This invention relates to a method and an apparatus for
forming profiled annular elastomeric tire components.
Background of the Invention
In the manufacture of tire components elastomeric strips
of rubber are prepared typically by extruding the parts into long continuous strips
which are cut to length and lapped or butt spliced onto a cylindrically shaped building
The tire building drum is then expanded radially in the
center and the ends are drawn in axially to shape the tire into a toroidial form.
Belts of cord-reinforced layers and a strip of tread rubber are applied over the
crown of the green carcass to form a "green" or unvulcanized tire assembly.
The finished tire assembly is then placed into a tire mold
and cured in a process called vulcanization to make a tire.
Since the tire components are assembled flat on a cylindrical
tire building drum and then expanded to a toroidial shape, each component has to
be placed in tension or compression prior to being molded. This stretching of the
various parts causes slippage between the various rubber parts as the components
heat up during vulcanization.
Attempts to minimize the slippage of the various parts
have been made. One area of particular concern is the bead apex. The bead apex is
a rubber component that lies directly above an annular tensile member commonly referred
to as a bead core. The shape of the bead apex is generally an elongated triangular
shape. The tire's carcass plies lie adjacent the radially inner surface of the bead
apex and generally wrap around the bead core and extend along the axially outer
surface of the bead apex in what is commonly referred to as the ply turnup.
When the tire is built flat the apex must be turned 90°
to an upright position. This forces the radially outermost tip of the bead apex
to stretch circumferentially a large amount resulting in high stresses and localized
thinning of the bead apex.
US-A- 6,298,893 to Vannan
precured bead apexes are manufactured so that the ply path of the carcass
plies can be more reliably controlled. As Vannan notes the tensioning of the ply
cords and their location relative to the natural ply path of the tire are mostly
controlled by the bead apex. Vannan's solution was to preassemble and precure the
bead core and the bead apex. While this approach improves the stability of the bead
apex it has the major drawback of lacking the adhesion properties found when green
or uncured components are assembled.
Attempts have been made to make uncured strips of bead
apexes but the elongated tip of these apexes when formed into an annular ring tend
to warp and buckle as the extrudate shrinks and reduces tension and cools. This
warping or buckling renders such parts useless. Accordingly, only very short squatty
apexes lend themselves to this type of preforming.
GB-A- 159 0378
discloses a method of forming an annular elastomeric tire component comprising
the steps of extruding a first strip of elastomeric material annularly onto a surface,
and shaping the first strip of elastomeric material to a predetermined profile by
compressing the first strip of material between a shaping die and the surface.
describes a method and an apparatus according to the preamble of claim
1 and 12 respectively.
It is one object of the present invention to provide a
method and apparatus that can form an annular elastomeric strip such as an apex
component without an unwanted stretching or warping of the tip.
It is a further object of the invention to provide a method
and apparatus for making an elongated apex or other strip of tire material in a
profile oriented very close to the shape of the finished molded tire.
It is yet a further object to provide a method for manufacturing
multilayered components of different materials or multilayered components of similar
It is yet another object to provide a method that creates
a smooth overlap of the beginning of an annular component and an end of the component
such that the part appears seamless.
Summary of the Invention
A method of forming an annular elastomeric tire component
according to claim 1 is disclosed. Furthermore, an apparatus for forming an annular
elastomeric tire component according to claim 12 is disclosed.
The predetermined profile may have non-parallel opposing
surfaces or non-linear parallel surfaces. Preferably each formed strip has a radially
inner end that is centered about the axis of rotation of the formed strip.
The method may include rotating the strip of elastomeric
material about an axis of rotation as the strip is applied onto the support surface
thereby forming the strip annularly. Alternatively, the support surface can be rotated
about an axis of rotation as the strip is applied to form the strip annularly following
the contour of the support surface, the forming die being spaced to achieve the
proper component dimension.
The strip, when applied to the support surface is formed
having a first end and upon about 360° revolution a terminal end can be formed
by stopping the flow of extrudate. The terminal end can be and preferably is overlying
the first end as a result of the relative movement of the material and the shaping
die thereby forming an overlapping joint that appears seamless. The uniformity of
the strip cross-sectional profile is preferably maintained by the shaping die and
the support surface and extrusion/injection rate.
The method may also include the step of applying additional
strips of elastomeric material by annularly overlapping at least a portion of the
at least one first strip or another previously applied strip. In this manner a subassembly
of uncured tire components can be laminated together.
These additional strips of elastomeric material can then
be shaped to predetermined cross sectional profiles by compressing the additional
strips of material between a shaping die and the overlapped previously formed strip
and the support surface. In one embodiment almost all of an entire green tire is
assembled using this method.
This method is used to make elongated bead apexes of uncured
elastomeric material. An annular bead core is placed on the support surface and
retained such that the axis of rotation is coincident to the axis of rotation of
the support surface or the circular path of the extruder. The bead then acts as
a material flow stop at the radially inner end. As the extruded strip is placed
annularly onto a support surface adjacent the bead core, the shaping die simultaneously
compresses the strip of material to a predetermined profile to join the strip to
the bead core forming a bead core and uncured apex subassembly.
The above method is performed by an apparatus having an
extruder means for forming the elastomeric strip, a support surface, the support
surface having a radially inner support rim, a means for rotating the extruder means
about the axis of the support rim or alternatively a means for rotating the support
surface about the axis of the support rim. The means for rotating creates a relative
motion between the extruder means and the support surface thereby enabling the strip
to be formed annularly. In close proximity to the outlet end or discharge end of
the extruder means is a shaping die. The shaping die in combination with the support
surface forms a cavity through which the elastomeric strip is compressed imparting
the desired profile or shape of the finished part. The die is designed to be oriented
at a low angle of attack at about 30° or less relative to the support surface.
Preferably, the leading portion of shaping die channels the strip of material to
the end of the shaping die which imparts the parts profile. The die can achieve
a completed profile in a rotation of just over 360° for parts. In the manufacture
of bead apex subassemblies the radially inner rim is adapted to fit inside the bead
core diameter thereby providing support for the bead core. To change bead diameters
concentric ring spacers or an adjustable ring mechanism can be attached to the support
rim quickly and efficiently.
The support surface can be flat and perpendicular to the
axis of rotation or flat and conical, while the shaping die can be of any desired
profile or contour. Alternatively, both the support surface and the shaping die
can be contoured if so desired. As used herein many of the formed parts are considered
oriented substantially perpendicular to the axis of rotation. Several of the formed
parts have only portions formed substantially perpendicularly. It is understood
that conical and contoured surfaces are not truly perpendicular to the axis; however,
if one bisects the formed part along a straight line through the formed part in
a portion that when placed in a tire for assembly lies below the tire's crown in
the sidewall regions of the tire, the angle relative to the axis is preferably oriented
at an angle greater than 45°, generally closer to 90°, relative to the
axis of rotation.
This feature greatly reduces the tensioning of parts when
compared to parts that were formed horizontal to the axis of rotation and then turned
to a more vertical orientation as is common or conventional with tire building drums.
In practice, it is desirable to transfer the formed parts
directly to a tire building station without separate storage and handling. In such
a case the formed bead apex subassembly can be removed from the support surface
and transferred directly to the tire building machine. Most preferably the method
can be configured such that the support surface is a toroidially shaped building
drum or core. In this method the formed strips are applied directly to the toroidially
shaped carcass structure. Using that method liners, sidewalls, chafers, gum strips,
ply coats, apexes and other elastomeric strips can be formed.
"Axial" and "axially" means lines or directions that are
parallel to the axis of rotation of the tire;
"Bead" means that part of the tire comprising an annular
tensile member with or without other reinforcement elements such as flippers, chippers,
apexes, toe guards and chafers, to fit the rim;
"Belt reinforcing structure" means at least two layers
of plies of parallel cords, woven or unwoven, underlying the tread, unanchored to
the bead, and having both left and right cord angles in the range from 17 degrees
to 27 degrees with respect to the equatorial plane of the tire;
"Carcass" means the tire structure apart from the belt
structure, tread, under tread, and sidewall rubber over the plies, but including
"Circumferential" means lines or directions extending along
the perimeter of the surface of the annular tread perpendicular to the axial direction;
"Chafers" refers to narrow strips of material placed around
the outside of the bead to protect cord plies from the rim, distribute flexing above
the rim, and to seal the tire;
"Chippers" means a reinforcement structure located in the
bead portion of the tire;
"Cord" means one of the reinforcement strands of which
the plies in the tire are comprised;
"Innerliner" means the layer or layers of elastomer or
other material that form the inside surface of a tubeless tire and that contain
the inflating fluid within the tire;
"Ply" means a continuous layer of rubber-coated parallel
"Radial" and "radially" means directions radially toward
or away from the axis of rotation of the tire;
Brief Description of the Drawings
The invention will be described by way of example and with
reference to the accompanying drawings in which:
Detailed Description of the Invention
- Figure 1 is a cross sectional view of a bead apex assembly of the present invention.
- Figure 2 is a cross-sectional view of a multilayer tire component of the present
- Figure 3 is a perspective view of an apparatus of the present invention.
- Figure 4 is an enlarged view of a shaping die and extruder head applying an
elastomeric strip onto a support surface of the present invention.
- Figure 4A is a view similar to Figure 4 showing a spiral layered formed strip.
- Figure 5 is a cross-sectional view of the apparatus of Figure 4.
- Figures 6 through 13 depict an embodiment of the invention wherein formed strips
are applied directly onto a toroidially shaped building core or bladder to create
a complete tire component.
- Figure 6 shows a tire building drum and a robotic controlled extruder head and
forming die connected to a robotic device.
- Figure 7 is an enlarged view of the extruder head and die assembly.
- Figure 8 is a cross-sectional view of the forming die assembly.
- Figure 9 is an enlarged perspective view of the forming die assembly.
- Figure 10 shows the robotic controlled extruder head and forming die abutted
to permit applying a complete innerliner.
- Figure 11 shows the robotic extruder head and forming die applying a ply coat
- Figure 12 shows the robotic controlled extruder heads and forming dies applying
a pair of apexes.
- Figure 13 shows the carcass having belt layers applied.
- Figure 14 shows a robotic controlled extruder head and forming die applying
a side wall and a crown cushion layer.
- Figure 15 shows a robotic controlled extruder head and forming die applying
a tread to the carcass belt assembly.
- Figure 16 shows a tire curing mold for molding the tire.
With reference to Figures 1 and 2, an exemplary tire component
is shown. The tire component as illustrated is a bead apex 10 made of elastomeric
material or a rubber compound 8 and radially inward of the bead apex 10 is an annular
tensile member commonly referred to as a bead core 6. In Figure 2 the bead apex
10 is shown as a multilayered elastomeric component formed by at least two distinct
rubber compounds 8A, 8B, and 8C. Such multilayered apex components are used in the
manufacture of commercial truck tires, for example.
These components actually space the carcass ply cords from
the ply turnup and tend to help structurally stiffen the tire structure. The use
of the bead apex 10 can actually reduce the amount of stresses and strains in the
tire during use. Ideally the apex is formed with an elongated triangular cross-sectional
In conventional tire building such components such as the
bead apex and rubber sidewalls are formed as an extruded strip of generally a flat
cross section. The components are spliced on a tire building drum and have their
axis of rotation parallel to the axis of the tire building drum. The assembled components
are then folded over in a procedure of tire building commonly known as the ply turnup
step. These uncured parts are then stitched to a carcass assembly. This procedure
rolls these parts 180° wherein the axially outer ends are turned axially inwardly.
After that a tire building bladder expands in a doughnut or toroidial shape as the
bead portions of the carcass are held in a clamped position. The beads are allowed
to move axially inwardly thereby allowing the carcass to be shaped torroidally by
the expanded bladder. The components such as the apex and the sidewalls are then
forced to an almost vertical or radially outwardly extending orientation wherein
the components' axis of rotation is shifted from parallel to the axis of the building
drum to almost perpendicular. The actual shaping of these green or uncured rubber
parts creates residual stress that during the tire vulcanization process caused
the various components to slip as they soften during curing. This slipping relaxes
the built-in strains and stresses but also means the location of and tension of
the ply and belt cords in the finished product is much less predictable giving rise
to tire non-uniformity.
Ideally, to make a uniform tire the components should be
built with no built-in internal stress. Reduction in such stresses is therefore
a desirable design goal.
These thin elongated parts of uncured rubber strips are
generally produced off line relative to the tire building station. This off-line
extruding means the parts must be sufficiently durable to survive material handling.
In the case of bead apexes this means the thin radially
outer tip portion must be terminated. The thin end is too susceptible to damage
and premature stretching and puckering. When puckering occurs the components cannot
be stitched without wrinkles.
Attempts to solve these problems have led many designers
to try precuring the bead apex assembly. In this way the molded bead apex becomes
much more durable; however, precured components are much harder to stick to the
other uncured tire components. Accordingly, the slippage problem between the cured
and uncured parts during vulcanization becomes exaggerated creating another form
of tire uniformity issues.
The present invention provides a novel way to form elastomeric
tire components quickly and efficiently. The method permits the components to be
made annularly in an uncured state and the axis of the annular components can be
non-parallel to the circumferential length of the part. In fact, the parts can be
made at any desired angle relative to the axis. In cases where the finished product
is oriented at 45° or more relative to the tire's axis the part can be formed
to that desired finished product angle. The method allows angles substantially perpendicular
to the tire's axis to be easily achieved which means the components can be formed
very close to the as-molded shape and orientation.
Such component fabrication is easily adapted to be coupled
to the tire building equipment thus avoiding storage problems. This enables parts
with very thin flimsy tips to be utilized without the fear of material handling
Alternatively, the parts can be made and stored for later
use, recognizing the associated issues of handling and aging of rubber parts.
The method to achieve this type of part is best illustrated
with reference to Figures 3 through 5 showing an exemplary apparatus 100.
The exemplary apparatus 100 has an extruder means 80 for
forming an elastomeric strip or apex bead 10, a support surface 60, and a means
70 for rotating the extruder means or alternatively the support surface about the
axis of rotation of the support rim 62.
As shown the support surface 60 has a radially inner support
rim 62. The support rim 62 acts like a ledge to provide an end for the formed component
10. The rim 62 as will be discussed holds a bead core 6 in place so an apex 10 can
be formed and attached directly to the bead core 6.
To make different bead diameter tires using the same support
surface 60, one simply can add concentric support rings onto the support rim 62
thereby increasing the diameter.
The support surface 60 can be flat, conical shaped or could
be profiled having a curved surface. It must be appreciated this support surface
60 is forming one of the radially extending surfaces of the formed strip. The surface
60 can be an axially inner or an axially outer surface or both depending on the
profile required to form the strip. The fact that the material is formed and applied
in the orientation very close to the toroidially shaped green or uncured tire means
the residual stresses particularly at the radially outer ends of the formed parts
are virtually non-existent. This greatly approves the overall quality and uniformity
of the formed components.
The extruder means 80 may be an extruder only or an extruder
in combination with a gear pump or injector. As shown the extruder means applies
the elastomeric material, typically rubber directly onto the support surface 60.
The extruder means 80 can be mounted for vertical discharge or horizontal discharges
dependent on the orientation of the support surface 60 as shown in Figure 7. The
tip or discharge end 81 of the extruder preferably has a rough initial profile forming
die 82 that shapes the part generally close to the shape of the finished product.
Accordingly, the extruded initial profile die 82 can be a thin rectangular strip
In practice the extruder discharges at an initial starting
point and the strip is applied annularly by either rotating the extruder means 80
or the support means 60 about an axis of rotation.
A final shaping die 84 follows directly behind the extruder
tip and as the rubber material is discharged onto the support surface 60 the final
shaping die 84 compresses the material into a cross-sectional profile of the desired
In practice both discharge end 81 of the extruder 80 and
the final shaping die 84 are oriented at an angle of less than 90° relative
to the support surface. The extruder discharge end 81 can be at any angle off normal
such that the angle as shown applies the material more uniformly. The final shaping
die 84 can be inclined at a much lower angle of attack having a leading or initial
contact angle of less than 45° and at the trailing or finish end where the
final shaping occurs preferably has a polishing or smearing angle of 0° to
A more sophisticated embodiment of the invention is shown
in Figures 6-16. In this embodiment a robot 90 with a multiple axis movable arm
92 is connected to the extruder means 80 and the elastomeric extrudate passes through
flexible hose 94 to the extruder forming assembly 80A which includes a discharge
end 81, initial profile die 82 and the final shaping die 84.
As in the previously discussed apparatus 100 of Figures
3-5 the extrudate is fed out in strips 2 onto a support surface 60. The support
surface 60 as shown is a toroidially expanded building drum 66. The drum 66 can
be radially expandable as shown using an incompressible fluid medium or high pressure
air, alternatively the toroidal shape may be formed of a rigid or solid core. The
primary advantage of applying the strip 2 to a toroidially shaped surface is the
finished part is accurately positioned in a green uncured state at the proper orientation
to be molded without requiring any change in orientation from the condition in which
the strip was initially formed.
As shown the apparatus is a tire building station 200.
The exemplary robot 90 employs a single universal forming assembly 80A which can
feed multiple compounds through a flexible hose assembly 94 with separate feed channels
for delivering the proper compound to the discharge tip 81. As the strip material
2 is fed into the initial profile forming die 82, the support surface 60 rotates
enabling the strip 2 to be formed annularly. The robotic arm 92 precisely moves
as required to insure the final forming die 84 spreads the elastomeric material
to the exact shape and thickness desired. This may be accomplished in as few as
one rotation of the support surface for small narrow components or may require several
rotations for thick or very wide components. The profile of each formed component
can be varied in a fashion such that the cross-sectional thickness is very thin
as in the tip of an apex or thick near the bead core. Also the entire profile can
be thin as in a liner component. The robotic arm can articulate moving in numerous
directions the numerous degrees of freedom enables the shaping die to form flat
convex or concave curvatures as the material is spread.
As shown in Figure 7 the forming assembly 80A is physically
attached to the robot by a bracket 93. A laser sensor 120 detects the distance from
the support surface 60. This measured distance is fed back to a computer which is
programmed to direct the robotic arm to move axially and radially along the flow
path as the precise amount of strip material is placed onto the support surface
or directly onto a previously formed component. As shown a pressure sensor 130 is
embedded in the forming die 82, the pressure sensor 130 reads the applied pressure
of the forming die to insure the extrudate is properly smeared. As can be easily
appreciated the smearing of the strip requires a pressure that does not overly squeeze
the material against the surface to which the part is being applied.
In Figures 10 through 16 the apparatus 200 is shown forming
a tire assembly. While the many components are shown being applied using the apparatus
200 several cord reinforced components such as the belts, carcass plies and the
chipper can be applied using previously calendered materials. Similarly the tread
may be provided in a strip or an annular ring in a more conventional manner. What
is important to note is some or all of these tire components can be formed using
this technique of the present invention. The tire manufacturer simply can choose
which components can be most efficiently produced using this technique.
In Figure 10, the innerliner 50 is being applied to the
support surface 60. The inner liner 50 generally is made of halobutyl rubber and
provides an air impervious barrier for tubeless tires.
In Figure 11, the ply stock coating 40 is shown being smeared
onto the liner. Assuming cord reinforcements are used they will be applied onto
the ply stock as a sheet or otherwise applied.
In Figure 12, the apex 10 is shown being applied directly
over the bead cores 6 and against the ply stock.
In Figure 13, the belt reinforcing structure 25 is shown
being applied in a conventional manner. The belt structure has two layers 27, 28
with oppositely oriented layers.
Figure 14 shows the sidewalls 20 and crown cushion layer
being applied using the present invention. Each sidewall is applied over the bead
apex and the ply coating 40.
Figure 15 shows the tread 22 being applied using the present
invention. Often the tread is a complex structure having multiple layers. In such
a case the tread 22 may be applied in multiple passes using the contouring profiling
techniques previously discussed.
In Figure 16 the uncured green tire 5 is shown being enveloped
by a mold right at the tire building station core. The mold 4 has a plurality of
radially outer segments 4A and a pair of side plates 4B and 4C. The tire can then
be cured under heat and pressure.
As shown in Figures 10 through 16 the entire tire building
process can be efficiently completed taking strips of components and applying them
on the support surfaces 60 shaping the components into a desired profile.