Abstract:
An excavation system includes a shroud having a first opening and a second opening, a nozzle for directing an air stream in a first direction through the first opening of the shroud, wherein the nozzle is surrounded by the shroud, a first pump configured to apply a suction within the shroud in a second direction through the second opening of the shroud, and a collection area in fluid communication with the second opening of the shroud for receiving contaminated material. The collection area includes a collector for separating the contaminated material via an impact plate and a filter. The contaminated material is then deposited into a bag supported by a box. A method for excavating the contaminated material from the ground is also disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims the benefit of Provisional Application No. 60/416,638, filed Oct. 7, 2002, entitled “Excavator Head”, which is hereby incorporated by reference in its entirety. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates to excavation of soil and, more particularly, the use of pneumatic excavation.  
           [0004]    2. Description of Related Art  
           [0005]    Throughout the twentieth century, various areas throughout the United States have become contaminated with various hazardous chemicals and radioisotopes. Specifically, these contaminants have been deposited on the ground and eventually make their way, in many cases, to the ground water supply. Heretofore, excavation primarily included removal of the soil by such means as bulldozers and other types of mechanical digging and lifting devices. Mechanical diggings may produce significant wind blown emissions when soil is excavated or dumped from one container into another container. After the soil is removed, it is then sifted and then disposed of at an appropriate site or incinerated. In many cases, a majority of the removed soil is not contaminated. It has been found that the contamination, in many cases, is found in fines, such as the size of sand particles contained in the soil and located near the soil surface. Prior art methods have typically removed the non-contaminated larger rocks. The more material that needs to be disposed, the greater the cost of the disposal. Therefore, it is an object of the invention to quickly and easily remediate soil where the contamination is only directed to fines found in the soil. It is a further object to reduce the amount of contaminated airborne dust during the removal process.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention is an excavation system designed to loosen the first couple of inches of soil and direct only the fine grain portion into a vacuum system. Preferably, the system includes a head that is held by the operator, roughly perpendicular to and in close proximity to the soil surface. The head is traversed or moved horizontally over the ground surface from about one-half to two feet per second by the operator. A supersonic air nozzle is provided at the center of the head to produce and direct a supersonic jet air stream at approximately Mach 2 towards the surface, loosening and agitating the top couple of inches of soil. Typically, many particles will pick up appreciable speed and be directed upwardly parallel to the axis of the jet air stream. A deflector plate may be provided to serve and intercept these high speed particles and cause them to fall back into the air stream flowing from outside the head. A gap is defined between the head and the ground so that air can be drawn into the head in a direction opposite to the jet air stream by a vacuum pump. The velocity of the air through this gap and up into the head will be at, or greater than, the floating velocity of the fine grained, i.e., sand-sized or smaller, particles of the soil. For a 2 millimeter sized sand particle, the floating, or terminal velocity, is about 1,150 feet per minute. After entering the head, the air and debris carried by the air is drawn by the vacuum pump and will rise in an annular fashion along an inside surface of the shroud. The distance between the shroud and the deflector plate is chosen such that the velocity in the gap is the same as the floating velocity for the sand. A first chamber or lower chamber is defined below the deflector plate and the jet air stream from the supersonic nozzle sets up a circulation bringing the fine-grained portion of the soil into contact with the rising air flow created by the vacuum pump limiting the vacuum flow velocity to the floating velocity of the sand so that only the fine-grained portion of the soil will be carried into a second chamber or an upper chamber of the head. The upper chamber is defined above the deflector plate. The upper chamber gradually narrows to attach to a vacuum hose leading to a collection area. The velocity above the deflector plate gradually increases to the level needed to transport the fine-grained material to the collection area through the hose. For example, a 3 inch diameter hose may utilize approximately 200 to 300 standard cubic feet per minute of air (scfm) to transport the fine material through the hose.  
           [0007]    These and other advantages of the present invention will be understood from the description of the preferred embodiments, taken with the accompanying drawings, wherein like reference numerals represent like elements throughout. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a side elevational view, partially in section, of an excavator head made in accordance with the present invention;  
         [0009]    [0009]FIG. 2 is a schematic elevational view of the excavation system having an excavator head and a collector made in accordance with the present invention;  
         [0010]    [0010]FIG. 3 is a side elevational view of an alternative embodiment of the excavator head of FIG. 1 and  
         [0011]    [0011]FIG. 4 is a side elevational view, partially in section, showing an alternative embodiment of the collector of FIG. 2.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0012]    An excavation system  10  made in accordance with the present invention is shown in FIGS.  1 - 4 . The system  10  includes a collection area  11 , a vacuum remedial head  12 , and a pneumatic tool  14  received by the head  12 . The pneumatic tool  14  operates in a similar fashion as a hand tool disclosed in U.S. Pat. No. 5,966,847 to Nathenson et al. (sold under the trademark AIR-SPADE®), which is hereby incorporated by reference. The pneumatic tool  14  includes a supersonic converging/diverging nozzle  16  fluidly coupled to a barrel  18 . The barrel  18  is coupled to a pump or air compressor  20 . Preferably, the pneumatic tool  14  is designed so that air exiting the supersonic converging/diverging nozzle  16  travels at a speed of Mach 2 and a volume of 25 to 60 standard cubic feet per minute (scfm) at 90 pounds per square inch gauge (psig). It is to be understood that the referenced speeds and corresponding volumes are described for exemplary purposes and may therefore vary depending on the specific dimensions and other physical characteristics of the present invention.  
         [0013]    The vacuum remedial head  12  includes a shroud  22  having a receiving cavity  24  defined by an inner surface of the shroud  22 . The shroud  22  includes a cylindrical entrance portion  26  attached at its upper end to a frusta-conical shaped converging portion  28 , although the converging portion  28  may be any suitable shape. An upper end of the converging portion  28  is attached to a cylindrical exit portion  30 . Preferably, the diameter of the cylindrical entrance portion  26  is greater than the diameter of the cylindrical exit portion  30 .  
         [0014]    The excavation system  10  includes a collection arrangement. Specifically, a conduit or hosing H 1  is provided and coupled to the cylindrical exit portion  30  and is coupled to a collector  32 . The collector  32  is a cylindrical vessel built to withstand a vacuum and houses a filter  34  and an impact plate  36 . The collector  32  is suspended above a spoils box B containing a soft-sided soil disposal bag R that acts as a removable liner. The collector  32  houses a primary chamber  38  where the majority of the incoming soil particles from the air stream are removed by impact and a secondary chamber  40  where the remaining dust is collected by the filter  34 . All of the collected material is continuously discharged from the collector  32  through a rotary valve  42  down directly into the spoils bag R. Special multi-layer soil disposal bags, such as the Lift-Liner™, have been qualified to transport hazardous or radioactive waste and may be used in this application. The filter  34  may be additionally of HEPA quality. The box B provides structural support to hold the bag during filling. A lid L is provided to contain any dust within the bag R. Alternately, the lid may be integral with the bag R connecting to the rotary valve  42  via a spout (not shown). The collector may also contain a blow back system, which typically uses compressed air to clean the filter  34 . A conduit or hosing H 2  connects the outlet of the collector  32  to the inlet of a vacuum pump  44 . The vacuum pump  44  draws the clean air from the inside of the filter  34  and exhausts the air through a silencer  46  to an exit port  48 . The vacuum pump  44  may be belt-driven by a gas or diesel engine or an electric motor  50 . Finally, the pump or air compressor  20  is also driven by the electric motor  50  and provides compressed air via a conduit or hosing H 3  to the barrel  18 . This collection arrangement, including the collection area  11  and the vacuum pump  44  may also be similar to that disclosed in U.S. Pat. No. 5,860,232, which is hereby incorporated by reference.  
         [0015]    Returning to the vacuum remedial head  12  of FIG. 1, the cylindrical entrance portion  26  has a lower open-faced end which defines an entrance  54  to the vacuum remedial head  12 . An optional cylindrical deflector plate  56  is positioned within the receiving cavity  24  defined in the cylindrical entrance portion  26 . The deflector plate  56  is preferably attached to the barrel  18  of the pneumatic tool  14 , although it may also be attached to the nozzle  16 . The deflector plate  56  defines an annular restricted flow area  58  between an outer edge of the deflector plate  56  and the inner surface of the cylindrical entrance portion  26 . This annular restrictive flow area  58  permits an increased flow velocity of air particles flowing through the annular restrictive flow area  58 . The deflector plate  56  defines a first or lower chamber  60  and a second or upper chamber  62  within the cylindrical entrance portion  26 . The lower chamber  60  and upper chamber  62  are in fluid communication with each other through the annular restricted flow area  58 .  
         [0016]    In practice, an operator positions a lower edge  64  of the vacuum remedial head  12  above the surface of the soil or ground  66 . Typically, the ground  66  contains fines or sand of fine-grain and other small debris, having a size of 2 millimeters or less. Preferably, the lower edge  64  is positioned about one inch above the ground  66 , forming a gap  68  between the lower edge  64  and the ground  66 . It is to be understood that the distance of the lower edge  64  and the ground or ground  66  can be varied to adjust the gap  68 , which in turn adjusts the flow rate and vacuum characteristics of the excavation system  10 . Flexible bristles  70  cover the resultant gap  68  between the lower edge  64  and the surface of the ground  66 . The bristles  70  maintain a flexible contact with the surface of the ground or ground  66 , thereby preventing any dislodged soil particles from exiting the remedial head  12 , yet allowing air to enter. It is understood that one or more layers of flexible bristles  70  may be used to cover the gap  68 . It is also to be understood that other types of flexible seal members may be used to maintain a flexible contact with the surface of the ground  66  including, one or more of such flexible seal members.  
         [0017]    The pump  20  of the pneumatic tool  14  is activated so as to cause an air stream exiting from the supersonic converging/diverging nozzle  16 . Preferably, the nozzle  16  is designed to permit the air to exit at approximately Mach 2 toward the ground  66 . The nozzle  16  and pump  20  should be designed so that the air stream exits at 25 to 60 scfm and at a pressure of 90 psig, although other flow rates, operating pressures, and jet stream velocities would suffice, depending on a case-by-case basis. Likewise, the vacuum pump  44  is activated so as to cause air to pass through the shroud  22  toward the collection area  11  at a volumetric rate of 200-300 scfm. The actual dimensions of the shroud  22 , cylindrical exit portion  30 , vacuum pump  44 , and volumetric flow rate depend on a case-by-case basis. For exemplary purposes, the floating or terminal velocity of a 2 millimeter sized particle is about 1,150 feet per minute. Generally, the appropriate flow rate should be such that the velocity of the air is sufficient to carry that size of a particle. However, the flow rate should not be so great as to carry a larger particle, such as rocks, etc.  
         [0018]    While the air compressor  74  and the vacuum pump  44  are activated, the operator moves the vacuum remedial head  12  over the surface of the ground  66  at an approximate rate from ½ to 2 feet per second. The air stream exiting the pneumatic tool  14  through the nozzle  16  exits in a supersonic air stream in a direction shown by arrow  72 . This air stream causes the ground  66  to break apart and become dislodged as loose particles. These particles then travel upwardly toward the shroud  22 . If the deflector plate  56  is provided, particles having a high velocity will contact the deflector plate  56  as shown by arrow  74 . Desirably, the deflector plate  56  is substantially parallel to the ground  66 . After making contact with the deflector plate  56 , the particles will then be directed toward the ground  66  in the direction as designated by arrow  76 . A pressure differential created by the vacuum pump  44  results in suction within and throughout the shroud  22  and the conduit and hosing H 1 . This upward air flow throughout the shroud  22  will carry the particles, such as the sand particles, in an upward direction as shown by arrow  78 , in the lower chamber  60 . The particles will be carried at a higher velocity through the restricted flow area  58  and will then be carried into the upper chamber  62  through the cylindrical exit portion  30  in the direction shown by arrow  80 . The particles are then routed to the collector  32 . Specifically, the contaminated particles, such as the fines or sands of fine-grain, have been excavated and stored for safe disposal in the bag R. The air accompanying the particles may then pass through the filter  34 . The filtered air may then be routed to the vacuum pump  44  and the silencer  46  and expelled through the exit port  48  into the environment. By loading the bag R directly for disposal, further contamination of the air is avoided as would be typical with mechanical excavators or conventional vacuum trucks, which have to be dumped, once full.  
         [0019]    [0019]FIG. 3 illustrates an alternative embodiment vacuum remedial head  82  having similar components as the vacuum remedial head  12  but embodied in a different configuration. The alternative embodiment vacuum remedial head  82  excludes the deflection plate  56  and has the exit portion  30  located below the barrel  18  in the frusta-conical shaped converging portion  28 . Additionally, the alternative embodiment vacuum remedial head  82  may include two sets of bristles  70 . The disclosed configurations of vacuum remedial heads are only for exemplary purposes and are not to be considered as limiting the invention.  
         [0020]    [0020]FIG. 4 illustrates an alternative embodiment collector  84  having somewhat similar components as the collector  32  but embodied in a different configuration. The alternative embodiment collector  84  eliminates the rotary valve  42 . Contaminated material enters the collector  84  via the conduit or hosing H 1  and strikes the impact plate  36 . The contaminated material is then directed into the spoils bag or removable liner R lining the box B. A vacuum causes the air in the contaminated material to pass through the filter  34  and be expelled through the exit port  48 . An additional filter  86  of HEPA quality may be added to the collector  84 . The flow path is indicated by arrows.  
         [0021]    The present invention has been described with reference to the preferred embodiments. Obvious modifications, combinations, and alterations will occur to others upon reading the preceding detailed description. It is intended that the invention be construed as including all such modifications, combinations, and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.