Method and system for producing a precured tread strip

Abstract

A method and system for producing a precured tread strip, whereby a rubber mixture is extruded into a continuous tread strip, from which the precured tread strip is detached; the bottom surface of the precured tread strip is buffed, and the precured tread strip then inserted inside a bag made of material impermeable to air and which is then sealed; and a vacuum is formed inside the bag just before the bag containing the precured tread strip is sealed.

1 ) A method of producing a precured tread strip ( 2 ); the method comprising the steps of: 
 forming a rubber mixture;    extruding the rubber mixture into a continuous tread strip ( 5 );    detaching the precured tread strip ( 2 ) from the continuous tread strip ( 5 ); and    buffing a bottom surface ( 10 ) of the precured tread strip ( 2 );    the method is characterized by comprising the further steps of:    inserting the precured tread strip ( 2 ) inside a bag ( 12 ), made of material impermeable to air, immediately after buffing the bottom surface ( 10 ) of the precured tread strip ( 2 );    forming a vacuum inside the bag ( 12 ) containing the precured tread strip ( 2 ); and    sealing the bag ( 12 ) containing the precured tread strip ( 2 ).    
   
   
       2 ) A method as claimed in  claim 1 , wherein the precured tread strip ( 2 ) is rolled up into a roll ( 14 ).  
   
   
       3 ) A method as claimed in  claim 2 , wherein the roll ( 14 ) is stabilized by applying a belt ( 15 ) about the roll ( 14 ).  
   
   
       4 ) A method as claimed in  claim 2 , wherein the precured tread strip ( 2 ) is rolled up into a roll ( 14 ) after the precured tread strip ( 2 ) is inserted inside the bag ( 12 ).  
   
   
       5 ) A method as claimed in  claim 2 , wherein the precured tread strip ( 2 ) is rolled up into a roll ( 14 ) before the precured tread strip ( 2 ) is inserted inside the bag ( 12 ).  
   
   
       6 ) A method as claimed in  claim 1 , wherein inert gas is fed into the bag ( 12 ) before the vacuum is formed.  
   
   
       7 ) A method as claimed in  claim 6 , wherein the inert gas is nitrogen.  
   
   
       8 ) A method as claimed in  claim 1 , wherein the bag ( 12 ) is made of heat-seal polyethylene.  
   
   
       9 ) A method as claimed in  claim 1 , wherein the step of inserting the precured tread strip ( 2 ) inside the bag ( 12 ) comprises: 
 unwinding a strip ( 16 ) of tubular packing material, impermeable to air, off a reel ( 17 );    inserting the precured tread strip ( 2 ) inside the strip ( 16 ) of tubular packing material;    sealing the bag ( 12 ) along the strip ( 16 ) of tubular packing material by means of two transverse seals on opposite sides of the precured tread strip ( 2 ); and    detaching the bag ( 12 ) from the strip ( 16 ) of packing material.    
   
   
       10 ) A method as claimed in  claim 1 , wherein the step of inserting the precured tread strip ( 2 ) inside the bag ( 12 ) comprises: 
 unwinding a strip ( 16 ) of flat packing material, impermeable to air, off a reel ( 17 );    placing the precured tread strip ( 2 ) on the strip ( 16 ) of packing material;    folding the strip ( 16 ) of packing material into a tube about the precured tread strip ( 2 );    stabilizing the tubular shape of the strip ( 16 ) of packing material by means of a longitudinal seal;    sealing the bag ( 12 ) along the strip ( 16 ) of packing material, folded into a tube about the precured tread strip ( 2 ), by means of two transverse seals on opposite sides of the precured tread strip ( 2 ); and    detaching the bag ( 12 ) from the strip ( 16 ) of packing material.    
   
   
       11 ) A method as claimed in  claim 1 , wherein the precured tread strip ( 2 ) is cured immediately after the precured tread strip ( 2 ) is detached from the continuous tread strip ( 5 ).  
   
   
       12 ) A system ( 1 ) for producing a precured tread strip ( 2 ); the system ( 1 ) comprising: 
 a mixing device ( 3 ) for producing a rubber mixture;    an extruding device ( 4 ) for extruding the rubber mixture into a continuous tread strip ( 5 );    a cutting device ( 6 ) for cutting the precured tread strip ( 2 ) from the continuous tread strip ( 5 ); and    a buffing device ( 9 ) for buffing a bottom surface ( 10 ) of the precured tread strip ( 2 );    the system ( 1 ) is characterized by comprising a packing station ( 11 ) located downstream from the buffing device ( 9 ) and in turn comprising:    an inserting device for inserting the precured tread strip ( 2 ) inside a bag ( 12 ), made of material impermeable to air, immediately after the bottom surface ( 10 ) of the precured tread strip ( 2 ) is buffed;    a suction device for forming a vacuum inside the bag ( 12 ) containing the precured tread strip ( 2 ); and    a sealing device for sealing the bag ( 12 ) containing the precured tread strip ( 2 ).    
   
   
       13 ) A system ( 1 ) as claimed in  claim 12 , wherein a rolling device ( 13 ) rolls the precured tread strip ( 2 ) up into a roll ( 14 ).  
   
   
       14 ) A system ( 1 ) as claimed in  claim 13 , wherein the rolling device ( 13 ) is located upstream from the packing station ( 11 ).  
   
   
       15 ) A system ( 1 ) as claimed in  claim 13 , wherein the rolling device ( 13 ) is located downstream from the packing station ( 11 ).  
   
   
       16 ) A system ( 1 ) as claimed in  claim 12 , wherein, upstream from the suction device, a feed device feeds an inert gas into the bag ( 12 ).  
   
   
       17 ) A system ( 1 ) as claimed in  claim 12 , wherein, upstream from the cutting device ( 6 ), a curing device ( 7 ) cures the continuous tread strip ( 5 ).  
   
   
       18 ) A molded, precured tread strip ( 2 ) for cold retreading a truck tyre; the precured tread strip ( 2 ) is characterized by having no cement, and by being enclosed in a vacuum-sealed bag ( 12 ) of material impermeable to air.