Note: Descriptions are shown in the official language in which they were submitted.
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Back~round of the Invention
The invention is especially suitable in the wire
reinforcement of the carcass plies and annular belt
reinforcement of tires used on large trucks and
earthmover-type vehicles. Such wire reinforcements
or cords are normally composed of a number of steel
strands which are cabled together to form the desired
cord construction~ each of the steel strands~ in turn~
being composed of a plurality of individual steel
filaments or wires which are twisted together. me
steel strands are designed to carry an equal share of
a load imparted to the cord during the operation of the
tire. Voids are inescapably formed within the cabled
cord. It has been found that moisture~ trapped within
the tire during the building and operation of the tire,
finds its way into these voids and eventually causes
the corrosion of the individual steel wires. Corrosion
can be prevented or greatly reduced by filling the
voids or interstices of a metal cord with corrosion
resistant material~ such as any suitable rubber cement
or adhesive~ or an appropriate hydrophobic material~
e.g. polyolefins~ such as polyethylene~ polypropylene,
polybutene and copolymers of such olefins. A centrally
disposed core of synthetic polyester fibers around
} 25 which the steel strands are wrapped, was found highly
effective in decreasing the corrosion of the steel wires.
Unfortunately~ such cores reduce the strength of the
cord reinforcement~ since the cores are simply not
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capable of carrying the loads th~t the steel strands
are able to carryl ~ typical example oP such a cord
is found in U. S, Patent No. 3,756,883 which describes
a core which is purposely designed to break to allow
the uncoiling of the strands that are cabled around
the core~ The invention is designed to provide a
steel cord reinforcement with a load carrying core
- which does not detract appreciably from the overall
strength of the reinforcement,
The invention accordingly comprises a composite
cord for a tire having a body of corrosion-resistant
material, comprising a plurality of metal strands'
having equal diameters and tensile strengths and-a
central disposed, non-metallic core having a generally
. 15 ' circular cross section around which the strands: are
' cabled~ The core has a diameter to spread the metal ~ - '
strands for penetration of the corrosion-resistant
: 'material between the strands so that the corrosion- .
resistant material may cover and adhere to the strands
to prevent exposure of the metal strands to moisture.
The core has-a-tensile strength and load-carrying - - '
- ' capability to maintain the strands in the spread ~ ' -
condition under tension and carry a proportional
. amount of the load on the cord,
Det'ail'ed Description -of'th'e I-nvention
- With reference-to the drawing, which is a cross-
section of a steel tire cord reinforcement 5 used in -
the carcass plies or annular reinforcement belts of
large earthmover tires, there is shown a centrally
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disposed, non--metallic core 6 composed D~ inorganic,
aramid filaments. An appropriate num~er of steel
strands 7-12 are cabled or spirally wrapped around the
.
multi~ilament core 6 of aramid. The steel strands
7-12 are each composed of a desired number of steel
filaments or ~ires 13-16 which are twisted together. The
individual steel wires 13-16, in this instance, have a
- diameter of .1-75-millLmeters, and the steel strands -7-12-
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~06073Z
each have a lay o~ 10 millimeters (mm) in an S
direction. m e steel strands 7-12~ in turn~ have a
lay around the aramid core 6 of 19 mm in a Z direction.
me aramid core 6 has a high tensile strength which is
substantially equal to~ or closely approximates that of
any one of the individual steel strands 7-12. A multi-
filament yarn or strand of aramid~ having a 1500 denier~
of minimal twist~ and treated with an agent for increas-
ing the adhesion between the multifilament and rubber
material in which the steel cord 5 is embedded~ was
successfully used as a core 6. Two slightly cabled
aramid yarns of 1000 denier each~ similarly treated~
were also successfully used as a core 6.
It is important that the aramid core 6 completely
fill the centrally disposed void created by the cabled
or spirally wrapped steel strands 7-12. To accomplish -
this~ the diameter of the aramid core 6 should be at
least equal to the diameter of each of the steel strands
7-12 which are equally si~ed. In some instances, it is
beneficial to use an aramid core 6 which is slightly
larger than the steel strands 7-12 to spread the strands
7-12 slightly to increase the penetration of the rubber --
material of the tire into the interstices of the steel
cord 5 to more nearly surround the individual steel
filaments 13-16 of each of the steel strands 7-12~
thereby reducing the voids in which moisture can become
trapped and corrode adjacent wires. me aramid core 6
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~060732
should not be too large to severely distort the con-
figuration or geometry of the steel cord 5 so as to
adversely affect the load-carrying characteristics or
capacity of the steel cord 5
Thus~ the aramid core 6 not only acts as a load-
carrying member of the composite steel and inorganic
cord 5~ but fills the center void created by the coiled
steel strands 7-12 to impede the flow of any moisture
through the cord~ thereby preventing or greatly reducing
corrosion of the individual steel filaments or wires
13-16 of each of the steel strands 7-12~
As previously mentioned~ attempts to use cores of
other synthetic fibers~ such as polyester~ have proven
unsuccessful. me polyester core reduced corrosion of
the steel w~res, but was not sufficiently strong to
carry its share of the load or tensile stress imparted
to the cord reinforcement during the operation of a tire
utilizing such cord reinforcements.
mus, there has been provided a composite cord
reinforcement which utilizes a core that not only helps
prevent corrosion of the steel strands of the reinforce-
ment but acts~ in unison~ with the steel strands to
shoulder a share of a load imparted to the composite
cord reinforcements. Such a composite cord is different
from prior art composite cords which utilize a low
tensile strength breakable core~ or a dissolvable core~
or an elastic core for holding spirally wrapped cords
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in coiled relation until such time as the cords are
tensioned to uncoil the cords and allow limited
expansion of the tire in the area of the tire in
which the cords are embedded. me composite cord
reinforcement of the invention is useful in passenger
tires as well as larger truck and earthmover tires.
While certain representative embodiments and details
have been shown for the purpose of illustrating the
invention~ 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.
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