Liquid applicator for cut sheets

Details Liquid applicator for cut sheets Liquid applicator for cut sheets

1998-04-27

2001-01-23

Yan, Ren (Department: 2854)

Printing

Planographic

Dampeners

C101S232000, C101S247000, C118S236000

Reexamination Certificate

active

06176180

ABSTRACT:

FIELD OF THE INVENTION
This invention generally relates to a liquid application system for offset and document printing, copying, imaging, converting, and related industries, and more particularly for a liquid applicator means for applying moisture and coatings to cut sheets.
BACKGROUND OF THE INVENTION
There have been countless attempts throughout the printing industry to apply and control moisture in paper. Attempts have been made in the past to add liquids such as dyes, low-viscosity coatings and moisture to a moving web in such a manner as to control the liquid application along the length and width of the web. Such attempts have consisted of application of atomized particles in the form of mist, steam or spray to the web which results in only partial coverage of the web by the atomized particles or uneven application thereof and lack of adequate control of the amount and density thereof.
Another system used in the past is by means of rolls wherein an uncontrollable quantity of liquid is applied to the web. Various other devices have been used such as scrapers, knives, blades, etc. as the sole means for controlling the thickness of liquid applied to the web from a roll. Such devices are undesirable because it is difficult to adjust flexible blades lengthwise and because the slightest adjustment of the blade may change the film thickness more than is desirable.
Environmental chambers, wherein a moving web is passed through a humid atmosphere within a chamber, have been unsatisfactory because only surface quantities are added to the web due to the limited time of exposure of the web to the humid atmosphere as it passes through the chamber. As a result, the web does not absorb sufficient quantity of the liquid. Furthermore, one side application is virtually impossible. Control of moisture by varying web speed through drying devices or by varying the drying temperatures and humidity is not only difficult but undesirable and costly.
Applying moisture (humidity) and/or coatings to one or both sides of a cut sheet has been previously impossible, or at least impractical, slow, and expensive, particularly where 100% coverage was required. Consequently, systems to date have been limited to application of moisture to a web of material rather than individual sheets.
SUMMARY OF THE INVENTION
The foregoing and other difficulties are overcome by the present invention, which is capable of controllably moisturizing cut sheets. Liquid applied to a cut sheet is supplied from a reservoir or other liquid supply source to the nip between a metering roll and a hydrophilic transfer roll. An abundant supply of liquid is supplied at the nip between the rolls which is metered by pressure contact between the metering roll and the transfer roll to a liquid film thickness which adheres to the surface of the transfer roll. The transfer roll rotates in contact with and applies liquid to the cut sheet. A backup roll having a resilient surface draws the cut sheet over the transfer roll, at a speed and in a direction desired, preferably in a direction opposite the surface of the transfer roll when moisture is applied. Individual free sheet edges are fed and guided to, through and away from the point of contact of the surfaces of the rolls. The relative speed of the transfer and backup rolls, thickness of the liquid film and pressure applied by the backup roll to the cut sheet can be varied to control the degree of moisturization. Two or more such assemblies may be used to apply liquid to both sides of a cut sheet and to apply a variety of liquid to the sheet.


REFERENCES:
patent: 3647525 (1972-03-01), Dahlgren
patent: 5207159 (1993-05-01), DeMoore et al.
patent: 5582087 (1996-12-01), Crowley et al.
Elementary Fluid Mechanics, John K. Vennard, 4 pages, 1961.
Controlled Moisture Addition to Moving Webs by a Roll System,Paper Trade Journal, C. C. Boggus and J. E. Taylor, 5 pages, Sep. 16, 1968.
“Web Rehumidification and Control,”The Journal of the Technical Association of the Pulp and Paper Industry, Harry J. Karakourtis, 8 pages, Jul. 1972.
“Laminator Adds Metallizing to the Mix, ” Paper Film Foil Converter, 2 pages, Sep. 1996.
Brochure : “Mini-LA: Liquid Application System”, Dahlgren USA, Inc., 1 page.
Brochure: “Liquid Application System”, Dahlgren USA, Inc., 4 pages.
Brochure: “Liquid Application System”, Dahlgren USA, Inc., 4 pages.
Brochure: Advertising Material, Dahlgren USA, Inc., 8 pages.
Advertising material, Dahlgren USA, Inc., 1 page.
Brochure: “Liquid Application Systems”, CMS, Inc., 8 pages.

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