U.S. patent number 3,861,996 [Application Number 05/124,766] was granted by the patent office on 1975-01-21 for paper web transfer system carrying the web from forming wire to press section.
This patent grant is currently assigned to A. Ahlstrom Osakeyhtio. Invention is credited to Gerhard Walter Dorfel.
United States Patent |
3,861,996 |
Dorfel |
January 21, 1975 |
PAPER WEB TRANSFER SYSTEM CARRYING THE WEB FROM FORMING WIRE TO
PRESS SECTION
Abstract
Apparatus for transferring a paper web from a papermaking
machine forming wire to a press section. A suction pick-up roll
located adjacaent the forward run of the forming wire is wrapped in
part by a first endless pick-up felt which picks the web up from
the forming wire and carries it through the first press nip of the
press section. Prior to contacting the paper web the first felt
passes through a press nip (for liquid removal) formed between the
suction pick-up roll and a press roll. A second felt (i.e., lower
support felt) contacts the web carried by the first pick-up felt
between the forming wire and press section.
Inventors: |
Dorfel; Gerhard Walter
(Weilheim/Tech., DT) |
Assignee: |
A. Ahlstrom Osakeyhtio
(Noormarkhv, SF)
|
Family
ID: |
8504530 |
Appl.
No.: |
05/124,766 |
Filed: |
March 16, 1971 |
Foreign Application Priority Data
Current U.S.
Class: |
162/274;
162/358.1; 162/360.3; 162/306 |
Current CPC
Class: |
D21F
1/36 (20130101) |
Current International
Class: |
D21F
1/00 (20060101); D21F 1/36 (20060101); D21f
002/00 (); D21f 001/32 () |
Field of
Search: |
;162/358,361,210,360,306,197,113,307,274 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Bashore; S. Leon
Assistant Examiner: Tushin; Richard H.
Attorney, Agent or Firm: Brooks, Haidt & Haffner
Claims
What is claimed is:
1. An improved press section in a web forming machine of the type
having at least two traveling endless felts for contacting and
carrying the web, which includes a pick-up roll urging a pick-up
felt against the web for transferring the web to the felt, said
pick-up felt passing around said pick-up roll and through a press
nip for the pick-up felt defined between a press roll and said
pick-up roll, a second press roll opposedly positioned to said
pick-up roll and defining a second press nip between said pick-up
roll and said second press roll through which the web, said pick-up
felt and a support felt pass, the web being carried through said
second press nip between said felts; a pair of further press rolls
located at a distance from said pick-up roll, said pair of press
rolls defining therebetween a third press nip through which said
support felt and said web pass, the distance between said second
press nip and said third press nip serving to eliminate slipping of
the felt and stretching of the web; said support felt supporting
the web between said second and third press nips; one roll of each
of said second and third press nips constituting a guiding roll for
said support felt, and roll means for separating the web from the
felt after said third press nip.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the field of pressing a fiber web in a
press section.
2. Description of the Prior Art
Various arrangements have been introduced previously for the
pressing of a paper web. U.S. Pat. No. 2,911,040 introduces a
pressing part which is situated at a distance from the pick-up roll
in the moving direction of the paper. The arrangement introduced in
this patent has, however, the disadvantage that the part of the
felt between the pick-up point and the first pressing point is
under tension and the wet paper web stretches in this area. This
takes place, in spite of the fact that the pick-up roll and the
pressing roll rotate at the same peripheral speed, since slipping
of the felt occurs at the pick-up roll. Due to stretching of the
paper web, an orientation of the fibers takes place in the
longitudinal direction which diminishes the longitudinal elasticity
of the finished paper. Owing to the different longitudinal and
transversal orientations of the fibers the finished paper sheet
will not remain even.
SUMMARY OF THE INVENTION
According to the invention the pick-up felt is pressed against the
pick-up roll by means of a press roll to eliminate slipping of the
felt and stretching of the web.
The paper produced in accordance with the invention has better
elasticity than paper manufactured by prior known methods.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates schematically a press section of a paper machine
for carrying out the method according to the invention, and
FIGS. 2-6 illustrate schematically alternative embodiments of the
press section.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In FIG. 1, 13 is the wire of the web-forming part, from where the
suction roll 2 working as a pick-up roll moves the paper web 12
with the suction effect of the roll to the endless felt 8. The
suction roll, together with roll 1, forms a press nip through which
the felt 8 runs. The felt and the paper web run to roll 3 at a
distance from roll 2; roll 3 and roll 4 together form another press
nip, where liquid is pressed out of the paper web 12. Thereafter
the paper web is separated from the felt and it runs to the next
pressing point which is formed by roll 4 together with roll 5. A
suitable roll combination is a suction roll 3, a stone roll 4, and
a grooved roll 5. The direction of the movement of the paper web is
illustrated by arrows.
Because the felt runs through two press nips at a distance from
each other, with no slipping occuring at the pressing points, it is
possible, by choosing a somewhat lower peripheral speed for roll 3
than for roll 2, to obtain a longitudinal shrinking of the felt and
thus also of the paper web between the pressing points, in which
case the elasticity of the finished paper increases. FIG. 1 also
illustrates the drying and cleaning devices 15 of the endless felt
8 and the respective devices 16 of the pressing felt 14.
To keep the felt and the paper track essentially horizontal between
the pressing points, an endless, synchronically moving, wire 9 can
be placed below them. An arrangement like this is illustrated in
FIG. 2. FIG. 5 illustrates a corresponding arrangement in a case in
which the rolls 6 and 7 of the supporting wire 9 participate in
forming the pressing points.
The felt and the web can be supported in other ways as well. In the
application according to FIG. 3, a suction box 10 has been fitted
above the felt to keep the felt part horizontal. In the case
according to FIG. 4, a blowing device 11 has been respectively
fitted below the felt; this device creates a cushion of air to
support the felt part.
The pair of rolls 1 and 2 forms the so-called washing press of the
felt and removes from the felt liquid that has been absorbed by it.
Because the paper web is supported between rolls 2 and 3, the felt
can be relatively dry there, in which case the proportionate
dryness of the paper web, also, will be high after the first
pressing point.
According to another embodiment, shown in FIG. 6, the paper web
travels from the upper pick-up felt 8 running around the pick-up
roll 2, to the lower support felt 9 at the pressing point formed by
pressing roll 6, which is inside the lower felt, together with the
pick-up felt. The paper track, supported by the lower felt, runs to
the next pressing point formed by pressing roll 7, which is inside
the lower-felt loop, together with pressing roll 3, onto which the
paper web moves following the pressing point. Thus the embodiment
of FIGS. 5 and 6 have in common the passage of the upper pick-up
felt alone through a press nip, a second press nip through which
the web is passed between two felts, and a third nip through which
the paper web passes along with the support felt. In both of these
cases the web is separated from the felt by appropriate guide means
as shown by the arrows and the small rolls for the departing felts
8 and 9 in the two embodiments.
On the straight part of the felt between the pressing points of
shrinking, or in certain cases also a so-called microcreping, of
the paper web can be obtained which improved the elasticity of the
paper. The pick-up roll is a positive one and the pressing roll in
contact with it may also be positive. Both or one of the rolls of
the pressing point after the straight felt part may be positive.
The numbers of revolutions of the first and the second pressing
points can be changed without gradation so that the speed of the
felt at these points may be the same or greater at the first
pressing point than at the second.
Suction rolls, rolls with different coatings, smooth rolls, or
grooved rolls, in suitable combinations, can be used as pressing
rolls, as in paper machines in general.
* * * * *