GB2039333A

GB2039333A - Bellows-type sealing element

Info

Publication number: GB2039333A
Application number: GB7944646A
Authority: GB
Original assignee: Klein Schanzlin and Becker AG
Current assignee: Klein Schanzlin and Becker AG
Priority date: 1979-01-02
Filing date: 1979-12-31
Publication date: 1980-08-06
Also published as: JPS5594079A; SE7910659L; FR2445917A1; DE2900011A1; NL7909169A; IT7928381A0

Abstract

A bellows-type sealing element 4 comprises a coil spring 7 the turns of which are slightly spaced apart and which is covered with an elastomer 8. The spring coil may be elastomer covered only on the inside of the coil, or only on the outside, whichever is the side which is subjected, in use, to the higher fluid pressure. Alternatively two or more coil springs may be interfitted, one or more being provided with the elastomer coating. The sealing element may be incorporated is a ball or gate type valve. <IMAGE>

Description

SPECIFICATION Bellows-type sealing element The invention relates to a bellows-type seal.

A corrugated metal expansion joint is one known type of sealing member of this kind. It is used to seal off spindles in valve fittings and the like, for length equalization in the case of compensation joints, in housing bushings for shaft, and the like. Although its sealing effect is reliable, its production is expensive and installation instructions have to be scrupulously maintained. For applications in which the sealing element specifications are less stringent, bellows made from elastomers have been used. Both constructions have the common feature that they are insensitive to longitudinal movements and bending but that torsional movements immediately result in damage and hence breakdown of this type of sealing element.If a component which performs angular movements has to be sealed off from a medium by means of a bellows of this kind, a bellows of the type disclosed, for example according to DE-OS 2641 671 is used, in which the bellows is bent and the rotary or angular movement causes its bending plane to shift.

This expensive type of seal is used only when it is really indispensable. A servo-drive cannot be readily fitted in such cases.

The object of this invention is to develop a sealing element which is easy to manufacture and which can be subjected to tensile, compressive, flexural and torsional stress. To this end, a coil spring, the turns of which are slightly spaced apart, is completely or partially covered with an elastomer and, in the case of partial covering, the elastomer is always fitted on that side of the coil spring which is subjected to the higher pressure. This construction is much easierto make than a metal corrugated expansion joint and has the advantage of taking torsional load as compared therewith. This type of seal can therefore be used for applications where hitherto sealing was possible only with expensive auxiliary constructions.

In one aspect of the invention, the ends of the coil spring are wound spirally so as to extend radially inwards and or outwards to form flanges. This step facilitates the clamping and sealing of the sealing element according to the invention. Depending upon the conditions of use, according to another aspect of the invention the coil spring may be pre-stressed.

The conditions of use will determine whether the prestressing is for tensile or compressive stress or for torsional forces. According to another aspect of the invention, two or more coil springs are interfitted, all the coil springs jointly, or each coil spring separately, being completely or partially covered with an elastomer, or with one of the coil springs not covered with an elastomer at all. This construction has a short axial length and can be used for higher stresses or to influence the introduced torque.

One exemplified embodiment of the invention is illustrated and described in detail hereinafter with reference to two fittings.

Figure 1 shows a ball-type stop valve equipped therewith and Figure 2 shows the invention applied to a gatetype valve.

Referring to Figure 1, a ball-type valve housing 1 is closed by a cover 3 which received the spindle 2. The bellows-type seal 4 according to the invention which is also disposed in this cover has flanged ends 5, 6 in this embodiment, these ends being connected in sealing-tight relationship to the spindle 2 and the housing 1. Embodiments are also possible in which the ends of the bellows-type seal do not have to be flanged. The bellows seal 4 consists of a coil spring 7 which in this case is completely covered by an elastomer 8. The individual turns of the spring are spaced apart so that forces are not transmitted directly by abutment of adjoining turns, when the spindle is moved angularly, which forces might damage the elastomer. Depending upon the conditions of use, the coil spring 7 may be firmly or loosely connected to the elastomer.The elastomer coating may alternatively be applied just partially, e.g. only on the inside of the spring coil or only on the outside, in which case the side selected to be the coated side is always that subjected to the higher pressure in operation of the seal. It is also possible so to provide two or more coil springs that the torque introduced into the drive of the valve spindle or the like is reduced, or its operative direction is influenced, as compared with the arrangement having just one spring. In such a case the springs may be disposed concentrically and all of the springs may be covered partly or wholly by a single body of elastomer, or the springs may be individually covered, partially or holly by respective bodies of elastomer, or one or more of the springs may not be covered with elastomer at all while one or more other springs are.In addition, the short overall length of this seal enables it to be fitted into the conventional gland compartments of valve fittings and also enables servo-drives to be fitted directly on the fitting.

Figure 2 shows the invention applied to a gatetype valve. The cover 3 of the valve housing 9 bears a spindle 2 with the valve member 10 connected thereto. The ends of the seal 4, which in this case is cylindrical, are firmly connected to the wedge 10 and the cover 3. The valve member 10 performs a purely linear movement in the conventional manner and is guided by means of the guide 11. Again, as in known constructions, a stroke limiting means 12 prevents any inadmissible compression of the seal 4. The permissible compression is such that the turns of the spring 7 never bear directly on one another; instead, elastomer 8 is always present between adjacent turns and the displaced elastomer swells out at the sides giving the seal a ribbed appearance similar to the pattern of a wash-board. The elastomer used is selected according to its material properties.

1. A bellows-type sealing element, comprising a coil spring, the turns of which are slightly spaced apart, and which is covered with an elastomer at least on that side of the coil which is subjected to the higher fluid pressure in use.

2. A sealing element according to claim 1 where

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Bellows-type sealing element The invention relates to a bellows-type seal. A corrugated metal expansion joint is one known type of sealing member of this kind. It is used to seal off spindles in valve fittings and the like, for length equalization in the case of compensation joints, in housing bushings for shaft, and the like. Although its sealing effect is reliable, its production is expensive and installation instructions have to be scrupulously maintained. For applications in which the sealing element specifications are less stringent, bellows made from elastomers have been used. Both constructions have the common feature that they are insensitive to longitudinal movements and bending but that torsional movements immediately result in damage and hence breakdown of this type of sealing element.If a component which performs angular movements has to be sealed off from a medium by means of a bellows of this kind, a bellows of the type disclosed, for example according to DE-OS 2641 671 is used, in which the bellows is bent and the rotary or angular movement causes its bending plane to shift. This expensive type of seal is used only when it is really indispensable. A servo-drive cannot be readily fitted in such cases. The object of this invention is to develop a sealing element which is easy to manufacture and which can be subjected to tensile, compressive, flexural and torsional stress. To this end, a coil spring, the turns of which are slightly spaced apart, is completely or partially covered with an elastomer and, in the case of partial covering, the elastomer is always fitted on that side of the coil spring which is subjected to the higher pressure. This construction is much easierto make than a metal corrugated expansion joint and has the advantage of taking torsional load as compared therewith. This type of seal can therefore be used for applications where hitherto sealing was possible only with expensive auxiliary constructions. In one aspect of the invention, the ends of the coil spring are wound spirally so as to extend radially inwards and or outwards to form flanges. This step facilitates the clamping and sealing of the sealing element according to the invention. Depending upon the conditions of use, according to another aspect of the invention the coil spring may be pre-stressed. The conditions of use will determine whether the prestressing is for tensile or compressive stress or for torsional forces. According to another aspect of the invention, two or more coil springs are interfitted, all the coil springs jointly, or each coil spring separately, being completely or partially covered with an elastomer, or with one of the coil springs not covered with an elastomer at all. This construction has a short axial length and can be used for higher stresses or to influence the introduced torque. One exemplified embodiment of the invention is illustrated and described in detail hereinafter with reference to two fittings. Figure 1 shows a ball-type stop valve equipped therewith and Figure 2 shows the invention applied to a gatetype valve. Referring to Figure 1, a ball-type valve housing 1 is closed by a cover 3 which received the spindle 2. The bellows-type seal 4 according to the invention which is also disposed in this cover has flanged ends 5, 6 in this embodiment, these ends being connected in sealing-tight relationship to the spindle 2 and the housing 1. Embodiments are also possible in which the ends of the bellows-type seal do not have to be flanged. The bellows seal 4 consists of a coil spring 7 which in this case is completely covered by an elastomer 8. The individual turns of the spring are spaced apart so that forces are not transmitted directly by abutment of adjoining turns, when the spindle is moved angularly, which forces might damage the elastomer. Depending upon the conditions of use, the coil spring 7 may be firmly or loosely connected to the elastomer.The elastomer coating may alternatively be applied just partially, e.g. only on the inside of the spring coil or only on the outside, in which case the side selected to be the coated side is always that subjected to the higher pressure in operation of the seal. It is also possible so to provide two or more coil springs that the torque introduced into the drive of the valve spindle or the like is reduced, or its operative direction is influenced, as compared with the arrangement having just one spring. In such a case the springs may be disposed concentrically and all of the springs may be covered partly or wholly by a single body of elastomer, or the springs may be individually covered, partially or holly by respective bodies of elastomer, or one or more of the springs may not be covered with elastomer at all while one or more other springs are.In addition, the short overall length of this seal enables it to be fitted into the conventional gland compartments of valve fittings and also enables servo-drives to be fitted directly on the fitting. Figure 2 shows the invention applied to a gatetype valve. The cover 3 of the valve housing 9 bears a spindle 2 with the valve member 10 connected thereto. The ends of the seal 4, which in this case is cylindrical, are firmly connected to the wedge 10 and the cover 3. The valve member 10 performs a purely linear movement in the conventional manner and is guided by means of the guide 11. Again, as in known constructions, a stroke limiting means 12 prevents any inadmissible compression of the seal 4. The permissible compression is such that the turns of the spring 7 never bear directly on one another; instead, elastomer 8 is always present between adjacent turns and the displaced elastomer swells out at the sides giving the seal a ribbed appearance similar to the pattern of a wash-board. The elastomer used is selected according to its material properties. CLAIMS

2. A sealing element according to claim 1 where in the spring is completely covered with an elastomer, inside and outside.

3. A sealing element according to claim 1 wherein the spring is covered with an elastomer only on the outside or only on the inside.

4. A bellows-type sealing element according to any of claims 1 to 3, in which the ends of the coil spring are wound spirally so as to extend radially inwards and!or outwards and afford flanges of the sealing element.

5. A bellows-type sealing element according to any preceding claim in which the coil spring is pre-stressed.

6. A bellows-type sealing element according to any preceding claim in which two or more coil springs are inter-fitted, all the coil springs jointly, or each coil spring separately, being completely or partially covered with an elastomer, or with one of the coil springs not covered with an elastomer at all.

7. A bellows-type sealing element, substantially as hereinbefore described with reference to, and as shown in, Figure 1 of the accompanying drawings.

8. A bellows-type sealing element, substantially as herein before described with reference to, and as shown in, Figure 2 of the accompanying drawings.

9. A valve substantially as hereinbefore described with referance to, and as shown in, Figure 1 of the accompanying drawings.

10. A valve substantially as hereinbefore described with reference to, and as shown in, Figure 2 of the accompanying drawings.

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