Abstract:
This invention is a filtration structure characterized by radial fluid flow through the wall of a cylindrical configuration that is established by a stack of serrated annular wafers which are constrained for slight axial movement with respect to each other, for the establishment of two conditions. In one condition, the wafers are axially compressed into snug contact under spring bias to establish a labyrinth of radial passages for fluid flow at a selected pressure. In the other condition, the axial compression of the disks is relieved and the disks are slightly separated by back flushing under an elevated pressure in such a way that cleansing is freely effected by reverse fluid flow.

Description:
RELATED APPLICATIONS 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the filtration of contaminated water and industrial waste fluids, and to systems for filtration of finely dispersed contaminants and waste products. 
     The present application is a continuation-in-part of application Ser. No. 07/588,572, filed Sep. 21, 1990 in the name of Sohail Zaite, now abandoned. 
     2. Background of the Invention 
     There have been proposed a variety of filtration structures characterized by fluid flow radially through the porous wall of a cylindrical configuration that is established by a stack of annular wafers. These wafers generally are characterized by opposed reticulated faces that establish a radial labyrinth of passages through which the fluid can pass between the interior and exterior surfaces of the cylindrical configuration. Such prior structures typically have been constituted by disposable packaging or have been prone to clogging problems, particularly when very fine particles have been involved. 
     SUMMARY OF THE INVENTION 
     The primary object of the present invention is to provide a filtration structure characterized by fluid flow radially through the wall of a cylindrical configuration that is established by a stack of serrated annular wafers which are constrained for slight axial movement with respect to each other for the establishment of two conditions. In one condition, the wafers are axially compressed into snug contact under spring bias to establish a labyrinth of radial passages for fluid flow at a selected pressure. In the other condition, the axial compression of the disks is relieved and the disks are slightly separated by back flushing under an elevated pressure in such a way that cleansing is freely effected by reverse fluid flow. 
     Preferably, the wafers are characterized by serrations which are skewed to intersect diameters through the center of the wafer at a selected angle. Preferably a plurality of columns of such wafers operate within a tank having two chambers that are separated by a hermetic plate. The columns are located within a first chamber and feed through ports in the plate into the second chamber. The arrangement is such that radial flow occurs into the outer peripheries of the tubular configurations in the first chamber, separation of impurities occurs in the interstices between the wafers, and axial flow of cleansed effluent occurs from the interstices into the interior of the columns and thence into the second chamber. The arrangement is such also that back flushing occurs from the second chamber through the interiors of the cylindrical configurations and from their external peripheries. 
     Other objects of the present invention will in part be obvious and will in part appear hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a fuller understanding of the nature and objects of the present invention, reference is made to the following detailed description, in reference to the accompanying drawings wherein: 
     FIG. 1 is a perspective view of a water purifier embodying the present invention; 
     FIG. 2 is a broken away cross section of the purifier of FIG. 1, with parts omitted for clarity; 
     FIG. 3 is a broken away elevation of a component of the purifier of FIGS. 1 and 2; 
     FIG. 4 is a perspective view of a broken-away stacked wafer sub-assemblage of the purifier of FIGS. 1 and 2; 
     FIG. 5A is a partly broken away, enlarged detail cross-sectional view of a portion of a wafer of FIG. 4; 
     FIG. 5B is a partly broken away, enlarged detail cross-sectional view of another portion of the wafer of FIG. 4; 
     FIG. 5C is a perspective view of a fragmentary detail of the wafer of FIGS. 5A and 5B; 
     FIG. 5D is a plan view of the wafer of FIGS. 5A and 5B; 
     FIG. 5E is a broken-away plan view of FIG. 5D, enlarged to show added details; and 
     FIG. 5F is a grossly magnified, broken-away cross-section of the wafer of FIGS. 5A and 5B. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to FIGS. 1, 2, 3 and 4, the illustrated filtration unit 20 is shown as comprising a pressure vessel 22. Within this vessel are a lower chamber 24 and an upper chamber 26 which are separated by an upper plate 28. Positioned near the bottom of lower chamber 24 is a lower plate 30 which is hung from and secured to upper plate 28 by tie rods 32. Tie rods 32 have threaded extremities on which are turned suitable hex nuts 34. Extending between the plates are a series of paraxial tubular, filtration columns 36, each of which is constituted by a stack of thin, annular, plastic wafers 37. The opposite faces of the wafers are serrated in a manner to be described more specifically below. 
     As shown in FIG. 4, the inner profiles of these wafers snugly fit onto a vertical guide 38 that consists of three rigid planar ribs 40, 42 and 44 which are equiangularly disposed. In other words, in cross section, adjacent ribs are angularly spaced at 120° with respect to each other. The lower extremity of each vertical guide 38 is affixed by bonding or welding to a collar 46. The upper extremity of each vertical guide snugly extends through an opening in upper plate 28. Extending downwardly from collar 46 is a pin 48 which projects through and is reciprocable within an opening 50 in lower plate 30. A helical spring 52 envelops pin 48 and is compressed between collar 46 and lower plate 30. 
     The arrangement is such that an aqueous flow into lower chamber 24 through an entrance port 54 permeates each column 36 peripherally, and deposits any dispersed particles in the interstices defined by the serrations at the surfaces of the wafers. This flow continues into the interior of column 36, upwardly into upper chamber 26, and outwardly from exit port 56. The system is cleansed by backwashing through a flush port 58 at an elevated pressure which causes the wafers to separate against the bias of spring 52 and the particulate agglomeration at the faces of the wafers to dislodge for flushing through an outlet. A drain 60 is provided at the bottom of vessel 22 for residual sludge and the like. 
     EXAMPLE 
     The geometry of the wafers are shown in FIGS. 5A to 5F. As indicated above compressed stacks of these wafers constitute tubular filtering elements that are critical to the present invention. These wafers are manufactured to very tightly controlled tolerances. 
     As shown in FIGS. 5A and 5B, dimensions 10A and 10B (0.00322 and 0.00995) are the passage widths at the inlet and outlet diameters, respectively. Dimensions 11A and 11B (0.00252 and 0.00602) are the passage depths at the inlet and outlet diameters, respectively. As shown in FIG. 5C, dimensions 10C and 11C (0.00425 and 0.00509) are the landing widths at the inlet and outlet diameters, respectively. As shown in FIG. 5E, the passages are equally distributed on the annular area surfaces at an angle 11E (18° to 28° ) with respect to a diameter line through the center of the wafer. As shown in FIGS. 5A and 5B, the passages define equilateral, triangular, cross-sectional contours. The passages are molded into both faces of the wafer, which has a thickness of from 0.020 to 0.040 inch. Preferably, the wafers are composed of a high density polymer, particularly, a high density polypropylene, polycarbonate, fluoropolymer, nylon, kadel or radel. 
     In one example of the illustrated embodiment, each wafer is 0.032 inch thick and has an outer diameter of 1.375 inches and an inner diameter of 1 inch. The vessel is approximately 19 inches in diameter. The wafer columns include several hundred randomly oriented wafers each and the guides are approximately 20 inches long. 
     Reticulation sizes are the critical factor in determining the largest particle allowed to pass. Hence, the smaller the reticulation size, the higher the filtering effect. With reference to FIGS. 5A to 5F, filtering effects of 10 micron, 20 micron, 30 micron and 40 micron are shown below. Columns, in various embodiments, have different numbers of elements, which correspond to the rate of flow required. Table 1 shows flow rates corresponding to various numbers of columns, elements and vessel sizes. 
     
                       TABLE I______________________________________FLOW RATE M.sup.3 /HR.NO. OF NO. OF                             VESSELCOL-   ELE-     10      20    30    40    DIA.UMNS   MENTS    MIC.    MIC.  MIC.  MIC.  (in.)______________________________________ 1     300       2       5       7.5                                10    4 3     500       5        12.5                           18.5                                25    6 6     300      12       30    45    60   10 6     500      20       50    75   100   1012     300      25       60    90   120   1212     500      35       90   135   180   1218     500      60      150   225   300   1436     400      90      225   337   450   1636     500      115     300   450   600   1660     400      150     400   600   800   2060     500      200     500   750   1000  20______________________________________ 
    
     OPERATION 
     Operation is as follows in reference to pressure vessel 20, service inlet valve 54, product outlet valve 56, drain valve 60, backflush inlet valve 58, backflush outlet valve 59, and pressure gauges (not shown). Liquid to be filtered enters the vessel at a pressure of 40-100 psi. By virtue of this pressure, the liquid is forced through the wafer interstices and through their interiors to the outlet chamber. Helical spring 52 is sufficiently strong to maintain tight contact. between the wafer when the liquid is at this pressure. This portion of the operation continues until the differential pressure between the inlet and outlet chamber exceeds 20 psi. At this point, a backwash cycle begins. Backwashing is carried out manually or automatically. In the automatic mode, an initiation signal from differential pressure switches at the inlet and outlet valve activates the sequence of operations shown below in Table II. 
     
                                           TABLE II__________________________________________________________________________                                      DURATIONSTEP    OPERATION       INLET            OUTLET                  AIR VENT                         BACK FLUSH                                 DRAIN                                      (mins.)__________________________________________________________________________1   Preparation       OPEN CLOSE OPEN   CLOSE   CLOSE2   Service OPEN OPEN  CLOSE  CLOSE   CLOSE3   Backwash       CLOSE            CLOSE CLOSE  OPEN    OPEN 2.04   Rinse   OPEN CLOSE CLOSE  CLOSE   CLOSE                                      0.5__________________________________________________________________________ 
    
     To ensure that the backwash cycle is initiated and completed, a control panel (not shown) annunciates the following: (1) indicator light illuminates showing high delta in pressure; (2) delayed flushing operation resumes after allowing the closure of valves 54, 56 and 60; (3) cycle indicator light (BACKWASH-ON) illuminates and remains &#34;ON&#34; during the timed cycle (0-2 minutes); (4) when backwash cycle ends, a delayed step takes place (RINSE CYCLE); (5) indicator light goes on while valves are changing status; (6) after 0.5 minutes of rinse cycle, the system returns to service cycle. 
     In the manual mode operation, the above sequences are carried out by an operator through the initiation of system shutdown and hand operation of the various valves in a sequence analagous to the one described above. 
     The present invention thus provides a unique design of a filtering element made from polypropylene, polycarbonate, flouropolymer, nylon, kadel or radel having specially designed passageways which act as a filtering labyrinth when stacked on top of each other. These passageways are sized for filter ratings of 10 micron, 20 micron, 30 micron and 40 micron. The filter system has a unique spring loading effect which allows successful backwash of the filtering elements. Backwashing: for a 10 micron rating is characterized by flow rates varying from 2 M 3  /Hr to 200 M 3  /Hr; for a 20 micron rating is characterized by rates varying from 5 M 3  /Hr to 500 3  /Hr; for a 30 micron rating is characterized by flow rates varying from 7.5 M 3  /Hr to 750 M 3  /Hr; and for a 40 micron rating is characterized by flow rates varying from 10 M 3  /Hr to 1000 M 3  /Hr.