US2827394A

US2827394A - Method and apparatus for electrostatically coating articles

Info

Publication number: US2827394A
Application number: US506914A
Authority: US
Inventors: Floyd A Sherman
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-05-09
Filing date: 1955-05-09
Publication date: 1958-03-18
Anticipated expiration: 1975-03-18

Description

March 18, 1958 F. A. SHERMAN 2,827,394

METHOD AND APPARATUS FOR ELECTROSTATICALLY COATING ARTICLES Filed May 9, 1955 5 SheetsShee'h 1 INVENTOR.

v Q m4 flow 4 .jHmM/w W ATTOR EV! March 18, 1958 F. A. SHERMAN I 2,827,394

METHOD AND APPARATUS FOR ELECTROSTATICALLY COATING ARTICLES Filed May 9, 1955 5 Sheets-Sheet 2 35 7 as 4,8 I6

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. INVENTOR. i How 4 514mm 4 rrop/vs s March 18, 1958 F. A. SHERMAN 2,827,394

METHOD AND APPARATUS FOR EILECTROSTATICALLY COATING ARTICLES Filed May 9, 1955 5 Sheets-Sheet a INVENTOR.

FLOYD A. SH ERMAN TORNEYS March 18, 1958 F. A. SHERMAN 15 6 METHOD AND APPARATUS FOR ELECTROSTATICALLY COATING ARTICLES Filed May 9, 1955 5 Sheets-Sheet 4 INVENTOR.

FLOYD A. SHERMAN March 18, 1958 F. A. SHERMAN 2,827,394

METHOD AND APPARATUS FOR ELECTROSTATICALL-Y COATING ARTICLES Filed May 9, 1955 5 Sheets-Sheet 5 ITEJE INVEN TOR.

FLOYD A. SHERMAN mu- WATTORNEYS 2,827,394 Patented-Mar. 18, 1958 METHOD AND APPARATUS FOR ELECTRO- STATICALLY COATING ARTICLES Floyd A. Sherman, Grosse Pointe Woods, Mich.

Application May 9, 1955, Serial No. 506,914

25 Claims. (Cl. 117-93) The present invention relates to an improved method and apparatus for painting or coating articles by simple electrostatic deposition. The invention is distinguished in this general respect from prior proposed procedures for painting in which an electrostatic deposition phase, in which particles of liquid coating material are given a high-potential electrostatic charge to condition the same for deposition on a surface to be painted, is only one phase or aspect in a very complicated operation. Such proposals have not been commercially practical in the degree hoped for, due to the extremely high initial cost and cost of installation and maintenance of the equipment required, its inconvenience and wastefulness in use, and other uneconomical factors.

For example, in accordance with one proposed system, a liquid coating material is blown by spray guns into a space between electrified grids and grounded articles which are to be coated, and which move past the grids and spray means. The grids are charged at a high potential, i. e., between 50,000/ 100,000 volts, charging the paint particles and causing same to diffuse or disseminate onto the articles.

This system requires a huge exhaust fan and associated collecting equipment. However, its major disadvantage, due possibly to the initial atomization of the coating material by the spray gun is that as much as 70% of the coating is blown through, above and below the grids, onto the floor and out the exhaust. Moreover, maintenance is xtremely expensive, for the spray guns must be taken apart and cleaned every day, the grid wires cleaned, the floor scraped, etc. Similar type operations must be performed it the paint is changed, and the position of the guns must be altered if the size or length of the coated surface is changed.

Another proposed procedure of a quite different character involves the discharge of paint by centrifugal action from a disk or other rotor rotating at a high speed. The disk is connected to a high voltage potential source causing the paint to be charged as it leaves the disk. Since the paint flies off the rotor in a straight line and all the way around its 360 perimeter, in order to paint a complete article surface it is necessary to move the disk vertically as it rotates. A unit to perform this process is, it is seen, an extremely cumbersome one of great initial cost and requiring a large installation expense. It is impractical in other ways, primarily in respect to maintenance, for if the article conveyor is stopped the disk must also be stopped and cleansed; and it must also be stopped and cleaned for any color change and reset for different iengths of articles to be painted.

Accordingly, it is the object of the present invention to provide an improved continuously operative rotary methed, and a relatively simple, inexpensive apparatus to perform it, in which the articles to be painted or coated are subjected, under the effect of an electrostatic phenomenon, pure and simple, to a mist-like spray of extremely fine particles of the coating material which are disseminated and electrostatically propelled to the surface to be coated.

Considered more specifically, it is an object to pro vide such a method and apparatus which are rotary in character, in the interest of obtaining continuous and high volume output.

A still further object is to provide a method and apparatus in which a multiplicity of elongated, parallel, electrostatically charged disseminator wires or filaments are mounted on a continuously traveling rotor to pass a dissemination station at which articles to be coated are exposed thereto, and in which adjustable provision is made to accurately meter, on to each filament, a proper amount of coating material to be disseminated thereby at the station aforesaid.

It is another object of the invention to provide a rotary electrostatic coating method and apparatus of the above type, wherein a surface to be coated is thoroughly and uniformly covered, and in which the improved means of metering the coating material on to the disseminator filaments insures that pratically all the material is deposited on the surface to be coated, reducing the loss of coating material to a maximum.

A further object is to provide rotary equipment which is particularly well adapted for the painting of articles by electrostatic dissemination while the articles are advanced along a predetermined path of travel by a conveycr, in a particular embodiment of which equipment the articles are given a counter-rotative movement by their conveyor.

Yet another object is to provide an improved distributor structure for an apparatus of the above character.

Further objects of the invention are to provide an improved electrostatic coating procedure which does not require the use of paint pumps, spray guns, high pressure air lines, exhaust fans and the like, hence in the performance of which the presence of paint fumes is reduced to a minimum and the loss of paint is negligible; in which the capital expenditure for equipment is small; in which colors can be changed with ease and little loss of time, signifying a minimum maintenance cost; in which articles of various lengths and sizes can be uniformly painted without necessarily stopping the travel of the article conveyor; and in which the safety factor is relatively high, so that the insurance cost factor is low.

The foregoing as well as other objects will be made more apparent as this description proceeds, especially when considered in connection with the accompanying drawings, wherein:

Fig. l is a somewhat diagrammatic side elevational view, partially broken away and in vertical section, illustrating an apparatus embodying the invention in accordance with one form or adaptation thereof;

Fig. 2 is a view in cross section on line 22 of Fig. 1;

Fig. 3 is an enlarged fragmentary sectional view along line 3-3 of Fig. 2;

Fig. 4 is a View in side elevation, partially broken away, of a modified apparatus embodying improvements and refinements of the features of the apparatus of Figs. 1, 2 and 3;

Fig. 5 is a top plan view of the modified apparatus, being partially in horizontal section to illustrate features of a paint control unit thereof;

Fig. 6 is an enlarged fragmentary view in vertical section on line 6-5 of Fig. 4, illustrating an improved nozzle construction;

Fig. 7 is a fragmentary view in enlarged scale and partially in section on line 7-7 of Fig. 4;

Fig. 8 is an enlarged view on line 8-8 of Fig. 4, showing a distributor header unit of the modified apparatus;

Figs. 9 and 10 are, respectively, views of the distributor unit in vertical section on lines 9-9 and 19-10 of Fig. 5;

Fig. 11 is a plan view schematically illustrating the improved method, in a counter rotating adaptation there- 7 of; and

Fig. 12 is a fragmentary view in vertical section illustrating a modified distributor head unit.

One embodiment of the apparatus in accordance with the present invention is illustrated in Figs. 1, 2 and 3 of the drawings. It includes a carrier or rotor 10 having a vertically extending driving shaft '11,'a hollow header disk unit 12 having its central portion secured to the upper end of the shaft 11 for rotation as a unit with the latter, and a bottom disk or plate 13 having its central portion secured to the shaft 11 in axially spaced relationship to the header 12 below the latter. The header 12 has a plurality of orifices 14 in its bottom adjacent the periphery of the latter, as shown. in Fig; 3. These orifices are arranged in a circle concentric with the axis of rotation of the rotor and are spaced circumferentially equal distances from one another.

Aplurality of vertically extending wires .or filaments 15 of electrical conducting material extending vertically between the header 12 and bottom plate 13, each filament projecting through an orifice 14. The upper ends of the filaments 15 also extend through the top wall or disk of the header 12, being soldered or otherwise secured to the same to provide a fluid tight joint with this disk, as Well as to establish an electrically conductive connection between the filament and header. The lower ends of the respective filaments 15 extend through the bottom plate 13 in alignment with the orifices 14 and are secured in any suitable manner to the plate 13.

The shaft 11 is rotatably supported by suitable fixed frame structure 16. This structure has an upright part 17 spaced to one side of the path of rotation of the rotor 10and arms 18 respectively extending inwardly in U-shaped disposition from opposite ends of the part 17, the arms passing above the top side of the header 12 and the bottom side of the plate 13. Vertically aligned bearings 19 on the inner ends of the arms 18 form journals forthe shaft 11. A suitable variable speed reduction gearing 20 connects the lower end of shaft 11 to an electric motor 21 for rotating the shaft 11 and associated rotor 10 at the required speed. This connection is made by means of an elongated, electrically insulated shaft 20' and coupling 20", as a safety provision in view of the high voltage potential applied to the above described operating parts, as will be described.

The upper end of the shaft 11 is axially bored (Fig. 3) to provide an intake passage 22, and a flexible supply line 23 for coating material is connected by a fluid tight swivelling connection 24 to the upper end of the shaft in communication with the passage 22. Supply line- 23 is in turn connected to the discharge of a suitable pump 25 and the intake side of pump. is connected to a source of supply for the coating material. This, in the present instance, is liquid paint of a suitable consistency. Valves 26 and 27 are included in the fluid connection between the supply line 23 and the pump 25. The valve 26 is a pressure regulator type rendering it possible to control the pressure applied to the coating material, while valve 27 can be set to regulate the quantity of paint introduced into the supply line 23'. 7

Paint or coating material supplied under pressure to 'the header intake passage 22 is admitted to the hollow header 12 through one or more ports 28'formed in the upper end of the shaft 11 and is distributed in header 12 to the various orifices 14; ,Here it is discharged under pressure 'by suitable nozzle or dispensing elements 29 and is caused to flow downwardly along the filaments 15 in the form of a thin film. Nozzles 29 are inhollow tubular, frusto-conical form, having their upper ends of greater diameter secured to the bottom wall of the header 12 in concentric relationship to the respective filaments 1 5, the lower ends being of a bore diameter slightly greater than the diameter of the filament.

The filaments extend axially through the. nozzles with an annular clearance space of limited width around each filament 15 for the metered passage of paint or coating material. In operation the paint or liquid coating material fiows relatively freely into each dispensing nozzle 29 and is directed on to the filament by the tapering wall of the nozzle to form a film on the filament. This film flows downwardly along the filaments 14 under the pres sure applied to the paint, assisted by the action of gravity. In accordance with the invention, the paint film along the filament 15 is' electrostatically disseminated and the particles are propelled in the form of a fine spray to the surface of an article to be coated. A plurality of articles 30, suitably grounded electrically, are advanced interval the latter-move throughout the remaining 270" apparatus, in anyembodi'ment thereof, in the interest of safety, and as specified by existing code regulations.

The voltage supplied by power pack 33 will depend on numerous variablessuch, for example, as the viscosity of the paint,;the speed of rotation of the rotor, and the width of the gap 34 between thesurfaceof the article 30 to be coated and the rotor. Since conveyor31 and articles 30 suspended therefrom are electrically, connected to ground potential, the potential of the filaments 15 is considerably, higher than the potential of the articles30 and an intense electrostatic field is produced in the gap 34 as the filaments 15 are successively moved by the rotor to positions directly opposite the path of travel of the articles 30. I

The difference in potential between ,the filaments 15 and articles 30 is sufiiciently high to provide an electrostatic field in thegap 34 of the intensity required to draw paint in the form of an exceptionally fine. spray or mist from the filament adjacent the path of travel of the articles and to deposit the paint particles on the surface of the registering article to completely cover this surface with a thin uniform coating of paint.

determined with respect to the. vertical dimension of the article surface to be coated, as well as with respect to the rate at which the paint flows downwardlyalong the filaments. It is desirable that the paint travel a distance corresponding to the vertical dimension of the article surface to be coated during the interval existing in the cyclebe-' travel throughout an arc of approximately 90, it follows that the speed of rotation of the rotor 10 for a given viscosity of paint and for a givenpressure applied to the paint should be such-that the paint willtravel the required distance downwardly along the filaments 15 during the arc of travel; -While it is important to assure movement of the paint along the filaments 15 a distance at least equal nevertheless-it is also important to avoid providing an determined in relationship tothe other variables affecting the flow of paint, along the filaments in order to reduce waste of paint to a'minimum. It will, of course, be under;

The rotor 10 is rotated ata speed of, say, up to one revolution per second, pres't'ood'that the time required for the paint to travel the full extent of the vertical dimension of the article surfaces to be coated'may be varied by altering the pressure applied to the paint. However, this pressure should be regulated in relationship to the voltage applied to the filaments so that it does not unduly oppose withdrawing the paint from the filaments by the available electrostatic forces.

It is apparent from the foregoing that the extent of downward travel of the paint along the filaments 15 during movement of the latter throu hout the 270 arc of travel aforesaid may be varied to enable coating article surfaces of difierent vertical dimensions. The rate of advancement of the articles 3% by the conveyor 31 is also predetermined with respect to the speed of rotation of the rotor Iii) so that the filaments 15 are successively brought into electrostatic relationship with the articles 39 at the proper intervals to assure application of a continu ous coating on the surfaces of the articles 36.

As shown in Figure 1 of the drawings, the filaments 15 have portions at opposite ends which respectively extend beyond the top and bottom edges of the articles 30. These portions are shielded by arcuate plates 35 respectively secured to the header l2 and to bottom plate 1 3 at the radially outer sides of the filaments 15, in radial registration with the latter. T connected to the filaments 15, are of the same potential as the filaments. Hence, the effect of the electrostatic field on the projecting end portions of the filaments is negligible and very little, if any, paint issues from said end portions.

It is further desired to restrict the width of the electrostatic field established as successive filaments 15 move into registration with the gap 34. This may be accomplished by shields 37 respectively itioned between adjacent filaments i and spaced radially outwardly from the filaments, as shown in Fig. 2 of the drawings. The opposite ends of the shields 3') are respectively fastened to the header 32 and plate so as to rotate as a unit with the filaments 15. The snieids 37 are also electrically connected to the filaments l5 and have the same potential as the filaments so as to prevent or dampen electrostatic action between the filaments and shields. The adjacent vertical edges of the shields are spaced from one another to afford slots 38 directly opposite the respective filaments which are of a width such that the shields do not interfere with free travel of paint particl s from the filaments 15 to the articles 3r; as the filaments are successively positioned in opposed relationship to the articles. As the rotor it? continues to rotate to move the filaments 15 out of opposed relationship to the articles 3%, the shields 37 act to cut off the electrostatic field in spade 3-4. The presence of the shields facilitates flow of the paint downwardly along the fi aments and, in addition, reduces paint loss to the atmosphere outside the rotor. Loss of paint is rninimized because the shield decreases and discontinues the electrostatic action even before the field is reduced in strength to such an extent that it becomes insufiicient to propel all of the paint to the article A considerably retr ed embodiment of an apparatus for performing the method of the invention, as well as a refinement in a counter-rotative conveyor system to increase the output rate, are illustrated in Figs. 4 through 11 of the drawings. As illustrated generally in Figs. 4 and 5, this installation, generally designed comprises an enclosed base 41 mounting a conventional vertical turntable unit 42 which is suitably powered to rotate the disseminator rotor unit 43 of the installation. in the alternative, the unit may be driven by a motor and coupled shaft arrangement such as is shown in Fig. 1. Base 41 may be provided with a sliding drawer 44 to receive paint or coating material gravitating from the rotor in the operation of the apparatus, thus afiording a simple means to collect and reuse this material.

The rotor unit 43 comprises a hollow brass shaft 45 having a circular plate or disk 46 coaxially secured thereto adjacent its top and a similar plate or disk 47 secured he plates 35, being electrically thereto adjacent its bottom.

Disks

46 and 47 are of light weight metal such as aluminum and constitute supports for mounting the travelling parts of disseminator rotor 43. These rotor parts are shielded at the right hand side of the apparatus, as viewed in Figs. 4 and 5, by an upstanding fixed shield 49 of semi-circular cross section, and the shield is provided with a segmental top plate 50 (Fig. 5), whose angular forward margin 51 extends well over the axis of rotation of rotor 43. A paint distributor unit or head, generally designated 52 and illustrated in detail in Figs. 8, 9, and 10, is mounted between the shield top plate 50 and the top rotor disk 46 to permit a directional control of the supply of paint or coating material inoperation of apparatus 46.

Distributor unit 52 comprises an upwardly opening, cuplike housing 53 of cylindrical cross section which is coaxially secured at its base to rotor disk 46 to rotate with the same. A fixed cylindrical distributor block 54 is slidably received in the interior of housing 53. The block 54 is rigidly mounted on the downturned extremity of an elbow supply fitting 55, which discharges axially of distributor block 54 into a hollow vertical bore 56 in the latter. Bore 56 extends only partially through the block and communicates at its lower end with a radial passage 57 which has an enlarged counterbored outer mouth 58 opening to the outside of block 54 distributor.

The cylindrical wall of distributor housing 53 is pro vided with a multiplicity of radial discharge ports 58 at the same elevation as passage 57, which bores are equipped with a multiplicity of radiating discharge tubes 59 mounted in sealed relation thereto. Upon rotation of distributor housing 53, the discharge tubes 59 come successively into radial communicating register with the enlarged mouth 58 of passage 57, receiving and forwarding as they do paint or coating material which is supplied under pressure from fitting 55 through axial distributor bore 56.

Provision is made to adjust the angular position of the distributor block 54 and thereby vary the point at which paint is discharged from passage 57 into the discharge tubes 59 passing the latter in succession. In order to seal the distributor unit or head 52, a felt sealing ring 69 is applied in an annular rabbet 61 surrounding the top of block 54, and a metal retainer ring 62 is disposed concentrically in an aperture in shield top plate 5%}, so as to have axially compressive engagementwith the felt ring 68 to seal the annular meeting Zone of distributor block 54 and its rotative housing 53. An indicator disk 63 may be employed to hold these parts in place; it is secured by screws 64 to the top of distributor block 54, the supply fitting 55 extending through a central aperture of the disk and being threaded in a top counterbore of the block. Indicator disk 63 carries a pointer 65 (Fig. 5), and is provided with arcuate slots 66 receiving screws 67 which have threaded engagement in the shield top plate 50, thus enabling the disk 63 to be adjustably positioned as desired and clamped fixedly to the top plate.

This correspondingly positions the discharge passage 57 in the otherwise fixed distributor block 54, since indicator pointer 65 is positioned in radial alignment with the passage; accordingly the exact angular disposition of the passage 57 may be ascertained at any time. The exact angular direction in which paint or coating material is discharged into each radiating tube 59 may thus be fixed as desired to insure a properly timed flow of the paint to the filaments of disseminator rotor 43, to be described, as the same approach the intended dissemination zone of the unit. This is an extremely important aspect of the invention.

As illustrated in Figs. 4, 5 and 6, each of the radiating and rotating discharge tubes 59 is connected at its outer end to an elbow fitting 69 having a downwardly disposed v discharge mouth 70. This mouth threadedly receives a tubular nozzle adapter, coupling or fitting 71 which [extends through an aperture 72 in top rotor disk 46 adjacent the outer periphery of the latter. Coupling 71 carries an integral intermediate flange 73 which is taken up tightly against opposite surfaces of top rotor disk 46 to seal the fitting 70 and coupling 71.

Each coupling 72 threadedly receives at its lower end a hollow tubular metering nozzle 74 having a downwardly conical extremity 75 terminating at a small nozzle orifice 7.7. This orifice surrounds a disseminator wire or filament 76 of unit 43 with a small and accurately predetermined radial clearance. The upper end of filament 76 is axially sustained by a disk-like spacer 78 locked coaxially between coupling 71 and nozzle, which spacer is provided with a plurality of apertures 79 through which paint or coating material may flow under pressure, after passing through the central bore 80 of.

coupling .71. A secondary reservoir 81 is thus afforded between spacer disk 73 and the nozzle extremity 75, so

as to maintain a constant supply at filament 76. The.

lower end of each filament 76 is anchored under tension to bottom rotor disk 47, as by means of a suitable takeup connector 82 in axial alignment with each nozzle 74. Asin the embodiment of Figs. 1, 2 and 3, provision may be made for adjusting the vertical length of the filaments 76 exposed to articles passing the unshielded side of unit 43, and this may be done at the top or bottom' of the unit by arcuate shielding elements of the sort shown in Figs. 1 2 and 3, designated 35 therein.

For the purpose of the present embodiment, a semi cir- V cular collecting shield 83 is disposed about the exposed front half of the unit, being coaxial with the upright, full height rear shield 49 and being radially spaced inwardly in concentric relation to the latter.

' The distributor head 55 receives its supply of paint or coating liquid througha plastic tube 85, Figs. 4 and 5, and in the interest of safety the control of this supply is effected from a relatively remote point. As illustrated in Figs. 4 and 5, a rugged supporting table 86 is provided at such point, on which a regulator unit generally designated. 87 is mounted. Unit 87 is enclosed in a well insulated. casing 88 and the operating control structure therein is best illustrated in Fig. 7, taken in conjunction with Figs. 4 and 5.'

' The plastic paint supply conduit or tube 85 is led into one axial end of a cylindrical control or selector block 90, in sealed relation thereto and in communication'with a main axial bore 90 extending axially therethrough. The opposite end of this bore is similarly connected with a conduit 92 through which a suitable solvent liquid may be supplied.

Selectorblock 99 is fixedly mounted within the insulatedrcasing 88 by any suitable means. 7 It is provided with a plurality of radially outwardly opening, threaded bores 92, 93, 94, 95 and 96 arranged to extend from main bore 91 in axially spaced progression therealong. intermediate angled bores 97 of smaller diameter extend radially inwardly of the selector block and open to each V of the larger threaded bores 93, 94 and 95. These small bores'97 are counterbored and tapped at 93 to receive .air and paint

supply tubes

99 and 19% respectively. .The

air tube 99 isjconnected'with a suitable source of air under pressure, while the paint tubes 1%, two in the illustrated unit, are each connected with a suitable supply of paint (not shown), for example of different colors. A radial straight line bore 101 of small diameter extends from main bore 91 on the downstream side of the bore control rod 106 to which an insulating hand piece 107 is applied externally of insulated casing 88. The threaded barrel portion has a relative rotative operating connection to a disk valve 108, which blocks off .the flow of solvent from tube 92 into bore 91 when in the operative advanced position shown in Fig. 7.

The second bore 93 rotatively receives a similar threaded portion 109 of a needle valve 110, this valve also being equipped with an external insulating hand piece 111. Valve 11% controls the flow of air under pressure through bore 97 to the axial main bore 91. barrel portions 113 of paint control needle valves 114 are threadedly fitted in the

bores

94, 95, having similar insulated control hand pieces 115. Finally, an enlarged threaded barrel portion 117 of a disk type'paint control valve 113 is threadedly received in bore 96. It has a rotation-permitting operating connection with flow control valve disk 107, and is manipulated by an insulated hand piece 119 from the exterior of insulated casing 88 to vary as desired the discharge of paint, pressurized by air as also desired, into the main supply conduit 85,

through which it passes to the supply fitting 55 0f distributor unit 52.

the disseminator unit is rotated at a desired speed, de-

pending upon the radial dimension of the unit, the length of the article to be painted, the speed of feed of the articles and other considerations. The desired paint color is selected by manipulation of one of the hand pieces 115.

The paint is pressure-fed to distributor 52, passes through the bore 56 of fixed distributor block 54, thence out its radial passage and into the discharge tubes 59 as the latter come successively into radial register with the passage 57. As indicated in Figs. 5 and 8 of the drawings, the passage '57 is preferably set by adjusting of pointer disk 63 so that discharge takes place to the tubes 59 as they traverse the side of the selector facing the upright rear shield 49. This permits the paint to be introduced through nozzles 74 and onto filaments 76 as the latter approach the exposed forward dissemin'ator unit 43, in radially spaced relation to that unit. In travelling, the racks 121 are rotated about their indi-' vidual axes by appropriate mechanism, preferably in the same direction as the rotation of unit 43. The conveyor itself is moved in a direction counter that of the rotation of the disseminator unit 43. A uniform coating is thus deposited on all surfaces coming into the electrostatic paint dissemination field.

By discharging the paint to a zone farthest from the grounded articles to be painted, the wires closest to those articles protect those being filled during rotation inasmuch.

improved method, in either embodiment thereof, the

electrostatic phenomenon may be compared with that of a magnetic field used in other methods. in an ele tromagnetic circuit, the magnetic field about a straight current carrying wire is circular. This is also true in the electrostatic circuit, as employed in the present method of painting. A wire attached vertically between two points as shown, with one end electrically connected to the positive terminal of a grounded electrostatic generator, 1

Similar enlarged such as is designated 12% in Fig. 4 and 33 in Fig. 1, will develop a rotating electrostatic field horizontally around the Wire. A few drops of liquid paint placed at the top of the wire will rotate in a clockwise direction on the surface of the wire around the electrostatic field. As the paint descends to the bottom of the wire the friction between the paint and the wire will cause a rotation of 180 opposite to that of the electrostatic field. These opposite motions cause an excellent final agitation of the paint which would be impossible to achieve mechanically. It also provides for uniform control of paint atomization, insuring uniform and consistent paint coverage for the articles. Thus, when the controlled amount of paint is placed on the vertical wire and this wire subjected to a stronger electrostatic field, the paint particles are atomized and fly to the negative charged electrode, which is the article to be painted.

The length of the vertical wires or paint disseminators, will depend upon, or rather, be overned by, the length of the longest article to be painted. Articles of shorter length can be easily painted by the same disseminator, by simply varying the speed of rotation of the disseminator, the paint pressure, and the strength of the electrostatic field, or in the alternative by structurally shielding the filaments at the top and/or bottom thereof.

During an overnight shut-down, or at the end of a prdouction run, solvent is run through the disseminator, and the wires cleaned electrostatically. In this way, the wires need not be touched manually at any time. In cleaning the apparatus, the procedure is as follows:

The valve 118 is closed, thus closing the feed line to the selection unit 9% of the disseminator, paint control valves 114 are opened, and pressure on the paint supply tank (not shown) is shut off, causing the paint in the feed tubes 1% to be free to return to the tank. The air pressure valve 110 is then opened, forcing all the paint from the selection unit and paint feed lines 1% back to the paint tank. Paint control valves 114 are then closed, and the solvent control valve 1% opened, which permits solvent from pipe 92 to clean out the selection unit 99.

The shut-off control valve 118 is next opened, whereupon solvent runs from the selection unit to the line 85 and thence to the distributor unit 52, tubes 59 and filaments 76 on disseminator rotor 43. The solvent will run down the wires and into the collector drawer or tray 44.

It is thus seen that I have provided a method of and apparatus for electrostatic painting or coating, which overcomes all of the disadvantages and shortcomings of existing methods of this character, and which does not require paint pumps, spray guns, high pressure air lines, or elaborately designed spray booths.

The method, moreover, is characterized by the absence of paint fumes, a negligible loss of paint, the ability to change colors without loss of time, low maintenance costs, the ability to paint articles of various lengths and sizes without stopping the conveyor, uniform paint cover age, and low insurance rates in connection with the use of the apparatus.

A modified type of distributor head, as an alternative to the head structure shown in Figs. 8, 9 and 10, is illustrated in Fig. 12 of the drawings. This unit ,generally designated 124, presents certain advantages over the unit 42 of Figs. 8, 9 and 10, particularly in respect to maintaining an efiectively sealed, leak-proof distribution of paint, despite the effect of wear. As depicted in Fig. 12, parts corresponding to parts shown in Figs. 1 through are designated by corresponding reference numerals, and further special description thereof will be dispensed with.

The unit 124 includes a circular, disk-like distributor plate 125 which rotates with the top plate 46 of the rotor unit of the apparatus, and the plate 46 may rest on and be partially supported by a heavy collar 47 secured to the tubular shaft of the rotor. Plate 46 may also be welded or otherwise secured to the upper surface of collar 47. A bearing sleeve 126 is telescoped within the upper end of the tubular shaft, in fixed relation thereto at the top extremity thereof, and a pivot spindle 127 which extends through top rotor disk or plate 46 is received in the sleeve 126 and appropriately secured concentrically to the disk above plate 46. An upwardly projecting end 123 of the spindle 127 is secured to the inner race 129 of a suitable bearing 130. The outer race of the bearing is fixedly received in a counterbore 121 of a fixed distributor or stator disk 132 beneath which the distributor disk 125 rotates with the rotor unit 43 of the apparatus. Stator 132 is urged downwardly against the top surface of rotor disk 125 by the means to be described.

Disk 132 has an axial bore 133 in alignment with its bearing counterbore 131, and the bore 133 receives a stationary, though rotatively adjustable bushing 134. Bushing 134 includes a ported lower portion 135, hereinafter to be further described, and an upper flange 136 which overlies the upper surface of stationary distributor disk 1'32. Bushing 7.34 is tightly fitted in the disk bore 13-3, so as to eliminate the possibility of leakage in this zone.

A hollow upper shaft 138 is similarly received tightly at its lower end in the bore of bushing 134, leakage being prevented at this point, and an adjustable nut 139 is threadedly received by shaft 138 immediately above the flange 136 of bushing 134. A coil compression spring 140 encircles this threaded portion of shaft 138, acting downwardly against the adjusting nut 139, and the upper end of spring 149 bears against a compression washer 141 which loosely surrounds the shaft 138, upwardly abutting the top plate 5% of the structure.

Shaft 138 extends upwardly through aligned apertures in the plate 59 and in the indicator disk 63 (similar to that of Figs. 8, 9 and 10), which is mounted above the plate Ed. Shaft 138 may be rotatively adjusted relative to the top plate 5% the aperture in the latter being circular, however the shaft is keyed to the indicator disk in an appropriate fashion, as by providing a flat surface of the shaft mating with a corresponding flat edge of the disk aperture.

Accordingly, as the disk 63 is appropriately adjusted angularly for the purpose described above in connection with the form of Figs. 8, 9 and 10, the shaft 138, bushing 134 and stator distributor disk 132 will be correspondingly adjusted rotatively. This sub-assembly is secured in its rotatively adjusted position by the screws 67 received in arcuate slots 66 of top plate 50, as in the other embodiment.

Shaft 138 has an axial bore 1'43 to which paint or coating material is supplied through the conduit 85 and appropriate coupling means, and bore 1 43 leads to a radial port 144 through the shaft and the lower bushing portion 135. This port is in turn communicated with a radial passage 145 in distributor stator 332, which passage has an axial downwardly opening portion or port 146 through the lower surface of stator disk 132, beneath which the upper surface of rotor distributor disk 135 slides.

The disk 125 is provided with a multiplicity of radially outwardly opening passages 247, similar to the passages 57 of the distributor unit 52, and the passages 147 are connected in the fashion shown in Figs. 8, 9 and 10 to radial distributor tubes 59. These distributor tubes are connected in turn to paint metering nozzles of the type illustrated in Pig. 6 of the drawings.

The construction of Fig. 12 is a leak-proof one, not subject to the effect of wear over long periods of operation, for the reason that the stator distributor member 132 is continually urged downwardly against the mating surface of the rotor distributor member 125 by coil spring 149. The force of the compression may be adjusted by manipulation of nut 139. As in the first described embodiment, the point at which paint or coating material is discharged from the stator distributor port 146 to.

11 the rotor bores 147 successively passing the same may be radially adjusted, thus determining the amount of time for the paint or coating material to traverse and distribute itself along the disseminatorwires 76.

What I claim as my invention is:

1. Apparatus for electrically coating articles, comprising a thin filament supported at substantially spaced points therealong for bodily translating the same, means so translating said filament, means to charge said filament electrically while so translated, and means supplying coating material to said filament for dissemination under the filament charge to an article to be coated which is at a different level of electrical potential than said filament.

2. Apparatus for electrostatically coating articles, comprising a thin filament means in fixed engagement with said filament at points spaced substantially along the length thereof to bodily translate said filament in a direction transverse of the length thereof, means to charge said filament electrically while so moved, and means supplying coating material to said filament for lengthwise distribution therealong and for dissemination under the filament charge to an article to be coated which is at a different level of electrical potential than said filament.

3. Apparatus for electrostatically coating articles, comprising a thin filament supported for bodily travel in an upright position, means rotatively transporting said filament about'an axis paralleling the length thereof, means to charge said filament electrically while so transported, V

and means supplying coating material to said filament for lengthwise distribution therealong and for dissemination'under the filament charge to an article to be coated which is at a different level of electrical potential than said filament. a

4. Apparatus for electrostatically coating articles, comprising a thin filament a movable support on which said filament is fixedly supported for bodily travel, means moving said support to bodily transport said filament, means to charge said filament electrostaticaily while so transported, and means supplying coating material to said filament for electrostatic dissemination under the filament charge to an article to be coated.

5. Apparatus for electrostatically coating articles, comupright position, means rotatively transporting said filament about an axis paralleling the length thereof, means to charge said filament electrostatically while so transported, and means supplying coating material to said filament for lengthwise distribution therealong and for electrostatic dissemination under the filament charge, to an article to be coated.

6. Apparatus for electrostatically coating articles, comprising a plurality of thin, electrically conductive filaments, 'movable means fixedly supporting said filaments at points spaced along their respective lengths and in a series in parallel relation to one another, means to move said supporting means and thus bodily transport said series, a device to supply coating material to said filaments at a. predetermined zone in their path of transportation, and means to charge said filaments electrically while coated by said supply device and whilebeing transported. 7. Apparatus for electrostatically coating articles, comprising a plurality of thin, electrically conductive filaments, means supporting said filaments in an annular series and in parallel relation to one another, means to rotate said series about an axis parallel to the filament lengths, a device to supply coating material to said filaments at a predetermined zone in their rotative path,

g and means to charge saidfilaments electrically while coated by said supply device and while being rotated by said rotating means. V

8. Apparatus for electrostatically coating articles, comprising a plurality of thin, electrically conductive filamentspmeans supporting said filaments in an annular series and in parallel relation to one another, means 'to rotate said series about an axis parallel to the filament ments at a predetermined zone in their rotative path, said device including means to adjust the angular position of said supply Zone in reference to said path, and means to charge said filaments electrically while coated by said supply device and while being rotated by said rotating means. 7

9. Apparatus for electrostati'cally coating articles, comprising a plurality of thin, electrically conductive filaments, means supporting said filaments in an annular series and in parallel relation to one another, means to rotate said series about an axis parallel to the filament lengths,'a device to supply coating material to said-fila' ments at a predetermined zone in their rotative path, said device including means to adjust the angular position of said supply zone in reference to said path and means to indicate said adjusted position, and means to charge said filaments electrically while coatedby said supply device and while being rotated by said rotating means.

10. Apparatus for electrostatically coating articles, comprising a plurality of thin, electrically conductive filaments, means supporting said filaments in an annular series and in parallel relation to one another, means to rotate said supporting means and series about an axis parallel to the filament lengths, a device to supply coating material to said filaments at a predetermined zone in their rotative path, said device including a header having a bore connected to a source of paint supply, a distributor rotatable with said'filament supportingmeans and having radial tubes successively communicating with said bore in the rotation of the distributor, said tubes discharging respectively to said filaments, means to adjust the relative angular position of said bore in reference to said rotative axis, and means to charge said filaments electrically while coated by said'supply device and while being rotated by said rotating means.

ll. The method of electrostatically coating articles with a liquid coating material which comprises advancing articles along a predeteramined path of travel relative to laterally spaced vertically extending filaments, fixedly supporting said filaments against lengthwise movement at spaced pointsalong the same, flowing coating material downwardly along the filaments from a source of said 7 coating material located in fixed vertical relation thereto, and creating an electrostatic field between the filaments and articles which acts'to disseminate the coating on the filaments in the lengththerof between said spaced support points and propel the coating particles to the surfaces of the articles to be coated.

12. The method of electrostatically coating articles with a liquid coating material which comprises successively moving vertically extending filaments into opposed relationship to articles having surfaces to be coated, advancing the articles relative to the filaments to bring successive areas of the article surfaces into registration with adjacent filaments, applying liquid coating material to the filaments during movement of the filaments to positions in opposed relationship to the articles, and establishing an. electrostatic field between the respective filaments and registering article to be-coated of sufiicient potential to disseminate the coating material on the filaments and propel the particles of 'the coating material to thearticles. a a

13. A method of electrostatically coating articles comprising the steps of depositing a film of coating material on each of a plurality of disseminator filaments, fixedly engaging said filaments at points spaced along the same and exposing an object to be painted to said disseminated material. V

' 14; A method'of electrostatically coating articles comprising the steps of depositing a film of coating material on each of a plurality of disseminator filaments while causing said material to flow lengthwise of said filaments and said filaments to travel bodily in a rotative path, charging said filaments electrostatically while travelling to disseminate said coating material, and exposing an object to be painted to said disseminated material.

15. A method in accordance with claim 14 in which said coating material is deposited on each of said filaments at a predetermined point in said rotative path, and in which the angular position of said point of deposition is varied in accordance with the speed of rotative travel of the filaments.

16. A method of electrostatically coating articles comprising the steps of depositing a film of coating material on each of a plurality of disseminator filaments while causing said material to flow lengthwise of said filaments and said filaments to travel bodily in a rotative path, charging said filaments electrostatically while travelling to disseminate said coating material, and exposing an object to be painted to said disseminated material While rotating said object counter to the direction of said rotative path.

17. Apparatus of the type described, comprising a distributor device, said device being operative to supply coating material, a plurality of rotary discharge tubes successively supplied by said device in a predetermined zone of their rotation, means to adjust said discharge zone angularly relative to the axis of said rotation, and a plurality of electrostatic disseminating units respectively supplied by said tubes.

18. Apparatus of the type described, comprising a distributor device, said device being operative to supply coating material, a plurality of rotary discharge tubes successively supplied by said device in a predetermined zone of their rotation, means to adjust said discharge zone angularly relative to the axis of said rotation, a plurality of electrostatic disseminating units respectively supplied by said tubes, a paint control unit having a main control bore communicating with said distributor device, means for introducing a cleaning liquid to said bore, means for introducing coating material to said bore, and selective control members regulating said respective last named means.

19. Apparatus of the type described, comprising a rotary distributor device, a fixed paint control unit having a main control bore communicating with said distributor device, means for introducing a cleansing liquid to said bore, means for introducing coating material to said bore, and selective control members regulating said respective last named means.

20. In apparatus of the type described, a distributor unit for liquid material comprising a rotating distributor member having a plurality of circumferentially spaced discharge passages opening radially outwardly thereof, a fixed distributor member in coaxial, rotatively sliding engagement with said first named distributor member, said fixed member having a passage including a radial portion opening through said fixed member and adapted to communicate successively with said passages of said first named member upon rotation thereof, said passage of said fixed member opening axially thereof and being provided with means to supply a liquid material thereto from the exterior of said distributor unit.

21. Apparatus for electrically coating articles, comprising a thin elongated filament having means fixedly engaging and supporting it for bodily transport in a direction transverse of its length, means so transporting said filament, means to charge said filament electrically while so transported, and means supplying coating material to said filament over a substantial exposed length thereof for dissemination from and along said exposed length under the filament charge to an article to be coated which is at a different level of electrical potential than said filainent.

22. Apparatus for electrically coating articles comprising a thin elongated filament, means translating said filament bodily to sweep a path extending transversely of the length thereof, means for charging said filament electrically while so translating the same, and means supplying coating material to said filament over a substantial exposed length thereof for dissemination from and along said exposed length under the filament charge to an article at a different electrical potential than said filament.

23. Apparatus for electrically coating articles comprising a thin elongated filament constituting a discharge member, means translating said filament unidirectionally and bodily to sweep a path extending transversely of the length thereof, means for charging said filament electrically while so translating the same, and means supplying coating material to said filament for lengthwise distribution therealong and for dissemination from and along said exposed length under the filament charge to an article at a dillerent electrical potential than said filament.

24. A method of electrically coating articles comprising moving bodily a thin elongated filament which is exposed along a major part of the length thereof in a Way to sweep a path extending transversely of the length there of, charging said filament electrically while so moving the same, and supplying coating material to said filament for dissemination from and along said exposed length under the filament charge to an article at a different electrical potential than said filament.

25. A method of electrically coating articles comprising moving unidirectionally and bodily a thin elongated filament which is exposed along a major part of the length thereof in a way to sweep a path extending transversely of the length thereof, charging said filament electrically while so moving the same, and supplying coating material to said filament for lengthwise distribution therealong and for dissemination from and along said exposed length under he filament charge to an article at a different electrical potential than said filament.

References Cited in the file of this patent UNITED STATES PATENTS 2,097,233 Meston Oct. 26, 1937 2,509,448 Ransburg May 30, 1950 2,658,472 Ransburg Nov. 10, 1953 2,684,656 Ransburg July 27, 1954 2,685,536 Starkey Aug. 3, 1954 2,695,002 Miller Nov. 23, 1954 2,706,964 Ransburg Apr. 26, 1955 Notice of Afiverse Becisien in Interference In Interference N 0. 90,181 involving Patent No. 2,827,394, F. A. Sherman, Method and apparatus for electrostatically coating articles, final judgment adverse to the patentee was rendered July '9, 1962, as to claim 19.

[Ofiicz'al Gazette December 4, 1 962.]

Claims

12. THE METHOD OF ELECTROSTATICALLY COATING ARTICLES WITH A LIQUID COATING MATERIAL WHICH COMPRISES SUCCESSIVELY MOVING VERTICALLY EXTENDING FILAMENTS INTO OPPOSED RELATIONSHIP TO ARTICLES HAVING SURFACES TO BE COATED, ADVANCING THE ARTICLES RELATIVE TO THE FILAMENTS TO BRING SUCCESSIVE AREAS OF THE ARTICLE SURFACES INTO REGISTRATION WITH ADJACENT FILAMENTS, APPLYING LIQUID COATING MATERIAL TO THE FILAMENTS DURING MOVEMENT OF THE FILAMENTS TO POSITIONS IN OPPOSED RELATIONSHIP TO THE ARTICLES, AND ESTABLISHING AN ELECTROSTATIC FIELD BETWEEN THE RESPECTIVE FILAMENTS AND REGISTERING ARTICLE TO BE COATED OF SUFFICIENT POTENTIAL TO DISSEMINATE THE COATING MATERIAL ON THE FILAMENTS AND PROPEL THE PARTICLES OF THE COATING MATERIAL TO THE ARTICLES.