Method of making tires for vehicle wheels

Abstract

At least one carcass ply ( 3 ) is formed by depositing a strip-like element ( 13 ) comprising longitudinal thread-like elements ( 13 a ) incorporated into a layer of elastomer material ( 13 b ), onto a toroidal support ( 11 ). Deposition of the strip-like element ( 13 ) takes place in alternated deposition sections ( 23, 24 ) each comprising two radially-extending side portions ( 23 a, 24 a, 23 c, 24 c ) and a crown portion ( 23 b, 24 b ) extending at a radially external position. The side portions of each deposition section ( 23, 24 ) are at least partly overlapped with side portions belonging to an adjacent deposition section. Associated with the carcass ply ( 3 ) are annular structures ( 4 ) comprising a circumferentially inextensible annular insert ( 32 ) axially external to an anchoring element ( 31 ). A belt structure ( 5 ), a tread band ( 8 ) and sidewalls ( 9 ) are combined with the thus formed carcass structure ( 2 ) to define a tire ( 1 ) to be submitted to a vulcanization step.

What is claimed is:  
     
         1 . A method of making a tire, comprising the steps of: 
 making a carcass structure ( 2 );    applying a belt structure ( 5 ) to the carcass structure ( 2 ) at a circumferentially external position thereof;    applying a tread band ( 8 ) to the belt structure ( 5 ) at a circumferentially external position thereof;    applying at least one pair of sidewalls ( 9 ) to the carcass structure ( 2 ) at laterally opposite positions;    vulcanizing the obtained tire ( 1 ),    wherein manufacturing of the carcass structure ( 2 ) involves formation of at least one carcass ply ( 3 ) by the following steps: 
 preparing at least one continuous strip-like element ( 13 ) comprising a plurality of longitudinal and parallel thread-like elements ( 13   a ) at least partly coated with at least one layer of raw elastomer material ( 13   b );  
 depositing the strip-like element ( 13 ) onto a toroidal support in alternated deposition sections ( 23 ,  24 ) each extending in a substantially U-shaped conformation about the profile in transverse section of the toroidal support ( 11 ), to define two side portions ( 23   a ,  23   c ,  24   a ,  24   c ) substantially extending in planes orthogonal to a geometric axis of rotation of the toroidal support ( 11 ) at mutually spaced apart positions in an axial direction, and a crown portion ( 23   b ,  24   b ) extending in a radially external position between the side portions ( 23   a ,  23   c ,  24   a ,  24   c );  
 the crown portions ( 23   b ,  24   b ) of each deposition section ( 23 ,  24 ) being disposed consecutively in side by side relationship along the circumferential extension of the toroidal support ( 11 ), whereas the side portions ( 23   a ,  23   c ,  24   a ,  24   c ) of each deposition section ( 23 ,  24 ) are each partly overlapped with a side portion of at least one consecutive deposition section.  
   
     
     
         2 . The method as claimed in    claim 1   , wherein the side portions ( 23   a ,  23   c ,  24   a ,  24   c ) in mutual-overlapping relationship are caused to mutually converge at the geometric axis of rotation of the toroidal support ( 11 ).  
     
     
         3 . The method as claimed in    claim 1   , wherein mutual overlapping of the side portions ( 23   a ,  23   c ,  24   a ,  24   c ) of the deposition sections ( 23 ,  24 ) progressively decreases starting from a maximum value at the radially inner ends of the side portions until a zero value at transition regions between said side portions and crown portions ( 23   b ,  24   b ).  
     
     
         4 . The method as claimed in    claim 1   , wherein the side portions ( 23   a ,  23   c ,  24   a ,  24   c ) in mutual-overlapping relationship are maintained joined to each other at a bending end region ( 25 ) where the strip-like element ( 13 ) is folded upon itself.  
     
     
         5 . The method as claimed in    claim 1   , wherein the individual deposition sections ( 23 ,  24 ) are sequentially laid down onto the toroidal support ( 11 ) according to a circumferential distribution pitch corresponding to the width of the strip-like element ( 13 ).  
     
     
         6 . The method as claimed in    claim 1   , wherein the individual deposition sections ( 23 ,  24 ) are sequentially laid down onto the toroidal support ( 11 ) according to a circumferential distribution pitch corresponding to a multiple of the width of the strip-like element ( 13 ).  
     
     
         7 . The method as claimed in    claim 1   , wherein the strip-like element ( 13 ) has a width corresponding to a submultiple of the circumferential extension of the toroidal support ( 11 ), as measured at its equatorial plane.  
     
     
         8 . The method as claimed in    claim 1   , wherein manufacturing of said at least one carcass ply ( 3 ) further involves a sequential pressing step of the strip-like element ( 13 ) at the side portions ( 23   a ,  23   c ,  24   a ,  24   c ) of the deposition sections ( 23 ,  24 ), to define regions of greater width close to the inner circumferential edges of the carcass structure ( 2 ).  
     
     
         9 . The method as claimed in    claim 8   , wherein the pressing step is carried out on the strip-like element ( 13 ) during the deposition step, by exerting a pressing action of the strip-like element at a section thereof upstream of the toroidal support ( 11 ).  
     
     
         10 . The method as claimed in    claim 8   , wherein concurrently with said pressing step, moving apart from each other of the thread-like elements ( 13   a ) comprised in the strip-like element ( 13 ) is carried out.  
     
     
         11 . The method as claimed in    claim 1   , wherein during the deposition step, at least one deposition section comprising an initial or leading end of the strip-like element is retained on the toroidal support ( 11 ) by a suction action produced through the toroidal support itself.  
     
     
         12 . The method as claimed in    claim 1   , wherein formation of each deposition section ( 23 ,  24 ) involves the steps of: 
 guiding the strip-like element ( 13 ) on a distributor element ( 22 ) movable about the profile in transverse section of the toroidal support ( 11 );    translating the distributor element ( 22 ) substantially radially away from the geometric axis of rotation of the toroidal support ( 11 ) to form a first side portion ( 23   a ,  24   a ) of the deposition section ( 23 ,  24 ) of the strip-like element ( 13 );    rotating the toroidal support ( 11 ) relative to the distributor element ( 22 ) according to an angular pitch corresponding to half the distribution pitch of the deposition sections ( 23 ,  24 ), concurrently with formation of said first side portion ( 23   a ,  24   a );    translating the distributor element ( 11 ) substantially in a direction parallel to the geometric axis of rotation of the toroidal support ( 11 ) to form the crown portion ( 23   b ,  24   b ) of the deposition section ( 23 ,  24 ) of the strip-like element ( 13 );    translating the distributor element ( 22 ) substantially radially close to the geometric axis of rotation of the toroidal support ( 11 ) to form a second side portion ( 23   c ,  24   c ) of the deposition section ( 23 ,  24 ) of the strip-like element ( 13 );    rotating the toroidal support ( 11 ) relative to the distributor element ( 22 ) according to said angular pitch, concurrently with formation of said second side portion ( 23   c ,  24   c ).    
     
     
         13 . The method as claimed in    claim 12   , wherein during formation of the first side portion ( 23   a ,  24   a ) of each deposition section ( 23 ,  24 ) the step of retaining the strip-like element ( 13 ) at a bending region ( 25 ) defined between the first side portion and the second side portion ( 23   a ,  24   a ) of the previously formed deposition section is carried out.  
     
     
         14 . The method as claimed in    claim 13   , wherein retention of the strip-like element ( 13 ) is carried out by disposing a retaining element ( 26 ) alongside the second side portion ( 23   a ,  24   a ) after translation of the distributor element ( 22 ) radially close to the geometric axis of rotation of the toroidal support ( 11 ), so that the strip-like element ( 13 ) is turned back about the retaining element ( 26 ) thereby forming the bending region ( 25 ) as a result of translation of the distributor element ( 22 ) radially away from the geometric axis of rotation of the toroidal support ( 11 ).  
     
     
         15 . The method as claimed in    claim 14   , wherein the retaining element ( 26 ) is axially disengaged from the bending region ( 25 ), after starting of formation of the crown portion ( 23   b ,  24   b ) of the deposition section ( 23 ,  24 ) being made.  
     
     
         16 . The method as claimed in    claim 1   , further comprising a step of pressing said side portions ( 23   a ,  23   c ,  24   a ,  24   c ) of the deposition sections against side walls of the toroidal support ( 11 ).  
     
     
         17 . The method as claimed in    claim 16   , wherein said pressing step is carried out repeatedly on a first and a second side portions ( 23   a ,  24   c ,  23   c ,  24   a ) belonging to two contiguous deposition sections ( 23 ,  24 ).  
     
     
         18 . The method as claimed in    claim 1   , wherein accomplishment of the carcass structure ( 2 ) further comprises the step of applying at least one inextensible annular structure ( 4 ) to an area close to each of the inner circumferential edges of the carcass ply ( 3 ) obtained from the deposition step.  
     
     
         19 . The method as claimed in    claim 18   , wherein accomplishment of the carcass structure ( 2 ) further comprises the step of turning back end flaps of the side portions ( 23   a ,  23   c ,  24   a ,  24   c ) about the respective inextensible annular structures ( 4 ).  
     
     
         20 . The method as claimed in    claim 1   , wherein accomplishment of the carcass structure ( 2 ) further comprises the step of forming a second carcass ply in the same manner as formation of the first carcass ply ( 3 ).  
     
     
         21 . A method of making a tire, comprising the steps of: 
 making a carcass structure ( 2 );    applying a belt structure ( 5 ) to the carcass structure ( 2 ) at a circumferentially external position thereof;    applying a tread band ( 8 ) to the belt structure ( 5 ) at a circumferentially external position thereof;    applying at least one pair of sidewalls ( 9 ) to the carcass structure ( 2 ) at laterally opposite positions;    vulcanizing the obtained tire ( 1 ),    wherein accomplishment of each inextensible annular structure ( 4 ) comprises the steps of: 
 depositing at least one thread-like element in concentric coils ( 32   a ) into a molding cavity ( 34 ) to form a circumferentially inextensible annular insert to be positioned substantially parallelly to adjacent surfaces of the carcass ply ( 3 );  
 positioning an annular anchoring element ( 31 ) into the molding cavity ( 34 ), at a position axially close to the circumferentially inextensible annular insert ( 32 );  
 injecting raw elastomeric material into the molding cavity ( 34 ) to make a filling body ( 33 ) intimately joined to the annular anchoring element ( 31 ) and the circumferentially inextensible annular insert ( 32 ).  
   
     
     
         22 . The method as claimed in    claim 21   , wherein said deposition step is preceded by a rubberizing step in which said thread-like element is coated with at least one layer of raw elastomer material.  
     
     
         23 . The method as claimed in    claim 21   , further comprising the step of magnetically retaining the circumferentially inextensible annular insert ( 32 ), at a predetermined position, within the molding cavity ( 34 ).  
     
     
         24 . The method as claimed in    claim 21   , wherein injection of the raw elastomer material is carried out through at least one circumferential admission hollow space ( 35 ) opening into the molding cavity ( 34 ).  
     
     
         25 . A method of making a tire, comprising the steps of: 
 making a carcass structure ( 2 );    applying a belt structure ( 5 ) to the carcass structure ( 2 ) at a circumferentially external position thereof;    applying a tread band ( 8 ) to the belt structure ( 5 ) at a circumferentially external position thereof;    applying at least one pair of sidewalls ( 9 ) to the carcass structure ( 2 ) at laterally opposite positions;    vulcanizing the obtained tire ( 1 ),    wherein application of the belt structure ( 5 ) comprises the steps of: 
 forming at least one continuous belt ribbon ( 36 ) comprising at least one layer of raw elastomer material ( 36   b ) at least partly incorporating a plurality of longitudinal parallel cords ( 36   a );  
 cutting said continuous belt ribbon ( 36 ) according to a predetermined inclination relative to its longitudinal extension to form belt lengths ( 42 ) having a predetermined size in width, measured perpendicularly to the cutting direction;  
 laying down the belt lengths ( 41 ) consecutively in circumferential alignment onto the carcass structure ( 2 ) to form at least one first continuous belt strip ( 6 ) having said cords ( 36   a ) disposed transversely according to an inclination corresponding to the cutting inclination of said lengths ( 42 ).  
   
     
     
         26 . The method as claimed in    claim 25   , wherein before said cutting step, the continuous belt ribbon ( 36 ) is submitted to a calendering step to give said lengths a circumferential size corresponding to a submultiple of the circumferential extension of the belt strip ( 6 ).  
     
     
         27 . The method as claimed in    claim 25   , wherein application of the belt structure ( 5 ) further comprises the step of forming at least one second belt strip ( 7 ) by winding of at least one continuous thread-like element ( 44 ) in coils disposed axially in side by side relationship and extending circumferentially about the first belt strip ( 6 ).  
     
     
         28 . The method as claimed in    claim 27   , wherein the winding coils formed by the elongated element ( 44 ) are disposed mutually in side by side relationship according to a variable axial-distribution pitch.  
     
     
         29 . The method as claimed in    claim 28   , wherein said axial-distribution pitch is greater close to the equatorial median plane (X-X) of the tire ( 1 ) relative to the opposite side edges of the belt structure ( 5 ).  
     
     
         30 . The method as claimed in    claim 1   , wherein application of the tread band ( 8 ) comprises the step of circumferentially winding at least one continuous sheet of raw elastomer material ( 49 ) about the belt structure ( 5 ) in a plurality of radially superposed coils (S).  
     
     
         31 . The method as claimed in    claim 30   , wherein the continuous sheet of elastomer material ( 49 ) is produced directly during its application to the belt structure ( 5 ).  
     
     
         32 . The method as claimed in    claim 30   , further comprising the step of progressively reducing the width of the elastomer material sheet ( 49 ), concurrently with formation of each winding coil (S) about the belt structure ( 5 ).  
     
     
         33 . The method as claimed in    claim 1   , wherein each of said sidewalls ( 9 ) is made by injection of elastomer material into a mold ( 53 ).  
     
     
         34 . The method as claimed in    claim 33   , wherein accomplishment of each of said sidewalls ( 9 ) comprises the following steps: 
 injecting a first elastomer material into a first cavity defined in said mold ( 53 ) to form a radially outer portion ( 9   a ) of the sidewall ( 9 );    defining a-second cavity in the mold ( 53 ), which is partly delimited by the radially outer portion ( 9   a ) of the sidewall ( 9 );    injecting a second elastomer material into the second cavity of the mold ( 53 ) to define a radially inner portion ( 9   b ) of the sidewall ( 9 ).    
     
     
         35 . The method as claimed in    claim 1   , wherein formation of the carcass ply ( 3 ) is preceded by a step of coating the toroidal support ( 11 ) with at least one air-proof layer or liner ( 10 ) of elastomer material.  
     
     
         36 . The method as claimed in    claim 35   , wherein said coating step is carried out by winding at least one ribbon-like band ( 12 ) of an air-proof elastomer material in coils disposed in side-by-side relationship along the profile in transverse section of the toroidal support ( 11 ).  
     
     
         37 . The method as claimed in    claim 1   , wherein before the vulcanization step the following steps are carried out: 
 disengaging the tire ( 1 ) from the toroidal support ( 11 );    inserting an air tube into the carcass structure ( 2 ).    
     
     
         38 . The method as claimed in    claim 1   , wherein during said vulcanization step, a step of stretching said carcass plies ( 3 ) and belt strips ( 6 ,  7 ) is carried out for achieving an expansion of the tire of a linear amount included between 2% and 5%.