Abstract:
A drill bit that is arranged to change the direction of drilling. A cone head is rotatably mounted on a shank portion extending from an elongate housing. When the housing is rotated, the cone head generates a concave hole. When a change in direction is required, the housing is rotated a few degrees in one direction and then counter-rotated in the opposite direction. This generates a partial but redirected pilot hole that is also substantially concave in configuration. Continued full rotation causes the drill bit to follow the partial pilot hole in the new direction.

Description:
FIELD OF THE INVENTION 
     This invention relates to drilling and more particularly to lateral underground drilling, e.g., to provide a conduit for communication lines. 
     BACKGROUND OF THE INVENTION 
     Communication lines are commonly placed underground. As permitted, a narrow trench is dug along the intended path of the line and the line is laid in the trench and then covered. This procedure is not complex and relatively inexpensive. However, often it happens that an obstruction lays in the path and digging a trench is not permitted or is too difficult. 
     In such instances, the alternative is to drill a hole through the ground and under the obstruction. For example, if the lines are to be buried to a four foot depth, a partial trench is first dug to the four foot depth prior to the obstruction and a drill bit mounted on an extendable pipe is fed laterally along the desired path. The pipe is moderately flexible and, in at least one version, the pipe is turned by a powerful motor to turn the bit and thereby auger through the ground with the pipe being fed behind it. A flushing slurry is fed through the pipe and into and through to the leading end of the drill bit. Material that is loosened by the drill bit is flushed by the slurry back through the hole. The line is then pulled through the hole formed by the drill bit and pipe. 
     All of the above is common to the art of directional drilling. Not referred to, however, and also common to the process explained above, is the need to control the direction of drilling. The drill bit is designed so that it can be maneuvered to change direction. The drill bit itself has a digging head that is non-symmetrical, i.e., teeth are projected angularly from the axis of the drill bit on one side only. During normal drilling, the drill bit is rotated so that the digging action is symmetrically applied and the drill bit travels in a straight line. To change direction, the rotation is stopped and the drill bit is pushed through the ground. At whatever direction the teeth are projected, that is the direction that the drill bit will turn toward (up, down or to either side). When the desired new direction is achieved, the rotation of the bit is commenced to head the digging action in the new direction. 
     The location of the drill bit and the position of the teeth on the drill bit is monitored through the use of a known detection device. Thus, an operator may determine that the hole is headed too deep, too shallow or otherwise off line in one direction or the other. He stops the rotation of the drill bit with the teeth facing the desired direction. He then pushes the bit forward until the bit is properly directed (which may include a sequence of side to side oscillation of the drill bit) and the normal drilling action is continued. 
     Whereas existing drill bits work quite well in dirt, they do not work so well in rock or shale. A cone-type drill bit cutting head has been developed to improve performance in rock or shale. Rows of circularly arranged teeth are provided on a conical cutter head that is rotatably mounted about its conical axis to the end of a forwardly protruded and outwardly directed shank of the drill bit. The base portion of the cone side of the conical head carries one of the rows of teeth and with the mounting arrangement described is adjacent to the shank and extends laterally outwardly of the shank. The axis of the rotatable cone is directed inwardly and forwardly. The apex of the cone side and the teeth adjacent the apex cuts the material from the center of the hole while the teeth adjacent the base provide the laterally outermost cutting which forms the hole side. 
     Whereas the conical cutter is considered an improvement when directional drilling through rock and shale, it is not completely satisfactory (and sometimes unsatisfactory), and an objective of the present invention is to improve on the above-described cone-type drill bit. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The present invention modifies the above-described cone-type drill bit. A shank provided on the drill bit is projected forwardly and inwardly. The base of a cone-type (conical) cutter head is rotatably secured to the shank in a manner whereby teeth near the base of the cone side of the cutter (the base portion of the cone side) cuts the material from the center of the hole and the apex of the cone side is projected laterally from the shank to cut the side wall of the hole. This difference can be viewed in the comparison of FIG. 1 (which illustrates the prior art) and FIG. 2 (which illustrates the present invention). 
     This modification is significant in terms of performance. Whereas the prior art drill bit head does not readily produce the desired directional change, such is readily produced by the device of the invention. The reason for the improved performance has not been verified and the following explanations are theories as to why such improvement is achieved. 
     FIGS. 1A and 2A, respectively, show the configuration of a hole being dug-by the prior art device and that of the present invention. When attempting to turn the drill bit, only one side of the hole is extended forwardly as indicated by dash lines  12  and  14  in FIGS. 1A and 2A, respectively. The desired change of direction is upwardly as viewed in the drawings and as indicated by the arrows. With reference to FIG.  1  and comparing it to FIG. 1A, it will be appreciated that the leading end of shank  16  will engage the upper side wall of the extended hole and resist turning of the tool in the upward direction. Applicant&#39;s shank  18  is on the opposite or bottom side of the hole and as it engages the extended portion of the hole, it urges the tool upwardly and in the direction of desired turning. 
     A second theory is suggested by the configuration of the hole being cut. Referring to the configuration of FIG. 2A, the center of the hole (point X) is the point of furthest extension. When full rotation of the tool is commenced, the bit will follow the path of least resistance and because the upper side is relieved, the bit will be urged upwardly. 
     In FIG. 1A, the center of the hole (point y) is inset from the side extensions. As the bit rotates to the bottom side of the hole, the inset center of the hole and the cam-like configuration that it produces will urge the bit back toward the bottom and directional change is resisted. 
     The above differences, advantages and benefits will, however, be more fully appreciated by reference to the following detailed description having reference to the accompanying drawings, referred to therein. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a tool of the prior art; 
     FIG. 1A is a side view of a hole produced by the tool of FIG. 1; 
     FIG. 2 is a side view of a drill bit of the present invention; 
     FIG. 2A is a side view of a hole produced by the tool bit of FIG. 2; 
     FIG. 3 is a side view of the tool of FIG. 2 illustrating also the profile of the hole produced in normal operation; 
     FIG. 4 is an end view as taken on view lines  4 — 4  of FIG. 3 illustrating a condition of partial rotation or oscillation of the drill bit; 
     FIG. 5 is a view similar to FIG. 3 illustrating the profile of the hole produced in a directional changing operation; and 
     FIG. 6 is a view illustrating a typical bore produced by the drill bit of FIGS.  2 - 5 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 3 illustrates a drill bit  20  for directional drilling a hole  70  (or bore) in the ground. The bit  20  has an elongate housing  22  that has a threaded end  24 . The end  24  is provided to connect the housing  22  to a pipe-line  26  (see FIG.  6 ). A shank portion  18  is fixedly mounted to the housing at the end opposite the threaded end  24 . As illustrated, the shank portion  18 , which is somewhat triangular in shape extends from the housing  22  and has edges (surfaces)  42 ,  44  inclined at an angle to the longitudinal axis  50  of the housing  22 . The peak  46 , whereat the surfaces  42 ,  44  meet, is at a greater distance from the longitudinal center line  50  (axis) of the housing  22  than an apex portion  38  of a conical cutting head  30 . The peak  46  will, however, very in height depending on the soil conditions. For example, when drilling rock, the peak  46  may have the same height as apex  38  (or it will quickly wear down to that height). 
     The conical cutting head  30  is rotatably mounted to the shank portion  18  about an axis a. The conical head  30  has a base side  32  and a cone shaped cutting side  34  including a base portion  37  and an apex  38 . Multiple cutting teeth  40  are provided on the cutting side  34  with the teeth  40  being spaced at intervals on the head  30  extending from the base side to the apex  38 . 
     The housing  22  and the pipe-line  26  as seen in FIG. 6 have a common axis of rotation  50 . The housing  22  (and the pipe-line  26 ) are rotatably driven in either rotative direction by a known power unit (not shown). The power unit also provides forward movement and retraction of the housing  22  and the pipe-line  26 . FIG. 6 illustrates the drill bit  20  boring a lateral hole  70  through the ground. 
     The housing  22  includes a conduit in communication with the hollow pipe for pumping a carrier such as water through the pipe-line  26  and through the housing conduit to an aperture  48 . Aperture  48  is provided in the end of housing  22  in close proximity to the conical head  30 . The water will carry the material cut away by the conical head  30  back through the hole  70  outside the pipe-line  26 . 
     A known sensor mechanism  52  (FIG. 6) is provided in the pipe-line  26 . The sensor mechanism  52  will provide data on the depth and location of the drill bit below the surface and will also provide the rotational orientation of the drill bit  20 , particularly the rotational orientation of the conical head  30 . The operator thus will have data on the depth as well as the rotational direction of the conical head  30 . 
     With reference now to FIG. 3, a hole or bore is produced by directing the drill bit  20  through the ground in a desired direction. For example, a trench is dug and the drill bit is directed in a lateral path (parallel to the surface) at a depth of, e.g., 4-6 feet. The power unit rotates the pipe-line  26  and the drill bit  20  attached thereto. As the drill bit is rotated the power unit will apply a force to the pipe-line  26  to force the drill bit through the ground. Water is pumped through the pipe-line  26  with the water discharging from the aperture  48 . 
     The conical head  30 , as it is rotated, will remove material and generate a leading hole  60 . The hole  60  is sized by the rotational path of the cone head  30 . As the cone head  30  progresses, the inclined edge  42  adjacent the peak  46  will enlarge the hole as illustrated by reference  70 . 
     When it is desired to change the directional path of the drill bit  20 , the drill bit  20  is stopped as well as the forward advancement of the pipe-line  26 . The sensor mechanism  52  conveys information to an above ground detector (known to the art) which provides the operator with the orientation of the cone head  30  of the drill bit  20  as well as the depth the drill bit is below the surface. The drill bit  20  is rotated, if required, until the cone head  30  is in the desired rotative position. The cone head  30  will be positioned with the apex  38  of the cone head  30  facing toward the new direction, which is upwardly as illustrated in the drawings. 
     The drill bit  20  is then rotated back and forth, clockwise and counter clockwise, e.g., 30° to 90° (hereafter sometimes referred to as oscillation) as the drill bit  20  is forced further through the ground. This oscillation is schematically illustrated in FIG. 4 with the degree of oscillation being indicated by arrow  43 . This action will produce a partially formed leading hole  60 ′ (see also FIG.  5 ). Only the upper portion of the material (as compared to hole  60 ) is removed to form the hole  60 ′ as best seen in the view of FIG.  5 . As the drill bit  20  is forced inwardly to form the partial hole  60 ′, the edge  42  of shank  18  (near peak  46 ) will be engaging the edge  66  of the hole  60  to urge the drill bit upwardly as indicated by arrow  64 . It is also believed that the leading end of edge  42  will also engage the partial hole  60 ′ and add to the upper urging of the drill bit. After a small advancement of the oscillating drill bit, the drill bit is retracted out of the hole  60 ′, full rotation is commenced and the drill bit is again advanced forward. The rotating drill bit is believed to center on the partial hole  60 ′ which functions as a pilot hole to direct the drill bit in the direction  68  as depicted in FIG.  5 . 
     It will be appreciated that the operation of changing direction of the drill bit  20  may have to be repeated more than once to accomplish the full directional change desired. 
     Whereas the above explanation of what produces the directional change is qualified as theoretical, the device has been built and placed in operation and the results demonstrate a significant improvement in directional drilling. 
     Those skilled in the art will recognize that modifications and variations may be made without departing from the true spirit and scope of the invention. The invention is therefore not to be limited to the embodiments described and illustrated but is to be determined from the appended claims.