GB2127370A

GB2127370A - Improved dispenser of powdered electrostatic varnish with auxiliary ducts for feeding compressed air

Info

Publication number: GB2127370A
Application number: GB08226524A
Authority: GB
Inventors: Gabriele Missier
Original assignee: MISSIER GABRIELE TRASMETAL; Trasmetal di Gabriele Missier
Current assignee: MISSIER GABRIELE TRASMETAL; Trasmetal di Gabriele Missier
Priority date: 1982-09-17
Filing date: 1982-09-17
Publication date: 1984-04-11
Also published as: FR2533463B1; DE3234802A1; GB2127370B; DE3234802C2; FR2533463A1

Abstract

The invention relates to a dispenser for a powder to be used for the electrostatic varnishing, in which the powder in admixture with air is fed into a reservoir 113 and thence through a gap 114 defined between two plates 111, 112 to deliver the powder to the outside. The reservoir 113 is divided into two chambers 115, 116 by an intermediate porous diaphragm 117, the chamber into which a first duct 118 for feeding compressed air opens, and the chamber 116 into which a second conduit 119 for feeding the airborne powder opens. Moreover, a third compressed air duct 120 can be provided to feed to the gap 114. <IMAGE>

Description

SPECIFICATION Improved dispenser of powdered electrostatic varnish with auxiliary ducts for feeding compressed air Powder dispensers for electrostatic varnishing are known, which comprise a disc connected to either pole of an electrostatic generator, so that the extremely tiny powder granules which are hurled away of the disc edge are electrized due to the corona effect of the disc itself and are attracted by the workpiece to be varnished, which is connected to the other grounded pole of the generator.

The medium for conveying the powder to the disc is compressed air or another mechanical means. More detailedly, said dispenser comprises a top disc and a bottom disc, in the interior of which the powder is fed and, under the fluidization compressed air, is hurled to the outside through an inter-disc gap.

The route of the powder from the feeding duct to the circumferential disc outlet is rather winding, that which entails pressure drops which cannot easily be controlled so that the regulation of the rate of flow of the air-powder suspension becomes difficult.

An objective of the present invention is to do away with the drawback aforementioned by providing a dispensing unit in which the rate of flow of the powder-air suspension can be adjusted with a certain accuracy, that which is highly desirable.

This object is achieved, according to the present invention, by providing a powder dispensing unit for electrostatic varnishing installations, which is vertically and reciprocably driven and is composed of two mutually spaced apart parallel surfaces which thus define a gap, the latter being in communication with a discrete reservoir which is partitioned into two chambers by a porous diaphragm, the first chamber of such a reservoir being fed with compressed air via a first conduit, whereas the second chamber being fed with a powder-air suspension via a second central conduit, coaxial with the reservoir and delivering its contents in counterflow relationship relative to the first conduit.

In addition, a third conduit for compressed air can be provided, the air being delivered parallely of the direction of delivery of the powder-air suspension, the conduit opening into the gap aforementioned.

The structural and functional features of the invention and its advantages over the known art will become still better apparent from the ensuring exemplary description added by the accompanying drawings, wherein Figs. 1, 2 and 3 are cross-sectional views of as many different embodiments of the dispensing unit made according to the invention in question.

In Fig. 1, the disc-shaped dispensing unit in question is generally indicated at 110 and is structurally composed of two discs, 111, 11 2, the top and the bottom disc, respectively, and a cylindrical reservoir, 113, which is integral with the bottom disc and is arranged perpendicularly to the latter. The discs may also be made in the form of noncircular plates.

As best viewed in Fig. 1, the discs 111, 11 2 are so spaced apart from one another that they can define a gap 114 which is in direct communication with the reservoir 11 3.

The interior of the reservoir 1 13 is partitioned into two chambers, 11 5, 11 6 by means of an intermediate porous diaphragm 117.

Into the chamber 11 5 opens a first conduit 118 for feeding compressed air and is contained within. a second conduit 11 9 for conveying the powder-air suspension into the interior of the chamber 116. The conduits in question are coaxial relative to one another and also relative to the reservoir 11 3.

By so doing, the compressed air coming from the conduit 118 fills the chamber 11 5 and flows through the porous diaphragm 11 7 to enter the chamber 11 6 in counterflow relationship relative to the powder-air suspension coming through the annular conduit 119.

As a result, the suspension is evenly scattered throughout the chamber 11 6 and is thrust and centrifuged homogeneously towards the outside through the gap 114.

It is thus apparent that such a compressed air feed in countercurrent relationship relative to the suspension not only encourages an even distribution of the suspension as such in the interior of the chamber 1 16, but also makes possible a fine adjustment of the rate of delivery. As a matter of fact, the dispensing unit in question enables the rate of flow of the suspension to be adjusted not merely by modifying the rate of flow of the air through the conduit 11 9 and by varying the (variable) distance between the discs 111, 112, but also by varying the rate of flow of the air through the conduit 11 8.

It is possible, moreover, to provide a third conduit 120, which is annular and has a variable cross-sectional area to feed with compressed air a delivery manifold 121, also annular in cross-section and with variable cross-sectional area, arranged within the gap 114 wherefrom the air emerges parallely to the surfaces of the discs 111, 11 2. Such an additional air stream brings about a better and more regular distribution of the powder in suspension, especially when comparatively high rates of flow of the powder are adopted.

At 1 22 there is shown a strongly insulated electric cable connecting a pole of the highvoltage generator with thread-like electrodes 1 23 which are arranged radially and originate an electrostatic field to change the delivered powder with electricity.

In Fig. 2, a dispensing unit, generally indi cated at 210, still of the disc type, is structurally composed of two discs 211, 212, upper disc and lower disc, respectively, which are arranged at an angle relative to a reservoir 213.

The discs 211, 212 as can best be seen in Fig. 2, are spaced apart from one another so as to provide a gap 214, which is in direct communication with the reservoir 213. The reservoir 21 3 is partitioned internally into two chambers 215, 216, by the agency of a porous diaphragm 217 in the middle.

Into the chamber 215, and coaxially therewith, a first duct 218 opens which is intended to feed with compressed air for evenly dispersing powder introduced into the chamber 216 through a second conduit 219. The conduit 219 enters the chamber 216 radially and delivers in the axial direction the powder suspension in countercurrent relationship relative to the air coming through the conduit 218.

A third conduit 220, arranged in a direction perpendicular to the discs 211, 212, delivers air to a dispensing chamber 221 which essentially conical and which conveys said air into the end portion of the gap 214 thus improving the ejection of the powder suspension.

Also in the distributor 210 aforementioned, a strongly insulated cable 222 is provided for connecting either pole of the high-voltage generator with thread-like electrodes 223 which are arranged radially to provide the electrostatic field for charging the powder with electricity.

The distributor 210 is also driven to rotary reciprocation in the direction of the arrow 224, about its axis 225 of suspension so that it is enabled to perform the varnishing operations also in corner areas of the workpiece to which access would be difficult when employing the conventional dispensers.

In Fig. 3, a dispensing unit indicated at 310 is of the pistol-grip type and is structurally composed in its end section of two faces 311, 312, the top and the bottom face, respectively, which are arranged perpendicularly relative to a reservoir 313. The faces 311, 312, for their being mutually spaced apart, provide a gap 314 which impresses the direction of deliver to the powder suspension.

The reservoir 313 is partitioned, in its interior, into two chambers, 315, 31 6, by the agency of a porous diaphragm 317 placed in an intermediate position.

In the first chamber 315 a first conduit 318 is formed to convey compressed air, which, flowing through the porous diaphragm 317 evenly scatters a suspension of powder coming through a second conduit 319.

The conduit 319 enters the chamber 316 in a radial direction and delivers axially the powder suspension in countercurrent relationship relative to the direction of the air coming through the conduit 318.

A third conduit 320 runs along the external section of the dispensing unit and carries air to a delivery chamber 321 which is formed through the top face 311 in the zone of the gap 314, thus contributing towards and improved orientation of the delivery of the powder suspension.

An electric cable 322 which strongly insulated connects either pole of the high-voltage generator with thread-like electrodes 323 which are arranged radially to provide the electric field which is required to charge the powder with electricity.

Claims

1. A powder-dispensing unit for electrostatic varnishing installations having a vertical reciprocation and consisting of two mutually spaced apart parallel surfaces so as to define a gap which communicates with a reservoir partitioned into two chambers by a porous diaphragm, the first chamber of said reservoir being fed with compressed air through a first conduit and the second chamber with a supension of powder and air through a second central conduit coaxially arranged relative to said reservoir and emitting in countercurrent relationship relative to the first conduit.

2. A dispensing unit according to Claim 1, characterized in that into said gap there opens a third conduit for compressed air which is delivered parallely to the direction of the delivery of the powder suspension towards the outside.

3. A dispensing unit according to Claim 1, characterized in that the parallel surfaces composing the gap are discs arranged perpendicularly relative to the reservoir.

4. A dispensing unit according to Claim 2, characterized in that the parallel surfaces which compose the gap are discs arranged at an angle relative to the reservoir.

5. A dispensing unit according to Claim 2, characterized in that it has a pistol-grip shape.

6. A dispensing unit according to Claim 4, characterized in that said dispensing unit is reciprocally rotated about its axis of suspension.

7. A powder dispensing unit substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

CLAIMS (3 Nov 1983)

1. A powder-dispensing unit for electrostatic painting installations having a vertical reciprocation and consisting of two mutually spaced apart parallel surfaces so as to define a gap which communicates with a reservoir partitioned into two chambers by a porous diaphragm, the first chamber of said reservoir being fed with compressed air through a first conduit and the second chamber with a suspension of powder and air through a second central conduit coaxially arranged relative to said reservoir and emitting in countercurrent relationship relative to the first conduit.