EP1305544A1

EP1305544A1 - Seal construction including a compressible spring mechanism for bearing preload

Info

Publication number: EP1305544A1
Application number: EP00930658A
Authority: EP
Inventors: Richard E. Peterson, Jr.; Merrill L. Karcher
Original assignee: Trostel Ltd
Current assignee: Trostel Ltd
Priority date: 2000-05-12
Filing date: 2000-05-12
Publication date: 2003-05-02
Also published as: AU2000248441A1; WO2001088415A1

Abstract

A seal assembly for providing a seal about a rotating shaft and for exerting a preloading force on a bearing assembly, such as in a horizontal axis washing machine (10) application. The seal assembly includes a seal member (100), a wear member (102), and a coil spring (104). The seal member is formed of a rigid ring (106) having an inner section (108) and an outer section spaced apart from each other. Resilient material is bonded to the ring, including an inner sealing section which engages the shaft (34) and an outer sealing section (110) which engages an inwardly facing surface of the wear member. The spring is located in the space between the inner and outer sections of the ring. The seal assembly is installed adjacent a bearing assembly (80) including an inner race (84), and the spring bears between the inner race and the ring of the seal member. The resilient material includes a sealing rib (120) extending in an axial direction, and the spring functions to seat the sealing rib against a transverse surface extending outwardly from the shaft, as well as to exert an axial preloading force on the inner race of the bearing assembly. The outer sealing section of the seal member bears against a wear surface defined by a wear member, which is press-fit into a recess in a housing within the bearing assembly is installed. The wear member and spring are pre-assembled to the seal member.

Description

SEAL CONSTRUCTION INCLUDING A COMPRESSIBLE

SPRING MECHANISM FOR BEARING PRELOAD

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates to seal assemblies, and more particularly to a seal assembly for sealing about a rotatable shaft and for providing a preloading force on a bearing assembly which rotatably supports the shaft.

Various seal constructions are known for sealing about a rotatable shaft.

In most applications, however, the seal is located in the vicinity of a bearing assembly which rotatably supports the shaft, such that there is typically no interaction between the bearing assembly and the seal assembly.

In certain applications, such as in a horizontal axis washing machine, a rotatable shaft is supported by a bearing assembly which is located in close proximity to a member mounted to the shaft and rotatable with the shaft, such as the end of a drum carried by the shaft. This application requires a seal construction which is capable of placement in a relatively small sealing space between the end of the drum and the bearing assembly. In such an application, it may be necessary to provide an axial preloading force on the inner race of the bearing assembly relative to the outer race, so as to provide proper functioning of the bearing assembly. It is necessary to control the preloading force to ensure that a sufficient amount of force is exerted on the inner race of the bearing assembly to provide proper functioning, and to also ensure that the preloading force does not exceed that which could cause failure of the bearing assembly.

It is an object of the present invention to provide a seal assembly for providing a seal between a rotatable shaft and a support member to which a bearing assembly is mounted and which rotatably supports the shaft relative to the support member. It is a further object of the invention to provide such a sealing assembly which provides an axial preloading force on an inner race of the bearing assembly, to ensure proper functioning of the bearing assembly. Yet another object of the invention is to provide such a seal assembly which accommodates manufacturing and installation tolerances and variations, and which is capable of providing a sufficient preloading force within acceptable limits throughout the range of manufacturing and installation tolerances in operation. A still further objection of the invention is to provide such a seal assembly which is relatively simple in construction and in the manner in which the seal assembly is installed. A still further object of the invention is to provide such a seal assembly having components which can be preassembled for shipment and installation.

The invention contemplates a seal assembly adapted for use in creating a seal between an axially extending shaft and a support member defining an axial passage through which the shaft extends. A bearing assembly is mounted to the support member and includes a stationary outer race and an inner race which rotates along with the shaft.

The seal assembly includes a seal member having an inner sealing section adapted to engage the shaft, and an outer sealing section located radially outwardly of the inner sealing section and adapted to engage an outer sealing surface. A space is located between the inner and outer sealing sections. A spring, such as a compressible coil spring, is located within the space between the inner and outer sealing sections. The spring is adapted to engage the inner race of the bearing assembly so as to provide an axial preloading force on the inner race of the bearing assembly relative to the outer race.

The inner and outer sealing sections are carried by a rigid ring, which includes an axial inner section and an axial outer section spaced radially outwardly from the inner section. The inner sealing section is formed by resilient material bonded to the axial inner section of the rigid ring and adapted for engagement with the shaft. The outer sealing section is formed by resilient material bonded to the axial outer section of the ring. The space within which the spring is located is defined between the axial inner and outer sections of the ring. The seal member includes outwardly facing seal structure adapted to engage a transversely extending surface of a member interconnected with the shaft at a location spaced axially outwardly from the bearing assembly. The compress- ible coil spring functions to exert an axial outward force urging the outwardly facing seal structure against the transversely extending surface, creating a frictional force preventing relative rotation and providing liquid exclusion from the bearing assembly. The coil spring also exerts an axial inward force on the inner race of the bearing assembly. The resilient material bonded to the ring is preferably formed so as to define one or more protrusions extending into the space within which the compressible coil spring is located, for maintaining the compressible coil spring in engagement with the seal member.

The outer sealing surface adapted for engagement by the outer sealing section is preferably in the form of an annular wear member adapted for engagement within a recess formed in the support member. The bearing assembly is mounted to the support member within the recess, and the annular wear member is preferably fitted into the recess and engaged with an inwardly facing surface of the support member which defines the recess. The wear member preferably includes an inner wall section which defines the outer sealing surface, and an outer wall section spaced radially outward from the inner wall section. The outer wall section is adapted for engagement with the inwardly facing surface defining the recess in the support member, and the wear member further includes a transverse wall extending between and interconnecting the inner and outer walls. The transverse wall is adapted to engage the outer race of the bearing assembly when the wear member is fitted into the recess formed in the support member. The wear member defines a central opening through which the seal member extends. One or more outwardly extending protrusions are formed on the resilient material bonded to the rigid ring member, and are adapted to engage the edge of the opening in the wear member for maintaining the wear member in engagement with the seal member. The resilient material forming the inner sealing section may be in the form of a series of axially spaced, inwardly extending ribs engageable with the shaft. The outer sealing section may be in the form of one or more outwardly facing lips which engage the inner surface of the wear member inner wall.

With this construction, the compressible coil spring provides a controlled preloading force on the inner race of the bearing assembly. The preloading force is within an acceptable range throughout varying manufacturing and operating conditions.

Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings illustrate the best mode presently contemplated of carrying out the invention. In the drawings:

Fig. 1 is a sectional view of a horizontal axis washing machine, illustrating a representative application of the seal assembly of the present invention;

Fig. 2 is an exploded partial section view of components incorporated into the assembly of Fig. 1, including the seal assembly of the present invention;

Fig. 3 is an enlarged partial section view of the components of Fig. 2 in assembled form with reference to line 3-3 of Fig. 1;

Fig. 4 is an enlarged partial section view illustrating the seal assembly of the present invention, with reference to line 4-4 of Fig. 3; and Fig. 5 is a further enlarged partial section view with reference to line 5-5 of Fig. 4.

DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 generally illustrates an application for the seal assembly of the present invention in the form of a horizontal axis washing machine 10 which generally includes a stationary cylindrical tub 12 which includes a rear end wall 14 and a side wall

16. Tub 12 defines an open front end, and washing machine 10 includes a door 18 which can be selectively opened or closed to provide access to the interior of a drum 20, in a known manner.

Drum 20 is disposed within tub 12, which may be formed of a material such as ABS plastic, and drum 20 includes a perforated side wall 22 and a rear end wall

24. Tub 12 includes an open front end, which allows items to be placed within the interior of drum 20 when door 18 is open. The rear end of drum 20 adjacent rear end wall 24 is mounted to a drum support member 26, which includes a central hub area 28 and a series of legs 30 extending outwardly therefrom. Drum support member 26 is constructed of a lightweight, strong and rigid material, such as cast aluminum, and drum

20 is preferably formed of a relatively lightweight and durable material, such as stainless steel, although it is understood that other satisfactory materials could be employed.

Openings are formed in side wall 22 adjacent end wall 24, and threaded fasteners such as screws 32 extend through the openings in side wall 22 and into threaded openings extending inwardly from the ends of legs 30 for mounting drum 20 to drum support member 26. As shown in Figs. 2 and 3, a shaft 34 extends rearwardly from hub area 28 of drum support member 26. Shaft 34 includes a forward mounting section 36 which is cast into the material of drum support member 26. Shaft 34 further includes a front bearing surface 38 located rearwardly of drum support member 26, a tapered surface 40 located rearwardly of front bearing surface 38, and a rear section 42 terminating at a shoulder 44. A rear bearing surface 46 extends rearwardly from shoulder 44, and a rear mounting hub 48 having an irregular cross section (such as including one or more flat areas) extends rearwardly from rear bearing surface 46.

A pulley 50 is adapted for mounting to rear mounting hub 48 of shaft 34. Pulley 50 includes a central hub 52 and a web 54 terminating in an outer flange area 56, which is adapted to receive a drive belt 58 (Fig. 1) driven by a motor in a conventional manner. Hub 52 of pulley 50 includes a recess 60 which mates with rear mounting hub 48 of shaft 34 for providing driving engagement of pulley 50 with drive shaft 34. A threaded fastener, such as a screw 62, extends through an opening in hub 52 and into a threaded passage extending inwardly into rear mounting hub 48 of shaft 34 for securing pulley 50 to shaft 34.

A bearing housing 64 is mounted to a central mounting section 66 of tub end wall 14. Bearing housing 64 has a series of projections 68 which form an irregular surface, and the material of central mounting section 66 is molded about projections 68 for providing a secure mounting of bearing housing 64 to tub 12. Bearing housing 64 includes an axially extending passage 70 through which shaft 34 extends. The internal wall of bearing housing 64, which defines passage 70, includes a forward side wall 72 terminating in a shoulder 74, which cooperate to define a forwardly facing recess, and a rear side wall 76 terminating in a shoulder 78, which cooperate to define a rearwardly facing recess.

A forward bearing assembly 80 is located within the forwardly facing recess defined by forward side wall 72 and shoulder 74. Forward bearing assembly 80 is of conventional ball bearing construction, including an outer race 82, an inner race 84, and a series of ball-type rollers 86 disposed between outer race 82 and inner race 84. Representatively, bearing assembly 80 may be a bearing assembly such as is available from SKF of South Africa, under its designation 6207-2RSI/C3, although it is understood that other ball-type bearing assemblies may be employed. Similarly, a rear ball-type bearing assembly 88 is located within the rearwardly facing recess defined by rear side wall 76 and shoulder 78. Rear bearing assembly 88 includes outer and inner races 90,92, respectively, and ball-type roller members 94 therebetween. Representatively, bearing assembly 88 may be a bearing assembly such as is available from SKF of Italy, under its designation 6206-2Z/C3 although it is understood that other satisfactory bearing assemblies may be employed.

Forward bearing assembly 80 is fitted into the forwardly facing recess defined by forward side wall 72 and shoulder 74 such that the rear surface of outer race 82 engages shoulder 74. A seal assembly constructed according to the invention, shown generally at 98, is engaged within the forward portion of the forwardly-facing recess defined by forward side wall 72 and shoulder 74. Seal assembly 98 provides a liquid- tight seal between bearing housing 64 and shaft 34, in a manner to be explained, so as to prevent liquids contained within tub 12 from entering into passage 70 in bearing housing 64, to maintain such liquids within tub 12 and to prevent contact of liquid with bearing assemblies 80,88.

Referring to Figs. 4 and 5, seal assembly 98 generally includes a seal member 100, a wear member 102, and a spring member 104.

Seal member 100 is formed of a rigid ring 106 with resilient material bonded thereto. Ring 106 is preferably formed of a metallic material, such as AISI 1008, although it is understood that other satisfactory materials could be employed. Ring 106 includes an axial inner leg 108 and an axial outer leg 110, which is spaced outwardly from and concentric with inner leg 108. A radially extending transverse section 112 extends outwardly from the forward end of inner leg 108, and a beveled section 114 extends between the outer edge of transverse section 112 and the forward end of outer leg 110. At its rearward end, outer leg 110 terminates in a radially extending flange 116, which is used to support ring 106 during molding. The resilient material of seal member 100 is bonded to ring 106 in a conventional manner, and may be a material such as nitrile rubber, although it is understood that other satisfactory materials could be employed. The resilient material is bonded to both the inner and outer surfaces of inner leg 108. The material located inwardly of inner leg 108, shown at 117, forms a series of inwardly extending parallel ribs 118. The material bonded to the outer surface of inner leg 108, shown at 119, extends into the space between inner and outer legs 110. The material bonded to the outer surfaces of transverse section 112 and beveled section 114, shown at 121, extends outwardly (forwardly) therefrom, and defines a bead or rib 120.

Resilient material is bonded to both the inner and outer surfaces of outer leg 110. The material bonded to the inner surface of outer leg 110, shown at 122, extends into the space between inner and outer legs 108,110, respectively. The resilient material 122 is molded so as to form a series of inwardly extending protrusions 124. The material bonded to the outer surface of outer leg 110, shown at 126, in combination with the portion of material 121 bonded to beveled section 114, defines a shoulder 128. A series of outwardly extending protrusions 130 are located forwardly of shoulder 128. Material 126 is formed so as to define a sealing section 132 located outwardly of flange 116. Sealing section 132 is capable of deflecting inwardly relative to flange 116 and outer leg 110, and defines a forward lip 134 and a rearward lip 136. Wear member 102 defines channel-like cross section including an outer wall 138 terminating in an outwardly extending forward flange 140. A concentric inner wall 142 is located inwardly of outer wall 138, and a transverse rear wall 144 extends between and interconnects the rearward ends of outer wall 138 and inner wall 142. At its forward end, inner wall 142 merges with an inwardly extending forward wall 146 which terminates in an inwardly facing edge 148 which defines a central opening in wear member 102. The diameter of the opening defined by edge 148 is such as to enable the forward end of seal member 100, located forwardly of shoulder 128, to pass through the opening defined by edge 148. Protrusion(s) 130 are deformable when seal member 100 is inserted through the opening in wear member in this manner, and in their undeformed condition as shown in Fig. 5, protrusion(s) 130 function to maintain wear member 102 in engagement with seal member 100.

Spring member 104 is shown as a compression-type coil spring. It is understood, however, that the spring member may take any other satisfactory form providing an axial biasing force. Examples include, but are not limited to, a wave spring, a canted coil spring (commonly known as a Bal-spring), spring fingers or other spring elements formed integrally with rigid ring 106 of seal member 100, or a circlip- type spring. The forward coil portion of spring 104, shown at 150, is received within the space between inner leg 108 and outer leg 110 of ring 106, as well as between the resilient material bonded to the outer surface of inner leg 108 and the inner surface of outer leg 110. Forward coil portion 150 of spring 104 is adapted to deform protrusions

124 upon application of an axial push-on force, to enable coil spring 104 to be assembled to seal member 100.

In assembly, seal assembly 98 is installed as follows. Initially, seal assembly 98 is assembled by and shipped in the condition shown in Fig. 2, in which the rearward portion of coil spring 104 extends rearwardly from wear member 102. Once forward bearing assembly 80 is installed within the forwardly-facing recess defined by side wall 72 and shoulder 74, wear member 102 is press-fit into the recess forwardly of bearing assembly 80 to attain an installed condition, as illustrated in Figs. 4 and 5. When installed in this manner, outer wall 138 of wear member 102 is securely seated within the recess defined by side wall 72, and flange 140 engages the forwardly facing surface of bearing housing 64. The channel-like construction of wear member 102 enables outer wall 138 to deflect inwardly a slight amount if required, to provide a secure press-type friction fit of wear member 102 to bearing housing 64. Rear wall 144 of wear member 102 engages outer race 82 of bearing assembly 80 when wear member 102 is press-fit into the recess in bearing housing 64 in this manner. Upon installation of seal assembly 98, coil spring 104 engages inner race 84 of forward bearing assembly 80. When wear member 102 is press-fit into the recess in bearing housing 64 as described, coil spring 104 compresses to the position as shown in Figs. 4 and 5. With coil spring 104 compressed in this manner, and axial force is exerted between ring 106 and inner race 84 of forward bearing assembly 80 due to engagement of coil spring 104 with inner race 84 and with transverse section 112 and beveled section 114 of ring 106. Engagement of shoulder 128 with forward wall 146 of wear member 102 maintains engagement of seal member 100 with wear member 102.

With seal assembly 98 installed in bearing housing 64 in this manner, shaft 34, with drum 20 mounted thereto, is then inserted into passage 70 in bearing housing 64. Shaft 34 passes through seal assembly 98, forward bearing assembly 80 and rear bearing assembly 88, to attain the assembled condition as shown in Figs. 3-5, wherein front bearing surface 38 engages inner race 84 of forward bearing assembly 80 and rear bearing surface 46 engages inner race 92 of rear bearing assembly 88. In this manner, shaft 34 is rotatably supported relative to bearing housing 64 by front and rear bearing assemblies 80,88, respectively. Pulley 50 is then mounted to the rear end of shaft 34, as described previously.

In operation, seal assembly 98 provides a liquid-tight seal about shaft 34.

Ribs 118 engage the outer surface of shaft 34 forwardly of bearing surface 38.

Forwardly-extending rib 120 engages the rearwardly facing surface of hub area 28 of drum support area 26, and the combination of ribs 118,120 functions to prevent ingress of liquid inwardly of ribs 118. Engagement of lips 134,136 with the inwardly facing surface of wear member inner wall 142 likewise prevents ingress of liquid through the space between wear member 102 and outer leg 110 of ring 106.

In operation, seal member 100 and spring 104 rotate along with shaft 34, while wear member 102 remains stationary. Lips 134,136 thus move on the inwardly facing surface of wear member inner wall 142 in operation, and the construction of lips 134,136 provides sealing engagement therebetween during such rotation of seal member 100.

Spring 104 provides the dual function of exerting a forward axial force to seat rib 120 against the rearwardly facing surface of hub area 28, and a rearward axial force on inner race 84 of forward bearing assembly 80. The size and strength of spring 104 is selected such that the preloading force exerted by spring 104 is sufficient to provide proper preloading of inner race 84 relative to outer race 82 to ensure that inner race 84 rotates with shaft 34, with a force which is sufficiently controlled so as to ensure that excessive force is not exerted on inner race 84. The degree of force exerted by compression spring 104 will vary somewhat according to manufacturing and installation tolerances, and throughout the range of possible tolerances spring 104 provides a satisfactory preloading force for bearing inner race 84.

In addition, the relationship between seal member 100 and shaft 34 is coordinated such that the amount of force required to axially move seal member 100 on shaft 34 does not exceed the force of spring 104. The fit of ribs 118 on shaft 34 is such as to ensure proper sealing while still enabling seal member 100 to move on shaft 34 by the force of spring 104, which preloads bearing assembly inner race 84.

Representatively, the axial sliding force between seal member 100 and shaft 34 is selected so as to be less than approximately 100 Newtons, and the force of spring 104 is selected so as to be approximately 250 Newtons. It is understood that other force ratios could be selected, but this example illustrates a ratio which has been found to be satisfactory.

In addition, lips 134,136 are designed such that drag forces exerted by lips

134,136 against the inner surface of outer wall 142 are less than the force required to turn seal member 100 relative to shaft 34, under the full range of operating conditions. For example, centrifugal forces exerted on lips 134,136 by rotation of shaft 34 increase the drag forces between lips 134,136 and wall 142, and lips 134, 136 are designed such that under maximum speeds of rotation the drag forces exerted by lips 134,136 do not exceed forces required to turn seal member 100 on shaft 34. In this manner, there is no relative rotation between seal member 100 and shaft 34 in operation.

The present invention thus provides a compact, efficient seal assembly which functions to provide a liquid-tight seal for a rotating shaft and which provides a preloading force for a bearing arrangement located adjacent the seal. The components of the bearing assembly are assembled together prior to installation, which reduces installation, assembly and shipment costs. The seal assembly occupies a minimum amount of space, and the axial force exerted by the spring both preloads the bearing assembly and assists in sealing about the shaft. The preloading force exerted by the spring is controlled throughout the full range of manufacturing and installation tolerances. Various alternatives and embodiments are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter regarded as the invention.

Claims

CLAIMSWe claim:

1. A seal assembly adapted for use in creating a seal between an axially extending shaft and a support member defining an axial passage through which the shaft extends, wherein a bearing assembly is mounted to the support member and includes a stationary outer race and an inner race which rotates along with the shaft, comprising: an inner sealing section adapted to engage the shaft; an outer sealing section located radially outwardly of the inner sealing section and adapted to engage an outer sealing surface associated with the support member, wherein a space is located between the inner and outer sealing sections; and a compressible spring member located within the space between the inner and outer sealing sections, wherein the spring is adapted to engage the inner race of the bearing assembly so as to provide an axial preloading force on the inner race relative to the outer race.

2. The seal assembly of claim 1, wherein the inner and outer sealing sections are carried by a rigid ring.

3. The seal assembly of claim 2, wherein the ring includes an axial inner section carrying resilient material forming the inner sealing section, and an axial outer section spaced radially outwardly from the inner section, wherein the axial outer section carries resilient material forming the outer sealing section.

4. The seal assembly of claim 3, wherein the space, within which the spring is located, is defined between the axial inner section and the axial outer section of the ring.

5. The seal assembly of claim 4, wherein the resilient material forming the inner sealing section includes a plurality of inwardly facing, axially spaced ribs adapted to engage the shaft, and wherein the outer sealing section includes a pair of outwardly facing, axially spaced lips adapted to engage the outer sealing surface associated with the support member.

6. The seal assembly of claim 4, wherein the shaft is interconnected with a member defining a transversely extending surface at a location spaced axially from the bearing assembly, and wherein the seal assembly further includes an axially facing sealing section adapted to provide sealing engagement with the transversely extending surface of the member.

7. The seal assembly of claim 6, wherein the ring includes a radial section extending between and interconnecting the axial inner and outer sections, wherein the axially facing sealing section is carried by the radial section of the ring.

8. The seal assembly of claim 7, wherein the inner sealing section, the outer sealing section and the axially facing sealing section comprise resilient sealing material bonded to the ring.

9. The seal assembly of claim 4, further comprising resilient material forming a spring-retaining protrusion in the space within which the spring is located, for maintaining the spring in position.

10. The seal assembly of claim 9, wherein the resilient material forming the inner sealing section is mounted to an inwardly facing surface defined by the axial inner section of the ring, and wherein the resilient material forming the spring-retaining protrusion is bonded to an outwardly facing surface defined by the axial inner section of the ring.

11. The seal assembly of claim 1, wherein the outer sealing surface associated with the support member comprises an annular wear member engaged within a recess formed in the support member.

12. The seal assembly of claim 11, wherein the bearing assembly is mounted to the support member within the recess formed in the support member.

13. The seal assembly of claim 12, wherein the annular wear member is press-fit within the recess and engaged with an inwardly facing wall defined by the support member and forming at least a portion of the recess.

14. The seal assembly of claim 13, further comprising one or more protrusions associated with the seal assembly between the inner and outer sealing sections, and wherein the wear member includes an annular edge defining an opening, wherein the seal assembly extends through the wear member opening and the edge of the wear member defining the opening is engageable with the one or more protrusions, to maintain the wear member in engagement with the seal assembly.

15. The seal assembly of claim 14, wherein the seal assembly comprises a rigid ring member and wherein the inner and outer sealing sections are formed by resilient material bonded to the rigid ring member, wherein the resilient material is formed so as to define the one or more protrusions.

16. The seal assembly of claim 13, wherein the annular wear member includes an outer wall engageable with the inwardly facing wall defined by the support member, and an inner wall engageable with the outer sealing section.

17. The seal assembly of claim 16, wherein the wear member defines a channel-like cross section and includes a transverse wall extending between and interconnecting the inner and outer wall.

18. The seal assembly of claim 17, wherein the transverse wall of the wear member is adapted to engage the outer race of the bearing when the wear member is press-fit into the recess formed in the support member.

19. A seal assembly adapted to provide a seal between an axially extending shaft and a hub member defining an axial passage through which the shaft extends, wherein an end of the hub member includes an outwardly opening recess having a shoulder which is adapted to support an outer race of a bearing assembly which includes an inner race engageable with the shaft, comprising: a wear member defining an inwardly facing wear surface spaced radially from the shaft, wherein the wear member is adapted to be received within the recess in the end of the hub member; a seal member including an inner sealing section adapted to engage the shaft, and an outer sealing section located radially outwardly of the inner sealing section and adapted to engage the wear surface defined by the wear member; and a compressible coil spring located between the inner and outer sealing sections, wherein the spring is adapted to engage the inner race of the bearing assembly so as to provide an axial preloading force on the inner race of the bearing assembly relative to the outer race.

20. The seal assembly of claim 19, wherein the seal member comprises a rigid ring member defining spaced inner and outer walls, and wherein resilient sealing material is bonded to the inner and outer walls of the rigid ring member to form the inner and outer sealing sections.

21. The seal assembly of claim 20, wherein the rigid ring member further includes a radial wall extending between and interconnecting the spaced inner and outer walls, and wherein the compressible coil spring is located between the inner and outer walls of the rigid ring member.

22. The seal assembly of claim 21, wherein resilient sealing material is bonded to the radial wall of the rigid ring member and is formed so as to define an outwardly facing seal structure adapted to engage an inwardly facing surface of a member carried by the shaft, wherein the compressible coil spring functions to provide an axial force adapted to urge the outwardly facing seal structure into engagement with the inwardly facing surface.

23. The seal assembly of claim 21, wherein the wear member includes an inner wall defining the inwardly facing wear surface, an outer wall spaced from the inner wall and adapted to engage an inwardly facing surface of the hub member defining the recess, and a transverse wall extending between and interconnecting the inner and outer walls.

24. The seal assembly of claim 23, wherein the wear member defines an opening through which the seal member extends, wherein the outer sealing section of the seal member engages the inwardly facing wear surface defined by the inner wall of the wear member at a location axially inwardly of the wear member opening.

25. The seal assembly of claim 24, further comprising retainer structure associated with the seal member and adapted to engage the wear member adjacent the opening for maintaining the wear member in engagement with the seal member.