Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND OF THE INVENTION
This invention relates to the production of
corrugated combined board. ~ore particularly, it relates to
the production of corrugated combined board on a single
papermaking machine. Sometimes this type o~ board is referred
to by other names, such as box board, corrugated container
board, container board and combined board to name a few. ~erein,
this product will be referred to as corrugated combined board,
or box board, but the invention is intended to be generic to
the board product ha`ving a top and bottom liners, or linerboards,
and an inner corrugated board, called corrugating medium in
the papermaking industry, regardless of how it is labeled.
Typically, this kind of board is used to ship bulky produc-ts,
such as appliances and furniture.
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Tradi-tionally, corrugated combined board has been
¦I manufactured by producing each of the layers separately on
i different papermaking machines and then producing -the composite
' board by bringing all of the hoar,d webs together on another
machine and causing them to be adhesively bonded together.
; Indeed, in the papermaking industry, the inner, or corrugated,
layer in box board is a commercial product which is manufactured
1l exclusively on some papermaking machines in some mills. This
l "corrugating medium", as it is known in -the trade, is produced
in continuous sheets or webs and wound into rolls after it has
¦I been dried. The corrugations are then formed in the sheets by
other machinery before the corrugating medium and top and
bottom linerboards are brought together to form the box board.
Since box board is almost always comprised of three
I, plies or layers - a top liner, a bottom liner and a corrugated
Ii inner layer, it now takes several machines to produce all o~ I
,~ the layers as well as additional machines to corrugate the inner ¦
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layer and glue the several layers toye-ther to form the
composite box board. The top and bottom layers in a corrugated
container board are commonly referred to as "linerboards" or
sometimes "liners" in the paper trade. Even if all of the
layers were somehow produced on a single papermaking machine, `
the production in terms of the composite box board would be
reduced by one-third since each layer would have to be
produced one at a time. In addition, each of the separate
layers has to be dried separately which requires a considerable
commitment in capital expenditure for drying apparatus as
well as energy to dry the board webs.
SUMMARY OF THE INVENTION
This invention obviates the aforementioned problems
by forming all oE the layers continuously, simultaneously
and sequentially on a single papermaklng machine. This is
accomplished by laying and dewatering the individual board
webs separately so that they are sufficiently formed to
enable them to be adhesively secured to one another or to
have corrugations formed in them, in the case of the corrugated
inner layer, wi-thout falling apart.
In the manufacture of composite, multi-ply paper
board products, it is important that the individual plies be
of approximately the same moisture content. This is true
regardless of whether the layers are bonded with an adhesive
or ply bonded by the moisture in the adjacent webs. In ply
bonding, the most effective bond is produced when both
bonded layers have approximately the same moisture content
at the lowest consistency while the webs are wet but capable
of maintaining th~ir integrity. Such a moisture level might ~;
range from about 6% bone dry to about 16% bone dry, depending
on the type of forming equipment, machine speed and pulp
stock used.
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In this invention, each of the web plies is separately
laid, dewatered and formed in the same general area of a single
papermaking machine. Accordingly, the moisture content of each
web ply can be controlled so that all the webs will have
approximately the same mois-ture content. The ply which is to
be the intermediate, or corrugating medium, ply is doctored off
either its forming roll or a pick-off roll to form the
characteristic flutes or corrugations. The first web formed
is the bottom liner which is laid onto a traveling foraminous
screen, such as a horizontally arrayed fourdrinier wire. The
forms producing the corrugating medium and top liner plies,
respectively, are mounted above the fourdrinier wire one after
the other. They are roll formers that dewater the web to the
desired consistency in the 6~ bone dry to about 16% bone dry
(84~ moisture) range. The corrugating medium is then doctored
off and guided onto the bottom liner which is passing beneath on
the fourdrinier wire. The next former is a roll former
essentially identical to the former producing the corruga-ting
medium and in turn places the top,liner on-to the corrugating
medium. In the preferred embodiment, a spray of adhesive
solution is applied to both the bottom liner and corrugating
medium plies before the nex-t ply is brought into con-tact with
them in order to bond the plies in-to the composite corrugated
combined board. The moisture in the webs also helps bond the
plies together by a phenomenon known as "ply-bonding" wherein
the fibrils of the pulp fibers in one ply are attracted to the
fibrils of the pulp fibers in contiguous ply to cause the plies
to bond toge-ther in much the same way that the individual fibers
within a single ply, or web, comingle to form the individual
ply itself.
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The composite board is then passed out of the forming
section and into a dryer of conventional design. All plies are
produced at the same time so no warehouse stora~e is required
for any previously made plies pending their being brough-t
together on another machine to manufacture the corrugated
combined board.
Accordingly, it is an object of this invention to
provide a method and apparatus for producing multi-ply corrugated !
box board on a single papermaking machine starting with an
aqueous slurry of pulp fibers for each layer.
Another object of this invention is to provide a
method and apparatus for forming and corrugating the inner layer
of corrugated box board while the inner layer is still in the
forming section of a papermaking machine.
Still another object of this invention is to provide
a method and apparatus for the simultaneous production of each
layer of a multi-ply corrugated box board and the,subsequent
continuous combination of the separate plies into a composite
corrugated box board in the forming section of a papermaking
machine.
A feature and advantage of this invention is that
it requires no storage for previously manufactured board webs
which comprise the box board.
Another feature and advantage of this invention is ~ ~,
that the apparatus can be adapted to manufacture box board
having more than three layers by mounting additional formers
down~ ream over the fourdrinie ~i~e.
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Still another advantage of this invention is that
it permits an ordinary fourdrinier machine to be adapted to
produce multi-ply corrugated box board.
These and other objects, features and advantages
of the invention will become readily apparent to those
skilled in the art when the description of the preferred
embodiments are read in conjunction with the attached drawings.
IN T~E DRAWINGS
Figure 1 is a side elevational view of the apparatus ¦ ;
as showing the bottom liner, corrugated, and top liner
¦ layers being formed and ccmbined to produce the composite
¦I box board.
I Figure 2 is a partial sectional view of -the forming
¦ roll shell used in the corrugating medium and top liner
¦ formers shown in Figure 1. ,
Figure 3 is a side elevational view of apparatus
similar to Figure 1 except that t~he corrugating medium is
creped off an intermediate pick-off roll.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
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As shown in Figure 1, a looped forming wire 1,
~; such as is used commonly on a fourdrinier-type papermaking
¦ machine, is shown traveling in the dlrection of arrow 22. A
~i first water laid web 4 of fibers is formed and supported on
-l¦ top of wire 1 from the pulp fiber slurry discharged from
¦¦ headbox 40 and is being carried thereon in the same direction
¦¦ at -the same speed. The headbox 40 and equipment, such as
breast roll 41, couch roll 43 and motor 42, for moving and
guiding the fourdrinier forming wire 1 and depositing the
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first web 4, which is the bot-tom liner, on-to the forming wire
may take any one of several forms, all of them well known
to those skilled in the art in the papermaking industry. As
such, they are no-t shown in detail and will not be described
in further detail. Web 4 is formed on screen or wire 1 as the
water drains through. A hydraulic former 5 is mounted in
position above the traveling forming wire 1 in such a manner
that its forming roll 6 rotates in the direction of arrow 23
about a horizontal axis which is parallel to the plane of the
traveling forming wire 1. Forming roll 6 is spaced above the
surface of traveling web 4. A supply header 7 supplies an
aqueous slurry of stock fibers to the slice 1~ which projects
a thin stream of comingled fibers and water onto the surface
of a foraminous element 11, such as a plastic or metal screen
or fabric, which in turn is looped about the periphery of the
cylindrical roll shell 9 which has perforations 10 uniformly
positioned over its operating surfa~e to remove water from the
newly laid layer of corrugating medium 8 into the interior of
the forming roll. This is shown ~ore clearly in Figure 2.
Foraminous screen 11 is shown looped about formlng roll 6 and
separate therefrom, but it could also be part of the integral
construction of the roll 6 surface itself.
Beneath the inner peripheral surface of forming roll
shell 9, are three vacuum, or suction, boxes 15, 16 and 17.
Relatively speaking, the suction in box 15 is less than box 16
which in turn has a greater suction than box 17. Naturally,
the aqueous slurry of board stock contains the most water at
the point where it leaves the former along the slice orifice
arcuately ex-tending substantially over the area of the forming
roll surface immediately above suction box 15 for the width
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of the machine in the cross machine direction. Suction
boxes 15, 16 and 17 similarly extend for substantially the
entire length of the roll shell beneath perforations 10 so
as to remove the water for the entire width of the formed
web 8 of corrugating medium.
Corrugating medium is usually made from chemical
or semi-chemical wood pulps, straw or reclaimed paper stock
in nominal grade weights of about 26 lbs/1000 ft and
approximately 9 points thickness, although heavier weights
are sometimes used. Most of the water is removed from -the
stock -to form the corrugating medium over the suction boxes
15 and 16. Since the pulp board stock contains the most
water when it is initially discharged from the slice opening
onto the foraminous fabric over the cylindrical forming
roll, the vacuum in the first suction box 15 need not be
great to effect substantial water removal and the concomitant
formation of the web on fabric 11. The web forms ~uite
rapidly since board pulp stock is of a fairly high consistency
(i.e. abou-t 1% - 1.2% fibers for corruga-ting medium and
about 0.5% fibers for liner~ both by weigh-t of fibers to
weight of mix (wet basis)), the suction in middle suction
box 16 is higher in order to withdraw more of the remaining
water through the resistance of the already formed board
web. At this point where the web has reached the lower
sector on the forming roll~ the web has been dewatered to
about 10% - 16% bone dry and the suction in the last suction
box 17 does not remove any appreciable amount of water, but
is maintained at a lower level primarily to offset the
centrifugal force on the web to hold it into position on the
forming fabric 11. As the web reaches the region of the
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¦ lower periphery on forming roll 6, a doctor 18 which is
bearing against the foraminous fabric ll, intercepts the
newly formed web 8 along line 26p and produces the corrugations
30, or flutes, in the web which characterizes corrugating
medium.
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The rotational speed of forming roll 6 is such
that the linear surface speed of web 8 is greater than the
i linear surface speed of the bottom web 4 being carried on
¦~ forming wire l. Thus, when the corrugations are produced in
¦I web 8 by the doctor 18, there is enough web material to
¦ permit the formation of corrugations, or flutes, in the web
as well as a slight drape 26 between the location 26p on the
¦I forming roll where the doctor contacts the web and where the
corrugated web falls into contact with bottom web 4 at 26a.
In the preferred embodiment, the corrugating
I medium is adhesively secured to the~bottom liner 4 and the
¦~ top liner l9 which is produced on a second former 5'. This
adhesive may be any suitable glue" such as latex, modified
starch and is applied by a spray from nozzles 27, 28. ~s
¦ the corrugating medium 26 falls upon the adhesive on the
¦ bottom liner, the tips of the corrugations become adhered
I thereto. However, it should be noted that the bonding
Ii between the corrugating medium and the top and bottom liners
is partly achieved without an adhesive undér certain conditions.
Such bonding is known in the paper trade as "ply-bonding"
and is most conducive when the adjacent component webs have
¦ about the same moisture content and are more wet than dry.
¦ Also, it is best when the adjacent webs are of about the
I same stock composition. The fibrils of the still wet fibers
l~ on the adjacent webs comingle when the webs are pressed
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together and this effects a ply-bond. Essentially, the
fibers in separate webs cause the webs to combine in the
same manner in which the fibers in a single web hold it
together.
In both Figures 1 and 3, the second, or downstream,
former is identical to the former producing the corrugating
medium. Therefore, the numerals referring to like components,
items and features are designated with the same numerals as
the former producing the corrugating medium, but the numerals
are primed in order to designate the particular former being
referred to. Further, in the embodiment shown in Figure 3 r
the numerals referring to like components, items and features
also have a subscript "a" for the same reason. The formers
themselves in Figures 1 and 3 are designa-ted with separate
!; numerals.
Former 5' produces a top liner web 19 on forming roll
6' which rotates in the direction of arrow 23' at a linear
surface speed matchiny the speed pf bottom liner 4. Former
5' is mounted to bear against and distend the forming wire 1,
bottom liner 4 and corrugating medium 26 downwardly over a
portion of its arcuate surface between a span defined by two
guide rolls 2, 3 over which the forming wire and newly formed
composite container board pass as the upper liner 19 is
pressed onto the upper flutes of corrugating medium 26 which
are adhesively coated by the spray from nozzle 28. This
positively effects adhesion between the top and bottom liners
19, 4, respectively, to the corrugating medium 26.
I Although the plies are bonded together under the
; ¦I combined effect of the adhesive and the moisture in -the plies
I themselves, the moisture will have the predominate bonding
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effect between the bottom liner and the corrugating medium
while the adhesive will have the predominate bonding effect
between the corrugating medium and the top liner A suction
box 20 is mounted benea-th the forming wire 1 after the last
guide roll 3 to ensure that the composite board web remains
on the forming wire for transfer into the drying section of
the papermaking machine. The remainder of the papermaking
machine downstream from the last former 5', which in this
case consists primarily of drying, reeling and slitting
apparatus are of a design and configuration which are well
known in the papermaking industry, as are their operational
characteristics. Such apparatus form no part of the present ~.
invention and, accordingly, will not be discussed in further
de-tail.
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A variation of the embodiment shown in Figure 1 is
illustrated in Figure 3. Former 34 shown in Figure 3 is
identical to the former 5 shown in Figure 1 except that it
~.¦ is turned around so that forming roll 6a rotates in the
I! direction 32 opposite to that of the forming roll on former
! 5 shown in Figure 1. The only operational difference between
¦¦ formers 34 and 5 is the presence of a pick-off roll 25 on. ;~
former 34 which is mounted- to nip acJainst the corrugating
l medium web over the lower portion of the forming roll 6a
! surface to pick-off the web 8a to reverse its direction to
travel in the same direction as bottom liner 4. A doctor
18a bears against the surface of pick-off roll 25 to form ¦ :¦
the flu-tes or corrugations in web 8a along line 26pa before
Il the web falls in-to contact with -the traveling bottom liner 4
¦ at 26aa. The advantage of the use of the pick-off roll 25
Il is that the doctor then bears against its smooth, continuous
¦¦ cylindrical surface and does not touch the foraminous forming
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fabric lla as the doctor does on former 5 in Figure 1. This
precludes any potential wearing or tearing of the forming
fabric.
In both the embodiments shown in Figures 1 and 3, the
formation of the webs in formers 34, 34' and 5, 5l, respec-
tively, is the same as is the manner in which the adhesive is
applied to the bottom liner and corrugating medium to effect
bonding between the corrugating medium and the bottom and top
liners to form the composite corrugated combined board. Either
embodimen-t can be expected to produce this board at speeds of
about 300 fpm to about 1200 fpm. The moisture level in the
top linerboard will range from about 88% to about 94%. The
moisture level in the corrugating medium will range from about
84% to about 88% and from about 86% to about 90% in the top
linerboard.
Thus, a method and apparatus for manufacturing
corrugated combined board having an inner corruga-ting medium
bonded to top and bottom liners has been described. Clearly,
this .;.nvention can be utilized to make more than three ply
board. Merely by adding another corrugating medium former
after the last liner former and then another liner former, a
five ply corrugated board can be made.
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