EP1588780A1 - Fluidising device containing electrodes for a powder coating equipement - Google Patents

Abstract

The fluidising plate (5) for fluidising a powder coating powder using a fluidising gas is made of a material permeable to the gas but not to the powder. The fluidising plate has an electrode (10) of electrically conductive material to remove static electricity from the coating material and reduce the risk of ignition of the air-powder mixture.

Description

The invention relates to a fluidizing body for fluidization a coating powder according to the preamble of Claim 1.

In powder coating plants, the coating powder is in usually in the fluidized state as a powder-air mixture transported, with the powder-air mixture similar to a liquid behaves and therefore easily promoted can. The generation of the powder-air mixture is also called Fluidization refers to and usually takes place in one Powder chamber, as for example from US 4,615,649 and WO 94/22589 is known. The powder chamber is here with the Coating powder filled, with the bottom of the powder chamber consists of a porous material that is permeable to air, but is powder impermeable. By also as a fluid floor designated bottom of the powder chamber is used to produce the Powder-air mixture compressed air injected into the powder chamber, whereby the coating powder is fluidized.

The fluid bottom usually consists of an electric insulating material, because the electrostatically charged Powder dust particles otherwise attracted to the fluid bottom would, resulting in contaminants on the fluid floor could lead.

A disadvantage of the above-described powder chamber for Fluidization of the coating powder is the fact that between the electrostatically charged coating powder and the electrically insulating fluid bottom or in reverse Direction electrical discharges can occur, the in a coating powder with a high particulate matter content and a correspondingly low minimum ignition energy to one Inflammation of the powder-air mixture can result.

Furthermore, from US 5 518 546 a fluidizing device in which two electrodes are arranged in the powder chamber are. The one electrode is in this case within the powder chamber arranged in the upper area and is in operation charged to high voltage. The other electrode is against it within the powder chamber in the lower area above the Fluid bottom arranged and electrically grounded. Operational An electric current forms between these two electrodes Field off, causing the located in the powder chamber Powder particles are electrostatically charged and therefore adhere better to the workpiece to be coated, therefore is electrically grounded. The grounded electrode is used but only as an earth electrode for electrical charging the powder particles and does not prevent their electrostatic Charging by the electrically insulating Fluid soil is caused. In addition, the grounded Electrode in this case a separate component, which the production cost elevated.

Furthermore, from DE-OS 27 04 714, US 3,660,136, US 4,078 519 and DE 32 37 830 A1 Fluidisierungsvorrichtungen with high voltage electrodes known. The high voltage electrodes serve but not for discharging static electricity, but have just the reverse the task, the To electrostatically charge powder particles in the powder chamber, so that the powder particles better to be coated on the Stick workpiece, which is therefore electrically grounded.

Finally, from WO 03/097247 A1 another conventional Fluidization device known that no electrode assembly having.

The invention is therefore based on the object, the beginning to improve the known fluid floor described above, that inflammations of the powder-air mixture by electrical Discharges between the coating powder and the fluid bottom or in the reverse direction even at a high particulate matter can be reliably prevented.

This object is achieved by a fluidizing body according to the invention solved according to the preamble of claim 1.

The invention comprises the general technical teaching, a Provide electrode assembly, via the static electricity is derived from the coating powder before the stored charge amount is sufficient for an electrical Discharge the ignition energy of the powder-air mixture to exceed.

The fluidizing body according to the invention therefore preferably has an electrode assembly, which in the fluidization body is integrated. A distinction must be made between electrode arrangements, the structurally of the fluidizing body are arranged separately and spatially spaced.

The electrode arrangement may be formed, for example, as a grid be, wherein the grid-shaped electrode arrangement is preferably embedded in the surface of the fluidizing body is. In a plate-shaped fluidizing body according to the above-mentioned prior art is the grid-shaped electrode arrangement, preferably on the side arranged the powder-air mixture.

Preferably, the grid-shaped electrode arrangement divides the surface of the fluidization body into a plurality of grid surfaces, each having a size of less than 500 cm ² , 250 cm ² , 100 cm ² , 50 cm ² , 25 cm ² , 20 cm ² , 16 cm ² or 4 cm ² have. This dimensioning of the lattice-shaped electrode arrangement is advantageous, since in this way it is also possible to use coating powders whose ignition energy is less than 3 mJ.

In another variant of the invention, the electrode arrangement for discharging static electricity at least a pointed electrode passing through the porous material the fluidizing body is guided, wherein the free tip of the electrode preferably in the powder chamber protrudes.

In a preferred embodiment of the invention the electrode assembly even a plurality of pointed electrodes due to the porous material of the fluidizing body through and over the fluidizing body are distributed so that the pointed electrodes quasi make a needle carpet.

The individual pointed electrodes of this needle carpet each include free surfaces of the fluidizing body, the size of the free surfaces preferably being less than 500 cm ² , 250 cm ² , 100 cm ² , 50 cm ² , 25 cm ² , 20 cm ² , 16 cm ² or 4 cm ² . This offers the advantage that it is also possible to use coating powder which has an ignition energy of less than 3 mJ.

In another variant of the invention, the electrode arrangement on the other hand, several electrode rings on the surface the fluidization body arranged and electrically connected to each other. For example, the electrode rings be circular or elliptical, however, are also non-circular configurations of the electrode rings possible.

Preferably, the electrode rings each include an annular area of less than 500 cm ² , 250 cm ² , 100 cm ² , 50 cm ² , 25 cm ² , 20 cm ² , 16 cm ² or 4 cm ² . This in turn offers the advantage that it is also possible to use a coating powder which has an ignition energy of less than 3 mJ.

It has already been discussed above in the discussion of the prior art The technique pointed out that the porous material of the Fluidizing body is preferably electrically insulating, an attraction between the fluidizing body material and the electrostatically charged powder dust particles to prevent. For the same reason is the porous material of the fluidization body according to the invention preferably also electrically insulating.

Furthermore, it should be mentioned that the invention is not based on plate-shaped Fluidizing body is limited, as in described in the cited prior art. Rather, the fluidizing body, for example, also be tubular, with the fluidizing air from the inside the tubular fluidizing body by the Wall blown outward into the powder chamber becomes.

In such a tubular design of the fluidization body can the electrode assembly for dissipation of static electricity, for example, on the lateral surface arranged the tubular fluidization body be, wherein the above-described different variants possible are.

However, the invention includes not only those described above Fluidizing body according to the invention as a single Component, but also a fluidization device with such a fluidizing body.

Here, the coating powder used has a specific Ignition, while between the coating powder and the fluid bottom or in the reverse direction electrical Discharges may occur due to design have a maximum discharge energy. The construction of the Fluid bottom and the other parts of the fluidization device is hereby preferably designed so that the maximum Discharge energy less than the ignition energy of the coating powder is, so that discharge-related ignitions of the powder-air mixture can be prevented. This is possible For example, achieve that the electrode assembly for dissipating static electricity from the coating powder has sufficiently many pointed electrodes. The maximum discharge energy can be in the inventive Fluidizing device also lower, that the free Area between the individual electrodes (e.g., pointed electrodes, Ring electrodes) of the electrode assembly reduced becomes.

Preferably, the maximum discharge energy is below this of 3 mJ, so that also coating powder with a high particulate matter and a correspondingly small Ignition energy of less than 3 mJ.

For dissipating the static electricity from the coating powder is the electrode assembly in the inventive Fluidizing device preferably grounded or is at least at a near-ground electric potential held. Preferably, the electrical voltage is between the electrode assembly and mass so in the range between 0 V and 10 kV, with any maximum values within this interval are possible. For example, the voltage less than 5kV, 1kV, 500V, 250V, 100V or 20V be. In contrast to the cited prior art lies the electrode arrangement of the fluidization body according to the invention So not at high voltage potential.

Furthermore, the invention also encompasses a complete powder coating system with such a fluidization device according to the invention and the use of an inventive Fluidizing body for fluidizing a coating powder in a coating plant.

Figur 1

eine vereinfachte Querschnittsansicht einer erfindungsgemäßen Fluidisierungsvorrichtung,

Figur 2

ein Ausführungsbeispiel des Fluidbodens der Fluidisierungsvorrichtung aus Figur 1 mit einer gitterförmigen Elektrodenanordnung,

Figur 3

ein anderes Ausführungsbeispiel des Fluidisierungsbodens der Fluidisierungsvorrichtung aus Figur 1 mit einer Elektrodenanordnung mit mehreren ringförmigen Elektroden,

Figur 4A und 4B

ein weiteres Ausführungsbeispiel des Fluidisierungsbodens der Fluidisierungsvorrichtung aus Figur 1 mit zahlreichen nadelförmigen Elektroden zur Ableitung statischer Elektrizität sowie

Figur 5

einen schlauchförmigen Fluidisierungskörper mit einer gitterförmigen Elektrodenanordnung zur Ableitung statischer Elektrizität.

Other advantageous developments of the invention are characterized in the subclaims or are explained in more detail below together with the description of the preferred embodiments of the invention with reference to FIGS. Show it:

FIG. 1

a simplified cross-sectional view of a fluidization device according to the invention,

FIG. 2

1 shows an exemplary embodiment of the fluid bottom of the fluidizing device of FIG. 1 with a grid-shaped electrode arrangement;

FIG. 3

another embodiment of the fluidization tray of the fluidization apparatus of Figure 1 with an electrode assembly having a plurality of annular electrodes,

FIGS. 4A and 4B

a further embodiment of the fluidization bottom of the fluidization device of Figure 1 with numerous needle-shaped electrodes for discharging static electricity and

FIG. 5

a tubular fluidizing body with a grid-shaped electrode arrangement for discharging static electricity.

The cross-sectional view in Figure 1 shows an inventive Fluidizing device 1 for fluidizing a coating powder in a powder coating plant, wherein the powder coating system be carried out conventionally can.

The fluidizing device 1 consists essentially of a bottom part 2, a patch on the bottom part 2 cylindrical Wall 3, a cover 4 and a Fluidisierungsboden 5, between the wall 3 and the bottom part of the second is fixed.

The lid 4, the wall 3 and the fluidization bottom 5 limit Here, a powder chamber 6, in which in operation a fluidized powder-air mixture is located.

Below the Fluidisierungsbodens 5 is located in the bottom part 2 a fluid air chamber 7, into which via a fluid air line 8 compressed air is blown.

The Fluidisierungsboden 5 consists of a porous, air-permeable, but powder-impermeable material, so that from the fluid air chamber 7 compressed air in the powder chamber 6 is blown and thereby in the powder chamber. 6 fluidized coating powder located.

In the wall 3 of the powder chamber 6 is a powder extraction line 9 arranged over which the fluidized powder-air mixture can be sucked out of the powder chamber 6.

In addition, in the wall 3 of the powder chamber 6 a Vent arranged, not shown for simplicity is and a derivative of excess compressed air allows the powder chamber 6.

Figure 2 shows a perspective view of a preferred Embodiment of the Fluidisierungsbodens 5, the in FIG 1 shown fluidizing device. 1

From this illustration it can be seen that at the top of the Fluidisierungsbodens 5 a grid-shaped electrode assembly 10 is inserted, wherein the electrode assembly 10th the fluidization tray 5 is electrically grounded to electrostatic Electricity from that in the powder chamber 6 located Derive coating powder. This prevents that in the powder chamber 6 located coating powder as far as can be charged that discharges with a Discharge energy can occur, which the ignition energy of the used coating powder exceeds, resulting in a Inflammation of the powder-air mixture could result.

In this case, the electrode arrangement 10 is designed such that a coating powder with an ignition energy of less than 3 mJ can be used. The maximum discharge energy is therefore less than 3 mJ in the fluidization device 1 and is below the powder-specific ignition energy. For this purpose, the grid-shaped electrode arrangement 10 includes in each case grid surfaces which have a size of less than 250 cm ² .

The illustrated in Figure 3 embodiment of an inventive Fluidization soil is largely consistent with the described above and shown in Figure 2 embodiment match, so as to avoid repetition referred to the above description of Figure 2 is, wherein for corresponding components the same reference numerals be used.

A special feature of this embodiment is that the electrode assembly 10 of a plurality of ring electrodes exist on the surface of the Fluidisierungsbodens 5 on the powder chamber 6 facing side embedded and electrically connected to each other, wherein the entire electrode assembly 10 is electrically grounded.

The individual ring electrodes each include an annular area which is smaller than 250 cm ² , so that it is also possible to use a coating powder whose ignition energy is less than 3 mJ.

The embodiment shown in Figures 4A and 4B a Fluidisierungsbodens invention is also true largely with the one described above and in FIG. 2 illustrated embodiment, so that to avoid from repetitions largely to the above description refer to Figure 2, wherein for corresponding Components are the same reference numerals.

A special feature of this embodiment is that the electrode assembly of a variety of needle-shaped Electrodes 11, which are axially through the fluidization bottom 5 are passed through, wherein the tip of the electrodes 11 on the powder chamber 6 facing side of Fluidization bottom 5 protrudes from the fluidization bottom 5, static electricity from that in the powder chamber 6 derived coating powder can be derived.

On the opposite side are the pointed electrodes 11 each have an electrode head 12, wherein the electrode heads 12 of the individual electrodes 11 of the electrode assembly 10 with each other by electrical connections 13th connected to each other.

The electrode assembly 10 thus forms a quasi one Electrode carpet, which is an excessive and safety-endangering Charging the powder-air mixture in the powder chamber 6 prevented.

FIG. 5 shows an alternative embodiment of a tubular fluidizing body 14, wherein the fluidizing body 14 a wall 15 made of a porous material which is permeable to air but powder-impermeable. For fluidization of coating powder is so hereby from inside the tubular fluidizing body 14 Compressed air through the wall 15 therethrough into a Blown powder chamber.

The outer circumferential surface of the tubular fluidizing body 14 is in this case with a grid-shaped electrode arrangement covered, circulating in the circumferential direction Electrodes 16 and axially extending electrodes 17, wherein this grid-shaped electrode assembly is electrically grounded is.

The invention is not limited to those described above Embodiments limited. Rather, one is Variety of variants and modifications possible, as well to make use of the idea of the invention and therefore fall into the scope.

LIST OF REFERENCE NUMBERS

1

fluidizing

2

the bottom part

3

wall

4

cover

5

fluidising

6

powder chamber

7

Fluid plenum

8th

Fluid air supply

9

Powder removal line

10

electrode assembly

11

electrodes

12

electrode head

13

connection

14

Fluidisierungskörper

15

wall

Claims (18)

Fluidizing body (5, 14) for fluidizing a coating powder with a fluidizing gas, wherein the fluidizing body (5, 14) consists at least partially of a permeable to the fluidizing gas and the coating powder impermeable material, characterized by an electrode assembly (10) made of an electrically conductive material for dissipating static electricity from the coating powder. Fluidizing body (5, 14) according to claim 1, characterized in that the electrode arrangement (10) has a grid. Fluidizing body (5, 14) according to claim 2, characterized in that the grid is embedded in the surface of the fluidizing body (5, 14). Fluidizing body (5, 14) according to claim 3, characterized in that the grid subdivides the surface of the fluidizing body (5, 14) into grid surfaces each having a size of less than 500 cm ² , 250 cm ² , 100 cm ² , 50 cm ² , 25 cm ² , 20 cm ² , 16 cm ² or 4 cm ² . Fluidizing body (5) according to claim 1, characterized in that the electrode arrangement (10) has at least one pointed electrode (11) which is guided through the porous material. Fluidizing body (5) according to claim 5, characterized in that the electrode assembly (10) has a plurality of pointed electrodes (11) which are passed through the porous material and distributed over the fluidizing body (5). Fluidizing body (5) according to claim 6, characterized in that between the pointed electrodes (11) there is a free surface of the fluidising body (5) having a size of less than 500 cm ² , 250 cm ² , 100 cm ² , 50 cm ² , 25 cm ² , 20 cm ² , 16 cm ² or 4 cm ² . Fluidizing body (5) according to claim 1, characterized in that the electrode assembly (10) comprises a plurality of electrode rings, which are arranged on the surface of the fluidization body (5) and electrically connected to each other. Fluidizing body (5) according to claim 8, characterized in that the electrode rings each have an annular area of less than 500 cm ² , 250 cm ² , 100 cm ² , 50 cm ² , 25 cm ² , 20 cm ² , 16 cm ² or 4 cm ² include. Fluidizing body (5, 14) according to any one of the preceding claims, characterized in that the porous material is electrically insulating. Fluidizing body (5, 14) according to any one of the preceding claims, characterized in that the fluidising body (5, 14) is plate-shaped or tubular. Fluidizing body (14) according to claim 11, characterized in that the electrode arrangement (16, 17) is arranged on the lateral surface of the tubular fluidizing body (14). Fluidizing device (1) with a fluidizing body (5) according to any one of the preceding claims. Fluidising device (1) according to claim 13, characterized in that the coating powder has a certain ignition energy, while electrical discharges between the coating powder and the electrode assembly (10) have a maximum discharge energy, wherein the maximum discharge energy is less than the ignition energy. Fluidizing device (1) according to claim 14, characterized in that the ignition energy of the coating powder is less than 3 mJ and / or that the maximum discharge energy is less than 3 mJ. Fluidizing device (1) according to any one of claims 13 to 15, characterized in that the electrode assembly (10) is grounded or is at a near-electrical potential. Powder coating plant with a fluidizing device (1) according to any one of the preceding claims. Use of a fluidization body (5, 14) after a of claims 1 to 12 for fluidizing a coating powder in a coating plant.

Images