Drying and gas or vapor contact with solids – Apparatus – Rotary drums or receptacles
Reexamination Certificate
2001-05-16
2004-03-16
Wilson, Pamela (Department: 3749)
Drying and gas or vapor contact with solids
Apparatus
Rotary drums or receptacles
C034S117000, C034S120000
Reexamination Certificate
active
06705024
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. §119 of German Patent Application No. 100 24 296.0, filed on May 17, 2000, the disclosure of which is expressly incorporated by reference herein in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a machine for producing a material web, in particular a cardboard or paper web, with at least one smooth roll wrapped by the material web.
2. Discussion of Background Information
In the multi-cylinder drying section of a paper machine, the paper web is guided over steam-heated cylinders or steam-heated cylinders and wire suction rolls for the purpose of drying the web. Especially at the beginning of the drying process, when the moist paper does not yet have sufficient strength, problems often occur with regard to the web guidance, which can especially be attributed to the fact that the moist web sticks to the smooth surfaces, which are absolutely necessary for good heat conduction, and the web is poorly ventilated. In order to be able to remove the web from the cylinders, a sufficient web tension is necessary, which can only be produced by means of pulling, i.e., a corresponding differential speed, before or directly after the first smooth contact surface. This often causes tears and an overstretching of the edges. Because these problems occur more intensely at higher speeds and the tension must be increased, the speed of the paper machine is limited.
SUMMARY OF THE INVENTION
An aspect of the invention is to create an improved machine of the type mentioned at the outset in which the above-mentioned problems are eliminated. Here, it should particularly be achieved that the amount of pulling and/or web tension necessary for removing the web from the smooth roll is reduced.
This aspect is attained according to the invention in that a blowing device is assigned to the roll, whose discharge stream is directed into the wedge-shaped opening between the roll and the material web, for the purpose of ventilating the web. Here, the discharge stream of the blowing device is preferably pointed directly into this wedge-shaped opening.
Because of this construction, an improved ventilation of the material web results, whereby the removal of the web sticking to the roll is facilitated. The blowing device can, in particular, be supplied with air. Preferably, the blowing device includes several discharge openings, in particular, embodied as nozzles, blowing holes, blowing slits, and/or the like.
In a preferred practical embodiment of the machine according to the invention, the blowing device includes at least one blowing tube. The blowing device can extend at least essentially over the entire web width. The discharge stream directed into the wedge-shaped opening of the blowing device is preferably directed slightly against the roll surface.
It is advantageous for the blowing speed of the discharge stream directed into the wedge-shaped opening to be variably adjustable. It can preferably be selected depending on the distance of the blowing device from the wedge-shaped opening. For example, the greater the distance from the wedge-shaped opening, the greater the blowing speed of the discharge stream must be.
The distribution of the discharge openings of the blowing device can vary over the web width. Thus, for example, the distance of the discharge openings in the edge region can be greater than or less than in the middle region. Here, the distance of the discharge openings in the edge region can be greater than or less than in the middle region. Correspondingly, the ventilation can optimally be adapted to the respective conditions such that excessive amounts of air can be prevented.
The blowing device can be integrated into a doctor assigned to the roll or can be attached to such a doctor such that a transfer from the doctor is possible, which means that the web does not run between the doctor and the blowing device in the case of a tear.
It is useful to provide the blowing device with a cover in order to ensure a sufficient protection, in particular from paper scraps. Thus, the possibility of the blowing device becoming a scrap catcher is eliminated.
The position of the doctor should be selected such that, on the one hand, it is arranged sufficiently close to the wedge-shaped opening to ensure sufficient ventilation, and on the other hand, is arranged at a sufficient distance from the wedge-shaped opening to prevent a blockage in the case of a tear.
It is useful to select the size and/or number of discharge openings of the blowing device depending upon the machine speed, the basis weight, the stock, and/or the paper type. Here, the discharge openings, which are, for example, circular, can have a diameter that, in particular, lies in the range of approximately 2 to approximately 12 mm and preferably in the range of approximately 4 to approximately 8 mm.
The blowing speed of the discharge stream of the blowing device is preferably greater than approximately 35 m/s and preferably greater than approximately 50 m/s. Optimal results can especially be achieved at higher air speeds using smaller amounts of air, i.e., no larger amounts of air are necessary.
The rolls in question can be formed, for example, by a drying cylinder. Here, the blowing device is usefully structured and/or insulated such that a thermal deformation and a deviation from the desired blowing direction caused thereby are excluded.
In a useful embodiment, the blowing device simultaneously serves the ventilation of one of the rolls and a hood assigned to the drying cylinder. It can be operated at the air inlet temperature of the hood.
In a preferred embodiment of the machine according to the invention, the roll is formed by the first cylinder of the drying section. However, it is also possible to assign a corresponding blowing device to at least one of the second to fifth cylinders of the drying section.
In a further advantageous embodiment, the roll is formed by a smooth pressing roll. In principle, however, at least one further cylinder and/or at least one further smooth roll can have a corresponding blowing device assigned to it.
According to an aspect of the present invention, the discharge stream of the blowing device is pointed directly into the wedge-shaped opening. According to another aspect of the present invention, the blowing device is supplied with pressurized air. In yet another aspect of the present invention, the blowing device includes several discharge openings formed in particular by nozzles, blowing holes, blowing slits, and/or the like.
In yet another aspect of the present invention, the blowing device includes at least one blowing tube. According to a further aspect of the present invention, the blowing device extends at least essentially over the entire width of the web. In another aspect of the present invention, the discharge stream of the blowing device, which is pointed into the wedge-shaped opening, is pointed slightly against the roll surface.
In another aspect of the present invention, the blowing speed of the discharge stream may be variably adjusted. According to a further aspect of the present invention, the blowing speed of the discharge stream may be selected depending on the distance of the blowing device from the wedge-shaped opening.
According to a still further aspect of the present invention, the distribution of the discharge openings of the blowing device varies over the web width. Other aspects of the invention include the distance of the discharge openings in the edge regions differing from that in the middle regions.
Further aspects of the invention include wherein the distance of the discharge openings in the edge region is less than in the middle region. According to other aspects of the present invention, the distance of the discharge openings in the edge region is greater than in the middle region.
According to another aspect of the present invention, the blowing device is integrated into a doctor assigned to the roll or is attached to such a doctor. Accordi
Kahl Peter
Mayer Roland
Oechsle Markus
Greenblum & Bernstein P.L.C.
Voith Paper Patent GmbH
Wilson Pamela
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