SE541709C2 - Bearing arrangement and method of mounting a bearing arrangement - Google Patents

Abstract

The invention relates to a bearing arrangement for a propeller shaft (5) comprising a bearing housing (13, 16), a radial bearing (1) and a thrust bearing (2) within said housing (13, 16) and a fixation assembly (3, 4, 6) for fixation of said bearing (1, 2) onto said shaft (5), wherein said fixation assembly (3, 4, 6) comprises a first clamping sleeve (4) for the radial bearing (1), a second clamping sleeve (6) for the thrust bearing (2) and a combi sleeve (3) fixedly connecting said first clamping sleeve (4) with said second clamping sleeve (6).

Description

BEARING ARRANGEMENT AND METHOD OFMOUNTING A BEARING ARRANGEMENT FIELD OF THE INVENTION The present invention relates to a bearing arrangement for a propeller/impeller shaft comprising a bearing housing, a radial bearing and a thrust bearing within said housing and a fixation assembly for fixation of said bearing onto said shaft.

BACKGROUND INFORMATION Many mechanical systems require a transfer of force from one object to another. This transfer of force between the two objects may impose a set of mechanical constraints on the objects (e.g., specifications on their dimensions and properties). These constraints are often more complex when one object moves against the other object. In some implementations (e.g., a shaft rotating in a housing) the objects should transfer some forces to each other (e.g., a normal force) but not transfer other forces (e.g., a shear force). Many such implementations utilize a bearing between the two objects.

A bearing may provide for the control (e.g., minimization) of friction between two objects moving against each other. In some cases, a bearing must transfer large normal forces between two objects, yet minimize friction between the two objects (reducing shear forces transferred from one object to the other). For example, a railway turntable that rotates about a base may have a bearing that supports large normal forces (e.g., the weight of a train) yet minimizes friction between the turntable and base as the turntable rotates. A thrust bearing may provide for an efficient transfer of axial force (e.g., from the turntable to the base).

A bearing may also control a distance between two objects that move against each other. An axle or shaft rotating about a central axis may require a bearing that keeps the shaft accurately "centered" about the axis of rotation (i.e., the axis of the shaft is coaxial with an axis describing the housing within which the shaft rotates). For some systems, a large normal force between the two objects may cause sufficiently large deformation that the objects are displaced from their desired positions. For example, a lightly loaded shaft may remain centered, while high loading offsets the shaft with respect to the housing. Such offset may increase wear, cause vibration, decrease lifetime, and the like.

A shaft rotating within a housing may require the transfer of both axial and radial normal forces, and provide for controlled displacement in multiple dimensions. For example, an application may require that the angle between the shaft axis and housing axis tilt with respect to each other. Such applications may benefit from the use of a spherical bearing, which permits for an angular rotation about two axes (e.g., a rotational axis of a shaft and an axis about which the shaft "tilts" with respect to the housing). A spherical bearing includes a center, which defines the point (in this example) at which the rotational axis and tilt axis intersect.

Some systems benefit from the use of multiple bearings. A first bearing (e.g., a thrust bearing) may provide for improved transfer of axial loads, and a second bearing (e.g., a spherical bearing) may provide for improved transfer of radial loads. Some applications use two or more spherical bearings, and may require very accurate positioning of these bearings, such that the centers of the spherical bearings are identical (i.e., the bearings are concentric). In such cases, the relative positions of the bearings, shaft, and housing should be accurately controlled.

A bearing and/or an assembly may be preloaded. In such cases, two objects and the bearing between them are assembled in a manner that creates a force (e.g., compression) between the objects after assembly. An expected elastic deformation associated with the preload may be incorporated into the design, such that the elastically deformed system "fits" the desired dimensional specifications of the system. Because preloading typically increases friction between the two objects separated by the bearing, the magnitude of the preloaded forces should be tightly controlled (e.g., high enough to achieve a desired position control but not so high as to increase friction too much).

Preloading forces are dependent upon the strain (e.g., the displacement) used to impose the preload force. These strains change the position of various objects with respect to each other. For assemblies requiring both accurate preload and accurate positioning, achieving both a desired preload and a desired positional accuracy may be challenging.

This challenge may be particularly difficult when using multiple spherical bearings (e.g., having desired preloads and concentric centers). Maintaining concentricity of the spherical bearings while maintaining a desired preload may require very accurate positioning, but should not increase friction between the two objects separated by the bearings.

Surmounting these positioning challenges has often entailed the use of complicated mechanical structures and/or processing methods. Some systems may use threaded attachments, but forming threads may increase costs and affect the strength of the shaft by introducing stress concentrations. Some systems may be press fit. In such cases, a pre-defmed mismatch between two mating dimensions causes an elastic deformation during assembly. After assembly, the elastic forces associated with this deformation affix the parts to each other. For example, a cork for a wine bottle may be elastically compressed prior to assembly, inserted into the neck of the wine bottle, then allowed to expand. The expansion of the cork against the neck after assembly holds the cork in place.

In some press fit applications, the "fitting force" resulting from the press fit is largely governed by the relevant part dimensions, and so may not be easily adjustable after these dimensions have been machined (e.g. during assembly or maintenance). In some systems, an outer part may be heated, such that it fits around a smaller part when heated, but contracts to grip the smaller part when cooled. Some applications may not tolerate the required heating, and maintenance of the assembled parts may be difficult (particularly for parts that may not be easily heated after assembly).

The use of an assembly that provides for a desired preload and positioning specification (e.g. for an assembly of spherical bearings) may substantially increase materials cost, machining costs, maintenance costs, and the like. It may be advantageous to have an assembly that provides for these specifications at lower cost than that of existing solutions.

Bearing arrangements for shafts to water jet propulsion units in ships have to withstand long-term thrust, radial forces and reversed thrust. So as to being able to withstand said forces said bearing arrangements comprise many parts which are designed purposely and specifically for the bearing arrangements. As a result of not being mass-produced said parts are relatively expensive to produce leading to high production costs, and/or relatively low life span. Further, known arrangements are often cumbersome and costly to mount/dismount. Another disadvantage is that normally key couplings are used to securely lock the inner sleeve of the bearing onto the shaft. The use of a wedge coupling implies numerous disadvantages, e.g. reduction of the strength of the shaft. Finally there is a general strive to avoid the need of threads in the shaft, which is indeed needed in some prior art solutions.

There are known bearing arrangements where wedge couplings have been eliminated, but such known arrangements are either incapable of handling all needed forces acting in a large water jet arrangement and/or to cumbersome to handle. In document US 6,170,991 a propeller thrust bearing assembly is described. Said propeller thrust bearing assembly includes a spherical rolling bearing provided on a shaft and abutting against a shoulder, and a spherical thrust bearing, incorporating a shaft washer fitted on the shaft, a housing washer provided in a housing surrounding the shaft and a set of rolling bodies provided between the shaft washer and the housing washer. A spacing sleeve is provided between the spherical rolling bearing and the spherical thrust bearing, and a lid member is attached to the housing. The lid member is adapted to urge the housing washer against the set of rolling bodies and via the rolling bodies against the shaft washer. The axial distance between the two bearings is such that their force lines meet at a point situated on the center axis of the shaft. The spherical rolling bearing has a taper bore and is mounted on a withdrawal sleeve, and the spacing sleeve has internal threads and is screwed onto the withdrawal sleeve. A tubular member is arranged about the shaft and is adapted to keep the shaft washer pressed against the rear end of the spacing sleeve facing away from the spherical rolling bearing. The tubular member is secured in position by means of a locking nut screwed onto the threads of the shaft. This arrangement has several disadvantages, e.g. the need of using threads on the shaft.

The document GB 324,587 describes a device for securing a pair of collars, such as ball races for bearings, or the like upon a shaft, wherein a pair of longitudinally split conical sleeves, slidable upon the shaft and adapted to fit conical bores in the collars, are forced into the cones bores of the collars or the like by a single screwing operation without necessitating rotation of either of the cones sleeves, the movement of which is effected by means of a screwed sleeve or nut engaging both the coned sleeves. Lateral movement is prevented by abutments which may comprise a split spring ring or a divided collar engaging a circumferential groove, and a collar engaging a shoulder on the shaft. Further, US 1,377,637 also presents a solution using split sleeves. Also these arrangements cannot normally meet the demands needed in relation to a large water jet arrangement.

SUMMARY OF THE INVENTION It is an object of the present invention to overcome or at least minimize at least one of the drawbacks and disadvantages of the above described techniques. This can be obtained as defined by the appended claims.

Thanks to the invention reliable and easy mounting and demounting of the bearing arrangement is facilitated. Furthermore the invention safeguards exact and controlled positioning of the bearings, which is a prerequisite to achieve a long life span. Further the design may enable less expensive production costs and enables slimmer shaft.

Further aspects of the invention will become apparent by the detailed description and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: Fig. 1 shows a bearing arrangement in a perspective view, according to the invention, Fig. 2 shows the details in a bearing arrangement, in a cross section view along B -B in figure 1, Fig. 3 shows a front view of a combi sleeve according to the invention, Fig. 4 shows a perspective view of a combi sleeve according to the invention, Fig. 5 shows a cross section along a - a in figure 3, and Fig. 6-11 show, in sequence, the bearing assembly according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following detailed description, and the examples contained therein, are provided for the purpose of describing and illustrating certain embodiments of the invention only and are not intended to limit the scope of the invention in any way.

Figure 1 shows a bearing arrangement 10 preferably intended for a shaft 5 to a water jet propulsion unit (not shown) used for ships but could also be used in other application areas. The bearing arrangement 10 is shown in a perspective view in figure 1 and in figure 2 it is shown in a cross sectional view, exposing details in the bearing arrangement 10. On the cylindrical shaft 5 with a first 52 and a second 53 raised part is shown/mounted from left to the right, a seal housing 12, an aft bearing housing 13, a radial bearing 1, a rear conical clamping sleeve 4, a combi sleeve 3, a front conical sleeve 6, a thrust bearing 2 and a front bearing housing 16, i.e. mostly standard products in combination with a preferred embodiment of a novel combi sleeve 3 according to the invention. To withstand high forces, all sleeves 3, 4, 6 are formed as contiguous annular sleeves, i.e. without any weakening longitudinal slit.

As is shown in Fig. 2 the first raised portion part 52 of the shaft 5 has larger diameter D than the diameter d of the second raised part 53. In a preferred embodiment the difference D-d is in the range of 10-40 mm, preferably less than 30 mm. A typical shaft would be in the range 150 - 500 mm. In the transition between the larger part 52 and the smaller part 53 there is a perpendicular shoulder 52A. Further, there is arranged a tapered front surface 53 A at the end of the second raised part 53 forming the transition to the general diameter DS of the shaft 5. It is evident that this transition must not be tapered, but may also be perpendicular. Moreover it is shown that the seal housing 12 in between the shaft 5 and the actual housing is arranged with first 120 and a second 121 seal arrangements. In the preferred embodiment the first seal arrangement 120 is in the form of a mechanical face seal and the second seal arrangement 121 in the form of lip seal. In between the aft bearing housing 13 and the shaft 5 there is a lip seal 131, acting against a seal sleeve 8, that has one side abutting the shoulder 52A of the first raised part 52. The inner annular part of the seal sleeve 8 has an L-shaped form, to provide an annular space 132 in between it and the second raised part 53 of the shaft 5. The general diameter DS of the shaft 5 is preferably in the range of 2-20 mm less than the diameter d of the second raised part 53.

The radial bearing 1 preferably comprises a spherical roller bearing 1 intended to take lateral forces from the shaft 5. The thrust bearing 2 preferably comprises an axial roller bearing 2 intended to take the thrust from the shaft 5. The centre of the spherical roller bearing 1 and the axial roller bearing 2 coincides, allowing biasing of the shaft 5. A force line 1 A from the radial bearing 1 and a force line 2A from the thrust bearing 2 coincides at a point 5A located on the central axis of the shaft 5, see figure 11 .

Figure 3 shows a front view and figure 4 shows a perspective view of a combi sleeve 3 in a preferred embodiment according to the invention. The combi sleeve 3 comprises an aft part 35, a front part 36 and a middle part 34.

In figure 5 is shown a cross section along A - A in figure 3. Said aft part 35 has an outer diameter DC in the interval 50 - 400 mm, preferably in the interval 100 - 300 mm and in the described embodiment about 200 mm. The inner surface of said aft part 35 comprises inner threads 32 intended to interact with said rear clamping sleeve 4 which will be described in more detail further on. The middle part 34 comprises a collar 343 that extend around the combi sleeve 3 on its exterior, forming an integrated part of the combi sleeve 3. The collar 343 has an aft side 340 that may be inclined an angle a against the front part 36. As is evident there is no absolute need to have an inclination, since the basic function of the collar 343 is to provide strength, but the inclination may assist in obtaining compactness. At its outer periphery there is a cylindrical surface 342. At the front side there is a perpendicular surface 341, intended to act as a support edge for the thrust bearing 2. The front part 36 comprises an inner conical surface 3 lwith an inclination ? intended to interact with the front clamping sleeve 6. The inclination of the inner conical surface 31 is, preferably in the range of 4 - 6 °, in this described example 4.76°. The skilled man realizes that the inclining and dimensions on different parts are arranged to match each other in each application. Between the inner surface of said aft part 35 and the inner conical surface 31 of the front part 36 there is an inwardly tapered surface 33 forming a smaller inner diameter on the front part 36 than at the aft part 35.

According to figures 6-11 the bearing assembly will now be described in sequence according to the invention. At stage for bearing assembly the seal housing 12 and the aft bearing housing 13 already are mounted onto the cylindrical shaft 5 (see figure 6) and comprises a seal sleeve 8 arranged to abut the shoulder 52A on the first raised part 52 of the shaft 5. Next sequence is to bring on the spherical roller bearing lwith the associated rear conical clamping sleeve 4 onto the shaft 5. Said rear conical clamping sleeve 4 with the associated spherical roller bearing 1 is mounted directly on the second raised part 53, such that the first edge thereof may enter into the annular space 132 in between the seal sleeve 8 and the shaft 5, such that it snugly fits onto the shaft and the first side of the inner part of the spherical roller bearing 1 bottoms against the seal sleeve 8.

Thereafter the spherical roller bearing 1 is pressed into fixed attachment with the shaft 5 by preloading a nut 14, (preferably a so called KM-nut that is a standard nut belonging together with a specific conical clamping sleeve), to a specified torque, which will move the rear conical clamping sleeve 4 in a direction away from said shoulder 52A and squeeze/clamps the spherical roller bearing 1 into desired fixation, see figure 7.

Thereafter said nut 14 is dismantled from the rear conical clamping sleeve 4. Thanks to the small inclination (?1, which may be about the same as ? mentioned above) of the rear conical clamping sleeve 4 the preload between the rear conical clamping sleeve 4 and the spherical roller bearing 1 enables to be retained also after the nut 14 has been dismantled. Said nut 14 is a standard part of the bearing assembly and is merely used during part of the assembly. Figure 8 shows the bearing arrangement 10 when the nut 14 has been dismantled from the rear conical clamping sleeve 4.

In the next step the combi sleeve 3, the front conical sleeve 6 and the thrust bearing 2 are put together. First the inner portion of the thrust bearing 2 is pressed onto the front part 36 of the combi sleeve 3 until it abuts the support edge 341. Thereafter the front conical sleeve 6 is placed in the bearing cone i.e. inside the combi sleeve 3 and the unit comprising the combi sleeve 3, the front conical sleeve 6 and the thrust bearing 2 is positioned directly onto the shaft 5. As shown in fig. 9 the unit 2, 3, 6 is moved onto the shaft 5 until the combi sleeve 3 gets in contact with the rear conical clamping sleeve 4. Then the inner threads 32 of said aft part 35 of the combi sleeve 3 are used in interaction with (standard)threads 40 on the exterior of the rear conical clamping sleeve 4. The unit 2, 3, 6 is threaded onto the rear conical clamping sleeve 4 until the aft part 350 of the combi sleeve 3 abuts the spherical roller bearing 1 and thereby also positions/secures the thrust bearing 2 axially. Thereafter the front conical sleeve 6 is pulled to a desired(predetermined) torque, by means of a second nut 15, preferably a standard KM-nut, i.e. threaded to preload the front conical sleeve 6 to achieve also radial fixation. The support edge 341 aids that the thrust bearing 2 is fixed in a correct axial position. The combi sleeve 3 offers a number of advantages, e.g. easy mounting/dismounting, securing of the spherical roller bearing 1 axially, transfer of axial load through the collar 34 and secure radial/axial positioning of the thrust bearing 2.

Thereafter the front bearing housing 16 is assembled on a conventional way. Between an outer face of the thrust bearing 2 and the front bearing housing 16 compression springs 7 are arranged (see figure 10). There are a plurality of compression springs, e.g. six compression springs 7 with 60° pitch. The compression springs 7 ensure that a minimum bearing load is achieved and since the spherical roller bearing 1 permits some axial movement the compression springs holds the thrust bearing 2. Figure 10 shows the bearing arrangement 10 when the front bearing housing 16 is mounted. The last step is to mount a shaft seal 17 and a sealing flange 18 that is seen in figure 11.

The above described bearing arrangement offers a plurality of advantages. The absence of a recess in the shaft (for a wedge coupling) and any threads on the shaft leads to less expensive production costs and enables slimmer shaft. Using this kind of clamping also excludes the need of heating at mounting/dismounting which leads to a more facilitated mounting/dismounting process.

Numerous changes and modifications may be made to the above described and other embodiments of the present invention, without departing from its scope as defined in the appending claims. For example, as is evident from the above, also the demounting of an arrangement according to the invention is easily performed, normally without any need of heating to loosen fittings. Further, it is evident that the second support member 350 of the combi sleeve 3 may also be in the form of a shoulder like arrangement (not shown), i.e. even if preferred, it is not necessary to use the outer end of the combi sleeve to axially fixate the first bearing. Moreover it is foreseen that a separate support member (not integrated with the combi sleeve 3) may also be used to achieve a desired distance between the bearings 1, 2.

Claims (13)

1. Bearing arrangement, for a propeller shaft (5) comprising a bearing housing (13, 16), a first bearing (2) and a second bearing (1) within said housing (13,16) and a fixation assembly (3, 4, 6) for fixation of said bearings (1, 2) onto said shaft (5), wherein said fixation assembly (3, 4, 6) comprises a first clamping sleeve (6) for the first bearing (2), a second clamping sleeve (4) for the second bearing (1), wherein a combi sleeve (3), having a first end, a support edge (341) for said first bearing and a second support member (350) for said second bearing, is arranged to fixedly connect said first clamping sleeve (6) with said second clamping sleeve (4), to fixate said first bearing (2) and said second bearing (1) a predetermined distance (1) them between, characterized by said first and second bearings (2, 1) being a thrust bearing (2) and a radial bearing (1) and said first and second clamping sleeves (6, 4) forming contiguous annular sleeves (4, 6), having different inner diameters (d, DS) wherein one of said support edge (341) and said second support member (350) is formed by a shoulder (341) at the exterior surface of said combi sleeve (3).

2. Bearing arrangement according to claim 1, characterized in that the other one of said support edge and said second support member (341,350) is formed by said first end of said combi sleeve (3).

3. Bearing arrangement according to claim 1 or 2, characterized in that said combi sleeve (3) is arranged with an inner surface (31) that, preferably merely partly, is tapered presenting a sharp angle (?).

4. Bearing arrangement according to claim 3, characterized in that said sharp angle (?) is the same as the tapering angle (?1) of the outer surface of said first clamping sleeve (6).

5. Bearing arrangement according to any of claims 2 to 4, characterize d in that said combi sleeve (3) at its inner surface adjacent said first end is arranged with threads (32) arranged to interact with corresponding threads at the part of the second clamping sleeve (4) facing said first end.

6. Bearing arrangement according to claim 5, characterized in that there is arranged a taper (33) adjacent the inner of said threads (32), which taper forms a transition to a neighbouring part of said combi sleeve having an inner surface (31) with a smaller maximum diameter than that of the said threads (32).

7. Bearing arrangement according to any preceding claim, characterized in that said combi sleeve (3) is fixedly attached onto said first clamping sleeve (6) by means of a nut (15) onto the end of the first clamping sleeve (6) facing away from said combi sleeve.

8. A bearing arrangement according to any preceding claim, characterized in that said bearing housing (13,16) includes two parts, a first part (13) encompassing said radial bearing (1) and a second part (16) encompassing said thrust bearing (2).

9. A method for mounting a bearing arrangement, onto a propeller shaft (5), comprising the steps of providing a bearing housing (13, 16), a radial bearing (1), a thrust bearing (2) and a fixation assembly (3, 4, 6) for fixation of said bearings (1, 2) onto said shaft (5), wherein firstly a second clamping sleeve (4) for the radial bearing (1) and, radial bearing (1) mounted onto said second clamping sleeve, is mounted onto the shaft (5) at a position (53) having a first diameter (d), and thereafter a first clamping sleeve (6) together with a combi sleeve (3) and the thrust bearing (2) is mounted onto the shaft (5) at a second position having a smaller diameter (DS) than said first diameter (d), wherein said combi sleeve (3) is threaded onto said second clamping sleeve until a second support member (350) of the combi sleeve abuts the radial bearing (1) and subsequently the thrust bearing is positioned so that it abuts a support edge (341) whereby the combi sleeve achieves a fixed, but releasable, connection between said second clamping sleeve (4) and said first clamping sleeve (6), and the support edge formed by a shoulder (341) at the exterior surface of said combi sleeve (3) is used to fixate said radial bearing (1) and said thrust bearing (2) with a predetermined distance (1) between them.

10. A method according to claim 9, characterized in that the distance between said support edge and second support member determines said predetermined distance (1).

11. A method according to claim 10, characterized in that said second support member (350) is formed by a first end of said combi sleeve (3).

12. A method according to claim 11, characterized in that said combi sleeve (3) at its inner surface adjacent said first end is provided with threads (32) arranged to interact with corresponding threads at the part of the second clamping sleeve (4) facing said first end (350).

13. A method according to any of claims 9-12, characterized in that said bearing housing (13,16) includes two parts, wherein a first part (13) for housing of said radial bearing (1) is mounted on said shaft (5) in a step prior to mounting a second part (16) for housing of said thrust bearing (2) onto said shaft (5).