Air assisted atomizing spray nozzle

An air assisted atomizing spray nozzle including: (a) a mixing chamber, (b) a liquid inlet opening for injecting a liquid stream axially into the mixing chamber, (c) a pair of air inlet openings for injecting a pair of air streams radially into the mixing chamber in directions substantially opposed to one another and substantially perpendicular to the liquid stream for atomizing the liquid stream, and (d) an exit orifice in axial communication with the mixing chamber for discharging atomized liquid therefrom.

TECHNICAL FIELD 
This invention is related generally to nozzles for spraying liquids, and 
more particularly, to improved air assisted atomizing spray nozzles. 
BACKGROUND OF THE INVENTION 
There are many different types of nozzles for spraying liquids. One type is 
a so-called air assisted atomizing spray nozzle. Such nozzles are capable 
of delivering a liquid in a finely divided, or atomized state. Atomization 
of a liquid in this type of nozzle is assisted by introducing air into the 
nozzle. More specifically, a liquid stream and an air stream are injected 
into a mixing chamber. The interaction of the air and liquid stream, among 
other factors, atomizes the liquid stream for discharge through an exit 
orifice of the nozzle. 
Air assisted atomizing spray nozzles are used to apply agricultural 
chemicals and in other applications, such as pest control, where it is 
important to achieve a uniform distribution of relatively small amounts of 
chemicals. They also are used in humidifying systems to assure rapid 
evaporation of water into the atmosphere. Another use is in scrubbing 
systems for coal furnaces where rapid and complete chemical absorption of 
sulfurous gases must be optimized. In general, this type of nozzle is used 
in a wide variety of applications where it is important to deliver liquid 
in a finely atomized state. 
One design for air assisted atomizing spray nozzles is shown in U.S. Pat. 
No. 5,082,185 to W. Evans. The nozzle shown therein is used with a 
hand-held spray gun which is particularly useful for applying pesticides. 
The air source for the gun can be either a high pressure tank or a tank 
which is pressurized by a hand pump. The design of the spray gun offers 
significant advantages, especially in that it reduces liquid leakage 
during shut-off. Nevertheless, the nozzle assembly shown in the 
above-mentioned Evans patent has room for improvement in several respects. 
First, certain components of the nozzle are relatively fragile, in 
particular, the parts that define the mixing chamber 15 shown in FIG. 2 of 
the Evans patent. The spraying equipment, with which the nozzle is used, 
typically is carried from location to location. It also is carried by hand 
as pesticide is applied at a particular location. Under such 
circumstances, and even during assembly and repair of the nozzle, the 
perforated annular disk-shaped structure at the downstream end of the 
mixing chamber 15 may be bent or broken. Such damage, of course, can 
interrupt or diminish the performance of the spray nozzle. 
Although durability may be less important if the nozzle is a component of a 
system which is more or less permanently installed, there are other 
problems with the design of the nozzle shown in the Evans patent. Nozzle 
parts very commonly are manufactured from cast or machined metal plugs, 
such as brass or stainless steel, which then are drilled or milled to 
provide the various openings and cavities. There are, however, a number of 
close-tolerance drillings which must be performed in order to form the 
mixing chamber 15 illustrated in the Evans patent. Consequently, 
manufacturing parts is relatively difficult and costly, and there are 
relatively high rejection rates during the manufacturing process. 
In certain applications a spray nozzle will be used to spray highly 
abrasive liquids, such as limestone slurries in a smoke stack scrubbing 
system. Under such conditions the mixing chamber parts are subject to 
considerable wear. It is possible to increase the wear resistance of 
nozzle parts by using more wear resistant compositions, such as ceramics, 
but such materials must be cast or molded and cannot be readily machined. 
The mixing chamber part of the Evans patent, as a practical matter, cannot 
be adapted for use in high wear applications because the relatively 
complex design does not lend itself easily to casting or molding 
processes. 
Moreover, it generally is desirable to minimize the quantity of air used to 
achieve a given degree of atomization of a given quantity of liquid. 
Improved air efficiency can permit the use of less expensive, lower 
capacity equipment and can lower operating costs in many systems. Air 
efficiency is especially important in equipment, such as that shown in the 
Evans patent, which relies on a portable air source. For example, the life 
span of high pressure tanks decreases as air consumption increases, and 
tanks have to be changed more frequently. If a hand pumped tank is used, 
work must be interrupted more frequently so that the tank can be pumped 
up. 
The atomization process in this type of spray nozzle also is relatively 
inefficient because it relies on what may be called "parallel flow" of 
liquid and air. As can be seen best in the front elevational view of part 
15 of the Evans patent, which view is shown in FIG. 2 and labeled 15a, the 
air streams and liquid streams are introduced into the mixing chamber 
parallel to each other. In other words, the liquid stream is introduced 
through the center aperture in part 15, and air is introduced through the 
four apertures radially disposed from the center hole but opening parallel 
to it. 
One general approach to increasing the efficiency of the atomization 
process in mixing chambers has been to provide so-called impingement 
surfaces. Air assisted atomizing spray nozzles comprising impingement 
surfaces are shown, e.g., in U.S. Pat. No. 4,899,937 to J. Haruch, U.S. 
Pat. No. 4,815,665 to J. Haruch, and U.S. Pat. No. 4,349,156 to J. Haruch. 
In general, these types of designs inject a liquid stream and an air 
stream into a mixing chamber perpendicular to each other with an 
impingement surface being situated at or near the point where the streams 
intersect. 
While this can create considerable turbulence, thereby improving the 
atomization process, the nozzle is more complex because it incorporates 
impingement surfaces. Generally, additional parts must be fabricated in 
order to provide an impingement surface. The relative alignment of the air 
inlet, liquid inlet, and impingement surface also must be relatively 
precisely controlled. As a consequence, it is more difficult and costly to 
manufacture nozzles of this type. 
OBJECTS AND SUMMARY OF THE INVENTION 
An object of this invention, therefore, is to provide an air assisted 
atomizing spray nozzle which is more durable in use and is less 
susceptible to bending or breaking. 
A further object of the subject invention is to provide an air assisted 
atomizing spray nozzle which is more easily and reliably manufactured. 
Another object of the subject invention is to provide an air assisted 
atomizing spray nozzle wherein wear susceptible components of the nozzle 
may be made by casting processes. 
Yet another object of the subject invention is to provide an air assisted 
atomizing spray nozzle which atomizes liquid more efficiently, thereby 
reducing the amount of air consumed. 
It also is an object of the subject invention to provide an air assisted 
atomizing nozzle wherein all of the above mentioned advantages are 
realized. 
The foregoing objects and advantages of the invention will be apparent to 
those skilled in the art upon reading the following detailed description 
and upon reference to the drawings.

While the invention is susceptible of various modifications and alternative 
constructions, certain illustrative embodiments thereof have been shown in 
the drawings and will be described below in detail. It should be 
understood, however, that there is no intention to limit the invention to 
the specific forms disclosed, but on the contrary, the intention is to 
cover all modifications, alternative constructions, and equivalents 
falling within the spirit and scope of the invention. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIGS. 1-3, there is shown an illustrative hand-held spray 
gun having a nozzle assembly in accordance with the present invention. 
This spray gun is constructed, except for incorporating the novel nozzle, 
substantially as described in the Evans patent discussed above. 
Accordingly, the text of that patent is incorporated in its entirety by 
this reference thereto. 
The gun basically comprises three subassemblies: a handle assembly 10, a 
wand assembly 20, and a nozzle assembly 30. The handle assembly 10 is 
provided with a pressurized liquid inlet 11 adapted to connect, through a 
hose (not shown) with an external pressurized liquid reservoir (not 
shown). Liquid flows through a passageway 12 in the handle assembly 10 and 
is controlled by valve means 13 which is actuated by a handle 14. When the 
valve means 13 is open, liquid is transported through the passageway 12 in 
the handle assembly 10 and passes through an outlet 15 into the wand 
assembly 20. 
The wand assembly 20 attaches to the outlet 15 of the handle assembly 10 
via a lock nut 21. The wand assembly 20 comprises an outer tube 22 which 
has a sealed first end 23. The outer tube 22 is supplied with air via a 
pressurized inlet 24 which is adapted to connect, through a supply hose 
(not shown), with an external pressurized air source (not shown). 
A capillary tube 25 is disposed within the outer tube 22. The capillary 
tube 25 has a first end 26 which passes through the sealed first end 23 of 
the outer tube 22 and communicates with the liquid outlet 15 in the handle 
assembly 10. The second end 27 of the outer tube 22 and the second end 28 
of capillary tube 25 both communicate with the spray nozzle assembly 30, 
thereby permitting liquid and air to enter the spray nozzle assembly 30. 
As can be seen best in FIG. 2, the spray nozzle assembly 30 comprises an 
internally threaded coupling 31, a connector 32, a an atomizing member 33, 
a spray tip 34, and an externally threaded lock screw 35. The threaded 
coupling 31 is suitably attached to the downstream end 27 of the outer 
tube 22. The nozzle assembly 30 may be assembled and disassembled by 
screwing and unscrewing the lock screw 35, thereby securing the atomizing 
member 30 upstream of the spray tip 34 and providing access to the other 
components of the nozzle assembly 30. 
The connector 32 has a nipple 36 at its upstream end which is inserted into 
the downstream end 28 of the capillary tube 25, thereby providing means 
for connecting the nozzle assembly 30 to the capillary tube 25. A 
passageway 37 extends through the connector 32 to its downstream end, 
where a plurality of shoulders and o-rings provide means for sealably 
engaging the upstream end of the atomizing member 33 to the connector 32. 
More particularly, the atomizing member 33 is generally cylindrical with 
its upstream end having a generally cylindrical projection of reduced 
external diameter. An annular channel is provided in the upstream 
projection of the atomizing member 33, in which is situated an o-ring. 
When assembled, the o-ring is compressed between opposing shoulders in the 
connector 32 and the atomizing member 33. 
The atomizing member 33 is provided with a passageway 38 at its upstream 
end which, together with the handle passageway 12, capillary tube 25, and 
connector passageway 37 communicate liquid to a liquid injection port 39. 
Further, in order to accelerate the liquid prior to its injection into a 
mixing chamber 42 and to assist in the atomization of the liquid, the 
liquid injection port 39 defines a reduced diameter passageway. That is, 
the passageway 38 is a generally cylindrical bore which tapers inwardly at 
its downstream end into communication with the liquid injection port 39. 
The passageway 38 has a diameter approximately 2 to 3 times the diameter 
of the liquid injection port 39. 
An air circulation chamber 40 is defined by a generally annular space which 
extends between the outer surfaces of the connector 32 and the atomizing 
member 33 and the inner surfaces of the nozzle housing, i.e., the threaded 
coupling 31 and the lock screw 35. The circulation chamber 40 communicates 
at its upstream end with the downstream end of the outer tube 22, thereby 
providing means for communicating air to a pair of air injection ports 41a 
and 41b. 
The liquid injection port 39 and the air injection ports 41a and 41b all 
communicate with a mixing chamber 42. As is described in more detail 
below, liquid is atomized in the mixing chamber 42, and atomized liquid 
flows from the mixing chamber 42 through a passageway 43 in the spray tip 
34 and is discharged through an exit orifice 44. 
The mixing chamber 42 is defined by a generally cylindrical bore in the 
downstream end of the atomizing member 33. The bore tapers outwardly from 
the downstream end of the liquid injection port 39. The mixing chamber 42 
has a diameter approximately 12 to 13 times the diameter of the liquid 
injection port 39. The liquid injection port 39 is located in the 
atomizing member 33 at the upstream end of the mixing chamber 42 
substantially along the longitudinal axis of the mixing chamber 42. Liquid 
introduced under pressure into the passageway 38 flows through the liquid 
injection port 39 and is injected axially as a stream into the mixing 
chamber 
The air injection ports 41a and 41b extend generally radially through the 
side walls of the atomizing member 33 providing radial communication 
between the air circulating chamber 40 and the mixing chamber 42. 
Preferably, the air injection ports 41 are located on diametrically 
opposed sides of the atomizing member 33. As a consequence, an opposing 
cross-flow of air is directed at the liquid stream as the liquid stream is 
injected into the mixing chamber 42. In other words, as can be seen best 
by the flow lines in FIG. 3, air is introduced under pressure into the 
circulation chamber 40 and flows through the air injection ports 41, 
thereby injecting a pair of air streams radially into the mixing chamber 
42. Those air streams are substantially opposed to each other and are 
substantially perpendicular to the liquid stream injected into the mixing 
chamber. 
If desired, an opposing cross-flow of air may be created by providing more 
than two air holes. For example, three openings could be provided spaced 
120.degree. apart, four openings could be provided spaced 90.degree. 
apart, or more could be provided so long as the air streams created 
thereby substantially oppose each other and are substantially 
perpendicular to the liquid stream. 
It will be appreciated that the novel nozzle assemblies, which utilize an 
opposing cross-flow arrangement, atomize the liquid stream more 
efficiently than prior art nozzles which use a parallel flow arrangement. 
In a parallel flow arrangement, atomization is dependent on differing 
velocities between the air streams and the liquid stream, a process which 
imparts relatively little direct force on the liquid stream. An opposing 
cross-flow arrangement exerts more direct shear force on the liquid stream 
and also creates more turbulence. 
For example, a Gold Crest.RTM. Actisol.RTM. model pesticide applicator 
which is commercially available from Roussel Bio Corporation, 
Jacksonville, Fla., incorporates a spray gun which is constructed 
substantially as described in the previously mentioned Evans patent. The 
spray gun was modified so that it incorporates a novel nozzle assembly as 
described above. More particularly, the original mixing chamber part was 
replaced with an atomizing member made pursuant to the present invention 
as described above. The cylindrical bore of the substituted atomizing 
member, which substantially defines the mixing chamber, had a diameter of 
approximately 0.25" and a depth of approximately 0.50". The liquid 
injection port was an axially disposed hole measuring approximately 0.020" 
in diameter. The pair of radial air injection ports were holes measuring 
approximately 0.03125" in diameter which were located opposite each other. 
The wand is designed for liquid flow rates of approximately 1-2 
gallons/hr. It was observed that this novel arrangement consumes air at 
the rate of approximately 0.5 standard cubic feet per minute. This is 
approximately 20-40% less than the air consumed by the commercially 
available model using the prior art mixing chamber part. 
It will be appreciated by those skilled in the art that the optimum degree 
of atomization and flow rate of liquid depends on the particular 
application and system in which the nozzle will be used. Liquid 
atomization and flow rate are dependent on a variety of well known 
factors, including the viscosity of the liquid, the cross section of the 
air and liquid injection ports, the volume of space in the mixing chamber, 
and the configuration of the exit orifice in the spray tip. These factors 
may be varied by those of ordinary skill in the art to produce a desired 
degree of atomization and flow rate. All other factors being equal, 
however, it is believed that an opposing cross-flow of air provides 
relatively higher air efficiency, thereby decreasing air consumption. 
It also will be appreciated that the atomizing member can be manufactured 
more easily and reliably. Fewer drillings are necessary to form the bore 
and injection ports in the atomizing member. Moreover, there are fewer 
drillings which require close tolerances and alignment of the air 
injection port is more easily accomplished. This design is relatively 
simple and has a minimum of parts, which can increase the economy of its 
manufacture and also lends itself to casting methods wherein more wear 
resistant materials, such as ceramics, may be used. It also should be 
appreciated that, being generally cylindrically shaped and lacking the 
perforated, annular disk-shaped structure which is part of the prior art, 
the atomizing member of the nozzle of the present invention is much more 
durable and less susceptible to bending or breaking. 
A second preferred embodiment of the subject invention is shown in FIG. 4. 
This embodiment is an air assisted atomizing spray nozzle which is part of 
a more or less permanently installed system, such as may be used to 
humidify rooms in which paper is processed. The nozzle 50 comprises a body 
portion 51, a generally cylindrically shaped atomizing member 52, a spray 
tip 53, and a locking screw 54. The nozzle body 51 has a pressurized air 
inlet 55 and a pressurized liquid inlet 56. 
In carrying out the invention, the atomizing member 52 of the second 
embodiment has a design identical to that of the atomizing member 33 
discussed above in reference to the first embodiment, and otherwise the 
functioning of the nozzle 50 is substantially identical to that of the 
nozzle assembly 30. Air flows through a circulating chamber 57, which is 
defined by a generally annular space which extends between the outer 
surface of the atomizing member 52 and the inner surface of the locking 
screw 54, and then is injected through radial air injection ports 58 into 
a mixing chamber 61. Liquid is introduced through the pressurized liquid 
inlet 56, and ultimately flows through a passageway 59, which is generally 
cylindrical and tapers inwardly at its downstream end to a liquid 
injection port 60, thereby providing a reduced diameter passageway through 
which liquid is accelerated prior to injection into the mixing chamber 61. 
The diameter of the passageway 59 is approximately 2 to 3 times the 
diameter of the injection port 60. 
The mixing chamber 61 is defined by a generally cylindrical bore in the 
downstream end of the atomizing member 52. The bore tapers outwardly from 
the downstream end of the liquid injection port 60. The diameter of the 
mixing chamber 61 is approximately 8 to 10 times the diameter of the 
liquid injection port 60. A liquid stream is injected axially into the 
mixing chamber 61 through the liquid injection port 60, where the stream 
is subjected to opposing cross air flows to finely atomize the liquid. 
A third preferred embodiment of the subject invention is shown in FIG. 5. 
This air assisted atomizing nozzle is especially suitable for spraying 
relatively large quantities of liquid, such as limestone slurry used in 
smoke stack scrubbing. The nozzle assembly 70 has a body portion 71, a 
generally cylindrically shaped atomizing member 72, a spray tip 73, and a 
locking nut 74. The nozzle body 71 has an air inlet 75 and a liquid inlet 
76 coupled to respective supply lines. 
The mixing chamber part 72 of this embodiment has substantially the same 
design as that shown in the previous embodiments, but it may be 
proportionately larger so that the spraying capacity of the nozzle may be 
increased. Air is introduced through the inlet 75, flows through a 
circulating chamber 77 which is defined by a generally annular space which 
extends between the outer surface of the atomizing member 72 and inner 
surfaces of a generally cylindrical bore in the body portion 71, and is 
injected through radial air injection ports 78 into a mixing chamber 81. 
Liquid is introduced through the inlet 76, and ultimately flows through a 
passageway 79, which is generally cylindrical and tapers inwardly at its 
downstream end to a liquid injection port 80, thereby providing a reduced 
diameter passageway through which liquid is accelerated prior to its 
injection into the mixing chamber 81. The diameter of the passageway 79 is 
approximately 2 to 3 times larger than that of the liquid injection port 
80. 
The mixing chamber 81 is defined by a generally cylindrical bore in the 
downstream end of the atomizing member 72. The bore tapers outwardly from 
the downstream end of the liquid injection port 80. The diameter of the 
mixing chamber 81 is approximately 6 to 7 times the diameter of the liquid 
injection port 80. A liquid stream is injected axially into the mixing 
chamber 81 through the liquid injection port 80. As with the other 
embodiments, the liquid stream is subjected to opposing cross-flow air 
streams in the mixing chamber 81. In order to vary the shape of the spray 
pattern, the spray tip 73 may have one or more exit orifices. For example, 
the spray tip 73 in this embodiment has a plurality of round orifices 82 
to generate a wide angle round spray. It also may be provided with a 
single round orifice to produce a narrow angle round spray, or it may have 
one or more elliptical orifices to generate a flat spray pattern.