Flow control valve having variable flow ring and seat cage

A valve comprises a valve body having an inlet and an outlet defining a flow passage through the valve body. A piston is mounted in a bore intersecting the flow passage and the piston divides the bore into first and second chambers. The piston remains substantially motionless during upstream pressure fluctuations after the desired fluid flow rate through the valve has been established. Springs in the second chamber bias the piston against the fluid pressure from the first chamber. A sleeve on the piston is configured to variably sheath a cover over the outlet such that reciprocation of the piston during initiation of fluid flow through the valve varies the effective area of openings in the cover to achieve the desired differential pressure across the flow control throttle, thus setting the flow rate constant unless the throttle position is changed. The equilibrium flow rate can be altered through variation of fluid flow between the piston and the valve body by a bladder ring which is inflated or deflated by an elastomeric ring which is deformed by liquid or structural forces, or by a metal or plastic ring that is circumferentially variable by mechanical actuators.

BACKGROUND OF THE INVENTION 
The present invention relates to constant fluid flow regulators and more 
particularly to a flow regulator having a spring biased piston and being 
capable of maintaining a constant fluid flow rate in both high pressure, 
low volume and low pressure, high volume environments with changes in 
inlet or outlet pressure. The present invention also accommodates high 
pressure, high volume and low pressure, low volume systems. Most prior art 
constant fluid flow regulators vary fluid flow through the piston by 
movement of the piston that varies the flow pressure through this piston 
or by change in the spring tension. More specifically, constant fluid flow 
regulators taught in the prior art regulate fluid flow by adjustment 
screws that directly vary spring tension by attachment to the piston 
spring itself. Other regulators change fluid flow by altering piston 
position via springs and ball bearings located over the piston. The system 
employing springs and ball bearings is subject to extreme torque due to 
the fluid pressure in the chamber. 
Additionally, multiple poppet type valves may be used for low pressure, 
high volume fluid flow regulation. The above prior art, however generally 
cannot accommodate high pressure, low volume fluid flow. This invention, 
on the other hand, is able to provide constant fluid flow in high or low 
pressure and high or low volume ranges. The present invention is also 
different from the above sliding sleeve and multiple poppet type valves in 
that the piston of the valves of the prior art move relative to the valve 
body to vary fluid flow as the pressure changes, while the piston of the 
present invention does not move substantially relative to the valve body 
after fluid flow has stabilized. Instead, constant spring force on the 
piston in the present invention allows constant pressure across the 
piston, therefore the flow is constant. The present invention thus 
experiences less wear and tear from moving parts. 
Furthermore, U.S. Pat. No. 4,893,649 issued to Skoglund and U.S. Pat. No. 
3,958,596 issued to Gerrard both disclose valves in which fluid flow 
variation is implemented by an adjustable valve seat. Adjustment of the 
valve seat adjusts the spring tension, which in turn alters the pressure 
differential across the piston. However, both of the above prior art 
patents employ threaded, screw-type mechanisms for adjusting the valve 
seat which are difficult to operate, have a narrow operating range, and 
are prone to breakage in high pressure environments. 
Also, the screw-type valve seat adjustment mechanisms of the above prior 
art references both impede fluid flow through the valve. U.S. Pat. No. 
4,893,649, discloses a valve in which the fluid outlet is oriented 
perpendicular to the fluid inlet in order to accommodate the valve seat 
adjustment mechanism. This angled fluid flow pathway results in a more 
complex valve design as well as increased fluid turbulence and higher 
pressure drops. U.S. Pat. No. 3,958,596 issued to Gerrard teaches a valve 
in which the fluid outlet passes axially through the valve seat adjustment 
screw. This valve seat adjustment mechanism configuration is difficult to 
use while the valve is in operation. 
The constant flow rate controller valves discussed in U.S. Pat. Nos. 
5,143,116 and 5,234,025, both issued to Skoglund, operate based on the 
following force balance equations. 
EQU P.sub.1 A.sub.piston =P.sub.2 (A.sub.piston -A.sub.pin)+KX+P.sub.3 
A.sub.pin 
Where 
P.sub.1 =pressure in the first chamber 
A.sub.piston =surface area of the piston 
P.sub.2 =pressure in the second chamber 
KX=spring force of the springs 
A.sub.pin =surface area of the piston pin which mates with the seat 
P.sub.3 =pressure at the outlet port 
Rearrangement of terms produces the following equations: 
##EQU1## 
Because A.sub.pin is small in comparison to A.sub.piston, and assuming 
P.sub.3 equals the flow pressure at the outlet port, the following 
equations characterize the force balance existing in these inventions. 
EQU KX=(P.sub.1 -P.sub.2)A.sub.piston +P.sub.2 A.sub.pin -P.sub.3 A.sub.pin 
(P.sub.2 A.sub.pin and P.sub.3 A.sub.pin being relatively small in size) 
EQU KX.apprxeq.(P.sub.1 -P.sub.2)A.sub.piston 
Thus, the differential pressure (P.sub.1 -P.sub.2) is a function of spring 
force (KX), but is not precisely equal to spring force (KX). 
The flow rate of water, for example, through a control valve is defined by 
the following equation: 
##EQU2## 
Where .DELTA.P=P.sub.1 -P.sub.2 
Q=flow rate 
P.sub.1 =pressure in the first chamber 
P.sub.2 =pressure in the second chamber 
C.sub.v =flow resistance across the orifice 
Sg=Specific gravity of fluid 
Note that because differential pressures (P.sub.1 -P.sub.2) is a function 
of spring force (KX), flow rate (Q) is also a function of spring force. 
Thus, these constant flow rate controller valves have a constant flow as 
long as spring force remains constant. This flow is constant regardless of 
the flow pressure at the inlet port. However, there is a pressure force 
exerted on the piston pin which mates with the valve seat, and against the 
remainder of piston defined by 
EQU P.sub.3 .multidot.A.sub.pin 
Where 
P.sub.3 =pressure at the outlet port 
A.sub.pin =surface area of the piston pin 
The above force must be minimized for these valves to function pressure 
independently. Therefore, for the valves to function, the surface area of 
the piston pin must be small when compared to the surface area of the 
piston as a whole. Note that this force would not be small and the flow 
rate would not be constant if the area of the piston pin was not small in 
value when compared to the surface area of the piston as a whole. These 
valves therefore can have a limited number of different configurations, 
and must usually be relatively large. 
However, in this invention the following equations apply: 
EQU P.sub.1 A.sub.1 =P.sub.2 A.sub.2 +KX 
EQU A.sub.1 =A.sub.2 
EQU P.sub.1 A.sub.1 -P.sub.2 A.sub.1 =KX 
EQU (P.sub.1 -P.sub.2)A.sub.1 =KX 
##EQU3## 
The area of the outlet A.sub.3 and outlet pressure P.sub.3 are no longer 
factors in the balance equation on the underside of the piston. These 
forces are transferred to the body and not to the piston. Therefore the 
P.sub.1 -P.sub.2 valve across the piston and control surfaces is not 
impacted by P.sub.3 and A.sub.3. This is a change from the prior art. 
SUMMARY OF THE INVENTION 
A valve comprises a valve body having an inlet and an outlet defining a 
flow passage through the valve body. A piston is mounted in a bore 
intersecting the flow passage and the piston divides the bore into first 
and second chambers. The piston remains substantially motionless during 
upstream pressure fluctuations after the desired fluid flow rate through 
the valve has been established. Springs in the second chamber bias the 
piston against the fluid pressure from the first chamber. A sleeve on the 
piston is configured to variably sheath a cover over the outlet such that 
reciprocation of the piston during initiation of fluid flow through the 
valve varies the effective area of openings in the cover to achieve the 
desired pressure across the piston. The sleeve locates such that a force 
balance is achieved on the piston between the first and second chambers 
set by the piston spring to cause equilibrium. 
The equilibrium flow rate can be altered through variation of fluid flow 
between the piston and the valve body by a bladder ring which is inflated 
or deflated by an elastomeric ring which is deformed by liquid or 
structural forces, or by a metal or plastic ring that is circumferentially 
variable by mechanical actuators. 
In operation, the piston is initially spring biased toward the top portion 
of the valve. Fluid flowing into the controller valve via the inlet port 
passage increases the pressure in the chamber above the piston, forcing 
the piston sleeve over the outlet cover. The piston sleeve thus blocks the 
outlet cover openings, preventing fluid flow to the outlet port. The 
pressure in the chamber below the piston builds as fluid enters through 
the openings in the piston sleeve until the pressure force in this lower 
chamber plus the piston spring force is greater than the pressure force in 
the chamber above the piston. The piston then lifts the sleeve from at 
least a portion of the outlet cover, and at least a partial fluid pathway 
through the cover openings to the outlet orifice is opened. An equilibrium 
flow rate is reached (i.e., when the pressure forces in the upper chamber 
equals the pressure forces in the lower chamber plus the spring force) by 
variation in the piston position based on the interaction of the above 
fluid pressure forces and spring force. 
Importantly, after the desired flow rate has been attained, the piston no 
longer moves substantially relative to the valve body unless fluid flow is 
altered by the valve's flow throttle. Minute movement of the piston does 
occur when there is a pressure change across the valve, but this piston 
movement only sets the pressure differential across the piston, and does 
not directly change the flow rate through the valve. Instead, constant 
flow rate is maintained despite pressure changes because the spring force 
maintains a constant pressure differential pressure between the two valve 
chambers, and not by piston sleeve movement relative to the outlet cover.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the FIGS. 1 through 16, the reference numeral 10 indicates the 
constant flow rate controller valve, as a whole. Valve 10 has a valve body 
12 having at its top portion an inlet port 14, and having at its bottom 
portion an outlet port 16. A bore 18 is formed within valve body 12. 
A piston 20 having a head 21 is disposed within bore 18 such that a portion 
of bore 18 is divided into chamber 22 above piston head 21 and chamber 24 
below piston 20. Piston 20 is preferably of a generally cylindrical 
configuration. 
Within chamber 24 are springs 30 which contact piston 20 and bias piston 20 
upwardly toward chamber 22. Springs 30 may be coil type springs for 
example. By employing coil type springs for springs 30, the desired 
differential pressure (P.sub.1 -P.sub.2) across the piston (chambers 22 
and 24) may be conveniently altered by changing the spring force. The 
differential pressure across the piston stabilizes after flow is adjusted 
with the variable ring means discussed below and constant flow is 
achieved. The valve is then pressure independent at the new flow setting, 
and piston 20 no longer moves substantially even if the upstream pressure 
does fluctuate. 
Referring again to piston 20, sleeve 31 is connected under piston head 21 
in chamber 24, and is preferably tubular. Sleeve openings 33 are one or 
more in number and are preferably radially disposed around sleeve 31. 
Sleeve openings 33 allow fluid to enter sleeve 31 of piston 20 and impart 
fluid pressure P.sub.2 on area A.sub.2 of piston head 21 in chamber 24. 
Cover 34 is located over outlet port 16, and resides in chamber 24. Cover 
34 is preferably cylindrical, having top 35 and sides 36. Cover openings 
37 are one or more in number and are preferably radially disposed on sides 
36 of cover 34. Cover openings 37 allow fluid to exit outlet port 16 from 
chamber 24. 
Sleeve 31 is aligned in registration with cover 34 such that cover 34 
guides reciprocation of piston 20 during initiation of fluid flow through 
valve 10. This reciprocation of piston 20 occurs only until the desired 
differential pressure set by springs 30 is established, after which piston 
20, and sleeve 31 thereof, remain substantially motionless regardless of 
the occurrence of upstream fluid pressure fluctuations. If there is a 
pressure change across the valve (i.e., P.sub.1 -P.sub.3), then there is a 
small movement of the piston 20 to rebalance the pressure differential 
(P.sub.1 -P.sub.2) which is set by the springs 30. However, flow does not 
change even though sleeve 31 alters its sheathing of cover openings 37. 
The valve 10 has to take the full pressure drop across it (P.sub.1 
-P.sub.3). The springs 30 set the differential pressure across the 
variable ring means discussed below (P.sub.1 -P.sub.2). The rest of the 
pressure drop must be taken by the sleeve 31 and cover 34. If the pressure 
P.sub.1 increases, the sleeve 31 and cover 34 must take the additional 
pressure drop across the valve 10 since the pressure differential across 
the variable ring means has not changed. By definition, if the sleeve 31 
and cover 34 are to take this higher pressure drop, the flow area through 
openings 37 must have decreased if the flow rate has not changed. As 
piston 20 reciprocates in bore 18 when fluid flow through valve 10 is 
initially being established, sleeve 31 variably sheaths cover 34 thereby 
varying the effective fluid flow area through cover openings 37 to achieve 
the desired pressure differential across the piston. While sleeve 31 has 
been described as tubular and cover 34 as cylindrical, these two 
components may have any shape as long as sleeve 31 variably sheaths cover 
34 to alter the effective fluid flow area of cover openings 37. 
The constant flow rate controller valve 10 operates based on the following 
force balance equations. 
EQU P.sub.1 A.sub.1 =P.sub.2 A.sub.2 +KX 
Where 
P.sub.1 =pressure in chamber 22 
A.sub.1 =surface area of piston head 21 in chamber 22 
P.sub.2 =pressure in chamber 24 
KX=spring force of springs 30 
A.sub.2 =effective surface area of piston head 21 in chamber 24 
It is important to note that, unlike prior art valves, the area (A.sub.3) 
of outlet port 16 and the outlet pressure (P.sub.3) thereof are not part 
of the force balance equation of the present invention because cover 34 
over outlet port 16 transfers the force defined by 
(P.sub.3).multidot.(A.sub.3) to body 12 of valve 10, and not to piston 20, 
as in prior art valves. 
Since A.sub.1 =A.sub.2, rearrangement of terms produces the following 
equations: 
EQU P.sub.1 A.sub.1 -P.sub.2 A.sub.1 =KX 
EQU (P.sub.1 -P.sub.2)A.sub.1 =KX 
##EQU4## 
The flow rate of water, for example, through the constant flow rate 
controller valve 10 is defined by the following equation: 
##EQU5## 
Where .DELTA.P=P.sub.1 -P.sub.2 
Q=flow rate 
P.sub.1 =pressure in chamber 22 
P.sub.2 =pressure in chamber 24 
C.sub.v =flow resistance 
Sg=Specific gravity of fluid 
Note that because differential pressures (P.sub.1 -P.sub.2) is a function 
of spring force (KX), flow rate (Q) is also a function of spring force. 
Thus, the constant flow rate controller valve 10 has a constant flow as 
long as (P.sub.1 -P.sub.2) across the variable ring means remains 
constant. This flow is constant regardless of the flow pressure at inlet 
port 14 and outlet port 16. 
The constant flow rate controller valve 10 operates as follows. Fluid 
passes through inlet port 14, around piston 20, and enters chamber 22. 
Piston 20, which is biased by springs 30 towards chamber 22, is pushed 
toward chamber 24 by the increased pressure in chamber 22, such that 
sleeve 31 blocks outlet cover openings 37, preventing fluid flow to outlet 
port 16. Chamber 24 is thus sealed. 
Fluid flows into chamber 24 through sleeve openings 33 of piston sleeve 31 
such that pressure P.sub.2 is ultimately achieved on the bottom position 
of piston 20 in chamber 24. When the flow pressure forces in chamber 24 
plus the spring force (KX) of spring 30 exceeds forces caused by the 
pressure in chamber 22, piston 20 is pushed towards chamber 22, piston 
sleeve 31 is lifted from at least a portion of outlet cover 34 such that 
at least a partial fluid pathway through cover openings 37 to outlet port 
16 is opened. A piston equilibrium position is next attained when the 
forces on piston 20 in chamber 22 equals the forces on piston 20 (which 
includes the spring force on spring 30) in chamber 24. 
The above piston equilibrium position also provides the desired pressure 
differential across the variable ring means, the desired flow rate being 
set by the variable ring means, which alters the flow resistance C.sub.v. 
Without further substantial change in the position of piston 20, the flow 
rate will remain constant despite pressure changes across the valve 
because the spring force of springs 30 maintains a constant pressure 
differential between chamber 22 and chamber 24 and reference pressure 
fluid passage 26. Thus, piston 20 moves substantially during initiation of 
fluid flow through valve 10 or when the variable ring means is altered. 
However, when there is a pressure change across the valve 10, piston 20 
will only move minutely to set the pressure differential (P.sub.1 
-P.sub.2) across piston 20 which, in turn, sets the flow rate; but this 
movement of piston 20 does not directly change the flow through valve 10. 
The various exemplary embodiments of the variable ring means for fluid flow 
rate control are next described. Referring to FIGS. 1-2, a ring-shaped 
inflatable bladder 38 is circumferentially disposed in recess 39 around 
the outer walls of piston 20 (FIG. 1), or the inner walls of body 12 (FIG. 
2). Inflatable bladder 38 is preferably comprised of a resilient natural 
or synthetic polymer such as, for example, SBR rubber, polychloroprene, 
EPDM, or neoprene. Fluid line 40 connects inflatable bladder 38 to fluid 
source 44. Fluid source 44 provides pressurized fluid, such as, for 
example, air, oxygen, or water, to inflatable bladder 38. The increased 
pressure within inflatable bladder 38 results in expansion of inflatable 
bladder 38. Inflatable bladder 38 can only expand in one direction, i.e. 
into the flow path between the inner walls of body 12 and the outer walls 
of piston 20 because inflatable bladder 38 is fitted with the aforesaid 
recess 39. As the circumference of inflatable bladder 38 is increased or 
decreased based on the pressure in inflatable bladder 38, as regulated by 
fluid source 44, fluid flow through the orifice 26 or between the inner 
walls of body 12 and the outer walls of piston 20 is varied. 
Now referring to FIGS. 3, 4, 5, 6 and 7, elastomer ring 46 is 
circumferentially disposed in a recess 48 around the inner walls of body 
12 (FIGS. 1, 3, 5 and 6) or the outer walls of piston 20 (FIGS. 4 and 7). 
Elastomer ring 46 is preferably comprised of SBR rubber, polychloroprene, 
EPDM, or neoprene. Elastomer ring 46 is thus a compressible elastic 
material. Elastomer ring 46 is compressed in width in ways described in 
further detail below such that the circumference of elastomer ring 46 
increases. Elastomer ring 46 can only increase circumferentially into the 
flow path between the inner walls of body 12 and the outer walls of piston 
20 because elastomer ring 46 is fitted in recess 48. As the circumference 
of elastomer ring 46 is either increased or decreased as the width of 
elastomer ring 46 conversely decrease or increases, fluid flow through 
orifice 26 or between the inner walls of body 12 and the outer walls of 
piston 20 is varied. 
In FIGS. 3 and 4, the width of elastomer ring 46 is compressed to increase 
the circumference thereof by means of compression member 50. Compression 
member 50 is pressed onto the external surface of elastomer ring 46 to 
compress the width of elastomer ring 46. A fluid reservoir 52 adjacent 
compression member 50 communicates via fluid line 54 with fluid source 56. 
Fluid source 56 contains pressurized fluid such as air, oxygen or water. 
As pressurized fluid from pressure source 56 increases the fluid pressure 
within fluid reservoir 52, compressor member 50, which is movable relative 
to piston 20 or body 12, is forced to press onto elastomer ring 46, thus 
compressing the width and increasing the circumference of elastomer ring 
46 (compressor member 50 may be an annular member). 
Referring now to FIG. 5, elastomer ring 46 can be compressed in width to 
increase its circumference by means of relative movement of top portion 60 
of body 12 with respect to bottom portion 62 of body 12. Top portion 60 
and bottom portion 62 are threadedly engaged by threads 64 such that the 
relative longitudinal dimension of body 12 can be varied. The longitudinal 
dimension of body 12 is decreased as top portion 60 is screwed into bottom 
portion 62, and the width of elastomer ring 46 is decreased and the 
circumference is increased to alter fluid flow as top portion 60 presses 
onto the exterior surface of elastomer ring 46. 
Now referring to FIGS. 6 and 7, elastomer ring 46 can be compressed in 
width to increase its circumference by means of fluid pistons 66. Fluid 
pistons 66 press compression plate 50 against the exterior surface of 
elastomer ring 46 to compress elastomer ring 46 against the walls forming 
recess 48. One of fluid pistons 66 is connected via fluid line 70 to fluid 
source 72, which contains pressurized fluid such as air, oxygen or water. 
The remaining fluid pistons 6 are connected to fluid line 70 by manifold 
74. One of fluid pistons 66 is connected via fluid line 70 to fluid source 
72, which contains pressurized fluid such as air, oxygen or water. The 
remaining fluid pistons 66 are connected to fluid line 70 by manifold 74. 
Now referring to FIGS. 8 through 16 circumferentially alterable ring 76 is 
employed to vary fluid flow through the flow path between the inner walls 
of body 12 and the outer walls of piston 20. Ring 76 is preferably 
substantially rigid, but can be circumferentially varied. Ring 76 is 
preferably comprised of a metal alloy such as stainless steel, steel, or 
brass; or a polymer such as rubber, EPDM, or polychloroprene that returns 
to its original configuration after being circumferentially altered. Ring 
76 can be an uninterrupted ring, or may be a split ring as shown in FIG. 
9. When split, one end of ring 76 can be secured to body 12 or piston 20, 
or both ends may be free. The circumference of ring 76 is varied in the 
manners described below. 
Referring specifically to FIGS. 8 and 9, ring 76 is located in recess 78 of 
body 12. Fluid pistons 80 are also located in recess 78. Fluid pistons 80 
are radially disposed around, and contact, the outer circumference of ring 
76 to force ring 76 toward the outer wall of piston 20 to alter fluid 
flow. One of fluid pistons 80 is connected via fluid line 82 to fluid 
source 84, which contains pressurized fluid such as air, oxygen or water. 
The remaining fluid pistons 80 are connected to fluid line 82 by manifold 
86. 
Referring to FIGS. 10 through 12, fluid pistons 88 and ring 76 are located 
on top of piston 20. As shown in FIGS. 10 and 11, fluid pistons 88 can be 
radially disposed within and contacting the inner circumference of ring 76 
to force ring 76 toward the inner wall of body 12 to alter fluid flow. 
Pistons 88 are connected to manifold 90 which, in turn, communicates with 
fluid line 92. Fluid line 92 is connected to fluid source 94, which 
contains pressurized fluid such as air, oxygen or water. 
Alternatively, as shown in FIG. 12, a single piston 96, attached to the two 
split ends 98 and 100, of ring 76 can be employed to alter the 
circumference of ring 76 to vary fluid flow. Piston 96 is connected to 
fluid line 102 which, in turn communicates with fluid source 104. Fluid 
source 104 contains pressurized fluid such as air, oxygen or water. 
Referring to FIGS. 13 and 14, ring 76 is located in recess 116 of body 12. 
Ring 76 is a split ring having end 118 fixedly secured to body 12 by, for 
example, bolt 120. Flange 124 is pivotally attached to one of shaft 122 
and ring 76, and is fixedly connected to the other of shaft 122 and ring 
76. Shaft 122 is threadedly connected to nut 126. As shaft 122 is rotated 
by turning handle 126, the threaded connection between shaft 122 and nut 
126 moves shaft 122 relative to nut 126. This movement of shaft 122 moves 
end 118 of ring 76 due to the connection of flange 124 to ring 76 and to 
shaft 122, thus altering the circumference of ring 76 to vary the fluid 
flow between the inner walls of body 12 and the outer walls of piston 20. 
Referring to FIGS. 15 and 16, ring 76 is located on top of piston 20. Ring 
76 is a split ring having end 130 fixedly secured to piston 20 by, for 
example, bolt 132. Flanges 134 and 138 are located on ends 130 and 136, 
respectively, of ring 76. Flexible shaft 140 threadedly passes through 
flanges 134 and 138. As shaft 140 is rotated by turning handle 142, the 
threaded connection between shaft 140 and flanges 134 and 138 moves free 
end 136 of ring 76 relative to fixed end 130 of ring 76, thus altering the 
circumference of ring 76 to vary the fluid flow between the inner walls of 
body 12 and the outer walls of piston 20. 
While particular embodiments of the present invention have been described 
in some detail herein above, changes and modifications may be made in the 
illustrated embodiments without departing from the spirit of the 
invention.