Technical field

The invention relates to segmented cages, in particular for tapered roller bearings, for housing wind turbine shafts.

State of the art

Wind turbines have very large bearing diameters. Tapered roller bearings are used in wind turbines with variously designed, mainly plastic cages, which have advantageous material properties due to the low thermal expansion and low thermal conductivity. These cages have a large diameter and they are therefore manufactured as segmented cages with different segment shapes which are then joined together at their faces. The joining of the segments creates a segmented cage which encircles the inner ring of the bearing and,, together with rolling elements, creates a bearing semi-assembly which is pressed onto the main shaft of the wind turbine. Because the cage has to ensure the cohesion of the bearing semi-assembly during manipulation and lifting, the individual segments have to be firmly connected together, so that the cage does not collapse when the semi-assembly is lifted

The prior art discloses a cage as introduced in document DE 10 2008 011 112 A1, which consists of a plurality of segments in the form of a circular arc, the side walls of which are provided with prismatic protrusions on one face and prismatic grooves on the opposite face, which correspond with its negative shape to the prismatic protrusions, so that adjacent arc segments of the cage fit together circumferentially like lodes, as shown in Fig. Inside the segment, three pairs of shaped projections are arranged to secure the position of the tapered roller elements, which have transverse holes into which pins by which the two opposite side sections of the cage are connected, fit.

In the document W02006094661A1, a bearing cage is presented where each arc- shaped segment contains central bridges and half-bridges on both sides which are provided with bottom feet of columnar portions, however, the connection of the segments is again provided on the side walls of the segments.

In the document US9810263 B2, a cage for a tapered bearing of a wind turbine is disdosed comprising arc-shaped segments, each segment comprises protrusions with feet separating the individual tapered rollers. The protrusions with feet act as guides for tapered roller elements. After connecting all segments, a gap is left between the first and the last segment, which serves as an dilatation joint.

The method of joining segments is then described in JP2007285507 A, wherein the ends of segments have shaped locks that fit together by mutually corresponding shapes. This is a variation of the connection shown in Figure 1.

In the document ON 111536160 a cage is presented consisting of arc-shaped segments having bridges, wherein the outermost bridge of the segment is always provided with rectangular locks with projections, while the outermost bridge of the adjacent segment is provided with locks of negative shape so that the two outermost bridges with locks fit into each other. The segments are of metal, and are welded together. This method of joining is not suitable for non-weldable materials.

The aim of the invention is to present a segmented cage for a large tapered roller bearing, especially for wind power plants, which would be functional and safe.

Summary of the invention

The above mentioned deficiencies are eliminated by the segment bearing cage according to the invention, which is characterised by the fact thatthe half-bridges of the segments are always provided with at least two holes which are angled towards the centre of the segment at an angle on the first half-bridge and with two holes, which are angled away from the centre of segment on the opposite second half-bridge, whereas the spacing between the holes, measured on the axes of the holes on the outer surface of the half- bridge, is equal to the spacing between the holes, measured on the axes of the holes on the outer surface of the opposite half-bridge, for the creation of mutual continuously aligned and concentric holes after two adjacent half-bridges are joined together, whereas in the holes the shanks of the rivets provided with an end part for clinching are arranged.

In preferred embodiment around the holes there are recesses for the head of the rivet, respectively later clinched end head of the rivet, whereas the spacing between the perpendicular axes of the recesses on the first half-bridge is smaller than the spacing between the perpendicular axes of the recesses on the opposite second half-bridge.

In another embodiment the angle of the holes is between 10 and 45°.

In another embodiment the holes and the recesses are always four and they are arranged in the comers of the half-bridges and are arranged in pairs axially below each other. In another embodiment the segments of the cage are created by injection molding technology.

Brief description of drawings

The invention will be further described using drawings, where Fig, 1 is a perspective view of a segmented bearing cage according to the prior art, Fig. 2 is a perspective view of a segment of a bearing cage according to the invention, Fig. 3 is a detailed view of a cross-section of a non-riveted joint of two cage segments of Fig. 2, and Fig. 4 is a detailed view of a cross-section of a riveted joint of two cage segments of Fig. 2.

Preferred embiment of the invention

Fig. 2 shows a segment 1 of a tapered roller bearing cage in perspective view. The segment 1 of the cage is arc-shaped and comprises a first outer side 2, an opposing second outer side 9, which are transversely connected at the middle of their length by a central bridge 4 and at the ends of their length they are connected by half-bridges 3, 3' which, after two segments 1 are joined, create a bridge as large as the central bridge 4.

For technological manufacturing reasons, the first outer side 2 is provided with two outer hollows 14 and one inner hollow 18 having a depth of almost the entire height of the outer side 2. Thus, the outer side 2 is formed by thin walls in order to prevent too much material being injected and to prevent shrinkage cavities in the material structure. For the same reasons, the second outer side 9 is from the outside provided with an arc groove 19. At the bottom, a relief 20 is provided under the hollows 14, 18 to prevent the cage from colliding in operation with the bearing ring.

The central bridge 4 is provided on both sides with lower guiding projections 6 on the lower curvature and upper guiding projections 5 arranged between them on the upper side. These projections 5, 6 fix the tapered roller bearing elements. The half-bridges 3, 3' are provided with these projections 5, 6 only on the inner side. The central bridge 4 is provided with a relieve recess 15 at the top. The half-bridges 3, 3* are provided with an opened recess 16. The recesses 15, 16 make the wall thinner and have the effect of making the wall more flexible, which helps to accommodate the tapered roller elements.

As mentioned above, a bearing semi-assembly consisting of an inner ring, cage and rolling elements is first pressed Onto the main shaft of the wind turbine. In order the segmented cage surrounds the inner ring, the connection of the segments 1 has to be well secured. According to the invention, this is done as follows: The half-bridges 3, 3' in the present embodiment are provided with four holes 7 in the comers of the segments 1 which are angled towards the centre of the segment 1 on the half-bridge 3 at an angle a preferably from 10 to 45° and at the same angle α four holes 7' are angled away from the centre of the segment 1 on the half-bridge 3'. A minimalist variant can also be imagined, where the half-bridges (3, 3') of the segments 1 are always provided with at least two holes 7 which are angled towards the centre of the segment 1 at an angle a on the half-bridge 3 and the two holes T are angled at the same angle a away from the centre of the segment 1 on the half-bridge 3'. The inclination is best seen in detail in Fig. 3 and 4.

The spacing H between the holes 7 measured on the axis of the holes 7 on the outer surface of the first half-bridge 3 is equal to the spacing h of the holes 7' measured on the axis of the holes 7' on the outer surface of the opposite second half-bridge 3', so that when two adjacent half-bridges 3, 3' of the two segments 1 are connected, the holes 7, 7' are smoothly aligned and concentric for easy insertion of a shank 11 of the rivet 17. This can be seen in detail in Fig. 3. The rivet 17 can obviously be inserted into the connection in the opposite way to that shown. Around the holes 7, 7', recesses 8, 8' are provided on the inner side for a head 10 of the rivet 17 or the later clinched end part 12 of the rivet 17 into the end head 13, which can be seen in Fig. 4. The spacing K between the perpendicular axes of the recesses 8 is smaller at the first half-bridge 3 than the spacing k between the perpendicular axes of the recesses 8' at the opposite second half-bridge 3' due to the inclination of the shank 11 of the rivet 17. In entire view, the spacings h, k are indicated in Fig. 2.

Due to the inclination of shanks 11 of the rivets 17 and of holes holes 7, 7 an increased clamping effect of adjacent segments 1 is secured