GB2347978A

GB2347978A - Fluid-tight face seal assembly for a rotating shaft

Info

Publication number: GB2347978A
Application number: GB9925158A
Authority: GB
Inventors: David Bramley
Original assignee: AES Engineering Ltd
Current assignee: AES Engineering Ltd
Priority date: 1998-11-12
Filing date: 1999-10-26
Publication date: 2000-09-20
Also published as: GB9824724D0; GB9925158D0

Abstract

Face seal assembly (10) comprises first and second sealing members (12, 24). The first sealing member (12) forms a water tight seal with housing (14) by means of O-ring (20) and has an opening (18) through which shaft (16) can pass and rotate. The sealing member (12) also has a first face seal (22) mounted on it. The second sealing member (24) comprises a first part (26) rotatably secured (eg grub screws in bore 38) to the shaft (16) which housing a biassing means (36) (e.g. spring) and a second sealing part (28). The second sealing part (28) has pegs (32) which engage slots (34), it also has a second face seal (48) which is urged against the first face seal (22) by the biassing means (36). A seal (40) provides a water-tight fit between the shaft (16) and the second sealing part (28). A clip (42) is provided so as to store the seal with the second sealing part (28) and biassing means (36) in a retracted position.

Description

SEALING ASSEMBLY This invention relates to sealing assemblies and especially to sealing assemblies for forming a fluid tight seal around a rotatable shaft leaving an enclosure.

In submersible pumps it is necessary that the motor driving the pump is not accessible to the liquid in which the pump is immersed. It is therefore necessary to create a good fluid tight seal at the region where the shaft driving the pump mechanism leaves the enclosure within which the motor is housed. It has been proposed to provide seal assemblies which comprise a first sealing member secured to the housing within which the motor is enclosed and sealing against the housing and a second sealing member secured to and rotatable with the shaft and sealing against the shaft, the two sealing members each supporting face seal means which abut one another and rotate relative to one another as the shaft rotates, to create a fluid tight seal between the first and second sealing members.

These known seal assemblies have not proved altogether satisfactory and are difficult to assemble.

According to the present invention there is provided a face seal assembly for forming a seal around a rotatable shaft leaving an enclosure, comprising a first sealing member having an outer periphery adapted to be received in a portion of a housing defining an enclosure, the outer periphery being adapted to form a fluid-tight seal against the portion of the housing, the first sealing member having an opening through which the shaft can pass and rotate relative to the first sealing member, the first member mounting a first face seal means, a second sealing member comprising a first part adapted to be secured to and rotate with the shaft, a second part which is retained captive by the first part with the second part adjacent the first sealing member when the assembly is, in use, and resilient means which, in use, urges the second part towards the first sealing member, the second part having an opening through which the shaft can pass with a fluid tight seal between the second part and shaft and the second part mounting second face seal means arranged to be urged by the resilient means to create a seal against the first face seal means, the first part of the second sealing member being secured to the shaft by means of at least one fixing element which is inclined at an oblique angle to the axis of rotation of the shaft.

Preferably the fixing element is inclined at an oblique angle of 30 to 60 , more preferably 40 to 50 , to the axis of rotation of the shaft. Most preferably the fixing element is inclined at an oblique angle of 45 to the axis of rotation of the shaft.

Preferably the fixing element is in the form of at least three grub screws.

Suitably, the first part of the second sealing member is a collar which extends around the shaft and the second part of the second sealing member is provided by a second collar of smaller diameter than the first which is received in a complementary recess formed within the first part. Conveniently, the second part is retained captive in the recess by pegs projecting outwardly from the second part and received in the slots formed in walls of the first part defining the recess, the slots extending in the direction parallel with the axis of the shaft to which the first sealing member is to be secured.

Preferably, a seal assembly in accordance with the invention comprises retaining means to retain the second part in a retracted position in the recess of the second sealing member with the resilient means compressed. In a preferred embodiment, the retaining means comprises elements interposed between an end wall of the slot in the first part and the peg projecting from the second part into the slot; conveniently this retaining means is provided by a spring circlip of which portions provide said elements and which can be released by prising the end portions out of the slot.

There now follows a detailed description to be read with reference to the accompanying drawings of a seal assembly in accordance with the invention, it will be realised that the seal assembly has been selected for description to illustrate the invention by way of example.

In the accompanying drawings: Figure 1 is a view, partly in section, showing a seal assembly embodying the invention mounted on a shaft projecting from a housing; Figure 2 is a diagrammatic plan view of retaining means of the illustrative seal assembly.

The illustrative seal assembly 10 comprises a first sealing member 12 having an outer periphery adapted to be retained in a housing 14 (shown-.-in the accompanying drawings). The housing 14 defines an enclosure within which is housed an electric motor (not shown) of a submersible pump. A shaft 16 adapted to be driven by the motor and to rotate the pump mechanism of a submersible pump extends from within the housing 14 through an opening 18 in the first sealing member 12; there is a clearance between the walls defining the opening 18 and the shaft 16. The outer periphery of the first sealing member 12 is adapted to form a fluid tight seal against the portion of the housing 14 within which the first member is received by means of an O-ring seal 20 received in a circumferential groove around the periphery of the first sealing member 12. The first sealing member also mounts first face seal means 22 in a recess of the first sealing member 12 facing outwardly from the enclosure.

The first face seal means is in the form on an annular ring of suitable hard material for example suitable steel commonly used to provide face seal means. The central opening in the first face seal means is a continuation of the opening 18 in the body of the first sealing member and the first seal means 22 projects beyond the body of the first sealing member 12, outwardly of the enclosure.

The illustrative seal assembly 10 also comprises a second sealing member 24 comprising a first part 26 adapted to be secured to and rotate with the shaft 16 and a second part 28 which is retained captive by the first part and is adjacent the first sealing member 12 when the illustrative assembly is in use.

The first part 26 comprises a recess 30 within which the second part 28 is received.

Pegs 32 project form the second part 28 into slots 34 formed opposite one another in the wall of the first part 26 defining the recess 30. The slots 34 extend parallel with the axis of rotation A of the shaft 16. The pegs 32 engaged in the slot 34 thus retain the second part 28 captive in the first part 26. A compression spring 36 is positioned in the recess 30 between the end wall of the first part 26 defining the recess 30 and the second part 28. The spring 36 provides resilient means which act to urge the second part 28 of the second sealing member 24 outwardly of the recess 30 towards the first sealing member 12 of the illustrative seal assembly 10.

The first part 26 of the second sealing member 24 is secured to the shaft 16 by means of three grub screws equally spaced about the axis of the shaft (not shown), the grub screws being received in threaded openings 38 in the first part 26. The openings 38 are inclined obliquely, at an angle of 45 to the axis A of the shaft 16. By angling the holes 38 in such a way, as shown in Figure 1, access to the grub screws is more readily gained both to secure the first part 26 on the shaft 16 and also, when necessary for example for maintenance purposes, to remove the first part of the seal assembly from the shaft 16.

The second part 28 of the second sealing member 24 has an opening through which the shaft 16 can pass with a fluid tight seal provided by a compressible O-ring seal 40 between the second part 28 and the shaft 16.

When the illustrative seal assembly 10 is first supplied, it is supplied with the second part 28 of the second sealing member 24 held in a retracted position within the recess 30 by retaining means in the form of a circlip 42 (see Figure 2 and shown broken away in Figure 1). The circlip comprises a semi circular body portion 44 around the first part 24, having a radius generally similar to the outer periphery of the first part and terminating with two opposed radial end portions 46 projecting inwardly from the body portion 44 (see Figure 2). The radial end portions 46 are, when the seal assembly is delivered, interposed between end walls of the slots 34 and the pegs 32 to force and to retain the pegs (and thus the second part 28) into the retracted condition.

The second part 28 and the peg 32 are shown in the retracted position in-.-in Figure I of the drawings.

The second part 28 of the second sealing member 24 also carries a second face seal means 48 similar to the first face seal means 22 and projecting from the second part 28 opposite the first face seal means 22 when the seal assembly is assemble. The flat faces of the face seal means 22,48 abut one another (shown in Figure 1) and provide a fluid tight face seal between the first and second sealing members as the shaft 16 rotates relative to the housing 14, and with flat faces of the face seal means bearing one another as the face seal means rotate relatively.

In assembling the illustrative seal assembly on a shaft 16, the first sealing member 12 is first assemble in the housing 14 around the shaft 16 and secured to the housing (as shown in Figure 1) by any convenient means eg screw clamps. The second sealing member with the second part 28 held in its retracted position in the recess 30 of the first part 26 by the retaining means 42 is slid onto the shaft 16 and pushed towards the first part 12 of the seal assembly until the first and second face seal means 22,48 abut one another, firmly. The grub screws (not shown) are then tightened in the threaded holes 38 to engage the shaft 16 and secure the first part 26 of the second sealing member 24 firmly to the shaft. At this time, the second part 28 is still held in the retracted position in the first part 26. When the first part 26 is properly secured to the shaft 16, the inward projections 46 are prised, for example using a screwdriver, from the slot 34 to release the second part 28 from its retracted position and allow the spring 36 to urge the second part towards the first sealing member.

The spring 36 is a very strong spring so that the effect of releasing the retaining means 42 urges the two face seal means 22,48 very firmly into engagement. The two face seal means 22,48 are thus heavily spring loaded into engagement with one another.

It has been found that this creates an improved seal between the face seal means which accommodates slight misalignments or roughness without losing sealing ability. The whole system provides an excellent, improved, seal assembly, for example for a submersible pump. The illustrative assembly is readily positioned on the shaft, assisted by the improved accessibility of the grub screws which hold the second sealing member in position on the shaft.

Claims

CLAIMS 1. A face seal assembly for forming a seal around a rotatable shaft leaving an enclosure, comprising a first sealing member having an outer periphery adapted to be received in a portion of a housing defining an enclosure, the outer periphery being adapted to form a fluid-tight seal against the portion of the housing, the first sealing member having an opening through which the shaft can pass and rotate relative to the first sealing member, the first member mounting a first face seal means, a second sealing member comprising a first part adapted to be secured to and rotate with the shaft, a second part which is retained captive by the first part with the second part adjacent the first sealing member when the assembly is, in use, and resilient means which, in use, urges the second part towards the first sealing member, the second part having an opening through which the shaft can pass with a fluid tight seal between the second part and shaft and the second part mounting second face seal means arranged to be urged by the resilient means to create a seal against the first face seal means, the first part of the second sealing member being secured to the shaft by means of at least one fixing element which is inclined at an oblique angle to the axis of rotation of the shaft.
2. A face seal assembly according to claim 1 wherein the fixing element is inclined at an oblique angle of 30 to 60 to the axis of rotation of the shaft.
3. A face seal assembly according to claim 1 wherein the fixing element is inclined at an oblique angle of 40 to 50 to the axis of rotation of the shaft.
4. A face seal assembly according to claim 3 wherein the fixing element is inclined at an oblique angle of 45 to the axis of rotation of the shaft.
5. A face seal assembly according to any of the preceding claims wherein the fixing element is in the form of at least three grub screws.
6. A face seal assembly according to any of the preceding claims wherein the first part of the second sealing member is a collar which extends around the shaft and the second part of the second sealing member is provided by a second collar of smaller diameter than the first which is received in a complementary recess formed within the first part.
7. A face seal assembly according to any of the preceding claims wherein the second part is retained captive in the recess by pegs projecting outwardly from the second part and received in slots formed in walls of the first part defining the recess.
8. A face seal assembly according to claim 7 wherein the slots extend in the direction parallel with the axis of the shaft to which the first sealing member is to be secured.
9. A face seal assembly according to any of the preceding claims further comprising retaining means to retain the second part in a retracted position in the recess of the second sealing member with the resilient means compressed.
10. A face seal assembly according to claim 9 wherein the retaining means comprises elements interposed between an end wall of the slot in the first part and the peg projecting from the second part into the slot.
11. A face seal assembly according to claim 10 wherein the retaining means is provided by a spring circlip of which portions provide said elements and which can be released by prising the end portions out of the slot.
12. A face seal assembly substantially as hereinbefore described with reference to the accompanying diagrams.