Field of the Invention

The present invention relates to a seal for a roller bearing. More in particular, the present invention relates to a seal for roller bearings having a wire cage, for example a meandering wire cage.

Background of the Invention

It is well known to use a cage in roller bearings to retain the rollers during assembly and disassembly of the bearing, and to space the rollers apart during use of the bearing. Roller bearing cages may have various designs and can be made of metal or plastic, for example. German patent DE102008014552 B4 (SKF), for example, discloses a wire cage of which the wire sections constitute a first ring, a second ring and pairs of elements extending between these rings. United States Patent US1389385 (Robson) discloses a much simpler design involving a single meandering wire which can be said to constitute an interrupted first ring, an interrupted second ring and elements extending between the interrupted rings so as to provide spaces for the rollers.

An important advantage of a wire cage is that it can be manufactured relatively

inexpensively, especially the relatively simple meandering design. However, it has been found that conventional bearing seals are not suitable for mounting on a wire cage.

United States Patent US6217223 (SKF) discloses a cage-guided seal with an annular support body formed from sheet metal. Several tongues distributed along the circumference of the support body are punched out or cut out to form retention sections which can bend around the side ring of the cage. . The retention sections are provided with hooks which prevent an easy release. In addition, this type of seal requires a sheet metal base and therefore consists of at least two parts.

International patent application WO 87/04502 (Machinenfabrik Horst Kabus) discloses an injection moulded roller bearing cage having a groove for mounting a seal. To this end, the seal is provided with a circumferential protrusion shaped to fit in the cage groove. Such a seal cannot be mounted on a wire cage as a wire cage has no such groove.

Summary of the Invention

It is an object of the present invention to solve these and other problems of the prior art by providing a seal for a roller bearing cage, in particular a wire cage, which can be removed more easily.

It is a further object of the present invention to provide a seal for a roller bearing cage, in particular a wire cage, which has a reduced friction. Accordingly, the present invention provides a seal for a roller bearing having an inner race, an outer race, and a cage having at least one wire part extending between the inner race and the outer race in a circumferential direction, characterized by at least female snap fitting for removably mounting the seal on the wire part of the cage.

By providing snap fittings, in particular female (that is, receiving) snap fittings, the seal can both be easily mounted on and be easily removed from a wire cage. It will be understood that snap fittings have no hooks as in US6217223 mentioned above. Instead, female snap fittings typically comprise two substantially flexible elements or tongues extending towards the object to be fitted to, the elements being spaced apart so as to define a space for receiving the object, each element having at least one protrusion facing the opposite element, such that when the object is forced between the elements and past the protrusions, the elements are temporarily pushed apart for passing the object. The protrusions are typically rounded or have sloping surfaces in both the insertion direction and the removal direction for letting the object pass. As a result, the object may be inserted and removed. When applied to a bearing seal, the seal may be easily installed but also easily removed for maintenance purposes.

It is noted that the snap fitting of WO 87/04502 mentioned above may be characterized as a male snap fitting, which is unsuitable for use with a wire cage.

Accordingly, in a preferred embodiment, each snap fitting of the seal comprises a pair of flexible tongues. Advantageously, each snap fitting may also comprise a spacer element arranged between the flexible tongues. Such a spacer element serves to define the position of the object (here: the cage wire) when it is received between the tongues. Using such a spacer element, the position of the seal relative to the cage is better defined. In addition, the design of the seal is made more flexible as the distance between the seal and the cage is primarily defined by the spacer, not by other parts. It will be understood that such a spacer element is not present in male seal snap fittings of the prior art.

The seal of the present invention may advantageously comprise at least one serrated surface for sealing against an outer surface of the inner race and/or of the outer race. A serrated surface may be provided with sealing ribs. In such an embodiment, the sealing ribs do not rest against opposing inner surfaces of the races, as in US6217223 mentioned above, and the slight spacing between the seal and the races is not determined by the resilience of the seal material. Instead, it is preferred that the spacing element is designed for spacing the seal relative to the inner race and/or outer race such that the at least one serrated surface slidably seals against the respective race. That is, the small gap between the seal and the races is determined by the spacing member, thus allowing a very precise positioning of the seal and an excellent trade-off between sealing and friction. Preferably, the seal is provided with at least two serrated surfaces, more preferably serrated surfaces extending over the entire circumference of the seal. Each serrated surface may comprise one or more sealing ribs, which preferably provide a circumferential seal.

In addition to the serrated surfaces, the seal of the present invention is preferably further provided with at least one circumferential element extending from the body of the seal so as to form a labyrinth seal together with one of the inner race and the outer race. By providing a labyrinth seal in addition to the sealing of the serrated surfaces, the sealing action is further improved without increasing friction. It is preferred that the seal has at least two such circumferential elements for labyrinth sealing against both races.

The seal of the present invention may be made of a suitable synthetic polymeric material, such as nylon, for example by injection moulding or by additive manufacturing (3D printing).

The present invention further provides a roller bearing provided with a seal as described above. The seal of the present invention is particularly useful for a roller bearing having a wire cage. A non-limiting example of a wire cage is a cage comprising a meandering wire constituting an interrupted first ring, an interrupted second ring and connecting sections extending between the interrupted rings, the connecting sections defining spaces for receiving rollers of the roller bearing. Such a wire cage may be provided with a plurality of separators for separating the rollers from each other and for separating the connecting sections from the rollers.

In a bearing having such a wire cage, it is preferred that the separators are mounted on the connecting sections, that is, on those parts of the wire cage which extend between the first and the second (interrupted) ring. This avoids mounting the separators on the rings themselves which would require additional space around the rings for fastening means. In addition, by mounting the separators on the connecting sections, any forces exerted by the rollers on the separators are directly transferred to the cage, thus improving its stability.

The present invention still further provides a wheel provided with a bearing as described above. The wheel may be designed for use in a train or a wind turbine, for example.

Brief description of the drawings

The present invention will further be explained with reference to exemplary embodiments illustrated in the drawings, in which:

Fig. 1 schematically shows, in a cross-sectional view, part of a roller bearing provided with a seal according to the present invention.

Fig. 2 schematically shows, in a cross-sectional view, a seal according to the present invention in more detail.

Fig. 3 schematically shows, in perspective, a seal according to the present invention mounted on a wire cage. Detailed description of embodiments

The bearing 1 illustrated in the cross-sectional view of Fig. 1 comprises an inner race 2, an outer race 3, a (wire) cage 4, rollers 5 and a seal 7. Part of a separator 6 (see also Fig. 3) is also shown. The seal 7 is shown to be mounted on the wire cage 4 and to seal against outer surfaces of the races 2 & 3.

The seal of the present invention is shown in more detail in the cross-sectional view of Fig. 2, where the female snap fitting 73 comprises a pair of flexible tongues 72 extending from the seal body, each tongue having a rounded protrusion near one end, the protrusion facing the other tongue. The tongues are able to bend when an object, such as the cage wire (4 in Fig. 1), passes between them. The rounded shape of the protrusions allows the object to be removed when desired.

The distance of the cage wire (4 in Fig. 1) from the body of the seal is defined by a spacer 71 which is located between the flexible tongues 72 and also extends from the seal body. By providing a spacer 71, a very precise position of the seal relative to the wire cage may be achieved. The spacer 71 further allows the tongues 72 to be longer and therefore more flexible.

The sealing is achieved by both a labyrinth seal, provided by circumferential elements 74 extending from the seal body, and by serrated surfaces 75. The elements 74 form a labyrinth seal together with inner surfaces of the inner race 2 and the outer race 3, while the serrated surfaces 75 slidably seal against outer surfaces of the inner race 2 and the outer race 3, as illustrated in Fig. 1. The serrated surfaces 75 comprise a number of circumferential serrations or sealing ribs, for example three, which may point slightly outwards. To provide resilient pressure against the outer surfaces of the races, the seal may be provided with a groove 77 which locally provides a reduced thickness and therefore an increased flexibility, thus reducing friction

It is noted that in the seal of the present invention, the longitudinal or circumferential direction of the seal substantially coincides with the longitudinal direction of the wire cage element on which the seal is mounted. That is, in Figs. 1 and 2 both the seal 7 and the cage wire 4 extend perpendicularly to the plane of the drawing. The tongues 72 may be constituted by continuous circumferential protrusions, in which case the seal has a single snap fitting, or may form pairs of tongues which are circumferentially spaced apart, in which case the seal can have multiple snap fittings.

In the partial perspective view of Fig. 3, the cage 4 is shown to be constituted by a meandering wire and provided with separators 6. The meandering wire is shown to constitute an interrupted first ring 41, an interrupted second ring 42 and connecting sections 43 extending between the two interrupted rings. The interrupted or partial rings 41 and 42 lie are parallel to each other, while the connecting sections 43 extend substantially perpendicularly relative to the planes of the rings. The meandering shape of the wire provides spaces for accommodating the rollers (not shown in Fig. 3). As can be seen in Fig. 3, any rollers are separated by the separators 6 which also space the meandering wire apart from the rollers.

The seal of the present invention is preferably made of a synthetic polymeric material, such as nylon or UHMWPE, but may also be made of other materials. It may be made by injection molding or by additive manufacturing.

The present invention is based upon the insight that the properties of a wire cage, such as a wire cage comprising a meandering wire, may advantageously be used to mount a seal on the wire. The present invention benefits from the further insight that the fittings used to mount a seal on a wire cage should preferably be releasable.

It will be understood that the description of the invention given above is not intended to limit the invention in any way. Singular nouns and the articles "a" and "an" are of course not meant to exclude the possibility of plurals.

It will further be understood by those skilled in the art that the present invention is not limited to the embodiments mentioned above and that many additions and modifications are possible without departing for the scope of the invention as defined in the appending claims.