US3620190A

US3620190A - Spraying apparatus

Info

Publication number: US3620190A
Application number: US826832A
Authority: US
Inventors: Otto Renner
Original assignee: Licentia Patent Verwaltungs GmbH
Current assignee: Licentia Patent Verwaltungs GmbH
Priority date: 1968-05-22
Filing date: 1969-05-22
Publication date: 1971-11-16
Anticipated expiration: 1988-11-16
Also published as: SE339919B; ES367506A1; DE1752410A1; AT304731B; GB1268391A; FR2009093A1; DE1808149A1; DE1808150A1

Abstract

An apparatus for electrostatically spraying powdery material. A conveyor extends into a vessel which contains a supply of the material to be sprayed, this conveyor moving the material from the vessel to a point near a spraying zone. Means are provided for moving the material from this point into the spraying zone.

Description

United States Patent Otto Renner Neu-laenburg, Germany May 22, 1969 Nov. 16, 1971 Llcentia Patent-Ver waltungs-GJmbJl Frankfurt am Main, Germany Inventor Appl. No. Filed Patented Assignee Priorities May 22, 1968, Germany, No. P 17 52 410.6

SPRAYING APPARATUS 12 Claims, 6 Drawing Figs.

1 1 8/308 Int. Cl. H B05b 5/02 Field Search 118/308,

[ 56] References Cited UNITED STATES PATENTS 1,581,322 4/1926 Reed 118/325 X 2,174,328 9/1939 Meston et al. 1 18/629 2,254,016 8/1941 Melton et a1... 118/627 3,439,649 4/1969 Probst et al 1 18/312 X FOREIGN PATENTS 251,626 5/1964 Australia 1 18/308 Primary Examiner-John P. McIntosh Attorney- Spencer & Kaye ABSTRACT: An apparatus for electrostatically spraying powdery material. A conveyor extends into a vessel which contains a supply of the material to be sprayed, this conveyor moving the material from the vessel to a point near a spraying zone. Means are provided for moving the material from this point into the spraying zone.

PAIENTEnunv 15 I9" 3, 20, 190

sum 1 or a Inventor OttO Ranna'r Hiiorn Q Ys PATENTEDNUV 1s l97l SHEET 2 BF 3 Inventor OM10 Rannm' HUI/464644662 5/ 2 6155 flltomays PATENTEnuuv 16 I97! SHEET 3 m: 3

FIG. 5

SPRAYING APPARATUS BACKGROUND OF THE INVENTION The present invention relates to an apparatus for electrostatically spraying a material which is in powder form, which apparatus includes a conveyor that extends into the vessel.

One way of coating work pieces is by means of the so-called whirl-sintering process, in which powdery material located in a vessel that is open at the top is maintained in a suspended state by means of a weak current of air which is introduced into the vessel through an air-permeable bottom. The work piece to be coated is preheated to a predetermined temperature and is then dipped into the thus-loosed coating material. In this way, a coating of predetermined thickness is formed on the surface of the workpiece, due to the temperature of the latter. Next, the coating is firmly bonded to the surface of the work piece, this being done in a suitable kiln. The thus-obtained coatings are normally sufficiently well attached to the work piece. One significant drawback of this process, however, is that only certain types of workpieces will lend themselves to being subjected to the preheating step before being dipped into the suspended material, inasmuch as the temperature to which the workpiece must be heated in order to cause the particles to adhere properly is quite high.

Various ways have been proposed in which to coat workpieces with powdery material, some of these ways involving electrostatic processes, namely, processes in which the material is brought into the spraying zone by applying a high voltage to one of the spraying parts. The difficulty here is that special measures are required in order to deposit the material uniformly along the entire length of the work piece.

SUMMARY OF- THE INVENTION It is therefore, the primary object of the present invention to provide a wayv of electrostatically spraying a workpiece which overcomes the above drawback, namely, to provide a way in which powdery material can beapplied uniformly by means of an electrostatic apparatus. In accordance with the present invention, this is accomplished by providing conveyormeans which bring the powdery material to a point near the spraying zone and by providing means which move the material from this point into the spraying zone. This is done because the electrostatic force between the workpiece to be coated and veyor, the same being constituted by an endless belt 4 which passes over at least two, rollers and which is driven so as to move in the direction of the arrow 5. The spray wires 6, which are located in the spraying zone and which are connected to a source of high voltage (not shown), are arranged in front of the conveyor belt 4, i.e., or that side thereof which is directed toward the spraying zone. A tapping mechanism 7 is located behind conveyor belt 4, i.e., at the side thereof which is directed away from the spraying zone, and is at the same level as the spray wires 6. The workpieces 8 which are to be coated with the material 2 are located at a suitable distance away from the conveyor belt 4, these work pieces being carried by a conveyor 9 which serves both to ground the work pieces and to carry them through the spraying zone in the direction of the arrow 10.

The conveyor belt 4 which carries the material to be sprayed to a point near the spraying zone may be made of insulating material. In order to make certain that the conveyor belt will-be able to convey sufficient material into the spraying zone, the belt is roughened or is deformed so as to be other than absolutely flat. Alternatively, the conveyor belt may be made of a strandlike material which is intertwined, interwoven or netted into a conveyor belt. Yet another possibility is to provide a conveyor belt one of whose sides has a hidelike or brushlike surface. The tapping mechanism 7 is suitably ar ranged so as periodically to tap the conveyor belt. This can be done, for example, by providing a tapping mechanism in the fonn of a vibrator. Alternatively, means can be provided which cause a gaseous stream to blow the material from the conveyor belt 4 and into the spraying zone; this, it will be understood, presupposes that the conveyor belt be air-permeable. In practice, the gaseous medium used to move the material from the conveyor belt to the workpieces to be coated will be an inert gas, thereby to prevent any possible danger or damage due to combustion. Yet another way in which the the spraying part forming part of the electrostatic equipment is normally not sufficient to effect this movement in such a way as to produce uniform coating.

BRIEF DESCRIPTION OF TI-IE DRAWINGS FIG. 1 is a schematic view of an electrostatic spraying apparatus according to the present invention.

FIG. 2 is a plan view of a multiple-unit electrostatic spraying apparatus according to the present invention.

FIG. 3 is a front view of the electrostatic spraying apparatus shown in FIG. 1.

FIG. 3a is a front view of a portion ofthe apparatus of FIG. 3 showing a preferred modification thereof.

FIG. 4 is a fragmentary view, on an enlarged scale, of a detail of the structure shown in FIG. 3.

FIG. 5 is a plan view of a multiple-unit electrostatic spraying apparatus according to the invention for simultaneously spraying a plurality of surfaces of a three-dimensional workpiece.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings and first to FIG. 1 thereof, the same shows an electrostatic spraying apparatus according to the present invention, the same incorporating an open vessel 1 containing a supply of the material 2 which is in powder form and which is to be applied by electrostatic spraying. This material 2 is loosened, in a manner known per se, in whirl sintering by means of an airstream, indicated by the arrows 3, which is passed upwardly through the air-permeable bottom of the vessel 1. The material is taken out of the vessel 1 by a conmaterial can be moved from the conveyor belt to the work pieces is by providing an ultrasonic wave source.

If the means for removing the material from the conveyor belt are in the form of the above-described tapping mechanism 7, the tension of the conveyor belt 4 may suffice to move the material out of the belt and into the spraying zone. Alternatively, the spray wires 6 may be used as abutments against which the tapping means strike. In order to prevent the wires from being subjected to undue mechanical wear, there may be provided a suitable powder-permeable abutment 11 which allows the powdery material 2 to pass through.

Normally, a single spray applicator unit of the type described above will suffice to coat flat workpieces to the desired thickness. If thicker coatings are desired, however, the apparatus may include a plurality of individual units each as described above, the same being represented schematically, in FIG. 2, by the respective conveyor belts 4a, 4b, 40. As will be seen from FIG. 2, the several units are arranged in a line extending generally in the same direction as that in which the workpieces 8 are conveyed. In order that the material 2 will be deposited uniformly, adjacent conveyor belts are run in opposite directions. Thus, the reaches of the two end conveyor belts 4a and 4c, for example, which face the spraying zone will, in the arrangement depicted in FIG. 2, run from top to bottom (as seen in FIG. 1) and the corresponding reach of the conveyor belt 4b-which is between the conveyor belts 4a and 4' wm run from bottom to top.

If the workpieces to be sprayed are relatively large in all three dimensions, i.e., if more than one surface of a workpiece is to be sprayed, the individual units may be so arranged that the conveyor belts of all units surround the workpiece on all sides. Such an arrangement is shown, for example, in FIG. 5 for a workpiece of rectangular cross section whereby four spraying units are utilized. I

FIG. 3 again shows the vessel 1 containing the material 2. Air is introduced into the bottom of the vessel 1 by way of the air inlet conduit 3. The conveyor belt 4' is here shown as being constituted by a loose web, the belt being run over rollers l2 and 13, the latter being mounted for rotation within vessel 1 and below the level of the material 2. The other roller 12, which is mounted above the vessel, is driven by a motor 14. The conveyor belt 4' is prevented from running off the rollers l2, 13, by means of a belt which has a V-shaped cross section and which itself runs in V-shaped grooves that are provided in the two rollers. The conveyor belt 4' is suitably secured to the surface of the V-shaped belt 15, as, for example, by being glued thereto. By appropriately inclining the axis of roller 12 at a small angle a relative to the axis of the roller 13, as shown in FIG. 3a, the conveyor belt 4' can be given a tendency to run onto the belt 15 rather than away from it.

FIG. 4 is similar to the upper part of FIG. 3 but shows the roller 12 as being provided with a helical ridge 19, the purpose of which is to prevent the belt 4 from running off the roller. If desired, both

rollers

12 and 13 may be provided with such helical ridges.

By virtue of the above, it will not be necessary periodically to stop the operation of the apparatus in order to readjust the position of the conveyor belt on the rollers. This is of particular significance where the conveyor belt is constituted by loose webbing or the like which, but for the above-described measures, would have a marked tendency to wander off the rollers.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations.

I claim:

1. In an apparatus for electrostatically spraying powdery material onto a surface, the improvement comprising, in combination:

a. a vessel for containing a supply of the powdery material to be sprayed;

b. means for maintaining the powdery material in said vessel in a fluidized state;

c. conveyor means including a conveyor belt and roller means for guiding said conveyor belt, said conveyor means extending down into said vessel for removing said powdery material from said vessel and moving same to a point adjacent an electrostatic spraying zone; and

d. means for causing said powdery material to be moved from said point into said spraying zone.

2. Apparatus as defined in claim 1, wherein the axes of said rollers are at an angle to each other.

3. Apparatus as defined in claim 1, wherein said means d comprise a tapping mechanism arranged on that side of said conveyor belt which is directed away from said spraying zone and an abutment which is on the opposite side of said conveyor belt and hence on that side which is directed toward said spraying zone, said abutment means being powder-permeable to allow the passage therethrough of said material.

4. Apparatus as defined in claim 3, wherein said abutment means comprise wires which are electrically connected to a source of high voltage and which themselves thus form part of a means for applying an electrostatic charge to said material to be sprayed.

5. Apparatus as defined in claim 1, wherein said vessel is open at its upper end and wherein said conveyor belt is guided by said rollers so that it moves in a substantially vertical direction.

6. Apparatus for electrostatically spraying powdery material, comprising, in combination:

a. a vessel for containing a supply of the material to be sprayed;

b. conveyor means extending into said vessel for moving the material from said vessel to a point near a spraying zone, said conveyor means including a conveyor belt and roller means for guiding said conveyor belt, said roller means include at least two rollers each having a V-shaped groove and said conveyor means further comprise a V- shaped belt connecting said rollers and running in said grooves thereof, at least one of said rollers having a helical ridge; and

c. means for moving the material from said point into said spraying zone.

7. Apparatus as defined in claim 5, wherein one edge of said conveyor belt is connected to said V-shaped belt.

8. In an apparatus for electrostatically spraying powdery material onto a surface, the improvement comprising, in combination:

a. a vessel for containing a supply of the powdery material to be sprayed;

b. means for maintaining said powdery material in said vessel in a fluidized state;

c. conveyor means including an air-permeable conveyor belt and roller means for guiding said conveyor belt, said conveyor means extending down into said vessel for removing said powdery material from said vessel and moving same to a point adjacent an electrostatic spraying zone; and

d. means for blowing a stream of gaseous medium through said conveyor belt from that side thereof which is directed away from said spraying zone to cause said powdery material to be conveyed into said spraying zone.

9. Apparatus as defined in claim 8, wherein said conveyor belt has a roughened or deformed surface.

10. Apparatus as defined in claim 8, wherein said conveyor belt is made of a strandlike material which is intertwined, interwoven or netted.

11. Apparatus as defined in claim 8, wherein said conveyor belt has a hidelike or brushlike surface.

12. An arrangement for electrostatically spraying powdery material onto all sides of a workpiece, comprising a plurality of apparatuses each as defined in claim 8, the said apparatuses being arranged such that the conveyor belts of all of said apparatuses surround the workpiece.

Claims

1. In an apparatus for electrostatically spraying powdery material onto a surface, the improvement comprising, in combination: a. a vessel for containing a supply of the powdery material to be sprayed; b. means for maintaining the powdery material in said vessel in a fluidized state; c. conveyor means including a conveyor belt and roller means for guiding said conveyor belt, said conveyor means extending down into said vessel for removing said powdery material from said vessel and moving same to a point adjacent an electrostatic spraying zone; and d. means for causing said powdery material to be moved from said point into said spraying zone.

6. Apparatus for electrostatically spraying powdery material, comprising, in combination: a. a vessel for containing a supply of the material to be sprayed; b. conveyor means extending into said vessel for moving the material from said vessel to a point near a spraying zone, said conveyor means including a conveyor belt and roller means for guiding said conveyor belt, said roller means include at least two rollers each having a V-shaped groove and said conveyor means further comprise a V-shaped belt connecting said rollers and running in said grooves thereof, at least one of said rollers having a helical ridge; and c. means for moving the material from said point into said spraying zone.

8. In an apparatus for electrostatically spraying powdery material onto a surface, the improvement comprising, in combination: a. a vessel for containing a supply of the powdery material to be sprayed; b. means for maintaining said powdery material in said vessel in a fluidized state; c. conveyor means including an air-permeable conveyor belt and roller means for guiding said conveyor belt, said conveyor means extending down into said vessel for removing said powdery material from said vessel and moving same to a point adjacent an electrostatic spraying zone; and d. means for blowing a stream of gaseous medium through said conveyor belt from that side thereof which is directed away from said spraying zone to cause said powdery material to be conveyed into said spraying zone.