Abstract:
An object detection system ( 24 ) is disclosed having a transducer ( 40, 40′ ) for detecting buried objects ( 26 ). The transducer is encapsulated within a robust, electromagnetically transparent construction ( 42 ).

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The present disclosure relates to a radiating structure for detecting buried objects. More particularly, the present disclosure relates to an antenna structure for detecting buried objects during mechanical excavations, and to a method for utilizing the same. 
         [0003]    2. Description of the Related Art. 
         [0004]    Many excavations are performed in well-developed, utility-congested areas. The congestion of underground space in many urban areas, combined with poor record keeping and difficulties in accurately locating buried utilities from the surface, has led to many inadvertent utility strikes during mechanical excavations. Utility strikes may lead to work-stop orders and delays, mechanical damage to buried utilities, and numerous costs associated with litigation, insurance, downtime, and repair. 
       SUMMARY 
       [0005]    According to an embodiment of the present invention, a construction vehicle is provided including a chassis; a plurality of traction devices positioned to support the chassis; a work tool supported by the chassis and configured to penetrate the ground; and a detector mounted to the work tool and configured to detect an object positioned in the ground during a penetration of the ground with the work tool. 
         [0006]    According to another embodiment of the present invention, a detector assembly is provided that is configured to detect an object positioned in the ground. The detector assembly includes at least one transducer configured to communicate a ground-penetrating signal; and a dielectric medium substantially encapsulating the at least one transducer to substantially reduce signal loss during a communication of the ground-penetrating signal between the at least one transducer and the ground. 
         [0007]    According to another aspect of the present invention, a detector is provided that is configured to detect an object positioned in the ground. The detector includes at least one transducer configured to communicate a ground-penetrating signal; and a dielectric medium positioned between the at least one transducer and the ground during a communication of the ground-penetrating signal to substantially reduce signal loss during the communication of the ground-penetrating signal between the at least one transducer and the ground. 
         [0008]    According to another aspect of the present invention, a method of detecting an object positioned in the ground is provided. The method includes the steps of: providing a detector that communicates a ground-penetrating signal between the object and the detector; penetrating the ground with a tool to create a penetration; positioning at least a portion of the detector in the penetration; and detecting the object while the portion of the detector is located in the penetration. 
         [0009]    According to another aspect of the present invention, a method is provided for reducing signal loss in the detection of an object positioned in the ground. The method includes the steps of providing a detector having at least one transducer and a dielectric medium; placing the detector in contact with the ground so that the dielectric medium is positioned between the at least one transducer and the ground; and communicating a ground-penetrating signal through the dielectric medium between the at least one transducer and the ground to substantially reduce signal loss. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The above-mentioned and other features of the present disclosure will become more apparent and the present disclosure itself will be better understood by reference to the following description of embodiments of the present disclosure taken in conjunction with the accompanying drawings, wherein: 
           [0011]      FIG. 1  is a side elevation view of an excavator showing the excavator excavating an area and having a ground penetrating radar positioned on a tip of the excavator bucket to detect objects located in the ground; 
           [0012]      FIG. 2  is a schematic diagram of ground penetrating radar showing the radar including a transmitting antenna and a receiving antenna that transmit and detect objections located in the ground; 
           [0013]      FIG. 3  is a perspective view of a portion of an excavator bucket tooth including an encapsulated transceiver antenna, shown in phantom; 
           [0014]      FIG. 4  is a plan view of the metallization layers of the encapsulated antenna of  FIG. 3 ; 
           [0015]      FIG. 5  is a view of the antenna of  FIG. 3  mounted on an excavator bucket; 
           [0016]      FIG. 6A  is a graphical representation of the signal detected by the antenna of  FIG. 2  with the transmitting and receiving antennas are positioned above the ground consisting of soil; 
           [0017]      FIG. 6B  is a view similar to  FIG. 6A  showing the signal detected by the antenna with the transmitting and receiving antennas positioned in contact with the ground and showing a peak indicative of a plastic pipe located in the ground; 
           [0018]      FIG. 7A  is a graphical representation of the signal detected by the antenna of  FIG. 3  with the transmitting and receiving antennas are positioned above the ground consisting of sandy soil with no object in the sandy soil; 
           [0019]      FIG. 7B  is a view similar to  FIG. 7A  showing the signal detected by the antenna with the transmitting and receiving antennas positioned in contact with the ground and showing a peak indicative of a steel pipe located in the sandy soil; 
           [0020]      FIG. 8A  is a graphical representation of the signal detected by the antenna of  FIG. 3  with the transmitting and receiving antennas are positioned above the ground consisting of sandy soil with no object in the sandy soil; 
           [0021]      FIG. 8B  is a view similar to  FIG. 8A  showing the signal detected by the antenna with the transmitting and receiving antennas positioned in contact with the ground and showing a peak indicative of a polyethylene pipe located in the sandy soil; 
           [0022]      FIG. 9A  is a graphical representation of a soil without an object located in the soil; 
           [0023]      FIG. 9B  is a view similar to  FIG. 9A  showing a graphical representation with an steel pipe located 6 inches (152 millimeters) deep in the soil; 
           [0024]      FIG. 9C  is a view similar to  FIG. 9A  showing a graphical representation with the steel pip located 10 inches (254 millimeters) deep in the soil; 
           [0025]      FIG. 10  is a perspective view of bucket tooth showing the tooth including four discone antennas and a Vivaldi antenna; 
           [0026]      FIG. 11  is an end view of a bucket tooth of  FIG. 10 ; 
           [0027]      FIG. 12  is an end view of an array of discone antennas; 
           [0028]      FIG. 13  is a top view of a combination of discone antenna arrays; and 
           [0029]      FIG. 14  is a view of an excavator bucket showing discone antenna arrays mounted thereon. 
       
    
    
       [0030]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate exemplary embodiments of the disclosure and such exemplifications are not to be construed as limiting the scope of the disclosure in any manner. 
       DETAILED DESCRIPTION 
       [0031]    The embodiments disclosed below are not intended to be exhaustive or limit the disclosure to the precise form disclosed in the following detailed description. Rather, the embodiments are described so that others skilled in the art may utilize its teachings. 
         [0032]    An excavator  10  is shown in  FIG. 1  that includes a chassis  12  and a plurality of traction devices  14 , such as tracks, that support and propel chassis  12  over the ground  16 . Excavator  10  further includes a boom  18  supporting a work tool or bucket  20  that is configured to penetrate the ground  16  to create a trench, hole, pit, or other depression  22  in the ground  16 . Excavator  12  further includes an object detection radar system  24 , shown in  FIG. 2 , which is configured to detect objects  26 , such as a utility pipes and wires, in the ground  16 . Although an excavator  10  is shown in  FIG. 1  and discussed in the application, other construction vehicles, such as backhoes, loaders, bulldozers, graders, and other constructions vehicles may be provided with objection detection system  24 . Further, although traction devices  14  are shown as tracks, other traction devices, such as wheels may be provided on construction vehicle  10 . 
         [0033]    Portions of object detection radar system  24  are mounted on bucket  20 . According to the preferred embodiment of the present disclosure, detection system  24  includes a transmitter  28  and/or a receiver/detector  30  mounted on bucket  20 . For example, according to the embodiment shown in  FIG. 1 , transmitter  28  and detector  30  are mounted on one or more teeth  32  of bucket  20 . Transmitter  28  and detector  30  may also be mounted on other construction equipment work tools, such as bull dozer or grader blades, loader or backhoe buckets, or other work tools. 
         [0034]    With transmitter  28  and detector  30  mounted on teeth  32 , transmitter  28  and detector  30  are in direct contact with the ground  16  during excavation of depression  22 . By placing transmitter  28  and detector  30  in direct contact with the ground  16 , signal losses are reduced during communication of the ground-penetrating signal between the transducer and the ground  16 . 
         [0035]    Transmitter  28  is configured to emit electromagnetic waves and receiver  30  is configured to detect electromagnetic waves. As shown in  FIG. 2 , detection system  24  includes a signal generator  34 , such as a Picosecond Pulse Labs Generator Model 4500D, and a signal detection monitor  36 , such as a Tektronix Oscilloscope Model DSA 8200). Signal generator  34  provides a signal to transmitter  34  that emits the ground-penetrating signal into the ground  16  and provides a trigger signal to monitor  36 . Objects  26 , such as a pipe, reflect the ground-penetrating signal and detector  30  detects signals reflected off of object  26 . Monitor  36  provides a visual representation of the reflected signal for visual analysis. A computer  37  with a processor  39  may also be used to analyze the signal provide from detector  30 . 
         [0036]    One embodiment of transmitter  28  and detector  30  is shown in  FIG. 3  as a Vivaldi antipodal antenna. Each of transmitter  28  and detector  30  includes a Vivaldi antenna  40  and body  42  that encapsulates antenna  40 . Antenna  40  is an electromagnetic transducer that detects/coverts electromagnetic waves into signals useable for analysis. As discussed below, other types of antennas and other transducers may also be used according to the present disclosure. 
         [0037]    After fabrication of antenna/transducer  40 , it is encased in one or materials that define body  42  to provide a protective casing or shell around antenna  40 . According to the preferred embodiment of the present disclosure, body  42  is made of a high strength dielectric medium. The dielectric material may be a polymer or a ceramic material that may include micro-fibers or nano-fiber to enhance the durability of body  42 . For example, according to one embodiment, body  42  is made of high modulus polyurea with a dielectric constant of approximately  4 . Other example materials include 100% solids rigid polyurethane, 100% solids epoxy, and other non-conductive materials. Body  42  may also be coated with materials to increase its durability. Body  42  may also be coated with carbon or other electromagnetic insulating materials to insulate antenna  40  from adjacent conductive surfaces to reduce or prevent signal leakage, ringing, or other interference. Preferably, the dielectric medium has a dielectric constant about equal to the ground  16 . According to the present disclosure, the dielectric medium has a dielectric constant ranging from about 1 to about 20, but may have other values. 
         [0038]    As shown in  FIG. 4 , antenna  40  includes three planes of material, which include upper and lower ground plates  44  with a conductive plate  46  sandwiched between ground plates  44 . Portions of conductive plate  46  positioned directly between ground plates  44  are shown in phantom in  FIG. 4 . The conductive plates  46  are preferably made of copper, but may be made of other metals, and other conductive materials. The dielectric/ground plates  46  may be made of epoxy, ceramic, Teflon -brand polytetrafluoroethylene (PTFE) or other materials. Antenna  40  is preferably 135 millimeters (5.2 inches) long and 45 millimeters (1.8 inches) high as shown in  FIG. 4 . 
         [0039]    In operation, antenna/transducer  40  and body  42  are mounted or otherwise coupled to tooth  32  as shown in  FIG. 5 . A signal from signal generator  34  is provided to antenna  40  through a cable  48 . During excavating, as shown in  FIG. 1 , antenna  40  and body  42  are repeatedly positioned in ground  16  as dirt and other materials are excavated. As a result, antenna  40  is often positioned below the lowest portions of tracks  14 . Further, antenna  40  is positioned into penetrations, such as depression  22 , created by excavator  10  during the excavation process. As shown in  FIG. 1 , antenna  40  of transmitter  28  and detector  30  are simultaneously positioned in the soil  16  as teeth  32  create penetrations in the soil  16 . 
         [0040]    While positioned in the penetrations, signals are transmitted and detected by antennas  40  of transmitter  28  and detector  30 . Because antenna  40  and dielectric body  42  are mounted on teeth  32 , they cooperate to define cutting elements of teeth  32  with portions of body  42  defining a cutting edge  50  of tooth  32 . Thus, simultaneously with excavation, objects  26  are being detected. Further, because bodies  42  and antennas are  40  are able to be lowered into penetrations  22  and assists in creating penetrations  22 , objects  26  are closer to antenna  40  and more easily detected than if one was attempting to detect objects  26  before any excavation started. Body  42  is positioned between antenna  40  and the soil to protect antenna  40  during excavation. As a result, the signals transmitted and received by antennas  40  pass through body  42  on their way from and antenna  40  during respective transmission of the signal and receipt of the reflected signal. 
         [0041]    Example outputs from detectors  30  are provided in  FIGS. 6A-9C . In  FIG. 6A , a signal is shown when antennas/transducers  40  of transmitter  28  and detector  30  are positioned above ground  16  without direct contact between the respective antennas  40  and ground  16 . A peak  52  is shown that indicates cross talk between antenna  40  of transmitter  28  and antenna  40  of detector  30 . In  FIG. 6B , antennas  40  of respective transmitter  28  and detector  30  are placed in direct contact with ground  16 . In addition to showing cross-talk peak  52 , a second peak  54  is shown indicating the presence of a 2 inch (51 millimeters) diameter polyethylene pipe that was buried 4 inches (102 millimeters) in the test soil. As a result, a perceptible indication is provided indicating that an object  26 , such as a plastic natural gas pipe, is in the path of bucket  20 . A trained operator of excavator  10  can notice this indication to avoid striking pipe  26 . Similarly, computer  37  can be programmed to recognize any peak after cross-talk peak  52  that satisfies a predetermined characteristic, such as slope. If computer  37  detects such a peak, or other predetermined characteristic, it can send an alarm, stop further movement of bucket  20 , or otherwise attempt to avoid bucket  20  striking pipe  26 . 
         [0042]    In addition to detecting objects  26 , the reflections detected by detector  30  can also be used to determine characteristics of objects  26  buried within the ground  16 . For example, 
         [0043]      FIGS. 7A and 7B  illustrate the output of detector  30  for a 2 inch (51 millimeters) metal pipe buried in sandy soil at a depth of 4 inches (102 millimeters). In  FIG. 7A , antennas/tranducers  40  of transmitter  28  and detector  30  are above the ground  16 . In  FIG. 7B , they are in direct contact with the ground and provide a distinctive, “cursive v”  53  pattern indicative of the metal pipe.  FIGS. 8A and 8B  illustrate the output of detector  30  for a 1 inch (25 millimeters) polyethylene pipe buried in sandy soil at a depth of 2 inches (51 millimeters). In  FIG. 8A , antennas  40  of transmitter  28  and detector  30  are above the ground  16 . In  FIG. 8B , they are in direct contact with the ground and provide a distinctive, “w” pattern  55  indicative of the plastic pipe. A trained operator of excavator  10  can notice the distinctive patterns  53 .  55  of metal, polyethylene, and other pipes do determine the type of pipe. Similarly, computer  37  can be programmed to recognize any peak after cross-talk peak  52  that satisfies a predetermined characteristic, such as the shape of patterns  53 ,  55 . If computer  37  detects such a pattern, or other predetermined characteristic, it can send an indication of the type of pipe, such as metal or plastic. 
         [0044]    In addition to determine the presence and type of object  26 , the reflections detected by detector  30  can also be used to determine the distance of object  26  from bucket  20  (or any other portion of excavator  10 ). Additional representations of the reflections detected by detector  30  are provided in  FIGS. 9A-9C . In  FIG. 9A , no object  26  is placed in the test soil so that no object  26  is detected when antennas  40  are placed in contact with ground  16 . In  FIG. 9B , a 2 inch (51 millimeters) diameter steel pipe was placed 6 inches (152 millimeters) deep in sandy soil and in  FIG. 9C , the same pipe was placed 10 inches (254 millimeters) deep in the sandy soil. As shown by the circled region in  FIGS. 9B and 9C , “cursive v” pattern  53  of the steel pipe occurs later in time in  FIG. 9B  than in  FIG. 9C  because the reflection took longer to reach detector  30  after being sent by transmitter  32 . A trained operator of excavator  10  can notice the gap in time between a feature, such as cross-talk peak  52 , and distinctive pattern  53  to determine the distance from object  26 . Similarly, computer  37  can be programmed to recognize the time delay and calculate the distance of tooth  32  of bucket  20  from object  26  and provide an indication to the operator of the distance and/or use the distance as a trigger for an alarm or otherwise. The operator may use this distance information when perform fine movements around objects  26 , such as known utility pipes or cables. 
         [0045]    Another embodiment of transmitter  28 ′ and detectors  30 ′ is shown in  FIG. 11  that includes four discone antennas/transducers  40 ′ performing as detectors  30 ′ and a Vivaldi antipodal antenna  40  performing as a transmitter  28 ′. Combined transmitter/detector  56  includes body  42 ′ that encapsulates antennas  40 ,  40 ′ in a manner similar to body  42 . To enhance the directionality of discone antennas  40 ′, if used as transmitters, they may be aligned in an array  58  as shown in  FIG. 12 . To further increase the directionality, a reflective metal plate (not shown) may be placed at the back of array  58 . In  FIG. 13 , several arrays  58  with differing numbers of discone antennas  40 ′ are provided as detectors and a transmitter to detect objects  26 . As shown in  FIG. 14 , arrays  58  may be placed on bucket  20  in locations other than on tooth  32 . 
         [0046]    While this invention has been described as having preferred designs, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.