Abstract:
A sludge filter is comprised of a mesh filter media secured to a support net. The support net includes a front surface adjacent the filter media and a rear surface opposite the filter media, the rear surface having a plurality of outwardly extending nodes to define flow channels for horizontal and vertical fluid flow intermediate the net and a container surface. The sludge filter is attached directly to the walls or floor of a container. In a preferred embodiment a border of the sludge filter comprises one part of a two-part fastener system with a second part of the two-part fastener system attached to a container along the perimeter of the filter coverage area, so that the filter medium may be removably attached to the container.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   Not Applicable. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not Applicable. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates generally to sludge filtration systems for separating sludge solids from sludge liquids. More specifically, this invention relates to a filter for use in a container, designed for sludge filtration. 
   2. Description of the Related Art 
   The separation of sludge solids from sludge liquid is commonly practiced as an initial step in disposing of waste sludge. Generally, sludge includes, among other things, solid-liquid sludge and slurries such as sewage and industrial waste. 
   When treating sludge, it is desirable to separate the sludge liquids from the sludge solids for further treatment or recovery or disposal of the solids and liquids separately. A typical filtering system involves a container having filter systems arranged around the container walls and the container floor. Such systems commonly involve a metal, plastic, polypropylene or vinyl liquid-permeable filter mesh with openings such that particulates above a predetermined size do not pass through the filter. Due to the weight of sludge, such filtering systems include a support structure for the filter. The support structure is often comprised of a perforated plate or expanded metal plate. The filter media may be attached to the support structure by retention bars. An opening is typically provided intermediate the support structure and the container wall to provide for drainage of the sludge liquids. Due to the expense of disposable filters, it is desirable that the filter media be relatively strong. 
   Due to clogging effects of sludge containing small particulates, it is desirable that the filter media be removable for cleaning or replacement. As a result, prior art systems commonly use retainer bars to hold the filters and perforated plate in place. The retainer bars are typically bolted to the support structure. Removal of the filters for washing involves removing the retainer bars. Replacement of the filters involves aligning openings in the filters, perforated plate and support structure. For a large sludge container, such as a commonly practiced roll on roll off container, the weight of the plate and filters increases the difficulty of removal and replacement. 
   In a typical prior art sludge-dewatering container, the combined width of a support structure and filter is in the range of three inches (˜7.5 cm) to six inches (˜15 cm). Such prior art filters extend within the container and reduce the volume of sludge that can be processed by the container. 
   This Applicant&#39;s U.S. Pat. No. 5,681,460 teaches a selectively removable sludge filtration system that provides for retrofit into a container and separation of the sludge solids from the sludge liquids therein. This Applicant&#39;s U.S. Pat. No. 6,146,528 teaches removable filter assemblies for containers that enable thorough and efficient cleaning of the filter system. U.S. Pat. Nos. 4,929,353 and 5,589,081, issued to Harris, disclose basket-like filter structures. U.S. Pat. No. 4,929,353 teaches a filter that is placed in an existing structure, and is held in place with the weight of the sludge independent any fastening system. U.S. Pat. No. 5,589,081 teaches a removable filter that relies on the hydrostatic pressure created by the mass of sludge to force positive flow of sludge liquids out the drains found in the collection container. 
   Multiple layer structures for filtering are known in the art. Such filters often comprise a filter media with a support backing to provide lateral rigidity to the filter media. U.S. Pat. No. 5,776,567 to Schilling, et al. teaches a disposable multi-layer filter for separating solid and liquid wastes. U.S. Pat. No. 5,098,364 to Schilling, U.S. Pat. No. 5,110,005 to Schilling, U.S. Pat. No. 5,741,208 to Moak and U.S. Pat. No. 4,385,953 to Beck each teach liners for waste containers. U.S. Pat. No. 5,131,709 to Spica teaches a cargo bed liner system utilizing a plurality of grid-like modules. 
   It would be an improvement to the art to provide a re-usable sludge filter that does not require a perforated plate, expanded metal or like support structure and that optimizes use of the interior space of a container for sludge filtration. 
   BRIEF SUMMARY OF THE INVENTION 
   Accordingly, the objects of my invention is to provide, inter alia, a sludge filtration system that: 
   minimizes interior container space required for the filter; 
   is attachable to the interior surface of a container; 
   is removable for periodic cleaning; 
   can be adapted to suit various container shapes and sizes; and 
   may be readily removed and replaced. 
   Other objects of my invention will become evident throughout the reading of this application. 
   To fulfill such objectives, my invention is a sludge filter comprised of a mesh filter media secured to a support net. The support net includes a front surface adjacent the filter media and a textured rear surface opposite the filter media. The sludge filter is attached directly to the walls or floor of a container. In a preferred embodiment a border of the sludge filter comprises one part of a two-part fastener system with a second part of the two-part fastener system attached to a container along the perimeter of the filter coverage area, so that the filter medium may be removably attached to a container. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a partially cut-away side view of an embodiment of the present system. 
       FIG. 2  is a perspective top view of the container of  FIG. 1 . 
       FIG. 3  is a cross-sectional view of the sludge filter. 
       FIG. 4  is a perspective view of a support net. 
       FIG. 5  is a cross-sectional view of the sludge filter disposed in a typical rectangular container. 
       FIG. 6  is a cross-sectional view of the sludge filter disposed in a container and including a vertical center filter panel. 
       FIG. 7  is a cross-sectional view of the sludge filter disposed in a typical rectangular container. 
   

   DESCRIPTION OF THE INVENTION 
   Referring to  FIGS. 1 and 2 , a sludge filter  10  of the present invention is depicted installed in a typical sludge container  30 . Referring to  FIGS. 1 and 2 , a typical container  30  includes a container floor  32 , opposed sidewalls  31 , a rear wall  36 , and a front wall  38 . The container floor  32 , sidewalls  32 , rear wall  36  and front wall  38  are sometimes referred to herein as container  30  surfaces. The top  34  is typically open to receive sludge. A cover, not shown, may be provided. 
   Referring to  FIG. 3 , in a cross-sectional view of the sludge filter  10 , the sludge filter  10  comprises a filter media  24  and a net  26 . In a preferred embodiment, filter media  24  comprises a planar mesh having multiple water-permeable openings extending transversely through the media  24 . A preferred material of filter media  24  is a pliable polypropylene, nylon, polyester or wire mesh material. 
   The openings in filter media  24  may be determined in relation to the maximum size of particulate matter that is acceptable to pass through the filter media  24 . 
   Referring to  FIG. 4 , net  26  comprises a generally planar material. Net  26  has perforations  42  transversely through the net  26 . The perforations  42  of net  26  are relatively large in comparison to the openings (not shown) of media  24  as net  26  is intended as a support and spacing structure and not as a filtering medium. Net  26  material comprises a relatively rigid material having some flexibility such as polypropylene, nylon, polyester or metal. The net  26  material resists compression in the transverse direction yet is bendable along the plane of the material. 
   Referring to  FIG. 3 , net  26  has a front surface  77  and a rear surface  79 . In the preferred embodiment, rear surface  79  has a pattern of indented sections  74  and extended nodes  76  relative to the plane of the net  26 . Front surface  77  may include a pattern of indented sections  70  and extended nodes  72  relative to the plane of the net  26 . For purposes of the sludge filter  10 , it is necessary that the rear surface  79  include indented sections  74  and extended nodes  76  to allow flow of filtered sludge liquids between rear surface  79  and container wall surface inner surface  37 . 
   The nodes  76  and indented sections  74  of net rear surface  79  create flow channels  64  intermediate rear surface  79  and wall surface  37 . As the nodes  76  and indented sections  74  extend laterally as well as vertically, the nodes  76  and indented sections  74  create multiple, interconnected fluid flow channels  64  intermediate rear surface  79  and wall surface  37 , such fluid flow channels  64  allowing liquid flow horizontally and vertically. 
   The nodes  72  and indented sections  70  of net front surface  77  create flow channels  62  intermediate front surface  77  and filter media  24 . As the nodes  72  and indented sections  70  extend laterally as well as vertically, the nodes  72  and indented sections  70  create multiple, interconnected fluid flow channels  62  intermediate front surface  77  and filter media  24 , such fluid flow channels  62  allowing liquid flow horizontally and vertically. 
   Referring to  FIG. 3 , a thread  21  representing attachment of media  24  to net  26  is depicted. Thread  21  is one of a plurality of threads connection media  24  and net  26 . 
   The depiction of rear wall  36  and inner wall surface  37  in  FIG. 3  is typical of a view of sludge filter  10  attached to any wall, floor or support plate of container  30 . 
   Referring to  FIG. 4 , a form of net  26  is depicted with the back surface  79  up. A plurality of nodes  76  are defined at intersecting net members  75 . The indented sections  74  are defined by the net members  75  intermediate nodes  76 . 
   In the preferred embodiment sheets of net  26  and filter media  24  are attached. A preferred method of attachment comprises placing a sheet of net  26  adjacent a sheet of filter media  24  and sewing the net  26  and filter media  24  together with sewn lines (partially represented by thread  21 ) extending around the perimeter of the sheets and, for large sheets, extending transversely at regular intervals. For appropriate sizes of net  26  and filter media  24 , commercially available sewing machines may be utilized to attach filter media  24  and net  26 . Alternatively, filter media  24  and net  26  may be attached by staples, glue or a thermal bonding process. In a typical installation, the thickness of net  26  is less than 0.5 inches (˜1.25 cm) and the thickness of filter media  24  is less than 0.4 inches (˜1.0 cm). 
   Referring to  FIGS. 1 ,  3 ,  5 ,  6  and  7 , in positioning sludge filter  10  in container  30 , net  26  is intermediate filter media  24  and an inner surface  37  of container wall  36 . In such position, sludge (not shown) introduced into container  30  will be disposed proximate surface  23  of filter media  24 . Accordingly, sludge liquids will pass through filter media  24  under pressure of gravity and the mass of the sludge and sludge solids (above a predetermined particle size) will not pass through filter media  24 . 
   In a preferred embodiment, container  30  is provided with a drain cavity  66  defined by rear wall  36 , sidewalls  31 , floor  32  and a cavity grate  52 . Cavity grate  52  is positioned within container  30 , adjacent to floor  32 , and is constructed out of a sturdy perforated material resistant to deformation under the weight of a container full of sludge. In an exemplary embodiment cavity grate is formed from perforated metal. Preferably, drain cavity  66  is positioned at the lowest section of container  30 . A drain  50  extends through sidewall  31 . Drain  50  is connectable to a drain line (not shown). The drain line typically is connectable at drain  50  and includes a valve for controlled release of sludge liquids for transmittal for disposal or further processing. Drain  50  may be located in floor  32  or rear wall  36  as desired depending on the orientation of the container  30 . 
   Referring to  FIG. 3 , in the preferred embodiment, sludge filter  10  is removably attached to container  30  by a two-part fastener system  28  extending around the perimeter of the sludge filter  10 . An exemplary embodiment uses a hook and loop fastener system (e.g., a Velcro® type fastener—Velcro® is a registered trademark of Velcro Industries B.V.) for fastener system  28 . A first fastener component  27  of the hook and loop fastener system is bonded to the interior surface  37  of container  30 . A second fastener component  29  is attached to filter media  24 . 
   In an exemplary embodiment, the net  26  is sized with smaller lateral dimensions than the filter media  24  sheet leaving a peripheral segment of filter media  24  extending around the sludge filter  10  outside net  26 . The fastener component  29  is attached to the filter media  24  at such peripheral segment. This allows the thickness around the perimeter of the sludge filter  10  to be the sum of the thickness of the filter media  24 , first fastener component  27  and second fastener component  29 . 
   First fastener portion  27  is attached to the inner surfaces  37  of container  30  along the perimeter of container  30  onto which sludge filter  10  is to be mounted. In the embodiment of  FIGS. 1 and 2 , the sections of container  30  onto which sludge filter  10  is to be mounted include rear wall  36 , cavity grate  52 , floor  32  and front wall  38 . 
   In the case of sections of container  30  that are proximate to container top  34 , a protective bar  81  may be attached to container  30 . Protective bar  81  prevents sludge (not shown) from dislodging the upper edges of second fastener component  29  from first fastener component  27 . 
   Alternatively, the sludge filter  10  may be attached to the container  30  by a plurality of retainer bars (not shown), such bars bolted, or otherwise fixed to said container. Alternatively, the sludge filter  10  may be attached to the container  30  by a plurality of washers (not shown) held in place by screws or bolts (not shown). The use of retainer bars, bolts and washers is known in the art for attaching prior art filters to a container  30 , and may be readily adapted for use with the filter  10  of the present invention. 
   Referring to  FIGS. 1 ,  3  and  4 , when sludge (not shown) is deposited in container  30 , sludge is disposed against sludge filter  10  in contact with filter media  24 . Filter media  24  permits that passage of sludge liquids, while impeding the passage of sludge solids (not shown) of a predetermined size based on perforation size in filter media  24 . Sludge liquids that pass through filter media  24  flow through perforations  42  of net  26  and through the various openings defined by indented sections  74  and rear wall surface  37 . In like manner, sludge liquids would flow through channels  64  between indented sections  74  and the inner surface (not show) of front wall  38  and floor  32 . As indented sections  74  allow vertical and horizontal flow intermediate rear surface  79  and inner rear wall surface  37 , the liquids eventually gravity-flow downward to drain cavity  66 . In a net  26  having nodes  72  and indentations  70  of net front surface  77 , liquids additionally flow through channels  62  intermediate net front surface  77  and filter media  24 . 
   In a preferred embodiment, sludge liquids are collected in drain cavity  66 . Drain  50  is selectively opened to permit the evacuation of sludge liquids from drain cavity  66 . Drain  50  is located in floor  32  in the embodiment of  FIG. 1 . Drain  50  may comprise a plurality of drains and may be located, as appropriate in floor  32  or in a rear, side or front wall of container  30  as appropriate. 
   After sludge liquids are separated from sludge solids, and sludge solids are removed from container  30 , sludge filter  10  may be removed from container  30  by separating first fastener component  27  and second fastener component  29  of two-part fastener system  28  and pulling sludge filter  10  from container  30 . Sludge filter  10  may be cleaned, inspected and repaired, then re-inserted into container  30  for subsequent use. 
   Referring now to  FIG. 5 , the sludge filter  10  of the present invention is depicted in a typical rectangular container  130 . Container  130  includes a container floor  132 , opposed sidewalls  131 , a rear wall  136 , and a front wall (not shown). The top container surface  134  is typically open to receive sludge. A cover, not shown, may be provided which seals container at top surface of  134 . 
   Container  130  is provided with two drain cavities  166 , each defined by rear wall  136 , sidewalls  131 , floor  132  and a cavity grate  152 . If applicable, an end (not shown) of each drain cavity  166  is defined by a front wall (not shown). In practice, the front wall of container  130  comprises a gate that may be selectively opened. Accordingly, a partition (not shown) defines a front wall of the drain cavity  166 . 
   Each cavity grate  152  is positioned within container  130  adjacent to floor  132 , and is constructed out of a sturdy perforated material. Preferably, each drain cavity  166  is positioned at the lowest section of container  130 . A drain  150  extends through floor  132  at each drain cavity  166 . Each drain  150  may be connected to manifold line  151 . Manifold drain line  151  is typically connected at drains  150  and includes a valve  153  for controlled release of sludge liquids for transmittal for disposal or further processing. Drains  150  may be alternatively located in sidewalls  131  or rear wall  136  as desired. A plurality of drains  150  may be provided for each drain cavity  166 . A plurality of manifold drain lines  151  may be provided. 
   In the embodiment of  FIG. 5 , filter media  24  and net  26  are depicted arranged along sidewalls  131  and rear wall  136 . Sludge liquids (not shown) migrate horizontally and vertically intermediate filter media  24  and sidewalls  131  and rear wall  136  as previously described herein. A drain cavity may be provided along rear wall  136 . However, a drain cavity is not required if the sludge filter  10  positioned on rear wall  136  is in fluid communication with drain cavities  166 . Alternatively, the sludge filter  10  may be disposed only along sidewalls  131 . 
   As in the embodiment of  FIGS. 1 ,  2  and  3 , sludge filter  10  is removably attached to container  130  by a two part fastener system  28  extending around the perimeter of the sludge filter  10  with first fastener portion  27  of a hook and loop fastener system bonded to the interior surface of container  30  as a first fastener component  27  and the fastener component  29  attached to filter media  24 . A protective bar  81  is attached to container  30  at the upper edge of sludge filter  10  to prevent sludge (not shown) from dislodging the upper edges of fastener component  29  from first fastener component  27 . 
   Referring now to  FIG. 6 , the sludge filter  10  of the present invention is depicted in a typical rectangular container  130  together with a center filter section  200 . Container  130  includes a container floor  132 , opposed sidewalls  131 , a rear wall  136  and a front wall (not shown). Container  130  is provided with four drain cavities  166 . The drain cavities adjacent sidewalls  131  are each defined by rear wall  136 , sidewalls  131 , floor  132 , a cavity grate  152  and a front wall (not shown) or partition (not shown) as described in relation to  FIG. 5 . 
   The center filter section  200  includes a vertical support plate  202 . Support plate  202  extends vertically upward from floor  132 . A sludge filter  10  is attached to each side of support plate  202  in the manner of attachment of sludge filter  10  to container  130  side walls  131  as described in relation to  FIGS. 1 ,  2  and  5 . Accordingly, center filter section  200  provides additional filter capacity within container  130 . Drain cavities  166  of center filter section  200  are each defined by rear wall  136 , support plate  202 , floor  132 , a cavity grate  152  and a front wall (not shown) or partition (not shown). A plurality of apertures  204  may be provided in support plate  202  to provide fluid communication through support plate  202 . 
   A drain  150  extends through floor  132  at each drain cavity  166 . Each drain  150  may be connected to a manifold drain line  151 . Each manifold drain line  151  typically is connected at drain  150  and includes a valve  153  for controlled release of sludge liquids for transmittal for disposal or further processing. A plug (not shown) may be provided in lieu of valve  153 . A plurality of drains  150  may be provided for each drain cavity  166 . A plurality of manifold drain lines  151  may be provided. 
   In the embodiment of  FIG. 6 , sludge filter  10  is depicted arranged along sidewalls  131  and support plate  202 . Sludge liquids (not shown) migrate horizontally and vertically intermediate filter media  24  and sidewalls  131  and intermediate filter media  24  and support plate  202  as previously described herein. 
   As in the embodiment of  FIGS. 1 ,  2 ,  3  and  5 , sludge filter  10  is removably attached to container  130  by a two part fastener system  28  extending around the perimeter of the sludge filter  10  with first fastener portion  27  of a hook and loop fastener system bonded to the interior surface of container  131  as a first fastener component  27  and the fastener component  29  attached to filter media  24 . A protective bar  81  is attached to container  131  at the upper edge of sludge filter  10  to prevent sludge (not shown) from dislodging the upper edges of fastener component  29  from first fastener component  27 . 
   Referring to  FIG. 7 , sludge filter  10  is depicted arranged along sidewalls  131 . The embodiment of  FIG. 7  does not include a support plate or a defined drain cavity  166 . In the embodiment of  FIG. 7 , drains  150  extend through floor  132  and sidewall  131  proximate floor  132 . Each drain  150  may be connected to a manifold drain line  151 . Each manifold drain line  151  typically is connected at drain  150  and includes a valve  153  for controlled release of sludge liquids for transmittal for disposal or further processing. A plug (not shown) may be provided in lieu of valve  153 . A plurality of drains  150  may be provided for each drain cavity  166 . A plurality of manifold drain lines  151  may be provided. 
   Sludge liquids (not shown) migrate horizontally and vertically intermediate filter media  24  and sidewalls  131  and intermediate filter media  24  as previously described herein. 
   As in the embodiment of  FIGS. 1 ,  2 ,  3  and  5 , sludge filter  10  is removably attached to container  130  by a two part fastener system  28  extending around the perimeter of the sludge filter  10  with first fastener portion  27  of a hook and loop fastener system bonded to the interior surface of container  131  as a first fastener component  27  and the fastener component  29  attached to filter media  24 . 
   The foregoing disclosure and description of the invention is illustrative and explanatory thereof. Various changes in the details of the illustrated construction may be made within the scope of the appended claims without departing from the spirit of the invention. The present invention should only be limited by the following claims and their legal equivalents.