Device in the drying section of a paper machine

In a drying section of a paper machine including drying cylinders and a drying fabric loop arranged such that a first group of at least one of said cylinders is located outside of said drying fabric loop and a second group of at least one of said cylinders is located within said drying fabric loop so that the web runs in a closed draw in a joint run with and supported by said fabric from a cylinder of one group to a cylinder of the other group, said joint run defining wedge-shaped spaces between said drying fabric and the shell of the drying cylinders, the improvement comprising

• at least one suction box situated adjacent to a joint run of said web and drying fabric,
• said suction box including suction apertures situated proximate to at least one of said wedge-shaped spaces to produce a suction effect mainly in said at least one of said wedge-shaped spaces,
• said at least one suction box thereby constituting means for producing a suction effect mainly in at least one of said wedge-shaped spaces,
• said suction effect being substantially higher than a suction effect, if any, produced by said suction box in the region of said closed draw run of said web between said wedge-shaped spaces,
• wherein said cylinders defining said wedge-shaped spaces each include a respective shell having a recessed surface,
• wherein said suction effects produced in said wedge-shaped spaces are communicated into said recessed surfaces to facilitate maintenance of the web in contact with the outer surface of the drying fabric as it curves over a sector of the cylinder, and
• wherein said recessed surface comprises axial grooves formed in each of said shells whereby the sector of said shell outside the sector thereof which is lapped by the drying fabrics, communicates with ambient pressure.

In a drying section of a paper machine including drying cylinders and a drying fabric loop arranged such that a first group of at least one of said cylinders is located outside of said drying fabric loop and a second group of at least one of said cylinders is located within said drying fabric loop, so that the web runs in a closed draw in a joint run with and supported by said fabric from a cylinder of one group to a cylinder of the other group, said joint run defining wedge-shaped spaces between said drying fabric and the shell of the drying cylinders, the improvement comprising

• at least one suction box situated adjacent to a joint run of said web and drying fabric,
• said suction box including suction apertures situated proximate to at least one of said wedge-shaped spaces to produce a suction effect mainly in said at least one of said wedge-shaped spaces,
• said at least one suction box thereby constituting means for producing a suction effect mainly in at least one of said wedge-shaped spaces,
• said suction effect being substantially higher than a suction effect, if any, produced by said suction box in the region of said closed draw run of said web between said wedge-shaped spaces,
• wherein said suction box is divided transversely into a plurality of compartments located in side-by-side relationship, each of said compartments producing a vacuum, and
• wherein the vacuum produced in said compartments nearest to the lateral sides of the fabric is higher than the vacuum produced in other ones of said compartments.