Note: Descriptions are shown in the official language in which they were submitted.
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PATENT APPLICATION
TITLE: A HEADBOX APPARATUS FOR FORMING A MULTI-PLY WEB
BACKGROUND OF THE INVENTION:
FIELD OF THE INVENTION:
The present invention relates to a headbox apparatus.
More particularly, the present invention relates to a
headbox apparatus for forming a multi-ply web from a first
and second flow of stock flowing through the apparatus.
INFORMATION DISCLOSURE STATEMENT:
In the formation of multi-ply webs, a primary headbox
would eject a first flow of stock onto a moving fourdrinier
where the first ply would be partially formed. Subsequently,
a secondary headbox disposed downstream relative to the
primary headbox would eject a top ply onto the partially
formed web, thereby producing a multi-ply web.
More recently, with the introduction of the STRATAFLO
headbox, a first and second flow of stock were simultaneously
ejected from a single headbox onto a forming wire, thereby
enhancing bonding between the respective plies and reducing
the complexity of the multi-ply formation process. STRATAFLO
is a common law mark of Beloit Corporation.
Although the STRATAFLO headbox provided numerous
improvements over the prior multi-headbox arrangements, the
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STRATAFLO headbox in certain applications resulted in
migration between the respective stock flows prior to and
during the initial stages of web formation.
More specifically, in the STRATAFLO headbox, as the
respective stock flows are ejected from the slice lip of the
headbox, the respective stock flows interface. Such
interfacing of the stocks occurs before and during the
initial dewatering stage. Accordingly, the stock, which
typically has a consistency of between 0.1 and 1.0 percent,
permitted mingling of the fibers of the respective stock
flows with fibers of one stock flow migrating into the
adjacent stock flow.
In the manufacture of liner board, it is usual to form
the lower, liner or wire side ply from a relatively cheap
and unbleached stock while the top side ply is formed from a
relatively expensive, high quality, bieached stock such that
the resultant multi-ply web is suitable for printing on the
top side thereof.
Therefore, the aforementioned migration between the
respective stock flows, particularly the migration of fibers
from the wire side stock into the top side stock, causes
blotches and mottling of the resultant multi-ply web making
such less suitable for printing thereon.
The present invention seeks to overcome the
aforementioned problem by separating the respective stock
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flows by a flow of water such that migration between the
respective plies is inhibited.
Therefore, it is a primary object of the present
invention to provide a headbox apparatus for forming a
multi-ply web which overcomes the aforementioned problems
associated with the prior art apparatus and which makes a
considerable contribution to the art of multi-ply forming.
Another object of the present invention is the provision
of a headbox apparatus which includes a first and a second
trailing element disposed within a slice chamber. The
elements define therebetween a channel for channeling a flow
of water, the flow of water flowing from an inlet end towards
an outlet slice of the chamber. The arrangement is such
that during ejection of a first and second flow of stock and
the flow of water through the outlet slice and downstream
thereof, the flow of water inhibits migration between the
first and the second flow of stock.
Another object of the present invention is the provision
of a headbox apparatus wherein a first flow of stock is
ejected through an outlet slice of the slice chamber as a top
ply and a second flow of stock is ejected through the outlet
slice as a liner ply.
Another object of the present invention is the provision
of a headbox apparatus in which white water extracted from
the multi-ply web during subsequent formation thereof is
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recirculated through the headbox apparatus for reducing a
loss of fines from the resultant multi-ply web.
Another object of the present invention is the provision
of a headbox apparatus in which white water extracted from
the multi-ply web during subsequent formation thereof is
recirculated through a third inlet disposed between a first
and second trailing element for reducing a loss of fines
from the resultant multi-ply web.
Other objects and advantages of the present invention
will be readily apparent to those skilled in the art by a
consideration of the detailed description contained
hereinafter taken in conjunction with the annexed drawings.
SUMMARY OF THE INVENTION:
The present invention relates to a headbox apparatus
for forming a multi-ply web from a first and second flow of
stock flowing through the apparatus. The apparatus includes
a headbox housing which defines a slice chamber for the
passage therethrough of the first and second flow of stock.
The chamber has an inlet end and an outlet slice. A first
trailing element is disposed within the chamber with the
first element having an upstream and a downstream edge
respectively. The upstream edge is pivotally connected to
the inlet end and the downstream edge freely floats adjacent
to the outlet slice. The first element is disposed between
the first and the second flows of stock. A second trailing
element is spaced relative to the first element and is
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disposed within the chamber. The second element has an
upstream and a downstream termination respectively. The
upstream termination is pivotally connected to the inlet end
and the downstream termination freely floats adjacent to the
outlet slice. The first and the second elements define
therebetween a channel for channeling a flow of water. The
flow of water flows from the inlet end towards the outlet
slice such that during ejection of the first and second flow
of stock and the flow of water through the outlet slice and
downstream thereof, the flow of water inhibits migration
between the first and the second flow of stock.
In a more specific embodiment of the present invention,
the headbox housing includes an inlet wall and a top wall
which is pivotally connected to the inlet wall.
An adjusting means is connected to the top wall such
that movement of the adjusting means relative to the top
wall varies the size of the outlet slice.
The inlet wall also defines a first inlet for the
passage therethrough of the first flow of stock and a second
inlet for the passage therethrough of the second flow of
stock. The inlet end wall also defines a third inlet which
is disposed between the first and the second inlets for the
passage therethrough of the flow of water.
In one embodiment of the present invention, the
downstream edge and termination, respectively, of the first
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and second trailing elements are disposed within the slice
chamber.
In an alternative embodiment of the present invention,
the downstream edge and termination of the first and second
elements, respectively, are disposed downstream relative to
the outlet slice.
In a preferred embodiment of the present invention, the
trailing elements are of LEXAN whereas in an alternative
embodiment of the present invention, the trailing elements
are manufactured from carbon fiber sheets. LEXAN is a
registered trademark of General Electric Company.
In a preferred embodiment of the present invention, the
first flow of stock is ejected through the outlet slice as a
top ply while the second flow of stock is ejected through
the outlet slice as a liner ply.
In the preferred embodiment of the present invention,
white water extracted from the multi-ply web during
subsequent formation thereof is recirculated through a third
inlet defined by the inlet wall for reducing a loss of fines
from the resultant multi-ply web.
Many modifications and variations of the present
invention will be readily apparent to those skilled in the
art by a consideration of the detailed description contained
hereinafter. However, such modifications and variations do
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not depart from the spirit and scope of the present
invention as defined by the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS:
Figure 1 is a side-elevational view of a headbox
apparatus according to the present invention; and
Figure 2 is a side-elevational view of a headbox
apparatus according to a further embodiment of the present
invention in which the trailing elements extend through the
slice lip; and
Figure 3 is a side-elevational view of a headbox
apparatus according to another embodiment of the present
nventlon .
Similar reference characters refer to similar parts
throughout the various embodiments of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS:
Figure 1 is a side-elevational view partially in
section showing a headbox apparatus generally designated 10
for forming a multi-ply web W from a first and second flow
of stock 12 and 14 respectively flowing through the
apparatus 10. The apparatus 10 includes a headbox housing
16 which defines a slice chamber 18 for the passage
therethrough of the first and second flow of stock 12 and 14
respectively. The chamber 18 has an inlet end 20 and an
outlet slice 22.
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A first trailing element 24 is disposed within the
chamber 18. The first element 24 has an upstream edge 26
and a downstream edge 28. The upstream edge 26 is pivotally
connected to the inlet end 20. The downstream edge 28
freely floats adjacent to the outlet slice 22. The first
element 24 is disposed between the first and second flows of
stock 12 and 14 respectively.
A second trailing element 30 is spaced relative to the
first element 24 and is disposed within the chamber 18. The
second element 30 has an upstream termination 32 and a
downstream termination 34. The upstream termination 32 is
pivotally connected to the inlet end 20. The downstream
termination 34 freely floats adjacent to the outlet slice
22. The first and second elements 24 and 30 respectively
define therebetween a channel 36 for channeling a flow of
water 38. The flow of water 38 flows as indicated by the
arrow 40 from the inlet end 20 towards the outlet slice 22
such that during ejection of the first and second flows of
stock 12 and 14 and the flow of water 38 through the outlet
slice 22 and downstream thereof, the flow of water 38
inhibits migration between the first and second flows of
stock 12 and 14.
As shown in Figure 1, the headbox housing 16 also
includes an inlet wall 42 and a top wall 44 which is
pivotally connected at 46 to the inlet wall 42. Adjusting
means 48 are connected to the top wall 44 such that movement
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of the adjusting means 48 relative to the top wall 44 varies
the size of the outlet slice 22.
As shown in Figure 1, the inlet wall 42 defines a first
inlet 50 for the passage therethrough of the first flow of
stock 12. The inlet wall 42 also defines a second inlet 52
for the passage therethrough of the second flow of stock 14.
Additionally, the inlet wall 42 defines a third inlet 54
which is disposed between the first and second inlets 50 and
52 respectlvely for the passage therethrough of the flow of
water 38.
As shown in Figure 1, the downstream edge 28 and the
downstream termination 34 of the first and second trailing
elements 24 and 30 respectively are disposed within the
slice chamber 18.
In an alternative embodiment of the present invention
as shown in Figure 2, a downstream edge 28A and a downstream
termination 34A of a first and second elements 24A and 30A
respectively are disposed downstream relative to an outlet
slice 22A. Such an arrangement in certain applications and
with use of particular types of stock results in better
formation and bonding between the respective plies.
In a preferred embodiment of the present invention, the
trailing elements 24,24A and 30,30A are manufactured from
LEXAN, but in an alternative embodiment of the present
invention, the trailing elements are manufactured from
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carbon fiber sheets.
In the preferred embodiment of the present invention as
shown in Figure 1, the first flow of stock 12 is ejected
through the outlet slice 22 as a top ply 56 while the second
flow of stock 14 is ejected through the outlet slice 22 as a
liner ply 58.
White water 60 that is extracted from the multi-ply web
during subsequent formation thereof, is recirculated through
the headbox apparatus 10 for reducing a loss of fines from
the resultant multi-ply web.
More specifically, the white water 60 extracted from
the multi-ply web W during subsequent formation thereof is
recirculated through the third inlet 54 for reducing a loss
of fines from the resultant multi-ply web.
Figure 3 shows an alternative embodiment of the present
invention in which a headbox apparatus generally designated
lOB includes a first and second flow of stock 12B and 14B
respectively separated by a flow of wate~ 38B. The
apparatus lOB also includes a third flow of stock 62, which
is a base ply. The base ply 62 is separated from the second
flow of stock 14B by a further flow of water 64.
The arrangement is such that a multi-ply web WB is
formed having a liner ply 14B sandwiched between a top ply
12B of relatively expensive stock and a base ply 62, which,
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like the stock of the top ply, may be printable thereon.
The flow of water 38B and the further flow of water 64
similarly may include white water extracted during the
subsequent formation of stock and such flows 38B and 64
inhibit migration between adjacent stocks thereby enhancing
the printability of the resultant product.
The present invention not only inhibits migration of
fibers between preformed plies in a multi-ply web but also
prevents undue loss of fines during the formation of a
multi-ply web.
