Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The invention relates to an insulated bead for a radial
or a steel ply radial tire.
Steel beads make it possible to securely affix tires to
rims. Tire beads are made from coiled wire. The individual
strands of the wire may be coated with rubber and the plurality of
rubber coated s~rands may be helically wrapped with a fabric or
cord. United States Patent 3,106,952 Rudder (1963) describes such
a tire bead. The Rudder patent i5 directed primarily to wrapping
the bead bundle with a heat-shrinkable material having widely
spaced turns. During heat curing of the tire, the heat shrinkable
material contracts and compress the wound bead wires (bead bundle),
thus preventing wild bead wires from getting into the sidewall or
some other portion of the tire where they could cause damage. The
heat shrinkable material does not keep the rubber around the bead
bundle in place. It has also been known in the prior art to wrap
the bead bundle with rubber prior to adding a flipper to provide
an insulating layer of rubber between the bead bundle and the next
adjacent body ply. In spite of the addition of the rubber wrap,
some failures continued to occur in the bead area of experimental
~20 steel ply radial tires. Wrapping a bead bundle with rubber and
adding a flipper is discussea in "The Story of Tire Beads and
:
Tires"j Niles Standard 1954, pages 80-82.
The invention as claimed is not intended to provide a
remedy for wild bead wires of steel ply radial tires. It solves
the problem of how to provide insulation between the bead bundle
and adjacent steel body ply of steel belted, steel ply radial
tires. In the practice of the present invention, the bead wires
and a steel body ply can no longer come into direct contact, and
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generate fretting corrosion, resulting in ultimate failure of the
tire.
The invention provldes a method of constructing a com-
posite bead ring structure for inclusion in a steel ply radial
tire comprising: a. producing a first-stage composite by forming
a strand of rubber covered wire into a multiple strand substantial-
ly circular configuration, the cross-sectional area of said first-
stage composite being of a substantially hexagonal shape, b. pro-
ducing a second-stage composite by envelope wrapping said first-
stage composite with natural rubber obtaining thereby a second-
stage composite having a substantially circular cross-section, c.
producing a third-stage composite by helically wrapping said
second-stage composite with a narrow width of fabric, and there-
after coating said third-stage composite with an appropriate lubri-
cant to produce said composite bead ring structure.
From another aspect, the invention provides a composite
bead ring structure for inclusion in a radial tire comprising a
central portion of substantially circular configuration having a
hexagonal cross-sectional area and consisting of multiple strands
of rubber-covered wire, said central portion being envelope wrapped
in natural rubber which is in turn helically wrapped with a narrow
width of fabric and coated with a lubricant.
The advantages offered by the invention are mainly that
the rubber insulation which is applied to the bead bundle of
rubber covered bead wires is tightly envelope wrapped or helically
wrapped with a fabric covering which prevents movement of the
insulation caused by turning the steel body ply up over the bead
bundle by the pressures incurred during tire molding of the tire
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and by forces incurred during tire operation. For the purposes of
the present invention, applying a flipper to a bead is not con-
sidered wrapping the bead.
There are a number of ways of carrying ou-t the invention
depending on what type of tire building drum is employed. For
example, if a zero-crown drum tire building machine is used, one
first envelope wraps the bead bundle with a layer of rubber, then
coats the rubber cover with zinc stearate or a comparable lubri-
cant 4; then applies a second rubber cover envelope wrapped; then
applies a tight fabric cover, helically wrapped or envelope
wrapped. The reason for this is that in forming a toroidal con-
figuration from the flat drum, green components adjacent to the
bead bundle must rotate in the tire. The lubricant allows the
adjacent components to the bead bundle to rotate with a minimum
of distortion. The fabric wrap holds the rubber around the bead
bundle in place during the various tire building operations. The
second layer of rubber and the fabric wrapping can be replaced by
a fabric rubber laminate. In the finished tire, the above-
described procedure prevents metal-to-metal contact between the
bead and the body ply and the resulting fretting corrosion. The
zinc stearate is applied as a 6 percent suspension in isopropyl
alcohol.
When a high-crown drum is employed and in other situa-
tions where the green components need not significantly move with
respect to the bead in the tire during tire building; the lubricant
and the second layer of rubber wrapping need not be employed.
In the preferred embodiment, sufficient rubber is applied
to the steel cord bundle to provide from 0.1 cm to 0.7 cm of
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additional rubber insulation in the area where the rubber covered
bead wires come into proximity with a steel body ply. The fabric
cover covers at least 80 percent and preferably 100 percent of
the outer surface of the insulating layer. It is particularly
important that the rubber insulating layer cover all areas oE ~he
bead that would otherwise be in contact with ply wire. When the
fabric bead cover is helically wrapped on~o the bead, the fabric
is preferably nylon impre~nated with rubber. The fabric used in
the preferred helical wrap has a width of from .5 to 3.0 cm.
When the fabric is enveloped wrapped over the rubber covered bead
bundle, the Eabric preferably has a width at least 30 percent
greater than the cross-sectional circumference oE the bead
bundle. This provides a locking overlap which in turn prevents
the package Erom opening and releasing the rubber insulation when
pressure is applied to the enveloped wrapped rubber covered bead
bundle during tire buildin~. Preferably the fabric completely
vers the surface of each rubber covered bead. It is also
preferred that no bead filler strip be present inside of the
~ wrap. Instead of separately covering the bead bundle with rubber
; 20 and fabric, the bead bundle can be wrapped with a rubber-fabric
laminate.
~ One way of carrying out the invention is described in detail
below with reference to the drawin~s which illustrate these
specific embodiments in which:
Fi~ure 1 is a cross-sectional view showing a hexagonal
bead having a rubber and fabric cover.
Figure 2 is a cross-sectional view showing an envelope
wrap.
Fi~ure 3 is a hexa~onal bead bundle covered with 2
layers of rubber and an outer cover of fabric wherein a
lubricant is interposed between the two rubber layers.
e figures show various rubber covered wrapped bead bundles.
In accordance with the invention, a hexa~onal bead bundle is
first formed by wrapping a single strand rubber covered wire 1 in
a circular configuration to form a bead bundle having a
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cross-sectional configuration of 72 wires. The bead bundle has a
cross-sectional diameter of 1~83 cm. The uncoated s~rand of wire
has a diameter of .13 cm and is coated with a thickness of .013 cm
of rubber. The bead forming machine is a National Standard Model
147 described in part in United States Patent 3,741,263. The bead
is then enveloped wrapped with a strip of rubber having a width of
5.84 cm and a thickness of .23 cm. There is approximately a .51
cm overlap along the top surface of the bead. The machine used to
apply the enveloped wrap is a RJS Corporation; Model 147 Covering
Machine; manufactured by RJS Corporation, Akron Ohio. The rubber
~overed bead bundle is then helically wrapped with a fabric 3.
The fabric is square woven nylon having a width of 1.59 cm and a
thickness of .028 cm. The fabric is a tackified nylon 6.6 Leno
woven material with a denier of 210. The wrapping machine employed
is a National Standard Model BSW Spiral Bead Wrapping ~lachine
manufactured by The N-S Machinery Division, Niles, Michigan. The
wrapped bead produced is then used to build a tire on a high-crown
drum in a conventional manner. The tires produced by the present
invention do not result in tire failure, due to the body ply
fretting while in direct contact with the bead bundle. Tires
produced without the fabric wrap over the rubber insulating com-
pound may result in such a failureO
The green rubber used to wrap the bead preferably has a
mooney viscosity of from 60 to 70 and when cured has a shore A
hardness of from 84 to 92.
Another method of wrapping the bead bundle with rubber
and fabric is designed to apply a rubber cover around the bead
bundle by the use of expanding bladders. Pertaining to this inven-
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tion, a rubber laminated fabric may be used. The laminated fabric
is placed under the bead bundle with the rubber in contact with
the bead and the fabric being the outer surface. A bladder on one
side expands and is pushed towards the bead bundle by the use of
push cans. The bladder forms the laminated fabric around the bead
bundle with its edge ending on the top surface of the bead~ The
other side performs the same operation, with the edge of the
laminate fabric overlapping the previously ~rapped edge. The
Henley invention forms an envelope wrap of rubber and/or rubber
laminated fabric.
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