JP5023376B2 - Printing apparatus and printing method - Google Patents

Description

  The present invention includes a pressing body such as a press roller and an impression cylinder that presses a printing medium toward a plate cylinder, and a plurality of printing speeds can be set. The present invention relates to a printing apparatus in which a pressing force to be pressed toward a cylinder is adjusted according to a set printing speed, and a printing method using the printing apparatus.

  Conventionally, for example, as described in [Patent Document 1] to [Patent Document 3], a printing medium such as a printing paper is applied to a stencil sheet called a master or the like wound around a plate cylinder, a press roller, a pressure roller, and the like. There is known a printing apparatus that performs printing by pressing with a pressing body such as a cylinder.

  Among such printing apparatuses, as described in [Patent Document 1], a printing apparatus capable of setting a plurality of printing speeds is known. Since the printing speed depends on the rotation speed of the plate cylinder, the rotation speed of the plate cylinder is adjusted according to the printing speed. When the rotation speed of the plate cylinder changes, the time for pressing the printing medium against the stencil sheet by the pressing body changes, but when the rotation speed is fast and the pressing time is short, the time for the ink to transfer from the stencil sheet to the printing medium is short. As a result, the density of the printed image becomes thin, and conversely, if the rotation speed is slow and the pressing time is long, the time for the ink to transfer from the stencil sheet to the printing medium becomes long, so the density of the printed image becomes high.

  If the density of the printed image changes depending on the printing speed, it is contrary to the request of the user who wants a constant printing density. If the printing density is too dark or too light, the value as a printed matter will be low, and it will be necessary to discard it. Therefore, it is a problem in terms of the usability of the printing apparatus, cost and environment.

  Therefore, in [Patent Document 1], in the paragraph “0030” or the like, a technique for changing the pressing force for pressing the pressing body toward the plate cylinder in accordance with the printing speed is proposed. [Patent Document 2] discloses a printing apparatus including a plurality of paper feeding means for supplying a printing medium toward a plate cylinder.

JP 2004-262128 A JP 2000-118116 A Japanese Patent Laid-Open No. 10-045578

  However, in the technique described in [Patent Document 1], when the printing speed is changed, printing is interrupted until the rotational speed of the plate cylinder is stabilized at a speed corresponding to the printing speed. There is a problem of becoming longer.

  Further, in a printing apparatus provided with a plurality of paper feeding means, such as the printing apparatus described in [Patent Document 2], the performance of the paper feeding speed may differ depending on the paper feeding means, and the printing speed depends on the paper feeding speed. May be limited. Therefore, depending on the selected paper feeding means, it may be necessary to change the printing speed. In this case, if the pressing body is pressed toward the plate cylinder with a constant pressing force, the printing density changes.

  The present invention performs printing without waiting for the end of the change in the rotational speed of the plate cylinder, performs printing at a constant density at this time, and also when the printing speed is changed with the change of the paper feeding means. It is an object of the present invention to provide a printing apparatus that performs printing at a constant density and a printing method using the printing apparatus.

In order to achieve the above object, according to the first aspect of the present invention, there is provided a printing speed setting means capable of setting the printing speed to a plurality of speeds, and the rotation speed changes in accordance with the printing speed set by the printing speed setting means. A plate cylinder, a pressing body that presses the printing medium toward the plate cylinder, a pressing force adjusting means for adjusting a pressing force by which the pressing body presses the printing medium toward the plate cylinder, and the pressing force. In a printing apparatus having control means for setting the pressing force by the adjusting means according to the rotational speed of the plate cylinder in order to obtain an image having a constant density, the printing medium is fed, and the feeding speeds are different from each other. A plurality of paper feeding means, and when printing is performed by feeding paper from one of the plurality of paper feeding means, the print paper of the paper feeding means runs out and the plurality of paper feeding means Feeding that feeds from the other one of the means In the printing apparatus capable of switching means, when the sheet feeding means switching operation is performed, the printing speed is set according to the sheet feeding speed of the sheet feeding means that is feeding, and The control means sets the pressing force by the pressing force adjusting means in accordance with a set printing speed so as to obtain an image having a constant density .

According to a second aspect of the present invention, in the printing apparatus according to the first aspect, when the printing speed is changed by the printing speed setting means, the rotational speed of the plate cylinder gradually increases to a speed corresponding to the changed printing speed. The control means changes the pressing force by the pressing force adjusting means according to the gradually changing speed so as to obtain an image having a constant density .

According to a third aspect of the invention, in the printing apparatus according to claim 2, wherein, when the rotational speed of the plate cylinder is changed during printing the one print medium, said by the pressing force adjusting means press The pressure is changed during printing of the one printing medium so as to obtain an image having a constant density .

According to a fourth aspect of the present invention, in the printing apparatus according to any one of the first to third aspects, the pressing device includes a pressing force input unit that changes the pressing force by the pressing force adjusting unit set by the control unit. it shall be the features a.

According to a fifth aspect of the present invention, there is provided a printing method for performing printing using the printing apparatus according to any one of the first to fourth aspects.

The present invention provides a printing speed setting means capable of setting a printing speed to a plurality of speeds, a plate cylinder whose rotational speed changes according to the printing speed set by the printing speed setting means, and a printing medium in the plate cylinder. A pressing body that presses toward the plate cylinder, a pressing force adjusting means for adjusting a pressing force with which the pressing body presses the printing medium toward the plate cylinder, and the pressing force by the pressing force adjusting means is a constant density. And a control unit configured to set the printing cylinder according to the rotational speed of the plate cylinder, and a plurality of paper feeding units that feed printing media and have different paper feeding speeds. When printing is performed by feeding paper from one of the paper feeding means, if there is no print medium in the paper feeding means, paper is fed from the other one of the plurality of paper feeding means. A printing device capable of switching the paper feed means Thus, when the paper feeding means switching operation is performed, the printing speed is set according to the paper feeding speed of the paper feeding means that is feeding, and the control means is configured to control the pressing force adjusting means. Is set according to the printing speed after setting so as to obtain an image having a constant density, so even if the printing speed has to be changed in accordance with the change of the paper feeding means, printing is performed. Runode can set the pressing force Kakaru according to the speed to print the predetermined concentration, discarding the print medium after printing due to the change in density is prevented or suppressed, cost, excellent in environmental A printing device can be provided.

When the printing speed is changed by the printing speed setting means, the rotation speed of the plate cylinder is gradually changed to a speed corresponding to the changed printing speed, and the control means obtains an image having a constant density. As described above, if the pressing force by the pressing force adjusting means is changed according to the gradually changing speed, printing at a constant density is performed without waiting for the end of the change in the rotational speed of the plate cylinder. can be, together with the feeling can print quickly is excellent, the pressing force Kakaru depending on printing speed even in the case changes forced the printing speed with the change of the paper feed unit Since printing can be performed at a constant density by setting , discarding of the print medium after printing due to a change in density can be prevented or suppressed, and a printing apparatus excellent in cost and environment can be provided.

When the rotational speed of the plate cylinder changes during printing of one printing medium, the control unit uses the pressing force by the pressing force adjusting unit to print the one sheet so as to obtain an image having a constant density. if changing during printing of the medium, is possible to perform the printing of constant density on the print medium one that even if the rotational speed changes of the plate cylinder during printing of one print medium can, in together when feeling can print more quickly is greater, waste of the printing medium after printing due to the change in density is prevented or suppressed, cost, excellent printing apparatus in environmental Can be provided.

If you have a pressure input means for changing the pressing force of the pressing force adjusting means which is set by the control unit, to obtain an optimized prints the desired concentration by changing the pressing force that written As a result, it is possible to prevent or suppress the disposal of the print medium after printing due to the change in density or the fact that the density does not like, and to provide a printing apparatus that is excellent in terms of cost and environment.

Since the present invention is a printing method for performing printing using the printing apparatus according to any one of claims 1 to 4 , the printing apparatus that exhibits the above-described effects is used to change the rotational speed of the plate cylinder. You can print at a constant density without waiting for completion, and you can change the printing speed with the advantage that the printing can be done quickly and the usability is excellent, and the paper feeding method is changed. Even if it is not, printing can be performed at a constant density by setting the pressing force according to the printing speed, so that disposal of the print medium after printing due to density change is prevented or suppressed, and the cost, It is possible to provide a printing method having the advantage of being excellent in terms of environment.

  FIG. 1 shows an outline of a stencil printing apparatus integrated with a thermal digital plate making as a printing apparatus to which the present invention is applied. The stencil printing apparatus 100 includes an apparatus main body 67 positioned at the center in the vertical direction, and an image scanner serving as an original reading unit disposed above the apparatus main body 67 as an original reading unit for reading an original image. 61 and a paper supply bank 47 which is disposed in the lower part of the apparatus main body 67 and stores printing paper P as a paper which is a large number of printing media.

  In the stencil printing apparatus 100, a printing unit 69 centering on a plate cylinder 68 that is rotatably supported and a master roll 70a in which an unused master 70 made of a heat-sensitive stencil sheet is rolled can be replaced in the apparatus main body 67. A plate-making device 71 is provided as a plate-making means as a plate-making unit that pierces the master 70 drawn from the master roll 70 a and feeds the plate-made master 70 to the plate cylinder 68.

  The stencil printing apparatus 100 also peels the printing paper P from the printing drum 68 and the press roller 20 as a pressing body for pressing the printing paper P against the printing drum 68 against the outer periphery of the printing drum 68. A peeling claw 75 which can be moved forward and backward, and a plate discharging device 76 which is a plate discharging means as a plate discharging portion for peeling the used master 70 wound around the plate cylinder 68 before the printing process are provided.

  The stencil printing apparatus 100 is also peeled off from the plate cylinder 68 by a peeling claw 75 and a paper feeding device 52 as a paper feeding unit that feeds the printing paper P toward the printing part 69. A sheet conveying device 84 that conveys the printing paper P, a paper ejection tray 85 that serves as a paper ejection tray on which the printed printing paper P that has been conveyed by the paper conveying device 84 is stacked, and is mainly located inside the plate cylinder 68. And a main motor 11 as a drive motor which is a plate cylinder driving means.

  The stencil printing apparatus 100 also has a pressing body displacing means 22 in the apparatus main body 67 for displacing the press roller 20 toward the plate cylinder 68 or holding the press roller 20 at a position separated from the plate cylinder 68, as shown in FIG. In addition, an operation panel 91 for an operator such as a user, that is, an operator, to operate the stencil printing apparatus 100 and a control unit 19 as a control means for controlling the overall operation of the stencil printing apparatus 100 are provided.

  As shown in FIG. 1, the plate cylinder 68 includes a clamp device 73 that is disposed on a part of the outer periphery of the plate cylinder 68 and grips an end of the master 70 that has been made, and an opening and a non-opening (not shown). A porous support cylinder (not shown), a multi-layer mesh screen (not shown) that is a resin or metal mesh covering the outer periphery of the porous support cylinder, and a drum (not shown) fixed to both ends of the porous support cylinder It has a flange and is connected to the main motor 11 via a gear train (not shown).

  The opening of the porous support cylindrical body is a portion in which a large number of small holes for allowing the ink supplied by the ink supply device 10 to pass therethrough, and the transmitted ink is configured to ooze out from the mesh screen. Yes.

  Each drum flange is rotatably supported by a drum shaft 25 as an ink supply pipe which is an ink supply shaft. The drum shaft 25 is supported by a main body side plate (not shown) of the apparatus main body 67. Therefore, the plate cylinder 68 is rotatably supported by the drum shaft 25 by the drum flange.

  The plate cylinder 68 is integrated with the gear 12 that is fixed to the drum flange and that has the drum shaft 25 as the rotation center. The main motor 11 is a stepping motor, and is fixed to the main body side plate and has a gear 13 that meshes with the gear 12. Therefore, the plate cylinder 68 is rotationally driven by the main motor 11. The plate cylinder 68 is driven to rotate in the clockwise direction in FIG.

  The clamp device 73 is disposed in a non-opening portion other than the mesh screen of the porous support cylindrical body along one of the bus bars of the plate cylinder 68, and the stage 14 made of a magnetic material and the stage 14 It has a clamper 42 that opens and closes and that clamps the tip of the master 70 with the stage 14 to which a magnet or the like is attached.

  The clamp device 73 is also arranged in parallel with the stage 14 in the direction perpendicular to the paper surface in FIG. 1, and forms a center of rotation of the clamper 42. In the position, an opening / closing device (not shown) that opens and closes the stage 14 is provided.

  The ink supply device 10 is disposed so as to face the inner peripheral surface of the plate cylinder 68 and supplies the ink 15 to the plate cylinder 68. The ink supply device 10 faces the ink roller 16 and has a slight gap in the ink roller 16. A doctor roller 18 as a second roller that forms a wedge-shaped space with the ink roller 16 and forms an ink reservoir 17 in the wedge-shaped space, and a drum shaft 25 that drops and supplies the ink 15 to the ink reservoir 17. And a pair of ink roller side plates (not shown) which are disposed opposite to each other inside the plate cylinder 68 and rotatably support the ink roller 16 and the doctor roller 18 therebetween.

  Although not shown, the ink supply device 10 supplies an ink pack connected to one end of the drum shaft 25 and positioned outside the plate cylinder 68 and ink in the ink pack toward the drum shaft 25. An ink pump located outside the plate cylinder 68, an ink sensor for detecting the amount of ink in the ink reservoir 17, and the driving force of the main motor 11 are transmitted to the ink roller 16 and the doctor roller 18, and the ink roller 16 and the doctor roller 18 are transferred to the plate. A driving force transmission mechanism constituted by gears, belts, and the like that is driven to rotate in the same direction as the plate cylinder 68 in synchronization with the cylinder 68.

  The drum shaft 25 is formed with a plurality of holes 25a as supply holes which are ink dropping holes in the axial direction, and has a function of an ink supply pipe. The drum shaft 25 has an ink roller side plate fixed to both ends thereof.

  The ink roller 16 has an ink roller shaft 21 that forms the center of rotation, and the ink roller shaft 21 is rotatably supported at both ends by an ink roller side plate. The doctor roller 18 is also rotatably supported on the ink roller side plate in the same manner as the ink roller 16.

  Accordingly, the ink roller 16 and the doctor roller 18 rotate to knead and extend the ink 15 in the ink reservoir 17, and the ink 15 in the ink reservoir 17 extends from between the ink roller 16 and the doctor roller 18 to the outer surface of the ink roller 16. After that, the ink is supplied to the inner peripheral surface of the plate cylinder 68.

The ink 15 supplied to the inner peripheral surface of the plate cylinder 68 oozes out to the outer peripheral surface of the plate cylinder 68 through the porous support cylindrical body and a plurality of layers of mesh screens.
When it is detected that the ink 15 has been consumed and the amount of ink in the ink reservoir 17 has been reduced by the ink sensor, the ink in the ink pack is sucked by the ink pump, and from the plurality of holes formed in the drum shaft 25, the ink reservoir 17 is supplied.

  The press roller 20 is located below the plate cylinder 68. The press roller 20 includes a cored bar and nitrile rubber or chloroprene rubber as an elastic body that is formed in a cylindrical shape and is mounted around the cored bar.

  The press roller 20 is displaced toward the plate cylinder 68 at a predetermined timing by the pressing body displacing means 22, and presses the printing paper P toward the plate cylinder 68 at the nip N that is a portion facing the plate cylinder 68. Then, the ink is pressed against the master 70 wound around the plate cylinder 68, and the ink oozing from the master 70 is attached to the printing paper P for printing.

The master 70 has a laminated structure in which a thermoplastic resin film having a thickness of about 1 to 3 μm is laminated with a Japanese paper fiber, a synthetic fiber, or a mixture of a Japanese paper fiber and a synthetic fiber, which is a support sheet of a porous support. .
The master roll 70a is rotatably supported around the roll core 37 by holder means (not shown) that only shows the roll core 37 that is a winding core.

  The plate making apparatus 71 includes a platen roller 77 for pulling out the master 70 from the master roll 70a, a thermal head 78 as a plate making head disposed so as to face the platen roller 77, and a cutter 80 for cutting the plate made master 70 to a predetermined length. And a pair of rollers 79 for transporting the master 70 that has been perforated by the thermal head 78 toward the plate cylinder 68, and a guide plate 74 that guides the master 70 that has been made toward the plate cylinder 68. ing.

  Although not shown, the plate making apparatus 71 also includes a stepping motor (not shown) that rotates the platen roller 77 in a clockwise direction in FIG. 1, a pair of plate making side plates that rotatably support the platen roller 77 therebetween, and a thermal head. And a spring that urges 78 toward the platen roller 77 and presses the platen roller 77 so as to be able to come into contact with and separate from the platen roller 77.

  The thermal head 78 has a myriad of heating elements. The thermoplastic resin film of the master 70 is located on the thermal head 78 side. The roller pair 79 is rotatably supported between the plate making unit side plates while being in pressure contact with each other.

  The conveyance speed of the master 70 by the roller pair 79 is set to be higher than the conveyance speed of the master 70 by the platen roller 77, and a predetermined tension is applied to the master 70 while causing a slip with the master 70. ing. The cutter 80 is provided with guillotine type upper and lower blades in this embodiment, but may be a rotary blade moving type rotary type or the like. The guide plate 74 is fixed between the plate making unit side plates.

  In the thermal head 78, the heating element generates heat based on image data based on the original read by the image scanner 61 and other image data input from an external device such as a personal computer, and the master 70 is punched.

  The plate removal device 76 peels off the master 70 from the plate cylinder 68 and conveys it, and the plate removal box 54 that stores the used master 70 that has been peeled off and conveyed from the plate cylinder 68 by the master peeling device 53. And have.

The paper conveyance device 84 includes a driving roller 55 and a driven roller 56, a conveyance belt 58 as a paper discharge belt wound around the driving roller 55 and the driven roller 56, and an adsorption for adsorbing the printing paper P on the conveyance belt 58. And a fan 57.
The paper discharge tray 85 discharges the printing paper P printed by the printing unit 69 and holds the printing paper P in a stacked manner.

  The operation panel 91 includes an operation key 26 for performing operations necessary for printing by the stencil printing apparatus 100, and a display unit 96 for performing display for notifying the operator of the state of the stencil printing apparatus 100. .

  The display unit 96 is a touch panel type liquid crystal display panel that displays information for notifying the operator of the state of the stencil printing apparatus 100 and the like. A predetermined operation on the printing apparatus 100 can be performed.

  The operation keys 26 are a plate making start key 92 for inputting a plate making start command signal for starting plate making in the plate making apparatus 71, a numeric key 93 for inputting numbers such as the number of prints, and printing as a printing speed setting means for setting a printing speed. A speed setting key 94 and a pressing force input key 95 as pressing force input means for adjusting a pressing force, that is, a printing pressure, by which the press roller 20 presses the printing paper P toward the plate cylinder 68 are included.

  The printing speed setting key 94 can set the printing speed of the printing apparatus 100 in one of five stages from the first speed to the fifth speed. As shown in FIG. 3 or 4, the first to fifth speeds correspond to 60 rpm, 75 rpm, 90 rpm, 105 rpm, and 120 rpm at the rotational speed of the plate cylinder 68, respectively.

  The setting of the printing speed by the printing speed setting key 94 can be performed not only before the start of plate making but also after the start of plate making and before the end of printing. FIG. 3 shows the case where the fifth speed is set before the start of plate making, and FIG. 4 shows the case where the first speed is set before the plate making starts and the speed is changed to the fifth speed at time T1 after the start of plate making.

  As is clear from these drawings, the stencil printing apparatus 100 is a slow-up method that gradually increases or decreases the rotational speed of the plate cylinder 68 until the rotational speed of the plate cylinder 68 reaches a speed corresponding to the set printing speed. Is adopted. As a result, the load applied when shifting the plate cylinder 69 is reduced, thereby extending the life of the apparatus.

  The paper feeding device 52 includes a paper feed base 81 on which the print paper P provided so as to be movable up and down, a paper feed roller 82 disposed above the paper feed base 81, and the paper surface of FIG. A plurality of paper sensors 88 are provided in the left-right direction and the vertical direction to detect the presence and size of the printing paper P on the paper feed 81st.

  The paper feeding device 52 is also driven at 180 rpm in synchronization with the rotational movement of the plate cylinder 68, and a pair of registration rollers 83 for feeding the printing paper P fed by the paper feeding roller 82 to the printing unit 69, and a paper feeding roller The printing paper P fed out by 82 is guided to the registration roller pair 83, and the printing paper P fed from the registration roller pair 83 toward the printing unit 69 is guided to the nip N between the plate cylinder 68 and the press roller 20. Guide plates 40 and 41, and a paper detection device (not shown) for detecting that the front end of the printing paper P has reached the vicinity of the nip N.

  The paper feed roller 82 feeds the uppermost print paper P among the print papers P stacked on the paper feed table 81, and is rotated at a fixed position. The paper feed table 81 is controlled to rise and fall according to the number and thickness of the printing paper P so that the uppermost printing paper P contacts the paper feeding roller 82. The registration roller pair 83 feeds the printing paper P to the nip N at a predetermined timing when the image area of the master 70 enters the nip N.

  The paper supply bank 47 is a paper supply unit having a paper supply base 50, a paper supply roller 51, and a paper sensor 89 corresponding to the paper supply table 81, the paper supply roller 82, and the paper sensor 88 in the paper supply device 82. A sheet feeding device 49 as a sheet feeding unit having a sheet feeding table 86, a sheet feeding roller 87, and a sheet sensor 90 corresponding to the sheet feeding device 81, the sheet feeding roller 82, and the sheet sensor 88, respectively. And a conveyance roller 34 for feeding the printing paper P fed from the paper feeding devices 48 and 49 to the registration roller pair 83.

  The configuration of the paper feed rollers 82 and 87 in the paper feed bank 47 is the same as that of the paper feed roller 82 in the paper feed device 52, but the rotational speed of the paper feed roller 82 is 180 rpm and high speed paper feed is performed. On the other hand, the rotation speed of the paper feed rollers 82 and 87 is 120 rpm. This is because the paper feed speed by the paper feed bank 47 is limited for the reason that the paper feed path from the paper feed bank 47 to the registration roller pair 83 cannot be linear. Therefore, the sheet feeding speed by the sheet feeding bank 47 is slower than the sheet feeding speed by the sheet feeding device 52.

  The size of the paper feed table 50 is smaller than the size of the paper feed table 81, and the size of the paper feed table 86 is the same as the size of the paper feed table 81. Further, in this embodiment, it is assumed that the size and orientation of the printing paper P placed on the paper feed tray 86 are the same as those of the printing paper P placed on the paper feed tray 81.

  The control unit 19 includes a CPU 97, a ROM 98 as a first storage unit that stores an operation program of the stencil printing apparatus 100 and various data necessary for the operation of the operation program, and a stencil such as image data read by the image scanner 61. The configuration includes a RAM 99 as second storage means for storing data necessary for the operation of the printing apparatus 100.

  The control unit 19 drives the main motor 11 according to the printing speed set by the printing speed setting key 94, and rotationally drives the plate cylinder 68 at any one of 60 rpm, 75 rpm, 90 rpm, 105 rpm, and 120 rpm. Here, the control unit 19 functions as plate cylinder driving speed control means.

  Since the stencil printing apparatus 100 employs the slow-up method, the control unit 19 gradually increases or decreases the rotational speed of the plate cylinder 68 until the set printing speed is reached. As shown in FIGS. 3 and 4, the control unit 19 performs the rotation of the plate cylinder 68 at each rotation speed for at least a predetermined time, and rotates the plate cylinder 68 at the time of shifting. After stabilizing, the speed is changed to the next rotational speed.

  The control unit 19 receives signals from the paper sensors 88, 89 and 90, determines whether or not the printing paper P is placed on the paper feed tables 81, 50 and 86, and the printing paper P is placed. If there is, the size and direction of the printing paper P are monitored.

  Then, when printing paper P runs out on the paper feed tray that has been feeding during printing, it is determined whether or not the print paper P having the same size and orientation is stacked on the other paper feed tray. Judgment is made, and when there is a loaded paper tray, paper is fed from that paper tray. Here, the control unit 19 functions as a paper feed switching control means for switching the paper feed. When it is determined that the printing paper P having the same size and orientation is not stacked on any paper feed tray, the fact is displayed on the display unit 96 and printing is stopped.

  Accordingly, when the printing apparatus 100 is feeding from one of the plurality of printing apparatuses 52, 48, and 49 and the print medium P of the paper feeding apparatus is exhausted, the printing apparatus 100 starts from another paper feeding apparatus. A sheet feeding means switching operation for feeding sheets can be performed.

  The image scanner 61 includes a carriage 60 having a lamp 63 for illuminating a document set on a contact glass 62, a plurality of mirrors 64, an imaging lens 65, a one-dimensional array CCD 66, and the like. Yes.

  A series of basic printing operations of the stencil printing apparatus 100 as a whole will be described. When the operator sets a document on the image scanner 61 and presses the plate making start key 92 or performs a predetermined operation on an external device or the like, when the plate making start command signal is issued, the image scanner 61 When reading of the original is started, the plate cylinder 68 is driven to rotate clockwise in FIG. 1 by the main motor 11, and in this process, a used master (not shown) is peeled off from the plate cylinder 68 by the plate discharging device 76 and discarded. The

  The plate cylinder 68 is further rotated, and then stops when the clamping device 73 occupies the substantially right end position in FIG. When the plate cylinder 68 stops, the clamper 42 is released by the opening / closing device, and the plate feed standby state is entered.

  On the other hand, plate making to the master 70 is performed by the plate making apparatus 71 according to the image information read by the image scanner 61. The master 70 may be made based on image data input from an external device.

  In the master making, the platen roller 77 and the roller pair 79 rotate to convey the master 70 by one line in the sub-scanning direction, and the voltage is applied to a specific resistance heating element of the thermal head 78 in accordance with image information. Is applied to the thermoplastic resin film constituting the master 70, and the plate is formed by dot formation in the main scanning direction.

  The master 70 that has been made in this manner is sent out toward the plate cylinder 68 by the roller pair 79 and is guided by the guide plate 74, and the tip of the master 70 enters between the stage 14 and the clamper 42. When it is determined by the number of steps of the stepping motor that the tip of the master 70 has reached the stage 14, the clamper 42 is closed by the opening / closing device, and the tip of the master 70 is clamped by the clamp device 73.

  When the clamper 42 is closed, the rotational drive of the plate cylinder 68 is resumed. The rotational speed of the plate cylinder 68 is the same as the conveying speed of the master 70. Due to the rotation of the plate cylinder 68, the master 70 which has been subjected to plate making is wound around the outer peripheral surface of the plate cylinder 68 so as to cover the opening of the porous support cylindrical body provided in the plate cylinder 68.

  When it is determined that the plate making has been completed based on the number of steps of the stepping motor, the cutter 80 is operated to cut the master 70, the rotational driving of the platen roller 78 and the roller pair 79 is stopped, and the cut master 70 is moved to the plate cylinder. With the rotation of 68, it is drawn out to the plate cylinder 68, and the winding around the plate cylinder 68 is completed.

  Thereafter, the printing process is executed. One of the paper feed rollers 82, 51, 87 is rotated to feed the uppermost printing paper P of any one of the paper feed stands 81, 50, 86, and the registration roller pair 83 with the leading end of the printing paper P stopped. The tip edge is aligned by abutting on the nip portion.

  The pressure roller displacing means 22 drives the registration roller pair 83 in synchronization with the rotation of the plate cylinder 68, and detects that the leading end of the printing paper P has reached the vicinity of the nip N by the paper detection device. When the press roller 20 is displaced upward and the printing paper P is continuously pressed against the master 70 on the plate cylinder 68 by the press roller 20, the ink in the plate cylinder 68 oozes out from the perforated portion of the master 70, and the plate The master 70 wound around the cylinder 68 comes into close contact with the plate cylinder 68 and is transferred to the printing paper P to perform printing.

  The printing paper P after printing is peeled off from the plate cylinder 68 by the peeling claw 75, guided to the paper transport device 84 as the plate cylinder 68 rotates, and discharged from the paper transport device 84 to the paper discharge tray 85 for loading. Is done.

  Thereafter, the printing paper P is fed until the printing of the number of prints set by the ten key 93 or the like is completed, and the fed printing paper P is pressed against the master 70 when the press roller 20 is displaced upward. Printing is performed.

  The configuration and operation of the pressing body displacement means 22 in the stencil printing apparatus 100 will be described in detail. Note that the master 70 is not shown in FIGS. 5 and 6 referred to below. Further, only one of the pair of members disposed at each end of the press roller 20 is illustrated as appropriate.

  As shown in FIG. 5 or FIG. 6, the pressing body displacing means 22 includes a contact / separation device 23 as contact / separation means for contacting / separating the press roller 20 to / from the plate cylinder 68, And a positioning device 24 as a pressing body positioning means for positioning the head.

  The contact / separation device 23 includes a cam 27 integrated with the plate cylinder 68, a support shaft 30 that protrudes from both ends of the press roller 20 and serves as a center of rotation of the press roller 20, and an L-shaped support shaft 30 at one end thereof. It has a pair of roller arms 31 as a pressing body support member that rotatably supports the press roller 20 by supporting both ends of the roller rotatably.

  The contact / separation device 23 also includes a pair of disc-shaped cam followers 32 as engagement members that come in contact with and separate from the cam 27, which are rotatably supported on one end side of each roller arm 31 and displaced integrally with the press roller 20, A support shaft 33 fixed to a main body side plate (not shown) of the main body 67 and rotatably supporting a bent portion of each roller arm 31; a tension spring 35 having one end fixed to the other end side of each roller arm 31; A pressing force adjusting device 101 is provided as a pressing force adjusting means for adjusting the pressing force by which the other end of the spring 35 is supported and the press roller 20 presses the printing paper P toward the plate cylinder 68.

  The cam follower 32 is rotatably supported by each roller arm 31 and rotates integrally with the press roller 20 around the support shaft 30. The cam follower 32 is smaller in the radius of rotation than the press roller 20. The cam follower 32 is made of plastic or the like.

  The cam 27 is disposed corresponding to the entire peripheral surface of the plate cylinder 68. The cam 27 has a width larger than the arrangement width of the clamping device 73 in the circumferential direction so as to include the arrangement position of the clamping device 73 in the circumferential direction of the plate cylinder 68 and the clamping device 73 from the outer peripheral surface of the plate cylinder 68. A large-diameter portion 28 formed higher than the height, a small-diameter portion 29 that constitutes most of the cam 27 and has a height lower than d1, and an inclined portion 27a that smoothly connects the large-diameter portion 28 and the small-diameter portion 29. And have. The large diameter portion 28 and the inclined portion 27 a are disposed corresponding to the non-opening portion of the plate cylinder 68, and the small diameter portion 29 is disposed corresponding to the opening portion of the plate cylinder 68.

  Each tension spring 35 urges each roller arm 31 clockwise about the support shaft 33 in FIG. That is, each tension spring 35 urges the press roller 20 toward the plate cylinder 68.

  The positioning device 24 is a locking means for locking the press roller 20 in a state in which the press roller 20 occupies a position separated from the plate cylinder 68 and the cam follower 32 occupies a position shown in FIG. 36.

  The locking means 36 includes a pair of pins 39 planted in a manner protruding from the side surface of each roller arm 31 at an intermediate position between the support shaft 30 and the support shaft 33, and has a hook shape, A pair of locking levers 44 that can lock the pins 39, a support shaft 45 that is fixed to a main body side plate (not shown) of the apparatus main body 67 and that rotatably supports the other end of each locking lever 44, and an apparatus main body 67 A pair of solenoids 46 fixed to a main body side plate (not shown) and having a distal end of a plunger 46a fixed to an intermediate portion of each locking lever 44 are provided.

  The press roller 20 is locked by the locking means 36 when not printing. When the press roller 20 is locked by the locking means 36, the cam follower 32 comes into contact with the large diameter portion 28 of the cam 27 as the plate cylinder 68 rotates.

  The solenoid 46 is energized and controlled by the control unit 19. When the solenoid 46 is energized, a force that rotates the locking lever 44 in the clockwise direction around the support shaft 45, that is, a force that releases the pin 39 is locked.

  The pressing force adjusting device 101 includes a rack gear 38 to which the other end of the tension spring 35 is fixed, a pinion gear 59 meshed with the rack gear 38, a pressing force adjusting motor 72 that is a stepping motor that rotationally drives the pinion gear 59, and a rack gear. When the pressing force adjusting motor 72 is not operated, the rack gear 38 is driven by the biasing force of the tension spring 35 when the roller arm 31 is moved to the roller arm 31. A one-way clutch (not shown) that prohibits movement to the side.

  The pressing force adjusting motor 72 rotates forward and backward by the energization control of the control unit 19. When the pressing force adjustment motor 72 operates and the pinion gear 59 rotates forward and backward, the rack gear 38 engaged with the pinion gear 59 is driven in the left-right direction in the drawing. When the rack gear 38 moves to the left in the figure, the tension spring 35 is stretched against the urging force of the tension spring 35, and the printing pressure at which the press roller 20 presses the printing paper P toward the plate cylinder 68 is increased. When 38 is moved to the right in the drawing, the tension spring 35 is contracted by its urging force and the printing pressure is lowered.

  The energization of the pressing force adjusting motor 72 is not performed in the state where the press roller 20 is locked by the locking means 36 shown in FIG. 5, but the locking by the locking means 36 shown in FIG. 6 is released. This is performed only when the press roller 20 is displaced toward the plate cylinder 68 side.

  In the pressing body displacing means 22 having such a configuration, as shown in FIG. 5, the locking lever 44 locks the pin 39 by the urging force of the tension spring 35, and the cam follower 32 faces the small diameter portion 29. In this state, the press roller 20 is separated from the plate cylinder 68, and the cam follower 32 is separated from the small diameter portion 29 of the cam 27. At this time, the solenoid 46 is not energized.

  In this state, the press roller 20, the roller arm 31, and the locking lever 44 occupy the home position. This state is maintained when the power of the stencil printing apparatus 100 is turned off and before the start of plate making.

  From this state, when the plate cylinder 68 rotates clockwise and the cam follower 32 faces the large diameter portion 28, the cam follower 32 rides on the large diameter portion 28 via the inclined portion 27a. During this riding, the roller arm 31 rotates counterclockwise about the support shaft 33 against the urging force of the tension spring 35, and the press roller 20 is further separated from the plate cylinder 68.

  In this state, the control unit 19 energizes the solenoid 46 on the condition that the printing paper P is conveyed from the registration roller pair 83 to the nip N, that is, on the condition that printing is performed. Is pivoted clockwise about the support shaft 45. This rocking is reliably performed by forming a gap between the locking lever 44 and the pin 39, and the pin 39 is reliably released from the locking lever 44.

  When the cam follower 32 rides on the large-diameter portion 28 with the locking lever 44 releasing the pin 39, the press roller 20 is separated from the plate cylinder 68. However, as shown in FIG. When facing the small-diameter portion 29, the roller arm 31 rotates about the support shaft 33 in the clockwise direction in the drawing by the urging force of the tension spring 35, so that the press roller 20 contacts the plate cylinder 68.

  Energization of the solenoid 46 is continued during the printing operation. Therefore, when the printing paper P passes through the nip N, the press roller 20 is pressed toward the plate cylinder 68 by the urging force of the tension spring 35, and the printing paper P is applied to the master 70 wound around the printing cylinder 68. , The print image is formed on the printing paper P, and when the clamp device 73 enters or passes through the nip N, the cam follower 32 rides on the large diameter portion 28 and the press roller 20 resists the biasing force of the tension spring 35. Therefore, the press roller 20 is prevented from colliding with the clamping device 73.

  When printing is completed, the pin 39 is locked by the locking lever 44 and the press roller 20 is positioned by cutting off the power to the solenoid 46 during the period when the cam follower 32 rides on the large diameter portion 28. .

  Here, the printing apparatus 100 can set the printing speed to a plurality of speeds of five stages from the first speed to the fifth speed by the printing speed setting key 94, but the printing pressure is constant. As a result, the printed image becomes lighter or darker.

  Since the printing speed depends on the rotation speed of the plate cylinder 68, the rotation speed of the plate cylinder 68 is set to any one of 60 rpm, 75 rpm, 90 rpm, 105 rpm, and 120 rpm as described above according to the set printing speed. However, when the rotational speed of the plate cylinder 68 changes, the time for pressing the printing paper P against the master 70 by the press roller 20 changes. Therefore, if the rotational speed is fast and the pressing time is short, ink is printed from the master 70. When the time for transferring to the paper P is shortened and the density of the printed image is reduced, and conversely, when the rotation speed is slow and the pressing time is long, the time for the ink to transfer from the master 70 to the printing paper P becomes long. The concentration of is increased.

  Therefore, in the printing apparatus 100, in order to obtain a print image having a constant density regardless of the changing printing speed, as shown in FIGS. 3 and 4, according to the rotational speed of the plate cylinder 68, that is, according to the printing speed. The printing pressure is adjusted.

  Specifically, the control unit 19 drives the pressing force adjustment motor 72 so that the printing pressure becomes a pressure corresponding to the set printing speed. For this reason, the ROM 98 stores the optimum printing pressure corresponding to each printing speed from the first speed to the fifth speed.

  As shown in FIG. 7, in order to obtain an appropriate range of printing density indicated by shading in FIG. 7, the printing pressure is increased as the rotation speed of the plate cylinder 68 is increased, and the rotation speed of the plate cylinder 68 is decreased. It is necessary to reduce the printing, and if the printing pressure is low even though the rotation speed of the plate cylinder 68 is high, a thin printed image is obtained. If the printing pressure is high even though the rotation speed of the plate cylinder 68 is low, It becomes a dark print image.

  In the printing apparatus 100, as shown in FIGS. 3 and 4, the printing pressures corresponding to the rotational speeds of the plate cylinder 68 of 60 rpm, 75 rpm, 90 rpm, 105 rpm, and 120 rpm are 16 kg, 17 kg, 18 kg, These relations are 19 kg and 20 kg, and these relationships are consistent with the conditions for obtaining the appropriate range in FIG. These printing pressures are optimum values for each rotational speed obtained by experiments.

  Since the printing pressure changes according to the number of driving steps of the pressing force adjusting motor 72, the ROM 98 has a printing speed at which step the driving force adjusting motor 72 is driven from the home position in the phase of the pinion gear 59. It is stored whether the optimum printing pressure can be obtained. The RAM 99 stores how many steps the pressing force adjusting motor 72 has been driven from the home position in the phase of the pinion gear 59 as needed.

  When shifting, the control unit 19 obtains a difference in the number of steps corresponding to the rotational speed before and after the shifting, and energizes the pressing force adjusting motor 72 by the difference step. Here, the control unit 19 functions as a pressing force control unit.

  The printing apparatus 100 employs a slow-up method. However, when a change in printing speed is set, if printing is interrupted until the rotational speed of the plate cylinder 68 is stabilized at a speed corresponding to the printing speed. Then, the time until the end of printing becomes long.

  Therefore, in the printing apparatus 100, when the change of the printing speed is set by the printing speed setting key 94 as in the example shown in FIG. 4, the rotation speed of the plate cylinder 68 is set by the control of the control unit 19. The control unit 19 changes the printing pressure by the pressing force adjusting device 101 according to the gradually changing rotational speed of the plate cylinder 68 so as to obtain a print image with a constant density. Even during the change of printing pressure and rotation speed, printing is performed by feeding paper as needed according to the phase of the plate cylinder 68 without interrupting printing.

  The example shown in FIG. 4 shows a case where the printing speed setting key 94 is used to change the first speed to the fifth speed so as to increase the printing speed, and when the rotational speed of the plate cylinder 68 gradually increases to the fifth speed, that is, acceleration. In this case, the printing pressure is gradually increased. However, when the printing speed is changed so as to decrease, the printing pressure is gradually decreased.

  The controller 19 increases or decreases the rotational speed of the plate cylinder 68 even during printing on one sheet of printing paper P. During printing on such one sheet of printing paper P, the printing speed of the printing cylinder 68 is increased. Even when the change is made, the printing pressure is changed during printing on the printing paper P so as to obtain a print image having a constant density.

  In the case where the rotational speed of the plate cylinder 68 increases or decreases during printing on one sheet of printing paper P, setting of changing the printing speed by the printing speed setting key 94 is performed during printing on one sheet of printing paper P. Thus, when the printing cylinder 68 is accelerated or decelerated, and the printing speed setting key 94 is set to change the printing speed before starting printing on a certain printing paper P, the printing plate P is printed during printing on one printing paper P. There is a case where the cylinder 68 is increased or decreased.

  An example of these cases is shown in FIG. In the figure, a symbol ΔT indicates a time required for printing from the start of printing to the end of printing on one printing paper P. The times T3 and T4 shown in FIG. 8 coincide with those shown in FIGS.

  In the former case, printing is started from time TA. At time T3 during printing on one sheet of printing paper P, the setting for changing the printing speed from the third speed to the fifth speed is performed by the printing speed setting key 94. The rotation speed of the plate cylinder 68 is increased from time T3 to time TC.

  In the latter case, the print speed setting key 94 is used to set the change of the print speed from any one of the first speed to the third speed before the print start time TB for a certain printing paper P. Since the printing is started at time TB between time T3 and time TC when the rotational speed of the plate cylinder 68 is increasing, the plate is printed from time TB to time TC during printing on the one printing paper P. The rotational speed of the barrel 68 is increasing.

  As shown in the figure, even when the plate cylinder 68 is shifted, a so-called rounding occurs at the rise of the change in the rotational speed of the plate cylinder 68. For example, when shifting from the third speed to the fourth speed, There is a time lag from time T3 to time T4 when changing from 90 rpm to 105 rpm. Although the falling is not shown in the figure, a rounding occurs similarly.

  Therefore, the responsiveness of the pressing force adjusting device 101 is good, that is, the responsiveness with respect to the change of the printing pressure is good, and it is assumed that there is no time lag when changing from 18 kg to 19 kg as shown by the thick line in the figure. For example, in the former case, a change in print density as shown in FIG. 9 occurs, and in the latter case, a change in print density as shown in FIG. 10 occurs.

  Therefore, when the rotational speed of the plate cylinder 68 increases or decreases during printing on one sheet of printing paper P, the control unit 19 adjusts the change in the printing pressure according to the response of the shift of the plate cylinder 68. It is supposed to be. The speed change responsiveness of the plate cylinder 68 is obtained by experiment and stored in the ROM 98. Further, the degree to which the printing pressure is changed, that is, the number of steps per driving time of the pressing force adjusting motor 72 is also obtained based on such responsiveness and stored in the ROM 98.

  In the printing apparatus 100, as described above, the sheet feeding speed by the sheet feeding bank 47 is slower than the sheet feeding speed by the sheet feeding apparatus 52. In such a configuration, it is necessary to change the printing speed between when the paper is fed by the paper feed bank 47 and when the paper is fed by the paper feeder 52.

  Therefore, in the printing apparatus 100, control is performed so that the printing speed when the paper feeding by the paper feeding bank 47 is performed is lower than the printing speed when the paper feeding by the paper feeding apparatus 52 is performed. The rotation speed of the plate cylinder 68 when the paper is fed by the paper feed bank 47 is set to be slower than the rotational speed of the plate cylinder 68 when the paper feeding device 52 is feeding. Yes. Here, the control unit 19 functions as a paper feed speed corresponding print speed control means for adjusting the print speed in accordance with the paper feed speed.

  In such a configuration, it is assumed that when the printing paper P is supplied from the paper feeding device 52 and printing is performed, all the printing paper P on the paper feed tray 88 is used. Then, as described above, the control unit 19 performs the paper feeding means switching operation and feeds paper from the paper feeding device 49. The printing speed when paper is fed from the paper feeding device 49 is slower than the printing speed when paper is fed from the paper feeding device 52. However, the printing speed is also changed when this paper feeding means switching operation is performed. If the pressure is constant, the density of the printed image after the sheet feeding means switching operation will be higher than that before the sheet feeding means switching operation.

  Therefore, when the sheet feeding unit switching operation is performed, the control unit 19 determines whether the printing speed must be changed because the sheet feeding speed is changed before and after the sheet feeding unit switching operation. It functions as a change determination means, and when it is determined that it must be changed, the printing pressure is changed according to the change in the printing speed. Here, the control unit 19 functions as a paper feed speed corresponding pressure control means for adjusting the printing pressure according to the paper feed speed. As a result, when the sheet feeding means switching operation is performed, the printing speed is set according to the sheet feeding speed of the sheet feeding apparatus that has started feeding, and the printing pressure obtains a print image with a constant density. It is set according to the printing speed after the shift.

  When the sheet feeding unit switching operation is performed in the change from the sheet feeding device 48 to the sheet feeding device 49 or in the change from the sheet feeding device 48 or the sheet feeding device 49 to the sheet feeding device 52. If the paper feed speed does not change before and after the paper feed means switching operation, such as when the paper feed roller 82 can be rotated at 120 rpm, the printing speed is not changed.

  Such an operation will be described with reference to FIG. 11 in the case where the paper feeding device 52 feeds paper.

  When the sheet feeding device 52 performs sheet feeding by rotating the sheet feeding roller 82 at 180 rpm, the control unit 19 sets the printing pressure according to this (S1), performs sheet feeding and prints (S2). Then, for each printing, it is determined whether or not the set number of printings has been performed (S3). When the set number of sheets has been printed, the printing is finished. When the set number of sheets has not been reached, the printing sheet P is printed until the sheet feeding device 52 runs out of the printing sheet P in the process of feeding and printing. (S4), and when there is no print paper P in the paper feeder 52, the other paper feeders 48 and 49 have the same size and orientation. (S5), if not, the printing paper P is displayed on the display unit 96 so that the printing paper P is no longer in the paper feeding device 52, and the size and orientation are the same. Is displayed on the paper feeding device 52 (S6), and printing is stopped (S7).

  If it is determined in step S4 that the printing paper P having the same size and orientation exists in the other paper feeding device 49, whether or not the printing speed should be changed according to the paper feeding speed of the paper feeding device 49 is determined. If it is determined (S8) and it is determined that it should be changed, the rotational speed of the plate cylinder 68 is changed according to the paper feed speed of the paper feeder 49 (S9), and the printing speed after changing the printing pressure is changed. (S10), the paper is fed from the paper feeder 49 to continue printing (S11), and the process returns to step S2. If it is determined in step S8 that it is not necessary to change the printing speed, printing is continued by simply switching the paper feeding device (S11).

  As described above, in the printing apparatus 100, printing is performed with the printing pressure obtained in the experiment according to the printing speed in order to obtain a print image with an appropriate density under the control of the control unit 19. The printing pressure set by the unit 19 may not meet the operator's needs.

  For example, an operator may want to save ink because the image may be thinner, prefer images with darker eyes, or increase noise due to increased printing pressure. There is a case where the printed image having the density automatically obtained only by the control of the control unit 19 does not meet the needs of the operator.

  For this reason, the printing apparatus 100 includes a pressing force input key 95 on the operation panel 91 and can change the printing pressure automatically set by the control unit 19. As a result, the fine wishes of the operator can be satisfied.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments, and the present invention described in the claims is not specifically limited by the above description. Various modifications and changes are possible within the scope of the above.

  For example, the printing apparatus may include a plurality of plate cylinders, or may perform color printing using a plurality of plate cylinders, for example. The printing apparatus may perform double-sided printing by including a mechanism for inverting printing paper. The pressing body may be an impression cylinder instead of a press roller.

  The configuration of the pressing force adjusting means is not limited to the above-described configuration as long as the pressing body can adjust the pressing force for pressing the print medium toward the plate cylinder, and is substantially stepless like the above-described pressing force adjusting means. In addition, the pressing force may be adjusted stepwise within a range that can be adjusted so that the printing density can be considered constant.

  In the above embodiment, the pressing force adjusting means is driven only when the pressing body is displaced toward the plate cylinder, but this driving is separated from the printing cylinder as necessary. It may be done when locked in position. When the pressing body is locked at a position away from the plate cylinder and the pressing force adjusting means is driven, if printing can be performed quickly or an image with a constant density can be obtained, The control means performs such control.

  The effects described in the embodiments of the present invention are only the most preferable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. is not.

1 is a front view showing an outline of a printing apparatus to which the present invention is applied. FIG. 2 is a block diagram illustrating a control unit provided in the printing apparatus illustrated in FIG. 1 and a part of a configuration controlled thereby. FIG. 2 is a correlation diagram illustrating an example of a relationship between a rotational speed of a plate cylinder and a printing pressure in the printing apparatus illustrated in FIG. 1. FIG. 6 is a correlation diagram illustrating another example of the relationship between the rotational speed of the plate cylinder and the printing pressure in the printing apparatus illustrated in FIG. 1. FIG. 2 is a schematic front view of a pressing force adjusting means provided in the printing apparatus shown in FIG. 1 and its peripheral configuration, showing a state in which a pressing body is locked at a position separated from a plate cylinder. FIG. 2 is a schematic front view of a pressing force adjusting unit provided in the printing apparatus shown in FIG. 1 and its surroundings, showing a state in which a pressing body is displaced toward a plate cylinder. FIG. 4 is a correlation diagram showing that the density of a printed image is determined by the relationship between printing speed and printing pressure, and that this relationship should satisfy a predetermined condition in order to obtain an appropriate density. FIG. 6 is a correlation diagram between the rotational speed of the plate cylinder and the printing pressure, showing that the printing pressure should be changed accordingly when the rotational speed of the plate cylinder changes during printing of one printing medium. In the case where the rotational speed of the plate cylinder changes when printing a single printing medium as shown in FIG. 8, the non-uniformity in the density of the printed image that can occur on the printing medium if the printing pressure does not change properly. It is a conceptual diagram which shows an example of a simple state. In the case where the rotational speed of the plate cylinder changes when printing a single printing medium as shown in FIG. 8, the non-uniformity in the density of the printed image that can occur on the printing medium if the printing pressure does not change properly. It is a conceptual diagram which shows the other example of a state. 2 is a flowchart illustrating an example of control regarding a change in printing pressure that may occur when a sheet feeding unit is switched in the printing apparatus illustrated in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 19 Control means 20 Press body 48, 49, 52 Several paper feeding means 68 Plate cylinder 94 Printing speed setting means 95 Pressing force input means 100 Printing apparatus 101 Pressing pressure adjustment means P Print medium

Claims (5)

A printing speed setting means capable of setting the printing speed to a plurality of speeds;
A plate cylinder whose rotational speed changes according to the printing speed set by the printing speed setting means;
A pressing body that presses the print medium toward the plate cylinder;
A pressing force adjusting means for adjusting a pressing force with which the pressing body presses the printing medium toward the plate cylinder;
In a printing apparatus having control means for setting the pressing force by the pressing force adjusting means according to the rotational speed of the plate cylinder in order to obtain an image having a constant density,
A plurality of paper feeding means for feeding printing media and having different paper feeding speeds;
When printing is performed by feeding paper from one of the plurality of paper feeding means, when there is no print medium of the paper feeding means, the other one of the plurality of paper feeding means is used. A printing apparatus capable of switching a paper feeding means for feeding paper,
When the paper feeding means switching operation is performed, the printing speed is set according to the paper feeding speed of the paper feeding means that is feeding paper, and the control means is configured to control the pressing force by the pressing force adjusting means. A printing apparatus , wherein the pressure is set in accordance with a set printing speed so as to obtain an image having a constant density . The printing apparatus according to claim 1.
When the printing speed is changed by the printing speed setting means, the rotation speed of the plate cylinder is gradually changed to a speed corresponding to the changed printing speed, and the control means obtains an image having a constant density. In this way, the pressing force by the pressing force adjusting means is changed according to the gradually changing speed . The printing apparatus according to claim 2 , wherein
When the rotational speed of the plate cylinder changes during printing of one printing medium, the control unit uses the pressing force by the pressing force adjusting unit to print the one sheet so as to obtain an image having a constant density. A printing apparatus characterized by being changed during printing of a medium . The printing apparatus according to any one of claims 1 to 3,
A printing apparatus comprising: a pressing force input unit that changes the pressing force by the pressing force adjusting unit set by the control unit . A printing method for performing printing using the printing apparatus according to claim 1.

Images