GB2441001A

GB2441001A - A releasable anchor plug and socket assembly securing under tension

Info

Publication number: GB2441001A
Application number: GB0616128A
Authority: GB
Inventors: Rae Younger
Original assignee: Oil States Industries UK Ltd; Oil States Industries Inc
Current assignee: Oil States Industries UK Ltd; Oil States Industries Inc
Priority date: 2006-08-14
Filing date: 2006-08-14
Publication date: 2008-02-20
Also published as: WO2008020168A1; GB0616128D0

Abstract

A releasable connector assembly to secure an elongate element under tension comprises an anchor plug and a socket. The plug comprises a core member 4 with a tip 8, an indexing sleeve 9 freely rotatably and axially slidably mounted on the core member 4, and an outer sleeve 7 concentrically mounted around the indexing sleeve 9 and secured to the tip 8. Locking dogs 17 are slidably mounted in and biased to extend from outer sleeve 7 slots 16 to engage socket lip 6. The indexing sleeve 9 when lowered relative to the outer sleeve 7 engages behind the dogs 17 to lock them in their extended position beneath lip 6 (fig. 17) but can be raised by lip 6 on further insertion of the plug to allow the dogs 17 to retract into the outer sleeve 7 so as to pass the lip for engagement and disengagement. Followers 15 extending from the sleeve 7 engage into channels 11 on sleeve 9 to constrain it to move relative to the outer sleeve 7 in a predefined sequence of rotational and axial movements. Locking pins 13 located in channels 12 can fall to engage followers 15 and hold the sleeve 9 raised or can be raised by engagement with lip 6 to allow the sleeve 9 to move down.

Description

CONNECTOR ASSEMBLIES FOR CONNECTING MEMBERS UNDER

TENSION

The present invention relates to connector assemblies for connecting members that, in use, are maintained under tension. In particular, the present invention relates to connector assemblies for connecting tendon strings to anchor templates in tether systems for tethered leg platforms.

Connector assemblies for connecting members that, in use, are maintained under tension are already known from GB2178101, which discloses an assembly comprising a socket body and an plug body, as shown in Figure 1, wherein each body is provided with radially extending, load bearing projections. In use, as the plug body is inserted into the socket body, radially extending tabs provided on the socket body engage into complementary channels recessed in the plug body to cause indexing of the plug in the socket by effecting relative rotation between the bodies for allowing their radially extending projections to pass between each other, and then to cause further relative rotation between the bodies such that said radially extending projections become axially aligned in the manner of a bayonet coupling.

Subsequently, upon tensioning of the members, whereby the plug body is urged to retract back out of the socket body, the tabs and channels co-operate to guide the axially aligned projections into abutment such that, in use, said members are maintained in tension. Upon release of tension, whereby the plug body is urged further into the socket body, the followers and cams then co-operate again to rotate the bodies relative to each other, this time such that the radially extending projections on the bodies can once more pass between each other, thus facilitating disconnection.

Such known connector assemblies have a drawback, however, in that they rely on complex and expensive castings. Accordingly, it is an object of the present invention to provide a connector assembly that has a simpler construction and is less expensive to manufacture.

According to one aspect of the present invention, there is provided an anchor plug for a releasable connector assembly comprising: a core member; an indexing sleeve freely rotatably and axially slidably mounted on the core member; an outer sleeve concentrically mounted around the indexing sleeve for both axial and rotary sliding movement relative to the indexing sleeve; first locking means mounted in the outer sleeve and radially moveable between a first extended position in which said locking means extend radially beyond the outer surface of the outer sleeve and a second retracted position in which said locking means is retracted into the locking sleeve; said indexing sleeve, in a first axial position relative to the outer sleeve, being retracted from behind the first locking means in order to enable them to move into their retracted position, and, in a second axial position, being engaged behind the first locking means in order to lock them in their extended position; complementary camming and follower means provided on said indexing and outer sleeves, said camming and follower means constraining the indexing sleeve to move relative to the outer sleeve in a predefined sequence of rotational and axial movement; and second locking means retTactably engagable with the complementary camming means in order to block relative movement between said indexing sleeve and said outer sleeve; wherein said predefined sequence of relative movement between said indexing and outer sleeves includes movement of the indexing sleeve between its first and second axial positions.

An anchor plug in accordance with the present invention has the advantage that it has a simple construction and is accordingly simple and inexpensive to manufacture. Furthermore, during the predefined sequence of relative movement between the indexing and outer sleeves, the camming arrangement effects automatic cycling of the indexing sleeve between its first axial position, in which it is retracted from behind the first locking means in order to enable them to move into their retracted position, and its second axial position, in which it engages behind the first locking means in order to lock them in their extended position. in this way, the anchor plug, in use, can effectively and reliably be locked in and released from a complementary socket automatically.

Preferably, the follower means comprises at least one guide pin provided in one of the outer sleeve and the indexing sleeve and the camming means comprises a plurality of interconnected camming channels recessed in the other of the outer sleeve and the indexing sleeve into which the at least one guide pin engages so as to constrain the indexing sleeve to move in the predefined sequence relative to the outer sleeve. However, it will be appreciated that any co-operative camming and follower means for constraining the indexing sleeve to move in the predefined sequence relative to the outer sleeve could alternatively be used.

In a particularly advantageous embodiment the or each guide pin is provided in the outer sleeve, projecting radially inward therefrom, and the caniming channels are provided in the outer cylindrical surface of the indexing sleeve. In the preferred embodiment, a plurality, in particular six identical sets of interconnected camming channels are provided one after the other around the indexing sleeve, and a corresponding plurality of guide pins are distributed around the outer sleeve so that each pin follows an identical sequence of paths as it passes through its associated set of camming channels.

The outer cylindrical surface of the indexing sleeve is preferably divided into at least two axially extending, cylindrical sections of differing diameters, the diameters of the sections decreasing sequentially towards the bottom of the plug. In a particularly preferred embodiment, the indexing sleeve is divided into three such axial sections, with the carnming means being provided on the middle surface, and the outer diameter of the lower surface is a clearance fit against the inner surface of the first locking means in its extended position such that when the lower surface engages behind the first locking means, said first locking means are locked in their extended position. Furthermore, the lower edge of the lower surface is also preferably chamfered such that it develops a caniming action with the locking means as it engages with them, thereby more easily.

The indexing sleeve furthermore preferably includes means, such as a radially outwardly extending lip on its upper end, which, in use, limits the downward movement of the indexing sleeve relative to the socket in which the anchor plug locks, such that the outer sleeve may move axially relative to the indexing sleeve under the weight of the plug in order to progress the predefined sequence of movement between the outer sleeve and the indexing sleeve.

The indexing sleeve furthermore advantageously includes an axial channel associated with each set of camming channels, the or each axial channel extending from the upper edge of the indexing sleeve and intersecting the associated set of camming channels, the second locking means comprising a locking pin associated with the or each axial channel. The or each locking pin then engages in and is axially slidable along its associated axial channel between a lower position in which the locking pin extends into its associated set of camming channels so as to prevent movement of the guide pin therealong, and an upper position in which the locking pin is retracted from its associated set of camming channels so as to release the guide pin -for movement therealong. The or each pin furthermore advantageously includes means, such as a radially outwardly extending lip at its upper end or magnetic attraction, for, in use, being raised from its lower to its upper position via co-operation with the socket into which the anchor plug locks.

The first locking means preferably comprises a plurality of load bearing dogs, each of which is slidably mounted in a radial through opening formed in the outer sleeve, each dog being moveable between an extended position in which its outer end projects beyond the outer surface of the outer sleeve, and a retracted position in which its outer end is flush with the outer surface of the outer sleeve.

The outer end of each dog preferably has inclined flanks forming ramped camming surfaces which, in use, engage with a part of the socket, developing a camming action in order to press the dog into its retracted position.

Each dog is preferably retained in its associated through opening by an axially extending retaining pin mounted in the indexing sleeve so as to extend through a slot in the dog, thereby permitting a limited degree of radially movement of the dog relative to the pin and hence the outer sleeve. Advantageously, biasing means, preferably a spring which cooperates with the retaining pin, is associated with each dog, biasing the dog into its extended position.

Preferably, the or each set of camming channels is composed of a first channel which extends from a first trough and has an upper surface which is inclined towards the top of the indexing sleeve and extends to a first crest, a second channel which extends axially downwards from the first crest to a third channel, the third channel extending away from the second channel and having a lower surface which is inclined downwards away from the second channel, the third channel extending to a second trough, a fourth channel which extends from above the second trough from the third channel to a second crest, the fourth channel having an upper surface which is inclined upwards away from the second trough so as to provide an upper ramp leading to the second crest, and a fifth channel which leads back to a position which is at the same axial height on the sleeve as the first trough. In the case of just a single set of channels being present on the sleeve, the set of channels extend around the entire circumference of the sleeve such that the finishing position to which the fifth channel leads is, in fact, the first trough. In the case of more than one set of channels, each set leads to the next set, so that the finishing position of one set of channels is the first trough of the second next set around the sleeve. When the or each guide pin is, then, engaged in the first crest, the indexing Sleeve is in its second axial position relative to the outer sleeve, and when engaged in the second crest, the indexing sleeve is in its first axial position relative to the outer sleeve. The or each axial channel preferably then intersects the fifth channel of one of the sets of channels such that, in its lowered position, the locking pin associated therein extends into and blocks the fifth channel, preventing the guide pin from moving therealong to the first trough, thereby preventing the guide pin from moving beyond the second crest and hence preventing the indexing sleeve from indexing beyond its first axial position relative to the outer sleeve.

The core member of the plug is preferably connected to a tether line and has a conical end housing on its end remote from the tether, which, in use, engages against a lower lip formed on the socket in order to limited the travel of the plug into the socket.

In a further advantageous development, at least one locking projection is desirably provided on the plug anchor, the or each locking projection being retractably extendable into the or each set of camming channels so as, in use, to prevent movement of the guide pin from the first crest and thus lock the indexing sleeve in the second axial position. In this way, the plug can, in use, be prevented from unintentional release from the socket member. Preferably, the or each locking projection is provided on the outer sleeve and is advantageously remotely operable.

However, it will be appreciated that the or each locking projection could, in use, alternatively be provided on the socket in which the plug locks.

According to another aspect of the present invention, there is provided a socket for use with the anchor plug according to the invention, comprising a socket body having a preferably cylindrical opening therein for receiving the anchor plug, the socket body having a first radially inwardly extending circumferential rib formed on its inner surface so as to form a constriction in the size of the opening which is a clearance fit with the outer cylindrical surface of the outer sleeve of the plug.

Preferably, the first rib has inclined axial faces which form ramp surfaces that are engaged, in use, by the first locking means of the of the anchor plug during insertion and removal of the plug from the socket.

In a preferred embodiment, a second inwardly extending circumferential rib is provided in the opening and is spaced axially below the first rib so as to be remote from the mouth of the opening, the second rib being wider than the first rib such that the constriction in the opening formed thereby is narrower than the outer dimension of the outer sleeve. In this way, the travel of the plug into the socket is advantageously limited.

The socket preferably has a frustro-conical guide ring surrounding the mouth of the opening, by means of which engagement of the plug in the socket is facilitated by providing a larger target for the plug and also enabling capture of the plug even if the plug is tilted relative to the axis of the socket.

According to another aspect of the present invention, there is provided a releasable connector assembly comprising the plug and socket according to the invention, wherein the plug is releasably lockable within the socket such that the assembly is suitable for connecting members that, in use, are substantially maintained under tension.

In order that the invention may be well understood, there will now be described an embodiment thereof, given by way of example, reference being made to the accompanying drawings, in which: Figures 1 to 13 are views of the plug member being mounted part-by-part onto the tendon string; and Figures 14 to 20 are side views of the plug member during various stages of insertion within the socket member.

A connector assembly 1 of the invention connects a tendon string 4 to an anchor template of a tether system for a tethered leg platform, wherein the tendon string 4 is, in use, maintained under tension. Specifically, the connector assembly 1 comprises a socket member 2 and a plug member 3, the socket body normally being fixed to the anchor template and the plug member 3 being mounted on the tendon string 4.

A flex element 19 is fastened to the bottom of the tendon 4, on which is supported an outer sleeve 7 of the plug member 3 as shown in Figrues 1 to 3. The sleeve 7 has an annular shape, the inner cylindrical surface having a larger radius than the outer radius of the tendon 4 so that a gap is maintained therebetween for engagement of an indexing sleeve 9 as described below.

The outer sleeve 7 has a generally cylindrical outer radial surface in which are formed a ring of six axially aligned and circumferentially equally angularly spaced radial holes 14 and a ring of six axially aligned and circumferentially equally angularly spaced circumferentially extending radial slots 16, the slots 16 being axially spaced below the holes 14 and each slot 16 penetrating through the annular wall of the outer sleeve 7. As clearly shown in Figure 3, each slot is intersected by an axially extending hole 18 that extends from the bottom of the sleeve 7, a pin 1 8a being engagable in the hole 18 from the bottom of the sleeve 7 so as to extend across slot 16.

A load bearing dog 17 is radially slidably mounted in each slot 16, each dog 17 having a central slot 1 7d formed therein, through which the pin I 8a passes so as to retain the dog 17 within its associated slot 16 whilst permitting limited radial movement of the dog 17 within its associated slot 1 6 between an extended position and a retracted position as described below. More particularly, each dog 1 7 is longer

O

than the thickness of the annular wall of the outer sleeve 7 such that in its extended position the outer end of each dog 17 projects radially outwardly beyond the outer cylindrical surface of the outer sleeve 7 whilst the inner end of each dog 17 still projects radially inwardly beyond the irmer circumferential surface of the outer sleeve 7. A spring element is mounted in each slot 16 between the pin 1 8a and the outer radial end of the central slot I 7d of the dog 17, the spring element urging the outer end of the central slot 1 7d away from the pin 1 8a and hence biasing the dog 1 7 into its extended position. As more clearly illustrated in Figure 5, the sides of each dog 1 7 taper towards each other towards the outer radial edge of the dog 17, forming inclined flanks I 7a, I 7b which operate as camming surfaces as described below.

The sleeve 7 is secured to the tendon against axial movement by means of a tip 8 which is fastened to the lower annular face of the sleeve 7 by means of bolts 21 which screw into axial tapped holes 22 formed in the sleeve 7, as shown in Figure 9.

Indexing sleeve 9, shown in more detail in Figure 10, is journal mounted on the tendon 4 so as to engage between the outer sleeve 7 and the tendon 4. The indexing sleeve 9 has a radially outer wall 23 that steps radially inwardly from the top towards a bottom end at two distinct stepping points so as to separate the outer wall 23 into three distinct radial platforms -an upper platform 23a which has the largest radius, a middle platform 23b whose outer surface is narrower than the upper platform, and a lower platform 23c whose outer surface is narrower than the middle platform. The upper edge of the indexing sleeve 9 furthermore tapers outwards to form an inclined lip 10 at its upper end, and the lower edge of the indexing sleeve 9 is chamfered inwards so as to form a ramp surface up to the lower platform 23c.

An indexing channel 11 is recessed into the outer cylindrical surface of and extends around the circumference of the middle platform 23b of the indexing sleeve 9.

Six equally angularly spaced axially extending channels 12 are also formed in the indexing sleeve, each channel 12 extending from the upper edge of the indexing -*10-sleeve 9 across the upper platform 23a and partially across the middle platform 23b so as to intersect the indexing channel 11.

Each channel 12 has a locking pin 13 slideably mounted therein and moveable between a raised position in which the pin is retracted from the indexing channel 12, thereby enabling progression of a follower along the indexing channel 11 passed the axial channels 12, and a lowered position in which the pin 13 extends into the indexing channel to block movement therealong. Each pin 13 has a radial step partially along its length so that it is thinner in the radial direction below the step than above, and also tapers radially outwards to form an inclined lip 13a at its upper end of similar shape to the inclined lip 10 at the top edge of the indexing sleeve 9, the inclined lip 1 3a of each pin 13 being aligned with the inclined lip 10 of the indexing sleeve 9 when the pin 13 is in its rasied position and projecting beyond the outer cylindrical surface of the indexing sleeve 9, below the inclined lip 10 thereof, when the pin 13 is in its lowered position.

The indexing channel 11 itself is divided into six identical portions, each of which extends between an adjacent pair of axial channels 12. As shown in Figure 10, each portion is formed of a number of sections which lead on from one another, starting at a first trough 1 la which underlies one of the axial channels 12, extends substantially to the bottom of the middle platform, and is flanked on one side by an axially extending wall 1 1 b which extends partially across the middle platform 23b. A first channel section 1 ic extends circumferentially and axially upwards from the top of the axially extending wall lIb to a first crest lid proximate to the top of the middle platform, so as to form an upper ramp surface 111 a. A second channel section 11 e extends axially downwards from the first crest 11 d partially towards the bottom of the middle platform 23b. A third channel section 1 if extends from the bottom of the second channel section circumferentially away from the first trough 11 a and axially downwards to a second trough 11 g proximate the lower edge of the middle platform 23b, so as to form a lower ramp surface 11 lb. The second trough I ig is flanked on its side remote from the first trough I la by an axially extending wall 1 lb which extends upwards, partially across the middle platform 23b to an opening 112, the opening 112 having an upper ramp surface 111 c which extends from across the second trough 11 g circumferentially away from the first trough ha and upwards partially across the middle platform 23b, terminating in a downwardly turned lip 11 i adjacent to the next axial channel 12 around the indexing sleeve 9 which forms a second crest 1 lj that is lower than the first crest 11 d. The opening also has a lower ramp surface 111 d which overlaps the upper ramp surface 111 c at one end and extends away from the first trough 1 la downwardly and under said next axial channel 12, where it terminates in a third trough, which forms the first trough of the next channel portion.

As a result, each channel portion forms a camming channel which operates to produce an indexing motion between the indexing sleeve 9 and the outer sleeve 7 as described below.

As shown in Figures 12 and 13, the indexing sleeve 9 engages between the outer sleeve 7 and the tendon 4 and is connected to the outer sleeve 7 by means of guide pins 15 which engage in the radial holes 14 of said outer sleeve 7 with their inner ends extending through the annular wall of the outer sleeve 7 and locating in the indexing channel 11 of said indexing sleeve 9. In this way, relative movement of the the indexing sleeve 9 with respect to the outer sleeve is constrained by the caruming action developed between the indexing channel 11 and the guide pins 15 located therein such that, as the indexing sleeve 9 rotates relative to the outer sleeve 7, it is caused to move axially upwards and downwards between a raised position and a lowered position. As the indexing sleeve 9 moves downwards relative to the outer sleeve 7 such that it assumes its lowered position as shown in Figure 17, the chamfered lower edge of the indexing sleeve 9 develops a carnming action with the inner end of the dogs 17 so as to drive said dogs 17 radially out as the lower platform 23c comes to overlap the slots 16 in the outer sleeve, preventing the dogs 17 being pressed inwardly through the outer sleeve and hence locking them in their extended positions. On the other hand, when the indexing sleeve moves to its raised position shown in Figure 14, the lower platform is raised above the slots 16, removing the obstruction and enabling the dogs 17 to move into their retracted position upon application of sufficient load to the outer end thereof to overcome the biasing force of their spring elements.

Referring to figure 14, the socket member 2, is formed by an annular body having a cylindrical recess 5 which is open at the top for receiving the plug member 3.

The inner radius of the socket member 2 is a generally clearance fit with the upper lip of the indexing sleeve and the outer edges of the dogs 17, so that plug 3 can easily move up and down in the socket 2. However, an inwardly extending circumferential lip 6 is formed on the inner wall of the socket 2, which forms a constriction which is a tolerance fit with the outer surface of the outer sleeve 7 of the plug 3 and hence is too narrow for either the dogs 17 to pass by when in their extended positions or for the inclined lip 10 of the indexing sleeve 9 or the inclined lips 13a of the pins 13 to move past. The inner wall of the socket 2 ramps up to the cirumferential lip 6 both above and below it, rather than a step change in cross section for reasons which will become clear below.

The plug and socket operate as follows: The plug 3 is prepared for initial insertion into the socket member'2, as shown in Figure 14, with each indexing pin 15 engaged in a second crest 1 lj of one of the channel portions, and the locking pins 13, under the influence of gravity, dropped into their lowered positions so that each extends into the indexing channel 11 -thereby blocking any movement of the indexing sleeve 9 relative to the outer sleeve 7. The location of the guide pins 15 in the second crests 1 lj hold the indexing sleeve 9 in its raised position relative to the outer sleeve 7, the lower, platform 23c being raised above the slots 16 in the outer sleeve 7 such that the load bearing dogs 17 are free to move to their retracted position within the outer sleeve 7 against the biasing action of the spring elements.

When the plug 3 locates in the socket 2, it moves freely axially down thereinto until the load bearing dogs 17 come into contact with the circumferential lip 6 of the socket 2, the upper ramped portion thereof developing a camming action with the dogs 17 under the weight of the plug 3, whereupon the dogs are pressed into the outer sleeve 7, against the biasing action of the spring elements, into their retracted positions. The dogs 17 are thereby able to move past the circumferential lip 6, as shown in Figure 15, and the plug 3 continues to move further axially into the socket 2.

As the plug member 3 continues to drop into the socket member 2, the inclined lips 13a of the locking pins 13 eventually reach the circumferential lip 6, and, being unable to pass due to their width, they engage the lip 6 and are prevented from dropping further into the socket. As a result, as the plug 3 drops further into the socket 2, the pms 13 move upwards relative to the plug 3, retracting from the indexing channel 11, until the lip 10 of the indexing sleeve 9 reaches the circumferential lip 6, at which point the pins 13a will have been fully lifted to their raised positions in which they are fully retracted from the indexing channel 11, as shown in Figure 16.

The lip 10 then prevents any further downward movement of the indexing sleeve 9 into the socket 2.

With the locking pins 13 fully retracted from the indexing channel 11, they no longer block the path of the guide pins 15 in the indexing channel 11. As a result, the guide pins 15, under the influence of gravity, drop down relative to the indexing sleeve 9 such that they contact and move along the lower ramps 111 d of the channel portions until, at the limit of their relative downward movement, they engage in the first troughs I Ia of the next channel portions.

The plug 3 and socket 2 are then placed under tension such that the plug 3 starts to rise out of the socket 2. Initially, the guide pins 15 of the outer sleeve 7 move upwards relative to the indexing sleeve 9, following the axially extending walls 1 lb and then contacting and moving along the upper ramp surfaces lila until, at the limit of their relative upward movement, they engage in the first crests lid. Subsequently, the sleeves 7, 9 of the plug 3 then begin to rise together relative to the socket 2, the location of the guide pins 15 in the first crests lid holding the indexing sleeve 9 in its lowered position relative to the outer sleeve 7 such that the lower platform 23c overlaps the slots 16 in the outer sleeve 7 and prevents the dogs 17 being pressed inwardly, thereby locking them in their extended positions. The plug 3 then continues to rise freely within the socket 2 until the load bearing dogs 17 come into contact with the lower ramped portion of the inner circumferential lip 6 of the socket 2 such that the plug 3 and socket 2 are maintained in engagement under tension, as shown in Figure 17. When the plug 3 and socket 2 are required to be brought out of

engagement, the tension therebetween is released, and, under the influence of gravity, the plug member 3 starts to drop freely into the socket member 2 until the lip 10 of the indexing sleeve 9 reaches the circumferential lip 6. As shown in Figure 18, the lip 10 then prevents any further downward movement of the indexing sleeve 9 into the socket 2 whilst the unimpeded outer sleeve 7 continues to move further into the socket body 2. Accordingly, with the locking pins 13 still in the retracted position such that they cannot prevent relative rotation of the sleeves 7, 9, the guide pins 15 move down the second channel section lIe, which extends axially down from the first crest lid, and then contact and move along the lower ramp surface 11 lb until, at the limit of their relative downward movement, they engage in the second crests 11g.

The plug 3 and socket 2 are then again placed under tension such that the plug 3 starts to rise back out of the socket 2. Initially, the guide pins 15 of the outer sleeve 7 move upwards relative to the indexing sleeve 9, contacting and moving along the -15 -upper ramp surfaces 111 c until, at the limit of their relative upward movement, they engage in the second crests I lj. Subsequently, the sleeves 7, 9 of the plug 3 then begin to rise together relative to the socket 2, the location of the guide pins 15 in the second crests 1 lj holding the indexing sleeve 9 in its raised position relative to the outer sleeve 7 such that the lower platform 23c is raised above the slots 16 in the outer sleeve 7 and once more enables the dogs 17 to move into their retracted position within the outer sleeve 7 against the biasing action of the spring elements. The plug 3 then continues to rise freely within the socket 2, whilst the locking pins 13 again dropping into their lowered positions under the influence of gravity, until the load bearing dogs 17 come into contact with the inner circumferential lip 6 of the socket 2, the lower ramped portion thereof developing a camming action with the dogs 17 under the tension between of the plug 3 and socket 2, whereupon the dogs are pressed into the outer sleeve 7, against the biasing action of the spring elements, into their retracted positions. The dogs 17 are thereby once more able to move past the circumferential lip 6, as shown in Figure 19, such that the plug 3 is free to be completely withdrawn from the socket 2, as shown in Figure 20.

Finally, it will be appreciated that many different variations of the described embodiments are possible. For example, whilst in this particular embodiment six indexing channel portions, axial channels, locking pins, guide pins and load bearing dogs are provided equally angularly spaced around the circumference of the plug body, it will be appreciated that the number of said features that are provided may alternatively be varied depending on the particular circumstances and design of the connector assembly. Furthermore, it will be appreciated that at least one moveable locking projection could also be provided in one of the socket member and plug member, the or each locking projection being extendable into at least one of the channel portions of the indexing channel so as, in use, to lock the guide pins in the at least one second crests, thereby preventing unintentional release of the plug member from the socket member. Additionally, it will be understood that any co-operative follower and camming means could alternatively be used to index the sleeve between the upper and lower positions of partial insertion within the outer sleeve.

Claims

Claims 1. An anchor plug for a releasable connector assembly

comprising: a core member; an indexing sleeve freely rotatably and axially slidably mounted on the core member; an outer sleeve concentrically mounted around the indexing sleeve for both axial and rotary sliding movement relative to the indexing sleeve; first locking means mounted in the outer sleeve and radially moveable between a first extended position in which said locking means extend radially beyond the outer surface of the outer sleeve and a second retracted position in which said locking means is retracted into the outer sleeve; said indexing sleeve, in a first axial position relative to the outer sleeve, being retracted from behind the first locking means in order to enable them to move into their retracted position, and, in a second axial position, being engaged behind the first locking means in order to lock them in their extended position; complementary cam and follower means provided on said indexing and outer sleeves, said camming and follower means constraining the indexing sleeve to move relative to the outer sleeve in a predefined sequence of rotational and axial movement; and second locking means retractably engageable with the complementary camming means in order to block relative movement between said indexing sleeve and said outer sleeve; wherein said predefined sequence of relative movement between said indexing and outer sleeves includes movement of the indexing sleeve between its first and second axial positions.

2. An anchor plug according to claim 1, wherein the follower means comprises at least one guide pin provided in one of the outer sleeve and the indexing sleeve and the camming means comprises a plurality of interconnected camming channels recessed in the other of the outer sleeve and the indexing sleeve into which the at least one guide pin engages so as to constrain the indexing sleeve to move in the predefined sequence relative to the outer sleeve.

3. An anchor plug according to claim 2, wherein the or each guide pin is provided in the outer sleeve, projecting radially inward therefrom, and the camming channels are provided in the outer cylindrical surface of the indexing sleeve.

4. An anchor plug according to claim 2 or claim 3, wherein the camming channels comprise a series of six identical sets of interconnected camming channels are provided one after the other around the indexing sleeve, and six guide pins are distributed around the outer sleeve, so that each pin follows an identical sequence of paths as it passes through its associated set of camming channels.

5. An anchor plug according to any of the preceding claims, wherein the outer cylindrical surface of the indexing sleeve is divided into at least two axially extending, cylindrical sections of differing diameters, the diameters of the sections decreasing sequentially towards the bottom of the plug.

6. An anchor plug according to claim 5, wherein the indexing sleeve is divided into three such axial sections, with the camming means being provided on the middle surface, and the outer diameter of the lower surface is a clearance fit with the inner surface of the outer sleeve such that such that when the lower surface engages behind the first locking means, said first locking means are locked in their extended position.

7. An anchor plug according to claim 6, wherein the lower edge of the lower surface (23c) is chamfered such that it develops a camming action with the first locking means (17) as it moves axially downwards.

8. An anchor plug according to any of claims 5 to 7, wherein the indexing sleeve includes a radially outwardly extending lip on its upper end, which, in use, limits the downward movement of the indexing sleeve relative to a socket in which the anchor plug locks. * 19

9. An anchor plug according to any of claims 5 to 8, wherein the indexing sleeve includes an axially extending channel associated with each set of camming channels, the or each axial channel extending from the upper edge of the indexing sleeve and intersecting the associated set of camming channels, the second locking means comprising a locking pin associated with the or each axial channel, which engages in and is axially slidable along its associated axial channel between a lower position in which the locking pin extends into its associated set of camming channels so as to prevent movement of the guide pin therealong, and an upper position in which the locking pin is retracted from its associated set of camming channels so as to release the guide pin for movement therealong.

10. An anchor plug according to claim 9, wherein the or each pin furthermore advantageously includes means which, in use, cooperates with the socket into which the anchor plug locks to effect axial movement of the pin along the channel.

I I. An anchor plug according to any of claims 2 to 10, wherein the or each set of camming channels is composed of a first channel which extends from a first trough and has an upper surface which is inclined towards the top of the indexing sleeve (9) and extends to a first crest, a second channel) which extends axially downwards from the first crest to a third channel, the third channel extending away from the second channel and having a lower surface which is inclined downwards away from the second channel, the third channel extending to a second trough, a fourth channel which extends from above the second trough from the third channel to a second crest, the fourth channel having an upper surface which is inclined upwards away from the second trough so as to provide an upper ramp leading to the second crest, and a fifth channel which leads back to a position which is at the same axial height on the sleeve as the first trough.

12. An anchor plus according to claim 11, wherein multiple sets of camming channels are provided on the indexing sleeve, the end of one set of channels is the first trough on the next set of channels. * 20

13. An anchor plug according to any of the preceding claims, wherein the first locking means comprises a plurality of load bearing dogs, each of which is slidably mounted in a radial through opening formed in the outer sleeve, each dog being moveable between an extended position in which its outer end projects beyond the outer surface of the outer sleeve, and a retracted position in which its outer end is at least flush with the outer surface of the outer sleeve.

14. An anchor plug according to claim 13, wherein each dog has a through slot formed in it extending radially to the outer sleeve and is retained in its associated through opening by an axially extending retaining pin mounted in the indexing sleeve so as to extend through the slot, and thereby permit a limited degree of radially movement of the dog relative to the pin and hence the outer sleeve.

15. An anchor plug according to claim 14, wherein biasing means, preferably in the form of a spring, is associated with each dog and cooperates with the retaining pin to bias the dog into its extended position.

16. A socket for use with the anchor plug according to any of the preceding claims, comprising a socket body having a cylindrical opening therein for receiving the anchor plug, the socket body having a first radially inwardly extending circumferential rib formed on its inner surface so as to form a constriction in the size of the opening which is a clearance fit with the outer cylindrical surface of the outer sleeve of the plug.

17. A socket according to claim 16, wherein the first rib has inclined axial faces which form ramp surfaces that are engaged, in use, by the first locking means of the anchor plug during insertion and removal of the plug from the socket.

18. A socket according to claim 16 or claim 17, wherein a frusto-conical guide ring surrounds the mouth of the opening, by means of which, in use, engagement of * 21 the plug in the socket is facilitated by providing a larger target for the plug and also enabling capture of the plug even if the plug is tilted relative to the axis of the socket.

19. A releasable connector assembly comprising the plug according to any of claims I to 15 and a socket according any of claims 16 to 18, wherein the plug is releasably lockable within the socket such that the assembly is suitable for connecting members that, in use, are substantially maintained under tension.