Abstract:
A device and method for removing petroleum based contaminants from the runoff water that passes into a storm drain. The device is a filter apparatus that can be added to a storm drain. The filter apparatus consists of a filter cage that defines an open central conduit and a filter cartridge that wraps around the periphery of the filter cage. During normal rain conditions, water enters the sewer grate near the edges of the sewer grate. This water falls through the filter cartridge and is filtered. Solid debris that is mixed with the water is deflected through the central conduit and falls through the filter apparatus. During flood conditions, excess water is allowed to pass through the center conduit of the filter cage unfiltered in order to preserve the water flow capacity of the storm drain.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    In general, the present invention relates to filter devices that are contained within the confines of a storm drain. More particularly, the present invention relates to the structure of such filters and the support devices used to position such filters within the storm drain.  
           [0003]    2. Description of the Prior Art  
           [0004]    In civil engineering design, many modern streets are designed and built with storm drains. The storm drains are periodically located along the curb of the street. The street is graded in such a manner so that any water falling onto the street will flow to one of the storm drains. This prevents water from collecting on the street and inhibiting the flow of traffic along the street.  
           [0005]    Traditionally, curbside storm drains contain a catch basin that is connect to a below lying sewer with a large diameter pipe. The catch basin is commonly covered with a grate. The grate enables water to flow into the catch basin but prevents large objects, such as tree branches, from passing into the catch basin and blocking the sewer pipe. The catch basin itself collects debris that is heavier than water but is washed into the storm sewer by the force of flowing water. As a result, storm drains need periodic maintenance, wherein the debris collected in the catch basin is removed.  
           [0006]    As water flows over a street to a storm sewer, the water often mixes with oil and other contaminants. The oil comes from automobiles that leak oil. Other petroleum based contaminants include grease, diesel fuel, hydraulic fluid and gasoline. The federal and state environmental protection laws set forth many guidelines governing the disposal of petroleum based contaminants. Generally, it is unlawful to dispose of petroleum based contaminants in the public sewer system or in any other flowing supply of water. As such, the rain runoff that passes into many curb side storm drains fails to meet the state and federal standards due to the petroleum based contaminants that wash into the storm drains with the rain water.  
           [0007]    The prior art contains many different types of filter systems that are intended to at least partially purify the runoff water that passes into a storm drain. Certain prior art devices are filters that pass over the grate above the storm sewer. Such a filter is exemplified by U.S. Pat. No. 5,403,474 to Emery, entitled Curb Inlet Gravel Sediment Filter. In such prior art arrangements, the filter itself is accessible above the sewer&#39;s grate. Consequently, the filter disrupts the smoothness of a street&#39;s surface and therefore is only good in certain temporary applications.  
           [0008]    Since the catch basins of many storm drains are made of poured cement, it is not practical to change the structure of existing storm drains in order for those storm drains to accept filters. As a result, many filter configurations have been made that are adapted to be added to existing storm sewer designs. In a typical storm sewer, a ledge is formed around the to rim of the catch basin. The drain grate rests upon the ledge, thereby covering the open top of the catch basin. The depth of the ledge typically corresponds to the thickness of the grate. As a result, the top of the grate will lay in the same plane as does the surface of the street.  
           [0009]    In the prior art, there are filter structures that hang in the storm drain catch basin below the grate. Typically, such prior art filter structures engage the same ridge of the catch basin that supports the grate. As a result, a portion of the filter structure must be place in between the grate and the ridge upon which the grate was designed to sit. Such prior art filter structures are exemplified by U.S. Pat. No. 5,223,154 to MacPherson, entitled System For Filtering Liquids In A Catch Basin Using Filters In Series And Overflow Channels; U.S. Pat. No. 5,372,714 to Logue, entitled Storm Sewer Catch Basin And Filter and U.S. Pat. No. 5,284,580 to Shyh, entitled Refuse Collecting Frame For Sewer. One of the problems associated with such prior art filter structures is that the presence of the filter structure under the grate prevents the grate from seating properly onto the ridge at the top of the catch basin. As a result, the grate is held above its normal height, which may cause the grate to protrude above street level. If the grate does extend above street level, the grate becomes a tripping hazard. Furthermore, the grate can be caught by street plows and car tires, wherein the grate can be damaged or accidentally moved out of place.  
           [0010]    U.S. Pat. No. 5,925,241, entitled Storm Drain Filter, and U.S. Pat. No. 6,368,499, entitled Storm Drain Assembly With Disposable Filter Cartridge, both belong to the applicant herein. In these patents, the applicant invented a filter structure that can be retroactively attached to a storm drain in a manner where the filter element does not extend above street level or cause the grate of the storm drain to extend above street level. However, in both patents, the filter is the same size as the sewer grate. Consequently, all the water that falls through the sewer grate flows through the filter. Although, this provides good filtration to the water, in certain situations the configuration can cause problems.  
           [0011]    During normal rain conditions, water flows into the grate of a sewer at a controlled rate. The water therefore falls through the sewer grate before the water travels more than six inches across the top of the sewer grate. As a consequence, the vast majority of water that flows into a sewer grate passes only through the peripheral areas of any filter that is supported below the sewer grate. The area in the center of the sewer grate receives a relatively small amount of water.  
           [0012]    However, during a heavy rain, the flow of water into a sewer grate can exceed the capacity of the sewer grate to receive water. Water therefore pools above the sewer grate and flows into the sewer grate at all points. It is also during period of heavy rain that a great deal of debris can be washed into a sewer grate. Certain types of debris, such as pine needles, leaves, paper, plastic bags and the like can pass through the sewer grate and become stuck on the filter suspended below the sewer grate. Once this happens, the filter becomes and obstruction and the flow capacity of the sewer grate is greatly reduced.  
           [0013]    A need therefore exits for a filter system for a sewer grate that can filter water during normal rain conditions, yet does not clog or otherwise restrict sewer flow capacity during heavy rain conditions. This need is met by the present invention as described and claimed below.  
         SUMMARY OF THE INVENTION  
         [0014]    The present invention is a device and method for removing petroleum based contaminants from the runoff water that passes into a storm drain. The device is a filter apparatus that can be added to a storm drain. The filter apparatus consists of a filter cage that defines an open central conduit and a filter cartridge that wraps around the periphery of the filter cage. During normal rain conditions, water enters the sewer grate near the edges of the sewer grate. This water falls through the filter cartridge and is filtered. Solid debris that is mixed with the water is deflected through the central conduit and falls through the filter apparatus. During flood conditions, excess water is allowed to pass through the center conduit of the filter cage unfiltered in order to preserve the water flow capacity of the storm drain. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    For a better understanding of the present invention, reference is made to the following description of exemplary embodiments thereof, considered in conjunction with the accompanying drawings, in which:  
         [0016]    [0016]FIG. 1 is an exploded perspective view of an exemplary embodiment of a filter apparatus, shown in conjunction with a typical prior art storm drain; and  
         [0017]    [0017]FIG. 2 is a cross-sectional view of the embodiment of the filter apparatus and storm drain shown in FIG. 1.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    Although the present invention filter apparatus can be used in many different types of storm drains, the filter apparatus is particularly well suited for use in curb side storm drains that are commonly designed into the sides of paved streets. As a result, by way of an example, the present invention filter apparatus will be described in conjunction with a typical curb side storm drain in order to set forth the best mode contemplated for the present invention.  
         [0019]    Referring to FIG. 1 in conjunction with FIG. 2, a first exemplary embodiment of the present invention filter apparatus  10  is shown with a common curb side storm drain  12 . The storm drain  12  contains a cement catch basin  14  that lays below the plane of a paved street  16  at a point near the curb  15  of the street  16 . The catch basin  14  has an open top  18  that terminates at street level. A ridge  20  is formed on the interior of the catch basin  14  a short distance D below the open top  18  of the catch basin  14 .  
         [0020]    A grate  22  is provided that covers the open top  18  of the catch basin  14 . The grate  22  is typically a cast metal structure having numerous parallel slats  24 , whereby water is free to flow through the slots  26  that exist in between each of the parallel slats  24 . The grate  22  has a length L 1  and a width W 1  (FIG. 1) that enables the grate  22  to pass thorough the open end  18  of the catch basin  14 . However, the grate  22  is not large enough to pass the ridge  20  in the catch basin  14 . Rather, the peripheral edges of the grate  22  abut against the ridge  20  and evenly support the grate  22  in a horizontal plane. The grate  22  has a thickness T that matches the depth D of the ridge  20  below street level. As a result, when the grate  22  is placed onto the ridge  20  in the catch basin  14 , the top surface of the grate  22  is supported at approximately the same level as the street  16 .  
         [0021]    A filter cage  30  is suspended below the grate  22  within the confines of the catch basin. The filter cage  30  defines a central conduit  32  that is open in the center of the filter cage  30 . Otherwise, the filter cage  30  has a generally hourglass shape. At the top of the filter cage  30  are sloped surfaces  33  that define the beginning of the central conduit  32 . At top of the filter cage  30 , the sloped surfaces  33  are at their widest point and define an area at least as large as the sewer grate  22 . Consequently any material that falls through the sewer grate  22  will pass into the peripheral area of the filter cage  30 .  
         [0022]    The sloped surfaces  33  slope inwardly and downwardly, thereby forming a funnel shape. In the center of the funnel shape is the central conduit  32  that passes through the center of the filter cage  30 . At the bottom of the filter cage  30  is a mesh support base  34 . The support base  34  provides a surface in which a filter cartridge  40  can rest. However, the support base  34  does not obstruct the central conduit  32  that passes through the filter cage  30 .  
         [0023]    The central conduit  32  that passes through the filter cage  30  is at its narrowest near the middle of the filter cage  30 . At its narrowest point, the central conduit  32  of the filter cage  30  is between 10% and 50% the area of the sewer grate  22 .  
         [0024]    A filter cartridge  40  is wrapped around the filter cage  30 . Once in place, the filter cartridge  40  has a torical shape. The cross-sectional diameter of the filter cartridge  40  at any point is preferably between three inches and fifteen inches. The overall periphery of the filter cartridge  40 , once wrapped around the filter cage  32 , is at least as large as the periphery of the sewer grate  22 . Consequently, any water that falls over the edge of the sewer grate  22  will fall into the material of the filter cartridge  40 . However, during flood condition, when water falls through the sewer grate  22  in the center of the sewer grate  22 , that water falls through the central conduit  32  in the filter cage  30 .  
         [0025]    The filter cartridge  40  receives any water that pours through the sewer grate within a predetermined range of the edge of the sewer grate  22 . The predetermined range being directly proportional to the cross-sectional width of the filter cartridge  40 . The filter cartridge  40  has a pillow construction. That is, the filter cartridge  40  is comprised of an outer scrim bag  37  that confines a loosely bound filter material  39 . The scrim bag  37  is made of a synthetic material having hydrophobic properties. The material is manufactured in such a manner so as to define voids in the material sufficient enough in size for water to readily pass. In this manner, the scrim bag  37  does not itself absorb water, and is porous enough to enable water to freely flow through its structure. Suitable materials for the scrim bag  37  include, but are not limited to, Dacron and non-woven polyester felt.  
         [0026]    The filter material  39  contained within the scrim bag  37  is a material that absorbs the oil that is mixed within the run-off water. Thus, the filter material  39  removes oil from the water passing through the filter cartridge  40 . The oil absorbing filter material  39  has both lipophilic properties and hydrophobic properties. Thus, the filter material  39  absorbs oil contained in the run-off water, yet does not absorb the water itself. Suitable filter material  39  for use in the filter cartridge  40  include, but are not limited to, melt blown polypropylene fibers. Melt blown polypropylene fibers have the appearance and texture of cotton. The loose fibers of the melt blown polypropylene fibers enable the fibers to be densely packed onto the scrim bag  37  without significantly effecting the water permeability of the overall filter cartridge  40 .  
         [0027]    There are materials other than melt blown polypropylene fibers that have hydrophobic and lipophilic properties. Any such material can be adapted for use in the present invention, provided the material is effective in removing oil from water while permitting a significant water flow rate through the material.  
         [0028]    Connection brackets  38  (FIG. 1) are disposed on the top of the filter cage  30 . Suspension elements, such as chains  41  or rods, are used to suspend the filter cage  30  below the grate  22  of the storm drain  12 . Chains  41  are described by way of example. The bottom of each of the chains terminates with a hook  42  (FIG. 1) or similar configuration that enables the chains  41  to be mechanically attached to the connection brackets  38  on the top of the filter cartridge  30 . The chains  41  attach to the filter cage  30  in a removable manner. As such, the filter cage  30  can be removed from the chains  41  and replaced periodically.  
         [0029]    The top end of each of the chains  41  attaches to an element that engages the grate  22  of the storm drain  12 . The attachment element can be any hook structure that engages the sewer grate. In the shown embodiment, a hook  44  is used to interconnect the chains  41  with the grate  22 .  
         [0030]    Although any plurality of suspension elements can be used to support the filter cage  30  and filter cartridge  40 , in the shown embodiment only two chains  41  are used. The chains attach to opposite ends of the filter cage  30  in line with the center of gravity for the filter cage  30  and filter cartridge  40 . In this manner, if the filter cage  30  were ever to inadvertently clog and a heavy rain were to occur, the flow of water into the storm sewer can cause the filter cage  30  and the filter cartridge  40  to tilt to one side, thereby providing an unobstructed pathway through which the storm water can pass.  
         [0031]    In operation, the present invention works as follows. First the filter cage  30  and filter cartridge  40  are suspended from a sewer grate  22 . Any water that trickles into the sewer grate  22  and flows into the sewer grate  22  near the edge of the sewer grate  22  falls into the filter cartridge  40 . During times of heavy rain or other flooding conditions, water will enter the sewer grate  22  across the entire area of the sewer grate  22 . Water entering near the edge of the sewer grate  22  will fall through the filter cartridge  40 . However, water entering the middle of the sewer grate  22  will fall down through the central conduit  32  in the filter cage  30 . Any debris that were to fall through the sewer grate  22  near the edge of the sewer grate  22  would land on the sloped surfaces  33  of the filter cage  30  above the filter cartridge  40 . Due to the slope of these surfaces  33  and the washing effect of the incoming water, any such debris would be washed down the center conduit  32  of the filter cage  30 . Likewise, any debris that would enter the sewer grate  22  in the middle of the sewer grate  22  would directly fall through the central conduit  23  in the filter cage  30 . Consequently, during normal rain conditions, most all of the water that passes through the sewer grate  22  is filtered by the filter cartridge  40 . Debris contacts the sloped surfaces  33  of the filter cage  30  and is deflected through the central conduit  23  in the filter cage  30 . During flood conditions, some water is let through the filter cage  30  unfiltered, however, the flow capacity of the sewer is not compromised and no debris will clog the system.  
         [0032]    If a tarp or some other unusual object is swept into the sewer and does block the filter cage  30  and filter cartridge  40 , a heavy flow of water will cause the entire filter cage  30  and filter cartridge  40  to tip to one side, thereby enabling the water to flow past the blocked filter assembly.  
         [0033]    From FIG. 1 and FIG. 2, it will be understood that in order to remove the filter cartridge  30 , the grate  22  of the storm drain  12  is engaged and lifted upwardly away from the catch basin  14 . Since the filter cage  30  is suspended from the structure of the grate  22 , the filter cage  30  lifts up and out of the catch basin  14  as the grate  22  is removed. Once the grate  22  and filter cage  30  are removed, the filter cartridge  40  can be replaced by removing the old filter cartridge and replacing it with a new clean filter cartridge. The oil soaked old cartridge can then be either sent to a recycling plant for oil extraction of can be disposed of in an environmentally safe manner.  
         [0034]    When storms drains are cleaned, the grate of the storm drain must be removed. Maintenance personnel therefore have the equipment needed to remove the grates from storm drains. As such, a maintenance team during the normal maintenance of the storm drain can easily replace old filter cartridges or add a new filter cartridge to a storm drain not previously containing a filter cartridge.  
         [0035]    It will be understood that the embodiments of the present invention described and illustrated herein are merely exemplary and a person skilled in the art can make many variations to the embodiment shown without departing from the scope of the present invention. It should also be understood that the various elements from different embodiment can be mixed together to create alternate embodiments that are not specifically described. All such variations, modifications and alternate embodiments are intended to be included within the scope of the present invention as defined by the appended claims.