US3027096A - Methods and apparatus for producing multi-component surface coatings - Google Patents

Description

March 27, 1962 J. GIORDANO 3,027,096

METHODS AND APPARATUS FOR PRODUCING MULTI-COMPONENT SURFACE COATINGS 2 Sheets-Sheet 1 Filed Jan. 21, 1960 INVENTOR.

JOSEPH GIOR DA NO may/ 44 6 ATTORNEYS March 27, 1962 J. GIORDANO 3,027,096

METHODS D APPARA u FOR PRO ING MULTI-C ONENT S ACE COAT S 2 Sheets-Sheet 2 Filed Jan. 21, 1960 Fig. 6

IN V EN TOR.

JOSEPH GIORDANO 9 5 gu /4 ATTORNEYS Ohio Filed .Ian. 21, 1960, Ser. No. 3,904 2 Claims. (Cl. 239304} This invention relates to methods and apparatus for producing surface coatings from a plurality of visually different coating liquids applied simultaneously to a surface to product what has been termed a spatter finish coating of uniform pattern, attractive appearance, and durable wearing qualities. In accordance with common practice, the plurality of coating liquids are propelled together through a common spray gun orifice as a composite stream that is atomized as it emerges from the orifice by air jets appropriately disposed to produce a spray of intermingled droplets of the two liquids and to give the spray a desired shape, such as a cone or a fan.

Spatter finishes are employed on many commercial products, particularly products having minor surface irregularities or blemishes. The pattern effect of such finishes tend to break up the reflection of light from the coated surface so as to render the surface irregularities or blemishes less noticeable than if a single solid color were used.

Spatter finishes of the general character to which the present invention relates have heretofore been formed by a single spray coating application in accordance with methods and apparatus described and claimed, for example, in U.S. Patents 2,511,626 and 2,511,627 granted June 13, 1950 to Henry B. Einbecker, in US. Patent No. 2,504,116 granted April 18, 1950 to Austin H. Downs, and in US. Patent No. 2,513,081 granted June 27, 1950 to Edward M. Clark and Fernand E. Ledecq. In accordance with all of said prior patents, a plurality of different liquid coating compositions are introduced into the main chamber of a more or less conventional type of paint spray gun, preferably as a pair of substantially parallel flowing streams of the different liquids. By employing a plurality of coating composition liquids that are visually diiferent when dry, either as a result of differences in color (hue, chroma, or intensity) or other differences in light reflecting properties, and by employing vehicles for the plurality of liquids that have some difference in their miscibility characteristic sso as to hinder blending of the liquids upon contact with each other and discharge together from the spray gun, a substantial degree of heterogeneity of the liquids can be maintained until they are atomized to produce a spray in which each discrete droplet is substantially entirely composed of only one or another of the liquids. Generally, one of the liquids is fed to spray gun at a greater rate than the other so that the liquid present in the greater quantity forms a substantially continuous background phase on the coated surface, the liquid or liquids present in lesser proportions being deposited as discrete droplets randomly distributed through the continuous background phase in a substantially uniform overall concentration.

While the methods and apparatus of the prior patents mentioned above were capable of producing and substantially reproducing spatter finish coatings of a fairly uniform character when the spray guns were carefully handled, some skill was required to achieve such uniformity. In some instances, the central portion of a spray directed toward a surface to be coated would not be composed of the same relative sizes and/or concentrations of droplets of the different liquids as some or all of the outer portions of the spray. In other instances, the relative concentrations and/or sizes of the droplets of the differ States Patent ent liquids in the spray would not remain constant with time, so that close uniformity of coatings over large areas or on separately coated surfaces or products was not achieved. Lack of uniformity of coatings seemed to occur most frequently when attempting to coat intersecting surfaces in the region of the surface intersections, possibly due to the fact that marginal portions of the spray would be concentrated on one of the surfaces while other portions were concentrated on the surface angularly related thereto.

Although the causes of the difficulties in obtaining a high degree of uniformity and reproducibility of spatter finish coatings are somewhat speculative and may have been different under various coating conditions, it is believed that the problem was largely one of maintaining a controlled degree of relative concentrations and heterogeneity of the different liquids until the composite stream emerged from the gun and the constituent liquids were atomized by impinging air jets. One of the probable causes of variations in the relative concentrations and degree of heterogeneity of the different liquids as they emerged from the spray gun orifice was that the liquids, while they were flowing together through the gun chamber toward the orifice, were irregularly intermingled in substantially laminar streams, possibly with some twisting and distortion of the laminations, so that the relative quantities of the intermingled liquids passing through the restricted gun orifice from one instant to another were not constant. An unsymmetrical and varying distribution of the plurality of liquids in the composite stream emerging from the gun orifice probably resulted and contributed to the lack of uniformity of distribution of droplets of the different liquids over the spray pattern at any given instant.

The foregoing difficulties have considerably restricted commercial acceptance of the foregoing methods and apparatus. Uncertainty as to the exact causes of those difficulties may have been responsible for the fact that they have long remained unsolved.

The principle object of the present invention is to provide methods and apparatus for producing spatter finish coatings with a greater degree of uniformity and reproducibility without the careful and skillful handling formerly required, even under conditions which formerly accentuated the difficulties described above.

More specific objects of the invention are to provide novel methods and apparatus for delivering a plurality of coating composition liquids to a spray gun orifice so as to produce a substantially symmetrical and highly uniform distribution of the different liquids in the composite stream emerging from the gun orifice, and to provide a particular distribution of a plurality of liquids in the composite stream which, when the stream is dispersed by impinging air jets, will substantially simultaneously and more uniformly distribute droplets of the different liquids throughout the resulting spray.

A characteristic of the invention contributing to the accomplishment of the foregoing object is that parallel flowing streams of the different liquids propelled toward the spray gun orifice are separated by a physical barrier therebetween until they are closely adjacent the orifice, whereby the cross-sectional configurations of the separate streams reaching the orifice are maintained substantially constant and in a predetermined pattern. According to the preferred forms of the invention, one of said streams is confined to a fixed annular cross-sectional form, and another of said streams is confined within the annular stream.

Important characteristics of the apparatus of the invention are that one of the different liquids to be sprayed is conducted substantially to the orifice of the gun through a reciprocable, axially extending, hollow needle, and is exhausted from the tip thereof centrally of an annular stream of another liquid conducted to the orifice around the hollow needle. The needle serves as a valve for controlling the discharge of the liquids from the gun, the discharge tip of the hollow needle normally closing the gun orifice and, when retracted to open the orifice, being disposed closely adjacent the orifice.

Still another characteristic of the apparatus of the invention is that the discharge tip of the aforesaid needle is formed of a soft rubber or the like adapted to be deformed against the orifice when the needle is in its orifice closing position so that the liquid passageway through the needle is squeezed to close the same against flow of liquid to the orifice through the needle, as well as around the needle from the gun chamber. This feature of the invention enables the introduction of liquid into the needle and control of the flow through the needle to be effected in a simple and efficient manner as hereinafter more fully explained.

Other objects, advantages, and characteristic features of the invention will be apparent from the following detailed description of illustrative embodiments thereof, as shown in the accompanying drawings, in which:

FIGURE 1 is a side elevation of apparatus constructed in accordance with the principles of the invention, a portion of the apparatus being shown on a reduced scale for simplicity of illustration;

FIG. 2 is a similar View of the spray gun shown in FIG. 1, with the main parts of the gun shown in longitudinal, vertical section;

FIG. 3 is a transverse, vertical, sectional view of the spray gun, taken as indicated by the line 3-3 in FIG. 2;

FIG. 4 is another transverse, vertical, sectional View of the spray gun, taken as indicated by the line 44 in FIG. 2;

FIG. 5 is another transverse, vertical, sectional view of the spray gun taken as indicated by the line 55 in FIG. 2;

FIG. 6 is a fragmentary view of the spray gun showing the spray cap or tip adjacent the discharge orifice thereof and the forward end of the hollow, reciprocable, valve needle in the relative positions in which these parts are disposed during normal spraying operations;

FIG. 7 is a view similar to FIG. 6 but showing the parts in the relationship which they occupy when the valve needle is seated in the discharge orifice to close the same and to close the passageway through the valve needle itself;

FIGS. 8 and 9 are similar to FIGS. 6 and 7, respectively, but show a modified form of the deformable, open, forward end of the valve needle;

FIG. 10 is a fragmentary, perspective view of the modified valve needle shown in FIGS. 8 and 9.

As shown in FIG. 1 of the drawing, pressure receptacles 7 and 8 are provided with hermetically sealed covers 9 and 10, respectively, for holding two supplies of different coating composition liquids under pressure for feeding them to a spray gun. Gas pressure is supplied to the receptacles through a gas supply line 11, a pressure reducing valve 12, a conduit 13, and branching conduits 14. The line 11 may be connected to a compressor or other suitable source of air pressure or inert gas pressure (not shown). The supply of gas pressure to the receptacles 7 and 8 is preferably such that they are both under a common pressure, as shown.

The coating composition liquids in the receptacles 7 and 8 are applied to a surface to be coated by means of a tool 15 resembling an ordinary spray gun in its outside appearance, but differing from an ordinary gun as regards the apparatus for supplying the coating liquids thereto and certain details of construction for controlling the flow of the coating liquids thereto and through the spray gun. Except for such differences, the structural details of the spray gun may be conventional, and the invention is illustrated herein as applied to a typical spray gain modified in the respects mentioned above. Accordingly, it will be unnecessary to describe with detailed particularity the well known features of the gun shown in the drawings for illustrative purposes.

Referring particularly to FIGS. 2-5, the gun shown therein may comprise a main body portion 16, having a nozzle and air cap assembly, generally designated 17, mounted on the forward end thereof, and being appropriately formed to provide a handle portion 18 integral with the main body portion of the gun. The gun may also comprise a valve actuating lever or trigger 19 connected to the main body of the gun for actuating the liquid and air control valves hereinafter described.

The handle portion 18 of the main body of the gun illustrated herein defines a gas passage 20 connected by a flexible conduit 21 to the gas supply line 11 through the pressure reducing valve 12. This valve is preferably so constructed that the pressure delivered to the conduit 21 is greater than that delivered to the conduit 13 supplying the receptacles 7 and 8. Alternatively, if preferred, two pressure reducing valves may be employed for maintaining this pressure differential. I have found that excellent results are obtainable with the present invention by employing air pressure of the same order of magnitude commonly employed heretofore in the prior art methods and apparatus referred to above, the specific pressures employed being varied in accordance with variations in the viscosity of the coating liquids employed and other considerations well understood by those skilled in the art.

The passage 20 in the handle portion 18 of the main body of the gun communicates with a second gas passage 22, which in turn communicates through a port 23 with the rear portion of a bore 24 extending longitudinally through the upper portion of the main body 16. A normally closed, main, gas shut-off valve 25 is interposed in the passage 22 and engages the trigger 19 for opening movement of the valve against an opposing spring upon retraction of the trigger.

The longitudinal bore 24 opens at the rear end of the main body 16 to receive a tube 26, which is threadedly engaged at its forward end with the main body 16 forwardly of a gas distributing port 27. The port 27 opens into the bore 24 exteriorly of the tube 26.

The forward end of the tube 26 communicates with an orifice 28 leading into a chamber 29 formed by the forward end of the main body 16. Gas under pressure is supplied through the tube 26 to the chamber 29, as regulated by a gas valve 31 at the forward end of this tube, and the gas under pressure is delivered from the chamber 29 through a chamber extension 32 defined by the air cap assembly 17, and thence into passages 33 in an air gap 34, from which it is discharged through openings 35 directed diagonally forwardly toward the longitudinal axis of the gun orifice. For convenience, this axis is commonly designated the longitudinal axis of the gun.

A portion of the gas from the port 23 bypasses the valve 31 and flows forwardly through the bore 24 exteriorly of the tube 26 to the distributing port 27 and thence into a chamber 36 defined by the main body portion 16 of the gun. Gas entering the chamber 36 then flows forwardly into an annular chamber 37 defined by the air cap 34, and is discharged through any desired inner array of openings 38. The openings 38 are also directed diagonally forwardly toward the longitudinal axis of the gun.

A main liquid chamber 41 is formed by a bore into the forward end of the main body 16 and by a tubular extension 42 threaded into this bore. The forward end of the tubular extension 42 converges forwardly toward the longitudinal axis of the gun, the converging portion defining a nozzle terminating in a restricted discharge orifice 43 having its axis coincident with the longitudinal axis of the gun. The discharge orifice 43 is controlled by a valve head 44 carried by a stem or needle 45 that extends rearwardly and coaxially with the orifice 43 into operative engagement with the trigger l9 and rearwardly therebeyond in the form of an enlarged plunger 46. The rear end of the plunger 46 engages a compression spring 47 that normally urges the valve head 44 forwardly into closing engagement with the orifice 43 and also urges the trigger 19 toward its normal retracted position. The unretracted position of the trigger is shown in FIGS. 1 and 2, with the orifice 43 closed by the valve head 44 and with the main gas shut-ofii valve 25 also in its closed condition.

The main liquid chamber 41 of the gun is connected in a conventional manner to receive one of the plurality of liquids from one of the receptacles 7 and 8. As shown in FIG. 1, it is connected to the receptacle 7 for this purpose by means of an inlet passage 48 communicating with the rear end of the chamber 41, a coupling 49, a rigid tube 50, a suitable, manually operable flow adjusting valve 51, a coupling 52, a length of flexible hose 53, and a coupling 54 connected to a rigid tube 55. The rigid tube 55 may suitably be provided with a manually operable shut-off valve 56, and the tube extends through receptacle cover 9 in sealed relationship therewith to near the bottom of the receptacle 7.

The hollow needle 45 is connected to receive a second liquid from the other receptacle 3. For this purpose it is provided with a generally cubical collar 57 having a bore extending therethrough axially of the gun to receive the needle to which the collar may be secured and sealed, as by welding. A transverse bore 58 is drilled into the collar 57 from one side thereof and through the Wall of the needle 45 to the hollow interior thereof, and an elbow fitting 59 is connected to the collar 57, as by welding, for feeding liquid through the fitting and the transverse bore 58 into the interior of the needle for flow therethrough to the valve head 44 at the forward end thereof. The elbow fitting is connected to the receptacle 8 by a coupling 64 a short length of flexible hose 61, a coupling 62, a manually operable flow adjusting valve 63, a coupling 64, a length of flexible hose 65, and a coupling 66 to a rigid tube 67, having a shut-off valve 68 interposed therein, the tube 67 extending into the receptacle 8 in the same manner as described with reference to the tube 55 and receptacle 7.

In order to lend support to the rigid tube 50 and flexible tube 61 and associated flow control valves 51 and 63, a strap or brace 69 is suitably shaped and drilled to freely receive three threaded nipples or the like, such as the nipple '71 for the air hose 21, which may be respectively threaded into the lower ends of the valves 51 and 63 and into the gun handle 18. The lower ends of such nipples, projecting through the brace 69, may respectively receive the couplings 52 and 64 for the liquid hoses 53 and 65 and a similar coupling 79 for the air hose 21. Tightening of these last-mentioned couplings on the respective nipples and against the brace 69 rigidifies the assembly and prevents any pull of the long hoses 53 and 65 from unduly stressing the parts of the assembly between the brace and the main body of the gun.

Referring finally to the details of the valve head 44 at the forward end of the needle, it may take any of a variety of forms, such as the hollow, tubular shape shown in FIGS. 6 and 7. This form of valve head, has a frustoconical forward portion adapted to project through the orifice 43. When the valve head of this shape is made of a suitably soft elastomeric substance, such as a synthetic rubber resistant to coating composition vehicles, it is easily squeezed so as to close the passage therethrough when forcibly moved forwardly into engagement with the wall of the orifice 43, as shown in FIG. 7. When the valve head 44 is pulled rearward, by retraction of the gun trigger 19, to the position relative to the nozzle orifice 43 shown in FIG. 6, the passage through the valve head opens, by the inherent elasticity of the material, to

6 its normal tabular form, allowing liquid supplied to the needle 45 to be discharged through the orifice.

The orifice head 44 may suitably be separately molded and held in place on the forward end of the needle 45 by means of a peripheral rib and groove interlock 72, with the aid of an adhesive over the mating surfaces of the valve head and needle. Alternatively, the valve head 44 may be molded in place on the end of the needle 45.

The valve head, by way of a further example, may take the form shown in FIGS. 8, 9, and 10.. This form of valve head, designated 44a, is also a hollow tubular shape made of a suitably soft elastomeric substance. The forward end portion of the valve head 44a has a pair of opposed flat surfaces 73 that are joined by a curved end surface 74 and a pair of opposed cylindrically curved side surfaces 75. When this form of valve head is forcibly held in engagement with the inner surface of the nozzle adjacent the orifice 43, as shown in FIG. 8, the passage through the valve head is closed, as indicated in FIG. 8, by a pinching action exerted substantially in the four directions indicated by arrows 11-11 and b-b in FIG. 10.

Obviously other configurations of the valve head on the needle 45 can be employed to achieve a similar, opening and closing, pinching action as the trigger 19 is retracted for spraying and is released for shutting off the flow of both of the coating liquids and the atomizing air. In accordance with the invention, as indicated above, the purposes of the design of the valve head are to close the orifice 43 and the central passage of the needle 45 substantially simultaneously when the trigger 19 is released, and to open both the orifice 43 and the passage through the needle 45 substantially simultaneously when the trigger 19 is retracted to produce the desired composite spray, while positioning the discharge tip of the valve head closely adjacent the orifice and within the converging nozzle portion of the tubular extension 42.

The apparatus of the invention may be operated in the following manner to perform the method and produce the improved results thereof. Assuming that the containers 7 and 8 are filled with different liquid coating compositions to a level well above the lower ends of the rigid tubes 55 and 67, air pressure of, for instance, about 30 p.s.i. is applied to the upper surfaces of the liquids in the containers by adjustment of the reducing valve 12, and a higher pressure is delivered to the spray gun through the flexible hose 21. The operator grips the gun by the handle portion 18, directs the nozzle toward the surface to be coated, positions it the requisite distance from such surface, as determined by experience, and retracts the trigger 19, moving it to the right as viewed in FIGS. 1 and 2. This action of the trigger 19 opens the air valve 25, permitting a flow of air under pressure to the several air orifices 35 and 38 defined by the air cap 34 itself and jointly by the air cap and the nozzle portion of the tubular extension 42. The needle 45 and its valve head 44 or 44a are retracted to open the orifice 43 and the passage through the needle and its valve head. The air pressure delivered to the receptacles '7 and 8 forces the two different coating liquids to the gun through the separate conduit assemblies described above, and these liquids are respectively admitted into the gun through the inlet passage 48 and the elbow fitting 59. The liquid entering at the passage 48 surrounds the needle 45 and valve head 44 or 44a as it flows toward the orifice 43. The liquid entering through the elbow fitting 4) flows forwardly through the hollow needle 45 and its valve head 44 or 44a and is discharged from the latter close to and axially through the center of the orifice, as a central stream, While the other liquid merges with it and flows through the orifice as a substantially concentric outer annular stream.

The resulting composite stream issuing from the orifice 43 obviously has little or no opportunity for distortion of the two stream components or for blending of one with the other before the composite stream is disrupted and atomized by collision with the air jets from the air orifices 35 and 38. As a result, substantially uniform conditions of the resulting spray are maintained throughout a spraying operation, producing the desired greater uniformity and reproducibility of a spatter finish coating applied to the surface or surfaces being coated.

The sizes of the droplets of the different coating liquids produced in the spray issuing from the gun, as will be well understood by those skilled in the art, are determined to some extent by the viscosities of the two liquids. The relative proportions or quantities of the two liquids in the spray are also affected by the liquid viscosities and by any restriction of the passages through which the liquids are conducted to the orifice'43. Various pattern effects may be obtained by adjusting the viscosities of the two liquids and changing the restriction of the passage through which the liquids flow by adjustment of the valves 51 and 63, and by varying the several other adjustments of the apparatus as a whole that are conventional in equipment of the general character shown and described, as well as by varying the visual differences between the coating liquids to produce differences in color, gloss, etc., between the contrasting portions of the resulting coating. As will be appreciated from the foregoing description of the method and apparatus of the invention, the uniformity and re producibility of the resulting coatings achieved by the invention are substantially unaffected by changing the several variables to produce a desired effect.

In addition to the improvements in the resulting coatings obtained as herein described, the invention provides simple, reliable, and inexpensive modifications of a conventional, single component, spray gun for introducing a plurality of coating liquids into the gun and separately conducting the liquids to the gun orifice for combination as described. The flow of both liquids is initiated and terminated at'the gun orifice itself, so that no blending of the liquids can occur within the gun during brief idle periods. The liquid supplied through the reciprocatable needle 45 is admitted thereto by simple modification of the needle at an exposed and accessible portion immediately ahead of the trigger 19, so as to require no sliding or rotating valves for the purpose or other modification of the structure of the gun body itself. The short length of flexible hose 61 interposed between the flow control valve 63 and the elbow fitting 59 permits the needle 45 to be reciprocated substantially without interference from the liquid conduit structure connected thereto.

While the invention has been illustrated and described herein with reference to particular exemplary apparatus,

it will be appreciated that the details of the apparatus, as

well as of the method carried out therewith, may be varied without departing from the principles of the invention or the proper scope of the appended claims.

What is claimed is:

1. In spray gun apparatus comprising a gun body de fining a liquid receiving chamber, a liquid discharge nozzle at a forward end of the chamber, said nozzle converging axially and forwardly toward a terminal orifice opening in a plane normal to the axis of the nozzle, a liquid inlet opening into said chamber at a point rearwardly of said nozzle, a valve in the form of a needle extending forwardly through said chamber axially of said nozzle and having a forward end normally seated in closing engagement with said orifice, said needle being reciprocable for opening and closing the orifice, air passages through said body terminating in openings disposed to direct atornizin-g jets of air forwardly into the discharge path of said orifice, a second valve for controlling the admission of air to said air passages, and manual control means movable for opening and closing both of said valves; the improvement wherein said valve needle is a hollow tube open at its forward end, and the open forward end of the needle, when fully retracted, is disposed within said nozzle between said plane of the orifice opening and a plane at which the nozzle begins to converge so as to define a passageway for flow of a first liquid from said chamber into the converging portion of said nozzle toward the orifice as an annular stream surrounding said needle, said forward end of said needle being a soft, elastically deformable material shaped to engage said nozzle adjacent said orifice with a pinching action for elastically deforming and closing the open end of the needle when it is normally seated in closing engagement with said orifice, said apparatus additionally including means for introducing a second liquid into said tube rearwardly of said nozzle for discharge from the forward open end of the tube, whereby said two liquids approach the orifice as an annular stream of the first liquid surrounding a central stream of the second liquid and separated therefrom by a physical barrier terminating adjacent the orifice.

2. The improvement of claim 1 wherein said gun body defines a rear wall of said liquid receiving chamber, the tube constituting said valve needle projects rearwardly through said rear wall in sealed relationship therewith to provide an exposed length of the tube, a fitting is connected to said exposed portion of the tube for introducing said second liquid into the tube, said fitting being reciprocable with said needle and having a length of flexible conduit having one end connected thereto for delivering liquid through the fitting into the tube, the opposite end of said flexible conduit being rigidly connected to said gun body with the flexible conduit disposed to flex with reciprocation of said fitting, and said valve needle projects rearwardly beyond said fitting to a mechanical connection between the valve needle and said gun body for reciprocating the needle relative to the gun body to open and close the forward end of the needle and said orifice simultaneously.

References Cited in the file of this patent UNITED STATES PATENTS 1,268,232 Furman June 4, 1918 1,462,020 Murray July 17, 1923 2,261,531 Thomas Nov. 4, 1941 2,511,626 Einbelker June 13, 1950 2,864,653 Liedberg et al Dec. 16, 1958 FOREIGN PATENTS 566,543 Great Britain Jan. 3, 1945 787,269 Great Britain Dec. 4, 1957

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