Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND AND SUl~MARY OF T~E _NVENTION
The present invention relates to a foam
generating nozzle for use in fire fighting or related
applications. More particularly, the invention relates to
a lightweight nozzle with a central bore or passage having
transverse means to create a turbulent, air entraining
flow within the fluid passing through the nozzle.
Foam generating nozæles may be used in fire
fighting as well as in other foam applications, such as
protective coverings for plants. Foams used in fine
fighting have different characteristics, depending on the
type of fire. Foam used on a Class B flamable liquid fire
must blanket and suffocate the first whereas when fighting
a Class A fire in ordinary material foams require a
quenching ability in addition.
To extinguish a Class A fire, desirably the foam
generated by a no~zle should have a low expansion ratio
and a long drain or dwell time to enhance the
effectiveness of the foam. Foams having a low expansion
will drain less rapidly from a surface which has been
covered, and will adhere for a sufficient time to vertical
surfaces to accomplish the necessary level of quenching or
insulation. Class B fires, on the other hand, are better
controlled by a medium expansion foam, with a higher
density bubble matrix to suffocate -the fire.
In order to develop a foam, it is necessary to
achieve a turbulent interaction of the fire fighting fluid
medium, usually water, a foaming agent, and a gas, usually
ambient air. Many factors appear to affect the foam
characteristics, including the proportions of foaming
agent in water, the amount and location of air applied to
the foam and, to a large measure, the structure and degree
of turbulent interaction of the mixture of water and
foaming agent with the air.
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Previous foam generating nozzles have utiliæP~
heavy metal structures with complex apertur~s and passages
therein.
U.S. Patent 2,388,508 to Timpson discloses a
nozzle with a central valve body having a pair of
converging ducts or passages to cause two streams of the
liquid mixture to impinge at a 60 angle within a
cylindrical baffle or spray straightener, before exiting
into a low pressure air chamber which then feeds foam
through a thxoat and pattern nozzles.
U.S. Patent 2,513,417 to Lindsay discloses a
complex nozzle with a venturi means for feeding foaming
agent into the wa-ter, with a conical spreader which
separates the stream of mixture in an air chamber. A
further tear drop shaped baffle is required to control the
velocity of the fluid to achieve a more uniform foam
quality~
Both of the foregoing patents require a complex
machined or cast product with specially designed -fluid
passages to generate an adequate foam.
The present invention, however, has achieved
improved foam characteristics, both in drain time and
adherence, with no increase in complexity or weight of
materials. Rather, significant simplification of design
has resulted in surprisingly economical manufacturing
capabilities while achieving even lighter weights and
improved fire fighting capabilities.
The present invention of a foam generating nozzle
has a nozzle body with a longitudinal passage
therethrough, an inlet at the up-stream end of the nozzle
body for receiving a pressurized mixture of water and
foaming agent, an outlet at the down-stream end of the
nozzle body for emitting a stream of foam, a plurality of
; contiguous apertured plates positioned transversely across
the passage between the inlet and outlet to permit passage
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of the mixture through the nozzle, wherein at least one
plate has at least one aperture and at least one other
plate has a plurality of apertures partially overlying a
portion of the at least one aperture to permit passage of
the mixture therethrough; and means down-stream of said
plates for the induction of air into the interior of the
nozzle.
It is an object of the present invention to
provide a simplified nozzle structure allowing for
economi~al and efficient manufacture, while also achieving
a desirable light weight and durability.
A -further object of the invention is to provide a
nozzle which will generate a low to medium expansion foam
with an extended drain time while retaining good range or
throw characteristics~
The nature and objects of the invention and the
various advantageous features are shown in the
accompanying drawings illustrating preferred forms by way
of example.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal cross-sectional view of
a foam generating nozzle illustrating the principles of
the present invention.
FIG. 2 is a cross-sectional view of the
turbulence generator of the nozzle taken along the line
2-2 of FIG. 1.
FIG. 3 is a cross-sectional view of the
turbulence genera-tor of the nozzle taken along the line
3-3 of FIG. 1.
FIG. 4 is a longitudinal sectional view o-f an
alternate embodiment of a nozzle utilizing the invention.
FIG. 5 is a plan view of an alternate
configuration of the turbulence generator plate of the
invention, and
FIG. 6 is the opposite plan view of the plate of
FIG. 5.
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The present inven~ion will be explained in
relat,ion to Figure 1 which illustrates one embodiment of
the invent,ion which achieves the objects of the invention.
A tubular nozzle body, generally illustrated as
1, has a circular inlet 10 and a circular outlet 20. A
source of pressurized fluid and foaming agent is supplied
to inlet 10. Commonly, a mixture of water and foaming
agent such as SILV-EX* or Monsanto WD~61 is supplied under
pressures ranging from 50 to 200 pounds per square inch
via a 1 1/2 inch fire hose. The hose is attached at inlet,
10 by any standard coupling such as by t'hreads 14. The
pressurized mixture passes through inlet, 10 into tubular
chamber 16 until obstructed by a turbulence generator
comprising a pair of contiguous transverse plates 18 and
20. Plate 18 comprises a diverter disc with a plurality
of circular apert,ures 22, which is in face to face contact
with plate 20 being a converter disc with a single
centrally located aperture 24. The pla~es or discs 18 and
20 are of a generally equal thickness, no greater than and
preferably less than the diameter of the apertures 22. As
illustrated in Figures 2 and 3 apertures 22 are generally
centered symmetrically on the circumference of aperture
24, but may be offset outwardly up t,o 1/3 of their radius
without significant diminution of nozzle performance.
Thus, manufac~uring tolerances will permit reasonable
dimensional variation without significant degradation of
performance.
Desirably, the cross-sectional area of aperture
24 is approximately equivalent ~.o the total cross-sectional
areas of apertures 22, and is determined on t,he basis of
the pressure available for supply of mixture to the nozzle
and the flow rate desired from the nozzle~
When the mixture of water and foam generating
agent passes from chamber 16 through the turbulence
generator it is diverted through apertures 22 and divided
.
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into a number of streams. It is believed that a portion
of the mixture in each stream impinges against the
up-stream surface of disc 20 which partly overlies
apertures 22, thereby generating back pressure and
significant turbulence. The s-treams of mixture escape
laterally into aperture 24 and appear to converge in some
observable degree.
Upon exiting through aperture 24, the converging
streams of mixture interact and expand into multiple
turbulent finely divided sprays within aspirating zone
26. A series of radial apertures 28 circumscribe barrel
30 of the nozzle at a point approximately one third of the
barrel diameter down-stream from the plates. The mixture
entering zone 26 creates a reduced aspirating pressure to
draw ambient air through aspiration holes 28 to interact
with the turbulent mixture. The consequence of the
interaction of aspirated air with the turbulent mixture
results in the production of a ~uality foam bubble
structure which fills barrel 30 shortly down-stream of the
aspiration holes 28. The foam then exits barrel 30 at
outlet 32 under pressure.
It has been found that the length of barrel 30 is
not critical, although desirably the barrel should exceed
three -times its diameter in order to allow full foam
formation and expansion before ejection from the nozzle
exit. In contrast, excessive barrel length is undesirable
as friction losses between the foam and the side of the
barrel will reduce the pressure in the foam exiting the
nozzle, thereby reducing the throw characteristics of the
foam stream.
The parameters of nozzles fulfilling the objects
of the invention are illustrated by example hereafter.
EXAMPLE 1
A medium flow capacity nozzle was constructed
with the following parameters.
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Inlet diameter - 1 1/2 inches
Barrel diameter - 1 1/4 inches
Barrel length - 12 inches
Disc diameters - 1 1/2 inches
Diverter disc ~ 4 x 1/4 inch diameter holes
symmetrically centered on
circumference of converter
disc hole
Converter disc - central 1/2 inch diameter hole
Aspiration holes - 6 x 3/8" diameter, 1/2" from
discs
Pressure - 70 p.s.i.
Flow Rate - 16 imperial gallons per minute
A high quality 10 to 1 expansion foam was
generated with a 25 percent drain time of 12 minutes
tested in accordance with N.F.P.A. 412 Foam Standard. The
foam was applied to a vertical surface with insignificant
slump when applied in thicknesses varying from 1/2 inch to
2 inches.
With operating pressures at 70 p.s.i., 16
imperial gallons of fluid produced 160 imperial gallons of
foam per minute with a throw distance or reach of stream
of 80 feet.
EXAMPLE 2
Inlet diameter - 1 1/2 inches
Barrel diameter - 1 1/2 inches
Barrel length - 14 inches
Disc diameters - 1 1/2 inches
Diverter disc - 4 x 5/16 inch diameter holes
symmetrically centered on
circumference of converter
disc hole
Converter disc - central 5/8 inch diameter hole
Aspiration holes - 6 x 1/2" diameter, 1/2" from
discs
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Pressure - 70 p.s.i.
Flow Rate - 32 imperial gallons per minute
The nozzles of Examples 1 and 2 were constructed
of light-weight ABS tubing with standard plumbing
connections. It has been found that such construction has
the advantage of light-weight, durability and readily
obtainable, economically priced parts.
In operation, the nozzle will throw a stream of
foam a distance varying up to 85 feet. Where the fluid
delivery pressure is high, and it is not desired to throw
a stream of foam -to maximum range, the range of throw can
be reduced simply by manually covering one or more of the
aspiration apertures. Such choking will result in a
dramatic ability to reduce and control the range of throw
while maintaining a consistent quality of foam.
Referring now to Figure 4, an alternate embodiment
of the invention is illustrated wherein threaded inlet
portion 410 is adapted to receive a fire fighting mixture
of water and foaming agent under pressure which -then
passes through the multiple orifices 422 of diverter disc
418 and then exits through orifice 424 of the converter
disc 420. Upon exiting from the orifice, the turbulent
mixture generates a low pressure which aspirates air
through orifices 428. Optionally, in order to obtain a
finer bubble matrix in the foam, a screen or mesh 429 may
be inserted in barrel 430.
EXAMPLE 3
Inlet diameter - 1 1/2 inch with fire hose
threaded connection
~arrel - 14 inches by 3 inch diameter
Disc diameters - 1 1/2 inches
Diverter disc - 4 x 5/16 inch diameter holes
symmetrically centred on
circumference of converter
disc hole
,
g
Converter disc - central 5/8 inch diameter hole
Aspirator holes - 18 x 3/16 inch diameter
Pressure - 85 psi
Rate - 32 gallons per minute
At a pressure of 85 psi, this nozzle produced a
medium expansion foam at a flow rate of 32 gallons per
minute, producing 320 gallons per minute of foam with a
reach of 50 feet. The reach of foam was not as great as
examples 1 and 2, due in part to the provision of a screen
corresponding to screen 429, but a finer bubble matrix was
achieved with the screen, resulting in a 25~ drain time in
excess of 15 minutes.
An alternate embodiment of turbulence generator
from plates 18 and 20 may be seen in Figures 5 and 6.
Turbulence generator 520 may be a unitary plate element in
which a larger hole 524 is formed partially through the
plate, and a number of smaller holes 618 are similarly
formed in the up-stream surface of the plate
(See Figure 6). Holes 524 and 618 partially penetrate the
plate from opposite sides, and intersect at a plane
intermediate surfaces 520 and 622, providing turbulence
generating passages for the mixture.
Additionally different combinations of apertures
may be utilized in the turbulence generator, such as the
six holes 618 overlying the central hole 524 shown in
Figures 5 and ~. Similar holes can be provided in
converter and diverter plates 18 and 20.
With any combination of apertures it is desirable
to maintain a correlation between the total
cross-sectional area of the diverter plate apertures equal
to the cross-sectional area of the orifice of the
converter plate. In any event, maximum efficiency of the
nozzle is achieved where the diverter plate orifices are
centered on the circumference of the converter plate
orifice without variation greater than 1/3 of the radius
of the converter plate o.ri~ice.
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Further variations in the lay-out of the orifices
of the converter and diverter plates may be achieved by
utilizing more than one orifice in the converter plate and
grouping the orifices of the diverter plate symmetrically
overlying the circumferences of the converter plate
orifices.
The embodiments shown and described above are
only exemplary. Various ~odifications can be made in the
construction, materials, arrangement and operation of the
nozzle and still be within the scope of the invention.
The limits of the invention and the bounas of the patent
protection are measured and defined by the following
claims.
