Induced air flow self-cleaning spray nozzle

A spray nozzle which is non-plugging and selfcleaning. The nozzle has a central main conduit with an externally mounted water discharge assembly encircling it at its front opened end. A mixture of air and a sealant is forced through the main conduit until it is expelled from the conduit's inwardly tapered front opened discharge end. The water discharge assembly, in the preferred embodiment, has two spaced concentric rings joined together. The rearmost ring serves to mount the assembly to the main conduit and to support a second ring having an internal hollow water conduit section. Near the discharge front end, the front ring is attached to the rear ring by several supporting mounts. The front or outer ring has a plurality of water discharge jets or openings which encircle the front of the main conduit and are fed through their internal hollow section by a water conduit. A tapered surface of the outer ring which faces towards the main conduit cooperates with the gradually tapered outer surface of the main conduit to form an air passage therebetween which encircles the discharge end. As the air-sealant mixture is forced through the main conduit, an air flow is induced in the air passage by the air flow in the main conduit. This induced air flow is between the main conduit and the front ring. This induced air flow serves to remove externally mixed material from the nozzle before the same falls on the water jets.

BACKGROUND OF THE INVENTION 
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. 
SUMMARY OF THE INVENTION 
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.

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: 
Table 1 
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Bag Weight of Sealant 50 lbs. 
Spray rate in bags per hour 
35 
Spray coverage in sq. ft. per bag at .5 in 
32 
Coverage rate in sq. ft. per hr. at .5 in 
1,120 
Sealant Coverage in lbs/sq. ft. at .5 in 
1.56 
Water rate in lbs per minute 
56 
Water-sealant ratio in lbs/1.00 lb. 
1.92 
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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.