Patent Application
20120097311
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.
The radial carcass reinforcements of aircraft tires generally comprise several plies of textile cords, which are anchored to at least one annular bead member. A first group of reinforcing plies are generally wound around said annular bead member from the inside to the outside, forming turn-ups, the respective ends of which are radially spaced from the axis of rotation of the tire. The second group of plies are generally wound around the annular bead member from the outside to the inside of the tire.
Aircraft tires typically use numerous layers of ply which can significantly contribute to the tire weight. The numerous layers of ply may result in bead durability issues. It is thus desired to provide a lightweight efficient tire structure having improved bead durability. It is a further desired to provide an improved bead structure wherein the use of inside turn-up plies and outside turndown plies and their respective locations are optimized. Thus an improved aircraft tire is needed, which is capable of meeting high speed, high load and with reduced weight.
“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'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.
The invention will be described by way of example and with reference to the accompanying drawings in which:
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 at least two inner carcass plies 1,2,3,4 and outer carcass plies 5,6, preferably oriented in the radial direction. Among these carcass plies, typically four axially inner plies 1,2,3,4 extend radially inward from the crown towards the bead area. At least two of the four axially inner plies 1,2,3,4 are wound around the annular bead member 14 from axially inside of the annular bead member toward axially outside thereof and extends radially outward towards the crown to form respective turnup portions 1′, 2′, 3′, 4′. Preferably, the ply adjacent the bead 4 has a turnup 4′ that is located between plane 28 and the outer radial end or tip 9 of an apex 11. As best shown in
The carcass further comprises at least two outer plies 5,6 which extend radially inward from the crown and are axially outward of the annular bead member 14 along the outside of the turnup portion of the inner carcass plies 24. The two outer carcass plies 5,6 extend down from the crown and further extend axially outward and are wrapped around the bead terminating in endings 5′, 6′, respectively. Preferably, one of the endings 5′, 6′ overlap with the one or more inner plies which has a terminal end having a radial location in zone B. Preferably, two of the endings 5′, 6′ overlap with the one or more inner plies which has a terminal end in zone B.
Each of these carcass plies 1-6 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.
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. More preferably, the second belt layer 60 is the widest belt layer of the belt package 40.
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.
