GB2242505A

GB2242505A - Valve sealing system

Info

Publication number: GB2242505A
Application number: GB9007253A
Authority: GB
Inventors: Frank Close
Original assignee: NAT OILWELL; National Oilwell LP
Current assignee: NAT OILWELL; National Oilwell Varco LP
Priority date: 1990-03-30
Filing date: 1990-03-30
Publication date: 1991-10-02
Also published as: GB9007253D0

Abstract

In a valve system comprising a central cylindrical valve stem (1) which rotates and/or slides in a concentric valve bonnet (3), an annular seal (5) is held between the stem (1) and a concentric, e.g. frusto-conical, surface (4) by a gland (6). At least one of the sides (8, 9) of the seal is ribbed (at 11) and/or the seal may be channel shaped so that pressure P inside the seal (5) may aid the seal. <IMAGE>

Description

VALVE SEALING SYSTEM The present invention relates to valve systems, and more particularly to a valve system having a seal suitable for sealing a metal valve stem and bonnet. The system is thought to be particularly suited for use in the oil industry.

An aim of the invention is to provide in a valve system a true seal which can generate low drag forces during relative movement of the valve stem through the valve bonnet and will not impair the functioning ability of the valve during rotational and/or linear motion of the stem.

A further aim is to provide a seal of simple design and low manufacturing cost.

According to the present invention there is provided a valve system comprising a valve bonnet, a valve stem which moves within a passage in the bonnet, and a seal between the bonnet and the stem, wherein the seal is of metallic or non metallic material, and is sandwiched between the valve stem and a surrounding wall of the valve bonnet, opposite annular walls of the seal bearing respectively on the surrounding wall and the valve stem to form a seal therebetween.

Other preferred features and advantages of the invention will be apparent from the following description and the accompanying claims.

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a cross-section part-view of a valve system of a first embodiment of the present invention, Figure 2 is a cross-section part-view of a valve system of a second embodiment of the invention, Figure 3 is a cross-section part-view of a valve system of a third embodiment of the invention, Figure 4 is a cross-section part-view of a valve system of a fourth embodiment of the invention; and Figure 5 is a cross-section through a seal of the valve system of Figure 4.

Referring to any of Figures 1 to 4, a valve system forming an embodiment of the invention comprises a metal cylindrical valve stem 1 which may rotate and/or move axially. The stem moves in a concentric cylindrical passage 2 in a metal valve bonnet 3. Above the passage 2 (as seen in the drawings) the valve bonnet 3 has a frusto-conical surface 4 which is concentric with the valve stem 1 and passage 2. A seal 5 which is a particular feature of the invention ,which varies in geometry according to the embodiment, forms a seal between the frusto-conical surface 4 and valve stem 1.

A gland 6 urges the seal 5 into the tapered space between the surface 4 and valve stem 1. The seal 5 may be of metal or of other suitable non-metallic material.

A first embodiment of the invention is illustrated in figure 1. The seal 5 is an annular ring, preferably of non-metallic material, having a solid body and has a flat upper surface 7 on which the gland 6 bears to urge the seal into the tapering space between the wall 4 and valve stem 1. Profiled sealing nibs on the radially inner wall 8 of the seal form ridges 11 which extend in a full circle and bear against the stem 1. The radially outer wall 9 of the seal is flat to form a generally planar contact with the frusto conical surface 4 of the valve bonnet 3.

A second embodiment of the invention is illustrated in figure 2, the seal 5 is an annular ring with a solid body. The ring has a flat upper surface 7 on which the gland 6 bears and inner and outer downwardly depending ribbed cylindrical walls 8 and 9. The ribs 11 extend in a full circle about the stem and bear on the stem 1.

A third embodiment of the invention is illustrated in figure 3, the seal 5 is an annular ring, with a generally solid body and ribbed walls 8 and 9 (as in the second embodiment). In this embodiment an annular channel 12 is provided in the underside of the solid body of the seal 1 to form two relatively flexible annular legs 13, 14.

A fourth embodiment is illustrated in figures 4 and 5.

The seal 5 is an annular ring of metal and has a generally channel-shaped cross-section which is open in the direction of positive pressure P. The ring has a flat upper surface 7 on which the gland 6 bears and inner and outer downwardly depending corrugated clindrical walls 8 and 9. Ridges 11 of the corrugations 10 of the walls 8 and 9 extend in a full circle about the stem 1 and bear respectively on the stem 1 and the frusto-conical surface 4.

It can be seen that initial sealing contact between the inner and/or outer walls 8 and 9 and the surface 4 and stem 1 is caused by the gland 6 urging the seal 5 into the tapering cavity formed between the surface 4 and stem 1. The tapered cavity also serves to inhibit movement of the seal 5 away from the gland 6. The pressure P which is being sealed against may act to urge the walls 8 and 9 outwardly against the surfaces.By corrugating either or both of the walls 8 and 9 they are better able to deform against the surface 4 and stem 1 and provide a largely line contact between the metal parts to provide an effective seal.

It will be appreciated that the cross-sectional shape of the seal 5 may vary, and the wall 4 need not be frusto-conical although this is particularly preferred.

Various modifications may be made to the described embodiments and it is desired to include all such modifications as fall within the scope of the accompanying claims.

Claims

CLAIMS:

1. A valve system comprising a valve bonnet, a valve stem which moves within a passage in the bonnet, and a seal between the bonnet and the stem, wherein the seal is sandwiched between the valve stem and a surrounding wall of the valve bonnet, opposite annular walls of the seal bearing respectively on the surrounding wall and the valve stem to form a seal therebetween.

2. A system as claimed in claim 1, wherein at least one wall of the seal is of arcuate cross-section to provide generally a line contact with the cooperating stem or bonnet wall.

3. A system as claimed in claim 2, wherein the said at least one wall is corrugated.

4. A system as claimed in any one of claims 1 to 3, wherein the surrounding wall is frusto-conical.

5. A system as claimed in claim 4, wherein the seal is urged into the tapering space between the surrounding wall and the valve stem.

6. A system as claimed in any one of claims 1 to 5, wherein the seal is of generally channel shaped cross -section.

7. A system is claimed in claim 6, wherein the space between the seal walls is open to the direction of excess pressure.

8. A system as claimed in any one of claims 1 to 7, wherein the seal is formed of metal.

9. A valve system substantially as hereinbefore described with reference to, and as illustrated in , the accompanying drawings.

10. A seal for a valve system as defined in any one of claims 1 to 8.

11. A valve seal of annular shape having a pair of downwardly depending walls which are corrugated in cross -section.