Control valve for a reverse osmosis water purification system

An improved control valve for a reverse osmosis (RO) water purification system for supplying relatively pure water for on-demand dispensing, wherein the improved control valve positively terminates pure water production and brine outflow to a waste or drain when a pure water reservoir reaches a substantially filled condition. The control valve responds to a predetermined pressure differential between a tap or feed water inflow and produced pure water to close a pure water outflow line when the pure water reservoir reaches a substantially filled condition, thereby positively preventing further production of pure water. Shortly thereafter, the control valve closes a brine outflow line thereby positively preventing further water flow through the system until at least a predetermined volume of the reservoir-stored pure water is dispensed. When this occurs, the control valve re-opens in sequence the brine outflow and the pure water outflow lines.

BACKGROUND OF THE INVENTION

This invention relates generally to improvements in water purification systems of the type having a reverse osmosis (RO) unit or the like for removing dissolved ionic material and other contaminants from an ordinary supply of tap water or the like. More particularly, this invention relates to an improved control valve for a reverse osmosis water purification system, the control valve for positively and preferably sequentially terminating pure water production and brine outflow to a waste or drain when a pure water reservoir reaches a substantially filled condition.

Water purification systems in general are well-known in the art of the type having a reverse osmosis (RO) unit or membrane for converting an incoming supply of ordinary tap or feed water into relatively purified water for use in cooking, drinking, etc. In general terms, the reverse osmosis unit comprises a semi-permeable RO membrane through which a portion of the tap water supply is passed, such that the membrane acts essentially as an osmotic filter to remove dissolved metallic ions and the like as well as other contaminants and undesired particulate matter from the tap water. In normal operation, these impurities are removed from one portion of the water flow to produce relatively pure water, with the removed impurities being concentrated in another portion of the water flow, commonly referred to as retentate or brine, which is normally discharged as waste to a drain. The thus-produced flow of relatively purified water is available for immediate dispensing for use, and/or for temporary storage within a suitable reservoir or vessel awaiting dispensing for use. A pure water dispense faucet mounted typically on or adjacent to a kitchen-type sink or the like is manually operable to dispense the produced purified water. While the specific construction and operation of such RO water purification systems may vary, such systems are exemplified by those shown and described in U.S. Pat. Nos. 4,585,554; 4,595,497; 4,657,674; and 5,045,197.

Reverse osmosis water purification systems of this general type rely upon a minimum pressure differential across the RO membrane to produce purified water. In this regard, this pressure differential is relatively maximized when a pure water storage reservoir is substantially empty, but progressively decreases as the pure water storage reservoir fills. Decreased pressure differential across the RO membrane has inherently resulted in a decreased volume of produced purified water. When the pure water storage reservoir reaches a substantially filled condition, prior art systems have generally functioned to turn the system “off” by closing or attempting to close a tap or feed water inflow valve, to halt system water flow-through and thereby minimize associated water waste in this “off” condition. Alternative proposals have envisioned a retentate or brine flow shut-off valve to halt system water flow-through while the system is “off”. However, these approaches undesirably leave unflushed concentrated contaminants at an upstream side of the RO membrane, whereat these contaminants can migrate through the RO membrane to the pure water side while the system is in the “off” condition. Accordingly, desirable minimization of waste water has been accompanied by undesirable potential contamination of the produced pure water.

There exists, therefore, a significant need for further improvements in and to reverse osmosis water purification systems, and particularly with respect to an improved control valve wherein water waste is substantially eliminated when a pure water reservoir reaches a substantially filled condition, but wherein such reduced water waste is not accompanied by any significant contamination of the already-produced pure water. The present invention fulfills these needs and provides further related advantages.

SUMMARY OF THE INVENTION

In accordance with the invention, a reverse osmosis (RO) water purification system is provided for supplying relatively pure water for on-demand dispensing. The RO system includes an improved control valve for positively terminating pure water production and brine outflow to a waste or drain, preferably sequentially, when a pure water storage reservoir reaches a substantially filled condition. By terminating pure water production before terminating brine or retentate outflow to a drain, the control valve permits a water flush flow across an upstream side of an RO membrane to flush accumulated contaminants to the drain. Thereafter, in response to pure water dispensing, the control valve resumes pure water production and brine outflow.

The control valve for the reverse osmosis water purification system comprises a multi-part valve housing having first and second ends. A pure water chamber is disposed at the first end of the valve housing and a brine water chamber is disposed at the second end. The pure water chamber has a pure water inflow port, a pure water outflow port and a pure water valve head slidably disposed therein. The brine water chamber has a brine water inflow port, a brine water outflow port and a brine water valve head slidably disposed therein, and is also coupled to a feed water source.

A central cavity is disposed between the pure water chamber and the brine water chamber. The central cavity is exposed to atmospheric pressure while being hermetically sealed from the pure water chamber by a first resilient diaphragm and from the brine water chamber by a second resilient diaphragm. A frame is disposed in the central cavity and operatively connected to the pure water valve head through the first resilient diaphragm and the brine water valve head through the second resilient diaphragm. The frame, pure water valve head and brine water valve head are slidable as a single structure within the valve housing between an open position and a closed position.

The pure water valve head and the brine water valve head may comprise a magnetically attractable material, such as stainless steel. Preferably, the frame carries a pair of magnets to operatively connect the frame to the pure water valve head and the brine water valve head.

Being operatively connected to the frame, the pure water valve head and the brine water valve head are slidable in response to a pressure differential between a back pressure from the pure water outflow port exerted on the first resilient diaphragm and a head pressure from the feed water source exerted on the second resilient diaphragm. Preferably, the first and second resilient diaphragms have relative surface areas configured to slide the pure water valve head and the brine water valve head from the open position to the closed position when the ratio of the back pressure from the pure water outflow port to the head pressure from the feed water source is greater than or equal to 2:3.

The brine water chamber includes an elongated brine valve stem operatively connected to the brine water valve head at a first end and proximate to a brine shut-off valve seat at an opposite second end. When the pure water valve head engages a pure water shut-off valve seat in the closed position, the elongated brine valve stem engages the brine shut-off valve seat when in the closed position. The elongated brine valve stem and the brine shut-off valve seat are configured to engage in the closed position a predetermined time period after the pure water valve head engages the pure water shut-off valve seat in the closed position. This predetermined time period is preferably one to three minutes.

A brine poppet valve is disposed between the brine water inflow port and the brine water chamber. The brine poppet valve has a poppet head biased against a poppet seat by fluid pressure from a brine water inflow and includes a shallow groove. The shallow groove defines a fixed flow orifice through the brine poppet valve when the poppet head is biased against the poppet seat. The brine poppet valve is spring biased away from the poppet seat when the brine water valve head is in the closed position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in the exemplary drawings, an improved reverse osmosis (RO) water purification system referred to generally inFIG. 1by the reference numeral10includes a reverse osmosis (RO) unit or cartridge12having a reverse osmosis (RO) membrane14illustrated schematically therein for separating a tap or feed water inflow via an inflow conduit16into relatively purified water18available for on-demand dispensing, and a so-called retentate or brine flow at a brine outlet port20having contaminants and impurities substantially concentrated therein. In accordance with the invention, the system10includes an improved control valve22for positively and preferably sequentially terminating pure water production and brine outflow to a waste or drain when a pure water storage reservoir24reaches a substantially filled condition. By terminating pure water production before terminating brine or retentate outflow to a drain26, the control valve22permits a water flush flow across an upstream side of an RO membrane14to flush accumulated contaminants to the drain26.

The illustrative reverse osmosis water purification system10is designed to provide a ready supply of substantially purified water18for drinking and cooking purposes, etc. The system10is generally designed for residential or household use, or for use in a commercial facility particularly such as an office or the like, installed typically within the compact cabinet space located beneath a kitchen-type sink (not shown) or the like, with a pure water dispense faucet28normally mounted on a countertop30on or adjacent the sink for on-demand pure water dispensing.

In general terms, tap or feed water flows via the inflow conduit16to the RO unit12. During normal pure water production this tap water inflow is separated by the RO membrane14into the relatively purified water18having contaminants substantially removed therefrom which flows outwardly from the RO unit12via a pure outflow port27through a pure water outflow conduit32, and the brine or retentate flow20having contaminants substantially concentrated therein which flows from the RO unit12via a brine outflow conduit34. The pure and brine outflow conduits32,34are both coupled in-line with the improved control valve22which, during normal pure water production, regulates pure water flow to the pure water storage reservoir24and/or to a dispense conduit36leading to the countertop-mounted dispense faucet28. As shown inFIG. 1, this storage reservoir24typically includes a dual-chamber canister or housing38having a resilient bladder40separating an upper air-filled chamber42from a lower chamber having the produced purified water18therein. The control valve22additionally regulates flow of the brine or retentate20to the drain26.

In normal operation, produced purified water18is available for on-demand dispensing by means of the faucet28, while produced brine or retentate is discharged to the waste or drain26. In accordance with the invention, the improved control valve22responds to a predetermined pressure differential between the tap water inflow and the produced purified water stored within the reservoir24to positively terminate pure water production when the storage reservoir24reaches a substantially filled condition. Thus, the control valve22positively terminates further production of pure water, unless and until some of the pure water is dispensed from the storage reservoir24. The control valve22also closes in a preferably sequential manner, with a time delay after terminating pure water production, the brine outflow to the drain26. In a preferred form, this time delay can be several minutes in duration, i.e., between one and three minutes. Accordingly, during the time delay after pure water production is halted, any accumulated contaminants present at an upstream side of the RO membrane14are flushed through the brine outflow conduit34to the drain26, followed by positive closure of the brine outflow conduit34to terminate further water flow through the RO system10.

Thereafter, when a sufficient quantity of produced purified water18has been dispensed from the storage reservoir24, the control valve22re-opens the pure water and brine outflow conduits32,34for resumed pure water production. In accordance with one aspect of the invention, re-opening of the brine outflow conduit34includes initial flushing of a flow restrictor or orifice119(shown best inFIG. 4) disposed in-line with the brine outflow conduit34, thereby preventing accumulation of contaminants and/or particulate at or within said orifice.

The improved control valve22is shown in more detail inFIGS. 2-7. As shown, the control valve22generally comprises a multi-part valve housing44including multiple stacked components normally held in assembled relation by means of a plurality of screws46or the like. A ported cap48is mounted at a lower end of the assembled valve housing44to support a porous inlet filter element50which is retained therein by a lower end plate52. This lower end plate52defines a pure water inflow port54for suitable coupling in-line with the pure water outflow conduit32from the RO unit12. Accordingly, the produced purified water18flowing through the conduit32is inputted via the inflow port54and further through an annular array of inflow ports56into a lower region within the valve housing44.

The produced purified water18within the lower control valve chamber56is applied against a lower face58of a pure water shut-off valve head60, which comprises a lower component of an elongated and linearly moveable valve structure contained within the valve housing44. More particularly, the pure shut-off valve head60is vertically reciprocal or slidably received within a cylindrical sleeve62for movement between a normal open position (FIGS. 2-3) with an annular seal member64thereon displaced downwardly into a radially enlarged lower cavity66defined by the sleeve62, and a closed position (FIG. 5) with the seal member64retracted upwardly into sealing relation with a smaller-diameter bore68defined by the sleeve62. Importantly, when the pure shut-off valve head60is in the open position, the pure water within the lower chamber56may flow upwardly through an annular space defined by the sleeve bore68and a smaller-diameter upper zone70of the valve head60, into an upper pure water chamber72defined at the underside of a lower resilient diaphragm74. From this upper pure water chamber72, when the pure shut-off valve60is in the open position (FIG. 2), the produced purified water18may flow further from the valve housing44via a suitable outlet port (not shown) for passage to the storage reservoir24(as viewed inFIG. 1), or alternately for passage to and dispensing from the faucet28.

The resilient diaphragm74separates the upper pure water chamber72from a central cavity78coupled via a vent80or the like to atmospheric pressure. An upper side of the central cavity78is closed by a comparatively smaller area upper or second resilient diaphragm81having an upper surface exposed to an upper chamber82coupled via a suitable port84(FIG. 1) and associated conduit86(also depicted inFIG. 1) to the tap or feed water. A pair of vertically separated magnets88,90are carried on a frame92within the central cavity78, and are attached magnetically and in a hermetically sealed manner respectively to the underlying pure water shut-off valve head60and to an overlying brine shut-off valve head94. In this regard, the pure water shut-off valve head60and the brine shut-off valve head94are preferably constructed from a magnetically attractable material, such as a magnetically attractable stainless steel.

With this construction, the linearly movable valve structure within the control valve22, including the pure water shut-off valve head60, is movably displaced according to the pressure differential between the tap water inflow pressure in the upper chamber82and the pressure of the produced purified water18at the lower chamber56. By selecting the relative areas of the lower and upper resilient diaphragms74,81, the pure water shut-off valve head60can be controlled to remain open unless and until the storage reservoir24reaches a substantially filled condition. That is, with the air-filled reservoir chamber42(FIG. 1), the back-pressure applied by means of the storage reservoir24increases progressively as the volume of the stored produced purified water within the reservoir increases. In one preferred embodiment of the invention, the relative areas of the diaphragms74,81are selected to shift the pure water shut-off valve head60from the open position to the closed position when the pressure differential of pure/tap water reaches a ratio of about 2/3. In a typical operating environment with a tap water inflow pressure of about 60 psi, this would result in movement of the pure water shut-off valve head60to the closed position when the pressure within the storage reservoir24reaches about 40 psi.

With the pure water shut-off valve head60in the normal open position for pure water production, the two diaphragms74,81are shifted slightly downwardly (as shown inFIGS. 2-3) to draw down on the brine shut-off valve head94. As shown, this brine valve head94carries a lower end of an elongated brine valve stem pin96which projects upwardly through a pair of vertically spaced seal bushings98and an elongated guide99to terminate in operative relation with a brine valve seat100lined by a O-ring seal member102or the like. In the open position as described, the upper tip or free end of this stem pin96is spaced a short distance below the associated valve seat100and the associated upper seal bushing98to permit brine flow passage therethrough. This permits the brine or retentate flow20from the RO unit12to pass through a brine inflow passage104(FIGS. 3 and 6) in the valve housing44and downwardly through the open valve seat100before exiting via a brine outflow passage106(FIGS. 2 and 5) for flow further through the brine conduit34to the drain26(FIG. 1).

A brine poppet valve108is mounted within the control valve housing44at an upper end thereof, and comprises a poppet head110having a face of generally conical cross sectional shape, with said head110being carried by an upwardly projecting poppet stem112. This poppet stem112is slidably carried within a track114defined by a threaded plug116mounted at an upper end of the control valve housing44. The poppet head110defines a relatively larger upper area and a smaller tapered conical face for normally engaging a matingly tapered valve seat118within the control valve at a position above and slightly upstream relative to the brine shut-off valve seat100. A shallow groove119(shown best inFIG. 4) is formed in the face of the poppet head110to define a fixed area flow restrictor or orifice through which brine or retentate20may flow when the shut-off valve stem pin96is in the normal open position (as shown inFIGS. 2-3). In this regard, brine inflow into a chamber120at the larger upper side of the poppet head110normally biases the poppet head110into seated engagement against the associated poppet seat118.

However, when the pure water shut-off valve head60at the lower end of the valve structure is shifted upwardly to the closed position (shown inFIGS. 5-6), the seal member64thereon sealingly engages with the smaller-diameter bore68of the sleeve62to halt further upward flow of produced purified water to the diaphragm chamber72and on to the pure water storage reservoir24(as previously described). In this regard, in accordance with a preferred form of the invention, the seal member64comprises a so-called quad-type seal having a substantially I-beam cross sectional shape to provide redundant axially spaced upper primary and lower secondary seal interfaces with the sleeve bore68. Such quad-type seal member is shown and described in more detail in U.S. Publication No. 2008/0087587, which is incorporated by reference herein.

More particularly, with the quad-type seal member64as shown, pure water production is halted as the upper primary seal ring structure engages the smaller-diameter bore68of the cylindrical sleeve62. Following this initial halting of pure water production, the pressure within the lower chamber56at the lower end of the pure water shut-off valve head60gradually increases to near or substantially the pressure of the feed or tap water, thereby slowly displacing the valve head60further in an upward direction. In this regard, initial pure water production as the primary seal ring engages the sleeve bore68is accompanied by short upward displacement of the brine shut-off valve stem pin96, but wherein this initial upward displacement is insufficient to close the stem pin96with the associated valve seat100. Accordingly, in the preferred form, brine flow through the control valve22continues for at least several minutes until the pressure within the lower chamber56builds sufficiently to displace the entire valve structure further upwardly for sealingly engaging the stem pin96with the valve seat100. An annular stop122within the valve housing44is abutted by the upper diaphragm81when this sealed brine-stop flow position is reached.

During this time delay, however, the brine flow continues for beneficially flushing any accumulated contaminants at an upstream side of the RO membrane14through the system to the drain26. Accordingly, any such accumulated contaminants are prevented from slowly migrating through the RO membrane14to undesirably provide a slug of contaminated water in the pure outflow lines when pure water production is resumed. Similarly, flushing of the accumulated contaminants from the upstream side of the RO membrane14also enhances membrane performance to produce purified water upon resumed flow to and through the membrane14.

When the brine shut-off valve stem pin96reaches the closed position in sealed engagement with the associated valve seat100, brine flow to the drain26stops. When this occurs, the pressure differential across the poppet head110is also eliminated, whereupon a light force spring124reacting between the valve housing44and the face of the poppet head110pushes the poppet head110to a fully opened or retracted position relative to its associated poppet seat118(FIGS. 5-6).

Thereafter, upon dispensing of sufficient purified water18from the storage reservoir24, the pressure at the underside of the lower diaphragm74is reduced sufficiently for the control valve structure including the pure water shut-off valve head60to displace downwardly for re-opening said valve head60(i.e., movement of the valve head60back to the open position as viewed inFIGS. 2-3) to resume pure water production. Concurrently, the brine shut-off valve stem pin96is retracted downwardly from the associated valve seat100to permit resumed brine flow to the drain26. Importantly, when the brine shut-off valve stem pin96is initially opened with the brine poppet head110retracted from its associated poppet seat118(as shown inFIGS. 5-6), brine water flow rushes through the seat118and against the head110and associated groove119for flushing contaminants and/or particulate therefrom. Such flush brine flow quickly re-establishes a pressure differential across the poppet head110, so that the poppet head110will move quickly against the light force spring124back to a position re-seated on the poppet seat118with the groove119defining a fixed area orifice (as viewed inFIGS. 5-6).

The control valve22remains in this open position for normal pure water production until the storage reservoir24again reaches a substantially filled condition, whereupon the control valve sequentially closes the pure water shut-off valve stem60and the brine shut-off valve stem pin96, all as described previously herein.

FIG. 8illustrates an alternative preferred form of the invention, wherein components identical to those previously shown and described with respect toFIGS. 1-7are referred to by common reference numerals. In this alternative embodiment, a modified stem pin196has a specially contoured tip197for progressively halting the brine flow as the pure water reservoir24fills with produced purified water.

More particularly, the modified brine shut-off valve stem pin196is carried and supported as previously shown and described for movement upwardly as the pure water reservoir24is filled with produced purified water to eventually seat against a valve seat100defined by a O-ring seal member102or the like. However, as viewed inFIG. 8, the tip197of the modified stem pin196is contoured to define an elongated and upwardly narrowing tapered shape. Accordingly, initial upward displacement of the stem pin196progressively decreases the available open flow area through the still-open valve seat100, for progressively and proportionally decreasing brine flow through said valve seat100to the drain26(FIGS. 1 and 2). Eventually, upon sufficient upward displacement of the stem pin196, the larger cylindrical outer diameter of the stem pin196engages and seats with the O-ring102to close the brine flow path (shown in dotted lines inFIG. 8).

Upon subsequent dispensing of sufficient pure water from the reservoir24, the stem pin196is shifted downwardly to re-open the brine flow path, as previously shown and described.

A variety of modifications and improvements in and to the reverse osmosis water purification system10and related improved control valve22of the present invention will be apparent to persons skilled in the art. By way of one limited example, it will be appreciated that the groove119formed in the poppet valve head110may if desired be formed in the associated valve seat118. Accordingly, no limitation on the invention is intended by way of the foregoing description and accompanying drawings.