Methods and apparatus for the rapid consolidation of moist porous webs
OwnerDouglas Wahreninventor
Life of this patent
Estimating the term…
Abstract
A moist, porous web is consolidated and dried by running it through the nip between two rotatable rolls, the surface of one of which is heated as it approaches the nip. One side of the web is in direct contact with the surface of the heated roll and the other side faces a permeable surface. The rolls are pressed together under high pressure to transfer heat from the heated roll to the web compressed therebetween to dry the same. The roll surface may be heated by hot gases from a fuel combustion burner or by a liquid medium. The dried and consolidated web may be removed from the heated roll by doctoring or it may be conveyed from the nip between the rolls to apparatus for processing it further.
Claims18
In a method for consolidating and drying a moist, porous web, the steps of running the web through the nip between a pair of rotatable rolls with one side in contact with one roll and its other side facing a permeable surface pressing the rolls together to develop a high pressure linear load in the press nip sufficient to produce good thermal contact between said one roll and the web at least in areas subjected to said high pressure linear load and to overcome any steam pressure developed between the web and said one roll, supplying heat to the outer surface of said roll as it approaches said nip at a rate such that the roll arrives at said nip with a temperature and heat content high enough to cause moisture in the web to be converted rapidly and violently into steam as the web passes through said nip, and heat is transferred rapidly from the surface of the roll directly to the web under high pressure, the steam thus formed tending to pass straight through the web, carrying with it any free water remaining in the cavities between the fibers of the web, whereby the steam is cooled and practically all of its heat energy is transferred to the web and the water remaining therein.
Apparatus for consolidating and drying a moist, porous web of material comprising:
- a pair of rotatable rolls defining a nip;
- means for running the web through said nip with one side in contact with the surface of one of said rolls and with the other side facing a permeable surface;
- heating means disposed externally of said one roll for supplying heat to a portion of the outer surface thereof as it approaches said nip so that said surface portion is brought to a temperature and heat content high enough to cause the moisture in the web to be converted suddenly and violently into steam as the web passes through said nip, said heating means including conduit means having outlet means generally conforming to the shape of part of said one roll in closely adjacent relation to the surface thereof and disposed upstream of said nip, and means for supplying a liquid heating medium to said conduit means;
- and
- means for pressing said rolls together so that a load is created which is sufficient to overcome any steam pressure developed between the web and said one roll in the nip area and sufficient to produce good thermal contact between the web and said one roll in said nip area, whereby heat is transferred rapidly from the surface of the roll directly to the web under high pressure, at least in said nip area.
Dependencies are inferred from the claim text.