PNEUMATIC SAFETY TIRE

PNEUMATIQUE DE SECURITE

English Abstract

Abstract
PNEUMATIC SAFETY TIRE
A pneumatic safety tire capable of being used in
the uninflated condition at a speed up to a maximum
predetermined value for a maximum predetermined dis-
tance which can then be repaired and returned to
normal service. The sidewalls of the tire have a
configuration such that the bending moment stresses
experienced in the sidewall when the tire is operated
in the uninflated state do not exceed a predetermined
value. The portion of the sidewall radially and axially
inward of the carcass ply structure is made of an
elastomeric material having a dynamic modulus at least
equal to or greater than 50 kg/cm2 and has a ratio of
hysteresis to dynamic modulus less than or equal to
.24%/kg/cm2.

Claims

-13-
The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. A pneumatic safety tire comprising a
circumferentially extending ground-engaging tread
portion, a pair of shoulder portions adjacent the
axially outer end of said ground-engaging tread
portion, a pair of bead portions, a pair of sidewall
portions which extend from said shoulder portions to
said bead portions, a carcass ply structure which
extends from said bead portion to said bead portion,
said tire characterized in that said sidewall portions
have a predetermined thickness selected to provide
that the average maximum stress developed in the
elastomeric material does not exceed approximately
8.7 x 105 N/m2 when said tire is operated in the
uninflated state, the inner sidewall portions radially
inward with respect to the internal cavity of said
tire of said carcass structure being made of an
elastomeric material having a hysteresis to dynamic
modulus ratio not greater than about .24%/kg/cm2 and
a dynamic modulus of elasticity not less than about
at least 50 kg/cm2.
2. A pneumatic safety tire according to claim 1
further characterized in that the mean thickness of
said sidewall portions measured at the maximum tire
section width of said tire corresponds to the follow-
ing relationship:
T = <IMG>
wherein,
T is the total sidewall thickness at the point of

-14-
maximum tire section width Rhom exclusive of any indicia
measured in millimeters;
L is the load in kilograms at which the tire will
be required to operate;
Rhom is the radius from the axis of rotation of
said tire to the point of maximum tire section width SD
measured in millimeters;
S70 is the maximum tire section width SD measured
from the radially outer surfaces of the sidewall,
exclusive of any adornment or indicia that may be
present and measured parallel to the axis of rotation,
measured in millimeters when said tire is mounted on a
rim which has the axial flange surface spaced 70% of
the maximum section width SD of the tire; and
K is equal to approximately 8.9 x 10 1.
3. A pneumatic tire according to claim 1 wherein
the inner sidewall portion radially inward with respect
to the internal cavity of said tire of said carcass
structure being made of an elastomeric material having
a dynamic modulus of elasticity not less than about
85 kg/cm2.
4. A tire according to claim 1 wherein each of said
sidewall portions have a cross-sectional configuration
such that the mean thickness of said sidewall portion
at the area adjacent said bead portions being at least
65% of the mean sidewall thickness at Rhom, the mean
thickness of said sidewall portion proceeding from said
point of maximum tire section width radially outward
toward its respective shoulder portion being equal to or
greater than the thickness of said sidewall portions at
said maximum tire section width.
5. A tire according to claim 2 wherein the radially
inner portion of each of said sidewall portions radially
inward of said carcass ply structure having a cross-

sectional mean thickness at the maximum tire section
width of said tire of at least 30% of the total
thickness of said sidewall portion at said point
exclusive of said carcass ply structure or inner
liner that may be present.
6. A tire according to claim 1 wherein the
radially outer ends of said inner portion of each of
said sidewall portions terminate at a point spaced
a distance from the tread edge which it lies beneath
of at least 35% of the distance from the tread edge
to the mid-circumferential centerplane of said tire.
7. A tire according to claim 1 wherein said
bead portions are each reinforced with a stiffening
member located radially outward of each of said bead
cores and between said carcass ply structure and the
ends of said carcass ply structure, said stiffening
members having a dynamic modulus of 125 kg/cm2 and a
maximum ratio of hysteresis loss to dynamic modulus
of .15%/kg/cm2.
8. A tire according to claim 1 wherein said
bead portions are each provided with a chafer portion
adjacent the rim flange contact area, said chafer
portion having a dynamic modulus of at least 125 kg/cm2.
9. A tire according to claim 1 wherein each of
said bead portions of said tire being further provided
with a narrow reinforcing strip located axially outward
of said respective bead core and said end of said
carcass ply structure extending circumferentially
about the tire.
10. A tire according to claim 1 wherein said tire
is provided with a coolant in the tire cavity when
operated in the underinflated or uninflated state.

Description

PNEUMATIC SAFETY TIRE
The foreoging abstract is not to be taken as limiting
the invention of this application, and in order to
understand the full nature and extend of -the technical
nature of this applica-tion, reference must be made to
the accompanying drawings and the following detailed
description.
Background of the Invention
This invention relates to a tire; more particularly,
to an improved pneumatic tire capable of being used in
the uninflated condition.
Various tire constructions have been suggested which
are capable of being used in the uninflated condition.
One approach taken is to strengthen the sidewall so that
the tire can support the vehicle load by itself when in
the uninflated sta-te. The sidewalls are generally
strengthened by increasing the cross-sectional thickness
of the sidewall members by a substantial amount in
relationship to the normal thickness. However, due to
the large amount of rubber required to stiffen the side-
wall members, heat build-up has become a major factor in
early tire failure when the tire is operated in the
uninflated condition, and to a lesser exten-t in -the
underinflated condition.
Brief Description of the Invention
Applicant has discovered an improved -tire construc-
tion in which the tire's durability during operation in
the uninflated condition is improved while at the same
time maintaining the desired tire performance in the
inflated condition, and which after being used in theun-
inflated condition at a speed up to a maximum predeter-
mined value for a distance up to a maximum predetermined
distance, can be repaired and returned to normal use.

--2--
In accordance with one aspect of the invention
there is provided a pneumatic safety tire comprising
a circumferentially extending ground-engaging tread
portion, a pair of shoulder portions adjacent the
axially outer end of said ground-engaging tread portion,
a pair of bead portions, a pair of sidewall portions
which extend from said shoulder portions to said bead
portions, a carcass ply structure which extends from
said bead portion to said bead portion, said tire
characterized in that said sidewall portions have a
predetermined thickness selected to provide that the
average maximum stress developed in the elastomeric
material does not exceed approximately 8.7 x 105 N/m2
when said tire is operated in the uninflated state, the
inner sidewall portions radially inward with respect
to the internal cavity of said tire of said carcass
structure being made of an elastomeric material having
a hysteresis to dynamic modulus ratio not greater than
about .24%/kg/cm2 and a dynamic modulus of elasticity
not less than about at least 50 kg/cm2.
Descrip-tion of the Drawin~
Fig. 1 is a cross-sectional view of a tire made in
accordance with the present invention mounted on a rim
for which it is designed and inflated to design inflation
pressures;
Fig. 2 in solid lines illustrates a cross-sectional
view of a tire made in accordance with the present
invention mounted on a rim for whic.h it is designed, in
the uninflated state at rated load, and in dash lines
there is illustrated a cross-sectional view of the tire
as shown in Fig. 1.

--3--
Fig. 3 is a cross-sectional view of a modified
tire made in accordance with the present invention;
~ig. Ll is a fragmentary side view of the tire of
Fig. 3 taken along line 4-4; and
Fig. 5 is an enlarged, fragmentary cross-sectional
view of the tire of Fig. 3 taken along line 5-5.
Detailed Description of Preferred Embodiment
Referring to Fig. 1, there is ill~lstrated a tire 10
made in accordance with the present invention. Tire 10
is provided with a ground-engaging tread portion 12.
A pair of sidewall portions 14,16 extend from the
shoulder portions 18,20 of the tread portion 12 and
terminate in a pair of bead portions 22,24 having annular
inextensible bead cores 26,28, respectively. The tire
is further provided with a carcass ply structu.re 30 which
extends from bead portion 22 to bead portion 24 and a
tread-reinforcing belt structure 32 which e~-tends
circumferentially about the carcass ply structure 30
beneath the tread portion 12. The tire may include a
conventional inner liner 13 forming the inner surface of
the tire 10 if the tire is to be of the +ubeless type.
The ends 34,36 are of the carcass ply structure 30 and
are wrapped about the bead cores 26,28, respectively,
as shown in Fig. 1.
The carcass ply structure 30 comprises at least
one layer of rubber-coated fabric cords and is preferably
of the radial type construction, that is, a carcass ply
s-tructure in ~hich the cords form an angle from about
75 degrees to 90 degrees with respect to the mid-
circumferential centerplane CP of the tire. However,
the present invention may also be applied to bias ply
tires, that is, tires in which the cords of the carcass
ply structure form an angle less than about 75 degrees
with respect to the mid-circumferential centerplane
CP of the tire. Any number of carcass plies may be used,
depending upon the size and load rating of the tire
and may be of any suitabIe material used in tire

a~ s
_L~_
reinforcement, for example, nylon, rayon, aramid,
polyester, steel. In the particular embodiment
illus-trated, carcass ply structure 30 comprises two ply
layers 42,44 having cords made of polyester. The
carcass ply structure 30 is located approximately midway
between the inner and outer surfaces of the tire in the
region A of the sidewall which extends a point spaced
from the nominal rim diameter NRD of about 35% of the
carcass section height SH of the tire to a second point
spaced a dis-tance from the nominal rim diameter NRD of
about 90% of the carcass section height SH of the tire.
The carcass aspect ratio may be any conventional
ratio used in tire constructions which generally range
from 50 to 95, preferably from 55 to ~,5, and in the
particular embodiment illustrated, the carcass aspect
ratio is approximately 75. For the purpose of this
invention, the carcass aspect ratio denotes the
relationship of the maximum carcass section heigh SH
divided by the maximum carcass section width CSW as
measured on an unloaded tire, inflated to design
inflation pressures, mounted on a 70% rim. For the
purpose of this invention, a 70% rim is a rim in which
the axial distance R70 between the rim flanges is 70%
of the maximum axial section width SD of the tire; the
maximum axial section width SD being measured from the
axially outer surfaces of the tire, exclusive of indicia,
adornment and the like. The carcass aspect ratio
is measured using the neutral carcass contour, which
in a single radial ply carcass is the ply itself, but in
a carcass ply structure having a plurality of plies,
is located midway between the outermost and innermost
plies. The maximum carcass section width CSW therefore
is the maximum axial distance measured parallel to the
axis of rotation between the neutral carcass contour

--5--
of the carcass structure 30. The maximum carcass section
height, therefore, is the maximum radial distance between
the neutral contour of the carcass structure 30
beneath the tread portion 12 and the nominal rim diameter
NRD as contained in the size designation of the tireO
Sidewall portions 14,16 have a cross-sectional
configuration, as illustrated in Fig. 1, such tha-t the
tire sidewall thickness at the area adjacent the bead
areas is at least 65% of the cross-sectional thickness
of the sidewall at Rhom. Preferably the sidewall
thickness at this area is the thinnest area of the
sidewall and proceeding radially outward to the point
of maximum tire carcass section width Rhm the tire
sidewall portions 14,16 gradually increase in cross-
sectional thickness. For the purpose of this invention,the sidewall thickness at any point along the outside
surface of the tire is -the distance from -that point
to the closest point along the interior surface of the
tire, exclusive of indicia, adornmnet or any other
markings on the tire sidewall surface.
The tread width TW is at least 60% of the maximum
axial carcass section width SD and is preferably not
greater than 80%. In the particular embodiment
illustrated, the tread width TW is approximately 70%.
For the purpose of this inven-tion, the tread width is
the axial distance across the tire perpendicular to the
mid-circumferential centerplane CP of the tire as
measured from the footprint of the -tire inflated to
design inflation pressure, at rated load and mounted on
a wheel for which it is designed.
In order to provide the support necessary in the
uninfla-ted state, the radially inner portions 46,48 of
the sidewall portions 14,16, respectively, have a
cross-sectional thickness of at least approximately

s
30~ of the -total sidewall thickness T at the maximum
tire section width Rhom exclusive of any indicia that
may be present.
The radially outer ends 50,52 of the inner portions
5 46,48, respectively, terminate beneath the tread portion
a distance B from the tread edge which it lies beneath;
'the distance B being not less than 35% of the distance
C from the tread edge to the mid-circumferential center-
plane CP, preferably not greater than 65%. In the
particular embodiment illustrated, the ends 50,52
terminate beneath the tread a distance from the tread
edge of approximately 45% of the distance C.
The belt reinforcing structure 32 comprises rubber
coated fabric cords made of a material normally used in
15 tires, for example, nylon, polyester, rayon, aramid,
glass fiber, steel, and have one or more plies.
In the particular embodiment illustrated, the reinforcing
belt structure 32 comprises two reinforcing belt layers
47,49 each having its cords disposed at conventional
angles with respect to the mid-circumferential plane
CP of the tire which are normally used in conventional
pneumatic tires, preferably from about 20 degrees to
25 degrees. In the particular embodiment illustrated the
cords of reinforcing belt layers 47,49 for~ an angle of
25 approximately 23 degrees with respect to the circumfer-
ential plane of the tire. Preferably, the cords of
belt ply layer 47 lie at an angle with respect to the
mid-circumferential plane of the tire which is opposite
in sign than the angle in which the cords of layer 47
lie with respect to the mid-circumferential plane of the
tire.
When the tire is operated in the uninflated
condition, as is illustrated in Fig. 2, the sidewall
portions 14,16 support the vehicle load such that the
internal surface of the tire does not contact any other

~art o~ -tlle internal surface of the tire. The sidewalls
14,16 must be able to withstand the stresses encountered
during operation of the tire in -the uninfla-ted condition.
Failure of the tire when run in the uninflated state is
primarily due to the chemical breakdown of the elasto-
meric material and the breakdown of the bond between the
rubber of the elastomeric ma-terial and the reinforcements
resulting from the excess heat build-up in the tire
sidewall. It is desirable that the sidewall be made of
a material that can support the vehicle load in the
uninflated or underinflated condition with a minimum
amount of heat build-up. Applicant has discovered that
the sidewall thickness at the maximum section width SD
of the carcass ply s-tructure 30 should be such that the
average maximum stress developed in the sidewall does
not exceed approximately 8.7 x 105N/m2 in this area
when operated in the uninflated state. In order to
minimize the heat build-up in the sidewalls and provide
the necess~ry support, the inner portions 46,48 are made
of an elastomeric material having a ratio of hysteresis
to dynamic modulus not greater than about .24%/kg/cm2,
and a dynamic modulus of elasticity of not less than
about 50 kg/cm2; preferably at least 85 kg/cm2. The
dynamic modulus is obtained from the Goodyear Vibra
Tester at about 60 cycles per second (ASTM D-2231) and
the hysteresis is obtained from the Goodyear hot rebound
test wherein hystersis is equal to 100% minus the percent
rebound (ASTM D-1054).
The stresses experienced in the sidewall of the
tire are dependent upon the particular load to which
the tire will be subjected in the uninflated condition
and the configuration of the tire such as the bead
spacing of the tire when mounted on a rim for which it
is designed and the cross-sectional configuration of
the tire sidewalls. The cross-sectional thickness of
the tire sidewalls at the point of maximum carcass
section width at Rhom of the tire 10 can be determined

--8--
in accordance with the following relationship:
T = ~ I _
V Rhom
wherein:
T ls the total sidewall thickness a-t the point of
maximum tire section width Rhom exclusive of any indicia
measured in millimeters;
L is the load in kilograms at which the tire will
: be required to operate;
Rhom is the radius from the axis of rotation of
the tire to the point of maximum tire section width SD
measured in millimeters;
S70 is the maximum tire section width SD measured
from the radially outer surface of the sidewall exclusive
of adornment or other indicia, measured in millimeters
when the tire is mounted on a 70% rim; and
K is a constant which takes into account the maxlmum
stresses that may be developed in the sidewall of the
tire and is approximately equal to 8.9 x 10 1.
By taking into account the configuration of the
- tire sidewall and the load to which the tire will be
subjected in the uninflated or partially uninflated
state applicant has discovered a particular tire
construction in which the tire's durability during
operation in the uninflated condition is improved while
at the same time maintaining the desired tire performance
in the inflated normal operating condition.
A tire made in accordance with the present invention
has been found to have acceptable commercial performance
characteristics in the inflated condition while at the
same time having satisfactory handling requirements in
the uninflated condition. A tire made in accordance
with the present invention having a ratio of hysteresis
to dynamic modulus of about .16~/kg/cm2 and a dynamic
modulus of about 104 kg/cm2 has been found to be capable

_9_
of beirlg operated in the uninflated condition for a
speed of up to 40 ~iles per hour for a distance of up
to approximately 40 miles, which then can be repaired
and returned to normal service.
In order to provide the stiffness in the bead area
and a smooth transition between the stiff bead cores
26,2~ and the respective sidewalls, stiffening members
38,40 are provided radially outwardly of the bead core
26,28 and between the carcass ply structure 32 and the
ends 34,36 of the carcass ply structure. Stiffening
members 38 9 40 are made of elastomeric material having
a dynamic modulus of at least 125 kg/cm2 and preferably
having a maximum ratio of hysteresis loss to dynamic
modulus of about .17%/kg/cm2. The dynamic modulus and
hysteresis values are determined by Goodyear Vibra
Tester and Goodyear hot rebound test per ASTM ~-2231
and ~STM D-1054, respectively.
The operating performance of tire 10 in the
uninflated state may be enhanced by the placement of
chafer portions 54, 56 in the bead area adjacent the rim
flange portions 60,62. When the tire is operated in the
uninflated condition, a severe bending action occurs in
the bead regions 22,24 about the rim flange portions 60,
62. Chafer portions 54,56 help counteract this bending
action and minimize the flexing of the tire adjacent
the rim flange portion 60,62. In the embodiment
illustrated, the chafer portions 54,56 are made of an
elastomeric material. However, chafer portions 54,56
may comprise a rubber-coated fabric. The chafer
portions 54,56 are made of a material resistant to
chafing and have a dynamic modulus at least equal to
the dynamic modulus of the elastomeric material axially
outward of the ply structure 30 and adjacent chafer
portions 54,56. In the embodiment illustrated, the
radially outermost points 64,66, of the chafer portions
54,56 respectively, extend radially outward beyond the
flange contact point not less than about ~5 of an
inch (12.7 mm) as determined when the tire is mounted
on a wheel for which it is designed to be used,
and inflated to design inflation pressure. For the

~ 3S
--10--
purpose of -this invention, -the flange contact poin-l shall
be the point at which the tire sidewall first contacts the
rim proceeding from the tread portion to the bead portion.
The performance of the tire in the uninflated state
5 may be further enhanced by providing the bead portions
22,24 with narrow reinforcing strips 58,59 axially
outwardly of bead cores 26,28 extending circumferentially
about the tire 10. In the embodiment illustrated
reinforcing strip 58,59 are located axially outwardly
of the ends 34,36 of the carcass ply structure 30.
Reinforcing strips 58,59 enhance the bead area's
resistance to compressive forces resulting from the tire
bending about the rim flange during operation in the
uninflated or par-tially uninflated condition. The
reinforcing strips 58,59 further provide an imporved
transition of stiffness from the stiff bead cores 26,28
to the softer sidewall compound. Reinforcing strips
58,59 comprise a plurality of parallel reinforcing
cords, the cords being made from a highly compressive
resistant material, for example, and not for the
purpose of limitation, fiberglass or any metal. In the
embodiment illustrated, the strips 58,59 comprise
a plurality of reinforcing cords made from steel.
To ensure continuity, the radially inner ends 68,70
should be located radially inward of the radially outer-
most point of the bead cores 26,28, respectively.
Applicant has discovered that when the radially inner
point of the reinforcing strips is above the radially
outermost point of the bead core, stress concentrations
may result and cause premature failure. The radially
outer endings 72,74 of reinforcing strips 58,59 are
preferably located radially outward from the rim
flange contact point by at least about . 2 of an inch
(5.4 mm)-
In order -co assure that lhe bead portions 22,24
do not move from their respective rim bead seats 65,67

3S
when tl~e -tire is opera-ted in the uninflated stat,e,
some l,ype of bead re-tention feature is preferably
used. It has been found that the standard safety hump
used on the JJ and JB rim, as specified by the Tire
and Rim Association, provide the necessary support to
retain the beads in their bead seat.
Prolonged use of the tire in -the uninflated
condition may be provided by providing a coolant in the
tire cavity. The coolant may be present in the tire
cavity during normal operating conditions or may be
dispensed into the tire cavity when the tire goes into
the underinflated or uninflated state. A tire made in
accordance with the present invention having a ratio of
hysteresis to dynamic modulus of about .16%/kg/cm2 and
a dynamic modulus of about 104 kg/cm2 and with the
introduction of one pint of polyethyleneglycol into the
tire cavity, has been found to be capable of traveling
upward of 190 miles at 40 miles per hour which could
then be inflated to normal operating pressures and
returned to normal service. This is an increase of
approximately 150 miles of additional travel of the
tire as opposed to opera-ting the tire wi-thout a
coolant. The amount of coolant necessary will, of
course, be dependent upon the size of the tire and the
physical properties of the particular coolant chosen.
Referring to Figs. 3, 4 and 5, there is illustrated
a modified tire 110 made in accordance with the present
invention. The radially inner surface 111 of the tire
is shaped to have a plurality of substantially
identically shaped corrugations 113 which extend in
a substantially radial direction with respect to the mid-
circumferential plane of the tire and are spaced apart
about the circumference of the tire 110. The cross-
sectional configuration of the corrugations 113 may be
sinusoidal as illustrated in Fig. 4 or may take a
variety of forms such as saw-toothed or stepped

tj;~5
-12-
(not illus-trated). Adclitionally, the configurations need
not be equally spaced about the circumference of the
tire. In the embodiment illustrated, the corrugations 111
113 ha~e a substantially sinusoidal cross-sectional
configuration, and are spaced substantially equidistant
from each other about the circumference of the tire and
extend substantially radially with respect to the mid-
circumferential centerplane of the tire, starting from
a point adjacent the bead area radially outward along
the interior surface of the tire to a point beneath
the tread portion terminating prior to reaching the
mid-circumferential centerplane CP of the tire 110.
Preferably the ends of the corrugations 113 beneath
the tread portion terminate at a point spaced a
distance from the tread edge equal to at least 35% of
the distance C from the tread edge to -the mid-
circumferential plane o~ the tire. The tire 110, Figs. 3
4 and 5 is similar to tire 10 of Fig. 1, except that the
sidewall thickness of the tire 110 takes into
consideration the thickness of the corrugations 113. m e
sidewalls of the tire 110 follow the same relationship
as the sidewalls 14,16 of the tire 10, except that
the total sidewall thickness T of tire 110 is the sum of
the mean corrugation height H and the interior sidewall
thickness G. The interior sidewall thickness ~ being
the distance from the base of the corrugation axially
outward to the outer surface of the tire e~clusive of
any indicia that may be present. The mean corru~ation
height H as is sho~Jn in Fig. 5, is the height from the
base of the corrugation to the point wherein half of the
cross-sectional area of the corrugation is above and
half of the cross-sectional area of the corrugation is
below.
While certain representative embodiments and details
have been shown for purposes of illustrating the inven-
tion, it will be apparent to those skilled in the art
that various changes and modifications may be made
therein without departing from the spirit or scope of
the invention.