Abstract:
An aviation tire including, a pair of side walls, the side walls having an outer surface, a tread portion spanning a radial outer extremity of the side walls, and a rotating assembly formed on the side wall or the tread portion, the rotating assembly having an increased resistance to wind when located at a lowermost portion of the tire.

Description:
TECHNICAL FIELD 
   The present invention relates to tires. More particularly, the present invention relates to a tire used in connection with aircraft landing gear. Most particularly, the present invention relates to an aviation tire that is adapted to rotate in the direction of the flight of the aircraft to reduce frictional forces at touchdown of the tires. 
   BACKGROUND OF THE INVENTION 
   As is well known, planes typically travel at significant speeds at the point of landing. To accommodate these speeds, wheels are provided on the aircraft landing gear such that the aircraft continues to move after the plane lands on the runway. Braking forces may then be applied either to the wheels or by means of jet reversers to bring the plane to a stop. 
   Considering the wheels in more detail, when in flight, the wheels are in a moving reference frame. In particular, the wheels have a velocity equal to the velocity of the plane just prior to impact relative to the surface on which the plane is landing. The typically large difference between the velocity of the wheel and velocity of the surface on which the plane is landing generates significant frictional forces between the surface of the wheel&#39;s tire and the landing surface. Initially the velocity of the tire relative to the landing surface is great enough to overcome the sliding friction between the tire and the landing surface. This causes the tire to slide until the tire has decelerated sufficiently for rolling frictional forces to take over. This initial sliding is evident from an audible chirp or screech made as the plane touches down. During the sliding phase, as the tire is essentially dragged across the landing surface, the landing surface abrades the tire at the contact patch leading to a flat spot on the tire. As will be appreciated such “flat spotting” of the tire makes the tire out of round decreasing its performance during the rolling phase. Repeated flatspotting greatly shortens the useful life of the tire. 
   As will be appreciated, the significant downforce of the plane exacerbates the wear of the tire. As a result, the frictional forces coupled with the downward force of the plane results in a great amount of wear and tear on the tire. This wear requires frequent replacement of the tires and increases the amount of downtime for the plane. 
   SUMMARY OF THE INVENTION 
   In light of the forgoing, it is an object of the present invention to reduce aviation tire wear. 
   It is an object of the present invention to provide a tire adapted to rotate in the direction of the flight of the aircraft, on which it is mounted, to reduce the frictional forces that occur upon impact of the tire on a landing surface. 
   In light of at least one of the foregoing objects, the present invention generally provides an aviation tire including, a pair of side walls, the side walls having an outer surface, a tread portion spanning a radial outer extremity of the side walls, and a rotating assembly formed on said side wall or said tread portion, said rotating assembly having an increased resistance to wind when located at a lowermost portion of the tire. 
   The present invention further provides an aviation tire including a pair of side walls having an outer surface, a tread portion spanning a radial ladder extremity of the side walls, and a rotating assembly formed on the side wall or the tread portion. The rotating assembly having a leading wall and a trailing wall, where the leading wall faces rearward at an upper most portion of the tire and faces forward in a lower most portion of the tire, the leading wall having an increased resistance to wind relative to the trailing wall. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a complete understanding of the objects, techniques and structure of the invention, reference should be made to the following detailed description and accompanying drawings wherein: 
       FIG. 1  is a side elevational view of a tire according to the concepts of the present invention; 
       FIG. 2  is a sectional view of a tire according to the concepts of the present invention as might be seen along line  2 — 2  in  FIG. 1 ; 
       FIG. 3  is an enlarged radial sectional view as might be seen along line  3 — 3  in  FIG. 1  depicting details of indents formed in the side wall of the tire of the present invention; 
       FIG. 4  is an enlarged side sectional view as might be seen along line  4 — 4  in  FIG. 2  depicting details of a ridge within the tread of the tire according to the concepts of the present invention; 
       FIG. 5  is a partially schematic view of a tire according to the concepts of the present invention depicting rotation of the tire relative to the wind direction and plane direction; 
       FIG. 6  is a side elevation view of a first alternative embodiment of the present invention having inflatable pockets located on the side wall of the tire; 
       FIG. 7  is a schematic top view of an inflatable pocket formed on the aviation tire according to the concepts of the present invention shown in a deflated condition and an inflated condition; 
       FIG. 7A  is a schematic top view of an inflatable pocket formed on the aviation tire similar to that shown in  FIG. 7 , where the pocket is shown at a position at the lower most portion of the tire with the pocket in an inflated condition; and 
       FIG. 8  is a second alternative embodiment of a tire according to the concepts of the present invention having a single row of large inflatable pockets. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A tire according to the concepts of the present invention is generally indicated by the numeral  10  in the accompanying drawings. Tire  10  includes sidewalls  11  and a tread portion, generally indicated by the numeral  12 , that spans the sidewalls  11  at the radial outer extremity of the tire  10 . A bead ring  13  is formed on the radial inner extremity of the tire  10  and defines a central opening  14  in which a rim (not shown) is received. To this extent, the tire  10  is of a conventional construction and may be manufactured according to methods known in the art. 
   As best shown in  FIG. 5 , when the tire  10  is in flight it travels in the direction of the plane, as indicated by the arrow P, and faces wind flow, generated by the movement of the plane, generally opposite the plane direction P and indicated by the wind direction arrow W. To reduce the relative velocity between the tire  10  and the landing surface S at impact, it is desirable to cause the tire  10  to rotate forwardly relative to the direction of the plane P. To accomplish this, the sidewalls  11  may be provided with one or more rotating assemblies, such as, indents, generally indicated by the numeral  20 . In general, the rotating assemblies, such as indents  20 , are adapted to provide the greatest resistance to the wind W at the lowermost portion  24  of tire  10  to cause tire rotation. It will be appreciated that only a single sidewall  11  may be provided with indents  20 , but it is believed preferable to have symmetrically located indents  20  on both sidewalls  11  of the tire  10  or balancing purposes. As shown in  FIGS. 1 and 5 , indents  20  may be arranged in radially spaced rows  21 ,  22 ,  23 . Indents  20  in rows  21 ,  22 ,  23  may be circumferentially offset relative to an adjacent indent  20  in an adjacent row. For example, as shown in  FIG. 1 , the indent  20  in an intermediate row  22  may be circumferentially spaced behind, relative to the direction of rotation R ( FIG. 5 ), the indent  20  in the outer most row  21 . Similarly, the innermost row  23  may have indents  20  circumferentially spaced behind those of adjacent intermediate rows  22 . As is further shown in  FIG. 1 , the size of the indents  20  may vary in terms of radial location. In the example shown in  FIG. 1 , the indent&#39;s size decreases as one travels radially inward on the sidewall  11  of the tire  10 . In other words, the largest indents  20  are located at the radially outer extremity of the tire  10  and the smallest indent are located at the radial inner extremity of the sidewall  11 . 
   One example of a possible structure for an indent  20  is shown in  FIG. 3 . Generally, indent  20  is shaped to catch the wind W or increase drag as it approaches the lowermost portion  24  of the tire  10  and create the least resistance to the wind W at the uppermost portion  25  of the tire  10 . To that end, indent  20  has a leading edge  26  that is recessed from the outer surface  28  of the sidewall  11 . At the uppermost portion  25 , this surface  26  is essentially hidden from the wind W. As the indent  20  reaches the lowermost portion  24  of the tire  10 , however, the trailing wall  27 , which is less resistant to the wind W in the uppermost position  25 , allows wind W to contact leading wall  26  imparting rotation to the tire  10 . In the example shown in  FIG. 3 , the leading wall  26  extends radially outward and is generally square to the direction of the wind W when in the lowermost position  24 . The trailing wall  27  slopes inwardly from the outer surface  28  of the sidewall  11 . Joining the leading wall  26  at a vertex  29 . 
   In the alternative or in addition to the indents  20 , the rotating assemblies may include ridges, generally indicated by the numeral  30  in  FIG. 4 , may be provided in the tread portion  12  of the tire  10 . Ridges  30  extend radially outward from the inner surface  31  of tread portion  12 . As best shown in  FIG. 4 , ridge  30  has a leading wall  32  and trailing wall  33  that join at a vertex  34 . Leading wall  32  is shaped such that it creates less drag than the trailing wall  33 , such that, the trailing wall  33 , when located at the lowermost portion  24 , of tire  10 , creates relatively increased drag allowing the wind W to impart rotation to the tire  10 . It will be appreciated that a number of face shapes may be used in accordance with the concept of reducing drag on the uppermost portion  25  of the tire  10  and increasing drag on the lowermost portion  24  of the tire  10  to impart rotation in the direction of the plane P. In the example shown, the leading wall  32  extends at an incline relative to the surface  31  of the tread portion  12  and the trailing wall  33  extends radially outward in a direction generally perpendicular to the face  31  of the tire  10 . In the example shown, ridges  30  are arranged consecutively about the circumference of tire  10  in a sawtooth pattern. It will be appreciated that ridges  30  may be spaced from each other about the circumference of tire  10 . 
   As shown in  FIG. 4 , the ridges  30  may reside completely within the circumferential plane defined by the tread surface  12 . Ridges  30  may reside within grooves  35  in the tire&#39;s tread portion  12  or form part of a tread element  36 . In the example shown, ridges  30  may be formed in a central groove  35 A of tire  10  to apply a force along the center line of tire  10 . It will be appreciated that ridges  30  may be formed in other grooves  35  or be part of the tread element  36  as mentioned above. Since ridges  30  may be formed as part of tread  12  without reducing the thickness of tire  10 , ridges  30  may be desirable in terms of tire strength. Like indents  20 , ridges  30  are adapted to have an increased wind resistance at a lowermost portion  24  of the tire  10  relative to the wind direction W and reduced resistance at the uppermost portion  25  to impart rotation R to the tire  10  in the direction of the plane&#39;s path P. In these examples, the leading wall provides the increased resistance. This rotation R reduces the speed differential between the tire  10  and landing surface S because, as best shown in  FIGS. 4 and 5 , the rotating tire  10  has a velocity (R) in the same direction as the landing surface velocity V. 
   An alternative tire according to the present invention is generally indicated by the numeral  110  and is shown in  FIGS. 6–8 . Since forming indentations in the sidewall  11  of the tire may create a concern as to the sidewall strength, pockets, generally indicated by the numeral  40  may be formed or attached on the exterior surface  28  of the sidewall  11 . As is shown in  FIG. 6 , pockets  40  have an open end  41  located downstream of the leading edge  42  of the pocket  40 . In the uppermost portion  25 , the pocket  40  is collapsed ( FIG. 7 ) by the force of the wind W flowing over the closed end  42  of the pocket  40 . At the lowermost portion  24  ( FIG. 7A ), however, the open end  41  of the pocket is exposed to the wind W and the pocket  40  is filled with air allowing the wind W to impart forward rotation of the tire  10 . As will be appreciated, the pockets  40  may be applied or attached to the outer surface  28  of sidewall  11  or an integral pocket  40 ′ ( FIG. 7A ) may be formed on the sidewall  11 . 
   As shown in  FIG. 6 , the pockets may be arranged in multiple rows  44  as described in the previous embodiment. Alternatively, as shown in a second alternate embodiment, generally indicated by the numeral  210  in  FIG. 8 , a single row of enlarged pockets  45  may be used. 
   In operation, the increased resistance of the indentations  20 , ridges  30 , or pockets  40 ,  45  at the lower portion  24  of the tire  10  allows the wind W to impart a forward rotation R to the tire  10 , such that, a relative velocity V between the tire  10  and the surface S on which the plane is landing is reduced resulting in decreased frictional wear on the tire  10 . An attendant result of the decrease in wear on the tire  10  would be less frequent changing of the tires  10  and less downtime for the aircraft. In this way, a cost savings in terms of tire replacement is achieved and an increase in the working time of the aircraft is achieved, which may result in the use of fewer planes to transport the same number of passengers or cargo or the ability to transport a greater number of passengers and cargo with the same number of planes. 
   In light of the foregoing, it should thus be evident that the aviation tire of the present invention, substantially improves the art. While, in accordance with the patent statutes, only the preferred embodiments of the present invention have been described in detail hereinabove, the present invention is not to be limited thereto or thereby. Rather, the scope of the invention shall include all modifications and variations that fall within the scope of the attached claims.