US2967667A - Electrostatic spray apparatus - Google Patents

Description

E. O. NORRIS ELECTROSTATIC SPRAY APPARATUS Jan. 10, 1961 mvg/vra@ fon/ARQ Q /Vo/Q/Q/s A 7 TOR/VE Y )United States Patent OI ELECTROSTATIC SPRAY APPARATUS Edward 0. Norrls, Roseville Road, Westport, Conn.

Filed June 17, 1957, Ser. No. 666,102

8 Claims. (Cl. 239-15) This invention relates to centrifugal spraying devices and has for au object to provide a spray device having novel and improved characteristics.

Another object is to provide a centrifugal spray device in which the spray width can be readily adjusted.

A more specic object is to provide, in a centrifugal distributor having a rotary collecting bowl, means for mixing the intercepted spray material with the fresh spray material before feeding the material to the distributor.

A further object is to provide in such an apparatus -wherein the spray material is fed from the collecting bowl by -a scoop, means to prevent scoop spatter from interfering with the spray characteristics.

A further object of this invention is to provide a rotary atomizer which sprays from only a predetermined portion of its periphery.

Another object is to provide an atomizer of the above type which has no stationary surfaces in 'the spray producing and controlling zone.

Another object is to provide an atomizer of the'above type which is suited for use in electrostatic spraying.

f Various other objects and advantages will be apparent as the nature of the invention is more fully disclosed.

This invention is an improvement on the painting device shown and described in U.S. Patent No. 2,063,048 dated December 8, 1936, to Edward O. Norris. The improved construction described herein provides a centrifugal sprayer which is suited to produce high quality finishes in automatic coating operations particularly when it is operated under the inuence of an electrostatic charge or field.

In accordance with the present invention a rotary distributor and -an intercepting bowl or collecting case are mounted to rotate about non-parallel axes and are so positioned that the collecting case intercepts the spray from a portion only of the periphery of the distributor. The intercepted spray and the fresh spray material are fed into a common annulus wherein they are mixed and picked up by a stationary scoop which delivers the mixture to the distributor for spraying. The scoop is disposed in a substantially closed chamber so that scoop spatter is prevented from affecting the uniformity of the spray.

- By mixing the intercepted spray with the new spray material any unevenness which might otherwise result from differences in the viscosity between the intercepted spray and the fresh spray material is avoided.

For use in electrostatic spraying the rotating parts may be made of nonconducting material such as plastic and suitable charging electrodes may be provided for applying an electrostatic charge to the spray material before it leaves the distributor.

The nature of the invention will be better understood by referring to the following description, taken in connection with the following drawings in which a specific embodiment has been set forth for purposes of illustration.

In the drawing:

vFig- 1 is a longitudinal axial sectionthrough a Vdistributor embodying the present invention with parts in elevation; and

Figs. 2 and 3 Iare transverse sections taken on the lines 272 and 3 3 respectively of Fig. l.

Referring to the drawing more in detail, the distributor is shown as mounted in a txed housing 10 which may be made of suitable material such as metal or plastic and carries axially thereof a shaft 11 which is mounted for rotation in an upper ball bearing 12 and a lower needle bearing 13. The ball bearings 12 are adapted to prevent axial movement of the shaft 11. At its lower end the shaft 11 is provided with a recess 15 in which a drive shaft 16 is disposed and which in turn is provided with an axial recess 17 for coupling to an external drive means not shown. An end cap 20 is screwed into the lower end of the housing 10 and is provided with a threaded bore 21 to receive an external coupling to a drive means housing not shown.

An inverted dished hub member 25 is secured to the top of the shaft 11 and is adjusted'to the desired 4axial position by means of a spacing washer 26. The hub mem- -ber 25 is provided with a dished inner surface 27 which is flared outwardly so that spray material is caused by centrifugal force to llow outwardly therealong to the periphery of the hub member 25.

A diffuser or distributor ring 28 is secured by screws 29 with its inner peripheral edge adjacent the lower peripheral edge of the hub member 25. The diffuser ring 28 is provided with a dished inner surface 30 which flares upwardly to a peripheral edge 31 from which the material i is ejected as a spray by centrifugal force. The outer edge of the'hub member 25 is provided with -a plurality of elongated slots32 which register with the surface' 30 of the atomizer ring 28. The slots 32 are so positioned that material which ows outwardly along the dished undersurface 27 of the hub 25 flows through the slots 32 onto the dished upper surface V30 of the diffuser ring 28 from which it is discharged by centrifugal force in the form of an atomized spray.

The hub member 25 maybe secured to the end of the shaft 11 by a nut 33 which holds the hub member against the spacer washer 26 and may be readily renewable to permit the spacer washer 26 to be changed for adjusting the axial position of the distributor.

An outwardly flared bracket 36 is threaded into the"up per end of housing 10 and carries at its upper end 37 the outer race 38 of a bearing 39, the axis of which is disposed at an angle to the axis of the shaft 11. The bearing 39 is provided with an inner race 40 which is carried by a ring 41 disposed internally of the bearing and an upper flange 42 extending above the bearing and attached to and integral with an outer ring 43 which extends downwardly on the outside of the bracket 36. The ring 43 carries near its lower end an external horizontal flange 44 having a plurality of vertical passages 45 extending therethrough. The flange `44 is externally threadedl and is secured to an annular vertical flange 46 having a flared internal wall surface 47 registering with the passages 45.

The flange 46 carries at its lower end a dished annular radial separating wall 48 to the outer periphery of which is secured or formed integral therewith a rotating case 49 having an upper inwardly inclined generally vertical wall S6 and a lower inwardly inclined substantially radial wall 51 forming at their junction an annular channel 52. The wall 50 terminates upwardly in an inwardly ared rim 53 having a sharp peripheral edge for spray cut olf. The wall 51 is spaced from the wall 48 to provide therebetween a radial scoop chamber terminating peripherally.

in the channel 52. The wall 48 serves toV separate and shield the scoop chamber from the spray intercepting,

zone of the rotary case. A bottom closure wall 54 is Patented Jan. 10, 1961 u screws 55. A plurality of passages A59 are disposed in the wall 48 adjacent the inner surface of the Wall 50 to pass material which is intercepted by the wall 50 downwardiy into the channel 52.

A closure ring 60 is secured to the upper end of the Ahousing by suitable means shown as `a set `screw 61 and is provided with a labyrinth seal 62 having a running t with the inner 4peripheral surfaces of the rotating Wall 54,!and with a labyrinth seal 63 having a running ilt with the lower end of the ring 43. The inner surface of the ring 41 Ybears against a `cone 68 which is slidably held on the shaft 11 and is provided with a conical outer surface 69 which is continuously held against the inner'surface of the ring l41 by means of a coiled spring 70. The cone member 68 is provided with a pair of slots 72 engaging tapered pins 73 by which it is keyed to the shaft 11. The slots 72 and pins 73 are formed with a clearance to `permit axial movement of the driving cone 68 along the cylindrical part of shaft 11 so that it is automatically maintained in driving engagement with the inner surface of the ring 41 throughout the life of the apparatus.

A scoop 75 is provided in the scoop chamber between the walls 48 and Si with an open end 76 disposed in the channel 52 and directed to receive the advancing film of material as the material is fed centrifugally along said channel (Fig. 2). The scoop 75 is secured to the fixed bracket 60. The inner end of the scoop 75 is disposed to eject material which is fed through `the scoop due to the pressure built up by the rotation of the bowl 49 against the portion of the inner surface 47 of the Wall 46 and is fed upwardly along said wall 46 by centrifugal force until it is discharged from the upper rim of the wall 46 onto the inner dished surface 27 of the rotating hub member 25.

A xed feed pipe 80 is attached to the xed ring 60 and is provided with a nozzle 81 disposed within the scoop chamber andpositioned to discharge material onto the flared under surface of the coned wall 48 by which it is fed outwardly by centrifugal force into the channel 52.

For producing an electrostatically atomized spray, all parts except the bearings may be made of non-conducting material, such as plastic, and an electrically charged material may be supplied through the supply pipe 80 as shown-in copending application Serial No. 585,224, tiled May 16, i956, now Patent No. 2,827,009.

Alternatively the shaft 11 may be ymade of metal or may be made of plastic and metal coated. The hub .'25 may be made of metal or may be metal coated on the underside to `provide a metal surface over which the material ilows, and the distributor ring 28 may be made of metal or may be made of plastic and coated with a conductive coating. In that event a high tension electric cable (not shown) may be connected to a connector 88 to supply high tension uni-directional potential through the bearing 13 to the metal Shaft 11 and thence to the conducting surfaces of the hub 2S and distributor 28. The bowl 49 may be made of plastic and may be provided with a metal coating 85 which may be used near a grounded electrode (not shown) for improving the potential distribution in the electrostatic field.

A lip 89 may be formed on the outer surface of the wall 49 for the centrifugal discharge of material that may be collected on the surface of the bowl.

In operation the material supplied through the pipe 30 is fed into the annular channel 52 and thence by the scoop onto the wall 46 from whence it is discharged onto the. under surface 27 of the hub 25 onto the inner surface 3l) of the distributor, whence it is discharged peripherally as an atomized spray. The angle of intercept of the bowl 49 with the material discharged from the distributor 28 depends upon the angular relationship between the axes of the bowl 49 and the distributor 28 and also theaxial relationof the distributor on the shaft 11; -Hence the yspray width can 4bedetermined by ad- 4 t justing the spacing washer 26. .Since .the .bowl 49 .is driven at substantially the same speed as the distributor 28 any material which is discharged from the edge of the bowl has similar spray characteristics to the material which is discharged from the distributor.

It is to be noted that the intercepted spray as well as the fresh material fortspraying are both fed into the scoop channel 52 and are mixed therein before being applied to the distributor. This Lpermits the intercepted material, which may ,become more viscous, .to be mixed with the fresh material prior -to spraying so that auniform spray ismaintained. `Also it -is 'tol befnoted that the scoop is disposed within a .Substantially closed chamber thereby preventing spatter which might otherwise be produced by the scoop and which by striking` the underside of the distributor would interfere with the production of a uniform spray.

As is Ytaught'intmyl'atent No.,2,063,048 material that collects on Ythe upper rim of the rotary case and sprays ofi has always constituted a problem. In this invention this gproblem Vhas 'been minimized by providing the atomzing ring 28 with .a ,dished inner surface 30 flared upwardly away from :the case opening. This type of operation results in imparting anupward component to the spray leaving :the atomizing'edge which causes a minimum of sprayedrmaterial tobe-deposited on the top edge of the rotary collecting case.

In one constructionwhich has'been found 4to be satisffactory theshaftlLmay :be made of steel, hub member 25 may be made of phenolic ,plastic with the under sur.- face27 made-conductive with a graphite layer; `distributor ring 28:maybe of :aluminum andthe rotary Acase as sembly may be made of phenolic resin and the scoop of non-.conducting nylon with the high voltage lead wire (not shown) being connected to connector 88 and with shaft extension and casing 10 `madeof phenolic plastic.

The maximum :electrostatic effect is obtained with a coned for saucer `,shaped atomizing ring operating with its convex side toward the interior of the intercepting and collecting case.

Since ,material `collects on the outer rim of the collecting case and thensprayslo'if, ait is important to insure, asfar .as possible, .that Athese spray particles `are in the the same range ofsize as the spray particles from the atomizing rotor. This. has Vbeen accomplished in the present invention ".by urotating the case `at substantially the same speed as thedistributor, also, by providing s ilange 89. The spray which is discharged from the case is attracted to the `work along withithe spray from the distributor.

It will be noted that the remaining external surface and edges of this case are Vrounded to minimize electrostatic interference with the atomizer.

What is claimed is:

l. A rotary spray device-comprisinga stationary housing, a rotary distributor supported by said housing and adapted to eject a spray centrifugally from -its entire outer periphery, a collecting case mounted on said hous ing .to rotate in a plane Vwhich is tilted with respect to the plane of said distributor, said case having -an annular peripheral wall defining a spray intercepting zone and positioned to intercept the Aspray ejected from a prede termine-d angular portionof the periphery of said distributar, said Wall having an annular channel displaced from said intercepting zone into which liquid intercepted by said annular wall flows and is collected by centrifugal action in the form of a rotating layer, a separating wall carried by said case between said channel and said intercepting zone and forming with said channel a scoop chamber shielded by said last wall from said ,intercepting zone, said separating wall having peripheral passages for the low of the intercepted liquid along said peripheral wall into said channel, a stationary scoop supported 'by said housing and disposed in said scoop Chamberland having 4an `open `end arranged 'to' 'dip Yinto and receive anexas? vliquid from said layer in said channel, said scoop being connected and arranged to feed said liquid to said distributor for spraying thereby.

2. A rotary spray device as set forth in claim 1 having a feed pipe carried by said housing and positioned to feed fresh spray material into said channel.

3. A rotary spray device as set forth in claim 1 in which said separating wall is substantially radial and stationary feed means carried by said housing is adapted to feed fresh spray material on to said radial wall inwardly of said channel whereby said last material ows outwardly along said wall by centrifugal action and is combined in said channel with the intercepted spray material. 4. A rotary spray device as set forth in claim 1 in which a driving shaft is mounted for rotation n said housing, a hollow hub member having a flared inner surface is disposed at one end of said shaft, said distributor is in the form of a ring attached to said hub member, means including said scoop is provided to feed material from said channel on to said dished inner surface of said hub member for advancing axially thereof by centrifugal action and said hub member is provided with passages positioned to permit the iiow of such material from said inner surface to the surface of said distributor disc.

5. A spraying apparatus as set forth in claim 4, in which at least the outer surface of the hub is non-conducting, at least the peripheral discharge surface of the distributor ring is conducting, and means is provided to apply an electrical potential to said conducting surface.

6. A spraying apparatus as set forth in claim 5, vin which said collecting case is made of noncond`uctin`g material. v

7. A spraying apparatus as set forth in claim 4, in which at least the peripheral discharge surface of the distxibutor ring is conducting and said collecting case and said scoop are non-conducting, and means is provided for applying an electrical potential to said conducting References Cited in the le of this patent UNITED STATES PATENTS 2,063,048 Norris Dec. 8, 1936 2,120,930 Cooper June 14, 1938 2,728,606 Smart Dec. 27, 1955 2,764,712 Iuvinall Sept. 25, 1956 FOREIGN PATENTS 710,852 Great Britain Iune 23. 1954

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