Abstract:
Pneumatic off-road tires having structure for improving sidewall puncture resistance to penetrating objects. The structure may include multiple deflection pads arranged concentrically about the sidewall or a single deflection pad extending in a spiral about the sidewall. Each deflection pad incorporates inclined surfaces arranged for deflecting penetrating objects in a radial direction so that the likelihood of a sidewall puncture is significantly reduced.

Description:
FIELD OF THE INVENTION 
   The present invention generally relates to tires and, more specifically, to pneumatic off-road vehicle tires. 
   BACKGROUND OF THE INVENTION 
   Pneumatic tires for off-road vehicles incorporate a tread designed to provide high traction in non-paved surfaces, such as soft earth or ground, frequently encountered by earthmoving equipment, agricultural vehicles, sport utility vehicles, military vehicles, lawn and garden vehicles, all-terrain vehicles (ATV&#39;s), and dirt bikes. Frequently, pneumatic tires for off-road applications have low operating pressures and minimal belt reinforcements. For example, ATV tires generally operate at a pressure of less than 5 pounds per square inch (psi) and frequently lack any belt reinforcing structure. 
   Pneumatic off-road tires are prone to sidewall punctures resulting in a loss of tire pressure or deflation. Sidewall punctures arise from penetrating or sharp objects such as rocks, thorns, sticks, stubble, or bushes, in the surrounding environment that contact and penetrate the sidewall causing the tire to lose tire pressure either quickly or gradually. The sidewall punctures may be manifested as perforations or slits affording an escape route for the pressurized fluid filling the tire. The occurrence of sidewall punctures is unpredictable and, typically, off-road vehicles carry a repair kit or a spare tire in anticipation of such an event. Repair kits are inconvenient to carry and, although simple perforations can be repaired using the repair kit, large perforations and slits are, at the least, more difficult to repair. In addition, repairs made using the repair kit may be time consuming and, in many conditions such as mud, snow, and uneven rocky terrain, may be challenging to perform. If a spare tire is unavailable or the repair kit is ineffective for repairing the sidewall puncture, the vehicle occupants, such as farmers, hunters, fishing enthusiasts and recreational ATV riders, must travel by foot from a remote location over potentially difficult terrain to obtain assistance. 
   Thickening the sidewall may reduce the likelihood that a sharp object can puncture the sidewall of an off-road tire. Conventional approaches for thickening the sidewall include either adding material in the form of additional plies or an increased rubber thickness. In particular, conventional run-flat or tires have been developed that incorporate relatively thick sidewalls having an increased rigidity capable of carrying the full vehicle load in the absence of inflation pressure. Due to the enhanced sidewall thickness, run-flat tires also provide tremendous puncture resistance. However, such conventional solutions do significantly increase the cost of manufacturing the off-road tire, which is ultimately transferred to the consumer in the retail price. 
   Pneumatic off-road tires may include a single, circumferential scuff rib that projects outwardly from the sidewall. Typically, the scuff rib provides resistance to sidewall scuffing arising from the abrasive effects of recurring contact between the tire sidewall and immovable objects, such as a curb or the like. The scuff rib typically extends from a planar outer surface toward the sidewall at an angle greater than about 45° measured relative to a base surface of the sidewall. However, the scuff rib can only assist in preventing sidewall punctures from sharp objects over the portion of the base surface actually covered by the scuff rib. The scuff rib cannot provide puncture resistance to sharp objects over the exposed base surface of the sidewall, which represents the greater part of the sidewall surface area. 
   For these and other reasons, it would be desirable to provide a pneumatic off-road tire having an improved sidewall puncture resistance while thickness of protective material incorporated into the sidewall. 
   SUMMARY OF THE INVENTION 
   The invention is directed to pneumatic off-road tires that significantly decrease the likelihood of a sidewall puncture. A pneumatic off-road tire constructed according to the principles of the invention includes a carcass having a circumferential sidewall, a tread radially outward of the carcass, and a plurality of axially-projecting deflection pads each of which extends circumferentially about the sidewall. In addition, each of the deflection pads includes a first tapered surface inclined in a first axial direction oriented generally toward the sidewall and a second tapered surface inclined in a second axial direction oriented generally away from the sidewall. 
   In an alternative embodiment of the invention, a pneumatic off-road tire includes a carcass having a circumferential sidewall, a tread radially outward of the carcass, and an axially-projecting deflection pad extending circumferentially about the sidewall in a spiral pattern. The deflection pad includes a first tapered surface inclined in a first axial direction oriented generally toward the sidewall and a second tapered surface inclined in a second axial direction oriented generally away from the sidewall. 
   A pneumatic off-road tire constructed with one or more deflecting pads according to the principles of the invention minimizes tire damage due to sidewall punctures without significantly increasing tire weight or degrading tire performance. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention. 
       FIG. 1  is a side view of an off-road tire according to the principles of the invention. 
       FIG. 2  is a cross-sectional view taken generally along line  2 — 2  in FIG.  1 . 
       FIG. 3  is an enlarged view of a portion of FIG.  2 . 
       FIG. 3A  is a cross-sectional view similar to  FIG. 3  depicting an alternative embodiment of a deflection pad according to the principles of the invention. 
       FIG. 3B  is a cross-sectional view similar to  FIGS. 3 and 4  depicting an alternative embodiment of a deflection pad according to the principles of the invention. 
       FIG. 4  is a perspective view of a portion of the off-road tire of FIG.  1 . 
       FIG. 5  is a side view of an off-road tire according to an alternative embodiment of the invention. 
   

   DEFINITIONS 
   “Axial” and “axially” means the lines or directions that are parallel to the axis of rotation of the tire. 
   “Axially Inward” means in an axial direction toward the equatorial plane. 
   “Axially Outward” means in an axial direction away from the equatorial plane. 
   “Bead” means the circumferentially substantially inextensible metal wire assembly that forms the core of the bead area, and is associated with holding the tire to the rim. 
   “Carcass” means a laminate of tire ply material and other tire components, excluding the tread. 
   “Circumferential” means circular lines or directions extending along the surface of the sidewall perpendicular to the axial direction. 
   “Inner” means toward the inside of the tire. 
   “Lugs” refer to discontinuous radial rows of tread rubber in direct contact with the road surface. 
   “Off-road tire” means a pneumatic tire having a primary use or working surface condition that is not on a paved road. Such tires include earthmover tires, agricultural tires, lawn and garden tires, and all-terrain vehicle tires, including, but not limited to off-road dirt bike tires and ATV tires. 
   “Outer” means toward the tire&#39;s exterior. 
   “Pneumatic tire” means a laminated mechanical device of generally toroidal shape usually an open-torus having beads and a tread and made of rubber, chemicals, fabric and steel or other materials. When mounted on the wheel of a motor vehicle, the tire through its tread provides traction and contains the fluid that sustains the vehicle load. 
   “Radial” and “radially” mean directions radially toward or away from the axis of rotation of the tire. 
   “Shoulder” means the upper portion of sidewall just below the tread edge. 
   “Sidewall” means that portion of a tire between the tread and the bead area. 
   “Tread” means a molded rubber component which, when bonded to a tire casing, includes that portion of the tire that comes into contact with the road when the tire is normally inflated and under normal load. 
   DETAILED DESCRIPTION 
   With reference to  FIGS. 1 ,  2  and  4 , a pneumatic off-road tire  10  according to the invention includes a carcass  12 , a ground-engaging tread  14 , an outer sidewall  16 , and an inner sidewall  18 . Sidewall  16  faces axially outward when tire  10  is mounted to a rim and attached to a wheeled apparatus, such as a motor vehicle. Sidewall  16  is unprotected or unshielded by surrounding structure of the wheeled apparatus and, as a result, is subject to contact by penetrating or sharp objects present in the environment of the wheel apparatus. Sidewall  16  extends from a radially-inward bead  20  to a radially-outward shoulder  22  defined where the sidewall  16  merges with the tread  14 . Tread  14  consists of a pattern of lugs  21  disposed radially outward of the carcass  12 . The lugs  21  may be arranged in any pattern and may have any construction suitable to provide the necessary traction and lateral stability for operation of an off-road vehicle in an off-road environment and to expel earth accumulated in the channels between adjacent lugs  21  laterally of the tire  10 . Carcass  12  and tread  14  have a conventional construction as apparent to persons of ordinary skill in the art, such as the tire construction for an all-terrain vehicle disclosed in U.S. Pat. No. 6,401,774. 
   Positioned on the sidewall  16  radially between bead  20  and shoulder  22  is a plurality of, for example, eight deflection pads  24 . Disposed among the deflection pads  24  is a single curb scuff rib  26  that projects axially outward from the sidewall  16  and that extends about a circumference of the sidewall  16 . The scuff rib  26  has a generally trapezoidal cross-sectional profile viewed in a direction tangent to the circumference of the sidewall  16  at any position about the circumference of tire  10 . The scuff rib  26  typically extends toward the sidewall  16  at an angle greater than about 45° from a radially-outermost planar surface  26   a  toward a base surface  30  (FIG.  3 ). It is contemplated that the scuff rib  26  may be omitted from tire  10  without departing from the spirit and scope of the invention. 
   With continued reference to  FIGS. 1 ,  2  and  4 , the deflection pads  24  are arranged in a substantially concentric pattern centered on a centerline  28  of the tire  10 . Typically, the centerline  28  coincides with an axis of rotation of the tire  10  when mounted to a motor vehicle. Each of the deflection pads  24  is continuous and uninterrupted in a circumferential direction about the sidewall  16 . Discontinuous structures raised axially from the sidewall  16  would result in the transfer of intermittent impulses or jolts to the motor vehicle from objects contacting the sidewall  16  of tire  10 . The number of deflection pads  24  is determined such that sufficient puncture protection from sharp objects is provided over the entire outwardly-facing area of the sidewall  16  as tire  10  rotates. Typically, the number of deflection pads  24  ranges between four and twelve, although the invention is not so limited. 
   With reference to  FIG. 3 , each of the deflection pads  24  projects axially outwardly from sidewall  16  an axial distance from the base surface  30  of the sidewall  16 . Base surface  30  extends radially and circumferentially over portions of the sidewall  16  exposed between adjacent pairs of deflection pads  24  and beneath the deflection pads  24 . Typically, the radial dimension of each of the exposed portions, which are not covered by the deflection pads  24 , is less than or equal to about 0.25 inches (6.4 mm). It is appreciated that the deflection pads  24  may be arranged on sidewall  16  such that the exposed portions are absent. The base surface  30  has a slight convex curvature with a radius of curvature of SW-R between the bead  20  and shoulder  22 , which causes each deflection pad  24  to possess a slight curvature. 
   Each deflection pad  24  includes an opposed pair of radial surfaces or sides  32 ,  34  that are interconnected by an apex or planar surface  36 . The deflection pads  24  operate for deflecting away objects impinging against the sidewall  16 , when in service on a moving motor vehicle, otherwise capable of puncturing the sidewall  16 . Specifically, the deflection pads  24  deflect objects radially, which reduces the axial component of a penetration force applied by the contacting object to sidewall  16 . The deflection pads  24  also increase the effective thickness of covered portions of base surface  30  for enhancing puncture resistance. 
   With continued reference to  FIG. 3 , the opposed radial sides  32 ,  34  of each deflection pad  24  have a dimension or thickness measured axially relative to base surface  30  that varies according to the radial position between the bead  20  and shoulder  22 . Radial side  32  is sloped radially inwardly at an inclination angle, α, measured relative to base surface  30  so that the thickness increases with increasing radius toward shoulder  22 . Radial side  34  is sloped radially outwardly at an inclination angle, β, measured relative to base surface  30 , so that the thickness decreases with increasing radius toward shoulder  22 . The inclination angle of each of the radial sides  32 ,  34  is typically in a range of less than, or equal to, about 30° and, more typically, between about 10° and about 20°. The slope of each of the radial sides  32 ,  34  is approximately linear so that, for example, the axial dimension of each is approximately halved at the respective midpoints between the base and planar surfaces  30 ,  36 . It is contemplated by the invention that the individual inclination angles of the radial sides  32 ,  34  may differ so that radial sides  32 ,  34  are asymmetrical relative to the mid-point of planar surface  36 . 
   Each of the deflection pads  24  also has an axial height, H, measured relative to the base surface  30  and, typically, measured between the base and planar surfaces  30 ,  36 . It is contemplated by the invention that the planar surface  36  may be omitted such that the radial sides  32 ,  34  converge at an apex formed by a circumferentially-extending ridge (not shown). Typically, the axial height of each deflection pad  24  is less than about 0.2 inches (5.1 mm) and may be as small as 0.1 inch (2.5 mm) for small-diameter tires, such as ATV tires. 
   Each of the radial sides  32 ,  34  has a dimension, B, proportional to the axial height and the corresponding inclination angle, which is measured in a direction tangent to the circumference of deflection pad  24 . In the illustrated embodiment, the radial dimension is the length of the hypotenuse of a right triangle defined by each of the radial sides  32 ,  34 . It is appreciated by persons of ordinary skill in the art that the tire manufacturing process will introduce concave or convex irregularities in radial sides  32 ,  34  that result in deviations from absolute planarity. Planar surface  36  typically has a radial dimension, A, of less than or equal to about 0.2 inches (5.1 mm) so as not to inhibit the ability of the deflection pads  24  to radially deflect objects encountered by the tire  10 . 
   With reference to  FIG. 3A  in which like reference numerals refer to like features in FIG.  3  and in an alternative embodiment, tire  10  is provided with deflection pads  40  each constructed according to the principles of the invention with cusped or concave radial surfaces or sides  42 , 44  joined by a planar surface  46 . Each of radial sides  42 , 44  deviates in geometrical shape from a planar surface, indicated diagrammatically by a dashed line  48  in FIG.  3 A. Specifically, the radial sides  42 ,  44  each have a corresponding radius of curvature, R 1A  and R 1B , capable of deflecting objects radially and away from contact with base surface  30 . Radial side  42  is sloped radially inwardly so that the thickness increases with increasing radius toward shoulder  22 . Radial side  44  is sloped radially outwardly so that the thickness decreases with increasing radius toward shoulder  22 . As used herein, the terms “sloped,” “tapered” and “inclined” may mean either planar or concave. The radius of curvature should provide a material thickness, measured axially relative to the base surface  30  and radially at the surface mid-point, B/2, which is at least 25 percent of the axial height, H, of the deflection pad  40  and less than 50% of the axial height. The length of the radius of curvature determines the degree of curvature of each of the radial sides  42 ,  44 . It is contemplated by the invention that the radius of curvature of radial side  42  may differ from the radius of curvature of radial side  44  may differ. 
   The deflection pads  40  are spaced apart in a radial direction such that portions of base surface  30  are exposed. Planar surface  46  typically has a radial dimension, Λ, of less than or equal to about 0.2 inches (5.1 mm) so as not to inhibit the ability of the deflection pads  40  to radially deflect objects encountered by the tire  10 . Typically, each deflection pad  40  projects outwardly from the base surface  30  by an axial height of less than 0.2 inches (5.1 mm). Typically, the radial dimension of each of the exposed portions, which are not covered by the deflection pads  40 , is less than or equal to about 0.25 inches (6.4 mm). 
   With reference to  FIG. 3B  in which like reference numerals refer to like features in  FIGS. 3 and 3A  and in an alternative embodiment of the invention, tire  10  is provided with a plurality of between four and twelve deflection pads, of which two deflection pads  50   a  and  50   b  are shown. Deflection pad  50   a  has a pair of cusped or concave radial surfaces or sides  52   a,b  joined by a planar surface  56 . Similarly, deflection pad  50   b  has a pair of cusped or concave radial sides or surfaces  54   a,b  joined by a planar surface  58 . Radial side  52   b  of deflection pad  50   a  is smoothly continuous with radial side  54   a  of the adjacent deflection pad  50   b . Specifically, radial sides  52   b  and  54   a  are curved about a shared or common radius of curvature, R 2 , which is selected in magnitude for deflecting objects radially and away from contact with base surface  30 . The radius of curvature should provide a material thickness, measured relative to the base surface  30  and radially at the mid-point of each of surfaces  52   b ,  54   a , which is at least 25 percent of the axial height, H, of the deflection pads  50   a,b . Radial side  52   b  is sloped with a decreasing thickness in a radial-outward direction toward the shoulder  22  and radial side  54   a  is sloped with a decreasing thickness in a radially-inward direction toward bead  20 . The length of the radius of curvature determines the degree of curvature of the radial sides  52   b ,  54   a . Adjacent pairs of radial sides of the remaining deflection pads on tire  10  may have a similar or identical construction to radial sides  52   b ,  54   a.    
   The radial sides  52   b ,  54   a  merge or converge so that base surface  30  is not exposed. Planar surfaces  56  and  58  typically have a radial dimension, A, of less than or equal to about 0.2 inches (5.1 mm) so as not to inhibit the ability of the deflection pads  50   a,b  to radially deflect objects encountered by the tire  10 . Typically, each of the deflection pads  50   a,b  projects outwardly from the base surface  30  by an axial height of less than 0.2 inches (5.1 mm). 
   With reference to  FIG. 5  in which like reference numerals refer to like features in  FIGS. 1 ,  2  and  4  and in an alternative embodiment of the invention, tire  10  may be provided with a single deflection pad  60  that traces a spiral path about the sidewall  18 . Deflection pad  60  progressively increases in radial dimension relative to centerline  28  between a terminal end  62  adjacent to the bead  20  and a terminal end  64  proximate to the shoulder  22 . The deflection pad  60  is continuous and uninterrupted in the circumferential direction and has a substantially uniform intra-pad spacing in the radial direction. The deflection pad  60  may have a cross-sectional profile, in a direction tangent to the circumference of the deflection pad  60 , similar or identical to any of the cross-sectional profiles shown herein in  FIGS. 3 ,  3 A and  3 B that is capable of deflecting objects encountered by the tire  10  in a radial direction. 
   While the present invention has been illustrated by the description of one or more embodiments thereof, and while the embodiments have been described in considerable detail, they are not intended to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the scope or spirit of applicant&#39;s general inventive concept.