Abstract:
An improvement in tire retreading is provided, and more specifically, a new device is provided for constraining a tread band onto the tire casing during retreading operations without requiring enclosure of the tread area. One or more membranes engage features on the tread band so as to apply a tensioning force to the tread band and thereby maintain the position of the tread band against the casing of the tire. The tensioning force is applied without enveloping the entire tread region of the tread band within the membrane(s).

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an improvement in tire retreading and, more specifically, to a new device for constraining a tread band onto the tire casing during retreading operations without requiring enclosure of the tread area. 
       BACKGROUND OF THE INVENTION 
       [0002]    In one type of tire retreading operation, a worn tread is stripped or buffed from the crown of the tire casing and a new tread rubber is bonded in place. A new, cured tread band is placed on the tire casing with a bonding layer of for example, gum rubber placed between the crown of the tire casing and the cured tread band. In order to cure the bonding material and any other uncured portions of the tire casing, traditionally the entire assembly is enclosed within a curing membrane, evacuated, and placed into an autoclave for heat and pressure treatment. The curing membrane acts to hold the tread against the casing and, due to the presence of a vacuum within the membrane, also assists in molding or smoothing the surface of the uncured bonding material used for joining the tread to the casing. The membrane can also assist in smoothing other locations such as repaired areas on the tire. The vacuum also assists in evacuating gases trapped in the casing or in a repair between the casing and the tread. 
         [0003]    The use of a curing membrane presents certain challenges in tire retreading operations. The entire tire assembly, including the tread rubber, must be placed within a relatively tight fitting membrane. This step can be manually intensive. Also, because the membrane envelopes the entire tire assembly and acts as an insulator, more energy is required to properly heat the assembly and achieve vulcanization. The impact of this insulation on curing can be particularly significant for the tread because the vacuum present between the tread grooves and the membrane further reduces the flow of heat into the bonding material. While necessary to affix the tread to the buffed tire, the pressure of the membrane or tension therein can also sometimes deform the tread undesirably. Finally, the membranes are relatively expensive and tend to have a short life. 
         [0004]    Therefore, a device for fixing the tread rubber against the tire casing while providing improvements in heat transfer, membrane life, handling, and other benefits would be useful. 
       SUMMARY OF THE INVENTION 
       [0005]    Objects 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. 
         [0006]    In one exemplary embodiment, the present invention provides a device for maintaining a tread band onto a tire during retreading operations. The tire defines a crown, bead portions, and sidewalls extending between the bead portions and crown. The tread band is positioned onto the crown of the tire and defines a tread region. The device includes a pair of opposing connectors with each connector positioned on a lateral side of the tread band. A pair of fastening elements are included, and each fastening element is attached to one of the opposing connectors. At least one membrane is connected to the fastening elements and extends over at least a portion of the sidewalls of the tire and away from the tread band without enclosing the tread region of the tire. The membrane and the fastening elements are configured to provide a tensioning force that holds the tread band onto the tire. 
         [0007]    Various additions or modifications can be made to this exemplary embodiment of the invention. For example, the membrane may extend over the bead portions and through the interior of the tire. The opposing connectors may each include a projection positioned along a lateral side of the tread band and extending circumferentially around the tire. Alternatively, the opposing connectors may each include a tread feature configured for complementary attachment with one of the fastening elements. The fastening elements may be formed integrally with the membrane or may be formed as a separate element that connected with or attached to the membrane. 
         [0008]    Additionally, each of the pair of opposing connectors may include a projection extending from the tread band along a lateral side of the tread band, and each of the fastening elements may include a hook-like element for attachment to the projection. Alternatively, each of the pair of opposing connectors may include a recess positioned along the tread band, and each of the fastening elements may include a finger for receipt into the recess. 
         [0009]    In another exemplary embodiment of the invention, a device is provided for maintaining a tread band onto a tire during retreading operations. The tire defines a crown, bead portions, and sidewalls extending between the bead portions and crown. The tread band is positioned onto the crown of the tire and defines a tread region. The device includes a pair of opposing connectors with each connector positioned on a lateral side of the tread band; a pair of fastening elements, with each fastening element attached to one of the opposing connectors; and a pair of membranes, with each membrane connected to one of the fastening elements. Each membrane extends along at least a portion of one of the sidewalls of the tire and away from the tread band without enclosing the tread region of the tire. The membranes, the fastening elements, or both are configured to provide a tensioning force holding the tread band onto the tire. 
         [0010]    A pair of base rings may also be provided with this exemplary embodiment. In such case, each base ring is positioned along a sidewall of the tire, and the membranes extend between one of the connectors and one of the base rings. Additionally, a pair of lips may also be provided with each lip positioned proximate to one of the base rings and configured for receipt of one of the bead portions of the tire. Each membrane may also include a port for the introduction of a vacuum between each membrane and the tire. 
         [0011]    In still another exemplary embodiment, the present invention provides a device for maintaining a tread band onto a tire during retreading operations. The tire includes sidewalls and bead portions. The tread band is positioned onto the tire and defines a tread region. The device includes a pair of connectors with each connector defined along a lateral side of the tread band and extending circumferentially around the tire; a pair of fastening elements with each fastening element attached to one of the opposing connectors; and a pair of membranes with each membrane connected to one of the fastening elements. Each membrane extends along a sidewall of the tire so as to enclose the sidewalls and bead portions of the tire within the membranes without enclosing the tread region of the tire. The membranes, the fastening elements, or both are configured to provide a tensioning force holding the tread band onto the tire. 
         [0012]    This exemplary embodiment may also include a pair of disks attached to each of the membranes. As such, the disks are positioned along the axis of rotation of the tire and may include apertures for the introduction of fluids such as hot air or steam into the interior of the tire. 
         [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]      FIGS. 1-3  are cross-sectional views, taken along the meridian plane of a tire, illustrating exemplary embodiments of the present invention. As used herein, meridian plane refers to a plane containing the axis of rotation of the tire. 
           [0016]      FIGS. 4-5  are perspective and cross-sectional views of additional exemplary embodiments of the present invention. 
           [0017]      FIGS. 6-9  are partial, cross-sectional views, taken along the meridian plane of a tire, illustrating still other exemplary embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    To provide advantageous improvements as described herein, the present invention provides a device for maintaining the position of a tread band against a tire (i.e. tire casing) during retreading operations without enclosing the entire tread region of the tread band in an insulating envelope. 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. 
         [0019]    As used herein, “meridian plane” refers to a plane containing the axis of rotation of a tire, and “equatorial plane” refers to the plane that is perpendicular to the tire&#39;s axis of rotation and passes through the center of the tire&#39;s tread. 
         [0020]    The use of similar reference numerals between the figures is intended to represent the same or analogous features among the various exemplary embodiments of the invention. 
         [0021]      FIG. 1  provides a cross-section view of an exemplary embodiment of a retaining device  160  of the present invention. Tire  100  represents a casing that has been prepared for retreading operations by e.g., buffing the crown  115  of the casing to remove worn tread and by performing other repairs as needed. Tire  100  includes a pair of bead portions  120  located on opposing sides (i.e. opposite sides of the equatorial plane P) of the tire. Also on each side of tire  100 , sidewalls  125  extend between the crown  115  and bead portions  120 . A layer of uncured bonding material  130  is disposed between a tread band  135  and crown  115 . 
         [0022]    During processing steps in which heat and pressure will be applied, bonding material  130  will join tread band  135  to crown  115 . In order to maintain the position of the tread band  135  for this part of the retreading operation, exemplary retaining device  160  of the present invention provides a clamping or tensioning force that pulls on each of the lateral sides  140  of tread band  135 . More specifically, each lateral side  140  of tread band  135  includes at least one of a pair of opposing connectors  145 —i.e., connectors  145  are located on each side of the equatorial plane P of tire  100 . For the exemplary retaining device  160  of  FIG. 1 , connectors  145  are constructed as a projection  146  extending circumferentially along each lateral side  140  of tread band  135 . Fastening elements  150  attach to each connector  145 . Fastening elements  150  are in turn attached to (or may be formed integrally with) a membrane  155  that extends along sidewalls  125  of tire  100 . For the exemplary embodiment of  FIG. 1 , membrane  155  also passes into the interior cavity  165  of tire  100  and extends through the equatorial plane P to span between opposing connectors  145 . Together, fastening elements  150  and membrane  155  provide a tensioning force to pull tread band  135  against crown  115 . As such, the position of tread band  135  can be maintained during retreading operations. 
         [0023]    During retreading operations, a vacuum can be applied to the space  170  located between membrane  155  and tire  100 . Such vacuum will pull membrane  155  against tire  100  and assist with molding or smoothing the exterior and interior of tire  100  as heat and pressure are applied. For example, at the interface between tread band  135  and tire  100 , membrane  155  can help smooth the bonding material  130 . A vacuum in space  170  will also contribute to the tensioning force provided to tread band  135  by membrane  155  and fastening element  150 . 
         [0024]    Membrane  155  may be constructed from a variety of materials including e.g., various rubbers, polymers, and composite materials. The resiliency of membrane  155  allows it to be stretched so as to attach fastening elements  150  to connectors  145  while maintaining a tensioning force. Fastening elements  150  may be formed integrally with the membrane  155  as illustrated in  FIG. 1 . Alternatively, fastening elements  150  may be constructed separately and then attached to or inserted within membrane  155 . For example, fastening elements  150  may include a hook-shape as shown in  FIG. 1 . However, other constructions for connectors  145  and fastening elements  150  will be discussed below and one of skill in the art, using the teachings disclosed herein, will understand that a variety of constructions could be used to attach the membrane to the sides of the tread band. 
         [0025]    Notably, membrane  155  does not cross the tread region  175  of tread band  135 . More specifically, while membrane  155  may overlap a portion of the tread band  135  along lateral sides  140  including portions of the tread region  175 , membrane  155  does not extend over the tread band  135  so as to envelope the tread region  175 . As such, membrane  155  does not insulate tread band  135  when tire  100  is placed into e.g., an autoclave for heating in order to vulcanize or activate bonding material  130  and does not create vacuum pockets in the features of tread region  175 . As a result, less energy is required to cure bonding material  130  because heat can now be directly applied to tread region  175 . Additionally, because membrane  155  does not contact tread region  175 , the vacuum applied to space  170  will not pull membrane  155  against the tread region  175  in a manner that could cause distortion of tread region  175  or create unwanted wear on membrane  155 . 
         [0026]    As described with regarding to the exemplary embodiment of  FIG. 1 , connectors  145  are created as a projection  146  extending circumferentially around the tire. It should be understood, however, that each of the opposing connectors could be constructed as a series or plurality of separated features spaced apart along the lateral sides  140  of tread band  135 . In complementary fashion, fastening elements  150  could be constructed as a plurality of separate elements that are spaced apart along the membrane  155  for attachment with connectors  145 . Fastening elements  150  could be also be reinforced with e.g., spokes extending radially along the membrane or a ring extending circumferentially along the membrane. One of skill in the art, using the teaching disclosed herein will understand that multiple variations fall with the scope of the present invention to apply a tensioning force (i.e., a force along the radial, circumferential, and/or axial directions of the tire) to maintain the position of a tread band upon a tire. 
         [0027]      FIG. 2  provides another exemplary embodiment of a retaining device  260  that operates to maintain the position of tread band  235  on the casing of tire  200 . Device  260  includes a pair of membranes  255  that extend between fastening elements  250  and attach to connectors  245 . In a manner different than the exemplary embodiment of  FIG. 1 , each membrane  255  spans between connectors  245  that are positioned on same side of the equatorial plane P of tire  200 , and neither membrane  255  intersects the equatorial plane P. As with the embodiment of  FIG. 1 , membrane  255  applies a tensioning force to the tread band  235  that can be increased by the introduction of a vacuum into the interior  265  of tire  200  and/or into the space between membrane  255  and sidewalls  225 . 
         [0028]    Referring now to  FIG. 3 , retaining device  360  also includes a pair of membranes  355  that each extend between fastening elements  350  located along one side of the equatorial plane P. Each membrane  355  includes a disk  385  centrally located along the axis A of tire  300 . After attaching membrane  355  to each side of tire  300 , disks  385  can be moved towards one another and held in place by e.g., clamping or attaching the disks  385  together. In addition to increasing the tensioning force applied to tread band  335 , the movement of disks  385  towards one another also provides a seal between each membrane  355  and bead portions  320 . This sealing effect allows a vacuum to be created between the membranes  355  and their respective sidewall portions  325 . At the same time, apertures  380  in each disk  385  allow for the introduction of heated gases into the interior  365  of tire  300  to further expedite the heating and curing of uncured materials such as e.g., bonding material  330 . 
         [0029]    Another exemplary retaining device  460  is illustrated in  FIG. 4 . For purposes of providing further clarity, retaining device  460  is shown unattached to a tire. In a manner similar to previous embodiments, device  460  includes a connector  450  for engaging a lateral side of a tread band. A membrane  455  extends between connector  450  and a base ring  490 . Base ring  490  provides further reinforcement for the application of a tension to a tread band using connector  450  and membrane  455 . As shown in  FIG. 4 , base ring  490  is integrated into the membrane  455  but other constructions such as, e.g., attaching ring  490  to the surface of membrane  455  may also be used. 
         [0030]    Adjacent to base ring  490 , device  460  includes a lip  495  with a sealing surface  496  that is configured for the receipt of a bead portion of a tire. As such, lip  495  can be used to further enhance the sealing capability of device  460  during vacuum operations. Illustrated here by way of example, port  418  allows for the introduction of a vacuum between membrane  455  and a tire. A similar port may be used with the other exemplary embodiments of the invention described herein. 
         [0031]    In an alternative to the exemplary embodiment of a retaining device  460 ,  FIG. 5  illustrates a similar retaining device  560  without a lip and sealing surface for receipt of a bead portion. Device  560  stills include a base ring  590  for reinforcement in providing a tensioning force to a tread band. Base ring  590  may be constructed of for example, a reinforced composite or rubber. 
         [0032]    The membrane is not required to extend down the entire length of the sidewall of the tire. For example,  FIG. 6  shows an exemplary embodiment of a retaining device  660  where the membrane  655  is considerably shortened relative to previously described embodiments. More specifically, the distance between fastening element  650  and the base ring  690  does not extend over the entire length of the sidewall  625  of tire  600 . Instead, membrane  655  is much shorter. However, in conjunction with a relatively inextensible base ring  690 , device  660  can still be used to apply an effective tensioning force to maintain the position of tread band  635  against the casing of tire  600 . In addition, under application of a vacuum between membrane  655  and tire  600 , membrane  655  will provide a smooth surface to help mold bonding material  630  when heat is applied during the curing process. 
         [0033]    Variations in the shape and respective functions of the connectors and fastening elements are also within the scope of the present invention. For example, in  FIG. 7  retaining device  760  includes a retaining ring  751  that extends circumferentially about tire  700 . Ring  751  provides a tension force that can be used to maintain the position of tread band  735  on tire  700 . As such, if necessary, ring  751  can be applied earlier in the retreading process to secure tread band  735  into position. Retaining device  760  includes a membrane  755  extending between the hook-like fastening element  750  and base ring  790 . Tire  700  can therefore be cured while leaving retaining ring  751  in place or it can be removed during the curing step while using retaining device  760  to maintain the position of tread band  735 . 
         [0034]    As with previous embodiments, it should be noted that the projection  746  may be a feature of the tire that remains after the retreading process to serve as a protective and/or decorative feature around the sidewall of the tire. Alternatively, projection  746  may be trimmed away as part of the retreading process. As shown in  FIG. 7 , projection  746  is shaped for the receipt of the hook-like shape of connector  745 . However, multiple other shapes and features may be used to provide for the application of a tensioning force to the tread band. 
         [0035]    For example, the retaining device  860  of  FIG. 8  uses a fastening element  850  that is connected with a tread feature  852 . More specifically, tread band  835  includes a groove  852  for receipt of fastening element  850 . Groove  852  may be a functional part of the tread region  875  or may be present solely for use in the retreading process. Fastening element  850  includes a finger  851  that is received in complementary fashion into groove  852 . As with previous embodiments, base ring  890  is relatively inextensible and allows membrane  855  to provide a tensioning force that is transferred to tread band  835  to maintain its position relative to tire  800 . 
         [0036]    By way of additional example,  FIG. 9  provides a retaining device  960  that illustrates another fastening element  950  for use in applying a tensioning force to tread band  935 . Relative to the previously described embodiments, the membrane  955  of retaining device  960  extends further along the sidewall  925  of tire  900  but, unlike the embodiment of e.g.,  FIG. 5 , does not extend to the bead portion of tire  900 . Multiple reinforcing rings  953  provide additional reinforcement for the anchoring of a tensioning force applied to tread band  935 . As such, the exemplary embodiment of  FIG. 9  also illustrates that the length of the membrane may be varied. 
         [0037]    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.