Note: Descriptions are shown in the official language in which they were submitted.
CA 02218043 1997-10-10
WO 96/32668 PCT/US96/05032
1
PRESSURE BALANCING FOAM VALVE
Field of the Invention
The present invention relates generally to valves used for delivering foam
into a liquid
P
stream and, more particularly, to a differential valve for delivering a
precise amount of fire-
fighting foam into a water stream operating at various volumetric flow rates.
Background of the Invention
The addition of foaming agents to fire-fighting water as a fire suppression
agent has
been recognized as early as the 1870s, when the first such use was reported to
have been
patented in England. Since then, through the years, further advances have been
made.
These advances have included better understanding of the function of the
foaming agent, the
type of delivery system needed to dispense and handle the foaming agent and,
most
significantly, the foam-to-water ratio for particular fire applications.
For many years, Class A type fire-fighting foams of the A-FFF type have never
been
used to combat fuel fires such as JP4 jet fuel, gasoline and diesel fuels.
More recently,
however, Class A foams, such as the agents sold under the trademark Sylvex of
the Annul
Company, have been found to increase the fire suppression efficiency of water
from three
to up to nine times when used on wild land, Class A structur~fires, and on
hydrocarbon
fires. This recognition has greatly expanded the utility and usage of foam as
an efficient fire-
fighting agent.
In the past, a fairly standard foam-to-water ratio of 6:94, or 6 parts foam to
94 parts
water, was used and an apparatus capable of maintaining such a ratio at
various water
volumetric flow rates was disclosed in a number of patents, such as U.S.
Patent No.
4,064,891 to Eberhart and U.S. Patent No. 4,448,256 to Eberhart, et al. The
'891 patent
to Eberhart discloses a balanced pressure valve. The '256 patent to Eberhart,
et aL, employs
a positive displacement gear pump to maintain the standard ratio of foam to
water despite
changes in water volumetric flow rates.
Most recently, it has been recognized that the foam-to-water ratio of 3:97
over water
volumetric flow rate variations from 20 to 1,000 gallons per minute (GPM) were
needed,
along with a more complex proportioning valve to ensure a stable foam-to-water
ratio over
the wide volumetric flow rate. U.S. Patent No. 4,633,895, also to Eberhart,
discloses a
proportioning valve comprising. a shuttle-type system for accommodating such
foam-to-water
ratio over the above-identified volumetric flow rate. However. with further
devei~nment ~f
foam suppression fire-fighting, it became apparent that foam-to-water ratios
as low as
0.2:99. 8 were needed and precise proportioning at 0.2 % increments up to a
foam-to-water
ratio of 1:99 could be important in various applications.
-1-
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CA 02218043 2005-12-22
U.S. Patent 5,165,442 to Fiala discloses a differential valve for
accommodating the mixing of foam and water at ratios as low as 0.2% and as
high as
1%, in 0.2% increments. Generally speaking, the differential valve is
constructed
having an internal mechanism that produces a pressure drop or reduction in
pressure
through the valve, between the water inlet and water outlet, which increases
in
proportion to an increase of water through the valve. The pressure
differential that is
produced by the valve is used to pressurize foam, contained in an external
foam
dispensing tank and the like, for delivery at a present ratio into the water
stream
passing through the valve. However, it has been discovered that at increasing
water
flow rates above about 150 GPM the delivery ratio of foam to water does not
remain
constant but, rather, varies from the desired constant ratio and is
unpredictable. The
inability of the differential valve to provide a desired consistent delivery
ratio of foam
to water at volumetric flow rates greater than about 150 GPM adversely affects
the
fire-fighting efficiency of the foam-water system.
With further development of foam suppression fire-fighting, it has become
apparent that foam-to-water ratios as low as 0.1:99.9 may be needed in certain
applications, and precise proportioning of foam to water up to a 1:99 ratio
could be
important in various applications under various water volumetric flow rates
that
include volumetric flow rates greater than 150 GPM, i.e., at volumetric flow
rates
where other known differential valves are usable to provide an accurate
proportion of
foam to water.
It is, therefore, desirable that a differential valve for delivering foam into
a
liquid stream be constructed in a manner that produces a predictable and
controlled
pressure differential, between the inlet and outlet of the valve in liquid
passing
through the valve, under a wide range of flow rate conditions to facilitate
accurate
foam delivery from the valve into the liquid passing therethrough. It is
desirable that
a differential valve be constructed so that it is compatible with existing
foam-water
delivery systems. It is also desirable that a differential valve be
constructed from
relatively conventional materials using conventional manufacturing techniques,
comprise a minimum number of moving parts, and be simple to operate.
Summary of the Inyention
There is, therefore, provided in practice of this invention a differential or
pressure balancing foam valve that is constructed in a manner that produces a
predictable and controlled pressure differential, i.e., pressure drop, within
the valve
between a high-pressure inlet port and a foam outlet port with changing inlet
liquid
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CA 02218043 2005-12-22
conditions to ensure accurate foam delivery into liquid passing through the
valve and
a constant foam to liquid proportion. A pressure balancing valve constructed
according to principles of this invention includes a body having a liquid
inlet at one
end and a liquid outlet at an opposite end, and having an annular passage
therethrough; a first stage pressure regulating assembly attached adjacent the
liquid
inlet comprising: a shaft extending axially within the annular passage,
wherein the
shaft is attached at a first end to the body adjacent the liquid inlet; a one-
piece
pressure disc having a central opening therethrough for slidable movement on
the
shaft; a spring interposed between the pressure disc and a second end of the
shaft for
urging the pressure disc into a seated position against an end of the liquid
inlet
annular passage at low flow conditions, wherein the spring is proportioned in
strength
to permit compression of the spring by force of the pressure disc from
increasing
liquid pressure to unseat the pressure disc and permit liquid flow through the
annular
passage and the valve; and a second stage pressure regulator comprising a
venturi-
shaped annular passage through the liquid outlet, wherein the pressure disc
and
venturi together act to provide a differential pressure within the valve.
The inlet body includes a liquid outlet portion that is not restricted by
seated
placement of the pressure disc and that is hydraulically connected to a foam
delivery
system comprising a foam tank and the like to pressurize the foam within the
tank.
The outlet body includes a plurality of foam injection ports disposed therein
that are
positioned circumferentially around a throat portion of the venturi. The foam
injection ports are connected to a foam injection manifold within the outlet
body that
facilitates passage of foam introduced into the valve through a foam outlet
port,
disposed through the outlet body, to the foam injection ports to effect foam
dispersement into liquid passing through the valve.
The pressure disc and venturi act together to provide a proportional change in
differential pressure within the valve, between the high-pressure inlet port
and the
foam outlet port, with changing liquid flow rate and pressure to ensure a
desired
degree of foam pressurization and, therefore, accurate foam delivery into the
liquid at
various volumetric flow rates to ensure a constant and predictable foam to
water ratio.
The present invention also provides a pressure balancing valve comprising: a
three-piece body comprising: an inlet body portion having an annular passage
extending therethrough; a central body portion having an annular passage
extending
therethrough; an outlet body portion having an annular passage extending
therethrough; wherein the central body is interconnected between the inlet and
outlet
body portions, and wherein the annular passages are coaxial with one another;
a first
-3-
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CA 02218043 2005-12-22
stage pressure regulating assembly axially disposed within the annular passage
of the
valve body comprising: a shaft extending axially within the annular passage
that is
mounted at a first end to the inlet body; a one-piece pressure disc having a
central
opening therethrough for slidable movement on the shaft; a spring interposed
between
S the pressure disc and a second end of the shaft for urging the pressure disc
into a
seated position against an end of the inlet body annular passage, wherein the
spring is
selected to permit compression of the spring by the pressure disc from force
of
increasing liquid pressure to unseat the pressure disc and permit liquid flow
through
the annular passage and the valve; and a second stage pressure regulator
comprising a
venturi-shaped annular passage through the outlet body, wherein the pressure
disc and
venturi together act to provide a differential pressure within the valve.
In a further aspect, the present invention provides a pressure balancing valve
comprising: a three-piece body comprising: an inlet body portion having an
annular
passage extending therethrough and having a web portion extending
diametrically
across the annular passage, and having a high-pressure inlet port extending
radially
through the inlet body from the annular passage to an outside surface; a
central body
portion connected at a first end to the inlet body and having an annular
passage
extending therethrough; an outlet body portion connected to a second end of
the
central body portion and having a venturi-shaped annular passage extending
therethrough for providing a differential pressure within the valve; a
pressure disc
disposed within the annular passage of the valve body; a shaft disposed
axially within
the annular passage of the valve that is attached at a first end to the web
portion of the
inlet body, wherein the pressure disc has a central opening therethrough to
accommodate slidable placement on the shaft; and a spring interposed between
the
pressure disc and a second end of the shaft for urging the pressure disc into
a seated
position against an end of the inlet body annular passage, wherein the spring
is
selected to permit compression by the pressure disc from force of increasing
liquid
pressure rate, and wherein the pressure disc and venturi together act to
provide a
differential pressure within the valve.
In a still further aspect, the present invention provides a method for
producing
a differential pressure within a valve comprising the steps of: passing liquid
that
enters an inlet portion of the valve through an annular passage and over a
slidably
displacable pressure disc, wherein the position of the pressure disc within
the annular
passage is controlled by a spring means acting to urge the pressure disc into
a seated
condition against an edge portion of the passage to prohibit flow
therethrough,
wherein the pressure disc is unseated and moved axially away from the inlet
portion
-3a-
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CA 02218043 2005-12-22
with increasing liquid pressure, wherein a differential pressure between the
inlet
portion and an outlet portion of the valve is produced by action of pressure
disc
restricting flow of liquid through the valve; and passing liquid through an
annular
passage of an outlet portion of the valve shaped in the form of a venturi,
wherein a
differential pressure between the inlet portion and outlet portion of the
valve is
produced by action of the venturi restricting flow of liquid through the
valve, wherein
the pressure disc and venturi act together to produce a differential pressure
within the
valve.
-3b-
CA 02218043 1997-10-10
WO 96/32668 PCTlUS96/05032
1 Brief Description of the Drawings
These and other features and advantages of the present invention will become
appreciated as the same becomes better understood with reference to the
specification, claims
and drawings wherein:
FIG. 1 is a vertical sectional view of a prior art differential valve
disclosed in U.S.
Patent No. 5, 165,422;
FIGS. 2a-2c are fragmentary sectional views of the prior art differential
valve of FIG.
1, showing different operating positions for flow responsive elements of the
differential
pressure valve;
FIG. 3 is a vertical sectional view of a pressure balancing foam valve
constructed
according to principles of this invention;
FIG. 4 is an end view of the pressure balancing foam valve in FIG. 3 at
section 4-4;
FIG. 5 is a perspective view of a foam delivery system incorporating use of
the
pressure balancing foam valve of FIG. 3; and
FIGS. 6a-6c are fragmentary sectional views of the pressure balancing foam
valve of
FIG. 3, showing different operating positions for a first stage pressure
regulating assembly.
Detailed Description
A differential valve for delivering fire-fighting foam into a water stream is
disclosed
in U.S. Patent No. 5,165,442 to Fiala, and is illustrated in FIG. 1. The
differential valve
10 comprises a one-piece body 12 constructed from a suitable structurally
rigid material.
The body 12 comprises a water inlet at a first end 14 and a water outlet at an
opposite second
end 16. The body comprises a centrally disposed inner chamber 18 extending
from the first
end 14 to the second end 16. The first end and second end are configured,
around an outside
surface, to accommodate attachment with conventional hydraulic or fire-
fighting-type fittings.
More specifically, the first end 14 has an exterior surface configured to
accommodate
attachment with a coupling ring 20.
The internal cavity includes a high-pressure section 24 adjacent the first end
14 that
communicates with a high-pressure annular fitting 25 that extends through a
wall portion of
the body. A low-pressure section 28 of the inner chamber 18 is disposed
adjacent the second
end 16 and communicates with a low-pressure annular fitting 29 that extends
through a wall
portion of the body. A high-pressure plate 32 and a low-pressure plate 34 are
disposed
centrally within the inner chamber 18 and are slidably displaceable within the
chamber via
a centrally mounted pressure plate shaft 36. The pressure plate shaft 36 is
fixedly attached
to a web portion 38 of the body 12 that extends diametrically across the
second end 16.
As shown in FIGS. 1, 2a-2c, the high-pressure plate 32 has a number of
openings 33
that extend axially through the high-pressure plate, i.e., are oriented
parallel with the
pressure plate shaft 36. The low-pressure plate 34 includes two diametrically
opposed bolts
CA 02218043 1997-10-10
WO 96!32668 PCT/US96/05032
1 40 that each extend through axially oriented openings (not shown) in the low-
pressure plate
surface and are threadably engaged with the high-pressure plate 32. Springs 42
are disposed
around outside diameters of the bolts 40 and extend from a head portion of
each bolt to a
facing surface of the low-pressure plate. Configured in this manner, the low-
pressure plate
34 is permitted to move under spring compression axially away from the low-
pressure plate.
The pressure plate shaft 36 comprises a shaft bushing 44, disposed around an
outside
surface of the shaft, and a spring 46 disposed around an outside surface of
the shaft bushing
44. The spring 46 extends from the web portion 38 of the second body end 16 to
a shoulder
bushing 47 that is disposed within a central opening (not shown) through the
low-pressure
plate 34. Accordingly, when installed on the shaft 36, the high-pressure plate
32 and the
shaft bushing 44 is permitted to move axially along the shaft, which slidable
movement is
controlled by compression action of the spring 46. Additionally, the low-
pressure plate 34
is permitted to move axially along the shaft 36 and the shaft bushing 44,
which slidable
movement is controlled by compression action of the springs 42 between the
surface of the
low-pressure plate and the bolts 40.
The high-pressure plate 32 and low-pressure plate 34 are disposed within the
inner
cavity 18 such that an outer diameter of each pressure plate communicates with
an adjacent
wall portion of the body 12. The outer diameter of the high pressure plate 32
partially
obstructs an entrance to the high-pressure fitting 25. Accordingly, as low
pressure water
enters the first end 14, a portion of the entering water is obstructed by the
surface of the
high-pressure plate 32 and is directed into the high-pressure fitting 25.
Water leaving the
high-pressure fitting is directed to a bladder or other type of foam dispenser
(see for example
FIG. 5) for effecting the dispersement of foam therefrom. If the pressure of
the water
entering the first body end 14 is less than a threshold pressure, neither the
low pressure plate
34 nor the high-pressure plate 32 will be slidably displaced along the
pressure plate shaft 36
to facilitate passage of water through the body and, therefore, will act as a
check valve, as
shown in FIG. 2a. This condition is referred to as a "no flow" condition.
As the pressure of the water entering the first body end 14 increases, water
will pass
through the openings 33 that extend through the high-pressure plate 32 and
impinge on the
low-pressure plate 34, causing the low-pressure plate to be slidably displaced
along the
pressure plate shaft 36 and spring retaining bolts 40 away from the high-
pressure plate 32,
as shown in FIG. 2b. Under such low pressure low flow conditions, foam
dispensed from
the foam dispenser is routed through a metering valve (not shown) to the low-
pressure fitting
29, where the foam is delivered into the low-pressure section of the inner
chamber 18 valve
body 12 adjacent the second end 16 and is mixed with the exiting water. This
condition is
referred to as a "low flow" condition.
As the pressure of the water entering the first body end 14 increases, the
water
continues to pass through the openings 33 in the high-pressure plate 32 until
the pressure
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CA 02218043 1997-10-10
WO 96!32668 PCT/US96105032
1 force of the water impinging against a surface portion of the high-pressure
plate 32 and the
surface of the low-pressure plate 34 is sufficient to cause both the high-
pressure plate 32 and
low-pressure plate 34 to be slidably displaced along the pressure plate shaft
36 towards the
second body end 16, as shown in FIG. 2c. Under such high-pressure conditions,
the water
is allowed to flow both through the openings 33 in the high-pressure plate 32
and over the ,
outside diameter of the high-pressure plate. In this position, the outer
diameter of the high-
pressure plate 32 is positioned away from the wall portions of the valve body
12. This
condition is referred to as a "high flow" condition.
As the pressure of the water entering the first body end 14 increases, the
high-pressure
plate 32 and low-pressure plate 34 both continue to be slidably displaced
along the pressure
plate shaft 36 according to the particular spring constant of the spring 46.
As the flow rate
and pressure of the water passing through the valve body 12 increases, it is
desired that the
differential pressure of the water between the high-pressure fitting 25 and
low-pressure fitting
29 also increase a proportional amount, thereby ensuring that a constant
proportion of foam
is dispensed into the water stream.
The construction of the above-described valve makes it difficult, if not
impossible, to
provide a constant proportion of foam with increasing water flow rate and
pressure due to
the spring-controlled action of the high and low pressure plates. When the
flow rate and
pressure of the water entering the valve is at a medium to high flow
condition, the spring
tension of the spring 36 imposes a force against the high and low pressure
plates in a
direction toward the first body end 14 to resist the force of the water acting
on the plates.
The position of the plates within the inner chamber 18 imposes a flow
restriction on the
water passing through the valve, thereby creating a pressure differential or
pressure drop
between the first and second ends 14 and 16, respectively, and differential
pressure between
the high and low pressure fittings. As the plates are moved further toward the
second end
16, in response to increasing water flow rate and pressure, it is desired that
the pressure
differential also increase a proportional amount to provide a constant
proportion of foam
dispersement.
At medium to high water flow rates and pressures, however, the above-
identified
spring-controlled mechanism is unable to provide a consistent proportion of
foam
dispersement because of fluctuations in the positioning of the high-pressure
plate 32 and low-
pressure plate 34 inherent in an exclusively spring-controlled pressure plate
mechanism. For
example, binding of the spring 46 relative to the pressure plate shaft 36 and
shaft bushing
44 can adversely affect the axial displacement of the high-pressure plate 32
and low-pressure
plate 34 during operation and, thereby, produce unwanted variations in the
differential ,
pressure between the high-pressure fitting 25 and low-pressure fitting 29. For
example, it
has been discovered that the spring-controlled mechanism is unable to provide
a predictable
and controlled differential pressure at pressures greater than approximately
150 GPM.
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CA 02218043 1997-10-10
WO 96!32668 PCTIUS96/05032
1 Additionally, fluctuations in the flow rate of water entering the valve can,
in some
instances, effect a harmonic oscillation of the high-pressure plate 32 and low-
pressure plate
34 vis-a-vis the pressure plate shaft 36, thereby also producing unwanted
uncontrollable
variation in the pressure differential between the high-pressure fitting 26
and low-pressure
fitting 30. Also, at very high water flow rates and pressures the high and low
pressure
plates can completely compress the spring, thereby completely disabling the
valves
differential pressure regulating mechanism.
Referring now to FIG. 3, a pressure balancing foam valve 50 constructed
according
to principles of this invention has a housing body 52 with a three-piece
construction
comprising an inlet body portion 54, a central body portion 56, and an outlet
body portion
. 58. The housing body has a generally cylindrical outside surface
configuration.
The inlet portion 54 includes a first end 60 having an outside surface
configured to
accommodate connection with a number of conventional hydraulic fittings, such
as hose
threads, pipe threads, quick connects, vitaculic fittings and the like. The
three-piece body
construction permits the valve to be assembled with differently configured
inlet portions to
facilitate use of the valve with such different inlet connections without
having to construct
and entirely different housing body, thereby maximizing application of the
valve with a
number differently configured liquid/foam systems. The inlet portion 54 may be
constructed
from a suitable structurally rigid material such as steel, steel alloy,
aluminum and the like.
It is desired that the selected material be both corrosion and chemically
resistant. In a
preferred embodiment, the inlet portion is formed from a hard anodized
aluminum such as
6061 that has a Rockwell C hardness of approximately 80. Aluminum is a
preferred material
because of its corrosion resistance and because it is not etched by contact
with Class A foam.
The inlet portion 54 includes an annular passage 62 that extends therethrough.
As
shown in FIGS. 3 and 4, a web 64 extends across an inside diameter of the
annular passage
62 adjacent an opening of the first end 60 so that water entering the inlet
portion passes
through the annular passage 62 on both sides of the web 64. The web extends
axially about
midway into the annular passage from the first end 60. The web has an opening
66 that is
centrally positioned and extends therethrough along an axis running along the
annular
passage. As discussed below, the opening 66 accommodates attachment with an
end of a
pressure disc.
The outside surface of the inlet portion includes an enlarged diameter section
68 that
extends axially from a second . end 70 a distance toward the first end 60. The
enlarged
diameter section has an outside diameter approximately equal to an outside
diameter of the
central body portion 56. A high-pressure inlet port 72 extends radially
through a wall
portion of the enlarged diameter section 70 from the annular passage 62 to the
outside surface
of the inlet portion 54. The high-pressure inlet port 72 may be configured
internally to
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CA 02218043 1997-10-10
WO 96/32668 PCTIUS96105032
1 accommodate connection with conventional pipe or hose attachments, such as
threaded
attachment and the like. The second end 70 e5ctends radially from a terminal
edge of the
annular passage 62 to an outer lip 76, defining a flat surface therebetween.
The surface
defined by the second end 70 is perpendicular to an axis running along the
annular passage
62.
The outer lip 76 extends circumferentially around an outside surface of the
second end
70 and includes a groove 78 that extends circumferentially a depth within the
lip. An edge
portion 80 is positioned adjacent the groove 78 and extends radially from the
groove to the
outside surface of the enlarged diameter section 68. The edge portion 80 is a
flat surface that
accommodates abutting placement against a complementary edge portion of the
central body
portion 52 during attachment therewith. The inlet body portion 54 includes a
number of
openings 82 that each extend axially through the enlarged diameter section 68
and are
positioned near a outside surface. In a preferred embodiment, the inlet
portion 54 includes
approximately six openings 82. The openings 82 are sized to accommodate
placement of
attachment bolts 84 therethrough.
In a preferred embodiment of the inlet body portion 54, the first end 60 has
an outside
diameter of approximately 2.875 inches, the annular passage 62 has a diameter
of
approximately 2.5 inches and a length of approximately 2.5 inches. The web 64
has a
thickness of approximately 0.25 inches and extends an axial distance into the
annular passage
of approximately 0.875. The web opening 66 has a diameter of approximately
0.375 inches.
The high-pressure inlet port 72 has a tapered configuration with a diameter of
approximately
0.5 inches at the annular passage 62 and a diameter of approximately 0.75
inches at the
outside surface. The lip 76 has a diameter of approximately 3.75 inches, and
the groove
extends radially inward a depth of approximately 0.125 inches. The bolt
openings 82 have
a diameter of approximately 0.257 inches and are arranged at six equidistant
locations near
the outside surface of the enlarged diameter section 68.
A first stage pressure regulating assembly 86 includes a pressure disc 88 that
is
slidable displaceable on a disc shaft 90. The pressure disc 88 comprises a
solid one-piece
circular disk formed from a hard material such as metal, wood, plastic and the
like. It is
desired that the material selected to form the pressure disc be a tough
lightweight material
that is corrosion and chemically resistant. A preferred material is Delrin''"
made by DuPont
de Nemours, E.I. & Co. The pressure disc 88 has first beveled or sloping
surface 90 that
extends axially along an outside surface of the disc from a first end 92 to
about a middle
position, and a second flat surface 94 that extends from the beveled surface
90 to a second
end 96. The beveled surface 90 serves to both promote water passage over the
disc during ,
passage of water through the valve and to provide a good seal against an edge
portion of the
annular passage 62 of the inlet body portion.
_g_
CA 02218043 1997-10-10
WO 96!32668 PC"T/US96/05032
1 The pressure disc 88 includes an opening (not shown) that extends axially
through the
disc for accommodating placement of the disc'-shaft 90 therethrough. The
second end 96
includes a recessed portion or counter bore (not shown) that is coaxial with
the disc opening
to accommodate placement of a bushing 98 therein.
. 5 In a preferred embodiment, the pressure disc 88 has a axial length of
approximately
one inch, a diameter across the flat surface 94 of approximately 2.5 inches,
and a diameter
across the first end 92 of approximately 2.1875 inches. The beveled surface 90
slopes
radially inward from the flat surface 94 to the first end 92 at an angle of
from 5 to 20
degrees. The opening has a diameter of approximately 0.375, and the counter
bore has a
diameter and depth of approximately 0.75 inches and 0.25 inches, respectively.
The pressure disc 88 is slidably positioned on the disc shaft 90. The disc
shaft can
be formed from any structurally rigid material such as steel, steel alloys and
the like. It is
desired that the material selected to form the disk shaft be corrosion and
chemically resistant.
A particularly preferred material is 303 stainless steel.
Moving from left to right in FIG. 3, a first end 100 of the disk shaft 90 has
a reduced
diameter section 102 that extends axially a distance along the shaft length.
The reduced
diameter section is sized to fit within the web opening 66 of the inlet body
portion 54. The
first end 100 has a threaded passage (not shown) that extends axially along a
distance of the
shaft. A bolt 104 is disposed through the web opening 66, is threadably
engaged with the
first end 100 of the shaft 90, and is tightened to fixedly attach the shaft to
the inlet body
portion 54. A washer 106 is interposed between the bolt head and the web 64.
A first bushing 108 is slidably disposed around an outside diameter of the
shaft 90 and
is interposed between the web 64 and the first end 92 of the pressure disc 88.
A second
bushing 98 is disposed around the diameter of the shaft and is interposed
between the second
end 96 of the disc 88 and a first spring retaining bushing 110. The second
bushing has a
diameter sized to fit within the recessed portion of the second end 96. The
first spring
retaining bushing 110 is disposed around the diameter of the shaft 90 and has
an outside
diameter greater than the diameter of a pressure spring 112. It is desired
that the first spring
retaining bushing have a reduced diameter section 111 sized that extends a
distance into' an
inside diameter of the spring 112. In a preferred embodiment, the first
bushing 108 has an
outside diameter of approximately 0.875 inches and a length of approximately
0.56 inches.
The second bushing 98 has an outside diameter of approximately 0.75 inches and
a length
of approximately 0.31 inches. The first spring retaining bushing 110 has an
outside diameter
of approximately 0.875 inches, and a reduced diameter section with a diameter
of
approximately 0.68 inches and a length of approximately 0.18 inches.
Alternatively, the second bushing 98 and first spring retaining bushing 110
may be
formed as one integral bushing having three different diameter sections to
facilitate placement
-9-
CA 02218043 1997-10-10
WO 96!32668 PCTIUS96/05032
1 within the recessed portion, to engage and retain an end portion of the
spring, and to fit
within the spring.
The spring 112 is disposed around the diameter of the shaft 90 and is
interposed
between the first spring retaining bushing 112 and a second spring retaining
bushing 114.
The second spring retaining bushing 114 is configured the same as the first
spring retaining
bushing and includes a reduced diameter section 116 disposed within the inner
diameter of
the spring. The reduced diameter sections 111 and 116 serve to center the
spring about the
shaft 90, thereby helping to prevent the spring from binding when compressed
about the
shaft. The second spring retaining bushing 114 is placed adjacent an enlarged
diameter
section 118 at a second end 119 of the shaft 90. The enlarged diameter section
is sized
larger than an inside diameter of the second spring retaining bushing 144 to
prevent slidable
displacement thereby. The second end 119 is configured having a tapered
surface to facilitate
water passage thereby.
The spring 112 may be formed from any conventional material. It is desired
that the
spring be formed from a material that has good corrosion and chemical
resistance. In a
preferred embodiment, the spring is formed from stainless steel. The spring
tension, i.e.
spring constant, will vary depending on the particular valve application,
e.g., the desired
range of foam to water ratio, the particular range of water flow rate and
pressure, and the
like. For example, in a valve application where up to one percent foam is
desired at water
flow rates up to 1000 GPM, a suitable spring may have a spring tension of
approximately
14 pounds. In a preferred embodiment, the spring 112 has an outside diameter
of
approximately 0.87 inches, and inside diameter of approximately 0.75 inches,
and a relaxed
length of approximately 2.37 inches.
A third bushing 120 is disposed around the diameter of the shaft 90, is
interposed
between the first and second spring retaining bushings 110 and 114, and is
positioned
concentrically within the inside diameter of the spring 112. The third bushing
120 is sized
having a length shorter than a relaxed length of the spring 112 to provide the
pressure disc
a desired amount of slidable travel on the shaft toward the second end 119. In
a preferred
embodiment, the third bushing 120 has an outside diameter of approximately 0.5
inches and
a length of approximately 1.25 inches.
It is desired that each of the above-identified bushings be formed from a
corrosion and
chemical resistant material. In a preferred embodiment, each of the bushings
are formed
from brass.
When attached to the inlet body, pressure disc 88 of the first stage pressure
regulating
assembly 86 is positioned with a portion of the beveled surface 90 seated
against the edge
of the annular passage 62. In the seated position the first end 92 of the disc
88 does not
block or otherwise impair the flow of water from the annular passage 62 to the
high-pressure
inlet port 72. The seated position of the disc during low pressure/low flow
conditions
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CA 02218043 1997-10-10
WO 96/32668 PCTIUS96/05032
1 ensures that an adequate supply of liquid is received by the high-
pressure
inlet port 72 to
pressurize the foam dispersement device (not shown).
The central body portion 56 is generally cylindrical in shape
and has an annular
passage 122 therethrough, extending from a first end 124 to a
second end 126. In a
preferred embodiment, the annular passage 122 has an inside diameter
of approximately 3.7
inches. The central body portion is formed from the same material
used to form the inlet
body portion. The first end 124 includes a number of holes 128
extending axially a distance
therein. In a preferred embodiment, the first end 124 has six
equidistant holes 128 that are
threaded to accommodate threaded engagement with bolts 84. The
inlet body portion 54 is
attached to the central body portion 56 by placing an O-ring seal
130 within the groove 78
adjacent the second end 70 of the inlet body, and placing the
edge 80 of the inlet body 54
against the first end 80 of the central body 56 and aligning the
bolt openings 82 with the
holes 128. Bolts 84 are inserted into the openings 82, threadably
engaged within the holes
128, and tightened to a desired tightness. The O-ring seal may
be formed from conventional
sealing materials such as natural or synthetic rubber. A particularly
preferred O-ring seal
material is Viton''". The O-ring seal serves to provide a liquid-tight
seal between the inlet
and central body portions.
The second end 126 of the central body 56 includes a number of
holes 131 extending
axially a distance therein. In a preferred embodiment, the holes
are threaded to
accommodate threaded engagement with bolts 132 used to connect
together the central and
outlet body portions as described in greater detail below.
The outlet body portion 58 has a generally cylindrical outside
surface and, in a
preferred embodiment, is a two piece construction comprising a
venturi portion 134 and a
flange portion 136. In a preferred embodiment, the flange and
venturi portions are fixedly
attached together by welding. The flange and venturi portions
are formed from the same
material used to form the inlet and central body portions.
The venturi portion 134 includes an annular passage 138 that extends
therethrough
from a first end 140 to a second end 142. The second end may have
an outside surface
configured to accommodate connection with a number of different
conventional hose or pipe
fittings, such as those previously discussed for the inlet body.
The annular passage 138 is
shaped in the form of a modified venturi and is a second stage
pressure regulator for the
valve. The venturi is configured having a reduced diameter throat
146 positioned adjacent
the first end 140. The venturi has a gradually increasing diameter
as it approaches the
second end 142. The venturi throat diameter is specific to the
particular application of the
valve, e.g., the desired foam to water ratio, the size of hosing
or piping connected to the
valve, the pressure and flow rate of the water, and the like.
For example, in one application
the venturi may have a throat diameter of approximately 1.35 inches
for water flow rates up
to approximately 800 GPM, and may have a throat diameter of approximately
1.5 inches for
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CA 02218043 1997-10-10
WO 96!32668 PCT/US96/05032
1 water flow rates up to approximately 1000 GPM. In a preferred embodiment,
the venturi
portion 134 has a length of approximately 3.5 inches and has an outside
diameter of
approximately 3.12 inches.
The venturi portion 134 includes a number of foam injection ports 148 that
extend
radially through a wall portion and are positioned adjacent the venturi throat
146. Each
injection port 148 is hydraulically connected with each other injection port
by an injection
port manifold 150 that extends circumferentially around a reduced diameter
section 152 of
the venturi portion 134. The injection ports 148 are positioned adjacent the
venturi throat
to ensure complete mixing together of foam dispensed therefore with the water
by the
turbulent flow conditions produced by the venturi at the venturi throat. In a
preferred
embodiment, the venturi portion 134 includes approximately 8 foam injection
ports 148 that
are positioned equidistantly around the venturi throat. The injection ports
148 each have a
diameter of approximately 0.25 inches.
The flange portion 136 includes a foam outlet port 154 that extends through a
wall
portion from an outside surface to an inside diameter 156. The inside diameter
156 is fitted
against the diameter section 152 of the venturi portion 134 so that the foam
outlet port 154
is aligned with the injection port manifold 150 to facilitate foam transport
therethrough. In
a preferred embodiment, the foam outlet port 154 is sized and configured the
same as the
high-pressure inlet port 72.
The flange portion 136 includes a first end 158 that is coterminating with the
first end
140 of the venturi portion 134. The first end 158 extends radially from the
venturi portion
to a lip 160. The lip 160 is identical to the lip 76 in the inlet body 54 and
includes a groove
162 that extends circumferentially around the lip 160. The flange portion 136
includes an
edge 164 that extends radially from the groove 162 to an outside surface of
the flange
portion. In a preferred embodiment, the first end 158, the lip 160, the groove
162, and the
edge 164 have the same dimensions as respective counterparts in the inlet body
portion 54.
The flange portion 136 includes a number of bolt openings 166 that extend
axially
therethrough from third end portion 168 to the edge 164. In a preferred
embodiment, the
flange portion includes six bolt openings 166 spaced equidistantly apart. The
outlet body
portion 58 is fixedly attached to the central body portion 56 by placing an O-
ring seal 170
into the groove 162, installing the lip 160 into the annular passage 122 until
the edge 164
abuts against the second end 126. The outlet and central body portion are
placed together
such that the bolt openings 166 are aligned with holes 131. Bolts 132 are
inserted through
the openings 166 and are threadably engaged with the holes 131 and are
tightened a desired
amount. The O-ring seal is formed from the same material described for O-ring
seal 130 and
provides a liquid-tight seal between the outlet and central body portions.
A pressure balancing foam valve constructed according to principles of this
invention
can be used with a number of different foam delivery systems, such as that
disclosed in U.S.
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CA 02218043 1997-10-10
WU 96/32668 PCT/US96/05032
1 Patent No. 5,165,442, which is incorporated herein by reference, comprising
a foam
dispensing tank, a metering valve, and a three way selector valve. FIG. 5
illustrates an
example of a foam delivery system comprising a foam dispensing tank 172, a
metering valve
174, a three way selector valve 176, and the pressure balancing foam valve 178
of this
invention. The valve provides consistently increasing or decreasing
differential pressure
between the high-pressure inlet port 72 and the foam outlet port 154 by the
combined
operation of the first stage pressure regulating system, i.e., action of the
pressure disc, and
the second stage pressure regulator, i.e., the venturi, to ensure accurate
foam delivery at a
constant and predictable foam to water ratio at a variety of different liquid
volumetric flow
rates.
Referring now to FIG. 6a, the valve 180 is shown in a low pressure no liquid
flow
condition, where the liquid entering the inlet body portion 182 is at a
pressure below a
threshold pressure needed to overcome the compression force of the spring 184
and move
the pressure disc 186 toward the outlet body portion 188. Under such low
pressure
conditions, the pressure disc remains seated against the edge of the annular
passage 189 and,
thereby, acts as a check valve to prohibit water from entering the central
body portion 190
and passing through the valve. The water that enters the inlet body portion
182 is allowed
to flow unobstructed to the high-pressure inlet port 192 where it is
transported to a foam tank
and is used to pressurize foam contained therein.
Referring now to FIG. 6b, the valve 194 is shown in a low flow condition,
where the
water entering the inlet body portion 196 is at pressure sufficient to
overcome the threshold
compression force of the spring 198, causing the pressure disc 200 to be moved
away from
its seated engagement with the edge of the annular passage 201 inlet body.
Under such
conditions, the water is allowed to flow around the disc 200, enter the
central body portion
202 and flow through the venturi 204 and flow out of the outlet body portion
206. Under
such low flow conditions, the first stage pressure regulating assembly, i.e.,
the pressure disc,
acts to provide a desired pressure differential between the high-pressure
inlet port 208 and
the foam outlet port 210. The second stage pressure regulator, i.e., the
venturi, also acts to
a lessor degree to provide a pressure differential within the valve. For
example, at a water
flow rate of up to about 150 GPM, the pressure disc acts as the primary
mechanism for
providing a desired pressure differential within the valve. At a water flow
rate of
approximately 150 GPM the contribution from the venturi in producing a desired
differential
pressure with the valve increases. As the flow rate and pressure of the water
entering the
valve continues to increase, the contribution by the venturi in providing the
desired pressure
differential increases and the contribution by the pressure disc levels off.
The differential
pressure is used to pressurize foam contained within a foam dispensing' tank.
The
pressurized foam is dispensed into the valve via the foam outlet port 210, and
is dispensed
into the water stream via the plurality of foam injection ports 211.
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CA 02218043 1997-10-10
WO 96/32668 PCT/US96105032
1 Referring to new FIG. 6c, the valve 212 is shown in a high flow condition,
wherein
the water entering the inlet body portion 214 is at a pressure sufficient to
overcome the
compression force of the spring 216 and cause the pressure disc 217 to be
moved to a
maximum position on the shaft 218 toward the outlet body portion 220. Under
these
conditions, the differential pressure contribution by the first stage pressure
regulating _
assembly, i.e., the pressure disc, is at a maximum and the venturi 222 acts to
provide the
remaining differential pressure needed to effect dispersement of a constant
proportion of foam ,,
into the water stream.
A key feature of this invention is the venturi shaped annular passage that is
positioned
within the outlet body portion because of its ability to produce a controlled
and predictable
increasing differential pressure in the valve as the water flow rate and
pressure entering the
valve reaches high levels where the differential pressure contribution from
the spring-
controlled pressure disc levels off, i.e., where the pressure disc is no
longer able to produce
by itself a proportionally increasing differential pressure. The use of such a
pressure disc
and venturi mechanism in producing a desired differential pressure within the
valve
eliminates the inherent uncontrollability and inaccuracies associated with a
pressure
disc/spring controlled only type mechanism. The contribution of the venturi
ensures that a
desired pressurizing force is imposed on the foam tank to effect accurate
dispersement of a
constant proportion of foam to water at increasing flow rates.
Table 1 summarizes test data gathered from using pressure balancing foam
valves
having increasing orifice sizes, constructed according to principles of this
invention, to
dispense Class A foam into a stream of water. In these tests the desired
proportion of foam
to water was set on a metering valve to be 0.5 percent, and the actual amount
of foam that
was dispensed into the water was measured.
TABLE 1
ORIFICE NOZZLE FOAM FOAM
SIZE GPM PSI SETTING ACTUAL
1/4" 22.5 150 .5 .56
3/8" 50 150 .5 .60
1/2" 90 150 .5 .50
5/8" 126 120 .5 .41
3/4" 166 100 .5 .48
3/4" 200 145 .5 .60
7/8" 249 . 120 .5 .64
1~~ 295 100 .5 .64
1 1/8" 355 90 .5 .66
1 1/8" 401 115 .5 .66
1 7./4" 452 96 .5 .64
1 1/4" 505 120 .5 .64
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WO 96/32668 PCTIUS96/05032
1 The data in Table 1 illustrates the ability of the valve to produce a
predictable and
controlled differential pressure to dispense foam throughout a wide range of
various water
flow rates, i.e., below and above 150 GPM, and yet maintain a good level of
foam
dispersement accuracy at a low foam to water ratios.
Table 2 summarizes test data gathered from using a pressure balancing foam
valve
of a constant orifice size, constructed according to principles of this
invention, to dispense
Class A foam into a stream of water. In these tests the flow rate and pressure
of the water
entering the valve was increased, the proportion of foam to be dispensed into
the water
stream was set on a metering valve to be 3 percent, and the actual amount of
foam that was
dispensed was measured.
TABLE 2
Metering Valve set at 3%
GPM/Flow Pressure (PSI) Actual Form
100 76 3.25
200 78 3.15
100 100 3.1
200 100 3.2
The data from Table 2 illustrates the ability of the valve to produce a
predictable and
controlled differential pressure within the valve to dispense foam at
increasing water flow
rates while maintaining a high level of foam dispersement accuracy at a high
foam to water
ratio.
Table 3 summarizes test data gathered from using a pressure balancing foam
valve
of a constant orifice size, constructed according to principles of this
invention, to dispense
Class A foam into a stream of water. In these tests the flow rate of the water
entering the
valve was increased, the pressure of the water was varied, the proportion of
foam to water
was set on a metering valve to be 0.4 percent, the pressure differential
within the valve was
measured and the actual amount of foam that was dispensed was measured.
35
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CA 02218043 1997-10-10
WO 96!32668 PCT/U596I05032
1 . TABLE 3
Metering Valve Setting - 40
GPM/Flow in Pressure out Foam
2 125 123 ,37
S 124 122 .34
124 120 .35
124 119 .37
119 117 .37
118 117 .30
50 119 114 .33
100 107 100 .30
10 150 225 210 .31
200 175 174 .34
275 80 36 .35
The data gathered from Table 3 illustrates the ability of the valve to produce
a
predictable and controlled differential pressure to dispense foam at
increasing water flow
15 rates while maintaining a high level of foam dispersement accuracy at a low
foam to water
ratio at both low and high flow rates.
The pressure balancing foam valve constructed according to principles of this
invention can be used to accurately dispense Class A foam into a stream of
water at foam
proportions as low as 0.05 percent to as high as 10 percent, depending on the
water flow
20 m~.
Although the valve has been specifically described as being used for
dispensing Class
A foam into a water stream, it is to be understood that the valve constructed
according to
principles of this invention may be used to dispense other types of fire
fighting foams, e.g.,
Class B foam, or may be used to dispense foams that have applications other
than fire
25 fighting, e.g., foams used for oil spill clean up, foams used for structure
preservation or the
like. Additionally, although the valve has been described as being used to
dispose foam into
a water stream it is to be understood that this valve can be used with liquids
other than
water.
Additionally, although specific dimensions have been provided for a preferred
embodiment of the valve, it is to be understood that such dimensions reflect
but one example
of a valve constructed according to principles of this invention and have been
provided for
purposes of clarity, reference and enablement and are not intended to be
limiting.
Although specific embodiments of the pressure balancing foam valve have been
specifically described and illustrated herein, many modifications and
variations will be
apparent to those skilled in the art. Accordingly, it is to be understood
that, within the scope
of the appended claims, the pressure balancing foam valve according to
principles of this
invention may be embodied other than as specifically described herein.
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