Abstract:
A liquid filter, having a housing having an inlet port to an interior chamber with an upper opening. A cover coupled to the housing, covering the upper opening has at least one filter element coupled to the cover, the filter element(s) projecting into the interior chamber. The filter element(s) having an inner area enclosed between the filter element and the cover. A purge inlet through the cover and an outlet through the cover connect to the inner area.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of US Provisional Patent Application titled “SELF CLEANING LIQUID FILTER”, Ser. No. 60/864,817 filed Nov. 8, 2006 by Mr. James Keller. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The present invention generally relates to liquid filters and or strainers. More specifically, the present invention relates to a cost efficient liquid filter usable in a reduced cycle time self cleaning liquid filter system. 
         [0004]    2. Description of Related Art 
         [0005]    Liquid filters are used in a wide range of processes to remove contaminants from liquids. An example of a self cleaning liquid filter and related process system for waste water recovery in a car wash is disclosed in U.S. patent application Ser. No. 11/060,112 filed Feb. 8, 2005, titled “Waste Water Recovery System” also invented by the inventor of the present application, Mr. James Keller. The application is co-owned with the present application by GKWF, Inc. and is hereby incorporated by reference in the entirety. 
         [0006]    The waste water recovery systems of commercial car washes are required to filter large volumes of water on a continuous basis. As the filter periodically becomes clogged with contaminants filtered from the process stream, a cleaning cycle including a reverse direction air and liquid purge is applied. To allow continuous operation of the waste water recovery system, a parallel filter assembly is supplied. While one filter is performing a cleaning cycle, the process stream is routed through the other filter by as series of automated flow control valves. The parallel filter arrangement, piping, valves and associated automation controls significantly increases both the cost and space requirements of the resulting system. 
         [0007]    Prior self cleaning filters, for example as shown in  FIG. 1 , have a filter element  10  suspended within a, for example, cylindrical housing  12  from a collar  14  that seats against an inward projecting shoulder  16  of the housing  12  sidewall  18 . In a filtering mode, process liquid flows from an inlet process line  20  into an inlet port  22  at the bottom of the housing  12 , through the filter element  10  and out a sidewall  18  outlet port  24  proximate the top of the housing  12  to an outlet process line  26 . The filter element  10  collar  14  is retained against the shoulder  16  by a spider arrangement  28  that extends from the collar  14  upward to contact a removable access cover  30  that seals the housing  12 . A sealing gasket  32  seals between the collar  14  and the shoulder  16 , preventing process flow from bypassing the filter element  10 . 
         [0008]    During a periodic back wash step, the inlet process line  20  is closed and a drain connection  36  of the inlet process line  20  opened to create a path from the housing  12  to drain. The outlet process line  26  is closed and a pressurized, for example air, purge is applied through a purge inlet  38  in the cover  30  to drive the process fluid filling the housing  12  in a reverse direction through the filter element  10  to the drain connection  36 , dislodging and flushing away any contaminants that have been captured against the outer surface  40  of the filter element  10 . After the back wash step has completed, an air purge step begins. In the air purge step, the purge inlet  38  is closed, an exhaust connection  44  in the cover  30  is opened, the drain connection  36  to the inlet process line  20  closed and the process flow reintroduced into the inlet process line  20  and housing  12 , pushing out the air through the exhaust connection  44  until the housing  12  is once again filled with process fluid, whereupon the exhaust connection  44  is closed and the outlet process line  26  opened to place the system back into filtering mode. 
         [0009]    Competition within the filter housing industry has focused attention upon minimization of materials and manufacturing costs. Also, size requirements of the filter housing and or surrounding process equipment are significant factors for commercial success. 
         [0010]    Therefore, it is an object of the present invention to provide an apparatus that overcomes deficiencies in the prior art. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0011]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
           [0012]      FIG. 1  is a partial cut-away side view of a prior art liquid filter assembly. 
           [0013]      FIG. 2  is a partial cut-away side view of an exemplary embodiment of a liquid filter assembly according to the invention. 
           [0014]      FIG. 3  is a partial cut-away side view of a multiple filter element embodiment of a liquid filter assembly according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    The inventor has recognized problems with the prior filter design. Specifically, the materials and manufacturing costs related to forming the close tolerance shoulder  16 , corresponding filter element  12  collar  14  and the spider arrangement  28 . Also, the sealing gasket  32  between the shoulder  16  and the collar  14  creates a failure point that can allow unfiltered process liquid to bypass the filter element  10  to damage and or contaminate downstream equipment if the sealing gasket  32  degrades over time and or fails to be properly installed during periodic inspection/manual cleaning of the housing  12 . A purge line  46  coupled to the purge inlet  38  typically does not extend deeply within the filter element  10  because the purge line  46  is relatively fragile and may either itself be damaged or cause damage to the filter element  10  unless the cover  30  it is attached to is removed and reseated with great care. 
         [0016]    Further, the inventor has recognized that the prior parallel dual filter systems that enabled continuous operation by providing an alternate filtering path while one of the parallel filter assemblies is in a self cleaning mode may be eliminated and replaced by a single filter assembly and a buffer tank, greatly reducing the overall system cost and complexity. A significant drawback of a buffer tank filter system configuration is the size of the buffer tank required to provide continuous operation while the filter is backwashed. The size of the buffer tank required is proportional to the desired system flow rate and the time required for the backwash cycle. 
         [0017]    According to the present invention, the time required for the backwash cycle may be minimized without impacting the period between cycles by reducing the volume of the filter assembly not dedicated to filter surface area, thereby resulting in faster backflush and air purge step times. 
         [0018]    As shown for example in  FIG. 2 , common elements from  FIG. 1  similarly notated, a filter assembly according to the invention may be formed by locating the outlet port  24  on the cover  30  at a location within the area of the filtered side of the filter element  10  which is also coupled to the cover  30  instead of a sidewall  18  mounted shoulder. The cover  30  is dimensioned to seal an upper opening  50  of the housing  12 . This arrangement allows the filter housing  12  and corresponding interior chamber  52  to be significantly shorter, eliminating the prior space between the collar  14  of the filter element  10  and the cover  30 , where the outlet port  24  was attached to the housing  12  sidewall  18 , as shown in  FIG. 1 . Thereby, the volume of the assembly not dedicated to filter surface area is minimized. As a result, applied to a similar waste water recovery system, a backwash cycle time of the prior liquid filter that previously required approximately 9 seconds is reduced to approximately 6 seconds. The air purge cycle time is similarly shortened. These time savings significantly reduce the system buffer volume required in a single filter assembly and buffer tank filtering system, increasing the cost efficiency of these systems, compared to prior parallel filter or single filter with larger buffer tank continuous filtration arrangements. 
         [0019]    Coupling the filter element  10 , for example a wedge wire basket, directly to the cover  30 , also introduces significant materials and manufacturing cost savings by eliminating the material, component manufacturing and assembly steps required to form and install the prior filter element  12 , collar  14 , shoulder  16  and spider arrangement  28 . 
         [0020]    A filter element  10 , for example a wedge wire basket, may be formed by mounting a generally triangular cross section wire with the triangle base along the perimeter of the basket and the triangle point facing inward to the filter element  10  interior. Adjacent wedge wires are mounted spaced apart by the desired filter gap. Thereby, the gap separated adjacent wedge wire triangle bases present a generally planar surface to the unfiltered side and a sloping open surface to the filtered side. The generally planar surface aids in collection/deposition of filtrate on the unfiltered side while the sloping open surface of the filtered side minimizes the opportunity for any disposition and or fouling on the filtered side, which improves the filter element cleanability via backflushing. 
         [0021]    The cover  30  and filter element  10  may be removably attached to one another, for example via fasteners between the cover  30  and a flange of the filter element  12 , sealed with a seal gasket  32 . However, by permanently attaching the filter element  10  directly to the cover  30  as shown in  FIG. 2 , for example by metal-to-metal or ultrasonic polymer/plastic welding, manufacturing costs are reduced and the failure point associated with the prior seal gasket  32  may be eliminated. Similarly, the purge line may be provided with a permanent connection to the purge inlet  38  on the cover  30 . 
         [0022]    The unfiltered inlet area of the housing where any fouling of the filter element  10  outer surface  40  not removed by the self cleaning cycle(s) is most likely to remain is still readily accessible by removing the cover  30  to access the outer surface  40  of the attached filter element  12 . In special circumstances, the filtered side of the filter element  10  may be accessed through the outlet port  24  and or any uncleanable matter dissolved via dipping of the cover/filter element assembly into a suitable corrosive and or caustic bath. 
         [0023]    A further improvement over the prior self cleaning filters is achieved by extending the length of the air purge line  46  from the cover  30  towards the bottom of the filter element  12 , for example to between 50 and 90 percent of the distance from the cover to the bottom  48  of the filter element  10 . This applies maximum air pressure at the bottom area of the filter element  10 , the area that experiences the worst fouling during operation due to its proximity to the inlet port  22 . Because the extended air purge line  46  is permanently surrounded by the filter element  10  when the cover  30  is removed, the danger of damaging the air purge line  46  and or damaging the filter element  12  by inadvertently hitting it with the air purge line  46  during servicing has been eliminated. 
         [0024]    To equalize flow as much as possible through the liquid filter, the housing  12 , filter element  10  and purge line  46  may each be applied with cylindrical outer dimensions oriented coaxial with one another. Further, locating the inlet port at a center of the housing bottom also aids in equalizing the flow distribution. 
         [0025]    The filter housing is demonstrated in  FIG. 2  with process piping connections directly to the various ports. These connections may also be provided with quick release features to simplify maintenance, inspection and or any required manual cleaning. 
         [0026]    In further embodiments, for example as shown in  FIG. 3 , to increase the potential filter element  10  surface area, and or provide filtered process liquid simultaneously to multiple independent process fluid consumers, multiple filter element(s)  10  may be applied to a common cover  30 . The outlet process connection  26  and purge line connection  44  of each filter element  10  may be ganged together or directed to independent process fluid consumers as desired. Where isolation valves are applied to the outlet process connection  26  and purge line connection  44  of each filter element  10 , the process controls may be arranged to backwash an individual filter element  10 , on demand. 
         [0027]    One skilled in the art will appreciate that the present invention represents a significant cost savings with respect to required materials, components, manufacturing and servicing. Further, the present invention reduces the level of complexity, automation and system footprint when incorporated into a system that replaces the prior parallel dual filter arrangement with a single filter according to the invention and a buffer tank. Compared to prior single filter/buffer tank systems, the present invention enables use of a buffer tank with smaller size and associated cost requirements than possible with systems utilizing a conventional filter housing. 
         [0000]    
       
         
               
             
               
               
             
           
               
                   
               
               
                 Table of Parts 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 10 
                 filter element 
               
               
                 12 
                 housing 
               
               
                 14 
                 collar 
               
               
                 16 
                 shoulder 
               
               
                 18 
                 sidewall 
               
               
                 20 
                 inlet process line 
               
               
                 22 
                 inlet port 
               
               
                 24 
                 outlet port 
               
               
                 26 
                 outlet process line 
               
               
                 28 
                 spider arrangement 
               
               
                 30 
                 cover 
               
               
                 32 
                 sealing gasket 
               
               
                 36 
                 drain connection 
               
               
                 38 
                 purge inlet 
               
               
                 40 
                 outer surface 
               
               
                 44 
                 exhaust connection 
               
               
                 46 
                 purge line 
               
               
                 48 
                 bottom 
               
               
                 50 
                 upper opening 
               
               
                 52 
                 interior chamber 
               
               
                   
               
             
          
         
       
     
         [0028]    Where in the foregoing description reference has been made to ratios, integers, materials, components or modules having known equivalents then such equivalents are herein incorporated as if individually set forth. 
         [0029]    While the present invention has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus, methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of applicant&#39;s general inventive concept. Further, it is to be appreciated that improvements and/or modifications may be made thereto without departing from the scope or spirit of the present invention as defined by the following claims.