The present invention relates to bearings, and more particularly to relatively large bearing assemblies used in mooring turrets.

Turrets for mooring ships, drill platforms or other floating structure are known and typically include a generally cylindrical body connected with the adjacent seafloor through a plurality of cables or other anchoring means. Generally, a plurality of risers extend between sections of the seafloor to the turret so as to transport fluids (e.g., oil, natural gas, etc.) to the mooring turret, and thereafter to the platform or vessel. A vessel, work platform (e.g., oil rig), or other structure is connected with the turret upper end so as to secure the structure generally at a specific location.

In certain applications, it is desired to permit oscillatory pivotal movement of the vessel or structure, referred to as "weathervaning". In such applications, the mooring turret includes a bearing assembly or similar means to enable angular displacement of the vessel/platform with respect to the turret.

SUMMARY OF THE INVENTION

In one aspect, the present invention is a bearing for a mooring turret for anchoring a vessel or a work platform to a seafloor, the turret having a lower end coupleable with the seafloor and an opposing upper end. The bearing comprises a generally annular rail having a central pivot axis and inner and outer circumferential surfaces, the rail being connectable with one of the turret upper end and the vessel or work platform . At least one inner roller is rotatable about a central axis extending generally parallel with respect to the rail axis and is disposed against the rail inner circumferential surface. At least one outer roller is rotatable about a central axis extending generally parallel with respect to the rail axis and is disposed generally against the rail outer circumferential surface. Further, a carriage is connectable with the other one of the turret upper end and the vessel or work platform, is connected with the at least one inner roller and the at least one outer roller, and is configured to retain the inner and outer rollers rollingly engaged with the rail. As such, the inner roller rolls along the rail inner surface and the outer roller rolls along the rail outer surface as the vessel or work platform angularly displaces generally about the pivot axis.

In another aspect, the present invention is again a bearing for a mooring turret for anchoring a vessel or a work platform to a seafloor, the turret having a lower end coupleable with the seafloor and an opposing upper end. The bearing assembly comprises a generally annular rail having a central pivot axis and inner and outer circumferential surfaces, the rail being connectable with one of the turret upper end and the vessel or work platform, at least one of the inner and outer surfaces including upper and lower surface sections. At least one roller is connectable with the other one of the turret upper end and the vessel or work platform, is rotatable about a central, generally vertical axis, and includes a roller upper portion and a roller lower portion. The roller upper portion is rollingly engaged with the rail upper surface section and the roller lower portion is rollingly engaged with the rail lower surface section such that the roller upper portion rolls along the rail upper surface section and the roller lower portion rolls along the rail lower surface section as the vessel or work platform angularly displaces generally about the pivot axis. The roller upper portion supports axial loading in a first direction along the pivot axis and the roller lower portion supports loading in a second, opposing direction along the pivot axis.

In a further aspect, the present invention is yet again a bearing assembly for a mooring turret for anchoring a vessel or a work platform to a seafloor, the turret having a lower end coupleable with the seafloor and an opposing upper end. The bearing assembly comprises a generally annular rail having a central pivot axis and inner and outer circumferential surfaces, the rail being connectable with one of the vessel and the turret upper end. A plurality of inner rollers are each rotatable about a separate central axis extending generally parallel with respect to the rail axis and disposed against the rail inner circumferential surface and a plurality of outer rollers are each rotatable about a separate central axis extending generally parallel with respect to the rail axis and disposed generally against the rail outer circumferential surface. Further, a plurality of carriages are spaced circumferentially about the pivot axis, each carriage being connectable with the other one of the turret upper end and the vessel or work platform and connected with a number of the plurality of inner rollers and with a number of the plurality of outer rollers. Each carriage is configured to retain the number of the inner rollers and the number of the outer rollers rollingly engaged with the rail such that the inner rollers roll along the rail inner surface and the outer rollers roll along the rail outer surface as the vessel or work platform angularly displaces generally about the pivot axis.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the detailed description of the preferred embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings, which are diagrammatic, embodiments that are presently preferred. It should be understood, however, that the present invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:

Fig. 1 is a more diagrammatic, side elevational view of a vessel having a turret with a bearing assembly in accordance with the present invention;

Fig. 2 is top plan view of the bearing assembly;

Fig. 3 is a partly broken-away, perspective view of the bearing assembly, showing a single bogie assembly;

Fig. 4 is a radial cross-sectional view of the bearing assembly taken through the inner and outer rollers of one bogie assembly;

Fig. 5 is a broken-away, top plan view of a rail of the bearing assembly;

Fig. 6 is an enlarged, radial cross-sectional view through a portion of the rail;

Fig. 7 is a top plan view of a preferred carriage plate;

Fig. 8 is an enlarged, radial cross-sectional view through one bogie assembly;

Fig. 9 is radial cross-sectional view of the bearing assembly, showing an alternative rail construction with adjustably mounted rollers;

Fig. 10 is a broken-away, top plan view of a section of the bearing assembly of Fig. 9, showing an adjustable coupler;

Fig. 11 is an alternative construction of the bearing assembly including horizontal rollers; and

Fig. 12 is a top plan view of the bearing assembly of Fig. 11.

DETAILED DESCRIPTION OF THE INVENTION Certain terminology is used in the following description for convenience only and is not limiting. The words "right", left", "lower", "upper", "upward", "down" and "downward" designate directions in the drawings to which reference is made. The words "inner", "inwardly" and "outer", "outwardly" refer to directions toward and away from, respectively, a designated centerline or a geometric center of an element being described, the particular meaning being readily apparent from the context of the description. Further, as used herein, the word "connected" is intended to include direct connections between two members without any other members interposed therebetween and indirect connections between members in which one or more other members are interposed therebetween. The terminology includes the words specifically mentioned above, derivatives thereof, and words of similar import.

Referring now to the drawings in detail, wherein like numbers are used to indicate like elements throughout, there is shown in Figs. 1-12 is a bearing assembly 10 for a mooring turret 1 for anchoring a vessel V or a work platform (e.g., an oil rig, etc. - none shown) to a seafloor F. The mooring turret 1 may be "internal" (as depicted in Fig. 1) or "external" and has a lower end Ib coupleable with the seafloor F and an opposing upper end Ia. Such a mooring turret 1 is also known a "chain table" and by other designations, and the term "mooring turret" as used in the present specification is intended to include all devices for movably securing a vessel V or platform P to a seafloor F, as generally described and depicted herein.

The bearing assembly 10 basically comprises a generally annular rail 12, one or more inner rollers 14, one or more outer rollers 16, and at least one carriage 18 connected with the inner and outer rollers 14, 16. The rail 12 defines a central pivot axis 13 extending generally vertically through the turret 1, has inner and outer circumferential surfaces 12a, 12b, and is connectable/connected with the vessel/platform or the turret upper end Ia. Each inner roller 14 is rotatable about a central axis 15 extending generally parallel with respect to the rail axis 13 and is disposed against the rail inner circumferential surface 12a. Further, each outer roller 16 is rotatable about a central axis 17 extending generally parallel with respect to the rail pivot axis 13 and is disposed generally against the rail outer circumferential surface 12b. Thus, the rotational or "rolling" axes 15, 17 of the inner and outer rollers 14, 16 are generally parallel with each other (and parallel with the pivot axis 13) and extend generally vertically.

Furthermore, each carriage 18 is connectable with the other one of the vessel/platform or the turret upper end Ia (i.e., whichever is not directly connected with the rail 12) and is connected with at least one and preferably a plurality of inner rollers 14 and with at least one and preferably a plurality of outer rollers 16. The carriage(s) 18 are configured to retain the inner and outer rollers 14, 16 rollingly engaged with the rail 12 such that each inner roller 14 rolls along the rail inner surface 12a and each outer roller 16 rolls along the rail outer surface 12b as the vessel/platform angularly displaces generally about the pivot axis 13. Thereby, the bearing assembly 10 supports the vessel/platform, and the turret 1, during a "weathervaning" oscillatory movement of the vessel/platform.

Preferably, the bearing assembly 10 includes a plurality of inner rollers 14 spaced circumferentially about the pivot axis 13 and generally disposed against the rail inner circumferential surface 12a and a plurality of outer rollers 16 spaced circumferentially about the pivot axis 13 and disposed generally against the rail outer surface 13. Also, as discussed below, the bearing assembly 10 preferably includes a plurality of carriages 12, with a number of inner rollers 14 (e.g., two, three, etc.) and the same number of outer rollers 16 each being connected with a separate one of the plurality of carriages 12. However, all of the inner and outer rollers 14, 16 may be connected with a single carriage 18, as is also discussed below, and/or the number of inner rollers 14 may differ from the number of outer rollers 16.

Referring to Figs. 3-9 and 11, the rail 12 preferably includes a first shoulder 20 extending generally radially inwardly toward the pivot axis 13 and providing the rail inner circumferential surface 12a, as described below, and a second shoulder 22 extending generally radially outwardly from the pivot axis 13 and providing the rail outer circumferential surface 12b, as discussed in further detail below. Each one of the rail first and second shoulders 20, 22 preferably has a generally triangular cross-section in each radial plane through the pivot axis 13 (see, e.g., Figs. 4 and 6), but may alternatively be generally frustaconical, generally semicircular, etc. Further, each one of the inner and outer rollers 14, 16 has an outer circumferential surface 24, 26, respectively, and a groove 25, 27, respectively, extending inwardly from the outer surface 24, 26 and toward the roller central axis 15, 17, respectively. With this structure, each inner roller groove 25 receives a portion of the rail first shoulder 20 and each outer roller groove 27 receives a portion of the rail second shoulder 22, as best shown in Figs. 4 and 8. As such, axial loading F _A on the bearing assembly 10 is transferred between the one or more inner rollers 14 and the rail first shoulder 20 and/or is transferred between the one or more outer rollers 16 and the rail second shoulder 22. Referring now to Figs. 2, 3, 5 and 6, the rail 12 is preferably generally circular, is centered about the pivot axis 13, and is preferably formed of two or more arcuate sections 19 (see Fig. 5) connected together by any appropriate means (e.g., weldment, fasteners, etc.), which may be one-piece (Figs. 3, 4, 6 and 8) or formed of upper and lower subsections 19a, 19b (see Fig. 9). However, the entire rail 12 may alternatively be of one-piece construction (e.g., as a single casting). Further, the rail first and second shoulders 20, 22 are preferably formed such that the rail inner and outer surfaces 12a, 12b each include an upper angled surface section 21 A, 23 A, respectively, and a lower angled surface section 2 IB, 23B, respectively, the inner and outer surface sections 21A/21B and 23A/23B being generally converging. The two upper surface sections 21 A, 23 A face generally in an upward axial direction Dj and the two lower surface sections 2 IB, 23B face generally in an opposing, downward axial direction D ₂ , for reasons discussed below. Further, the rail 12 preferably includes a plurality of threaded openings or through holes 31 to facilitate attachment of the rail 12 to the vessel/platform or turret 1.

Referring to Figs. 9 and 11, in alternative constructions of the rail 12, the rail 12 includes upper and lower support extensions 35, 37 each providing inner and outer vertical support surfaces 35a, 35b, and 37a, 37b, respectively. The vertical support surfaces 35a, 35b, 37a, 37b provide additional contact area for each of the inner and outer rollers 14, 16 in order to support relatively greater "overturning" moments Moi or M ₀₂ , as indicated in Fig. 9. The support extensions 35, 37 may have substantially equal axial lengths, as depicted in Fig. 9, or the upper extension 35 (or lower extension 37) may have a lesser length to provide space for one or more radial rollers, as shown in Fig, 11 and discussed below.

As best shown in Fig. 2, the bearing assembly 10 preferably includes a plurality of carriages 18 (e.g., 10-20) spaced circumferentially about the pivot axis 13 as discussed above, with at least one and preferably a number of inner rollers 14 (e.g., two, three, etc.) and at least one and preferably the same number of outer rollers 16 being connected with each one of the carriages 18. As such, each carriage 18 and the number of connected inner and outer rollers 14, 16 form one bogie assembly 11. Further, the number of bogie assemblies 11 of a particular bearing assembly 10 is selected for the particular loading requirements of the turret 1 and/or the required diametrical size of the turret 1. Thus, a plurality of different sized bearing assemblies 10 may be readily constructed from a quantity of substantially identically constructed bogie assemblies 11, each particular bearing assembly 10 including a particular number of the bogies assemblies and an appropriately sized rail 12, which itself may be formed of number of standard- sized arcuate sections 19 as required for a particular application of the bearing assembly 10. Referring to Figs. 2 and 7, each of the one or more carriages 18 preferably includes a generally rectangular plate 28 having upper and lower surfaces 29 A, 29B, with one or more inner rollers 14 being connected with one of the plate surfaces 29 A, 29B and one or more outer rollers

16 being connected with the same plate surface 29A, 29B. Preferably, each plate 28 has inner and outer edges 28a, 28b curved to at least generally conform to the curvature of the rail 12 and a plurality of attachment openings 33 for mounting the shafts 30 of the rollers 14, 16, as described below. Although a plurality of separate carriages 18 forming a plurality of bogie assemblies 11 is presently preferred, the bearing assembly 10 may alternatively include a single, generally annular carriage to which all of the inner and outer rollers 14, 16 are attached, thus forming a single bogie assembly (structure not shown).

Referring now to Figs. 4, 8 and 9, each one of the inner and outer rollers 14, 16 is preferably constructed so as to include a shaft 30, a roller body 32, and at least one roller bearing 34. Each shaft 30 is connected with the single carriage 18 or one of the preferred plurality of carriages 18, and preferably adjustably connected as described below, with each roller axis 15,

17 of the particular roller 14 or 16 extending generally longitudinally through the shaft 30. Specifically, each shaft 30 preferably has opposing upper and lower ends 30a, 30b, one end 30a or 30b being connected with one surface 29 A or 29B of the carriage 12 and the other end 30b, 30a being spaced from the carriage 18. As such, the roller axis 15 or 17 extends generally perpendicular with respect to the plate surface 29A or 29B, and also preferably generally vertically. Further, each roller body 32 is disposed about the associated shaft 30 and is rollingly engageable with the rail 12, with the at least one roller bearing 34 rotatably coupling the roller body 32 with the shaft 30. As such, each roller body 32 is angularly displaceable about the particular roller axis 15 or 17 as the body 32 rolls along or against one of the rail surfaces 12a or 12b.

Preferably, each roller body 32 has an upper body portion 40 and a lower body portion 42 spaced axially along the shaft 30 from the upper body portion 40. Each one of the upper and lower body portions 40, 42 is rotatably coupled with the shaft 30 by a separate roller bearing 34. Further, a lower end 40a of the upper body portion 40 of each one of the rollers 14, 16 is preferably disposed generally against an upper end 42a of the lower body portion 42 of the particular roller 14, 16. As such, each circumferential groove 25, 27 of the inner and outer rollers 14, 16, as discussed above, is defined between the angled contact surfaces 41, 43 of the upper and lower body portions 40, 42, as described below.

As best shown in Fig. 4, the roller bearing 34 of each of the upper and lower body portions 40, 42 of both the inner and outer rollers 14, 16 is preferably a double-row tapered roller bearing having two bearing rows 34a, 34b, so as to support both axial and radial loading on the roller 14 or 16, but may be any other appropriate type of bearing. Further, the bearing 34 of each of the upper and lower body portions 40, 42 is preferably provided by a commercially available sealed bearing unit, most preferably an SKF ^® standard railway bearing, but may be any other commercially available type of bearing or even be specially manufactured. However, if a non- sealed bearing is alternatively used, the upper and lower roller body portions 40, 42 should each be provided with one or more suitable seals (e.g., contact HBNR lip seal, labyrinth seal, etc.) in order to exclude contaminants, such as dirt, salt water, etc., from entering the bearing 34 and to retain lubricants within the bearing 34. In any case, by having double-row tapered roller bearings 34, the rollers 14, 16 are able to support and/or transfer both radial and axial loads between the rail 12 and the carriage 18, and thus between the vessel/platform and turret 1, or vice- versa. As shown in Figs. 9 and 11 , in applications utilizing non-sealed bearings and in which relatively greater overturning moments Moi, Mo ₂ are anticipated, the rollers 14, 16 may be provided with an additional (i.e., a third row) radial bearing 39 between the two preferred rows 34a, 34b, such as a cylindrical or spherical roller bearing, to provide increased support of the higher radial forces generated within the rollers 14, 16 by the moments Moi, Mo _2.

Referring again to Figs. 4 and 8, the upper body portion 40 of each one of the inner and outer rollers 14, 16 has a generally vertical, circumferential contact surface 45, a lower end 40a, and an angled circumferential contact surface 41 adjacent to the lower end 41 and facing generally in the downward axial direction D ₂ . The contact surface 41 of the inner roller upper body portion 40 is rollingly engaged with the upper surface section 21 A of the rail inner surface 12a and the contact surface 41 of the outer roller upper body portion 40 is rollingly engaged with the upper surface section 23 A of the rail outer surface 12b. As such, at least one of the upper body portions 40 of the inner and outer rollers 14, 16 interacts with the rail 12 to support axial loading in the downward direction D ₂ along the central pivot axis 13. Also, with rail constructions that include support extensions 35, 37, the upper body vertical contact surfaces 45 roll against inner and outer vertical support surfaces 35a, 35b to provide additional support against overturning moments Moi or Mo ₂ -

Further, the lower body portion 42 of each one of the inner and outer rollers 14, 16 has a generally vertical, circumferential contact surface 47, an upper end 42a, and an angled circumferential contact 43 located surface adjacent to the upper end and facing generally in the upward axial direction D ₁ . The contact surface 43 of the inner roller lower body portion 42 is rollingly engaged with the lower surface section 21B of the rail inner surface 12a and the contact surface 43 of the outer roller lower body portion 42 is rollingly engaged with the lower surface section 23B of the rail outer surface 12b. As such, at least one of the lower body portions 42 of the inner and outer rollers 14, 16 interacts with the rail 12 to support axial loading in the upward direction Di along the axis 13. Additionally, with a rail structure having support extensions 35, 37, the lower body vertical contact surfaces 47 roll against inner and outer vertical support surfaces 37a, 37b to increase resistance to overturning moments Moi, Mo2-

Referring to Figs. 9 and 10, each of the inner and outer rollers 14, 16 is preferably adjustably connected with the associated carriage 18, by any appropriate means, so as to establish or maintain contact between the various surfaces of each roller 14, 16 and the associated surfaces of the rail 12, as described in detail above. For example, the upper end 30a of each shaft 30 may be connected with the carriage plate 28 by an offset cam lobe 50 attached to the shaft end 30a and interacting with a counterbore opening 52 so as to displace the shaft 30, and thus the associated roller 14 or 16, generally radially toward or away from the rail 12 (see Fig. 10). Alternatively, the roller shafts 30 may be adjusted relative to the carriage 18, and thus the rail 12, by means of an electromechanical device(s), such as for example, a worm gear and worm wheel operated by a motor. By having an electromechanical adjustment means, the rollers 14, 16 may be automatically adjusted to compensate for variations in dynamic operating conditions (e.g., duty cycles, loads, rotational forces, etc.), particularly when such automatic adjustment means incorporate one or more sensors to monitor contact between the rollers 14, 16 and the rail 12, such as position sensors, contact pressure sensors, etc. However, as shown in Fig 4, each roller 14, 16 may alternatively be fixedly connected with the carriage 18, such as by a threaded fastener, etc.

Referring now to Figs. 1 1 and 12, in certain constructions, the bearing assembly 10 may further include at least one and preferably a plurality of axial support rollers 60 disposed generally between the inner and outer rollers 14, 16 and configured to rollingly engage an upper, generally horizontal radial surface 62 of the rail 12. More specifically, each radial roller 60 is rotatable about a generally horizontal axis 61 extending generally perpendicularly to the inner and outer roller axes 15, 17, respectively, and are all preferably spaced circumferentially about the pivot axis 13, as best shown in Fig. 12. As such, the axial support rollers 60 provide increased support of axial or thrust forces, such as generated by the weight of the turret 1 and/or vessel/platform.

Furthermore, the bearing assembly 10 may further include one or more sensors (none shown), particularly in the bearings 34 of the rollers 14, 16, and/or an automatic lubrication system (not shown) for automatically lubricating the bearings 34.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined in the appended claims.