PRIORITY CLAIM

[0001] This application claims priority to Patent Cooperation Treaty (PCT) application no. PCT/AU2019/051292, filed November 26, 2019, which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

[0002] The present disclosure relates to drill bits used to bore through earth, concrete and other hard materials.

BACKGROUND

[0003] Any references to methods, apparatus or documents of the prior art are not to be taken as constituting any evidence or admission that they formed, or form part of the common general knowledge.

[0004] Specialized drill bits are used to drill wellbores, boreholes, and other holes in the earth for a variety of purposes, including water wells, oil and gas wells, injection wells, geothermal wells, monitoring wells, holes used in mining, and the like. These drill bits come in two common types: roller cone drill bits and fixed cutter drill bits.

[0005] Well bores and other holes in the earth are typically drilled by attaching or connecting a drill bit to a means of rotating the drill bit. The drill bit can be attached directly to a shaft that is rotated by a motor, engine, drive, or other means of providing torque to rotate the drill bit. In oil and gas drilling, for example, the drill bit is typically connected to the lower end of a drill string that is in turn, connected at the upper end to a motor or drive at the surface, with the motor or drive rotating both the drill string and the drill bit together. The drill string typically comprises several elements that may include a special down-hole motor configured to provide additional or, if a surface motor or drive is not provided, the only means of turning the drill bit.

[0006] PDC bits are a type of rotary drag bit used for boring through subterranean rock formations when drilling oil and natural gas wells. As a PDC bit is rotated, typically by rotating a drill string to which it is attached, discrete cutting structures affixed to the face of the bit drag across the bottom of the well, scraping or shearing the formation. PDC bits use cutting structures, referred to as “cutters,” each having a cutting surface or wear surface comprised of a polycrystalline diamond compact (PDC), hence the designation “PDC bit.” Each cutter of a rotary drag bit is positioned and oriented on a face of the drag bit so that a portion of it, which will be referred to as its wear surface, engages the earth formation as the bit is being rotated. The cutters are spaced apart on an exterior cutting surface or face of the body of a drill bit in a fixed, predetermined pattern. The cutters are typically arrayed along each of several blades, which are raised ridges extending generally radially from the central axis of the bit, toward the periphery of the face, usually in a sweeping manner (as opposed to a straight line). The cutters along each blade present a predetermined cutting profile to the earth formation, shearing the formation as the bit rotates. Drilling fluid may be pumped down the drill string, into a central passageway formed in the center of the bit, and then out through ports formed in the face of the bit, both cools the cutters and helps to remove and carry cuttings from between the blades.

[0007] The shearing action of the cutters on the rotary drag bits is substantially different from the crushing action of a roller cone bit, which is another type of bit frequently used for drilling oil and gas wells. Roller cone bits are comprised of two or three cone-shaped cutters that rotate on an axis an acute angle such as at a thirty-five degree angle to the axis of rotation of the drill bit. As the bit is rotated, the cones roll across the bottom of the hole, with the teeth crushing the rock as they pass between the cones and the formation.

[0008] One of the problems associated with such roller cone bits and fixed bits is the issue of selecting replacing some of the bits in order to recondition the drill bit for prolonged use. Therefore, it is desirable to provide drill bits that allow the plurality of roller cone bits to be selectively replaced in a convenient manner to prolong the working life of these drill bits.

SUMMARY

[0009] In one aspect, the disclosure provides a drill bit operable for making a hole in a subterranean formation, the drill bit comprising: a bit body defining a central axis about which said bit body rotates while drilling; a plurality of blades extending from a leading face of the bit body away from said central axis; a plurality of cutter insert assemblies mounted on one or more of said blades wherein each of the cutter insert assemblies comprises: an insert body extending between a first end and a second end along a longitudinal axis of the insert body with a connecting arrangement positioned at the first end of the insert body for coupling the insert body to the blade; a cutter including a leading tip portion for cutting into the subterranean formation and a trailing receiving portion for receiving the second end of the insert body in an internal cavity defined by the receiving portion to allow the cutter to be removably coupled to the second end of the insert body; a retaining pin structured to be received within an internal passage of the insert body for detachably interlocking the cutter and the insert body, the retaining pin being coupled to a retaining arrangement comprising a detent assembly such that a first movement of the pin along the internal passage of the insert body effects engagement of the detent assembly with inner walls of the cutter to interlock the cutter with the insert body and wherein a second movement of the retaining pin results in release of the cutter from the insert body.

[0010] In another aspect, there is provided a cutter insert assembly adapted for being mounted on a blade of a bit body for a drill bit operable for making a hole in a subterranean formation, the cutter insert assembly comprising: an insert body extending between a first end and a second end along a longitudinal axis of the insert body with a connecting arrangement positioned at the first end of the insert body for coupling the insert body to the blade; a cutter including a leading tip portion for cutting into the subterranean formation and a trailing portion for coupling the second end of the insert body in an internal cavity defined by the trailing portion to allow the cutter to be removably coupled to the second end of the insert body; a retaining pin structured to be received within an internal passage of the insert body for detachably interlocking the cutter and the insert body, the retaining pin being coupled to a retaining arrangement comprising a detent assembly such that a first movement of the pin along the internal passage of the insert body effects engagement of the detent assembly with inner walls of the cutter to interlock the cutter with the insert body and wherein a second movement of the retaining pin results in release of the cutter from the insert body.

[0011] In an embodiment, the detent assembly comprises: a detent groove positioned along an inner wall defining the internal cavity of the cutter; one or more detents provided at or adjacent the second end of the insert body; wherein the first movement comprises a first axial movement of the retaining pin within the passage of the insert body to push the one or more detents into engagement with the detent groove of the cutter in a radially outward direction thereby interlocking the cutter with the insert body and wherein the second movement comprises a second axial movement of the retaining pin to effect radially inward movement of the detent out of the detent groove of the cutter and into a notch provided on said pin resulting in the release of the cutter from the insert body.

[0012] In an embodiment, the detent comprises a detent arranged to be pushed in a radially inward direction towards a longitudinal axis of the retaining pin. [0013] In an embodiment, the insert body comprises radially disposed detent openings for allowing a portion of said detent to pass through and engage the detent groove of the cutter in at least one operable configuration.

[0014] In an embodiment, the diameter of the detent openings is smaller than the diameter of the detent to retain at least a portion of the detent within the detent opening.

[0015] In an embodiment, an outer body of the retaining pin comprises engagement structures to engage with inner walls of the passage of the insert body to effect axial movement of the retaining pin along the passage.

[0016] In an embodiment, the engagement structures comprises helical grooves to engage with complementary grooves along the inner walls of the internal passage of the insert body such that rotational movement of the pin in a clock-wise or anti-clockwise direction results in axial translation of the retaining pin along the passage of the insert body.

[0017] In an embodiment, the retaining pin comprises a head portion with a driver receiving interface for interfacing with a driving tool.

[0018] In an embodiment, the cutter insert further comprises a removable cap adapted to be positioned into an opening of the internal passage of the insert body to prevent ingress of dust and/or debris into the internal passage when the pin is retained within the passage of the insert body.

[0019] In an embodiment, the cutter insert assembly further comprises a circumferential sealing member adapted to be positioned in a groove provided along an outer surface of the insert body for resiliently engaging an inner wall portion of the cutter to prevent ingress of dirt and/or debris into an inner volume of the cutter.

[0020] In an embodiment, the insert body comprises a flared stop member positioned along an outer wall of the insert body to limit axial movement of the trailing portion of the cutter towards the first end of the insert body.

[0021] In an embodiment, the connecting arrangement of the insert body comprises one or more helical threads provided along an outer wall portion at or adjacent the first end of the insert body to couple the insert body to the blade of the drill bit.

[0022] In an embodiment, the leading portion of the cutter comprises a convergent tip portion.

[0023] In an embodiment, the tip portion comprises a polycrystalline diamond compact

(PDC) material. [0024] In yet another aspect, the disclosure provides a method of drilling by using a cutting head coupled with a cutting insert assembly mounted on a drill bit operable for making a hole in a subterranean formation, the drill bit comprising: a bit body defining a central axis about which said bit body rotates while drilling and a plurality of blades extending from a leading face of the bit body away from said central axis wherein a plurality of the cutter insert assemblies are mounted on one or more of said blades, the method comprising the steps of: providing said cutter insert assembly with an insert body extending between a first end and a second end along a longitudinal axis of the insert body with a connecting arrangement positioned at the first end of the insert body for coupling the insert body to the blade; positioning the cutting head such that a leading tip portion of the cutting head is positioned for cutting into the subterranean formation and a trailing receiving portion is positioned for receiving the second end of the insert body in an internal cavity defined by the receiving portion to allow the cutter to be detachably coupled to the second end of the insert body; locating a retaining pin within an internal passage of the insert body for detachably interlocking the cutter and the insert body, the retaining pin being coupled to a retaining arrangement comprising a detent assembly and effecting at least a first movement of the pin along the internal passage of the insert body to engage the detent assembly with inner walls of the cutter to interlock the cutter with the insert body.

[0025] In an embodiment, the method further comprises further comprising the step of effecting at least a second movement of the retaining pin to release of the cutter from the insert body.

BRIEF DESCRIPTION OF THE DRAWINGS [0026] Preferred features, embodiments and variations according to the present disclosure may be discerned from the following Detailed Description. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary in any way. The Detailed Description will make reference to a number of drawings as follows:

[0027] Fig 1 is a side view of a drill bit 10 in accordance with an embodiment of the present disclosure.

[0028] Fig 2 is an end view of the drill bit 10.

[0029] Fig 3 is an exploded perspective view of a cutting insert assembly 100 in accordance with an embodiment of the disclosure.

[0030] Fig 4 is an exploded side view of the cutting insert assembly 100. [0031] Fig 5 is a partially exploded side view of the cutting insert assembly 100 wherein the retaining pin 150 is shown in an inserted configuration within the insert body 110 in whilst the cutting head 120 has been shown in a decoupled or detached configuration relative to the insert body 110.

[0032] Figure 6 is a side view of the cutting insert assembly 100 with the insert body 110 being shown in a coupled or interlocked configuration relative to the cutting head 120.

[0033] Figure 7 is a top perspective view of the cutting insert assembly 100 in the coupled or interlocked configuration.

[0034] Figure 8 is a top perspective view of the cutting insert assembly 100 in the decoupled or detached configuration.

[0035] Figure 9 is a side view of the cutting insert assembly 100 shown in the in the coupled or interlocked configuration.

[0036] Figure 10 is a sectional side view of the cutting insert assembly 100 in the coupled or interlocked configuration.

[0037] Figure 10A is also an enlarged sectional view of cutting insert assembly 100 with inset B.

[0038] Figure 10B is an enlarged view of the inset B shown in Figure 10A.

[0039] Figure IOC shows an enlarged view of the inset B for the assembly 100 in the inter locked or coupled configuration.

[0040] Figure 10D shows an enlarged view of the inset B in an intermediate configuration detailing the movement of the detent ball 134 after downward movement of the retaining cutting head 120.

[0041] Figure 10E shows an enlarged view of the inset B where the cutting head 120 has been uncoupled or detached from the insert body 110.

[0042] Figure 10F shows an enlarged view of the inset B in another intermediate configuration detailing the gradual upward movement of the retaining pin 150.

[0043] Figure 10G shows another enlarged view of the inset B in a subsequent configuration detailing further upward movement of the retaining pin which results in the detent ball being pushed into the detent groove 125.

[0044] Figures 11 A to 1 ID illustrate isolated views of the cutting head 120 without the cutting tip 122. [0045] Figures 12A to 12C illustrate isolated views of the cutting tip 122.

[0046] Figures 13A to 13C illustrate isolated views of the cap member 170.

[0047] Figures 14A to 14D illustrate isolated views of the insert body 110. Figure 14E illustrates a sectional view of the insert body 110 with the retaining pin 150 received therein.

[0048] Figure 15 illustrates an isolated view of the retaining pin 150.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS [0049] FIG. 1 shows a cutter drill bit 10 including cutter insert assemblies 100 of the present disclosure. The drill bit 10 has a central axis of rotation 13 and a bit body 14 having a leading face 16, an end face 18, a gauge region 20, and a shank 22 for connection to a drill string (not shown). A plurality of blades 26 extend from the leading face 16 of the bit body away from the central axis of rotation 13 of the bit 10. Each blade 26 terminates in a gauge pad 28 having a gauge surface 29 which faces a wall of a borehole (not shown).

[0050] A number of detachable cutter insert assemblies 100 are mounted on the blades 26 at the end face 18 of the bit 10 in both a cone region 36 and a shoulder region 38 of the end face 18. Each cutter assembly 100 partially protrudes from its respective blade 26 and the cutter assemblies 100 are spaced apart along the blade region 26, in a pre-determined manner to produce a particular type of cutting pattern. The mounting location of these cutter insert assemblies 100 is in no way limiting and the drill bit 10 shown in Figures 1 and 2 is one of many possible ways in which the cutter assemblies 100 may be mounted. The structure and function of the cutter assemblies 100 will be explained in greater detail in the foregoing sections.

[0051] The cutter insert assembly 100 may also may find application in a reamer which may form part of a reaming assembly that has not been shown here. Such a reamer may follows a roller cone bit of conventional design and a reamer section. The roller cone bit may be joined to the reamer section with a threaded connection and another threaded connection may be provided to join the reamer section to a drill string. The reamer section usually includes a plurality of blades and each blade may include a plurality of the cutter insert assemblies 100, constructed in accordance with the embodiments, as will now be described.

[0052] Figures 3 to 10 illustrate a drill bit assembly 100 in accordance with an embodiment of the present disclosure and include an insert body 110 (detailed views shown in Figures 4 to 6 and Figures 14A to 14E) extending between a first end 112 and a second end 114 along a longitudinal axis 111 of the insert body 110. At the first end 112, helical threads 115 are provided for allowing the insert body 110 to be threadably engaged into openings provided on the blade surface 26 and be mounted to the blade surface 26 for the bit body 10 (explained in previous sections).

[0053] The second end 114 of the insert body 110 is detachably coupled to a cutting head (or cutter) 120 (detailed views shown in Figures 11 A to 1 ID and 12A to 12C) that includes a frusto- conical body 121 with a leading cutting tip 122 comprised of polycrystalline diamond material that is provided in the form of a PDC insert 122 positioned in a frontal cavity 123 to assist with cutting into earth or other hard materials. While the cutting tip 122 in the exemplary drill bit assembly 100 detailed throughout the specification is a PDC insert, it should be clearly understood that other types of cutting elements such as cubic boron nitride, or other super hard material, or hard material such as a metal carbide, may also be used in a cutting head 120 made according to other embodiment of the disclosure. The cutting head 120 comprises a generally frusto-conical body 121 converging towards the PDC tip 122 to form an apex portion of the tip 122 in the cutting head 120. The cutting tip 122 may comprise a plug section 129 that can be inserted and fastened with the body 121 of the cutting head 120 to form the tip portion 123 of the cutting head 120. The cutting head 120 also includes a trailing receiving portion 124 for receiving the second end 114 of the insert body 110 into an internal cavity 126 defined by the receiving portion 124 to allow the cutting head 120 to be removably coupled to the second end 114 of the insert body 110. Detailed views of the cutting tip 122 have been shown in Figures 12A to 12C.

[0054] A novel retaining arrangement is provided to retain the second end 114 of the insert body 110 within the receiving portion 124 of the cutting head 120. The retaining arrangement comprises a retaining pin 150 that is housed within an internal passage or cavity 118 of the insert body 110 and provides a mechanical arrangement to allow the cutting head 120 to be released from insert body 110 by utilising a detent assembly 130. As a result, the cutting head 120 is detachably coupled or interlocked to the second end 114 of the insert body 110 by way of the detent assembly 130.

[0055] Referring to Figures 8 and 10 and 10A to 10G, the detent assembly 130 comprises: a detent groove 125 positioned around an inner wall 127 that defines the internal cavity of the receiving portion 124 for the cutting head 120. Detent balls 134 (shown in Figures 8 and 10) form part of the detent assemblies 130 that are provided along the insert body 110. The structure of the insert body 110 adjacent the second end 114 includes radially disposed apertures 117 (best shown in Figures 10A to 10G and 14A to 14E) that allow the detent balls 134 to pass through each of the apertures 117. The detent balls 134 are arranged to be pushed radially inwards towards the central longitudinal axis 111 of the insert body 110 in at least one operable configuration.

[0056] During use, the retaining pin 150 is inserted into the internal passage 118 of the insert body 110 by rotating the pin 150 in a clockwise or anti-clockwise direction (best shown in sectional views of Figure 10 and Figure 14E). Outer walls of the pin 150 include helical threads 152 that are configured to engage complementary threads 119 provided along internal walls of the internal passage 118. The pin 150 includes a head 153 with a driver interface such as but not limited to a hexagonal head that can interface with an alien key. Rotation of the retaining pin 150 within the internal passage 118 results in axial translation of the pin 150 along the internal passage 118 of the insert body 110. The pin 150 includes a notch 155 that is dimensioned to receive a portion of the detent balls 134 in at least one operable configuration for effecting release of the cutting head 120. The arrangement of the detent balls 134 (towards the retaining pin 150 in the inserted configuration) and the detent groove 125 along the inner walls 127 of the cutting head 120 allows a portion of the detent ball 134 to be pushed into the notch 155 when the notch 155 is in alignment with the detent aperture 117 (See Figure 10) which in turn results in the detent balls 134 being dislodged out of the detent groove 125 of the cutting head 120.

[0057] Referring to Figures 10A and 10B, sectional views show an initial position when the retaining pin 150 is axially displaced to position the notch 155 to be in alignment with the detent ball aperture 117. Once the notch 155 is aligned with the detent aperture, the cutting head 120 may be moved in a downward direction as shown in Figures IOC and 10D. The detent groove 125 consists of a recessed surface bounding by inwardly slanting guiding surfaces which typically guide the detent ball to become engaged with the recessed surface. The downward movement of the cutting head 120 results in a shoulder region or edge of the detent groove 125 to push against the detent ball 134 (best shown in Figure 10D) which in turn pushes the detent ball 134 into the notch 155 and effectively detaches or uncouples the detent groove 125 (and the cutting head 120) from the insert body 110 as shown in Figure 10E.

[0058] Referring to Figures 10F and 10G, in order to couple or inter-lock detent groove 125 with the detent ball 134, the insert body 110 needs to be received into the trailing portion 124 of the cutting head 120 to align the detent groove 125 with the detent ball 134 and the detent aperture 117 as shown in Figure 10F. The next step involves effecting axial movement of the retaining pin 150 (by turning the retaining pin in a clockwise or anticlockwise direction) to move the notch 155 out of alignment relative to the detent aperture. The notch 155 also consists of a recessed receiving surface that is bound by two slanting surface which typically guide the detent ball 134 into the notch 155. The upward movement of the retaining pin 150 as shown in Figure 10G results in a shoulder or edge portion of the notch 155 coming into engagement with the detent 134 which effectively pushes the detent ball 134 back into the detent groove 125. The diameter for the body of the retaining pin 150 is substantially equal to the diameter of the internal passage 118 of the insert body 110 which effectively prevents the detent ball 134 from being dislodged out of the detent groove 125 unless the notch 155 is axially moved to come back into alignment with the detent aperture and the detent groove 125.

[0059] One of the non-limiting problems addressed by the cutter insert assemblies 100 of the presently described embodiment relates to easily replacing the cutting head 120 whilst also reducing maintenance times which can be readily achieved by axial movement of the retaining pin 150 within the internal passage 118 of the insert body 110 to align the notch 155 of the retaining pin 150 with the detent ball apertures 117 for effecting release of the cutting head 120 from the insert body 110. As shown most clearly in Figure 15, the walls of the notch 155 comprise slanted surfaces 159 which assist in guiding the detent balls 134 into and out of the notch 155 as the retaining pin 150 is moved into alignment with the detent ball apertures 117. [0060] In a second operable configuration, the retaining pin 150 may be axially moved to a new location (such as in an upwardly direction) to move the notch 155 of the pin 150 out of alignment relative to the detent ball aperture 117. Such an upward movement of the retaining pin 150 results in the body of the pin 150 (which is dimensioned to be substantially flush with the inner walls of the internal passage 118) pushing against the detent balls 134 which in turn results in the detent balls 134 being pushed into the detent groove 125 for the cutting head 120. As a result of the outwardly radial movement of the detent balls 134 into the detent groove 125, the cutting head 120 becomes interlocked with the insert body 110 via the retaining pin 150. In the interlocked configuration, the cutting head 120 can rotate relative to the insert body 110 whilst still being maintained in the interlocked position until the retaining pin 150 is axially moved to align the notch 155 with the detent ball apertures 117 for releasing the cutting head 120 from the insert body 110 for repairs or replacement as previously discussed.

[0061] In the preferred embodiment, the height of the internal passage 118 in the insert body 110 is greater than the height of the retaining pin 150 in order to accommodate a cap member 170 as shown in Figures 3 and Figures 13A to 13C. The cap member 170 includes a sealing head 172 that can be pushed against the opening of the internal passage 118 to prevent any debris or other particles from entering the internal passage 118 of the insert body 110 which may inadvertently damage the retaining pin 150 and/or the insert body 110. The cap member 170 comprises a cylindrical body 174 which depends downwardly from the sealing head 172. The cylindrical body 174 of the cap member 170 includes lugs 176 which can register with the internal walls of the passage 118 as the cap member 170 is pushed into the opening of the internal passage 118 so that the sealing head 172 sits flush with the wall portions defining the opening for the internal passage 118.

[0062] The insert body 110 also includes a profiled stop member 113 that is positioned along an outer wall of the insert body 110 to limit axial movement of the receiving portion 124 of the cutting head 120 towards the first end 112 of the insert body 110. Referring to inset A shown in Figure 1 ID, the opening of the trailing portion 124 comprises a convergent configuration with a seat 128 for engaging the profiled stop member 113 and limiting movement of the insert body 110 within the internal cavity 126 of the cutting head 120. An O-Ring 160 may also be used for forming a seal between the outer wall of the inert body 110 and the inner walls 127 of the cutting head 120 to prevent any debris from getting lodged within the internal hollow volume of the cutting head 120.

[0063] Once again, the provision of the detent assembly 130 not only allows the cutting head 120 to be easily replaced decoupled from the insert body 110 by undertaking axial movement of the retaining pin 150 but also allows the cutting head 120 to freely rotate relative to the insert body 110 because the detent balls 134 provide a bearing arrangement to enable relative rotational movement between the insert body 110 and the cutting head 120.

[0064] In compliance with the statute, the disclosure has been described in language more or less specific to structural or methodical features. The term “comprises” and its variations, such as “comprising” and “comprised of’ is used throughout in an inclusive sense and not to the exclusion of any additional features. [0065] It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect.

[0066] The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted by those skilled in the art.