The invention relates to a pole part for a low-, medium- or high voltage circuit breaker, with an insert in an insulating housing, and method for manufacturing the same, according to the preamble of claim 1 and 7.

In production of an epoxy or another embedded pole part by using the direct embedding technology, there it is necessary to use a compensation layer at the insert, in order to reduce the mechanical stress inside the part after the production process.

Actually the mechanical and residual stress of the material after the embedding process is compensated by the use of a warm shrinkage tube or by the use of silicone material at first at the insert part.

For the shrinkage tube there is a heat shrinkage device necessary and a well adapted process to get a tight connection between the shrinkage tube an the insert part.

Furthermore the insert has to be cylindrical because the shrinkage tube can cover these parts with some steps in between. In case of the silicon rubber use, there is more flexibility to cover the insert part, here can be used a more intrinsic part, for example a group assembly inside the embedded pole part.

The disadvantage of the silicone layer there is needed to get primer at first to the insert part to the silicone layer and after the process there is need to clean the silicone from the silicone-oil and to primer again to get good wetting to the epoxy material. It is the object of the invention, to enhance the dielectric performance, as well as the effectivity of manufacturing steps with high reproductivity.

With that, the invention is, that the compensation layer consist of a potting material on epoxy basis, with a shore hardness of 12 to 90 shore A.

By that, this new suggestion is to use a thin layer of a potting material, based on epoxy, or polyurethane material, with a shore hardness similar or less than the actual warm shrinkage tube.

In case of the use of that type of potting material, there is no need of the use of a primer application to the insert part, nor the need of primer to the epoxy resin as used today. The dielectric strength of the material can be covered and is similar to the actual solution. In case of this type of material, the sensitivity to micro tips especially at the ceramic metal connection of the vacuum interrupter is limited by the type of potting material.

In a further advantageous embodiment, the insulating housing consist of epoxy or polyurethane material, with a shore hardness bigger than the selected shore hardness of the aforesaid potting material of the compensation layer.

It is important to realize this relation between the hardness of the epoxy housing and the compensation layer.

In a further advantageous embodiment, the insert is a vacuum interrupter or an embedding device.

In that embodiment, the aforesaid use of such a compensation layer is important, because the vacuum interrupter has a ceramic body, which has importantly different thermal expansion parameters then the insulating epoxy housing. For the use in medium voltage, up to 72 kV, such compensation layer is important for the preservation of a high insulation standard.

In a further advantageous embodiment, the compensation layer extends from the complete internal interface of the insert to the complete interface of an upper connection part integrally, which is finally covered by the aforesaid insulating housing. Internal interface means the mechanical coverage interface between the insert and the upper connection part at one side, and the resulting inner surface of the insulating housing in that region at the other side.

In a further advantageous, but alternative embodiment, the compensation layer covers the interface of the insert and the interface of an upper connection part at least partly, which is finally covered by the aforesaid insulating housing.

According to a method for manufacturing a pole part for a medium or high voltage circuit breaker, with an insert in an insulating housing, and a compensation layer between the insert and the insulating housing, the inventionis, with a look to the aforesaid object of the invention, that the compensation layer consist of a potting material on epoxy or polyurethane basis, with a shore hardness of 12 to 90 shore A, and is moulded on the surface of the insert, before the insert with deposed

compensation layer is moulded into an outer insulating material housing.

In a further advantageous embodiment of the aforesaid method, the insulating housing, moulded on the with a compensation layer covered insert, consist of epoxy material, with a shore hardness bigger than the selected shore hardness of the aforesaid potting material of the compensation layer, wherein the aforesaid hardness relation will be reached at the end of the final moulding step of the insulating housing.

In a further advantageous embodiment, the compensation layer is moulded in such, that it extends from the complete interface of the insert to the complete interface of an upper connection part integrally, which is finally covered by the aforesaid insulating housing.

In a final advantageous embodiment, the compensation layer is moulded in such, that it covers the interface of the insert and the interface of an upper connection part at least partly, which is finally covered by the aforesaid insulating housing.

An embodiment of the invention is shown in the drawing. The figure shows a longitudinal cut of a pole part 1 . An insert 2, here a vacuum interrupter, I covered with the compensation layer 3, made of potting material on epoxy or polyurethane basis, with a shore hardness of 12 to 90 shore A.

In this embodiment, the compensation layer extends from the complete surface of the vacuum interrupter 2 up to the upper connection part 4, respectively.

At the bottom of the vacuum interrupter, a movable contact stem 5 is mechanically coupled to a sliding contact system 6, which is electrically connected to the lower connection part 7. The movable contact stem is mechanically coupled to a pushrod 8, which is coupled to an external drive.

The complete arrangement is moulded into an insulating housing 9.

By that, the aforesaid thin compensation layer 3 of a potting material, based on epoxy or polyurethane material, with a shore hardness similar or less than the actual warm shrinkage tube.

In case of the use of that type of potting material, there is no need of the use of a primer application to the insert part, nor the need of primer to the epoxy polyurethane resin, like already mentioned above. The dielectric strength of the material can be covered and is similar to the actual solution. In case of this type of material, the sensitivity to micro tips especially at the ceramic metal connection of the vacuum interrupter is limited by the type of potting material.

Importantly, the insulating housing, moulded on the with a compensation layer covered insert, consist of epoxy or polyurethane material, with a shore hardness bigger than the selected shore hardness of the aforesaid potting material of the compensation layer, wherein the aforesaid hardness relation will be reached at the end of the final moulding step of the insulating housing.

This relation in the choice of material parameters is important, to result a mechanical compensation. Numberinq

1 Pole part

2 Insert, vacuum interrupter

3 Compensation layer

4 Upper connection part

5 Movable contact stem

6 Sliding contact system

7 Lower connection part

8 Push rod