Abstract:
A water filter system ( 10 ) for home use, includes a valve ( 34 ) that passes pressured water from a municipal water supply ( 30 ) though the inlet ( 20 ) of a passage ( 14 ) containing bidirectional filter elements ( 16 ) so the water has to pass though the filter elements to reach an outlet ( 22 ) that leads to a faucet ( 24 ). A water pressuring device ( 52 ) such as one that includes a bladder ( 56 ), has one side that faces a water outlet storage region ( 54 ) and an opposite side that faces a pressing apparatus such as compressed air ( 64 ). At intervals such as every 24 hours at 3:00 a.m., a timer ( 70 ) operates the control valve to connect the inlet ( 20 ) to a drain ( 50 ) instead of to the municipal water supply, for a period such as 20 seconds. Then, water backflushes though the bidirectional filter elements to a drain, to clean the filter elements. An ultraviolet light ( 104 ) at the outlet storage region kills bacteria to prevent bacteria buildup in the outlet region.

Description:
CROSS-REFERENCE  
       [0001]     Applicant claims priority from U.S. provisional application 60/648,310 filed Jan. 28, 2005. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     Many municipal water supplies provide water that does not taste good, that is not reliably safe to drink, or that people do not trust, and many people wish to pass water from the municipal water supply though a filter system. Presently available filter systems should be cleaned at intervals such as every day or every several days to avoid the buildup of bacteria. Some systems recommend that people clean the filters every several days and replace them at intervals , but many people do not do such cleaning or replacement on a regular basis. This can result in bacteria growing in the system that makes the water unhealthy or unsafe. A water filter system that cleaned itself at regular intervals without requiring human intervention, and that was of simple construction and used a minimum of water, would be of value.  
       SUMMARY OF THE INVENTION  
       [0003]     In accordance with one embodiment of the invention, a water filter system is provided that is of simple construction and that is self cleaning. The system includes a valve structure that can carry pressured feed water such as from a municipal water supply, to a passage containing a bidirectional filter arrangement such as hollow fibers with microscopic pores. The water flows forward through the hollow fibers to an outlet storage region from which water can be drawn to flow to a faucet, nozzle or other flow control. A water pressurizing device, such as a bladder having one side facing the water outlet storage region and an opposite side facing a pressured air chamber, maintains water in the outlet storage region under pressure. At intervals such as every 24 hours, in the middle of the night, a timer operates the valve structure to open a connection to a drain, for a period such as 20 seconds. Then, water in the outlet storage region is moved by the bladder in a reverse or backward direction though the bidirectional filter elements to the drain. This results in a backwashing of the filter elements and of the passage, to eliminate debris, which may include bacteria, that has accumulated on the filter elements and in the passage. The filter elements are preferably small diameter porous plastic tubes with very small pores or with a coating of a filtering layer such as polysulfone.  
         [0004]     One water filtration system includes a water pressuring device that contains only enough water in the outlet storage region to clean the filter elements and passage by backflushing. The output of water from the system is then limited by the flow rate of water though the filtering elements. A second water filtration system includes a water pressuring device that stores much more water than is required for flushing. This allows a person to open the faucet and rapidly withdraw water at a rate much faster than water can pass though the filter elements, until the store of water has been exhausted. Where a lot of water is stored, auxiliary filters such as carbons filter cylinders, can lie within the water storage volume.  
         [0005]     In another system, backflushing is enhanced by allowing pressured feed water to flow across the outside of the fibers while filtered water in the outlet storage region flows backward through the fibers to their outer surfaces to clean the pores in the fibers. The filtered water that has cleaned the fiber pores then flow out with the pressured feed water to the drain.  
         [0006]     Water in the water pressuring device is kept clean, even if it lies dormant in a concave wall, by an ultraviolet light that shines such light at the outlet region.  
         [0007]     The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a sectional side elevation view of a water filter system of the invention.  
         [0009]      FIG. 2  is a partially sectional isometric view of a portion of the system of  FIG. 1 .  
         [0010]      FIG. 3  is an enlarged view showing the way a fiber end is mounted.  
         [0011]      FIG. 4  is a sectional view of a group of fibers of the system of  FIG. 1 .  
         [0012]      FIG. 5  is a partially sectional isometric view of a water filtration system of another embodiment of the invention.  
         [0013]      FIG. 6  is a sectional side view of a water filter system of another embodiment of the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]      FIGS. 1-4  illustrate a water filter system  10  for home, office, or the like which includes a conduit  12  and walls forming a filter passage  14  of the conduit that surrounds a filter arrangement  15  that includes a plurality of filter elements  16 , such as tubular filters. The conduit has an inlet  20  that receives feed water to be filtered and has an outlet  22  for dispensing filtered water. The outlet is shown connected to a faucet  24  such as a household faucet that dispenses water for drinking or cooking. Feed water is received from a pressured feed water source  30  such as a municipal water system. The water flows though a valve structure  32  formed by a three-way valve  34  (or two 2-way valves). In the usual mode of operation, but with the faucet closed, the pressure of the feed water is maintained throughout the passage  14  but there is no water flow. In the usual mode of operation, but with the faucet opened so outflow from the outlet is unobstructed, feed water flows from a feed port  40  of the valve to a common port  42  of the valve that connects to the inlet  20 . The feed water flows downstream D into the filter passage  14  and forward through the filter elements to an outlet storage region  54 . In the outlet storage region  54 , a quantity of water is stored under pressure, and filtered water can flow out though the outlet  22  to flow to the faucet.  
         [0015]     The valve  34  includes a drain port  46  that connects to a drain  50  such as a sink drain. A water pressure device  52  stores water in the outlet storage region  54  that lies adjacent to the outlet  22 , at a pressure equal to the pressure of water in the feed water source  30 , when water is not exiting the outlet. The particular water pressure device  52  includes a bladder  56  with one face  60  in contact with water in the outlet storage region  54  and an opposite face  62  in contact with pressured air  64  in a tank  66 . In the usual mode of operation and with the faucet closed, the bladder is held deflected in direction D by the pressure of water in the inlet and outlet regions, and air  64  in the tank  66  is under the same pressure. A municipal water supply usually supplies water under a pressure of 10 to 100 psi, such as 50 psi.  
         [0016]     When the system is in the usual mode of operation and with the faucet closed, the valve  34  may be switched to a backflush mode, wherein the common port  42  of the valve is connected to the drain port  46  and therefore to the drain  50 . In the backflush mode, water under pressure in the outlet storage region  54  flows upstream U and backward through filter elements  16  in the passage  14  and into the passage  14 , out through the inlet  20 , and though the valve drain port  46  to the drain  50 . There is zero water pressure in the drain  50  (plus any head pressure required to reach upward to a drain end), while there is considerable water pressure in the water pressurizing device  52 . The water pressure in the outlet storage region  54  decreases as water flows upstream U, but the pressure is still high enough to assure that there will be a backflush. It is desirable but not necessary that the volume of water flowing upstream though the passage equal the volume of the passage, especially if such backflushing is performed often.  
         [0017]     Operation of the valve  34  is controlled by a control in the form of an electronic timer  70 . The timer may switch the valve  34  to the backflush mode for a short period of time such as  10  to  30  seconds, which is long enough to allow a large portion, usually a majority, of water stored in the relatively small water pressurizing device  52  to be backflushed. Applicant sets the timer so it switches the valve  34  to the backflush mode and then back to the usual mode every day at a time when it is very unlikely that the faucet  24  will be opened. The backflush time is between 11:00 PM one day and 7:00 AM the next day, and is preferably about 2:00 AM to 3:00 AM. If the faucet is open when the system is in a backflush mode, then a complete backflush will not occur, and the water pressure at the faucet will quickly drop until the system returns to the normal mode. However, occasionally missing a backflush will not noticeably affect the system. The system should be switched to the backflush mode at least once a week, and preferably once a day. The timer can run on batteries, because it operates briefly only once a day, although the municipal electric system is preferred, to energize ultraviolet lights. Other automatic or manually controlled devices can initiate each backwash.  
         [0018]      FIGS. 3 and 4  show that the filter elements  14  are in the form of tubular fibers with the distance between adjacent fibers being less than the outside diameter of each fiber. Each fiber is made of a material that is porous to water. The pores are micro (less than 1 micron), ultra (less than 0.1 micron), or nano. Applicant prefers a fiber material with pores between 1.0 and 0.01 microns for good filtration with a moderate flow rate. It is also possible to use a fiber with large pores and with a coating lying on the inside or outside and having small pores. Applicant prefers to mount the downstream ends of the fibers as shown in  FIG. 3 , with the downstream ends extending though holes  82  of an adhesive (e.g. epoxy) disc  84  that seals itself to the fibers and to the inside of a pipe  90  that forms the passage  14 . The inside of the upstream ends of the tubular fibers are blocked, so water in the passage  14  that lies around the fibers must pass forwardly from the outside of the fibers through the walls of the fibers (including any fiber coating) to the inside of the fibers and along the passageways at the inside, to reach the outlet storage region  54 . The forward flow can instead be from the inside of the fibers to their outside. A screen (not shown) can be placed upstream of the inlet to block moderately small particles, such as particles above 5 microns diameter.  
         [0019]      FIGS. 1 and 2  show that the passage  14  preferably contains auxiliary filters  100 ,  102  such as a filter disc  100  that blocks very small particles (e.g. about 0.5 microns) and a disk  102  of carbon that absorbs many chemical substances (or e.g. a specialized disc for absorbing arsenic). Each auxiliary filter  100 ,  102  includes a bed of contaminant retainer material and a multiplicity of pores. The bed material can be chosen to filter out contaminants present in large amounts in a particular locality. The filter discs can lie at either end of the passage  14 . The fiber filter elements  16  are bidirectional in that water to be further filtered can flow from its outer surface  94  to its inner surface  96 , or in the opposite direction.  
         [0020]     Applicant provides an ultraviolet light source  104  at the outlet storage region  54 . The purpose is to kill bacteria, or other potentially harmful particles that might grow in static water areas of the outlet region. In the passage  14 , up to the downstream mount disc  84 , water is backflushed so the buildup of bacteria is less likely.  
         [0021]     Applicant has designed a water filter system of the type shown in  FIGS. 1-4 . The passage  14  had an inside diameter of three inches and a length of twelve inches, for a volume of about eighteen cubic inches, or about one-eighth gallon. The water pressure device  52  had a holding capacity in the outlet storage region that was less than half the volume of the passage  14 . The passage  14  held a bundle of about 2000 fibers, each having an outside diameter of 0.050 inch. The flowthrough rate of water was 0.5 gallon per minute. Applicant prefers to use on the order of magnitude of 2000 fibers.  
         [0022]      FIG. 5  illustrates another water filter system  110  which is characterized by its ability to store considerable filtered water of at least one-half gallon such as 5 gallons. The system  110  includes a bladder tank  112  and a bladder  114  in the tank, with pressured air  120  on one side of the bladder and filtered water  122  on the other side that forms an outlet storage region  170 . The tank has a top that is sealed by a main cover  124 , and by a small access cover  126  within the main cover. Pressured feed water from a municipal supply passes though a valve structure formed by a three way valve  130  similar to that of  FIG. 1 . The pressured water passes though a feed water port  132  and a common port  134  to flow though an initial filter element  136  that traps microscopic particles (particles of 1 micron to 0.01 micron). The water then flows through a filter element  140  (e.g. carbon) that traps chemicals. The water then flows from the filter  140  into an upstream end  142  of a filter arrangement  143  (or from the filter arrangement  143  to the filters  136 ,  140 ). The water flows through a passage  144  of the filter arrangement that contains filter elements in the form of fibers similar to those of  FIG. 1 . Water that has flowed forward though the fibers exits the passage though an exit  146  that leads to the water side of the bladder  114 . A cup  146  with a hole at its center is fixed to the bladder to distribute forces from the bladder to the exit end of the filter arrangement. The bladder is intended to expand below the exit end of the filter arrangement. Water under pressure exits the bladder though an outlet  150  whenever a faucet is opened that is attached to the outlet.  
         [0023]     In the usual mode of operation, water flows slowly into the bladder until the pressure of air against the bladder at  120  equals the pressure of water supplied by the water source  30 , and the bladder then can be said to be full. The bottom of the tank which contains air can be initially pressured so the bladder holds a predetermined amount of water, such as five gallons, when the bladder is full (assuming a predetermined municipal water pressure). Whenever a person opens the faucet, water flows rapidly out of the faucet. In one example, the filter arrangement has a flow capacity of 0.25 gallons per minute. A person can fully open the faucet and withdraw water at a rate of two gallons per minute for almost three minutes, with the water coming from the reservoir on the water side of the bladder. This arrangement allows a person to withdraw considerable water, using a filter arrangement that has only a low flow capacity.  
         [0024]     A timer  160  operates the valve  130  at times when the faucet is least likely to be used (opened). The timer switches the valve to pass water from the common port  134  to a drain port  162  for a period such as 20 seconds to backwash, or backflush, the filters. The system uses a minimum amount of water during backwashing. The fiber filters are expected to last for about a year. The initial filter element  136  and the carbon filter  140  each must be changed at intervals such as every month. To change the filters, the valve  130  is first set in a position wherein the common port is connected to the drain, to allow the bladder to empty. Preferably the timer is provided with a manually operated button  164  that produces such complete emptying. Then, the access cover  126  is removed, the filter cartridges  136  and  140  are replaced, and the access cover is replaced.  
         [0025]     Ultraviolet light(s)  166  are positioned in the outlet region  170  to kill bacteria that might grow there. The timer preferably has a circuit that energizes a light and/or occasionally makes a sound if the filters are not changed every month, which is sensed by the fact that the button  164  for draining has not yet been depressed after more than a month.  
         [0026]     The water pressurizing device such as  52  ( FIG. 1 ) is shown as including a bladder. Other pressurizing device can be used such as a piston that moves in a cylinder that separates pressured water from pressured air or a spring, or a bellows that is biased by pressured air or a spring (e.g. of resilient foam or coiled wire), or a spring that helps move a bladder. Instead of a bladder, a nonelastic flexible bag can be used.  
         [0027]     The back washing can be performed by a timer. It also can be performed by a sensor that requires manual operating of a switch, a sensor that operates backwashing after a present number of gallons have flowed, or a sensor that senses less than optimum conditions.  
         [0028]     While applicant has described multiple hollow fiber filter elements as a filter arrangement, other types can be used. For example, two parallel and slightly-spaced sheet of microporous material can be wound into a spiral and used, with feed water flowing from the space between sheets to the space outside the sheets. Such pair of sheets can be spiral wound or in other formats. Another filter arrangement is a honeycomb arrangement.  
         [0029]     In  FIGS. 1 and 5 , where feed water from the outside to the inside of the fibers, substantially the entire area of the fiber ends is in communication with the outlet storage region  54  ( FIG. 1 ),  170  ( FIG. 5 ) without any pipes to connect them. This results in saving the amount of water used during backwashing, in that there are no narrow and elongated pipes between the fiber downstream ends (e.g.  180 ,  FIG. 1 ) and the outlet region  54 . This arrangement also reduces the number of pipe connections. Applicant prefers that the diameter at  172  of a circle  182  ( FIG. 2 ) that surrounds the fiber ends be at least 80% of the diameter at  172  of the outlet storage region  54  and preferably with no pipes between them, and that 80% of the area of the circle  182  open to the outlet storage region.  
         [0030]      FIG. 6  shows another system  200  that is similar to the system of  FIG. 1 , except that it provides more water and provides water at a largely constant high pressure for backflushing to a drain. Also, additional and pressurized backflush water is provided without using more of the filtered water lying in the outlet storage region  202  during a backflush. In  FIG. 6 , a conduit  203  has a sleeve with a passage  204  that contains a filter arrangement  206  comprising multiple fiber filter elements. The system is illustrated with the passage extending vertically, although it could extend horizontally. Pressured feed water from a source  210  flows into an inlet  213  through a feed pipe  212  and then flows through a feed extension pipe  214  that extends partially through the passage  204  with the extension pipe far end  205  which forms an outlet, lying in an upper portion  207  of the passage (downstream D of a passage middle  217 ). In the usual operation, when water is being drawn from the outlet region  202  to flow from a filtrate outlet  211  to a faucet  216 , water flows through the fiber filter elements to the outlet region  202 .  
         [0031]     When it is time to backflush the system, a control  220  opens a valve  222  that allows water to flow through holes  228  in a disc and into a drain extension pipe  224  at a valve port  225 . The pipe  224  has an open end  226  in communication with the passage  204  through the holes  228 , and water flows through another valve port  229  and a drain line  230  to a drain  232 .  
         [0032]     In many cases, a far end  234  of the drain line  230  which opens to the drain, must lie many inches above the filter arrangement  206 , such as 18 inches. If all of the backflush water has to flow backward through the fiber filter elements to clean them and then through the passage  204  to clean the outside of fiber elements to sweep away particles on the elements and in the passage, and then upward through the drain line, only a limited amount of water may flow during a backflush. In the system of  FIG. 6 , filtered water in the outlet storage region  202  flows backward from the inside to the outside of the fiber filter elements to clean the pores of the fiber filter elements. Downward (upstream U) flow along the outside of the fiber filter elements and through the passage, is primarily a flow of feed water (unfiltered) through the passage. Substantially all feed fluid discharged through pipe end  205  flows upstream U through the passage  204  toward the drain during a backflush (rather than forwardly through the filter elements). Since the backflushing lasts only a short period of time, a limited amount of feed water is used for a backflush. At the end of the backflush, the valve  222  is closed. A constriction  240  controlled by the control  220 , is preferably placed along the feed pipe  212  to assure that the pressure of water at the extension pipe outlet  205  is always below the pressure of water in the outlet storage region  202  during a backflush.  
         [0033]     Thus, the invention provides a water filter system that regularly cleans itself without requiring human intervention. This is accomplished by providing a water pressure device that stores water under pressure at the outlet region of the system, a valve structure at the inlet that can be switched to carry backflushed water to a drain, and a timer or sensor, etc. that controls the valve to switch to the drain mode at intervals. Applicant provides an ultraviolet light source that illuminates the outlet region to kill bacteria and other microscopic life forms that might grow there and that would not be filtered before being dispensed though a faucet.  
         [0034]     Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art, and consequently, it is intended that the claims be interpreted to cover such modifications and equivalents.