Abstract:
A road wheel for a tracked vehicle is provided with a circular mounting flange having a dished wall extending radially outwards and circumferentially therefrom, a peripheral rim having a first edge and a second edge with the rim connected to an outer edge of the dished wall at an intermediate region of the rim, and a first lip extending from the first edge. Another road wheel for a tracked vehicle is provided with a mounting flange, a peripheral rim, at least one inner dished wall, at least one outer dished wall offset from the inner dished wall along the flange, and at least two connector walls with each connector wall extending between the inner dished wall, outer dished wall, and the peripheral rim.

Description:
[0001]    The invention was made in part with Government support. The Government may have certain rights to the invention. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The invention relates to non-pneumatic tires for use with tracked vehicles. 
         [0004]    2. Background Art 
         [0005]    Tracked vehicles have applications in military use, heavy commercial use, and others where the vehicle may be travelling over uneven terrain, carrying a heavy load, or the like. The vehicles have a track which interfaces with the ground to support or propel the vehicle. Wheels are located within the track to drive or support it. Some of the wheels are connected to the drivetrain of the vehicle. A tire is placed over the rim of the wheels to interface with the track to improve ride quality characteristics. The tires are typically made from a natural or synthetic rubber and are solid, or non-pneumatic. 
         [0006]    Typical failure modes of these rubber tires are blow-out and heat checking from high operating temperatures, cutting and chunking from sharp debris, and bonding failure at the rubber-wheel interface. Failure of the elastomer rubber tire on the road wheel may account for more than ninety-five percent of all road wheel failures. For temperature failures, the primary source of heat generation is hysteretic heating from the rubber, with vehicle speed and ambient temperatures as strong contributors. The higher the operating speed of the vehicle, the greater the number of hysteretic cycles the elastomer goes through, and consequently the higher the operating temperature. The thickness of the elastomer has a major affect on the hysteretic heating. Typically a thicker tire and a lower modulus generate greater hysteretic heating, but provide better damping for reduced vehicle vibrations. As a result the compound is blended for a compromise in these design features. 
         [0007]    For cutting and chunking, sharp pointed debris material indents the elastomer. Once the elastomer tensile forces at the tip of the debris exceed the tensile strength of the elastomer, a crack initiates and then begins to propagate. Two usual methods to prevent crack initiation include using a higher modulus elastomer or a thicker tire. Unfortunately, the tensile strength of elastomer decreases drastically with higher operating temperatures over 175 F or 200 F. The higher temperatures promote crack initiation by weakening the tire. 
         [0008]    Currently, tire improvements are being sought through use of higher temperature formulations, polyurethane or poly urea, or optimized width and thickness of the rubber. 
         [0009]    The cutting and chunking characteristics may be improved with polyurethane, but drawbacks include a lower operating temperature threshold, a harder ride with increased vibrations, additional cost, and greater susceptibility to contaminants and humidity during adhesion molding. 
       SUMMARY 
       [0010]    In one embodiment, a tire assembly for a tracked vehicle has an inner tire layer forming a first tube sized to substantially cover an outer surface of a rim of a wheel, and an outer tire layer forming a second tube with a larger diameter than the first tube, the outer tire layer adapted to contact a track of a vehicle. At least one carcass layer is interposed between the inner and outer tire layers to provide tensile and impact strength to prevent crack propagation from reaching the inner tire layer of the tire assembly, thereby prolonging the useful life of the tire assembly and reducing the frequency of replacement of the tire assembly. The inner and outer tire layers encapsulate the carcass layer to protect it from an environment of use. 
         [0011]    In another embodiment a wheel assembly for a tracked vehicle has a wheel with a circular mounting flange with a wall extending radially outwards and circumferentially therefrom, and a peripheral rim connected to an outer edge of the wall. The peripheral rim has an outer surface. The wheel assembly also has a tire with an inner layer sized to substantially cover the outer surface of the peripheral rim, at least one intermediate fabric carcass layer bonded to an outer surface of the inner layer, and an outer layer bonded to an outer surface of the at least one carcass layer. The outer layer is adapted to contact a track of a vehicle. The at least one intermediate carcass layer provides tensile and impact strength to prevent crack propagation from reaching the inner layer of the tire, thereby prolonging the useful life of the tire and reducing the frequency of replacement of the tire. 
         [0012]    Yet another embodiment provides a method of forming a tire assembly for a wheel of a tracked vehicle. An inner tire layer is provided as a first tube about a rim of a wheel. The inner tire layer is sized to substantially cover an outer surface of the rim. An outer tire layer is positioned about the inner tire layer as a second tube with a larger diameter than the first tube. The outer tire layer is adapted to contact a track of a vehicle. At least one carcass layer is interposed between the inner and outer tire layers. The carcass layer provides tensile and impact strength to prevent crack propagation from reaching the inner tire layer of the tire assembly, thereby prolonging the useful life of the tire assembly and reducing the frequency of replacement of the tire assembly. The inner and outer tire layers encapsulate the carcass layer to protect it from an environment of use. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a perspective view of an embodiment of a tracked vehicle; 
           [0014]      FIG. 2  is a perspective view of a pair of wheels and a section of track of the vehicle of  FIG. 1 ; 
           [0015]      FIG. 3  is a perspective section view of a tire and wheel according to another embodiment; 
           [0016]      FIG. 4  is a top section view of the tire and wheel of  FIG. 3 ; 
           [0017]      FIG. 5  is a perspective section view of the tire and wheel of  FIG. 3 ; 
           [0018]      FIG. 6  is a partial section view of a tire according to yet another embodiment; 
           [0019]      FIG. 7  is a schematic view of a tire and debris according to another embodiment; 
           [0020]      FIG. 8  is a section schematic view of a tire according to yet another embodiment; 
           [0021]      FIG. 9  is a section schematic view of a tire according to another embodiment; 
           [0022]      FIG. 10  is a partial view of a tire assembly according to an embodiment; 
           [0023]      FIG. 11  is a schematic view of a tire assembly according to another embodiment; and 
           [0024]      FIG. 12  is a schematic view of a tire assembly according to yet another embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for the claims and/or as a representative basis for teaching one skilled in the art to variously employ the present invention. 
         [0026]      FIG. 1  illustrates a tracked vehicle  20 . The tracked vehicle  20  may be an armored tank as shown, and may also be any military, commercial, or other tracked vehicle as is known in the art. The vehicle  20  has a track  22  to interact with an underlying surface  24 . The underlying surface may be a road, or uneven terrain such as dirt, rock, or the like. The track  22  is continuous and is supported by wheels  26 . The wheels  26  may include drive wheels  28  at the front or rear of the vehicle  20  to transfer power to the track  22 , and road wheels  30  to support the vehicle  20  on the track  22 . 
         [0027]      FIG. 2  illustrates a pair of wheels  26  interacting with a track section  22  of the tracked vehicle  20 . The pair of wheels  26  has a first wheel  32 , or outer wheel, and a second wheel  34 , or inner wheel, connected to one another along the mounting flange  36  of each wheel  26 . A gap  38  is formed between the wheels  32 ,  34 , which interacts with a guide  40  on the track  22  to retain and align the pair of wheels  26  with the track  22 . The interface between the guide  40  and one of the wheels  32 ,  34  transmits a lateral vehicle load to the track  22  during side slope operations and vehicle cornering, and maintains track alignment. Each wheel  26  also has a wear ring  44  on the inner surface of each wheel  26  adjacent to the gap  38 . The wear rings  44  interface with the guide  40  and protect the surface of the wheels  26 , which may extend the lifetime of the wheels  26 . 
         [0028]    Each wheel  32 ,  34  has a tire  42 , or an elastomeric pad, located circumferentially around each wheel  32 ,  34 . The tires  42  act as an interface between the wheels  32 ,  34  and the track  22 . 
         [0029]      FIGS. 3-5  illustrate an embodiment of a wheel assembly  46  with a wheel  48  and a tire  50 . The wheel  48  has a circular mounting flange  52  which allows for attachment to an adjacent wheel to form a pair of wheels to interact with a track. A wall  54  extends from the mounting flange  52  radially outwards and circumferentially. A rim  56  is connected to the outer edge of the wall  54 . The rim  56  has an outer surface  58 . The wheel  48  may be fabricated from steel, aluminum, magnesium, alloys, and other metals or materials as is known in the art. The wheel  48  may be forged or cast. Other shapes and cross sections for the wheel  48  are also contemplated as are known in the art. 
         [0030]    A tire  50  is positioned around the outer surface  58  or the rim  56  or the wheel  48 . The tire  50  may be a non-pneumatic structure that substantially covers the outer surface  58  of the rim  56 . The use of the phrase “non-pneumatic” with respect to the tire  50  does not preclude having air or another gas or fluid within the tire  50  structure. For example, an air bladder, a honeycomb layer containing a gas, or the like are contemplated for the tire  50 . The tire  50  has an inner layer  60  positioned adjacent to the rim  56 . An intermediate layer  62  is positioned on the outer surface of the inner layer  60 . An outer layer  64  is positioned on the outer surface of the intermediate layer  62  and designed to be in contact with the track of the vehicle. The inner and outer layers  60 ,  64  are made from natural rubber, synthetic rubber, or another material with similar properties. In one embodiment, the inner tire layer  60  has a stiffer compliance than the outer tire layer  64 . The intermediate layer  62  has at least one fabric carcass layer. The carcass layer  62  provides tensile and impact strength to the tire  50  and prevents crack propagation through the tire  50 , as shown in  FIG. 6 . The carcass layer  62  also has natural abrasion and tear resistance which is beneficial as the tire  50  wears. By preventing crack propagation from the outer layer  64  through the tire  50 , a crack cannot reach the inner layer  60  of the tire  50 , the useful life of the tire  50  is prolonged, and the frequency of replacement of the tire  50  is reduced. The inner and outer layers  60 ,  64  may encapsulate the carcass layer  62  to protect it from the environment of use when the vehicle is in the field. 
         [0031]    Referring back to  FIGS. 3-5 , the fabric carcass layer  62  may be made from polyester, nylon, steel, aramid, para-aramid, or other fibers as are known in the art. The fabric in the carcass layer  62  may be single ply or multiple ply. In one embodiment, the fabric in the carcass layer  62  is unidirectional and may be aligned with the direction of rotation of the wheel  46 , orthogonal to the direction of rotation of the wheel  46 , or positioned otherwise. In another embodiment, the fabric in the carcass layer  62  has a weave pattern with a first set of fibers in the weave positioned in a first fiber direction and a second set of fibers in the weave positioned in a second fiber direction. The first set of fibers may be made from the same material or a different material as the second set of fibers. The first fiber direction may be orthogonal to the second fiber direction, or alternatively, may be arranged at any angle relative to the other. For example, as shown in  FIG. 7 , the first fiber direction is generally aligned with a rotational direction of the wheel with the second fiber direction generally orthogonal to the first fiber direction. Alternatively, the first fiber direction is offset from a rotational direction of the wheel with the second fiber direction generally orthogonal to the first fiber direction. 
         [0032]    Referring back to  FIGS. 3-5 , the inner layer  60 , intermediate layer  62 , and the outer layer  64  may be bonded together during the manufacturing process for the tire  50  by using an adhesive or through another process as is known in the art. 
         [0033]    In one embodiment the tire  50  is bonded to the wheel  48  using an adhesive. In another embodiment, the tire  50  is undersized relative to the rim  56  of the wheel  48 , which retains the tire  50 . Alternatively, one or two axial rings  66  (in phantom) are positioned on the outer surface  58  of the rim  56  and on either side of the tire  50  to mechanically retain the tire  50  on the wheel  48 . In another embodiment, the outer surface  58  of the rim  56  is machined to have a specified roughness or a machined pattern to mechanically retain the tire  50  on the wheel  48 . 
         [0034]      FIG. 8  illustrates another embodiment of a tire  70  for use with a wheel  26 . The tire has an inner layer  72  and an outer layer  74 . The inner and outer layers may be different thicknesses to provide varying damping and wear characteristics. The intermediate layer  76  has multiple fabric carcass layers. The intermediate layer as shown has a pair of outer fabric layers  78 , a central fabric layer  80 , and additional elastomer layers  82  separating them. The elastomer layer  82  may be a natural or synthetic rubber or a polymer material. The pair of outer fabric layers  78  and the central fabric layer may contain the same or different weave patterns or fiber material. 
         [0035]      FIG. 9  illustrates an embodiment of a tire  84  for use with a wheel  26 . The tire has an inner layer  86  and an outer layer  88 . The intermediate layer  90  has multiple fabric carcass layers. The intermediate layer  90  as shown has a pair of fabric layers  92  and an additional elastomer layer  94  separating them. The elastomer layer  94  may be a natural or synthetic rubber or a polymer material. The pair of fabric layers  92  may contain the same or different weave patterns or fiber material. 
         [0036]    Referring back to  FIG. 2 , the tire  42  may be manufactured in several ways including: a molded continuous loop belt or splicing a belt that is prepared to length. A tire  100  with a spliced belt connection is shown in  FIG. 10 . For a spliced belt tire  100 , a vulcanized step splice may be used with a series of steps prepared on the two tire ends  102 ,  104 . These ends  102 ,  104  overlap the functional layers within the tire  100 . The splice then undergoes a vulcanizing process for curing. When prepared properly, a vulcanized step splice can have similar load and bend ratings as the continuous portion of the tire  100 . 
         [0037]    The spliced belt tire may be attached to the wheel  32  using compression molding as shown in  FIG. 11 . The tire  100  has an inner layer  106  and an outer layer  108  which may be made from an uncured rubber. The intermediate layer  110  includes a fabric carcass layer. The layers of the tire  100  are placed within the compression mold  112 . The outer piece  114  of the compression mold  112  is an outer die. The inner piece  116  of the compression mold  112  is either an inner die to fabricate a tire  100  alone, or the wheel  32  for direct compression molding of the tire  100  to the wheel  32 . The outer piece  114  compresses the tire  100  against the inner piece  116  and heats it to form and cure the circular tire  100 . Final curing of the tire in the compression mold  112  may also eliminate the joint as a potential weak spot. Compression molding the tire  100  directly onto the wheel  26  provides a strong bond between the inner layer  106  the rim of the wheel  32 . 
         [0038]    Referring back to  FIG. 3 , in other embodiments, the tire  50  may be attached and retained to the wheel  46  using a tensile force in the tire  50  to maintain a friction fit between the tire  50  and the wheel  46  or a structural adhesive may be used to bond the tire  50  to the wheel  46 . In addition to the friction fit or the use of adhesive, the tire  50  may be mechanically retained on the wheel  46 , and not molded directly to the wheel  46 . This allows for replacement of the tire  50  in the field instead of returning them for reconditioning. An axial ring  66 , or retention ring, retains and supports the tire  50  on one or both ends of the rim  56  to prevent the tire  50  from “walking off” the rim  56 . In this configuration, the one of the two rings  66  is fixed while the other one of the rings  66  may be removed for assembly and disassembly of the tire  50 . 
         [0039]    The use of an adhesive bond or a friction fit with the tire  50  allows a tire  50  to be replaced in the field without the need for a remote refurbishment process to replace the tire  50 . 
         [0040]    For a friction fit tire  50 , the tire  50  is undersized relative to the wheel  46  circumference. When the tire  50  is pressed over the wheel  46  a tensile force is developed in the tire  50 , which creates a static contact pressure between the wheel  46  and tire  50 . Depending on the initial preload based on the tire  50  sizing, the contact pressure can be relatively high, creating a significant friction force to resist tire slippage and shear off of the wheel  46 . In one embodiment, the tire pretension is combined with an adhesive for a stronger bond. One method of assembling the tire  50  to the wheel  46  is depicted in  FIG. 12 , showing a press operation. The tire  50  is placed over a mandrel  120 , which is adjacent to the wheel  48 . A force is applied to the tire  50  causing it to slide on the mandrel and onto the wheel  48 . Disassembly the tire  50  from the wheel  48  may include cutting the tire  50  and peeling it from the wheel  48 . The wheel  48  rim may need to be cleaned if an adhesive is used before assembling a replacement tire  50  to the wheel  48 . 
         [0041]    The wheel  46  may additionally have a surface finish applied to the outer surface  58  of the rim  56 , which may include scoring, blasting, machined grooves or ridges, or alternate wheel rim  56  geometry such as a convex or a concave profile to aid in retention of the tire  50 . 
         [0042]    While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, features of various implementing embodiments may be combined to form further embodiments of the invention.