Straight steel monofilament for a belt ply

Abstract

A straight steel monofilament ( 10, 42 ) for the reinforcement of belt ply ( 40 ) of a pneumatic tyre wherein the straightness is determined by the arc-height of the straight steel monofilament ( 10, 42 ). The steel monofilament ( 10, 42 ) is plastically deformed by a twisting action along the axis of the steel monofilament ( 10 ) on a double-twist apparatus ( 2 ). The plastic twist deformation eliminates the surface stress difference on the steel monofilament ( 10, 42 ) and provides a straight steel monofilament ( 10, 42 ) having an arc-height of less than 30 mm By these means a simple solution is provided to manufacture a straight steel monofilament ( 10, 42 ) suitable for tire reinforcement with high speed for mass production by using a known apparatus ( 2 ).

1 - 17 . (canceled) 
     
     
         18 . A straight steel monofilament for the reinforcement of belt ply of a pneumatic tire, wherein the arc-height of the straight steel monofilament is less than 30 mm. 
     
     
         19 . A straight steel monofilament as claimed in  claim 18 , wherein the arc-height of the straight steel monofilament is less than 20 mm. 
     
     
         20 . A straight steel monofilament as claimed in  claim 18 , wherein the median of arc-height of the straight steel monofilament is less than 20 mm. 
     
     
         21 . A straight steel monofilament as claimed in  claim 20 , wherein the median of arc-height of the straight steel monofilament is less than 10 mm. 
     
     
         22 . A straight steel monofilament as claimed in  claim 18 , wherein the standard deviation of arc-height of the straight steel monofilament is less than 3 mm. 
     
     
         23 . A straight steel monofilament as claimed in  claim 22 , wherein the strand deviation of arc-height of the straight steel monofilament is less than 2 mm. 
     
     
         24 . A straight steel monofilament as claimed in  claim 18 , wherein the steel monofilament has been plastically twisted around its own axis so that a surface twist angle is created, the surface twist angle of said straight steel monofilament ranging between 0.5 and 15 degree. 
     
     
         25 . A straight steel monofilament as claimed in  claim 24 , wherein the surface twist angle of said straight steel monofilament is between 1 and 5 degree. 
     
     
         26 . A belt ply of a pneumatic tire, wherein the belt ply is reinforced by plurality of parallel straight steel monofilaments as  claim 18 . 
     
     
         27 . A belt ply of a pneumatic tire according to  claim 26 , wherein said plurality of parallel straight steel monofilaments are twisted in same direction, and are embedded in the belt ply. 
     
     
         28 . A belt ply as claimed in  claim 26 , wherein said plurality of parallel straight steel monofilaments are twisted in different directions, and are alternatively embedded in the belt ply so that an S-twisted monofilament alternates with a Z-twisted monofilament and vice versa. 
     
     
         29 . A belt ply as claimed in  claim 26 , wherein said plurality of parallel straight steel monofilaments are twisted in different directions, monofilaments twisted in S forming first groups and monofilaments twisted in Z forming second groups, a first group alternating with a second group and vice versa. 
     
     
         30 . A belt ply as claimed in  claim 26 , wherein said plurality of parallel straight steel monofilaments are twisted in different directions and are forming groups, each group comprising monofilaments twisted in different direction. 
     
     
         31 . A pneumatic tire, wherein the pneumatic tire comprises at least one belt ply as in  claim 26 . 
     
     
         32 . A process to manufacture straight steel monofilament, wherein the steel monofilament is plastically deformed by a twist along the axis of the steel monofilament. 
     
     
         33 . A process as claimed in  claim 32 , wherein ratio R between the twist pitch and the diameter of the steel monofilament is between 7 and 240. 
     
     
         34 . A process as claimed in  claim 33 , wherein ratio R between the twist pitch and the diameter of the steel monofilament is between 20 and 120. 
     
     
         35 . A pneumatic tire, wherein the pneumatic tire comprises at least one belt ply as in  claim 27 . 
     
     
         36 . A pneumatic tire, wherein the pneumatic tire comprises at least one belt ply as in  claim 28 . 
     
     
         37 . A pneumatic tire, wherein the pneumatic tire comprises at least one belt ply as in  claim 29 .