GB2305981A

GB2305981A - Seals

Info

Publication number: GB2305981A
Application number: GB9520484A
Authority: GB
Inventors: Andrew Hugh Longdon
Original assignee: Dowty Seals Ltd
Current assignee: Dowty Seals Ltd
Priority date: 1995-10-06
Filing date: 1995-10-06
Publication date: 1997-04-23
Also published as: GB9520484D0; WO1997013992A1

Abstract

A seal comprises a resilient sealing member (1) adapted to bridge an annular gap between two relatively rotatable concentric parts (6,9) so that it is loaded in bending and is resiliently urged into sealing engagement with one of said two parts. A dust seal (5) is formed integrally with the sealing member (1) and extends away from a side face of the sealing member (1) at an angle. When assembled between said relatively rotatable parts (6,9), the sealing member (1) is deformed axially to form an annular seal at its free peripheral edge, and to move the dust seal (5) so that its free peripheral edge (10) is located closely adjacent to or touches the other rotatable part. The sealing member (1) may be a flat disc or a frusto-conical shape. The invention may be used in a shaft seal or a face seal.

Description

SEALS This invention relates to seals of the kind commonly used as shaft seals comprising a resilient sealing member which is adapted to bridge an annular gap between two relatively rotatable concentric parts so that it is loaded in bending and thereby resiliently urges a side face of the seal radially into sealing engagement with one of said two parts.

The sealing member of a seal of the aforesaid kind is generally formed as a flat ring which is secured at one peripheral region to one of said parts. and is over-sized in relation to said gap so that it is defonned axially as it extends radially towards its other free peripheral region in sealing engagement with the other of said parts. Thus, in use, the sealing member assumes a tubular shape in that peripheral region which sealingly engages with the other of said parts, which would be the shaft in the case of a shaft seal.

It is well known to provide shaft seals with a dust seal to control the ingress of dust and dirt that can cause wear between the sealing member and the rotatable part against which it seals. The dust seal is located axially alongside the primary seal on that side to be protected from dust, and commonly comprises a sealing member similar to the primary seal. This dust sealing member is secured at one peripheral region to the same part as the primary sealing member, and is deformed axially as it extends radially to bridge the gap and contact the other of said rotatable parts at its other free peripheral region. The dust sealing member is, however, different in size to the primary sealing member so that it is deformed axially less and only makes light touching contact at its free peripheral edge with said other rotatable part.In one particular arrangement shown in EP-A-0133928 both the primary sealing member and the dust sealing member are formed integrally from the same flat ring of resilient plastics by a radial cut formed in it.

According to the present invention, a seal of the aforesaid kind is provided with a dust seal in the fonn of a dust sealing member which is integral with the primary sealing member and which, in the un-assembled state of the seal, extends away from a side face of the primary sealing member at an angle. When assembled between said relatively rotatable parts, the primary sealing member is deformed axially to form a tubular seal over its free peripheral region, and this deformation of the primary sealing member moves the dust sealing member radially so that is free peripheral edge is located in the required position closely adjacent to or touching the other rotatable part.

This arrangement offers the advantage of a shorter dust sealing member, which therefore reduces the axial space required to accommodate it within the overall seal assembly, and produces a production cost saving by reducing the amount of plastics material used compared with using a separate dust sealing member.

The invention also offers the advantage of a mutually beneficial inter-action between the primary sealing member and the dust scaling member, in that the former acts to positively locate the latter in the required dust sealing position, and the later helps support the former against bellmouthing, this being a common problem with seals of this kind caused by the stresses of deformation within the sealing member which cause it to lift away from the a annular sealing surface over some portions of its circumference.

The invention will now be described by way of example with reference to the accompanying drawing, in which: Figure 1 is a partial section of a sealing member constituting an embodiment of the present invention and shown in the relaxed, un-assembled state; and Figure 2 is a partial section of a shaft seal fitted with the sealing member of Figure 1.

The scaling member 1 shown in Figure 1 is machined from resilient plastics material such as PTFE and takes the form of a ring with an outer peripheral region 2, an inner peripheral region 3, and a side face 4 formed at an intermediate region with a dust lip 5 that extends away from it at an acute angle towards the inner peripheral region 3.

In use, as shown in Figure 2, the sealing member I is secured in an outer annular carrier 6 by clamping of the outer peripheral region 2 of the sealing member in an annular groove 7 in the inner face of the carrier 6. The central apertures of the sealing member 1 receives the shaft 9 within it, and because the aperture 8 is smaller in diameter than the shaft 9, the sealing member 1 is resiliently deformed axially and radially, as shown in Figure 2, so that the inner peripheral region 3 assumes a tubular shape in resilient sealing contact with the shaft 9 over an extended axial portion thereof.

Deformation of the sealing member 1 on the shaft 9 causes the dust lip 5 to turn radially inwards towards the shaft so that its free edge 10 is located in the required dust-sealing position relative to the shaft, either closely adjacent to the shaft surface or touching it.

It will be appreciated that the dimensions of the sealing member 1 and sealing lip 5, and their relative positioning and angle between them. are all selected to suit the dimensions of the gap to be sealed and the desired sealing cooperation between the sealing member 1 and shaft 9 at the inner peripheral region 3 and the free edge 10 of the dust lip 5.

Typically. the angle between the dust lip S and shaft 9 is approximately 60 degrees.

The invention is applicable to seals which seal against an inner member as shown in Figure 2, or seals which seal against an outer member. Also, the invention is applicable to seals in which the sealing member incorporates a hydrodynamic sealing feature, such as a spiral groove in its sealing face.

Claims

1. A seal comprising a resilient primary sealing member which is adapted to bridge an annular gap between two relatively rotatable concentric parts so that it is loaded in bending and thereby resiliently urges a side face of the sealing member into sealing engagement with one of said two parts, characterised in that a dust sealing member is formed integrally with the primary sealing member so that when the seal is in the unassembled state, the dust sealing member extends away from a side face of the primary sealing member at an angle.

2. A seal as claimed in claim 1 in which the primary sealing member is formed as a substantially flat ring with the dust sealing member extending away from one side thereof.

3. A seal as claimed in claim 2 comprising an annular seal carrier to which the primary sealing member is connected concentrically at a peripheral edge so as to extend substantially radially therefrom.

4. A seal as claimed in claim 3 comprising a part concentric with and rotatable relative to the carrier and which has a sealing face contacted by the free peripheral edge of the primary sealing member, the relative dimensions of said sealing face and peripheral edge being such that the primary sealing member is deformed axially and causes the dust sealing member to contact the sealing face.

5. A seal as claimed in claim 4 in which said part is a shaft which is inserted through a central aperture of the primary sealing member.

6. A seal as claimed in claim 1 in which the primary sealing member is formed as a substantially frusto-conical member with the dust sealing member formed on a conical face thereof so as to extend away from said face.

7. A seal as claimed in claim 6 comprising an annular seal carrier to which the primary sealing member is connected concentrically at a peripheral edge so as to extend therefrom radially and axially to one side of the carrier.

8. A seal as claimed in claim 7 in which the primary sealing member extends radially inwardly from the carrier and the dust sealing member is formed on its outwardly directed face.

9. A seal as claimed in claim 7 or 8 comprising a part concentric with and relatively rotatable to the carrier and which has a flat sealing face contacted by the free peripheral edge of the primary sealing member, the axial spacing between the sealing face and the carrier being such that the primary sealing member is deformed axially and causes the dust sealing member to contact the sealing face.

10. A seal substantially as herein described with reference to Figures 1 and 2 or Figures 3 and 4 of the accompanying drawings.