EP0620045B1 - Electrostatic spray device - Google Patents

Electrostatic spray device Download PDF

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Publication number
EP0620045B1
EP0620045B1 EP94102449A EP94102449A EP0620045B1 EP 0620045 B1 EP0620045 B1 EP 0620045B1 EP 94102449 A EP94102449 A EP 94102449A EP 94102449 A EP94102449 A EP 94102449A EP 0620045 B1 EP0620045 B1 EP 0620045B1
Authority
EP
European Patent Office
Prior art keywords
electrode
counter
spray
powder
charging
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP94102449A
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German (de)
French (fr)
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EP0620045A1 (en
Inventor
Eugen Thomas Bühlmann
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.)
Gema Switzerland GmbH
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Gema Switzerland GmbH
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • 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
    • B05B5/0535—Electrodes specially adapted therefor; Arrangements of electrodes at least two electrodes having different potentials being held on the discharge apparatus, one of them being a charging electrode of the corona type located in the spray or close to it, and another being of the non-corona type located outside of the path for the material
    • 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
    • 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

Definitions

  • the invention relates to an electrostatic Spray device according to the preamble of claim 1.
  • the invention is suitable for powdered Coating material such as Plastic powder or enamel powder.
  • An electrostatic spray device of this type is known from US-A-4,774,102. With her is as Counter clamp provided a clamp on the front end portion of a sprayer can be put on. According to another Embodiment from this document acts Do not clamp yourself as an electrode, but it carries a over sticking rods annular electrode or needle electrodes. In In all cases, the clamp is schematic over one shown, not described electrical Line connected to earth potential.
  • Electrodes are used for this, in the following charging electrodes called which to an electrical High voltage in the range between 40 KV and 140 KV are connected.
  • the objects to be coated have a different electrical potential, preferably Earth potential.
  • the atomized powder particles move along electric field lines that pass through the high voltage between the charging electrode and the object to be coated are generated. After yourself a thin layer on the object to be coated made of powder, this layer bumps through their electrical charge coming off powder particles because they are electrostatically charged in the same way. This means that only one can be used in one operation Layer thickness generated on the object to be coated will.
  • the electrostatic attraction of the material to be coated The object is at corners and edges as well as at openings this object differently than on even larger ones Surfaces. Usually corners and edges get worse or less coated than adjacent ones larger areas.
  • the powder particles fly under the influence of the electrostatic field around the Outer peripheral edges and around the edges of openings of the coating object around and are then as a result the electrostatic attraction of the object pulled on the back, so that here too Back of the object to be coated coated becomes. This can be referred to as "electrical wrap" will.
  • the object of the invention is to be achieved Create means by which one or more Counter electrodes inexpensive and with little space requirement Spray devices can be provided and in particular also commercially available spray devices subsequently (retro-fit) with at least one Counter electrode can be provided. This means and the counter electrode is said to be easy to handle Do not interfere with the spray device.
  • the spray device shown in Figures 1 and 2 or spray gun 2 for electrostatic Spray coating objects 4 or 6 has a spray body 3 with an inlet 8 for pneumatic promoted coating powder, an outlet 10 to Atomize or spray the powder onto you Item 4 or 6, and at least one axially in Powder stream lying charging electrode 12.
  • the Charging electrode 12 is located in outlet 10 or in close proximity upstream or downstream of the Outlet 10 and is at one High voltage generator 16 connected, which one electrical output voltage in the range between 40 KV and generated 140 KV.
  • the high voltage generator 16 can according to the drawings within the housing 18th the spray gun 2 or be arranged externally. Both embodiments are known. Of the High voltage generator 16 of FIGS.
  • the spray gun 2 shown is on one Machine part or a robot 22 one Spray coating system attached. Instead, could they also have a handle and a hand-held spray gun be used.
  • the object 4 or 6 to be coated becomes usually from a transport device, which is not shown, worn and by a Spray coating cabin transported through.
  • the Transport device is grounded, so that of her worn item 4 or 6 by the Transport device is grounded.
  • the electrical high voltage creates electrical Field lines 24, which from the tip 26 of the Charging electrode 12 to be coated Item 4 or 6 run.
  • the outlet 10 sprayed powder particles move along these Field lines 24 on the object to be coated 4 or 6. They also penetrate into recesses 28 of the coating object and through openings 30 through this object. This will get the Particles due to the "electrical wrap-around effect" in Edge areas of the object also on its back 32, as shown in FIG. 1 by the opening edge 34 "Comprehensive" field lines 36 is shown.
  • protruding edges 38 or corners result from electrostatic interactions a stronger one Layer thickness than on raised areas 40 or larger flat surfaces 42 of the object 4 to be coated.
  • the sprayed powder has seen the in longitudinal section Shape of a particle cloud, as shown in Figures 1 and 2 is represented by the field lines 24.
  • the counter electrode 44 is coaxial with the charging electrode 12 arranged annular counter electrode 44, which a different electrical potential than the charging electrode 12 and serves to suck free ions, which are associated with electrostatic charging of the powder be generated.
  • the counter electrode 44 also pulls some electrons. This ion current and its path from the charging electrode 12 to the counter electrode 44 is with the reference numeral 46 denotes.
  • the counter electrode 44 can at a higher or lower electrical potential lie than the charging electrode 12. Is preferred the counter electrode 44 is connected to ground potential 20.
  • the counter electrode 44 is preferably in accordance with FIG. 1 against the flow direction 48 of the powder upstream of the tip 26 of the charging electrode 12 arranged coaxially to her, and thus outside and upstream of the electric field lines 24 corresponding powder cloud.
  • the outer surface 50 of the powder cloud which the electric field lines 24 in size and shape is not a sharp cloud boundary, but a diffuse transition between areas even particle distribution and the surrounding The atmosphere.
  • Outer surface 50 of the powder cloud the area understood where the particles are no longer targeted Field lines 24 on the object to be coated 4 or 6 fly, but vagabond out of the field line area.
  • the distance “d” between the Counter electrode 44 and charging electrode 12, between the counter electrode 44 and the tip 26 of the Charging electrode 12, and between the counter electrode 44 and the outer surface 50 of the powder cloud should be smaller than the distance "D" between the tip 26 the charging electrode 12 and the one to be coated Item 4 or 6.
  • the distance is “d” between the tip 26 of the charging electrode 12 and the Counter electrode 44 only a third to half of that Distance "D” between the tip 26 of the Charging electrode 12 and the one to be coated Item 4 or 6.
  • a compressed air nozzle assembly 52 blows air over the Counter electrode 44 or in the space between Counter electrode 44 and charging electrode 12 to a Coating the counter electrode 44 with powder prevent. Compressed air is only needed if not otherwise coating the counter electrode 44 can be prevented.
  • the counter electrode 44 is preferably provided by the housing 18 the spray gun 2 worn.
  • a charging electrode 12 or one Counterelectrode 44 can also each have a plurality of electrodes to be available.
  • Fig. 2 Spray gun 2 is identical to that of Fig. 1, with Exception of at least one counter electrode 64, which in the embodiment shown in FIG is needle-shaped wire electrode. It will be coaxial from Compressed air 66 washed and thereby by Keep coating material clear. Are preferred several coaxial to the charging electrode 12 Counter electrodes 64 arranged. These counter electrodes 64 are preferably the same circumferential distance from each other arranged around the charging electrode 12. In Fig. 2 are parts which correspond to parts of Fig. 1 with provided with the same reference numbers.
  • means 68 for axial or / and radial positioning of the counter electrode 44 or 64 be provided relative to the charging electrode 12.
  • At least one charging electrode 12 which corresponding to Figures 1 and 2 an axial Can be needle electrode, or in the form of a A variety of such or other electrodes are available can be under high electrical voltage Electrons released. Near the high electric field 24 of the charging electrode 12 a small part (approx. 1% to 5%) of the electrons on the Coating material, in the present case powder, loaded. The rest fly to the closest one grounded point, for example about 80% towards the coating article 4 or 6, about 10% on the Walls of the cabin in which the objects are coated and about 5% to 20% of the downstream End of the spray gun, depending on the distance between the Charging electrode 12 and the one to be coated Item 4 or 6.
  • the electrostatically charged powder finds its way onto the object to be coated 4 or 6 and stays there for the most part.
  • the powder forms an electrical on the object insulating layer.
  • Form the excess electrons along with the powder on the surface of the Item 4 or 6 an increased electrical charge and repel powder particles arriving later.
  • On the Surface of the object 4 or 6 arises electrostatically unstable balance of power.
  • This Mechanism leaves one on the surface "Hilly landscape", which after burning in the layer is called “orange peel”.
  • the free ions in the air between the charging electrode 12 and coating object 4 or 6 move with a very high speed of over 100 m / s. you follow the stronger electrostatic field in question, the is called the electrostatic forces.
  • the electrostatic charged powder particles are subject to kinematic Flow forces as they are in a gas stream or air stream be transported.
  • the speed of movement of the Powder particles are much smaller than those of the ions and is only about 10 to 15 m / s. This means, that the ions are independent of the powder particles move.
  • the free Ions are attracted to and out of the counter electrode 44 or 64 derived from the powder stream.
  • the counter electrode must be in be close to the charging electrode.
  • the distance “d" between the charging electrode 12 and the Counter electrode 44 or 64 is preferably approximately one Third to half the distance “D" between the Counter electrode and the object to be coated 4 or 6. If the distance "d” is greater, the loses Counter electrode their effect; the free electrons and Ions become stronger from the object to be coated 4 or 6 attracted as from the counter electrode 44 or 64. If the distance "d” is smaller, the flow is too large electric current between the charging electrode and the counter electrode, causing the high voltage electrical at the tip 26 of the charging electrode and thus that electrostatic necessary to charge the powder Field 24 is reduced.
  • the Counter electrode 44 or 64 causes an increased electrical current flow at the tip 26 of the Charging electrode 12. This causes the Charging electrode 12 much more free ions or Electrons for electrostatically charging the powder on Outlet 10 of the device 2 generated and are then available electrostatic charge available. The This causes electrostatic charging of the powder significantly improved. It will also make the Application efficiency of the powder to the coating object 4 or 6 significantly improved.
  • the counter electrode 44 or 64 conducts the essential Part of the ions, about 60 to 80% off. Towards the coating object 4 or 6 only fly the charged powder particles, namely only 2% to 8% of the total electrical current. So one succeeds Separation of the unwanted free ions from the powder stream. The ion space charge still exists here, however the flow of free ions concentrates on the Counter electrode 44 or 64.
  • the Faraday effect is very strong on the counter electrode, but only very small on the object 4 or 6 to be coated electrostatically charged powder particles penetrate through it better in depressions and grooves of the object 4 or 6 a.
  • the "electrostatic wrap" is also better. On the surface of the object 4 or 6 does not arise Accumulation of free ions.
  • the electrostatic forces are 4 or 6 on the surface of the object much smaller. There is no unstable condition on the surface. The formation of an orange peel is inhibited. It can be a much thicker powder layer on item 4 or 6 in one Spraying process can be applied. Because of the danger that the counter electrode 44 or 64 from the electrostatic charged powder is also coated, it is expediently the counterelectrode 44 or 64 with compressed air do the washing up. To avoid coating the Counter electrode 44 or 64, it is useful if they is arranged outside the powder stream, being preferably with respect to the downstream tip 26 the charging electrode 12 upstream reset is, and not between the charging electrode 12 and the Coating object 4 or 6 is arranged.
  • the electrical current at the charging electrode is at Use a counter electrode 44 or 64 higher. Of the Current rose in experiments of approximately 70 ⁇ A about 100 ⁇ A. .
  • the powder cloud forms one electrical resistance and favors the flow of ions to the Counter electrode 44 or 64.
  • the electrostatic shown in Figs. 3 and 4 Spray device 2 consists essentially of a tubular spray body 3, at its downstream end a slot nozzle 70 for atomizing the pneumatically conveyed powder is attached. Within the Spray nozzle 70 or the spray body 3 is located at least one charging electrode 12 for electrostatic charging of the powder. On the downstream section 72 of the spray body 3 which the spray nozzle 70 is attached to is a annular body 74 plugged, which one Counter electrode forms and / or several needle-like Counter electrodes 76 which protrude from it. The Counter electrodes 74 and 76 are connected to an electrical one Potential, preferably connected to earth potential, which is different from the electrical potential of the Charging electrode 12.
  • the annular body 74 is at downstream end of a connecting web 78 attached, which is axially parallel to the spray body 3rd extends and with its upstream end 80 in inserted a holder 22 and there by a screw axially positioned with a knurled screw head 84 is.
  • FIG. 4 shows the spray device 2 from FIG. 3 with removed counter-electrode device 86, with Arrows 88 the direction of movement for attaching the annular body 74 on the downstream portion 72 is shown. Furthermore, the arrow 90 Direction of insertion for the screw 84 in a Threaded bore 91 shown in the holder 22.
  • Fig. 4 shows an earth potential connection 20.
  • the earth potential connection 20 can be connected directly to the connecting web 78 be when he and the annular body 74 out consist of electrically conductive material. If at least the connecting web 78 made of electrically insulating Material is, is a ground potential terminal 20th electrical connecting to the counter electrodes 76 Line 73 provided which is through the Connecting web 78 and the annular body 74 extends.
  • the annular body 74 consists of electrically conductive material when used as a counter electrode works. If it should not act as a counter electrode, it can he consist of electrically insulating material. Of the Earth potential connection 20 can be formed by the carrier 22 if it is made of electrically conductive material.
  • 5 is a pistol-shaped electrostatic Spray device 2 shown. Near the upstream end 94 of its spray body 3 is the Provide the spray body with a handle 95. The upstream end 80 of the connecting web 78 and the Screw 84 are located immediately above the handle 95 on the spray body 3. This can the electrical Ground line 73 on the handle 95 or through it to Earth potential connection 20 are performed. This has the Advantage that the material focus of the Spray device 2 in or near the handle 95 so that the pistol is held without fatigue is possible.
  • 5 is the charging electrode 12 shown as an axial electrode, while in Fig. 3rd and 4 it was assumed that several needle-like Charging electrodes 12 distributed around the powder path are arranged.
  • the annular body is 74 preferably relative to different axial positions adjustable to spray body 3. In all cases the annular body 74 when it is as Counter electrode acts or carries counter electrodes 76, upstream of the tip 26 of the charging electrode 12.

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  • Electrostatic Spraying Apparatus (AREA)

Abstract

Electrostatic spray device. It contains a tube-like spray body (3), at least one charging electrode (12) for transmitting electrostatic charges to the powder, at least one counter-electrode (44) which is arranged in the vicinity of the charging electrode (12) and is connected to a different electric potential (20) to the charging electrode (12) so that it receives at least some of the free ions generated during electric charging of the powder, at least one annular body (44; 68; 74) which forms or bears the counter-electrode (44; 64; 74, 76) and extends around the downstream section (72) of the spray body (3), on which it is supported radially, at least one connection web (78) outside the spray body (3) which bears at its downstream end (79) the annular body (74) and is fastened with its upstream end on the spray body (3), and an electric connection through the connection web (78) between an electric potential connection (20) and the counter-electrode (44). <IMAGE>

Description

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

Die Erfindung eignet sich für pulverförmiges Beschichtungsmaterial wie beispielsweise Kunststoffpulver oder Emailpulver.The invention is suitable for powdered Coating material such as Plastic powder or enamel powder.

Eine elektrostatische Sprühvorrichtung dieser Art ist aus der US-A-4 774 102 bekannt. Bei ihr ist als Gegenelektrode eine Schelle vorgesehen, die auf den vorderen Endabschnitt einer Sprühvorrichtung aufgesetzt werden kann. Gemäß einer weiteren Ausführungsform aus dieser Schrift wirkt die Schelle nicht selbst als Elektrode, sondern sie trägt über nach vorne wegragende Stäbe eine ringförmige Elektrode oder Nadelelektroden. In allen Fällen ist die Schelle über eine schematisch dargestellte, nicht näher beschriebene elektrische Leitung an Erdpotential angeschlossen.An electrostatic spray device of this type is known from US-A-4,774,102. With her is as Counter clamp provided a clamp on the front end portion of a sprayer can be put on. According to another Embodiment from this document acts Do not clamp yourself as an electrode, but it carries a over sticking rods annular electrode or needle electrodes. In In all cases, the clamp is schematic over one shown, not described electrical Line connected to earth potential.

Bei der elektrostatischen Sprühbeschichtung von Gegenständen wird das Pulver an einer Auslaßöffnung der Sprühvorrichtung versprüht und entweder unmittelbar vor dieser Auslaßöffnung oder nach dieser Auslaßöffnung positiv oder negativ elektrostatisch aufgeladen. Hierzu dienen Elektroden, im folgenden Aufladungselektroden genannt, welche an eine elektrische Hochspannung im Bereich zwischen 40 KV und 140 KV angeschlossen sind. Die zu beschichtenden Gegenstände haben ein anderes elektrisches Potential, vorzugsweise Erdpotential. Die zerstäubten Pulver-Partikel bewegen sich entlang von elektrischen Feldlinien, welche durch die Hochspannung zwischen der Aufladungselektrode und dem zu beschichtenden Gegenstand erzeugt werden. Nachdem sich auf dem zu beschichtenden Gegenstand eine dünne Schicht aus Pulver gebildet hat, stößt diese Schicht durch ihre elektrische Ladung nachkommende Pulver-Partikel ab, weil diese in gleicher Weise elektrostatisch aufgeladen sind. Dadurch kann in einem Arbeitsgang nur eine begrenzte Schichtdicke auf dem zu beschichtenden Gegenstand erzeugt werden. Ferner entsteht infolge der gegenseitigen Abstoßung der Pulver-Partikel auf der Oberfläche des zu beschichtenden Gegenstands ein instabiles Kräfteverhältnis. Dieses instabile Kräfteverhältnis führt dazu, daß sich keine glatte, ebene Beschichtungsoberfläche bildet, sondern eine Art "Hügellandschaft", welche beim anschließenden Einbrennen der Schicht eine sogenannte "Orangenhaut" bildet und deshalb nach Möglichkeit verhindert werden soll. With electrostatic spray coating from Objects become powder at an outlet sprayed the sprayer and either immediately before or after this outlet opening Outlet opening positive or negative electrostatic charged. Electrodes are used for this, in the following charging electrodes called which to an electrical High voltage in the range between 40 KV and 140 KV are connected. The objects to be coated have a different electrical potential, preferably Earth potential. The atomized powder particles move along electric field lines that pass through the high voltage between the charging electrode and the object to be coated are generated. After yourself a thin layer on the object to be coated made of powder, this layer bumps through their electrical charge coming off powder particles because they are electrostatically charged in the same way. This means that only one can be used in one operation Layer thickness generated on the object to be coated will. Furthermore arises as a result of the mutual Repulsion of the powder particles on the surface of the coating object an unstable Balance of power. This unstable balance of power leads to ensure that there is no smooth, level surface Coating surface forms, but a kind "Hilly landscape", which is then burned in the layer forms a so-called "orange peel" and therefore should be prevented if possible.

Die elektrostatische Anziehung des zu beschichtenden Gegenstandes ist an Ecken und Kanten sowie an Öffnungen dieses Gegenstandes anders als auf ebenen größeren Flächen. Üblicherweise werden Ecken und Kanten schlechter oder weniger stark beschichtet als danebenliegende größere Flächenbereiche. Die Pulver-Partikel fliegen unter Einwirkung des elektrostatischen Feldes um die Außenumfangsränder und um die Ränder von Öffnungen des zu beschichtenden Gegenstandes herum und werden dann infolge der elektrostatischen Anziehungskraft des Gegenstandes auf dessen Rückseite gezogen, so daß hier auch die Rückseite des zu beschichtenden Gegenstandes beschichtet wird. Dies kann als "elektrischer Umgriff" bezeichnet werden.The electrostatic attraction of the material to be coated The object is at corners and edges as well as at openings this object differently than on even larger ones Surfaces. Usually corners and edges get worse or less coated than adjacent ones larger areas. The powder particles fly under the influence of the electrostatic field around the Outer peripheral edges and around the edges of openings of the coating object around and are then as a result the electrostatic attraction of the object pulled on the back, so that here too Back of the object to be coated coated becomes. This can be referred to as "electrical wrap" will.

Durch die Verwendung einer Gegenelektrode, welche aus dem versprühten Pulverstrom freie Ionen absaugt, kann die Oberflächengüte und das Eindringvermögen des Pulvers in Vertiefungen der zu beschichtenden Gegenstände verbessert werden. Ferner kann in einem Sprühvorgang eine dickere Pulverschicht auf die zu beschichtenden Gegenstände aufgetragen werden, ohne daß übermäßig viel Pulver-Partikel vom Gegenstand abprallen oder elektrostatisch abgestoßen werden. Insbesondere kann eine "Orangenhaut"-artige Schichtoberfläche vermieden werden.By using a counter electrode, which is made of the sprayed powder stream sucks free ions, the Surface quality and the penetration of the powder in Improved deepening of the objects to be coated will. Furthermore, a thicker one can be applied in one spraying process Powder layer on the objects to be coated can be applied without excessive powder particles bounce off the object or electrostatically be repelled. In particular, an "orange peel" type Layer surface can be avoided.

Durch die Erfindung soll die Aufgabe gelöst werden, Mittel zu schaffen, durch welche eine oder mehrere Gegenelektroden preiswert und mit wenig Platzbedarf bei Sprühvorrichtungen vorgesehen werden können und insbesondere auch handelsübliche Sprühvorrichtungen nachträglich (retro-fit) noch mit mindestens einer Gegenelektrode versehen werden können. Diese Mittel und die Gegenelektrode sollen die leichte Handhabung der Sprühvorrichtung nicht beeinträchtigen.The object of the invention is to be achieved Create means by which one or more Counter electrodes inexpensive and with little space requirement Spray devices can be provided and in particular also commercially available spray devices subsequently (retro-fit) with at least one Counter electrode can be provided. This means and the counter electrode is said to be easy to handle Do not interfere with the spray device.

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

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

Die Erfindung wird im folgenden mit Bezug auf bevorzugte Ausführungsformen als Beispiele beschrieben. In den Zeichnungen zeigen

Fig. 1
eine bekannte Sprühvorrichtung zum elektrostatischen Sprühbeschichten von Gegenständen, bei welcher eine Gegenelektrode in Form eines Ringes koaxial zu einer Aufladungselektrode angeordnet ist,
Fig. 2
eine weitere bekannte Ausführungsform einer Sprühvorrichtung zum elektrostatischen Sprühbeschichten von Gegenständen, bei welcher als Gegenelektrode mehrere stabförmige Drähte vorgesehen sind,
Fig. 3
eine Seitenansicht einer elektrostatischen Sprühvorrichtung nach der Erfindung,
Fig. 4
eine Seitenansicht der Sprühvorrichtung von Fig. 3 mit abgenommener Gegenelektrodenvorrichtung,
Fig. 5
eine Seitenansicht einer pistolenartigen elektrostatischen Sprühvorrichtung nach der Erfindung.
The invention is described below with reference to preferred embodiments as examples. Show in the drawings
Fig. 1
a known spray device for the electrostatic spray coating of objects, in which a counter electrode in the form of a ring is arranged coaxially to a charging electrode,
Fig. 2
a further known embodiment of a spraying device for the electrostatic spray coating of objects, in which a plurality of rod-shaped wires are provided as the counter electrode,
Fig. 3
a side view of an electrostatic spray device according to the invention,
Fig. 4
3 shows a side view of the spray device from FIG. 3 with the counter-electrode device removed,
Fig. 5
a side view of a gun-like electrostatic spraying device according to the invention.

Die in den Figuren 1 und 2 dargestellte Sprühvorrichtung oder Sprühpistole 2 zur elektrostatischen Sprühbeschichtung von Gegenständen 4 oder 6 und weist einen Sprühkörper 3 mit einem Einlaß 8 für pneumatisch gefördertes Beschichtungs-Pulver, einen Auslaß 10 zum Zerstäuben oder Versprühen des Pulvers auf einen Gegenstand 4 oder 6, und mindestens eine axial im Pulverstrom liegende Aufladungselektrode 12 auf. Die Aufladungselektrode 12 befindet sich im Auslaß 10 oder in unmittelbarer Nähe stromaufwärts oder stromabwärts des Auslasses 10 und ist an einen Hochspannungserzeuger 16 angeschlossen, welcher eine elektrische Ausgangsspannung im Bereich zwischen 40 KV und 140 KV erzeugt. Der Hochspannungserzeuger 16 kann entsprechend den Zeichnungen innerhalb des Gehäuses 18 der Sprühpistole 2 oder extern davon angeordnet sein. Beide Ausführungsformen sind bekannt. Der Hochspannungserzeuger 16 der Fig. 1 und 2 ist an eine extern von der Sprühpistole 2 angeordnete, nicht dargestellte Gleichstrom-Niederspannungsquelle und außerdem an Erdpotential 20 angeschlossen. Statt einer axialen nadelförmigen Aufladungselektrode 12 im Auslaß 10 könnten mehrere Aufladungselektroden im Kern des Beschichtungsmaterial-Stromes oder um ihn herum, innerhalb des Gehäuses 18 oder in einer den Auslaß 10 bildenden Düse, am stromabwärtigen Ende des Gehäuses 18 angeordnet sein. In der Praxis sind verschiedene Aufladungselektroden und Anordnungen von Aufladungselektroden bekannt. Ferner könnte eine oder mehrere Aufladungselektroden auch außerhalb der Sprühpistole 2 in oder neben dem Strom von zerstäubtem Pulver angeordnet sein. Auch solche Ausführungsformen sind bekannt.The spray device shown in Figures 1 and 2 or spray gun 2 for electrostatic Spray coating objects 4 or 6 and has a spray body 3 with an inlet 8 for pneumatic promoted coating powder, an outlet 10 to Atomize or spray the powder onto you Item 4 or 6, and at least one axially in Powder stream lying charging electrode 12. The Charging electrode 12 is located in outlet 10 or in close proximity upstream or downstream of the Outlet 10 and is at one High voltage generator 16 connected, which one electrical output voltage in the range between 40 KV and generated 140 KV. The high voltage generator 16 can according to the drawings within the housing 18th the spray gun 2 or be arranged externally. Both embodiments are known. Of the High voltage generator 16 of FIGS. 1 and 2 is connected to a arranged externally from the spray gun 2, not illustrated DC low voltage source and also connected to earth potential 20. Instead of one axial needle-shaped charging electrode 12 in the outlet 10 could several charging electrodes in the core of the Coating material flow or around it, inside the housing 18 or in an outlet 10 forming nozzle, at the downstream end of the housing 18th be arranged. In practice there are different ones Charging electrodes and arrangements of Charging electrodes known. Furthermore, an or several charging electrodes also outside the Spray gun 2 in or next to the stream of atomized Powder can be arranged. Even such embodiments are known.

Die dargestellte Sprühpistole 2 ist an einem Maschinenteil oder einem Roboter 22 einer Sprühbeschichtungsanlage befestigt. Stattdessen könnte sie auch einen Handgriff aufweisen und als Hand-Sprühpistole verwendet werden.The spray gun 2 shown is on one Machine part or a robot 22 one Spray coating system attached. Instead, could they also have a handle and a hand-held spray gun be used.

Der zu beschichtende Gegenstand 4 oder 6 wird üblicherweise von einer Transportvorrichtung, welche nicht dargestellt ist, getragen und durch eine Sprühbeschichtungskabine hindurchtransportiert. Die Transportvorrichtung ist geerdet, so daß auch der von ihr getragene Gegenstand 4 oder 6 durch die Transportvorrichtung geerdet ist.The object 4 or 6 to be coated becomes usually from a transport device, which is not shown, worn and by a Spray coating cabin transported through. The Transport device is grounded, so that of her worn item 4 or 6 by the Transport device is grounded.

Die elektrische Hochspannung erzeugt elektrische Feldlinien 24, welche von der Spitze 26 der Aufladungselektrode 12 zu dem zu beschichtenden Gegenstand 4 oder 6 verlaufen. Die am Auslaß 10 versprühten Pulverpartikel bewegen sich entlang diesen Feldlinien 24 auf den zu beschichtenden Gegenstand 4 oder 6. Dabei dringen sie auch in Vertiefungen 28 des zu beschichtenden Gegenstandes ein und durch Öffnungen 30 dieses Gegenstandes hindurch. Dadurch gelangen die Partikel durch den "elektrischen Umgriffeffekt" in Randbereichen des Gegenstandes auch auf seine Rückseite 32, wie dies in Fig. 1 durch den Öffnungsrand 34 "umgreifende" Feldlinien 36 dargestellt ist. An vorstehenden Kanten 38 oder Ecken ergibt sich durch elektrostatische Wechselwirkungen eine stärkere Schichtdicke als auf erhobenen Flächen 40 oder größeren ebenen Flächen 42 des zu beschichtenden Gegenstandes 4.The electrical high voltage creates electrical Field lines 24, which from the tip 26 of the Charging electrode 12 to be coated Item 4 or 6 run. The outlet 10 sprayed powder particles move along these Field lines 24 on the object to be coated 4 or 6. They also penetrate into recesses 28 of the coating object and through openings 30 through this object. This will get the Particles due to the "electrical wrap-around effect" in Edge areas of the object also on its back 32, as shown in FIG. 1 by the opening edge 34 "Comprehensive" field lines 36 is shown. On protruding edges 38 or corners result from electrostatic interactions a stronger one Layer thickness than on raised areas 40 or larger flat surfaces 42 of the object 4 to be coated.

Das versprühte Pulver hat im Längsschnitt gesehen die Form einer Partikel-Wolke, wie sie in den Figuren 1 und 2 durch die Feldlinien 24 dargestellt ist.The sprayed powder has seen the in longitudinal section Shape of a particle cloud, as shown in Figures 1 and 2 is represented by the field lines 24.

In Fig. 1 ist koaxial zur Aufladungselektrode 12 eine ringförmige Gegenelektrode 44 angeordnet, welche ein anderes elektrisches Potential als die Aufladungselektrode 12 hat und dazu dient, freie Ionen abzusaugen, welche bei der elektrostatischen Aufladung des Pulvers erzeugt werden. Dabei zieht die Gegenelektrode 44 auch einige Elektronen an. Dieser Ionenstrom und sein Weg von der Aufladungselektrode 12 zur Gegenelektrode 44 ist mit der Bezugszahl 46 bezeichnet. Die Gegenelektrode 44 kann auf einem höheren oder niedrigeren elektrischen Potential liegen als die Aufladungselektrode 12. Vorzugsweise ist die Gegenelektrode 44 an Erdpotential 20 angeschlossen. Die Gegenelektrode 44 ist vorzugsweise entsprechend Fig. 1 entgegen der Strömungsrichtung 48 des Pulvers stromaufwärts von der Spitze 26 der Aufladungselektrode 12 koaxial zu ihr angeordnet, und damit außerhalb und stromaufwärts der den elektrischen Feldlinien 24 entsprechenden Pulver-Wolke.1 is coaxial with the charging electrode 12 arranged annular counter electrode 44, which a different electrical potential than the charging electrode 12 and serves to suck free ions, which are associated with electrostatic charging of the powder be generated. The counter electrode 44 also pulls some electrons. This ion current and its path from the charging electrode 12 to the counter electrode 44 is with the reference numeral 46 denotes. The counter electrode 44 can at a higher or lower electrical potential lie than the charging electrode 12. Is preferred the counter electrode 44 is connected to ground potential 20. The counter electrode 44 is preferably in accordance with FIG. 1 against the flow direction 48 of the powder upstream of the tip 26 of the charging electrode 12 arranged coaxially to her, and thus outside and upstream of the electric field lines 24 corresponding powder cloud.

Die äußere Oberfläche 50 der Pulver-Wolke, welche größenmäßig und formmäßig den elektrischen Feldlinien 24 entspricht, ist keine scharfe Wolkenbegrenzung, sondern ein diffuser Übergang zwischen einem Bereich gleichmäßiger Partikel-Verteilung und der umgebenden Atmosphäre. In der hier gegebenen Beschreibung wird unter "äußerer Oberfläche 50" der Pulver-Wolke der Bereich verstanden, wo die Partikel nicht mehr gezielt entlang Feldlinien 24 auf den zu beschichtenden Gegenstand 4 oder 6 fliegen, sondern aus dem Feldlinienbereich herausvagabundieren. Der Abstand "d" zwischen der Gegenelektrode 44 und der Aufladungselektrode 12, zwischen der Gegenelektrode 44 und der Spitze 26 der Aufladungselektrode 12, und zwischen der Gegenelektrode 44 und der äußeren Oberfläche 50 der Pulver-Wolke sollte kleiner sein als der Abstand "D" zwischen der Spitze 26 der Aufladungselektrode 12 und dem zu beschichtenden Gegenstand 4 oder 6. Vorzugsweise beträgt der Abstand "d" zwischen der Spitze 26 der Aufladungselektrode 12 und der Gegenelektrode 44 nur ein Drittel bis die Hälfte von dem Abstand "D" zwischen der Spitze 26 der Aufladungselektrode 12 und dem zu beschichtenden Gegenstand 4 oder 6.The outer surface 50 of the powder cloud, which the electric field lines 24 in size and shape is not a sharp cloud boundary, but a diffuse transition between areas even particle distribution and the surrounding The atmosphere. In the description given here, under "Outer surface 50" of the powder cloud the area understood where the particles are no longer targeted Field lines 24 on the object to be coated 4 or 6 fly, but vagabond out of the field line area. The distance "d" between the Counter electrode 44 and charging electrode 12, between the counter electrode 44 and the tip 26 of the Charging electrode 12, and between the counter electrode 44 and the outer surface 50 of the powder cloud should be smaller than the distance "D" between the tip 26 the charging electrode 12 and the one to be coated Item 4 or 6. Preferably the distance is "d" between the tip 26 of the charging electrode 12 and the Counter electrode 44 only a third to half of that Distance "D" between the tip 26 of the Charging electrode 12 and the one to be coated Item 4 or 6.

Eine Druckluft-Düsenanordnung 52 bläst Luft über die Gegenelektrode 44 oder in den Zwischenraum zwischen Gegenelektrode 44 und Aufladungselektrode 12, um ein Beschichten der Gegenelektrode 44 mit Pulver zu verhindern. Druckluft wird nur dann benötigt, wenn nicht auf andere Art ein Beschichten der Gegenelektrode 44 verhindert werden kann.A compressed air nozzle assembly 52 blows air over the Counter electrode 44 or in the space between Counter electrode 44 and charging electrode 12 to a Coating the counter electrode 44 with powder prevent. Compressed air is only needed if not otherwise coating the counter electrode 44 can be prevented.

Die Gegenelektrode 44 wird vorzugsweise vom Gehäuse 18 der Sprühpistole 2 getragen.The counter electrode 44 is preferably provided by the housing 18 the spray gun 2 worn.

Anstelle einer Aufladungselektrode 12 oder einer Gegenelektrode 44 können jeweils auch mehrere Elektroden vorhanden sein.Instead of a charging electrode 12 or one Counterelectrode 44 can also each have a plurality of electrodes to be available.

Die in Fig. 2 dargestellte Ausführungsform einer Sprühpistole 2 ist identisch mit der von Fig. 1, mit Ausnahme von mindestens einer Gegenelektrode 64, welche bei der in Fig. 2 dargestellten Ausführungsform eine nadelförmige Drahtelektrode ist. Sie wird koaxial von Druckluft 66 umspült und dadurch von Beschichtungsmaterial freigehalten. Vorzugsweise sind koaxial zur Aufladungselektrode 12 mehrere Gegenelektroden 64 angeordnet. Diese Gegenelektroden 64 sind vorzugsweise mit gleichem Umfangsabstand voneinander um die Aufladungselektrode 12 herum angeordnet. In Fig. 2 sind Teile, welche Teilen von Fig. 1 entsprechen, mit gleichen Bezugszahlen versehen.The embodiment shown in Fig. 2 Spray gun 2 is identical to that of Fig. 1, with Exception of at least one counter electrode 64, which in the embodiment shown in FIG is needle-shaped wire electrode. It will be coaxial from Compressed air 66 washed and thereby by Keep coating material clear. Are preferred several coaxial to the charging electrode 12 Counter electrodes 64 arranged. These counter electrodes 64 are preferably the same circumferential distance from each other arranged around the charging electrode 12. In Fig. 2 are parts which correspond to parts of Fig. 1 with provided with the same reference numbers.

Falls gewünscht, können Mittel 68 zur axialen oder/und radialen Positionierung der Gegenelektrode 44 oder 64 relativ zur Aufladungselektrode 12 vorgesehen sein.If desired, means 68 for axial or / and radial positioning of the counter electrode 44 or 64 be provided relative to the charging electrode 12.

Funktionsweisen der Ausführungsformen nach Fig. 1 und 2:Functions of the embodiments according to FIGS. 1 and 2:

a) Ohne Gegenelektrode 44 oder 64:a) Without counter electrode 44 or 64:

An der mindestens einen Aufladungselektrode 12, welche entsprechend den Figuren 1 und 2 eine axiale Nadelelektrode sein kann, oder aber in Form einer Vielzahl von solchen oder anderen Elektroden vorhanden sein kann, werden unter hoher elektrischer Spannung Elektronen freigesetzt. In der Nähe des hohen elektrischen Feldes 24 der Aufladungselektrode 12 wird ein kleiner Teil (ca. 1% bis 5%) der Elektronen auf das Beschichtungsmaterial, im vorliegenden Falle Pulver, geladen. Der Rest fliegt an die am nächsten liegende geerdete Stelle, beispielsweise ungefähr 80% auf den zu beschichtenden Gegenstand 4 oder 6, ungefähr 10% auf die Wände der Kabine, in welcher die Gegenstände beschichtet werden, und ungefähr 5% bis 20% auf das stromabwärtige Ende der Sprühpistole, je nach Distanz zwischen der Aufladungselektrode 12 und dem zu beschichtenden Gegenstand 4 oder 6. Das elektrostatisch geladene Pulver findet seinen Weg auf den zu beschichtenden Gegenstand 4 oder 6 und bleibt dort zum größten Teil haften. Dabei bildet das Pulver auf dem Gegenstand eine elektrisch isolierende Schicht. Die überschüssigen Elektronen bilden zusammen mit dem Pulver auf der Oberfläche des Gegenstandes 4 oder 6 eine erhöhte elektrische Ladung und stoßen später ankommende Pulver-Partikel ab. Auf der Oberfläche des Gegenstandes 4 oder 6 entsteht ein elektrostatisch instabiles Kräfteverhältnis. Dieser Mechanismus hinterläßt auf der Oberfläche eine "Hügellandschaft", welche nach dem Einbrennen der Schicht als "Orangenhaut" bezeichnet wird. Die freien Ionen in der Luft zwischen Aufladungselektrode 12 und zu beschichtendem Gegenstand 4 oder 6 bewegen sich mit einer sehr hohen Geschwindigkeit von über 100 m/s. Sie folgen dem betreffenden stärkeren elektrostatischen Feld, das heißt den elektrostatischen Kräften. Die elektrostatisch geladenen Pulver-Partikel unterliegen den kinematischen Strömungskräften, da sie in einem Gasstrom oder Luftstrom transportiert werden. Die Bewegungsgeschwindigkeit der Pulver-Partikel ist wesentlich kleiner als jene der Ionen und beträgt nur ungefähr 10 bis 15 m/s. Dies bedeutet, daß sich die Ionen unabhängig von den Pulver-Partikeln bewegen. On the at least one charging electrode 12, which corresponding to Figures 1 and 2 an axial Can be needle electrode, or in the form of a A variety of such or other electrodes are available can be under high electrical voltage Electrons released. Near the high electric field 24 of the charging electrode 12 a small part (approx. 1% to 5%) of the electrons on the Coating material, in the present case powder, loaded. The rest fly to the closest one grounded point, for example about 80% towards the coating article 4 or 6, about 10% on the Walls of the cabin in which the objects are coated and about 5% to 20% of the downstream End of the spray gun, depending on the distance between the Charging electrode 12 and the one to be coated Item 4 or 6. The electrostatically charged powder finds its way onto the object to be coated 4 or 6 and stays there for the most part. Here the powder forms an electrical on the object insulating layer. Form the excess electrons along with the powder on the surface of the Item 4 or 6 an increased electrical charge and repel powder particles arriving later. On the Surface of the object 4 or 6 arises electrostatically unstable balance of power. This Mechanism leaves one on the surface "Hilly landscape", which after burning in the layer is called "orange peel". The free ions in the air between the charging electrode 12 and coating object 4 or 6 move with a very high speed of over 100 m / s. you follow the stronger electrostatic field in question, the is called the electrostatic forces. The electrostatic charged powder particles are subject to kinematic Flow forces as they are in a gas stream or air stream be transported. The speed of movement of the Powder particles are much smaller than those of the ions and is only about 10 to 15 m / s. This means, that the ions are independent of the powder particles move.

Jedes einzelne Ion hat sein eigenes elektrostatisches Feld. In der Nähe eines Objektes ist dieses Feld aufgrund der kurzen Distanz zum geerdeten Objekt sehr stark. Deshalb ist auch der Faraday-Effekt entsprechend stark. Die freien Ionen bilden in ihrer Gesamtheit eine hohe elektrostatische Raumladung. Als Gesamtheit wirkt diese Raumladung deshalb als starker Faraday-Käfig an allen Ecken und Kanten des zu beschichtenden Gegenstandes, so daß sie ein gutes Eindringen der Pulver-Partikel in Vertiefungen und Nuten behindert.Every single ion has its own electrostatic Field. This field is due to the proximity of an object the short distance to the grounded object very strongly. Therefore the Faraday effect is correspondingly strong. The free ions form a high total electrostatic space charge. This works as a whole Space charge therefore as a strong Faraday cage on everyone Corners and edges of the object to be coated, see above that they have a good penetration of the powder particles into Depressions and grooves hampered.

b) Mit Gegenelektrode oder Gegenelektroden 44 oder 64:b) With counter electrode or counter electrodes 44 or 64:

Bei Verwendung einer Gegenelektrode werden die freien Ionen von der Gegenelektrode 44 oder 64 angezogen und aus dem Pulver-Strom abgeleitet. Die Gegenelektrode muß in der Nähe der Aufladungselektrode sein. Der Abstand "d" zwischen der Aufladungselektrode 12 und der Gegenelektrode 44 oder 64 beträgt vorzugsweise etwa ein Drittel bis die Hälfte des Abstandes "D" zwischen der Gegenelektrode und dem zu beschichtenden Gegenstand 4 oder 6. Wenn der Abstand "d" größer ist, verliert die Gegenelektrode ihre Wirkung; die freien Elektronen und Ionen werden stärker vom zu beschichtenden Gegenstand 4 oder 6 angezogen als von der Gegenelektrode 44 oder 64. Bei einem kleineren Abstand "d" fließt ein zu großer elektrischer Strom zwischen der Aufladungselektrode und der Gegenelektrode, wodurch die elektrische Hochspannung an der Spitze 26 der Aufladungselektrode und somit das zur Aufladung des Pulvers notwendige elektrostatische Feld 24 reduziert wird. Die Gegenelektrode 44 oder 64 bewirkt einen erhöhten elektrischen Stromfluß an der Spitze 26 der Aufladungselektrode 12. Dadurch werden von der Aufladungselektrode 12 wesentlich mehr freie Ionen oder Elektronen zur elektrostatischen Aufladung des Pulvers am Auslaß 10 der Vorrichtung 2 erzeugt und stehen dann zur elektrostatischen Aufladung zur Verfügung. Die elektrostatische Aufladung des Pulvers wird dadurch wesentlich verbessert. Außerdem wird dadurch auch der Auftragungswirkungsgrad des Pulvers auf den zu beschichtenden Gegenstand 4 oder 6 wesentlich verbessert. Die Gegenelektrode 44 oder 64 leitet den wesentlichen Teil der Ionen, ungefähr 60 bis 80% ab. Auf den zu beschichtenden Gegenstand 4 oder 6 fliegen nur noch die geladenen Pulver-Partikel, nämlich nur noch 2% bis 8% des gesamten elektrischen Stromes. Es gelingt also eine Trennung der unerwünschten freien Ionen vom Pulverstrom. Die Ionen-Raumladung besteht auch hier noch, jedoch konzentriert sich der Fluß von freien Ionen auf die Gegenelektrode 44 oder 64. Der Faraday-Effekt ist sehr stark an der Gegenelektrode, jedoch nur sehr klein an dem zu beschichtenden Gegenstand 4 oder 6. Die elektrostatisch geladenen Pulver-Partikel dringen dadurch besser in Vertiefungen und Nuten des Gegenstandes 4 oder 6 ein. Auch der "elektrostatische Umgriff" ist besser. An der Oberfläche des Gegenstandes 4 oder 6 entsteht keine Anhäufung von freien Ionen. Die elektrostatischen Kräfte an der Oberfläche des Gegenstandes 4 oder 6 sind wesentlich kleiner. Es herrscht kein instabiler Zustand an der Oberfläche. Die Bildung einer Orangenhaut ist gehemmt. Es kann eine wesentlich dickere Pulver-Schicht auf den Gegenstand 4 oder 6 in einem einzigen Sprühvorgang aufgebracht werden. Da die Gefahr besteht, daß die Gegenelektrode 44 oder 64 von dem elektrostatisch geladenen Pulver ebenfalls beschichtet wird, ist es zweckmäßig die Gegenelektrode 44 oder 64 mit Druckluft zu spülen. Zur Vermeidung einer Beschichtung der Gegenelektrode 44 oder 64 ist es zweckmäßig, wenn sie außerhalb des Pulverstromes angeordnet ist, wobei sie vorzugsweise mit Bezug auf die stromabwärtige Spitze 26 der Aufladungselektrode 12 stromaufwärts zurückgesetzt ist, und nicht zwischen Aufladungselektrode 12 und dem zu beschichtenden Gegenstand 4 oder 6 angeordnet ist.When using a counter electrode, the free Ions are attracted to and out of the counter electrode 44 or 64 derived from the powder stream. The counter electrode must be in be close to the charging electrode. The distance "d" between the charging electrode 12 and the Counter electrode 44 or 64 is preferably approximately one Third to half the distance "D" between the Counter electrode and the object to be coated 4 or 6. If the distance "d" is greater, the loses Counter electrode their effect; the free electrons and Ions become stronger from the object to be coated 4 or 6 attracted as from the counter electrode 44 or 64. If the distance "d" is smaller, the flow is too large electric current between the charging electrode and the counter electrode, causing the high voltage electrical at the tip 26 of the charging electrode and thus that electrostatic necessary to charge the powder Field 24 is reduced. The Counter electrode 44 or 64 causes an increased electrical current flow at the tip 26 of the Charging electrode 12. This causes the Charging electrode 12 much more free ions or Electrons for electrostatically charging the powder on Outlet 10 of the device 2 generated and are then available electrostatic charge available. The This causes electrostatic charging of the powder significantly improved. It will also make the Application efficiency of the powder to the coating object 4 or 6 significantly improved. The counter electrode 44 or 64 conducts the essential Part of the ions, about 60 to 80% off. Towards the coating object 4 or 6 only fly the charged powder particles, namely only 2% to 8% of the total electrical current. So one succeeds Separation of the unwanted free ions from the powder stream. The ion space charge still exists here, however the flow of free ions concentrates on the Counter electrode 44 or 64. The Faraday effect is very strong on the counter electrode, but only very small on the object 4 or 6 to be coated electrostatically charged powder particles penetrate through it better in depressions and grooves of the object 4 or 6 a. The "electrostatic wrap" is also better. On the surface of the object 4 or 6 does not arise Accumulation of free ions. The electrostatic forces are 4 or 6 on the surface of the object much smaller. There is no unstable condition on the surface. The formation of an orange peel is inhibited. It can be a much thicker powder layer on item 4 or 6 in one Spraying process can be applied. Because of the danger that the counter electrode 44 or 64 from the electrostatic charged powder is also coated, it is expediently the counterelectrode 44 or 64 with compressed air do the washing up. To avoid coating the Counter electrode 44 or 64, it is useful if they is arranged outside the powder stream, being preferably with respect to the downstream tip 26 the charging electrode 12 upstream reset is, and not between the charging electrode 12 and the Coating object 4 or 6 is arranged.

Der elektrische Strom an der Aufladungselektrode ist bei Verwendung einer Gegenelektrode 44 oder 64 höher. Der Strom stieg bei Versuchen von ungefähr 70 µA auf ungefähr 100 µA. . Die Pulver-Wolke bildet einen elektrischen Widerstand und begünstigt den Ionenfluß zur Gegenelektrode 44 oder 64.The electrical current at the charging electrode is at Use a counter electrode 44 or 64 higher. Of the Current rose in experiments of approximately 70 µA about 100 µA. . The powder cloud forms one electrical resistance and favors the flow of ions to the Counter electrode 44 or 64.

Die in den Fig. 3 und 4 dargestellte elektrostatische Sprühvorrichtung 2 besteht im wesentlichen aus einem rohrartigen Sprühkörper 3, an dessen stromabwärtigem Ende eine Schlitzdüse 70 zum Zerstäuben des pneumatisch geförderten Pulvers befestigt ist. Innerhalb der Sprühdüse 70 oder des Sprühkörpers 3 befindet sich mindestens eine Aufladungselektrode 12 zum elektrostatischen Aufladen des Pulvers. Auf den stromabwärtigen Abschnitt 72 des Sprühkörpers 3, an welchem die Sprühdüse 70 befestigt ist, ist ein ringförmiger Körper 74 aufgesteckt, welcher eine Gegenelektrode bildet und/oder mehrere nadelartige Gegenelektroden 76 trägt, welche aus ihm herausragen. Die Gegenelektroden 74 und 76 sind an ein elektrisches Potential, vorzugsweise an Erdpotential, angeschlossen, welches verschieden ist vom elektrischen Potential der Aufladungselektrode 12. Der ringförmige Körper 74 ist am stromabwärtigen Ende eines Verbindungssteges 78 befestigt, welcher sich achsparallel zum Sprühkörper 3 erstreckt und mit seinem stromaufwärtigen Ende 80 in einen Halter 22 eingesteckt und dort durch eine Schraube mit einem gerändelten Schraubenkopf 84 axial positioniert ist.The electrostatic shown in Figs. 3 and 4 Spray device 2 consists essentially of a tubular spray body 3, at its downstream end a slot nozzle 70 for atomizing the pneumatically conveyed powder is attached. Within the Spray nozzle 70 or the spray body 3 is located at least one charging electrode 12 for electrostatic charging of the powder. On the downstream section 72 of the spray body 3 which the spray nozzle 70 is attached to is a annular body 74 plugged, which one Counter electrode forms and / or several needle-like Counter electrodes 76 which protrude from it. The Counter electrodes 74 and 76 are connected to an electrical one Potential, preferably connected to earth potential, which is different from the electrical potential of the Charging electrode 12. The annular body 74 is at downstream end of a connecting web 78 attached, which is axially parallel to the spray body 3rd extends and with its upstream end 80 in inserted a holder 22 and there by a screw axially positioned with a knurled screw head 84 is.

Fig. 4 zeigt die Sprühvorrichtung 2 von Fig. 3 mit abgenommener Gegenelektroden-Vorrichtung 86, wobei mit Pfeilen 88 die Bewegungsrichtung zum Aufstecken des ringförmigen Körpers 74 auf dem stromabwärtigen Abschnitt 72 dargestellt ist. Ferner ist durch einen Pfeil 90 die Einsetzrichtung für die Schraube 84 in eine Gewindebohrung 91 im Halter 22 dargestellt. Fig. 4 zeigt einen Erdpotentialanschluß 20. Der Erdpotentialanschluß 20 kann direkt an den Verbindungssteg 78 angeschlossen sein, wenn er und der ringförmige Körper 74 aus elektrisch leitendem Material bestehen. Wenn mindestens der Verbindungssteg 78 aus elektrisch isolierendem Material besteht, ist eine den Erdpotentialanschluß 20 mit den Gegenelektroden 76 verbindende elektrische Leitung 73 vorgesehen, welche sich durch den Verbindungssteg 78 und den ringförmigen Körper 74 erstreckt. Der ringförmige Körper 74 besteht aus elektrisch leitendem Material, wenn er als Gegenelektrode wirkt. Wenn er nicht als Gegenelektrode wirken soll, kann er aus elektrisch isolierendem Material bestehen. Der Erdpotentialanschluß 20 kann durch den Träger 22 gebildet sein, wenn er aus elektrisch leitendem Material besteht. FIG. 4 shows the spray device 2 from FIG. 3 with removed counter-electrode device 86, with Arrows 88 the direction of movement for attaching the annular body 74 on the downstream portion 72 is shown. Furthermore, the arrow 90 Direction of insertion for the screw 84 in a Threaded bore 91 shown in the holder 22. Fig. 4 shows an earth potential connection 20. The earth potential connection 20 can be connected directly to the connecting web 78 be when he and the annular body 74 out consist of electrically conductive material. If at least the connecting web 78 made of electrically insulating Material is, is a ground potential terminal 20th electrical connecting to the counter electrodes 76 Line 73 provided which is through the Connecting web 78 and the annular body 74 extends. The annular body 74 consists of electrically conductive material when used as a counter electrode works. If it should not act as a counter electrode, it can he consist of electrically insulating material. Of the Earth potential connection 20 can be formed by the carrier 22 if it is made of electrically conductive material.

In Fig. 5 ist eine pistolenförmige elektrostatische Sprühvorrichtung 2 dargestellt. Nahe des stromaufwärtigen Endes 94 ihres Sprühkörpers 3 ist der Sprühkörper mit einem Handgriff 95 versehen. Das stromaufwärtige Ende 80 des Verbindungssteges 78 und die Schraube 84 befinden sich unmittelbar über dem Griff 95 am Sprühkörper 3. Dadurch kann die elektrische Erdungsleitung 73 am Griff 95 oder durch ihn hindurch zum Erdpotentialanschluß 20 geführt werden. Dies hat den Vorteil, daß der Material-Schwerpunkt der Sprühvorrichtung 2 im oder in der Nähe des Griffes 95 liegt, damit ein ermüdungsfreies Halten der Pistole möglich ist. In Fig. 5 ist die Aufladungselektrode 12 als axiale Elektrode dargestellt, während in den Fig. 3 und 4 angenommen wurde, daß mehrere nadelartige Aufladungselektroden 12 um den Pulverweg herum verteilt angeordnet sind.5 is a pistol-shaped electrostatic Spray device 2 shown. Near the upstream end 94 of its spray body 3 is the Provide the spray body with a handle 95. The upstream end 80 of the connecting web 78 and the Screw 84 are located immediately above the handle 95 on the spray body 3. This can the electrical Ground line 73 on the handle 95 or through it to Earth potential connection 20 are performed. This has the Advantage that the material focus of the Spray device 2 in or near the handle 95 so that the pistol is held without fatigue is possible. 5 is the charging electrode 12 shown as an axial electrode, while in Fig. 3rd and 4 it was assumed that several needle-like Charging electrodes 12 distributed around the powder path are arranged.

Bei allen Ausführungsformen ist der ringförmige Körper 74 vorzugsweise auf verschiedene axiale Positionen relativ zum Sprühkörper 3 einstellbar. In allen Fällen befindet sich der ringförmige Körper 74, wenn er als Gegenelektrode wirkt oder Gegenelektroden 76 trägt, stromaufwärts der Spitze 26 der Aufladungselektrode 12.In all embodiments, the annular body is 74 preferably relative to different axial positions adjustable to spray body 3. In all cases the annular body 74 when it is as Counter electrode acts or carries counter electrodes 76, upstream of the tip 26 of the charging electrode 12.

Claims (10)

  1. An electrostatic spray apparatus for the electrostatic spray coating of articles with powder, which has the following features:
    a tubular spray body (3); at least one charging electrode (12) at the downstream end portion (72) of the spray body (3) for the transmission of electrostatic charges to the powder; the charging electrode (12) has an electrical potential which is different from the electrical potential of the article to be coated in such a way that the charged powder is electrostatically attracted by the article; at least one counter-electrode (44; 64; 74, 76) which is arranged in the proximity of the charging electrode (12) at the downstream end portion (72) of the spray body (3) and which is connected by way of an electrical connecting means (22, 84, 91) to a different electrical potential (20) from the charging electrode (12) so that it receives at least a part of the free ions produced upon electrostatic charging of the powder; and at least one annular body (44; 68; 74) which forms or carries the counter-electrode (44; 64; 74, 76) and which extends around the downstream end portion (72) of the spray body (3) on which it is radially supported;
       characterised in that the electrical connecting means (22, 84, 91) is arranged at the upstream end portion of the spray body (3), that there is provided at least one connecting bar (78) which extends from the electrical connecting means (22, 84, 91) at the upstream end portion of the spray body (3) to the annular body (44; 68; 74) at the downstream end portion of the spray body (3) outside the spray body (3) and parallel thereto, that the connecting bar (78) comprises electrically insulating material and an electrical line (73) extending through the insulating material, that the downstream end (79) of the connecting bar (78) carries the annular body (74) and the upstream end of the connecting bar (78) is releasably fixed to the electrical connecting means (22, 84, 91) in the proximity of the upstream end of the spray body (3), wherein the electrical line (73), the electrical connecting means (22, 84, 91) and the counter-electrode (44; 64; 74, 76) are electrically connected together.
  2. A spray apparatus according to claim 1 characterised in that the electrically insulating material of the connecting bar (78) is a tube.
  3. A spray apparatus according to one of the preceding claims characterised in that a plurality of counter-electrodes (76) in the form of needle electrodes project out of the annular body (74).
  4. A spray apparatus according to one of the preceding claims characterised in that the spacing (d) between the charging electrode (12) and the counter-electrode (44; 64, 64/2) is smaller than the spacing (D) between the charging electrode (12) and the article (4; 6) to be coated.
  5. A spray apparatus according to claim 4 characterised in that the spacing (d) between the charging electrode (12) and the counter-electrode (44; 64) is a third to half the spacing (D) between the charging electrode (12) and the article (4; 6) to be coated.
  6. A spray apparatus according to one of the preceding claims characterised in that there are provided means (52; 66) by which compressed air (66) is caused to flow around the counter-electrode (44; 64) in order to keep it free from coating material.
  7. A spray apparatus according to one of the preceding claims characterised in that the counter-electrode (44; 64; 74, 76) is arranged upstream of the downstream end (26) of the charging electrode (12).
  8. A spray apparatus according to one of the preceding claims characterised in that the counter-electrode (44; 64) is arranged at a spacing from the atomised powder cloud and that the spacing (d) between the counter-electrode (44; 64) and the powder cloud is smaller than the spacing (D) between the charging electrode (12) and the article (4; 6) to be coated.
  9. A spray apparatus according to one of the preceding claims characterised in that the counter-electrode (44; 64) is connected to earth potential.
  10. A spray apparatus according to one of the preceding claims characterised in that the counter-electrode (44; 64) is displaceable in the axial and/or radial direction relative to the charging electrode (12) and can be arrested in the selected position by positioning means (68; 84).
EP94102449A 1993-04-15 1994-02-18 Electrostatic spray device Expired - Lifetime EP0620045B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4312262 1993-04-15
DE4312262A DE4312262A1 (en) 1993-04-15 1993-04-15 Electrostatic spray device

Publications (2)

Publication Number Publication Date
EP0620045A1 EP0620045A1 (en) 1994-10-19
EP0620045B1 true EP0620045B1 (en) 1998-07-29

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EP94102449A Expired - Lifetime EP0620045B1 (en) 1993-04-15 1994-02-18 Electrostatic spray device

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US (1) US5584931A (en)
EP (1) EP0620045B1 (en)
CN (1) CN1072527C (en)
AT (1) ATE168903T1 (en)
DE (2) DE4312262A1 (en)
ES (1) ES2118991T3 (en)
TW (1) TW258672B (en)

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Also Published As

Publication number Publication date
ES2118991T3 (en) 1998-10-01
DE59406528D1 (en) 1998-09-03
EP0620045A1 (en) 1994-10-19
TW258672B (en) 1995-10-01
US5584931A (en) 1996-12-17
DE4312262A1 (en) 1994-10-20
CN1072527C (en) 2001-10-10
ATE168903T1 (en) 1998-08-15
CN1101305A (en) 1995-04-12

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