US 3773263 A
This atomizing head for paint spray-gun is of the type wherein the front face is designed for utilizing the action of wall effect for directing the lateral air jets and thus wrap and flatten the axial paint jet.
Description (OCR text may contain errors)
United States Patent Binoche Nov. 20, 1973 PAINT SPRAY-GUN HEAD Prima Examiner-M. Henson Wood Jr. 75 I ntor: Michel G. B noche Paris, France ry 1 me I Assistant ExaminerM1chael Mar  Assignee: S.K.M., Stains, France Attorney-Amster & Rothstein 22 Filed: Jan. 14, 1972  ABSTRACT 1  Appl' 217742 This atomizing head for paint spray-gun is of the type wherein the front face is designed for utilizing the ac-  US. Cl. 239/296, 239/544 tion of wall effect for directing the lateral air jets and  B05b l/04 thus wrap and flatten the axial paint jet.  Field of Search 239/290, 291, 296, The structure of this head is such that at least one 239/544 7 fraction of these lateral jets develops on its front face and symmetrically in relation to its central aperture  References Cned limiting the axial paint jet, so as to surround same UNITED STATES PATENTS completely. 3,463,395 8/1969 Binoche 239/296 X N paint d it takes place during the operation of 1,751,787 3/1930 Bmks 239/299 this head so that it constantly remains very clean. 2,646,314 7/1953 Peeps 239/296 3,062,483 11/1962 Davidson 239/DIG. 7 4 Claims, 15 Drawing Figures I lllllllllllllll PAINT SPRAY-GUN HEAD BACKGROUND OF THE INVENTION The present invention relates in general to paint spray guns and has specific reference to an improved atomizing head therefor.
Conventional atomizing spray heads comprise a central nozzle for the paint driven or carried along by a concentric annular jet of compressed air. This axial jet or spray of paint and compressed air is flattened by a pair of lateral air jets delivered from diametrally opposite points so as to atomize the paint in the form of a flat jet more convenient for rapidly coating the surfaces to be painted.
In conventional paint spray-gun heads these lateral air jets are supplied through vent holes formed in the atomizing heads and the latters are frequently provided to this end with orifices; this relatively simple arrangement may prove adequate in the case of relatively moderate paint outputs and jet widths, although said vent holes must be drilled with a considerable degree of precision; however, it is not satisfactory whenever it is desired to obtain relatively wide paint jets and considerable paint outputs with a suitable atomization thereof. In fact, in this case the action of said lateral vent holes must be complete by many auxiliary jets delivered through generally smaller orifices and therefore these smaller orifices must be drilled with greater accuracy than the preceding ones. Now these vent holes are difficult to drill since they require the use of large-size machines having a high degree of precision, and on the other hand said smaller vent holes are frequently choked in operation and this constitutes a cause of jet unbalance, of serious impairment in the paint quality and also of frequent hold-ups leading therefore to a decreased efficiency.
These inconveniences have already been avoided to a considerable extent notably through the use of the paint spray-gun head disclosed in the French Patent No. 1,473,093 and wherein said vent holes are replaced by grooves formed in the front surface of the atomizing head, the so-called wall-effect being used for directing the lateral air jets supplied to the upstream end of said grooves towards the main axial jet of paint.
Now although the risk of choking these grooves is eliminated, in contrast to the vent holes of the preceding structures, the presence of these grooves is not sufficient for eliminating completely the undesired deposits of paint on the paint spray-gun head, which deposits may tend at any time to be carried along by the air jet and be projected against the article or surface being painted, so as to render this article or surface useless or at least impair its quality.
The afore-mentioned deposits are due to the fact that the two lateral jets developing freely in the atmosphere as they emerge from the vent holes or grooves meet each other and produce eddies and even countercurrents with the possibilities of returning these jets against the front face of the spray head, thus carrying along the paint and causing the latter to be deposited thereon. This effect can be understood more clearly if we consider the butterfly shape of the burner of an acetylene lamp; in this burner two convergent jets of acetylene impinged against each other like the jets from the lateral vent holes of the paint spray-gun head; now the flame formed at the outlet of said butterfly burner constitutes a close approximation of the jet shape obtained by causing two elementary jets to converge towards each other; in fact, it will be seen that the major fraction of the acetylene is rejected below the meeting point of the two jets by the eddies formed thereby.
The same phenomenon, although of lesser amplitude, is observed during the operation of the atomizing heads according to the aforesaid French Patent No. 1,473,093.
SUMMARY OF THE INVENTION It is the essential object of the present invention to provide a paint spray-gun head of the type broadly set forth hereinabove and notably in the aforesaid French Patent, but designed to positively prevent any soiling thereof.
To this end, this atomizing or spray head designed for utilizing the so-called wall effect for properly directing the lateral air jets towards the axial or central paint jet, is characterized in that its structure is such that at least one fraction of said jets develop on its front surface, symmetrically in relation to its central opening limiting the axial paint jet, and surrounds completely said axial jet.
Thus, this axial paint jet is properly surrounded in a perfectly symmetrical fashion by the air jets, so that on the one hand the paint jet is suitable flattened and balanced, with a regular distribution of the paint feed therethrough, and on the other hand the lateral ends of this jet are well shaped and adequately atomized.
According to a preferred form of embodiment of this invention, said lateral jets are obtained by means of grooves formed to this end in the front surface of the spray head. Moreover, these grooves may terminate at a relatively substantial distance from the central, jetforming orifice. The width of said grooves may be greater than the diameter or width of said central orifice, and their depth may decrease towards said central orifice. Consequently, and in any case, these grooves may be so designed that the jets be spread over the front face of the spray head while surrounding completely said central orifice.
According to a modified form of embodiment of this invention, said lateral jets are obtained by means of vent holes adapted to direct symmetrical air jets towards the front face of the atomizing head, at a relatively great distance from its axis, tangentially to said front face or slightly incident thereto, and develop as a consequence of the impingement of said lateral air jets against said front face of the spray head. The building up of the paint jet may be further improved as well as the air sheet enveloping it by using not a pair of symmetrical grooves or vent holes, but two or more pairs of grooves or vent holes.
Experience teaches that a spray-gun head comprising two pairs of grooves inclined to an angle 20: 30 (FIG. 2 of attached drawing) delivers a flat paint jet producing a proper atomization, a satisfactory paint distribution in the jet and eliminating any soiling of the head itself. It is the equivalent of extremely elaborate heads designed on the basis of the conventional system, the shrouding effect on the control jet, obtained by spreading one fraction of the air jet over the head surface, being considerably more accentuated than what is observed when using a single pair of grooves.
Without providing further correcting grooves it is also possible to obtain different jet characteristics by modifying certain parameters of these double grooves, such as the width 21 of grooves 18 to (FIG. 2c), the groove angle 20: (FIG. 2b), the position of their point of convergence :1 (FIG. 2c).
For instance, given the same dimensions of the outlet orifices and d 0, a thicker, narrower jet was obtained with an angle 2a 45 than with an angle 20: with 2a 15, the jet is thinner and wider but it has a tendency to display undesired breaks therein.
In another case it was observed that with a high atomizing pressure the paint jet tended to become divided into three sections. This effect had already been observed with conventional heads; the jet is somewhat thicker at its central and marginal portions.
In this case, the jet can be improved by increasing 1, reducing a and giving a negative value, i.e., below 0, to d.
Alternatively, other parameters may be modified, for example the curvatures at the bottom of the grooves, in the vicinity of the central orifice, and in their intermediate portions, the value and shape of the crosssectional contour as well as the variations in width and height of these grooves in the downstream direction.
In the case of heads producing jets of relatively great width and operating with compressed or atomizing air under a relatively high pressure, a still better result may be obtained by utilizing three pairs of grooves.
Finally, as the downstream ends of the grooves supplied with the lateral air jets may be relatively remote from the axis of the spray-gun head, these grooves, instead of being formed or machined in the head surface, or consisting of ribs carried by the head so as to limit these air jets laterally, may be replaced by millings in the rings or annular nuts provided for fastening the head to the spray-gun or other spraying apparatus constituting the rear extensions of said head. These millings are adapted to direct lateral air jets towards the spraygun head having in this case a convex front face which, if desired, may be completely of revolution so as to be lighter in weight and more economical to manufacture.
BRIEF DESCRIPTION OF THE DRAWING The attached drawing illustrates diagrammatically by way of example a few typical forms of embodiment of the invention, in which:
FIG. 1 is side elevational view of a spray-gun with its atomizing head shown in axial longitudinal section;
FIG. 1a is a front elevational view and FIG. 1b a plan view from above of the head incorporated in the assembly of FIG. 1;
FIG. 2 is an axial sectional view showing on a larger scale a modified form of embodiment of the head;
FIGS. 2a, 2b, 2c are front views showing different forms of embodiment of the head of this invention;
FIG. 3 is a section similar to FIG. 2 showing another modified form of embodiment of said head;
FIGS. 4 and 4a are an axial sectional view and a front view, respectively, of another form of embodiment of the spray-gun head;
FIGS. Sand 5a are a sectional view and a front view, respectively, of anothe form of embodiment; I
FIGS. 6 and 6a are corresponding views of another head construction;
FIG. 7 is a sectional view of a different form of embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENT The paint spray-gun 1 illustrated in FIG. 1 is of conventional construction and comprises a central device 2 through which-the paint is carried along by a concentric air jet directed to a chamber 3 surrounding the device 2 and then through an annular central orifice formed in the atomizing head 4 concentrically to said device 2 and secured to the front portion of the spraygun by a ring nut 5.
The atomizing head 4 illustrated in FIGS. 1a and 1b comprises a spherical zone 4a in which the pair of symme-tric grooves 6 and 7 opposed on a common diameter are milled and extend to a relatively great distance 8 from the central orifice 8 through which the paint-carrying air jet is directed.
Thus, the wall effect continuing towards the axis of the spray-gun head, the lateral air jets are somewhat spread on the head and surround the central jet loaded with paint particles, all around the central orifice, so as to convert said paint jet into a flat jet and prevent the deposition of any trace of paint on the head proper; in fact, this paint jet is extremely regular and homogeneous, as long as relatively moderate values are used for the jets of atomizing air.
In the modified form of embodiment illustrated in FIG. 2 this result is improved in that the head 10 comprises a pair of diametrally opposed grooves 11, 12 gradually decreasing to zero because the height of the walls limiting these grooves laterally decreases gradually from their root to their end relatively remote from the central orifice 13.
With this arrangement, a regular and homogeneous jet can be preserved with higher pressures of the atomizing air jets, since a lesser volume of air if retained by the walls and the action exerted by the lateral jets on the main central jet is moderate in relation to this action in the case of FIG. 1. I v This head is fitted in an intermediate ring 14a of which the radial play in relation to the fastening ring 14 permits of absorbing a possible out-of-centre of the screw-threads of the spray-gun with respect to the nozzle to which the atomizing head is secured.
The intermediate ring 14a is retained within the fastening ring 14 by a resilient ring or circlip 15 engaging to this end a groove 16 formed in said ring 14.
The atomizing heads illustrated in FIGS. 2a, 2b and 2c differ essentially from that illustrated in FIG. 2 by the fact that instead of comprising a single pair of groove 10, 11, they comprise each two pairs of grooves 17, 18 and 19, 20 disposed symmetrically in relation to a diametral plane of symmetry of the atomizing head; these pairs of grooves 18-20 may converge to a point disposed short of the central annular sperture 21 of the atomizing head 22 (d 0), as shown in FIG. 2a, or this point may coincide with the axis of said central aperture 21 (d 0), as shown in FIG. 2!), or lie beyond this axis (d 0), as shown in FIG. 2c.
The atomizing head illustrated in FIG. 3 differs from that shown in FIG. 2 in that the height of the groove walls if reduced to zero at a relatively short distance from the central orifice. This arrangement is preferred in case the diameter of the central orifice is inferior to the groove width in order to ensure a proper spreading of the lateral air jets all around the central orifice.
If it is desired to use grooves considerably wider than the central orifice, said grooves may extend as far as said central orifice where they meet so as to form on the front surface of the atomizing head just a continuous groove extending from edge to edge, with said orifice in its intermediate portion. In this case, the residual height of the groove in this intermediate portion should remain relatively moderate to avoid any interference in the flattening of the paint jet in an axial plane perpendicular to the groove.
In the form of embodiment illustrated in FIGS. 4 and 4a the spray-gun head 23 is entirely of revolution and free of any groove; the grooves of the preceding forms of embodiment are replaced by diametrally opposite millings 24, 25 formed in the outer ring 26 constituting in this case the rear extension of the head, said ring being retained in position by a mounting nut 27 and a circlip or like resilient member 28.
Instead of a single pair of milled notches formed in the outer ring 26 as illustrated in FIGS. 4 and 4a, the head 29 may also comprise two pairs of symmetric millings 24, 25 and 24a, 25a formed in the outer ring 29a and converging to the axis of the central orifice 30, as shown in FIGS. 5 and 5a. Of course, also in this case these milled notches could extend to a point of convergence located either before or beyond the axis of said central orifice, as explained hereinabove with reference to FIGS. 2a, 2b and 2c; if desired, a number of grooves or millings greater than two, for instance three, may be contemplated, which are disposed symmetrically about a pair of central grooves or millings.
In the form of embodiment illustrated in FIGS. 6 and 6a, the atomizing head 31 is completely of revolution as in the preceding cases, without any groove, but the millings formed in lieu thereof, which in the last instances had been formed in the outer ring 26 or 29a, are replaced by vent holes or orifices not liable to become choked, in contrast to conventional atomizing heads, for on the one hand they are located at a relatively great distance from the central atomizing orifice, and on the other hand the two pairs of vent holes or orifices 32, 32a and 33, 330 are formed in the ring 34 so as to direct their jets in such a way that these jets impinge with a certain incidence or at least tangentially on the front convex surface of the head 31; under these conditions, as in the case of FIGS. 5 and 5a, the lateral jets are properly spread on the head surface all around the central orifice, and the central jet of paintentraining air is wrapped completely as it emerges from said central orifice, thus safely protecting this head from any tendency to become soiled.
Possibly, as illustrated in FIG. 7, these vent holes may be arranged for distributing a plurality of jets of which some are either incident or tangential, as already explained in the foregoing, the others being directed towards a point located at a certain distance beyond he apex of the atomizing head, and provided that a sufficient air output is delivered by he first vent orifices, satisfactory results may be expected.
Of course, various modifications and variations may be brought to the specific forms of embodiment described and illustrated herein by way of illustration, without inasmuch departing from he spirit and scope of the invention as set forth in the appended claims.
What I claim is:
1. In a paint spray-gun or the like device for spraying paint onto a surface, an atomizing head of the type comprising a central aperture delivering a main central jet of air compress-loaded with or entraining paint particles with lateral means for channelling auxiliary air jets towards the axis of said main central jet in order to flatten, wrap up and widen the paint jet, notably with the assistance of the so-called wall effect, wherein said lateral means include grooves which are at a relatively substantial distance from said central aperture, diametrally opposed, and adapted to cause the auxiliary air jets to develop on he front surface of the head, symmetrically in relation to said central aperture limiting the axial paint jet, and thus surround completely said axial paint jet, and wherein said grooves are formed in said front surface to constitute at least two symmetrical pairs of grooves disposed themselves symmetrically in relation to said central aperture wherein each pair of adjacent grooves converge towards the axis of the atomizing head.
2. An atomizing head according to claim 1 wherein the grooves of each pair of adjacent grooves form with each other an angle of about 30.
3. In a paint spray-gun or like device for spraying paint onto a surface, an atomizing head of the type comprising a central aperture delivering a main central jet of air compress-loaded with or entraining paint particles with lateral me ans for channelling auxiliary air jets towards the axis of said main central jet in order to flatten, wrap up and widen the paint jet, notably with the ssistance of the so-called wall effect, wherein said lateral means include grooves which are at a relatively substantial distance from siad central aperture diametrally opposed, and adapted to cause the auxiliary air jets to develop on the front surface of the head, symmetrically in relation to said central aperture limiting the axial paint jet, and thus surround completely said axial paint jet, and wherein said grooves are formed in said front surface to constitute at least two symmetrical pairs of grooves disposed themselves symmetrically in relation to said central aperture wherein each pair of adjacent grooves converge to a point located before the axis of said head.
4. In a paint spray-gun or like device for spraying paint onto a surface, an atomizing head of the type comprising a central aperture delivering a main central jet of air compress-loaded with or entraining paint particles with lateral means for channelling auxiliary air jets towards the axis of said main central jet in order to flatten, wrap up and widen the paint jet, notably with the assistance of the so-called wall effect, wherein said lateral means include grooves which are at a relatively substantial distance from said central aperture, diametrally opposed, and adapted to cause the auxiliary air jets to develop on the front surface of the head, symmetrically in relation to said central aperture limiting the axial paint jet, and thus surround completely said axial paint jet, and wherein said grooves are formed in said front surface to constitute at least two symmetrical pairs of grooves disposed themselves symmetrically in relation to said central aperture wherein each pair of adjacent grooves converge to a point located beyond the axis of said head.