Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to irnprovements in the
manufacture of wire cloths and, in particular, relates to an
improved plastic-wire cloth and a method of making the same.
The invention is particularly applicable to flexible wire cloth
which is woven in continuous lengths on wire fabric looms.
Prior to the present invention, flexible wire cloth
fabricated either from rnetallic or non-metallic wires, has been
used for insect screening, filtering and similar uses. In
addition, screening has been fabricated from textile filaments,
lo usually monofilaments of nylon or saran or coated multifilaments
of glass fiber. While such plastic screen fabrics have many
desirable characteristics, the consurning public appears to prefer
wire cloth for use as insect screening.
There have been attempts to improve the characteristics
of wire cloth in order to incorporate many of the desirable
features of plastic screening, but such attempts have not been
entirely successful commercially. However, wire cloth is
presently available which is galvanized or zinc-dipped, or
painted to protect the wire elements from corrosive constituents
in the environment where the cloth is used. The treatment of
wire cloth in the latter fashion is expensive and time-consuming,
and requires severe measures to avoid polluting the atmosphere
and the waterways. The present invention provides a preferable
alternative to such treatment.
The present invention combines the desirable character-
istics of plastic and wire cloth screening by providing a plastic-
wire cloth screening consisting of a base fabric of conventional
wire coL~ponents in which the wire components are protected from
corrosive elernents by encapsulating the components in plastic to ~ -
provide an exposed surface consisting of an unbroken plastic
film protecting the wire components from corrosive atmospheres,
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when used as screening and/or corrosive solutions when used in
industrial filtering applications.
The improved screening of the present invention is
fabricated by weaving a flexible wire fabric and applying a
plastic film to the components of the fabric after weaving by
coating the woven components with a powdered resin and curing
the resin in place on the woven screening to generate an un-
interrupted plastic film on the components.
In particular, the powdered resinous material is
deposited on the woven wire by electrostatic deposition which
is readily controlled so as to effectively deposit an uninter-
rupted coating upon the component which, when cured, forms an
integral film thereon.
Thus the present invention provides a method of
making a plastic-wire cloth comprising the steps of weaving a
continuous length of fabric of wire elements of electrically
conductive material, passing said woven~wire fabric first through an
alkaline bath to remove the dirt, grease or other foreign matter
from the surface of the wire elements, second through a spray rinse
to complete the cleansing, third through a drying oven to dry the
woven-wire fabric, and fourth from said oven through a cloud of
charged particles of a film-forming powdered resinous material
at a rate of feed to deposit a continuous layer of particles on
the wire elements of said fabric in a thickness suitable for
forming a continuous film, and then heating said continuous length
of woven-wire fabric to heat-flow said particulate material into
a continuous unbroken integral film which is cured and encap-
sulates the individual wire elements of said fabric.
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The present invention provides a plastic-wire cloth
which is flexible and rnay readily bend without fracturing the
film or causing the filr~ to flake. The encapsulated components
provide a substantially improved strength-to-weight ratio
enabling either the use of a lighter cloth for a comparable
purpose or improving the durability of the cloth without
increasing its weightO
The fabric made in accordance with the present inventic~
provides an irnproved appearance over prior treated wire cloth
screening without the irregularities or bare spots which are
norrnally present in prior treated wire screens.
The present invention eliminates the necessity for
providing a woven selvage in the wire screen while avoiding the
danger of raveling during subsequent handling and thereby
enabling substantial economies in the manufacture and use of
the wire screen material.
The plastic-wire cloth screen of the present invention
is an improvement over the plastic screening in that the screen-
ing of the present invention is resistant to damage from
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concentrated heat or inadvertent impact, does not bag or sag,
or melt, and cannot be gnawed by rodents or other animal lifeO
The present invention enables the use of a film of
plastic which is sufficiently thin to avoid obstructing the
interstices of the woven wire, thereby avoiding impairment of
visibility through the wire and airflow through the wire. On
the other hand, the screen may be made in accordance with the
present invention so as to increase the thickness of the film
of plastic to fill up the interstices of the woven wire and
thereby obtain a controlled degree of permeability or percentage
of open area.
All of the objects of the invention are more fully set
forth hereinafter with reference to the accompanying drawings,
wherein:
Figo 1 is a plan view of a plastic-wire fabric made in
accordance with the present invention;
Fig. 2 is an enlarged cross-section through the fabric
shown in Fig. l;
Fig. 3 is a greatly enlarged view of an intersection
portion of Fig. 2 encircled at 3 illustrating the film thickness
obtained on the intersection of the wires in accordance with the
present invention;
Fig. 4 is a schematic view of the preferred apparatus
employed for incorporating the plastic on the woven wire base
fabric of the present invention; and
Fig. 5 is a diagrammatic perspective view illustrating
a preferred apparatus for depositing the powdered resinous
material upon the woven wire.
Referring to the drawing, Figo 1 illustrates a flexible,
plastic-wire cloth made in accordance with the invention for use
as insect screening. In this embodiment of the invention, the
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wire cloth is woven on a loom with a plain weave having eighteen
warp wires 11 to the inch and sixteen weft wires 12 to the inch.
In this example, the fabric is woven from 0.011 wire drawn frorn
an aluminum-clad rod through a succession of dies. The spacing
of the wires provides interstices 14, the size of which determines
the porosity or the percentage of open area of the wire clothO
In accordance with the present invention, the wire cloth
is provided with a continuous film which encapsulates the
elements of the wire cloth, in the present instance, the warp
wires 11 and the weft wires 12. As shown in Fig. 3, the contin-
uous uninterrupted plastic film is designated by the reference
character 15 and in the present instance has a thickness less
than 0.1 times the thickness of the wire, for example in the
range of 0.0007". A fllm of this thickness does not substantially
affect the size of the interstices 14 in the woven wire, but is
effective to lock the warp and weft elements together and to
protect the wire elements from the corrosive elernents in the
environment where the cloth is used. Where the film is of sub-
stantially greater thickness, it is effective to reduce the size
of the interstices 14 and will affect the percentage of open area
of the fabric. As shown in Fig. 3, the wire fabric of the
present invention assures intimate contact between the weft wires
12 and the warp wires 11 at each intersection~ the degree of
which is controlled in conventional manner by the settings of
the loom on which the wire is woven and the diameter and hardness
of the wire used in fabricating the cloth~
In the present instance, the cloth of the present
invention is fabricated in a two-stage process. In the first
stage, the wire cloth is woven on a conventional wire loom
without selvages and is collected on a cloth roll 21 in con-
tinuous lengths suitable for handling in the mill. In the second
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stage, the roll 21 of wire cloth from the loom is treated to
encapsulate the elements of the cloth in a plastlc film.
As diagrammed in Fig. 4, the operations in the second
stage operate to cleanse and rinse the wire fabric to remove the
dirt, grease or other foreign matter from the surface of the wire
elements of the cloth. Preferably, the cleansing is accomplished
by unwinding the fabric from the roll 21 through a tension device
22 into a cleansing bath 23~ After several passes through an
alkaline solution in the bath 23, the cloth is subjected to a
spray rinse in the rinse section 24.
From the rinse section 24, the wire cloth is passed over
a chill roll 31 in two runs 25 and 26 in a drying oven 30 and
into a powder-coating structure 270 In this structure, the
cleansed wire cloth is passed through an electrostatically-
charged cloud of a particulate powdered resin which deposits a
layer of powdered particulate material on the wire cloth passing
therethrough.
In the present instance, the powder-coated wire cloth
is then passed through the oven 30 in runs 28 and 29 which
parallel the drying runs 25 and 260 The heat of the oven fuses
and flows the powder into a continuous unbroken integral film
which encapsulates the wire elements of the cloth, the composite
plastic-wire cloth reversing direction at the top of the oven
through the use of a suitably cooled chill roll 32 which permits
reversal of the travel of the plastic-wire material without
stripping the plastic film or otherwise destroying its integrityO
Completion of the passage of the plastic-wire cloth through the
oven completes the cure of the plastic film and the plastic-wire
cloth is drawn by a variable speed drive 33 onto the takeup roll
34.
The powdered resinous particula~e material is fed to
the powder-depositing apparatus 27 from a suitable supply
chamber 35 which feeds from the bottom through a suitable metered
and controlled feed device indicated diagrammatically at 36 and
excess material is withdrawn from the apparatus and returned to
the feed chamber, as indicated schematically at 37 ~ sO as to mix
with the fresh material supplied directly to the chamber.
Fluidizing air is also introduced into the apparatus and is dis-
charged with the excess powdered resinous material.
In operation, the rolls of cloth from the looms are fed
sequentially through the apparatus with the leading end of each
roll being attached to the trailing end of the preceding roll so
that the fabricating line may be operated continuously at an
economical rate of speed as determined by the cleaning and
rinsing operation and the depositing apparatus. The height of
the oven is designed to insure complete drying of the wire cloth
entering the depositing apparatus and complete curing of the
plastic film leaving the oven.
A preferred embodiment of the powder-depositing apparatus
is shown in Fig. 5 wherein the cleansed wire cloth is introduced
from the drying run 26 under a suitable feed roller 41 and
upwardly between a pair of baffle plates 42 and 43~ The cloth
passes outwardly at the upper end of the plates into a shroud 44
having an exit slot 45 at its upper extremity through which the
cloth with powder deposited thereon is advanced into the first
heating run 2~o A cloud of ionized resinous powder is formed
within the shroud 44 on opposite sides of the cloth path above
the upper edges of the baffle plates 42 and 43~ To this end,
dry fluidizing air is introduced into manifolds 52 and 53 on
opposite sides of the baffle plates 42 and 43~ respectively, as
indicated by the arrows 51~ At their upper side, the chambers
52 and 53 corqmunicate with ionizing chambers 54 and 55
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respectively, having high voltage electrodes therein for
ionizing the air passing upwardly from the manifolds 52 and 53.
Resinous powdered material is introduced above the ionizing
chambers 54 and 55, for example in powder chambers 56 and 57,
and the powdered material introduced therein is ionized by the
charged air flowing upwardly therethrough.
The upward flow of air in the charging chambers 56 and
57 generates a floating cloud of powdered resinous material
within the shroud 44 on opposite sides of the cloth path, The
air is withdrawn from the chamber between the baffle plates 42
and 43 and is discharged between the baffle plates and through
the bottom countercurrent to the direction of travel of the cloth,
as indicated by the arrows at 61. The ionized powder is deposited
on the grounded ~ire cloth passing upwardly between the baffles
and the thickness of the powder layer deposited on the cloth is
accurately controlled by controlling the ionizing voltage applied
to the devices 54 and 55 and by line speed of the wire cloth in
relation to the airflow introduced at 51. The discharged-air
flow 61 is slightly greater than the flow of air introduced at
51 so that there is a net inflow of air through the discharge
slot 45O
In its passage between the baffle plates 42 and 43 and
through the shroud 44, the ~ire cloth receives a thorough deposit
of thepowdered material from the charged powdered cloud within the
shroudO The powder is fluidized by the airflow through the
charging chamber so that a uniform deposition of the powder on
the screen is obtained in accordance with the line speed of the
wire cloth, the charging characteristics of the powder and the
voltage applied to the ionizing devicesD As the powder particles
become charged, they repel each other to such a degree that they
rise above the fluidizing chamber and form a cloud of powdered
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resinous material. The presence of a cloud of powdered resinous
material on opposite sides of the cloth path at the exit end of
the baffle plates 42 and 43 within the shroud 44 insures uniform
depositing of the powder on opposite sides of the cloth. The
charged powder is attracted to the wire cloth and the powder
insulates the grounded wire cloth as it is deposited thereon~
In the event bare spots free of powder are left on the wire,
the ionized powder is attracted to the bare spots and thus, the
apparatus automatically tends to close any gaps which might be
present in the deposited powder, and an uninterrupted coating
of powder is obtained. As the cloth is thereafter passed
through the oven in its upward run 2~, the deposited powder is
heat-flowed to form a continuous unbroken film which encapsulates
the wire elements. The nature of the film formed on the wire
cloth insures continuous encapsulation of the elerlents regardless
of the presence or absence of an actual adherence of the plastic
film to the wire elementsO Thus, the plastic rnaterial employed
to encapsulate the elements may be selected without regard to
its bonding characteristics relative to the wire forrning the
body of the plastic-wire clothO The plastic material of the
preferred embodiment is readily available in powdered particulate
form, but other film-forming particulate substances may be used
which comprise a suspension of particles in a suitable carrier
which is driven off when the material is formed into a continuous
filmO
The plastic-wire cloth produced in accordance with the
present invention provides a flexible fabric having a strength
determined primarily by the strength of the wire elements in
the body of the fabric. The cloth of the present invention has
been fabricated from both alurninum and steel wire in various wire
sizes and meshO The wire elernents are provided ~ith a continuous
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film of substantially uniforrn thickness ~hroughout, including
the intersections where the warp and weft wire elements cross
over one another in direct contact, as shown in Fig. 3O The
continuous film encapsulating the woven wire enables the wire
to be woven without providing the conventional selvages which
are deemed necessary in untreated wire to avoid raveling. The
freedom from raveling provided by the plastic-wire fabric of
the present invention also enables the use of the wire in
situations requiring irregular shapes or sizes of clothO The
plastic film may be inert and may include fillers, pigments, or
other additives to produce a wide variety of characteristics in
the plastic-wire clothO The resin used in the commercial insect
screening embodying the present invention has been a thermo-
setting, thin-filrll, epoxy resin which is electrically non-
conductive, having a smooth velvet-like finish and a dark color
such as gun-metal gray or black to provide good visibility through
the screening. The plastic resin may be formulated to provide
any desired degree of modification of the flexibility or
rigidity of the cloth, and as noted above, the thickness of the
film may be increased to reduce the permea~ility or percentage
of open area of the screen by partially closing or completely
closing the interstices in the woven wireO
While particular embodiments of the present invention
have been illustrated and described, it is not intended to limit
the invention to such disclosure, but changes and modifications
may be made therein and thereto within the scope of the following
claims.
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