US2684656A - Electrostatic coating apparatus - Google Patents

Description

July 27, 1954 M. RANSBURG I 2,684,656

ELECTROSTATIC COATING APPARATUS Filed July 30, 1949 4 Sheets-Sheet l INVENTOR.

EDWIN M. RAN SB URG ATTORNEY July 27, 1954 E, M. RANSBURG 2,534,656

ELECTROSTATIC COATING APPARATUS 4 Sheets-Sheet 2 Filed July 30, 1949 INVENTOR. EDWIN M. RANSBURG ATTORNEY July 27, 1954 E, M. RANSBURG 2,684,656

ELECTROSTATIC COATING APPARATUS Filed July so, 1949 4 Sheets-Sheet s INVENTOR.

E DWIN M. RANSBURG ATTORNEY July 27, 1954 E. M. RANSBURG ,684,656

ELECTROSTATIC COATING APPARATUS Filed July 50, 1949 4 Sheets-Sheet 4 INVENTOR.

EDWIN M. RANSBURG ATTORNE Y Patented July 27, 1954 ELECTROSTATIC COATING APPARATUS Edwin M. Ransburg, Indianapolis, Ind., assignor to Hamburg Electro-Coating Corp., Indianapolis, Ind., a corporation of Indiana Application July 30, 1949, Serial No. 107,687

12 Claims.

This invention relates to electrostatic coating and more particularly to improved coating apparatus in which liquid coating material is both electrostatically atomized and electrostatically deposited upon an article to be coated.

This application is a continuation in part of the co-pending application of Edwin M. Ransburgjserial No. 57,260, filed October 29, 1948.

In apparatus employed for electrostatically atomizing and electrostatically applying liquid coating material to discrete articles or sheet material, it is known to move the articles or sheet material through a coating zone in which the coating material is applied to them by an electrostatic atomizing head. In some of these prior applications the atomizing head comprised an elongated discharge member having an atomizing surface or surfaces to which the coating material was fed through a series of restricted orifices. In other atomizing heads of the prior art which have been provided with elongated dis charge members, the coating material was fed to the surface of such members by means of an elongated orifice with an extended opening substantially of the same extent as a discharge result that'the spray pattern produced is not of uniform density throughout its extent. Even when the coating material is distributed uniformly along the discharge member it sometimes happens that the atomized material leaves the member in more or less discrete streams or jets and hence tends to be deposited in a striped pattern.

It is an object of this invention to overcome the disadvantages heretofore attendant upon the electrostatic atomization of coating material from an elongated atomizing head. Another object of this invention is to arrange in a novel Way an electrostatic atomizing head whereby an improved, uniform coating on articles and a sheet material is obtained. A further object of this invention is to arrange a plurality of electrostatic atomizing heads along a path of articlemovement for coating the articles moved over the article-path. A still further object of this invention is to provide novel apparatus so constructed and so disposed relative to the horizontal that any tendency of the material to be deposited in stripes is eliminated. Still another object of this invention is to provide an apparatus having the above characteristics which will be simple in construction and durable in use and which can be readily inspected, serviced and repaired in the field. Other objects and features of the invention will be apparent from the specifications and claims.

In the accompanying drawing Fig. 1 is a fragmental isometric view illustrating a coating apparatus; Fig. 2 is a fragmental rear elevation of the apparatus shown in Fig. 1; Fig. 3 is a View taken along line 3-3 of Fig. 1 with the article and its support shown in both a tilted and untilted position; Fig. 4 is a View taken along line 4-6 of Fig. 1; Figs. 5 and 8 are fragmental, isometric views illustrating other embodiments of my invention; Fig. 7 is an orthographic view of the article and discharge member shown in Fig. 6 with a section through the discharge member to aid in showing the form of discharge member and its edge; Fig. 8 is a circuit diagram illustrating a circuit which is adapted to control the apparatus shown in Fig. 6; and Fig. 9 is a View like Fig. 4 of a modified form of the invention.

In Fig. 1 I have illustrated an arrangement of apparatus suitable for coating articles II! which are illustrated as acoustic pans which are rectangular metal panels provided with narrow peripheral flanges. Such apparatus embodies a conveyor which includes chain I I in engagement with sprockets I2, only one of which is shown. The conveyor may be driven in the direction indicated by the arrows (Figs. 1 and 2 by connecting to one of the sprockets I2 a motor with suitable speed reducing means or other suitable driving means. A plurality of article supports I3 are connected to the chain I I for carrying the articles It in succession along a predetermined path as illustrated in Fig. 1. Each article support I3 comprises a vertical rod I4 and horizontal cross bars I5. A cam member I! (Figs. 2 and 3) is disposed along the conveyor and is adapted to engage the horizontal bars I5 of the article supports I 3 to tilt the article supports and the articles at an angle to the horizontal just prior to their moving past the atomizing apparatus (which will be described hereafter) and to maintain them tilted until they are moved past the atomizing apparatus.

Disposed above the articles near the forward end of the conveyor is a preheat unit 26 for heating the articles prior to their passing past the electrostatic atomizing apparatus. This preheat unit is not essential to the invention and may be used. to dry articles which have just been cleaned or to improve the initial setting or" the coating material applied to the articles.

Farther along the conveyor there is disposed above it an electrostatic atomizing device 2! from which liquid coating material is electrostatically atomized and electrostatically deposited on the articles. To effect electrostatic atomization of the coating material and electrostatic deposition thereof on the articles iii, an electrostatic field of appropriate strength is maintained between the device 2! and the ar ticles. For this purpose the articles may be grounded through the conveyor while the device 2! is insulated from ground and connected to one terminal of a high voltage source 22, the other terminal of which is grounded.

The electrostatic atomizing device 21, which is" also shown in Figs. 3 and 4, comprises structural members 23 which may be supported in any suitable manner. Mounted on the structural members 23 are two elongated discharge members 24 and 25 which are shown as shaped in cross section to present toward the articles l relatively sharp edges 25 and 2'! respectively. The dis charge members are arranged on the structural members 255 so that upwardly presented surfaces 28 and 2e are sloped downwardly toward the edges is and 27 and these edges are themselves inclined at an angle to the horizontal along their longitudinal extent. Also, transverse to their elongation the members 24 and 25 are arranged at an angle to the vertical with their edges 26 and 2'? directed toward each other. An average potential gradient of the order of 10,000 volts per inch is maintained between the members 24 and 25 and the articles Iii moving past them, and as a result an electrical dischage will exist along the edges 26 and 2'! and an electrostatic field will exist between the members 24' and 25 and the articles is so that liquid coating material fed to the edges 26 and 2? will be electrostatically atomized and electrostatically deposited onto the articles Hi, as more fully set forth and described in my co-pending application above referred to.

The coating material distributing means which supplies liquid coating material to the surfaces 28 and 29 of members 2d and 25 and which is shown in Figs. 1 and 4, comprises a reciprocator 36 arranged to reciprocate parallel to discharge members 24 and 25 a supporting structure 3| carrying liquid dispensing devices 35 and 36.

The upper end of each dispenser is adapted to be connected to a flexible hose 34 by which liquid coating may be supplied to each dispenser either by gravity or by positively produced pressure. The lower ends of dispensers 35 and 36 are provided with nozzles 31 and as which are positioned adjacent discharge members 24' and 25 and are spaced therefrom as shown in Figs. 1 and 4 to direct streams of coating material onto surfaces 28 and 29 rearwardly of edges 25 and 21. While the nozzles 31? and 38 are shown as being spaced from the discharge members 24 and 25, the in-- vention is not limited to this arrangement, as nozzles arranged in sliding engagement with corresponding discharge members would operate satisfactorily. While the detailed construction of the reciprocator is not shown in Figs. 1, 3 and 4, it may be of the type shown in Fig. 6 which will be described hereafter or any other suitable reciprocator well known in the finishing industry.

Disposed along the conveyor beyond the electrostatic atomizing device 2!, there is shown a drying oven 39 which may be used when it is desired to accelerate drying of the coated articles is prior to their removal from the conveyor. F

It is understood, however, that the drying oven is not an essential part of my invention.

In operation of the apparatus shown in Figs. 1-4 inclusive, articles I0 are placed on supports l3 and moved by the conveyor past the preheat unit which serves to thoroughly dry the articles and preheat them, where such treatment is necessary, to accelerate the setting of the liquid coating material applied by the electrostatic atomizing device 2|. After passing the preheat unit 20 the articles are tilted so that the major surface to be coated is generally parallel to the edges 26 and 21. While the articles are in this tilted position they are moved past the electrostatic atomizing device 2|.

The coating material supplied to the reciproeating dispensers 35 and 35 is distributed along the longitudinal extent of surfaces 28 and 29 rearwardly of the discharge edges 26 and 21 from where the coating material flows to these edges under the influence of gravity and is electrostatically atomized therefrom and electrostatically deposited on the articles Hi passing the edges 26 and 21 by the eelctrostatic field which exists between these edges and the articles. The rate at which coating material is supplied to the nozzles 31 and 38 is controlled so as to insure that the discharge members 24 and will not receive more coating material than can be atomiz'ed from their discharge edges. The rate of reciprocation of the structure 31 and the dispensers and 3B is adjusted as necessary to maintain a supply of coating material for electrostatic atomization along the desired extent of the edges 26 and 21.

It is to be noted that the articles to be coated need not be electrical conductors. When articles made of highly effective insulating material such as glass are being coated, it is desirable that the surface to be coated be backed by a grounded, electrical conductor. However, if the articles are of poor insulating material, such as wood, no conductive backing is necessary.

Generally speaking, it is advisable that the length of the discharge edges 26 and 2? be longer than the parallel dimension of the surface or surfaces opposed to them and that coating material be distributed to a portion of each edge of approximately the same dimension as the parallel dimension of the opposed surface. The dimension of the portion of the discharge edge to which coating material is distributed, however, may in many instances depending upon the nature of the article be somewhat less than the parallel dimension of the opposed surface of the article without causing undue lack of uniformity on such surface.

Where the article or articles have flanges to be coated or similar surfaces such as the flanges of article l0, special consideration should be given to the distribution of coating material on each discharge member and to the location and orientation of the discharge members with respect to the articles and the flanges. To aid in the coating of the side flanges (those parallel to the direction of article movement) it will be advisable to distribute coating material to a longer portion of the edges 26 and 27 than would be required if only the top surface of articles H] were to receive a satisfactory coating. To aid in coating the two transverse flanges of the articles l9 (those normal to the direction of article movement), it will be advisable to orient one of the discharge members at an angle so that its discharge edge is generally parallel to one of the transverse flanges and coating material distributing surface is sloped downwardly toward the discharge edge and toward one of the transverse flanges in such a manner that an extension of the coating material distributing surface will intersect the transverse flange at least during a portion of the travel of the article through the coating zone.

' The second discharge member should be tilted in the manner described to improve the coating on the other transverse flange. Fulfilling these conditions for the articles shown, these discharge members may thus be oriented so that their coating material distributing surfaces are sloped downwardly toward each other as shown in Fig. 1 or they may be oriented so that their coating material distributing surfaces are sloped downwardly in opposed directions as shown in Fig. 9. As the parts of Fig. 9 are the same as those described with reference to Fig. 4 (with the exception of the slope of the material distributing surfaces just mentioned), similar parts have been given similar, but primed, reference numerals, and further detailed description is believed unnecessary.

Coating material electrostatically atomized from an extended discharge edge, such as the edge of either of the members 24 and 25, (or 24 and 25) tends to leave such edge in the form of more or less well defined streams spaced from each other along the edge. I have discovered that by arranging the discharge edge at an angle to the horizontal when the electrostatic coating apparatus is in operation, these separate streams of coating material progress continuously toward the lower end of the edge as a result of gravity. The action resulting from the inclined positioning of the discharge member eliminates the striping tendency which would otherwise exist and aids in obtaining a coating of improved uniformity. I have found that for most liquid coating materials a blade-inclination in the neighborhood of 20 degrees to 25 degrees will be sufficient to eliminate the striping tendency. With relatively viscous materials, greater inclinations may be needed; but ordinarily little if any benefit is to be derived from inclinations greater than 60 degrees.

Since the inclined positioning of the discharge member causes liquid coating material deposited on its upwardly presented surface to move downwardly longitudinally of its extent prior to its reaching the discharge edge, the movement of the liquid distributing nozzle should be adjusted so that its path is displaced slightly upwardly and longitudinally along the discharge member relative to the desired extent of the spray pattern issuing from the discharge edge.

The slope of the surfaces 28 and 29 transversely of the respective edges 26 and 21 causes the material to flow to these edges by gravity from the points at which it is deposited on the sloping surfaces. As a result, it is possible to dispose the nozzles 31 and 38 well back from the edges 26 and 21 where they will be electrostatically shielded by the members 24 and 25. The members 24 and 25 are conveniently formed entirely of goodconducting material, such as metal, in which case the film of coating material from the edge where atomization occurs will be in direct contact with the conducting material and connected therethrough to the high-voltage source. Such a direct connection is not absolutely essential, as it is necessary only that the edge of the film be located in a region where the local potential gradient is great enough to efiect atomization and that a field exists for urging the atomized material toward the article for deposition'thereon.

The two members 24 and 25 should be located far enough apart so that the presence of one does not objectionably reduce the strength of the field at the edge (26 or 21) of the other. If the distance between the edges 25 and 21 is equal to or greater than their distance from the articles, no such objectionable mutual shielding will exist. Besides the advantage previously mentioned, the use of more than one discharge member permits the application of heavier coatings than could be obtained from a single member. a certain amount of spacing between discharge members is desirable, a single means may be utilized for reciprocating both of the coating material supplying nozzles associated with each discharge member,

In Fig. 5 I have illustrated an arrangement of apparatus which is suitable for coating sheet material 40. Such apparatus embodies a conveying means which includes the rollers 4| and 42 which guide the sheet material over a predetermined path through a coating zone. Disposed at one side of the path of sheet-movement through the coating zone is an atomizing device 44 from which liquid coating material is electrostatically atomized. To effect electrostatic atomization of the coating material and electrostatic deposition of the atomized material on the sheet 40 as it passes the device 44, an electro static field of appropriate strength is maintained between the device 44 and the sheet material 40. For this purpose the sheet material may be grounded through the roller 4! while the device 44 is insulated from ground and connected to one terminal of a high voltage source 46, the other terminal of which is grounded.

The atomizing device 44 includes vertical insulating posts 48 and 49 which sup-port a beam 50. The beam 50 supports housing 5| which is pivotally connected thereto as shown. The housing 5| may be held at various positions relative to the horizontal by an adjustable strut 52 which is connected to the beam 50 as shown.

At one side of the housing 5| there is supported in any convenient manner an elongated discharge member 54 which is preferably of electrically conducting material and connected to the ungrounded terminal of the high voltage source 45. The member 54 is shown as shaped in cross section to present toward the sheet 40' a relatively sharp edge 55. It also is provided with an upwardly presented surface 56 which may be sloped downwardly toward the edge 55.

An average potential gradient of the order of 10,000 volts per inch is maintained between the elongated member 54 and the sheet 40 moving past it, and as a result an electrical discharge will exist along the edge 55 and an electrostatic field will exist between the member 54 and the sheet 40 so that liquid coating material fed to the edge 55 will be electrostatically atomized and electrostatically deposited onto the sheet 40. The liquid coating material is fed to the surface 56 along the edge 55 in the form of a film extending along the edge between more or less definite limits, such film being created and maintained by any suitable supplying means. One such means may comprise a carriage 51 mounted for reciprocation along slot 58 which extends longitudinally of housing 5|. This carriage may bear at its outer end a short length of tube or Even though pipe 59 disposed transversely of the slot 58. One end of the tube 59 is connected through a flexible hose 60 with a source of liquid coating material which is adapted to be fed to the tube 59 by gravity or by positively produced pressure. To the opposite end of the tube 59 there is connected a nozzle 6| having its outer end disposed rearwardly of the edge 55 so as to be electrically shielded by the discharge member 55 while discharging coating material onto the surface 56. The surface 56 between the edge 55 and the path of nozzle BI is sloped downwardly sufiiciently so that gravity will cause the coating material to flow to the edge 55,

Means which may be employed for reciprocating the carriage 51 and the nozzle 6| may take any form, such as that shown and described in my co-pending application, previously referred to, or that shown in Fig. 6 of the drawings and described hereinafter.

The operation of the apparatus just described is similar to the operation of the apparatus shown in Fig. 1 except that the surface being coated is moved in a vertical rather than a horizontal direction.

As previously stated the housing is pivotally connected to the beam 50 at one end thereof. This permits positioning the discharge edge 55 at any convenient angle relative to the horizontal. This angle may be varied depending upon the viscosity of the liquid coating material to effect the desired gravity induced stream movement referred to above.

Referring to Fig. 6, I have illustrated still another form of coating apparatus which is adapted for coating articles such as the illustrated cylindrical object 70. Such apparatus embodies a conveyor 'II which is provided with a plurality of longitudinally spaced spindles I2. Each spindle I2 has afiixed thereto a pulley I3 which is adapted to engage a belt 14. The belt 14 is adapted to be driven in any convenient manner in the direction of the arrow placed adjacent the belt for rotating the spindle I2 and the article mounted thereon. The conveyor H may have associated with it a switch I6 normally biased to a closed position provided with a lever 17 arranged in the manner shown to intermittently stop the conveyor and bring the articles I0 successively to rest opposite the atomizing device 80 now to be described. The circuit in which the switch I6 is incorporated is shown in Fig. 8 and will be described in greater detail hereafter.

The atomizing device 80, from which liquid coating material is electrostatically atomized, is disposed at one side of the conveyor II. To effect electrostatic atomization of coating material and electrostatic deposition thereof on the article 18, an electrostatic field of appropriate strength is maintained between the device 80 and the article 78. For this purpose the article I0 may be ground through the conveyor II as shown and the device 80 insulated from ground and connected to the ungrounded terminal of a high voltage source in the manner shown in Figs. 1 and 5.

The atomizing device 80 comprises frame 8! which is mounted on vertically reciprocable rod 82. A reciprocating device 83 is connected to rod 82 for moving it and the frame 8I vertically between suitable, predetermined limits. The reciprocating device 83 may be of the type described in my co-pending application previously referred to or of any other suitable type. A bracket 85 is affixed to the rod 82 for supporting 8' an element 86 which is adapted to operate switches 81 and 88 which are biased to a normally open position and are included in the control circuit illustrated in Fig. 8.

On the side of the frame 8| nearest the article I0 and along an inclined portion thereof, there is provided an elongated discharge member 89 which may be of conducting material and which has an upwardly presented surface 90 sloped downwardly toward a sharp discharge edge 9I. The member 89 is formed so that the edge 9| follows a helically inclined path which generally follows and is spaced from the cylindrical surface of the article 10, as is clearly illustrated in Fig. '7. The member 89 also is provided with a cam surface 92 whose function will be described hereafter.

An average potential gradient of the order of 10,000 volts per inch is maintained between the discharge member 89 and the article 10 spaced from it, and as a result an electrical discharge will exist along the discharge edge 9| and an electrostatic field will exist between the member 89 and the article I9 so that liquid coating material fed to the edge 9| will be electrostatically atomized and electrostatically deposited on the surface of the article 18. The liquid coating material fed to the surface 90 forms a film supported on such surface extending along the edge BI between more or less definite limits. Although the film can be created and maintained by any suitable supplying means, the coatin material supplying means shown comprises a pipe 93 which is biased forwardly by a compression spring 94 mounted on the pipe 93 between a shoulder formed thereon and a sleeve H2. One end of the pipe 93 is connected as through a flexible hose 95 with a source of coating material which is adapted to be fed to the pipe 93 either by gravity or by positively produced pressure. The supply of the coating material may be turned on and off by an air-controlled valve 98. The compressed air is supplied to valve 98 through pipe 99 and is controlled by valve III. To the opposite end of the pipe 93 there is connected nozzle 96 having its outer end disposed rearwardly from edge 9| so as to be electrically shielded thereby. A cam follower 91 is affixed to the pipe 93- and is adapted to engage the cam surface 92 of the member 89 to guide the nozzle 96 in its path of movement rearwardly of the discharge edge 9| and over the surface 90. The cam follower 91 is held in engagement with the cam surface 92 by the spring 94.

The means employed to reciprocate the pipe 93 and the nozzle 96 may take various forms. In Fig. 6 such means is shown as comprising a cylindrical cam I09 with threads WI and I02 which is rotatably mounted in brackets I83 and I04 on frame 8|. The cam I08 is adapted to be driven by air motor I05 which may be connected to a source of compressed air through flexible hose [06, in which there is provided the valve III. A carriage I08, which is movably mounted on rails I09 and I I8 and which includes a key (not shown) adapted to follow threads IOI or I02, is reciprocated along such rails by the cam I00 in known manner. The sleeve I12 is pivotally mounted intermediate its ends on pins H3 which are supported on the carriage I08, and pipe 93 is slidably mounted within the sleeve H2. A spring plate H5 mounted on the carriage I08 is adapted to engage the forward end of sleeve H2 so as to bias the nozzle 96 into continual engagement with the surface 90 of the .discharge'member 89. The threads IOI and I02 in cam I are of variable pitch to vary the speed ofthe carriage I08 so that the nozzle 96 moves along the helical discharge edge 9| with a generally uniform rate of speed. If it is desired to move carriage I08 at a uniform speed, the threads I6I and I02 in cam I00 should be of constant pitch.

The control circuit for controlling the operation of the apparatus shown in Fig. 6 is shown in Fig. 8 and includes switches 16, 81 and 88 previously described and relays I22, I23 and I24. The control circuit also includes a manual bypass switch I46 which is connected to conductors I50 and II leading to the high voltage source for independently controlling the high voltage source and manual by-pass switch I41 connected in the circuit including solenoid I for independently controlling the air valve III. Relay I22 comprises coil I26 and contacts I21, I28, I29, I and I3I. Relay I23 comprises coil I33 and contacts I34, I and I36. Relay I24 comprises coil I38 and contacts I39, I40, I4I, I42, I43 and I 44.

As shown in Fig. 8 the control circuit is in the condition when the conveyor H is moving and the electrostatic coating device 80 is inoperative. Under this condition the relay I22 is energized and holding-circuit contact I21 and conveyormotor contacts I28, I29 and I30 are closed and contact I3I is open. Contact I3I controls ('1) a circuit which includes coil I33 of relay I23, (2) circuits which include solenoids H1 and I I8, and (3) a circuit which includes coil I38 of the relay I24. The circuit by which coil I26 of relay I22 is maintained in an energized condition and which is referred to as a holding circuit consists of conductors I52, I53, contact I21, conductor I54, switch 16, conductors I55 and I56, coil I26 and conductors I5I and I58.

When one of the spindles 12 on the conveyor 1I engages lever 11 of switch 16, this switch is temporarily opened and coil I26 of relay I22 is de-energized opening holding circuit contact I21 and conveyor motor contacts I28, I29 and I30, and closing contact I3 I. This stops the conveyor motor. The closing of contact I3I energizes the circuit which includes solenoid I I8 which actuates the valve I I 9 to initiate the upward movement of the reciprocator 83-. v This circuit consists of conductors I52, I60, contact I3I, conductors I6I, I62, I63, switch 88, conductors I64, I65 and I66, contact I36 (which is closed when relay I23 is deenergized) conductor I61, coil H8 and conductors I68, I69, I10, HI and I58. The closing of contact I3I also energizes the circuit which controls relay I24. This circuit consists of the same portion of the previous circuit from conductor I52 to junction I12 and therefrom it consists of conductor I13, contact I 44, conductors I14 and I 15, coil I38 and conductors I16, HI and I58. Upon the energization of coil I38 through the circuit just described contact I44 opens and thereafter coil I38 is energized through the circuit which consists of conductors I52, I60, contact I 3I, conductors I6I, I62, I18, contact I39, conductors I19, I15, coil I38, conductors I16, HI and I58. Upon the energization of coil I38 contacts I43, I42, MI and I 40 are closed in addition to contact I44 being opened and contact I 39 being closed. Closing contacts I42 and I43 closes a circuit which energizes the high voltage source. This circuit consists of conductors I8I, I82, contact I43, conductors I83, I50, I5I, I84, contact I42, conductors I85 and I86. When contacts I 40 and I are closed 10 a current source is connected to the solenoid I20 which controls the air valve-I I I. This is done by means of a circuit which consists of conductors I88, I89, contact I4I, conductors I90 and I3I, coil I20, conductors I92, I93, contact I48 and conductors I94 and I95.

Switch 88 is opened upon the initiation of the upward movement of the rod 82 of air reciprocator 83. After the air reciprocator moves the atomizing device upward a predetermined distance, it actuates switch 81 by means of element 86 and momentarily closes switch 81. This energizes coil II1 through the circuit which consists of conductors I52, I60, contact I3I, conductors I6l, I91, I98, switch 81, conductors I99 and 200, coil II1, conductors 20I, I69, I10, HI and I58. The energization of coil II1 actuates valve II9 which reverses the movement of the rod 82 of the reciprocator 83 to a downward direction. Closing switch 81 also energizes coil I33 of relay I28 through the circuit which consists of conductors I52, I60, contact I3I, conductors I6I, I91, I98, switch 81, conductors I99, 203, 204, coil I33, conductors 205, I10, Ill and I58. Upon the energization of coil I33 contacts I34 and I35 are closed and contact I36 is opened. After the switch 81 again opens after its momentary closing, the coil I33 remains energized through the circuit which includes contact I34. This circuit consists of conductors I52, I60, contact I3I, conductors I6I, I91, 201, contact I84, conductors 288, 204, coil I33, conductors 205, I10, HI and I58.

When the element 86 reaches and engages the switch 88 on the downward movement of the rod 82 of the reciprocator 83, switch 88 is closed. This momentarily energizes coil I26 of relay I22 through the circuit which consists of conductors I52, I50, contact I3I, conductors I6I, I62, I63, switch 88, conductors I64, I65, 2I0, contact I35, conductors 2II, I56, coil I26 and conductors I51 and I58. After coil I26 is energized holding circuit contact I21 and conveyor motor contacts I28, I29 and I30 are closed and contact I3I is opened. Upon the closing of contact I21, coil M6 is energized through the circuit previously described. The closing of conveyor motor contacts I28, I29 and I30starts the conveyor motor. The opening of contact I3I at the same time deenergizes relay I23 and I24 and the circuits including the solenoids H1 and 'I I8. This makes solenoids II1, I I8 and I20 and the high voltage source inoperative. A feature essential to the operation of the circuit just described is that the switch 88 be held closed when the reciprocator 83 comes to rest at the bottom of its stroke.

In the operation of the apparatus of Figs. 6 and 8, the connections established as shown in Fig. 8 cause the conveyor to move including the spindles 12 in the direction of the conveyor arrow shown in Fig. 6. During movement of the conveyor, the rod 82 is at the bottom of its stroke, thus maintaining switch 88 closed through element 86. When one of the spindles 12 engages lever 11 of switch 16, this switch is momentarily opened to break the holding circuit of relay I22 whereby the conveyor motor is stopped and the spindle which has actuated switch 16 is stopped adjacent the electrostatic atomizing device 80 in the position shown in Fig. 6. The de-energization of relay I22 also closes contact I3I which permits energization of solenoid I I8 to start the operation of the reciprocator 83 for causing upward movement of the atomizing device. The closing of contact I3I also permits energization of relay I24 which permits the energization of the high voltage source which creates an electrostatic field between the discharge member 89 and the article Hi and also permits energization of solenoid I21": which opens air valve l H for supplying coating material to the nozzle 98 and energizes the air motor Hi5. While air motor I reciprocate the carriage Hi8, the spring 94, acting between the sleeve I I2 and a shoulder on the pipe 93, holds the cam-follower 9'! against the cam 92, which is so shaped that the nozzle 96 moves parallel to the edge 9| as it discharges coating material onto the surface 99. Coating material discharged from nozzle 95 flows down the radial slope of the surface 98 to the edge 9|. As atomizing device 86 is moved upwardly theelectrostatic field between it and the article H3 electrostatically atomizes the coating material and electrostatically deposits it on the article '59. When'the atomizing device 80 has moved upwardly its predetermined distance, the element 86 actuates switch 81 to de-energize solenoid H8 and to energize solenoid H1 which actuates valve H9 and reverses the movement of the atomizing device 80 to a downward direction. During the downward movement of the atomizing device 89 the supply of coating material is continued'to the edge 9i and coating of the article iii i continued during the downward movement of the atomizing device 80. After the atomizing device has made its predetermined downward movement, the element 86 closes switch 38 whereby relay I22 is energized and relays I23 and I2 3 are d-e-energized. This de-energizes the high voltage source, cuts off the supply of coating material to the nozzle 55 and stops the reciprocation of the nozzle 96 and the atomizing device 80. Also, upon the re-energization of relay I22 the conveyor motor is started to move the article that has just been coated along the conveyor and to permit another article to move into coating position relative to the atomizing device.

It is evident that valve means could be provided which would permit shutting off the supply of coating material during any part of the reciprocating cycle of the atomizing device all. The helical inclination of the edge 9! in Fig. 6 and the longitudinal inclination of the edge 55 in Fig. 5 function to eliminate striping tendencies in the same manner as does the inclination of the edges 2-6 and 2? in Figs. 1 to 4. The state ments made above, in connection with the apparatus of Figs. 1 to 4, relative to the conducting character of the members 24 and 25, apply equally well to the discharge member 54 of Fig. 5 and discharge member 89 of Fig. 6. Also applicable to the arrangements shown in Figs. 5 and 6 are the statements previously made relative to the necessity of a. backing electrode if the article being coated is made of highly effective insulating material.

I claim as my invention:

1. In an electrostatic atomizing system for use in the electrostatic deposition of liquid coating material on an article, a support for the article to be coated, a discharge member having an extended, discharge edge, a support for supporting said member in a position with said edge spaced from an article on said support and inclined at an angle to the horizontal of between and 60 degrees, and means for distributing liquid coating material to said member along said edge for atomization therefrom, the spacinggbetween said edge and the article being sufficient to permit substantial dispersion of the particles 12 under the influence of electrostatic forces dur-' ing their movement toward the article.

2. In an electrostatic atomizing device for use in electrostatic deposition of liquid coating material, a plurality of discharge members, each of said members having a generally upwardly presented surface terminating at an extended, discharge edge, means for supporting said members in spaced relation to each other and for maintaining said edges in substantially inclined positions and generally parallel to each other and with, each of said associated surfaces sloping downwardly toward said edges, and a liquid dispensing means associated with each of said members for supplying liquid coating material to each of said upwardly presented surfaces.

3. In an electrostatic atomizing device for use in electrostatic deposition of liquid coating material, a pair of discharge members, each of said members having a generally upwardly presented surface terminating at an extended, discharge edge, means for supporting said members in spaced relation to each other and with their upwardly presented surfaces sloping downwardly toward their respective discharge edges and toward each other, and a liquid dispensing means associated with each of said members for supplying liquid coating material to each of said upwardly presented surfaces.

l. The invention set forth in claim 2 wherein adjacent ones of said members are sup-ported with their upwardly presented surfaces sloping downwardly and away from each other.

5. Electrostatic coating apparatus having, in combination, a discharge member having a generally upwardly presented surface terminating at an extended discharge edge, means for supporting said member with said edge inclined to the horizontal and with said surface sloping downwardly toward said edge, a conveyor, a plurality of article supports on said conveyor for carrying articles successively past said edge in spaced relation thereto, means for adjusting each of said article supports prior to their movement past said edge for presenting the surfaces of the articles to be coated in a plane generally parallel to said edge, means for supplying liquid coating material to said member surface, and means including a high voltage source for creating between the articles on said article-supports and coating material on said edge an electrostatic field for electrostatically atomizing the coating material and electrostatically precipitating it onto the articles.

6. In electrostatic coating apparatus, means for conveying an article along a predetermined path, a plurality of discharge members spaced along said path, each of said members having an extended, discharge edge presented laterally of said predetermined path and toward and in spaced relation to an article on said conveying means, a liquid dispensing means associated with each of said members for distributing liquid coating material at a controlled rate to each of said members for effecting a uniform distribution thereof along each of said edges to maintain on said edges liquid coating material for atomization from a plurality of spaced points therealong, and means including a high voltage source for creating between an article on said conveying means and coating material on the edges of said discharge members an electrostatic field capable of electrostatically atomizing such coating material and electrostatically dispersing and precipitating it onto the article, said article conveying means and said discharge members being so relatively disposed that the distance between the article surface and said edges will be materially greater than the distance between adjacent ones of the points at which atomization takes place, whereby the atomized particles during their movement to the article by the action of the field will be widely dispersed.

7. The invention set forth in claim 6 with the addition that each of said discharge members includes a generally upwardly presented surface sloped downwardly toward and terminating at said edge and said edge being substantially inclined at an angle to the horizontal of between 26 and 60 degrees relative to its extent.

8. The invention set forth in claim 6 with the addition that said liquid distributing means comprises a nozzle and means for reciprocating said nozzle along said edge and spaced therefrom.

9. In an electrostatic coating system for use in the electrostatic deposition of liquid coating material on an article, a support for the article to be coated, a plurality of discharge members, each of said members having a surface terminating in an extended discharge edge, means for supporting said members in spaced relation to each other and with the edge of each of the members spaced from an article on said support, liquid dispensing means associated with each of said members for supplying liquid coating material to each of said surfaces for flow to said edges, means for creating an electrostatic field of high potential between an article on said support and the coating material at each of said edges capable of electrostatically atomizing and dispersing such coating material and electrostatically precipitating it onto the article, the spacing between each of said edges and the article being sufiicient to permit substantial dispersion of the particles during their movement toward the article under the influence of said field.

10. In an electrostatic atomizing system for use in electrostatic deposition of liquid coating material on an article, a support for the article to be coated, a discharge member having a generally upwardly presented surface terminating at an extended edge, means for supporting said member with said edge inclined to the horizontal and with said surface sloping downwardly toward the edge, means for adjusting said supporting means for changing the angle of inclination of said edge, and means for supplying liquid coating material to said member-surface for atomization from a plurality of streams spaced along said edge, said edge being inclined to the horizontal at an angle of not more than 60 but sufiicient to cause the 14 streams of coating material to progress continuously toward the lower end of the edge, the spacing between said edge and the article being sufficient to permit substantial dispersion of the particles under the influence of electrostatic forces during their movement toward the article.

11. An electrostatic atomizing system for use in the electrostatic deposition of liquid coating material on an article, a support for the article to be coated, a discharge member having an extended edge, means for supplying liquid coating material to said member and for forming the material into a substantially continuous body having a relatively thin terminus extending along said edge, means for creating an electrostatic field between the terminus of said body and the article capable of atomizing said material from a plurality of streams spaced along said terminus, the spacing between said terminus and an article on said support being sufiicient to permit substantial dispersion of the atomized particles by said field during their movement toward the article, and means for maintaining said edge inclined to the horizontal at an angle sufficient to cause the streams of coating material, during said atomization, to progress continuously toward the lower end of the edge.

12. In an electrostatic atomizing system for use in the electrostatic deposition of liquid coating material on an article, a support for the article to be coated, a discharge member having an extended edge, means for supplying liquid coating material to said member and for forming the material into a substantially continuous film along said edge for atomization from a plurality of streams spaced along said edge, the spacing between said edge and an article on said support being sumcient to permit substantial dispersion of the atomized particles under the influence of electrostatic forces during their movement toward the article, and means for maintaining said edge inclined to the horizontal at an angle sufiicient to cause the streams of coating material, during said atomization, to progress continuously toward the lower end of the edge.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,855,869 Pugh Apr. 26, 1932 2,070,972 Lindenblad Feb. 16, 1937 2,224,391 Huebner Dec. 10, 1940 2,247,963 Ransburg et al July 1, 1941 2,408,143 Huebner Sept. 24, 1946 2,438,561 Kearsley Mar. 30, 1948 2,451,288 Huebner Oct. 12, 1948

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