Directional drill bit assembly with separable drive coupler

Abstract

A drill bit (400) includes a body defining a proximal end and a distal end spaced along a longitudinal axis from the proximal end, the distal end configured to face toward a ground formation. A mounting feature of the drill bit includes an internal connecting cavity (402) extending into the body from the proximal end. A drive coupler (300) adapts the proximal end of the body for connection with an internal connecting cavity of a transmitter housing (100) to form a drill head (10). The drive coupler (300) includes a distal external mounting feature (302) to mate with the drill bit internal connecting cavity (402) to form a first rotation-transmitting joint. The drive coupler (300) includes a spline to mate with the transmitter housing internal connecting cavity to form a second rotation-transmitting joint. The spline enables establishing and breaking the second joint while the first joint remains in a secured configuration.

Description

DIRECTIONAL DRILL BIT ASSEMBLY WITH SEPARABLE DRIVE COUPLERCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application No. 63 / 579,155, filed August 28, 2023, the entire contents of which are incorporated by reference herein.BACKGROUND

[0002] The invention described in this disclosure is an arrangement for mounting a drill bit to a transmitter housing, alternatively called a sonde housing, to form a drill head that is used with a horizontal directional drilling (HDD) machine.SUMMARY

[0003] In one aspect, the invention provides a multi-piece drill bit assembly for use in a directional drilling apparatus. The multi-piece drill bit assembly includes a drill bit and a drive coupler. The drill bit includes a body defining a proximal end and a distal end spaced along a longitudinal axis from the proximal end, the distal end configured to face toward a ground fomiation to be drilled. A mounting feature of the drill bit includes an internal connecting cavity extending into the body from the proximal end thereof. The drive coupler is configured to adapt the proximal end of the drill bit body for connection with an internal connecting cavity of a transmitter housing to form a drill head. The drive coupler includes a distal external mounting feature configured to mate with the internal connecting cavity of the drill bit to form a first rotation-transmitting joint. The drive coupler further includes a proximal external mounting feature configured to mate with the internal connecting cavity of the transmitter housing to form a second rotation-transmitting joint. The proximal external mounting feature is a spline configured to enable establishing and breaking the second rotation-transmitting joint while the first rotation-transmitting joint remains in a secured configuration.

[0004] In another aspect, the invention provides a directional drilling drill head. A drill bit assembly of the drill head includes a proximal end and a distal end spaced along a longitudinal axis from the proximal end. The drill bit assembly includes at the proximal end a drive coupler joined with a drill bit body by a tapered thread joint. A transmitter housing of the drill head isconfigured for attachment with a drill string and has an electronic transmitter configured to steer the directional drilling head, wherein the transmitter housing has at a distal end thereof an internal cavity. The tapered thread joint between the drive coupler and the drill bit body is formed within the drill bit body. A spline joint is formed between the internal cavity of the transmitter housing and an external mounting feature of the drive coupler.

[0005] Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 is a plan view of a drill head according to one embodiment of the present disclosure.

[0007] FIG. 2 is a side elevation view of the drill head.

[0008] FIG. 3 is a plan view of a distal portion of the drill head, with a drill bit assembly separated from the drill head.

[0009] FIG. 4 is a side elevation view of the distal portion of the drill head, with the drill bit assembly separated from the drill head.

[0010] FIG. 5 is a plan view of the drill bit assembly showing a drive coupler separated from a drill bit body that supports a cutting element.

[0011] FIG. 6 is a side elevation view of the drill bit assembly showing the drive coupler separated from the drill bit body that supports the cutting element.

[0012] FIG. 7 is a plan view of the drill bit assembly as shown in FIG. 5, with the cutting element further separated from the drill bit body.

[0013] FIG. 8 is a side elevation view of the drill bit assembly as shown in FIG. 6, with the cutting element further separated from the drill bit body.

[0014] FIG. 9 is a perspective view of the drive coupler of the drill bit assembly.

[0015] FIG. 10 is a perspective view of the front of a sonde or transmitter housing.

[0016] FIG. 11. is a perspective view of a second embodiment of a drill bit for use with the drive coupler and the drill head.

[0017] FIG. 12 is a side elevation view of a drill head constructed with the transmitter housing, the drill bit, and a drive coupler of an alternate embodiment that fits entirely within the transmitter housing and the drill bit.DETAILED DESCRIPTION

[0018] Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.

[0019] HDD machines are used to bore holes through the ground, in order to install underground utilities. The bore holes are formed by a drill head attached at the front end of a drill string. The HDD machine pushes the drill string and the drill head, typically made-up of a drill bit and a transmitter housing, through the ground. There is a wide variety in the ground conditions, from soft compressible soils to solid rock.

[0020] A wide variety of drill bits have been developed, enabling the HDD machines to operate efficiently in the variety of ground conditions, each specific bit having characteristics that have been developed to optimize performance in specific conditions. The transmitter housing is typically configured with a mount feature for interchangeably supporting the drill bit. In that way the drill head can be easily adapted to match the expected ground conditions, by installing an appropriate drill bit. This arrangement provides flexibility in configuration of the drill head, and it also provides a benefit in the ability to extend the longevity of the transmitter housing. During the boring process the drill bit is known to experience wear as it engages and cuts through the ground. Some ground conditions will generate a higher rate of wear during the boring process than others, but in most instances some portion of the drill head will experience wear. The known arrangements are configured such that the drill bits experience the most wear,while the transmitter housing experiences the least amount of wear. With this arrangement, not only can different drill bits be installed onto the transmitter housing to match variations in the ground conditions, but drill bits can be removed and replaced as they wear-out, to extend the life of the assembly. As an example, one transmitter housing may be used with a hundred or more drill bits. When one drill bit wears out, it can be removed, and a different drill bit can be installed to extend the life of the transmitter housing.

[0021] Operators monitor the condition of the drill bits, replacing them as required to maintain the efficiency of cutting, and to protect the transmitter housing. Drill bits are known to have cutting features that are important for efficient cutting including: surfaces intended for direct contact with the ground formation; apertures for supporting cutting elements that are intended for direct contact with the ground formation; apertures for directing drilling fluids that aid the cutting action. Any of these features can and do wear during use.

[0022] The drill bits also have mounting features to allow them to be removably mounted to a transmitter housing, they are configured to mate with mounting features of the transmitter housing. When the cutting features of drill bits are worn to the point where the drill bit should be replaced, the drill bit’s mounting features are often times in good condition. It is known to rebuild drill bits, by replacing the cutting features, in order to re-use the portion that has the mounting features. The rebuild process typically includes building-up material that was worn by welding or cutting off some portion of the drill bit and then welding-on a new portion of the drill bit.

[0023] If the drill bit is not replaced in a timely manner, it can wear to the point that a portion of the transmitter housing can wear, and there is a potential for damaging the transmitter housing.

[0024] With the mounting arrangement of the drill bit to the transmitter housing configured with the transmitter housing having an internal mounting feature, the potential for damage to the transmitter housing if the drill bit is not replaced soon enough is minimized. However, with the known configurations, the mating drill bit will have an external mount feature that will not be worn-out at the time that the cutting features or elements are worn out. When the bit is replaced, with the mounting portion of the bit still in good condition, there is a lost opportunity to re-usethe portion of the drill bit with the mounting features. The drill bits can be rebuilt, as noted above, but the known methods are costly and relatively complex.

[0025] With the mounting arrangement of the drill bit to the transmitter housing configured with the transmitter housing having an external mounting feature, there is potential for damage of the transmitter housing if the drill bit is used too long. With this arrangement, when the cutting features or elements of the drill bit are worn out, the mounting features of the drill bit are likely also no longer functional.

[0026] There is a need for a more efficient way to replace the cutting portion of a drill bit, in an arrangement where the transmitter housing is configured with the transmitter housing having an internal mounting feature.

[0027] FIGS. 1 and 2 illustrate a drill bit assembly 200 mounted to a transmitter housing 100 to form a drill head 10. This illustrates typical features of a drill head with a transmitter (or “sonde”) 20 positioned and supported by the transmitter housing 100. The transmitter or sonde is retained in the housing 100, held in a specific relative rotational position relative to an asymmetrical aspect of the drill bit assembly 200 which enables the drill head 10 to change direction of the bore hole. The transmitter 20 can be an electromagnetic device. The transmitter 20 can be used to generate a signal to an operator so that the rotational orientation of the drill head 10 can be positioned to steer the drill head 10 with respect to a central longitudinal axis A thereof to form a bore hole in a desired direction. The details of how the transmitter 20 is mounted in the housing 100 are not shown, as various optional configurations are well-known. Likewise, the electrical operation of the transmitter 20 is not discussed further herein, as it is already known to those of skill in the art and not the focus of the present disclosure. As indicated in the drawings and described in further detail below, the drill bit assembly 200 includes a drive coupler 300 and a cutting structure 400 that are that configured for separation from each other. The cutting structure 400 includes the portions required to form a functioning drill bit, and the cutting structure 400 may simply be referred to as the drill bit. Although not separately called out in each instance, the components joined together to construct the drill head 10 each include a proximal end and a distal end spaced along the central longitudinal axis A from the proximal end, wherein distal refers to the tip or working end that is forward in thedrilling direction. The drive coupler 300 is configured to adapt the proximal end of the drill bit400 for connection with a distal opening of the transmitter housing 100 to form the drill head 10.

[0028] FIGS. 3 and 4 illustrate the drill bit assembly 200 as removed from the transmitter housing 100. The drill bit assembly 200 is removed by taking out assembly pins 106 (e.g., roll pins) from retaining pin apertures 102 in the transmitter housing 100. When the drill bit assembly 200 is mounted properly to the transmitter housing 100, notches 306 in the drill bit assembly 200 (particularly in the drive coupler 300) align with the apertures 102, and the pins 106 pass through both to retain or lock the drill bit assembly 200 in the axial direction. This forms an easily separable connection. For example, the joint or mounting formed between the transmitter housing 100 and the drive coupler 300, although rotation-transmitting, is not a torqued (e.g., threaded) joint. With the pins 106 removed, the transmitter housing 100 and the drill bit assembly 200 maintain a torque-transmitting (rotation-transmitting) connection therebetween. The torque-transmitting connection is established simply by sliding the drill bit assembly 200 into the transmitter housing 100, for example by way of a spline connection. As such, once the pins 106 are removed, the torque-transmitting connection is broken simply by sliding the drill bit assembly 200 out of the transmitter housing 100. No tools or additional process steps are required. The pins 106 and corresponding notches 306 and apertures 102 extend transverse to the central longitudinal axis A.

[0029] FIGS. 5 and 6 illustrate the drill bit assembly 200, in a disassembled state with the drive coupler 300 and the drill bit 400 separated from each other. The drive coupler 300 has a first external mounting feature 302 at a first (distal) end and a second external mounting feature 304 at a second (proximal) end. Within the drive coupler 300, a central fluid passage 308 is formed. In the illustrated construction, the first external mounting feature 302 of the drive coupler 300 is a tapered thread configured to mate with an internal mount feature 402 of the drill bit 400, a mating tapered threaded aperture. In other words, the first external mounting feature 302 includes a male threaded portion, and the internal mount feature 402 includes a female threaded portion. The details of the threads are not illustrated in the figures. The drill bit 400 of the illustrated construction has fluid passage(s) 404 in fluid communication with and configured to receive drilling fluid from the fluid passage 308 of the drive coupler 300 and direct the drilling fluid to appropriate locations at or near the distal end of the drill head 100 to aid the boringprocess. It will be appreciated that the first external mounting feature 302 of the drive coupler 300 is configured to be mated with the internal mount feature 402 of the drill bit 400 to form a semi-permanent mount. This connection is made by torquing-up the joint to a significant makeup torque, wherein the make-up torque exceeds the torque expected during use. The connection and disconnection thus requires tools and processing time when it is desired to separate the drill bit 400 from the drive coupler 300. However, the joint or mounting between the drive coupler 300 and the drill bit 400 is configured to be made without permanent means such as welding and is configured to be broken without destructive means such as cutting.

[0030] As mentioned above, the drive coupler 300 is configured to form an easily separable connection with the transmitter housing 100, and this is facilitated by the second external mount feature 304 of the drive coupler 300, along with an internal mount feature of the transmitter housing 100. In some embodiments, the transmitter housing 100 includes an internal connecting cavity 104 (FIG. 10). The internal connecting cavity 104 has a parallel key spline connection comprising a plurality of (e.g., six) straight-sided teeth 108 having a first width, along with a straight-sided tooth 110 (e.g., a single one) having a second width. The second width is different from the first width, for example significantly greater than the first width (e.g., double the first width or more). The widths referred to herein are taken in the circumferential direction (i.e., along the circumference of a circle centered about the central longitudinal axis A), or a straight line tangent to the circumferential direction. Due to the different widths of the different teeth 108, 110, the transmitter housing 100 has a particular rotational orientation or “timing” such that it is not rotationally symmetrical. The second external mount feature 304 of the drive coupler 300 is configured to mate with the parallel key spline of the internal connecting cavity 104.

[0031] The second external mount feature 304 of the drive coupler 300 as illustrated has a keying or timing feature that matches that of the internal connecting cavity 104. For example, the second external mount feature 304 comprises a plurality of (e.g., seven) straight-sided teeth and between them a plurality of spaces including one space between its coupling teeth that is wider than the spaces between the other coupling teeth. The narrower tooth spaces 310 (e.g., six) on the mount feature 304 are configured for mating with the teeth 108 of the first width in the transmitter housing 100. A wider tooth space 312 (e.g., a single one) on the mount feature 304 is configured for mating with the wider tooth 110 of the transmitter housing 100. Otherconstructions of keying the drive coupler 300 to the transmitter housing 100 will be easily appreciated including, but not limited to, reversal of the spline tooth formations on the internal connecting cavity 104 and the mount feature 304. Regardless of the specific configuration of the second external mount feature 304 and the internal connecting cavity 104 (and whether or not it has any keying or timing feature), the two are broadly defined as splined, as each has a plurality of teeth and a plurality of tooth spaces that enable the components to slide together axially into a torque-transmitting joint, and likewise slide axially away from each other to break the torquetransmitting joint. As can be appreciated from the drawings, the first and second external mount features 302, 304 are in separate, non-overlapping axial spans of the drive coupler 300.

[0032] FIGS. 7 and 8 illustrate a cutting element 500, separated from a body 420 of the drill bit 400. In the illustrated embodiment the cutting element 500 is a flat plate, often referred to as a plate bit. The cutting element 500 can be configured to be mounted to the body 420 with any number of well-known mounting structures or methods. Such a mounting may include one or more threaded fasteners such as bolts. It will be understood that the features described above and illustrated in the drawings have additionally applicability to drill bits of a variety of constructions, and not just the drill bit 400 with the plate bit cutting element 500 that is shown in FIGS. 1-8. Some alternate drill bits may have cutting structures with different types of cutting elements like tungsten carbide buttons, or rock picks for example, among others. FIG. 11 illustrates a drill bit 400’ according to a second embodiment including a plurality of cutting elements 500’ secured to the body 420’. The cutting elements 500’ can be tungsten carbide buttons secured to the body 420’ of the drill bit 400’, for example by permanent means such as welding. The drill bit 400’ can have the internal mount feature 402 (e.g., tapered threaded aperture) as described above for mating with the drive coupler’s first external mounting feature 302.

[0033] A drill head such as the drill head 100 shown in FIGS. 1-4 is configured by several steps. In one step, one or more cutting elements 500, 500’ are secured to form a drill bit 400, 400’ of the drill bit assembly 200. The drill bit 400, 400’ is then mounted to the drive coupler 300 in a semi-permanent manner. This forms the drill bit assembly 200. In the illustrated embodiment the drill bit 400, 400’ has an internal mount feature 402 comprising a tapered threaded aperture. The drive coupler 300 has an external mount feature 302 comprising atapered threaded end. The drill bit 400, 400’ is threaded onto the drive coupler 300, and the connection is torqued with an installation torque that is more than the torque that is expected to be applied to the drill bit assembly 200 during operation. This step can include manual or mechanized means, such as hydraulically-powered vises.

[0034] FIG. 12 illustrates a drill head of a further embodiment that is similar in most respects to that of the preceding disclosure. However, the drill head is configured such that the drive coupler 300’ nests fully into the transmitter housing 100 and the drill bit assembly 200. As such, the drive coupler 300’ is substantially enclosed and not exposed to the exterior. Moreover, the drive coupler 300’ does not add any length to the drill head, with the length being made up solely by the length of the transmitter housing 100 and the length of the drill bit 400. Although the first and second external mount features 302, 304 remain in separate, non-overlapping axial spans as with the preceding embodiment, these separate axial spans are directly adjacent such that there is no axial gap therebetween. This facilitates the proximal end of the drill bit body 420 meeting the distal end of the transmitter housing 100, and thus the nesting of the drive coupler 300’ as noted above.

[0035] In addition to facilitating re-use of the drive coupler 300, 300’ when the drill bit 400, 400’ requires refurbishment or replacement due to use, the specific configuration of the drive coupler 300, 300’ having two external or male mount features 302, 304 yields additional benefits. On the proximal end of the drive coupler 300, the external mount feature 304 enables use with an internal mounting feature such as the internal connecting cavity 104 of the transmitter housing 100. The configuration of the internal connecting cavity 104 can conform to pre-existing available components, for example the Ultra X3 drilling system of Vermeer Manufacturing Co. As such, the new drill bit assembly 200 can be compatible for use with legacy systems and parts. Due to the geometry of the drill bit 400, 400’ requiring larger diameters than the rest of the components back to and including the transmitter housing 100, there is more room available in the cross-section of the drill bit 400, 400’ for the internal mount feature 402 therein. Also, by providing the mount feature 304 for the transmitter housing 100 as part of the drive coupler 300 and not integrally as part of the drill bit 400, 400’, material removal for bit manufacturing is reduced and yields better heat treating of the splined connection. For example, providing the mount feature 304 for the transmitter housing 100 as an integral part ofthe drill bit 400, 400’ would require material removal throughout the axial span of the mount feature 304, all the way down from the largest diameter of the drill bit 400, 400’ down to the diameter of the spline of the mount feature 304. Keeping the drill bit 400, 400’ tight to the housing 100 in the axial direction is important to minimize the stress on the spline connection from bending. A large female thread in the drive coupler would require the overall bit length to increase since the male thread on the drill bit would extend the drill bit length, and there is not sufficient material inside the spline connection to receive the threaded joint therein. Alternatively, reducing the size of the female thread to fit within the spline connection would sacrifice strength and robustness due to size and internal geometry aligned to external spline features, which would result in stress risers.

[0036] Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of one or more independent aspects of the invention as described.

Claims

CLAIMSWhat is claimed is:

1. A multi-piece drill bit assembly for use in a directional drilling apparatus, the multi -piece drill bit assembly comprising: a drill bit including: a body defining a proximal end and a distal end spaced along a longitudinal axis from the proximal end, the distal end configured to face toward a ground formation to be drilled, and a mounting feature including an internal connecting cavity extending into the body from the proximal end thereof; and a drive coupler configured to adapt the proximal end of the drill bit body for connection with an internal connecting cavity of a transmitter housing to form a drill head, the drive coupler including: a distal external mounting feature configured to mate with the internal connecting cavity of the drill bit to form a first rotation-transmitting joint, and a proximal external mounting feature configured to mate with the internal connecting cavity of the transmitter housing to form a second rotation-transmitting joint, wherein the proximal external mounting feature is a spline configured to enable establishing and breaking the second rotation-transmitting joint while the first rotationtransmittingjoint remains in a secured configuration.

2. The multi-piece drill bit assembly of claim 1, wherein the drill bit includes one or more cutting features removably mounted to the body.

3. The multi-piece drill bit assembly of claim 2, wherein the one or more cutting features removably mounted to the body includes a flat plate.

4. The multi-piece drill bit assembly of claim 1, wherein the drill bit has at least one fluid passage formed therein and configured to direct drilling fluid to aid cutting of the ground formation.

5. The multi-piece drill bit assembly of claim 1, wherein the distal and proximal external mounting features of the drive coupler are in separate, non-overlapping axial spans of the drive coupler.

6. The multi-piece drill bit assembly of claim 5, wherein the separate, non-overlapping axial spans are directly adjacent such that there is no axial gap between the distal and proximal external mounting features to facilitate the proximal end of the drill bit body meeting the distal end of the transmitter housing.

7. The multi-piece drill bit assembly of claim 1, wherein the first rotation-transmitting joint between the drive coupler and the drill bit is a torqued connection.

8. The multi-piece drill bit assembly of claim 1, wherein the distal external mounting feature is a tapered thread configured to mate with a tapered threaded aperture at the internal connecting cavity of the drill bit to form the first rotation-transmitting joint mounting.

9. The multi-piece drill bit assembly of claim 1, wherein within the proximal external mounting feature, the drive coupler includes transverse notches configured to receive respective pins configured to axially secure the drive coupler to the transmitter housing.

10. The multi-piece drill bit assembly of claim 1, wherein the proximal external mounting feature includes a plurality of spline teeth and a corresponding plurality of tooth spaces, one of the plurality of tooth spaces having a greater width than all the others.

11. The multi-piece drill bit assembly of claim 10, wherein the one of the plurality of tooth spaces having the greater width than all the others has a width that is at least double a width of all the others.

12. The multi-piece drill bit assembly of claim 10, wherein the plurality of spline teeth and the corresponding plurality of tooth spaces includes seven spline teeth and seven tooth spaces.

13. A drill head comprising: the multi-piece drill bit assembly of claim 1; and the transmitter housing, wherein the internal connecting cavity of the transmitter housing forms a splined connection with the proximal external mounting feature of the drive coupler and is locked in place axially with a transverse pin.

14. The drill head of claim 13, wherein the internal connecting cavity of the transmitter housing includes a plurality of spline teeth and a corresponding plurality of tooth spaces, one of the plurality of spline teeth having a greater width than all the others, and wherein the proximal external mounting feature includes a plurality of spline teeth and a plurality of tooth spaces, one of the plurality of tooth spaces having a greater width than all the others to accommodate the one of the spline teeth having the greater width.

15. The drill head of claim 14, wherein the one of the plurality of spline teeth having the greater width than all the others has a width that is at least double a width of all the others.

16. The drill head of claim 13, wherein the internal connecting cavity of the transmitter housing includes seven spline teeth and seven tooth spaces, one of the spline teeth having a greater width than all the others, and wherein the proximal external mounting feature includes seven spline teeth and seven tooth spaces, one of the seven tooth spaces having a greater width than all the others to accommodate the one of the spline teeth having the greater width.

17. A directional drilling drill head comprising: a drill bit assembly including a proximal end and a distal end spaced along a longitudinal axis from the proximal end, wherein the drill bit assembly includes at the proximal end a drive coupler joined with a drill bit body by a tapered thread joint; and a transmitter housing configured for attachment with a drill string and having an electromagnetic transmitter configured to steer the directional drilling head, wherein the transmitter housing has at a distal end thereof an internal cavity, wherein the tapered thread joint between the drive coupler and the drill bit body is formed within the drill bit body, and wherein a spline joint is formed between the internal cavity of the transmitter housing and an external mounting feature of the drive coupler.

18. The directional drilling drill head of claim 17, further comprising one or more transverse pins engageable with the spline joint to axially lock the drill bit assembly in place with respect to the transmitter housing.

19. The directional drilling drill head of claim 17, wherein the spline joint includes a plurality of spline teeth and a corresponding plurality of tooth spaces, one of the plurality of spline teeth having a width at least double a width of all the others.

20. The directional drilling drill head of claim 17, wherein the drive coupler includes a central fluid passage in fluid communication to supply drilling fluid to a plurality of fluid passages formed in the drill bit body.

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