Abstract:
A filter apparatus separates fine particles such as pine needles, threads, hairs and seeds from a liquid influent. A rotating grid assembly has multiple grid sections mounted by top-to-bottom connected links, supporting a filter media having specified openings sufficient for entrainment of miniscule particles. Grid sections are interchanged for collection and discharge of various sized particles using the same apparatus.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to a grid assembly for filtering particles from water or other liquid mixtures for which filtering a volume of 100 gallons per minute up to 100 million gallons a day is needed. More particularly, it refers to an improved filtering apparatus with replaceable grids for filtering large volumes of liquid influent.  
       BACKGROUND OF THE INVENTION  
       [0002]     Prior art of U.S. Pat. No. 4,812,231, owned by this assignee, has resulted in improvement of removing solid particles from a liquid influent by providing a cost effective apparatus, utilizing a rotating filter assembly with a flushing device mounted so as to discharge the debris that accumulates, greatly decreasing the need for manpower with respect to cleaning and removal of the unwanted particles. U.S. Pat. No. 5,102,536, an improvement over the rotating filter assembly, further improved the removal of solid particles from liquid influents by utilizing a projecting foot on link members mounted on the rotating filter so as to complete the break up of solids, such as fecal matter, that were not always broken up and discharged by the prior art assemblies. Further prior art of U.S. Pat. No. 6,177,020 and U.S. Pat. No. 6,669,854, also owned by this assignee, describes an alternative means of filtering waste streams containing solids by the use of a stepping screen assembly with a grid structure of bars. Multiple parallel alternate static and dynamic bars are driven by a pneumatic cylinder, lifting solids out of a liquid waste stream. Each bar has multiple vertically spaced apart shelves at a right angle to the vertical axis of the bar. The solid material moves upwards and over the top of the grid structure to fall by gravity onto a conveyor for delivery of the solids to a waste receptacle while the liquid moves through the grid structure without impediment.  
         [0003]     Though these inventions provide an improvement over prior filtering methods, unwanted particles such as pine needles, textile threads, hair, seeds and other similarly sized debris are not removed using the present methods found in the prior art. These miniscule particles fall back into the filtered liquid influent. The mesh screens found in current filter assemblies cannot be supported if the openings are less than two millimeters in diameter. Miniscule particles such as pine needles, textile threads, hair or seeds are, therefore, not filtered by current screen assemblies. In addition, the assemblies for collection and discharge of large sized debris cannot be used for removal of smaller particles and vice versa, as the filter grids are not easily interchangeable. An improvement is needed that will support grids with smaller openings, allowing removal of these smaller unwanted particles in an efficient and cost effective manner, while still allowing interchangeability of filter grids to allow for easy maintenance and variation in the grid opening size within the same apparatus.  
       SUMMARY OF THE INVENTION  
       [0004]     The present invention overcomes the problem of smaller particles passing through openings of the grids of filtering assemblies in the prior art, while at the same time allowing interchangeable grids for a cost effective means of removing all solids from liquid influents.  
         [0005]     The invention is directed to an improved filter grid section, utilizing links having a slot opening of length sufficient to accommodate insertion of filter media grids having specified openings, within the slot opening in each link. The additional support provided by the links encasing the grid sections allows for the use of a filter media of stainless steel cloth, polymer mesh, perforated stainless steel plates or an equivalent, having grid openings of less than two millimeters in diameter. In particular, the present invention allows stainless steel cloth, or alternatively polymer mesh or perforated stainless steel plate, with openings as small as 0.25 millimeters in diameter, to be used as a filter grid for removal of unwanted particles. The grid is supported by links; the longitudinally connected links support a filter grid assembly for entraining miniscule debris particles on the filter media and on the surface of the links to be carried upward as the links rotate. The particles are unloaded and discharged from the filter grid during the rotation of the system. Furthermore, the grid sections may be interchanged with grid sections having different sized openings for versatility within the same filter apparatus. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     The invention is best understood by those having ordinary skill in the art by reference to the following detailed description when considered in conjunction with the accompanying drawings in which:  
         [0007]      FIG. 1  is a perspective view of three grid sections of a grid assembly with openings in a filter media of polymer mesh or stainless steel cloth.  
         [0008]      FIG. 2  is an exploded view of the three grid sections viewed in  FIG. 1 .  
         [0009]      FIG. 3  is an exploded view of one of the grid sections viewed in  FIG. 2  showing the outer frames and inner filter media of a grid section.  
         [0010]      FIG. 4  is a perspective view showing three grid sections of a grid assembly, as seen in  FIG. 1  with a catch shelf attached to the protruding spikes on two of the grid sections.  
         [0011]      FIG. 5  is a perspective view showing three grid sections of a grid assembly, as seen in  FIG. 1  with an end cap located between each drive element and corresponding grid section.  
         [0012]      FIG. 6  is an exploded view of the three drive elements with end caps, as shown in  FIG. 5 .  
         [0013]      FIG. 7  is a perspective view of the apparatus containing the grid assembly positioned in a stream in one embodiment of the invention.  
         [0014]      FIG. 8  is an exploded view of the apparatus shown in  FIG. 7  with the cover plate removed and showing a grid assembly.  
         [0015]      FIG. 9  is an exploded view showing two grid assemblies side by side.  
         [0016]      FIG. 10  is a perspective view of the grid assembly in an alternate frame structure.  
         [0017]      FIG. 11  is an exploded view of the structure shown in  FIG. 10  with the cover plate removed and showing a grid assembly.  
         [0018]      FIG. 12  is an exploded view showing two grid assemblies side by side in the frame structure of  FIG. 10 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]     Throughout the following detailed description, the same reference numerals refer to the same elements in all figures.  
         [0020]     Referring to  FIGS. 1 and 2 , the improved filter grid assembly  10  is formed by multiple grid sections  12 , each grid section  12  supported by links  14  of stainless steel, or alternatively a suitable alloy or a polymer, each link mounted vertically on grid shafts  16  which fit through bore holes  18  on each end of individual links  14 . The grid shafts  16  are preferably made of stainless steel and connect the links  14  to drive elements  20  on each side of the grid sections  12 . Spikes  22 , protruding outwardly from some or all links  14 , entrain additional debris for discharge.  
         [0021]     Each link  14  contains a slot  24  through which a grid section  12  is inserted as shown in  FIG. 2 . A link washer  26 , made from a polymer, is placed between the links  14  for reduction of friction while a link spacer  28 , made from a polymer, is placed between links  14  to accommodate variation in space between links  14  on each grid section  12 . The range of space between links  14  is ½ inch to five inches with about three inches preferred.  
         [0022]     As shown in  FIG. 2 , each grid section  12  is capped on each side by a gear tooth engaging drive element  20 . The drive elements  20  are preferably made of a high strength polymer with a means for fastening  30 , such as a cotter pin, nut, snap pin or other known fastener, and a washer  32 , made from stainless steel or alternatively a suitable alloy, placed at each end of grid shaft  16  to secure the drive element  20  in place adjacent each grid section  12 . Each drive element  20  has an outside surface  34  and an inside surface  36  containing a notch  38 , shown in  FIGS. 1 &amp; 4 . A first end portion  40  and a second end portion  42  of the drive element  20  is located on each side of the notch  38 . The end portions  40  and  42  have a recess  44  in the drive element  20 . A through bore  46  is located at the center of each recess  44  for insertion of the grid shaft  16  ends  48 . The drive element  20  forms an endless elliptical loop that is the grid assemblies  10  and  10   a , shown in  FIGS. 8 and 11 . In one embodiment, an end cap  49  is located between a drive element  20  and a grid section  12  as shown in  FIGS. 5 and 6 . The end cap  49  further prevents smaller debris from falling between the drive element  20  and grid section  12 .  
         [0023]     Referring to  FIG. 3 , each grid section  12  is formed of two grid section frames  50  and  51  with filter media  52  of stainless steel cloth or polymer mesh encased between the two grid section frames  50  and  51 . The grid section frames  50  and  51  are preferably made of stainless steel. The perimeter  54  of the frames  50  and  51  is joined with multiple vertical bars  58 . The perimeter  54  and the vertical bars  58  fit through the link slots  24 . The filter media  52  is made preferably of stainless steel cloth, or alternatively of polymer mesh or perforated stainless steel plate, with openings  60  ranging from 0.25 mm to 25 mm in diameter; preferably of one millimeter for entrapment of small particles, i.e. pine needles, textile threads, hair, seeds. Alternatively, filter media  52  with openings  60  at the larger end of the range are interchanged within the same grid section  12  for removal of larger debris. Grid sections  12  range in vertical height from four to twelve inches, with six inches preferred. The range of space between vertical bars  58 , and subsequently between links  14  on each grid section  12 , is ½ inch to five inches with three inches preferred.  
         [0024]     Debris contained within the influent, whether particles larger than 0.5 millimeters or smaller, i.e. pine needles, textile threads, hair, seeds, are entrained on the surface of the grid sections  12 . Links  14 , with the spikes  22 , capture larger particles. In one embodiment, one or more catch shelves  62  attached to the spikes  22  as shown in  FIG. 4  are used to entrain larger particles. One or more adjacent grid assemblies  10  or  10   a , are used in a filter apparatus  106  or  106   a . Two grid assemblies  10  are shown in  FIG. 9  and two grid assemblies  10   a  are shown in  FIG. 12 . Additional grid assemblies  10  or  10   a  can be added.  
         [0025]     The filter grid sections  12  mounted in supporting housing frame  64  have the protruding spikes  22  of the links  14  facing inwardly as shown in  FIGS. 7, 8  and  9 . Alternatively, the filter grid sections  12  are mounted in a supporting housing frame  65  having the protruding spikes  22  of the links  14  facing outwardly as shown in  FIGS. 10, 11  and  12 . In each embodiment of the filter apparatus  106  and  106   a  shown in  FIGS. 7 and 10 , the housing frame  64  or  65  is placed in a tank or channel  66  of influent. Two weirs  68 , shown in  FIGS. 7-12 , are open for water flow through the grid assembly  10  or  10   a . In the embodiment shown in  FIG. 8 , a rear wall  70  deflects the influent so it exits at the bottom  72  or sides  74  of the filter apparatus  106 . Alternatively, in the embodiment shown in  FIG. 10  the grid assembly  10   a  faces the influent which flows directly through the grid assembly  10   a  and out the rear of the apparatus  106   a.    
         [0026]     The mechanical drive  76 , utilizing an electric motor  75  shown in  FIGS. 8 &amp; 11 , or alternatively hydraulic or pneumatic compression, is attached at the top of the housing  64  or  65  adjacent the top frame  78 . A discharge mechanism  80 , either a spray wash or air knife, mounted within the top frame assembly  78  unloads the unwanted debris caught between the links  14  on the rotating grid assemblies  10  and  10   a  into a discharge apparatus  84 , either a chute shown in  FIG. 7 , or alternatively a conveyor (not shown), by which the debris is carried out of the filter apparatus  106  and  106   a.    
         [0027]      FIG. 8  and  FIG. 11  show grid assemblies  10  and  10   a  engaged by a drive sprocket  86  at each side  88  of the grid assemblies  10  and  10   a . A drive gear turns the drive shaft  92  and is connected to a gear reducer  94  that is driven by the mechanical drive  76  mounted near the top of the filter apparatus  106  and  106   a . Rotation of the drive elements  20  driven by the drive shaft  92  causes the lugs  96  to engage within the notch  38  of the drive element  20  and causes each grid assembly  10  or  10   a  to turn. At least two lugs  96  are always in engagement with adjacent drive elements  20  while the grid assembly  10  or  10   a  is moving.  
         [0028]     A horizontal frame support  98  shown in  FIGS. 7-9  and  FIGS. 11-12  supports the grid assembly  10  within the apparatus  106 , while an external frame support  99  shown in  FIG. 10  supports the grid assembly  10   a  within the apparatus  106   a . In the embodiment shown in  FIG. 11 , a cleaning brush  102  sweeps the interior of the grid assembly  10   a  for self cleaning of the grid sections  12 .  
         [0029]     The above description has described specific structural details for embodiments of the invention. However, it will be within one having skill in the art to make modifications without departing from the spirit and scope of the underlying inventive concept of this filter grid assembly. The inventive concept is not limited to the structures described, but includes such modifications and equivalents within the knowledge of one having skill in the art.