Ex parte YASUTOSHI AOKI, et al. - Page 5

          Appeal No. 94-3608                                                          
          Application 07/844,980                                                      

               tires tend to wear irregularly and wander.  Narrow-                    
               width grooves can be employed to improve wear and                      
               decrease wandering.                                                    
                    In such a tire, with a tread having a pair of                     
               upper and lower rubber layers with different moduli of                 
               elasticity, deforming stress concentrates in the                       
               boundary surface bordering the two rubber layers when                  
               the tire rolls normally or rides on a curb stone.                      
          The appellants go on to describe their discovery that the                   
          deforming stress which concentrated in the boundary surface                 
          adversely affected the bottom of the fine groove, causing cracks            
          to occur, and that their invention solves this problem by a tire            
          construction having a plurality of features.                                
               The following requirements manifest the appellants'                    
          invention in both of the independent claims:                                
               (1) Upper and lower tread layers having different moduli of            
               300% elasticity at room temperature with the layer located             
               on the tread surface side having a smaller modulus than the            
               other layer.                                                           
               (2) Plural circumferential main grooves on the tread surface           
               side of the tire.                                                      
               (3) A narrow-width fine circumferential groove in the layer            
               on the tread surface side of the tire and having                       
                    (a) a radius of curvature of its bottom of 1.5mm or               
                    less, and                                                         
                    (b) a width in a range of not less than 15% and not               
                    more than 30% of the width of one of the main grooves.            
               (4) The shortest distance between the bottom of the fine               
               groove and a boundary surface bordering between the pair of            
               upper and lower layers being within a range of 1mm and 3mm.            

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