JP2008308781A - Method and apparatus for suppressing re-humidification of wet paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the re-humidification of wet paper after wet paper is dehydrated by a press device in a press part of a paper machine. <P>SOLUTION: Provided is a re-humidification suppressing apparatus for suppressing the back flow of released white water w at a press part 2 of a paper machine and on the downstream side of a press device 4 for pressing and dehydrating wet paper 1 across a water-absorptive felt. The re-humidification suppressing apparatus comprises pickup blades 35a-35c disposed just downstream of the press device 4 and on the back of an upper felt 6a for scooping the white water w separated to the back side of the upper felt, means 353 and 354 for establishing a vacuum pressure between the back face of the upper felt and the blade faces 351 and 352, which confront the back face of the upper felt, of the pickup blades, and guide means 16 for guiding a lower felt 6b so that the lower felt may leave the upper felt 6a from the starting point of the set positions of the pickup blades. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  In the press part of the paper machine, the wet paper after passing through the press roll for dehydration can suppress the white water separated from the wet paper from flowing back to the wet paper and improve the water-squeezing ability. The present invention relates to a method and an apparatus.

  The operating speed of a paper machine is required to increase even in existing paper machines from the viewpoint of increasing production speed and production efficiency. Double felt roll press or double felt shoe press that presses with wet paper sandwiched between two felts from both sides for the purpose of improving required water-squeezing capability and ensuring high-speed stable running by this speed increase. It has become.

  However, in the double felt method, water is squeezed on both sides of the wet paper (water moves from the wet paper to the felt on both sides). In such a case, a so-called “re-wetting phenomenon” occurs in which white water squeezed from the wet paper and transferred to the felt flows backward from the felt to the wet paper, causing a problem that the squeezing ability is not improved.

  Patent Document 1 (Japanese Patent Laid-Open No. 60-215893) discloses a tandem type press configuration using the double felt roll press and the double felt shoe press in the press part of a paper machine. Patent Document 1 proposes an improved paper machine press mechanism capable of removing a large amount of water from wet paper and capable of satisfactory dewatering at a high speed. Patent Document 1 discloses a double felt roll press or It is only disclosed that the wet paper is carried on the upper felt by a suction shoe provided on the back surface of the upper felt on the downstream side of the double felt shoe press, and there is no disclosure about a rewetting suppression mechanism.

JP-A-60-215893

  Conventionally, in the press part of a paper machine, an effective measure against the rewetting phenomenon that occurs downstream of a double felt roll press or a double felt shoe press has not yet been taken. After the dehydration by the press module, when the wet paper moisture increases due to the re-wetting phenomenon, it is necessary to apply a high linear pressure to the press device in advance and squeeze the water, which increases the density of the paper made.

  On the other hand, thick and light bulky paper is currently in demand as paper for books. As described above, if the density of the paper produced by applying a high linear pressure to the press device is increased, this demand is reversed and effective measures against the rewetting phenomenon are required.

  An object of the present invention is to suppress the rewetting phenomenon of the wet paper after the wet paper is dehydrated by the press device in the press part of the paper machine.

In order to achieve the above-mentioned object, the wet paper rewetting suppression method of the present invention comprises
In the press process of the paper machine, after dewatering between the press devices with the wet paper sandwiched between water-absorbing felts, in the rehumidification suppression method that suppresses the backflow of the dehydrated white water to the wet paper,
Picking up white water separated on the back side of the upper felt with a pickup blade provided on the back side of the upper felt on the downstream side of the press roll,
Forming a negative pressure between the back surface of the upper felt and the blade surface of the pick-up blade facing the back surface of the upper felt, thereby causing the upper felt to suck the wet paper;
The lower felt is guided so that the lower felt is separated from the upper felt starting from the installation position of the pickup blade, whereby the wet paper is supported only on the upper felt.

In addition, the wet paper rewetting suppression device of the present invention suitable for carrying out the method of the present invention comprises:
In the press part of the paper machine, on the downstream side of the press device that pressurizes and dehydrates the wet paper with water-absorbing felt, in the rehumidification suppression device that suppresses the reverse flow of the dehydrated white water to the wet paper,
A pickup blade provided on the back surface of the upper felt on the downstream side of the press roll and scooping white water separated on the back surface side of the upper felt;
Means for creating a negative pressure between a back surface of the upper felt and a blade surface of the pickup blade facing the back surface of the upper felt;
Guide means for guiding the lower felt so as to separate the lower felt from the upper felt starting from the installation position of the pickup blade;
The wet paper web is supported only by the upper felt on the downstream side of the press device.

  In the press device, white water separated from the wet paper from the nip portion of the press device to the downstream side passes through the upper and lower felts and scatters to the back side of the upper and lower felts, or is accompanied by a phenomenon of accompanying the back of the upper and lower felts. . As described above, the white water separated from the wet paper flows back into the wet paper again when the wet paper is accompanied by the felt on the downstream side of the press device for a long time.

  In the present invention, the pickup blade is provided on the back surface of the upper felt on the downstream side of the press device, so that it is separated from the wet paper at the nip portion of the press device and scattered on the back surface side of the upper felt or the upper felt. You can scoop up the white water that is accompanied on the back. Thereby, the rewetting phenomenon on the back side of the upper felt can be suppressed.

  On the other hand, since the white water separated from the wet paper and scattered on the back side of the lower felt falls down due to gravity, the scattered white water does not flow back to the wet paper. However, the rewetting phenomenon is that the wet paper is compressed and deformed by the nip pressure of the press device, and then the white water contained in the felt is released from the felt to the wet paper when the nip pressure is released and the wet paper is deformed and recovered. Therefore, it is possible to suppress rewetting by separating the felt from the wet paper as soon as possible after the nip in the press device.

From this point of view, in the present invention, the wet paper is provided on the upper side by providing the negative pressure forming means and separating the lower felt from the upper felt starting from the installation position of the pickup blade provided on the back side of the upper felt. It is carried only on the felt. As a result, the white water separated from the wet paper and transferred to the lower felt at the nip portion of the press device does not flow back to the wet paper.
Thus, according to the present invention, the rewetting phenomenon in which white water flows backward from the upper and lower felts to the wet paper on the downstream side of the press device can be effectively suppressed with a simple device configuration.

  In the present invention, preferably, the blade surface of the pickup blade facing the back surface of the upper felt is provided with a curvature having a cross-sectional arc shape protruding toward the back surface of the upper felt, and the lower felt is defined as the upper felt starting from the curvature portion. Guide away from Thus, by providing the pickup blade with a circular arc-shaped curvature, the wet paper can be easily separated from the lower felt at the curved portion.

In the method of the present invention, it is preferable that a negative pressure be formed between the back surface of the upper felt and the blade surface by forming a negative pressure in a concave groove or a through-hole provided in the blade surface of the pickup blade. . With this configuration, it becomes easy to form a negative pressure on the blade surface of the pickup blade, thereby increasing the suction force for sucking the wet paper to the upper felt and making it easier to separate the wet paper from the lower felt. In addition, the running stability of the wet paper increases.
Furthermore, the combination of this configuration and the above configuration (providing the pickup blade with a circular arc-shaped curvature) makes it easier to separate the wet paper from the lower felt and carry it only by the upper felt.

  In the device of the present invention, the negative pressure forming means may be constituted by a concave groove or through hole provided in the pickup blade and opening in the blade surface of the pickup blade, and a vacuum suction device for sucking the inside of the concave groove or through hole. . By providing a concave groove or through hole on the blade surface of the pickup blade and forming a negative pressure inside the concave groove or through hole by a vacuum suction device, the negative pressure can be reliably formed on the blade surface.

  If the groove is arranged in a direction in which the atmosphere in the groove is sucked by the vacuum suction device, the resistance of the groove to the flow of white water sucked through the groove is reduced. As a result, the white water in the upper felt can be easily removed. The through hole may be formed in a direction perpendicular to or inclined from the blade surface of the pickup blade. Furthermore, if the through hole is inclined toward the direction sucked by the vacuum suction device, the resistance of the through hole to the flow of white water flowing in the through hole is reduced. White water removal becomes easy.

  As another configuration of the negative pressure forming means, the concave groove, a compressed air flow path connected in the vicinity of the end of the concave groove, and a compressed air supply device for supplying compressed air to the compressed air flow path are configured. Good. In such a configuration, by supplying compressed air to the concave groove, a high-speed air flow is generated in the concave groove, and thereby, the inside of the concave groove can be set to a negative pressure. In this case, there is an advantage that a vacuum suction device is unnecessary.

  In the apparatus of the present invention, it is preferable that the pickup blade, the discharge path for guiding the white water scooped up by the pickup blade to the discharge port for discharging to the outside, and the negative pressure forming means are integrally configured. With such a configuration, scooping of white water and suction of the wet paper to the upper felt can be performed at the same time, whereby the wet paper can be stably transferred at high speed, and high speed operation becomes possible. Further, since the device of the present invention can be made compact, the distance from the nip portion of the press device until the wet paper separates from the lower felt can be shortened, thereby further reducing the backflow of white water from the lower felt to the wet paper. be able to.

  In the apparatus of the present invention, the pickup blades are provided in a plurality of stages at intervals along the wet paper web transfer direction, the curvature is provided on the blade surface of the pickup blade on the most upstream side, and the blade surface of the subsequent pickup blade is a flat surface. You may comprise. By adopting such a configuration, it becomes easy to separate the lower felt from the wet paper with the most upstream pickup blade, and by making the blade surface of the subsequent pickup blade flat, damage to the upper felt can be reduced. Felt hair removal can be reduced. Further, by providing a gap between the most upstream pickup blade and the subsequent pickup blade, it becomes easy to apply a negative pressure between the upper felt and the blade surface by the vacuum suction device through the gap.

  Further, in the device of the present invention, the groove depth of the groove may be constant, but the groove depth toward the suction direction by the vacuum suction device or toward the downstream side in the flow direction of the compressed air. It is good to comprise so that may increase gradually. With this configuration, the foil effect can be easily developed, and the reduced pressure state can be surely formed up to the end of the groove due to the foil effect.

  In the apparatus of the present invention, the concave grooves may be provided on the blade surface of the pickup blade so as to be inclined in the wet paper width direction, or the through holes may be arranged in a distributed manner in the wet paper width direction. Accordingly, the openings of the concave grooves or the through holes are uniformly dispersed in the wet paper width direction and face the back surface of the upper felt, so that a uniform history including a uniform suction action in the wet paper width direction can be given. it can. Thereby, quality unevenness in the wet paper width direction can be reduced.

  In the device of the present invention, the pickup blade may be made of ceramic. As a result, wear resistance and corrosion resistance are improved, so that the life of the pickup blade can be extended, heat resistance is improved, and thermal expansion is reduced, so that dimensional accuracy is improved.

According to the present invention, since the pickup blade is provided on the back side of the upper felt on the downstream side of the press device, white water separated from the wet paper is scooped up on the back side of the upper felt. Rewetting phenomenon can be suppressed on the back side.
Further, by forming a negative pressure between the back surface of the upper felt and the blade surface of the pickup blade facing the back surface of the upper felt, the wet paper is sucked into the upper felt, and the installation position of the pickup blade As a starting point, the lower felt is guided away from the upper felt, so that the white water separated from the wet paper at the nip portion of the press device and transferred to the lower felt does not flow back to the wet paper.

  As described above, according to the present invention, the rewetting phenomenon of white water to the wet paper can be effectively suppressed with a simple device. Since the linear pressure can be reduced, it is possible to produce bulky paper with high demand.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the present invention to that only, unless otherwise specified.
(Embodiment 1)

  FIG. 1 is a configuration diagram showing a press part and a dryer part of a paper machine according to a first embodiment of the present invention. In FIG. 1, the wet paper 1 carried on the wire 8 from a wire part (not shown) is sucked by the suction roll 5a and carried on the upper felt 6a. Thereafter, the wet paper 1 is conveyed to the final press 4 for dehydration while being supported on the upper felt 6a or being sandwiched from both sides by the upper felt 6a and the lower felt 6b. The final press 4 for dehydration includes a shoe module 4a and a press bottom roll 4b. Moisture contained in the wet paper 1 is moved to the upper and lower felts 6a and 6b by the nip pressure applied at these nip portions. Squeezing water. In addition, a in the figure indicates the conveyance direction of the wet paper web 1.

  The wet paper 1 squeezed by the final dewatering press 4 is conveyed to the nip suction roll 21 while being sandwiched between the felts 6 a and 6 b, but directly downstream of the nip portion of the final dewatering press 4. In the back side of the upper felt 6a, the rehumidification suppressing device 30, which is the main part of the present invention, is provided. The white water that has been dehydrated by the final dehydrating press 4 and separated on the back side of the upper felt 6 a is scooped by the rehumidification suppressing device 30 so as not to flow back to the wet paper 1. Further, the lower felt 6b is guided by the guide roll 16 so as to be separated from the wet paper web 1 at a position where the rehumidification suppressing device 30 is installed.

The wet paper web 1 is adsorbed to the surface of the nip suction roll 21 via the upper felt 6 a on the downstream side of the rehumidification suppressing device 30. In the downstream side, the nip de suction roll 21 forms a first nip N ₁ between the Smoother lower roller 12b, the wet web 1 is directed toward the first nip N _1.

Wet web 1 the surface pressure imparted by the first nip N ₁ is carried on the felt 6a, since the surface smoothness of the Smoother lower roller 12b is higher than the felts 6a, a first outlet of the nip portion N ₁ And separated from the felt 6a and transferred to the surface of the smoother bottom roll 12b. Wet web 1 is transferred to the surface of the Smoother lower roller 12b is transported to the second nip N _2.

A first downstream side of the nip portion N _1, smoother bottom roll 12b forms a second nip N ₂ between the smoother top roll 12a. The smoother top roll 12a and the smoother bottom roll 12b are provided with a hard cover (for example, hard rubber or ceramic spray) as a hard material on the surface in order to increase the surface smoothness.

Paper feeding belt 13 which is passed along with the wet web 1 through the guide roll 18 to the second nip N _2, the elastic member (e.g., rubber) and smooth surface made of fine breathable (ie possible slight water absorption) Have The paper passing belt 13 improves the paper passing property of the wet paper 1 by passing through the nip portion N ₂ together with the wet paper 1 and causes elastic deformation at the nip portion N ₂ so as to ensure the nip width.

The paper feeding belt 13, to have a lower surface smoothness than the surface smoothness of the smoother bottom roll 12b, so as to transfer to the surface of Smoother lower roller 12b the wet paper 1 at the exit of the nip portion N ₂ ing. The wet paper 1 is applied with a nip pressure at the nip portion N ₂ of the smoother top roll 12 a and the smoother bottom roll 12 b together with the paper passing belt 13, and smoothing processing is performed on both sides of the wet paper 1. Thereafter, since the smoother bottom roll 12b has a higher surface smoothness than the paper passing belt 13, the wet paper 1 is continuously conveyed while adhering to the surface of the smoother bottom roll 12b.

  Thereafter, the wet paper 1 is transferred to the dryer part 3 together with the canvas 7c, and the wet paper 1 is dried through the first dryer roll 3a, the second dryer roll (not shown), and the third dryer roll in this order. Reference numerals 20a and 20b in FIG. 1 are vacuum rolls. Reference numerals 14 to 19 and 22 denote guide rolls that support the wet paper 1, the felts 6a and 6b, the paper passing belt 13, and the like and determine their moving paths. FIG. 1 shows a machine configuration in which a smoother press is installed on the downstream side of a double felt press. However, the present invention has two double felt roll presses or two double felt shoe presses (usually called tandem presses). It is also possible to apply to individual press nips.

  Next, the structure of the rehumidification suppression apparatus 30 which is the principal part of this embodiment is demonstrated based on FIG.2 and FIG.3. FIG. 2 is a vertical elevation view of the rehumidification suppressing device 30, and FIG. 3 is a perspective view of a pickup blade disposed on the most upstream side. 2 and 3, the rewetting suppression device 30 is provided on the back side of the upper felt 6 a just downstream of the nip portion between the shoe module 4 a and the press buttom roll 4 b constituting the final press 4 for dehydration. The housing 31 of the rehumidification suppressing device 30 is partitioned into a white water recovery space 32 and a vacuum forming space 33 by a partition wall 34. The partition wall 34 includes a side wall 341 that partitions the white water recovery space 32 and the vacuum forming space 33 in the wet paper transport direction, and a bottom wall 342 that extends upstream in the wet paper transport direction and forms the bottom surface of the white water recovery space 32. Become.

  On the lower surface of the housing 31, a first pickup blade 35a, a second pickup blade 35b, and a third pickup blade 35c are provided in this order from the upstream side in the wet paper web transfer direction. These pickup blades are made of ceramic. A space i is provided between these pickup blades, and a suction path 331 that is partitioned by a bottom wall 342 and communicates with the vacuum forming space 33 is provided on the back side of the pickup blade. Further, the vacuum forming space 33 is provided with a connection port 36 connected to a vacuum pump (not shown) for decompressing the vacuum forming space 33, and at the back of the white water recovery space 32, a discharge port opening in the bottom wall 342. A white water discharge pipe 37 connected to 37a is attached.

When the wet paper 1 passes through the nip portion between the shoe module 4a and the press bottom roll 4b of the final press 4 for dehydration, a splash s is generated in which the white water w is separated from the wet paper 1 and scattered from the upper and lower felts 6a and 6b. Alternatively, white water w is sent along with the upper felt 6a on the back surface of the upper felt 6a.
On the other hand, the rewetting suppression device 30 is provided with an opening 311 between the housing 31 and the bottom wall 342 so as to face the upstream side in the wet paper transport direction, and is separated from the wet paper 1 and scattered on the back side of the upper felt 6a. The white water w enters the white water recovery space 32 in the housing 31 through the opening 311.

  Further, the white water that is carried on the back surface of the upper felt 6 a is scooped up on the top surface of the first pickup blade 35 a and enters the white water collection space 32 through the opening 311. The white water w that has entered the white water recovery space 32 flows on the upper surface 342a of the bottom wall 342, reaches the discharge port 37a, and is discharged to the outside through the discharge pipe 37.

FIG. 3 is a cross-sectional view showing the tip of the first pickup blade 35a. The blade surface 351 of the first pickup blade 35a is disposed along the upper felt 6a at a position substantially in contact with the upper felt 6a. The distal end of the first pickup blade 35a is, _{R 1} suitable 1.0~10.0mm to scoop the white water coming to feed Ban on the back of the upper felt 6a is formed.

  Concave grooves 353 and 354 as shown in FIGS. 4 and 5 are formed on the blade surfaces 351 and 352 in contact with the upper felt 6a of the first pickup blade 35a and the second pickup blade 35b. The concave groove 353 or 354 opens in a rectangular shape with respect to the blade surface 351 or 352. In FIG. 4, a plurality of concave grooves 353 are arranged in parallel on the blade surface 351 of the first pickup blade 35 a with a certain inclination angle α with respect to the wet paper web transport direction a. The groove 353 is configured such that the groove depth gradually increases from the upstream side to the downstream side in the wet paper web transport direction a.

  On the other hand, on the blade surface 352 of the second pickup blade 35b, a plurality of concave grooves 354 inclined in parallel with the concave grooves 353 with respect to the wet paper web transport direction a by −α are arranged. Similarly to the concave groove 353, the concave groove 354 is configured such that the groove depth gradually increases from the upstream side to the downstream side in the wet paper web transport direction a.

  In the rehumidification suppressing device 30, by operating a vacuum pump (not shown), the air in the vacuum forming space 33 is discharged to the outside, whereby the vacuum forming space 33 is brought into a vacuum state. The vacuum forming space 33 communicates with the back side of each pickup blade via a suction path 331. Therefore, the upper felt 6a is sucked from the interval i between the pickup blades, and white water in the upper felt 6a is sucked. Further, since the concave grooves 353 and 354 formed in the blade surfaces 351 and 352 of the first pickup blade 35a and the second pickup blade 35b are also communicated with the suction path 331, the vacuum state is established, and even in these concave grooves, the upper felt 6a. It has an action to suck.

  Since the groove depths 353 and 354 are configured so that the groove depth gradually increases from the upstream side to the downstream side in the wet paper web transfer direction, the structure is easy to express the foil effect. A vacuum state can be maintained. In this way, the distance i between the pickup blades and the suction action from the concave grooves 353 and 354 act on the wet paper 1 through the upper felt 6a, so that the wet paper 1 is carried by the upper felt 6a and conveyed.

As shown in FIG. 4, the blade surface 351 of the first pickup blade 35a has a curvature with a large radius of curvature R _2, and forms an arc shape protruding upward the felt 6a side. Further, the lower felt 6 b is guided by the guide roll 16 at the position of the blade surface 351 so as to be separated from the wet paper 1. With this configuration, the lower felt 6 b can be easily separated from the wet paper 1.

  The white water splashed downward from the lower felt 6b falls as it is under the action of gravity, and further, as described above, the lower felt 6b is separated from the wet paper web 1 at the position of the first pickup blade 35a. The backflow of white water from the felts 6a and 6b to the wet paper 1 is reduced. It should be noted that the blade surfaces in contact with the upper felt 6a of the second pickup blade 35b and the third pickup blade 35c are formed in a flat shape.

  As described above, according to the present embodiment, the rehumidification suppressing device 30 is provided immediately downstream of the final press 4 for dehydration, and the lower felt 6 b is separated from the wet paper web 1 at the installation position of the rehumidification suppressing device 30. By providing the roll 16, white water splashed downstream in the wet paper web transport direction at the nip portion of the final press 4 for dehydration and white water accompanying the back surface of the upper felt 6a downstream of the nip portion is wet paper web. The water content of the wet paper 1 is reduced by suppressing the backflow to 1 and reducing the time (in other words, the distance is determined when the speed is determined) between both the wet paper upper felt and the lower felt. Can be reduced. The increase in wet paper web moisture due to rewetting is about 2 to 6% by weight, and the final wet paper web moisture can be reduced by suppressing the increase in wet paper web 1 moisture due to rewetting.

  In this embodiment, the concave grooves 353 and 354 are provided on the blade surfaces 351 and 352 of the first pickup blade 35a and the second pickup blade 35b. However, the foil effect is also applied to the blade surface 355 of the third pickup blade 35c. In order to provide the above, a concave groove may be provided. Conversely, only the first pickup blade 35a may have a concave groove, and the downstream second and third pickup blades 35b and 35c may have no concave groove. This can be changed depending on the weight of the wet paper (basis weight g / m 2 / wet paper density% / 100) and the paper making speed.

  Further, in the present embodiment, as shown in FIG. 5, by inclining the concave groove 351 and the wet paper web transport direction a by α, the suction action can be made to act uniformly in the paper width direction of the wet paper web 1. it can. Therefore, a uniform history including a uniform suction action in the paper width direction of the wet paper web 1 can be given, and there is no possibility of local damage to the felt such as local hair loss.

  Further, since the concave groove 353 has an inclination angle α with respect to the wet paper web transport direction a by the first pickup blade 35a, when the wet paper 1 passes through the concave groove 353, a component force biased to one side in the paper width direction is generated. Therefore, the wet paper web 1 may meander, but in this embodiment, as shown in FIG. 5, the concave groove 354 of the second pickup blade 35b is defined as the concave groove 353 with respect to the wet paper web transport direction a. Since it is inclined symmetrically by −α, the component force in the paper width direction received by the wet paper web 1 by the first pickup blade 35a and the component force in the paper width direction received by the second pickup blade 35b can be suspended. Therefore, the wet paper web 1 does not deviate to one side in the paper width direction or meander.

In the present embodiment, the first to third pickup blades 35a, 35b, and 35c are made of ceramic, so that they do not rust like metal and have good heat resistance and wear resistance. Compared to resin or metal, the service life can be extended significantly. Moreover, since it does not thermally expand, good dimensional accuracy can be obtained.
(Embodiment 2)

  A second embodiment of the present invention will be described with reference to FIG. FIG. 6A shows an embodiment in which a concave groove having a shape different from that of the first embodiment is provided on the blade surface 401 of the first pickup blade 40a and the blade surface 402 of the second pickup blade 40b. The groove provided in the blade surfaces 401 and 402 has a rectangular opening with respect to the blade surface, and the left half is a groove 403a having an inclination angle α with respect to the wet paper web transport direction a. The right half is composed of a concave groove 403b having an inclination angle -α with respect to the wet paper web transport direction a. Other configurations are the same as the grooves 353 and 354 shown in FIG. For example, the groove depth gradually increases toward the downstream side in the wet paper web transfer direction.

  Due to the concave grooves 403a and 403b having such a configuration, the wet paper 1 can be given a uniform history in the paper width direction of the wet paper 1, there is no possibility of local damage, and the paper width direction applied to the wet paper 1 Are added so that the left side is directed to the left and the right side is directed to the right from the center of the wet paper 1, and the right and left component forces are equal. A so-called wet paper width-expanding action in which a force acts in the direction works, so that the wet paper 1 does not wrinkle or meander.

  FIG. 6B shows another example of the concave groove. In FIG. 6B, the concave groove 503 formed on the blade surface 501 of the first pick-up blade 50a is disposed so as to be inclined with respect to the wet paper web transport direction a and on the downstream side in the wet paper web feed direction. It is formed so as to gradually become wider. The concave groove 504 engraved on the second pickup blade 50b is inclined in the opposite direction so as to be symmetrical with the concave groove 503 with respect to the wet paper web transport direction a, and gradually widens toward the downstream side in the wet paper web transport direction. It is formed to become. Other configurations are the same as the concave grooves 353 and 354 shown in FIG.

  Since the concave grooves 503 and 504 having such a configuration are inclined with respect to the wet paper web transport direction a, a uniform history can be given in the paper width direction of the wet paper web 1 and there is no possibility of causing local damage. In addition, since it is formed so as to gradually become wider toward the downstream side in the wet paper web transport direction, the opening area of the concave groove is larger than the concave grooves 353 and 354 in FIG. It is easy to form a vacuum state up to the upstream end, and the wet paper web 1 can be held more stably.

  FIG. 6C further shows another example of the concave groove. In FIG. 6C, the concave groove 603 formed on the blade surface 601 of the first pickup blade 60a is disposed so as to be inclined with respect to the wet paper web transport direction a and on the upstream side in the wet paper web transport direction. It is formed to be wide and gradually narrow toward the downstream side. The concave groove 504 carved in the second pickup blade 50b is inclined in the opposite direction so as to be symmetric with the concave groove 503 with respect to the wet paper web transport direction a, and gradually increases in width toward the downstream side in the wet paper web transport direction. It is formed to be narrow. Other configurations are the same as the concave grooves 353 and 354 shown in FIG.

  In the concave grooves 603 and 604 having such a configuration, in addition to the function and effect of being inclined with respect to the wet paper web transport direction a, it is possible to reliably form a vacuum state at the tip of the concave groove in the wet paper web transport direction . Therefore, the vacuum state can be surely formed up to the tips of the blade surfaces 601 and 602.

FIG. 6D shows an example in which a large number of through holes 702 are dispersedly arranged on the blade surface 701 in contact with the upper felt 6a of the pickup blade 70 instead of the concave grooves. The through-hole 702 is disposed so as to be inclined in the direction of the wet paper web transport direction a. The through hole 702 may be arranged in a direction orthogonal to the blade surface 701. However, as shown in FIG. 6D, if it is inclined toward the wet paper web transport direction a, it is sucked from the upper felt 6a. The flow resistance of white water can be reduced and the suction effect can be increased.
(Embodiment 3)

  Next, a third embodiment of the present invention will be described with reference to FIGS. In FIG. 7, the pickup blade 80 is not limited to either the first pickup blade arranged on the most upstream side or the pickup blade arranged subsequent thereto, and is a pickup blade used in common for both. On the blade surface 81 in contact with the upper felt 6a of the pickup blade 80, a plurality of concave grooves 82 are formed in the wet paper web transport direction a. Similar to the groove 353 or 354 in FIG. 5, the shape of the opening in which the groove 82 opens in the blade surface 81 is rectangular, and the longitudinal axis direction of the rectangle is inclined with respect to the wet paper web transport direction a. At the same time, the groove depth gradually increases toward the downstream side in the wet paper web transfer direction.

  A compressed air supply hole 83 is formed in the paper width direction on the upstream side of the pickup blade 80 in the wet paper transport direction, and the compressed air supply hole 83 is communicated with a compressed air supply device 85 (not shown) through a pipe line 86. Further, the upstream end of the compressed air supply hole 81 and each concave groove 82 in the wet paper transport direction is communicated with an air flow path 84. The downstream side of each concave groove 82 in the wet paper conveyance direction communicates with the white water recovery space 32 via a suction path 331 shown in FIG. In FIG. 7, the concave grooves 82 are arranged at equal intervals in the paper width direction, but only a part of the concave grooves 82 and the air flow paths 84 are illustrated, and the others are omitted.

  In this configuration, when compressed air c is supplied from the compressed air supply device 85 to the compressed air supply hole 83, the compressed air c flows into the upstream end of each concave groove 82 in the wet paper transport direction through the air flow path 84. To do. If the compressed air c flows in each ditch | groove 82 at high speed toward the wet paper web conveyance direction a, the inside of each ditch | groove 82 will become negative pressure. The negative pressure in each concave groove 82 causes a suction force to suck the upper felt 6a, and white water can be sucked from the upper felt 6a. Thus, in this embodiment, since the suction | attraction force which attracts | sucks the upper felt 6a with the compressed air c can be generated, a vacuum formation means becomes unnecessary.

  FIG. 8 shows a modification of the third embodiment using compressed air. In FIG. 8, the pick-up blade 90 is a pick-up blade that is not limited to either the first pick-up blade disposed on the most upstream side or the pick-up blade disposed subsequent thereto, similarly to the pick-up blade 80 of FIG. In this modification, instead of forming the compressed air supply hole 83 inside the pickup blade 80 in the third embodiment, a container 93 is attached to the upstream end surface of the wet paper web transport direction a outside the pickup blade 90, This is an alternative to the compressed air supply hole 83.

  A plurality of concave grooves 92 are arranged side by side on the blade surface 91 in contact with the upper felt 6 a of the pickup blade 90, and the plurality of concave grooves 92 and the container 93 communicate with each other through an air flow path 94. The concave groove 92 has the same configuration as the concave groove 82 shown in FIG. With this configuration, when compressed air c is supplied from the compressed air supply device 95 to the container 93 via the pipe 96, the compressed air c is connected to the upstream end of each concave groove 92 in the wet paper transport direction via the air flow path 94. To supply. When compressed air c is supplied to each concave groove 92 and compressed air c flows in each concave groove 93 at a high speed in the wet paper web transport direction a, the negative pressure is generated in each concave groove 92 as in the third embodiment. As a result, a suction force for sucking the upper felt 6a to the pickup blade 90 works. Therefore, white water can be sucked from the upper felt 6a.

  According to this modification, instead of forming the compressed air supply hole 83 inside the pickup blade 80 as in the third embodiment, it is only necessary to attach the container 93 to the pickup blade 90. There is an advantage that the processing cost can be reduced.

  According to the present invention, in the press part of the paper machine, the white water separated from the wet paper to the felt side is prevented from flowing back to the wet paper after passing through the dehydrating press device, thereby improving the dewatering efficiency. Can be improved.

It is a block diagram of 1st Embodiment of this invention. It is a vertical elevation view of the rehumidification suppressing device 30 of the first embodiment. FIG. 3 is a partially enlarged view of the rewet suppression device 30. 3 is a partially enlarged perspective view of the rehumidification suppressing device 30. FIG. (A) is a schematic diagram of a part of the rehumidification suppressing device 30, and (b) is a cross-sectional view taken along line AA in (a). (A)-(c) is a schematic diagram which shows 2nd Embodiment of this invention and its modification, (d) is sectional drawing which shows another modification. It is a perspective view of 3rd Embodiment of this invention. It is a perspective view of the modification of the said 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wet paper 2 Press part 4 Final press for dehydration 4a Shoe module 4b Press bottom roll 6a Upper felt 6b Lower felt 16 Guide roll (guide means)
30 Rewetting suppression device 33 Vacuum forming space 35a First pickup blade 35b Second pickup blade 35c Third pickup blade 36 Connection port to pump (vacuum suction device) 37a Discharge port 84, 94 Air channel (compressed air channel)
85, 95 Compressed air supply device 331 Suction passage 342a Bottom wall upper surface (discharge passage)
351, 352 Blade surface 353, 354 Concave groove 702 Through hole i Interval R ₂ Radius of curvature w White water s Splash

Claims (12)

In the press process of the paper machine, after dehydrating under pressure through the press device with the wet paper sandwiched between water-absorbing felts, in the rehumidification suppressing method for suppressing the dehydrated white water from flowing back to the wet paper,
While scooping white water separated on the back side of the upper felt with a pick-up blade provided on the back side of the upper felt on the downstream side of the press device,
Forming a negative pressure between the back surface of the upper felt and the blade surface of the pick-up blade facing the back surface of the upper felt, thereby causing the upper felt to suck the wet paper;
The lower felt is guided so as to separate the lower felt from the upper felt from the installation position of the pickup blade, and the wet paper is supported only on the upper felt immediately downstream of the press device. How to control rewetting of wet paper.   The blade surface of the pick-up blade facing the back surface of the upper felt is provided with a cross-section arc-shaped curvature protruding toward the back side of the upper felt, and the lower felt is separated from the wet paper and the upper felt starting from the curved portion. The method for suppressing rewetting of wet paper according to claim 1.   A negative pressure is formed between the back surface of the upper felt and the blade surface by forming a negative pressure in a concave groove or a through hole provided in the blade surface of the pickup blade facing the back surface of the upper felt. The method for suppressing rewetting of wet paper according to claim 1 or 2. In the press part of the paper machine, on the downstream side of the press device that pressurizes and dehydrates the wet paper with water-absorbing felt, in the rehumidification suppression device that suppresses the reverse flow of the dehydrated white water to the wet paper,
A pickup blade provided on the back surface of the upper felt on the downstream side of the pressing device and scooping up white water separated on the back surface side of the upper felt;
Means for creating a negative pressure between a back surface of the upper felt and a blade surface of the pickup blade facing the back surface of the upper felt;
Guide means for guiding the lower felt so as to separate the lower felt from the upper felt starting from the installation position of the pickup blade;
A wet paper re-wetting suppression device, wherein the wet paper is supported only by the upper felt on the downstream side of the press device.   The blade surface of the pick-up blade facing the back surface of the upper felt is provided with a cross-section arc-shaped curvature protruding toward the back side of the upper felt, and the lower felt is separated from the wet paper and the upper felt starting from the curved portion. The wet paper web rewetting suppression device according to claim 4.   The negative pressure forming means includes a concave groove or a through hole provided in the pickup blade and opening on a blade surface of the pickup blade, and a vacuum suction device for forming a negative pressure in the concave groove or the through hole. The apparatus for suppressing rewetting of wet paper according to claim 4.   The negative pressure forming means includes a concave groove provided in the pickup blade and opening on a blade surface of the pickup blade, a compressed air flow path connected to one end of the concave groove, and a compressed air in the compressed air flow path. 5. The wet paper web rewetting suppression device according to claim 4, wherein a negative pressure is formed by supplying compressed air into the groove.   The said pick-up blade, the discharge path which leads to the discharge port which discharges the white water scooped up with this pick-up blade to the outside, and the said negative pressure formation means were comprised integrally, The said negative pressure formation means was comprised integrally. Wet paper rewetting suppression device.   The pickup blade is provided in a plurality of stages at intervals along the wet paper web transfer direction, the curvature is provided on the blade surface of the most upstream pickup blade, and the blade surface of the subsequent pickup blade is flat. The wet paper web re-wetting suppression device according to claim 5.   8. The moisture according to claim 6, wherein the groove is configured such that the groove depth gradually increases toward a suction direction by the vacuum suction device or toward a downstream side in a flow direction of the compressed air. Paper rewetting suppression device.   8. The wet paper web rewetting suppression device according to claim 6, wherein the concave grooves are provided so as to be inclined in the wet paper width direction, or the through holes are dispersed in the wet paper width direction.   10. The wet paper web rewetting suppression device according to claim 4, wherein the pickup blade is made of ceramic.

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