Printing apparatus having plate discharge mechanism with air blowing unit

A plate discharger includes a peeling claw, a transport device and an air blowing device. The transport device has a rotary shaft, first transport rollers rotatable about the rotary shaft, a driven rotary shaft connected to a drive gear meshed with and driven by a transmission gear disposed sideways from the first transport rollers, second transport rollers rotatable about the driven rotary shaft, peeling rollers pivotable about the rotary shaft, and belts wound around the first transport rollers and peeling rollers. When a printing plate is passed between the first transport rollers and second transport rollers, the air blowing device blows air to the undersurface of the printing plate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a printing apparatus having a plate discharge mechanism for transporting used printing plates mounted peripherally of a plate cylinder, and discharging the printing plates to a plate discharge station.

2. Description of the Related Art

A known printing apparatus having such a plate discharge mechanism includes transport rollers and transport belts for contacting opposite ends of used printing plates and transporting the printing plates from peripheries of a plate cylinder to a discharge station that stores the printing plates successively stacked one upon the other. This printing apparatus can reduce the space required for the plate discharge station.

However, ink and dampening water remain adhering to the surfaces of the printing plates used in printing. In such a printing apparatus, therefore, when used printing plates are discharged to the plate discharge station, a printing plate already stored in the plate discharge station contracts the ink and dampening water adhering to a next printing plate discharged to the plate discharge station. When such a phenomenon occurs, the viscosity of the ink and dampening water causes a cohesion between the printing plate already stored in the plate discharge station and the next printing plate discharged to the plate discharge station. The cohesion poses a problem of errors in transportation of the printing plates.

Japanese Unexamined Patent Publication No. 2003-266639 describes a printing apparatus including a clamp mechanism for pinching one end of each printing plate and drawing the printing plate. This construction prevents the errors in transportation of used printing plates, thereby reliably discharging the printing plates.

However, the printing apparatus described in the above publication requires the clamp mechanism for pinching an end of each printing plate, a moving mechanism for moving the clamp mechanism toward the plate discharge station from a position for pinching the end of the printing plate peeled from the plate cylinder, and an open/close mechanism for opening and closing the clamp mechanism in the position for pinching the end of the printing plate peeled from the plate cylinder and in the discharge station. Thus, the above printing apparatus is complicated in construction and is costly.

SUMMARY OF THE INVENTION

The object of this invention, therefore, is to provide a printing apparatus simple in construction, and yet capable of preventing errors in transportation of used printing plates.

The above object is fulfilled, according to this invention, by a printing apparatus having a plate discharge mechanism for removing used printing plates mounted peripherally of a plate cylinder from the plate cylinder, and discharging the printing plates to a plate discharge station that successively stores the printing plate as stacked one after another, the plate discharge mechanism comprising a transport device for passing the printing plates through a transport path disposed between the plate cylinder and the plate discharge station to discharge the printing plates to the plate discharge station, and an air blowing device for blowing air to an undersurface of each of the printing plates passing through the transport path.

This printing apparatus is simple in construction, and yet is capable of preventing errors in transportation of used printing plates.

In a preferred embodiment, the air blowing device is arranged to blow air at least to an undersurface in a forward region of each of the printing plates passing through the transport path.

The air blowing device may be arranged to blow air in a way to prevent a forward end of each of the printing plates from contacting a printing plate already stored in the plate discharge station.

In another aspect of the invention, the transport device includes a rotary shaft, a first transport roller rotatable about the rotary shaft, and having a larger diameter at opposite ends than in an intermediate portion thereof transversely of the printing plates, and a second transport roller rotatable synchronously with rotation of the first transport roller and arranged to pinch the printing plates with the first transport roller in portions of the printing plates between the opposite ends of the first transport roller.

Other features and advantages of the invention will be apparent from the following detailed description of the embodiments of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of this invention will be described hereinafter with reference to the drawings.FIG. 1is a schematic side view of a printing apparatus in a first embodiment of this invention.

This printing apparatus records images on printing plates mounted, two each, on first and second plate cylinders11and12in a prepress process, feeds inks to the plates having the images recorded thereon, and transfers the inks from the plates through blanket cylinders to printing paper held on impression cylinders15and16, thereby printing the images on the printing paper.

The printing apparatus has the first plate cylinder11, the second plate cylinder12, a plate feeder100for feeding printing plates to be mounted on the peripheral surface of the first plate cylinder11, a plate feeder200for feeding printing plates to be mounted on the peripheral surface of the second plate cylinder12, a plate discharger300for removing used printing plates from the peripheral surface of the first plate cylinder11and discharging the printing plates to a plate discharge cassette301, a plate discharger400for removing used printing plates from the peripheral surface of the second plate cylinder12and discharging the printing plates to a plate discharge cassette401, a first blanket cylinder13contactable with the first plate cylinder11, a second blanket cylinder14contactable with the second plate cylinder12, the first impression cylinder15contactable with the first blanket cylinder13, and the second impression cylinder16contactable with the second blanket cylinder14. The printing apparatus further includes a paper feed cylinder17for transferring printing paper supplied from a paper storage station31to the first impression cylinder15, a transfer cylinder18for transferring the printing paper from the first impression cylinder15to the second impression cylinder16, and a paper discharge cylinder19disposed adjacent the second impression cylinder16.

The first impression cylinder15movable into contact with the first blanket cylinder13has half the diameter of the first plate cylinder11and first blanket cylinder13. The second impression cylinder16movable into contact with the second blanket cylinder14has half the diameter of the second plate cylinder12and second blanket cylinder14. The first and second impression cylinders15and16have grippers, not shown, for holding and transporting the forward end of printing paper.

The paper feed cylinder17disposed adjacent the first impression cylinder15has the same diameter as the first impression cylinder15. The paper feed cylinder17has a gripper, not shown, for holding and transporting the forward end of each sheet of printing paper successively fed from the paper storage station31. When the printing paper is transferred from the feed cylinder17to the first impression cylinder15, the gripper of the first impression cylinder15holds the forward end of the printing paper which has been held by the gripper of the feed cylinder17.

The transfer cylinder18disposed between the first impression cylinder15and second impression cylinder16has the same diameter as the first and second plate cylinders11and12and the first and second blanket cylinders13and14. The transfer cylinder18has a gripper, not shown, for holding and transporting the forward end of the printing paper received from the first impression cylinder15, and transferring the forward end of the printing paper to the gripper of the second impression cylinder16.

The paper discharge cylinder19disposed adjacent the second impression cylinder16has the same diameter as the first and second plate cylinders11and12and the first and second blanket cylinders13and14. The discharge cylinder19has a pair of chains wound around opposite ends thereof. The chains are interconnected by coupling members, not shown, having grippers arranged thereon. When the second impression cylinder16transfers the printing paper to the discharge cylinder19, one of the grippers on the discharge cylinder19holds the forward end of the printing paper having been held by the gripper of the second impression cylinder16. With movement of the chains, the printing paper is transported to a paper discharge station32to be discharged thereon.

The first and second impression cylinders15and16, paper feed cylinder17, paper discharge cylinder19and first and second blanket cylinders13and14are interlocked to one another through gears attached to ends thereof, respectively. Further, the first blanket cylinder13and first plate cylinder11are interlocked to each other, and the second blanket cylinder14and second plate cylinder12are interlocked to each other, through gears attached to ends thereof, respectively. Thus, the first and second plate cylinders11and12, first and second impression cylinders15and16, paper feed cylinder17, paper discharge cylinder19and first and second blanket cylinders13and14are synchronously rotatable by a drive motor.

The first plate cylinder11is surrounded by an ink feeder20afor feeding an ink of black (K), for example, to a printing plate mounted peripherally of the first plate cylinder11, an ink feeder20bfor feeding an ink of magenta (M), for example, to a printing plate mounted peripherally of the first plate cylinder11, a dampening water feeder21afor feeding dampening water to areas of the printing plate to which the ink is to be fed from the ink feeder20a, and a dampening water feeder21bfor feeding dampening water to areas of the printing plate to which the ink is to be fed from the ink feeder20b. The second plate cylinder12is surrounded by an ink feeder20cfor feeding an ink of cyan (C), for example, to a printing plate mounted peripherally of the second plate cylinder12, an ink feeder20dfor feeding an ink of yellow (Y), for example, to a printing plate mounted peripherally of the second plate cylinder12, a dampening water feeder21cfor feeding dampening water to areas of the printing plate to which the ink is to be fed from the ink feeder20c, and a dampening water feeder21dfor feeding dampening water to areas of the printing plate to which the ink is to be fed from the ink feeder20d.

Further, arranged around the first and second plate cylinders11and12are the plate feeder100for feeding plates stored in a storage cassette41to the peripheral surface of the first plate cylinder11, the plate feeder200for feeding plates stored in a storage cassette43to the peripheral surface of the second plate cylinder12, an image recorder35for recording images on the plates mounted peripherally of the first plate cylinder11, an image recorder36for recording images on the plates mounted peripherally of the second plate cylinder12, the plate discharger300for removing used printing plates P from the peripheral surface of the first plate cylinder11and discharging the printing plates P to the plate discharge cassette301, and the plate discharger400for removing used printing plates P from the peripheral surface of the second plate cylinder12and discharging the printing plates P to the plate discharge cassette401.

A blanket cylinder cleaning device700and a blanket cylinder cleaning device800are arranged around the first blanket cylinder13and second blanket cylinder14, respectively, for cleaning these blanket cylinders13and14.

The plate feeder100extends between the storage cassette41for storing a printing plate stock in rolled form, and the first plate cylinder11. The plate feeder100includes a cutter42for cutting the printing plate stock to a predetermined length, and a guide mechanism having a guide plate and transport rollers for transporting printing plates from the storage cassette41to the first plate cylinder11. The plate feeder200extends between the storage cassette43for storing a printing plate stock in rolled form, and the second plate cylinder12. The plate feeder200includes a cutter44for cutting the printing plate stock to a predetermined length, and a guide mechanism having a guide plate and transport rollers for transporting printing plates from the storage cassette43to the second plate cylinder12. Each guide mechanism includes a support member135(FIG. 8), a presser601(FIG. 8) disposed on the support member135for pressing each printing plate to the peripheral surface of the first or second plate cylinder11or12immediately before the printing plate is clamped by a forward end clamp mechanism50, and a presser moving mechanism600(FIG. 8) for moving the presser601between a position for contacting the peripheral surface of the first or second plate cylinder11or12and a position spaced from the peripheral surface of the first or second plate cylinder11or12.

FIG. 2is a perspective view showing forward end clamp mechanisms50and rear end clamp mechanisms70arranged on the first or second plate cylinder11or12.FIG. 3is a front view showing one of the forward end clamp mechanisms50and one of the rear end clamp mechanisms70.

Each of the first and second plate cylinders11and12has forward end clamp mechanisms50for holding the forward ends of printing plates supplied by the plate feeder100or200, and rear end clamp mechanisms70for holding the rear ends of the printing plates. In the printing apparatus in this embodiment, as noted hereinbefore, two printing plates are mounted peripherally of each of the first and second plate cylinders11and12. Thus, each of the first and second plate cylinders11and12has two forward end clamp mechanisms50and two rear end clamp mechanisms70. The forward end clamp mechanisms50are 180 degrees spaced from each other, and so are the rear end clamp mechanisms70.

Each forward end clamp mechanism50includes a forward end clamp59, a clamp seat60and a forward end clamp opening and closing device. Each rear end clamp mechanism70includes a rear end clamp79, a clamp seat80, a rear end clamp opening and closing device, a stretching device and a pop-up device (FIG. 6). Each of the forward end clamp opening and closing device and the rear end clamp opening and closing device has one air cylinder55or75mounted on an end surface of the first or second plate cylinders11or12.

FIG. 4is an explanatory view of a section taken on line A—A ofFIG. 3.FIG. 5is an explanatory view of a section taken on line B—B ofFIG. 3.FIG. 6is an explanatory view of a section taken on line C—C ofFIG. 3.

The forward end clamp opening and closing device of each forward end clamp mechanism50includes an air cylinder55acting as a drive source, a pin51for fixing the proximal end of the air cylinder55to the end surface of the first or second plate cylinder11or12, a link56having an end pivotally connected by a pin52to a cylinder rod of the air cylinder55, a shaft53fixed to the other end of the link56and extending axially of the first or second plate cylinder11or12, a transmission gear57fixed to the shaft53, a drive gear58meshed with the transmission gear57, a shaft54having the drive gear58fixed thereto and extending axially of the first or second plate cylinder11or12, and brackets61for fixedly connecting the shaft54and forward end clamp59.

As shown inFIGS. 3 and 5, transmission gears57and77and drive gears58and78are arranged in a substantially middle region axially of the first or second plate cylinder11or12. Thus, drive is transmitted to substantially middle regions of the forward end clamp59and rear end clamp79. This arrangement can reduce a disagreement, axially of the first or second plate cylinder11or12, in the timing of driving the forward end clamp59and rear end clamp79. Though simple in construction, this allows the printing plates to be attached without being displaced axially of the first or second plate cylinder11or12. Elastic elements85are mounted on a shaft74for biasing the rear end clamp79toward the clamp seat80. Thus, even when the air cylinder75fails to function properly in time of recording an image, the rear end clamp79may be fixed to a position for contacting the clamp seat80. The same construction may be employed also for the forward end clamp59.

The forward end clamp opening and closing device is set such that, when the cylinder rod of the air cylinder55is extended, the forward end clamp59is positioned to contact the clamp seat60as shown in solid lines inFIGS. 4 and 5. When the cylinder rod of the air cylinder55is contracted from this state, the link56swings about the shaft53and rotates the shaft53. As a result, the transmission gear57fixed to the shaft53rotates counterclockwise inFIG. 5. With this rotation of the transmission gear57, the drive gear58meshed with the transmission gear57rotates clockwise inFIG. 5. This rotation of the drive gear58is transmitted to the forward end clamp59through the shaft54and brackets61. Consequently, the forward end clamp59is moved away from the clamp seat60as shown in two-dot chain lines inFIGS. 4 and 5.

The rear end clamp opening and closing device of each rear end clamp mechanism70includes an air cylinder75acting as a drive source, a pin71for fixing the proximal end of the air cylinder75to the end surface of the first or second plate cylinder11or12, a link76having an end pivotally connected by a pin72to a cylinder rod of the air cylinder75, a shaft73fixed to the other end of the link76and extending axially of the first or second plate cylinder11or12, a transmission gear77fixed to the shaft73, a drive gear78meshed with the transmission gear77, a shaft74having the drive gear78fixed thereto and extending axially of the first or second plate cylinder11or12, and brackets81for fixedly connecting the shaft84and rear end clamp79. The shafts53,54and73are arranged by the same brackets62in predetermined positions of the first or second plate cylinder11or12.

The rear end clamp opening and closing device is set such that, when the cylinder rod of the air cylinder75is extended, the rear end clamp79is positioned to contact the clamp seat80as shown in solid lines inFIGS. 4 and 5. When the cylinder rod of the air cylinder75is contracted from this state, the link76swings about the shaft73and rotates the shaft73. As a result, the transmission gear77fixed to the shaft73rotates clockwise inFIG. 5. With this rotation of the transmission gear77, the drive gear78meshed with the transmission gear77rotates counterclockwise inFIG. 5. This rotation of the drive gear78is transmitted to the rear end clamp79through the shaft74and brackets81. Consequently, the rear end clamp79is moved away from the clamp seat80as shown in two-dot chain lines inFIGS. 4 and 5.

The stretching device of the rear end clamp mechanism70includes the shaft73, and a fixing member, not shown, for fixing the shaft73, shaft74and clamp seat80. The fixing member is rotatably supported by the shaft73. When the shaft73rotates after the rear end clamp79contracts the clamp seat80, the fixing member rotates about the shaft73counterclockwise inFIG. 5, with the rear end clamp79contacting the clamp seat80. As a result, the rear end of the printing plate pinched between the rear end clamp79and clamp seat80also rotates counterclockwise, whereby the printing plate is stretched.

As shown inFIG. 6, the pop-up device of the rear end clamp mechanism70includes pop-up elements82, and pop-up element moving mechanisms83for moving the pop-up elements82between a depressed position having distal ends thereof disposed inwardly of the peripheral surface of the first or second plate cylinder11or12as shown in a solid line inFIG. 6, and a protruding position having the distal ends disposed outwardly of the peripheral surface of the first or second plate cylinder11or12as shown in a two-dot chain line inFIG. 6. Each pop-up element moving mechanism83includes the shaft74, a pin84attached to the shaft74, and an elastic element86(FIG. 3) for biasing the pop-up element82toward the depressed position.

FIG. 7is an explanatory view showing a principal portion of the pop-up device in enlargement.

The illustrated pop-up element82defines a recess82ashaped to correspond to the pin84. When the rear end clamp79is in the position for contacting the clamp seat80as shown in solid lines inFIG. 7and the pin84is placed in a position84aat an extreme end of the recess82ain the clockwise wise direction inFIG. 7, the rear end clamp79is also rotated about the shaft74to a position A inFIG. 7. In this state, the pop-up element82is placed in the depressed position by the biasing force of elastic element86(FIG. 3). When the shaft74rotates counterclockwise, the pin84is moved to a position84bat the other extreme end of the recess82a. When, in this state, the shaft74rotates further, the pop-up element82is pressed by the pin84counterclockwise to a protruding position shown in two-dot chain lines inFIG. 7. At this time, the rear end clamp79rotates further about the shaft74to a position B inFIG. 7.

The angle about the shaft74between the position84aand position84bis 22 degrees. The angle about the shaft74between the position84band position84cis 20 degrees. Until the rear end clamp79rotates 22 degrees about the shaft74from the position contacting the clamp seat80, the pop-up element82remains in the depressed position. With a further rotation of the shaft74after the pin84is placed in the position84b, the rear end clamp79is rotated 20 degrees along with the pop-up element82about the shaft74.

FIG. 8is an explanatory side view showing the presser601and presser moving mechanism600of the guide mechanism for guiding printing plates to the first or second plate cylinder11or12.

The presser601has a function for assisting the forward end clamp mechanism50in an operation for clamping the printing plates. The presser601is constructed to press each printing plate transported from the storage cassette43upon the peripheral surface of the first or second plate cylinder11or12immediately before the printing plate is clamped by the forward end clamp mechanism50.

The presser moving mechanism600includes an air cylinder606acting as a drive source, a pin605attached to a cylinder rod of the air cylinder606, an arm604defining a slot604afor engaging the pin605, a rotary shaft603for supporting the arm604to be pivotable relative to the support member135of the plate feeder100, and an arm602connecting the rotary shaft603and presser601. With this construction, when the cylinder rod of the air cylinder606is contracted, the presser601is placed in the position spaced from the peripheral surface of the first or second plate cylinder11or12as shown inFIG. 8. When the cylinder rod of the air cylinder606is extended, the presser601is moved to the position contacting the peripheral surface of the first or second plate cylinder11or12.

In the printing apparatus with the guide mechanism having the above construction, when attaching a printing plate to the peripheral surface of the first or second plate cylinder11or12, the forward end of the printing plate is first transported to the forward end clamp mechanism50of the first or second plate cylinder11or12. The forward end of the printing plate is inserted between the forward end clamp59and clamp seat60, with the forward end clamp59being in the position away from the clamp seat60. When the forward end of the printing plate has been inserted between the forward end clamp59and clamp seat60, the presser moving mechanism600moves the presser601to the position for contacting the peripheral surface of the first or second plate cylinder11or12. As a result, the printing plate is pinched between the first or second plate cylinder11or12and the presser601. In this state, the forward end clamp59is moved to the position to contact the clamp seat60and pinch the forward end of the printing plate with the clamp seat60. Once the forward end of the printing plate is pinched between the forward end clamp59and clamp seat60, the presser601is moved away from the peripheral surface of the first or second plate cylinder11or12.

With the forward end of the printing plate held by the forward end clamp mechanism50as described above, the printing plate may be attached without being displaced.

FIG. 9is a side view of the plate discharger400of the printing apparatus in the first embodiment.FIG. 10is a plan view of the plate discharger400. The plate discharger300has the same construction as the plate discharger400, and its description will be omitted.

This plate discharger400includes a peeling claw411, a transport device for discharging a printing plate P peeled by the peeling claw411to the plate discharge cassette401, and an air blowing device430for blowing air to the undersurface of the printing plate P passing through a transport path.

The transport device transports and discharges the printing plate P to the plate discharge cassette401through the transport path extending between the second plate cylinder12and plate discharge cassette401. The transport device includes a rotary shaft421, first transport rollers422rotatable on the rotary shaft421, a driven rotary shaft423disposed laterally of the first transport rollers422, second transport rollers424rotatable on the driven rotary shaft423, peeling rollers426rotatable on a rotary shaft425, and belts427wound around the first transport rollers422and peeling rollers426. The driven rotary shaft423is connected to a drive gear, not shown, rotatably meshed with a transmission gear not shown.

The first transport rollers422and second transport rollers424are arranged adjacent each other for pinching the printing plate P therebetween. The rotary shaft421is connected to a motor428through a gear421ato be rotatable with rotation of the motor428. The rotation of this rotary shaft421rotates the first transport rollers422which in turn rotates the driven rotary shaft423and second transport rollers424through the transmission gear and drive gear.

Of the first transport rollers422arranged in the direction of width of the printing plate P (in the vertical direction inFIG. 10), the end rollers422bhave a larger diameter than the middle roller422a. The second transport rollers424are arranged between the first transport rollers422(i.e. inwardly of the first transport rollers422b) for contacting transversely intermediate positions of the printing plate P. Consequently, the printing plate P can be transported as curved into a U- or V-shape when seen from the direction of arrow A inFIG. 10. The printing plate P is thereby maintained firm, with the forward end thereof prevented from drooping.

The rotary shaft421and rotary shaft425are fixed by links441. These links441are connected to the cylinder rod of an air cylinder506(FIG. 12). The rotary shaft425, peeling rollers426and belts427are pivotable about the rotary shaft421by extension and contraction of the air cylinder506.

The peeling claw411is provided for peeling off the printing plate P mounted peripherally of the second plate cylinder12. The peeling claw411is fixed to the links441, to be pivotable with the links441about the rotary shaft421by extension and contraction of the air cylinder506.

Thus, the peripheries of the peeling rollers426and the forward end of the peeling claw411are pivotable about the rotary shaft421between a position adjacent the second plate cylinder12as shown in solid lines inFIG. 9and a position spaced away from the second plate cylinder12as shown in two-dot chain lines inFIG. 9. In this way, the peeling device is prevented from interfering with the printing plates mounted on the plate cylinders during a printing or platemaking operation.

The air blowing device430is arranged to blow air to the undersurface of the printing plate P in positions downstream of the first transport rollers422and second transport rollers424with respect to the direction in which of the printing plate P is transported by the transport device. The air blowing device430includes a compressor507(FIG.12) acting as an air source, and air nozzles431connected to the compressor507.

A side wall90is disposed between the first and second transport rollers422and424, and the plate discharge cassette401. The plate discharge cassette401is fixed to the side wall90. The side wall90defines an opening91for passage of the printing plate P.

FIG. 11is an explanatory view showing a state of air being blown from the air nozzles431to the printing plate P to be discharged to the plate discharge cassette401. InFIG. 11, the dotted line shows a state where air is not blown from the air nozzles431to the printing plate P.

The air nozzles431are arranged to have tip ends lying downstream in the direction of transport of the printing plate P, and directed slightly upward. The air nozzles431blow air in directions indicated by arrows inFIGS. 9,10and11to the undersurface of the printing plate P to be discharged to the plate discharge cassette401. The air applies a lifting force to the undersurface of the printing plate P to be discharged. Thus, when air is blown from the air nozzles431, the forward end of the printing plate P touches down further downstream in the direction of transport of the printing plate P than when air is not blown from the air nozzles431. Consequently, the printing plate P discharged to the plate discharge cassette401has a reduced range of contact with a printing plate already stored in the plate discharge cassette401.

FIG. 12is a block diagram showing a principal electrical structure of the plate discharger400. This plate discharger400includes a control unit500having a ROM501for storing operating programs necessary for controlling the discharger, a RAM502for temporarily storing data and the like during a control operation, and a CPU503. The control unit500generates driving signals and applies the signals through an interface504to the motor428for rotating the rotary shaft421, the air cylinder506acting as the power source for swinging the peeling rollers426, the compressor507acting as the air source for the air blowing device430, and a regulator508.

The regulator508is provided for adjusting a flow rate of air spouted from the compressor507. By operating the regulator508, the flow rate of air blown from the air nozzles431may be adjusted according to the size, weight, flexibility, discharge speed and so on of the printing plate P. With the above construction, the plate discharger400is controlled by the control unit500.

FIGS. 13A and 13Bare explanatory views showing a state of the printing plate P being peeled from the peripheral surface of the second plate cylinder12.

The plate discharger400having the above construction detaches used printing plates P mounted peripherally of the second plate cylinder12from the second plate cylinder12and discharges the printing plates P to the plate discharge cassette401which stores the printing plates P as successively stacked one upon the other. First, as shown inFIG. 13A, the pop-up element82described hereinbefore is set to the protruding position shown in the two-dot chain lines inFIGS. 6 and 7. As a result, an end of the printing plate P is ejected off the peripheral surface of the second plate cylinder12.

As the second plate cylinder12rotates in the direction indicated by an arrow inFIG. 13A, the end of the printing plate P ejected enters between the peeling claw411and belts427. At this time, the rotary shaft421is rotated by the motor428. The rotation of the rotary shaft421rotates the first transport rollers422, which in turn rotates the second transport rollers424. The rotation of the first transport rollers422swings the belts427. Consequently, the end of the printing plate P is transported in the direction of the first transport rollers422and second transport rollers424. As shown inFIG. 13B, the printing plate P is pinched between and transported by the first transport rollers422and second transport rollers424. As the printing plate P passes between the first transport rollers422and second transport rollers424, the air blowing device430shown inFIGS. 9 and 10blows air to the undersurface of the printing plate P. This applies a lifting force to the printing plate P upward inFIG. 9. The undersurface of the printing plate P can possibly avoid contact with the surface of a printing plate already placed in the plate discharge cassette401. Thus, the surface tension of ink and water adhering to the undersurface of the printing plate P produced through contact with another printing plate is reduced, thereby avoiding errors in transportation of the printing plate P.

When the printing plate P has been discharged to the plate discharge cassette401, the air cylinder506is contracted to swing the rotary shaft425, peeling rollers426and belts427about the rotary shaft421. As a result, the peripheries of the peeling rollers426and the forward end of the peeling claw411move to the position spaced away from the second plate cylinder12as shown in the two-dot chain lines inFIG. 9. Thus, the peeling device is prevented from interfering with a next printing plate P, if any, mounted peripherally of the second plate cylinder12.

FIG. 14is an explanatory view, seen from the direction of arrow A inFIG. 10, showing first transport rollers422and second transport rollers424in a printing apparatus in a second embodiment of this invention.

In the first embodiment, the first transport rollers422arranged in the direction perpendicular to the direction of transport of the printing plate P include end rollers422bhaving a larger diameter than the middle roller422a. The second embodiment further includes push-up elements422carranged at ends of the first transport rollers422bto act as a push-up device for pushing up the printing plate P. The push-up elements422care rotatable about the same rotary shaft421as the first transport rollers422aand422b. The printing plate P transported by the first transport rollers422and second transport rollers424is held inwardly of the push-up elements422c.

According to the printing apparatus in the second embodiment, the printing plate P can be transported as curved into a U- or V-shape as shown in a two-dot chain line inFIG. 14. This is effective to reduce drooping of the forward end of printing plate P.

While the push-up elements422cin the second embodiment described above are rotatable about the same rotary shaft421as the first transport rollers422aand422b, the apparatus may be modified such that the push-up elements422care rotatable about a different rotary shaft disposed in substantially the same position as or downstream of the first transport rollers422aand422bwith respect to the direction of transport of the printing plate P. The push-up elements422cwill serve the purpose as long as these elements422chave the function to push up ends of the printing plate P in substantially the same position as or downstream of the first transport rollers422aand422bwith respect to the direction of transport of the printing plate P, and may be fixed directly to a side wall or the like of the printing apparatus.

In the embodiments described hereinbefore, the first transport rollers422bhave a larger diameter than the first transport roller422a. Instead, the first transport rollers422aand422bmay have the same diameter.

In the embodiments described hereinbefore, the second transport rollers424are rotatable by rotation of the first transport rollers422. It is not absolutely necessary for the second transport rollers424to be rotatable by rotation of the first transport rollers422. The second transport rollers424will serve the purpose as long as they are rotatable synchronously with the first transport rollers422.

This application claims priority benefit under 35 U.S.C. Section 119 of Japanese Patent Application No. 2004-129347 filed in the Japanese Patent Office on 26 Apr. 2004, the entire disclosure of which is incorporated herein by reference, and Japanese Patent Application No. 2005-005826 filed in the Japanese Patent Office on 13 Jan. 2005, the entire disclosure of which is incorporated herein by reference.