EP1731230A1 - coating powder sieving device - Google Patents

Abstract

The coating powder filter (6-8) has a filter surface for filtering through a coating powder sand an ultrasonic source for stimulating vibrations of the filter surface. The filter surface is angular, e.g. rectangular with sides of different lengths, and is inclined to the horizontal so that dirt particles that have been filtered out pass off to the side.

Description

The invention relates to a coating powder screening device for a powder coating system.

In powder coating systems so-called powder management centers (PMC) are used for powder supply, in which the coating powder is fluidized so that it can be fed into the powder circuit of the powder coating plant. Such powder management centers essentially consist of a cylindrical container with a round ultrasound sieve arranged on top and a likewise round fluidization bottom arranged on the underside.

The powder management center is filled with the coating powder via the ultrasound sieve by applying fresh powder and / or recycling powder to the upper side of the sieve surface of the ultrasound sieve so that suitable coating powder is sieved through the sieve surface into the container.

The fluidization of the coating powder in the container takes place by blowing air through the fluidization bottom into the container, so that the coating powder in the container is always in a fluidized state during operation.

The fluidized coating powder may then pass through a side outlet in the container from a powder feed pump, such as a DDF pump, and pumped to an application device such as a powder atomizer.

A disadvantage of the known powder management center described above, the relatively large space requirement, since the screen surface of the ultrasonic sieve and the Fluidisierungsbehälter must have a sufficient cross-section.

Out DE-AS 25 06 981 . DE-PS 919 758 and DE 196 21 448 C1 sieve devices are known which have a square sieve surface, however, these sieve devices are based on a technically different sieve principle, since the sieve surface itself does not perform any transversal oscillations transverse to the sieve surface plane. Instead, in this case the entire screen frame is offset with the screen surface in low-frequency tumbling oscillations. In addition, these known screening devices are not suitable for use in a powder coating system.

The citations DE 202 20 680 U1 and DE- US 2,223,146 disclose further screening devices with a round screen surface and are also unsatisfactory.

Further, citation discloses DE 81 11 525 U1 a seal for a screening device.

Finally is off WO 99/10111 A1 a screening device is known in which a square screen surface rests loosely on a screen frame, wherein the screen surface is excited by an imbalance motor to low-frequency vibration oscillations in a frequency range from 0 to 480 Hz. This is therefore not a generic ultrasonic sieve device, so that the shape of the screen surface due to the low-frequency vibration excitation does not matter here.

The invention is therefore based on the object to reduce the space required in the known powder management center described above.

This object is achieved by a coating powder screening device according to the main claim.

The invention comprises the general technical teaching of providing a rectangular sieve surface in a coating powder sieve device with an ultrasound sieve in order to reduce the space requirement in the lateral direction for a given size of the sieve surface. Thus, for a given screen area size, the width of a square screen area is about 11% smaller than the corresponding width of a circular screen area. The smaller footprint in the lateral direction is particularly important if laterally next to a paint line several powder management center for each paint color to be set up because the individual powder management centers must then be put together tightly.

It should be mentioned here that the coating powder screening device according to the invention fundamentally differs from the known tumble screens described above, in which the screen surface carries out a tumbling oscillation parallel to the sieve surface. In contrast, in the coating powder screening device according to the invention, the screen surface oscillates transversely to the screen surface, whereas plane-parallel vibrations of the screen surface are preferably prevented by a screen surface bearing.

The term used in the context of the invention an angular screen surface is not strictly mathematical-geometric to understand, but also includes, for example, screen surfaces with rounded corners or slightly curved side edges.

Moreover, in tests on conventional ultrasonic sieves with a circular sieve surface, it has been found that the outer regions of the sieve surface are hardly used, whereby the effectively usable sieve area is reduced. In contrast, tests on the coating powder screening devices according to the invention with an angular screen surface have shown that almost the entire screen surface is utilized, so that the coating powder screening device according to the invention operates more effectively. This advantage is based on the fact that the vibration propagates in a caro shape on the angular sieve surfaces according to the invention and extends over the entire sieve surface.

Preferably, the screen surface is rectangular in the coating powder screening device according to the invention, wherein a square screen surface is also suitable. In a preferred embodiment of the invention, however, the screen surface has different lengths side edges, whereby the width of the coating powder screening device according to the invention in the direction of the shorter side edge can be further reduced. For example, the aspect ratio of the side edges of the screen surface may range between 1: 1.5 and 1: 2.5, with an aspect ratio of approximately 1: 1.8 having been found to be advantageous.

In a variant of the invention, the screen surface is inclined relative to the horizontal, so that the dirt particles retained by the screen surface laterally migrate laterally due to gravity at the top of the screen surface Adding the screen surface is prevented by the dirt. The optimum angle of inclination of the screen surface depends on the coating powder used and the structural conditions of the coating powder screening device. For example, the angle of inclination of the screen surface in the coating powder screening device according to the invention between 2 ° and 10 ° (based on a full circle with 360 °) are, with an angle of inclination of the screen surface in the range between 2 ° and 6 ° has been found to be advantageous. Furthermore, in the context of the invention, there is also the possibility that the angle of inclination of the sieve surface is adjustable, which makes it possible, for example, to adapt to different powder properties.

In the case of an inclined screen surface, the screen surface at its downwardly inclined side edge preferably opens into a dirt discharge, via which the screened-out dirt particles can be removed in a collected manner. Such a dirt discharge may, for example, have a channel which extends along the downwardly inclined side edge of the screen surface and which catches the dirt particles migrating laterally over the screen surface.

The coating powder screening device according to the invention has an ultrasound generator for vibrational excitation of the screen surface, as is the case with the conventional ultrasound screens mentioned briefly above. The ultrasound generator in this case has an excitation frequency, which is preferably greater than 20 kHz, 30 kHz or even greater than 50 kHz.

It should also be mentioned that the screen surface in the coating powder screening device according to the invention has a mesh width which is preferably in the micrometer range lies. For example, the mesh size of the screen surface can be in the range of 60 μm to 200 μm.

It should also be mentioned that the coating powder screening device according to the invention has a screening capacity which can, for example, be in the range from 20 kg / h to 200 kg / h.

In one embodiment of the invention, the screen surface is mounted in a special way. Thus, the storage of the screen surface in the conventional ultrasonic sieves with a circular screen surface by a plurality of punctiform support points on the underside of the screen surface and two annular circumferential hollow profile rubber, which press from above and below on the screen surface and thereby fix them. In the case of the coating powder screening device according to the invention, in contrast, it is provided in one exemplary embodiment that the screen surface is fixed in the region of its side edges by at least one sponge rubber element and / or at least one solid rubber element. For example, along the side edges of the screen surface at the top and at the bottom of the screen surface each have a foam rubber element are arranged so that the screen surface between the upper foam rubber element and the lower foam rubber element is fixed. However, the invention is not limited to sponge rubber with respect to the material of the rubber elements, but also with other solid rubber elements or sealing profiles for fixing the screen surface feasible.

Furthermore, in a preferred embodiment of the invention, a baffle plate is arranged above the screen surface, which distributes the coating agent on the screen surface. The baffle plate is in this case preferably from above, ie approximately at right angles to the screen surface with the coating powder flowed on, so that the baffle plate deflects the coating agent laterally and thus distributed over the screen surface.

In the embodiment described above with an inclined screen surface of the baffle plate is preferably arranged in the upper region of the inclined screen surface, since the coating powder passes independently due to the inclination of the screen surface in the lower region of the screen surface. The baffle plate is thus preferably arranged in the upper half, the upper third or even the upper quarter of the inclined screen surface, wherein the optimal arrangement of the baffle plate within the screen surface also depends on the inclination angle of the screen surface.

Moreover, the inventive idea of a square design is applicable not only to a screen surface in a coating powder screen, but also to a powder application container such as a powder management center. The invention therefore also encompasses such a powder application container with an angular cross section in the horizontal direction.

Here, too, the cross section may be square or generally rectangular, with the above statements regarding the screening surface of the coating powder screening device according to the invention being correspondingly valid for the aspect ratio of the side surfaces, so that reference is made in this regard to the above description.

In the case of such a powder application container according to the invention, a coating powder sieve device according to the invention, as described above, is located on the upper side, wherein the sieve surface of the coating powder sieve device is adapted in shape and size to the cross section of the powder application container.

In the powder application container according to the invention, a side wall of the powder application container can consist partially or completely of a fluidization body which can be blown from the outside, whereby powder caking on the inner wall of the powder application container in the region of the fluidization body is prevented. The side wall of the powder application container can therefore be angled in the region of the fluidizing body with respect to the vertical, so that the cross section of the powder application container widens upward, wherein the blowing in the region of the fluidizing body despite the oblique orientation prevents the coating powder inside of the Deposits fluidizing body.

The deposition of coating powder on the inner wall of the powder application container can also be prevented within the scope of the invention in that the powder application container has inner walls which run substantially vertically below the coating powder sieve and have no bevels, whereas the powder application container in the known powder described above Management Centers flared conically upwards, which can lead to caking of the coating powder on the inner wall.

In addition, the powder application container according to the invention preferably has a fluid level sensor for measuring the fluid level of the fluidized coating powder present in the powder application container, wherein the fluid level sensor may be of conventional design (eg as an ultrasonic sensor).

A further advantage of the rectangular design of the powder application container according to the invention is that more than six outlets for connecting application pumps can be arranged in the side wall of the powder application container, whereby the individual connections can be cleaned better and are exposed to more constant suction conditions than with the known powders described above Management Centers with a circular cross-section. For example, eight or more connections for application pumps can be arranged in the side wall of the powder application container according to the invention.

Finally, the invention also encompasses a complete powder coating system with a coating powder screening device according to the invention and / or with a powder application container according to the invention.

Preferably, a plurality of powder application containers are arranged in succession next to a painting line in the longitudinal direction of the painting line, wherein the adjacent powder application containers contain different coating powders. For example, the adjacent powder application containers may contain coating powders of different colors along the coating line.

Furthermore, in a variant of the powder coating system according to the invention, a fluid density control is provided so that the fluidized coating powder present in the powder application container always has a predetermined constant fluid density. In this case, a powder feed pump is provided for conveying the coating powder into the powder application container and a fluid level sensor for measuring the fluid density in the powder application container. The regulation The fluid density in the application container is effected by an air quantity regulator which controls the amount of fluid air in such a way that the density calculated from the measured fluid height and the mass of the powder coating located in the container corresponds to the predetermined value.

Finally, the invention also encompasses the novel use of a screening device according to the invention for screening coating powder in a powder coating system.

Figur 1

eine Perspektivansicht eines erfindungsgemäßen Pulver-Management-Centers (PMC) zur Pulverversorgung in einer Pulverbeschichtungsanlage,

Figur 2

eine vereinfachte Querschnittsdarstellung des Pulver-Management-Centers gemäß Figur 1,

Figur 3

eine Aufsicht auf die Siebfläche des Ultraschallsiebs des Pulver-Management-Centers gemäß Figur 1,

Figur 4A

eine Querschnittsdarstellung einer neuartigen Fixierung der Siebfläche in dem Ultraschallsieb bei dem Pulver-Management-Center gemäß Figur 1,

Figur 4B

eine alternative herkömmliche Fixierung der Siebfläche in dem Ultraschallsieb,

Figur 4C

eine alternative Fixierung der Siebfläche in dem Ultraschallsieb,

Figur 5

eine Querschnittsansicht eines anderen Ausführungsbeispiels eines erfindungsgemäßen Pulver-Management-Centers,

Figur 6

eine Querschnittsansicht durch den Pulverapplikationsbehälter des Pulver-Management-Centers gemäß Figur 5,

Figur 7

eine Perspektivansicht einer geneigten Siebfläche bei einem alternativen Ausführungsbeispiel eines erfindungsgemäßen Ultraschallsiebs,

Figur 8

eine schematisierte Seitenansicht der geneigten Siebfläche gemäß Figur 7,

Figur 9

eine Aufsicht auf eine Lackierstraße mit mehreren erfindungsgemäßen Pulver-Management-Centern sowie

Figuren 10A, 10B

Explosionsdarstellungen des Pulver-Management-Centers, aus denen der modulare Aufbau ersichtlich ist.

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 perspective view of a powder management center (PMC) according to the invention for supplying powder in a powder coating plant,

FIG. 2

2 is a simplified cross-sectional view of the powder management center according to FIG. 1,

FIG. 3

a plan view of the sieve surface of the ultrasonic sieve of the powder management center according to Figure 1,

FIG. 4A

a cross-sectional view of a novel fixation of the screen surface in the ultrasonic sieve in the powder management center according to Figure 1,

FIG. 4B

an alternative conventional fixation of the sieve surface in the ultrasonic sieve,

FIG. 4C

an alternative fixation of the sieve surface in the ultrasonic sieve,

FIG. 5

a cross-sectional view of another embodiment of a powder management center according to the invention,

FIG. 6

a cross-sectional view through the powder application container of the powder management center according to Figure 5,

FIG. 7

a perspective view of an inclined screen surface in an alternative embodiment of an ultrasonic sieve according to the invention,

FIG. 8

2 is a schematic side view of the inclined screen surface according to FIG. 7;

FIG. 9

a view of a painting line with several powder management centers according to the invention and

FIGS. 10A, 10B

Exploded views of the Powder Management Center showing the modular design.

The exemplary embodiment of a powder management center 1 (PMC) according to the invention shown in FIGS. 1 and 2 serves for powder supply in a powder coating installation, as used, for example, for painting motor vehicle body parts.

For fluidizing the coating powder, the powder management center 1 has a powder container 2 with a rectangular cross section, wherein the cross section of the powder container 2 is constant in a lower region 2.1, while the cross section of the powder container 2 in an upper region 2.2 of the powder container. 2 extended on one side upwards, wherein in the oblique side wall of the powder container 2 in the upper region 2.2 a fluidizing body 3 is arranged, whereby in the region of the slope caking of the coating powder can be prevented.

The underside of the powder container 2 is formed by a fluid base 4, which is impermeable to the coating powder and permeable to air, is blown through the fluid bottom 4 in operation air in the powder container 2, so that a filled into the powder container 2 coating powder 5 is fluidized ,

On its upper side, the powder container 2 has a peripheral frame 6, on which a lid 7 is pivotally mounted, wherein the lid 7 can be fixed by means of a clamping closure 8 in the closed state. Between the cover 7 and the frame 8 is a rectangular screen surface 9, wherein the rectangular screen surface 9 is excited in a conventional manner by an ultrasonic generator, which is not shown for simplicity. The screen surface 9 here consists of a screen fabric 9.1, which is mounted on a screen frame 9.2, as can be seen in particular from Figure 2.

In addition, a powder inlet for fresh powder and another powder inlet for recycling powder open into the lid 7 above the sieve surface 9, wherein the supplied coating powder is distributed on the upper side of the sieve surface 9 and sieved through the screen surface 9 therethrough. However, the two powder containers for fresh powder or recycled powder are not shown here for the sake of simplicity.

To remove the fluidized coating powder 5 from the powder management center 1 six outlets 10 are arranged on the side wall of the powder container 2 in the lower portion 2.1 of the powder container 2 below the slope, can be connected to the application pumps. The arrangement of the outlets 10 on the longer side wall of the rectangular powder container 2 offers the advantage that prevail at the individual outlets 10 approximately constant Absaugbedingungen.

FIG. 4A shows the fixing of the sieve surface 9 between the cover 7 and the frame 6 of the powder management center 1. It can be seen that the sieve surface 9 is in each case surrounded by a rectangular encircling foam rubber element 11 or 12 at the upper side or at the lower side is fixed, resulting in a good vibration behavior.

FIG. 4B shows an alternative possibility for fixing the screen surface 9 between the frame 6 and the cover 7. In this case, rectangular hollow rubber profiles 13, 14 are provided on the outside of the screen surface 9, which support the screen surface 9 in a vibration-damped manner in the vertical direction. On the underside of the screen surface 9 more rigid supports 15 are also provided within the rectangular circumferential hollow rubber profile 14, wherein the supports 15 are each a point-shaped support form. Further, a buffer element 16 is disposed between the frame 6 and the lid 7.

In addition, the powder management center 1 allows a fluid density control, so that via the outlets 10 a powder flow with a constant fluid density is discharged. For this For example, the powder management center 1 has a fluid level sensor 17 with a measuring tube 18, wherein the measuring tube 18 protrudes into the upper area 2.2 of the powder container 2, so that the fluid level is measured there. The fluid height thus measured can then be supplied to an air flow regulator, which controls the amount of fluid air so that the fluid density calculated from the measured fluid height and the mass of the coating powder 5 present in the powder container 2 corresponds to a default value.

FIG. 4C shows a further alternative variant for fixing the screen surface 9 between the frame 6 and the cover 7. This variant is partially identical to the variants described above, so that reference is made to the above description to avoid repetition, wherein the same applies to corresponding elements Reference numerals are used.

A special feature of this variant is that in a ring-shaped circumferential shoulder between the cover 7 and the frame 6 a likewise annular circumferential seal 14 'is arranged.

Figure 5 shows a cross-sectional view of an alternative embodiment of a powder management center 1, which is largely consistent with the embodiment described above, so to avoid repetition, reference is made largely to the above description, wherein the same reference numerals are used for corresponding parts.

In particular, it can be seen from this cross-sectional view that below the fluid bottom 4 an air chamber 19 is arranged, into which air is blown, which is then blown through the air Fluid bottom 4 passes through the top into the powder container 2. Furthermore, in this case, an inlet 18 for fresh powder and an optional inlet 20 for recycling powder are shown in the lid 7.

The actual difference of this embodiment from the embodiment shown in Figure 1 is that the side walls of the powder container 2 are substantially perpendicular and have no bevels, whereby caking of the coating powder 5 on the inner wall of the powder container 2 are largely prevented.

Figure 6 shows the arrangement of the outlets 10 in the side wall of the powder container 2. From this representation, it can be clearly seen that the individual outlets 10 are exposed to approximately the same extraction conditions.

Figures 7 and 8 show a schematic representation of a screen surface 22, which is inclined relative to the horizontal by an inclination angle of α approximately equal to 5 °, so that dirt particles on the top of the screen surface 22 of gravity following the lower side edge of the screen surface 22 to migrate where the dirt particles are taken up by a dirt discharge 23. The dirt discharge 23 in this case extends in the shape of a channel along the downwardly inclined side edge of the sieve surface 22, so that the dirt particles are collected by the entire sieve surface 22 in the dirt discharge 23.

The powder coating charge takes place here via a powder feed 24, which is directed to a baffle plate 25, which is located in the upper third of the inclined screen surface 22.

FIG. 9 shows a plan view of a material supply of a coating line 26 with several powder management centers 27-32, which are arranged laterally next to the coating line. The rectangular design of the Powder Management Center 25-30 allows for a tight setup, which allows a multi-color concept.

Finally, FIGS. 10A and 10B illustrate the modular structure of the powder management center 1 according to the invention, comprising the lower area 2.1 of the powder container 2, the upper area of 2.2 of the powder container 2 and a screening device 33.

This modular structure of the powder management center 1 makes it possible to retrofit conventional powder management centers by exchanging the upper region 2.2 of the powder container 2 and the sieve device 33.

The invention is not limited to the preferred embodiments described above. Rather, a variety of variants and modifications is possible, which also make use of the inventive idea and therefore fall within the scope.

LIST OF REFERENCE NUMBERS

1

Powder Management Center

2

powder container

2.1

Lower area of the powder container

2.2

Upper area of the powder container

3

Fluidisierungskörper

4

fluid base

5

coating powder

6

frame

7

cover

8th

Lever Release

9

Screen area

9.1

mesh

9.2

screen frame

10

outlets

11, 12

Foam rubber elements

13, 14

Hollow rubber profiles

14 '

poetry

15

In stock

16

buffer element

17

Fluid level sensor

18

measuring tube

19

air chamber

20

inlet

21

inlet

22

Screen area

23

waste discharge

24

powder feed

25

baffle plate

26

Material supply of a paint line

27-32

Powder Management Center

33

screening

Claims (17)

Coating powder screening device (6-9) for a powder coating machine, with a) a sieve surface (9, 22) for sifting through a coating powder and b) an ultrasound generator for vibrating the sieve surface (9, 22),
characterized in that c) the sieve surface (9; 22) is square. Coating powder sieve device (6-9) according to claim 1, characterized in that the sieve surface (9; 22) is rectangular. Coating powder sieve device (6-9) according to one of the preceding claims, characterized in that the sieve surface (9; 22) has differently long side edges. Coating powder sieve device (6-9) according to one of the preceding claims, characterized in that the sieve surface (9; 22) is inclined relative to the horizontal, so that sieved-out dirt particles migrate laterally. Coating powder screening device (6-9) according to claim 4, characterized in that the sieve surface (9; 22) opens at its downwardly inclined side edge in a dirt discharge (23) through which the sifted debris are removed. Coating powder screening device (6-9) according to one of the preceding claims, characterized in that the screen surface (9; 22) is fixed in the region of its side edges by at least one sponge rubber element (11, 12) and / or at least one solid rubber element. Coating powder sieve device (6-9) according to one of the preceding claims, characterized in that above the sieve surface (9; 22) a baffle plate (25) is arranged which distributes the coating agent to the sieve surface (9; 22). Coating powder screening device (6-9) according to claim 4 and claim 7, characterized in that the baffle plate (25) in the upper region of the inclined screen surface (22) is arranged. Coating powder screening device (6-9) according to any one of the preceding claims, characterized in that below the screen surface (22) a Pulverfluidisierungsbehälter (2) is arranged, which has a polygonal cross-section. Coating powder screening device (6-9) according to claim 9, characterized in that a side wall of the Pulverfluidisierungsbehälters (2) at least partially consists of a fluidization body (3). Coating powder screening device (6-9) according to claim 10, characterized in that the fluidizing body (3) in the side wall of the Pulverfluidisierungsbehälters (2) is angled relative to the vertical. Coating powder screening device (6-9) according to any one of claims 9 to 10, characterized by inner walls of the Pulverfluidisierungsbehälters (2), below the screen surface (22) are substantially perpendicular and have no slopes. Coating powder screening device (6-9) according to one of Claims 9 to 12, characterized by a fluid level sensor (17) for measuring the filling level of the fluidized coating powder (5) in the powder fluidizing container (2). Coating powder screening device (6-9) according to one of claims 9 to 13, characterized by more than six outlets (10) in the powder fluidizing container (2) for connecting application pumps for taking out the fluidized coating powder (5). Coating powder screening device (6-9) according to any one of claims 9 to 14, characterized in that laterally next to a Lackierstrasse several Pulverfluidisierungsbehälter (27-32) are arranged, wherein the adjacent Pulverfluidisierungsbehälter (27-32) contain different coating powder. Coating powder screening device (6-9) according to claim 15, characterized by a) a powder feed pump for conveying the coating powder into the powder fluidizing tank (2), b) a fluid level sensor (17) for measuring the level in the Pulverfluidisierungsbehälter (2) and c) an air flow regulator for controlling the fluid density of the fluidized coating powder (5) in the powder fluidizing tank (2), d) wherein the air quantity controller in response to the measured filling level of the fluidized coating powder (5) drives a fluidizing air pump. Use of an ultrasonic sieve device with an angular sieve surface, in particular according to one of the preceding claims, for sieving coating powder in a powder coating plant.

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