FIELD OF THE INVENTION

This invention relates to an accessory for a drill bit and to a drill bit assembly that includes the accessory.

BACKGROUND TO THE INVENTION

Drill bits are used in combination with drill strings for drilling through ground in oil, gas, and mining applications. During the drilling process, the drill bit can encounter various different types of geological formations. These can be competent formations, broken formations, gravels, and sands.

Various different types of drill bits are used with such drill strings, including polycrystalline diamond compact (PDC) drill bits. These include poly-crystalline diamond cutters that are fitted to either a machined steel body or a tungsten matrix body. The cutters are the operative components of the drill bit and so suffer the most damage during the drilling process. In particular, when drilling competent formations, broken formations and other relatively hard materials, the cutters can experience shock and be chipped or broken and fail prematurely. It will be appreciated that such shock includes rotational shock, for example, when the drill bit is stopped suddenly, and then restarts.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided an accessory for a drill bit, the accessory comprising: an upper connector having an upper end and a lower end, and defining a bore opening at the upper and lower ends, and including a threaded shank terminating at the upper end for threaded engagement with a drill rod, and a threaded shank or a threaded socket terminating at the lower end for threaded engagement with a lower connector or a drill bit; and a resiliently flexible shock absorbing member located at either of the upper end or the lower end of the upper connector to be interposed between the upper connector and one of the drill rod, the drill bit, and the lower connector, to absorb a degree of relative longitudinal and rotational movement of the drill bit and the drill rod in operation. The accessory may include the lower connector, the lower connector having an upper end and a lower end and defining a bore opening at the upper and lower ends and including a threaded shank or a threaded socket terminating at the upper end that is threadedly engaged with the threaded socket or the threaded shank terminating at the lower end of the upper connector and including a threaded shank or a threaded socket terminating at the lower end of the lower connector.

The upper connector may have a threaded socket that terminates at its lower end and the lower connector may have a head and a threaded shank that extends from the head and that terminates at the upper end, the head and the shank defining a shoulder, the shock absorbing member being interposed between the lower end of the upper connector and the shoulder of the lower connector.

The lower end of the upper connector may define a recess, such that the socket and the recess define a shoulder, the shock absorbing member being located on the shoulder with the shoulder of the second connector bearing against the shock absorbing member.

The shoulder of the lower connector may define a recess, the shock absorbing member being located in the recess and bearing against the shoulder of the upper connector.

The head of the lower connector may define a threaded socket so that a threaded shank of a drill bit can threadedly engage the lower connector.

The head may define a passage that opens at the threaded socket and at the upper end of the lower connector, the head further having a lower internal shoulder intermediate ends of the passage, the socket of the upper connector defining a narrowed upper end portion so that the upper connector has an upper internal shoulder. The accessory may include a retaining pin having a head and a threaded shank extending from the head, the retaining pin being received in the threaded socket of the lower connector, with the shank of the retaining pin being threaded into the narrowed upper end portion with the head bearing against the lower internal shoulder so that the lower connector is retained on the upper connector.

The threaded shank of the retaining pin may have an opposite thread hand to that of the threaded socket and threaded shank of the upper and lower connectors.

A depth of the narrowed upper end portion may be such that the relative longitudinal movement of the upper and lower connectors is accommodated. A further shock absorbing member may be positioned on the internal shoulder of the upper connector so that the upper end of the lower connector bears against the shock absorbing member.

A further shock absorbing member may be positioned on the internal shoulder of the lower connector so that the head of the pin bears against the shock absorbing member.

According to a second aspect of the invention, there is provided a drill bit assembly that comprises the accessory of the first aspect and a drill bit.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows an exploded view of a first embodiment of an accessory for a drill bit, in accordance with the invention.

Figure 2 shows the accessory of figure 1 in an assembled condition.

Figure 3 shows an exploded view of a second embodiment of an accessory for a drill bit, in accordance with the invention.

Figure 4 shows the accessory of figure 3 in an assembled condition.

Figure 5 shows an exploded view of a third embodiment of an accessory for a drill bit, in accordance with the invention.

Figure 6 shows the accessory of figure 5 in an assembled condition.

Figure 7 shows an exploded view of a fourth embodiment of an accessory for a drill bit, in accordance with the invention.

Figure 8 shows the accessory of figure 7 in an assembled condition.

Figure 9 shows an exploded view of a fifth embodiment of an accessory for a drill bit, in accordance with the invention.

Figure 10 shows the accessory of figure 9 in an assembled condition.

Figure 11 shows a sectioned view of a shock absorbing member for an accessory for a drill bit.

Figure 12 shows an exploded view of a sixth embodiment of an accessory for a drill bit, in accordance with the invention. Figure 13 shows the accessory of figure 12 in an assembled condition.

Figure 14 shows an exploded view of a seventh embodiment of an accessory for a drill bit, in accordance with the invention.

Figure 15 shows the accessory of figure 14 in an assembled condition.

Figure 16 shows an exploded view of a first embodiment of a drill bit assembly, in accordance with the invention.

Figure 17 shows the drill bit assembly of figure 16 in an assembled condition.

Figure 18 shows an exploded view of a second embodiment of a drill bit assembly, in accordance with the invention.

Figure 19 shows the drill bit assembly of figure 18 in an assembled condition.

Figure 20 shows a third embodiment of a drill bit assembly, in accordance with the invention.

Figure 21 shows a side view of a drill bit of the drill bit assembly of figure 20.

Figure 22 shows a front view of the drill bit of figure 21 .

DETAILED DESCRIPTION

In figures 1 and 2 reference numeral 10 generally indicates a first embodiment of an accessory for a drill bit, in accordance with the invention.

The accessory 10 includes an upper connector 12 having an upper end 14 and a lower end 16. The upper connector 12 defines a bore 18 opening at the upper and lower ends 14, 16. A threaded shank 20 terminates at the upper end 14 and is configured for threaded engagement with a box end of a drill rod. The upper connector 12 has a threaded socket 22 that terminates at the lower end 16.

The accessory 10 includes a lower connector 24 having an upper end 26 and a lower end 28. The lower connector 24 defines a bore 30 opening at the upper and lower ends 26, 28. The lower connector 24 includes a head 32 that terminates at the lower end 28 and a threaded shank 34 that terminates at the upper end 26.

The shank 34 is received in and threadedly engaged with the socket 22. The shank 34 and the socket 22 have complementary tapered, multi-start threads 36. When secured together, the bores 18, 30 are aligned to define a bore 44 that extends through the connectors 12, 24.

The head 32 and the shank 34 define an upwardly facing shoulder 38. The lower end 16 of the upper connector 12 defines a recess 40, the socket 22 and the recess 40 defining a shoulder 42.

The connectors 12, 24 are generally cylindrical so that the accessory 10 is generally cylindrical when assembled.

The accessory 10 includes a shock absorbing member in the form of a ring 46 of a predetermined thickness. The ring 46 is of a resilient material such as nylon, urethane, rubber, elastomeric material, or any other material that is resilient and has a relatively low friction coefficient. The ring 46 can also be a composite of such materials. The ring 46 is shown in further detail in figure 11 . As can be seen, the ring 46 can have a laminated structure, for example three layers with outer layers 48.1 , 48.3 and an intermediate layer 48.2, each being of a suitable material. This may be useful in that the intermediate layer 48.2 may be more rigid that the outer layers 48.1 , 48.3, such that the intermediate layer 48.2 provides structural integrity while the outer layers 48.1 , 48.3 provide suitable resilient deformation to accommodate relative movement of the components between which the ring 46 is positioned.

It will be appreciated that the ring 46 also serves to substantially seal an interface between the upper and lower members 12, 24 to inhibit the ingress of detritus, compressed water or air, and other materials that may damage the threads 36 by corrosion or abrasion.

The head 32 has a tapered threaded socket 50 that terminates at the lower end 28. A threaded shank of a drill bit can be screwed into the socket 50 to fasten the drill bit to the accessory 10.

The ring 46 is seated on the shoulder 42 and projects from the lower end 16. Thus, when the shank 34 is threaded into the socket 22, the shoulder 38 bears against the ring 46 to compress and pre-load the ring 46. This serves to secure the lower connector 24 to the upper connector 12, during relative rotation of the upper and lower connectors 12, 24 by maintaining axial pressure on the respective threads 36. This inhibits the connectors 12, 24 from being in loose threaded engagement with each other, which would be undesirable. Thus, the ring 46 can absorb a degree of relative longitudinal and rotational movement of the drill bit and the drill rod, in operation, while still retaining the sealing function referenced above. This may occur when, for example, the drill bit is subjected to shock. In those cases, the drill bit is stopped and restarted momentarily, while the shank 34 and socket 22 rotate reciprocally with respect to each other via the threads 36. This effectively tightens and loosens the lower connector 24 and causes reciprocal relative longitudinal movement of the shank 34 and socket 22, which is absorbed by the ring 46. As a result, shock experienced by the drill bit is reduced when compared with a drill bit assembly without the ring 46. This can reduce the risk of the cutters of the drill bit being chipped or broken, or other impact damage to the drill bit, both of which may cause the drill bit to fail prematurely.

As can be seen in figure 2, there can be a slight gap 19 between the upper and lower connectors 12, 24, when the upper and lower connectors 12, 24 are secured to each other to accommodate the reciprocal relative longitudinal movement, during said tightening and loosening, and which is occupied by the ring 46 that compresses and expands during operation. The fact that the ring occupies the gap 19 serves to inhibit the ingress of detritus. Furthermore, the gap 19 inhibits the upper and lower connectors 12, 24 making repeated impulse contact with each other during repetitive tightening and loosening.

The threads 36 are right hand threads and can have an appropriate pitch and pitch angle to facilitate the reciprocal relative rotational and longitudinal movement referred to above. For example, the threads 36 can have a 60-degree pitch angle and can have any appropriate configuration such as V-thread, ACME thread, Buttress thread, etc.

In figures 3 and 4, reference numeral 60 generally indicates a second embodiment of an accessory for a drill bit, in accordance with the invention. With reference to the preceding drawings, like reference numerals refer to like parts, unless otherwise specified.

In this embodiment, the shoulder 38 defines a recess 62 in which the ring 46 is seated, to project from the shoulder 38. Thus, when the shank 34 is screwed into the socket 22, the lower end 16 of the upper connector 12 bears against the ring 46 to preload the ring 46 for the reasons set out above. In operation, the ring 46 can respond to shock experienced by the drill bit such that this configuration works in the same way as the accessory 10. In figures 5 and 6, reference numeral 70 generally indicates a third embodiment of an accessory for a drill bit, in accordance with the invention. With reference to the preceding drawings, like reference numerals refer to like parts, unless otherwise specified.

In this embodiment, the upper connector 12 has a socket 72 terminating at the lower end 16 and having a multi-start parallel thread 74. The thread 74 can have thread specifications, such as the pitch and pitch angle of the threads 36, to facilitate the reciprocal rotational movement described above. The socket 72 and the recess 40 define a shoulder 75 on which the ring 46 is seated. The lower connector 24 has a shank 76 that projects from the head 32 to define a shoulder 79. The shank 76 has the multi-start parallel thread 74 so that it can be screwed into the socket 72 with the shoulder 79 bearing against the ring 46 to achieve the same effect as that described with reference to the accessory 10.

The head 32 defines a passage 78 that opens at the threaded socket 50 and at the upper end 26 of the lower connector 24. The head 32 has a lower internal shoulder 80 intermediate ends of the passage 78. The socket 72 of the upper connector 12 defines a narrowed upper end portion 82 so that the upper connector 12 has an upper internal shoulder 84.

The accessory 70 includes a retaining pin 86. The retaining pin 86 has a head 88 and a threaded shank 90 extending from the head 88. The head 88 and the threaded shank 90 define a bore 89 that corresponds with the bores 18, 30. The retaining pin 86 is received in the threaded socket 50 of the lower connector 24, with the shank 90 being threaded into the narrowed upper end portion 82 with the head 88 bearing against the lower internal shoulder 80 so that the lower connector 24 is retained on the upper connector 12 and the bores 18, 30, 89 in alignment with each other. Thus, fluids used during operation can pass through the accessory 70, via the bores 18, 30, 89. It will be appreciated that the retaining 86 is not fastened to the lower connector 24. Thus, relative rotation of the upper and lower connectors 12, 24, is allowed, during shock loading.

The shank 90 and the narrowed upper end portion 82 of the socket 72 have a thread hand that is opposite to that of the complementary threads 36, 74. For example, the shank 90 and the narrowed upper end portion 82 have a left-hand thread 91 . This configuration serves to inhibit detachment of the lower connector 24 from the upper connector 12 during operation because the relative loosening rotation of the upper and lower connectors 12, 24, resulting from shock loading, will tend to tighten the retaining pin 86 rather than loosen the retaining pin 86. A depth of the narrowed upper end portion 82 of the socket 72 is such that an extent of threaded engagement of the shank 90 with the upper connector 12 is limited to preserve the gap 19 and to accommodate the reciprocal linear movement referred to above. The left-hand thread 91 of the shank 90 and the narrowed upper end portion 82 causes the retaining pin 86 to tighten during drilling operations, particularly during the loosening stroke of rotational vibration or shock. The length of the retaining pin 86 is such that there are substantially no air gaps at interfaces between the ring 46 and the shoulder 75 and the ring 46 and the shoulder 79. An upper end of the retaining pin 86 faces up against an internal shoulder 87 defined between the narrowed portion 82 and the bore 18, at the end of the narrowed portion 82. During assembly, the pin 86 is torqued up to an extent that will inhibit the pin 86 from loosening during drilling operations. An epoxy such as Loctite (trade mark) is applied to the left-hand threads 91 further to secure the pin 86.

In figures 7 and 8, reference numeral 100 generally indicates a fourth embodiment of an accessory for a drill bit, in accordance with the invention. With reference to the preceding drawings, like reference numerals refer to like parts, unless otherwise specified.

The accessory 100 includes the shank 34 with the tapered, multi-start thread 36. Thus, the upper connector 12 has a socket 102, the socket 102 and the recess 40 defining a shoulder 104 on which the ring 46 is seated. The socket 102 therefore has the tapered, multi-start thread 36. The socket 102 has a narrowed upper end portion 106 with the left-hand thread of the shank 90. The accessory 100 functions in the same way as the accessory 70.

In figures 9 and 10, reference numeral 110 generally indicates a fifth embodiment of an accessory for a drill bit, in accordance with the invention. With reference to the preceding drawings, like reference numerals refer to like parts, unless otherwise specified.

A recess 112 is defined in the shoulder 79. The ring 46 is seated in the recess 112 to function as described with reference to the preceding embodiments.

In figures 12 and 13, reference numeral 120 generally indicates a sixth embodiment of an accessory for a drill bit, in accordance with the invention. With reference to the preceding drawings, like reference numerals refer to like parts, unless otherwise specified. The accessory 120 includes a further shock absorbing member in the form of a ring 122 of a material similar to that of the ring 46. The ring 122 is dimensioned to seat on the upper internal shoulder 84. Thus, when the shank 76 is received in the socket 72, the upper end 26 bears against the ring 122 to preload the ring 122. This serves the same purpose as the preloading of the ring 46 described above. This provides further absorption of the reciprocal rotational and longitudinal movement referred to above. Furthermore, the ring 122 serves to seal an interface between the shank 76 and the socket 72 to protect the threads 74 against the ingress of detritus, compressed water and air, and other potentially abrasive and corrosive materials, during operation, and particularly during rotational shock loading.

In figures 14 and 15, reference numeral 130 generally indicates a seventh embodiment of an accessory for a drill bit, in accordance with the invention. With reference to the preceding drawings, like reference numerals refer to like parts, unless otherwise specified.

The accessory 130 includes a further shock absorbing member in the form of a ring 132 of a material similar to that of the ring 46, 122. The ring 132 is dimensioned to seat on the lower internal shoulder 80. Thus, when the retaining pin 86 is screwed into position, the ring 132 is interposed between the head 88 and the internal shoulder 80. The ring 132 functions in the same way as the ring 46, 122. This provides still further absorption of the reciprocal rotational and longitudinal movement referred to above. Furthermore, the ring 132 serves to inhibit the ingress of detritus, compressed water and air, and other potentially abrasive and corrosive materials into the bore 44, during operation, and particularly during rotational shock loading.

In figures 16 and 17, reference numeral 140 generally indicates a first embodiment of a drill bit assembly, in accordance with the invention. With reference to the preceding drawings, like reference numerals refer to like parts, unless otherwise specified.

The drill bit assembly 140 includes a drill bit in the form of a PDC drill bit 142. The drill bit 142 has a conventional cutting configuration. Thus, the drill bit 142 has a drill bit head 146 with rows of poly-crystalline diamond cutters 147 mounted on the head 146. A shank 144 extends from the head 146 of the drill bit 142. The shank 144 is threaded so that it can be threadedly engaged with the socket 22 of the upper connector 12. Thus, the thread of the shank 144 is the thread 36.

The head 146 and the shank 144 define a shoulder 149. A recess 148 is defined in the shoulder 149 so that the ring 46 can be seated in the recess 148 to project from the shoulder 146. Thus, when the shank 144 is screwed into the socket 22 to be secured to the upper connector 12, the ring 46 can operate to absorb relative longitudinal and rotational movement of the drill string and the drill bit 142, in the manner described above. As with the previous embodiments, when the shank 144 is secured to the upper connector 12, a gap 145 can be defined between the head 146 and the upper connector 12 to accommodate the reciprocal relative longitudinal movement and which is occupied by the ring 46 that compresses and expands during operation. In this configuration, the ring 46 functions as described above. Thus, as before, the fact that the ring 46 occupies the gap 145 serves to inhibit the ingress of detritus.

In figures 18 and 19, reference numeral 150 generally indicates a second embodiment of a drill bit assembly, in accordance with the invention. With reference to the preceding drawings, like reference numerals refer to like parts, unless otherwise specified.

The drill bit assembly 150 includes a drill bit in the form of a PDC drill bit 152. The drill bit 152 has a conventional cutting configuration. Thus, the drill bit 152 has a drill bit head 154 with the rows of polycrystalline diamond cutters 147 mounted on the head 154.

The head 152 and the shank 144 define a shoulder 156. The shoulder 156 bears against the ring 46 seated on the shoulder 42. Thus, when the shank 144 is screwed into the socket 22, the ring 46 can operate to absorb relative longitudinal and rotational movement of the drill string and the drill bit 152, in the manner described above.

In figure 20, reference numeral 160 generally indicates a third embodiment of a drill bit assembly, in accordance with the invention. With reference to the preceding drawings, like reference numerals refer to like parts, unless otherwise specified.

The upper connector 12 and the threaded shank 20 define a shoulder 162. A recess 164 is defined in the shoulder 162. The ring 46 is seated in the recess 164 to project from the shoulder 162. Thus, the ring 46 can be preloaded by the box end of the drill rod when the shank 20 is screwed into the box end. In this embodiment, the box end, and the shank 20 can be machined or modified to provide the thread 36. Thus, in operation, the ring 46 can operate to accommodate the reciprocal longitudinal and rotational movement described with reference to the preceding embodiments. The thread 36, 74 can be plated with zinc, nickel, or any other hard-wearing coating to inhibit spalling of the threads. Furthermore, it can be desirable to have threads of different hardness under load. It follows that the threads of the connectors 12, 24 that engage the drill bit can be case hardened or subjected to a nitrite hardening process so that the drill bit can be changed without the need to change the connectors 12, 24.

The threads 36, 74 have a suitable thread lead to accommodate an appropriate relative reciprocal rotational movement described above.

In the various embodiments described herein, the ring 46, 122, 132 serves to absorb relative rotational movement of a drill bit and a drill string that may occur when the drill bit experiences shock during a drilling process. Furthermore, the ring 46, 122, 132 can serve to maintain axial pressure between the complementary threads 36, 74, during a loosening stroke resulting from shock loading to inhibit loose threaded engagement of the components. Absorption of that relative movement allows the drill string to momentarily continue to rotate while the drill bit is stationary. When the drill bit resumes rotation, the resiliency of the ring 46, 122, 132 serves to drive the drill bit back into a position with respect to the drill string, prior to the stoppage of the drill bit. This reciprocal movement is both rotational and longitudinal and is facilitated by the configuration of the threads 36, 74. It follows that the rings 46, 122, 132 and the threads 36, 74 in combination with the other components of the various embodiments provides a means whereby breakage or chipping of the cutters 147 can be mitigated. This can result in an extended useful life of the drill bit, when compared with drill bits that do not have the accessory as described herein.

During drilling operations with conventional drill bit assemblies, such drill bit assemblies can experience “chatter” or vibration. The ring 46, 122, 132, in combination with the other components of the embodiments described herein, serves to absorb such chatter or vibration by accommodating the reciprocal rotational and longitudinal movement, so enhancing the life of a drill bit when compared with drill bits without the accessory as described herein.

It will readily be appreciated that the accessory for the drill bit, as described herein, can be used with a variety of drill bits, such as drag bits, floor bits and roller bits, to extend the life of such bits. Those drill bits can be machined or modified to be connected to the various embodiments of the accessory described herein. In particular, they can be machined or modified to replace the standard conventional threads with a multi-start thread that corresponds with the thread 36, 74 of the various embodiments described herein. The appended claims are to be considered as incorporated into the above description.

Throughout this specification, reference to any advantages, promises, objects or the like should not be regarded as cumulative, composite, and/or collective and should be regarded as preferable or desirable rather than stated as a warranty.

Throughout this specification, unless otherwise indicated, "comprise," "comprises," and "comprising," (and variants thereof) or related terms such as "includes" (and variants thereof)," are used inclusively rather than exclusively, so that a stated integer or group of integers may include one or more other non-stated integers or groups of integers.

When any number or range is described herein, unless clearly stated otherwise, that number or range is approximate. Recitation of ranges of values herein are intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value and each separate subrange defined by such separate values is incorporated into the specification as if it were individually recited herein.

Words indicating direction or orientation, such as “front”, “rear”, “back”, etc, are used for convenience. The inventor(s) envisages that various embodiments can be used in a non-operative configuration, such as when presented for sale. In particular, the words “upper” and “lower” are used with reference to an operative orientation of the drill bit assembly and drill string referred to in this specification, which would be generally vertical. Thus, such words are to be regarded as illustrative in nature, and not as restrictive.

The term “and/or”, e.g., “A and/or B” shall be understood to mean either “A and B” or “A or B” and shall be taken to provide explicit support for both meanings or for either meaning.

Features which are described in the context of separate aspects and embodiments of the invention may be used together and/or be interchangeable. Similarly, features described in the context of a single embodiment may also be provided separately or in any suitable sub-combination.

It is to be understood that the terminology employed above is for the purpose of description and should not be regarded as limiting. The described embodiments are intended to be illustrative of the invention, without limiting the scope thereof. The invention is capable of being practised with various modifications and additions as will readily occur to those skilled in the art.