Paper making and fiber liberation – Apparatus – With cutting – scoring – perforating or tearing
Reexamination Certificate
1997-12-26
2001-07-03
Alvo, Steve (Department: 1731)
Paper making and fiber liberation
Apparatus
With cutting, scoring, perforating or tearing
C162S290000, C162S297000, C162S306000, C162S307000, C162S310000, C162S353000
Reexamination Certificate
active
06254731
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a steam box for use, e.g., in a paper or board machine, which comprises a steam chamber for blowing steam toward a paper or board web that runs on support of a wire and a suction zone arranged at the trailing side of the steam chamber of the steam box to provide suction for steam mist.
BACKGROUND OF THE INVENTION
In the prior art, a steam box is known which is used in connection with a board or paper machine and through which hot steam is passed into connection with a board or paper web in order to reduce the viscosity of the water contained in the web and thereby to improve the removal of water from the web, i.e., increase the dry solids in the web. Steam boxes are used for the above-mentioned purpose, for instance, in wire and press sections of a board or paper machine.
One particular problem in the steam boxes used in wire sections is the blowing-out of non-condensing steam from the active area of the steam box which wets the structures in the press section and even in the entire paper machine hall. This mist cloud of non-condensing steam produced by the blowing-out of steam from the steam box causes, in the worst cases, even water to drip from the ceiling of the machine hall. Steam blows out mainly from the trailing edge of the steam box and to some extent from the sides of the steam box.
In view of this blowing phenomenon, the capacity of the whole steam box cannot be used efficiently for increasing dry solids in the web because in that case, the formation of mist is intense and the structures of the machine become too wet. One solution to this problem known from the prior art is to provide for suction on the trailing side of the steam box. However, this has not made it possible to sufficiently eliminate the spreading of steam as mist to surrounding structures and the machine hall, and thus it has nevertheless been necessary to operate the steam box at reduced capacity because of the blowing-out of steam from the active area of the steam box.
As another solution to this problem, attempts have also been made to arrange general exhausts in the area of the wire section. However, this has not made it possible to sufficiently prevent the spreading of steam and its condensation on structures and the resulting dripping of water therefrom.
Another serious problem in the steam box of a wire section is keeping the steam box clean in the area of edge cutting, i.e., in the vicinity of the cutting means which cut the lateral areas of the web along the width thereof to form edges of the web. During edge cutting, fibers and fillers become separated from the web and they adhere to and accumulate on the edges of the steam box and drop therefrom onto the web causing runnability problems and even web breaks on some machines.
This has led to the fact that it has been necessary to place the edge cutting devices far from the headbox which, however, cannot always be done because of lack of space, and thus it may have been necessary to give up the use of the steam box when increasing drying capacity of the paper or board machine.
Attempts have also been made in the prior art to prevent the soiling problems of the steam box caused by edge cutting by means of an air curtain arranged in front of the steam box. However, this problem will be further aggravated when the running speeds of machines increase and when the aim is to provide machines that are more compact than before.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the invention is to provide a steam box that does not have the problems of prior art steam boxes described above.
Another object of the invention is to provide a steam box in which the problems caused by the blowing-out of steam are eliminated or at least minimized such that, if desired, the steam box can be operated at full capacity.
Still another object of the invention is to provide a steam box in which problems are not caused by the fibers and fillers which become separated during edge cutting.
In order to achieve the objects stated above and others, the steam box according to the invention includes means defining a suction zone on the sides of the steam chamber so as to extend the suction zone to lateral areas or sides of the web, and edge cutter devices arranged in the area of action of the suction zones extending to the sides of the web so as to remove the fibers and fillers produced during the edge cutting in order to prevent soiling of the edges of the steam box. The suction zones on the sides of the web thus extend beyond the transverse locations at which the web is cut.
In accordance with the invention, the suction zone of the trailing side of the steam box is arranged to also extend to the sides of the steam box and edge cutting is performed in the area of the suction zone of the steam box and the fibers and fillers coming off during edge cutting are removed by means of vacuum into the same suction zone as the steam mist.
The steam box in accordance with the invention is suitable for use in connection with both new and existing machines.
In one preferred embodiment of the invention, a blow nozzle is arranged in the steam box at the trailing side of the suction zone of the steam box in order to produce a blowing of air so as to prevent spreading of steam mist and to ensure the passage of the steam mist into the suction zone.
In accordance with the invention, a blow nozzle, preferably a foil nozzle directing a blowing against the running direction of the web, is arranged after the suction zone of the trailing side of the steam box in the running direction of the web, which nozzle slows down the flow of steam with the web past the suction zone. Warm air is supplied to the blow nozzle preferably through an end structure insulated by means of a double wall, which end is heated to prevent condensing of steam thereon and dripping of water formed thereby. The steam box in accordance with the invention substantially prevents oil mist from being carried away from the area of the steam box and, at the same time, ensures that the steam mist is passed to an exhaust through the suction zone.
A suction box and a blowing end can be constructed to be in the steam box structure or they can be constructed to form separate units in connection with the steam box.
Thus, the steam box for increasing the removal of water from a web supported on a wire, while keeping the steam box clean, in accordance with the invention includes means defining a steam chamber from which steam is blown toward the web and means defining a suction zone at a trailing side of the steam chamber in a running direction of the web. The suction zone has an area of action from which steam mist is drawn into the suction zone. The steam box also includes means defining lateral suction zones on lateral sides of the steam chamber such that each lateral suction zone extends over a respective lateral area of the web. The lateral suction zones have an area of action from which steam mist is drawn therein. The steam box further includes edge cutter devices arranged adjacent a respective lateral area of the web for cutting the respective lateral area of the web to form edges of the web. Each edge cutter device is arranged to cut the respective lateral area of the web in the area of action of the suction zone and/or the lateral suction zone extending over the respective lateral area of the web such that fibers and fillers produced during the cutting of the lateral areas of the web are drawn into the suction zone and/or lateral suction zones and do not soil the steam box.
The means defining the suction zone and the means defining the lateral suction zones may comprise a single frame such that a continuous suction zone is formed extending from one lateral side of the steam chamber to the trailing side of the steam chamber to the other lateral side of the steam chamber and a continuous area of action is formed extending over the lateral areas of the web and the web at the trailing side of the steam chamber. In other words, the means defining the suction zone may encompass th
Hannus Lars Håkan Mikael
Lindstrom Jan
Puurtinen Ari
Viertola Mika
Alvo Steve
Steinberg & Raskin, P.C.
Valmet Corporation
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