US3169883A - Electrostatic coating methods and apparatus - Google Patents

Electrostatic coating methods and apparatus Download PDF

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US3169883A
US3169883A US148793A US14879361A US3169883A US 3169883 A US3169883 A US 3169883A US 148793 A US148793 A US 148793A US 14879361 A US14879361 A US 14879361A US 3169883 A US3169883 A US 3169883A
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Prior art keywords
orifice
spray
article
inch
film
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US148793A
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James W Juvinall
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Ransburg Corp
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Ransburg Corp
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Priority to BE624075D priority Critical patent/BE624075A/xx
Application filed by Ransburg Corp filed Critical Ransburg Corp
Priority to US148793A priority patent/US3169883A/en
Priority to NO146042A priority patent/NO118260B/no
Priority to DE19621777329 priority patent/DE1777329A1/de
Priority to DER33708A priority patent/DE1291659B/de
Priority to DER24964U priority patent/DE1925142U/de
Priority to ES281775A priority patent/ES281775A1/es
Priority to AT843462A priority patent/AT249224B/de
Priority to FR913450A priority patent/FR1343806A/fr
Priority to CH1252562A priority patent/CH410697A/fr
Priority to NL284722.A priority patent/NL156619B/xx
Priority to DK460962AA priority patent/DK133616B/da
Publication of US3169883A publication Critical patent/US3169883A/en
Application granted granted Critical
Priority to DK450472A priority patent/DK130734C/da
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
    • B05B5/08—Plant for applying liquids or other fluent materials to objects
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
    • B05B5/025—Discharge apparatus, e.g. electrostatic spray guns
    • B05B5/035—Discharge apparatus, e.g. electrostatic spray guns characterised by gasless spraying, e.g. electrostatically assisted airless spraying

Definitions

  • This invention relates to electrostatic spray coating methods and apparatus for the application of liquid coating material, particularly paint, to provide a protective or decorative coating on a surface.
  • an electrostatic depositing field is of material benefit in improving paint deposition efficiency in spray painting. Particularly where automatic spray systems are used in connection with a conveyorized production line, the use of an electrostatic depositing field results in avoidance of a substantial loss of paint which otherwise takes place, both as under-spray falling out before it reaches the articles being coated and as over-spray passing beyond or away from the articles and eventually going onto the booth walls or out the exhaust stack. Suitable charging of the spray particles and the utilization of an electrostatic field to the surface being coated results in the deposition on such surface of spray particles which would not otherwise have been deposited thereon, deposition efficiency being materially improved by the electrostatic effects.
  • fineness of atomization has a very important function in achieving optimum field effects and deposition efiiciency regardless of the quality of finish desired.
  • Charge on a liquid droplet is primarily a function of surfacearea under optimum electrical charging conditions; and since reduction in droplet diameter reduces its volume more rapidly than its surface area, fine droplets have a larger charge-to-rnass ratio than larger droplets, and therefore may be better controlled by the trostatic spray coating installations have, in many cases,
  • a solid circular stream of liquid even though traveling through the surrounding air at very high relative velocities, does not give atomization of a desired type suitable for desired field control and for quality paint finishes; but issuance of the liquid in an expanding thin film, whether in the form of a hollow cone or fan-like, if certain conditions as to velocity and form are present, results in atomization into the very fine particles which result in the desired field control and a high quality finish; and optimum electrostatic deposition may be approached by use of such an atomizing device under proper conditions of spacing and field strength.
  • the use of a hydrostatic jet while still obviating the disadvantages of a carrier air blast in an electrostatic system, provides control factors not heretofore available with elimination of the air spraygun.
  • the jet with a high velocity,expanding thin film not only permits control of fineness of atomization despite other factors not under ready control (as paint type and viscosity) but also directional and particle momentum control enabling control of film thickness under situations otherwise providing difficulties in an electrostatic system, as providing sufiicient paint in the bottom of a depression or otherareawhere the field alone might result in an undesirably thin coating. 5
  • One method of determining whether atomization is suitable as to particle size is to measure the diameter of spots formed by spray particles impinging on an appropriate target under controlled conditions.
  • Conditions which have been used in practice involve passing a 4" by 6" fiat target through the spray longitudinally of its longest dimension with one 'face in a plane perpendicular to the spray axis and at a distance of about 12" from the spray source with sufficient rapidity that the'exposed face of the target is substantially free of overlapping'spots.
  • the spray spot size is less than about 0.015 inch
  • the spray is capable of producing finishes of grasses high quality, although where finish requirements are less stringent sprays producing a spray spot size of 0.020 inch may be satisfactory, and spray with a spray spot size above 0.020 inch should only be used where the quality of finish is not critical, for example, in maintenance painting of factory walls or the coating of heavy equipment, such as farm machinery.
  • the size of spots produced by deposited spray particles it is to be understood that the size referred to is the spray spot size determined under the conditions just indicated.
  • an electrostatic system In general, deposition of a qualityfin'ish with high efficiencies in, an electrostatic system is obtained by use of a jet with a very small orifice arranged to cause the liquid coating material, which is supplied thereto at very high pressures, to issue invthe form of an expanding film, with very high liquid velocities. In certain instances such velocities at least initially can be, of the order of 10,000 feet per minute or more.
  • the particles of spray so formed are capable both of producing satisfactory finishes and of possessing in an electrostatic field, charge-to-mass ratios great enough to render them highly responsive to electrostatic forces and to attain high deposition efiiciencies.
  • the electrostatic field employed may be one maintained either to the forward portion of the atomizer, the leading edge of, the paint-film, or it may extend to a spray-chargiug electrode disposed close to the zone of atomization. In any event, such field should have an average potential gradient of at least 5,000, and preferably at least 10,000,
  • FIGURE 1 is a perspective view of a system utilizing a high pressure jet atomizing device and embodying the invention here disclosed;
  • FIGURE 2 is an enlarged view of a jet nozzle tip and the film issuing therefrom;
  • FIGURE 3 is an end view of the nozzle shown in FIG- URE 2, at half scale relative thereto and looking front the right of such FIGURE 2;
  • FIGURE 4 is a perspective view of another embodiment of my. invention. 7
  • FIGURE 5 is a vertical sectional view along the axis of the atomizer
  • FIGURE 6 is illustrative of various operating conditions and comprises portions 6A, 6B and 6C, illustrative of operation in three diflerent positions of the control'cam;
  • FIGURE 7 is a longitudinal sectional view illustrating an atomizing apparatus incorporating another embodiment of the invention.
  • FIGURE 8 is a side elevational view partly broken contact with the actuating finger 23a terminates it, so that paint is not wasted between the articles.
  • the paint which may for example be a conventional synthetic channel, is here shown as being applied at two stations.
  • One of these comprises the jet atomizer mounted on an insulator carried by the movable portion 41 of a hydraulic reciprocator 42.
  • This reciprocator is actuated by conventional hydraulic means (not shown) to reciprocate the spray jet vertically a desired number of times during the passage of a cabinet thereby.
  • the other spray source is here shown as the jet 43 mounted on a fixed insulating support 44 and so placed'as to coat the undersides of the cabinets as they pass down the line.
  • a similar arrangement, at another point in the line could be used to paint the other sides and'the tops of the cabinets.
  • the source of paint is here illustrated as a paint tank 45 mounted on insulated supporting legs 46.
  • the paint being withdrawn from the tank passes through afirst filter 47 and then through a pair of supply tubes 48 and 49 to pumps 59 and 51 in the housing 52.
  • the pump is of the variable volume, positive displacement piston type, the piston being here shown as driven by a scotch-yoke drive arrangement '53, preferably. with adjustable eccentrics, from an insulating shaft 54 extending down through an insulating supporting sleeve 55 to drive means in the base 56.
  • a variable drive means is provided as, for example, one utilizing a variable speeddrive arrangement in conjunction with an'electric motor.
  • the high'pressure outlet of the pump is connected through pipe 57, a solenoid operated three-way valve 58 and an ultra-fine filter 59 to the outlet fitting 60. Connection is made through a suitable high pressure hose 61 to the jet 43.
  • the ultra-fine filter is of a commercially available type preferably passing only particles of less than the order of twenty-five microns in diameter.
  • a pulse damper 62 Connected to the pipe 57 is a pulse damper 62 comprising a housing having therein a diaphragm exposed to the very high pressure in the line, the diaphragm being capable of compressing sufficiently to smooth out the pulses of the positive displacement pump and insuring a very uniform, high pressuredelivery of paint to illustrated, by suitable means such as the hooks 18 and 19 and the holding members 20land 21.
  • the overhead conveyor illustrated is adapted to move the articles along at an appropriate rate as, for example, at a speed of 10 feet per minute, throughthe coating 'zone provided by one or more jet spray heads.
  • Microswitches 22 and 23 are adjustably mounted on and supported by the conveyor track 10, and are provided with pivotally movable switch actuating fingers 22a and 23a which are contacted by the hooks, asthe hook 18, during passage of the articles along the conveyor path. Contact of the book 18 With the. ac-
  • tuating finger 22a for example, initiates spraying
  • a pressure relief valve 63 having a return connection to the inlet side of the pump and adjusted to open at some pressure slightly above the pressure being used, preventing darnage in the event of a stoppage in the outlet.
  • the solenoid operated three-way'valve' 58 also communicates with the inlet side of the pump 51, this connection being here shown as 'efiected by the pipe 64.
  • the pipe 57 corn-mum cates with'the filter 59 and thus feeds liquid to the jet 43
  • actuation of the solenoid causes communication between the pipe 57 and the pipe 64,'with' resultant recirculation through the pump which is still running and substantially instantaneous cessation of delivery from the jet 43. This charspray from a remote point.
  • the system in the other side of the casing 52 is similar. Accordingly, the liquid coating material would be similarly supplied to the jet 3% through the outlet fitting 65 and the hose 66.
  • the jets '30 and 43 are spaced apart by the d-istancebetween the conveyor hangers 12 and 13, so that both guns canbe triggered simultaneously even though one jet is painting the side
  • the jet nozzle indicated in general as 30, is of a type providing a fan-like film substantially in a single plane.
  • passage 31 is delivered through a very small orifice 32 which is elongated in cross-section; i.e., as viewed from the right of FIGURE 2.
  • the orifice should have a major and minor dimension which produce an orifice which is equivalent in cross-sectional area to a circular orifice which is no larger than of the order of .015 inch in diameter.
  • One very satisfactory orifice is .012 of an inch along its major outlet opening diameter, and .005 of an inch across its transverse or minor diameter; and this has given very satisfactory results at suitable pressures.
  • the discharge orifice is recessed somewhat below the outermost portions of the face of the nozzle, being here shown at the bottom of a semi-cylindrical depression 33 which extends parallel to the major diameter of the elongated outlet opening 32.
  • the fan-like film issuing from the opening 3.2 when the liquids are supplied thereto at very high pressures is of a character illustrated in FIGURE 2.
  • the particular film illustrated has almost exactly straight sides 34 and 35 with an included angle of about 30 therebetween.
  • FIGURE 2 comprises a magnification of several items, as it has been found in practice that the distance from the front edge of the film where it is breaking up into discrete particles, to the orifice 32, is preferably no more than an inch and most desirably not more than A of an inch, very satisfactory operating results being secured when this distance is of the order of A of an inch.
  • the nozzle For production line painting it is important to make the nozzle, or at least the portion having the projection orifice therein, of highly wear-resistant material. Tungsten carbide or a jewel such as a diamond are very satisfactory, and stainless steel has also proven satisfactory. The orifice must be of small enough size that in conjunction with the very high pressures used it will produce the desired fineness of atomization at the required delivery rate.
  • open articles such as tubular steel chair frames or bicycle frames
  • delivery rates of less than 250 cc. per minute are most satisfactory and, in the painting of such articles, the greatest benefit from the electrostatic forces is realized. With less open articles, delivery rates can be increased to 400 cc. .per minute, and the delivery rate may be further increased as the ratio of surface area to open area of the article also increases.
  • the atomization is substantially entirely a function of the mechanical effects set up in the high velocity expanding film by virtue of its relative movement with respect to the surrounding air and by virtue of the turbulent or nonlaminar fiow through the orifice, with any electrostatic field applied to the film having little atomizing effect.
  • suitable'high voltage power packs 68 and 69 have one terminal grounded and the other or hot terminal connected to the jet, so that the nozzle or the paint-film projected from it acts as one electrode of the field having the grounded article as the other electrode.
  • the total potential difference of the field at least 40,000 volts.
  • the field exists between the atomizer and the articles it is usually desirable that the atomizer be so located with respect to the articles that a substantial dispersion of the spray particles and a substantial decrease in their momentum will occur before they reach the immediate vicinity of the articles, as the tendency of the particles to be carried past the articles and lost as overspray may thereby be reduced.
  • the momentum of the particles may be employed as a control factor to produce adequate coating, and in that event it may be desirable to position the atomizer close enough to the articles to insure that the particles being deposited retain suflicient of their initial momentum to insure an adequate coating.
  • the distance between the atomizer and the articles, measured along the spray axis be at least 20 inches. Where the spray axis is perpendicular to the article path very satisfactory results have been obtained by spacing the atomizer 30 inches or a little more from that path. Closer spacings can be employed without substantial decrease in deposition efficiency if the atomizer is arranged to discharge at an acute angle to the article path. It has been found that with either of the gun orientations just menioned, particle charging is improved as the voltage gradient is increased.
  • the voltage supply output and the electrostatic system configuration should be such as to maintain average potential gradients of at least about 5,000 volts per inch and preferably at least 10,000 volts per inch.
  • the nozzle or liquid film serves as the high voltage electrode and it is not deemed desirable to minimize the effect of particle momentum imparted by the hydrostatic of a reciprocator.
  • supply voltages may be as low as 40,000 volts. When larger spacings are employed it may be desirable to employ supply voltages of 100,000 to 150,000 volts or even more.
  • FIGURES 1 to 3 The form of my invention illustrated in FIGURES 1 to 3, and heretofore described, is very satisfactory for most production lines, but there are situations where greater control of the rate of delivery from a given sized orifice is desirable. For example, where short runs of articles differing markedly in size are being painted in batches, it may be undesirable to have to remove and replace jets frequently during a shift in order to provide the widely varying paint deliveriesnecessary for maintenance of a desired film thickness on articles of substantially diiferent size moving at the same conveyor speed.
  • atomizer comprising the hydrostatic jet orifice 71 is againshown as mounted upon the vertically movable rod '72 i
  • This rod carries a first or main support bracket 73 having upturned ends 73:: and 73b.
  • the end 73a carries a motor '74; and since the bracket and associated parts are at high voltage during operation of the system, this would be energized through an isolating transformer, or may be an air or hydraulic motor.
  • a splined shaft 75 is journaled in the bracket ends and adapted to be rotated by the motor at some suitable and preferably relatively low speed as, for example, 300 r.p.m.
  • the splined shaft carries a control cam member 76, this cam having a raised portion 76a and a recessed portion 76b. As may be best seen in FIGURE 4, the
  • FIG- 8 URES 6A,”6B and 6C show representative cam portions along the section lines indicated on FIGURE 4.
  • a second bracket member 77 is fixedly mounted on the first bracket '73, and in turn carries the hydrostatic jet atomizer (to the left as viewed in FIGURE 5) and the arrangement for controlling the average volume of liquid coating material atomized therefrom in a given length of time.
  • a yoke 73 is slidable in ways in the bracket 77, being adapted to move right and left a viewed in this figure.
  • the yoke surrounds the control cam .76, and has mounted in one of its legs a cam follower or roller 79.
  • the yoke is constantly urged to the left (as viewed in FIGURE 5) by a spring 80in a spring housing 81, the spring bearing against a reciprocable rod member 82 mounted on the yoke 78.
  • Rotation of the cam '76 thus permits the spring to move the yoke to the left when a recessed portion of the cam is adjacent the roller 79, and moves the yoke to the right an appreciable distance when a raised portion of the cam surface is in contact with the roller '79.
  • the jet nozzle 83 having the orifice 71 therein is mounted in a body member 84 in such a manner as to provide a supply cavity 35 immediately behind the jet orifice '71 and adapted to be in communication therewitln'lhe atomizing orifice is of one of the type heretofore described in this application, as for example, an elongated orifice which may be 0.010 inch in vertical dimension and 0.004 or 0.005 inch as in transverse dimension.
  • 'Liquid coating material is kept under high hydrostatic pressure in the supply chamber 85 at all times during operation of the equipment, preferably by a circulatingsystem wherein a pump delivers liquid coating material through a supply tube 86 and has such material returned through tube $7.
  • the return passage would be provided at some point with a restrictive orifice so related to the capacity of the supply pump that it can at all times maintain in the supply chamber 85 a desired operating pressure, as 1,000 pounds per square inch.
  • a valve rod 88 has one end 'closeto the inner end of the orifice 71 and its other (or right-hand end as viewed in FIGURE 5) mounted on the yoke '78 to be moved thereby, and provides means for interrupting the supply to the orifice, and for minimizing clogging.
  • a suitable packing arrangement is provided to prevent loss of liquid from the supply chamber 85 while permitting reciprocation of the valve rod 83, this being here shown as packing means 89 held in place by e a gland nut 90.
  • Average volume of flow from the'jet orifice 71 in a 1 given length of time, as one minute, is thus regulated by ,location by suitable adjustment means.
  • valve rod moves away from the orifice it substantially instantaneous (within a few thousands of an inch of valve rod movement) provides full connection between the high pressure liquid in the supply chamber and'the orifice, resulting in immediate goodquality atomization continuing for as long as such communication remains open.
  • Control of the effective rates of flow of the liquid coating material, the average volume atomized in a given length of time, is obtained by varying the relative duration between the period when the atomizing orifice is in open communication with the supply chamber and the period when such communication is interrupted.
  • the cam 76 is movable along the splined shaft 75, being moved to and held in a desired
  • the adjustment means is here shown as a bracket member 91 adapted to be moved by a threaded shaft 92, threaded into the e end 7312 of the main mounting bracket.
  • Rotation of this threaded member 92 changes the position of the cam along the splined shaft to provide an increase or decrease of the period of time when flow is permitted through the atomizing orifice 71 relative to the period of time during which such flow is interrupted.
  • FIGURES 6A, 6B and 6C are representative of flow relationships which may be obtained.
  • the control cam is moved far down to the lower right (as viewed in FIGURE 3) until the section AA is in line with the cam following roller 79, it will be seen in FIGURE 6A that liquid flow communication is kept open a large percentage of the time, so that the average volume of liquid coating material delivered would be about 85% of that which would be delivered if the jet were uninterrupted and operating at the same pressure.
  • FIGURE 6B shows the communication between the jet orifice '71 and the supply chamber 85 when the cam is in mid-position (as illustrated in FIGURE 4) the communication between the jet orifice '71 and the supply chamber 85 is open half of the time and closed half of the time, resulting in delivering an average volume of coating material which is half that which would be delivered by the same jet without any control means.
  • FIGURE 6C shows the operative cam section and associated graph when only a very small flow is desired, communication between the atomizing orifice and the supply chamber being only about 15% of
  • the substantially instantaneous operation of the valve rod 88 provides a substantially square wave form, as illustrated, maintaining good uniformity and quality of atomization despite the periodic interruption.
  • the movement 'of the valve rod, and the ability to use a larger orifice at low delivery rates avoidsclogging of the nozzle by paint solids.
  • this arrangement enables desired atomizing pressures (as 800 to 1000 pounds per square inch) to be maintained at all times in the supply chamber 85; permits a wide range of control of the volume of coating material delivered by use of the control arrangement heretofore described; provides for continuous recirculation of coating materials requiring it; and eliminates clogging of the atomizing orifice.
  • a spraying device 100 having a barrel 101 of insulating material.
  • the barrel 101 is secured to a metal body 103 in a suitable manner and the body is electrically grounded.
  • Extending through the body 103 and barrel 101 is an insulation covered lead line 104 connected to the hot terminal of a power pack (not shown) and by means of an electrical connection 105 to a resistor 106.
  • the resistor 106 may have a resistance of the order of 160 megohms, and is connected at its righthand end to a contact member 106a which in turn is connected to a fine wire electrode 107 having a terminal portion 108 which extends outwardly of an end cap 109 and nozzle plate 100a, both of which may be of electrically insulating material, and lies closely adjacent but radially spaced from an orifice 110 from which the paint is expelled.
  • the distance from the electrode terminal portion to the closest grounded gun part (the forward end of atomizer body 103) is about six inches. It is preferred to use a slim electrode, one of no more than about 0.1 inch in diameter and most desirably one about .01 or .02 inch in diameter.
  • the electrode is preferably pointed.
  • the orifice 110 is formed in a nozzle member 126 of highly wear-resistant material such as tungsten carbide or diamond and has a .005 inch minimum or minor diameter, and a .015 inch major diameter, the combination producing an orifice approxiately equivalent to a circular orifice having a diameter of .009 inch.
  • Paint is delivered to the atomizer from a source (not shown) through a passage 111 in the atomizer body which connects to a longitudinally extending passage 112 in the barrel which is terminated by a valve seat 1113 located at the end of the passage immediately adjacent nozzle 126 and communicating with the orifice 110.
  • the valve is controlled by the tapered end of a valve member 11 connected to an actuating rod 115 of insulating material, in turn connected to operating means not shown.
  • Paint under the high pressures previously described herein is supplied to the atomizer through passage 111 and emerges from the orifice 110 in the form of a fanshaped film 121 as shown in FIGURES 8 and 9, which at a zone of atomization 122 breaks up into a fan-shaped spray 123 of atomized particles. Leakage of paint into the area of the barrel occupied by the resistor 106 is prevented by an O-ring 132 surrounding a fitting 133 through which the electrode contact member 106a passes.
  • the fitting 133 is made of insulating material.
  • the end 103 of electrode 107 is spaced from one surface of the film fan 121 and also terminates short of the zone of atomization 122.
  • the electrode wire is positioned out of the paint stream issuing from the orifice and its terminal portion is located intermediate the orifice and the zone of atomization where the film breaks up into spray particles.
  • the exposed portion of the electrode is offset about inch from the surface of the film and the terminal portion 103 is about Ms inch rearward of the zone of atomization 122.
  • locating the electrode tip rearwardly of the zone of atomization in this embodiment provides more efiective charging of the spray particles, and thus higher deposition efiiciency than would be obtained if the electrode projected forwardly to or beyond the atomizing zone. Locating the electrode spaced from the film prevents electrical blunting of the electrode by the paint and also prevents the electrode from interfering with formation of the desired film and with the atomizing process. While one electrode is shown and is preferred for obtaining the best deposition efficiency, more than one electrode may be used.
  • the electrode 107 is maintained at high electrostatic potential by being connected in the manner described to a power pack so as to produce normally a potential on the electrode terminal portion 108 of the order of 50,000 volts.
  • the forward end of the atomizing gun 100 is adjacent the electrode 107 and is insulated from ground it acquires a potential normally substantially equal to the potential on the electrode 107 or, at least a pottential which differs drom the potential on the electrode by not more than a small percentage (normally less than 10%) of the voltage applied to the electrode.
  • the relatively short distance between the charging electrode and the grounded body makes it possible to achieve a high local potential gradient adjacent the electrode tip and hence effective charging of the atomized paint with a lower voltage applied to the electrode, and the use of a lower applied voltage in turn makes possible the use of a smaller and less expensive power pack and a lighter and more fiexible high voltage lead line, the latter being of particular importance when the atomizer is to be hand operated.
  • a further reduction in electrode potential can be achieved without serious loss in deposition efiiciency by still further reducing the distance between the charging electrode and the grounded body. Very satisfactory results have been obtained with a device of this type providing an electrode-to-ground spacing of about three inches and opera ing with an electrode potential in the order of 25,009 volts.
  • the atomizing devices can be adapted for use as a hand-held spray gun by forming the metal body 1&3 at the rear end of the gun to provide a handle.
  • the use of the resistor 1% is particularly advantageous in a handheld gun as it serves to limit the intensity of any electrical discharge which would occur upon approach of the electrode 167 to any grounded objector any portion of the operators body, and thereby reduces fire and shock hazards. Where reduction of such hazards is important, it is advisable to vmake the contact member idea and the electrode 137 as small as possible in order to reduce their electrical capacitance.
  • the nozzle member 126, the valve seat 113, and at least the forward end of the valve member 114 of insulating material. If the forward portion of the gun is made or" conducting material the foregoing hazards will not be eliminated.
  • the method of electrostatics-Hy spray-coating an article which comprises continuously supplying liquid coating material under high hydrostatic pressure of at least two hundred fifty pounds per square inch to a small orifice in a single-fluid atomizing head, said orifice having an effective opening equivalent to a circular orifice of not greater than about fifteen thousandths of an inch in dil2 ameter, projecting the coating material therefrom into the surrounding atmosphere with a very high velocity, the coating material forming a thin expanding film with gen erally straight sides defining an angle of at least 15 and having'a forward edge, the thickness of said film being less than the transverse extent thereof'throughout the length of said film, to effect atomization of thecoating material from said edge into fine spray particles, the distance of the centerof saidfilm edge from said orifice being not in excess of about three-quarters of an inch, whereby the particles are of a size providing on deposition a spray spot size of not greater than of the order of twenty thousandths of an inch in diameter, e
  • the method of electrostatically spray-coating an article which comprises supplying liquid coating material under high hydrostatic pressure to a small orifice, projecting the coating material therefrom into the surrounding atmosphere with a very high velocity as a thin expanding fan-like film with generally straight sides defining an angle of at least 15 and having an edge, said pressure being great enough that the projection of said film from said orifice to said edge is not in excess of aninch, and said'film having a thickness less than its width throughout the length thereof, to effect atomization of the coating material from the film edge into fine spray particles of a size providing on deposition a spray spot size of less than twenty thousandths of an inch in diameter, effecting relative movement between said head and the article surface transverse to the general direction of spray particle move ment while maintaining the space between the article and said head great enough to permit substantial dispersion of the spray particles and at least several inches, main raining a quiescent-zone in the atmosphere adjacent the article,
  • the method of electrostatically spray-coating an article which comprises supplying liquid coating material under high hydrostatic pressure to a small orifice and projecting the coating material therefrom into the surrounding atmosphere as a thin expanding fan-like film having an edge and substantially straight opposite sides which diverge to define an angle of at least said pressure being sufiicient that the length of said thin expanding film to said edge is no more than approximately one inch, to effect atomization of the coating material from the film edge into fine spray particles which when deposited have a spray spot size no greater than of the order of .020 inch, maintaining a quiescent zone in the atmosphere adjacent the article, the distance of the article from the orifice being sufiicient to permit substantial dispersion of the spray particles and at least several inches, providing an electrostatic charging field extending from a terminus between said orifice and the edge of said film and between the sides of the film, said field having an average potential gradient of at least five thousand volts per inch, electrostatically .to charge and carry through said quiescent atmosphere and deposit on said article while still in
  • the method of electrostatically spray-coating an article which comprises supplying liquid coating material under high hydrostatic pressure to a small orifice having an effective opening equivalent to a circular orifice of not greater than fifteen thousandths of an inch in diameter and projecting the coating material therefrom into the surrounding atmosphere with a very high velocity as a thin expanding film having an edge and generally straight diverging sides which define an angle of at least 15, said pressure being at least three hundred pounds per square inch and suificient that the length of said thin expanding film to the center of said edge is no more than approximately one inch, to atomize the coating material from the film edge into fine spray particles which when depos ited have a spray spot size no greater than of the order of .020 inch maintaining a quiescent zone in the atmosphere adjacent the article, the distance of the article from the orifice being sufiicient to permit substantial dispersion of the spray particles and at least several inches, providing an electrostatic field extending from an electrode adjacent the film to the article having a total potential difference of at least twenty-five thousand volts electrostatically
  • said pressure being sutficient that the projection of said film from said orifice to said edge is between about 1% and 10% of the distance of the article from the orifice but in no event in excess of one inch, to effect atomization of the coating material'from the film edge into fine spray particles of a size providing on deposition a spray spot size no greater than .020 inch, maintaining a quiescent zone in the atmosphere adjacent the article, the distance of the article from the orifice being sufiicient to permit substantial dispersion of the spray particles and at least several inches, providing an'electrostatic field to the article having a total potential difierence of at least twenty five thousand volts electrostatically to charge and carry through said quiescent atmosphere and deposit on said article while still'in liquid state a substantial portion of the spray particles which would not otherwise have been deposited thereon, and efi'ecting relative movement between the orifice and the article surface transverse to the general direction of spray particle movement duringparticle deposition.
  • the method of electrostatically spray-coating an article which comprises supplying liquid coating material under high hydrostatic pressure to a small orifice and projecting the coating material therefrom into the surrounding atmosphere with a very high velocity as a thin expanding film with substantially straight diverging sides which defines an angle of at least 15 and a forward edge, said pressure being sufiicient that the distance from said orifice to said edge is no more than one inch, the thickness of the film at said edge being substantially less than the extent of such edge, to atomize the coatingmaterial from the film edge into fine spray particles which upon deposition on said article provide a spray spot size no greater than of the order of .020 inch, frequently interrupting the supply of coating material to said orifice for regulating the average rate of coating material delivery therefrom, maintaining a quiescent zone in the atmosphere adjacent the article, the distance of the article from the orifice being sufiicient to permit substantial dispersion of the spray particles, providing an electrostatic field to the article having a total potential difference of at least forty thousand volts electrostatically to charge and
  • Apparatus for electrostatically spray-coating an article comprising: a single-fluid vatomizing device having therein means defining a small elongated orifice with a ratio of length to width of at least 2 and so formed that liquid supplied under high hydrostatic pressure to said orifice will be ejected therefrom as a thin expanding fanlike film having an edge and almost exactly straight sides with an included angle of at least 15; means for supplying liquid coating material to said orifice under hydrostatic pressure so high that the length of the film to the center of said film edge is no greater than about one inch and that the coating material is atomized from the film edge into fine spray particles having a size providing on deposition a spray spot size of not greater than of the order of twenty thousandths of an inch in diameter; and a high voltage power pack connected to said areasss atomizing device providing an electrostatic field having an average gradient of at least five thousand volts per inch extending between said atomizing device and the article to be coated, electrostatically to afiect deposition
  • said atomizing device includes a slender electrode connected with said high voltage power pack and having a terminal portion disposed in a position spaced from but close to one face of said film but between the sides of said film.
  • Apparatus for electrostatically spray-coating an article comprising: a single-fluid atomizing head having therein means defining a small elongated orifice with a maximum dimension not greater than about fifteen thousandths of an inch; means for supplying liquid coating material to said orifice under high hydrostatic pressure well in excess of three hundred pounds per'square inch, to effect projection of the coating material from said orifice means into the surrounding atmosphere at a rate of less than about four hundred cubic centimeters per minute but with a very high velocity, said orifice means having a configuration such that said coating material is projected as a thin expanding film having substantially straight sides with an included angle of at least 15 and a forward edge from which coating'material is atomized into fine spray particles of a size providing on deposition a spray spot size of less than about twenty thousandths of an inch; means for frequently interrupting the supply of coating material to said orifice for regulating the volume of liquid coating material atomized from said orifice in a given length of time; means for moving the
  • a single-fluid atomizing head having therein means defining a small elongated orifice having an effective opening equivalent to a circular opening not greater than about .015 of an inch in diameter and so formed that liquid supplied under high hydrosta tic pressure to the orifice will be ejected therefrom as a thin expanding film having an edge and substantially straight sides defining an angle of at least 15; means for supplying liquid coating material to said orifice under hydrostatic pressure so high that the length of the film to the center of said film edge is no greater than about one inch and that the coating material is atomized from the film edge into fine spray particles having a size providing on deposition a spray spot size of not greater than about .020 of an inch in diameter; means for moving the article through quiescent atmosphere along a path such that the distance of the article frorn said orifice when the path intersects the axis of the orifice is great enough to permit substantial dispersion of the spray particles; a thin wire electrode mounted on the atomizing head and extending

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  • Electrostatic Spraying Apparatus (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
US148793A 1961-10-25 1961-10-25 Electrostatic coating methods and apparatus Expired - Lifetime US3169883A (en)

Priority Applications (13)

Application Number Priority Date Filing Date Title
BE624075D BE624075A (de) 1961-10-25
US148793A US3169883A (en) 1961-10-25 1961-10-25 Electrostatic coating methods and apparatus
NO146042A NO118260B (de) 1961-10-25 1962-10-10
DE19621777329 DE1777329A1 (de) 1961-10-25 1962-10-18 Vorrichtung zum elektrostatischen UEberziehen von Gegenstaenden
DER33708A DE1291659B (de) 1961-10-25 1962-10-18 Vorrichtung zum elektrostatischen UEberziehen von Gegenstaenden
DER24964U DE1925142U (de) 1961-10-25 1962-10-18 Vorrichtung zum elektrostatischen ueberziehen durch zerstaeuben.
ES281775A ES281775A1 (es) 1961-10-25 1962-10-22 Método y aparato para el revestimiento mediante pulverización electrostática de un artículo
AT843462A AT249224B (de) 1961-10-25 1962-10-25 Verfahren und Einrichtung zur elektrostatischen Sprühbeschichtung eines Gegenstandes
FR913450A FR1343806A (fr) 1961-10-25 1962-10-25 Procédé et appareil d'enduisage électrostatique
CH1252562A CH410697A (fr) 1961-10-25 1962-10-25 Procédé et installation pour l'application à un objet, par voie électrostatique, d'une matière de revêtement
NL284722.A NL156619B (nl) 1961-10-25 1962-10-25 Werkwijze en inrichting voor het elektrostatisch met verstoven materiaal bedekken van een voorwerp.
DK460962AA DK133616B (da) 1961-10-25 1962-10-25 Apparat til elektrostatisk sprøjtemaling af en genstand.
DK450472A DK130734C (da) 1961-10-25 1972-09-13 Apparat til sprøjtemaling, især til elektrostatisk sprøjtemaling.

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US148793A US3169883A (en) 1961-10-25 1961-10-25 Electrostatic coating methods and apparatus

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US3169883A true US3169883A (en) 1965-02-16

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US (1) US3169883A (de)
AT (1) AT249224B (de)
BE (1) BE624075A (de)
CH (1) CH410697A (de)
DE (3) DE1291659B (de)
DK (1) DK133616B (de)
ES (1) ES281775A1 (de)
NL (1) NL156619B (de)
NO (1) NO118260B (de)

Cited By (32)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3265306A (en) * 1963-01-30 1966-08-09 Fischer & Co H G Spray gun
US3292860A (en) * 1963-10-28 1966-12-20 Ransburg Electro Coating Corp Electrostatic spray coating apparatus
US3459374A (en) * 1965-07-07 1969-08-05 Ransburg Electro Coating Corp Electrostatic coating apparatus
US3463121A (en) * 1966-09-19 1969-08-26 Fischer & Co H G Spray gun
US3463395A (en) * 1966-01-06 1969-08-26 S K V Sa Spray gun nozzle heads
US3512502A (en) * 1966-10-21 1970-05-19 Ransburg Electro Coating Corp Electrostatic coating apparatus
DE2209896A1 (de) * 1971-03-03 1972-09-07 Electrogasdynamics, Inc., Hanover, N.J. (V.St.A.) Zerstäubungsgerät
US3713873A (en) * 1970-11-18 1973-01-30 Gillette Co Electrostatic spray coating methods
US3767115A (en) * 1971-12-27 1973-10-23 Graco Inc Electrostatic spray gun apparatus
US3906122A (en) * 1973-02-02 1975-09-16 Ici Ltd Method for coating metal anodes with electroconductive paint
US3938740A (en) * 1973-10-04 1976-02-17 Atlas Copco Aktiebolag Nozzle for electrostatic spray gun
US3938739A (en) * 1973-04-19 1976-02-17 Atlas Copco Aktiebolag Nozzle for electrostatic spray gun
DE2446022A1 (de) * 1974-09-26 1976-04-01 Esb Voehringer Vorrichtung zum elektrostatischen beschichten von gegenstaenden mit fluessigem oder pulverfoermigem beschichtungsmaterial
US4066041A (en) * 1975-04-11 1978-01-03 Gema Ag Apparatebau Apparatus for electrostatically applying coating material to articles and the like
US4258655A (en) * 1976-04-21 1981-03-31 Caterpillar Tractor Co. Electrostatic spray apparatus
EP0152200A2 (de) * 1984-02-08 1985-08-21 Willett International Limited Verfahren und Vorrichtung zum Zersprühen von Flüssigkeiten
US5029553A (en) * 1981-12-11 1991-07-09 Trion, Inc. Apparatus for providing a uniform coating on a continuous horizontally moving metal strip
US5284684A (en) * 1992-03-03 1994-02-08 Alltrista Corporation Method and apparatus for coating glassware
US5289977A (en) * 1993-01-06 1994-03-01 Graco Inc. Electrostatic spray gun power supply connection
US5351715A (en) * 1992-02-25 1994-10-04 Abb Flakt, Inc. Integrally piloted, pneumatically actuated valves
US5707013A (en) * 1993-06-11 1998-01-13 Nordson Corporation Apparatus and method for dispensing electrically conductive coating material including a pneumatic/mechanical control
US20050011975A1 (en) * 2003-07-17 2005-01-20 Baltz James P. Dual purge manifold
US20070231499A1 (en) * 2004-02-10 2007-10-04 Robert Worsham Apparatus and method for electrostatic spray coating of medical devices
US20090224076A1 (en) * 2008-03-10 2009-09-10 Altenburger Gene P Circuit Board Configuration for Air-Powered Electrostatically Aided Coating Material Atomizer
WO2009114296A1 (en) 2008-03-10 2009-09-17 Illinois Tool Works Inc. Controlling temperature in air-powered electrostatically aided coating material atomizer
WO2009114322A1 (en) 2008-03-10 2009-09-17 Illinois Tool Works Inc. Sealed electrical source for air-powered electrostatic atomizing and dispensing device
WO2009114295A1 (en) 2008-03-10 2009-09-17 Illinois Tool Works Inc. Method and apparatus for retaining highly torqued fittings in molded resin or polymer housing
USD608858S1 (en) 2008-03-10 2010-01-26 Illinois Tool Works Inc. Coating material dispensing device
WO2010132154A2 (en) 2009-05-12 2010-11-18 Illinois Tool Works Inc. Seal system for gear pumps
US7918409B2 (en) 2008-04-09 2011-04-05 Illinois Tool Works Inc. Multiple charging electrode
US7926748B2 (en) 2008-03-10 2011-04-19 Illinois Tool Works Inc. Generator for air-powered electrostatically aided coating dispensing device
US8770496B2 (en) 2008-03-10 2014-07-08 Finishing Brands Holdings Inc. Circuit for displaying the relative voltage at the output electrode of an electrostatically aided coating material atomizer

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BE791343A (fr) * 1971-11-16 1973-03-01 Nordson Corp Pulverisateur electrostatique
US4079894A (en) * 1976-07-14 1978-03-21 Nordson Corporation Electrostatic spray coating gun

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US2302289A (en) * 1938-12-06 1942-11-17 Union Oil Co Electrified spray method and apparatus
US2491889A (en) * 1942-01-21 1949-12-20 Owens Corning Fiberglass Corp Production of coated glass and the like products
US2685536A (en) * 1944-09-29 1954-08-03 Ransburg Electro Coating Corp Method for electrostatically coating articles
US2710773A (en) * 1952-08-27 1955-06-14 Sedlacsik John Electrostatic spray coating apparatus

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GB679751A (en) * 1949-03-25 1952-09-24 Gen Motors Corp Improved method of and apparatus for spray coating articles
BE519260A (de) * 1952-04-18

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US2302289A (en) * 1938-12-06 1942-11-17 Union Oil Co Electrified spray method and apparatus
US2491889A (en) * 1942-01-21 1949-12-20 Owens Corning Fiberglass Corp Production of coated glass and the like products
US2685536A (en) * 1944-09-29 1954-08-03 Ransburg Electro Coating Corp Method for electrostatically coating articles
US2710773A (en) * 1952-08-27 1955-06-14 Sedlacsik John Electrostatic spray coating apparatus

Cited By (44)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3265306A (en) * 1963-01-30 1966-08-09 Fischer & Co H G Spray gun
US3292860A (en) * 1963-10-28 1966-12-20 Ransburg Electro Coating Corp Electrostatic spray coating apparatus
US3459374A (en) * 1965-07-07 1969-08-05 Ransburg Electro Coating Corp Electrostatic coating apparatus
US3463395A (en) * 1966-01-06 1969-08-26 S K V Sa Spray gun nozzle heads
US3463121A (en) * 1966-09-19 1969-08-26 Fischer & Co H G Spray gun
US3637420A (en) * 1966-09-19 1972-01-25 Graco Inc Method of electrostatically coating with highly conductive materials
US3512502A (en) * 1966-10-21 1970-05-19 Ransburg Electro Coating Corp Electrostatic coating apparatus
US3713873A (en) * 1970-11-18 1973-01-30 Gillette Co Electrostatic spray coating methods
DE2209896A1 (de) * 1971-03-03 1972-09-07 Electrogasdynamics, Inc., Hanover, N.J. (V.St.A.) Zerstäubungsgerät
US3767115A (en) * 1971-12-27 1973-10-23 Graco Inc Electrostatic spray gun apparatus
US3906122A (en) * 1973-02-02 1975-09-16 Ici Ltd Method for coating metal anodes with electroconductive paint
US3938739A (en) * 1973-04-19 1976-02-17 Atlas Copco Aktiebolag Nozzle for electrostatic spray gun
US3938740A (en) * 1973-10-04 1976-02-17 Atlas Copco Aktiebolag Nozzle for electrostatic spray gun
DE2446022A1 (de) * 1974-09-26 1976-04-01 Esb Voehringer Vorrichtung zum elektrostatischen beschichten von gegenstaenden mit fluessigem oder pulverfoermigem beschichtungsmaterial
US4066041A (en) * 1975-04-11 1978-01-03 Gema Ag Apparatebau Apparatus for electrostatically applying coating material to articles and the like
US4258655A (en) * 1976-04-21 1981-03-31 Caterpillar Tractor Co. Electrostatic spray apparatus
US5029553A (en) * 1981-12-11 1991-07-09 Trion, Inc. Apparatus for providing a uniform coating on a continuous horizontally moving metal strip
EP0152200A2 (de) * 1984-02-08 1985-08-21 Willett International Limited Verfahren und Vorrichtung zum Zersprühen von Flüssigkeiten
EP0152200A3 (de) * 1984-02-08 1986-10-15 Willett International Limited Verfahren und Vorrichtung zum Zersprühen von Flüssigkeiten
US5351715A (en) * 1992-02-25 1994-10-04 Abb Flakt, Inc. Integrally piloted, pneumatically actuated valves
US5284684A (en) * 1992-03-03 1994-02-08 Alltrista Corporation Method and apparatus for coating glassware
US5289977A (en) * 1993-01-06 1994-03-01 Graco Inc. Electrostatic spray gun power supply connection
US5707013A (en) * 1993-06-11 1998-01-13 Nordson Corporation Apparatus and method for dispensing electrically conductive coating material including a pneumatic/mechanical control
US20050011975A1 (en) * 2003-07-17 2005-01-20 Baltz James P. Dual purge manifold
US6918551B2 (en) 2003-07-17 2005-07-19 Illinois Tool Works Inc. Dual purge manifold
US20070231499A1 (en) * 2004-02-10 2007-10-04 Robert Worsham Apparatus and method for electrostatic spray coating of medical devices
US7556842B2 (en) * 2004-02-10 2009-07-07 Boston Scientific Scimed, Inc. Apparatus and method for electrostatic spray coating of medical devices
US8016213B2 (en) 2008-03-10 2011-09-13 Illinois Tool Works Inc. Controlling temperature in air-powered electrostatically aided coating material atomizer
US7926748B2 (en) 2008-03-10 2011-04-19 Illinois Tool Works Inc. Generator for air-powered electrostatically aided coating dispensing device
WO2009114322A1 (en) 2008-03-10 2009-09-17 Illinois Tool Works Inc. Sealed electrical source for air-powered electrostatic atomizing and dispensing device
WO2009114276A1 (en) 2008-03-10 2009-09-17 Illinois Tool Works Inc. Circuit board configuration for air- powered electrostatically aided spray gun
WO2009114295A1 (en) 2008-03-10 2009-09-17 Illinois Tool Works Inc. Method and apparatus for retaining highly torqued fittings in molded resin or polymer housing
USD608858S1 (en) 2008-03-10 2010-01-26 Illinois Tool Works Inc. Coating material dispensing device
US9616439B2 (en) 2008-03-10 2017-04-11 Carlisle Fluid Technologies, Inc. Circuit for displaying the relative voltage at the output electrode of an electrostatically aided coating material atomizer
US8770496B2 (en) 2008-03-10 2014-07-08 Finishing Brands Holdings Inc. Circuit for displaying the relative voltage at the output electrode of an electrostatically aided coating material atomizer
US8590817B2 (en) 2008-03-10 2013-11-26 Illinois Tool Works Inc. Sealed electrical source for air-powered electrostatic atomizing and dispensing device
WO2009114296A1 (en) 2008-03-10 2009-09-17 Illinois Tool Works Inc. Controlling temperature in air-powered electrostatically aided coating material atomizer
US7988075B2 (en) 2008-03-10 2011-08-02 Illinois Tool Works Inc. Circuit board configuration for air-powered electrostatically aided coating material atomizer
US20090224076A1 (en) * 2008-03-10 2009-09-10 Altenburger Gene P Circuit Board Configuration for Air-Powered Electrostatically Aided Coating Material Atomizer
US8496194B2 (en) 2008-03-10 2013-07-30 Finishing Brands Holdings Inc. Method and apparatus for retaining highly torqued fittings in molded resin or polymer housing
US7918409B2 (en) 2008-04-09 2011-04-05 Illinois Tool Works Inc. Multiple charging electrode
US8225968B2 (en) 2009-05-12 2012-07-24 Illinois Tool Works Inc. Seal system for gear pumps
US20100288793A1 (en) * 2009-05-12 2010-11-18 Illinois Tool Works Inc. Seal system for gear pumps
WO2010132154A2 (en) 2009-05-12 2010-11-18 Illinois Tool Works Inc. Seal system for gear pumps

Also Published As

Publication number Publication date
NL284722A (de)
AT249224B (de) 1966-09-12
BE624075A (de)
DE1777329A1 (de) 1972-04-27
DE1291659B (de) 1969-03-27
ES281775A1 (es) 1963-04-16
NL156619B (nl) 1978-05-16
CH410697A (fr) 1966-03-31
NO118260B (de) 1969-12-01
DK133616B (da) 1976-06-21
DE1925142U (de) 1965-10-07

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