DE7717280U1 - Atomizer head for an electrostatic spray gun - Google Patents

Description

, INGKALI-MINtIII . ^. . ^, ^,. ; ₂ HAMBURG 1, the UÄ..1SLZZ.

PATENT ADVOCATE ealllndamm 15 _{M / F1}

Telephone: 33 51 15

Bank; Commerzbank AG, account no. 38/57 554

Postal check: Hamburg 2509 00

My files: 5930/77

S. K. M. S.A.

150, avenue de Stalingrad

93240 Stains (France)

ATOMIZER HEAD FOR AN ELECTROSTATIC SPRAY GUN

(For this application, the priority is taken from the corresponding French application No. 76 17325 of Claimed June 9, 1976.)

The invention relates to an atomizer head for an electrostatic Spray gun for applying paints, varnishes or the like. Liquids, which consists of a housing an electrically insulating material comprising an atomizing nozzle made of metal and at least one with respect to Ground and the material to be sprayed on a direct current high voltage - (_ needle-shaped main ionization electrode which can be brought into potential and is arranged in the vicinity of the spray of paint atomized by the atomizing nozzle having, the atomizing nozzle being electrically isolated from the main ionizing electrode is.

Sprühzerstäubervorrichtungen for applying paints, varnishes and the like. Liquids using electrostatic Forces are commonly referred to as electrostatic spray guns. With these spray guns the paint, the varnish or a corresponding liquid splashes and atomizes either in a purely pneumatic way,

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in a purely hydrostatic manner or by means of a combination of hydrostatic and pneumatic effects. The color particles finely atomized in one of these three ways are formed by means of a main ionizing electrode charged and directed against the material to be sprayed or coated by means of a directed electric field, which is generally at earth or ground potential. This directed electric field is for example generated by a field electrode, which in turn protrudes, for example, freely in the air (i.e. not embedded) is arranged and charged by the main ionization electrode by the effect of influence.

Electrostatic spray guns of this type are used in many cases in flammable or potentially explosive atmospheres used in which the generation of strong sparks must be avoided if possible. Can cause sparking it come, for example, when that is on earth or Spray material located at ground potential in the vicinity of the parts of the spray gun that are under high voltage, in particular the main ionization and field electrodes, which are located on the spray head of the gun.

To avoid sparks between these electrodes and one that is close to them and is at ground potential Various measures have already been proposed. For example, immediately behind the electrodes, i.e. on their upstream side, have high impedances (Resistors) are interposed by which the spark energy is limited. They can also Main ionization and field electrodes are fed by a voltage source of limited power, so that no greater capacitance can develop between the voltage source and the electrodes. In this case, call

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the approach of a ground or ground potential Object to the main ionization or the field electrode, a so-called tip discharge emerges, through which the voltage of these electrodes is lowered depending on the approach of the object. To ensure that this protection is fully effective, regardless of the direction in which the atomizer head the object on earth potential! is approached are generally around the atomizing head J the electrostatic spray gun around small auxiliary | electrodes provided and connected to the main electrodes. ^ These auxiliary electrodes are designed to achieve a perfect Operation of the spray gun advantageously in the insulating one that forms the housing of the atomizer head Material embedded.

In electrostatic spray guns, however, the atomizing nozzle is generally made of metal and is attached to the brought the same direct current high voltage potential as the main ionization electrode. With such a structure there are no difficulties as long as the color, the varnish or otherwise by means of the atomizer head

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^ The sprayed liquid is not conductive or has a high electrical resistance. If, however, the sprayed paint or the like. Liquid has good electrical conductivity, the DC high voltage applied to the atomizer nozzle is transmitted by means of the conductive paint or liquid to the parts of the spray gun that supply the paint or the liquid, which is why they are therefore isolated from ground otherwise dangerous contact voltages result for the user of the electrostatic spray gun. Atomizer heads for electrostatic spray guns have also been used to eliminate this potential source of danger

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proposed in which the atomizer nozzle is electrically isolated from the main ionization electrode. In this case, the atomizing nozzle has a high capacity, which is due to its close proximity to charge main ionization and field electrode by influence from these electrodes and a very can absorb significant electrical charge.

If the atomizer head is therefore approached an object which is at ground potential, the through the atomizer nozzle The capacity that has formed can be brought to a sudden discharge, resulting in strong sparking comes. Since this spark can be very powerful, there is a possibility that it could be in a fire or explosion hazard An atmosphere that has, for example, solvent vapors contained in the paint, a deflagration or even cause a violent explosion.

On the other hand, conductive paints and varnishes are generally water-soluble. From this side there is somithin a low risk of fire and explosion, and the hazard is only to the operator given. It must therefore be avoided that with current transfer between the electrodes under high voltage and a high current discharge may occur to an operator. Must in all cases it must be ensured that the charge stored in the atomizer nozzle flows "into the air", so that no Spark transfer to an object at ground potential or to a person coming too close to the nozzle can be done. Even if the conductivity of the paint is sufficiently high, this charge cannot pass through it be brought to drain to earth, since the discharge of the charge in this way only at the expense of the high voltage

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could occur and this would collapse if too high a current transfer from the nozzle through the paint to earth would take place.

The invention is therefore based on the object of providing one for atomizing electrically conductive or non-conductive To create paints, varnishes and the like. Liquids suitable atomizer head, in which the atomizer nozzle in with respect to the main ionization and field electrodes is electrically isolated, and still has a high level of operational reliability against strong discharges of the atomizer nozzle representing a capacity.

The atomizer head proposed to solve the problem posed the embodiment mentioned at the beginning is characterized according to the invention in that the atomizer nozzle electrically with at least one free in the air and to avoid affecting the emission of the Main ionization electrode is connected sufficiently far away from this arranged, pointed auxiliary electrode.

Due to this pointed auxiliary electrode, the the "in the open air" atomizer nozzle and the paint feed and supply circuit of the spray gun, which for highly conductive paint is isolated from ground, capacitance formed when one approaches ground potential too closely object or person to the nozzle due to the tip effect, whereby the Reduced potential and a strong discharge from the nozzle to the object or a ground potential Person is avoided.

The atomizer head proposed according to the invention is in

It · · ·! III MM

• · · ■ · ■ · ·

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explained in more detail below with reference to the exemplary embodiment shown in the drawing. In the drawing is

Fig. 1 is an end plan view of a

atomizer head designed according to the invention,

Fig. 2 is a cross section along the line II-II of Fig. 1 and

Fig. 3 is a cross section along the line III-III of Fig. 1.

The atomizer head 1 shown in the drawing consists of a housing 2 made of an electrically insulating one Material which can be fastened in a manner known per se to the front end of a spray gun, not shown here is. The housing 2 has, in a manner known per se, a cylinder part 3 which has a metal in its center produced atomizer nozzle 4 carries, and two projections 5 and 6, which protrude over the cylinder part 3 to the front and are formed opposite one another on both sides of the atomizing nozzle 4.

The atomizer nozzle 4 can be of a design known per se and in particular from a hydrostatic paint atomizer nozzle exist, which creates a flat, fan-shaped jet of paint.

In the two projections 5 and 6 can in a known manner for supplying compressed air or another Cross channels 7 and 8 (FIG. 2) serving compressed gas and longitudinal channels 9 and 10 connected to these may be provided. There these channels do not affect the subject matter of the invention not discussed further here. It is here

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only noted that the number, shape and location of these channels according to the desired effect and the atomization process used (purely pneumatic atomization, purely hydrostatic atomization or hydrostatic atomization with additional compressed air jets) can be adapted.

The projection 5 carries, in a manner known per se, a needle-shaped main ionization electrode 11 which can be connected via a conductor 12 and a contact 13 to a direct current high voltage generator, not shown here. The projection 6 carries, in a manner known per se, a field electrode 14 with a rounded tip, which protrudes freely into the air and is arranged opposite the main ionization electrode 11. The two electrodes 11 and 14 are located in an axial plane which is perpendicular to the horizontal axial plane which runs through the slot of the atomizer nozzle 4 and in which the flat, atomized ink jet is emitted. The two electrodes 11 and 14 are practically perpendicular to the flat, atomized paint jet and sized in its dimensions so that their mutually opposite on both sides of the flat paint jet \ J ends in relatively small distances from the two flat side surfaces of the ink jet, but outside of the same.

A violent discharge of the field electrode 14 when an object at ground potential approaches To avoid from the front or from the side, the field electrode 14 is electrically connected in a manner known per se pointed auxiliary discharge electrodes 15 and 16 connected, which at the same time play a role in the functioning of the atomizer head. Guarantee due to their excellent effect they ensure a continuous current transfer

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by means of corona discharge between the main ionization electrode 11 and the field electrode located in the open air 14. Therefore the color always penetrates an ionized space between the last two electrodes mentioned.

As can be seen in particular from FIG. 2, the metallic atomizer nozzle 4 is opposite the two electrodes 11 and 14 electrically insulated and therefore forms a high capacitance, which starts from the electrodes 11 and 14 through the influence of the influence can be charged. In order to avoid that this capacitance is at ground potential when one approaches The object suddenly deflates and, under certain circumstances, dangerous spark formation occurs, According to the invention, two small auxiliary electrodes 17 and 18 are provided and electrically connected to the metallic one Atomizer nozzle 4 connected. These two auxiliary electrodes 17 and 18 protrude freely into the air and must be a sufficient distance away from the main ionization electrode 11 be arranged so that they do not hinder the emission of this electrode. The auxiliary electrodes 17 and 18 discharge thus the atomizing nozzle 4 due to the tip discharge effect when approaching a ground potential

P \ J borrowed object or person.

£ apparent in particular from FIG. 1, the two

Auxiliary electrodes 17 and 18 in the horizontal axial plane, i.e. arranged in a plane perpendicular to the perpendicular axial plane containing the two electrodes 11 and 14. As can also be seen from FIG. 3, the two auxiliary electrodes 17 and 18 extend laterally Direction from the atomizer head 1 outwards and forwards so that their tips over the side surfaces of the two projections 5 and 6 protrude and in each case at least one tip when approaching a ground potential

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union object from the front or from the side facing this and, so to speak, "seen from the object" will".

The two auxiliary electrodes 17 and 18 be formed from a thin conductor wire 19, which is in electrical Contact with at least a portion of the atomizing nozzle located inside the insulating housing 2 4 stands. In particular, the conductor wire 19 can be in electrical contact with part of the peripheral surface of a Stand ring body 20, which is normally arranged around the atomizing nozzle 4 and with this in electrical Contact is available. As Fig. 3 shows, these are the two auxiliary electrodes 17 and 18 forming ends of the conductor wire 19 carried out through two openings 21 and 22 in the front wall of the insulating housing 2 and are from this outward.

Although the invention corresponds to that described above and the embodiment shown in the drawing using an atomizer head for an electrostatic Spray gun is described in which the atomization of the paint jet hydrostatically with additional Compressed air blasting takes place, it must be pointed out that the invention also applies to all other types of Atomizer heads can be used in which the atomizer nozzle is electrically isolated from the main electrodes 11 and 14 is. If this condition is met, the invention can be applied in particular to atomizer heads for electrostatic Use spray guns in which the paint atomization is purely hydrostatic or purely pneumatic Way done.

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Many modifications and further refinements are possible. Thus the number and the position of the auxiliary electrodes assigned to the atomizing nozzle 4 can be changed according to the conditions of use, provided of course /
that the auxiliary electrodes are the emission of the main electrodes
11 and 14 do not interfere and are always sufficiently visible for objects that are approaching the atomizer head and are at ground potential. In addition, the shape and / or the position of the main ionization electrode 11 and field electrode 14 can be adapted in the same way to different and known designs of atomizer heads
will.

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Claims (1)

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• r · · · «Ff * ff -11 - -Pafe claims Atomizer head for an electrostatic spray gun for applying paints, varnishes or the like. Liquids on a spray material, consisting of a housing made of an electrically insulating material, the one made of metal atomizer nozzle and at least one, with respect to mass and the spray material to one Direct current high voltage potential can be brought in the vicinity of the spray of paint atomized by the atomizer nozzle having arranged needle-shaped main ionization electrode, the atomizing nozzle opposite the main ionization electrode is electrically isolated, characterized in that the Atomizer nozzle (4) electrically with at least one free in the air and to avoid impairment the emission of the main ionization electrode (11) arranged sufficiently far away from it Auxiliary electrode (17 or 18) is connected. The atomizer head of claim 1, wherein the insulating Housing a cylinder part with the atomizer nozzle held in the middle and two protruding forward, has opposing projections on opposite sides of the nozzle, one of which carries the main ionization electrode, the tip of which is directed against the jet of paint emitted by the atomizing nozzle is directed, while the other projection is a protruding into the air, the main ionization electrode the other side of the color beam opposite field electrode carries, the main xonization electrode and the field electrodes are arranged essentially in a first axial plane, characterized in that 7717280 02/23/78 that the atomizer nozzle (4) electrically with two, in a perpendicular to the first axial plane, second Auxiliary electrodes arranged in the axial plane (17 and 18) connected is. 3. Atomizer head according to claim 2, characterized in that the two auxiliary electrodes (17 and 18) laterally outwards and towards the front of the atomizer head (1) protrude, their tips protrude beyond the side surfaces of the projections (5, 6) and at least a tip when approaching an object at ground potential from the front or the side facing this. 4. atomizer head according to claim 2 or 3, characterized in that that the two auxiliary electrodes (17 and 18) formed by a single, thin conductor wire (19) are in electrical contact with at least one located inside the insulating housing (2) Section of the atomizer nozzle (4) stands, and its ends through two openings (21 and 22) in the front wall of the housing (2) are guided and protrude from this. 77172M 02/23/78