Patent Publication Number: US-7222570-B2

Title: Planographic printing plate supply unit including carrying roller with hollow convex portions

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application claims priority under 35 USC 119 from Japanese Patent Application No. 2004-266627, the disclosure of which is incorporated by reference herein. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a planographic printing plate supply unit and more particularly, a planographic printing plate supply unit which supplies pairs of planographic printing plates and covering papers one by one from a stacking bundle in which the planographic printing plates and the covering papers are stacked alternately. 
   2. Description of the Related Art 
   Generally, an image recording face of a planographic printing plate is covered with a protective covering paper attached thereto and a plurality of these units are stacked in a thickness direction so as to compose a bundle of the planographic printing plates. If an image is recorded on the planographic printing plate with an exposure unit or the like, it is necessary to pick up the planographic printing plates one by one from the bundle and supply then to the exposure unit. 
   For example, according to an image recording material sheeting unit described in Japanese Patent Application Laid-Open (JP-A) No. 2003-182904, printing plates and covering papers are stacked alternately in a cassette of the sheet transporting portion and a sucker suctions the covering paper and planographic printing plate from above the covering paper and raises them to bring them out of the cassette. After the printing plate and covering paper are taken out, the covering paper is separated from the suctioned printing plate by means of a fan. However, because the structure uses the sucker to supply the printing plate, there are concerns that the structure may become complicated and cost may increase. 
   Contrary to this, JP-A No. 60-202028 has disclosed a structure in which the covering paper is fed out by a roller and the planographic printing plate is sent out by a vacuum pad. However, according to this configuration, because the planographic printing plates or the covering papers are taken out one by one, a next planographic printing plate cannot be taken out until the covering paper is taken out, thereby taking much time. Further, because the planographic printing plate and the covering paper each need a taking-out mechanism, the quantity of components increases thereby possibly inducing increases in size of the unit and manufacturing costs. 
   Although conveying a planographic printing plate and a covering paper with a roller as a pair is conceivable, often only a planographic printing plate is carried separately from the covering paper or two pairs of the planographic printing plate and the covering paper are carried simultaneously due to penetration of air into gaps between the planographic printing plates. 
   SUMMARY OF THE INVENTION 
   In views of the above-described problems, an object of the present invention is to provide a planographic printing plate supply unit capable of reliably removing a single pair of a planographic printing plate and a covering paper from a stacking bundle of the planographic printing plates and covering papers, and having a simple structure. 
   To achieve the above object, according to a first aspect of the invention, a planographic printing plate supply unit comprises: carrying rollers rotating while pressing a stacking bundle in which planographic printing plates and covering papers are stacked alternately so as to carry a planographic printing plate and covering paper at the top of the stacking bundle, wherein convex portions which are elastically deformed when pressing the stacking bundle and whose contact area with the planographic printing plate is larger after being elastically deformed than before are provided on the outside periphery of the carrying roller. 
   In the planographic printing plate supply unit having the above-mentioned structure, its carrying rollers rotate while pressing the stacking bundle so as to carry the planographic printing plate and covering paper. As a consequence, a supplying time of the planographic printing plate can be reduced. 
   If a difference occurs between water content in the air and the water content in the covering paper, wrinkles are generated in the covering paper and due to the wrinkles, air enters between the stacked planographic printing plates thereby reducing friction between the covering paper and the planographic printing plate. As a consequence, the planographic printing plate located uppermost is conveyed away from above a gap into which much air enters. As a result, two pairs of the planographic printing plate and the covering paper are carried away or only a single planographic printing plate is carried separately from the covering paper, so that a planographic printing plate and covering paper cannot be carried in single pairs. 
   If the pressing force for eliminating the wrinkles in the covering paper is increased, the front end of the planographic printing plate is distorted so that air invades between the planographic printing plates from the front end portion and the same result as described above occurs. 
   According to the invention, the outside periphery of the carrying roller is provided with convex portions which are elastically deformable. The convex portion is elastically deformed when the carrying rollers press the planographic printing plate, so that the contact area with the planographic printing plate becomes larger than it was before being elastically deformed. Thus, the carrying rollers make contact with the planographic printing plate over a large area. Due to the contact, air existing between the planographic printing plate and the covering paper throughout the large contact area can be released thereby making it possible to prevent feeding of only a planographic printing plate separately or two pairs of the planographic printing plate and the covering paper at the same time. 
   Further, because the load on the planographic printing plate is dispersed as the contact area between the carrying roller and the planographic printing plate is large, the distortion of the planographic printing plate can be minimized and the flow-in of air can be blocked. 
   In the first aspect, the convex portions are permitted to have a hollow portion. 
   By forming the hollow portion in the convex portion, even if material which is difficult to deform due to high hardness and excellent durability is used, it can be deformed easily so as to secure a large contact area. 
   Further, the convex portions may be provided along at least one of the axial direction or the circumferential direction of the carrying roller at a predetermined interval. 
   If the convex portion is disposed in such a way, space is formed between the convex portions, so that individual convex portions become easy to elastically deform. 
   According to a second aspect of the invention, a planographic printing plate supply unit comprises: a carrying roller rotating while pressing a stacking bundle in which planographic printing plates and covering papers are stacked alternately so as to carry a planographic printing plate and covering paper at the top of the stacking bundle, wherein an outside peripheral portion of the carrying roller is composed of a rubber layer and the hardness of the rubber layer is from 20 degrees to 40 degrees. 
   Generally, the hardness of rubber used as the carrying roller is about 50 degrees. Under this hardness, deformation of a contact portion with the planographic printing plate is small, so that carrying of only a planographic printing plate separately or two pairs of the planographic printing plate and the covering paper simultaneously occurs due to flow-in of air like the above-described case. 
   According to the above-described structure, the hardness of rubber constituting the rubber layer is set to from 20 degrees to 40 degrees. In this range, the contact area with the planographic printing plate can be made large due to the deformation of the rubber and air existing between the planographic printing plate and covering paper can be released throughout the large contact area, thereby making it possible to prevent carrying of only a planographic printing plate separately or two pairs of the planographic printing plate and the covering paper simultaneously. 
   According to the second aspect, the carrying roller may be disposed at a position in which an elastically deformed portion thereof formed when the carrying roller presses the planographic printing plate contacts with a corner of the planographic printing plate. 
   The flow of air into the gap between the planographic printing plate and the covering paper is likely to occur from the front end in the carrying direction. Thus, as described above, the carrying rollers are disposed at the position in which the corner of the planographic printing plate contacts with the portion elastically deformed by the pressing force. As a consequence, air at the contact portion can be released and the flow-in of air from the front end in the carrying direction can be avoided thereby making it possible to prevent the carrying of only a planographic printing plate separately or two pairs of the planographic printing plate and the covering paper simultaneously. 
   According to a third aspect of the invention, a planographic printing plate supply unit comprises: a carrying roller rotating while pressing a stacking bundle in which planographic printing plates and covering papers are stacked alternately so as to carry a planographic printing plate and covering paper at the top of the stacking bundle, wherein an outside peripheral portion of the carrying roller is composed of an adhesive layer which adheres to the planographic printing plate. 
   In the above-mentioned planographic printing plate supply unit, the carrying rollers rotate while pressing the stacking bundle so as to carry the planographic printing plate and the covering paper. Thus, the supplying time of the planographic printing plates can be reduced. Because the adhesive layer formed on the outside periphery of the carrying roller adheres to the planographic printing plate, the planographic printing plate can be carried with a small load. Therefore, the pressing force does not need to be increased for the carrying, and in this case, it is possible to avoid the flow-in of air due to distortion of the planographic printing plate end portion which may occur when the pressing force is increased, thereby making it possible to prevent the carrying of only a single planographic printing plate separately or two pairs of the planographic printing plate and the covering paper simultaneously. 
   According to a fourth aspect of the invention, a planographic printing plate supply unit comprises: a carrying roller rotating while pressing a stacking bundle in which planographic printing plates and covering papers are stacked alternately so as to carry a planographic printing plate and covering paper at the top of the stacking bundle, wherein an outside peripheral portion of the carrying roller is elastically deformed when pressing so that a contact area thereof with the planographic printing plate is larger after being elastically deformed than before. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view showing a planographic printing plate supply unit according to a first embodiment of the present invention; 
       FIG. 2  is a perspective view showing a loading unit and a carrying unit of the planographic printing plate supply unit of  FIG. 1 ; 
       FIG. 3  is a perspective view showing a plate bundle to be set in the planographic printing plate supply unit of  FIG. 1 ; 
       FIG. 4  is a perspective view of part of a pick-up roller according to a first embodiment of the invention; 
       FIG. 5A  is a side view showing the relation between the pick-up roller and the planographic printing plate/covering paper according to the first embodiment of the invention and a condition in which the pick-up roller and the planographic printing plate are not in contact with each other; 
       FIG. 5B  is a side view showing a condition in which the pick-up roller and the planographic printing plate shown in  FIG. 5A  are in contact with each other; 
       FIG. 5C  is a side view showing a condition in which the uppermost planographic printing plate and covering paper are being fed out together by the pick-up roller shown in  FIG. 5A ; 
       FIG. 6  is a perspective view of part of the pick-up roller according to a second embodiment of the invention; 
       FIG. 7A  is a side view showing the relation between the pickup roller and the planographic printing plate/covering paper according to the second embodiment of the invention and a condition in which the pick-up roller and the planographic printing plate are not in contact with each other; 
       FIG. 7B  is a side view showing a condition in which the pick-up roller and the planographic printing plate shown in  FIG. 7A  are in contact with each other; 
       FIG. 7C  is a side view showing a condition in which the uppermost planographic printing plate and covering paper are being fed out together by the pick-up roller shown in  FIG. 7A ; 
       FIG. 8  is a perspective view of part of the pick-up roller according to a third embodiment of the invention; 
       FIG. 9A  is a side view showing the relation between the pick-up roller and the planographic printing plate/covering paper according to the third embodiment of the invention and a condition in which the pick-up roller and the planographic printing plate are not in contact with each other; 
       FIG. 9B  is a side view showing a condition in which the pick-up roller and the planographic printing plate shown in  FIG. 9A  are in contact with each other; and 
       FIG. 9C  is a side view showing a condition in which the uppermost planographic printing plate and covering paper are being fed out together by the pick-up roller shown in  FIG. 9A . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   FIRST EMBODIMENT 
     FIG. 1  shows the entire structure of a planographic printing plate supply unit  12  according to the first embodiment of the present invention.  FIG. 2  shows a loading portion  14  and a carrying portion  16  of the planographic printing plate supply unit  12  in a condition in which a bundle  18  is mounted on the loading portion  14 . 
   As shown in  FIG. 3 , in a planographic printing plate  20 , sensitizing agent face  20 E is formed by coating a face of a supporting body formed in the form of sheet with aluminum or the like with a sensitizing agent. A covering paper  22  for protecting the sensitizing agent face  20 E and the planographic printing plate  20  are stacked alternately so as to compose a bundle  18 .  FIG. 3  represents a condition in which they are stacked with the sensitizing agent face  20 E facing upward with the covering paper  22  which protects the sensitizing agent face  20 E of the uppermost planographic printing plate  20  already removed. 
   As shown in  FIG. 1 , the planographic printing plate supply unit  12  is equipped with a base  26  and the loading portion  14  and the carrying portion  16  are disposed on the top of the base  26 . The base  26  is provided with casters  28  so that the entire planographic printing plate supply unit  12  can be moved so that, for example, it can be attached to/detached from a planographic printing plate insertion portion or the like of an exposure unit. 
   As shown in  FIG. 2 , the loading portion  14  has a flat, square loading tray  30  and two side end guide plates  32  and a rear end guide plate  34  are disposed within the loading tray  30 . The side end guide plates  32  slide in a direction of an arrow W by means of a sliding mechanism (not shown) so as to arrange side faces of a plate bundle  18 , that is, the plural planographic printing plates  20  and covering papers  22  neatly corresponding to the size of the planographic printing plate  20 . Likewise, the rear end guide plate  34  slides in a direction of an arrow F (and in an opposite direction) by means of a sliding mechanism (not shown) so as to arrange the rear end of the plate bundle  18  neatly. 
   The loading portion  14  is provided with plural covers  36  for covering the surroundings of the loaded plate bundle  18 . When attached to the exposure unit, a cover  36 A for covering the end portion in the downstream in the transportation direction of the plate bundle  18  is pressed upward by a pressing member (not shown) and rotated around a hinge  38  so that it is swung upward as shown in  FIG. 1 . 
   As shown in  FIG. 2 , a holder  40  is stretched over the loading portion  14  along the width direction of the planographic printing plate  20 . A pick-up roller  42  is mounted rotatably on the holder  40  such that it is located over the plate bundle  18  loaded on the loading portion  14  and a drive force of a drive motor  44  acts via an endless belt  46 , and it is rotated in the direction of carrying the planographic printing plate  20  (or covering paper  22 ) (hereinafter, the rotation in this direction is referred to as “forward rotation”, indicated by an arrow J). Meanwhile, the direction of carrying the planographic printing plate  20  is indicated by an arrow F (hereinafter referred to as “carrying direction F”) and a direction perpendicular thereto (width direction of the planographic printing plate  20 ) is indicated by an arrow W (hereinafter it is referred to as “width direction W”). 
   The holder  40  is rotatable around a supporting shaft  48  provided at both ends in the width direction and downstream in the transportation direction. The pick-up roller  42  is rotated by a rotation driving force from a drive unit  50  provided sideway of the holder  40  between a carrying position in which the pick-up roller  42  applies a predetermined pressure and contacts with the plate bundle  18  and a removed position in which it is removed from the plate bundle  18 . 
   The bottom portion of the loading tray  30  is a loading plate  52  which swings by a hinge (not shown) provided upstream in the carrying direction. With the plate bundle  18  loaded on the loading plate  52 , the loading plate  52  is urged upward by an urging member (not shown) so that the uppermost planographic printing plate  20  makes firm contact with the pick-up roller  42 . A pressing force from the pick-up roller  42  to the plate bundle  18  is controlled to an extent that allows a pair of the planographic printing plate  20  and the covering paper  22  to be carried together. 
   As shown in  FIG. 4 , the pick-up roller  42  is so constructed that block wheels  43  are mounted around the outer peripheral portion of a cylindrical shaft portion  42 A. The block wheel  43  has a ring shape and plural blocks  43 A disposed at an equal interval along the circumference of the pick-up roller  42 . The block wheels  43  are arranged at an equal interval from an end to the other in the axial direction of the pick-up roller  42 . Each block  43 A is made of substantially rectangular parallelepiped rubber, which is elastically deformable. A hollow portion  43 B passes through the block  43 A in the axial direction of the pick-up roller  42 . Although the hollow portions  43 B are not absolutely necessary, the hollow structure allows the block  43 A to be elastically deformed easily even under a small pressing force even if it is made of material difficult to elastically deform due to high hardness and excellent durability. 
   As shown in  FIG. 5A , the pick-up roller  42  is disposed at the front end of the plate bundle  18 . As shown in  FIG. 5B , the block  43 A contacting with the planographic printing plate  20  located at the top of the stacking bundle, is elastically deformed by a pressing force from the pick-up roller  42  and crushed, so that it contacts with the front end corner of the planographic printing plate at the top of the stacking bundle at a contact area N 1  including the front end corner of the planographic printing plate  20 . 
   As shown in  FIG. 1 , two guide plates  54 ,  56  are disposed at a predetermined interval in the carrying direction F downstream in the carrying direction relative to the loading portion  14 . The planographic printing plate  20  is carried while supported by these guide plates  54 ,  56 . 
   A covering paper separating unit  58  is disposed between the guide plates  54  and  56 . The covering paper separating unit  58  has a carrying roller unit  60  and a retard roller unit  62  disposed along the carrying direction F. As shown in  FIG. 2 , each of these is constituted of a rotatable shaft  64  stretched along the width direction W and a plurality of rubber rollers  66  fixed on the shaft  64  at a predetermined interval. If the shaft  64  is rotated by receiving a drive force from a drive motor  61 , the rubber rollers  66  of the carrying roller unit  60  are rotated (forward) in the direction of an arrow R 1  and the rubber rollers  66  of the retard roller unit  62  are rotated (inversely) in the direction of an arrow R 2  which is an opposite direction to the arrow R 1 . 
   The retard roller unit  62  is moved from a position in which it contacts with the covering paper being carried and a position in which it is removed from the covering paper  22  by the drive unit  68  provided at an end thereof. Because the retard roller unit  62  is rotated inversely while making contact with the covering paper  22 , the covering paper  22  can be separated from the planographic printing plate  20 . The rubber rollers  66  of the retard roller unit  62  contacts with the rubber rollers  66  of the carrying roller unit  60  to nip the covering paper  22  between the rubber rollers  66  of the carrying roller unit  60  and the rubber rollers  66  of the retard roller unit  62 . 
   The nip roller  70  is stretched rotatably over the carrying roller unit  60  in the width direction. The nip roller  70  contacts with the planographic printing plate  20  and the covering paper  22  such that it is capable of nipping them between the nip roller  70  and rubber rollers  66  of the carrying roller unit  60  due to its own weight. 
   Covering paper carrying roller units  72 A,  72 B are disposed below the carrying roller unit  60  and the retard roller unit  62 . The covering paper carrying roller units  72 A,  72 B are constituted of a shaft  64  and rubber rollers  66  like the carrying roller unit  60  and the retard roller unit  62 , so that the covering paper  22  can be nipped between the rubber rollers  66  of the covering paper carrying roller units  72 A and  72 B. If the covering paper carrying roller units  72 A,  72 B rotate with the covering paper  22  nipped between the rubber rollers  66 , the nipped covering paper  22  can be carried downward along a carrying belt  74 . 
   An collection box  76  in which the covering papers  22  are to be collected, is provided below the covering paper carrying roller units  72 A,  72 B. 
   Next, the operation of this embodiment will be described. 
   When the planographic printing plates  20  are supplied to an exposure unit from the planographic printing plate supply unit  12  having the above-described structure, first, the plate bundle  18  is loaded on the loading portion  14 . At this time, the plate bundle  18  is arranged neatly with the rear end  18 B of the plate bundle  18  in contact with the rear end guide plate  34  and the side end  18 S in contact with the side end guide plate  32 . 
   When the planographic printing plate supply unit  12  is mounted at a predetermined position of the exposure unit, as shown in  FIG. 1 , the cover  36 A rotates upward so that part (portion in the vicinity of the front end) of the plate bundle  18  is exposed. Before the pick-up roller  42  contacts with the plate bundle  18 , as shown in  FIG. 5A , wrinkles are generated in the covering paper  22  under the planographic printing plate  20  due to a difference in water content between air and the covering paper  22 , so that air E is contained between the planographic printing plate  20  and the covering paper  22 . When the holder  40  is driven by the drive unit  50  and the pick-up roller  42  contacts with the plate bundle  18 , as shown in  FIG. 5B , the block  43 A is elastically deformed and crushed due to a pressing force from the pick-up roller  42  to the plate bundle  18 , so that it contacts with the planographic printing plate  20  at a larger contact area N 1  than before being elastically deformed. Because the uppermost planographic printing plate  20  is pressed downward at the contact area N 1 , air E existing between the planographic printing plate  20  and the covering paper  22  is released. Further, because the contact area between the pick-up roller  42  and the planographic printing plate  20  is large, the pressing force of the planographic printing plate  20  is dispersed so as to reduce distortion of the planographic printing plate  20  and prevent air from flowing in. Further, because the pick-up roller  42  keeps contact over the contact area N 1  including the front end corner of the planographic printing plate  20 , flow-in of air from the front end corner can be prevented. In this state, when the pick-up roller  42  is rotated in the direction of an arrow J, as shown in  FIG. 5C , a pair of the planographic printing plate  20  and the covering paper  22  are carried together in the direction of an arrow F. 
   In the pick-up roller  42  having the above-described structure, it is possible to prevent only the planographic printing plate or two pairs of the planographic printing plate and the covering paper from being carried because of air existing between the planographic printing plate  20  and the covering paper  22 . 
   Separation of the planographic printing plate  20  and the covering paper  22  is carried out in the covering paper separating unit  58 . When commencement of transportation of the planographic printing plate  20  and the covering paper  22  is detected by a sensor, the carrying roller unit  60  and the retard roller unit  62  rotate so that the retard roller unit  62  lifts up. Then, if the rubber rollers  66  of the retard roller unit  62  are rotated inversely, coming into contact with the covering paper  22 , a force in the carrying direction from the carrying roller unit  60  and a force in an opposite direction to the carrying direction from the retard roller unit  62  act on the covering paper  22 , so that the covering paper  22  is separated from the planographic printing plate  20 . The covering paper  22  is carried downward while nipped by the rubber rollers  66  of the carrying roller unit  60  and the retard roller unit  62  with its intermediate portion bent and collected in the collection box  76 . The planographic printing plate  20  is carried further in the carrying direction F and sent to the exposure unit. 
   SECOND EMBODIMENT 
   Next, the second embodiment of the present invention will be described. Because the planographic printing plate supply unit of this embodiment is the same as the first embodiment except in the structure of the pick-up roller, only the structure of the pick-up roller will be described. 
   As shown in  FIG. 6 , the pick-up roller  90  of the embodiment is provided with a soft rubber layer  92  having a specified thickness around the outside periphery of a cylindrical shaft portion  42 A. The soft rubber layer  92  is composed of rubber having a hardness of 30 degrees. As shown in  FIG. 7A , the pick-up roller  90  is disposed at the front end portion of the plate bundle  18 . Then, as shown in  FIG. 7B , the soft rubber layer  92  making contact with the uppermost planographic printing plate  20  is elastically deformed and crushed due to a pressing force from the pick-up roller  90 , so that it comes into contact with the front end corner of the planographic printing plate  20 . As shown in  FIGS. 7B and 7C , the soft rubber layer  92  making contact with the planographic printing plate  20  is elastically deformed and crushed due to the pressing force from the pick-up roller  90  to the planographic printing plate  20 , so that it keeps contact with a contact area N 2  including the front end corner of the planographic printing plate  20 . 
   Although the soft rubber layer  92  of this embodiment is composed of rubber having a hardness of 30 degrees, the hardness does not always need to be 30 degrees, but only needs to be from 20 degrees to 40 degrees. 
   Next, the operation of this embodiment will be described. 
   Before the pick-up roller  90  contacts with the plate bundle  18 , as shown in  FIG. 7A , wrinkles are generated in the covering paper  22  under the planographic printing plate  20 , so that air E may be contained between the planographic printing plate  20  and the covering paper  22 . When the holder  40  is driven and the pick-up roller  90  comes into contact with the plate bundle  18  as in the first embodiment, as shown in  FIG. 7B , the bottom portion of the soft rubber layer  92  is elastically deformed and crushed due to the pressing force from the pick-up roller  90  to the plate bundle  18 , so that it contacts with the planographic printing plate  20  over a contact area N 2  larger than before being elastically deformed. In the contact area N 2 , the uppermost planographic printing plate  20  is pressed downward so that air E existing between the planographic printing plate  20  and the covering paper  22  is released. Further, because the contact area between the pick-up roller  90  and the planographic printing plate  20  is large, the pressing force to the planographic printing plate  20  is dispersed so as to reduce distortion of the planographic printing plate  20  and prevent air from flowing into gaps. Because the pick-up roller  90  contacts over the contact area N 2  including the front end corner, air is prevented from flowing in from the front end corner. When the pick-up roller  90  is rotated in the direction of the arrow J in this state, as shown in  FIG. 7C , a pair of the planographic printing plate  20  and the covering paper  22  are carried together in the direction of the arrow F. 
   In the pick-up roller  90  having the above-described structure, it is possible to prevent only the planographic printing plate or two pairs of the planographic printing plate and the covering paper from being carried because of air existing between the planographic printing plate  20  and the covering paper  22  like the first embodiment. 
   THIRD EMBODIMENT 
   Next, the third embodiment of the present invention will be described. Because the planographic printing plate supply unit of this embodiment is the same as the first embodiment except in the structure of the pick-up roller, only the structure of the pick-up roller will be described. 
   As shown in  FIG. 8 , the pick-up roller of the embodiment is provided with an adhesive rubber layer  96  having a specified thickness around the outside periphery of a cylindrical shaft portion  42 A. The adhesive rubber layer  96  is composed of rubber having adhesive force. As the rubber having adhesive force, butyle rubber may be used. As shown in  FIG. 9A , the pick-up roller  94  is disposed at the front end portion of the plate bundle  18 . Then, as shown in  FIG. 9B , the adhesive rubber layer  96  contacts with the uppermost planographic printing plate  20  at a contact area N 3  including the front end corner of the planographic printing plate  20 . 
   Next, the operation of this embodiment will be described. 
   When the holder  40  is driven and the pick-up roller  90  comes into contact with the plate bundle  18  as in the first embodiment, as shown in  FIG. 9B , the bottom portion of the adhesive rubber layer  96  contacts with the planographic printing plate  20  at a contact area N 3 . In the contact area N 3 , the adhesive rubber layer  96  adheres to the planographic printing plate  20  detachably. Due to this adhesion, the uppermost planographic printing plate  20  and covering paper  22  can be carried with a small pressing force. When the pressing force can be set so as to be small, distortion of the planographic printing plate  20  can be reduced, so that air can be prevented from flowing into the gaps between the planographic printing plates  20 . Further, because the pick-up roller  94  contacts with the contact area N 3  including the front end corner of the planographic printing plate  20 , flow-in of air from the front end corner can be prevented. When the pick-up roller  94  is rotated in the direction of the arrow J under this condition, as shown in  FIG. 9C , the uppermost planographic printing plate  20  and covering paper  22  are carried together in the transportation direction F. 
   With the pick-up roller  94  having the above-described structure, it is possible to prevent only the planographic printing plate or two pairs of the planographic printing plate and the covering paper from being carried because of air existing between the planographic printing plate  20  and the covering paper  22  like the first embodiment and the second embodiment. 
   Because the planographic printing plate supply unit of the embodiment of the present invention has the above-described structure, such a simple structure makes it possible to reliably remove a planographic printing plate and covering paper pair by pair from a stacking bundle of the planographic printing plates and covering papers.