Sheet accumulating device, sheet accumulating method and sheet feeding device

Abstract

 A sheet accumulating device, a sheet accumulating method and a sheet feeding device are provided. The sheet accumulating device (2) includes a sheet feeding section (4), a front stopper (20), an attenuation section of the front stopper, an accumulating portion in which sheets whose front ends are caught by the front stopper are accumulated, and a damping force controlling section (8) that controls damping force in the attenuation section based on a mass of the sheets, a speed of feeding the sheets, or a product of the mass of the sheets and the speed of feeding, thereby causing no damage to the sheets even in a case in which two or more types of sheets having the different masses are fed in at a high speed.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

[0001] The present invention relates to a sheet accumulating device, a sheet accumulating method and a sheet feeding device, and particularly to a sheet accumulating device, a sheet accumulating method and a sheet feeding device, each of which causes no damage to product sheets even when the product sheets are fed at a high speed.

Description of the Related Art

[0002] Planographic printing plates are stacked in an accumulating device in the direction of the thickness thereof, and a bundle of planographic printing plates is formed in such a manner that two sheets of protective cardboard are inserted between the planographic printing plates at each time when a predetermined number of planographic printing plates are stacked.

[0003] The accumulating device is equipped with a front stopper that catches planographic printing plates and protective cardboard fed into the device so as to avoid damage to the planographic printing plates and protective cardboard.

[0004] At this point, the planographic printing plate and protective cardboard are different from each other both in thickness and in mass. Therefore, it is preferred that the damping force of the front stopper is switched between the case of feeding planographic printing plates and the case of feeding protective cardboard.

[0005] As the accumulating device described above, a sheet accumulating device has been proposed which includes: a stopper unit having plural front stoppers having different stopper conditions, for example, different damping coefficients, and also having a stopper switching section that locates one of the aforementioned front stoppers at a position in which it catches a front edge of sheets; and a stopper switching section controller that operates the stopper switching section in the aforementioned stopper unit so as to select an optimum one of the aforementioned plural front stoppers based on the speed of feeding sheets, or the mass of sheets (see Japanese Patent Application Laid-Open (JP-A) No. 63(1988)-134465).

[0006] Further, various feeding devices are used to feed planographic printing plates and protective cardboard into the accumulating device. However, it is preferable that both planographic printing plates and protective cardboard can be fed in the accumulating device by a single feeding device, which leads to no need to use two feeding devices.

[0007] As the feeding device as described above, for example, a division sheet synchronously-feeding device has been proposed which can feed planographic printing plates and protective cardboard at the same time. Some of the division sheet synchronously-feeding device described above is specifically composed of: a product sheet conveying section; a division sheet conveying section provided below a product sheet feeding section and extending to the vicinity of a position at which product sheets are accumulated; a product sheet guide plate that leads product sheets onto the division sheet conveying section; a product-sheet-position detecting section that detects the position of product sheets on the product sheet conveying section; and a division sheet conveyance timing adjustment section which is connected to the aforementioned division sheet conveying section and which conveys the division sheets, based on an input from the aforementioned product-sheet-position detection section, at a timing when the division sheets are superposed on desired product sheets led to the aforementioned division sheet conveying section (JP-A No. 59(1984)-203061).

[0008] However, if the planographic printing plates protrude further toward the front side in a sheet feeding direction than the protective cardboard, in a case in which the protective cardboard and the planographic printing plates are fed into the accumulating device in a stacked state, the front ends of planographic printing plates first hits against the front stopper of the accumulating device.

[0009] Accordingly, when the speed at which the planographic printing plates and protective cardboard are fed in increases, there may arise a problem that the front ends of planographic printing plates are damaged due to the impact of hitting against the front stopper.

[0010] Further, when plural front stoppers having different attenuation coefficients are provided in the accumulating device and these front stoppers are used in a switchable manner in accordance with a mass of planographic printing plates or protective cardboard to be fed in, or a sheet feeding speed, the accumulating device is made larger and a mechanism thereof becomes complicated. As a result, the accumulating device becomes expensive.

SUMMARY OF THE INVENTION

[0011] The present invention has been achieved in order to solve the aforementioned problems, and is directed to a sheet accumulating device in which plural types of sheets having the different masses, such as planographic printing plates and protective cardboard can be accumulated without being damaged while the structure thereof is made simpler, a sheet accumulating method, and a sheet feeding device which allows division sheets such as protective cardboard to be fed into a sheet accumulating device in a state in which the division sheets protrude further toward the front side in a feeding direction than products sheets such as planographic printing plates.

[0012] The first aspect of the present invention is a sheet accumulating device including: a sheet feeding section that feeds a sheet; a front stopper that catches a front end of the sheet fed by the sheet feeding section; an attenuation section that attenuates backward and forward movement of the front stopper with a predetermined damping force; an accumulating section that accumulates the sheet whose front end is caught by the front stopper; and a damping force controlling section that controls the damping force in the attenuation section based on at least one of a mass of the sheet, a speed of feeding the sheet, and/or a product of the mass of the sheet and the speed of feeding the sheet.

[0013] In the aforementioned sheet accumulating device, when at least one of the mass of sheet and the feeding speed is large, the damping force in the attenuation section is increased by the damping force controlling section. When at least one of the mass of sheet and the feeding speed is small, the damping force in the attenuation section is decreased.

[0014] Accordingly, even in a case in which two or more types of sheets whose masses are greatly different, for example, product sheets such as planographic printing plates and division sheets such as protective cardboards, are accumulated, the front stopper can catch (receive to stop) the front ends of sheets with damping force corresponding to the mass of each type of sheet. Hence, in a case of feeding a sheet having a large mass such as a division sheet, it is effectively prevented that, due to the damping force being insufficient, the shock from the sheet is not absorbed even if the front stopper has performed full-stroke. Further, damage to the front end of the sheet is effectively prevented, which damage is caused by the state in which at the time of feeding a sheet having a small mass such as a product sheet, due to the damping force being excessive, the front stopper has not sufficiently performed stroke even if the sheet hits against the front stopper. Further, it is desirable that the damping force may be increased and decreased not only based on the mass of sheet, but also based on the speed of feeding sheet, and/or the product of the mass of sheet and the speed of feeding.

[0015] Moreover, in the sheet accumulating device, there is no need of providing plural front stoppers and attenuation sections. Therefore, a sheet accumulating device having the substantially same structure and size as those of the conventional sheet accumulating device can be realized.

[0016] According to the second aspect of the present invention, the sheets include a product sheet and a division sheet which is inserted between the product sheets each time that a predetermined number of product sheets are accumulated.

[0017] Usually, the mass of one division sheet is larger than that of one product sheet. However, in the aforementioned sheet accumulating device, each of the division sheet and the product sheet is caught by the front stopper with the damping force corresponding to the mass of each type of sheet. Therefore, even in a case in which the sheets are fed into the device at a high speed, the product sheets are not damaged.

[0018] According to the third aspect of the present invention, at a time of feeding the division sheet, the sheet feeding section feeds the division sheet such that the division sheet and the product sheet are stacked in such a manner that the division sheet precedes (extends beyond) the product sheet by a predetermined distance.

[0019] In the aforementioned sheet accumulating device, the division sheet is fed into the device together with the product sheet, and therefore, it is not necessary to stop feeding of the product sheet at the time of feeding the division sheet.

[0020] Further, as the division sheet is inserted in a state of preceding the product sheet by a predetermined distance, first, the division sheet hits against the front stopper, and thereafter, the product sheet moves forward on the division sheet due to the inertial thereof. Accordingly, the friction generated at this time causes the product sheet to reduce its speed, and the product sheet is caught by the front stopper at a less shock. As a result, damage to the product sheet at the time of feeding is effectively prevented.

[0021] According to the fourth aspect of the present invention, the sheet accumulating device further includes: a division sheet detecting section which is located at an upstream side with respect to the accumulating section and which detects the division sheet fed into the accumulating section by means of the sheet feeding section, wherein the damping force controlling section increases the damping force in the attenuation section when the division sheet detecting section detects a leading end portion of the division sheet, and resets (sets back) the damping force in the attenuation section to an original strength when the front stopper catches the division sheet.

[0022] In the aforementioned sheet accumulating device, when the division sheet is fed, the division sheet and the product sheet are fed synchronously in a state in which the division sheet precedes the product sheet by a predetermined distance.

[0023] Accordingly, as already described in the third aspect, the product sheet fed together with the division sheet is made to reduce its speed due to a friction generated between the division sheet and the product sheet.

[0024] Further, the division sheet detecting section detects the leading end portion of the division sheet so as to increase the damping force in the attenuation section.

[0025] Accordingly, even when the division sheet whose mass is larger than that of the product sheet hits against the front stopper, the front stopper does not make a large stroke.

[0026] Then, the aforementioned damping force is set back to its original value when (after) the division sheet hits against the front stopper. Therefore, when the product sheet hits against the front stopper, the front stopper makes a large stroke so as to absorb the shock caused by the product sheet hitting against the front stopper.

[0027] Hence, in a case in which the product sheet and the division sheet are fed in synchronously, damage to the product sheet can be more effectively prevented.

[0028] According to the fifth aspect of the present invention, the division sheet detecting section is an optical detecting section that optically detects the division sheet.

[0029] The aforementioned sheet accumulating device has a feature that the division sheet can be detected in a non-contact manner. The sheet accumulating device is suitably used when the optical characteristics such as brightness, color tint and the like are greatly different between the division sheet and the production sheet.

[0030] According to the sixth aspect of the present invention, the division sheet detecting section is a mechanical detecting section that mechanically detects the division sheet.

[0031] In the aforementioned sheet accumulating device, even in a case in which there is not a great difference in the optical characteristics between the division sheet and the production sheet, the division sheet can be reliably detected.

[0032] According to the seventh aspect of the present invention, the attenuation section includes a brake section that controls backward and forward movement of the front stopper, and the damping force controlling section operates the brake section so as to increase the damping force in the attenuation section.

[0033] According to the eighth aspect of the present invention, the brake section is a mechanical brake section that mechanically controls backward and forward movement of the front stopper.

[0034] According to the ninth aspect of the present invention, the brake section is an electromagnetic brake section that controls backward and forward movement of the front stopper by an electromagnetic force thereof.

[0035] In the aforementioned sheet accumulating device, if the division sheet detecting section detects the leading end portion of the division sheet, the damping force controlling section operates the brake section. Then, if the front stopper catches the division sheet, then, the brake section is released from operating. Accordingly, there is almost no possibility that the front stopper moves backward by the shock at the time of catching the division sheet, and when the front stopper catches the product sheet, it moves backward by a great distance to reduce the shock. Thus, damage to the product sheet can be particularly effectively prevented.

[0036] According to the tenth aspect of the present invention, the attenuation section is a damping force adjustable damper that can vary the damping force, and the damping force controlling section increases or decreases the damping force of the damping force adjustable damper.

[0037] In the aforementioned sheet accumulating device, if the division sheet detecting section detects the leading end portion of the division sheet, the damping force controlling section increases the damping force of the damping force adjustable damper. Then, if the front stopper catches the division sheet, then, the damping force of the damping force adjustable damper is decreased to its original value. Therefore, when the front stopper catches the division sheet, it does not move backward by a great distance. Further, when the front stopper catches the product sheets, it moves backward by a great distance so as to reduce the shock. Accordingly, damage to the product sheet can be particularly effectively prevented.

[0038] As the damping force adjustable damper, an air damper, a friction damper, a magnetic damper and the like can be used in addition to the hydraulic damper.

[0039] According to the eleventh aspect of the present invention, the product sheet is a planographic printing plate, and the division sheet is a protective cardboard that is a cardboard superposed on each of both sides of a bundle of planographic printing plates stacked in a direction of the thickness of the planographic printing plates.

[0040] According to the aforementioned sheet accumulating device, even in a case in which the planographic printing plates are accumulated at a high speed, these plates can be accumulated without being damaged.

[0041] The twelfth aspect of the present invention is a sheet accumulating method in which sheets are accumulated in an accumulating section in such a manner that a front end of the sheet which is fed is caught by a front stopper having an attenuation section that attenuates backward and forward movement of the front stopper with a predetermined damping force, the method including: when at least one of a mass of the sheet, a speed of feeding the sheet, and a product of the mass of the sheet and the speed of feeding the sheet is large, increasing the damping force in the attenuation section, and when at least one of the mass of the sheet, the speed of feeding the sheet, and the product of the mass of the sheet and the speed of feeding the sheet is small, decreasing the damping force in the attenuation section.

[0042] As already mentioned with respect to the first aspect, according to the sheet accumulating method described above, even in a case in which two or more types of sheets whose masses are greatly different, for example, product sheets such as planographic printing plates and division sheets such as protective cardboards are accumulated, the front stopper can catch the front ends of the sheets with the damping forces corresponding to the mass of respective types of the sheets.

[0043] Hence, in a case of feeding a sheet having a large mass such as a division sheet, it is effectively prevented that, due to the damping force being insufficient, the shock from the sheet is not absorbed even if the front stopper has performed full-stroke. Further, damage to the front end of the sheet is effectively prevented, which damage is caused by the state in which at the time of feeding a sheet having a small mass such as a product sheet, due to the damping force being excessive, the front stopper has not sufficiently performed stroke even if the sheet hits against the front stopper. Further, it is desirable that the damping force may

[0044] According to the thirteenth aspect of the present invention, the sheets include a product sheet and a division sheet which is inserted between the product sheets each time that a predetermined number of product sheets are accumulated.

[0045] Usually, the mass of one division sheet is larger than that of one product sheet. However, according to the aforementioned sheet accumulating method, each of the division sheet and the product sheet is caught by the front stopper with the damping force corresponding to the mass of each type of the sheets. Therefore, even in a case in which the sheets are fed at a high speed, the product sheets are not damaged.

[0046] According to the fourteenth aspect of the present invention, the sheet accumulating method further includes, at a time of feeding the division sheet, feeding the division sheet such that the division sheet and the product sheet are stacked in such a manner that the division sheet precedes the product sheet by a predetermined distance.

[0047] According to the fifteenth aspect of the present invention, the sheet accumulating method further includes: at the time of feeding the division sheets, detecting presence of division sheet by a division sheet detecting section which is provided at an upstream side with respect to the accumulating section in which the product sheet and the division sheet are accumulated, when a leading end of the division sheet is detected by the division sheet detecting section, increasing damping force in the attenuation section, and when the division sheet is caught by the front stopper, resetting (setting back) the damping force in the attenuation section to an original strength.

[0048] In the aforementioned sheet accumulating method as well, the product sheet fed in together with the division sheets is made to reduce its speed due to the friction generated between the division sheet and the product sheet.

[0049] Further, the division sheet detecting section detects the leading end portion of the division sheet so as to increase the damping force in the attenuation section. Therefore, in a case in which the division sheet having a large mass compared with the product sheet hits against the front stopper, the front stopper does not make a large stroke.

[0050] If the division sheet hits against the front stopper, then, the damping force is set back to its original value. Therefore, when the product sheet hits against the front stopper, the front stopper makes a large stroke to reduce the shock caused by the product sheet hitting against the front stopper.

[0051] Hence, in a case in which the product sheet and the division sheet are fed in synchronously, damage to the product sheet can be more effectively prevented.

[0052] The sixteenth aspect of the present invention is a sheet feeding device including a product sheet conveying section that conveys a product sheet, a division sheet conveying section that conveys a division sheet toward an outlet of the product sheet conveying section, a sheet merging portion that causes the product sheet conveyed by the product sheet conveying section and the division sheet conveyed by the division sheet conveying section to merge with each other in a stacked state, and a sheet feeding section that feeds the division sheet and product sheet, which are stacked in the sheet merging portion, into the accumulating section, wherein in the sheet merging portion, the division sheet and the product sheet are stacked in such a manner that a leading end of the division sheet further protrudes forward along a direction of feeding than the product sheet by a predetermined amount.

[0053] According to the aforementioned sheet feeding device, the division sheet and the product sheet can be fed into the sheet accumulating device according to the first to eleventh aspects in a state of being stacked such that the division sheet protrudes from the product sheet a predetermined distance toward the front side.

[0054] According to the seventeenth aspect of the present invention, the sheet merging portion and the sheet feeding section are formed integrally.

[0055] ln the aforementioned sheet feeding device, the sheet merging portion and the sheet feeding section are formed integrally, and therefore, the structure of the device is further simplified.

[0056] As described above, the present invention provides a sheet accumulating device in which plural types of sheets, for example, a planographic printing plate and a protective cardboard having different masses, can be accumulated without being damaged, a sheet accumulating method, and a sheet feeding device that makes it possible to feed sheets into a sheet accumulating device in a state in which a division sheet such as the protective cardboard protrude further forward than a product sheet such as the planographic printing plate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Embodiments of the invention will be described in detail with reference to the following figures, wherein:

Fig. 1 is a schematic diagram showing the structure of a planographic printing plate accumulation line according to a first embodiment of the present invention;

Figs. 2A and 2B are partial enlarged views each showing the structure of an example of a damping force controller provided in an accumulating device on the planographic printing plate accumulation line according to the first embodiment;

Figs. 3A and 3B are partial enlarged views each showing the structure of another example of a damping force controller provided in an accumulating device on the planographic printing plate accumulation line according to the first embodiment;

Figs. 4A to 4D are partial enlarged views each showing the structure of a further alternative example of a damping force controller provided in an accumulating device on the planographic printing plate accumulation line according to the first embodiment;

Fig. 5 is a schematic diagram showing a state in which feeding of planographic printing plates and protective cardboard is started on the planographic printing plate accumulation line according to the first embodiment;

Fig. 6 is a schematic diagram showing a state in which protective cardboard is discharged on the planographic printing plate accumulation line according to the first embodiment;

Fig. 7 is a schematic diagram showing a state in which planographic printing plates and protective cardboard are conveyed toward a merging conveyor on the planographic printing plate accumulation line according to the first embodiment;

Fig. 8 is a schematic diagram showing a state in which planographic printing plates and protective cardboard are conveyed together on the planographic printing plate accumulation line according to the first embodiment;

Fig. 9 is a schematic diagram showing a situation in which planographic printing plates and protective cardboard are fed into the accumulating device on the planographic printing plate accumulation line according to the first embodiment;

Fig. 10 is a schematic diagram showing a situation in which a protective cardboard sensor detects the front end of protective cardboard in the accumulating device;

Fig. 11 is a schematic diagram showing a situation in which protective cardboard is caught by a front stopper after it is fed into the accumulating device; and

Figs. 12A, 12B and 12C are schematic diagrams showing respective motion of a planographic printing plate, protective cardboard and a front stopper after the protective cardboard is caught by the front stopper.

DETAILED DESCRIPTION OF THE INVENTION

[0058] As shown in Fig. 1, a planographic printing plate accumulation line 100 according to the first embodiment is equipped with an accumulating device 2 in which planographic printing plates P are accumulated, a feeding device 4 for feeding planographic printing plates P and protective cardboard Q into the accumulating device 2, a feeding-timing controller 6 that controls the timing of feeding in the feeding device 4, and a damping force switching controller 8 that controls switching of damping force in the accumulating device 2. The accumulating device 2 and the feeding device 4 correspond to a sheet accumulating device and a sheet feeding device, respectively, of the present invention. Further, the planographic printing plate P and protective cardboard Q are respective examples of a product sheet and a division sheet.

[0059] The feeding device 4 includes: a merging conveyor 40 in which the planographic printing plate P conveyed in the direction indicated by arrow a and the protective cardboard Q conveyed in the direction indicated by arrow b are made to merge together; a cutter 49 for cutting a planographic printing plate web W wound in the form of a roll into predetermined sizes to form the planographic printing plates P; a planographic printing plate conveyor 42 that conveys planographic printing plates P cut by the cutter 49 toward the merging conveyor 40 in the direction indicated by arrow a; a protective cardboard conveyor 44 that conveys the protective cardboard Q in the direction indicated by arrow b; a protective cardboard feeding device 46 for feeding the protective cardboard Q into the protective cardboard conveyor 44; and a protective cardboard feeding conveyor 47 that feeds the protective cardboard Q from a protective cardboard accumulating portion 50 into the protective cardboard feeding device 46. The merging conveyor 40 corresponds to a sheet merging portion and a sheet feeding portion in the sheet feeding device of the present invention. The planographic printing plate conveyor 42 and the protective cardboard conveyor 44 correspond to a product sheet conveying section and a division sheet conveying section, respectively, in the sheet feeding device of the present invention.

[0060] The planographic printing plate conveyor 42 is equipped with a downstream side conveyor 42A that extends backward from the merging conveyor 40 along the conveying direction a, and an upstream side conveyor 42B disposed adjacent to the downstream side conveyor 42A at the upstream side thereof. The downstream side conveyor 42A and the upstream side conveyor 42B are both driven by a pulse motor 43. Provided above the inlet side of the downstream side conveyor 42A is a planographic printing plate sensor 41 that optically detects the planographic printing plate P.

[0061] The protective cardboard feeding device 46 includes: a protective cardboard setting table 46A on which the protective cardboard Q fed by the protective cardboard feeding conveyor 47 is placed; a pair of nip rollers 46B provided between the protective cardboard setting table 46A and the protective cardboard conveyor 44; a protective cardboard stopper 48; and a pusher 46C provided at the rear side of the protective cardboard setting table 46A and pressing, toward the nip rollers 46B, the protective cardboard Q placed on the protective cardboard setting table 46A.

[0062] The protective cardboard stopper 48 is disposed between the nip rollers 46B and the protective cardboard conveyor 44.

[0063] The nip rollers 46B are nipped (caught) by an actuator 46D and are driven by a pulse motor 46F. The protective cardboard stopper 48 moves up and down by an actuator 48A. The pusher 46C moves backward and forward on the protective cardboard setting table 46A by means of an actuator 46E.

[0064] A suction cup 51 is provided above the protective cardboard accumulating section 50 so as to stick to the protective cardboard Q and place it on the protective cardboard feeding conveyor 47.

[0065] When the planographic printing plate sensor 41 detects the front end portion of the planographic printing plate P, the detected result is inputted to the feeding timing controller 6. Further, the pulse motor 43 is provided with a tachometer (not shown), and a signal from the tachometer is also inputted to the feeding timing controller 6. Incidentally, the actuator 46D, actuator 46E and actuator 48A are each driven by a command from the feeding timing controller 6.

[0066] The accumulating device 2 includes: a front stopper 20 that catches (receives to stop) the planographic printing plates P and the protective cardboard Q fed by the feeding device 4 by moving backward and forward; a cushioning spring (shock absorbing spring) 24 that attenuates movement of the front stopper 20 in forward and backward directions; a damping force controller 22 that controls damping force in the cushioning spring 24; a loading table 26 on which the planographic printing plates P and the protective cardboard Q caught by the front stopper 20 are placed; a rear stopper 28 disposed so as to face the front stopper 20 with the loading table 26 interposed between these stoppers; and a protective cardboard sensor 29 that is disposed above the loading table 26 in the vicinity of the front stopper 20 and detects optically the front end portion of the protective cardboard Q fed into the accumulating device 2. The cushioning spring 24, the damping force controller 22, loading table 26 and protective cardboard sensor 29 correspond to an attenuation section, a damping force controlling section, an accumulating portion and a division sheet detecting section, respectively, in the present invention.

[0067] When the protective cardboard sensor 29 detects the protective cardboard Q, a detection signal is inputted to a damping force switching controller 8. Further, the damping force controller 22 is controlled by the damping force switching controller 8.

[0068] As shown in Figs. 2A and 2B, the front stopper 20 is equipped with a base 20A, an abutting surface 20B that catches the planographic printing plates P and/or the protective cardboard Q, and a cushioning layer 20C inserted in a portion between the base 20A and the abutting surface 20B. The cushioning layer 20C is formed of, for example, an elastomer, vulcanized rubber, soft resin or the like. The cushioning layer 20C may also be a foamed resin layer, a foamed elastomer layer, a foamed rubber layer or the like.

[0069] The front stopper 20 is supported by a spline 21 on a fixed wall 28 fixed to the planographic printing plate accumulation line 100. The spline 21 includes a spline shaft 21A fixed perpendicular to a rear surface of the base 20A of the front stopper 20, and an external cylinder 21B that supports the spline shaft 21A in an inner cavity thereof in a reciprocable manner and that is fixed to the fixed wall 23. Accordingly, the front stopper 20 is supported in such a manner as to be reciprocable with respect to the fixed wall 23 as indicated by arrows d and e.

[0070] The cushioning spring 24 is inserted between the base 20A of the front stopper 20 and the fixed wall 23. As the cushioning spring 24, for example, a coil spring is used.

[0071] The damping force controller 22 is composed of a shoe 22A pressed against the spline shaft 21A, a fixed arm 22B fixed on a surface of the fixed wall 23 opposite to the front stopper 20, two links 22C each connecting the shoe 22A and the fixed arm 22B, and an air cylinder 22D inserted between the shoe 22A and the fixed arm 22B. The air cylinder 22D extends and contracts based on a command from the damping force switching controller 8. When the air cylinder 22D contracts, the shoe 22A is separated from the spline shaft 21A as shown in Fig. 2A, and the front stopper 20 can thereby freely move to reciprocate. To the contrary, when the air cylinder 22D extends, the shoe 22A is pressed against the spline shaft 21 A as shown in Fig. 2B, the movement of the front stopper 20 is braked (or stopped). Hence, the air cylinder 22D and the shoe 22A each correspond to a brake section in the present invention.

[0072] In the accumulating device 2, a damping force controller 122 or a damping force controller 222 can also be used in place of the damping force controller 22.

[0073] As shown in Figs. 3A and 3B, the damping force controller 122 includes an electromagnet 122A that sticks to a suction portion 122B fixed at a distal end of the spline shaft 21A, and an electromagnet supporting member 122C fixed to the fixed wall 23 at one end thereof and supporting the electromagnet 122A at the other end thereof. The electromagnet 122A is brought into an energized or non-energized state based on a command from the damping force switching controller 8. When the electromagnet 122A is not energized, the electromagnet 122A does not stick to the suction portion 122B. Therefore, as shown in Fig. 3A, the front stopper 20 can freely move to reciprocate. When the electromagnet 122A is energized, as shown in Fig. 3B, the electromagnet 122A sticks to the suction portion 122B, and movement of the front stopper 20 is thereby braked (stopped). Hence, the electromagnet 122A and the suction portion 122B each correspond to a brake section in the present invention.

[0074] As shown in Figs. 4A through 4D, the damping force controller 222 is a hydraulic damper that allows switching of damping force between the two power levels, i.e., high power and low power. The damping force controller 222 includes a cylinder 222A fixed to the fixed wall 23 with an arm-like member 222C, and a piston 222B that slides inside the cylinder 222A. At this point, the cross section of the damping force controller 222 along the axis line thereof is shown in Figs. 4A and 4B, and the cross section of the piston 222B along a plane orthogonal to the axis line thereof is shown in Figs. 4C and 4D.

[0075] As shown in Figs. 4A and 4B, the inside of the cylinder 222A is filled with hydraulic oil, and the piston 222B is mounted at a distal end of the spline shaft 21A. The piston 222B is composed of a cylindrical piston main body 222D and a rotary valve 222E provided inside the piston main body 222D in such a manner as to be rotatable around the axis line.

[0076] A mounting hole is provided in the central portion of the rotary valve 222E along the axis line, and the distal end portion of the spline shaft 21 A is fixed by being inserted halfway through the mounting hole. The distal end portion of the spline shaft 21A is structured so as to be rotatable with respect to the spline 21. Accordingly, when the spline shaft 2 1 A rotates, the rotary valve 222E also rotates together. To the contrary, the piston main body 222D is provided so as to slide with respect to the cylinder 222A along the axial direction thereof, but not to rotate.

[0077] As shown in Figs. 4A through 4D, a pair of communication holes 222F is provided in the piston main body 222D along the axial direction in such a manner as to face each other with the axis line therebetween. The communication holes 222F each have an opening on the front side of the piston main body 222D, that is, on the end surface of the piston main body 222D facing the fixed wall 23, and are bent inward at the ends thereof on the side opposite to the fixed wall 23.

[0078] The rotary valve 222E includes two sets of communication holes 222G and 222H formed in the radial direction thereof. The communication holes 222G and the communication holes 222H, which are each formed to make a pair, are each provided so that the pair of holes face each other with the axis line therebetween. By rotating the rotary valve 222E, either the communication holes 222G or the communication holes 222H can be made to communicate with the communication hole 222F of the piston main body 222D. The communication holes 222G have an inner diameter dimension larger than that of the communication holes 222H.

[0079] The rotary valve 222E rotates around the axis line thereof based on a command from the damping force switching, controller 8, and is positioned at any one of a position in which the communication hole 222F and the communication holes 222G communicate with each other as shown in Figs. 4A and 4C, and a position in which the communication hole 222F and the communication holes 222H communicate with each other as shown in Figs. 4B and 4D. At this point, the communication holes 222H have an inner diameter dimension smaller than that of the communication holes 222G. Therefore, the flow resistance of hydraulic oil when the communication hole 222F and the communication holes 222H communicate with each other is larger than that when the communication hole 222F and the communication holes 222G communicate with each other. Accordingly, the resistance at the time of reciprocating movement of the piston 222 when the communication hole 222F and the communication holes 222H communicate with each other is larger than that when the communication hole 222F and the communication holes 222G communicate with each other. Therefore, a larger damping force is applied to the front stopper 20.

[0080] In this manner, the damping force controller 222 causes the rotary valve 222E to rotate around the axis line thereof, thereby allowing switching of the damping force between the two power levels.

[0081] In the planographic printing plate accumulation line 100, the planographic printing plate sensor 41, the protective cardboard sensor 29, and the protective cardboard stopper 48 are disposed based on the relationship described below. That is to say, assuming that a merging position at which the planographic printing plate P and the protective cardboard Q are made to be together in the merging conveyor 40 is represented by X, a distance between the planographic printing plate sensor 41 and the merging position X is represented by L₁, a distance between the protective cardboard stopper 48 and the merging position X is represented by L₂, and a distance between the protective cardboard sensor 29 and the front stopper 20 is represented by L₃, the planographic printing plate sensor 41, the protective cardboard sensor 29 and the protective cardboard stopper 48 are disposed so as to satisfy the expression below.

[0082] Next, a description will be given of operation of the planographic printing plate accumulation line 100.

[0083] The planographic printing plates P prepared by cutting a rolled planographic printing plate web W with the cutter 49 are conveyed by the planographic printing plate conveyor 42 in the direction indicated by arrow a, and further conveyed through the merging conveyor 40 and accumulated in the accumulating device 2. At this time, the damping force controller 22 does not operate, and therefore, the front stopper 20 moves back and forth without being braked, and reduces the impact of catching the planographic printing plates P. The planographic printing plates P caught by the front stopper 20 are placed on the loading table 26.

[0084] When a predetermined number (n sheets) of planographic printing plates P is fed into the accumulating device 2, as shown in Fig. 5, one sheet of protective cardboard Q is taken out from the protective cardboard accumulating portion 50 by the suction cap 51, and is placed on the protective cardboard feeding conveyor 47. In this state, the protective cardboard Q is conveyed toward the protective cardboard setting table 46A as indicated by arrow c. As shown in Fig. 6, if two sheets of protective cardboard Q are placed on the protective cardboard setting table 46A, the protective cardboard feeding conveyor 47 is temporarily stopped.

[0085] Then, when the n-th planographic printing plate P is fed by the upstream side conveyor 42B and the front end thereof is detected by the planographic printing plate sensor 41, a signal indicating that the planographic printing plate P is detected in the planographic printing plate sensor 41 is inputted to the feeding timing controller 6. When the aforementioned signal is inputted to the feeding timing controller 6, after a predetermined time has passed, the feeding timing controller 6 inputs a signal, which indicates that the protective cardboard Q needs to be fed into the protective cardboard conveyor 44, to the protective cardboard feeding device 46. The predetermined time mentioned herein is set as a time period over which the planographic printing plate P is conveyed on the planographic printing plate conveyor 42 by a distance L₄ = L₁ - L₂ - L₃.

[0086] In the protective cardboard feeding device 46, as shown in Fig. 7, the actuator 46E is actuated based on a command from the feeding timing controller 6, and two sheets of protective cardboard Q placed on the protective cardboard setting table 46A are inserted, by the pusher 46C, between the nip rollers 46B. Then, the front ends of the protective cardboard Q abut against the protective cardboard stopper 48, thereby causing the two sheets of protective cardboard Q to be positioned at the same position in the conveying direction (the edges of the two sheets of protective cardboard Q are positioned at the same position).

[0087] If these protective cardboards Q are aligned so as to be positioned at the same position, the actuator 46D operates to cause the two sheets of protective cardboard Q to be nipped by the nip rollers 46B, and the protective cardboard stopper 48 is moved downward by the actuator 48A so as not to impede the path of the protective cardboard Q. Then, the nip rollers 46B are driven by the pulse motor 46F and the two sheets of protective cardboard Q are fed toward the protective cardboard conveyor 44.

[0088] The two sheets of protective cardboard Q fed onto the protective cardboard conveyor 44 are conveyed by the protective cardboard conveyor 44 along the conveying direction indicated by arrow b. In the protective cardboard conveyor 44, when the two sheets of protective cardboard Q are made to merge with the planographic printing plate P, these protective cardboards Q are conveyed at such a feeding speed as to precede the planographic printing plate P by the length L₃. At this point, the aforementioned feeding speed is generally set so that the length L₃ is in the range of 10 to 100 mm. As shown in Fig. 8, in an area between the merging conveyor 40 and the front end portion of the protective cardboard conveyor 44, the planographic printing plate P and the protective cardboard Q are made to merge with each other in a state in which the protective cardboards Q precede the planographic printing plate P by the length L₃, and overlap with each other. Then, as shown in Fig. 9, the planographic printing plate P and the protective cardboards Q are fed in the aforementioned state into the accumulating device 2.

[0089] When the planographic printing plate P and the protective cardboards Q are fed into the accumulating device 2, as shown in Fig. 10, the protective cardboards Q are detected by the protective cardboard sensor 29 at the point at which a distance between the front ends of the protective cardboards Q and the front stopper 20 becomes L₃. A signal which indicates the aforementioned state is inputted from the protective cardboard sensor 29 to the damping force switching controller 8. When the aforementioned signal is inputted to the damping force switching controller 8, it controls the damping force controller 22 to brake the spline shaft 21A or to set the damping force of a hydraulic damper connected to the spline shaft 21A at a "high" level. Accordingly, as shown in Fig. 11, the front stopper 20 hardly moves backward when it catches the protective cardboards Q.

[0090] When the front stopper 20 catches the protective cardboards Q, then, the damping force switching controller 8 controls the damping force controller 22 to release the brake of the spline shaft 21A or to reset the damping force of the hydraulic damper connected to the spline shaft 21 A at a "low" level. The timing at which the brake is released by the damping force switching controller 8 or at which the damping force of the hydraulic damper is reset at a "low" level may be set by means of a timer. Alternatively, the timing may be set as a timing when detecting that the front stopper 20 catches the protective cardboards Q.

[0091] Accordingly, as shown in Fig. 12A, the front stopper 20 moves forward as indicated by arrow d due to the inertial force of the protective cardboards Q and the planographic printing plate P. At the same time, as shown in Figs. 12B and 12C, the planographic printing plate P moves forward on the protective cardboards Q toward the front stopper 20 due to the inertial force thereof, but the movement speed of the planographic printing plate P is reduced due to the frictional force generated between the protective cardboard Q and the planographic printing plate P. In the meantime, the front stopper 20 also moves back to its original position by the force of the cushioning spring 24 as indicated by arrow e. Then, as shown in Fig. 12C, the front stopper 20 stops moving at its initial position, and can catch the planographic printing plate P in a nearly non-shocked state.

[0092] In this manner, a bundle of planographic printing plates P is formed in such a manner that two sheets of protective cardboard are inserted between the planographic printing plates P at each time when n planographic printing plates P are accumulated.

[0093] In a case in which two sheets of protective cardboard Q are inserted between the planographic printing plates P at each time when n planographic printing plates P are accumulated, the planographic printing plate accumulation line 100 allows the planographic printing plates P to be accumulated without being damaged even if the feeding speed of the planographic printing plates increases.

[0094] Further, the timing at which the planographic printing plate P and the protective cardboards Q are fed at the feeding device 4 is controlled based on the detection results in the planographic printing plate sensor 41 and the protective cardboard sensor 29, and the damping force of the front stopper 20 in the accumulating device 2 is also controlled. Therefore, the present invention also has a feature that the number of component parts to be added to conventional feeding device and accumulating device can be reduced.

[0095] The present invention is suitably applicable not only to accumulation of photosensitive, heat-sensitive, or laser-exposure type planographic printing plates, but also to accumulation of various steel plates such as aluminum plates, stainless steel plates, ordinary (common) steel plates, corrosion-resisting steel plates, high-tensile steel plates and the like, metal sheets such as painted steel plates, various types of paper, plastic sheets and the like.

Claims

1. A sheet accumulating device comprising:

a sheet feeding section that feeds in a sheet;

a front stopper that catches a front end of the sheet fed by the sheet feeding section;

an attenuation section that attenuates backward and forward movement of the front stopper with a predetermined damping force;

an accumulating section that accumulates the sheet whose front end is caught by the front stopper; and

a damping force controlling section that controls the damping force in the attenuation section based on at least one of a mass of the sheet, a speed of feeding the sheet, and a product of the mass of the sheet and the speed of feeding the sheet.

2. The sheet accumulating device according to claim 1, wherein the sheets include a product sheet and a division sheet which is inserted between the product sheets each time that a predetermined number of product sheets are accumulated.

3. The sheet accumulating device according to claim 2, wherein at a time of feeding the division sheet, the sheet feeding section feeds the division sheet such that the division sheet and the product sheet are stacked in such a manner that the division sheet precedes the product sheet by a predetermined distance.

4. The sheet accumulating device according to claim 3, further comprising:

a division sheet detecting section which is located at an upstream side with respect to the accumulating section and which detects the division sheet fed into the accumulating section by means of the sheet feeding section,

wherein the damping force controlling section increases the damping force in the attenuation section when the division sheet detecting section detects a leading end portion of the division sheet, and resets the damping force in the attenuation section to an original strength when the front stopper catches the division sheet.

5. The sheet accumulating device according to claim 4, wherein the division sheet detecting section is an optical detecting section that optically detects the division sheet.

6. The sheet accumulating device according to claim 4, wherein the division sheet detecting section is a mechanical detecting section that mechanically detects the division sheet.

7. The sheet accumulating device according to claim 1, wherein the attenuation section comprises a brake section that controls backward and forward movement of the front stopper, and the damping force controlling section operates the brake section so as to increase the damping force in the attenuation section.

8. The sheet accumulating device according to claim 7, wherein the brake section is a mechanical brake section that mechanically controls backward and forward movement of the front stopper.

9. The sheet accumulating device according to claim 7, wherein the brake section is an electromagnetic brake section that controls backward and forward movement of the front stopper by an electromagnetic force thereof.

10. The sheet accumulating device according to claim 1, wherein the attenuation section is a damping force adjustable damper that can vary the damping force, and the damping force controlling section increases or decreases the damping force of the damping force adjustable damper.

11. The sheet accumulating device according to claim 2, wherein the product sheet is a planographic printing plate, and the division sheet is protective cardboard which is cardboard superposed on both sides of a bundle of planographic printing plates stacked in a direction of the thickness of the planographic printing plates.

12. A sheet accumulating method in which sheets are accumulated in an accumulating section in such a manner that a front end of the sheet which is fed is caught by a front stopper having an attenuation section that attenuates backward and forward movement of the front stopper with a predetermined damping force, the method comprising:

when at least one of a mass of the sheet, a speed of feeding the sheet, and a product of the mass of the sheet and the speed of feeding the sheet is large, increasing the damping force in the attenuation section, and

when at least one of the mass of the sheet, the speed of feeding the sheet, and the product of the mass of the sheet and the speed of feeding the sheet is small, decreasing the damping force in the attenuation section.

13. The sheet accumulating method according to claim 12, wherein the sheets include a product sheet and a division sheet which is inserted between the product sheets each time that a predetermined number of product sheets are accumulated.

14. The sheet accumulating method according to claim 13 further comprising, at a time of feeding the division sheet, feeding the division sheet such that the division sheet and the product sheet are stacked in such a manner that the division sheet precedes the product sheet by a predetermined distance.

15. The sheet accumulating method according to claim 14, further comprising:

at the time of feeding the division sheets, detecting presence of division sheet by a division sheet detecting section which is provided at an upstream side with respect to the accumulating section in which the product sheet and the division sheet are accumulated,

when a leading end of the division sheet is detected by the division sheet detecting section, increasing damping force in the attenuation section, and

when the division sheet is caught by the front stopper, resetting the damping force in the attenuation section to an original strength.

16. A sheet feeding device comprising a product sheet conveying section that conveys a product sheet, a division sheet conveying section that conveys a division sheet toward an outlet of the product sheet conveying section, a sheet merging portion that causes the product sheet conveyed by the product sheet conveying section and the division sheet conveyed by the division sheet conveying section to merge with each other in a stacked state, and a sheet feeding section that feeds the division sheet and product sheet, which are stacked in the sheet merging portion, into the accumulating section,
wherein in the sheet merging portion, the division sheet and the product sheet are stacked in such a manner that a leading end of the division sheet further protrudes forward along a direction of feeding than the product sheet by a predetermined amount.

17. The sheet feeding device according to claim 16, wherein the sheet merging portion and the sheet feeding section are formed integrally.

Drawing