WO2008028613A1

WO2008028613A1 - Powder feed pump for feeding coating powder in a powder coating installation and associated operating method

Info

Publication number: WO2008028613A1
Application number: PCT/EP2007/007679
Authority: WO
Inventors: Marcus Treppschuh; Hans-Georg Fritz; Thomas Dürr
Original assignee: Dürr Systems GmbH
Priority date: 2006-09-05
Filing date: 2007-09-03
Publication date: 2008-03-13
Also published as: DE102006041527A1; EP2059346A1

Abstract

The application relates to a powder feed pump (1) for feeding coating powder in a powder coating installation, with an integrated sieve (5) for sieving the coating powder. The application also comprises a corresponding operating method.

Description

DESCRIPTION

Powder feed pump and associated operating method

The invention relates to a powder feed pump for conveying coating powder in a powder coating plant and a corresponding operating method according to the juxtaposed claims.

From EP 1 454 675 A2 a powder feed pump is known, which can be used in a powder coating plant to convey coating powder from a powder source, such as a so-called big bag emptying station, to an application device, such as a powder bell atomizer ,

A disadvantage of this known powder feed pump is the fact that it must be supplied with screened powder coating. For this reason, conventional powder coating plants have separate powder sieves, which are arranged in front of the powder feed pump.

The invention is therefore based on the object to improve the known powder feed pump described above accordingly.

This object is achieved by a powder feed pump according to the invention and a corresponding operating method according to the independent claims.

The invention comprises the general technical teaching of integrating a sieve into the powder feed pump in order to obtain the coating. sieve powder in the powder feed pump, so that can be dispensed with a separate powder sieve. Such integration of a sieve is not possible with the above-described known powder feed pump according to EP 1 454 675 A2, because a powder withdrawal tube protrudes from the top into the powder container up to its bottom, thereby preventing the installation of a sieve.

The powder feed pump according to the invention thus combines two functions, namely, on the one hand a pump functionality and, on the other hand, a screen functionality. In addition, the powder feed pump according to the invention preferably has a third function in that the coating powder is fluidized in the powder feed pump.

In a preferred embodiment of the invention, the powder feed pump has a pressure-resistant powder container with an inlet chamber and an outlet chamber, between which the sieve is arranged.

The pressure resistance of the powder container in this case need not be particularly great, but merely sufficient to blow out the coating powder contained in the powder container, for which a compressive strength of about 0.8 bar is sufficient. The pressure resistance of the powder container in the powder feed pump according to the invention is therefore preferably greater than 0.5 bar, 0.8 bar, 1 bar, 2 bar or even greater than 5 bar.

In this case, the powder container has a powder inlet, which opens into the inlet chamber of the powder container for supplying the coating powder. Furthermore, the powder feed pump in this embodiment has a powder outlet, which opens out of the outlet chamber of the powder container, to dispense the coating powder. Furthermore, in this embodiment, a compressed air connection is provided, which opens into the powder container to blow the coating powder through the powder outlet from the powder container, the compressed air connection preferably opens into the outlet chamber of the powder container.

In the operation of this embodiment, therefore, the inlet chamber of the powder container is first filled via the powder inlet. The coating powder in the inlet chamber is then screened through the screen into the outlet chamber. Subsequently, the coating powder located in the outlet chamber of the powder container can then be blown out through the powder outlet from the outlet chamber of the powder container by blowing compressed air into the powder container via the compressed air connection.

It has already been mentioned above that the conventional powder feed pump according to EP 1 454 675 A2 has a discharge tube as a powder outlet, which protrudes into the powder container from above and only ends shortly above the bottom of the powder container in order to remove fluidized coating powder there. However, this sampling tube prevents the integration of a sieve in the powder feed pump, since the sampling tube would have to go through the sieve. In the case of the powder feed pump according to the invention, the powder outlet is therefore preferably arranged in the inlet chamber in the wall of the powder container, so that it is possible to dispense with a removal tube. This offers the advantage that the interior of the powder container remains free without interference from a sampling tube, which allows the integration of the sieve. For example, the powder outlet can be arranged laterally in the wall of the powder container in the region of the inlet chamber. The term used in the context of the invention of a compressed air connection is to be understood in general and not limited to the use of atmospheric air for blowing out the coating powder. Rather, other gases can be supplied via the compressed air connection. In conventional painting but usually compressed air lines are available, which can also be used for the powder feed pump according to the invention.

In a variant of the invention, the inlet chamber and the outlet chamber of the powder container respectively directly adjoin the screen. This means that the sieve is arranged directly between the inlet chamber and the outlet chamber.

In another variant of the invention, on the other hand, an additional central chamber is arranged between the inlet chamber and the outlet chamber of the powder container, wherein the sieve is arranged between the central chamber and the outlet chamber, while a controllable valve connects the inlet chamber with the central chamber. This design offers the advantage that the coating powder does not immediately load the screen mechanically when filling the inlet chamber, but first enters the inlet chamber. This is particularly advantageous if the powder feed to the powder feed pump intermittently takes place in such large quantities that would mechanically overload the sieve. After filling the inlet chamber, the coating powder in the inlet chamber can then be gradually transferred to the center chamber for sieving by correspondingly driving the valve between the inlet chamber and the outlet chamber. The transfer of the coating powder from the inlet chamber into the middle chamber preferably takes place so slowly that the sieve is not overloaded. The transfer of the coating powder The inlet chamber into the middle chamber is therefore preferably slower than the filling of the inlet chamber itself. For example, the filling of the inlet chamber may be intermittent, whereas the transfer of the coating powder from the inlet chamber into the central chamber takes place continuously or in smaller increments.

It should also be mentioned that the inlet chamber and / or the middle chamber of the powder container is preferably arranged above the sieve, while the outlet chamber of the powder container is preferably arranged below the sieve. The individual chambers of the powder container are thus preferably arranged above one another. However, the invention is not limited to embodiments in which the individual chambers of the powder container are arranged one above the other.

It should also be mentioned that the powder feed pump according to the invention preferably has a conventional fluid bottom in order to fluidize the coating powder. Such a fluid floor is known, for example, from patent application EP 1 454 675 A2, already mentioned at the outset, and from patent application DE 10 2005 024 854, so that the content of these two patent applications is to be fully attributed to the present description with regard to the structural design of the fluid floor ,

Furthermore, the powder feed pump according to the invention preferably has a balance to measure the weight of the powder container with the coating powder therein. Such a weight measurement advantageously makes it possible to determine the mass of the coating powder in the powder container. The powder container is therefore preferably mounted on a balance in the powder feed pump according to the invention. It is also within the scope of the invention to provide a level sensor which measures the level of the coating powder in the powder container, wherein the level sensor is preferably arranged in the inlet chamber of the powder container and measures the level in the inlet chamber of the powder container.

Preferably, the sieve integrated in the powder feed pump is angular and thus has an angular sieve surface, which is known per se from the patent application DE 10 2005 024 854.

It should also be mentioned that the screen is preferably designed as an ultrasound screen and has an ultrasound transmitter in order to excite the screen surface to ultrasonic vibrations. However, the invention is not limited to ultrasound sieves with regard to the sieve type, but in principle can also be implemented with other sieve types which allow sieving of the coating powder.

In addition, it goes without saying that various types of controllable valves can be used within the scope of the invention. Preferably, however, pinch valves are used in the invention, which are preferably pneumatically controllable.

It should also be mentioned that the invention is not limited to a powder feed pump as a single component, but also includes a powder coating system with a powder feed pump according to the invention.

Here, the powder feed pump according to the invention is connected on the input side to a powder source, which is, for example, a so-called big-bag emptying station, a Powder container emptying station or a powder feed pump can act, the powder feed pump can be configured for example as a DDF pump (DDF: digital dense phase promotion) or as a vacuum feed pump. The connection of the powder feed pump according to the invention with the powder source is preferably carried out without the interposition of another sieve and / or without the interposition of another pump, which makes possible a simplification of the powder coating system according to the invention. However, the invention is not limited to those powder coating systems in which upstream of the powder feed pump according to the invention is dispensed with a sieve or a pump. Rather, within the scope of the invention it is also possible to arrange an additional screen and / or an additional pump upstream of the powder feed pump according to the invention.

On the output side, the powder feed pump according to the invention is preferably connected directly to an application device, such as a Pulverglockenzerstäuber. This means that preferably no additional pump, no separate sieve and / or no application container is arranged between the powder feed pump according to the invention and the application device. An advantage of this construction is the fact that the sieve is arranged as the last component directly in front of the appli- cation device, whereby the painting result is improved.

In another variant of a powder coating installation according to the invention, on the other hand, the powder feed pump is connected on the outlet side to an application container which feeds an application device, such as a powder bell atomizer. Again, the connection of the powder feed pump according to the invention with the application container ter preferably without the interposition of another pump and / or an additional screen.

However, the invention is not limited to such powder coating systems in which downstream of the powder feed pump according to the invention no additional sieve and no additional pump is arranged. Rather, it is also possible within the scope of the invention for an additional screen and / or an additional pump to be arranged downstream of the powder feed pump according to the invention.

In addition, it should be mentioned that the invention also encompasses a novel method of operating a powder feed pump, the coating powder in the powder feed pump being screened through an integrated sieve within the scope of the operating method according to the invention.

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 exemplary embodiments of the invention with reference to the figures. Show it:

1 shows a preferred embodiment of a powder feed pump according to the invention with an integrated sieve which separates an inlet chamber from an outlet chamber,

FIG. 2 shows an alternative exemplary embodiment of a powder feed pump according to the invention, in which a middle chamber is arranged between the inlet chamber and the outlet chamber,

FIG. 3A shows a schematic representation of a powder coating installation according to the invention with a powder conveying pump according to FIG. 1, wherein the powder feed pump is connected on the input side to a big bag emptying station and on the output side directly to an applicator,

FIG. 3B shows a modification of the exemplary embodiment according to FIG. 3A, in which the powder feed pump is connected to the applicator on the output side via an application container,

FIG. 3C shows a modification of the embodiment according to FIG. 3A, in which the powder feed pump is connected to a powder container on the input side via a DDF pump,

Figure 3D shows an alternative embodiment of a powder coating system according to the invention, in which the powder feed pump is connected on the input side via a DDF pump with a powder container and the output side via an application container with an applicator and

FIG. 4 shows the operating method of the powder feed pump according to FIG. 2 in the form of a flow chart.

FIG. 1 shows a powder feed pump 1 that can be used in a powder coating plant to convey coating powder from a powder source, such as a so-called big bag emptying station, to an applicator, such as a powder bell atomizer.

The powder feed pump 1 has a powder container 2 with an inlet chamber 3 and an outlet chamber 4, wherein the Inlet chamber 3 is arranged above the outlet chamber 4 and is separated from the outlet chamber 4 by a sieve 5.

A powder inlet 6, via which the inlet chamber 3 of the powder container 2 can be filled with coating powder, opens into the inlet chamber 3 of the powder container 2 via a pneumatically controllable pinch valve QV 1.

In the outlet chamber 4 of the powder container 2 opens via a pneumatically controllable pinch valve QV2 a Druckluftanschluss 7, can be injected via the compressed air into the outlet chamber 4. When using the powder feed pump 1 in a paint shop, the compressed air connection 7 is fed by the already existing compressed air line of the paint shop with compressed air.

Furthermore, from the outlet chamber 4 of the powder container 2 via a pneumatically controllable pinch valve QV3 from a PuI- verauslass 8, can be discharged via the fluidized coating powder from the outlet chamber 4 of the powder container 2.

The bottom of the outlet chamber 4 consists in a conventional manner of a semi-permeable fluid tray 9, which is permeable to compressed air, but impermeable to the coating powder. Below the fluid bottom 9 there is a fluidization chamber 10, into which a compressed air connection 11 opens via a pneumatically controllable pinch valve QV4. When the powder feed pump 1 is used in a coating system, the compressed air connection 11 is also supplied with compressed air by the already existing compressed air line of the painting installation. To fluidize the coating powder located in the outlet chamber 4 of the powder container 2, the pinch valve QV4 is opened and compressed air is introduced into the fluid. blown idisierungskammer 10. From the fluidization chamber 10, the compressed air then enters the outlet chamber 4 through the semi-permeable fluid base 9 and fluidises the coating powder located there.

On its underside, the powder feed pump 1 according to the invention rests on a balance 12, wherein the balance 12 measures the weight of the powder container 2 with the coating powder contained therein. This weight measurement makes it possible to determine the mass of the coating powder located in the powder container 2.

During operation of the powder feed pump 1, first the pinch valve QV1 is opened in order to introduce coating powder into the inlet chamber 3 of the powder container 2 via the powder inlet 6.

The coating powder located in the inlet chamber 3 is then sieved through the sieve 5 into the outlet chamber 4 of the powder container 2 and fluidized there by opening the pinch valve QV4, so that compressed air via the compressed air connection 11 and the semipermeable fluid tray 9 into the inlet chamber 4 of the powder container 2 is blown.

To blow out the fluidized coating powder located in the outlet chamber 4, the two pinch valves QV2 and QV3 are then opened, so that compressed air is blown into the outlet chamber of the powder container 2 via the compressed air connection 7. By this injection of compressed air, the fluidized coating powder is displaced from the outlet chamber 4 of the powder container 2 and blown out of the outlet chamber 4 through the powder outlet 8. During operation, the interior of the powder container 2 can be vented through a vent valve, wherein the vent valve is not shown for simplicity.

FIG. 2 shows an alternative exemplary embodiment of a powder feed pump 1 according to the invention, which largely corresponds to the exemplary embodiment according to FIG. 1, so that reference is made to the above description to avoid repetition, the same reference numerals being used below.

A special feature of this embodiment is that between the inlet chamber 3 and the outlet chamber 4 of the powder container 2, a central chamber 13 is arranged. The middle chamber 13 is separated from the outlet chamber 4 of the powder container 2 by the sieve 5 and is connected to the inlet chamber 3 by another pneumatically controllable pinch valve QV5. When filling the inlet chamber 3, the coating powder thus does not reach the screen 5 immediately, but only when the pinch valve QV5 is opened. This is particularly advantageous if the filling with coating powder intermittently in large quantities, since the respectively supplied amounts of coating powder could overload the screen 5.

FIG. 3A schematically shows an exemplary embodiment of a powder coating installation according to the invention with the powder feed pump 1 according to FIG. 1. In this exemplary embodiment and in the following exemplary embodiments of a powder coating installation according to the invention, however, the powder feed pump 1 according to FIG Figure 2 are used. On the input side, the powder feed pump 1 is connected here via the pinch valve QV1 to a conventional big-bag emptying station 14, wherein neither an additional sieve nor an additional pump is arranged between the big-bag emptying station 14 and the powder feed pump 1.

On the output side, the powder feed pump 1 is connected directly to an applicator 15 via the pinch valve QV3, wherein the applicator 15 may be formed, for example, as a powder bell atomizer. This direct supply of the applicator 15 from the powder feed pump 1 with the integrated sieve 5 offers the advantage that the sieve is arranged in the flow path of the coating powder immediately in front of the applicator 15, which contributes to an improved coating result compared to sieves arranged further upstream.

The control of the pinch valves QV1-QV4 is carried out by a control unit 16 via pneumatic control lines, which are shown in dashed lines in the drawing.

Furthermore, the powder coating system in this embodiment, a compressed air source 17, which may be a compressed air ring line, which is available anyway in conventional paint shops.

FIG. 3B shows a modification of the exemplary embodiment according to FIG. 3A, so that reference is made to the above description to avoid repetition, the same reference numerals being used for corresponding components.

A special feature of this embodiment is that the powder feed pump 1 is not directly connected to the applicator 15, but with the interposition of an application container 18th The embodiment according to FIG. 3C largely corresponds to the exemplary embodiment described above and illustrated in FIG. 3A, so that reference is made to the above description to avoid repetition, the same reference numerals being used for corresponding components.

A special feature of this embodiment is that the powder feed pump 1 on the input side via a DDF

Pump 19 (DDF: digital dense phase conveying) is connected to a conventional powder container 20.

FIG. 3D shows a combination of the input-side supply of the powder feed pump 1 according to FIG. 3C with an outlet-side connection according to FIG. 3B.

The operating method of the powder feed pump according to the invention according to FIG. 2 will now be described below with reference to the flowchart according to FIG.

In a first step Sl, the pinch valve QVl is opened while the pinch valves QV2-QV5 are closed.

In a further step S2, the inlet chamber 3 of the powder container 2 is then filled with coating powder via the powder inlet 6 and the opened pinch valve QV1, wherein this filling can also occur intermittently in large quantities, since the filled coating powder does not start immediately due to the closed pinch valve QV5 gets on the sieve 5, whereby an overload of the sieve 5 could occur. After filling the inlet chamber 3 of the powder container 2, the pinch valve QVl is then closed in a step S3, while the pinch valve QV5 is slowly opened to gradually transfer the coating powder filled into the inlet chamber 3 into the center chamber 13.

The coating powder transferred into the middle chamber 13 of the powder container 2 is then screened through the sieve 5 into the outlet chamber 4 of the powder container 2 in a further step S5.

After passing the coating powder into the outlet chamber 4, the pinch valve QV5 is then closed in a step S6 while the pinch valve QV4 is opened so that the compressed air injected into the outlet chamber 4 through the semipermeable fluid tray 9 fluidizes the coating powder in a further step S7.

In a further step S8, the two pinch valves QV2 and QV3 are then opened, so that compressed air is blown into the outlet chamber 4 of the powder container 2, whereby the fluidized coating powder located in the outlet chamber 4 is opened via the open pinch valve QV3 and the powder outlet 8 is blown out, which takes place in a further step S9.

The invention is not limited to the preferred embodiments described above. Rather, a multiplicity of variants and modifications is possible, which likewise make use of the concept of the invention and therefore fall within the scope of protection. List of reference numbers:

1 powder feed pump

2 powder containers

3 inlet chamber

4 outlet chamber +

5 sieve

6 powder inlet

7 compressed air connection

8 powder outlet

9 fluid floor

10 Fludisation chamber

11 compressed air connection

12 Libra

13 middle chamber

14 big bag emptying station

15 applicator

16 control unit

17 compressed air source

18 application container

19 DDF pump

20 powder containers QV1-QV5 pinch valves

Claims

1. powder feed pump (1) for conveying coating powder in a powder coating plant, characterized by an integrated sieve (5) for sifting through the coating powder.

Second powder feed pump (1) according to claim 1, characterized by a) a pressure-resistant powder container (2) with an inlet chamber (3) and an outlet chamber (4), between which the sieve (5) is arranged, b) a powder inlet (6) c) a powder outlet (8) discharging from the outlet chamber (4) of the powder container (2) to discharge the coating powder, c) a powder outlet (8) opening into the inlet chamber (3) of the powder container (2) for supplying the coating powder; and d) a compressed air connection (7) which opens into the powder container (2) in order to blow the coating powder out of the powder container (2) through the powder outlet (8).

3. powder feed pump (1) according to claim 2, characterized in that between the inlet chamber (3) and the outlet chamber (4) of the powder container (2) has a central chamber (13) is arranged, wherein the sieve (5) between the central chamber (13 ) and the outlet chamber (4), while a controllable valve (QV5) connects the inlet chamber (3) to the central chamber (13).

4. powder feed pump (1) according to claim 2, characterized in that the inlet chamber (3) and the outlet chamber

(4) of the powder container (2) each directly to the sieve

(5) adjoin.

5. powder feed pump (1) according to one of claims 2 to 4, characterized in that the inlet chamber (3) and / or the central chamber (13) of the powder container (2) above the sieve

(5) is arranged while the outlet chamber (4) of the powder container (2) under the sieve (5) is arranged.

6. powder feed pump (1) according to any one of the preceding claims, characterized in that the powder container (2) has a fluid bottom (9) to fluidize the coating powder.

7. powder feed pump (1) according to any one of the preceding claims, characterized by a balance (12) for measuring the weight of the powder container (2) with the coating powder therein.

8. powder feed pump (1) according to any one of the preceding claims, characterized by a level sensor for determining the level of the coating powder in the powder container (2).

9. powder feed pump (1) according to any one of the preceding claims, characterized in that the sieve (5) is angular.

10. Powder coating system with a powder feed pump (1) according to one of the preceding claims.

11. Powder coating system according to claim 10, characterized in that the powder inlet (6) of the powder container ters (2) without the interposition of another sieve and / or without the interposition of another pump with a powder source (14, 19, 20) is connected.

12. Powder coating installation according to claim 11, characterized in that the powder source (14, 19, 20) a) a big bag emptying station (14), b) a powder container emptying station (19, 20) or c) a powder feed pump (1), in particular a DDF pump (19) or a vacuum feed pump.

13. powder coating installation according to one of claims 10 to 12, characterized in that: the powder outlet (8) of the powder container (2) without interposition of a further pump and / or without the interposition of another screen with an application container (18) is connected, which feeds an application device (15).

14. powder coating installation according to one of claims 10 to 12, characterized in that the powder outlet (8) of the powder container (2) without interposition of another pump and / or without the interposition of another screen and / or without the interposition of an application container directly with a Application device (15) is connected.

15. Operating method for a powder feed pump (1) for conveying coating powder in a powder coating plant, characterized in that the coating powder in the powder feed pump (1) through an integrated sieve (5) is sieved.

16. Operating method according to claim 15, wherein the powder feed pump (1) comprises a powder container (2) with an inlet ^¬ chamber (3), a central chamber (13) and an outlet chamber (4) and the screen (5) is disposed between the center chamber (13) and the outlet header (4) while a controllable valve is disposed between the inlet chamber (3) and the central chamber (13), characterized by the following Steps: a) closing the valve (QV5) between the inlet chamber (3) and the middle chamber (13), b) filling the inlet chamber (3) with the coating powder with the valve closed (QV5) between the inlet chamber (3) and the center chamber (13), c) opening the valve (QV5) between the inlet chamber (3) and the middle chamber (13) and transferring the coating powder from the inlet chamber (3) into the central chamber (13), d) passing through the located in the middle chamber (13)

Coating powder through the screen (5) into the outlet chamber (4), e) closing the valve (QV5) between the inlet chamber (3) and the middle chamber (13), f) blowing out the coating powder in the outlet chamber (4).

17. Operating method according to claim 16, characterized in that the coating powder is gradually transferred from the inlet chamber (3) in the central chamber (13) so as not to mechanically overload the wire (5).

18. Operating method according to one of claims 15 to 17, characterized by the following step: weighing the powder container (2) with the coating powder therein by a balance (12) to determine the mass of the powder container (2) located in the coating powder.

19. Operating method according to one of claims 15 to 18, characterized by the following step:

Measuring the level of the coating powder in the powder container (2), in particular in the inlet chamber (3) of the powder container (2).

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