US2975757A

US2975757A - Electrostatic paint spray

Info

Publication number: US2975757A
Application number: US717673A
Authority: US
Inventors: Harold J Reindl
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1958-02-26
Filing date: 1958-02-26
Publication date: 1961-03-21
Anticipated expiration: 1978-03-21

Description

March 21, 1961 H. J. REINDL 2,975,757

ELECTROSTATIC PAINT SPRAY Filed Feb. 26, 1958 2 Sheets-Sheet 1 INVENTOR.

Harold J. Reina! HIS ATTORNEY March 21, 1961 H. J. REINDL 2,975,757

ELECTROSTATIC PAINT SPRAY Filed Feb. 26, 1958 2 Sheets-Sheet 2 INVENTOR.

Hawk J. Reina! Y HIS ATTORNEY United States Patent 2,975,757 ELECTROSTATIC PAINT SPRAY Filed Feasts, 1958, Ser. No. 717,673

7 Claims. Cl. 118627) This invention relates to electrostaticpainting operations and is particularly concerned with electrostatic paint sprays having controlled directional effects.

It is, therefore, the main object of the invention to provide an electrostatic paint spray apparatus and method wherein the paint spray can be controlled and directed and concentrated into a given field.

In carrying out this object, it is a further object to mechanically atomize the paint and subsequently charge and mechanically direct the paint to the article tobe' painted in a predetermined spray pattern.

A still further object of the invention is to provide an atomizing gun for the paint from which paint is emitted and is directed tangentionally against a rotary air moving device which charges and atomizes the paint particles and directs them toward'the article to be painted.

In carrying out the above object, it is a further object to direct the supply of paint tangentially against a squirrel-cage rotor rotating at high speeds and bearing an electrostatic charge whereby paint particles are thrown from the rotor in the direction of the article to be painted an are simultaneously atomized and charged.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

Figure 1 is a diagrammatic view of one form of the invention.

Figure 2 is a top view Figure 1. i I I Figure 3 is a view of another type for the same purpose.

Figure 4 is .a top view Figure 3. r

Figure 5' is a view of still another used for the same purpose.

Figure 6 is a top view of the apparatus shown in Figure 5. Electrostatic paint spray apparatus and methods now in use operate on severaldiiferent principles, .In my copending application, S.N; 717,665,] disclose .a method and apparatus wherein paint is fed 'by gravity to asta tionary charging plate whence it is drawn into the ingress of a rotary blower which then throws and directs the paint outwardly thereof in an expanding circular pattern to paint articles spaced therearound which bear an opposite charge to that on the charging plate. This type of apparatus is particularly useful where conveyors are. provided for conveying the articles to be painted around the paint spray apparatus.

It is also well known that paint may be atomized and passed over charged stationary electrodes whence a f'the apparatus shown in of apparatus used of the apparatus shown in charge is picked up by the paint particles which causes them to be attracted to the articles to be painted which bear an opposite charge and are spaced from the atomizing gun. In this type of apparatus, the field of spray type of apparatus is large and diflicult to control and, furthermore, since only a portion of the particles can possibly impinge upon the charging electrodes, the electrostatic effect is not fully used in many instances.

The present invention attacks the problem in a diiferw cut manner wherein the paint is either atomized or sup-- plied under pressure in a stream from a gun, which is not charged, and is directed tangentially against a rotating airmoving device which bears a charge. As the paint impinges against the surface of this rotating device, it is fully charged and simultaneously broken up and thrown in a directional pattern, which is predetermined, toward the article to be painted which article bears the opposite charge to the charge on the air moving device.

The present invention, therefore, permits rather accurate directional painting wherein the paint particles are fully charged and, therefore, is quite useful in'connection with linear type conveyors where the articles pass the painting device in a line and are desired to be painted.

Referring specifically to the drawings, in Figure 1,'one form of the invention is shown wherein a squirrel-cage rotor 20 is shown which is carried by the shaft of a motor 22 driven either by air or electricity, etc. An electrostatic power source 24 has one pole thereof connected to the rotor so that the rotor bears a charge. The other pole of the electrostatic power source is connected to an article 126 spaced a distance from the rotor. At the opposite side of the rotor and spaced therefrom is a nozzle 28 which may be an atomizing nozzle. Paint is supplied to the nozzle through a tube 30 and air through a tube 32 in'a conventional manner to atomize the paint being emitted from the nozzle.

7 In this respect, it is to be understood that, in some cases, the air may be omitted and paint merely ejected from the nozzle under pressure in a stream.

In either event, the paint fromthe nozzle 28 is directed tangentially against the outer periphery of the squirrel-cage rotor 20 as shown in Figure 2. When the rotor is rotated, at speeds in the order of 1000 to 3000 r.p.m., the paint, as it impinges thereon, picks up a charge from the rotor and simultaneously ricochets off the rotor in a pattern which is substantially a vertical plane having a vertical width slightly in excess of the height of the rotor. This plane, by proper positioning of the nozzle with respect to the rotor and the article to be painted, can be directed at the article to be painted whereby a directional pattern of paint may be maintained. If the positioned one and one-half inches .(dimensionA) from a five inch diameter, one and one-half inch wide squirrelcage rotor with vertical louvers and operating in normal blowing direction at 3000 rpm. The paint was directed tangentially to the rotor. The article to be painted was positioned about twenty-four inches from the point B on the rotor and the paint coming off the rotor assumed a path about 30 (angle X) from a tangent to the circle at the point of paint impingement. The width of the deposited paint patern was graduated with a concentrated central coverage of about one foot in width and with a height of about eight inches. The effect of the rotor speed was shown by slowing the rotor to 2000 r.p.m. with all other conditions the same. In this case, the width of pattern was increased to about eighteen inches while the height remained substantially constant. The

electrostatic power pack was operated at a voltage of 110,000 volts.

Similar results may be obtained when using a jet of paint instead ,of ,a spray. :In ,this case, the nozzle may be farther removed :from the .rotoralthough the degree of atomization is not as great; in most cases, however, it is fully satisfactory for most painting purposes.

Referring to Figure 3, another device is shown wherein a fan blade.40 isdepended from a shaft of a motor 42. The ,fan blade 40 is attached to one pole of an electrostatic power source 24 while the other pole is attached to the article 26 to be painted. The same supply source 28 is utilized and, in this case, again, the sourcemay be an atomizing gun or ajet which source 28 supplies paint to the circumference of the fan pattern noted at 4-1 in dotted lines andpreferably ina tangential manner as explainedhereinbefore. The fan 40 picks up the paint, charges the same andthrows the paint outwardly toward the article .26 whereby the paint is atomized and directed.

Figures 5 and 6 show a third modification using a plurality of paint supply guns60, in this case, mounted on a common manifold 61. ;T he guns 60 are aligned vertically to fully cover the width of the rotating air moving devices 62, in this case, a drum driven by a suitable motor. Thedrum 6 2 is preferably metal and is connected to one pole ofa source of electrostatic power 24 as in the other examples, all other factors being the same as in connection with Figures 1 and 2. Here again, the guns 60 may be air atomizing paint nozzles or may be pressurizednozzles to supply paint in a jet stream. In either case, the paint is directed so as to impinge substantially tangentially on the drum surface.

In allcases, the angle of the blades of the squirrelcage or the fan may be varied to vary the field of painting or width of pattern and, similarly, the speeds of rotation may be varied to increase the field of painting and improve atomizing. Higher speeds decrease the transverse area covered since the paint ricochets from the blades quicker whereas lower speeds permit the paint to carry around a greater distance whereby a wider pattern is obtained. In each case, the electrostatic power source should supply voltages in the order of about 90,000 volts and above. The polarity of the distributing device and the article is of no great importance and is, therefore, a matter of choice although, in most cases, it is desirable to ground the article for reasons of safety.

The entire device, including the gun and air moving means, may be reciprocated as a unit or may be tilted, rocked or otherwise manipulated to yield desired paint patterns. Also, the paint supply may be one or a plurality of guns or jets set at varying distances from the rotary device. In this manner, the Width of the pattern may be increased. Also, a single jet may be used. In this case the jet support is reciprocated relative to the rotary device when a drum or squirrel-cage is used as shown in Fig. 5 by a conventional reciprocating device to the upper and lower dotted till'le positions. In this modification, the rotary device should have a vertical width greater than the extent of the paint spray impinging thereon. Thus, an undulating paint density is obtained Since the paint is being thrown from the rotary 4 device from different levels because of the movement of the paint supply.

While the embodiments of the present invention as herein disclosed constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows.

1. Apparatus for electrostatically painting an article, comprising in combination; a pressurized paint source, means for conveying paint from said source to an orifice, a rotating air moving device located remote from said orifice and adapted to be rotated at speeds above one thousand r.p.m., said orifice being positioned so that paint being emitted therefrom as supplied by said source will impinge tangentially upon the outer surface of said air moving device, and an electrostatic power means having opposite poles thereof connected respectively to said air moving device and to said article.

2. The apparatus as claimed in claim 1 wherein the air moving device is afan blade.

3. Apparatus as claimed in claim 1 wherein the air moving device is a squirrel-cage rotor.

4. The apparatus as claimed in claim 3 wherein the orifice is relatively recipro'cable within the limits of the squirrel cage rotor.

5. The apparatus as claimed in claim 1 wherein the air moving device is a rotating drum.

6. The apparatus as claimed in claim 5 wherein the orifice is relatively reciprocable within the limits of the rotating drum.

7. Apparatus for electrostatically spraying paint upon an article to be painted, comprising in combination; an air atomizing paint spray gun including a jet wherein the jet is directed in a predetermined direction, pressure means for supplying paint to said jet, a squirrel rotor located remote from said jet and positioned so that the effluent from the jet impinges tangentially upon the outer periphery of said rotor, means for rotating the rotor at speeds above 10 00 r.p.rn.', and electrostatic power means for charging only the rotor so that paint particles impinging thereon pick up said charge, said rotor throwing ,said charged paint particles therefrom at an angle from said tangential point of contact in a direction different from said predetermined direction and onto an article to be painted spaced therefrom, which article carries a charge opposite to the charge imposed on the rotor.

References Cited in the file of this patent UNITED STATES PATENTS 1,659,683 Dougan Feb. 21, 1928 1,753,019 Page Apr. 1, 1930 2,231,324 Crompton Feb. 11, 1941 2,245,301 Schacht June 10, 1941 2,294,221 Bowen et al. Aug. 25, 1942 2,387,362 Stewart Oct. 23, 1945 2,567,781 .Ransburg Sept. 11, 1951 2,730,460 Ransburg Jan. 10, 1956 2,780,565 Juvinall Feb. 5, 1957 2,789,866 Umbricht Apr. 23, 1957 2,814,527 Peebles et a1 Nov. 26, 1957 2,933,414 Beck Apr. 19, 1960