Abstract:
A sheet feeder for use, with a stack having plates and sheets alternating. Sheets are removed by being reliably suction adhered with a sucker. The sheet feeder includes a suction device, and the sucker and device are mounted at a supporting portion. In order to allow suction adhering of the plates and sheets alternately stacked in a magazine, the suction device is operated when the sucker is brought into contact with the sheet, and the sheet is raised separately from the plate. Thereafter, the sheet is suction adhered to the sucker by suction. This makes it possible to prevent the sucker from suction adhering to the plate together with the sheet, and only the sheet is reliably from the stack.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a sheet feeder and a sheet feeding method, for plate-shaped members such as printing plates, which are taken out one-by-one from a state in which plate-shaped members and interleaf papers for protecting printing surfaces of the plate-shaped members are alternately stacked with one another.  
           [0003]    2. Description of the Related Art  
           [0004]    A technique has been developed, wherein a printing plate such as a photopolymer plate having a photosensitive layer (for example, a photopolymerization layer) provided on a support is used and an image is directly recorded on the photosensitive layer (photopolymerization layer) of the printing plate by a laser beam or the like (an automatic exposure apparatus for printing plates). In such a technique, an image can be rapidly recorded on the printing plate.  
           [0005]    In the automatic exposure apparatus for printing plates for image recording on printing plates, a magazine accommodates a large number of printing plates in a stack, and the printing plates are removed from the magazine one-by-one and transferred to an exposure section.  
           [0006]    There are cases in which the printing plates may be stacked with interleaf papers interposed therebetween so as to protect the printing surfaces of the plates. Due to the printing plates and the interleaf papers being alternately stacked with one another, scratch or the like of the light-sensitive layer and the support for a printing plate adjacent thereto, contacting each other, is substantially prevented.  
           [0007]    On the other hand, in a sheet feeder, the uppermost printing plate within the magazine is taken out one-by-one with a sucker (suction cup). In the sheet feeder at this time, first the interleaf paper which covers the uppermost printing plate is taken out by suction. Thereafter, the uppermost printing plate is sucked to the sucker and removed from the magazine.  
           [0008]    However, in this arrangement in which interleaf papers and printing plates are alternately stacked, an interleaf paper and a printing plate adjacent thereto can stick together. Therefore, there is a disadvantage in that when the interleaf paper is adhered to a sucker, a printing plate disposed immediately below the interleaf paper is lifted up together with the interleaf paper.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention has been devised in view of the above-described circumstances, and an object thereof is to provide a sheet feeder in which when plate-shaped members such as printing plates and sheet materials such as interleaf papers, of which rigidity or weight is lower than that of the plate-shaped members, are alternately stacked, the plate-shaped members and the sheet materials can be more reliably removed one at a time.  
           [0010]    In accordance with a first aspect of the present invention, there is provided a sheet feeder in which plate-shaped members and sheet materials in a state of being alternately stacked are taken out one by one, comprising: at least one sucker which adheres to the plate-shaped members and sheet materials due to negative pressure by being brought into contact with the plate-shaped members and sheet materials; a suction fan which operates at a position close to a sheet material disposed at the uppermost position and sucks in air in the vicinity of the surface of the sheet material; and an elevator which moves the sucker and the suction fan in directions of approaching and moving apart from the stacked plate-shaped members and/or sheet materials, to thereby raise a plate-shaped member and/or a sheet material, which is adhered to the sucker.  
           [0011]    According to the present invention, a sucker and suction fan are provided. The sucker suction adheres to elevate the plate-shaped member and the sheet material. The suction fan draws in air in the vicinity of the surface of the sheet material for suction adherence to the sucker to thereby suction adhere to and raise the sheet material. Although the suction force of the suction fan is smaller than that of the sucker, the sheet material can be removed from an underlying plate-shaped member by suction from the fan in the vicinity of the surface of the sheet material.  
           [0012]    By means of the above-described suction fan, the sheet material is reliably separated from the plate-shaped member and can be removed by suction adherence to the sucker.  
           [0013]    In accordance with a second aspect of the present invention, there is provided a sheet feeder in which plate-shaped members and sheet materials in a state of being alternately stacked are taken out one by one, comprising: a pair of side plates; a suction portion which is supported between the side plates in a movable manner in a direction perpendicular to the plate-shaped members and/or the sheet materials placed in a stack, and adheres to the plate-shaped members and/or sheet materials due to negative pressure; a suction device which is supported between the side plates in a movable manner in a direction perpendicular to the plate-shaped members and/or the sheet materials placed in a stack, and when the sheet material is disposed at the uppermost position, the suction device being operated at a position adjacent to the sheet material and sucking in air in the vicinity of the surface of the sheet material; an elevator which moves the suction portion and the suction device in a direction perpendicular to the plate-shaped members and/or the sheet materials placed in a stack to thereby elevate a plate-shaped member and/or a sheet material, stuck to the suction portion; and a sensor which is provided between the side plates so as to be movable in a direction substantially parallel to a direction in which the suction portion is movable, and detects and determines a state in which the suction portion and the plate-shaped member and/or sheet material contact each other.  
           [0014]    In the present invention, preferably, when the sheet material is disposed at the uppermost position, the suction fan is operated in a state of being moved close to the sheet material, and thereafter, negative pressure is applied for the sucker at a predetermined timing to allow the sucker to adhere to the sheet material.  
           [0015]    According to the aforementioned, in order to allow suction of the sheet material, first, the suction fan is operated to raise the sheet material from the plate-shaped member. Thereafter, the sheet material is suction adhered to the sucker. Since the suction force of the suction fan is smaller than that of the sucker, there is reduced possibility of suction adhering the plate-shaped member together with the sheet material, and only the sheet material is lifted.  
           [0016]    As a result, the sheet material is adhered to the sucker in a state in which the sheet material and the plate-shaped member closely contact each other. Therefore, the plate-shaped member is prevented from being sucked together with the sheet material, and only the uppermost sheet material can reliably be removed from an underlying plate-shaped member.  
           [0017]    Further, in the present invention, preferably, the suction fan is operated in a state in which the sucker is brought into contact with the sheet material.  
           [0018]    According to the aforementioned, with the sucker brought into contact with the sheet material, the suction fan is operated at the position in which for example, wind force of the suction fan applied onto the sheet material becomes maximum, to partially raise the sheet material. Subsequently, the sheet material is removed from an underlying plate-shaped member, and thereafter, the sheet material is suction adhered to the sucker.  
           [0019]    At this time, preferably, the sucker and suction fan are moved so that the sheet material is separated from the plate-shaped member, and the sheet material is moved upward away from the plate-shaped member. Thereafter, the sheet material is suction adhered to the sucker by suction.  
           [0020]    Moreover, in the present invention, preferably, the suction fan is provided so as to face one end of the sheet material.  
           [0021]    According to the aforementioned, the suction fan is disposed so as to face an end, such as a peripheral edge, of the sheet material. As a result, the sheet material can more easily be separated from the plate-shaped member due to the suction force of the suction fan.  
           [0022]    Still further, in the present invention, preferably, the suction fan is provided in the proximity of at least one of the suckers.  
           [0023]    According to the aforementioned, the suction fan and the sucker are disposed adjacent to each other, and a region of the sheet material raised by the suction fan is suction adhered to the sucker. As a result, only the sheet material can be reliably lifted away from an underlying plate-shaped member.  
           [0024]    In accordance with a third aspect of the present invention, there is provided a sheet feeding method in which first materials having high rigidity and second materials having flexibility in a state of being alternately stacked are taken out one by one from a magazine, comprising the steps of: (a) making a determination as to whether a material disposed at the uppermost position of the stacked materials is the first material or the second material; (b) when it is determined that the second material is disposed at the uppermost position, causing at least one sucker to abut against the uppermost material; (c) sucking in air in the vicinity of the surface of the uppermost material by a suction device; (d) moving the suction device upward by a small distance to separate the uppermost material from the stacked materials; (e) feeding negative pressure for the sucker to cause the sucker to adhere to the uppermost material; (f) stopping operation of the suction device; (g) moving upward the sucker and the suction device to completely separate the uppermost material from the stacked materials; (h) delivering the adhered uppermost material to a conveying portion; and (i) stopping application of negative pressure for the sucker. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]    [0025]FIG. 1 is a structural diagram which schematically shows an automatic exposure apparatus in accordance with the present invention.  
         [0026]    [0026]FIG. 2 is a structural diagram which schematically shows the main portion of the automatic exposure apparatus having the sheet feeding section to which the present invention is applied.  
         [0027]    [0027]FIG. 3 is a schematic structural diagram of substantially only the sheet feeding section to which the present invention is applied.  
         [0028]    [0028]FIG. 4 is a schematic diagram which shows relative positions of a sucker and a suction fan with respect to the surface of photopolymer plates and interleaf papers accommodated in a magazine.  
         [0029]    [0029]FIG. 5 is a schematic diagram showing the relative positions of the sucker and the suction fan with respect to the surface of a photopolymer plate accommodated in the magazine, when seen from a side different from the view of FIG. 4.  
         [0030]    [0030]FIGS. 6A to  6 F are schematic diagrams which show the flow of an interleaf paper removal operation using a sucker and a suction fan: FIG. 6A illustrates a state prior to removal of interleaf paper; FIG. 6B illustrates a state in which the sucker is moved downward to contact the interleaf paper; FIG. 6C illustrates a state immediately after the suction fan has been operated; FIG. 6D illustrates a first-stage rising step in which the interleaf paper is lifted up to such a degree that the photopolymer plate is slightly pressed by the sucker; FIG. 6E illustrates a second-stage rising step in which the interleaf paper is lifted up to such a degree that the photopolymer plate is not pressed by the sucker; and FIG. 6F illustrates a state in which the suction fan is stopped with the interleaf paper adhered to the sucker.  
         [0031]    [0031]FIGS. 7A and 7B are a flow diagram which shows an example of sheet feeding process for photopolymer plates and interleaf papers in the sheet feeding section to which the present invention is applied. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0032]    [0032]FIG. 1 shows an automatic exposure apparatus  100  for photopolymer plates according to an embodiment of the present invention.  
         [0033]    The automatic exposure apparatus  100  includes a sheet feeding section  106  by which a plate accommodating section  104 , in which photopolymer plates  102  (see FIG. 3) placed on a carriage  200  are accommodated, and the photopolymer plates  102  accommodated in the plate accommodating section  104  are removed and a surface table  110  for positioning and holding the photopolymer plates  102 , a plate supplying section  108  for transferring the photopolymer plates  102  removed by the sheet feeding section  106  to the surface table  110 , and an exposure section  112  in which an image is recorded on a photopolymer plate  102  positioned on the surface table  110 .  
         [0034]    An automatic processing apparatus  116  can be provided at a downstream side of the automatic exposure apparatus  100  via a buffer section  114 , and supplying of plates, exposure, and processing can all be automatically processed.  
         [0035]    As illustrated in FIG. 2, the carriage  200  in which plural photopolymer plates  102  are placed against an inner wall thereof can be accommodated in the plate accommodating section  104 .  
         [0036]    The plate accommodating section  104  includes a floor portion  104 A at a position higher than the floor surface, and the carriage  200  is formed so as to ride on the floor portion  104 A above the floor surface. That is, the carriage  200  is supported via casters  120  with respect to the floor surface and the casters  120  can each be moved to a position at which it projects from the carriage  200  (that is, the position indicated by the phantom lines in FIG. 2) and also to a position at which it is accommodated in the carriage  200  (that is, the position indicated by solid lines in FIG. 2).  
         [0037]    When the casters  120  are moved to the accommodated position in such a manner as to be made retractable toward the upper side corresponding to an operation of accommodating the carriage  200  in the plate accommodating section  104 , auxiliary rollers  212  simultaneously correspond to the floor portion  104 A. Thereafter, the carriage  200  is supported by the floor portion  104 A via the auxiliary rollers  212 .  
         [0038]    An accumulating portion  206  is provided in the carriage  200  and a magazine  208  is mounted in the accumulating portion  206  in such a manner as to be inclined at a predetermined angle. A large number of (for example, several tens of) photopolymer plates  102  are in advance accommodated in the magazine  208  in a stack, and the photopolymer plates  102  are loaded in the plate accommodating section  104  by mounting the carriage  200  in the plate accommodating section  104 .  
         [0039]    As shown in FIG. 3, the photopolymer plates  102  are each protected in such a manner that the surface thereof (on which a light-sensitive layer formed by a photopolymerization layer is provided) is covered by interleaf paper  118 . The photopolymer plates  102  and interleaf papers  118  are thus alternately stacked in the magazine  208 . As shown in FIGS. 1 and 2, the magazine  208  is equipped with a shutter  210 , and due to the shutter  210  being closed in cases other than when it is placed in a dark room, the photopolymer plates  102  are prevented from being undesirably exposed to light.  
         [0040]    The photopolymer plates  102  are disposed to face the sheet feeding section  106  in a state of being inclined at a predetermined angle by mounting the carriage  200  in the plate accommodating section  104 . The carriage  200  is placed in the plate accommodating section  104  and the plate accommodating section  104  is placed into a light shielding state, and the shutter  210  of the magazine  208  is opened. Therefore, the photopolymer plates  102  can be removed from the magazine  208 .  
         [0041]    The sheet feeding section  106  provided above the plate accommodating section  104  is equipped with suckers  124 . A predetermined position at an upper end of each of the interleaf paper  118  and the photopolymer plate  102  adheres to the suckers  124  when operated, and the interleaf paper  118  and the photopolymer plate  102  are sequentially removed from the magazine  208  and transferred to the plate supplying section  108 .  
         [0042]    The plate supplying section  108  is mainly divided into the following four parts: a shared conveying portion  128  in which the photopolymer plate  102  or interleaf paper  118  is received from the sheet feeding section  106  and conveyed; a photopolymer plate conveying portion  130  which receives the photopolymer plate  102  and conveys the same to the surface table  110 ; an interleaf paper conveying portion  134  which receives the interleaf paper  118  and conveys the same to an interleaf paper receiving box  132  provided in the carriage  200 ; and a conveying switch portion  136  which functions as a guide from the shared conveying portion  128  to any one of the photopolymer plate conveying portion  130  and the interleaf paper conveying portion  134  by a switching operation.  
         [0043]    As the photopolymer plates  102  and the interleaf paper  118  are alternately stacked in the plate supplying section  108 , and therefore, the conveying switch portion  136  is switched each time the photopolymer plate  102  or the interleaf paper  118  is suction adhered in the sheet feeding section  106 , and the photopolymer plate  102  and the interleaf paper  118  are each conveyed in a predetermined direction.  
         [0044]    As shown in FIG. 2, in the shared conveying portion  128 , a roller  128 A is disposed apart from a roller  128 B (indicated by the broken line in FIG. 2), and when the photopolymer plate  102  or the interleaf paper  118  is removed by the sheet feeding section  106 , the roller  128 A moves toward the roller  128 B (indicated by the solid line in FIG. 2) and nips and conveys the leading end of the removed photopolymer plate  102  or interleaf paper  118  to the conveying switch portion  136 . When the interleaf paper  118  is removed from the magazine  208 , the conveying switch portion  136  is provided to switch the conveying path so as to convey the interleaf paper  118  to the interleaf paper conveying portion  134  (indicated by the broken line in FIG. 2).  
         [0045]    The carriage  200  is provided with the interleaf paper receiving box  132 , and the interleaf paper  118  removed from the magazine  208  by the sheet feeding section  106  is guided by the interleaf paper conveying portion  134  to the interleaf paper receiving box  132  provided in the carriage  200 . A pair of rollers  144  is provided at an insertion opening  142  for the interleaf paper  118 , which are formed in an upper side of the interleaf paper receiving box  132 . These rollers are driven to rotate at a linear velocity which is slightly higher (about 1.1 times) than the conveying speed in the interleaf paper conveying portion  134 . As a result, when the interleaf paper  118  extends across a region between the interleaf paper conveying portion  134  and the rollers  144 , it is conveyed while maintaining a predetermined tension therein, and occurrence of jamming caused by a slack or the like can be prevented.  
         [0046]    Further, guide plates  146  formed in such a manner that a distance therebetween (in a direction along a thickness of the interleaf paper  118 ) gradually decreases from top to bottom in a tapered manner, are further provided at the upstream side of the insertion opening  142  in the direction of the conveying path of the interleaf paper  118 . The guide plates  146  formed in the tapered shape and facing each other. Each is provided with a charge removing brush  148  so as to remove electric charge (static electricity) from the interleaf paper  118  insertion in the insertion opening  142 .  
         [0047]    The pair of rollers  144  are skewered rollers. Partition plates  150  (disposed at the side of the rollers) have recesses which are complementary to the rollers of the skewered rollers, such that the rollers are disposed within these recesses. As a result, even if a portion of the interleaf paper  118  received in the interleaf paper receiving portion  132  contacts the rollers  144 , lapping of the interleaf paper  118  around the rollers  144  can be prevented by the partition plates  150 .  
         [0048]    On the other hand, when the photopolymer plate  102  is removed from the magazine  208 , the conveying switch portion  136  switches the conveying path so as to guide the photopolymer plate  102  to the photopolymer plate conveying portion  130  (indicated by the solid line in FIG. 2). As a result, the photopolymer plate  102  removed from the magazine  208  is transferred by the photopolymer plate conveying portion  130  to the surface table  110  (see FIG. 1) in a state of being conveyed substantially horizontally.  
         [0049]    As illustrated in FIG. 1, the upper surface of the surface table  110  is disposed at a position lower than a position at which the photopolymer plate is horizontally conveyed in the photopolymer plate conveying portion  130 . Further, there is a space or gap between the surface table  110  and the photopolymer plate conveying portion  130  in the direction in which the photopolymer plate is conveyed. For this reason, the photopolymer plate  102  conveyed from the photopolymer plate conveying portion  130  arrives at the surface table  110  in such a manner that the leading end thereof slightly hangs, and the trailing end of the photopolymer plate  102  in the conveying direction is positioned further at the upstream side of the surface table  110  in the conveying direction of the plate  102 . A movable body  152  is provided at this upstream side of the surface table  110  so as to be capable of moving close to and apart from the surface table  110 .  
         [0050]    The movable body  152  includes a temporary supporting plate, a pressing plate, a puncher, and the like, which are all not shown. Hanging of the photopolymer plate  102  conveyed onto the surface table  110  is prevented by the temporary supporting plate.  
         [0051]    Further, the pushing plate (not shown) provided in the movable body  152  pushes the trailing end of the photopolymer plate  102  so as to cancel a diagonal feed of the photopolymer plate  102 , and the photopolymer plate  102  is conveyed to a predetermined reference position in the conveying direction. The reference position is set in such a manner that the trailing end of the photopolymer plate  102  in the conveying direction slightly protrudes from the surface table  110 .  
         [0052]    At the reference position, sensors (not shown) are respectively provided at plural positions including two corners at the trailing end of the photopolymer plate  102  in the conveying direction. Due to the trailing end of the photopolymer plate  102  being detected by the above-mentioned sensors, pushing by the pushing plate is stopped. Further, these sensors are also used to detect positions on the photopolymer plate  102  along the transverse direction perpendicular to the conveying direction. That is, the corners of the photopolymer plate  102  and the sensors are caused to coincide with each other by the surface table  110  moving in the transverse direction of the photopolymer plate  102  perpendicular to the conveying direction, and the position at which the corners of the photopolymer plate  102  and the sensors coincide with each other is registered as an initial position of the photopolymer plate  102 .  
         [0053]    The position of the photopolymer plate  102  moved to the initial position is set so as to become a relative position for a scanning/exposure starting position in the exposure section  112 . In this state, the photopolymer plate  102  is sucked and held by negative pressure supplied to a suction groove (not shown) provided in the surface table  110 . The puncher provided in the movable body  152  punches holes in the photopolymer plate  102  sucked and held by the surface table  110 .  
         [0054]    The surface table  110  is movable in a reciprocating manner (which is common to a movement for positioning in the transverse direction perpendicular to the conveying direction) at approximately a uniform velocity between a first position (indicated by the solid line in FIG. 1) at which the photopolymer plate  102  is received from the photopolymer plate conveying portion  130  and a second position (indicated by the phantom line in FIG. 1) at which the photopolymer plate  102  is accommodated in the exposure section  112 .  
         [0055]    In the exposure section  112 , a scanning unit  164  is provided at a position above the conveying path on the surface table  110 . Main scanning (in a direction perpendicular to the moving direction of the surface table  110 ) is carried out using laser beams which are controlled so as to be modulated on in accordance with an image signal. Forward movement of the surface table  110  is sub-scan movement. Thus, during the forward movement of the surface table  110  to the exposure section  112 , an image is recorded on the photopolymer plate  102  held on the surface table  110 , and the photopolymer plate  102  is moved back to an original position by backward movement of the surface table  110 . After the photopolymer plate  102  placed on the surface table  110  has been moved back to the original position, vacuum application is terminated thereby releasing the plate  102 .  
         [0056]    The surface table  110  on which the photopolymer plate  102  with an image being recorded is moved back to the original position and a discharging mechanism section  166  placed in a waiting state at the side of the trailing end of the photopolymer plate  102 , in the conveying direction of the plate  102  by the photopolymer plate conveying portion  130 , passes above the surface table  110  and moves to the leading end of the photopolymer plate  102 .  
         [0057]    The discharging mechanism section  166  is provided with hook portions  166 A for supporting the trailing end of the photopolymer plate  102 . Due to the trailing end of the photopolymer plate  102  protruding from the surface table  110  being lifted up by the temporary supporting plate provided in the movable body  152  and the discharging mechanism section  166  being moved in the direction in which the photopolymer plate  102  is conveyed, the photopolymer plate  102  is conveyed to the downstream side of the surface table  110  by being caught by the hook portions  166 A and accompanied with the movement of the discharging mechanism section  166 . A buffer section  114  and the automatic processing apparatus  116  are sequentially provided at the downstream side of the surface table  110 , and the photopolymer plate  102  is conveyed out smoothly while eliminating a difference between a speed at which it is discharged by the discharging mechanism section  166  and a speed at which it is conveyed in the automatic processing apparatus  116  by the buffer section  114 .  
         [0058]    FIGS.  3  to  5  each show the sheet feeding section  106  to which the present invention is applied. In the embodiment of the present invention, the photopolymer plate  102 , which is one kind of printing plate, is used as a plate-shaped member and the interleaf paper  118  is used as a sheet material. The photopolymer plates  102  and the interleaf papers  118  are accommodated in the magazine  208  in a state of being alternately stacked. As described above, in the sheet feeding section  106 , the interleaf paper  118  and the photopolymer plates  102  are each removed from the magazine  208  and conveyed into the plate supplying section  108 . In FIGS. 4 and 5, the transverse direction of the photopolymer plate  102  (i.e., the direction perpendicular to the plane of FIG. 3) perpendicular to the direction in which the photopolymer plate  102  is conveyed between the shared conveying portion  128  and the photopolymer plate conveying portion  130 , is indicated by a double-headed arrow W.  
         [0059]    As illustrated in FIG. 3, in the sheet feeding section  106 , a shaft  22  is disposed spanning between a pair of side plates  20  (in FIG. 3, only one of them is shown) at upper portions of the side plates  20  (at the upper side in FIG. 3). Sprockets  24  are respectively mounted at both ends of the shaft  22  (at the sides of the side plates  20 ). Further, a sprocket  26  is mounted in the side plate  20  at the side of the magazine  208 , and a chain  28  is entrained around the sprockets  24  and  26 .  
         [0060]    Further, an elevating motor  30  serving as an elevator is mounted at one of the side plates  20 , and a gear  32  mounted on a driving shaft  30 A of the elevating motor  30  meshes with a gear  34  mounted at the shaft  22 . As a result, when the elevating motor  30  is driven, the sprockets  24  and  26  are rotated and the chain  28  is moved between the sprockets  24  and  26  in a direction substantially perpendicular to the surface of the photopolymer plates  102  stacked in the magazine  208 .  
         [0061]    A suction frame  36  is disposed between the side plates  20 . The suction frame  36  is connected to the chain  28  via a bracket  38 . Further, guide rails  40  are respectively mounted to the side plates  20  on the surfaces thereof facing each other.  
         [0062]    The suction frame  36  is provided with side bases  42  which face the side plates  20 ) respectively. Sliders  44  are mounted at the side bases  42  so as to face the guide rails  40 . Each of the sliders  44  is provided with a plurality of guide blocks  46  for holding the guide rail  40 . As a result, when the elevating motor  30  is driven, the suction frame  36  moves along the guide rail  40  and moves up and down substantially perpendicular to the photopolymer plate  102  in the magazine  208 .  
         [0063]    The suction frame  36  includes a supporting base  48  facing the magazine  208 . Three shafts  50 ,  52 , and  54  extend through the supporting base  48  along the transverse direction of the photopolymer plate  102 .  
         [0064]    As illustrated in FIG. 4, a bracket  56  is mounted so as to straddle over the shafts  50  and  52 , and a bracket  58  is mounted so as to straddle over the shafts  50 ,  52 , and  54 . The brackets  56  and  58  are mounted, for example, in such a manner that the shafts  50 ,  52 , and  54  pass through slide blocks (not shown) provided at the rear side thereof.  
         [0065]    The bracket  56  faces a transverse-direction intermediate portion of the photopolymer plate  102  accommodated in the magazine  208 , and the brackets  58  respectively face both the transverse-direction end portions of the photopolymer plate  102 . The bracket  56  is fixed at a predetermined intermediate position between the shafts  50  and  52 , and the brackets  58  are disposed respectively at sides of both ends of the shafts  50 ,  52 , and  54  and can each be moved in directions in which it moves away and towards the bracket  56  in accordance with the size of the photopolymer plate  102  accommodated in the magazine  208  (this operation is not shown).  
         [0066]    A fan base  60  is disposed below the bracket  56  and a fan base  62  is further disposed below each of the brackets  58 . The fan base  60  and the fan bases  62  are supported in such a manner as to be respectively connected to the brackets  56  and  58  by a plurality of shafts  64 . As shown in FIG. 5, respective lower surfaces of the fan bases  60  and  62  are each disposed linearly and parallel to the surface of the photopolymer plate  102  accommodated in the magazine  208 .  
         [0067]    As illustrated in FIGS. 4 and 5, the fan base  60  is provided with plural (in the present embodiment, for example, three) suction fans  126  along the transverse direction of the photopolymer plate  102 , and each of the fan bases  62  is provided with one suction fan  126 . The suction fan  126  includes a vent opening portion at the central portion thereof, and is constructed to suck air from the fan bases  60  and  62  at the side of the magazine  208  by driving a fan motor (not shown) to blow out air upwardly (see FIG. 6A).  
         [0068]    In the sheet feeding section  106 , when the interleaf paper  118  is removed from the magazine  208 , first, the suction fans  126  are operated and the interleaf paper  118  is raised by suction force due to the suction fans  126 . Thereafter, the interleaf paper  118  is held by being stuck to the sucker  124 .  
         [0069]    As illustrated in FIG. 4, the bracket  56  is provided with the suckers  124  which are respectively mounted at both sides of the bracket  56  with the fan base  60  interposed therebetween. The brackets  58  are each provided with the sucker  124  mounted at an outer side of the bracket along the transverse direction of the photopolymer plate  102 . As illustrated in FIGS. 4 and 5, these suckers  124  are each disposed near the suction fan  126 .  
         [0070]    As shown in FIG. 5, the suckers  124  are each connected to a negative pressure source such as a vacuum pump  82  via, for example a pipe line  80 A or a pipe line  80 B. Further, the pipe lines  80 A and  80 B are respectively provided with solenoid valves  84 A and  84 B. Due to the solenoid valves  84 A and  84 B being opened in a state in which the vacuum pump  82  is actuated, negative pressure is fed for each of the suckers  124 .  
         [0071]    Further, as illustrated in FIG. 6A, an end of the sucker  124  slightly protrudes from the rear surface of the fan base  60  or  62  (that is, the surface which faces the photopolymer plate  102 ), and therefore, when the end of the sucker  124  abuts against the photopolymer plate  102  or the interleaf paper  118 , the sucker  124  is apt to be flattened. Due to the sucker  124  being apt to be flattened by abutting against the photopolymer plate  102  or the interleaf paper  118 , the photopolymer plate  102  and the interleaf paper  118  can reliably be suction adhered by the sucker  124 .  
         [0072]    In the present embodiment, as an example, a dimension d between the lower surface of the fan base  60  or  62  and the end of the sucker  124  is set to be about 3.5 mm (d=3.5 mm). When the sucker  124  contacts the photopolymer plate  102  or the interleaf paper  118 , a small clearance is formed between the fan base  60  or  62 , and the photopolymer plate  102  or the interleaf paper  118  without the fan base contacting the surface of the photopolymer plate  102  or interleaf paper  118 . As a result, damage to the photopolymer plate  102  caused by the fan base  60  or  62  contacting the photopolymer plate  102  is prevented, and a suction efficiency of the suction fan  126  when the interleaf paper  118  is suction held by the suction fan  126  is greater.  
         [0073]    In the sheet feeding section  106 , the sucker  124  and the suction fan  126  are integrally moved up and down due to operation of the elevating motor  40  with respect to the photopolymer plate  102  (or the interleaf paper  118 ) accommodated in the magazine  208 , and the upper end of the photopolymer plate  102  or the interleaf paper  118  accommodated in the magazine  208  is lifted up by being suction held to the sucker  124 . Further, in the sheet feeding section  106 , when the interleaf paper  118  is removed from the magazine  208 , first, the suction fans  126  are operated so as to slightly lift up the interleaf paper  118  due to suction force of the suction fans  126 , and thereafter, the interleaf paper  118  is suction adhered to the suckers  124 .  
         [0074]    As illustrated in FIG. 4, the magazine  208  is provided with separation plates  66  which are mounted so as to face both transverse-direction ends of the photopolymer plate  102 . When the photopolymer plate  102  is lifted up by being suction adhered to the sucker  124 , the transverse-direction ends of the photopolymer plate  102  abut against the separation plates  66  and bend. Therefore, the photopolymer plate  102  adhered to the sucker  124  is reliably separated from the interleaf paper  118  located at a rear side thereof and only the uppermost photopolymer plate  102  is caused to move upward.  
         [0075]    Further, the magazine  208  is also provided with interleaf paper keepers  68  which face the upper end of the interleaf paper  118 . When the magazine  208  is mounted on the carriage  200  in an inclined manner, the interleaf paper keepers  68  are provided to abut against the uppermost interleaf paper  118  to prevent curling and falling of the interleaf paper  118 , which is typically not firm.  
         [0076]    As illustrated in FIG. 3, the suction frame  36  is provided with a contact sensor  70 . The contact sensor  70  is, for example, disposed in a transverse-direction intermediate portion of the photopolymer plate  102  (in the vicinity of the bracket  56 ) and protrudes from a block  72  mounted at the shaft  54  toward the magazine  208 . When the sucker  124  abuts against the photopolymer plate  102  or the interleaf paper  118 , the contact sensor  70  contacts the photopolymer plate  102  or the interleaf paper  118  and is placed in an on state (begins operating). That is, when the sucker  124  is moved upward, it can be confirmed by the contact sensor  70  as to whether the photopolymer plate  102  or the interleaf paper  118  is adhered to the sucker  124 .  
         [0077]    Further, the suction frame  36  is equipped with a plate/paper discrimination sensor  72 . In the plate/paper discrimination sensor  72 , light irradiated from a light projecting portion and reflected by the photopolymer plate  102  or the interleaf paper  118  is received by a light receiving portion by using, for example, a reflection type photosensor. At this time, an amount of the received light varies due to a difference in reflectance between the photopolymer plate  102  and the interleaf paper  118 , and therefore, a determination can be made as to whether the uppermost layer is the photopolymer plate  102  or the interleaf paper  118 .  
         [0078]    The distinction between the photopolymer plate  102  and the interleaf paper  118  may also be made, using a pressure sensor provided in a pipe line for feeding negative pressure for the sucker  124 , on the basis of the difference between a pressure generated when the interleaf paper  118  is suction adhered to the sucker  124 , and a pressure generated when the photopolymer plate  102  is suction adhered to the sucker  124 . That is, when the photopolymer plate  102  is located at the uppermost position, a predetermined negative pressure is detected by the pressure sensor. When the interleaf paper  118  is located at the uppermost position, negative pressure to be fed for the sucker  124  leaks through the interleaf paper  118  and the negative pressure to be detected by the pressure sensor is reduced (approximately to zero).  
         [0079]    Next, operation of the present embodiment will be described.  
         [0080]    In the automatic exposure apparatus  100 , when an instruction for exposure of images on the photopolymer plate  102  is given in a state in which the carriage  200 , in which the magazine  208  having the photopolymer plates  102  accommodated therein is loaded, is mounted in the plate accommodating section  104 , the photopolymer plates  102  are removed.  
         [0081]    Processing in the sheet feeding section  106  will hereinafter be described with reference to the flow chart shown in FIGS. 7A and 7B and the diagrams shown in FIGS. 6B to  6 F.  
         [0082]    The flow chart shown in FIGS. 7A and 7B are executed when an instruction for removal of the photopolymer plate  102  is given. In the first step  300 , it is confirmed as to whether the uppermost layer in the magazine  208  is the interleaf paper  118 . When it is determined that the uppermost layer is the interleaf paper  118 , the process proceeds to step  302 , first, removal of the interleaf paper  118  is carried out. A determination as to whether the uppermost layer at this time is the interleaf paper  118  is made by the plate/paper discriminating sensor  72 .  
         [0083]    When the interleaf paper  118  is removed, the conveying path is changed by the conveying switch portion  136  so as to convey the interleaf paper  118  from the shared conveying portion  128  to the interleaf paper conveying portion  134 . Further, when the uppermost layer is always the interleaf paper  118 , step  300  can be omitted.  
         [0084]    In step  302 , the elevating motor  40  is operated in a state in which feeding of negative pressure for the sucker  124  and the suction fan  126  are placed in an off state (are stopped), and the suction frame  36  is moved downward (toward the magazine  208 ). As a result, the sucker  124  moves toward the interleaf paper  118  together with the fan bases  60  and  62  in which the suction fans  126  are mounted.  
         [0085]    In step  304 , it is determined whether the sucker  124  abuts against the interleaf paper  118  based on the determination as to whether the contact sensor  70  contacts the interleaf paper  118 . When it is determined that the sucker  124  abuts against the uppermost interleaf paper  118  (when the decision of step  304  is affirmative), the process proceeds to step  306  and movement of the suction frame  36  in the downward direction is stopped (the elevating motor  40  is stopped).  
         [0086]    As a result, as illustrated in FIG. 6B, the fan base  60  or  62  is moved slightly apart from the interleaf paper  118 , while the interleaf paper  118  is still being pressed by the sucker  124 .  
         [0087]    In the subsequent step  308 , the suction fan  126  is turned on and the uppermost interleaf paper  118  pressed by the sucker  124  is attracted to the suction fan  126 . As a result, as illustrated in FIG. 6C, the state in which the uppermost interleaf paper  118  tends to be drawn away from the underlying photopolymer plate  102  so that close contact therebetween is released.  
         [0088]    Subsequently, in step  310 , the suction frame  36  is moved upward slightly (for example, by a distance of about 3 mm) while maintaining the state in which the interleaf paper  118  is pressed by the sucker  124 . As a result, as illustrated in FIG. 6D, the fan base  60  or  62  is slightly lifted up and the uppermost interleaf paper  118  is partially raised due to suction force of the suction fan  126 .  
         [0089]    In step  312 , the suction frame  36  is moved upward (for example, by a distance of about 2 mm) until the sucker  124  is raised. As a result, as illustrated in FIG. 6E, the uppermost interleaf paper  118  is released from the state of closely contacting the photopolymer plate  102  due to the suction fan  126  being separated from the photopolymer plate  102 .  
         [0090]    As described above, when the fan bases  60  and  62  are moved upward step by step and the uppermost interleaf paper  118  is raised away from an underlying photopolymer plate  102  due to the suction force of the suction fan  126 , in step  314 , negative pressure is fed for the sucker  124 , for example, by opening an electromagnetic valve for feeding the sucker  124  with negative pressure, and the interleaf paper  118  is attracted to the sucker  124 . As a result, as illustrated in FIG. 6F, the interleaf paper  118  is adhered to the sucker  124  and more reliably lifted away from the photopolymer plate  102 .  
         [0091]    In the present embodiment, the fan bases  60  and  62  are moved upward at two stages, but these fan bases may also be moved upward to a position corresponding to the position in step  312  in a single operation without carrying out the process of step  310 .  
         [0092]    In the subsequent step  316 , it is determined whether the interleaf paper  118  is suction adhered to the sucker  124 . This determination is made based on a determination as to whether the contact sensor  70  contacts the interleaf paper  118  lifted up by the sucker  124 . When it is determined that the interleaf paper  118  has been lifted up by the sucker  124  (when the decision of step  316  is affirmative), the process proceeds to step  318 , in which the suction fan  126  is turned off. On the other hand, the determination as to whether the interleaf paper  118  has been adhered to the sucker  124  may also be made after the suction fan  126  has been turned off (that is, step  316  may be executed after execution of step  318 ).  
         [0093]    When the suction fan  126  is turned off and the interleaf paper  118  is suction adhered to the sucker  124 , in step  320 , the elevating motor  40  is driven in reverse to move the suction frame  36  upward. In step  322 , the interleaf paper  118  is passed to the shared conveying portion  128 . To pass the interleaf paper  118  to the shared conveying portion  128 , the suction frame  36  is moved upward to a predetermined position and the leading end of the interleaf paper  118  thus moved upward is nipped by the rollers  128 A and  128 B, and application of negative pressure for the sucker  124  is stopped. As a result, the interleaf paper  118  is released from the sucker  124  while being nipped by the rollers  128 A and  128 B.  
         [0094]    The interleaf paper  118  passed to the shared conveying portion  128 , and conveyed from the shared conveying portion  128  to the interleaf paper conveying portion  134  via the conveying switch portion  136 , while being pulled out from the magazine  208 , and received in the interleaf paper receiving box  132 .  
         [0095]    When the interleaf paper  118  is not suction adhered to the sucker  124  (when the decision of step  316  is negative), the process proceeds to step  324 , and retry is set in which the suction frame  36  is moved downward again and the interleaf paper  118  is removed.  
         [0096]    When the interleaf paper  118  covering the photopolymer plate  102  is removed from the magazine  208  as described above, the process proceeds to step  326  and removal of the photopolymer plate  102  is carried out. In comparison, when the photopolymer plate  102  is located at the uppermost position in the magazine  208  and the decision of step  300  is negative, removal of the photopolymer plate  102  is immediately started. Further, in carrying out removal of the photopolymer plate  102 , the conveying switch portion  136  is switched and the conveying path from the shared conveying portion  128  to the photopolymer plate conveying portion  130  is formed.  
         [0097]    In the sheet feeding section  106 , when the process proceeds to step  326 , movement of the suction frame  36  in the downward direction is started. Further, in step  328 , feeding the sucker  124  with negative pressure is started (the sucker  124  is activated). As a result, the sucker  124  moves downward toward the photopolymer plate  102  within the magazine  208 , in a state of being capable of suction adhering to the photopolymer plate  102 .  
         [0098]    In the subsequent step  330 , it is confirmed by the contact sensor  70  as to whether the sucker  124  has been brought into contact with the photopolymer plate  102 , and when the contact sensor  70  is activated to cause the sucker  124  to move downward to a position at which it contacts the photopolymer plate  102  (when the decision of step  330  is affirmative), the process proceeds to step  332  and movement of the suction frame  36  in the downward direction is stopped.  
         [0099]    Subsequently, in step  324 , the sucker  124  to which the photopolymer plate  102  is stuck is moved upward by lifting up the suction frame  36 , and the photopolymer plate  102  is thereby raised. At this time, in step  336 , it is confirmed as to whether the contact sensor  70  is turned on, to thereby confirm whether the photopolymer plate  102  is raised by suction adherence to the sucker  124 . That is, whether the photopolymer plate  102  is reliably suction adhered to the sucker  124 .  
         [0100]    When the photopolymer plate  102  is stuck to the sucker  124  (when the decision of step  336  is affirmative), the suction frame  36  is lifted as is. As a result, the uppermost photopolymer plate  102  accommodated in the magazine  208  is raised in such a manner that an upper end thereof is adhered to the sucker  124 . At this time, as shown in FIG. 5, both transverse-direction ends of the photopolymer plate  102  are bent by the separation plates  66  provided in the magazine  208 , and the raised photopolymer plate  102  can be separated from the interleaf paper  118  located immediately therebelow, and from a subsequent photopolymer plate  102 .  
         [0101]    When the photopolymer plate  102  is thus removed from the magazine and lifted up to a predetermined height, in step  338 , the photopolymer plate  102  is passed to the shared conveying portion  128 . Thereafter, the sucker  124  is turned off (application of negative pressure is stopped) and the sucker  124  releases the photopolymer plate  102 .  
         [0102]    As a result, the photopolymer plate  102  lifted up by the sucker  124  is conveyed to the surface table  110  along the conveying path formed by the shared conveying portion  128 , the conveying switch portion  136 , and the photopolymer plate conveying portion  130  while being pulled out from the magazine  208 . When the photopolymer plate  102  is not adhered to the sucker  124  (when the decision of step  336  is negative), the process proceeds to step  340 , retry is set in which, preferably, the suction frame  36  is moved downward again and the photopolymer plate  102  is removed.  
         [0103]    When the photopolymer plate  102  is thus removed, in step  342 , it is determined as to whether removal of the photopolymer plates  102  requires completion. That is, it is confirmed as to whether a predetermined number of photopolymer plates  102  have been removed. When photopolymer plates  102  are continuously removed (when the decision of step  342  is negative), the process proceeds to step  302  and removal of the interleaf paper  118  prior to removal of a subsequent photopolymer plate  102  is carried out.  
         [0104]    As described above, in the sheet feeding section  106 , the interleaf paper  118  and the photopolymer plate  102  are more reliably removed alternately from the magazine  208  mounted in the plate accommodating section  104  and conveyed to the plate conveying section  108 .  
         [0105]    The present embodiment is merely one example of the present invention, and the structure of the sheet feeder of the present invention is not limited to the same. The present embodiment was described using the photopolymer plate  102  as the plate-shaped member, but the present invention can be applied to feeding of various printing plates, for example, pre-sensitized plates (PS plates), in addition to the photopolymer plates  102 .  
         [0106]    Further, in the present invention, various plate-shaped members can be used in addition to printing plates such as photopolymer plates, and the present invention can also be applied to sheet feeding for removing such plate-shaped members and flexible or light sheet materials such as the interleaf papers  118 , of which rigidity is lower than that of the plate-shaped members, when the plate-shaped members and the sheet materials are alternate with one another in a stack.