WO2016096430A1

WO2016096430A1 - Seal for a roller bearing

Info

Publication number: WO2016096430A1
Application number: PCT/EP2015/078328
Authority: WO
Inventors: Jos Holsnijders; Stellario Barbera
Original assignee: Aktiebolaget Skf
Priority date: 2014-12-15
Filing date: 2015-12-02
Publication date: 2016-06-23
Also published as: GB2533554B; GB2533554A

Abstract

A seal (7) for a roller bearing (1) having an inner race (2), an outer race (3), and a cage (4). A first seal part (71) is arranged for mounting on the inner race (2), a second seal part (72) for mounting on the outer race (3), and a third seal part (73) for mounting on the cage (4). The first seal part (71) is provided with a first circumferential rim, wherein the second seal part (72) is provided with a second circumferential rim. The third seal part (73) is configured for receiving the first circumferential rim and the second circumferential rim so as to provide a contactless labyrinth seal.

Description

SEAL FOR A ROLLER BEARING

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 which is suitable for roller bearings having a wire cage, for example a meandering wire cage, but which may also be used with other roller bearings.

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 connecting sections extending between the interrupted rings so as to provide spaces for the rollers.

A wire cage can be manufactured relatively inexpensively, especially the meandering design. However, it has been found that a meandering wire may cause a relatively high friction between the cage and the rollers. In addition, it has been found that the distribution of lubricant in a bearing having a wire cage is often not optimal, thus adding to the friction.

United States Patent US6217223 (SKF) discloses a cage-guided seal with an annular support body, formed preferably from sheet metal. The peripheral edges of the support body extend close to the sealing surfaces of the inner and outer bearing races and are provided with sealing lips that engage opposite inner surfaces of the inner and outer races. The seal is fastened with snap-in elements provided with hooks which prevent an easy release.

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 has a reduced friction and can be removed more easily.

Accordingly, the present invention provides a seal for a roller bearing having an inner race, an outer race, and a cage, characterized by a first seal part for mounting on the inner race, a second seal part for mounting on the outer race, and a third seal part for mounting on the cage, wherein the first seal part is provided with a first circumferential rim, wherein the second seal part is provided with a second circumferential rim, and wherein the third seal part is configured for receiving the first circumferential rim and the second circumferential rim so as to provide a contactless labyrinth seal.

By providing a seal consisting of three parts, one part being connected to the inner race, one part to the outer race, and one part to the cage, the speed difference between the inner race and the outer race is distributed over two partial seals, resulting in less friction when any lubricant is bridging the gap between seal parts. The two partial seals are preferably contactless labyrinth seals, at least part of the labyrinths being provided by the circumferential rims.

The seal of the present invention preferably comprises at least one snap fitting for removably mounting the seal on the cage, in particular on a section of the cage, which may advantageously be a wire section that extends in a circumferential direction between the inner race and the outer race. It will be understood that the seal of the present invention may also be used with cages which have no wire sections, but which may have parts suitable for snap fitting a seal.

By providing snap fittings, the seal can both be easily mounted and easily removed. It will be understood that snap fittings have no hooks as in the prior art. Instead, 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.

In a preferred embodiment, a snap fitting may be provided on a seal base on which the third seal part is mounted. That is, the third seal part may be mounted on a separate element having at least one snap fitting. It is possible to also provide the third seal part with protruding tongues which constitute snap fittings. The seal base may be made of another, for example more flexible, material such as rubber, and may serve to both position the third seal element and to provide additional sealing by filling up part of the labyrinth.

Advantageously, the third seal part may be provided with a first circumferential raised edge and a second circumferential raised edge for receiving the first and the second circumferential rims there between. By providing raised edges on the third seal part for receiving the rims of the first and second seal parts, a well sealing labyrinth seal is provided. The sealing action of the labyrinth seal may be further improved when the third seal part is provided with a central ridge between the first raised edge and the second raised edge for forming a labyrinth with the first circumferential rim and the second circumferential rim. In a preferred embodiment, the first circumferential rim and the second circumferential rim have sloping sides, and the first circumferential raised edge and the second circumferential raised edge have matching sloping sides. By having sloping sides of the labyrinth parts, the air passage is lengthened, thus improving the sealing action. Although it is possible to use rims and raised edges extending at approximately 90° from the seal parts, it is preferred that these elements have an angle between approximately 40° and 80°, for example 70°. In such an embodiment the central ridge may also have sloping sides, which preferably have a similar angle as the sloping elements referred to above.

To better position the seal relative to the other parts of the bearing it is preferred that at least one of the first seal part and the second seal part is further provided with a ridge for resting against the inner race and the outer race respectively. Such protruding ridges define the position of the seal relative to the races while improving the sealing action by effectively preventing the ingress of foreign materials between the seal parts and the races.

The seal of the present invention may further comprise a dust lip for avoiding the ingress of dust into the labyrinth.

The seal of the present invention may be made of a suitable plastic, 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 cut-away perspective view, part of a roller bearing provided with an embodiment of a seal according to the present invention.

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

Fig. 3 schematically shows, in a cross-sectional view, an embodiment of a seal according to the present invention in more detail.

Fig. 4 schematically shows, in a cross-sectional view, part of an embodiment of a seal according to the present invention in more detail.

Detailed description of embodiments

The bearing 1 illustrated in the cutaway view of Fig. 1 comprises an inner race 2, an outer race 3, a (wire) cage 4, rollers 5, separators 6 and a seal arrangement 7. The separators 6 are shown to be mounted on the wire cage 4 and serve to separate the rollers 5. The seal 7 is shown also to be mounted on the wire cage 4 and to seal against outer surfaces of the races 2 and 3. The cage 4 in this embodiment is shown to be constituted by a meandering wire, but the invention is not so limited.

The seal arrangement 7 is shown to comprise a first seal part 71, a second seal part 72 and a third seal part 73. The third seal part 73 is shown to be connected to the cage 4 by snap fittings 70.

The bearing 1 of Fig. 1 is also shown in the cross-sectional view of Fig. 2. An optional grease scraper 8 is shown to be mounted on the wire cage 4, adjacent to the thirds seal part 73, using a snap fitting. As shown in Fig. 1, the third seal part 73 is preferably also provided with a snap fitting arrangement.

The seal 7 of the present invention is shown in more detail in the cross-sectional view of Fig.

3. The sealing is achieved by a labyrinth seal, provided by circumferential rims 74A and 74B extending from the first seal part 71 and the second seal part 72 respectively, in conjunction with the third seal part 73. More in particular, the first and second circumferential raised edges 76A and 76B of the third seal part 73 are arranged for matching the rims 74A and 74B, that is, by having substantially parallel surfaces at small spacings. It can be seen that the raised edges 76A and 76B extend from the base of the third seal part 73 at an acute angle a (see Fig. 4), that is, they slope inward, towards the middle of the third seal part, to provide a better sealing against the ingress of undesired material.

The third seal part 73 is shown in more detail in the cross-sectional view of Fig. 4, which cross-section is taken through the third seal part 73 where it is provided with a snap-fitting section 70. It can clearly be seen in Fig. 4 that the raised edges 76A and 76B slope inward at an angle a, as mentioned above. The angle a may be, for example 60° or 70°, but may be between approximately 40° and 80°. It can also be seen that the third seal element 73 is provided with a central ridge 77, which in the embodiment shown also has sloping sides to match the rims 74A and 74B.

In the embodiment of Fig. 4, the angle of the sloping sides of the central ridge 77 is different (that is, closer to 90°) from the angle a, however, this is not essential and the angles may be the same. This central ridge 77 substantially fills up the gap between the rims 74A and 74B.

It is noted that the seal 7 of the present invention is preferably contactless, that is, the first seal part 71, the second seal part 72 and the third seal part 73 do not touch each other during operation of the bearing. By avoiding any contact between these seal parts, friction and wear are avoided. The seal parts form a labyrinth that significantly reduces the ingress of dust and moisture. The seal 7 may further be provided with a dust lip (not shown) to further reduce the ingress of undesired substances.

The seal 7 of the present invention spreads the speed difference between the inner race 2 and the outer race 3 over two interfaces, as the third seal element 73, being coupled to the cage, will typically have half the speed of the outer race (assuming the inner race is fixed and the outer race is rotating). Accordingly, by reducing the speed differences between the moving parts, any friction and wear due to accidental contact between the moving parts or due to the presence of excess lubricant is reduced.

The seal of the present invention is preferably made of a synthetic polymeric material, such as nylon or UHMWPE (ultra-high-molecular-weight polyethylene), 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.

Claims

1. A seal (7) for a roller bearing (1) having an inner race (2), an outer race (3), and a cage (4), characterized by a first seal part (71) for mounting on the inner race (2), a second seal part (72) for mounting on the outer race (3), and a third seal part (73) for mounting on the cage (4), wherein the first seal part (71) is provided with a first circumferential rim (74A), wherein the second seal part (72) is provided with a second circumferential rim (74B), and wherein the third seal part (73) is configured for receiving the first circumferential rim (74A) and the second circumferential rim (74B) so as to provide a labyrinth seal.

2. The seal according to claim 1, further comprising at least one snap fitting (78) for removably mounting the third seal part (73) on the cage (4).

3. The seal according to any of the preceding claims, wherein the third seal part (73) is provided with a first circumferential raised edge (76A) and a second circumferential raised edge (76B) for receiving the first and the second circumferential rims (74A, 74B) there between.

4. The seal according to claim 3, wherein the third seal part (73) is further provided with a central ridge (77) between the first raised edge (76A) and the second raised edge (76B) for forming a labyrinth with the first circumferential rim (74A) and the second circumferential rim (74B).

5. The seal according to claim 3 or 4, wherein the first circumferential rim (74A) and the second circumferential rim (74B) have sloping sides, and wherein the first circumferential raised edge (76A) and the second circumferential raised edge (76B) have matching sloping sides.

6. The seal according to claims 4 and 5, wherein the central ridge (77) also has sloping sides.

7. The seal according to any of the preceding claims, wherein at least one of the first seal part (71) and the second seal part (72) is further provided with a ridge (75A; 75B) for resting against the inner race (2) and the outer race (3) respectively.

8. The seal according to any of the preceding claims, further comprising a dust lip.

9. The seal according to any of the preceding claims which is made of a synthetic polymeric material.

10. The seal according to any of the preceding claims which is made by additive manufacturing.

11. A roller bearing (1) provided with a seal (7) according to any of the preceding claims.

12. The roller bearing according to claim 11, wherein the cage (4) comprises a meandering wire constituting an interrupted first ring (41), an interrupted second ring (42) and connecting sections (43) extending between the interrupted rings, the connecting sections (43) defining spaces for receiving rollers (5) of the roller bearing.

13. The roller bearing according to claim 12, further comprising at least one separator (6) for separating the rollers (5) of the bearing, the at least one separator being mounted on a connecting section (43),

14. The roller bearing according to claim 13, wherein the at least one separator (6) is moveably mounted on the connecting section (43).

15. A wheel provided with a roller bearing (1) according to any of claims 11-14.