Abstract:
The present invention relates to a coupling system for coupling two floating structures together. The coupling system is able to accommodate the relative rotational and translation motions between the two floating structures without becoming disconnected. Furthermore, the coupling system has an engagement and disengagement mechanism that may be implemented remotely and efficiently.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to a system for coupling a first floating structure to a second floating structure. More particularly, this invention relates to a system having a plurality of joints and a plurality of arms whereby the combination of joints and arms are used to couple a first floating structure to a second floating structure, which is kept in position by its own deep sea mooring system, even in harsh ocean conditions. The coupling system also provides for the quick decoupling of these two floating structures. 
       PRIOR ART 
       [0002]    Floating structures such as offshore well drilling platforms have been widely used by oil-drilling companies over the past few decades. Relatively smaller floating structures such as floating tender assist drilling units are usually moored to such drilling platforms to assist in the drilling and production operations. The use of such tender drilling units provide a major economic benefit in that other systems such as the mud systems, power, pipe deck, accommodation, and so on, may be contained on the tender drilling unit and not on the drilling platform, thereby freeing up valuable space on the drilling platform and negating the need for an integrated drilling platform. Such units typically act as a platform for supplies and are usually stationed alongside a main drilling platform. 
         [0003]    The drilling platforms are typically held in place using mooring systems that utilize combinations of wire ropes, polyester ropes or chains during the drilling and/or oil production processes. Tender assist drilling units are usually moored next to the drilling platforms and coupled to the drilling platform using nylon hawser ropes. These two floating structures are coupled together to restrict the relative movement between these two structures to facilitate the transfer of equipment or personnel. The nylon hawser rope system allows the relative distance between the two structures to be maintained within predetermined limits. However, the nylon hawser rope system does not prevent both floating structures from colliding. The nylon hawser rope system only prevents the floating structures from drifting too far apart. When faced with harsh environmental conditions, such as hurricanes, or stormy conditions, the distance between the two floating structures may be increased while maintaining the linkage between the two structures by simply increasing the length of the rope. Typically, a safe stand-off distance about 150-200 meters needs to be maintained between the tender assist drilling unit and the main drilling platform. Under such rough sea conditions, it is a requirement that the coupling system has relatively low stiffness to ensure that the coupling of the rotational and translational motions between the two floating structures is minimized. Under even further extreme weather conditions, the nylon rope coupling the two floating structures may even need to be abruptly disconnected in order to prevent both structures from capsizing. 
         [0004]    A system for restraining an offshore drilling vessel temporarily to a drilling platform is described in U.S. Pat. No. 5,423,632 as published on 13 Jun. 1995 in the name of Anders G. C. Ekvall et al. In the disclosed system, the offshore drilling vessel is provided with a plurality of engaging members such as keys. These engaging members which extend outwardly of the drilling vessel are hingedly connected to the drilling vessels in such a manner that these engaging members are able to pivot about a horizontal plane of the hinges and pivot along a vertical plane of the hinges. The vertical pivoting motion of the engaging members allows the engaging members to engage with vertical sliding tracks disposed along the sides of the drilling platform thereby restraining the drilling vessel to the drilling platform when engaged. In operation, the drilling vessel will be guided towards the drilling platform either through the use of guide lines or the drilling vessel may be driven carefully towards the drilling platform. The drilling vessel then aligns each of the engaging members with each of the sliding tracks on the drilling platform. Once aligned, the engaging members will slide into position thereby restraining the drilling vessel to the drilling platform. The hinges on the engaging member allows for the vertical and horizontal movement of the drilling vessel relative to the drilling platform thereby compensating for some of the movements caused by the waves. However, under harsh sea conditions, the rougher waves may cause the drilling vessel to pitch, yaw, and roll relative to the drilling platform. Under such conditions, the engaging members would have to be rapidly disengaged and the two floating structures would have to be separated to a safe distance in order to prevent both structures from capsizing. 
         [0005]    Another system for lashing a tender assist drilling unit to a floating production platform is disclosed in U.S. Pat. No. 7,383,784 as published on 10 Jun. 2008 in the name of Terje W. Eilertsen. The lashing system disclosed in this publication comprises a plurality of winches on the forward end of the tender assist drilling unit, a plurality of sheaves on the upper portion of the hull of the platform, a plurality of connection devices on the lower portion of the hull of the platform and a set of lashing lines. A lashing line extends from one of the winches, through a corresponding one of the sheaves, and vertically down alongside the platform hull to a corresponding one of the connection devices. In use, the winches reel in and pay out the lashing lines to control the separation distance between the two floating vessels. Under calm sea conditions, the lines would be shortened, and under rough sea conditions, the lines would be lengthened allowing the two structures to reach a safe separation distance. 
         [0006]    Yet another lashing system for connecting a semisubmersible tender to a deep draft caisson vessel is disclosed in U.S. Pat. No. 6,619,223 as published on 16 Sep. 2003 in the name of Christopher Louis Beato. This publication discloses of a system that uses winches, connectors, and hawser winches. The winches are disposed on the tender and the connectors are disposed on the deep draft vessel. Hawsers constructed of a polyamide material such as nylon pass through the winches on the tender and also through the connectors on the deep draft vessel. The separation distance between the tender and the deep draft vessel may be shortened or increased by either shortening or lengthening the hawser length accordingly. 
         [0007]    A connecting apparatus for connecting two offshore units is disclosed in PCT Application No. PCT/NL2005/00156 as published on 22 Sep. 2005 in the name of Marine Structure Consultants (MSC) B.V. The connecting apparatus disclosed in this publication comprises resetting facilities disposed on a first offshore unit for compensating the movements between the two offshore units and a coupling element for coupling the two offshore units together. The coupling element includes a frame that is attached to each offshore unit using a set of coupling means that allows pivotal and rotational movement. This means that the each offshore unit is able to pivot and rotate relative to the frame. The resetting facilities comprises of resilient elements that are connected to an offshore unit. The frame&#39;s coupling elements are then connected to these resilient elements. When an offshore unit is brought further away from the other unit by the ocean, the resilient elements will stretch and extend, allowing the other offshore unit to drift away. When the condition of the ocean becomes calm again, the resilient element would revert to its original condition, returning the two offshore units back to their original separation distance. 
         [0008]    The abovementioned documents disclose systems and devices for temporarily connecting or coupling two offshore vessels together. However, these systems do not allow for the vessel to be rapidly disconnected in the event of worsening weather conditions. In systems that employ hawsers made of nylon, these hawsers would have to be quickly released from their winches or worse, cut into two to allow the offshore vessels to float away to safer distances. Furthermore, most of these systems which utilize hawsers, connectors and winches usually do not have a mechanism in place that prevents both offshore vessels from colliding. Some of the disclosed systems also employ overly complicated connecting or coupling mechanisms whereby both offshore vessels may only be coupled together under calm sea conditions. 
       SUMMARY OF INVENTION 
       [0009]    The above and other problems in the art are solved and an advance in the art is made in accordance with this invention. In accordance with a first aspect of the invention, there is provided a system for coupling a first floating structure to a second floating structure. The system has a receiving member that is disposed on the first floating structure for receiving an engaging member. When the engaging member has received the receiving member, these two members will engage together when the receiving member moves relative to the engaging member. The system also has a first joint that is connected to the engaging member and a first arm having a first end and second end wherein the first end is operatively coupled to the first joint. The first joint is configured such that the engaging member may move along planes that are normal to the longitudinal axis of the first arm. The system also has a second joint that is operatively coupled to the second end of the first arm and a second arm having a first end and a second end, wherein the first end is operatively to the second joint. The second joint is configured such that the second arm is movable along planes that are normal to the longitudinal axis of the second joint. The system also has a coupling apparatus disposed on the second floating structure for coupling to the second end of the second arm. This system allows for two floating structures to be easily coupled together using a receiving member that engages with a receiving member when the receiving member moves relative to the engaging member. This also means that the coupling between these two floating structures may be easily disconnected by reversing the movement carried out to engage the receiving member to the engaging member. Furthermore, as the engaging member is only configured to move along planes that are normal to the longitudinal axis of the first arm, any unintentional movement by the engaging arm will not cause the receiving member to disengage from the receiving member once these two members have engaged. The rigid coupling arms also ensure that the two floating structures maintain a minimum stand-off distance and do not collide with one another. 
         [0010]    Preferably, the coupling apparatus further comprises a third joint that is operatively coupled to the second end of the second arm and a third arm that has a first end and a second end. The first end of the third arm has a protrusion that extends into the third joint, operatively coupling the third arm to the third joint. The third joint is also configured such that the third arm is rotatable about the longitudinal axis of the third arm. The rotational movement of the third arm combined with the movement of the second arm along planes that are normal to the longitudinal axis of the second joint allows for the system to compensate for the heave, pitch, roll, yaw and sway from large waves. Unlike systems that utilize hawsers, this system is able to maintain both floating structures at a safe distance while being able to absorb the random movements brought about by the ocean&#39;s waves. In accordance with a further embodiment of this invention, the third joint is further configured such that the third joint is movable along planes that are normal to the longitudinal axes of the second arm. 
         [0011]    In accordance with another embodiment of this invention, the coupling apparatus further comprises a third joint operatively coupled to the second end of the second arm and a third arm that has a first end and a second end. The first end of the third arm is operatively coupled to the third joint. The third joint is configured such that the third arm is movable along planes that are normal to the longitudinal axis of the third joint. In accordance with a further embodiment of this invention, the third joint is further configured such that the third joint is movable along planes that are normal to the longitudinal axis of the second arm. 
         [0012]    In accordance with another embodiment of this invention, the coupling apparatus further comprises a hydraulic piston adapted to connect to the second end of the second arm and a skid assembly that is connected to the hydraulic piston. The usage of the hydraulic piston and the skid assembly allows for the distance between the two coupled floating structures to be lengthened or shortened as required. The hydraulic piston and skid assembly also absorbs the relative surge motions between the floating structures. 
         [0013]    In accordance with yet another embodiment of this invention, the receiving member has a conical receptacle that is used to align the engaging member with the receiving member when the two floating structures are to be coupled together. This conical receptacle assists in the engagement of the receiving member with the engaging member by guiding the engaging member towards the required portion of the receiving member. 
         [0014]    In accordance with a further embodiment of this invention, a plurality of male lugs are provided on an interior surface of the conical receptacle and a plurality of female lugs are disposed around a circumference of the engaging member. Each of the plurality of female lugs are engageable with each of the plurality of male lugs that are provided on the interior surface of the conical receptacle. 
         [0015]    In accordance with another embodiment of this invention, the receiving member moves rotatably relative to the engaging member. This rotational movement causes the receiving member to engage with the engaging member. By reversing this rotational movement, this causes the receiving member to disengage from the engaging member. 
         [0016]    In accordance with a further embodiment of this invention, a motor is located adjacent to the receiving member. This motor may be used to actuate the receiving member, causing the receiving member to rotate relative to the engaging member. 
         [0017]    In accordance with yet another embodiment of this invention, the first joint comprises a first section. The first section has a first bracket that receives the first end of the first arm, a resilient material that is positioned such that the resilient material envelops the first end of the first arm and a first hook that is fixed to the first bracket to pivotably coupled the first end of the first arm to the first bracket. This means that the first arm is able to move along planes that are normal to the longitudinal axis of the first joint or the first joint is able to move along planes that are normal to the longitudinal axis of the first arm. Such a configuration does not allow for a rotational movement about the longitudinal axis of the first arm. 
         [0018]    In accordance with yet another embodiment of this invention, the second joint comprises a first section and second section. The first section has a first bracket that receives the second end of the first arm, a first resilient material positioned in the first bracket such that the first resilient material envelops the second end of the first arm and a first hook that is fixed to the first bracket for coupling the second end of the first arm to the first bracket. The second section has a second bracket that receives the first end of the second arm, a second resilient material positioned in the second bracket such that the second resilient material envelops the first end of the second arm and a second hook that is fixed to the second bracket for coupling the first end of the second arm to the second bracket. 
         [0019]    In accordance with yet another embodiment of this invention, the third joint comprises a first section and second section. The first section has a first bracket that receives the second end of the second arm. The second section has a second bracket that receives the first end of the third arm wherein the protrusion of that end extends through an opening in the second bracket. The protrusion engages with the opening thereby allowing the third arm to rotate about the longitudinal axis of the third arm. A resilient material is also positioned such in the second bracket that the resilient material envelops the first end of the third arm. 
         [0020]    In accordance with yet another embodiment of this invention, the third joint comprises a first section and a second section. The first section comprises a first bracket that receives the second end of the second arm, a first resilient material positioned in the first bracket such that the first resilient material envelops the second end of the second arm and a first hook that is fixed to the second bracket for coupling the second end of the second arm to the first bracket. The second section has a second bracket that receives the first end of the third arm wherein the protrusion of that end extends through an opening in the second bracket. The protrusion engages with the opening thereby allowing the third arm to rotate about the longitudinal axis of the third arm. A second resilient material is also positioned such in the second bracket that the second resilient material envelops the first end of the third arm. 
         [0021]    In accordance with yet another embodiment of this invention, the third joint comprises a first section and a second section. The first section has a first bracket that receives the second end of the second arm. The second section has a second bracket that receives the first end of the third arm, a resilient material positioned in the second bracket such that the resilient material envelops the first end of the third arm and a second hook that is fixed to the second bracket for coupling the first end of the third arm to the second bracket. 
         [0022]    In accordance with yet another embodiment of this invention, the third joint comprises a first section and second section. The first section has a first bracket that receives the second end of the second arm, a first resilient material positioned in the first bracket such that the first resilient material envelops the second end of the second arm and a first hook that is fixed to the first bracket for coupling the second end of the second arm to the first bracket. The second section has a second bracket that receives the first end of the third arm, a second resilient material positioned in the second bracket such that the second resilient material envelops the first end of the third arm and a second hook that is fixed to the second bracket for coupling the first end of the third arm to the second bracket. 
         [0023]    In accordance with further embodiments of this invention, the resilient material, the first resilient material and the second resilient material comprise a flexible elastomeric element. 
         [0024]    In accordance with yet further embodiments of this invention, the hydraulic piston and the skid assembly are disposed on an extended platform on a pipe rack deck of the second floating structure. 
         [0025]    In accordance with yet further embodiments of this invention, the hydraulic piston and the skid assembly are disposed on a main deck of the second floating structure. 
         [0026]    In accordance with yet further embodiments of this invention, the hydraulic piston and the skid assembly are disposed in a box bottom of a main deck of the second floating structure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    The above advantages and features of a system in accordance with this invention are described in the following detailed description and are shown in the drawings: 
           [0028]      FIG. 1  illustrating a tension leg platform coupled to a tender assist drilling platform using a coupling system in accordance with an embodiment of this invention; 
           [0029]      FIG. 2  illustrating a side view of the coupling system in accordance with an embodiment of this invention; 
           [0030]      FIG. 3   a  illustrating a perspective view of the receiving member in accordance with an embodiment of this invention; 
           [0031]      FIG. 3   b  illustrating a side cross sectional view of the receiving member in accordance with an embodiment of this invention; 
           [0032]      FIG. 4  illustrating a side view of an engaging member in accordance with an embodiment of this invention; 
           [0033]      FIG. 5   a  illustrating a cross sectional view of an engaging member in accordance with an embodiment of this invention; 
           [0034]      FIG. 5   b  illustrating a cross sectional view of an engaging member in that is engaged with a receiving member in accordance with an embodiment of this invention; 
           [0035]      FIG. 5   c  illustrating a cross sectional perspective view of an engaging member in that is engaged with a receiving member in accordance with an embodiment of this invention; 
           [0036]      FIG. 6   a  illustrating a cross sectional view of a joint having a flexible bendable section in accordance with an embodiment of this invention; 
           [0037]      FIG. 6   b  illustrating a cross sectional perspective view of a joint having a flexible bendable section in accordance with an embodiment of this invention; 
           [0038]      FIG. 6   c  illustrating a cross sectional view of a joint having a first section for receiving an arm and a second flexible bendable section in accordance with an embodiment of this invention; 
           [0039]      FIG. 7  illustrating a cross sectional view of a joint having a first bendable section and a second bendable section in accordance with an embodiment of this invention; 
           [0040]      FIG. 8   a  illustrating a cross sectional view of a joint having a rotational section in accordance with an embodiment of this invention; 
           [0041]      FIG. 8   b  illustrating a cross sectional perspective view of a joint having a rotational section in accordance with an embodiment of this invention; 
           [0042]      FIG. 8   c  illustrating a cross sectional view of a joint having a first section for receiving an arm and a second rotational section in accordance with an embodiment of this invention; 
           [0043]      FIG. 9  illustrating a cross sectional view of a joint having a first bendable section and a second rotational section in accordance with an embodiment of this invention; 
           [0044]      FIG. 10  illustrating a side view of the coupling system in accordance with an embodiment of this invention with the hydraulic piston and skid assembly; 
           [0045]      FIG. 11  illustrating a side view of the coupling system in accordance with an embodiment of this invention with the extended hydraulic piston and skid assembly; 
           [0046]      FIG. 12  illustrating a side view of the coupling system in accordance with an embodiment of this invention showing the movement of the first joint; 
           [0047]      FIG. 13  illustrating a side view of the coupling system in accordance with an embodiment of this invention showing the movement of the first joint and the second arm; 
           [0048]      FIG. 14  illustrating a side view of the coupling system in accordance with an embodiment of this invention showing the movement of the first joint and the second arm together with the rotational movement of the third arm; 
           [0049]      FIG. 15  illustrating a side view of the coupling system in accordance with an embodiment of this invention showing the movement of the first joint and the second arm. This figure also illustrates the movement of the first section of the third joint and the rotational movement of the third arm; 
           [0050]      FIG. 16  illustrating a side view of the coupling system in accordance with an embodiment of this invention showing the movement of the first joint, the second arm and the third arm; 
           [0051]      FIG. 17  illustrating a side view of the coupling system in accordance with an embodiment of this invention showing the movement of the first joint, the second arm, the third joint and the third arm; and 
           [0052]      FIG. 18  illustrating a side cross sectional view of a coupling system in accordance with an embodiment of this invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0053]    This invention relates to a system for coupling a first floating structure to a second floating structure. More particularly, this invention relates to a system having a plurality of joints and a plurality of arms whereby the combination of joints and arms are used to couple a first floating structure to a second floating structure. The coupling system also provides for the quick decoupling of two floating structures. Furthermore, the coupling system accommodates for the movement of the first floating structure relative to the second floating structure. 
         [0054]    The floating structures that may be coupled together using this invention may include, but are not limited to, tender assist drilling units, oil wellhead platforms, oil production platforms and most types of semi-submersible platforms. One skilled in the art will recognize that this invention may be used to couple any two floating vessels or floating structures together and to maintain the two floating structures at a predetermined distance. Typically, the separation distances between the two floating structures are between 15 meters-20 meters. 
         [0055]      FIG. 1  illustrates a tender assist drilling platform  105  being coupled to a tension leg platform  110  using coupling system  100  in accordance with an embodiment of this invention. Coupling system  100  ensures that tender assist drilling platform  105  remains at a safe distance away from tension leg platform  110 . Coupling system  100  utilizes a combination of rigid arms that are connected using bendable and rotatable joints. The rigid arms prevent the two floating structures from colliding while the bendable and rotatable joints allow coupling system  100  to compensate for the pitch, heave, roll, sway and yaw of the two floating structures relative to one another. Tender assist drilling platform  105  and tension leg platform  110  therefore may move independently of one another. Under extreme weather conditions, coupling system  100  will disengage allowing tender assist drilling platform  105  to drift away from tension leg platform  110 , preventing these two floating structures from colliding in case of mooring failures of the two floating structures. The detailed workings of the various components in coupling system  100  are illustrated in detail in  FIGS. 2-11  and in the following paragraphs. 
         [0056]      FIG. 2  illustrates a side view of an embodiment of coupling system  100 . In this embodiment, coupling system  100  has engaging member  210  that is connected to first joint  215 . One end of arm  220  is operatively coupled to first joint  215  and the other end of arm  220  is operatively coupled to second joint  225 . Second joint  225  is also operatively coupled to arm  230 . Coupling system  100  also has coupling apparatus  235  that may be disposed on tender assist drilling platform  105 . In certain embodiments of the invention, coupling apparatus  235  may be housed on an extended platform on the pipe rack deck of tender assist drilling platform  105 . This position is selected so that coupling apparatus  235  does not interfere with any of the equipment and structures on the deck. In another embodiment of the invention, coupling apparatus  235  is located on the main deck, which is structurally stronger than the pipe rack deck. In yet another embodiment of the invention, coupling apparatus  235  is located inside the box bottom of the main deck. One skilled in the art will recognize that coupling apparatus  235  may be positioned at various locations at tender assist drilling platform  105  without departing from this invention. 
         [0057]    Coupling apparatus  235  is connected to the other end of arm  230  as shown in  FIG. 2 . Coupling system  100  also comprises receiving member  205  that is disposed on tension leg platform  110  for receiving engaging member  210 . Engaging member  210  will engage with receiving member  205  when tender assist drilling platform  105  is to be coupled together with tension leg platform  110 . One skilled in the art will recognize that the positions of coupling apparatus  235  and receiving member  205  may be varied without departing from this invention, that is, coupling apparatus  235  may be positioned at various locations at tension leg platform  110  and that receiving member  205  may be positioned at tender assist drilling platform  105 . 
         [0058]    A perspective view of receiving member  205  is illustrated in  FIG. 3A . In an embodiment of the invention, receiving member  205  may have a cavity or a receptacle that is shaped as cone for receiving engaging member  210 . Cone cavity  310  is designed to be bigger than engaging member  210  so that cone cavity  310  may assist in the alignment of engaging member  210  with receiving member  205 . By using cone cavity  310 , engaging member  210  does not have to align precisely with the middle of cone cavity  310  before engaging member  210  is able to engage with receiving member  205 . During deep sea operations, maneuvers that require precise movements and timings are often difficult, if not impossible to execute due to the unpredictable movement of the ocean&#39;s waves. When engaging member  210  is to engage with receiving member  205 , engaging member  210  just has to be guided towards the general vicinity of receiving member  205 . Upon contact with the inner surface of cone cavity  310 , due to the tapered shape of cone cavity  310 , engaging member  210  will slide towards the center of receiving member  205 . Receiving member  205  will then move relative to engaging member  210  causing receiving member  205  to engage with engaging member  210 . This relative movement may involve either a sliding movement or a rotational movement. 
         [0059]    As shown in  FIGS. 3   a  and  3   b , a plurality of female lugs  305  is positioned around the inner circumference of cone cavity  310 . Correspondingly, a plurality of male lugs  405  is positioned around the external circumference of engaging member  210  as shown in  FIG. 4 . One skilled in the art will recognize that any number of female and male lugs may be used without departing from this invention. In the embodiment shown in  FIGS. 3 and 4 , 8 female lugs are provided with an angular separation of 22.5 degrees in the interior of cone cavity  310  and 8 male lugs are provided on engaging member  210 . After engaging member  210  has been received by receiving member  205 , receiving member  205  may rotate in either direction, relative to engaging member  210 , as indicated by the directions shown on arrow E, causing female lugs  305  to engage with male lugs  405 . By reversing the direction of the rotational movement, this will cause female lugs  305  to disengage from male lugs  405 . A steering wheel-like handle is provided at the rear of receiving member  205  to assist in the rotation of receiving member  205  either manually or through mechanical means. A motor located adjacent to receiving member  205  may be used to rotate receiving member  205 . This motor may be remotely controlled allowing for the two floating structures to be rapidly disengaged or engaged as required. This means that under extreme weather conditions, the two floating structures may easily and rapidly disengage, without requiring workers to manually actuate the handle to release engaging member  210  from receiving member  205 . This is advantageous as conditions on these floating structures become quite hazardous under extreme weather conditions. It would not be safe for workers on these floating structures if they had to manually handle or manipulate hawsers under these conditions. The mechanism disclosed above for coupling system  100  addresses these safety issues as the mechanism allows for the engaging and disengaging actions to be carried out remotely and efficiently. 
         [0060]    Referring to  FIG. 4 , engaging member  210  is shown to have a bulbous shape. This shape was chosen as this shape may be easily guided into the receptacle in receiving member  205  by cone cavity  310 . One skilled in the art will recognize that engaging member  210  may be of other shapes without departing from this invention. As shown in the cross sectional view of engaging member  210  in  FIG. 5   a , one end of first joint  215  is attached to engaging member  210  and the other end is operatively coupled to first arm  220  through bracket  505 , hook  515  and opening  510 . Hook  515  is fixed onto bracket  505  and passes through opening  510  in first arm  220 . The connection between hook  515  and opening  510  is such that it allows first joint  215  to pivot about this connection. In other words, engaging member  210  may move along planes that are normal to the longitudinal axis of first arm  220 . This freedom of movement about the pivotable connection allows engaging member  210  and first arm  215  to move in response to the relative heave, yaw, pitch and swaying motions between the two floating structures while allowing first  220  to remain rigid, maintaining the distance between the two floating structures. In an embodiment of this invention, the pivotable connection forms by hook  515  and opening  510  allows for movement of more than 15 degrees about the longitudinal axis of first arm  220 . The connection between first joint  215  and first arm  220  is designed to be a pivoting motion so that first joint  215  may not rotate relative to first arm  220  and vice versa. This is to prevent the accidental rotation of engaging member  210  due to the motions of the two floating structures. 
         [0061]    The section of first arm  220  that is contained within bracket  505  is surrounded by a resilient material. Resilient material  520  may comprise of any type of flexible elastomer that is able to compress and expand when a pressure is applied and removed. The flexible elastomer must be able to absorb heavy compressive and shear loads as well. In other words, resilient material  520  acts as a damper, damping the heaving and swaying motions of engaging member  210  by compressing and expanding. 
         [0062]    In yet another embodiment of the invention, cone cavity  525  protrudes out of receiving member  205 . The cross sectional side view of this embodiment is illustrated in  FIG. 5   b . Cone cavity  525  in this embodiment performs the same function as that previously described, which is to guide engaging member  210  towards the receptacle in receiving member  205 . In  FIG. 5   b , receiving member  205  has rotated relative to engaging member  210 , causing female lugs  305  to interlock or engage with male lugs  405 . Likewise, female lugs  305  and male lugs  405  may be disengaged by rotating receiving member  205  in an opposing direction.  FIG. 5   c  illustrates a cross sectional perspective side view of the embodiment illustrated in  FIG. 5   b.    
         [0063]      FIG. 6   a  illustrates the cross sectional view of second joint  225 . Second joint  225  may be divided into two sections, section  605  (shown in  FIG. 6   c ) and section  610 . Section  610  is provided with pivoting means so that arm  230  may pivot relative to second joint  225  and vice versa. In section  610 , arm  230  is pivotably connected to bracket  626  through hook  615 . Hook  615  is fixed onto bracket  626  and passes through opening  630  in arm  230 . The connection between hook  615  and opening  630  is such that it allows arm  230  to pivot about this connection. In other words, arm  230  may move along planes that are normal to the longitudinal axis of second joint  225 . As this embodiment only allows for the movement of arm  230  along planes normal to the longitudinal axis of second joint  225  or the movement of second joint  225  along planes normal to the longitudinal axis of arm  230 , this ensures that engaging member  210  does not accidentally disengage due to the relative pitch, roll and yaw motions of the two floating structures. The relative translational motions of the two floating structures may be accommodated by this joint. Resilient material  625  is positioned adjacent the end of arm  230  located within bracket  626  thereby damping and absorbing the relative heave, sways and surge motions of the two floating structures. A cross sectional perspective side view of section  610  is shown in  FIG. 6   b .  FIG. 6   c  illustrates a cross sectional side view of section  605  and section  610  of first joint  225 . Unlike section  610 , pivoting means are not provided in section  605 . Instead, section  605  has bracket  606  that is used to connect an end of first arm  220  to second joint  225 . 
         [0064]    Another embodiment of second joint  225  is illustrated in  FIG. 7 . In this embodiment, section  605  is provided with pivoting means so that second joint  225  may pivot relative to first arm  220  and vice versa. In section  605 , first arm  220  is pivotably connected to bracket  606  through hook  705 . Hook  705  is fixed onto bracket  606  and passes through opening  715  in first arm  220 . The connection between hook  705  and opening  715  allows first arm  220  to pivot about this connection. In other words, first arm  220  may move along planes that are normal to the longitudinal axis of second joint  225 . Similarly, as this embodiment only allows for the movement of first arm  220  along planes normal to the longitudinal axis of second joint  225  or the movement of second joint  225  along planes normal to the longitudinal axis of first arm  220 , this ensures that engaging member  210  may not accidentally disengage due to the motions of the two floating structures. To dampen the movement between first arm  220  and second joint  225 , resilient material  710  is placed surrounding the end of first arm  220  that is located within bracket  606 . This configuration dampens the relative translational movements between the two floating structures. 
         [0065]    In other embodiments of the invention, a third joint that is connected to another that arm may be connected between arm  230  and coupling apparatus  235 . This third joint in combination with this arm could be a rotatable joint-arm combination that allows the first floating structure to rotate relative to the second floating structure and vice versa. Such a joint is illustrated in  FIG. 8   a . Third joint  240  consists of two sections, section  805  (shown in  FIG. 8   c ) and section  810 . As shown in  FIG. 8   a , third arm  245  has protrusion  820  that extends through an opening of bracket  811 . Anchor  830 , which is wider than opening  825 , is positioned at the end of protrusion  820 . As the width or diameter of protrusion  820  is smaller than the opening at the end of bracket  811 , protrusion  820  is not in contact with opening  825 . Therefore, arm  245  may rotate freely about its own longitudinal axis. Anchor  830  prevents protrusion  820  from dislodging from bracket  811 , maintaining the coupling between arm  24  and joint  240 . Resilient material  815  is positioned adjacent the end of arm  245  located within bracket  811 . Resilient material  815  acts to limit and damp the rotational movement of arm  245 . In some embodiments of the invention, a dry lubricant layer may be disposed at the interface between resilient material  815  and the end of arm  245  that is in contact with resilient material  815 . This dry lubricant layer minimizes the friction between these two components thereby assisting in the rotation of arm  245 . In operation, the torsional oscillations would be absorbed by the resilient material. This ensures that the lifespan of the system is enhanced as the resilient element is able to accommodate all the small movements and motions better than other types of mechanical components, e.g. bearing caps. A cross sectional side perspective view of section  810  is shown in  FIG. 8   b . Sections  805  and  810  of joint  240  are shown in  FIG. 8   c . Unlike section  810 , section  805  has not been provided with rotatable or pivoting means. Section  805  has bracket  806  that is used to connect to an end of arm  230 . Joint  240  allows for the relative pitch, roll and yaw motions between the two floating structures to be accommodated. 
         [0066]    In further embodiments of the invention, section  805  is provided with pivoting means. As illustrated in  FIG. 9 , bracket  916  is provided with hook  910  that passes through opening  905  on arm  230 . Arm  230  is pivotably connected to third joint  240  through the connection between hook  910  and opening  905 . This connection thereby allows arm  230  to move along planes that are normal to the longitudinal axis of third joint  240  or allows third joint  240  to move along planes that are normal to the longitudinal axis of arm  230 . The end of arm  230  positioned within bracket  916  is surrounded by resilient material  915  which acts as a damper, absorbing the motion of the arm relative to the joint. Protrusion  820  passes through opening  825  of bracket  811  into bracket  916 . Anchor  830  moves freely around an hollow area in bracket  916  allowing arm  245  to rotate freely about its longitudinal axis. Not only does this embodiment allow joint  240  to accommodate for the relative rotational movements between the two floating structures, this embodiment also allows for the translational movement to be accommodated as well. 
         [0067]    In other embodiments of the invention, coupling apparatus  235  is replaced by hydraulic piston  255  and skid assembly  260  as illustrated in  FIG. 10 . In this configuration, one end of arm  230  will be connected to hydraulic piston  255  while skid assembly  260  will be positioned at a specific location on tender assist drilling platform  105  as previously discussed. Hydraulic piston  255  is powered by pressurized hydraulic fluid, such as oil. Typically, hydraulic piston  255  will have a barrel, in which a piston connected to a rod moves in and out from. When the distance between the two floating structures is to be increased, the rod will extend out of hydraulic piston  255  moving the two floating structures away from one another. When the two floating structures are to be brought closer, the rod retracts back into the hydraulic piston drawing the two structures closer together. The hydraulic piston and skid assembly also absorbs the relative surge motions between the floating structures. Furthermore, after engaging member  210  has disengaged from receiving member  205 , hydraulic piston  255  will retract, causing the arm and joint system to pull away from receiving member  205 . Skid assembly  260  is used to allow the separation between the two structures to be increased or decreased accordingly. Skid assembly  260  consists of tracks positioned on tender assist drilling platform  105  on which hydraulic piston  255  may slide along. In an exemplary embodiment, skid assembly  260  may consist of tracks that are 10 metres in length while hydraulic piston  255  may extend up to 5 metres.  FIG. 11  illustrates an embodiment of the invention when hydraulic piston  255  is fully extended. One skilled in the art will recognize that the hydraulic piston and skid assembly configuration may be connected to the ends of either arm  230  or the end of subsequent arms, e.g. arm  245 , etc., without departing from this invention. 
         [0068]    The movements of the arms and joints relative to one another will be described with reference to  FIGS. 12 to 17 . In these drawings, it is assumed that tender assist drilling platform  105  has been successful coupled to tension leg platform  110  using an embodiment of coupling system  100 . As shown in  FIG. 12 , engaging member  210  is connected to first joint  215 . First joint  215  is provided with pivoting means that allow engaging member  210  to move along planes that are normal to the longitudinal axis of first arm  220 . As an example, arrow A shows that engaging member  210  is able to move upwards, downwards, and sideways following the wave induced motions of tension leg platform  110 .  FIG. 13  illustrates another embodiment of the invention in which second joint  225  is provided with pivoting means at the section that is connected to arm  230 . Therefore, arm  230  is now able to move along planes that are normal to the longitudinal axis of the second joint. As an example, arrow B shows that arm  230  is able to move upwards, downwards and sideways, following the motions of tension leg platform  110  in the ocean. In this embodiment, there are now two joints that are able to compensate for the relative translational movements of the two floating structures. 
         [0069]    In yet another embodiment of the invention, third joint  240  is connected between arm  230  and arm  245 . This embodiment is illustrated in  FIG. 14 . Third joint  240  is provided with rotatable means thereby allowing arm  245  to rotate about its longitudinal axis. Arrow C illustrates the rotational movement of arm  245 . In this embodiment, these three joints allow for the relative translational and rotational movements of the two floating structures to be accommodated. In the embodiment shown in  FIG. 15 , the section of third joint  240  that is coupled to arm  230  is provided with pivoting means. Therefore, second joint  240  is now able to move along planes that are normal to the longitudinal axis of arm  230 . Arrow D illustrates an exemplary direction of such a movement. In such an embodiment, the two floating structures may be heaving, pitching, swaying, surging, and rolling relative to each other and coupling system  100  would still be able to remain connected between these two structures as all the random movements would be absorbed by these three joints. 
         [0070]    Yet another embodiment of the invention is illustrated in  FIG. 16 . In this embodiment, unlike the previous embodiment, third joint  240  is provided with pivoting means instead. This means that arm  245  is able to move along planes that are normal to the longitudinal axis of third joint  240 . Arrow C shows the direction of such an exemplary movement.  FIG. 17  illustrates yet another embodiment of the invention whereby third joint  240  is provided with yet another pivoting means allowing third joint  240  to move along planes that are normal to the longitudinal axis of arm  230 . An example of such movement is illustrated by the directions of arrow D. 
         [0071]      FIG. 18  illustrates an embodiment of coupling system  100 . In this embodiment, engaging member  210  has been received by receiving member  205 . The lugs on the respective modules have interlocked with one another creating a stable connection. Arm  220  is connected to first joint  215  and second joint  225 . First joint  215  and second joint  225  are both provided with pivoting means. Arm  230  is connected to second joint  225  and third joint  240  while arm  245  is connected to third joint  240  and to a coupling apparatus disposed on the second floating structure. Third joint  240  is provided with rotational means allowing arm  245  to rotate about its longitudinal axis. This combination of arms and joints allows this embodiment of coupling system  100  to easily accommodate the for the relative translational and rotational movements of the two floating structures while maintaining the two floating structures at safe operating distances. 
         [0072]    The above is a description of a coupling system for coupling first floating structures to a second floating structure. It is foreseen that those skilled in the art can and will design alternative embodiments of this invention as set forth in the following claims.