Patent Description:
It is known to anchor, for example, a tidal power machine, to the seabed using a self-boring anchor, such as described in <CIT>. The anchor described therein comprises a substantially solid shaft or anchor stem having a drill head at its distal end. The drill head has a cutting tip and a frustoconical outer surface. A sleeve or outer casing having hinged articulated fingers at its distal end is axially slidable on the shaft such that the articulated fingers are selectively movable over the drill head of the shaft and flare outwardly as the sleeve moves towards the distal end. Each finger has a cutter on its tip to thereby form an undercut in the substrate when the sleeve is axially moved in the distal direction along the shaft. The undercut prevents the anchor from being withdrawn from the hole when it is subjected to a tensile load.

However, this form of anchor is limited in relation to its size, scalability and applicability. For example, if a relatively large-scale application required the anchor to have a diameter of around <NUM>, the volume of substrate to be removed would be around <NUM><NUM> based on the anchor being around <NUM> long, which would be inefficient, time and energy consuming, and costly, and therefore often not commercially viable or possible, particularly if the substrate is hard rock. The anchor is also not suitable for use in relatively soft substrate, such as a sand. Furthermore, the configuration and hinge pin coupling of the hinged fingers limits the minimum size the anchor can be which further limits the range of applications for the anchor.

It is an aim of certain embodiments of the present invention to provide a fixation device for securing an offshore structure to the seabed which is scalable in size and which resists tensile, compressive and lateral loading, and a combination thereof.

It is an aim of certain embodiments of the present invention to provide a fixation device for securing an offshore structure to the seabed which is relatively quick to install in a substrate and which requires less energy to install than conventional fixation devices, particularly into relatively hard substrate.

According to a first aspect of the present invention there is provided a fixation device comprising:.

Optionally, the flareable end formation comprises a plurality of finger elements each selectively moveable about a hinge axis with respect to the outer sleeve, and wherein each finger element is mounted at a hinge end portion to a travel sleeve slidably coupled to the distal end of the outer sleeve.

Optionally, the hinge end portion of each finger element comprises a substantially curved hinge surface defining the hinge axis.

Optionally, the substantially curved hinge surface of each finger element is located in a correspondingly curved annular groove of the travel sleeve.

Optionally, the travel sleeve is rotationally constrained to the outer sleeve by at least one projection extending from the outer sleeve and engaged in at least one longitudinally oriented slot in the travel sleeve.

Optionally, the travel sleeve is axially constrained to the outer sleeve during a first mode of operation by at least one first coupling element configured to axially unconstrain the travel sleeve with respect to the outer sleeve during a further mode of operation.

Optionally, each finger element comprises a longitudinal channel extending at least partially along its length and at least one lateral channel extending from the longitudinal channel to a side face of the finger element.

Optionally, the fixation device comprises at least one second coupling element configured to couple the outer sleeve to the inner sleeve during a first mode of operation wherein the inner and outer sleeves are rotatable and translatable together, and selectively decouple the outer sleeve from the inner sleeve during a further mode of operation wherein the outer sleeve is rotatable and translatable with respect to the inner sleeve.

Optionally, the at least one first coupling element and the at least one second coupling element each comprise a shear pin.

Optionally, the guide body is rotatable about the longitudinal axis with respect to the inner sleeve.

Optionally, the fixation device comprises an end formation fixed to a proximal end region of the outer sleeve and configured to allow a torque driver to couple thereto and apply a drive torque to the outer sleeve.

Optionally, the end formation comprises a through bore for accommodating a shaft coupled to and extending from a proximal end region of the inner sleeve and axially through and beyond the end formation, the shaft being at least partially threaded and supporting a tensioning nut for engagement with the end formation to impart a tensional load in the device.

Optionally, the fixation device comprises one or more resilient elements mounted on the shaft and located in the end formation to apply a reaction force responsive to the tensional load.

Optionally, the fixation device comprises a moveable disc element located between the tensioning nut and the one or more resilient elements.

Optionally, the one or more resilient elements comprises a stack of disc springs.

Optionally, the shaft comprises a torque coupling region at its proximal end to allow a torque driver to couple thereto and apply a drive torque to the inner sleeve.

Optionally, the torque coupling region is rotationally constrained to the shaft by a splined arrangement and axially constrained to the shaft by at least one frangible coupling element.

Optionally, the shaft comprises a through bore extending from a proximal end to a distal end disposed in the inner sleeve.

Optionally, the outer sleeve comprises a tapered formation defining an outer surface which tapers outwardly towards a proximal end region of the device.

According to a second aspect of the present invention there is provided a method of installing a fixation device in a substrate, comprising:.

Optionally, translating the outer sleeve with respect to the inner sleeve shears at least one coupling element constraining the outer sleeve to the inner sleeve.

Optionally, the method comprises urging the inner sleeve proximally relative to the outer sleeve to impart a tensional load in the device.

Optionally, urging comprises:
driving a tensioning nut located on an at least partially threaded shaft coupled to and extending from a proximal end region of the inner sleeve to engage said tensioning nut with an end formation fixed to a proximal end region of the outer sleeve.

Optionally, flaring the end formation comprises urging each of a plurality of finger elements outwardly about a hinge axis defined by a curved hinge end region of each finger element located in a correspondingly curved recess of a travel sleeve coupled to the outer sleeve.

There is also provided a fixation device comprising:.

Optionally, the pin-less coupling arrangement comprises a curved hinge surface of each finger element and a correspondingly curved surface in a coupling member coupled to the outer sleeve.

Optionally, the coupling member comprises a sleeve member having a circumferential groove defining the curved surface for engagement the curved hinge surface of each finger element.

Optionally, the coupling member is axially moveable with respect to the outer sleeve.

Optionally, the coupling member is rotationally constrained to the outer sleeve.

Certain embodiments of the present invention will now be described with reference to the accompanying drawings in which:.

As illustrated in <FIG> and <FIG>, a fixation device <NUM> includes an inner sleeve <NUM> and an outer sleeve <NUM> mounted thereon. Each sleeve has a proximal end region <NUM> and a distal end region <NUM> relative to the surface of a substrate, such as the seabed, when the device is in situ. The distal end region of each sleeve is substantially open. The inner and outer sleeves <NUM>,<NUM> are coupled together for a first mode of operation by at least one shear pin (not shown), aptly a pair of diametrically opposed shear pins, aptly located near their distal end regions.

A drill head <NUM> is mounted on the distal end region of the inner sleeve <NUM> and includes a plurality of cutting elements <NUM> to form a pilot drill bit. Each cutting element <NUM> may comprise any suitable material for drilling a substrate, such as a diamond impregnated cutting element, a tungsten cutting element, a hardened steel cutting element, a polycrystalline diamond cutting element, or the like. The drill head <NUM> also includes a guide body in the form of a tapered collar portion <NUM> defining a tapered outer surface which tapers inwardly towards a longitudinal axis <NUM> of the device and in a direction towards the proximal end region. The tapered collar portion <NUM> may be fixed to the distal end of the inner sleeve or may be rotatable relative thereto, as further described below.

The distal end region of the outer sleeve <NUM> includes a circumferential undercut <NUM> extending axially in the proximal direction along its inner surface from the distal end.

The circumferential undercut <NUM> is configured to slidably accommodate a travel sleeve <NUM> as illustrated for example in <FIG>.

As illustrated in <FIG>, the travel sleeve <NUM> includes a proximal end portion <NUM> which is sized to slidably engage in the circumferential undercut <NUM> of the outer sleeve <NUM>, and a distal end portion <NUM> which has a larger radius than the proximal end portion <NUM>. The distal end portion <NUM> is castellated such that it includes a plurality of equally sized and circumferentially spaced notches <NUM> around its distal end. Each notch <NUM> has a base surface and opposed and substantially parallel inner wall surfaces configured to receive a hinge end portion <NUM> of a respective finger element <NUM>, as illustrated in <FIG>, <FIG>.

As illustrated in <FIG>, the opposed outer surfaces of the hinge end portion <NUM> of each finger element <NUM> are substantially parallel such that they slidably engage with the inner wall surfaces of a respective one of the notches <NUM> when moving from a retracted position (<FIG>) to a deployed position (<FIG>). The hinge end portion <NUM> of each finger element <NUM> terminates with a substantially curved hinge surface <NUM> which locates in a correspondingly curved circumferential recess <NUM> disposed in the inner surface of the travel sleeve <NUM> and proximal to the base of each notch <NUM>. The engagement between the curved hinge surface <NUM> of each finger element <NUM> and the curved recess <NUM> of the travel sleeve <NUM> is illustrated in <FIG>. This arrangement radially retains the hinge end portion <NUM> of each finger element <NUM> in the travel sleeve <NUM>, whilst allowing each finger element <NUM> to rotate outwardly towards the deployed position (as illustrated in <FIG> and <FIG>) about a hinge axis defined by the curved hinge surface <NUM>. Aptly, the radius of the curved hinge surface <NUM> is around <NUM>. This pin-less coupling arrangement allows the finger elements to be efficiently located into the travel sleeve when assembling the fixation device and also efficient removal of each finger for easy and quick maintenance and reduced downtimes. One or more finger elements can be interchanged and easily removed and replaced if needed. The pin-less arrangement reduces the number of components required and also reduces frictional effects, e.g. wear, and related maintenance issues. The pin-less finger coupling also allows the fixation device to be scaled down to relatively small diameters which allows the device to be used for more technical applications than a conventional anchor device. The finger elements can be located relatively close together which in turn provides a greater cutting area. The bearing area about which each finger element rotates is also increased providing additional strength in that area of the coupling. Desirably, this pin-less finger coupling arrangement may be used on other forms of anchor device, such as the anchor described in <CIT>.

As illustrated in <FIG>, each finger element <NUM> has an elongate body portion <NUM> having substantially tapered side faces <NUM> to allow adjacent finger elements <NUM> to rotate inwardly to a retracted position without clashing. Each finger element <NUM> has at least one cutting surface <NUM> at its free end which may be provided by a cutting element mounted to the finger element or by an integral part of the finger element itself. Each finger element may also have a cutting surface extending along one or both side faces <NUM>. Each cutting surface/s <NUM> may comprise any suitable material, such as a diamond impregnated cutting surface, a tungsten cutting surface, a hardened steel cutting surface, a polycrystalline diamond cutting surface, or the like. The outer surface of the body portion <NUM> includes a longitudinal channel <NUM> extending at least partially along its length and a pair of opposed lateral channels <NUM> extending from the longitudinal channel <NUM> to each tapered side face <NUM>. These channels allow for drilled/reamed material to move away from the cutting surface/s during a drilling operation. Alternatively, the channels may be used to locate and attach separate cutting elements to the finger element.

As illustrated in <FIG>, the travel sleeve <NUM> includes a plurality of holes <NUM> in its proximal end portion <NUM>. Aptly, the travel sleeve <NUM> has four holes circumferentially and equally spaced around the sleeve. Each hole <NUM> is configured to receive a shear pin <NUM> (as illustrated in <FIG> and <FIG>) locatable in a respective corresponding hole in the outer sleeve <NUM> of the fixation device <NUM>. These shear pins <NUM> axially and rotationally retain the travel sleeve <NUM> with respect to the outer sleeve <NUM> during a first mode of operation of the fixation device <NUM>, as will be described further below.

The proximal end portion <NUM> of the travel sleeve <NUM> further includes a plurality of axially oriented slots <NUM> each located between adjacent ones of the shear pin holes <NUM>. These slots <NUM> slidably engage with a respective pin <NUM> inwardly extending from the outer sleeve <NUM> (as illustrated in <FIG> and <FIG>). These pin and slot arrangements rotationally constrain the travel sleeve <NUM> with respect to the outer sleeve <NUM> during the first mode of operation whilst allowing the outer sleeve <NUM> to move axially with respect to the travel sleeve <NUM> during a later mode of operation, as described further below. An alternative mechanical arrangement to the pin and slot arrangement may be used to rotationally constrain the travel sleeve <NUM> with respect to the outer sleeve <NUM> whilst allowing the same to move axially, such as a key, spline, or the like.

As illustrated in <FIG> and <FIG>, the proximal end region of the inner sleeve <NUM> is closed by an end cap <NUM> fixed thereto by welding or the like. A shaft <NUM> extends axially in the proximal direction from the end cap <NUM>. The shaft <NUM> is located in a central aperture in the end cap <NUM> and is fixed thereto by welding or the like. The shaft <NUM> includes an axial through bore <NUM> to allow a fluid, e.g. water, to be pumped into the inner sleeve to aid the drilling process and/or to remove drilled material from the drill head <NUM>. At least the proximal end region of the shaft <NUM> comprises an external screw thread <NUM> to engage with a tensioning nut <NUM>. The proximal end region of the shaft <NUM> also includes an enlarged head portion <NUM> having a bayonet coupling portion <NUM> to allow a drive tool of, for example, a drill rig to couple to the proximal end of the shaft <NUM> and rotatably drive the inner sleeve <NUM>. Alternatively, other suitable means of coupling a rotational drive tool to the shaft may be used, such as a hex or square section head portion.

As illustrated in <FIG> and <FIG>, the proximal end region of the outer sleeve <NUM> is closed by an end cap <NUM> fixed thereto by welding or the like. The end cap <NUM> extends outwardly beyond the outer sleeve wall to provide a shoulder region for a swivel collar <NUM> to engage. An annular flange <NUM> is provided below the swivel collar for the same to also engage such that the end cap <NUM> and flange <NUM> axially constrain the swivel collar <NUM> with respect to the outer sleeve <NUM> whilst allowing the swivel collar to rotate with respect to the outer sleeve <NUM>. A bearing element may be provided between the swivel collar and the outer sleeve to reduce any frictional effects. The swivel collar <NUM> includes a plurality of outwardly extending lugs <NUM>, in this case four lugs, each having a hole <NUM> for attaching one or more tethers to the fixation device <NUM> when in situ. The rotatable swivel collar <NUM> allows for some movement of the tether/s with respect to the fixation device, e.g. as a result of a floating or subsea structure being moved by waves, tidal streams, wind, or the like.

The end cap <NUM> on the outer sleeve <NUM> further includes a through hole to allow the shaft <NUM> coupled to the inner sleeve <NUM> to pass through the end cap <NUM>. The end cap <NUM> also includes a hollow cylindrical portion <NUM> mounted on the upper surface of the wider flanged portion of the end cap to thereby define an end cap having a top-hat cross section, as illustrated for example in <FIG>. The cylindrical portion <NUM> of the end cap <NUM> includes a bayonet coupling portion <NUM> in its outer surface on opposed sides to allow a suitable rotational drive tool, e.g. of a drill rig, to couple to the end cap and rotatably drive the outer sleeve. Other suitable torque coupling arrangements can be used, as described above, e.g. a hex or square drive head or the like. The cylindrical portion <NUM> houses a stack of spring washers <NUM> located on the upper surface of the flanged portion and the shaft <NUM>. A moveable disc element <NUM> having a central aperture is provided on the stack of spring washers <NUM> and the shaft <NUM>. A tensioning nut <NUM> is located on the threaded portion <NUM> of the shaft <NUM> such that when the nut <NUM> is driven in a first rotational direction, the shaft <NUM> and inner sleeve <NUM> coupled thereto are drawn upwardly with respect to the outer sleeve <NUM>. The spring washers <NUM> compress when a tensional load is imparted in the fixation device <NUM> when in situ, as described further below.

A plurality of longitudinally oriented and tapered ribs <NUM> are circumferentially arranged and equally spaced around the proximal end region of the outer sleeve <NUM> and below the swivel collar <NUM>. These ribs cut a proximal taper in the substrate as the outer sleeve is being rotatably driven therein which provides the fixation device <NUM> with additional lateral resistance when in situ and also reacts against the opposed distal taper formed by the finger elements <NUM> when in a deployed state and when a tensional force is imparted in the device, as described further below. Aptly, each rib <NUM> provides a cutting surface comprising a suitable cutting material, such as diamond, tungsten, or the like.

In use, a first drive tool, of for example a drill rig, is coupled to the outer sleeve <NUM> by way of the bayonet coupling portion <NUM> and a second drive tool, of the for example the drill rig, is coupled to the inner sleeve <NUM> by way of the bayonet coupling portion <NUM> of the shaft <NUM>. The inner and outer sleeves <NUM>,<NUM> are rotated in a first direction, e.g. clockwise, by their respective drive tools to start drilling a pilot hole in a substrate, e.g. the seabed, by the drill head <NUM> mounted on the distal end of the inner sleeve <NUM>. Alternatively, only one of the sleeves may be rotated which would rotate the other sleeve in view of the shear pin coupling the sleeves together. The finger elements <NUM> are in the retracted position, as illustrated in <FIG> and <FIG>, and are within the outer limits of the drill head <NUM> so trail unaffected behind the drill head <NUM> into the circular hole being formed thereby in the substrate. The first drilling operation is stopped when the fixation device reaches a desired depth in the substrate, e.g. when the tops of the ribs <NUM> are just below the substrate surface. Alternatively, when the fixation device reaches a desired depth in the substrate, the ribs may protrude above the surface of the substrate by a distance which is around the same as the length of each finger element.

In a second mode of operation, the first drive tool then rotatably drives the outer sleeve <NUM> with respect to the inner sleeve <NUM> and a downward force is also applied to the outer sleeve which compromises the integrity of the at least one shear pin coupling the inner and outer sleeves together. Downward axial movement of the outer sleeve <NUM> moves the travel sleeve <NUM> and finger elements <NUM> downwardly in the distal direction such that the finger elements <NUM> move over the tapered outer surface of the flared collar portion <NUM> and outwardly to a deployed position, as illustrated in <FIG> and <FIG>. The upper ribs <NUM> move axially the same distance into the substrate as the fingers do in view of both being coupled to the outer sleeve. This brings the ribs below the surface if they protruded slightly above the surface before the second mode of operation commenced.

In a subsea application, the void between the distal end cap <NUM> and the proximal end cap <NUM> may fill with water in view of the interface between the central aperture in the proximal end cap <NUM> and the shaft <NUM> not being sealed. To prevent this, a seal may be provided at this interface. Alternatively, it may be desirable to allow water to enter into this void. The interface between the distal end cap <NUM> and the inner surface of the outer sleeve <NUM> may be sealed with, for example, an O-ring to prevent water entering between the inner and outer sleeves <NUM>,<NUM>. The diameter of the central aperture in the proximal end cap <NUM> may be selected to allow water to exit the void at a predetermined rate to thereby allow the outer sleeve <NUM> to controllably move axially with respect to the inner sleeve when the shear pins are broken. Additionally, or alternatively, one or more apertures/valves may be provided in the proximal end cap <NUM> to allow water to enter and/or exit the void in a predetermined to ensure the outer sleeve <NUM> moves axially in the distal direction in a controlled manner when the shear pins are intentionally broken. Such an arrangement may be desirable if the drive coupling to the outer sleeve was axially unsecure, such as a drive tool on a hex section drive nut, and not an axially secure arrangement, such as a bayonet coupling.

In view of the outer sleeve <NUM> being rotated during said axial movement, the cutting surfaces of the finger elements <NUM> form a tapered annular undercut in the substrate. The shear pin <NUM> and pin and slot arrangements <NUM>,<NUM> coupling the travel sleeve <NUM> to the outer sleeve <NUM> ensure the travel sleeve and finger elements rotate and translate with the outer sleeve as it moves downwardly along the inner sleeve. The tapered collar portion <NUM> may be fixed with respect to the inner sleeve <NUM> or it may be rotationally mounted thereto to allow the same to rotate with the finger elements <NUM> as they form the undercut in the substrate. Allowing the tapered collar portion to rotate with the finger elements reduces/eliminates undesirable frictional effects, such as heat, wear, noise or the like, otherwise caused when the finger elements <NUM> rotate over a fixed tapered collar portion <NUM>. Furthermore, less energy is required to form the tapered undercut if friction between the finger elements and the tapered collar portion are minimised. The undercut formed by the deployed finger elements <NUM> secures the device <NUM> in the substrate and prevents the device being pulled out of the substrate when subjected to a tensional load.

In a third mode of operation, the first drive tool or a further drive tool is then engaged with the tensioning nut <NUM> and rotated whilst the shaft is rotationally fixed to move the nut down the shaft <NUM> and urge the same against the disc plate <NUM>. This action draws the inner sleeve <NUM> axially upwardly such that the tapered collar portion <NUM> is further forced against the deployed finger elements <NUM> to further secure them in the formed tapered undercut. As the inner sleeve is unable to move upwardly when the tensioning nut <NUM> is tightened in view of the engagement of the tapered collar portion <NUM> with the deployed finger elements <NUM> in the tapered undercut, a tension is applied in the inner sleeve <NUM> and the outer sleeve <NUM> is urged downwardly which causes the shear pins <NUM> coupling the travel sleeve <NUM> to the outer sleeve <NUM> to fail and thus allows the outer sleeve <NUM> to move axially towards the distal drill head <NUM>. This movement is resisted by a reaction force applied by the compressed disc springs <NUM> which acts to further secure the fixation device <NUM> in the substrate and to withstand loads applied in use to the fixation device in all directions via the lugs <NUM>. The tapered ribs <NUM> also act to withstand a downward movement of the outer sleeve <NUM> and provides for lateral resistance of the fixation device in use.

A further embodiment of the fixation device is illustrated in <FIG>. The fixation device <NUM> includes an inner sleeve <NUM> and an outer sleeve <NUM>. The proximal end region of the outer sleeve is closed by an end cap <NUM> fixed thereto by welding or the like and which is substantially disc-like and has a central aperture for accommodating the shaft <NUM> fixed to the inner sleeve <NUM> via the inner sleeve end cap <NUM>. A swivel collar <NUM> (lug/s not shown) is mounted between the end cap <NUM> and a flange <NUM>. A tapered section <NUM> of the outer sleeve <NUM> equivalent to the tapered ribs <NUM> of the above-described embodiment may connect to the lower section of the outer sleeve <NUM> by a reverse screw thread configured to tighten during the drilling operations.

A first square section drive nut <NUM> is fixed by welding or the like to the end cap and threadably mounted on the shaft <NUM> such that rotation of the drive nut rotates the outer sleeve <NUM>. A square section tensioning nut <NUM> is located on the shaft <NUM> above the first drive nut <NUM> and below a second drive nut <NUM> fixed to the proximal end of the shaft <NUM> which also has a square section.

In use, the drive nuts <NUM>,<NUM> and tensioning nut <NUM> are aligned to allow a drive tool, of for example a drill rig, to engage over and rotate all three components together in a first rotational direction, e.g. clockwise. The fixation device <NUM> is rotated about its axis to thereby form a pilot hole in the substrate to a desired depth using the drill head <NUM> mounted on the distal end of the inner sleeve <NUM>. The first drive nut <NUM> is then rotated whilst an axial force is applied to the proximal end cap <NUM> to thereby rotate the outer sleeve <NUM> and move the same and the finger elements <NUM> downwardly in the axial direction with respect to the inner sleeve <NUM>. The finger elements <NUM> are moved over the flared collar portion <NUM> and outwardly to the deployed position whilst rotating to form a tapered undercut in the substrate wall of the drilled hole. The tensioning nut <NUM> is then tightened to urge the inner sleeve <NUM> upwardly and apply a tension therein, whilst urging the outer sleeve <NUM> downwardly which breaks the shear pins (not shown) coupling the travel sleeve <NUM> to the outer sleeve <NUM>. The pin/slot arrangement, as described above, allows the outer sleeve <NUM> to move downwardly, albeit by a relatively small distance, over the travel sleeve <NUM> to further apply the tensional load in the fixation device <NUM>.

If the fixation device <NUM>,<NUM> needs removing from the substrate, the tensioning nut <NUM>,<NUM> is loosened to release the tensional load in the device and relieve the secure engagement between the finger elements <NUM> and the tapered undercut in the substrate. The outer sleeve <NUM>,<NUM> is then lifted upwardly until each pin (e.g. <NUM> in <FIG>) engages with the upper limit of its respective slot (e.g. <NUM> in <FIG>) which thereby pulls the travel sleeve <NUM>,<NUM> and finger elements <NUM> upwardly. Engagement of the finger elements <NUM> with the drilled hole wall moved them back into the retracted position to allow the fixation device to pulled out of the drilled hole in the substrate.

The square section drive nuts <NUM>,<NUM> may alternatively have other suitable cross sections such as hexagonal or means to couple to the or a respective drive tool. Further alternatively, the second drive nut <NUM> may not be fixed to or be an integral part of the shaft <NUM>. Instead, the second drive nut <NUM> may be a separate component coupled to the proximal end of the shaft <NUM> by a splined engagement. The second drive nut <NUM> may be axially secured to the shaft <NUM> by at least one shear pin/screw such that, in the event of a power supply failure to the drive tool/drill rig, the nut can be sheared off the shaft to recover the drive tool/drill rig otherwise coupled to the fixation device. The drill rig may rely on an electrically, pneumatically, or hydraulically-operated mechanism to securely attach the drive head to the fixation device, particularly for forcing fluid, e.g. water, into the device via the bore in the shaft <NUM>, and in the event of a power failure, safe and immediate release of the drill rig from the fixation device may not otherwise be possible.

As an example, the length of the illustrated fixation device <NUM> is aptly around <NUM>-<NUM>. The swivel collar <NUM> is around <NUM> long and around <NUM> wide. The tapered section <NUM> of the outer sleeve <NUM> is around <NUM> long and the remaining distal portion of the outer sleeve is around <NUM> long. The distance between the finger elements <NUM> and the tapered surface of the flared collar portion <NUM> is around <NUM>. The outer diameter of the outer sleeve <NUM> is around <NUM> and the inner diameter of the inner sleeve <NUM> is around <NUM>. The cutting diameter of the drill head <NUM> is around <NUM>. The travel sleeve <NUM> is around <NUM> long and the distal end portion <NUM> is around <NUM> in diameter. The finger elements <NUM> are each around <NUM> long and around <NUM> thick. The radius of the curved hinge surface of each finger element is around <NUM>. These dimensions are examples only and the fixation device <NUM>,<NUM> can be sized according to a particular application, such as having a diameter of from around <NUM> to around <NUM> and/or a length of from around <NUM> to around <NUM>.

Claim 1:
A fixation device (<NUM>) comprising:
an elongate and hollow inner sleeve (<NUM>) rotatable about a longitudinal axis (<NUM>) and having at least one first cutting element (<NUM>) at an open distal end region (<NUM>) thereof for coring through substrate;
a guide body (<NUM>) located on the inner sleeve having a tapered guide surface which tapers outwardly towards the distal end region;
an elongate and hollow outer sleeve (<NUM>) mounted on the inner sleeve and rotatable about the longitudinal axis and translatable with respect to the inner sleeve; and
a flareable end formation (<NUM>) located at an open distal end region of the outer sleeve and comprising at least one second cutting element, wherein the flareable end formation is configured to flare outwardly towards a deployed position when moved over the tapered guide surface of the guide body to form a tapered undercut in the substrate.