Paper making and fiber liberation – Processes and products – Running or indefinite length work forming and/or treating...
Patent
1996-03-06
1998-10-13
Hastings, Karen M.
Paper making and fiber liberation
Processes and products
Running or indefinite length work forming and/or treating...
162205, 162210, 162301, 1623602, D21F 100
Patent
active
058207317
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method for dewatering the web in a paper or board machine. The invention relates also to an apparatus for carrying out the method.
BACKGROUND OF THE INVENTION
Within the end zone of a wire section upstream of a pick-up suction roll, paper and board machines are generally provided with a wire suction roll in an effort to give the web a sufficiently high dry matter content upstream of the press section. This also creates a sufficiently strong web prior to the action occurring in the press section.
One such solution is disclosed in U.S. Pat. No. 4,075,056, wherein the wire suction roll guides the wire and a web lying on top of it within the end zone of the wire section as they are curving upon said suction roll in a certain sector towards a pick-up suction roll. In line with the suction sector provided by the wire suction roll there is a press roll, a so-called lump-breaker roll, placed thereagainst from the side of a web in an effort to seal the web against the wire suction roll, to consolidate the forming web, and to reduce the amount of fiber lumps in the web.
On the other hand, U.S. Pat. No. 3,846,233 discloses a twin-wire papermaking machine wherein, within the end zone of a twin-wire dewatering zone, water is removed by means of a suction roll at which the lower wire deflects towards a pick-up suction roll while water is simultaneously removed through the upper wire as a result of tension of the wires as well as centrifugal force.
In modern paper and board machines, however, the wire suction roll is one of the major consumers of energy as it requires a vacuum system. It is also expensive in terms of its construction. The wire suction roll also creates a noise problem during operation of the machine. In addition, the use of a vacuum reduces the web temperature, which is harmful in the press section. All the above problems associated with suction are further emphasized due to the fact that the increasing machine speeds require an increased vacuum capacity.
SUMMARY OF THE INVENTION
An object of the invention is to eliminate the above drawbacks and to introduce a method for dewatering the web prior to its passage to the press section without a wire suction roil, i.e. without the need for creating a vacuum at this point. Water is removed from the web by means of a open-surfaced roll included in a pair of rolls. The open-surfaced roll and a roll mounted on the opposite side are used to develop pressing on the web so that water is removed from the web into the open places in the roll surface and is discharged from the roll through centrifugal force. Thus, neither of the rolls included in the pair of rolls need be provided with suction and all the problems associated with a suction roll will be eliminated.
Another object of the invention is to introduce an apparatus which does not involve the above drawbacks. In view of fulfilling this object, the pair of rolls provides a press nip, wherein one of the rolls is an open-surfaced roll for effecting the dewatering into the open places in its surface.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in more detail with reference made to the accompanying drawings, in which
FIG. 1 shows an apparatus of the invention in a side view,
FIG. 2 shows a second embodiment for an apparatus of the invention in a side view,
FIG. 3 shows a third embodiment for an apparatus of the invention in a side view, and
FIG. 4 shows a fourth embodiment for an apparatus of the invention in a side view.
DESCRIPTION OF PREFERRED EMBODIMENTS
FIG. 1 depicts the end zone of a Fourdrinier wire section in a papermaking machine, that is, a point at which a web W is transferred from a wire 1, upon which it has formed, into a press section. The end section includes a roll 2, guiding the wire 1 of a wire section in such a manner that the wire 1 and the web W lying on top of it are curving or deflecting in a certain sector .alpha. towards a drive roll 5, which at the same time serves as a reversing roll for the w
REFERENCES:
patent: 2821120 (1958-01-01), Thomas et al.
patent: 3198694 (1965-08-01), Justus
patent: 3285806 (1966-11-01), Justus
patent: 3846233 (1974-11-01), Kankaanpaa
patent: 3861996 (1975-01-01), Dorfel
patent: 4075056 (1978-02-01), Ely et al.
patent: 5389205 (1995-02-01), Pajula et al.
patent: 5522959 (1996-06-01), Ilmarinen
Holle "Siebbespannung fur die Pressenpartie-VACOFLEX" Zellcheming Apr. 1989 .
Hastings Karen M.
Valmet Corporation
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