US2706964A - Apparatus for electrostatic atomization - Google Patents

Description

April 26, 1955 E. M. RANSBURG ETAL APPARATUS FOR ELECTROSTATIC ATOMIZATION Filed April 14, 1950 2 Sheets-Sheet 1 INVENTORS.

EDW1N M. RANSBURG 8 EMERY P. MILLER ATTORNEY April 26, 1955 E. M. RANSQURG ET AL APPARATUS FOR ELECTROSTATIC ATOMIZATION 50 Filed April 14, 19

2 Sheets-Sheet 2 H14 5%Mwv I ATTO R NE Y United States Patent APPARATUS FOR ELECTROSTATIC ATOMIZATION Edwin M. Ransburg and Emery P. Miller, Indianapolis, Ind., assignors to Ransburg Electro Coating Corp., Indianapolis, Ind., a corporation of Indiana Application April 14, 1950, Serial No. 155,802 14 Claims. (Cl. 118-51) This invention relates to a new and improved apparatus for electrostatically atomizing liquid materials and to an apparatus adapted for use in the application of liquid coating materials with electrostatic forces.

One object of the invention is to counteract or compensate for the tendency of gravity to cause an uneven distribution of liquid along an inclined or vertically disposed discharge member from which the liquid is to be atomized.

A further object of the invention is to provide an extended continuous source of atomized material which the shielding member.

The above and further objects of the invention will be apparent from the following description and figures:

Fig. 1 is a partially sectioned isometric of the appaliquid supply 1 veyor so that the articles the atomizer. The atomizer is oriented with respect to the articles in such a way that the movable elongated discharge member 4 of the head is nearest the articles and extends approximately parallel to the surface to be coated.

A high-voltage source 5 has one of its terminals 6 connected to said head and hence to the discharge mem- 2,706,964 Patented Apr. 26, 1955 ber. The other terminal 7 is grounded. Since the conveyor is grounded as at 8 the articles to be coated are likewise grounded by way of the holders 2. An electrostatic field is thus maintained between the discharge member and the article surface. Due to the character of the discharge member and the separation between it and the article to be coated the field adjacent the member is one of steep potential gradient.

In Fig. 1 these cusps drawn solely for the purposes of illustration are shown for a short portion only of the lower section of the discharge mem- From the apexes of these cusps atomized material is projected into the space in front of the member and by the field is precipitated on the article.

it toward the article.

the plug surface 1s equal to of complete sections.

Diametrically opposite and across the plug from the a longitudinally extending port In this manner a tight fit to plug 13 into lengths is all the pumps tions of the atomizer. These pumps and their drives la e ngore fully explained and shown in connection with The holes 12 exit onto an exposed surface 19 of the body of the atomizer. Extending across this surface and sloping generally downward are a series of flow-directing elements 20. Each of orifices 12 terminate on the surface 19 between two such elements.

The extreme forward edge of the body member 9 is grooved to accept the discharge member 4. This discharge member during length in this groove and over the two end castings in a continuous loop. A top casting 21 is formed to seal off the upper end of the hole carrying plug 10. A similar bottom casting 22 seals off the lower end of this same serves as a drive shaft by which the plug 10 can be rotated with respect to body member 4 as it passes over the top of A groove 25 may be provided to accept as it moves along the rear of the discharge member passes through a cleaning member 28 which is arranged to wipe the remaining liquid from the discharge member and collect it in a catch basin for return to the supply by way of pipe 29. Between the two rolls on the bottom casting the discharge member by two additional cleaning members 30 and 31 arranged with catch pans that feed the reclaimed material to the supply by way of pipe 32. These cleaning devices 30 and 31 are supported by brackets extending from the lower casting 22.

The roller which is keyed to shaft 27 and over which discharge member 4 passes is rotated by worm 33 an worm gear 34. Worm 33 in turn is rotated by flexible shaft 35 which also is shown in Fig. 3. The discharge member will thus be moved progressively along the forward part of the body member, across the upper end, past the cleaner 28, down the rear of body member, and across the lower end. The speed of travel of the discharge member is thus independent of rotation of plug and adjustable by speed control 237 shown in Fig. 3.

Located along the back of body member 9 is an idler wheel 36 which is mounted on springs 37. This idler is arranged to maintain tension on the discharge member 4 as it travels down the groove in the back of body member 9.

Fig. 3 shows the fluid supply and drive mechanism used in conjunction with the atomizer shown in Fig. I. In this figure a motor 236 drives the speed reducer 237 having two output speed drives 238 and 239. Drive 238 rotates at a constant speed while drive 239 is variable under control of knob 240. Drive 239 by a flexible shaft is connected to shaft of Fig. l and thus drives discharge member 4. Drive 238 drives shaft 241 on which are positioned gear 242 and cams 243. Meshed with gear 242 is gear 244 and gear box 252 that drives flexible shaft 223 which in turn is connected to shaft 23 of Fig. l and thus is used to rotate plug 10. Cams 243 are arranged to activate pins 245 that move the bellowspumps 17. Motion of these pumps transfers material from supply tank 247 by way of base reservoir 248 to outlet pipes 16. Part 250 is in engagement with grooves on shaft 241 and thus maintains its endwise position. By loosening 250 shaft 241 can be moved endwise to engage a different group of cams 243 with pins 245. The strokes of the bellows-pumps are thus modified and the fluid per stroke delivered to each section of atomizer 1 is therefore altered. Pipes 29 and 32 of Fig. l are connected to pipe 251 on fluid supply tank so coating material removed from the discharge member 4 by scrapers 28, 30 and 31 is returned to the reservoir.

Fig. 4 illustrates by a plane development of the surface of plug 10 the relationship of the holes 11 and the holes 12 in the body 9. The circles marked I, II and III in line A are representative of holes 12 in the body 9 while those marked IV, V and VI represent in the plug 10. The holes IV, V and VI are spaced about the circumference of the plug so that a circumferential distance equal to their diameter exists between them. The relationship which exists between the moving and fixed orifices can be simulated by passing lines (a) (b) (c) (d) (2) etc. in succession over line A. When line (a) coincides with line A hole IV is connected to hole I and remains so as (b) and (c) are in turn brought over line A. When ((1) coincides with A no connection between holes is established. As (2), (f) and (g) in turn pass over line A, hole II is connected to hole V. It is thus evident that only one hole at a time is connected in any section. With this arrangement the particular pump supplying the section is coordinated with the rotation of plug 10 so that the pump moves upward on intake when (0), (d) and (e) successively coincide with A and moves downward to deliver fluid as (e), (f) and (g) move into coincidence with A. Gearing in gear box 252 permits this coordination between pumps and the rotation of plug 10.

In operation the following sequence takes place, the drive motor 236 rotates shaft 23 and operates pumps 17 in timed relation. Material to be atomized is therefore brought from the supply 247 by each pump 17 and introduced into'the corresponding section of port 13. The rotation of plug 10 as above described is so timed with the motion of the bellows of pump 17 that fluid will be delivered to the port 13 only when one of holes 11 in the particular section is open to its corresponding orifice 12. In this way positive delivery is assured and the holes 11 til) plugging of delivery tubes will be reduced to a minimum. As the rotation of the plug 10 continues material will be delivered progressively along each section of the blade as each hole in the plug is matched with its corresponding orifice 12 and the particular pump strokes to deliver the appropriate fluid quantity. Fluid is thus delivered progressively onto the surface 19 between successive pairs of the flow-directing elements 20. The quantity of fluid delivered to each orifice 12 can be controlled as above mentioned by regulating the stroke of the pump.

The liquid delivered to the flow surface 19 moves over this surface to the forward edge thereof where it is delivered to discharge member 4. On this surface the material is formed by the electrostatic field into cusps which tend to be carried along with the discharge member as it moves upward. Additional material is fed to these cusps from that flowing across surface 19 while material is being atomized from the apexes of the cusps into the space adjacent the discharge member for precipitation upon the article. Because gravity would normally cause the cusps to move downward along the discharge member it is evident that by regulating the rate of linear motion of the discharge member by controlling knob 240 the cusps can be made to move upward, downward or remain at rest as desired.

By this construction one can fully utilize the known advantages of a fine smooth cylindrical surface as a discharge member. By backing such a member with a shielding member such as body member 9 the tendency of such cylindrical surfaces to discharge into the entire area about them is confined and restricted to that area which is unshielded. A directional effect can thus be obtained. Whereas, complete electrical shielding of the rear section of the discharge edge is preferably obtained with a metal body member 9, such body members may be of insulating material. The discharge member likewise can be of insulating material if the liquid material has sufficient electrical conductivity to allow one to establish at its exposed surface the necessary electrical potential gradient.

Whereas the arrangement shown in Fig. 1 illustrates the invention being used to coat articles of manufacture it is to be understood that the operation described can be used for any purpose wherein one desires to produce a dispersion of finely divided liquid particles. The object being coated is not an essential part of the function of the device. Such a device will atomize liquid material into the space about the discharge member quite readily if it is placed alone in the center of a room. One only needs to establish adjacent the liquid on the discharge member a sufficient potential gradient and atomization will result.

Whereas the atomizer shown in Fig. l embodies the delivery of the liquid material from the distributing means 10 to orifices l2 and then onto an exposed surface 19 across which it flows to the surface of the discharge member, the arrangement shown in Fig. 2 is equally operable. In this modification of the invention the material from port section 113 flows through holes 111 in plug body and into orifices 112. in this modification the orifices 112 terminate not on a free surface, but at the base of groove 115 cut in the forward part of body member 109 to receive discharge member 104. Material from orifices 112 then flows around wire 104 to the exposed surface thereof to be atomized therefrom.

By rearranging the holes 11 in the plug it is possible to use in place of the bellows-pumps 17 a series of geartype pumps which deliver fluid at a constant rate. This arrangement of holes is shown in development in Fig. 5 where the circles VII, VIII and IX represent holes 11 spaced apart about the circumference of the plug by a distance equal to their radius. It will be evident that as (m) and (11) are moved over line A port I will be connected to port VII and that as (0) and A coincide port I will lose connection with port VII and port II connects with port VIII. The sequence of connection is thus one of alternate connection to single and double ports. It is thus evident that this arrangement permits the use of a constant flow pump because it is never shut completely off but is connected alternately to one orifice alone and then to two adjacent orifices. Plugging of orifices is equally avoided by this arrangement.

From the above description the method of operation of the invention is evident. It is understood that the method described is only one possible arrangement and others may be employed Without departing from the spirit of the invention.

What we claim is:

1. In an apparatus for applying material to the surface of an article, a support for the article to be coated, an extended discharge member positioned in spaced relation to the article on said support, a surface shielding member adjacent and extending along said discharge member on that side thereof which is remote from the article, means for creating relative movement between said shielding member and said discharge member in the direction in which said discharge member extends, feed material to that surface of said disfaces the article and high-voltage means to establish adjacent the material on said discharge member a potential gradient to transfer said material from said discharge member to said article surface, said motion producing means being power driven and operative during the material transfer operation.

2. In apparatus for atomizing liquid, an elongated discharge, a distributing means comprising a rotary multiported valve for distributing liquid progressively along said discharge member,

3. In apparatus for charge member, an

and means for supplying liquid coating exposed portion of said discharge member for atomiza tion therefrom.

4. Liquid atomizing apparatus comprising a discharge member with an elongated continuous discharge surface, means including an elongated rotary member arranged distribution of liquid to it, means for effecting relative movement between said discharge member and said elongated rotary member in the direction of elongation of said members, and means for atomizing the liquid from said elongated discharge surface.

5. In an atomizer, an extended discharge member, an elongated shielding member adjacent said discharge member and extending parallel to the discharge member along one side thereof to leave a portion of the discharge member exposed, means for producing relative motion of said discharge member and said shielding member along a path generally parallel to the extent of said discharge member, means for supplying liquid to said exposed portion for atomization therefrom, and a high voltage source connected to said discharge member for establishing the liquid on said exposed portion as one terminal of an electrostatic field for influencing the paths of the atomized particles leaving said liquid, said motion producing means being power-driven and operative during the atomization operation.

6. The invention claimed in claim with the addition that the liquid to be atomized is fed to an exposed surface of said shielding member for flow thereover to said discharge member.

7. The invention claimed in claim 6 with the addition of a series of flow-directing elements on said exposed surface of said shielding member and disposed at an angle to the direction of extent of said discharge member.

8. In an atomizer, an extended discharge member, an elongated shielding member adjacent said discharge member and extending parallel to the discharge member at one side thereof to electrically shield a portion of said producmgrelative motion along a path generally parallel to the extent of said discharge member, means for supplying liquid to said unshielded portion for atomization therefrom, and a high voltage means connected to said discharge member for establishing the liquid on said unshielded portion as one terminal of an electrostatic field for influencing the paths of the atomized particles leaving said liquid, said motion producing means being power-driven and operative durmg the atomizing operation.

9. In an electrostatic coating apparatus; a device for charge member having first and In an atomizer, an extended discharge member mounted for movement in a direction parallel to its extent, moving sa d discharge member, an elongated from said discharge member.

14. The invention claimed in claim 11 with the addition that said power operated means is connected to said discharge member to produce said relative motion, and means for maintaining said shielding member at an electrical potential of the same sign as said discharge member.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. IN AN APPARATUS FOR APPLYING MATERIAL TO THE SURFACE OF AN ARTICLE, A SUPPORT FOR THE ARTICLE TO BE COATED, AN EXTENDED DISCHARGE MEMBER POSITIONED IN SPACED RELATION TO THE ARTICLE ON SAID SUPPORT, SURFACE SHIELDING MEMBER ADJACENT AND EXTENDING ALONG SAID DISCHARGE MEMBER ON THAT SIDE THEREOF WHICH IS REMOTE FROM THE ARTICLE, MEANS FOR CREATING RELATIVE MOVEMENT BETWEEN SAID SHIELDING MEMBER AND SAID DISCHARGE MEMBER IN THE DIRECTION IN WHICH SAID DISCHARGE MEMBER EXTENDS, FEED MEANS FOR SUPPLYING MATERIAL TO THAT SURFACE OF SAID DISCHARGE MEMBER WHICH FACES THE ARTICLE AND HIGH-VOLTAGE MEANS TO ESTABLISH ADJACENT THE MATERIAL ON SAID DISCHARGE MEMBER A POTENTIAL GRADIENT TO TRANSFER SAID MATERIAL FROM SAID DISCHARGE MEMBER TO SAID ARTICLE SURFACE, SAID MOTION PRODUCING MEANS BEING POWER DRIVEN AND OPERATIVE DURING THE MATERIAL TRANSFER OPERATION.

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