PRESS FELT

FEUTRE DE PRESSE

English Abstract

A needled press felt for dewatering of cellulose pulp in a paper
making machine consists of a multi layer base fabric having
longitudinal and transversal threads. In order to improve the
dewatering capability of the press felt and making it easy to
assemble, the dewatering side of the press felt consists of
layer of coarse yarn , which has a weight per unit of length,
which is at least twice as great as the one of the remaining
parallell yarns of the base fabric. Further a seam which
can be opened is arranged transversally to the running direction
of the felt in the paper making machine.

Claims

WE CLAIM:
1. A needled press felt having a dewatering side and a non-dewatering side for
dewatering of cellulose pulp in a drying machine comprising:
a woven multi layer base fabric having filament threads and binding threads;
a layer of coarse yarns threads, on said dewatering side, which are woven with
said binding threads to said multi layer base fabric,
the coarse yarn threads having a weight per unit length which is at least twice
as great as that of the filament threads; the base fabric consists of a tubular fabric having
turning edges and having a releasable seam extending substantially transversely to the
direction of the movement of the press felt on the machine, said seam consisting of loops
formed by the transverse threads along one of the turning edges and a fastening means;
the coarser yarns are cut such that they extend along a line substantially parallel
with and close to said loops, said coarse yarn being no part of said seam.
2. The press felt of claim 1, wherein the rigidity of the felt is increased by means
of a layer of wadding, said wadding consisting of fibers which are fastened to the upper
side of the fabric by means of a needling process and wherein said fibers are cut
transversely to the felt along the same line as the coarse yarn threads such that an endless
fabric is formed which can be opened and seamed.
3. The press felt of claim 1, wherein the filament threads have a weight per length
of unit of 80-430 tex and the coarse yarn threads have a weight per unit of length which
is at least 160 tex.

Description

20 1 q854
PRESS ~ELT
This invention concerns a needled press felt for dewatering of
cQllulose pulp in a paper making machine, which felt consists of
a multi layer base fabric having longitudinal and transversal
threads.
At pulp drying machines for cellulose the pulp is dewatered and
formed into a web in a first step on a forming wire, in a second
step in the press section and ths final drying takes place in a
hot flow of air in a fan dryer or on heated drums. In the case
when the pulp is dried by air, a large contact surface between
air and the web is desirable in order that the drying shall be
carried out as effectively as possible. A press felt having a
rough surface is preferably used in order to increase the speci-
fic surface of the pulp web, the rough surface giving the pulp
web a markedly embossed surface. A rough surface of the pulp web
has a negative effect on drum dryers, because the heat transmis-
sion from the surface of the drum to the web will be small
because of a smaller contact surface.
In order that the press felt shall give the wanted effect, it
must be formed by thick yarns on the side, which is turned to
the pulp web 80 that this will be embossed. A problem is however
that the thick filaments will make the felt heavy and stiff and
it will be difficult to install the felt in the paper making
machine and this in turn will limit the use of such a press
felt.
The object of the invention is to solve this problem 80 that it
will not be necessary to narrow the press felt in order to guide
it through the small openings in the machine. The characterizing
features of the invention will be found in the enclosed patent
claims.
~5

la 201 '~854
According to this invention there is provided a nee~lled press felt having a
d~;~dleling side and a non-d~rdte~ g side for d~dtel-ng of cellulose pulp in a drying
m~ ine comprising:
a woven multi layer base fabric having fil~ment threads and binding threads;
a layer of coarse yarns threads, on said d~;wdt~ling side, which are woven with
said binding threads to said multi layer base fabric,
the coarse yarn threads having a weight per unit length which is at least twice
as great as that of the fil~ment threads; the base fabric consists of a tubular fabric
having turning edges and having a releasable seam PYt~n~ling subst~nti~lly transversely
to the direction of the movement of the press felt on the machine, said seam con~ ting
of loops formed by the transverse threads along one of the turning edges and a
f~t~ning means;
the coarser yarns are cut such that they extend along a line subst~nti~lly
parallel with and close to said loops, said coarse yarn being no part of said seam.
An embodiment of the invention will be described below with reference to the
enclosed drawing.
C

201 ~854
Fig 1 is thereby a part of a cross section of a final press
felt, whereby the running direction through the paper making
machine is transverse to the plane of the drawing.
Fig. 2 is a schematic view of a cross section of the fabric in a
weaving machine.
Fig. 3 i8 a schematic plan view over the stitch of the fabric
with the locking wire assembled.
Thus fig. 1 shows a fabric consisting of two layers of filaments
1 and 2, which form weft threads during weaving. A thicker yarn
i8 woven on that side of the fabric which forms the dewatering
side. The yarns 3 have a weight per length, which is at least
twice as large as the one of the yarns 1 and 2. The thicker yarn
3 forms an upper layer and this layer gives the wanted embossing
to the cellulose pulp. In the shown embodiment the binding of
the yarns 3 is according to the pattern 4-shaft cross twill in
two pattern repeats. As known per se,the weaving will form loops
along one of the turniny edges by the weft thread ~ and 2. The
loops are formed around a selvedge end 6. The loops are used to
form a seam which can be opened.
In fig. 2 is schematically shown a cross section of a 80 called
tubular fabric. The loops 5 have hereby been formed by the
threads 1 and 2 around the selvedge end 6. The thicker yarns 3
are not formed with loops. Furthermore it should be emphazised
that no binding with the warp yarns is shown in fig. 2. When the
fabric thus being a tubular fabric, shall be adapted to be a
press felt, the yarns 3 are cut close to thH loops and along a
line which is parallel to the loops or to the selvedge end 6.
When later the selvedge end is drawn out, the felt can be unfol-
ded to its entire length. Before that the felt may be supplied
with a layer of wad which is needled to the felt and gives it a
better rigidity. A reinforced flap of wad is achieved over the

2019854
area where the loops are, and thus over the seam which is pos-
sible to open, see Swedish patent 447 140. It is known per se
from the Swedish patent 429 982 how to form such a seam.
When the selvedge end is taken away the felt can be insertQd
with its entire length in the press of the pulp drying machine
and when the felt hAs been inserted the both ends are joined by
that the loops 5 meet and a locking wire 7 can be inserted
through the loops. The press felt i~ hereby made tubular, see
fig. ~.
The yarns 1 and 2, which thus are the weft threads during the
weaving but are longitùdinal when being used in the paper making
machine, are preferably monofilament from polyamide or polymer
having similar properties and having a diameter of 0.~-0.7 mm
corresponding to a tex No. of about 80 - 430. The yarn 3 is
either monofilament or a twistQd thin monofilament or m~lti-
filament having a weight per length, which is at least twice aL
great as for the yarns 1 and 2 J thus at least 160 tex. Twisted
thin monofilament or multifilament are preferably used. The warp
yarn or the binding yarn 4 are suitably a ~imple monofilament or
twisted thin monofilament.

Representative Drawing