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Title:
RING FOR A DRIVE UNIT BEARING OF A MARINE VEHICLE INCLUDING A SEGMENTED ACTIVE PART
Document Type and Number:
WIPO Patent Application WO/2017/220478
Kind Code:
A1
Abstract:
A ring for shaft bearing of a marine vehicle drive unit has an annular body (20) and a cylindrical active part intended to provide a sliding contact function with another ring at the bearing level. The cylindrical part is segmented into several cylindrical surfaces, each cylindrical surface being attached in a removable manner to the annular body (20).

Inventors:
JULLIAND, Lionel (24 Avenue du Marechal Juin, Belfort, 90000, FR)
FIEBERLING, Bruno (Boughton Road, Rugby Warwickshire, GB)
FAN, Xinmin (29 Alicia Close, Rugby Warwickshire, GB)
Application Number:
EP2017/064906
Publication Date:
December 28, 2017
Filing Date:
June 19, 2017
Export Citation:
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Assignee:
GE ENERGY POWER CONVERSION TECHNOLOGY LTD (Boughton Road, Rugby Warwickshire CV21 1BU, CV21 1BU, GB)
International Classes:
F16C17/02; B63H23/32; F16C17/10; F16C33/04; F16C33/10; F16C33/26; F16C43/02
Domestic Patent References:
WO2002016789A12002-02-28
Foreign References:
EP2993365A12016-03-09
DE102008037677A12010-02-18
GB191305619A1914-03-06
Other References:
None
Attorney, Agent or Firm:
SERJEANTS LLP (Dock, 75 Exploration Drive, Leicester Leicestershire LE4 5NU, LE4 5NU, GB)
Download PDF:
Claims:
CLAIMS

1. A ring (10, 12) for a shaft bearing (8) of a marine vehicle drive unit, comprising an annular body (20), a cylindrical active part (28) designed to ensure a sliding contact function with another ring (12, 10) of the shaft bearing (8), wherein the active cylindrical part (38) is segmented into several cylindrical surfaces, each cylindrical surface being attached in a removable manner to the annular body (20).

2. A ring (10, 12) according to claim 1, wherein the annular body (20) is segmented in several retractable annular modules (34), each annular module (34) having a cylindrical surface as part of the active cylindrical part (38).

3. A ring (10, 12) according to claim 2, wherein each annular module (34) is mobile compared to others in drive according to an axial direction (6) to the ring (10, 12).

4. A ring (10, 12) according to claim 2 or claim 3, wherein each annular module (34) has a support (36) and a radial buffer (42), the radial buffer (42) including the cylindrical surface, the radial buffer (42) can be detached from the support (36).

5. A ring (10, 12) according to any of claims 2 to 4, with a cylindrical frame (18) including, for each annular module (34), two rods (52) directed according to an axial direction (6) to the ring (10, 12), each annular module (34) including two through holes (40), each rod (52) being inserted in a through hole (40) of the associated annular module (34) so that it can slide inside of it.

6. A ring (10, 12) according to any of claims 2 to 5, wherein all of the annular modules (34) extend between two circle arcs underpinned by the same center angle.

7. A ring (10, 12) according to claim 6, wherein the center angle is between about 20° and about 40°.

8. A ring (12) according to any preceding claim, with an active frontal part (30, 32) intended to provide a sliding contact function with an axial stop (14, 16) of the shaft bearing (8), the frontal active part (14, 16) being segmented into several frontal surfaces, each frontal surface being fixed in a removable manner to the annular body (20).

9. A ring (12) according to claim 8, wherein the annular body (20) is segmented in several retractable annular modules (34), each annular module (34) having a frontal surface, the frontal surface being a part of the frontal active part (30, 32).

10. A ring (12) according to claim 8 or claim 9, wherein each annular module (34) is mobile between a position in which such annular module (34) is axially located on one side of the active frontal side (30, 32) and a position in which such annular module (34) is axially located across the active frontal part (32, 32).

11. A ring (12) according to any of claims 8 to 10, in which each annular module (34) includes support (36) and an axial support (48, 50), the axial buffer (48, 50) including the frontal surface, the axial buffer (48, 50) can be detached from the support (36).

12. A ring (12) according to any of claims 8 to 11, with a second frontal active part (32, 30) to ensure a function of the sliding contact with a second axial stop (16, 14) of the shaft bearing (8), the active cylindrical part (38) axially located between the frontal active parts (30, 32).

13. A shaft bearing (8) designed to be mounted on a shaft (2) of a water vehicle drive unit, comprising an inner ring (12) and an outer ring (10), at least one of the inner and outer rings (10, 12) being a ring according to any preceding claim.

14. A shaft bearing (8) according to claim 13, including a first axial stop (16) and a second axial stop (14), the first axial stop (16) being mobile according to an axial direction (6) of the bearing (8), the first axial stop (16) comprising a first frontal active part (62) providing a sliding contact function with the inner ring (12), the inner ring (12) including a second frontal active part (30) providing a sliding contact function with the second axial stop (14).

15. Use of a bearing (8) according to claim 13 or 14 for the disassembly of a surface forming an active part (28, 30, 32, 62) of such a bearing (8).

Description:
RING FOR A DRIVE UNIT BEARING OF A MARINE VEHICLE INCLUDING A

SEGMENTED ACTIVE PART

DESCRIPTION

[0001] This invention concerns the field of drive units of marine vehicles, such as ships, submarines or even oil platforms. More particularly, the present invention concerns the field of platform drive units.

[0002] These drive units, also known as a "propulsion oriented drive", or "POD", generally include: a mobile housing, or mobile platform, mechanically connected to the marine vehicle with a pivot link around an axis such as for example the vehicle's yaw axis, a drive shaft extending according to the mobile housing longitudinal direction and mechanically connected with a pivot link around its own axis to the marine vehicle, and a drive element, such as a propeller or a pump rotor, mounted on the drive shaft.

[0003] In general, in order to achieve the pivot link mechanically connecting the drive shaft and the drive element, two shaft bearings are mounted on both ends of the drive shaft. The two shaft bearings are designed to maintain the drive shaft on its radial direction, in other words the radial guide. For example, the shaft bearings can be friction type bearings, including two rings fastened to the mobile housing and the drive shaft respectively. One of the two rings has a cylindrical part ensuring a sliding contact function with a sliding surface provided on the other ring.

[0004] One of the two shaft bearings is also designed to ensure the drive shaft support function according to its axial direction, i.e. axial guidance. To do this, one of the concerned shaft rings has a front active part providing a sliding contact function with a sliding surface mounted on an axial stop of the drive bearing.

[0005] In order to preserve the shaft bearing life span, it's usually necessary to replace its active parts regularly.

[0006] To do so, the drive unit can be disassembled from the marine vehicle and transported in the workshop. A operator shall then have the space and tools required to open the drive bearings, disassemble the active parts and replace them with new ones. However, such a solution requires to immobilize the marine vehicle in dry docks for the time needed to replace the active parts.

[0007] In order to compensate for this drawback, arrangements can be provided within the mobile housing, so as to allow the operator to enter and work inside the drive unit of the mobile housing. In this case, it is not necessary to disassemble the drive unit and to immobilize the marine vehicle in dry docks.

[0008] However, the operator's work inside the mobile housing is usually rendered difficult, if not impossible, because of the reduced space and congestion caused by the presence of the drive bearings and other elements such as an drive shaft propulsion electric engine. This difficulty is further increased at the shaft bearing end providing both radial support function and axial support function of the drive shaft.

SUMMARY

[0009] In the light of the foregoing, the invention is intended to provide a shaft bearing or a component part of a shaft bearing addressing the aforementioned disadvantages.

[0010] In particular, the invention is intended to allow mounting or unmounting more easily of the shaft bearing active parts, including where a such a shaft bearing combines the radial guidance and axial guidance functions.

[0011] For this purpose, a ring for a marine vehicle drive unit shaft bearing is proposed, including an annular body, a cylindrical active part intended to ensure a sliding contact function with another ring of the shaft bearing.

[0012] According to a general feature of this ring, the cylindrical active part is segmented into multiple cylindrical surfaces, each cylindrical surface being attached in a removable manner to the annular body.

[0013] The use of a segmented cylindrical active part simplifies the mounting and dismounting by an technician, especially if the latter works in confined spaces such as inside the mobile housing. [0014] Conveniently, the ring including a segmented active part is designed to be mobile against the housing of the drive unit. For example, the ring can be fastened to the drive shaft. In this case, the other ring is preferably fixed against the housing. Such a provision is particularly convenient because it facilitates the dismounting of the active parts.

[0015] According to one embodiment, the annular body is segmented in several retractable annular modules, each annular module having a cylindrical surface part of the cylindrical active component.

[0016] The operator, using such a ring, can actuate the movement of one of the annular modules up to a position in which the cylindrical surface is accessible, to easily disassemble it.

[0017] We can also specify that each annular module is mobile compared to others moving on an axial direction of the ring.

[0018] According to one embodiment, each annular module includes a support and a radial buffer, the radial buffer includes the cylindrical surface and can be detached from the support.

[0019] There would also be a cylindrical frame comprising, for each annular module, two rods directed according to an axial direction of the annular, every ring module including two through holes, each rod being inserted in a through hole of the associated annular module so that it can slide inside of it.

[0020] According to one embodiment, all annular modules extend between two circular arcs underpinned by the same angle to the center.

[0021] Advantageously, the center angle interval is 20° to 40°, and more conveniently between 25° and 35°.

[0022] A design of the annular modules with a center angle ideally positioned in such intervals around 30° is convenient in that the cylindrical surfaces are small enough to be easily removable, and aren't too many to unnecessarily increase the working time of the operator.

[0023] According to one embodiment, the ring has a frontal active part to ensure a sliding contact function with an axial stop of the shaft bearing, the front active part being segmented into several frontal surfaces, each frontal face being fixed in a removable manner to the annular body.

[0024] Such a ring ensures both radial and axial guidance functions, while generating a reduced footprint and with frontal and cylindrical active parts easy to dismantle.

[0025] Preferably, the annular body is segmented in several retractable ring modules, each annular module having a frontal surface, the frontal surface being part of the frontal active part.

[0026] Conveniently, each annular module is mobile between a position wherein the respective annular module is axially located on one side of the frontal active part and a position in which the respective annular module is axially located across the frontal active part.

[0027] According to one embodiment, each annular module includes a support and an axial buffer, the axial buffer including the frontal surface, the axial buffer that can be detached from the support.

[0028] A second frontal active part can be also provided to ensure a sliding contact function with a second axial stop of the shaft bearing, the cylindrical active part being axially located between the frontal active parts.

[0029] According to another aspect, a shaft bearing is intended to be mounted on a shaft of a water vehicle drive unit, including one inner ring and one outer ring, at least one of the inner and outer rings is a ring as described previously.

[0030] Conveniently, the inner ring is a ring such as described previously according to the invention, the outer ring is a classic design ring. The interest of such a provision arises from the fact that the inner ring is most of the time the mobile ring and the outer ring is fixed.

[0031] According to one embodiment, the shaft bearing includes a first axial stop and a second axial stop, the first axial stop being mobile according to an axial direction of the bearing, the first axial stop comprising a first active frontal part providing a sliding contact function with the inner ring, the inner ring includes a second frontal active part providing a sliding contact function with the second axial stop.

[0032] According to another aspect, a use of a bearing as previously described for the dismounting of a surface forming an active part of the said bearing is proposed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Other purposes, characteristics and advantages of the invention will be revealed while reading the following description, given only as a non-limiting example, and related to the attached drawings attached on which:

[0034] Figure 1 schematically represents a shaft bearing according to a first embodiment,

[0035] Figure 2 is a perspective view of a bearing ring of Figure 1 ,

[0036] Figure 3 is a perspective view of a ring annular module of Figure 2,

[0037] Figure 4 is a cross-axial view of the ring in Figure 2 with all annular modules arranged in an operating position,

[0038] Figure 5 is a cross-axial view of the ring in Figure 2 with an annular module arranged in an assembly/disassembly position, and

[0039] Figure 6 is a cross-axial view of a shaft bearing ring according to a second example of the invention embodiment.

DETAILED DESCRIPTION

[0040] With reference to Figure 1 , a propulsion shaft 2 supporting a propulsion element (not shown) of a drive unit is described. The drive unit has a mobile housing schematically represented in Figure 1 by a framework 4. The drive unit is intended to be mounted on a marine vehicle (not shown) that can be a ship, a submarine or an oil rig. The drive element mounted on the drive shaft 2 may for example be a propeller or a pump rotor.

[0041] The propulsion shaft 2 extends according to an axial direction 6 and is mechanically connected to the mobile housing 4 by a pivot link around the axial direction 6. In the illustrated embodiment, the drive shaft 2 is rotated by an electric machine (not shown). The drive shaft 2 has one free end 9 and a driven end (not shown) across the free end 9. The driven end corresponds to the end of the shaft 2 on which the drive element is mounted. In other words, the free end 9 corresponds to the end of the shaft 2 opposite to the drive element against the electric machine. To allow for the achievement of the pivot link of the shaft 2 against the framework 4, the drive unit has a shaft bearing 8. The shaft bearing 8 ensures the relative guidance of the shaft 2 against the housing 4, according to the radial direction against the axis 6. The bearing 8 is also a function of axial stop preventing the displacement of the shaft 2 against the housing 4, depending on the axis 6 direction.

[0042] A second shaft bearing (not shown) is mounted on the driven end of the propulsion shaft 2. Thus, two shaft bearings are mounted at one end of the shaft 2 respectively. Although in the embodiment example shown in Figure 1, the shaft bearing 8, which ensures a double function of radial and axial guidance, is mounted on the free end 9, within the scope of the invention, the position of the two shaft bearings can be inverted.

[0043] The bearing 8 includes an outer ring 10, an inner ring 12, a first axial stop 14 and a second axial stop 16. The outer ring 10 and the axial stop 14 are recessed from the mobile housing 4. The inner ring 12 contains a cylindrical frame 18 and an annular body 20 mounted on the frame 18. The cylindrical frame 18 is mounted fastened to the propulsion shaft 2. For example, the cylindrical frame 18 can be fretted on the shaft 2. The annular body 20 is mechanically connected to the cylindrical frame 18 by a slide type mechanical link guided by the axial direction 6. In other words, the annular body 20 is able to move forward according to the axis 6 direction, from the frame 18.

[0044] The outer ring 10 includes a cylindrical sliding surface 22, radially located inside the outer ring 10. The sliding surface 22 extends over the entire inner circumference of the ring 10.

[0045] The axial stop 14 contains a frontal sliding surface 24 and extending in a plane substantially perpendicular to the direction of the axis 6. The sliding surface 24 spans the entire circumference of the axial stop 14, to have an annular shape extending around the axis 6.

[0046] The axial stop 16 has a frontal sliding surface 26 ranging significantly in a plane parallel to one of the sliding surface 24, i.e. in a plane substantially perpendicular to the direction of the axis 6. The surface 26 spans the entire circumference of the axial stop 16, to have an annular shape extending around the axis 6.

[0047] The 22, 24 and 26 sliding surfaces are made of materials designed to promote their friction with another surface of the inner ring 12. Another term commonly used by the skilled person to refer to the 22, 24 and 26 sliding surfaces is 'ice'.

[0048] The axial stop 16 is able to move forward compared to the mobile housing 4 according to the direction of the axis 6. Specifically, the stop 16 is able to move axially between a functioning position, as illustrated in Figure 1, and an assembly/disassembly position, axially shifted to the outside of the bearing 8, that is to say shifted to the right of Figure 1. Between the assembly/disassembly position and the operating position, the stop 16 is conveniently offset with a distance between the thickness of the inner ring 12 and three times the thickness.

[0049] We will now describe the structure of the annular body 20 of the inner ring 12, with reference to Figures 1 and 2. Figure 2 represents schematically the inner ring 12. For more clarity, only the cylindrical body 20 is represented in Figure 2, the cylindrical frame 18 having been voluntarily omitted.

[0050] The body 20 consists of an active cylindrical part 28 extending around the axial direction 6. As shown in Figure 1, the active part 28 provides a sliding contact, oriented according to the radial direction against the axis 6, with the sliding surface 22. The cylindrical body 20 consists of a first frontal active part 30 forming a substantially perpendicular plane to the axial direction 6. As shown in Figure 1 , the active part 30 provides a sliding contact, oriented according to the axial direction of the axis 6, with the sliding surface 24. Similarly, the body 20 has a second front active part 32, forming a plane substantially perpendicular to the axial direction 6. The active part 32 is axially opposed to the active part 30, compared to the ring 12. As shown in Figure 1, the active part 32 provides a sliding contact, oriented according to the axial direction of the axis 6, with the sliding surface 26.

[0051] Conveniently, a hydraulic fluid is supplied to be inserted between the active parts 28, 30, 32 and their sliding surfaces 22, 24, 26 respectively. The hydraulic fluid may consist of a thin layer of oil to allow for a transfer of efforts between the rings by generating a limited friction. [0052] In reference to Figures 2 and 3 , the annular body 20 is divided into twelve annular modules 34 substantially identical. In the illustrated embodiment example, all annular modules 34 extend between two circle arcs underpinned by the same center angle (not referenced) being substantially equal to 30°. However, considering a different number of annular modules, or a different center angle is within the invention framework. We can still specify that some of the annular modules extend between two circle arcs underpinned by a first value of center angle, the other annular modules extending between two circle arcs underpinned by a second center angle value, separate from the first.

[0053] Referring to Figure 3, each annular module 34 includes a support 36 delimited lengthwise by two planes parallel and perpendicular to the axial direction 6, and orthoradially by two secant planes and forming between them an angle roughly equal to 30°. The support 36 extends radially inward by a protruding part 38. The protruding part 38 includes two through holes 40. The through holes 40 are substantially directed according to the axial direction 6.

[0054] Each annular module 34 has a radial buffer 42 extending radially outward the support 36. The radial buffer 42 is made of a material limiting friction with the sliding surface 22. The radial buffer 42 is attached to a mounting tab 44. The mounting tab 44 can be connected to the base 36 with two screws 46.

[0055] The annular module 34 includes also a first axial buffer 48. The first axial buffer 48 can be attached to a tab similar to tab 44, such tab can be connected to the base 36 by means similar to the screws 46. Same as the buffer 42, the buffer 48 is made of a material limiting friction with the sliding surface 24.

[0056] The annular module 34 includes also a second axial buffer 50. The buffer 48 and buffer 50 extend the support 36 according to the axial direction 6, each respectively according to an opposite direction. Same as the buffer 48, the buffer 50 can be attached to a tab to allow its fixation in a removable manner on the support 36. The buffer 50 is preferably made of a material limiting friction with the sliding surface 26.

[0057] As this is visible in Figure 2, when the twelve annular modules 34 are placed side by side, the twelve buffers 42 form a substantially cylindrical surface as the cylindrical active part 28. Similarly, the twelve axial buffers 48 realize a substantially flat and annular surface constituting the frontal active part 30. Similarly, the twelve axial buffers 50 realize a substantially flat and annular surface constituting the frontal active part 32.

[0058] The two through holes 40 of the protuberance 38 of each module 34 are each for the passage of a pin 52 (see Figure 5) of the cylindrical frame 18. Frame 18 includes 24 pins 52 that extend in the same direction parallel to the axis 6. This results in the possibility, for each module 34, to move forward compared to the frame 18 according to the axial direction 6. In other words, each of the modules 34 can move forward according to the axial direction 6, compared to the other modules 34.

[0059] In reference to Figures 4 and 5, the axial stop 16 is mounted on a mobile sleeve 56. The sleeve 56 is arranged around the shaft 2 and is especially able to move forward according to the axial direction 10 against the shaft 2. In this way, the axial stop 16 can be moved between the operating position (fig. 4), in which it's in support and connected with the outer ring 10, and an assembly/disassembly position (see Figure 5), in which it is shifted axially outward from level 8. In order to limit the axial shift of sleeve 56 compared to the shaft 2, the said shaft 2 has a stop radial protrusion 58.

[0060] When the axial stop 16 is arranged according to the operating position, the active cylindrical part 28 is in contact with the sliding surface 22, the frontal active parts 30, 32 being in contact with the sliding surfaces 24, 26 respectively. The rotating bearing 8 provides the radial and axial guidance functions of the inner ring 12 compared to the outer ring 10, against the axis 6. Fixation means 57, in this case screws, allow for the connection of the outer ring 10 with the axial stop 16.

[0061] When, as shown in Figure 5, the sleeve 56 is shifted axially outwards from the bearing 8, the axial stop 16 is arranged according to its assembly/disassembly position. It is then possible to shift each of the modules 34 axially outward from the outer ring 10 according to an assembly/disassembly position of the module 34. In particular, it is possible to shift each of the 34 modules, so that the buffer 48 of the module 34 is located outside the space axially between the frontal active parts 30 and 32. In order to limit the axial shift of a module 34 from the frame 18, the pins 52 each have a stop item 54.

[0062] It is then possible for an operator to easily access the buffer(s) 42, 48 or 50 of the module 34 which has been shifted, and disassemble the said buffer(s). To do this, the operator disengages the fastening means 57 then drives the axial displacement of the sleeve 56 from its operating position to its assembly/disassembly position. The operator can then remove the buffers 50 constituting the active part 32 and replace them. Then, the operator drives one of the modules 34 in an axial direction from its operating position to the assembly/disassembly position. He then dismantles and replaces the buffer 42 and buffer 48 of the moved module 34. The operator then resets the module 34 in its operating position. He rotates the shaft 2 by a 30° angle, and then implements the same actions on the 34 module which took the place of the module 34 for which the buffers are to be replaced. When the operator has replaced the buffers of all the modules 34 and reset them in their operating position, he shifts the axial stop 16 from its assembly/disassembly position until its operating position, then he engages again the fastening means 57. This manipulation is easier when the buffers have reduced dimensions thanks to the segmentation of the annular body 20. Thus, the operator is not obstructed to manipulate them inside the mobile housing 4.

[0063] In addition, by operating small rotations of the shaft 2 against the housing 4, the operator can make sure to always place the module 34 on which he works in one place, for example in a place located vertically above the axis 6. The operator then only needs to access a small space within the mobile housing 4 to easily disassemble the active parts of the bearing 8.

[0064] In the illustrated embodiment example, we chose to segment the annular body 20 into twelve annular modules 34. However we could have, without exceeding the invention scope, consider a different number of annular modules. In particular, by choosing a higher number of annular modules, the size of the radial and axial buffers to handle is reduced for the replacement of the active parts, so as to facilitate the operator's work for a single annular module. However, the increase in the number of annular modules multiplies the assembly or disassembly actions of radial or axial buffers, so as to lengthen the time necessary for the operator to replace all the buffers of the annular modules. The number of twelve modules 34 is a good compromise, allowing easy handling of the buffers, while avoiding an unnecessarily increase of the duration of the active parts replacement operations.

[0065] In this embodiment example, the inner ring has a cylindrical active part and two front active parts. However, the scope of the invention is not exceeded by considering a rotating bearing, in which the active parts are laid out differently. [0066] According to a first (not shown) alternative to this first embodiment example, the front active part 32, formed by the buffers 48, is no longer part of the inner ring 10, but is fixed on the axial stop 16. However, the annular body 20 includes the sliding surface 26. According to a second variant (not shown), the active part 30 is attached to the axial stop 14, cylindrical body 20 including the sliding surface 24. Each of these variants is technically feasible and allows the bearing 8 to perform its function, facilitating the replacement of at least some of the active parts by an operator. The first variant, however, is more interesting than the second, because it allows, as the first example of realization, to axially shift the three buffers 42, 48 and 50 outside of the space axially positioned between the active parts 30 and 32.

[0067] In the first example of realization and its first and second variants, the active cylindrical part 38 is part of the inner ring 12, the outer ring 10 having the sliding surface 22. As a result, it is easier for the operator to access the buffer 42 constituting the active part 38.

[0068] According to a third variant (not shown), the cylindrical active part is mounted on the outer ring, the inner ring including the corresponding sliding surface. Although such variant makes the dismantling by the operator of the buffers forming the cylindrical active part more complicated, this variant simplifies the overall design of the shaft bearing compared to the first example of realization. It may result in a reduced cost of bearing design and manufacture, as well as a smaller footprint.

[0069] Moreover, the invention has been described in reference to a bearing 8 combining the radial and axial guidance functions of the shaft 2 compared to the frame 4. However, it is possible to specify a bearing according to the invention and providing the only radial guide function. In other words, the invention can be also implemented with the shaft bearing set on the driving end of the shaft 2. In this case, this bearing is different from the bearing 8 in that it lacks the axial stops 14 and 16 and active parts 30 and 32. Furthermore, it is of course possible to envisage without exceeding the scope of the invention a ring including a segmented cylindrical active part, and one or two front active parts not segmented.

[0070] Referring now to Figure 6, a second example of the invention embodiment is represented. Identical items carry the same references. [0071] As in the first example, the inner ring 12 includes a frame 18 and an annular body 20 segmented in several annular modules (not referenced). The second example of embodiment differs especially from the first example, in that each annular module is also segmented according to the radial direction from the axis 6, in an internal portion 64 and an external portion 66. The external portion 66 extends radially projecting outward from the inner portion 64. The portion 64 may be moved forward, relatively compared to the portion 66, according to the direction of the axis 6. When the annular modules are in operating conditions, a locking mechanism 68 prevents the relative movement of the internal portion 64 of each module from the external portion 66. For example, the locking mechanism 68 may include a snap ring.

[0072] In addition, according to the second example, the inner ring 12 includes a frontal sliding surface 60, noticeably flat and perpendicular to the axis 6, and an axial sliding contact with an frontal active part 62 mounted on the axial stop 16. Thus, the distribution of the active parts between the rings 10, 12 and stops 14, 16 is the first alternative of the first example of realization. As noted, this provision allows the bearing to properly insure its double function of radial and axial guidance, while optimizing the space to facilitate the replacement operations of the bearing active parts.

[0073] By means of a bearing according to the second example of embodiment, an operator can implement the following procedure for the disassembly of the active part 30.

[0074] As a first step, the operator removes the locking mechanism 68. Then, the operator moves the internal portion 64 in displacement, relatively against the external portion 66, according to the axis direction 6, until the active part 30 is axially shifted outside the space axially delimited by stops 14 and 16. As a result, it is easier for an operator to remove the buffers 48 forming the active part 30.

[0075] Once the buffers 48 are dismantled and replaced, the operator moves the internal portion 64 to its original position and replaces the locking mechanism 68.

[0076] In view of the two examples which have been detailed in reference to the figures, the invention allows an operator to replace the active parts of a marine vehicle drive unit bearing ring more easily. It results, in particular, in the possibility to maintain the shaft bearings without having to disassemble the drive unit and therefore without having to put the ship in dry docks.

[0077] The invention is even more interesting when the shaft bearing, for which the active parts are to be replaced provides a dual function of guidance according to the radial and axial directions.

[0078] Indeed, it appears already that a bearing including especially both a cylindrical active part and two frontal active parts in which the cylindrical active part is arranged axially between the frontal active parts presents a much smaller footprint than a conventionally used bearing, which includes a first rotary bearing ensuring the radial guidance and an axial stop bearing providing axial guidance.

[0079] In addition, with a bearing consistent with the invention, the operator can remove and replace the buffers forming the front and cylindrical active parts by working in the same place. The result is the possibility of increasing the volume of this space, so as to further facilitate the replacement of the active parts of the bearing from the inside of the mobile housing of the drive unit.