US3032277A - Spray gun for multicolor paints - Google Patents

Description

y 1, 1962 J. L. PETTY 3,032,277

SPRAY GUN FOR MULTICOLOR PAINTS Filed July 2'7, 1959 INVENTOR. JOHN LEE 'PETTY E5 E I 5 E/Le, Mm, g a

HTTO NEIS rates 3,032,277 SPRAY GUN FDR MULTICGLOR PAINTS Uiiiid John L. Petty, Chicago, Ill., assignor to The Sherwin- Wiiliams Company, Cleveland, Ohio, a corporation of This invention relates, as indicated, to an apparatus which is characterized in that it possesses a plurality of stages for dispersing relatively immiscible materials, a particular type of apparatus being that especially adapted for the controlled spraying of multicolor paint.

Certain multicolor paint compositions are composed of an emulsion of a binder dispersed as microscopic particles in an aqueous medium which emulsion, has dispersed therethrough macroscopic particles of a liquid composition immiscible and non-emulsifiable with the binder emulsion. Certain of these compositions tend to be what is known as metastable. By this it is meant that the macroscopic particles dispersed in the microscopic emulsic-n tend. to coalesce forming undesirably large particles. In amulticolor paint, for example, the macroscopic particles may comprise liquid globules or particles, of one or more pigmented resins or binder compositions, while the microscopic emulsion is also a pigmented composition such as a styrene-butadiene latex paint. Upon standing, these liquid-liquid dispersions are somewhat unstable in that the macroscopic particles tend to coalesce forming undesirably large particles of color dispersed in the latex binder. A coating applied from a composition which has stood overnight, such coating being applied in juxtaposition to previously coated areas, will become readily apparent to the eye because the color fiecks will appear to have increased in size. The result is unsatisfactory where uniformity of appearance on a multicolor paint decorated surface is desired.

It is a primary object of the present invention, therefore, to provide an apparatus to control the character of the liquid-liquid dispersion in terms of the size of the macroscopic particles dispersed therein, and to thereafter disperse this controlled liquid-liquid dispersion in particulate form in a gas stream, such as an air stream.

Other objects of the invention will appear as the description proceeds.

To the accomplishment of the foregoing and related ends, said invention, then consists of the mean hereinafter fully described and particularly pointed out in the appended claims, the following description and annexed drawing setting forth in detail certain illustrative embodiments of the invention, such disclosed means constituting, however, but a few of the various forms in which the principles of this invention may be employed.

Briefly stated, the present invention is in the provision of an apparatus for dispensing a liquid as a spray, i.e. a dispersion of a liquid in a gas, such apparatus including a chamber having an inlet and an outlet. Means are provided adjacent the outlet for dispersing the liquid passing therethrough into a spray. Removable means in cluding a plurality of apertures disposed in a plane transverse to the flow of liquid are provided spaced from the outlet and adjacent the inlet, the purpose of which is to selectively control the size of the macroscopic liquid particles in the liquid medium as dispensed.

In the annexed drawings:

FIG. 1 is a partial cross-sectional view of an apparatus constructed in accordance with the principles of this invention. I

FIG. 2 is an enlarged illustration of a screen forming a part of the apparatus hereof.

FIG. 3 is an enlarged View of a portion of the screen shown in FIG. 2.

3,032,277 Patented May 1, 1952 ECQ FIG. 4 is an enlarged cross-sectional view of apertures illustrated in FIG. 2, taken on the line 44.

Generally speaking, the apparatus of the present invention includes a gun which comprises a handle by which it may be held and manipulated, a nozzle from which liquid and compressed gaseous propellant are discharged, and suitable passages and valves by which the discharge of gas and liquid are controlled.

Referring now particularly to FIG. 1, there is illustrated a gun of this general character. The body of the gun is indicated by 16, the nozzle generally by 17, the handle by 18, and the valve controlling lever or trigger by 19. The handle includes a passage which is con nected through a nipple 21 to a suitable source of compressed gas, e.g. air. The passage 20 communicates with a second passage 22 which communicates through a port 23 with the rear portion of the bore 24. A main, nor mally closed, shut-off valve 25 is provided in the passage 22 and is adapted to be opened by operation of the trigger 19 in a well known manner.

The bore 24 opens at the rear end of the body 16 to receive a tube 26 which is threaded at its forward end in a restricted portion of the bore 24 in advance of a port 27, and the forward end of the tube communicates with the orifice 28 through which gas is supplied to the chamber 29. The flow of gas through the tube 26 will be regulated by the valve 31, and this gas is delivered from the chamber 29 through the annular chamber 32 into the passage 33 in the head 34 of the nozzle 17, from whence it is discharged from the nozzle openings 35 diagonally toward the longitudinal axis of the gun. The gas from the bore 24 surrounding the tube 26 passes through the annular port 27 into the chamber 36, from which it is discharged at the nozzle through the ports 37, 38 and 39.

A receiving chamber 41, formed by a bore in the housing 16 and a tubular extension 42 threaded into the bore, is provided with a discharge orifice 43 positioned coaxially with the nozzle head 34. The discharge orifice 43 is controlled by a valve 44 carried by a stem 45 which is connected with the trigger 19. A plunger 46 and an expansion spring 47 normally urge the valve' 44 into a position to close the orifice 43 and hold the trigger 19 in the position shown in FIG. 1.

The receiving chamber 41 is connected to receive the liquid being sprayed from a container (not shown) at tached to the flexible hose 7. A passage 48 communieating with the rear end of the chamber 41 is connected by a coupling,49 of enlarged diameter. Clamped be tween the male and female portions of the coupling 49 is a screen 50, a preferred embodiment of which is more clearly shown in enlarged view in FIGS. 2, 3 and 4.

FIG. 2 illustrates a circular metallic screen member which may be used transversely of the path of flow of liquid from the supply container, not shown, through the flexible conduit '7, into the spray gun 16. The screen member thus employed has special characteristics enabling it to perform the desired function of controlling the character of the dispersion of the macroscopic particles in the liquid medium. Ordinary window screen, for eX-' ample, will not sufiice for the purposes of the present invention. While the screen 50 may be located at any. point between the paint source and the gun, it is most conveniently located as shown in FIG. 1.

In a preferred embodiment of the present invention, the screen. 50 is .in essence a circular section of slotted screen havingja plurality of slots 51 arranged in end-to-Z end relation defining rows, successive rows being ar ranged in staggered relationship with the next-adjacent row. As shown in FIGS. 3 and 4, in enlargement'and in cross-section, the slots 51 have a trapezoidalv shape. 1 If a cross-sectional view'were taken transversely to'the sec tion shown in FIG. 4, i.e. the long way of the slot, the opening would also appear as a trapezoidal shape. The surface described by the walls of the opening is regarded in the present specification as that of a frusto-rectangular pyramid. The screens 50 are conveniently made of thin metallic sheet material having slotted perforations, each slot of which, isfrom about 4 to about 10 times longer than it is wide. The thickness ofthe screen is suchthat it is approximately the same as the slot width, and the open area of the screen to the closed plate area of the screen is, in the preferred case, of the order of from about 20% to about 40% of the total screen area.

The slot width of the perforations which are of rectangular configuration is the controlling dimension for the purposes-of the present invention. It is the slot width, or the measure of the smallest dimension of the perforation which controls the size of the macroscopic particles which are immiscible with, but dispersed in the liquid medium, as hereinafter more particularly described. It should be understood that the gradation in slot size from one face to the other of the preferred screens for use in accordance herewith, i.e. the frusto-rectangular pyramidal surface, is provided by electroplating techniques. A variety of durable metals including nickel may be used to produce the screen structure desired. It does not appear to make any. difference in the spraying operation or uniformity of control which sideof the screen is toward the on-corning liquid stream.

Instead of elongated slots in end-to-end relation as above described, the screens of the present invention may also be made by perforating a thin metallic plate with circular holes defining small cylindrical bores and having random, or regular, orientation and from 10 to 70 openings'per, lineal inch, andfrom 15% to 60% open area. The side walls of the perforations regardless of planar shape of the opening may be parallel or diverging. The smallest dimension may range from about 0.005" to about 0.05";

Whatever the screen nature may be, it is preferred that the; screen element be a disc having a diameter of at least abouttwice the diameter of the flexible tube 7. It has been found that if the disc is substantially smaller, in standard spray guns there is a tendency to uneven distribution of the macroscopic color particles in the liquid binder. Best results are obtained, therefore, where the screen blank is a one inch circular member of the slotted type screen described above, with inlet tube 7 diameters of from /8" to /8".

The multicolor coating composition applied through the multi-stage dispersion apparatus of the present invention generally may comprise a paint latex emulsion which is normally pigmented containing microscopically dispersed particles of interpolymers of two or more ethylenically unsaturated monomers, e.g., butadiene-styrene, which as formulated, are preferably, but not essentially, capable of depositing continuous films. Dispersed in visibly discreet macroscopic particles in the latex paint carrier is stillanother'liquid phase which is immiscible and nonemulsifiable in the emulsion paint latex system. The macroscopic phase is formulated generally to be of differing hue, value, and chroma over the pigmented latex emulsion paint which serves as a suspension medium for the macroscopically dispersed particles or globules. Upon application to surfaces and films by spray application, the product of this nature provides a base coat originating primarily from the microscopic particles of one color, and interspersed throughout the base coat are a plurality of macroscopic globules or particles of the second liquid paint system of distinct and different physical properties from that of the first or emulsion system, and generally one or more different colors. Macroscopic particles are eXclusiveof microscopic-particles found in emulsion systemsand include particles of at least 0.01 in diameter upwards. Particles as large as 0.25 in diameter are not uncommon in the macroscopic dispersed phase. Referonce may be had to my copending application Serial Nos. 729,513 and 729,514, filed April 21, 1958 for detailed description of the preparation of multicolor coating compositions which may be applied by the apparatus of the present invention.

The particle sizes of the liquid-liquid dispersion in the gas stream is controlled in the usual manner for spray ,gun application of paints by regulating the valves 31, 44

and 25 to provide aequate coverage without sagging or too light deposition of coating. Particle sizes within the liquid phase are controlled by selection of the desired screen size to produce a given multicolor effect. Time of standing of the metastable system is no longer a critical factor affecting the decorative result.

There has thus been provided an apparatus for dispensing liquid-liquid dispersions of macroscopic liquid particles of controlled size in a liquid medium immiscible therewith in spray dispersions of liquid in a gas medium also of controlled size or a multi-stage dispersion apparatus. It includes a chamber having an inlet and an outlet. At the outlet are provided means for dispersing a liquid in a gas as a spray. Before the liquid-gas dispersion is produced, the liquid passes through a means impervious to liquid having a plurality of apertures therein for selectively controlling the size of the macroscopic particles dispersed in the liquid medium.

Other modes of applying the principle of this invention maybe employed instead of those specifically set forth above, changes being made as regards the details herein disclosed, provided the elements set forth in any of the following claims, or the equivalent of such being employed.

It is, therefore, particularly pointedout and distinctly claimed as the invention:

1. An apparatus for dispensing a liquid-liquid. dispersion of macroscopic liquid particles in a liquid medium,

non-reactive therewith in a gas spray including a chamber having an inlet and an outlet, conduit means for conducting fluid to said inlet, means adjacent the outlet for dispersing'a liquid passing therethrough as a mixture of discrete immiscible particles into a spray, and removable means impervious to liquid including a plurality of rectangular apertures disposed in said conduit in a plane transverse to the flow of liquid spaced from said outlet and toward said inlet to selectively control the size of said macroscopic liquid particles in said liquid medium as dispensed, said apertures having a length 4 to 10 times the width thereof, and said apertures occupying no more than about 66% of the total area of said removable means, the total area of said removable means being at least about twice the cross-sectional area of said conduit.

2. In a spray gun apparatus for dispensing a multicolor paint comprising a gun body defining a liquid receiving chamber and having a discharge orifice communicating with said chamber atone end thereof for discharging a. liquid stream therefrom and a single inlet opening into said chamber, conduit means for conducting fluid to said inlet, a liquid control valve associated with sad orifice for opening and closing the same, passages in said body for receiving a gas under pressure and exhausting the same as a plurality of atomizing jets into the path of liquid discharged from said orifice, a gas control valve controlling the admission of gas to said passages, and manual control means for simultaneously opening both of said valves, the improvement which comprises a removable means impervious to liquid including a plurality of rectangular apertures disposed in said conduit in a plane chamber, said apertures having a length 4 to 10 times the width thereof, and having from 10 to 70 openings of substantially the same size per linear inch and from 15% to 66% open area, the total areaof said removable means being at least about twice the crosssectional area of said conduit.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Thompson Sept. 23,

6 Einbecker June 13, 1950 Clark et a1. June 27, 1950 Peeps Mar. 26, 1957 Preiswerk et a1. Apr. 9, 1957 FOREIGN PATENTS Great Britain June 29, 1927

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