Endless yarn tensioning strip and method for producing the same

Abstract

An endless yarn braking strip for a yarn tensioning device consists of precipitation hardened stainless steel (S). The endless yarn braking strip is produced by first manufacturing an endless blank from a sheet of precipitation hardening steel, shaping the blank into a truncated cone in its endless form, and then hardening the strip by precipitation hardening.

1 . Endless braking strip (B) for a yarn brake, the braking strip having the shape of a frustocone coat produced by cold deformation of a flat blank (Z) made from thin metal sheet (M), characterised in that the braking strip (B) consists of precipitation hardened stainless steel (S) of the class “Precipitation Hardening Stainless Steel” containing chromium and nickel as main alloy ingredients.  
     
     
         2 . Method for manufacturing an endless braking strip for a yarn brake according to  claim 1 , wherein the method comprises the following sequential method steps, 
 cutting the endless flat blank (Z) from the sheet metal (M),    cold forming of the blank (Z) into the shape of a frustocone,    precipitation hardening of the frustoconical blank (Z 1 ).    
     
     
         3 . Method as in  claim 2 , characterised by 
 stamping the blank (Z),    deep drawing the stamped blank (Z) into the frustoconical shape, and    precipitation hardening of the deep drawn blank (Z 1 ) an in an austenite conditioning step (I), a subsequent austenite-martensite-transforming step (II) and a final precipitation hardening step (III) .    
     
     
         4 . Method as in  claim 2 , characterised by heating the deep drawn blank (Z 1 ) to slightly below 1000° C., preferably to 955° C., and maintaining this temperature for about ten minutes, and cooling down in ambient air to ambient temperature (RT) during the austenite conditioning step (I), 
 cooling the blank (Z 1 ) subsequently within one hour to about −73° C., maintaining this cooling temperature over about eight hours during the austenite-martensite-transforming step (II),  
 and warming in ambient air to ambient temperature,  
 and heating the blank to somewhat above 500° C., preferably 510° C., maintaining this temperature over about ninety minutes, and cooling down in ambient air to ambient temperature (RT) during the precipitation hardening step (III).  
 
     
     
         5 . Method as in  claim 2 , characterised by 
 stamping the blank (Z) as a flat annulus with over dimensions in radial direction and cutting the blank in radial direction to the target dimensions (di, da) first after the deep drawing and prior to the precipitation hardening process.    
     
     
         6 . Method as in  claim 2 , characterised by stamping the blank (Z) as a flat annulus with over dimensions in radial direction and cutting the blank in radial direction to the target dimensions (di, da) first after the precipitation hardening step.  
     
     
         7 . Method as in  claim 2 , characterised by deep drawing the blank into a uniform wall thickness within a range (y) between 0.01 mm and 0.5 mm, preferably between 0.05 mm and 0.3 mm.  
     
     
         8 . Method as in at least one of  claims 2  to  7 , characterised by annealing the sheet metal (M) prior to stamping the blank (Z).