Pneumatic radial tire and method for manufacturing same

Abstract

A pneumatic radial tire and a method for manufacturing the same, a device for forming a band of radial tire, and a method of and device for forming a belt-band-tread rubber assembly. The pneumatic tire including a belt arranged on the radially outer side or a carcass, and a band arranged on the radially outer side of the belt and composed of continuous one to several organic fiber cords wound spirally and approximately parallel to the circumferential direction of the tire. The radial tire manufacturing method including the steps of laminating the predetermined number of belt plies on a belt drum or belt ring for forming a belt, and winding one to several organic fiber cords continuously and spirally in the cicumferential direction of the belt on the outer surface of the formed belt in order to form a band. The band forming device including a means for drawing out a cord to be wound, a means for traversing the letting-off means in the widthwise direction of the belt, and a means for controlling the traverse of the letting-off means. The method of forming belt-band-tread rubber assemblies comprising a step of expanding the diameter of belt drum so that the shape in axial section of belt drum becomes the same or approximately the same as the finished shape of the band in vulcanization mold. The assembly forming device including a diameter-variable belt drum comprising a stretchable forming annular body made of an elastomer, and a means for expanding and contracting the diameter of the annular body, wherein the shape in axial section of the circumferential surface of the annular body in the diameter.

1 . A pneumatic radial tire comprising: 
 a pair of bead cores disposed at bead portions of the tire;    a carcass having at least one ply of radially arranged cords turned up around said bead cores;    a tread portion over said carcass;    a belt arranged on the radially outer side of said carcass and having at least two plies of metallic cords arranged at an angle of 10 to 30 degrees to the circumferential direction or the tire; and    a band located on the radially outer side of said belt, wherein    said band is composed of continuous one to several organic fiber cords spirally wound approximately parallel to the circumferential direction of the tire.    
     
     
         2 . The tire as set forth in    claim 1   , wherein said band comprises a full band layer extending over the entire width of said belt and a pair of edge band layers arranged near the both edge portions of said belt, and 
 the width of each of the edge band layers in the axial direction of the tire is within a range of 20 to 30% of the width of said full band layer in the axial direction of the tire.    
     
     
         3 . The tire as set forth in    claim 1   , wherein said band comprises a full band layer extending over the entire width of said belt, and 
 the elongation at given load of the organic fiber cord of said full band layer decreases from the crown portion of the tire toward the shoulder portions.    
     
     
         4 . The tire as set forth in    claim 1   , wherein said band has a spiral structure symmetric with regard to the tire equatorial plane.  
     
     
         5 . The tire as set forth in    claim 1   , wherein the pitch of said organic fiber cord in the axial direction of the tire is from 0.5 to 5.0 mm at the circumferential surface of said belt at the shoulder portions and from 0.5 to 15.0 mm at the center portion of said belt.  
     
     
         6 . The tire as set forth in    claim 1   , wherein a plurality of organic fiber cords of said band are embedded in a rubber and formed into a tape shape.  
     
     
         7 . The tire as set forth in    claim 1   , wherein said band is folded back at both edges.  
     
     
         8 . The tire as set forth in    claim 1   , wherein in the final finished shape of said band in a vulcanization mold, the difference in stretch between the center portion and the shoulder portion is from 0% to 2%.  
     
     
         9 . A method for manufacturing radial tires comprising steps of: 
 deforming a cylindrical tire carcass into a toroidal shape; and    adhering a belt and a tread onto its outer surface, characterized in that said method comprises steps of:    laminating the predetermined number of belt plies on a belt ring or a belt drum to form said belt; and    winding one to several organic fiber cords on the outer surface of said formed belt continuously and spirally in the circumferential direction of the belt to form a band for reinforcing said belt.    
     
     
         10 . The method as set forth in    claim 9   , wherein the organic cords of said band ply are coated with a rubber.  
     
     
         11 . The method as set forth in    claim 10   , wherein the thickness of the rubber coating is 0.1 to 0.2 mm; and 
 the pitch of adjacent organic fiber cords in the axial direction of the tire is substantially equal to the sum of twice said thickness and the diameter of said organic fiber cord.    
     
     
         12 . The method as set forth in    claim 9   , wherein said organic fiber cord is not coated with a rubber, and said step of winding the cord comprises steps of: 
 winding a wide rubber sheet on the outer surface of said belt in advance of winding the cords; and    further winding a wide rubber sheet on the wound cords.    
     
     
         13 . The method as set forth in    claim 9   , wherein the tension applied to said organic fiber cord when winding the cord is changed so as to be minimum at the crown portion of the tire and maximum at the shoulder portions of the tire.  
     
     
         14 . The method as set forth in    claim 9   , wherein the tension applied to said organic cord when winding the cord is constant; and 
 the diameter of the cord in the wound state gradually decreases from the crown portion toward the shoulder portions of the tire.    
     
     
         15 . The method as set forth in    claim 9   , wherein the pitch in the tire axial direction of said organic fiber cord is from 0.5 to 5.0 mm at the circumferential surface of the shoulder portion of said belt.  
     
     
         16 . The method as set forth in    claim 8   , wherein the pitch in the tire axial direction of said organic cord is from 0.5 to 15.0 mm at the middle portion of said belt.  
     
     
         17 . A band forming device to form a band by winding one to several organic fiber cords continuously and spirally on the circumferential surface of a belt formed on a belt drum or a belt ring in the production of radial tires by deforming a cylindrical tire carcass into a toroidal shape and adhering a belt and a troad onto its circumferential surface, which comprises: 
 a let-off means for drawing out the cord to be wound toward the belt side;    a traverse means for traversing the let-off means in the widthwise direction of the belt; and    a traverse controlling means for controlling the traverse of said let-off means.    
     
     
         18 . The device as set forth in    claim 17   , wherein said let-off means comprises: 
 a moving frame capable of traversing;    an arm mounted on the moving frame; and    a plurality of guide pulleys supported by the arm and guiding the cord to be wound.    
     
     
         19 . The device as set forth in    claim 17   , wherein said traverse means comprises: 
 a screw shaft driven to be rotated and screwed with the let-off means; and    a guide shaft for guiding the traverse of the let-off means.    
     
     
         20 . The device as set forth in    claim 19   , wherein said traverse controlling means comprises: 
 a motor for driving said screw shaft;    the drive unit thereof; and    a pulse counter for the belt ring or belt drum.    
     
     
         21 . The device as set forth in    claim 17   , wherein said let-off means includes a tension control means for controlling the winding tension of the cord.  
     
     
         22 . The device as set forth in    claim 21   , wherein said tension control means comprises a brake pulley and its power supply unit.  
     
     
         23 . The device as set forth in    claim 21   , wherein said tension control means is composed of a plurality of guide pulleys threaded with a cord to be wound.  
     
     
         24 . A method of forming an assembly composed of a belt, a band and a tread rubber by using a belt drum capable of changing the diameter, comprising the steps of: 
 forming a cylindrical belt by winding a plurality of belt plies made of an inorganic or organic fiber cord on the circumferential surface of said belt drum whose diameter is not expanded so that the angle of the cord with regard to the circumferential direction is from 10 to 40 degrees;    expanding the belt drum so as to make the sectional shape of said belt drum in the axial direction identical or close to the finishing shape of the band in a mold;    forming a band composed of organic fiber cords arranged at an angle of 0 to 5 degrees with regard to the circumferential direction, on the radially outer outside of said belt on the belt drum which has been expanded into said shape; and    winding a tread rubber on the radially outer side of said and making them into one body.    
     
     
         25 . The method as set forth in    claim 24   , wherein the axial section shape of said belt drum in the diameter expanded state is convex such that the value of the difference between the stretch at the center portion of the band and the stretch at the shoulder portions of the band is from 0 to 2%.  
     
     
         26 . The method as set forth in    claim 24    or    25   , wherein said band forming step comprises a step of winding one to several organic fiber cords on the radiallY outer side of the belt on the belt drum in the diameter-expanded state continuously and spirally at an angle of approximately 0 to 5 degrees with regard to the circumferential direction.  
     
     
         27 . The method as set forth in    claim 25    or    26   , wherein the tension in winding said organic fiber cords is constant both at the center portion and the both edge portions of the belt.  
     
     
         28 . The method as set forth in    claim 25    or    26   , wherein the tension in winding said organic fiber cords is maximum at the both edge portions of the belt and minimum at the center portion of the belt.  
     
     
         29 . The method as set forth in    claim 26    or    28   , wherein the pitch of said organic fiber cords is from 0.5 to 5.0 mm at the both edge portions of the belt.  
     
     
         30 . A method as set forth in    claim 26   , wherein said organic fiber cords are coated with a rubber.  
     
     
         31 . A device of forming an assembly composed of a belt, a band and a tread rubber for radial tires, equipped with a diameter-variable belt drum comprising a forming annular body made of an elastomeric material, which is continuous in the circumferential direction and is stretchable, and a means for expanding and contracting the diameter of the forming annular body, wherein 
 the circumferential surface of the forming annular body in the diameter-nonexpanded state is linear in axial section and forms the surface for winding the belt, and    the circumferential surface of the forming annular body in the diameter-expanded state is in a shape identical or close to the finishing shape of the band in a mold in axial section and forms the surface for winding the band.    
     
     
         32 . The device as set forth in    claim 31   , wherein the shape of said circumferential surface of the forming annular body in the diameter-expanded state is convex such that the difference between the stretch at the center portion and that at the shoulder portions of the band is from 0 to 2%.  
     
     
         33 . The device as set forth in    claim 31   , wherein said expanding and contracting means comprises: 
 a multiplicity of segments which are arranged inside the entire circumference of the forming annular body, and of which sectional shape in the axial direction is convex such that the difference between the stretch at the center portion and that at the shoulder portions of the band on the forming annular body is from 0 to 2%; and    a driving means for making the forming annular body into expanded state or contracted state by advancing or going back said segments synchronously in the radial direction.    
     
     
         34 . The device as set forth in    claim 31   , wherein said expanding and contracting means is a fluid in the forming annular body of which pressure is increased and decreased.  
     
     
         35 . An apparatus for forming a belt-band-tread rubber assembly comprising a diameter-variable belt drum and a band forming device for forming a band by winding one to several organic fiber cords continuously and spirally on the outer surface of a bell formed on said belt drum; 
 said belt drum comprising a forming annular body made of an elastomer which is continuous in the circumferential direction and is stretchable, and a means for expanding and contracting the diameter of the forming annular body, wherein the circumferential surface of the forming annular body in the diameter-non-expanded state is linear in axial section and forms the surface for winding the belt thereon, and the circumferential surface of the forming annular body in the diameter-expanded state is in a shape same or similar to the finished shape of the band in a mold in axial section and forms the surface for winding the band, and    said band forming device comprising a let-off means for drawing out the cord to be wound toward the belt, a traverse means for traversing the let-off means in the widthwise direction of the belt, and a traverse controlling means for controlling the traverse of said let-off means.    
     
     
         36 . The apparatus as set forth in    claim 35   , wherein said let-off means includes a tension control means for controlling the winding tension or the cord.  
     
     
         37 . The apparatus as set forth in    claim 35   , wherein said let-off means is provided with a copying plate, the shape of which is the same as the shape in axial section of the belt drum in the diameter-expanded state.  
     
     
         38 . The method as set forth in    claim 24   , wherein said band forming step includes a step of sequentially winding a plurality of tape-like materials on the radially outer side of the belt on the expanded and deformed belt drum at an angle of about 0 to 5 degrees with regard to the circumferential direction of the drum respectively, where said tape-like material is obtained by: 
 coating a cord fabric of a multiplicity of organic fiber cords with a rubber to form a long sheet;    cutting it to the width to cover the entire width of the belt;    cutting it to the length at least as long as one cycle of the belt plus an overlap joint width; and    dividing it into plural pieces in the widthwise direction.