Abstract:
A waste water filter has a perforated conveyor made up of a plurality of segments. Each of the segments has a shelf portion to lift trapped filtered material. Drive chains on opposite sides of the conveyor rotate the conveyor in an oblong loop. End plates on the ends of each segment have leading and trailing edges that extend at an acute angle relative to one another. Each of the end plates is rigidly mounted to a link of one of the chains. A socket mounted on a first edge of each of the segments engages a rod mounted on a second edge of an adjacent segment. Seal plates are located between the chains and the end plates. Each of the seal plates is rigidly mounted to one of the end plates and has an overlapping portion that extends alongside in sliding contact with an adjacent one of the end plates.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority to provisional application 60/561,964, filed Apr. 14, 2004. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates in general to large screen filters, and particularly to a filter that utilizes a conveyor of perforated plates with the flow entering a central area between the upward and downward runs of the conveyor.  
       BACKGROUND OF THE INVENTION  
       [0003]     Large filtration units are used by municipalities and various industries to filter material from the water. One type of filter uses a perforated conveyor having a large number of apertures. The conveyor is rotated in an oblong loop as the water flows through the conveyor. The conveyor is made up of a number of segments pivotally linked to each other. Each segment has a shelf portion that lifts filtered material trapped by the conveyor.  
         [0004]     One type of unit is oriented normal to the direction of flow. The water flows through the upward moving run of the conveyor, then the downward moving run. Another type of unit, referred to herein as a center-flow unit, is oriented with the upward and downward moving runs in planes parallel with the direction of flow. The water enters an inlet between upward and downward moving runs and flows out both runs simultaneously.  
         [0005]     In both types, chains are located on opposite ends of the segments to drive the conveyor. A variety of devices are employed to connect the segments to the chains. Different types of seal members are used to block fluid flow outward past the ends of the segments. In one type that orients normal to the flow, the unit has end plates mounted to each segment, each end plate being rigidly fastened to one of the links of the chain. That unit also has a seal plate mounted to each end plate. In that unit, the leading and trailing edges of each end plate are parallel with each other. The edges of adjacent end plates are close together on the linear portions of the conveyor and separate at the curved portions. The seal plate has a portion that overlaps an adjacent end plate to block a portion of the gap created at the curved portions. The seal plates have concave and convex edges that slidingly engage each other. While workable for a normal-to-flow filter, a conveyor with end plates and seal plates as described would not work with a center flow type filter.  
       SUMMARY OF THE INVENTION  
       [0006]     In this invention, the filter has a perforated conveyor for placement in a fluid flow to trap filtered material. The conveyor has a plurality of segments pivotally linked together, each of the segments having a shelf portion to lift trapped filtered material. A socket is mounted on a first edge of each of the segments. A rod is rigidly mounted to a second edge of each of the segments. The rod of each of the segments fits within the socket of an adjacent one of the segments to pivotally link the segments together.  
         [0007]     End plates are rigidly mounted on opposite ends of each of the segments. Each of the end plates has leading and trailing edges that extend at an acute angle relative to one another. The leading edge of each of the segments is at an acute angle relative to the trailing edge of an adjacent one of the segments while on a linear portion of the conveyor, creating a V-shaped gap. The gap closes up while the segments round the axis at each end.  
         [0008]     A plurality of seal plates located between the chains and the end plates. Each of the seal plates has a first portion rigidly mounted to one of the end plates and a second portion that overlaps with and is pivotal to an adjacent one of the end plates to block fluid flow through the V-shaped gap.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a schematic sectional view taken along the line  1 - 1  of  FIG. 2  of a center flow perforated plate filter constructed in accordance with this invention.  
         [0010]      FIG. 2  is a schematic sectional view of the filter of  FIG. 1 , taken along the line  2 - 2  of  FIG. 3 .  
         [0011]      FIG. 3  is a front view of the filter of  FIG. 1 .  
         [0012]      FIG. 4  is an enlarged partial sectional view, taken along the line  4 - 4  of  FIG. 7 , of two of the screen members and portions of the chain drive.  
         [0013]      FIG. 5  is a sectional view of one of the screen members of  FIG. 4 , taken along the line  5 - 5  of  FIG. 4  but not showing the end seal plates.  
         [0014]      FIG. 6  is an elevational view of one of the end seal plates utilized with the screen members of  FIG. 4 .  
         [0015]      FIG. 7  is a sectional view of three of the screen members as shown in  FIG. 4 , taken along the line  5 - 5 , and also showing the end seal plates.  
         [0016]      FIG. 8  is a sectional view of a portion of the conveyor, taken along the line  8 - 8  of  FIG. 7 .  
         [0017]      FIG. 9  is a view similar to  FIG. 7 , but taken at an upper turnaround of the conveyor run.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]     Referring to  FIGS. 1-3 , filter  11  is typically mounted in a flow channel  13 , but it could also be connected into a flow line. Filter  11  has a rotating conveyor  15  that has an upward run  15   a  and a downward run  15   b , shown in  FIG. 2 . While upward run  15   a  is shown on the right side in  FIG. 2 , conveyor  15  could alternately be made to rotate clockwise. A drive member  17  rotates conveyor  15 , drive member  17  preferably being a pair of chain sprockets driven by an electrical motor  19 . Drive member  17  could alternately be powered by a hydraulic or pneumatic motor. Drive member  17  could also be located on the outer side of the housing of filter  11 . Drive member  17  and motor  19  are preferably located on the upper end. A lower turn around member  21 , such as guides or sprockets, is located at the lower end. Drive member rotates conveyor  15  along an oblong path with two straight portions  15   a ,  15   b  and arcuate upper and lower ends.  
         [0019]     A pair of deflector plates  23  mounts to the forward side of filter  11 . Deflector plates  23  extend from filter  11  to the side walls of channel  13 . Deflector plates  23  converge toward each other to direct all of the flow in channel  13  into the interior of filter  11  between the two conveyor runs  15   a ,  15   b . Filter  11  has a frame or housing with a closed downstream wall  25 , forcing all of the fluid to flow simultaneously through conveyor runs  15   a ,  15   b  and trapping filtered material or filtered material on the inner sides of conveyor runs  15   a ,  15   b . Conveyor  15  is configured in a stair-step configuration. Upward run  15   a  lifts the filtered material until reaching drive member  17 , where the filtered material is dislodged, such as by brushes or downwardly directed spray nozzles  26 . The filtered material falls into a chute  27  or conveyor that delivers the filtered material from channel  13 .  FIG. 2  also discloses an access door  31  to provide access to conveyor  15 . Additionally,  FIG. 3  shows a gear reducer  29  that couples motor  19  to drive member  17  ( FIG. 2 ).  
         [0020]     Referring to  FIG. 4 , conveyor  15  is made up of a plurality of individual segments or screen members  33 . Each screen member  33  is pivotally linked to adjacent screen members  33  to make up conveyor  15 . As shown in  FIG. 5 , each screen member  33  has a lifting shelf  33   a  that rotationally leads a riser  33   b  that extends diagonally from the lifting shelf  33   a . Screen members  33  have a plurality of perforations  35  extending throughout, although only a few are shown in  FIG.4 .  
         [0021]     Referring to  FIGS. 5, 7  and  9 , in this embodiment, screen members  33  are pivotally linked and sealed to each other by a rod  37  and a socket  39  in engagement with each other. Rod  37  is mounted to one edge of each screen member  33 , which is shown in this embodiment to be the leading edge. Socket  39  is semi-cylindrical and is located on the opposite edge of each screen member  33 . Rod  37  of one screen member  33  slides into socket  39  of the adjacent screen member  33 , forming a seal. Socket  39  has a slot  41  through which the leading edge of screen  33  extends. Rod  37  could alternately be located on the trailing edge of screen member  33  and socket  39  on the leading edge.  
         [0022]     Referring to  FIGS. 5 and 7 - 9 , an end plate  43  is rigidly mounted to each end of screen  33 , preferably by welding. End plate  43  has a leading edge  45 , a trailing edge  47 , an inner edge  49 , and an outer edge  51 . In the preferred embodiment, inner edge  49  is slightly concave and outer edge  51  is straight. Leading and trailing edges  45 ,  47  are inclined to converge toward each other from outer edge  51  to inner edge  49 . An angle between two lines projecting from leading and trailing edges  45 ,  47  is acute. Cutouts are formed on leading edge  45  and trailing edge  47  to provide access to rod  37  and socket  39 . The cutouts enable rod  37  to slide from one end into socket  39 .  
         [0023]     In this embodiment, a leading hole  50  and a trailing hole  52  are located in each end plate  43 . Holes  50 ,  52  are located on a line that it is parallel to outer edge  51  and intersects rod  37  and socket  39 . Outer edge  51  is parallel to conveyor runs  15   a ,  15   b . Lifting shelf  33   a  is at an angle that is preferably slightly less than 90 degrees relative to outer edge  51  for retaining filtered material on upward conveyor run  15   a.    
         [0024]     Referring to  FIGS. 6-9 , a seal plate  53  is rigidly secured to the outer side of each end plate  43 . Seal plates  53  serve to prevent leakage of channel fluid and the passage of filtered material laterally outward through gaps between the leading and trailing edges  45 ,  47  of adjacent end plates  43 . Each seal plate  53  is preferably formed of an elastomeric material, such as ultra-high molecular weight plastic, but they could also be of metal. Each seal plate  53  has a leading edge  55  that is concave. The trailing edge has an outer portion  57   a  that is straight and an inner portion  57   b  that is concave at approximately the same radius as leading edge  55 . Seal plate  53  has an inner edge portion  59  that is straight and parallel to an outer edge  61  in this embodiment. Trailing edge outer portion  57   a  extends from trailing edge inner portion  57   b  to outer edge  61  at an angle that is about 45 degrees in this embodiment.  
         [0025]     Seal plate  53  has a leading hole  63  and a trailing hole  65  for receiving fasteners. Holes  63 ,  65  are located on a line that is parallel with outer edge  61 . A recess or cutout  67  extends from trailing edge outer portion  57   a  selected distance inward to allow pivotal movement of each seal plate  53  with the end plate  43  of an adjacent screen member  33 .  
         [0026]     Each end plate  43  has an overall axial length Le measured parallel to inner edge  51  from socket  39  to rod  37 . Each seal plate  53  has a greater overall axial length Ls measured from the junction of trailing edge portions  57   a ,  57   b  to where the inner tip of leading edge  55  extends. The curved leading and trailing edges  55  and  57   b  of adjacent seal plates  53  are closely spaced to each other to block outward flowing leakage. The transverse distance or height from inner edge  59  to outer edge  61  of each seal plate  53  is greater than the transverse distance or height from outer edge  51  to inner edge  49  of each end plate  43 . Consequently, seal plates  53  protrude inwardly more than end plates  43 , as shown in  FIGS. 7 and 9 .  
         [0027]     As illustrated in  FIG. 4 , preferably chains  69  on each end of conveyor  15  engage the sprockets of drive member  17  ( FIG. 2 ) to rotate conveyor  15 . Preferably, tension does not pass through rods  37  and sockets  39 , rather the tensional force due to movement of conveyor  15  passes through chains  69 . End plates  43  and seal plates  53  are fastened to each link of chains  69  for being pulled along conveyor runs  15   a  and  15   b . The ends of rods  37  are spaced from chains  69  by clearances and are not directly connected to chains  69 .  
         [0028]     Each seal plate  53  is mounted to a single end plate  43 , but it is axially offset so that a leading edge  45  of each end plate  43  leads the end plate  43  to which it is attached. Trailing edge  47  of each end plate  43  leads trailing edge portions  57   a ,  57   b  of its mating seal plate  53 . Each seal plate  53  overlaps in sliding engagement a substantial portion of the adjacent trailing end plate  43 .  
         [0029]     Leading hole  63  of seal plate  53  aligns with trailing hole  52  of end plate  43  for receiving a fastener that also extends through a link of chain  69 . Trailing hole  65  of seal plate  53  is aligned with rod  37  and a pin of chain  69  ( FIG. 8 ). A separate fastener or a protruding end of rod  37  locates in trailing hole  65  to prevent pivotal movement of seal plate  53  with the end plate  43  to which it is fastened. Leading hole  50  of end plate  43  does not connect to any of the seal plates  53  in this embodiment. Rather, a fastener extends from hole  50  into engagement with one side of a link of chain  69 . Cutout  67  in seal plate  53  allows arcuate pivotal movement of each seal plate  53  relative to the adjacent lagging end plates  43  as they pass over drive member  17  or lower arcuate portion  21  ( FIG. 2 ). The fastener that extends from hole  50  in the adjacent end plate  43  into engagement with chain  69  moves in cutout  67 , as can be seen by comparing  FIG. 7  and  FIG. 9 . Each end plate  43  is thus secured to a link of chain  69  by two fasteners. Each seal plate  53  is secured to one of the end plates  43  at two points.  
         [0030]     Referring to  FIGS. 7-9 , sidewall portions  71   a ,  71   b  of the housing of filter  11  extend along the outer sides of seal plates  53 . A recess for each of the chains  69  is formed between sidewall portions  71   a ,  71   b . The upper and lower portions of the outer sides of plates  53  slidingly engage frame portions  71   a ,  71   b  to prevent water and filtered material from flowing between frame portions  71   a ,  71   b  and end plates  43  into contact with chains  69 . Sidewall portions  71   a ,  71   b  are curved at the lower arcuate portion  21  and at the upper end, as shown in  FIG. 9 .  
         [0031]     In operation, the upward run  15   a  will appear as shown in  FIG. 7 . Chains  69  ( FIG. 4 ) rotate conveyor  15 , bringing filtered material up on shelves  33   a . Water enters between runs  15   a ,  15   b  ( FIG. 2 ) and flows outwardly in opposite directions through perforations  35  in screen members  33 . The engagement of rods  37  with sockets  39  prevents any significant leakage from between the individual screen members  33 . The contact of seal plates  53  with end plates  43  and housing portions  71   a ,  71   b  ( FIGS. 7 and 8 ) prevent leakage through the gaps between trailing edge  47  and leading edge  45  of each plate  43 .  
         [0032]     When going over drive member  17  or lower arcuate curved portion  21 ( FIG.2 ), the gaps between leading edge  45  and trailing edge  47  of adjacent end plates  43  close up. Leading edge  45  of one end plate  43  becomes parallel and approximately touches trailing edge  47  of the adjacent end plate  43 , as shown in  FIG. 9 . The gap between end plate edges  45 ,  47  becomes smaller in the curved portions of the conveyor. Each seal plate  53  is fixed relative to the end plate  43  to which it is attached, but pivots relative to the adjacent end plate  43 . Consequently, the curved leading and trailing edges  55  and  57   b  of the adjacent seal plates  53  slide relative to one another. The clearance is small, preventing substantial leakage.  
         [0033]     While in the upward moving run  15   a , as shown in  FIG. 7 , or the downward moving run  15   b , each seal plate  53  fully eclipses or blocks the entire gap between end plate edges  45  and  47  of adjacent end plates  43 . Similarly, while in the arcuate upper portion, shown in  FIG. 9  or the arcuate lower portion, each seal plate  53  fully eclipses or blocks the entire gap between end plate edges  45 ,  47 .  
         [0034]     The invention has significant advantages. The rod and socket linkage provides an effective seal. The connection of the end plates with the chains transfers weight to the chains rather than through the rod and socket joint. The seal plates create a labyrinth seal, effectively sealing both during the linear portions and curved portions of the conveyor.  
         [0035]     While the invention has been shown in only one of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes without departing from the scope of the invention. For example, one could also employ the rod and socket between screen members with a filter that mounts the conveyor normal to the flow.