Abstract:
An aircraft tire having improved wear properties is provided. The tire includes a belt reinforcement structure that provides a flatter crown and reduces localized tensions. The belt reinforcement structure includes at least four hybrid belt plies having free ends that are positioned radially inward of at least one non-hybrid belt ply. The hybrid belt plies allow for reductions in the overall mass of the tire and improved thermal properties while still meeting requirements for burst pressure and size for aircraft tires.

Description:
FIELD OF THE INVENTION 
       [0001]    The subject matter of the present disclosure relates generally to a pneumatic aircraft tire having certain reinforcements in the crown portion of the tire. 
       BACKGROUND OF THE INVENTION 
       [0002]    Tires suitable for use on aircraft must be capable of performing under high speeds and large loads. Preferably, aircraft tires should also be able to endure the wear conditions associated with repeated taxiing, take off, and landing. Such tires must also be manufactured under strict limitations on burst pressure, size, and weight that are necessitated by their use and storage on the aircraft. 
         [0003]    Aircraft tires are typically inflated to relatively high inflation pressures such as e.g., 12 bar or greater. Such high inflation pressures and conventional constructions for the crown portion of the tire have typically provided very rounded profiles as viewed along a meridian plane. These rounded profiles, which include a rounded tread portion, tend to provide undesirable tread wear performance because of e.g., poor contact pressure distribution. 
         [0004]    Difficulties are encountered when attempting to flatten the crown portion of an aircraft tire so to improve wear. For example, adding additional material to the crown portion to flatten the profile can unacceptably increase the size and mass of the tire. Removing materials in other locations in order to compensate may help reduce size and mass but may e.g., decrease burst pressure below the minimum required for aircraft use. Specialized materials such as cords constructed from aramids can be used for increased strength. However, these types of cords tend to have poor adhesion properties with the rubbers typically used in constructing the tread portion of the tire. These materials are also known to create localized tension differences between various materials in the crown portion of the tire during the high deflection and high speed applications associated with aircraft tires and particularly with military aircraft tires. Such localized tension differences further increase the wear problems. 
         [0005]    Accordingly, a tire particularly suited for aircraft applications would be useful. More particularly, a tire having a flatter crown portion that can provide improved tread wear would be beneficial. Such a tire that can meet the mass and size limitations typically associated with aircraft tires while also having a burst pressure that can withstand the stresses associated with taxiing and high speed take-offs and landings would be particularly useful. Such a tire that can also reduce the localized tension differences and, in some embodiments, provide a tire with less mass would also be very beneficial. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides an aircraft tire having improved wear properties. The tire includes a belt reinforcement structure that provides a flatter crown and reduces localized tensions. The belt reinforcement structure includes at least four hybrid belt plies having free ends that are positioned radially inward of at least one non-hybrid belt ply. The hybrid belt plies allow for reductions in the overall mass of the tire and improved thermal properties while still meeting requirements for burst pressure and size for aircraft tires. Additional objects and advantages of the invention will be set forth in part in the following description, or may be apparent from the description, or may be learned through practice of the invention. 
         [0007]    In one exemplary embodiment of the present invention, an aircraft tire is provided that defines radial and axial directions. The tire includes a pair of opposing bead portions and a pair of opposing sidewall portions, with each sidewall portion connected to one of the respective bead portions. A crown portion extends axially between and connects the opposing sidewall portions. The crown portion includes a tread portion. At least two body plies extend between the bead portions and through the crown portion and opposing sidewall portions. A belt reinforcement structure is positioned in the crown portion at a position radially inward of the tread portion and radially outward of the body plies. 
         [0008]    For this embodiment, the belt reinforcement structure includes at least four hybrid belt plies located in the crown portion, positioned radially adjacent to the at least two body plies, and radially inward of any other belt ply in the crown portion. Each hybrid belt ply has a width along the axial direction extending between opposing free ends. Each hybrid belt ply includes cord elements extending parallel to each other within the hybrid belt ply and crossing from one hybrid belt ply to the next hybrid belt ply. The cord elements of the hybrid belt plies form an angle in the range of 18 degrees to 35 degrees from an equatorial plane of the tire. The cord elements include a combination of aliphatic polyamide yarns and aromatic polyamide yarns twisted together. 
         [0009]    For this exemplary embodiment, the belt reinforcement structure also includes at least one non-hybrid belt ply positioned radially outward of the at least four hybrid belt plies and having a width along the axial direction that is greater than the width along the axial direction of the at least four hybrid belt plies, the at least one non-hybrid belt ply having cord elements including aliphatic polyamide yarns. 
         [0010]    These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which: 
           [0012]      FIG. 1  illustrates a cross-sectional view of an exemplary embodiment of a tire of the present invention. The cross-section is taken along a meridian plane of the tire. 
           [0013]      FIG. 2  is a magnified cross-sectional view of  FIG. 1  along one side of the equatorial plane (EP) of the exemplary tire, it being understood that the construction of the tire is substantially symmetrical about the equatorial plane. 
           [0014]      FIGS. 3 and 4  are schematic diagrams illustrating certain geometric details of exemplary embodiments of the present invention. 
           [0015]      FIG. 5  is a cross-sectional view of an exemplary cord of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    For purposes of describing the invention, reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment, can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
         [0017]    As used herein, the following definitions apply: 
         [0018]    “Meridian plane” is a plane within which lies the axis of rotation of the tire.  FIGS. 1 and 2  are both cross-sections of exemplary tires of the present invention taken along a meridian plane. 
         [0019]    The “center line” (C/L) of the tire is a line that bisects the tire, as viewed in the meridian plane, into two halves. 
         [0020]    “Equatorial plane” is a plane perpendicular to the meridian plane that bisects the tire along its center line (C/L). The equatorial plane is designated with EP in  FIGS. 1 and 2 . 
         [0021]    The “crown portion” of the tire is the portion that, as viewed along a meridian plane of the tire, extends along the axial direction A (which is the direction parallel to the axis of rotation of the tire) between the sidewall portions of the tire and includes the tread and components positioned radially inward of the tread. 
         [0022]    The “radial direction” is perpendicular to the axis of rotation of the tire. “Radially outward” means along a radial direction away from the axis of rotation whereas “radially inward” means along a direction towards the axis of rotation. 
         [0023]    “Body ply” or “carcass” or “carcass ply” is a ply that, as viewed along a meridian plane of the tire, extends between and from the bead portions on opposing sides of the tire, through the opposing sidewall portions, and across the crown portion of the tire. As used herein, a body ply has reinforcements such as e.g., cords that are at an angle of 10 degrees or less from the meridian plane unless a lesser angle is specified. 
         [0024]    “Belt ply” is a ply that, as viewed along a meridian plane of the tire, is located primarily in the crown portion, radially inward of the tread portion, and radially outward of the body ply or plies. A belt ply does not extend past shoulder portions of the tire. 
         [0025]    Burst pressure can be determined by a burst test in which a tire is filled with water to rated pressure such as the maximum pressure noted on the sidewall. The pressure is maintained for a time period sufficient to determine that the tire will not rupture. The pressure is then increased to a higher pressure and maintained for a time period sufficient to determine that the tire will not rupture. The process is repeated until reaching the pressure at which the tire ruptures or bursts—denoted as the burst pressure. 
         [0026]    The use of terms such as belt, bead, and/or ply herein and in the description and claims that follow does not limit the present invention to tires constructed from semi-finished products or tires formed from an intermediate that must be changed from a flat profile to a profile in the form of a torus. 
         [0027]    An exemplary embodiment of a tire  100  of the present invention is shown in a cross-sectional view along the meridian plane in  FIGS. 1 and 2  of which  FIG. 2  is a more magnified view of one side of the cross-sectional view of  FIG. 1 . Although a particular shape is illustrated by way of example, the present invention is not limited to only the overall shape shown in the figures. Tire  100  includes a pair of opposing bead portions  102  and  104  that are opposing in the sense of being on opposite sides of the equatorial plane EP. Bead portions  102  and  104  include bead cores  120  and  122 , respectively, which may be constructed e.g., of a plurality of metal cords or other relatively inextensible materials wrapped about the axis of rotation in the form of a ring or hoop. Bead portions  102  and  104  have a shape and construction configured for seating tire  100  onto a rim. 
         [0028]    Tire  100  includes a pair of opposing sidewall portions  106  and  108  positioned about equatorial plane EP. Each sidewall portion  106  and  108  is connected with a respective bead portion  102  and  104 , respectively. Each sidewall portion  106  and  108  extends overall along radial direction R. Sidewall portions  106  and  108  include one or more rubber materials to protect body plies  114  and  116 . 
         [0029]    A crown portion  110  extends along axial direction A between, and connected to, opposing sidewall portions  106  and  108 . Crown portion  110  includes a tread portion  112 . For this exemplary embodiment, tread portion  112  includes a plurality of ribs  126  separated by grooves  124 . The present invention is not limited to the particular shape, thickness, or other details shown for tread portion  112  and, instead, includes other treads having different features as well. An inner liner  118  extends along the interior of tire  100 . Inner liner  118  provides an air impermeable layer to help maintain gas pressure when tire  100  is mounted onto a rim and inflated. 
         [0030]    For this exemplary embodiment, tire  100  includes at least two body plies  114  and  116  that extend from opposing bead portions  102  and  104 , through opposing sidewall portions  106  and  108 , and through crown portion  110 . While tire  100  may have more than two body plies  114  and  116 , at least two body plies are present. Body plies  114  and  116  are each shown wrapped around, or with ends turned radially outward of, bead cores  120  and  122 . However, the present invention includes other constructions where body plies  114  and  116  extend into bead portions  102  and  104  without each necessarily wrapping about bead cores  120  and  122 . 
         [0031]    In certain embodiments, body plies  114  and  116  each include cord elements CD formed from aliphatic polyamide yarns. In still other embodiments, body plies  114  and  116  each include cord elements CD formed from aliphatic polyamide yarns and do not include aromatic polyamide yarns. As shown in  FIG. 3 , along the sidewall portions  106  and  108  the cord elements CD of body plies  114  and  116  extend along radial direction R at an angle of either +α or −α from the meridian plane MP. In certain exemplary embodiments, angle α has an absolute value of two degrees or less. 
         [0032]    Returning to  FIGS. 1 and 2 , tire  100  includes a belt reinforcement structure  128  ( FIG. 2 ) that extends around the circumferential direction C of the tire and is positioned in crown portion  110 . Belt reinforcement structure  128  is located radially inward of crown portion  110  and radially outward of body plies  114  and  116 . For this exemplary embodiment, belt reinforcement structure  128  includes at least four hybrid belt plies  130 ,  132 ,  134 , and  136  located in crown portion  110 . Belt plies  130 ,  132 ,  134 ,  136  are positioned radially adjacent to the body plies  114  and  116 , which means that no other belt ply is positioned between belt plies  130 ,  132 ,  134 ,  136  and body plies  114 ,  116 . 
         [0033]    Each hybrid belt ply  130 ,  132 ,  134 ,  136  includes multiple cord elements extending parallel to each other within each respective belt ply. As shown in  FIG. 4 , the cord elements CD in each hybrid belt ply form an angle of either +β or −β from the equatorial plane EP. In particular embodiments, the absolute value of β for the cord elements in the hybrid belt plies  130 ,  132 ,  134 ,  136  is in the range of 18 degrees to 35 degrees. In other particular embodiments, the absolute value of β for the cord elements in the hybrid belt plies  130 ,  132 ,  134 , and  136  is in the range of 18 degrees to 22 degrees. In other particular embodiments, the absolute value of β for the cord elements in the hybrid belt plies  130 ,  132 ,  134 , and  136  is about 20 degrees. 
         [0034]    Within belt reinforcement structure  128 , the cord elements of adjacent hybrid belt plies cross from one belt ply to the next. For example, if the cord elements in belt ply  130  are at positive angle β from the equatorial plane EP, then the cord elements in belt ply  132  are at a negative angle β from the equatorial plane EP, and so forth. Stated alternatively, the angles β alternate between positive and negative values of angle β from belt ply to belt ply along the radial direction R. 
         [0035]    The cord elements of the hybrid belt plies  130 ,  132 ,  134 ,  136  include a combination of aliphatic polyamide yarns and aromatic polyamide yarns that are twisted together.  FIG. 5  provides an example of a cord element  144  as may be included in hybrid belt plies  130 ,  132 ,  134 ,  136 . For this exemplary embodiment, cord element  144  includes yarns  146 A and  148 A that are each constructed from aromatic polyamide filaments  147 A and  149 A, respectively. By way of example, each yarn  146 A or  148 A may include  330  aromatic polyamide filaments  147 A or  149 A, respectively. Cord element  144 , in this embodiment, includes yarn  150 N constructed from aliphatic polyamide filaments  151 N. For example, yarn  150 N may include  188  aliphatic polyamide filaments  151 N. Other filaments counts may be used as well. Cord element  144  is twisted along its length. For example, cord element  144  may be twisted at a rate of 250 turns per meter along its length. Other constructions for hybrid belt plies using a combination of aliphatic polyamide yarns and aromatic polyamide yarns may also be used. 
         [0036]    As shown in  FIGS. 1 and 2 , hybrid belt plies  130 ,  132 ,  134 ,  136  have a width along axial direction A between free ends  130   e ,  132   e ,  134   e , and  136   e  on opposing sides of the equatorial plane EP. Using belt ply  130  as an example, as used herein “free ends” means that, as viewed in the meridian plane, the opposing ends  130   e  of belt ply  130  are not enclosed or encased by any other belt ply—i.e. a line (straight or having the same curvature as belt ply  130 ) can be drawn from a free end  130   e  to the exterior of tire  100  without crossing another belt ply. Additionally, “free ends” means that ends  130   e  are not wrapped or turned over onto belt ply  130  and are not wrapped or turned over other belt plies in crown portion  110 . 
         [0037]    In particular embodiments, the width along axial direction A of each hybrid belt ply  130 ,  132 ,  134 ,  136  is in the range of 45 percent to 90 percent of the corresponding width of the narrowest non-hybrid belt ply (such as e.g., belt ply  138 ) in belt reinforcement structure  128 . In other particular embodiments, the width along axial direction A of each hybrid belt ply  130 ,  132 ,  134 ,  136  is in the range of 70 percent to 90 percent of the corresponding width of the narrowest non-hybrid belt ply in belt reinforcement structure  128 . 
         [0038]    Belt reinforcement structure  128  also includes at least one non-hybrid belt ply  138  that is positioned radially outward of the hybrid belt plies  130 ,  132 ,  134 ,  136 . The non-hybrid belt ply  138  has a width along axial direction A that is greater than the width along axial direction A of hybrid belt plies  130 ,  132 ,  134 ,  136 . The non-hybrid belt ply  138  includes cord elements constructed from aliphatic polyamide yarns. For this exemplary embodiment, the non-hybrid belt ply  138  does not include cords having any aromatic polyamide yarns. 
         [0039]    Along the circumferential direction C, the cords of non-hybrid belt ply  138  extend sinusoidally. More particularly, non-hybrid belt ply  138  is formed by sinusoidally depositing a strip member that includes the cord elements across the width (along axial direction A) of belt ply  138 . This results in a double layer appearance as shown in  FIGS. 1 and 2  but creates a single, non-hybrid belt ply  138 . The strip member includes the cord elements within a rubber coating. In one embodiment, the strip members form and angle of 8 to 10 degrees from the equatorial plane EP as they extend between opposing sides of crown portion  110 . 
         [0040]    Tire  100  includes at least one protector ply  140  positioned in crown portion  110 . Protector ply  140  is located radially outward of belt reinforcement structure  128  and radially inward of tread portion  112 . In particular embodiments, protector ply  140  may include one or more inextensible elements (e.g., metal cables) arranged at an angle of 45 degrees. By way of example, protector ply  140  shields belt reinforcement structure  128  from punctures into crown portion  110 . Protector ply  140 , in particular embodiments, does not include aromatic polyamide yarns. 
         [0041]    While the present subject matter has been described in detail with respect to specific exemplary embodiments and methods thereof, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing may readily produce alterations to, variations of, and equivalents to such embodiments. Accordingly, the scope of the present disclosure is by way of example rather than by way of limitation, and the subject disclosure does not preclude inclusion of such modifications, variations and/or additions to the present subject matter as would be readily apparent to one of ordinary skill in the art using the teachings disclosed herein.