Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR THE MANUFACTURING OF BUNDLES OF STEEL WIRE PIECES
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The ;nvention relates to a process for the manufacturing of
bundles of steel wire pieces for the strengthening o~
building elements, such as beams or roadway surfaces. In
order to come into consideration for that purpose, the wire
pieces shall have an essentially oblon~ form, with a
thickness of 0.3 to 1.5 mm, a length-to-thickness ratio ,
between 40 and 120, and a maximal length of 120 mm. By
"oblong" is meant, that the wire piece is not so bent or ~ ~ -
curled, that it would no longer be possible to distinguish a
general length direction in which the wire piece has to exert
its strengthening effect. In this respect, the apparent
length of the wire piece, i.e. the distance between both ends
of the wire piece, has not to be smaller than 0.7 times the --
length, as measured along the wire piece. The thickness of
the wire piece, for non-circular cross-sections, is ~ ;r -
calculated as the diameter of the circle having the same
area.
Such steel wire pieces are used for the reinforcement of
cementitious concrete, and are mixed into the wet mixture, ;
that is dumped thereafter, deformed and compacted and then
hardens in the desired form. When these wire pieces are
dumped into the mixture, without any further precaution, then
this leads to the conglomeration of the wire pieces into
balls, instead of an equal distribution in the concrete. For
that reason, those steel wire pieces are introduced into the
wet mixture in the form of bundles of such steel wire pieces,
that are held together in a bundle by means of a binding
substance that loses its binding power during mixing, more
specifically by the fact that the binding substance
dissolves, totally or partially, in the water of the
cementitious mortar or concrete. Such bundle preferably -~
contains 5 to 40 steel wire pieces. The bundle mustnot
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necessarily have a nearly circular cross-section, but can -~
also be a flat bundle of wire pieces that are glued together
side by side. ~ `
It is known from US-Patent 4.284.667 to manufacture such -~
bundles of wire pieces by a method in which a number oF wires ~ --
are bundled and glued together, by applying an emulsion or
solution in water of such binding substance that thereafter, -~
after drying, will be capable of dissolving and/or emulgating
again in the concrete, and the so obtained bundle is
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subsequently dried in a drying furnace, and is finally cut
transversally into pieces.
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It is an object of the present invention to provide an
alternative for this method, whereby more or less advantages
can be obtained in dependence on the circumstances, such as
the intended use.
The invention is based on the finding that the glueing
substance, although known as a substance that has to be
totally or partially soluble in water, mustnot for that
reason necessarily be applied in the form of an emulsion or
solution in water, but can also be applied in the form of a
hot molten liquid. This can even be applicable for substances
that mustnot be soluble in water at all, but that are adapted
to disintegrate by melting. This is interesting for
applications where the steel wire pieces must be mixed into
hot mixtures, such as hot bituminous concretes, and where the
fibre bundles disintegrate by the temperature of the mixture.
Applying the glue in a molten form has the advantage that the ;~ i~
glue must no longer be dried in a drying furnace, but that it
can solidify by simply rapid cooling, before the bundle is
transversally cut into pieces. In this way the production
speed can be raised and drying energy saved. And the method
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of applying a molten glue doesnot prevent to use a glue that
still is totally or partially soluble in water, in such a way -~
that the bundles of wire pieces are usable both in cold
cementitious mortar or concrete and in hot bituminoùs
concrete. A further advantage in the manufacturing lies in
the fact that a glue to apply by melting takes much less room
for storage, and can be preserved undefinitely in time.
The invention is consequently characterized by the fact that
glueing occurs by means of a glue in molten state, and that
this glue solidifies thereafter by cooling down. `~~
The glue in a "molten state" is to be understood here in the
sense that the glue, under influence of temperature, has lost -
its solidity, not necessarily completely by heating above a
sharply defined melting point that the glue should have, but
that it has lost sufficient solidity to be applied to the
wire bundle. For substances that are composed of different
molecules with different melting points, as e.g. for
synthetic resins, the loss of solidity occurs by gradually
softening through a softening temperature range, and it is
sufficient that the substance is sufficiently soft to be
applied as a ylue. For such substances the temperature level
of softening is determined here by the softening point ~ -
according to the Ring & Ball Test. And for the substances
with sharply defined melting point, the "softening" occurs at
the melting point. This is what is meant hereinafter by ~b
softeni~g point.
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When the fibre bundles are intended for use in bituminous
concrete, a glue will be chosen that is adapted to
disintegrate by ~elting when mixed into such hot bituminous
concrete. This means then that the glue, under influence of
temperature, loses sufficient solidity to allow the bundles `~
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of wire pieces to disintegrate into indiv;dual w;re pieces
under the mixing movement, where this loss of solidity is due
to the substance passing wholly or partially from the sol;d
into the molten state. As the mixing temperature of ~ ~-
bituminous concrete ranges from about 80C to 200C, and as
the mixing temperature has preferably to be 30 to 50 degrees ;` i
centigrade above the softening point, a glue will be chosen
having a soften;ng point in the range between 50C and 170C.
Below 50C, the risk increases indeed, that the bundles begin
to st;ck to each other when exposed to the sun or to warm
climate circumstances.
As a glueing substance, a bitumen can be chosen preferably of
the same composit;on as used in the bituminous concrete, if
the fibre bundles are intended for mixing into such
bituminous concrete. As known, a bitumen is a mixture of
ma;nly hydrocarbons with residual ;mpur;ties, as obtained as
residues from ref;ning coal or petroleum, such as p;tch or
tar or asphalt. They are hard at room temperature and
suffic;ently liquid at the m;xing temperature to flow between
the other components of the bitum;nous concrete (that further
comprises a mixture of filling material, such as sand, lime,
and/or stone pieces of a dimension of 2 mm up to 20 ~m) and
to form, after hardening, the binding component for the
bituminous concrete. ``
It is also poss;ble, for the glueing substance, to use a ;~
thermoplastic polymer or copolymer, preferably in the form of
a conventional hot melt glue, which, depend;ng from one
manufacturer to the other, also comp~ises res;ns, waxes,
softeners, stab;l;zers and possibly f;llers, ;n addition.
Accordingly, a polyester-polyurethane glue can be used, e.g.
according to U.S. Patent No. 2.801.648, of which the
softening point can be set by adding less or more
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di-isocyanate during the manufacturing of the glue. An
EVA-glue (ethylene-vinylacetate copolymer) can also be used,
of which the softening point can be adapted by means of the
proportion ethylene/v; nyl acetate. When a hot melt glue is
necessary that can dissolve or emulgate in water, then a
typical hot melt glue can be taken, as used for applying in
molten state to paper or cardboard, where the glue can
therafter become tacky again by moistening with water. In
practice, a choice can be made among the different hot melt
glues available on the market, and that are e.g. des~ribed in
the book of D.L. BATEMAN "Hot melt adhesives", Third Edition
(Noyes Data Corporation).
The glue can be applied in di~ferent ways. It is possible to
pass a bundle of wires continuously through a bath of molten
glue, and to wipe off the excess of glue at the exit of the
bath before cooling the bundle, e.g. in an air jet or in
water, when a glue is used that is not soluble in water.
Another method, when the glue is in powder form, consists of ~ -
heating up a continuous bundle of wires and passing this hot
bundle through a fluidized bed of such powder. The powder
then melts against the wire bundle, and the glue solidifies
again at the exit of the fluidized bed. It is also possible
to use conventinnal appliers with a nozzle that continuously
delivers the molten glue under pressure on or around the
bundle and a wiping piece. It is also possible to apply the
glue on the individual wires first, and to bundle the wires
thereafter, where the wires can be glued together, e.g. by
heating up and cooling down again.
In order to glue the wire pieces easily together, and so that
the wire pieces can easily be separated thereafter, it is ` `~
preferred to glue the wires side by side into a flat bundle.
It is however also possible to manufacture a round bundle, in
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which the glue doesnot completely penetrate towards the core
of the bundle, but keeps all the wires together because it
acts as a tight sleeve around the bundle. Glueing the w;res
together does consequently not necessarily mean that all wire
pieces are brought in contact with the glue, but only that,
after solidification of the glue, the wires are kept together -
into a bundle.
When the wires are conducted side by side in order to be
grouped into one flat bundle in one plane, and when the wire
pieces are to be provided with undulations or deformations
and/or hooks or bendings at the extremities, those
deformations shall preferably be applied on the continuous
bundle, before the cutting thereof. This is then preferably
done by conducting the flat bundle continuously between two
rotating rollers with undulating cross-sectional
circumference or with another profile, where the protrusions
of one profile match the indentations of the other one. In
such a way, deformations are applied in a plane that
comprises the longitudinal direction of the bundle, and that
is perpendicular to the plane of this bundle. g
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It is clear that the process is very adapted for a continuous -~-~
process, in which a number of wires are unwound from their
respective spools, and in which these wires after unwinding
are caused to converge towards the entrance of a machine, in
which they are bundled and glued. In this machine, the bundle ;~
passes a glueing station first, where the glue is applied,
and then passes a cooling station, where the glue is caused `~
to cool down for solidification, and then further optionally
passes a deforming station, where the bundle is deformed
between two rotating wheels, and finally passes a cutting
station, where the bundle is cut into pieces, and the bundles
of wire pieces are collected in a container. ";--` ;
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