Drying and gas or vapor contact with solids – Apparatus – Rotary drums or receptacles
Reexamination Certificate
1999-10-20
2001-02-20
Ferensic, Denise L. (Department: 3749)
Drying and gas or vapor contact with solids
Apparatus
Rotary drums or receptacles
C034S122000, C034S123000, C034S124000
Reexamination Certificate
active
06189232
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns a blow-suction box or equivalent for a paper machine or board machine, which box comprises at least a pressure chamber and which box is placed in the vicinity of a cylinder, roll, or equivalent, from which cylinder, roll or equivalent a web and/or a wire is/are fitted to run past the box.
BACKGROUND OF THE INVENTION
With respect to the prior art related to the present invention, reference can be made to the DE Utility Model Publication 29601543, to the DE Patent 3910600, to the U.S. Pat. Nos. 5,515,619 and 4,856,205, from which publications a mechanical seal is known which is used in connection with a blow-suction box or equivalent, which is in contact with, or in a near proximity of, a wire or equivalent, and which seals the closing nip between the box and the adjacent cylinder in order to cut off a boundary-layer air flow. A boundary-layer air flow follows a paper web and a wire when they come from a drying cylinder towards a reversing cylinder or roll. In the prior-art solutions, the seal is mechanical and often also rigid, in which case it may damage the wire coming from the cylinder, or it can be broken itself. These physical seals can be broken as a result of prolonged operation, and, moreover, owing to deterioration or damaging of a seal, the capacity of blow-suction boxes is lowered considerably in paper machines.
One problem in the prior-art blow-suction boxes has been the problems of runnability as air is pumped through the wire in a nip, which results in separation of the web from the wire and, at the same time, causes wrinkles and bag formation.
One object of the present invention is to provide a solution in which the problems mentioned above have been eliminated or at least minimized.
With respect to the prior art, reference is also made to the applicant's FI Patent No. 80,491 (equivalent to U.S. Pat. No. 4,905,380), in which a method and a dryer group in a multi-cylinder dryer in a paper machine are described, in whose connection a blow-suction box is employed which includes a suction and/or closing compartment, by whose means the upper free sectors of reversing cylinders between the adjacent wedge spaces have been covered. In the gaps between drying cylinders, said combined blow-suction boxes are placed, which have a plane wall at the inlet side of the drying wire and of the web, into whose edge a nozzle opening or openings is/are opened, by whose means a flow is blown which ejects in the direction opposite to the direction of movement of the drying wire placed facing said nozzle opening(s), by means of which flow a field of vacuum is induced in the gap space between said wall and the straight run of the drying wire and the web as well as in the following wedge space. An object of the present invention is further development of the blow-suction box so that the effects of the boundary-layer air flow are eliminated and that the effect achieved by means of the blow-suction box on the support and runnability of the paper is improved.
As is known from the prior art, multi-cylinder dryers in paper machines usually consist of two horizontal rows of drying cylinders placed one row above the other, between which the paper web runs meandering. In connection with the drying cylinders, currently, drying wires permeable to air are employed. In the dryer section of a paper machine, single-wire draw and/or twin-wire draw is/are employed. Single-wire draw is understood as a draw in which the web runs from one drying cylinder onto the other on support of one and the same drying wire also between the rows of cylinders. In twin-wire draw, in which an upper wire and a lower wire are employed, the web has free unsupported draws when it runs from one row of cylinders to the other. The present invention is suitable for use most advantageously in applications with single-wire draw.
OBJECTS AND SUMMARY OF THE INVENTION
The blow-suction box or equivalent in accordance with the present invention for a paper machine is mainly characterized in that, in connection with the pressure chamber, a nozzle slot has been arranged, out of which a sealing blowing is fitted to be applied towards the cylinder, roll or equivalent and/or towards the web and/or wire running on its face in order to disintegrate the boundary-layer air flow carried along with the web and/or the wire, and that, in connection with the nozzle slot, an air guide made of a resilient material has been fitted in order to direct the sealing blowing and to enhance the sealing further.
In accordance with the invention, the effects of the boundary-layer air flow are eliminated by cutting off the boundary-layer air flow by means of a blow-suction box or by means of an equivalent combined air-sealing blowing. The sealing blowing prevents pumping of air into the nip. In connection with the sealing-blowing nozzle, favourably a mechanical, resilient air guide has been fitted, which extends to a distance from the wire or equivalent and which, thus, yields resiliently in the event of a possible wire contact, and, at the same time, the air guide provides aid in directing of the sealing blowing. By means of sealing blowing, the gap between the blow-suction box or equivalent and the wire/cylinder or equivalent can be sealed so that the boundary-layer air flow does not cause problems of runnability or other problems.
In accordance with the invention, in the top portion of the blow suction box, a narrow nozzle has been fitted, below which an air guide has been fitted. The air guide is made of a resilient material, e.g. plastic, rubber or of a fabric, and it is not in direct contact with the wire or equivalent. The distance between the air guide and the wire or equivalent is, for example, from about 5 mm to about 10 mm. The air guide directs and supports the sealing blowing and divides the areas of the suction zone and the sealing-blowing zone in the blow-suction box and, at the same time, the air guide prevents loss of the sealing air partly by the effect of the suction effect of the suction zone.
According to a preferred additional feature of the invention, the face of the blow-suction box following after the sealing-blowing nozzle is corrugated. The corrugated face produces microturbulence in its valley areas, in which case the removal and elimination of the boundary-layer air flow are enhanced. The valley areas in the corrugated face are provided with suction openings, through which the suction effect is produced. The pressure in the box and the support of the paper can be controlled by choosing the holes that are used in the desired way.
One object of the corrugated face is to reduce the volume of the suction zone area, in which case it is possible to suck small amounts of air in order to produce a suitable vacuum and to keep the paper web in contact with the wire. By means of a corrugated face, the suction area is automatically divided into an area formed by a number of smaller zones, in which case the keeping of the paper on the wire is controlled by sucking air out of each zone. In this way the paper remains on the wire evenly. The peaks in the corrugated face do not extend up to the wire, and the distance from the top of a wave to the wire is, for example, from about 5 to about 10 mm, and, if necessary, in connection with the corrugated face, in order to guide the wire, wire guide devices are fitted in connection with said walls.
A blow-suction box in accordance with the invention also enhances the operation of a lower reversing cylinder or roll, because, for its own part, it also eliminates air flows that are detrimental to the operation of said lower cylinders or rolls.
According to a favourable additional characteristic feature of the invention, sealing blowing in accordance with the invention has been arranged at each side of the box.
According to a favourable embodiment of the invention, it is also possible to reduce the consumption of energy by applying ideas in accordance with the present invention in connection with a what is called box for a whole pocket, a box of said sort being
Milosavljevic Nenad
Saarikivi Pekka
Ferensic Denise L.
Joyce Andrea M.
Steinberg & Raskin, P.C.
Valmet Corporation
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