Patent Publication Number: US-9890005-B2

Title: Sheet manufacturing apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. patent application Ser. No. 14/635,092 filed on Mar. 2, 2015. This application claims priority to Japanese Patent Application No. 2014-044765 filed on Mar. 7, 2014. The entire disclosures of U.S. patent application Ser. No. 14/635,092 and Japanese Patent Application No. 2014-044765 are hereby incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a sheet manufacturing apparatus. 
     2. Related Art 
     JP-T-2006-525435 discloses that a suction box is provided in an enclosure of a transfer wire of an apparatus for forming, in a dry way, a cloth material formed of two sheets of nonwoven fabric. 
     In the apparatus disclosed in JP-T-2006-525435, since a space is needed, in which a suction unit (suction box) is provided in a transfer wire, the transfer wire has to be lengthy and thus, the apparatus is increased in size. 
     SUMMARY 
     The invention can be realized in the following forms or application examples. 
     According to one aspect of the invention, a sheet manufacturing apparatus that forms a sheet using a web comprises an accumulation unit, a first transport unit, a second transport belt, a suction unit, a suction chamber, and a current plate. The accumulation unit is configured to accumulate the web containing at least a fiber on a first transport belt. The first transport unit is configured to cause the first transport belt to circle around so as to transport the web. The second transport belt is spaced from the first transport unit in a perpendicular direction perpendicular to a surface of the web, and is disposed with a part thereof shifted from the first transport unit toward a downstream side in a transport direction of the web. The suction unit is positioned on an outer side of the second transport belt in a direction orthogonal to the transport direction of the web. The suction chamber is positioned in an inner side of the second transport belt which circles around the suction chamber, and the suction unit is configured to create suction inside the suction chamber to suck the web onto the second transport belt. The current plate is positioned inside of the suction chamber to adjust an air current. The current plate has a plurality of holes. The current plate is spaced apart from a surface of the second transport belt such that the air current is diffused between the current plate and the surface of the second transport belt to achieve a uniform suction force in a width direction of the second transport belt. 
     According to the aspect of the invention, the current plate is disposed parallel to the surface of the second transport belt. 
     According to the aspect of the invention, the holes on a side closer to the suction unit have a smaller ratio of opening of the holes per unit area on the surface than that of the holes on a side farther from the suction unit. 
     According to the aspect of the invention, at least one hole of the holes on the side closer to the suction unit is smaller in size than at least one hole of the holes on the side farther from the suction unit. 
     According to the aspect of the invention, the holes on the side closer to the suction unit have a greater center-to-center distance of the holes adjacent to each other in the direction orthogonal to the transport direction of the web along the surface of the web than the holes on the side farther from the suction unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is a view schematically illustrating a sheet manufacturing apparatus according to an embodiment. 
         FIG. 2  is a perspective view schematically illustrating a second transport unit. 
         FIG. 3  is a view schematically illustrating the second transport unit. 
         FIGS. 4A to 4D  are views schematically illustrating examples of a current plate. 
         FIGS. 5A and 5B  are views schematically illustrating examples of a current plate. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, a preferred embodiment of the invention will be described with reference to the drawings. The details of the invention described in the claims are not inappropriately limited to the embodiments to be described below. In addition, the entire configurations to be described below are not the essential requirements of the invention. 
     1. Entire Configuration 
       FIG. 1  is a view schematically illustrating a sheet manufacturing apparatus  100  according to an embodiment. As illustrated in  FIG. 1 , the sheet manufacturing apparatus  100  includes a crushing unit  10 , a defibrating unit  20 , a classification unit  63 , a mixing unit  30 , a disentanglement unit  70 , an accumulation unit  75 , a first transport unit  79 , a second transport unit  40 , a pressurizing unit  50 , a heating unit  52 , and a cutting unit  90 . 
     The crushing unit  10  cuts (crush), in the air, a raw material (source material) such as a pulp sheet or paper (for example, A4-size waste paper) put therein into strips. A shape or size of the strip is not particularly limited; however, the strip forms a quadrangle of several centimeters. In an example illustrated in the drawings, the crushing unit  10  has a crushing blade  11  and it is possible to cut the raw material put in by the crushing blade  11 . The crushing unit  10  may be provided with an automatic put-in section (not illustrated) for continuously putting in the raw material. 
     The strip cut by the crushing unit  10  is received in a hopper  15  and then, is transported to the defibrating unit  20  via a pipe  81 . The pipe  81  communicates with a guiding-in opening  21  of the defibrating unit  20 . 
     The defibrating unit  20  defibrates the strip (defibration object). The defibrating unit  20  generates fibers fibrillated in a fiber shape through the defibrating process of the strip. 
     Here, the term “defibrating process” indicates the refining of the strip (defibration object) of a plurality of bonded fibers into individual fibers. The term “defibrated material” indicates the material that has passed through the defibrating unit  20 . The term “defibrated material” also includes resin particles (resin for mutual bonding of a plurality of fibers) and ink particles of inks, toners, and blur-preventing agents when the fibers are refined, in addition to the refined fibers. In the following description, the “defibrated material” is at least a part of materials that passed through the defibrating unit  20  and may be mixed with a substance that is added after passing through the defibrating unit  20 . 
     The defibrating unit  20  separates resin particles, or ink particles such as ink, toner, or a blur preventing material which are attached to the strip from the fiber. Along with the defibrated material, the resin particles and the ink particles are discharged from a discharge opening  22 . The defibrating unit  20  performs the defibrating process on the strip guided in through the guiding-in opening  21  using a rotating blade. The defibrating unit  20  defibrates in a dry type system in the atmosphere (in air). 
     It is preferable that the defibrating unit  20  has a mechanism for producing an air current (airflow). In this case, the defibrating unit  20  generates an air current and uses the generated air current to draw in the defibration object from the guiding-in opening  21 , defibrates, and transfers the defibrated material to the discharge opening  22 . The defibrated material discharged from the discharge opening  22  is guided into the classification unit  63  via a pipe  82 . In a case where the defibrating unit  20  which does not have an air current generating mechanism is used, a mechanism that generates an air current for introducing the strip to the guiding-in opening  21  may be provided externally. 
     The classification unit  63  separates and removes the resin particles and the ink particles from the defibrated material. As the classification unit  63 , an air current type classifier is used. The air current type classifier produces a swirling air current and performs separation by a centrifugal force and a size or density of a substance to be classified such that it is possible to adjust a classification point by adjusting a speed or centrifugal force of the air current. Specifically, a cyclone, an Elbow-jet, an eddy classifier, or the like is used as the classification unit  63 . Particularly, since the cyclone has a simple structure, it is possible for the cyclone to be appropriately used as the classification unit  63 . Hereinafter, a case of using the cyclone as the classification unit  63  will be described. 
     The classification unit  63  has at least a guiding-in opening  64 , a lower discharge opening  67  provided in the lower portion, and an upper discharge opening  68  provided in the upper portion. In the classification unit  63 , an air current containing the defibrated material guided in from the guiding-in opening  64  is caused to move in a circling motion and thereby, the centrifugal force is applied to the defibrated material guided in such that the fiber material (fibrillated fiber) is separated from waste (resin particles and ink particles) which is lower in density than the fiber material. The fiber material is discharged from the lower discharge opening  67  and is guided into a guiding-in opening  71  of the disentanglement unit  70  through a pipe  86 . The waste is discharged to the outside of the classification unit  63  from the upper discharge opening  68  through a pipe  84 . 
     It is described that the fiber material is separated from the waste by the classification unit  63 ; however, the separation is not performed with accuracy. In some cases, a relatively small fiber material or a fiber material with low density is discharged to the outside along with the waste. In addition, in some cases, waste with relatively high density or waste entangled with the fiber material is guided into the disentanglement unit  70  along with the fiber material. In this application, a substance discharged from the lower discharge opening  67  (substance having a higher ratio of long fibers than waste) is referred to as the “fiber material”. A substance discharged from the upper discharge opening  68  (substance having a lower ratio of long fibers than a fiber material) is referred to as the “waste”. In a case where the raw material is not waste paper but a pulp sheet, since no substance corresponding to waste is contained, the classification unit  63  may be omitted from the configuration of the sheet manufacturing apparatus  100 . 
     A supply opening  87  for supplying a resin which binds the fibers to each other is provided in the pipe  86 . A resin supplying unit  88  supplies the resin in the air into the pipe  86  from the supply opening  87 . That is, the resin supplying unit  88  supplies the resin on a path of the fiber material from the classification unit  63  toward the disentanglement unit  70 . There is no particular limitation to the resin supplying unit  88  as long as the resin is supplied into the pipe  86 ; however, a screw feeder, a circle feeder, or the like is used as the resin supplying unit  88 . The resin supplied from the resin supplying unit  88  is a resin for binding the plurality of fibers. At a point in time when the resin is supplied into the pipe  86 , the plurality of fibers are in a state of not being bound to one another. The resin is a thermoplastic resin or a thermoset resin, may have a fiber shape, or may be powdery. An amount of the resin supplied from the resin supplying unit  88  is appropriately set depending on a type of sheet to be manufactured. In addition to the resin for binding the fibers, the resin supplying unit  88  may supply a colorant for coloring the fiber or an aggregation inhibitor for inhibiting aggregation of the fibers depending on a type of sheet to be manufactured. The resin supplying unit  88  may be omitted from the configuration of the sheet manufacturing apparatus  100 . 
     The resin supplied from the resin supplying unit  88  is mixed with the fiber material which is classified by the classification unit  63 , by the mixing unit  30  provided in the pipe  86 . The mixing unit  30  mixes the fiber material and the resin and performs the transport thereof to the disentanglement unit  70 . 
     The disentanglement unit  70  disentangles the fiber material which is entangled. Further, the disentanglement unit  70  disentangles the entangled resin in a case where the resin supplied from the resin supplying unit  88  has the fiber shape. In addition, the disentanglement unit  70  accumulates the fiber material or the resin uniformly in the accumulation unit  75  to be described below. That is, the word, “disentangle”, means both an action of disentangling the entangled substance into pieces and an action of a uniform accumulation. When there is no entangled substance, the disentanglement unit  70  performs the action of the uniform accumulation. A sieve is used as the disentanglement unit  70 . The disentanglement unit  70  is a rotating sieve in which a net section rotates by a motor (not illustrated). Here, the “sieve” used as the disentanglement unit  70  may not have a function of selecting a specific target object. This means that the “sieve” used as the disentanglement unit  70  has the net section with a plurality of openings and the disentanglement unit  70  may discharge the entire fiber material and resin guided into the disentanglement unit  70  to the outside from the openings. The disentanglement unit  70  may be omitted from the configuration of the sheet manufacturing apparatus  100 . 
     In a state in which the disentanglement unit  70  rotates, the mixture of the fiber material and the resin is guided into the inside the disentanglement unit  70  formed of a cylindrical net section from the guiding-in opening  71 . The mixture guided into the disentanglement unit  70  travels to the side of the net section by the centrifugal force. As described above, in some cases, the mixture guided into the disentanglement unit  70  contains the entangled fiber or resin and then, the entangled fiber or resin are disentangled in the air through the rotating net section. Then, the disentangled fiber or resin passes through the openings. 
     The fiber material and resin which passed through the opening of the disentanglement unit  70  are accumulated in the accumulation unit  75 . The accumulation unit  75  is positioned under the disentanglement unit  70  and causes the fiber material and resin which passed through the opening of the disentanglement unit  70  to be accumulated on a first transport belt  76  such that a web W (accumulated material) is formed. 
     The first transport unit  79  has the first transport belt  76  and a stretching roller  77  and transports the web W. The first transport belt  76  stretched by the stretching roller  77  is an endless mesh belt in which a mesh is formed. The first transport belt  76  travels (circles around) by the rotation of the stretching roller  77 . The fiber material and the resin are continuously dropped and accumulated from the disentanglement unit  70  while the first transport belt  76  continuously travels and thereby, the web W having a uniform thickness is formed on the first transport belt  76 . 
     A suction device  78  that sucks the accumulated material downward is provided below the disentanglement unit  70  interposing the first transport belt  76  (the accumulation unit  75 ) therebetween. The suction device  78  produces an air current (air current which travels toward the accumulation unit  75  from the disentanglement unit  70 ) which is directed vertically downward. In this way, it is possible to suck in the fiber material and the resin dispersed in the air and thus, to increase a discharge speed from the disentanglement unit  70 . As a result, it is possible to increase productivity of the sheet manufacturing apparatus  100 . In addition, it is possible to form a downflow in a dropping path of the fiber material and the resin by the suction device  78  and thus, to prevent the fiber materials or the resins from entangling with each other during the dropping. 
     The second transport unit  40  transports, toward the pressurizing unit  50 , the web W that is formed on the first transport belt  76  and is transported by the first transport unit  79 . In addition, the second transport unit  40  transports the web W while sucking the web W vertically upward (a direction in which the web W is separated from the first transport belt  76 ). In addition, the second transport unit  40  is disposed to be spaced from the first transport unit  79  (the first transport belt  76 ) vertically upward (a direction perpendicular to the surface of the web W) and is disposed with a part thereof shifted on the downstream side from the first transport unit  79  (the first transport belt  76 ) in the transport direction of the web W. A transport zone of the second transport unit  40  becomes a zone from a stretching roller  77   a  on the downstream side of the first transport unit  79  to the pressurizing unit  50 . 
     The second transport unit  40  includes a second transport belt  41 , a stretching roller  42 , a suction chamber  43 , and a suction unit (refer to  FIG. 2 ). The second transport belt  41  stretched by a stretching roller  42  is an endless mesh belt in which a mesh is formed. 
     The suction chamber  43  is positioned on the inner side of the second transport belt  41  and the inner space of the suction chamber  43  is sucked by the suction unit that produces the air current (suction force) such that the web W is adsorbed onto the second transport belt  41 . That is, the suction unit and the suction chamber  43  produce the air current directed vertically upward from the first transport belt  76 , thereby sucking the web W upward, and adsorb the web W onto the second transport belt  41 . The second transport belt  41  travels (circles around) by the rotation of the stretching roller  42  and transports the web W. The stretching roller  42  rotates such that the second transport belt  41  travels at the same speed as that of the first transport belt  76 . When there is a difference between the speeds of the first transport belt  76  and the second transport belt  41 , the web W is stretched to end up breaking or buckling, which may be prevented at the same speed. 
     A part of the suction chamber  43  is overlapped with the first transport belt  76  when viewed upward and, since the suction chamber  43  is disposed at a position on the downstream side which is not overlapped with the suction device  78 , the web W on the first transport belt  76  is peeled off from the first transport belt  76  at a position facing the suction chamber  43  and is adsorbed onto the second transport belt  41 . 
     The pressurizing unit  50  is configured of a pair of pressurizing rollers and the web W transported by the second transport unit  40  is nipped between the rollers and is pressurized. The heating unit  52  is disposed on the downstream side of the pressurizing unit  50 , is configured of a pair of heating rollers, and heats and pressurizes the web W by nipping the web W between the rollers. The web W which is the accumulated material formed by accumulation of the fiber material and the resin is heated and pressurized by passing through the pressurizing unit  50  and the heating unit  52 . The heating causes the resin to function as a binding agent so as to bind the fibers to each other and, by the pressurizing, a sheet P is shaped to be thin and to have a smooth surface. 
     As the cutting unit  90  that cuts the sheet P, a first cutting section  90   a  that cuts the sheet P in a direction intersecting with a transport direction of the sheet P and a second cutting section  90   b  that cuts the sheet P along the transport direction of the sheet P are disposed on the downstream side of the heating unit  52 . The first cutting section  90   a  has a cutter and cuts the long-continuous sheet P to a sheet shape in accordance with cutting positions set to have a predetermined length therebetween. The second cutting section  90   b  has a cutter and cuts the sheet P to a sheet shape in accordance with a predetermined cutting positions in the transport direction of the sheet P. In this way, a sheet with a desired size is formed. The cut sheets P are loaded in a stacker  95  or the like. A configuration may be employed, in which the sheet P is not cut, but is rolled by a winding roller in a continuous shape. As above, it is possible to manufacture the sheet P. 
     2. Configuration of Second Transport Unit 
       FIG. 2  is a perspective view schematically illustrating the second transport unit  40 . As illustrated in  FIG. 2 , the suction chamber  43  disposed on the inner side of the second transport belt  41  has a hollow of a box shape which has a top surface and four side surfaces that are in contact with the top surface and the bottom (facing a lower surface of the second transport belt  41 ) is opened. 
     The two side surfaces of the four side surfaces of the suction chamber  43  face the second transport belt  41 . An opening  49  that communicates with a pipe  45  is provided on at least one of the two side surfaces which do not face the second transport belt  41 . The suction unit  44  (blower) and the suction chamber  43  are connected to each other via the pipe  45 . The air inside the suction chamber  43  is sucked to the suction unit  44  via the pipe  45  and the air flows in from the bottom of the suction chamber  43 . In this way, an air current directed upward (a +Y axial direction in  FIG. 2 ) is produced and it is possible to suck the web W upward (the web W is adsorbed onto the second transport belt  41 ). In an example illustrated in  FIG. 2 , since ends of a part of the side surfaces of the suction chamber  43  are in contact with the stretching rollers  42 , a brush-like sealing material is provided at the ends. In this way, the air is suppressed not to flow in from a gap between the ends and the stretching rollers  42 . In addition, in this way, it is possible to lengthen a zone in which the suction is performed, in the transport direction of the web W. 
     In the second transport unit  40  of the embodiment, the suction unit  44  is not disposed on the inner side of the second transport belt  41 , but the suction unit  44  is provided on the outer side of the second transport belt  41  in a direction (a +Z axial direction in an example illustrated in  FIG. 2 ) orthogonal to the transport direction of the web W (a +X axial direction in  FIG. 2 ) along the surface of the web W. That is, the suction is not performed from the top surface of the suction chamber  43  but a configuration is employed, in which the suction is performed from side surfaces of the suction chamber  43  which do not face the second transport belt  41 . In this way, since it is possible to reduce a space surrounded by the second transport belt  41 , it is possible to reduce the length of the second transport belt  41  and to decrease the apparatus in size. 
     When the suction unit  44  is disposed on the outer side of the second transport belt  41  and is configured to perform the suction from the side surfaces of the suction chamber  43 , the suction force is not uniform on the side closer to and on the side farther from the suction unit  44  (opening  49 ). That is, in a width direction of the second transport belt  41 , the suction force becomes weaker on the side farther from the suction unit  44  than on the side closer to the suction unit  44 . 
     As illustrated in  FIG. 3 , the current plate  46  is provided in the suction chamber  43  and thereby, the suction force may be caused to be uniform in the width direction of the second transport belt  41 . The current plate  46  is plate-like having a plurality of holes on the surface thereof, and is disposed at a position between the lower transport surface  41   a  (surface of the second transport unit  40  on which the web W is sucked and transported) of the second transport belt  41  and the opening  49  in the suction chamber  43  so as for the surface having the holes to be substantially parallel to the transport surface  41   a  of the second transport belt  41 . In addition, ends of the current plate  46  are in contact with the side surfaces of the suction chamber  43 . In addition, on the surface of the current plate  46 , the ratio of the opening (hole) per unit area is smaller on the side closer to the suction unit  44  than on the side farther from the suction unit  44 . 
       FIGS. 4A to 4D  are views schematically illustrating examples of the current plate  46 .  FIG. 4A  and  FIG. 4C  illustrate examples of the current plate  46  in which the round holes  47  are provided and  FIG. 4B  and  FIG. 4D  illustrate examples of the current plate  46  in which the rectangular (slit shaped) holes  47  are provided. In addition,  FIG. 4A  and  FIG. 4B  illustrate examples in which the size (diameter and width) of the hole  47  is adjusted such that a ratio of the opening per unit area is adjusted and  FIG. 4C  and  FIG. 4D  illustrate examples in which a pitch L of the hole  47  (center-to-center distance of the holes  47  adjacent to each other in a suction direction SD orthogonal to the transport direction CD) is adjusted such that a ratio of the opening per unit area is adjusted. 
     In the current plate  46  illustrated in  FIG. 4A  and  FIG. 4B , the diameter and width of the holes  47  on the side closer to the suction unit  44  (side in the suction direction SD) is less than the diameter and width of the holes  47  on the side farther from the suction unit  44  and thereby, the ratio of the opening per unit area on the side closer to the suction unit  44  becomes low. In the current plate  46  illustrated in  FIG. 4C  and  FIG. 4D , the pitch L of the holes  47  on the side closer to the suction unit  44  is greater than the pitch L of the holes  47  on the side farther from the suction unit  44  and thereby, the ratio of the opening per unit area on the side closer to the suction unit  44  becomes low. In an example illustrated in  FIG. 4A  and  FIG. 4B , the pitch L of the holes  47  in a direction orthogonal to the transport direction CD of the web is constant and in an example illustrated in  FIG. 4C  and  FIG. 4D , the size of the holes  47  is constant; however, in the current plate  46 , both the pitch L of the holes  47  and the size of the holes  47  may be changed together. 
     As above, the current plate  46  is provided in the suction chamber  43  and on the surface of the current plate  46 , the ratio of the opening per unit area is smaller on the side closer to the suction unit  44  (opening  49 ) than that on the side farther from the suction unit  44  and thereby, it is possible to achieve a uniform suction force on the side closer to the suction unit  44  and the side farther from the suction unit  44  even when the second transport unit  40  is configured to perform the suction from the side surfaces of the suction chamber  43  and it is possible to perform reliable suction (adsorption) of the web W over the width direction of the second transport belt  41 . 
     It is preferable that the current plate  46  is disposed to be spaced from the transport surface  41   a  of the second transport belt by a certain distance. In a case where the current plate  46  is in contact with the transport surface  41   a  of the second transport belt, the suction force is unlikely to act on another region of the opening (holes  47 ) of the current plate  46 . Therefore, a region in which strong adsorption of the web W is performed and a region in which adsorption of the web W is not performed are present and, in some cases, it is not possible to uniformly adsorb the web W. In a case where the current plate  46  is disposed to be spaced from the transport surface  41   a  of the second transport belt, an air current is diffused between the current plate  46  and the transport surface  41   a  of the second transport belt. Therefore, the suction force also acts on at the region other than the opening of the current plate  46  and it is possible to uniformly adsorb the web W. 
     In addition, in the examples above, a case is described, in which the suction is performed from one of two side surfaces of the suction chamber  43  which do not face the second transport belt  41 ; however, the openings  49  are provided on the two side surfaces which do not face the second transport belt  41 , respectively, and the second transport unit  40  may be configured to perform the suction from both of the two side surfaces using two suction units  44  (or one suction unit  44 ). In this case, in the width direction of the second transport belt  41 , the suction force becomes weaker on the center side compared to the end side. Accordingly, in a case where the suction is performed from both of the two side surfaces of the suction chamber  43 , as illustrated in  FIGS. 5A and 5B , in the current plate  46 , when the ratio of the opening per unit area is lower on the end side (side closer to the suction unit  44 ) than on the center side (side father from the suction unit  44 ), it is possible to achieve the uniform suction force in the width direction of the second transport belt  41 . In the current plate  46  illustrated in  FIG. 5A , the diameter of the hole  47  on the end side is less than the diameter of the hole  47  on the center side, and in the current plate  46  illustrated in  FIG. 5B , the pitch L of the hole  47  on the end side is greater than the pitch L of the hole  47  on the center side. 
     In addition, instead of providing the current plate  46  in the suction chamber  43 , a mesh of the second transport belt  41  is configured to have a smaller ratio of the opening (opening formed on the mesh, an example of “hole” of the invention) per unit area on the side closer to the suction unit  44  than on the side farther from the suction unit  44  in a width direction (direction orthogonal to the transport direction) of the second transport belt  41  and thereby, the suction force may be uniform in the width direction of the second transport belt  41 . For example, the mesh of the second transport belt  41  may be configured to have a smaller opening in size on the side closer to the suction unit  44  than on the side farther from the suction unit  44  in the width direction of the second transport belt  41 , or to have a pitch (center-to-center distance of the adjacent openings) of the openings on the side closer to the suction unit  44  greater in size than the pitch of the opening on the side farther from the suction unit  44 . 
     In addition, the shape of the hole  47  is not limited to the circle or the rectangle, but may be any shape as long as the suction can be performed. In the suction direction SD in  FIG. 4A  and  FIG. 4B , the size of the holes  47  is gradually decreased; however, the configuration is not limited thereto, and the size of the holes  47  is the same by two rows in the suction direction SD and in this way, the size may be gradually changed. The holes  47  may have the same size not by two rows, but by three or more rows. Similarly, in  FIG. 4C  and  FIG. 4D , the pitch L is gradually changed; and two or more rows of the holes have the same pitch and thereby, the size may gradually be changed. The ratio of the opening of the holes  47  per unit area corresponds to a ratio of an area of the opening of the holes  47  in an area of a divided region when a space between the hole  47  and the hole  47  is divided at the center along the suction direction SD. In  FIG. 4A  and  FIG. 4B , the pitch L is constant. Thus, when the space between the hole  47  and the hole  47  is divided at the center, the divided area is constant in the suction direction SD. Since the holes  47  are gradually decreased in size in the suction direction SD, the ratio of the holes  47  per unit area is also gradually decreased. In  FIG. 4C  and  FIG. 4D , the pitch L is gradually increased. Thus, when the space between the hole  47  and the hole  47  is divided at the center, the area of the divided region is gradually increased in the suction direction SD. However, since the area of the hole  47  is the same, the ratio of the holes  47  per unit area is gradually decreased. 
     3. Modification Example 
     The invention includes practically the same configuration (configuration having the same function, method, and effect or configuration having the same object and effect) as the configuration described in the embodiments. In addition, the invention contains a configuration in which a non-essential part of the configuration described in the embodiments is substituted. In addition, the invention includes a configuration which achieve the same operation effects as the configuration described in the embodiments or a configuration in which it is possible to achieve the same object. In addition, the invention includes a configuration obtained by applying a known technology to the configuration described in the embodiments. 
     A sheet manufactured by the sheet manufacturing apparatus  100  mainly indicates a sheet-shaped one. However, the sheet is not limited to the sheet-shaped one, but may be board-shaped or web-shaped. The sheet in this specification is divided into paper and nonwoven fabric. The paper includes an aspect or the like in which pulp or waste paper as a raw material is formed into a thin sheet shape and includes recording paper used for writing or printing, wallpaper, wrapping paper, colored paper, drawing paper, Kent paper, or the like. The nonwoven fabric is thicker one or one having lower strength than the paper and includes common nonwoven fabric, fiberboard, tissue paper, kitchen paper, a cleaner, a filter, a liquid absorber, a sound absorber, a cushioning material, a mat or the like. Examples of the raw material may include a plant fiber such as cellulose, a chemical fiber such as polyethylene terephthalate (PET) or polyester, or an animal fiber such as wool or silk. 
     In addition, a moisture sprayer for adding moisture by spraying to the accumulated material accumulated in the accumulation unit  75  may be provided. In this way, it is possible to achieve high strength of a hydrogen bond when the sheet P is shaped. The moisture is added by spraying to the accumulated material before passing through the heating unit  52 . Starch, polyvinyl alcohol (PVA) or the like may be added to water moisture which is sprayed by the moisture sprayer. In this way, it is possible to increase strength of the sheet P. 
     The crushing unit  10  may not be provided in the sheet manufacturing apparatus  100 . For example, when the raw material is obtained by being crushed by an existing shredder or the like, there is no need to use the crushing unit  10 . 
     In addition, in the above embodiments, a case where the invention is applied to a dry-type sheet manufacturing apparatus; however, the invention may be applied to a wet-type sheet manufacturing apparatus. 
     According to an aspect of the embodiment, a sheet manufacturing apparatus that forms a sheet using a web includes: an accumulation unit that accumulates a web containing at least a fiber on a first transport belt; a first transport unit that causes the first transport belt to circle around so as to transport the web; and a second transport unit that is spaced from the first transport unit in a direction perpendicular to a surface of the web, is disposed with a part thereof shifted from the first transport unit toward the downstream side in a transport direction of the web, and sucks the web in a direction in which the web is spaced from the first transport belt and transports the web. The second transport unit includes a suction unit that generates a suction force, a second transport belt that circles around, and a suction chamber which is positioned in an inner side of the second transport belt circling around and of which an inner space is sucked by the suction unit such that the web is adsorbed onto the second transport belt. The suction unit is positioned on the outer side of the second transport belt in a direction orthogonal to the transport direction of the web along the surface of the web. 
     In the sheet manufacturing apparatus, the suction unit is not provided on the inner side of the second transport belt but is provided on the outer side of the second transport belt in a direction orthogonal to the transport direction of the web along the surface of the web and thereby, it is possible to decrease the suction chamber in the second transport belt. Therefore, it is possible to decrease the length of the second transport belt and thus, it is possible to decrease the apparatus in size. 
     In the sheet manufacturing apparatus according to the aspect of the embodiment, a plurality of holes may be provided on a surface of the second transport unit which faces the first transport belt. The holes on a side closer to the suction unit may have a smaller ratio of opening of the holes per unit area on the surface than that of the holes on a side farther from the suction unit. 
     In the sheet manufacturing apparatus, the plurality of holes are provided on the surface of the second transport unit which faces the first transport belt, the holes on the side closer to the suction unit may have a smaller ratio of opening of the holes per unit area on the surface than that of the holes on the side farther from the suction unit. Thus, even when the suction unit is provided on the outer side of the second transport belt, it is possible to achieve a uniform suction force on the side closer to the suction unit and on the side farther from the suction unit. 
     In the sheet manufacturing apparatus according to the aspect of the embodiment, the hole on the side closer to the suction unit may be smaller in size than the hole on the side farther from the suction unit. 
     In the sheet manufacturing apparatus, the holes on the side closer to the suction unit and on the side farther from the suction unit are changed in size and thus, it is possible to easily change the ratios of the opening of the holes per unit area on the side closer to the suction unit and on the side farther from the suction unit and it is possible to have a uniform suction force on the side closer to the suction unit and on the side farther from the suction unit. 
     In the sheet manufacturing apparatus according to the aspect of the embodiment, the holes on the side closer to the suction unit may have a greater center-to-center distance of the holes adjacent to each other in the direction orthogonal to the transport direction of the web along the surface of the web than the holes on the side farther from the suction unit. 
     In the sheet manufacturing apparatus, the center-to-center distances of the adjacent holes on the side closer to the suction unit and on the side farther from the suction unit can be changed from each other and thus, it is possible to easily change the ratio of the opening of the holes per unit area on the side closer to the suction unit and on the side farther from the suction unit and it is possible to achieve a uniform suction force on the side closer to the suction unit and on the side farther from the suction unit. 
     In the sheet manufacturing apparatus according to the aspect of the embodiment, the plurality of holes may be a plurality of holes provided in a current plate disposed in the suction chamber. 
     In the sheet manufacturing apparatus according to the aspect of the embodiment, the plurality of holes may be a plurality of holes disposed in the second transport belt.