Mooring line connector assembly and tensioner

Abstract

A locking mechanism for a connector assembly is described. The locking mechanism comprising complementary male (2) and female portions (3). The female (3) portion comprising an inclined surface (36) and engaging members (20) arranged thereon. The male and female portions comprising grooved surfaces (9,29), wherein the grooves are asymmetric. The male portion (2) extends through the female portion (3), and the grooved engaging members are arranged radially inward of the inclined surface (36), between the male portion and outer sleeve (30); the load being transferred from the male portion (2) to the grooved engaging members (20) and from the grooved engaging members to the outer sleeve (30), wherein the load is transferred from the grooved engaging members to the outer sleeve only at the interface of the inclined surfaces of the grooved engaging members and outer sleeve.

Description

[0001] Mooring Line Connector Assembly and Tensioner

[0002] Technical Field of the Invention

[0003] The present invention relates to a locking mechanism, in particular a locking mechanism for a mooring line connector assembly and tensioner, such as a mooring line connector assembly and tensioner for connecting a mooring line to a tension leg platform (TLP) (including extended tension leg platforms (ETLPs)), subsea production buoys, or spar platforms. It is especially intended for the renewals market, e.g. connecting mooring lines to offshore wind turbines via TLPs at the surface, and to wave power generators at the surface or subsea.

[0004] Background to the Invention

[0005] A tension-leg platform (TLP) is a vertically moored floating structure (or buoy) normally used in the offshore production of oil or gas and in floating offshore wind turbines. TLPs are particularly suited for water depths greater than 300 metres and less than 1500 metres. The use of TLPs for floating offshore wind turbines drastically increasing the number of sites where wind farms are viable. Furthermore, as they are not permanently fixed, installation and maintenance costs can be drastically reduced as the turbines can be towed to and from maintenance facilities as required.

[0006] The TLP is secured in position by a plurality of tendons (typically steel, or composite, rope, pipes or chains) which are connected substantially vertically to anchoring points on the seabed.

[0007] As set out above, subsea buoys, and TLPs (whether supporting oil and gas production facilities or wind turbines) must be tethered to the seabed, as must wave power generators. These tendons are very long and since they are so long, even a small difference in the amount of stretch per tendon (which seems inevitable at present) can result in different lengths of tether once the tendons are under tension.

[0008] To ensure a stable and upright tethered structure despite differing lengths, tensioning systems are used. Typically, as discussed in US5,244,313A these take the form of ratcheting tensioners, normally supported on flexible joints. The end of the tendon is provided with a tubular section with a helictical thread, this mates with a female connector comprising a plurality of segments with a radially inner threaded surfaces. As the tubular section is drawn through the female connector the plurality of segments ratchet against the helictical thread, once tensioned to the desired amount a cam ring is turned locking it in place to engage the segments with the helical thread.

[0009] Such systems are complex and require a large number of components. It has also been determined by the inventors that the threaded surfaces can be subjected to large sheer forces which may cause failure, in particular to the portion of the thread closest to the load, where most of the load is applied.

[0010] The present invention seeks to provide an improved mooring line connector assembly.

[0011] Summary of the Invention

[0012] According to a broad aspect of the invention there is provided a locking mechanism, the locking mechanism comprising complementary male and female portions. The male and / or female portions may have a longitudinal axis. The locking mechanism may have a first, optionally load facing, end. The locking mechanism may have a second, optionally tensioning, end. The male portion may comprise a rigid rod with a grooved outer surface. Each groove may have a load facing flank and an opposing flank. The load facing and opposing flanks may have different angles. The load facing flank may be substantially orthogonal to the longitudinal axis of the locking mechanism. The female portion may comprise an outer sleeve. The outer sleeve may surround a plurality of grooved engaging members. The grooved engaging members may comprise a grooved surface and an opposing inclined surface. The outer sleeve may have an inclined inner surface. The inclined inner surface may decrease in cross section in the direction of the load facing end. The male portion may extend through the female portion. The grooved engagement elements may be arranged radially inward of the included surface. The grooved engagement elements may be arranged between the male portion and the outer sleeve. The load may be transferred from the male portion to the grooved engaging members. The load may be transferred from the grooved engaging members to the outer sleeve. The load may be transferred from the grooved engaging members to the outer sleeve only at the interface of the included surface of the grooved engaging members and outer sleeve.

[0013] Accordingly, in a first aspect of the invention there is provided a locking mechanism, the locking mechanism comprising complementary male and female portions having a longitudinal axis, the locking mechanism having a first, load facing, end and a second, tensioning, end; the male portion comprising a rigid rod with a grooved outer surface; each groove having a load facing flank and an opposing flank, wherein the load facing and opposing flanks have different angles and the load facing flank is substantially orthogonal to the longitudinal axis of the locking mechanism assembly; the female portion comprising an outer sleeve, the outer sleeve surrounding a plurality of grooved engaging members; the grooved engaging members comprising a grooved surface and an opposing inclined surface, the outer sleeve having an inclined inner surface which decreases in cross section in the direction of the load facing end; wherein the male portion extends through the female portion, and the grooved engaging members are arranged radially inward of the inclined surface, between the male portion and outer sleeve; the load being transferred from the male portion to the grooved engaging members and from the grooved engaging members to the outer sleeve, wherein the load is transferred from the grooved engaging members to the outer sleeve only at the interface of the inclined surfaces of the grooved engaging members and outer sleeve.

[0014] Advantageously the combination of differing angles on the grooved engaging members and the opposing inclined surface produces a locking mechanism which inherently self-engages and more evenly distributes the load along the length of the interface between the male and female portions.

[0015] The locking mechanism may comprise at least two grooved engaging members. The locking mechanism may comprise at least three grooved engaging members. The locking mechanism may comprise at least four grooved engaging members. The locking mechanism may comprise at least five engaging members. The locking mechanism may comprise at least six grooved engaging members. The locking mechanism may comprise six grooved engaging members. The locking mechanism may comprise at least 7 engaging members. The locking mechanism may comprise at least eight grooved engaging members. The locking mechanism may comprise eight grooved engaging members. The grooved engaging members may be arranged in a single row. That is the grooved engaging members may all be arranged in the same axial location. The plurality of grooved engaging members may be movable to move along the inclined surface. The grooved engaging members may move between an engaged position and a disengaged position. The engaged position may correspond to a position in which the grooved engaging members engage with the grooved outer surface of the male portion. The disengaged position may correspond to a position in which the male portion can move along the longitudinal axis of the locking mechanism. In the disengaged position the grooved engaging members may be radially outward and axially displaced from the load facing end relative to engaged position. The grooved engaging members may be biased to the engaged position. The or each grooved engaging member may be biased by a biasing member. The biasing member may be a spring, such as a wire compression spring, or may be a gas strut or the like.

[0016] The load facing flanks of the male portion grooves may have an angle of more than 70°, preferably more than 75°, more preferably more than 80°, for example more than 85°, such as between 85° and 90°, to the longitudinal axis of the locking mechanism.

[0017] Advantageously, as the angle of the load facing flanks of the male portion grooves approaches perpendicular to the longitudinal axis, the load applied is more directly transferred via the flanks.

[0018] The opposing flanks of the male portion grooves may have an angle of between 10° and 60°, preferably between 20° and 50°, more preferably between 30° and 50°, for example between 40° and 50°, to the longitudinal axis of the locking mechanism. Advantageously, by providing the opposing flank with an angle as outline above, the load of the load facing flank can be readily transferred from the body of the male connector.

[0019] Each groove of the grooved surface of the female portion may comprise a load facing flank and an opposing flank. The load facing flank of the female portion grooves may have an angle of more than 70°, preferably more than 75°, more preferably more than 80°, for example more than 85°, such as between 85° and 90°, to the longitudinal axis of the locking mechanism.

[0020] Advantageously, as the angle of the load facing flanks of the female portion grooves approaches perpendicular to the longitudinal axis, the load applied is more directly transferred via the flanks.

[0021] The opposing flank of the female portion grooves may have an angle of between 10° and 60°, preferably between 20° and 50°, more preferably between 30° and 50°, for example between 40° and 50°, to the longitudinal axis of the locking mechanism.

[0022] Advantageously, by providing the opposing flank with an angle as outline above, the load of the load facing flank can be readily transferred to the body of the female connector.

[0023] The grooves of the male portion and engaging members may have the same profile. The load facing flanks of the male and female portions may have the same angle. The opposing flanks of the male and female portions may have the same angle. In use, the load facing flank of the male portion may face the load facing flank of the female portion. Advantageously, the grooves on the male and female portions having the same profile allows the two portions to bear against one another over their entire surfaces, distributing the load.

[0024] The grooved surface of the engaging members may be curved. The grooved surface of the engaging members may be concavely curved. The grooved surface of the male portion may be curved. The grooved surface of the male portion may be convexly curved. The radius of curvature of the grooved surface of the engaging members and the grooved surface of the male portion may have the same radii of curvature.

[0025] The inclined surface of the grooved engaging member may be at an angle of between 5° and 60° from the longitudinal axis, preferably between 10° and 40°, more preferably between 20° and 30°, for example between 20° and 25°. The inclined surface may have a single pitch.

[0026] The inclined surface of the outer sleeve may be at an angle of between 5° and 60° from the longitudinal axis, preferably between 10° and 40°, more preferably between 20° and 30°, for example between 20° and 25°. The inclined surface may have a single pitch.

[0027] The inclined surfaces of the engaging member and outer sleeve may have the same angle.

[0028] Advantageously, where the incline is angled as outlined above the engaging members are inherently drawn down the taper towards an engaged position, and the load is directed radially which compounds the locking effect. The tapered bore may have a circular cross-section. The inclined surface of the outer sleeve may have a circular cross-section. That is the inner surface of the outer sleeve may define a frustoconical bore. The tapered bore may be frustoconical.

[0029] The tapered bore may have a polygonal cross-section. The inclined surface of the outer sleeve may have a polygonal cross-section. That is, the inner surface of the outer sleeve may define a frustopyramidal bore. The tapered bore may be frustopyramidal. The inclined surface of the outer sleeve may have at least three faces. The inclined surface of the outer sleeve may have at least four faces. The inclined surface of the outer sleeve may have at least six faces. The inclined surface of the outer sleeve may have at least eight faces. The faces may have the same profile.

[0030] The provision of a tapered bore with a polyogonal cross-section is advantageous as it allows the inclined surfaces of the taper (and those of the engaging members) to be planar. Planar inclined surfaces more evenly distribute the load between the two surfaces and avoid localised points of stress.

[0031] The locking mechanism may comprise an equal number of grooved engaging members as faces of the inclined surface of the outer sleeve. The grooved engaging members may rest entirely upon the inclined surface of the outer sleeve.

[0032] The inclined surface of the grooved engaging member and the corresponding inclined surface of the outer sleeve may have the same pitch. The inclined surface of the outer sleeve may be longer than the inclined surface of the grooved engaging members.

[0033] The grooved engaging members may comprise at least 3 grooves, preferably at least 5 grooves, more preferably at least 10 grooves, for example at least 15 grooves. The male portion may comprise a rigid bar, preferably a hollow bar, but optionally a solid bar. A solid bar can provide a greater ratio of tensile strength to width than a hollow bar, whereas a hollow bar can provide a greater circumference and better resistance to bending, for a given weight. The male portion may be at least Im, 3m, 5m or 7m long. The male portion may be straight. The male portion may have a circular transverse cross section.

[0034] The shape defined by the inner edges of the engaging members may be smaller in the engaged position than the disengaged position. For example, in a female connector comprising a circular bore, with locking members arranged circumferentially around the bore, the locking members may extend further radially inwardly in the engaged position than in the disengaged position, such that a separation between opposing engaging members in the engaged position is smaller than a separation between opposing engaging members in the disengaged position. In the engaged position the grooves of the engaging members may be in contact with the grooves on the male portion. In the disengaged position the grooves of the engaging members may be disengaged from the grooves on the male portion.

[0035] The female portion may comprise a first open end defining the entrance of a bore into which the male portion is inserted and an opposing second end, and the engaging members may move between an engaged position closer to the first open end and a disengaged position closer to the second end. The engaging members may be biased towards the first open end. The second end is preferably open, allowing the male portion to be pulled through from the first end to the second end. This movement means that if the male portion is pulled towards the first open end (i.e. out of the entrance), and attempts to move the locking members, they are pulled into engagement, whereas, when the male portion is inserted, it can push the engaging members towards the second end, moving them to the disengaged position (optionally, against the bias). Thus insertion is easy and when under tension, the male portion is not pulled out.

[0036] The second end of the female portion may be shaped for connection to a tensioner, or release mechanism. Shaping the female portion to receive a tensioner allows for the tensioner to pull the male portion through the female portion in a straight line, even if the angle of the female portion to the structure is variable. The shaped second end may be planar.

[0037] The engaging members may comprise a coupler. Each engaging member may comprise a coupler. The coupler(s) may be arranged at the second end of the female portion, optionally arranged to extend out of the second end of the female portion. By extending out of the second end of the female portion the coupler may be configured to engage with a tensioner or release mechanism.

[0038] The female portion or, preferably, the male portion may be connectable to a tether. For this purpose, the male or female portion may comprise a terminal for connection to a tether, the terminal may comprise an aperture for receiving a clevis pin at the terminus of the tether, or a clevis for attachment to an aperture at the terminus of the tether.

[0039] In particular, male connector may comprise a terminal at one end for connection to the tether and a terminal at the opposite end for connection to a guide wire. The locking mechanism may be provided in a connector. The locking mechanism may be provided in an adjustable connector. The connector may be a subsea connector. The subsea connector may be a connector for connecting subsea cables to wind turbine generators. The subsea connector may be a connector for connecting tension leg platforms to the sea bed.

[0040] Detailed Description of the Invention

[0041] In order that the invention may be more clearly understood an embodiment thereof will now be described, by way of example only, with reference to the accompanying drawings, of which:

[0042] Figure 1 shows an isometric view of a connector assembly comprising the locking mechanism according to a first embodiment of the invention;

[0043] Figure 2 shows an exploded view of the connector assembly of figure 1;

[0044] Figure 3 shows a cross-sectional view of the interface between the male connector and female connector of the connector assembly of figure 1 in a disengaged position;

[0045] Figure 4 shows a cross-sectional view of the locking mechanism of the connector assembly of figure 1 in a disengaged position;

[0046] Figure 5 shows a cross-sectional view of the locking mechanism of the connector assembly of figure 1 in an engaged position;

[0047] Figure 6 shows an isometric view of a connector assembly comprising the locking mechanism according to a second embodiment of the invention; Figure 7 shows an exploded view of the connector assembly of figure 6;

[0048] Figure 8 shows a cross-sectional view of the interface between the male connector and female connector of the connector assembly of figure 6 in a disengaged position;

[0049] Figure 9 shows a cross-sectional view of the locking mechanism of the connector assembly of figure 6 in a disengaged position; and

[0050] Figure 10 shows a cross-sectional view of the locking mechanism of the connector assembly of figure 6 in an engaged position.

[0051] In the following description, terms such as upper and lower are used when referring to the connector assembly as shown in the drawings. It is to be understood that this is merely for convenience and ease of understanding. Of course, the connector assembly may be used in other orientations than that shown, in which case “upper” parts may be lower than their so-called “lower” counterparts.

[0052] Referring to figures 1 to 5, a mooring line connector assembly 1 comprising a locking mechanism according to a first embodiment of the invention is shown. The connector assembly 1 comprises a male connector 2 and a female connector 3. To aid in the description of the mooring line connector assembly the male connector 2 can be considered to define a longitudinal axis A-A aligned along its length.

[0053] Unless specified elsewhere, all the major components of the connector assembly 1 will be formed from suitable metallic materials, and formed by machining operations, easily determined by those skilled in the manufacture of subsea connectors. The male connector 2 and the female connector 3 are complementary, with the female connector 3 (best seen in figures 2 to 5) having a cylindrical bore 7 therethrough which is slightly wider than the outer diameter of a straight, rigid, bar 8 of circular transverse cross section which forms the main constituent part of the male connector 2.

[0054] As best seen in figures 3 to 5, the rigid bar of the male connector 2 is formed with a number of circumferential grooves 9 therein. The grooves 9 are provided along the majority of the length of the bar 8 and define different points at which the female connector 3 may be connected to the male connector 3 so as to vary the tension applied to the mooring line.

[0055] At one end of the male connector 2, just above the first groove, a proximate terminal 10 is provided with an eye for receiving a guide wire 11 (guide wire terminal shown) used to pull the male connector 2 through the female connector 3.

[0056] At the opposite, distal, end of the male connector 2 a distal terminal 12 is provided for connection to a tether 13 (or tendon) via a tether terminal 15, thus the distal end of the male connector is the load end 12. The distal terminal 12 is provided with a joint 14 pivotable about one transverse axis orthogonal to the longitudinal axis of the male connector 2, and having a bore extending therethrough perpendicular to the transverse axis about which it pivots (and again orthogonal to the longitudinal axis A- A of the male connector 2). The bore allows the tether terminal 15 to be connected to the joint 14 by means of a shackle formed in the terminal tether 15 and a corresponding bolt 16. The arrangement of the axes about which the joint 14 pivots and the axis of the bolt 16 about which the terminal 15 of the tether pivots allow the tether to extend in a straight line away from its terminal 15, avoiding stress from bending. As mentioned above, each groove 9 in the male connector 2 represents a different point along the length of the male connector 2 where the female connector 3 may be connected to it (so as to vary the relative position of the male connector 2 and the female connector 3 and thereby vary the tension on the tether 13).

[0057] In order to connect to any of the grooves, the female connector 3 comprises four engaging members 20 arranged circumferentially about the cylindrical bore 7 within the female connector 3. Together the four engaging members 20 have a frustoconical shape with the cylindrical bore 7 extending between the upper and lower faces.

[0058] Each of the engaging members 20 has the same shape and therefore only a single engaging member 20 is described in detail. Each engaging member 20 has a quarter annular cross section, with a radially inner wall 21, a radially outer wall 22, an upper face 23 and a lower face 24, which in use is facing the tendon as will be explained in greater detail below.

[0059] The radially inner wall 21 is perpendicular to the lower face 24 and has a concavely curving surface with the same radius of curvature as the male connector. The radially inner wall 21 is also provided with a plurality of transversely extending grooves 29, in this embodiment there are 19 grooves.

[0060] The radially outer wall 22 is convexly curved and tapered such that the radius of curvature increases from the lower face 24 to the upper face 23. In this embodiment the taper, as measured relative to the radially inner wall 21 (which is parallel to the longitudinal axis A-A), has an angle (A) of 20°, however as expanded upon below in other embodiments the angle may be between 5° and 60°. As the radially inner wall 21 is perpendicular to the lower face 24 whilst the radially outer wall 22 is tapered, the thickness of the engaging members, as measured between the two walls decreases between the upper face 23 and lower face 24 such that the engaging member 20 is thinner proximate to the lower face 24.

[0061] The upper face 23 is angled such that it is perpendicular to the radially outer wall 22. In this embodiment the connector is configured for use with an optional release mechanism (not shown), in order to connect to the release mechanism, the female connector 3 comprises couplers, which will be described in detail below. Arranged centrally on the upper face 23 is a coupler connection point 25, in this embodiment the coupler connection point is provided by a threaded hole extending perpendicular to the upper face 23.

[0062] As is best shown in figure 3, the grooves 9 in the male connector 2 and the grooves 29 in the engaging members 20 are asymmetric and have the same, but inverted, “V”-shaped profile. Each groove 9,29 comprises a load facing flank 9A,29A and an opposing flank 9B,29B. On the male connector 2 the load facing flank 9A faces the load end 13 of the connector 2 and on the engaging members 20 the load facing flank 29A faces the upper face 23 of the member 20.

[0063] In this embodiment the load facing flanks 9A,29A are approximately perpendicular to the longitudinal axis A-A of the connector (and thus the tensional force applied thereto) with an angle C of between 85° to the longitudinal axis A-A. In this embodiment the opposing flanks 9B,29B slope at an angle D of 45° degrees to the longitudinal axis A-A.

[0064] In order to avoid sheer damage to the tapered point between two grooves 9,29 the point 9C,29C is squared, or alternatively rounded off. Whilst described as grooves 9,29, those skilled in the art will appreciate that the load facing flank 9A,29A and the adjacent opposing flank 9B,29B of the adjacent groove 9,29 can equally be considered a projection, or ridge 9’, 29’.

[0065] As noted above, the engaging members 20 comprise part of the female connector 3. The female connector 3 is formed of a generally cuboid outer casing 30 with a top face 31, bottom face 32 (which in use faces the tendon), and four side faces 33. The top face 31 is provided with a top aperture 34 and the bottom face 32 is provided with a bottom aperture 35, extending between the two apertures is a tapered bore 36, which extends along the longitudinal axis A- A of the connector. The taper is arranged such that the diameter of the bore 36 decreases between the top aperture 34 and the bottom aperture 35. The angle (B) of the taper is the same as the taper on the engaging members, in this embodiment 20°, as measured relative to the longitudinal axis A-A.

[0066] On two opposing side faces 33, there are provided a pair of marine bearings 33A to provide pivotal mounting of the female connector 3.

[0067] The engaging members 20 are arranged around the tapered bore 36 such that their radially outer walls 22 abut the tapered bore 36 and the lower faces 24 of the engaging members are proximate to the bottom face 32 of the casing 30. To retain the engaging members 20 in the casing 30 the top 34 and bottom 35 apertures are partially sealed with top 37 and bottom 38 retention plates. The retention plates 37,38 are annular plates with an outer diameter greater than their respective apertures 34,35 and a concentrically arranged opening 37A,38A in their centre sized to allow the male connector 2 to pass through as explained in detail below. In this example the retention plates 37,38 are secured to the casing 30 by a plurality of bolts. In addition to retaining the engaging members 20, the top 37 and bottom 38 retention plates in some embodiments the concentrically arranged openings 37A,38A may be provided with environmental seals (such as rubber O-rings or gaskets) to reduce or prevent the ingress of foreign objects into the connector.

[0068] Where a release mechanism is provided, the top retention plate 37 is also provided with four coupler holes 39 equally spaced radially about the plate and aligned with the coupler connection points 25 on the engaging members 20. Extending through each of the coupler holes 39 and engaging with the corresponding coupler connection point 25 is a coupler 40. Each coupler 40 comprises a rod 41 with a circular cross section, a distal end of the rod 41 is provided with a threaded portion 43. At the opposing proximal end is provided a head 45 which forms a radially extending step to which a release mechanism can be attached.

[0069] With reference to figures 4 and 5, operation of the connector, and in particular to the locking mechanism thereof, is described.

[0070] In use the female connector 3 may be pivotally mounted on a Tension Leg Platform (TLP) via the marine bearings 33A, optionally the female connector may be pivotally mounted in a cradle which in turn is pivotally mounted to the TLP via a hang- off porch such that the axis of pivot of the female connector 3 in the cradle is orthogonal to the axis of rotation of the cradle on the TLP.

[0071] The TLP is provided with the necessary number of female connectors 3, by attaching them via hang-off porches, supporting the cradles, in which the female connectors are pivotably mounted. This mounting of the female connector 3 in the cradle allows it to pivot about an angle of up to 10 degrees either side of the normal, and the mounting of the cradle in the hang off porch allows for pivoting at an angle of up to 10 degrees either side of the normal in a direction perpendicular to the axis of the pivot of the female connector 3 in the cradle.

[0072] A corresponding number of male connectors 2 are provided, each connected to a respective tether 13 via the terminal 12. The opposite end of the tether 13, which may for example be a composite fibre rope, is attached to the seabed in the usual manner.

[0073] A guidewire (not shown) is attached to the eye 11 of the male connector 2 and threaded through the bore 7 in the female connector 3 from the bottom to the top. This guidewire is then pulled through the respective female connector 3 for the relevant male connector 2.

[0074] As the male connector 2 is pulled through the female connector 3 using a tensioner, the opposing flanks 9B of the male connector 2 grooves 9 bear against the opposing flanks 29B of the engaging members 20 grooves 29, this forces the engaging members to slide up and radially outward along the tapered bore 36. As the engaging member 20 continue to move radially outwards the amount of the respective opposing flanks 9B,29B in contact will decrease until the two flanks 9B,29B are no longer in contact (and the engaging members are thus in a disengaged position) at which point the engaging members move back down the tapered bore 36 towards the bottom aperture 35 (and thus toward the engaged position) in doing so the engaging members 20 also move radially inwards and thus engage with the opposing flanks 29B engage with the opposing flank 9B of the next groove 9. This process is repeated ratcheting the male connector 2 through the female connector 3 until the desired tension is applied to the tether 13.

[0075] Whilst the slope of the tapered bore 36 inherently urges the engaging members 20 into the engaged position this motion can be augmented by the provision of biasing means. The biasing means may be provided by one or more springs 50 as in the present embodiment, or alternatively, gas struts, or similar mechanisms may be used.

[0076] Once the desired tension has been applied to the tether 13 the tensioner is removed and the tension on the tether 13 pulls the male connector 2 downward such that the load facing flanks 9A,29A come into contact and the tension on the tether 13 is transferred to the female connector 3 via the engaging members 20. As the tension is transferred through the engaging members 20, they are drawn further towards the bottom aperture 35. As the engaging members 20 are drawn further towards the bottom aperture the slope of the tapered bore 36 also forces the engaging members 20 radially inwards, the angle B of the slope results in a large component of the force between the male connector 2 and the engaging members 20 being exerted in a radial direction, this reduces the strain on individual ridges 9’, 29’ as less of the force is applied “across” the ridges and thereby reduces the risk of failure via sheering of the ridges 9’, 29’.

[0077] This large radial component of the force also more evenly distributes the load over all of the ridges 9 ’,29’. The inventors have determined that in known connectors the load is predominantly distributed over the first few ridges proximate to the load end and there is a diminishing return on any additional ridges. In the present invention however, because as noted above the engaging members 20 are to a large extent forced radially inwards, the remaining lateral force is more evenly distributed between the ridges 9’, 29’ thereby further reducing the risk of sheer damage to the ridges closest to the distal end.

[0078] In addition to the female connector 3 providing an improve engagement with the male connector 2 to reduce the risk of damage to the grooves 9,29 or ridges 9’, 29’, the asymmetric nature of the grooves 9,29 also improves the durability of the grooves 9,29 or ridges 9’, 29’. As the load facing flanks 9A,29A are substantially perpendicular to the force being applied, and the opposing flank is tapered towards the base of the ridge the transfer of the force from the bulk of the male connector 2 to the load facing flank 9A, and from the load facing flank 29A to the remainder of the engaging member is improved.

[0079] Likewise due to the flanks 9A,29A being substantially perpendicular to the force being applied (in this embodiment being 5° from perpendicular) the force is applied to the engaging elements substantially in line with the force applied to the tether and thus the engaging members 20 are urged substantially along the longitudinal axis. That is, only a small component of the force applied to the engaging members 20 by the male connector 2 urges the engaging members 20 radially outward.

[0080] In order to ensure the engaging members 20 can bear against the male connector 2 to the greatest extent the tapered bore 36 is provided as a single pitched surface sized to allow the engaging members 20 to remain entirely on the tapered slope to the lowermost position (i.e. where their lateral edges touch).

[0081] In some embodiments it may be desirable to provide a means of releasing the connector, for example to allow removal of the TLP for servicing. In such instances the connector 1 may be provided with a plurality of couplers 40. As outlined above, each coupler 40 comprises a rod 41 with a circular cross section, a distal end 42 of the rod 41 is provided with a threaded portion which engages with a corresponding engaging member 20. At the opposing proximal end is provided a head 45 which forms a radially extending step to which a release mechanism can be attached.

[0082] To release the connector a release mechanism engages with the head 45 of the coupler 40 and pulls on it. This causes the engaging member 20 to move up the tapered bore 36 to the disengaged position, which allows the male connector 2 to be removed from the female connector 3.

[0083] Referring to figures 6 to 10, a further mooring line connector assembly 101 comprising a locking mechanism according to a second embodiment of the invention is shown. The connector assembly 101 of this embodiment is similar to the connector assembly 1 of the previous embodiment, with like features provided with reference numerals advances by 100. The connector assembly 101 comprises a male connector 102 and a female connector 103. To aid in the description of the mooring line connector assembly the male connector 102 can be considered to define a longitudinal axis A- A aligned along its length.

[0084] Unless specified elsewhere, all the major components of the connector assembly 101 will be formed from suitable metallic materials, and formed by machining operations, easily determined by those skilled in the manufacture of subsea connectors.

[0085] The male connector 102 and the female connector 103 are complementary, with the female connector 103 (best seen in figures 6 to 8) having a cylindrical bore 107 therethrough which is slightly wider than the outer diameter of a straight, rigid, bar 108 of circular transverse cross section which forms the main constituent part of the male connector 102.

[0086] As best seen in figures 6 to 10, the rigid bar of the male connector 102 is formed with a number of circumferential grooves 109 therein.

[0087] The grooves 109 are provided along the majority of the length of the bar 108 and define different points at which the female connector 103 may be connected to the male connector 103 so as to vary the tension applied to the mooring line.

[0088] At one end of the male connector 102, just above the first groove, a proximate terminal 110 is provided with an eye for receiving a guide wire 111 (guide wire terminal shown) used to pull the male connector 102 through the female connector 103.

[0089] At the opposite, distal, end of the male connector 102 a distal terminal 112 is provided for connection to a tether 113 (or tendon) via a tether terminal 115, thus the distal end of the male connector is the load end 112. The distal terminal 112 is provided with a joint 114 pivotable about one transverse axis orthogonal to the longitudinal axis of the male connector 102, and having a bore extending therethrough perpendicular to the transverse axis about which it pivots (and again orthogonal to the longitudinal axis A- A of the male connector 102). The bore allows the tether terminal 115 to be connected to the joint 114 by means of a shackle formed in the terminal tether 115 and a corresponding bolt 116. The arrangement of the axes about which the joint 114 pivots and the axis of the bolt 116 about which the terminal 115 of the tether pivots allow the tether to extend in a straight line away from its terminal 115, avoiding stress from bending. As mentioned above, each groove 109 in the male connector 102 represents a different point along the length of the male connector 102 where the female connector 103 may be connected to it (so as to vary the relative position of the male connector 102 and the female connector 103 and thereby vary the tension on the tether 113).

[0090] In order to connect to any of the grooves, the female connector 103 comprises six engaging members 120 arranged circumferentially about the cylindrical bore 107 within the female connector 103. Together the six engaging members 120 have a sixsided frustopyramidal shape with a cylindrical bore extending between the upper and lower faces.

[0091] Each of the engaging members has the same shape and therefore only a single engaging member is described in detail. Each engaging member 120 has an isosceles trapezium cross section, with an inner wall 121, an outer wall 122, an upper face 123 and a lower face 124, which in use is facing the tendon as will be explained in greater detail below.

[0092] The inner wall 121 is perpendicular to the lower face 124 and has a concavely curving surface with the same radius of curvature as the male connector 102. The inner wall 121 is also provided with a plurality of transversely extending grooves 129, in this embodiment there are 19 grooves.

[0093] The outer wall 122 is tapered such that the separation between the inner 121 and outer 122 walls increases from the lower face 124 to the upper face 123. In this embodiment the taper, as measured relative to the radially inner wall 121, has an angle (A) of 20°, however as expanded upon below the angle in other embodiments the angle may be between 5° and 60°. As the radially inner wall 121 is perpendicular to the lower face 124 whilst the radially outer wall 122 is tapered, the thickness of the engaging members, as measured between the two walls decreases between the upper face 123 and lower face 124, such that the engaging member 120 is thinner proximate to the lower face 124.

[0094] The upper face 123 is angled such that it perpendicular to the radially outer wall 122. In this embodiment the connector is configured for use with an optional release mechanism (not shown), in order to connect to the release mechanism, the female connector 103 comprises couplers 140, which will be described in detail below. Arranged centrally on the upper face 123 is a coupler connection point 125, in this embodiment the coupler connection point is provided by a threaded hole extending perpendicular to the upper face 123.

[0095] As is best shown in figure 8, the grooves 109 in the male connector 102 and the grooves 129 in the engaging members 120 are asymmetric and have the same, but inverted, “V”-shaped profile. Each groove 109,129 comprises a load facing flank 109A,129A and an opposing flank 109B,129B. On the male connector 102 the load facing flank 109A faces the load end 113 of the connector 102 and on the engaging members 120 the load facing flank 129A faces the upper face 123 of the member 120.

[0096] In this embodiment the load facing flanks 9A,29A are approximately perpendicular to the longitudinal axis A-A of the connector (and thus the tensional force applied thereto) with an angle of between 85° to the longitudinal axis A-A. In this embodiment the opposing flanks 109B,129B slope at an angle of 45° degrees to the longitudinal axis A-A. In order to avoid sheer damage to the tapered point 109C,129C between two grooves 109,129 the point 109C,129C is squared, or alternatively rounded off.

[0097] Whilst described as grooves 109,129, those skilled in the art will appreciate that the load facing flank 109A,129A and the adjacent opposing flank 109B,129B of the adjacent groove 109,129 can equally be considered a projection, or ridge 109’, 129’.

[0098] As noted above, the engaging members 120 comprise part of the female connector 103. The female connector 103 is formed of a generally cuboid outer casing 130 with a top face 131, bottom face 132 (which in use faces the tendon), and four side faces 133. The top face 131 is provided with a top aperture 134 and the bottom face 132 is provided with a bottom aperture 135, extending between the two apertures is a tapered bore 136, which extends along the longitudinal axis A-A of the connector and has a hexagonal cross section. The taper is arranged such that the cross section of the bore 136 decreases in area between the top aperture 134 and the bottom aperture 135. The angle (B) of the taper is the same as the taper on the engaging members 120, in this embodiment 20°, as measured relative to the longitudinal axis A-A.

[0099] On two opposing side faces 133A, there are provided a pair of marine bearings 133A to provide pivotal mounting of the female connector 103.

[0100] The engaging members 120 are arranged around the tapered bore 136 such that their outer walls 122 abut the tapered bore 136 and the lower faces 124 of the engaging members are proximate to the bottom face 132 of the casing 130. To retain the engaging members 120 in the casing 130 the top 134 and bottom 135 apertures are partially sealed with top 137 and bottom 138 retention plates. The retention plates 137,138 are annular plates with an outer diameter greater than their respective apertures 134,135 and a concentrically arranged opening 137A,138A in their centre sized to allow the male connector 102 to pass through as explained in detail below. In this example the retention plates 137,138 are secured to the casing 130 by a plurality of bolts.

[0101] In addition to retaining the engaging members 120, the top 137 and bottom 138 retention plates in some embodiments the concentrically arranged openings 137A,138A may be provided with environmental seals (such as rubber O-rings or gaskets) to reduce or prevent the ingress of foreign objects into the connector.

[0102] Where a release mechanism is provided the top retention plate 137 is also provided with six coupler holes 139 equally spaced radially about the plate and aligned with the coupler connection points 125 on the engaging members 120. Extending through each of the coupler holes 139 and engaging with the corresponding coupler connection point 125 is a coupler 140. Each coupler 140 comprises a rod 141 with a circular cross section, a distal end of the rod 141 is provided with a threaded portion 142. At the opposing proximal end is provided a head 145 which forms a radially extending step to which a release mechanism can be attached.

[0103] With reference to figures 9 and 10, operation of the connector 101, and in particular to the locking mechanism thereof, is described.

[0104] In use the female connector 103 may be pivotally mounted on a Tension Leg Platform (TLP) via the marine bearings 133A, optionally the female connector 103 may be pivotally mounted in a cradle which in turn is pivotally mounted to the TLP via a hang-off porch such that the axis of pivot of the female connector 103 in the cradle is orthogonal to the axis of rotation of the cradle on the TLP. The TLP is provided with the necessary number of female connectors 103, by attaching them via hang-off porches, supporting the cradles, in which the female connectors are pivotably mounted. This mounting of the female connector 103 in the cradle allows it to pivot about an angle of up to 10 degrees either side of the normal, and the mounting of the cradle in the hang off porch allows for pivoting at an angle of up to 10 degrees either side of the normal in a direction perpendicular to the axis of the pivot of the female connector 103 in the cradle.

[0105] A corresponding number of male connectors 102 are provided, each connected to a respective tether 113 via the terminal 112. The opposite end of the tether 113, which may for example be a composite fibre rope, is attached to the seabed in the usual manner.

[0106] A guidewire (not shown) is attached to the eye 111 of the male connector 102 and threaded through the bore 107 in the female connector 103 from the bottom to the top. This guidewire is then pulled through the respective female connector 103 for the relevant male connector 102.

[0107] As the male connector 102 is pulled a through the female connector 103 using a tensioner, the opposing flanks 109B of the male connector 102 grooves 109 bear against the opposing flanks 129B of the engaging members 120 grooves 129, this forces the engaging members to slide up and radially outward along the tapered bore 136. As the engaging members 120 continue to move radially outwards the amount of the respective opposing flanks 19B,129B in contact will decrease until the two flanks 119B, 129B are no longer in contact (and the engaging members are thus in a disengaged position) at which point the engaging members move back down the tapered bore 136 towards the bottom aperture 135 (and thus toward the engaged position) in doing so the engaging members 120 also move radially inwards and thus engage with the opposing flanks 129B engage with the opposing flank 109B of the next groove 109. This process is repeated ratcheting the male connector 102 through the female connector 103 until the desired tension is applied to the tether 113.

[0108] Whilst the slope of the frustopyramidal bore 136 inherently urges the engaging members 120 into the engaged position this motion can be augmented by the provision of biasing means. The biasing means may be provided by one or more springs 150 as in the present embodiment, or alternatively, gas struts, or similar mechanisms may be used.

[0109] As compared to the previous embodiment the provision of a frustopyramidal bore 136 over a frustoconical bore is advantageous as it means that the engaging members 120 bear against the bore 136 over their entire outer wall 122 as both the bore and wall are planar. Whereas in the first embodiment the bore 36 and outer wall 22 have a curved surface with a varying radius of curvature, this means that as the engaging member 20 moves along the bore 36 the radii of curvature may not be the same for the outer wall 22 and bore 36 resulting in localised points where the load is transferred. By using a planar interface the load is evenly distributed over the entire outer wall 122.

[0110] Once the desired tension has been applied to the tether 113 the tensioner is removed and the tension on the tether 113 pulls the male connector 102 downward such that the load facing flanks 109A,129A come into contact and the tension on the tether 113 is transferred to the female connector 103 via the engaging members 120. As the tension is transferred through the engaging members 120, they are drawn further towards the bottom aperture 135. As the engaging members 120 are drawn further towards the bottom aperture the slope of the tapered bore 136 also forces the engaging members 120 radially inwards, the angle B of the slope results in a large component of the force between the male connector 102 and the engaging members 120 to be exerted in a radial direction, this reduces the strain on individual ridges 109’, 129’ as less of the force is applied “across” the ridges and thereby reduces the risk of failure via sheering of the ridges 109 ’,129’.

[0111] This large radial component of the force also more evenly distributes the load over all of the ridges 109’, 129’. The inventors have determined that in known connectors the load is predominantly distributed over the first few ridges proximate to the load end and there is a diminishing return on any additional ridges. In the present invention however, because as noted above the engaging members 120 are to a large extent forced radially inwards, the remaining lateral force is more evenly distributed between the ridges 109’, 129’ thereby further reducing the risk of sheer damage to the ridges closest to the distal end.

[0112] In addition to the female connector 103 providing an improve engagement with the male connector 102 to reduce the risk of damage to the grooves 109,129 or ridges 109’, 129’, the asymmetric nature of the grooves 109,129 also improves the durability of the grooves 109,129 or ridges 109’, 129’. As the load facing flanks 109A,129A are substantially perpendicular to the force being applied, and the opposing flank is tapered towards the base of the ridge the transfer of the force from the bulk of the male connector 102 to the load facing flank 109A, and from the load facing flank 129A to the remainder of the engaging member is improved. Likewise due to the flanks 109A,129A being substantially perpendicular to the force being applied (in this embodiment being 5° from perpendicular) the force is applied to the engaging elements substantially in line with the force applied to the tether and thus the engaging members 120 are urged substantially along the longitudinal axis. That is, only a small component of the force applied to the engaging members 120 by the male connector 2 urges the engaging members 120 radially outward.

[0113] In order to ensure the engaging members 120 can bear against the male connector 102 to the greatest extent the tapered bore 136 is provided as a single pitched surface sized to allow the engaging members 120 to remain entirely on the tapered slope to the lowermost position (i.e. where their lateral edges touch).

[0114] In some embodiments it may be desirable to provide a means of releasing the connector, for example to allow removal of the TLP for servicing. In such instances the connector 101 may be provided with a plurality of couplers 140. As outlined above, each coupler 140 comprises a rod 141 with a circular cross section, a distal end of the rod 141 is provided with a threaded portion 142 which engages with a corresponding engaging member 120. At the opposing proximal end is provided a head 145 which forms a radially extending step to which a release mechanism can be attached.

[0115] To release the connector a release mechanism engages with the head 145 of the coupler 140 and pulls on it. This causes the engaging member 120 to move up the tapered bore 136 to the disengaged position, which allows the male connector 102 to be removed from the female connector 103. The above embodiment is described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims. For example, whilst the locking mechanism of the current invention has been described as applied to an adjustable connector for TLPs it is envisioned that the locking mechanism may be used in other applications including non-adjustable connectors.

Claims

CLAIMS1. A locking mechanism, the locking mechanism comprising complementary male and female portions having a longitudinal axis, the locking mechanism having a first, load facing, end and a second, tensioning, end; the male portion comprising a rigid rod with a grooved outer surface; each groove having a load facing flank and an opposing flank, wherein the load facing and opposing flanks have different angles and the load facing flank is substantially orthogonal to the longitudinal axis of the locking mechanism assembly; the female portion comprising an outer sleeve, the outer sleeve surrounding a plurality of grooved engaging members; the grooved engaging members comprising a grooved surface and an opposing inclined surface, the outer sleeve having a tapered inner bore which decreases in cross section in the direction of the load facing end; the tapered bore comprising an inclined surface; wherein the male portion extends through the female portion, and the grooved engaging members are arranged radially inward of the inclined surface, between the male portion and outer sleeve; the load being transferred from the male portion to the grooved engaging members and from the grooved engaging members to the outer sleeve, wherein the load is transferred from the grooved engaging members to the outer sleeve only at the interface of the inclined surfaces of the grooved engaging members and outer sleeve.

2. A locking mechanism according to claim 1 comprising at least 4 grooved engaging members.

3. A locking mechanism according to claim 1 or 2 wherein the grooved engaging members are arranged in a single row.

4. A locking mechanism according to any preceding claim wherein the grooved engaging embers are movable to move along the inclined surface between an engaged position and a disengaged position.

5. A locking mechanism according to claim 4 wherein the engaged position corresponds to a position in which the grooved engaging members engage with the grooved outer surface of the male portion, and the disengaged position corresponds to a position in which the male portion can move along the longitudinal axis of the locking mechanism.

6. A locking mechanism according to claim 4 or 5 wherein in the disengaged position the grooved engaging members may be radially outward and axially displaced from the load facing end relative to the engaged position.

7. A locking mechanism according to any of claims 4 to 7 wherein the engaging members a biased to the engaged position.

8. A locking mechanism according to any preceding claim wherein the load facing flanks of the male portion grooves have an angle of more than 70° to the longitudinal axis of the locking mechanism.

9. A locking mechanism according to any preceding claim wherein the load facing flanks of the male portion grooves have an angle of more than 80° to the longitudinal axis of the locking mechanism.

10. A locking mechanism according to any preceding claim wherein the opposing flanks of the male portion grooves have an angle of between 10° and 60° to the longitudinal axis of the locking mechanism.

11. A locking mechanism according to any preceding claim wherein the grooves of the male portion and engaging members have the same profile.

12. A locking mechanism according to any preceding claim wherein the tapered bore is frustoconical.

13. A locking mechanism according to any of claims 1 to 11 wherein the tapered bore is frustopyramidal.

14. A locking mechanism according to claim 13 wherein the tapered bore has at least 6 faces.

15. A locking mechanism according to claim 14 comprising 6 grooved engaging members.

16. A locking mechanism according to any of claims 13 to 15 wherein the number of grooved engaging members is equal to the number of faces of the tapered bore.

17. A locking mechanism according to any preceding claim wherein the inclined surface of the grooved engaging member and the corresponding inclined surface of the outer sleeve have the same pitch.

18. A locking mechanism according to any preceding claim wherein the inclined surface of the outer sleeve is at an angle of between 10° and 40° from the longitudinal axis.

19. A locking mechanism according to any preceding claim wherein the inclined surface of the outer sleeve has a single pitch.

20. A locking mechanism according to any preceding claim wherein the inclined surface of the outer sleeve may be longer than the inclined surface of the grooved engaging members.

21. A locking mechanism according to any preceding claim wherein the locking mechanism is provided in a connector.

22. A locking mechanism according to claim 21 wherein the connector is a subsea connector.

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