Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to improvements in methods of
and means for forming multi-ply paper webs from a single headbox.
More particularly, the presen-t invention is an improvement upon
the disclosure in U.S. Patent 3,923,593 relating to a high speed
multi-ply paper web forming arrangement.
As pointed out in said prior patent, in the formation
of multi-ply webs, increases in machines speeds and increases
in requirements of stock specifications have created operating
problems in that the demand for improved high quality paper
webs has been accelerating, and competitive considerations
have encouraged higher manufacturing speeds of the papermaking
machines. According to the techni~ue disclosed in said prior
patent, a plurality of di~ferent stocks o~ di~ferent physical
characteristics are delivered from a slice to the forming area
between twin forming surface wires while at the same time
maintaining the different stocks generally in their multi-ply
layer arrangement between flexible divider sheets in the slice
chamber, the divider sheets terminating short of the slice
opening. Fine scale turbulence is relied upon within each of
the stocks to prevent flocculation, but the turbulence generat-
ing means terminate substantially upstream ~rom the slice
opening so as to substantially avoid carry-over of the turbulence
and undesirable intermixture of the stock for the plies on
the wire, while nevertheless permitting interlacing of the
fibers between plies.
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The aforesaid arrangement has functioned reasonably .
well to prevent fiber intermixing at moderate speeds and where
turbulence levels have been maintained sufficiently low in the
delivery jet from the slice opening. However, the demand for
higher speed operation, and corresponding increased jet velo-
city from the slice aggravates a tendency for the different
stocks to intermix undesirably after leaving the flexible flow
passage dividers in the slice chamber.
A principal reason for multi-ply paper webs is to
provide one or more surface layers on the resulting sheet having
particular desirable characteristics, such, for example, as
finer grade for ink receptivity in printing, or to provide an
ash barrier where a high ash content intermediate layer is sur-
faced by long fiber stock to prevent draining of ash during the
dewatering of the forming web, and the like. As slice jet velo-
city increases, maintaining of the necessary integrity in the
stocks forming the respective multi-ply layers becomes more and
more difficult.
An important object of the present invention is to
overcome the problem of maintaining ply int~grity in forming
multi-ply paper webs at high speed in machines emplo~ing a
single headbox delivering a plurality of different stock fiber
: suspensions to a multi-ply web forming zone.
Anotherobject of the invention is to provide a new
and improved method of and means for forming multi-ply paper
web in a single headbox papermaking machine in a manner to
maintain excellent ply integrity but with thorough interlacing
of fibers at the interface between plies for securing the plies :.
into an integral web. .-
According to features of the invention there is pro-
vided a method useful in a machine for making multi--ply. web
such as a paper from stocks having a slurry of fibers in a
liquid carrier and having a headbox provided with a main chamber
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communicating with a slice chamber defined by spaced walls
leading to a slice opening, and which comprises delivering
stoc~s which may have different physical characteristics to
each of a plurality of subchambers into which the main chamber
of the headbox is divided, dividing the slice chamber into
separate flow passages aligned respectively with different ones
of the headbox subchambers, receiving streams of the stocks
from the respective s~bchambers in said flow passages, main-
taining the stock streams separated in the flow passages, dis-
charging the streams in contiguous substantially laminar stock
jets from the slice opening into a forming zone between conver- ~.
gently co-travelling forming surfaces, and maintaining the stock
jets separated between divider means extending a substantial
distance out of said slice opening in the direction of flow of
the stock jets for an interval sufficient to permit drainage
and partial formation into a ply of the stock delivered by one
of the stock jets onto one of the forming surfaces before the
stock in a second of the stock jets joins in fiber felting
multi-ply laminar relation with the contiguous surface of the
partially formed ply.
According to other features of the invention there is
provided for use in a machine for making multi-ply webs such as
a paper from stocks having a slurry o fibers in a liquid car-
rier, a headbox having a main chamber communicating with a
slice chamber defined by spaced walls leading to a slice open-
ing, means dividing the main chamber into a plurality of sepa-
rate stock subchambers, separate stock supply means for deli-
vering stocks which may have different physical characteristics .
to each of said subchambers, divider means in the slice cham-
ber dividing the slice chamber into separate flow passagesaligned respectively with different ones of said headbox main
chamber subchambers to receive streams of the stock from the
respective subchambsrs and maintain the streams separated, said
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flow passages leading to said slice opening for discharging
the streams in contiguous s~bstantially laminar stock jets
from the slice opening into a forming zone between conver~ently
co-travelling forming surfaces, and divider extension means
extending from said divider means a substantial distance out
of said slice opening in the direction of flow of t~e stock
jets whereby to maintain the stock jets separated for a suffi-
cient interval after leaving the slice opening to permit drain-
age and partial formation into a ply of the stock delivered by
one of the stock jets onto one of the forming surfaces before
the stock in a second of the stock jets joins in fiber felting
multi-ply laminar relation with the contiguous surface of the
partially formed ply.
Other objects, features and advantage,s of the inven-
tion will be readily apparent from the following clescrip-
tion of certain representative embodiments thereof, taken ,'
in conjunction with the accompanying drawing although variations
and modifications may be effected without departing from the
spirit and scope of the novel concepts embodied in the dis-
20 closure and in which: '
FIG. 1 is a schematic illustration demonstrating one
pre~erred ~orm of the invention; and
FIG. 2 is a schamatic illustration demonstrating a
modified form of the invention.
According to the principles of the present invention,
any pre~erred number o~ plies may be formed advantageously in
the course of making a multi-ply paper web, ~rom a two-ply web
to as many plies as desirable. Commonly no more than three ''
plies are necessary. For example, where it is desired to pro-
duce paper having differently coloured opposite sides such as
white on one side and brown on the other, the paper slurry '~
stocks may be selected to supply white fibers in one, ply and
brown fibers in the second ply. A three-ply web ~ay be
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produced to provide a paper sheet or paper board having a
cheaper grade of stock surfaced by higher grade stock, or
where, for example, the paper web has an intermediate high ash
content layer and opposite or outer layers of long fibered
stock, and the like.
Fig. 1 illustrates schemati.cally as much as needed
for the present purposes, a papermaking machine 5 adapted for
producing a three-ply paper web by means of a single headbox
7. Within the headbox 7 a main chamber 8 communicates with a
slice chamber 9 defined b~ converging spaced walls 10 and 11
which lead to a slice opening 12. Means comprising partitions
13 divide the main chamber 8 into a plurality of separate stock
subchambers 14, 15 and 17 wherein the subchamber 15 is inter-
mediate the chambe,rs 14 and 17. Separate stock supply means
for delivering stoc~s which may have different physical charac-
teristics to each of the subchambers comprise a delivery means
18 communicating with the subchamber 14, a delivery means 19
communicating with the subchamber 15 and a delivery means 20
communicating with the subchamber 17. It will be appreciated,
of course, that each of the delivery means, 18, 19 and 20 will
: have communication ~ith a suitable stock source and will supply
the stock to the associated headbox subchamber at the propqr :
consistency and under adequate pressure to produce the desired
stock flow velocity for high speed operation. ~:
Within the slice chamber 9, streams of the stock
rom the respective subchambers 14, 15 and 17 are received in
separate flow passages aligned respectively with the different
ones of the subchambers. For this purpose, divider means such
as a 1exible divider sheet member 21 in alignment with the
divider 13 separating the subchambers 14 and 15 extends longi-
tudinally through the slice chamber 9 and divides a flow pas-
sage 22 aligned with the subchamber 14 from a flow passage 23
aligned with the subchamber 15. To the same effectl a flexible
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,Idivider sheet member 24 is aligned with the divider 13 which
separates the subchamber 15 from the subchamber 17 and extends
longitudinally through the slice chamber 9, separating the
passage 23 from a flow passage 25 aligned with the subchamber
17. The divider members 21 and 24 may be made from any suit-
able sheet material such as a plastic malterial of adequate
quality and weight for the purpose. Preferably the divider
members 21 and 24 are secured fixedly at their upstream ends
within the headbo~ structure while throughout the remainder of
their length they may be unsupported and self-positionable by
virtue of the hydraulic forces of the stock flowing through
the slice chamber, Within each of the passages 22, 23 and 25,
means for generating fine scale turbulence may comprise self-
positionable elements 27 which may be flexible sheet members
made from material on the order of that from which the divider
members 21 and 24 are made; or the turbulence generators may
be strand-like elements~ In any event, the turbulence genera-
tor members are secured fixedly at their upstream ends within
the headbox and are free in the downstream direction. By pre-
ference, the turbulence generators 27 extends short of theslice opening 12~ Each of the divider members 21 and 24, at
least, extends across the ull width of the slice chamber 9 so
as to maintain continuous separation between the flow passages
whereby to maintain substantial integrity of the stocks flow-
ing through the passages. From the slice opening 12, the stock
from the slice chamber 9 is delivered into a forming zone be-
tween co-travelling forming surfaces 28 and 29 which, in Fig. 1,
comprise means such as endless foxming wires partially wrapping
respective breast rolls 30 from which the forming surface wires
generally converge past the slice opening 12 and define a for-
ming zone 31 receptive of the stock delivered from the slice
opening. Along the forming zone either or both of the porous
forming surfaces 28 and 29 may be equipped with drail~age
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promoting foils 32 or other desirable drainage promoting means.
Velocity of the streams of stock delivered from the
slice chamber passages through the slice opening 12 effects a
substantially jet propulsion, that is a stock jet 33 from the
passage 22, a s-tock jet 34 from the intermediate passage 23
and a stock jet 35 from the passage 25.
)Normally the tendency of the jet streams 33l 34 and
35 would be to substantially commingle to at least a substantial
depth at their interfaces so that the intermediate stock jet
34 may substantially lose integrity of its stock content by ad-
mixture with the stock content of the stock jets 33 and 35.
Further, the result may be to contaminate the outer stock jets
33 and 35 with undesired stock fiber or other material such as
ash or the like from the intermediate stock jet 34 to the ex-
tent that the Eorming surfaces of the web plies at the forming
surfaces 28 and 29 may be undesirably affected. To the allevi-
ation of this problem, the stock jets 33, 34 and 35 are, accor-
ding to the present invention, maintained separte beyond the
slice opening 12 long enough to permit sufficient drainage of
the fiber suspension delivered in the outer jets 33 and 35 to
reduce the mobility o the fibers in the plies formed by the
stock in the outer jets before the intermediate stock jet iber
suspension joins with the par~ially formed outer plies. Effi-
cient means for this purpose comprise extending the downstream -
ends of the divider members 21 and 24 to project beyond the
slice opening 12 into the forming zone 31 a sufficient distance,
depending upon various factors such as types of fiber suspen-
sions, velocity, speed of the web former, and the like, to
maintain the intermediate stock jet 34 substantially separated~
from both of the outer stock jets 33 and 34 to permit drainage
as indicated by directional arrows and partial forming of res-
pective web plies 37 and 38 before the stock jet 34 enters be~
tween the partially formed plies 37 and 38 to form an
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lU~9~intermediate ply 39. As thus joined to the partially formed
plies 37 and 38, there is still sufficient looseness in the
fibers at the interfaces of the forming outer plies 37 and 38
to interlock with and effect a satisfactory felted bond with
the stock in the forming inner ply 39 which drains through
the partially formed outer plies 37 and 38. However, the depth
of commingling of the inner ply stock with the outer ply stock
is efficiently limited by reason of the substantial decrease in
mobility of the stocks in the partially formed outer plies. In
a preferred arrangement, as shown, the divider members 21 and
24 may extend an equal distance beyond the slice opening 12.
To accommodate conditions where ~ontact between the intermediate
ply stock jet with either of the outer ply stock jets should
be effected ~ooner than contact between the inne~ ply stock
jet and the remaining outer ply stock jet, then a suitable
differential in length of proiection of the divider members may
be effected.
The invention is also advantageous for high speed
operation of a single headbox multi-ply web papermaking machine
40 (Fig. 2) of the type known as a roll former. In such a
machine converging web forming surfaces are provided by an end-
less porous forming member 41 such as a foraminous wire kelt
which wraps around a breast roll 42 and runs convergently toward
the perimeter of a large diameter forming roll 43 running in
the same direction. This arrangement provides a gradually di-
minishing forming zone 44 into the mouth of which a slice
opening 45 of a headbox 47 delivers a plurality of separate
stock supplies. Similarly as in Fig. 1, the headbox has a pair
of convergently related walls 48 and 49 defining a s:Lice cham-
ber 50 terminating in the slice opening 45. Division of theslice chamber 5G into separate flow passages aligned respec-
tively with different ones of subchambers in a main chamber of
the headbox 47, similarly as described in Fig. 1, t:o receive
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streams of the stock from the respective subchambers and main-
tain the streams separated, is effected by means comprising at
lea~t one divider where a two-ply web is to be formed, but, as
shown, where a three-ply web is to be formed respective dividers
51 and 52 separating the slice chamber 5() in~o an intermediate
ply flow passage 53 and respective outer ply flow passages 54
and 55. Each of the dividers 51 and 52 Inay be formed from sui-
table sheet plastic material, similarly as described for the
dividers in Fig. 1. Suitable turbulence generating means such
as sheets or strands as indicated in Fig. 1, may be mounted in
the flow passages 53, 54 and 55, or any other pre~erred type of
turbulence generator may be employed as desired. By means of
the dividers 51 and 52, the flow passages are controlled to
discharge the skreams ~rom the flow passages in contiguous
substantially laminar stock jets from the slice opening 45 into
the forming zone 44, the stock from the flow passage 54 dischar-
ging as a jet 57, the stock from the intermediate stream 53
discharging as a jet 58, and the stock discharging from the
stream 55 forming a jet 59.
In order to maintain the contiguous substantially
laminar stock jets 57, 58 and 59 sepaxated for a sufficient
interval after leaving the sli~e o~ening 45 to permit drainage
and partial formation into a ply of the stock delivered by at
least one of the stock jets to one of the forming surfaces be-
fore the stock in a second of the stock jPts joins in fiber
felting multi-ply laminar relation with the contiguous surface
of the partially formed ply, divider extension means are provi-
ded comprising integral extensions from the dividers 51 and 52,
comprising an extension 60 from the divider 52 and an e~tension
61 from the divider 51, such extensions extending from the divi-
ders a substantial distance out o the slice openi~g 45 in the
direction of flow of the stock jets. Since in the roll former
axrangment disclosed, liquid drainage from the papermaking
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stock in the forming zone 44 is through the porous forming
surface 41, as indicated by the directional arrows in Fig. 2,
and the stock jet 57 is the nearest to and engages the forming
surface 41, the divider extension 61 extends from the slice
opening 45 a sufficient distance to assure adequate separation
of the intermediate jet 58 from thejet 57 during the initial
dewatering of the stock in the jet 57 to avoid contact between
the jets 57 and 58 until dewatering of the stock in the jet 57
.. has progressed for an interval of advance with the travelling
forming surface 41, as indicated by the brace 62 for a suffi~
cient distance to reduce the mobility of fibers in the develo-
ping ply of stock on the forming surface 41 to avoid undesirable :
intermingling of the stock in the jet 58 upon engAgement with
the stock from the jet 57, but with still sufficient looseness
of the fibers at the interface between the forming, less mobile
stock from the jet 57 and the still highly mobile and substan- :
tially turbulent stock in the jet 58. For this purpose the
divider extension 60 terminates at the end of the extent indi~
cated by the brace 62. The stock in the jet 58 then engages
upon the partially formed web ply from the jet 57, immediately
beyond the end of the divider extension 60, and drainage through
the partially formed jet S7 ply effects partial formation of
; the jet 58 ply. Such ply on ply formation occurs throughout a
suitable length indicated by the brace 63 while the divider . .
extension 61 maintains the jet 53 separated from the forming
jet 58 ply. The length of the dlvider extension 61 is just
sufficiently longer than the length of the divider extension
60 to attain partial formation of the jet 58 ply so that upon
joining of the jet 59 with such partially formed ply, there
will be adequate fiber felting at the interfaces withou~ un~
desirable depth comminglin~ of the fibers in the jet 59 with
the fibers in the jet 58 ply. ~s a result, as the preliminary
drainage of liquid from the jet 59 ply progresses as indicated
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by the brace 64 beyond the end of the divider extension 61, all
three plies will be joined together in a unitary, integral
multi-ply web by ample fiber felting at their interfaces while
nevertheless maintaining substantial integrity of the fibers
and other materials which may be present in the respective plies.
It will thus be apparent, that the princ:iples of the present
invention are applicable to one sided drainage as demonstrated
in Fig. 2, as well as the two sided drainage demonstrated in
Fig. 1.
It will be understood that variations and modifications
may be effected without depar-ting from the spirit and scope of
the novel concepts of this invention.
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