Patent Publication Number: US-8967213-B2

Title: Aircraft tire

Description:
FIELD OF THE INVENTION 
     This invention relates to pneumatic tires having a carcass and a belt reinforcing structure, more particularly to high speed heavy load tires such as those used on aircraft. 
     BACKGROUND OF THE INVENTION 
     Pneumatic tires for high speed applications experience a high degree of flexure in the crown area of the tire as the tire enters and leaves the area of the footprint. This problem is particularly exacerbated on aircraft tires wherein the tires can reach speed of over 200 mph at takeoff and landing. 
     When a tire spins at very high speeds the crown area tends to grow in dimension due to the high angular accelerations and velocity, tending to pull the tread area radially outwardly. Counteracting these forces is the load of the vehicle which is only supported in the small area of the tire known as the footprint area. 
     Current tire design drivers are an aircraft tire capable of high speed, high load and with reduced weight. It is known in the prior art to use zigzag belt layers in aircraft tires, such as disclosed in the Watanabe U.S. Pat. No. 5,427,167. Zigzag belt layers have the advantage of eliminating cut belt edges at the outer lateral edge of the belt package. The inherent flexibility of the zigzag belt layers also help improve cornering forces. However, a tire designed with zigzag belt layers cannot carry as heavy a load as required by current commercial aircraft design requirements. Further, there is generally a tradeoff between load capacity and weight. Thus an improved aircraft tire is needed, which is capable of meeting high speed, high load and with reduced weight. 
     DEFINITIONS 
     “Carcass” means the tire structure apart from the belt structure, tread, undertread, and sidewall rubber over the plies, but including the beads. 
     “Circumferential” means lines or directions extending along the perimeter of the surface of the annular tread perpendicular to the axial direction. 
     “Cord” means one of the reinforcement strands of which the plies in the tire are comprised. 
     “Equatorial plane (EP)” means the plane perpendicular to the tire&#39;s axis of rotation and passing through the center of its tread. 
     “Ply” means a continuous layer of rubber-coated parallel cords. 
     “Radial” and “radially” mean directions radially toward or away from the axis of rotation of the tire. 
     “Radial-ply tire” means a belted or circumferentially-restricted pneumatic tire in which the ply cords which extend from bead to bead are laid at cord angles between 65° and 90° with respect to the equatorial plane of the tire. 
     “Zigzag belt reinforcing structure” means at least two layers of cords or a ribbon of parallel cords having 1 to 20 cords in each ribbon and laid up in an alternating pattern extending at an angle between 5° and 30° between lateral edges of the belt layers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view of a first embodiment of half of a tire according to the invention; 
         FIG. 2  is a schematic perspective view of a zigzag belt layer in the middle of the formation; 
         FIG. 3  is a schematically enlarged cross-sectional view of a first embodiment of half of a composite belt package for a tire showing the belt layer configuration; 
         FIG. 4  is a schematically enlarged cross-sectional view of a second embodiment of a composite belt package showing the belt layer configuration; 
         FIG. 5  is a schematically enlarged cross-sectional view of a third embodiment of a composite belt package showing the belt layer configuration; 
         FIG. 6  is a schematically enlarged cross-sectional view of a fourth embodiment of a composite belt package showing the belt layer configuration; 
         FIG. 7  is a schematically enlarged cross-sectional view of a fifth embodiment of a composite belt package showing the belt layer configuration; 
         FIG. 8  is a schematically enlarged cross-sectional view of a sixth embodiment of a composite belt package showing the belt layer configuration; 
         FIG. 9  is a schematically enlarged cross-sectional view of a seventh embodiment of a composite belt package showing the belt layer configuration; and 
         FIG. 10  is a schematically enlarged cross-sectional view of an eighth embodiment of a composite belt package showing the belt layer configuration. 
         FIG. 11  is an enlarged cross-sectional view of a ninth embodiment of a belt package. 
         FIG. 12  is a close up view of a section of the belt package of  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates a cross-sectional view of one half of a radial aircraft tire  10  of the present invention. The tire is symmetrical about the mid-circumferential plane so that only one half is illustrated. As shown, the aircraft tire comprises a pair of bead portions  12  each containing a bead core  14  embedded therein. One example of a bead core suitable for use in an aircraft tire is shown in U.S. Pat. No. 6,571,847. The bead core  14  preferably has an aluminum, aluminum alloy or other light weight alloy in the center portion  13  surrounded by a plurality of steel sheath wires  15 . A person skilled in the art may appreciate that other bead cores may also be utilized. 
     The aircraft tire further comprises a sidewall portion  16  extending substantially outward from each of the bead portions  12  in the radial direction of the tire, and a tread portion  20  extending between the radially outer ends of the sidewall portions  16 . Furthermore, the tire  10  is reinforced with a carcass  22  toroidally extending from one of the bead portions  12  to the other bead portion  12 . The carcass  22  is comprised of inner carcass plies  24  and outer carcass plies  26 , preferably oriented in the radial direction. Among these carcass plies, typically four inner plies  24  are wound around the bead core  14  from inside of the tire toward outside thereof to form turnup portions, while typically two outer plies  26  are extended downward to the bead core  14  along the outside of the turnup portion of the inner carcass ply  24 . Each of these carcass plies  24 ,  26  may comprise any suitable cord, typically nylon cords such as nylon-6,6 cords extending substantially perpendicular to an equatorial plane EP of the tire (i.e., extending in the radial direction of the tire). Preferably the nylon cords have an 1890 denier/2/2 or 1890 denier/3 construction. One or more of the carcass plies  24 ,  26  may also comprise an aramid and nylon cord structure, for example, a hybrid cord, a high energy cord or a merged cord. Examples of suitable cords are described in U.S. Pat. No. 4,893,665, U.S. Pat. No. 4,155,394 or U.S. Pat. No. 6,799,618. 
     The aircraft tire  10  further comprises a belt package  40  arranged between the carcass  22  and the tread rubber  20 .  FIG. 3  illustrates a first embodiment of one half of a belt package  40  suitable for use in the aircraft tire. The belt package  40  is symmetrical about the mid-circumferential plane so that only one half of the belt package is illustrated. The belt package  40  as shown comprises a first belt layer  50  located adjacent the carcass. The first belt layer  50  is preferably formed of cords having an angle of 5 degrees or less with respect to the mid-circumferential plane. Preferably, the first belt layer  50  is formed of a rubberized strip  43  of two or more cords made by spirally or helically winding the cords at an angle of plus or minus 5 degrees or less relative to the circumferential direction. The first belt layer  50  is the narrowest belt structure of the belt package  40 , and has a width in the range of about 13% to about 100% of the rim width (width between flanges), and more particularly in the range of about 20% to about 70% of the rim width (width between flanges), and most particularly in the range of about 30% to about 42% of the rim width (width between flanges). 
     The belt package  40  further comprises a second belt layer  60  located radially outward of the first belt layer  50 . The second belt layer  60  is preferably formed of cords having an angle of 5 degrees or less with respect to the mid-circumferential plane. Preferably, the second belt layer  60  is formed of a rubberized strip  43  of two or more cords made by spirally or helically winding the cords at an angle of plus or minus 5 degrees or less relative to the circumferential direction. The second belt layer has a width in the range of about 101% to about 120% of the rim width, and has a width greater than the first belt layer  50 . 
     The belt package  40  further comprises at least one zigzag belt reinforcing structure  70 . The zigzag belt reinforcing structure  70  is comprised of two layers of cord interwoven together formed as shown in  FIG. 2 . The zigzag belt structure is formed from a rubberized strip  43  of one or more cords  46 , that is wound generally in the circumferential direction while being inclined to extend between alternating lateral edges  44  and  45  of a tire building drum  49  or core. The strip is wound along such zigzag path many times while the strip  43  is shifted a desired amount in the circumferential direction so as not to form a gap between the adjoining strips  43 . As a result, the cords extend in the circumferential direction while changing the bending direction at a turnaround point at both ends  44 ,  45 . The cords of the zigzag belt structure cross with each other, typically at a cord angle A of 5 degrees to 30 degrees with respect to the equatorial plane EP of the tire when the strip  43  is reciprocated at least once between both side ends  44  and  45  of the ply within every 360 degrees of the circumference as mentioned above. The two layers of cords formed in each zigzag belt structure are embedded and inseparable in the belt layer and wherein there are no cut ends at the outer lateral ends of the belt. 
     It is preferred that the zigzag belt structure  70  is the most radially outward belt structure of the belt package  40 . It is additionally preferred that there is only one zigzag belt structure. The zigzag belt structure  70  is preferably wider than the first belt structure, and more preferably is wider than both the first belt structure and the second belt structure  60 . The ratio of the zigzag belt width Wz to the second belt structure  60  width Ws is preferably as follows:
 
0.6&lt; Ws/Wz&lt; 1  (1)
 
       FIG. 6  illustrates an additional embodiment wherein the belt structure further includes a second zigzag belt structure  92  located radially outward of the first zigzag belt structure  70 . The second zigzag belt structure  92  has a width less than the first zigzag belt structure  70 . The zigzag belt structure  70  is the widest belt, and has a width greater than the width of the belt layer  60 . This embodiment further includes 4 low angle belts,  60 ,  50 ,  55 ,  57  wherein the narrowest belt  55  is located radially inward of all the belts, the next widest belt  57  is located radially outward of belt  55 , the next widest belt  50  is located radially outward of belt  57 , and then the widest belt  60 . 
       FIG. 8  illustrates yet another embodiment of the invention. The belt package  40  includes two radially outer zigzag belts  92 ,  70  wherein the zigzag belt  70  is the widest belt of all. The embodiment further includes four low angle belts  52 ,  54 ,  56 ,  58 . Two of the low angle belts  56 ,  58  have the widest width of the low angle belts. The radially outward belt  58  is slightly wider than belt  56 . There are also two radially inner low angle belts  52 ,  54  which have a width of about 25-20% of the width of the belts  56 ,  58 . 
       FIG. 9  illustrates still another embodiment of the present invention. The embodiment of  FIG. 9  includes two radially inner low angle belts  50 ,  60 . The belt package further includes two additional zigzag belt structures  68 ,  69  wherein both belt structures are located radially outward of the first zigzag belt structure  70 . The belt structures  68 ,  69 ,  70  have decreasing belt widths so that the radially innermost belt is the widest belt, and the radially outermost belt  68  is the narrowest.  FIG. 10  illustrates a variation of the embodiment of  FIG. 9  wherein a third low angle belt  51  is located radially inward of low angle belt  50  and has a width in the range of about 13% to about 47% of the rim width between the flanges. 
       FIG. 11  illustrates yet another embodiment of the invention. This embodiment includes a first and second belt  100 ,  105  having of low angle of 5 degrees or less with respect to the circumferential plane. The first and second belts  100 ,  105  are preferably helically wound. The first belt  100  is the radially innermost belt, and has a width Bw s . The first belt  100  is the narrowest belt of all the belts. The second belt  105  is located radially outward of the first belt, and has a slightly larger width than the first belt. The embodiment further includes a third  110  and fourth belt  115 , having a low angle of 5 degrees or less with respect to the circumferential plane. The third and fourth belts are preferably helically wound. The third belt  110  is located radially outward of the second belt, and is substantially wider than the first and second belts. The third belt has a width bw 3 . The fourth belt  115  is located radially outward of the third belt, and is the widest of the low angle belts. The fourth belt has a width slightly larger than the third belt. The embodiment further includes a first  120  and second  130  zigzag belt structure that are both located radially outward of the first through fourth belts. The first zigzag belt  120  is located radially outward of the fourth belt  115 , and has the widest width BwZ of all of the belts. The ratio of the zigzag belt width BWz to the narrowest cut belt Bws is as follows:
 
0.3&lt; BWs/BWz&lt; 0.6, and more preferably in the range of 0.3&lt; BWs/BWz&lt; 0.5  (1)
 
     In the above embodiment, it is additionally preferred that the ply be made of nylon and that the belt be made of an aramid/nylon blend, such that the ply cord % elongation is greater than the belt cord % elongation at break. It is additionally preferred that the maximum belt cord elongation at break be less than 18%. 
     Near the axially outer ends  122  of the first zigzag belt, a first cut strip  140  is placed between the first zigzag belt end and the fourth belt. A second cut strip  150  is placed between the first and second zigzag belt structures  120 ,  130 . The first cut strip  140  extends axially inward from the axially outer edge of the first zigzag belt a defined width W 2 . The second strip extends axially inward from the axially outer edge of the second zigzag belt a defined width W 1 . The defined width W 1  and W 2  is in the range of 1% to 12% of the width of the widest zigzag belt  120 . The thickness of each strip Et is in the range of:
 
0.5 Cd≦Et&lt; 3 Cd,  
 
wherein Cd is the diameter of the cord of the zigzag belt structure.
 
     The thickness of the strip Et is preferably in the range of:
 
0.5 Cd≦Et&lt; 2 Cd  
 
     The thickness of the strip Et is more preferably in the range of:
 
 Cd≦Et&lt; 2 Cd  
 
       FIG. 12  is a close up view of  FIG. 11 , illustrating the placement of the first and second strips between the fourth belt and the first zigzag belt, and between the first and second zigzag belts. 
     
       
         
           
               
               
             
               
                   
                 TABLE 1 
               
             
            
               
                   
                   
               
               
                   
                 Ex. 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Ply 
                 Nylon 
                 Nylon 
                 Nylon 
                 Nylon 
                 Nylon 
                 Nylon 
                 Nylon 
               
               
                   
                 1890d/3 
                 1890d/2/2 
                 1890d/3 
                 1890d/3 
                 1890d/3 
                 1890d/3 
                 1890d/3 
               
               
                 Belt 
                 Nylon 
                 Nylon 
                 Nylon 
                 Aramid 
                 Aramid/Nylon 
                 Aramid/Nylon 
                 Aramid/Nylon 
               
               
                   
                 1890d/3 
                 1890d/2/2 
                 1890d/2/2 
                 3000d/3 
                 3000d/2 + 1680d/2 
                 3000d/2 + 1680d/3 
                 3000d/2 + 1680d/4 
               
               
                 Ply cord 
                 22 
                 23 
                 22 
                 22 
                 22 
                 22 
                 22 
               
               
                 Elong. % 
               
               
                 Belt cord 
                 25 
                 23 
                 25 
                 25 
                 14 
                 14 
                 14 
               
               
                 % elong. 
               
               
                 BWs/BWZ 
                 .63 
                 .63 
                 .63 
                 .63 
                 .41 
                 .41 
                 .41 
               
               
                 Et/Cd 
                 0.25 
                 0.26 
                 0.26 
                 0.30 
                 0.30 
                 1.10 
                 1.25 
               
               
                 Belt ends 
                 22 
                 20 
                 20 
                 18 
                 18 
                 18 
                 18 
               
               
                 per in 
               
               
                 Tread cut 
                 Blew 
                 Blew 
                 Blew 
                 Pass 
                 Pass 
                 Pass 
                 Pass 
               
               
                 test 
               
               
                 Tire 
                 100 
                 103 
                 105 
                 98 
                 99 
                 160 
                 160 
               
               
                 durability 
               
               
                 index 
               
               
                 Weight 
                 100 
                 97 
                 98 
                 86 
                 86 
                 86 
                 87 
               
               
                 index 
               
               
                   
               
            
           
         
       
     
     The first cut strip  140  may also be placed between belts  60  and  70  of  FIGS. 3 through 10  in the manner as described above. The second cut strip may also be placed between belts  70  and  90  of  FIG. 5 , and belts  70  and  92  of  FIGS. 6-8 , and between belts  69  and  70  of  FIGS. 9 and 10 . 
     In the table I above, a series of tires having size 46×17.0R20 30PR were made. The tires were tested at the following conditions: Rated load: 46000 lbs, Rated pressure: 222 psi, 40 mph speed. Durability test condition: FAA TSO C62e. Tread cut test condition: dropping metal blade between tire and drum during rotating tire under rated condition. 
     Three tires labeled as 1-3, were made from nylon ply and nylon belts. All three tires had a BWs/BWz of 0.63 and a Et/Cd ratio in the range of 0.25-0.26. All three examples failed the tread cut test, although tire durability index ranged from 100 to 105. The weight index ranged from 100 to 97. Tire example 4 had the same characteristics as the other three examples, except that the belt was made of aramid, and the Et/Cd ratio was increased to 0.3. The tire passed the tread cut, but the durability index decreased to 98. The weight index was significantly decreased to 86. In example 5, the belt was made of an aramid/nylon cord, the belt width ratio BWs/BWz was significantly decreased to 0.41 and the Et/Cd ratio was 0.3. The tire passed the tread cut test and tire durability slightly improved. In example 6, the Et/Cd ratio was significantly increased to 1.1 and the tire durability significantly increased to 160 from 99 of example 5. Examples 5 and 6 are essentially the same except for the Et/cd ratio. Example 7 is similar to 6, except the Et/Cd ratio was increased to 1.25, which resulted in same durability. 
     In any of the above described embodiments, the cords are preferably continuously wound from one belt structure to the next. 
     The cords of any of the above described carcass, spiral or zigzag belt layers described above may be nylon, nylon 6, 6, aramid, or combinations thereof, including merged, hybrid, high energy constructions known to those skilled in the art. One example of a suitable cord construction for the belt cords, carcass cords (or both), may comprise a composite of aramid and nylon, containing two cords of a polyamide (aramid) with construction of 3300 dtex with a 6.7 twist, and one nylon or nylon 6/6 cord having a construction of 1880 dtex, with a 4.5 twist. The overall merged cable twist is 6.7. The composite cords may have an elongation at break greater than 11% and a tensile strength greater than 900 newtons. Optionally, the original linear density may be greater than 8500 dtex. Elongation, break, linear density and tensile strength are determined from cord samples taken after being dipped but prior to vulcanization of the tire. 
     Variations of the present invention are possible in light of the description as provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the subject inventions, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the scope of the subject inventions.