Chemical injection system for high pressure washers

The present invention relates to an improved immediate action chemical injection system for selectively adding a chemical solution to the high velocity water spray discharged by a high pressure water washer. A common supply conduit has an inlet end adaptable for engagement with a low pressure source of water and has a first outlet end attached to the inlet of the high pressure water delivery system of the washer and a second outlet end attached to a completely separate chemical injection system. The high pressure water delivery system emits a spray of highly pressurized water having a substantially fan-shaped pattern which is intersected by a spray of chemical solution emitted from the chemical injection system, with the result being a high velocity spray of water and chemical being provided for use against a work surface.

BACKGROUND OF INVENTION 
The present invention relates to high pressure water washers and more 
particularly to a chemical injection system for selectively adding a 
chemical solution to the high velocity water spray discharged by the high 
pressure water system. 
For modern pressure washer systems to be truly effective, it is necessary 
for such systems to be able to selectively deliver in a rapid and reliable 
manner a high velocity spray of water both with and without the addition 
of a chemical cleaning solution. However, for reasons which will become 
clear, many known pressure washer systems have proven less than completely 
satisfactory. 
In one type of known pressure washer, both water and chemical are injected 
into the inlet of a high pressure pump assembly with the water and 
chemical being mixed during the pressurization process. In order to educe 
a flow of chemical solution into the high pressure pump inlet, it is 
necessary to create an inlet suction condition in the pump inlet as 
opposed to an inlet pressure condition. The required pump inlet suction 
condition might be achieved by an inlet pressure regulator or inlet float 
assembly. Such a system, referred to hereafter as a pump inlet injection 
system, also requires check valves and needle and metering valves for 
controlling the feed rate of water and chemical into the pump. 
Furthermore, the on-off and metering functions must be done at the pump 
rather than at the work location itself. Finally, the reaction time 
required to actually transport the chemical through the high pressure pump 
and the relatively long output hose or the like is usually at least ten 
seconds and can even take two minutes or more. 
The elaborate and sophisticated components necessary to educe a flow of 
chemical solution through the high pressure pump makes for a cumbersome 
and complex washer system which can be exceedingly difficult to maintain 
and rendered inoperable by failure of one or more of the many working 
components forming the various valves, as well as the required pressure 
regulator assembly. 
In an attempt to overcome the problems associated with the eductor type of 
pump inlet injection system, it has been suggested that the chemical 
solution be mixed with a body of water while in a float tank, with the 
mixture of water and chemical then being introduced as a single stream 
into the inlet of the high pressure pump. A main drawback of such a system 
resides in the inability to selectively control or stop the addition of 
chemical to the high pressure water stream of the washer system. In other 
words, there is no effective way to turn off the supply of chemical and 
provide only an impact spray of pressurized water. This inability to 
selectively control the flow of chemical eliminates the desirable option 
of a high pressure water rinse and can result in wasting excessive amounts 
of the chemical cleaner. In addition, because the chemical always flows 
through the pump assembly, water control valve and water nozzle orifice, 
the chemical solution can cause buildups of chemical deposits in these 
assemblies during regular use and flow stoppage. Where corrosive chemicals 
are used, this flow path may also result in corrosion and failure of these 
components. As a result of high maintenence costs, relatively slow 
response times, and relatively ineffective flow control, pressure washers 
wherein the chemical solution is injected into an inlet of the high 
pressure pump have proven less than completely satisfactory. 
In a further effort to overcome the problems associated with delivering 
chemical solution through the water pump inlet, it has been suggested that 
a second, separate pump assembly be employed for pressurizing the chemical 
solution to a pressure sufficient to permit its injection downstream of 
the high pressure pump outlet. This further complicates the overall 
structure of the chemical injection system, making maintenance of the 
interrelated pump and valving assemblies time-consuming and costly. 
In yet a further effort to overcome the problems associated with providing 
a chemical solution in the high pressure stream of water, it has been 
suggested that the high pressure discharge from the pump be routed through 
a low pressure bypass line in parallel with the usual high pressure line 
containing the pressure nozzle. This alternate line serves as a chemical 
application flow path and ends in a separate chemical application nozzle 
having a large orifice for providing water flow at sufficiently low 
pressure to permit operation of an eductor for educing chemical into the 
bypass line. During eductor operation, a significant fraction of the 
relatively constant pump output is routed through the bypass line, greatly 
reducing the pressure in both this line and the main line so that the 
chemical solution is applied to the work surface at relatively low 
pressure. Low pressure application of the chemical solution is then 
followed by a high pressure rinse using the usual high pressure flow path 
and nozzle. The cleaning efficiency of this system is much less than that 
achievable by impacting a chemical solution at the high velocity available 
from routing the full pump output through the high pressure water nozzle. 
A further drawback of such a washer system is that a relatively large 
reaction time is still required to reroute the flow and reduce the 
pressure in the stream to a sufficiently low level so as to allow the 
eductor assembly to function. Furthermore, the eductor is near the pump 
and if the length of the line between the eductor and outlet nozzle is 
increased, as by adding additional hose to the washer system while in the 
field, the back pressure necessary to overcome the additional pressure 
drop often makes it impossible to reduce the pressure sufficiently so as 
to actuate the chemical eductor assembly. Also, any kinks in the hose, 
chemical deposits in the nozzle or other flow restrictions that may occur 
during use of the washer system can increase the back pressure to a level 
where it is difficult, if not impossible, to actuate the chemical eductor 
assembly in the bypass line. 
In conjunction with the aforementioned approaches of chemical delivery 
systems, the use of electrically controlled solenoid valves, actuation 
switches at the operators handle, transformers and other electrical and 
electronic components sometimes appear to improve speed, economy and 
convenience of chemical delivery. 
However, besides being unusually expensive in various degrees of 
sophistication, inherently such installations become inoperable after 
short initial operation periods. The maintenance trouble shooting on such 
over sophisticated systems is usually beyond the capability of ordinary 
maintenance personnel and these machines therefore become unusable. 
As will become clear hereafter, the present invention provides an immediate 
action chemical addition system which overcomes the problems confronting 
known pressure washer assemblies as discussed hereabove, such as avoiding 
excessively complex mechanisms having relatively long reaction times and 
other drawbacks. 
SUMMARY OF THE INVENTION 
A principal object of the present invention is to provide an injection 
system capable of immediately adding or cutting off chemical additives to 
the high velocity water spray of a high pressure water washer. 
A further object of the present invention is to provide a pressure washer 
with chemical injection wherein normal city water pressure is used to 
transport chemical additives to a chemical outlet nozzle for selective 
mixing with a spray of high velocity water emitted from a high pressure 
water nozzle. 
Another object of the present invention is to provide a pressure washer 
with chemical injection wherein only water flows through the high pressure 
components. 
Each of these, as well as additional objects, is achieved by the preferred 
embodiments of the present invention, which include a high pressure pump 
module having a fluid inlet in flow communication with a source of water 
or other liquid at a relatively low pressure. City tap water is normally 
supplied at pressures in the range of 15 to 100 psig and provides a 
satisfactory source of water for the pressure washer system of the present 
invention. A fluid outlet from the high pressure pump module is connected 
to a normally closed water control valve via high pressure conduits 
extending therebetween. The water control valve is part of a wand-like 
assembly which includes a spray head mounted at the opposite end of the 
wand from the water control valve and a rigid interconnecting high 
pressure conduit. The spray head, in turn, includes a water pressure 
nozzle in flow communication with the rigid high pressure conduit. In a 
preferred embodiment, the water nozzle includes an orifice capable of 
generating a substantially flat, fan-shaped spray of high velocity water 
in response to selective actuation of the water control valve. Upon 
actuation the water control valve preferably goes from a fully closed to a 
fully open position. It is to be understood that the water control valve 
can be omitted in some installations, and the pump selectively actuated to 
initiate or terminate high pressure water flow. 
A chemical injection system is also in flow communication with a source of 
low pressure water, preferably the same city tap water as the high 
pressure pump inlet. The chemical injector includes an eductor head having 
a venturi passageway for transporting low pressure water while creating 
sufficient vacuum to draw chemical concentrate through an attached pickup 
line in flow communication with an appropriately positioned opening in the 
venturi passageway. Low pressure water flow through the eductor head 
assembly thus provides a stream of chemical solution at the eductor 
outlet. A filter or strainer assembly is preferably provided in the pickup 
line along with a check valve preventing back flow through the pickup line 
to the chemical container or reservoir. 
Mounted in a chemical solution conduit extending from the outlet of the 
chemical eductor assembly to a separate chemical injection nozzle is a 
normally closed chemical control valve for selectively controlling or 
stopping the flow of chemical solution through the chemical conduit and 
nozzle. The chemical nozzle is also mounted on the spray head assembly and 
a portion of the chemical conduit is preferably rigid and forms part of 
the wand assembly. The chemical nozzle includes an orifice preferably 
constructed so as to provide a substantially conically shaped spray of 
chemical solution responsive to selective opening of the chemical control 
valve. The water pressure nozzle and the chemical nozzle are oriented in 
the spray head such that the chemical spray flowing along the longitudal 
axis of the chemical nozzle intersects the water spray flowing along the 
longitudinal axis of the pressure nozzle at about 1/8 inch or less from 
the pressure nozzle and about 5/16 to 1/4 inch from the chemical nozzle. 
During operation of the preferred embodiment, a liquid stream of 
low-pressure, such as tap water from a city utility system, well water 
pump and tank system, or the like is supplied to both the inlet of the 
high pressure pump module and the inlet of the eductor head portion of the 
chemical injector. Water is pressurized in the pump to pressures in the 
range of 200 to 10,000 psig, preferably 500 to 3,000 psig, and is 
discharged as a highly pressurized stream of water flowing through high 
pressure conduits toward the water control valve. Upon selective opening 
of the normally closed high pressure water control valve, the stream of 
water flows through the rigid water conduit of the wand member and enters 
the water nozzle mounted in the spray head. The water is then ejected 
through the water nozzle orifice as a high velocity spray having 
preferably a substantially thin and flat fan-shaped configuration. 
Simultaneously, tap water supplied to the chemical injection system 
communicates with the venturi-shaped passageway in the eductor head 
assembly for creating a suction force to draw chemical concentrate through 
the attached filter, pick-up tube and check valve. When flow is initiated, 
the chemical concentrate directly enters and mixes with the low pressure 
stream of water. A solution of water and chemical is then available in the 
downstream conduit containing the normally closed chemical control valve. 
Upon selective opening of the chemical control valve, the chemical and 
water solution flows from the chemical nozzle mounted on the spray head. 
The chemical solution is emitted as a generally conically shaped spray 
which intersects with the spray of pressurized water to form a single 
spray of high velocity water and chemical as required. If a high velocity 
water rinse spray is desired, only the water control valve is selectively 
actuated while the chemical control valve is kept in its normally closed 
position. 
The pressure nozzle provides a relatively thin, flat diverging spray 
pattern having the aforementioned fan shape, the major plane of which is 
preferably substantially perpendicular to a plane defined by the 
longitudinal axes of the chemical and water nozzles. The angle of 
divergence of the fan spray in its major plane is approximately in the 
range of 10.degree.-70.degree.; preferably 15.degree.-65.degree. and most 
preferably about 25.degree.. 
While the chemical nozzle preferably provides a conically-shaped spray 
pattern, it is also considered within the scope of the present invention 
for the chemical nozzle to provide a flat, fan-like spray pattern similar 
to the spray pattern provided by the pressure nozzle. The orifice of the 
chemical nozzle is in a plane approximately prerpendicular to that of the 
fan water spray, and the chemical nozzle is positioned so that the 
chemical spray rapidly converges and mixes with the high velocity water 
spray at a mixing location exteriorly of both nozzles and the spray head 
but relatively close to the point at which the high pressure water exits 
the high pressure orifice. In the preferred embodiment, the angle of 
convergence "C" between the longitudinal axis A of the water orifice and 
the longitudinal axis B of the chemical orifice is in the range of 
20.degree. to 90.degree., preferably 30.degree. to 60.degree., and most 
preferably about 45.degree.. At the initial juncture of the two sprays, 
the chemical spray pattern should extend across or "cover" at least 50%, 
preferably 90%, of the transverse width of the fan water spray to insure 
adequate distribution and mixing of the chemical with the water before the 
fan spray reaches the work piece. As explained in the detailed description 
below, the chemical nozzle is positioned so that little or no chemical 
spray divergence is required to accomplish this coverage. 
Because the only mechanically moving parts in the chemical injection system 
of the present invention are the chemical control and eductor check 
valves, this system has an exceptionally high level of reliability during 
normal operations over extended periods of use. Likewise, because the 
chemical stream does not at any time flow through the high pressure pump 
and associated components in the pump module or through the water control 
valve, pressure nozzle and related conduits, the chance of the chemical 
solution plugging up, corroding or otherwise adversely affecting these 
pressure washer components is eliminated, making the system practically 
maintenance free. Finally, because tap water pressure is present in the 
eductor and downstream conduit at all times, a stream of chemical solution 
immediately responsive to actuation of the chemical control valve is 
assured. A check valve in the pickup line between the supply of chemical 
concentrate at ambient pressure and the eductor prevents backflow through 
the pickup line when the chemical control valve is closed. 
The chemical injection system of the present invention requires no 
significant overall reaction time for chemical addition as compared to 
known chemical injection systems for pressure washers. In addition, the 
composite chemical injector-pressure washer apparatus is relatively 
maintenance free, highly portable and easy to use in the field. Although 
designed primarily for portable pressure washer units, the invention can 
also be used with fixed industrial pressure washer installations. With 
either fixed or portable units, both the high pressure pump module and the 
chemical container and eductor can be located remotely, at 100 or more 
feet, from the washer wand used at the work location. The wand is light 
weight and easily held and directed by hand. The relatively flexible 
pressure hose and chemical tube communicating with the pump and eductor, 
respectively, do not adversely restrict such wand movement.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
Referring now to the attached drawings, an improved chemical injection 
washer system is shown which is capable of injecting a chemical solution 
into a spray of highly pressurized water utilizing low city tap water 
pressure or the like for transporting and injecting the chemical into 
highly pressurized water spray. 
As shown in FIG. 1, the washer system itself is generally indicated by 
numeral 10. The washer system includes a water delivery assembly for 
supplying a spray of highly pressurized water and a further chemical 
injection assembly for selectively injecting a spray of chemical solution 
into the highly pressurized water spray before the spray strikes a work 
surface to be cleaned. A common supply conduit 11, which preferably takes 
the shape of a flexible hose, includes an end attached to a source of low 
pressure water such as city tap water having a pressure of between 
approximately 15 and 100 psi, not shown for purposes of simplicity. Supply 
conduit 11 includes a flow divider 12 which may take the form of a 
T-shaped fitting adaptable for allowing two separate outlet conduits to be 
attached to common supply conduit 11. 
A first outlet conduit 13 extending from fitting 12 joins an inlet of a 
conventional high pressure pump module indicated in block diagram at 14. 
For purposes of simplicity, the internal drive mechanism of high pressure 
pump module 14 has not been shown. During operation, pump module 14 
functions to raise the pressure of the tap water entering pump module 14 
via conduit 13 from its original pressure of between 15-100 psi to a new 
pressure level of between approximately 500-2,500 psi or greater. 
A high pressure hose 15 includes an end portion attached to an outlet of 
high pressure pump module 14 to provide a passageway for a stream of 
highly pressurized water leaving the pump. High pressure hose 15 includes 
a further end portion detachably connected to an inlet portion of a water 
control valve 16, via a detachable coupling assembly 17 positioned 
therebetween. Detachable coupling assembly 17 may include compatibly 
threaded sleeves mounted in confronting surfaces of hose 15 and water 
valve 16 to provide a threaded connection when concentrically disposed. 
Alternatively, coupling assembly 17 may comprise a convention key and 
groove coupling, a bayonet coupling or the like. 
In a preferred embodiment, water control valve assembly 16 comprises a 
hollow, pistol grip shaped handle including a valve member, not shown, 
normally biased into a position blocking a flow passageway extending 
through the hollow handle. A trigger 18 is pivotally attached to the 
pistol grip housing and is connected to the valve member. Selective 
pivoting of trigger 18 causes trigger 18 to move the valve member against 
its biasing assembly to open the flow passageway through the pistol grip. 
A rigid, high pressure pipe 19 includes a first end portion forming a 
fluid-tight connection with an outlet portion of water control valve 16, 
with an opposite end of rigid pipe 19 joining a spray head assembly 20 to 
be described in greater detail hereafter. Pipe 19 and spray head 20 
function as a wand which can be selectively directed toward a work surface 
by movement of attached water control valve 16. A hand grip 38 surrounds a 
portion of pipe 19 to allow an operator to grip and steady pipe 19 when a 
stream of highly pressurized water flows therethrough. 
Referring again to FIG. 1, it is noted that a further outlet conduit 21 
also extends from flow divider 12 to an inlet of a chemical injection 
assembly generally indicated at 22. Chemical injection assembly 22 
includes an eductor portion 23 having a flow passageway, not shown, 
wherein an intermediate portion of the flow passageway is restricted in 
size as compared to opposite end portions of the flow passageway, creating 
a venturi effect on liquids flowing therethrough. Positioned vertically 
below and attached to eductor portion 23 is an outlet portion check valve 
assembly 24. Check valve assembly 24 includes an inlet attached to an 
upper end portion of a substantially vertically extending chemical pick-up 
tube 25. Attached to an opposite, lower end portion of tube 25 is a filter 
26. The lower end portion of tube 25 along with filter 26 is immersed in a 
container 27 storing a quantity of chemical concentrate, not shown. 
Container 27 is vented to ambient pressure and may be of any convenient 
size and shape. For example, conventional 55 gallon drums of detergent or 
other chemical cleaning agents may be employed. Of course, the present 
invention is not limited to such relatively large containers. Rather, the 
chemical pick-up tube 25 and filter 26 may be immersed into a quantity of 
chemical agent contained in a metal or plastic bucket for smaller 
applications such as with pressure washer systems stocked by rental 
equipment dealers for use around the home or in other consumer 
applications. If container 27 constitutes a 55 gallon drum, pick-up tube 
25 may preferably comprise a tubular member having a length of 
approximately 8 feet. 
A continuous liquid passageway is formed through filter 26, pick-up tube 25 
and check valve 24, with an outlet of the passageway joining the flow 
passageway passing through eductor portion 23 of chemical injector 
assembly 22. During operation, the normal flow of low pressure water 
through the variable size venturi-type passageway in head portion 23 acts 
to generate a suction force sufficient to draw chemical concentrate from 
container 27 through the above mentioned liquid passageway and into the 
flow passageway, causing the chemical to mix with the water flowing 
therethrough. 
A chemical conduit 28, preferably comprising a flexible tube, includes an 
end portion forming a fluid-tight connection with an outlet of eductor 23. 
The chemical conduit may have a length substantially similar to the length 
of high pressure conduit 15, with a further end portion of chemical 
conduit 28 joining an inlet of a detachable coupling assembly 29. Coupling 
assembly 29 has an outlet which joins an end portion of a further, rigid 
conduit 30 which, in turn, has a further end portion joining an inlet 
portion of a chemical valve control assembly 31. 
In a preferred embodiment of the present invention, intermediate portions 
of high pressure conduit 15 are clamped to intermediate portions of 
chemical conduit 28 via heat shrinkable fastening members 32 and 33. 
Members 32 and 33 may comprise a sleeve extending about adjacently 
disposed portions of conduits 15 and 28, with the sleeves shrinking into 
tight contact with the conduits when heated. Of course, it is considered 
within the scope of the present invention to substitute any conventional 
fastening assembly for the heat shrinkable fastening members 32 and 33. 
A further fastening assembly 34 extends between intermediate portions of 
rigid conduits 19 and 30 in order to fixedly attach these conduits to one 
another. Fastening assembly 34 may comprise a bracket having a pair of 
openings of sufficient size so as to allow conduits 19 and 30 to pass 
therethrough. Finally, chemical control valve 31 may be suspended from 
conduit 19 via a clamp 35 attached to valve 31 and extending about pipe 
19. 
Like water control valve 16, chemical control valve 31 includes a valve 
member normally biased to a position blocking the flow of fluid through 
chemical control valve 31. The valve and biasing assembly has not been 
shown for purposes of simplicity. Chemical control valve 31 also contains 
an actuator, which preferably takes the form of a push button 36 which is 
directly connected to the valve member. Upon selective depression of push 
button 36, the valve member is moved against its biasing assembly, thus 
opening a flow passageway through chemical valve 31. When the pressure is 
removed from push button 36, the biasing assembly returns the valve member 
to its original position, thereby cutting off the flow of liquid through 
the valve assembly. 
A further chemical conduit 37 joins an outlet of chemical valve control 
assembly 31 with a further inlet formed in spray head 20. 
Turning to FIGS. 2-4, spray head 20 will now be discussed in detail. In a 
preferred embodiment, spray head 20 is molded of a metal or plastic 
material and includes a pair of liquid passageways 40 and 41 each 
extending substantially parallel to one another throughout spray head 20. 
Passageway 40 has a cross-sectional configuration greater than a 
cross-sectional configuration of passageway 41. In addition, passageway 40 
and passageway 41 are substantially in the same plane as the pistol grip 
of water control valve 16, with an inlet of passageway 40 being attached 
to high pressure water conduit 19. 
A high pressure water nozzle assembly 42 is releasably connected to spray 
head 20, with an inlet portion of high pressure nozzle 42 engaging an 
outlet portion of passageway 40. High pressure nozzle 42 has a 
longitudinal axis A--A which substantially coincides with the longitudinal 
axis of passageway 40. As best shown in FIG. 4, high pressure nozzle 42 
further includes an orifice 43 which is preferably of elliptical 
cross-sectional configuration. The major axis M--M of the substantially 
elliptically-shaped orifice 43 forms a substantially perpendicular angle 
with a vertical plane N--N formed between high pressure nozzle 43 and a 
further chemical nozzle 45 also releasably connected to spray head 20. 
Because of the elliptical shape of orifice 43, high pressure water flowing 
through orifice 43 will be emitted as a thin, flat water spray having a 
fan-shaped pattern. Furthermore, because of the orientation of elliptical 
orifice 43, the water emitted therefrom will initially form a spray in a 
horizontal plane forming an extension of major axis M--M. 
Turning again to FIG. 2, it is noted that flow passageway 41 includes an 
outlet portion 44 which is angled toward the longitudinal axis A--A. In 
particular, the outlet portion 44 may form an angle of substantially 
45.degree. with the remaining portion of flow passageway 41. As shown in 
FIG. 2, an inlet portion of flow passageway 41 is connected to chemical 
conduit 37, with outlet portion 44 passing through a chemical nozzle 45 
threaded in the outlet of passage 41. 
Chemical nozzle 45 has a generally annular orifice 46 which is best shown 
in FIG. 4. Furthermore, chemical nozzle 45 has a longitudinal axis B--B 
which substantially coincides with the longitudinal axis of outlet portion 
44 of flow passageway 41. Because chemical nozzle 45 forms an angle of 
substantially 45.degree. with the remaining portion of passageway 41, 
which extends parallel to passageway 40 and nozzle 42, the direction of 
liquid spray emitted from chemical nozzle 45 will differ from the 
direction of liquid spray emitted from high pressure nozzle 42. In 
particular, spray emitted from nozzle 45 will converge toward and actually 
intersect spray emitted from nozzle 42. The angle C of convergence between 
the two sprays is equal to the angle formed between longitudinal axes A--A 
and B--B which is substantially 45.degree. in the preferred embodiment. 
During operation of the pump assembly, low pressure tap water flows through 
attached conduits 11 and 13 and enters pump module 14. Pump module 14 is 
normally designed to deliver a constant flow rate which will dictate the 
specific size of the high pressure orifice 43 to be employed. For example, 
if the pump module 14 output volume is 3.0 gpm, a pressure nozzle with a 
#8 orifice will produce a line pressure of 600 psi. The pressure rating of 
this pump should be at least 600 psi or greater. If the pump output volume 
is 4 gpm, a pressure nozzle with a #8 orifice will produce a line pressure 
of 1,000 psi. In this case the pressure rating of the pump should be at 
least 1,000 psi or greater. 
As the highly pressurized water is emitted through high pressure orifice 
43, it forms water spray WS which begins to diverge in a substantially 
horizontal plane forming an extension of the axis M--M. As best shown in 
FIG. 3, the angle of divergence "D" is determined by measuring the angle 
from one side of the diverging water spray to the opposite side in its 
major plane defined by axis M--M. The orifice 43 of the high pressure 
nozzle is carefully selected to provide the desired angle "D" of fan spray 
divergence, with wider angles of convergence giving more spray coverage 
but at reduced impact pressure. The operable range for the angle of 
divergence D is between about 10.degree. and 70.degree., with the coverage 
and cleaning characteristics of angles in the range of 15.degree. to 
65.degree. being preferred. In a most preferred embodiment, the pressure 
nozzle 42 will have an orifice 43 capable of generating generally a fan 
pattern of water having an angle of divergence D of about 25.degree.. The 
fan spray maintains its divergence angle fairly closely until about 11/2 
to 2 feet from the pressure nozzle, at which point the divergence tends to 
decrease as illustrated in FIG. 3. 
As stated hereabove, for purposes of simplicity in design as well as 
overall cost savings, a standard round orifice 46 is preferred for use in 
the chemical spray nozzle 45. The round orifice 46 provides a generally 
conically shaped spray pattern C-S which usually diverges at angles in the 
range of 5.degree. to 10.degree.. If a wider chemical spray pattern C-S is 
desired for better distribution of the chemical solution, the chemical 
nozzle may also have an orifice similar in shape to the orifice 43 and 
capable of delivering a fan pattern of spray similar in shape to the high 
pressure nozzle. 
During operation, a stream of low pressure tap water or the like flows 
through attached conduits 11 and 21 and then passes through chemical 
injector 22. Because of the venturi effect generated during passage 
through head portion 23 of injector 22, a stream of chemical concentrate 
is sucked into the low pressure water stream. Upon selective actuation of 
chemical control valve assembly 31 from its normally closed position to an 
alternative, open position, the stream of the low pressure water and 
chemical is allowed to enter and flow through control valve 31 and then 
travel toward spray head 20. As the stream of water and chemical flows 
through nozzle 45, it is emitted as the conically-shaped spray discussed 
hereabove. Because the longitudinal axis B--B of the chemical nozzle 45 
intersects the longitudinal axis A--A of the high pressure nozzle, the 
chemical spray C-S intersects the water spray W-S emitted from nozzle 42. 
To ensure that the chemical spray C-S initially intersects with at least 
50% and preferably 90% of the transverse width of the fan water spray W-S, 
the two sprays preferably should intersect as close as practicable to the 
orifice 43 of the high pressure nozzle 42. In the preferred embodiment, 
this line of intersection is less than 1/8" to 3/16" from the exterior 
surface of the high pressure nozzle surrounding orifice 43. At this 
location, the fan pattern is still quite narrow and can be adequately 
covered by the intersecting chemical spray, even where the latter has a 
more gradually diverging cone pattern. To provide a greater axial length 
for chemical spray divergence before intersection between the two sprays 
occurs, the chemical orifice 46 is spaced farther away from the line of 
intersection than is the orifice 43, with the chemical orifice 46 being 
spaced between 5/16" and 1/2" from the line of intersection in the 
preferred embodiment. 
The spacing of both orifices 43 and 46 from the line of intersection is 
also a function of the angle of convergence C defined hereabove. While in 
the preferred embodiment the angle of convergence C between longitudinal 
axis A--A and B--B is substantially 45.degree., the angle of convergence 
may vary between 90.degree. and 20.degree. and is preferably within the 
range between 60.degree. and 30.degree.. As the angle of convergence drops 
below 30.degree., the distribution of chemical into the high pressure 
water spray W-S may be inadequate to provide effective cleaning. Likewise, 
when the angle of convergence C rises above 60.degree. the chemical spray 
C-S impact on the water spray W-S may adversely affect the momentum of the 
water spray. 
The size of the chemical orifice 46 may also be varied, depending on the 
flow rate of chemical agent actually desired. When tap water is employed 
as the low pressure source for transporting the chemical to chemical 
nozzle 45, a flow rate of about 1/2 gpm may be obtained through the 
eductor portion of the chemical injector 22, requiring a chemical orifice 
46 having a size of about 3/16" in order to delivery approximately 4 
ounces of chemical per gallon of water in the final impact stream 
generated by a pressure nozzle 42 having an orifice 43 with a 3.0 gpm flow 
rating. The total volume of the water and chemical is equal to the volume 
of the water pressure nozzle 42 and the chemical nozzle 45. For example, 
if the water pressure nozzle has a 3.0 gpm rating and the chemical nozzle 
a 0.5 gpm rating, the total volume would be 3.0+0.5=3.5 gpm. Larger or 
smaller chemical orifices 46 will provide greater or lesser chemical 
concentrations, respectively, assuming there are no other limiting 
conditions in the injector system design. For example, concentrations as 
low as 1.0 ounces chemical agent per gallon of total water may provide 
satisfactory cleaning, depending on the particular chemical agent 
employed. A 1/2 gpm injector flow and a 1/16" chemical orifice will 
provide a concentration of approximately 1.0 ounces of chemical per gallon 
of impact water. 
The chemical injection system employed in the present invention is 
completely independent of the high pressure water supply system. This 
allows the chemical supply system to be used in cooperation with existing 
high pressure water washer systems provided that a spray head using 
nozzles arranged according to the present invention is employed for 
emitting both the high pressure water and chemical solution. Furthermore, 
while the chemical injection system is preferably powered by ordinary low 
pressure tap water, the present invention is equally adapable for being 
powered by water supplied by a low pressure pump from a portable container 
or the like, or from a well water system. 
The present invention is not to be limited to the embodiments described 
hereabove, but is only to be limited by the scope of the claims following 
hereafter.