VALVE

FIELD OF THE INVENTION

The present invention relates to a bellows for a vacuum interrupter, exhaust compensator or valve.

BACKGROUND OF THE INVENTION

Low voltage (LV), medium voltage (MV) and high voltage (HV) vacuum interrupters (VI) usually are provided with bellows to seal the inner vacuum and for the moveable contact. The bellows are subjected to frequent operations, especially at relatively high strokes, operating speeds and vibrations. Regarding the mechanical life of a VI, the bellows are often the part of the VI that limits the lifetime of the VI. The same applies to bellows used for exhaust compensators and valves, where the bellows for these devices can also be the limiting factor for the lifetime of such devices.

There is a need to address this problem.

SUMMARY OF THE INVENTION

Therefore, it would be advantageous to have an improved bellows for a vacuum interrupter, exhaust compensator or valve.

The object of the present invention is solved with the subject matter of the independent claims, wherein further embodiments are incorporated in the dependent claims.

In an aspect, there is provided a bellows for a vacuum interrupter, exhaust compensator or valve, the bellows comprising: a main body comprising a first material. The main body comprises a first end portion and comprises a second end portion. The first end portion is configured to be connected to a first part of a vacuum interrupter, exhaust compensator or valve. The second end portion is configured to be connected to a second part of the vacuum interrupter, the exhaust compensator or the valve. The main body comprises a flexible section. The flexible section is configured such that the first end portion can move relative to the second end portion. At least a portion of an inner surface of the flexible section comprises a second material different to the first material; and/or at least a portion of an outer surface of the flexible section comprises the second material.

In an example, the first material is stainless steel.

In an example, a thickness of the second material is in the range from 0.5pm to 100 pm.

In an example, a thickness of the second material for the inner surface is different to a thickness of the second material for the outer surface.

In an example, a thickness of the second material for the inner surface is the same as a thickness of the second material for the outer surface.

In an example, a hardness of the second material is less than a hardness of the first material.

In an example, the bellows is for a vacuum interrupter, and the second material comprises a galvanic coating of: gold, silver, chromium or nickel.

In an example, the bellows is for an exhaust compensator or valve, and the second material comprises a galvanic coating of: gold, silver, chromium, nickel zinc or tin.

In an example, the second material is formed from a surface treatment of the first material. ln an example, at least a portion of the inner surface of the flexible section comprises a third material different to the first material and different to the second material; and/or at least a portion of the outer surface of the flexible section comprises the third material.

In an example, the at least a portion of the inner surface of the flexible section that comprises the second material also comprises the third material; and/or the at least a portion of the outer surface of the flexible section that comprises the second material also comprises the third material.

In an example, a thickness of the third material is in the range from 0.5pm to 100 pm.

In an example, a thickness of the third material for the inner surface is different to a thickness of the third material for the outer surface.

In an example, wherein a thickness of the third material for the inner surface is the same as a thickness of the third material for the outer surface.

In an example, a hardness of the third material is less than a hardness of the first material.

In an example, the bellows is for a vacuum interrupter and wherein the third material comprises a galvanic coating of: gold, silver, chromium or nickel.

In an example, the bellows is for an exhaust compensator or valve and wherein the third material comprises a galvanic coating of: gold, silver, chromium, nickel zinc or tin.

In an example, the third material is formed from a surface treatment of the first material.

In an other aspect, there is provided a vacuum interrupter, exhaust compensator or valve, comprising a bellows according to the first aspect.

The above aspects and examples will become apparent from and be elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments will be described in the following with reference to the following drawings:

Figure. 1 shows a cross-section through an example of a vacuum interrupter in an open position with an example of a bellows as described here;

Figure. 2 shows an example of a bellows as described here, with a cross section and expanded view also shown; and

Figure. 3 shows an example of a bellows as described here, with a cross section and expanded view also shown.

DETAILED DESCRIPTION OF EMBODIMENTS

Figures 1-3 relate to a bellows for a vacuum interrupter, exhaust compensator or valve. In an example, the bellows comprises a main body comprising a first material. The main body comprises a first end portion and comprises a second end portion. The first end portion is configured to be connected to a first part of a vacuum interrupter, exhaust compensator or valve. The second end portion is configured to be connected to a second part of the vacuum interrupter, the exhaust compensator or the valve. The main body comprises a flexible section. The flexible section is configured such that the first end portion can move relative to the second end portion. At least a portion of an inner surface of the flexible section comprises a second material different to the first material. Additionally or alternatively at least a portion of an outer surface of the flexible section comprises the second material.

Reference is made here to a bellows for a vacuum interrupter, exhaust compensator or valve, however that does not mean that exactly the same bellows could be fitted to the vacuum interrupter, exhaust compensator or valve. Rather, the bellows having the structural features as described could in different forms be utilised with a vacuum interrupter, exhaust compensator or valve.

According to an example, the first material is stainless steel.

According to an example, a thickness of the second material is in the range from 0.5pm to 100 pm. According to an example, when both the inner and outer surfaces or portions of those services comprise a second material, a thickness of the second material for the inner surface is different to a thickness of the second material for the outer surface.

However, alternatively a thickness of the second material for the inner surface can be the same as a thickness of the second material for the outer surface.

According to an example, a hardness of the second material is less than a hardness of the first material.

According to an example, the bellows is for a vacuum interrupter. In this example, the second material can comprise a galvanic coating of: gold, silver, chromium or nickel.

According to an example, the bellows is for an exhaust compensator or valve. In this example, the second material can comprise a galvanic coating of: gold, silver, chromium, nickel zinc or tin.

However, according to an example the second material need not be a coating but can be formed from a surface treatment of the first material.

According to an example, at least a portion of the inner surface of the flexible section comprises a third material different to the first material and different to the second material. Additionally or alternatively at least a portion of the outer surface of the flexible section comprises the third material.

According to an example, the at least a portion of the inner surface of the flexible section that comprises the second material also comprises the third material. Additionally or alternatively the at least a portion of the outer surface of the flexible section that comprises the second material also comprises the third material.

According to an example, a thickness of the third material is in the range from 0.5pm to 100 pm.

According to an example, when the inner and outer surfaces the least portion of the bellows comprises the third material, a thickness of the third material for the inner surface is different to a thickness of the third material for the outer surface.

Alternatively, a thickness of the third material for the inner surface can be the same as a thickness of the third material for the outer surface.

According to an example, a hardness of the third material is less than a hardness of the first material.

According to an example, the bellows is for a vacuum interrupter and the third material can comprise a galvanic coating of: gold, silver, chromium or nickel.

According to an example, the bellows is for an exhaust compensator or valve and the third material can comprise a galvanic coating of: gold, silver, chromium, nickel zinc or tin.

According to an example, the third material need not be a coating and the third material can be formed from a surface treatment of the first material.

From the above description, it is clear that A vacuum interrupter, exhaust compensator or valve can have a bellows as described above.

When, the bellows is used for a vacuum interrupter the first end portion of the bellows can be connected to a moveable contact carrier of a vacuum interrupter, and the second end portion of the bellows can be connected to a lower lid of the vacuum interrupter. The skilled person would appreciate that the bellows could be connected elsewhere, whilst maintaining vacuum integrity during movement of the movable contact.

The usual main material for bellows is stainless steel. It is compatible with the high temperatures in a vacuum oven for the manufacturing of the VI and it provides a good corrosion protection. It is further a material that provides the required mechanical stiffness and structure to withstand the vacuum forces and to enable a reasonable mechanical life for many of today’s applications like e.g. distribution circuit breakers (CBs). For other applications, like e.g. CBs that operate arc furnaces several times a day or contactors, the mechanical life is too short or complex drives have to be used to operate the Vis smoothly. The inventors realised that by coating the bellows with a second material, the mechanical stress at the most exposed regions of the bellows could be reduced. The event is also realised that the stainless steel can be surface treated to change the properties of the surface to provide a similar or same effect. Those regions where cracks in the relatively hard stainless steel form, are then covered with a second material that distributes the mechanical stress. The final structure is a sandwich structure where both layers can combine their specific advantages for an improved mechanical life of the bellows - the stainless steel provides the stability and the coating reduces the risk that the bellows become brittle after many operations. Cracks that begin to form cannot then easily travel through the total wall thickness of the bellows formed from the main material undercoating, as a different crystalline structure at the border between the two materials is an obstacle for the progression of cracks.

The coating can also be used to increase the mechanical stiffness of the bellows, e.g. to increase the pressure that can be withstood.

The inventors also realised that the bellows has applicability not just for vacuum interrupters, but also can be applied to other devices such as exhaust compensators or valves. Thus for these devices, the bellows can be fortified and / or their mechanical lifetime can be increased using the above described coating.

Again, the above advantages provided for the surface treated stainless steel main body, in addition to the coated main body. Also, it is possible to use other main body materials to stainless steel, and still coat those materials as described above. It is anticipated that surface treatment of these of the materials will also then be possible to provide the same advantages.

Continuing with the figures, Figure 1 shows a cross-section of a VI in open position. When the VI is closed, the current is conducted by the fixed contact carrier 40, the fixed contact piece 50, the movable contact piece 60 and the movable contact carrier 70.

The vacuum is kept inside by the surrounding shell that consists of the upper lid 10, the insulator 20, the lower lid 30 and the bellows 80. The bellows 80 is the new bellows as described above, and as described in more detail below. Figure 2 shows an example of such a bellows 80. It basically consists of a main material 82 and in this example the outside 82 of the main body 80 is coated with a coating material 84. The coating can also be limited to a certain region of the inside or the outside of the bellows, as shown in Figure 3, where only the upper end and the lower end of the outside of the bellows are coated. Coating 84 ends (or begins; a matter of perspective) at the location 85. The coated regions are shown in more detail at the expanded portion 86. The purpose of a partial coating can be to protect only the mechanically most loaded regions of the bellows.

Suitable coatings are galvanic coatings of e.g. gold, silver, chromium and nickel. For VI applications metals like zinc or tin are not suitable because of the high temperatures during the manufacturing process of the VI. However, for applications like valves or exhaust compensators, also these metals are suitable.

The following provides specific details relating to specific possible embodiments.

A suitable thickness of such a galvanic coating is 0.5pm to 1 OOpm.

As an example, the inside of the bellows is coated.

As an example, the outside of the bellows is coated.

As an example, both the inside and the outside of the bellows are coated with the same material and with the same thickness or with different thicknesses.

As an example, both the inside and the outside of the bellows are coated with different materials and with the same thickness or with different thicknesses.

As an example, the inside and / or the outside of the bellows are coated with more than one material, e.g. a combination of nickel as the first coating and chrome as the second coating on the same side of the bellows.

As an example, the inside and/or the outside of the bellows are partly coated.

As an example, the hardness of the coating is lower than the hardness of the bellows. Also as described above, rather than coating inner and/or outer surfaces or portions of those services of the main body material of the bellows, such as stainless steel, the outer surface of the stainless steel can be treated to changes properties in order to provide the above described advantages.

Reference numerals

1 Vacuum Interrupter (VI ) 10 Upper lid

20 Insulator 30 Lower lid 40 Fixed contact carrier 50 Fixed contact piece 60 Movable contact piece

70 Movable contact carrier

80 Bellows

82 Main material of bellows 80 84 Coating of bellows 80 85 End / beginning of a partial coating

86 Region of a partial coating