Note: Descriptions are shown in the official language in which they were submitted.
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RELIEF VALVE
Technical Field and Background of the Invention
This application relates to a relief valve used to relieve pressure in a
pressurized fluid
system. The novel relief valve is described in this application for purposes
of illustration and
explanation as being installed on a water heater shutoff/thermal expansion
control valve such
as an Apollo 78T .F-RV Series valve manufactured by Conbraco Tndustries, Inc.
of
Matthews, North Carolina. However, the relief valve has application in a wide
variety of
uses, and its description in this application installed on a specific device
carries no
implication that its use is limited to use on that device.
Conventional relief valves include a body that is positioned in fluid
communication
with a pressurized fluid system, for example a shutoff valve, backflow valve,
or pipe. A
spring-loaded rubber ball bears against the walls of a relief port in the
valve, pipe, etc. The
spring is designed for a specific relief setting. If pressure in the system
exceeds a
predetermined value, that excessive pressure exerts sufficient force against
the ball to unseat
it from the relief port walls, allowing fluid to flow past the ball to
atmosphere, an expansion
tank or other resorvoir. As the pressure is reduced, the ball is again, urged
back into sealing
contact with the wall of the relief port. The spring is mounted in a conduit
in the relief valve
and is held in an aligned position by the walls of the conduit and a shoulder
of reduced
diameter against which the end of the spring remote from the ball resides.
These prior art
relief valves are prone to delivering inaccurate performance as a result of
the spring being
compressed during an over pressure event to the extent that the coils contact
each other and
the spring becomes, iii practical effect, a solid object that restricts fluid
flow from the valve.
This condition can result in false pressure readings, delayed pressure relief
and simi.lar
conditions,
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Summary of the Invention
Therefore, it is an object of the invention to provide a pressure relief valve
that
provides accurate, reliable and rapid pressure relief in a pressurized fluid
system to which the
relief valve is attached.
It is another object of the invention to provide a pressure relief valve that
permits
pressure relief by full fluid flow from a fluid system hi an over pressure
condition.
It is another object of the invention to provide a pressure relief valve that
provides
support to the sealing ball during both seated and unsealed positions.
It is another object of the invention to provide a pressure relief valve that
prevents
defOrmation of the ball in both sealed and unsealed positions.
These and other objects and advantages of the present invention are achieved
in the
preferred embodiment disclosed below by providing a relief valve for relieving
pressure in a
fluid conduit that includes a valve body adapted for being positioned in fluid
communication
with a fluid pressure system. A relief valve conduit is formed in the relief
valve body and has
a valve seat positioned around a pressure relief port at one end of the
conduit adapted for
communication with the fluid pressure system and a discharge vent in an
opposite end of the
conduit. A cradle is positioned in the relief valve conduit and includes a
ball support surface
with a hall mounted on the ball support surface and adapted for sealing
against the valve seat
of the pressure relief pert. A spring support surface is provided normal to a
longitudinal axis
of the relief valve conduit, The spring is positioned in the pressure relief
conduit for urging
the ball carried in the cradle into sealing position against the valve seat of
the pressure relief
port, The spring has .a predetermined load, When pressure is exerted on the
spring in excess
of the wedetermined load, the spring will compress, withdrawing the ball out
of sealing
position against the valve seat of the pressure relief port to allow a
discharge of fluid from the
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fluid pressure system,
According to another embodiment of the invention, the cradle includes a pair
of
spacers positioned between the ball support surface and the spring support
surface.
According to another embodime-nt of the invention, the cradle includes a pair
of
spacers positioned between the ball support surface and the spring support
surface and at least
one flow port for permitting fluid flow through and around the cradle.
According to another embodiment of the invention, the bail support surface of
the
cradle includes an annular scgmcnt corresponding in shape to a portion of the
surface of the
ball.
According to another embodiment of the invention, the spring support surface
includes a planar surface defined by an inner and outer circumference of the
cradle.
According to another embodiment of the invention, the relief valve conduit
includes a
shoulder of reduced diameter for supporting an end of the spring remote from
the ball.
According to another embodiment of the invention, the ball is fabricated of
ethylene
propylene diene monomer.
According to another embodiment of the invention, the Wilms a 70 Shore A
bardru.',ss.
According to another embodiment of the invention, the spring has a compression
of
about 50 percent between a free length and a fully compressed length.
According to another embodiment of the invention, a relief valve is provided
for
relieving pressure in a fluid conduit, and includes a valve body adapted for
being positioned
in fluid communication with a fluid pressure system and a relief valve conduit
formed in the
relief valve body having a valve seat positioned around u pressure relief port
at orro end of the
conduit adapted for communication with the fluid pressure system and a
discharge vent in an
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opposite end of the conduit. A cradle is positioned in the relief valve
conduit and includes a
bail support surface and a ball mounted on the ball support surface adapted
for sealing against
the valve seat of the pressure relief port. The ball support surface of the
cradle includes an
annular segment conesponding in shape to a portion of the surface of the ball.
A spring
support surface normal to a longitudinal axis of the relief valve conduit has
a planar defined
by an inner and outer circumference. A spring is positioned in the pressure
relief conduit for
urging the cradle and the, ball into sealing position against the valve seat
of the pressure relief
port. The spring has a predetermined load in excess of which the spring will
compress,
withdrawing the hall out of sealing position against the valve seat of the
pressure relief port to
allow a discharge of fluid from the fluid pressure system. A pair of spacers
Is positioned
between the ball support surface and the spring support surface and at least
one flow port for
permitting fluid flow through and around the cradle. A shoulder of reduced
diameter is
formed in the relief valve conduit for supporting an end of the spring remote
aom the hall,
According to another embodiment of the invention, a water heater
shutoffithermal
expansion control valve adapted for being positioned in flow communication
with a water
pressure system is provided, and includes a pressure relief valve for
relieving pressure in the
system above a pTudetermined level. The pressure ref id valve Includes a valve
body adapted
for being positioned in fluid communication with a fluid pressure system. A
relief valve
conduit is formed in the relief valve body and has a valve seat positioned
around a pressure
relief port at one end of the conduit adapted for communicatIon with the fluid
pressure
system and a discharge vent in an opposite end of the conduit. A cradle is
positioned in the
relief valve conduit and includes a ball support surface and a ball mounted on
the ball support
surface and adapted for scaling against the valve seat of the pressure relief
port, A spring
support surface normal to a longitudinal axis of the relief valve conduit is
provided, and a
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spring is positioned in the pressure relief conduit for urging the cradle and
the ball into
sealing position against the valve seat of the pressure relief port. = The
spring has a
predetermined load in excess of which the spring will compress, withdrawing
the ball out of
sealing position against the valve seat of the pressure relief port to allow a
discharge of fluid
from the fluid pressure system,
Brief Description of the Drawiogs
Some of the objects of the invention have been set forth above, Other objects
and
advantages of the invention will appear as the description of the invention
proceeds when
taken in eon] unetion with the following drawings, in which:
Figure 1 is a vertical longitudinal cross section of a water heater
shutoff/thermal
expansion control valve equipped with a prior art pressure relief valve;
Figure 2 is a vertical longitudinal cross section of the prior art pressure
relief valve of
Figure 1 in a sealing position;
Figure 3 is a vertical longitudinal cross section of the prior art pressure
relief valve of
Figure 1 in an unsealed, pressure relief position;
Figure is a vertical longitudinal cross section of a water heater
shutoff/thertnal
expansion control valve equipped with a pressure relief valve according to a
preferred
embodiment of the invention;
Figure 5 is a side elevation view of the water heater shutoff/thermal
expansion control
valve of Figure 4, with the components of the pressure rul ief valve shown in
an exploded
view;
Figure 6 is a vertical longitudinal cross section of the pressure relief valve
of Figure 4
in a sealing position;
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Figure 7 is a vertical longitudinal cross section of the pressure relief valve
of Figure 4
in an unsealed, pressure relief position;
Figure 8 is an enlarged view of the ball and spring support cradle of the
invention; and
Figure 9 is a cross-section of the ball and spring support cradle shown in
Figure R.
Description of the Preferred Embodiment and Best Mode
Referring now to Figures I, 2 and 3 of the application, a water heater -
shutoff/thermal
expansion control valve 10 is shown, and includes a valve body 12 defining a
conduit 14 that
passes water from a supply connection 16 through the conduit 14 and out
through a discharge
connection 18 to, for example, a water heater, Valve 10 is controlled by a
valve ball 20
rotated by a stem 22 connected to a quarter-turn handle 24.
A prior art relief valve 30 includes a valve body 32 that communicates with
the
conduit 14 through a chamfered relief port. 34 in The valve body 12, The valve
body 32
defines a relief valve conduit 36 that vents fluid to atmosphere or a suitable
reservoir, A
relief valve :fitting sub-assembly 38 is threaded onto the valve body 32 of
the relief valve 30.
The valve body 32 defines a conduit 40 with a shoulder 42 that supports a
spring 44 that
directly contacts and urges a ball 46 against the relief port 34 to effect a
scat during normal
pressure operation of the valve 10, See Figure 2.
This design presents several disadvantages. First, rapid, accurao discharge is
obstructed by tho coils of the spring 44 as water is vented to the atmosphere;
as shown in
Figure 3. Delay in venting may result In a false reading or the discharge rate
that fails to
satisfy the performance requirements of TAPMO IGC 128-2008, Second, the ball
46 Is seated
directly on the top of spring 44, The pressure of the spring 44 against the
ball 46 can cause
an impression on the surface of the ball 46 and, eventually damage to the
surface, As the
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spring 44 impresses itself into the surface of the ball 46, the in-place
length a the spring
inereases and reduces the load applied to the ball 46 as the impression on the
surface of the
ball 46 increases.
Referring now to Figures 4-9, a relief valve 60 accordiug to the invention is
shown in
place on a valve 10 of the same design and operation as the valve 10 of
Figures 1-3. Relief
= valve 60 includes a valve body 62 that communicates with the conduit 14
through
chamfered relief port 64 in the valve body 12. The relief valve body 62
defines a relief valve
conduit 66 that vents fluid to atmosphere or a suitable reservoir. A relief
valve fitting sub-
assembly 6a is threaded onto the valve body 62 of the relief valve 60. See
Figures 5, 6 and 7.
A hall 70 and spring 72 operate the relief valve 60, and as is shown in
Figures 8 and
9, in accordance with the invention, a cradle 80 is provided and includes an.
annular ball
support surface 82 and a ring-shaped, radially-extending spring support
surface 84. The ball
support surface 82 and spring support surface 84 are separated by a pair of
spacers 86, 88 that
define flow ports 90, 92.
Referring now to Figures 6 and 7, the spring 72 now engages the spring support
surface 84 of the cradle 80 instead of the ball 70. The ball 70 is supported
on the much larger
surface area of the ball support surface 82. The ball 70 is uniformly urged
against the relief
port 64 by operation of the spring support surfaue 84. The ball 80 is
preferably EPDM rubber
(ethylene prnpylene dime monomer) with a 70 Shore A hardness. EPDM is a
particularly
appropriate material because of its resistance to softening and degradation by
hot water.In
one embodiment, the ball has a diameter of .250 in, (635 mm), the spring has a
.390 in. (9
min) free length and a .213 in, (5,4 mm) uompressed length. The ball support
surface 82 has
a radius of ,125 in. (3.18 mm), and the spring support surface has an inner
circumference of
.260 in. (6.6 mm) and an outer circumference of 370 in, (9,4 mm),
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A relief valve is described above. Various details of the invention may be
changed
without departing from its scope. Furthermore, the foregoing description of
the preferred
embodiment of the invention and the best mode for practicing the invention are
provided for
the purpose of illustration only an4 not for the purpose of limitation¨the
invention being
= defined by the claims.
=µ
..= -
