US 20020112894 A1
A drill bit for use in horizontal boring includes a bit body with a central axis of rotation including a forwardmost pilot section, a reaming section rearwardly of the pilot section including a forwardly inclined arcuate steering surface and a plurality of gauge cutting teeth disposed rearwardly of the pilot section in opposed relationship to the inclined steering section, the gauge teeth extending farther from the central axis in a radial direction than the steering section such the arcuate steering section lies entirely within a circular profile corresponding to the path of the gauge teeth when the bit is rotated 360° and a coupling section at a rear end portion of the body configured for attachments to an adjacent component of the drill sting.
1. A drill bit for use in horizontal boring comprising:
a bit body with a central axis of rotation including a forwardmost pilot section, the pilot section configured to form a pilot bore during drilling operations and stabilize the bit body during rotary operation;
a reaming section rearwardly of the pilot section, the reaming section including a forwardly inclined arcuate steering surface and a plurality of gauge cutting teeth disposed rearwardly of the pilot section in opposed relationship to the inclined steering section the gauge teeth extending farther from the central axis in a radial direction than the steering section such the arcuate steering section lies entirely within a circular profile corresponding to the path of the gauge teeth when the bit is rotated 360°; and
a coupling section at a rear end portion of the body configured for attachments to an adjacent component of the drill sting.
2. The drill bit of
3. The drill bit of
 This application claims priority of U.S. Provisional Patent Application Serial No. 60/263,151, filed Jan. 22, 2001.
 The invention relates to a method and apparatus for directional boring in rocky formations and an improved bit for drilling therein.
 Directional boring apparatus or trench less drills for making holes through soil are well known. The directional borer generally includes a series of drill rods joined end to end to form a drill string. The drill string is pushed or pulled though the soil by means of a powerful device such as a hydraulic cylinder. See McDonald et al. U.S. Pat. No. 4,694,913, Malzahn, U.S. Pat. Nos. 4,945,999 and 5,070,848, and Cherrington, U.S. Pat. No. 4,697,775 (RE 33,793). The drill string may be pushed and rotated at the same time as described in Dunn, U.S. Pat. No. 4,953,633 and Deken, et al., U.S. Pat. No. 5,242,026. A spade, bit or head having one or more angled faces configured for boring is disposed at the end of the drill string and may include an ejection nozzle for water or drilling mud to assist in boring.
 In one known directional boring system, the drill bit is pushed through the soil without rotation in order to steer the tool by means of the angled face, which is typically a forwardly facing sloped surface. For rocky conditions, a row of teeth may be added to the drill bit and the bit operated in the manner described in Runquist et al. U.S. Pat. No. 5,778,991. Other toothed bits for directional boring through rock are shown in European Patent Applications Nos. EP 0 857 852 and EP 0 857 853, Cox U.S. Pat. No. 5,899,283, Skaggs U.S. Pat. No. 5,647,448 and Stephenson U.S. Pat. No. 5,799,740. Steering systems for use with these devices require keeping track of the angle of rotation of the sloped face of the bit and/or the teeth.
 According known systems, a transmitter or sonde mounted in a tubular housing is mounted behind and adjacent to the bit and sends a signal that indicates the angle of rotation of the bit. The sonde is mounted in a predetermined alignment relative to the steering portion of the bit. The sonde enables steering of the bit during the horizontal drilling operation. See generally Mercer U.S. Pat. Nos. 5,155,442, 5,337,002, 5,444,382 and 5,633,589, Hesse et al. U.S. Pat. No. 5,795,991, and Stangl et al. U.S. Pat. No. 4,907,658.
 According to one known directional boring system, the drill bit is pushed through the soil without rotation to steer the tool by means of an angled face which is typically a forwardly sloping face. For rocky conditions, a row of teeth may be added to the drill bit and the bit operated in the manner described in Runquist et al., U.S. Pat. No. 5,778,991. Other toothed bits for directional drilling through rock are shown in Cox U.S. Pat. No. 5, 899,283, Skaggs U.S. Pat. No. 5,647,488 and Stephenson U.S. Pat. No. 5,799, 740.
 The “duckbill” style of bit, conventionally mounted directly on a forwardly sloped face of a sonde housing, is inexpensive, generally easy to replace, and has the advantage of simplicity. Six bolts, which may be countersunk, hold the duckbill in place. The bit itself is little more than a flat steel plate that protrudes beyond the front end of the sonde housing. The bit may have teeth to aid in directional drilling through rocky conditions. The bolts that hold the bit on, however, tend to loosen or fail under the large shear forces to which the bit is subjected, and once the bit breaks off, the bore must be discontinued and the drill head withdrawn.
 A dual-purpose bit designed for directional boring through soil and horizontal drilling in rock, known as the Trihawk™ is described in PCT publication No. 00/11303, published Mar. 2, 2000. The Trihawk bit has three replaceable canted teeth set to cut a series of annular grooves which form the outer part the borehole when drilling in rock. A mound or cone forms at the center of the borehole that is progressively broken down against the steering face as the bit advances. This bit is effective for drilling in dirt, soft rock and medium rock. The present invention provides a bit with similar capabilities without canted teeth.
 In the accompanying drawings, wherein like numerals denote like elements:
FIG. 1 is perspective view of the bit of the invention;
FIG. 2 is a side view of the bit of the invention;
FIG. 3 is a front view of the bit of the invention;
FIG. 4 is a rear view of the bit of the invention;
FIG. 5 is a top view of the bit of the invention positioned in an outline of a bore profile;
FIG. 6 is a side view of the bit of the invention positioned in an outline of a bore profile;
FIG. 7 is a front view of the bit of the invention positioned in an outline of a bore profile;
 FIGS. 8-10 are side, top and side views of the bit of the invention;
FIG. 11 is a partial cross sectional view of the bit of the invention taken along line C-C of FIG. 7; and
FIG. 12 is a partial cross sectional view of the bit of the invention taken along line B-B of FIG. 7.
 While the making and using of various embodiments of the present invention are discussed in detail below, it should be appreciated that the present invention provides many applicable inventive concepts which can be embodied in a wide variety of contexts. The embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not limit the scope of the invention.
 Referring now to FIGS. 1-12 a bit 10 in accordance with the invention comprises a bit body 12 including a pilot section 14 and reaming section 16, the reaming section having a larger diameter than pilot section 14. Pilot section 14 includes a nose section 18, a slightly concave face 28 with a plurality of forwardly projecting nose inserts (carbide studs) 20 disposed in holes 34, a shoulder section 22 including a plurality of spaced apart shoulder inserts 24 located in holes 36, and a cylindrical pilot body 26. A plurality of cut outs 30 are formed in shoulder section 22 and circumferentially located around the perimeter of shoulder section 22. As shown, shoulder section 22 forms a curved transition from nose section 18 to body section 22.
 A plurality of outlets 32 located in nose section 18 provide for the flow of a pressurized fluid to the pilot section 14 to lubricate the bit during drilling operations and to sweep away material such as dirt, rock and debris from the pilot section 14. Cut outs 30 facilitate the sweeping action of the pressurized fluid, providing a passageway through with the mixture of drilling fluid and debris may pass during the drilling operation. Nose inserts 20 and shoulder inserts 24 are preferably carbide studs and are secured with an interference fit or may be brazed in place. Nose inserts 20 serve to cut into and grind away the face of the borehole as it is being drilled, especially rock formations. Shoulder inserts 24 are strategically placed so as to protect the base metal of pilot section 14 from abrasion while simultaneously cutting and widening the pilot bore created by the nose section 18 as well as grinding up material and debris dislodged in the drilling operation.
 Reaming section 16 of bit body 12 includes a pair of substantially flat, parallel opposed sides 40 and an acuate, forwardly inclined steering section 42 extending between sides 40 on a first side of the bit. The steering section 42 is semi frustro conical in shape, being inclined, arcuate and circumscribing less than 180° of the perimeter or circumference of reaming section 16 of bit body 12. As best shown in FIG. 10, steering section 42 is forwardly inclined at an angle α of approximately 20°, although a greater or lesser angle may be used.
 A plurality of reaming ribs 44, including a central rib 44′, also extend between sides 40 in opposed relationship to steering section 42 on a second side of the bit and are forwardly inclined toward pilot section 14. Each rib 44 includes a row of cutting or gauge teeth 46 disposed in spaced apart relationship along the length of the rib. As illustrated, a plurality of intermediate inserts, (two shown) between the gauge teeth 46 of central rib 44′ and shoulder section 22 of pilot section 14. As best shown in FIG. 6, intermediate teeth 47 are positioned inside the pilot bore profile 49 and engage the bore only when the bit is operated in the push-to-steer or push and partial rotate to steer modes as described below. Intermediate teeth 47 also serve to protect the base metal of the corresponding portion of cylindrical pilot body 26. Preferably, gauge teeth 46 and intermediate teeth 47 comprise carbide studs and are positioned so as to protect the base metal of the bit while simultaneously cutting and widening the bore formed by pilot section 14. Gauge teeth 46 and intermediate teeth 47 may be interference fit or brazed into apertures 48.
 As best shown in FIG. 7, forwardly inclined steering surface 42 circumscribes less than 180° of the perimeter or circumference of the bit body 12. Likewise reaming ribs 44 also circumscribe less than 180° of the perimeter or circumference of bit body 12. Ribs 44 are also positioned opposite inclined steering surface 42. It will also be appreciated that gauge teeth 46 project farther out form the central axis 60 of the bit than does inclined steering surface 42. Thus, when the bit is operated in the rotary mode, normally inclined steering surface 42 will have no contact, or minimal contact with the outside perimeter or profile 53 of the bore. In other words, inclined steering section 42 circumscribes less than 180° of the perimeter of the reaming section. Similarly, the gauge teeth being positioned so as to cover a portion of the reaming section circumscribing less than 180° of the perimeter of the reaming section opposite the steering section 42. Since the gauge teeth 46 extend farther from the central axis in a radial direction than the steering section 42, the steering section will lie entirely within a circular profile 53 corresponding to the path of the gauge teeth when the bit is rotated 360° irrespective of the rotary position of the bit 10.
 A fluid outlet 57 (one shown) is located on each of longitudinally inclined ribs 44 for the passage of drilling fluid to lubricate the reamer section and to sweep cutting away during drilling operations. Each fluid outlet 32, 57 communicates with an interior passage 62 (FIG. 11) in bit body 12 to supply the reaming section 16 of bit 10 with drilling fluid. Extending longitudinally between ribs 44 are cut outs 50 that facilitate the flow of drilling fluid and debris around and past the bit 10 during drilling operations.
 Bit 10 also includes a coupling section 52. Coupling section 52 includes a grooved socket 54 designed to receive a splined projection at the front of an adjoining sonde housing component as described in U.S. Pat. No. 6,148,935 to Wentworth et al and assigned to Earth Tool Company L.L.C., of Oconomowoc Wis., the entire contents of which are incorporated herein for all purposes. A pair of transverse holes 56, 58 on either side of central longitudinal axis 60 of bit body 12 are provided for insertion of roll pins or other retainers that hold bit 10 on the front end of a sonde housing or other adjacent drill string component or tool. Alternatively, coupling section 52 may comprise a splined projection rather than a socket or any other connection suitable for mounting a bit on a drill string as known in the art such as by a threaded connection or an end portion profiled to fit against a surface of a sonde housing or similar tool with holes there through for bolts. Bit 10 also includes one or more fluid passages 62, (FIGS. 11 and 12) extending through bit body 12 to carry pressurized drilling fluid from socket 54 to outlets 32 in nose 18 to lubricate bit 10 and sweep away debris generated in the drilling operation.
 In normal rotary operation, bit 10 will drill a straight bore with pilot section 14 stabilizing the bit. In this mode, steering section 42 will have minimal or no contact with the bore as illustrated by FIG. 7 wherein the steering section lies entirely within circular bore profile 53. In a push-to-steer mode of operation, inclined steering section 42 may be used to steer bit through dirt by forward thrust without rotation. In particular, in dirt and/or soft formations, longitudinally inclined ribs 44 will, as best shown in FIG. 3, present a smaller transverse cross sectional area than the inclined steering section 42, positioned on the opposite side of the bit. Thus, the side or portion of reaming section 16 where ribs 44 are positioned will present less resistance to forward movement through soft strata. Since the side of the bit 10 where ribs 44 are positioned will penetrate soft strata with less resistance than steering section 42, with its larger transverse cross section, the operator may steer bit 10 by orienting the bit with steering surface 42 positioned on the side of the bore opposite the direction in which is desired to steer the bit. Additionally, ribs 44 and gauge teeth 46 will selectively loosen the formation in the desired direction of travel, allowing pressurized drilling material to sweep the loosened material away, thereby aiding the steering function.
 In order to steer the bit 10 through a hard formation in the desired direction, such as up or down, bit 10 may be utilized in a push-and-partial-rotate mode. In this mode, bit 10 is rotated through an arc less than 360° causing the gauge teeth to cut a semicircular profile in the desired direction of travel. Steering section 42 of reamer section 16 provides an angled surface to push the bit 10 in the desired direction as the bit is rotated though the arc. After the arc is cut, bit 10 is retracted and rotated back a like distance, or the rotation is completed with the bit is withdrawn so that no cutting occurs. Bit 10 is then returned to engagement at the same location and the steps are repeated. This process gradually results in a change in boring direction, after which the mode of operation is returned to normal to form a circular borehole.
 Used in the above-described modes, the bit of the invention can drill a borehole through a soft or hard substrate, the bore being curved or having several angled segments representing, for example, initial entry into the ground, horizontal boring under an obstacle such as a roadway, and upward travel towards the surface at the end of the borehole.
 While certain embodiments of the invention have been illustrated for the purposes of this disclosure, numerous changes in the invention presented herein may be made by those skilled in the art, such changes being embodied within the scope and spirit of the present invention as defined in the appended claims.