Patent Publication Number: US-2021188401-A1

Title: Dual axes connection device

Description:
TECHNICAL FIELD 
     The present invention relates to offshore mooring systems. More specifically it relates to a connection system between a mooring line and an earth-fixed structure or a floating vessel, where the connection system provides a dual axis hinge. 
     BACKGROUND 
     Mooring lines are typically connected to a structure on the seabed (anchor) at one end and to a floating body or vessel at the other end. Especially towards the floating vessel the connection preferably needs to provide a dual axis hinge (typically two axes rotated 90 degrees relative each other) to avoid excessive loading and wear of the mooring components from the relative motion between the floating vessel and the mooring line. Some mooring line designs may also require a dual axis connection towards the seabed due to similar relative motions, such as mooring lines for deep water applications, where the complete mooring line is lifted of the seabed in all conditions. It is also beneficial that the hook-up of the mooring line can be done diver less and that the connection can provide an easy way to disconnect and reconnect a mooring line during the life time, e.g. in case a mooring line needs to be repaired or replaced due to damages. A dual axis hinge is especially important if the connection is towards a chain segment of the mooring line, because chain is sensitive to wear, tear and fatigue, and increased degree of rotational freedom in the connection will improve the situation for the chain. 
     Related prior art is disclosed in U.S. Pat. No. 5,845,893, US20010029878A1, U.S. Pat. No. 7,240,633B2, US201000175604A1, U.S. Pat. No. 7,926,436B2, US20120031320A1, US20120160146A1, WO2014339485A1, WO20160687717A1 and WO2016118006A1. 
     The present invention solves some of the mentioned problems. Further, the loading on the connection device is reduced when the mooring line is pulled up/tightened because the funnel follows the movements of the chain and the connection device is relieved of all forces originating from the anchor line. When the line is fixed for an anchored position the connection device follows the anchor line and transfers only the pull of the anchor line to the floating body. 
     The connection device shall also manage a diver less connection and disconnection of the mooring line from the body with the attached connection device. 
     SHORT SUMMARY OF THE INVENTION 
     The invention describes a dual axes connection device for use with a mooring line, a line guide and pulling means for connecting a floating body and a fixed body. The mooring line, the line guide and the connection device are positioned in one plane. The connecting device comprises a dual axes hinge unit, with orthogonal rotational axes x and y, and means for fastening the unit to the floating or fixed body. The connection device further comprises a connecting link fastened to the hinge unit, a funnel enveloping the mooring line, and locking means for locking the mooring line to the funnel. The invention is characterized by the connecting link comprising two parallel arms, and the funnel being rotationally connected to the two parallel arms by means of trunnions and mating formations in the outer ends of the two arms. 
     Furthermore the invention describes two uses of the connection device wherein: a) the hinge unit of the connection device is connected to a floating body with pulling means temporarily or permanently onboard the floating body and the guiding structure temporarily or permanently fixed to the floating body, and b) the hinge unit of the connection device is connected to the mooring anchor, the guiding structure is fixed to the mooring anchor and the pulling means are on board an auxiliary vessel or temporarily attached to the mooring anchor 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Below, various embodiments of the invention will be described with reference to the figures, in which like numerals in different figures describes the same features 
         FIG. 1  shows a typical general arrangement of a moored unit with its mooring lines. 
         FIG. 2  shows the general arrangement of the connection device and interfacing components/structures. 
         FIG. 3  shows the assembly of the connection device (presented with an exploded view). 
         FIG. 4  shows the pull-through operation of the chain, where locking element(s) are not activated. 
         FIG. 5  shows the general arrangement of the connection device after the pull-in operation has been completed, and locking device(s) have been activated. 
         FIGS. 6 a, b  and  c    show a fixing device from a top view, a vertical section and horizontal section. 
         FIGS. 7 a  and  b    show a connection device connected to an anchor in a pulling state and locked state. 
         FIG. 8 a - e    show a connection device with a fixed funnel instead of a hinged funnel. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     This invention describes a dual axes mooring connection device  2  for managing a mooring line  8 , comprising, in one embodiment, a first line section  9  extending between a fixed body  11  on the seafloor and the connection device  2  attached to a floating body  1 , or vice versa, and a second line section  10  extending between the connection device  2  and pulling means  21  like a winch on the floating body or an auxiliary vessel using a winch or its bollard pull. The first and second sections  9 ,  10  of the mooring line are defined by their position relative to the connection device when the mooring line is in a locked state. 
     The main difference from earlier dual axes connection devices is that the device according to the invention is not handling the forces associated with a directional change of the mooring line when the mooring line is winched. These forces are absorbed by a guide structure  15  guiding the second section  10  of the mooring line  8  towards the pulling means  21  making it easier to locate and design the guiding structure  15  and thus make the guiding structure simple and robust for both short-term and long-term use. The connection device itself is only handling pull in the direction of the mooring line when in a locked state. 
     In order to ease the explanation we use an axis system with x and y axis being perpendicular to the z axis, which is going through the centerline of the connection device  2  when taught. The mooring line is located in a vertical plane that includes the z-axes. Obviously the mooring line  8  will deviate somewhat from this condition due to currents and wave action. In the figures we have chosen the x-axis to be parallel to the rotational axis of the trunnions (explained below) and perpendicular to the mentioned vertical plane, while the y- and z-axes largely resides in the vertical plane. We will use the words inner and outer when describing the connection device, where outer is on the side towards the first section  9  of the mooring line  8  and inner is the side connected to the floating or fixed body. Normally the fixed body would be an anchor. We will also use line and chain interchangeably to describe the mooring line. 
       FIG. 1  gives an overall view of the arrangement using the mooring connection device  2  according to the invention. In this embodiment the anchor line  8  can be of any type, such as chain, steel wire rope or synthetic rope, but the section  9  towards the connection device  2  is chain. Operation of the connection device can be performed by pulling the second chain section  9  with pulling means  21 , such as a winch onboard the floating body  1 . An auxiliary vessel on the sea surface  12  in combination with an ROV (Remotely Operated Vehicle) is also in most cases needed for connecting the line on the winch to the mooring line  8  via the connection device  2  when setting up the mooring. The pulling means, such as the said winch, may also be located on another unit, but the pull is via a guiding structure  15  close to the inner side of the connection device  2 . The mooring connection device can also be located on an earth-fixed structure (body), such as a mooring anchor  11  on the sea floor  13 . The winch will then typically be onboard an auxiliary vessel on the sea surface  12 . 
       FIG. 2  shows three mooring connection devices  2  connected to three mooring lines  8  in a taught and locked state. This is a common configuration associated with turrets. The mooring connection device comprises a dual axes hinge unit  3 , which in turn comprises an inner connecting link  3   b  with a single axis hinged joint obtained with an x-pin  3   a  connected to a floating body  1  (such as a moored vessel  1 , either directly to the hull of the vessel or via a turret  14 ) or an earth-fixed body (such as a mooring anchor  11 ). The hinge unit further comprises a y-pin  3   c  rotating around the y-axis. The connection device  2  further comprises an outer connecting link  4  connected to the inner connecting link  3   b  by means of the y-pin  3   c.  The axis of rotation obtained by pin  3   c  is perpendicular to the axis of rotation obtained by pin  3   a,  thus providing two degrees of rotational freedom for the connection device. It is possible to lock the connection device  2  to the chain by chain locking means  5  provided on the funnel  7 . When locked, the second chain section  10  of the mooring line  8  is hanging with enough slack to obtain the targeted dual direction angular working envelope of the connecting device  2  with only limited load variations in chain section  9  caused by chain section  10 . 
       FIG. 3  shows an exploded view of an embodiment of the connection device  2  with all the main components. The inner end of the connection device  2 , which normally is attached to the floating body  1 , comprises a dual axis hinge unit  3  which in this embodiment comprises an inner connection link  3   b  with an x-pin  3   a  rotating around the x-axis in the mentioned axis system. The x-pin  3   a  is fastened to the floating body by means of two eyes  23   a, b  as shown in  FIG. 2 . The inner connection link  3   b  is further rotationally connected to an outer connecting link  4  via a y-pin  3   c,  which has an axis of rotation around the y-axis of the mentioned axis system indicated in this figure by dotted lines. The invention does also work with the same functionalities if the said x-pin and y-pin switch position, i.e. the y-pin is towards the body and the x-pin is towards the outer connecting link. The x-pin and the y-pin can also be arranged as a cardan joint. 
     The outer connecting link  4  comprises two parallel arms  20   a, b  connected to a funnel  7  in their outer ends. The funnel envelopes the mooring line  8 , 9  and has in the shown embodiment integrated chain locking means  5 . The purpose of the funnel is to guide the connection device in an orientation suitable for locking the mooring line. Different chain and line locking solutions are well known and the options are numerous. Hooks, wedges, clamps and pins may be used on a chain, and clamps splices, knots and wedges or a combination of those may be used for wires and ropes and their terminations. 
     In the embodiment shown in  FIG. 3  the locking means comprise two hinged identical, but mirrored chain locking components  22   a, b  fitting into mating formations at the inner end of the funnel and having a distance between them that allows a link in the chain in a given orientation to pass, but locking the next link which is oriented close to 90 degree relative to the first mentioned link and thus preventing the mooring line from being pulled out of the connecting device in an opposite direction of the main pull-direction. The components may further comprise grooves that mate with a link in the chain. In one embodiment the locking components  22   a, b , are pre-tensioned to provide self-engagement after tightening the mooring line. 
     The funnel  7  has in one embodiment a rotational freedom relative to the outer connecting link  4 , which is obtained by trunnions  6  and interfacing structure in arms  20   a,b  of the outer connecting link  4 . In a configuration wherein the mooring line is not subjected to large movements, the funnel  7  can also be fixed to the arms  20   a,b  of outer connecting link  4  without any rotational freedom as shown in  FIG. 8 , but then the inside shape and length of the funnel must be arranged such that the chain is not subject to bending loads when the chain is fully connected by the locking elements  5  and not subject to bending loads during the chain pull-through operation. The length of the arms  20   a, b  should be such that the mooring line  9  connected to the funnel  7  at the opposite end of the arms from base  25  do not suffer excessive wear and stresses due to combined tension and angular motions of the line. In the case of the mooring line being a chain, it would typically mean at least the length of two links in the chain. 
       FIG. 4  shows the chain pull-through situation, where a main chain pull-direction  17  forces the outer connecting link  4  in a direction  19  that differs from the pull-direction  17  and the orientation of the line section  9 . The funnel  7  rotates about the trunnions  6  such that it aligns with the pull-direction  17  and the orientation of the line section  9  at the position of the funnel. This allows the connection device  2  to remain in contact with the chain and remain available for locking of the chain to the funnel  7 , while all anchoring load is taken up by the chain section  9  and  10 . The floating body  1  or fixed body  11  is fitted with a chain guide  15  that allows a secondary pull-direction  18  of the upper end of chain section  10 , without affecting the main pull-direction and the orientation of the chain section  9 . 
     The mooring line  8 , the guide structure  15  and the z-axis of the connection device  2  must roughly be in the same plane, usually a vertical plane. This implies that the connection device will only function when the mooring line is within a given sector in relation to the guide structure  15 . The possible deviation from the vertical plane is limited, but can be increased if rotational means rotating around the y-axis are fitted to the funnel  7  close to the rotation around the x-axis provided by the trunnions  6 . In another embodiment rotational means for rotation around the z-axis is provided close to the dual axes hinge unit  3 . This will have same effect as the said rotational means near the trunnions. If additional rotational means are fitted to the funnel  7  the mentioned sector could approach 90 degrees. In a typical configuration such freedom of movement is not required and hence a connection device without such additional rotational means will suffice. 
     Furthermore the connection device  2  must be mounted a distance away from the position of the mooring line  8  when it is pulled by the pulling means  21 . This distance must obviously be less than the length L cd  of the connection device  2  from the inner end to the trunnions, but large enough to provide an angle between the connection device and the mooring line such that the mooring line is moving freely between the parallel arms  20   a, b  and do not interfere with the outer connecting link when the mooring line is in its tightest state. Also the connection device must be mounted close to the guide structure  15 , preferable less than L cd  such that the connection device is less vulnerable to deviations from the mentioned vertical plane and also are able to handle slacker states of the mooring line when the mooring line is approaching vertical (or horizontal if connected to an anchor). A typical positioning would be ½ L cd  from the guide structure and ⅓ L cd  at a right angle from the taught mooring line. However, if the deviations in position of the mooring line is small, the distance between the guide structure and the connection device  2  may be bigger. 
       FIG. 5  shows a situation where the pull-through operation has been completed and the chain locking means  5  have been activated. The second chain/line section  10  is then slack, and all the loads from the mooring line is going via the first chain section  9  and is transferred via the connection device  2  into the fixed body  11  or floating body  1 , 14 . 
     When the mooring line  8  is to be disconnected from the fixed or floating body the second chain section  10  must be tensioned up to a level such that all the loads from chain section  9  is transferred into the second chain section  10 , and not the connection device  2 . At this stage the locking means  5  can be released, preferably with the help of an ROV, and thus allowing the chain to be let out through the connection device. 
     The above description and associated drawings refers to a device connected to a mooring line  8 , where the first section  9  and second section  10  are chain. Same principals and functionality also applies to mooring lines where these sections are not chain. If the first section  9  of mooring line  8  is something else than chain then the upper end of the mooring line  9  will have a line locking component attached to the end that can mate with the locking means  5  on the funnel  7  and be locked to the funnel, confer example in  FIG. 6 . Line locking components of different kinds are available technology and will not be described closer. A pull line can also replace the second chain section  10 , and when the first section  9  is locked to funnel  7  via locking means  5  the pull line or second section  10  can be removed. 
       FIGS. 4 and 5  shows the guiding structure  15  as a fixed guiding structure on a floating body  1 ,  14 . Alternatively, means of guiding the second line section  10  can be a permanent or temporary sheave arrangement attached to the floating body  1 , the mooring anchor  11  or the turret  14 . 
       FIG. 6 a, b  and  c    show a top view, a vertical section and a horizontal section of a fixing device  24  for connecting the first section  9  with the second section  10  and also locking it to the funnel. The fixing device  24  comprises a fixed line side  25  and a pulling side  26  with a fastening means in each end for fixing to the respective first and second sections  9 ,  10 . In the embodiment shown in  FIG. 6  the fixed line side  25  has a pin suitable for attachment to an eye in a steel wire rope socket, thimble for a synthetic rope or similar. For a steel wire rope the fixing device  24  can also be an integrated part of the wire rope socket. The fastening means on the pulling side  26  has a shape that locks a mating shape attached to the end of the second section  10 . Preferably the funnel and fixing device has mating conical surfaces. This ensures that when the first section, with the fixing device  24  attached, is pulled into the funnel the fixing device will stop at a predetermined position. Preferably such that locking means  5  for fixing the fixing device to the funnel can be activated. The embodiment shown in  FIG. 6  shows that the locking means  5  are two fixing pins  28  mating with a fixing groove  27  in the fixing device, wherein the fixing pins are operated by fixing pin insertion means  29 . The fixing pin insertion means should be operable by a ROV. When using a fixing device  24  as described the length of the first section  9  is to some extent fixed. In many installations this is acceptable and a more stable connection with less wear is obtained 
     In one use of the connection device, the hinge unit  3  of the connection device is connected to a floating body  1  with pulling means  21  temporarily or permanently onboard the floating body and the guiding structure  15  temporarily or permanently fixed to the floating body. An example of this setup is shown in  FIGS. 4 and 5 . 
     In another use of the connection device the hinge unit  3  of the connection device is connected to the mooring anchor, the guiding structure  15  is fixed to the mooring anchor and the pulling means are on board an auxiliary vessel or temporarily attached to the mooring anchor. An example of this setup is shown in  FIGS 7 a  and  b   .  7   a  shows the mooring line being tightened and  7   b  shows the device and mooring line in a locked state. Section  9  in this setup leads to a floating device and section  10  leads to pulling means most commonly located on an auxiliary vessel. 
       FIG. 8 a - e    show a funnel  7  without trunnions  6  being fixed to the parallel arms  20   a, b . Preferably, if the line is not a chain, the funnel is short and has an inside guide structure like a rounded double cone with an apex angle similar to the angle between vertical and the expected mooring line position at the location of the funnel (allowing the mooring line to be pulled in a straight line, or close to a straight line, through the funnel, when the longitudinal axis of the connecting link  4  and the integrated funnel  7  is not parallel with the main pull direction  17  of the mooring line). 
     In another embodiment, when the line  8  is a chain, the inner guide structure of the funnel has the shape of a cross giving room for the two orientations of the links as illustrated in  FIG. 8 a - e   .  FIG. 8 a    shows the mooring line in a taught state with the line/chain locked in the funnel.  FIG. 8 b    is a section along the x-y plane of the connection device at the height of the locking means  5  and shows the locking means  5  in a locked state.  FIG. 8 c    is a section in the y-z plane showing the locking means in a locked state.  FIGS. 8 d  and  e    shows the chain  8  in a pulling state and a taught state respectively.  FIGS. 8 a  and  d    also illustrate how the funnel must be shaped to handle the different angles between the connection device and the mooring line. The inner side of the funnel  7  which is the furthest away from the guiding structure  15  is widening towards the outer end of the funnel. 
     REFERENCE NUMERALS 
     
         
           1  Moored vessel/floating body 
           2  Dual axes connection device 
           3  Dual axes hinge unit 
           3   a  X-Pin of hinge unit  3   
           3   b  Inner connecting link 
           3   c  Y-Pin of hinge unit  3   
           4  Outer connecting link 
           5  Locking means on funnel 
           6  Trunnions on funnel for rotational freedom between funnel and outer connecting link 
           7  Funnel 
           8  Mooring line, 
           9  First line/chain section 
           10  Second line/chain section 
           11  Mooring anchor 
           12  Sea surface 
           13  Sea floor 
           14  Turret 
           15  Guiding structure for chain 
           16  Pull-direction during hook-up of chain 
           17  Main pull-direction of the chain 
           18  Secondary pull-direction of the chain 
           19  Longitudinal axis of outer connecting link 
           20   a, b  Parallel arms of connecting link  4   
           21  Pulling means, such as a winch 
           22   a, b  Locking components 
           23   a, b  Connection eyes 
           24  Fixing device 
           25  Fixed line side 
           26  Pulling side 
           27  Fixing groove 
           28  Fixing pin(s) 
           29  Inserting means for fixing pins