Abstract:
A precured tire tread for use in retreading tires contoured to have a flat road-contacting tread surface when applied to the casing.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to the field of pneumatic tires and more specifically to precured treads used in retreading. 
     2. Description of the Prior Art 
     When retreading a tire, the old tire casing is buffed to remove remnants of the old tread and to remove dirt and other contamination to leave a clean surface to receive the new tread. The buffing generally leaves the casing with a curved profile on which the new tread is bound. In the prior art, the precured tread, and particularly the road-contacting surface thereof, when applied to the tire casing, assumes a curved profile similar to that of the underlying tire casing. In a tire having this profile, the center of the tread tends to wear out more quickly than the edges thereof. This is because the curved profile, in which the center is forced radially outwardly, results in the maximum tire force, and hence the maximum wear, being concentrated near the center, rather than across the entire tread face. A lessened force at the edges of the tread also results in the tire having a lower cornering ability than would be the case if the force were uniform across the tread face. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide a new and improved precured tire tread for use in retreading used tires having a road-contacting surface with a preselected profile. 
     It is yet another object of the invention to provide a tire tread profiled so that the tread, when situated on a curved buffed tire casing, has a flat road-contacting surface. 
     In brief, the invention provides a precured tire tread for use in retreading molded to have a concave tread surface and a flat rear surface, the rear surface adapted to be bound to the buffed tire casing. The contour of the road contact surface and the rear surface is such that when the tread is applied to the casing, the road-contact surface is flat to the road. In a modification, the tread is molded having a flat tread surface and a rear surface concave to conform to the casing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The aforementioned objects and features of the hereindisclosed invention, as well as other objects and advantages thereof, will be better understood upon consideration of the following detailed description when read in conjunction with the drawings, in which: 
     FIG. 1 is a perspective view of the new tread; 
     FIG. 2 is a cross-section taken along lines II--II in FIG. 1; 
     FIG. 3 is a cross-section of the tread applied to a tire casing; and 
     FIG. 4 is a cross-section of a modification of the embodiment shown in FIG. 1. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to the drawings, the invention provides an elongated precured tire tread 10 having a flat bonding surface 11, two side surfaces 12 and a concave contoured road contacting surface 13. Tread 10 further includes two butt ends 14, which may be skived so as to overlap when applied to the tire casing. 
     Road-contacting surface 13 includes a selected tread pattern formed in the face thereof. The concave contour of surface 13 is selected so that when tread 10 is attached to a tire casing as described hereinbelow, surface 13 will be flat. 
     With reference to FIG. 3, a cross-section of a tire casing 15 is shown with a tread 10, according to the invention, bonded thereto. The tire casing 15 may include a plurality of beads 16, and may have several plies and belts (not shown). In preparing to receive a new tread, casing 15 was buffed to a preselected profile. The tread 10 was then wrapped circumferentially around the casing with bonding surface 11 proximate thereto. The edges of side surfaces 12 are then drawn back around the casing so that surface 11 conforms to the rounded surface thereof. This draws the edges of road-contacting surface 13 back so that it is flat. Thus, when the tire is placed on the road, surface 13 will be flat against the road, and the road-contacting surface 13 will grip the tire uniformly across the face thereof. 
     Since the tread 10 is cured prior to its being applied to the tire casing 15, tread 10 will resist being curved around casing 15, which will tend to force the tread to attempt to flex back to its original concave configuration. This causes the edges of road-contacting surface 13 to be forced radially outwardly and the center therebetween to be forced inwardly. This results in the edges of the tread more firmly gripping the road than would otherwise be the case. 
     With reference to FIG. 4, a modification of the new tread provides a tread 17 having a flat road-contacting surface 18 and a concave rear bonding surface 19. Tread 17 is applied to a tire casing in the same manner as set forth with reference to FIG. 3. Rear surface 19 is profiled to conform to the casing without the necessity of drawing back the edges of the tread 17. Contacting surface 18 therefore retains its flat profile across the width thereof. 
     It will thus be seen that the objects set forth above, along with those made apparent from the preceding description, are efficiently attained. The invention provides a precured tire tread having a substantially flat road-contacting surface when attached to a tire and a uniform tire contact force across the entire face of the road-contacting surface. Since certain changes may be made in carrying out the invention without departing from the scope thereof, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.