Bearing assemblies

Abstract: A bearing assembly comprises a bearing (21) rotatably supporting a shaft (9) in a housing (15) and a grease expelling bearing seal (3) disposed between the shaft (9) and the housing (15). A grease distributor (5) is provided on the side of the bearing seal (13) from which grease is expelled during operation. The grease distributor (5) has a collar (7) mounted on the shaft (9) and at least one grease spreading blade (13) extending radially outwards from only part of the circumference of the collar (7) towards to the housing (15). The rotation of the collar (7) and blade (13) serves in operation to spread the grease expelled from the bearing seal (3) evenly around the circumference of the seal so as to improve the sealing between the shaft and the housing.

Description: Field of the Invention The present invention relates to a bearing assembly that incorporates a grease expelling bearing seal. Background of the invention Typically a wheel bearing and rotor nut assembly of a motor vehicle includes a cylindrical housing within which a rotor nut rotates. The rotor nut includes a short shaft extending from its rear face towards the wheel bearing. This serves to space the rear face of the rotor nut from the wheel bearing and its sealing elements. Typically the wheel bearing includes a central rotating member and a circumferential seal which bridges the gap between the rotating and non rotating members of the bearing. This is the main bearing seal which ensures that dirt and liquid do not enter the moving assembly. A circlip is mounted around the edge of the bearing assembly in a groove within the housing wall. In order to enhance the seal and provide further lubrication in any such assembly, a lubricant needs to be introduced in the annular space defined behind the rear face of the rotor nut. In an attempt to improve the waterproof seal, wheel bearings are being designed which include bearing seals that expel grease, through at least their outermost seals. The grease is intended to act as a tertiary seal between the rotor nut and the bearing seal. The term 'grease expelling wheel bearing' will be used in the specification to mean any wheel bearing including a bearing seal which is designed to so expel grease. A typical example of such a grease expelling wheel bearing is sold by The Timken Co of 1835, Dueber Avenue SW, P.O. Box 6930, Canton, Ohio 44706/0930, U.S.A. Although the seal of such a grease expelling wheel bearing assembly is intended to expel grease equally around the edge of the assembly, in practice, the grease expulsion is at times uneven. This can lead to a build up of grease that may become packed between the back face of the rotor nut arid the bearing seal. Over a period of time this grease becomes contaminated with debris and could then abrade the seal. Such abrasion inevitably leads to wear and degradation of the seal and of the wheel bearing. If measures are taken to insert a physical barrier such as a shield between the bearing seal and the rotor nut to prevent the grease building up on the rotor nut, this can cause different problems. If the grease expulsion is uneven, there may also be areas where little or no grease is expelled. The presence of a shield can mean that no tertiary seal is formed and then water can enter the assembly. United States Patent No 1,954,685 is concerned with a bearing lubricator for a shaft supported in a bearing in which the shaft is provided with a sleeve provided with impeller blades which serve to disseminate lubricant. The impeller blades are not tilted with respect to the plane normal to the axis of rotation of the bearing which is an important feature of the invention now to be described. Summary of the Invention According to the invention, there is provided a bearing assembly comprising a bearing rotatably supporting a shaft in a housing and a grease expelling bearing seal disposed between the shaft and the housing, characterised in that a grease distributor is provided on the side of the bearing seal from which grease is expelled during operation, the grease distributor having a collar mounted on the shaft and at least one grease spreading blade extending radially outwards from only part of the circumference of the collar towards to the housing, the leading face of the grease spreading blade being tilted with respect to the plane normal to the axis of rotation of the bearing, the rotation of the collar and blade serving in operation to spread the grease expelled from the bearing seal evenly around the circumference of the seal so as to improve the sealing between the shaft and the housing. The blade acts to spread grease about the face of the seal but also tends to push the grease onto the cylindrical face of the housing which is the most efficient position for the tertiary sealing action of the seal. Preferably the collar is cylindrical with a diameter slightly greater than the diameter of the journalled shaft so that the collar rotates with the shaft. However in order to ensure that the collar does not crack due to expansion of the shaft, it is preferred that the diameter of the collar should be greater than the greatest possible diameter of the shaft and the collar include resilient means to grip the shaft to ensure that it rotates with the shaft. Conveniently, the resilient means includes at least one but preferably three resilient fingers urged towards the shaft. Advantageously, the resilient fingers are integral with the collar forming projections which bend inwards towards the shaft. The grease distributor may include a plurality of blades, the maximum number being decided by the area covered by the blades. It is preferred that area of the blade should not cover more than half of the area of the annulus between the collar and the edge of the housing. This results in sufficient space for the grease to pass to the edge of the rear face of the shaft. It is also preferred that the grease distributor include an even number of blades, comprising one or more diametrically opposed pairs. This provides a balanced arrangement. Preferably the grease distributor includes two or four blades, most preferably it includes two blades. The grease distributor can be of a number of materials such as metal, rubber or nylon. Since it should be lightweight, cheap and hard wearing, preferably it is of nylon. Each blade should extend to as close to the housing wall as possible without interfering with the rotation of the shaft within the housing. Typically the edge of the blade extends to within lmm of the housing wall. Since one area where grease often is expelled and can accumulate is in the region of the holes of the circlip, preferably the blade extends to the holes of the circlip so that any grease accumulating-in this area is contacted by the blade and distributed around the housing wall. The grease distributor is preferably arranged such that the edge of the blade lies at a distance of between 0.5mm and 1.0mm from the plane of the circlip. Although the blade may be planar lying in a plane substantially parallel to the plane of the circlip, preferably the leading face of the blade (in the direction of rotation) is tilted to the plane of the circlip so that the leading edge is tilted towards the face of the bearing assembly. Preferably the leading face of the blade lies at an angle of substantially 30° to the plane of the circlip. Although the blade may be of constant cross section, it is preferred that the blade taper for its leading edge (in the direction of rotation) to form a sharp edge of small cross section to aid in 'scooping up' the grease, especially from the region of the circlip holes. For ease of manufacture it is preferred that the grease distributor should not be left or right handed. If the bearing assembly is a vehicle wheel hearing assembly in which the shaft is constituted by a rotor nut, this feature allows the same design to be used on all wheels of the car. It is therefore preferred that each blade be symmetrical about a plane parallel to a diametral plane of the shaft with the blade tapering in two directions from the plane towards each edge. Brief Description of the Drawings Three grease distributors and wheel bearing assemblies in accordance with the invention will now be described ,by way of example only, with reference to the accompanying drawings, in which :- Figure 1 is a cross section through a first wheel bearing assembly; Figure 2 is a perspective view of a second grease distributor; Figure 3 is a plan view of a third grease distributor; Figure 4 is a partial section of the grease distributor of figure 3; Figure 5 is a sectional elevation taken along line I-I of figure 3; and, Figure 6 is a part side elevation of the grease distributor of figure 3. Description of the Preferred Embodiments A grease expelling wheel bearing assembly 1 comprises a grease expelling seal 3, and a grease distributor 5. The grease distributor 5 comprises a collar 7 for mounting about the shaft 9 of the rotor nut 11 and, projecting from the collar 7, at least one grease spreading blade 13 extending radially outwards from the collar towards the assembly housing 15, part 17 of the area between the collar 7 and the housing 15 not being covered by a blade 13, the arrangement being such that rotation of the blade 13 causes the grease expelled from the bearing seal 3 to be spread evenly around the circumference of the seal, but not prevent the grease from contacting the rotor nut 11. In the assembly illustrated in figure 1, the grease distributor 5 includes four blades 13. Only two of the blades can be seen in the drawing, each of the blades illustrated having a diametrically opposed blade which is not illustrated. The shape of the blades are all the same and can be clearly seen. Each blade 13 is of constant cross section and symmetrical about a diametral plane 19 of the shaft. The blade is in the form of a shallow inverted V-shape so that its leading face 22 lies at an angle to the plane of the circlip 27. The leading edge thus is tilted towards the bearing 21. The blade operates effectively irrespective of the direction of rotation of the collar and can be regarded as consisting of two halves 23, only one of which operates at any one time. The edge of the blade is close to the surface of the circlip 27. The distance is between 0.5mm and 1mm. The radial edge 29 of the blade is spaced at lmm from the housing wall so that the blade overlaps the circlip but allows sufficient clearance between the rotating members and the housing. In operation the bearing seal 3 between the parts of the bearing 21 expels grease, and this expulsion may be uneven especially in the region of the holes of the circlip 27. In order to prevent build up of the grease behind the rear face 31 of the rotor nut in space 33, the blades 13 of the grease distributor 5 scoop up the grease from the region of the circlip holes and distribute the grease around the walls of the housing 15. This grease will extend to the edge of the rotor nut 11. Thus there will be grease in the region of the peripheral edge of the rotor nut 11 so preventing the ingress of water or debris by this route, but without a build up of grease in the space 33. This extends the life of seal 3. Figure 2 illustrates a second example of a grease distributor 35 which includes two blades 37. Each blade is not of constant cross section with the blade tapering from a central diametral plane 39 to each edge 41. Figures 3 to 6 illustrate a third example of a grease distributor 43, which comprises an essentially annular collar 45 having two diametrically opposed grease spreading blades 47 which project radially outwards from the collar 45. Although the collar 45 is essentially annular, it includes three equally spaced cut out projections 49 which form resilient fingers. The collar 45 includes three sets of parallel slots 51 as illustrated in figure 5 which define between them an area 49 which is bent towards the inside of the annulus, i.e. towards the shaft onto which the collar is to be mounted. The collar is made of glass nylon which would crack if the collar were to fit too tightly on a shaft which subsequently expanded. By mounting the collar so that there is some clearance between the inner annular surface 53 and the surface of a shaft onto which it is to be mounted, the collar will not crack, the resilient fingers bearing on the shaft to hold the collar firmly in position on the shaft so that it rotates with the collar. The blade 47 is symmetrical about diametral plane 55 and tapers from its centre to its two outer edges 57. The leading face 58 of the blade lies at an angle of 30° to the plane 59 forming the upper rim of the collar, which is parallel to the surface of the circlip (not shown) over which the blade will pass. The inner face 61 of the blade lies at 20° to the leading face 58. This shape of blade provides an optimum spreading surface for the distributor.

Claims: A bearing assembly (1) comprising a bearing (21) rotatably supporting a shaft (9) in a housing (15) and a grease expelling bearing seal (3) disposed between the shaft (9) and the housing (15), characterised in that a grease distributor (5) is provided on the side of the bearing seal (3) from which grease is expelled during operation, the grease distributor (5) having a collar (5) mounted on the shaft (9) and at least one grease spreading blade (13) extending radially outwards from only part of the circumference of the collar (7) towards to the housing (15), caracterized in that the leading face of the grease spreading blade (13) is tilted with respect to the plane normal to the axis of rotation of the bearing, the rotation of the collar (7) and blade (13) to serve in operation to spread the grease expelled from the bearing seal (3) evenly around the circumference of the seal (3) so as to improve the sealing between the shaft (9) and the housing (15). A bearing assembly as claimed in claim 1, wherein the spreading blade (13) is in the form of a shallow inverted V-shape in which the leading and trailing faces of the V-shaped blade are tilted with respect to the plane normal to the axis of rotation of the bearing (21). A bearing assembly as claimed in either claim 1 or claim 2, in which the leading face of the blade (13) lies at an angle of substantially 30° to the plane normal to the axis of rotation of the bearing. A bearing assembly as claimed in any preceding claim, in which each grease spreading blade (13) tapers, being thinner at its leading edge. A bearing assembly as claimed in any preceding claim, wherein each grease spreading blade (13) is symmetrical about a plane containing the axis of rotation of the shaft. A bearing assembly as claimed in any one preceding claim, in which the collar (7) of the grease distributor (5) is cylindrical with a diameter slightly greater that the diameter of the shaft (9). A bearing assembly as claimed in claim 2, in which the collar (7) of the grease distributor (5) has a diameter greater than the expanded diameter of the shaft (9) and the collar (7) includes resilient means for gripping the shaft (9). A bearing assembly as claimed in claim 7, in which the resilient means includes at least one resilient finger projecting towards the shaft (9). A bearing assembly as claimed in claim 7 or 8, in which the collar (7) includes integral projections which bend inwards towards the shaft (9). A bearing assembly as claimed in any preceding claim, in which the blade (13) covers an area less than half of the area of the gap between the collar (7) and the housing (15). A bearing assembly as claimed in any preceding claim, wherein the grease distributor (5) has an even number of blades (13) arranged in one or more diametrically opposed pairs. A bearing assembly as claimed in any preceding claim, wherein the grease expelling bearing seal (3) is retained in the housing (15) by means of a circlip (27) having at least one hole and wherein each blade (13) of the grease distributor (5) extends to a position overlying the hole(s) of the circlip (27). A bearing assembly as claimed in any preceding claim, in which the bearing assembly is a vehicle wheel bearing assembly and in which the shaft is the shaft of a rotor nut. A bearing assembly as claimed in claim 13 insofar as it is dependent on claim 2 having, because the spreading blade is V-shaped, the facility for use on all wheels of the motor vehicle.

Inventors: ADKINS DAVID P, FORD MARK S, ADKINS, DAVID P., FORD, MARK S.
Applicants: JAQUAR CARS LTD, JAQUAR CARS LIMITED
Application year: 1997
Main classification: F16C33
IPC codes: F16C33, B60B35, F16N7