GB2084666A - Improvements in cylindrical roller bearings - Google Patents

Abstract

A cylindrical roller bearing comprises a hub 5, a set of cylindrical rollers and an outer part 6. Each roller 4 has a cylindrical surface 12 in rolling contact with races formed on the hub 5 and outer part 6. Each roller additionally has portions of variable cross section 13 (for instance a biconical portion) cooperating with mating portions of the hub and outer portion for centering purpose. For reducing frictional forces, when an axial thrust causes the outer part to shift with respect to the hub 5, the rollers are formed with end portions 11 of tapering cross section arranged to come into abutment with lateral walls 7. <IMAGE>

Description

SPECIFICATION Improvements in cylindrical roller bearings Background and summary of the invention The invention relates to cylindrical roller bearings, i.e. bearings of the type including rollers having cylindrical surfaces in rolling abutment against an inner race and an outer race and more particularly to bearings of the type for supporting thrusts which are substantially radial in direction.

Cylindrical roller bearings have been designed in which the inner and outer races are retained against relative axial displacement from a determined position bythe rollers. In Belgian Patent Specification No. 390,696, there is disclosed a bearing having rollers formed with circumferential serrations into which circumferential ridges of the races project.

Lateral disks are provided for retaining the rollers at appropriate intervals and the bearing should be constructed from a substantial number of separate and different parts. German Patent 436,331 describes several types of bearings having cylindrical rollers formed with at least one bulged portion for restraining relative axial movement of the races.

Again, the rollers are retained by lateral disks.

It is an object of the invention to provide a cylindrical roller bearing which is of moderate cost, rugged and simple in construction, and able to withstand substantial radial loads without premature wear. It is another object of the invention to provide a cylindrical roller bearing in which axial relative movement of the races from their normal position is restrained without substantial friction forces opposing rotation of the outer race with respect to the inner race.

A cylindrical roller bearing according to the invention comprises a hub formed with an inner race having an axis; an outer part formed with an outer race and rotatable about said axis with respect to the hub; and at least one set of cylindrical rollers each having cylindrical surface means in rolling contact with said races and portions whose cross-sections axially vary in opposite directions and which cooperate with portions of mating shape of said races for restraining relative axial movement of the rollers and races, wherein said rollers are substantially in contact with each other and are maintained by said races only and wherein each of said rollers has end portions of reduced cross section for abutment against lateral wall means connected to the hub, upon axial shift of said outer part from a predetermined position.

Since the axial thrusts are taken by cylindrical rollers rather than by balls, substantial forces can be accepted even if the roller material is relatively soft, for instance of plastics. Substantial clearances, associated with high manufacturing tolerances and accompanying low manufacturing costs, may be accepted without correlative high frictional losses, since any lateral offset due to axial thrust will result in abutment through small areas only. The bearing will typically consist of three different parts only (hub, outer part and rollers) and may consequently be manufactured at a low cost, of plastics material each time it is not subjected to continuous rotation in operation.

The field of use of the invention is quite broad and includes pulleys (particularly pulleys for sailing ships), wears for sliding doors, toys, garden appliances and all apparatuses for intermittent or light duty use.

The end surfaces may have a variety of different shapes, although frustoconical shapes and end spherical caps will most frequently be used.

The portions of variable cross section may also have a number of different shapes, which may be symmetrical or not. However, each roller will frequently be symmetrical with respect to midplane orthogonal to the bearing axis. Examples of acceptable shapes are as follows: - A portion of each roller has a peripheral groove of female biconical cross section and cooperates with mating male biconical ridges of the races, the reverse arrangement (male ridge on the rollers, female grooves on the races) being possible; - Each roller has two separate frustoconical portions with the conicities in opposite directions, said frustoconical portions being typically adjacent the end portion.

Any combination of the above shapes is acceptable, as well as any other combination which causes a centering axial force to appear responsive to abutment of the surfaces of variable cross section.

The arrangement can additionally be duplicated or cascaded for fulfilling specific purposes.

In specific cases, particularly when heavy radial loads are expected, each roller may be fractioned and include one or more elementary rollers having a purely cylindrical surface (for supporting the radial ioad) arranged coaxiallywith elementary rollers having a centering action. Such centering rollers will typically straddle the purely cylindrical roller(s) to restrain axial movement thereof. The adjacent end portions of the elementary rollers may preferably be of tapering cross section for abutment to occur through reduced areas and/or balls may be located between the end portions. The elementary rollers of a same roller may have cylindrical surfaces of identical or different diameters.

If the bearing is made of a material having sufficient resiliency, it may be assembled quite simply: all rollers but one (or more) are located in final position between the races and the last roller(s) is (or are) forced in place. If the parts are too rigid for such an assembling process to be successful, one at least of the parts should be in two halves which are secured to each other after insertion.

The invention will be better understood from a consideration of the following description of particular embodiments, given by way of examples. The description refers to the accompanying drawings.

Short description of the drawings Figure 1 is a partial cross section of a bearing according to a first embodiment of the invention, ,along a plane passing through the axis ofthe bearing, Figures 2,3, 4 and 5, similarto Figure 1, illustrate other embodiments of the invention, Figure 6 is an illustration of a pulley including a bearing ofthetype illustrated in Figure 1, in cross section along a diametral plane.

Detailed description ofparticular embodiments Referring to Figure 1, there is shown a part of a cylindrical roller bearing having a set of rollers 4 located between a hub 5 and an outer rotating part 6.

Two lateral walls 7 straddling the bearing are secured to the hub, for instance by an axle 9.

The circumferential surface of each roller 4 has two cylindrical portions 12 in rolling abutment against races formed on the hub 5 and outer part 6.

That circumferential surface also includes a biconical female portion 13 cooperating with male portions of corresponding shape of the hub and outer part. The roller will typically be symmetrical with respect to the midplane 14, as illustrated in Figure 1.

The end portions of roller 4 each assume the shape of a spherical cap 11. The amount of projection of the cap with respect to the hub 5 and outer portion 6 is selected for abutment to occur between the roller and the corresponding wall 7 (rather than between the outer part and the wall) upon axial movement of the outer portion 6 within the amount corresponding to taking up of the clearance, upon application of an axial force onto the outer part.

Assuming for instance that a force is exerted to move the outer part to the right, the components of the bearing will assume the positions indicated in dash dot lines in Figure 1. Sliding contact will occur on the small terminal areas of some rollers only, rather than through a larger surface of the outer part 6.

Referring now to Figure 2, where the elements corresponding to those in Figure 1 have been designated by the same reference numerals, the arrangement of the parts of variable cross section along the axis may be considered as the reverse of th > s inFigure 1.

In the embodiment of Figure 3, each roller4 has a circumferential surface whose axially inner portion is cylindrical. The portion of variable cross section includes two frustoconical portions 16 separated by the cylindrical portion 15. The two frustoconical portions taper axially inwardly and cooperate with two respectivefrustoconical surfaces 17 of the outer part 6 and 18 of hub 5.

As indicated above, each of the rollers, hub and outer parts may be solid, if they are sufficiently deformableforthe last roller to be insertable by forcing it in place.

The construction illustrated in Figure 4 may be considered as reverse from that of Figure 3. It will be appreciated however that the bearing of Figure 4 will generally not be adapted to assembling by force insertion of the last roller.

Referring now to Figure 5, there is shown a portion of a bearing in which each roller consists of several individual rollers. In the embodiment of Figure 5, where the elements corresponding to those in Figures 1 and 2 are designated by the same reference numeral, each roller 4 consists of a fully cylindrical elementary roller 20, which takes the greater part of the radial force, and two centering rollers 21 located one on each side of elementary roller 20. In Figure 5, each roller 21 has a construction similartothatillstrated in Figure 1, but other constructions would of course be possible. In addition, it may be preferable to select a shape of the portion of variable cross section 13 which is not symmetrical (as indicated in full lines), but dissymetrical (as indicated in dash dot lines).

Again, the elementary rollers 21 have end portions of progressively reducing cross section. The elementary roller 20 similarly has end portions of progressively reducing cross section to minimize the contact areas between the rollers. While the cylindrical surfaces of all rollers 20 and 21 have the same diameter in Figure 5, different diameters may be used in specific cases.

Rather than spherical caps as indicated in Figures 1-5, frustoconical end portions or even projections of reduced diameter may be used and the elements of the bearing may each consist of several assembled parts.

Turning nowto Figure 6, there is shown a pulley assembly including a roller bearing of the type illustrated in Figure 1. Part 6 consists of a sheave of a pulley for receiving a cord 10. The lateral walls 7 consist of two lateral cheeks reinforced by two metal strips 8 located in recesses of the cheeks. The cheeks 7 and strips 8 are connected together by axle 9 and by a pin 22. A spacer block 23 traversed by pin 22 additionally retains an attachement ring 24.

It can be seen that the construction of the pulley is quite simple. Since the rollers 4 contact each other, no additional means are necessary for maintaining them at proper locations. Most parts can be manufactured at low cost from plastics, using conventional molding processes. Service life is satisfactory. The shape of the parts, particularly of the rollers, may be taylored to fit particular conditions. For instance, the shape of the portions of variable cross section is quite flexible and the generatrix thereof can be curved rather than rectilinear, as in the illustrated embodiments. Numerous variations will appear two those familiar with the art and it is to be understood that the scope of the invention is limited only by the appended claims.

Claims (10)

1. A cylindrical roller bearing comprising a hub formed with an inner race having an axis, an outer part formed with an outer race and rotatable about said axis with respect to the hub, and at least one set of cylindrical rollers each having cylindrical surface means in rolling contact with said races and portions whose cross sections axially vary in opposite directions and which cooperate with portions of mating shape of said races for restraining relative axial movement of the rollers and races, wherein said rollers are substantially in contact with each other and are maintained by said races only and wherein each of said rollers has ene portions of reduced cross section for abutment against lateral wall means connected to the hub, upon axial shift of said outer part from a predetermined position.

2. Bearing according to claim 1, wherein said end portions are of convex shape.

3. Bearing according to claim 2, wherein said end portions are frustoconical or in the form of spherical caps.

4. Bearing according to any preceding claim, wherein each roller is symmetrical with respect to a midplane orthogonal to the bearing axis and a central portion of each roller has a peripheral groove or ridge of biconical cross section which cooperates with mating biconical ridges or grooves of the races.

5. Bearing according to any one of claims 1-3, wherein each roller is fractioned and includes at least one first elementary roller having a purely cylindrical surface for supporting radial loads and secondary elementary rollers having a centering action arranged coaxially with said first roller.

6. Bearing according to claim 5, wherein said first elementary roller is straddled by a pair of said second elementary rollers.

7. Bearing according to claim 5, wherein the adjacent end portions of the elementary rollers are of tapering cross section for abutment to occur through reduced areas.

8. Bearing according to claim 5, wherein balls are located between adjacent end portions of said elementary rollers.

9. Bearing according to any one of claims 1-8, wherein said hub, outer part and rollers are of molded plastics material.

10. Bearing according to claim 1, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.