Abstract:
In some underground boring applications the exit location of the underground bore may be located such that drill pipe and material pipe sections cannot be conveniently deployed therefrom (e.g., a basement of a building, the inside of another pipe, or a small manhole space). In such applications, push reaming functionality is often the preferred method of reaming because the pipe section can be deployed and installed from a pit where the bore is started during a push reaming operation. The present disclosure provides a new push reaming drill head as well as a new method of push reaming.

Description:
[0001]    This application is being filed on 15 Nov. 2013, as a PCT International patent application, and claims priority to U.S. Provisional Patent Application No. 61/726,999, filed Nov. 15, 2012, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates generally to trenchless drilling equipment. More particularly, the present disclosure relates to tunneling equipment capable of reaming a pre-bored hole to enlarge the diameter of the hole. 
       BACKGROUND 
       [0003]    Modern installation techniques provide for the underground installation of services required for community infrastructure. Sewage, water, electricity, gas and telecommunication services are increasingly being placed underground. 
         [0004]    One method for installing underground services involves excavating an open trench. However, this process is time consuming and is not practical in areas supporting existing construction. 
         [0005]    Other methods for installing underground services involve boring an underground hole. In some underground applications an underground hole is bored from above the ground surface and back up through the ground surface (e.g., horizontal drilling machines). In other applications the underground hole is bored from a first pit to an exit location, which may be a second pit (e.g., on grade drilling machines). Vermeer Manufacturing&#39;s PCT International Publication No. 2012/040190 (WO 2012/166905) and U.S. Pat. No. 7,942,217, U.S. Pat. No. 8,151,906 discloses a micro-tunneling system and apparatus capable of boring and back-reaming an underground micro-tunnel at precise grade and line, these publications are all hereby incorporated by reference in their entirety. 
       SUMMARY 
       [0006]    In on grade application (drilling straight bores), a first pit is typically formed sufficiently large to allow for the set up drill apparatus which receives and deploys drill casings during boring, and the second pit is formed generally sufficiently large to deploy the pipe sections that are installed during a pullback reaming operation. However, in some circumstances the exit location of the underground bore may be located such that the pipe sections cannot be deployed therefrom (e.g., a basement of a building, the inside of another pipe, or a small manhole space under a busy roadway). In such applications, push reaming functionality is often the preferred method of reaming because the pipe section can be deployed and installed from the first pit during a push reaming operation. 
         [0007]    One aspect of the present disclosure relates to a thrust/push reaming system for enlarging the diameter of a pre-bored hole. In one example, the reaming system includes a cutter mounting plate that is rotated by a rotational driver of the system about a central axis of rotation. The cutter mounting plate includes a front face having a peripheral portion that surrounds the axis of rotation. A plurality of reaming cutters is mounted to the peripheral portion of the front face. In one example, the reaming cutters can include bits (e.g., tri-cone bits) that are rotatable relative to the cutter mounting plate. In one example, the bits can each include a main body rotatably mounted on a shaft/pin secured to the cutter mounting plate, and a plurality of cutting elements (e.g., carbide buttons) embedded in or otherwise anchored to the main body. The system can also include a guide or centralizer that advances in front of the cutter mounting plate within the pre-bored hole during reaming. The guide is configured to fit within the pre-bored hole in advance of the cutter mounting plate so as to center the cutter mounting plate relative to the pre-bored hole. In one example, the centralizer can be a cylindrical sleeve having a hollow interior. An attachment structure (e.g., a plurality of robust bars, rods, plates, etc.) extends forwardly from the cutter mounting plate and connects the centralizer to the cutter mounting plate. In one example, the cutter mounting plate, the attachment structure and the centralizer can all rotate together as a unit about the central axis of rotation during reaming operations. In other examples, relative rotation can be provided between the centralizer and the cutter mounting plate such that during reaming the cutter mounting plate rotates to enlarge the hole while the centralizer does not rotate within the pre-bored hole. To allow for relative rotation, bearings can be provided between the centralizer and the attachment structure, between the attachment structure and the cutter mounting plate, or elsewhere. In one example, the centralizer is hollow to allow any cuttings or other material present in the pre-bored hole to pass through the centralizer to the cutter mounting plate. The cutter mounting plate can define one or more through-holes for allowing cuttings generated during reaming and/or material that passes through the centralizer to pass through the cutter mounting plate from the front side to a back side of the cutter mounting plate. A vacuum intake of a cuttings removal system can be provided near the back side of the cutter mounting plate for drawing-in material that passes through the through-holes and evacuates the material from the reamed hole. Gasketing can be provided between the vacuum intake and the back side of the cutter mounting plate to enhance suction. Fins or other structures can be provided on a front side of the cutter mounting plate for directing/lifting cuttings from the bottom of the reamed hole toward the through-holes. In one example, the reaming cutters define a cutting diameter that is at least 5, 10, or 20 percent larger than a cross-dimension (e.g., outer diameter) of the centralizer. 
         [0008]    A variety of additional aspects will be set forth in the description that follows. The aspects can relate to individual features and to combinations of features. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the broad inventive concepts upon which the embodiments disclosed herein are based. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a schematic depiction of a push reaming apparatus having features in accordance with the principles of the present disclosure; 
           [0010]      FIG. 2  is an enlarged view of a portion of  FIG. 1 ; 
           [0011]      FIG. 3  is a top elevation view of an alternative embodiment of a push reaming apparatus in accordance with the principles of the present disclosure; 
           [0012]      FIG. 4  is a cross-sectional view along line  4 - 4  of  FIG. 3 ; 
           [0013]      FIG. 5  is a first end view of the push reaming apparatus of  FIG. 3 ; and 
           [0014]      FIG. 6  is a second end view of the push reaming apparatus of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0015]      FIG. 1  shows a push reaming apparatus  20  having features in accordance with the principles of the present disclosure. The push reaming apparatus is configured to enlarge a pre-bored hole  200  using a push reaming process. During the push reaming process, the push reaming apparatus  20  reams the pre-bored bole  200  to create a reamed hole  202  having a larger diameter than the pre-bored bole  200 . 
         [0016]    Generally, the apparatus  20  includes a plurality of pipe sections  22  that are coupled together in an end-to-end relationship to form a drill string  24 . Each of the pipe sections  22  includes a drive shaft  26  rotatably mounted in an outer casing assembly  28 . A drill head  30  is mounted at a distal end of the drill string  24 , while a drive unit  32  is located at a proximal end of the drill string  24 . The drive unit  32  includes a torque driver adapted to apply torque to the drill string  24  and an axial driver for applying thrust or pull-back force to the drill string  24 . Thrust or pull-back force from the drive unit  32  is transferred between the proximal end to the distal end of the drill string  24  by the outer casing assemblies  28  of the pipe sections  22 . Torque is transferred from the proximal end of the drill string  24  to the distal end of the drill string  24  by the drive shafts  26  of the pipe sections  22  which rotate relative to the casing assemblies  28 . The torque from the drive unit  32  is transferred through the apparatus  20  by the drive shafts  26  and ultimately is used to rotate a cutter mounting plate  33  of a push reaming unit  34  of the drill head  30 . Optional skids  204  can be provided at bottom sides of the outer casing assemblies for assisting in centering the drill string within the reamed hole  202 . Other types of centralizers could also be used. 
         [0017]    The pipe sections  22  can also be referred to as drill rods, drill stems or drill members. The pipe sections are typically used to form an underground bore, and then are removed from the underground bore when product (e.g., piping) is installed in the bore. 
         [0018]    The drill head  30  of the drilling apparatus  20  can include a drive stem  46  rotatably mounted within a main body  38  of the drill head  30 . A distal end of the drive stem  46  is configured to transfer torque to the cutter mounting plate  33 . A proximal end of the drive stem  46  couples to the drive shaft  26  of the distal-most pipe section  22  such that torque is transferred from the drive shafts  26  to the drive stem  46 . In this way, the drive stem  46  functions as the last leg for transferring torque from the drive unit  32  to the push reaming unit  34 . The outer casing assemblies  28  transfer thrust and/or pull back force to the main body  38  of the drill head. The drill head  30  preferably includes bearings (e.g., axial/thrust bearings and radial bearings) that allow the drive stem  46  to rotate relative to the main body  38  and also allow thrust or pull-back force to be transferred from the main body  38  through the drive stem  46  to the push reaming unit  34 . 
         [0019]    To assist in drilling, the tunneling apparatus  20  can also include a fluid pump  63  for forcing drilling fluid from the proximal end to the distal end of the drill string  24 . In certain embodiments, the drilling fluid can be pumped through a central passage  45  defined through the drive shafts  26 . The central passage  45  defined through the drive shafts  26  can be in fluid communication with at least one fluid delivery port provided at a front face of the cutter mounting plate  33  such that the drilling fluid is readily provided at a reaming interface of the push reaming unit  34 . 
         [0020]    During reaming, the cutter mounting plate  33  is rotated by the rotational driver of the drive unit  32  about a central axis of rotation  206 . The cutter mounting plate  33  includes a front face  208  having a peripheral portion  210  that surrounds the axis of rotation  206 . A plurality of reaming cutters  211  are mounted to the peripheral portion  210  of the front face  208 . In one example, the reaming cutters  211  can include bits (e.g., tri-cone bits) that are rotatable relative to the cutter mounting plate  33 . In one example, the bits can each include a main body rotatably mounted on a shaft/pin secured to the cutter mounting plate  33 , and a plurality of hardened elements (e.g., carbide buttons) embedded in or otherwise anchored to the main body. 
         [0021]    The system can also include a guide or centralizer  212  that advances in front of the cutter mounting plate  33  within the pre-bored hole  200  during reaming. The centralizer  212  is configured to fit within the pre-bored hole  200  in advance of the cutter mounting plate  33  so as to center the cutter mounting plate  33  relative to the pre-bored hole  200 . In one example, the centralizer  212  has an outer diameter that is only slightly smaller than the diameter of the pre-bored bole  200 . In one example, the centralizer  212  can be a cylindrical sleeve having a hollow interior  214 . 
         [0022]    An attachment structure  216  (e.g., a plurality of robust bars, rods, plates, etc.) extends forwardly from the cutter mounting plate  33  and connects the centralizer  212  to the cutter mounting plate  33 . In one example, the cutter mounting plate  33 , the attachment structure  216  and the centralizer  212  can all rotate together as a unit about the central axis of rotation  206  during reaming operations. In other examples, relative rotation can be provided between the centralizer  212  and the cutter mounting plate  33  such that during reaming the cutter mounting plate  33  rotates to enlarge the pre-bored hole while the centralizer  212  does not rotate within the pre-bored hole. To allow for relative rotation, bearings can be provided between the centralizer  212  and the attachment structure  216 , between the attachment structure  216  and the cutter mounting plate  33 , or elsewhere. 
         [0023]    In one example, the centralizer  212  is hollow to allow cuttings or other material present in the pre-bored hole  200  to pass through the centralizer  212  to the cutter mounting plate  33  as the drill string is forwardly advanced (e.g., thrusted forwardly via thrust provided by the drive unit  32 ) during reaming. The cutter mounting plate  33  can define one or more through-holes  218  for allowing cuttings generated during reaming and/or material that passes through the centralizer  212  to pass through the cutter mounting plate  33  from the front side  208  to a back side  220  of the cutter mounting plate  33 . A vacuum intake  222  of a cuttings removal system can be provided near the back side  220  of the cutter mounting plate  33  for drawing-in material that passes through the through-holes  218 . The cuttings removal system can include a vacuum source  65  (e.g., a vacuum source above ground or at the distal end of the hole) that applies vacuum to a vacuum passage that extends from the vacuum source, through the drill string, to the vacuum intake  222 . In this way, the cuttings removal system can draw cuttings and drilling fluid out of the reamed hole and can convey the cuttings and drilling fluid to a storage receptacle outside the reamed hole. 
         [0024]    Gasketing can be provided between the vacuum intake and the back side of the cutter mounting plate to enhance suction. Fins or other structures can be provided on a front side of the cutter mounting plate for directing/lifting cuttings from the bottom of the reamed hole toward the through-holes. In one example, the reaming cutters define a cutting diameter that is at least 5, 10, or 20 percent larger than a cross-dimension (e.g., outer diameter) of the centralizer. 
         [0025]    Referring to  FIGS. 3-6 , an alternative embodiment of a push reaming apparatus is described in further detail. In the depicted embodiment the drill head  100  is configured to connect to a distal end of the drill string  24  via a connection interface  102  on a second end portion  104  of the drill head  100 . The drill head includes a main body  106  that supports a rotatable drive stem  108  that extends coaxially therethrough. The drive stem  108  is configured to rotate the cutter mounting plate  110 . The cutter mounting plate  110  includes a front face  112  that includes a plurality of reaming cutters  114  mounted to peripheral portion  116  of the cutter mounting plate  110 . The cutter mounting plate  110  includes a plurality of spaced apart through-holes  118  located around the periphery portion  116  of the cutter mounting plate  110 . In the depicted embodiment the through-holes  118  are open to and coincident with the periphery edge  120  of the cutter mounting plate  110 . 
         [0026]    In the depicted embodiment the drill head  100  includes an attachment structure  122  that extends forwardly from the cutter mounting plate  110 . The attachment structure  122  connects a centralizer  124  to the drill head  100 . In the depicted embodiment centralizer  124  can idle (not rotate) while the cutter mounting plate  110  rotates. 
         [0027]    In the depicted embodiment the drill head  100  includes a finished bore guide  126 . The finished bore guide  126  provides additional stabilization to the drill head and also collects the cutting from the bore via vacuum intake  128  that faces and is rearward of the back side  130  of the cutter mounting plate  110 . As the drill head  100  advances, cuttings are driven into the vacuum intake  128  and vacuumed through the central passage  130  of the drill head  100 . In the depicted embodiment the finished bore guide  126  is generally cylindrical in shape with an outer diameter that is slightly smaller than the diameter of the reamed bore diameter. In the depicted embodiment the finished bore guide includes straight sidewalls  170  (i.e., the finished bore guide is in the shape of a constant diameter cylinder) and includes small tapers  172 ,  174  at both the leading edge and the trailing edge. It should be appreciated that in alternative embodiments the finished bore guide could include a tapered side wall, for example, wherein the diameter of the finished bore guide increases from the distal end to the proximal end. In the depicted embodiment the finished bore guide  126  includes a two-piece construction including a first section  176  and a second section  178  such that the finished bore guide  126  can be attached and detached from the drill head  100 . 
         [0028]    Referring to  FIG. 4  the assembly of the drill head  100  is described in further detail. In the depicted embodiment the drive stem  108  is coaxially positioned within sleeve  132 . The sleeve  132  is fixed to the main body  106 , which is generally cylindrical. The drive stem  108  is hex fit into an end plate  134 . The end plate  134  is bolted to an inner bearing housing  136 . The bearing housing  136  is bolted to the cutter mounting plate  110  and rotates with the cutter mounting plate  110 . 
         [0029]    In the depicted embodiment, a first bearing assembly  138  is arranged within the bearing housing  136  to allow the bearing housing  136  to rotate relative to the sleeve  132 , which is fixed to the main body  106 . The first bearing assembly  138  includes a pair of thrust bearings  150 ,  152  positioned between a pair of radial bearings  154 ,  156 . A second bearing assembly  140  is arranged within the bearing housing  136  and allows a centralizer shaft  142  to remain stationary or idle relative to the drive stem  108  and the cutter mounting plate  110 . The second bearing assembly  140  includes a pair of thrust bearings  158 ,  160  that are located on the centralizer shaft  142  between a shoulder  162  and a collar  164 . 
         [0030]    In the depicted embodiment the bearing housing  136  includes a first portion that encloses the first bearing assembly  138 . The first portion includes a rear portion  143  and a front portion  146 . The front portion  146  includes telescoping construction with a shoulder for seating the cutter mounting plate  110 . The bearing housing  136  includes a second portion  148  that encloses the second bearing assembly  140 . The second portion  148  has an outer diameter that is less than a central aperture in the mounting plate  110 . This configuration allows the mounting plate  110  to be connected and disconnected from the drill head  100  without disassembling the bearing housing  136 . 
         [0031]    In the depicted embodiment the centralizer  124  is bolted to a distal end  180  of the centralizer shaft  142 . The centralizer shaft includes a stepped first shoulder  166  and second shoulder  168  that cooperatively seat and provides stability to the centralizer  124 . The configuration enables the centralizer  124  to be connected and disconnected to the drill head without disassembling the bearing housing  136  and without removing the cutter mounting plate  110 . In the depicted embodiment the distal end  180  of the centralizer shaft  142  is threaded to receive a nut  144  that secures the centralizer  124  to the centralizer shaft  142 . 
         [0032]    The drill head  100  is configured such that it can be used to enlarge a bore by thrusting/pushing it through a pilot bore. Product material such as sections of sewer pipe, water lines, conduit, etc. can be attached rearward of the finished bore guide  126  and be pulled into the bore simultaneous with the reaming process. In one embodiment the product material would be attached to the drill head  100  at a first pit and dragged by the drill head  100  to an end location. The end location could be a second pit, another pipe, a crawl space, the basement of a building, etc. This method of installing product material deployed from the first pit wherein the boring machine is especially useful wherein the far end of the bore (the exit of the bore) is not conducive to the deployment of product material. For example, when the far end of the bore is in the basement of a building, it can be difficult to get product material into the basement so that it can be pulled back through the bore during a back reaming operation. In such an application, push reaming provides significant advantages. 
         [0033]    In the depicted embodiment the drill head  100  is constructed such that the centralizer  124 , the cutter mounting plate  110 , and the finished bore guide  126  are all interchangeable. In the depicted embodiment the centralizer  124 , the cutter mounting plate  110 , and the finished bore guide  126  can all be replaced without opening up the bearing housing  136 . As discussed above, the centralizer  124  can be removed by removing a single nut  144 . Once removed, the cutter mounting plate  110  can be removed by unbolting it from the bearing housing flange  182 . The finished bore guide  126  can be removed by unbolting the first section  176  and a second section  178 . The finished bore guide can be removed and replaced independently. In other words, it can be removed and replaced without first removing the centralizer  124  or the cutter mounting plate  110 . This modular configuration provides advantages as the selection of components can be optimized based on ground conditions. For example, when drilling through softer materials, the outer size of the centralizer  124  may be very close to the diameter of the pilot hole, and the other size of the bore guide may be very close to the diameter of the bore that is reamed by the cutters on the cutter mounting plate  110 . In ground conditions that are more stable or harder, it may be desirable to allow for more clearance between the pilot bore and the centralizer by using a smaller centralizer and more clearance between the reamed bore and the finished bore guide. 
         [0034]    In the embodiment depicted above, the push reaming unit comprises the following features: a cutter mounting plate that rotates about an axis of rotation, the cutter mounting plate including a front side having a peripheral portion, the cutter mounting plate defining at least one through path that extends through the cutter mounting plate from the front side to a rear side; a plurality of reaming cutters mounted at the peripheral portion of the front side of the cutter mounting plate, the reaming cutters being spaced about the axis of rotation; a centralizer positioned in front of the cutter mounting plate, the centralizer being co-axially aligned along the axis of the rotation; an attachment structure that connects the centralizer to the cutter mounting plate; and a finished bore guide located rearward of the cutter mounting plate, the finished bore guide being removable without first removing the cutter mounting plate or centralizer. In the depicted embodiment the centralizer is attached to a centralizer shaft which is supported by a housing that rotates with the cutter mounting plate such that the shaft can rotate independent of the housing. The centralizer is cylindrical and has a maximum diameter that is smaller than a maximum diameter of the cutter mounting plate and the finished bore guide includes a maximum diameter that is larger than a maximum diameter of the centralizer. The unit also includes a finished bore guide located rearward of the cutter mounting plate, the finished bore guide includes a vacuum intake to receiving cuttings from the bore and directing the cuttings into the drill string. In the depicted embodiment the through path that extends through the cutter mounting plate from the front side to a rear side is open to a periphery edge of the cutter mounting plate. It should be appreciated that many alternative configurations are also possible. 
         [0035]    In one embodiment a push reaming unit according to the present disclosure includes: a generally cylindrical main body portion configured to mate with a drill string; the main body including a sleeve fixedly mounted coaxially therein; a drive stem supported within the sleeve; a bearing housing fixed to the drive stem such that the bearing housing rotates with the drive stem; a first bearing assembly located within the bearing housing and configured to allow for relative rotation between the drive stem and the sleeve; a cutter mounting plate connected to the bearing housing such that the cutter mounting plate rotates with the bearing housing; a centralizer shaft extending forwardly of the cutter mounting plate from the bearing housing; a second bearing assembly located within the bearing housing and configured to allow for relative rotation between the bearing housing and the centralizer shaft; a centralizer supported on the centralizer shaft forward of the cutter mounting plate; and a finished bore guide coaxially arranged with the main body positioned rearward of the cutter mounting plate, the finished bore guide including a cutting vacuum inlet. In the embodiment depicted in  FIGS. 3-5  the cutter mounting plate has a scalloped periphery edge with the scallops located between adjacent cutter mountings. The cutter mounting plate is shown bolted to a radially extending flange of the bearing housing. The centralizer shaft includes a step shoulder configuration that secures the centralizer in the radial direction. The vacuum inlet is located on the bottom portion of the finished bore guide and is configured to funnel cuttings into the cuttings conduit of the main body which position below a sight path that extends through the main body of the drill head. It should be appreciated that many alternative configurations are also possible which may include more or fewer features as well as different features. For example, it should be appreciated that fluid such as water can be delivered to the bore via hoses to aid in flushing of the cutting out of the bore. 
         [0036]    The present disclosure provides a method of push reaming that in one embodiment includes the following steps: selecting a centralizer or a drill head based on the diameter of a pilot bore; selecting a finished bore guide based on the diameter of the final reamed bore diameter and also in part on the ground condition in which the reaming will be done; connecting the centralizer to a drill head forward of a cutter mounting plate; connecting the finished bore guide rearward of the cutter mounting plate; thrusting the drill head into the pilot bore while rotating the cutter mounting plate; and removing cuttings from the bore via a vacuum inlet located rearward of the cutter mounting plate and forward of a rear portion of the finished bore guide. In the embodiment disclosed in  FIGS. 3-5 , the centralizer is not driven to rotate even when the cutter mounting plate rotates. As discussed above the finished bore guide in the embodiment depicted in  FIGS. 3-5  can be detached from the drill head without detaching the centralizer or the cutter mounting plate from the drill head. As discussed above, the cutter mounting plate in the embodiment depicted in  FIGS. 3-5  is bolted to an annular flange of a bearing housing. It should be appreciated that alternative embodiments may include fewer steps, different steps, and/or a different combination of steps 
         [0037]    Various modifications and alterations of this disclosure will become apparent to those skilled in the art without departing from the scope and spirit of this disclosure, and it should be understood that the scope of this disclosure is not to be unduly limited to the illustrative examples set forth herein.