Keith Peyton Thomas

43598285, Nov 23, 1982

Feb 17, 1981

6/235313

Keith V. Thomas - Tacoma WA

Weyerhaeuser Company - Tacoma WA

F26B 1308

34114

An improved vacuum box is described for holding a paper web onto a supporting fabric wherever velocity stresses would otherwise separate the web from its supporting fabric and expose the web to those stresses. Specially shaped vacuum boxes are fitted into the dryer "pockets" formed between the rows of a double row of adjacent drying cylinders and the web traveling a serpentine path between them. Pressure differential zones of the box hold the web onto its supporting fabric as the web and fabric travel between heated drying cylinders. A first zone leads the departure of the web and fabric from the web-wrapped cylinder to ensure that the web is positively held to the fabric as it leaves the cylinder. A second arcuate suction zone adjacent a fabric-wrapped cylinder evacuates grooves in the adjacent cylinder. This system holds the web onto its fabric, overcoming centrifugal stresses on the web, as the web-fabric combination passes about a cylinder with the fabric in direct contact with the cylinder and the web in indirect contact.

43598277, Nov 23, 1982

Feb 17, 1981

6/234288

Keith V. Thomas - Tacoma WA

Weyerhaeuser Company - Tacoma WA

F26B 324

34 16

An improved paper drying process and machine are described in which the paper web is supported independently of velocity-induced stresses thus permitting operation at speeds significantly in excess of the prior art for each paper grade. The process requires: (1) transporting the web on a supporting fabric that travels from the last press nip through at least the initial portion of a drying section; and (2) holding the web onto its supporting fabric by employing forces normal to the major web surfaces sufficient to overcome those forces which tend to lift the web from its supporting fabric. The web on its supporting fabric travels a serpentine path through the drying section about drying cylinders with the web alternating between direct contact with a drying cylinder followed by indirect contact with the subsequent cylinder. The principal holding forces are preferably pressure differentials created by vacuum boxes arranged to effectively hold the web to its supporting fabric on all portions of the web-fabric combination where the web is not in direct wrapping contact with the drying cylinders. The fabric supports the web at least until the web has attained sufficient strength through increased dryness to resist breaking stresses at the selected machine speed.