Rock bit

A steerable rock bit attached by a drill string to a horizontal directional drill. The bit comprises a plurality of flanges radially extending from a central hub and a slanted face formed in the body of the bit. Cutting elements such as polycrystalline diamond compacts are disposed on the flanges on one side of the flanges such that they will provide cutting force when the bit is rotated in the direction of the cutting elements. The bit is advanced generally straight when the bit is rotated and is advanced at an angle away from the slanted face when the bit is not rotated.

FIELD

This invention relates generally to steerable bits for utility installation.

BACKGROUND

Horizontal Directional Drilling (HDD) is a construction alternative to open trenching for installation of underground utilities, conduit and pipelines. HDD is particularly useful for installing utilities or conduit in areas where open trenching would be impractical due to natural features or existing infrastructure. By using a steerable pilot tool, HDD allows the operator to drill a bore path that avoids existing features in the project area.

Many underground installation projects occur in areas with congested easements or space limitations that require smaller bore paths. When bore paths become smaller due to space considerations and project complexity, the need for responsive and accurate pilot tools increases.

Additionally, HDD projects occur in a variety of ground conditions from hard compacted soils to various loose and solid rock formations. In addition to being responsive and accurate in steering, it is desirable for a pilot tool to be capable of drilling through various ground conditions. Therefore, there is a need for a steerable rock bit that is accurate and responsive and that can drill effectively through hard various soil conditions, including solid rock.

SUMMARY

The present invention is directed to a bit. The bit comprises a body, a plurality of projecting flanges, and a plurality of cutting elements. The body has a threaded connector. The threaded connector is symmetric about a longitudinal axis. The body additionally has a hub situated on the longitudinal axis and is shaped asymmetrically with respect to the longitudinal axis. The plurality of projecting flanges are supported by the body and extend radially from the hub. Each flange is characterized by a pair of spaced sides. The plurality of cutting elements is supported on only one side of each flange.

In another embodiment the present invention is directed to a bit. The bit comprises a body, a plurality of projecting flanges supported by the body, a slanted face disposed on a portion of the body having no flanges, and a plurality of cutting elements. The body has a hub situated on a longitudinal axis. The plurality of flanges extend from the hub and are characterized by a pair of spaced sides. The plurality of cutting elements are supported on each flange and installed on the side of each flange that would lead if the hub were rotated about the longitudinal axis in a single selected direction.

DETAILED DESCRIPTION

With reference now to the figures in general, andFIG. 1in particular, shown therein is a horizontal directional drill (HDD)6for use with the current invention. The drill6rotates and advances a drill string8with a drill bit10attached to a distal end of the drill string to create a borehole9in the subsurface11.

With reference toFIG. 2, shown therein is the rock bit10for drilling a bore hole in HDD operations. The rock bit10has an elongate bit body12disposed along a longitudinal axis13. The bit body12comprises a first end14and a second end16. The first end14has a connection structure18for attaching the bit body12to a drill string (not shown), either directly or through a transmitter housing (not shown). While the connection structure18ofFIG. 2comprises threads19, splines or other known connection methods may be utilized to connect the rock bit10to the drill string without departing from the spirit of the invention. Preferably, the connection structure18is symmetrical about the longitudinal axis13. As will be described with more particularity below, a slanted face52may be formed in the bit body12. A pullback adaptor71may attach to the bit body12at a bolt hole72.

With reference toFIG. 3, the bit body12comprises a central hub20and a plurality of flanges22. The central hub20is generally disposed about the longitudinal axis13. Each of the flanges22extends from the central hub20and is defined by a first face24, a second face26, a leading edge28and a trailing edge30. Preferably, the first face24and the second face26are spaced apart to provide a thickness for the flanges22. As shown, the first face24and second face26are generally parallel. A plurality of cutters40are disposed on the first face24of each of the plurality of flanges22. Preferably, the cutters40are disposed on only one face of each flange22, such as the first face24. The first face24is the face of each flange22that is disposed on the leading side of the flange22when the rock bit10undergoes rotation. When the bit10is viewed from a forward position, as shown inFIG. 3, the first face24of each flange22faces in a counter-clockwise direction. This positioning allows the cutters40to lead when the bit10is rotated in a counter-clockwise direction. Preferably, the bit10is rotated in only a single selected direction, such as the counter-clockwise direction. As shown, each of the flanges22extends radially from the central hub20, though curved or angled flanges22may likewise be used. As shown, there are four flanges22extending from the central hub, though other numbers of flanges, such as two to six, may be utilized. The flanges22extend, at least partially, outside the radius of the bit body12.

The cutters40are preferably polycrystalline diamond compact (PDC) inserts, which are generally cylindrical in shape and disposed on the first face24of the flanges22. As shown, the leading edge28of the plurality of flanges22is even with an edge of one of the plurality of cutters40such that the cutters engage rock and soil during rotation of the rock bit10. Cutters40may additionally be utilized at the trailing edge30of each of the flanges22. As shown, each flange22supports up to four cutters40, though other numbers of cutters may be utilized per flange. Additionally, cutters40may be placed on the second face26of the flanges22to provide some cutting ability to the rock bit10in application where rotation in other than the primary direction of rotation of the rock bit is desired.

Fluid ports80may be provided in the second end16of the bit body12. The fluid ports80convey drilling fluid from the horizontal directional drill6(FIG. 1) to the rock bit10through centrally disposed conduits (not shown) within the bit body12. Fluid may loosen or soften the existing subsurface11to help the cutters40drill.

With reference now toFIG. 4, the bit body12further comprises a steering feature50formed at the second end16of the bit body. As shown, the steering feature50is a slanted face52disposed on a portion of bit body12and oriented obliquely to the longitudinal axis13of the bit body. Other steering features50that impart an asymmetrical shape to the body12with respect to the longitudinal axis13may be used in lieu of, or in combination with, the slanted face52. These include gage towers, wear pads, bent shaping of the body12, non-planar faces, and the like. The slanted face52is located on a portion of the bit body12that does not have flanges22protruding from the central hub. As shown inFIG. 5, the steering feature50is contained within a central angle θ2about the axis13having a size of less than about one hundred eighty degrees and more than about ninety degrees. In one embodiment, the central angle θ2is about 140 degrees. The flanges22are disposed on the remainder of the bit body12not occupied by the steering feature50. In one embodiment, the flanges22are contained within a central angle θ1about the axis13having a size about 220 degrees.

With reference toFIGS. 4 and 5, the bit body12comprises a wear pad60located in line with the steering feature50of the bit body. The wear pad60is a generally raised, hardened pad. The wear pad60may comprise carbides62for additional hardness. The carbides62may crush soil dislodged by the cutters40further before they are carried uphole. In typical HDD operations, a steerable bit such as the rock bit10will deflect in a direction away from the slanted face52when the rock bit is not rotating. During deflection, portions of the bit body12on the side of the slanted face52will increase their exposure to soil and rock within the subsurface11(FIG. 1). The wear pad60protects the bit body12from damage associated with such exposure. Additionally, the wear pad60may provide additional deflection to help the bit10turn when the bit is not rotated.

The bit body12defines a slot70for placement of a pullback adaptor71(FIG. 2). The pullback adaptor71utilized may be of the type described in U.S. Pat. No. 8,122,979, issued to Wright, et. al. (“Wright”), the contents of which are incorporated herein by reference. The pullback adaptor71comprises an attachment aperture74and a pullback eye76. The slot70of the present invention, and of Wright, is centrally formed in the slanted face52of the rock bit10. Thus, the slanted face52may preferably comprise an adjacent pair of two coplanar surfaces in the embodiment of the figures. With reference again toFIG. 2, an aperture, such as a bolt hole72, passes through the bit body12and the slot70for securing the attachment aperture74of the pullback adaptor71to the bit body12. The pullback eye76may be attached to a pulling mechanism (not shown) such as a tow rope or shackle. Preferably, the pullback eye76is centered on the longitudinal axis13.

In operation, the rock bit10advances generally straight through the subsurface11when rotated in the direction of the cutters40and advanced by the horizontal directional drill6. The rock bit10is deflected in a direction away from the slanted face52and wear pad60when advanced by the drill6without rotation.

Various modifications can be made in the design and operation of the present invention without departing from its spirit. Thus, while the preferred construction and modes of operation of the invention have been explained in what is now considered to represent its best embodiments, it should be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.