GB2459503A

GB2459503A - Seal assembly comprising inner and outer rings which are rotatable relative to each other and each having annular sealing means

Info

Publication number: GB2459503A
Application number: GB0807572A
Authority: GB
Inventors: David Mcintosh
Original assignee: Pioneer Weston International Ltd
Current assignee: Pioneer Weston International Ltd
Priority date: 2008-04-25
Filing date: 2008-04-25
Publication date: 2009-10-28
Also published as: GB0807572D0

Abstract

A seal assembly 10, for example a radial lip seal, has an inner ring 12 and an outer ring 14 which are rotatable relative to each other. Each of the inner ring 12 and the outer ring 14 has an annular seal 24a, 24b, 28a, 28b and a sealing surface 20, 36, the annular seal 24a, 24b, 28a, 28b of each ring 12, 14 being in sealing engagement with the sealing surface 36, 20 of the other ring. The annular seals 24a, 24b, 28a, 28b may be resiliently deformable and may be deformed in a direction away from each other by engagement with the sealing surfaces 20, 36. The diameter of the sealing surface 20 on the inner ring 12 may be greater than the diameter of the undeformed seal 24a, 24b on the outer ring 14 and the diameter of the sealing surface 36 on the outer ring 14 may be less than the diameter of the undeformed seal 28a, 28b on the inner ring 12. The sealing surfaces 20, 36 on the rings may be frusto-conical.

Description

DESCRIPTION

SEAL ASSEMBLY

The present invention relates to seal assemblies and in particular, but not exclusively, to radial lip seals.

Mechanical face seals are used in a number of applications, for example in the iron and steel industry, where they are often used to provide a seal between a roller in a steel mill and the bearings on which the roller is mounted. The environment in the vicinity of the rollers is extremely hostile, as a result of high temperatures, water, steam and the production of hot iron scale. The function of the seal is to protect the roller bearings from contamination by material from the vicinity of the rollers.

When the function of the seal is impaired as a result of wear, the water, steam and iron scale can reach the roller bearings and cause them to fail, requiring an expensive and time-consuming replacement.

Many existing bearings are therefore continually fed with a lubricant in an attempt to prevent ingress of contaminants, although this results in a continuous discharge of lubricant which is costly and which can also present an environmental hazard.

In addition, the existing sealing arrangements have a relatively long axial length. This increases the stresses on the rollers and can cause them to fail.

It is an object of the present invention to overcome or alleviate

problems associated with the prior art.

In accordance with the present invention, a seal assembly comprises an inner ring and an outer ring which are rotatable relative to each other, each ring comprising annular seal means and a sealing surface, the annular seal means of each ring being in sealing engagement with the sealing surface of the other ring.

By providing inner and outer rings, the axial length (or depth) of the seal can be significantly reduced as compared with the prior art, and also provides two sealing interfaces.

Preferably, the seal means of the inner ring and/or of the outer ring comprises a seal, and preferably the seal is resiliently deformable.

Preferably, the diameter of the sealing surface on the inner ring is greater than the diameter of the undeformed seal ring on the outer ring and/or the diameter of the sealing surface on the outer ring is less than the diameter of the undeformed seal on the inner ring. In this way, engagement of the seal with the sealing surface necessarily deforms the seal.

Preferably, the seal on the inner ring projects radially outwardly and/or the seal on the outer ring projects radially inwardly.

It is preferred that the seals on the inner and outer rings are deformed in a direction away from each other, by engagement with the sealing surface on the outer and inner rings respectively. In this way, each of the sealing engagements is effective to prevent the ingress of contaminants in a direction towards the area between the two seals.

In one embodiment, the seal means of the inner ring and/or of the outer ring comprises a plurality of seals, for example two seals.

The seal means on the inner ring may be mounted on a radially outwardly projecting annular protrusion. Alternatively, or in addition, the seal means on the outer ring may be mounted on a radially inwardly projecting annular protrusion.

Preferably, the sealing surface of the inner ring and/or of the outer ring is frusto-conical.

Preferably, the inner ring and the outer ring further comprise a mounting surface for mounting on a component. Preferably, the mounting surface of the inner ring and/or of the outer ring is cylindrical.

The present invention also includes a roller assembly comprising a seal assembly in accordance with the present invention.

By way of example only, a specific embodiment of the present invention will now be described with reference to the accompanying drawings, in which:-Fig. 1 is a diametrical cross-sectional view through an embodiment of seal assembly in accordance with the present invention, with the portion marked as A shown to a larger scale; and Fig. 2 is a cross-sectional view of the seal assembly of Fig. 1 fitted to a roller assembly of a steel mill.

With reference to Fig. 1, a radial lip seal assembly 10 in accordance with the present invention comprises an inner circular ring 12 located within an outer circular ring 14, both of which are made from mild steel.

As seen in Fig. 1, the inner ring 12 has a tubular body portion 16 and a radially outwardly projecting rim 18 at one end of the body portion 16. The inner face 19 of the tubular body portion 16 is smooth and cylindrical and the outer circumferential face of the body 16 is formed into a smooth sealing surface to receive deformable sealing members 24a, 24b of the outer ring 14, as will be explained. The sealing surface 20 is not circumferential but instead tapers slightly radially inwardly towards the end of the tubular body portion 16 remote from the rim 18 and is therefore slightly frusto-conical in shape. The corners of the tubular body portion at the end remote from the rim 18 are also chamfered, as can be seen in Fig. 1. Two deformable annular sealing members 28a, 28b also project radially outwardly from the outer face of the projecting lug 18, for engagement with a portion of the outer ring 14, as will be explained.

The outer ring 14 comprises a central tubular portion 30, a radially inwardly directed rim 32 at one end of the tubular portion, located radially outwardly of the sealing face 20 of the inner ring and a radially outwardly directed rim 34 at the opposite end of the tubular portion, located axially beyond the rim 18 of the inner ring 12. The inner face 36 of the central tubular portion is smooth and is slightly frusto-conical in shape, increasing in diameter towards the outwardly directed rim 34. The outer face 38 is smooth and cylindrical.

The inner face 36 of the outer ring 14 engages sealingly with, and deforms, the sealing members 28a, 28b projecting from the outwardly projecting rim 18 of the inner ring 12. Similarly, the two sealing members 24a, 24b are secured to, and project radially inwardly from, the radially inwardly projecting rim 32 of the outer ring 14. The sealing members 24a, 24b abut, and are deformed by engagement with, the outermost sealing face 20 of the tubular portion 16 of the inner ring 12.

The sealing members 24a, 24b, 28a, 28b mounted on both the inner ring 12 and the outer ring 14 are made from filled PTFE and the space between each pair of seals is filled with conventional anti-washout grease. The undeformed diameter of the sealing members 24a, 24b, is smaller than 28a, 28b, and the undeformed diameter of all sealing members is greater than the diameter of the portion of the ring which they are intended to engage, so that engagement of the seals necessarily deforms them.

It will be observed that the sealing members 28a, 28b projecting from the inner ring 12 and engaging the outer ring 14 are deformed to the right as seen in Fig. 1, in order to prevent the ingress of unwanted material towards the left. Conversely, the sealing members 24a, 24b connected to the outer ring 14 and engaging the outer surface 20 of the inner ring 12 are directed in the opposite direction, to prevent the ingress of material towards the right as seen in Fig. 1.

By attaching the inner ring to a first member and the outer ring to a second member, the two members being relatively rotatable, the seal arrangement allows relative rotation of the inner and outer rings, 12, 14.

As explained previously, the seals 24a, 24b attached to the outer ring 14 and engaging the inner ring 12 are designed to prevent the passage of material from left to right as seen in Fig. 1, and conversely the seals 28a, 28b attached to the inner ring 12 and engaging the outer ring 14 are intended to prevent the passage of material from right to left, as seen in Fig. 1.

Fig. 2 shows the seal of Fig. 1 as fitted to a roller assembly 40 of a steel mill. Only a portion of the roller 42 is illustrated, the roller, in use, rotating about a rotational axis X -X. In addition, in practice a further seal assembly 10 would be arranged on the other side of the roller but has been omitted for reasons of simplicity.

As shown in Fig. 2, the roller 42 is mounted on a rotatable tubular spindle 44 which also rotates about axis X -X. A silicone rubber annular gasket 46 is located between the inner face of the spindle 44 and the outer face of the roller 42 and a silicone rubber 0-ring seal 48 is located between the inner cylindrical face of the spindle 44 and the outer cylindrical wall of the roller 42.

The spindle 44 carries the inner ring 12 of the radial lip seal assembly 10, the inner cylindrical face 19 of the inner ring being seated on a cylindrical shoulder portion 50 and held in place as an interference fit.

The outer ring 14 is fitted to a portion 52 of the roller assembly which forms part of the housing of the roller assembly 40 and therefore does not rotate, a silicone rubber gasket 54 being located between the outwardly projecting rim 34 and the fixed portion 52 of the roller assembly.

Roller bearings 56, illustrated schematically in dotted lines in Fig. 2, permit rotation of the roller 42 with respect to the housing of the roller assembly.

As can be seen in Fig. 2, the sealing members 28a, 28b of the inner ring 12 are deformed towards the roller 42 and therefore are effective in preventing the passage of water, steam, scale and other unwanted products from the vicinity of the roller 42 towards the roller bearings 56.

Conversely, the sealing members 24a, 24b of the outer ring 14 are deformed towards the roller bearings 56, thereby effectively preventing, or greatly reducing, the passage of lubricant from the vicinity of the roller bearings 56.

Consequently, the ingress of potentially harmful products into the vicinity of the roller bearings 56 is greatly reduced, thereby significantly increasing their working life and reducing the frequency with which they must be replaced. Moreover, since the lubricant in the vicinity of the roller bearings is retained by the seal assembly 10, the amount of the lubricant needed is greatly reduced, thereby reducing cost and removing the need to dispose of discharged lubricant.

The invention is not restricted to the details of the foregoing embodiment. For example, each of the inner and outer rings 12, 14 may be provided with only a single seal 24, 28 or may have more than two seals 24, 28. Indeed, the number of seals 24 on the inner ring 12 may differ from the number of seals 28 on the outer ring 14.

Claims

CLAIMS1. A seal assembly comprising an inner ring and an outer ring which are rotatable relative to each other, each ring comprising annular seal means and a sealing surface, the annular seal means of each ring being in sealing engagement with the sealing surface of the other ring.
2. A seal assembly as claimed in claim 1, wherein the seal means of the inner ring and/or of the outer ring comprises a seal.
3. A seal assembly as claimed in claim 2, wherein the seal is resiliently deformable.
4. A seal assembly as claimed in claim 3, wherein the diameter of the sealing surface on the inner ring is greater than the diameter of the undeforrned seal on the outer ring and/or the diameter of the sealing surface on the outer ring is less than the diameter of the undeformed seal on the inner ring.
5. A seal assembly as claimed in any of claims 2 to 4, wherein the seal on the inner ring projects radially outwardly and/or the seal on the outer ring projects radially inwardly.
6. A seal assembly as claimed in any of claims 2 to 5, wherein the seals on the inner and outer rings are deformed in a direction away from each other by engagement with the sealing surface on the outer and inner rings respectively.
7. A seal assembly as claimed in any of claims 2 to 5, wherein the seal means of the inner ring and/or the outer ring comprises a plurality of seals.
8. A seal assembly as claimed in any of the preceding claims, wherein the seal means on the inner ring is mounted on a radially outwardly projecting annular protrusion.
9. A seal assembly as claimed in any of the preceding claims, wherein the seal means on the outer ring is mounted on a radially inwardly projecting annular protrusion.
10. A seal assembly as claimed in any of the preceding claims, wherein the sealing surface of the inner ring and/or of the outer ring is frusto-conical.
11. A seal assembly as claimed in any of the preceding claims, wherein the inner ring and the outer ring further comprise a mounting surface for mounting on a component.
12. A seal assembly as claimed in claim 11, wherein the mounting surface of the inner ring and/or of the outer ring is cylindrical.
13. A seal assembly substantially as herein described with reference to, and as illustrated in, the accompanying drawings.
14. A roller assembly comprising a seal assembly as claimed in any of the preceding claims.