EP1083292A1

EP1083292A1 - Interchangeable bit system for directional boring

Info

Publication number: EP1083292A1
Application number: EP00119678A
Authority: EP
Inventors: Steven W. Wentworth; Robert F. Crane
Original assignee: Earth Tool Co LLC
Current assignee: Earth Tool Co LLC
Priority date: 1999-09-10
Filing date: 2000-09-08
Publication date: 2001-03-14

Abstract

A directional boring bit assembly of the invention includes a headpiece (12) having a rear portion configured for attachment to and removal from a front end of a generally cylindrical drill head section (15). The headpiece (12) preferably has a passage therethrough for conveying fluid therein from the drill head section (15) to a fluid ejection port on the headpiece, and a frontwardly opening lengthwise socket (30). A bit (14) having a front portion configured for directional boring and a rear portion configured for sliding insertion into the socket (30) is held in the socket by a manually removable retainer such as a roll pin. The roll pin secures the bit (14) in the socket so that sliding movement of the rear portion of the bit (14) out of the socket (30) is prevented during directional boring with the bit assembly. The directional boring bit assembly of the invention provides interchangeability of bit styles in combination with a more secure system for mounting the bit.

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates, in general, to a method and apparatus for directional boring and, in particular to an interchangeable bit system for directional boring.

BACKGROUND OF THE INVENTION

Directional boring machines 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 hydraulic device such as a hydraulic cylinder. The drill string may be pushed and rotated at the same time as described in Dunn, U.S. Patent No. 4,953,633 and Deken, et al., U.S. Patent 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.
According to 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. Patent No. 5,778,991. Other toothed bits for directional boring through rock are shown in Skaggs U.S. Patent No. 5,647,448, Stephenson U.S. Patent No. 5,799,740 and Cox U.S. Patent No. 5,899,283.
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 to one known system, 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. Since the sonde housing is generally made of steel, a series of longitudinal slots or windows are provided through the wall of the sonde housing to permit reception of the signal. Mounting of the sonde in its housing has been accomplished by end loading as illustrated by Stangl et al. U.S. Patent No. 4,907,658 or through a side opening which is closed by a door or cover during use, as illustrated in Lee et al. U.S. Patent No. 5,253,721.
The "duckbill" style of bit, conventionally mounted directly on a forwardly sloped side face of the sonde housing, is inexpensive, generally easy to replace, and has the advantage of simplicity. Six bolts, which may be counterbored, 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 blade may have teeth to aid in directional boring 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 oft the bore must be discontinued and the drill head withdrawn. A need persists for a directional boring system has the simplicity of the duckbill, but does not rely on bolts or other similar fasteners to hold the bit on. The present invention addresses this concern.
In addition, as underground utilities become more and more common in urban areas, directional boring machines must maintain a very straight line during drilling or risk hitting a neighboring gas line, water main, or optic fiber cable. This becomes more difficult when the bore must pass through a rocky formation, e.g. chalk or coral, such that carbide tipped drilling teeth must be used on the bit. The present invention provides a bit which can be used with a trenchless rock drill in urban conditions and stay on line better than other trenchless rock drills presently in commercial use.

SUMMARY OF THE INVENTION

A directional boring bit assembly of the invention includes a headpiece having a rear portion configured for attachment to and removal from a front end of a generally cylindrical drill head section. The headpiece preferably has a passage therethrough for conveying fluid therein from the drill head section to a fluid ejection port on the headpiece, and a frontwardly opening lengthwise socket. A bit having a front portion configured for directional boring and a rear portion configured for sliding insertion into the socket is held in the socket by a manually removable retainer. The retainer generally takes the form of an elongated rod or pin lacking a head. It secures the bit in the socket so that sliding movement of the rear portion of the bit out of the socket is prevented during directional boring with the bit assembly. The drill head section that the headpiece attaches to may be any such section commonly used in directional boring or rock drilling, such as a sonde housing, impactor housing, or starter rod.
According to a preferred form of the invention, the headpiece has a transverse hole therethrough which becomes aligned with a transverse hole in the rear portion of the bit when the bit is fully inserted into the socket. The retainer is inserted into the aligned transverse holes so that the bit cannot be withdrawn from the socket while the retainer engages the transverse holes.
According to another aspect of the invention, a kit or set for directional boring is provided which includes at least one headpiece and at least two bits of varying cutting characteristics, e.g., one with a flat edge (non-toothed) and one with rock cutting teeth. These permit the operator to select the right bit for the conditions at the start of the job. A method of use is also contemplated wherein the operator interchanges bits in response to changing soil conditions. These and other aspects of the invention are described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the features and advantages of the present invention, reference is now made to the detailed description of the invention along with the accompanying figures in which corresponding numerals in the different figures refer to corresponding parts and in which:
FIGURE 1 is a bottom view of an interchangeable bit boring tool of the invention with a first embodiment of an interchangeable bit;
FIGURE 2 is a lengthwise section taken along the line 2-2 in Figure 1;
FIGURE 3 is a front view of the tool of Figure 1;
FIGURE 4 is a side view of the tool of Figure 1;
FIGURE 5 is a top view of the tool of Figure 1;
FIGURE 6 is a lengthwise sectional view taken along the line 6-6 in Figure 5;
FIGURE 7 is a cross sectional view along the line 7-7 in Figure 4;
FIGURE 8 is a cross sectional view along the line 8-8 in Figure 4;
FIGURE 9 is a partial, exploded, perspective view of the interchangeable bit system of Figure 1;
FIGURE 10 is a side perspective view of a headpiece according to the invention;
FIGURE 11 is a cross sectional view taken along the line 11-11 in Figure 5, showing a roll pin in its retracted position;
FIGURE 12 is a front perspective view of a headpiece of the invention having an alternative bit mounted thereon;
FIGURE 13 is a side view of the assembly of Figure 12;
FIGURE 14 is a rear perspective view of the assembly of Figure 10.

DETAILED DESCRIPTION OF THE INVENTION

While various embodiments of the 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 are not to limit the scope of the invention.
Referring now to Figures 1 to 11, a drilling or boring head 10 incorporating the interchangeable bit system of the invention includes a headpiece 12 and a replaceable bit 14. Headpiece 12 is generally a cylinder with selected cutaway portions designed to provide a secure, torque transmitting connection between boring head 10 and the drill head section(s) behind it. To protect headpiece 12 from abrasion, one or more holes 13 may be provided into which rounded head tungsten carbide studs (not shown) may be mounted. Headpiece 12 has a rear recess 16 having a series of longitudinal grooves 18 into which the splines 19 of a splined projection 21 on the adjoining drill head section 15 fit. Retainers such as coiled roll pins are inserted through a pair of parallel, spaced transverse holes 20 so that headpiece 12 is removably secured as described in co-pending U.S. Serial No. 09/373,395, filed August 12, 1999, and incorporated by reference herein for all purposes. The adjoining drill head section 15 is most commonly a tubular sonde housing in which a drill head-orienting sonde is mounted in a predetermined configuration. An enlarged master spline 23 on the projection 21 of the sonde housing 15 engages a master groove 22 in recess 16, ensure that the sonde and bit 14 are in proper alignment for accurate steering.
Headpiece 12 has a top cut-away face 28 that slopes forwardly and inwardly toward the axis of rotation of head 10. A lengthwise fluid passage 24 extends through headpiece 12 as shown in Fig. 6 and terminates in a fluid ejection port 26 disposed on a front face 27 of headpiece 12. Passage 24 receives water or drilling mud from a similar passage 25 that opens on the front end of splined projection 21. A pair of threaded bolt holes 29 on either side of port 26 permit the installation of a nozzle over port 26 in a manner known in the art for regulating the fluid flow.
A socket 30 is provided in headpiece 12 in the form of a pair of lengthwise, outwardly opening square grooves 32 that are spaced from a bottom cut-away face 34 forming a T-slot that slopes forwardly and inwardly toward the axis of rotation of head assembly 10, such that top and bottom faces 28, 34 converge from opposite sides of headpiece 12 as shown. A pair of parallel holes 36 extend into headpiece 12 at an angle sufficient to avoid passage 24 and open on one side of a cylindrical top surface 37 of headpiece 12. Holes 36 cooperate with holes 44 in bit 14 as described below.
Bit 14 has a rear portion 40 having a pair of L-shaped, lengthwise flanges 41 that slide into grooves 32 of socket 30. These may be most conveniently formed by machining out a central recess 42 in rear portion 40, which is otherwise generally rectangular. A pair of spaced holes 44 extend through rear portion 40. (Additional fixture mounting holes 45 are used only during manufacture.) Holes 44 are set at the same angle as holes 36 and come into alignment with holes 36 when bit 14 is fully inserted into grooves 32. Roll pins 46 are then inserted into aligned holes 36, 44 to prevent disengagement of bit 14 from headpiece 12. According to a preferred form of the invention, holes 36 and 44 each have an internal stop therein, such as annular steps 47, 48 respectively. The distance between steps 47, 48 is such that each roll pin 46 can be fully inserted (but not overinserted) into its hole 36 as shown in Figure 11. After insertion of the pins, bit 14 is slid into position so that its rear end engages a thrust reaction lip 49 that prevents any thrust forces from being applied to pins 46. A hammer and chisel or pin are then used to manually slide pins 46 from the position shown in Figure 11 to engage steps 48. The process is reversed when it is time to remove bit 14, i.e., the hammer and chisel are used from the other side to force the roll pins 46 back to the position shown in Figure 11.
A front end or cutting portion 50 of bit 14 extends forwardly from rear portion 40. While rear portion 40 is the same or essentially the same for different bits in a set or kit according to the invention, front portion 50 may vary from a plain flat blade 74 with a tapered end (Figs. 12-14) from suitable for directional boring in ordinary soil to the rock cutting bit 14 shown. Front portion 50 continues at the original angle at which rear portion 40 is mounted, and has a greater thickness such that it overhangs as shown in Fig. 4 to a point where its forwardmost, outermost corner 51 extends to or beyond cylindrical top surface 37 of headpiece 12.
Front portion 50 splits into a pair of forwardly extending projections 52, 54 having frontwardly facing sockets 56, 58 into which a pair of replaceable rock cutting teeth 60, 62 are installed. Teeth 60, 62 are preferably the same as those described in co-pending U.S. Serial No. 09/373,395, filed August 12, 1999, which include back-up carbide inserts 61 behind the main carbide cutting tips 63. Tap out holes 64, 65 comprising straight, narrowed passages from the bottoms of sockets 56, 58 through to the outer surface of the device are provided so that teeth 60, 62 can be removed and replaced as needed separately from the rest of bit 14.
Teeth 60, 62 are angled in the cutting direction indicated by the arrow in Figure 3. Teeth 60, 62 are each canted at an angle of from about 30° to 60° relative to a line normal to an imaginary curved front surface in the direction of rotation of cutting head 10. The exact angle will depend in part on the slope of the conical end portions of the cutting teeth, with a more tapered, sharper point requiring greater canting for the associated tooth to provide the desired degree of shearing force to the formation being bored. A canting angle of less than about 30 degrees, especially 25 degrees or less, provides no significant improvement in cutting. Teeth 60, 62 as shown are at the same cutting orientation as the first and third teeth of the three toothed bit described in the foregoing U.S. Serial No. 09/373,395, filed August 12, 1999. To provide effective boring, teeth 60, 62 preferably extend beyond the outer diameter of headpiece 12 and bit 14. In this manner, a smoother cutting action is achieved than with substantially straight teeth known in the art.
A vertical notch 66 between projections 52, 54 adjoins a lengthwise hole 68 that comes into alignment with port 26 and receives fluid therefrom. Such fluid is sprayed through a gap 69 between front portion 40 and headpiece 12, which may be partly occupied by the nozzle, if used. In this manner, notch 66 functions as a space for receiving cuttings from trailing tooth 62 which are then washed away. This contrasts with known directional boring blades wherein the fluid eject port is located behind the blade. In such prior art systems, the fluid cannot pass through the bit and is deflected laterally by its rear surface.
A bit according to Figures 1-11 of the invention has proven almost as effective in directional rock drilling as the much larger, three-toothed bit described in the foregoing U.S. Serial No. 09/373,395, filed August 12, 1999. It has also proven able to resist deviation from a straight line when operating through soil in push-and-turn mode, or when drilling through rock using a shelfing action such as the one described in Runquist et al. U.S. Patent No. 5,778,991.
In operation, it may be desirable to interchange bits. For example, if the strata being bored changes from hard or rocky material to relatively soft soil, it may be advantageous to change from the toothed bit 14 illustrated in Figures 1-11 to an alternate bit 74 having a front portion 76 which is no more than a flat blade that tapers to an edge 77. According to the invention, this can be readily accomplished by pounding back the roll pins and installing the new bit 74. When one bit is badly worn and must be replaced by another, the same procedure can be followed. There is no need to try to loosen and remove a large number of bolts which may have been damaged by abrasion and torque that occurs during use. The bit system of the invention, since it provides a socket and projection style connection that is substantially stronger than bolts, is much less likely to fail than conventional duckbills.
While certain embodiments of the invention have been illustrated for the purposes of this disclosure, numerous changes in the method and apparatus of 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. The number of cutting teeth may vary from one to several, but two are most preferred. The socket and projection connection between the bit and headpiece may be reversed, or vary widely in design and may, for example, require complete insertion of a rear end portion of the bit into a single frontwardly opening socket in the headpiece. However, from the standpoint of ease of manufacture and use, and providing additional strength, the design shown in the drawings is preferred. Transverse holes 36, 44 may, if desired, be located in staggered positions in the widthwise direction on opposite sides of passage 24 and extend straight through (at a 90 degree angle) rather than at a 60 degree angle as shown. These and other modifications are within the scope of the invention as expressed in the appended claims.

Claims

A directional boring bit assembly, comprising:

a headpiece having a rear portion configured for attachment to and removal from a front end of a generally cylindrical drill head section, including a passage therein for conveying fluid therein from the drill head section to a fluid ejection port on the headpiece, the headpiece further having a frontwardly opening lengthwise socket; and

a bit having a front portion configured for directional boring and a rear portion configured for sliding insertion into the socket, wherein the headpiece and bits are configured to receive a removable retainer that secures the bit in the socket, so that sliding movement of the rear portion of the bit out of the socket is prevented during directional boring with the bit assembly.
The directional boring assembly of claim 1, wherein the headpiece has a transverse hole therethrough which becomes aligned with a transverse hole in the rear portion of the bit when the bit is fully inserted into the socket, and the retainer is inserted into the transverse holes, so that the bit cannot be withdrawn from the socket while the retainer engages the transverse holes.
The directional boring assembly of claim 1, wherein the drill head section comprises a sonde housing.

a removable retainer that secures the bit in the socket, so that sliding movement of the rear portion of the bit out of the socket is prevented during directional boring with the bit assembly.
The directional boring assembly of claim 1, further comprising at least one retainer.
The directional boring assembly of claim 4, wherein the retainer comprises a coiled roil pin.
A directional boring bit set, comprising:

a headpiece having a rear portion configured for attachment to and removal from a front end of a generally cylindrical drill head section, including a passage therein for conveying fluid therein from the drill head section to a fluid ejection port on the headpiece, the headpiece further having a frontwardly opening lengthwise socket;

a first bit having a toothed front portion configured for directional boring and a rear portion configured for sliding insertion into the socket; and

a second bit having a non-toothed front portion configured for directional boring and a rear portion configured for sliding insertion into the socket, wherein the headpiece and bits are configured to receive a removable retainer that secures each bit in the socket, so that sliding movement of the rear portion of each bit out of the socket is prevented during directional boring.
The directional boring bit set of claim 6, wherein the headpiece has a transverse hole therethrough which becomes aligned with a transverse hole in the rear portion of each bit when each bit is fully inserted into the socket, and the retainer is inserted into the transverse holes, so that each bit cannot be withdrawn from the socket while the retainer engages the transverse holes.
The directional boring bit set of claim 7, further comprising at least one retainer.
The directional boring bit set of claim 8, wherein the retainer comprises a coiled roll pin.