EP2997226A2

EP2997226A2 - Self-boring shield anchor apparatus and method

Info

Publication number: EP2997226A2
Application number: EP14728602.5A
Authority: EP
Inventors: Alan Vasey; Ian Murray
Original assignee: Technical Services Team Ltd
Current assignee: Technical Services Team Ltd
Priority date: 2013-05-07
Filing date: 2014-05-07
Publication date: 2016-03-23
Also published as: WO2014181105A2; GB201308152D0; GB201520092D0; GB201400830D0; GB2529109B; WO2014181105A3; GB201520062D0; GB2529109A; GB2513942B; GB201520171D0; GB2513942A

Abstract

A drill bit for cutting a hole comprising an undercut into a substrate is provided. The drill bit comprises a shaft having a first cutting tip, a mandrel on the shaft, and a flareable sleeve comprising a second cutting tip drivable separately from the first cutting tip. The mandrel and the sleeve are arranged so that urging the sleeve distally over the mandrel flares part of the sleeve outward from the shaft for reaming out the undercut outwardly from the hole.

Description

Self-Boring Shield Anchor Apparatus and Method

The present disclosure relates to methods and apparatus for anchoring a tensile load to a substrate, and more particularly to self-boring shield anchors, and methods of deploying a shield anchor, aspects of the disclosure find particular application in marine engineering.

It is known to use anchors to secure tensile loads to solid substrates. Some anchors comprise a tendon coupled to a broad body. Typically the body is secured in a hole in the substrate, and the tendon can then secure a tensile load to the substrate. So called "grouted anchors" are secured in place by inserting the anchor body into the hole and then filling in the hole around the tendon with a setting compound such as cement to grout the anchor in place. An alternative approach is to provide a hole in a substrate that comprises a broad internal hollow, or undercut, and a narrower opening. The anchor can then be inserted into this hole, and a "shield" or body of the anchor can be opened up inside the hole to prevent the anchor from being withdrawn through the narrow opening, thereby securing the anchor to the substrate.

In marine engineering it may be desirable to fix anchors to submerged structures. To use conventional shield anchors under water, it is necessary for divers, or remotely operated vehicles to perform relatively complex and lengthy tasks in order to ream out the undercut holes, and using grouting anchors requires the use of cements which may be challenging underwater. The use of cements in ecologically sensitive marine environments may be undesirable.

Aspects and examples of the present disclosure address related technical problems.

In an aspect there is provided a drill bit for cutting a hole comprising an undercut into a substrate, the drill bit comprising a shaft having a first cutting tip, a mandrel on the shaft, and a flareable sleeve comprising a second cutting tip drivable separately from the first cutting tip, wherein the mandrel and the sleeve are arranged so that, urging the sleeve distally over the mandrel flares part of the sleeve outward from the shaft for reaming out the undercut outwardly from the hole.

In an embodiment the shaft comprises a shaft drive coupling for applying torque to the shaft for driving the first cutting tip, and the sleeve comprises a sleeve drive coupling for applying torque to the sleeve to drive the second cutting tip.

We have also found that surprisingly, this drillbit can be used to provide an anchor - e.g. to be used as a rockbolt, or to secure a tensile load to a substrate. In an embodiment the sleeve drive coupling is operable to be driven into the hole, distal to a surface of the substrate, and is arranged to be releasable so that the flareable part of the sleeve can be detached from the sleeve and the sleeve drive coupling can be withdrawn from the hole. This has the advantage that the undercut can be place deep in the hole, and the flared part of the sleeve can be held secured in the hole by the mandrel without the need to abandon a length of the sleeve along with the flared part.

In an embodiment the sleeve drive coupling and the shaft drive coupling comprises at least one of a thread, a bayonet fitting and a non-circular surface (e.g. a keyed, cammed, irregular, or polygonal surface).

In an embodiment the mandrel surface is operable to bear against part of the sleeve to hold the sleeve extended into the undercut and inhibit removal of the shaft from the hole.

In an embodiment the second cutting tip is carried on the end surface of the flared part of the sleeve. In an embodiment a flareable part of the sleeve comprises a pivot arranged to allow the flareable part of the sleeve to bend about the pivot as it is flared outward by the mandrel surface.

In an aspect there is provided a method of securing an anchor to a substrate comprising: boring a hole into a surface of a substrate with a first cutting tip carried on a shaft of the anchor; urging a sleeve carrying a second cutting tip, drivable separately from the first cutting tip, over a mandrel surface carried by the shaft to flare part of the sleeve outward from the shaft to ream out an undercut in the substrate from the hole, and holding the mandrel surface against the flared sleeve to hold the flared sleeve extended in the undercut and inhibit removal of the anchor from the hole.

In an embodiment the sleeve comprises a drive coupling for driving the cutting tip, the method comprising decoupling the drive coupling from the flared part of the sleeve, and withdrawing the drive coupling from the hole. In an embodiment the second cutting tip is carried on the end surface of the flared part of the sleeve.

In an embodiment the undercut comprises cutting a reverse taper into the substrate from the hole, wherein the angle of the taper corresponds to the angle of the mandrel surface.

In an embodiment the flared part of the sleeve comprises a pivot arranged to allow the part of the sleeve to bend about the pivot as it is flared outward by the mandrel surface.

In an embodiment holding the mandrel surface against the flared part of the sleeve conforms the flared part of the sleeve to the mandrel so that the pivot is immobilised.

In an embodiment the flared part of the sleeve is straightened about the pivot by the mandrel. In an embodiment the method comprises applying a first tensile load to the shaft of the tool to hold the mandrel surface against the flared part of the tool, and coupling a second tensile load to the tool so that the second tensile load is at least partially transverse to the shaft. In an embodiment the second tensile load is coupled to the shaft by a lateral member arranged at the surface of the substrate to provide a lateral spacing between the second tensile load and the shaft. ln an embodiment there is provided a method for anchoring a buoyancy device to a bed of a body of water comprising:

securing at least two anchors to the bed of the body of water according to the method of any preceding claim,

coupling a first one of the anchors to the buoyancy device with a first length of anchor line,

coupling a second one of the anchors to the buoyancy device with a second length of anchor line;

and reducing the length of the first anchor line and the second anchor line so that the angle between the shaft of each anchor and a tensile load applied to each anchor by the buoyancy device is increased as the tensile load increases.

In one aspect there is provided a method of coupling a tensile load to a substrate, the method comprising:

boring a cylindrical hole into a substrate with a cutting tool;

reaming out an undercut inside the hole with said tool;

extending a portion of the tool into the undercut to inhibit removal of the cutting tool from the hole; and

coupling the tensile load to the tool so that the load is at least partially carried by the cutting tool.

The tool may be configured so that the portion of the tool extended into the undercut also reams out the undercut. The tool may further be configured not to crack the substrate upon coupling a tensile load to the tool. For example, extending a portion of the tool into the undercut may comprise a splaying of the portion of the tool extended into the undercut to form an angle relative to a longitudinal axis of the tool. The angle of splaying of the portion of the tool extended into the undercut may be limited. For example, the splaying of the portion of the tool may be limited to at most 10 degrees, for example at most 6 degrees, for example at most 5 degrees, and may be limited to for example at least 1 degree, for example at least 2.5 degrees, for example at least 3 degrees. The splaying of the portion of the tool extended into the undercut may be limited by the shape of the cutting tool. For example, the cutting tool may comprise a mandrel, and the splaying of the portion of the tool extended into the undercut may be limited by the length and angle of the mandrel. In some examples, coupling of the tensile load to the tool does not cause the radius of the portion of the tool extended into the undercut to change. For example, coupling of the tensile load to the tool does not cause the radius of the portion of the tool to change by more than 10 %, for example more than 5 %, for example more than 1 %. In some examples, coupling of the tensile load to the tool does not cause the radius of the portion of the tool to change so that it is less than or equal to the radius of the cylindrical hole. In some examples, coupling of the tensile load to the tool does not cause the radius of the portion of the tool to change so that it is greater than the radius of the undercut.

In some examples, extending a portion of the tool into the undercut to inhibit removal of the cutting tool from the hole comprises wedging at least a part of the tool in the undercut. The method may comprise:

arranging a plate against the substrate adjacent to the hole; and

securing the cutting tool in the hole to the plate, wherein

the cutting tool is configured so that the tool holds the portion of the tool extended in the undercut in the hole.

The method may comprise:

arranging a plate against the substrate adjacent to the hole; and

securing the cutting tool in the hole to the plate, wherein

the cutting tool is configured so that tension between the cutting tool and the plate holds the portion of the tool extended in the undercut in the hole.

The method may be a method for coupling a tensile load to the bed of a body of water. ln another aspect there is provided a method of securing a tensile load to the bed of a body of water, the method comprising boring a cylindrical hole into a substrate with a cutting tool, reaming out an undercut inside the hole with said tool; extending a portion of the tool into the undercut to inhibit removal of the cutting tool from the hole and coupling the tensile load to the tool so that the load is at least partially carried by the cutting tool. The method may comprise arranging a plate against the substrate adjacent to the hole, and securing the cutting tool in the hole to the plate, wherein the cutting tool is configured so that the plate holds the portion of the tool extended in the undercut in the hole.

In another aspect there is provided a self-boring shield anchor comprising: a first shaft for carrying a tensile load; a cutting tip at the distal end of the first shaft for boring a hole into a substrate; a lateral cutter configured to be extended laterally for creating an undercut inside the hole, and a sleeve operable to expand laterally into the undercut to provide a shield to inhibit removal of the anchor from the hole. In some examples there may be more shields provided. The lateral cutter may be operable independently of the cutting tip, for example the anchor may comprise a second shaft arranged to drive the lateral cutter independently of the cutting tip. These and other examples of the disclosure provide an anchor that may be deployed in a single action without the need to first bore a hole, remove the boring tool, ream out an undercut, and remove the reaming tool, before inserting and deploying the anchor.

The anchor may comprise a plate arranged to be seated against a surface of the substrate outside the hole, wherein the first shaft is configured to be fixed to the plate, thereby to restrain the sleeve and the second shaft in the hole. Fixing the first shaft to the plate may urge the sleeve to expand into the undercut, for example by pulling a tapered mandrel into the sleeve. A tensile load may then be coupled to the plate, for example the plate may comprise a fixture for coupling a tensile load to the plate so that the tensile load is not coaxial with the first shaft. This may enable the extension of the sleeve to be controlled because although the first shaft provides the tendon of the anchor, the tensile load does not act directly on the mandrel. The plate may comprise spikes arranged to bite into the substrate when the plate is fixed to the first shaft. This may provide improved stability of the anchor by inhibiting lateral movement of the first shaft with respect to the substrate. The first shaft may carry a mandrel operable to extend the lateral cutter to create the undercut. For example, the mandrel may be operable to expand the sleeve. The mandrel may comprise a tapered portion. For example, the angle formed by the mandrel relative to the longitudinal axis of the first shaft may be at most 10 degrees, for example at most 6 degrees, for example at most 5 degrees, and may be limited to for example at least 1 degree, for example at least 2.5 degrees, for example at least 3 degrees. The mandrel may comprise the cutting tip.

The lateral cutter may extend laterally with at least a component of movement in a direction perpendicular to the longitudinal axis of the first shaft by longitudinal movement over the mandrel in a direction parallel to the longitudinal axis of the first shaft.

The shield may comprise a hinge with the sleeve so that the shield can splay outwards relative to the sleeve and expand laterally into the undercut. The shield may comprise a pivot to allow the shield to flex when expanding laterally into the undercut. The distal end of the shield (or shields if applicable) may form a radius larger than the radius of the cylindrical hole, such that when a tensile load is coupled to the anchor, the radius formed by the shield (or shields) does not change by more than a selected amount. For example, coupling the tensile load to the anchor does not cause the radius formed by the shield (or shields) to change by more than 10%, for example more than 1 %, for example more than 0.1 %. For example, coupling of the tensile load to the tool does not cause the radius formed by the shield (or shields) to change. For example, coupling of the tensile load to the tool does not cause the radius of the portion of the tool to change so that it is less than or equal to the radius of the cylindrical hole. In some examples, coupling of the tensile load to the tool does not cause the radius of the portion of the tool to change so that it is greater than the radius of the undercut.

The sleeve may comprise the lateral cutter. For example, the lateral cutter may be disposed on the distal end of the shield.

The anchor may further comprise a plate arranged to be seated against a surface of the substrate outside the hole, wherein the first shaft is configured to be fixed to the plate, thereby to restrain the sleeve in the hole. For example, the plate may comprise spikes arranged to bite into the substrate when the plate is fixed to the first shaft.

The anchor may comprise a fixture secured to the plate to enable a tensile load to be secured to the anchor by the fixture. For example, the fixture may be arranged so that the tensile load is not coaxial with the first shaft.

The tensile load may not be coaxial with the cylindrical hole.

In another aspect there is provided a drill bit comprising:

a first shaft for carrying a tensile load;

a cutting tip at the distal end of the first shaft for boring a hole into a substrate; and

a lateral cutter configured to be extended laterally for creating an undercut inside the hole.

The drill bit may comprise a sleeve operable to expand laterally into the undercut to provide a shield to inhibit removal of the drill bit from the hole. The sleeve may comprise the later cutter. The first shaft and the lateral cutter may be operable such that they are independently driven.

In another aspect there is provided a method of removing a self-boring shield anchor from a hole comprising:

relieving a tensile load from the anchor;

retracting a portion of the anchor from an undercut in the hole;

applying a tensile load to the anchor to remove the anchor from the hole.

Embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a section through an anchor;

Figure 2 shows a section through the anchor of Figure 1 in a first stage of use;

Figure 3 shows a section through the anchor of Figure 1 in a second stage of use;

Figure 4 shows a section through the anchor of Figure 1 in a third stage of use;

Figure 5 shows the anchor of Figure 1 installed in a substrate;

Figure 6 shows a perspective view of an example sleeve;

Figure 7 shows a perspective view of the example sleeve of Figure 6 in a closed configuration;

Figure 8 shows a perspective view of the example sleeve of Figure 6 in an open configuration;

Figure 9 shows another perspective view of the example sleeve of Figure 6;

Figure 10 shows another perspective view of the example sleeve of Figure 6 in a closed configuration;

Figure 1 1 shows another perspective view of the example sleeve of Figure 6 in an open configuration;

Figures 12a and 12b show a cross-section through an example first shaft, an example sleeve and the locking mechanism of the sleeve with a drive shaft;

Figures 13a and 13b show a cross-section through another example first shaft, an example sleeve and the locking mechanism of the sleeve with a drive shaft;

Figure 14a shows a perspective view of an example anchor with the sleeve in a closed configuration; and

Figure 14b shows a perspective view of the example anchor of Figure 14a with the sleeve in an open configuration:

Figure 15 shows a cross-section through another example anchor:

Figure 16 shows a section through a drill bit.

Figure 1 shows a section through a self-boring shield anchor 1 that aims to enable anchoring operations to be performed quickly and efficiently underwater.

The anchor 1 is arranged so that tensile load can be coupled to a substrate 100, so that the load is at least partially carried by the anchor. This may be done by boring out a cylindrical hole in the substrate with the anchor, reaming out an undercut inside the hole with the anchor, extending a portion of the anchor into the undercut to inhibit removal of the anchor from the hole, and coupling the tensile load to the anchor.

The anchor 1 comprises a first shaft 10 which carries a cutting tip 12 at its distal end for boring a hole into a substrate 100. A mandrel 14 is carried on the shaft. The mandrel 14 tapers outwardly from the shaft 10 so that it is narrower at its proximal end than its distal end. A length of the shaft 10 extends between the distal end of the mandrel 14 and the cutting tip 12. The mandrel forms an angle with the longitudinal axis of the shaft of between 1 to 10 degrees, preferably 3 to 6 degrees, more preferably 2.5 to 5 degrees.

A second shaft 16 comprises a cavity 18, and the first shaft 10 is arranged to extend through the cavity 18 in the second shaft 16. The second shaft 16 also carries two lateral cutters 20, 22. Accordingly, the second shaft 16 surrounds a length of the first shaft 10, and the mandrel 14, and the cutting tip 12 are distal of the second shaft 16.

A sleeve 26 surrounds part of the length of the second shaft 16, so that the first and second shaft extend distally out from the sleeve 26. In this example, the distal end of the sleeve 26 carries two shields 24, 28, each of which extend around a portion of the circumference of the second shaft 16, and are operable to be deflected laterally outward from the anchor 1.

Inset A-A shows a cross section through the anchor 1 along the line A-A marked in Figure 1. As can be seen in this inset, the first shaft 10, and the second shaft 16 can be substantially concentric. The shields 24, 28 lie outside the second shaft 16, and are separated from each other to enable them to be extended laterally outward from the anchor 1. Inset B-B shows a cross section through the anchor 1 along the line marked B-B in Figure 1. The lateral cutters 20, 22 each comprise a respective pivot 21 , 23, and are biased so that they pivot inwardly to lie against the shaft 10. In operation, the first shaft 10 rotates to drive the cutting tip 12 for cutting into a substrate 100. This bores a hole into the substrate. Once a hole has been cut into the substrate, the second shaft 16 can be driven to rotate so that the lateral cutters 20, 22 orbit the first 5 shaft 10. The second shaft can then be urged distally along the first shaft 10 so that the lateral cutters 20, 22 are pushed down onto the mandrel 14. The tapering of the mandrel 14 causes the lateral cutters 20, 22, to be turned about their pivots 21 , 23 so that the tips of the lateral cutters 20, 22, extend laterally out from the shaft. Accordingly, the cutters 20, 22 cut (for example to ream) out an undercut within the hole that follows the frusto- 10 conical form of the mandrel 14. Because the anchor 1 may be used to cut the hole and the undercut, it may also be called a cutting tool.

Once the lateral cutters 20, 22, have been pushed past the distal end of the mandrel 14, they can be retracted by pivoting back in against the first shaft 10 between the mandrel 15 14 and the cutting tip 12.

Figure 2 illustrates an example of the anchor of Figure 1 in use. As shown in Figure 2, rotating the first shaft 10 about its axis causes the cutting tip 12 to bore a cylindrical hole into a substrate 100. As shown in inset B-B of Figure 2, during this stage of operation, 20 the lateral cutters 20, 22 are folded in against the first shaft 10.

Once the hole in the substrate has reached a desired depth, the first shaft 10 is stopped so that the cutting tip 12 and the first shaft 10 are braced against the bottom of the hole.

25 The second shaft 16 can then be rotated about its axis to drive the lateral cutters 20, 22 to rotate about the first shaft 10. As shown in Figure 3, with the cutting tip 12 and the first shaft braced against the bottom of the hole, the second shaft 16 can be urged down onto the mandrel 14 and into the hole. This action causes the mandrel 14 to force the lateral cutters 20, 22, to pivot outwardly as the cutters 20, 22 are forced along the length of the

30 tapered mandrel 14.

The result is that the lateral cutters 20, 22 carve out a frusto-conical cavity which extends laterally outward from the hole bored by the cutting tip 12 to provide an undercut. The shields 24, 28 can then be extended out into the undercut to secure the anchor in place. One such configuration is illustrated in Figure 4. As shown in Figure 4, once the lateral cutters 20, 22 have been pushed distally past the end of the mandrel 14 they can fold in against the first shaft 10. The mandrel 14 and the second shaft 26 can then be drawn proximally with respect to the sleeve 26 to push the shields 24, 28 outward into the undercut thereby restraining the anchor 1 in the substrate 100.

Figure 5 shows an anchor 1 in which the shields 24, 28 are extended out into an undercut in a substrate 100 to secure the anchor in place. In Figure 5 a part of the second shaft, and the sleeve 26 have been detached from the anchor 1 , and a plate 110 has been arranged over the hole so that the first shaft 10 passes through the plate 110.

The first shaft 10 comprises a threaded portion 50 which extends out through the plate 1 10, and a threaded nut 1 15 can be screwed down over the first shaft 10 to clamp the plate 110 against the substrate 100. This ensures that the mandrel 14 pushes the shields out into the undercut. In addition, the plate 1 10 carries spikes 112, 114 which are arranged to bite into the substrate 100 as the nut 1 15 is screwed down. The combination of the shields 24, 28 in the undercut, the plate 1 10 and the spikes 1 12, 1 14 act to secure the anchor in place in the substrate, in a wedged configuration. The plate 1 16 carries a fixture 1 16 for securing a tensile load to the anchor 1. In this way, the first shaft 10 acts as a tendon, that may be used for coupling a load to the anchor 1.

The plate 1 10 holds the sleeve 26 in the hole, and thereby secures the anchor in place. The anchor 1 may be removed from the substrate by releasing the first shaft 10 from the plate, and allowing the first shaft and mandrel to pass distally in to the hole. This allows the shields 24, 28 to fold inward thereby permitting the anchor 1 to be withdrawn from the hole.

To facilitate this process, a proximal end of the sleeve 26 may be threaded, and a third shaft surrounding the first and second shafts may be provided having a threaded end for engaging with the sleeve. Accordingly, to deploy the anchor, when the mandrel holds the shields 24, 28 in the expanded position, the sleeve can be unscrewed from the third shaft before the plate 1 10 is secured over the hole. When it is desired to remove the anchor, the plate can be removed, and a threaded shaft used to connect to the sleeve 26, thereby enabling the sleeve 26, and shields 24, 28 to be withdrawn to release the anchor from the hole.

In some configurations the first shaft 10 and the cutting tip 12 comprise a channel for delivering fluid to the cutting tip. In some configurations the cavity 18 between the first shaft and the second shaft may be configured to allow fluid to be pumped into the hole to allow drilling debris to be removed from the hole. In some configurations, the first shaft 10 and the cutting tip 12 have at least one flush channel to allow fluid to be pumped into the hole. For example, fluid may be pumped into the hole through at least one flush channel in the first shaft 10 and cutting tip 12 and extracted through the cavity 18. The at least one flush channel runs through the centre of the first shaft 10 and cutting tip 12 and extends for substantially the entire length of the first shaft 10. Alternatively, fluid may be pumped into the hole through the cavity 18 and extracted through at least one extraction channel in the first shaft 10 and cutting tip 12. The at least one extraction channel runs through the centre of the first shaft 10 and cutting tip 12 and extends for substantially the entire length of the first shaft 10.

In some examples the sleeve 26 may not be present, and the lateral cutters 20, 22 can be held extended outward by the mandrel 14 to inhibit the anchor 1 from being withdrawn from the hole.

Although the sleeve 26 is shown as comprising two shields 24, 28, in some examples a single shield, or more than two shields may be used. For example three shields may be used. In some examples no separate shield is used at all. For example, the sleeve itself can be configured to be expanded by the mandrel 14, for example the sleeve may be resilient. Although the example described with respect to Figures 1 to 5 has a second shaft, this is optional.

The sleeve 126 in the example illustrated in Figures 6 to 1 1 is similar to sleeve 26 shown in Figures 1 to 5. The sleeve 126 has a shaft body 127 that connects the distal and proximal ends. The sleeve 126 is cylindrical with a hollow centre. The sleeve therefore has a circular cross-section in a direction perpendicular to its longitudinal axis. The sleeve 126 has three shields 124, 128, 130 at its distal end. The three shields are substantially the same shape and size, and have the same thickness as the wall of the shaft body 127 of the sleeve 126. The three shields each have an arcuate cross-section in a direction perpendicular to the longitudinal axis of the sleeve 126, and are shaped so that when then three shields are aligned with the sleeve, their outer circumference matches the outer circumference of the sleeve 126, and their inner circumference matches the inner circumference of the sleeve 126. The three shields each comprise lateral cutters 136 at their distal ends.

Each shield is coupled to the sleeve 126 through a respective hinge 132 at its proximal end. Each shield further comprises a pivot 134. The pivot 134 is roughly half-way along the length of the shield between its proximal and distal ends.

The sleeve 126 shown in Figures 6 to 1 1 , 12b and 13a and 13b is used with a modified shaft 160. The modified shaft 160 is similar to first shaft 10 in that it has a threaded portion 150 at its proximal end. The sleeve 126 has an inner diameter that is greater than the outer diameter of the shaft 160. The modified shaft 160 comprises a tapered cutting tip 152 at its distal end. The cutting tip 152 of the shaft 160 has a frusto-conical portion that tapers outwardly from the shaft 160 to a distal face that has a greater diameter than the shaft. The angle of the taper relative to a longitudinal axis of the anchor 1 and shaft 160 is between 1 and 10 degrees, preferably between 2.5 and 6 degrees, most preferably between 3 and 5 degrees. The distal face has a diameter substantially matching that of the outer diameter of the sleeve 126. The distal face of the shaft 160 carries the cutting tip 152. The shaft 160 and cutting tip 152 also comprise at least one flush channel 144. The flush channel 144 runs through the centre of the shaft 160 and extends for substantially the entire length of the shaft 160.

Sleeve 126 comprises a bayonet housing 138 at the sleeve's 126 proximal end, as shown in Figures 12b, 13a and 13b. The bayonet housing 138 has a longitudinal slot feeding to a transverse slot for slidably receiving a complementary pin 140 on drive shaft 142. The bayonet housing 138 also has a retaining slot 139 perpendicular to the transverse slot. Drive shaft 142 is hollow and designed to be able to pass over and coaxial with shaft 160. Drive shaft 142 has substantially the same thickness as the sleeve 126.

The sleeve 126 can be slidably received over the shaft 160, because the inner diameter of the hollow sleeve 126 is greater than the outer diameter of the shaft 160. Because of this difference in diameters, a cavity is formed between the sleeve 126 and shaft 160, The pivot 134 on each shield allows the shield to bend slightly in use. The pivot 134 and hinge 132 combined mean that each shield extends around a portion of the circumference of the cutting tip 152 and is operable to be deflected laterally outward from the anchor 1. The shields are therefore operable in a closed configuration, shown in Figure 7, and an open configuration shown in Figure 8. In the open configuration the shields are splayed about the hinges 132 and pivots 134. In the closed configuration the shields are substantially in line with the outer circumference of the sleeve 126 and cutting tip 152. Therefore, in the closed configuration the sleeve 126 and shields 124, 128, 130 are passed into the hole to reach a selected depth in the hole where the undercut is to be cut. The depth of the hole is selected based on the amount of load that is to be applied to the anchor 1.

Sleeve 126 is coupled to drive shaft 142 through the use of the bayonet fitting. Pin 140 on drive shaft 142 slides through the longitudinal slot and into the transverse slot of the bayonet housing 138. Once in the transverse slot, the pin 140 is securely held by the bayonet housing 138 and allows the effective transfer of rotational and longitudinal force from the drive shaft 142 to the sleeve 126. The bayonet fitting is advantageous because it does not require holding the sleeve 126 against rotation when removing the drive shaft. The retaining slot 139 permits the removal of the sleeve 126 by securely receiving pin 140 on drive shaft 142 when tension is applied to the drive shaft 142.

The flush channel 144 is for the passage of cutting fluid and other substances to the cutting tip 152. Cutting fluid and other substances may be extracted through a cavity between the sleeve 126 and shaft 160.

In operation, the shaft 160 is rotated to drive the cutting tip 152 into a substrate. Once a hole has been bored into the substrate by cutting tip 152, the sleeve 126 can be driven to rotate so that the lateral cutters 136 orbit the shaft 160. The sleeve 126 is driven by drive shaft 142 coupled through the bayonet housing 138. As shown in Figures 14a and 14b, the sleeve 126 can then be urged distally along the shaft 160, in a direction parallel to the longitudinal axis of the shaft 160, so that the lateral cutters 136 are pushed down onto the cutting tip 152 and the sleeve 126 is substantially coaxial with shaft 160.

The tapering of the cutting tip 152 causes the lateral cutters 136 to splay about their respective pivots 134 and hinges 132 so that the tips of the lateral cutters 136 extend laterally out from the shaft. The tapering of cutting tip 152 therefore provides a mandrel for the lateral cutters 136. The tapering of the cutting tip 152 and hence the angle of the mandrel is shaped to limit the angle of splaying of the lateral cutters 136. If the tapering of the cutting tip 152 is too steep such that the angle of the mandrel is too large, the lateral cutters 136 will not effectively splay.

The lateral cutters 136 cut out an undercut within the hole that follows the outward tapering of the cutting tip 152 as the sleeve 126 is moved longitudinally over the cutting tip 152. In other words, the lateral cutters 136 extend laterally as the sleeve 126 is moved onto the mandrel. In this way, the lateral cutters 136 ream out an undercut inside the hole by the application of force in a direction parallel with the longitudinal axis of the shaft 160. The tapering of the cutting tip 152 and hence the angle of the mandrel therefore dictates the angle of the undercut.

The shields 124, 128 and 130 are then extended out into the undercut to secure the anchor 1 in place. A tensile load is coupled to the shaft 160, and the anchor 1 is configured such that coupling a tensile load to the anchor 1 does not cause the substrate to crack. Once the shields have been extended into the undercut, their distal ends form a radius that is larger than the hole bored by cutting tip 152. In this way, a part of the 5 anchor 1 is wedged in the undercut. A component of the tensile load is applied to the undercut through the shaft 160 and sleeve 126 in a direction parallel to the longitudinal axis of the shaft 160 and sleeve 126.

The application of a tensile load on the shaft 160 does not cause the radius formed by 10 the distal ends of the shields to change. This is because the frusto-conical portion of the cutting tip 152 applies the load uniformly to the shields 124, 128 and 130. Because the radius formed by the distal ends of the shields does not change, the hole and undercut in the substrate is not subjected to high transverse forces and hence the substrate is less likely to crack.

15

Note, however, that due to the frusto-conical shape of the undercut, a component of the tensile load will still be applied to the undercut through the shaft 160 and sleeve 126 in a direction perpendicular to the longitudinal axis of the shaft 160 and sleeve 126, but the component of the tensile load perpendicular to the longitudinal axis will be smaller than 20 the component of the tensile load parallel to the longitudinal axis.

Furthermore, if the tapering of the cutting tip 152 and hence the angle of the mandrel is relatively shallow (for example between 1 and 10 degrees), then the shields 124, 128 and 130 effectively extend into the undercut whilst maintaining contact with the cutting tip

25 152. In this way, the tensile load applied through the shaft 160 is evenly distributed through the cutting tip 152 to the shields, such that there are no pressure points and instead pressure is evenly distributed. This means that the substrate is less likely to crack when a load is applied to the shaft 160. When the tapering of the cutting tip 152 and hence the angle of the mandrel is relatively shallow, it is desirable to have relatively

30 thick shields.

To securely retain the anchor 1 in tension in the hole and undercut, a plate 110 is fixed to the surface of the substrate by use of a locking nut 1 15 on thread 150 of shaft 160. The plate 1 10 is the same as described above in relation to Figure 5. As described above, the plate 110 carries spikes 112, 1 14 which are arranged to bite into the substrate 100 as the nut 1 15 is screwed down. The shaft 160 therefore acts as a tendon, and the locking nut 1 15 is tightened against the plate 1 10 until the anchor is held in tension and securely wedged in the hole and undercut. This may help to prevent the substrate from cracking under the application of the tensile load. Holding the anchor 1 in tension in this way also means that the cutting tip 152 of shaft 160 is wedged into a portion of the sleeve 126. This ensures that the shields 124, 128 and 130 of sleeve 126 remain in the undercut and prevent the anchor 1 from accidentally falling out.

To remove the anchor 1 from the hole and undercut, tensile load is first relieved. The locking nut 1 15 and plate 1 10 are then removed. The portion of the anchor 1 extending into the undercut (for example the shields) is then extracted by applying a tensile load to the sleeve 126. This may be through the coupling of the drive shaft 142 through the bayonet housing 138, with pin 40 being received within retaining slot 139. The entire sleeve 126 need not be removed so long as the portion of the anchor 1 extending into the undercut has been extracted from the undercut. Once the portion of the anchor 1 extending into the undercut is extracted, the anchor 1 can be removed by applying a tensile load to the shaft 160. In this way the anchor 1 may be reusable.

In some configurations, the diameter of the distal face of the shaft 160 comprising the cutting tip 152 may be greater than the outer diameter of the sleeve 126. In some configurations, the shields may be thicker or thinner than the wall of the shaft body 127 of sleeve 126. For example, if the taper of the cutting tip 152 is relatively shallow, such that the angle that the mandrel forms relative to a longitudinal axis of the anchor 1 and shaft 160 is relatively shallow, it is desirable for the shields to be relatively thick. For example, the shields may be thicker than the wall of the shaft body 127 of sleeve 126.

The shields may have more than one pivot 134, or the pivot may be located elsewhere on the shield to facilitate the shield bending slightly in use. In some configurations, the shields do not have a pivot 134. In some configurations, the shields do not have a hinge 132. The sleeve 126 may have one or two shields, or may have more than three shields. ln some configurations the sleeve 126 described with reference to Figures 6 to 1 1 may be used with the first shaft 10.

In some configurations, there is no flush channel 144. In some configurations, the cavity between the sleeve 126 and the shaft 160 is configured to allow fluid to be pumped into the hole to allow drilling debris to be removed from the hole. In some configurations, cutting fluid and other substances is pumped into the hole through a cavity between the sleeve 126 and shaft 160, and extracted through the at least one flush channel 144 in the shaft 160 and cutting tip 152. In some configurations, there is no cavity between the sleeve 126 and the shaft 160.

In some configurations, the shaft body 127 of sleeve 126 is removed entirely, as shown in Figures 13a and 13b. In these configurations, the sleeve 126 comprises a bayonet housing 138 as described above, coupled to the shields 124, 128 and 130. The bayonet housing 138 may have a hinge 142 so that each shield can hinge about the bayonet housing 138. In use, the drive shaft 142 couples with the bayonet housing 138 and extends into the hole to deliver and operate the sleeve 126 to the correct location. These configurations of a sleeve 126 without a shaft body 127 are particularly useful where the hole is drilled quite deep (for example approximately 5 metres), because it means that the amount of material (i.e. the shaft body 127 of sleeve 126) left in place in the hole is reduced. These configurations are particularly effective when a plate 110 is used to hold the anchor in tension.

In some configurations only one shield extends into the undercut to secure the anchor 1 in place. In some configurations two shields extend into the undercut to secure the anchor 1 in place.

In some configurations, the drive shaft 142 screws onto the sleeve 126. For example, both or either of the shaft 160 and the sleeve 126 may have a threaded coupling for connecting to a drive shaft. For example, the shaft and the sleeve may have a left handed or a right handed threaded coupling. In some configurations, the shaft 160 also has a bayonet fitting for coupling to a drive shaft. It will be understood that the hole can be drilled with the cutting tip 152 with or without the sleeve 126 in place. If the hole is drilled without the sleeve 126 in place, the sleeve 126 can be inserted into the drilled hole over the shaft 160 to cut the undercut. In some configurations, the depth of the hole drilled is selected based on the material the substrate is made of.

In some configurations the plate 1 10 does not have any spikes. In some configurations, the anchor 1 is used without a plate 1 10 or locking nut 1 15. In these configurations, the anchor 1 cannot be removed from the hole when a portion of the tool (for example the shields) extends into the undercut, However, in some configurations the anchor 1 may be further secured within the hole and undercut by wedging the anchor 1 in place by the application of a tensile load. For example the cutting tip 152 may wedge into a portion of the sleeve 126. When the tensile load is removed, the anchor 1 still remains in place.

Both the sleeve 126 and the shaft 160 may be driven by rotary techniques. However, in some configurations the sleeve 126 and the shaft 160 may be driven by percussive techniques.

The lateral cutters 20, 22, 136 and/or the cutting tip 12, 152 may comprise an industrial diamond cutting surface. In some configurations, the lateral cutters 20, 22, 136 and/or the cutting tip 12, 152 comprise a mill cutter. For example, the lateral cutters 136 may be configured such that the distal ends of the shields 124, 128, 130 act as a face mill. The cutting tip 12, 152 may also be configured such that it acts as a face mill. The cutting tip 12, 152 and lateral cutters 20, 22, 136 may comprise a number of cutting tips. For example, the cutting tip 12, 152 and/or lateral cutters 20, 22, 136 may comprise disposable carbide tips. In some configurations the cutting tip 12, 152 may comprise an industrial diamond cutting surface and the lateral cutters 20, 22, 136 comprise a mill cutter, as shown in e.g. Figs. 14a and 14b.

In some configurations no shields may be required. In some configurations, the anchor 1 may cut out only one lateral cut along the depth of the hole. In some configurations, the anchor 1 may cut out a plurality of lateral cuts. The lateral cuts may not be frusto-conical in profile. For example, the cuts may be perpendicular to the longitudinal axis of the anchor 1. Fig. 15 shows another example anchor 1. In operation, the first shaft 210 rotates to drive the cutting tip 212 for cutting into a substrate. This bores a hole into the substrate. Once a hole has been cut into the substrate, the outer sleeve 226 can be driven to rotate so that the lateral cutters 220, 222 orbit the first shaft 210. A second shaft 216 can then be urged distally along the first shaft 210 so that the first lateral cutters 220 are pushed laterally outward by wedge 214. The tapering of the wedge 214 causes the lateral cutters 220, to be turned about their pivots 221 so that the tips of the lateral cutters 220 extend laterally out from the first shaft 210. As the second shaft is driven further into the hole the second lateral cutters 222 are also pushed laterally outward by wedge 214. Accordingly, the cutters 220, 222 cut out a plurality of undercuts within the hole. The second shaft may be pushed distally into the hole until it hits the cutting tip 212.

As with the other configurations described above, a tensile load may be applied to the first shaft 210. A plate 1 10 may be arranged over the hole against the substrate 100. A threaded nut may be screwed down onto a threaded portion of the first shaft 210 to hold the first shaft 210 in tension. The plate 1 10 may also act to hold the second shaft 216 and the outer sleeve 226 in place so that the lateral cutters 220, 222 can transmit at least a portion of the load to the undercut. This may help to prevent the substrate from cracking under the application of the tensile load.

In some examples the anchor may comprise, or consist essentially of titanium, or a titanium alloy. In these examples, the ability to retrieve the anchor in a single simple operation may be particularly desirable.

Figure 16 shows a section through a drill bit 300 for enabling anchoring operations to be performed quickly and efficiently underwater.

The drill bit 300 comprises a first shaft 310 which carries a cutting tip 312 at its distal end for boring a hole into a substrate. A mandrel 314 is carried on the shaft 310. The mandrel 314 tapers outwardly from the shaft 310 so that it is narrower at its proximal end than its distal end. A length of the shaft 310 extends between the distal end of the mandrel 314 and the cutting tip 312. The mandrel forms an angle with the longitudinal axis of the shaft of between 1 to 10 degrees, preferably 3 to 6 degrees, more preferably 2.5 to 5 degrees.

5 A sleeve 316 comprises a cavity 318, and the first shaft 310 is arranged to extend through the cavity 318 in the second shaft 316. The sleeve 316 also carries two lateral cutters 320, 322. Accordingly, the sleeve 316 surrounds a length of the first shaft 310, and the mandrel 314, and the cutting tip 312 are distal of the sleeve 316. The drill bit 300 is configured so that the sleeve 316 and the shaft 310 can be independently 10 operated, such that the cutting tip 312 and lateral cutters 320, 322 can be independently operated.

In operation, the first shaft 310 rotates to drive the cutting tip 312 for cutting into a substrate. This bores a hole into the substrate. Once a hole has been cut into the

15 substrate, the sleeve 316 can be driven to rotate so that the lateral cutters 320, 322 orbit the first shaft 310. The second shaft can then be urged distally along the first shaft 10 so that the lateral cutters 320, 322 are pushed down onto the mandrel 314. The tapering of the mandrel 314 causes the lateral cutters 320, 322, to extend laterally out from the shaft. Accordingly, the cutters 320, 322 cut (for example to ream) out an undercut within

20 the hole that follows the frusto-conical form of the mandrel 314.

In some configurations, the lateral cutters 320, 322 remain in the undercut such that the sleeve 316 acts as a shield and prevents the first shaft 310 from being withdrawn from the hole. The mandrel 314 of the first shaft 310 may become wedged into the sleeve 25 316 upon application of a tensile load to securely hold the drill bit in place.

In the context of the present disclosure other examples and variations of the apparatus and methods described herein will be apparent to a person of skill in the art.

Claims

CLAIMS:

1. A drill bit for cutting a hole comprising an undercut into a substrate, the drill bit comprising a shaft having a first cutting tip, a mandrel on the shaft, and a flareable sleeve comprising a second cutting tip drivable separately from the first cutting tip, wherein the mandrel and the sleeve are arranged so that urging the sleeve distally over the mandrel flares part of the sleeve outward from the shaft for reaming out the undercut outwardly from the hole.

2. The drill bit of claim 1 wherein the shaft comprises a shaft drive coupling for applying torque to the shaft for driving the first cutting tip, and the sleeve comprises a sleeve drive coupling for applying torque to the sleeve to drive the second cutting tip.

3. An anchor comprising the drill bit of claim 1 or 2 wherein the sleeve drive coupling is operable to be driven into the hole, distal to a surface of the substrate, and is arranged to be releasable so that the flareable part of the sleeve can be detached from the sleeve when the drive coupling is withdrawn from the hole.

4. The anchor of claim 3 wherein at least one of the sleeve drive coupling and the shaft drive coupling comprises at least one of a thread, a bayonet fitting and a non- circular surface.

5. The anchor of claim 3 or 4, or the drill bit of claim 1 wherein the mandrel surface is operable to bear against part of the sleeve to hold the sleeve extended into the undercut and inhibit removal of the shaft from the hole.

6. The anchor of claim 3 or 4, or the drill bit of claim 1 or 2 wherein the second cutting tip is carried on the end surface of the flared part of the sleeve.

7. The anchor or drill bit of any preceding claim wherein a flareable part of the sleeve comprises a pivot arranged to allow the flareable part of the sleeve to bend about the pivot as it is flared outward by the mandrel surface.

8. The anchor or drill bit of claim 7 wherein the flareable part of the sleeve is coupled to the rest of the sleeve by a hinge.

5 9. A method of securing an anchor to a substrate, the anchor comprising a shaft having a first cutting tip, a mandrel on the shaft, and a flareable sleeve comprising a second cutting tip drivable separately from the first cutting tip, the method comprising: boring a hole into a surface of a substrate with the first cutting tip;

urging the sleeve over the mandrel to flare part of the sleeve outward from the 10 shaft to ream out an undercut in the substrate from the hole, and

securing the anchor such that the mandrel surface bears against part of the flared sleeve to hold the flared sleeve extended in the undercut and inhibit removal of the anchor from the hole.

15 10. The method of claim 9 wherein boring the hole comprises applying a first torque to the shaft, and subsequently applying a second torque to the sleeve whilst urging the sleeve over the mandrel.

1 1. The method of claim 9 or 10 wherein the sleeve comprises a sleeve drive 20 coupling for driving the second cutting tip, the method comprising decoupling the sleeve drive coupling from the flared part of the sleeve, and withdrawing the drive coupling from the hole.

12. The method of claim 10 wherein the anchor comprises a fastening to secure the 25 anchor such that the mandrel surface bears against part of the flared sleeve, and at least one of an attachment for securing a load to the sleeve, and a shaft drive coupling for driving the cutting first cutting tip via the shaft.

13. The method of claim 12 wherein the fastening is coupled to or comprises at least 30 one of the attachment and the shaft drive coupling.

14. The method of claim 12 or 13 wherein the sleeve drive coupling is distal of the shaft drive coupling.

15. The method of any of claims 9 to 14 wherein the second cutting tip is carried on the end surface of the flared part of the sleeve.

5

16. The method of claim 15 wherein reaming the undercut comprises cutting a reverse taper into the substrate from the hole, wherein the angle of the taper corresponds to the angle of the mandrel surface.

10 17. The method of claim 16 wherein the flared part of the sleeve comprises a pivot arranged to allow the part of the sleeve to bend about the pivot as it is flared outward by the mandrel surface.

18. The method of claim 17 wherein holding the mandrel surface against the flared 15 part of the sleeve conforms the flared part of the sleeve to the mandrel so that the pivot is immobilised.

19. The method of claim 18 wherein the flared part of the sleeve is straightened about the pivot by the mandrel.

20

20. The method of any of claims 9 to 19 comprising applying a first tensile load to the shaft of the tool to hold the mandrel surface against the flared part of the tool, and coupling a second tensile load to the tool so that the second tensile load is at least partially transverse to the shaft.

25

21. The method of claim 20 wherein the second tensile load is coupled to the shaft by a lateral member arranged at the surface of the substrate to provide a lateral spacing between the second tensile load and the shaft.

30 22. A self-boring shield anchor comprising:

a first shaft for carrying a tensile load;

a cutting tip at the distal end of the first shaft for boring a hole into a substrate; a lateral cutter configured to be extended laterally for creating an undercut inside the hole, and

a sleeve operable to expand laterally into the undercut to provide a shield to inhibit removal of the anchor from the hole.

23. The anchor of claim 22 in which the first shaft carries a mandrel operable to extend the lateral cutter to create the undercut.

24. The anchor of claim 23 in which the mandrel is further operable to expand the sleeve.

25. The anchor of claim 23 or 24 wherein the mandrel comprises a tapered portion.

26. The anchor of any one of claims 22 to 25 wherein the mandrel comprises the cutting tip.

27. The anchor of any one of claims 22 to 26 wherein the lateral cutter extends laterally with at least a component of movement in a direction perpendicular to a longitudinal axis of the first shaft by longitudinal movement over the mandrel in a direction parallel to the longitudinal axis of the first shaft.

28. The anchor of any one of claims 22 to 27 wherein the shield comprises a hinge with the sleeve so that the shield can splay outwards relative to the sleeve and expand laterally into the undercut.

29. The anchor of claim 28 wherein the shield comprises a pivot to allow the shield to flex when expanding laterally into the undercut.

30. The anchor of claim 28 or 29 wherein the distal end of the shield forms a radius larger than the radius of the cylindrical hole, such that when a tensile load is coupled to the anchor the radius formed by the shield does not change by more than a selected amount.

31. The anchor of claim 30 wherein coupling the tensile load to the anchor does not cause the radius formed by the shield to change by more than 10%.

5 32. The anchor of any one of claims 22 to 31 wherein the sleeve comprises the lateral cutter.

33. The anchor of claim 32 wherein the lateral cutter is disposed on the distal end of the shield.

10

34. The anchor of any one of claims 22 to 33 comprising a second shaft arranged to drive the lateral cutter.

35. The anchor of claim 34 in which the second shaft comprises a cavity and the first 15 shaft passes through the cavity.

36. The anchor of any one of claims 12 to 35 further comprising a lateral member such as a plate, arranged to be seated against a surface of the substrate outside the hole, wherein the first shaft is configured to be fixed to the lateral member, thereby to

20 restrain the sleeve in the hole.

37. The anchor of claim 36 in which the lateral member comprises spikes arranged to bite into the substrate when the plate is fixed to the first shaft.

25 38. The anchor of claim 36 or 37 comprising a fixture secured to the plate to enable a tensile load to be secured to the anchor by the fixture.

39. The anchor of claim 38 wherein the fixture is arranged so that the tensile load is not coaxial with the first shaft.

30

40. The anchor of any of claims 22 to 39 having the features of any one of claims 1 to 8.

41. A method of removing the self-boring shield anchor of any one of claims 22 to 29 from a hole, comprising:

relieving a tensile load from the anchor;

retracting a portion of the anchor from an undercut in the hole;

applying a tensile load to the anchor to remove the anchor from the hole.

42. A self-boring shield anchor substantially as described herein with reference to the accompanying drawings.

43. A drill bit substantially as described herein with reference to the accompanying drawings.

44. A method of securing a tensile load substantially as described herein with reference to the accompanying drawings.