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EP-4736205-A1 - METHOD FOR PRODUCING A CONTACT LAYER

EP4736205A1EP 4736205 A1EP4736205 A1EP 4736205A1EP-4736205-A1

Abstract

The invention relates to a method for producing a contact layer (2) on a contact electrode (1) of a vacuum interrupter (100), a layer of contact-layer printing paste (300) being printed onto a front face (7) of the contact electrode (1) by way of screen printing in order to form the contact layer (2).

Inventors

  • KARMAZIN, ROMAN
  • BRAUNER, THOMAS
  • GRASKOWSKI, FRANK

Assignees

  • Siemens Aktiengesellschaft

Dates

Publication Date
20260506
Application Date
20240731

Claims (9)

  1. 1. Method for producing a contact layer (2) on a contact electrode (1) of a vacuum interrupter (100), wherein a layer of contact layer printing paste (300) for forming the contact layer (2) is printed onto an end face (7) of the contact electrode (1) by means of a screen printing process.
  2. 2. The method according to claim 1, wherein, before the layer (300) of contact layer printing paste is printed, at least one layer (200) of intermediate layer printing paste is printed onto the end face (7) of the contact electrode (1) by means of a screen printing process to form at least one intermediate layer (2) arranged between the end face (7) of the contact electrode (1) and the contact layer (3).
  3. 3. The method according to claim 2, wherein after printing a layer (200) of intermediate layer printing paste, this layer (200) is dried before a further layer (200, 300) of printing paste is printed onto the layer (200) of intermediate layer printing paste.
  4. 4. Method according to one of the preceding claims, wherein after the layer (300) of contact layer printing paste has been printed, the one or more layers (200, 300) of printing paste printed on the contact electrode are sintered.
  5. 5. Method according to one of the preceding claims, wherein the contact layer printing paste is produced by mixing particles of a contact material comprising a material with good electrical conductivity and/or a hard material resistant to erosion with a binder to form a printing paste.
  6. 6. The method according to claim 5, wherein the contact material comprises one of the following material pairings: copper-chromium, tungsten-copper, tungsten carbide-silver, tungsten carbide-copper.
  7. 7. A method according to any one of the preceding claims, wherein the interlayer printing paste is prepared by mixing particles of stainless steel, copper, silver, a silver-stainless steel alloy or a copper-stainless steel alloy with a binder to form a printing paste.
  8. 8. Method according to one of the preceding claims, wherein the surface of the contact electrode has a depressed region (5) into which the at least one layer (2, 3) of printing pastes is printed.
  9. 9. Switching contact (30, 40) of a vacuum interrupter (100), comprising a contact layer (3) produced by means of a screen printing process.

Description

Description Method for producing a contact layer The present invention relates to a method for producing a contact layer and a switching contact of a vacuum interrupter. In vacuum interrupters, the most expensive material is usually the contact material used for the contact layer of the switching contacts, which is also simply referred to as "contact material": mixtures of copper and chromium (CuCr), tungsten carbide and silver (WC-Ag) or tungsten and copper (WCu) are often used. Contact plates are usually manufactured from these composite materials using sintering or melting techniques as separate components. These contact plates are soldered onto the current-carrying contact electrodes of the vacuum interrupter, where they form the contact layer. Since the contact plates are manufactured as separate components, the contact material must have a minimum thickness of a few millimeters. In many applications, particularly with diffuse arcs and few switching cycles, contact erosion is so low that only a smaller thickness of contact material is really required. In these cases, a contact material thickness of less than 1 mm is often sufficient. It therefore makes sense to only apply the contact material to the contact electrodes in the layer thickness actually required. The difficulty, however, lies in applying the contact material in an economical process as a dense, temperature-resistant, crack-free and sufficiently smooth layer and to bond it securely to the substrate, i.e. the contact electrodes. Known processes by which contact materials can be applied as a contact layer directly onto the contact electrodes are powder metallurgical processes, see e . g . EP1844486A1 (ABB Technology AG [CH] ) October 17, 2007, and cold gas spraying, see, for example, W02022/130604A1 (Mitsubishi Electric Corporation [JP] ; Osaka University [JP] ) June 23, 2022. However, both processes are complex and therefore relatively expensive. There is therefore a need for an improved process by which contact materials can be applied as a contact layer directly onto contact electrodes. This object is achieved according to the invention by a method having the features specified in claim 1 and a switching contact having the features specified in claim 9. The method according to the invention is a method for producing a contact layer on a contact electrode of a vacuum interrupter. A vacuum interrupter generally has an evacuated switching chamber enclosed by a housing, in which a stationary switching contact and a switching contact movable in the axial direction are arranged. In a closing process, the movable switching contact can be brought into contact with the stationary switching contact by means of an axial movement and, in an opening process, can be brought into distance from the stationary switching contact by means of an opposite axial movement. The two switching contacts each have a current-carrying contact electrode, on the mutually facing end faces of which a contact layer is arranged, which contact each other when the vacuum interrupter is in the current-conducting state and the two switching contacts are pressed against each other. The material used for the contact electrode is an electrically conductive material, in particular a metallic material such as copper, a copper alloy, or stainless steel. The process is characterized by the fact that a layer of contact layer printing paste, which serves to form the contact layer, is printed onto the end face of the contact electrode using a screen printing process. The term screen printing also refers to stencil printing, i.e. Screen printing is a printing process similar to screen printing, in which a stencil is used without a supporting screen. Screen printing is used to coat the contact electrode with the contact layer printing paste. The desired shape of the contact layer, e.g., a circular area, is reproduced on a screen or stencil, and the contact layer printing paste is then applied to the contact electrode, which serves as the substrate. A multi-layer contact layer can be achieved with repeated printing. The object is also achieved according to the invention by a switching contact of a vacuum interrupter which has a contact layer which was produced by means of a screen printing process. The invention is based on the discovery that screen printing is suitable for producing a contact layer on a contact electrode at high throughput and at low cost. Screen printing technology is highly developed and ideal for parallel production processes. Compared to screen printing, the previously used processes of sintering and cold spraying are considerably more complex, expensive, and slower. Screen printing also offers a great deal of freedom with regard to the size and shape of the contact layer. Screen printing is also significantly more flexible than previously used methods for producing contact layers: it makes it easy to apply multiple layers or gradient layers and to vary the thickness