Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND OF THE INVENTION
This invention relates generally to a pressure responsive
fluid shut-off device and, more particularly, to a device for
shutting off a supply of liquid propane (LP) gas in the event
that a malfunction in a supply system results in excessive gas
pressures.
The appearance of excessive gas pressures in LP gas supply
systems introduces substantial risk of fire and explosion. In
most domestic LP gas systems, fire and explosion hazards are
prevented by a regulator located between an LP gas supply tank
and a supply line feeding appliances encompassed by the system.
The regulator functions to reduce supply tank pressure, typically
above 100 psi, to a safe line pressure of less than 1 psi.
However, malfunctions in such regulators often lead to the ap-
pearance of hazardous gas pressures in supply lines. A common
cause of regulator malfunction is a blockage of vent openings
that establish atmospheric reference pressures in typical dif-
ferential pressure responsive regulators. Upon loss of an
accurate atmospheric pressure reference, a regulator can cease
to function properly and in some instances, allow a hazardous
increase in gas pressure. The use of an atmospheric pressure
reference in conventional LP gas regulators leads also in certain
instances to the occurrence of dangerous gas leakage. Such
leaks can result from an internal seal failure that permits gas
leakage into an atmospheric reference chamber and out of an
atmospheric vent opening into the immediate environment.
The object of this invention, therefore, is to provide a
pressure responsive shut-off device that will eliminate the
problems inherently present in LP gas regulators that utilize
atmospheric reference pressures.
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SUMMARY OF THE INVENTION
The invention is a pressure responsive shut-off valve in-
cluding a valve housing that defines a fluid inlet and a fluid
outlet separated by a valve seat. A valve closure accommodated
by the valve seat moves between open and closed positions to
control fluid flow between the inlet and outlet. Controlling
the valve is a valve operator including a pressure responsive
Piston that moves between a set position in which the valve
closure is separated from the valve seat and a release position
in which the closure is seated on the seat to prevent fluid flow
between the inlet and outlet. Retaining the piston is a cylinder
body that defines an activating volume communicating with the
inlet and establishing on one face of the piston a fluid pressure
forcing the piston toward its release position, and a reference
volume communicating with the inlet and establishing on the oppo-
site face of the ~iston, a reference volume. An internal seal
isolates the inlet from the reference volume with the piston in
its set position while allowing fluid communication therebetween
with the piston in its release position. Maintaining the piston
in the set position is a latching mechanism that, after activa-
tion of the piston to its release position by excessive pressure,
can be restored by a manual reset. The use of an internally
sealed reference volume eliminates problems normally associated
with regulator devices that employ a vent opening to establish
an atmospheric reference pressure.
In a preferred embodiment of the invention, the valve opera-
tor comprises a reciprocal actuator rod extending between the
valve closure and the piston. The actuator rod includes a
first longitudinal portion of one diameter and a second longi-
tudinal portion of smaller diameter disposed between the pistonand the first longitudinal portion. The reference volume seal
comprises an O-ring retained by the cylinder at one end of the
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reference chamber and disposed so as to encompass the first rod
portion with a piston in its set position and to encompass the
second rod portion with the piston in its release position.
Movement of the first rod portion into the O-ring establishes a
fluid tight seal for the reference chamber, while movement of
the second rod portion into the O-ring allows fluid communication
between the reference chamber and the inlet. The actuator rod
with portions of different diameter provides the automatic venting
of the reference chamber required both to establish a significant
valve closure stroke and to permit reset of the piston into its
set position.
Another feature of the invention is the provision of a
latching mechanism composed of an annular rib located between
the first and second rod portions and extending radially from the
one diameter. During reset of the valve to an open position, the
annular rib is forced through the O-ring and becomes engaged
therewith so as to inhibit movement of the piston into its re-
lease position. This reset of the valve is accomplished by
activation of a reset button that projects out of the housing so
as to be manually accessible. Activation of the reset button pro-
duces longitudinal movement of the cylinder body and forces the
O-ring over the annular latching rib to thereby latch the piston
in its set position.
DESCRIPTION OF THE DRAWINGS
These and other objects and features of the present inven-
tion will become more apparent upon perusal of the following
description taken in conjunction with the accompanying drawings
wherein;
Fig. 1 is a schematic cross-sectional view of a shut-off
valve according to the present invention and shown in an open
position; and
Fig. 2 is a partial schematic cross-sectional view showing
the shut-off valve of Fig. 1 in a closed position.
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DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the Figures, there is shown a valve assembly
11 including a housing 12 that defines a gas inlet 13 and a gas
outlet 14 separated by a passage 15 that forms a valve seat 16.
Located within the housing 12 is a valve closure 17 that reci-
procates between an open position (Fig. 1) away from the valve
seat 16 wherein gas flow is permitted between the inlet 13 and
the outlet 14 and a closed position (Fig. 2) against the valve
seat 16 wherein fluid flow is prevented. A connecting rod 19
is coupled between the closure 17 and a coil spring 18 that biases
the valve toward its open position. Enclosing the spring 18 is
a cover 21 that forms a vented chamber 22 sealed from the valve
inlet 14 by a flexible diaphragm 23.
Also located within the valve housing 12 is an operator
mechanism 25 that controls operation of the valve 11. The opera-
tor 25 includes a cylind~r body 26 that defines both an activating
volume 27 and a reference volume 28 separated by a reciprocable
piston 29. Connecting the cylinder body 26 to the piston is a
compressed spring 30. The activating volume 27 is sealed from
the reference volume 28 by an O-ring 31 retained by a groove in
the periphery of the piston 29. Extending between the piston 29
and the closure 17 is an actuator rod 32 that is also a part of
the operator mechanism 25. The actuator rod 32 includes a first
longitudinal rod portion 33 of one diameter and a second longi-
tudinal rod portion 34 of a smaller diameter. Located between
the rod portions 33 and 34 is an annular rib 35 that projects
radially beyond the outer surface of the first rod portion 33.
At the end of the reference volume 28 opposite to the piston 29
is an annular groove 38 formed by a pair of washers 36 and 37
retained by internal shoulders on the cylinder body 26. An O-ring
seal 39 is received by the groove 38 and possesses an internal
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diamater that seals against the first actuator rod portion 33
with the operator 25 in the position shown in Fig. 1. However,
with the ope ator 25 in the position shown in Fig. 2, the O-ring
seal 39 allows fluid flow around the second rod portion 34 be-
tween the inlet 13 and the reference volume 28. Enclosing the
cylinder body 26 is a cylindrical housing 40 that extends from
and is secured by threads to the main housing 12.
Providing fluid communication between the inlet 13 and the
activating volume 27 are a passage 41 through the cylinder body
26 and an annular clearance 42 between the c~linder body 26 and
the cylindrical housing 40. Also retained by the cylindrical
housing 40 and coupled to the cylinder body 26 by a spring 43
is a reset mechanism 44. The reset mechanism 44 includes a
reset button 45 that projects out of the housing 44 and is ex-
ternally threaded to receive a reset nut 46. An O-ring 47
retained by an annular groove in the reset mechanism 44 seals
the interior of the valve housing 12 from the atmosphere.
An annular solenoid winding 51 is positioned over the cylin-
drical housing 40 and activates the cylinder body 26 that func-
tions as a solenoid plunger. Longitudinally retaining the sole-
noid winding 51 on the cylindrical housing 40 is a pair of
washers 52 and 53 that straddle a winding enclosing cylinder 54.
The inner washer 52 engages a flange 55 on the cylindrical hous-
ing 40 and is abutted by one end of the enclosing cylinder 54.
The opposite end of the cylinder 54 receives and is secured to
the outer washer 53 by the nut 46.
Also mounted within the housing 12 is a spiral spring 60
that removes particulate impurities being transmitted with the gas
flowing between the inlet 13 and the outlet 14. The spiral spring
60 is compressed between an annular planar surface 61 encircling
the orifice 16 and a surface 62 defined by the housing 40. The
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spiral spring 60 surrounds an~ is actually aligned with the
plunger 26 so as to accommodate longitudinal movement thereof.
In typical use of the valve 11, the outlet 14 is connected
directly to a gas appliance such as a stove, hot water heater,
refrigerator, etc., and the inlet 13 is connected to a source of
LP gas, The solenoid winding 51 is electrically connected for
energization by a temperature controller (not shown) associated
with the appliance being served. In the absence of a call for
fuel, the solenoid 51 is de-energized and the compressed spring
43 forces the plunger 26 into the position shown by dotted lines
in Fig. 1 to thereby close the orifice 15 and prevent gas
flow between the inlet 13 and the outlet 14. In response to a
call for gas, however, the solenoid winding 51 is energized to
move the plunger 26 into the position shown by solid lines in
Fig. 1. This allows the spring member 18 to force the closure
17 into its open position and initiate gas flow between the inlet
13 and the outlet 14.
During such normal operation of the valve 11, the operator
mechanism 25 is inactive and the parts thereof remain in the
relative positions shown in Fig. 1. With the operator 25 in
that set position, there exists a resultant force tending to
move the actuator rod 32 into the release position shown in
Fig. 2 and thereby eliminate gas flow between the inlet 13 and
the outlet 14. This resultant force includes the gas pressure
at the inlet 13 times the area of the piston 29 minus the cross-
sectional area of the first rod portion 33 plus the force exerted
by the spring member 30. It will be noted that the force pro-
vided by the pressure in the activating volume 27 against the
full face of the piston 29 is opposed only by inlet gas pressure
times t~e cross-sectional area of the first rod portion 33 because
the reference volume 28 is sealed from the inlet 13 by the O-ring
seal 39 with the piston 2'3 in the set position of Fig. 1. The
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resultant force tending to move the piston 29 into its release
position of Fig. 2 is restrained during normal operating condi-
tions by the latching effect created by engagement between the
annular rib 35 and the O-ring 39. However, as inlet gas pressure
increases, the resultant force on the actuator rod 32 also in-
creases because of the differential pressure characteristic des-
cribed above. At some predetermined inlet pressure, the closing
force on the rod 32 is sufficient to overcome the effect of the
latch 35 and the actuator rod 32 moves the valve closure 17
against the seat 16 as shown in Fig. 2 and thereby prevents gas
flow between the inlet 13 and the outlet 14. It will be noted
that once the latching rib 35 has been forced through the O-ring
seal 39, the reduced diameter of the second rod portion 35 pro-
vides a fluid communication path between the inlet 13 and the
reference volume 28. Consequ~ntly, the decreasing volume of the
reference chamber 28 does not experience a pressure build-up
that would prevent closure of the valve.
Once the operator 25 has functioned to close the valve ori-
fice 15, reopening of the valve can be accomplished only by a
manual reset of the device. To accomplish reset, the reset nut
46 is backed off of the reset button 45 as shown in Fig. 2. The
button 45 is then depressed forcing the reset mechanism 44 and
the cylinder plunger 26 into the cylinder housing 40 as shown
by dotted lines in Fig. 2. During this movement the actuator
rod 32 is abutted against the seated closure 17 and remains
stationery. In this manner, the O-ring seal 39 is forced over
the latching rib 35 to again become latched therewith. It will
be noted again that during this reset movement by the plunger
cylinder 26, a pressure build-up does not occur in the reference
chamber 28 because of the communication path provided around the
reduced diameter second rod portion 34. Next the nut 46 is
gripped and pulled outwardly drawing the plunger cylinder 26 and
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latched therewith actuator rod 32 back to their original set
positions shown in Fig. 1. After reset, the spring member 18
moves the closure 17 off of the seat 16 to open the valve 11 and
permit control thereof by the solenoid winding 51.
Obviously, many modifications and variations of the present
invention are possible in light of the above teachings. It is
therefore to be understood that within the scope of the appended
claims the invention can be practised otherwise than as specific-
ally described.
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