Induced Air Flow Self-Cleaning Spray Nozzle

1. Field of the Invention

Our invention relates to spray nozzles which are nonplugging and/or self-cleaning.

2. Description of the Prior Art

The prior nozzle art teaches it is old to provide a set of holes around an inner tube. In the U.S. Pat. No. 3,460,764 (Wallis) such an arrangement is disclosed in which air is supplied to the holes to control divergence of the coating particles from the inner tube and to produce a protective air stream. The U.S. Pat. Nos. 3,364,970 and 3,484,044 (both to Dombruch et al) show a center oxygen stream with a high velocity which induces the gas in an intermediate stream to flow towards the outer periphery of the center stream. Other United States patents of interest include U.S. Pat. Nos. 743,777 (Tucker et al), 1,991,894 (Forney), and 2,881,826 (Spies).

What the known prior art does not disclose is a simple and effective selfcleaning non-plugging spray nozzle having an inner nozzle conduit with an externally mounted fluid ring having holes therein, wherein a narrow space between the ring mount and the inner nozzle conduit induces an air flow to clean the nozzle.

The invention described herein was disclosed in the United States Bureau of Mines Report of Investigation (RI) 8266 entitled "Dry-Process Sprayed Coal Mine Sealants, An Updated Progress Report" first published in Nov. 17, 1977 and authored by Jack E. Fraley. The contents of this report are specifically incorporated by reference herein.

The spray nozzle forming the subject matter herein relates to a main central material coating conduit with a fluid spray assembly mounted on it near its discharge end opening. The spraying assembly has a series of discharge holes facing in the same direction as the main conduit opening and encircling it. The front discharge section of the main conduit is gradually tapered so that it narrows down towards the opened end. Between the tapered front end of the main conduit and the closest inner side surface of the spray assembly there is formed a space which encircles the main conduit. An airflow is induced through this space as air discharges occur at the main conduit. This induced airflow acts to clean the nozzle and prevent plugging by externally mixed material.

The primary object of the invention is an improved self-cleaning non-plugging spray nozzle.

FIG. 1 schematically shows how the invention would be used with the preferred embodiment thereof.

FIG. 2 is a perspective view of the preferred embodiment of the invention showing how it can be operated.

Although FIG. 1 is a schematic representation of how the preferred embodiment (FIG. 2) would work, corresponding parts have been given the same numbers for ease in understanding the invention. The main conduit 1, as illustrated in FIG. 1, is a hollow elongated cylinder through which the coating material to be sprayed is forced. Generally the conduit is of a uniform diameter along its entire length until it nears the area located immediately before the material discharge opened end 3. Near the discharge end the conduit's surface gradually tapers down in the area 5 from its uniform diameter to a narrower diameter until it terminates at the discharge end. Mounted on the conduit by set screws or the like at the area just before the taper begins and extending until coplanar with opening 3 is the water ring assembly 7. Essentially the ring assembly has an inner mounting ring 9 and an outer water ring 11 having a plurality of water discharge holes 13 therein. A small water hose 15 with appropriate control valving 17 supplies water to the internal hollow portion 18 of the outer ring for discharge through its holes. The inner mounting ring has a series of support members 19 to rigidly hold the outer ring thereto. The inner ring also serves to support the water hose which extends traversely through it. Located between the front sections of the surface 5 of the main conduit near its discharge opening and the nearest inner surface 23 of the water ring is a space 21 which is generally circular in shape when viewed from the front in the direction (FIG. 1) of the arrow. This restricted opening serves the function of inducing an air flow, in the FIG. 1 direction shown, as rapidly flowing air is discharged from opening 3 in the form of an air and sealant mixture.

It is critical to the operation of our invention to note the function and shape of the space 21. The schematic of FIG. 1 would correspond to a cross-sectional top view of the nozzle with the flow of air, water, and material being from the figure's bottom towards the top. As viewed frontally in the direction of the arrow in FIG. 1, the space 21 would be a ringed area whose boundaries are the circular edge formed by the outer surface of the tapered front end of conduit 1 and the circular front edge of surface 23 which is the nearest part of the ring 11 to the main conduit. Each boundary would thus appear to be a circle concentric with the center of the circle forming opening 3. FIG. 2 more clearly shows this disclosed relationship.

The preferred embodiment of the schematic of FIG. 1, FIG. 2, shows the externally mounted water ring with thirty-two equally spaced holes 13 which provide external mixing of water and sealant downstream of the conduit 1. The inwardly tapered surface 5 eliminates material from clinging to the inside of the cylinder just behind the tip. And the induced air flow through space 21 removes mixed material (water, sealant and air) that hangs to the conduit tip before it can fall on the water jets 13.

The illustrated (FIG. 2) preferred embodiment was designed to pneumatically transport dry (sealant) material to the water-adding nozzle to provide external mixing and dust-free spraying without plugging the nozzle and at the same time be self-cleaning. The material was used in a coal mine to reduce shale sloughing in areas sensitive to weathering from varying moisture-temperature cycles. Mixing external to the equipment was selected to eliminate the problems commonly associated with internal mixing such as plugging of pumps and/or lines, cleanup, etc. For the particular purpose mentioned, the sealant was a medium-sized mineral wool nodule about 0.75 of an inch long. Additional modifications to the machinery used can be found on pages 2-4 of the referenced RI. Although optimum design characteristics have not been firmly established they can be easily determined by routine testing. Very satisfactory results have been obtained when the angle .theta. was 30 degrees or less and the distance "d" was less than 1/4-inch. Variations therefrom are contemplated and well within the scope of our invention. Using the preferred embodiment of the invention for one five hour spray period resulted in the following performance characteristics therefore:

Other uses sprayed materials, configurations, and spray rates, etc. are, of course, possible with this invention. Thus, although the invention has been described in detail with respect to an exemplary use and embodiment thereof, it will be understood by those skilled in the art that variations and modifications may be effected within the scope and spirit of the claims that follow.