Abstract:
A microbial resistant water purification and collection system generally comprises a reverse osmosis filter assembly having a filter inlet in selective fluid communication with a system inlet and a filter outlet in fluid communication with a water storage container. The filter inlet is separated from the filter outlet by a filter membrane. At least a portion of the storage container is located at an elevation above the filter membrane such that filling of the storage container creates a head pressure in the storage container relative to the filter membrane. A shut-off valve is interposed the system inlet and the filter inlet to block fluid communication from the system inlet to the filter inlet upon reaching a minimum head pressure in the storage container relative to the filter membrane.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to water filtration. More particularly, the invention relates to a reverse osmosis water filtration system wherein gentle periodic back pressure across the filter membrane is utilized to avoid the aggregation of microbial bioburden within the filtration system.  
         BACKGROUND OF THE INVENTION  
         [0002]    The need to control microbial bioburden has led to point-of-use bacterial sterilization using filter membranes to remove particles and bacteria from various fluids. It is important, however, that the utilized filter membranes be regularly maintained in order to prevent the buildup of microbial biological fouling on the upstream side of the filter membrane. In reverse osmosis filter technology, such regular maintenance generally entails the replacement of the reverse osmosis filter membrane and/or the entire reverse osmosis filter assembly. Unfortunately, depending upon the remoteness of the filter implementation or the skill level of the user, the filter assembly may be neglected, ultimately resulting in failure or even health hazard.  
           [0003]    Because microbial bioburden is most prevalent in stagnant water, Applicant has found it desirable to implement extra precaution against the biological fouling of reverse osmosis filter membranes. To this end, it is an object of the present invention to provide a reverse osmosis filter system wherein there is provided a continuous flow of water across the filter membrane. Contrary to the general state of the art, this requires the back flow of filtered water across the filter membrane. Although U.S. Pat. No. 5,658,457 issued Aug. 19, 1997 to Schoenmeyr (“Schoenmeyr”) at least contemplates such a back flow for the purpose of particle removal, Schoenmeyr falls short of enabling a system capable of resisting microbial buildup. In particular, Schoenmeyr fails to provide sufficient back flow pressure at the time of forward flow shut-off as necessary for actual reverse flow across the membrane. As a result, the apparatus of Schoenmeyr is susceptible to the buildup of biological material. It is therefore an overriding object of the present invention to improve upon the prior art by providing a reverse osmosis filter system that provides for the continuous flow of water across the reverse osmosis membrane, thereby greatly diminishing the opportunity for the aggregation of biological fouling.  
         SUMMARY OF THE INVENTION  
         [0004]    In accordance with the foregoing objects, the present invention—a microbial resistant water purification and collection system—generally comprises a reverse osmosis filter assembly having a filter inlet in selective fluid communication with a system inlet and a filter outlet in fluid communication with a water storage container. The filter inlet is separated from the filter outlet by a filter membrane. At least a portion of the storage container is located at an elevation above the filter membrane such that filling of the storage container creates a head pressure in the storage container relative to the filter membrane.  
           [0005]    A shut-off valve is interposed the system inlet and the filter inlet to block fluid communication from the system inlet to the filter inlet upon reaching a minimum head pressure in the storage container relative to the filter membrane. In the preferred embodiment of the present invention, the minimum head pressure is at least 0.5 pounds per square inch in order to ensure back flow across the membrane upon shut-off to the filter assembly of the source water.  
           [0006]    The water storage container preferably comprises a substantially freely expandable and substantially freely collapsible, flexible bag while the shut-off valve preferably comprises a mechanical valve, actuated by the filling of the flexible bag. In particular, the mechanical valve comprises a valve inlet, a valve outlet and a plunger, depression of the plunger operating to block fluid flow from the valve inlet to the valve outlet. To this end, the shut-off valve further comprises a lever arranged between the mechanical valve and the flexible bag such that the lever is adapted to depress the plunger upon substantial filling of the flexible bag.  
           [0007]    In at least one embodiment of the present invention, the reverse osmosis filter assembly is located in a space entirely beneath the storage container, thereby providing maximum head pressure to the filter membrane. In this embodiment, the filter outlet communicates with the storage container through a container inlet in a base portion of the storage container. The same inlet may also then double as an outlet for the water collected in the storage container. To this end, a transfer pump, which may be demand activated, gas powered, remotely switched or a combination thereof, may also be provided for delivery of the water.  
           [0008]    A booster pump may be interposed the system inlet and the filter inlet for low source pressure applications. In this case, a shut-off switch adapted to interrupt electrical power to the booster pump upon substantial filling of the storage container is also provided. Preferably, the shut-off switch is actuated by the same lever as controls flow to the filter assembly. Additionally, a clean water inlet for collection of water other than through the filter assembly may be provided. In this case, a pressure relief, having an integral check valve, is provided for release from the collected water of gasses such as carbon dioxide.  
           [0009]    Finally, many other features, objects and advantages of the present invention will be apparent to those of ordinary skill in the relevant arts, especially in light of the foregoing discussions and the following drawings, exemplary detailed description and appended claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    Although the scope of the present invention is much broader than any particular embodiment, a detailed description of the preferred embodiment follows together with illustrative figures, wherein like reference numerals refer to like components, and wherein:  
         [0011]    [0011]FIG. 1 shows, in a front perspective view, the preferred embodiment of the water purification and collection system of the present invention;  
         [0012]    [0012]FIG. 2 shows, in a rear perspective view, the water purification and collection system of FIG. 1;  
         [0013]    [0013]FIG. 3 shows, in a bottom perspective view, the water purification and collection system of FIG. 1;  
         [0014]    [0014]FIG. 4 shows, in a partially cut away top plan view, certain details of the automatic shut-off valve of the water purification and collection system of FIG. 1; and  
         [0015]    [0015]FIG. 5 shows, in a partially cut away cross-sectional view taken through line  5 - 5  in FIG. 4, certain other details of the automatic shut-off valve of the water purification and collection system of FIG. 1. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]    Although those of ordinary skill in the art will readily recognize many alternative embodiments, especially in light of the illustrations provided herein, this detailed description is exemplary of the preferred embodiment of the present invention, the scope of which is limited only by the claims appended hereto.  
         [0017]    Referring now to the figures, the water purification and collection system  10  of the present invention is shown to generally comprise a storage container  12 , for holding filtered or otherwise clean water, and a reverse osmosis (“R/O”) filter assembly  19  located, for reasons that will be apparent further herein, in a container subspace  41  beneath the storage container  12 . An automatic shut-off valve assembly  27  is provided to control the flow, through an unfiltered water inlet  11 , of water to the water purification and collection system  10 . As will be better understood further herein, this flow is controlled according to the amount of water in the storage container  12 . As also will be better understood further herein, the specific arrangement of the foregoing components enables the automatic and periodic back flush cleansing of an R/O membrane  21  encapsulated within a membrane vessel  20  of the R/O filter assembly  19 .  
         [0018]    As particularly shown in FIGS. 1 and 2, the storage container  12  preferably comprises a freely expandable and freely collapsible, flexible plastic bag. Filtered water from the R/O filter assembly  19  may enter the storage container through a combination filtered water inlet and clean water outlet  13 . Similarly clean water returned from other devices may enter the storage container  12  through a clean water inlet  14 . An overflow and pressure relief outlet  15  is provided to ensure that the storage container  12  does not become excessively filled. Additionally, because water processed through the reverse osmosis membrane may have trace concentrations of CO 2  and other gasses—causing the formation of acid solutions in the permeate, the overflow and pressure relief outlet  15  is further provided to allow such gases to freely escape out of the stored water at atmospheric pressure. In this manner the stored water returns quickly to a normal pH level and is thereafter maintained in a non-aggressive state. In order to preserve the integrity of the water, however, the overflow and pressure relief outlet  15  is preferably provided with an integral, one-way check valve  16 .  
         [0019]    As shown in FIGS. 1 through 3, the clean water inlet  14  and overflow and pressure relief outlet  15  serve to dependently affix the storage container  12  to the chassis  36  of the water purification and collection system  10 . To this end, the storage container is provided with a plurality of integral bag fittings  17  adapted to mate, through a clean water inlet aperture  37  and an overflow and pressure relief outlet aperture  38 , with couplings  18  on the clean water inlet  14  and overflow and pressure relief outlet  15 . Likewise, a bag fitting  17  is provided to mate, through a filtered water inlet and clean water outlet aperture  40 , with a coupling  18  on the combination filtered water inlet and clean water outlet  13 , thereby securing the lower portion of the storage container  12  to a container shelf  39  mounted to the chassis  36 .  
         [0020]    The R/O filter assembly  19  of the present invention generally comprises an R/O membrane  21 , encapsulated within a vessel  20 , and plurality of membrane vessel mounting brackets  22 . In a critical aspect of the present invention, the membrane vessel mounting brackets  22  are affixed to the chassis  36  in such a manner as to secure the membrane vessel  20  in a horizontal orientation in the container subspace  41  beneath the container shelf  39 . In this manner, as will be better understood further herein, a sufficient head pressure of water in the storage container  12  may be achieved to enable back flush cleansing of the R/O membrane  21  during any time that flow of unfiltered water to the water purification and collection system  10  is interrupted by the automatic shut-off valve assembly  27 . Because, contrary to conventional practice in the art, the present invention contemplates allowing clean water to flow back into the membrane vessel  20  through the filtered water outlet  24  during such periods, it is also critical to the present invention that the membrane vessel  20  be modified to accommodate this flow. In particular, it is necessary to omit the check valve ordinarily provided within a membrane vessel, which would otherwise prevent the return flow of water through the filtered water outlet  24  to the R/O membrane  21 .  
         [0021]    For implementation of the present invention, Applicant has found that a 100 gallon per day encapsulated nanofiltration membrane module may be utilized in the R/O filter assembly  19 . Although those of ordinary skill in the art will recognize other substantial equivalents, Applicant predicts that this implementation will allow membrane performance achieving 85 to 90% sodium chloride rejection and 95 to 98% divalent rejection, so long as recovery is maintained at about 4 or 5 to 1. As in other R/O implementations, a reject water drain  26  is provided in fluid communication with a reject water outlet  25  from the membrane vessel  20 . Preferably, the reject water drain  26  is provided with a trademark “TEFLON” capillary flow restrictor.  
         [0022]    As particularly shown in FIGS. 2 through 5, the automatic shut-off valve assembly  27  of the present invention generally comprises a normally open valve  32  adapted to be mechanically operated through a paddle  28  according to the level of water within the storage container  12 . As shown in the figures, normal flow of unfiltered water is through the unfiltered water inlet  11  to an inlet  33  on the valve  32  via interposed tubing. So long as the storage container  12  is not full or nearly full, water flows freely through the valve  32  and out of an outlet  34  through plastic tubing to an unfiltered water inlet  23  on the membrane vessel  20 . Clean water then crosses the R/O membrane  21  and flows from the filtered water outlet  24  of the membrane vessel  20 , through provided plastic tubing and a four-way union  45 , the purpose of which will be more apparent further herein, and into the storage container  12  through the combination filtered water inlet and clean water outlet  13 . As in other R/O implementations, reject water that does not pass across the R/O membrane  21  flows from the reject water outlet  25  of the membrane vessel  20  and through the flow-restricted reject water drain  26 .  
         [0023]    When the storage container  12  becomes full, the paddle  28 , which acts as a lever across a fulcrum  31  formed in the chassis  36 , serves to close the valve  32 . Specifically, as the flexible storage container  12  fills, horizontal pressure is exerted against the extended arm  29  of the paddle  28  resulting in depression of a plunger  35 , integral with the valve  32 , through the lever action of the actuating arm  30  of the paddle  28  across the fulcrum  31 . Depression of the plunger  35  closes the valve  32 , interrupting water flow to the R/O membrane vessel  20 . Although those of ordinary skill in the art will recognize many possible variations, Applicant has found it preferable to adapt the automatic shut-off valve assembly  27  such that about 40 psi pressure against the plunger  35  is created upon filling of the storage container  12 . In this manner, utilizing a readily available commercial diaphragm valve, about 60 psi line pressure may easily be interrupted.  
         [0024]    As previously described, the storage container  12  of the present invention generally comprises a freely expandable and freely collapsible, flexible plastic bag. According to the preferred implementation of the present invention, the storage container  12  is sized to hold approximately 5 gallons of water. Additionally, the automatic shut-off valve assembly  27  is adapted to close the valve  32  as the storage container is filled to approximately 80% capacity (approximately 4 gallons). In this manner, a head pressure of approximately 0.5 to 1 psi is created to produce a gentle back pressure across the R/O membrane  21  within the membrane vessel  20  at any time that the storage container  12  is full. Although it is critical to the present invention to orient the membrane vessel, as shown in the figures, in the container subspace  41  in order to produce sufficient back pressure across the R/O membrane  21  for cleaning, excessive head pressure must be avoided. To this end, the implementing engineer is cautioned to maintain the back pressure at or below 5 psi in order to prevent delaminating of the R/O membrane  21 .  
         [0025]    As previously mentioned, a four-way union  45  is provided in the fluid connection between the R/O filter assembly  19  and the combination filtered water inlet and clean water outlet  13  interfacing with the storage container  12 . In this manner, the single opening to the storage container  12  may be utilized for filling of the storage container  12  as well as dispensing of the clean water therefrom. To this end, one connection from the four-way union  45  is placed in fluid communication with an inlet  49  of a transfer pump  48 . The outlet  50  from the transfer pump  48  is then connected to a pump clean water outlet  46 . In the preferred embodiment of the present invention, the transfer pump  48  comprises a pressure switch operated, intermittent duty cycle, self priming, positive displacement pump. Such a pump is commercially available from the Shurflo Pump Mfg. Co. of Santa Anna, Calif. under their model number 402-140-033. As will be appreciated by those of ordinary skill in the art, the pumped clean water outlet  46  may then be connected to such devices as may demand clean water, but lack internal pumping apparatus. For the provision of clean water to devices having an internal pump, the remaining connection to the four-way union  45  is fluidly connected directly to a gravity flow clean water outlet  47 .  
         [0026]    In an alternative to the demand activated transfer pump  48 , however, those of ordinary skill in the art will recognize that a gas operated pump my be conveniently used in those applications where the water purification and collection system  10  of the present invention is utilized with soda machines and the like. In such an application, a portion of the carbonating gas is simply diverted to drive the transfer pump. Likewise, a lower-cost impeller or turbine pump may be utilized by providing a remote actuator switch. In one implementation, such a remote switch may comprise a magnetic reed switch place in proximity to the solenoid coil operating an inlet valve to a user machine. Actuation of the solenoid will cause closure of the reed switch and operation of the transfer pump notwithstanding the fact that no actual interface wiring to the user machine need be provided.  
         [0027]    While the foregoing description is exemplary of the preferred embodiment of the present invention, those of ordinary skill in the relevant arts will recognize the many variations, alterations, modifications, substitutions and the like as are readily possible, especially in light of this description, the accompanying drawings and claims drawn thereto. For example, a booster pump  43  may be provided between the unfiltered water inlet  11  and the R/O filter assembly  19  for use in low-pressure applications wherein there may lack sufficient forward pressure for operation of the R/O filter assembly  19 . In this case, a normally closed mini switch  51  is also provided, as shown in FIGS. 1, 2 and  4 , for controlling delivery of power to the booster pump  43  according tot the level of water in the storage container  12 . In particular, as the storage container  12  becomes full, the paddle  28  operates against the booster pump switch  51  to open the switch  51 , thereby interrupting electrical power from the power source  44  to the booster pump  43 .  
         [0028]    Likewise a power source  44 , such as a battery pack or alternating current adapter, may be provided for operation of the transfer pump  48  and/or the booster pump  43 . Additionally, the chassis  36  is preferably provided with a plurality of mounting slots  42 , whereby the water purification and collection system  10  of the present invention may be readily mounted to a frame, a wall, a related device or the like. In any case, because the scope of the present invention is much broader than any particular embodiment, the foregoing detailed description should not be construed as a limitation of the scope of the present invention, which is limited only by the claims appended hereto.