EP1551558A1

EP1551558A1 - Method and device for transporting pulverulent material

Info

Publication number: EP1551558A1
Application number: EP03816207A
Authority: EP
Inventors: Andreas Kleineidam; Wilhard Kleineidam
Original assignee: H Borger & Co GmbH
Current assignee: Nordson Corp
Priority date: 2002-10-14
Filing date: 2003-10-01
Publication date: 2005-07-13
Also published as: WO2004087331A1; DE10393291D2; US7481605B2; DE20321762U1; JP5241996B2; US20070081865A1; US8491226B2; CA2491391A1; US7648312B2; US8057129B2; US8256996B2; US20100086368A1; EP2279796A2; US20120045287A1; EP2279796A3; US20050095071A1; JP2006521979A; US20080184931A1; US20120308315A1; US7478976B2

Abstract

The invention relates to a method and a device (2) for pneumatically transporting pulverulent material (4). According to said method, a cylindrical chamber (10, 12), which can be connected to a storage container (6) by a sealable inlet (14, 16) and to a transport conduit (28) by a sealable outlet (18, 20), is alternately filled with and emptied of material from the storage container (6), when the outlet (18, 20) is closed and the inlet is open (14, 16), by a vacuum action in the chamber, achieved by means of a delimiting partition in the form of a gas-permeable filter element (50), in order to suck material out of the storage container (6) into said chamber (10, 12). When the inlet is closed (14, 16) and the outlet is open (18, 20), the chamber (10, 12) is supplied with a pressurised gas, in order to expel the material that has been sucked into the chamber (10, 12) into the transport conduit (28). To increase the service life of the filter element (50) and to prevent the contamination of the latter in a simple manner, said filter element (50) is configured as a hollow cylinder and surrounds at least part of the chamber (10, 12).

Description

Method and device for conveying powdery material

The invention relates to a method and a device for conveying powdery material according to the preamble of claim 1 and 8 respectively. The method and the device are used in particular in powder coating systems to powder powder by means of compressed air in a dense stream from a storage container into a conveyor line and through it a spray gun or other spray application device.

Until now, powder coating systems in powder coating systems have usually been conveyed pneumatically in a thin-stream process through hose-shaped delivery lines from a storage container to the spray gun. However, this causes problems, firstly because relatively large amounts of compressed air are required, secondly because the diameter of the tubular delivery line has to be relatively large, and thirdly because of wear problems in the area of kinking delivery paths. For this reason, attempts have been made in some powder coating plants in recent years with the so-called plug or dense phase conveying, in which the powder coating is introduced cyclically either by gravity or by means of negative pressure into a chamber and then ejected from the chamber again with compressed air and in the form of successive ones "Grafting" is conveyed through the delivery line to the spray application device.

A method and a device of the type mentioned at the outset for the plug or dense phase conveyance of powdery substances with suction by means of negative pressure are already known from DE 196 43 523, DE 196 54 649 or EP 0 937 004 B1. The known device has a cylindrical pump chamber, which is provided at its lower end with a discharge opening for the conveyed material and at its upper end with a plate-like filter element impermeable to the conveyed material, through which the pump chamber is alternately connected to a vacuum pump or to a compressed gas source become can, in order to fill the pumping chamber, to draw material to be conveyed from a storage container through a nozzle opening into the side of the pumping chamber, or to push the material to be conveyed through the discharge opening into a discharge line to empty the pumping chamber. In order to enable precise dosing of the material to be conveyed and, at the same time, a high flow rate, the pump chamber should have the smallest possible filling volume and be filled and emptied in the shortest possible working cycle. In order to achieve the latter, however, the gas must be sucked out of the pump chamber or fed into the pump chamber relatively quickly, for which purpose the highest possible pressure difference between the interior of the pump chamber and the vacuum source or the compressed gas source is required. A high pressure difference at the filter element, however, leads to a greater bending and pressure load on the latter and thus to a shortening of its service life, which is why the filter element must be supported with support grids or the like. However, this in turn leads to a reduction in its passage cross section, which is why there is a choice between a higher load and thus a shorter service life of the filter element and a higher gas throughput and thus a shorter working cycle. In the pneumatic conveying of powder coating, there is also the fact that it has a grain size <80 μra, with about 10 to 15% being in a grain size range <5 μm. Since this is in the range of the pore diameter of the filter materials used, particles with a small grain size can penetrate deeply into the filter element or even pass through it. Some of the particles mentioned first remain in the filter element when they are subsequently pressurized with the compressed gas, where they may not dissolve for a long time, which can lead to contamination of the painted surfaces if the color changes. The latter particles can lead to their damage, at least when membrane pumps are used as vacuum generators. However, a smaller pore diameter to avoid these problems would in turn result in a lower gas throughput and thus longer working cycles. Moreover In the known device, when the chamber is emptied, color residues can also remain within the intake manifold, which can also result in paint contamination when changing colors.

Proceeding from this, the object of the invention is to improve a method and a device of the type mentioned at the outset such that the service life of the filter element is prolonged and contamination of the same can be avoided more easily.

This object is achieved according to the invention in that the gas-permeable filter element is a hollow cylinder which, unlike in the prior art, does not form a chamber end wall but part of the peripheral wall of the chamber. The invention is based on the idea that this measure allows the filter area of the filter element to be increased in a simple manner and thus the pressure difference between the outer and the inner surface of the filter element to be reduced with the same gas throughput, without thereby increasing the volume of the chamber and consequently the Dosing accuracy is deteriorated. Unlike in the case of an end-side arrangement of the filter element, a filter element designed as a U wall portion also allows conveying in a straight line through the chamber in the axial direction, thereby ensuring a smoother conveying. In addition, no moving parts are required except at the chamber inlet and outlet.

The hollow cylindrical filter element expediently consists of a sintered material, preferably of sintered plastic powder, since a support material can be dispensed with when using such rigid filter materials. A cylindrical filter element made of a rigid filter material also has a higher stability than a flat filter element of the same size and can therefore be made with a smaller wall thickness with appropriate permeability. It is useful Pore size of the sintered material is smaller than the smallest grain size of the conveyed powdery material, that is to say preferably less than 5 μm when conveying powder coating.

In order to ensure a uniform application of negative pressure or compressed gas, the filter element is expediently surrounded by a housing which is separated from the filter element by a cylindrical annular space. The annular space can alternately be connected to a vacuum source or a compressed gas source, either through a single connection or preferably through two connections, one of which is arranged near its end facing the outlet and can be subjected to negative pressure, while the other near it arranged in front of the inlet end face and can be acted upon with compressed gas. With the last-mentioned arrangement, a considerable increase in the delivery capacity is made possible as a result of a faster filling of the chamber and a greater degree of filling, and as a result of a faster and more complete emptying of the chamber.

A further increase in the conveying capacity can be achieved by selecting an optimal ratio between the length and the inner diameter of the hollow cylindrical filter element, which should preferably be in the range between 10 and 30.

Experiments have shown that relatively short working cycles of less than 0.5 s are possible between two successive aspirations without affecting the life of the filter element if the latter extends more than a third of the length of the chamber between the inlet and the outlet and preferably has a length which is approximately half the length of the chamber.

Another preferred embodiment of the invention provides that the on the two ends of the filter element adjacent cylindrical peripheral wall sections of the chamber are designed to be flexible, and that the inlet and the outlet are arranged in the region of the flexible peripheral wall sections and are each closed gas-tight by a pneumatically operating pinch valve.

The inlet and the outlet of the chamber are preferably arranged at their opposite ends, so that when a single chamber alternately pressurized with gas and vacuum, the conveying path in the area of the latter is straight, i.e. without kinks or bends. The smallest possible pressure drop along the conveying path is also achieved in that the filter element and the rest of the chamber have an inner diameter that essentially corresponds to the inside diameter of a feed line between the storage container and the chamber or the conveying line, and so the conveying path is not subject to major cross-sectional changes.

According to a further preferred embodiment of the invention, the compressed gas is fed into the chamber during the conveyance of the powdery material through the filter element in order to clean the inside of the chamber facing the chamber from adhering powdery material. Since, as a result of a triboelectric charging of the powdery material during the conveyance, electrostatic adhesion of powder particles can also occur at other points in the chamber, for the cleaning of which the compressed gas surge generated by the filter element may not be sufficient, compressed gas on the filter element is expedient for cleaning passed through a cleaning valve into the chamber.

In order to prevent powdery material from escaping from the chamber through this cleaning valve when pressurized gas is supplied to the chamber during the conveyance through the filter element, the cleaning valve preferably has a membrane, which during the supply of Pressurized gas is deformed elastically by the cleaning valve and releases an inlet opening for the pressurized gas into the chamber and which, when the pressurized gas supply is terminated, is deformed back into its original shape by the cleaning valve, in which it tightly closes the inlet opening. The membrane can be formed, for example, by a rubber-elastic piece of hose which is drawn over the circumferential wall provided with through openings of a pipe socket which is closed at its free end and, when compressed gas is supplied to the inside of the pipe socket, is lifted from its circumferential surface by the gas pressure, so that Pressurized gas can flow into the chamber between the membrane and the peripheral wall.

While it would be possible in principle to generate the negative pressure required for the suction of powdery material into the chamber by means of a diaphragm pump, a further preferred embodiment of the invention provides for the use of a so-called vacuum injector, which is pressurized with compressed air from the compressed air source and after the venturi -Principle creates a vacuum.

In order to achieve an even faster working cycle, the device is expediently provided in a known manner with two chambers, one of which is always filled while the other is emptied. In this case, the two chambers are preferably aligned parallel to one another and by Y-shaped line sections with a common feed or. Conveying line connected, the angles between the foot and the two arms of the Y and at the ends of the arms at the transition to the parallel chambers are preferably each less than 30 degrees in order to ensure the most unobstructed material delivery with low pressure drops.

In order to simplify the construction of the device with a double chamber, the inlets and the outlets of both chambers are opened and opened with only two locking mechanisms closed, one of which closes the inlet of the first chamber and at the same time opens the inlet of the second chamber and the other opens the outlet of the second chamber and simultaneously closes the outlet of the first chamber. The two locking mechanisms expediently each comprise a double-acting pneumatic cylinder with two opposite piston rods, the free ends of which press in the resilient wall of the adjacent chamber in order to close its inlet or outlet.

The pneumatic cylinders are preferably controllable in their compressed air supply lines by means of two electromagnetic multi-way switching valves, so that it is possible to open the inlet and the outlet of a chamber for cleaning purposes at the same time, for example to blow out this chamber together with the feed line and the delivery line from the storage container ,

A further simplification of the construction of the double-chamber device is possible in that a single four- or five-way switching valve is used for the simultaneous application of pressure to one chamber with negative pressure and the other chamber, one or two inputs of which have a compressed air source and the other (s) are connected to a vacuum generator, which is preferably designed as a vacuum injector, while its two outputs are each connected to one of the chambers and are alternately connected to the compressed air input or to one of the vacuum inputs by switching the valve.

The invention is explained in more detail below on the basis of an exemplary embodiment shown in the drawing. Show it:

1: a plan view of a device according to the invention for the pneumatic conveying of powder coating in the dense phase process with two conveying chambers; 2: a partially sectioned and somewhat schematic view of the device corresponding to FIG. 1;

3 shows an enlarged longitudinal sectional view of a part of one of the two delivery chambers of the device;

4: a simplified pneumatic circuit diagram of part of the device;

5 shows a sectional view of a preferred vacuum generator of the device;

6 shows a longitudinal sectional view of an alternative cleaning valve for supplying cleaning compressed air into the delivery chambers;

FIG. 7: a plan view of a further device according to the invention corresponding to FIG. 1;

FIG. 8: a view of the device from FIG. 7 corresponding to FIG. 2;

9 is an enlarged longitudinal sectional view of a portion of one of the two delivery chambers of the device of FIGS. 7 and 8

) according to Fig. 3;

10: a simplified pneumatic circuit diagram of part of the device from FIGS. 7 and 8.

The devices 2 shown in FIGS. 1, 2, 7 and 8 of the drawing are used to convey powder coating 4 for the electrostatic powder coating of objects pneumatically in a dense phase process from a storage container 6 to a spray gun 8.

For this purpose, the devices 2 have two parallel cylindrical delivery chambers 10, 12, the opposite of which are open Each end forms an inlet 14, 16 and an outlet 18, 20 for the powder coating 4 being conveyed and with a Y-shaped line section 22 of a feed line 24 leading to the storage container 6 and with a Y-shaped line section 26 of a flexible line leading to the spray gun 8 Delivery line 28 are connected.

Each of the two delivery chambers 10, 12 can be closed in the region of its inlet 14, 16 and its outlet 18, 20 by means of a pinch valve 30. The pinch valves 30 for the two inlets 14, 16, like the pinch valves 30 for the two outlets 18, 20, can each be actuated by means of a double-acting pneumatic cylinder 32 arranged between the two delivery chambers 10, 12. The pneumatic cylinders 32 each have two piston rods 34 which protrude on opposite sides and whose spherically rounded free ends 36 at the inlet 14, 16 and at the outlet 18, 20 respectively through recesses 38 in a rigid cylindrical outer wall section 40 of the adjacent delivery chamber 10, 12 engage with an elastically deformable resilient inner wall portion 42 of the chamber 10, 12 in order to press it against an opposite chamber wall part and to close the inlet 14, 16 and the outlet 18, 20 airtight. Except in the area of the recesses 38, the elastic inner wall sections 42 are firmly connected to the rigid outer wall sections in order to prevent their contraction when a negative pressure is applied in the chamber 10, 12.

The two pneumatic cylinders 32 are each connected to a compressed air tank 48 (FIGS. 4 and 10) by an electromagnetic multi-way switching valve 44, 46 (FIGS. 1 and 7). In the conveying mode, the two switching valves 44, 46 are always switched so that the pneumatic cylinders 32 are pressurized with compressed air so that in one chamber 10 the inlet 14 is open and the outlet 18 is closed, while in the other chamber 12 the inlet 16 is closed and the Outlet 20 is open, or vice versa (as shown in Figures 2 and 8).

In order to suck powder paint 4 from the storage container 6 into the chamber 10 or 12 with the opened inlet 14 or 16 and to expel the suctioned powder paint 4 from the chamber 12 or 10 with the open outlet 20 or 18 into the delivery line 28 to enable, the two chambers 10, 12 are each provided with an air-permeable and for powder coating 4 impermeable hollow cylindrical filter element 50 which the chamber 10, 12 between its inlet 14, 16 and its outlet 18, 20 over part of its length in the circumferential direction limited and forms a peripheral wall portion of the chamber 10, 12.

The hollow cylindrical filter element 50 consists of sintered polyethylene with a wall thickness between 2 and 4 mm and one

Pore size of about 5 microns and has an inner diameter between 5 and 30 mm, which corresponds essentially to the inner diameter of the wall sections 40, 42 adjoining on both sides, the Y-shaped line sections 22 and 26 as well as the loading line 24 and the delivery line 28. The filter element 50 extends approximately over half the chamber length (measured between the centers of the pinch valves 30), it expediently having a length between 20 and 70 mm. At its two ends, the filter element is connected in an airtight manner to the respectively adjoining peripheral wall section 40, 42.

As best shown in FIGS. 3 and 9, each filter element 50 is surrounded by a housing 52 which is separated from the filter element 50 by a cylindrical annular space 54. In the device from FIGS. 1 and 2, the housing 52 has a connection 56 which can be acted upon alternately with negative pressure from a negative pressure generator 58 (FIG. 4) and with compressed air from the compressed air container 48 (FIG. 4). At the two opposite ends of the housing 52 and Filter element 50 is provided with a hose connector 58, onto which the adjoining elastically flexible peripheral wall section 42 can be pushed and fastened by means of hose clips (not shown). The hose sockets are screwed 58 to the housing 52 by means of union nuts 60. Sealing rings 62, 64 inserted between the hose connector 58 and the filter element 50 or the housing 52 ensure that when the chamber 10, 12 is pressurized with compressed air, no compressed air from the chamber 10, 12 or from the annular space 54 of the housing in this area 52 escapes and no air enters the chamber 10, 12 or the annular space 54 from the outside when the chamber 10, 12 is subjected to negative pressure.

As best shown in Fig. 4, the compressed air / vacuum port 56 around housing 52 of each delivery chamber 10, 12 is alternately connected to the vacuum generator 58 and to the compressed air tank 48 via an electromagnetic 5-way switching valve 66 to the respective Apply vacuum to the chamber 10, 12 for suction of powder coating 4 from the storage container 6 with the inlet 14 or 16 open and the outlet 18 or 20 closed, or the powder coating 4 sucked into the chamber 10, 12 with the inlet 14 or closed. 16 and open outlet 18 or 20 by supplying compressed air into the chamber 10, 12 from the chamber 10, 12 and pushing through the delivery line 28 in the dense stream or so-called plug delivery method.

The compressed air container 48, which can be filled with compressed air by a compressor 68, is connected via a pressure regulator 70 and a throttle 72 to one of the three inputs of the 5-way switching valve 66. The other two inputs of the 5-way switching valve 66 are connected by a line 82 to the vacuum generator 58, which is designed as a vacuum injector in the embodiment shown in the drawing. As best shown in FIG. 5, the vacuum injector 58 has an injector nozzle 74 fed with compressed air P from the compressed air container 48. When compressed air is fed into the injector nozzle 74, a vacuum is generated in an annular space 78 surrounding the outlet 76 of the injector nozzle 74 according to the Venturi principle, which is connected via a connecting piece 80 and the line 82 to the two inlets of FIG. 5 connected to the vacuum generator 58 -Way switching valve 66 and each time it is switched alternately to one of the two chambers 10, 12, while the other chamber 12, 10 is simultaneously pressurized with compressed air.

Instead of a 5-way switching valve, a 4-way switching valve could also be used, the two inputs of which are connected to the compressed air tank 48 and the other to the vacuum generator 58, while the two outputs are each connected to one of the two chambers 10, 12 are connected so that each time the valve is switched, compressed air or a vacuum is alternately applied to them.

Simultaneously with the switching of the 5-way switching valve 66, the two multi-way switching valves 44, 46 (FIG. 1) in the compressed air supply lines of the pneumatic cylinders 32 are also switched over to the outlet 18 or in the chamber 10 or 12 which was emptied immediately beforehand. 20 to close and open the inlet 14 or 16, as well as to close the inlet 16 or 14 in the chamber 12 or 10 filled immediately before and to open the outlet 20 or 18.

As best shown in FIG. 2, by applying a negative pressure U when the inlet 16 is open, powder coating 4 is sucked from the storage container 6 or from the feed line 24 into one chamber 12, while that through the filter element 50 into the other chamber 10 Compressed air P supplied the powder coating 4 previously sucked into this chamber 10 through the outlet 18 and through one arm of the Y-shaped line section 26 in the delivery line 28 presses. In order to ensure the smoothest possible delivery without major pressure losses, the Y-shaped line section 26, like the Y-shaped line section 22, is in the region of its bends, ie at the connection points between the foot and the two arms of the Y and between the respective Arm and the inlet 14, 16 of the associated chamber 10, 12 each curved by less than 30 degrees.

The compressed air fed through the filter element 50 into the respective chamber 10, 12 not only presses the powder coating 4 contained in the chamber 10, 12 into the conveying line 28, but also cleans the adhering powder coating 4 from the cylindrical inner surface of the filter element 50, which has been sucked onto this surface due to the negative pressure previously applied. However, it has been shown that the pressure surge generated when the chamber 10, 12 is pressurized with compressed air within the chamber 10, 12 is not always sufficient to also clean the other inner surfaces of the chamber 10, 12 from powder particles, since these are due to a triboelectric Charge can adhere relatively firmly to the surfaces of the chamber 10, 12.

Basically, it is possible to clean a delivery chamber, for example the chamber 10, by opening the multi-way switching valves 44, 46 of the pneumatic cylinders 32 accordingly, both the inlet 14 and the outlet 18 of this chamber 10 (and the inlet 16 and close the outlet 20 of the other chamber 12) in order to then blow this chamber 10 together with the delivery line 26 and the feed line 24 from the storage container 6 or from the spray gun 8.

However, since such cleaning of the entire conveyor line is not always desirable, the two chambers 10, 12 are each provided with an additional cleaning valve 84 (FIGS. 2 and 9) through which compressed air is used to clean the chamber 10, 12 can be blown inside the same. The cleaning valve 84 which opens between the filter element 50 and the inlet 14, 16 (or the outlet 18, 20) radially from the side into the chamber 10, 12 essentially consists of a metallic pipe nipple 86 with an annular cross section, which is connected by means of an external thread its thicker end facing away from the chamber 10, 12 is screwed airtightly into an internal threaded bore of a pipe socket 88 projecting beyond the chamber wall 42 and the thinner end facing the chamber 10, 12 is closed at the end and has a plurality of radial bores 90 in its cylindrical peripheral wall 92 (cf. also Fig. 6). On the thinner end of the nipple 86, a membrane in the form of a tube piece 94 made of a rubber-elastic material is fastened, which rests loosely against its outer circumferential surface under tension and closes the bores 90, as shown in FIGS. 2 and 9 below. During the supply of compressed air to the cleaning valve 84, the diaphragm 94 is lifted by the compressed air from the outer circumferential surface of the nipple 86, so that the compressed air can flow between the diaphragm 94 and this circumferential surface into the chamber 10, as in FIGS. 2 and 9 shown above. At the end of the supply of compressed air, the deformed membrane 94 rests against the circumferential surface of the nipple 86 due to its elastic restoring force and prevents powder coating 4 from escaping through the cleaning valve 84 when the chamber 10, 12 is subsequently pressurized with compressed air.

In the cleaning valve 84 shown enlarged in FIG. 6, a ball check valve 96 is provided in addition to the membrane, the ball 98 of which is pressed out of its seat against the force of a spring 102 when compressed air is fed into the valve 96.

In contrast to the device 2 from FIGS. 1 to 6, the device 52 in FIGS. 7 to 10 has the housing 52 of each filter element 50 with two connections 104 and 106, respectively Mistake. While one connection 104 is arranged near the outlet end of the filter element 50 and can be subjected to negative pressure, the other connection 106 is arranged near the inlet end of the filter element 50 and can be pressurized with compressed air P from the compressed air tank 48.

For this purpose, as best shown in FIG. 10, a line 108 branches between the 5-way switching valve 66 and the housing 52 of each filter element 50, a spring-loaded line in each of the two branch lines 110 and 112 leading to the connections 104 and 106, respectively Check valve 114, 116 is inserted with the opposite direction of installation, so that when compressed air is fed into line 108, check valve 114, which is arranged before connection 104, opens against the spring force, while check valve 116, which is arranged before connection 106, remains closed. Conversely, when a negative pressure is applied in line 118, check valve 116 opens against the spring force, while check valve 114 remains closed.

In order to further increase the conveying capacity of the device 2, the hollow cylindrical filter elements 50 in the device in FIGS. 7 to 10 also have a greater length or a greater length / inner diameter ratio, namely a length of 80 or 250 mm an inner diameter of 6 or 12 mm and an associated chamber length between the middle of the inlet and outlet side pinch valve 30 of 180 and 400 mm.

Claims

claims

1. A method for the pneumatic conveying of powdery material, in particular powder coating, in which a cylindrical chamber which can be connected through a closable inlet with a storage container and through a closable outlet with a conveying line is alternately filled and emptied with material from the storage container by the chamber at closed outlet and when the inlet is open, a negative pressure is applied through a boundary wall formed by a gas-permeable filter element in order to suck material from the storage container into the chamber, and then by pressurizing the chamber with a pressurized gas when the inlet is closed and the outlet is open is, in order to press the material sucked into the chamber into the delivery line, characterized in that the gas-permeable filter element (50) is designed as a hollow cylinder and encloses at least a part of the chamber (10, 12).

2. The method according to claim 1, characterized in that the chamber (10, 12) for emptying through the filter element (50) is acted upon by compressed gas.

3. The method according to claim 1 or 2, characterized in that the chamber (10, 12) for cleaning past the filter element (50) is pressurized with compressed gas which is fed through a cleaning valve (84) into the chamber (10, 12) ,

4. The method according to any one of the preceding claims, characterized in that the negative pressure is generated by a vacuum injector (58) charged with compressed gas.

5. The method according to any one of the preceding claims, characterized in that conveyed in parallel with two chambers (10, 12), one of which is filled from the storage container (6), while the other is emptied into the delivery line (28).

6. The method according to claim 5, characterized in that the inlets (14, 16) and the outlets (18, 20) of both chambers (10, 12) are opened and closed by means of two locking mechanisms (30, 32), one of the locking mechanisms (30, 32) closes the inlet (14; 16) of one of the two chambers (10; 12) and at the same time opens the inlet (16; 14) of the other chamber (12; 10) and the other closing mechanism

(30, 32) opens the outlet (18; 20) of one chamber (10; 12) and at the same time closes the outlet (20; 18) of the other chamber (12; 10).

7. The method according to claim 5 or 6, characterized in that the application of a chamber (10; 12) with a negative pressure and the simultaneous application of the other chamber (12; 10) with compressed gas by a single multi-way switching valve (66) ,

8.Device for the pneumatic conveying of powdery material, in particular powder coating, with a cylindrical chamber which can be connected alternately through a closable inlet to a storage container and through a closable outlet with a conveying line which has a boundary wall formed by a gas-permeable filter element, which can be acted upon by the filter element with negative pressure in order to draw off gas from the chamber and fill the chamber with material from the storage container through the open inlet when the outlet is closed, and which can be acted upon with a pressurized gas to the material sucked into the chamber to press into the delivery line through the open outlet when the inlet is closed, characterized in that the filter element (50) is designed as a hollow cylinder and encloses at least part of the chamber (10, 12).

9. The device according to claim 8, characterized in that the filter element (50) over more than a third of the length the chamber (10, 12) extends between the inlet (14, 16) and the outlet (18, 20).

10. The device according to claim 8 or 9, characterized in that a peripheral wall portion (42) of the chamber (10, 12) is resilient on both sides of the filter element (50), and that at the inlet (14, 16) and at the outlet (18, 20) a pneumatic pinch valve (30) is arranged in each case.

11. The device according to one of claims 8 to 10, characterized in that an inner diameter of the filter element (50) substantially the inner diameter of adjoining peripheral wall sections (42) of the chamber (10, 12), the inner diameter of a feed line (24) between the chamber (10, 12) and the storage container (6) and / or the inner diameter of the delivery line (28) corresponds.

12. Device according to one of claims 8 to 11, characterized in that the inlet (14, 16) and the outlet (18, 20) are arranged on opposite ends of the chamber (10, 12).

13. Device according to one of claims 8 to 12, characterized in that the filter element (50) consists of a sintered material.

14. The apparatus according to claim 13, characterized in that the filter element (50) consists of sintered plastic powder.

15. Device according to one of claims 8 to 14, characterized in that the filter element (50) has a pore size of less than 20 microns, preferably less than 5 microns.

16. Device according to one of claims 8 to 15, characterized in that the filter element (50) is surrounded by a housing (52) which is separated from the filter element (50) by a cylindrical annular space (54) and at least one with a vacuum generator (58) and / or with a pressure gas source (48) connectable connection (56).

17. Device according to one of claims 8 to 16, characterized in that the housing (52) has an outlet-side vacuum connection (104) and an inlet-side compressed gas connection (106).

18. Device according to one of claims 8 to 17, characterized in that the chamber (10, 12) for cleaning by a cleaning valve (84) past the filter element (50) can be acted upon with compressed gas.

19. The apparatus according to claim 18, characterized in that the cleaning valve (84) has a membrane (94) which is elastically deformed by the cleaning valve (84) during the supply of compressed gas and releases an inlet opening into the chamber (10, 12) and deforms back at the end of the compressed gas supply and closes the inlet opening.

20. Device according to one of claims 8 to 19, characterized by at least one vacuum injector (58) for applying pressure to the chamber (10, 12).

21. Device according to one of claims 8 to 20, characterized by two chambers (10, 12), one of which can be connected to the storage container (6) by opening its inlet (14; 16) and the other essentially simultaneously by opening its outlet (20; 18) can be connected to the delivery line (28), and vice versa.

22. The apparatus according to claim 21, characterized by two locking mechanisms (30, 32), one of which is the inlet (14; 16) of one chamber (10; 12) closes and at the same time opens the inlet (16; 14) of the other chamber (12; 10) and the other the outlet (18; 20) of the one chamber (10; 12) opens and at the same time the outlet. (20; 18) of the other chamber (12; 10) closes.

23. The device according to claim 22, characterized in that each locking mechanism (30, 32) has a double-acting pneumatic cylinder (32) with two opposing piston rods (34), the ends (36) of a resilient peripheral wall section (42) of the adjacent chamber (10, 12) to close their inlet (14, 16) or outlet (18, 20).

24. Device according to one of claims 21 to 23, characterized by a single multi-way switching valve (66) for the simultaneous application of a chamber (10; 12) with negative pressure and the other chamber (12; 10) with compressed gas.

25. The device according to claim 24, characterized in that the multi-way switching valve (66) together with at least one further multi-way switching valve (44, 46) in a compressed air supply line to the pneumatic cylinders (32) of the two locking mechanisms (30, 32) can be actuated ,

26. Device according to one of claims 21 to 25, characterized in that the two chambers (10, 12) by Y-shaped line sections (22, 26) with a supply line (24) leading to the storage container (6) or with the delivery line (28) are connected.

27. The device according to claim 26, characterized in that the conveying path in the region of the Y-shaped line sections (22, 26) has bends of less than 30 degrees.