AU2011244894A1

AU2011244894A1 - Lock Washer

Info

Publication number: AU2011244894A1
Application number: AU2011244894A
Authority: AU
Inventors: Monte Hocking
Original assignee: Montrae Mining Pty Ltd
Current assignee: Montrae Mining Pty Ltd
Priority date: 2011-10-31
Filing date: 2011-10-31
Publication date: 2013-05-16
Anticipated expiration: 2031-10-31
Also published as: AU2011244894B2

Abstract

A lock washer (10) for assisting with connection between at least a first section (26) and a second section (28) of a drill string (24), the first section having a zone (30) at or towards an end of the first section (26), the first section zone (30) having an outer perimeter (34) with a cross-sectional shape and size, and the second section (28) having a zone (32) at or towards an end of the second section (28), the second section zone (32) having an outer perimeter (36) with a cross-sectional shape and size, the lock washer (10) including: a first part (12) having an inner perimeter (16) with a cross-sectional shape and size which substantially complements the first section zone (30) cross-sectional shape and size such that the first part (12) is able to slide along the first section zone (30) in a direction parallel to a notional axis of the first section zone (30), and such that the first part (12) is substantially prevented from rotating with respect to the first section zone (30); and a second part (14) having an inner perimeter (18) with a cross-sectional shape and size different from the first part inner perimeter (16) cross-sectional shape and size, and which substantially complements the second section zone (32) cross sectional shape and size such that the second part (14) is able to slide along the second section zone (32) in a direction parallel to a notional axis of the second section zone (32), and such that the second part (14) is substantially prevented from rotating with respect to the second section zone (32), wherein the first part (12)and the second part (14) are joined such that they are prevented from rotating with respect to each other. 18912 Specification 3, 2-0 -0 4-3 2 PIdC).

Description

1 MONTRAE MINING PTY LTD AUSTRALIA Patents Act 1990 PATENT SPECIFICATION FOR THE INVENTION ENTITLED "LOCK WASHER" This invention is described in the following statement:- 2 LOCK WASHER FIELD OF THE INVENTION [001] The present invention relates to a lock washer, and may be particularly useful for connecting two sections of a drill string in mining applications. BACKGROUND OF THE INVENTION AND PRIOR ART [002] In mining, it is often required to connect two sections of a drill string together, for example, when such drill string requires extension for drilling a bore hole. Many drill rigs have a carousel with four drill rods. When drilling, a first drill rod is used to drill a bore hole to an initial depth, the first drill rod is screwed off, the rig is raised, and then the next drill rod is screwed on, before re-commencing the drill down with the extended drill string to create a deeper bore hole. [003] This process may be repeated so as to attach further drill rods to extend the drill string, thereby creating a bore hole of desired depth. When the hole is at the desired depth, the procedure can be reversed, with the drill string being rotated out of the bore hole and drill rod section being progressively disconnected, until the first drill rod is removed from the drilled bore hole. [004] A drill rig has a rotary head which turns the drill rods. The drill rods may be connected to the rotatory head using a cross-over sub or a saver sub. In other circumstances, it is possible to use a shock cushion sub (cushion sub), whereby the cushion sub is connected to the rotary head and the drill rods, in turn, are connected to the piston thread of the cushion sub using a cross-over sub. [005] Drill rigs often use a rotary head that may have a different thread from the drill rods. For example, a manufacturer of a rotary head may use threads such as: API = 3", 4 1/4", 5 1/2", 6 5/8", or BECO = 4 1/2", 5", 5 1/2", 6", 6 1/2", etc. Often a drill rod will use different threads from those used by the manufacturer of the rotary head. Such differences cause expenses and extra effort in requiring cross-over 18912 Specification 3 subs or saver subs, so as to connect the drill rig rotary head with the drill string (the drill rods). Sometimes, it is desired to use a cushion sub to connect a rotary head with a drill rod, where the rotary head and drill rod have different threads. [006] As the cross-over sub turns in both directions under pressure during the drilling process, it is necessary to weld one or more lugs between the "top sub" (which may be the piston thread of the cushion sub or the rotatory head) and the "bottom sub" (which may be the cross-over sub or the saver sub). In some applications three lugs are required to be welded between the top sub and the bottom sub. [007] In other example applications, the top sub and the bottom sub are joined for the drilling process by using a thread sealant. Such thread sealant is applied in a substantially liquid form, which subsequently dries and locks the top sub and the bottom sub. [008] By using welded lugs or a thread sealant, the top sub is prevented from unscrewing from the bottom sub when drilling, or when reversing the drill string from the bore hole. [009] Welding the lugs can be problematic as, during the welding process, the drill rig must be isolated. Further, the welding process can be quite dangerous, which poses an occupational health and safety risk. Moreover, when the drilling process has been completed, it is necessary to disconnect the top sub from the bottom sub, which is commonly effected by cutting tag off with a grinder. The grinding process may also cause further risks. [0101 Another problem with the welding and grinding process is that skilled operators who are qualified to perform such tasks may in short supply, and therefore can be expensive. Furthermore, an operator of a drill rig may need to wait an unfeasibly long time before such a skilled operator becomes available, thus losing time and potential profits. 18912 Specification 4 [011] Use of a thread sealant also has a number of problems. When disconnecting the top sub from the bottom sub, it is required to "oxyheat" the top sub/bottom sub assembly so as to liquefy the thread sealant and allow disconnection of the subs. Such oxyheating also causes an occupational health and safety problem. [012] It is an object of the present invention to overcome, or at least ameliorate, one or more of the above-identified problems in the prior art, or to provide a useful alternative to such prior art. The present invention may also overcome, or at least ameliorate, other problems in the prior art, not been identified above. The present invention may also at least provide a useful alternative to prior art not identified above. SUMMARY OF THE INVENTION [013] Accordingly, in one aspect, the present invention provides a lock washer for assisting with connection between at least a first section and a second section of a drill string, the first section having a zone at or towards an end of the first section, the first section zone having an outer perimeter with a cross-sectional shape and size, and the second section having a zone at or towards an end of the second section, the second section zone having an outer perimeter with a cross-sectional shape and size, the lock washer including, a first part having an inner perimeter with a cross sectional shape and size which substantially complements the first section zone cross-sectional shape and size such that the first part is able to slide along the first section zone in a direction parallel to a notional axis of the first section zone, and such that the first part is substantially prevented from rotating with respect to the first section zone, and a second part having an inner perimeter with a cross-sectional shape and size different from the first part inner perimeter cross-sectional shape and size, and which substantially complements the second section zone cross-sectional shape and size such that the second part is able to slide along the second section zone in a direction parallel to a notional axis of the second section zone, and such that the second part is substantially prevented from rotating with respect to the second 18912 Specification 5 section zone, wherein the first part and the second part are joined such that they are prevented from rotating with respect to each other. [014] In another aspect, the present invention provides a method for assisting with connection between at least a first section and a second section of a drill string, the first section having a zone at or towards an end of the first section, the first section zone having an outer perimeter with a cross-sectional shape and size, and the second section having a zone at or towards an end of the second section, the second section zone having an outer perimeter with a cross-sectional shape and size, the method including, providing a lock washer, including a first part having an inner perimeter with a cross-sectional shape and size which substantially complements the first section zone cross-sectional shape and size such that the first part is able to slide along the first section zone in a direction parallel to a notional axis of the first section zone, and such that the first part is substantially prevented from rotating with respect to the first section zone and a second part having an inner perimeter with a cross sectional shape and size different from the first part inner perimeter cross-sectional shape and size, and which substantially complements the second section zone cross sectional shape and size such that the second part is able to slide along the second section zone in a direction parallel to a notional axis of the second section zone, and such that the second part is substantially prevented from rotating with respect to the second section zone, wherein the first part and the second part are joined such that they are prevented from rotating with respect to each other, sliding the lock washer on to and along the first section zone, in a first direction parallel to the notional axis of the first section zone, such that the lock washer is positioned on and substantially away from an end of the first section zone, at least partially connecting the first section to the second section, sliding the lock washer along the first section zone in a direction opposite the first direction, such that the second part slides on to and along the second section zone, in a direction parallel to the notional axis of the second section zone, wherein an end of the first part which is adjacent the second part is close to or abuts a part of an end of the second section zone, such that, the first section and the second section are connected and prevented from rotating with respect to each other. 18912 Specification 6 [015] In a further aspect, the present invention provides a method for assisting with connection between at least a first section and a second section of a drill string, the first section having a zone at or towards an end of the first section, the first section zone having an outer perimeter with a cross-sectional shape and size, and the second section having a zone at or towards an end of the second section, the second section zone having an outer perimeter with a cross-sectional shape and size, the method including providing a lock washer, including, a first part having an inner perimeter with a cross-sectional shape and size which substantially complements the first section zone cross-sectional shape and size such that the first part is able to slide along the first section zone in a direction parallel to a notional axis of the first section zone, and such that the first part is substantially prevented from rotating with respect to the first section zone and a second part having an inner perimeter with a cross sectional shape and size different from the first part inner perimeter cross-sectional shape and size, and which substantially complements the second section zone cross sectional shape and size such that the second part is able to slide along the second section zone in a direction parallel to a notional axis of the second section zone, and such that the second part is substantially prevented from rotating with respect to the second section zone, wherein the first part and the second part are joined such that they are prevented from rotating with respect to each other, sliding the lock washer on to and along the second section zone, in a first direction parallel to the notional axis of the second section zone, such that the lock washer is positioned on and substantially away from an end of the second section zone, at least partially connecting the first section to the second section, sliding the lock washer along the second section zone in a direction opposite the first direction, such that the first part slides on to and along the first section zone, in a direction parallel to the notional axis of the first section zone, wherein an end of the second part which is adjacent the first part is close to or abuts a part of an end of the first section zone, such that, the first section and the second section are connected and prevented from rotating with respect to each other. 18912 Specification 7 SUMMARY OF EMBODIMENTS OF THE INVENTION [0161 In an embodiment, the first part inner perimeter cross-sectional shape and size is further configured to prevent the first part from sliding along the second section zone in a direction parallel to the notional axis of the second section zone, and wherein, the second part inner perimeter cross-sectional shape and size is further configured to enable the second part to slide along the first section zone in a direction parallel to the notional axis of the first section zone. [017] In another embodiment, the second part inner perimeter cross-sectional shape and size is further configured to prevent the second part from sliding along the first section zone in a direction parallel to the notional axis of the first section zone, and wherein, the first part inner perimeter cross-sectional shape and size is further configured to enable the first part to slide along the second section zone in a direction parallel to the notional axis of the second section zone. [018] In a further embodiment, the cross-scetional shapes of the first part inner perimeter and the first section zone outer perimeter are polygonal. The polygonal shape may be a regular polygon. Further, the polygonal shape may be a dodecagon. [019] In an optional embodiment, the cross-sectional shapes of the second part inner perimeter and the second section zone outer perimeter are splines. Each spline tooth may have a substantially triangular longitudinal cross-section. Optionally, the splines may include approximately 180 teeth. [020] In an embodiment, a notional circle meeting the centres of all sides of the polygon of the first part has a diameter less than the diameter of a notional circle meeting each inner-most ridge of the spline of the second part. [021] In another embodiment, a notional circle meeting the centres of all sides of the polygon of the first part has a diameter greater than the diameter of a notional circle meeting each inner-most ridge of the spline of the second part. 18912 Spccification 8 1022] In yet another embodiment, the lock washer further includes at least one threaded bore, each at least one bore having a notional axis which is radial with respect to a notional longitudinal axis of the lock washer, wherein each at least one bore is adapted to accept a threaded grub screw for securing the lock washer with respect to either or both the first section zone and the second section zone. Optionally, the at least one bore is located in the first part. Further optionally, the at least one bore includes three bores which are evenly spaced around the circumference of the lock washer. [023] In an embodiment of the method aspect, the method further includes securing the lock washer with respect to either or both the first section zone and the second section zone by screwing the at least one grub screw in to the at least one bore and tightening the at least one grub screw against either or both the first section zone and the second section zone. BRIEF DESCRIPTION OF THE DRAWINGS [024] One or more embodiments of the present invention are described below with reference to the accompanying Figures in which: [025] FIG. 1 is a perspective view of a lock washer according to an embodiment of the present invention; [0261 FIG. 2 is a bottom-plan view of the lock washer as shown in FIG. 1; [027] FIG. 3 is a side elevation view of the lock washer as shown in FIG. 1; [028] FIG. 4 is a cross-sectional side elevation view of the lock washer as shown in FIG. 1, across line A-A in FIG. 2; 18912 Specification 9 [0291 FIG. 5 is a cut-away section perspective view of the lock washer, applied to connecting a first section of a drill string with a second section of a drill string in accordance with an embodiment of the present invention; [030] FIG. 6 is a top perspective view of an embodiment of the present invention, wherein the lock washer is applied to connecting a first section of a drill string with a second section of the drill string. FIG. 6 shows a step of a method in accordance with an embodiment of the present invention, wherein the first and second sections of the drill string are to be connected using the lock washer, and wherein the lock washer has been slid along a part of the first section of the drill string; [031] FIG. 7 is a side elevation view of the embodiment shown in FIG. 6, also showing the step in the method for connecting a first section of the drill string with a second section of the drill string, using the lock washer; [032] FIG. 8 is a top perspective view of another step in the method to connect the first section of the drill string with the second section of the drill string, wherein the second section is at least partially connected to the first section, with the lock washer still in the position on the first section of the drill string, as per FIG. 6; [033] FIG. 9 is a side elevation view similar to that shown in FIG. 8; [0341 FIG. 10 is a top perspective view of an embodiment of the present invention showing another step in the method for connecting the first section of the drill string with the second section of the drill string, wherein, once the first and second sections have been at least partially connected, the lock washer is slid along the first section towards the second section, so as to connect the first section of the drill string with the second section of the drill string; [035] FIG. 11 is a side elevation view similar to that shown in FIG. 10; 18912 Specification 10 [036] FIG. 12 is a side elevation cross-sectional view of an embodiment of the present invention, wherein the lock washer is applied to connect the first section of the drill string with the second section of the drill string; and, [037] FIG. 13 is a similar view to that shown in FIG. 12, wherein the lock washer has been slid along the first section, thus disengaging from the second section, in preparation for disconnection of the first section from the second section. DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION [0383 Referring to FIG. 1, the lock washer 10 is substantially circular in shape around its outer perimeter. The lock washer 10 includes a first part 12 and a second part 14, the first and second parts being integrally formed with each other in the embodiment shown in FIG. 1. [039] The first part 12 has an inner perimeter 16. In this embodiment, the inner perimeter 16 is a regular dodecagon. Also, in this embodiment, top edges of the sides of the inner perimeter 16 are chamfered so as to facilitate sliding of the lock washer 10. [040] The first part 12 has three bores 22, which are evenly spaced around the circumference of the lock washer 10. An opening of each bore 22 is located in a centre position of a face of the dodecahedron of the inner perimeter 16. As there are three bores 22 in the dodecahedron of the inner perimeter 16, each bore is spaced four sides of the dodecahedron away from its neighboring bore. [041] Each bore 22 is threaded so as to receive a grub screw 20, each grub screw having a complementary thread. As will be described later, the grub screws 20 assist with securing the lock washer 10 on a part of a drill string (not shown in FIG. 1). [042} The lock washer 10 also includes a second part 14 with an inner perimeter 18. The inner perimeter 18 is a spline. 18912 Specification 11 [043] In the embodiment of the lock washer 10 shown in FIG. 1, the dodecagon inner perimeter 16 of the first part 12 substantially complements a part of the drill string (not shown), which has a dodecagon shaped outer perimeter. Further, the spline of the inner perimeter 18 of the second part 14 is substantially complementary to a part of the drill string (not shown in FIG. 1), which is also spline shaped. [044] Referring to FIG. 2, it can be seen that the inner perimeter 18 of the second part 14 generally has a greater diameter than the inner perimeter 16 of the first part 12. By this configuration, the lock washer 10 is able to slide freely along a zone of the drill string which substantially complements the shape and size of the first part 12. However, where the drill sting substantially complements the shape and size of the second part 14, only that second part will be able to slide along that particular zone of the drill string, but the lock washer 10 will be prevented from sliding any further when that particular zone of the drill sting abuts against the bottom of the inner perimeter 16 of the first part 12. [045] FIG. 3 is a side elevation view of the lock washer 10, perhaps better showing a bore 22 having a thread which is substantially complementary to the thread of the grub screw 20. [046] FIG. 4 is a cross-sectional side elevation view of the lock washer 10 shown in FIGS. 1, 2 and 3, across line A-A in FIG. 2. As can be seen, the inner perimeter 18 of the second part 14 is generally of wider diameter than the inner perimeter 16 of the first part 12. [047] FIG. 5 shows the lock washer 10 in the context of a drill string 24. There is shown a first section 26 and a second section 28 of the drill string 24. Of course, the view shown in FIG. 5 is only a partial view of the drill string 24, which extends upwardly and extends downwardly. 18912 Specification 12 [048] In the embodiment shown in FIG. 5, the first section 26 of the drill string 24 is a bottom part of a cushion-sub. The cushion-sub (mostly not shown in FIG. 5) may be connected to a rotary head (also not shown in FIG. 5) for turning the drill string 24 when drilling. [049] The second section 28 of the drill string 24 is a cross-over sub, a lower part of which (not shown in FIG. 5) may be connected to a drill rod (also not shown in FIG. 5). [0501 The first section 26 includes a lower part, being a first section zone 30. The first section zone has an outer perimeter 34 with a cross-sectional shape and size, being a dodecagon. The dodecagon outer perimeter 34 of the first section zone 30 is substantially complementary to the dodecagon inner perimeter 16 of the first part 12 of the lock washer 10. [0511 Accordingly, the lock washer 10 may freely slide along the first section zone 30. As the diameter of the inner perimeter 18 of the second part 14 is wider than the diameter of the inner perimeter 16 of the first part 12, the inner perimeter 18 of the second part 14 will not interfere with the lock washer 10 sliding along the first section zone 30. [052] The second section 28 of the drill string 24 includes a second section zone 32. The second section zone 32 has an outer perimeter 36 with a cross-sectional shape and size, being a spline. The spline of the second section zone 32 substantially complements the cross-sectional shape and size of the inner perimeter 18 of the second part 14 of the lock washer 10. [053] Due to the inner perimeter 16 of the first part 12 of the lock washer 10 having a diameter which is smaller than the diameter of the inner perimeter 18 of the second part 14 of the lock washer 10, when the spline inner perimeter 18 of the second part 14 engages with and slides along the spline of the second section zone 32, when the lock washer is slid sufficiently along the spline of the second section 18912 Specification 13 zone 32, the top of the second section zone 32 will abut against the bottom of the inner perimeter 16 of the first part 12 of the lock washer, thus preventing the lock washer from sliding further along the second section zone 32. [054] The first section 26 of the drill string 24 includes a bore 37. A lower part of the bore has a substantially frusto-conical shape, with a thread 38. The second section 28 of the drill string includes a projection 39, which is also substantially frusto-conical in shape. The projection 39 of the second section 28 also has a thread 40. [055] In a process for connecting the first section 26 with the second section 28 of the drill string 24, the projection 39 of the second section 28 is inserted into the bore 37 of the first section 26. When the projection 39 has been inserted far enough into the bore 37, the thread 40 of the projection 39 will come into contact with the thread 38 of the bore 37, such that the second section 28 can be at least partially connected to the first section 26 by screwing in the projectile 39 to the bore 37. [056] As previously mentioned, at this point of connecting a first section with a second section of a drill string in prior art methods, it would be necessary to either weld lugs to prevent the second section from turning with respect to the first section during the drilling process. Alternatively, in the prior art method, a thread sealant would be used between the thread of the projection of the second section and the thread of the bore of the first section, in such prior art systems. [057] The lock washer 10 is configured such that when the inner perimeter 16 of the first part 12 is slid along the outer perimeter 34 of the first section zone 30, the lock washer 10 and the first section 26 are prevented from rotating with respect to each other. Similarly, the lock washer 10 is configured such that, when the inner perimeter 18 of the second part 14 is slid along the outer perimeter 36 of the second section zone 32, the lock washer 10 and the second section 28 are prevented from rotating with respect to each other. The first part 12 and the second part 14 of lock washer 10 are also prevented from rotation with respect to one another. In the 18912 Specification 14 embodiment shown, the lock washer is integrally formed from a single piece of metal, thus inherently providing the property that the first part 12 and the second part 14 are unable to rotate with respect to one another. [058] The projection 39 of the second section 28 of the drill string 24 has an upper end which forms a seal 42. The seal 42 includes two O-rings 44, which, when the projection 39 is inserted into the bore 37 of the first section 26, abut firmly against the inner perimeter of a cylindrical part of the bore 37. The cylindrical part of the bore is located above the frusto-conical lower part of the bore. The seal 42 prevents liquid, and materials suspended in liquids, from leaking when such liquids or suspensions move through the internal bore of the drill string 24. [059] FIGS. 6 and 7 show, respectively, perspective and side elevation views of a step in connecting the first section 26 with the second section 28 of the drill string 24, when using the lock washer 10. [060] In the step of the method, an operator (not shown) slides the lock washer 10 along the first section zone 30. The lock washer should be slid far enough along the first section zone 30 such that a bottom part of the lock washer is located substantially away from a bottom part of the first section zone 30 (as can be seen, perhaps, most clearly in FIG. 7). [061] For convenience, the grub screws 20 can be tightened so that the lock washer 10 is held in a desired position when located along the first section zone 30. Further, in an optional embodiment, the first section zone 30 can include divots which assist with securing the lock washer 10 onto the first section zone, wherein ends of the grub screws 20 are able to project into the divots, thus assisting with the securing of the lock washer along the first section zone. [062] FIGS. 8 and 9 show, respectively, perspective and side elevation views of the drill string 24, with the first section 26 and the second section 28 being connected 18912 Specification 15 together with the lock washer 10. FIGS. 8 and 9 show another step in an embodiment method for effecting the connection. [063] As can be seen, the lock washer 10 has been slid along the first section zone 30 (refer to FIGS. 6 and 7). In FIGS. 8 and 9, as previously described, the projection 39 of the second section 28 has been slid into the bore 37 of the first section 26 of the drill string 24, such that the first section 26 and the second section 28 are at least partially connected. [064] When the partial connection of the first section 26 and the second section 28 has occurred, grub screws 20 are unscrewed from the bores 22 in the lock washer 10, such that the lock washer is able to slide along the first section zone 30. Accordingly, an operator is able to slide the lock washer downwardly toward the second section zone 32. [0651 FIGS. 10 and 11 show, respectively, perspective and side elevation views of the next step in the embodiment method, wherein the inner perimeter 18 of the second part 14 of lock washer 10 has been slid along the second section zone 32. As previously described, the first part 12 is prevented from sliding along the second section zone, so that the lock washer, in this particular embodiment, remains in the position shown in FIGS. 10 and 11 due to gravity. [066] The grub screws 20 may then be screwed into the bores 22 so as to more firmly secure the lock washer 10 in its position, as shown in FIGS. 10 and 11. Optionally, the first section zone 30 may include further divots (different from the divots described in respect of the FIGS. 6 and 7) when the grub screws are screwed into the bores 22, ends of the grub screws project into the divots, so as to assist in securing the lock washer 10 in its position as shown in FIGS. 10 and 11. [067] Of course, it will be understood that, the embodiment method described for connecting the first section 26 with the second section 28 of the drill string 24 can be substantially reversed. In this regard, an operator may unscrew the grub screws 20, 18912 Specidication 16 slide the lock washer 10 along the second section zone 32 and the first section zone 30, so as to move the lock washer away from the second section zone. The grub screws can then be re-fastened so as to hold the lock washer in place along the first section zone 30 (similar to the methods step shown in FIGS. 6 and 7). The second section 28 can then be fully disconnected from the first section 26. [068] FIGS. 12 and 13 show cross-sectional side elevation views of the drill string 24 when connected (FIG. 12) and the drill string 24 when being disconnected (FIG. 13). [069] The invention, and embodiments thereof, is susceptible to variations, modifications, and/or additions other than those specifically described or claimed, and it is to be understood that the invention includes all such variations, modifications and/or additions, which fall within the scope of the following claims. [070 Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. [071] The reference to any prior art in this specification is not and should not be taken as an acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge. 18912 Specification

Claims

1. A lock washer for assisting with connection between at least a first section and a second section of a drill string, the first section having a zone at or towards an end of the first section, the first section zone having an outer perimeter with a cross sectional shape and size, and the second section having a zone at or towards an end of the second section, the second section zone having an outer perimeter with a cross-sectional shape and size, the lock washer including: a first part having an inner perimeter with a cross-sectional shape and size which substantially complements the first section zone cross-sectional shape and size such that the first part is able to slide along the first section zone in a direction parallel to a notional axis of the first section zone, and such that the first part is substantially prevented from rotating with respect to the first section zone; and a second part having an inner perimeter with a cross-sectional shape and size different from the first part inner perimeter cross-sectional shape and size, and which substantially complements the second section zone cross-sectional shape and size such that the second part is able to slide along the second section zone in a direction parallel to a notional axis of the second section zone, and such that the second part is substantially prevented from rotating with respect to the second section zone, wherein the first part and the second part are joined such that they are prevented from rotating with respect to each other.

2. A lock washer according to claim 1, wherein the first part inner perimeter cross-sectional shape and size is further configured to prevent the first part from sliding along the second section zone in a direction parallel to the notional axis of the second section zone; and wherein, the second part inner perimeter cross-sectional shape and size is further configured to enable the second part to slide along the first section zone in a direction parallel to the notional axis of the first section zone. 18912 Specification 18

3. A lock washer according to claim 1, wherein the second part inner perimeter cross-sectional shape and size is further configured to prevent the second part from sliding along the first section zone in a direction parallel to the notional axis of the first section zone; and wherein, the first part inner perimeter cross-sectional shape and size is further configured to enable the first part to slide along the second section zone in a direction parallel to the notional axis of the second section zone.

4. A lock washer according to any one of claims 1 to 3, wherein the cross sectional shapes of the first part inner perimeter and the first section zone outer perimeter are polygonal.

5. A lock washer according to claim 4, wherein the polygonal shape is a regular polygon.

6. A lock washer according to either claim 4 or claim 5, wherein the polygonal shape is a dodecagon.

7. A lock washer according to any one of claims 1 to 6, wherein the cross sectional shapes of the second part inner perimeter and the second section zone outer perimeter are splines.

8. A lock washer according to claim 7, wherein each spline tooth has a substantially triangular longitudinal cross-section.

9. A lock washer according to either claim 7 or claim 8, wherein the splines include approximately 180 teeth.

10. A lock washer according to any one of claims 7 to 9 when appended to claim 2, wherein a notional circle meeting the centres of all sides of the polygon of the first part has a diameter less than the diameter of a notional circle meeting each inner-most ridge of the spline of the second part. 18912 Specification 19

11. A lock washer according to any one of claims 7 to 9 when appended to claim 3, wherein a notional circle meeting the centres of all sides of the polygon of the first part has a diameter greater than the diameter of a notional circle meeting each inner-most ridge of the spline of the second part.

12. A lock washer according to any one of claims 1 to 11, further including at least one threaded bore, each at least one bore having a notional axis which is radial with respect to a notional longitudinal axis of the lock washer, wherein each at least one bore is adapted to accept a threaded grub screw for securing the lock washer with respect to either or both the first section zone and the second section zone.

13. A lock washer according to claim 12, wherein the at least one bore is located in the first part.

14. A lock washer according to either claim 12 or claim 13, wherein the at least one bore includes three bores which are evenly spaced around the circumference of the lock washer.

15. A method for assisting with connection between at least a first section and a second section of a drill string, the first section having a zone at or towards an end of the first section, the first section zone having an outer perimeter with a cross sectional shape and size, and the second section having a zone at or towards an end of the second section, the second section zone having an outer perimeter with a cross-sectional shape and size, the method including: providing a lock washer according to claim 1; sliding the lock washer on to and along the first section zone, in a first direction parallel to the notional axis of the first section zone, such that the lock washer is positioned on and substantially away from an end of the first section zone; at least partially connecting the first section to the second section; sliding the lock washer along the first section zone in a direction opposite the first direction, such that the second part slides on to and along the second section zone, in 18912 Specificahon 20 a direction parallel to the notional axis of the second section zone, wherein an end of the first part which is adjacent the second part is close to or abuts a part of an end of the second section zone, such that, the first section and the second section are connected and prevented from rotating with respect to each other.

16. A method for assisting with connection between at least a first section and a second section of a drill string, the first section having a zone at or towards an end of the first section, the first section zone having an outer perimeter with a cross sectional shape and size, and the second section having a zone at or towards an end of the second section, the second section zone having an outer perimeter with a cross-sectional shape and size, the method including: providing a lock washer according to claim 1; sliding the lock washer on to and along the second section zone, in a first direction parallel to the notional axis of the second section zone, such that the lock washer is positioned on and substantially away from an end of the second section zone; at least partially connecting the first section to the second section; sliding the lock washer along the second section zone in a direction opposite the first direction, such that the first part slides on to and along the first section zone, in a direction parallel to the notional axis of the first section zone, wherein an end of the second part which is adjacent the first part is close to or abuts a part of an end of the first section zone, such that, the first section and the second section are connected and prevented from rotating with respect to each other.

17. A method for assisting with connection between at least a first section and a second section of a drill string according to either claim 15 or claim 16, wherein, when the lock washer is provided in accordance with any one of claims 12 to 14, the method further includes securing the lock washer with respect to either or both the first section zone and the second section zone by screwing the at least one grub screw 18912 Specification 21 in to the at least one bore and tightening the at least one grub screw against either or both the first section zone and the second section zone.

18. A lock washer according to claim 1, substantially as hereinbefore described with reference to the Figures.

19. A method according to either claim 15 or claim 16, substantially as herein before described with reference to the accompanying Figures. 18912 Specification