The present invention relates to the manner of installing a bearing on a shaft, to a shaft assembly produced thereby, and to a bearing assembly suitable for such installation.

According to one aspect of the present invention, there is provided a shaft assembly comprising a shaft provided with at least one detent, a resiliently compressible assembly mounted on the shaft, a first end of the compressible assembly being restrained in a predetermined position along the shaft from movement along the shaft in the direction of the first end, a bearing assembly slidable along the shaft so that one end abuts the second end of the compressible assembly, and a sleeve slidable along the shaft to abut the other end of the bearing assembly, the sleeve including at least one catch portion in engagement with said at least one detent when the sleeve and bearing assembly have been subjected to a force towards the compressible assembly, which is thereby compressed, said engagement of said at least one catch with said at least one detent resisting movement in the opposite direction, under the influence of decompression of said compressible assembly, when said force is released.

Such an assembly is formed by sliding the compressible assembly along the shaft to, or close to, its predetermined location, followed in turn by the bearing assembly and the sleeve. Force on the sleeve then compresses the compressible assembly, permitting the catch and detent to engage. The latter engagement, on relaxation of the force, and subjected to a contrary force provided by decompression of the compressible assembly, is such as to resist

disassembly and to provide an accurate axial location for the bearing on the shaft.

The detent may be a slot though the shaft, or a recess or groove formed in the external shaft surface, and the catch portion may be a member which is sprung inwardly of the sleeve, for example a finger the end of which co-operates with a corresponding end surface of the detent to resist said movement in the opposite direction. In a preferred embodiment, the end of the finger and the end surface of the detent are both square to the shaft axis, but it would be possible to provide surfaces (e.g. a detent which an end surface which is undercut or has a lateral V-groove, and a correspondingly shaped finger end) for providing a positive camming action holding the finger in place, provided care was taken that the finger could not under-ride the sleeve. In such a case, it might be necessary to re-compress the compressible assembly to a significant degree to permit removal of the sleeve.

The resiliently compressible assembly may include at least one elastomeric or metallic spring (e.g. a disc spring) .

To restrain the first end of the compressible assembly in its predetermined position along the shaft, the shaft can provided with an abutment, which could be integral therewith, such as a yoke (for example, when the shaft is part of a steering column assembly) . However, it will be clear that there are many other ways available to the skilled person for achieving the same function, e.g. a circlip (an abutment not integral with the shaft) , or a means of fastening the assembly at its first end to the shaft (such as a pin) .

Preferably, the bearing assembly, and at least one of the resiliently compressible assembly and the sleeve, are provided with co-operating cone faces for ensuring accurate radial location of the bearing assembly. Preferably, at least one of the resiliently compressible assembly and the sleeve has an external cone face portion and is split thereat; either of itself, or under the influence of forces in the shaft assembly, the external split cone face portion may grip the shaft and so provides accurate radial location of the bearing assembly. In a preferred embodiment, the external cone face portion of the compressible assembly is provided by a separate split cone member which of itself grips the shaft.

In a preferred embodiment the shaft is part of a vehicle steering column and is hollow with a generally triangular external axial cross-section, the detent is a slot provided at an apex thereof, and the catch portion is an inwardly sprung finger. Preferably there are three detents and fingers. In this embodiment, the sleeve has a generally circular internal cross-section, but with internal projections which engage the sides of triangular cross- section, so to locate the sleeve circumferentially on the shaft with fingers and slots aligned.

However, it should be understood that the invention may be employed with shafts having different cross-sectional shapes, and with solid shafts. Where a shaft has a circular external cross-section, alignment of catches and detents may need to be performed visually or by trial and error. However, it is also possible to avoid the need for circumferential alignment altogether, for example by using a detent in the form of a circular groove.

The invention also provides a bearing assembly for use in a shaft assembly as described above, which comprises an inner race having cone faces at one or both ends, an outer race spaced from the inner race by bearing members, and a housing accommodating the outer race.

According to another aspect of the present invention, there is provided, a shaft assembly comprising, a shaft having at least one detent; a means for biasing mounted on the shaft, and a bearing assembly mounted on the shaft with a first end of the bearing assembly abutting the means for biasing; characterised by a retention means for axially retaining the bearing assembly, the retention means abutting a second end of the bearing assembly, the means for biasing the retention means into engagement with said at least one detent.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:

Figure 1 shows a shaft forming part of a vehicle driving column assembly;

Figure 2 shows a detail of the shaft of Figure 1 in partial cross-section;

Figure 3 shows part of a preferred embodiment of shaft assembly in longitudinal cross-section; and

Figure 4 is an axial cross sectional view taken along the line 4-4 of Figure 3.

Figure 1 shows a shaft 1 which could form part of a vehicle steering column assembly providing for reach adjustment, by mutual sliding action between two parts of the column.

This steering column assembly could additionally have rake adjustment and/or a collapsible safety portion. Relative rotation between two nested shafts which are capable of undergoing mutual sliding can be avoided by giving the shafts a non-circular cross-section.

The shaft of Figure 1 comprises a hollow tube with a generally equilateral triangular section, as shown in more detail in Figure 4, although the apices 2 thereof are rounded. The end of the shaft at which the bearing is to be secured is terminated by a yoke 3.

Near the yoke 3 a recess 4 is formed in the shaft, in an apex of its cross-section, for example by stamping. Preferably such a recess is formed in two apices, or, more preferably, in each apex, at the same longitudinal location. The end 5 of the recess is square to the length of the shaft.

Figure 3 shows part of a shaft assembly including a compressible assembly 6, the latter comprising an elastomeric spring in the form of a rubber annulus 8 sandwiched between an acetal spacer 7 and a split cone 9 having an external cone surface 10. This assembly is slid along the shaft 1 until the spacer abuts the yoke 3 (neither the shaft nor its yoke are shown in Figure 3), for longitudinal location, with the split cone 9 gripping the shaft 1 for radial location.

The bearing assembly 12 shown in Figure 3 is of annular form, and consists of an inner race 13 separated from an outer race 14 by a single row of metallic ball bearings 15. The inner race is of conventional grooved tubular

construction with end bores having internal cone surfaces 10' 19', the surface 10' coacting with cone surface 10. The outer race, with external part-spherical surface, is mounted in an acetal liner 16, which, in turn, is axially located inside a housing 17 of moulded glass reinforced nylon, or of zinc based die cast construction.

The bearing assembly 12 is slid along shaft 1 to abut the compressible assembly 6 with the conical surfaces 10, 10' in engagement.

A generally cylindrical sleeve 18 is then slid along the shaft 1 until the surface 19 of an external cone at one end thereof engages with the conical surface 19' . The sleeve 18 has six internal projections 20 pairs of which engage respective sides of the shaft and provide rotational location of the sleeve on the shaft. The latter function can be provided by other means known per se, and the number of projections can be varied.

The sleeve is formed with a number of internally sprung fingers 21, the number and location thereof corresponding to the number and location of detents on the shaft. As shown, each finger has an enlarged end portion 22 with a camming surface 23 enabling the finger to rise as it slides over the end of the shaft, and along an apex of the tube cross-section.

Once in abutment with the bearing assembly 12, the sleeve is pushed further to compress the spring 8, whereupon the finger end(s) 22 snaps into the detent (s) 4. When the sleeve is released, the spring 8 exerts a force in the opposite direction, thus bringing end surface (s) 24 of the

finger(s) , which is (are) formed square to the length of the sleeve, into contact with the squared surface 5, and axially locking the bearing assembly 12 in the desired position on the shaft 1. The bearing assembly is accurately located concentrically of the shaft by virtue of the cone surfaces 10, 10' 19, 19'.

In this preferred embodiment, the parts 7-9 of the assembly 6, and the sleeve 18 are annular, but there is nothing to prevent other shapes being adopted (for example, the annulus may be interrupted, or a shape conforming more closely to the external tube shape) as long as (a) the assembly 6 and sleeve 18 can be slid over the shaft 1; (b) the parts 7-9 coact as necessary; and (c) the end surfaces of the compressible assembly and sleeve (in the preferred form, cone surfaces 10, 19) coact at least in part with the end surfaces (in the preferred form, internal cone surfaces 10', 19') of the bearing assembly 12 (thus if the bearing assembly was formed with a generally triangular internal aperture in lieu of the more conventional circular aperture 12, at least some of the sleeve 18 and the components 6-8 of assembly 6 could likewise be generally triangular) .