Patent Publication Number: US-2006013951-A1

Title: Coater and method for producing coated sgeet and air floating mini-turn bar

Description:
TECHNICAL FIELD  
      The present invention relates to an apparatus and method, which are used in paper-making machines, resin-film manufacturing machines, etc., for applying a coating solution to the surface of a web such as paper, resin film, etc., and also relates to an air-flotation type mini turn bar that is suitably used in the coating apparatus.  
     BACKGROUND ART  
      In paper-making machines, resin-film manufacturing machines, etc., there is provided an apparatus for applying a coating solution to the surface of a web such as paper, resin film, etc.  
       FIG. 14  is a simplified side view showing a conventional coating apparatus. As illustrated in the figure, a web  1 , such as paper, etc., is fed from a previous step and passes between the web-nipping portions  20  of two applicator rolls  2  which are formed when they are pressed against each other. After the web  1  is coated with a coating solution, it goes into a drier  6  via a turn bar (air-flotation/non-contact type web-travel supporting unit)  5  that conveys the web  1  while floating it.  
      The application of a coating solution to both sides of the web  1  is performed as follows:  
      Each applicator roll  2  includes a main body  2   a  made of metal such as steel, etc. The roll main body  2   a  has an elastic film  2   b  such as a film of rubber on the outer periphery. Each applicator roll  2  rotates at the same circumferential speed as the travel speed of the web  1 . The applicator roll  2  is equipped with a coater head  3 , which is a means of supplying a coating solution to the surface of the elastic film  2   b.    
      The coater head  3  contains measurement means such as a coating solution supply passage, measuring rod, blade, etc. After a sufficient quantity of coating solution is supplied from the coater head  3  to the surface of the applicator roll  2 , at the exist of the coater head the measuring rod is pressed against the surface of the applicator roll  2  to form a film of coating solution with a predetermined thickness on the surface of the applicator roll  2 .  
      Note that the film thickness of the coating solution on the applicator roll  2  is adjusted by controlling the force of pressing the measuring rod or blade against the applicator roll  2 . The technique of forming a film of coating solution on the applicator roll  2 , described above, is well known in the prior art (see, for example, Y. Miura, “Trend of the Latest Coater-Size Press Technique,” Paper-Pulp Technique Times, No. 12, 1997) and is not particularly limited.  
      A film of coating solution formed on each of the applicator rolls  2  by the above-described technique is transferred and applied to each side of the web  1  as it passes between the web-nipping portions  20  of the applicator rolls  2  which are formed when they are pressed against each other.  
      The web  1  with a film of coating solution transferred and applied to each side is conveyed to a drier  6 . At this time, as shown in  FIG. 14 , if the coating solution, transferred and applied from the applicator rolls  2  to the web  1 , is in an undried state and contacts a solid object such as a conveyance roll during conveyance, the coated surface will be flawed and the quality will be considerably degraded. Because of this, in the web conveyance between the web-nipping portions  20  of the applicator rolls  2  and drier  6 , there is used an air floater, or a turn bar  5  called a non-contact type guide member.  
      The non-contact type guide member  5  is used to support and convey the web  1  without contacting the web surface by floating the web  1  with the force of air. Therefore, the web  1  can be conveyed to the drier  6  without degrading the quality of the coated surface in an undried state, formed on the surface of the web  1 .  
      Now, a description will be given of problems found in the above-described conventional technique.  
      In the case where the web  1  is paper that absorbs water, water absorption sometimes causes elongation and shrinkage of the web  1 , if a coating solution is transferred and applied to the web  1 . Also, in the case where the web  1  is resin film, etc., and is elongated or shrunk by the temperature of a coating solution, elongation and shrinkage sometimes occurs in the web  1 , if a film of coating solution is transferred and applied to each side of the web  1  at the web-nipping portions  20  of the applicator rolls  2 .  
      On the other hand, the above-described conventional technique, as shown in  FIG. 14 , does not have any device that regulates the path of the web  1  between the web-nipping portions  20  of the applicator rolls  2  and the turn bar  5 .  
      Therefore, in the case where there occurs elongation and shrinkage in the web  1 , and the web  1  is elongated particularly at the exist of the web-nipping portions  20 , the web  1  sometimes travels while sticking to the surface of one of the upper and lower applicator rolls  2  because of the stickiness of a coating solution, as shown in  FIG. 15 .  
      When the web  1  is wide (in the width direction of the applicator roll  2 ), the state of sticking becomes uneven in the width direction of the web  1 . That is, one portion of the web  1  in the web width direction sticks to the upper applicator roll  2 , while another portion sticks to the lower applicator roll  2 . Therefore, there are cases where the web  1  vibrates between the surfaces of the upper and lower applicator rolls  2 .  
      In the case where coating operations are performed at high speeds, there are cases where the state of uneven sticking starts to fluctuate temporally and becomes unstable. This phenomenon is disclosed, for example, in Japanese Laid-Open Patent Publication No. HEI 7-163924.  
      When the position and angle at which the web  1  is separated from the applicator roll  2  are uneven and unstable, there are cases where coating unevenness, called peeling patterns such as that shown by reference numeral  11  in  FIG. 16 , take places in the coated film on the web  1 . This phenomenon is, for example, the same as that shown in FIGS. 4 and 8 of Japanese Patent No. 2578183.  
      The above-described phenomenon is considered to take place for the following reasons: when the coating solution between the surface of the web  1  and the surface of the applicator roll  2  is split between the applicator roll side and the web surface side after the web  1  passes between the web-nipping portions of the applicator rolls  2 , the meniscus of the split solution becomes unstable; as a result, the transfer rate of the coating solution that is transferred from the applicator roll  2  to the web surface becomes temporally and spatially unstable; and the film thickness of the coating solution formed on the web surface becomes uneven.  
      In addition to the peeling patterns, there is a fear of a misting phenomenon occurring. That is, in the case of high-speed coating operations, a coating solution scatters in drops because of the above-described meniscus unstableness. If this phenomenon takes place, the coating apparatus and coated paper will be stained with a coating solution and there will be a possibility of operations being suspended.  
      The present invention has been made in view of the circumstances described above. Accordingly, it is the object of the present invention to provide a coating apparatus and coating method which are capable of evenly forming a film of coating solution on each side of a web by suppressing the occurrence of a mist and coating unevenness, while preventing the occurrence of flaws in the coated surfaces.  
     DISCLOSURE OF THE INVENTION  
      To achieve this end, there is provided an apparatus that transfers and applies a film of coating solution on each of two applicator rolls to each side of a web as it passes between web-nipping portions of the two applicator rolls which are formed when they are pressed against each other. The apparatus includes an air-flotation type mini turn bar, which is provided to the downstream side of the web-nipping portions. The air-flotation type mini turn bar is used to convey the web while holding the web on the surface of one of the two applicator rolls, after the web passes between the web-nipping portions.  
      According to the coating apparatus of the present invention, the air-flotation type mini turn bar is able to convey the web while holding the web on the surface of one of the two applicator rolls, after the web passes between the web-nipping portions. By forcibly holding the web on the surface of one of the two applicator rolls, the position at which the web is separated from the applicator roll becomes stable. For instance, the occurrence of coating unevenness called peeling patterns can be prevented, and consequently, coating quality can be considerably enhanced.  
      Preferably, the coating apparatus of the present invention further includes a mechanism that moves the mini turn bar. Preferably, the mini-turn-bar moving mechanism is constructed to adjust the distance that the wed is held on one of the two applicator rolls, or adjust the distance between the one applicator roll and the mini turn bar. By providing the mini-turn-bar moving mechanism, the separation of the web from one of the two applicator rolls and the application of a coating solution from the one applicator roll to the web can be adjusted.  
      Preferably, the coating apparatus of the present invention further includes a paper roll, which is provided to the upstream side of the web-nipping portions. The paper roll is used to convey the web while holding the web on the surface of the other of the two applicator rolls, before the web passes between the web-nipping portions. By providing the paper roll, the application of a coating solution from the other applicator roll to the web can be suitably adjusted.  
      In this case, the coating apparatus of the present invention preferably includes a mechanism that moves the paper roll. By providing the paper-roll moving mechanism (position adjustment mechanism), the application of a coating solution from the other applicator roll to the web can be suitably adjusted.  
      In accordance with the present invention, there is provided an air-flotation type mini turn bar that causes a web to travel so as to form an arcuately curved portion around the bar by floating the web with air. The air-flotation type mini turn bar includes a first air pocket arranged inside the arcuately curved portion of the web; a second air pocket provided adjacent to the first air pocket and arranged near an entrance portion of the curved portion; a third air pocket provided adjacent to the first air pocket and arranged near an exit portion of the curved portion; a first air nozzle provided between the first air pocket and the second air pocket for squirting air toward the web; and a second air nozzle provided between the first air pocket and the third air pocket for squirting air toward the web.  
      According to the above-described air-flotation type mini turn bar, the bottom surface of the curved portion of the web can be stably supported by both the dynamic pressure of air squired from each of the air nozzles and the static pressure of air within each of the air pockets, and the web is able to travel so as to form an arcuately curved portion around the mini turn bar without being contacted by the mini turn bar. Therefore, in the case where the web is coated paper, there is no possibility that the coated surfaces of the web will contact the mini turn bar, and the problem of flaws in coated surfaces can be prevented.  
      Preferably, the air-flotation type mini turn bar further includes a third air nozzle that squirts higher-pressure air than atmospheric pressure into the first air pocket. According to the third air nozzle, the static pressure within the first air pocket is made higher. This can compensate for a reduction in the dynamic pressure component of the wake air in the partition wall portion between air pockets, particularly the first air pocket and third air pocket. Therefore, the web and partition wall portion can be prevented from contacting each other because of negative pressure.  
      Preferably, a shape from the second air pocket to the third air pocket is formed symmetrically with respect to the center line of the first air pocket. According to this shape, the web can travel along a path having a fixed radius of curvature and stable web travel becomes possible.  
      Furthermore, the air-flotation type mini turn bar preferably adopts a labyrinth structure. That is, the air-flotation type mini turn bar further includes a plurality of first baffle walls, which are provided in the direction of the width of the web within the first air pocket so that the first air pocket is segmented into a plurality of sections. Also, the air-flotation type mini turn bar includes a plurality of second baffle walls and a plurality of third baffle walls. The second baffle walls are provided in the direction of the width of the web within the second air pocket so that the second air pocket is segmented into a plurality of sections. The third baffle walls are provided in the direction of the width of the web within the third air pocket so that the third air pocket is segmented into a plurality of sections. According to this labyrinth structure, the web can be supported by the static pressure within each section. Therefore, even when the web shifts in the width direction, a fluctuation in the supporting pressure is slight. Also, since each baffle wall is resistant to the wake air, the interior static pressure becomes higher. Therefore, according to such a labyrinth structure, the web can be more stably supported and the web can be prevented from vibrating and making a noise.  
      Preferably, the second air nozzle includes a second air-jet surface and a second slit-shaped air-jet groove, which are provided on a third surface extending in the direction of the width of the web. The second air-jet surface has a great number of air-jet bores and is provided near the first air pocket. The second air-jet groove extends in the direction of the width of the web and is provided near the third air pocket.  
      The structure of the second air nozzle can reliably prevent contact of the web at the baffle wall portion between the first air pocket and third air pocket where contact with the web is liable to occur because of a reduction in the dynamic pressure component of the wake air. Preferably, the first air nozzle has the same structure as the second air nozzle. That is, the first air nozzle includes a first air-jet surface and a first slit-shaped air-jet groove, which are provided on the third surface extending in the direction of the width of the web. The first air-jet surface has a great number of air-jet bores and is provided near the first air pocket. The first air-jet groove extends in the direction of the width of the web and is provided near the second air pocket. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention will be described in further detail with reference to the accompanying drawings wherein:  
       FIG. 1  is a simplified side view showing a coating apparatus constructed in accordance with a first embodiment of the present invention;  
       FIG. 2  is a simplified side view showing a mini turn bar constructed in accordance with the first embodiment of the present invention;  
       FIG. 3A  is a simplified sectional view showing an example of the mini turn bar of the first embodiment;  
       FIG. 3B  is a simplified sectional view showing another example of the mini turn bar of the first embodiment;  
       FIG. 4  is a simplified side view showing a coating apparatus constructed in accordance with a second embodiment of the present invention;  
       FIG. 5  is a simplified side view showing a coating apparatus constructed in accordance with a third embodiment of the present invention;  
       FIG. 6  is a simplified side view showing an alteration of the coating apparatus constructed in accordance with the third embodiment of the present invention;  
       FIG. 7  is a simplified sectional view showing a first mini turn bar that is preferable in structure to the mini turn bar of the first embodiment;  
       FIG. 8  is a simplified sectional view showing a second mini turn bar that is preferable in structure to the mini turn bar of the first embodiment;  
       FIG. 9  is a simplified sectional view showing a third mini turn bar that is preferable in structure to the mini turn bar of the first embodiment;  
       FIG. 10  is a simplified sectional view showing a fourth mini turn bar that is preferable in structure to the mini turn bar of the first embodiment;  
       FIG. 11  is a simplified sectional view showing a fifth mini turn bar that is preferable in structure to the mini turn bar of the first embodiment;  
       FIG. 12A  is a simplified sectional view showing a sixth mini turn bar that is preferable in structure to the mini turn bar of the first embodiment;  
       FIG. 12B  is a plan view of the mini turn bar seen from A direction of  FIG. 12A  and denotes the baffle plate by hatching for distinction;  
       FIG. 13  is a simplified sectional view showing a seventh mini turn bar that is preferable in structure to the mini turn bar of the first embodiment;  
       FIG. 14  is a simplified side view showing a conventional coating apparatus;  
       FIG. 15  is a simplified side view of web-nipping portions used to explain problems found in the conventional coating apparatus; and  
       FIG. 16  is a simplified plan view of a web used to explain problems found in the conventional coating apparatus. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION  
      Embodiments of the present invention will hereinafter be described with reference to the drawings.  
     (A) First Embodiment  
      First, a first embodiment of the present invention will be described in conjunction with the drawings.  
      As illustrated in  FIG. 1 , a coating apparatus is equipped with two applicator rolls  2 ,  2 , which are arranged opposite each other so as to form web-nipping portions  20  when they are pressed against each other. A film of coating solution, supplied to each of the applicator rolls  2 , 2  by a coater head  3 , is transferred and applied to each side of a web  1  as it passes between the web-nipping portions  20 . The coated web  1  is guided without being contacted by a turn bar (air-flotation/non-contact type web-travel supporting unit)  5  and goes into a drier  6 . Each applicator roll  2 , as with the above-described conventional applicator roll, includes a main body  2   a  made of metal such as steel, etc. The roll main body  2   a  has an elastic film  2   b  such as a film of rubber on the outer periphery.  
      The coating apparatus, as illustrated in  FIGS. 1 and 2 , further includes an air-flotation type mini turn bar  4  (which is an air-flotation/non-contact type web-travel support unit and smaller in size than the turn bar  5 , and which will hereinafter be referred to simply as a mini turn bar). The mini turn bar  4  functions as a web-separating unit and is arranged in close proximity to a portion of one of the two applicator rolls  2  (e.g., the upper applicator roll  2  in the first embodiment) which is downstream from the web-nipping portion  20 . The mini turn bar  4  is used to convey the web  1  while holding it on the surface of the upper applicator roll  2 . In this way, the position at which the web  1  with a film of coating solution is separated from the upper applicator roll  2  is stabilized, and the web-separating position is kept constant in the direction of the width of the web  1 .  
      This mini turn bar  4  has, for example, a cross section such as that shown in  FIGS. 2 and 3 A and extends in the width direction of the web  1 . The mini turn bar  4  is equipped with an internal space (flow passageway)  4   a  to which compressed air is supplied, a guide surface  4   b  disposed opposite the web  1 , and nozzles  4   c ,  4   d  provided in the guide surface  4   b . The nozzles  4   c ,  4   d  are used to squirt the compressed air within the interior space  4   a  toward the web  1 .  
      With this arrangement, the mini turn bar  4  presses the web  1  toward the surface of the upper applicator roll  2  without contacting the web  1  by the compressed air squirted from the nozzles  4   c ,  4   d . That is, the path of the web  1  is directed toward the upper applicator roll side by the mini turn bar  4 .  
      As a result, the web  1  contacts the surface of the upper applicator roll  2  a little longer, but since the angle α at which the web  1  is separated from the upper applicator roll  2  becomes greater, the position at which the web is separated becomes stable.  
      That is, as shown in  FIGS. 1 and 2 , by arranging the mini turn bar  4 , the web  1  from the web-nipping portions  20  of the applicator rolls  2  travels while it is being held on the surface of the upper applicator roll  2 . And at the position of the mini turn bar  4 , the web  1  is forcibly separated toward the position of the turn bar  5 . At this time, the mini turn bar  4  creates a layer of air between the web  1  and the guide surface  4   b  of the mini turn bar  4 . Since this layer of air prevents the surface of the coated web  1  from contacting the mini turn bar  4 , degradation in the quality of the coated web  1  is prevented.  
      To create a layer of air between the guide surface  4   b  of the mini turn bar  4  and the web  1 , the guide surface  4   b  facing the web  1  is provided with nozzles  4   c ,  4   d . Also, the surface  4   b  facing the web  1  is formed as an air-jet guide surface that has a smoothly curved cross section.  
      The nozzles  4   c ,  4   d  are constructed as a great number of holes juxtaposed in the longitudinal direction of the mini turn bar  4 , or they are constructed as two slits extending in the longitudinal direction, or they are constructed as a combination of such holes and slits.  
      Also, in the first embodiment, the nozzles  4   c ,  4   d  are provided on the front side (downstream side in the traveling direction of the web  1 ) and rear side (upstream in the traveling direction of the web  1 ) of the guide surface  4   b , respectively. The nozzles  4   c ,  4   d  are constructed to squirt compressed air in the directions of arrows a 1  and a 2 , respectively. This is for the purpose of creating a stable layer of air between the guide surface  4   b  and the web  1  and stably causing the path of the web  1  to be close to one of the two applicator rolls  2 .  
      To stably cause the path of the web  1  to be close to one of the two applicator rolls  2 , it is effective not only to squirt compressed air toward the web  1 , but also to create a stable layer of air between the web guide surface  4   b  and the web  1  so that air is stored between the web guide surface  4   b  and the web  1 . If both nozzles  4   c ,  4   d  are actuated, air is stored between the guide surface  4   b  and the web  1  and a stable layer of air can be created between the guide surface  4   b  and the web  1 . Hence, the nozzles  4   c ,  4   d  are formed in the front and rear portions of the guide surface  4   b , respectively.  
      To effectively utilize the energy of the squirted air for floating the web  1  off the guide surface  4   b , it is preferable that the air-jet angle θ of each of the nozzles  4   c ,  4   d  (i.e., the angle of the air-jet direction relative to the reference surface  4   e  of the mini turn bar  4 ) be within a predetermined range (e.g., a range of approximately 15 to 90 degrees).  
      That is, if the air-jet angle θ becomes 90 degrees or greater, the greater part of a flow of air from each of the nozzles  4   c ,  4   d  will flow out of the front and rear portions of the guide surface  4   b . As a result, the force acting on the web  1  is greatly reduced, the force of pressing the web  1  toward the upper applicator roll  2  becomes weak, and it becomes difficult to cause the web  1  to move along a predetermined path.  
      On the other hand, if the air-jet angle θ is too small (e.g., less than 15 degrees), the force of pressing the web  1  toward one of the two applicator rolls  2  is similarly weakened, it becomes difficult to cause the web  1  to move along a predetermined path, and there is a possibility that the web  1  will come into contact with the mini turn bar  4 .  
      Note that even if the air-jet force that acts on the web  1  is weak, it is possible to cause the web  1  to move along a predetermined path by lowering web tension. However, in this case, as shown by a two-dot chain line in  FIG. 3A , the web  1  bulges out in the vicinity of the central portion of the guide surface  4   b , and consequently, the web  1  cannot travel smoothly. Therefore, web tension cannot be lowered greatly, and if the air-jet force acting on the web  1  is weak, it is fairly difficult to cause the web  1  to move along a predetermined path.  
      Thus, it is preferable that the angle of the air-jet direction of each of the nozzles  4   c ,  4   d  relative to the reference surface  4   e  be within a predetermined range (e.g., a range of approximately 15 to 90 degrees).  
      Also, for the position at which the web  1  is separated from the surface of the upper applicator roll  2  to be stable and constant in the width direction of the web  1 , it is preferable to set the radius R of curvature of the front surface (guide surface)  4   b  of the mini turn bar  4  within a predetermined range (e.g., a range of 20 to 400 mm). And it is also preferable to cause the web  1  to travel along a path curved so as to correspond to the radius R of curvature.  
      Note that an optimum value for the radius R of curvature of the guide surface  4   b  (which corresponds to the radius of the path of the web  1  at the position of the guide surface  4   b ) varies with the layout of a roll, drier, etc., and web tension. The optimum value also varies with the viscosity of a solution that is applied to the web  1  by the coater head  3 . For example, when the viscosity of a solution is low and there is no need to separate the web  1  from the surface of the applicator roll  2  abruptly, the radius R of curvature may be great. However, when the viscosity of a solution is high and the web  1  needs to be separated from the surface of the applicator roll  2  abruptly, the radius R of curvature has to be small.  
      In addition to the radius R of curvature of the guide surface  4   b , it is preferable to optimally set the specification of the mini turn bar  4 , such as the air-jet angle and air-jet strength of the nozzles  4   c  and  4   d , etc., in accordance with the viscosity of a solution to be applied to the web  1 , web tension, and layout of each element.  
      Note that there is a relation of P=T/R between the radius R of curvature, the tension T of the web  1 , and the pressure P applied to the web  1  by the nozzles  4   c ,  4   d . The radius R of curvature, web tension T, and pressure P (air-jet angle θ and air-jet strength of the nozzles  4   c ,  4   d ) are set so as to meet the above-described relation.  
      As shown in  FIG. 3B , the guide surface  4   b  of the mini turn bar  4  facing the web  1  may be provided with a concave static pressure pocket  4   f . By reliably holding a jet of air on the guide surface  4   b  by the static pressure pocket  4   f , the jet of air can be effectively utilized for floating the web  1  off the mini turn bar  4 . That is, the energy of air squirted from the nozzles  4   c ,  4   d  can be effectively converted into pressure that presses the web  1  toward one of the two applicator rolls  2 .  
      Since the coating apparatus of the first embodiment of the present invention is constructed as described above, the application of a coating solution to the web  1  is performed in the following steps (method of applying a coating solution to the web  1 , constructed in accordance with the first embodiment).  
      That is, the web  1  is fed into the coating apparatus from a previous step, and a coating solution is applied to each side of the web  1  at the web-nipping portions of the upper and lower applicator rolls  2 . At this time, a film of coating solution is formed on each side of the web  1 . The coated web  1  is conveyed to the turn bar  5  and drier  6 .  
      In the coating apparatus and method of the first embodiment, the web  1  first passes between the web-nipping portions  20 . Then, the web  1  travels while it is being held on the surface of one (upper) of the two applicator rolls  2  by a predetermined circumferential length by the mini turn bar  4 . Next, the web  1  is forcibly separated from the upper applicator roll  2  along the guide surface  4   b  of the mini turn bar  4 .  
      That is, by air squirted from the nozzles  4   c ,  4   d  of the mini turn bar  4 , the path of the web  1  from the web-nipping portions  20  toward the turn bar  5  is forcibly pushed toward the surface of one (upper) of the two applicator rolls  2  so that the web  1  is brought into contact with the surface of the one applicator roll  2  for a long time and that the angle α at which the web  1  is separated from the surface of the one applicator roll  2  becomes great. Generally, if the angle α at which the web  1  is separated is small, the web  1  is liable to vibrate at the position where the web is separated (see  FIG. 15 ), and therefore the position at which the web  1  is separated becomes unstable. Conversely, if the angle α at which the web  1  is separated is great, the web  1  is less liable to vibrate and therefore the position at which the web  1  is separated becomes stable.  
      Further, since the position at which the web  1  is separated becomes stable, a meniscus, which is formed as a film of coating solution is split between the applicator roll side and the web surface side, becomes stable and the occurrence of a mist can be suppressed.  
      Thus, in the coating apparatus of the first embodiment, the separation angle α of the web  1  from the applicator roll  2  becomes greater by being guided along the mini turn bar  4 , the separation position of the web  1  from the applicator roll  2  becomes stable and becomes constant in the width direction of the web  1 , and the occurrence of a mist can be suppressed.  
      Hence, coating unevenness, called peeling patterns such as that shown in  FIG. 16 , and a mist, which are found in prior art, can be prevented from occurring in the coated film on the web  1 .  
      Of course, because the mini turn bar  4  is of an air-flotation type, there is no possibility that the surface of the web  1  with a film of coating solution will make contact with the mini turn bar  4  and degrade the coating quality.  
      Thus, the occurrence of coating unevenness and a mist in the web  1  can be prevented, while preventing the occurrence of a flaw in the coated surfaces of the web  1 . Therefore, the formation of an even film of coating solution becomes possible and the coating quality and operating environment are greatly enhanced.  
      Also, by setting the angle θ of the air-jet direction of each of the nozzles  4   c ,  4   d  within a predetermined range (e.g., a range of approximately 15 to 90 degrees), the energy of an air jet can be efficiently utilized for floating the web  1  off the guide surface  4   b  and there is no possibility that the web  1  will bulge out at the central portion thereof (see the two-dot chain line in  FIG. 3A ). The path of the web  1  is reliably altered by the mini turn bar  4 , so the separation position of the web  1  from the applicator roll  2  can be stabilized.  
      As shown in  FIG. 3B , if the guide surface  4   b  of the mini turn bar  4  is provided with the static pressure pocket  4   f , the energy of a jet of air can be more efficiently converted into pressure that floats the web  1  off the guide surface  4   b . As a result, the flotation of the web  1  by the mini turn bar  4  (toward one of two applicator rolls  2 ) can be reliably performed.  
      In the first embodiment, the contact (contact distance) of the web  1  with one (upper) of the two applicator rolls  2  becomes longer, so coating conditions for both sides of the web  1  will differ. Because of this, as shown by reference numeral  1 ′ and a two-dot chain line in  FIG. 1 , the angle at which the web  1  enters between the web-nipping portions  20  can be adjusted so that the contact of the web  1  with the other (lower) applicator roll  2  becomes longer. In this way, coating conditions for both sides of the web  1 , particularly the capillary osmotic conditions of a coating solution into the web  1  (base paper) can be made equal. Also, the quantities of a coating solution that are applied to both sides of the web  1  can be balanced as the coating conditions required for each side of the web  1 . In this case, the coating apparatus may further include a guide roll (paper roll)  7 , which is arranged to the upstream side of the web-nipping portions  20  to adjust the angle at which the web  1  enters between the web-nipping portions  20 .  
      Note that by permeating a coating solution into the web  1  while holding it on the surface of the applicator roll  2 , as described above, the thickness of the coating solution in the meniscus is reduced. At the same time, a rise in the concentration of the coating solution in the meniscus loses the fluidity of the meniscus, so the meniscus breaks up in its early stages and the advantage of reducing the occurrence of a mist is also obtained.  
     (B) Second Embodiment  
      Now, a second embodiment of the present invention will be described in conjunction with the drawings.  
       FIG. 4  shows a simplified side view of a coating apparatus constructed in accordance with the second embodiment of the present invention. In the figure, the same reference numerals as  FIG. 1  denote the same parts and a description of these parts will be partly omitted.  
      As illustrated in  FIG. 4 , the coating apparatus of the second embodiment has the same mini turn bar  4  as the first embodiment to the downstream side of web-nipping portions  20 . The coating apparatus further has the same guide roll (paper roll)  7  as the alteration of the first embodiment (see the two-dot chain line in  FIG. 1 ) to the upstream side of the web-nipping portions  20 .  
      In the second embodiment, the mini turn bar  4  is arranged so that the web  1  is wound around a lower applicator roll  2 . The paper roll  7  is arranged so that the web  1  is wound around an upper applicator roll  2 . However, the mini turn bar  4  and paper roll  7  may be arranged in reverse order with respect to the upper and lower applicator rolls  2 , 2 .  
      In the second embodiment, a drier  6  and turn bar  5  are arranged to the downstream side of the applicator rolls  2 , 2  in the reverse order of the first embodiment. However, they are arranged properly in accordance with device-installation environment, etc.  
      And in the second embodiment, the mini turn bar  4  and paper roll  7  are provided with moving mechanisms (not shown), respectively. Because various moving mechanisms are well known in the prior art, a description of the detailed structures will not be given.  
      The mini-turn-bar moving mechanism is used to properly move the mini turn bar  4  in a direction away from or toward the applicator roll  2  or circumferential direction of the applicator roll  2  or combined direction of these directions (e.g., a direction from the position of reference numeral  4 ′ in  FIG. 4  to the position of reference numeral  4 ). By moving the mini turn bar  4  in that direction, the contact length that the web  1  contacts one (lower) of the two applicator rolls  2  (i.e., the distance that the web  1  is held on the lower applicator roll  2 ) can be adjusted.  
      Also, the paper-roll moving mechanism is used to properly move the paper roll  7  in the required direction so that the angle at which the web  1  enters between the web-nipping portions  20  can be adjusted.  
      Since the coating apparatus of the second embodiment of the present invention is constructed as described above, the same advantages as the first embodiment can be obtained by applying a coating solution to the web  1  with the coating apparatus. In addition, the position of the mini turn bar  4  is adjusted with the mini-turn-bar moving mechanism, whereby the contact length that the web  1  that contacts one (lower) of the two applicators  2  can be adjusted. And the angle at which the web  1  enters between the web-nipping portions  20  is adjusted by adjusting the position of the paper roll  7  with the paper-roll moving mechanism, whereby the contact length that the web  1  contacts the other (upper) applicator roll  2  can be adjusted. Thus, the separation condition of the web  1  from one of the two applicator rolls  2  and coating conditions for both sides of the web  1  can be freely adjusted.  
     (C) Third Embodiment  
      Now, a third embodiment of the present invention will be described in conjunction with the drawings.  
       FIG. 5  shows a simplified side view of a coating apparatus constructed in accordance with the third embodiment of the present invention. In the figure, the same reference numerals as  FIGS. 1 and 4  denote the same parts and a description of these parts will be partly omitted.  
      As illustrated in  FIG. 5 , the coating apparatus of the third embodiment has the same mini turn bar  4  as the second embodiment to the downstream side of web-nipping portions  20 . The coating apparatus further has the same guide roll (paper roll)  7  as the second embodiment to the upstream side of the web-nipping portions  20 .  
      In the third embodiment, the mini turn bar  4  is arranged so that the web  1  is wound around an upper applicator roll  2 , and the paper roll  7  is arranged so that the web  1  is wound around a lower applicator roll  2 . However, the mini turn bar  4  and paper roll  7  may be arranged in reverse order with respect to the upper and lower applicator rolls  2 , 2 .  
      In the third embodiment, a turn bar  5  and drier  6  are arranged to the downstream side of the applicator rolls  2 , 2  in the recited order, as with the first embodiment. However, they are arranged properly in accordance with device-installation environment, etc.  
      And in the third embodiment, the same mini turn bar  4  and paper roll  7  as those of the second embodiment are provided with moving mechanisms (not shown), respectively.  
      The paper-roll moving mechanism is the same as that of the second embodiment. The mini-turn-bar moving mechanism is able to adjust the contact length that the web  1  contacts one (upper) of the two applicator rolls  2  (distance that the web  1  is held on one of the two applicator rolls) by moving the mini turn bar  4  in the diameter direction of the applicator roll  2 . The mini-turn-bar moving mechanism is also able to move the mini turn bar  4  from the web  1  to the position indicated by reference numeral  4 ′ in  FIG. 4 .  
      Since the coating apparatus of the third embodiment of the present invention is constructed as described above, the same advantages as the second embodiment can be obtained by applying a coating solution to the web  1  with the coating apparatus. In addition, the mini turn bar  4  can be moved away from the path of the web  1 , so working space can be ensured by moving the mini turn bar  4  away from the path of the web  1  during paper travel or maintenance of equipment. Thus, the advantage of enhancing operation efficiency is obtained.  
      The paper-roll moving mechanism may also be constructed so that it can move the paper roll  7  away from the path of the web  1  to enhance operation efficiency.  
      In the case where there is a need for the web  1  to travel horizontally for reasons such as an enhancement in the operation efficiency of paper passage, etc., there is an alteration such as the one shown in  FIG. 6 . Note that in the figure, the same reference numerals as  FIGS. 1, 4 , and  5  denote the same parts.  
      In this case, as illustrated in  FIG. 6 , one of the two applicator rolls  2  (e.g., an upper application roll in  FIG. 6 ) is constructed so that it is movable in a direction away from and toward the web  1  (vertical direction in  FIG. 6 ) at a position where the center axis of the upper applicator roll  2  is offset horizontally from the center axis of the other applicator roll  2  (e.g., a lower application roll in  FIG. 6 ). By moving the upper applicator roll  2  from reference numeral  2 ′ to reference numeral  2  in an arrow-indicating direction and pressing the upper applicator roll  2  against the lower applicator roll  2 , the web  1  can be wound around the lower applicator roll  2 .  
      To adjust the length that the web  1  is wound around the lower applicator roll  2 , there are provided a paper roll  7  and a paper-roll moving mechanism (not shown) to the side upstream of the applicator rolls  2 . Also, there are provided an air-flotation type mini turn bar  4  and a mini-turn-bar moving mechanism (not shown) to the downstream side of the applicator rolls  2 . Therefore, the paper roll  7  is movable from reference numeral  7 ′ to reference numeral  7  (see a arrow) and the mini turn bar  4  is movable from reference numeral  4 ′ to reference numeral  4  (see an arrow). The embodiment shown in  FIG. 6  further includes a downstream paper roll (fixed position)  7 , which is mounted between the mini turn bar  4  and drier  6 .  
      In the above-described case, a coating solution on the applicator roll  2  is permeated into the web  1  while the web  1  is being held on the applicator roll  2 , and the fluidity and tack strength diminish. Therefore, even if the separation angle α of the web  1  from the applicator roll  2  is small, the separation position of the web  1  from the applicator roll  2  becomes stable and the advantage of reducing the quantity of a mist is obtained.  
      Of course, the length that the web  1  is wound around one of the two applicator rolls  2  and the separation angle of the web  1  from the applicator roll  2  can be altered by adjusting the position of the applicator roll  2  and/or the position of the mini turn bar  4 . Also, the length that the web  1  is wound around the other applicator roll  2  can be altered by adjusting the position of the upstream paper roll  7 .  
      (D) Others  
      While the present invention has been described with reference to the preferred embodiments thereof, the invention is not to be limited to the details given herein, but may be modified within the scope of the invention claimed. For example, the structure of the mini turn bar (air-flotation type mini turn bar) used in the coating apparatus of the present invention is not limited to the structure shown in  FIGS. 3A and 3B . Preferred examples are the structures of mini turn bars  30 A,  30 B,  30 C,  30 D,  30 E,  30 F, and  40  shown in FIGS.  7  to  13 .  
      The mini turn bar  30 A shown in  FIG. 7  is a first preferred structure example. This mini turn bar  30 A is equipped with a box-shaped main body  31  that has no cover. Compressed air from an air supply source (not shown) is supplied to the interior space  31   a  of the bar main body  31 . The upper portions of the side walls  31   b  and  31   c  of the bar main body  31  diminish in width toward an opening, in which a U-shaped cover member  32  is arranged with its opening downward. Between the upstream side wall  31   b  and the cover member  32 , there is provided an upstream gap (slit-shaped groove). The upstream gap serves as the exit of a first air nozzle  35 A that is formed by the side wall  31   b  of the bar main body  31  and the side wall  32   b  of the cover member  32 . Similarly, between the cover member  32  and the downstream side wall  31   c , there is provided a downstream gap (slit-shaped groove). The downstream gap serves as the exit of a second air nozzle  35 B that is formed by the side wall  32   c  of the cover member  32  and the side wall  31   c  of the bar main body  31 .  
      In close proximity to the exits of the air nozzles  35 A and  35 B, partition members  34 A,  34 B in the form of a round bar are provided on the top surface  32   a  of the cover member  32  and extend in the width direction of the web  1 . Also, L-shaped plates  33 A,  33 B are attached to the exterior surface of the side walls  31   b ,  31   c  of the bar main body  31  and extend in the width direction of the web  1 . With this arrangement, between the air nozzles  35 A and  35 B there is formed a static pressure pocket (first air pocket)  36 A that is defined by the partition members  34 A,  34 B and the top surface  32   a  of the cover member  32 . Also, a static pressure pocket (second air pocket)  36 B is formed to the upstream side of the air nozzle  35 A and is defined by the upstream L-shaped plate  33 A and the side wall  31   b  of the bar main body  31 . Further, a static pressure pocket (third air pocket)  36 C is formed to the downstream side of the air nozzle  35 B and is defined by the downstream L-shaped plate  33 B and the side wall  31 C of the bar main body  31 .  
      According to the mini turn bar  30 A constructed as described above, the web  1  can be stably supported by both the dynamic pressure of compressed air that is squired out of the first and second air nozzles  35 A,  35 B and the static pressure of a layer of air within the first static pressure pocket  36 A. Because the second and third static pressure pockets  36 B,  36 C are also provided at the inlet portion and outlet portion of the arcuately curved portion of the web  1 , the flap of the web  1  against the mini turn bar  30 A at the inlet and outlet portions can be suppressed by the static pressure of the air layers within the second and third static pressure pockets  36 B,  36 C. Thus, the web  1  can be prevented from contacting the mini turn bar  30 A. As illustrated in  FIG. 7 , the shape of the mini turn bar  30 A, which leads from the second static pressure pocket  36 B on the inlet side to the third static pocket  36 C on the outlet side, is symmetrically formed with respect to a center line L passing through the center of the first static pressure pocket  36 A. Therefore, the web  1  is able to travel in a fixed radius of curvature and stable web travel becomes possible. Thus, according to the mini turn bar  30 A, the web  1  is able to travel with a sufficient quantity of flotation and the problem of flaws in a coated surface due to contact can also be prevented.  
      In experiments using the mini turn bar  30 A, in the case where the pressure of compressed air is 2000 mmAq (19.6 kPa) in gage pressure and the radius R of curvature of the web  1  is 160 mm, good results have been obtained when the slit width t of the exits of the air nozzles  35 A,  35 B is in a range of 0.5 to 5.0 mm and the diameter φ of the partition members  34 A,  34 B in a range of 1 to 10 mm. The radius R of curvature of the web  1  is determined by the shape of the mini turn bar  30 A, and as the radius R of curvature becomes smaller, the reaction force that the mini turn bar  30 A undergoes from the web  1  through a layer of air becomes greater. Since the mini turn bar  30 A has along and narrow structure extending in the width direction of the web  1 , it is preferable that the radius R of curvature be 100 mm or greater, if rigidity is taken into consideration.  
      The mini turn bar  30 B shown in  FIG. 8  is a second preferred structure example. This mini turn bar  30 B is an alteration of the first mini turn bar  30 A. The side walls  31   b ,  31   c  of the bar main body  31  of the second mini turn bar  30 B are partly different from the first mini turn bar  30 A. That is, the upper portions of the side walls  31   b ,  31   c  of the bar main body  31 , as with first example, diminish in width toward an opening, but the upper ends are vertically formed and are parallel to the side walls  32   b ,  32   c  of a cover member  32 . With such a construction, the air-jet directions of air nozzles  35 A,  35 B in the second example are approximately parallel to a center line L, and as illustrated in  FIG. 8 , a second static pressure pocket  36 B and third static pressure pocket  36 C at the inlet and outlet portions can be made deeper than the first example.  
      The mini turn bar  30 C shown in  FIG. 9  is a third preferred structure example. While the first mini turn bar  30 A forms the static pressure pocket  36 A by installing the partition members  34 A,  34 B in the shape of a bar on the top surface  32   a  of the cover member  32 , the mini turn bar  30 C of the third example is characterized in that a static pressure pocket  36 A is formed by mounting a U-shaped plate  38  with left and right side walls  38   b ,  38   c  on the top surface  32   a  of a cover member  32 . The U-shaped plate  38  is formed from a thick member, and the upper round corners of the left and right side walls  38   b ,  38   c  has a radius r of curvature, as shown in  FIG. 9 .  
      The mini turn bar  30 D shown in  FIG. 10  is a fourth preferred structure example. This mini turn bar  30 D is an alteration of the third mini turn bar  30 C, and the upper portions of the side walls  31   b ,  31   c  of a bar main body  31  are formed the same as the second example. In the third and fourth mini turn bars  30 C and  30 D, under the same conditions as the first example, good results have been obtained when the height d of the side walls  38   b ,  38   c  of the U-shaped plate  38  (pocket depth d) is 1 to 20 mm, the difference h in height between the side walls  38   b ,  38   c  of the U-shaped plate  38  and the side walls  31   b ,  31   c  of the bar main body  31  is −5 to 3 mm, and the radius r of curvature of the side walls  38   b ,  38   c  of the U-shaped plate  38  is 0.5 to 5 mm. The upper ends of the side walls  38   b ,  38   c  of the U-shaped plate  38  may be chamfered instead of being rounded.  
      The mini turn bar  30 E shown in  FIG. 11  is a fifth preferred structure example. This mini turn bar  30 E is an alteration of the fourth mini turn bar  30 D, and within a static pressure pocket  36 A, there is provided an air nozzle (third air nozzle)  39  from which compressed air is squirted. The air nozzle  39  has an opening in the top surface of a U-shaped plate  38  and is connected to an air supply source (not shown). The air supply source to which the third air nozzle  39  is connected may be the same system as an air supply source to which first and second air nozzles  35 A,  35 B are connected, or a different system. Preferably, the air supply system is constructed so that the third air nozzle  39  can squirt compressed air higher in pressure than the first and second air nozzles  35 A,  35 B.  
      The above-described mini turn bar  30 E has the following advantages. That is, as the web  1  travels near the mini turn bar  30 E, the air within the central static pressure pocket  36 A passes over the side wall  38   c  of the U-shaped plate  38  that is the partition wall portion between the static pressure pockets  36 A and  36 C, and flows into the downstream static pressure pocket  36 C. At this partition wall portion the web  1  is supported by the pressure of the wake air, but the flow passage area of the wake air at that partition wall portion widens gradually from the center static-pressure pocket  36 A toward the downstream static-pressure pocket  36 C, as shown in  FIG. 11 . Therefore, the dynamic pressure component of the wake air at the partition wall portion is gradually reduced as the flow passage area enlarges. Because of a reduction in the dynamic pressure of the wake air, if the pressure of the wake air becomes smaller than the tension of the web  1  or force of pushing the web  1  toward the mini turn bar  30 E such as atmospheric pressure, etc., then the web  1  will contact the partition wall portion. However, in this mini turn bar  30 E, the static pressure component of the wake air flowing out from the static-pressure pocket  36 A is enhanced by compressed air squirted from the air nozzle  39 , so a compensation for a reduction in the dynamic pressure can be made and contact between the web  1  and the partition wall portion can be prevented.  
      The mini turn bar  30 F shown in  FIGS. 12A and 12B  is a sixth preferred structure example. This mini turn bar  30 F is an alteration of the fourth mini turn bar  30 D and is characterized in that there is provided a labyrinth structure in each of the static pressure pockets  36 A,  36 B, and  36 C. That is, as shown in  FIGS. 12A and 12B , the static pressure pockets  36 A,  36 B, and  36 C are provided with a plurality of baffle plates (partition wall)  37 A,  37 B, and  37 C, which are arranged at predetermined intervals in the longitudinal direction of the mini turn bar  30 F (width direction of the web  1 ). The baffle plates  37 A,  37 B, and  37 C segment each of the static pressure pockets  36 A,  36 B, and  36 C into a plurality of sections.  
      According to the mini turn bar  30 F, the baffle plates  37 A,  37 B, and  37 C give strong resistance to air flowing between the web  1  and the mini turn bar  30 F. That is, the baffle plates  37 A,  37 B, and  37 C form a sort of labyrinth structure between the web  1  and the mini turn bar  30 F. The labyrinth structure converts the kinetic energy of air into pressure, so the static pressure within each of the static pressure pockets  36 A,  36 B, and  36 C rises. Also, when the web  1  shifts laterally, there is a possibility that pressure will leak from gaps formed in the width direction of the web  1 , but since each of the static pressure pockets  36 A,  36 B, and  36 C is segmented into a plurality of sections, a fluctuation in web-supporting pressure due to the lateral shift of the web  1  can be minimized. Therefore, the mini turn bar  30 F is capable of supporting the web  1  more stably by such a labyrinth structure and preventing the web  1  from vibrating and making a noise. In the mini turn bar  30 F, while each of the static pressure pockets  36 A,  36 B, and  36 C is provided with a labyrinth structure, all the static pressure pockets  36 A,  36 B, and  36 C does not always need to have a labyrinth structure. For instance, even when only the center static pressure pocket  36 A has a labyrinth structure, the above-described advantages are obtained.  
      The mini turn bar  40  shown in  FIG. 13  is a seventh preferred structure example. This mini turn bar  40  is equipped with a box-shaped main body  41  having no cover, and compressed air from an air supply source (not shown) is supplied to the interior space  41   a  of the bar main body  41 . Within the opening of the bar main body  41 , a U-shaped cover member  42  is arranged with its opening downward. Between the side walls  41   b ,  41   c  of the bar main body  41  and the side walls  42   b ,  42   c  of the cover member  42 , there are formed passages  45 A,  45 B, which are in communication with the interior space  41   a . These passages  45 A,  45 B serve as air nozzles that squirt compressed air out of the interior space  41   a . They will hereinafter be referred to as air nozzles. L-shaped flange members  48 A,  48 B are attached to the interior surface of the side walls  41   b ,  41   c  of the bar main body  41 , and between the upper ends of the flange members  48 A,  48 B and the lower ends of the side walls  42   b ,  42   c  of the cover member  42 , the inlet portions of the first and second air nozzles  45 A,  45 B into which compressed air flows from the interior space  41   a  are narrowed down.  
      U-shaped partition members  44 A,  44 B are arranged left and right on the top surface  42   a  of the cover member  42  with their openings downward. The lower ends of the inner side walls  44 Ab,  44 Bb of the partition members  44 A,  44 B are mounted on the top surface  42   a  of the cover member  42 , and between the lower ends of the outer side walls  44 Ac,  44 Bc and the top surface  42   a  of the cover member  42 , there are formed gaps through which the interiors of the partition members  44 A,  44 B communicate with the air nozzles  45 A,  45 B. The side walls  41   b ,  41   c  of the bar main body  41  extend near the top surfaces  44 Aa,  44 Ba of the partition members  44 A,  44 B, and between the upper end portions of the side walls  41   b ,  41   c  of the bar main body  41  and the partition members  44 A,  44 B, there are formed slit-shaped grooves  451 B and  451 C extending in the width direction of the web  1 . The top surfaces  44 Aa,  44 Ba of the partition members  44 A,  44 B are formed into curved surfaces, which correspond to the curved path of the web  1 . The curved tope surfaces  44 Aa,  44 Ba have a great number of bores  452  arranged evenly in zigzags. The grooves  451 B,  451 C and bores  452  form the exits of the air nozzles  45 A,  45 B. The grooves  451 B,  451 C will hereinafter be referred to as air-jet grooves and the bores  452  will hereinafter be referred to as air-jet bores. Also, the top surfaces  44 Aa,  44 Ba of the partition members  44 A,  44 B in which the air-jet bores  452  are formed will hereinafter be referred to as air-jet surfaces.  
      The above-described partition members  44 A,  44 B form a static pressure pocket (first air pocket)  46 A along with the top surface  42   a  of the cover member  42 . Within the static pressure pocket  46 A, there is arranged a reinforcement plate  47  through which both partition members  44 A and  44 B are connected. Also, L-shaped plates  43 A,  43 B are attached to the exterior surfaces of both side walls  41   b ,  41   c  of the bar main body  41  and extend in the width direction of the web  1 . With this construction, a static pressure pocket (second air pocket)  46 B, which is defined by the upstream L-shaped plate  43 A and the side wall  41   b  of the bar main bar  41 , is formed to the downstream side of the air nozzle  45 A. Similarly, a static pressure pocket (third air pocket)  46 C, which is defined by the downstream L-shaped plate  43 B and the side wall  41 C of the bar main bar  41 , is formed to the upstream side of the air nozzle  45 B.  
      According to the mini turn bar  40  with such a construction, the web  1  can be stably supported by both the dynamic pressure of the compressed air squired from the air nozzles  45 A,  45 B and the static pressure of the layer of air within the static pressure pocket  46 A formed on the top surface  42   a  of the cover member  42 . In addition, in this mini turn bar  40 , the static pressure pockets  46 B,  46 C are provided at the inlet and outlet portions of the curved portion of the web  1 , so the flap of the web  1  against the mini turn bar  40  at the inlet and outlet portions can be suppressed by the static pressure of the air layers formed within the static pressure pockets  46 B,  46 C, and the contact of the web  1  with the mini turn bar  40  can be prevented.  
      Also, as the web  1  travels near the mini turn bar  40 , the air within the central static pressure pocket  46 A passes over the partition member  44 B that is the partition wall portion between the static pressure pockets  46 A and  46 C, and flows into the downstream static pressure pocket  46 C. At this partition wall portion the web  1  is supported by the pressure of the wake air, but the flow passage area of the wake air widens gradually from that partition wall portion toward the downstream static-pressure pocket  46 C. Therefore, the dynamic pressure component of the wake air at the partition wall portion is gradually reduced as the flow passage area enlarges. Because of a reduction in the dynamic pressure of the wake air, if the pressure of the wake air becomes smaller than the tension of the web  1  or force of pushing the web  1  toward the mini turn bar  40  such as atmospheric pressure, etc., then the web  1  will contact the baffle wall portion. However, in this mini turn bar  40 , the top surface  44 Ba of the partition member  44 B that is the partition wall portion is used as the air-jet surface, so contact between the web  1  and the partition member  44 B can be prevented by a layer of compressed air that is squired out of the air-jet surface  44 Ba. Also, by forming the air-jet groove  451 B on the downstream side of the air-jet surface  44 Ba, a curtain of compressed air from the air-jet groove  451 B can prevent the air squirted out of the air-jet surface  44 Ba from leaking out as the web  1  travels, and a layer of air can be reliably formed between the web  1  and partition member  44 B.  
      Moreover, the shape of the mini turn bar  40 , which leads from the upstream static pressure pocket  46 B to the downstream static pocket  46 C, is symmetrically formed with respect to a center line L passing through the center of the center static pressure pocket  46 A, so the web  1  is able to travel in a fixed radius of curvature and stable travel of the web  1  becomes possible.  
      According to these mini turn bars  30 A,  30 B,  30 C,  30 D,  30 E,  30 F, or  40 , the web  1  is able to travel stably with a sufficient quantity of flotation without contacting the mini turn bar. Therefore, if a coating solution is applied to the web  1  by the coating apparatus equipped with the mini turn bar  30 A,  30 B,  30 C,  30 D,  30 E,  30 F, or  40 , the quality of the coated paper can be further enhanced.  
      Also, the respective characteristic constructions of the mini turn bars  30 A,  30 B,  30 C,  30 D,  30 E,  30 F, and  40  can be combined together. For instance, the labyrinth structure of the six mini turn bar  30 F can be provided in the other mini turn bars  30 A,  30 B,  30 C,  30 D,  30 E, and  40 . The third air nozzle  39  of the fifth mini turn bar  30 E can also be provided in the other mini turn bars  30 A,  30 B,  30 C,  30 D,  30 F, and  40 .