Drying and gas or vapor contact with solids – Apparatus – With means to treat gas or vapor
Patent
1981-02-17
1982-11-23
Schwartz, Larry I.
Drying and gas or vapor contact with solids
Apparatus
With means to treat gas or vapor
34 23, 34114, 34116, F26B 324
Patent
active
043598277
ABSTRACT:
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. The products made by the process of this invention possess a unique toughness or stretchability not found in conventionally prepared papers that have been strained or stretched during manufacture. Processes and machine arrangements designed to balance stretchability with certain desirable stiffness properties are disclosed. Pulp furnishes may now be selected for their contribution to product qualities, such as higher finished product tensile strength, rather than principally for wet strength. For example, chemical pulps may be significantly reduced or eliminated from newsprint furnishes where their purpose has been principally to permit economic paper machine speeds. The invention makes attainable speeds approaching twice current operating levels for each paper grade.
REFERENCES:
patent: 3237316 (1966-03-01), Sachs
patent: 3816941 (1974-06-01), Holik et al.
patent: 3874997 (1975-04-01), Kankaanpaa
Article by D. A. Ely, "A Look at Papermaking Concepts for the Future", Paper Age, Apr. 1981; pp. 38-40+2 pp. drawings.
Schwartz Larry I.
Weyerhaeuser Company
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