DE102007049170A1 - Powder spray coater or powder feeder of a powder spray coater - Google Patents

Abstract

A method of conveying coating powder and a powder spray coating device and a powder feed device of a powder spray coating device comprising a powder seal pump (10) and a flexible powder delivery hose (28) connected or connectable to the powder discharge side (26) of the powder seal pump (10) for dispensing coating powder the tube wall is completely or at least on the tube inner surface of an electrically insulating material, characterized in that the tube inner surface has a roughness which is between 2 microns and 7 microns.

Description

The The invention relates to a powder spray coating device or a powder delivery device of a powder spray coating device according to claim 1.

Further The invention relates to a method for conveying coating powder by means of such a powder spray coating device or such a powder conveying device according to another Claim.

Dense phase powder pump (dense phase powder pumps) contain at least one delivery chamber, which with a powder inlet valve and a powder outlet valve is provided. The delivery chamber is alternatively during a suction phase with a vacuum source or during a Delivery phase connectable to a transport compressed air source. through the vacuum of the vacuum source becomes powder through the open powder inlet valve sucked into the delivery chamber while the powder outlet valve closed is. By means of the transport compressed air of the transport compressed air source is the powder located in the delivery chamber through the discharged powder outlet valve while the powder inlet valve closed is. The powder seal pumps usually have two Delivery chambers, which work out of phase with each other, so that alternately sucked in each case in a conveying chamber coating powder while out of the relevant other delivery chamber Coating powder is discharged.

Various types of coating powder delivery devices which comprise a powder sealant pump are known, for example, from the following documents: JP 09/071325 A . DE 196 11 533 B4 . US 2006/0193704 A1 (= EP 1 644 131 A2 ) US 7,150,585 B2 (= WO 2004/087331 A1 ) and the US 2005/0178325 A1 (= EP 1 566 352 A2 ). A vacuum inlet of the at least one delivery chamber, in some embodiments also the compressed air inlet of the delivery chamber, is provided with a filter which is permeable to air but impermeable to coating powder. The filter material used is preferably sintered material. The powder inlet valve and the powder outlet valve are mostly pinch valves.

The funded by a powder seal pump per unit time The amount of powder depends in particular on the size (Volume) of the delivery chamber, from the frequency with which Coating powder sucked into the delivery chamber and then released again, from the strength of the vacuum, from the opening period of the powder inlet valve during the suction phase and the flow resistances in the powder lines upstream and in particular downstream the powder seal pump. The flow resistance are in particular of the length and the inner cross section the powder lines, mostly powder hoses, dependent. The transport compressed air mixes only slightly with the coating powder and pushes the coating powder in front of the delivery chamber through the powder outlet valve.

Other Conditions are in the powder-thin-stream promotion given, in which an injector as a powder pump to promote of coating powder is used. In the injector is by means of a transport compressed air flow generates a negative pressure. through of the sub-pressure coating powder is sucked into the transport compressed air flow. The mixture of transport compressed air flow and powder flows then from the injector to a target site, such as a container or a sprayer. The promoted by the injector Quantity of powder per unit of time depends on the time unit through the injector flowing transport compressed air.

Pulversprühbeschichtungsvorrichtungen with an injector as a powder pump are known for example from the following writings: US 4,284,032 . US 4,357,900 . EP 0 412 289 B1 and EP 0 636 420 A2 ,

In the known devices, the powder delivery lines for conveying coating powder from a powder pump (injector or powder seal pump) to a target object, such as a powder container or a spray device, from a flexible hose, which consists of at least on its inner tube forming the wall layer of electrically insulating material , The friction of the powder particles on the hose inner wall can create high electrical potentials, which are dangerous because they can cause sparking and explosion. To derive such electrical charges and thus to reduce the electrical potentials, it is known to integrate into the tube wall, which consists of electrically insulating material, an electrical conductor which can be grounded. Hoses with an integrated electrical conductor are known, for example, from the following documents: Utility Model DE-G 75 34 723.8 , Utility model DE-G 79 34 101.8 U1 . EP 0 974 779 B1 (= US 6,202,701 B1 ) US 4,027,659 and US 3,070,132 ,

In the powder delivery line of a powder sealant pump, the powder flow has a much higher density of powder than in a powder exhaust line of an injector. Because of the batchwise powder delivery of a powder seal pump there is a risk that the powder flow, in particular in the flow longitudinal direction, but often also over the powder flow cross-section, a varying powder has density.

By The invention aims to solve the problem, to simple Way to even out the density distribution of a powder stream, which is discharged from a powder seal pump.

These Task is according to the invention by the features of claim 1 solved.

Further the object is achieved according to the invention by a Method according to another claim solved.

The Invention has the advantage that the density distribution of a powder stream, which is discharged from a powder seal pump, to simple Way can be made uniform. Another Advantage of the invention is that in this case no powder deposits arise in the powder delivery line or at least the risk for this not larger than in known powder delivery lines.

Further Features of the invention are contained in the subclaims.

The The invention will be described below with reference to the accompanying drawings based on preferred embodiments as examples described. In the drawings show

1 schematically a powder spray coating device according to the invention with a powder sealant pump,

2 1 is a schematic cross section of a flexible hose according to the invention as a powder discharge line of the powder sealant pump;

3 schematically a cross section of another embodiment of a flexible hose as a powder discharge line of a powder seal, and

4 a diagram concerning the definition of surface roughness.

In the 1 illustrated coating powder conveyor 2 forms together with a sprayer 4 a powder spray coater, however, may also be used to convey coating powder to a container, rather than to a sprayer 4 , be used. The sprayer 4 preferably includes a high voltage generator 6 for generating high voltage at at least one high voltage electrode 8th for electrostatic charging of coating powder.

The spray coating powder conveyor 2 contains a powder sealant pump 10 preferably with two delivery chambers 12 and 14 (instead of just one or more than two funding chambers). Each delivery chamber 12 and 14 has seen in the chamber longitudinal direction a powder inlet 16 with a powder inlet valve Q1 or Q2 at one end of the chamber and a powder outlet 18 with a powder outlet valve Q3 or Q4 at the opposite end of the chamber. The valve outlet side 20 of the two powder outlet valves Q3 and Q4 is via powder delivery branch lines 22 respectively. 24 , preferably via a Y-branching element 26 to a common powder delivery line 28 connected, the other end with the sprayer 4 is connectable.

The powder inlet valves Q1 and Q2 are preferably pinch valves. They can be of any known type. Preferably, there are pinch valves whose valve channel 40 through a flexible elastic hose 42 is formed by a pneumatic chamber 44 is surrounded and closing the valve by means of compressed air, which in the pneumatic chamber 44 can be introduced, is radially zusammenquetschbar.

The powder inlet 16 and the powder outlet 18 and the valve channels 40 of the powder inlet valves Q1 and Q2 and the powder outlet valves Q3 and Q4 are aligned with each delivery chamber 12 respectively. 14 preferably with the chamber centerline 32 respectively. 34 ,

1 shows at the one delivery chamber 12 the powder inlet valve Q1 is opened and the powder outlet valve Q3 is closed, while at the other delivery chamber 14 the powder inlet valve Q2 is closed and the powder outlet valve Q4 is opened. The one delivery chamber 12 is in the suction phase for sucking in coating powder. The other delivery chamber 14 is in the dispensing phase for dispensing coating powder. These phases change continuously during powder delivery.

The powder inlet side 46 of the two powder inlet valves Q1 and Q2 can be passed through powder feed branch lines 48 respectively. 50 be connected separately with a powder container or, according to the in 1 shown preferred embodiment, by a preferably Y-shaped branching element 52 with a common powder feed line 56 be connected to spray coating powder 58 from a powder container 60 to suck.

Each delivery chamber 12 and 14 is alternatively during a suction phase (in 1 the delivery chamber 12 ) with a vacuum source 62 connectable or during a dispensing phase (in 1 delivery chamber 14 ) with a transport compressed air source 64 connectable. The transport compressed air source 64 receives compressed air preferably via a pressure regulator from a pressure source 66 , For example, a compressed air network in a company. By means of the vacuum of the Va kuumquelle 62 becomes coating powder 58 through the open powder inlet valve Q1 or Q2 in the delivery chamber 12 respectively. 14 sucked while the powder outlet valve Q3 and Q4 is closed. By means of the transport compressed air of the transport compressed air source 64 that will be in the delivery chamber 12 respectively. 14 are discharged through the powder outlet open valve Q3 or Q4, while the powder inlet valve Q1 or Q2 is closed. The two delivery chambers 12 and 14 are operated out of phase with respect to time, so that in each case alternately into the one delivery chamber (eg delivery chamber 12 ) Coating powder is sucked while from the relevant other delivery chamber, for. B. delivery chamber 14 , Coating powder is discharged, after which then from the one delivery chamber, for. B. delivery chamber 12 , the coating powder is discharged while in the other chamber, z. B. delivery chamber 14 , is sucked in.

The Powder inlet valves Q1 and Q2 and the powder outlet valves Q3 and Q4 are preferably separately controllable.

For controlling the powder seal pump 10 is a control device 70 provided, which contains a plurality of control valves and at least one, preferably a plurality of pressure regulator for generating the pressure at the outlet of the transport compressed air source 64 and for generating the pressure of the control compressed air for actuating the powder valves Q1, Q2, Q3 and Q4 from the compressed air of a compressed air source 66 , Furthermore, the control device contains 70 also control valves for alternative admission of the delivery chambers 12 and 14 with compressed air of the transport compressed air source 64 or with vacuum of the vacuum source 62 , The branching element 26 the two powder delivery branch lines 22 and 24 forms the powder delivery side of the powder seal pump 10 at which the powder delivery line 28 is connectable. In a powder seal pump, which only a single delivery chamber 12 or 14 has, forms the valve outlet side 20 of the powder discharge valve Q3 and Q4, the powder discharge side of the powder seal pump. Instead of a Y-branching element 26 Other branching elements can also be used. Instead of one or two funding chambers 12 and 14 , a powder seal pump may also have three or more delivery chambers 12 respectively. 14 contain. By means of the powder discharge line 28 can be a powder sealant pump 10 Coating powder not only to a sprayer 4 but instead also promote to another powder container. The embodiments of the powder delivery line described below 22 can be used for all mentioned applications.

The powder delivery line 28 is complete, or at least on its side forming the tube inner surface of an electrically insulating material. The electrically insulating material may be, for example, polyvinylchloride (PVC) or a thermoplastic such as polyethylene or vinyl polymer or another plastic or rubber.

According to the invention, the hose inner surface of the powder discharge line 28 a roughness Ra which is between 2 μm and 7 μm. Preferred ranges are between 2 microns and 6 microns and a range between 3 microns and 5 microns, preferably a range between 3.5 microns and 4.5 microns.

The roughness Ra can according to 4 To be defined. The roughness Ra is the arithmetic mean, which is calculated from individual arithmetic mean values of individual measuring distances Lr. The basis for the calculation is the centerline "x" of the roughness profile, ie the inner surface of the tube.The center line "x" intersects the diagram in such a way that within a single measurement section Lr the sum of the surface sections lying on one side 74 equal to the sum of the surface sections lying on the other side 76 becomes. The value Ra of the roughness of the individual measuring sections is the arithmetic mean of the deviations of the diagram from the center line "x", irrespective of the sign of the deviations The roughness (roughness Ra) is determined by SN EN ISO 4287 Are defined. The hatched areas 74 lie on the positive side "+ y." The dashed hatched areas 76 ' are the negative areas folded up about the centerline x 76 the negative side "-y." The areas defined by solid lines 74 are in their sum equal to the sum of hatched areas in dashed lines 76 ,

The flexible hose from which the powder delivery line 28 may consist of a single wall layer or of several wall layers.

2 shows in cross section a preferred embodiment of a hose which the powder discharge line 28 can form. This preferred embodiment contains at least one, preferably two electrical conductors 80 and, which are partially embedded in the tube wall and extend in the tube longitudinal direction through the tube wall. 2 shows two such electrical conductors 80 and 82 , which are arranged diametrically to the tube diameter and protrude into the tube channel, but more than half of its circumference are embedded in the material of the tube wall. The radially inner tip 81 respectively. 83 the electrical conductor 80 and 82 can, instead of as in 2 into the hose channel, with the inner surface of the hose 86 be flush, but be free, ie the electrically isolated material of hose 22 not be covered.

3 shows in cross section another possible embodiment of a flexible hose according to the invention, which as a powder discharge line 28 is usable and in 3 With 2.28 is designated. In the hose wall is at least one, preferably two diametrically opposite arranged electrical conductors 90 and 92 completely embedded, which are completely enclosed by the material of the tube wall and thereby neither into the tube inner surface 86 still protrude into the hose outer surface 96 protrude or protrude.

All electrical conductors 80 . 82 . 90 and 92 For example, they may be electrically conductive plastics, which are electrically conductive, for example by admixing carbon. The electrical conductors may also be metal wires or strand or other materials. The electrical conductors are preferably flexible.

By one or more electrical conductors 80 . 82 or 90 . 92 For example, electrical charges can be dissipated to ground potential caused by friction of the coating powder on the rough hose inner surface 86 arise.

According to the preferred embodiment of the invention, the hose inner diameter 98 in all embodiments, between 5 mm and 8 mm, depending on the powder flow rate of the powder sealant pump to be delivered per unit time.

An inventive hose, as he for the powder discharge line 28 is provided, can also be used as a powder supply line 56 (Suction) can be used advantageously.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - JP 09/071325 A [0004]
• - DE 19611533 B4 [0004]
• US 2006/0193704 A1 [0004]
• - EP 1644131 A2 [0004]
• - US 7150585 B2 [0004]
• WO 2004/087331 A1 [0004]
• US 2005/0178325 A1 [0004]
• - EP 1566352 A2 [0004]
• - US 4284032 [0007]
• US 4357900 [0007]
• - EP 0412289 B1 [0007]
• - EP 0636420 A2 [0007]
• - DE 7534723 U [0008]
• - DE 7934101 U [0008]
• - EP 0974779 B1 [0008]
• - US 6202701 B1 [0008]
• - US 4027659 [0008]
• US 3,070,132 [0008]

Cited non-patent literature

• - SN EN ISO 4287 [0031]

Claims (7)

A powder spray coating device or a powder feed device of a powder spray coating device, comprising a powder seal pump ( 10 ) and a flexible powder delivery hose ( 28 ; 2.28 ), which to the powder delivery side ( 26 ) of the powder sealant pump ( 10 ) is connected or connectable to the dispensing of coating powder, wherein the tube wall completely or at least on the inner tube surface of an electrically insulating material, characterized in that the inner tube surface ( 86 ) has a roughness of between 2 μm and 7 μm. Powder spray coater or powder feeder a powder spray coating apparatus according to claim 1, characterized in that the hose inner surface has a roughness which is between 2 μm and 6 μm, preferably between 3 μm and 5 μm, and also preferably between 3.5 microns and 4.5 microns. Powder spray coating device or powder delivery device of a powder spray coating device according to any one of the preceding claims, characterized in that the wall of the powder delivery hose ( 28 ; 2.28 ) total or at least one the inner surface of the tube ( 86 ) forming tube layer of at least one of the taking place electrically insulating materials: plastic, in particular polyvinyl chloride or a thermoplastic, in particular polyethylene or vinyl polymer. Powder spray coating device or powder conveying device of a powder spray coating device according to one of the preceding claims, characterized in that at least one electrical conductor ( 80 . 82 ; 90 . 92 ) is at least partially embedded in the electrically insulating material of the tube wall and extends in the tube longitudinal direction through the tube wall. A powder spray coating device or powder delivery device of a powder spray coating device according to claim 4, characterized in that more than half of the circumference of the electrical conductor ( 80 . 82 ) embedded in the electrically insulating material of the tube wall and is covered by this material, and that the remaining smaller part of the circumference of the electrical conductor ( 80 . 82 ) is exposed in the inner surface of the tube or from the inner surface of the tube ( 86 ) protrudes out into the hose channel. Powder spray coating device Powder spray coating device or powder conveying device of a powder spray coating device according to one of the preceding claims, characterized in that the tube inner diameter ( 98 ) is between 5 mm and 8 mm. Method for conveying coating powder, characterized in that a powder spray coating device or a powder conveying device of a powder spray coating device according to one of the preceding claims is provided, which comprises a powder sealing current pump ( 10 ) and that the coating powder by means of the powder sealant pump ( 10 ) by a flexible powder delivery hose ( 28 ; 2.28 ) is promoted according to one of the preceding claims.