Patent Document

FIELD OF THE INVENTION 
       [0001]    The subject matter of the present invention relates to a compliant hub as may be used in a non-pneumatic wheel. 
       BACKGROUND OF THE INVENTION 
       [0002]    The details and benefits of non-pneumatic tire constructions are described e.g., in U.S. Pat. Nos. 6,769,465; 6,994,134; 7,013,939; and 7,201,194. Certain non-pneumatic tire constructions propose incorporating a shear band, embodiments of which are described in e.g., U.S. Pat. Nos. 6,769,465 and 7,201,194, which are incorporated herein by reference. Such non-pneumatic tires provide advantages in tire performance without relying upon a gas inflation pressure for support of the loads applied to the tire. A typical example of such non-pneumatic tires possess a central hub, an inner interface member joined to the central hub, a tread band to interface with the ground surface, an outer interface member joined to or integral with the tread band, and a plurality of web elements connecting the inner interface member to the outer interface member or tread band. 
         [0003]    Such non-pneumatic rims or hubs require a relatively thin mounting surface through which fasteners, such as lug bolts or studs, may pass to mount the tire to the vehicle and a relatively wide web element mounting surface to allow a more uniform deformation and stress distribution across the web elements. The hub, generally constructed of metal, may be constructed as two pieces, a vertical central portion and a substantially cylindrical piece or “can” which are fastened together, or cast as a single piece of a large mass of metal. The hub may represent a significant cost of the non-pneumatic tire. 
         [0004]    Occasionally a non-pneumatic tire, like a pneumatic tire, experiences an impact event that exceeds a certain force causing undesired permanent damage. Such events may occur when encountering a curb or other obstacle at excessive speed. During such an event, sometimes referred to as a “pinch shock event” permanent plastic deformation or fracturing of the rim or damage to other wheel or tire components is possible. 
         [0005]    Accordingly, a hub that can simplify and reduce the cost of construction while increasing durability of the wheel would be beneficial. Such a hub that can be incorporated into a variety of non-pneumatic tire constructions would be particularly useful. 
       SUMMARY OF THE INVENTION 
       [0006]    Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
         [0007]    In one exemplary embodiment, the present invention provides a partially compliant hub for securing a non-pneumatic structurally supported wheel having a disk shaped center portion and a toroidal shaped outer portion circumferentially placed about the periphery of said disk shaped center portion, where said center disk shaped center portion has a higher modulus of elasticity than the toroidal shaped outer portion. 
         [0008]    In another exemplary embodiment, the partially compliant hub&#39;s disk shaped center portion is constructed of stamped steel. 
         [0009]    In another exemplary embodiment, the partially compliant hub&#39;s disk shaped center portion is constructed of cast metal. 
         [0010]    In another exemplary embodiment, the partially compliant hub&#39;s disk shaped center portion possesses a plurality of apertures circumferentially spaced near the periphery of the disk and the toroidal shaped outer portion 
         [0011]    In another exemplary embodiment, a non-pneumatic structurally supported wheel comprises: a hub portion comprising a mounting disk possessing a generally circular outer periphery and an axially elongated toroidal structure securely mounted concentrically with the mounting disk and encapsulating said outer periphery of the mounting disk; a compliant load supporting band disposed radially outward and concentrically with said hub; a plurality of tension based web elements extending between said hub portion and said compliant load supporting band; wherein said mounting disk is constructed of a material that has a modulus of elasticity greater than the modulus of elasticity of the material used to construct said outer toroidal structure wherein said plurality of web elements and said toroidal structure are molded as a unitary structure. 
         [0012]    These embodiments, and the embodiments that follow, allow for a less expensive partially compliant hub structure that is more resistant to plastic deformation, lighter weight, and results in a wheel structure that is even more compliant than a wheel having a rigid hub structure. 
         [0013]    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 
         [0014]    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: 
           [0015]      FIG. 1  provides a perspective view of an exemplary embodiment of a non-pneumatic tire as may incorporate a partially compliant hub of the present invention. 
           [0016]      FIG. 2  provides a side view of the embodiment of the compliant hub as viewed from the side to which it is mounted to the vehicle. 
           [0017]      FIG. 3  provides a radial section view of the tire of  FIG. 2  as taken along line  3 - 3  in  FIG. 2 . 
           [0018]      FIG. 4  is a radial section view of a portion of an exemplary embodiment of a compliant hub having a toroidal portion secured to an inner interface element. 
           [0019]      FIG. 5  is a side view of the inside surface of the disk portion of the hub without the encapsulating toroidal portion. 
           [0020]      FIG. 6  is a partial perspective view of a portion of an exemplary embodiment of a compliant hub having cut out portions and web portions extending radially. 
           [0021]      FIG. 7  is a side view of an exemplary embodiment having web elements effectively shortened by bridging two adjacent web elements at the inner interface element or toroidal portion of the hub. 
       
    
    
       [0022]    The use of identical or similar reference numerals in different figures denotes identical or similar features. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    The present invention provides a partially compliant hub that may be used e.g., in a non-pneumatic tire. For purposes of describing the invention, reference now will be made in detail to embodiments and/or methods of the invention, one or more examples of which are illustrated in or with 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 or steps illustrated or described as part of one embodiment, can be used with another embodiment or steps to yield a still further embodiments or methods. 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. 
         [0024]    The following terms are defined as follows for this disclosure: 
         [0025]    “Axial direction” or the letter “A” in the figures refers to a direction parallel to the axis of rotation of for example, the shear band, tire, and/or wheel as it travels along a road surface. 
         [0026]    “Radial direction” or the letter “R” in the figures refers to a direction that is orthogonal to the axial direction and extends in the same direction as any radius that extends orthogonally from the axial direction. 
         [0027]    “Equatorial plane” means a plane that passes perpendicular to the axis of rotation and bisects the shear band and/or wheel structure. 
         [0028]    “Radial plane” means a plane that passes perpendicular to the equatorial plane and through the axis of rotation of the wheel. 
         [0029]      FIG. 1  provides an exemplary embodiment of a non-pneumatic tire  101  as may incorporate a partially compliant hub  201  of the present invention. The compliant hub  201  of the present embodiment allows for resistance to permanent deformation in an impact event by allowing elastic deformation during the event, and return to its original shape afterwards. 
         [0030]    In a test performed using a pendulum impact device, for example, a conventional metal “can” hub was compared to a hub constructed in accordance with the invention disclosed and having a metal inner hub disk shaped portion having an outer periphery surrounded by a polyurethane toroid shaped outer hub portion. The conventional metal “can” hub plastically deformed after an impact having 1390 Joules and 6257 kilograms force while the hub constructed in accordance with the invention withstood 3426 Joules and 9471 kilograms force without plastic deformation. 
         [0031]      FIG. 2  provides a side view of the embodiment of the non-pneumatic tire  101 . The embodiment shown possesses a tread band  109 , an outer interface band  119 , tension bearing web elements  129 , an inner interface band  139 , and an inner hub  201 . A plurality of wheel hub fastener apertures  209  are shown placed in a circular pattern. Each wheel hub fastener aperture  209  allows a portion of a wheel hub fastener to pass through to secure the wheel to the vehicle. Generally, the wheel hub fastener is a threaded wheel stud which is secured on the outside of the hub  201  with a lug nut. Alternatively, the wheel hub fastener may be a wheel bolt passing through from the outside of the wheel into a threaded aperture on the vehicle. It should be understood that while these two fasteners represent two alternatives, any style fastener may be utilized with the invention. It should also be understood that the number and placement of the fastener apertures  209  may vary. 
         [0032]    The hub  201  of the current embodiment is comprised of a center disk portion  205  and a relatively more flexible outer toroidal portion  259 . The inner interface band  139  may be a separate component bonded to the outer surface of the outer toroidal portion  259  or the inner interface band  139  may be integral with outer toroidal portion  259  such as where the web elements  129 , and outer cylindrical portion  259  are molded from a continuous mold cavity. In the case where the inner interface element is integral with the outer toroidal portion, the term “inner interface element” may be used to refer to the “outer toroidal portion” and vice versa. 
         [0033]    The disk portion  205  of the hub  201  present embodiment is formed from a stamped sheet of metal, bent into a generally flat disk-like shape. It should be understood that the center disk portion  205  may also be cast or forged, and may be constructed from a material having a stiffness greater than that of the toroidal portion  259  which, in the present embodiment is constructed of a material having a lower stiffness than the disk portion  205 . The toroidal portion  259  of the present embodiment possesses a toroidal shape which is elongated in the axial direction forming a generally cylindrical shape. The outer circumference of the center disk portion  205  is bonded to the outer toroidal portion  259 . 
         [0034]      FIG. 3  shows a cross-sectional view tire  201  taken along line  3 - 3  in  FIG. 2 . This view is perpendicular to the equatorial plane of the tire. The outer periphery  207  of the center disk portion  205  of the present embodiment is encapsulated by the toroidal portion  259  of the hub  201 . 
         [0035]    The disk portion  205  of the present embodiment  101  is positioned parallel with an equatorial plane of the tire. Disk portion  205  possesses bend  219  in the outer periphery  207  so that the outer portion is circumferentially bent approximately 90 degrees forming a lip around the outer circumference of the disk  205 . The bend  219  exposes a larger surface area to the radial forces generated by the weight carried by the tire and allows for greater bonded surface area of the disk portion  205  to the toroidal portion  259 . 
         [0036]    The toroidal portion  259  of the present embodiment possesses a cross section with an inside concave curved portion  265  between the disk  205  and inside portion  115  of the wheel and an inner concave portion  269  transitioning to a sloped but flat portion  271  between the disk  205  and the outside portion  117  of the wheel. The sloped and concave portions  271 ,  269  and  265  create a tapering of the toroid away from the disk  205 . 
         [0037]    In the present embodiment, the web elements  129  and toroidal portion  259  are formed of the same material. In this embodiment, the disk portion  205  of the hub  201  and tread band  109  are positioned within a mold. An elastomeric material is then poured into the mold forming the outer interface band  119 , web elements  129  and toroidal hub portion  259  as a unitary structure. The elastomeric material in the present embodiment may be any suitable elastomeric material such as a natural or synthetic rubber, polyurethane, foamed rubber and foamed polyurethane, segmented copolyesters and block co-polymers of nylon. Molding of the toroidal portion and web elements simplifies construction of the wheel and reduces cost, while allowing for a compliant composite hub particularly suited for a tension based non-pneumatic wheel. Cost savings and simplification of construction are evident by simplification of the construction of the hub by eliminating the need to construct a cylindrically shaped portion extending in the wheel&#39;s axial direction to support the load of the web elements. 
         [0038]    Alternatively, the hub portion  201  is formed in a previous step by placing a center disk  205  within a mold, molding the toroidal portion  259 , removing the hub  201  from the mold then placing the formed hub  201  and tread band  109  in a different mold and pouring an elastomeric material forming the outer interface band  119 , web elements  129  and inner interface band  139 . This alternative embodiment  103 , as shown in  FIG. 4 , allows the designer to select a material having a different stiffness for the toroid portion  259  of the hub  201  than the outer interface band  119 , web elements  129  and inner interface band  139 . In this particular embodiment, the toroidal portion of the hub may be constructed a polymer including an elastomer, plastic, or composite, such as glass filled nylon. Thus the toroidal portion  259  of the hub  201  may have a different modulus than the material used to form the web elements  129 . 
         [0039]    It should be understood that in any of the embodiments herein the outer interface band  119  may possess reinforcing elements, such as metallic cords or natural or synthetic cords or textiles, or the tread band  109  may possess reinforcing elements, or some combination of both the interface element  119  and tread band  109  possessing reinforcing elements such as metallic cords or natural or synthetic cords or textiles. 
         [0040]    In yet another embodiment, the tread band may be omitted and the outer interface band may serve functionally as a tread band, possessing both reinforcing elements and interfacing with the surface on which the wheel operates. 
         [0041]      FIG. 5  shows a view of the inside surface  223  of the disk  205  portion of the hub  201  without the encapsulating toroidal portion  259 . The outer periphery  207  of the disk  205  possesses a plurality of apertures  213  spaced circumferentially about the disk. In the present embodiment, when the outer toroidal portion is molded around the periphery  207  of the disk  205 , the apertures  213  are embedded within the elastomeric material. During the molding process, the apertures  213  promote the flow of the elastomeric material prior to curing. The apertures  213  also allow the elastomeric material to encircle localized portions of the disk further securing the disk  205  to the toroidal portion  259  of the hub  201 . In alternative embodiments the apertures  213  may be present in a different quantity or absent altogether. A central axle aperture  221  may be positioned on the disk  205  to allow for initial alignment of the wheel on a vehicle, such as a vehicle hub. Wheel fastener apertures  209  spaced circumferentially allow the assembled wheel to be securely fastened to the vehicle. While four fastener apertures  209  are shown, it should be understood that the number and/or spacing of the apertures  209  may vary depending upon the application. 
         [0042]    The embodiments illustrated above show a toroidal portion possessing a smooth surface. Alternatively, as shown in  FIG. 6 , the toroidal portion  259  of the present invention may possess depressions  231  and webs  233  along the central facing surface of the toroidal portion, the central facing surface being along the inside surface  265  and/or outside surface  269 ,  271  such as shown in  FIG. 6 . It should be understood that as used herein, a “toroidal” shape includes toroidal shapes which may have webbed or cut-out features, or surfaces which are textured or otherwise marked. 
         [0043]    Another embodiment is shown in  FIG. 7  wherein each web element  129  of an adjacent pair of web elements  129  is effectively shortened by partially filling the void space adjacent to the hub and between the adjacent web elements  129 . This filled area  131  or “rib” increases the stiffness of the hub and increases the torsional stiffness of the wheel. 
         [0044]    It should be understood that other web element configurations and geometries may be used within the scope of the invention, including web elements which are interconnected such as where they may form a honeycomb or other pattern. 
         [0045]    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.

Technology Category: 7