TECHNICAL FIELD
[0001] The present invention relates to a twin wire former that supplies a suspension of
fibers between a pair of looped wires facing each other and dewaters the suspension
of fibers held between the wires to form a web.
BACKGROUND ART
[0002] The first dewatering part of a twin wire former is equipped with two forming wires
(hereinafter referred to as wires) that are in the form of a loop. A suspension of
fibers (raw material liquid for paper) is supplied between the two wires from a head
box. When the fiber suspension held between the wires is traveling, it receives dewatering
pressure from a plurality of dewatering equipments. The dewatering pressure removes
water from the fiber suspension. The dewatered fiber suspension is gradually formed
into a mat of fibers, which grows into a web.
[0003] Thereafter, the web is further condensed by vacuum suction and is compressed and
dewatered by a press part. After the web is dried with a drier, it is surface-treated
by a calender part and is wound up into paper by a reel part. The thus-manufactured
paper is required to have various qualities and properties, depending on uses. Many
of the required qualities and properties are greatly influenced in the process of
forming a mat of fibers that determines the basic structure of paper.
[0004] In the process of forming a mat of fibers, between the mat formed by the dewatering
pressure applied with a dewatering equipment and a suspension of fibers, a difference
in speed and the change occur in the directions of plane and thickness. Because of
this, it is considered that the state of dispersion of fibers changes. Therefore,
it may safely be said that the dispersed state of the fiber mat is influenced by the
magnitude and operating time of the dewatering pressure, a fluctuation pattern in
the dewatering pressure, etc.
[0005] Incidentally, one paper quality that is regarded as important is formation that represents
the state of dispersion of fibers. In order to enhance the above-described formation,
it is necessary to disperse fibers evenly. To obtain even dispersion of fibers, until
a mat of fibers is formed as a web since a suspension of fibers was supplied from
the head box, it is vital to suitably apply a change in the dewatering pressure to
the fiber suspension. In conventional methods of dewatering, however, the fiber suspension
held between two wires on a forming roll is dewatered to form a mat of fibers, but
the maximum dewatering pressure is determined by the wire tension and the diameter
of the forming roll, and there is a change in pressure that increases gradually to
this maximum dewatering pressure as the amount of the fiber mat formed increases by
the progress of dewatering. Because of this, the fibers in the suspension cannot be
dispersed evenly and therefore there is a problem that the above-described paper formation
is not good.
[0006] Hence, there have been proposed methods of dewatering such as those disclosed in
Japanese Laid-Open Patent Publication Nos. SHO 55-137294 and HEI 6-235185. In these
methods of dewatering, dewatering equipments 9, 10, 11, and 12 and a vacuum unit 13
are arranged along the traveling paths of wires 1 and 2, as shown in Fig. 4. The dewatering
equipments 9, 10, 11, and 12 are used for applying dewatering pressure on suspension
4 held between the wires 1, 2. The dewatering equipment 9 is arranged opposite a forming
roll 5. A blade member 8 provided on the tip end of the dewatering equipment 9 is
pressed against the forming roll 5 to apply pulse-dewatering pressure on the forming
roll 5. Note that the wires 1, 2 are both in the form of a loop and are guided by
a plurality of rolls 6, 7. The suspension 4 is squirted from a head box 3 onto the
forming roll 5 and is held in a wedge-shaped gap formed by the wires 1, 2.
[0007] Fig. 5 is a simplified diagram for explaining how dewatering is performed at the
suction forming roll shown in Fig. 4, and Fig. 6 is a distribution diagram of a cumulative
quantity to be dewatered to the opposite side of the suction forming roll of Fig.
4. The forming roll 5 is the first dewatering part of the former, so a quantity to
be dewatered from the suspension 4 at the forming roll 5 is extremely great. Particularly,
within a wire warp angle of 10 degrees, about 25% of the flow rate squirted from the
head box 3 is dewatered to the opposite side of the forming roll 5, as shown in Fig.
6. White water dewatered to the forming roll side is suctioned by the suction box
10 of the forming roll 5, but white water 15 dewatered to the opposite side scatters
along the traveling direction of the wires 1, 2, as shown by arrows in Fig. 6.
[0008] In such a situation of dewatering, as shown in Fig. 4, if the blade 8 of the dewatering
equipment 9 is pressed against the forming roll 5 from a position opposite the forming
roll 5 for the purpose of improving the above-described formation, a great quantity
of whit water 15 dewatered to the upstream side of the dewatering equipment 9 will
collide violently with the blade 8. Because of this, deformation of the blade 8 due
to a collision with the white water 15 occurs, or the bite of the blade 8 into the
forming roll 5 due to the deformation occurs. As a result, the problem of a paper
defect, uneven wear on the blade 8, damage to the wires 1 and 2, etc., is sometimes
caused. Also, even when there is no deformation of the blade 8, white water 15 colliding
with the tip end of the blade 8 sometimes enters between the blade 8 and the wire
2 and causes a defect in paper such as streaks. In such a case, paper with uneven
dispersion of fibers is manufactured.
[0009] The present invention has been made in view of the above-described problems. Accordingly,
it is the object of the present invention to provide a twin wire former that is capable
of manufacturing defect-free paper that has even dispersion of fibers, while preventing
damage to blades that is caused by a collision with white water during dewatering.
DISCLOSURE OF THE INVENTION
[0010] In the present invention, the above-described problems are solved by preventing white
water dewatered to the opposite side of aroll from interferingwithpressure elements
(blades, etc.). That is, a twin wire former according to the present invention is
equipped with white-water withdrawal means for withdrawing white water dewatered to
the opposite roll side, which is arranged to the upstream side of a pressure element.
Note that the present invention is applied to twin wire formers in which (1) a suspension
of fibers is supplied between first and second looped wires arranged opposite each
other, (2) the looped interior surface of the first wire and the looped exterior surface
of the second wire run around a roll, and (3) a pressure element for applying dewatering
pressure on the looped interior surface of the secondwire is arranged on the looped
interior surface side of the second wire and opposite the roll.
[0011] According to the twin wire former of the present invention, white water dewatered
to the opposite roll side is withdrawn by white-water withdrawal means, whereby the
interference of white water with the pressure element can be suppressed. This can
avoid deformation of the pressure element and a bite into the roll due to the deformation.
Also, even when there is no deformation of the pressure element, white water colliding
with the tip end of the pressure element can be prevented from entering between the
pressure element and the wire and causing a defect in paper such as streaks. As a
result, damage to the pressure element can be prevented, defect-free and high-quality
paper with uneven dispersion of fibers can be manufactured, and stable operation becomes
possible.
[0012] In the case where a plurality of pressure elements are arranged along the direction
in which the second wire travels, it is preferable that the white-water withdrawal
means be provided in the forefront pressure element. The forefront pressure element
is the most influenced by white water. Therefore, if the white-water withdrawal means
is provided in the forefront pressure element, the interference between the forefront
pressure element and white water is suppressed and problems due to the interference
can be prevented. Of course, it is also possible to provide the white-water withdrawal
means in each of the pressure elements.
[0013] A simple example of the white-water withdrawal means is a blade. That is, the blade
is arranged inside the second wire and opposite the roll. This blade is not for the
purpose of applying dewatering pressure on the looped interior surface of the second
wire like the pressure element, but for the purpose of guiding and withdrawing white
water in a direction away from the second wire along the blade surface and preventing
white water from colliding with the pressure element. Therefore, the white-water withdrawal
blade can be arranged at a position farther away from the second wire than the pressure
element. It is also preferable that the withdrawal blade be higher in rigidity than
the blade used as the pressure element (note that it is preferable that the pressure
element have flexibility). It is also preferable that the white-water withdrawal blade
have a tip end curved toward the upstream side to guide white water to the outside
along the blade surface so that the white water colliding with the blade tip end does
not collide with the wire surface again. The white-water withdrawal blade may be equipped
with white-water suction means for forcibly suctioning white water withdrawn. By forcibly
suctioning white water withdrawn, it can be withdrawn more effectively. Note that
the white-water suction means can employ a vacuum box, etc.
[0014] Regarding the position of the white-water withdrawal blade in the roll direction,
it is preferable that the tip end be arranged at a position about 15 mm away from
the second wire. If the white-water withdrawal blade is too away from the first wire
the efficiency of withdrawing white water declines, and if the white-water withdrawal
blade is pressed into the first wire (that is, if distance becomes negative) there
are cases where streaks due to the entry of white water occur and the white-water
withdrawal blade itself is deformed. Preferably, there is provided position adjustment
means so that the position of the white-water withdrawal blade in the roll direction
can be freely adjusted to a position where white water is efficiently withdrawn. Note
that white water dewatered to the opposite roll side applies pressure on the white-water
withdrawal blade. This pressure varies with the position in the roll direction of
the white-water withdrawal blade. Hence, if there is provided pressure detection means
for detecting pressure that acts on the white-water withdrawal blade, and the white-water
withdrawal blade is moved so that the detected pressure is proper, the white-water
withdrawal blade can be readily adjusted to a proper position.
[0015] On the other hand, regarding the position of the pressure element in the roll direction,
it is preferable that the tip end be about 1 mm pressed into the interior surface
of the first wire toward the roll side so that fibers can be dispersed by the application
of pressure. Preferably, there is provided position adjustment means so that the position
of the pressure element in the roll direction can be freely adjusted to a position
where proper fiber dispersion can be performed. More preferably, by providing pressure
detection means for detecting pressure that acts on the pressure element, the position
of the pressure element in the roll direction is adjusted and moved so that the detected
pressure is proper pressure.
[0016] The pressure detection means can employ an ordinary pressure sensor. In the case
where a pressure sensor is provided in the white-water withdrawal blade or pressure
element, pressure acting on the white-water withdrawal blade or pressure element can
be directly detected. Also, the reaction to the pressure acting on the white-water
withdrawal blade and pressure element acts on the surface of the roll. Hence, by providing
a pressure sensor on the roll surface, the pressure that acts on the white-water withdrawal
blade and pressure element may be indirectly detected from the pressure acting on
the roll surface through white water, wires, and a suspension of fibers.
[0017] Note that the above-described roll opposite which the pressure element and white-water
withdrawal blade are arranged may be a solid roll, a roll with a porous band wrapped
around the surface to withdraw surplus white water, or a roll with various grooves
in the surface. However, it is preferable that the roll be a suction forming roll.
In the case of a suction forming roll, white water dewatered to the roll side can
be forcibly suctioned, and consequently, the quantity of white water to be dewatered
to the opposite roll side because of the influence of centrifugal force can be reduced.
[0018] By employing the above-described twin wire former, papermaking can be performed by
the following methods. That is, paper is manufactured by detecting pressure that acts
on a white-water withdrawal blade by pressure detection means, and adjusting the position
of the white-water withdrawal blade in the roll direction by position adjustment means
so that the detected pressure is within a proper range. According to this papermaking
method, the entry of white water to the tip end of the pressure element is surely
prevented and defect-free and high-quality paper with even dispersion of fibers can
be manufactured.
[0019] Paper can also be manufactured by detecting pressure that acts on the white-water
withdrawal blade by first pressure detection means and also detecting pressure that
acts on the pressure element by second pressure detection means, and adjusting the
position of the white-water withdrawal blade in the roll direction by first position
adjustment means so that the detected pressure is within a first proper range and
also adjusting the position of the pressure element in the roll direction by second
position adjustment means so that the detected pressure is within a second proper
range. According to this method, dewatering pressure to be applied by the pressure
element can be made proper and high-quality paper with even dispersion of fibers can
be manufactured.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020]
FIG. 1 is a side view showing the principal part of a twin wire former constructed
in accordance with a first embodiment of the present invention;
FIG. 2 is a side view showing the principal part of a twin wire former constructed
in accordance with a second embodiment of the present invention;
FIG. 3A is a diagram showing the relationship between a distance d from a roll surface
to each blade tip end and the roll surface pressure, for explaining a method of controlling
proper positions of the white-water withdrawal blades and loadable blades;
FIG. 3B is a diagram for explaining the definition of the distance d shown in FIG.
3A;
FIG. 4 is a side view showing the construction of the dewatering part of a conventional
twin wire former;
FIG. 5 is a simplified diagram for explaining how dewatering is performed at the suction
forming roll shown in FIG. 4; and
FIG. 6 is a distribution diagram of a cumulative quantity to be dewatered to the opposite
side of the suction forming roll of FIG. 4.
BEST MODE FOR CARRYING OUT THE INVENTION
[0021] Embodiments of the present invention will hereinafter be described in conjunction
with the drawings.
(A) First Embodiment
[0022] Fig. 1 is a side view showing the principal part of a twin wire former constructed
in accordance with a first embodiment of the present invention. Note in the figure
that the same parts as the conventional twin wire former shown in Fig. 4 are represented
by the same reference numerals.
[0023] As shown in Fig. 1, a pair of wires 1, 2 run around a forming roll 5 and are both
in the form of a loop. The looped interior surface of one (first wire 1) of the two
wires runs around the forming roll 5, while the looped exterior surface of the other
wire (second wire 2) runs around the forming roll 5. Within the range that the wires
1, 2 run around the forming roll 5 (wire wrap range), there is provided a suction
box 10. Inside the wire 2 and at positions opposite the suction box 10, a plurality
of flexible loadable blades (pressure elements) 30 are arranged along the direction
in which the wires 1, 2 travel. These loadable blades 30, 30 constitute a dewatering
equipment, which disperses fibers evenly by applying pulse-dewatering pressure on
a fiber suspension 4 which is a raw material liquid held between the wires 1 and 2.
[0024] In the first embodiment, a deflector blade (white-water withdrawal blade) 20 for
withdrawing white water 15 is arranged upstream in close proximity to the forefront
loadable blade 30. This white-water withdrawal blade 20 has a tip end gently curved
toward the upstream side and is higher in rigidity than the loadable blade 30. Also,
the position of the white-water withdrawal blade 20 in the roll direction (direction
of the forming roll 5) is set so that the tip end is arranged in close proximity to
the interior surface of the wire 2 or contacts the interior surface to the degree
of a kiss touch.
[0025] The white-water withdrawal blade 20 is provided with a pressure sensor 40 and a moving
device 50 with a displacement sensor for position detection. The pressure sensor 40
is a sensor to detect pressure that acts on the white-water withdrawal blade and is
primarily used for detecting pressure from white water that collides with the white-water
withdrawal blade during dewatering. Also, the moving device 50 is a device to move
and adjust the position in the roll direction of the white-water withdrawal blade
20 and is able to confirm the current position by the displacement sensor.
[0026] With such a construction, the fiber suspension 4 supplied between the wires 1 and
2 from a head box 3 is transferred onto the suction box 10 while being held between
the wires 1 and 2. The fiber suspension 4 is dewatered by the surface pressure of
the wires 1, 2 and the suction force of the suction box 10. On the opposite side of
the suction forming roll 5, dewatering is also performed by the surface pressure of
the wires 1, 2 and centrifugal force. The dewatered white water 15 is discharged inside
the wire 2 along the direction in which the wires 1, 2 travel.
[0027] At this time, the white water 15 dewatered to the opposite side of the forming roll
5 is guided and withdrawn in a direction away from the wire 2 along the surface of
the white-water withdrawal blade 20. This withdrawal suppresses the amount that the
white water 15 collides with the loadable blade 30. As a result, deformation of the
loadable blade 30 due to a collision with a large quantity of white water 15, and
the occurrence of streaks due to the entry of the white water 15 into the space between
the loadable blade 30 and wire 2, can be prevented. That is, the twin-wire former
of the first embodiment is capable of manufacturing paper of even fiber dispersion
that is free from a paper defect such as streaks, while preventing damage to the loadable
blades 30 due to a collision with white water 15.
[0028] Note that the white-water withdrawal blade 20 can be adjusted to a proper position
by detecting pressure that acts on the white-water withdrawal blade 20 with the pressure
sensor 40, and then performing position adjustment with the moving device 50 so that
the detected pressure is proper pressure. Since the white-water withdrawal blade 20
has no purpose of enhancing dispersion of fibers, there is no need to generate high
dewatering pressure in the fiber suspension 4. The proper position of the white-water
withdrawal blade 20 and position control method will be described later (in a second
embodiment). However, as at least described above, if the position of the white-water
withdrawal blade 20 is adjusted so that it is arranged very close to the wire 2 or
contacts the wire 2 to the degree of a kiss touch, there is no possibility that the
white-water withdrawal blade 20 will be pressed against the wire 2. As a result, the
problem of the occurrence of streaks due to the entry of the white water 15 into the
space between the loadable blade 30 and wire 2, bite of the white-water withdrawal
blade 20 into the wire 2 due to deformation of the white-water withdrawal blade 20,
etc., can be avoided.
(B) Second Embodiment
[0029] Fig. 2 is a side view showing the principal part of a twin wire former constructed
in accordance with a second embodiment of the present invention. Note in the figure
that the same parts as the first embodiment are represented by the same reference
numerals.
[0030] In the second embodiment, flexible loadable blades 35, 36, and 37 arranged in the
traveling direction of a wire 2 are respectively provided with white-water withdrawal
blades 25, 26, and 27, as shown in Fig. 2. The white-water withdrawal blades 25, 26,
and 27 are arranged upstream in close proximity to the corresponding loadable blades
35, 36, and 37 and are fixed to moving devices 55, 56, and 57 along with the corresponding
loadable blades 35, 36, and 37. Each of the moving devices 55, 56, and 57 has a displacement
sensor. In Fig. 2, three units 65, 66, and 67, which consist of the loadable blade,
white-water withdrawal blade, and moving device, are arranged along the traveling
direction of the wire 2.
[0031] With such a constitution, white water 15 dewatered to the opposite side of the forming
roll 5 is withdrawn by the units 65, 66, and 67. The cumulative amount of white water
15 dewatered is maximum at the forefront loadable blade 35, but dewatering of white
water 15 is also performed between the loadable blades 35 and 36 and between the loadable
blades 36 and 37. Therefore, since the units 65, 66, and 67 are provided with white-water
withdrawal blades 25, 26, and 27 for withdrawing white water 15, the white water 15
dewatered between the loadable blades 35 and 36 and between the loadable blades 36
and 37 can be prevented from colliding with the loadable blades 36, 37. This makes
it possible to prevent damage to these loadable blades 36, 37 and to manufacture paper
that has even dispersion of fibers.
[0032] In the second embodiment, a pressure sensor 60 is arranged inside the forming roll
5 to detect roll-surface pressure. The pressure sensor 60 rotates integrally with
the forming roll 5 and serially detects pressure that acts at each position in the
circumferential direction. The reaction to the pressure acting on the white-water
withdrawal blades 25, 26, 27 and loadable blades 35, 36, 37 acts on the surface of
the forming roll 5. Hence, if a change in the pressure applied on the roll surface
is detected with the pressure sensor 60, the pressure that acts on the white-water
withdrawal blades 25, 26, 27 and loadable blades 35, 36, 37 can be indirectly detected.
[0033] Fig. 3 is an explanatory diagram for explaining a method of controlling positions
of the white-water withdrawal blades 25, 26, 27 and loadable blades 35, 36, 37. Fig.
3A is a diagram showing the relationship between a distance d from the roll surface
to each blade tip end and the roll surface pressure, and Fig. 3B is a simplified diagram
for explaining the definition of the distance d shown in Fig. 3A. Note that the position
control method hereinafter described can also be applied to the position control of
the white-water withdrawal blade 20 of the first embodiment.
[0034] First, regarding the positions of the white-water withdrawal blades 25, 26, and 27,
if the white-water withdrawal blades 25, 26, and 27 are too away from the wire 2 the
efficiency of withdrawing white water 15 declines, and if the white-water withdrawal
blades 25, 26, and 27 are pressed into the wire 2 there is a need to take into account
the occurrence of streaks due to the entry of white water 15, and deformation of the
white-water withdrawal blades 25, 26, and 27. Therefore, proper positions of the white-water
withdrawal blades 25, 26, and 27 are within a white-water collision pressure region
from a reference position, as shown by a black bar in Fig. 3A. The reference position
is away from the surface of the forming roll 5 by the sum of the thickness of the
two wires 1, 2 and the thickness of the fiber suspension 4 held between the wires
1, 2. More specifically, the proper positions are in a range of 0 to 15 mm from the
reference position (interior surface of the wire 2).
[0035] On the other hand, proper positions of the loadable blades 35, 36, and 37 are within
an inter wire deformation region from the above-described reference position as shown
by a white bar in Fig. 3A, because they must compress the fiber suspension 4 held
between the wires 1 and 2 to disperse fibers. More specifically, the proper positions
are in a range of 1 to 3 mm from the reference position toward the forming roll 5.
[0036] The position control of the white-water withdrawal blades 25, 26, 27 and loadable
blades 35, 36, 37 is performed based on values detected by the pressure sensor 60
provided in the forming roll 5. That is, a pressure diagram such as that shown by
a solid line in Fig. 3A is previously prepared and a proper pressure range corresponding
to proper positions is computed. And by controlling the moving devices 55, 56, and
57 so that values detected by the pressure sensor 60 are within the proper pressure
range, the positions of the white-water withdrawal blades 25, 26, 27 and loadable
blades 35, 36, 37 are adjusted. The above-described position control can be performed
automatically, or it can be performed manually by an operator. In the case of automatic
control, the pressure diagram is previously stored in a controller, and signals from
the moving devices 55, 56, and 57 are fed back to the controller so that values detected
by the pressure sensor 60 are within the proper pressure range.
[0037] If papermaking is performed while performing the position control of the white-water
withdrawal blades 25, 26, 27 and loadable blades 35, 36, 37 in the above-described
manner, the dewatering pressure to be applied by the loadable blades 35, 36, 37 can
be made optimum. In addition, the occurrence of streaks due to the entry of white
water into the space between the loadable blade (35, 36, or 37) and the wire 2 can
be surely prevented. As a result, it becomes possible to manufacture high-quality
paper that has even dispersion of fibers.
[0038] Note that since the fiber suspension 4 becomes thinner in thickness as dewatering
moves, the reference position shown in Fig. 3A (which is away from the surface of
the forming roll 5 by the sum of the thickness of the two wires 1, 2 and the thickness
of the fiber suspension 4 between the wires 1, 2) moves closer to the surface of the
forming roll 5 toward the downstream side. Therefore, the pressure diagram shown in
Fig. 3A varies with blade positions. Hence, to perform accurate position control,
it is preferable to previously input a pressure diagram corresponding to each blade
to a controller.
(C) Others
[0039] While the present invention has been described with reference to two embodiments,
the invention is not to be limited to the details given herein, but may be modified
within the scope of the invention hereinafter claimed.
[0040] For instance, in the second embodiment, while the white-water withdrawal blades 25,
26, 27 are formed integrally with the loadable blades 35, 36, 37, the white-water
withdrawal blades 25, 26, 27 may be formed separately from the loadable blades 35,
36, 37, and the moving devices may be provided in the blades 25, 26, 27, 35, 36, and
37, respectively. Also, in the second embodiment, each of the blades 25, 26, 27, 35,
36, and 37 may be provided with a pressure sensor so that optimum position control
can be performed based on values detected by the pressure sensor.
[0041] In the first and second embodiments, while one white-water withdrawal blade is arranged
to the upstream side of each loadable blade (second embodiment) or to the upstream
side of the loadable blade group (first embodiment), a plurality of white-water withdrawal
blades may be arranged to the upstream side of each blade or blade group.
[0042] Also, each white-water withdrawal blade may be provided with suction means (such
as a suction box, etc.) so that the white water withdrawn by the blade can be forcibly
suctioned. Withdrawn white water can be continuously removed to the outside, so it
becomes possible to withdraw white water more efficiently.
[0043] In addition, the white-water withdrawal means of the present invention is not to
be limited to the blades constructed in accordance with the above-described embodiments.
The white-water withdrawal means may have any shape if it can prevent the white water
withdrawn to the opposite side of the forming roll 5 from colliding with loadable
blades. Therefore, for example, it may have a shape that becomes thicker in the traveling
direction of the wire, or it may have a guide plate shape if rigidity is assured.
Also, the pressure elements are not to be limited to the blades constructed in accordance
with the above-described embodiments. They may be roll members or rod members , if
they can applypulse-dewatering pressure on the fiber suspension held between the wires.
In the case of blades, they may be not a flexible type like the embodiments, but a
fixed type.
1. A twin wire former for supplying a suspension of fibers between first and second looped
wires arranged opposite each other, and dewatering said suspension of fibers held
between said first and second wires, running a looped interior surface of said first
wire and a looped exterior surface of said second wire around a roll, said former
comprising:
a pressure element, arranged on the looped interior surface side of said second wire
and opposite said roll, for applying dewatering pressure on the looped interior surface
of said second wire; and
white-water withdrawal means arranged to the upstream side of said pressure element
for withdrawing white water dewatered to the looped interior surface side of said
second wire.
2. The twin wire former as set forth in claim 1, wherein:
said pressure element comprises a plurality of pressure elements arranged along a
direction in which said second wire travels; and
said white-water withdrawal means is provided in the forefront pressure element of
said pressure element group.
3. The twin wire former as set forth in claim 1 or 2, wherein said white-water withdrawal
means comprises a white-water withdrawal blade arranged on the looped interior surface
side of said second wire and opposite arranged said roll.
4. The twin wire former as set forth in claim 3, wherein said white-water withdrawal
blade has a tip end curved toward an upstream side.
5. The twin wire former as set forth in claim 3 or 4, further comprising white-water
suction means for suctioning white water withdrawn by said white-water withdrawal
blade.
6. The twin wire former as set forth in any one of claims 3 through 5, further comprising
first position adjustment means for adjusting the position of said white-water withdrawal
blade in the direction of said roll.
7. The twin wire former as set forth in claim 6, further comprising first pressure detection
means for detecting pressure that acts on said white-water withdrawal blade.
8. The twin wire former as set forth in claim 6 or 7, further comprising second position
adjustment means for adjusting the position of said pressure element in said roll
direction.
9. The twin wire former as set forth in claim 8, further comprising second pressure detection
means for detecting pressure that acts on said pressure element.
10. The twin wire former as set forth in any one of claims 1 through 9, wherein said roll
comprises a suction forming roll.
11. A method of manufacturing paper by employing the twin wire former as set forth in
claim 7, comprising the steps of:
detecting pressure that acts on saidwhite-water withdrawal blade by said first pressure
detection means; and
adjusting the position of said white-water withdrawal blade in said roll direction
by said first position adjustment means so that the detected pressure is within a
proper range.
12. A method of manufacturing paper by employing the twin wire former as set forth in
claim 9, comprising the steps of:
detecting pressure that acts on saidwhite-water withdrawal blade by said first pressure
detection means and also detecting pressure that acts on said pressure element by
said second pressure detection means; and
adjusting the position of said white-water withdrawal blade in said roll direction
by said first position adjustment means so that the detected pressure is within a
first proper range, and also adjusting the position of said pressure element in said
roll direction by said second position adjustment means so that the detected pressure
is within a second proper range.