GB2255141A - Sealing element - Google Patents

Abstract

A sealing element, particularly for control valves comprises a braided band having an elastic care (2) and lubricated sleeve (3) made of different materials. Preferably the core (2) is braided PTFE-impregnated yarns of carbon-fibre and the sleeve (2) braided PTFE-impregnated and lubricated yarns of PTFE. <IMAGE>

Description

SEALING ELEMENT The present invention relates to a sealing element made of a braided or plaited band. The element finds particular use in relating to packing for sealing a control valve.

In the generally known prior art relating to sealing of control valves, it is customary for such packing and sealing elements to be manufactured from one synthetic material.

However, a difficulty arises in that such materials are required to exhibit on the one hand, particularly when used in regulating or control instruments, high elasticity combined with high rigidity and low friction. Previously known packing and sealing elements specifically for this type of application are a compromise between the various requirements, and are unable to fully satisfy all practical requirements.

It is, therefore, an object of the present invention to provide a sealing element of the aforementioned type which is capable of exhibiting, particularly when used with control instruments, high elasticity and rigidity as well as low friction and high chemical resistance.

Accordingly, the invention provides a sealing element comprising a braided band, which band includes an elastic core of one material and a forged lubricated sleeve of another, different material. Suitably both the core and sleeve are braided. Owing to the specific arrangement of materials in the present packing, improved adaptability to the various conditions to which the packing will be subjected is obtainable, i.e. high elasticity, high rigidity, low friction and high chemical resistance.

In an embodiment of the present invention, the core of the sealing element can be formed from braided yarns, preferably PTFE-impregnated carbon-fibre yarns, and the sleeve braided or plaited PTFE-impregnated and lubricated PTFE yarns.

Furthermore, the core may preferably have a larger crosssectional surface than the sleeve.

The packing of the present invention may be used without support rings. However, in certain applications, for example, in the presence of particular loads, it is possible to utilise support rings to bound or confine the packing.

Embodiments of the invention will now be described in more details, with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of several layers of the packing; Fig. 2 is a possible application of the packing, shown sectionally and partially open; and Fig. 3 is a perspective view of the packing showing the sleeve and core.

Fig. 3 shows a sealing element which is to be used in particular as packing 1 for sealing a control valve. The sealing element is made from a braided band. The braided band, i.e. the packing, is made of two different materials.

Firstly an elastic core 2 of one material and a lubricated sleeve 3 of another material. According to this embodiment, the core 2 is made of braided, PTFE-impregnated carbon-fibre yarns, whereas the sleeve 3, of comparatively relatively fine weave, is composed of PTFE-impregnated and lubricated PTFE yarns.

Fig. 3 further shows that the core 2 has a larger crosssectional surface than the sleeve 3.

In the present embodiment the core 2 of the carbon-fibre yarns provides elasticity, resiliency and dimensional stability for the sealing element. At the same time, the core 2 is a heat deflector which also exhibits chemical resistance.

The finely braided sleeve 3 of PTFE-impregnated and lubricated PTFE yarns is also resistant to chemicals, protects the core 2 and advantageously offers a very low friction coefficient.

Fig. 1 illustrates that several layers of the present packing may be stacked. For this purpose, the opposite ends of the packing 1 have correspondingly slanting surfaces, so that when they abut may establish parallel surfaces relative to the top and bottom side of the packing 1.

According to Fig. 2, the novel packing is arranged in a pocket bore 13 of valve housing 12 of a control valve 4. The bottom of the pocket bore 13 is provided with a support ring 10, on which rest the different layers of the present packing or sealing elements 1. A further support ring 9 is positioned on top of these layers of packing.

Above this support ring 9 is a so-called lantern ring 15, which is constructed so that it is guided or supported at the each end in the wall of the pocket bore 13 and equipped with installation aids 16. The valve housing 12 has a bore 17 which communicates with an outer intermediate space which is defined by upper and lower guides. The lantern ring 15 itself has a bore 20 which establishes a connection to the outer interior space which is also defined by the guides. Above the lantern ring 15 is a further support ring 21 which is loaded by a sleeve 14. This sleeve 14 is affected or acted upon by a gland (not illustrated in detail) which is supported or guided on both sides of the spindle 11 by a bolt 18.The spindle 11 extends through the sleeve 14, the support ring 21, the lantern ring 15, the support ring 9, several layers of packing 1, the support ring 10 and a bore 19 to an operating element (not illustrated in detail).

The entire arrangement is such that, by way of the present packing 1, an excellent seal of the valve spindle 11 relative to the exterior region is achieved. The present sealing element, i.e. the packing 1, can be used without support rings up to specified temperature and pressure values. If these values are exceeded, for example at a temperature of more than 1000C and/or a pressure of more than 200 bar, then support rings 9 and 10, which keep the packing 1 in position can be applied as is shown in Fig. 2, thereby ensuring appropriate adaptation.

A particular embodiment of the present sealing element, having an elastic core 2 of braided, PTFE-impregnated carbonfibre yarns and a finely braided sleeve 3 of PTFE-impregnated and lubricated PTFE yarns advantageously permits optimal adaptation to practical conditions, in particular relative to control instruments. The two products which form the novel sealing element have different deformation and elasticity characteristics, in which respect the lubricated sleeve advantageously offers a much lower friction coefficient.

Claims (12)

1. Sealing element, in particular a packing for sealing a control valve, comprising a braided band having an elastic core braided from a first material and a lubricated sleeve braided from a second, different material.

2. Sealing element according to claim 1, wherein the core comprises braided PTFE-impregnated carbon-fibre yarns.

3. Sealing element according to claim 1 or 2, wherein the braided sleeve comprises PTFE-impregnated and lubricated PTFE yarns.

4. Sealing element according to any one of the preceding claims, wherein the core has a larger cross-sectional surface than the sleeve.

5. Sealing element according to any one of the preceding claims wherein the sleeve of the braided band is of finer weave than the core.

6. Sealing element according to any one of the preceding claims wherein the sleeve has a lower friction coefficient than the core.

7. Sealing element according to any one of the preceding claims having parallel slanting end surfaces.

8. Sealing element substantially as hereinbefore described and illustrated with reference to the accompanying drawings.

9. Sealing arrangement for a control valve having a pocket bore in a housing which includes a sealing element according to any one of the preceding claims bounded by one or more support rings.

10. Sealing arrangement according to claim 9 which includes a lantern ring in the region of a support ring.

11. Sealing arrangement according to claim 10, in which each end of the lantern ring is supported in the pocket bore.

12. Sealing arrangement substantially as hereinbefore described and illustrated with reference to the accompanying Fig. 2.