Drying and gas or vapor contact with solids – Apparatus – Rotary drums or receptacles
Reexamination Certificate
2000-10-12
2001-11-20
Walberg, Teresa (Department: 3742)
Drying and gas or vapor contact with solids
Apparatus
Rotary drums or receptacles
C034S117000
Reexamination Certificate
active
06317999
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to a sealing nozzle arranged in a blow box used in the drying section of a paper machine defined in the preamble of the first claim presented below.
In the drying section of a paper machine the web is conveyed in a known manner by using either a single or a twin wire run. Single wire run means such a run where the web passes from one drying cylinder to the next supported by a single drying wire; the web passes also between the drying cylinders supported by the same wire. The web passes over the drying cylinder between the cylinder and the drying wire.
Twin wire run means such a run where separate top and bottom wires are used to support the web when it passes alternately over the lower and alternately over the upper drying cylinders. Also in this case the web passes over the drying cylinders between the cylinder and the drying wire. However, from an upper cylinder to a lower cylinder, or in the opposite direction, the web passes partly free, without support. The guide rolls of the drying wires are often located so that the wire and the web would disengage simultaneously from the drying cylinder, and so that the wire supports the web over a short distance as it passes from one cylinder row to the next.
In ever faster paper machines it has become a problem in that the web tends to become detached from the surface of the drying wire, at a point where the wire and the web together should travel from a drying cylinder to a redirecting cylinder or a guide roll located at a lower level.
The disengagement of the web from the wire leads easily to a wire break, or at least to the wire forming sacks or folds. The disengagement of the web from the wire leads thus to runnability problems, which are further emphasized when the speeds of the paper machines increase.
It is previously known, for instance from U.S. Pat. No. 4,905,380, to use different blow boxes in order to improve the runnability of a paper machine. The ejection blow created by the blow box induces a negative pressure region in the gap space between the drying wire and the wall of the blow box, and this negative pressure region keeps the web attached to the drying wire when the web passes from the drying cylinder to the guide roll below the cylinder.
However, a problem in the above-described solution is to have the negative pressure region induced by the blows safely sealed from the region left outside of the negative pressure region. In connection with running disturbances paper waste is generated, which as so called paper lumps or paper clumps are entrained by the web also to the blow boxes. Due to these bulges present in the web a blow box cannot be mounted at a short distance from the wire run, which would be optimal regarding the sealing. The blow box must be mounted at a certain safe distance, which is typically >50 mm, in which case the negative pressure region is not sealed in the best possible way. The effects of the ejection blows are also often insufficient when the blow nozzles of the blow boxes must be located at said safe distance from the wire.
It is known as such, for instance from U.S. Pat. No. 4,996,782, to use pivotable flaps to direct the air blows to a desired object, where the air is wanted to flow through the wire in order to ventilate the pocket formed by the wire loop. The object of the flap is not to seal the gap between the blow box and the wire.
The object of the present invention is to provide an improved sealing nozzle for the blow box in a paper machine.
An object is particularly to develop the previously known blow box solution so that the negative pressure effect can be even further intensified during the run.
An important goal of the invention is also to provide such a sealing nozzle of a blow box, with which the air blows providing the negative pressure, are generated as close as possible to the supporting fabric of a paper machine, such as a wire, moving past the blow box, and which nozzle is available both during the normal run and the threading.
A further object of the invention is to provide a sealing nozzle for a blow box which can be safely brought very close to the wire in order to provide ejection blows or ventilation of the pocket. Then an object is particularly to provide a sealing nozzle with a blow which can be directed accurately and which can provide the required pressure differences, however, retaining the operating safety of the structures.
In order to achieve the above-presented objects the new sealing nozzle for a blow box in the drying section of a paper machine according to the invention is characterized in what is presented in the characterizing part of the first claim presented below.
A typical blow box in which the invention is applied and used in the drying section of a paper machine is arranged in said drying section in the pocket space defined by the wire passing from the first drying cylinder to the second drying cylinder and a redirecting member arranged in this wire run, such as a redirecting cylinder, a guide roll, a suction roll or the like, in order to eject air away from said pocket space and to create a negative pressure region in at least a part of this pocket space. In the blow box, at the border between the desired negative pressure region and the region outside it, there is arranged one or more sealing nozzles according to the invention projecting from the blow box against the wire up to a certain distance “d” as seen from the wire, in order to create a seal between the negative pressure region and the region left outside the negative pressure region. Said sealing nozzle is advantageously combined with the blow box so that the member can be moved away from the wire by pushing or with the aid of an actuator, to a distance “d′” which is larger than the distance “d”.
In this description of the invention and in the claims a blow box means typically box-like structures extending across the web or even structures of other shapes extending across the web, such as beam-like or tube-like structures, with which ejection air can be supplied into the pocket or a part of it.
A wire in this description means typically a drying wire, a felt or another corresponding fabric, with which the web is supported, for instance when the web passes over a drying cylinder.
The invention is applicable in the drying sections of paper machines utilizing both single wire runs and twin wire runs. In drying sections provided with a single wire run a blow box using a nozzle according to the invention can be used to create a negative pressure region and to seal it both in the travel direction in the region of the wire run from the first drying cylinder, or in the region called the “inlet side” in this description, and in the region of the wire run going to the next drying cylinder, or in the region called “outlet side” in this description, when the blow box is arranged in the pocket space defined by two drying cylinders, the wire runs between them and the redirecting cylinder below them.
In drying sections provided with twin wire runs a blow box according to the invention arranged in the wire pocket space defined by two drying cylinders, the wire runs between them and the wire guide roll, can be used to create a negative pressure region and seal it in the region of the wire run coming from the first drying cylinder, or at the inlet side. In the region of the wire run to the next drying cylinder, or on the outlet side, the blow box can be used to generate blows causing ventilation of the pocket.
The sealing solution according to the invention could of course be used also more generally in a paper machine or the like at a supporting fabric or e.g. at a roll, for preventing air from entering between this supporting fabric or roll and the blow box by ejecting air away from this intermediate space.
In an advantageous embodiment of the invention the sealing is conducted with a sealing nozzle having a sealing member which is arranged very close to the wire, and the actual nozzle part of the sealing member blows air fr
Jokinen Reijo
Kokkala Hannu
Virta Raimo
Fastovsky Leonid
Metso Paper Inc.
Nixon & Vanderhye P.C.
Walberg Teresa
LandOfFree
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