WO2016096426A1

WO2016096426A1 - Roller bearing wire cage

Info

Publication number: WO2016096426A1
Application number: PCT/EP2015/078321
Authority: WO
Inventors: Jos Holsnijders; Gerrit-Jan Dop; Philipp Krebs; Sebastian Ziegler
Original assignee: Aktiebolaget Skf
Priority date: 2014-12-15
Filing date: 2015-12-02
Publication date: 2016-06-23
Also published as: GB2533301A

Abstract

A cage (4) for a roller bearing (1) 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) define spaces for receiving rollers (5) of the roller bearing. Separators (6) are provided for separating the rollers (5) from each other and for separating the connecting sections (43) from the rollers. The separators (6) are radially suspended from the connecting sections (43), for example by means of snap fittings, which permits each separator to swivel somewhat about an axis defined by a connecting section.

Description

Roller bearing wire cage

Field of the Invention

The present invention relates to a roller bearing wire cage. More in particular, the present invention relates to a cage for roller bearings, which cage comprises a meandering wire.

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.

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 roller bearing cage of which the body is constituted by a meandering wire and which has a reduced friction and a better lubricant distribution.

Accordingly, the present invention provides a cage for a roller bearing, comprising a meandering wire constituting an interrupted first ring, an interrupted second ring and connecting sections extending between the interrupted rings. The connecting sections extend in a direction that is essentially parallel to the bearing axis of rotation and define spaces for receiving rollers of the roller bearing. The cage further comprises a plurality of separators for separating the rollers from each other and for separating the connecting sections from the rollers. Each separator has at least one fitting that grips around the wire of a connecting section, such that the separator is radially suspended from the connecting section in a manner that permits the separator to swivel somewhat about an axis defined by the connecting section.

By providing a plurality of separators, it is possible to better separate the rollers and to avoid direct contact between the wire cage and the rollers. The separators of the present invention separate the rollers from each other, thus defining their spacing. The separators of the present invention also separate the meandering wire from the rollers, thus reducing friction. In addition, the separators may be suitably shaped to improve the lubricant distribution in the bearing. Furthermore, the separators assist in holding the rollers during the assembly of a bearing, thus facilitating the manufacture of a bearing provided with such a cage.

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. The radial suspension of the separators from the connecting sections also facilitates the compactness of the cage construction. 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 separators are mounted on the connecting sections in such a way that they have a limited freedom to swivel about an axis defined by the connecting section on which it is mounted. This enables the cage to "settle" relative to the rollers. In addition, a slight movement of the rollers when under load may be absorbed. In this respect, it is noted that wire cages will typically exhibit some degree of flexibility. Another disadvantage of a typical cage according to the prior art is that it is only suitable for one type of rollers having a certain shape and certain dimensions. When replacing the rollers with rollers having a different shape or different dimensions, it is also necessary to replace the cage. In a particularly advantageous embodiment of the present invention, the separators are provided with snap fittings for detachably mounting the separators on the connecting sections. By providing snap fittings, or equivalent releasable fittings, the separators may be mounted, removed and/or replaced relatively easily.

The separators are preferably designed so as to match the shape of the rollers and thereby provide an optimal spacing. Accordingly, in a preferred embodiment of the cage which is designed for rollers having a rectangular cross-section in the plane of their axis (that is, cylindrical rollers), the separators are also designed for separating cylindrical rollers. In other embodiments, however, the separators may be designed for accommodating and separating tapered rollers or spherical rollers. Thus, the separators are preferably designed to match (the rolling surface of) the rollers, a contact surface (that is, roller facing surface) of the separators having a shape which is similar or identical to the corresponding surface of the rollers. When using cylindrical rollers, for example, the contact surfaces of the separators may be approximately straight to match the cylindrical surface of the roller. In a particularly preferred embodiment, however, the contact surface of at least one separator will not exactly match the surfaces of the rollers but will have an enlarged clearance near the middle of their cylindrical surfaces, when seen in the axial direction of the rollers. Such an enlarged clearance, or slight spacing, improves the distribution of lubricant over the rollers by allowing more lubricant to accumulate near the middle than near the sides of the cylindrical surfaces.

In some embodiments, all separators have the same design. In other embodiments, some separators may have a different design. For example, only one or two separators having an enlarged centre clearance may be provided, the other separators having a uniform clearance (when seen in the axial direction of both the roller and the separator). Also, some separators may be made from another material than other separators. Furthermore, at least the contact surface of the separators may have a porous structure, so as to retain and release lubricant.

The separators may be made of various materials. It is however preferred that at least some, but preferably all separators are made of synthetic polymeric material, for example but not limited to nylon or ultra-high-molecular-weight polyethylene (UH MWPE). The separators may be made by injection moulding, for example, but may also be made by additive manufacturing (also known as 3D printing). The present invention also provides a separator for use in the cage as described above, as well as a bearing provided with a cage as described above.

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 perspective, a roller bearing provided with a cage according to the present invention.

Fig. 2 schematically shows, in perspective, rollers held in a cage according to the present invention in more detail.

Fig. 3 schematically shows, in perspective, a separator according to the present invention. Fig. 4 schematically shows, in side view, a separator according to the present invention arranged between two rollers. 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 cage 4, rollers 5 and a seal 7. Part of the outer ring 3 and of the seal 7 is not shown in Fig. 1 to better illustrate the rollers 5 and the cage structure 4. The cage 4 is shown to comprise a cage body 40 constituted by a meandering wire and provided with separators 6. This is shown in more detail in Fig. 2, where the meandering wire 40 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 40 provides spaces for accommodating the rollers 5. As can be seen in Fig. 2, the rollers 5 are separated by the separators 6 which also space the meandering wire 40 apart from the rollers. In the embodiment of Figs. 1 and 2, therefore, there is no contact between the cage body 40 and the rollers 5. By avoiding contact between the wire cage body 40 and the rollers, all contact between the rollers and the cage is via the separators. This allows friction to be minimized by a suitable choice of shape and material of the separators.

The separators 6 are connected to the wire 40 by way of snap fittings, which are shown in more detail in Fig. 3. These snap fittings allow the separators 6 to swivel relative to the connecting sections 43, thus allowing the cage some flexibility to adapt to pressure exerted by the rollers and thereby to further reduce friction. In addition, the snap fittings allow the separators to be easily mounted and removed. This is particularly advantageous when one or more separators have to be replaced. It further allows all separators to be replaced so as to adapt the cage to rollers having a different shape and/or different dimensions. The separators are suitably designed to match the shape and dimensions of the rollers, and different separators may be provided to fit different rollers. Instead of the cylindrical rollers shown in Figs. 1 and 2, tapered rollers may for example be provided, together with matching separators.

As can be seen in Figs. 1 and 2, in the embodiment shown the separators 6 are mounted on the connecting sections 43, and not on the first ring sections 41 or second ring sections 42. This offers the advantage of leaving the first ring sections and second ring sections free, and more in particular, that no separator parts (such as the snap fittings) extend beyond the first and second rings. This provides a compact design.

A preferred embodiment of a separator is shown in more detail in Fig. 3. The separator 6 is provided with snap fittings 62 which each provide an opening 63 for accommodating the meandering wire (40 in Figs. 1 and 2) which constitutes the cage body. In the embodiment shown, four snap fittings 62 are shown, but it will be understood that a separator may also be provided with a different number of snap fittings, for example two, three or five. The separator has a contact surface 61 at each side which faces towards an adjacent roller 5. In the embodiment of Fig. 3, the contact surface is slightly curved so as to provide an increased clearance towards the middle of the roller. The increased clearance between the contact surface 61 and a roller is shown more clearly in Fig. 4, where a separator 6 is arranged between two rollers 5 which have a rotational axis A. It can be seen that the contact surface 61 has the greatest clearance near the middle of the roller, when seen in the direction of the rotational axis A, while having a very small (or virtually no) clearance near the edges of the roller. The increasing clearance in axial direction towards the center of a roller results in an improved lubrication of the rollers and hence a reduced friction. The increasing clearance may be realised, as shown, by means of a curvature of the contact surface 6. A stepped surface or other suitably shaped surface is also possible.

The contact surfaces 61 are provided at opposite sides of an intermediate section 65 of the separator. The snap fittings 62 extend in a radially outward direction from the intermediate section 65. In the depicted embodiment, the separator further comprises reinforcing ribs 61A and wall sections 67 that extend from the intermediate section 65 in a radially inward direction. The wall sections 67 have a smaller thickness, viewed in circumferential direction, than the circumferential thickness of the intermediate section 65 and the reinforcing ribs 61A. This creates recesses underneath the intermediate section 65 where lubricant e.g. grease can accumulate. In applications where the bearing inner ring is the rotational bearing ring, grease gets flung out due to the action of centrifugal force. The radially inner surface of the intermediate section 65 will catch grease that gets flung out, providing a grease reservoir close to the rolling contact surface of the rollers. The presence of wall sections 67 and reinforcing ribs 61A below the intermediate section 65 is preferred, so as to enhance the stiffness of the separators. These features are, however, optional. The separator 6 of Figs. 3 & 4 is also provided with flanges 64 at each longitudinal end for collecting and distributing lubricant. As shown in Fig. 2, these flanges extend beyond the rollers and collect lubricant from the end surfaces of the rollers.

The separators of the present invention are preferably made of a synthetic polymeric material, such as nylon or UHMWPE, but may also be made of other materials. They 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, in particular a wire cage comprising a meandering wire, can be significantly improved by providing separators which are mounted on the wire. It will be understood that the description of the invention given a bove 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. Although the invention has been described with reference to cylindrical rollers, it is not so limited and also comprises tapered rollers having a conical surface, for example.

It will therefore 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 cage (4) for a roller bearing (1), comprising 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, characterized in that the cage further comprises a plurality of separators (6) for separating the rollers (5) from each other and for separating the connecting sections (43) from the rollers (5), wherein each separator (6) has at least one fitting (62) that grips around the wire of a connecting section (43), such that the separator is radially suspended from the connecting section in a manner that permits the separator (6) to swivel somewhat about an axis defined by the connecting section (43).

2. The cage according to claim 1, wherein the separators (6) are provided with snap fittings (62) for detachably mounting the separators on the connecting sections (43).

3. The cage according to claim 1 or 2, wherein the separators (6) are designed for

separating cylindrical rollers (5).

4. The cage according to any of the preceding claims, wherein at least one separator (6) has an intermediate section (65) from which the at least one fitting (62) extends in a radially outward direction, the intermediate section (65) having a contact surface (61) that faces towards an adjacent roller (5).

5. The cage according to any of the preceding claims, wherein the contact surface (61) is arranged for having an enlarged clearance at a midsection of the roller (5), relative to an edge of the roller, when seen in its axial direction.

6. The cage according to any of the preceding claims, wherein at least some separators (6) have a different shape from other separators.

7. The cage according to any of the preceding claims, in which at least some separators (6) are made of a synthetic polymeric material, such as nylon.

The cage according to any of the preceding claims, wherein at least some separators (6) are made by additive manufacturing.

A separator (6) for use in the cage (4) according to any of the preceding claims.

10. A roller bearing (1) provided with a cage (4) according to any of claims 1-8.