Abstract:
A pneumatic tire is disclosed having circumferential grooves having an asymmetrical cross-sectional shape. The circumferential grooves may also be located asymmetrically on the outer tread surface.

Description:
CROSS REFERENCE TO OTHER APPLICATIONS 
       [0001]    This application claims the benefit of and incorporates by reference U.S. Provisional Application No. 61/317,605 filed Mar. 25, 2010. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention is directed to a pneumatic tire. More specifically, the invention is directed to a tire tread pattern having grooves of a particular configuration. 
       BACKGROUND OF THE INVENTION 
       [0003]    Tires used in industrial settings such as port applications or other industrial applications may often have circumferential grooves. Cracks may develop in the base of the groove due to the heavy loading of the vehicles. It is thus desired to have an improved tread configuration which solves the problem of the groove base cracking. 
       Definitions 
       [0004]    The following definitions are controlling for the disclosed invention. 
         [0005]    “Axial” and “axially” are used herein to refer to lines or directions that are parallel to the axis of rotation of the tire. 
         [0006]    “Circumferential” means lines or directions extending along the perimeter of the surface of the annular tire parallel to the Equatorial Plane (EP) and perpendicular to the axial direction. 
         [0007]    “Equatorial plane (EP)” means the plane perpendicular to the tire&#39;s axis of rotation and passing through the center of its tread. 
         [0008]    “Groove” means an elongated void area in a tread that may extend circumferentially or laterally about the tread in a straight curved, or zigzag manner. Circumferentially and laterally extending grooves sometimes have common portions and may be sub classified as “wide,” “narrow,” or “slot.” A “slot” is a groove having a width in the range from about 0.2% to 0.8% of the compensated tread width, whereas a “narrow groove” has a width in the range from about 0.8% to 3% of the compensated tread width and a “wide groove” has a width greater than 3% thereof. The “groove width” is equal to tread surface area occupied by a groove or groove portion, the width of which is in question, divided by the length of such groove or groove portion; thus, the groove width is its average width over its length. 
         [0009]    “Lateral” means an axial direction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The invention will be described by way of example and with reference to the accompanying drawings in which: 
           [0011]      FIG. 1  is a perspective view of a tire tread of the present invention; 
           [0012]      FIG. 2  is a front view of a tire tread of  FIG. 1 ; 
           [0013]      FIG. 3  is a cross-sectional view of the tire of  FIG. 1 ; 
           [0014]      FIG. 4  is a closeup cross-sectional view of a groove of  FIG. 3 ; and 
           [0015]      FIG. 5  is a cross sectional view of a second embodiment of a tire of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    The following language is of the best presently contemplated mode or modes of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. The reference numerals as depicted in the drawings are the same as those referred to in the specification. For purposes of this application, the various embodiments illustrated in the figures may use the same reference numeral for similar components. The structures employed basically the same components with variations in location or quantity thereby giving rise to the alternative constructions in which the inventive concept can be practiced. 
         [0017]      FIG. 1  is a tire tread  10  for a pneumatic tire  20  of the present invention. The tread configuration has at least one circumferential groove  30 , and preferably has at least two circumferential grooves. The circumferential groove  30  is preferably continuous along the outer surface of the tread. The tread configuration preferably has no lateral grooves. The circumferential groove may be located on the centerline of the tire, or in close proximity to the centerline of the tire. The circumferential groove is preferably located in an asymmetric location on the outer tread surface (i.e., not centered on the midcircumferential plane).  FIG. 5  illustrates one example of an asymmetric location for circumferential groove  30 . In other words, the groove is not placed on the centerline of the tire. If two grooves  30 ,  40  are used, one groove  30  is preferably located closer to the midcircumferential plane than the other groove. More preferably, the groove orientation  40  is the mirror image of the groove  30 . 
         [0018]    The cross-sectional shape of the groove  30  is shown in  FIG. 4 . The groove  30  has opposing groove walls  32 ,  34  which are non-parallel and are planar. The first groove wall  32  is inclined at an angle β of about 3 to about 8 degrees relative to a line perpendicular to a tangent to the tread surface, and more preferably in the range of about 4 to about 6 degrees, and most preferably about 4 to about 5 degrees. The second groove wall  34  is inclined at an angle α in the range of about 4 to about 7 degrees wherein the angle α is inclined relative to a line perpendicular to a tangent to the tread surface. Preferably α is greater than β. It is also preferred that α have a different angular value than β so that they are not equal. The second groove wall  34  extends into the tread a depth h, wherein h is about ⅓ to about ½ of the total groove depth H. The first groove wall  32  extends substantially the total depth of the groove H. 
         [0019]    The groove wall  34  is joined with a middle portion  36  that has a large radius of curvature in the range of about 8 to about 15 inches, more preferably about 10 inches. Alternatively the middle portion  36  may also be planar and be inclined at an angle γ relative to a line perpendicular to a tangent to the tread surface in the range of about 18-22 degrees. The middle wall portion  36  is joined to the first groove wall via a large radiused groove bottom  39 . The groove bottom is defined by a radius of curvature R of in the range of about 8 inches to about 15 inches, and more preferably about 10 inches.