Abstract:
An apparatus for retreading tires is disclosed. The apparatus has a rotatable hub for the mounting of a buffed tire casing. The apparatus also has a cushion gum applicator that is configured to stretch a length of cushion gum onto a tire casing. Further, the apparatus has a tread dispenser that is configured to automatically dispense a length of tire tread based on the circumference of at least one of the tire casing and the tire casing plus the cushion gum. Further still, the apparatus includes a tread applicator that is configured to stretch the length of tire tread onto the cushion gum. The entire apparatus including the cushion gum applicator, the tread dispenser, and the tread applicator are integrated into a single tire bench machine.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention relates generally to a method and apparatus for making retreaded tires and particularly to a method of and apparatus in which the steps in making a retreaded tire are combined on a single integrated machine.  
         BACKGROUND OF THE INVENTION  
         [0002]    Retreaded tires are readily available and provide an economical way to gain additional use out of tire casings after the original tread or retread has become worn. According to a conventional method of retreading, sometimes referred to as cold process retreading, worn tire tread on a used tire is removed by a special buffing machine that grinds away old tread and leaves, a buffed surface to which a new layer of tread may be bonded.  
           [0003]    Removal of old tread from the tire casing provides a generally smooth treadless surface about the circumference of the tire casing. The tire casing may then be examined for injuries, which are skived and filled with a repair gum. After completion of the skiving process, the buffed surface may be sprayed with a tire cement that provides a tacky surface for application of bonding material and new tread. Next a layer of cushion gum is applied to the back, i.e., the inside surface of a new layer of tread, or alternatively, the layer of cushion gum is applied directly to the tacky surface on the tire casing. Conventionally, the cushion gum is a layer of uncured rubber material. The cushion gum and tread may be applied in combination about the circumference of the tire casing to create a retreaded tire assembly ready for curing. Alternatively, a length of tire tread is wrapped around the tire casing with the cushion gum already applied. The cushion gum forms the bond between the tread and the tire casing during curing.  
           [0004]    Following assembly of the tire casing, cement, cushion gum and tread, the overall retreaded tire assembly is placed within a flexible rubber envelope. An airtight seal is created between the envelope and the bead of the tire. The entire envelope tire assembly is placed within a curing chamber, and subjected to pressure and a raised temperature for a specific period of time. The combination of pressure, temperature, and time binds a layer of cushion gum to both the tire casing and the new tire tread.  
           [0005]    The above-described method of cold process retreading is often accomplished on a tire builder. Conventional tire builders include a spindle on which a tire is mounted and a spindle on which a roll of tire cushion gum is mounted for dispensing. Typically the cushion gum may be dispensed by hand as the tire is rotated to adhere the cushion gum to the tire casing.  
           [0006]    In certain applications, it may be advantageous to eliminate the spray cement completely. This may be particularly true in geographical areas where there is increased regulation of the use of chemicals within spray cement products. Further, use of spray cement can also add to the cost of producing retreaded tires due to the product cost and equipment cost. Various solutions to enable a cementless process have been suggested, for example, extruding heated cushion gum directly to a tire casing. This process however, is costly due to equipment costs and is unnecessarily complex.  
           [0007]    After the cushion gum has been applied, the circumference of the tire casing with cushion gum is measured and an applicable length of tread is measured out, conventionally on a separate bench. The tire tread is manually cut to length.  
           [0008]    In all tire building systems once the cushion gum has been applied and the tread has been cut to length, the tread must be applied to the cushion gum and casing. Due to errors in the cut length of the tire tread it may be desirable to stretch the tire tread around the perimeter of the tire casing and cushion gum in order to create an appropriately sized splice.  
           [0009]    Further, it is often desirable, for aesthetic and structural strength purposes, to match the tire tread design at each end of the tire tread length so that where the two ends of the tire tread length match at the splice, the repetitive pattern of the tire tread design is substantially continuous. To create such a splice, it may be necessary to stretch the tire tread around the circumference of the tire casing and cushion gum because the tire tread length may have been cut to an extra shortened length in order to cause the matching of the tire tread design at the two ends of the tire tread.  
           [0010]    Accordingly, there is a need for an integrated tread bench that combines the processes of cushion application, tread cutting and tread application into a single work bench machine while semi-automating the plurality of steps required to produce a finished retread tire prior to curing. There is also a need for a cushion gum application process and apparatus that controls the stretch of the cushion gum during application to the tire casing. Further, there is a need for a method and apparatus for applying cushion gum to a tire casing that uses a cementless application and stitching process. Further, there is a need for a semi-automatic method and apparatus for cutting an appropriate length of tire tread. Further still, there is a need for a semi-automatic method and apparatus of applying tire tread in a controlled stretch to a casing with an applied cushion gum to produce a tire with a predetermined range of splice size. Yet further still, there is a need for a semi-automatic method and apparatus of cutting and applying tire tread lengths such that the periodic tire tread design is substantially continuous in the retread tire.  
         SUMMARY OF THE INVENTION  
         [0011]    An exemplary embodiment of the invention relates to an apparatus for retreading tires. The apparatus includes a tire casing mount configured to have a tire casing mounted thereto. The apparatus also includes a cushion gum applicator configured to stretch a length of cushion gum onto the tire casing. Further, the apparatus includes a tread dispenser configured to automatically dispense a length of tire tread based on the circumference of at least one of the tire casing and the tire casing plus the cushion gum. Further still, the apparatus includes a tread applicator configured to stretch the length of tire tread onto the cushion gum. The cushion gum applicator, the tread dispenser, and the tread applicator are integrated into a single machine.  
           [0012]    Another exemplary embodiment of the invention relates to an apparatus for retreading tires. The apparatus includes a hub for mounting a tire casing. The apparatus also includes a cushion gum applicator configured to stretch a length of cushion gum onto the tire casing, the stretch being controlled during application. Further, the apparatus includes a tread dispenser configured to automatically dispense a length of tire tread based on the circumference of at least one of the tire casing and the tire casing plus the cushion gum. Further still, the apparatus includes a tread applicator configured to apply the length of tire tread onto the cushion gum.  
           [0013]    Yet another exemplary embodiment of the invention relates to an apparatus for retreading tires. The apparatus includes a rotatable hub for mounting a tire casing. The apparatus also includes a cushion gum applicator configured to stretch a length of cushion gum onto the tire casing. Further, the apparatus includes a tread dispenser configured to automatically dispense a length of tire tread based on the circumference of at least one of the tire casing and the tire casing plus the cushion gum. The length of tire tread has a first end and a second end and a periodically repeating tread pattern. Further still, the apparatus includes a tread cutter configured to cut the tread to a determined length and a tread applicator configured to apply the length of tire tread onto the cushion gum.  
           [0014]    Yet further still, an exemplary embodiment of the invention relates to a method of retreading tires. The method includes mounting a tire casing on a hub, the hub being rotatable. The method also includes stretching a length of cushion gum around the circumference of the tire casing, the stretch being controlled during application. Further, the method includes measuring the circumference of the tire casing with the cushion gum applied. Further still, the method includes dispensing, automatically, a length of tire tread based on the circumference of the tire casing with the cushion gum applied. Yet further still, the method includes applying the length of tire tread to the cushion gum. The stretching, measuring, dispensing, and applying are performed on an integrated machine. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    The Invention will become more fully understood from the following detailed description, taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like elements, in which:  
         [0016]    [0016]FIG. 1 is a mechanical drawing of an integrated tire bench system;  
         [0017]    [0017]FIG. 2 is a perspective view of an integrated tire bench system;  
         [0018]    [0018]FIG. 3 is a partial elevation view of an integrated tire bench system;  
         [0019]    [0019]FIG. 4 is a cross-sectional view of a tire casing in an application or stitching operation; and  
         [0020]    [0020]FIG. 5 is a depiction of the kinematics of a cushion gum application process. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]    Referring to FIGS. 1 and 2, an integrated tire bench  10  is depicted. Tire bench  10  is a semi-automated retread tire building apparatus configured to assemble retread tires. In an exemplary embodiment, tire bench  10  includes a rotatable hub  20  for mounting a tire casing thereon. In an exemplary embodiment, hub  20  may be a variable size hub that incorporates an automated inflation system and is configured to accommodate tires having different sizes (widths and radii).  
         [0022]    Tread bench  10  includes an operator control panel  25  having a plurality of buttons and gauges  26  to partially control and monitor operations of tread bench  10 . Tread bench  10  also includes a cushion gum applicator system  30 . Cushion gum applicator system  30  includes a spindle  32  to which may be mounted a roll of cushion gum  34  provided for dispensing onto a tire casing  22  mounted on hub  20 .  
         [0023]    Cushion applicator system  30  also includes a drive wheel  36  that is configured to engage the surface of a tire casing and is driven by the rotation of tire casing  22 . In an exemplary embodiment, drive wheel  36  is coupled to spindle  32   a  via a system of gears and/or belts  37 , such that spindle  32   a  rotates with a surface velocity that is proportional to the surface velocity with which casing  22  is rotated by a drive system  23 , rotating hub  20 .  
         [0024]    Further still, in an exemplary embodiment, tread bench  10  includes a set of applicator/stitcher wheels  40 . Applicator/stitcher wheels  40  are movable relative to one another and may be moved adjacent one another to form a single applicator/stitcher wheel. Applicator/stitcher wheels  40  may be moved apart to perform stitching operations. Applicator/stitcher wheels  40  may also be moved in a direction substantially normal to the surface of the tire casing to apply a variably controlled force to the surface in contact with applicator/stitcher wheels  40 .  
         [0025]    A measurement wheel  50  is provided on a measurement arm  52 . Measurement arm  52  is pivotable by actuation through a pneumatic cylinder  54  to engage a surface (either a tire casing, or cushion gum applied to a tire casing). Measurement wheel  50  rotates, as a tire casing  22  is rotated on an axis  24 . Measurement wheel  50  is coupled to an encoding device which encodes the angular variation of measurement wheel  50  for communication to a central processing unit or control unit. In combination, wheel  50  with control unit yields appropriate measurement of wheel circumference. In alternative embodiments, other measurement devices may be incorporated into the design without departing from the spirit and scope of the invention.  
         [0026]    Tread bench  10  also includes a tread dispensing system  60 . Referring now to FIG. 3, tread dispensing system  60  includes a tread rollers  62  on which a roll of rubber tire tread  64  may be mounted. Tread dispensing system  60  also includes a set of drive rollers  66  which may be used to pull tire tread  68  from roll  64  and push out a length of tire tread  79  away from rollers  66 . Tread dispensing system  60  also includes a knife  70  for cutting a length of tire tread  79  from uncut tread  68 . Further still, tread dispensing system  60  includes a first clamp  72  and a second clamp  74 . First clamp  72  is configured to clamp tire tread  68  at or near a first end  76 . Second clamp  74  is configured to clamp tire tread  68  at or near a second end  78 , created by knife  70 .  
         [0027]    Tire bench  10  includes a curved track that may be a set of rollers  82  mounted along curved track  80 . Curved track  80  is configured as a curve to provide a desirable height for operator access at or near knife  70 . Further, curved track  80  is configured to deliver tire tread section  79  to the end of track  80  adjacent casing  22 , for assembly thereon, without introducing any substantial bending or stretching caused by abrupt changes in the path of travel of section  79  and further to facilitate the movement of first clamp  72  and second clamp  74  along track  80 . Curved track  80  is also appropriately curved to allow a desirable height for operator access near knife  70  while providing adequate height at the opposite end to accommodate tires of large size.  
         [0028]    In an exemplary embodiment, first clamp  72  pulls tread section  79  along track  80  to provide tread section  79  to contact casing  22 . As tread section  79  is applied to tire casing  22 , second end  78  is at a known location because clamp  74  includes an encoder (in communication with a central processing unit or control unit) configured to track the location of end  78  relative to end  76  which is engaged with casing  22 . Both clamps  72  and  74  have encoders incorporated therein to track the location of clamps  72  and  74  along track  80 . In an exemplary embodiment, the encoders of clamps  72  and  74  are able to measure changes every millimeter. However, encoders of clamps  72  and  74  are not limited to receiving data every millimeter but may be configured to receive information on larger or smaller scales. The measurement of changes every millimeter provides a substantially continuous location signal to a central processing unit or control unit used to control the application process. However, it may be desirable to provide substantially continuous monitoring with coarser or finer measurements.  
         [0029]    In operation, an operator mounts a tire casing  22  to hub  20 . Hub  20  may be moved laterally, along the axis of rotation in order to center hub  20  relative to a longitudinal center line of tread bench  10 , which corresponds to the center line of cushion gum  34  and tire tread roll  64 . Once the casing has been mounted, the casing is then inflated and centered. Therefore, the first step for the operator after mounting and inflating casing  22  is to align the center line of tire casing  22  with the center line of the cushion gum  34  and tire tread roll  64 , which are automatically aligned with the tread bench  10  centerline by a system of clamps, guides, rollers, or other alignment devices. Next, measurement wheel  50  is brought into contact with the outer surface of casing  22 . Tire casing  22  is rotated to provide a measurement of the circumference of casing  22 . While casing  22  is rotated a full revolution, measurement wheel  50  encodes rotations of measurement wheel  50  which are communicated to a central processing unit or control unit where a determination of the circumference of tire casing  22  is calculated. From the measurement of the circumference of casing  22 , a desired maximum angular velocity is determined, based on a desired value of the tangential velocity of points on the surface of casing  22  during cushion gum application.  
         [0030]    In an exemplary embodiment it may be desirable to obtain a maximum tangential velocity of points on the surface of casing  22  during cushion gum application, for casings of various sizes, the maximum tangential velocity being constant across the range of sizes. To provide a constant maximum velocity across the range of sizes requires knowledge of the size (i.e., the circumference) of each casing. Alternatively, it may be desirable to vary the tangential velocity based on size, or it may be desirable to provide a constant angular velocity over the range of sizes.  
         [0031]    Next, drive roller  36  is brought into contact with the outer surface of casing  22 . A length of cushion gum is dispensed from roll  34  and applied to the surface of casing  22 . Casing  22  is rotated and consequentially rotates both drive wheel  36  and spindle  32  causing the cushion gum to stretch and be applied to casing  22 . To produce the controlled stretch of cushion gum  34 , casing  22  is driven by the rotation of hub  20  through drive system  23 . Drive wheel  36 , which engages casing  22 , is caused to rotate and drive a system of gears and/or belts  37  thereby driving spindle  32   a  at a linear surface velocity based proportionally on the linear surface velocity of casing  22 . Gearing  37  is configured such that a linear velocity of cushion gum being dispensed from roll  34  is less than the tangential velocity of points on the perimeter of casing  22 . Therefore, the differential velocity, that is the tangential velocity of a point on the perimeter of casing  22  minus the linear velocity of cushion gum leaving roll  34 , is non-negative. The differential velocity therefore produces a stretching of cushion gum  34  as it is being applied to the exterior of casing  22 .  
         [0032]    Referring now to FIG. 5, to fully illustrate the cushion gum stretching process, roll  34  is depicted having an angular velocity ω 2 . Cushion gum  34  is shown being applied to casing  22 , casing  22  having an angular velocity ω 1 . To cause stretching of cushion gum  34 , a point  90  on the surface of casing  22  has a velocity V 1 , a point  91  on the cushion gum, being dispensed from the roll  34 , has a velocity V 2 . Because ω 1  and ω 2  are geared to provide different V 2  and V 1 , where V 1  is greater than V 2 , a differential velocity ΔV=V 1 −V 2 , that is non-negative is created. Therefore, due to the differential velocity, the cushion gum is necessarily stretched.  
         [0033]    As depicted in FIG. 4, casing  22  has a curved crown section  27 . Crown  27  is substantially the surface to which cushion gum  34  is applied. In an exemplary embodiment, cushion gum  34  has a polyethylene protective layer  35  adhered thereto, to prevent adhesion to other layers of cushion gum while rolled and to prevent adhesion to application rollers  40  during application. The controlled stretching of cushion gum  34 , by the differential velocity introduced by gears  37 , provides improved conformity of cushion gum  34  to the contoured crown  23  of casing  22 . The improved conformity provides uniform adhesion and contact of cushion gum  34  to crown  23 , causing the cushion gum edge to substantially contact casing  22  wrinkle-free and further reduces the need for providing extra strips of cushion gum along shoulders  21  of crown  23  (i.e., cushion gum stripping).  
         [0034]    Because measurement of the circumference of casing  22  was provided by measurement wheel  50 , the known length of cushion gum  34  is dispensed to fully encompass the perimeter of casing  22 .  
         [0035]    After cushion gum  34  has been applied to casing  22 , rollers  40  are moved to engage and provide a force onto cushion gum  34 . Casing  22  is rotated while rollers  40  provide a force, in a direction indicated by arrow  37  in FIG. 4, onto cushion gum  34 . In an exemplary embodiment, wheels  40  begin in the middle of crown  23  and, during subsequent rotations, wheels  40  are moved towards shoulders  21  of crown  23  in the directions indicated by arrows  41 . This operation, often referred to as stitching, provides desirable adherence of cushion gum  34  to the surface of casing  22  (crown  27  and shoulders  21 ), while aiding in removing any trapped air pockets between cushion gum  34  and casing  22 . After the stitching operation is completed, a measurement of the circumference of tire casing  22  plus cushion gum layer  34  is taken by measurement wheel  50  as casing  22  is rotated. Polyethylene layer  35  is then removed.  
         [0036]    Based on the measured circumference of tire casing  22  with cushion gum layer  34  adhered thereto, a desired length of tire tread may be determined. In an exemplary embodiment, the determined length is dispensed from tread roll  64 , as depicted in FIG. 3. The tread  68  is dispensed by drive rollers  66  beneath a retracted cutter  70  and through clamps  72  and  74  to a stop  75  which is extended upwardly above track  80 . When end  76  engages stop  75 , clamp  72  is selectively commanded to engage tread section  79  (adjacent end  76 ) to carry tread  79  along with movements of clamp  72 . Stop  75  is then lowered and based on a determined length, roller  66  drives tread  68  pushing end  76  along track  80  and past clamp  74 , while clamp  72  cooperatively propels tread end  76  along track  80 . When an approximate desired length has been reached, based on aforementioned circumferential measure, drive  66  stops deploying tread  68  and clamp  72  stops propelling tread end  76 .  
         [0037]    In an exemplary embodiment, an operator may, once an approximate length of tread  68  has been deployed, make minor adjustments to a location of cut  78  in tread  68 . It may be desirable for an operator to match the periodically repeating tread design of end  76  with the tread design at end  78 . Matching the designs of ends  76  and  78  provide a preferred aesthetic appeal and structural strength, at the splice region in a completed retread tire by providing a continuously repeating tread design substantially unbroken by the splice. (In an alternative embodiment, the process of selecting the appropriate splice location, based on the tread design may be carried out by image processing devices which control the deployment of tread  68 , location of end  78 , and matching of designs on ends  76  and  78 ). Once the targeted location of end  78  is determined by an operator, or alternatively by automated methods, cutter  70  is used to cut section  79  away from tread  68  remaining behind knife  70  and on roll  64 . Further, clamp  74  is clamped in a position adjacent end  78 .  
         [0038]    After end  78  has been created by cutter  70 , clamp  72 , which moves along track  80 , pulls section  79  along track  80 . End  76  is then put in contact with cushion gum  34  on casing  22  and application wheels  40  are lowered to engage end  76  of tread  79 . An encoder is used to determine the location of end  76  relative to casing  22 . The location of end  76  is substantially continuously communicated to a central processing unit or control unit. Casing  22  is then rotated while applicator wheels  40  provide a variably controlled pressure to tread  79 . The applied pressure by wheels  40  provide adherence of tread  79  to cushion gum  34  and extend the overall length of tread  79  due to the force being exerted by applicator wheels  40  and the associated Poisson effect.  
         [0039]    As casing  22  is rotated, the location of clamp  74  and hence end  78  of tread  79  is monitored. Further, because the location of edge  76  and the circumference of casing  22  with cushion gum  34  applied thereto is known, the circumferential distance yet to be covered by tread  79 , may be deduced. By comparing the remaining circumferential distance to be covered and the amount of tread not yet applied, an appropriate force may be commanded to be applied by applicator wheels  40 , to provide the appropriate amount of stretching and ultimately to match ends  76  and  78  with a gap having a gap length falling within a predetermined range.  
         [0040]    Once the tread  79  has been applied, the operator may manually provide finishing operations to the splice area, or alternatively devices may be added to automatically finish the splice area. Finally, tire casing  22 , may be removed from hub  20 , and placed in a pressurized flexible envelope for curing.  
         [0041]    Those who have skill in the art will recognize that the present invention is applicable with many different hardware configurations, software architectures, sensing and communication devices, and mechanical configurations.  
         [0042]    While the detailed drawings, specific examples, and particular formulations given describe exemplary embodiments, they serve the purpose of illustration only. The materials and configurations shown and described may differ depending on the chosen performance characteristics and physical characteristics of tires and tire treads. For example, the layout and configuration of the tread bench may differ. The systems shown and described are not limited to the precise details and conditions disclosed. Furthermore, other substitutions, modifications, changes, and omissions may be made in the design, operating conditions, and arrangement of the exemplary embodiments without departing from the spirit of the invention as expressed in the appended claims.