Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H11/00—Apparatus or processes specially adapted for the manufacture of electric switches
  • H01H11/04—Apparatus or processes specially adapted for the manufacture of electric switches of switch contacts

Definitions

• the invention is based on a method with the features specified in the preamble of claim 1. Such a method is known from EP-A-0 062 243.
• a method for producing contact pieces from strip material in which the contacting material lies between two layers of a further material with which they are inserted into a recess of a contact carrier. In this process, the contact pieces are finally formed by a two-stage pressing process.
• Contact rivets are required on a large scale, for example in automotive engineering, for riveting onto contact carriers, which switch in air and offer sufficient security against welding. It is an application in which the contact rivets are exposed to direct current. When switching under direct current load, material migration takes place from one contact to the opposite contact. The contact rivets should show the lowest possible material migration during switching operations. Under these conditions, contact materials based on silver-tin oxide are often used. Silver-tin oxide offers sufficient security against welding of the contact rivets.
• contact rivets usually takes place by starting with wire sections which are inserted into a molding tool and compressed therein with an enlarged cross-section.
• a wire section made of silver-tin oxide and a wire section made of copper are inserted one after the other into the tool and compressed therein, whereby their mutual abutment surfaces are enlarged and cold-welded to one another or also welded to one another by electric current (spot welding process).
• silver-tin oxide is a relatively less ductile, brittle material compared to copper. Therefore, cracks can form in the silver-tin oxide in the edge region of the rivet head, both on the contacting side and in the connection zone between the silver-tin oxide and the copper, which reduce the service life of the contact rivet. This tendency to crack also limits the options for shaping the rivet. Because the brittleness of silver-tin oxide increases with increasing tin oxide content, the tendency to crack further limits the tin oxide content.
• the object of the invention is to remedy this and to produce contact rivets with a reduced tendency to form cracks.
• the sheath wire is used to form the rivet head, the sheath of which consists of a more ductile metal material than the core of the sheath wire covered by the sheath.
• the brittle contact material is therefore covered both during the forming of the rivet head and in the finished contact rivet by a more ductile contact material than by a sleeve, which counteracts cracking in the brittle contact material. and some cracks in the brittle contact material are still smeared during the forming process.
• the desired advantages occur: longer service life, less testing, fewer restrictions in the shape of the contact rivets and the degree of deformation and finally the possibility of using brittle materials, in particular silver materials with a higher oxide content.
• These advantages are paid for by the fact that the contact rivets on the contacting side have a contact material which is less favorable than the brittle contact material in the center of the rivet head in terms of security against welding of the contact rivets and in terms of material migration during switching operation.
• contact is not regularly made at the edge of the rivet head, but in the center, i.e.
• the material with the favorable switching properties is, so that the advantages of the more ductile contact material in the edge area of the rivet head far outweigh its disadvantages, especially if - as preferred - the rivet head is molded so that its contacting surface is spherical, whereby contact at the edge of the rivet head can be reliably prevented.
• the invention is particularly suitable for the production of contact rivets, the contacting material of which is a material based on silver-tin oxide, which material can contain additional components which are suitable for keeping the contact point temperature low, in particular tungsten oxide, molybdenum oxide, tungsten carbide, molybdenum carbide, Germanium oxide, copper oxide and / or bismuth oxide, individually or in combination.
• silver or a silver alloy in particular silver with up to 20% by weight of nickel or made of silver with up to 30% by weight of copper are particularly suitable as the material for the jacket.
• the invention is also applicable to other contact material combinations of a brittle core material and a more ductile jacket material.
• a base material is suitable as the contacting material, a base contact material, in particular copper, can also be used as the jacket material.
• the core material in addition to a material based on silver-tin oxide, materials made of silver with other oxidic or carbide components, such as cadmium oxide, zinc oxide, lead oxide, indium oxide, bismuth oxide, copper oxide, tungsten oxide, tungsten carbide, molybdenum oxide, molybdenum carbide or the like, are particularly suitable.
• the invention resides in the fact that contact rivets can be made with them, which have silver as the contacting material with a high proportion of 30 to 80% by weight of nickel.
• Contact rivets with a contacting material based on silver with tin oxide can be produced with a higher tin oxide content than was previously the case, in particular with a tin oxide content of 13 to 18% by weight. There is a need for this in the area of the automotive industry that has so far not been satisfied.
• the invention is applicable to contact rivets in which the head and shaft are made of the same material. To produce such contact rivets, individual sheathed wire sections are compressed to form the rivet head.
• the invention is also applicable to bimetal contact rivets. In this case, a base wire section, generally made of copper, and a sheath wire section containing noble metal are successively placed in a mold inserted and welded together with an enlarged cross-section, thereby forming the rivet head.
• a suitable method and a tool with which the method can be carried out are disclosed, for example, in EP-B-0 062 243.
• the invention is also applicable to the production of contact rivets with a base shaft, generally made of copper, and a head containing noble metal at both ends of the shaft.
• a first noble metal-containing sheathed wire section, a base wire section and a second noble metal-containing wire section are arranged one after the other in a tool and welded to one another with an increase in cross-section by upsetting, with a rivet head initially being formed at one end only, the diameter of which is larger than the shank, whereas the second rivet head is formed only when the contact rivet is riveted into a contact carrier.
• a method suitable for producing such contact rivets and an apparatus for use in the methods are disclosed in EP-B-0 062 248.
• a range of 1.2 to 2 is preferred for the ratio of the diameter of the sheathed wire to the diameter of the core, and the diameter ratio and the increase in diameter due to the compression of the wire sections are preferably coordinated with one another in this way that in the finished rivet head the jacket is still between 0.4 mm and 0.8 mm thick.

Landscapes

• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Manufacture Of Switches (AREA)
• Contacts (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=6437900

Family Applications (1)

Country Status (4)

Families Citing this family (3)

Family Cites Families (8)

• 1991
  • 1991-08-08 DE DE4126220A patent/DE4126220A1/de not_active Withdrawn
• 1992
  • 1992-07-31 DE DE59204779T patent/DE59204779D1/de not_active Expired - Fee Related
  • 1992-07-31 WO PCT/EP1992/001739 patent/WO1993003511A1/de active IP Right Grant
  • 1992-07-31 ES ES92917125T patent/ES2085639T3/es not_active Expired - Lifetime
  • 1992-07-31 EP EP92917125A patent/EP0597989B1/de not_active Expired - Lifetime

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