Note: Descriptions are shown in the official language in which they were submitted.
CA 02400949 2002-09-13
PCT/V8 20/06848
IPli40 15 OCT 2001
15-535
FLUID TREATMENT SYSTEM
Technical Field
The present invention relates generally to fluid
treatment systems and, in particular, to a storage tank
and storage tank control valve for use with a fluid
treatment system, such as a reverse osmosis system.
Background Art
It is known to use a storage tank to store a
processed fluid produced by a fluid treatment system.
For example, reverse osmosis systems are used to produce
potable or drinking water from water sources that contain
undesirable contaminants, etc. In a typical reverse
osmosis system, especially in the type of reverse osmosis
system used in homes, the rate at which treated water or
"permeate" is produced by the system can be very low. As
a result, a storage tank is used to store permeate, so
that relatively large quantities can be made available
when the consumer opens the tap or faucet. In the past,
"precharged" storage tanks are used. In this type of
storage tank, a bladder is used to define a pressurized
chamber, usually filled with a compressible gas, such as
nitrogen. The bladder isolates the gas from the
processed water received by the tank. As processed water
or "permeate" (in the case of a reverse osmosis system)
is received by the tank, it gradually compresses the gas
in the pressurized chamber. As a result, the permeate is
stored under pressure, such that when the faucet is
opened, the pressure in the storage tank exerted by the
compressed gas, forces permeate out of the tank and to
the faucet.
AMENDED SHEET
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Although these storage tanks are widely used and
provide a suitable means for storing permeate, they do
have a significant drawback. As more and more permeate
is received by the tank, the pressure needed to effect
flow of permeate into the tank increases because as the
gas chamber is compressed, forces on the bladder
increase. Accordingly, in order to completely fill the
storage tank, a significant pressure must be applied to
the permeate as the capacity of the tank is reached.
This resistance to flow exerted by the tank in itself
decreases production rate of the reverse osmosis system,
since the reverse osmosis system relies on differential
pressures between the source and the output to effect
flow across the membrane. In addition, as permeate is
discharged by the tank, its delivery pressure is
gradually reduced as the pressurized gas chamber expands.
As a result, the delivery pressure varies significantly
between a full tank and a nearly empty tank.
Disclosure of Invention
The present invention provides a new and improved
fluid treatment system that includes a storage system for
storing processed fluid such as water. The storage
system receives the processed fluid at substantially zero
pressure and discharges the stored fluid at a pressure
that is substantially the pressure of the source of fluid
being treated.
In the preferred and illustrated embodiment, the
invention is disclosed in connection with a reverse
osmosis unit. It should be understood, however, that the
invention has'broader applicability and should not be
limited to a reverse osmosis application.
In accordance with the invention, a storage system
is disclosed for storing treated or processed water
discharged by a water treatment unit. The storage system
includes a tank assembly having an outer tank housing
that encloses an expandable bladder. A pressurizing
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region is defined between an outside of the bladder and
an inside of the outer tank housing. A control valve is
disclosed that controls the communication of source water
under pressure with the pressurizing region and also
controls the communication of the pressurizing region
with a drain, so that under predetermined operating
conditions, source water in the pressurizing region is
allowed to flow'to a drain in order to allow the bladder
to expand as it receives treated water.
In the illustrated embodiment, the control valve
includes a fluid pressure operated control device that is
responsive to a dispensing device through which the
treated water:is dispensed. In particular, the control
device is operative to connect the source water to the
pressurizing region when the dispensing device is
dispensing treated water and is operative to communicate
the pressurizing region with the drain when the
dispensing device is not dispensing water.
In the preferred embodiment, the control device
includes a pilot valve responsive to fluid pressure in a
supply conduit feeding the dispensing device and is
movable between at least two positions. A servo valve
also forms part of the control device and is responsive
to the positions of the pilot valve.
The pilot valve includes a source water port, a
common port and a drain port and further includes a
piston operated flow control member for controlling the
communication between the common port and the source port
and between the common port and the drain port.
Similarly, the servo valve includes a source water port,
a common port and a drain port, as well as a piston
operated flow control member for controlling the
communication of the common port with either the source
water port or the drain port. The ports of the servo
valve are sized to permit relatively unrestricted flow
and, hence, the servo valve controls the flow of source
water to the pressurizing region of the tank assembly,
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and the flow of source water from the pressurizing region
to the drain.
In a more preferred embodiment, the water treatment
unit disclosed is a reverse osmosis module having a
permeate output, a source water input and a concentrate
output. In the illustrated reverse osmosis system a
prefilter is positioned upstream of the reverse osmosis
module and filter source water before it enters the
reverse osmosis unit and the pressurizing region of the
tank. According to a further feature of this embodiment,
a post filter filters permeate before it is delivered to
the dispensing device, e.g., a faucet or tap.
According to a preferred embodiment, the control
valve assembly for controlling the pressurization and
depressurization of the pressurizing region of the tank
is mounted directly to the tank. In accordance with this
embodiment, the tank includes an internally threaded neck
which is adapted to receive external threads formed on
the control valve or housing. The control valve assembly
is threaded into the neck of the tank and is easily
removed for service or replacement.
According to another feature of the invention, a
lower portion of the control valve assembly includes a
depending, threaded segment which, in conjunction with a
internally threaded retaining nut serves as a securement
for the elastomeric bladder contained within the tank.
According to this preferred embodiment, the retaining nut
includes a radial flange which supports a bladder
retaining bearing. As the retaining nut is threaded onto
the lower segment of the valve, the bearing captures a
neck of the bladder between itself and a tapered segment
on the control valve, thus securing the bladder to the
control valvef. The bearing ring facilitates rotation of
the retaining nut when either installing or removing the
bladder.
Additional features of the invention will become
apparent and a fuller understanding obtained by reading
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the following detailed description made in conjunction
with the accompanying drawings.
Brief Description of Drawings
Figure 1 is a schematic representation of a reverse
osmosis system constructed in accordance with the
preferred embodiment of the invention, shown in a state
in which it is delivering treated water or permeate;
Figure 2 is another schematic representation of the
reverse osmosis system shown in a state in which it is
not delivering permeate;
Figure 3 is a top plan view of a control valve and
associated storage tank assembly constructed in
accordance with the preferred embodiment of the
invention;
Figure 4 is a sectional view of the control valve
and storage tank assembly as seen from the plan indicated
by the line 4-4 in Figure 3;
Figure 5 is an enlarged fragmentary view of a
portion of the control valve and tank assembly as
indicated by the detail line 5-5 in Figure 4;
Figure 6 is a sectional view of the control valve
and tank assembly as seen from a plane indicated by the
line 6-6 in Figure 3; and,
Figure 7 is an enlarged, fragmentary view of a
portion of the control valve and tank assembly as
indicated.by the detail line 7-7 in Figure 6.
i
Best Mode for Carrying Out the Invention
Figures 1 and 2 schematically illustrate a reverse
osmosis system for producing potable water and that
embodies the present invention. Figure 1 schematically
illustrates the operation of the system when processed
water is not being delivered, i.e., a tap or faucet is
closed; whereas Figure 2 illustrates the operation of the
system when processed water is being delivered to a tap
or faucet.
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The system is connected to a source of water to be
processed, indicated generally by the reference character
10. In the illustrated embodiment, the processed water
is delivered to a faucet indicated generally by the
reference charac.ter 12. The illustrated system includes
a conventional reverse osmosis (RO) unit 14. Those
skilled in the art will recognize that the RO unit 14
houses a reverse osmosis membrane (not shown) and
includes an inlet port indicated generally by the
reference character 16, through which the unit 14
receives water to be processed from the source 10. The
unit 14 also includes a"permeate" outlet port indicated
generally by the reference character 18 and a
"concentrate " output indicated generally by the
reference character 20 which communicates with a drain
22. The RO unit 14 may operate in a conventional manner.
As is known, water to be processed is communicated to
the inlet port 16 and is delivered to an internal chamber
(not shown) containing the reverse osmosis membrane,
Relatively pure water termed ''permeate'' is allowed to
pass or permeate through the membrane and is discharged
from the unit 14 by way of the permeate outlet port 18.
Contaminants and other material remain on the input or
concentrate side of the membrane and are ultimately
discharged through the concentrate output 20 and dumped
to the drain 22. A thorough explanation of the operation
of an RO unit that may be utilized with the present
invention can be found in U.S. Patent Nos. 4,629,568 and
4,650,586, which are owned by the assignee of the present
application.
The illustrated system also includes a prefilter 30
which filters large particle contaminants out of the
source water to inhibit plugging of the reverse osmosis
unit and a post filter 32 for performing a final
filtering or "polishing " of the treated water before
delivery to the faucet 12. The post filter 32 may be in
the form of a carbon filter to further improve the
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quality and taste of the processed water. The prefilter
30 and post filter 32 are considered conventional and do
not form part'of the present invention.
Permeate produced by the RO unit 14 is delivered to
the faucet 12'from a storage tank 40 under the control of
a control valve assembly indicated by the phantom line
44. As will be explained, the tank 40 and control valve
44 may form a single, integrated assembly.
The tank 40 includes a relatively rigid outer
housing 42 and an internal elastomeric bladder 50. The
bladder 50 is the component which actually stores
permeate and expands to accommodate permeate delivered to
the bladder via passage 52. As permeate is delivered to
the bladder 50, the bladder expands until it fully
conforms to an inside surface 42a of the tank at which
time the tank is considered full or at capacity.
Permeate;.in the bladder 50 is delivered to the
faucet 12 by pressurizing an outside surface 50a of the
bladder 50 with water at source pressure via passage or
line 54. To facilitate the explanation, the region
between the outside surface 50a of the bladder 50 and the
inside surface 42a of the tank shell 42 will be referred
to as a region 62. The pressurization and
depressurization of the region 62 is controlled by the
control valve assembly 44.
As seen schematically in Figures 1 and 2, the
control valve assembly 44 includes a pilot valve 70 and a
servo valve 72. As will be explained, the pilot valve 70
responds to the opening and closing of the faucet 12.
The servo valve 72 controls the pressurization and
depressurization of the region 62 and, in particular,
controls the communication of the source water to the
region 62 and the venting of the region 62 to the drain
22. The position or state of the servo valve 72 is
controlled by the pilot valve 70.
The pilot valve 70 includes a diaphragm/piston 76
and a isolated piston chamber 78. When the piston
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chamber 78 is;pressurized the piston 76 is driven
downwardly to the position shown in Figure 1. As will be
explained, the piston chamber is pressurized via a signal
passage 80 which pressurizes when the faucet is closed.
Referring also to Figure 2, the pilot valve 70 includes a
source water port 82, a common port 86 and a drain port
90. A spool-like element 94 defining a single land 94a
is connected to the piston 76 controls the communication
between the source port 82 and the drain port 90 with the
common port 86. The spool member 94 reciprocates within
a spool chamber 96. As seen in Figure 1, when the faucet
12 is closed,;the source water port 82 is communicated
with the common port 86.
The servo valve 72 is similar in operation to the
pilot valve 70. However, the servo valve is constructed
such that it can sustain much higher flow rates through
its ports. The servo valve 72 includes a diaphragm
supported piston 100 and an isolated, piston actuation
chamber 102. The servo valve 72 includes a piston
chamber port 106 which is connected via signal line or
passage 108 to the common port 86 of the pilot valve 70.
When the piston chamber 102 is pressurized, the piston
100 is driven upwardly (as viewed in Figure 1) to the
upper position shown in Figure 1. In the absence of
fluid pressure in the piston chamber 102, the piston 100
moves downwardly to the position shown in Figure 2 at
which point it abuts a stop 110.
The servo valve 72 includes a common port 112, a
drain port 114 and a source water port 116. The fluid
communication between these ports is controlled by a
spool element 120 having a single land 120a. The spool
element is connected to and is preferably integrally
formed with the piston 100. The land 120a reciprocated
within a spool chamber 122. the ports 112, 114 and 116
communicate with the spool chamber 122.
Referring first to Figure 1, when the servo valve
piston 100 (and hence the land 120a) is moved to its
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upper position as viewed in Figure 1, the common port 112
is communicated with the drain port 114 via the spool
chamber 122. In this position, water in the region 62 of
the tank 40 is allowed to proceed to the drain 22 via
tank line 54, which communicates with spool chamber 122
via the common port 112. The source water then flows out
of the spool chamber 122 through the drain port 114 and
is communicated to the drain 22 via a common drain line
130. Thus, as the bladder 50 expands to receive permeate
being produced by the RO unit 14 during water production,
any source water is driven out of region 62 and is
discharged to the drain 22. This allows the bladder 50
to expand completely to conform to the inside surface 42a
of the tank shell 42.
The piston 100 of the servo valve 72 is driven to
the upper position as viewed in Figure 1 by a signal
pressure received from the pilot valve 70. In
particular, when the faucet is closed the pilot valve
chamber 78 is,pressurized driving the piston 76
downwardly to the position shown in Figure 1. In this
position, source water is communicated to the spool
chamber 96 via the source water port 82. The water in
the spool chamber 96 is delivered to the servo valve
piston chamber 102 via the common port 86 of the pilot
valve 70 and the signal line 108. As explained above, in
this state, source water in the region 62 is vented to
the drain 22 and the permeate in the bladder 50 is at
substantially zero pressure. It should be noted that the
bladder 50 does exert some minimal pressure on the
permeate due to its resistance to expansion.
The inside of the bladder 50 is cominunicated with
the output port 18 of the RO unit 14 via the supply line
52. Since the pressure in the bladder 50 is
substantially;zero, the RO unit 14 begins producing
permeate and delivering that permeate to the bladder 50
via the supply line 52. As the bladder 50 expands,
source water in the region 62 is discharged to the drain
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22 via the circuit explained above.
Referring now to Figure 2, the operation of the
system when permeate is being dispensed from the faucet
12 is as follows. When the faucet 12 is opened, pressure
in the signal line 80 drops to substantially zero. The
absence of pressure in the pilot chamber 78 allows the
source water pressure communicated to the spool chamber
96 via source water line 136 and source port 82 to drive
the piston 76 to its upper position shown in Figure 2.
LO In this position, the pilot valve common port 86 is
communicated with the drain port 90. As a consequence,
fluid in the servo valve piston chamber 102 is allowed to
proceed to the common drain line 130 and, hence, the
drain 22 via signal line 108 and the spool chamber 96 of
L5 the pilot valve 70. As seen in Figure 2, when the land
94a is in its:upper position as viewed in Figure 2, the
spool chamber 96 cross communicates the common port 86
and the drain port 90.
The communication.of the servo valve piston chamber
~0 102 with the drain 22 causes the servo valve piston 100
to move downwardly (as viewed in Figure 2) due to the
application of source water pressure to an upper surface
121 (as viewed in Figure 2) of the land 120a of spool 120
via the source water line 136, branch line 136a and port
116. When the piston moves to its lower position (as
viewed in Figure 2) the source water port 116 of the
servo valve 72 is communicated with its common port 112.
This allows source water pressure to flow into the tank
region 62 via the source water line 138. The application
30 of source water pressure to the region 62 produces a
contraction force on the permeate bladder 50 driving
permeate from.the bladder to the open faucet 12 via the
permeate supply line 140 which communicates with the post
filter 32. The post filter 32 in turn communicates with
35 the faucet 12 via branch line 144. It should be noted
here that the supply line includes a check valve 148
which prevents reverse flow of the permeate in the line
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into the tank 40 and maintains pressurization of the line
140 when the faucet 12 is closed.
It should also be noted here that both the pilot
valve.70 and servo valve 72 are operated by differential
pressures applied to their associated pistons. Turning
first to the pilot valve 70, the effective pressure area
of the piston chamber side of the piston/diaphragm is
equal to the cross-sectional area of the piston chamber
78. The effebtive pressure area of the underside of the
diaphragm/piston (which is exposed to the fluid pressure
in the spool chamber 96) is equal to the cross-sectional
area of the piston chamber 96 minus the cross-sectional
area of the control element or spool member 94. Thus, if
source water pressure is applied to the spool chamber 96
of the pilot valve 70 via the source port 82 concurrently
with the application of permeate pressure as exerted by
source water pressure in the region 62, a net upwardly
directed force is applied to the piston/diaphragm 76 (as
viewed in Figure 2), which causes the piston to move
upwardly.
The same,relationship exists for the servo valve
piston/diaphragm so that when source water pressure is
applied to the servo valve piston chamber 102,
concurrently with source water pressure applied to the
end surface 121 of the control spool/land 120a via the
source water port 116 of the servo valve 72, a net
upwardly directed force is applied to the
piston/diaphragm 100 causing the piston to move to its
upper position shown in Figure 1.
With the present system, the overall delivery rate
and permeate production are substantially improved.
During permeate production, i.e., when the faucet 12 is
closed, the permeate reservoir (as provided by the
bladder 50) is at substantially zero pressure and, hence,
the RO unit 14 sees very little resistance to flow thus
maximizing flow through the RO unit 14. During delivery
of permeate through the faucet 12, substantially full
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supply pressure is applied to the bladder 50 and, hence,
permeate is delivered to the faucet 12 at substantially
source pressure minus pressure losses due to flow
restrictions due to lines and passages. As a
consequence, the flow rate of permeate from the faucet 12
is substantially constant since at all times supply
pressure is applied to the exterior surface of the
bladder 50 as compared to bladder tanks that utilize a
precharge which results in reduced pressure as permeate
in the tank is depleted.
Turning now to Figure 3-7, a control valve and tank
assembly constructed in accordance with the preferred
embodiment of the invention is illustrated. For purposes
of reference, the apparatus shown in Figures 3-7
generally corresponds to the items referenced as 44 and
40 in Figures 1 and 2. To facilitate the explanation,
like components in the apparatus shown in Figures 3-7
will be given the same reference characters used in
Figures 1 and 2 followed by an apostrophe.
Accordingly. the control valve/storage tank assembly
includes a control valve 44' which is threadedly received
by a tank 40'. As previously described, the tank 40'
includes a relatively rigid tank shell 42' having an
inside surface 42a'. In the illustrated embodiment the
tank is made from two tank halves that are joined by a
spin welding process, Details of this type of tank
construction can be found in U.S. Pat. No. 4,579,242 that
is owned by the present assignee. The bladder 50' is
disposed within the tank shell 42' and expands to receive
permeate and contract to expel permeate. The region 62'
located between the outside of a bladder 50' and the
inside 42a' of the tank 42' receives source water in
order to apply contracting forces on the bladder to expel
permeate, whenever the faucet 12 (shown in Figures i and
2) is opened.
Referring now to Figure 5, the components that
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comprise the control valve 44' (represented
schematically in Figures 1 and 2) are shown in an actual
control valve constuction. The valve housing 44a which
may be in assemblage of individual housing elements,
5, defines a plurality of ports (shown best in Figure 3).
In particular, the housing defines a tank outlet port
150, a source water feed port 152, a permeate or product
port 154, a drain port 156 and a signal port 158.
Referring to Figures 1 and 2, in an actual system the
above-identified ports would be connected as follows.
The tank port'150 would connect to the conduit 140. The
feed port 152 would connect to the conduit 136. The
permeate port 154 would connect to the permeate supply
port 18 of the RO unit 14 via conduit 52. The signal
port 158 would be connected to the conduit 80.
The housing 44a at least partially defines the pilot
valve 70'. Referring, in particular to Figure 5, the
housing 44a reciprocally mounts the diaphragm carried
pilot piston 76' in the piston chamber 78' at least
partially defined by the valve 44a. The piston chamber
78' communicates with the signal port 158. As explained
above the port 158 is connected to the signal line 80
(shown in Figures 1 and 2) which in turn, communicates
with the faucet feed line 144 (shown schematically in
Figure 1). In the actual embodiment, flexible conduit is
used to connect the port 158 with the faucet supply line
and/or the output port of the post filter 32 using a
suitable fitting.
The piston 76' is connected to a spool 94' including
a land 94a'; the land 94a' sealingly engages the inside
of the spool chamber 96'. An 0-ring 159 effects a seal
between the land 94a' and the spool chamber 96' while
permitting reciprocating movement in the land 94a'. As
described in aonnection with Figures 1 and 2, the land
94a controls the communication of a common port 86'
(shown in phantom) with either the source water port 82'
or the drain port 90'. In the actual valve construction,
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the ports 82' and 90' may be formed by wall openings
defined in the body of the valve, rather than precisely
defined ports. This is the construction shown in Figure
5.
5> The servo valve 72' (the position of which is
controlled by"the pilot valve 70) is located immediately
adjacent the pilot valve 70'. It includes a diaphragm
supported piston 100' that at least partially defines a
piston chamber 102'. A stop 110' determines the
lowermost position of the piston 100'. As explained
above, the piston is connected to a spool 120' which
carries a land 120a' that is slidably movable within a
spool chamber 122'. An 0-ring 161 is mounted to the
land 120a'and sealingly engages the inside of the spool
chamber 122'. The spool 120a' controls the
communication of the common port 112' with the a drain
port 114' and the source water port 116'. As explained
above, the ports themselves may be defined by openings
formed in the valve body/housing, rather than precisely
defined ports.
As seen in Figure 5, the piston chamber 102' is at
least partly formed by a bottom cap 160 that is secured
to the rest of the valve body by a plurality of threaded
fasteners 162 (only one is shown). The interface between
the cap and the rest of the valve body is sealed by an 0-
ring 164.
As seen best in Figure 5, source water from the
source water port 152 is delivered to the spool chamber
122' by the passage 136' which is connected to the spool
chamber by a branch passage 136a'. When the servo piston
100' is moved'to its lowest position as viewed in Figure
2, source water is communicated from the port 116' to the
common port 112' (via the spool chamber 122'). The
common port 112' delivers the source water to a cavity
170 formed in the control valve that communicates with
the region 62' via passage 170a.
When the piston 100' moves to its upper position,
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the common port 112' communicates with the drain port
114' which, as seen in Figure 5, communicates directly
with the drain port 90' of the pilot valve 70'. A
passage (not shown) communicates these drain ports with
5: the drain 22 (see figure 1) via the control valve drain
port 156 which is connected to an actual drain via a
suitable conduit.
When the servo valve piston 1001 is in its upper
position (shown in Figure 1), the region 62' is
communicated with the drain 22 (Figure 1) and, hence,
permeate produced by the RO unit 14 (shown in Figure 1)
enters the bladder 50' gradually expanding the bladder.
The actual passage 52 that is shown schematically in
Figure 1, is suitably molded within the valve housing.
When permeate is being delivered to the faucet 12
(shown in Figure 1) the region 62' is pressurized upon
movement of the servo valve piston 100' to its lower
position at which point the common port 112' communicates
with the source water port 116'. In this position of the
piston 100' source water under source pressure to is
delivered to the region 62' tending to contract the
bladder 50' thus, driving permeate from the bladder.
As seen best in Figure 7, permeate is delivered
through a passage 180 formed in the body of the control
valve which communicates with a check valve 148'. The
check valve 148' in turn communicates with the discharge
or tank port 150 formed in the valve housing. The
discharge/tank port 150 is connected to the post filter
32 by a conduit (not shown) represented by the line 52 in
Figures 1 and 2.
Referring to both Figures 4 and 5, the control valve
44' is threadedly mounted to the top of the tank 40'. In
particular, the tank 40' includes a neck 200 having an
internal thread 200a. A complementary thread 204 is
formed on the outside of the valve body and is threadedly
engageable with the neck 200 of the tank 40'. An 0-ring
208 seals the interface between the tank 40' and the
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control valve 44', but allows the control valve 44' to be
removed from the tank 40' for replacement and/or service.
As seen best in Figure 5, the bottom portion of the
control valve 44' includes a depending, threaded portion
5, indicated generally by the reference character 220. The
threaded portion provides a releasable securement for the
bladder 50'. In particular, a threaded collar or
retaining nut 222, is threadedly received by the lower
portion 220 of the control valve 44'. The retainer 222
includes an inwardly directed flange portion 222a, which
supports a bladder retaining bearing 226; the bearing 226
facilitates rotation of the retaining nut 222 and
simplifies installation of the bladder 50'. The bladder
50' includes a neck portion 51 that is captured between
the bladder retaining bearing 226 and a tapered or cone-
shaped segment 228 defined on the lower portion 220 of
the control valve 44'. When the collar 222 is threaded
onto the control valve portion 220, the bearing 226 is
urged into sealing contact with the neck 51 of the
bladder 50' and secures the bladder to the cone-shaped
portion 228 of the control valve 44'.
With the disclosed storage system, permeate is
delivered at a substantially constant pressure to the tap
and, as a result, maximum flow rates to the tap are
maintained regardless of the amount of permeate in the
tank. In addition, because the pressurizing region 62 is
substantially zero when permeate is being produced by the
reverse osmosis system, the production rate of the RO
unit is maximized since it does not see increased
resistance as the storage tank fills, as is the case with
precharged storage tanks.
Although the invention has been described with a
certain degree of particularity, it should be understood
that various changes can be made to those skilled in the
art without departing from the spirit or scope of the
invention as hereinafter claimed.
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