U.S. patent number 3,644,866 [Application Number 05/105,175] was granted by the patent office on 1972-02-22 for tightly bound bundle of filaments and method of producing same.
This patent grant is currently assigned to Owens-Corning Fiberglas Corporation. Invention is credited to Lawrence R. Deardurff.
United States Patent |
3,644,866 |
Deardurff |
February 22, 1972 |
TIGHTLY BOUND BUNDLE OF FILAMENTS AND METHOD OF PRODUCING SAME
Abstract
This invention relates to a tightly bound textile strand product
suitable for use as a core element in a jacketed composite product
in which coated filaments are held together by helically wrapping
two separate strands of filaments around the bundle in opposite
directions. More particularly, it relates to an improved
high-resistance automotive ignition conductor and a method of
producing the conductor wherein the overwrapping strands are glass
filaments and the ignition conductor is a bundle of glass filaments
coated with electrically conductive material.
Inventors: |
Deardurff; Lawrence R. (Newark,
OH) |
Assignee: |
Owens-Corning Fiberglas
Corporation (N/A)
|
Family
ID: |
22304451 |
Appl.
No.: |
05/105,175 |
Filed: |
January 11, 1971 |
Current U.S.
Class: |
338/214; 57/232;
174/130; 385/115; 427/434.3; 428/377; 428/392; 57/229; 156/166;
338/66; 427/122; 427/434.2; 427/434.6; 428/378 |
Current CPC
Class: |
H01C
17/04 (20130101); H01B 7/0063 (20130101); D02G
3/385 (20130101); Y10T 428/2936 (20150115); Y10T
428/2938 (20150115); Y10T 428/2964 (20150115) |
Current International
Class: |
D02G
3/38 (20060101); H01C 17/00 (20060101); H01C
17/04 (20060101); H01B 7/00 (20060101); H01c
003/00 () |
Field of
Search: |
;161/47,170,176
;57/14G,144 ;338/210-214,66 ;156/166 ;29/613 ;174/128,130,131 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Goldberg; E. A.
Claims
I claim:
1. A core element for processing through a jacketing orifice in
forming a jacketed composite product, comprising a bundle of coated
filaments interbonded by said coating, a first and second plurality
of filaments helically wrapped about said bundle of coated
filaments, said first plurality of filaments being wrapped in a
direction opposite to the direction of wrap of said second
plurality of filaments, said first and second plurality of
filaments securing said bundle of coated filaments together in more
tight intimate association than said coating alone binds said
bundle, said first and second plurality of filaments being wrapped
about said bundle a sufficient number of turns along the length of
said bundle to present a uniform outer dimension for smooth
snag-free passage through a jacketing orifice.
2. A core element for processing through a jacketing orifice in
forming a jacketed composite product, comprising a bundle of
filaments, a coating of functional particles secured to said bundle
of filaments, a double overwrap comprising two strands of filaments
helically wrapped about said bundle of filaments in opposite
directions to each other, said functional particles of said coating
being held in a stable functional relation by said double overwrap
and said double overwrap imparting a uniformity of outer dimension
for smooth passage through a jacketing orifice.
3. An electrically conductive element suitable for applying an
insulating jacket while passing the element through a die,
comprising a bundle of continuous glass filaments coated with a
coating material including an electrically conductive material, a
first overwrap of a plurality of continuous glass filaments
helically wrapped around said bundle of coated filaments in one
direction, a second overwrap of a plurality of continuous glass
filaments helically wrapped around said bundle of coated filaments
in a direction opposite to said direction of said first overwrap,
said first and second overwrap being wrapped about said bundle a
sufficient number of turns along its length to hold said bundle
together tightly enough to maintain substantially unimpaired the
electrical conductivity of said coating and to impart a uniformity
of outer dimension for smooth passage through said die.
4. A high resistance electrical conductor such as for use in the
ignition system of internal combustion engines comprising a bundle
of glass filaments coated with a coating material including
carbonaceous electrically conductive material distributed
throughout the coating and imparting electrical conductivity to the
bundle, a first overwrap of glass filament yarn helically wound
over said bundle of coated filaments in one direction, a second
overwrap of glass filament yarn helically wound in close engaging
relation over said bundle of coated filaments in a direction
opposite to said direction of said first overwrap in snug engaging
relation thereover, and an insulating jacket surrounding said
bundle of coated filaments and said first and second overwrap
contiguous with said bundle and overwraps to exclude air pockets
between said jacket and said bundle, said first and second
overwraps holding said bundle of coated filaments together in
stable uniform electrically conductive relation.
5. A high resistance electrical conductor as defined in claim 4
wherein said insulating jacket is of elastomeric material.
6. A high resistance electrical conductor as defined in claim 4
wherein said insulating jacket is of neoprene material.
7. The method of manufacturing a core element for processing
through a jacketing orifice in forming a jacketed composite
product, comprising the steps of:
coating a bundle of substantially aligned filaments with a liquid
coating material, the coating on said filaments being sufficient in
quantity to provide a matrix for said bundle;
heating said bundle of coated filaments to secure the coating
material thereto;
helically wrapping first and second pluralities of filaments about
said bundle of coated filaments in opposite directions to each
other, each said plurality being wrapped a sufficient number of
turns along the length of said bundle to maintain said matrix
material intact upon passage through a jacketing orifice and assure
uniform smooth passage therethrough.
8. The method of manufacturing a core element for processing
through a jacketing orifice in forming a jacketed composite
product, comprising the steps of:
coating a bundle of substantially aligned filaments with a liquid
coating, the coating on said filaments being sufficient in quantity
to provide a matrix for said bundle upon drying;
helically wrapping first and second pluralities of filaments about
said bundle of coated filaments in opposite directions to each
other, each said plurality being wrapped a sufficient number of
turns along the length of said bundle to maintain said matrix
material intact upon passage through a jacketing orifice and assure
uniform smooth passage through the jacketing orifice;
heating said bundle of coated filaments to secure the coating
material to the filaments of said bundle and to said first and
second pluralities of overwrapped filaments.
9. The method of manufacturing an electrically conductive element
suitable for applying an insulating jacket while passing the
element through a jacketing die, comprising the steps of passing a
bundle of substantially aligned glass filaments through a liquid
containing carbonaceous electrically conductive particles therein
whereby the bundle of glass filaments is coated therewith, heating
the bundle of coated filaments to dry the coating and to adhere the
conductive particles to the filaments, and helically wrapping first
and second pluralities of glass filaments about said bundle of
coated filaments in opposite directions to each other to present a
uniform outer dimension for smooth snag-free passage of said
element through said jacketing die and to maintain said conductive
particles in stable uniform electrically conductive relation.
10. The method of making a high resistance electrical conductor
such as for use in the ignition system of internal combustion
engines, comprising the steps of:
coating a plurality of glass filaments with a coating material
including electrically conductive material;
heating said plurality of coated filaments to dry said coating
material and adhere said electrically conductive material to said
filaments;
overwrapping first and second yarns of glass filaments helically
around said plurality of coated glass filaments in opposite
directions to each other to present a uniform outer dimension for
smooth snag-free passage of the overwrapped bundle through a
jacketing extrusion die and to maintain stable uniform electrical
conductivity of the conductor;
passing said overwrapped bundle through a jacketing extrusion die
to apply a covering jacket of electrical insulating material
thereto.
Description
BACKGROUND OF THE INVENTION
This invention relates to an improved textile strand product
incorporating a core element of a bundle of continuous elements and
adaptable to such use as high resistance electrical cable. In the
method of manufacturing the cable, bundles of filaments,
particularly glass filaments, are coated with electrically
conductive material and are physically unified by this invention
into a tight integral body. In this use, the invention provides
greater bundle integrity than that given by the adhesion of
individual conductive coatings on the filaments and facilitates the
further processing step of enveloping the bundle with a jacket of
insulating material.
High resistance electrically conductive elements incorporating
glass fibers have been described in U.S. Pat. No. 3,247,020 and
U.S. Pat. No. 3,269,883. Conductive elements of this type have
found particular commercial usefulness as high voltage conductors
in the ignition system of automobile engines. In this use, as in
others, it is important that the filaments of the bundle are held
tightly together. If the filaments separate from the compact
bundle, the continuity of the conductive coating material is
impaired. And a break in the conductive material of the conductor
creates excessive electrical resistance at that location. Uniform
electrical resistance through the bundle is no longer possible when
these breaks occur. Lack of uniformity results in a poor quality
product. Because of such breaks in the coating, it has been
difficult to manufacture conductive elements of this type within
good tolerances. For example, conductors to be used in automobile
engine ignition systems have been manufactured to a desired
resistance of 7,000 ohms per linear foot of conductor. Insufficient
integrity of the bundle has caused resistance variations up to
3,000 ohms per foot of conductor. Such wide variations are
undesirable in most applications.
The conductive coating material on the bundle of filaments creates
a matrix for the bundle and effects some interbonding of the
filaments. But under certain rugged conditions matrix strength
alone may be insufficient to maintain the matrix intact. Such
rugged conditions could occur when passing the bundle through an
extrusion orifice to jacket the bundle. Additional binder material
may be added to the conductive coating material to improve bonding.
Preferably, the binder material, if used, is a carbonaceous
material which will decompose to form carbon when heated. For
example, sugar, starch, glucose, sorbitol, glycerol and the like
may be used. It is preferable, however, to avoid or minimize the
use of a binder material because the resultant electrical
properties when a binder is used are not as good as when the binder
is not used, due to the resulting heterogeneity of the coating. In
order to allow flexibility in selecting the coating material,
additional, external binding must be added to the bundle.
In the past, additional binding has been accomplished by braiding a
nonconductive material such as rayon or nonconductive glass yarn
over the bundle prior to jacketing it with the insulating material.
However, this was not entirely satisfactory because the interlacing
of the braided covering resulted in voids where the yarns crossed
over and under each other. It has been difficult to jacket the
bundle so that the jacketing completely filled these voids or air
pockets. Air and moisture present in these voids caused corona
discharge in the finished product. To cure this, the conductive
bundle after being covered with the braid was run through a
suspension of graphite in neoprene and then through a tower to set
and cure the neoprene. This additional step was costly, time
consuming, and not always entirely successful in eliminating the
voids. In addition, this braided overwrap did nothing toward
remedying damage caused to the bundle by bending which might occur
because of unusually rough handling prior to applying the
overwrap.
This braided overwrap was also not satisfactory for another reason;
it interfered with the subsequent process step of jacketing the
bundle. The jacketing process consists of enveloping the bundle in
an elastomeric insulating material such as neoprene, silicone, or
Hypalon--a synthetic rubber manufactured by DuPont. This process
has been carried out by pulling the bundle through an extrusion die
where the insulating material is extruded over the bundle. In this
step, the bulkiness and irregular shape of the braided coverings
interfered with the smooth passage of the bundle through the
die.
In the foregoing discussion it has been stressed that conductive
elements of the type discussed must have good bundle integrity. In
the past, bundle integrity has been accomplished with a braided
overwrap or by the less desirable method of adding binder to the
coating material. The braided overwrap has not been entirely
satisfactory as indicated above. With these problems in view, it is
an object of the present invention to provide a method for
manufacture of novel electrically conductive bundles with
sufficient bundle integrity to avoid filament separation or breaks
in the conductive coating even under highly rugged operating
conditions.
Another object of this invention is to provide a method of
manufacture of electrically conductive bundles which will impart
good bundle integrity and allow completely contiguous coverage of
the bundle with a later applied insulating jacketing.
A further object of this invention is to manufacture electrically
conductive bundles with good bundle integrity and which will
facilitate snag-free passage of the assemblage through an extrusion
die without interference in the extrusion step process in which the
insulating jacket is applied.
A feature of the invention is its provision of a product
incorporating electrically conductive bundles with good bundle
integrity and with a minimum or no tendency toward corona discharge
problems in use of the final product.
Still a further feature of this invention is provision of an
electrically conductive product of filament bundles having good
bundle integrity imparted by a step incorporated into the
manufacturing process at a point before damage could occur to the
bundle by unusually rough handling.
BRIEF SUMMARY OF THE INVENTION
These objects are accomplished according to the present invention
by helically wrapping two separate small strands or yarns of glass
filaments over the bundle in opposite directions to each other. The
strands are small and in the form of relatively flat, substantially
untwisted bundles of fibers. Therefore, the overwrap causes
substantially no air spaces or voids where the strands cross each
other. This type of overwrap exposes a large percentage of the
bundle surface to easy access by the jacketing material. The result
is that the jacketing material can be placed in completely
contiguous relationship with the overwrapped bundle, and the
neoprene graphite treatment is not required. Thus, allowing the
bundle with the glass yarns served thereon to be fed directly to
the extrusion die rather than first being treated with graphite
suspended in neoprene. The overwrap of the bundle is not bulky and
irregular and therefore, passes easily through the extrusion die.
Overwrapping in this manner results in exceptionally good bundle
integrity. This method of binding the bundle also has the feature
of being easily incorporated into the manufacturing process at a
point before the bundle can be subjected to injurious bending and
flexing by unusually rough handling. With overwrapping in this
manner ignition conductors for automobile engines having a
resistance of 7,000 ohms per linear foot of conductor have been
manufactured within tolerances of plus or minus 1,000 ohms per
foot. This is compared to a tolerance of plus or minus 3,000 ohms
per foot without the overwrap of this invention.
Other objects, advantages and features of this invention will
become apparent when the following description is taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a segment of a tightly bound bundle of coated
glass filaments using the double overwrap binding of this
invention;
FIG. 2 illustrates a method of manufacturing a bundle of conductive
glass filaments including the overwrap of this invention; and
FIG. 3 illustrates an enlarged view of an illustration of the
overwrapping step of this invention.
An embodiment of this invention is shown in FIG. 1 as a bundle of
filaments 4 bound tightly together by clockwise wrapped yarn 5 and
counterclockwise wrapped yarn 6.
The major steps in a method of manufacturing a bundle of conductive
glass filaments are shown in FIG. 2. Strands of uncoated glass
filaments are supplied from a creel 11. The strands are coated with
the electrically conductive material at the applicator 19. The
coated strands are subjected to a source of heat 29 to cure the
coating. The overwrap is applied at the overwrap servers 34 and 44.
And the coated, cured, and bound bundle of strands is collected on
the spool 61.
DETAILED DESCRIPTION OF INVENTION
The bundle of filaments as shown in FIG. 1 may be coated or
uncoated, but when used as an electrical conductor, the glass
filaments will be coated with a carbonaceous electrically
conducting material. The size and number of filaments in the bundle
can be varied, depending upon conductor size and flexibility
desired. An example of a satisfactory product is one having
approximately 12,000 filaments of a 0.00036 inch diameter.
The overwrap material 5 and 6 is preferably a low twist yarn.
Although the terms yarn and strand are not always considered
synonymous, they are used interchangeably in this discussion and
are intended to mean both a twisted yarn of continuous filaments as
well as an untwisted strand of continuous filaments. As one of the
features of this invention is to avoid air spaces where the
overwrap yarns cross, it is important that the yarn size is small.
By way of example, it has been found that a plurality of uncoated
glass filaments having approximately 204 filaments of 0.00036 inch
diameter has worked successfully for each overwrap yarn. The number
of wraps per inch of bundle can be varied from 4 wraps per inch to
2/3 wraps per inch and give satisfactory results. It has been found
that 2 wraps per inch is particularly satisfactory.
Glass in filament form is not the only material which can be used
for overwrap. Filaments of other materials, such as rayon, nylon,
polyester, as well as carbon and boron can be used. Yarns of
natural staple fiber, such as cotton, sisal, and the like, can also
be used. It is preferable that nonconductive or semiconductive
material be used because it would not be desirable to have the
overwrap conduct any substantial amount of the electricity. If the
overwrap were too conductive, it might have an undesirable effect
upon producing the desired resistance of the bundle. Glass
filaments are particularly desirable as the overwrap material
because of their low electrical conductivity in addition to other
qualities such as high strength and low elasticity. Glass filaments
are especially desirable where the bundle is to be used as
automobile engine ignition conductor because glass maintains its
strength in the presence of high temperatures. This feature will
become even more desirable as more pollution control devices are
added to automobiles. The addition of these devices may increase
the temperature under the hood of the cars to the 350.degree. to
400.degree. F. range.
The use of two overwraps wrapped in opposite directions is critical
to this invention. Single overwraps have been tried in the past to
bind the bundle together with unsatisfactory results. The single
overwrap creates unbalanced forces on the bundle which tends to
distort the bundle into catenaries. The bundle distortion impedes
smooth passage of the bundle through the jacketing extrusion die.
The single overwrap is skinned back by the extrusion die and causes
jams and breakouts. In contrast, the double overwrap of this
invention establishes a more balanced relation of forces on the
bundle because the forces created by one overwrap are
counterbalanced by the opposite forces of the other overwrap. The
result is a more uniform cross section which passes smoothly and
easily through the orifice of the extrusion die.
A detailed description of a method of manufacturing a bundle of
conductive glass filaments with the double overwrap binding
follows. Referring to FIG. 2, there are mounted a number of bobbins
of glass strands 13 on the creel 11. The number of bobbins will
vary depending upon the size of the strands and the desired size of
the finished bundle. FIG. 2 shows four bobbins for illustrative
purposes, but a larger number would probably be used. For example,
a satisfactory product has been made pulling from sixty bobbins of
glass strand where each bobbin holds glass strand having
approximately 204 filaments of a 0.00036 inch diameter. The strands
are pulled from the creel 11 and through a guide eye 15, where they
are gathered into a bundle and then to the coating applicator
19.
To describe the operation more specifically at the coating
applicator 19, the bundle of uncoated glass filaments passes
through a reservoir of coating media 23 held in a container 21 and
then through a die 25. The bundle is routed through the container
by passing over roller bar 17 and under other roller bars (not
shown) submerged in the reservoir of coating media. The die 25
wipes off the excess coating to maintain a uniform coating
thickness and also forces the individual filaments together to
achieve some degree of mechanical bond between them. The coating
media 23 consists of small particles of carbonaceous electrically
conducting material in liquid suspension. A number of different
electrically conductive particles may be used to coat the glass
fibers. For example, one suitable commercially available material
which has been used with success is sold under the trade name
"Aquadag." This material is a concentrated colloid dispersion of
pure electric-furnace graphite in water. The material is preferably
diluted with water, for example, three parts water to one part
Aquadag, to obtain a fluid which will give the desired surface
coating thickness. The amount of coating desired is that amount
which will give carbonaceous particles between 1.5 and 8.5 percent
by weight of the composite of glass and cured coating.
After passing through the die 25, the coated bundle 27 is advanced
to the source of heat 29. The heating step cures the coating by
drying the coated bundle, adhering the conductive particles to the
filaments and interbonding the filaments to each other. The heating
can be carried out in a number of different ways such as by passing
the bundle through an oven. However, a particularly satisfactory
arrangement is that of helically wrapping the coated bundle of
glass filaments about a heated drum. The rotation of the drum pulls
the bundle of glass from the creel and through the coating
applicator. As will be appreciated, the drum diameter, temperature
and the number of times the bundle is wrapped around the drum may
be varied to obtain the desired curing. It has been found that with
the bundle travelling at 35 feet per minute through 10 wraps about
the drum, drum temperatures in the range of from 550.degree. to
650.degree. F. are satisfactory.
The foregoing description illustrates a method of producing an
electrically conductive bundle of glass filaments up to the
improvement step of this invention. While this description alone is
sufficient to enable one to produce a satisfactory product,
additional description may be found in U.S. Pat. No. 3,247,020 and
U.S. Pat. No. 3,269,883, and the disclosures in these patents are
intended to be a part of this specification.
After completing the heating step, the bundle is advanced to the
overwrap servers 34 and 44 where the improvement step of this
invention takes place. In this step the coated bundle of glass
filaments 31 is passed through server 34 where one overwrap is
wound over the bundle in one direction and then through server 44
where the other overwrap is wound over the bundle in the opposite
direction. The bundle 33, held tightly together by the two
overwraps, is then wound on the collecting spool 61 into a package.
In this package, it will be transferred to the place where the
insulating jacket will be applied.
To more specifically describe the overwrapping step, reference is
made to FIG. 3 which shows an enlarged view of the overwrapping
process. Counterclockwise rotating overwrap server 34 consists of a
bobbin of glass yarn 35 mounted on a rotatable spindle 37. The
coated bundle 31 passes through a hole in the spindle 37. The
spindle 37 and bobbin of yarn 35 rotate about the bundle 31 and
wind the overwrap yarn 41 counterclockwise about the bundle 31.
After passing through the clockwise server 34, the bundle 32, with
one overwrap, advances through clockwise server 44 where the second
overwrap is applied. Clockwise rotating overwrap server 44 consists
of a bobbin of glass yarn 45 mounted on a rotatable spindle 47. The
spindle 47 and bobbin of yarn 45 rotate about the bundle 32 and
wind the overwrap yarn 51 about the bundle 32 as it passes through
the bobbin. The number of wraps of the overwrap material per linear
inch of the bundle is dependent upon the speed of the bundle
passing through the overwrap server and the rotational speed of the
servers. For example, if the bundle is travelling at 35 feet per
minute and it is desired to have one wrap per inch, then the
rotational speed of the overwrap server must be 420 r.p.m.
The illustration of FIG. 2 shows the overwrapping step being
carried out after the heating step. It should be noted, however,
that the overwrapping step can be carried out before the heating
step. In fact, there may be a desired advantage in overwrapping
before heating, because the cured coating will adhere somewhat to
the overwrap yarns and give even greater integrity to the bundle.
This invention contemplates carrying out the overwrapping step
either before or after the heating step. It should also be noted
the designation herein of the first overwrap as being
counterclockwise is only for illustrative purposes and the process
will also work successfully if the directions of both overwraps
were reversed.
The specific description of this process was given for an example
only. It will be obvious to one skilled in the art that many
variations can be made within the spirit of this invention. For
example, the manner in which the overwrap material is served can be
varied. The server shown is only one of many workable methods. The
size and configuration of the overwrap material can be varied and
still obtain satisfactory results. And, as already stated, the
overwrap material is not limited to glass. This invention is not
intended to be limited to electrically conductive bundles of glass
filaments. It also includes binding of bundles of filaments coated
with functional particles other than electrically conductive
material where that material does not sufficiently adhere the
filaments together. For example, glass or other filaments, coated
with a magnetic material could be advantageously bound by the
overwrap of this invention. And the coating of magnetic material,
as well as the electrically conductive material, can be of either
metallic or nonmetallic material. This invention also includes
binding of uncoated filaments. Other variations are obvious in view
of the present disclosure and it is to be understood that
variations and modifications are contemplated within the spirit and
scope of the appended claims.
* * * * *