Supplying device for planographic printing plates

Abstract

 A planographic printing plate supplying device comprises: a discharging device 42 that pulls out an uppermost planographic printing plate 20, from a plate stack 18 in which at least multiple planographic printing plates 20 are stacked in a layered state, by pulling on the surface of the uppermost planographic printing plate 20 with the force of friction, and a sloped leading edge guide 100 arranged so as to adjoin the downstream side in the direction in which the uppermost planographic printing plate 20 pulled out with the discharging device 42 is conveyed, the sloped leading edge guide 100 comprising a separating guide slope 102 inclined at a slant from bottom to top from the upstream side in the conveying direction to the downstream side. The uppermost planographic printing plate 20 pulled out by the discharging device 42 is pulled out with a planographic printing plate 20 layered underneath, the leading edge of the planographic printing plate 20 layered underneath the uppermost planographic printing plate 20 is stopped by the separating guide slope 102, and the leading edge of the uppermost planographic printing plate 20 is guided by the separating guide slope 102 whereby it is separated and discharged.

Description

BACKGROUND OF THE INVENTION

Technical Field

[0001] The present invention relates to a device for supplying planographic printing plates by separating planographic printing plates one at a time from a stack of multiple layered plates and discharging them.

Description of the Related Art

[0002] Planographic printing plates are generally used in offset printing. In the field of planographic printing plates, a photosensitive planographic printing plate is laser exposed based on the digital data of a device such as a computer, and a latent image formed on the planographic printing plate is converted to a visible image by developing with an automated developer. This type of computer-to-plate (CTP) system that produces direct printing plates has been widely put into practical use.

[0003] The planographic printing plates used in this type of CTP system include what are known as photosensitive planographic printing plates (also known as "PS plates") where a photosensitive layer such as a photo-polymerized (i.e., radical polymerized) layer is formed on the surface of a substrate made from a material such as aluminum.

[0004] CTP systems using these PS plates layer a protective slip sheet on the photosensitive layer of the PS plate followed by another PS plate, such that protective slip sheets are layered in order between the plates on the photosensitive layers thereof. A plate stack of multiple sets of PS plates and protective slip sheets layered on the photosensitive layers thereof is set in a PS plate supplying device. A sheet supplying device separates a set each of PS plate layered with a slip sheet, and further disposes of the slip sheet. The device is made so as to discharge only the PS plates to the next processing step one at a time.

[0005] Conventional technologies teach that the sheet supplying device used in this type of CTP system is provided with special slip sheet rollers that turn and contact the slip sheets and remove them with a sending carrying means. The planographic printing plate is suctioned with a vacuum pad and then lifted and moved, after which it is mounted on a conveying route. The suction of the vacuum pad is released and the plate is sent with the carrying means. (See, for example, the Official Gazette of Japanese Patent Application No. 60-202028.)

[0006] When utilizing the sheet supplying device proposed in this type of conventional device, the carrying means using the vacuum pad that catches the PS plate and the carrying means using rollers to catch the slip sheet are operated separately, so the next planographic printing plate cannot be removed until after the slip sheet has been removed. The operation of supplying one PS plate at a time takes time, thus making the process inefficient. Further, this configuration is problematic in that separate carrying means are necessary for carrying the PS plate and the slip sheet. The structure of the device becomes complicated, thus increasing both the size and cost of the device.

[0007] Here, the carrying rollers are made to turn in contact with the surface of the uppermost PS plate on the plate stack of PS plates, and the uppermost PS plate and the slip sheet below it are made into one set and carried (i.e., sent layered together). A state of vacuum adherence occurs between this set of the uppermost PS plate and slip sheet and the set of the PS plate and slip sheet layered beneath them. It has been discovered that there is a problem in that, in this state, when air enters between these sets and a further lower set of another PS plate and slip sheet layered beneath them, multiple sets of PS plates and slip sheets are simultaneously carried (i.e., multiple sets are sent together).

SUMMARY OF THE INVENTION

[0008] The present invention was made in light of the above-described problems, and proposes a new type of planographic printing plate supplying device that has a simple configuration and which can separate and carry one planographic printing plate at a time.

[0009] The planographic printing plate supplying device of a first aspect if the present invention comprises: a discharging device that pulls out an uppermost planographic printing plate, from a plate stack in which at least multiple planographic printing plates are stacked in a layered state, by pulling on the surface of the uppermost planographic printing plate with the force of friction; and a sloped leading edge guide arranged so as to adjoin the downstream side in the direction in which the uppermost planographic printing plate pulled out with the discharging device is conveyed, the sloped leading edge guide comprising a separating guide slope inclined at a slant from bottom to top from the upstream side in the conveying direction to the downstream side. When the uppermost planographic printing plate pulled out by the discharging device is pulled out and discharged with a planographic printing plate layered underneath, the leading edge of the planographic printing plate layered underneath the uppermost planographic printing plate is stopped by the separating guide slope; and the leading edge of the uppermost planographic printing plate is guided by the separating guide slope whereby it is separated and discharged.

[0010] By configuring the device as described above, when a planographic printing plate layered and adhered underneath the uppermost planographic printing plate that has begun to be carried hits against the separating guide slope, the carrying action relative to the planographic printing plate underneath the uppermost plate stops. Furthermore, when the uppermost planographic printing plate is conveyed, the leading edge of the uppermost planographic printing plate along the separating guide slope in the conveying direction elastically deforms while moving so as to raise in the direction perpendicular to the conveying direction (i.e., the widthwise direction). That is, the curved surfaces of the uppermost planographic printing plate and the planographic printing plate layered underneath flex at different curvatures. A space opens between the respective leading edges of the plates and air is allowed to enter inside between them so the state of vacuum adherence between the two is broken and the plates separate, whereby the sending of multiple layers can be prevented. Accordingly, the occurrence of simultaneous conveyance of the uppermost planographic printing plate and the planographic printing plate layered underneath, and jamming due to such conveyance, can be effectively suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] 

FIG 1 is an outline perspective drawing of a CTP system provided with the planographic printing plate supplying device of an embodiment of the present invention;

FIG 2 is an outline explanatory drawing showing the structure of the main portions of the planographic printing plate supplying device of an embodiment of the present invention;

FIG 3 is an outline perspective drawing of the structure of the main portions of the planographic printing plate supplying device of an embodiment of the present invention;

FIG 4 is a main portion outline explanatory drawing for explaining the operational principle of the planographic printing plate supplying device of an embodiment of the present invention showing a state where a planographic printing plate is starting to be pulled out;

FIG 5 is a main portion outline explanatory drawing for explaining the operational principle of the planographic printing plate supplying device of an embodiment of the present invention showing a state where layered planographic printing plates are starting to be separated;

FIG 6 is a main portion outline explanatory drawing for explaining the operational principle of the planographic printing plate supplying device of an embodiment of the present invention showing a state where layered planographic printing plates are finishing being separated;

FIG 7 is a main portion outline explanatory drawing for explaining the operational principle of the planographic printing plate supplying device of an embodiment of the present invention showing a state where layered planographic printing plates are finished being separated;

FIG 8 is a main portion outline explanatory drawing for explaining the operational principle of the planographic printing plate supplying device provided with the elastic support bracket of an embodiment of the present invention showing a state where a planographic printing plate is starting to be pulled out;

FIG 9 is a main portion outline explanatory drawing for explaining the operational principle of the planographic printing plate supplying device provided with the elastic support bracket of an embodiment of the present invention showing a state where layered planographic printing plates are starting to be separated;

FIG 10 is a main portion outline explanatory drawing for explaining the operational principle of the planographic printing plate supplying device provided with the elastic support bracket of an embodiment of the present invention showing a state where layered planographic printing plates are finishing being separated;

FIG 11 is a main portion outline explanatory drawing for explaining the operational principle of the planographic printing plate supplying device provided with the elastic support bracket of an embodiment of the present invention showing a state where layered planographic printing plates are finished being separated;

FIG 12 is a main portion outline explanatory drawing for explaining the operational principle of the separating guide slope in the planographic printing plate supplying device of an embodiment of the present invention where the guide slope has a width greater than the side widths of the largest sized planographic printing plate; and

FIG 13 is a main portion outline explanatory drawing showing a comparative example of a separating guide slope in the planographic printing plate supplying device of an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0012] Examples of the embodiments relating to the planographic printing plate supplying device of the present invention will be explained using FIGS. 1 - 13. The planographic printing plate supplying device of the present embodiment can be favorably used with a CTP system that produces direct printing plates where: offset printing photosensitive planographic printing plates (i.e., PS plates) are used as the recording medium; laser exposure processing is performed based on digital data from a device such as a computer; and developing processing is performed where a latent image formed on a photosensitive planographic printing plate is converted to a clear image with an automated developer.

[0013] The overall structure of a CTP system provided with the planographic printing plate supplying device of the present embodiment is shown in FIG 1. This CTP system is provided with a sending unit 200 that is detachably connected to a planographic printing plate mounting unit configured as a cart; a sheet-supplying device 202 that separates one planographic printing plate (i.e., recording medium) at a time from PS plates mounted on the mounting unit; an inner drum exposure device 204; a buffer device 206; and a developing processor 208.

[0014] The recording medium that is to undergo exposure processing in this CTP system can be, for example, a PS plate having an image-recording layer including a photosensitive material formed on a thin aluminum plate. Another option is to use a planographic printing plate 20 as a photopolymer plate or a silver salt-type photosensitive material.

[0015] As shown in FIG 4, this CTP system layers and arranges slip sheets 22 on the photosensitive surfaces of the planographic printing plates 20 in order to protect those surfaces, so a plate stack 18 comprises alternately layered planographic printing plates 20 and slip sheets 22. It should be noted that the plate stack 18 can comprise only planographic printing plates 20 in a state where these are layered on each other.

[0016] As shown in FIG 2, the plate stack 18 comprising a preset number of planographic printing plates 20 stacked together is set on a mounting unit 14 that is configured as a cart. This CTP system is configured so that the mounting unit 14 on which the plate stack 18 is set is connected to the sending unit 200. The system is designed so that the planographic printing plates 20 can be separated one by one from the plate stack 18 by the sheet-supplying device 202 and supplied to the inner drum exposure device 204.

[0017] The portions of the sending unit 200 and the sheet-supplying device 202 shown in FIG 2 are such that, with the mounting unit 14 set so as to be detachably connected, the plate stack 18 is arranged so that the photosensitive surfaces of the planographic printing plates 20 face upwards. These are set in a state where the slip sheet 22 protecting the photosensitive surface of the uppermost planographic printing plate 20 has been removed.

[0018] The mounting unit 14 formed as a cart is provided with a carriage 26, on which a stand setting unit is arranged where the plate stack 18 is mounted. Casters 28 are attached to this carriage 26, thus making the entire mounting unit 14 movable.

[0019] As shown in FIG 3, the stand setting unit on the mounting unit 14 is configured as a flat four-cornered mounting tray 30. Two side edge guide panels 32 and one rear edge guide panel 34 are attached to this mounting tray 30. The side edge guide panels 32 slide in the directions of the W arrows with slide mechanisms (not shown) so that these can match the size of the planographic printing plates 20 and be positioned along the side surfaces of the plate stack 18. The rear edge guide panel 34 slides in the direction of the F arrow (and in the direction opposite thereto) with a slide mechanism, also not shown, and the rear edge guide panel 34 is positioned along the rear edge of the plate stack 18.

[0020] As shown in FIG 2, a cover 36 configured so as to cover the perimeter of the mounted plate stack 18 is provided at the mounting unit 14. An opening/closing cover 36A is attached to the cover 36 with a hinge 38 at the downstream portion in the conveying direction of the plate stack 18. This is configured such that when the portion of the opening/closing cover 36A is connected so as to be inserted into the interior of the sending unit 200, the upper portion is pressed and operated by a pressing component (not shown) so as to pop up such that the door is in an open state.

[0021] As shown in FIG 3, a holder 40 is set along the widthwise direction of the planographic printing plate 20 at an upper position of the set mounting unit 14 at a portion where the mounting unit 14 of the sending unit 200 is detachably connected.

[0022] A pick-up roller 42 made from a rubber roller that acts as a discharging device that pulls on the top surface of the uppermost planographic printing plate 20 of the plate stack 18 with friction force is set such that it can turn and contact the upper surface of the plate stack 18 mounted on the mounting unit 14.

[0023] Driving force from a drive motor 44 is conveyed to this pick-up roller 42 via an endless belt 46, and the pick-up roller 42 is turned in the direction indicated with the J arrow. The pick-up roller 42 turned in this manner performs an operation where it conveys the planographic printing plate 20 or the slip sheet 22 in the sending-out direction indicated with the F arrow by turning in contact with the planographic printing plate 20 or the slip sheet 22.

[0024] The holder 40 is fitted with support axes 48 at both ends in the widthwise direction. Further, this holder 40 is connected to a drive unit 50 set so as to adjoin one end portion of the holder 40. This drive unit 50 connected to the holder 40 is configured to be movable between a conveying position, where the pick-up roller 42 of the holder 40 contacts the upper surface of the plate stack 18 with a preset crimping force, and a separated position, where the pick-up roller 42 has pulled away from the plate stack 18.

[0025] A mounting board 52 is attached to the bottom portion of the mounting tray 30 so it can pivot towards the edge of the upstream side in the conveying direction due to a hinge (not shown). The free edge of this mounting board 52 is biased upwards by a biasing means (not shown) in a state where the plate stack 18 is mounted on the mounting board 52, whereby it pivots centered on the portion axially supported by the hinge. This is configured so that the uppermost planographic printing plate 20 (or slip sheet 22) is pressed against the pick-up roller 42.

[0026] Two guide plates 54, 56 are arranged at the sending unit 200 further downstream from the mounting unit 14 in the conveying direction F with a preset interval opened between them in the conveying direction. The planographic printing plate 20 is conveyed while being supported by these guide plates 54, 56.

[0027] As shown in FIGS. 4 - 7, a sloped leading edge guide 100 is arranged on the conveying path between the plate stack 18 mounted on the mounting board 52 and the guide plate 54.

[0028] A separating guide slope 102 is provided at the sloped leading edge guide 100. The separating guide slope 102 is set so that it inclines from the upstream side of the conveying direction to the downstream side at a preset angle S from top to bottom (i.e., at an angle relative to the standard surface of a planar surface of the conveying route).

[0029] That is, the sloped leading edge guide 100 is provided with the separating guide slope 102 that has a width greater than the side width of the largest sized planographic printing plate 20 so it is formed in, for example, a columnar cross-sectional trapezoid.

[0030] This sloped leading edge guide 100 is arranged on the conveying path in the vicinity of the downstream side in the conveying direction of the plate stack 18 such that the planographic printing plate 20 rubs against the top of the separating guide slope 102 while both edges of the widest planographic printing plate 20 in the widthwise direction do not stick out (i.e., do not protrude farther than the outer edges of the separating guide slope 102).

[0031] For this reason, the sloped leading edge guide 100 is arranged at a position higher than the bottom surface of the planographic printing plate 20 (which is at the uppermost portion of the plate stack 18, i.e., is the first plate on the stack) by a preset height at the upper side edge facing the conveying path. (Note: References to "first" and "second", etc. indicate the actual position order of the items in the stack.) Furthermore, this sloped leading edge guide 100 is configured such that when this sloped leading edge guide 100 is made to simultaneously send out, on the conveying route, at least the uppermost first planographic printing plate 20 and second slip sheet 22 and the third planographic printing plate 20 and the fourth slip sheet 22, the lower side edge of the separating guide slope 102 is positioned lower than the fourth slip sheet 22 in order to make these come into contact with the separating guide slope 102.

[0032] With the sheet-supplying device 202 provided with the sloped leading edge guide 100 configured in this manner, the sets are closely adhered such that, for example, the amount of air between the set of the first planographic printing plate 20 and second slip sheet 22 at the top of the plate stack 18 mounted on the mounting unit 14 and the set of the third planographic printing plate 20 and the fourth slip sheet 22 is at a minimum, almost to the point where these are in a state of vacuum. Furthermore, there are cases when a lot of air interposes between the set of the third planographic printing plate 20 and fourth slip sheet 22 and the set of the fifth planographic printing plate 20 and sixth slip sheet 22 in a state where the friction that exists is lower than the friction between the planographic printing plate 20 and the slip sheet 22. When the pick-up roller 42 is made to turn and contact the uppermost first planographic printing plate 20 in order to perform an operation where the planographic printing plate 20 is to be discharged, the set of the third planographic printing plate 20 and fourth slip sheet 22 in close adherence with the set of the first planographic printing plate 20 and the second slip sheet 22 begins to slip on the top surface of the fifth planographic printing plate 20 while simultaneously being discharged as well.

[0033] Then, as shown in FIG 4, when the set of the third planographic printing plate 20 and the fourth slip sheet 22 closely adhered to the first planographic printing plate 20 and the second slip sheet 22 hits against the separating guide slope 102, the discharging operation for the set of the third planographic printing plate 20 and the fourth slip sheet 22 is stopped.

[0034] Furthermore, when the set of the uppermost first planographic printing plate 20 and second slip sheet 22 is discharged or carried out by the pick-up roller 42, as shown in FIG 5, the front edge in the conveying direction of the set of the first planographic printing plate 20 and the second slip sheet 22 crosses along the entire width of the separating guide slope 102 in a direction perpendicular to the conveying direction (i.e., crosses the widthwise direction) and moves while elastically deforming so as to be lifted upwards.

[0035] That is, the set of the uppermost first planographic printing plate 20 and second slip sheet 22 and the set of the third planographic printing plate 20 and the fourth slip sheet 22 flex such that the curvatures of their curved surfaces differ. A space opens between their leading edges and a large amount of air is made to enter in between them so the state of vacuum adherence between the two is broken and both of these sets separate, whereby the sending of multiple layers can be prevented.

[0036] Accordingly, simultaneous conveyance and jamming of the set of the first planographic printing plate 20 and second slip sheet 22 and the set of the third planographic printing plate 20 and fourth slip sheet 22 can be effectively suppressed.

[0037] In this state, as shown in FIG 12, the leading edges of the set of the uppermost first planographic printing plate 20 and second slip sheet 22 in the conveying direction are pulled apart along the entire width so as to separate from the set of the third planographic printing plate 20 and fourth slip sheet 22. Due to this, air enters between the second slip sheet 22 and the third planographic printing plate 20 and, as shown in FIG 6, the set of the uppermost first planographic printing plate 20 and second slip sheet 22 is separated and discharged.

[0038] This separating guide slope 102 provided at the sloped leading edge guide 100 is arranged so as to correspond to the entire width of the largest sized planographic printing plate 20, as shown in FIG 12, so air quickly flows in between the surfaces of the set of the uppermost first planographic printing plate 20 and second slip sheet 22 and the third planographic printing plate 20 from across the entire width of the leading edges in the conveying direction and these separate. Accordingly, discharging of only the set of the uppermost first planographic printing plate 20 and second slip sheet 22 can be performed with certainty.

[0039] It should be noted that, as seen in the comparative example shown in FIG 13, when the device is configured such that the separating guide slope 102 is made to correspond with only a portion of the planographic printing plate 20 in the widthwise direction, there is a problem in that the state of close adherence between the surfaces of the second slip sheet 22 and the third planographic printing plate 20 cannot be disengaged with certainty just by making air flow in between them. In contrast, as shown in FIG 12, when placing the separating guide slope 102 so as to correspond to the entire width of the largest sized planographic printing plate 20, the operation can be performed with certainty where the state of close adherence between the surfaces of the second slip sheet 22 and the third planographic printing plate 20 are disengaged and these sheets are separated.

[0040] Further, as shown in FIG 7, when the operation of discharging the set of the uppermost first planographic printing plate 20 and second slip sheet 22 is completed, the discharging operation for the set of the third planographic printing plate 20 and fourth slip sheet 22 is stopped at the separating guide slope 102 and placed in a state of standby.

[0041] Next, another configuration example relating to the sloped leading edge guide 100 arranged on the conveying route between the plate stack 18 mounted on the mounting board 52 and the guide plate 54 will be explained while referring to FIGS. 8-11.

[0042] In this configuration example relating to the sloped leading edge guide 100 shown in FIGS. 8 - 11, the sloped leading edge guide 100 is fixed to the free end of an elastic support bracket 106 provided so as to stand from a stand 104, which is a fixing component of the sheet-supplying device 202. This elastic support bracket 106 is configured so as to be elastically movable and can be made from, for example, a long board-shaped spring material of stainless steel having a board thickness of 0.8 mm.

[0043] With this configuration example relating to the sloped leading edge guide 100 shown in FIGS. 8-11, there are cases where, for example, the state of adherence between the set of the uppermost first planographic printing plate 20 and second slip sheet 22 and the set of the third planographic printing plate 20 and fourth slip sheet 22 are in a near-vacuum state due to a minimum amount of air existing between the sets. Further, when a large amount of air is interposed between the set of the third planographic printing plate 20 and fourth slip sheet 22 and the set of the fifth planographic printing plate 20 and sixth slip sheet 22, and a state of friction exists where the friction is less than the friction between the planographic printing plate 20 and the slip sheet 22, as shown in FIG 8, when an operation is performed where the pick-up roller 42 is made to rotate and contact the uppermost first planographic printing plate 20 to discharge it, the set of the third planographic printing plate 20 and fourth slip sheet 22 that was closely adhered to the set of the first planographic printing plate 20 and second slip sheet 22 begins to slip on the upper surface of the fifth planographic printing plate 20 while simultaneously being discharged.

[0044] Then the set of the third planographic printing plate 20 and fourth slip sheet 22 that was closely adhered to the set of the first planographic printing plate 20 and second slip sheet 22 that has simultaneously begun to be discharged hits against the separating guide slope 102, presses the elastic support bracket 106, and makes the elastic support bracket 106 flex. As shown in FIG 9, when the elastic support bracket 106 flexes as much as needed, the set of the third planographic printing plate 20 and fourth slip sheet 22 receives the rebound force generated by the elastic deformation at that time, so the discharging operation for that set is ceased and the set is stopped. A specific example of the amount of flexure and movement at this time of the elastic support bracket 106 in the conveying direction is in the range of from 0.4 to 0.7 mm.

[0045] Further, when the set of the uppermost first planographic printing plate 20 and second slip sheet 22 is discharged or carried off by the pick-up roller 42, as shown in FIG 9, the leading edges in the conveying direction of the set of the uppermost first planographic printing plate 20 and second slip sheet 22 elastically deform while moving so as to be lifted upwards across the entire width in the direction perpendicular to the conveying direction (i.e., the widthwise direction) along the separating guide slope 102.

[0046] That is, the set of the uppermost first planographic printing plate 20 and second slip sheet 22 and the set of the third planographic printing plate 20 and fourth slip sheet 22 flex such that the curvatures of their curved surfaces differ. A space opens between the respective leading edges and a large amount of air is made to enter inside between them so the state of vacuum adherence between the two is broken and both of these sets separate, whereby the sending of multiple layers can be prevented.

[0047] Accordingly, simultaneous discharge and jamming of the set of the uppermost first planographic printing plate 20 and second slip sheet 22 and the set of the third planographic printing plate 20 and fourth slip sheet 22 can be prevented.

[0048] In this state, as shown in FIG 12, the leading edge in the conveying direction along the entire width of the set of the uppermost first planographic printing plate 20 and second slip sheet 22 is pulled apart so as to separate from the set of the third planographic printing plate 20 and fourth slip sheet 22. Accordingly, air enters in between the second slip sheet 22 and the third planographic printing plate 20 and, as shown in FIG 10, the set of the uppermost first planographic printing plate 20 and second slip sheet 22 is separated and conveyed.

[0049] The separating guide slope 102 provided at this sloped leading edge guide 100 is arranged to correspond to the entire width of the largest sized planographic printing plate 20, as shown in FIG 12. Air quickly flows in between the surfaces of the set of the uppermost first planographic printing plate 20 and second slip sheet 22 and the third planographic printing plate 20 along the entire widths of the edges in the conveying direction, thus ensuring that only the set of the uppermost first planographic printing plate 20 and second slip sheet 22 is discharged.

[0050] Further, when the carrying operation for the set of the uppermost first planographic printing plate 20 and second slip sheet 22 is finished, the pick-up roller 42 raises to a standby position apart from the uppermost planographic printing plate 20. For this reason, the force of friction pulling in the conveying direction, when the set of the uppermost first planographic printing plate 20 and second slip sheet 22 rub against the set of the third planographic printing plate 20 and fourth slip sheet 22, when the first set is being conveyed is released. Further, the elastic support bracket 106 elastically deforming so as to flex in the conveying direction is pressed and returned towards the side of the mounting board 52 in the opposite direction of the conveying direction due to the elastic rebounding force of the elastic support bracket 106. Accordingly, the set of the third planographic printing plate 20 and fourth slip sheet 22 is completely separated from the set of the uppermost first planographic printing plate 20 and second slip sheet 22 and retained in a state of standby on the mounting board 52.

[0051] It should be noted that the force (i.e., spring force) at this time that presses and returns the set of the third planographic printing plate 20 and fourth slip sheet 22 when the elastic support bracket 106 elastically rebounds can be specifically in the range of, for example, 0.6 to 1.0 kg.

[0052] Next, the experiment performed in order to find the angle S of the separating guide slope 102 provided at the sloped leading edge guide 100 necessary for the appropriate function will be explained.

[0053] In the experiment for finding the angle S of this separating guide slope 102, a sloped leading edge guide 100 where the separating guide slope 102 formed thereon was configured with differing angles S was used. A planographic printing plate 20 and slip sheet 22 were actually conveyed with these components and the states of conveyance were evaluated.

[0054] The results of the experiment are shown in the following Chart 1.

Chart 1

Angle	40°	42°	45°	50°	55°	57°
Evaluation	F	B	A	A	B	F

A: Optimum conveyance exhibited

B: Satisfactory conveyance exhibited

F: Unsatisfactory conveyance exhibited

[0055] The results of the experiment showed that separation and conveyance of only the set of the uppermost first planographic printing plate 20 and second slip sheet 22 could not be performed when the angles were respectively 40° or less or 57° or more. It became evident that the appropriate angle S of the separating guide slope 102 provided at the sloped leading edge guide 100 was between 42° and 55°.

[0056] Further, the above-described sloped leading edge guide 100 shown in FIGS. 4-11 and the configurations relating thereto are simple and do not require highly accurate attachments, so this guide can be manufactured easily, thus making the provision of a reasonably priced product possible.

[0057] As shown in FIGS. 2 and 3, a slip sheet-separating device 58 is provided between the guide plate 54 and the guide plate 56 at a portion of the sheet-supplying device 202 of this CTP system. The slip sheet-separating device 58 is for removing the slip sheet 22 from the set of the uppermost first planographic printing plate 20 and second slip sheet 22 separated and discharged by the sloped leading edge guide 100.

[0058] This slip sheet-separating device 58 has a conveying roller unit 60 and a retard roller unit 62 arranged in this order along the conveying direction F. As shown in FIG 2, both of these comprise rotatable shafts 64 set across and along the widthwise direction W and multiple rubber rollers 66 fixed at preset intervals along the shafts 64.

[0059] These shafts 64 are connected so as to be rotatably driven with a drive motor 61. These are configured so that the rubber rollers 66 of the conveying roller unit 60 rotate (i.e., turn consecutively) in the direction of the R1 arrow and the rubber rollers 66 of the retard roller unit 62 rotate (i.e., turn in reverse) in the opposite direction indicated with the R2 arrow.

[0060] Further, the retard roller unit 62 is configured to be movable between a position contacting the slip sheet 22 during conveyance and a position separated from the slip sheet 22 due to a drive unit 68 provided at the side of one end thereof. The slip sheet 22 separates from the planographic printing plate 20 due to the conveying roller unit 60 reverse turning in a state of contact with the slip sheet 22 at a contact position.

[0061] Furthermore, the rubber rollers 66 of the retard roller unit 62 are configured to contact the rubber rollers 66 of the conveying roller unit 60 and to nip the slip sheet 22 between the rubber rollers 66 of the conveying roller unit 60 and convey it.

[0062] A nip roller 70 is set across so as to be rotatable in the widthwise direction above the conveying roller unit 60. The nip roller 70 can contact and nip the planographic printing plate 20 and the slip sheet 22 between the rubber rollers 66 of the conveying roller unit 60 with its own weight.

[0063] Slip sheet-conveying roller units 72A, 72B are respectively arranged beneath the conveying roller unit 60 and the retard roller unit 62. The slip sheet-conveying roller units 72A, 72B also comprise a shaft 64 and rubber rollers 66 like the conveying roller unit 60 and retard roller unit 62. The slip sheet-conveying roller units 72A, 72B are designed to be able to nip the slip sheet 22 between the rubber rollers 66. This is configured so that the nipped slip sheet 22 is conveyed downwards along the conveying belt 74 with rotation of the slip sheet 22 nipped between the rubber rollers 66 of the slip sheet-conveying roller units 72A, 72B.

[0064] Further, a collection box 76 that accumulates the slip sheets 22 is arranged below the slip sheet-conveying roller units 72A, 72B.

[0065] With the slip sheet-separating device 58 configured in this manner, when the planographic printing plate 20 and the slip sheet 22 come to be conveyed, the conveying roller unit 60 and the retard roller unit 62 are turned and the retard roller unit 62 is raised. Then the rubber rollers 66 of the retard roller unit 62 spin in reverse while in contact with the slip sheet 22, whereby force in the conveying direction from the conveying roller unit 60 and force in the opposite direction of the conveying direction from the retard roller unit 62 act upon the slip sheet 22, and the slip sheet 22 is separated from the planographic printing plate 20.

[0066] Then the slip sheet 22 is pinched between the conveying roller unit 60 and the rubber rollers 66 of the retard roller unit 62 in a state where the middle portion of the slip sheet 22 is folded and bent and then conveyed downwards and collected in the collection box 76. The planographic printing plate 20 is further conveyed in the conveying direction F and sent to the inner drum exposure device 204.

[0067] The present invention can be designed such that in the planographic printing plate supplying device, the separating guide slope is formed to have a width wider than the side width of the largest sized planographic printing plate.

[0068] Due to the above-described configuration, air quickly flows in from the entire width of the leading edge in the conveying direction of the uppermost planographic printing plate, whereby this plate is separated from the planographic printing plate layered beneath it. Accordingly, the uppermost planographic printing plate can be discharged alone with certainty.

[0069] Furthermore, the sloped leading edge guide can be fixed to the free end of an elastic support bracket provided so as to stand from a fixing component, the bracket being made to be elastically movable.

[0070] With the above-described configuration, the planographic printing plate layered beneath and closely adhered to the uppermost planographic printing plate that has begun to be discharged hits the separating guide slope, whereby the elastic support bracket elastically deforms and the discharging operation for the planographic printing plate layered underneath is stopped. Further, when the uppermost planographic printing plate is guided by the separating guide slope and thus separated and discharged, the friction force pulling in the conveying direction while the uppermost planographic printing plate rubs against the planographic printing plate layered underneath is released. For this reason, when the elastic support bracket flexes in the conveying direction, the plate underneath receives the rebound force generated by the elastic deformation and is pressed in the opposite direction, whereby it is completely separated from the uppermost planographic printing plate.

[0071] Furthermore, the incline of the separating guide slope can be set at an angle in the range of 42° to 55° with the planar surface of the conveying route acting as the standard surface therefor.

[0072] With the above-described configuration, separation of the uppermost planographic printing plate and the plate underneath it can be performed with certainty with the separating guide slope.

[0073] The supplying device for planographic printing plates of the present invention exhibits an effect where, with a simple structure, planographic printing plates can be separated one at a time and discharged.

[0074] It should be noted that the present invention is not limited to the above-described examples. It is obvious that various types of configurations can be employed within the scope of the present invention.

Claims

1. A planographic printing plate supplying device comprising:

a discharging device that pulls out an uppermost planographic printing plate, from a plate stack in which at least multiple planographic printing plates are stacked in a layered state, by pulling on the surface of the uppermost planographic printing plate with the force of friction; and

a sloped leading edge guide arranged so as to adjoin the downstream side in the direction in which the uppermost planographic printing plate pulled out with the discharging device is conveyed, the sloped leading edge guide comprising a separating guide slope inclined at a slant from bottom to top from the upstream side in the conveying direction to the downstream side, wherein

when the uppermost planographic printing plate pulled out by the discharging device is pulled out and discharged with a planographic printing plate layered underneath, the leading edge of the planographic printing plate layered underneath the uppermost planographic printing plate is stopped by the separating guide slope, and the leading edge of the uppermost planographic printing plate is guided by the separating guide slope whereby it is separated and discharged.

2. The planographic printing plate supplying device of claim 1, wherein the separating guide slope is formed to have a width wider than the side width of the largest sized planographic printing plate.

3. The planographic printing plate supplying device of claim 2, wherein the sloped leading edge guide is fixed to the free end of an elastic support bracket provided so as to stand out from a fixing component, the bracket being made to be elastically movable.

4. The planographic printing plate supplying device of any one of claims 1 to 3, wherein the incline of the separating guide slope is set at an angle in the range of 42° to 55° with the planar surface of the conveying route acting as the standard surface therefor.

Drawing