Abstract:
A process for forming a reinforcement for a resilient, structurally supported wheel includes the steps of placing a supporting member, such as a stay, on a cylindrically shaped mandrel, winding a reinforcing wire on the mandrel over the supporting member while heating the wire to embed the wire in the supporting member, wherein, upon cooling, the wire is bonded to and supported by the supporting member to maintain a cylindrical shape

Description:
BACKGROUND AND SUMMARY OF THE INVENTION  
       [0001]     The invention relates to structural reinforcements for resilient wheels and wheel-tires, and in particular, to reinforcements for non-pneumatic tires that are formed by molding processes. More particularly, the invention is directed to a method for forming a wire reinforcement for a non-pneumatic resilient wheel-tire that is self-supporting, which allows the reinforcement to be made independent of the tire forming process.  
         [0002]     U.S. application Ser. No. 10/618,924, owned in common with the present application, discloses a non-pneumatic resilient wheel-tire having a deformable, load supporting ring and a plurality of webs connecting the ring to a hub. The webs act in tension to transmit the load on the ring to the hub, which is similar to the load supporting and transmitting mechanism of a pneumatic tire. The ring is capable of deforming on the ground contact surface, which provides the tire the ability to transmit traction and steering forces similar to a pneumatic tire. The ring includes a support ply embedded in the ring to control the deformation of the ring when loaded. According to one embodiment, the support ply is a cylindrical wire coil.  
         [0003]     A non-pneumatic tire as described in the aforementioned application may be made in a molding process, in which the ring and webs are formed of the same material injected or caused to flow into a mold. In such a process, a difficulty arises in forming the support ply and correctly positioning it in a mold for the non-pneumatic tire. It would be convenient to form the support ply in a separate step, and insert and position it in the mold before the ring and web material is injected.  
         [0004]     The invention provides a method for forming a wire reinforcement structure that is self-supporting and allows the reinforcement structure to be made separate from the tire itself, for example, at a more convenient time, and inserted in the tire mold.  
         [0005]     According to the invention, a wire support structure is formed on a mandrel, and the method includes the steps of placing a supporting member on a cylindrically shaped mandrel, winding a reinforcing wire on the mandrel over the supporting member while heating the wire to embed the wire in the supporting member, wherein, upon cooling, the wire is bonded to and supported by the supporting member to maintain a cylindrical shape.  
         [0006]     The wire may be heated by resistance heating, inductance heating, or another convenient method.  
         [0007]     According to one embodiment of the invention, the supporting member comprises a sheet of plastic material wrapped on the mandrel. According to a preferred embodiment, the supporting member comprises at least two plastic stays or ties placed on the mandrel. In accordance with a more preferred embodiment, the supporting member includes three plastic stays, which are disposed so that respective free ends extend from an end of the wire coil to provide positioning spacers for correctly positioning the supporting member in a mold for making a resilient wheel-tire.  
         [0008]     According to the invention, the step of placing the plastic ties includes placing the ties in equally spaced relation on the mandrel.  
         [0009]     The method according to the invention further comprises the step of providing a mandrel having grooves for accepting the plastic ties.  
         [0010]     According to another aspect of the invention, the method includes the step of applying an adhesive to at least one of the supporting member and the at least two plastic ties, wherein the step of heating the wire activates the adhesive. According to a further embodiment, the adhesive is a UV cured adhesive and includes the step of applying UV energy to the coated wire to activate the adhesive. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The invention will be better understood by reference to the following detailed description in conjunction with the appended drawings, in which:  
         [0012]      FIG. 1  is a perspective view of a wire coil reinforcement in accordance with the invention;  
         [0013]      FIG. 2  is a perspective view of a wire coil reinforcement according to an alternative embodiment of the invention; and,  
         [0014]      FIG. 3  is a schematic view of an illustrative apparatus for making the wire coil reinforcement of  FIG. 2 . 
     
    
     DETAILED DESCRIPTION  
       [0015]     A wire coil reinforcement  10  for a tire is shown in  FIG. 1 . The reinforcement  10  is intended to be embedded in the outer supporting band of a non-pneumatic tire of the type described in commonly owned US patent application Ser. No. 10/618,924, the disclosure of which is incorporated herein by reference. The wire coil reinforcement  10  of the present invention is useful in other tire constructions or tire-like structures, as will be apparent to those skilled in the art, and the description here is meant to be illustrative, rather than limiting.  
         [0016]      FIG. 1  shows a wire coil  12  wrapped on a supporting member  14 , which in the illustrated embodiment is a sheet of plastic material. The wire coil  12  and supporting member  14  are formed in a cylindrical shape, and are intended to be embedded in an outer ring of a resilient wheel tire as described in the aforementioned US patent application.  
         [0017]      FIG. 2  shows an alternative, preferred embodiment of the wire coil reinforcement, in which the supporting member comprises a plurality of plastic stays or ties  16 . The supporting member sheet  14  and stays  16  help maintain the wire coil in the cylindrical shape so that the wire reinforcement may be readily handled and placed in a mold for forming the wheel tire. An outer edge  15  of the sheet  14  and the free ends  17  of the stays  16  extend beyond the last turn of the wire coil  12 , and are disposed to provide a level base for accurately positioning the supporting member in a mold.  
         [0018]      FIG. 2  has been simplified for clarity by illustrating only a front of the coil and omitting illustration of rear portion of the wire turns. At least one, and preferably a plurality of, stays or ties  14  supports the wire  12  in the cylindrical shape. Three stays  14  are illustrated in  FIG. 1 , although it should be understood that a fourth stay opposite the centrally positioned stay in  FIG. 2  is omitted. According to one aspect of the invention, at least three stays  14  are needed to provide a base for the coil allowing it to stand with a central axis perpendicular to the supporting surface. This is useful in accurately positioning the coil in a mold.  
         [0019]     The number and spacing of stays  16  is determined as that needed to provide the necessary or desired dimensional stability to the coil. A number of stays other than as shown may be used depending on the size of the coil and size of the wires used. The stays  14  are bonded to the wire  12 , and the wire is preferably embedded in the stays. The stays  14  are narrow bars having a length preferably greater than the axial length of the wire coil to provide the base described above, and having a thickness sufficiently greater that the thickness of the wire  12  to allow the wire to become embedded in the stay.  
         [0020]     The supporting member sheet  14  or stays  14  are advantageously formed of a material that is compatible with the material of the supporting band of such a tire to facilitate bonding and integrating in the load supporting band of a resilient wheel tire. In such a case, an adhesive or bonding agent may be applied to the stays  14  during the process for forming the supporting band. A heat-activated adhesive could be applied to the wire, and activated during the heating step. Preferably, the sheet  14  or stays  16  are formed of the same material as the load supporting band of the wheel, which facilitates bonding to the band and ensures that that the material properties of the stays are compatible with the supporting band material.  
         [0021]     The wire  12  is formed to have sufficient tensile strength to perform the supporting function. Advantageously, steel cord used in tire tread belts has been found to be useful. Steel cord may be coated or treated to facilitate bonding with the material of the stay and the supporting band, as will be appreciated by those skilled in the art. The diameter of the wire may be selected according to the tensile properties needed for the particular wheel.  
         [0022]      FIG. 3  illustrates schematically an apparatus for forming a wire reinforcement of the type shown in  FIG. 2  in accordance with the invention. Those of skill in the art will understand that a supporting sheet  14  may be substituted for the stays  16  described below. The apparatus includes a mandrel  20  attached by a shaft  22  to a motor  24 . The mandrel  20  surface includes grooves  26  formed in the axial direction of the mandrel for retaining the stays during the winding process.  
         [0023]     A wire supply reel  30  fees wire to a distributor  34  which travels on a reciprocating drive  36  to place the wire  12  on the mandrel with appropriate tension and pacing.  
         [0024]     According to one embodiment, an electric contact  40  on wire supply  30  provides electric current to the wire  12  during the winding process. The mandrel  20  has an electrically conductive surface, and the wire  12  wound in contact with the mandrel shorts the electric current, thus allowing current to flow between the contact  40  and the mandrel. Resistance in the wire  12  causes it to heat and embed into the plastic stays  16 . When the winding process is complete, the wire  12  and stays  16  are allowed to cool, which bonds the wire to the stays.  
         [0025]     Alternatively, other heating means could be provided, for example, an inductive heater  42  can heat the wire immediately prior to it being laid on the mandrel. Other heating means could be used.  
         [0026]     Heating the wire is preferred as a way to control the resultant heating of the stays or sheet to be sufficient for embedding the wire, but not causing other change to the stays or sheet, for example, allowing the wire to cut through the stay or sheet, or causing a change in shape of the stay or sheet.  
         [0027]     The formed coil  10  may then be removed from the mandrel  20 . To facilitate removal, a collapsible mandrel may be provided. The coil  10  is self-supporting, and may conveniently be stored or held until needed for the tire molding process. The coil  10  may also be conveniently handled, in particular, when placing in a mold.