Carbon brush and method and material for the production thereof

Abstract

Carbon brush comprising a base body produced from carbon material by pressing and optionally sintering and a layer of a metallic material applied to an outer surface of the base body by pressing and possibly sintering, the metal layer being connectable to a metallic carrier by welding or soldering.

1 . Carbon brush comprising a base body produced from carbon material and a metal layer which is applied to an outer surface of the base body and can be connected by welding or soldering to a metal carrier, the metal layer being a layer made from metal powder by pressing and optionally sintering and undetachably bonded to the base body by pressing and optionally sintering, 
 characterized in that the metal layer contains a base metal (A) and at least one further metal (B) of higher ductility and lower melting point than the base metal (A), the further metal (B) being present at least predominantly as a metal phase which is separate from the base metal (A) and is intimately bonded to the base metal (A) by pressing and optionally sintering but predominantly does not form an alloy therewith.    
   
   
       2 . Carbon brush according to  claim 1 , characterized in that the further metal (B) is so chosen that at sintering temperature in the liquid phase it wets the base metal (A) but does not diffuse into said base metal, or only slightly.  
   
   
       3 . Carbon brush according to  claim 1 , characterized in that the further metal (B) is composed of tin, indium or bismuth or an alloy thereof.  
   
   
       4 . Carbon brush according to  claim 1 , characterized in that the further metal (B) has a melting point of not more than 400° C. and a breakage elongation of not less than 5%.  
   
   
       5 . Carbon brush according to  claim 1 , characterized in that the further metal (B) is present in a proportion between 1.5 and 15% by weight of the metal layer.  
   
   
       6 . Carbon brush according to  claim 1 , characterized in that the metal layer additionally contains an additive (C) of non-metallic, organic and/or inorganic material.  
   
   
       7 . Carbon brush according to  claim 6 , characterized in that the non-metallic additive (C) contains stearates, graphite, talcum, SiC or Al 2 O 3 .  
   
   
       8 . Carbon brush according to  claim 1 , characterized in that the metal layer thereof is connected to a carrier of metal by welding or soldering.  
   
   
       9 . Carbon brush according to  claim 8 , characterized in that the carrier is a leaf spring.  
   
   
       10 . Material for producing a weldable and/or solderable layer of a carbon brush comprising a powder mixture which contains a pulverulent main metal (A), in particular copper or copper alloy, and a pulverulent additive metal (B) of greater ductility and lower melting point than the main metal, the main metal (A) being copper or a copper alloy and the additive metal (B) being tin, indium or bismuth or an alloy thereof.  
   
   
       11 . Material according to  claim 10 , characterized in that it contains a pulverulent additive (C) of non-metallic, organic and/or inorganic material.  
   
   
       12 . Material according to  claim 10 , characterized in that the additive metal (B) is present in a proportion of 1.5 to 15% by volume of the powder mixture.  
   
   
       13 . Method for producing a carbon brush comprising a base body of carbon material and a metal layer undetachably bonded thereto, comprising the steps: 
 a) producing the base body by pressing and sintering of a pulverulent carbon-containing material;    b) simultaneously with or following step a): producing the metal layer by pressing and sintering a pulverulent metallic material, the metal layer being bonded undetachably to the base body by pressing and sintering;    c) the pulverulent metallic material contains a mixture of a pulverulent base metal A and at least one pulverulent further metal B of greater ductility and lower melting point than the base metal A; and    d) the further metal B and the sintering temperature are so selected that during the sintering the further metal in the liquid phase wets the base metal A but does not, or only slightly, diffuse into the latter, whereby the further metal B is present at least predominantly as a metal phase separate from the base metal A and predominantly not alloyed therewith.    
   
   
       14 . Method according to  claim 13 , characterized in that the main metal A comprises copper or copper alloy and the further metal B comprises tin, indium or bismuth or an alloy thereof.  
   
   
       15 . Carbon brush according to  claim 2 , characterized in that the further metal (B) is composed of tin, indium or bismuth or an alloy thereof.  
   
   
       16 . Carbon brush according to  claim 2 , characterized in that the further metal (B) is present in a proportion between 1.5 and 15% by weight of the metal layer.  
   
   
       17 . Carbon brush according to  claim 3 , characterized in that the further metal (B) is present in a proportion between 1.5 and 15% by weight of the metal layer.  
   
   
       18 . Carbon brush according to  claim 4 , characterized in that the further metal (B) is present in a proportion between 1.5 and 15% by weight of the metal layer.  
   
   
       19 . Carbon brush according to  claim 2 , characterized in that the metal layer additionally contains an additive (C) of non-metallic, organic and/or inorganic material.  
   
   
       20 . Material according to  claim 11 , characterized in that the additive metal (B) is present in a proportion of 1.5 to 15% by volume of the powder mixture.