Note: Descriptions are shown in the official language in which they were submitted.
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The inv~ntion relates to fire-fighting fluid discharge nozzles
and, more particularly to mechanism for maintaining a substantially constant
discharge pressure at the orifice of such nozzles as the supply volume or
pressure varies. ~xamples of such constant-pressure nozzles can be found
in McMillan United States Patent No. 3,863,844; Burnam et al. United States
Patent No. 2,56~,429 and Allenbaugh United States Patent No. 3,904,125.
All of these prior art patents utilize a yieldably-mounted pressure-
responsive baffle to progressively enlarge the nozzle discharge orifice
or opening as fluid pressure or volume in the nozzle increases. The
enlargement of the orifice permits a greater volume of discharge to relieve
the increased pressure in the nozzle, and thereby attempts to achieve
constancy in the discharge pressure.
The discharge pressure affects the reach of the fire-fighting
st~eam. To maintain a desirable uniformity in the reach of the stream,
a uniformly maintained discharge pressure is required. That is the object-
ive of automatically self-regulating constant-pressure nozzles of the
type mentioned above.
~owever, it has been found that, although most of such pressure-
regulating mechanisms are reasonably effective within a very narrow range
of operating pressures, they are characterized by increasingly larger
deviations from the desired pressure-constancy as the high-volume limits
of operation are approached. Under such circumstances, the straight-line
response fails to maintain constancy of pressure, and the mechanisms, by
nature of their operating structure, tend to cover a pressure range which
is broader than desirable.
The straight-line response problem was addressed in Allenbaugh
United States Patent No. 3,904,125 by substituting a special tubular resilient
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element for the conventional coil spring, and thereby obtaining an improved
load-deflection characteristic and greater sensitivity of response.
Another solution to the response problem was presented in
Allenbaugh United States Patent No. 4,172,559 by use of a contained piston
so arranged as to inhibit the effect of pressure on the orifice-sizing
baffle element as the higher operating gallonage limits are approached.
It is a primary object of the present invention to provide
a simplified, yet highly effective, means for modulating the baffle
responsiveness of spring-loaded, pressure-regulating nozzles to achieve a
substantial constant-pressure characteristic over the entire range of
operating pressures, including the high pressure limits of the range.
The invention provides in an automatic pressure-regulating mechanism
for a flow nozzle, the combination of: a nozzle body presenting a discharge
orifice, a piston rod fixedly secured within said body and extending down-
stream therein, an open-ended baffle cylinder slidably mounted on said
piston rod for reciprocable movement thereon relatively to said orifice,
said cylinter having a closed end in the path of fluid flow discharge through
said nozzle body, said cylinder having an opposite open end downstream of
said closed end and out of the path of fluid flow through said body, a
piston slidably contained in the open end of said cylinder and secured to
said rod, spring means interposed between said piston and said cylinder to
yieldably maintain said baffle cylinder in a predetermined orifice-restricting
position, said closed end of said cylinder presenting a pressure-responsive
first baffle face to the fluid flow, whereby said cylinder is displaced in
Opposition to said spring to enlarge said discharge orifice in response to
increased fluid pressure thereon, an extension provided on said cylinder
upstream of said first baffle face and presenting a second bafle face
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opposed to the direction of fluid flow and movable with said cylinder, and
a stem connecting said first baffle face to said second baffle face
by a stepped portion to create a low-pressure zone between said faces in
response to discharge fluid flow, whereby to modulate any increased dis-
placing force on said first baffle face in response to increased fluid
pressure in said nozzle body.
The baffle structure described herein can be utilized over a much
broader range of operating pressures than prior art devices.
Other advantages will become apparent during the course of the
following description and with reference to the following drawings in which
like numerals are used to designate like parts throughout the same.
Figure 1 is a longitudinal cross-sectional view of a nozzle
structure embodying the invention.
Pigure 2 is a fragmentary enlarged portion similar to Figure l,
showing the position of the parts after high-pressure displacement.
Pigure 3 is a fragmentary cross-sectional view showing the
alternative disposition of the piston for another range of operating
pressures.
Referring to Pigure 1, a nozzle body 10 is provided, at one end
thereof, with a conventional coupling member ll adapted to secure the
nozzle to a hose or other source of pressure water supply. The nozzle
body has a central water flow passageway 12 which, by means of an inwardly-
tapered or convergent body wall 13, is gradually restricted or diminished
in flow area to a point of restriction defining a discharge opening or
orifice 14. The orifice 14 leads into a conical or divergently-e~tending
throat 15 which, in combination with a baffle element 16, defines a variable
flow discharge passageway 17. By means of an adjustably-mounted sleeve 18
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on the body lO, the fluid discharge from passageway 17 is formed into
a desired spray or other discharge pattern, as is known in the art.
The baffle element 16 is a hollow cylinder having a closed upstream
end 19 which is perforated, as indicated at 20, with one or more openings
which provide hydraulic communication between the interior 21 of the baffle
cylinder and the fluid flow upstream and exteriorly thereof.
The end l9 presents a pressure-responsive face or surface 22
to the discharge flow in the nozzle body, which exerts a displacing force
tending to move the baffle cylinder 16 downstream and further away from
the divergent walls of the throat 15, so as to enlarge the discharge
passageway 17.
To permit such pressure-responsive displacement of the element
16, it is slidably mounted on a shaft or rod 23 which extends centrally
and longitudinally of the body flow passageway 12. The rod 23 is secured
ixedly within the body 10 by means of a nut 24 which clamps a shouldered
portion 25 of the rod against a spider structure 26 formed within the body.
The opposite end of the rod 23 has a piston 27 slidably mounted
thexeon so as to seal the open end 28 of the cylinder and slidably engage
the interior thereof, as by means of sealing ring 29.
A coil spring 30 has one end thereof seated in a recess 31 in
one face 32 of the piston, and has its other end bearing against the
cylinder so as to yieldably maintain the cylinder spaced from the piston.
A nut 33 threadetly engages the end 34 of the rod exteriorly of the piston
to provide an abutment limiting outward, spring-induced movement of the
piston.
Rearwardly or upstream of the baffle element 16, the cylinder is
provided with an integrated extension 35 which includes a tapered stem 36,
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which diverges in the upstream direction, and terminates in a disk-like
enlarged head portion 37 presenting a second pressure-responsive surface
or baffle face 38. It will be noted that there is an abrupt step or
shoulder 39 formed at the juncture of the taper and the head 37, as well as
a step or shoulder 40 at the smaller end of the taper 41.
In Figure 1, the described parts are illustrated in the "at rest"
position, such as exists when there is no fluid flow through the nozzle
passageway 12~or when fluid flow is just initiated. When fluid flow
commences, the water discharges through the orifice 14, but there is initially
insufficient fluid pressure to cause displacement of the baffle element.
As the volume and pressure of the supply water increases, it creates an
increasing force on the baffle faces 22 and 38 which, when sufficient to
overcome the opposition of the coil spring 30, causes downstream displace-
ment of the baffle element 16 to enlarge the flow passageway 17 and thereby
maintain the discharge pressure within a predetermined narrow operating
range. If, for any reason, the supply pressure or gallonage increases
further, it causes greater displacement of the baffle element and further
compression of the spring 30 to further enlarge the flow passageway 17
and thereby maintain the desired constant discharge pressure of the fluid.
It will be noted that the openings 20 provide pressure-equalizing
ports, so that the effective pressure-induced force on the baffle element
16 is reflected in the differential between the interior and exterior areas
of the cylinder which are exposed to like pressure. This effective dis-
placing force is considerably smaller in magnitude than the force to which
the element 16 would be subjected if the pressure-equalizing ports were not
provided. This smaller effective force permits the use of a weaker spring
30, with greater sensitivity of response than would be the case if a stronger
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and heavier spring 30 were required, in the absence of the equalizing ports 20.
The sensitivity of response is further enhanced by the use of
sized openings 20 which~ when made small enough, will meter the flow to
cause a slight, but deliberate, time lag in the pressure-equalizing function
and thereby magnify the effective force differential for faster response
to abrupt pressure changes, particularly increases. The appropriate size
of the ports 20 can be empirically determined to achieve the desired enhanced
sensitivity of response within the operating range of discharge pressure.
It is an inherent characteristic of the load-deflection curves of
conventional compression coil springs, such as spring 30, that there is
a straight line or linear response to load, so that there is a uniform
rate of response to pressure variations. This characteristic adversely
affects the constant-pressure operation of the nozzle when operating pressure
fluctuations occur to change the effective displacing force on the baffle
element. As fully explained with reference to Figure 3 of the previously
mentioned United States Patent No. 4,172,559, the straight line load-
deflection curve of the spring results in inadequate displacement of the
baffle element to maintain a reasonably constant pressure.
The stepped baffle extension 35 has a dual function in overcoming
or minimizing the above-described problem of coil spring straight line
reaction. Its primary function is to present the steps or recesses 39 and
40 adjacent to the main-stream path of flow of water through nozzle passage-
way 12 and thereby, in accordance with Bernoulli's principle, create a
low-pressure area by turbulence and slip-stream effect which will dimipish
the back pressure on surfaces 39 and 40 to modulate the effective displacing
pressure on the baffle element to increase the displacing force as flow
volume increases. Although both steps or recesses 39 and 40 contribute
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to creating the low pressure zone affecting the displacing force on baffle
16, the recess 40 is deliberately positioned radially inward of the step
39 to pr0vent excessive and counter-productive modulation of the fluid
pressure. The smooth, connecting taper 36 also contributes to this function.
The proper balance between the radial positions of the steps 39 and 40
can be empirically determined. Thereby, the full effect of such higher
pressures on the baffle element 16 is modulated so as not to be translated
entirely into increased displacing force. As a result, the deflection
load on spring 30 does not change at the same rate as it would if a
straight line response existed, and the over-deflection of the spring is
avoided or minimized.
Secondly, as baffle element 16 is increasingly displaced as a re-
sult of higher forces, the head 37 of the extension 35 is simultaneously
displaced, as is the shoulder 40. This downstream movement of head 37
and shoulder 40 brings it into closer proximity to the converging wall
13 and diminishes the area of the flow passageway to increase flow velocity
and further reduce the fluid pressure in this area which affects the
displacing force on the baffle surface 22. The higher the pressure and
the greater the fluid velocity and baffle displacement) the greater is
this extension-created restriction of the nozzle flow passageway 12. This
flow restriction and velocity-increasing action of the baffle extension
upstream of the orifice 14 further modulates the high-pressure effect on
baf1e 16 and minimizes baffle over-reaction and excessive orifice opening
in the upper zone of the supply range.
Figure 2 shows the position of the parts in response to a high
supply pressure condition, as above described. The reference numeral 42
indicates the general area in which the low pressure zone is created by
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the baffle extension 35. The enlarged discharge passageway 17 resulting
from displacement of the baffle element 16 is clearly evident when compared
with the at rest position of the parts shown in Figure 1.
The increase~ sensitivity of response achieved by the sized
pressure-equalizing ports 20 and the modulating effect on high volume
displacement achieved by the dual functions of the baffle extension,
serve to produce an improved uniformity and constancy in the automatic
regulation of discharge pressure at the nozzle.
In Figure 3 of the drawings, a modified form of the invention is
shawn in which the same parts are utilized for operation in a volume
operating range which is considerably higher than previously described.
The position of the piston 27 is reversed so that its face 32 is exterior
of the cylinder. Instead of seating in the recess 31, the coil spring 30
bears against the non-recessed opposite surface 43 of the piston. This
re-arrangement of the piston causes a considerably greater initial com-
pression or pre-loading of the coil spring 30 thereby substantially
increasing the pressure required to initiate displacement of the baffle
element 16 in opposition to the spring. Thereby, the same parts can be
utilized for two entirely different pressure ranges simply by reversal of
the piston position. Although the surface 43 has been illustrated as non-
recessed, a shallow spring-receiving recess could be provided, and the
described reversal of the piston position would still serve for the described
function.
It will be apparent that minor adjustments in the calibration of
the constant operating pressure of the discharge fluid can be accomplished
by manipulation of the nut 33 on threaded end 34 of the rod to increase or
decrease the pre-loading of the spring.
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It will also be evident that, as no seal is provided between
the rod 23 and the piston 27, there can be sufficient leakage there-
between to permit any necessary bleeding or venting of the interior 21
of the baffle cylinder.
It is to be understood that the forms of this invention, herewith
shown and described, are to be taken as preferred examples of the same
and that various changes in the shape, size and arrangement of the parts may
be resorted to without departing from the spirit of the invention or the
scope of the subjoined claims.
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