Chain tensioner with chain rattle

Abstract

The invention relates to an assembly comprising a tensioning chain and a chain tensioner for adjustment of the length of the tensioning chain that extends between a floating offshore facility and an offshore anchor, wherein the chain tensioner comprises a frame with a retainer abutment surface, and a chain rattle that is rotatable with respect to the frame between a chain locking position and a chain hauling in position, wherein the chain rattle comprises a chain jaw having a front jaw abutment surface and a left rattle tooth and a right rattle tooth, wherein in the chain locking position the front jaw abutment surface abuts the retainer abutment surface and the left rattle tooth and the right rattle tooth engage a chain link.

Description

[0001] P143094PC00

[0002] Chain tensioner with chain rattle

[0003] BACKGROUND

[0004] The invention relates to an assembly comprising a tensioning chain and a chain tensioner for adj ustment of the length of the tensioning chain that extends between the chain tensioner and a floating offshore facility .

[0005] SUMMARY OF THE INVENTION

[0006] A known chain tensioner comprises a frame that bounds a chain passage for the tensioning chain, a chain passage opening where the chain enters the frame, and a chain retainer wall that is rotatable with respect to the frame and that is provided with a notch that engages a chain link of the tensioning chain to lock the tensioning chain with respect to the chain tensioner . When the tensioning chain is tensioned with respect to the chain tensioner, the retainer wall rotates away along with the tensioning chain to allow the notch to disengage and to engage the next following chain link .

[0007] A disadvantage of the known chain tensioner is that the rotatable chain retainer wall can withstand relatively limited retaining forces , while there is a need for heavy duty chain retainers . Therefore an alternative design approach is necessary that can be scaled up with the necessary holding forces on the tensioning chain .

[0008] The invention provides an assembly comprising a tensioning chain and a chain tensioner for adj ustment of the length of the tensioning chain that extends between a floating of fshore facility and an offshore anchor, wherein the tensioning chain has a chain center line and comprises a series of connected chain links each having a main plane, wherein the chain links alternatingly have their main plane in a first orientation and in a second orientation that is under an angle with respect to the first orientation, wherein the chain tensioner comprises a frame that bounds a chain passage for the tensioning chain, wherein the frame comprises a retainer body having a retainer abutment surface and a chain passage opening through the retainer body towards the chain passage, wherein the tensioning chain is moveable through the chain passage in a hauling in direction and a paying out direction with respect to the chain tensioner, and wherein the chain tensioner comprises a chain rattle that is rotatable mounted to the frame to rotate around a rattle rotation axis that extends transverse to the chain center line, wherein the chain rattle comprises a chain j aw having a front j aw abutment surface for abutment of the retainer abutment surface, and a left rattle tooth and a right rattle tooth that face the chain passage to engage a chain link that extends in between, wherein the chain rattle is rotatable around the rattle rotation axis between a chain locking position and a chain hauling in position, wherein in the chain locking position the front j aw abutment surface abuts the retainer abutment surface, and the left rattle tooth and the right rattle tooth engage a chain link to lock a movement of the tensioning chain in the paying out direction, and wherein in the chain hauling in position the front j aw abutment surface is spaced apart from the retainer abutment surface , and the left rattle tooth and the right rattle tooth are at least partially retracted from the engaged chain link, wherein the rattle rotation axis extends in a direction parallel to the chain center line at a longitudinal rotation axis distance from the retainer abutment surface , and wherein the rattle rotation axis extends in a direction transverse to the chain center line at a transverse rattle rotation axis distance from the chain center line, wherein the longitudinal rotation axis distance is larger than the transverse rattle rotation axis distance .

[0009] The chain tensioner according to the invention comprises a frame and a chain rattle that is rotatable mounted to the frame . The chain rattle has a chain j aw with a left rattle tooth and a right rattle tooth to engage the tensioning chain in its chain locking position to provide a form lock . The chain aw has a front j aw abutment surface for abutment of a retainer abutment surface that forms part of the frame so as to trans fer high tensioning loads from the tensioning chain onto the frame . The chain rattle can rotate with respect to the frame around a rattle rotation axis that extends transverse to the chain center line to be rotated to a chain hauling in position . The rattle rotation axis extends in a direction parallel to the chain center line at a longitudinal rotation axis distance from the retainer abutment surface, and the rattle rotation axis extends in a direction transverse to the chain center line at a transverse rattle rotation axis distance from the chain center line, wherein the longitudinal rotation axis distance is larger than the transverse rattle rotation axis distance . This ensures a substantial transverse movement of the left rattle tooth and the right rattle tooth . Thereby the left rattle tooth and the right rattle tooth can be optimi zed in its dimensions to provide sufficient strength to withstand and transfer the high tensioning loads from the tensioning chain onto the frame . This assembly can be scaled up to the required tensioning forces onto the tensioning chain .

[0010] In an embodiment the chain links comprise an oval surrounding member that extends in the main plane, that has a link thickness transverse to the main plane , a longest link length in the main plane in the direction of the chain center line , and a link width in the main plane and transverse to the chain center line, wherein the longitudinal rotation axis distance is at least four times the link thickness , and wherein the transverse rattle rotation axis distance is at least one time the link thickness .

[0011] In an embodiment the rattle rotation axis extends under the center of gravity of the chain rattle, whereby the chain rattle can fall into its chain locking position under the action of gravity .

[0012] In an embodiment the rattle rotation axis extends downstream from the retainer abutment surface in the hauling in direction of the tensioning chain, whereby a movement of the tensioning chain in its hauling in direction facilitates a rotation of the chain rattle from its a chain hauling in position .

[0013] In an embodiment the left rattle tooth and the right rattle tooth extend in a proj ection parallel to the rattle rotation axis , in the chain hauling in position of the chain rattle with respect to the chain center line at the opposite side of the rattle rotation axis , whereby a movement of the tensioning chain in its hauling in direction facilitates a rotation of the chain rattle from its a chain hauling in position .

[0014] In an embodiment the chain links have semi round ends and exposed convex chain link shoulders on the semi round ends , wherein the convex chain link shoulders of the subsequent chain links with the main plane in the same first orientation are facing each other and the convex chain link shoulders of the subsequent chain links with the main plane in the same second orientation are facing each other, wherein the left rattle tooth comprises a left chain link shoulder pocket , and the right rattle tooth comprises a right chain link shoulder pocket for receiving the convex chain link shoulders of the engaged chain link . The left chain link shoulder pocket and the right chain link shoulder pocket keep the received chain link well positioned with respect to the chain rattle to ensure a proper engagement of the tensioning chain in the locking position of the chain rattle .

[0015] In an embodiment thereof the left chain link shoulder pocket and the right chain link shoulder pocket are concave having a curvature that corresponds with a curvature of the convex chain link shoulders . This ensures that high holding forces can be trans ferred from the chain link to the chain rattle without deformation of the engaged chain link . Thereby local fatigue in the chain link metal of the engaged chain link can be limited on the long term or over the operative li fe span of the installed tensioning chain .

[0016] In an embodiment the chain links have semi round ends and exposed convex chain link shoulders on the semi round ends , wherein the convex chain link shoulders of the subsequent chain links with the main plane in the same first orientation are facing each other and the convex chain link shoulders of the subsequent chain links with the main plane in the same second orientation are facing each other, wherein the left rattle tooth comprises a left rattle lift surface , and the right rattle tooth comprises a right rattle lift surface that both extend oblique to the chain center line in the chain locking position of the chain rattle to abut the convex chain link shoulders . The rattle lift surfaces ensure that the rattle tooth are moved away from the tensioning chain by sliding over its chain links , whereby the chain rattle rotates from its chain locking position into its chain hauling in position .

[0017] In a compact embodiment of the chain rattle, the left rattle lift surface and the right rattle li ft surface merge into the front j aw abutment surface of the chain rattle .

[0018] In an embodiment the chain rattle comprises a left side body and a right side body that extend spaced apart from each other on opposite sides of the chain passage, wherein the left rattle tooth and the right rattle tooth each have a base as from which they proj ect from the respective left side body and right side body to face the chain passage . The left side body and the right side body define a part of the chain passage to keep the tensioning chain well positioned with respect to the left rattle tooth and the right rattle tooth .

[0019] In an embodiment thereof the chain links have semi round ends and exposed convex chain link shoulders on the semi round ends , wherein the convex chain link shoulders of the subsequent chain links with the main plane in the same first orientation are facing each other and the convex chain link shoulders of the subsequent chain links with the main plane in the same second orientation are facing each other, wherein the left rattle tooth and the right rattle tooth have at their base a largest longitudinal length in a direction parallel to the chain center line that is larger than the smallest intermediate space between the facing convex chain link shoulders . Thereby the left rattle tooth and the right rattle tooth can be optimi zed in its dimensions to have an optimal amount of steel material to provide suf ficient strength to withstand and transfer the high tensioning loads from the engaged chain link of the tensioning chain onto the frame .

[0020] In an embodiment the chain rattle comprises a left chain guide on the left side body, and a right chain guide on the right side body, both having a same and constant curvature around the rattle rotation axis to support chain links of which the main plain extends parallel to the rattle rotation axis . The left chain guide and the right chain guide define a part of the chain passage to keep the tensioning chain well positioned with respect to the left rattle tooth and the right rattle tooth .

[0021] In an embodiment the chain tensioner is configured for employment on a bottom of a water body, wherein the chain tensioner comprises a bottom wall or skid under the frame to stand on the bottom of the water body .

[0022] The various aspects and features described and shown in the specification can be applied, individually, wherever possible . These individual aspects , in particular the aspects and features described in the attached dependent claims , can be made subj ect of divisional patent applications .

[0023] BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention will be elucidated on the basis of an exemplary embodiment shown in the attached drawings , in which :

[0025] Figure 1 shows an of fshore setup having a floating of fshore facility that is anchored to a sea bottom by means of a tensioning chain that runs through a chain tensioner according to a first embodiment of the invention;

[0026] Figures 2A-2D are an isometric side view and a corresponding longitudinal section thereof , an isometric front view and a top view of the chain tensioner with the tensioning chain as shown in figure 1 ;

[0027] Figure 3 is an isometric rear view of the chain tensioner and the tensioning chain of figure 1 , wherein some parts have been removed for illustrative purposes ;

[0028] Figures 4A-4E are an isometric side view and a corresponding longitudinal section thereof , a side view of that longitudinal section, a front view and a rear view of a chain rattle of the chain tensioner of figure 1 ;

[0029] Figures 5A-5E are subsequent positions of the chain rattle of figures 4A-4E during the tensioning of the tensioning chain in the chain tensioner;

[0030] Figure 6 is an isometric side view of a chain tensioner according to a second embodiment of the invention; and

[0031] Figure 7 is an isometric side view of a chain tensioner according to a third embodiment of the invention . DETAILED DESCRIPTION OF THE INVENTION

[0032] Figure 1 shows an offshore setup in a water body, in this example a sea 1 , above a water body bottom, in this example a seabed 3 . The of fshore setup is configured with a floating offshore facility at the level of the water surface 2 , such as a Floating Production, Storage and Offloading ( FPSO) facility, or a floating wind turbine 6 for generating electricity offshore . The floating wind turbine 6 is connected to multiple mooring chains that are distributed around it to form a plurality of catenaries to secure the position of the floating wind turbine 6 with respect to the seabed 3 . For illustrative purposes figure 1 shows only one mooring chain 7 thereof in detail .

[0033] The mooring chain 7 is connected to a chain tensioner 30 according to a first embodiment of the invention through which a tensioning chain 25 is fed . The chain tensioner 30 is suspended between the floating wind turbine 6 and the upper surface 4 of the seabed 3 . As shown in figures 1 and 2A, the chain tensioner 30 divides the tensioning chain 25 in a notional operational tensioning chain section 27 that extends between the chain tensioner 30 and a heavy marine anchor 21 by which it is anchored to the sea bed 3 , and a not operational adj ustment chain section 28 that extends freely from the chain tensioner 30 . The tensioning chain 25 can pass through the chain tensioner 30 in a hauling in direction A towards the chain tensioner 30 , and a paying out direction B away from the chain tensioner 30 . The heavy marine anchor 21 is for example a 10-30 tons marine anchor, such as the Vryhof Stevpris MK6 30-tons anchor .

[0034] As best shown in figure 2A, the tensioning chain 25 has a chain center line S and comprises a series of connected ring shaped or donut shaped steel chain links 26 each having a main plane M, N that is equal one of the planes of symmetry . The chain links 26 have with respect to the chain center line S of the tensioning chain 25 alternatingly a first orientation and a second orientation in which the respective main planes M, N thereof are oriented under right angles with respect to each other, normally under about 90 degrees in particular when the tensioning chain 25 is under tension . In this example the chain links 26 have in the first orientation their main plain M practically upright, and in the second orientation their main plane N practically horizontal .

[0035] As shown in the detail of figure 2B, the chain links 26 are made of a cylindrical steel rod, that is bend into an oval shape to form an oval surrounding member having semi round ends and interconnecting sides that extend in this example parallel to the chain center line S . The chain links have a link thickness D transverse to the main plane M, N, a longest link length L in the main plane M, N in the direction of the chain center line S , and a link width W in the main plane M, N and transverse to the chain center line S . The links 26 having the same orientation are kept spaced apart from each other over an intermediate distance Q in the direction of the chain center line S when the tensioning chain 25 is under tension . As common in the art of chain links , the dimensions of the chain links 26 are related to the link thickness D that originates from the cylindrical steel rod they are made from . The longest link length L is larger than four times the link thickness D (L>4D) . In this example the longest link length L is six times the link thickness D (L=6D) . The link width W is larger than three times the link thickness D (W>3D) . In this example the link width W is equal to 3 , 35 times the link thickness D (W=3 , 35D) . The intermediate distance Q is smaller than three times the link thickness D ( Q<3D) . In this example the intermediate distance Q is equal to two times the link thickness D (Q=2D) .

[0036] As shown in figures 2B and 3 , the chain links 26 have exposed convex chain link shoulders 29 on the semi round ends , wherein the chain link shoulders 29 of the subsequent chain links 26 with the main plane M in the same first orientation are facing each other, and the chain link shoulders 29 of the subsequent chain links 26 with the main plane N in the same second orientation are facing each other . The chain links 26 have exposed chain link shoulders 29 at the ends where they hook into each other .

[0037] As best shown in figures 2A and 2B the chain tensioner 30 comprises a steel frame 31 that is formed with a left side body 36 and a right side body 37 that are interconnected and that have the same outer contour . The left side body 36 and the right side body 37 are both made from a straight steel plate and extend parallel to each other and spaced apart from each other . The frame 31 has a bottom side 42 that is destined to extend during a tensioning operation below the chain center line S of the incoming operational tensioning chain section 27 of the tensioning chain 25 , and the frame 31 has a top side 43 that is destined to extend during the tensioning operation above the chain center line S of the incoming operational tensioning chain section 27 of the tensioning chain 25. The center of gravity of the chain tensioner 30 is located under the center line S of the incoming tensioning chain section 27 .

[0038] The frame 31 of the chain tensioner 30 comprises a bearing shaft 38 that extends between and through the left side body 36 and the right side body 37 . The chain tensioner 30 comprises a steel chain wheel 90 having a central bushing 91 that is rotatable around the bearing shaft 38 around a chain wheel rotation axis C . The chain wheel 90 comprises a left chain disk 92 and a right chain disk 93 on the central bushing 91 that extend spaced apart from each other over a distance at which the chain links 26 in their second orientation with their main plane N parallel to the chain wheel rotation axis C fit over their width in their main plane N between the left chain disk 92 and the right chain disk 93 under a positive tolerance . As best shown in figure 2C, the chain wheel 90 comprises a left sprocket wheel 94 against the inner side of the left chain disk 92 , and a right sprocket wheel 96 against the inner side of the right chain disk 93 . The left sprocket wheel 94 comprises multiple left chain link pockets 95 around its perimeter, and the right sprocket wheel 96 comprises multiple right chain link pockets 97 around its perimeter that extend aside each other and that are each dimensioned to receive , enclose and support a chain link 26 in the second orientation of which its main plain N spans between the left chain disk 92 and right disk 93 and parallel to the chain wheel rotation axis C . The left sprocket wheel 94 and the right sprocket wheel 96 extend spaced apart from each other over a distance that allows the chain links 26 in their first orientation with their main plane M transverse to the chain wheel rotation axis C to enter and fit in between under a positive tolerance , whereby these chain links 26 span directly between the chain links 26 that are supported in the consecutive left chain link pockets 95 and right chain link pockets 97 .

[0039] As best shown in figure 2B, the frame 31 of the chain tensioner 30 comprises a left chain guide 100 on the left side body 36 , and a right chain guide 101 on the right side body 37 , having a same position and curvature to follow the chain wheel 90 so as to keep the chain links 26 that are supported in the left chain link pockets 95 and right chain link pockets 97 enclosed therein . The left chain guide 100 and the right chain guide 101 extend spaced apart from each other over a distance that allows chain links 26 in their first orientation with their main plane M transverse to the chain wheel rotation axis C to enter in between under a positive tolerance . The left chain guide 100 , the right chain guide 101 and the chain wheel 90 define a tensioning chain exit opening 41 for the adj ustment chain section 28 of the tensioning chain 25 .

[0040] As best shown in figure 2B, the frame 31 of the chain tensioner 30 comprises at one end a plate shaped mounting body 44 that interconnects the left side body 36 and the right side body 37 and that proj ects therefrom . The mounting body 44 comprises a mounting hole 45 to which a shackle 46 on the end of the anchor chain 20 is attached, whereby the chain tensioner 30 can hinge around a hinge axis E transverse to the tensioning chain section 27 of the anchor chain 20 .

[0041] As best shown in figures 2D and 3 , the frame 31 of the chain tensioner 30 comprises a plate shaped retainer body 50 at the opposite side of the mounting body 44 that interconnects the left side body 36 and the right side body 37 . The retainer body 50 has an inwardly directed and straight retainer abutment surface 59. The retainer body 50 has a cross shaped chain passage opening 51 having dimensions that allow the chain links 26 with their alternating main planes M, N to pass through under a positive tolerance towards the chain wheel 90 . As best shown in figure 2C, the frame 31 comprises in this example four elongated chain entry bodies 52 in front of the retainer body 50 that are connected with the left side body 36 or the right side body 37 . The four chain entry bodies 52 are positioned in the four quadrants aside and flush with the edges of the cross shaped chain passage opening 51 to lead the chain links 26 therein and to define a tensioning chain entry opening 40 for the operational tensioning chain section 27 of the tensioning chain 25. The four chain entry bodies 52 each have a sloping surface 53 to rotate the incoming chain links 26 around the chain center line S so as to align them with the cross shaped chain passage opening 51 . The frame 31 of the chain tensioner 30 comprises a hoisting eye 54 on the upper two chain entry bodies 52 . As best shown in figures 3 and 5E , the frame 31 of the chain tensioner 30 comprises a central chain guide 32 that is at one side connected to the retainer body 50 and that proj ects towards the intermediate space between the left chain guide 100 and the left chain guide 101 . The central chain guide 32 has a straight chain guide surface 33 to contact the chain links 26 that leave the cross shaped chain passage opening 51 in the first orientation with their main plane M transverse to the chain wheel rotation axis C .

[0042] The chain center line S of the tensioning chain 25 is substantially straight between the retainer body 50 and the chain wheel 90 . The chain center line S of the tensioning chain 25 has a constant radius when engaged by the chain wheel 90 , and the chain guide surface 33 extends parallel thereto . During the tensioning operation the chain center line S is substantially straight along the adj ustment chain section 28 of the tensioning chain 25 as from the chain wheel 90 , and extends upwards or away from the bottom side 42 of the frame 31 .

[0043] As best shown in figure 2B, the frame 31 of the chain tensioner 30 comprises a hinge pin 39 that interconnects the left side body 36 and the right side body 37 . The chain tensioner 30 comprises a steel chain rattle 55 that is rotatable mounted around the hinge pin 39 to rotate around a rattle rotation axis F that extends parallel to the chain wheel rotation axis C and transverse to the chain center line S of the tensioning chain 25 between the chain entry opening 40 and the chain wheel 90 . The chain rattle 55 is shown in more detail in figures 4A- 4E .

[0044] As best shown in figures 4A and 4D, the chain rattle 55 comprises a left side body 56 and a right side body 57 that have the same outer contour . The left side body 56 and the right side body 57 are both made from a straight steel plate and extend parallel to each other and spaced apart from each other . The chain rattle 55 comprises a hinge tube 58 that connects the left side body 56 and the right side body 57 to each other . The hinge pin 39 of the frame 31 extends through the hinge tube 58 for hinging the chain rattle 55 around the rattle rotation axis F . As best shown in figures 4B and 4E , the chain rattle 55 comprises a left chain guide 64 on the left side body 56, and a right chain guide 65 on the right side body 57 , both having the same constant curvature around the hinge tube 58 to support chain links 26 of which the main plain M extends parallel to the rattle rotation axis F . The left chain guide 64 and a right chain guide 65 extend spaced apart from each other over a distance that allows chain links 26 in their first orientation with their main plane M transverse to the rattle rotation axis F to enter in between under a positive tolerance .

[0045] As best shown in figure 4A, the chain rattle 55 comprises a chain j aw 60 above and spaced apart from the rattle rotation axis F . The chain j aw 60 comprises a front j aw bridge 61 and a rear j aw bridge 62 that are connected to the left side body 56 and the right side body 57 . The front j aw bridge 61 is embodied as a hoisting eye to connect a not shown hoisting cable to the rattle 55 for releasing the tensioning chain 25. As best shown in figures 4C and 4D, the chain j aw 60 is bound by a straight front j aw abutment surface 70 on the left side body 56 and the right side body 57 . The chain rattle 55 is rotatable with respect to the frame 31 around the rattle rotation axis F between a chain locking position and multiple chain hauling in positions . In the chain locking position chain rattle 55 engages and locks a movement of the tensioning chain 25 in the paying out direction B away from the chain tensioner 30 while the straight front j aw abutment surface 70 abuts the retainer abutment surface 59 over substantially its entire surface, and in the chain hauling in positions the tensioning chain 25 slides along and through the chain rattle 55 in the hauling in direction A. The hinge pin 39 has some play inside the hinge tube 58 to allow the chain rattle 55 to slide in the direction of the chain center line S towards and away from the retainer body 50 to bring the straight front j aw abutment surface 70 in abutment with the retainer abutment surface 59 and to release it therefrom in the direction of the chain center line S .

[0046] As best shown in figures 4A and 4D, the chain j aw 60 comprises a left rattle tooth 65 on the left side body 56 and a right rattle tooth 66 on the right side body 57 that face each other and that extends inwards as from the front j aw abutment surface 70 . The left rattle tooth 65 comprises a left rattle lift surface 67 , and the right rattle tooth 66 comprises a right rattle li ft surface 68 that both extend oblique to the chain center line S in the chain locking position of the rattle 55 and that both merge into the front aw abutment surface 70 of the rattle 55. In a proj ection parallel to the chain rattle rotation axis F the left rattle li ft surface 67 and the right rattle lift surface 68 extend on both sides of the chain center axis S .

[0047] The left rattle li ft surface 67 merges into a left rattle tooth inner surface 80 , and the right rattle lift surface 68 merges into a right rattle tooth inner surface 81 that extend parallel to each other and spaced apart from each other over a distance that allows the chain links 26 in their first orientation with their main plane M transverse to the chain rattle rotation axis F to enter and fit in between under a positive tolerance . The left rattle lift surface 67 and the left rattle tooth inner surface 80 both merge at their upper side into a left chain centering surface 69 that merges into the front j aw abutment surface 70 . The right rattle lift surface 68 and the right rattle tooth inner surface 81 both merge at their upper side into a right chain centering surface 71 that merges into the front j aw abutment surface 70 . The left rattle lift surface 67 and the left rattle tooth inner surface 80 both merge at their lower side into a left rattle tooth slide surface 77 , and the right rattle lift surface 68 and the right rattle tooth inner surface 81 both merge at their lower side into a right rattle tooth slide surface 78 . The left rattle tooth slide surface 77 and the right rattle tooth slide surface 78 extend in the same plane that in the chain locking position extends parallel with the chain center line S . The left rattle tooth inner surface 80 merges in a left rattle tooth rear surface 74 , and the right rattle lift surface 68 merges into a right rattle tooth rear surface 75 that are both cylindrical convex towards the respective left side body 56 and the right side body 57 .

[0048] Figure 4C shows the side view of the longitudinal section of the chain rattle 55, wherein for illustrative purposes also the retainer body 50 with its retainer abutment surface 59 of the frame have been added . The left rattle tooth 65 and the right rattle tooth 66 have at their base where they merge into the left side body 56 and the right side body 57 , or as from which the proj ect from the left side body 56 and the right side body 57 , over their height H a largest longitudinal length Z in the direction parallel to the chain center line S . This longitudinal length Z is larger than the intermediate distance Q between the chain links 26 in both the chain locking position and the multiple chain hauling in positions .

[0049] The left rattle tooth 65 comprises a concave left chain link shoulder pocket 72 , and the right rattle tooth 66 comprises a concave right chain link shoulder pocket 73 that are complementary formed to the convex chain link shoulders 29 so that they fit therein with surface contact over substantially the entire surface within the left chain link shoulder pocket 72 and the right chain link shoulder pocket 73 .

[0050] As shown in figure 4C, the rattle rotation axis F extends downstream from the retainer body 50 in the hauling in direction A of the tensioning chain 25 , wherein the rattle rotation axis F extends parallel to the chain center line S at a longitudinal rotation axis distance X from the side of the retainer body 50 it abuts . The longitudinal rotation axis distance X is at least four times the link thickness D (X>4D) . In this example the longitudinal rotation axis distance X is six times the link thickness D (X=6D) . The rattle rotation axis F extends in this example under the center of gravity of the chain rattle 55, wherein the rattle rotation axis F extends transverse to the chain center line S at a transverse rattle rotation axis distance Y from the chain center line S . The transverse rattle rotation axis distance Y is at least one time the link thickness D (Y>D) . In this example the transverse rattle rotation axis distance Y two times the link thickness D (Y=2D) . The longitudinal rotation axis distance X is larger than the transverse rattle rotation axis distance Y (X>Y) .

[0051] The tensioning operation is performed by using an anchor handling vessel 140 comprising a hull 141 with a first winch 142 around which a first pulling line 143 is wound, and a second winch 152 around which a second pulling line 153 is wound . The first pulling line 143 is attached to the end of the adj ustment chain section 28 , and the second pulling line 153 is attached to the front j aw bridge 61 of the chain rattle 55.

[0052] Figures 5A-5E show the subsequent positions of the chain rattle 55 with respect to the tensioning chain 25 during the tensioning thereof in the hauling in direction A.

[0053] Figure 5A shows the chain rattle 55 in its chain locking position in which its front j aw abutment surface 70 abuts the retainer body 50 of the frame 31 . In the chain locking position the chain link shoulders 29 of the of the chain link 26 that is between the retainer body 50 and the chain wheel 90 and that is nearest to the retainer body 50 and having its main plane N in the second orientation is confined in the left chain link shoulder pocket 72 and the right chain link shoulder pocket 73 of the chain rattle 55. Any pulling force that acts in the paying out direction B onto the tensioning chain section 27 is thereby trans ferred via the chain link shoulders 29 onto the chain j aw 60 of the chain rattle 55 and subsequently onto the retainer body 50 of the frame 31 .

[0054] Figure 5B shows a first chain hauling in position of the chain rattle 55 in which the tensioning chain section 27 has been moved in the hauling in direction A and the confined chain link shoulders 29 are released from the left chain link shoulder pocket 72 and the right chain link shoulder pocket 73 . In this first chain hauling in position the left rattle li ft surface 67 and the right rattle lift surface 68 are in a first sliding spot contact Cl with the facing chain link shoulders 29 of the next incoming chain link 26 having its main plane N in the same second orientation . In this first chain hauling in position the chain rattle 55 has been rotated around rattle rotation axis F to rotate the chain j aw 60 in direction G away from the chain center line S .

[0055] Figure 5C shows a subsequent second chain hauling in position of the chain rattle 55 in which the tensioning chain section 27 has been moved further in the hauling in direction A and the left rattle tooth slide surface 77 and the right rattle tooth slide surface 78 are in a second sliding spot contact C2 with the incoming intermediate chain link 26 having its main plane M in the first orientation .

[0056] Figure 5D shows a subsequent third chain hauling in position of the chain rattle 55 in which the tensioning chain section 27 has been moved further in the hauling in direction A and the left rattle tooth rear surface 74 and the right rattle tooth rear surface 75 are in a third sliding spot contact C3 with the shoulders 29 of the next following chain link 26 with its main plane N in its second orientation to be engaged . In this third chain hauling in position the rattle 55 has been rotated around rattle rotation axis F to rotate the chain aw 60 in direction H back towards the chain center line S .

[0057] Figure 5E shows a subsequent fourth chain hauling in position of the chain rattle 55 in which the tensioning chain section 27 has been moved further in the hauling in direction A and the left rattle lift surface 67 and the right rattle lift surface 68 are in a fourth sliding spot contact C4 with the chain link shoulders 29 of the next incoming chain link 26 having its main plane N in the same second orientation and that face the chain link shoulders 29 to be engaged . By slightly releasing the tensioning chain section 27 in the paying out direction, the rattle 55 rotates around rattle rotation axis F to rotate the chain j aw 60 further in direction H towards the chain center line S whereby the chain link shoulders are engaged in the left chain link pocket 72 and the right chain link shoulder pocket 73 .

[0058] When the tensioning chain 25 has to be paid out in the paying out direction, the second hoisting cable 153 is hauled in to rotate the rattle 55 around the rattle rotation axis F in direction G to release the tensioning chain section 27 .

[0059] As the longitudinal length Z of the left rattle tooth 65 and the right rattle tooth 66 at their base where they merge into the left side body 56 and the right side body 57 is larger than the intermediate distance Q between the chain links 26 in both the chain locking position and the multiple chain hauling in positions , the left rattle tooth 65 and the right rattle tooth 66 have an optimal amount of steel material to withstand high holding forces that are trans ferred to them by the engaged chain link 26 of the tensioning chain 25.

[0060] Figure 6 shows a chain tensioner 130 according to a second embodiment of the invention . The parts that correspond with the chain tensioner 30 according to the first embodiment are provided with identical reference numbers . Only the deviating parts are discussed hereafter . The chain tensioner 130 comprises a mud plate or mud skid or bottom wall 49 under and connected to the frame 31 to rest on the upper surface 4 of the seabed 3 . The shackle 46 is connected to the marine anchor 21 via an anchor chain 20 . The tensioning chain section 27 is relatively long and is connected to the wind turbine 6. The chain tensioner 130 is destined to remain positioned on the sea floor 3 , that is , during the operational lifespan of the floating wind turbine 6 or the marine anchor, except in extreme cases where it can be temporary li fted by the tensioning chain section 27 . In this setup also the tensioning chain section 27 normally rests on the sea floor 3 over practically its entire length due to its high own weight, even when sideward wind forces act on the wind turbine 6 .

[0061] Figure 7 shows a chain tensioner 230 according to a third embodiment of the invention . The parts that correspond with the chain tensioner 30 according to the first embodiment are provided with identical reference numbers . Only the deviating parts are discussed hereafter . The chain tensioner 230 comprises two parallel plate shaped mounting body 44 that interconnects the left side body 36 and the right side body 37 and that proj ects therefrom . The mounting bodies 44 both comprise a mounting hole 45 to which a steel mounting bracket 47 is attached by means of a steel hinge pin 48 , whereby the chain tensioner 230 can hinge around the hinge axis E transverse to the tensioning chain section 27 of the anchor chain 20 . The mounting bracket 47 is suitable to be mounted against a floating offshore facility under its water line, for example against a floater of the floating wind turbine 6. The mounting bracket 47 can be hinged around a hori zontal hinge axis H .

[0062] It is to be understood that the above description is included to illustrate the operation of the preferred embodiments and is not meant to limit the scope of the invention . From the above discussion, many variations will be apparent to one skilled in the art that would yet be encompassed by the scope of the present invention .

Claims

C L A I M S1 . Assembly comprising a tensioning chain and a chain tensioner for adj ustment of the length of the tensioning chain that extends between a floating offshore facility and an offshore anchor, wherein the tensioning chain has a chain center line and comprises a series of connected chain links each having a main plane, wherein the chain links alternatingly have their main plane in a first orientation and in a second orientation that is under an angle with respect to the first orientation, wherein the chain tensioner comprises a frame that bounds a chain passage for the tensioning chain, wherein the frame comprises a retainer body having a retainer abutment surface and a chain passage opening through the retainer body towards the chain passage, wherein the tensioning chain is moveable through the chain passage in a hauling in direction and a paying out direction with respect to the chain tensioner, and wherein the chain tensioner comprises a chain rattle that is rotatable mounted to the frame to rotate around a rattle rotation axis that extends transverse to the chain center line, wherein the chain rattle comprises a chain aw having a front j aw abutment surface for abutment of the retainer abutment surface, and a left rattle tooth and a right rattle tooth that face the chain passage to engage a chain link that extends in between, wherein the chain rattle is rotatable around the rattle rotation axis between a chain locking position and a chain hauling in position, wherein in the chain locking position the front j aw abutment surface abuts the retainer abutment surface, and the left rattle tooth and the right rattle tooth engage a chain link to lock a movement of the tensioning chain in the paying out direction, and wherein in the chain hauling in position the front j aw abutment surface is spaced apart from the retainer abutment surface ,and the left rattle tooth and the right rattle tooth are at least partially retracted from the engaged chain link, and the chain rattle is in sliding contact with the tensioning chain, wherein the rattle rotation axis extends in a direction parallel to the chain center line at a longitudinal rotation axis distance from the retainer abutment surface, and wherein the rattle rotation axis extends in a direction transverse to the chain center line at a transverse rattle rotation axis distance from the chain center line, wherein the longitudinal rotation axis distance is larger than the transverse rattle rotation axis distance .2 . Assembly according to claim 1 , wherein the chain links comprise an oval surrounding member that extends in the main plane , that has a link thickness transverse to the main plane, a longest link length in the main plane in the direction of the chain center line , and a link width in the main plane and transverse to the chain center line, wherein the longitudinal rotation axis distance is at least four times the link thickness , and wherein the transverse rattle rotation axis distance is at least one time the link thickness .3 . Assembly according to any one of the preceding claims , wherein the rattle rotation axis extends under the center of gravity of the chain rattle .4 . Assembly according to any one of the preceding claims , wherein the rattle rotation axis extends downstream from the retainer abutment surface in the hauling in direction of the tensioning chain .

5. Assembly according to any one of the preceding claims , wherein in a proj ection parallel to the rattle rotation axis , the left rattle tooth and the right rattle tooth extend in the chain hauling in position of the chain rattle with respect to the chain center line at the opposite side of the rattle rotation axis .

6. Assembly according to any one of the preceding claims , wherein the chain links have semi roundends and exposed convex chain link shoulders on the semi round ends , wherein the convex chain link shoulders of the subsequent chain links with the main plane in the same first orientation are facing each other and the convex chain link shoulders of the subsequent chain links with the main plane in the same second orientation are facing each other, wherein the left rattle tooth comprises a left chain link shoulder pocket, and the right rattle tooth comprises a right chain link shoulder pocket for receiving the convex chain link shoulders of the engaged chain link .7 . Assembly according to claim 6 , wherein the left chain link shoulder pocket and the right chain link shoulder pocket are concave having a curvature that corresponds with a curvature of the convex chain link shoulders .8 . Assembly according to any one of the preceding claims , wherein the chain links have semi round ends and exposed convex chain link shoulders on the semi round ends , wherein the convex chain link shoulders of the subsequent chain links with the main plane in the same first orientation are facing each other and the convex chain link shoulders of the subsequent chain links with the main plane in the same second orientation are facing each other, wherein the left rattle tooth comprises a left rattle lift surface , and the right rattle tooth comprises a right rattle lift surface that both extend oblique to the chain center line in the chain locking position of the chain rattle to abut the convex chain link shoulders .

9. Assembly according to claim 8 , wherein the left rattle lift surface and the right rattle li ft surface merge into the front j aw abutment surface of the chain rattle .10 . Assembly according to any one of the preceding claims , wherein the chain rattle comprises a left side body and a right side body that extend spaced apart from each other on opposite sides of the chain passage , wherein the left rattle tooth and the right rattle tootheach have a base as from which they proj ect from the respective left side body and right side body to face the chain passage .11 . Assembly according to claim 10 , wherein the chain links have semi round ends and exposed convex chain link shoulders on the semi round ends , wherein the convex chain link shoulders of the subsequent chain links with the main plane in the same first orientation are facing each other and the convex chain link shoulders of the subsequent chain links with the main plane in the same second orientation are facing each other, wherein the left rattle tooth and the right rattle tooth have at their base a largest longitudinal length in a direction parallel to the chain center line that is larger than the smallest intermediate space between the facing convex chain link shoulders .12 . Assembly according to claim 10 or 11 , wherein the chain rattle comprises a left chain guide on the left side body, and a right chain guide on the right side body, both having a same and constant curvature around the rattle rotation axis to support chain links of which the main plain extends parallel to the rattle rotation axis .13 . Assembly according to any one of the preceding claims , wherein the chain tensioner is configured for employment on a bottom of a water body, wherein the chain tensioner comprises a bottom wall or skid under the frame to stand on the bottom of the water body .-o- o-o-o-o- o-o-o-FG / HZ

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