Pneumatic tire

This disclosure relates to a method of manufacturing a pneumatic tire having a cast body of viscoelastic material, a road-engaging tread surface and a girdle member of reinforcing cords located in the crown area of the cast body. The method comprises the steps of assembling an annular hoop assembly with the girdle member (having a predetermined radius of curvature, its reinforcing cords at the exact cord centerline diameter desired in the finished tire, and a predetermined tension on the cords) located on the inner periphery of the hoop assembly and a spacing support member located on the outer periphery of the hoop assembly; inverting or turning the hoop assembly inside out thereby locating the girdle member on the outer periphery (without changing its cord diameter, its radius of curvature and its cord tension) and the spacing support member on the inner periphery; mounting the inverted hoop assembly on the annular core of a tire mold so that the girdle member has its reinforcing cords at the exact cord centerline diameter desired; closing the tire mold; filling it with a viscoelastic material and curing the material. The method of this invention may be used to manufacture a tire with a tread of viscoelastic material or of conventional, carbon black reinforced, rubber. In the method of this invention wherein a conventional rubber tread is used, an additional step is necessary wherein the precured conventional tread is placed in the tread section of the mold prior to the injection of the viscoelastic material.

BACKGROUND OF THE INVENTION 
Cast tires comprised of a body without reinforcing cords which are made by 
a liquid casting, or injection molding, process using a viscoelastic 
material are known. Such tires with cast viscoelastic material treads or 
with conventional rubber treads are known. It is now believed that cast 
tires require a conventional rubber tread to have adequate traction and 
tread wear. 
The dimensional stability of a cast body tire has long been known to be a 
major drawback. This feature manifests itself by the growth of the tire; 
that is, an increase in the overall diameter of the tire and/or the 
section width of the tire and a decrease in the tread radius of the tire 
upon inflation and use. Several constructions have been successful to 
control this growth. The most successful has been the incorporation of a 
girdle member in the crown area of the tire below the road-engaging tread 
surface. 
This girdle member is comprised of parallel reinforcing cords that form a 
layer or a series of layers or plies. The reinforcing cords within each 
ply are parallel to one another. Where two or more plies are used, the 
cords from ply to ply may have various angulations or their angulation may 
be identical. 
A major drawback to the use of a girdle member in the cast tire has been 
the lack of an accurate and reproducible method for locating the girdle 
member at the desired location in the tire. This is due to the fact that 
the girdle member must be located in the mold at a position that is 
surrounded by the flowable material during the casting operation. 
The location of the girdle member in the cast tire is critical and must be 
closely controlled. If the girdle member is not properly located, proper 
dynamic balance and the dimensional stability of the tire may not be 
attained. The tire would therefore be unsatisfactory and would not give 
the performance characteristics that are required. 
One attempt to locate such a member is set out in German 
Offenlegungsschrift No. 2,619,942. This disclosure provides a ply of 
inextensible, parallel wires with retaining brackets that have pins which 
extend radially outward from the parallel cords. The pins are set into a 
precured and prepositioned tread in the mold. The retaining brackets for 
the pins also are in contact with and supported by the mold at the lateral 
ends of the brackets. This technique has the drawbacks that the location 
of a precured tread in the mold and the dimensions of the precured tread 
itself are not accurate enough to ensure the accurate and reproducible 
location of the girdle member. 
Prior methods of belt placement have not had the important capability of 
maintaining a selected tension on the cords in the belt member. The 
tension on the cords predetermines the forces in the cords. When the 
designed cord tensions are maintained a better performance and more 
uniform tire results. The method of this invention enables an accurate 
control of the tension on the girdle member cords all the way through the 
manufacturing process and into the final product. The method of this 
invention also enables uniform cord tension even when the girdle member 
has a designed radius. 
The applicant has devised a new method of manufacturing a cast tire 
containing a girdle member that enables the accurate, reproducible 
placement of the girdle member at the designed location in the cast tire. 
The method also provides for the maintenance of a predetermined tension on 
the girdle member cord throughout the process and the capability of 
providing the girdle member with a radius. 
It is an object of this invention to provide a method of manufacturing a 
cast tire wherein the dimensional stability is obtained by a girdle member 
located in the crown area of the tire. The method of this invention 
enables the accurate, reproducible location of this girdle member at the 
desired, predetermined optimum place in the tire, the maintenance of a 
preselected tension on the girdle member cords throughout the 
manufacturing process, and the presence of a radius in the girdle member, 
if desired. 
SUMMARY OF THE INVENTION 
This invention resides in a method of manufacturing a pneumatic tire with a 
cast body and a stabilizing girdle member located in the crown area of the 
cast body. The method enables the accurate, reproducible location of the 
girdle member in the tire. The location is at the designed cord centerline 
diameter for the cord members of the girdle member thereby attaining 
optimum results in the finished tire. 
This method comprises the steps of assembling the girdle member on an 
annular member with the cord diameter of the reinforcing cords in the 
girdle member on the annular member being identical to the desired cord 
diameter in the finished tire. The annular member has sufficient rigidity 
to permit the application of a predetermined tension to the cords and the 
maintenance of this tension until the girdle member is assembled and 
fixed. The girdle member-annular member assembly is placed in a first mold 
that contains a means to form a spacing support member for the girdle 
member on the outer periphery of the girdle member. A viscoelastic 
material is injected into the first mold, either while the mold is at rest 
or spinning, around the girdle member to form the spacing support member 
on the radially outer side of the girdle member. After the viscoelastic 
material is cured to an extent which maintains its dimensional stability, 
the resulting hoop assembly which is comprised of the girdle member and 
the spacing support member is removed from the mold. 
This hoop assembly is then inverted or turned inside out so that the girdle 
member is on the outer periphery of the inverted hoop and the spacing 
support member is on the inner periphery. The removal from the mold and 
inversion does not alter the tension on the girdle member cords. The 
dimension of the spacing support member is predetermined to reference it 
to the desired location of the girdle member in the finished tire in 
relation to the distance between this desired location and the annular, 
internal core of the final tire mold. 
The inverted hoop assembly is then placed on the internal annular core of 
the tire mold with the spacing support member resting on the outer 
periphery of the core. This accurately and reproducibly locates the girdle 
member at the exact cord centerline diameter that is designed for the 
finished tire. The tension on the girdle member cords is also maintained. 
The hoop assembly-core member assembly is then placed in a conventional 
casting mold for the manufacture of tires, the mold is filled with a 
viscoelastic material and the material is cured to form the finished 
pneumatic tire. 
The tire made by the method of this invention with the girdle member 
located in the crown area of the tire below the road-engaging tread 
surface may be comprised entirely of a high modulus viscoelastic material 
wherein the bead areas, sidewalls, crown area beneath the tread and the 
road-engaging tread surface are a viscoelastic material. Alternatively, 
the tire manufactured by the method of this invention may have a 
conventional rubber, road-engaging tread with the girdle member located in 
the crown area of the cast body radially below the tread. Such a tire 
would comprise the conventional rubber tread and a cast body which would 
extend from one bead to the other and encompass the sidewalls and crown 
area of the tire radially inward of the road-engaging, conventional 
rubber, tread surface. 
The girdle member may be embedded in the viscoelastic material of the cast 
body or it may be located at the junction of the crown area of the cast 
body and the conventional rubber tread, when such a tread is used. The 
girdle member may be embedded in a conventional rubber skim compound when 
it is located at either of the above positions. 
When used, the carbon black reinforced, conventional rubber tread may be 
any of the standard tire treads utilized in the industry and known in the 
art. Such rubber treads comprise natural or synthetic rubber or blends 
thereof, are reinforced with various types of carbon black, most commonly 
furnace blacks, and contain other ingredients, such as processing and 
extender oils, preservatives (antioxidants, antiozonants and waxes) and 
vulcanized ingredients (accelerators and sulfur). The exact composition of 
the rubber tread is not a part of this invention and any standard rubber 
tread compound commonly used as such may be employed. Preferably, however, 
the tread should have a Durometer hardness of between 55 and 65, 
preferably 60. 
The material utilized in the cast body and the cast tread, when one is 
present, may be any of the known high modulus viscoelastic materials that 
have been recommended for use in a cast tire having no cord reinforcing 
members in the body as long as the material meets the physical limitations 
set out below. The limitations are critical to attain the proper balance 
between the composition of the cast body and the girdle member. 
Preferably, the viscoelastic material should have a tensile strength of 
212.degree. F. equal to or greater than 1,800 psi, a crescent tear 
strength at 212.degree. equal to or greater than 200 psi, a De Mattia flex 
life at 176.degree. F. equal to or greater than 200,000 cycles; and at 
ambient temperature, a tensile strength equal to or greater than 2,800 
psi, an elongation equal to or greater than 400%, a Young's modulus of 
between 5,000 and 15,000 psi and a Poisson's ration of about 0.5, or less, 
preferably between 0.4 and 0.5. 
Polyurethane rubbers, particularly of the type disclosed in U.S. Pat. No. 
Re. 28,424 and U.S. Pat. No. 4,006,767 are particularly useful as the 
material in the body of the tire of this invention. This rubber should 
have a molecular weight of 800 to 5,000 between the electrostatic 
cross-links and a molecular weight of 5,100 to 40,000 between the covalent 
cross-links and a Poisson's ratio of 0.48. 
It is understood that the viscoelastic properties of the body material 
should not permit excessive creep which results in dimensional 
instability. Creep is an increase in elongation of the material as a 
function of time for a given load. The creep of the material is correlated 
to the reduction of the stress with time at a constant elongation. A 
material which has an excessive reduction of the stress with time is found 
to exhibit unacceptable dimensional stability or growth in service over a 
period of time. 
The polyurethane elastomer as described above will exhibit acceptable creep 
during the normal service life of the tire. Materials which exhibit creep 
significantly greater than that of the described material would be 
expected to have unacceptable growth if used for a cast tire body. 
The viscoelastic material may be uniform in physical properties throughout 
the tire or it may vary depending on its location in the tire. For 
example, when it varies, the material used for the tread will be designed 
for wearing and traction properties, the sidewalls for flexing and 
dimensional stability and the bead area for adhesion to the bead wire. 
These differences are obtained by charging different materials into the 
tire mold at different times and locations. 
The bead member in the bead area of the tire may be any of the standard 
bead construction normally used, and known in the art, for pneumatic 
tires. Such bead constructions may comprise layer beads or cable beads and 
may be manufactured from strands of inextensible materials, such as steel, 
glass or aramid. The structure of the beads and the strength of the beads 
is dictated by the strength required to retain the tire on the rim. 
The carbon black-reinforced rubber skim compound that the girdle member may 
be embedded in may be any of the known rubber skim compounds that are 
normally used in the art with the cord material that is utilized in the 
girdle member. Such compounds normally contain natural rubber or blends of 
natural rubber with various synthetic rubbers, carbon black or other 
reinforcing agents, processing or extender oils, preservatives, such as 
antiozonants, and vulcanizing agents, such as accelerators and sulfur. 
The adhesive that may be utilized at the interface of the rubber tread and 
the cast body is specifically designed to provide adhesion between the 
dissimilar materials; that is, the rubber tread compound and the 
polyurethane cast body. Examples of adhesives of this type are described 
in U.S. Pat. Nos. 3,880,810; 3,880,808; 3,916,072 and 3,925,590. 
The girdle member used in the tire that is manufactured as a result of a 
method of this invention may be constructed of a single cord that is 
spiral wrapped around the outer periphery of the annular member. 
When the girdle member is formed by the spiral wrapping techniques, 
preferably it will comprise a series of parallel cords that have an angle 
which is parallel, or approximately parallel, to the circumferential 
centerline of the finished tire. In other words, the cords will be 
substantially circumferential of the tire. It is understood that the cords 
could also be angulated in relation to the circumferential centerline by 
this technique. 
If the cords are applied as a separate ply layers, the cords within each 
ply layer will be parallel to each other and may have any of the known 
angulations for reinforcing belts. The angle from ply to ply may vary or 
be the same or be oppositely directed. 
Preferably, the girdle member in the method of this invention is formed by 
adjacent parallel cords that are essentially parallel to the 
circumferential centerline of the tire. These adjacent, parallel cords are 
formed by either a preassembled ply of paralled cords being located in the 
tire such that the cords are parallel to the circumferential centerline of 
the tire or, preferably, circumferentially or spirally wrapping a single 
cord on a core to form the member. With this spiral wrapping construction 
there is no splice in the cord layer but merely two single cord ends, one 
at the beginning of the spiral wrap operation and the other at the end. 
The girdle member is preferably a single ply but two or more plies may be 
used, if desired. 
The material used for the reinforcing cord in the girdle member may be any 
of the known reinforcing materials used in pneumatic tires. Examples of 
these materials are aramid, polyesters, steel, glass, rayon, polyvinyl 
alcohol or nylon. The last material is the least acceptable due to its 
inherent growth characteristics, whereas the relatively inextensible 
materials (aramid, steel and glass) are the preferred materials due to 
their inextensible nature. 
An important feature of the girdle member in the method of this invention 
is its ability to have a predetermined uniform tension applied to its 
cords and the maintenance of the uniform tension into the final product. 
This is possible by this method in that the cords are applied to an 
annular member under a predetermined tension and stabilized in the hoop 
assembly at this predetermined tension. This uniform tension is 
mechanically maintained on the cords on the annular member until the hoop 
assembly is formed by the injection and curing of the viscoelastic 
material. The annular member is sufficiently rigid to withstand the 
tension forces applied to the cords and to maintain the tension on the 
cords. The viscoelastic material is cured to a sufficient extent to 
maintain the dimensional integrity of the hoop assembly and to hold to 
tension on the cords. This uniform tension is maintained throughout the 
remaining steps of inverting the hoop assembly, mounting it on the core 
member, injecting the tire viscoelastic material and curing the tire. This 
tension may vary depending upon the type cords that are used in the girdle 
member, but the tension is uniform from cord to cord in the girdle member. 
Another important feature of the method of this invention is its capability 
to permit a predetermined radius of curvature to be accurately, 
reproducibly present in the girdle member. Normally, the finished tire 
tread radius would be between 10 inches and infinity (flat). The radius of 
curvature of the girdle member may also be within this range. 
The radius of curvature of the girdle member is attained by the outer 
periphery of the annular member on which the girdle member is assembled 
having a radius of curvature. This annular member radius yields an 
identical radius in the girdle member in the hoop assembly. If the outer 
periphery of the annular member is flat, the girdle member will be flat 
(radius of infinity); if its 10 inches, the girdle member will be 10 
inches. 
The inversion of the hoop assembly will not alter the radius of the girdle 
member. Each cord diameter is fixed in the hoop assembly and the inversion 
doesn't alter it. This means if the girdle member is concave radially 
inward in the first mold; it will remain so after removal and inversion. 
It is understood that the surface of the outer periphery of the annular 
member upon which the girdle member is assembled may contain notches to 
receive the cords when the radius of curvature is low. These notches hold 
the cords in proper position until the viscoelastic material is applied 
and cured. 
The structural relationships of the periphery of the spacing support member 
and the outer periphery of the annular core member in the second molding 
(tire molding) step may be varied to cooperate with each other to yield 
the proper location and radius in the girdle member in the finished tire. 
That is, the outer periphery of the annular core member may be flat, 
concave or convex so long as inner periphery of the inverted spacing 
support member is compatible therewith to yield the proper girdle member 
location. Likewise, the inner periphery of the inverted spacing support 
member may be flat, concave or convex (it is understood that the molding 
of the non-inverted spacing support member may be designed to yield these 
conditions in the inverted structure) in order to be compatible with the 
outer periphery of the annular core member in the second molding step to 
yield the proper location of the girdle member in the finished tire. 
The spacing support member may be any mechanical structure that will permit 
the hoop assembly to be inverted or turned inside out which has a 
predetermined height to accurately locate the girdle member at the desired 
location in the finished tire. The diameter of the spacing support member 
is decreased by the inversion of the hoop assembly so that excessive 
compression forces could exist in the spacing support member depending 
upon its required height or thickness. If the height of the spacing 
support member is not too great, it may be a solid sheet with a smooth 
surface without creating excessive compression forces on inversion. If the 
heighth is too great and undesired, excessive compression forces would 
result in the spacing member support when the hoop assembly is inverted, 
the spacing support member may be comprised of an interrupted surface in 
the form of protruding pins, lateral bars, angulated bars, and other 
structural equivalence, to release the compression forces. If the spacing 
support member has some type of interruption (a series of pins or bars), 
the gaps between the pins or bars will be filled with the viscoelastic 
material during the final molding operation for the finished tire. 
In the preferred method of this invention the finished tire contains a 
conventional rubber tread. The preferred method comprises the forming of 
the girdle member by spiral wrapping at a predetermined uniform tension 
one continuous cord onto an annular member which is the core mold member 
for the first mold and the assembly of the hoop. The outer periphery of 
the annular core has a radius of curvature of infinity (flat) which yields 
a radius of curvature of infinity in the girdle member. This is identical 
to the designed radius of curvature of the tread in the tire as molded. 
The girdle member-annular core is then placed in the remainder of the mold 
for forming the hoop assembly. The remainder of the mold has a means for 
forming the spacing support member radially outward from the newly formed 
girdle member. The cord centerline diameter that is attained as a result 
of the application of the girdle cord to this annular mold cord is the 
desired cord centerline diameter in the finished tire. 
The viscoelastic material is then injected into the mold and, in the case 
of a polyurethane as described previously, is cured at a temperature of 
100.degree.-130.degree. C. for a sufficient time so that it will attain 
dimensional stability (usually from 5 to 60 minutes). The mold is then 
opened and the resulting annular hoop assembly of polyurethane material, 
spacing support member and the girdle member is removed. In this assembly 
the girdle member is located on the inner periphery and the spacing 
support member on the outer periphery. 
This hoop assembly is then inverted or turned inside out so that the girdle 
member is located on the outer periphery and the spacing support member on 
the inner periphery. In this condition, the hoop assembly is placed into a 
tire mold onto the outer periphery of its annular core member. In this 
manner the spacing support member rests on the core and the girdle member 
is fixed in its proper location in relation to the finished tire 
structure. A precured conventional rubber tread is placed in the tread 
portion of the mold and an adhesive is applied to its inner periphery. The 
mold is then closed and polyurethane is injected into the mold in the tire 
sidewalls. The polyurethane is then cured at 100.degree.-130.degree. C. 
for from 5 to 60 minutes, depending upon the specific composition of the 
material. After this curing cycle, the mold is opened and the finished 
tire is removed. 
The polyurethane in the second molding operation (tire) may contain a 
wetting agent to assist in the bond between it and the polyurethane that 
is employed during the first molding (hoop assembly molding) operation. 
Aliphatic perfluorocarbon esters, such as one marketed under the Trademark 
"Fluorad FC 430", have been found useful as such wetting agents. 
The known methods of molding a cast tire may be used in the final curing 
operation. Such known methods are centrifugal molding wherein the mold is 
rotated, or static liquid injection methods such as reaction injection 
molding (known in the art as RIM) or liquid injection molding (known in 
the art as LIM).

FIG. 1 shows the tire generally as 10 with a ground-engaging tread, 11, 
body 12, and annular beads, 15 and 16. The body, 12, extends continuously 
from bead 15 to bead 16 encompassing sidewalls, 13, and connecting body 
crown portion, 14, which is located in the crown area of the tire radially 
beneath the road-engaging tread, 11. The road-engaging tread is shown as 
the same cast material that is used to manufacture the body. 
In FIG. 1 the girdle member, 17, is comprised of reinforcing cords, 18, 
which are embedded in the connecting crown portion, 14, of the body, 12. 
In FIG. 2 the structural parts that are identified in FIG. 1 are identified 
by the same references in FIG. 2. FIG. 2 differs in that the road-engaging 
tread, 11, is shown as a material, a conventional rubber tread, different 
than the body, 12. The junction between the tread and the body is shown at 
the interface, 20. Also, in this embodiment the girdle member, 17, is 
shown as comprising parallel reinforcing cords, 18, that are embedded in a 
rubber skim, 19. An adhesive may also be provided at the interface, 20, of 
the conventional rubber tread, 11, rubber skim, 19, and the body, 12. 
In FIG. 3 the structural parts that are identified in FIGS. 1 and 2 are 
identified by the same reference numbers in FIG. 3. FIG. 3 differs from 
FIG. 1 in that the road-engaging tread, 11, is a material different than 
the body 12; it is a conventional rubber tread as shown in FIG. 2. As in 
FIG. 1 the girdle member, 17, is totally embedded in the crown portion of 
the body, 14. It is located in FIG. 3 at a position beneath the junction 
of the tread and the body. 
FIGS. 4 through 8 depict the method of this invention at its various 
stages. FIG. 4 is a partial, cross-sectional view of the annular member 
for forming the girdle member which is also the core for the first mold. 
This annular member is comprised of an annular piece, 30 with a 
predetermined annular outer periphery, 31. This annular outer periphery is 
dimensioned so that the reinforcing cords, 18, of the girdle member, 17, 
have a cord centerline diameter that is the desired cord centerline 
diameter in the finished tire. 
In FIG. 4 the radius of curvature of the outer periphery, 31, of the 
annular member, 30, is shown as R. In FIG. 4 the radius is infinity 
(flat). This yields a girdle member with the same radius (infinity) as 
shown in FIGS. 4-8. It is understood that the outer periphery, 31, may be 
varied to any desired radius depending upon the design required in the 
finished tire. The outer periphery, 31, may be concave or convex. Such 
outer periphery configurations will yield girdle members with identical 
configuration throughtout the method of this invention and in the final 
product. 
In FIG. 4 the girdle member, 17, is obtained by spiral wrapping a cord, 18, 
in successive parallel turns around the outer periphery, 31, of the 
annular member, 30, at a specified uniform tension. It is also understood 
that one or more layers of the cords may be used in the girdle member. 
FIG. 5 depicts the first molding step wherein the annular member, 30, with 
its companion girdle member, 17, mounted thereon, is placed into the 
remaining portions, 40, of the first mold. The inner periphery, 41, of the 
first mold forms the cavity that defines the spacing support member. The 
inner periphery, 41, of the mold portions, 40, may be smooth or it may be 
provided with interruptions, 42, which form an irregularity in the outer 
periphery of the molded hoop assembly (see FIG. 6). In the method of this 
invention, a viscoelastic material is injected into the mold cavity formed 
by mold members 40 and 30 through an aperture, 43. After the viscoelastic 
material has been cured to a sufficient extend to maintain its dimensional 
stability and hold the cords in tension, the mold is opened and the hoop 
assembly (50, in FIG. 6) removed. The hoop assembly is an annular piece 
with the girdle member, 17, on its inner periphery and the spacing support 
member, 51, on its outer periphery. 
FIG. 6 is a partial sectional view of a portion of the hoop assembly, 50, 
taken at the line A--A in FIG. 5 looking in the direction of the arrows. 
In FIG. 6 the girdle member reinforcing cords, 18, are shown on the inner 
periphery of the hoop assembly and the spacing support member, 51, is 
shown on the outer periphery. In this embodiment the spacing support 
member is a series of lateral ridges. It is understood that the spacing 
support member may have any mechanical structure that permits the 
inversion of the hoop assembly and has the appropriate height dimension 
from the girdle member to the outer periphery of the spacing support 
member. 
FIG. 7 is a partial sectional view of the hoop assembly of FIG. 6 after it 
has been inverted or turned inside out. FIG. 7 shows a partial sectional 
view of the inverted hoop assembly, 50, as it would appear in the final 
tire molding step which is depicted in FIG. 8. FIG. 7 represents the view 
of the lateral partial cross-section of the hoop assembly at line B--B 
looking the direction of the arrows in FIG. 8. 
In FIG. 7 the inversion of the hoop assembly has placed the girdle member, 
17, on the outer periphery and the spacing support member, 51, on the 
inner periphery. This inversion will not alter the cord diameter of the 
girdle member, the tension on the girdle member cords and the radius of 
curvature of the girdle member. 
FIG. 8 is a partial sectional view of the tire mold used in the last step 
of the method of this invention with the girdle member mounted in the 
mold. The hoop assembly, 50, is shown in its inverted positon, as depicted 
in FIG. 7, with the girdle member cords, 18, located on the outer 
periphery and the spacing support member, 51, located on the inner 
periphery and resting upon the annular core mold member, 60. 
In the method of this invention the inverted hoop assembly of FIG. 7 is 
placed upon the outer periphery of the annular core of the mold, 60, with 
the spacing support member, 51, of the hoop assembly resting on the outer 
periphery of the mold. The height of the spacing support member is 
designed to accurately and reproducibly locate the girdle member in the 
desired location of the finished tire. The annular core member with the 
girdle member mounted thereon is then placed inside the tire mold, 61, a 
viscoelastic material is injected into the mold and is cured by standard, 
known methods. 
As previously stated the radius of curvature of the outer periphery of 
core, 60, may be varied to cooperate with the spacing support member to 
yield the designed radius of curvature in the girdle member. In 
accomplishing this the core radius may be infinity (flat) or of any other 
length so long as it is coordinated with the radius of the spacing support 
member to yield to designed radius in the girdle member. 
If a tread of a viscoelastic material is used, the tire may be formed by 
standard techniques. If a conventional rubber tread is used in the method 
of this invention, the conventional rubber tread is precured in a 
separate, known step. This precured tread strip is then placed in the tire 
mold in the tread ring area. An adhesive, as described earlier, is 
preferably applied to the inner periphery of the tread. The annular 
core-hoop assembly is then placed in the mold and the injection and curing 
steps are followed to complete the manufacture of the tire. 
The cord angle of the reinforcing cords in the girdle member may be 
substantially 0.degree.; that is, parallel to the circumferential tread 
centerline of the tire or of any angulation restrictive in the hoop 
direction. 
The method of this invention has been successfully employed to manufacture 
suitable tires. Such tires had a cast body, a conventional rubber tread, 
and the girdle member was embedded entirely in the cast body. The tire was 
an A78-13 size. The compositions of the body, rubber tread, adhesive, 
girdle member and bead members is as follows. 
The rubber tread comprised a solution styrene/butadiene copolymer with the 
standard compounding ingredients, such as reinforcing carbon black, 
sulfur, accelerators and the like, as is well known in the art. The 
physical properties of the rubber tread in this specific tire were a 
tensile strength of about 2500 psi, a Shore A durometer hardness of about 
59, a modulus of about 950 psi at 300% elongation, and elongation at break 
of about 600% and a hysteresis value of 40% as measured on a ball rebound 
test at room temperature. 
The entire tire body, including spacing support member, was comprised of a 
polyurethane polymer. At 212.degree. F. its tensile strength was 2560 psi 
and its cresent tear strength was 345 psi. At ambient temperature its 
tensile strength was 4900 psi, its elongation as 550% at break and its 
Young's modulus was 9,600 psi. Its Poisson's ratio was 0.48. 
The adhesive at the interface of the body and tread was spcifically 
designed to promote adhesion between a polyurethane member and a rubber 
member. The particular adhesives employed were similar to one described in 
U.S. Pat. Nos. 3,880,810; 3,880,808; 3,916,072 and 3,925,590. 
The girdle member comprised an aramid cord as the reinforcing cord. The 
girdle member was obtained by spiral wrapping a continuous cord of aramid 
around a core. The radius of curvature of the core was infinity (flat) so 
the girdle member had a flat radius of curvature. The tension on the cord 
in the girdle member was between 10 to 20 pounds. 
The aramid cord in the girdle member had 10 parallel cords per inch (ends 
per inch), all parallel to the circumferential centerline of the tire 
tread. The girdle member had a width of 2.5 inches. The aramid fiber used 
had a 1500/3 construction and a tensile strength of 165 pounds minimum and 
an ultimate elongation of 5 to 7%. The girdle member had a Poisson's ratio 
of 0.50 and a modulus of 155,000 psi. 
The bead members comprised a cable bead construction as is well known in 
the art. This particular construction comprised a cable of one strand 
wrapped by eight. 
In this embodiment wherein the girdle member is entirely embedded in the 
cast body, after being inflated on a standard 13 inch diameter rim with a 
4.5 inch rim width for a period of 24 hours at 24 psi, the tire had a 
circumference of 73.88 inches, a section width of 6.5 inches and a tread 
radius of 14 inches. The tire so described was tested on a 67-inch 
diameter indoor test wheel under standard conditions for the U.S. 
Department of Transportation Endurance Test as defined in Federal Motor 
Vehicle Standard 109. Under the conditions of this test tires are run at a 
constant speed, 50 mph, at rated inflation, 24 psi. The load was increased 
during the test cycle. In the first four hours it was 100% of rated load 
of the tire, the next six hours it was 108% and the last 24 hours it was 
115%. The test was completed after these cycles with the tire running a 
total of 1,700 miles. The tire of this invention completed the test with 
no failures, thereby qualifying as passing this test. 
The Table below sets out the tire measurements taken on the tires during 
this test with zero miles and hours being the initial measurement before 
the test was started. These figures indicate very little growth during 
service and are well within the Tire & Rim Association specifications for 
tire growth. 
TABLE 
______________________________________ 
Department of Transportation Endurance Test (FMVSS 109) 
______________________________________ 
Hours 0 4 hours 34 hours 
Circumference in center (in.) 
73.88 74.4 74.5 
Radius (in.) 14 15.5 15.5 
Section Width (in.) 
6.5 6.78 6.80 
______________________________________ 
The tire manufactured by the method was also tested on the U.S. Department 
of Transportation (DOT) High Speed Test as defined in Federal Motor 
Vehicle Safety Standard 109. Under the conditions of this test tires are 
run at a constant load (100% of rated load) and a constant inflation 
pressure (30 psi). The speed of this test is variable comprising a 
break-in period of 2 hours at 50 mph and then 1/2 hour running time at 5 
mile increments beginning at 75 mph. The tire of this invention completed 
0.4 hours at the 110 mph step and was removed due to a tread chunk out. 
The tire significantly exceeded the accepted Government high speed 
standard for this test.