EP1752399B1 - Device and method for conveying powder material - Google Patents

Abstract

The powder transport device has a transport chamber (FK1) arranged between a powder inlet valve and a powder outlet valve. The transport channel is connected via a first channel (8) to a vacuum valve (W1) via which a vacuum is produced in the transport chamber and via a second channel (9) opposite the first channel to a compressed air valve (DV1). An independent claim is also included for a powder transport method.

Description

Technical area

A powder coating plant is a plant for coating workpieces with powder. For this purpose, the powder is conveyed by means of a conveying device from a powder storage container and transported to a powder spray gun, in order then to be applied by means of the powder spray gun to the workpiece to be coated. The conveyor may be, for example, a pump or a venturi-type injector. As a rule, the system also includes a booth into which the workpieces are coated. The excess, not adhering to the workpiece powder is collected, transported to egg nem powder container and can then be used again for coating.

The invention relates to a device for conveying powder, which is also referred to below as a conveying device, and a method for operating the device. The conveying device can be used, for example, for transporting the powder to the spray gun or also for the return transport of the excess powder.

State of the art

From the state of the art WO 2005/051549 A1 is known a pump for coating powder. The pump includes a pump chamber into which powder is sucked by vacuum and from which the powder is blown out by means of compressed air. By means of several pinch valves, the transport of the powder into the pump chamber and out of the pump chamber is controlled. The pump chamber is formed by a luttdurchlässige, for example made of porous polyethylene sleeve. By the powder inlet valve is opened and the air is sucked from the outside through the sleeve from the pump chamber, powder is sucked into the sleeve. Subsequently, the powder inlet valve is closed, the powder outlet valve is opened and the powder sucked into the sleeve is blown out of the sleeve by means of purging air. To suck the air through the porous wall of the sleeve sufficiently quickly, a lot of energy is needed. Otherwise, the required negative pressure builds up slowly inside the sleeve. From a control point of view, the sleeve forms a delay element. Another disadvantage is that powder can close the pores of the sleeve. This in turn reduces the suction and delivery rate of the pump, the pump will not operate at a constant rate over time, the operating characteristics of the pump will change and the sleeve will wear out. If the parameters of the pump change too much, replace the sleeve with a new sleeve.

Furthermore, from the prior art WO 2004/087331 A1 a pump for conveying coating powder is known, which has an air-permeable filter element and operates according to the principle described above. Also This pump suffers from the above-mentioned disadvantages.

From the publication EP 1 566 352 A2 are known a powder feed pump and the associated operating method. The powder feed pump comprises a feed chamber with an inlet which can be closed by an inlet valve, and an outlet which can be closed by an outlet valve. In addition, a vacuum connection is provided in order to generate a negative pressure in the delivery chamber through which powder can be sucked. The vacuum connection can be closed by a suction valve.

In addition, from the prior art DE 199 59 468 A1 a device for the pneumatic conveying of powdery substances known. The device comprises a pipe system, wherein a volume is sucked in with negative pressure and discharged with overpressure for continuation. Within the piping systems, a metering chamber, which can be alternately filled and emptied via a control device, is provided for metering the pulverulent substance. To this metering chamber on the one hand - with the interposition of a filter - a gas pressure line and a suction line and on the other hand, a supply line and a discharge line connected.

From the publication DE 24 37 799 a pneumatic conveying device for dusty or granular material, such as cement, flour, grain or fertilizer with a suction device is known. The conveying device comprises two containers and a compressor. The containers are operated alternately with suction or pressure conveying. The switched on pressure conveying container is connected to a pressure conveying line.

Finally, from the publication DE 101 21 934 A1 a method for the pneumatic conveying of powdery substances and its application in cold gas spraying known. In this case, the powdery substance is sucked in a pipe system in a volume with negative pressure and discharged with overpressure for continuation. Within the pipe system is a metering chamber, which is alternately filled and emptied for metering the powdery substance.

Presentation of the invention

An object of the invention is to provide a device for conveying powder and a method for operating the device, wherein the number of moving parts and the wear are minimized.

Advantageously, the device according to the invention also works over a longer period of time with constant power.

The object is achieved by a device for conveying powder with the features of claim 1.

The device according to the invention for conveying powder has a delivery chamber which is arranged between a powder inlet valve and a powder outlet valve. The delivery chamber is connected via a first channel to a vacuum valve via which in the delivery chamber a negative pressure can be generated. In addition, the delivery chamber is connected via a second and a third channel with a compressed air valve. The third channel is arranged so that compressed air can be blown through it in the direction of the inlet valve.

The object is also achieved by a method for spreading the device for conveying powder with the features of patent claim 8.

The inventive method for conveying powder with the powder conveying device comprises the following work cycles. In a first power stroke, a negative pressure is generated in the delivery chamber. Then, in a second cycle, the powder is sucked into the delivery chamber and then the powder is blown out of the delivery chamber in a third operating cycle.

Advantageous developments of the invention will become apparent from the features indicated in the dependent claims.

In one embodiment of the device according to the invention, the second channel is arranged opposite to the first channel. As a result, when the powder is blown out of the delivery chamber, compressed air is also blown into the first channel, which connects the negative pressure valve with the delivery chamber, and this is cleaned.

Advantageously, in the device according to the invention, the third channel is provided to connect the delivery chamber to the compressed air valve. The third channel is arranged so that compressed air can be blown through it in the direction of the inlet valve. This allows the powder to be blown even better from the delivery chamber.

In addition, it is advantageous if in the device according to the invention, the compressed air valve and the vacuum valve are designed as solenoid valves.

In addition, in the device according to the invention, the vacuum valve may be connected to an injector or other vacuum generator.

To solve the problem is also proposed in the inventive device to connect the vacuum valve with a vacuum tank. The tank forms a vacuum reservoir and relieves the vacuum pump.

In the device according to the invention, according to a further feature of the invention, the inlet valve and the outlet valve may be formed as hose valves.

In a further development of the inventive device, the delivery chamber is formed as a straight channel and arranged the inlet valve at one end of the straight channel and the outlet valve at the other end of the straight channel. This has the advantage that the powder is transported in a straight path, thereby reducing the risk of caking or sintering of the powder at the walls of the delivery chamber.

In a further development of the method according to the invention, the inlet valve and the outlet valve are closed in the first cycle and the vacuum valve is opened. In the second working cycle, the vacuum valve is closed and the inlet valve is opened. In the third stroke, the inlet valve is closed and the outlet valve and the compressed air valve are opened.

In a further embodiment of the method according to the invention for conveying powder with two of the above-mentioned devices, the working cycles of the two devices are carried out offset in time from one another. This can increase the flow rate and make the powder flow more uniform. The powder flow then pulsates less.

Finally, in the method according to the invention, the delivery rate can be adjusted via the frequency of the power strokes, the discharge air pressure, the vacuum, the opening time of the vacuum valve, the opening time of the inlet valve and / or the volume of the delivery chamber.

Brief description of the drawings

Figur 1

zeigt eine Ausführungsform der erfindungsgemäßen Fördervorrichtung in einer dreidimensionalen Ansicht.

Figur 2

zeigt die in Figur 1 dargestellte Fördervorrichtung im Querschnitt.

Figur 3

zeigt einen zweiten Querschnitt der in Figur 1 dargestellten Fördervorrichtung.

Figur 4

zeigt in einem Blockschaltbild den ersten Arbeitstakt der Fördervorrichtung.

Figur 5

zeigt in einem zweiten Blockschaltbild den zweiten Arbeitstakt der Fördervorrichtung.

Figur 6

zeigt in einem dritten Blockschaltbild den dritten Arbeitstakt der Fördervorrichtung.

Figur

7 zeigt in einem Blockschaltbild der Fordervorrichtung mit zwei Förderkammern.

In the following the invention will be explained with several embodiments with reference to seven figures.

FIG. 1

shows an embodiment of the conveyor device according to the invention in a three-dimensional view.

FIG. 2

shows the in FIG. 1 illustrated conveyor in cross section.

FIG. 3

shows a second cross section of in FIG. 1 shown conveyor.

FIG. 4

shows in a block diagram the first power stroke of the conveyor.

FIG. 5

shows in a second block diagram, the second power stroke of the conveyor.

FIG. 6

shows in a third block diagram, the third power stroke of the conveyor.

figure

7 shows a block diagram of the conveying device with two delivery chambers.

Ways to carry out the invention

in FIG. 1 is a possible embodiment of the conveyor device according to the invention shown in a three-dimensional view. The conveyor comprises two parallel powder conveyors, which are summarized in an assembly. In principle, any number of powder conveyors can be combined to form an assembly. The first powder conveyor has an intake valve EV1, a vacuum valve VV1, a compressed air valve DV1 and an exhaust valve AV1. The second powder conveyor also has an inlet valve EV2, a vacuum valve VV2, compressed air valve DV2 and an outlet valve AV2. The delivery chambers of the two powder conveyors are housed in a common housing 5. About a pressure air connection 6, which is attached to the housing 5, the two powder conveyors can be supplied with compressed air DL. In addition, a vacuum port 7 is provided on the housing 5. The vacuum port 7 can be connected to a vacuum pump, which in FIG. 1 not shown, to be able to generate a negative pressure in the delivery chambers of the two powder conveyors can. The two intake valves EV1 and EV2 as well as the two exhaust valves AV1 and AV2 are at the in FIG. 1 shown embodiment designed as pneumatically controlled pinch valves. The two compressed air valves DV1 and DV2 as well as the two vacuum valves VV1 and VV2, on the other hand, are opened and closed via an electric actuator.

In FIG. 2 the Pulverfordervorrichtung is shown in cross section along the section line AA. The first inlet valve EV1 can be connected via an intake 4 with a powder hose or a powder line. In the interior of the inlet valve EV1, an elastic valve tube 2 is arranged, the inner cross section of which is reduced when it is acted upon by the valve control port 3 with compressed air DL. The powder channel in the inlet valve EV1 is thereby closed. The valve tube 2 is guided inside the housing 1 of the inlet valve EV1. The inlet valve housing 1 is funnel-shaped on the inlet side and on the outlet side, so that on the inlet side, the conically shaped intake manifold 4 in the mounted state presses the valve tube 2 to the funnel-shaped inlet of the inlet valve housing 1. On the outlet side, the inlet valve housing 1 is provided with an external thread, so that it can be screwed into the housing 5. The housing 5 is conically shaped on the inlet side and presses in the assembled state the valve tube 2 against the funnel-shaped inner wall of the inlet valve housing 1. Thus, the valve tube 2 is fixed at its ends and also forms a sufficient seal. When the valve tube 2 is pressurized with compressed air, a pressure chamber is formed between the inlet valve housing 1 and the valve tube 2, which becomes larger the higher the air pressure generated by the compressed air DL. Finally, when the air pressure is high enough, the vertical hose 2 deforms so much that the powder intake passage in the intake valve EV1 is completely closed.

The exhaust valve AV1, which is arranged on the downstream side of the delivery chamber FK1, is identical to the Inlet valve EV1. At the outlet 22 of the outlet valve AV 1, a powder hose or a powder line for removing the powder can be connected. The control of the exhaust valve AV2 is via the valve control port 21 which is screwed into the Auslaßventilgehäuse 19. The valve tube of the exhaust valve AV1 is indicated by the reference numeral 20.

At the in FIG. 2 In the embodiment of the powder requestor shown, the vacuum valve VV1 is arranged in the upstream section of the delivery chamber FK1. The vacuum valve VV1 is formed as a solenoid valve or electrically driven valve. The valve stem 13 of the vacuum valve VV1 is guided in a guide sleeve 12 and moved by an electromagnetic valve drive 11. If the vacuum valve VV1 is open, so that the valve tappet 13 releases the channel 8 to the delivery chamber FK1, a negative pressure can be generated in the delivery chamber FK1.

Also in the upstream portion of the delivery chamber FK1, the compressed air valve DV1 is disposed. The pressure air valve DV1 may also be formed as a solenoid or solenoid valve. Its valve tappet 17 is guided in a guide sleeve 16 and moved over the valve drive 15. If the compressed air valve DV1 is opened, the two channels 9 and 10 are free, so that compressed air can flow into the delivery chamber FK1. The channel 9 is arranged in the housing 5 so that an upstream compressed air flow is formed. As a result, the residual powder present in the upstream end of the delivery chamber FK1 can also be blown out of the delivery chamber 1. The channel 10 is located directly opposite the channel 8, so that the through the channel 10 flowing compressed air DL the channel 8 freed of powder residues.

If a color change is to be made, the vacuum valve VV1 and the inlet valve EV1 are closed, the outlet valve AV1 is opened and compressed air is blown through the delivery chamber FK1 in the direction of the outlet connection 22 via the open compressed air valve DV1. In order to be able to clean the powder conveying device also upstream, the vacuum valve VV1 and the exhaust valve AV1 are closed, and the inlet valve EV1 and the compressed air valve DV 1 are opened. As a result, compressed air flows through the two compressed air ducts 9 and 10 upstream through the inlet valve EV1 to the intake manifold 4. The powder still in the powder conduit is thus blown back into the powder reservoir. The longitudinal axis of the powder conveying device is identified by the reference LA and the conveying direction of the powder by P.

The above applies mutatis mutandis to the second powder conveyor.

In FIG. 3 is the in FIG. 1 shown powder conveying device along the section line BB shown in cross section. Via the bore 40 and the channel 10, compressed air DL is blown into the delivery chamber FK 1 when the first compressed air valve DV1 is opened. If, however, the compressed air valve DV2 is opened, compressed air DL is blown into the delivery chamber FK2 via the channel 40 and the channel 42. If the compressed air valve DV1 is closed and the vacuum valve VV1 is opened, air is sucked out of the delivery chamber FK1 from the delivery chamber FK1 via the channel 8 and the bore 41. Is the compressed air valve DV2 closed and the vacuum valve VV2 open, air is sucked from the delivery chamber FK2 via the channel 43 and the channel 41 from the delivery chamber FK2.

The following is the operating principle for the first of the two powder conveyors based on the FIGS. 4 to 6 further explained. The same applies mutatis mutandis to the second and any other powder conveyor. In FIG. 4 is shown in the form of a block diagram of the first cycle of the Pulverforderers. The function of the first working cycle can also be described as "creating underpressure" or "building up underpressure". In this case, the inlet valve EV1, which is connected via a powder line with a powder reservoir 30, closed. The outlet valve Av1, which is connected via a powder line 31 with a powder spray gun 32, is closed. In addition, the compressed air valve DV1, which is connected via a compressed air line with a compressed air tank 34 and a compressed air pump 33, closed. On the other hand, the negative pressure valve VV1 connected to a negative pressure tank 35 and a vacuum pump 36 is opened. As a result, a negative pressure is generated in the delivery chamber FK1.

As soon as the desired negative pressure has been reached in the delivery chamber FK1, a second operating cycle is initiated in FIG. 5 is shown, the vacuum valve VV1 closed and the inlet valve EV1 open. The function of the second cycle can also be described as "aspirate powder". As a result, the powder flows from the powder reservoir 30 into the delivery chamber FK1.

As soon as a sufficient amount of powder has been sucked into the delivery chamber FK1, in a third working cycle, which in FIG. 6 is shown, the inlet valve EV1 closed again. Now, the exhaust valve AV1 and the compressed air valve DV1 are opened so that the powder flows in the direction of the powder spray gun 32 by means of the compressed air injected into the delivery chamber FK1. The function of the third working cycle can also be described as "blow out powder".

As soon as the powder has blown out of the delivery chamber FK1, it is again possible to start the working cycle 1 "generate negative pressure".

In FIG. 7 is shown in the form of a block diagram, the powder delivery device with two delivery chambers FK1 and FK2. The control of the valves DV1, VV1, EV1, AV1, DV2, VV2, EV2 and AV2 by means of a controller 45. The controller 45 generates at its outputs S1 to S4 electrical control signals for controlling the electrically operated valves DV1, DV2, VV1 and V V2. Via the compressed air connections S5 to S8, the controller 45 controls the two intake valves EV1 and EV2 and the two exhaust valves AV1 and AV2 by means of compressed air.

The compressed air tank 34 and the vacuum tank 35 are optional. They serve to relieve the two pumps 33 and 36. The tanks 34 and 35 are particularly helpful when several powder conveyors are connected. As the pump 36 for generating the negative pressure, for example, an injector, a piston pump, a diaphragm pump or other vacuum generator can be used.

The Forderleistung the Fordervorrichtung can be adjusted, inter alia, on the frequency of the power strokes. Since no damping element, such as a porous sleeve or an air filter is arranged between the delivery chamber FK1 / FK2 and the vacuum valve VV1 / VV2, but only an air duct, the required negative pressure in the delivery chamber FK1 / FK2 is reached very quickly. As a result, if desired, the first power stroke during which the delivery chamber is evacuated can be kept very short in time. In addition, the delivery rate is determined by the air pressure used to blow out the powder from the delivery chamber, the amount of negative pressure, the time during which the negative pressure valve is open, the time during which the inlet valve is open, the time duration during which the compressed air valve is open and set for the length of time the outlet valve is open. The volume of the delivery chamber also has an influence on the delivery rate. As a rule, it is favorable to design the delivery chamber oblong. The ratio of diameter to length is preferably between 1: 2 and 1:10. The mentioned parameters can be adjusted by means of the controller 45.

The valves can be designed as self-closing valves.

The powder conveying device according to the invention is not limited to the embodiment shown in the figures. For example, the intake valves EV1 and EV2 and the exhaust valves AV1 and AV2 may be formed as non-return valves or as ball valves instead of pinch valves.

Advantageously, the conveyor device according to the invention can be operated in any spatial orientation. The conveyor can thus be installed both standing and lying depending on the structural conditions.

A further advantage of the invention is that the delivery chambers FK1 and FK2 have no dead space, so that the same amount of powder is conveyed with each powder delivery cycle. As a result, a high constancy in the delivery rate can be achieved.

If two powder conveyors operated in parallel with respect to time, the powder delivery rate can be further increased. In addition, the powder transport can be made more continuous. Pulsation of the powder flow is avoided. One possibility is, for example, that when the first powder conveyor executes the second power stroke "suction powder", the second powder conveyor performs the first power stroke "build-up of negative pressure". Thus, the second Fulverförderer delayed by one clock compared to the first powder conveyor. Instead, however, it is also possible for the second powder conveyor to follow the power stroke of the first powder conveyor with two decelerations. That is, when the first powder conveyor performs the third power cycle "blow out powder", the second powder conveyor performs the first "generate negative pressure" power stroke. The control of the two powder conveyors takes place, as already mentioned, by means of the controller 45.

The foregoing description of the embodiments according to the present invention is for illustrative purposes only, and not for the purpose of limiting the invention.

LIST OF REFERENCE NUMBERS

1

Inlet valve housing

2

valve hose

3

Valve control port

4

intake

5

casing

6

Compressed air connection

7

Vacuum port

8th

first channel

9

second channel

10

third channel

11

valve drive

12

guide sleeve

13

tappet

14

thread

15

valve drive

16

guide sleeve

17

tappet

18

thread

19

outlet valve

20

valve tube

21

Valve control port

22

outlet

23

valve drive

24

guide sleeve

25

tappet

26

valve drive

27

guide sleeve

28

tappet

30

Powder reservoir

31

tube

32

spray gun

33

Compressed air pump

34

Compressed air tank

35

Pressurized tank

36

vacuum pump

40

Compressed air duct

41

Vacuum channel

42

channel

43

channel

45

control

EV1, EV2

intake valves

DV1, DV2

Pneumatic valves

VV1, VV2

Vacuum valves

AV1, AV2

exhaust

FK1, FK2

delivery chambers

LA

longitudinal axis

P

Conveying direction of the powder

DL

compressed air

V

vacuum

Claims (11)

1. A device for conveying powder,

   - wherein a conveying chamber (FK1) is provided which is located between a powder inlet valve (EV1) and a powder outlet valve (AV1),

   -- wherein the conveying chamber (FK1) is connected, via a first duct (8), with a vacuum valve (VV1) over which a vacuum can be generated in the conveying chamber (FK1), and

   - wherein the conveying chamber (FK1) is connected, via a second duct (9), with a compressed air valve (DV1), and

   - wherein a third duct (10) is provided, over which the conveying chamber (FK1) is connected with the compressed air valve (DV1) and is located in such a way that Lhe third duct (10) can be blown through with compressed air (DL) in the direction of the inlet valve (EV1).
2. The device according to claim 1,
   wherein the second duct (9) is located opposite the first duct (8).
3. The device according to claim 1 or 2,
   wherein the compressed air valve (DV1) and the vacuum valve (VV1) are designed as solenoid valves.
4. The device according to one of the claims 1 to 3,
   wherein the vacuum valve (VV1) is connected with a vacuum generator (29).
5. The device according to one of the claims 1 to 4,
   wherein the vacuum valve (VV1) is connected Lo a vacuum reservoir tank (28).
6. The device according to one of the claims 1 to 5,
   wherein the inlet valve (EV1) and outlet valve (AV1) are designed as hose valves.
7. The device according to one of the claims 1 Lo 6,
   wherein the conveying chamber (FK1.) is designed as a straight duct and the inlet valve (EV1) is located at one end of the straight duct and the outlet valve (AV1) is located at the other end of the straight duct.
8. A method for conveying powder with a device according to one of the claims 1 to 7, including the following operating cycles:

   - in a first operating cycle, a vacuum is generated in the conveying chamber (FK1),

   - then, in a second operating cycle, the powder is sucked into the conveying chamber (FK1), and

   - then, in a third operating cycle, the powder is blown out of the conveying chamber (FK1).
9. The method according to claim 8,

   - wherein, in the first operating cycle, the inlet valve (EV1) and the outlet valve (AV1) are closed and the vacuum valve (VV1) is opened,

   - wherein, in the second operating cycle, the vacuum valve (VV1) is closed and the inlet valve (EV1) is opened, and

   - wherein, in the third operating cycle, the inlet valve (EV1) is closed and the outlet valve (AV1) and the compressed air valve (DV1) are opened.
10. The method for conveying powder with two of the devices according to one of the claims 1 to 9,
    wherein the operating cycles of both devices are executed temporally offset with each other.
11. The method according to one of the claims 1 to 10,
    wherein the conveying performance is adjusted via the frequency of the operating cycles, the blowing out air pressure, the vacuum, the opening time of the vacuum valve (VV1), the opening time of the inlet valve (EV1) and/or the volume of the conveying chamber (FK1).

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