GB2141789A

GB2141789A - Seals for rolling bearings

Info

Publication number: GB2141789A
Application number: GB08313912A
Authority: GB
Inventors: Hubert Walter Thomas Neal
Original assignee: SKF AB
Current assignee: SKF AB
Priority date: 1983-05-19
Filing date: 1983-05-19
Publication date: 1985-01-03
Also published as: GB8313912D0; US4557612A; GB2141789B

Abstract

A ball bearing fitted with seals mounted on the outer bearing ring and co-operating with sealing surfaces on the inner bearing ring to prevent or restrict entry of fluid into the bearing. The axially outer face of each seal is formed with protrusions spaced at equal intervals around the seal and positioned adjacent its sealing surface, each protrusion having deflecting surfaces arranged to throw or deflect any debris on the sealing surface outwards away from the bearing upon relative rotation between the two members. Each seal comprises an annular disc-like body of resilient material and an annular reinforcing skirt of rigid material, the inner periphery of the body having an annular lip which projects into an annular groove in its sealing surface.

Description

1 GB 2 141 789 A 1

SPECIFICATION

Improvements in seals for bearings This invention relates to seals for bearings, and is concerned more particularly but not exclusively with seals for rolling bearings for use in oil lubricated machinery, such as for example gear boxes in vehicles.

The rolling bearings in an oil lubricated gear box in a vehicle are generally packed with grease and fitted with annular seals for retaining the grease within the bearing. It is common practice to use a grease which is compatible with the oil in the gear box, and to provide seals which allow a sufficient amount of gear box oil to enter the bearing for the purpose of supplementing and/or replacing the initial grease-fill in the bearing.

The lubricating oil in the gear box of a vehicle is generally contaminated with small particles of metal or other solid matter which originates from unclean components of the gear box or wear debris from the surfaces of the gears. In gear boxes where a gear wheel is mounted adjacentto a support bearing having a seal or inner ring land of a diameter similar to the diameter of the gear wheel, the bearing can be subjected to continuous impingement of gear box lubricating oil due to an axial jet of oil which can be forced out from between the teeth of the gear wheel meshing with an adjacent gear. To protect the rolling elements of the bearing from contaminants carried in the jets of oil or in the oil dispersed within the gear box by general movement of the parts, it has until now been the practice to use bearings fitted with side plates or contact rubbing seals and/or flingerbarriers mounted alongside the bearing. Such bearings however have the following disadvantages.

In bearings fitted with side plates, there is normally an excessive clearance between the bore of the side plate and the land of the bearing. Furthermore the gap between the inner periphery of the side plate and the land of the bearing provides an unobstructed opening in the axial direction leading into the interior of the bearing.

Bearings fitted with contact rubbing seals have the 110 disadvantage that the exposed lip of the seal becom- - es worn with prolonged use. Moreover the seal lip tends to become damaged, probably due to contaminants in the oil becoming lodged between the seal lip and the land of the bearing. With contact seals there also exists the uncertainty whether oil will or will not enter the bearing in sufficient quantity to provide adequate lubrication or if only sufficient oil will pass into the bearing which in effect will leech the pre-packed grease from the bearing.

Bearings fitted with flingers/barriers have the disadvantage that they tend to operate with excessive clearance and form ineffective restriction to the ingress of contaminance. In addition they can take up a significant amount of axial and radial space around the bearings.

According to the invention there is provided a bearing comprising two coaxial bearing members at least one of which is rotatable relative to the other, and an annular seal mounted on one of the members 130 and co-operating with an annular sealing surface on the other member to prevent or restrict entry of fluid between the two members, wherein the annular seal is formed with one or more protrusions arranged to throw or deflect any debris on the sealing surface outwards away from the bearing upon relative rotation between the two members. The or each protrusion is preferably formed on the outboard side of the annular seal, but may also or alternatively be formed on the periphery of the seal adjacent the sealing surface on the other member.

The annular seal is preferably also provided on the inboard side with an annular lip projecting into an annular groove on the sealing surface of the other bearing member to provide a barrier to ingress of debris and excessive volumes of oil into the bearing when operating under dynamic conditions.

The annular seal can conveniently be spaced with small clearance from the sealing surface on the other bearing member. This construction has the advantage that, since there is no sliding contact with the seal, there is no problem of change in torque with changes of temperature and pressure within the bearing.

A rolling bearing having inner and outer bearing rings rotatable relative to one another by rolling elements such as balls between the two rings is preferably provided with two annular seals mounted one on each side of the outer bearing ring and co-operating with sealing surfaces on the inner bearing ring, each seal being provided on its outboard side with one or more protrusions arranged to deflect any debris on the sealing surfaces away from the bearing, and each seal being provided on its inner periphery on the inboard side thereof with an annular lip engaged in an annular groove in the associated sealing surface.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a cross section of part of a single row ball bearing assembly having seals in accordance with the invention, Figure 2 is a side elevation of one of the seals of the bearing assembly of Figure 1, the cross section in Figure 1 being taken along the line 1-1 in Figure 2, Figure 3 is a detail view on an enlarged scale of part of one of the seals and the co-operating sealing surface on an inner bearing ring of the bearing assembly as shown in Figure 1, Figure 4 is a detail view similar to Figure 3 but showing the seal in cross section as viewed along the line IV1V in Figure 2, Figure 5 is a detail view of part of the seal of Figure 2 as viewed in the direction of arrow A in Figure 2, Figure 6 is a cross section of part of a ball bearing assembly having seals of a different construction to those shown in Figure 1, Figure 7 is a side elevation of one of the seals of the bearing assembly of Figgure 6, the cross section in Figure 6 being taken along the line V]-V1 in Figure 7, Figure 8 is a detail view on an enlarged scale of part of one of the seals and the co-operating sealing surface on the inner bearing ring of the bearing 2 GB 2 141 789 A 2 assembly as shown in Figure 6, Figure 9 is a detail view similarto Figure 8 but showing the seal in cross section as viewed along the line IX-1X in Figure 7, Figure 10 is a detail view of part of the seal of 70 Figure 7 as viewed in the direction of arrow B in Fig u re 7, Figure 11 is a cross section of part of another construction of seal and the co-operating sealing surface on the inner bearing ring of a bearing assembly according to the invention, and Figure 12 is a view of the underside of the seal of Figure 11 as viewed in the direction of arrow C.

The ball bearing assembly of Figures 1-5 compris- es an outer bearing ring 10 and an inner bearing ring 11 rotatably mounted within the outer ring 10 by a plurality of balls 12 in rolling engagement with groove tracks on the inner and outer surfaces of the rings 10, 11 respectively. The balls 12 are held in spaced relationship around the bearing rings by a cage 13. Two annular seals 14 are mounted one on each side of the outer bearing ring, the inner periphery of the two seals being spaced with small clearance from the outer surface of the inner bearing ring so that the two seals co-operate with the two bearing rings to form an annular chamber 15 in which the balls are enclosed.

Each seal 14 comprises an annular disc-like body 20 of rubber or other resilient material, and an annular reinforcing skirt 21 of metal or other rigid material bonded to the outboard side of the body 20, the radially outer rim of the skirt 21 being turned axially inwards to form a flange 22 which is embedded in the body 20. The radially outer portion of the body 20 has a greater thickness than the centre portion thereof, and the outer periphery of the body is of rounded section and is a snap fit in an annular groove 23 in the inner surface of the outer bearing ring. The radially inner portion of the body 20 has the inboard side thereof inclined axially and radially inwards to provide a thicker section at the inner periphery, and the inboard side of the inner periphery is formed with an annular lip 24 of substantially square section projecting radially in- wards. The remainder of the inner periphery of the body 20 has a cylindrical surface 25. The inboard side of the body 20 immediately above the lip 24 is formed with an annular groove 26 for a purpose described hereinafter.

The centre portion of the skirt 21 of the seal is 115 cranked axially and radially inwards as shown at 27 in Figure 4. The radially inner portion of the skirt 21 lies in a radial plane as shown in Figure 4 throughout the major portion of its periphery, but is inclined axially outwards and radially inwards as shown in Figure 3 at three spaced locations around the skirt to form three protrusions 28 on the outboard side of the seal as shown in Figure 2. The sides of each protrusion are chamfered as shown in Figure 5 to form deflecting surfaces 29. The body 20 is moulded into the cavities formed on the inboard side of the skirt by the protrusions 28, and the inner peripheral surface 30 of the skirt 21 is flush with the cylindrical surface 25 on the inner periphery of the body 20.

Each side of the inner bearing ring 11 is formed on its outer periphery with an annular groove 35 spaced axially inwards from the adjacent side of the bearing ring. The groove 35 has a cylindrical base 36 and two side walls which diverge from one another in the radially outwards direction. The width of the base 36 is substantially greater than that of the lip 24 on the associated seal. The peripheral surface 39 between the groove 35 and the side of the inner bearing ring is cylindrical.

In the assembled bearing the lip 24 on the inner periphery of each seal projects into the groove 35 on the inner bearing ring and is spaced with only a small clearance gap 40 from the base 36 of the groove. The surfaces 25 and 30 on the remainder of the inner periphery of the seal are spaced with only a relatively small clearance gap 41 from the cylindrical surface 39 on the inner bearing ring. The bearing chamber 15 is charged with grease.

In operation, the co-operation of the lip 24 of each seal with its groove 35 and the narrow clearance gaps 40,41 between the seal and the inner bearing ring provide an effective barrier against ingress of debris or excessive quantities of oil into the bearing chamber. In addition, debris which may accumulate on the surface 39 of the inner bearing ring at the mouth of the clearance gap 41 is deflected axially outwards away from the bearing by the surfaces 29 on the protrusions upon rotation of the inner bearing ring inside the outer bearing ring or upon rotation of the outer bearing ring on the inner bearing ring. The protrusions also serve to deflect awayfrom the mouth of the gap 41 an excess of oil which may be circulating around the bearing due to rotation of adjacent gearing.

The tapering cross section of the protrusions 28 as shown in Figure 3 effectively avoids debris being trapped between the protrusions and adjacent rotating machinery. Each of the protrusions 28 may have its two deflecting surfaces 29 converging towards one another in the radially outward direction as shown at 42 in Figure 2 as an additional precaution to prevent debris being trapped between the protrusions and adjacent rotating machinery.

When the bearing is stationary, the lips 24 increase the effectiveness of the clearance gaps 40,41 in preventing entry of foreign matter into the bearing chamber.

The annular seals 14 may be mounted in the bearing by the following procedure. Each seal is first mounted on a cylindrical dolly having a diameter substantially equal to the external diameter of the inner bearing ring, with the skirt 21 inboard of the body 20, so that the lip 24 will be deflected radiaily outwards. Such deflection is possible due to the clearance provided by the annular groove 26. The dolly and the seal are then presented to the side face of the inner bearing ring and the seal moved axially off the dolly and on to the cylindrical surface 39 of the bearing ring. The seal can then be moved further axially onto the inner bearing ring until the lip 24 engages,in the groove 35 and the outer periphery of the seal engages in the groove 23 in the outer bearing ring. The seal is retained by the groove 23 in the outer bearing ring and is, in operation, normally stationary with respect to the outer bearing ring.

3 GB 2 141 789 A 3 The ball bearing assembly of Fig ures6-10 is similar in construction to that of the bearing of Figures 1-5, except for details of the construction of the seals, and the like parts are denoted by like 5 reference numerals in Figures 1-10.

In the seals of Figures 6-10 the reinforcing skirt45 comprises a flat annular disc having the inner and outer rims turned axially inwards to form flanges 46, 47 and the skirt 45 is embedded wholly within the body 48 of the seal. Protrusions 49, identical in shape to the protrusions 28 of Figures 1-5, are moulded in the outboard side of the body 48 of the seal.

The seal of Figures 11 and 12 is similar to the seal of Figures 6-10 except that the inner peripheral surface 52 is stepped and the side wal 153 of the step at spaced locations around the seal is shaped to form protrusions 54, one of which is shown in Figure 12 as viewed from the underside of the seal. The side edges of each protrusion are chamfered as shown in Figure 12 to form deflecting surfaces 55 arranged to deflect axially outwards any small debris which may accumulate on the outer surface 39 of the inner bearing ring, upon relative rotation between the seal and the inner bearing ring.

Claims

1. A rolling bearing comprising two co-axial bearing members rotatably mounted relative to one another by rolling elements disposed between the two members, one of said bearing members being formed with an annular sealing surface co-axial with the bearing member, and an annular seal mounted on the other bearing member and co-operating with the annular sealing surface to prevent or restrict passage of fluid therebetween, wherein the side of the annular seal facing away from the rolling elements is formed with one or more protrusions positioned adjacent said sealing surface and arranged to throw or deflect debris on the sealing surface outwards away from the bearing upon relative rotation between the two members.

2. A rolling bearing as claimed in claim 1, wherein the or each protrusion has deflecting sur- faces at the leading edges thereof in both directions of relative rotation between the bearing members, the deflecting surfaces converging towards one another in the axial direction awayfrom the rolling elements.

3. A rolling bearing as claimed in claim 2, 115 wherein said deflecting surfaces converge towards one another in the radial direction away from the sealing surface.

4. A rolling bearing as claimed in claim 2, wherein the axially outer surface of the projection extending between said deflecting surfaces is inclined axially outwards in the radial direction towards the sealing surface.

5. A rolling bearing as claimed in any of claims 1-4, wherein the annular seal comprises an annular disc-like body of resilient material and an annular reinforcing skirt of rigid material bonded to the side of the body facing away from the rolling elements, a periphery of the skirt being spaced with small clearance from the sealing surface, and the part of the skirt adjacent the sealing surface being formed with said protrusion or protrusions.

6. A rolling bearing as claimed in claim 5, wherein the centre portion of the skirt is cranked axially inwards and the peripheral portions of the skirt between said protrusions are inset axially inwards relative to the remainder of the skirt in the direction towards the rolling elements.

7. A rolling bearing as claimed in any of claims 1-6, wherein the peripheral surface of the annular seal which is adjacent the sealing surface is formed with an annular step, and the radial face of the step is formed with said protrusion or protrusions.

8. A rolling bearing as claimed in any of claims 1-7, wherein the seal comprises an annular disc-like body of resilient material and an annular reinforcing skirt of rigid material, the side of the sealing surface adjacent the rolling elements is formed with an annular groove, and the peripheral surface of the resilient body of the seal is formed with an annular lip which projects into the annular groove.

9. A rolling bearing as claimed in claim 8, wherein the body of the seal is spaced with small clearance from the sealing surface, and the lip is spaced with small clearance from the base of said annular groove.

10. A rolling bearing as claimed in claim 9, wherein the axially inner side of the resilient body of the seal is formed with an annular groove adjacent the lip to facilitate flexure of the lip upon mounting the seal in the bearing.

11. A rolling bearing comprising an inner bearing ring rotatably mounted in an outer bearing ring by rolling elements between the two rings, the outer periphery of the inner bearing ring being formed with annular sealing surfaces one on each side of the roiling elements, and two annular seals mounted on the outer bearing ring and each co-operating with a separate one of the sealing surfaces to prevent or restrict passage of fluid into the bearing, wherein the side of each annular seal facing away from the rolling elements is formed with one or more protrusions positioned adjacent its sealing surface and arranged to throw or deflect any debris on the sealing surface outwards away from the bearing upon relative rotation between the two bearing rings.

12. A rolling bearing as claimed in claim 11, wherein each seal comprises an annular disc-like body of resilient material and an annular reinforcing skirt of rigid material, each of the sealing surfaces is formed with an annular groove at the end thereof adjacent the rolling elements, and the inner periphery of the body of each seal is formed with an annular lip which projects into the annular groove in the associated sealing surface, the annular seal being spaced with small clearance from the sealing surface and the lip being spaced with small clear ance from the base of the annular groove.

13. A rolling bearing as claimed in claim 12, wherein the or each protrusion has deflecting sur faces at the leading edges thereof in both directions of relative rotation between the bearing members, the deflecting surfaces converging towards one another in the axial direction away from the rolling 4 GB 2 141789 A 4 elements, and the axially outer surface of the projection extending between said deflecting surfaces is inclined axially outwards in the radialiy inwards direction.

14. A rolling bearing as claimed in claim 13, wherein each seal is formed with three protrusions spaced at equal intervals around the seal.

15. A rolling bearing substantially as hereinbefore described with reference to Figures 1-5 or Figures 6-10 or Figures 11, 12 of the accompanying drawings.

Printed in the UK for HMSO, D8818935,10/84,7102. Published by The Patent Office, 25 Southampton Buildings, London, WC2A IlAY, from which copies may be obtained.