Patent Description:
Underground drilling operation often requires connecting a drill tool (e.g., drill bit, backreamer, etc.) to a drill string. It is desirable to connect the drill tools to a drill string in a manner that facilitates quick and easy assembly and disassembly. Low torque coupling, commonly referred to as "torque-less" connection, can provide such functionality. The useful life and strength of such connections can be improved upon. The present disclosure provides a low torque coupling with improved strength and durability. <CIT> discloses a connector having the features of the preamble of claim <NUM> or claim <NUM>. <CIT> discloses a threaded connection having the features of the preamble of claim <NUM>.

The invention provides an adapter for use in connecting components of a drill string in a low torque coupling, having the features of claim <NUM> or claim <NUM>.

Referring to <FIG> a drilling machine <NUM> is shown driving a drill string <NUM> into the ground. The distal end of the drill string includes a drill tool assembly <NUM>. The coupling between an end of the drill string <NUM> and the drill tool assembly <NUM> is shown in greater detail in <FIG>.

Referring generally to <FIG>, a coupling between a starter rod <NUM> and a sonde housing <NUM> is shown. The starter rod <NUM>, also referred to as a pilot rod or generically a first member, is threadly connected to the distal most (down hole most) drill rod <NUM> via a torque connection. The sonde housing <NUM> is configured to house a sonde therein and supports a drill bit (not shown) at its distal end <NUM>.

In the depicted embodiment an adaptor <NUM> is threadly connected in the proximal end <NUM> of the sonde housing <NUM> via a torque connection. The adaptor <NUM> and sonde <NUM> are also referred to herein generically as a second member. A collar <NUM> is provided to slide over a distal end <NUM> of the starter rod <NUM> and a portion of the adaptor <NUM> to prevent relative rotation between the starter rod and adaptor (and hence also prevent relative rotation between the starter rod <NUM> and the sonde housing <NUM>).

In the depicted embodiment an inner surface of the collar <NUM> is configured to engage external structural features on the distal end <NUM> of the starter rod <NUM> and on the exterior surface of the adaptor <NUM>. In the depicted embodiment the collar includes internal flats <NUM> that engage flats <NUM> on the distal end <NUM> of the starter rod <NUM> and flats <NUM> on the exterior of the adaptor <NUM>. The connection between the distal end <NUM> of the starter rod <NUM> and the proximal end <NUM> of the adapter <NUM> is described in greater detail below.

In the depicted embodiment the coupling includes first member including a driving end and a driven end. In the depicted embodiment, the first member is shown as the starter rod <NUM>. The drive end is shown as the distal end <NUM> and the driven end is shown as the proximal end <NUM>. The proximal end <NUM> is threadly connected to the down hole most drill rod <NUM> via a torque connection.

In the depicted embodiment the driving end of a first member (e.g., the distal end <NUM> of the starter rod <NUM>) includes a tapered portion (recess <NUM> shown in <FIG> or protrusion <NUM> shown in <FIG>) including threads thereon. The driving end includes a first land <NUM> (<FIG>) adjacent a distal end of the tapered portion (e.g., the protrusion <NUM> or recess <NUM>) and a second land <NUM> (<FIG>) adjacent a proximal end of the tapered portions (protrusion <NUM> or recess <NUM>).

In the depicted embodiment the second member (adaptor <NUM>) includes a drive end <NUM> and a driven end <NUM>. The drive end <NUM> includes a threaded connection for attaching to a cutting tool (e.g., a sonde housing <NUM> supporting a drill bit). The driven end <NUM> is adapted for connection with the driving end <NUM> of the first member <NUM>. The driven end <NUM> includes a tapered portion (e.g., recess <NUM> shown in <FIG> or protrusion <NUM> shown in <FIG>) including threads thereon. The driven end <NUM> includes a third land portion <NUM> (<FIG>) adjacent a distal end of the tapered portion (e.g., recess <NUM> or protrusion <NUM>). The drive end <NUM> also includes a fourth land portion <NUM> adjacent a proximal end of the tapered portion.

In the depicted embodiment the first land <NUM> is configured to engage the fourth land <NUM> and the second land <NUM> is configured to engage the third land <NUM> when the tapered threads on the first member <NUM> are engaged with the tapered threads on the second member <NUM>. In the depicted embodiment the clearance between the first land <NUM> and fourth land <NUM> and the clearance between the second land <NUM> and the third land <NUM> is sufficient to allow a user to slidably engage the first and second members by hand. In the depicted embodiment the first land and the fourth land are cylindrical having diameters that are at least <NUM> inches (<NUM> millimiters) different from each other (for example, within <NUM> inches to <NUM> inches (<NUM> to <NUM> millimeters) of each other). In other words, the clearance between the surfaces of the lands in a radial direction (radial clearance) is between. <NUM> inches (. <NUM> to <NUM> millimeters). It should be appreciated that in alternative embodiment the lands could be of different geometric configurations and have different clearance therebetween.

In some embodiment the peaks <NUM> of the threads on the tapered portion of second member and valleys <NUM> of the threads of the first member are offset by at least <NUM> inches (<NUM> millimeters) even when the threads are engaged. In the depicted embodiment the pitch diameter between the threaded portions on the first and second members are offset by at least <NUM> inches. On a tapered thread like the ones shown the pitch diameter at a given position on the thread axis is the diameter of the pitch cone at that position. It should be appreciated that when the crest of the thread is truncated beyond the pitch line, the pitch diameter and pitch cylinder or pitch cone would be based on theoretical extension of the threaded flanks.

As discussed above, the second member is depicted as an adapter <NUM>. However, it should be appreciated that in alternative embodiments the first member can be different components including, for example, a drill bit or a sonde housing.

In the depicted embodiment the threads on the tapered recess and threads of the tapered protrusions are asymmetric having a tooth width W to height H ratio between <NUM> to <NUM> (<FIG>). The asymmetric short threads facilitate self-alignment and maintain the above-described offset between peaks and valleys of corresponding threads.

In the depicted embodiment the first member <NUM> includes structure that abuts structure on the second member <NUM> to limit the offset between the peaks of the threads on the tapered recess and valleys of the threads of the tapered protrusions. The structure on the first member is shown as front face <NUM> and the structure on the second member is shown as an annular shoulder <NUM>.

In the depicted embodiment, a portion <NUM> (<FIG>) of the tapered recess at its distal end is enlarged and does not include threads thereon. In the depicted embodiment, a portion of the tapered recess at its proximal end is also enlarged (portion <NUM> of <FIG>) and does not include threads thereon. These portions are configured to receive foreign matter (e.g., rock and dirt) and thereby prevent the matter from jamming the connection between the first and second members. In addition, these portions also act as stress relief zones that distribute load at the transition, thereby avoiding stress concentrations, which increases the durability of the coupling <NUM>. In the depicted embodiment the enlarged portion comprises an annular notch that is part of the tapered recess. It should be appreciated that in alternative embodiments the enlarged portion (e.g., notch) can be part of the tapered protrusion or both a part of the tapered recess and the tapered protrusion.

In the depicted embodiment the proximal end of the coupling <NUM> (e.g., adaptor) which is shown threaded to the sonde housing <NUM> includes a tapered threaded portion configured to engage mating threads of a sonde housing to torque level in excess of <NUM> foot pounds (<NUM>). As discussed above, the distal end includes a tapered portion between a first unthreaded portion and a second unthreaded portion. The first and second unthreaded portions include a constant maximum cross- sectional dimension. As discussed above, the coupling includes a stop that engages an end face of the first member to prevent full engagement of the threads (i.e., maintains the above define offset). The stop is positioned on a predetermined location on the second unthreaded portion such that it ensures an offset of at least <NUM> inches (<NUM> millimeters) between the peaks on the threads of the tapered threaded portion with the valleys on threads that the taper threaded portion is configured to engage. In the depicted embodiment the pitch diameter between the threaded portions on the first and second members are offset by at least <NUM> (<NUM> millimeters) inches.

The present disclosure also provides a method of connecting a drill tool to a drill rod. The method includes the steps of: contacting threads located at a proximate end of a drill tool member with threads located at a distal end of a drill rod member; threading the drill tool member to the drill rod member by relatively rotating the drill rod member and the drill tool member; and aligning structural features on an external surface of the drill tool member with structural features on an external surface of the drill rod member. In the depicted embodiment the step of aligning the structural features includes counter rotating the drill rod assembly relative to the drill tool between one to ninety degrees.

The method further includes the step of sliding a collar over a portion of the drill tool member and drill rod member, wherein the collar is configured to engage the structural features on the external surface of the drill tool member and drill rod member thereby preventing relative rotation between the drill tool member and the drill string member.

In the depicted embodiment the step of threading the drill tool member to the drill rod member simultaneously inserts a boss on the distal end of the drill tool member with an aperture on the drill rod member and inserts a boss on the proximal end of the drill tool member with an aperture on a distal end of the drill rod member. The method also includes the step of maintaining at least <NUM> inch (<NUM> millimeters) offset between a peak of the threads located on the proximate end of the drill tool member and a valley of the threads located at a distal end of the drill rod member at least when structural features on the external surface of the drill tool member are aligned with the structural features on the external surface of the drill rod member. In the depicted embodiment the pitch diameter between the threads on the drill tool and mating threads on the drill rod are offset by at least <NUM> inches (<NUM> millimeters).

In the depicted embodiment the threading step is accomplished by rotating the drill tool member while holding the drill rod member stationary. It should be appreciated that alternatively the drill rod could be rotated while the drill tool is held stationary. In the depicted embodiment, the threading step includes relatively rotating the drill rod member and drill tool member between one to four full revolutions. In alternative embodiments the threading step may include more or fewer revolutions.

In the depicted embodiment the torque needed to unthread the drill rod assembly from the drill tool assembly is less than <NUM> foot pounds (<NUM>). The step of threading the drill tool assembly to the drill rod assembly includes rotating the drill tool member until a portion of the drill tool member (e.g., annular shoulder) abuts a portion of the drill rod member (e.g., end face) and limits further rotation. In the depicted embodiment at least <NUM> inches (<NUM> millimeters) offset is maintained when the portion of the drill tool assembly abuts the portion of the drill string assembly. The at least <NUM> inches (<NUM> millimeters) offset is maintained even if as much as <NUM> foot pounds (<NUM>) of torque are applied to the connection between the drill rod member and drill tool member during the threading step.

In the depicted embodiment the boss on the distal end of the drill tool includes a maximum cross-sectional dimension that is within <NUM> to <NUM> inches (<NUM>-<NUM> millimeters) of a maximum cross-sectional dimension of the aperture of the drill rod assembly.

Referring to <FIG>. an example not according to the invention is shown. The depicted example is similar to the above-described embodiment, however, the threads on the tapered protrusion and aperture are removed. Instead, pins <NUM>, <NUM> secure the tapered protrusion within the tapered aperture and resist tension forces between the adapter <NUM> and the starter rod <NUM>. The pins <NUM>, <NUM> extend through a portion of the distal end <NUM> of the starter rod and driven end <NUM> of the adapter <NUM>. The collar <NUM> slides over the end of the pins and retains them in place.

Referring to <FIG>, another example not according to the invention is shown. In the depicted example the tapered aperture <NUM> and protrusion <NUM> are not threaded. Instead, the tapered protrusion <NUM> includes grooves <NUM>, <NUM>, <NUM> that engage pins <NUM>, <NUM>, <NUM>, <NUM>. <NUM>, <NUM>, which are retain in pin receiving apertures that extend through a portion of the tapered aperture <NUM>. The above described pin
configuration secures the tapered aperture <NUM> to the protrusion <NUM> against tension forces applied to the connection during operation (e.g., as the drill string is pulled back through the hole). In the depicted embodiment the pins can be removed after removal of the collar <NUM> via driving a punch through smaller apertures that extend to the back side of the pin receiving apertures. It should be appreciated that although the tapered aperture and protrusion are shown with a gradual taper they could alternative have a stepped profile or the taper could be non-linear.

Referring to <FIG>, another example not according to the invention is shown. In the depicted example the tapered protrusion <NUM> includes a spiral groove <NUM> that is configured to mate with locking pins similar to those shown in <FIG>, which are retained in pin receiving apertures that extend through a portion of the tapered aperture <NUM> in a manner to intersect the spiral groove. In this example the groove <NUM> acts as a single enlarged thread member that secures the tapered aperture and tapered protrusion together. This configuration provides a quick connection and disconnection between the tapered protrusion and tapered aperture. The locking pins that mate with the spiral grooves on the tapered aperture and the receiving apertures in the aperture <NUM> resist tension forces applied to the connection. The collar <NUM> prevent the tapered protrusion from rotating relative to the tapered aperture.

It should be appreciated that many more alternative examples are possible. For example, although the examples not according to the invention shown in <FIG> are shown to include annular stress relief zone recess into the tapered protrusion similar to those described above with reference to <FIG> and <FIG> (portions <NUM> and <NUM>), some alternative examples do not include stress relieve zones.

Claim 1:
An adapter for use in connecting components of a drill string in a low torque coupling, the adapter comprising:
an adapter body (<NUM>);
a non-threaded first cylindrical portion (<NUM>) having a first outer diameter;
a non-threaded second cylindrical portion (<NUM>) having a second outer diameter that is larger than the first outer diameter;
a tapered portion (<NUM>) between the first cylindrical portion (<NUM>) and the second cylindrical portion (<NUM>);
an annular shoulder on an outer surface of the adapter body, said annular shoulder being perpendicular to a longitudinal axis of the adapter, the annular shoulder at a first longitudinal end of the second cylindrical portion (<NUM>); and
the tapered portion having a threaded portion, and an annular notch adjacent a second longitudinal end of the second cylindrical portion (<NUM>) providing a transition between the threaded portion and the second cylindrical portion (<NUM>);
wherein the first cylindrical portion (<NUM>), the second cylindrical portion (<NUM>), and the tapered portion (<NUM>) are part of a first male connection structure;
characterized in that the first male connection structure is provided at a first longitudinal end of the adapter body (<NUM>), wherein the adapter body (<NUM>) has a second longitudinal end defining a second male connection structure (<NUM>), wherein the second male connection structure (<NUM>) comprises a tapered section having major and minor outer diameters, wherein the adapter body (<NUM>) defines an intermediate region longitudinally between the first and second male connection structures, and wherein a plurality of flats (<NUM>) are provided on an outer surface of the adapter body (<NUM>) at the intermediate region.