At large rotor shafts, e. g. rotor main shafts of wind turbines, the shaft is often supported in very large rolling bearings, where the outer diameter of the bearing can amount to 1500 mm and more, and it is thereby very difficult to exchange the bearing in case of bearing failure. Without special solutions it should be necessary at a bearing break-down to dismount the main shaft itself, which can be situated at a level of 80 meters or more above the ground, to lower the heavy main shaft with its bearing to the ground and to replace the bearing which has failed, and thereafter again to lift up the main shaft with its new bearing and mount it in the turbine. This is of course a time-wasting and expensive task and particularly as the wind turbines are often located in areas, which are difficult to reach with mobile cranes, which have sufficient lifting range and lifting power for the rather heavy lifts concerned.

In order to facilitate this replacement of bearings and avoid the necessity to dismount the main shaft and lower it to the ground, it has earlier been suggested to use split bearing rings, which means that it has been possible to separate the parts of the split rings in a bearing which has failed and to replace them for other such parts in the position of the shaft in the turbine, thus eliminating the need for bearing exchange at ground level.

However, this solution has certain drawbacks as the split rings are more expensive to produce than one-piece rings, at the same time as the split bearing ring never will get the same performance as the one-piece rings. This is particularly expressed regarding the grip between the bearing rings and their seats, which can result in fretting corrosion.

Purpose and most relevant features of the invention The purpose of he present invention is now to propose a spare shaft bearing by means of which the above mentioned drawbacks are substantially reduced in order to give a substantially extended service life to the bearing assembly, without the need of dismounting it and making the replacement of the failed bearing at ground level, and this has been achieved with a spare shaft bearing as defined in claim 1 of the accompanying claims.

The invention also incorporates a method for replacing a failed bearing, supporting a shaft, without need for separating the shaft from a wind power turbine or another machine equipment with which it cooperates, and this method is characterized by the features defined in the characterizing part of claim 5.

Finally the invention incorporates a means for effecting the bearing replacement operation defined in claim 5, and this means is characterized by the contents in claim 9.

Brief description of the drawings Hereinafter the invention will be further described with reference to the accompanying drawings, which show an embodiment of the spare shaft bearing according to the invention, and the means for mounting it.

Fig. 1 shows schematically a shaft with a bearing supporting the shaft shown in section, and also a spare bearing according to the invention, also shown in longitudinal section.

Fig. 2 is a schematic view of a portion of a shaft and a spare bearing during mounting by means of a means also encompassed by the present invention.

Description of the preferred embodiment Fig. 1 shows a shaft 1, for instance a rotor shaft of a wind power mill. The shaft 1 in this embodiment is made as an externally tapering tubular shaft, which at one side has a cylindrical section 2. The shaft 1 is supported in a rolling bearing 3, in the embodiment shown a toroidal roller bearing, which has the-ability of mutual axial displacement and angular misalignment between the inner and outer bearing rings. The inner ring of the

bearing 3 has a tapering bore and is fitted to the shaft via an adapter sleeve 4, and secured in position by means of a locating nut 5. The bearing 2 is enclosed in a housing intimated at 6 and 7, and where at least a cover part 7 of the housing is detachably connected to the other part 6 of the housing, thus that the bearing is accessible after dismounting of the housing part 7, which is also split in two parts (not further shown) for allowing it to be readily removed. Around the shaft 1, at a position axially spaced apart from the bearing housing 6,7 along the reduced portion of the tapering shaft is provided an one-piece outer bearing ring 8, an one-piece inner bearing ring 9 and a one-piece locating nut 10, which together form a set of components for a spare bearing. With these components 8,9 and 10 positioned at a distance from the ordinary bearing 3, where they are retained in a (not shown) manner, they are in a semi-mounted position ready for substituting the ordinary bearing, if this should fail, or measurements should prove that it would soon fail.

In case such an ordinary bearing should break down or a condition monitoring system or the like should indicate that a failure is near at hand, it is comparatively easy to open the bearing housing by removing the split bearing housing cover 7, which due to its two-piece form can be easily removed from the shaft 1 without the necessity of dismounting the shaft.

When the bearing housing then is open, it is easy to reach the bearing and to dismount it from the adapter sleeve 4 in conventional manner after loosening the locating nut 5, thereby driving the bearing out off the housing 7. Then the outer and inner bearing rings of the ordinary bearing and its locating nut 5 are each cut up to make it possible to remove them from the shaft 1.

Thereupon, a set of rolling bodies 16, as can be seen in Fig. 2 (in the present case designed as toroidal rollers) is inserted between the outer and inner rings 8,9 of the spare bearing, possibly together with a split cage (not shown) for separating and guiding the rollers.

With the rollers inserted between the bearing rings 8,9 this spare bearing is pushed axially to the left in Fig. 1 until it engages and enters on the adapter sleeve 4.

In this position the mounting means according to the invention is fitted around the shaft 1 as can be seen in Fig. 2 showing a longitudinal section of a portion of the shaft and the spare bearing 8,9 during mounting at the position of the now removed ordinary bearing 3,

shown in Fig. 1. The mounting means consists of a tool kit incorporating a split support ring 11, a split hydraulic drive up tool comprising a number of individual tool segments 12, which are held together around the adapter sleeve 4 by means of a flat chain 13 or the like.

Each one of the individual tool segments 12 has at least one recess 14, preferably of cylindrical shape and in which is movably fitted a plunger 15. To each such recess 14 is connected a (not shown) conduit which can be connected to a conventional hydraulic pump (not shown).

When the mounting means has been fitted with the front ends of the plungers 15 engaging the inner bearing ring 9, the plungers 15 are urged outward from their recesses 14 by injection of hydraulic oil, whereby the inner bearing ring 9 is pushed upon the adapter sleeve 4 until a desired grip is obtained between bearing ring 9, adapter sleeve and shaft 1.

When the desired grip has been reached during the drive-up operation, the recesses 14 are drained and the support ring 11 is loosened, whereupon the chain 13 is disconnected and the tool segments are removed. The spare locking ring 10 (Fig. 1) then is screwed up on the threaded portion of the adapter sleeve 4 to secure the inner bearing ring 9 of the spare bearing in its position. Thereupon the split housing cover 7 (see Fig. 1) can be easily attached and the rotor shaft is retrofitted with a new bearing having the same good performance as that of the ordinary bearing, also regarding interference fit, which can not be guaranteed with bearings with split rings, and which can result in seating wear.

At a bearing breakdown or indications of a coming breakdown it is possible, in this manner to make a required exchange of the failing bearing for a new bearing having non-split bearing rings and locating nut, in a time span which is very short as compared to the earlier used dismounting of the rotor shaft and with bearing rings which are not weakened or otherwise impaired by being split.

The spare bearing components arranged about the rotor shaft are preferably coated with an anti-corrosive agent, and the components are kept apart during their rest time, whereby no wear will occur. This is not the case if a complete spare bearing was arranged around the shaft. Before the spare bearing is mounted, the components are cleaned to remove the anti- corrosive rest time coating.

In addition to the pair of un-split bearing rings and the locating nut arranged about the shaft there must be kept in store sets of rollers 16, a split cage (not shown) and a tool kit 11-15.

However for a wind power park having e. g. 100 turbines, it is probably sufficient to store only two or three sets of rollers and split cages and only one tool kit.

The invention is not limited to the embodiments shown in the attached drawings and described in connection thereto, but modifications and variants are possible within the scope of the accompanying claims. Although it has been described and shown that a one- piece locating nut is arranged about the shaft together with the one-piece bearing rings, it is of course possible to use a locking device made in more than one part, which can be readily mounted around the shaft without the necessity to dismount the shaft or to position the locking device around the shaft as a spare part.