US2992778A

US2992778A - Liquid spray apparatus

Info

Publication number: US2992778A
Application number: US479353A
Authority: US
Inventors: Martin William Mck
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-01-03
Filing date: 1955-01-03
Publication date: 1961-07-18
Anticipated expiration: 1978-07-18

Description

' July 18, 1961 w. MQK. MARTIN LIQUID SPRAY APPARATUS Filed Jan. 3, 1955 2 Sheets-Sheet 1 INVENTOR MAL/AM Ala/f 44,4277

.Tial" TTORNE'YS W. M K. MARTIN LIQUID SPRAY APPARATUS July 18, 1961 2 Sheets-Sheet 2 Filed Jan. 5, 1955 i. .4. T a INVENTOR MAL/AM Mc/f. M41? T/N ATTORNEYS United Stfl Patent 2,992,778 LIQUID SPRAY APPARATUS William McK. Martin, 457 Virginia Ave., San Mateo, Calif. Filed Jan. 3, 1955, Ser. No. 479,353 4 Claims. (Cl. 239-223) This invention relates to apparatus and a process for applying surface coatings, and is more specifically directed towards apparatus and a method for applying a lacquer or similar protective coating on the inner peripheral surface of a hollow cylindrical article.

As is well known in the art, it is in many instances desirable and often necessary to provide a protective coating over the entire exposed inner surface of containers such ascans in which food is packaged as well as larger units such as pails and metal drums. Usually, this coating is a lacquer or enamel which is painted on the required surfaces .or sprayed thereon with conventional spraying equipment. No particular difiiculty is encountered in the application of the lacquer to the flat end walls of the container as this operation may be readily performed either before or after attachment of the end walls to the cylindrical body. However, in applying the lacquer to the inner surface of the body, it is preferable to perform such operation after the rolling and longitudinal seaming of the body so as to prevent cracking or rupture of the lacquer film or coating, and it will be .appreciated that the application of a coating to the inner .wallsof a tubular member presents difliculties not found in applying such a coating to a flat surface or even to the external surface of a. cylindrical member if the latter was desired. 1 I

Furthermore, in using conventional spraying equipment, liquid is ejected from a nozzle by a high velocity airstream withthe liquid droplets being carried bythe airjstream towards the surface to be painted. However, it is well understood that an air stream will not confine 'itself to its original cross-sectional form, but will leave the nozzlein a gradually diverging shape. This spreading out of the air stream results in a certain proportion of the more finely dispersed droplets likewise moving outwardly, and consequently only the larger and heavier droplets will continueon in a, substantially straight path to engage and be deposited on the surface. This typeof operation not only results in an irregular andinferior coating, but actually promotes the formation of, undesirable air pockets between the surface and coating or, in the coating itself. a l a It is therefore anobject of the present invention to provide an improved apparatus and method for applying a lacquer orsimilar coating to theinner surface of a cylindrical containerin which the coating will possess uniform consistency and thickness over the entire surface area and will be. free from undesirable entrapment of air Another objectof the invention is toprovide a method .and apparatus of the typedescribed in whichcentrifugal force is utilized to project the liquid towards the, surface to be coated whereby the above mentioned disadvantages accompanying conventional air stream-spraying opera- .tions may be eliminated.

A further object of the invention is to provide apparatus of the above character which is simple in construction and operation and in which the method utilized is' extremely elfic ie nt and adapted for mass production .operations.

A s tillfurther object of my invention is to provide a 'ice vapor atmosphere whereby a more impervious air-free coating may be obtained.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of the preferred form of the invention which is illustrated in the drawing accompanying and forming part of the specification. It is to be understood, however, that variations in the showing made by the said drawing and description may be adopted within the scope of the invention as set forth in the claims.

Referring to said drawing:

FIGURE 1 is a vertical view, mostly in section, of the novel apparatus which may be utilized in carrying out the method of the present invention, the apparatus being shown in operation on a cylindrical container.

FIGURE 2 is an enlarged vertical cross-section view on an enlarged scale of the rotor assembly.

FIGURE 3 is a cross-sectional view taken substantially in the plane indicated by line 3-3 of FIGURE 2.

FIGURE 4 is a diagrammatic view of a modifiedform of spray apparatus.

In broad terms, the method employed herein for coating the inner walls of a cylindrical container comprises heating the lacquer or other coating to a temperature above the boiling point of the solvent contained therein, casting droplets of the lacquer towards the surface to be sprayed by means of centrifugal force, and elfecting axial movement between the lacquer spraying apparatus and the container whereby the entire length of the latter will be coated.

There are several reasons for heating the lacquer, and include a reduction in the viscosity thereof so as to facilitate its breaking up into droplets, and by raising the temperature to above the boiling point of .the solvents in the lacquer, solvent vapors will be released and impelled against the surface with the spray, and result in a scavenging or sweeping of all air from the surface on which the droplets are deposited. In other words, there will be a vapor atmosphere on the surface instead of air, thus precluding any undesirable entrapment of air under the deposit of the lacquer film or coating. It will likewise be appreciated that the initial evaporation of the solvents will materially reduce the time required for baking the coating in ovens or the like, and it is believed that the deposit of a hot lacquer film will provide a more impervious coating with a higher gloss. It should be made clear that while the term lacquer may be extensively used throughout this specification, I do not mean to limit the coating to a shellac and alcohol composition, but the coating may consist of other varnishes, paints or the like.

As hereinabove discussed, certain disadvantages and short comings arise from the use of conventional spraying equipment in which a high velocity air stream is utilized to eject and carry the liquid to be sprayed. Accordingly, as a principal feature of this invention, a physical force is imparted to the liquid so that the liquid droplets may be impelled against the surface to be coated without being carried in an air stream or jet. This force is preferably created by a high velocity rotor having peripheral openings through which the liquid is cast, the rotating rotor setting up a high centrifugal force on the liquid.

Further operational details will be discussed in connection with an explanation of the apparatus disclosed in the accompanying drawings. Referring first to FIG- URE l, a drum or cylindrical container 12 having a side wall and a bottom and an open top is shown in position to receive an inner surface coating of lacquer or the like. In view of the fact that the lacquer is to be sprayed, the container is preferably placed into a cylindrical open top receptacle having side walls 13 and abottom 14, such receptacle serving to prevent the hurling of lacquer outside the vicinity of the apparatus, and to trap excess lacquer for subsequent reuse.

Disposed medially of the walls 13 is a rotor 16 arranged to be rotated aboutthe axis of the cylindrical receptacle. The rotor is designed to receive a quantity of lacquer, and by providing the rotor periphery with suitable openings, the centrifugal "force upon the liquid during rotor rotation will cause thelatter to leave the rotor tangentially and be impelled against the side wall of the container 12 which encompasses the rotor. As the force at which the liquid leaves the rotor will increase in proportion to the square of the rotor speed, by rotating the rotor in the neighborhood of several thousand r.p.m., a substantial force is created which insures the liquid engaging the container wall. The particular speed will of course be determined with reference to the diameter of the rotor and the inner diameter of the article being sprayed.

In practically all instances, the'width or vertical height of the liquid impelled from the rotor will be substantially less than the height of the container being sprayed. Accordingly, during the spraying operation, there must be a relative axial movement between the rotor and container so that all surface portions of the latter will be coated. This could be done by axially moving the rotor along the length of the 'conta'inenbut the necessary movement is now shown by moving the container relative to "the rotor. This may be easily accomplished by pro viding conventional clamping mechanism 17 which usually includes -a center support element 18 for attachment to an overhead crane hook or the like, links 19 pivotal-1y secured thereto, links "21 pivotally mounted at the ends of links 19, and head or rim engaging hooks 22. This type of mechanism is widely used for moving steel drums or the like, but it will be appreciated 'that any other means m ay 'be equally well used for'the foregoing purpose of moving the container in an axial path relative'to the rotor '16.

Rotor16 may be cast or-otherwise formed to provide a downwardly directed'hub 26'having a central bore 27 communicating with ia'diametrically reduced counter-bore '28, and a radialflange'29 extending normal to the hub axis. An upper centrally located boss "31 having a threaded bore '30 is provided as a support for a cover plate "32, the *l-atter being held in position by a bolt or screw 33 in engagement with the boss bore 30. The flange '29 and'plate32, as will be more fully explained hereinafter, cooperate to define a liquid distribution chamber 34.

It is naturally desirable that the liquid be impelledin relatively small droplets rather than in a continuous stream, and accordingly means are provided on the rotor for-breaking up the liquid into droplets for uniform dispersion and application to the container surface. As here shown, such means comprise a band 36 having a 'plurality of small perforations 37 over the area thereof positioned at'the peripheral outlet of the cham'ber34. 7 The upper edge of the 'band may be secured to the plate 32 asby welding, and the'lower edge thereof may be seated in a groove 38 provided on the upper surface of flange 29 when the plate is attached to the boss31. Preferably, 'a second perforated metal band 39, mounted in the same manner as hand '36 is provided and positioned radially inwardly of the latter. By using the two bands in radially spaced relation, liquid in chamber 34 will be thoroughly dispersed into droplets'hefore leaving the rotor. By way of example, the bands could comprise a metal screen having approximately a 20-50 mesh.

Additional means are also utilized for properly distributing the liquid entering the rotor chamber. As will be later explainedin more detail, the lacquer tank or supply communicates with chamber 34 through counterbore 28 andia plurality-of ports 41 extending from thecounteribore upwardly and outwardly to emerge adjacent the lower end of boss 31. As the liquid emerges from the ports, it strikes a dished surface '42 of an annular bafiie 43, the latter being held in position around boss 31 by means of a radial shoulder 44 clamped between the upper end of the boss and plate 32. Flange 29 immediately subjacent the bafiie is provided with a concave portion 46. Thus, liquid entering through ports 41 engages surface 42 and is swirled around'the latter to evenly distribute the liquid to all parts-0 f the chamber. The liquid will actually connectin flange portion 46 from which it will enter the chamber.

Rotor 16 is mounted for rotation on a drive shaft 51 of hollow construction, the reason for such construction being to permit the flow of fluid therethrough as well as to permit a valve to be inserted to control such 'fluid flow, these features being hereinafter explained "in detail. To avoid splashing of thelacquer on the shaft drive mechanism, I prefer to position the latter exteriorly of the receptacle bottom '14. Thus, shaft 51 may pass through said bottom wall and be supported on a'bearing 52 depending from-such wall, while a suitable packing gland 53 prevents leakage between the shaft and wall. The upper end of the shaft is inserted within and secured to hub 26 of the rotor and the lower end is provided with a sprocket'54 for connection to abelt 56, the latter being driven by a motor 57 through a motor sprocket 58. From the foregoing, it will be understood that while motor 57 is operating, rotation will be imparted to the rotor through shaft '51, and any liquid in rotor chamber '34 will be hurled outwardly by centrifugal force, and diffused by passage through the multi-perforate band or hands before striking the container surface.

Lacquer is 'suppliedto chamber 34 from any suitable source, such as a tank -60, and a pipe 62 connected to the bottom'wall 14'of the splash receptacle may'serve to "divert excess lacquer accumulating in the latter'to the tank. Mounted within the bore of drive shaft 51 is a stationary sleeve'63through'which lacquer is introduced into the rotor chamber. The sleeve is preferably radially spaced from the inner surface of the drive shaft bore with bearings 64 disposed in such space, and "extends beyond the lower end of the shaft for connection to a feed pipe 66 leading from tank 60. This connection may include a nipple 67 provided radially on the sleeve and communicating with a radial bore which intersects the main passage 68 of the sleeve. A pump 69,positioned in pipe '66 is utilized toinsure passageof liquid from the itanktolthe rotor, and in order to heat the liquid *as it passes from the'tank to the sleeve, a heat exchanger 61 is provided in the feedpipe 66.

The upper end of the sleeve is positioned adjacent or the counterbore 28 of the rotorhub .and is tapered inwardly to provide an axial discharge nozzle 71. So long as this nozz'le'or opening is unrestricted, lacquer willflow from the'tank tothe rotor for discharge from the latter. However, when no container is overlying the rotor, it is obviousthat no spraying be needed, and the lacquer flow wouldbe wasted.

Therefore, to permit a closing of this opening, and a control of lacquer flow, -I provide a needle valve 72 arranged to selectively open and close the opening 71. The

valve is slidably carried within the sleeve 'by providing "the samewith aplurality ofribs 73 so as to 'permitaxial movement'without any lateral displacement. The lower endofithe valve is carried onan axially extending rod 74 which extends beyond the sleeve bottom for actuation-thereof. A packing 76 will be disposed between the sleeve bottom and .the rodto"prevcnt filiquid leakage therebetween.

.Any suitable-means, either manual or automatic, .may be utilized to move the rod for opening and 'closing of the valve, but I:prefer to use an automatic mechanism .under which :the valve will remain closed until 'arcontainer .is inserted -=over the rotor at which .time;.the valve will :open. This may be done as diagrammatically illustrated in FIGURE 1 wherein a solenoid 81 having a plunger 82, normally extended, is secured to the rod 74. Actuation of the solenoid to retract its plunger and consequently open the valve may be controlled by any suitable switch mechanism such as a first switch 83 arranged to be engaged by the container to energize the solenoid, and a second switch 84 operatively associated therewith which will be engaged by the coated container upon reaching its lowermost position to deenergize the solenoid. Naturally, by virtue of the valve arrangement, pipe 66 is provided with a by-pass 86 around the pump 69.

In FIGURE 4, a diagrammatic showing is made of a slight modification of the foregoing apparatus wherein a pair of rotors 91 and 92 are utilized, with each rotor turning in an opposite direction to the other. The reason for such an arrangement is that with a single uni-directional rotor it is possible that projections, such as rivets on the container surface would not be fully coated, as the leading edge portion of the projection (i.e., with respect to rotor rotation) can be left uncoated. Obviously the dual direction rotation of a pair of rotors would overcome this possible source of difficulty.

For the foregoing description, both the apparatus and its mode of operation are believed apparent. In use, the lacquer in tank 61 is first heated to a temperature just above the boiling point of the alcohol or other solvent contained therein. Motor 57 is actuated to effect rotation of the rotor and pump 69 is likewise operated. However, the needle valve 72 will keep the opening 71 closed, so no lacquer will enter the rotor. However, when a container is lowered over the apparatus into the splash receptacle, and switch 83 engaged, the solenoid Will move rod 74 to open the nozzle 71 whereby lacquer under pressure will be forced through the sleeve bore, through opening 71, into counterbore 28, and through the ports 41 to engage the baffle or deflector 43 for distribution in rotor chamber 34. The centrifugal force will impell the lacquer as well as the solvent vapors towards the container surface, such vapors serving to sweep all air from the surface on which the lacquer droplets are deposited. By then lowering the container, the entire surface will be uniformly and properly coated.

What is claimed is:

1. Liquid spray apparatus of the character described comprising a rotor including a hub and a flanged body extending radially outward therefrom provided with an annular surface portion having a relatively shallow substantially inverted frusto-conical configuration terminating outwardly in a raised continuous peripheral lip disposed in a substantially single radial plane, passage means associated with said hub disposed to supply liquid to inner peripheral regions of said surface to flow thereover and be uniformly discharged from said lip by rotational forces, a cover plate disposed in spaced relation above said flanged body and defining therewith a chamber enclosing at least the area bounded by said lip into which ingress of air is prevented, and an annular member provided with a plurality of perforations and disposed in spaced relation to and surrounding said peripheral lip of said annular flange surface portion and upon which liquid discharged from such portion impinges and is expelled tangentially outward in a finely dispersed form substantially free of admixture with dispelled air.

2. Liquid spray apparatus of the character described comprising a rotor including an axially bored hub and a flanged body extending radially outward therefrom provided with an annular surface portion having a relatively shallow substantially inverted frusto-conical configuration terminating outwardly in a raised continuous peripheral lip disposed in a substantially single radial plane, passage means communciating with the central bore of said hub and including an annular groove overlying the bore to receive liquid therefrom and arranged to supply liquid uniformly to inner peripheral regions of said surface to flow thereover and be uniformly discharged from said lip by rotational forces, a cover plate disposed in spaced relation above said flanged body and defining therewith a chamber enclosing at least the area bounded by said lip into which ingress of air is prevented, and an annular member provided with a plurality of perforations and disposed in spaced relation to and surrounding said peripheral lip of said annular flange surface portion and upon which liquid discharged from such portion impinges and is expelled tangentially outward in a finely dispersed form substantially free of admixture with expelled air.

3. Liquid spray apparatus of the character described comprising a rotor including an axially bored hub adapted to be attached to a hollow drive shaft and a flanged body extending radially outward therefrom provided with a shallow frusto-conical annular upper surface portion terminating outwardly in a raised continuous peripheral lip disposed in a substantially single radial plane inwardly of the edge of said flange, passage means communicating with the axial bore of said hub and arranged to supply liquid uniformly to the inner periphery of said surface to flow thereover and be uniformly discharged from said lip by rotational forces, a cover plate disposed in spaced relation above and coextensive with said flanged body defining therebetween a chamber and preventing axial ingress of air, and at least one annular screen member provided with a plurality of perforations and disposed between said flange and cover plate spaced outwardly from and surrounding said peripheral lip and upon which liquid discharged therefrom impinges and is expelled tangentially outward in a finely dispersed form substantially free of admixed expelled air.

4. Apparatus as defined in claim 3 wherein said passage means includes a plurality of axially diverging passages communicating with the axial bore of said hub and terminating in an annular concave downwardly oriented passage overlying the central portion of the upper surface portion of the body.

References Cited in the file of this patent UNITED STATES PATENTS 1,939,364 Peebles et al. Dec. 12, 1933 2,085,765 Peters July 6, 1937 2,508,709 Goetchius May 23, 1950 2,668,080 Peebles et al. Feb. 2, 1954- FOREIGN PATENTS 302,980 Great Britain Dec. 24-, 1928 367,890 Great Britain Feb. 29, 1932 911,116 Germany May 10, 1954 OTHER REFERENCES- The Problems Conquered to Make Hot Spraying Successful (Bede), published in Organic Finishing, January 1951, pages 1519.

Airless Spray Painting (Bede), Pamphlet published by Bede Products, Incorporated.