Paper making and fiber liberation – Apparatus – Running or indefinite length product forming and/or treating...
Reexamination Certificate
2000-06-29
2004-03-09
Fiorilla, Christopher A. (Department: 1731)
Paper making and fiber liberation
Apparatus
Running or indefinite length product forming and/or treating...
C162S132000, C162S304000
Reexamination Certificate
active
06702926
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a wire section of a fiber web forming machine, particularly a paper making machine for forming a multi-ply fiber web, particularly a paper web. The wire section includes a wire section belt of a paper machine on which a first fiber ply is formed. It includes a twin-wire part of the wire section designed as a gap former and having a first and a second wire in which part a second fiber ply is formed. The two wires wrap around a forming roll at the beginning of the twin wire part. It further includes a combining section, in which the first and the second fiber plies are combined, for forming the multi-ply fiber web.
The invention further relates to a process for forming a multi-ply fiber web, including the steps of forming a first fiber ply, forming a second fiber ply, and then combining the first fiber ply, which is running in on a belt, and the second fiber ply, which is running in on a first wire, in a combining section.
Such a wire section and a process of this type for forming a multi-ply fiber web are disclosed in DE 44 02 274 A1, equivalent to U.S. Patent No, 5,584,967. This known wire section comprises a conventional Fourdrinier unit for forming a first fiber ply on a belt in the form of a horizontal wire. A second fiber ply is formed by a twin-wire part arranged above the first belt. The first and second plies are couched together, forming a multi-ply fiber web, particularly a paper or board web. According to
FIG. 5
of DE '274, the twin-wire part is designed as a gap former.
The twin-wire part for forming the second fiber ply has a headbox or flowbox, has an evacuated forming roll downstream of the headbox, has a so-called D part which typically dewaters the web through a wire by suction and also applies pressure pulses on the wire and has a second forming roll. The two wires of the twin-wire part are led approximately horizontally and counter to the running direction of the belt, between the first forming roll and the second forming roll.
In the outlet region of the second forming roll, the top wire is lifted off the second fiber ply, and the second fiber ply is led to the couch roll on the bottom wire, at an angle of about 80° to the first wire.
Another wire section for forming a multi-ply fiber web is disclosed in WO 92/01111. In this wire section too, a first fiber ply is brought up on a belt which is a wire belt that runs approximately horizontally. A twin-wire part for forming a second fiber ply is arranged above the belt. The twin-wire part for forming the second fiber ply has a headbox and a forming board arranged downstream of the headbox. The board has a multiplicity of forming foils, which form a convexly slightly curved running surface for the first and the second wires and which engage the wire to produce pressure pulses. A wiper is provided on the top side at the outlet of the forming board. The top wire is lifted off the second fiber web upstream of the entry region of a couch roll. The bottom wire wraps around the couch roll by about 120°. A guide roll is provided on the underside of the belt so that the belt and the first wire wrap around the couch roll by about 45°. In the wire section in WO 92/01111, dewatering of the second fiber ply takes place solely on account of the tensile stress of the wires acting on the forming board, by centrifugal forces and by the force of gravity.
It is not possible to achieve high running speeds using these known wire sections. In addition, the twin-wire part arranged above the Fourdrinier unit needs considerable space. It is particularly unfavorable that the twin-wire part is located above that part of the Fourdrinier unit in which the finally formed (but still moist) multi-ply fiber web runs, on the belt, in the direction toward the following treatment stations (e.g. wire suction roll, press section, etc.). The quality of the web is thereby impaired.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide a wire section of a paper machine and a process for forming a multi-ply fiber web that is as compact as possible and a process for forming a multi-ply fiber web that is of as high a quality as possible at high speeds.
The invention concerns a wire section for forming a multi-ply fiber web.
The wire section includes a belt which advances a first fiber ply toward a couch roll defining a combining section. A twin wire part of the wire section includes first and second wires between which a second fiber ply is initially formed. The second wire separates from the first wire and then the first wire which is supporting the second fiber ply meets the belt supporting the first fiber ply at the couch roll of the combining section to form the multi-ply fiber web. The twin wire part is arranged upstream of the combining section along the running direction of the belt. The second fiber ply runs on the first wire into the combining section at an angle less than 90° with respect to the belt entering the combining section. A suction box or arrangement holds the second fiber ply to the first wire when the first and second wires separate.
The wire section mentioned at the beginning achieves this object by the inflow direction of the fiber suspension into the gap former substantially corresponding to the running direction of the belt and furthermore, by the twin-wire part being upstream of the combining section in the running direction of the belt and by the second fiber ply on the first wire of the twin wire part running into the combining section at an angle of less than 90° with respect to the belt.
The process mentioned at the beginning for forming a multi-ply fiber web achieves this object because the second fiber ply is formed at least predominantly in the running direction of the belt and in a region which lies upstream of the combining section in the running direction of the belt, and because the second fiber layer on the first wire runs into the combining section at an angle of less than 90° with respect to the belt.
By the measures described above, the belt as well as the first and the second wires in the web forming section run substantially in the same running direction. It is therefore not necessary for the running direction of the second fiber ply to be deflected so sharply as in prior art before being combined with the first fiber ply. This eliminates the risk of the web lifting off the wire on which the web is carried at a location in the region of the couch roll, particularly if a relatively large diameter couch roll is provided. The runability of the overall wire section is increased. Thus, the limitation of the speed that is necessary with known wire sections is avoided. The multi-ply fiber web can therefore be formed at much higher speeds than was possible previously.
In addition, the smaller deflection at a higher speed allows higher moisture content directly upstream of the combining section, which produces an improved ply bond strength.
Furthermore, as a result of the invention the second fiber ply is formed above the initial part of the Fourdrinier unit, that is, above, where the first fiber ply is located on the belt. This avoids the second ply being formed above the combined, multi-ply fiber web. The combined multi-ply fiber web is therefore not interfered with by the twin-wire part which forms the second fiber ply. Such interference, for example, may be by condensate droplets falling on the combined web. This improves the quality of the finished multi-ply web.
Finally, arranging the twin-wire part upstream of the combining section in the running direction of the belt provides more space for the arrangement of dewatering and suction elements in the initial part of the Fourdrinier unit, since the combining point can be located closer to a wire suction roll of the Fourdrinier unit, for example. This produces a particularly compact construction of the wire section according to the invention.
The belt for the first ply can be designed as a wire or as a felt.
Moreover, it has been shown that an entry angle range of less than 90
Bachler Josef
Baumann Wolf Dieter
Bubik Alfred
Egelhof Dieter
Halmschlager Günter
Fiorilla Christopher A.
Ostrolenk Faber Gerb & Soffen, LLP
Voith Sulzer Papiermaschinen GmbH
LandOfFree
Process for forming a multi-ply fiber web does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for forming a multi-ply fiber web, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for forming a multi-ply fiber web will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3271930