US3463395A

US3463395A - Spray gun nozzle heads

Info

Publication number: US3463395A
Application number: US606798A
Authority: US
Inventors: Michel L Binoche
Original assignee: S K V
Current assignee: S K V
Priority date: 1966-01-06
Filing date: 1967-01-03
Publication date: 1969-08-26
Anticipated expiration: 1986-08-26
Also published as: DE1575057A1; FR1473093A; GB1163033A

Description

g 26, 1959 M. L. BINOCHE 3,463,395

SPRAY GUN NOZZLE HEADS 2 Sheets-sheet 1 7 Filed Jan. 5, 1967 w M m fl 3 M m 2 3 g 4 1 W 2 Cl cl 8. M M m 6, 1969 M. L. BINOCHE 3,463,395

SPRAY GUN NOZZLE HEADS Filed Jan. 5, 1967 2 Sheets-Sheet 2 United States Patent 3,463,395 SPRAY GUN NOZZLE HEADS Michel L. Binoche, Paris, France, assignor to S.K.V., Societe Anonyme, Stains, Seine St. Denis, France, a French company Filed Jan. 3, 1967, Ser. No. 606,798 Claims priority, application France, Jan. 6, 1966,

Int. on. Bush 5/08, 1/26 U.S. Cl. 239-15 7 Claims ABSTRACT OF THE DISCLOSURE This invention relates in general to pneumatic spray guns of the type used for applying paints and varnishes, and specifically to an improved nozzle head for spray guns of this type.

More particularly, it is known that the most popular method in the art of spraying paints or the like by means of compressed air consists of utilizing a jet of paint sucked by a vacuum effect of a concentric jet of compressed gas.

In this conventional method the paint is delivered through an orifice, usually of circular cross-sectional configuration, located at the outlet end of a paint spray nozzle; the paint is sucked by the vacuum effect produced in the nozzle orifice by the compressed gas which forms a concentric jet; however, if desired, the nozzle may be fed with paint under pressure.

This method utilizes as a rule, a pair of lateral jets issuing from the vent holes disposed in ears of the spray nozzle head; the function of these lateral jets is to flatten the jet of atomized paint, this flat shape of the jet of paint being more convenient for rapidly coating the surfaces to be painted.

it is relatively easy to carry out this method in the case of moderate outputs and spray widths, although it requires very accurately bored vent holes. On the other hand, when it is desired to obtain considerable outputs and relatively wide jets, many auxiliary jets must be used for correcting the defects of the simple device broadly described hereinabove.

As a consequence, the manufacture of spray nozzle heads requires the precision boring of a large number of small vent holes.

The spray nozzle head according to this invention, which avoids the drawbacks set forth hereinabove, is characterized in that it is designed with a view to utilize the so-called Wall effect for producing the lateral jets of compressed air which are necessary for flattening the jet of atomized paint.

This well known effect may be briefly described as follows:

A jet of compressed air or gas is directed substantially tangentially towards the bottom of a convex groove. By induction it tends to create a vacuum in the space extending from this jet to the bottom of the groove. This vacuum deflects the jet of compressed air which thus follows the bottom of said groove. Now the shape and direction of the air jet depend on the shape and direction of the groove at the point of emergence of the jet.

To obtain this result, the atomizing head according to this invention comprises on its front portion a cap or a set of ears providing an axial passage for the jet of paint entrained by the jet of compressed air, this cap or this set of cars being provided on their front face with lateral grooves adapted to receive in their rear portion a tangent auxiliary air jet, the front portion of :said grooves being directed as a function of the direction of the jet of paint. Specifically, the cap may be of spherical configuration and formed with a pair of symmetric grooves disposed on a common great circle of the cap.

In order to afford a clearer understanding of this invention and of the manner in which the same may be carried out in practice, reference will now be made to the accompanying drawings illustrating diagrammatically, by way of example, two typical forms of embodiment of the invention.

In the drawings:

FIGURE 1 is a longitudinal cross-sectional view showing a first form of embodiment;

FIGURE 2 is a cross-sectional view taken upon the line IIII of FIGURE 1;

FIGURE 3 is a cross-sectional view similar to FIG- URE 1, showing another form of embodiment;

FIGURES 4 to 7 inclusive are cross-sectional views illustrating modified details of the cap member;

FIGURE 8 is a perspective view showing another possible form of embodiment of the atomizing head; and

FIGURES 9 and 10 are cross-sectional views illustrating other possible forms of embodiment of these atomizing heads.

In the first embodiment illustrated in FIGURE 1 of the drawings the body 1 of a spray gun has screwed thereon a paint nozzle 2 connected to an atomizing or spray head 3 by means of a retaining ring nut 4.

The atomizing or spray nozzle head 3 is convex, for example semispherical; the ring nut 4 has a part-spherical inner face corresponding to this head for properly holding same.

The body 1 is arranged to permit the ejection of paint through the paint nozzle 2 and comprises two

compressedair inlets

6, 7 feeding, respectively, a pair of

circular grooves

8 and 9 concentric to the paint nozzle; in the outer surface of the spray nozzle head 3 a pair of grooves 10 symmetric in relation to the axis of the spray head, is formed; the lower end of these grooves open into the circular groove 9 and, as already explained herein-above, the air jet from groove 9 follows the bottom of groove 10 and leaves this groove 10 with an angle at with respect to the spray axis. This angle is variable according to the desired effect or result.

In the embodiment illustrated in FIGURE 3 the spray nozzle head is very similar to those shown in FIGURE 1; therefore, the same reference numerals designate the corresponding elements of the spray nozzle head. It differs therefrom only in that the spray nozzle head 11 comprises a shoulder 12 adapted to lock the ring nut 13, so that the inner part-spherical surface of the ring nut 4 of FIGURE 1 may be dispensed with.

The use of these spray nozzle heads wherein the jet is deflected by the wall effect permits solving a problem having hitherto caused many difficulties with conventional ear-type heads. To ensure a uniform flattening of the jet of paint, the width of the lateral jets must be sufficient to act upon the whole of the central jet; otherwise the central jet might be cut and divided into two branches.

To this end, the action of convergent auxiliary jets is used in combination with the main lateral jets, for flattening the last-named jets before they engage the central jet.

With the groove system a flat jet having the width and shape consistent with the desired object can be obtained. The simplification thus achieved is considerable in comparison with a system comprising only bored vent holes. These orifices of very small diameter and requiring a high degree of precision are always difficult to make at the proper angles and positions; thus, slight defects, clogging or damages (frequently resulting from attempts at clearing these orifices) may considerably modify the jets of compressed air and thus introduce a state of unbalance in the operation of the device. Grooves are sturdier and easy to clean; their shape is adapted to the desired configuration of the lateral jets; these grooves for example, a rectangular cross-sectional contour as shown in FIGURE 2; and their width is subordinate to the desired jet width. To avoid an excessive initial width of these grooves, the groove width can increase from the inlet end to the outlet end; if desired, the cross-sectional contour of these grooves can also be adapted to concentrate more air in the central zone than at the edges, and in this case a triangular contour is adequate, so that the central jet flattening force be greater than the enveloping efiect of this central jet.

Another difficulty encountered in the use of conventional atomizing head is due to the clog ing thereof by the back flow of the atomized paint. This is due mainly to the eddies produced by the mutual impingement of the two lateral jets, for part of the compressed air tends to flow back towards the nozzle head. This defect is avoided in the present apparatus by various methods applicable to the spray nozzle head of this invention; thus, to this end, two auxiliary jets deflected in an axial plane extending at right angles to that of the main lateral jets are used; in fact, the deposits of back-flowing paint usually tend to occur in this plane.

These spray nozzle heads may be machined or moulded, and made of metal or plastic material.

Instead of the lateral jets emerging downstream from the surface in which the orifice producing the central jet is bored, as shown in FIGURES 1 and 3, these lateral jets emerge either from the surface itself as shown in FIGURES 4 and 5, or upstream thereof, as shown in FIGURE 6. In the first case, they can be tangent to this surface as shown in FIGURE 4, or form an angle cc therewith, as shown in FIGURE 5; this angle should be relatively small in order to spread the central jet, a proper selection of this angle permitting a corresponding adjustment of the resulting spreading action. In the second case the jets form an angle [3 With the base of this surface; preferably, these jets are utilized as auxiliary jets completing the action of the main lateral jets. In either case the arrangement is advantageous since it permits spreading one fraction of the lateral jet over said central head surface, provided that the angle of incidence of the lateral jet to the central head surface be properly selected. This fraction of the lateral jets will improve the enveloping effect applied to the central jet while avoiding any soiling of the head by possible eddies produced by the mutual impingement of the lateral jets.

Another arrangement for spreading one fraction of the lateral jets consists of utilizing grooves of gradually decreasing cross-sectional area. Thus, one fraction of the jet will overflow from the groove and spread onto the central surface as shown in FIGURE 7.

Instead of providing a cap-shaped atomizing head formed with grooves 10, as shown in FIGURE 2, these grooves may be formed in the ears 14 as shown in FIG- URE 8; this arrangement being advantageous in that it reduces considerably the weight of the nozzle head.

The atomizing nozzle heads according to this invention permit the use of relatively low speeds for the atomized paint jets, whereby the device is particularly advantageous for electrostatic painting processes. On the other hand their easy fabrication from plastic materials constitutes a beneficial factor for their use in this specific technical field.

The voltage-applying electrode can be disposed coaxially to the nozzle as shown in FIGURE 9, and consist of a relatively long and sharp needle 15 emerging from the paint outlet orifice of the nozzle. In this case the jet of paint issuing from the device is circular and produced in the annular gap formed between the nozzle and the outer extension of the electrode-forming painting needle.

This electrode may also be designed in the form of a pin 16 carried by the body 1 of the spray gun, as shown in FIGURE 10. The electrode extends through the body 1 to make contact with a suitable high-voltage terminal provided to this end, as in the preceding case.

Various embodiments of the invention which are shown and described herein are given by way of example only and should not be construed as limiting the present invention since many modifications may be brought thereto without departing from the spirit and scope of the invention. Thus, notably, although the present disclosure refers only to paints and varnishes, it would not constitute a departure from the scope of the invention to utilize the nozzle head of this invention for spraying other liquids or aerosols.

I claim:

1. A head for atomizing a liquid by use of a flowing compressed gas comprising: a nozzle having a surface defining an orifice for the liquid; a convex cap having an orifice concentric with said ozzle orifice thereby defining a passageway for receiving the flowing compressed gas whereby the liquid is drawn from said nozzle orifice, means on said cap defining a pair of symmetrical grooves having a curvature corresponding to the curvature of the outer surface of said convex cap, said grooves having discharge ends facing the liquid that has been drawn from said nozzle orifice, said grooves adapted to receive the flowing compressed gas tangentially with respect to said cap; whereby the flowing compressed gas will travel in said grooves by the wall effect and will emerge from said grooves lateral to the liquid for controlling the shape of the spray of the liquid as it leaves said nozzle orifice.

2. An atomizing head as set forth in claim 1 wherein the bottom of said grooves open into said surface in which the nozzle orifice producing the central jet of liquid is formed.

3. An atomizing head as set forth in claim 2, wherein said bottom is tangent to said surface.

4. An atomizing head as set forth in claim 2, wherein said bottom forms a relatively small angle with respect to said surface.

5. An atomizing head as set forth in claim 2, wherein saaid bottom terminates at a point located upstream of said surface.

6. An atomizing head as set forth in claim 1, adapted for use in electrostatic painting processes and made for this purpose of a plastic material, and further comprising a voltage-applying electrode disposed coaxially thereto and comprises a relatively long and sharp needle emerging well beyond the nozzle orifice.

7. An atomizing head as set forth in claim 1, adapted for use in electrostatic painting processes and made for this purpose of adequate plastic material, and further comprising a voltage-applying electrode disposed in said head laterally of the nozzle orifice.

References Cited UNITED STATES PATENTS 1,751,787 3/1930 Binks 239--299 2,261,279 11/1941 Pellar 239290 3,169,882 2/1965 Juvinall et al. 239-15 X 3,169,883 2/1965 Juvinall 23915 X M. HENSON WOOD, IR., Primary Examiner M. Y. MAR, Assistant Examiner US. Cl. X.R. 239-291, 296, 544