Patent Application
20160362943
The present invention relates to a drill string component coupling device positionable at a joint within a drill string assembly to rotatably couple a first drill string component to a second drill string component and in particular, although not exclusively, to a coupling device to couple the drill string to a drive unit part of the assembly.
Rotary drilling is conventionally used for drilling mining blast holes or geothermal wells and relies on high rotational speeds and thrust on the drill bit in order to drill the hole. The rotary drill bit is advanced into the bore by successive joining of sections of pipe or rod to create a drill string. The drill rig and in particular the drive unit is located at ground level and is coupled to the drill rods via a ‘bull’ shaft and an intermediate adaptor.
Drill rods, depending on their specific configuration, may weigh between ten to twenty kilograms each and measure approximately two to three meters in length. Conventionally, the drill rods are interconnected by male and female threaded connections provided at the respective rod ends. Additionally, it is typically unavoidable to have to service the drill head or other tools at the lowermost end of the drill string at regular intervals during drilling. This process involves retrieving the entire drill string from the borehole, exchanging the lowermost portion and then reinstalling the string. As will be appreciated, the rotational uncoupling or ‘breakout’ of the threaded connections between the drill string components is provided by the drive unit operating in reverse. Due to a large number of breakout manipulations required, it is not uncommon for the drill string to become unintentionally decoupled from the bull shaft at the drive unit. Accidental decoupling of the string represents a significant safety hazard as the entire string becomes unanchored and may either be lost down the borehole (when lowered under gravity) or to spill uncontrollably adjacent the drive unit if in an inclined drilling orientation. Various drill pipe couplings have been proposed to try and prevent unintentional rod decoupling and examples are described in GB 292332; WO 80/01305; U.S. Pat. No. 2,717,789; U.S. Pat. No. 2,864,629 and U.S. Pat. No. 3,637,238.
However, existing coupling devices suffer from a number of significant disadvantages. In particular, existing joint couplings often necessitate specific modification of the drill string components by way of radially extending flanges that are then engaged by a surrounding sleeve. Accordingly, it is often difficult and in some cases impossible to conveniently adapt existing drill string assemblies to fit a safety coupling device of the type found in the art. Additionally, conventional couplings require specific tools to enable detachment and decoupling which can be problematic if the tools become damaged or are unavailable on-site. Additionally, due to the significant torques encountered during drill string extractions, it is not uncommon for existing safety couplings to fail by becoming decoupled themselves from their region of attachment particularly where such couplings rely on threaded connections and/or are anchored inadequately onto the outside surface of the drill string components. Accordingly, what is required is a drill string assembly safety coupling device that addresses the above problems.
It is an objective for the present invention to provide a safety coupling device for a drill string assembly and in particular a coupling arrangement for positioning at the interface region between a drill string rotational drive unit and an axially rearward section of the drill string. It is a further specific objective of the subject invention to provide a coupling unit that may be conveniently mounted and dismounted from the drive unit and/or drill string components using readily available non-specific tools in a quick and convenient manner.
It is a further specific objective of the present invention to provide a safety joint coupling compatible for use with existing drill string drive units and drill string components without a need to specifically modify the radially outward facing regions of such units and components.
The objectives are achieved by providing a sleeve and wedge arrangement in which a coupling sleeve may be conveniently locked axially at the radially outer facing surface of a drive shaft and drill component via a convenient axial adjustment of the wedges positioned radially between the sleeve and the joint of the drive shaft and drill string component.
Advantageously, the coupling device comprises a plurality of rotational stops that projects axially forward from the locking sleeve so as to extend axially over the joint region between the two components of the drill string. The rotational stops are engaged by a part of the second component or an element attached to the second component so as to rotationally lock the drill string first component with the drill string second component.
According to a first aspect of the present invention there is provided a drill string coupling device positionable about a threaded joint formed by a threaded end of a first drill string component axially coupled in direct contact to a threaded end of a second drill string component, the device comprising: a first sleeve positionable around an axial end region of the first component exclusively to one side of the joint; a second sleeve positionable around or a collar extending radially outward at an axial end region of the second component exclusively to one side of the joint; a plurality of first wedges, each wedge having a thickness between a radially inward and outward facing surface that tapers axially along a length of each wedge, the radially outward facing surface of each wedge capable of mating in contact against a radially inward facing surface of the first sleeve so that each wedge is configured to be wedged in position radially between the first sleeve and the first component, each of the wedges mounted to be moveable axially relative to the sleeve and the first component; a plurality of rotational stops projecting axially forward from the sleeve to engage a part of the second sleeve or collar attached to the second component; characterised in that: each of the wedges comprise an integrally formed radially extending flange; the device further comprising a plurality of locking bolts, each bolt configured to engage a respective flange and i) the first sleeve or ii) a part of the second component or an element attached to the second component to force the wedges in an axial direction relative to the sleeve such that the tapered thickness of the wedges and the contact with the inward facing surface of the sleeve acts to force the radially inward facing surface of the wedges radially inward relative to the sleeve so as to allow the wedges to clamp onto the first component at the one side of the joint to lock the sleeve axially at the first component and prevent independent rotation of the first component relative to the second component.
Preferably, each wedge comprises a tapered axial length that extends substantially the full length of the wedge. Preferably, an axial length of each wedge is approximately equal to an axial length of the sleeve such that the wedges, when positioned to extend radially inside the sleeve do not project axially beyond the end of the sleeve from which the rotational stops project. Preferably, each wedge comprises a flange that projects radially outward at a second end of each wedge to sit over or against a first axial end surface of the sleeve. Such an arrangement is advantageous to provide a convenient portion of the wedge to receive the axial locking component to extend axially through the flange and into the sleeve. Preferably, a thickness of each flange in the axial direction is approximately equal to a thickness of the wedge in a radial direction such that the flange is not susceptible to fracture from the main length of the wedge. Preferably, the flange and wedge are formed integrally.
Optionally, the locking bolts and the rotational stops are separate components of the coupling device; the locking bolts and the rotational stops are the same components of the coupling device; or the rotational stops are provided by axial end regions of each of the wedges configured to engage a respective second wedge positioned at the second component and prevent independent rotation of the first component relative to the second component. Such embodiments are advantageous to provide both the axial displacement of the sleeve relative to the wedges so as to force the wedges radially inward into clamping engagement and to provide the rotational coupling of the two drill string components via the rotational stops.
Preferably, the locking bolts are attached to each flange of each respective wedge and the sleeve and extend axially relative to the sleeve. The bolts may be conveniently interfaced with the sleeve (and optionally the flange) via cooperating screw threads provided at the sleeve (and optionally the wedge). The use of bolts is advantageous to provide convenient manipulation by conventional tools. According to the preferred embodiment, the flange of each wedge comprises a bore or slot to receive each bolt and respective regions of the sleeve comprise respective bores or slots to receive each bolt such that an axial adjustment of each bolt relative to the sleeve acts to force each respective wedge radially inward from the sleeve. Preferably, each wedge comprises a slot that is convenient to allow radial movement of the wedge via the tapered radial thickness without affecting alignment of the bolt and creating stress within the coupling. That is, the bolt is configured to move radially within the slot of the wedge that is preferably un-threaded and/or comprises a size being greater than a diameter of the bolt to allow the bolt to move freely within the slot.
Preferably, the coupling device is formed from two primary components in the form of a first and a second half. Preferably, the device further comprises a first half having a first sleeve, a first set of wedges, a first set of locking bolts and the rotational stops; and a second half having a second sleeve, a second set of wedges and a second set of locking bolts. The rotational stops extend axially between the first and second sleeves so as to provide ‘bridging components’ between the first and second halves and hence the rotational locking of the first half and the second half in turn provides the rotational locking of the first and second drill string components.
Optionally, the first half is capable of positioning around the axial end region of the drill string first component and the second half is capable of positioning around the axial end region of the drill string second component; wherein the first and second sets of locking bolts are separate to provide independent axial movement of the first set of wedges relative to the second set of wedges; and the rotational stops are configured to engage the sleeve of the second component to couple the first sleeve and the second sleeve to prevent independent rotation of the first half and the second half. Advantageously, the rotational stops engage into the sleeve of the second component so as to provide a secure rotational lock and prevent decoupling of the rotational stops from the second half. Preferably, the rotational stops comprise a plurality of lugs extending from a second axial end face of the sleeve. Preferably, the lugs are realisably attached to the sleeve and the sleeve comprises a plurality of bores into which each respective lug is at least partially inserted such that an axial length section of each lug projects axially forward from the second axial end face of the sleeve. Such an arrangement is advantageous to allow the convenient coupling and decoupling of the halves of the coupling device via a straightforward alignment of the sleeves and the lugs. Any misalignment of the two halves of the device is accordingly prevented so as to provide a robust and reliable couple. Preferably, each lug is mated with each bore of each sleeve via an interference or friction fit plug-like arrangement. Optionally, the lugs may be permanently attached to one of the sleeves with the second sleeve comprising suitable bores to receive the lugs.
Preferably, the device comprises three wedges. Such an arrangement is advantageous to provide a secure attachment of the coupling device around the radially outer facing surface of the drill string component independently of any ‘misshaping’ of the drill string component resultant from extended use. However, and as will be appreciated, the drill string coupling device may comprise at least three wedges. Preferably, each of the first and second halves of the coupling device comprise three respective sets of wedges.
Optionally, the rotational stops comprise a plurality of lugs; the rotational stops are formed by the locking bolts that extends axially between the first and second halves; or the rotational stops comprise axial end regions of each of the first set of wedges and axial end regions of each of the second set of wedges such that the end regions of the first and second set of wedges overlap axially.
According to a second aspect of the present invention there is provided a drill string assembly comprising: a drill string drive unit having a drive shaft to impart rotational drive to a drill string; an adaptor to be coupled axially between the drive shaft and the drill string; and a coupling device as claimed herein positioned at a joint between the drive shaft and adaptor so as to rotatably lock and prevent independent rotation of the drive shaft and the adaptor relative to one another.
Reference within the specification to a ‘drive shaft’ encompasses a bull shaft or other shaft component that projects directly from the motor that imparts the rotational drive to the drill string. Additionally, the term ‘drive shaft’ encompasses intermediate components positioned between the drive shaft (that extends directly from the drive unit) and the drill string including adaptors, shock absorbers and the like. Additionally, reference within the specification to ‘an adaptor’ encompass components of the drill string that may be coupled directly or indirectly to the axially rearwardmost drill rod. This term encompasses reference to ‘top subs’, ‘saver subs’, drill pipes and ‘shock subs’ as will be known to those skilled in the art.
The present coupling device is configured for positioning at any region between the rotational drive unit and the axially rearwardmost drill rod so as to prevent undesirable uncoupling of the two components positioned between the drive unit and the drill string.
Preferably, the coupling device is attached to the drill string assembly at the interface region between a rotational drive unit of the assembly and an axially rearward part of the drill string. Optionally, the coupling device is secured between a bull shaft that forms a part of the drive unit and an adaptor that is positioned axially between the bull shaft and an axially rearwardmost drill rod. Coupling at this region is advantageous to avoid unintentional decoupling of the drill string from the drive unit that is typically encountered via conventional drill string arrangements during drill string extractions and drill rod breakout procedures.
Preferably, where the device comprises two halves (having a first sleeve and a second sleeve with each sleeve independently axially locked by the respective sets of wedges), the first half is positioned around an axial end region of the drill string first component and the second half is positioned around an axial end region of the drill string second component. The present coupling device is advantageous via the use of a sleeve and wedge arrangement such that the total axial length of the device can be minimised to be conveniently installed at the drive unit shaft where access and available space may be restricted.
In one aspect, the coupling device may comprise a single sleeve and corresponding set of wedges that is capable of being coupled to a specifically adapted second component part of the drill string. In particular, the second component of the drill string may comprise a radially extending collar such that the rotational stops projects axially forward from the sleeve and are configured to engage the collar to couple the sleeve to the collar and prevent independent rotation of the first component (for example the drive shaft) relative to the second component (for example an adaptor or rearwardmost part of the drill string).
Optionally, the first component is a drive shaft forming a part of a drill rig configured to impart a rotational drive to the drill rods. Optionally, the second component comprises: a drill rod; or an adaptor positioned axially between the drive shaft and an axially rearwardmost drill rod.
A specific implementation of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which:
Referring to
Coupling device first half 102 comprises a first sleeve 107 and a plurality of independent wedges 105 that are positioned radially between sleeve 107 and drive shaft 100. Similarly, device second half 103 comprises a second sleeve 108 and a corresponding set of independent wedges 105 for positioning in touching contact with the radially outward facing surface 111 of cylindrical adaptor 101. Each sleeve 107, 108 is formed as a single-piece annular ring having an inside diameter being greater than an outside diameter of the respective shaft 100 and adaptor 101 so as to accommodate wedges 105 between each sleeve 107, 108 and the respective shaft 100 and adaptor 101. Each sleeve 107, 108 comprises a first end face 110 and second end face 109 with end face 109 configured for positioning opposite one another in near touching contact such that sleeves 107, 108 are co-aligned at axis 117. Accordingly, sleeve end faces 110 are respectively orientated towards drive unit (not shown) extending from drive shaft region 112 and the drill string (not shown) extending axially from adaptor end region 113.
Each of the plurality of wedges 105 comprises a main axial length 106 and a radially extending flange 104 that projects radially from one end of main length 106. Each flange 104 is configured to sit opposed to each respective sleeve end face 110 whilst wedge main length 106 is positioned radially in between each sleeve 107, 108 and the respective drive shaft 100 and adaptor 101.
Each wedge 105 is secured and axially adjustable at each respective sleeve 107, 108 via a locking bolt 114. Each half 102, 103 comprises three bolts 114 to engage and connect each respective wedge 105 to each sleeve 107, 108. Each bolt 114 comprises an elongate shaft 120 having a threaded region 118 positioned towards one end and a head 119 at an opposite end and is capable of being driven by a key or screw driver tool. Bolt 114 and in particular threaded region 118 is received within a slot 115 extending axially within wedge flange 104. Slot 115 is dimensioned and orientated in a radial direction so as to allow a relatively small radial displacement of bolt 114 during tightening and untightening. Additionally, each sleeve 107, 108 comprises a corresponding threaded bore 116 to align with wedge slot 115 such that each bolt 114 may be threaded through each respective wedge 105 to engage into each sleeve 107, 108. Accordingly, each wedge 105 may be axially adjusted relative to each respective sleeve 107, 108 via a tightening or untightening of bolt 114 at each sleeve 107, 108.
Referring to
Each wedge main length 106 (between ends 204 and 205) comprises a tapered thickness in a radial direction between surfaces 200, 201. That is, a radial thickness of each wedge is less at end 204 than end 205. Accordingly, as each bolt 114 is tightened within each respective sleeve 107, 108, the mating contact between wedge surface 201 and sleeve surface 206 forces the wedge surface 200 radially inward into clamping engagement onto the respective shaft surface 303 and adaptor surface 111. Each slot 115 is accordingly elongate in a radial direction so as to allow each flange 104 to move radially relative to bolt 114 as the wedge 105 is radially displaced via the wedging action against each respective sleeve 107, 108.
Advantageously, each half 102, 103 of the present coupling device comprises three wedges 105. Such an arrangement is advantageous to provide a uniform clamp onto the shaft and adaptor outer surfaces 303, 111 particular where shafts 100 and adaptor 101 are misshaped and non-cylindrical due to damage incurred during use.
Referring to
According to a further specific embodiment, adaptor 101 may comprise a radially extending collar being shaped and dimensioned so as to correspond approximately to sleeve 108. The collar may comprise corresponding bores 400 to receive lugs 302 that project from the sleeve end face 109 so as to allow first half 102 to be rotatably locked at adaptor 101 via the integrally formed radial collar. According to the further embodiment, sleeve 107 of first half 102 is axially locked at shaft 100 via the same wedge and bolt arrangement 105, 114 as described with reference to
The present coupling device is capable of securing and rotatably locking two axially adjacent components of a drill string assembly conveniently and reliably. The present coupling device may be positioned at any location between two drill string components including in particular a joint between a top sub, a bull shaft, a saver sub, a drill pipe or a shock sub forming part of a drill string as will be appreciated by those skilled in the art. The present coupling device is conveniently friction fitted over and about the external surface of the cylindrical drill string components and is adapted specifically to prevent undesirable uncoupling of the two components during drill string extractions from the borehole and breakout connections between threaded couplings of the drill string components.
According to a further specific implantation, the embodiment of
According to a further embodiment, the embodiment of
| Number | Date | Country | Kind |
|---|---|---|---|
| 14154665.5 | Feb 2014 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2015/052631 | 2/9/2015 | WO | 00 |
