Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
  • H01H1/00—Contacts
  • H01H1/02—Contacts characterised by the material thereof
  • H01H1/021—Composite material
  • H01H1/023—Composite material having a noble metal as the basic material
  • H01H1/0237—Composite material having a noble metal as the basic material and containing oxides
  • H01H1/02372—Composite material having a noble metal as the basic material and containing oxides containing as major components one or more oxides of the following elements only: Cd, Sn, Zn, In, Bi, Sb or Te
  • H01H1/02376—Composite material having a noble metal as the basic material and containing oxides containing as major components one or more oxides of the following elements only: Cd, Sn, Zn, In, Bi, Sb or Te containing as major component SnO2
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
  • B23K20/22—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating taking account of the properties of the materials to be welded
  • B23K20/233—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating taking account of the properties of the materials to be welded without ferrous layer
• • 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
  • H01H11/041—Apparatus or processes specially adapted for the manufacture of electric switches of switch contacts by bonding of a contact marking face to a contact body portion

Definitions

• the invention is based on a method with the features specified in the preamble of claim 1.
• contact plates for welding onto contact carriers are required on a large scale, which switch in air and offer sufficient security against welding.
• This is an application in which the contact plates are under direct current load.
• material migration takes place from one contact to the opposite contact.
• the contact plates should show the lowest possible material migration in switching operation.
• Contact materials based on silver-tin oxide are frequently used under these boundary conditions. Silver-tin oxide offers sufficient security against
• bimetallic contact plates which have the contact material based on silver-tin oxide on the contacting side and have a silver backing with which they can be welded onto a contact carrier. It is known to produce such contact platelets by first producing a strip-shaped semi-finished product by composite extrusion, starting from a cylindrical block which has a core of powder-metallurgically produced silver-tin oxide and a silver jacket, which on one side consists of Silver-tin oxide and on its other side made of silver (DE-A-34 26 240). Square or rectangular contact plates can be formed from such a band-shaped semi-finished product by cross-cutting.
• indium is a not unproblematic metal with regard to environmental compatibility and that the contact point temperature can become undesirably high.
• indium cannot be dispensed with if the silver-tin oxide material is to be oxidized internally, and oxidic additives which are known to be suitable for reducing the contact temperature, in particular tungsten oxide, molybdenum oxide, copper oxide and bismuth oxide , can be distributed with reasonable effort only in powder-metallurgically produced, but not in silver-tin oxide materials produced by internal oxidation.
• Another disadvantage of the internally oxidized silver-tin oxide-indium oxide contact material is that the distribution of the oxides in the material is not homogeneous; because the internal oxidation is a process that only slowly penetrates into the interior "of the material, the oxide concentration increases with increasing distance from the Ober ⁇ surface of the contact plate from, one that in the middle a poor of oxides zone has that could be avoided only when the internal oxidation of very long If the internally oxidized contact layer gradually burns off during switching operation, the low-oxide zone becomes the contacting surface at some point, which increases the risk that the contacts weld together.
• the use of internally oxidized contact plates on the The basis of silver-tin oxide is therefore not a convincing alternative to contact plates with a contact layer made of powder-metallurgically produced silver-tin oxide material.
• the present invention is based on the object of specifying a more economical method for producing contact plates which have on their front side a powder-metallurgically produced material based on silver-tin oxide and a back made of silver.
• the invention makes use of a method which has hitherto been used to form contact rivets, which are made of precious metal on their contacting side and on the back of the rivet head as well as in its shank from a base metal, generally copper.
• This method is now used according to the invention in order to form, instead of such bimetallic contact rivets, contact platelets which have noble metal both on their contacting side and on their rear side.
• the use of this method must therefore be contradictory to a person skilled in the art who knows that this method has only been invented and has hitherto been used to replace noble metal with base metal.
• the invention leads to extraordinary advantages:
• the platelets are manufactured without waste. This results in a great price advantage over the prior art processes.
• the method can work with powder metallurgically produced material for the contacting layer; Therefore, the silver-tin oxide material can contain oxidic and also carbidic constituents which are particularly suitable for lowering the contact point temperature and improving the switching behavior and the service life, in particular tungsten oxide, molybdenum oxide, tungsten carbide, molybdenum carbide, germanium oxide , Copper oxide and bismuth oxide, individually or in combination.
• oxidic and also carbidic constituents which are particularly suitable for lowering the contact point temperature and improving the switching behavior and the service life, in particular tungsten oxide, molybdenum oxide, tungsten carbide, molybdenum carbide, germanium oxide , Copper oxide and bismuth oxide, individually or in combination.
• silver-nickel alloys are much easier to weld than pure silver.
• the nickel content is expediently at least 10%, but not more than 40%. If the nickel content is too high, the silver-nickel alloy is too difficult to deform.
• the silver contains no more than 30% nickel. The optimal nickel content is 20%. So far, contact plates with a contact layer based on silver-tin oxide with a silver-nickel backing have not been state of the art.
• the contact plates can be used at least until the layer made of the silver-tin oxide material has burned down to the layer below it made of the silver material. If the back of the contact platelets, as preferred according to the invention, consists of a silver-nickel alloy, there is the further advantage that the switching properties of silver-nickel are much better if it becomes a contacting layer after it has burned off than that of pure silver, so that after the contact layer made of the silver-tin oxide material has burned down, the underlying silver-nickel layer still ensures proper emergency switching properties.
• Figure 1 shows the contact plate in a section at right angles to the contacting surface, and in which Figure 2 shows the contact plate in the view of its back.
• the contact plate shown consists of a contact-making layer 1 made of a material based on silver-tin oxide, for example of silver with 12% by weight of tin oxide, and of a back 2 made of silver with 10 to 40% by weight of nickel.
• a short stump 3 which serves as a welding nipple for spot welding, by means of which such a contact plate is welded onto a contact carrier.
• the outer surface of the contact plate is a truncated cone surface, the angle underlying the contact plate is 12 ° to the central axis.
• the starting point is wires with a diameter of 1.5 mm, the silver-nickel wire being 8.9 mm long Section and a 4.7 mm section is separated from the silver-tin oxide wire.
• wire sections are cold-welded to one another by the method described in EP-B-0 062 243, in that they are arranged one behind the other in a die with a bore of 1.5 mm in diameter and between a forward-moving compression needle and a counter-punch, which moves back at 0.465 times the speed of the upsetting needle, is dipped into a bore of 2.2 mm in diameter, their contact surfaces enlarging accordingly and being cold welded to one another.
• an approximately cylindrical bimetallic blank with a diameter of 2.2 mm is produced, which is then placed in a mold, the cavity of which has the shape shown in the drawing with the dimensions given above has been reshaped.
• the contact plate produced in this way has a good and flawless structure for the intended use. There is no waste during its production.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Composite Materials (AREA)
• Materials Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Contacts (AREA)
• Manufacture Of Switches (AREA)

Applications Claiming Priority (2)

Publications (1)

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Cited By (1)

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Citations (2)

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• 1991
  • 1991-08-08 DE DE19914126219 patent/DE4126219A1/de active Granted
• 1992
  • 1992-07-31 WO PCT/EP1992/001740 patent/WO1993003490A1/de active Application Filing

Patent Citations (2)

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