Abstract:
A self-cleaning prefilter system generally includes a system inlet  11,  a sediment filter  13  having a selectively openable drain port  18,  a chemical injector  21,  a pressure accumulator  28  having a upper chamber  31  in open fluid communication with the filter outlet  16,  and a system outlet  12.  A controller  33  in communication with a plurality of valves (V 1,  V 2,  V 3 ) initiates a backwashing mode such that upon opening of the drain valve V 3,  fluid within the upper chamber  31  of the pressure accumulator is driven back towards the sediment filter to backwash the filter screen thereof. Contemporaneously, chemicals within the chemical injector  21  are driven along with the backwash flow via capillary  24.

Description:
FIELD OF THE INVENTION 
     The present invention relates to liquid filtration. More particularly, the invention relates to a water pre-filter that utilized stored pressure to periodically back flush a sediment filter, removing any cleared detritus from the system through a drain port. 
     BACKGROUND OF THE INVENTION 
     Water filtration often involves the use of multiple pre-filtration steps in order to remove sediment of gradually decreasing size. In practice, a large screen filter is first used to remove large objects from the water followed by filtration with screens of gradually decreasing mesh size. While it would be desirable to remove all of the sediment with a single filtering operation, use of a filter with small enough mesh size to clear the water in an initial step leads to rapid clogging of the filter screen by larger particles. As a result, water users have been forced to implement very expensive pre-filter systems in order to ensure uninterrupted water sources. It is therefore an overriding object of the present invention to provide a water pre-filter system wherein a fine mesh filter may be utilized in an initial filtering stage without the problems of clogging that have plagued previous designs. 
     SUMMARY OF THE INVENTION 
     In accordance with the foregoing objects, the present invention—a self-cleaning pre-filter system—generally comprises a system inlet; a sediment filter having a filter inlet in selective fluid communication with the system inlet, a selectively openable drain port and a filter outlet, separated from the filter inlet and the drain port by a filter screen; a pressure accumulator having a first chamber in open fluid communication with the filter outlet and having a sealed second chamber containing a compressible medium, the first chamber and the second chamber being separated one from the other by a flexible diaphragm; and a system outlet in selective fluid communication with the filter outlet and the first chamber. 
     In order to provide the desired selective fluid communications and the selective state of the drain port, the preferred embodiment of the present invention comprises an inlet valve between the system inlet and the filter inlet; a drain valve in the drain port; and an outlet valve between the first chamber and the system outlet. Preferably, each valve comprises a solenoid operated flow control valve, which may each be controlled by a provided system controller. In order to ensure maximum operational efficiency, the drain valve is also preferably a high capacity flow control valve relative to the inlet valve and the outlet valve. While the controller may comprise a dedicated state machine or micro-controller, those of ordinary skill in the art will recognize that the control function may also be integrated within the controller of a related device. 
     In operation, the controller operates the valves to periodically back flush the sediment filter utilizing energy stored in the pressure accumulator. Any detritus removed from the filter screen during the back flush process is immediately discharged from the system through the drain port. The controller then returns to the filter system to normal operation. 
     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 
     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: 
     FIG. 1 shows, in schematic block diagram, a first preferred embodiment of the self-cleaning pre-filter system of the present invention; 
     FIG. 2 shows, in a cross-sectional front elevational view, a sediment filter as appropriate for use in implementation of the filter system of FIG. 1; 
     FIG. 3 shows, in a cross-sectional front elevational view, a chemical injector as appropriate for use in implementation of the filter system of FIG. 1; 
     FIG. 4 shows, in flowchart, a first preferred method of operation of the filter system of FIG. 1; 
     FIG. 5 shows, in flowchart, details of the filter back flushing step of the method of FIG. 4; and 
     FIG. 6 shows, in schematic block diagram, a second preferred embodiment of the self-cleaning pre-filter system of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     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. 
     Referring now to FIG. 1, the self-cleaning pre-filter system  10  of the present invention is shown to generally comprise a sediment filter  13 , a pressure accumulator  28  and a plurality of solenoid actuated flow control valves V 1 , V 2  and V 3  arranged in the fluid flow between a system inlet  11  and system outlet  12 . In operation, the solenoid actuated flow control valves V 1 , V 2  and V 3  are utilized to periodically interrupt normal fluid flow from the system inlet  11  to the system outlet  12  for backflush cleaning of the sediment filter  13 . As will be better understood further herein, the pressure accumulator  28  provides the necessary energy for creating a reverse fluid flow through the sediment filter  13  thereby removing therefrom any detritus lodged therein. 
     As particularly shown in FIG. 2, the sediment filter  13  as appropriate for use in implementation of the present invention generally comprises a cylindrical filter cartridge  19  dependently interposed a filter top  14  and filter bowl  17 . During normal usage, fluids enter the sediment filter  13  through an inlet  15  on the filter top  14  and are directed to the interior of the cylindrical filter cartridge  19 . The cylindrical filter cartridge  19 , which comprises a caged, wire mesh filter screen  20 , prevents the passage of detritus as the fluids flowing through the sediment filter  13  are forced through the cartridge&#39;s wall and out of an outlet  16  into the filter top  14 . A drain port  18  is provided in the base of the filter bowl  17  in fluid communication with the interior of the cylindrical filter cartridge  19 . Although those of ordinary skill in the art will recognize many substantial equivalents for implementation of the principles of the present invention, applicant has found that the in-line strainer commercially available from Ron-Vik, Inc. of Minneapolis Minn. is suitable for implementation of the present invention. 
     As particularly shown in FIG. 1, the pressure accumulator  28  generally comprises a pressure vessel  29  with an upper chamber  31  and a compressible medium  32  separated by an internal diaphragm  30 . The model 181-201 pre-pressurized accumulator tank commercially available from ShurFlo Pump Mfg. Co. of Santa Ana, Calif. is exemplary of such a pressure accumulator  28 . In operation, normal flow results in some fluid entering the upper chamber  31  of the pressure vessel  29 . This entry causes deflection of the diaphragm  30  and compression of the compressible medium  32 . Upon interruption of normal flow, the compressible medium expands against the diaphragm  30 , thereby forcing the entered fluid from the upper chamber  31  of the pressure vessel  29 . In this manner, as will be better understood further herein, fluid flow may be reversed through the sediment filter  13  for cleaning of the cylindrical filter cartridge  19  housed therein. 
     In an alternative embodiment, the pressure accumulator  28  as previously described may be dispensed with in favor of a system wherein incoming water pressure is utilized to drive a volume of stored filtered water back through the filter cartridge  19 . The additional plumbing and valves for implementation of this alternative are well within the ordinary skill in the art, especially in light of this present exemplary disclosure. As will be apparent to those of ordinary skill in the art, it is only necessary that some provision be made for the backward flow across the filter cartridge  19  of clean, filtered water. 
     As will be better understood further herein, fluid flow through the self-cleaning pre-filter system  10  of the present invention normally comprises entry through the system inlet  11 , passage through the sediment filter  13  and exit through the system outlet  12 . A normally open, solenoid controlled outlet valve V 1  is provided, however, downstream from the pressure accumulator  28  to disrupt flow from the system outlet  12 . (Although the outlet valve V 3  is shown in the figures as a component of the pre-filter system  10 , those of ordinary skill in the art will recognize that this valve V 3  may in fact comprise an inlet valve to a host equipment item.) Likewise, a normally open, solenoid controlled inlet valve V 2  is provided at the system inlet  11  in order to disrupt flow to the self-cleaning pre-filter system  10  as well as to isolate the pre-filter system  10  from its fluid source during cleaning of the sediment filter  13 . Finally, a normally closed, solenoid controlled drain valve V 3  is provided in the drain port  18  of the filter bowl  17  for evacuation of detritus from the self-cleaning pre-filter system  10 . Because, as will be better understood further herein, it is desirable to fully and completely open the drain port  18  with minimal fluid resistance it is important in implementation of the present invention that the solenoid controlled drain valve V 3  be of a large volume capacity. To this end, applicant has found that the series 1000 solenoid piloted one inch port electric control valve commercially available from Evolutionary Concepts, Inc. of San Dimas, Calif. under the trademark “ECI” is suitable for use in the present invention. As also will be better understood further herein, each solenoid actuated control valve V 1 , V 2  and V 3  is in electrical communication with a controller  33 . As will be readily appreciated by those of ordinary skill in the art, such a controller may comprise a simple state machine or may be microprocessor-based, as will depend upon the greater application with which the self-cleaning pre-filter system  10  of the present invention is utilized. 
     Referring now to FIG. 4, a timer-based control scheme  37  for operation of the present invention is now detailed. Under such a timer-based control scheme  37 , upon starting  38  of filtering operation a counter is set equal to a pre-determinable value  39 . The controller  33  then determines whether the count value is greater than zero  40 . If yes, normal flow as previously described, is maintained  41  and the counter value is decremented  42 . If it is then determined that a system shut-down is desired  43 , the system  10  is shut down  44  without having performed a filter cleaning. If, on the other hand, a system shut-down is determined to not be desired  43 , the counter state is rechecked  45 . If, upon checking the counter state it is determined that the counter has reached zero  40 , a flushing sequence  46  is then performed. 
     As detailed in FIG. 5, the flushing sequence  46  begins with the closing  47  of the solenoid controlled outlet valve V 1 , thereby terminating fluid flow through the pre-filter system  10  at the pressure accumulator  28 . The solenoid controlled inlet valve V 2  is then closed  48  in order to isolate the pre-filter system  10  from the source of fluid flow. The solenoid controlled drain valve V 3  is then opened  49 , thereby allowing the reverse fluid flow from the pressure accumulator  28  to enter the outlet of the sediment filter  13 . The reverse flow of fluid through the sediment filter  13  serves to dislodge any detritus from the filter screen  20 . A pause  50  may be implemented at this stage to allow the dislodged detritus to evacuate through the drain port  18 . Preferably, the solenoid controlled inlet valve V 2  is then opened  51  to further flush the dislodged detritus from the sediment filter  13 . The solenoid controlled drain valve V 3  is then closed  52  and the solenoid controlled outlet valve V 1  is then opened  53  to resume normal flow. 
     As shown in FIGS. 1 and 3, a chemical injector  21  is preferably interposed in the fluid flow between the sediment filter  13  and the pressure accumulator  28 . The chemical injector  21  generally comprises a chemical container  22  in communication with the fluid flow path  25  through a capillary  24 . During normal flow from the inlet  26  to the outlet  27  of the chemical injector  21 , pressure in the fluid flow path  25  squeezes a compressible pillow  23  within the chemical container  22 . During periods of reduced pressure in the fluid flow path  25 , such as during the pause  50  after opening  49  of the solenoid controlled drain valve V 3  for evacuation of the sediment filter  13 , the compressible pillow  23  expands causing a small amount of chemical within the chemical container  22  to be forced through the capillary  24  and into the fluid flow path  25 . In this manner, the chemical injector  21  may be utilized to automatically treat the fluid contemporaneously with the removal of detritus from the pre-filter system  10 . Those of ordinary skill in the art will recognize other substantially equivalent implementations and will appreciate the relative merits of various treatment chemicals, such as, for example, chlorine, bromine, iodine or any surfactant biostat. In one exemplary implementation, Applicant has found it preferable to practice the present invention with the chlorinator module commercially available from Pure 1 Systems of New Rochelle, N.Y. 
     When using a chemical injector  21  as previously described, it may be desirable to take extra caution to ensure that only safe levels of the injected chemical remain in the fluid passing from the system outlet  12 . This is especially important in implementations wherein the self-cleaning pre-filter system  10  of the present invention is used for the filtering of drinking water and the like. To this end, Applicant has found it desirable to include an in-line chemical filter between the solenoid controlled outlet valve V 1  and the system outlet  12 . As known to those of ordinary skill in the art, such an in-line chemical filter  36  may comprise a granular activated carbon (“GAC”) chlorine removal filter for cases where chlorine is injected by the chemical injector  21 . Likewise iodine removal filters may be provided if the injected chemical is iodine, and so forth. 
     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, in an alternate embodiment for the control of the present invention, an upstream pressure transducer  34  and a downstream pressure transducer  35 , as particularly shown in FIG. 6, may be provided for detection through the controller  33  of an increased pressure differential across the sediment filter  13 . As will be appreciated by those of ordinary skill in the art, such an increased pressure differential would indicate the build up of detritus within the cylindrical filter cartridge  19  of the sediment filter  13 . Detection of the differential may then be utilized as a triggering signal for the initiation of the flushing sequence  46 . In this manner, flushing of the sediment filter  13  may be performed as often as necessary but without waste of power, as may be important for remote, battery-operated implementations. 
     Additionally, those of ordinary skill in the art will recognize that a flow meter may be implemented, whereby the flushing sequence  46  is triggered upon a predetermined amount of water having passed through the pre-filter system  10 . Likewise, those of ordinary skill in the art will recognize that in a minimal configuration the pre-filter system  10  may be implemented with no controller whatsoever, in which case the valves V 1 , V 2  and V 3  may be operated strictly manually. Finally, in implementations wherein the outlet valve V 3  is or doubles as an inlet valve to a host equipment item, the flushing sequence may be initiated (1) on demand, just prior to delivery of filtered water to a host machine, (2) during periods where demand is absent, or (3) upon any combination of demand-based cues and/or the methods previously described. Likewise, the flushing sequence may be initiated under the control of the host equipment item&#39;s internal controller. 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.