U.S. patent application number 11/860230 was filed with the patent office on 2008-04-03 for fabric for protection against electric arc hazards.
Invention is credited to George JR. GEHRING.
Application Number | 20080081529 11/860230 |
Document ID | / |
Family ID | 39261656 |
Filed Date | 2008-04-03 |
United States Patent
Application |
20080081529 |
Kind Code |
A1 |
GEHRING; George JR. |
April 3, 2008 |
FABRIC FOR PROTECTION AGAINST ELECTRIC ARC HAZARDS
Abstract
An improved knit fabric system for protecting against electrical
arch hazards and promoting garment visibility is provided. The
inventive knit fabric is either a solid fabric substrate or of a
mesh construction that absorbs the thermal energy of an electric
arc and, especially for the mesh construction, absorbs thermal
energy or heat flux to prevent garment combustion. The solid or
mesh version of the inventive knit fabric incorporates conductive
fibers for draining away and thereby dissipating accumulated
electrical charges. Such conductive fibers are incorporated into
the fabric of the invention, by either being knitted into the
fabric as it is formed or by the process of yarn spinning.
Inventors: |
GEHRING; George JR.; (Garden
City, NY) |
Correspondence
Address: |
GOTTLIEB RACKMAN & REISMAN PC
270 MADISON AVENUE
8TH FLOOR
NEW YORK
NY
10016-0601
US
|
Family ID: |
39261656 |
Appl. No.: |
11/860230 |
Filed: |
September 24, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60847305 |
Sep 26, 2006 |
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60847186 |
Sep 26, 2006 |
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60847002 |
Sep 25, 2006 |
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60847307 |
Sep 26, 2006 |
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Current U.S.
Class: |
442/308 ;
442/304; 442/316; 66/202 |
Current CPC
Class: |
Y10T 442/425 20150401;
D04B 21/12 20130101; Y10T 442/40 20150401; Y10T 442/475
20150401 |
Class at
Publication: |
442/308 ;
442/304; 442/316; 066/202 |
International
Class: |
D04B 1/10 20060101
D04B001/10; D04B 1/00 20060101 D04B001/00; D04B 1/14 20060101
D04B001/14 |
Claims
1. A fabric comprising: a knit construction made from high
performance yarns that are resistant to melting, dripping and
burning at a temperature of at least 700.degree. F.; and conductive
yarns intermixed with said high performance yarns.
2. The fabric of claim 1, wherein the high performance yarns are
selected from the group consisting of modacrylic yarns, aramid
yarns and polybenzimodazole yarns.
3. The fabric of claim 2, wherein the high performance yarns have a
yarn count of between about 12/2 c.c. and 32/2 c.c.
4. The fabric of claim 2, wherein the high performance yarns
comprise modacrylic yarns having an LOI value of between about 28
and 33.
5. The fabric of claim 2, wherein the high performance yarns
comprise aramid yarns having an LOI value of between about 28 and
30.
6. The fabric of claim 5, wherein the aramid yarns comprise
para-aramid fibers having a tenacity of between about 28 and 32
grams/denier.
7. The fabric of claim 2, wherein the high performance yarns
comprise polybenzimodazole having an LOI value of between about 35
and 40.
8. The fabric of claim 2, wherein the knit construction comprises a
knitted mesh.
9. The fabric of claim 8, wherein the fabric has a mesh count of
between about 3 and 5 meshes/inch in width and between about 4 and
5 meshes/inch in length.
10. The fabric of claim 2, wherein the high performance yarns are
present in an amount between about 85 and 95 weight percent and
conductive yarns are present in the fabric in an amount between
about 3 and 5 weight percent.
11. The fabric of claim 2, wherein the conductive yarns are
selected from the group consisting of conductive carbon fiber
yarns, nylon fiber yarns coated with a metal, and metal fiber
yarns.
12. The fabric of claim 2, wherein the conductive yarns are knitted
together with the high performance yarns.
13. The fabric of claim 2, wherein the conductive yarns are arrayed
in a diamond-like configuration.
14. The fabric of claim 2, wherein the knit construction is
produced by either a warp or weft knit system.
15. The fabric of claim 11, wherein the carbon fiber yarns comprise
a conductive carbon core surrounded by a non-conductive polymer
cover.
16. The fabric of claim 11, wherein the carbon fiber yarns comprise
carbon particles embossed along a filament surface.
17. The fabric of claim 4, wherein the modacrylic yarns have a
tenacity of up to 2.8 grams/denier and fusing temperature of
between about 371 and 410.degree. F.
18. The fabric of claim 4, wherein the modacrylic yarns have a
moisture regain of between about 0.4 and 4.0%.
19. The fabric of claim 2, wherein the high performance yarns
comprise modacrylic yarns and the conductive yarns comprise nylon
fibers coated with silver.
20. A fabric comprising a knit construction made from spun
modacrylic yarns in an amount between about 85 and 95 weight
percent and conductive yarns in an amount between about 3 and 5
weight percent.
21. The fabric of claim 20, wherein the conductive yarns are
selected from the group consisting of conductive carbon fiber
yarns, nylon fiber yarns coated with a metal, and metal fiber
yarns.
22. The fabric of claim 20, wherein the fabric has a mesh
construction.
23. A method for producing a fabric comprising knitting together
high performance yarns selected from the group consisting of
modacrylic yarns, aramid yarns and polybenzimodazole yarns with
conductive yarns.
Description
[0001] This application claims priority of Provisional Application
No. 60/847,305 filed Sep. 26, 2006. The subject application is also
related to the following applications:
Knit Elastic Mesh Loop Pile Fabric for Orthopedic and other
Devices
60/847,186 filed Sep. 26, 2006; U.S. patent application Ser. No.
______ filed ______,
Improved High Performance Fire Resistant Fabrics and the Garments
Made Therewith
60/847,002 filed Sep. 25, 2006; U.S. patent application Ser. No.
______ filed ______, and
Under Body Armor Cooling Vest and Fabric Thereof
60/847,307 filed Sep. 26, 2006; U.S. patent application Ser. No.
______ filed ______.
BACKGROUND OF THE INVENTION
[0002] This invention relates to a fabric for protection against
electrical arc hazards, and, more particularly, to a fabric that is
both highly visible and which reduces the hazards of electrical
arcs.
[0003] A. Garment Visibility
[0004] Personnel employed in all modes of traffic control, utility
and survey work, emergency response, construction, equipment
operation and vehicle roadway traffic are exposed to accident
hazards due to insufficient conspicuity of ordinary workwear worn
by them. These hazards are due to the workers' low visibility,
which are intensified by the often complex and varying backgrounds
of the above mentioned occupations and job assignments.
[0005] A major hazard issue involves situations in which objects
can be visible, but are not consciously recognized by the vehicle
driver within sufficient time to take corrective action in order to
avoid an accident. This conscience recognition is often influenced
by the level of task activities, varying daytime or nighttime
lighting conditions, the complexity of backgrounds, vehicle speed
and the visual performance of the operator. Thus, worker safety is
compromised by insufficient decision/reaction time resulting from
the use of workwear not designed to provide sufficient visibility.
It is thus important that workers are readily perceived by drivers
when, for example, directing traffic, operating equipment, digging
roadside trenches and doing maintenance work.
[0006] In order to reduce hazards to which the workers are exposed
in performance of their tasks, special high visibility garments are
available for their protection. These are covered by the
requirements of both the American National Standard Institute
(ANSI) and ISEA--The Safety Equipment Association. The garments may
take the form of a coverall, jacket, vest, trousers, harness/sash
belt and others, depending on the work performed by the wearer.
[0007] Fluorescent dyed materials emit optical radiation at
wavelengths longer than absorbed. They enhance daytime visibility,
especially during dawn and dusk. Accordingly, garments may be
provided with strips of retroreflective material placed in
appropriate locations in order to enhance their conspicuity. Such
retroreflective materials have the property of returning light to
its source.
[0008] Garments instead may be made with a fabric dyed with one of
three approved fluorescent colors; such colors are intended to be
highly conspicuous to ensure visibility against most backgrounds
found in urban and rural situations. The three colors are:
yellow-green, orange-red and red. The chromaticity (the x and y
coordinates) and the minimum luminance factor are stipulated by
ISEA standards (see TABLE 1 and 2), as are all the fabric
parameters applicable to the fabric. Performance requirements of
garments must be tested and verified for conformance with these
standards by an accredited testing lab.
[0009] Fabrics currently in use in high visibility garments are of
the woven type. While such fabrics are adequate in performance,
they leave much to be desired in wearing comfort, durability and
economics. Particularly, woven fabrics are, by their nature,
tightly configurated in their system of warp and filling threads.
This limits the air permeability and hence the comfort factor,
which is of a particular importance for workers exposed to the sun
for prolonged periods of time.
[0010] Woven fabrics that meet the ISEA performance requirements
are relatively stiff and, therefore, to some extent, inhibit the
garment wearer's freedom of movement. Also, woven fabrics are prone
to ripping, tearing and fraying. This limits the useful life of the
garment, which suffers much physical stress when worn at high rough
work sites. Finally, there is the question of economics. Woven
fabrics that meet the ISEA standards are relatively expensive due
to the cost of suitable yarns and the involved processing
cycles.
[0011] B. Electrical and Thermal Discharge
[0012] In addition to the problem of personnel workwear and
insufficient conspicuity, workers attending to electrical utility
lines and related equipment are also exposed to the risk of
electrical arc flash hazards, against which such workwear must
provide adequate protection.
[0013] In particular, electrical utility linemen, industrial
electricians, electrical contractors and electrical service
personnel are routinely exposed to the momentary electric arc flash
and its related thermal hazards. As a consequence, many workers
have been electrocuted, burned or severely injured. In fact, recent
U.S. Department of Labor statistics identified electrical workers
as being the 3.sup.rd most dangerous profession.
[0014] An arc flash is the explosive release of energy caused by
the passage of electrical current between two electrodes through
ionized gases or plasma, characterized by a temperature reaching
several thousands degrees centigrade. As workers perform their
tasks on or near energized wire systems or circuitry, an arc flash
may occur as a result of their inadvertent movement, accidental
contact or some equipment failure. The electrical energy supplied
in the forming arc is converted into an explosive fireball-like
phenomenon that is likely to impact or even envelop the worker. The
resultant explosive effect of the arc produces intense thermal
radiation, noise, melting and even vaporization of metal components
of the equipment around the arc. Depending on the severity of the
arc flash, burns will occur on bare or unprotected skin. Also, if
the worker is wearing non-flame retardant clothing, the arc is
likely to ignite it.
[0015] Thus, to provide a safer workplace for the utility workers,
the NFPA (National Fire Prevention Assn.) has issued a standard
NFPA 70 E-2000 for electrical safety requirements. The standard
calls for protective clothing to be tested and rated to the level
of the arc flash energy hazards to which the electricity workers
could be exposed.
[0016] In addition to the dangers posed by electrical arc
discharge, utility workers are also exposed to thermal hazards from
the heat of the flash fires caused by ignited gas, combustible
vapors, volatile solvents or chemical dust. Flash fires are defined
as those lasting no more than three seconds.
[0017] Thus, thermal performance of garments is covered by the AMTM
(American Society for Testing Materials) test F 1950, which uses
the electric arc to determine the number of calories required to
create second degree burns in terms of calories per square cm.
There is also an ASTM F 1506 standard for clothing worn around
electric arc hazards.
[0018] Yet another consideration in the production of utility
workers' protective garments is the hazard of static electricity
spark discharge. Such discharge is likely to ignite a flash fire of
the kind mentioned above. Static electricity charges of several
thousands volts may be generated simply by rubbing one part of the
garment against another or against a car seat or a plastic object.
These charges can create a spark of sufficient length to ignite
gas, fuel vapors, solvents, etc., thus causing a flash fire.
[0019] Yet a further hazard to utility workers is when they come
close to high tension equipment such as transformers, switchgear,
overhead wires, etc.--the corona discharge. Such discharge occurs
from electrodes with sharp points or angles. It is due to the
ionization of the air surrounding these points, which makes
possible the escape of electrical energy through the air. Corona
discharge takes the form of luminous glow; the higher the voltage
the more intense the corona discharge. Corona discharge can be
hazardous to utility workers servicing high tension installations
where the coronal discharge may induce dangerous levels of
electrical energy flux in the workers apparel.
[0020] At the present time, protective garments are made with
densely woven, heavy fabrics using flame resistant fibers such as
modacrylic, Kevlar, Nomex, PBI, FR rayon and others. These fibers
not only must withstand the very high arc temperature for a brief
span of time, but must also be resistant to melting and dripping,
which can cause severe burns. A frequently used fiber in garments
is modacrylic spun into medium count yarns. Modacrylics are the
copolymers of acrylonitrile fibers, which are very difficult to
ignite and have self extinguishing properties. These fibers also
have good weathering properties, resistance to acids, alkalis and
wide range of chemicals. Their dielectric strength exceeds 1500
volts per mil. of plastic film, which constitutes an important
consideration in electrical applications.
[0021] A distinct advantage of modacrylic yarns is their relatively
moderate price in comparison with other types of yarns available on
the market. Modacrylics feature also superior processability during
manufacture.
[0022] Nonetheless, woven fabrics incorporating flame resistant
fibers and used in making electric arc protective garments are less
than desirable. In the first place, since woven fabrics must be
dense and tightly constructed in order to preserve their structural
integrity. They have reduced porosity properties, resulting in
reduced wearing comfort. In a warm environment, for example,
garments made with such fabrics may feel excessively hot and
clammy. The consequence being that some workers avoid wearing them
altogether. Also, relative stiffness of woven fabrics and the lack
of any "give" encumber the freedom of movement of the garment
wearer.
[0023] In addition, weaving is essentially a slow process and
generally limited to narrow width fabrics. This causes wovens to be
relatively expensive in comparison with other fabricating systems
like warp and weft knitting.
[0024] Furthermore, woven fabrics have a propensity to distort, rip
and fray. Because the yarn components of warp and weft are held in
the structure by frictional forces only, there is a tendency for
them to slip on each other and distort the fabric in forming cracks
and open areas on its face. In that regard, the peculiar geometry
and interlacing of the yarn components of woven fabrics renders
them susceptible to ripping. Thus, even a minor cut or puncture in
the garment caused by a sharp part of the equipment can propagate
itself into a long tear or rip, thereby destroying the garment.
[0025] A related problem with woven garments is seam failure. This
may be caused by the problem of fraying of the threads from a cut
edge of the fabric. This may produce seam failure due to the
individual fabric threads "combing out" from the seamed edge. Seam
failure may have serious consequences in that it could allow the
heat flux of the electric arc to penetrate inside a protective
garment so as to cause burns to its wearer.
[0026] Accordingly, it would be desirable to provide a fabric or
garment which overcomes the above disadvantages.
SUMMARY OF THE INVENTION
[0027] Generally speaking, in accordance with the invention, an
improved knit fabric system for protecting against electrical arch
hazards and promoting garment visibility is provided. The inventive
knit fabric is either a solid fabric substrate or of a mesh
construction and consists predominantly of high performance yarns
that are resistant to melting, dripping and burning at high
temperatures. The knit fabric absorbs the thermal energy of an
electric arc and, especially for the mesh construction, absorbs
thermal energy or heat flux to prevent garment combustion.
[0028] In accordance with the invention, either the solid or mesh
version of the inventive knit fabric incorporates conductive fibers
for draining away and thereby dissipating accumulated electrical
charges. Such conductive fibers are incorporated into the fabric of
the invention by either being knitted into the fabric as it is
formed or by the process of yarn spinning.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] For a fuller understanding of the invention, reference is
now made to the following drawings in which:
[0030] FIG. 1 depicts one form of the inventive fabric in which the
conductive yarns are arrayed in a diamond-like configuration;
and
[0031] FIG. 2 depicts a second form of the inventive fabric
comprising a mesh construction.
DETAILED DESCRIPTION OF THE INVENTION
[0032] The fabric of the invention is a knitted fabric produced on
either a warp or weft knit system. For warp knits, suitable
equipment is either tricot or Raschel machine of a suitable gauge.
For weft knits, suitable equipment is either a circular or flat
knitting machine. The circular machines may be in 16-18 cut
(needles per inch) with the interlock or double knit needle set
out.
[0033] In the embodiment with a mesh design, making mesh fabric
utilizing circular weft knit machine involves pelerine transfer
stitch technology, as is well known in the art; this creates
eyelets through the transfer of sinker loops.
[0034] The warp knit version of the inventive fabric is preferred
due to its superior physical characteristics. This is because warp
knit mesh fabrics are more stable and run-resistant that their weft
knit counterparts. Warp knit fabrics can also be made in a much
wider variety of mesh openings than is possible for weft knit
fabrics. Further, warp knit mesh fabrics are, in general, easier
and more economical to construct.
[0035] The yarns used in the inventive fabric are high performance
yarns such as those that are resistant to melting, dripping and
burning at high temperature conditions (at least 700.degree. F.).
The high performance yarns are present in the inventive fabric in
an amount between about 85% and 95% weight percent. The preferred
high performance yarns are spun modacrylics. Modacrylics are
polymers that have between 35 to 85% acrylonitrile units, and which
may be modified by other chemicals such as vinyl chloride.
[0036] The choice of modacrylic fibers or yarns for application in
the fabric material of the invention is based on their excellent
fire retardancy performance combined with their non-melt, non-drip
and self-extinguishing properties. These are critically important
attributes in many working environments. If sufficiently high
temperatures are reached on exposure to fire or explosion, a
garment made with the inventive fabric will just carbonize by
forming a protective charred barrier. This prevents propagation of
flames, thereby protecting the wearer from severe burn
injuries.
[0037] Modacrylics have a high so-called LOI value as compared with
other fibers. The LOI represents the minimum oxygen concentration
of an O.sub.2/N.sub.2 mix required to sustain combustion of a
material. The LOI is determined by the ASTM Test D 2862-77.
Modacrylics have an LOI value preferably between about 28 and 33
while conventional polyesters have a much lower value of 20-22.
[0038] Additionally, a very important aspect of wearing comfort is
the so-called "moisture management" factor. This is often
represented as the moisture vapor transport index of MVT, which
reflects the efficiency in which a fabric moves perspiration away
from the skin or underlying garment and causes it to evaporate into
the ambient atmosphere. The MVT of the modacrylics used in the
inventive fabric is approximately 2500 g/meter squared/24 hours
ASTME96.
[0039] Modacrylics are spun from an extensive range of copolymers
of acrylonitrile. The types of modacrylic fibers that can be
produced within this broad category are capable of wide variation
in properties, depending on their composition. Some examples of
commonly available modacrylics are: "Vere" by Eastman Corp.,
"Creslan" by Am Cyanamic Co., "Acrillan" by Mosanto Corp.,
"Kanecaron" by Kaneka Co. and "Orlon" by DuPont Co.
[0040] Modacrylic fibers used in the inventive fabric preferably
have a tenacity of up to 2.8 grams/denier, an elongation at break
of between about 35 and 40%, and a fusing temperature of between
about 371 and 410.degree. F. The modacrylic fibers used in the
inventive fabric also have a moisture regain (the amount of water
by weight held by the fiber under controlled atmospheric
conditions) of between about 0.4 and 4.0%.
[0041] Modacrylic fibers and yarns are moderately priced as
compared with other materials of good thermal performance. They are
readily available in the industry; they have good knitting
performance, ease of fabric processing and dyeing.
[0042] A significant attribute of modacrylics is their charring on
prolonged exposure to flames, rather than simply burning and
dripping. The charred portions of the fabric protect the wearer
from the effects of fire.
[0043] Other high temperature resistant (high performance) fibers
or yarns may also be used in the inventive fabric, either in
combination with modacrylics or entirely on their own. One such
fiber comprises aramid fibers, such as Kevlar and Nomex. Such
fibers feature excellent thermal thermal stability and are
virtually non-flammable. These fibers have a very high resistance
to heat and are resistant to melting, dripping and burning at a
temperature of at least 700.degree. F. Moreover, their LOI value is
preferably in the range of between about 28 and 30.
[0044] Kevlar, made by Dupont Co., is a para-aramid fiber having a
very high tenacity of between 28 and 32 grams/denier and
outstanding heat resistance. Other para-aramid fibers suitable for
the inventive fabric include Twaron by AKZO Co. and Technora by
Teijin Co.
[0045] Another type of aramid fiber suitable for the inventive
fabric is "Nomex", made by DuPont and "Conex" made by Teijin
Co.
[0046] Yet other types of flame resistant fibers are organic fibers
composed of polybenzimidazole, such as PBI made by Celanese Corp.
These fibers have an LOI of between about 35-40 and are resistant
to melting, dripping and burning at a temperature of at least
750.degree. F.
[0047] Further high temperature resistant fibers or yarns may
comprise certain polyester yarns that are resistant to melting,
burning and dripping at a temperature of at least 700.degree.
F.
[0048] In general, the high performance yarns used in the inventive
fabric have a yarn count of between about 12/2 c.c. and 32/2 c.c.
(two ply yarn).
[0049] In accordance with the invention, the modacrylic or other
high performance fibers are blended with from between about 3 and 5
weight percent of conductive fibers in order to impart anti-static
properties to the fabric. Such fibers are available from several
sources. The conductive yarn fibers are preferably intermixed with
the high performance yarns; in other words, the conductive yarns
are knitted together with the high performance yarns.
[0050] One example of such conductive fiber is Negastat.RTM.
produced by DuPont & Co. This is a carbon fiber comprising a
carbon core of conductive carbon surrounded by non-conductive
polymer cover, either nylon or polyester. Another example is
Resistat.RTM. made Shakespeare Conductive Fibers LLC. This is a
fiber where the fine carbon particles are embossed on the surface
of a nylon filament. The yarns of both such fibers are available in
a denier of at least 40.
[0051] Instead of conductive fabric fibers, one may use a very fine
wire made of steel, copper or other metal. By way of example, a
steel wire suitable for use in the inventive fabric is available
under the names Bekinox and Bekitex from Bekaert S.A. in a diameter
as small as 0.035 millimeter.
[0052] A very effective conductive fiber that is suitable for the
inventive fabric is the product X-static made by Noble Fiber
Technologies. This is a nylon fiber coated with a metal layer,
namely a silver layer; it provides excellent static draining
performance as well as germicidical properties. The latter prevents
development of objectionable odors. The X-static fibers are blended
with modacrylics in the process of yarn spinning. A content of
between about 3 and 5% of the X-static in the inventive fabric is
sufficient to substantially control the static problem. The
X-static fibers in the fabric must meet the standards of static
control set forth by Noble Fiber Technologies, Inc.
[0053] The conductive fibers may be introduced in the inventive
fabric from warps or individual packages placed on a creel, the
latter being the case with circular knitting system. For warp
knits, one or two guide bars threaded with the conductive yarns may
be employed. These bars could move in a zigzag or diamond
configuration in order to provide optimum anti-static coverage.
[0054] In the one preferred embodiment of the present invention,
the conductive yarns are arrayed in a diamond-like configuration
(See FIG. 1). This provides optimum anti-static protection for the
entire fabric surface.
[0055] In a second preferred embodiment, the inventive knitted
fabric is a knitted mesh. The advantages of such a mesh
construction include increasing the permeability of air so as to
enhance evaporation of perspiration. This significantly improves
wearing comfort, especially in heat stressful applications. The
presence of mesh openings in the inventive fabric also contributes
to improved visibility by breaking up the fabric texture.
[0056] The mesh openings should have a mesh count of between about
3 and 5 meshes/inch in width and between about 4 and 6 meshes/inch
in length. Larger mesh openings will adversely affect the
chromaticity and conscupicuity characteristics of the fabric. An
embodiment of the inventive warp knit fabric having a mesh
construction is shown in FIG. 2.
EXAMPLE 1
[0057] One type of warp knit fabric according to the present
invention contains the following yarns: [0058] 30/1's c.
modracrylic (90%), polyester (10%) blend--to produce the ground
fabric; and
[0059] 30/1's c. modacrylic (87%), polyester (8%), X-static (5%)
blend--to produce the diamond overlay for anti-static protection.
TABLE-US-00001 KNITTING CONSTRUCTION DETAILS Beam Inches Ends
Number Rack Total Yarn 1(front) 90'' 234 30/1 Modacrylic (87%) 2
90'' 234 30/1 Modacrylic (87%) 3 90'' 2340 30/1 Modacrylic (90%) 4
156'' 2340 30/1 Modacrylic (90%) (back)
[0060] The threading chart for Example 1 is as follows:
TABLE-US-00002 Bar 1 (front) ....................| .........|
....|............. 1 ..... Bar 2 ............|.......| .........|
.................. 0 ..... Bar 3 ...........|||||||||| ||||||||||
||||||||||.......... 1 ..... Bar 4 ...........|||||||||| ||||||||||
||||||||||........ 3 .....
[0061] Stitch construction for example, is as follows:
TABLE-US-00003 BAR 1 BAR 4 (front) BAR 2 BAR 3 (back) 1-0 6-7 1-0
3-4 1-2 6-5 1-2 1-0 2-3 5-4 3-4 4-3 4-5 3-2 5-6 2-1 6-7 1-0 6-5 1-2
5-4 2-3 4-3 3-4 3-2 4-5 2-1 5-6
[0062] The finished fabric of Example 1 has a width of 2.times.60
inches, a fabric weight of 6.5 oz/square yard and a count of 27
courses/inch.times.18 wales/inch.
[0063] In Example 1, the finished fabric is jet dyed to the desired
color and then stabilized and set by tenter framing at a
temperature of 250.degree. F. at the speed of 15 yds/min.
EXAMPLE 2
[0064] Another type of warp knit fabric according to the present
invention contains the following yarns: [0065] 30/1's c. modacrylic
(90%), polyester (10%); and [0066] 30/1's c. modacrylic (87%),
polyester (8%), X-static (5%) blend.
[0067] The fabric in Example 1 is produced on an 18-20 gauge,
tricot or raschel machine.
[0068] In constructing the fabric of Example 1, the threading is 5
in, 1 out for both back guide bars and 1 in, 5 out for both front
guide bars.
[0069] The threading chart for Example 2 is as follows:
TABLE-US-00004 Bar 1 ........||||.....||| .||||| .|||||.|||....
(back) Bar 2 ........||||||.||||| .||||| .|||||.|||.... Bar 3
.............|.....| .....| .............. Bar 4
.................... .|.... .|............ (front)
[0070] Stitch construction for Example 2, is as follows:
TABLE-US-00005 BAR 1 BAR 4 (back) BAR 2 BAR 3 (front) 4-5 1-0 6-7
1-0 4-3 1-2 6-5 1-2 4-5 1-0 6-7 1-0 3-2 2-3 4-3 3-4 1-0 4-5 1-0 6-7
1-2 4-3 1-2 6-5 1-0 4-5 1-0 6-7 -3 3-2 -4 4-3
[0071] The finished fabric of Example 2 has a width of 60 inches
and a weight of 6 oz/yd squared. Moreover, the finished fabric has
a mesh count of 4 holes per inch in width and 5 holes per inch in
length.
[0072] In Example 2, the finished fabric is jet dyed to a desired
color and then stabilized and set by tenter framing at a
temperature of 335.degree. F. at the speed of 15 yds/min.
[0073] In general, the knitted fabric of the invention is
advantageous over their prior art woven counterparts.
[0074] For example, knit fabrics, but the virtue of their inherent
stretch, elasticity and porosity, are more comfortable to wear than
wovens. Both stretch and porosity parameters of knit fabrics may be
engineered into the structure to the required degree. The stretch
factor contributes to the freedom of movement and comfort of the
protective suit wearer, an important consideration for workers.
Knitted fabrics are also cheaper to produce than woven fabrics due
to substantially higher manufacturing rates of the knitting
equipment. Also, the wider width of knit fabrics improves
processing economics and reduces the cutting waste in garment
manufacture.
[0075] Knit fabrics, by the virtue of their locked loop structure,
do not rely on friction between the yarn members of the structure
to preserve the fabric integrity. Consequently, there is not
fraying from cut edges of the fabric, no ripping from holes or
tears, and no distortion due to slippage of the yarn members.
[0076] Furthermore, the so called "overlock" seam used on knit
fabrics is superior to what is found in wovens. The "overlock" seam
has a system of three sewing threads, which together securely
encase the seam in a triple-laced thread system so as to hold it
securely in place regardless of the stresses and strains imposed
during the course of wearing the garment.
[0077] Moreover, because knit structures are interlooped and
therefore not subject to any slippage of constituent threads, mesh
fabrics may be constructed with greater ease and economy on a knit
basis, especially of the warp type. The latter allows for making
the mesh openings into any desired size and shape.
[0078] And by no means of least importance, knit fabrics, in
contrast to woven fabrics, allow for the ready introduction of
conductive yarns into the thread structure. This is because a
weaving system involves the use of one type of yarn that is put up
on the beam of a loom. Therefore, to introduce other yarns of
different size and characteristics in the weaving process requires
setting up a cumbersome external creel in order to accommodate the
yarn packages. This in turn impairs the weaving process, thereby
causing weaving defects. In contrast, for warp knitting, the
different yarns are put up on separate beams and thus carried on
appropriate guide bars.
[0079] The scope of the invention will now be set forth in the
following claims.
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