[0001] The present invention relates to a multilayer headbox structure for a fiber web machine,
such as a paper or board making machine, for forming a fiber web, and to a method
for forming a fiber web in a forming section of a fiber web machine.
Description of the prior art
[0002] At the beginning of a wet end of a paper or board making machine, a headbox structure
basically serves to supply mainly liquid substances such as water and/or a pulp suspension
liquid onto a wire of a forming section. Additives such as refined fibers, fillers,
cationic polymers such as cationic starch, etc. can be added to the water and/or pulp
suspension liquid. These liquid substances are fed to a headbox by means of a water
supply or feed water supply. In the forming section, the substances applied onto a
forming wire are then dewatered to form a fiber web, such as a paper or board web.
Afterward it is then further transferred to a press section for additional dewatering
and a dryer section in which the formed fiber web is dried. Further treatment depends
on the respective requirements of the product.
[0003] Thus, it is the main task of such a headbox to evenly distribute these liquid substances
in the width direction ("cross direction" or "CD") of the paper or board making machine
as well as in the running direction of the fiber web to be formed ("machine direction"
or "MD") on the wire. In this regard, it is also important to supply the liquid substances
in a layered manner in order to ensure the required properties and quality of the
later paper or board web.
[0004] A multilayer headbox for a fiber web machine, such as a paper or board making machine,
is known from
WO 2009/115479 A1. According to this headbox, first supply means serve to supply a fibrous suspension
into a guide device which is connected to a nozzle out of which the fibrous suspension
emerges via a gap. A dosing device serves to dose at least one additive such as a
filler material or a chemical of any type, in particular a paper chemical such as
a retention agent. The headbox has two layers comprising a suspension and a central
layer comprising water. All of these layers are guided separately in the guide device.
In order to improve the formation of different liquid layers, blades are provided
in the nozzle to achieve the formation of the liquid layers.
[0005] Nevertheless, there still exists the problem that, because of turbulences in the
individual liquid layers, the mixing of the liquid layers largely takes place as soon
as the liquid layers have passed the blades. Accordingly, the individual layers do
no longer exhibit the required consistency but rather a mixture of respectively adjacent
liquid layers. Thus, unwanted interaction as well as a chemical reaction among the
additives may take place, so that a degradation of the quality of the fiber web to
be formed has to be expected.
[0006] EP 2 784 213 A1 shows a multilayer headbox structure for a fiber web machine for forming a fiber
web, comprising a multilayer headbox having a turbulence generator and a nozzle chamber
having two converging walls forming a nozzle outlet. The turbulence generator has
a plurality of diffusers creating turbulence in liquids supplied into each respective
diffuser via feeding means for feeding the liquids, each of the diffusers having an
outlet into the nozzle chamber. A single central diffuser is provided which is connected
with feeding means feeding fresh water, dilution water, and/or white water into said
central diffuser. The central diffuser has two blades arranged at its outlet and extending
into the nozzle chamber in a converging manner, the blades separating the fresh water,
dilution water, and/or white water as the liquid flowing through the central diffuser
from the liquids flowing through adjacent diffusers. The central diffuser is arranged
between a top ply diffuser and a back ply diffuser, in which top ply diffuser top
ply pulp suspension as the liquid flows through the top ply diffuser for forming a
top ply of the fiber web and in which back ply diffuser back ply pulp suspension as
the liquid flows through the back ply diffuser for forming a back ply of the fiber
web.
Summary of the invention
[0007] Thus, it is an object of the present invention to provide a multilayer headbox structure
for a fiber web machine for forming a fiber web and a method for forming a fiber web
in a forming section of a fiber web machine, which are capable of enabling formation
of individual pure liquid surface side layers having clear boundaries and supplying
these pure liquid layers into a forming section of the fiber web machine, such as
a paper or board making machine.
[0008] The object of the present invention is achieved by a multilayer headbox structure
having the features of claim 1 for a fiber web machine for forming a fiber web and
by a method having the features of claim 11 for forming a fiber web in a forming section
of a fiber web machine.
[0009] Further advantageous developments of the present invention are defined in the dependent
claims.
[0010] According to an advantage of the present invention, it is possible that a three layer
fiber web (also called as a "three ply product") can be formed by one headbox structure
(one headbox with one forming unit) which dewatering capacity is able to dewater stock
which is fed to the forming section of the fiber web machine.
[0011] According to an aspect of the present invention, a multilayer headbox structure for
a fiber web machine for forming a fiber web is provided, which comprises a multilayer
headbox having a turbulence generator and a nozzle chamber having two converging walls
forming a nozzle outlet. The turbulence generator has a plurality of diffusers creating
turbulence in liquids supplied into each respective diffuser via feeding means for
feeding the liquids, each of the diffusers having an outlet into the nozzle chamber,
wherein central diffusers of the plurality of diffusers comprise a first central diffuser
and a second central diffuser, the first central diffuser is connected with feeding
means feeding fresh water, dilution water, and/or white water into the first central
diffuser, the first central diffuser has two blades arranged at its outlet and extending
into the nozzle chamber in a converging manner, the blades separating the fresh water,
dilution water, and/or white water as the liquid flowing through the first central
diffuser from the liquids flowing through adjacent diffusers, the second central diffuser
is connected with feeding means feeding pulp suspension into the second central diffuser,
the second central diffuser has an additional blade and a blade arranged at its outlet,
the additional blade and the blade extend into the nozzle chamber in a converging
manner, and the additional blade has a shorter length than the adjacent blade of the
first central diffuser and the blade of the second central diffuser, and the central
diffusers are arranged between a top ply diffuser and a back ply diffuser, in which
top ply diffuser top ply pulp suspension as the liquid flows through the top ply diffuser
for forming a top ply of the fiber web and in which back ply diffuser back ply pulp
suspension as the liquid flows through the back ply diffuser for forming a back ply
of the fiber web.
[0012] In the structure of the headbox as described above, the plurality of diffusers at
least comprises four diffusers, i.e. the top ply diffuser, the first central diffuser,
the second central diffuser and the back ply diffuser. The top ply diffuser is configured
to form the top ply (top surface side) of the fiber web to be formed, and the back
ply diffuser is configured to form the back ply (back surface side) to the fiber web
to be formed.
[0013] Furthermore, the central diffusers comprise at least the first central diffuser and
the second central diffuser, which are arranged between said top ply diffuser and
back ply diffuser. According to the aspect of the present invention, the first central
diffuser is connected with the feeding means feeding fresh water, dilution water,
and/or white water into the first central diffuser, which is either arranged next
(adjacent) to the top ply diffuser or the back ply diffuser. Here, the first central
diffuser has the two blades which are arranged at its outlet and which extend into
the nozzle chamber in a converging manner such that these blades separate the fresh
water, dilution water, and/or white water as the liquid flowing through the first
central diffuser from the liquids flowing through the adjacent diffusers, i.e. either
between the top ply diffuser and the second central diffuser or between the back ply
diffuser and the second central diffuser. The second central diffuser is connected
with the feeding means for feeding pulp or stock suspension.
[0014] Further, the second central diffuser has the additional blade arranged at the outlet
and adjacent to one of the two blades of the first central diffuser, which additional
blade of the second central diffuser has a shorter length than said adjacent blade
of the first central diffuser. Due to this positioning of the blade tips of the first
and second central diffusers, a first central layer of the fiber web to be formed,
which layer consists mainly of water (fresh water, dilution water, and/or white water),
does not get mixed with the adjacent pulp suspension layers. Accordingly, the first
central diffuser is configured to form a boundary layer between the adjacent pulp
suspension layers. Thus, while in each of the adjacent diffusers, caused by the generated
turbulences, a good distribution of the substances in the respective liquid takes
place, the individual liquids stay separated from each other due to the blades of
the first central layer. Furthermore, another effect of the blades is to maintain
the turbulence in the boundary areas of each liquid layer. The second central layer
forms a middle layer, which pulp or stock properties advantageously differs from the
top ply suspension and the bottom ply suspension. For example, the second central
layer purity can be less or lower than the top ply purity, but it is still good enough
to separate stock properties. This helps dewatering capacity in the forming section.
[0015] Accordingly, the different liquids can be supplied to a wire in a forming section
in a layered manner, thus maintaining the purity of the individual liquid layers.
Since no mixing of the layers can take place, various additives such as filler materials,
refined fibers, cationic starch, etc. in the water layer maintain their position in
the center of the web to be formed, but are not distributed to the adjacent pulp suspension
layers. Accordingly, a degradation of the additives caused by mixing and a subsequent
interaction with materials from an adjacent liquid layer can be avoided. Thus, the
desired properties of the additives are maintained. Accordingly, adjusting the required
properties of the fiber web to be formed is easily enabled by supplying the respective
materials with the respective layer, because a degradation of the individual material
properties of the additives due to mixing with the respectively adjacent layer cannot
take place.
[0016] Besides, different pulp suspension qualities can be fed via the top ply diffuser,
the second central diffuser and the back ply diffuser. Generally, the top ply suspension
has the best quality and the second central layer suspension has the worst quality
among said pulp suspensions. Thus, raw material and their cost for forming a fiber
web can be reduced.
[0017] In case there are more than four diffusers provided in said multilayer headbox structure,
a second central diffuser stock (for example, formed of two second central diffusers)
is separated from the adjacent top ply diffuser or back ply diffuser by means of a
further blade arranged at the outlet, which the further blade has a longer length
than the adjacent blade(s) of the second central diffuser and of the top ply diffuser
or back ply diffuser. That is, one may say that blade lengths in the slice channel
(nozzle chamber) are configured in such a manner that blades between different stock
layers (i.e. between the back/top ply layer and the second central layer) are longer
than blade(s) which are in the middle of such stock layers. The length of such further
blade(s) may be as long as the length of said two blades. Advantageously, further
tip blade distance from the nozzle outlet (slice opening) can, for example, be from
1 to 50 mm, wherein the tip of blade is inside the nozzle outlet.
[0018] Furthermore, the multilayer headbox structure for a fiber web machine for forming
a fiber web according to the present invention is preferably used for manufacturing
(forming) SBS (Solid Bleached Board) or FBB (Folding Boxboard) grades, wherein its
middle layer stock is typically hardwood, softwood, CTMP (Chemi Thermo Mechanical
Pulp) or broke. Accordingly, a bulky middle layer can be provided.
[0019] Preferably, the top ply diffuser is connected with feeding means feeding the top
ply pulp suspension into the top ply diffuser, and the back ply diffuser is connected
with feeding means feeding the back ply pulp suspension into the back ply diffuser.
Accordingly, different pulp suspensions can be fed to the respective ply diffusers.
[0020] Alternatively, the top ply diffuser and the back ply diffuser can be connected with
a single feeding means feeding the same pulp suspension as the top ply pulp suspension
and the back ply pulp suspension into the top ply diffuser and into the back ply diffuser.
Thus, the same pulp suspension can be used for forming the top ply and the back ply.
Besides, the structure of the multilayer headbox and forming section can be simplified
and thus its cost can be further reduced.
[0021] Preferably, the top ply diffuser is formed between an adjacent blade of the first
central diffuser and one of the two converging walls of the nozzle chamber, and the
back ply diffuser is formed between the additional blade of the second central diffuser
and the other of the two converging walls of the nozzle chamber. Thus, a compact and
cheap multilayer headbox structure is provided for forming a three layer fiber web.
[0022] Preferably, the blades are arranged in a staggered manner in the above-mentioned
headbox structures. Thereby, the accuracy of the different liquid layers can be improved.
[0023] Preferably, at least the blades of the first central diffuser extend beyond the nozzle
chamber to an outside of the multilayer headbox. Thereby, the formation of the liquid
layers directly on the wire is ensured. Accordingly, no mixing at the boundaries between
the first central water layer and the pulp suspension layers takes place.
[0024] This can also be applied in case said further blade(s) is(are) provided. That is,
the further blade(s) may also extend beyond the nozzle chamber to the outside of the
multilayer headbox. Thus, mixing at the boundaries between the second central pulp
suspension layer and the adjacent pulp suspension layers can be further reduced.
[0025] Preferably, tips of the blades of the first central diffuser are arranged inside
the nozzle chamber. Thereby, a distance to a nozzle outlet (also referred to as slice
opening) can be set to be as small as possible in order to have the central water
layer contact the other liquid layers as late as possible. A distance between the
tips of the blades of the first central diffuser and the nozzle outlet (slice opening)
can, for example, be set from 1 to 50 mm.
[0026] Preferably, the blades are mounted at the respective diffuser outlet in a pivoted
manner. Preferably, each blade is arranged in a freely pivotable manner. Thereby,
the blade pivots about a hinge or joint provided at the end of the respective diffuser
tube. Accordingly, pressure differences between the various liquid layers can be balanced,
leading to a further reduction of turbulences at the boundaries of the individual
liquid layers.
[0027] Preferably, wall surfaces of each of the diffusers as well as of the blades have
a smooth and uniform structure in order to prevent agitation of the respective liquid
at its boundary. Thus, while flowing through and along diffuser tubes and then between
the blades through the nozzle chamber, the respective liquid layers are calmed down
at their boundaries such that an interaction between the different liquid layers after
their unification is avoided.
[0028] Preferably, at least one adjustable slice tip is provided at the nozzle outlet. Thus,
it is possible to adapt the size of the nozzle outlet, thereby adjusting the output
of the liquid layers.
[0029] Preferably, the length of the additional blade is smaller than or equal to 95% of
the length of the blades of the first central diffuser. Thus, a compact multilayer
headbox structure can be provided.
[0030] According to another aspect of the present invention, a fiber web machine is provided
which comprises a forming section having a wire guided around guiding rolls and forming
a closed loop, and the multilayer headbox structure as mentioned above which is configured
to eject the top ply pulp suspension, back ply pulp suspension, middle ply pulp suspension,
and fresh water, dilution water and/or white water in a layered manner onto the wire
to form a fiber web having multiple plies.
[0031] According to a further aspect of the present invention, a method for forming a fiber
web in a forming section of a fiber web machine is provided, comprising the steps
of feeding fresh water, dilution water, and/or white water into a first central diffuser
of a multilayer headbox structure, feeding pulp suspension into a second central diffuser
of the multilayer headbox structure, which second central diffuser is adjacently arranged
to the first central diffuser within a multilayer headbox of the multilayer headbox
structure, feeding top ply pulp suspension into a top ply diffuser of the multilayer
headbox structure, which top ply diffuser forms a top ply of the fiber web which is
adjacently arranged to the first central diffuser, feeding back ply pulp suspension
into a back ply diffuser of the multilayer headbox structure, which back ply diffuser
forms a back ply of the fiber web which is adjacently arranged to the second central
diffuser, guiding the fresh water, dilution water, and/or white water, and the respective
pulp suspensions through the corresponding diffusers to eject them onto a wire of
the forming section as stock plies of liquid substances such that the first central
ply consisting of the fresh water, dilution water, and/or white water forms a boundary
layer between the top ply consisting of the pulp suspension and the second central
ply pulp consisting of the pulp suspension, and dewatering the liquid substances to
form the fiber web.
[0032] Preferably, in the feeding steps of the top ply pulp suspension and the back ply
pulp suspension, the same pulp suspension as the top ply pulp suspension and the back
ply pulp suspension are fed into the top ply diffuser and into the back ply diffuser.
Thus, the same quality for the top ply and the back ply of the fiber web to be formed
can be achieved.
[0033] In particular, the above aspects of the present invention provide an advantage in
that the first central water layer and the pulp suspension layers (also known as stock
layers) can be combined at the nozzle outlet, but can maintain their purity because
turbulences in the boundary areas of the respective layers are sufficiently maintained
to such an extent that a mixing of the individual layers is prevented. The combination
of layers preferably takes place at a short distance upstream of the nozzle outlet.
However, in certain cases, the blades may extend beyond the nozzle outlet, so that
the individual layers are combined only outside of the nozzle, or the blade lips may
be arranged in the slice channel, which is formed by the adjustable slice lip.
Brief description of the drawings
[0034] Further effects, advantages and features of the present invention will become apparent
from a disclosure of the enclosed drawings showing preferred embodiments of the present
invention, which are discussed below in further detail.
Fig. 1 schematically shows a sectional view of a headbox structure according to a
first embodiment of the present invention.
Fig. 2 schematically shows a sectional view of a headbox structure according to a
second embodiment of the present invention.
Detailed description of the preferred embodiments
[0035] Figure 1 is a sectional view of a multilayer headbox structure according to the present
invention for a fiber web machine, such as a paper or board making machine, for forming
a fiber web.
[0036] In Figure 1, from the left to the right, a headbox comprises headers 40, 41, 42,
43 which are arranged in said figure at the bottom of the left side. The liquids,
such as pulp suspension liquid and water, are supplied from the headers 40, 41, 42,
43 to intermediate chambers 65, 66, 67, 68 via manifold pipes 60, 61, 62, 63 acting
as feeding means, respectively.
[0037] The intermediate chambers 65, 66, 67, 68 acting as equalizing chambers are optionally
provided. That is, the headers 40, 41, 42, 43 can be directly or integrally connected
to the headbox.
[0038] Further, a diffuser chamber in which diffuser tubes 1, 3, 4, 5, 7, 8, 9 acting as
diffusers are provided, and a nozzle chamber having converging walls 21, 22 forming
a slice opening (nozzle outlet) 24 are provided. Each of the diffuser tubes 1, 3,
4, 5, 7, 8, 9 consists of several diffuser tubes arranged in the cross machine direction.
[0039] Turbulence generator pipes 71, 73, 75, 77 acting as feeding means establish communication
from the headers 40, 41, 42, 43 to the diffuser tubes 1, 3, 4, 5, 7, 8, 9. Blades
11, 12, 13, 14, 15, 16 are respectively attached to outlets of the diffuser tubes
1, 3, 4, 5, 7, 8, 9 via joints 31, 32, 33, 34, 35, 36.
[0040] The blades 11, 12, 13, 14, 15, 16 may have a wedge-shaped cross-section, in which
a thick end is attached to the respective diffuser tubes while a thin end projects
towards the slice opening 24. The blades 11, 12, 13, 14, 15, 16 are provided in a
staggered manner.
[0041] Furthermore, a dilution water header 57 is provided and connected with the manifold
pipe 61 via dilution water valves 59 for controlling the web basis weight profile
in cross machine direction. The dilution water valves 59 are arranged in 30 to 150
mm intervals in cross machine direction of the headbox.
[0042] From the headers 40, 41, 42, 43, various liquids are pumped via the manifold pipes
60, 61, 62, 63 and the intermediate chambers 65, 66, 67, 68 to the turbulence generator
pipes 71, 73, 75, 77 and thus to the respective diffuser tubes 1, 3, 4, 5, 7, 8, 9.
[0043] According to the present invention, water such as fresh water, dilution water, and/or
white water is fed from the header 41 to the diffuser tubes 3 via the manifold pipe
61, the intermediate chamber 66 and the turbulence generator pipes 71, while the other
diffuser tubes 1, 4, 5, 7, 8 and 9 are supplied with a stock or pulp suspension. After
having entered the respective diffuser tubes, turbulence is generated in the respective
liquids in order to achieve a desired distribution of the additives and materials
present in the respective liquids. In particular, in the water supplied via the turbulence
generator pipe 71 to the diffuser tubes 3 (first central layer liquid), a high amount
of filler, here water, is present. The fiber consistency in this first central layer
liquid fed from the header 41 is remarkably lower than the fiber consistency of the
other liquid layers.
[0044] In the nozzle chamber, the blades 11, 12, 13, 14, 15, 16 maintain the individual
liquid layers separate before the liquids are ejected towards a forming section of
a fiber web making machine. Each of the blades 11, 12, 13, 14, 15, 16 is attached
to a wall portion between the respective diffuser tubes 1, 3, 4, 5, 7, 8, 9 via the
joints 31, 33, 35, and 37 in a freely pivotable manner. Thus, apart from the uppermost
and lowermost diffuser tubes 5 and 9, each of the diffuser tubes 1, 3, 4, 7 and 8
is respectively continued by two of blades 11, 12, 13, 14, 15, 16. The uppermost and
lowermost diffuser tubes 5 and 9 are continued by the blade 15 and a nozzle chamber
wall 22 and the blade 16 and a nozzle chamber wall 21, respectively.
[0045] At the right side end of the diffuser tubes 1, 3, 4, 5, 7, 8, 9 in Figure 1, a transition
from the diffuser tubes 1, 3, 4, 5, 7, 8, 9 towards the nozzle chamber, i.e. the respective
blades 11, 12, 13, 14, 15, 16 and the nozzle chamber walls 21 and 22, is formed in
a uniform and smooth manner in order to avoid obstacles agitating the respective flow
and liquid. This serves to avoid a further generation of turbulences and a corresponding
agitation of the boundaries of the respective liquid layers emerging from the diffuser
tubes 1, 3, 4, 5, 7, 8, 9 in between the blades 11, 12, 13, 14, 15, 16 and nozzle
chamber walls 21 and 22, respectively.
[0046] Accordingly, the individual liquids flowing towards the slice opening 24 through
the nozzle chamber are still separated by the respective blades 11, 12, 13, 14, 15,
16. Surface friction of the blades 11, 12, 13, 14, 15, 16 maintains turbulence in
the boundary areas of the individual liquid layers. Therefore, when unifying the stock
or pulp suspension liquid flows which are separated by the blades 11, 14 and 16 at
their tip ends, an interaction between the individual liquid layers does not take
place, since the turbulence in the respective boundary regions is still small-scale.
Thus, stock or pulp suspension liquid flows will then merge together downstream of
the tip ends of said blades. The length of the blades 11, 14 and 16 can be chosen
such that there is sufficient distance to the tip ends of the blades 12, 13 and 15
for ensuring that individual stock or pulp suspension will merge together. The length
of the blades 11, 14 and 16 is preferably up to 95% of the length of the central blades
12, 13 and 15. The blades 12, 13 and 15 and the nozzle chamber walls 21 and 22 maintain
turbulence in the water, stock or pulp suspension liquid flows.
[0047] The same effect as described above occurs when unifying the above-described liquid
layers consisting of stock or pulp suspension liquid with the water layer flowing
between blades 12 and 13 at their tip ends, respectively. As already mentioned above,
the tip ends of these blades 12 and 13, respectively, are arranged closer towards
the slice opening 24 than the tip ends of the blades 11, 14, 16. That is, the lengths
of blades 12 and 13 separating the water layer from the stock or pulp suspension liquid
layers exceed the lengths of blades 11, 14 and 16, respectively. In this regard, it
also has to be noted that, although the lengths of the blades 12 and 13 correspond
to each other in the drawings, blades 12 and 13 can have different lengths, but it
is important that their lengths exceed the respective lengths of the other blades
11, 14 and 16. Because the fiber consistency in the water layer is very low, turbulence
will remain active in the slice flow from the headbox until the web forming process
starts in the forming section.
[0048] Preferably, the length of the blade 15 is equal to one of the lengths of the blades
12 and 13.
[0049] After unifying the water layer with the stock or pulp suspension liquid layers, the
liquids are ejected via the slice opening 24 in a layered manner onto a wire or fabric
of a forming section for further treatment (not shown), such as dewatering, pressing
and drying. The distance from the tip ends of the blades 12, 13 and 15 to the forming
section is short for ensuring the layered structure.
[0050] For adjusting the ejected liquid flow, a slice lip 23 is provided at the upper nozzle
chamber wall 22. The slice lip 23 can be adjusted in its position, i.e. in particular
its reach can be adjusted by known means such as horizontal or vertical slice positioners,
micro adjusters, etc. To simplify matters, these are not shown in the drawing.
[0051] Furthermore, due to the layered structure of the liquids, i.e. the water layer being
sandwiched between the stock or pulp suspension liquid layers, the additives and other
substances present in the respective liquid layers do not interact with each other,
because a mixing of the individual liquid layers can be surely excluded. Thus, adjusting
the properties of the web, i.e. paper or board web, to be formed by introducing additives
or other substances into the stock or pulp suspension liquids/water is facilitated.
Furthermore, particularly the amount of filler in the water layer can be increased,
thereby achieving a remarkable cost reduction compared to paper or board having a
comparably high filler content.
[0052] In other words, as shown in the embodiment of Figure 1, seven diffusers 1, 3, 4,
5, 7, 8, 9 are provided in said multilayer headbox structure. Here, the central diffusers
comprise a first central diffuser 3 and a second central diffuser stack formed by
second central diffusers 1 and 7. The first central diffuser 3 is connected with the
feeding means for feeding fresh water, dilution water, and/or white water into the
first central diffuser 3. The first central diffuser 3 has the two blades 12, 13 arranged
at its outlet and extending into the nozzle chamber in a converging manner, the blades
separating the fresh water, dilution water, and/or white water as the liquid flowing
through the first central diffuser 3 from the liquids flowing through adjacent diffusers
1, 4. The second central diffuser stack is formed by the second central diffusers
1 and 7. This second central diffuser stack is separated from the adjacent back ply
diffuser stack formed by the back ply diffusers 8 and 9 by means of the elongated
blade 15 (the further blade) arranged at the diffuser outlet, which elongated blade
has a longer length than the adjacent blades 14, 16 of the second central diffuser
stack and of the back ply diffuser stack. The second central diffuser stack thus has
the additional blade 14 arranged at the outlet, and the additional blade 14 has a
shorter length than the adjacent blade 13 of the first central diffuser 3. The first
central diffuser 3 is arranged between a top ply diffuser stack formed by the top
ply diffusers 4, 5 and the second central diffuser stack. In the top ply diffusers
4, 5 top ply pulp suspension as the liquid flows through the top ply diffusers 4,
5 for forming the top ply of the fiber web and in the back ply diffusers 8, 9 back
ply pulp suspension as the liquid flows through the back ply diffusers 8, 9 for forming
the back ply of the fiber web.
[0053] That is, one may generally say that blade lengths in the slice channel (nozzle chamber)
are configured in such a manner that blades between different stock layers (i.e. between
the back/top ply layer and the second central layer) are longer than blade(s) which
are in the central of such stock layers. The length of such further blade(s) may be
as long as the length of said two blades of the first central diffuser 3.
[0054] Figure 2 shows another embodiment of a multilayer headbox structure according to
the present invention. In Figure 2, the same and equivalent elements already described
above have been assigned the same reference signs; the description thereof will not
be repeated.
[0055] Here, the top ply of the web to be formed is arranged at the bottom of the figure,
and the back ply of the web to be formed is arranged at the top of the figure. Further,
the second central layer is formed from three diffuser tubes 1, 6 and 7 and respective
blades 13 to 15 as shown in said figure.
[0056] Furthermore, instead of providing a dilution water header at the top ply side of
the multilayer headbox structure as shown in Figure 1, a dilution water header 57
is provided and connected with the manifold pipe 62 via a dilution water valve or
valves 59 for controlling the web basis weight profile in cross machine direction.
That is, the second central layer of the web to be formed can be provided with such
a dilution water header so that raw material for forming the pulp suspension for the
second central layer can be further reduced.
[0057] While the present invention has been described by means of the above-described preferred
embodiments, it has to be noted that the present invention is not limited thereto,
i.e. the scope of the present invention is defined by the attached claims.
[0058] For example, the headbox itself is not limited to the described structure comprising
the turbulence generator pipe, the diffuser chamber and the nozzle chamber, but one
may employ a headbox in which the header is directly connected to the diffuser. In
such a headbox, there is only one set of tubes (diffuser tubes) present between the
header and the diffuser chamber.
[0059] Apart from what has been mentioned above, the present invention may also be applied
to other headbox structures, such as a headbox comprising a mixing chamber where dilution
water is introduced into the pulp suspension liquids.
[0060] While in the above description the terms "filler" and "additives" have been used
as an example of substances added to the stock, pulp suspension or water, it is to
be noted that, apart from the ones already mentioned, such additives can be refined
fibers, cationic polymers, in particular cationic starch, retention chemicals or retention
aid helpers, in particular microparticles or colloidal silica.
[0061] In a paper or board making machine, to which the headbox of the present invention
can be applied, the additives can be admixed to the pulp in a machine chest where
the stock and the white water are mixed. In this way, the additives will become easily
distributed and diluted within the pulp without any additional process elements having
to be arranged.
[0062] However, it is desired to further increase the bonding strength of the paper to be
produced. That is, if the bonding strength between the stock fibers can be further
increased, the percentage of stock within the pulp can be further reduced, for instance.
This missing percentage can then be replaced by fillers which are less expensive.
An increased bonding strength can, however, certainly also lead to a more resistant
paper.
[0063] According to the present invention, the water layer can be formed as the first central
layer being adjacently arranged to either the top ply or the back ply of the web to
be formed, and the purity of the water layer can be maintained when ejecting the unified
liquids out of the slice opening. Further, additives can also be added to the water
forming the first central water layer. Such additives can be refined fibers, cationic
polymers, in particular cationic starch, fillers (like PCC or GCC), retention chemicals
or retention aid helpers, in particular microparticles or colloidal silica. This is
advantageous insofar as there is no interaction between the different liquid layers
and it is possible to remarkably increase the filler content. Thus, the cost involved
in the production of paper or board can be remarkably reduced while the desired paper
or board properties, in particular paper strength, can nevertheless be achieved.
[0064] Furthermore, according to the present invention, the above-mentioned multilayer headbox
structure and its forming method for forming a fiber web can be preferably used for
manufacturing (forming) SBS (Solid Bleached Board) or FBB (Folding Boxboard) grades,
wherein its middle layer stock is typically hardwood, softwood, CTMP (Chemi Thermo
Mechanical Pulp) or broke. Thus, a bulky middle layer can be provided.
1. A multilayer headbox structure for a fiber web machine for forming a fiber web, comprising
a multilayer headbox having a turbulence generator and a nozzle chamber having two
converging walls (21, 22) forming a nozzle outlet (24),
the turbulence generator having a plurality of diffusers (1, 3, 4, 5, 6, 7, 8, 9)
creating turbulence in liquids supplied into each respective diffuser (1, 3, 4, 5,
6, 7, 8, 9) via feeding means (71, 73, 75, 77) for feeding the liquids, each of the
diffusers (1, 3, 4, 5, 6, 7, 8, 9) having an outlet into the nozzle chamber, wherein
central diffusers (1, 3, 7) of the plurality of diffusers (1, 3, 4, 5, 6, 7, 8, 9)
comprise a first central diffuser (3) and a second central diffuser (1, 6, 7),
the first central diffuser (3) is connected with feeding means (71) feeding fresh
water, dilution water, and/or white water into the first central diffuser (3),
the first central diffuser (3) has two blades (12, 13) arranged at its outlet and
extending into the nozzle chamber in a converging manner, the blades (12, 13) separating
the fresh water, dilution water, and/or white water as the liquid flowing through
the first central diffuser (3) from the liquids flowing through adjacent diffusers
(1, 4),
the second central diffuser (1, 6, 7) is connected with feeding means (75) feeding
pulp suspension into the second central diffuser (1, 6, 7),
the second central diffuser (1, 6, 7) has an additional blade (14) and a further blade
(15) arranged at the outlet, the additional blade (14) and the further blade (15)
extend into the nozzle chamber in a converging manner, and the additional blade (14)
has a shorter length than the adjacent blade (13) of the first central diffuser (3)
and the further blade (15) of the second central diffuser (1, 6, 7), and
the central diffusers (1, 3, 7) are arranged between a top ply diffuser (4, 5) and
a back ply diffuser (8, 9), in which top ply diffuser (4, 5) top ply pulp suspension
as the liquid flows through the top ply diffuser (4, 5) for forming a top ply of the
fiber web and in which back ply diffuser (8, 9) back ply pulp suspension as the liquid
flows through the back ply diffuser (8, 9) for forming a back ply of the fiber web.
2. The multilayer headbox structure for a fiber web machine for forming a fiber web according
to claim 1, wherein
the top ply diffuser (4, 5) is connected with feeding means (73) feeding the top ply
pulp suspension into the top ply diffuser (4, 5), and
the back ply diffuser (8, 9) is connected with feeding means (77) feeding the back
ply pulp suspension into the back ply diffuser (8, 9).
3. The multilayer headbox structure for a fiber web machine for forming a fiber web according
to claim 1, wherein
the top ply diffuser (4, 5) and the back ply diffuser (8, 9) are connected with a
single feeding means feeding the same pulp suspension as the top ply pulp suspension
and the back ply pulp suspension into the top ply diffuser (4, 5) and into the back
ply diffuser (8, 9).
4. The multilayer headbox structure for a fiber web machine for forming a fiber web according
to any of claims 1 to 3, wherein
at least parts of the top ply diffuser (4, 5) is formed between an adjacent blade
(12) of the first central diffuser (3) and one (22) of the two converging walls (21,
22) of the nozzle chamber, and
at least parts of the back ply diffuser (8, 9) is formed between the further blade
(15) of the second central diffuser (1, 6, 7) and the other (21) of the two converging
walls (21, 22) of the nozzle chamber.
5. The multilayer headbox structure for a fiber web machine for forming a fiber web according
to any of claims 1 to 4, wherein the blades (11 to 16) are arranged in a staggered
manner.
6. The multilayer headbox structure for a fiber web machine for forming a fiber web according
to any of claims 1 to 5, wherein the blades (12, 13) of the first central diffuser
(3) extend beyond the nozzle chamber to an outside of the multilayer headbox.
7. The multilayer headbox structure for a fiber web machine for forming a fiber web according
to any of claims 1 to 5, wherein tips of the blades (12, 13) of the first central
diffuser (3) are arranged inside the nozzle chamber.
8. The multilayer headbox structure for a fiber web machine for forming a fiber web according
to any of claims 1 to 7, wherein at least one adjustable slice lip (23) is provided
at the nozzle outlet (24).
9. The multilayer headbox structure for a fiber web machine for forming a fiber web according
to any of claims 1 to 8, wherein the length of the additional blade (14) is smaller
than or equal to 95% of the length of the blades (12, 13) of the first central diffuser
(3).
10. A fiber web machine comprising:
a forming section having a wire guided around guiding rolls and forming a closed loop,
and
the multilayer headbox structure according to any of claims 1 to 9 configured to eject
the top ply pulp suspension, back ply pulp suspension, pulp suspension, and fresh
water, dilution water and/or white water in a layered manner onto the wire to from
a fiber web having multiple plies.
11. A method for forming a fiber web in a forming section of a fiber web machine, comprising
the steps of:
feeding fresh water, dilution water, and/or white water into a first central diffuser
(3) of a multilayer headbox structure,
feeding pulp suspension into a second central diffuser (1, 6, 7) of the multilayer
headbox structure, which second central diffuser (1, 6, 7) being adjacently arranged
to the first central diffuser (1) within of a multilayer headbox of the multilayer
headbox structure,
feeding top ply pulp suspension into a top ply diffuser (4, 5) of the multilayer headbox
structure, which top ply diffuser (4, 5) forming a top ply of the fiber web being
adjacently arranged to the first central diffuser (3) or the second central diffuser
(1, 6, 7)
feeding back ply pulp suspension into a back ply diffuser (8, 9) of the multilayer
headbox structure, which back ply diffuser (8, 9) forming a back ply of the fiber
web being adjacently arranged to the second central diffuser (1, 6, 7) or the first
central diffuser (3),
guiding the fresh water, dilution water, and/or white water, and the respective pulp
suspensions through the corresponding diffusers (1, 3, 4, 5, 6, 7, 8, 9) to eject
them onto a wire of the forming section as stock plies of liquid substances such that
the first central ply consisting of the fresh water, dilution water, and/or white
water forms a boundary layer between the top ply or back ply consisting of the pulp
suspension and the second central ply pulp consisting of the pulp suspension, and
dewatering the liquid substances to form the fiber web.
12. The method for forming a fiber web in a forming section of a fiber web machine, comprising
the steps of according to claim 11, wherein
in the feeding steps of the top ply pulp suspension and the back ply pulp suspension,
the same pulp suspension as the top ply pulp suspension and the back ply pulp suspension
are fed into the top ply diffuser and into the back ply diffuser.
1. Mehrschichtige Stoffauflaufstruktur für eine Faserstoffbahnmaschine zum Ausbilden
einer Faserstoffbahn, die einen mehrschichtigen Stoffauflauf mit einem Turbulenzerzeuger
und einer Düsenkammer mit zwei konvergierenden Wänden (21, 22) aufweist, die einen
Düsenauslass (24) ausbilden, wobei
der Turbulenzerzeuger eine Vielzahl von Diffusoren (1, 3, 4, 5, 6, 7, 8, 9) hat, die
eine Turbulenz in Flüssigkeiten erzeugen, die in jeden zugehörigen Diffusor (1, 3,
4, 5, 6, 7, 8, 9) über eine Fördereinrichtung (71, 73, 75, 77) zum Fördern der Flüssigkeiten
zugeführt werden, wobei jeder der Diffusoren (1, 3, 4, 5, 6, 7, 8, 9) einen Auslass
in die Düsenkammer hat,
zentrale Diffusoren (1, 3, 7) der Vielzahl von Diffusoren (1, 3, 4, 5, 6, 7, 8, 9)
einen ersten zentralen Diffusor (3) und einen zweiten zentralen Diffusor (1, 6, 7)
aufweisen,
der erste zentrale Diffusor (3) mit einer Fördereinrichtung (71) verbunden ist, die
Frischwasser, Verdünnungswasser und/oder Weißwasser in den ersten zentralen Diffusor
(3) fördert,
der erste zentrale Diffusor (3) zwei Klingen (12, 13) hat, die an seinem Auslass angeordnet
sind und sich in die Düsenkammer in einer konvergierenden Weise erstrecken, wobei
die Klingen (12, 13) das Frischwasser, Verdünnungswasser und/oder Weißwasser als die
Flüssigkeit, die durch den ersten zentralen Diffusor (3) strömt, von den Flüssigkeiten,
die durch benachbarte Diffusoren (1, 4) strömen, trennt,
der zweite zentrale Diffusor (1, 6, 7) mit einer Fördereinrichtung (75) verbunden
ist, die eine Pulpensuspension in den zweiten zentralen Diffusor (1, 6, 7) fördert,
der zweite zentrale Diffusor (1, 6, 7) eine zusätzliche Klinge (14) und eine weitere
Klinge (15) hat, die an dem Auslass angeordnet sind, wobei sich die zusätzliche Klinge
(14) und die weitere Klinge (15) in die Düsenkammer in einer konvergierenden Weise
erstrecken, und die zusätzliche Klinge (14) eine kürzere Länge hat als die benachbarte
Klinge (13) des ersten zentralen Diffusors (3) und die weitere Klinge (15) des zweiten
zentralen Diffusors (1, 6, 7), und
die zentralen Diffusoren (1, 3, 7) zwischen einem Oberlagendiffusor (4, 5) und einen
Rücklagendiffusor (8, 9) angeordnet sind, wobei in dem Oberlagendiffusor (4, 5) eine
Oberlagenpulpensuspension als die Flüssigkeit durch den Oberlagendiffusor (4, 5) zum
Ausbilden einer Oberlage der Faserstoffbahn strömt und in dem Rücklagendiffusor (8,
9) eine Rücklagenpulpensuspension als die Flüssigkeit durch den Rücklagendiffusor
(8, 9) zum Ausbilden einer Rücklage der Faserstoffbahn strömt.
2. Mehrschichtige Stoffauflaufstruktur für eine Faserstoffbahnmaschine zum Ausbilden
einer Faserstoffbahn nach Anspruch 1, wobei
der Oberlagendiffusor (4, 5) mit einer Fördereinrichtung (73) verbunden ist, die die
Oberlagenpulpensuspension in den Oberlagendiffusor (4, 5) fördert, und
der Rücklagendiffusor (8, 9) mit einer Fördereinrichtung (77) verbunden ist, die die
Rücklagenpulpensuspension in den Rücklagendiffusor (8, 9) fördert.
3. Mehrschichtige Stoffauflaufstruktur für eine Faserstoffbahnmaschine zum Ausbilden
einer Faserstoffbahn nach Anspruch 1, wobei
der Oberlagendiffusor (4, 5) und der Rücklagendiffusor (8, 9) mit einer einzelnen
Fördereinrichtung verbunden sind, die dieselbe Pulpensuspension als die Oberlagenpulpensuspension
und die Rücklagenpulpensuspension in den Oberlagendiffusor (4, 5) und in den Rücklagendiffusor
(8, 9) fördert.
4. Mehrschichtige Stoffauflaufstruktur für eine Faserstoffbahnmaschine zum Ausbilden
einer Faserstoffbahn nach einem der Ansprüche 1 bis 3, wobei
zumindest Teile des Oberlagendiffusors (4, 5) zwischen einer benachbarten Klinge (12)
des ersten zentralen Diffusors (3) und einer (22) der zwei konvergierenden Wände (21,
22) der Düsenkammer ausgebildet sind, und
zumindest Teile des Rücklagendiffusors (8, 9) zwischen der weiteren Klinge (15) des
zweiten zentralen Diffusors (1, 6, 7) und der anderen (21) der zwei konvergierenden
Wände (21, 22) der Düsenkammer ausgebildet sind.
5. Mehrschichtige Stoffauflaufstruktur für eine Faserstoffbahnmaschine zum Ausbilden
einer Faserstoffbahn nach einem der Ansprüche 1 bis 4, wobei Klingen (11 bis 16) in
einer gestaffelten Weise angeordnet sind.
6. Mehrschichtige Stoffauflaufstruktur für eine Faserstoffbahnmaschine zum Ausbilden
einer Faserstoffbahn nach einem der Ansprüche 1 bis 5, wobei sich die Klingen (12,
13) des ersten zentralen Diffusors (3) über die Düsenkammer zu einer Außenseite des
mehrschichtigen Stoffauflaufs erstrecken.
7. Mehrschichtige Stoffauflaufstruktur für eine Faserstoffbahnmaschine zum Ausbilden
einer Faserstoffbahn nach einem der Ansprüche 1 bis 5, wobei Spitzen der Klingen (12,
13) des ersten zentralen Diffusors (3) innerhalb der Düsenkammer angeordnet sind.
8. Mehrschichtige Stoffauflaufstruktur für eine Faserstoffbahnmaschine zum Ausbilden
einer Faserstoffbahn nach einem der Ansprüche 1 bis 7, wobei zumindest eine einstellbare
Blendenlippe (23) an dem Düsenauslass (24) vorgesehen ist.
9. Mehrschichtige Stoffauflaufstruktur für eine Faserstoffbahnmaschine zum Ausbilden
einer Faserstoffbahn nach einem der Ansprüche 1 bis 8, wobei die Länge der zusätzlichen
Klinge (14) kleiner ist als oder gleich ist wie 95% der Länge der Klingen (12, 13)
des ersten zentralen Diffusors (3).
10. Faserstoffbahnmaschine, die Folgendes aufweist:
eine Formierpartie mit einem Sieb, das um Führungswalzen herum geführt ist und eine
geschlossene Schleife ausbildet, und
die mehrschichtige Stoffauflaufstruktur nach einem der Ansprüche 1 bis 9, die gestaltet
ist, um die Oberlagenpulpensuspension, Rücklagenpulpensuspension, Pulpensuspension
und Frischwasser, Verdünnungswasser und/oder Weißwasser in einer geschichteten Weise
auf das Sieb auszusto-βen, um eine Faserstoffbahn mit mehreren Lagen auszubilden.
11. Verfahren zum Ausbilden einer Faserstoffbahn in einer Formierpartie einer Faserstoffbahnmaschine,
das die folgenden Schritte aufweist:
Fördern von Frischwasser, Verdünnungswasser und/oder Weißwasser in einen zentralen
Diffusor (3) einer mehrschichtigen Stoffauflaufstruktur,
Fördern einer Pulpensuspension in einen zweiten zentralen Diffusor (1, 6, 7) der mehrschichtigen
Stoffauflaufstruktur, wobei der zweite zentrale Diffusor (1, 6, 7) benachbart zu dem
ersten zentralen Diffusor (1) innerhalb eines mehrschichtigen Stoffauflaufs der mehrschichtigen
Stoffauflaufstruktur angeordnet ist,
Fördern einer Oberlagensuspension in einen Oberlagendiffusor (4, 5) der mehrschichtigen
Stoffauflaufstruktur, wobei der Oberlagendiffusor (4, 5), der eine Oberlage der Faserstoffbahn
ausbildet, benachbart zu dem ersten zentralen Diffusor (3) oder dem zweiten zentralen
Diffusor (1, 6, 7) angeordnet ist,
Fördern einer Rücklagenpulpensuspension in einen Rücklagendiffusor (8, 9) der mehrschichtigen
Stoffauflaufstruktur, wobei der Rücklagendiffusor (8, 9), der eine Rücklage der Faserstoffbahn
ausbildet, benachbart zu dem zweiten zentralen Diffusor (1, 6, 7) oder dem ersten
zentralen Diffusor (3) angeordnet ist,
Führen des Frischwassers, Verdünnungswassers und/oder Weißwassers und der jeweiligen
Pulpensuspensionen durch die korrespondierenden Diffusoren (1, 3, 4, 5, 6, 7, 8, 9),
um sie auf ein Sieb der Formierpartie als Stocklagen von flüssigen Substanzen derart
auszustoßen, das die erste zentrale Lage, die aus dem Frischwasser, Verdünnungswasser
und/oder Weißwasser gebildet ist, eine Grenzschicht zwischen der Oberlage oder Rücklage,
die durch die Pulpensuspension gebildet ist, und der zweiten Zentrallagenpulpe, die
durch die Pulpensuspension gebildet ist, ausbildet, und
Entwässern der flüssigen Substanzen, um die Faserstoffbahn auszubilden.
12. Verfahren zum Ausbilden einer Faserstoffbahn in einer Formierpartie einer Faserstoffbahnmaschine,
das die Schritte nach Anspruch 11 aufweist, wobei
in den Förderschritten der Oberlagenpulpensuspension und der Rücklagenpulpensuspension
dieselbe Pulpensuspension als die Oberlagenpulpensuspension und die Rücklagenpulpensuspension
in den Oberlagendiffusor und in den Rücklagendiffusor gefördert werden.
1. Structure de caisse d'arrivée multicouche pour une machine de bande continue fibreuse
pour former une bande continue fibreuse, comprenant une caisse d'arrivée multicouche
ayant un générateur de turbulence et une chambre de buse ayant deux parois convergentes
(21, 22) formant une sortie de buse (24),
le générateur de turbulence ayant une pluralité de diffuseurs (1, 3, 4, 5, 6, 7, 8,
9) créant une turbulence dans des liquides fournis dans chaque diffuseur respectif
(1, 3, 4, 5, 6, 7, 8, 9) par l'intermédiaire de moyens d'alimentation (71, 73, 75,
77) pour réaliser l'alimentation en les liquides, chacun des diffuseurs (1, 3, 4,
5, 6, 7, 8, 9) ayant une sortie donnant sur la chambre de buse, dans laquelle
des diffuseurs centraux (1, 3, 7) de la pluralité de diffuseurs (1, 3, 4, 5, 6, 7,
8, 9) comprennent un premier diffuseur central (3) et un second diffuseur central
(1, 6, 7),
le premier diffuseur central (3) est raccordé à un moyen d'alimentation (71) réalisant
l'alimentation en eau fraîche, eau de dilution, et/ou eau blanche dans le premier
diffuseur central (3),
le premier diffuseur central (3) a deux lames (12, 13) agencées à sa sortie et s'étendant
dans la chambre de buse de manière convergente, les lames (12, 13) séparant l'eau
fraîche, l'eau de dilution, et/ou l'eau blanche, en tant que liquide s'écoulant à
travers le premier diffuseur central (3), des liquides s'écoulant à travers des diffuseurs
adjacents (1, 4),
le second diffuseur central (1, 6, 7) est raccordé à un moyen d'alimentation (75)
réalisant l'alimentation en suspension de pâte dans le second diffuseur central (1,
6, 7),
le second diffuseur central (1, 6, 7) a une lame additionnelle (14) et une lame supplémentaire
(15) agencées à la sortie, la lame additionnelle (14) et la lame supplémentaire (15)
s'étendent dans la chambre de buse de manière convergente, et la lame additionnelle
(14) a une longueur plus courte que la lame adjacente (13) du premier diffuseur central
(3) et la lame supplémentaire (15) du second diffuseur central (1, 6, 7), et
les diffuseurs centraux (1, 3, 7) sont agencés entre un diffuseur de jet supérieur
(4, 5) et un diffuseur de jet arrière (8, 9), dans lequel diffuseur de jet supérieur
(4, 5) une suspension de pâte de jet supérieur, en tant que liquide, s'écoule à travers
le diffuseur de jet supérieur (4, 5) pour former un jet supérieur de la bande continue
fibreuse et dans lequel diffuseur de jet arrière (8, 9) une suspension de pâte de
jet arrière, en tant que liquide, s'écoule à travers le diffuseur de jet arrière (8,
9) pour former un jet arrière de la bande continue fibreuse.
2. Structure de caisse d'arrivée multicouche pour une machine de bande continue fibreuse
pour former une bande continue fibreuse selon la revendication 1, dans laquelle le
diffuseur de jet supérieur (4, 5) est raccordé à un moyen d'alimentation (73) réalisant
l'alimentation en la suspension de pâte de jet supérieur dans le diffuseur de jet
supérieur (4, 5), et le diffuseur de jet arrière (8, 9) est raccordé à un moyen d'alimentation
(77) réalisant l'alimentation en la suspension de pâte de jet arrière dans le diffuseur
de jet arrière (8, 9).
3. Structure de caisse d'arrivée multicouche pour une machine de bande continue fibreuse
pour former une bande continue fibreuse selon la revendication 1, dans laquelle le
diffuseur de jet supérieur (4, 5) et le diffuseur de jet arrière (8, 9) sont raccordés
à un moyen d'alimentation unique réalisant l'alimentation en la même suspension de
pâte que la suspension de pâte de jet supérieur et la suspension de pâte de jet arrière,
dans le diffuseur de jet supérieur (4, 5) et dans le diffuseur de jet arrière (8,
9).
4. Structure de caisse d'arrivée multicouche pour une machine de bande continue fibreuse
pour former une bande continue fibreuse selon l'une quelconque des revendications
1 à 3, dans laquelle
au moins une partie du diffuseur de jet supérieur (4, 5) est formée entre une lame
adjacente (12) du premier diffuseur central (3) et une (22) des deux parois convergentes
(21, 22) de la chambre de buse, et
au moins une partie du diffuseur de jet arrière (8, 9) est formée entre la lame supplémentaire
(15) du second diffuseur central (1, 6, 7) et l'autre (21) des deux parois convergentes
(21, 22) de la chambre de buse.
5. Structure de caisse d'arrivée multicouche pour une machine de bande continue fibreuse
pour former une bande continue fibreuse selon l'une quelconque des revendications
1 à 4, dans laquelle les lames (11 à 16) sont agencées de manière décalée.
6. Structure de caisse d'arrivée multicouche pour une machine de bande continue fibreuse
pour former une bande continue fibreuse selon l'une quelconque des revendications
1 à 5, dans laquelle les lames (12, 13) du premier diffuseur central (3) s'étendent
au-delà de la chambre de buse vers un extérieur de la caisse d'arrivée multicouche.
7. Structure de caisse d'arrivée multicouche pour une machine de bande continue fibreuse
pour former une bande continue fibreuse selon l'une quelconque des revendications
1 à 5, dans laquelle des bouts des lames (12, 13) du premier diffuseur central (3)
sont agencés à l'intérieur de la chambre de buse.
8. Structure de caisse d'arrivée multicouche pour une machine de bande continue fibreuse
pour former une bande continue fibreuse selon l'une quelconque des revendications
1 à 7, dans laquelle au moins une lèvre de règle ajustable (23) est prévue à la sortie
de buse (24).
9. Structure de caisse d'arrivée multicouche pour une machine de bande continue fibreuse
pour former une bande continue fibreuse selon l'une quelconque des revendications
1 à 8, dans laquelle la longueur de la lame additionnelle (14) est inférieure ou égale
à 95 % de la longueur des lames (12, 13) du premier diffuseur central (3).
10. Machine de bande continue fibreuse, comprenant :
une section de formation ayant une toile guidée autour de rouleaux de guidage et formant
une boucle fermée, et
la structure de caisse d'arrivée multicouche selon l'une quelconque des revendications
1 à 9 configurée pour éjecter la suspension de pâte de jet supérieur, la suspension
de pâte de jet arrière, la suspension de pâte, et de l'eau fraîche, de l'eau de dilution
et/ou de l'eau blanche de manière stratifiée sur la toile pour former une bande continue
fibreuse ayant de multiples jets.
11. Procédé pour former une bande continue fibreuse dans une section de formation d'une
machine de bande continue fibreuse, comprenant les étapes de :
l'alimentation en eau fraîche, eau de dilution, et/ou eau blanche, dans un premier
diffuseur central (3) d'une structure de caisse d'arrivée multicouche,
l'alimentation en suspension de pâte, dans un second diffuseur central (1, 6, 7) de
la structure de caisse d'arrivée multicouche, lequel second diffuseur central (1,
6, 7) étant agencé de façon adjacente au premier diffuseur central (1) à l'intérieur
d'une caisse d'arrivée multicouche de la structure de caisse d'arrivée multicouche,
l'alimentation en suspension de pâte de jet supérieur, dans un diffuseur de jet supérieur
(4, 5) de la structure de caisse d'arrivée multicouche, lequel diffuseur de jet supérieur
(4, 5) formant un jet supérieur de la bande continue fibreuse étant agencé de façon
adjacente au premier diffuseur central (3) ou au second diffuseur central (1, 6, 7)
l'alimentation en suspension de pâte de jet arrière, dans un diffuseur de jet arrière
(8, 9) de la structure de caisse d'arrivée multicouche, lequel diffuseur de jet arrière
(8, 9) formant un jet arrière de la bande continue fibreuse étant agencé de façon
adjacente au second diffuseur central (1, 6, 7) ou au premier diffuseur central (3),
le guidage de l'eau fraîche, de l'eau de dilution, et/ou de l'eau blanche, et des
suspensions de pâte respectives à travers les diffuseurs correspondants (1, 3, 4,
5, 6, 7, 8, 9) pour les éjecter sur une toile de la section de formation en tant que
jets de stock de substances liquides de telle sorte que le premier jet central constitué
de l'eau fraîche, de l'eau de dilution, et/ou de l'eau blanche forme une couche limite
entre le jet supérieur ou jet arrière constitué de la suspension de pâte et
la pâte de second jet central constituée de la suspension de pâte, et
la déshydratation des substances liquides pour former la bande continue fibreuse.
12. Procédé pour former une bande continue fibreuse dans une section de formation d'une
machine de bande continue fibreuse, comprenant les étapes de selon la revendication
11, dans lequel
dans les étapes d'alimentation de la suspension de pâte de jet supérieur et de la
suspension de pâte de jet arrière, l'alimentation en la même suspension de pâte que
la suspension de pâte de jet supérieur et la suspension de pâte de jet arrière est
effectuée dans le diffuseur de jet supérieur et dans le diffuseur de jet arrière.