Abstract: A method and apparatus for removing sprayed material from the air exhausted from a spray booth comprising an enclosure in which the material is sprayed. Air supply means are arranged to supply air to the enclosure, and outlet fans are provided for extracting air laden with the sprayed material from the enclosure. Two physically separate air outlet paths are provided for the extracted air and respective washing means for removing the sprayed material from the laden air are associated with each said path. The washing means are arranged to bring the material laden air into intimate contact with a cleaning liquid. Means are provided for controlling the volume of air flowing through each outlet path such that the volume flowing along each outlet path can be varied in dependence upon the volume of air exhausted from the spray booth. This enables the efficiency of the respective washing means to be maintained.

Abstract: A powder coating installation comprising a cabin having walls made of a non-conductive plastic material. The lower part of the cabin has a V-shaped section and terminates in a collecting channel which is connected to a suction device. The installation further comprises a cleaning device with a hollow frame, the form of which compliments the contours of the internal form of the cabin and which comprises gas outlet holes along its periphery. The frame is connected to a source of pressurized fluid, e.g., air. The cleaning device further comprises cleaning means such as sponges, cloths and the like, which may be provided on the same frame or on a separate frame. Use of a non-stick, non-conductive cabin and of the cleaning device enables the installation to be easily and quickly color converted and eliminates much of the previously wasted colored powder.

Abstract: A method of and apparatus for the electrostatic coating of poorly or non-conductive materials such as pellets seeds and powders, in which the product material is set in motion, preferably turbulent or agitating motion relative to at least one electrostatic coating material spraying device which is directed toward the moving product and has applied thereto a high potential difference whereby the coating material is given an electrostatic charge and an electrostatic charge of opposite polarity is induced on the product causing electrostatic attraction between the coating material and the product. The invention is applicable both to continous and batch production of coated material and preferably involves moving the product past the or each spraying device in a plurality of spraying passes. Charged atomised liquid and diffused powder may be sprayed onto the product either in sequence or at the same time.

Abstract: A method for electrostatically applying a thermoplastic resin coating on a threaded portion of a fastener to provide a self locking element thereon. A plurality of fasteners are moved by a spaced pair of endless belts passed a spray station where a stream of powdered resin is directed toward the threaded ends of the fasteners. The fasteners and resin are polarized to opposite polarities at the spray station whereby the powdered resin is attracted to and clings to the threaded ends of the fastener and extends completely about the circumference of said ends. Air jet nozzles located downstream of the spray station may direct streams of compressed air against certain portions of the powdered resin to remove the resin therefrom to provide uncoated lead threads and to regulate the distance that the resin extends circumferentially about the threaded ends to provide a coating extending between 180 degrees and 360 degrees about the threaded ends.

Abstract: Enameling of long, bar-shaped objects such as shaped sections for doors and/or windows made of plastic or of plastic coated metals shall be made possible in a simple manner without additional, time-consuming manual operations by means of an apparatus for electrostatically spray-enameling plastic parts in a spray booth while employing a conducting liquid which prior to the enameling process is deposited by spraying on the surfaces of the parts.To that end the invention provides at least one roller conveyor before and after the spray booth, at least one part of the conveyor rollers being driven and the conveyor rollers, which preferably are made of steel, simultaneously acting as current returns and being grounded.

Abstract: An apparatus and method is detailed for the application of non-conductive material, generally of a powder or fine fiber form from bulk storage onto a conductive filament or plurality of filaments. A series of vibrating troughs are used to store, convey, unpack and load particulate material at a controllable rate into a gas stream traversing a converging-diverging nozzle. High aerodynamic shear in the nozzle reduces the material's size. Divergent nozzle exit geometry slows the material to speeds where electrostatic forces can predominate, as the material is injected upwardly into a chamber fitted with a cascade of conical forms. Each cone is electrified about its circumference in one or more locations, with respect to a centrally located upward moving filament. Conventional electrostatic charging and deposition on the filament is augmented by the convergent geometry of the cones. Excess material falls on the outside of the cones, and eventually downward to a recovery area.

Abstract: Electrostatic powder coating apparatus having an outer filter belt from which excess powder is removed by an elongated pick-up tube which extends across the width of the belt. The ends of the filter belt, instead of being joined, are overlapped, such that the uppermost end of the belt faces the direction which is opposite to the travel direction of the belt, avoiding interference with the powder pick-up tube.

Abstract: Inside the enclosing wall (1) of the electrostatic coating plant for applying dry or wet color coatings to electrically conductive surfaces of articles (2) set up in an insulated position is located an electrostatically chargeable curtain (9), the charge polarity of which is the same as that of the spraying gun (7) used for the coating operation. The article (2) set up in an insulated position is supplied with opposite polarity, which is necessary for the electrostatic coating, by an inductor arrangement (16) arranged above the article (2), the inductor arrangement (16) applying an electrostatic field produced by means of a peak inductor (19) to an electrically conducting layer (18), which is located on the rear of a casing piece (17) made of insulating material.

Abstract: A powder spray booth for use in the electrostatic coating of articles is disclosed. The spray booth is of a basically symmetrical configuration allowing the spray coating of articles passing therethrough on a conveyor from either side thereof. At each end of the spray booth and positioned at a lower elevation than the spray region is an exhaust blower which may be effectively coupled to a powder cart located therebetween and below the spray region for the automatic recovery of the overspray. The powder carts are portable and when in a cooperative position with respect to the spray booth, include self-cleaning filters and automatic recovery and recirculation of the overspray. A plurality of powder carts may be used to form a sort of magazine to provide very fast color change capability. The spray booth itself may also be mounted on rail-like members so as to readily movable between different positions in a conveyor line or different conveyor lines according to the needs at the particular time.

Abstract: A robot painting system for electrostatically painting an automobile body that includes a paint module adapted to maintain the automobile body in a stationary position relative to at least two painting robots, each of which carries a rotary bell-type atomizing device and provides programmed movement thereof about five control axes at a speed which prevents the cone-shaped pattern of atomized paint particles from being distorted due to any gyroscopic effect developed by the atomizing device as it is moved about the control axes.

Abstract: Enameling of long, bar-shaped objects such as shaped sections for doors and/or windows made of plastic or of plastic coated metals shall be made possible in a simple manner without additional, time-consuming manual operations by means of an apparatus for electrostatically spray-enameling plastic parts in a spray booth while employing a conducting liquid which prior to the enameling process is deposited by spraying on the surfaces of the parts.To that end the invention provides at least one roller conveyor before and after the spray booth, at least one part of the conveyor rollers being driven and the conveyor rollers, which preferably are made of steel, simultaneously acting as current returns and being grounded.

Abstract: In the electrostatic application of a coating material on to a product to be coated, the product leaves a supply hopper over a tube enlargement and falls freely in a chamber in the form of a tubular curtain. The tubular curtain falls around a central, elongate, vertical corona discharge electrode so that a high voltage electrostatic charge of one sign is applied to the falling curtain of the product. Coating material is sprayed on to the product by atomizers in the chamber. A high voltage electrostatic charge of opposite sign is applied to the coating material by way of the atomizers.

Abstract: A spray-coating booth having on its side walls several air cleaners with easily interchanged and cleaned filter units that are relatively light in weight and can be carried by hand. In accordance with the design of the booth, the dimensions of the spray-coating area can be varied and the filter units can be interchanged with other types of units such as sprayers. Undesirable accumulation of powder is avoided because the air cleaners continuously precipitate powder filtered from the air. Powder transporting means within the booth, which may be inclined chutes with a fluidized bed, transport this excess powder from beneath the air cleaners at the side wall to the floor of the booth. The floor of the booth extends below the entire spray coating region and thereby also serves to collect excess spray powder which falls directly upon it. The powder is then returned for use to the spray-coating region.

Abstract: Apparatus for electrostatically depositing powder on objects which move continuously through a powder-depositing booth of modular type having a powder depositing module (B) on each side of which there is an air filter module (A and C); the powder depositing module (B) has two compartment (B1, B2) next to each other each compartment having a distinct powder store tank (11, 12) which allows two layers of powder to be applied successively to the object to be treated. Application to enamelling objects.

Abstract: A spray booth is disclosed for applying powder coating to substrates. There is a self contained recovery/filter system located beneath the floor of the booth, which recovery/filter system is removably attached to the booth so that another recovery/filter system may be conveniently substituted when changing spray powders, or to facilitate cleaning or repair of the recovery system. The recovery/filter system is so constructed that there are no restrictions in the air flow passages between the booth and the recovery/filter system, with the result that there are no confined areas wherein fires may cause explosions. Powder is collected in the hoppers located in the bottom of the recovery/filter system. The hoppers are generally funnel shaped and are open at the bottom to air transfer pumps which recycle the powder back to the spray system. Vibrators mounted upon the hoppers periodically vibrate the hopper walls to prevent powder from collecting on the walls.

Abstract: An apparatus and method of using the apparatus for electrostatically depositing powder on moving objects. The apparatus includes powder-spraying chamber, air-filtering units adjacent the entrance and exit of the chamber, and at least one re-ionization chamber disposed between an air-filtering unit and the powder-spraying chamber. Each re-ionization chamber has walls extending transversely to the direction of motion of the objects through the apparatus to direct powder towards the objects on which powder is to be deposited.

Abstract: An electrostatic powder-depositing installation for depositing powder on hollow parts of large dimensions. It includes a powder-depositing cage (1) which is open at the top and a powder-depositing unit (41) placed beneath this opening (2) so that the hollow parts vertically fit over the powder-depositing unit as they pass through the opening of the powder-depositing cage. Application is to installations for coating parts and, in particular, metal parts.

Abstract: A coating booth for the electrostatic application of powdery materials onto workpieces. The coating booth has a generally tubular configuration which when viewed in side elevation is generally oval but with a spiral curved bottom front wall which melds into a flat bottom surface extending toward an outlet at the bottom of the rear wall of the booth. On the rear of the booth there is a fixed fan module to which a removable filter module may be attached so as to interconnect the booth air outlet with the suction fan module. This construction facilitates quick color changes of the powdery material by maintaining a minimum deposit of powder on the interior of the booth and by enabling the filters to be interchanged without the necessity of first cleaning the filters or of interchanging individual filter media before restarting the booth with a new color.

Abstract: A method and apparatus are disclosed by which electrical conductor cable can be produced utilizing electrostatic coating means, which method and apparatus are highly convenient, uncomplicated and economical to carry out. An outstanding and unique feature of the cable produced in accordance herewith resides in the presence of a web portion of reduced cross-section connecting the individual conductors, by which manual severence of one from another is facilitated. Most desirably, the apparatus and method provide means for producing individual insulating coatings on each of the conductors, which means ideally utilizes an electrostatic cloud coating technique.

Abstract: A booth forming a spraying chamber for workpieces to be coated with powder particles has a substantially fully open front side, giving access to an electrostatic spray gun, and a substantially fully open rear side adjoining a housing of a detachable powder-collecting unit which is open toward the chamber while being separated therefrom by an apertured screen. Tubular filter elements in the housing of the powder-collecting unit, having air-permeable peripheral surfaces, communicate with the suction end of a blower in an overlying clean-air unit, thereby giving rise to an air stream which passes generally horizontally through the chamber from its front side to its rear side and entrains particles discharged by the spray gun. Particles bypassing the workpiece to be coated may traverse the apertured screen and cling to the surfaces of the filter elements from which they may be intermittently dislodged by an air blast directed into these elements from the clean-air unit.

Abstract: Apparatus for electrostatically coating an elongated object of indefinite length which is aligned with the straight line path of the elongated object in a continuous manufacturing and finishing process. Electrostatic applicators are mounted to direct the coating into a substantially closed chamber at a portion of the elongated object passing therethrough. To substantially eliminate the explosive hazard occasioned by the use of an organic solvent-based coating material in the presence of electrical equipment, a combustibly inert atmosphere is maintained in the chamber and in an exhaust system leading therefrom. To maintain the electrostatic field, the coating chamber and associated coating equipment must be electrically isolated from ground.

Abstract: An electrostatic painting system has a charged conductor (22) extending along the path of travel of article carriers (11) through a coating zone (15, 16). A plenum (33) with a perforate wall (25) extends along the length of the charged conductor and is connected with a blower (30). A unidirectional flow of air is directed across the charged conductor.

Abstract: This invention relates to a process for electrostatically coating a substantially axially symmetrical object with pulverized material, characterized by supporting said object maintained at a temperature below the melting point of said pulverized material in an electrostatic coating chamber having a substantially axially symmetrical shape and equipped with silent discharge plate electrodes on the inside of said chamber; feeding electrically charged pulverized material into said chamber; electrostatically coating said object with said pulverized material by the action of silent discharge from said electrodes; and removing surplus pulverized material from specific parts of said object by suction.

Abstract: An installation for electrostatic deposition of powder on objects travelling continuously, by means of a conveyor, through a treatment cage with a side entrance and exit comprises a filtering system, a system for supplying powder and compressed air and a tank for recovery of powder. The cage comprises at least two modules, namely, a first module for storing, projecting and recovering powder, which contains elements for projection of powder onto the objects to be processed, and a second module for filtering and recycling the air in which the air loaded with powder originating from the first module is filtered and recycled to the first module. The cage includes at least one air lock to prevent escape of powder laden air to the exterior of the cage.

Abstract: A spray booth includes a housing having an internal surface with an opening through which are passed objects to be coated. First and second guides are positioned at opposed ends of the housing. A suction device is movable within the housing and includes an inlet opening facing the internal surface for sucking-in spray material which has not adhered to the object being sprayed. The suction device includes end portions which are guided by the first and second guides during its movement. The inlet surface extends across substantially the entire width of the internal surface between the guide-carrying ends of the housing. A drive mechanism is operably connected to the end portions of the suction device for moving the latter within the housing.

Abstract: A system for the fixing of prints with reactive and vat dyes in the two phase printing method on textiles made of cellulose and, in particular, continuously running webs of material made of textile, knitted material, fleece, and the like, wherein the required auxiliary means for fixing is applied onto the web of material by electrostatic spraying. The system is characterized by the provision of a device for the electrostatic spraying of the auxiliary means onto the web of material which is positioned in the fixing device.

Abstract: Cable core units comprising conductors grouped together by twisting are fed through a fluidized bed to fill voids with fluidized powder by flow of the powder between the grouped conductors. While still in the bed, the units are then deflected around rollers to cause relative displacement of the conductors which causes more complete filling of the voids with powder and powder redistribution to create uniformity of powder fill. Cable cores may also be filled with the core units closed together or separated in the bed but with units closed together when a core is deflected around the rollers.

Abstract: A device for recovering powder, in particular from powder-spray housings, includes a filter unit mounted in a separate housing, which unit has at least one filter element mounted between the crude gas side and the pure gas side thereof. The pure gas side is coupled to an exhaust and a cleaning device is provided for the filter element for a continuous removal of the drawn-in powder. The filter element is moveable along a pure gas channel as an endless filter band fed around a drive roller and a tension roller. The band has opposed band portions which form the separation between the crude gas side and the pure gas side and which are subjected to a subsequent cleaning device.

Abstract: Electrostatic powder coating installation includes an enclosure through which a movable filter belt extends. A suction device draws air and excess powder towards one face of the filter belt which has a predetermined permeability so as to collect the powder on one face thereof and to allow air to flow therethrough to an exhaust plenum. A second movable belt formed of a coarse, monofilament, screen material is disposed in registry with the other face of the filter belt to prevent contact between the filter belt and the exhaust plenum. A cleaning device removes the excess powder from the one face of the filter belt; which powder, through a separator, is collected in a supply container for reapplication to the workpiece.

Abstract: This invention relates to a method of and apparatus for forming a colored shade band on an elongated area of a flexible sheet of interlayer material comprising applying a dye composition by electrostatic spraying against an elongated area of a surface of a flexible sheet of non-conductive interlayer material such as polyurethane or plasticized polyvinyl butyral. A flexible sheet to be coated is mounted on a support carriage at a loading and unloading chamber in a substantially horizontal support plane, is transferred to a coating chamber, is tilted into an oblique plane at said coating chamber where it is aligned with a platen mask, electrostatic spray means disposed to one side of said platen mask supplies an electrostatic spray of a dye composition through said platen mask to the elongated area of said flexible sheet.

Abstract: For powder filling of cables, in a fluidized powder bed, it has been proposed to pass the cable core through the bed in a substantially closed condition. There is a limit to the number of conductors a core can have for effective filling. In the present invention the cable core is opened up into a number of core units by passing through an opening member. The opening member is freely ridable on the cable core and has a hole for each unit. The opener is held against a support member and an air bearing formed between the two members. Air is also usually fed to the holes in the opener member through which the core units pass to prevent flow of powder out from the bed. The opening member can be positioned in the fluidized bed or outside immediately prior to passage of the cable core through the bed. The units are each in a substantially closed condition in the bed and the units close to a single core also in the bed.

Abstract: This invention relates to apparatus for handling a flexible sheet of interlayer material while forming a colored shade band on an elongated area thereof comprising applying a dye composition by electrostatic spraying against an elongated area of a surface of a flexible sheet of non-conductive interlayer material such as polyurethane or plasticized polyvinyl butyral. A flexible sheet to be coated is mounted on a support carriage at a loading and unloading chamber in a horizontal support plane. The carriage is transferred a finite distance to a coating chamber into alignment with carriage tilting means, which engages the carriage, preferably at its geometric center, to tilt the latter into an oblique plane at said coating chamber aligned with an obliquely disposed platen mask. Electrostatic spray means disposed to one side of said platen mask supplies an electrostatic spray of a dye composition through said platen mask to the elongated area of said flexible sheet.

Abstract: This invention relates to a continuous process for electrostatically coating a substantially axially symmetrical object with pulverized material, characterized by conveying said object by means of a conveyor-type holding device into an electrostatic coating chamber equipped with silent discharge plate electrodes on both sides of the chamber walls: feeding electrically charged pulverized material into said chamber: electrostatically coating said object with said pulverized material by the action of silent discharge from said electrodes: and removing surplus pulverized material from the specific parts of said object by suction.

Abstract: Powder filling of a cable, or cable unit, is improved by passing the cable, or unit through a fluidized bed of powder, and vibrating or shaking the cable, or unit in a direction substantially normal to the direction of movement of the cable, or unit, through the bed.

Abstract: Apparatus for generating and substantially uniformly electrostatically dispersing very finely divided lubricating particles onto the surface of an electrically conductive substrate. In this apparatus, lubricant material is atomized into a spray of particles of various sizes. Larger particles are removed from the spray by gravity, airflow and other forces. The remaining cloud of extremely small particles is delivered to a housing. The housing is preferably constructed from electrically non-conductive material and is structured to maintain the cloud of small particles in a substantially quiescent suspension between electrodes spaced from the conductive substrate within the housing. An ionization discharge is maintained by a voltage differential between the electrodes and the substrate to electrically charge the small particles in the cloud for deposition substantially entirely by electrostatic forces.

Abstract: A protected conveyor for a spray chamber or spray booth is provided with a pressurized housing and an air curtain means which substantially isolates the conveyor from the deleterious fluids within the spray booth and substantially isolates the articles from droppings from the conveyor. More specifically, a blower supplies air under pressure to a plenum connected to a nozzle means which discharges a thin curtain of air transversely across a slot in the housing wall and transversely across depending conveyor hangers extending downwardly through the slot. The blower also supplies air under pressure to the housing to provide air discharge out of the housing slot. The transverse air discharge combines with and redirects the air discharge through the slot as common continued air movement transversely away from the conveyed articles and toward an external air exhaust from the booth. The housing, conveyor and air curtain means are formed in an inexpensive manner.

Abstract: The invention relates to an improvement in an electrostatic coating apparatus comprising a booth, air flow means, conveyor means and a powder spray gun, wherein the improvement comprises an endless conveyor belt and gaseous projection means for redirecting particles of coating material falling toward the floor to the articles to be coated and electrostatic means for recharging the particles.

Abstract: Apparatus generates and substantially uniformly electrostatically deposits very finely divided lubricating particles onto the surface of an electrically conducting substrate. A lubricant material is sheared into droplets of various sizes. The larger particles are filtered out of a flow of particles by gravity, baffles, and other forces leaving only a cloud of extremely small particles to be deposited. Deposition occurs within a housing that includes a plurality of sections arranged longitudinally on at least one side of the substrate and includes electrode means transversely positioned in each such section. The cloud of particles is uniformly provided to each of a plurality of longitudinal sections of the substrate and permitted to drift or migrate relatively slowly between the electrodes and the substrate. The particles in the cloud are electrostatically charged by high voltage applied to the electrodes and deposited on the surface of the substrate as a uniform dispersion of spaced particles of lubricant.

Abstract: An electrostatic powder coating installation is disclosed, incorporating a spray booth in which there are arranged electrostatically charged powder spraying means whereby the powder spray means may apply a coating of said powder to an article. One portion of the internal walls of the spray booth is provided with a filter which is movable through the booth to a cleaning position outside the booth. The movable filter is arranged within the booth so that one face thereof is exposed to the interior of the booth and the opposite face thereof confronts the intake side of a suction device which is effective through the filter to maintain a slightly negative pressure within the booth. The overspray of powder directed at the article will therefore be attracted to and deposited on the exposed face of the movable filter.

Abstract: A closed paint spray booth and method of spray painting an article therein which air inlet means is provided around the upper perimeter of the booth. Air exhaust means along lower portions of upstanding walls for the booth withdraws paint laden air from the booth. Inlet air is directed inwardly of the spray booth in position to be drawn downwardly and around the object being painted to define an air curtain around the object which is then drawn outwardly away from said object to the air exhaust means.

Abstract: A metal wick to be used for the absorption of molten solder is deoxidized and flux coated by a process that does not involve the application of heat to the wick or the flux. In one embodiment the wick is cleaned by heating in a reducing atmosphere and is then immersed in a coating bath containing a solution of a rosin flux in an organic solvent. On leaving the bath the welted wick enters a low-pressure chamber in which the solvent rapidly evaporates at room temperature. In another embodiment the deoxidized wick is coated with comminuted solid resin by electro-static means.

Abstract: A cabin for an electrostatic powder coating installation comprising a filter communicating with an internal compartment or space of the cabin, the side of the filter facing away from such internal compartment being exposed to the action of a negative pressure. A cleaning device is operatively associated with the filter. The cleaning device and the filter are relatively movable with respect to one another. The filter is constructed as a rotatable filter drum arranged in a chamber bounding and connected with the internal compartment of the cabin. There also is provided a stationary suction nozzle spanning the filter drum along a generatrix or surface line, and the suction nozzle is connected via a separator with a suction blower.

Abstract: An apparatus for collecting powder exhausted from an electrostatic fluidized bed coater, in which exhaust air passes from the cloud chamber of the coater into an inner exhaust chamber and then passes through a porous plate to an outer exhaust chamber, the powder carried by the exhaust air being stopped by the porous plate and thereafter collected from the inner chamber.

Abstract: A ventilated enclosure, for example a paint-spraying booth, is divided into two or more zones by one or more isolating curtains of rapidly-flowing air. One longitudinal curtain is used on each side of the object to be treated in the enclosure, to provide a central longitudinal zone for the surface treatment process and two side zones for the workmen. The two curtains converge downwardly toward each other so that the ventilating air flowing downwardly between the curtains exits from the central zone largely by way of the space between said objects. Transverse curtains and/or additional longitudinal curtains may also be used with special advantages, particularly when the speeds and positions of the curtains are specially selected.

Abstract: A method for flocking a wire garment hanger in which electrostatically-charged fibrous flock particles are applied to an adhesive film on a portion of the hanger and the hanger is immediately heated to set the adhesive while the fibers remain radially oriented on the wire. The invention also contemplates blowing air sequentially on various portions of the surface of a bed of flock to cause the fibers to become suspended in air above the bed, through which suspension the hangers are passed.

Abstract: A build control is disclosed, for controlling the thickness of a coating on different sides of an elongated member such as a wire. The build control is a tube which is positioned around the wire as the wire passes through a fluidized powder. The end of the tube which is in the fluidized powder is notched so that the build of powder on each of the sides of the elongated member is more or less than would otherwise result.

Abstract: A coating system for efficient electrical precipitation of powder to articles. Articles are conveyed through a coating chamber where they are coated with a powder. Electrogasdynamic guns direct a cloud of charged particles into the coating chamber. Dilution air moves the cloud through the chamber with the articles. As the cloud moves with the articles, the charged particles precipitate to the articles. An exhaust section draws off the dilution air as the coated articles leave the chamber. Electrically conductive articles may be grounded through the conveyor system to provide a discharge path from the charged particles. For nonconducting or hard to ground articles, a precharge section places on the articles an initial charge of opposite polarity from the charged particles. A powder feed using a cylinder and piston arrangement to contain fluidized powder supplies a uniform powder suspension to the guns.

Abstract: A face-silent discharge electrode which includes plural parallel electrode bars separated from each other at a distance and arranged in a face is disposed to confront a substrate. A powder coating material is supplied in the space between said electrode and said substrate. An AC voltage is impressed on the electrode bars adjacent each other to generate a silent electric discharge over the entire surface of said face-silent discharge electrode. Concurrently, a DC voltage is impressed between the electrode bars and the substrate so that the powder coating material may adhere to a surface of the substrate to form a layer of uniform thickness.

Abstract: Apparatus and method for electrostatically depositing a layer of particulate material on a substrate surface from a gaseous suspension of particulate, thermoplastic material. Classifying means removes oversized particles from a supply of particulate, thermoplastic material and feeds properly-sized particulate material to a metering feed device. A pressure responsive sensing means is associated with the metering feed device, and energizes a control circuit associated with the classifying means to direct properly-sized particulate material from the classifying means into the metering feed device to maintain a substantially constant, predetermined amount of properly-sized particulate material in the metering feed device.