Note: Descriptions are shown in the official language in which they were submitted.
PNEUMATIC TRUCK TIRE
The foregoing abstract is not to be taken as
limiting the invention of this application 9 and in
order to understand the ~ull nature of the technical
nature of this application, reference must be made to
the accompanying drawings and -the ~ollowing detailed
description.
Back~round of the Invention
This invention relates to pneumatic tires, and
more particularly, to an improved heavy truck radial
tire for use primarily on the road, preferably in
the steering and driving positions.
It is well known in the industry that a choice
; of a particular tread design involves trade~o~
between specific tire performance characteristics
in order to achieve the overall desired tire perfor-
mance. Among such characteris-tics are those
directed to high mileage, uniform wear, traction,
cool running and the like. The foregoing perfor-
mance characteristics are generally at odds with
each other; for example, a tire which exhibits high
mileage and good lateral stability may have poor
traction characteristics. Conversely, a tire which
has good traction may have poor mileage potential,
lateral stability and even wear.
It is important that heavy -truck tires~
especially those used in the steering position have
high mileage, uniform wear and lateral stability.
Additionally, it is important th~t -the tire runs
as cool as possible so that the casing may be
retreaded at least once.
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Applicants have discovered a particular
arrangement by which high mileage and uniform wear
characteristics may be obtained in a heavy duty
truck tire for use primarily on the road which also
has good handling performance, traction and runs
cool.
Summary_of_the Invention
In accordance with one aspect of the present
invention, there is provided a heavy -truck -tire for
use primarily over the road comprising:
a ground engaging tread portion having a pair
of shoulder portions, one at each lateral edge, a
pair of sidewall portions extending from each of
said shoulder portions of said tread portions
radially inward terminating in a pair of bead
portions, respectively, the carcass ply structure
extending from said bead portion to said bead por-
tion, characterized by said tread portion comprising
a plurality of independent projections, said
independent projections having a configuration and
being arranged about said tread portion so as to
provide a plurality of substantially parallel
circumferentially extending rows of independent
projections and a plurality of substantially
circumferentially extending zig-zag grooves between
said rows of independen-t projections, said
independent projections in each of said rows are
oriented and have a configuration such that each
projection has one side, one in either circumferen-
- tial direction which is parallel to the adjacent
projections on either circumferential side o~ said
projection in said row, said independent projections
in each of said ro~s being spaced apart so that the
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sides of adjacent projections which face each other
are separated by a narrow groove having a width
less than 1 mm so that when the adjacent projections
are in the footprint of the tire, the narrow grooves
close so that the adjacen-t projections act together
to resist lateral and circumferential forces, said
sides of said projections which face the circum-
ferentially adjacent projection form an angle from
about 70 to 85 degrees with respect to the mid-
circumferential centerplane of said tire.
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Descrip~La~L~Lh:.LL~lLL~
Fig. l is a perspec-tive view of a tire made in
accordance with the presen-t inven-tion, i-t being
understood that the tread portion is repeated
throughout the circumference of the tire;
Fig. 2 is an enlarged, fragmentary front plan
view of the tread portion;
Fig 3 is a cross-sectional view o~ the tread
portion according to the present invention taken
along line 3-3 of Fig. 2;
Fig. 4 is a diagrammatical representation of
three adjacent projections in one row of independent
projections of said tread portion; and
Fig. 5 is an illustration of a modified
configuration of an independent projection made in
accordance with the present invention.
Detailed Description o~ the Invention
Referring to Figs. l and 2 there is illustrated
a heavy truck tire lO having a ground-engaging tread
portion 12. For the purpose of this invention, a
- heavy truck tire shall be considered a tire which
has a nominal rim diameter from about 20 inches to
approximately 24.5 inches. However, heavy truck
tires having nominal rim diameters as ~ow as about
17.5 inches are known and considered to be part of
the presen-t invention. The tire 10 has a pair of
sidewall portions 14,16 which extend from each of the
shoulder portions of the tread portion 12 radially
inward terminating in a pair of bead portions 22,24
respectively. A carcass ply structure (now shown)
extends frorn bead portion to bead portion.
Preferably, -the carcass ply structure is of the
radial type wherein the cords of each carcass ply
forrn an angle with respect to the mid-circumferential
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plane of the tire from a~out 75 degrees to 90
do~rees. Thc cords of ~;he c~rcass ply s-t,ructu~e
may comprise of any material normally used for cord
reinforcemen-t in pneumatic tires. For eY~ample, and
not by way of limitation~ nylon, rayon, polyester,
steel. The tire 10 may be further provided with a
belt reinforcing ply structure (not shown) beneath
the tread portion and radially outward o~ the carcass
structure. The cords of the belt ply structure may
comprise of any conventional material normally used
in belt reinforcemen-t and may lie at any conventional
angle used in pneumatic tires.
In the embodiment illustrated in Fig. 1 and 2,
the tread portion 12 of the tire 10 is provided with
continuous circumferentially extending shoulder ribs
26,28 in the shoulder portions 18,20. The remaining
portion of tread 12 is provided with a plurality of
substantially identically shaped independent pro-
jections 30 arranged in a plurality of rows. In the
embodiment illustrated, three rows 32,34,36 are
shown. The actual number of rows will depend upon
the size of the tire and configuration of the
projection, and generally there are from about two
to four rows of independent projections. While the
present invention is shown as having two continuous
circumferentially extending ribs 26,28 in the
shoulder regions, ribs 26,28 may be replaced by rows
of independent projections similar in configuration
to rows 32,34,36. Preferably, the circumferentially
1 30 extending ribs 26,28 are used so as to minimize
shoulder wear and increase lateral stability. The
ribs 26,28 or rows (in the case when rows are used
instead of continuous shoulder ribs) have a cross
sectional width W which ranges from about 15 percent
to 25 percent o~ the tread width T, preferably aboùt
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18 percent. For the purpo~e of this invention, -the
tread width and width o~ the ribs or rows are
measured from -the footprin-t of the tire inflated to
normal inflation pressure and loaded -to normal load
on a rim for which it is designed. The cross-
sectional width W of the ribs 26,28 is -the distance
from the tread edge to the circumferential center-
line of the adjacent zig-zag groove 38. The
circumferential centerline is the line axially
midway the axial outermost points of the zig-zag
grooves (See Fig. 2).
The projections 30 have a configuration such
that the rows 32,34,36 form wide zig-zag grooves 38
in between rows 32, 34,36 and ribs 26 and 28. The
zig-zag grooves 38 have a width sufficiently large
such that when in the footprint of the tire grooves
3~ remain open to provide water channeling passages
Preferably, the grooves 38 all have substantially
the same width.
The use of independent projections 30 provides
good flexibility of the tire as it enters and leaves
the footprint of the tiret thereby contributing to
good wear and cool running temperatures. The use of
independent projections allow the portion of the tire
entering and leaving the footprint to act indepen~
dently of the tread portion mainly before and after.
However, the use of independent projections has the
disadvantage of reduced lateral stability and possible
heel and toe wear. To overcome this problem, the
projections 30 have a configuration and are spaced
apart from each other such thatt when the projectio~s
are in the footprint of the tire, they act together to
resist both lateral and circumferential forces exerted
on the tire. The projections 30 when in the
footprint of the tire seat or nest next to the
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adjacent projection (See Fig. 4). This type of
nesting allows the projection to come together
and act as a continuous rib when in the footprint
to minimize the heel and toe wear normally
experienced by independent projections and provide
improved lateral stability. The projections 30, as
it travels through the footprint of the -tire,
experience varying lateral forces. The maximum la-teral
force occurs in the central portion of the ~ootprint
and proceeding toward the edges of the footprin-t the
lateral force decreases in magnitude. Since the pro-
jections in the center experience a greater lateral
force these projections tend to displace an axial
distance greater than the circumferentially adjacent
projections. The nes-ting action of the projection
allows the projection to act as a continuous rib,
when in the footprint of the tire, to transmit and
spread the greater lateral force experienced by the
projections in the central por-tion of the footprint
to -the circum*erentially adjacent projections. This
nesting action improves the lateral stability of
the tire yet allows the tread portion of the tire to
have enough flexibility to minimize the bending
stresses in the tire. The grooves 46 separate the
adjacent projections 30 so as -to allow the projections
30 to act independently of the immediately adjacent
projections when entering and leaving the footprint,
but are small enough to allow the projections to
nest as it proceeds through the footprint of the
tire. The grooves 46 are less than about 1 mm and
preferably are made as small as possible. Generally,
the grooves 46 range from abou-t .2 mm to .8 mm. In
the particular embodiment illustrated, the grooves
46 are approximately .5 mm.
The depth d of the grooves 46 is at least
30 percent of the non-skid depth D (See Fig. 3 ).
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preferably, at least 60 percent, and in the
particular embodiment illus-trated, the dep-th o~ the
grooves 46 is approximately 80 percent o~ the non-
skid depth D.
The con~iguration of projections 30 should be
such that only one side is common with the circum-
~erentially adjacent projec-tion 30 in the same row.
Therefore, each projection has two sides 44, one in
either circumferential direction which is in parallel
relationship to the immediately adjacent projection.
Preferably the sides are substantially straight. In
the particular embodiment shown, the projections 3G
have an overall configuration of a pentagon.
However, it can be seen that sides 43,45 and 47 of
the projections 30 may be varied without departing
from -the scope of the present invention. Preferably,
the portion of the projections 30 which are not
common to the adjacent projections have a configuration
such that a zig-zag groove is formed between adjacent
rows of independent projectionsO Fig. 5 illustrates
a modified configuration of projections 30 made in
accordance with the present invention.
Projections 30 have a configuration such -that
-the grooves 46 ~orm an angle with respect to the mid- ;
circumferential centerplane of the tire from about
70 degrees to 85 degrees, preferably from about 75 to
85 degrees. It is important that the angle formed
be within prescribed limitations so as to assure
proper nesting. The particular angle in which the
groove 46 form with the mid-circumferential plane
will, of course, be dependent upon the exact config-
uration of the projection and the pitching sequence
of the tread pattern.
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The projections 30 have a configuration such
that the mean circumferential width CW divided by
-the mean axial length L ranges from approximately
.6 to 1.9, preferably from about .6 to 1Ø Here
again, the exact ratio that is ob-tained will be
dependent upon the configuration of the projection
and pitching variation in the tread portion. For
the purposes of this invention9 the mean width of
the projections 30 is the width of the projection
which is mid~way between the maximum and minimum
width of said projection and the mean height of the
projection as being the height which is midway
between the maximum and minimum height of the
projection.
While certain representative embodiments and
details have been shown for the purpose of
illustra-ting the invention, it will be apparent to
those skilled in this art that various changes and
modifications may be made therein without departing
from the spirit or scope of the invention.
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