Paper making and fiber liberation – Processes and products – Multi-layer waterlaid webs or sheets
Reexamination Certificate
2000-04-05
2001-09-11
Hastings, Karen M. (Department: 1731)
Paper making and fiber liberation
Processes and products
Multi-layer waterlaid webs or sheets
C162S304000, C162S306000
Reexamination Certificate
active
06287420
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention.
The present invention relates to an apparatus for forming a fiber web, and, more particularly, to an apparatus for forming a multi-ply fiber web.
2. Description of the related art.
A paper-making machine is used for forming a fiber web, such as a paper web, from a prepared fiber suspension, such as a wood fiber suspension. The fiber suspension is discharged onto a traveling forming fabric, such as a wire, with a predetermined cross-sectional profile and is formed within the paper-making machine to produce the fiber web. Typically, the fiber suspension is discharged onto the forming fabric at a single location to form a single ply fiber web. However, it is also known to form a multi-ply fiber web in a paper-making machine. With a multi-ply machine, the fiber suspension is discharged onto the same or another forming fabric at a different location in the paper-making machine. The two plies are joined together to form the multi-ply fiber web. Typically, starch or another bonding agent is applied to one or both plies to join the two plies together.
Although a multi-ply paper-making machine as described above is effective to produce a high quality fiber web, the additional processing which is required to apply the starch or other bonding agent to one or both plies of the fiber web requires additional equipment, space and material cost.
What is needed in the art is an apparatus and method for manufacturing multi-ply fiber webs which does not require the application of additional bonding agents to the multiple plies in the fiber web.
SUMMARY OF THE INVENTION
The present invention provides a multi-ply fiber web forming apparatus which joins the multiple plies in a transfer area utilizing water under pressure which wets the plies.
The invention comprises, in one form thereof, a multi-ply fiber web forming apparatus including a lower forming fabric defining a lower forming fabric run. A first headbox is positioned above the lower forming fabric for discharging a fiber suspension onto the lower forming fabric. An upper forming fabric defines an upper forming fabric run. A second headbox is positioned above the upper forming fabric for discharging a fiber suspension onto the upper forming fabric. A wet forming box is positioned below the lower forming fabric for applying a liquid to the lower forming fabric. A transfer roll is positioned above the upper forming fabric. The transfer roll and the wet forming box are positioned in close opposing relationship to each other, whereby each of the lower forming fabric and the upper forming fabric pass therebetween in a transfer area.
An advantage of the present invention is that the multiple plies may be joined together using only water, without the use of starch or other bonding agents.
Another advantage is that the extent to which the multiple plies are wetted can be easily varied by controlling the flow rate and/or pressure of the water which is transported into the transfer area.
Yet another advantage is that a vacuum may be drawn on the transfer roll to further assist in wetting the multiple plies of the fiber web.
REFERENCES:
patent: 3625814 (1971-12-01), DeNoyer
patent: 4154645 (1979-05-01), Kankaanpaa
Hastings Karen M.
Taylor & Aust P.C.
Voith Sulzer Paper Technology North America Inc.
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