Paper making and fiber liberation – Processes and products – With cutting and/or slitting
Patent
1995-02-27
1996-11-05
Czaja, Donald E.
Paper making and fiber liberation
Processes and products
With cutting and/or slitting
162193, 162198, 162255, 83 53, 83177, 83428, D21F 700
Patent
active
055713815
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for producing a fibre web by a paper machine comprising a yankee cylinder, wherein pulp is supplied to a wire where it is dehydrated, strips are cut out from the edges of the produced fibre web by water jets directed through the fibre web, and the cut fibre web as well as the strips cut out from it are conducted around the yankee cylinder for drying and are then detached from the surface of the yankee cylinder.
The invention also relates to an apparatus for cutting out a strip from the edge of a fibre web in a paper machine comprising a yankee cylinder, the apparatus comprising nozzles arranged at the wire to provide a water jet needed for cutting out a strip from the edge and to direct the water jet through the fibre web towards the wire, and means for feeding water into the nozzles.
When a fibre web is produced by a paper machine, the edge of the web is conventionally cut by a water jet. In the instant application and claims, a paper machine is understood to mean a paper or board machine or the like in which a fibre web is dried by a so-called yankee cylinder. In machines where drying is carried out by yankee cylinders, the edges cut out from the web are not removed until after the yankee cylinder, but they are cut at the Wire portion. A fibre web is here understood to mean a paper or board web or some other web produced in a corresponding manner by the above paper machines.
In order that the fibre web might be made to adhere to the surface of the yankee cylinder and, correspondingly, might be easily detached from it after drying, a coating agent is sprayed onto the surface of the cylinder to facilitate adhesion of the moist fibre web and its easy detachment from the yankee cylinder when it has travelled almost around it.
The problem with the method Concerned is that when the coating agent is sprayed onto the surface of the yankee cylinder, the conditions should be fairly constant in order that the coating agent might operate between the fibre web and the surface of the cylinder in the manner desired. When a paper web with cut edges winds around a yankee cylinder, no pulp is found in the areas where the edges of the web have been cut. Since the cut forms a gap in which the coating agent can become hotter and dry faster than in the area around it, pulp articles adhere to the coating agent therein and burn onto the surface of the yankee cylinder. Since the edges of the web have always been cut out at the same point, pulp also accumulates on the yankee cylinder; the accumulation grows until it begins to bend the already cut web in such a way that the edge of the web begins to tear and thus causes breaks in the web and faults in the edges. The faults in the edges cause breaks immediately after the yankee cylinder or later during cutting or other after-treatment. This in turn interrupts the production, which decreases productivity and increases the costs of use.
The object of the present invention is to provide a method by which the above problems are avoided and by which accumulation of a streak of pulp onto the surface of the yankee cylinder and faults in the edges of the fibre web are eliminated. The method of the invention is characterised in that the water jet cutting out a strip from the edge of the fibre web is moved back and forth in a transverse direction with respect to the fibre web at a predetermined width so that the edge of the fibre web undulates at the cut and the place where the cut of the fibre web comes against the surface of the yankee cylinder varies.
Another object of the invention is to provide an apparatus by which the above problems are avoided and the production process is rendered reliable. The apparatus of the invention is characterised by comprising transfer means for moving the nozzle back and forth at a predetermined width in a transverse direction with respect to the fibre web during the production of the fibre web.
The essential feature of the invention is that the water jet cutting out a strip from the edge of the web is deflected back and fo
REFERENCES:
patent: 3190628 (1965-06-01), Litzka
patent: 3809606 (1974-05-01), Stansbrey
patent: 4540496 (1985-09-01), Lundstrom
patent: 4567796 (1986-02-01), Kloehn et al.
patent: 4931140 (1990-06-01), Peltola et al.
Kimari Tapani
Vessari Reijo
Czaja Donald E.
Fortuna Jos'e A.
Metsa-Serla Oy
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