Note: Descriptions are shown in the official language in which they were submitted.
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Backqround of the Invention
1. Field of the Invention
This invention pertains to relief valves.
2. Description of the Prior Art
A relief valve in a liquid flow system is
used as a bypass means for bleeding off a portion of
the flowing liquid when, for example, one or more of
the outlet passages of the flow system is closed to flow
of the liquid. ThiS often gives rise to a phenomenon
known as relief valve "pressure droop", a detrimental
drop in the pressure in the system as the bypass flow
through the relief valve is reduced. In a conventional
relief valve, small bypass flow rates therethrough
correspond to small valve plug lift heights, correspond-
lS ing to small spring deflections where a spring acts to
urge the relief valve plug against its corresponding
seat. In a conventional relief valve, the force
required to lift the valve plug off its seat is determin-
ed solely by the compressive spring force. This orce
is opposed by the liquid pressure acting upwardly on a
surface (hereinafter called the control surface) located
above the liquid plenum associated with the valve, the
control surface being connected with the æurface upon
which the spring force acts. The pressure at which the
2$ system operates is controlled by adjusting the initial
compression of the spring. An equilibrium is established
in which the spring deflection force equals the control
surface pressure lifting force. If the flow rate through
the relief valve is increased, the plug must be lifted
higher off its seat to pass the increased flow at the
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same pressure. As the flow rate is reduced, back
pressure throttled through the valve is also reduced;
thus, a reduced pressure acts on the control surface
and the upward force opposing the spring force is
reduced. The spring then urges the valve downwardly,
and a new, lower equilibrium plenum pressure is
established corresponding to a smaller upward spring
deflection. The accompanying undesirable decrease in
plenum pressure as the flow rate is reduced is commonly
known as "pressure droop".
United States patent No. 3,107,894 to Quinn
teaches a valve plug and seat arrangement wherein the
liquid flowing through the valve creates a force acting
on the underside of the valve plug, tending to further
open the valve. Quinn uses a frusto-conically shaped
valve seat wall portion and a tapered valve plug to
create a Venturi effect whereby the associated pressure
differential assists in the rapid openin~ of the valve.
United States patent No. 2,622,613 to McNeal
discloses a pressure control valve wherein the hydro-
kinetic force of the liquid, which is perpendicularly
incident upon the control surface of the valve, holds
the valve in an open position, and cylinders within the
valve passageway create a dampening action to stabilize
operation of the valve.
United States patents No~ 7.V804~089 and
No. 2~75~9815 to Siefferle and Erle, respectively,
disclose pressure regulating val~es with substantially
different structures from the apparatus herein disclosed,
such structures using the hydrokinetic forces of the
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flowing liquid to maintain a fairly constant discharge
pressure in the valve over a range of flow rates.
Summary of the Invention
According to one aspect of the invention there
is provided in a fluid flow system including a pump, a
consumption device, a fluid flow line communication
between said device and said pump, and a relief valve
assembly including a valve housing having an inlet port
connected to said fluid flow line and a bypass port for
bypassing fluid from said fluid flow line, and bypass
conduit means connected to said bypass port for receiving
bypass flow from said valve assembly, wherein said valve
assembly includes a valve seat having a bypass passageway
extending therethrough which permits bypass flow from
said inlet port to said bypass port, plug means which is
centered relative to the inlet of said bypass passageway
and which is shiftable from said valve seat for permitting
bypass flow through said bypass passageway, said plug
means including a control surface means exposed to the
fluid pressure in the valve for creating a lifting force
on the plug means which shifts said plug means relative
to said seat to permit said bypass flow when the fluid
pressure in the fluid flow system exceeds a desired
magnitude, and spring means for biasing said plug means
toward said seat counter to said lifting force, said
spring means exerting increasingly greater biasing force
on said plug means as said plug means is shifted away
from said seat in response to increasing lifting force
created by said control surface means, the improvement
comprising means disposed circumferentially about the
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inlet to said bypass passageway for producing a stagnation
pressure acting on said plug which is additive to said
lifting force and which is thus opposed to said biasing
force, said stagnation pressure producing means including
opposed, parallel, and flat annular surfaces on said plug
means and seat for directing bypass flow radially inwardly
to impinge upon itself directly below the center of the
bottom surface of said plug means, said housing including
a membrane having a bore for guiding said plug means, said
plug means including means forming a substantially fluid-
tight sliding seal within said bore, and said housing
including a member forming a chamber for said spring
means which exposes the end of said plug means which is
distal from said plug bottom surface to atmpspheric
pressure, with said stagnation pressure producing means
producing greater stagnation pressure with increasing
energy of the stagnating bypass flow into the contiguous
bypass passageway to thereby counteract increasing
biasing forces resulting from said plug means being
shifted further away from said seat, whereby the pressure
in said fluid flow system may be maintained substantially
constant over a wide range of flow rates to said
consumption device irrespective of the diameter of said
bypass passageway in said seat.
According to another aspect of the invention
there is provided an improved spray system of the type
including a plurality of spray nozzles, a fluid flow line
connected to said nozzles, means for supplying fluid to
be sprayed under pressure to said flow line, and a relief
valve assembly operatively associated with said flow line
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for bypassing fluid from said line when the pressure in
said line exceeds a preselected magnitude, wherein the
improvement comprises a relief valve assembly including:
a valve housing having an inlet port which communicates
with said fluid flow line and a bypass port for bypassing
fluid from said fluid flow line; a valve seat having a
bypass passageway extending therethrough which permits
bypass flow from said inlet port to said bypass port;
said housing including a member having a bore therein
which is axially aligned with said bypass passageway and
a spring chamber means aligned with said bore which is
exposed to atmospheric pressure; plug means which is
centered relative to the inlet of said bypass passage-
way and which is shiftable within said housing bore from
said valve seat for permitting bypass flow through said
bypass passageway, said plug means including means for
forming a substantially fluid-tight sliding seal with
said bore; spring means within said spring chamber means
for biasing said plug means toward said seat; control
surface means exposed to the fluid pressure in the valve
for creating a lifting force on the plug which shifts
said plug means counter to the biasing force exerted by
said spring means when the fluid prossure at said inlet
port exceeds preselected magnitude, thereby permitting
bypass flow through said bypass passageway to maintain
the pressure in said flow line at a constant level, with
said spring means exerting increasingly greater biasing
force on said plug means as said plug means is shifted
away from said seat, and means disposed circumferentially
about the inlet to said bypass passageway for producing
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a stagnation pressure acting on said plug means which is
additive to the lifting force and provided by the fluid
flow pressure on the control surface means and which is
thus opposed to said biasing force, said stagnation
pressure producing means including opposed, parallel, and
flat annular surfaces on said plug means and seat for
directing bypass flow radially inwardly to impinge upon
itself directly below the center of the bottom surface
of said plug means, with said stagnation pressure produc-
ing means producing greater stagnation pressure with in-
creasing energy of the stagnating bypass flow into the
contiguous bypass passageway to thereby counteract in-
creasing biasing forces resulting from said plug means
being shifted further away from said seat, whereby the
pressure in said fluid flow line may be maintained sub-
stantially constant over a wide range of flow rates
through the fluid flow line irrespective of the diameter
of said bypass passageway in said seat.
Brief Description of the Drawings
Figure 1 is a vertical section through the
relief valve of the present invention.
Figure 2 is a schematic representation of
the relief valve as used in a typical environment, e.g.,
to control discharge pressure in a spray boom.
Figure 3 is an enlarged section of the valve
seat and plug area of the relief valve of Figure 1,
particularly showing the liquid flow pattern developed.
Figure 4 is a section similar to Figure 3 but
showing the liquid flow pattern developed in a second
embodiment of the invention.
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Figure 5 is a section similar to Figure 3 but
showing the liquid flow pattern developed in a third
embodiment of the invention.
Figure 6 is a section through a relief valve
which is representative of the prior art.
Figure 7 is a detail sectional view of the
valve seat. and plug area of a fourth embodiment of the
present învention, such embodiment including a pressure
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pulsation dampening apparatus.
Figure 8 is a partial vertical section through
a fifth embodiment of the present invention which
utilizes a modified va~ve plug mountinq arrangement.
~igure 9 is a graph showing valve internal
pressure developed as a function of liquid flow rate for
the representative prior art relief valve of Figure 6.
Figure 10 is a chart showing valve internal
pressure developed as a fùnction of liquid flow rate
for the valve of Figure 2.
Description of the Preferred Embodiment
Figure 2 schematically illustrates a repre-
sentative application of the relief valve 11 of the
present invention in a spray boom system. The spray
liquid is transported under pressure (e.g., 500 psi) by
a pump P to the relief valve and thence to a spray boom
~or deposit on a farm crop or the like through a
plurality of spxay nozzles. If one or more of the spray
nozzles is closed, the internal pressure in the system
will increase accordingly unless a portion of the liquid
is bled off via the relief valve bypass to maintain
the internal pressure at the predetermined value (500
psi). The subject invention provides means for
controlling the separation of plug and seat in the relief
~5 valve so as to maintain nearly constant internal pressure
within the valve even though the flow rates through the
- valve will vary greatly as anywhere from one to six of
the illustrated spray nozzles are operated.
With reference to Figure 1, the relief valve
of the present invention will be seen to comprise a
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valve housing member 13 which defines a vertical
passageway, or bypass, passageway 15 used for bypass of
liquid in the xelief valve. A bypass pipe 17 is
threadedly mounted in and coaxial with the passageway
15 for passing the bypassed fluid~ at substantially zero
pressure, to the pump reservoir or to another discharge
location. A valve seat 19 of annular configuration is
force fitted against the vpper inner circumference of
the passageway 15 of housing 13, and an annular ceramic
insert 21 is secured snugly within the inner circum-
ference of the valve seat 19 b~ a heat-shrinking process
so as to define an axial passageway 23 therethrough.
The ceramic insert serves to protect the metal surfaces
of the seat 19 from erosion by the high velocity liquid.
The valve plug will be seen to comprise a
lower plug component 25 of ceramic with a flat lower
face which is arranged to abut against the upper
annular surface of the ceramic insert 21 and an upper
plug component 27 of metal which includes a cylindrical
recess that securely mounts the lower plug component.
The aforementioned heat-shrinking process is used to
secure the ceramic lower component 25 within the
cylindrical recess of the upper plug component 27. A
valve stem 29 e~tends vertically upwardly from the plug
to which it is tightly secured by a set screw 29a.
With regard to the heat shrinking process as
applied to the construction of the valve seat, for
example, one begins with an annular ceramic insert 21 of
uniform cross-section whose outer radius is slightly
larger, at room temperature, than the interior radius of
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the metal outer component 19 of the valve seat to which
it is to be fitted. The portion of the valve seat
adjacent to the ceramic insert must also be of uniform
cross-section to avoid development of any localized or
point stresses when metal and ceramic contact on~
another after cooldown; if localized stresses develop
and are of sufficient magnitude, the ceramic insert may
crack or split under the forces. By insuring that the
metal outer component 19 is also of uniform cross-section
in this area, one insures that the circumferential
stresses developed upon cooldown will be reasonably
uniform over the circumferential area of contact.
In performing the operation, the metal outer
component 19 is heated to a temperature where the
lS associated circumferential thermal expansion of the
inner circumference is sufficient to permit the annular
ceramic insert 21 to be slipped within the inner cir-
cumference. The outer seat component 19 is now allowed
to ~ool down slowly so as to contact the ceramic insert
2~ uniformly along the outer circumference of the insert.
As a result of the subsequent cooldown, the metal outer
component will shrink and be placed in circumferential
tension while the ceramic insert will be in circumfer-
ential compression. Ceramic material is known to be weak
and susceptible to cracking when said material is in
tension, but the material develops addit-ional strength
when it is placed in compressior. as in the d~ssribed
process. The use of the heat shrinking process to fit
the ceramic inserts 21 and 25 to the outer metal
components 19 and 270 respectively, avoids the necessity
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for "gluing" ceramic and metal together which has been
found to produce an uncertain bond between metal and
ceramic and to leave the ceramic susceptible to cracking.
As a peripheral benefit, where the heat shrinking pro-
cess is employed the ceramic insert may be removed for
replacement by merely reversing the process, i.e., the
metal outer component is reheated and the ceramic insert
is removed.
Ingress of the system l;quid to the relief
valve occurs via the passageway 31 in the valve housing
13, a liquid egress occurs via the passagewa~ 35 in the
housing 13 with the liquid passing around the valve
plug component 27 as it flows through the valve. It
will be recognized, however, that only one passageway
~5 is necessary where the relief valve does not function to
pass the system flow as, for example, where the relief
valve is positioned in a bypass conduit rather than in
the main flow conduit as shown. The incoming pressurized
liquid in the passageway 31 enters a plenum 39 defined
by the annular region surrounding the valve plug
components 25 and 27, moves around the plug, and exits
via the passageway 35 when the valve plug closed upon
its seat. With the valve plug and seat spaced apart,
a portion of this flowing liquid is bypassed through
the passageway 15. A portion of the li~uid about the
plug also flows into an upper plenum 41 which is defined
by the annular region surrounding the upper valve plug
component 27. The liquid in the plenum 41 exerts
upwardly directed vertical forces upon an annular piston
43 through a packing member 33 tending to move the
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piston, the valve plug, and the attached valve stem 29
upwardly. The piston 43 vertically reciprocates inside
a cylindrical bearing 44 fitted within a retainer 44a
which is secured to the housing 13 and which is protected
5. against leakage by an 0-ring seal 45 strategically
placed as shown.
~ying above the two plenums 39 and 41 is a
cylindrically shaped sprin~ housing 47 which is bolted
at its lower end to the valve housing 13. The spring
housing defines a vertically extending cavity 49
containing a pair of ~ertically oriented springs 51 and
53 used to urge the valve plug 25 downwardly upon the
valve seat 21. The springs 51 and 53 are used to
obtain the necessary spring force, nominally about 800
pounds spring force where the relief valve is set to
open at 500 psi. The two springs seat upon the upper
face of the piston 43 surrounding the valve stem 29.
At the upper end of the spring housing an upper spring
retainer 57, which is positioned about the upper end of
2Q the stem 29, acts as an adjustable base against which
each spring is referenced. The springs resist the
upward movement of the valve plug and piston which is
caused ~y the presence of the pressurized liquid within
the Iplenum 41. The springs are chosen so that they
just suff ice to keep the valve plug 25 closed upon the
valve seat 21 when the f luid in the system is pressurized
to the maximum desired pressure.
The upper portion of the stem 29 is provided
with a cap 59 which fits slidably around said stem at
the top and acts as a guide for said stem. The cap
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also serves to mount the upper spring retainer 57 in its
desired position. The top portion of this cap contains
a rotatable sphere 61. A cam 63 journaled at 65 is
mounted upon a moun-ting me~ber 66 so that the lower
surface of the cam can be moved into engagement with the
sphere 61~ The cam 63 is attached to a handle 67 which
serves to raise and lower the cap 59 and the upper
spring retainer 57 as the cam 63 is rotated to engage
sphere 61. With the handle at the phantom line posi-
tion, shown in Figure 1, the upper spring retainer 57,
the springs 51 and 53, and the valve plug will be driven
downwardly so that the plug closes upon the valve seat
with its desired initial spring compression~ When the
handle is rotated to the full line position shown in
Figure 1, the valve stem 29 is released to move upwardly
and the initial spring compression is removed. The
valve plug may then be lifted and spaced apart from the
valve seat 21 with a minimum of liquid pressure allowing
liquid to flow through the discharge passageway 15 for
the purpose of bypass at low pressure.
Finally, a cap 69 surrounds the upper portion
of the spring housing 47 wherein the springs 51 and 53
are placed. This cap is threaded to the housing and
secures the mounting member 66 in posit ion to thereby
provide a means for adjusting initial spring ~ompression
and thus adjusting the discharge pressure in the system.
Referring now to the detail view of Figure 3
it will be seen that as soon as the valve plug 25 is
raised off the valve seat 21, a flow pattern will develop
3~ as shown. The liquid, under more or less uniform
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pressurc on all sides of the valve plug, moves radially
inward and impinges upon itself at the top center 71 of
the axial ~assageway 23. At this point the liquid
changes direction, losiny much of its hydrokinetic
energy in the process. This creates a region 73 (shown
roughly by the dot~ed lines in Fig. 3) of stagnation
pressure, reflecting the local loss of hydrokinetic
energy of the liquid. This stagnation pressure acts
approximately equally in all directions, normal to the
imaginary sphere 73 as shown. In particular, this
stagnation pressure acts with a net upward force upon
the lower face of the lower plug component 25 and thus
provides an additional liftinq force acting to urge
the valve plug upwardly against the downwardly directed
spring forces. It must be remembered that this pressure
will increase as the flow through the valve increases.
Thus, while the resisting spring force will increase
as the springs 51 and 53 are compressed further for
larger flows~ the stagnation pressure will increase
accordingly to ofset this increase in the spring force
and the sy~tem pressure will remain approximately the same.
Figures 4 and 5 disclose modified configura-
tions for the valve plug and the valve seat of the
relief valve of the present invention. In Figure 4,
the valve plug 85 and the valve seat 81 are onfigured
so that the fluid makes approximately a 120 turn in
direction at the center of the underside of the plug
before entering the axial passageway 83 through the
valve seat. The hydrokinetic energy loss here is of a
higher magnitude than the corresponding loss in the
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embodiment of Figure 1, and the stagnation pressure
thereby developed under the valve plug can be expected
to be larger; this will result in increased lift;ng
forces acting on the underside of the plug as the flow
rate increases whereby greater increases in resisting
spring force can be equalized.
- In the Figure 5 embodiment, the valve plug 95
and valve seat 91 are configured so that the liquid
undergoes three ~0~ turns before precedlng down the
axial passageway 93 in the valve seatO Some hydro-
~inetic energy is lost at each turn. By thus restrict-
ing the stream expansion, a greater force is developed
~eneath the valve plug for increasing flow rates to
counteract increasing spring forces.
Figure 6 discloses a representative prior art
relief valve 100 with the lower portion of the valve
plug 101 being a downwardly converging frusto-conical
element 102. With the valve plug spaced slightly apart
from the annular rim defining the valve seat 104, the
- 20 liquid in the valve is deflected downwardly so as not
to lose too much of its kinetic energy and does not
impinge upon itself. Thus, any increase in spring force
at larger valve openings will mean a correspondingly
higher system pressure at such larger valve openings.
The subject invention disclosed in Figures
2-5, utili~ing a flat or upwardly converging plug lower
face, achieves a positive pressure differential keneath
the plug which increases with increasing flow between
valve plug and seat so as to approximately equalize the
internal valve system pressure for most flow rates.
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Figure 7 discloses an alternative embodiment of
the invention which includes means for dampening pressure
pulsations or other rapid changes in system pressure
which may occur during flow through the valve. In the
Figure 7 embodiment, the valve body 120 is provided
with a passageway 122 which is in communication with
the main flow conduit in the flow system. A bypass
passageway 124 is connected with the passageway 122 and
is arranged to be normally sealed off by the lower face
of a cylindrical plug member 126. The valve plug
member ;s forced by spring 128 into engagement with a
flat annular surface surrounding the upper end of the
~assageway 1240 The valve body includes a narrow
projecting wall 120a which surrounds the cylindrical
1~ plug member 126 but is slightly spaced therefrom so as
to provide a narrow annular passageway 130 therebetween~
Above the wall 120a a variable chamber 132 is provided,
the size of such chamber depending on the position of
packing member 134 within the recess 135 within which
the valve plug and its supporting structure reciprocate
as flow increases or decreases through the valve. It
will be seen that any increases or decreases in flow
rate (while the relief valve is open) require liquid to
pass through the narrow annular passageway 130 either
to or from the chamber 132~ Since the passageway 130
is restricted, such flow can occur only at a limited
rate, and, thus, therestricted passageway acts to damp
out any rapid pressure variations in the system.
In contrast to the oil-filled hydraulic
dampeners of the prior art~ it will be seen that the
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dampener of the present invention, which utilizes only
the liquid flowing in the system, is more easily
maintained and is more reliable since no additional
sealing members or externa~ hydraulic control system are
xequired. Also, heat build-up in the dampener is
eliminated.
Referring now to Figure 8, a further embodi-
ment of the invention is shown wherein the valve plug
member is mounted for universal movement so that greater
manufacturing tolerances can be used in machining the
valve plug and the valve seat thus making the valve more
economical to produce. ~s seen in Figure 8, the valve
pluy 140 is formed as a partial sphere with a flat lower
surface 141 being adapted to seal against the upper
annular face of a ceramic valve seat 146~ In the manner
previously described, the ceramic valve seat 146 can be
inserted within the metallic mounting member 148 by a
heat shrinking process. The valve plug 140 is swaged
into a retainer member 142 in a spherically shaped
.socket so that it will be slightly loose and free to
swivel in the socket. The retainer 142 is attached to
a valve stem 144 for operation in the manner previously
descri~ed.
With no upward pressure on the valve plug the
force imposed by spring 149 forces the plug and its
retainer 142 downwardly against the valve seat 146.
When the plug engages the seat the plug will swivel in
its retainer until perfect alignment is achieved. Thus,
a perfect seal is assured when fluid pressure is applied
to the valve. When fluid pressure in the valve overcomes
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the force of spring 149, the plug is lifted off the
seat to relieve the pressure. In order to insure that
- the face 141 of the plug and t'he seat remain parallel
when the plug is lifted, a pressure bleed hole 150 is
. provided in the retainex so that fluid pressure will
be applied to the spherical top surface of the plug to
force it dcwnwardly against the swaged lip 143 of the
retainer and prevent it from swiveling~
Figures 9 and 10 illustrate the internal
pressures developed in the representative prior art
relief valve of Figure 6 and in the relief valve of
the present invention as shown in Figure 2, respectivelyt
for varlable flow rates. It will be noted that the
internal pressures within the prior art valve vary
considerably as the flow rate decreases. By contrast,
the relief valve of the present inventlon maintains a
nearly uniform pressure (to within 15% of the reference
value) down to flow rates of approximately 5 gallons pex
minute. It has recently been determined that the
"knee" in each of the curves in Figure 9 can be made to
occur at 1/2-1 gallon per minute flow rate with the
relief valve of the present invention.
Although the best modes contemplated for
carrying out the present invention has been herein shown
and described, it will be apparent that modification
and variations may 'be made without departing from what
is regarded to be the subject matter of the invention.
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