Patent Publication Number: US-9902585-B2

Title: Stacking apparatus, recording apparatus and stacking method

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a stacking apparatus, a recording apparatus and a stacking method. 
     2. Related Art 
     Some recording apparatuses, such as a printer or the like, are provided with a stacking apparatus that holds a printed recording medium discharged from the recording apparatus. For example, a stacking apparatus disclosed in JP-A-6-255869 is provided with sheet guiding means for guiding a sheet (recording medium) which is discharged from a sheet discharging unit toward one side of sheet supporting means and direction changing means for changing a direction of the discharged sheet toward the other side of the sheet supporting means. Hence, according to JP-A-6-255869, the sheet that has been discharged from an image output apparatus (recording apparatus) can be held while hanging down on the sheet supporting means. 
     The stacking apparatus according to JP-A-6-255869 is configured to include a sheet guiding plate as the sheet guiding means that protrudes from the sheet discharging unit of the recording apparatus and a rotating rod as the direction changing means that is mounted at an outer side of the sheet guiding plate. The use of such a component protruding from the apparatus or a component with a large moveable range makes the structure of the stacking apparatus in JP-A-6-255869 large. 
     SUMMARY 
     The invention can be realized in the following aspects or application examples. 
     Application Example 1 
     According to an aspect of the invention, there is provided a stacking apparatus that includes: a stacking member that stacks a recording medium discharged from a recording apparatus such that the recording medium hangs on the stacking member; a guiding part that is a part of the stacking member and guides the recording medium down to a point lower than the top of the stacking member; and an urging unit that controls movement of the recording medium. 
     According to this application example, the stacking apparatus includes the guiding part that guides the recording medium discharged from the recording apparatus downward in one direction from the top of the stacking member which stacks the recording medium such that the recording medium hangs on the stacking member. Once the downward movement of the recording medium, which moves along the guiding part, is controlled by the urging unit disposed at the side of the urging unit, the recording medium that is being discharged from the recording apparatus is then guided downward along the guiding part at the other side of the urging unit. The recording medium that has been completely discharged from the recording apparatus is held in a state where the recording medium hangs on the stacking member with the both ends thereof are hung at respective sides of the stacking member. Since the stacking apparatus can be realized with such a simple configuration having the stacking member and the urging unit that stops the movement of the recording medium moving along the guiding part of the stacking member, it is possible to make the stacking apparatus smaller. Accordingly, it is possible to provide a smaller stacking apparatus. 
     Application Example 2 
     In the stacking apparatus according to the above aspect of the invention, it is preferable that the guiding part guide the recording medium toward the recording apparatus. 
     In this application example, the recording medium is guided toward the recording apparatus by the guiding part. As a result, it becomes possible to mount the urging unit that controls the movement of the recording medium at the place between the guiding part and the recording apparatus. Accordingly, the size of the entire apparatus including the stacking apparatus and the recording apparatus can be made smaller. 
     Application Example 3 
     In the stacking apparatus according to the above application example, it is preferable that the stacking member has a convex shape with the top at a center. 
     According to this application example, when the recording medium is stacked on the stacking member, it is possible to ease a tendency for the stacked recording medium to be folded by the weight thereof since the stacking member has a convex shape with the top at a center. 
     Application Example 4 
     In the stacking apparatus according to the above application example, it is preferable that the urging unit control the movement of the recording medium by pressing the recording medium against the guiding part. 
     According to this application example, the urging unit presses, against the guiding part, the recording medium that moves downward along the guiding part. Since the recording medium moves in a state of being in contact with the guiding part, the urging unit that stops the movement can be configured with a component with a small moveable range. Hence it is possible to make a smaller stacking apparatus. 
     Application Example 5 
     In the stacking apparatus according to the above application example, it is preferable that the urging unit press the recording medium against the guiding part at a position lower than the top of the stacking member. 
     According to this application example, the urging unit presses the recording medium against the guiding part at the position lower than the top of the stacking member. When the urging unit has a structure in which the urging unit presses the recording medium at the top of the stacking member, a component of the urging unit needs a large moveable range and, as a result, the stacking apparatus becomes large. However, when the urging unit has a structure in which the urging unit presses the recording medium against the guiding part at a position lower than the top of the stacking member, a component of the urging unit does not need a large moveable range, and thereby it is possible to make a smaller stacking apparatus. 
     Application Example 6 
     According to this application example, there is provided a recording apparatus that includes the stacking apparatus of any one of Application Examples 1 to 5. 
     According to this application example, since the recording apparatus includes a small stacking apparatus, it is possible to provide a small recording apparatus. 
     Application Example 7 
     According to this application example, there is provided a stacking method that is performed by a stacking apparatus including a stacking member that stacks a recording medium discharged from a recording apparatus such that the recording medium hangs on the stacking member, a guiding part that is a part of the stacking member and guides the recording medium down to a point lower than the top of the stacking member, and an urging unit that controls movement of the recording medium. The stacking method includes: guiding the recording medium down to the point lower than the top of the stacking member; and controlling the movement of the recording medium. In the guiding of the recording medium, the recording medium is guided toward the recording apparatus, and in the controlling of the movement of the recording medium, the recording medium is guided away from the recording apparatus. 
     According to this application example, the stacking method performed by a stacking apparatus includes guiding the recording medium down to the point lower than the top of the stacking member that stacks the recording medium discharged from a recording apparatus such that the recording medium hangs on the stacking member, and controlling the movement of the recording medium. The recording medium is guided toward the recording apparatus along the guiding part in the guiding of the recording medium. Once the movement of the recording medium is controlled in the controlling of the movement, the recording medium that is being discharged from the recording apparatus is guided away from the recording apparatus. Accordingly the recording medium that has been completely discharged from the recording apparatus is held in the state where the recording medium hangs on the stacking member in the both ends thereof are hung at respective sides of the stacking member. Since the stacking method allows the stacking apparatus to be realized with a simple configuration in which the stacking member and the urging unit that stops the movement of the recording medium which moves along the guiding part which is a part of the stacking member are included, it is possible to make a smaller stacking apparatus. Therefore, it is possible to provide a stacking method that allows a stacking apparatus to be downsized. 
    
    
     
       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 schematic diagram illustrating a schematic configuration of a stacking apparatus and a recording apparatus that discharges a recording medium to the stacking apparatus according to a first embodiment. 
         FIG. 2  is a side view of the stacking apparatus and the recording apparatus. 
         FIG. 3  is a sectional view illustrating a configuration of a movement amount-detecting sensor. 
         FIG. 4  is an electrical block diagram illustrating an electrical configuration of the stacking apparatus. 
         FIG. 5  is a flow chart illustrating a stacking method performed by the stacking apparatus. 
         FIG. 6  is a side view illustrating an operation of the stacking apparatus. 
         FIG. 7  is a side view illustrating the operation of the stacking apparatus. 
         FIG. 8  is a side view illustrating the operation of the stacking apparatus. 
         FIG. 9  is a side view illustrating the operation of the stacking apparatus. 
         FIG. 10  is a side view illustrating the operation of the stacking apparatus. 
         FIG. 11  is a side view of a stacking apparatus and a recording apparatus that discharges a recording medium to the stacking apparatus according to a second embodiment. 
         FIG. 12  is an electrical block diagram illustrating an electrical configuration of the stacking apparatus. 
         FIG. 13  is an electrical block diagram illustrating an electrical configuration of the recording apparatus. 
         FIG. 14  is a flow chart illustrating a stacking method performed by the stacking apparatus. 
         FIG. 15  is a partial sectional view of a recording apparatus according to a third embodiment. 
         FIG. 16  is an electrical block diagram illustrating an electrical configuration of the recording apparatus. 
         FIG. 17  is a flow chart illustrating a stacking method performed by the recording apparatus. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, embodiments of the invention will be described with reference to the drawings. Since each of the following drawings illustrates each layer and member in recognizable sizes, the actual sizes of each layer and member are different from the sizes in the following drawings. 
     In  FIGS. 1 to 3 ,  FIGS. 6 to 11 , and  FIG. 15 , for convenience of explanation, three axes, the x-axis, the y-axis and the z-axis, which are orthogonal to each other, are illustrated. The front ends of the arrows indicate a “positive direction” and the rear ends indicate a “negative direction”. A direction parallel to the x-axis will be referred to as an “x-axis direction”, a direction parallel to the y-axis will be referred to as a “y-axis direction”, and a direction parallel to the z-axis will be referred to as a “z-axis direction”. 
     First Embodiment 
       FIG. 1  is a schematic diagram illustrating a schematic configuration of a stacking apparatus and a recording apparatus that discharges a recording medium to the stacking apparatus according to a first embodiment.  FIG. 2  is a side view of the stacking apparatus and the recording apparatus. First, a schematic configuration of a stacking apparatus  50 , and a schematic configuration of a recording apparatus  10  that discharges a recording medium to the stacking apparatus  50  according to the embodiment will be described. 
     Schematic Configuration of Recording Apparatus 
     As shown in  FIGS. 1 and 2 , the recording apparatus  10  is a large format printer (LFP) that records an image or the like onto a long sheet S which is an example of the recording medium. Other recording media, including various types of paper, fabric, and film, can be used as well. In the embodiment, a recording apparatus, having a configuration in which the long sheet S in a roll is supplied, is described as an example of the recording apparatus. However, the recording apparatus is not limited thereto. For example, a recording apparatus having a configuration in which a sheet cut in a predetermined length in advance is supplied in a single-sheet feeding system may be used. 
     The recording apparatus  10  is provided with a pair of legs  13  of which wheels  12  for moving the recording apparatus  10  are attached at lower ends, and a recording unit housing  14  that is assembled on the legs  13 , or the like. In the embodiment, an up-and-down direction along the direction of gravity will be represented by the z-axis and the positive direction of the z-axis will be referred to as “upward”. A longitudinal direction (width direction) of the recording unit housing  14  that crosses (in the embodiment, is orthogonal to) the z-axis will be represented by the x-axis and the positive direction of the x-axis will be referred to as “left”. A direction that crosses (in the embodiment, is orthogonal to) both of the z-axis and the x-axis (a front-and-rear direction) is represented by the y-axis and the positive direction of the y-axis will be referred to as “front”. 
     In the recording unit housing  14 , a controller  40  that controls an operation of the recording apparatus  10  is provided. An operation panel  23  for a setting operation and an input operation is also provided on the upper right end of the recording unit housing  14 . The operation panel  23  is electrically connected to the controller  40 . 
     Under the recording unit housing  14 , liquid containers  24  capable of containing ink are provided on a right end side, that is, an outer side of a transporting path of the sheet S in a width direction (x-axis direction). A plurality of liquid containers  24  are provided depending on the number of different types or colors of ink. In the embodiment, there are four liquid containers  24  that contain four different colors of ink (for example, cyan: C, magenta: M, yellow: Y, and black: K). 
     Under the rear side of the recording unit housing  14 , a feeder  15  that is supported by the legs  13  and feeds the sheet S toward the recording unit housing  14  is disposed. In the recording unit housing  14 , a medium guiding member  17  is provided along the transporting path of the sheet S. 
     A roller R 1  around which an unused sheet S is wound in a roll is held in the feeder  15 . In the feeder  15 , the roller R 1  is loaded in a manner in which the roller R 1  can be replaced by rollers R 1  of different sizes in which the width (length in the x-axis direction) of the sheet S or the number of times the sheet S being wound is different. The roller R 1  of any size is loaded in the feeder  15  in a state where the roller R 1  leans against the right end in the x-axis direction (the negative direction of the x-axis). Once the feeder  15  rotates the roller R 1  counterclockwise in  FIG. 2 , the sheet S is fed into the recording unit housing  14  along the medium guiding member  17  after being unwound from the roller R 1 . 
     The front end of the medium guiding member  17  protrudes from the recording unit housing  14  toward the front and the rear end of the medium guiding member  17  is housed in the recording unit housing  14 . On the front side of the recording unit housing  14  and above the medium guiding member  17 , a discharging port  14   a  for discharging the sheet S from the recording unit housing  14  is provided. 
     In the recording unit housing  14 , a pair of transporting rollers  25  that transports the sheet S in a transporting direction F and a transporting motor  28  that supplies rotary power to the pair of transporting rollers  25  are provided. The recording unit housing  14  also houses a recording unit  26  that is provided on the downstream side of the transporting rollers  25  in the transporting direction F and implements printing (recording) onto the transported sheet S. In addition, a medium supporting unit  27  that is a part of the medium guiding member  17  and that supports the sheet S is provided at a position facing the recording unit  26  with the sheet S being placed between the recording unit  26  and the medium supporting unit  27 . 
     In the recording unit  26 , there are guide shafts  29  and  30  that are provided to extend in the width direction (x-axis direction), a carriage  31  that is supported by the guide shafts  29  and  30 , and a liquid ejection unit  32  that is held under the bottom of the carriage  31 . The carriage  31  reciprocates, along the guide shafts  29  and  30 , within a movement region which extends in a main scanning direction (x-axis direction) that crosses the transporting direction F of the sheet S. 
     At both ends of the guide shafts  29  and  30  in the main scanning direction (x-axis direction), there is provided a regulating mechanism  33  that changes a height of the liquid ejection unit  32  (a position in the z-axis direction) to regulate a distance between the liquid ejection unit  32  and the sheet S. A reflective sensor  34  as a paper width sensor is held at a position on the downstream side of the liquid ejection unit  32  in the transporting direction F under the bottom of the carriage  31 . 
     The reflective sensor  34  is an optical sensor provided with a light source unit and a light receiving unit (not shown). The light receiving unit receives reflected light obtained by light being emitted downward from the light source unit, and a detected value V (voltage value) that varies depending on the intensity of the reflected light received by the light receiving unit is output to the controller  40 . The controller  40  calculates a width (length in the x-axis direction) of the sheet S based on the detected value V while the reflective sensor  34  moves the carriage  31  in the main scanning direction to detect a changing position of an object from which light is reflected, that is, a position of both ends of the sheet S in the width direction (x-axis direction). 
     In accordance with the detected width of the sheet S, the liquid ejection unit  32  moves along with the carriage  31  in the main scanning direction and ejects ink supplied from the liquid container  24  onto the sheet S transported along the transporting path, thereby implementing the recording (printing) of an image or the like on the sheet S. After a cutter (not shown) cuts the sheet S on which printing has been completed in a predetermined size (length in the y-axis), the sheet S is discharged from the discharging port  14   a  to the stacking apparatus  50  which will be described later. 
     In the embodiment, as the liquid ejection unit  32 , a serial head type that is mounted in a movable carriage  31  and ejects ink while moving in the width direction of the sheet S (x-axis direction) has been described but a line head type, in which the liquid ejection unit  32  that is mounted over the entire sheet S (x-axis direction) in the width direction, may be used. 
     Schematic Configuration of Stacking Apparatus 
     Hereinafter, a schematic configuration of the stacking apparatus  50  will be described. The stacking apparatus  50  according to the embodiment is configured to be a separate apparatus from the recording apparatus  10 . The stacking apparatus  50  is mounted at a side of the discharging port  14   a  from which the sheet S is discharged from the recording apparatus  10 . In addition, the stacking apparatus  50  holds the sheet S on which an image or the like is recorded by the recording apparatus  10 . 
     As illustrated in  FIGS. 1 and 2 , the stacking apparatus  50  includes a pair of stacking unit housings  61  and a beam  62  that connects the pair of stacking unit housings  61 . The legs  13  of the recording apparatus  10  include horizontal legs  13   a  that extend in the y-axis direction and the stacking apparatus  50  is mounted on the pair of horizontal legs  13   a . In one of the stacking unit housings  61 , a controller  80  that controls an operation of the stacking apparatus  50  is provided. In addition, on top of the one of the stacking unit housings  61 , an operation panel  68  for a setting operation and an input operation is provided. The operation panel  68  is electrically connected to the controller  80 . 
     The stacking apparatus  50  includes a stacking member  51  that guides the sheet S as the recording medium which is discharged from the recording apparatus  10  to a point lower than the top of the stacking member  51  to stack the sheet S such that the sheet S hangs down thereon, a guide supporting unit  52  that supports the stacking member  51  and an urging unit  65  that controls the movement of the sheet S. 
     The guide supporting unit  52  is supported by tips of a pair of arm members  53  that extend from the pair of stacking unit housings  61 . The guide supporting unit  52  has a width larger than the maximum width of the sheet S, in the x-axis direction, which can be used for the recording apparatus  10 . The guide supporting unit  52  is at a position lower than and in front of the medium guiding member  17  that extends towards the front (positive direction of the y-axis) from the recording unit housing  14  of the recording apparatus  10 . 
     The stacking member  51  includes guiding parts  51   a  and  51   b  that are integrated with each other. The guiding part  51   a  is shaped to guide the sheet S that has been discharged from the recording apparatus  10  in a direction approaching the recording apparatus  10 . The guiding part  51   b  is in a shape symmetrical with the guiding part  51   a  with respect to the guide supporting unit  52  when seen from a side in the x-axis direction. The width of the stacking member  51  in the x-axis direction is larger than the maximum width of the sheet S used for the recording apparatus  10  and the length of the stacking member  51  along its shape in the y-axis direction is larger than the minimum length of the sheet S that is discharged from the recording apparatus  10 . The stacking member  51  is provided so as to cover the guide supporting unit  52 . In the embodiment, described is a configuration where the stacking member  51  in which the guiding parts  51   a  and  51   b  are integrated with each other covers the guide supporting unit  52 . Instead, a configuration in which guiding parts  51   a  and  51   b  are formed separately and extend from the guide supporting unit  52  may be adopted. A configuration without the guiding part  51   b  being provided may be adopted as well. 
     In the embodiment, the stacking member  51  curves so as to be convexed upward to peak at the guide supporting unit  52  when seen from the side in the x-axis direction. Specifically, the stacking member  51  is shaped in an inverted catenary such that a sheet S with the smallest length in the y-axis direction and the highest rigidity, among the sheets S that can be discharged from the recording apparatus  10 , is held at a position where the center line of the inverted catenary divides the inverted catenary into two halves in the y-axis direction, or is shaped in a slighter curve than such an inverted catenary. Therefore, it is unlikely for the sheet S to come off of a holding surface of the stacking member  51  when the stacking member  51  holds the sheet S, and it is possible to stack and hold a sheet S with a high rigidity and a small length since the sheet S is held in a stable manner. It is also possible to ease a tendency for the sheet S to be folded by the weight thereof since the sheet S is held to hang down on the stacking member  51 . In addition, a tendency for the sheet S to curl after being wound in a roll can be corrected as well. 
     The urging unit  65  includes a pad  66  that is held by a pad holding portion and a lifting lever  67  that lifts the pad  66 . The pad  66  is in a rectangular shape that extends in the x-axis direction and a width thereof in a longitudinal direction (the x-axis direction) is larger than the maximum width of the sheet S used for the recording apparatus  10  and is equal to the width of the stacking member  51 . The pad  66  is formed of a material, for example, which has high surface friction, is less likely to be affected by compressive residual stress and absorbs shock well. 
     One end of the lifting lever  67  is connected to the pad holding portion and the other end is connected to the stacking unit housing  61 . Between the one end and the other end of the lifting lever  67 , a cam  63  is provided. Once a lifting motor  64  rotates the cam  63 , the lifting lever  67  lifts the pad holding portion connected to the one end of the lifting lever  67  and the pad  66  held by the pad holding portion such that the pad holding portion and the pad  66  pivot around the other end of the lifting lever  67  as a fulcrum. 
     The urging unit  65  controls the movement of the sheet S by pressing the sheet S as the recording medium against the guiding part  51   a  that is a part of the stacking member  51 . The urging unit  65  presses, at a position lower than the top of the stacking member  51 , the sheet S as the recording medium against the guiding part  51   a . In other words, the urging unit  65  is provided at a position where the pad  66  comes into contact with the guiding part  51   a  at a position near a lower end of the guiding part  51   a  and lower than the top of the stacking member  51  when the lifting lever  67  is lowered. The pad  66  of the urging unit  65  presses the sheet S against the guiding part  51   a  from the rear surface on which an image is not recorded such that a wide contact area of the sheet S over the entire width thereof is pressed when the lifting lever  67  is lowered. Accordingly, it becomes possible to reduce damage to the image resulting from being pressed against the guiding part  51   a  since friction required to control the movement of the sheet S is distributed. 
     Once the sheet S is discharged from the recording apparatus  10  in a state where the lifting lever  67  has been raised, the sheet S is guided in the direction approaching the recording apparatus  10  along the guiding part  51   a  of the stacking member  51  and is moved downward between the guiding part  51   a  and the pad  66 . Once the lifting lever  67  is lowered, the sheet S that has been moved along the guiding part  51   a  is pressed against the guiding part  51   a  by the pad  66 , thereby controlling the movement of the sheet. In a case where an urging unit that presses the sheet S against the top of the stacking member  51  is provided, it is required to use a component with a large moveable range. However, since the urging unit  65  in the embodiment presses the sheet S against the guiding part  51   a  at a position lower than the top of the stacking member  51 , it is possible to configure the urging unit  65  with a component with a small movable range. Accordingly, it is possible to configure a small stacking apparatus  50 . Since the stacking apparatus  50  includes the guiding part  51   a  that guides the sheet S in the direction approaching the recording apparatus  10 , it is possible to provide the urging unit  65  between the guiding part  51   a  and the recording apparatus  10 . As a result, the size of the entire apparatus can be made smaller when the stacking apparatus  50  is provided in the recording apparatus  10 . 
     The stacking apparatus  50  includes a movement amount-detecting sensor  70  that detects a movement amount of the sheet S. The movement amount-detecting sensor  70  acquires the movement amount of the sheet S by imaging a surface of the sheet S that is discharged from the recording apparatus  10  and is moved downward along the guiding part  51   a  at predetermined time intervals and by comparing consecutive pieces of image data in a time series. The movement amount-detecting sensor  70  is provided at a position facing the guiding part  51   a  with the sheet S being placed therebetween. 
       FIG. 3  is a sectional view illustrating a configuration of a movement amount-detecting sensor. As illustrated in  FIG. 3 , the movement amount-detecting sensor  70  includes a light emitting unit  72 , a condenser  73 , an imaging element  74  or the like inside a case  76 . 
     The case  76  is an exterior structure of the movement amount-detecting sensor  70 . The case  76  is in a shape of a cylinder with a truncated cone on top and a tip of the case  76  (an upper end) is attached to a translucent glass  71 . The translucent glass  71  faces a surface of the sheet S in a state where clearance is provided between the translucent glass  71  and the sheet S in the y-axis direction. 
     The light emitting unit  72  emits light toward the sheet S. The light emitting unit  72  is provided on an inner wall of the case  76  and at an angle that allows the light emitting unit  72  to emit light toward the translucent glass  71 . A light emitting diode (LED) or the like can be used as the light emitting unit  72 , for example. 
     Once the light emitted from the light emitting unit  72  is transmitted through the translucent glass  71  and is reflected from a surface of the sheet S, the light is transmitted back through the translucent glass  71  and is incident to the inside of the case  76 . Then the condenser  73 , provided in a cylindrical portion of the case  76 , converges this reflected light. 
     The imaging element  74  captures an image of a surface of the sheet S converged by the condenser  73  and includes an imaging surface  74   a  at a position where the image is formed. The imaging element  74  is provided on an inner bottom surface of the case  76 . A holding member  75  holds the condenser  73  at a height that allows the image of the surface of the sheet S to be formed on the imaging surface  74   a  of the imaging element  74 . 
     The movement amount-detecting sensor  70  outputs image data captured by the imaging element  74  to the controller  80 . The controller  80  acquires a total movement amount of the sheet S by comparing consecutive pieces of image data in a time series, captured at predetermined time intervals, and by integrating the movement amount of the sheet S for each predetermined time interval. 
     It is preferable for the movement amount-detecting sensor  70  to maintain a certain distance to the sheet in order to focus on the image that is the surface of the sheet S when capturing the image. Accordingly, the position of the movement amount-detecting sensor  70  may be adjusted depending on the thickness of the sheet S or the number of the sheets S being stacked on the stacking member  51 . Instead, the movement amount-detecting sensor  70  may be configured to allow focus adjustment, adjusting focus depending on the thickness of the sheet S or the number of the sheets S being stacked on the stacking member  51 . 
     Electrical Configuration of Stacking Apparatus 
       FIG. 4  is an electrical block diagram illustrating an electrical configuration of the stacking apparatus. The electrical configuration of the stacking apparatus  50  will be described with reference to  FIG. 4 . 
     The controller  80  is a control unit that controls the stacking apparatus  50 . The controller  80  is configured to include a central processing unit (CPU)  81 , a control circuit  82  and a memory unit  83 . The CPU  81  is an arithmetic processing unit that controls processing for input signals from the movement amount-detecting sensor  70  and the entire stacking apparatus  50 . The controller  80  controls each part of the stacking apparatus  50  in accordance with a command that has been input from the operation panel  68 . In addition, the controller  80  displays a state of the stacking apparatus  50  on the operation panel  68 . 
     The memory unit  83  secures an area to store programs or a work area of the CPU  81  and includes memory elements such as a random access memory (RAM), an electrically erasable programmable read-only memory (EEPROM), or the like. The memory unit  83  stores the image data captured by the movement amount-detecting sensor  70 . 
     The CPU  81  controls the lifting motor  64  that lifts the urging unit  65  which presses the sheet S against the guiding part  51   a , through the control circuit  82 . 
     Stacking Method 
       FIG. 5  is a flow chart illustrating a stacking method performed by the stacking apparatus.  FIGS. 6 to 10  are side views illustrating an operation of the stacking apparatus. A stacking method for the stacking apparatus  50  will be described with reference to  FIGS. 4 to 10 . 
     Step S 1  is a preparing step. In the preparing step, information regarding a size of the sheet S (width in the x-axis direction and length in the y-axis direction) that is discharged from the recording apparatus  10  is input from the operation panel  68 . 
     Step S 2  is a guiding step.  FIG. 6  is a sectional view at a time when a leading end of the sheet S (an end on the downstream side in the transporting direction F) is in contact with the stacking member  51 . In the guiding step, the sheet S as the recording medium that has been discharged from the recording apparatus  10  is guided in the direction approaching the recording apparatus  10 . In other words, the stacking apparatus  50  is provided at a position where an orientation of the leading end of the sheet S is changed in the direction approaching the recording apparatus  10  at a time when the leading end of the sheet S that has been discharged from the recording apparatus  10  is in contact with the guiding part  51   a  of the stacking member  51  that curves so as to be convexed upward to peak at a point supported by the guide supporting unit  52 . 
     Step S 3  is a calculating step of a movement amount of the sheet S.  FIG. 7  is a sectional view at a time when the sheet S has moved down toward the recording apparatus  10  along the guiding part  51   a  and has reached the movement amount-detecting sensor  70 . The controller  80  controls the movement amount-detecting sensor  70  such that the surface of the sheet S is imaged at every predetermined time interval and then the captured image is stored in the memory unit  83 . The controller  80  compares consecutive pieces of image data in a time series and acquires the movement amount of the sheet S for every predetermined time interval. Then, the controller  80  integrates the movement amounts for predetermined time intervals to acquire a total movement amount of the sheet S. In steps S 1  to S 3 , the urging unit  65  remains stopped in a state of being raised. 
     Step S 4  is a movement controlling step.  FIG. 8  is sectional view at a time when a movement of the sheet S has been stopped. In the controlling step, the sheet S as the recording medium is guided in a direction away from the recording apparatus  10 . The controller  80 , based on the movement amount of the sheet S acquired in step S 3 , acquires a distance between the leading end of the sheet S and the top of the stacking member  51 . The controller  80  drives the lifting motor  64  to rotate the cam  63 , so that the urging unit  65  is lowered at a time when the leading end of the sheet S reaches a position at which the distance between the leading end of the sheet S and the top of the stacking member  51  is equal to approximately half the length of the sheet S, which is being discharged, in the y-axis direction. Accordingly, the sheet S is pressed by the urging unit  65  against the guiding part  51   a  and the sheet S is prevented from moving down toward the recording apparatus  10 . 
       FIG. 9  is a sectional view illustrating a state of the sheet S after the movement of the sheet S has been stopped. As illustrated in  FIG. 9 , once the sheet S is prevented from moving down toward the recording apparatus  10 , the sheet S that is being discharged from the recording apparatus  10  is extruded in a U-shape along the shape of the stacking member  51 , and is guided in the direction away from the recording apparatus  10 . 
     Step S 5  is a releasing step.  FIG. 10  is a sectional view at a time when the sheet S is released. Once the recording of the image has been completed and the sheet S that has been cut in a predetermined size is discharged from the recording apparatus  10 , a trailing end of the sheet S (an end on the upstream side in the transporting direction F) slips off along the guiding part  51   b  of the stacking member  51 . Accordingly, the sheet S hangs down equally in the positive and negative directions of the y-axis at the midpoint, that is, the top of the stacking member  51 , when seen from the side in the x-axis direction. The controller  80  calculates the time required for the trailing end of the sheet S to be discharged based on a sheet size and a moving speed of the sheet S acquired in step S 3 . Once the time required for the trailing end of the sheet S to be discharged from the recording apparatus  10  has passed, the controller  80  drives the lifting motor  64  and rotates the cam  63  to raise the urging unit  65 . 
     Step S 6  is a determining step. The controller  80  determines if a termination operation has been input from the operation panel  68 . In a case where the termination operation has been input (step S 6 : Yes), the controller  80  terminates the operation thereof. In a case where the sheet S is being discharged in a size which is equal to the size of the sheet S that has been discharged immediately before without the termination operation being input (step S 6 : No), steps S 2  to S 6  are repeated, after going back to step S 2 . 
     The stacking apparatus  50  includes the guiding part  51   a  that guides the sheet S down toward the recording apparatus  10  and the urging unit  65  that controls the downward movement of the sheet S to guide the sheet S in the direction away from the recording apparatus  10  along the stacking member  51 . Since the stacking apparatus  50  can be realized with a simple configuration in which the stacking member  51  and the urging unit  65  are included, the stacking apparatus  50  can be made small. 
     As described above, the following effects can be obtained with the stacking apparatus  50  and the stacking method according to the embodiment. 
     In the embodiment, the stacking apparatus  50  includes the guiding part  51   a  that guides the sheet S down in the direction approaching the recording apparatus  10  (one direction) from the top of the stacking member  51  on which the sheet S as the recording medium that is discharged from the recording apparatus  10  hangs down. The stacking apparatus  50  also includes the urging unit  65  that controls the downward movement of the sheet S to guide the sheet S in the direction away from the recording apparatus  10  (the other direction) by the stacking member  51 . Accordingly, the stacking apparatus  50  holds the sheet S that has been discharged from the recording apparatus  10  in a state where the sheet S hangs down at the top of the stacking member  51  in the both directions. Since the stacking apparatus  50  can be realized with a simple configuration in which the stacking member  51  and the urging unit  65  are included, the size of the stacking apparatus  50  can be made small. As a result, it is possible to provide a small stacking apparatus  50 . 
     Since the stacking apparatus  50  includes the guiding part  51   a  that guides the sheet S in the direction approaching the recording apparatus  10 , it is possible to provide the urging unit  65  between the guiding part  51   a  and the recording apparatus  10 . Accordingly, it is possible to reduce the size of the entire apparatus when the stacking apparatus  50  is mounted in the recording apparatus  10 . Since the stacking apparatus  50  can be operated independently of the recording apparatus  10  by necessary information (the size of the sheet S or the like) being input, the stacking apparatus  50  can be mounted in various types of recording apparatuses. 
     Since the urging unit  65  presses the sheet S against the guiding part  51   a  at a position lower than the top of the stacking member  51 , the urging unit  65  can be configured with a component with a small movable range. As a result, it is possible to configure a small stacking apparatus  50 . 
     Since the stacking member  51  is shaped in an inverted catenary that curves so as to have a convex shape with the top as a center, the sheet S with a high rigidity and a small length can be held stably. It is also possible to ease the tendency for the sheet S to be folded by the weight the sheet S since the sheet S is held so as to hang down on the stacking member  51 . In addition, the tendency for the sheet S to curl after being wound in a roll can be corrected as well. 
     In the embodiment, the stacking method includes the guiding step in which the leading end of the sheet S as the recording medium is guided toward the recording apparatus  10  along the guiding part  51   a , and the controlling step in which the leading end of the sheet S is prevented from moving downward toward the recording apparatus  10  and the sheet S, which is discharged from the recording apparatus  10 , is guided away from the recording apparatus  10  along the stacking member  51 . These steps allow the sheet S that has been discharged from the recording apparatus  10  to be held in a state where the sheet S hangs down at the top of the stacking member  51  of the stacking apparatus  50  in both directions. Since the stacking method makes it possible for the stacking apparatus  50  to be realized with a simple configuration in which the stacking member  51  and the urging unit  65  are included, the stacking apparatus  50  can be made small. Accordingly, it is possible to provide the stacking method through which the size of the stacking apparatus  50  can be reduced. 
     Second Embodiment 
       FIG. 11  is a side view of a stacking apparatus and a recording apparatus that discharges a recording medium to the stacking apparatus according to a second embodiment.  FIG. 12  is an electrical block diagram illustrating an electrical configuration of the stacking apparatus.  FIG. 13  is an electrical block diagram illustrating an electrical configuration of the recording apparatus. A stacking apparatus  150  and a recording apparatus  110  that discharges a recording medium to the stacking apparatus  150  according to the embodiment will be described with reference to  FIGS. 11 to 13 . Parts that are included in the first embodiment will be denoted by the same reference numerals and the description thereof will not be repeated. 
     In the second embodiment, the stacking apparatus  150  is not provided with the operation panel  68  and the movement amount-detecting sensor  70  that are included in the stacking apparatus  50  described in the first embodiment. Instead, the stacking apparatus  150  includes a communication unit  170  and the recording apparatus  110  includes a communication unit  120 . 
     The electrical configuration of the stacking apparatus  150  will be described with reference to  FIGS. 11 and 12 . The stacking apparatus  150  is provided with the communication unit  170  in which an antenna  172  for a wireless communication is included. The communication unit  170  wirelessly transmits and receives data to and from the recording apparatus  110 . 
     Wireless communication can be achieved with methods including various types of wireless systems such as wireless LAN, Bluetooth (registered trademark), Zigbee (registered trademark), Worldwide Interoperability for Microwave Access (WiMAX), Personal Handy-phone System (PHS), specific low power, a mobile phone and the like. 
     Hereinafter, the electrical configuration of the recording apparatus  110  will be described with reference to  FIGS. 11 and 13 . 
     The recording apparatus  110  is provided with the controller  40 . The controller  40  is a control unit that controls the recording apparatus  110 . The controller  40  is configured to include a control circuit  42 , an interface unit (I/F)  44 , a central processing unit (CPU)  41  and a memory unit  43 . The interface unit  44  is used for transmitting and receiving data between the recording apparatus  110  and an external apparatus  46  that deals with images, such as a computer, a digital camera and the like. The CPU  41  is an arithmetic processing unit that controls processing for input signals from a group of various detectors  47  and the entire recording apparatus  110 . 
     The memory unit  43  secures an area to store programs or a work area of the CPU  41  and includes memory elements such as a random access memory (RAM), an electrically erasable programmable read-only memory (EEPROM), or the like. 
     The CPU  41  controls the transporting motor  28  that drives the pair of transporting rollers  25  which transports the sheet S, the recording unit  26  that ejects ink toward the sheet S while moving the carriage  31  in a direction (x-axis direction) that intersects with the transporting direction F (y-axis direction) and other parts not illustrated in the drawings, through the control circuit  42 . 
     The recording apparatus  110  is provided with the communication unit  120  in which an antenna  122  for wireless communication is included. The communication unit  120  wirelessly transmits and receives data to and from the stacking apparatus  150 . The same wireless systems as in the stacking apparatus  150  can be used as a communication method. 
     Stacking Method 
       FIG. 14  is a flow chart illustrating a stacking method performed by a stacking apparatus. A stacking method for the stacking apparatus  150  will be described with reference to  FIG. 14 . 
     Step S 11  is a guiding step. In the guiding step, the sheet S as the recording medium that has been discharged from the recording apparatus  110  is guided in a direction approaching the recording apparatus  110 . In other words, the stacking apparatus  150  is provided at a position where an orientation of the leading end of the sheet S is changed in the direction approaching the recording apparatus  110  at a time when the leading end of the sheet S that has been discharged from the recording apparatus  110  is in contact with the guiding part  51   a  of the stacking member  51  that curves so as to have a convex shape with the top as a center. 
     Step S 12  is a receiving step of a movement amount of the sheet S. The controller  40  for the recording apparatus  110  controls driving of the transporting motor  28  through the control circuit  42  to rotate the pair of transporting rollers  25  and to transport the sheet S in the transporting direction F. Then, the controller  40  transmits, as transportation data, a transported amount of the sheet S calculated based on a rotation amount of the transporting motor  28  sequentially to the communication unit  120 , to begin with. In addition, the controller  40  appropriately transmits data such as information on a state of printing onto the sheet S to the communication unit  120  first. 
     The controller  80  for the stacking apparatus  150  receives transportation data related to the sheet S that is being transmitted from the recording apparatus  110 . From steps S 11  to S 12 , the urging unit  65  remains stopped in a state of being raised. 
     Step S 13  is a controlling step. In the controlling step, the sheet S as the recording medium is guided in a direction away from the recording apparatus  110 . The controller  80 , based on the movement amount of the sheet S acquired in step S 12 , acquires a distance between the leading end of the sheet S and the top of the stacking member  51 . The controller  80  drives the lifting motor  64  to rotate the cam  63 , so that the urging unit  65  is lowered at a time when the leading end of the sheet S reaches a position at which the distance between the leading end of the sheet S and the top of the stacking member  51  is equal to approximately half the length of the sheet S, which is being discharged, in the y-axis direction. Accordingly, the sheet S is pressed by the urging unit  65  against the guiding part  51   a  and the sheet S is prevented from moving down toward the recording apparatus  110 . Once the sheet S is prevented from moving down toward the recording apparatus  110 , the sheet S that is being discharged from the recording apparatus  110  is extruded in a U-shape along the shape of the stacking member  51 , and is guided in the direction away from the recording apparatus  110 . Information of the length of the sheet S in the y-axis direction is transmitted from the recording apparatus  110  by step S 12 , and is stored in the memory unit  83  in advance. Since it takes time for the sheet S that is discharged from the recording apparatus  110  to reach the stacking member  51  after the controller  40  for the recording apparatus  110  transmits the transported amount of the sheet S as the transportation data calculated based on the rotation amount of the transporting motor  28  to the communication unit  120  to begin with, the controller  80  controls the urging unit  65  given the time taken from the calculation of the transported amount of the sheet S to the arrival of the sheet S at the stacking member  51 . 
     Step S 14  is a releasing step. Once the recording of the image has been completed and the sheet S that has been cut in a predetermined size is discharged from the recording apparatus  110 , the trailing end of the sheet S slips off along the guiding part  51   b  of the stacking member  51 . Accordingly, the sheet S hangs down equally in the positive and negative directions of the y-axis at the midpoint, that is, the top of the stacking member  51 , when seen from the side in the x-axis direction. The controller  80  drives the lifting motor  64  and rotates the cam  63  to raise the urging unit  65  based on data on a state of printing onto the sheet S (for example, cutting termination data of the sheet S). 
     Step S 15  is a determining step. The controller  80  determines if data on printing operation termination has been received from the recording apparatus  110 . In a case where a signal for printing operation termination has been received (step S 15 : Yes), the controller  80  terminates the operation of the stacking apparatus  150 . In a case where the signal for printing operation termination has not been received (step S 15 : No), steps S 11  to S 14  are repeated, after going back to step S 11 . 
     In the embodiment, it is described that the stacking apparatus  150  and the recording apparatus  110  wirelessly communicate with each other. Without being limited thereto, however, the stacking apparatus  150  and the recording apparatus  110  may conduct wired communication by being connected through wires such as Universal Serial Bus (USB), Ethernet (registered trademark), or the like. 
     As described above, the following effects can be obtained with the recording apparatus  110  according to the embodiment. 
     The stacking apparatus  150  is provided with the communication unit  170  that receives the transportation data on the sheet S transmitted from the recording apparatus  110  or various types of data related to printing. Based on the data, the lifting motor  64  is controlled to lift the urging unit  65 . As a result, it is possible to stack the sheet S that is discharged from the recording apparatus  110  on the stacking member  51 . Accordingly, the movement amount-detecting sensor  70  for calculating the movement amount of the sheet S and the operation panel  68  provided in the first embodiment are unnecessary in the second embodiment, and it becomes possible to configure an even smaller and more affordable stacking apparatus  150 . 
     Third Embodiment 
       FIG. 15  is a partial sectional view of a recording apparatus according to a third embodiment.  FIG. 16  is an electrical block diagram illustrating an electrical configuration of the recording apparatus. A recording apparatus  210  according to the embodiment will be described with reference to  FIGS. 15 and 16 . In the third embodiment, the recording apparatus  210  is configured to include and be integrated with a stacking apparatus  250 . Parts that are included in the first and second embodiments will be denoted by the same reference numerals and the description thereof will not be repeated. 
     As illustrated in  FIG. 15 , the recording apparatus  210  includes the stacking apparatus  250  that is supported by a pair of supporting portions  13   b  which extend from the pair of legs  13  toward the discharging port  14   a  (positive direction of the y-axis) from which the sheet S is discharged. On the pair of supporting portions  13   b , a pair of stacking unit housings  261  of the stacking apparatus  250  are provided, and a pair of arm members  253  extend from the pair of supporting portions  13   b . The guide supporting unit  52  is provided on tips of the pair of arm members  253  and supports the stacking member  51 . In one of the stacking unit housings  261 , the cam  63  that lifts the urging unit  65  and the lifting motor  64  that rotates the cam  63  are provided. 
     As shown in  FIG. 16 , the controller  40  controls the stacking apparatus  250 . Specifically, the CPU  41  controls, through the control circuit  42 , the lifting motor  64  that lifts the urging unit  65  which presses the sheet S against the guiding part  51   a.    
     Stacking Method 
       FIG. 17  is a flow chart illustrating a stacking method performed by the recording apparatus. The stacking method for the recording apparatus  210  will be described with reference to  FIGS. 16 and 17 . 
     Step S 21  is an image forming step. The controller  40  controls each part that configures the transporting motor  28  or the recording unit  26 , and forms an image or like onto the sheet S by repeating the transportation of the sheet S and the ejection of ink. 
     Step S 22  is a guiding step. In the guiding step, the sheet S as the recording medium that has been discharged from the discharging port  14   a  is guided in the direction approaching the recording apparatus  210 . In other words, the stacking apparatus  250  that is built in the recording apparatus  210  is provided at a position where an orientation of the leading end of the sheet S is changed in the direction approaching the main body of the recording apparatus  210  from the stacking apparatus  250  at a time when the leading end of the sheet S that has been discharged from the recording apparatus  210  is in contact with the guiding part  51   a  of the stacking member  51  that curves so as to have a convex shape with the top as a center. 
     Step S 23  is a controlling step. In the controlling step, the sheet S as the recording medium is guided in a direction away from the recording apparatus  210 . The controller  40  calculates the transported amount of the sheet S based on the rotation amount of the transporting motor  28  and acquires a distance between the leading end of the sheet S and the top of the stacking member  51  based on the movement amount of the sheet S. The controller  40  drives the lifting motor  64  to rotate the cam  63 , so that the urging unit  65  is lowered at a time when the leading end of the sheet S reaches a position at which the distance between the leading end of the sheet S and the top of the stacking member  51  is equal to approximately half the length of the sheet S, which is being discharged, in the y-axis direction. Accordingly, the sheet S is pressed by the urging unit  65  against the guiding part  51   a , and the sheet S is prevented from moving down toward the main body of the recording apparatus  210 . Once the sheet S is prevented from moving down toward the main body of the recording apparatus  210 , the sheet S that is being discharged from the discharging port  14   a  is extruded in a U-shape along the shape of the stacking member  51 , and is guided in the direction away from the recording apparatus  210 . Since it takes time for the sheet S that is discharged from the recording apparatus  210  to reach the stacking member  51  after the controller  40  calculates the transported amount of the sheet S based on the rotation amount of the transporting motor  28 , the controller  40  controls the urging unit  65  given the time taken from the calculation of the transported amount of the sheet S to the arrival of the sheet S at the stacking member  51 . 
     Step S 24  is a releasing step. Once the recording of the image has been completed, the controller  40  controls a cutter (not shown) such that the sheet S is cut in a predetermined size and then the sheet S is discharged from the discharging port  14   a . Then, the trailing end of the sheet S slips off along the guiding part  51   b  of the stacking member  51 . Accordingly, the sheet S hangs down equally in the positive and negative directions of the y-axis at the midpoint, that is, the top of the stacking member  51 , when seen from the side in the x-axis direction. After the sheet S has been cut, the controller  40  controls the lifting motor  64  and rotates the cam  63  to raise the urging unit  65 . 
     Step S 25  is a determining step. The controller  40  determines whether to continue printing or not. In a case where it is determined to continue printing (step S 25 : Yes), steps S 21  to S 24  are repeated, after going back to step S 21 . Accordingly, the sheet S is stacked and held on the stacking member  51 . In a case where it is determined not to continue printing (step S 25 : No), the controller  40  terminates the operation of the recording apparatus  210 . 
     As described above, the following effect can be obtained with the recording apparatus  210  according to the embodiment. 
     Since the recording apparatus  210  is provided with the stacking apparatus  250  that has been made smaller by the use of the aforementioned stacking method, it is possible to provide a small recording apparatus  210  that has a stack function. 
     This application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2015-161675, filed Aug. 19, 2015. The entire disclosure of Japanese Patent Application No. 2015-161675 is hereby incorporated herein by reference.