Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR PREPARING
TIRE TREAD FOR A RETREAD TIRE
FIELD OF THE INVENTION
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
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.
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
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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.
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.
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.
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.
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.
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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.
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.
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.
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In another aspect, the present invention provides another exemplary
embodiment of the invention, which relates to a tread
application apparatus for use in applying a length of tire tread to a tire
casing. The apparatus includes a rotatable hub for mounting a tire casing,
the tire casing having a circumference. The apparatus also includes a
track configured to provide the length of tire tread to the casing, the
length of tire tread having a first end and a second end. Further, the
apparatus includes a variable force applicator configured to apply the
length of tire tread onto the casing.
Another exemplary embodiment of the invention relates to a
tread application apparatus for use in applying a length of tire tread to a
tire casing having an applied cushion gum. The tread application
apparatus includes a rotatable hub for mounting a tire casing, the tire
casing having a circumference. The tread application apparatus also
includes a track configured to provide the length of tire tread to the
cushion gum, the length of tire tread having a first end and a second end.
Further, the tread application apparatus includes a variable force
applicator configured to apply the length of tire tread onto the cushion
gum.
Still another exemplary embodiment of the invention relates
to a method of applying a length of tire tread to a tire casing having a
layer of cushion gum applied thereto. The method includes mounting a
tire casing on a hub, the hub being rotatable. The method also includes
applying the length of tire tread to the cushion gum. Further, the method
includes controlling the pressure applied to the tire tread during
application. Further still, the method includes monitoring the distance
needed to be covered by the tire tread and monitoring the length of tire
tread not applied to the cushion gum.
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In another aspect, the present invention provides another exemplary
embodiment of the invention, which relates to a
cushion gum application system. The cushion gum application system
includes a rotatable hub for mounting a tire casing. The cushion gum
application system also includes a drive configured to rotate the hub and
casing combination. Further, the cushion gum application system
includes a cushion gum dispenser configured to stretch a length of
cushion gum substantially as the cushion gum is being applied to the tire
casing.
Another exemplary embodiment of the invention relates to a
cementless cushion gum application system. The cementless cushion
gum application system includes a rotatable hub for mounting a tire
casing and a drive configured to rotate the hub and casing combination.
The cementless cushion gum application system also includes a cushion
gum dispenser configured to provide a controlled stretch of a length of
cushion gum substantially as the cushion gum is being applied to the tire
casing. The stretched cushion gum substantially adheres to the contour
of the tire casing.
Still another exemplary embodiment of the invention relates
to a method of applying cushion gum in a cementless process. The
method includes mounting a tire casing on a hub, the hub being rotatable.
The method also includes rotating the tire casing. Further, the method
includes stretching a length of cushion gum around the circumference of
the tire casing while the casing is rotated and controlling the stretch of
the cushion gum during application.
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In a further embodiment, the invention provides another exemplary
embodiment of the invention, which 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
io 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.
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.
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
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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.
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.
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CA 02790019 2012-09-17
1
SUMMARY OF THE INVENTION
An exemplary embodiment of the invention relates to a tire
tread cutting apparatus for cutting a length of tire tread to be affixed to a
tire casing having a cushion gum. The apparatus includes a measuring
device configured to measure at least one of the circumference of the tire
casing and the circumference of the tire casing plus the cushion gum.
The apparatus also includes a tread dispenser configured to automatically
io 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.
Another exemplary embodiment of the invention relates to a
tire tread cutting apparatus for cutting a length of tire tread to be affixed
to a tire casing having a cushion gum. The tire tread cutting apparatus
includes a measuring device configured to measure at least one of the
circumference of the tire casing and the circumference of the tire casing
plus the cushion gum. The apparatus also 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 pattern. Further, the apparatus includes a
tread cutter configured to cut the tread to a determined length.
Yet another exemplary embodiment of the invention relates
to a method of cutting a length of tire tread for a retread tire having a tire
casing and a cushion gum applied to the tire casing. The method includes
measuring a circumference of the tire casing with the cushion gum
applied. The method also includes communicating, electronically, the
circumference of the tire casing with the cushion gum applied to the tire
tread dispenser. Further, the method includes dispensing, automatically, a
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length of tire tread based on the circumference of the tire casing with the
cushion gum applied.
BRIEF DESCRIPTION OF THE DRAWINGS
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:
FIG. 1 is a mechanical drawing of an integrated tire bench
system;
FIG. 2 is a perspective view of an integrated tire bench
system;
FIG. 3 is a partial elevation view of an integrated tire bench
system;
FIG. 4 is a cross-sectional view of a tire casing in an
application or stitching operation; and
FIG. 5 is a depiction of the kinematics of a cushion gum
application process.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
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).
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
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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.
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 32a via a system of gears and/or belts 37, such
that spindle 32a 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.
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.
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.
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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
i
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.
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.
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
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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.
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.
In an exemplary embodiment it may be desirable to obtain a
maximum tangential velocity of points on the surface of casing 22 during
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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.
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 32a 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.
Referring now to FIG. 5, to fully illustrate the cushion gum
stretching process, roll 34 is depicted having an angular velocity C02.
Cushion gum 34 is shown being applied to casing 22, casing 22 having
an angular velocity co,. To cause stretching of cushion gum 34, a point
90 on the surface of casing 22 has a velocity V1, a point 91 on the
cushion gum, being dispensed from the roll 34, has a velocity V2.
Because co, and w2 are geared to provide different V2 and V1, where V1
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is greater than V2, a differential velocity AV =Vl-V2, that is non-
negative is created. Therefore, due to the differential velocity, the
cushion gum is necessarily stretched.
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).
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.
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 38 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
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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.
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.
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
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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.
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.
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.
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.
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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.
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.
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