Advancing material of indeterminate length – With material-responsive control means – To position material laterally
Patent
1998-02-13
1999-07-13
Mansen, Michael
Advancing material of indeterminate length
With material-responsive control means
To position material laterally
34362, 34369, 226 973, 24261511, B23Q 1500, B65H 2000, F26B 308
Patent
active
059214511
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method for changing the position of a web in a suspension dryer and to a suspension dryer for accomplishing this web position change.
DESCRIPTION OF THE PRIOR ART
DE 39 05 472 A1 describes a dryer, wherein the slits of a diversion arrangement are adjustable in order to control the position of a web.
From DE 26 44 618 A1 a device for drying and for the suspended guidance of a web by means of blown jets is known. The web has a wave-shaped course of travel. These blown jets can be changed for increasing the wave formation in the web. A change of direction is intended to take place by means of this wave formation, so that the waves in the web are larger on that side of the web, in whose direction the web extends. However, tests have shown that the desired change of direction is not caused by changing the waves in the web.
DE 29 41 282 A1 describes a blower nozzle of a suspension dryer. An air flow with a component transversely to the conveying direction of a web is generated.
These transverse components of the air flow are not used for changing a position of a web, instead even drying of the web is intended to result.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide a method for changing the position of a web, and to provide a suspension dryer.
In accordance with the present invention, this object is attained by utilizing a web dryer that is provided with a plurality of blowing jets that emerge from blower nozzles. A distance between the blower nozzles, and the web which is supported in the dryer by the blowing jets from the nozzles, can be changed. The distance from the nozzles to the web can be changed from one side of the web to the other. This will act to shift the path of travel of the web in the dryer. Alternatively, the pressure of the drying medium issuing from the nozzles can be changed on one side of the web in order to shift the path of travel of the web within the dryer.
It is not easy to bring the paper web, printed in several colors on both sides, freely suspended through the suspension dryer. Each contact with components of the suspension dryer smears the fresh print and causes waste.
Since the residence time of a web to be dried in the suspension dryer must be considered to be approximately one second, these dryers used to be 3 to 6 m long; today they are often 10 m long or, with a web speed of 15 m/s, even 15 m long. The freely suspended web is under considerable paper web tension in the suspension dryer for stabilization. In addition, the blower nozzle tubes for the gaseous drying medium above the paper web are customarily arranged offset by one-half division in respect to the blower nozzle tubes underneath the paper web. Because of this, the paper web moves through an elongated, approximately sine-shaped serpentine shape path with, for example, 40 wave crests spaced 250 mm apart over a 10 m length.
During operation, the paper web wave appears to stand still between the stationary blower tubes. In fact the paper elements pass the troughs and tips of the paper web generated by hot blown air in the dryer at speeds of 5 to 15 m/s.
With the web running, the required paper web tension is continuously maintained with great accuracy. To this end, cooling rollers arranged downstream of the suspension dryer convey slightly more paper by running at a higher speed than the last. printing unit located upstream of the suspension dryer delivers.
In the ideal case, the paper web runs through the entire length of the dryer exactly parallel with the longitudinal center axis of the dryer.
Unfortunately, because of their great length, previously known hot air suspension dryers have considerable problems, with so-called lateral web extension. This complicated behavior appears to different degrees result of numerous factors such as different web speeds, different paper weights, different selected web tension, differently selected hot air temperature depending on paper weight with natural or coated paper, different printi
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patent: 4197973 (1980-04-01), Daane
patent: 4292745 (1981-10-01), Caratsch
patent: 4322026 (1982-03-01), Young, Jr.
patent: 4480777 (1984-11-01), Suzuki et al.
patent: 4833794 (1989-05-01), Stibbe et al.
patent: 5152080 (1992-10-01), Wimberger
patent: 5272819 (1993-12-01), Wimberger et al.
patent: 5353979 (1994-10-01), Gartmann
Koenig & Bauer-Aktiengesellschaft
Mansen Michael
LandOfFree
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