Dry end

Details Dry end Dry end

1998-09-09

1999-11-23

Bennett, Henry

Drying and gas or vapor contact with solids

Process

Gas or vapor contact with treated material

34455, 34461, 34465, 34114, 34117, 34120, F26B 300, D21F 500

Patent

active

059877774

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

The invention relates to a dry end for drying a material web, in particular a paper or cardboard web in a paper machine.


BACKGROUND OF THE INVENTION

Dry ends and methods of the type in question here are known DE 39 41 242 A1. At the start of the manufacture of a material web, for example on a paper manufacturing machine, the material web emerging from a press is firstly diverted into a spoil collection area upstream of the first dry end or drying group adjoining the press. It is also conceivable to direct the material web from the press as far as the first dry cylinder of the dry group adjoining the press and to divert it on from there into a spoil collection area. In order to thread the material web through the dry end, a threading strip which is also referred to as a band is cut off from the leader edge of the material web in the longitudinal direction (running direction of the machine) and that edge is threaded through the dry end, preferably at full working speed of the paper manufacturing machine, without displacing it sideways. For this purpose, the threading strip must run through the dry cylinder and web guiding rollers of the dry end along a winding path. For this reason, it is necessary to guide and to stabilize this strip so that it does not become wound around the dry cylinder, which would cause the threading procedure to be interrupted. The known dry end has nozzle devices, for example compressed air pipes which extend at least over the width of the threading strip and serve to pick off said strip from a dry cylinder and transfer it to the following web guiding roller viewed in the conveying direction of the material web. It has become apparent that the transfer of the threading strip does not take place reliably in all cases, with the result that a threading procedure frequently has to be aborted and repeated, and it becomes necessary to clean the dry end.


SUMMARY OF THE INVENTION

For this reason, an object of the invention is to provide a dry end which is distinguished by improved threading characteristics.
In order to achieve this object, a dry end is proposed which is distinguished by the fact that at least one/two nozzle devices are arranged one behind the other for transferring a threading strip from a dry cylinder to a following web guiding roller, said nozzle devices applying a stream of gas to the same side of the material web. Such a dry end is distinguished by simple design and by reliable threading characteristics.
An embodiment of the dry end is preferred in which the nozzle devices are mounted on a scraper which interacts, for example, with a dry cylinder and is arranged directly in the transfer region between a dry cylinder and an adjacent web guiding roller which is preferably acted on by vacuum. The airstream generated by the nozzle devices can thus act directly on the material web which is located in the region of the free running section between the dry cylinder and the web guiding roller.
A further preferred embodiment of the dry end which is distinguished by the fact that the nozzle devices emit a gas stream with defined flow direction. The various nozzle devices or their gas streams are directed in such a way that, on the one hand, the material web is reliably released from the dry cylinder, that said web is, on the other hand, reliably applied to the web guiding roller and, finally, that it can be transferred from the web guiding roller (with vacuum support) to the next dry cylinder.
In particular, an embodiment of the dry end which is distinguished by the fact that the nozzle devices have individual nozzles or slit nozzles is preferred. The use of individual nozzles makes it possible to apply to the material web a strong, directional air stream which brings about, for example, reliable release of the material web from the dry cylinder. The use of slit nozzles leads to stabilization of the threading strip so that during the threading operation the latter cannot become twisted, which would lead to disruption of the operation of the machine for manufactu

REFERENCES:
patent: 4986009 (1991-01-01), Haessner et al.
patent: 5337490 (1994-08-01), Griffin et al.
patent: 5477624 (1995-12-01), Haessner et al.
patent: 5600897 (1997-02-01), Sollinger et al.
patent: 5718058 (1998-02-01), Atzinger
patent: 5735060 (1998-04-01), Atzinger et al.

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