Abstract:
A releasable connector assembly comprising a socket body  2  and a plug body  3 . The socket body  2  has a set of channels  15  formed therein and the plug body  3  having a corresponding set of radial tabs  7  formed thereon, the channels  15  forming a keyway for the tabs  7  such that load bearing projections  5, 14  on the bodies are releasably engageable in the manner of a bayonet coupling. The assembly is characterised in that a set of locking pins are provided on the socket member that are extendable into the channels  15  so as, in use, to trap the tabs  7  in undercuts  15   k  of the channels  15 , thereby preventing unintentional release of the plug  3  from the socket  2 , and retractable from the channels  15  so as to enable release of the plug  3  from the socket  2.

Description:
This is a 371 national phase application of PCT/GB2007/001145 filed 28 Mar. 2007, claiming priority to United Kingdom Patent Application No. 0606806.8 filed 4 Apr. 2006, the contents of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     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. 
     BACKGROUND OF THE INVENTION 
     GB2178101 discloses a tether anchor arrangement comprising a socket body and an plug body, as shown in  FIG. 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 guide channels recessed in the plug body which effect relative rotation between the bodies as they are interengaged so as to bring the radially extending projections into axial alignment in the manner of a bayonet coupling. Subsequently, upon tensioning of the tether, the plug body is raised in the socket body, whereupon the tabs and channels co-operate to guide the axially aligned projections into abutment such that the plug is locked in the body. Upon release of tension the plug body drops back into the socket body, whereupon the followers and cams 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, in use, they can become disconnected upon a temporary drop in the tension in the tether. In particular, this is widely known to be problematic in applications such as connecting tendon strings to anchor templates in tether systems for tethered leg platforms, wherein members can occasionally become un-tensioned during use due to alternating sea water forces acting thereon. 
     It is an object of the present invention to provide a connector assembly that, in use, cannot become undesirably disconnected upon an incidental release in tension. 
     According to a first aspect of the present invention there is provided a releasable connector assembly comprising: 
     a socket member having a substantially cylindrical receptacle formed therein which includes at least one load bearing projection; and 
     a plug member including at least one load bearing projection; 
     one of the socket member and the plug member having at least one channel formed therein and the other of the socket member and the plug member having at least one radial tab formed thereon, the or each channel forming a keyway for the or each tab, and the or each load bearing projection of the members being releasably engageable in the manner of a bayonet coupling such that, in a first angular position, they are axially misaligned to allow insertion or removal of the plug from the socket, and in a second angular position, they are axially aligned to prevent removal of the plug from the socket;
 
the or each channel including a first and second passageway, a first camming surface which extends circumferentially and axially, a second camming surface which extends axially in the opposite direction to and circumferentially away from the first camming surface to a blind undercut, and a third camming surface which extends axially in the same direction as the first camming surface and circumferentially away from the second camming surface;
 
wherein, upon insertion of the plug member into the socket member with the or each load bearing projection of the members arranged in the first angular position, the at least one tab enters the at least one channel via the first passageway and, engages with the first camming surface, the camming action thereof causing relative rotation between the members as the plug is inserted into the socket so that when the plug is fully inserted into the socket, the tab underlies the second camming surface;
 
upon subsequent raising of the plug from the socket, the tab engages with the second camming surface, the resulting camming action continuing the plug further to rotate relative to the socket, guiding the tab into the undercut such that the or each load bearing projection of the members are arranged in the second angular position so as to prevent removal of the plug from the socket with any tension on the plug member being transmitted to the socket through the or each projection;
 
and wherein re-lowering of the plug into the socket brings the tab into engagement with the third camming surface, the resulting camming action continuing the relative rotation between the plug and socket so as to bring the tab into alignment with the second passageway and to move the or each load bearing projection of the members back towards their first angular position, whereupon the plug may be completely removed from the socket;
 
characterised in that at least one moveable locking pin is provided in the one of the socket member and the plug member, the or each pin being extendable into the or each channel so as, in use, to trap the tab in the undercut, thereby preventing unintentional release of the plug from the socket, and being retractable from the or each channel so as to enable release of the plug from the socket.
 
     In an alternative aspect, the or each channel forms a keyway for at least one pair of tabs, wherein: 
     upon insertion of the plug member into the socket member with the or each load bearing projection of the members arranged in the first angular position, a first and second tab of the or each pair of tabs enter the or each channel, via the first and second passageways respectively, such that the second tab of the or each pair engages with the first camming surface, the camming action thereof causing relative rotation between the members as the plug is inserted into the socket so that when the plug is fully inserted into the socket, the first tab of the or each pair underlies the second camming surface;
 
upon subsequent raising of the plug from the socket, the first tab of the or each pair engages with the second camming surface, the resulting camming action continuing the plug to rotate further relative to the socket, guiding said first tab of the or each pair into the undercut such that the or each load bearing projection of the members are arranged in the second angular position;
 
and wherein re-lowering of the plug into the socket brings the first tab of the or each pair of tabs into engagement with the third camming surface, the resulting camming action continuing the relative rotation between the plug and socket so as to bring said first tab into alignment with the second passageway and the second tab of the at least one pair into alignment with a further passageway, and to move the or each load bearing projection of the members back towards their first angular position, whereupon the plug may be completely removed from the socket.
 
     A connector assembly in accordance with the present invention has the advantage that the locking pin prevents the plug from dropping back into the socket, thereby preventing unintentional release of the connector, whilst any upward load applied to the plug is carried by the load bearing projections. As a result, the pin only carries the weight of the plug and any tether attached thereto and hence does not need to be especially strong, and the resulting system is therefore very reliable and robust. Furthermore, it also provides a particularly cost effective construction. 
     Desirably, the or each locking pin and the or each channel are provided on the socket member whilst the or each tab is provided on the plug member. However, the opposite configuration is also possible. 
     Preferably, the or each axially extending undercut, tab and locking pin are arranged such that, in use, there is axial play between the or each tab and the or each locking pin. In this way, the plug member can advantageously drop down slightly before contacting the or each locking pin. Desirably, the axial play is substantially 1.0 m. 
     In an advantageous development, the or each locking pin, in a first position, extends from the other said member via at least one vent hole provided therein. Furthermore, the first position of the at least one locking pin is such that it advantageously directly traps the tab in the undercut, preferably by extending into the mouth of the undercut. Alternatively, however, the first position of the at least one locking pin is such that it indirectly traps the tab in the undercut, desirably by blocking the movement of a base on which the at least one tab is mounted. 
     Preferably, the or each locking pin, or alternatively an activation means thereof, is accessible from an outer surface of the one of the socket member and plug member such that it is remotely operable between its extended and retracted positions. In particular, the or each locking pin is desirably operable via remotely operated vehicle (ROV). However, it will be appreciated that the or each locking pin could alternatively be operable via a server motor or any other known means. 
     Advantageously, the socket body is provided with a plurality of equally angularly spaced load bearing projections that co-operate with complementary load bearing projections provided on the plug body. Furthermore, a plurality of equally angularly spaced channels are likewise preferably provided on one of the bodies, which desirably co-operate with a complementary number of tabs, whereby the channels are preferably linked together such that the tabs rotate from one channel to another as the connector is engaged and disengaged, each entry portion for one channel also operating as the exit portion for the preceding channel. A locking pin is then advantageously associated with the blind undercut of each channel, although it will be understood that the number of locking pins and channels provided may be varied depending on the particular circumstances and design of the connector assembly. 
     In one development, the or each channel comprises first, second and third camming surfaces only. Accordingly, during engagement, the or each locking pin is desirably retracted from the or each channel so as to allow the or each tab to rise into the or each undercut, the or each locking pin subsequently being extended into the or each channel ready for use. In this way, the tab is advantageously guided into the undercut via a simple camming system. However, during engagement, the or each locking pin is alternatively biased to extend into the or each channel by at least one spring and is provided with a camming surface such that it automatically retracts when engaged by the or each associated tab as it rises into the or each undercut. In this way, effective locking of the plug in the socket is ensured without the need to actively operate the or each locking pin. Either way, the pin has to be actively retracted to allow release. 
     In an alternative development, the or each channel includes at least one further camming surface such that the or each locking pin can advantageously be extended during engagement. In particular, a the or each fourth camming surface preferably extends axially in the same direction and circumferentially towards the or each first camming surface such that, whilst the plug is being raised from the socket during engagement, the or each second camming surface guides the or each tab under the or each locking pin and undercut and into engagement with the or each fourth camming surface, the resulting camming action rotating the plug relative to the socket in a reverse sense and guiding the or each tab over the or each locking pin and into the or each undercut. In this way, effective locking of the plug in the socket is again ensured without the need to actively operate the or each locking pin, although it does have to be actively retracted to allow release. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the invention may be well understood, there will now be described an embodiments thereof, given by way of example, reference being made to the accompanying drawing, in which: 
         FIG. 1  is an axial section through an embodiment of a connector assembly according to the first aspect of the invention; 
         FIG. 2  is a section perpendicular to the axis through the connector assembly of  FIG. 1 ; 
         FIG. 3  is a developed view of a set of channels of the connector assembly according to  FIG. 1 ; 
         FIG. 4  is a developed view, in use, of a set of channels of a first embodiment of the alternative aspect of the invention; and 
         FIG. 5  is a developed view, in use, of a set of channels of a second embodiment of the alternative aspect of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1-3 , there is shown an embodiment of a connector assembly according to the first aspect of the invention, which is substantially similar to the known connector assembly according to GB2178101 and comprises a socket body  2  and a plug body  3 , which, in use, are each connected to a member maintained under tension. 
     The socket body  2  provides a generally cylindrical receptacle  2   a  for the plug body  3 , which receptacle may be closed at its lower end. At the upper end, the socket body  2  is provided with a generally frustro-conical guide ring  4  surrounding the upper end for guiding the plug body  3  into the receptacle  2   a , and the region of the upper end is provided with regularly spaced radially inwardly extending projections  5  each of which have an axially directed shoulder for load bearing. As shown in  FIG. 2 , in this particular embodiment, four projections  5  are provided equally angularly spaced around the circumference of the receptacle  2   a . It will be appreciated, however, that the number of projections  5  provided may be varied depending on the particular circumstances and design of the connector assembly. Below the projections  5 , a corresponding number of radially inwardly projecting tabs  7  are provided. 
     The plug body  3  has a generally cylindrical outer surface that, at its upper end, is provided with radially outwardly extending projections  14 , corresponding to the projections  5  of the socket body  2 , which provide axially directed shoulders  14   a  for abutment with the shoulders  5   a . Specifically, the projections  14  are arranged relative to the projections  5  such that, as the plug body  3  is inserted into the socket body  2 , they can pass between and beyond each other, as shown in  FIG. 2 . Rotation of the bodies  2 ,  3  relative to each other then brings the projections  5 ,  14  into axial alignment with each other such that tensioning of the bodies  2 ,  3  brings the shoulders  5   a ,  14   a  into abutment. 
     Below the projections  14 , the plug body  3  is provided with channels  15  that form keyways for receiving the tabs  7  of the socket body  2  (see  FIG. 3 ) such that, as the plug body  3  is inserted into the socket body  2 , the tabs  7  are received into the channels  15  and initially cause any relative rotation between the bodies  2 ,  3  necessary for allowing the projections  14  to pass between the projections  5 . Subsequently, as the plug body  3  is inserted further into the socket body  2 , the tabs  7  co-operate with the channels  15  to cause further relative rotation of the bodies in order to axially align the shoulders  5   a ,  14   a  such that, in use, they can be brought into abutment. 
     As the bodies  2 , 3  are moved axially together, and before the projections  5 , 14  inter-engage, each tab  7  enters a first guide portion  15   a  of the respective channel  15 , which provides converging walls  15   b . If the projections  14  are not in the required position for inter-engagement with the projections  5 , each tab  7  will contact one of the walls  15   b  to cause the pug body  3  to rotate as the tabs  7  move along the walls  15   b  to bring the tabs  7  to generally axial portions  15   c . At this point the projections  14 ,  5  will have the required orientation and during passage of the tabs  7  along portions  15   c , projections  15  will pass between and through projections  5 . At the point that the projections  14  are clear of projections  5 , the tabs  7  contact and move along inclined walls  15   d  causing further rotation of the plug body  3  until the projections  14  are in partial alignment with projections  5 . When the keys reach points  15   e  at the limit of downward movement of body  3  relative to body  2  (shown on the left-hand side of  FIG. 1 ), body  3  is then lifted. The tabs  7  then run along inclined walls  15   f  causing the plug body  3  to rotate slightly in the reverse direction and then run along walls  15   g  causing further rotation of the plug body  3  in the forward direction. Finally the tabs  7  assume positions  15   h  in which each is located in an undercut  15   k . At this point the plug body  3  has rotated to bring projections  14  into full alignment with projections  5  and shoulders  5   a ,  14   a  are in abutment (shown on the right-hand side of  FIG. 1 ). Further angular movement of body  3  relative to body  2  is prevented by the lateral walls of each undercut  15   k  and the recess is sufficiently deep that the respective key is not in contact with the base of the recess (which could prevent full abutment between shoulders  5   a , 14   a ). 
     For disengagement purposes, the channels  15  are designed so that the overall relative direction of rotation on disengagement is the same as that for engagement. However, it is possible that the channels could be arranged so that the path followed by each key is the reverse of that for engagement. For disengagement, then, tension between the bodies is released and the plug body  3  moves downwardly relative to socket body  2 , initially axially to release the tabs  7  from undercuts  15   k  and bring them into contact with inclined walls  15   l  which cause partial rotation of the plug body  3  until the tabs  7  reach positions  15   m . At this point the plug body  3  is lifted and the tabs  7  run along walls  15   n  causing reverse rotation of the plug body  3  until the tabs contact inclined walls  15   p  when the direction of rotation reverses and continues in the forward direction to bring the tabs  7  into the axial portions  15   c  of the adjacent channels  15 . At this point the projections  5 ,  14  are in a relative position whereby they can pass between and beyond each other and hence become disengaged. 
     Finally, in difference to the known connector assembly according to GB2178101, the socket body  2  includes remotely operable locking pins  150  located in vent holes  35 , each of the locking pins  15   o  having a handle  36  provided thereon which is operable via ROV between an extended and retracted position, wherein, during engagement, the locking pins  15   o  are retracted inside the socket body  2 , and, in use, they are extended into the mouth of the undercuts  15   k  so as to trap the tabs therein and lock the bodies in engagement. During engagement, the or each locking pin  15   o  is alternatively biased to extend into the or each channel by at least one spring  37  and is provided with a camming surface  38  such that it automatically retracts when engaged by the or each associated tab  7  as it rises into the or each undercut. 
     In an embodiment of the alternative aspect of the invention, there is provided a connector assembly comprising a socket body  20  and plug body  30  arranged substantially according to the bodies  2 ,  3  of the embodiment of the first aspect of the invention. Consequently, the general arrangement of and features of the bodies  20 ,  30  that are identical to those of bodies  2 ,  3  will not be repeated and substantially like components will be referred to by reference numerals multiplied by ten. Referring to  FIG. 4 , then, the channels  150  of the socket body  20  of the second embodiment are arranged differently to the channels  15  of the socket body  2  of the first embodiment in that they each form keyways for receiving a pair of the tabs  70  provided on the plug body  30 . Furthermore, the locking pin  160  is extended from the socket body, rather than retracted therein, during engagement. 
     As the bodies  20 ,  30  are moved axially together for the purpose of engagement, each tab  70  enters a guide portion between the projections  140 . If the radially extending projections  50 ,  140  are not already in a rotational position such that they can pass between each other, each tab  70  will contact one of the diverging walls  140   b  of the projections  140  to cause the plug body  30  to rotate as said tabs  70  move along said walls  140   b  so as to bring a first set of alternate tabs  70   a  into axial path  150   a  of the channels  150  and a second set of alternate tabs  70   b  into axial path  150   b  of the channels  150 . During passage of the tabs  70   a ,  70   b  along paths  150   a ,  150   b , the projections  50 ,  140  then pass between and through each other until, at the point where they are clear of each other, the tabs  70   b  contact and move along inclined walls  150   c  causing the plug body  30  to rotate until the projections  140  move to a position in partial alignment with the projections  50 . When the tabs  70   a  and  70   b  reach positions  150   d  and  150   e  respectively, at the limit of downward movement of the plug body  30  into the socket body  20 , the plug body  30  is then lifted. Accordingly, the tabs  70   a  raise to contact and move along inclined walls  150   f , which causes the plug body  30  to rotate further in the forward direction, before sliding under the extended locking pins  160  and contacting and moving along inclined walls  150   g , which, in turn, cause the plug body  30  to rotate slightly in the reverse direction. Finally, having moved to the end of the inclined walls  150   g , the tabs  70   a  locate above the locking pins  160  in the axial undercut  150   h , at which point the plug body  30  has rotated to bring the projections  140  into full alignment with the projections  50  and the shoulders  140   a  have been brought into abutment with the shoulders  50   a  such that the bodies  20 ,  30 , in use, can be maintained under tension. 
     Specifically, locking pins  160  extend into channels  150  at a position adjacent to inclined walls  150   i , which extend under the mouth of the undercuts  150   h . Accordingly, any subsequent attempt to lower the plug body  30  relative to the socket body  20  in an attempt to disengage the connector assembly causes the tabs  70   a  to foul against the remotely operated locking pins  160 . In this way, the tabs  70   a  are, in use, trapped in the undercuts  150   h  such that further relative angular movement of the bodies  20 ,  30  is prevented and the connector is maintained in engagement. 
     For disengagement purposes, the locking pins  160  are, in use, remotely retractable from the channels  150  by ROV prior to a planned disengagement at a future date. Once the pins  160  have been retracted, a release in tension results in the plug body  30  moving downwardly relative to the socket body  20  such that, in the absence of the locking pins  160 , the tabs  70   a  come into contact and follow along inclined walls  150   i , which cause the plug body  30  to rotate slightly in the forward direction. At the end of the walls  150   i , the tabs  70   a  then follow an axial path until they come into contact and follow inclined walls  150   j , which cause the plug body  30  to rotate further in the forward direction. When the tabs  70   a  reach position  150   k , the limit of downward movement of the plug body  30  into the socket body  20 , the plug body  30  is then lifted such that the tabs  70   a  contact and move along to the end of inclined walls  150   l , which cause the plug body  30  to rotate yet further in the forward direction such that the tabs  70   a  and  70   b  are guided into axial paths  150   b  and  150   a  of the channels  150  respectively. At this point, the projections  50 ,  140  are in a relative position whereby, upon retraction of the plug body  30 , they can pass between and beyond each other such that the bodies  20 ,  30  can disengage. 
     In a second embodiment of the alternative aspect of the invention, there is provided a connector assembly comprising a socket body  200  and plug body  300  arranged substantially according to the bodies  20 ,  30  of the second embodiment. Consequently, the general arrangement of and features of the bodies  200 ,  300  that are identical to those of bodies  20 ,  30  will not be repeated and like components will be referred to by reference numerals multiplied by 10. Referring to  FIG. 5 , then, the channels  1500  of the socket body  200  of the second embodiment are arranged slightly differently to the channels  150  of the socket body  20  of the first embodiment in that the inclined wall  1500   f  leads straight into the undercut  1500   h . Furthermore, the locking pins  1600  accordingly do not extend into the channels  1500  during engagement and are instead retracted into the projection  1700  forming the inclined surface  1500   j  whereby, in use, they are remotely operable by ROV to extend from said projections  1700 , though vent holes in the socket body  200 , such that they indirectly trap the tabs  700   a  in the undercuts  1500   h  via extended load lugs  1800  on which the tabs  700  are mounted. 
     In use, the locking pins  1600  are retractable back into the socket body  200  prior to a planned disengagement at a future date. Once the pins  1600  have been retracted, a release in tension results in the plug body  300  moving downwardly relative to the socket body  20  such that, in the absence of the locking pins  1600 , the tabs  700   a  are free to travel axially down to inclined surface  1500   h  and exit therefrom in the same manner as the second embodiment. 
     Finally, it will be appreciated that many different variations of the described embodiments are possible. For example, it will be understood that the locking pins and radially extending projections could be provided on the plug body whilst the tabs are provided on the socket body, and that the locking pins could be retracted or extended from the body on which they are mounted by any known means other than ROV.