Patent Publication Number: US-11383801-B2

Title: Mooring device and a floating unit comprising at least one mooring device

Description:
The present invention is related to a mooring device for mooring of a floating unit to a floating or non-floating structure and a floating unit and a non-floating structure comprising one or more such mooring devices. 
     Floating units of various types such as semi-submersible units, ships, barges and other types of floating unit, for various reasons, at times usually need to be moored to a floating structure, such as a semi-submersible unit, a ship, a barge or other types of floating vessels, or to a non-floating structure, such as a quay, a pier or similar non-floating structure that the floating unit can be moored to. 
     Transfer of temperate fluids from ship to shore is today achieved, among other methods, through a submerged flexible hose, which is lifted from the seabed and connected directly to the vessel manifold. 
     The handling of pipes for cryogenic applications will, however, often be difficult for the ship&#39;s lifting equipment and manifold since the transfer of cryogenic fluids through the pipes will cause accumulation of an external ice layer. The transfer of cryogenic liquids through any pipe in contact with water therefore requires the pipe to be extensively insulated, resulting in considerably larger weight per meter than pipes for transfer of temperate fluids. The insulation is also required to avoid excessive heat loss. 
     The use of loading systems comprising various types of floating concepts are known in the offshore petroleum industry. Environmental conditions offshore are often harsh, which significantly increases the requirements and cost for systems to operate in these conditions. 
     A few mooring devices, other than traditional ropes, wires or the like, are known in the art. For example, to overcome at least some of the problems of the prior art, a floating unit for transfer of a fluid or electric power between a floating structure and a floating or non-floating structure has been proposed and described in the publication WO 2015/107147 A1. There is, however, a need for further improvement of the mooring system that is disclosed in this publication that can be used to moor a floating unit to a floating or non-floating structure. 
     Other known mooring systems are disclosed in the publications US 2004/154518 A1 and WO 2009/048342 A2. 
     An objective of the present invention has therefore been to provide a mooring device for mooring a floating unit to a floating or non-floating structure that allows vertical translational motion and rotational motion about any horizontal axis of the floating unit relative to the floating or non-floating structure while lateral translational motion and rotational motion about a vertical axis of the floating unit relative to the floating or non-floating structure is substantially restricted. 
     Another objective of the present invention has been to optimize the transfer of loads through the mooring device where the loads are caused by relative motions between a floating unit and a floating or non-floating structure when the floating unit is moored to the floating or non-floating structure with one or more mooring devices according to the present invention. 
     Another objective has been to make it possible to obtain a close mooring distance between a floating unit and a floating or non-floating structure also when there is a large freeboard difference between the floating unit and the floating or non-floating unit. 
     Another objective has been to obtain a mooring device that provides a robust and reliable connection between the floating unit and the floating or non-floating structure to which the floating unit is moored. 
     Another objective has been to obtain a mooring device with low manufacturing and installation costs and low maintenance costs. 
     These objectives are achieved by a mooring frame as defined in claim  1 , a floating structure as defined in claim  21 , a non-floating structure as defined in claim  22 , and use of the mooring frame as defined in claims  29  and  30 . The independent claims define further embodiments of mooring frame and the floating structure. 
     The mooring device disclosed herein can be used to temporarily moor a floating unit, such as a vessel or a platform, to another floating or non-floating unit, vessel or structure. The mooring device absorbs forces and energy that arise from relative motions between the floating unit and the floating or non-floating structure. The forces and energy that arises from relative motions taking place in two main directions in a horizontal plane, a first direction and a second direction, which are typically the x-direction and y-direction in a Cartesian coordinate system, are absorbed by the mooring device. 
     Typically, two mooring devices may be used to moor the floating unit which are connected to the floating unit or to the floating or non-floating unit, vessel or structure with a joint that allows rotational motion about three independent axes, for example universal joints. The frames are provided with vacuum pads or electromagnetic pads for temporary mooring of the floating unit to the floating or non-floating unit or vessel and thereby transferring loads that arise from the relative motion. The mooring devices may be provided with mooring units and support elements that absorb energy from relative translational motion in the horizontal plane by using integrated stiffness elements, for example spring elements. Damping elements may also be included if that is required. 
     There is disclosed a mooring device for mooring of a floating unit to a structure where the structure is floating or non-floating. The mooring device is adapted to be mounted on the structure and the mooring device comprises:
         a first mooring arm for transferring and/or absorbing forces and energy that arises when the floating unit is moored to the structure and the floating unit moves relative to the structure, the first mooring arm having a longitudinal axis,   a second mooring arm for transferring and/or absorbing forces and energy that arises when the floating unit is moored to the structure and the floating unit moves relative to the structure, the second mooring arm having a longitudinal axis,   a joint device comprising a support element, a support element joint device and an attachment unit joint device, the support element joint device being connected to the support element and the attachment unit joint device being attached to or connected to the support element,   an attachment unit that is attached to the attachment unit joint device, the attachment unit joint device allowing rotation of the attachment unit about two or three independent axes of rotation relative to the support element, wherein   the support element joint device comprises a first mooring arm joint device connected to or attached to the support element and a second mooring arm joint member connected to or attached to the support element,   the first mooring arm comprises a first end portion and a second end portion, the second end portion being adapted for attachment to the floating unit or the structure, and the first end portion being attached to the first mooring arm joint device,   the second mooring arm comprises a first end portion and a second end portion, the second end portion being adapted for attachment to the floating unit or the structure, and the first end portion being attached to the second mooring arm joint device,   the support element joint device allows rotation of the support element about one rotational axis A only, relative to the first mooring arm and/or the second mooring arm in all positions of the axis A, the rotational axis A being perpendicular to a plane that is formed by the longitudinal axis of the first mooring arm and the longitudinal axis of the second mooring arm in all positions of the first mooring arm and the second mooring arm.       

     The second mooring arm joint device may allow rotation of the second mooring arm about zero, one or two or three independent axes of rotation relative to the support element. 
     The first mooring arm joint device may allow rotation of the first mooring arm about one or two or three independent axes of rotation relative to the support element. 
     The first mooring arm is telescopic and comprises first telescopic part comprising the first end portion of the first mooring arm, and a second telescopic part comprising the second end portion of the first mooring arm. 
     The second mooring arm is preferably telescopic and comprises first telescopic part comprising the first end portion of the second mooring arm, and a second telescopic part with the second end portion of the second mooring arm. 
     The first mooring arm may comprise a first double-acting, hydraulic cylinder and that the second arm comprises a second double-acting, hydraulic cylinder. 
     The first double-acting hydraulic cylinder and the second double-acting hydraulic cylinder are preferably passive hydraulic cylinders. 
     The first mooring arm joint device of the support element joint device or the second mooring arm joint device of the support element joint device is preferably securely attached to the support element. 
     The support element preferably comprises a base plate element, a first side plate element that is securely attached to the base plate element and a second side plate element that is securely attached to the base plate element, the first mooring arm and the second mooring arm being rotatably connected to the first side plate element and the second side plate element. 
     The support element joint device further preferably comprises a bolt element that goes through the first mooring arm joint device, the second mooring arm joint device, the first side plate element and the second side plate element such that the first mooring arm and the second mooring arm are rotatably connected to the support element about a longitudinal axis A of the bolt element. 
     In an embodiment, the first mooring arm joint device may be fork-shaped, the second mooring arm joint device is plate-shaped and adapted to fit into the fork-shaped first mooring arm joint device, the support element may be fork-shaped and the fork-shaped first mooring arm joint device may be adapted to fit into the fork-shaped support element, such that the bolt element goes through the first mooring arm joint device, the second mooring arm joint device, the first side plate element and the second side plate element. 
     The fork-shaped first mooring arm joint device may be securely attached to the support element, i.e. the first side plate element and/or the second side plate element. 
     The second end portion of the first mooring arm may be attached to a first attachment joint device that is adapted for attachment to the floating unit or the structure and allows rotation of the first mooring arm about three independent axes relative to the floating unit or the structure. 
     The second end portion of the second mooring arm may be attached to a second attachment joint device that is adapted for attachment to the floating unit or the structure and allows rotation of the second mooring arm about three independent axes relative to the floating unit or the structure. 
     This arrangement allows each of the first and second mooring arms to rotate about two different axes—about the axis A that is perpendicular to the plane formed by the longitudinal axes of the first and second mooring arms as defined above and about a second axis that passes through the first and second attachment joint devices respectively. When the arms are moving sideways, i.e. the first and second mooring arms move in a plane that is perpendicular to axis A, the axis A will be parallel to the rotational axes passing through the first and second attachment joint devices. 
     In an embodiment, the support element may comprise a plate element to which the first mooring arm joint device and the second mooring arm joint device are securely attached, the first mooring arm joint device and the second mooring arm joint device allowing rotation of the first mooring arm and the second mooring arm respectively about three independent axes of rotation. 
     The first mooring arm joint device and the second mooring arm joint device are preferably ball joints and/or universal joints. 
     The support element joint device preferably further comprises a restricting arm comprising a first end portion and a second end portion, the second end portion being adapted for attachment to the floating unit or the structure, and the first end portion being securely attached to the support element. 
     The restricting arm is preferably telescopic comprising a first telescopic part comprising the first end portion of the restricting arm, and a second telescopic part comprising the second end portion of the restricting arm. 
     The second end portion of the restricting arm is attached to an attachment joint device that is adapted for attachment to the floating unit or the structure and allows rotation of the restricting arm about two independent axes relative to the floating unit or the structure. The attachment joint device may for example be a cardan joint. 
     The restricting arm may be provided with a polygonally shaped cross-section such that rotation of the support element about a longitudinal axis of the restricting arm is prevented. 
     The first end portion of the restricting arm may be securely attached to the support element by welding or with at least one bolt element. 
     In an embodiment, the support element may comprise a holder element, a first pin element that is securely attached to the holder element and a second pin element that is securely attached to the holder element, the first mooring arm and the second mooring arm being rotatably connected to the first pin element and the second pin element respectively about an axis A that passes through the first pin element and the second pin element. 
     The fork-shaped first mooring arm joint device may be securely attached to the support element, for example to the holder element of the support element and/or to the first and/or second pin element of the support element. Alternatively, the fork-shaped second mooring arm joint device may be securely attached to the support element, for example to the holder element of the support element and/or to the first and/or second pin element of the support element. 
     The first mooring arm joint device may be fork-shaped and adapted to be rotatably connected to the first pin element and the second pin element of the holder element, and the second mooring arm joint device may be fork-shaped and adapted to be rotatably connected to the first pin element and the second pin element of the holder element. 
     The first pin element may be attached to a first side face of the holder element and the second pin element may be attached to a first side face of the holder element, where the first side face and the second side face are opposite exterior sides of the holder element. 
     The mooring device further may comprise a support arm comprising a first end portion to which a first attachment joint device is attached that is attached to the support element, and a second end portion to which a second attachment joint device is attached that is adapted for attachment to the floating unit or the structure, the first attachment joint device allowing rotation of the support arm about three independent axes relative to the support element and the second attachment joint device allowing rotation of the support arm about three independent axes relative to the floating unit or the structure. 
     Instead of one support arm for every mooring device, a support arm for every mooring arm may also be used. 
     The support arm is preferably telescopic and comprises a first telescopic part comprising the first end portion of the support arm and a second telescopic part comprising the second end portion of the support arm. 
     The attachment unit joint device may comprise a ball element that is securely attached to the support element and a ball support element that is securely attached to the attachment unit. 
     The attachment unit joint device may comprise a ball element that is securely attached to the attachment unit and a ball support element that is securely attached to the support element of the joint device. 
     The attachment unit preferably comprises a frame device to which at least one attachment member is rotatably attached and to which the attachment unit joint device is attached. 
     The at least one attachment member preferably comprises a vacuum pad or an electromagnetic pad. 
     A floating unit is also provided comprising at least one mooring device as described above, wherein the at least one mooring device is attached to the floating unit for mooring of the floating unit to a structure, the structure being floating or non-floating. 
     A non-floating structure is also provided comprising at least one mooring device as described above, wherein the at least one mooring device is attached to the non-floating structure for mooring of a floating unit to the non-floating structure. 
     The floating unit or the non-floating structure to which the at least one mooring device is attached, may comprise at least one fender device to prevent or cushion impacts against the at least one mooring device. 
     The at least one fender device is preferably compressible in a direction towards the floating unit or the non-floating structure. 
     The at least one fender device, in an uncompressed state, preferably extends further out from the floating unit or the non-floating structure than the at least one mooring device when mooring device is fully retracted. 
     The at least one fender device, in a compressed state, preferably extends substantially equally far out from the floating unit or the non-floating structure as the at least one mooring device when mooring device is fully retracted. 
     The floating unit or the non-floating structure may comprise one or a plurality of mooring devices and at least one fender device mounted to the floating unit or the non-floating structure, on either side of the mooring device or mooring devices. 
     The mooring device may be mounted on a floating unit, centrally along a side of floating unit. 
     A use of the mooring device as described above would be for mooring of a floating unit to a floating or non-floating structure, wherein the mooring device is attached to the floating unit. 
     A further use of the mooring device as described above would be for mooring of a floating unit to a floating structure or a non-floating structure, wherein the mooring device is attached to the floating structure or the non-floating structure. This means that instead of mounting the mooring device to the floating unit, the mooring unit is mounted on the floating or non-floating structure that the floating unit is moored to, for example a ship, a pier or any other type of floating or non-floating structure to which a floating unit may be moored. 
    
    
     
       In the following, some non-limiting embodiments of the present invention will be described in more detail, with reference to the figures where: 
         FIG. 1  shows a first embodiment of a mooring device according to the present invention. 
         FIG. 2  shows the first mooring arm, the second mooring arm and the joint device of the first embodiment of the present invention shown in  FIG. 1 . 
         FIG. 3  shows the first mooring arm, the second mooring arm, the support arm and the joint device of the first embodiment of the present invention shown in  FIGS. 1 and 2 . 
         FIG. 4  shows the joint device of the first embodiment of the present invention shown in  FIGS. 1-3 . 
         FIG. 5  shows a frame device of the attachment unit of the first embodiment of the present invention shown in  FIGS. 1-4 . 
         FIG. 6  shows the frame device in  FIG. 5  provided with a weight element. 
         FIG. 7 a    shows a second embodiment of a mooring device according to the present invention. 
         FIG. 7 b    shows the cross-section A-A of the restricting arm of the second embodiment of the present invention as indicated in  FIG. 7   a.    
         FIG. 8  shows a top view of a third embodiment of a mooring device according to the present invention. 
         FIG. 9  shows a side view of the third embodiment of a mooring device according to the present invention as shown in  FIG. 8 . 
         FIG. 10  shows a variant of the support element of the third embodiment of a mooring device according to the present invention as shown in  FIGS. 8 and 9 . 
         FIG. 11  shows a side view of a floating unit including a mooring device according to the present invention where the support arm is mounted below the first and second mooring arms. 
         FIG. 12  shows a side view of a floating unit including a mooring device according to the present invention where the support arm is mounted above the first and second mooring arms. 
         FIG. 13  shows a ship including a mooring device according to the present invention. 
         FIG. 14  shows a top view of a floating unit including a mooring device according to the present invention and two fender devices mounted to the floating unit on either side of the mooring device. 
         FIG. 15  shows a top view of a floating unit including two mooring devices according to the present invention and two fender devices mounted to the floating unit on either side of the two mooring devices. 
         FIG. 16  shows a front view of a floating unit including a mooring device according to the present invention and two fender devices mounted to the floating unit on either side of the mooring device. 
         FIG. 17  shows a side view of a floating unit including a mooring device according to the present invention with the attachment unit in two different positions, i.e. positions before and after a movement of the floating unit relative to the floating or non-floating structure to which the floating unit is moored. 
         FIG. 18  shows a front view of a floating unit including a mooring device according to the present invention where the attachment unit remain in the same position while the floating unit is shown in two different positions, before and after the floating unit has tilted about a rotational axis that is substantially vertical to the floating or non-floating structure to which the floating unit is moored. 
         FIG. 19  shows a side view of a floating unit including a mooring device according to the present invention where the attachment unit remain in the same position while the floating unit is shown in two different positions, before and after the floating unit has tilted about a rotational axis that is substantially parallel to the floating or non-floating structure to which the floating unit is moored. 
     
    
    
     The figures show three different embodiments of a mooring device  10  according to the present invention and two variants of one of the embodiments. The mooring device  10  comprises a joint device  28  that can be designed in different ways, and the three embodiments shown in the figures illustrate three different embodiments of the joint device  28  with two variants of one of the variants. It should be noted that the same features of the different embodiments of the invention shown in the figures have been provided with the same reference numbers. 
       FIGS. 1-6  show a mooring device  10  according to the present invention. The mooring device  10  comprises a first mooring arm  12  comprising a first end portion  15  and a second end portion  16 . The first end portion  15  is attached to a joint device  28 , for example with one or more bolts, as indicated in the figures, by welding or any other suitable fastening device or method. The mooring device  10  further comprises a second mooring arm  20  comprising a first end portion  23  and a second end portion  24 . The first end portion  23  is attached to the joint device  28 , for example with one or more bolts, as indicated in the figures, by welding or any other suitable fastening device or method. The first mooring arm  12  comprises a longitudinal axis passing through the first mooring arm in its longitudinal direction and passing through the first end portion  15  and the second end portion  16 . The second mooring arm  20  comprises a longitudinal axis passing through the second mooring arm in its longitudinal direction and passing through the first end portion  23  and the second end portion  24 . 
     To the second end portion  16  of the first mooring arm  12 , a first attachment joint device  17  is securely attached, for example with one or more bolt elements, by welding or any other suitable fastening method. The first attachment joint device  17  is adapted to be securely attached to a floating unit  110  or a floating or non-floating structure  125 , for example by bolts, welding or any other suitable fastening means or methods for fastening the first attachment joint device  17 . The first attachment joint device  17  preferably allows the first mooring arm  12  to rotate about three independent axes relative to a floating unit  110  or the floating or non-floating structure  125  that the mooring device  10  is attached to. For example, the first attachment joint device  17  may be a ball joint or a universal joint but may also be any other joint device that allows movement of the first mooring arm  12  about three independent axes relative to the floating unit  110  or the floating or non-floating structure  125  that the mooring device  10  is attached to. 
     The first mooring arm  12  is preferably telescopic as is shown in for example  FIG. 13 , comprising a first telescopic part  13  and a second telescopic part  14  where the first telescopic part  13  is arranged slidingly within the second telescopic part  14  or vice versa. The first mooring arm  12  will typically comprise a piston/cylinder assembly comprising shock absorbing elements, such as one or more springs, and/or one or more damping devices. Such piston/cylinder assemblies are well known in the art and will not be described in further detail here. 
     As indicated in  FIGS. 14 and 15 , the first telescopic part  13  of the first mooring arm  12  comprises the first end portion  15  of the first mooring arm  12  as indicated in the figures. Likewise, the second telescopic part  14  of the first mooring arm  12  comprises the second end portion  16  of the first mooring arm  12  as indicated in the figures. 
     The first attachment joint device  17  is therefore preferably attached to the second telescopic part  14  of the first mooring arm  12  and adapted for attachment to a floating unit  110  or a floating or non-floating structure  125 . 
     To the second end portion  24  of the second mooring device  20 , a second attachment joint device  25  is securely attached, for example with one or more bolt elements, with welding or any other suitable fastening method. The second attachment joint device  25  is adapted to be securely attached to a floating unit  110  or a floating or non-floating unit  125 , for example by bolts, welding or any other suitable fastening means or methods for fastening the second attachment joint device  25 . The second attachment joint device  25  preferably allows the second mooring arm  20  to rotate about three independent axes relative to a floating unit  110  or the floating or non-floating structure  125  that the mooring device  10  is attached to. For example, the second attachment joint device  25  may be a ball joint or a universal joint but may also be any other joint device that allows movement of the second mooring arm  20  about three independent axes relative to the floating unit  110  or the floating or non-floating structure  125  that the mooring device  10  is attached to. 
     The second mooring arm  20  is preferably telescopic as is shown in for example  FIG. 14 , comprising a first telescopic part  21  and a second telescopic part  22  where the first telescopic part  21  is arranged slidingly within the second telescopic part  22  or vice versa. The second mooring arm  20  will typically comprise a piston/cylinder assembly comprising shock absorbing elements, such as one or more springs, and/or one or more damping devices. Such piston/cylinder assemblies are well known in the art and will not be described in further detail here. 
     As shown clearly in  FIGS. 14 and 15 , the first telescopic part  21  of the second mooring arm  20  comprises the first end portion  23  of the second mooring arm  20  as indicated in the figures. Likewise, the second telescopic part  22  of the second mooring arm  20  comprises the second end portion  24  of the second mooring arm  20  as indicated in the figures. 
     The second attachment joint device  25  is therefore preferably attached to the second telescopic part  22  of the second mooring arm  20  and adapted for attachment to a floating unit  110  or a floating or non-floating structure  125 . 
     The mooring device  10  further comprises an attachment unit  66  that is attached to the joint device  28  of the mooring device  10 . 
     The attachment unit  66  comprises a frame device  67  and at least one, but preferably a plurality of attachment members  85 ,  87 ,  89 ,  91  that are independently attached to the frame device  67  with respective joint devices that allows the attachment members  85 ,  87 ,  89 ,  91  to rotate about one, two or three independent axes relative to the frame device  67 . The joint devices may for example be a bolt element, a cardan joint, a ball joint, a universal joint or any other joint device that will allow the attachment members  85 ,  87 ,  89 ,  91  to move independently about the desired number of independent axes. Vulcanized vacuum pads may also be used which are fairly free to move but is almost completely locked in their positions. 
     The frame device  67  may obviously be designed in many different ways. One example is shown in  FIGS. 1-6  where the frame device  67  comprises a first frame member  68 , a second frame member  74  and a third frame member  80 . The third frame member  80  is shown in a substantially vertical position in the figures and the first frame member  68  is securely attached to first end portion  81  of the third frame member  80  while the second frame member  74  is securely attached to a second end portion  82  of the third frame member  80  as shown in  FIGS. 5 and 6 . 
     The first frame member  68  comprises a first end portion  69  where a first joint device  70  is arranged or mounted. The first attachment member  85  is connected to the first joint device  70  such that the first attachment member  85  is rotatably attached to the frame device  67 . The first joint device  70  shown is a bolt element which will allow the first attachment member  85  to rotate about one axis relative to the frame device  67 . However, other types of joint devices may also be employed to connect the first attachment member  85  to the first end portion  69  that will allow the first attachment member  85  to rotate about one, two or three axes relative to the first end portion  69  and the frame device  67  as mentioned above. 
     The first frame member  68  further comprises a second end portion  71  where a second joint device  72  is arranged or mounted. The fourth attachment member  91  is connected to the second joint device  72  such that the fourth attachment member  91  is rotatably attached to the frame device  67 . The second joint device  72  shown is a bolt element which will allow the fourth attachment member  91  to rotate about one axis relative to the frame device  67 . However, other types of joint devices may also be employed to connect the fourth attachment member  91  to the second end portion  71  that will allow the fourth attachment member  91  to rotate about one, two or three axes relative to the second end portion  71  and the frame device  67  as mentioned above. 
     The second frame member  74  comprises a first end portion  75  where a third joint device  76  is arranged or mounted. The second attachment member  87  is connected to the third joint device  76  such that the second attachment member  87  is rotatably attached to the frame device  67 . The third joint device  76  shown is a bolt element which will allow the second attachment member  87  to rotate about one axis relative to the frame device  67 . However, other types of joint devices may also be employed to connect the second attachment member  87  to the first end portion  75  that will allow the second attachment member  87  to rotate about one, two or three axes relative to the first end portion  75  and the frame device  67  as mentioned above. 
     The second frame member  74  further comprises a second end portion  77  where a fourth joint device  78  is arranged or mounted. The third attachment member  89  is connected to the fourth joint device  78  such that the third attachment member  89  is rotatably attached to the frame device  67 . The fourth joint device  78  shown is a bolt element which will allow the third attachment member  89  to rotate about one axis relative to the frame device  67 . However, other types of joint devices may also be employed to connect the third attachment member  89  to the second end portion  77  that will allow the third attachment member  89  to rotate about one, two or three axes relative to the second end portion  77  and the frame device  67  as mentioned above. 
     By choosing other types of joint devices, the attachment members  85 ,  87 ,  89 ,  91  may therefore be made to be rotatable about two or three independent axes relative to the frame device  67  instead of one axis as shown in  FIGS. 1-6 . 
     As an alternative to what is mentioned above, the attachment members  85 ,  87 ,  89 ,  91  may be provided with respective spherical joints which are mounted to the bolt elements  70 ,  72 ,  76 ,  78 . This arrangement will allow the attachment members  85 ,  87 ,  89 ,  91  to move in three degrees of freedom. 
     As shown in  FIG. 1 , the attachment unit  66  may be provided with four attachment members, a first attachment member  85  comprising a first attachment element  86  that is rotatably attached to the frame device  67  with a joint device in the form of a bolt element  70 , a second attachment member  87  comprising a second attachment element (not visible on  FIG. 1 ) that is rotatably attached to the frame device  67  with a joint device in the form of a bolt element  76 , a third attachment member  89  comprising a third attachment element  90  that is rotatably attached to the frame device  67  with a joint device in the form of a bolt element  78  and a forth attachment member  91  comprising a fourth attachment element  92  that is rotatably attached to the frame device  67  with a joint device in the form of a bolt element  72  as further indicated in  FIGS. 5 and 6 . 
     It should, however, be mentioned that the attachment unit  66  may be provided with any suitable and desirable number of attachment members other than four as shown in  FIG. 1 . The attachment unit  66  may for example be provided with two attachment members  85 ,  87  as indicated in  FIGS. 15 and 17 , or any other number of attachment members. 
     As shown in  FIG. 6 , the attachment unit  66  may comprise a weight element  95 . The weight element  95  is shown attached to the third frame member  80  or may form the second end portion  82  of the third frame member  80 . The weight element  95  extends in a direction away from the attachment members  85 ,  87 ,  89 ,  91  of the attachment unit  66  and towards the floating unit  110  or floating or non-floating structure  125  on which the mooring device  10  is mounted. The weight element  95  acts as a counter weight and helps to balance the attachment unit  66  and keep it in a desired, substantially vertical position when the attachment unit is not attached to any floating unit or floating or non-floating structure. 
     The frame device  67  may further comprise, as shown in  FIGS. 5-6 , a recess for attachment of an attachment unit joint device  61  for attachment of the attachment unit  66  to the joint device  28  mentioned above. The attachment of the attachment unit  66  to the attachment unit joint device  61  varies slightly between the three embodiments of the mooring device  10  shown in the figures and will be further described below. 
     The first, second, third and fourth attachment members  85 ,  87 ,  89 ,  91  are preferably vacuum pads or electromagnetic pads that can be attached to an outer surface of a floating unit  110  or a floating or non-floating structure  125 , for example to the outer surface of the hull of an LNG-carrier, and later be detached from said outer surface. Such vacuum pads and electro-magnetic pads are well known in the art and will not be described in any further detail here. 
     It should also be mentioned that the attachment unit  66  described above and shown in  FIGS. 1-6 , may also be included in the second embodiment of the mooring device  10  shown in  FIGS. 7 a - b    and the third embodiment of the mooring device  10  shown in  FIGS. 8-9 . 
     The mooring device  10  comprises a joint device  28  as mentioned above. The joint device  28  comprises three main parts, a support element  30 , an attachment unit joint device  61  that is attached or connected to the support element  30  and a support element joint device  43  that is attached or connected to the support element  30 . The joint device  28  is what separates the three embodiments of the mooring device  10  shown in the figures from each other, and the three different designs of the joint device  28  will be described in connection with the description of each embodiment. 
     The joint device  28  of the first embodiment of the mooring device  10  shown in  FIGS. 1-6 , comprises a support element  30  that comprises a base plate element  32 , a first side plate element  33  that is securely attached to the base plate element  32 , for example by welding, and a second side plate element  34  that is securely attached to the base plate element  32 , for example by welding. As can be seen from the figures, the support element  30  is preferably generally U-shaped or fork-shaped. 
     The joint device  28  of the first embodiment of the mooring device  10  further comprises a support element joint device  43  comprising a first mooring arm joint device  44  and a second mooring arm joint device  45 . 
     The first mooring arm joint device  44  is securely attached to the first end portion  15  of the first mooring arm  12 , for example by welding or by one or more bolts. The second mooring arm joint device  45  is securely attached to the second mooring arm  20 , for example by welding or by one or more bolts. 
     The first mooring arm joint device  44  may have a generally U-shape or fork-shape as indicated in  FIGS. 1-4  and a size so that it fits snugly within the gap of the fork-shaped support element  30 . The second mooring arm joint device  45  may be generally plate-shaped and have a size so that it fits snugly within the gap of the fork-shaped first mooring arm joint device  44 . 
     The support element joint device  43  further comprises a bolt element  46  that goes through or passes through corresponding holes in the first side plate element  33  and the second side plate element  34  of the fork-shaped support element  30 , the fork-shaped first mooring arm joint device  44  of the support element joint device  43  and the second mooring arm joint device  45  of the support element joint device  43 . 
     This allows a configuration where both the first mooring arm  12  and the second mooring arm  20  are rotatably connected to the support element joint device  43 , i.e. the first mooring arm  12  and the second mooring arm  20  are both rotatable about an axis A that passes through the bolt element  46 . The axis A is indicated on  FIGS. 2 and 4 . 
     However, it may be advantageous if only one of the first mooring arm joint device  44  and the second mooring arm joint device  45  is allowed to rotate relative to the support element  30 , since this will allow the movements and the position of the attachment unit  66  to be tracked and controlled. 
     The first mooring arm joint device  44  may therefore, preferably, be securely attached to the support element  30 , for example by welding or by bolting or any other suitable method of securely attaching the first mooring arm joint device  44  to the support element  30 . On the other hand, the second mooring arm joint device  45  is preferably rotatably connected to the bolt element  46 , i.e. the second mooring arm joint device  45  is rotatable relative to the support element  30  about the axis A passing through the bolt element  46 . Alternatively, it would obviously be possible to securely attach the second mooring arm joint device  45  to the support element  30 , for example by welding bolting or any other suitable fastening method, while the first mooring arm joint device  44  is connected to the support element rotatable relative to the support element  30  about the axis A passing through the bolt element  46 . 
     This configuration with the plate and fork-shaped first mooring arm joint device  44  and plate-shaped second mooring arm joint device  45  that fits into the fork of the first mooring arm joint device  44 , ensures that the one of the first mooring arm joint device  44  and the second mooring arm joint device  45  that is rotatable relative to the support element  30 , can only rotate about the axis A passing through the bolt element  46 . 
     The support element joint device  43  thereby allows the support element  30  to rotate about one axis only which is perpendicular to a plane formed by the longitudinal axis of the first mooring arm and the longitudinal axis of the second mooring arm, where the axis A passes through the bolt element  46  as indicated in  FIGS. 2 and 4 . 
     The joint device  28  of the first embodiment of the mooring device  10  further comprises an attachment unit joint device  61  for attachment of the joint device  28  to the attachment unit  66 . The attachment unit joint device  61  may be a cardan joint, allowing the attachment unit  66  to rotate about two independent axes relative to the support element  30 . Alternatively, as shown in  FIGS. 1-6 , the attachment unit joint device  61  may be a ball joint which will allow the attachment unit  66  to rotate about three independent axes relative to the support element  30 . A ball element  64  may be securely attached to the support element  30  and a ball support element  63  may be mounted in the frame device  67  of the attachment unit  66  (see  FIGS. 5 and 6 ). 
     The joint device  28  of the second embodiment of the mooring device  10  shown in  FIGS. 7 a - b    comprises a support element  30  that comprises a plate element  36 . 
     The joint device  28  of the second embodiment of the mooring device  10  further comprises a support element joint device  43  comprising first mooring arm joint device  48  and a second mooring arm joint device  49 . The first mooring arm joint device  48  and the second mooring arm joint device  49  are securely attached to the plate element  36  of the support element  30 , for example by welding, by bolting or by any other suitable fastening means. 
     The first mooring arm joint device  48  preferably allows the first mooring arm  12  to rotate about three different axes of rotation relative to the support element  30 . The first mooring arm joint device  48  may for example be a ball joint where the ball element is securely attached to the first end portion  15  of the first mooring arm  12  and the ball support element is securely attached to the plate element  36  of the support element  30  as indicated on  FIG. 7   a.    
     The second mooring arm joint device  49  preferably allows the second mooring ai n  20  to rotate about three different axes of rotation relative to the support element  30 . The second mooring arm joint device  49  may for example be a ball joint where the ball element is securely attached to the first end portion  23  of the second mooring arm  20  and the ball support element is securely attached to the plate element  36  of the support element  30  as indicated in  FIG. 7   a.    
     The support element joint device  43  further comprises a restricting arm  51 , i.e. a movement restricting arm  51  that restricts the movements of the support element  30 . 
     The restricting arm  51  comprises a first end portion  54  and a second end portion  53 . The first end portion  54  is securely attached to the support element  30  of the joint device  28 , for example by welding, as indicated in  FIG. 7 a   , or by bolting or any other suitable fastening means. The second end portion  53  is attached to the floating unit  110  or the floating or non-floating structure  125  with an attachment joint device  56  that allows the restricting arm to rotate about two independent axes relative to the floating unit  110  or the floating or non-floating structure. The restricting arm  51  comprises a longitudinal axis passing through the restricting arm  51  in its longitudinal direction and passing through the first end portion  54  and the second end portion  53 . 
     The restricting arm  51  is preferably telescopic as is shown in  FIG. 7 a   , comprising a first telescopic part  52  and a second telescopic part  53  where the first telescopic part  52  is arranged slidingly within the second telescopic part  53  or vice versa. The restricting arm  51  will typically comprise a piston/cylinder assembly and may comprise shock absorbing elements, such as one or more springs, and/or one or more damping devices if that is desired. Such telescoping assemblies and piston/cylinder assemblies are well known in the art and will not be described in further detail here. 
     The cross-section A-A of the restricting arm  51 , as indicated in  FIG. 7 a   , is shown in  FIG. 7 b   . As shown, the cross section of the restricting arm  51 , is made polygonal, for example rectangular or square as shown in  FIG. 7 b   , but other polygonal shapes such as hexagonal or triangular, may also be used. The cross section of the first telescopic part  52  and the second telescopic part  53  are both polygonal and of similar size and shape so that the first telescopic part  52  slides easily within the second telescopic part  52 . The polygonal shape of the cross section of the restricting arm  51  ensures that there is no twisting movements of the first telescoping part  52  relative to the second telescoping part  53 , i.e. there is no rotational movement of support element  30  about the longitudinal axis of the restricting arm  51 . 
     The attachment joint device  56  may be a cardan joint as indicated in  FIG. 7 a    which allow the restring arm to rotate about two independent axes relative to the floating unit  110 . One axis is the axis A as indicated in  FIG. 7 a   , which passes through the attachment joint device  56  and is perpendicular to a plane formed by the longitudinal axis of the first mooring arm  12  and the longitudinal axis of the second mooring arm  20 . 
     This configuration of the joint device  28  of the second embodiment of the mooring device  10 , where the restricting arm  51  is securely attached to the plate element of the support element  30  and to the floating unit  110  with a cardan joint  56  and the first mooring arm  12  and the second mooring arm  20  are attached to the support element with ball joints  48  and  49 , ensures that the support element joint device  43  allows rotation of the support element  30  about one axis only, i.e. about the axis A which will always be perpendicular to the plane formed by the longitudinal axes of the first mooring arm  12  and the second mooring arm  20 . 
     The support element joint device  43  thereby allows the support element  30 , i.e. the plate element  36 , to rotate about one axis only, i.e. the axis A indicated in  FIG. 7 a   , which is, as mentioned above, perpendicular to a plane formed by the longitudinal axis of the first mooring arm and the longitudinal axis of the second mooring arm. 
     The joint device  28  of the second embodiment of the mooring device  10  further comprises an attachment unit joint device  61  for attachment of the joint device  28  to the attachment unit  66 . 
     The attachment unit joint device  61  may be a cardan joint, allowing the attachment unit  66  to rotate about two independent axes relative to the support element  30 . Alternatively, as shown in  FIG. 7 a   , the attachment unit joint device  61  may be a ball joint which will allow the attachment unit  66  to rotate about three independent axes relative to the support element  30 , i.e. the plate element  36 . A ball element  64  may be securely attached to the support element  30  and a ball support element  63  may be mounted in the frame device  67  of the attachment unit  66  (see  FIGS. 5 and 6 ). 
     The joint device  28  of the third embodiment of the mooring device  10  shown in  FIGS. 8-10 , comprises a support element  30  that comprises a holder element  38  with first side face  41  and a second side face  42 . A first pin element  39  is securely attached to the first side face and a second pin element  40  is securely attached to the second side face  42 . The axis A passes through the first pin element  39  and the second pin element  40  as indicated in  FIG. 9 . 
     The holder element  38  comprises a cavity in which the ball support element  63  of the attachment unit joint device may be mounted. As can be seen on  FIGS. 8 and 9 , the ball element  64  of the attachment unit joint device  61  is in this embodiment securely attached to the attachment unit  66  and the ball element  64  of the ball joint is arranged in the ball support element  63  which is arranged in the holder element  38 . This arrangement of the attachment unit joint device  61 , when the attachment unit joint device  61  is a ball joint, is advantageous in that it reduces the distance between the attachment unit  66  and the axis A to an extent where the attachment system joint device  61  and the axis A coincides. This passively reduce uncontrolled rotations and/or hinged motion of the attachment unit joint device  61  relative to the axis A. 
     The joint device  28  of the third embodiment of the mooring device  10  further comprises a support element joint device  43  comprising a first mooring arm joint device  58  that is generally fork-shaped or U-shaped and a second mooring arm joint device  59  that is generally fork-shaped or U-shaped and has a size and shape that makes it fit into the fork-shaped first mooring arm joint device  58 . 
     The first mooring arm joint device  58  is securely attached to the first end portion  15  of the first mooring arm  12  and the second mooring arm joint device  59  is securely attached to the first end portion  23  of the second mooring arm  20 . 
     The first mooring arm joint device  58  and the second mooring arm joint device  59  may be rotatably connected to the first pin element  39  and the second pin element  40  of the support element  30  allowing the support element  30  to rotate relative to both the first mooring arm  12  and the second mooring arm  20 . 
     However, it is preferable that the first mooring arm joint device  58  is securely attached to the support element  30 , for example to the first pin element  39  and/or the second pin element  40 , and that the second mooring arm joint device  59  is rotatably connected to the support element  30 , i.e. to the first pin element  39  and the second pin element  40 . Alternatively, the second mooring arm joint device  59  is securely attached to the support element  30 , for example to the first pin element  39  and/or the second pin element  40 , and the first mooring arm joint device  58  is rotatably connected to the support element  30 , i.e. to the first pin element  39  and the second pin element  40 . 
     A slightly different variant of the third embodiment is shown in  FIG. 10 . The support element  30  still comprises a holder element  38  which in this embodiment has a cylinder-shape instead of a box-shape as shown in  FIGS. 8-9 . The ball support element (not shown in  FIG. 10 ) of the attachment unit joint device  61  will be arranged in the holder element  38  in the same way as in  FIGS. 8-9 . 
     The first mooring arm joint device  58  of the support element joint device  43  is here shown as an element  58  that is securely attached to the support element  30 , for example to the holder element  38 , by welding, bolting or any other suitable fastening method. The first end portion  15  of the first mooring arm  12  is securely attached to the element  58  and is thereby securely attached to the support element  30 . It would also be possible to leave out the first mooring arm joint device  58  and just weld or bolt the first end portion  15  of the first mooring arm  12  directly to the support element  30 . The first mooring arm joint device  58  would then simply be a weld or bolts/boltholes that connects the first end portion  15  to the support element  30 . 
     The second mooring arm joint device  59  is fork-shaped in the same way as shown in  FIGS. 8-9  and is rotatably connected to the first and second pin elements  39 ,  40  of the support element  30  as shown in  FIGS. 8-9 . As in  FIG. 8-9 , the axis A passes through the pin elements that the fork-shaped second mooring arm joint device  59  is connected to. It should be noted that the configuration of the first mooring arm joint device  58  and the second mooring arm joint device  59  can be arranged the opposite way, i.e. that the second mooring arm joint device  59  is formed by an element that is securely attached to the support element  30  and the first mooring arm joint device  58  is fork-shaped and rotatably connected to the first pin element  39  and the second pin element  40  about the axis A passing through the pin elements  39 ,  40 . 
     This configuration of the joint device  28  of the third embodiment of the mooring device  10 , including the fork-shaped first mooring arm joint device  58  and fork-shaped second mooring arm joint device  59  as shown in  FIGS. 8-9 , or a first mooring arm joint device  58  comprising an element  58  that is securely attached to the support element  30  and a fork-shaped second mooring arm joint device  59  that is rotatably connected to the pin elements  39 ,  40  about the axis A passing through the pin elements  39 ,  40 , ensures that the one of the first mooring arm joint device  58  and the second mooring arm joint device  59  that is rotatable arranged relative to the support element  30 , can only rotate about the axis A passing through the first pin element  39  and the second pin element  40 . 
     The support element joint device  43  thereby allows the support element  30  to rotate about one axis only which is perpendicular to a plane formed by the longitudinal axis of the first mooring arm and the longitudinal axis of the second mooring arm, where the axis A passes through the bolt element  46  as indicated in  FIG. 9 . 
     It was mentioned above that the joint device  28  of the third embodiment of the mooring device  10  further comprises an attachment unit joint device  61  for attachment of the joint device  28  to the attachment unit  66 . The attachment unit joint device  61  may be a cardan joint, allowing the attachment unit  66  to rotate about two independent axes relative to the support element  30 . Alternatively, as mentioned above and shown in  FIGS. 8-10 , the attachment unit joint device  61  may be a ball joint which will allow the attachment unit  66  to rotate about three independent axes relative to the support element  30 . A ball element  64  may be securely attached to the attachment unit  66  and a ball support element  63  may be mounted in the holder element  38  of the support element  30  as mentioned above. 
     The various embodiments of the mooring device  20  preferably further comprises one or more support arms  97  comprising a first end portion  100  and a second end portion  103  as indicated in for example  FIG. 3 . The first end portion  100  is attached to the joint device  28  and the second end portion is attached to the floating unit  110  or the floating or non-floating structure  125 . The support arm  97  comprises a longitudinal axis passing through the support arm  97  in its longitudinal direction and passing through the first end portion  100  and the second end portion  103 . The main purpose of the support arm is to support the weight of the mooring device  10 . 
     The support arm  97  is preferably telescopic as is shown in for example  FIGS. 11-12 and 14 , comprising a first telescopic part  98  and a second telescopic part  99  where the first telescopic part  98  is arranged slidingly within the second telescopic part  99  or vice versa. The support arm  12  will typically comprise a piston/cylinder assembly comprising shock absorbing elements, such as one or more springs, and/or one or more damping devices. Such piston/cylinder assemblies are well known in the art and will not be described in further detail here. 
     The first telescopic part  98  of the support arm  97  comprises the first end portion  100  of the support arm  97 . Likewise, the second telescopic part  99  of the support arm  97  comprises the second end portion  103  of the support arm  20 . 
     A first attachment joint device  101  is preferably attached to the first telescopic part  98  of the support arm  97  and is adapted for attachment of the first attachment joint device  103  to a support element  30  of the joint device  28 . The first attachment joint device  101  preferably allows the support arm  97  to rotate about three independent axes relative to the support element  30  and may be a ball joint or a universal joint or any other type of joint that allow the support arm  97  to rotate about three independent axes relative to the support element  30 . 
     A second attachment joint device  104  is preferably attached to the second telescopic part  99  of the support arm  97  and is adapted for attachment of the second attachment joint device  104  to a floating unit  110  or a floating or non-floating structure  125 . The second attachment joint device  104  preferably allows the support arm  97  to rotate about three independent axes relative to the floating unit  110  or a floating or non-floating structure  125  to which the mooring arm  10  is attached, and may be a ball joint, a universal joint or any other type of joint that allow the support arm  97  to rotate about three independent axes relative to the floating unit  110  or a floating or non-floating structure  125 . 
     The support arm or support arms  97  may be arranged above the first mooring arm  12  and the second mooring arm  20 , as indicated in for example  FIGS. 1-6, 10 and 12 . Alternatively, the support arm  97  or support arms  97  may be arranged below the first mooring arm  12  and the second mooring arm  20 , as indicated in for example  FIG. 11 . The support arm or support arms  97  are preferably attached to the floating unit  110  or the floating or non-floating structure  125  at the second end portion of the support arms  97  and to the first mooring arm  12 , and/or to the second mooring arm  20 , and/or to the restring arm  51  and/or the joint device  28  depending on the number of support arms  97  used with the mooring device  10 , the weight of the first mooring arm  12 , the second mooring arm  20 , the restricting arm  51  and the joint device  28  etc. A purpose of the support arm  97  or support arms  97  would be to carry the weight of the attachment unit  66  and to control the position of the attachment unit  66  in space. As mentioned, one or more support arms  97  may be used, which may be connected to both the restricting arm  51  and/or the support element  30  and/or the support element joint device  43 . 
       FIG. 13  illustrates a mooring device  10  mounted on a large ship  110  enabling the ship to be moored to another floating or non-floating structure, or another floating or non-floating structure to be moored to the ship  110 . It should be mentioned that any desired number of mooring devices  10  may be mounted on the ship  110 . 
       FIGS. 11-12 and 14-18  illustrates a floating unit  110  with one or two mooring devices  10  mounted on it. Again, it should be understood that any desired number of mooring devices  10  could be mounted to the floating unit  110 . 
     The configuration of the mooring device  10  described herein will allow the floating unit  110  some freedom to move relative to the floating or non-floating structure  125 . The attachment unit  66  of the mooring device  10  will be attached to the floating or non-floating structure  125  when the floating unit  110  is moored to the floating or non-floating unit  125 . In  FIGS. 17-19  some relative movements between the floating unit  110  and the floating or non-floating structure  125  is shown. During the motion of the floating unit  110  relative to the floating or non-floating structure  125 , the attachment elements  85 ,  87 ,  89   91  of the attachment unit  66  keep the position of the floating or non-floating structure  125  while the deck portion  112  of the floating unit  110 , the first and second support arms  12 ,  20  and other parts of the floating unit  110  and the mooring device(s)  10  will move relative to the attachment elements  85 ,  87 ,  89   91  and the floating or non-floating structure  125 . 
       FIG. 17  illustrates a combined relative vertical motion and horizontal motion between the floating unit  110  and the floating or non-floating structure  125 .  FIG. 18  illustrates a relative rotational motion between the floating unit  110  and the floating or non-floating structure  125  about a horizontal axis that is substantially perpendicular to the side face of the floating or non-floating structure  125  that the attachment elements  85 ,  87 ,  89   91  are attached to.  FIG. 19  illustrates a relative rotational motion between the floating unit  110  and the floating or non-floating structure  125  about a horizontal axis that is substantially parallel to the side face of the floating or non-floating structure  125  that the attachment elements  85 ,  87 ,  89   91  are attached to. 
     The floating unit  110  may be provided with at least one, but preferably at least two fender devices  120 ,  121 , a first fender device  120  and a second fender device  121  as indicated in  FIGS. 14-19 . The first and second fender devices  120 ,  121  will help to prevent the mooring device  10  or mooring devices  10  from being compressed beyond their capabilities and thereby prevent damaging the mooring devices  10  and to prevent the floating unit  110  from hitting the floating or non-floating structure  125  to which the floating unit  110  is moored. 
     The first and second fender devices  120 ,  121  may be flexible to a certain degree as indicated in  FIGS. 12, 14, 15, 17 and 19  where a compressed fender line is indicated where the first and second fender devices  120 ,  121  are subjected to forces from the floating or non-floating structure  125 , and a uncompressed fender line is indicated where the first and second fender devices  120 ,  121  are not affected by external forces acting on them. 
     The flexibility and compressibility of the first and second fender devices  120 ,  121  may be obtained by using air pressurized elements that are made of a flexible material such as a rubber material. The fender elements  120 ,  121  may further be filled with foam or rubber. The pressure of air or the stiffness of the foam or rubber inside the fender elements  120 ,  121  may be adjusted so that a desired compressibility of the first and second fender devices  120 ,  121  is obtained. As shown in the figures, the floating unit  110  may be provided with one or two mooring devices  10  arranged between the first fender device  120  and the second fender device  121 . However, any number of mooring devices  10  may mounted on the floating unit  110  and any number of fender devices  120 ,  121  may be mounted on the floating unit  110 . The arrangement and the relative and mutual positions of the individual fender devices  120 ,  121  and the mooring device  10  or mooring devices  10  may also vary from one floating unit  110  to another floating unit  110 . The fender devices  120 ,  121 , if located on the outside of the mooring devices  10 , will help absorb yaw moments of the floating unit  110 . Providing a floating unit  110  with one or more fender devices  120 ,  121  in addition to one or more mooring devices  10 , therefore enhances the usability of the mooring devices  10  since external loads acting on the floating unit  110  can at least partly be handled by the one or more fender devices  120 ,  121 , thus reducing the design requirements for the mooring devices  10 . 
     Finally, it should be mentioned that all the above-mentioned embodiments illustrate the invention. However, without limiting the invention, the skilled artisan in the field will be able to contemplate many alternative embodiments without deviating from the scope of the enclosed claims. In the claims, reference numbers in brackets shall not be construed as limiting. 
     It should be mentioned that the use of the verb “to comprise” herein and its different forms do not exclude the presence of elements or steps which are not mentioned in the claims. The article “a” before an element do not exclude the presence of several such elements.