The invention relates to a vacuum interrupter with a ceramic body and at least one tubelike inner shielding, which is located around the area of a fixed contact and a movable contact, wherein the ceramic body is vacuumtightly closed at it both ends with metal caps, according to the preamble of claim 1 , and method of producing the same, according to the preamble of claim 1 , and claim 4.

The actual solution of the vacuum interrupter which are used, to get a shielding on floating potential is to have two ceramics where the middle shield will be brazed in between. There are some other solutions available in the state of the art, to fix a middle shield inside a single ceramic as there are grooves or steps inside the ceramic cylinder to get a board where the metallic part can be fixed. All these solutions are needing a number of parts or there are tools needed to get burling at the shield.

A further problem is, to secure the shielding in its position, which is important for the technical performance of such a vacuum interrupter used in low- or medium voltage at the level of up to 72 kV.

So the object of the invention is, to enhance the positioning of the aforesaid middle shielding and to secure it in its final positon with easy means.

Acording to that, the invention for a vacuum interrupter with a ceramic body and at least one tubelike inner shielding, which is located around the area of a fixed contact and a movable contact, wherein the ceramic body is vacuumtightly closed at it both ends with metal caps is,

that the ceramic body is provided at its inner surface with a diameter reducing integrated collar, and the shielding is provided with complementary outer bulges or convexities in its structure, adapted to that afroiesaid integrated collar in such, that the shiedling lies against one side of the aforesaid collar, and is fixed in that position at the opposed side of the collar with a ringformed countering element.

In a further advantageous embodiment, that the ringformed countering element is a wire spiral spring, which is furthermore the contact spring of the shielding.

In a further advantageous embodiment, the shielding is provided with a circumferential concave groove or a local diameter reducing trench, in order to secure the position of the ringformed countering element.

In a further advantageous embodiment, the ringformed countering element is a so called worm spring.

According to the method for assembling a shielding inside a vacuum interrupter, with a ceramic body and at least one tubelike inner shielding, which is located around the area of a fixed contact and a movable contact, wherein the ceramic body is

vacuumtightly closed at it both ends with metal caps, the invention is,

that the ceramic body is provided at its inner surface with a diameter reducing integrated collar, and the shielding is provided with complementary outer bulges or convexities in its structure, that the shielding is positioned against one side of the aforesaid collar, and is fixed in that position at the opposed side of the collar with a ringformed countering element, and that after assembling or the ringformed countering element, the vacuum interrupter is treated by a brazing process, andt that after the brazing process, the metal parts tends to shrink more than the ceramic body in such, that the shielding exatly fits to its final position at the collar inside the ceramic body of the vacuum interrupter.

In a further advantageous embodiment of the that, the worm spring is premanufactured out of a basical spring wire in such, that in a first step the worm spring will be treated by coating material, and in a second step cutting in its needed length, and in a third step positioned at the aforesaid postion on the shielding.

Simuilar to that is the case of getting a spiral contact belement.

An embodiment of the invention is shown in the figure.

A vacuum interrupter in vacuumtightly enclosed by a ceramic body with at least one tubelike inner shielding, which is located around the area of a fixed contact and a movable contact, not shown here, wherein the ceramic body is vacuumtightly closed at it both ends with metal caps.

Concerning to the invention, the ceramic body is provided at its inner surface with a diameter reducing integrated collar. This collar is an integrated part of the tubelike cylindrical ceramic body. The shielding is provided with complementary outer bulges or convexities in its structure, adapted to that afroresaid integrated collar in such, that the shiedling lies against one side of the aforesaid collar, and is fixed in that position at the opposed side of the collar with a ringformed countering element.

The ringsformed countering element itself lies safe in this position in a groove or trench in the shielding and additionally versus the lower edge of the aforesaid collar.

By that, the shielding is safely locked in its position, due to silver plated part, the spring will be brazed during the warming treatment process to the shielding in the case, when the part is made of copper, the brazing will occure in situ.

Furthermore the ringsformed countering element is a worm spring.

The worm spring is premanufactured out of a basical spring wire in such, that in a first step the worm spring will be treated by coating material, and in a second step cutting in its needed length, and in a third step positioned at the aforesaid postion on the shielding.

The method of manufacture such a vacuum interrupter is, that the ceramic body is provided at its inner surface with a diameter reducing integrated collar, like described before, and the shielding is provided with complementary outer bulges or convexities in its structure, that the shielding is positioned against one side of the aforesaid collar, and is fixed in that position at the opposed side of the collar with a ringformed countering element, and that after assembling or the ringformed countering element, the vacuum interrupter is treated by a brazing process, and that after the brazing process, the metal parts tends to shrink more than the ceramic body in such, that the shielding exatly fits to its final position at the collar inside the ceramic body of the vacuum interrupter.

So in order to get this simple solution to fix a metal shielding at a single ceramic part there will be used an inner board where the formed shielding can be placed at the board, like described above. On the other side of the board, there will be placed the worm spring element witch snaps inside the groove or trench of the metallic shielding. By the application of a jig in combination with the inserted metal shield, the ceramic collar will be placed in between.

In case the shield will be made of copper and the spring or worm spring will be made of a metal part covered with silver the brazing alloy will be established in-situ. During the brazing and the thermal expansion of the metal shield compared with the ceramic the metal part will shrink to the ceramic step during the cooling down to environment temperature. Due to that effect the part will be fixed by clamping to the ceramic board and fixed on floating potential.

Numberinq

1 ceramic body, insulator

2 shielding, middle shielding

3 bulge, convexity

4 integrated collar

5 wire spring, worm spring

6 groove or diameter reducing trench