Abstract:
A scroll compressor has a pair of interleaved scrolls. An Oldham coupling is attached to the orbiting scroll to prevent of the orbiting scroll. This Oldham coupling has keys that are sliding received in slots. One side of each key is loaded while the opposite side is non-loaded. The non-loaded side of the key has stepped or profiled surface to provided clearance to allow deflection of the key. In another embodiment, the stepped or profiled surface is provided on the non-loaded side of the slot.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a plate exchanging apparatus and method in a rotary printing press, which automatically removes an,old plate from a plate cylinder and setting a new plate on the plate cylinder. 
     As a plate exchanging apparatus of this type, one is generally disclosed in Japanese Patent Laid-Open No. 11-77968. The plate exchanging apparatus disclosed in this reference has a cassette which is swingably supported by frames and has a new plate setting unit for setting a new plate and an old storage unit for storing an old plate, and an actuator for reciprocating the cassette between a plate mounting position and a retreat position. In this arrangement, when the cassette is moved from the retreat position to the plate mounting position by the actuator, the distal end of the cassette opposes the plate fixing unit of the plate cylinder. When the plate cylinder rotates almost one revolution from this state, an old plate whose leading and trailing edges are released from the plate fixing unit of the plate cylinder is stored in the old plate storage unit of the cassette. 
     In the conventional plate exchanging apparatus described above, however, the old plate may contact the inner surface of the old plate storage unit during the storage of the old plate in the old plate storage unit, thereby damaging the surface of the old plate. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a plate exchanging apparatus and method in a rotary printing press, which can prevent damage to the surface of an old plate during plate removal and bending of the old plate, thereby reliably reusing the old plate. 
     In order to achieve the above object of the present invention, there is provided a plate exchanging apparatus in a rotary printing press for removing an old plate unfixed from a plate cylinder having a plate fixing unit and setting a new plate on the plate cylinder by the plate fixing unit, comprising first control means for executing a full-automatic plate exchanging mode to automatically remove the old plate from the plate cylinder and automatically set the new plate on the plate cylinder using plate holding means, and second control means for executing a semi-automatic plate exchanging mode to remove the old plate from the plate cylinder by a combination of automatic and manual operations and set the new plate on the plate cylinder by a combination of automatic and manual operations. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view showing the schematic structure of a whole rotary printing press according to the first embodiment of the present invention; 
     FIG. 2 is a view seen from the arrow II of FIG. 1; 
     FIG. 3 is a view seen from the arrow III of FIG. 2; 
     FIG. 4 is an enlarged side view of the driver of the plate holder shown in FIG. 3; 
     FIG. 5 is a view seen from the arrow V of FIG. 4; 
     FIGS. 6A and 6B are sectional views taken along the line VI—VI of FIG. 2; 
     FIGS. 7A and 7B are sectional views taken along the line VII—VII of FIG. 2; 
     FIG. 8A is a sectional view taken along the line VIIIA—VIIIA of FIG. 2, and FIG. 8B is a view seen from the arrow VIIIB of FIG. 8A; 
     FIG. 9 is a block diagram of the main part of the rotary printing press according to, the present invention to show its electric arrangement; 
     FIG. 10 is a flow chart showing selection between full-automatic plate mounting and semi-automatic plate mounting in the rotary printing press according to the present invention; 
     FIG. 11 is a flow chart showing the operation of full-automatic plate mounting in the rotary printing press according to the present invention; 
     FIG. 12 is a flow chart following FIG. 11 to show the operation of full-automatic plate mounting; 
     FIG. 13 is a flow chart showing the operation of semi-automatic plate mounting in the rotary printing press according to the present invention; 
     FIGS. 14A and 14B are sectional views taken along the line XIIII—XIIII of FIG. 2 to show states in full-automatic plate exchanging operation wherein a new plate is set on the plate holder and a plate catch is opened, respectively; 
     FIGS. 15A and 15B are sectional views taken along the line XIIII—XIIII of FIG. 2 to show states in full-automatic plate exchanging operation wherein a safety cover is opened and the plate holder is moved to the second position, respectively; 
     FIGS. 16A and 16B are sectional views taken along the line XIIII—XIIII of FIG. 2 to show states in full-automatic plate exchanging operation wherein an old plate is removed and a new plate is inserted in the plate fixing unit of a plate cylinder, respectively; 
     FIGS. 17A and 17B are sectional views taken along the line XIIII—XIIII of FIG. 2 to show states in full-automatic plate exchanging operation wherein the new plate is set on the plate cylinder and the safety cover is closed, respectively; 
     FIGS. 18A and 18B are sectional views taken along the line XIIII—XIIII of FIG. 2 to show states in semi-automatic plate exchanging operation wherein the safety cover is closed and opened, respectively; 
     FIGS. 19A and 19B are sectional views taken along the line XIIII—XIIII of FIG. 2 to show states in semi-automatic plate exchanging operation wherein the fixed old plate is unfixed from the plate fixing unit of the plate cylinder and the old plate is being removed, respectively; 
     FIGS. 20A and 20B are sectional views taken along the line XIIII—XIIII of FIG. 2 to show states in semi-automatic plate exchanging operation wherein the new plate is being inserted in the plate fixing unit of the plate cylinder and the new plate is set on the plate cylinder, respectively; and 
     FIG. 21 is a sectional view taken along the line XIIII—XIIII of FIG. 2 to show a state in semi-automatic plate exchanging operation wherein the safety cover is closed. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will be described in detail with reference to the accompanying drawings. 
     FIG. 1 schematically shows the structure of a rotary printing press according to the first embodiment of the present invention. Referring to FIG. 1, a double-sided sheet-fed rotary printing press  1  is schematically comprised of a sheet feed unit  2 , four printing units  3 A to  3 D for face side printing lined up on the upper side, four printing units  4 A to  4 D for reverse side printing lined up on the lower side, and a delivery unit  5 . 
     The sheet feed unit  2  has a conventional widely known sucker unit (not shown) for feeding out sheets  11  stacked on a sheet pile plate  10  to a feeder board  12  one by one. Each sheet  11  fed out to the feeder board  12  is gripped by the grippers of a transfer cylinder  13  of the first-color printing unit  3 A by a swing unit (not shown) provided at the distal end of the feeder board  12 . 
     Each of the four printing units  3 A to  3 D for face side printing has a plate cylinder  15  on which a plate is set, a blanket cylinder  16  in contact with the plate cylinder  15 , and an impression cylinder  17  in contact with the blanket cylinder  16  and having a diameter twice that of the blanket cylinder  16 . An inker  18  for storing an inking device is provided above the plate cylinder  15 . The sheet  11  gripped by the grippers of the transfer cylinder  13  is then transferred to the grippers of the impression cylinder  17  and gripped by them. While the sheet  11  is being conveyed between the blanket cylinder  16  and impression cylinder  17 , first-color printing is performed on its face side. 
     Each of the four printing units  4 A to  4 D for reverse side printing has a plate cylinder  20  on which a plate is set, a blanket cylinder  21  in contact with the plate cylinder  20 , and an impression cylinder  22  in contact with the blanket cylinder  21  and having a diameter twice that of the blanket cylinder  21 . An inker  23  for storing an inking device consisting of a group of a large number of rollers (not shown) is provided below the plate cylinder  20 . 
     The sheet  11  is transferred from the grippers of the impression cylinder  17  of the face side printing unit  3 A to the grippers of the impression cylinder  22  of the reverse side printing unit  4 A and gripped by them. While the sheet  11  is being conveyed between the impression cylinder  22  and blanket cylinder  21 , first-color printing is performed on its reverse side. After that, second- to fourth-color printing operations are sequentially performed on the face and reverse sides of the sheet  11  by the face side printing units  3 B to  3 D and reverse side printing units  4 B to  4 C. 
     The sheet  11  gripped by the grippers of the impression cylinder  22  of the fourth-color reverse side printing unit  4 D is transferred to a gripper unit provided to a gripper bar extending between the pair of right and left delivery chains of the delivery unit  5 , and gripped by them. The sheet  11  gripped by the gripper unit is conveyed by the delivery chains and released from the gripper unit by a cam mechanism. Thus, the sheet  11  falls on a sheet pile plate  24  and is piled there. 
     As shown in FIG. 3, a leading edge plate clamp  25  and trailing edge plate clamp  26  are provided in a notch formed in the outer surface of the plate cylinder  20 . The two clamps  25  and  26  have bottom clamping rails  25   a  and  26   a  and gripper boards  25   b  and  26   b , respectively. A pair of reference pins  27  lined up in the axial direction of the plate cylinder  20  vertically stand on the upper surface of the bottom clamping rail  25   a  of the leading edge plate clamp  25 . The reference pins  27  engage with a pair of notches  7  formed in the leading edge of a new plate P 2  to position the new plate P 2  in the circumferential and widthwise directions. The arrangement of the cylinders and the plate clamp units described above are not different from those of a conventional widely known double-sided sheet-fed rotary printing press. 
     A plate mounting unit in the sheet-fed rotary printing press, which is employed by each of the reverse side printing units  4 A to  4 D will be described with reference to FIGS. 2 to  21 . Plate inserting apparatuses employed by the respective printing units  4 A to  4 D have completely the same structure, and accordingly only the plate mounting unit employed by the printing unit  4 A will be described. 
     Referring to FIG. 2, the printing unit  4 A has a pair of opposing frames  30 , and a pair of chain guides  31  are fixed to the inner sides of the upper portions of the frames  30 . A pair of chains  32  are supported by the chain guides  31  to be vertically slidable, and a plurality of elongated blocking plates  33  horizontally extend between the chains  32 . 
     As shown in FIG. 3, a safety cover  34  formed by the plurality of blocking plates  33  is driven by sprockets  35  to open/close the front surface of the plate cylinder  20 . The teeth of each sprocket  35  oppose the inside of the corresponding blocking plate  33 . More specifically, the teeth of the sprockets  35  mesh with the chains  32 , and the sprockets  35  are rotated clockwise or counterclockwise in FIG. 3 by a safety cover drive motor  87  (FIG. 9) which drives in the forward/reverse directions. When the sprockets  35  rotate clockwise, the safety cover  34  moves upward to open the front surface of the plate cylinder  20 . When the sprockets  35  rotate counterclockwise, the safety cover  34  moves downward to close the front surface of the plate cylinder  20 . A pair of reference pins  36  stand vertically from a lowermost blocking plate  33 A of the plurality of blocking plates  33 . The reference pins temporarily position the plate before holding. 
     A plate inserting apparatus  40  will be described with reference to FIGS. 2 to  5 . Referring to FIG. 5, the plate inserting apparatus  40  is comprised of a plate holder  41  for holding the new plate P 2  by drawing by suction its leading edge, a pair of guide rails  42  serving as posture changing means to guide the plate holder  41 , and actuators  43  for moving the plate holder  41 . 
     Each actuator  43  is constituted by a first actuator  43 A for the plate holder and second actuator  43 B for the plate holder. The rear portions of the two actuators  43 A and  43 B are connected and fixed to each other. The driving states, i.e., the operative state (ON) and the inoperative state (OFF), of the actuators  43 A and  43 B are combined to selectively position the plate holder  41  at three points A, B, and C described later. 
     The plate holder  41  has an elongated rectangular parallelepiped shape, and has two rows of a large number of suction pads  45  on its front surface. Suction air from a suction pump  86  (FIG. 9) is supplied to the suction pads  45  as a negative pressure. As shown in FIG. 4, a pair of blind hole-type fitting insertion holes  46  are formed in the rear surface of the plate holder  41 . Spherical sliding bearings,  47  are fixed to the openings of the fitting insertion holes  46 . As shown in FIG. 5, two pairs of rollers  48  are rotatably supported at the right and left ends of the plate holder  41 . 
     The pair of guide rails  42  respectively have a pair of guide grooves  50  with a U-shaped section. As shown in FIG. 5, the guide rails  42  are fixed to the inner sides of the right and left frames  30  such that the guide grooves  50  face each other. As shown in FIG. 4, each guide rail  42  is comprised of a lower straight portion  42   a  extending substantially vertically, a curved portion  42   b  with one end connected to the straight portion  42   a , and an upper straight portion  42   c  connected to the other end of the curved portion  42   b  and inclined obliquely upward toward the plate cylinder  20 . 
     As shown in FIG. 16B, the inclination of the straight portion  42   c  is set such that it is substantially the same as that of the upper surface of the bottom clamping rail  25   a  of the leading edge plate clamp  25  which is positioned at a predetermined position when inserting the new plate. When the rollers  48  of the plate holder  41  are engaged in the guide grooves  50  of the guide rails  42 , the plate holder  41  is movably supported to be guided by the guide grooves  50 . 
     Referring to FIG. 5, a pair of round rod-shaped driving levers  52  stand between the central portion and the ends of a driving shaft  51  rotatably supported between the frames  30 . The distal ends of the driving levers  52  are slidably and inclinably coupled to the spherical sliding bearings  47  of the plate holder  41 . That is, the plate holder  41  is swingably supported by the driving levers  52  to be movable in the longitudinal direction of the levers. The two ends of the driving shaft  51  project outwardly from the frames  30 . One end of each of a pair of intermediate levers  53  is fixed to the corresponding projecting end of the driving shaft  51 . The other end of each intermediate lever  53  is fixed with a rotor  54 , and the rotor  54  is fixed to the rod of the corresponding first actuator  43 A. The distal ends of the rods of the second actuators  43 B are fixed to the frames  30 . 
     Referring to FIG. 4, when the rods of the two actuators  43 A and  43 B are at the retreat position, the plate holder  41  is positioned at the point A of the straight portion  42   a  of each guide rail  42 . At the point A, the suction surfaces of the suction pads  45  are substantially vertical and substantially leveled with the front surface of the blocking plate  33 A so that the new plate P 2  can be set on the plate holder  41 . The posture of the plate holder  41  in this state is defined as the first posture at which the new plate P 2  is to be set on the plate holder  41 , and the point A is defined as the first position. When the plate holder  41  is in the first posture, the new plate P 2 , the leading edge of which is drawn by suction with the suction pads  45 , also becomes vertical. The plate holder  41  positioned at the first position is located immediately under the lowermost blocking plate  33 A of the closed safety cover  34 , as shown in FIG.  3 . 
     When the rod of each first actuator  43 A is moved forward, the driving shaft  51  pivots clockwise in FIG.  4  through the corresponding rotor  54  and intermediate lever  53 , and the plate holder  41  is positioned at the point B of the curved portion  42   b  of each guide rail  42 . At the point B, the suction surfaces of the suction pads  45  of the plate holder  41  are inclined from the horizontal plane by an angle α, as shown in FIG. 16A, and the leading edge of the new plate P 2  drawn by suction with the suction pads  45  is also inclined by the angle α. In this state, the leading edge of the new plate P 2  to be drawn by suction with the suction pads  45  is retreated from an old plate removal port  62  to open the front side of the old plate removal port  62 . An old plate P 1  can accordingly be removed from the old plate removal port  62 . The posture of the plate holder  41  at this time is defined as the second posture that enables removal of the old plate P 1 , and the point B is defined as the second position. 
     When the rod of each second actuator  43 B is also moved forward, the driving shaft  51  pivots further clockwise in FIG. 4, and the plate holder  41  is positioned at the point C of the straight portion  42   c  of each guide rail  42 . When the plate holder  41  is positioned at the point C, the upper surface of the bottom clamping rail  25   a  of the leading edge plate clamp  25  of the plate cylinder  20  is located on the extension of the suction surfaces of the suction pads  45 , as shown in FIG.  16 B. The posture of the plate holder  41  at this time is defined as the third posture that enables insertion of the new plate P 2  between the bottom clamping rail  25   a  and gripper board  25   b , and the point C is defined as the third position. 
     Referring to FIG. 4, the plate holder  41  is slidably supported by each driving lever  52 . While the plate holder  41  moves along the straight portion  42   a  and straight portion  42   c  of each guide rail  42 , when each driving lever  52  pivots, the plate holder  41  moves in the radial direction of this pivot movement as well. Thus, the pivot movements of the driving shaft  51  and driving lever  52  are converted into the linear movement of the plate holder  41  along the straight portions  42   c  and  42   a.    
     In this manner, the plate holder  41  can be moved along the straight portions  42   a  and  42   c  of the guide rails  42  without using link mechanisms or cam mechanisms having a complicated structure, and the pivot movements of the driving shaft  51  and driving levers  52  are converted into the linear movement of the plate holder  41 . The number of components is therefore reduced, and the structure is simplified. 
     A stationary cover and a plate removal cover will be described with reference to FIGS. 2,  3 ,  6 A,  6 B,  7 A, and  7 B. Referring to FIG. 3, a plate removal cover  55  is arranged immediately under the plate holder  41  positioned at the first point A. As shown in FIG. 2, the plate removal cover  55  is fixed to a stationary cover  57  at its lower end through a pair of hinges  56 , and can fall to the inside of the printing press about the hinges  56  as the pivot center, as shown in FIG.  6 B. In the normal state, the plate removal cover  55  is supported vertically. 
     As shown in FIG. 3, the stationary cover  57  is comprised of a front plate  58 , horizontal plate  59 , and rear plate  60 , and has a crank-shaped section. The two ends of the stationary cover  57  are attached to the inner sides of the frames  30 . An ink fountain  23   a  of the inking device stored in the inker  23  is provided below the horizontal plate  59 . To supply ink to the ink fountain  23   a , an opening  58   a  is formed below the front plate  58  of the stationary cover  57 . 
     As shown in FIG. 6A, the lower ends of a pair of cover opening/closing actuators  61  are pivotally mounted on the rear surface of the front plate  58  of the stationary cover  57 , and the distal ends of rods  61   a  of the cover opening/closing actuators  61  are pivotally mounted on the rear surface of the plate removal cover  55 . When the rods  61   a  move forward, the plate removal cover  55  pivots counterclockwise about the hinges  56  as the pivot center to close the front surface of the printing unit  4 A. When the rods  61   a  move backward, the plate removal cover  55  pivots clockwise about the hinges  56  as the pivot center, as shown in FIG.  6 B. The front surface of the printing unit  4 A is thus opened to form the old plate removal port  62 . 
     Referring to FIGS. 2 and 6A, a guide member  63  is comprised of a guide  63   a  formed by bending a rod into a U shape, and a pair of legs  63   b  formed by bending the two ends of the guide  63   a  at the right angle to support it in the cantilevered manner. Of the guide member  63 , the legs  63   b  stand vertically at one end of the upper portion of the stationary cover  57 , and the guide  63   a  extends horizontally parallel to the stationary cover  57  at a predetermined distance from it toward the central portion of the stationary cover  57 . Thus, the old plate P 1  held by a plate catch member (to be described later) is removed from the open end of the guide  63   a.    
     Referring to FIG. 2, a pair of rectangular windows  64  are formed in the two ends of the front plate  58  of the stationary cover  57 . Referring to FIGS. 2,  7 A, and  7 B, a pair of elongated rectangular fitting insertion holes  65  are formed in the two ends of the horizontal plate  59  of the stationary cover  57 . 
     Referring to FIGS. 2 and 7A, link members (link mechanisms)  66  respectively have upper ends pivotally mounted on levers  67  fixed to the rear surface of the plate removal cover  55 , and lower ends pivotally mounted on flat plate-like plate approach regulating members  68 . The plate approach regulating members  68  have proximal ends pivotally supported by the rear surface of the front plate  58  of the stationary cover  57 . In the state of FIG. 7A wherein the plate removal cover  55  closes the old plate removal port  62 , the plate approach regulating members  68  are horizontally supported so that their swing end sides are parallel to the fitting insertion holes  65 . From this state, when the plate removal cover  55  pivots clockwise in FIG. 7B about the hinges  56  as the pivot center through a predetermined angle smaller than 90°, the plate approach regulating members  68  pivot clockwise through 90° through the link members  66  about their proximal ends as the pivot center, so that they pass through the fitting insertion holes  65  to close the upper portion of the opening  58   a.    
     Referring to FIGS. 2,  8 A, and  8 B, plate pushout members  70  oppose the rear sides of the windows  64 . The lower ends of the plate pushout members  70  are fixed to the pivot shafts of plate pushout actuators  71  fixed to the front plate  58  of the stationary cover  57 . When the pivot shafts of the plate pushout actuators  71  pivot counterclockwise in FIG. 8A, the plate pushout members  70  also pivot counterclockwise to project to the outside of the front plate  58  through the windows  64 . 
     A plate catch structure will be described with reference to FIGS. 2,  3  and  14 . Referring to FIGS. 2 and 3, a bracket  74  with a crank shape when seen from the side surface horizontally extends between the lower ends of the frames  30 , and has an upper surface  74   a  and lower surface  74   b . A flat plate-like plate catch  75  has an elongated rectangular shape when seen from the front surface, and has a lower end connected to the lower surface  74   b  of the bracket  74  through hinges  76 . The plate catch  75  is supported to be pivotal about the hinges  76  as the pivot center to open/close the lower portion of the opening  58   a.    
     A pair of support members  77  are provided to the two ends of the front surface of the plate catch  75 . Refection type photosensors  77   a  directed toward the inside of the plate catch  75  are attached to the rear portions or near the rear portions of the support members  77 . A pair of plate catch driving actuators  78  are pivotally mounted on the upper surface  74   a  of the bracket  74 , and the distal ends of rods  78   a  of the actuators  78  are pivotally mounted on the rear surface of the plate catch  75 . When the rods  78   a  of the actuators  78  are moved backward, the plate catch  75  pivots clockwise in FIG. 3 about the hinges  76  as the pivot center to close the lower portion of the opening  58   a . When the rods  78   a  of the actuators  78  are moved forward, the plate catch  75  pivots counterclockwise in FIG. 3 about the hinges  76  as the pivot center to open the lower portion of the opening  58   a.    
     As shown in FIG. 14A, when the plate catch  75  is closed, as the leading edge of the new plate P 2  is to be drawn by suction with the suction pads  45  of the plate holder  41 , the support members  77  support the trailing edge of the new plate P 2 , as will be described later. From this state, when the plate catch  75  is opened as shown in FIG. 14B, the trailing edge of the new plate P 2  separates from the support members  77 , and abuts against the distal end of the plate catch  75  to be supported by it. At the same time, the trailing edge of the removed old plate P 1  is supported by the rear surface of the plate catch  75 , as will be described later. 
     FIG. 9 shows the main part of the rotary printing press. Referring to FIG. 9, the rotary printing press has a full-automatic plate mounting button  80 , a semi-automatic plate mounting button  81 , a plate suction button  82  for operating the suction pump  86 , and a plate catch button  83  for operating the actuators  78 . A plate mounting start button  84  automatically removes the old plate and starts the operation of supplying the new plate in the full-automatic plate exchanging mode. An operation button  85  drives leading and trailing edge plate clamp opening/closing actuators  89  and  90  in order to supply the new plate P 2  in the semi-automatic plate exchanging mode. A drive motor  88  rotates all the cylinders of the printing press. When exchanging the plate, the drive motor  88  rotates the plate cylinder  20  for a predetermined amount in the forward/reverse directions. A control unit  91  controls the operations of the actuators and the like described above upon operation of the buttons described above. 
     The actuator  89  serves to open/close the leading edge plate clamp. When the actuator  89  is operated, the leading edge cam shaft (not shown) of the leading edge plate clamp  25  in FIG. 3 pivots in the forward/reverse directions by a predetermined amount through a lever (not shown). When the leading edge cam shaft pivots, the gripper board  25   b  swings to grip and release the leading edge of the plate with the bottom clamping rail  25   a . When the trailing edge plate clamp actuator  90  is operated, the trailing edge cam shaft (not shown) of the trailing edge plate clamp  26  in FIG. 3 pivots in the forward/reverse directions by a predetermined amount through a lever. When the trailing edge cam shaft pivots, the gripper board  26   b  swings to grip and release the trailing edge of the plate with the bottom clamping rail  26   a.    
     The operation of changing the plate full-automatically will be described with reference to FIGS. 10,  11 ,  12 , and  14 A to  17 B. 
     As shown in FIG. 14A, the first and second actuators  43 A and  43 B are set inoperative to position the plate holder  41  at the first position. The full-automatic plate mounting button  80  is turned on to select full-automatic plate exchanging mode (step S 1  in FIG.  10 ). In FIG. 14A, the trailing edge of the new plate P 2  is placed and supported on the support members  77  of the plate catch  75 , and the leading edge of the substantially vertical new plate P 2  is set on the suction pads  45  of the plate holder  41  from the outside of the guide  63   a  of the guide member  63  (step S 3  in FIG.  11 ). Hence, the notches  7  of the new plate P 2  engage with the reference pins  36  of the lowermost blocking plate  33 A of the safety cover  34 . At this time, since the new plate P 2  is deflected between the support members  77  and reference pins  36 , its notches  7  are pushed by the reference pins  36  so that the new plate P 2  is reliably positioned before set by the plate holder  41 . 
     Then, the plate suction button  82  is turned on (step S 4 ) to operate the suction pump  86  (step S 5 ). The leading edge of the new plate P 2  is drawn by suction with the suction pads  45  of the plate holder  41 , so that the new plate P 2  is held by the plate holder  41 . At this time, the suction force of the suction pump  86  is adjusted to such a degree that the new plate P 2  is drawn by suction to be slidable with respect to the suction pads  45 . When the plate catch button  83  is turned on (step S 6 ), the actuators  78  are operated to move the rods  78   a  forward (step S 7 ). 
     Hence, as shown in FIG. 14B, the plate catch  75  is opened, and the trailing edge of the new plate P 2  is unfixed from the support members  77 . The new plate P 2  is accordingly supported on the distal end of the plate catch  75  in a slightly inclined state. The holding operation of the new plate P 2  is thus completed. At this time, since the leading edge of the new plate P 2  is held by the plate holder  41  and the trailing edge thereof is supported on the distal end of the plate catch  75 , the rear surface of the upper portion of the new plate P 2  covers the removal path of the old plate P 1  (to be described later) which is to be removed from the old plate removal port  62 . 
     When the plate mounting start button  84  is turned on (step S 8 ), the safety cover drive motor  87  is driven in the forward direction (step S 9 ), and the sprockets  35  rotate clockwise, as shown in FIG.  15 A. Hence, the safety cover  34  moves upward to open the front surface of the plate cylinder  20 , and the reference pins  36  of the blocking plate  33 A disengage from the notches  7  of the new plate P 2 . 
     The actuators  61  are then operated (step S 10 ) to pivot the plate removal cover  55  such that its upper end falls toward the plate cylinder  20 , thereby opening the old plate removal port  62 . Simultaneously, as the plate removal cover  55  falls, the plate approach regulating members  68  pivot through the link members  66 . The pivoting plate approach regulating members  68  close the upper portion of the opening  58   a . The first actuators  43 A are operated (step S 11 ) to position the plate holder  41  at the point B as the second position, as shown in FIG.  15 B. At the second position, the plate holder  41  is switched to the second posture that allows removal of the old plate P 1 , as described above. 
     The drive motor  88  is driven in the reverse direction (step S 12 ) to pivot the plate cylinder  20  in the reverse direction by a predetermined amount. When the plate cylinder  20  stops (step S 13 ), the actuator  89  is operated (step S 14 ) to open the leading edge plate clamp  25  of the plate cylinder  20 , thereby releasing the gripped leading edge of the old plate P 1 . Subsequently, the plate cylinder  20  pivots in the reverse direction by a predetermined amount and stops (steps S 15  and S 16 ). After that, the actuator  90  is operated (step S 17 ) to open the trailing edge plate clamp  26  of the plate cylinder  20 , thereby releasing the gripped trailing edge of the old plate P 1 . Subsequently, when the plate cylinder  20  rotates in the reverse direction (step S 18 ), the trailing edge of the old plate P 1  is unfixed from the plate cylinder  20  and is guided by the plate removal cover  55 , so that the old plate P 1  is removed outside the printing press through the old plate removal port  62 . 
     As shown in FIG. 16A, when the old plate P 1  is removed, its trailing edge is guided downward along the inner side of the guide  63   a  of the guide member  63 . The leading edge of the old plate P 1  disengages from the leading edge plate clamp  25 , and the trailing edge of the old plate P 1  is supported by the plate catch  75 . At this time, since the trailing edge of the old plate P 1  is detected by the photosensors  77   a , it is confirmed that the old plate P 1  is stored in the plate catch  75 , and the control unit  91  stops rotation of the plate cylinder  20  upon reception of output signals from the photosensors  77   a  (step S 19 ). In this manner, since completion of removal of the old plate P 1  is detected by the photosensors  77   a , the next new plate P 2  can be supplied safely and reliably. 
     At this time, the leading edge plate clamp  25  faces the end faces of the straight portions  42   c  of the guide rails  42 . When the actuators  43 B are operated (step S 20 ), the plate holder  41  moves to the straight portion  42   c  of each guide rail  42 , as shown in FIG. 16B, and is positioned at the third point C. The inclination of the straight portion  42   c  and the inclination of the upper end face of the bottom clamping rail  25   a  of the leading edge plate clamp  25  become substantially equal, and the upper end face of the bottom clamping rail  25   a  is located on the extension of the suction surfaces of the suction pads  45  of the plate holder  41  positioned by the straight portions  42   c . Hence, the leading edge of the new plate P 2  drawn by suction with the suction pads  45  is inserted between the bottom clamping rail  25   a  and gripper board  25   b.    
     At this time, the plate holder  41  is positioned at the third point C such that the notches  7  of the new plate P 2  are pushed by the reference pins  27 . When the notches  7  of the new plate P 2  engage (come into contact) with the reference pins  27 , the plate holder  41  pushes the new plate P 2  toward the reference pins  27 , while sliding on the new plate P 2 , against the suction force of the suction pads  45 . Therefore, the notches  7  of the new plate P 2  are further urged against the reference pins  27 , and the new plate P 2  is positioned to face the leading edge plate clamp  25 . Subsequently, the actuator  89  is operated (step S 21 ), and the leading edge of the new plate P 2  is gripped between the gripper board  25   b  and bottom clamping rail  25   a.    
     Regarding insertion of the new plate P 2  to the leading edge plate clamp  25 , since the guide rails  42  have the curved portions  42   b  in addition to the straight portions  42   c  that serve for plate insertion, the guide rails  42  do not project between the adjacent printing units more than necessary. Thus, the plate holder  41  positioned at a position other than the third position where the new plate P 2  is to be inserted does not project between the adjacent printing units. As a result, the work space between the adjacent printing units is not narrowed, and the workability of maintenance and inspection is improved. 
     Since the guide rails  42  have the straight portions  42   a  serving to set the new plate, the suction surfaces of the suction pads  45  of the plate holder  41  positioned at the first position become vertical. Hence, in the operation of holding the new plate P 2  with the suction pads  45 , since the new plate P 2  can also be set in the vertical state by its own weight and drawn by suction with the suction pads  45 , it can be set on the plate holder  41  easily. Since the new plate P 2  is held by the plate holder  41  only at its leading edge, the plate holder  41  itself can be downsized. 
     When the suction pump  86  becomes inoperative (step S 22 ), the new plate P 2  drawn by suction with the suction pads  45  of the plate holder  41  is released. Therefore, the new plate P 2  is held only by the leading edge plate clamp  25 . Subsequently, the plate cylinder  20  pivots in the forward direction by a predetermined amount and stops (steps S 23  and S 24 ). After that, the actuator  90  is operated (step S 25 ) to grip the trailing edge of the new plate P 2  with the gripper board  26   b  and bottom clamping rail  26   a , and the new plate P 2  is set on the plate cylinder  20 , as shown in FIG.  17 A. Both the first and second actuators  43 A and  43 B become inoperative (step S 26 ), and the plate holder  41  is moved from the third position to the first position along the guide rails  42  and positioned there, as shown in FIG.  17 B. 
     Then, the actuators  61  become inoperative (step S 27 ), and the plate removal cover  55  closes the old plate removal port  62 . When the actuators  71  are operated (step S 28 ), the plate pushout members  70  project from the windows  64  of the stationary cover  57 , and the leading edge of the removed old plate P 1  is pushed by the plate pushout members  70  to the outside of the stationary cover  57 . The motor  87  is then driven in the reverse direction (step S 29 ) so that the safety cover  34  moves downward to close the front surface of the plate cylinder  20 . 
     The operator manually removes the old plate P 1  (step S 30 ), and turns off the plate catch button  83  (step S 31 ). Thus, the actuators  78  become inoperative (step S 32 ), and the plate catch  75  pivots to close the lower portion of the opening  58   a . Simultaneously, the actuators  71  become inoperative, and the plate pushout members  70  are stored in the stationary cover  57 . 
     The operation of exchanging the plate in the semi-automatic manner will be described with reference to FIGS. 10,  13 , and  18 A to  21 . 
     If the full-automatic plate mounting button  80  is not turned on but the semi-automatic plate mounting button  81  is turned on (step S 2  in FIG.  10 ), semi-automatic plate exchanging mode is selected. When the plate mounting start button  84  is turned on (step S 40 ), the motor  87  is driven in the forward direction (step S 41 ). Hence, from the closed state shown in FIG. 18A, the safety cover  34  moves upward, as shown in FIG. 18B, to open the front surface of the plate cylinder  20 . The plate cylinder  20  pivots in the reverse direction by a predetermined amount and stops (steps S 42  and S 43 ). After that, the actuator  89  is operated (S 44 ) to open the leading edge plate clamp  25  of the plate cylinder  20 , so that the gripped leading edge of the old plate P 1  is released. 
     When the plate cylinder  20  pivots in the reverse direction by a predetermined amount and stops (steps S 45  and S 46 ), the trailing edge plate clamp opening/closing actuator  90  is operated (step S 47 ) to open the trailing edge plate clamp  26  of the plate cylinder  20 , so that the gripped trailing edge of the old plate P 1  is released. When the plate cylinder  20  subsequently rotates in the reverse direction (step S 48 ), the trailing edge of the old plate P 1  is unfixed from the plate cylinder  20 , as shown in FIG.  19 A. Hence, the operator manually holds the trailing edge of the old plate P 1 , as shown in FIG.  19 B. When the plate cylinder  20  subsequently rotates in the reverse direction through  25  substantially one revolution and stops (step S 49 ), the leading edge of the old plate P 1  is also unfixed from the plate cylinder  20 . Thus, the operator manually removes the old plate P 1  (step S 50 ). 
     The operator then manually holds the new plate P 2  (step S 51 ), inserts it between the bottom clamping rail  25   a  and gripper board  25   b  of the leading edge plate clamp  25  of the plate cylinder  20 , as shown in FIG. 20A, and turns on the operation button  85  (step S 52 ). When the actuator  89  is operated (step S 53 ), the trailing edge of the new plate P 2  is gripped by the gripper board  25   b  and bottom clamping rail  25   a . When the operator turns on the operation button  85  again (step S 54 ), the plate cylinder  20  pivots in the forward direction by a predetermined amount, and stops, as shown in FIG. 20B (steps S 55  and S 56 ). 
     The trailing edge plate clamp actuator  90  is then operated (step S 57 ) to pivot a trailing edge cam shaft  26   c . The trailing edge of the new plate P 2  is thus gripped by the gripper board  26   b  and bottom clamping rail  26   a , and the new plate P 2  is set on the plate cylinder  20 . The motor  87  is then driven in the reverse direction (step S 58 ), so that the safety cover  34  moves downward to close the front surface of the plate cylinder  20 , as shown in FIG.  21 . 
     The functional block of the control unit  91  shown in FIG. 9 will now be described. The control unit  91  in FIG. 9 is comprised of a plate exchanging mode determination unit  91 A for determining one of the full- and semi-automatic plate exchanging modes as a selected mode in accordance with the operation of a corresponding one of the buttons  80  and  81 , a full-automatic plate mounting controller  91 B for executing the full-automatic plate exchanging mode selected by the plate exchanging mode determination unit  91 A, and a semi-automatic plate mounting controller  91 C for executing the semi-automatic plate exchanging mode selected by the plate exchanging mode determination unit  91 A. 
     The plate exchanging mode determination unit  91 A executes steps S 1  and S 2  in FIG.  10 . The full-automatic plate mounting controller  91 B executes steps S 5 , S 7  and S 9  to S 19  in FIG.  11  and steps S 20  to S 29  and S 32  in FIG.  12 . The semi-automatic plate mounting controller  91 C executes steps S 41  to S 49 , S 53 , and S 55  to S 58  in FIG.  13 . 
     In this embodiment, the present invention is applied to a sheet-fed rotary printing press for printing on sheet paper. The present invention can also be applied to a web rotary printing press for printing on a web. 
     In steps S 6  and S 8  in the full-automatic plate mounting process in FIG. 11, the plate catch button  83  and the plate mounting start button  84  are manually operated. However, in steps S 3  to S 5 , the buttons  83  and  84  need not be manually operated by arranging a detecting means for detecting that the new plate P 2  is held in the plate holder  41 . The flow automatically advances to the next step. As this detecting means, a photoelectric sensor for detecting that the new plate P 2  is held in the plate holder  41  or a pressure sensor for detecting a decrease in pressure of the suction pump  86  when the suction pads  45  draw the new plate P 2  by suction can be used. 
     Similarly, when this detecting means may be arranged, the plate mounting start button  84  need not be manually operated in step S 40  in the semi-automatic plate mounting process in FIG. 13, and the safety cover drive motor  87  can be automatically driven. 
     As has been described above, according to the present invention, the old plate is removed while being gripped by the operator in the semi-automatic plate mounting function process. The old plate will not contact other members during plate removal. The old plate will not be damaged or bent during plate removal, thereby allowing reuse of the old plate.