Note: Descriptions are shown in the official language in which they were submitted.
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2002-4l2 DRYEP~ FELT FABRIC
JTE:tm
BACKGROUND OF THE INVENTION
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l. Field of the Invention
The invention relates to paper machine clothing
and more particularly relates to fabrics useful as dryer
felts, and their use.
2. Brief Description of the Prior Art
The art i5 replete with descriptions of dryer felts
and dryer felt fabrics. In spite of the wide variety of
materia1s available, the ideal dryer fabric is yet to be
follnd.
In recent years, dryer fabrics have been developed
which are constructed partially or entirely from monofilaments.
~owever, such fabrics have not been entirely satisfactory when
employed to fashion dryer felts. The monofilaments are
subject to abrasion and moist heat hydrolysis. In the
prior art constructions the load bearing machine direction
monofilament yarns may be rapidly degraded under some conditions
o use so thdt the life of the d yer felt is shortened.
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With the structured faorics of the present invention,
employed as dryer felts, the cross-machine direction yarns
support the paper sheet being dried. The monofilament machine
direction yarns are thus protected from direct contact with
degradative elements. The overall operating life of the
dryer felt is significantly increased over felts where the
monofilament machine direction yarns are in contact with the
paper sheet being dried.
SUM~!IARY OF THE INVENTI ON
The invention comprises a fabric for use as a paper
machine dryer felt, which comprises;
a first sinuous layer of cross-machine direction yarns,
providing a fabric first periphery of peaks and valleys wherein
a plurality of peaks are in a first outside plane and the valley
floors are in a first inside plane;
a second sinuous layer of cross-machine direction yarns,
providing a fabric second periphery of peaks and valleys
wherein a plurality of peaks are in a second outside plane and the
valley ~loors are in a second inside plane;
a plurality of monofilament machine direction yarns
positioned between the first and second outside planes and
interweaving the cross-machine direc,ion yarns of the first
and second layers at points between the outside and inside
planes of at least one of said first ~nd second layers and
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at points within the periphery of the other of said first
and second layers.
BRIEF DESCRIPTION OF THE DRAWINGS
. _ __ _ . _
Figure 1 is a cross-sectional, side elevation of
a portion of a preferred embodiment fabric of the invention.
Figure 2 is a schematic view of a portion of a drying
section in a paper making machine.
DETAILED DESCRIPTION OF THE PREFERRED
E~ODIMENTS OF THE INVENTION
Figure 1 is an enlarged, cross-sectional, side
elevation of a portion of a fabric 10 of the invention.
The fabric 10 comprises a first sinuous layer 12 of mono-
filament cross-machine direction yarns 14. The layer 12
~orms a periphery of fabric 10 which in side profile shows
peaks 16 and valley floors 18. A plurality of at least
two peaks 16 in layer 12 are in a single plane forming an
outer periphery of fabric 10. Preferably at least about
50 percent, most preferably all or substantially all of the
peaks 16 are in the aforesaid plane. Valley floors 18 are
in a separate plane inside of the plane formed by the peaks 16.
A second sinuous layer 20 of monofilament cross-
machine direction yarns 14' forms another periphery of the
fabric 10 whic~ also appears, in side profile, as peaks 16'
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and valley floors 18'. A plurality of at least two of the
peaks 16' are in a single plane forming the outer periphery
~preferably at least about 50 percent, most preferably all
of the peaks 16' are in the periphery). Valley floors 18'
are in a separate, single plane inside of the plane formed
by peaks 16'.
A plurality of monofilament machine direction yarns
22 are posi~ioned between the outer fabric periphery formed
by the out~ide planes, formed by the peaks 16 ~nd the peaks
16' and interweave with the cross-machine direction yarns
14, 14' at points between the respective planes of peaks 16,
valley floors 18 and peaks 16', valley floors 18'. ~hus, I
as shown in Figure 1, the knuckles of load bearing machin~
direction yarns 22 are below the peaks 16, 16' at the point
where they int:erweave with the cross-machine direction
yarns 14, 14' and do not come into direct contact with the
sheet 24 of paper carried on fabric 10, when fabric 10
is employed as a dryer fabric on a paper making machine.
The sheet 24 is supported on the peaks 16 of the cross-
machine direction yarn 14~ On the side of fabric 10 facing
away from the carried sheet, the machine direction yarns 22
are also protected by the outwardly projecting peaks 16'
from contact with elements of the paper making machine which
might hasten abrasion or other dPgradation of the important
load bearing machine direction yarns. However, it will be
l appreciated that the greates~ degradation of yarns in a dryer
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fabric occurs in those monofilament yarns in contact with
sheet 24. Thus, it is not critical that yarns 22 be pro~ected
by peaks 16' on the side of the fabric facing away from the
carried sheet 24 although such is obviously preferred, Within
the scope of the invention are fabrics where the yarns 22 are
on the outer periphery of layer 20 where they pass through
layer 20.
In the embodiment fabri.c 10 the machine direction yarns
22 within layer 12 are paired with the yarns 22 within layer 20
and the yarns ~ithin the pairs are slightly offset from each
other in regard to ~ertical alignment, as they knuckle over
the cross-machine direction yarns 14, 14'. There are, in the
weaving patte.rn, 4 sets of maclline direction yarn 22 pairs.
One pair interweaves with every fourth of c~ross-machine
direction yarn,s 14, 14' and then the pattern repeats.
Preferably, the machine direction yarns pass over at least
one cross-machine direction yarn, under at least one following
cross-machine direction yarn and over at least one further
following cross-machine direction yarn of the upper cross-
machine direction layer before running down to interconnect
the lower cross-machine direction layer with the upper cross-
machine direction layer, the machine yarns and cross-machine
direction yarns being thus interconnected in a repeat pattern.
Il Of course the weave will be such that the relationship of the
machine direction yarns and the upper layer of cross-machine
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direction yarns will be such that the plane of the
upper surfaces of the portions of the cross-machine
direction yarns of the upper layer over which the
machine direction yarns pass is relatively elevated
in a direction away from the plane of the upper
surface of the fabric; and the plane of the exposed
upper surfaces of the portions of the machine direction
yarns in the uppe.r layer under which the cross-machine
direction yarns pass is relatively depressed in the
opposite direction, ~ereby the differences i.n elevation
between the exposed upper surface portions of the machine
direction yarns are protected from contact with paper
sheet which contacts the surface of the cross-machine
direction yarns in the upper layer.
Th.e yarns 14, 14' and 22 may be monofilaments on
any synthetic polymeric resin. The yarns 14 and 14'
may also be multifilament yarns. Representative of
.ll such multi- and monofilaments are yarns of polyester,
1~ polyamide, polyolefin, polyaramid, polyimide and the
'li like. Generally such yarns having diameters of from
10 to 40 mils are advantageously employed in the fabrics
of the invention.
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Following the weaving of the fabrics of the invention,
theyare heat set to stabilize the fabric and to draw the yarns into
their desired relative positions. The machine direction yarns
22 are drawn inwardly of the outer surfaces of the fabric 10
~ and this pressure "crimps" the yarns 18, 18' so that the peaks
16,16' are displaced to the outside plane of the fabric as
previously ~escribed. The degree of heat-setting required to
achieve the desired structure of the fabric 10 will of course
vary depending on the nature of the yarns 14, 14' and 22.
~ ~Iowever, optim~ times, temperatures and tensions placed on
the fabric during heat-setting can be determined by those
skilled in the art, employing trial and error technique for
the different ~arn materials. In general, heat-setting may be
carried out at temperatures of from about 150 F. to 375F for
from 15 to 60 minutes, The fabrics of the invention may be
woven flat and the ends joined by conventional seaming methods,
known to those skilled in the art. The seamed belts so made
are readily employed as dryer felts in the dryer section 30
of a paper making machine as shown in Figure 2. As shown in
Figure 2, the paper sheet 24 is held against the steam
cylinders 32 by the endless belt 34 of fabric 10 during
passage of sheet 24 through dryer section 30.
The following example sets forth the best mode con-
templated by the inventors of making and using the invention
~ but are not to be considered as limiting.
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EXAMPLE 1
A fabric is prepared in a duplex weave of 0.020"
diameter polyester monofilament (24 per inch) machine direction
yarns and 0.020" diameter polyamide monofilament machine
I direction yarns (24 per inch) for a total of 48 machine direction
yarns per inch interwoven with 0.020" diameter polyester mono
filament (48 per inch; 24 top and 24 bottom) filling or cross-
machine direction yarns. After heat setting, a fabric is
obtained having only cross-machine direction yarns in the
~ outer plane of the fabric. A representative portion of the
fabric prepared is subjected to physical testing. The physical
properties found are shown in Table I, below.
EXAMPLE 2
This is not an example of the invention, but is
made for comparison purposes. A fabric is woven in a duplex
weave (4 warps and 8 pick repeat) with machine and cross-
machine direction yarns as follows.
machine direction ~ .020" diameter polyester monofilament
at 24 per inch.
.020" diameter polyamide monofilament
at 24 per inch.
"laid out in a two and two arrangement"
filling - .020" diameter polyester monofilament
at 25 per inch. 12.5 top and 12.5 bottom.
~fter heat-setting, a fabric is obtained wherein the
machine direction yarns are in the outer plane of the fabric
where they knuckle over the cross-machine direction yarns.
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A representative portion of the fabric is tested
for its physical properties. The test results are given in
I Table I, below.
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~, TABLE I
.
~ Fabric of
Example 1 Example 2
Weight 3.70 oz/ft2 3.0 oz/ft2
Thickness 0.083" 0.085l'
Il Air Permeability: 436 700
l, (measured by Frazier Air
¦~ Permeability Tester;
Ii cubic ft/min of air per
l sq. ft. of area at 1/2"
Il H2O pressure drop)
li Tensile Strength:
~! (lbs/inch)
machine direction1140 923
cross-machine direction 950 512
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I Thermal Sta i ~
~_ ,~(Hot Plate Degradtion)(350F. + 5)
¦ EXAMPLE 1 EXAMPLE 2
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Fabric Percent Fabric Percent
Strength Strength Strength Strength
1 Hours of Exposure Lbs./in. Retained Lbs /in. Retained
, 0 1140 100 923 100
1120 98 8g8 97
1090 96 866 94
1110 97 851 92
, 100 112155 98 7885 9
Taber Abrasion Test
- Machine Direction Cross Machine
Nylon Polyester Direction
EXA~IPLE 1 Lbs.!end % Retained Lbs./end % Retained Lbs./end ~O Retaine~
l, New17.4 - 22.2 - 16 9
500 Cycles 17.0 98 22.2 100 14 1 83
1000 Cycles 15.5 91 22.6 100' 12.8 76
EX~PLE 2
iNew 18.0 - 22.7 - 20.9
500 Cycles 10.2 57 16.8 74 19.5 93
1000 C~cl~s 5.5 31 10.6 47 18.9 90
_g
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Those skilled in the art will appreciate that
many modifications of the preferred embodiments described
above may be made without departing from the spirit and
the scope of the invention. For example, the fabric of
~ the invention may be woven to include various stuffer
picks, to obtain fabrics of different permeabilities as
will be appreciated by those skilled in the art.
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