114 are arranged uniformly around the outlet opening 105.
  • the effectiveness of the electrodes is not only directed radially, but also goes aside in the context of the electrostatic field. Therefore, secondary air that flows in through area I is influenced by an electrode 114, while two electrodes are effective in the areas II in between. This results in a fairly uniform ionization of the supplied secondary air all around.
  • a material outlet opening 205 which can be shut off by a valve rod 209, is supplied with material almost without pressure via a channel 220.
  • An atomizing air nozzle 225 is provided concentrically to this and is supplied with atomizing air via an annular space 226 and a channel 227.
  • two horns 228 and 229 are provided which have auxiliary air outlet openings 230.
  • a guide body 212 is connected upstream of the end face 211 of the spray head 202.
  • the high-voltage electrodes 214 are located at the transition point.
  • the electrodes 214 can, as shown in FIG. 4, be located partially below the horns, so that auxiliary air is forcibly supplied to them. In most cases, however, it is more favorable for the uniform ionization if the electrodes 214 are arranged offset circumferentially to the horns.
  • the auxiliary air outlet openings 230 should be directed so that the auxiliary air impinges on the spray jet before the tangents described reach the outlet axis. This improves atomization and ionization.
  • the horns 228 and 229 can also be used with the hydrostatic atomizing nozzles of FIGS. 1 and 2.
  • the auxiliary air directed by them onto the material not only supports the atomization process so that a lower hydrostatic pressure can be used, but it is also ionized and thereby improves the charging.
  • the guide body can also have a different external shape, for example curved.
  • the electrodes do not have to be placed exactly on the base of the guide body, but can be arranged in a certain area in front of or behind it, without losing the advantages described.
  • the spray gun can also be operated in an atmosphere from a gas equivalent to the air.

Landscapes

  • Electrostatic Spraying Apparatus (AREA)
  • Combustion Methods Of Internal-Combustion Engines (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)

Abstract

The nozzle assembly of an electrostatic spray gun has an adapter which is made of an electrically insulating material and has a front surface facing in the direction of propagation of material issuing from the orifice of the nozzle. The adapter has a frustoconical extension which surrounds the orifice and whose external surface defines with the front surface of the adapter an annular space for the tips of electrodes which ionize air flowing toward the spray of material that issues from the orifice. The locations of the tips of electrodes (preferably very close to the front surface of the adapter) and the inclination of the external surface of the frustoconical extension determine the location of contact of ionized air with the spray. The tips of the electrodes are shielded from mechanical damage by being located in the annular space.

Description

Die Erfindung bezieht sich auf eine elektrostatische Sprühpistole mit einem Sprühkopf aus elektrisch isolie­rendem Werkstoff, der eine Material-Austrittsöffnung und mindestens eine Hochspannungselektrode trägt, mit deren Hilfe das Material nach dessen Austritt aufgeladen wird.The invention relates to an electrostatic spray gun with a spray head made of electrically insulating material, which carries a material outlet opening and at least one high-voltage electrode, with the aid of which the material is charged after it has emerged.

Bei einer bekannten Sprühpistole dieser Art (DE-AS 24 46 022) weist der Sprühkopf eine ebene Stirnfläche auf, in der zentrisch eine Düsenbohrung als Material-Aus­trittsöffnung und auf einem konzentrisch hierzu angeord­neten Kreis eine Anzahl von Düsenbohrungen als Zerstäuber­luft-Austrittsöffnung vorgesehen sind. Auf einander gegen­überliegenden Seiten stehen zwei Hörner vor, in denen sich Hilfsluft-Austrittsöffnungen befinden, die von bei­den Seiten her Hilfsluft zur Verbesserung der Zerstäubung oder zur Formung auf das austretende Material richten. In mindestens einer Hilfsluft-Austrittsöffnung oder in deren unmittelbarer Nähe befinden sich ein oder mehrere Hochspannungselektroden, die um mehrere Millimeter aus der Oberfläche des aus elektrisch isolierendem Werkstoff bestehenden Sprühkopfes vorstehen. An diesen Elektroden wird Hilfsluft oder durch Hilfsluft aus der Umgebung angesaugte Sekundärluft ionisiert. Wenn diese Luft an­ schließend mit dem Material in Berührung kommt, wird die Ladung an Materialtröpfchen abgegeben, so daß diese beim Weiterflug dem Verlauf der elektrostatischen Feld­linien folgen können. Bei dieser Sprühpistole ist die Auftreffstelle der ionisierten Luft auf das Material durch die Hauptfunktion (Zerstäubung oder Formung) vorge­geben.In a known spray gun of this type (DE-AS 24 46 022), the spray head has a flat end face in which a nozzle bore is provided centrally as a material outlet opening and a number of nozzle bores are provided as an atomizing air outlet opening on a circle arranged concentrically therewith. On opposite sides are two horns, in which there are auxiliary air outlet openings, which direct auxiliary air from both sides to improve the atomization or to form the emerging material. In at least one auxiliary air outlet opening or in its immediate vicinity there are one or more high-voltage electrodes which protrude by several millimeters from the surface of the spray head, which is made of an electrically insulating material. Auxiliary air or secondary air drawn in from auxiliary air is ionized at these electrodes. When this air comes on finally comes into contact with the material, the charge is given off to material droplets so that they can follow the course of the electrostatic field lines as they continue to fly. With this spray gun, the point of impact of the ionized air on the material is determined by the main function (atomization or shaping).

Es ist auch schon eine elektrostatische Sprühpistole bekannt (US-PS 3 764 068), bei der insgesamt sechs Hoch­spannungselektroden etwa gleichmäßig verteilt auf einem Kreis angeordnet sind, der sich um eine ringförmige Mate­rial-Austrittsöffnung und eine diese konzentrisch umgeben­de, ringförmige Zerstäuberluft-Austrittsöffnung erstreckt. Die Elektroden befinden sich nahe dem äußeren Umfang der geringfügig profilierten Stirnfläche und stehen erheb­lich über diese Stirnfläche vor. Sie sind hohl ausgebil­det, so daß über sie eine Hilfsflüssigkeit, gegebenenfalls im Gemisch mit Luft, zugeführt werden kann. Tröpfchen der Hilfsflüssigkeit werden ionisiert und dem austretenden Produkt zugeführt. Diese Elektroden sind stark durch versehentliche Berührungen gefährdet.An electrostatic spray gun is also already known (US Pat. No. 3,764,068), in which a total of six high-voltage electrodes are arranged approximately uniformly distributed on a circle which extends around an annular material outlet opening and an annular atomizing air outlet opening which concentrically surrounds this . The electrodes are located near the outer circumference of the slightly profiled end face and protrude considerably beyond this end face. They are hollow so that an auxiliary liquid, possibly in a mixture with air, can be fed through them. Droplets of the auxiliary liquid are ionized and fed to the emerging product. These electrodes are very vulnerable to accidental contact.

Der Erfindung liegt die Aufgabe zugrunde, eine elektro­statische Sprühpistole der eingangs beschriebenen Art anzugeben, bei der eine bessere Aufladung des Sprühstrahls möglich ist.The invention has for its object to provide an electrostatic spray gun of the type described above, in which a better charging of the spray jet is possible.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß von der Stirnfläche des Sprühkopfes ein zur Material-Aus­trittsöffnung etwa konzentrischer, sich nach vorn verjün­gender Leitkörper vorsteht und daß die mindestens eine Hochspannungselektrode im Bereich der Basis des Leitkör­pers angeordnet ist.This object is achieved in that from the end face of the spray head protrudes approximately concentrically to the material outlet opening, tapering forward guide body and that the at least one high-voltage electrode is arranged in the region of the base of the guide body.

Bei dieser Konstruktion befinden sich die Spitzen der Hochspannungselektroden in einer durch die vom Umfang des Sprühkopfes ausgehende Stirnfläche und den Leitkör­per gebildeten Hohlkehle. Die Hohlkehle liegt im Bereich der Strömung der durch das austretende Material ange­saugten Sekundärluft. Diese trifft in einem durch den Leitkörper bestimmten Abschnitt auf das austretende Mate­rial. Durch die Form und Anordnung des Leitkörpers kann man den Auftreffabschnitt so wählen, daß eine optimale Aufladung des Materials erfolgt. Zur besseren Aufladung trägt auch bei, daß der Leitkörper aus isolierendem Mate­rial in der ersten Phase als dielektrischer Isolator zwischen den Einzelelektroden und dem austretenden Mate­rial mit niedrigem elektrischen Potential wirkt. Außerdem sind die Elektroden in der Hohlkehle gut gegen versehent­liche Berührungen geschützt. Die radial verhältnismäßig weit innen liegende Anordnung der Elektroden erhöht auch die Sicherheit gegen Funkenbildung bei Annäherung an geerdete Bauteile im Vergleich zu radial weiter außen angeordneten Elektroden.In this construction, the tips of the high-voltage electrodes are located in a groove formed by the end face extending from the circumference of the spray head and the guide body. The fillet lies in the area of the flow of the secondary air sucked in by the exiting material. This strikes the exiting material in a section determined by the guide body. Due to the shape and arrangement of the guide body, the impact section can be selected so that the material is optimally charged. For better charging also contributes to the fact that the guide body made of insulating material acts in the first phase as a dielectric insulator between the individual electrodes and the emerging material with a low electrical potential. In addition, the electrodes in the fillet are well protected against accidental contact. The radially relatively far inner arrangement of the electrodes also increases the security against sparking when approaching grounded components in comparison to electrodes arranged radially further out.

Günstig ist es, daß mehrere Hochspannungselektroden etwa gleichmäßig um die Material-Austrittsöffnung herum ver­teilt angeordnet sind. Die Ionisierung erfolgt dann an mehreren, gleichmäß um die Material-Austrittsöffnung herum angeordneten Stellen, so daß auch die Übergabe der Ladung an das Material gleichmäßig von allen Seiten her erfolgt. Die Wirkungsbereiche der Elektroden über­lappen sich, so daß man eine hohe Aufladung des Materials erhält.It is favorable that several high-voltage electrodes are arranged approximately uniformly distributed around the material outlet opening. The ionization then takes place at a number of points which are arranged uniformly around the material outlet opening, so that the charge is also transferred to the material uniformly from all sides. The effective areas of the electrodes overlap, so that a high charge of the material is obtained.

Die Berührungssicherheit wird noch weiter verbessert, wenn die Hochspannungselektroden nicht oder nur unwesent­lich über die Stirnfläche des Sprühkopfes vorstehen. Der Überstand sollte höchstens 6 mm und vorzugsweise weniger als 1 mm betragen. Auch bei nahezu versteckten Elektrodenspitzen ergibt sich wegen der Vielzahl der Elektroden eine ausreichende Aufladung.The safety against contact is further improved if the high-voltage electrodes do not protrude or only insignificantly over the end face of the spray head. The protrusion should be at most 6 mm and preferably be less than 1 mm. Even with almost hidden electrode tips, there is sufficient charge due to the large number of electrodes.

Die Vereinigungsstelle der ionisierten Luft und des ausge­tretenen Materials kann man nicht nur durch die äußere Form des Leitkörpers, sondern auch dadurch beeinflussen, daß der Leitkörper eine zentrische Aussparung besitzt und die Material-Austrittsöffnung einen Abstand vom vorde­ren Ende des Leitkörpers hat. Hierdurch wird der Abstand zwischen der Austrittsöffnung und der Auftreffzone ver­größert.The junction of the ionized air and the leaked material can be influenced not only by the outer shape of the guide body, but also by the fact that the guide body has a central recess and the material outlet opening is at a distance from the front end of the guide body. This increases the distance between the outlet opening and the impact zone.

Die besten Ergebnisse zeigen sich, wenn der Leitkörper so geformt ist, daß eine von der Elektrodenspitze aus gezogene, den Leitkörper berührende Tangente die Achse der Material-Austrittsöffnung an einer Stelle schneidet, an der das Produkt beginnt, sich in Tröpfchen zu zerlegen. In diesem Bereich ist die Ladungsübergabe besonders inten­siv.The best results are obtained if the guide body is shaped in such a way that a tangent drawn from the electrode tip and touching the guide body intersects the axis of the material outlet opening at a point at which the product begins to break down into droplets. In this area the charge transfer is particularly intensive.

Bei einer Luftzerstäubung sollte eine die Material-Aus­trittsöffnung konzentrisch umgebende Zerstäuberluft-Aus­trittsöffnung innerhalb des Basisdurchmessers des Leit­körpers liegen. Die Elektroden werden dann von der durch die Zerstäuberluft angesaugten Sekundärluft überstrichen.With air atomization, an atomizing air outlet opening concentrically surrounding the material outlet opening should lie within the basic diameter of the guide body. The electrodes are then swept by the secondary air drawn in by the atomizing air.

Bei einer Ausführungsform sind auf einander gegenüber­liegenden Seiten der Material-Austrittsöffnung Hörner mit Hilfsluft-Austrittsöffnungen vorgesehen, die Hilfsluft auf das austretende Produkt richten. Dies ergibt unabhän­gig von der Ionisierung eine Zerstäubungshilfe oder Strahlformung.In one embodiment, horns with auxiliary air outlet openings are provided on opposite sides of the material outlet opening, which direct auxiliary air at the emerging product. Irrespective of the ionization, this results in an atomization aid or beam shaping.

Ferner empfiehlt es sich, daß wenigstens ein Teil der Hochspannungselektroden in Umfangsrichtung versetzt zu den Hörner angeordnet sind. Hierbei wird unabhängig von der Hilfsluft genügend Sekundärluft zugeführt, damit der Materialstrahl möglichst stark aufgeladen wird.It is also recommended that at least some of the high-voltage electrodes be arranged offset in the circumferential direction from the horns. Sufficient secondary air is supplied regardless of the auxiliary air so that the material jet is charged as strongly as possible.

Insbesondere können die Hilfsluft-Austrittsöffnungen so gerichtet sein, daß ihre Achsen die Symmetrieebene zwischen den Hörnern zwischen der Material-Austrittsöff­nung und dem Schnittpunkt der Tangenten mit der Achse der Material-Austrittsöffnung schneiden. Auch diese Maß­nahme trägt dazu bei, daß das konzentrierte elektrostati­sche Feld erst dort im Sprühstrahl wirksam ist, wo dieser beginnt, sich in Tröpfchen zu zerlegen.In particular, the auxiliary air outlet openings can be directed such that their axes intersect the plane of symmetry between the horns between the material outlet opening and the intersection of the tangents with the axis of the material outlet opening. This measure also contributes to the fact that the concentrated electrostatic field is only effective in the spray where it begins to break down into droplets.

Eine besonders bevorzugte Anwendung ist die Verarbeitung eines Materials mit mittlerer bis höherer elektrischer Leitfähigkeit, wie wasserlösliche Lacke oder Trennmittel. Mit Hilfe des Leitkörpers ergibt sich nämlich eine längere Strecke zwischen Elektroden und dem aufzuladenden Mate­rial, so daß eine direkte Kontaktierung mit dem Material verhindert ist.A particularly preferred application is the processing of a material with medium to high electrical conductivity, such as water-soluble lacquers or release agents. With the aid of the guide body, there is a longer distance between electrodes and the material to be charged, so that direct contact with the material is prevented.

Die beschriebene Elektrodenanordnung läßt sich sowohl für Pistolen mit Luftzerstäubung als auch für solche mit hydrostatischer Zerstäubung ("airless-Verfahren") anwenden. Wenn Hilfsluft verwendet wird, kann diese bei Luftzerstäubung der Formung des Sprühstrahls und bei hydrostatischer Zerstäubungshilfe als Zerstäubungshilfe im airless/Luft-Verfahren ("airless-plus") dienen.The electrode arrangement described can be used both for guns with air atomization and for those with hydrostatic atomization ("airless method"). If auxiliary air is used, it can be used for air atomization to shape the spray jet and for hydrostatic atomization aid as an atomization aid in the airless / air process ("airless-plus").

Die Erfindung wird nachstehend anhand in der Zeichnung dargestellter, bevorzugter Ausführungsbeispiele näher erläutert. Es zeigen:

  • Fig. 1 einen Längsschnitt durch den Kopfbereich eines ersten Ausführungsbeispiels einer elektrostatischen Sprühpistole,
  • Fig. 2 einen Schnitt durch eine abgewandelte Ausführungs­form,
  • Fig. 3 eine Vorderansicht auf die Ausführungsform der Fig. 2,
  • Fig. 4 einen Schnitt durch eine weitere Ausführungsform und
  • Fig. 5 eine Vorderansicht auf die geringfügig abgewandelte Ausführungsform der Fig. 4.
The invention is explained in more detail below with reference to preferred exemplary embodiments illustrated in the drawing. Show it:
  • 1 shows a longitudinal section through the head region of a first exemplary embodiment of an electrostatic spray gun,
  • 2 shows a section through a modified embodiment,
  • 3 is a front view of the embodiment of FIG. 2,
  • Fig. 4 shows a section through a further embodiment and
  • 5 is a front view of the slightly modified embodiment of FIG. 4th

Bei der Ausführungsform nach Fig. 1 weist der Körper 1 einer Sprühpistole einen Sprühkopf 2 auf, der aus einem Einsatz 2ʹ aus elektrisch isolierendem Werkstoff und einer ihn mit dem Körper 1 verbindenden Überwurfmutter 3 besteht. Im Zentrum des Sprühkopfes 2 befindet sich ein Düsenkörper 4 mit einem Schlitz als Material-Aus­trittsöffnung 5. Dahinter ist eine Dichtscheibe 6 und ein Einsatz 7 angeordnet, der einen Ventilsitz 8 trägt und eine Ventilstange 9 umschließt. Eine Schrägschulter 10 des Körpers 1 hält die Hintereinanderschaltung von Düsen­körper 4, Dichtscheibe 6 und Einsatz 7 an Ort und Stelle.In the embodiment according to FIG. 1, the body 1 of a spray gun has a spray head 2, which consists of an insert 2ʹ made of electrically insulating material and a union nut 3 connecting it to the body 1. In the center of the spray head 2 there is a nozzle body 4 with a slot as the material outlet opening 5. A sealing disk 6 and an insert 7 are arranged behind it, which carries a valve seat 8 and encloses a valve rod 9. A sloping shoulder 10 of the body 1 holds the series connection of the nozzle body 4, the sealing disk 6 and the insert 7 in place.

Der Sprühkopf 2 besitzt eine Stirnfläche 11, von der in der Mitte ein Leitkörper 12 mit konusartiger Ober­fläche 13 vorsteht und die bis zum Umfang des Sprühkopfes 2 reicht. Der Düsenkörper 4 befindet sich am vorderen Ende des Leitkörpers 12. An der Basis des Leitkörpers, also an der Übergangsstelle zwischen der Stirnfläche 11 und der konischen Oberfläche 13 befinden sich vier Hoch­ spannungselektroden 14, die mit 90° Abstand auf einem Kreis angeordnet sind. Sie stehen nicht oder nur unwesent­lich hervor. Da sie sich in einer Hohlkehle befinden, sind sie außerordentlich gut gegen Berührungen geschützt.The spray head 2 has an end face 11, from which a guide body 12 with a conical surface 13 protrudes in the middle and which extends to the circumference of the spray head 2. The nozzle body 4 is located at the front end of the guide body 12. At the base of the guide body, that is to say at the transition point between the end face 11 and the conical surface 13, there are four highs voltage electrodes 14 which are arranged at a 90 ° distance on a circle. They do not protrude or only slightly. Since they are located in a groove, they are extremely well protected against contact.

Jede Elektrode 14 ist über eine Leitung 15 mit einem Verteilerring 16 verbunden. Dieser steht mit einer einen Schutzwiderstand 18 aufweisenden Hochspannungs-Verbin­dung 19 in Kontakt.Each electrode 14 is connected to a distributor ring 16 via a line 15. This is in contact with a high-voltage connection 19 having a protective resistor 18.

Wenn ein Material unter hohem Druck über einen Kanal 20 zugeleitet und das Ventil 8, 9 geöffnet wird, gibt die Material-Austrittsöffnung 5 einen Sprühstrahl 21 ab. Unmittelbar hinter der Austrittsöffnung, beispielsweise bis zum Abstand a, ist noch ein zusammenhängender Schleier vorhanden. Dahinter zerfällt er in viele kleine Tröpfchen. Das mit großer Geschwindigkeit austretende Material reißt Luft mit sich, so daß Sekundärluft gemäß dem Pfeil 22 an der Stirnfläche 11 und der Konusfläche 13 entlang strömt. Diese Luft wird durch die Hochspannungselektro­den 14 ionisiert. Sie folgt dem Strömungsantrieb und dem elektrostatischen Feld. Auf dieses Feld hat der Leit­körper 12 einen gewissen Einfluß. Die von den Elektro­denspitzen ausgehenden und den Leitkörper 12 berührenden Tangenten 23 treffen die Achse der Austrittsöffnung im Abstand b, also dort, wo das Material beginnt, sich in Tröpfchen zu zerlegen. Da der überwiegende Teil der Luft erst in diesem Bereich auf den Sprühstrahl 21 auftrifft, ist eine gute Tröpfchenaufladung sichergestellt. Dies gilt insbesondere, weil die Ionisation von allen Seiten her, also konzentrisch erfolgt.If a material is supplied under high pressure via a channel 20 and the valve 8, 9 is opened, the material outlet opening 5 emits a spray jet 21. Immediately behind the outlet opening, for example up to the distance a, there is still a coherent veil. Behind it breaks up into many small droplets. The material emerging at high speed entrains air so that secondary air flows along the end face 11 and the cone face 13 according to the arrow 22. This air is ionized by the high voltage electrodes 14. It follows the flow drive and the electrostatic field. The guide body 12 has a certain influence on this field. The tangents 23 starting from the electrode tips and touching the guide body 12 meet the axis of the outlet opening at a distance b, that is, where the material begins to break down into droplets. Since the predominant part of the air only hits the spray jet 21 in this area, good droplet charging is ensured. This applies in particular because the ionization takes place from all sides, that is to say concentrically.

Es kann sich sogar um ein Material mit mittlerer bis höherer Leitfähigkeit, wie Wasserlack, handeln. Denn die Abstände zwischen den Elektroden und der Austritts­ öffnung bzw. dem Sprühstrahl sind ausreichend groß, um Überschläge zu vermeiden.It can even be a medium to high conductivity material such as water-based paint. Because the distances between the electrodes and the outlet The opening or the spray jet are large enough to avoid flashovers.

Bei der Ausführungsform nach Fig. 2 werden für entspre­chende Teile um 100 erhöhte Bezugszeichen verwendet. Unterschiedlich ist es im wesentlichen, daß der Leitkör­per 112 eine Oberfläche 113 mit einem kleineren Konuswin­kel besitzt und daß im Innern das Leitkörpers eine zentri­sche Aussparung 124 vorhanden, also der Düsenkörper 104 um ein Stück nach hinten zurückgesetzt ist. Beides führt dazu, daß die ionisierte Luft erst in einem größeren Abstand von der Austrittsöffnung auf den Sprühstrahl 121 auftrifft, wie es wiederum durch die von den Elektroden­spitzen ausgehenden und den Leitkörper 112 berührenden Tangenten 123 veranschaulicht ist; hier hat der Schnitt­punkt mit der Achse der Austrittsöffnung 105 den Abstand c von dieser Austrittsöffnung.In the embodiment according to FIG. 2, reference numerals increased by 100 are used for corresponding parts. It is essentially different that the guide body 112 has a surface 113 with a smaller cone angle and that there is a central recess 124 in the interior of the guide body, that is to say the nozzle body 104 is set back a bit to the rear. Both lead to the fact that the ionized air only hits the spray jet 121 at a greater distance from the outlet opening, as is again illustrated by the tangents 123 starting from the electrode tips and touching the guide body 112; here the point of intersection with the axis of the outlet opening 105 is at a distance c from this outlet opening.

Fig. 3 zeigt, wie die Elektroden 114 gleichmäßig um die Austrittsöffnung 105 herum angeordnet sind. Die Wirksam­keit der Elektroden ist nicht nur radial gerichtet, son­dern geht im Rahmen des elektrostatischen Feldes auch zur Seite. Daher wird Sekundärluft, die über den Bereich I zuströmt, von einer Elektrode 114 beeinflußt, während in den dazwischen liegenden Bereichen II jeweils zwei Elektroden wirksam sind. Dies ergibt eine ringsum recht gleichmäßige Ionisierung der zugeführten Sekundärluft.3 shows how the electrodes 114 are arranged uniformly around the outlet opening 105. The effectiveness of the electrodes is not only directed radially, but also goes aside in the context of the electrostatic field. Therefore, secondary air that flows in through area I is influenced by an electrode 114, while two electrodes are effective in the areas II in between. This results in a fairly uniform ionization of the supplied secondary air all around.

Bei der Ausführungsform nach den Fig. 4 und 5 werden für entsprechende Teile um 200 erhöhte Bezugszeichen benutzt. Eine durch eine Ventilstange 209 absperrbare Material-Austrittsöffnung 205 wird über einen Kanal 220 nahezu drucklos mit Material versorgt. Konzentrisch hierzu ist eine Zerstäuberluftdüse 225 vorgesehen, die über einen Ringraum 226 und einen Kanal 227 mit Zerstäuberluft versorgt wird. Auf einander gegenüberliegenden Seiten sind zwei Hörner 228 und 229 vorgesehen, die Hilfs­luft-Austrittsöffnungen 230 besitzen. Auch hier ist wie­derum der Stirnfläche 211 des Sprühkopfes 202 ein Leit­körper 212 vorgeschaltet. An der Übergangsstelle befinden sich die Hochspannungselektroden 214.In the embodiment according to FIGS. 4 and 5, reference numerals increased by 200 are used for corresponding parts. A material outlet opening 205, which can be shut off by a valve rod 209, is supplied with material almost without pressure via a channel 220. An atomizing air nozzle 225 is provided concentrically to this and is supplied with atomizing air via an annular space 226 and a channel 227. On opposite sides two horns 228 and 229 are provided which have auxiliary air outlet openings 230. Here, too, a guide body 212 is connected upstream of the end face 211 of the spray head 202. The high-voltage electrodes 214 are located at the transition point.

Die Elektroden 214 können sich zwar, wie in Fig. 4 gezeigt ist, zum Teil unterhalb der Hörner befinden, so daß ihnen zwangsweise Hilfsluft zugeführt wird. In den meisten Fällen ist es jedoch für die gleichmäßige Ionisierung günstiger, wenn die Elektroden 214 in Umfangsrichtung versetzt zu den Hörnern angeordnet sind. Außerdem sollten die Hilfsluft-Austrittsöffnungen 230 so gerichtet sein, daß die Hilfsluft auf den Sprühstrahl auftrifft, ehe die beschriebenen Tangenten die Austrittsachse erreichen. Auf diese Weise wird die Zerstäubung und die Ionisierung verbessert.The electrodes 214 can, as shown in FIG. 4, be located partially below the horns, so that auxiliary air is forcibly supplied to them. In most cases, however, it is more favorable for the uniform ionization if the electrodes 214 are arranged offset circumferentially to the horns. In addition, the auxiliary air outlet openings 230 should be directed so that the auxiliary air impinges on the spray jet before the tangents described reach the outlet axis. This improves atomization and ionization.

Die Hörner 228 und 229 können auch bei den hydrostati­schen Zerstäuberdüsen der Fig. 1 und 2 angewendet werden. Die von diesen auf das Material gerichtete Hilfsluft unterstützt nicht nur den Zerstäubungsvorgang, so daß mit einem kleineren hydrostatischen Druck gearbeitet werden kann, sondern sie wird auch ionisiert und verbes­sert dadurch die Aufladung.The horns 228 and 229 can also be used with the hydrostatic atomizing nozzles of FIGS. 1 and 2. The auxiliary air directed by them onto the material not only supports the atomization process so that a lower hydrostatic pressure can be used, but it is also ionized and thereby improves the charging.

Der Leitkörper kann auch eine andere äußere Form haben, beispielsweise gewölbt sein. Die Elektroden müssen nicht genau an der Basis des Leitkörpers plaziert sein, sondern können in einem gewissen Bereich davor oder dahinter angeordnet werden, ohne daß die geschilderten Vorteile verlorengehen. Die Sprühpistole kann auch in einer Atmo­sphäre aus einem der Luft äquivalenten Gas betrieben werden.The guide body can also have a different external shape, for example curved. The electrodes do not have to be placed exactly on the base of the guide body, but can be arranged in a certain area in front of or behind it, without losing the advantages described. The spray gun can also be operated in an atmosphere from a gas equivalent to the air.

Claims (10)

1. Elektrostatische Sprühpistole mit einem Sprühkopf aus elektrisch isolierendem Werkstoff, der eine Mate­rial-Austrittsöffnung und mindestens eine Hochspan­nungselektrode trägt, mit deren Hilfe das Material nach dessen Austritt aufgeladen wird, dadurch gekenn­zeichnet, daß von der Stirnfläche (11; 111; 211) des Sprühkopfes (2; 102; 202) ein zur Material-Austritts­öffnung (5; 105; 205) etwa konzentrischer, sich nach vorn verjüngender Leitkörper (12; 112; 212) vorsteht und daß die mindestens eine Hochspannungselektrode (14; 114; 214) im Bereich der Basis des Leitkörpers angeordnet ist.1. Electrostatic spray gun with a spray head made of electrically insulating material, which carries a material outlet opening and at least one high-voltage electrode, with the aid of which the material is charged after it emerges, characterized in that from the end face (11; 111; 211) of the spray head (2; 102; 202) protrudes a guide body (12; 112; 212) which is approximately concentric with the material outlet opening (5; 105; 205) and tapers towards the front and that the at least one high-voltage electrode (14; 114; 214) in the area the base of the guide body is arranged. 2. Elektrostatische Sprühpistole nach Anspruch 1, dadurch gekennzeichnet, daß mehrere Hochspannungselektroden (14; 114; 214) etwa gleichmäßig um dia Material-Aus­trittsöffnung (5; 105; 205) herum verteilt angeordnet sind.2. Electrostatic spray gun according to claim 1, characterized in that a plurality of high-voltage electrodes (14; 114; 214) are arranged approximately uniformly distributed around the material outlet opening (5; 105; 205). 3. Elektrostatische Sprühpistole nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Hochspannungselektroden (14; 114; 214) nicht oder nur unwesentlich über die Stirnfläche (11; 111; 211) des Sprühkopfes (2; 102; 202) vorstehen.3. Electrostatic spray gun according to claim 1 or 2, characterized in that the high-voltage electrodes (14; 114; 214) do not or only insignificantly protrude beyond the end face (11; 111; 211) of the spray head (2; 102; 202). 4. Elektrostatische Sprühpistole nach einem der Ansprü­che 1 bis 3, dadurch gekennzeichnet, daß der Leitkör­per (112) eine zentrische Aussparung (124) besitzt und die Material-Austrittsöffnung (105) einen Abstand vom vorderen Ende des Leitkörpers (112) hat.4. Electrostatic spray gun according to one of claims 1 to 3, characterized in that the guide body (112) has a central recess (124) and the material outlet opening (105) is at a distance from the front end of the guide body (112). 5. Elektrostatische Sprühpistole nach einem der Ansprü­che 1 bis 4, dadurch gekennzeichnet, daß der Leitkör­per (12; 112) so geformt ist, daß eine von der Elektro­denspitze aus gezogene, den Leitkörper berührende Tangente (23; 123) die Achse der Material-Austrittsöff­nung (5; 105) an einer Stelle schneidet, an der das Produkt beginnt, sich in Tröpfchen zu zerlegen.5. Electrostatic spray gun according to one of claims 1 to 4, characterized in that the guide body (12; 112) is shaped so that a drawn from the electrode tip, the guide body tangent (23; 123) the axis of the material outlet opening (5; 105) cuts at a point where the product begins to break down into droplets. 6.Elektrostatische Sprühpistole nach einem der Ansprü­che 1 bis 5, dadurch gekennzeichnet, daß bei Luftzer­stäubung eine die Material-Austrittsöffnung (205) konzentrisch umgebende Zerstäuberluft-Austrittsöffnung (225) innerhalb des Basisdurchmessers des Leitkörpers liegt.6. Electrostatic spray gun according to one of claims 1 to 5, characterized in that in the case of air atomization, the material outlet opening (205) concentrically surrounding atomizing air outlet opening (225) lies within the base diameter of the guide body. 7. Elektrostatische Sprühpistole nach einem der Ansprü­che 1 bis 6, dadurch gekennzeichnet, daß auf einander gegenüberliegenden Seiten der Material-Austrittsöffnung Hörner (228, 229) mit Hilfsluft-Austrittsöffnun­gen (230) vorgesehen sind, die Hilfsluft auf das aus­tretende Material richten.7. Electrostatic spray gun according to one of claims 1 to 6, characterized in that on opposite sides of the material outlet opening horns (228, 229) with auxiliary air outlet openings (230) are provided, which direct auxiliary air onto the escaping material. 8. Elektrostatische Sprühpistole nach Anspruch 7, dadurch gekennzeichnet, daß wenigstens ein Teil der Hochspan­nungselektroden (214) im Umfangsrichtung versetzt zu den Hörnern (228, 229) angeordnet sind.8. Electrostatic spray gun according to claim 7, characterized in that at least part of the high-voltage electrodes (214) are arranged offset in the circumferential direction to the horns (228, 229). 9. Elektrostatische Sprühpistole nach Anspruch 5 und 7, dadurch gekennzeichnet, daß die Hilfsluft-Austritts­öffnungen (230) so gerichtet sind, daß ihre Achsen die Symmetrieebene zwischen den Hörnern (228, 229) zwischen der Material-Austrittsöffnung (205) und dem Schnittpunkt der Tangenten (223) mit der Achse der Material-Austrittsöffnung schneiden.9. Electrostatic spray gun according to claim 5 and 7, characterized in that the auxiliary air outlet openings (230) are directed so that their axes the plane of symmetry between the horns (228, 229) between the material outlet opening (205) and the intersection of the Cut the tangents (223) with the axis of the material outlet opening. 10. Elektrostatische Sprühpistole nach einem der Ansprü­che 1 bis 9, gekennzeichnet, durch die Anwendung auf das Verarbeiten eines Materials mittlerer bis höherer elektrischer Leitfähigkeit.10. Electrostatic spray gun according to one of claims 1 to 9, characterized by the application to the processing of a medium to higher electrical conductivity material.
EP88102711A 1987-02-24 1988-02-24 Electrostatic spray gun Expired - Lifetime EP0283747B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT88102711T ATE67692T1 (en) 1987-02-24 1988-02-24 ELECTROSTATIC SPRAY GUN.

Applications Claiming Priority (2)

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DE3705815 1987-02-24
DE19873705815 DE3705815A1 (en) 1987-02-24 1987-02-24 ELECTROSTATIC SPRAY GUN

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EP0283747A2 true EP0283747A2 (en) 1988-09-28
EP0283747A3 EP0283747A3 (en) 1990-01-10
EP0283747B1 EP0283747B1 (en) 1991-09-25

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ID=6321610

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EP88102711A Expired - Lifetime EP0283747B1 (en) 1987-02-24 1988-02-24 Electrostatic spray gun

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US (1) US4842203A (en)
EP (1) EP0283747B1 (en)
AT (1) ATE67692T1 (en)
DE (2) DE3705815A1 (en)
ES (1) ES2026216T3 (en)

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Also Published As

Publication number Publication date
ES2026216T3 (en) 1992-04-16
US4842203A (en) 1989-06-27
DE3865053D1 (en) 1991-10-31
ATE67692T1 (en) 1991-10-15
EP0283747A3 (en) 1990-01-10
EP0283747B1 (en) 1991-09-25
DE3705815A1 (en) 1988-09-01
DE3705815C2 (en) 1990-03-29

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