Patent Application
20210146727
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.
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 helps 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.
“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 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. Nos. 4,893,665, 4,155,394, or U.S. Pat. No. 6,799,618.
The aircraft tire 10 further comprises a main belt package 40 arranged between the carcass 22 and the tread rubber 20.
The main belt layer 40 further includes one or more zigzag belt layers 44. Preferably, there are at least two zigzag belt layers 44,46. More preferably, there are three zigzag belt layers 44,46,48. The angle of the zigzag belt layers range from ten degrees to 40 degrees. The zigzag belt layers are formed by winding a strip of one or more cords in a zigzag pattern on a drum. The main belt layers are preferably formed from a hybrid or merged cord of nylon and aramid. More preferably, the main belt cord construction is 3000 d/2 aramid and 1680 d/1 nylon.
The belt package 40 further comprises an auxiliary belt layer 50 located radially outward of the main belt layer 50. The auxiliary belt layer 50 is preferably a zigzag belt layer formed of nylon cords having a 1890 d/4 cord construction. The angle of the zigzag belt layer may range from 10 degrees to 40 degrees. The second belt layer has a width less than the main belt layer 40.
A cushion gum layer 60 is located radially outward of the auxiliary belt layer 50. The cushion gum layer 60 is formed from a stiff rubber compound, and preferably has a modulus of elasticity of 20-22 mpa.
A cut protector belt 70 is located radially outward of the cushion gum layer 60. The cut protector belt may be formed of nylon, but is preferably made of a hybrid or merged cord of nylon and aramid. Preferably, the cut protector belt 70 is formed of a merged cord having a 3000 d/2 Aramid, and 1680 d/1 nylon cord construction which are twisted together to form a merged cord. The cut protector belt may be a zigzag belt or more preferably, a geodesic belt. The geodesic belt is shown in
Variations in the present invention are possible in light of the description of it provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the full intended scope of the invention as defined by the following appended claims.
