Timepiece shaft

Abstract

A timepiece shaft ( 1 ), especially a balance shaft ( 1 ), comprising a first functional portion ( 2 a; 2 b ) including at least one part ( 221 a, 221 b ) of a pivot-shank ( 22 a; 22 b ) and/or at least one part ( 211 a, 211 b ) of a pivot ( 21 a, 21 b ), the first functional portion being made of ceramic and a first outer diameter (D 1 ) of the first functional portion being less than 0.5 mm, or less than 0.4 mm, or less than 0.2 mm, or less than 0.1 mm

1 . A timepiece shaft comprising:
 a first functional portion including at least one of (i) at least one part of a pivot-shank and (ii) at least one part of a pivot,   the first functional portion being made entirely of ceramic and a first outer diameter of the first functional portion being less than 0.5 mm.   
     
     
         2 . The shaft as claimed in  claim 1 , wherein the ceramic is for the most part composed of:
 zirconium oxide, or   alumina, or   a combination of these two oxides.   
     
     
         3 . The shaft as claimed in  claim 1 , wherein the ceramic is for the most part composed of silicon nitride. 
     
     
         4 . The shaft as claimed in  claim 1 , wherein the first portion has a surface of revolution. 
     
     
         5 . The shaft as claimed in  claim 1 , wherein the shaft or the first functional portion has a convex or concave or conical or truncated conical end. 
     
     
         6 . The shaft as claimed in  claim 1 , which comprises a second functional portion. 
     
     
         7 . The shaft as claimed in  claim 7 , wherein the second functional portion has a second outer diameter less than 2 mm. 
     
     
         8 . The shaft as claimed in  claim 7 , wherein the ratio of the dimension of the first diameter to the dimension of the second diameter is less than 0.9. 
     
     
         9 . The shaft as claimed in  claim 1 , wherein the shaft is made entirely of ceramic. 
     
     
         10 . An assembly comprising a shaft as claimed in  claim 1  and at least one guide, the shaft being designed to perform at least one of the following:
 rotate or pivot in the at least one guide; and 
 move in translation in the at least one guide. 
 
     
     
         11 . The assembly as claimed in  claim 10 , wherein the at least one guide comprises a bearing stone and an endstone, the stones cooperating with the pivot or pivot-shank to guide the shaft in the guide. 
     
     
         12 . The assembly as claimed in  claim 10 , wherein the at least one guide comprises a ball race way and balls, the balls cooperating by contact with the pivot to guide the shaft in the guide. 
     
     
         13 . An oscillator of the sprung balance type comprising an assembly as claimed in  claim 10 . 
     
     
         14 . A watch movement comprising an oscillator as claimed in  claim 13 . 
     
     
         15 . A timepiece comprising a watch movement as claimed in  claim 14 . 
     
     
         16 . The timepiece shaft as claimed in  claim 1 , which is a balance shaft. 
     
     
         17 . The timepiece shaft as claimed in  claim 1 , wherein the first outer diameter of the first functional portion is less than 0.4 mm. 
     
     
         18 . The timepiece shaft as claimed in  claim 1 , wherein the first outer diameter of the first functional portion is less than 0.2 mm. 
     
     
         19 . The timepiece shaft as claimed in  claim 1 , wherein the first outer diameter of the first functional portion is less than 0.1 mm. 
     
     
         20 . The shaft as claimed in  claim 2 , wherein the ceramic comprises one or more elements selected from the group consisting of:
 carbon nanotubes,   graphene,   fullerenes,   yttrium oxide,   cerium oxide,   zirconium carbide,   silicon carbide,   titanium carbide,   zirconium boride,   boron nitride,   titanium nitride, and   silicon nitride.   
     
     
         21 . The shaft as claimed in  claim 3 , wherein the ceramic comprises one or more elements selected from the group consisting of:
 carbon nanotubes,   graphene,   fullerenes,   zirconium oxide,   aluminum oxide,   yttrium oxide,   cerium oxide,   zirconium carbide,   silicon carbide,   titanium carbide,   zirconium boride,   boron nitride, and   titanium nitride.   
     
     
         22 . The shaft as claimed in  claim 4 , wherein the surface of revolution is selected from the group consisting of a cylindrical surface, a conical surface, a truncated conical surface, and a curve generating surface. 
     
     
         23 . The shaft as claimed in  claim 6 , wherein the second functional portion is selected from the group consisting of:
 a second functional portion adapted for receiving a timepiece component,   a second pivoting portion adapted for a timepiece component on the shaft, and   a second intermeshing portion.