Note: Descriptions are shown in the official language in which they were submitted.
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FILLED COMPOSITE SOLID RUBBER TIRE FOR VEHICLES
BACKGROUND AND SUMMARY OF THE INVENTION
This invention pertains to composite solid tires for vehicles
and to a method of making a consolidated ~iller segment there~or.
Proposals hereto~ore have been made to make a composite solid
rubber tire ~or vehicles by reducing scrap rubber articles to the
form of small pieces, consolidating a quantity of such pieces into
the shape of a solid rubber ring, and inserting the resulting ring
into a tire casing. Such products have been hard to make~ almost
impossible to inser~ inside the casing, and of relatively shor~ ser-
vice life.
I the rings are made in segments and the segments inserted
into the casing to form a jointed core, as also is shown in the
prior art, the segments are prone to become dislodged during use
of the tire. As a result, insofar as we are aware, there is no
composite tire marketed today o~ the class under consideration.
There is need for such a product, however, particularly under
heavy duty conditions, such as are met by lift truck tires, mobile
irrigation sprinkler system carriage tires, certain truck tires, etc.
The need for such a tire exists particularly in order to provide a
large scale commercial outlet for scrap rubber products, thereby con-
serving the petroleum resource from which the rubber for present day~ires is produced, and to provide a serviceable, low cost, tire
product.
It is the general obJect of the present invention to prov;de
a composite solid tire made from consolidated scrap rubber pieces.
It is a ~urther object of the present invention to provide a
method of making from scrap rubber pieces consolidated rubber tire
filler segments suitable for use in such composite tires.
Broadly stated, the presently described method o~ making such
segments comprises reducing scrap rubber articles to the ~orm of
small pieces, placing the pieces in a mold having the configuration
of the desired segment, and heating the pieces in the mold at a
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temperature of from 100 to 600F. while applying pressure of from
500 to 4,000 psi for a time sùfficient to bring the central portion
of the mold contents to a temperature of from 200 to 300F. The
mold contents are consolidated to a density of ~rom 15 to 75 pounds
per cubic foot, after which the mold and contents are cooled. The
consolidated mixture then is removed from the mold and applied to its
intended use.
The herein described vehicle tire product comprises a tire
casing and within the casing a filler comprising abutting segments
resulting from the above described procedure.
DESC~IPTION OF SPECIFIC EMBODIMENTS
OF THE INVENTION
As stated above, the raw material for our invention preferably
comprises scrap rubber articles reduced to the form of small pieces.
Such scrap rubber articles may comprise vehicle tires, tire tubes,
shoe soles, rollers, rubber mats, etc. They preferably comprise
scrap rubber tires available in substantially unlimited quantity at
very low cost.
Another primary source of raw material for our new tire product
comprises the waste rubber byproduct from the tire retreading indus-
try. In this industry it is conventional to buff off with grindingwheels the tread and under tread rubber from the tires to be re-
capped. This produces annually an enormous quantity of rubber par-
ticles ranging in size from dust to about 1/4". This waste product
poses a very real disposal problem to the retread houses. However,
it is ideal for use in the composite solid rubber tire products of
our invention.
The rubber raw material may be prepared in two principal cate-
gories.
In the first, the scrap rubber articles are reduced severely
to the form of very small pieces ranging in size from dust to par-
ticles having a maximum screen size of about 1/4" mesh.
The other category comprises a quantity of larger pieces such
as may be manu~actured by chipping the scrap rubber articles to the
form of chips having a maximum size o~ approximately 3" x 3".
The first named category may readily be obtained as a by-pro-
duct of the tire recapping industry, as outli.ned above. The second
categDry may be produced inexpensively by chipping scrap automobile
tires, including the whole casing with bead. The fabric content and
wire content of the resulting chips does not interfere with the
successful application of the material to our purposes and may even
improve the properties of the resulting product.
The consolidated tire segments may comprise totally consolidated
rubber pieces of the first category. However, they also may com-
prise a mixture of small pieces of the first category and up to 75%
by weight of the chips of the second category, thus providing an
inexpensive raw material.
As is clear from the foregoing discussion, scrap rubber tires
are intended as a primary source of raw material for the practice
of our invention. The chemical identity of the rubber suitable
therefor accordingly is determined by the identity of the rubbers
used in the tires. Such rubbers are:
isoprene-type rubber
neoprene-type rubber
butadiene-type rubbers
Buna N
Buna L
Buna GRS
These materials may be used in admixture with each other and in
admixture with a proportion of natural rubber, although the e~ten-
sive use of natural rubber is discouraged by its high cost.
It is a feature of the invention that using the present day
synthetic rubbers the scrap particles may be consolidated and wel-
ded together under the influence of heat and pressure without the
necessity of using a bonding agent and/or vulcani~ing agent. This
is in counterdistinction to the rubber mixtures described in the
prior art. It is an important consideration, since elimination of
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bonding and vulcanizing agents substantially simpliies the processing
procedures and reduces the cost of the product.
In the fabrication of the rubber pieces described above into a
consolidated rubber tire filler segment, a quantity of pieces of the
desired size and characteristics first is formed.
This raw material then is charged into a mold of suitable con-
tour having the configuration of the desired tire filler segment.
To be suitable for such application, the contour of the segment
should be arcuate, with planar end faces. Where there are four
segments for each tire, these faces should be substantially perpen-
dicular to each other. As a result, when they are abutted in the
tire casing, they meet face to face without a substantial gap be-
tween.
Also, and importantly, the joints between the meeting spaces
will not be perpendicular to the point of contact of the tire with
the ground. As a consequence, the faces will overlie each o~her so
that one face bears against the meeting face. This forms a unitary
whole and prevents the individual segments from working out of place
and distorting the casing in which they are contained.
The mold preferably is dimensioned to be somewhat wider than
the cross section of the tire casing in which the molded segment is
to be inserted. This insures a snug fit.
Within the mold, the pieces are first subJected to a preliminary
consolidation to the desired density, e.g. a density of from 15-75
pounds per cubic foot. The mold and contents then are placed in an
oven and heated at a temperature of from 100 to 600, preferably
350-450F. while applying a pressure of rom 500 to 4,000, preferably
1,000-3,000 psi.
The mold and contents are heated at this temperature for a time
sufficient to bring the central portion of the mold contents to a
temperature of from 200-300F. Under these conditions the individual
pieces within the mold consolidate and bond to each other, either by
sintering together or through chemical reaction. This may be accom-
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plished without the use of a solvent~ or vulcanizing agent.
At the conclusion of the heat and pressure treatment, the moldand contents are cooled, the mold oper,ed and the finished tire fil-
ler sègmen~ iemoved.
To incorporate the segments ili~ a composite solid tire, a
conventional tire casing, which also may be a discarded used casing,
is provided. The casing is spread and the segments inserted end to
end. Thereupon they will nest snugly within the tire casing which
next may be mounted on a suitable split rim for application to the
intended use of providing a solid rubber tire ~or a vehicle.
As indicated above, such vehicles comprise especially automobi-
les and trucks. However, they also may comprise lift trucks, golf
carts, wheelbarrows, mobile irrigation equipment and the like. In
this use the tires serve as efficient, heavy duty tires. Their use
is attended by the further advantage that in the event the casing
accidentally is slashed and rendered useless, the filler segments
can be removed from the slashed casing and used in a replacemen~
casing.
EXAMPLE
To make a rubber tire filler segment for use in a composite
industrial truck tire, the ollowing procedure is illustrative.
A mixture o 25% of up to 1/4" mesh rubber particles and 75%
o up to 3 x 3 inch rubber chips is prepared.
The resulting mixture is placed in a mold of arcuate contour
representing 1/4 of the circumference of the finished tire. The
material is compressed in the mold to a density of 45 pounds per
cubic feet. This re~uires a pressure of about 2,000 pounds per squ-
are inch.
The mold and its contained charge is placed in an oven and
heated at 380-400F. until the material in the interior o the mold
charge has attained a curing temperature of 230-280F. The cure time
is approximately 4 hours.
The mold and contents are cooled to ambient temperature, the
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mold opened and the consolidated tire ~iller segment removed.
Four such segments then are inserted in an appropriately sized
tire casing, which is mounted on a rim to produce the finished com-
posite tire.
