Drying and gas or vapor contact with solids – Apparatus – Rotary drums or receptacles
Patent
1985-11-27
1987-07-21
Schwartz, Larry I.
Drying and gas or vapor contact with solids
Apparatus
Rotary drums or receptacles
34117, 34158, 68 5D, F26B 1308
Patent
active
046808736
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method for controlling or regulating shrinking and/or stretching of a paper web transversely to the transport direction of the web in the drying section of a paper machine in the form of a cylinder drier and/or a fan dryer.
The invention also relates to arrangements for controlling shrinkage and/or stretching of a paper web in the drying section of a paper machine in the form of a cylinder dryer and/or a fan dryer, transversely to the transport direction of the web.
BACKGROUND ART
A number of mutually different drying sections intended for paper machines are known to the art, the majority of which sections incorporate a cylinder dryer and/or a fan dryer with which to effect drying of the web. It has long been known that, when drying a paper web in the drying section of a paper machine, the web tends to shrink in both the longitudinal and transverse directions thereof
It is also known that shrinking of the web in its transport direction or machine direction can be controlled by driving mutually adjacent drying means in the drying section at different speeds. It is also known that improved values, or an improved index, can be achieved with regard to the strength properties of paper, by controlled reduction of shrinkage of the paper web in its axial or transport direction.
It is also known that controlled reduction in web shrinkage transversely to the web axis cannot be achieved in dryers of the aforesaid kind.
It has been shown, however, that a small force of certain magnitude acts across the whole width of the paper web, from the centre of the web outwards, as a result of the friction prevailing between the peripheral surface of a drying cylinder and the web. In connection with the known art there is described and illustrated in U.S. Pat. No. 3,650,043 an arrangement designed to stabilize a dried paper web by blowing air thereonto in a manner to stretch the web.
U.S. Pat. No. 3,452,447 also describes an arrangement for stabilizing a dried paper web by blowing streams of air thereonto so that the web is stretched.
It should be emphasized here that these paper webs have a dryness in excess of 75% and preferably about 95%.
DISCLOSURE OF THE PRESENT INVENTION
Technical Problems
With regard to the prior technical standpoint in this art, the realization that the final strength properties of a dried paper web are dependent on the extent to which the finished paper has been permitted to shrink in different directions and that different degrees of shrinkage will result in varying properties in different directions means that a technical problem must be considered to exist in the provision of conditions, with the aid of simple means, which enable all strength properties of a dried paper to be controlled or regulated, by "all strength properties" we include flexural rigidity, tensile strength, tensile rigidity, and compression strength in the various directions.
It must also be considered a more qualified technical problem to take measures such that the strength properties can be regulated in a simple fashion transversely to the transport direction of a paper web to be dried.
Another technical problem in this regard is one of providing with the aid of simple means conditions which enable shrinkage of a paper web to be dried to be controlled and counteracted transversely to the transport direction of the web, and also to provide conditions whereby the web can be stretched in the transverse direction.
When considering the fact that a varying degree of stretch, to counteract shrinkage or elongation in different directions, will impart varying properties to the finished paper in different directions, it must be considered a technical problem in relation to the present standpoint of the art to create with the aid of simple means conditions which enable these properties to be substantially equalizied in the various directions.
Another technical problem is one of enabling measures to be taken which ensure that the paper web in the dryer section is dimensionally mor
REFERENCES:
patent: 1104759 (1914-07-01), Sheahan
patent: 1707015 (1929-03-01), Jones
patent: 3452447 (1969-07-01), Gardner
patent: 3650043 (1972-03-01), Overly et al.
Fellers Christer
Hansson Torbjorn
Htun Myat
Flakt AB
Schwartz Larry I.
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