US 4,905,380 AGranted

Method and apparatus in a paper machine single-wire drying group

AssigneeValmet Paper Machinery Inc.

InventorsPekka Eskelinen, Raimo Virta, Vesa Vuorinen

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Abstract

A single-wire drying group in a paper machine is disclosed including a plurality of drying cylinders whose axes are situated in a substantially common plane, a drying wire carrying a web between successive drying cylinders, one or more deflection rolls, each situated between a pair of successive drying cylinders and wherein the web-carrying drying wire has an incoming run from a drying cylinder to a deflection roll whereupon the drying wire runs over a deflection sector of the deflection roll and then to a subsequent drying cylinder. A blow box has a wall which defines a gap space with the incoming run of the web-carrying wire and a gas flow is directed through the gap space to induce an under pressure on the incoming run to fix the web on the drying wire. The deflection roll has a perforated shell in the perforations of which an underpressure is maintained to ensure that the web remains in contact with the outer surface of the drying wire as the drying wire travels over the deflection or closed sector of the deflection roll.

Claims16

Dependent claims

In a multi-cylinder drying section of a paper machine, a single-wire drying group comprising the combination of:

a looped drying wire;
a plurality of successively arranged drying cylinders located outside said drying wire loop having respective axes of rotation situated in a substantially common plane, said drying wire carrying a web between successive drying cylinders and passing over a covering sector of each of said drying cylinders with the web interposed between said drying wire and a heated drying surface of said drying cylinder;
at least one deflection roll having a perforated shell with perforations thereof extending through said shell and communicating with an interior of said roll, each deflection roll located within said drying wire loop in an inter-cylinder region between a pair of successive drying cylinders, said web-carrying drying wire having an incoming run traveling from a first one of said pair of successive drying cylinders to said deflection roll whereupon said drying wire runs over a deflection sector of said deflection roll shell, said incoming run of said web-carrying drying wire and said deflection roll shell defining a first wedge-shaped space or nip at the end of said incoming run, said deflection roll shell having an open sector free of said web-carrying drying wire;
at least one box means, each located in a respective inter-cylinder region proximate to said deflection roll, for directing a first ejecting gas flow adjacent to said incoming run of said web-carrying drying wire in a direction opposite to the direction of travel thereof for inducing a first underpressure on said incoming run and in a space including said first wedge-shaped space, and for covering said open sector of said deflection roll by at least one of a closing compartment and an underpressure compartment of said box means.

1 more element

A method in a single-wire drying group of a multi-cylinder drying section of a paper machine including a plurality of successively arranged drying cylinders having respective axes of rotation situated in a substantially common plane, at least one deflection roll having a perforated shell with perforations thereof extending through said shell and communicating with an interior of said roll, located in an inter-cylinder region between a pair of successive drying cylinders, a web-carrying looped drying wire conducted so that said drying cylinders lie outside and said at least one deflection roll lies inside the loop of the drying wire, said drying wire carrying the web over covering sectors of said drying cylinders with said web situated between the drying cylinder surfaces and the drying wire and over a deflection sector of each of said at least one deflector rolls with said web situated on an outer side of said drying wire, comprising the combination of steps of:

as the web-carrying drying wire departs from a first one of a pair of successive drying cylinders and travels over an incoming substantially straight run towards said deflection roll, maintaining the web supported on said incoming drying wire run by inducing a first underpressure on the incoming run said web-carrying drying wire by an ejection gas flow, said first underpressure being induced in a first gap space defined between said incoming drying wire run and a first wall of a blow box;
and
maintaining the web supported on the outer surface of said drying wire over said deflection sector of said deflection roll by creating and maintaining an underpressure in said perforations formed through said shell of said deflection roll;
maintaining said perforation underpressure in said perforations by at least one of the steps of closing a free sector of said deflection roll not covered by said web-carrying drying wire and communicating said free sector with an underpressure zone;
and
conducting said web-carrying drying wire from said deflection roll to the second one of said pair of successive drying cylinders.

3 more elements

Dependencies are inferred from the claim text.