Fluid cutout valve

A valve disposed in a fluid system for cutting off the flow of fluid from a ource of that fluid to a fluid-using environment upon the occurrence of either an excess or unduly high fluid flow rate or an excess pressure condition experienced in or near the environment. An obturator, disposed in a flow chamber between the valve inlet and outlet, is controlled by two independent assemblies which are responsive to either the flow rate through the valve or the pressure downstream of the valve in the environment. A bias spring, part of a cutout obturator assembly and located in the obturator, maintains the obturator in an open position until an excess flow rate promotes a seating of the obturator. A spindle slidingly connects the obturator to a sensing piston assembly so that when an excess pressure condition is experienced in the environment the obturator is pulled into the seated position causing a cessation of fluid flow through the valve and an isolation of the environment from the fluid source.

BACKGROUND OF THE INVENTION 
The present invention relates generally to cutoff valves, and more 
particularly to a fluid cuttoff valve for use in fluid systems in which 
flow is controlled between a source of high pressure and an environment at 
a reduced pressure such that excess flow rates and excess pressures are 
not experienced in the environment. 
Fluid systems having a fluid supply source and an environment in which the 
fluid is subjected to a controlled use are old and well known. In some 
applications the source is at a relatively high pressure, e.g. 3,000 psig 
and the environment is at a relatively low pressure, e.g. 5 psig, and thus 
a fluid system necessarily requires a flow control mechanism and/or a 
pressure reducing station. Such a station might comprise a pressure 
regulator which ensures that the environment experiences the desired 
pressure. However, an additional device is usually necessary to protect 
that portion of the system downstream of the pressure reducing station 
from excess pressure in the event that the station malfunctions or excess 
flow in the event of a loss of system integrity, e.g., a pipe or hose 
bursting between the fluid supply source and the environment. 
Devices to protect against excess pressure have traditionally taken the 
form of relief or safety valves, rupture discs or electrical trip cutout 
valves. Excess flow rate protection has been accomplished by conventional 
devices commonly referred to as flow fuzes or pneumatic fuzes. This latter 
device is exemplified by U.S. Pat. No. 3,621,873, issued to Kenann et al, 
issued Nov. 23, 1971. 
Certain fluid systems require simultaneous protection against the 
possibility of an excess pressure condition, which results possibly from 
the malfunction of the regulating or control device, and an excess flow 
rate condition which is symptomatic of a structural failure in the fluid 
system boundary. This is particularly true in the fluid systems of 
submersibles or marine research vessels which handle highly combustible 
life support fluids such as oxygen and wherein some of the usual methods 
for disposal or containment of excess fluids are not available. For 
example, in an oxygen bleed system on a submersible because of the limited 
and strictly confined environment, there is no feasible alternative for 
absorbing any excess fluid. Also, discharge outside of the hull of the 
submersible is usually impractical due to the possibility of detection by 
unfriendly sensors and because the ambient pressure surrounding the 
submersible is generally much higher than that within the environment of 
the submersible. 
For these reasons, no relief protection is provided for the above mentioned 
system and presently malfunctions such as a jammed regulator poppet or a 
torn sensing diaphragm can result in an overpressure condition producing 
material damage and injury to personnel. Further, because oxygen is being 
used, an untoward combustion hazard exists. If there is a fire anywhere in 
the fluid system, e.g., in the regulator, possibly caused by high velocity 
throttle impingement, or at some other location downstream in the fluid 
system, the regulator will open fully because it senses a flow demand. The 
full opening of the regulator will feed the combustion process by dumping 
out the entire capacity of the oxygen storage tanks into an area of the 
submersible where the combustion is occurring. It is clear that the 
potential for seriously jeopardizing the survival of a submersible is 
greater by not providing a fluid protection device. A current solution to 
this problem has been the installation of flow limiting orifice in front 
of the regulating valve. Unfortunately this is an entirely futile approach 
because of the range over which the source pressure can vary, e.g., 60 to 
3000 psig. 
A requirement thus exists for a single fluid cutoff valve which can quickly 
and reliably respond simultaneously to either an excess pressure or excess 
flow rate condition in order to isolate a fluid supply from an environment 
in which the fluid is used. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a new and 
improved fluid cutoff valve. 
Another object of the present invention is to provide a new and improved 
cutoff valve which simultaneously responds to an excess pressure and 
excess flow rate condition. 
Still another object of the instant invention is to provide a cutoff valve 
which responds to either an excess pressure or excess flow rate condition 
more rapidly than current devices. 
A further object of the invention is to provide an improved cutoff valve 
which can be relatively inexpensive yet very reliable. 
These and other objects of the invention are obtained in a fluid cutoff 
valve for use in fluid systems in which fluid is supplied to an 
environment from a fluid source via a pressure regulator comprising the 
disposition and control of an obturator or poppet body in a flow chamber 
which is located between the inlet and outlet of a valve housing such that 
the poppet body is seated upon the sensing of either an excess flow rate 
condition or an excess pressure condition downstream of the regulator. A 
bias spring, located within the poppet body, determines the pressure 
differential at which the poppet body is seated. The distance of the 
poppet body from the valve seat determines the flow rate at which the 
pressure differential is experienced. This distance can be adjusted in 
order to determine the flow rate at which the excess pressure drop is 
experienced. A spindle slidingly connects the poppet body to a sensing 
piston assembly which causes the seating of the poppet body upon the 
sensing of a predetermined excess pressure signal developed downstream of 
the pressure regulator.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings, wherein like reference characters designate 
identical or corresponding parts throughout the several views, and more 
particularly to FIG. 1 thereof wherein an embodiment of the present 
invention is shown in cross-section, and includes a valve housing 10 
having an inlet 12 and an outlet 14. Disposed in a flow chamber 16, 
juxtaposed in housing 10 between inlet 12 and outlet 14, is a cutout 
obturator or poppet assembly 18 which is slidingly mounted on spindle 22. 
Located in a control piston housing or chamber 20 and connected to cutout 
poppet assembly 18 by spindle 22 is a sensing piston assembly 24. 
Cutout poppet assembly 18 comprises a generally cylindrical hollow 
open-ended obturator or poppet body 26 having a resilient seating insert 
or seal 28 fixedly held in place by a seating insert retaining nut 30 
which is on the outer extremity of the truncated cone surface 32 of poppet 
body 26. When the poppet body is seated or in the closed position, as 
shown in FIG. 2, seating insert 28 abuts seat 34 of the valve. 
With the poppet body 26 in the position shown in FIG. 1, and with fluid 
flowing from a source of fluid pressure to the inlet 12 and around the 
poppet body 26 in the valve chamber 16 to an environment where the fluid 
undergoes a controlled use, via the outlet passage 14, there is a pressure 
drop which urges the poppet body 26 toward a closed position or toward the 
seat 34, as shown in FIG. 2. The closing pressure force is opposed by a 
bias spring 36 located within a chamber 38, formed in poppet body 26. 
Spring 36 is compressed between the head 40 of spindle 22 and a threaded 
end plate 42 which closes off the open end of chamber 38. Circumferential 
grooves 44 and 46, located in head 40 and plate 42, respectively, maintain 
a fixed position for spring 36. A guide post 48 preferably intregal with 
end plate 42, rides in a guide bore 50 formed in a quill assembly 52 
disposed in a bottom cover 54, attached to valve housing 10 and sealed by 
O-ring 56 and comprises the lower purchase for bias spring 36. 
Quill assembly 52 comprises a quill or plug 58 having O-rings 60 and an 
adjusting screw 62 fixed by a lock nut 64. Quill assembly 52 constitutes 
an adjusting means for changing the rate of flow at which the valve 
operates. The amount of pressure drop around the poppet body 26 depends 
not only upon the rate of flow of the fluid passing through the valve but 
also upon the spacing of the poppet body 26 from the valve seat 34. If 
this spacing is reduced and the cross-section for the flow of fluid is 
subsequently cut down the pressure drop at a given rate of flow is thereby 
increased. It is possible therefore to change the rate of flow at which 
the pressure drop will be sufficient to overcome the force of bias spring 
36 by changing the spacing of the poppet body 26 from seat 34. Control of 
the spacing is effected by turning the adjusting screw 62 so as to move it 
up or down in the threads formed in the bottom cover 54. When the screw 62 
is turned in a direction to move it downward, the quill 58, guide post 48 
and thus the poppet body 26 are displaced downward on spindle 22 by the 
bias spring 36 so that the truncated conical face 32 of the body 26 is 
further away from the seat 34. Conversely, the spacing of the poppet body 
26 from the seat 34 can be decreased by turning the screw 62 so that it 
permits a compression of bias spring 36 to cause face 32 and thus insert 
28 to be closer to seat 34. 
As was mentioned, fluid enters the cutout valve via the inlet 12 and exits 
via outlet 14. A fluid passage network 66 prevents fluid entrappment which 
could impede the movement of the cutout poppet assembly. Passage network 
66 also allows the inlet pressure to act under the cross-sectional area of 
the guide post 48 thereby insuring a more rapid closing of the poppet 
body. 
The upper purchase for bias spring 36 is formed by head 40 of spindle 22 
which is fixed to sensing piston assembly 24. The sensing piston assembly 
comprises a piston 68 attached to the end of spindle 22 by a threaded lock 
nut 70. Compressed between piston 68 and a spring plate 72 in a control 
spring 74 which biases piston 68 downward and thus helps to compress bias 
spring 36 inasmuch as spindle 22 freely reciprocates through poppet body 
26 while it is sealed by an O-ring 76. Sensing piston assembly 24 is 
adjusted and preloaded by means of a control spring adjusting screw 78 
which is fixed in a specified position by a lock nut 80. 
A feedback port 82, formed in valve body 10, permits the pressure from a 
remote downstream location of the fluid system, e.g. downstream of a 
pressure regulator, to be sensed by sensing piston assembly 24. Unduly 
high or excess pressure downstream of the pressure regulator acts on the 
undersurface 84 of piston 68 against the force of spring 74 tending to 
move piston 68 upwards as viewed in FIG. 1 and as shown in FIGS. 3 and 4. 
O-rings 86, 88, and 90 prevent the escape of high pressure fluid from an 
expansible chamber 92 formed between the piston 68 and the lower surface 
94 of chamber 20. A top cover 96 closes the other end of chamber 20 and 
provides a support for adjusting screw 78 and lock nut 80. A vent port 98 
prevents alteration of the cutout valve setting or pressure at which the 
piston 68 begins to move against spring 74, i.e., port 98 prevents an 
inadvertent pressure buildup within control piston chamber 20. 
When there is pressure on the upstream side of a closed valve 10, i.e., 
when poppet body 18 is seated on seat 34 as shown in FIG. 2, it may be 
necessary to unlock the poppet body. One may release the valve from its 
closed position by equalizing the pressure on both sides of the poppet 
valve or at least by bringing the pressures on opposite sides of the 
poppet body near enough to a value which allows bias spring 36 to move 
poppet body 26 downwardly away from seat 34. By-pass passages 100 and 102, 
controlled by plug assembly 104, are thus provided thereby allowing a 
balancing pressure within the valve when the downstream portion of a fluid 
system is dead ended. Plug assembly 104 comprises a threaded plug or 
needle 106 and a sealing O-ring 108. The operation of assembly 104 is 
explained, infra. 
In operation when the fluid cutout valve is in the normal position shown in 
FIG. 1, the cutout poppet assembly 18 is biased into an open position 
against the quill assembly 52 by the bias spring 36. Upstream fluid from a 
pressure source flows into the inlet 12 through the valve and out of 
outlet 14 to an environment thereby creating a pressure differential at 
the seating area which acts upon the net unbalanced cross-sectional area 
of the cutout poppet assembly 18. The cutout poppet assembly is thus urged 
upwards towards valve seat 34. No closing movement of the cutout poppet 
assembly 18 occurs until the net upward force on the assembly, created by 
the pressure drop, exceeds the preload downward force exerted by bias 
spring 36. When the preset threshold pressure drop occurs as a result of 
an excess flow condition, a closing movement of the cutout poppet assembly 
18 commences and the cutout poppet assembly 18 will snap closed in an 
essentially instantaneous movement. This is due to the fact that the 
closure movement increases the pressure drop across the valve face 32 
because it is closer to the valve seat which in turn accelerates the 
closure or closing movement thereby including a snowballing effect. The 
cutoff valve is shown in FIG. 2 in the completely closed position. 
Closure of the cutout valve in response to an overpressure or excess 
pressure condition in the downstream fluid system, e.g., downstream of a 
pressure regulator, is initiated by a completely different sequence of 
events. In an overpressure closure event the flow rate through the valve 
is a relatively immaterial factor. Inasmuch as feedback port 82 
communicates with expansible pressure chamber 92 and thus with sensing 
piston assembly 24, pressure in the fluid system downstream of the cutout 
valve is continuously sensed. When the downstream pressure rises above a 
level established by the preload imposed upon control spring 74 by 
adjusting screw 78 the sensing piston assembly begins to move upwardly as 
viewed in FIG. 3. This movement displaces spindle 22, which is fixed to 
the sensing piston assembly 24 until the lower shoulder 110 of head 40 
abuts against the shoulder 112 of poppet body 26. This contact will move 
the cutout poppet assembly 18 upwardly toward valve seat 34. When the 
downstream fluid pressure has risen a predetermined amount the cutout 
poppet assembly 18 is forced into a closed position by the upward movement 
of the assembly 24 and spindle 22. Thus a pressure source can be isolated 
from an environment where the fluid experiences a controlled use. 
Due to the fact that there is a fluid flow through the cutout valve during 
the time that the sensing piston assembly 24 begins to cause an upward 
movement of the cutout poppet assembly 18, the cutout poppet 18 will snap 
itself shut even before the upward movement, imposed by the sensing piston 
assembly 24, is completed. This phenomenon is shown in FIG. 4 and is 
caused by the ever increasing pressure drop created as the cutout poppet 
assembly 18 moves toward seat 34. It is made possible by the floating 
action of the cutout poppet assembly 18 on the spindle 22 as described 
supra. This self-initiating closure characteristic vastly improves the 
speed at which the cutout valve responds to an excess pressure condition 
compared to conventional solid-mounted poppet assemblies. This critical 
factor enormously improves the value and effectiveness of a valve of this 
type as a protective device in fluid systems. 
As is clear, the threshold pressure differential at which the cutout poppet 
assembly 18 closes is established by the bias spring 36. However, a 
critical factor is the flow rate at which this threshold pressure drop 
occurs which is determined by the distance between the face 32 of the 
cutout poppet assembly 18 and seat 34. As was mentioned this distance can 
be adjusted by quill assembly 52. The amount which screw 62 is threaded 
into the bottom cover 54 determines the initial position of the cutout 
poppet assembly 18 relative to the valve seat 34 and thus the pressure 
differential at any given set of the inlet pressures and flow rate of the 
fluid which causes a closing of the valve. 
Upon the closure of the valve due to an overpressure condition or an excess 
flow rate condition the cutout valve can be reopened or unlocked, after 
the fluid system has returned to a normal or ready state, by balancing the 
pressure across the cutout poppet assembly 18. A balancing pressure can be 
accomplished by opening plug assembly 104 to allow pressure to equalize 
across the cutout poppet assembly 18. Bias spring 36 can then force 
assembly 18 down to the full open position against the quill assembly 52. 
Plug assembly 104 is opened by unscrewing the plug or needle valve 106. 
After the pressure is balanced the needle valve 106 can be closed allowing 
the fluid cutout valve to be in an operative state. 
Thus, what has been described is a fluid cutout valve which is capable of 
isolating a pressure source from an environment experiencing excess fluid 
pressure upon the occurrence of a regulator failure or excess fluid flow 
upon a loss of the integrity of the downstream system. Containment of the 
fluid at its source, being the safest conceivable solution, is 
accomplished in a self-contained valve requiring no electrical, hydraulic 
or other auxiliary inputs. The valve operates in a direct, certain and 
positive manner with response times controlled by fluid flow in the 
downstream system. Finally, cutout functions due to either an overpressure 
or excess flow condition occur independently without unfavorable 
mechanical interaction in a single, simply constructed valve. 
Obviously numerous modifications and variations of the present invention 
are possible in the light of the above teachings. It is therefore to be 
understood that within the scope of the appended claims the invention may 
be practiced otherwise than as specifically described herein.