Abstract:
In a sheet collecting apparatus having a collecting table on which a sheet charged by a charging means is collected, a suctioning/transporting means for suctioning and transporting the sheet charged by the charging means along a charging direction and releasing the sheet above the collecting table, back stoppers for receiving the sheet transported by the suctioning/transporting means downstream of the collecting table along a transport direction of the sheet, and a back guide disposed downstream of the collecting table along the transport direction of the sheet for regulating a position along the transport direction of the sheet received by the back stoppers, the sheet collecting apparatus positions the sheet charged by the charging means at a predetermined position and stacks it in a layer state.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority under 35 USC 119 from Japanese Patent Application No. 2008-048522, the disclosures of which is incorporated by reference herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a sheet collecting apparatus and a sheet collecting method. 
         [0004]    2. Description of the Related Art 
         [0005]    As disclosed in Japanese Patent Application Laid-Open (JP-A) No. 2006-327713, there is a sheet collecting apparatus which has a back stopper for receiving a sheet charged by a charging means downstream of a collecting table and a sheet holding means for receiving the sheet above the collecting table, releases the sheet after it is received by the sheet holding means from the below, and drops the sheet onto the collecting table as a sheet collecting apparatus for collecting an planographic printing plate like a computer-to-plate (CTP) printing plate which has no slip sheet placed on the printing surface thereof and of which printing surface is liable to be scratched. 
         [0006]    However, when the CTP printing surface is charged at a higher speed, the CTP printing surface may flutter because the kinetic energy of the charged CTP printing surface is not sufficiently absorbed by the back stopper. In this case, since the sheet holding means must wait while holding the CTP printing surface until fluttering of it is ceased, a pitch at which the CTP printing surface is collected cannot be increased so much. 
         [0007]    If the CTP printing surface being held is released before fluttering thereof caused by the collision thereof against the back stopper is not completely ceased, since the CTP printing surface is collected on the collecting table before the kinetic energy is not completely released, there is a possibility that not only the CTP printing surface is not securely positioned on the sheet collecting table but also a scratch is generated to the periphery of the CTP printing surface. 
       SUMMARY OF THE INVENTION 
       [0008]    An object of the invention, which was made to solve the above problem, is to provide a sheet collecting apparatus which does not generate a damage such as a scratch and the like on the sheet surface of a sheet such as a CTP printing plate of which surface is liable to be scratched even if the sheet is charged at a high charge speed without a protection member such as slip sheet at a high collection pitch. 
         [0009]    A first aspect for solving the above problem relates to a sheet collecting apparatus for positioning a sheet charged by charging means at a predetermined position and stacking it in a layer state comprising: a collecting table on which the sheet charged by the charging means are collected; a suctioning/transporting means for suctioning and transporting the sheet charged by the charging means along a charging direction and releasing the sheet above the collecting table; back stoppers for receiving the sheet transported by the suctioning/transporting means downstream of the collecting table along a transport direction of the sheet; and a back guide disposed downstream of the collecting table along the transport direction of the sheet for regulating a position along the transport direction of the sheet received by the back stoppers. 
         [0010]    In the sheet collecting apparatus of the first aspect, a sheet charged by the charging means is sucked and transported above the collecting table by the suctioning/transporting means and released therefrom above the collecting table. 
         [0011]    Since the sheet released from the suctioning/transporting means is received by the back stoppers and the kinetic energy thereof is absorbed thereby, occurrence of fluttering of the sheet can be prevented. The sheet received by the back stoppers is collected on the collecting table in a state that the downstream side of the sheet in the charging direction is positioned by the back guide. 
         [0012]    A second aspect for solving the above problem relates to the sheet collecting apparatus according to the first aspect having a pair of side guide members for regulating a charge path of the sheet transported by the suctioning/transporting means and released from the suctioning/transporting means above the collecting table. 
         [0013]    In the sheet collecting apparatus of the second aspect, the sheet released from the suctioning/transporting means above the collecting table is received by the back stoppers in a state that the two sides of the sheet along the charging direction are positioned by the side guide members and collected on the collecting table in a state that the downstream side of the sheet in the charging direction is positioned by the back guide. Therefore, the sheet is collected in the state that the three sides in total of the sheet, i.e., the two sides along the charging direction and the downstream side in the charging direction are positioned. 
         [0014]    According to the sheet collecting apparatus of the second aspect, the charged sheet is collected on the collecting table in the state that the three sides thereof are positioned by the side guide members and the back guide member as described above. Therefore, disturbance of a sheet on the collecting table can be more effectively reduced than a sheet collecting apparatus having no side guide members. 
         [0015]    A third aspect for solving the above problem relates to the sheet collecting apparatus according to the second aspect including edge support members disposed so that they can appear or disappear from the side guide members and receiving the sheet from the below by projecting from the side guide members when the sheet is released from the suctioning/transporting means. 
         [0016]    In the sheet collecting apparatus of the third aspect, when a sheet is released from the suctioning/transporting means, the edge support members project from the side guide members and hold the sheet from the below. By this operation, the sheet is dropped onto the collecting table in a state that the drop energy of the sheet is almost absorbed. 
         [0017]    According to the third aspect, the sheet released from the suctioning/transporting means is held by the edge support members from the below and dropped onto the collecting table in the state that the drop energy thereof is almost absorbed as described above. Therefore, occurrence of a damage such as a scratch and the like on a sheet surface can be more effectively suppressed than a sheet collecting apparatus having no edge support members. 
         [0018]    A fourth aspect for solving the above problem relates to the sheet collecting apparatus according to any of the first to third aspects comprising a front stopper disposed opposite to the back stoppers and the back guide member across the collecting table. 
         [0019]    In the sheet collecting apparatus of the fourth aspect, a sheet released from the suctioning/transporting means above the collecting table is received by the back stoppers in a state that the two sides of the sheet along the charging direction are positioned by the side guide members and collected on the collecting table in a state that the side of the sheet downstream of a charge side is positioned by the back guide and the side of the sheet upstream in the charging direction is positioned by the front stopper. 
         [0020]    According to the fourth aspect, the charged sheet is collected on the collecting table in the state that the four sides of the sheet, i.e., the two sides along the charging direction and the two sides downstream and upstream in the charging direction are positioned. Therefore, disturbance of a sheet bundle on the collecting table can be more effectively reduced than a sheet collecting apparatus having no front stopper. 
         [0021]    A fifth aspect for achieving the above object relates to the sheet collecting apparatus according to any of the first to fourth aspects wherein the suctioning/transporting means include a breathable suction belt rotating in a predetermined direction and suction boxes disposed inside the suction belt for suctioning the sheet on the front surface of the suction belt by suctioning air through the suction belt. 
         [0022]    In the sheet collecting apparatus of the fifth aspect, by suctioning the air in the suction boxes while rotating the suction belt so that the surface thereof facing the collecting table moves in the same direction as the charging direction a sheet charged by the charging means is sucked onto the outer surface of the suction conveyer and moved along the charging direction of the sheet. When the sheet moves above the collecting table, the sheet can be released from the front surface of the suction conveyer and dropped downward by supplying air into the suction boxes. 
         [0023]    According to the fifth aspect, a timing at which a sheet is released from the suction conveyer can be set by setting timing at which a pressure reduced state is disrupted by supplying air into the suction boxes. Therefore, there is provided a sheet collecting apparatus wherein timing at which a charged sheet is released toward the collecting table can be easily set. 
         [0024]    A sixth aspect for achieving the above object relates to the sheet collecting apparatus according to any of the first to fifth aspects wherein the back guide member is formed so as to have a sheet receiving height that is a height for receiving the sheet set higher than the lower edges of the back stoppers. 
         [0025]    In the sheet collecting apparatus of the sixth aspect, since the side guide member is formed so that the sheet receiving height of the back guide is higher than the lower edges of the back stoppers, the sheet released from the suctioning/transporting means won&#39;t pass under the lower edges of the back stoppers because the height is regulated by the back guide. 
         [0026]    According to the sixth aspect, a sheet released from the suctioning/transporting means is received at a position higher than the lower edges of the back stoppers in the back guide as described above. Therefore, the front edge of a sheet is effectively prevented from entering between the back stoppers and the back guide. 
         [0027]    A seventh aspect for achieving the above object relates to the sheet collecting apparatus according to any of the second to sixth aspects wherein a sheet receiving height as a height for receiving the sheet by the back guide member is lower than a positioning height for positioning the sheet by the side guide members and the front stopper in. 
         [0028]    In the sheet collecting apparatus of the seventh aspect, the sheet receiving height, which is the height in which a sheet is received by the back guide member, is lower than the position determination height in which the sheet is positioned by the side guides and the front stopper. Therefore, a sheet released from the suctioning/transporting means is at first received by the back stopper and is moved to the front stopper side. The upstream side of the sheet in the transport direction thereof is positioned by being butted against the portions of the positioning height of the side guides and then the two sides of the sheet along the transport direction are positioned by being butted against the portions of the side guides located at the positioning height thereof. Finally, the downstream side of the sheet in the transport direction is positioned by being butted against the portion of the side guide member located at the sheet receiving height thereof. 
         [0029]    According to the seventh aspect, as described above, a sheet released from the suctioning/transporting means is positioned in the sequence of the side guides, the front stopper, and the back guide and finally collected on the collecting table in the state that all the four sides thereof are positioned. Therefore, since when the sheets are dropped after being held by the edge support member from the below, disturbance of sheets on the collecting table are more effectively suppressed, it can be more effectively prevented that the sheets are scratched by being rubbed with each other when they are dropped onto a collecting surface. 
         [0030]    An eighth aspect for achieving the above object relates to the sheet collecting apparatus according to any of the first to seventh aspects having an auxiliary air nozzle that is disposed below the inlet side edge of the suctioning/transporting means from which the sheets are charged so as to lift the sheet sucked and transported by the suctioning/transporting means upward by jetting air upward. 
         [0031]    In the sheet collecting apparatus of the eight aspect, a charged sheet can be pressed against the suctioning/transporting means by jetting air from the auxiliary air nozzle to the sheet. 
         [0032]    According to the eighth aspect, since a charged sheet is caused to come into intimate contact with the suctioning/transporting means by jetting air from the auxiliary air nozzle, the sheet can be securely sucked to the suctioning/transporting means even if it is curved in the charging direction or a width direction. 
         [0033]    A ninth aspect for achieving the above object relates to the sheet collecting apparatus according to any of the fourth to eighth aspects wherein the front stopper is formed such that the position thereof can be changed according to the measurement of a sheet to be charged in the charging direction thereof. 
         [0034]    In the sheet collecting apparatus of the ninth aspect, when a sheet having a larger measurement in the charging direction is collected the front stopper is moved farther away from the back stoppers than in a case when a sheet having a smaller measurement in the charging direction is collected. 
         [0035]    According to the ninth aspect, since the position of the front stopper is adjusted according to the measurement of a sheet in the charging direction, the relative positional relation of the sheet to the back stoppers when the sheet is released from the suctioning/transporting means can be kept constant at a time when a sheet having a large measurement in the charging direction is collected or at a time when a sheet having a small measurement in the charging direction is collected. Therefore, since a sheet can be collected while keeping a sheet separating condition in the suctioning/transporting means and timing at which the sheet is held from the below constant, a damage of the sheet due to disturbance of a sheet surface can be particularly effectively prevented. 
         [0036]    A tenth aspect for achieving the above object relates to a method of collecting a sheet charged by a charging means along a predetermined direction in a layer state on a collecting table of a sheet collecting apparatus which has the collecting table, a suctioning/transporting means disposed above the collecting table, back stoppers disposed downstream of the collecting table along a transport direction of the sheets, and a back guide member disposed downstream of the collecting table along the transport direction of the sheet adjacent to the back stoppers, the method comprising a step of suctioning by the suctioning/transporting means the sheet charged by the charging means, transporting the sheet along the charging direction of the sheets, and releasing the sheet above the collecting table, a step of receiving the sheet released from the suctioning/transporting means downstream of the collecting table along the transport direction of the sheet by the back stoppers, and a step of regulating a position along the transport direction of the sheet, which is received by the back stoppers, by the back guide member. 
         [0037]    In the sheet collecting method of the tenth aspect, a sheet charged by the charging means is sucked and transported above the collecting table by the suctioning/transporting means and released from the suctioning/transporting means above the collecting table. 
         [0038]    Since the sheet released from the suctioning/transporting means is received by the back stoppers and the kinetic energy thereof is absorbed thereby, occurrence of fluttering of the sheet can be prevented. The sheet received by the back stoppers is collected on the collecting table by that the downstream side of the sheet in the charging direction is positioned by the back guide. 
         [0039]    In the sheet collecting method of the tenth aspect, a sheet charged as described above is sucked and transported by the suctioning/transporting means, released therefrom above the collecting table, and collected on the collecting table while being positioned by the back guide after it is received by the back stoppers and the kinetic energy thereof is absorbed. 
         [0040]    Accordingly, there can be provided a sheet collecting apparatus which can collect a sheet at a high collection pitch without causing a damage such as a scratch and the like on a sheet surface even when a sheet whose surface is liable to be damaged is collected without a protection member such as a slip sheet and the like. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0041]      FIG. 1  is a perspective view showing an overall arrangement of a sheet collecting apparatus according to a first exemplary embodiment. 
           [0042]      FIG. 2  is a schematic plan view showing a relative positional relation among side guide members, edge support members, and back guide plates in the sheet collecting apparatus according to the first exemplary embodiment. 
           [0043]      FIG. 3  is a schematic sectional view showing a relative positional relation when a collecting table, the side guide members, the edge support members, back stoppers, a front stopper, and a suction belt in the sheet collecting member according to the first exemplary embodiment are viewed from the side surfaces of them. 
           [0044]      FIG. 4  is an enlarged view showing a detailed arrangement of suction conveyers in the sheet collecting apparatus according to the first exemplary embodiment. 
           [0045]      FIG. 5  is an enlarged view showing another example of the suction conveyers in the sheet collecting apparatus according to the first exemplary embodiment. 
           [0046]      FIG. 6  is an enlarged view showing still another example of the suction conveyers in the sheet collecting apparatus according to the first exemplary embodiment. 
           [0047]      FIG. 7  is a partial sectional view showing a mechanism for causing the edge support members to appear or disappear with respect to the side guide members when it is viewed from above it. 
           [0048]      FIG. 8  is a partial sectional view showing the mechanism for causing the edge support members to appear or disappear with respect to the side guide members when it is viewed from a side thereof. 
           [0049]      FIG. 9  is a partial sectional view showing the mechanism for causing the edge support members to appear or disappear with respect to the side guide members when it is viewed forward of a direction in which an planographic printing plate is charged. 
           [0050]      FIG. 10  is an enlarged sectional view showing a detailed arrangement of the back stoppers. 
           [0051]      FIG. 11  is an explanatory view showing an operation of the sheet collecting apparatus according to the first exemplary embodiment. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     1. Exemplary Embodiment 1 
       [0052]    An example of a sheet collecting apparatus of the present invention will be explained below. 
       [Arrangement] 
       [0053]    As shown in  FIG. 1 , the sheet collecting apparatus  100  according to the exemplary embodiment 1 has a pair of back stoppers  4  for receiving an planographic printing plate P, which is charged by a belt conveyor  200  along the direction of an arrow ‘a’, by the front edges thereof, a collecting table  2  which is disposed upstream of the back stoppers  4  with respect to the charging direction ‘a’ of the planographic printing plate P, on which the planographic printing plate P received by the back stoppers  4  is collected, and which can be moved upward and downward by a lifter (not shown), a front stopper  6  located opposite to the back stoppers  4  across the collecting table  2 , and a pair of side guide members  8  which are disposed on both the side edges of the collecting table  2  along the charging direction ‘a’ and guide the planographic printing plate P charged onto the collecting table  2  from both the sides thereof. 
         [0054]    The sheet collecting apparatus  100  further has back guide plates  1  as an example of a back guide member of the invention. The back guide plates  1  are disposed at positions where they confront the front stopper  6  across the collecting table  2  on both the sides of the back stoppers  4  when viewed from the charging direction ‘a’. The planographic printing plate P is an example of a sheet collected on the sheet collecting apparatus of the invention and placed on the uppermost surface of an planographic printing plate bundle  50  which has been collected on the collecting table  2 , i, e., on a sheet collecting surface  51 . 
         [0055]    A pair of suction conveyers  10  are disposed in the vicinity of side guide members  8  located above the collecting table  2 . 
         [0056]    Further, as shown in  FIG. 3 , an auxiliary air nozzle  7  is disposed upstream of the front stopper  6  with respect to the charging direction ‘a’ to eject air upward. 
         [0057]    As shown in  FIGS. 1 and 2 , each of the side guide members  8  has a vertical portion  8 A that is orthogonal to a collection surface  2 A of the collecting table  2  on which the planographic printing plate P is collected and a tilt portion  8 B extending upward of the vertical portion  8 A and tilting to the outside. The distance between the right and left side guide members  8  is preferably 0.2 to 1 mm larger than the measurement of the planographic printing plate P in the width direction thereof, i.e., the measurement thereof in the direction orthogonal to the charging direction ‘a’. 
         [0058]    The vertical portion  8 A of each side guide member  8  has four laterally long rectangular openings  80  formed therethrough, and edge support plates  9  are disposed to the openings  80  so as to appear or disappear therefrom so that they hold the charged planographic printing plate P from the below. As shown in  FIG. 2 , the edge support plates  9  hold the planographic printing plate P in the state that they project from the openings  80 . The edge support plates  9  project from the vertical portions  8 A preferably in the amount of about 5 to 50 mm. Further, as shown in  FIG. 3 , a sheet receiving height H 4 , which is a height at which the edge support plates  9  receive a sheet, is preferably set to about 50 mm from the collecting table  2 . Further, the distance H 5  from the suction conveyer  10  to the edge support plates  9  in the height direction thereof is preferably set to about 150 to 200 mm from the viewpoint of preventing an planographic printing plate P charged by the suction conveyer  10  later coming into contact with an planographic printing plate P charged previously. 
         [0059]    As shown in  FIG. 3 , each of the back guide plates  1  is formed so that a height H bg  that is a height from the collecting table  2  to the top of the back guide plate  1  is larger than a height H bp  that is a height of the lower edges of the back stoppers  4 . The back guide plate  1  has a vertical portion  1 A orthogonal to the collection surface  2 A and a curved portion  1 B disposed on top of the vertical portion  1 A and curved downstream along the charging direction ‘a’. 
         [0060]    Further, as shown in  FIG. 3 , the front stopper  6  also has a vertical portion  6 A orthogonal to the collection surface  2 A and a curved portion  6 B located on top of the vertical portion  6 A. However, the curved portion  6 B of the front stopper  6  curves upstream in the charging direction ‘a’. Note that when the planographic printing plate P, which is intended to be charged, has a large measurement along the charging direction ‘a’, the front stopper  6  can preferably move upstream along the charging direction ‘a’, and when the planographic printing plate P has a small measurement, the front stopper  6  can preferably move downstream along the charging direction ‘a’. 
         [0061]    The back guide plates  1  guide the planographic printing plate P by the curved portions  1 B and receive it by the vertical portions  1 A. Accordingly, as shown in  FIG. 3 , the sheet receiving height H 1  of the back guide plate  1  is the height of the boundary portion between the vertical portion  1 A and the curved portion  1 B. Likewise, the front stopper  6  and the side guide members  8  also guide the planographic printing plate P by the curved portion  6 B and the tilt portions  8 B and position it by the vertical portion  6 A and the vertical portions  8 A. Accordingly, as shown in  FIG. 3 , the positioning height H 2  of the front stopper  6  is the height of the boundary between the vertical portion  6 A and the curved portion  6 B, and the positioning height H 3  of the side guide member  8  is the height of the boundary between the vertical portion  8 A and the tilt portion  8 B. 
         [0062]    As shown in  FIG. 3 , the back side plates  1 , the front stopper  6 , and the side guide members  8  are formed such that the sheet receiving height H 1  of the back guide plates  1  is lower than any of the positioning height H 2  of the front stopper  6  and the positioning height H 3  of the side guide members  8  and the positioning height H 3  of the side guide members  8  is lower than the positioning height H 2  the front stopper  6 . Note that the distance from the front stopper  6  to the back guide plates  1  is preferably about 0.05 to 1 mm larger than the measurement of the planographic printing plate P along the charging direction ‘a’. 
         [0063]    The back guide plate  1  is composed of a metal sheet by which the vertical portion  1 A and the curved portion  1 B are constituted integrally. However, the curved portion  1 B may be formed of a resin material of various resins, an elastomer material such as vulcanized gum or non-vulcanized gum, or a soft material such as a soft vinyl chloride resin in place of that it is formed of metal, and it may be covered with the soft material. When the curved portion  1 B is formed of or covered with the resin material and the soft material, it can more effectively prevent that the planographic printing plate P is damaged by coming into contact with the back guide plate  1  as compared with the case that the curved portion  1 B is composed of the metal sheet and conveyed. 
         [0064]    The front stopper  6  is composed of a metal sheet which has a curved upper edge and forms the vertical portion  6 A and the curved portion  6 B integrally. 
         [0065]    As shown in  FIGS. 1 and 4 , the suction conveyer  10  has a suction belt  11 , which is an endless belt having a lot of suction holes  11 A formed on the entire surface thereof, a pair of drive rollers  12  around which the suction belt  11  is stretched and which drives the suction belt  11 , and suction boxes  13  disposed in a row inside the suction belt  11 . The suction belt  11  is stretched such that the inner surface thereof slides on the lower surfaces of the suction boxes  13 , and a predetermined number of communication holes are formed on the lower surfaces of the suction boxes  13 . 
         [0066]    As shown in  FIG. 4 , the suction boxes  13  has a suction line  15  connected thereto for suctioning air from inside thereof and a discharging line  16  connected thereto for supplying air therein. The suction line  15  is normally opened, while the discharging line  16  is opened only at a time when supplying air into the suction boxes  13 . By closing the discharging line  16  and suctioning air inside the suction boxes  13  through the suction line  15 , the pressure inside the suction box is reduced to a reduced pressure or to vacuum, the planographic printing plate P is sucked onto the suction belt  11 . On the contrary, the planographic printing plate P is released by supplying air into the suction boxes  13  by opening the discharging line  16  while opening the suction line  15  so as to break the vacuum inside the suction boxes  13 . 
         [0067]    Note that, in addition to the example shown in  FIG. 4 , as shown in  FIG. 5 , the suction conveyer  10  includes an embodiment wherein the suction boxes  13  and discharging boxes  14  are alternately arranged inside the suction belt  11 , and the suction line  15  may be connected to the suction boxes  13  and the discharging line  16  is connected to the discharging boxes  14 . Further, as shown in  FIG. 6 , the suction line  15  and the discharging line  16  may be connected to some of the suction boxes  13 , for example, the two suction boxes  13  on the upstream side with respect to the charging direction ‘a’ and only the suction line  15  may be connected to the remaining suction boxes  13 . Note that, in the above aspects, a predetermined number of discharge holes are formed also to the lower surfaces of the discharging boxes  14 , and the inner surface of the suction belt  11  slides on the lower surfaces. 
         [0068]    When the planographic printing plate P is sucked, the insides of the suction boxes  13  are made to a pressure-reduced state or to a vacuum state by closing the discharging line  16  and discharging the air in the suction boxes  13  through the suction line  15  in any of the aspects shown in  FIGS. 5 and 6 . In contrast, the planographic printing plate P is released from the front surface of the suction belt  11  by supplying air to the discharging boxes  14  by opening the discharging line  16  and pressurizing the insides of the discharging boxes  14 . Note that when the planographic printing plate P is released in the aspect shown in  FIG. 6 , the pressure-reduced state or the vacuum state in the discharging boxes  14  is disrupted by supplying air into the discharging boxes  14  as well as supplying air from the discharging line  16  into the two suction boxes  13  on the upstream side with respect to the charging direction ‘a’ at the same time. 
         [0069]    The height from the collection surface  2 A of the collecting table  2  to the suction conveyer  10  is set preferably in the range of 200 to 250 mm to prevent an planographic printing plate P charged later from interfering with an planographic printing plate P charged previously and fell along the back guide plates  1 . 
         [0070]    As shown in  FIGS. 1 and 7  to  9 , the mechanism for causing the edge support plates  9  to appear or disappear from the side guide members  8  has a shaft  20  disposed outside the vertical portions  8 A of the side guide members  8  with respect to the collecting table  2 , a motor  21  for rotating the shaft  20 , and speed reduction gears  23 ,  22  for transmitting the rotation of the motor  21  to the shaft  20 . The edge support plates  9  are fixed to the shaft  20  along the longitudinal direction thereof. When the motor  21  rotates, the shaft  20  is also rotated, thereby the edge support plates  9  also rotate about the axial line of the shaft  20 . With this operation, the edge support plates  9  project from the side guide members  8  toward the collecting table  2  as shown by a solid line in  FIG. 9  and retracted outside the side guide members  8  as shown by a double-dashed line. 
         [0071]    As shown in  FIG. 10 , each of the back stoppers  4  has a back stopper plate  40  which is in contact with the charged planographic printing plate P and a shock absorber device  43  for absorbing a shock along the charging direction ‘a’ of the back stopper plate  40 . 
         [0072]    As shown in, for example, Japanese Patent Application Laid-Open (JP-A) No. 8-290860, the shock absorber device  43  has a first shock absorbing mechanism  41  for absorbing shock caused when the planographic printing plate P falling along the charging direction ‘a’ is abutted against the back stopper plates  40  and a second shock absorbing mechanism  42  continuously disposed to the first shock absorbing mechanism  41  for absorbing reaction force caused by the first shock absorbing mechanism  41  returning toward upstream with respect to the charging direction ‘a’. 
         [0073]    The first shock absorbing mechanism  41  is composed of a spline shaft  41 A to which the back stopper plate  40  is fixed, a moving cylinder  41 B positioned outside the spline shaft  41 A, a ball holder  41 C disposed inside the moving cylinder  41 B and holding the spline shaft  41 A so that it advances and retracts upstream and downstream with respect to the charging direction ‘a’, and a coil spring  41 D interposed between the back stopper plate  40  and the moving cylinder  41 B and urging the back stopper plate  40  upstream with respect to the charging direction ‘a’. 
         [0074]    In contrast, the second shock absorbing mechanism  42  has a fixed external cylinder  42 A, a ball holder  42 B holding the moving cylinder  41 B inside the fixed external cylinder  42 A so that it advances and retracts upstream and downstream with respect to the charging direction ‘a’, and a coil spring  42 C urging the moving cylinder  41 B upstream with respect to the charging direction ‘a’. 
         [0075]    The coil spring  42 C has a spring constant larger than that of the coil spring  41 D. Accordingly, the inertia received by the back stopper plate  40  is at first absorbed by the coil spring  41 D. Then, the reaction force caused by the first shock absorbing mechanism  41  when returning to the original position thereof is absorbed by the coil spring  42 C. 
         [0076]    Note that the measurement or position of the back stoppers  4  as well as the back guide plate  1  can be changed in accordance with the measurement of the planographic printing plate P to be charged along the charging direction ‘a’ thereof. Specifically, when the planographic printing plate P having a small measurement along the charging direction ‘a’ is charged, the back stoppers  4  and the back guide plates  1  are positioned near to the front stopper  6 , whereas when the planographic printing plate P having a large measurement along the charging direction ‘a’ is charged, the back stoppers  4  and the back guide plates  1  are positioned away from the front stopper  6 . 
       [Operation] 
       [0077]    An operation of the sheet collecting apparatus  100  will be explained below. 
         [0078]    First, the collecting table  2  is moved upward by a lifter (not shown). 
         [0079]    When the collecting table  2  is moved upward to a predetermined height, the belt conveyor  200  charges the planographic printing plate P along the charging direction ‘a’. At the time when the planographic printing plate P is charged, air is jetted toward the planographic printing plate P from the auxiliary air nozzle  7  and the planographic printing plate P is lifted toward the suction conveyer  10 . 
         [0080]    The charged planographic printing plate P is sucked by the suction conveyer  10  and transported along the charging direction ‘a’. When the planographic printing plate P is transported over the collecting table  2 , suction of the planographic printing plate P onto the suction conveyer  10  is released by supplying air into the suction boxes  13  to break the reduced pressure or vacuum state therein or by supplying air into the discharging box  14  so that the planographic printing plate is released from the suction belt  11  as shown by P 1  in  FIG. 11 . 
         [0081]    When the planographic printing plate P is released from the suction belt  11 , the upstream one side of the planographic printing plate P is guided first by the front stopper  6  with respect to the charging direction ‘a’, and next the two sides of the planographic printing plate P along the charging direction ‘a’ are guided by the side guide members  8  as well as the planographic printing plate P is received by the upper edge of the back guide plates  1  and by the approximate central portions of the back stopper plates  40  in the back stoppers  4  as shown by P 2  in  FIG. 11 . 
         [0082]    When the back stopper plate  40  receives and stops the planographic printing plate P, the shock received by the back stopper  40  is absorbed by the shock absorber device  43  as described below. 
         [0083]    First, as shown by a solid line in  FIG. 11 , the back stopper  4  is moved downstream along the charging direction ‘a’ by the shock from the planographic printing plate P. As a result, the coil spring  41 D of the first shock absorbing mechanism  41  is contracted. Next, the force of extending the coil spring  41 D causes to move the moving cylinder  41 B downstream along the charging direction ‘a’. However, since the moving cylinder  41 B is urged upstream with respect to the charging direction ‘a’ by the coil spring  42 C of the second shock absorbing mechanism  42  and moreover the coil spring  42 C has the spring constant larger than that of the coil spring  41 D, the moving cylinder  41 B is returned to an original position by the urging force of the coil spring  42 C. As a result, although the back stopper plate  40  also receives force for causing it to return upstream with respect to the charging direction ‘a’ as shown by a double-dashed line in  FIG. 11 , the force is absorbed by the coil spring  41 D. 
         [0084]    Accordingly, although the planographic printing plate P is pushed back toward the front stopper  6  as shown by P 3  in  FIG. 11 , since force of pushing back the planographic printing plate P is caused by the coil spring  41 D having a small spring constant, the planographic printing plate P is not pushed back toward the front stopper  6  by a large amount of force. 
         [0085]    As described above, in the sheet collecting apparatus  100  of the exemplary embodiment 1, by disposing the back guide plates  1 , the back stoppers  4  can be employed only for absorbing shock. Thus, the spring reaction in the back stoppers  4  is reduced as much as possible by arranging them as described above so that the force for pushing and returning the planographic printing plate P toward the front stopper  6  can be reduced as much as possible. 
         [0086]    Then, the final one side, i.e., the downstream side of the planographic printing plate P is guided along the charging direction ‘a’ by the back guide plate  1  as well as the planographic printing plate P is received by the edge support plates  9  from the downstream side thereof as shown by P 3  in  FIG. 11 . 
         [0087]    When the planographic printing plate P is received by the edge support plates  9 , it is dropped onto the collecting table  2  by pulling the edge support plates  9  to the outsides of the side guide members  8 . 
         [0088]    When the sheet collecting apparatus  100  is used as described above, not only planographic printing plates P can be collected but also a shock in a height direction, which is generated when a new planographic printing plate is dropped onto the collecting table  2  or onto the sheet collecting surface  51 , can be absorbed in a state that a movement in a direction along the charging direction ‘a’ is almost eliminated between the collecting table  2  or the planographic printing plate P, which is already collected onto the collecting table  2  and forms the sheet collecting surface  51 , and a newly charged planographic printing plate P. Accordingly, even if an planographic printing plate such as CTP whose printing layer is liable to be damaged can be collected without a slip sheet.