U.S. patent number 3,653,961 [Application Number 05/010,627] was granted by the patent office on 1972-04-04 for papermakers fabrics.
This patent grant is currently assigned to Huyck Corporation. Invention is credited to Leonard R. Lefkowitz.
United States Patent |
3,653,961 |
Lefkowitz |
April 4, 1972 |
PAPERMAKERS FABRICS
Abstract
This invention relates to papermakers fabrics for use in the
dryer section of papermaking machinery characterized by having
bulky, resin impregnated cross-machine direction yarns.
Inventors: |
Lefkowitz; Leonard R. (Latham,
NY) |
Assignee: |
Huyck Corporation (Rensselaer,
NY)
|
Family
ID: |
21746613 |
Appl.
No.: |
05/010,627 |
Filed: |
February 11, 1970 |
Current U.S.
Class: |
442/187;
139/383A; 442/210; 442/215 |
Current CPC
Class: |
D21F
1/0027 (20130101); D03D 25/00 (20130101); Y10T
442/3236 (20150401); Y10T 442/3276 (20150401); Y10T
442/3049 (20150401) |
Current International
Class: |
D03D
25/00 (20060101); D21F 1/00 (20060101); B32b
017/04 (); C03c 025/02 () |
Field of
Search: |
;139/383A ;117/126GB
;161/91,93 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Martin; William D.
Assistant Examiner: Cohen; David
Claims
I claim:
1. A woven dryer fabric for use in a papermaking machine comprising
bulky, resin impregnated yarns in the cross-machine direction, said
yarns, prior to impregnation, comprising fibers which have poor
resistance to mutual abrasion.
2. The dryer fabric described in claim 1 wherein said
cross-direction yarns are made from fiberglass.
3. The dryer fabric described in claim 2 comprising machine
direction yarns made from manmade material characterized by being
substantially stable, physically and chemically over a long period
of time to the ambient conditions to which the fabric is exposed
when in use.
4. The dryer fabric described in claim 3 wherein said cross-machine
direction yarns are textured.
5. The dryer fabric described in claim 1 in which said
cross-machine direction yarns are textured fiberglass.
6. The dryer fabric described in claim 3 wherein said machine
direction yarns do not extend substantially above the flat surfaces
of said fabric.
7. The dryer fabric described in claim 6 wherein said machine
direction yarns are made from high temperature tolerant
polyamide.
8. The dryer fabric described in claim 4 in which the machine
direction yarns are made from high temperature tolerant polyamide
material.
Description
BACKGROUND OF THE INVENTION
In the manufacture of paper and paper-like materials, such as
writing paper, newsprint, board, corrugating paper, and the like,
typically the final portion of the process of removing water from
the paper web is carried out in the dryer section of the
papermaking machine. In a typical fourdrinier papermaking machine,
the dryer section comprises upper and lower parallel arrays of
large, steam-heated rolls or "cans," in combination with endless
textile conveyor belts usually referred to as "dryer felts" and/or
"dryer fabrics." Usually, upper and lower dryer felts or fabrics
are used and perform the function of pressing the web of paper
against the outer periphery of the dryer rolls in intimate contact
as the web travels seriatum from roll to roll and between arrays of
rolls through the dryer section. Thus, these dryer felts or fabrics
are exposed to extremely severe conditions of high heat, high
moisture concentrations, and (frequently) chemically active
environments. Thus, there is a tendency for them to degrade
physically and chemically very rapidly and for this degradation to
be manifested in the form of such things as dimensional variations,
tearing or other destruction of the fabrics, and losses in tensile
strength. Since the replacement of a papermakers fabric normally
consumes considerable amounts of downtime on the machine, which are
very costly in terms of loss of production in addition to the cost
of the replacement materials, it has been a long-sought objective
in the papermaking art to extend the life of papermakers fabrics as
much as possible.
In the papermaking art, the endless textile belting used in the
dryer section of the papermaking machine, as noted above, is
referred to variously as "dryer felts" or "dryer fabrics."
Technically, the term "dryer felt" is a misnomer since, as noted in
the publication Modern Pulp and Papermaking (by John P. Calkin,
Reinhold Publishing Co. 1957, at Page 349), "The dryer felt is
actually not a felt, but a heavy duck made essentially of cotton.
By papermakers' usage it is termed a `felt`." Historically, such
"felts" have been made from cotton, or cotton and asbestos,
although in some cases, material such as wool has also been used.
More recently, "dryer fabrics" have come into widespread use in the
dryer sections of papermaking machines. Dryer fabrics are usually
made from synthetic materials, such as polyesters and/or
polyamides, in the form of monofilaments or multifilaments that are
woven into open-weave structures. Although in the ambient
conditions normally encountered in dryer sections of papermaking
machines such dryer fabrics exhibit a significiantly longer life
than did the previously used dryer felts, there are, nevertheless,
continuing efforts to increase the useful life of such dryer
fabrics even beyond that previously achieved.
Thus, it is an object of the present invention to produce a dryer
fabric which will have a significantly longer useful life than that
attainable with prior art dryer clothing.
It is another object of this invention to provide a dryer fabric
that will have improved strength and dimension-retaining
characteristics.
Yet another object of this invention is to provide a dryer fabric
less susceptible to degradation than prior art structures.
Another object is to provide a dryer fabric with improved heat,
moisture, and/or chemical stability.
SUMMARY OF THE INVENTION
These and other objects, which will be readily apparent to those
skilled in the art, are attainable through practice of the present
invention, one embodiment of which comprises a dryer fabric for use
in a papermaking machine comprising bulky resin impregnated yarns
in the cross-machine direction.
DESCRIPTION OF PREFERRED EMBODIMENTS
For purposes of this patent application and, more particularly, the
claims set forth herein, the following terms and their variants are
intended to have the meanings indicated below:
"Yarn" means any continuous structure useful as a constituent
member in the weaving of fabrics, whether a monofilament, a
multifilament, a plurality of multifilaments bundled together, or a
plurality of spun staple fibers.
"Filament" means a single thread, or a thin flexible thread-like
object.
"Crinkled" means having many short bends or turns.
"Bulky" (as applied to yarns) means having a relatively large
percentage of its cross-sectional area unoccupied by constituent
filament material, whereby impregnation of the yarn by treating
resins and consequent substantial entire encapsulation of the
constituent filament material may be facilitated.
"Textured" (as applied to yarns) means having rendered bulky a yarn
comprising a plurality of filaments made from man-made materials
which are not originally or inherently "crinkled" by causing said
filaments to become crinkled; said plurality of filaments being, or
being comprised of, a group of more than one substantially
continuous filaments or a plurality of such groups of filaments
(such yarns are also sometimes referred to in the textile arts as
"textured"yarns).
"Machine direction" means the normal direction of travel of the
dryer fabric when it is in use on the papermaking machine.
"Cross-machine direction" means a direction substantially normal to
the machine direction.
It has been known for some time that materials, such as glass, are
available having qualities of chemical and/or thermal resistance
that would appear to make them highly desirable for use in ambient
environments which may be encountered in the dryer sections of
papermaking machines. However, characteristically, such materials
also tend to be hard and brittle and therefore to exhibit poor
mechanical characteristics. Thus, for example, although it has been
suggested in the prior art to use fiberglass as a constituent in
the manufacturing of a papermakers dryer fabric (e.g., see Wagner,
U.S. Pat. No. 3,279,504), such prior art does not disclose how such
materials might be utilized practically in a fabric which is
sufficiently supple and flexible to be used in the dryer section of
a papermaking machine without those materials being so hard as to
mark the paper or to prematurely cause abrasion of the other
constituent yarns with which it is associated or to cause the
fiberglass yarn itself to deteriorate through fracturing derived
from its inherent brittleness and poor resistance to mutual
abrasion. It is also known in the textile making arts that the
self-destructive tendencies of a fiberglass yarn can be improved
somewhat by treating the individual constituent filaments with
resin, but even these treatments have not proved satisfactory to
produce yarns for use in papermakers dryer fabrics because the
process is much too costly and will not produce yarns of
satisfactory bulkiness to impart the selective degree of
flexibility desirable and/or necessary to the successful operation
of such fabrics. Although it is also known from the prior art
(e.g., Barrell U.S. Pat. No. 2,098,993) that through use of bulked,
cross-direction, asbestos fiber-bearing filling members,
dimensional stability may be imparted to papermakers dryer felts,
and that preservation of the mechanical and structural integrity of
the machine direction yarns of such papermakers dryer felts may be
enhanced, the prior art does not teach how these advantages may be
imparted to open weave dryer fabrics. Furthermore, this art is not
of use to produce an improved papermakers dryer fabric because the
inherent low strength of asbestos yarns makes it necessary to
supplement the asbestos with some strength imparting material such
as cotton (as the Barrell patent shows) which inherently imposes
limitations on the strength, thermal, and chemical resistances of
the resulting structure. Neither does the prior art teach how dryer
fabrics may be made with bulky cross-machine direction filling
yarns that are made from fiberglass or other materials having
comparable thermal and chemical resistance qualities without
simultaneously rendering those yarns susceptible to rapid
mechanical degradation in use.
But in no prior art of which I am aware has it ever been proposed
to make clothing for the dryer section of a papermaking machine
utilizing bulky fiberglass filling yarns.
I have found that fiberglass may be incorporated into a papermakers
dryer fabric and rendered suitable for the intended use by using,
and subsequently resin impregnating, fiberglass yarns which have
been rendered bulky (as defined above) by any of a variety of
methods, including "texturizing" (methods for achieving which are
disclosed in Cobb et al., U.S. Pat. No. 3,262,177 and the
publication Textile World for December, 1969, (Vol.119, No. 12) at
Pages 60 through 63).
EXAMPLE
A papermakers dryer fabric was made 162 feet long by 165 inches in
width. For warp yarns it had 36 ends per inch of 1,200 denier, 600
filament NOMEX, high temperature polyamide yarns, as manufactured
by E.I. duPont de Nemours & Co. For filling yarns, it had
Owens-Corning textured fiberglass type No. 401, DE75 5/3 (which is
a code to indicate that the yarns consisted of filaments comprising
7,500 yards per pound, 5 ends of which were plied, and 3 such plies
being themselves plied together). Obviously, other materials having
the requisite characteristics of suppleness, strength, and heat,
moisture, and chemical resistance, suitable for use in the dryer
section of a papermaking machine, could have been used in place of
the aforesaid warp yarns. So also with respect to the filling yarns
provided they are susceptible to being rendered bulky, and had been
rendered bulky. These filling yarns, at a density of 20 picks per
inch, were woven together with the warp yarns at 36 ends per inch
in a four harness double satin weave. In this instance the fabric
was woven so that the warp yarns did not extend above the flat
surfaces of the fabric. This was done in the interests of removing
the load-bearing warp yarns from an abrasive exposure. The fabric
was also rendered less susceptible to machine direction stretch
with attendant cross-machine direction narrowing through crimp
interchange. The fabric was treated with a resin according to a
known technique substantially in accordance with Wagner U.S. Pat.
No. 3,192,599, such that the fabric was rendered sufficiently
limber to permit it to be used in the papermaking process, while
keeping the constituent members of the fiberglass yarns from
abrading each other. Before this fabric was supplied to the
papermaker for installation in the dryer section of a papermaking
machine, it was tested and found to have a machine direction
tensile strength of 402 lbs. per lineal inch and a cross machine
tensile strength of 254 lbs. per lineal inch. The fabric was
operated on the papermaking machine for 8 months, at which time it
was removed, but not for reason of any failure of the fabric, and
inspection after removal indicated it would have operated for
several more months. This 8-month period was the longest that any
conventional dryer fabric had operated up to that time on this
papermachine position. When the fabric was removed, it was
subjected to various measurements an and found to have a length of
159 feet, a width of 164 1/2 inches, a machine-direction tensile
strength of 257.89 lbs. per inch, and a cross-machine direction
tensile strength of 284 lbs./in. Thus, it is apparent that, as
evidenced by the degree to which it retained its dimensional and
strength characteristics, this fabric was more highly resistant to
the derogatory effects of high heat, high tension, and the chemical
environment to which it was exposed throughout its useful life on
the papermaking machine than were any of the conventional clothing
previously used on this papermachine position.
Without intending to be bound by any theory, it is believed that
this increase in useful life is due, at least in substantial part,
to the use of the bulked filling yarns. Apparently, the effect of
these yarns having been bulked is to provide a means by which the
load-bearing machine direction yarns may be significantly imbedded
and protected from abrasion, thereby enhancing preservation of the
machine direction and cross-machine dimensional stability of the
fabric, as well as the machine direction tensile strength. At the
same time, because of having used fiberglass cross-direction yarns
which were bulky, it became possible to utilize the desirable
characteristics of the fiberglass while, at the same time, being
able to impregnate the glass yarns after the fabric had been made
with sufficient quantities of resin to preclude substantially
self-destruction of the fiberglass yarns through mutual abrasion of
their constituent members.
In this connection, it should be noted that the present invention
is limited to papermakers dryer fabrics having bulky
cross-direction yarns, regardless of the exact means by which they
were rendered bulky.
It will also be apparent to those skilled in the art that the
present invention may be practiced in a wide variety of embodiments
without materially departing from the spirit and scope of the
present invention.
It is to be understood that in the foregoing specification the
specific embodiments and components thereof which have been
illustrated and discussed are by way of illustration and not of
limitation and that this invention may be practiced by those
skilled in the art utilizing a wide variety of materials and
configurations without department from the true spirit and scope of
this invention.
* * * * *