US3292045A

US3292045A - Electrostatic powder sprayer

Info

Publication number: US3292045A
Application number: US362106A
Authority: US
Inventors: Warren G Buhler
Original assignee: Oxy Dry Sprayer Corp
Current assignee: Oxy Dry Sprayer Corp
Priority date: 1964-04-23
Filing date: 1964-04-23
Publication date: 1966-12-13
Anticipated expiration: 1983-12-13
Also published as: AT255900B

Description

Dec. 13, 1966 w. G. BUHLER 3,292,045

ELECTROSTATIC POWDER SPRAYER Filed April 23, 1964 6 Sheets-Sheet l j MQ ,M Z7 "WMLLW Dec. 13, 1966 w. G. BUHLER 3,292,045

ELEoTRosTATIc POWDER SPRAYER Filed April 2:5, 1964 e sheets-sheet 2 INVENTOR. A44/Gef 6. Ja//Af Dec. 13, 1966 w. G. BUHLER 3,292,045

lELEGTROSTTIG POWDER SPRAYER Filed April 23, 1964 6 Sheets-Sheet 5 BY W7, @Md/xxx@ Dec- 13, 1966 w. G. BUHLER ELECTROSTATIC POWDER SPRAYBR 6 Sheets-Sheet 4 Filed April 25, 1964 lINVENTOR.

/f/fefE/V @ulb/1.51.

lLllllll Il W. G. BUHLER ELECTROSTATIC POWDER SPRAYER Dec. 13, 1966 v 6 Sheets-Sheet 5 Filed April 23, 1964 oovowwowsrol Q33? o VAYO . INVENTOR, fraz/P51 6. Ms/5? Dec; 13, 1966 w. G. BUHLER 3,292,045

ELECTROSTATIC POWDER SPRAYER Filed April 23, 1964 6 sheets-smet 6 United States Patent ce 3,292,945 Patented Dec. 13, 1966 3,292,045 ELECTROSTATIC POWDER SPRAYER Warren G. Buhler, Westfield, NJ., assignor to OXY-Dry Sprayer Corporation, New York, N.Y., a body corporate of New York Filed Apr. 23, 1964, Ser. No. 362,106 3 Claims. (Cl. 317-3) This invention relates to electrostatic powder sprayers, and more particularly to powder sprayers capable of laying down a substantially uniform layer of ne powder material.

The prior electrostatic powder sprayers have usually included 1a :powder box, la metering mechanism for dispensing powder material from the powder box at a substantially uniform rate, and apparatus for providing an electrostaic field to free powder particles from the metering mechanism 4and to disperse the powder particles. Typically, the electrostatic iield would be created by a single gas filled discharge tube secured in a fixed position relative to the metering mechan-ism. Substantial success has been -achieved with these prior units when designed to dispense a particular type of powder material with Ia limited range -of dispensingrates.

An object -of this invention is to provide an electrostatic powder sprayer capable of dispensing a wide variety of powder materials without any signilicant limitation upon the available dispensing rates.

Another object yof the invention is to provide a powder sprayer which is adjustable so as to vary they field pattern and strength of the electrostatic eld used to free the powder particles from the metering mechanism and to disperse the powder particles.

Still yanother `object is to provide an electrostatic powder sprayer which can be adjusted to provide symmetrical or non-symmetrical electrostatic field so as to control the downward direction `of falling powder particles.

Another object is to provide an electrostatic powder sprayer wherein the discharge tubes utilized to create the electrostatic field are detachably secured and easily replaced.

The Amanner in which the 'foregoing and other objects are achieved is set forth more fully in the following specication which describes a few illustrative embodiments within the scope of this invention. The drawings form a part -of this specification wherein:

FIG. 1 is a perspective view, with portions broken away, illustrating one end of the powder sprayer;

FIG. 2 is a perspective view illustrating the other end of the powder sprayer with the journal structure partially disassembled;

FIG. 3 is a plan view of the powder sprayer and associated driving mechanism;

FIG. 4 is a side view of the powder sprayer;

FIG. 5 is an end view -of the powder sprayer taken along line 5 5 as indicated in FIG. 4;

FIG. 6 is a cross sectional view of the powder sprayer taken along line 6 6 `as indicated in FIG. 4:

FIG; 7 is :a longitudinal cross sectional view of the powder sprayer illustrating the journal structure and taken along line 7 7 as indicated in FIG. 3;

FIG. 8 is an enlarged partial cross sectional view of the structure shown in FIG. 6 illustrating the details of the wiping blade assembly;

FIG. 9 is an illustration of the roller surface in accordance with one embodiment of the invention as seen from line 9 9 in FIG. 8;

FIG. 10 is an illustration -of an Ialternative surface structure for the roller as seen along line 9 9 in FIG. 8;

FIG. 11 is a cross sectional view illustrating the socket structure for retaining one end of a discharge tube; and

FIGS. 12 and 13 are cross sectional views of one of the end brackets taken along line 12-12 in FIG. 4 and illustrating the adjustable discharge tube support structure.

GENERAL DE'scRrPrroN The powder sprayer in accordance with this invention includes la dispensing roller and a pair of wiping blades which tangentially engage the dispensing roller on opposite sides. As the r-oller rotates, powder is dispensed at a substantially uniform rate from a powder box llocated above the dispensing roller. A separate electrostatic discharge tube is positionable beneath each of the wiping blades. Each of these discharge tubes is detachably secured bet-Ween a spring biased socket at one end and :a rigid socket at the other end. A discharge tube is inserted by first forcing one end into the spring biased socket, thereby compressing a spring within the socket, and by thereafter releasing the discharge tube so that the `other end is retained in the rigid socket by means of spring pressure. The discharge tube is easily removed by moving the tube longitudinally to `again compress the spring, and by then removing the discharge tube from the The end portions Iof the receptacle forming the powder box are constructed to provide arcuate surfaces which are eccentric with respect to the cylindrical surface of the dispensing roller. A pair of arcuate support brackets are attached to slidably engage these arcuate surfaces land are constructed to provide pivotable support for the sockets which engage the ends of the discharge tubes. Thus, the discharge ltubes can be placed in virtually any desired position parallel to the dispensing roller because of the double adjustments achieved by means of the pivotable and slidable support structure. By varying the position of the discharge tubes, the eletrostatic field pattern and the strength of the electrostatic field can be vari-ed as desired. As 1a result, the electrostatic powder sprayer can be :adjusted for a wide variety of powder materials and -operating conditions.

POWDER BOX, WIPER BLADES AND AIR CURTAIN First, referring to FIGS. 1-13, an ladvantageous embodiment of the invention is illustrated wherein the powder sprayer includes a powder box 1, defined by a pair of spaced apart side panels 2 and 3,

end brackets

4 and 5 and a dispensing roller 11. The side panels are secured between the end brackets by means of two pairs of support blocks 9 and 10, these support blocks being formed as an integral portion of the end brackets. The side panels :are secured to the support blocks by means of suitable screws as illustrated. A spacer member 12 is secured intermediate the ends of `the side panels and is flush with the upper edge thereof. A lid 6 is secured to the upper edge of side panel 2 by means of a hinge 9 and i-s dimensioned t-o cover the top of the powder box and wrap over the upper edge of side panel 3 when in the closed position. Dispensing roller 11 is journaled in the end brackets .and is disposed between the lower edges of side panels 2 and 3.

The side panels, best seen in FIGS. l, 6 and 8, are preferably integral extruded aluminum panels. Side panel 3 includes a vertical outer portion 14, a sloping portion 15 and a lower horizontal portion 16, which portions define a plenum chamber 17 having a generally triangular cross section and extending through the side panel from end to end. The sloping surface 15 lies in a plane tangential to dispensing roller 11 and meets vertical portion 13 somewhat below the upper edge of the side panel. Surface 15 extends beyond the horizontal portion 16 and forms one surface of a lower extended portion 18. The other flat surface of extended portion 18 is a blade retaining surface 19 which lies in a plane which meets the plane of surface 15 at the point of tangency with the roller, or somewhat below the point of tangency. The right dihedral angle between these planes is approximately 20 degrees. The lower edge of extended portion 13 is rounded as shown.

A longitudinal V-shaped groove 25, best seen in FIG. 8, is machined into the lower surface of horizontal portion 16. This groove forms an outer vertical groove surface 26 and inwardly sloping groove surface 27. Preferably, the groove is located directly below the outer portion of plenum chamber 17. A plurality of holes 28 are drilled through bottom portion 16 extending between the apex of groove 25 and plenum chamber 17.

When the side panel is secured in position, end bracket 4 seals off one end of plenum chamber 17, and end bracket seals ofl the other end. A hose connecting nipple 29 is threaded into a threaded bore 30 passing through end bracket 4 so as to communicate with plenum chamber 17. A suitable air pump can be coupled to the plenum chamber Via an air hose (not shown) to create a pneumatic pressure within the chamber. As a result, a plurality of air jets are formed via holes 28. Because of groove 25, these jets tend to fan out elliptically and thus provide a relatively uniform air curtain extending between adjacent holes throughout the entire length of the side panel. Due to sloping groove surface 27, a portion of each of these jets is directed inwardly to prevent accumulation of powder on retaining member 20, adjusting screws 22 and wiping blade 23 located beneath the side panel.

Side panel 2 is identical to side panel 3 and includes components 33-49 corresponding, respectively, to components 13-29 of side panel 3. As shown in FIG. 6, the bracket 4 seals off one end of Aplenum chamber 17, and end bracket 5 seals off the other end. Preferably, a sealing gasket is cemented in position between the end brackets and the side panels. A hose connecting nipple 29 is threaded into a threaded bore 30 passing through end bracket 4 so as to communicate with plenum chamber 17. A suitable air pump can be coupled to the plenuml chamber via an air hose (not shown) to create a pneumatic pressure within the chamber. As a result, a plurality of air jets are formed via holes 28. Because of groove 25, these jets tend to fan out elliptically and thus provide a relatively uniform air curtain extending between adjacent holes throughout the entire length of the side panel. Due to sloping groove surface 27, a portion of each of these jets is directed inwardly to prevent accumulation of powder on retaining member 20, adjusting screws 22 and wiping blade 23 located beneath the side panel.

Side panel 2 is identical to side panel 3 and includes components 33-49 corresponding, respectively, to components 13-29 of side panel 3. As shown in FIG. 6, v

the powder material to be dispensed is placed in the powder box between sloping surfaces 15 and 35 and above dispensing roller 11. Thus, the sloping surfaces serve to funnel the powder downwardly toward the dispensing roller. It should be noted that the plenum chambers are therefore located in an area which would otherwise be wasted space. Plenum chambers 17 and 37 are suiciently large so that the air pressure therein is substantially uniform over the entire length of the side panels.

Wiping blades 23 and 43 are each constructed from a thin, flexible strip of blue spring steel and are preferably coated with a fluorocarbon material. These blades are approximately one inch wide and have a length equal to the length of side panels 2 and 3. Holes are drilled through the blade near the upper edge and are spaced on two inch centers.

Semi-rigid retaining member 20, best seen in FIG. 8, is preferably an extruded aluminum strip equal in length to wiping blade 23 and side panel 3. Longitudinally spaced holes are drilled through retaining member 20 corresponding in position to the holes in blade 23, and

corresponding tapped holes are drilled into extended portion 18 of side panel 3, these holes being normal to blade retaining surface 19. Wiping blade 23 is positioned between extended portion 18 of the side panel and retaining member 20, and this assembly is secured by means of suitable round head adjusting screws 22. Preferably, the holes in the wiping blade, retaining member and extended portion of the side panel are accurately aligned so that the wiping blade can easily be replaced.

Retaining member 20 includes a flat blade engaging surface which curves into an inwardly extending rib 21 at the lower edge thereof. The distance between screw 22 and rib 21 must be greater than the distance between screw 22 and the lower edge of extended portion 18. The distance between screw 22 and the upper edge 24 of the retaining member is preferably somewhat greater than the distance along surface 19 between screw 22 and the lower surface of bottom portion 16. Thus, when screw 22 is tightened, moving retaining member 20 toward retaining surface 19, the upper edge 24 strikes the lower surface of bottom portion 16. Thereafter, when screw 22 is further tightened, retaining member 24 pivots about edge 24 and applies pressure along the longitudinal center line of blade 23 via rib 21. As a result, the blade is bent inwardly by rib 21 along the center line of the wiping blade which is located between extended portion 18 and line of tangency on roller 11. Thus, the wiping blade is laterally deformed and takes on an S-shaped bend as shown in FIG. 8. In this manner, the exible blade becomes rigid and substantially straight in the longitudinal direction. Each of the screws 22 are separately adjustable, and hence, the pressure applied by the wiping blade against dispensing roller 11 can be adjusted as desired at selected points along the blade. This permits adjustments to compensate for uneven wear or for tolerances in the dispensing roller surface or the side panel. Also, it is possible to adjust the blade so that greater pressure is exerted against the dispensing roller in selected areas to thereby obtain a non-uniform dispensing rate when desired.

END BRACKETS AND DISCHARGE TUBE MOUNTING

STRUCTURE End brackets

4 and 5 are identical to one another and are secured abutting the ends -of side panels 2 and 3 by l.means of support blocks 9 and `10 respectively which form inte-gral portions of the end brackets. The end brackets thus serve as closure members for the ends of the powder box and the en-ds of the plenum chambers within the side panels. Also, the end brackets support bearings .for the journals `for dispensing roller 11, arcuate surfaces for cooperating with the discharge tube supporting structure, and bracket portions 4for securing the powder sprayer to associated apparat-us or a suitable support frame structure.

End bracket 4 is an integral structure including an end closure member y60, a substantial circular boss 61 extending horizontally away Afrom the -surface of closure member, and a support leg `62 extending horizontally from the flat sunface of the boss. The diameter of circular boss 61 is approximately equal to the distance between the outer surfaces of side walls 2 and 3. Boss 61 is positioned to acco'mrnodate an off-center journal housing 63 for dischange roller 11, the discharge roller being located -as Ishown Iin FIG. 12. The lower portion of closure member 60, i.e., the portion lying below the horizontal center line of boss 61, is curved and conforms to the circular configuration `of the boss. Support blocks 9 are secured to the edges lof closure member 60 and extend in the direction of the side panels. Support blocks 9 are spaced apart so that they will lie Ion the outer surfaces `of the side panels when the end bracket is secured in position. The upper edges `of closure member 60 and boss 61 are flush with the upper edges -of si-de panels 2 and 3.

Support leg `62. can have any desired coniiguration and includes a pair of slots 64 and 65 therein extending through the support leg from top to bottom. A-s shown in FIG. 7, support leg `62 is positioned slightly below the upper surface of boss 61 and is strengthened by means of `a tapered rib 66 extending from boss 61 along the upper surface olf the support leg. The support leg can be either horizontal as shown, or can be vertical to facilitate side mounting.

End support bracket 5 is an integral structure identical to end support bracket 4 and includes an end closure member 70, a substantially circular boss 71, a pair of spaced apart support blocks 10, and a support leg 72 with an associated strengthening ri-b 76 and

slots

74 and 75. Thus, when ,the end brackets are secured in the positions as shown in FIGS. 1 and 2,A the brackets close the ends of the powder lbox and lalso close the ends of the plenum chambers within the si-de panels. Preferably a sealing gasket is cemented in position between the end brackets and the ends of the side panels. As previously mentioned, a pair of bores 30 and 50 are provided extending th-rough end bracket 4 and are each positioned to communicate with a different one of the plenum chambers 17 and 37 respectively. The threa-ded bores are adapted to accommodate threaded hose connecting nipples 29 and 39 respectively. End bracket 5 likewise includes a pair of threaded bores so that this end bracket will be identical to end bracket 4. The threaded bores in end bracket 5, howeve-r, are lnot used and are therefore sealed -by means of suitable threaded plugs 77 and 78. The 4assembled powder sprayer can be positioned as desired by mea-ns of suitable bracket members (not sh-own) bolted to support

legs

62 and 72 or by bolting the support legs directly to a sui-table supporting structure.

Discharge tubes

80 and 81 are similarly constructed a-nd each include a cylindrical glass tube which is evacuated and then lled with an inert rgas .such as argon. The glass tubes are slightly l-onger than the side panels and are internally coated with a suitable phosphorous material. The discharge tubes include a cathode at one end only. As shown in FIG. 1l, the cathode end of the discharge tube includes a cup shaped cathode member S2 connected to a conductive metallic end cap 83 by means of a suitable support condu-ctor 84.

It is `desirable that the .discharge tubes be positioned generally parallel to dispensing roller 11 and that they be adjustable in position with respect to the roller. Also, it is desirable tha-t the tubes be detachably 'secured so that they can easily be replaced.

The -dischange tube support structure yfor tube 81 includes a support arm 90 having an arcuate inner surface with the same radius of curvature as the arcuate surface 91 at the periphery of boss 61. Thus, the inner surface of support arm 90 is adapted to engage arcuate surface 91 as show-n in FIG. 1, and is adjustatble with respect to the boss. Support arm 90 includes an elongated locking slot 92 including an elongated annular shoulder 93 (best seen in FIGS. l2 and 13) which is concentric with the arcuate surface `of boss 61. A tapped hole is bored into boss 61 along the horizontal center line and is dimensioned to accommodate a socket type cap screw 94 which passes through slot 92. Thus, when cap .screw 94 is loosely placed in position, -support arm 90 can slide from an upper position as shown in FIG. l2 to a lower position shown in FIG. 13. It should be noted that arcuate surface 91 is eccentric with respect to the dispensing roller surface due to the |off-center locati-on of the journal housing with respect to boss 61. Support aum 90 can be rigidly secure at any position by tightening cap screw 94 so that the head of the screw engages shoulder 93 of the locking slot.

The lower porti-on of support `arm 90 (as viewed in FIG. 1) is offset and is constructed to provide a bifurcated end portion 95 dimensioned -to accommodate a tab 96 extending from a spring lbiased 4tube socket 97. As .shown in FIG. 11, a pair of axially aligned threaded apertures pas-s through the leg portions of bifurcated end 95 and a smaller diameter, axially aligned, aperture passes through tab 96. A pair of socket type, headless, set

screws

98 and 99 are threaded into the leg portions of bifurcated end so that the dog point ends of the .set screws reside within the aperture passing through tab 96. In this manner, socket 97 is pivotably secured to support arm 90 (as illustrated in FIG. 13) and can be rigidly maintained in any desired pivoted position by appropriate adjustment of set .screws 98 and 99.

A support arm `100, which is a mirror image of support arm 90, is adapted to engage the arcuate surface 101 located at the periphery of boss 71 of end bracket 5. Su' port arm is secured to end bracket 5 by means of a cap screw 104 which passes through an elongated locking slot 102 and engages .shoulder 103 within the slot. A tab 106 extending 'from a cup shaped tube .socket 10.7 is pivotably secured to support .arm 100 by means of an olfset bifurcated end portion 105. Tube socket 107 is preferably constructed :from a material having a high electrical resistance and is dimensioned internally to accommodate the end of electrostatic tube 81.

Spring biased socket 97 includes a generally cylindrical outer housing 110 which is partially closed at one end. An insulated conductor 111 passes through the partially closed end of housing 110 and through the center of a retaining washer 112. The free end of the conductor is embedded in a globule or bead of solder 113 to provide a relatively large conductive surface and to prevent conductor 111 from pulling out of the washer. A spring 114 is disposed between retaining washer 112 and the partially closed end portion -of housing 110 to urge the retaining washer away from the partially closed end of the housing. As previously mentioned, tab 96, which extends radially from housing 110, is pivotably secured bythe bifurcated end portion of support arm 901. Housing 110 is preferably an integral structure constructed from a material having a high electrical resistance.

Conductor 111 after emerging from the end of socket 97, is connected to one end of a high voltage secondary winding 115 of a transformer 116, the other end of the secondary winding being connected to a suitable ground, which may be the side panels of the powder sprayer or a ground surface located at some point below the sprayer. Primary winding 117 of transformer 116 is connected to a suitable 60 cycle alternating current source. Transformer 116 is preferably constructed to provide approximately 10,000 volts to electrode S2 via conductor 111.

Discharge tube 81 is installed by inserting the electrode end into spring biased socket 97 thereby compressing spring 114. The other end of the discharge tube is then inserted into socket 107, and when released, is retained in socket 107 by virtue of the force extended by spring 114. Thereafter, discharge tube 81 can easily be adj-usted to any desired position parallel to dispensing roller 11 by means of the pivotable connection between the sockets and support

arms

90 and 100, or by adjusting the position of the support arms relative to end

brackets

4 and 5.

The adjustable supportl structure for discharge tube 80 is essentially the same as the supporting structure for discharge tube 81, except that it is attached to position tube `80 on the opposite side of dispensing roller 11. The components comprising the adjustable supporting structure for discharge tube 80 are designated with reference numerals 1Z0-144 corresponding respectively to reference numerals 90-114. Conductor 141 emerging from socket 127 is also connected to the ungrounded end of secondary winding 115 (FIG. 11).

ROLLER ASSEMBLY Roller 11 can be a solid steel roller with longitudinal extending shafts, as shown in the drawings, or can include a hollow cylindrical roller with suitable roller gudgeons secured to the ends to form the longitudinal extending shaft portions. The length of the roller portion is slightly less than the distance between

end brackets

4 and 5 as determined by the length of the side panels.

Journal shaft 150, extending from one end of roller 11, passes through a journal opening 151 in end bracket 5 forming part of journal housing 73, and through a flanged bearing 152 constructed from a suitable bearing material, preferably a fluoro-carbon material. Journal opening 151 is dimensioned to accommodate flanged bearing 152 and includes an annular recess dimensioned to seat the flange of the bearing. As shown in FIG. 2, flanged bearing 152 is slid into position from outside end bracket 5 and is thereafter secured to the end bracket by means of set .screws 153 passing through the ange of the bearing. An annular recess is also provided on the inner side of end bracket 5 surrounding journal opening 1'51, to accommodate a felt washer 154 which provides a jou-rnal seal and prevents powder from entering the bearing structure. A collar 155 is slid over the end of shaft 150 and is rigidly secured to the shaft by means of a set screw 156. This collar is positioned adjacent bearing 152 and prevents longitudinal movement of the roller with respect to the end bracket. A sprocket gear 157 is secured near the end of shaft 150 by means of a suitable set screw passing through the hub of the gear. As shown in FIG. 3, a chain 158 couples sprocket gear 157 to an associated lsprocket gear mounted on the shaft of an electric motor 159. Motor 159 is preferably of a va-riable speed drive type capable of rotating roller 11 at speeds ranging from small fractions of one `r.p.m. to Iifty r.p.rn.

Journal 63 in end bracket 4 is similar to journal 73 previously described and incudes a flanged bearing 162 secured in a journal opening 161 by mean-s of set screws 163 so that the bearing surrounds shaft 160 extending longitudinally from the end of roller 11. A felt sealing washer 164 is provided surrounding the shaft on the inner side of end bracket 4, and a collar 165 is secured to shaft 160 adjacent bearing 162 by means of set screws 166.

The cylindrical surface 170 of roller 11 is advantageously coated with a liuoro-carbo-n material and thereafter further processed to provide a powder receptive surface. The process surface of the roller is illustrated in a. magnified view of the roller surface shown in FIG. 9 and `includes an almost infinite number of powder carrying cavities. As illustrated in FIG. 8, the powder material in powder box 1 is fed by gravity into the area between roller 11 and wiping blade 23. As the roller rotates, a thin layer of powder wedges past the wiping blade. The thickness of the powder layer, and hence, the quantity of powder dispensed, depends on the adjustment of screws 22, which in turn determines the blade pressure against the roller. The minimum rate at which powder can be dispensed is determined by the capacity of the powder carrying cavities and the minimum rotation speed of the dispensing roller. The dispensing rate can be increased by either increasing the rotation speed of the roller or by decreasing the blade pressure against the surface of the dispensing roller.

An alternative surface structure for the dispensing roller is illustrated in FIG. l0 where the cylindrical surface is engraved to present a uniform waffle-like pattern. This structure increases the capacity of the powder carrying cavities which is desirable where high dispensing rates are required or large powder particles are being di-spensed. Preferably, the engraved dispensing roller is coated with a fluorocarbon material. With the dispensing roller surface shown in FIG. 10, the dispensing rate can also be varied by adjusting the speed of rotation for the dispensing roller and the wiping blade pressure.

Although it has been mentioned that the dispensing rate for a given roller surface can be adjusted by varying the 4roller speed and blade pressure, there is a practical limit to these adjustments since eventually the powder will begin to sift, that is, the powder will begin to come through in uneven chunksresulting in an uneven and relatively uncontrolled powder distribution. The maximum dispensing rate for a particular roller varies in accordance with the type of powder being dispensed. When a particular roller does not achieve the desired dispensing rate, the roller is replaced with another roller having larger powder carrying cavities.

It is significant that the roller `and the wiping blades are coated with a iluorocarbon material and that the roller bearings are likewise constructed from a iluorocarbon material. The iluorocarbon material used for coating the roller and wiping blades is preferably the polymer of triuorochloroethylene such as marketed under the brand name Kel-F and characterized by the formula (CF2-CFCl)x. First, these -materials exhibit a high chemical resistance so that other material, such as the powder being dispensed, cannot readily adhere to the roller and wiping blade surfaces. Second, tluorocarbon materials have substantially a zero moisture absorption characteristic and therefore reduce the possibility of moisture contamination of the powder being dispensed. Third, these materials have a relatively high compression strength and hence, excellent wear characteristics. This is significant in the bearings, and also with respect to the roller and wiping blade arrangement which is subjected to the constant rubbing action as the powder material, which may be abrasive, passes between the roller and wiping blade. Further, uorocarbon materials have a high electric resistance and high resistance to electrostatic charges. It should be noted that the steel roller, due to the flanged fluorocarbon bearing and iluorocarbon coating is electrically isolated and hence, is electrically insulated from the electrostatic lfield. If the dispensing rolle-r were not isolated, there would be same electric charge, from the electrostatic field created by discharge tubes Si) and 81, which would be carried into the powder box by means of the roller and thereby electrostatically contaminate the powder material. This electrostatic contamination would adversely effect the dispensing of the powder material.

ASSEMBLY AND OPERATION The powder sprayer in accordance with this invention is of a generally symmetrical design so as to minimize the number of different components. The side panel and wiping blade assembly on one side of the roller is identical to the side panel and wiping blade assembly on the other side. The end lbrackets are identical to one another, and the two discharge tubes supporting structures are also substantially identical. This symmetrical construction in also advantageous since the dispensing roller can be rotated in either direction and'the entire unit can Ibe installed with either side panel facing outwardly.

The powder sprayer is installedwith the dispensing roller positioned horizontally, usually less than a foot above the surface to be coated with the powder material. Usually, the powder receiving surface is in the form of a moving web or sheet.

The powder or dusting material to be dispensed is either placed directly in the powder box above dispensing roller 11 or is supplied by a suitable feed mechanism. Thereafter, the drive motor is energized to rotate motor 11. The roller, if rotating in a clockwise direction, forces powder past wiping blade 23, in which case wiping blade 43 acts as a `seal between the side :panel and the other side of the roller. On the other hand, if the dispensing roller -rotates in a counter-clockwise direction, wiping blade 43 provides the metering function and wiping blade 23 acts as the seal. In either event, the powder material is metered out at a uniform rate. Thereafter, the force of `gravity and the force created by the electrostatic fiel-d pro- |vided by the discharge tubes, strips the roller clean so that the powder material falls to the surface below.

When discharge tubes and 81 are ener-gized, potential gradients are created surrounding the tubes which in turn ionize some of the air molecules in the vicinity of the discharge tu'be. This eifect is known as corona. The ionized particles having the same polarity as th-at appearing in the surface of the discharge tube stream away from the Idischarge tubes creating air currents referred to as electronic winds. These electronic winds are in a .generally downward direction in the area beneath dispensing r-oller 11. The downwardly directed electronic wind and the electr-ostatic attraction of the powder particles, assist the forces of gravity in removing the particles from the roller. A large number of the released particles become charged with the same polarity as the surrounding air molecules. This effect creates a powder cloud beneath the dispensing roller and brings about a more uniform dispersion of powder particles than could otherwise be achieved.

As previously mentioned, the dispensing rate is determined by the rotational speed of dispensing roller 11, and the blade pressure against the dispensing roller surface. -It should be noted that the wiping blade is relatively narrow and that the retaining member, which controls the blade pressure, is relatively close to the dispensing roller. With this arrangement the blade pressure can 'be controlled with considerable accuracy. Furthermore, since the adjusting screws are individually adjustable, the blade pressure can be adjusted separately in diierent selected areas.

After the powder sprayer unit is placed in operation, the powder distribution is observed and the roller speed and blade pressure are adjusted until a desired dispensing rate is achieved. If the powder ldistribution is uneven, las may be caused by inaccuracies in the dispensing roller or side panels or by uneven wear, this is easily corrected iby adjusting the blade pressure in appropriate selected areas. In cases where a particular uneven distribution is desired, for example, more powder in the center than at the ends, such uneven distribution can be attained by adjusting the blade pressure so that it is greater at the ends than at the center.

The position of the ydischarge tubes can be adjusted so that one or both of the tubes are effective, and hence, the effective strength of the electrostatic iield can be varied over a relatively wide range. Also, the tube position can Ibe adjusted to provide an electrostatic field which is nonsymmetrical and which thus tends to propel powderparticles in other than a directly downward direction. The non-symmetrical iield can be used, for example, to compensate for the effect of ambient air curtains on the powder particles as they fall from the dispensing roller to the surface below.

When the unit is placed in operation, a pneumatic pressure is created in the plenum chambers by means of a suitable air pump to thereby create an air curtain on each side ofthe roller. These air curtains extend between the side panels and the surface below and thereby protect the enclosed area from ambient air currents.

Although only a few illustrative embodiments of the 10 invention have been described in detail, it should be obvious to persons skilled in the art that there are numerous additional variations and embodiments within the scope of this invention. This invention is more particularly defined in the appended claims.

What is claimed is:

1. In an electrostatic powder sprayer, the combination a pair of spaced apart end members;

means between said end members defining a receptacle for powder material to be dispensed;

a cylindrical noller journaled between said end members within an opening below said receptacle;

wiping blade means secured to said receptacle and positioned to engage said roller for forming a dispensing mechanism for metering out powder material from said receptacle at a substantially uniform rate;

means providing a like arcuate surface on each of said end members, said arcuate surfaces being eccentric with respect to the cylindrical surface of said roller;

an elongated electrode means capable of providing an electrostatic field;

a pair of spaced-apart socket members adapted to secure the ends of said elongated electrode;

a pair of socket support members each adapted to slidably engage a different one of said arcuate surfaces, each of said socket members bein-g secured to a different one of said support members so that said tubular means is adjustable to various positions generally parallel to the axis of said dispensin-g roller and in the .vicinity of said wiping blades; and

means for energizing said tubular means to create an electrostatic ield to free powder material from said roller and to disperse the same so that said powder can fall evenly to the surface below. y

2. Apparatus in accordance with claim 1 wherein said socket members are pivotably secure to said socket support members.-

3. Apparatus is accordance with claim 1 wherein said tubular means is detachably secured between said pair of spaced-apart socket members.

References Cited by the Examiner UNITED STATES PATENTS 1,986,047 1/1935 Dawley et al 118-3213 X 2,027,307 1/1936 Schacht 117-17 X 2,027,308 1/1936 Schacht 117-17 X 2,394,657 2/ 1946 Beregh 95-1.7 X 2,972,332 2/ 1961 Limberger 95-1.7 X 3,114,482 12/ 1963 Dunaway 222-328 X 3,221,938 12/1965 Yonkers et al 317-2 X MILTON O. HIRSHFIELD, Primary Examiner. MAX L. LEVY, SAMUEL BERNSTEIN, Examiners. I A. SILVERMAN, Assistant Examiner.

Claims

1. IN AN ELECTROSTATIC POWDER SPRAYER, THE COMBINATION OF A PAIR OF SPACED APART END MEMBERS; MEANS BETWEEN SAID END MEMBERS DEFINING A RECEPTACLE FOR POWDER MATERIAL TO BE DISPENSED; A CYLINDRICAL ROLLER JOURNALED BETWEEN SAID END MEMBERS WITHIN AN OPENING BELOW SAID RECEPTACLE; WIPING BLADE MEANS SECURED TO SAID RECEPTACLE AND POSITIONED TO ENGAGE SAID ROLLER FOR FORMING A DISPENSING MECHANISM FOR METERING OUT POWDER MATERIAL FROM SAID RECEPTACLE AT A SUBSTANTIALLY UNIFORM RATE; MEANS PROVIDING A LIKE ARCUATE SURFACE OF EACH OF SAID END MEMBERS, SAID ARCUATE SURFACES BEING ECCENTRIC WITH RESPECT TO THE CYLINDRICAL SURFACE OF SAID ROLLER; AN ELONGATED ELECTRODE MEANS CAPABLE OF PROVIDING AN ELECTROSTATIC FIELD; A PAIR OF SPACED-APART SOCKET MEMBERS ADAPTED TO SECURE THE ENDS OF SAID ELONGATED ELECTRODE; A PAIR OF SOCKET SUPPORT MEMBERS EACH ADAPTED TO SLIDABLY ENGAGE A DIFFERENT ONE OF SAID ARCUATE SURFACES, EACH OF SAID SOCKET MEMBERS BEING SECURED TO A DIFFERENT ONE OF SAID SUPPORT MEMBERS SO THAT SAID TUBULAR MEANS IS ADJUSTABLE TO VARIOUS POSITIONS GENERALLY PARALLEL TO THE AXIS OF SAID DISPENSING ROLLER AND IN THE VICINITY OF SAID WIPING BLADES; AND MEANS FOR ENERGIZING SAID TUBULAR MEANS TO CREATE AN ELECTROSTATIC FIELD TO FREE POWDER MATERIAL FROM SAID ROLLER AND TO DISPERSE THE SAME SO THAT SAID POWDER CAN FALL EVENLY TO THE SURFACE BELOW.