GB2046373A

GB2046373A - Corrugated metal bellows

Info

Publication number: GB2046373A
Application number: GB8010114A
Authority: GB
Original assignee: Klein Schanzlin and Becker AG
Current assignee: Klein Schanzlin and Becker AG
Priority date: 1979-03-31
Filing date: 1980-03-26
Publication date: 1980-11-12
Also published as: SE8001266L; FR2453337A1; IT8020306A0; DE2913022A1

Abstract

A sealing element 4 for use, for example, to seal a valve member 8 or actuating spindle 2 therefor relative to a valve casing 1 with a cap 3, has the form of a helically corrugated metal bellows 5, with a correspondingly helical spring 6 disposed on the lower-pressure side of the bellows, i.e. within the bellows, in the embodiment illustrated, within the helical trough of the corrugation. The provision of the spring 6 allows the bellows to withstand torsional stresses. <IMAGE>

Description

SPECIFICATION Corrugated metal bellows The invention relates to corrugated metal bellows, for example for sealing pipe fittings.

It is known to use corrugated bellows, of metal or plastics, as sealing elements to seal flexible portions of piping, lead-throughs, sliding-ring seals and compensators and also to seal the spindles or the like actuating elements of pipe fittings such as valves.

The main disadvantage of such known bellows is that they may not safely be subjected to twisting forces about their axes, i.e. to torsional stresses. To deal with this eventuality, the prior art as disclosed by German Offenlegungsschrift 2 641 671 discloses an arrangement wherein such twisting or rotational movements are converted kinetically into bending movements of such a bellows. This solution of the problem is very complicated and therefore correspondingly expensive and has so far been used only when it was really impossible to solve the problem in any other way. Another disadvantage of this system is that it is very difficult to associate it with an actuating drive.

It is the object of the invention to develop a flexible sealing element suitable for high pressure and/or temperature ranges, which is simple to produce and use and able to withstand tension, compression, bending and torsion.

According to one aspect of the invention there is provided a metal bellows which is corrugated and has a spring or springs accommodated in the recesses on one side of the bellows afforded by the corrugations.

The spring is preferably disposed on that side of the diaphragm which is subjected to the lower fluid pressure in use.

According to another aspect of the invention there is provided a corrugated metal bellows, suitable for sealing pipe fittings, which has an overall cylindrical form affording an inner side and an outer side, and which is helically corrugated, and has a helical spring or springs having the same or substantially the same pitch as the bellows corrugations, the helical spring or springs being disposed on the lower-pressure side of the bellows and accommodated in the corrugations thereof.

According to a preferred feature, of use in cases in which the stressing of the bellows is predominantly torsional, the helical corrugation of the bellows is multistart in form, i.e. has a form similar to that of a multi-start, helical thread. In this case, each helically extending corrugation trough, on the appropriate side of the bellows, may have a respective helical spring disposed therein, or only a fraction of these helical troughs may be so occupied.

The pitch angle of the helical corrugations in the wall of the bellows, when the latter is of the preferred, generally cylindrical overall form, that is to say the angle which the respective helix makes with respect to an intersecting line parallel with the axis of the cylinder, may be selected according to the desired characteristics of the bellows.Thus, for some applications the pitch angle may be less than 45 , for others more than 45 , even 70" or greater, while in the extreme, the pitch angle may be greater than 80 , and even as great as 90". In the lastmentioned case, of course, the corrugations take the form of ribs and grooves parallel with the axis of the generally cylindrical bellows, and the inserted springs would then take the form of bendable rods.

An embodiment of the invention is described below by way of example with reference to the accompanying drawing which shows, in axial section, the relevant part of a poppet valve incorporating a bellows embodying the invention.

Referring to the drawing, a valve casing 1 is closed by a cover 3 through which a spindle 2 extends to a valve member 8. Extending between the valve member 8 and the junction between the casing 1 and cover 2 is a metal sealing element 4 comprising a helically corrugated, generally cylindrical bellows 5 and, disposed in the convolutions thereof, a correspondingly helical spring 6. That end of the bellows 5 which is at the top in the drawing is sealingly secured to, or integral with, a dished member 7 clamped. between casing 1 and cover 3. That end of bellows 4 which is at the bottom in the drawing is rigidly and sealingly connected to valve member 8.

Depending upon where the bellows shown are used, lifting and rotary movements can be transmitted and combined lifting and rotary movements and stresses can be taken up. Advantageously, fine-pitch bellows are preferred for the transmission of pure lifting motions and relatively coarse-pitch bellows are preferred to transmit rotary motions or stresses. This feature lengthens the working life of the bellows. An appropriately adapted construction can be used for cases of combined loading.

The bellows construction described with reference to the drawing forms a sealing element which solution provides considerable advantages yet calls for little in the way of production engineering. The corrugated bellows seal described can take up tensile, compressive, bending and twisting forces and is also unaffected by pressure surges, which tend to flatten the corrugations on the pressure side in known constructions. The bellows described with reference to the drawings is less sensitive to pressure surges than prior art devices because the high pressure side corrugation of the bellows at risk bears on the inserted spring.

1. A metal bellows which is corrugated and has a spring or springs accommodated in the recesses on one side of the bellows afforded by the corrugations.

2. A corrugated metal bellows, suitable for sealing pipe fittings, which has an overall cylindrical form affording an inner side and an outer side, and which is helically corrugated, and has a helical spring or springs, having the-same or substantially the same pitch as the bellows corrugations, the helical spring or springs being disposed on the lower-pressure side of the bellows and accommodated in the corrugations thereof.

3. A bellows according to claim 2, in which the or each spring has been located in said corrugations by

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Corrugated metal bellows The invention relates to corrugated metal bellows, for example for sealing pipe fittings. It is known to use corrugated bellows, of metal or plastics, as sealing elements to seal flexible portions of piping, lead-throughs, sliding-ring seals and compensators and also to seal the spindles or the like actuating elements of pipe fittings such as valves. The main disadvantage of such known bellows is that they may not safely be subjected to twisting forces about their axes, i.e. to torsional stresses. To deal with this eventuality, the prior art as disclosed by German Offenlegungsschrift 2 641 671 discloses an arrangement wherein such twisting or rotational movements are converted kinetically into bending movements of such a bellows. This solution of the problem is very complicated and therefore correspondingly expensive and has so far been used only when it was really impossible to solve the problem in any other way. Another disadvantage of this system is that it is very difficult to associate it with an actuating drive. It is the object of the invention to develop a flexible sealing element suitable for high pressure and/or temperature ranges, which is simple to produce and use and able to withstand tension, compression, bending and torsion. According to one aspect of the invention there is provided a metal bellows which is corrugated and has a spring or springs accommodated in the recesses on one side of the bellows afforded by the corrugations. The spring is preferably disposed on that side of the diaphragm which is subjected to the lower fluid pressure in use. According to another aspect of the invention there is provided a corrugated metal bellows, suitable for sealing pipe fittings, which has an overall cylindrical form affording an inner side and an outer side, and which is helically corrugated, and has a helical spring or springs having the same or substantially the same pitch as the bellows corrugations, the helical spring or springs being disposed on the lower-pressure side of the bellows and accommodated in the corrugations thereof. According to a preferred feature, of use in cases in which the stressing of the bellows is predominantly torsional, the helical corrugation of the bellows is multistart in form, i.e. has a form similar to that of a multi-start, helical thread. In this case, each helically extending corrugation trough, on the appropriate side of the bellows, may have a respective helical spring disposed therein, or only a fraction of these helical troughs may be so occupied. The pitch angle of the helical corrugations in the wall of the bellows, when the latter is of the preferred, generally cylindrical overall form, that is to say the angle which the respective helix makes with respect to an intersecting line parallel with the axis of the cylinder, may be selected according to the desired characteristics of the bellows.Thus, for some applications the pitch angle may be less than 45 , for others more than 45 , even 70" or greater, while in the extreme, the pitch angle may be greater than 80 , and even as great as 90". In the lastmentioned case, of course, the corrugations take the form of ribs and grooves parallel with the axis of the generally cylindrical bellows, and the inserted springs would then take the form of bendable rods. An embodiment of the invention is described below by way of example with reference to the accompanying drawing which shows, in axial section, the relevant part of a poppet valve incorporating a bellows embodying the invention. Referring to the drawing, a valve casing 1 is closed by a cover 3 through which a spindle 2 extends to a valve member 8. Extending between the valve member 8 and the junction between the casing 1 and cover 2 is a metal sealing element 4 comprising a helically corrugated, generally cylindrical bellows 5 and, disposed in the convolutions thereof, a correspondingly helical spring 6. That end of the bellows 5 which is at the top in the drawing is sealingly secured to, or integral with, a dished member 7 clamped. between casing 1 and cover 3. That end of bellows 4 which is at the bottom in the drawing is rigidly and sealingly connected to valve member 8. Depending upon where the bellows shown are used, lifting and rotary movements can be transmitted and combined lifting and rotary movements and stresses can be taken up. Advantageously, fine-pitch bellows are preferred for the transmission of pure lifting motions and relatively coarse-pitch bellows are preferred to transmit rotary motions or stresses. This feature lengthens the working life of the bellows. An appropriately adapted construction can be used for cases of combined loading. The bellows construction described with reference to the drawing forms a sealing element which solution provides considerable advantages yet calls for little in the way of production engineering. The corrugated bellows seal described can take up tensile, compressive, bending and twisting forces and is also unaffected by pressure surges, which tend to flatten the corrugations on the pressure side in known constructions. The bellows described with reference to the drawings is less sensitive to pressure surges than prior art devices because the high pressure side corrugation of the bellows at risk bears on the inserted spring. CLAIMS

3. A bellows according to claim 2, in which the or each spring has been located in said corrugations by screwing orforming the spring into the corrugations.

4. A bellows according to claims 2 or 3, in which the or each spring is pre-stressed by the bellows.

5. A bellows according to claim 4 wherein the or each spring is biased in tension or compression or torsion by the bellows.

6. A bellows according to any preceding claim in which bellows ti- - helical corrugation o the bellows is multistart in fo. m.

7. A bellows according to any of claims 2 to 6, in which the pitch angle of the corrugations of the bellows is greater than 45".

8. A bellows according to any of claims 2 to 6, in which the pitch angle of the corrugations of the bellows is greater than 70".

9. A bellows according to any of claims 2 to 6, in which the pitch angle of the corrugations of the bellows is greater than 80".

10. A bellows according to claim 1 which has an overall cylindrical form but has the corrugations in its wall extending parallel with the longitudinal axis ofthe bellows.

11. A bellows substantially as hereinbefore described with reference to, and as shown in, the accompanying drawing.

12. Any novel feature or combination of features described herein.