GB2078876A

GB2078876A - Shaft seal

Info

Publication number: GB2078876A
Application number: GB8020325A
Authority: GB
Original assignee: APV Corp Ltd
Current assignee: SPX Flow Technology Crawley Ltd
Priority date: 1980-06-20
Filing date: 1980-06-20
Publication date: 1982-01-13
Also published as: DK156448C; SE449651B; SE8103815L; DK265781A; DK156448B; DE3123891A1; GB2078876B

Abstract

A shaft seal comprises a sealing member which is mechanically supported by a member and is in the general form of a grommet with a central boss (6) carrying sealing lips (4 and 5), radial flange 8 forming a cleanable face exposed to the process fluid and a deformable flange (7) adapted to pass through the aperture of the member and to expand into mechanical engagement therewith. The member is held between flanges 7 and 8. <IMAGE>

Description

SPECIFICATION Shaft seal This invention relates to shaft seals of the lip type in which a resilient sealing member has a pair of lips longitudinally spaced along a shaft with which a seal is to be formed, Such seals are conventionally used, inter alia, around the operating shafts of flow control valves.

The use of lips is advantageous since the sealing force increases with the operating pressure. Also, it is possible to form the lip seal as a hygienic, crevice-free construction suitable for use in the food processing industry. In order to prevent the whole seal from deforming in the form of a bellows, the lips are normally formed as a sealing member moulded onto a metal insert.

Conventionally, the lipseal is produced by compressing moulding rubber onto a stainless steel insert which has been previously prepared by degreasing, glass-blasting and finally coating with a suitable bonding agent to effect good adhesion between the rubber and the insert.

Despite this preparation, and despite experimentation with various rubber compounds and bonding agents to achieve optimum bonding, failures of the lipseals have occurred due to blistering close to the rubberibond interface at temperature above 90"C.

This blistering phenomenon persisted when a transfer moulded design was tested although the bond was improved.

In order to avoid blistering, trials have been carried out using high permeability rubber, low integrity bonds and sintered, and therefore porous, insert.

It has however been found that the best results have been obtained by avoiding a bond between the sealing member and the insert and relying on mechanical retention.

Accordingly, the present invention consists in a shaft seal wherein a resilient sealing member supported by a insert has a pair of sealing lips arranged to be longitudinally spaced along a shaft, in which the sealing member is in mechanical engagement with the insert.

Preferably the sealing member is readily replaceable on the insert. This has the advantage that if the seal should fail for any reason, a new sealing member can be supplied far more cheaply than the complete shaft seal. Also, the rubber or other elastic material used for the sealing member may be readily chosen for compatibility with or resistance to particular process fluids to which the seal is likely to be exposed.

Since the elastomeric material has no longer to be bonded to the insert, the range of choice is much wider. Also, the sealing members can now be manufactured separately from the inserts, which simplifies manufacturing procedures and eliminates possible bottle necks in production due to shortage of inserts.

The sealing member preferably has a central boss carrying the spaced lips and in addition to this, narrow and wide radial flanges for mechanically inter-engaging on the insert. It thus takes on the general structure of a grommet with wide and narrow flanges. The wide flange presents a full face to the process fluid and is thus crevice-free and wholly cleanable. This makes it suitable for use in the food industry.

It will also be appreciated that the absence of a bond between the sealing member and the insert avoids the problem of blistering to between the sealing member and the insert.

The invention will be further described with reference to the accompanying drawing, in which: Figure 1 is one end elevation of an insert forming part of a preferred form of shaft seal according to the invention; Figure 2 is a sectional view of the insert of Figure 1; and Figure 3 is a partial section of the sealing member.

Referring first to Figures 1 and 2, a reinforcing insert is shown as having a central aperture 1 to receive an operating shaft e.g. of an air operated flow control valve, with a comparatively small clearance. On the process side of the aperture 1, there is a lead- in surface 2, and on the opposite or atmosphere side there is provided a rebate 3.

Figure 3 shows, to a somewhat enlarged scale, a partial section of a sealing member to be fitted in the aperture 1 to provide a pair of sealing lips 4 and 5 engaging on the operating shaft. The lips 4 and 5 are formed as part of a central boss 6 of the sealing member, and from this boss there is a first and narrow radial flange 7 which fits in the rebate 3. A second and wider radial flange 8 fits on the process fluid side of the insert and has an inclined internal surface 9 matching the lead in surface 2. It will be seen that the resilient sealing member of Figure 3 may be fairly readly fitted to and removed from the insert of Figures 1 and 2 since the central boss can be deformed sufficiently to allow the narrow flange 7 to pass through the aperture 1 and then expand into engagement with the rebate 3.The broader flange 8 then fits flat against the surface of the insert and present a cleanable and crevice-free surface to the process fluid. A reduced thickness circumferential zone 10 is provided to be trapped in the housing of the valve, in conjunction with the insert.

Various modifications may be made within the scope ofthe invention.

1. A shaft seal wherein a resilient sealing member supported by an insert has a pair of sealing lips arranged to be longitudinally spaced along a shaft, in which the sealing member is in mechanical engagement with the insert.

2. A shaft seal as claimed in claim 1, in which the sealing member is readily replaceable on the insert.

3. A shaft seal as claimed in claim 1 or 2, in which the sealing member has a central boss carrying the spaced lips and narrow and wide radial flanges mechanically inter-engaging on the insert.

4. A shaft seal substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Shaft seal This invention relates to shaft seals of the lip type in which a resilient sealing member has a pair of lips longitudinally spaced along a shaft with which a seal is to be formed, Such seals are conventionally used, inter alia, around the operating shafts of flow control valves. The use of lips is advantageous since the sealing force increases with the operating pressure. Also, it is possible to form the lip seal as a hygienic, crevice-free construction suitable for use in the food processing industry. In order to prevent the whole seal from deforming in the form of a bellows, the lips are normally formed as a sealing member moulded onto a metal insert. Conventionally, the lipseal is produced by compressing moulding rubber onto a stainless steel insert which has been previously prepared by degreasing, glass-blasting and finally coating with a suitable bonding agent to effect good adhesion between the rubber and the insert. Despite this preparation, and despite experimentation with various rubber compounds and bonding agents to achieve optimum bonding, failures of the lipseals have occurred due to blistering close to the rubberibond interface at temperature above 90"C. This blistering phenomenon persisted when a transfer moulded design was tested although the bond was improved. In order to avoid blistering, trials have been carried out using high permeability rubber, low integrity bonds and sintered, and therefore porous, insert. It has however been found that the best results have been obtained by avoiding a bond between the sealing member and the insert and relying on mechanical retention. Accordingly, the present invention consists in a shaft seal wherein a resilient sealing member supported by a insert has a pair of sealing lips arranged to be longitudinally spaced along a shaft, in which the sealing member is in mechanical engagement with the insert. Preferably the sealing member is readily replaceable on the insert. This has the advantage that if the seal should fail for any reason, a new sealing member can be supplied far more cheaply than the complete shaft seal. Also, the rubber or other elastic material used for the sealing member may be readily chosen for compatibility with or resistance to particular process fluids to which the seal is likely to be exposed. Since the elastomeric material has no longer to be bonded to the insert, the range of choice is much wider. Also, the sealing members can now be manufactured separately from the inserts, which simplifies manufacturing procedures and eliminates possible bottle necks in production due to shortage of inserts. The sealing member preferably has a central boss carrying the spaced lips and in addition to this, narrow and wide radial flanges for mechanically inter-engaging on the insert. It thus takes on the general structure of a grommet with wide and narrow flanges. The wide flange presents a full face to the process fluid and is thus crevice-free and wholly cleanable. This makes it suitable for use in the food industry. It will also be appreciated that the absence of a bond between the sealing member and the insert avoids the problem of blistering to between the sealing member and the insert. The invention will be further described with reference to the accompanying drawing, in which: Figure 1 is one end elevation of an insert forming part of a preferred form of shaft seal according to the invention; Figure 2 is a sectional view of the insert of Figure 1; and Figure 3 is a partial section of the sealing member. Referring first to Figures 1 and 2, a reinforcing insert is shown as having a central aperture 1 to receive an operating shaft e.g. of an air operated flow control valve, with a comparatively small clearance. On the process side of the aperture 1, there is a lead- in surface 2, and on the opposite or atmosphere side there is provided a rebate 3. Figure 3 shows, to a somewhat enlarged scale, a partial section of a sealing member to be fitted in the aperture 1 to provide a pair of sealing lips 4 and 5 engaging on the operating shaft. The lips 4 and 5 are formed as part of a central boss 6 of the sealing member, and from this boss there is a first and narrow radial flange 7 which fits in the rebate 3. A second and wider radial flange 8 fits on the process fluid side of the insert and has an inclined internal surface 9 matching the lead in surface 2. It will be seen that the resilient sealing member of Figure 3 may be fairly readly fitted to and removed from the insert of Figures 1 and 2 since the central boss can be deformed sufficiently to allow the narrow flange 7 to pass through the aperture 1 and then expand into engagement with the rebate 3.The broader flange 8 then fits flat against the surface of the insert and present a cleanable and crevice-free surface to the process fluid. A reduced thickness circumferential zone 10 is provided to be trapped in the housing of the valve, in conjunction with the insert. Various modifications may be made within the scope ofthe invention. CLAIMS

3. A shaft seal as claimed in claim 1 or 2, in which the wide flange has a circumference zone of reduced thickness adapted to be trapped in the housing.

5. A flow control valve having an operating shaft fitted on a shaft seal as claimed in any of claims 1 to

4.

New claims or amendments to claims filed on 5th June1981 Superseded claims 1 and 3

1. A shaft seal wherein a resilient sealing member supported by an insert has a pair of sealing lips arranged to be longitudinally spaced along a shaft, in which the sealing member has a central boss carrying the spaced lips and narrow and wide radial flanges mechanically interengaging on the insert, and the wide flange fitting flat against and covering one face of the insert.