JP4340490B2 - Duplex printing machine - Google Patents

Description

The present invention relates to a perfecting press.

  Conventional double-sided printing machines, particularly stencil double-sided printing machines, can be broadly classified into two types: a type having a single printing unit as shown in FIG. 8 or FIG. 9 (see Patent Documents 1 and 2, etc.), and FIG. As described above, there is a format (see Patent Document 3 or the like) that includes two printing sections that respectively print one side and the other side of a sheet.

  The double-sided printing machine shown in FIG. 8 includes a single printing unit 101 composed of a plate cylinder 102, a pressure roller 109, and the like, and a paper feed tray 106 and a final paper receiving tray 107 are arranged on both sides of the printing machine main body 105. An intermediate paper receiving base 108 is disposed below the paper supply base 106 so as to be movable up and down, and a reverse conveying device 111 having a U-shaped reverse conveying path is arranged from the printing unit 101 to the intermediate paper receiving base 108. It is. The reverse conveying device 111 includes a large number of conveying roller pairs 112 and the like. A switching mechanism 110 is provided in the middle of the reverse conveyance path to switch the path to the final paper tray 107 and the path to the intermediate paper tray 108.

  When double-sided printing is performed with the printing machine of FIG. 8, first, when printing one side, the switching mechanism 110 is set to the intermediate paper tray 108 side, and one side of the paper supplied from the paper tray 106 is printed. Printing is performed by the unit 101, and reversely conveyed on the conveying path by the reverse conveying device 111, and returned to the intermediate paper tray 108 in the reversed state. After the printing on one side is completed, an image for the other side is made by the plate making apparatus 113, the stencil sheet after the plate making is replaced with the used one-side stencil sheet of the plate cylinder 102, and the printing operation on the other side is started. In the printing operation on the other side, the switching mechanism 110 is switched to the final paper receiving tray 107 side, and the intermediate paper receiving tray 108 is raised to the paper feed position, and the single-side printed has been resupplied from the intermediate paper receiving tray 108. The other side of the paper is printed by the printing unit 101. The paper after double-sided printing is passed through the switching mechanism 110 to be the final paper receiving tray 107.

  The double-sided printing machine shown in FIG. 9 includes a single printing unit 201 composed of a plate cylinder 202, a pressure roller 209, and the like, as in FIG. A table 207 is arranged, and a reverse conveying device 211 laid out in a large U-shape is arranged from the printing unit 201 to an upper position of the paper feeding / paper receiving table 207. The reverse conveying device 211 includes a large number of conveying roller pairs 212 and the like.

  When double-sided printing is performed by the printing machine of FIG. 9, first, one side of the paper supplied from the paper feeding and paper receiving tray 207 is printed by the printing unit 201, and fed by the reverse conveyance device 211 through the reverse conveyance path. Return to the double paper tray 207 from above in an inverted state. After the required number of single-sided printings are completed, the plate-making device 213 makes the image for the other side, replaces the stencil sheet after the plate-making with the used one-sided stencil sheet of the plate cylinder 202, and then performs the printing operation on the other side. start.

  In the double-sided printing machine shown in FIG. 10, the first printing unit 301 and the second printing unit 302 are arranged with a vertical gap therebetween, and the first paper feed is provided to the side of the lower first printing unit 301. A table 307 is arranged, a paper receiving table 308 is arranged on one side of the upper second printing unit 302, a second sheet feeding table 309 is arranged on the other side, and the discharging unit of the lower first printing unit 301 is arranged. A reversing and conveying device 311 for reversing and conveying one-side printed paper is arranged from the second printing unit 302 to the upper side. The reverse conveying device 311 includes a large number of conveying roller pairs 312 and the like.

When double-sided printing is performed by the printing machine shown in FIG. 10, the sheets stacked on the first paper feed tray 307 are first supplied to the first printing unit 301, printed on one side, raised by the reverse conveyance device 311, and reversed. Then, the paper is supplied to the upper second printing unit 302, and the other side is printed and discharged to the paper tray 308. On the other hand, when printing on only one side, the paper stacked on the second paper feed tray 309 is printed on one side by the second printing unit 302 and discharged to the paper tray 308.
JP-A-9-188057. JP 2000-10194A. Japanese Patent Laid-Open No. 2002-370437.

(1) In any of the reverse conveying devices 111, 211, and 311 provided in the double-sided printing machine of FIGS. 8, 9, and 10, the paper immediately after one side is printed by the printing unit 101, 201, or 301 is printed on the front and back sides. Since it is configured so as to be reversed and conveyed from both sides by the conveyance roller pairs 112, 212, and 312, the print surface on which ink is not dried immediately after printing comes into contact with the conveyance rollers 112, 212, or 312 to thereby print images. In addition, there is a high possibility that the ink is transferred to the transport roller 112 and the transport roller 112 and the like is soiled and re-transferred to the subsequent paper and the print quality is deteriorated.

  In order to cope with the re-transfer problem, the printing press of FIG. 8 is provided with a special re-transfer prevention mechanism. However, this is expensive, and the structure is complicated, causing a paper jam.

(2) In the double-sided printing machine having a single printing section shown in FIGS. 8 and 9, once the required number of sheets is printed on one side, the stencil sheet of the plate cylinder must be replaced, and then printing on the other side must be started. Therefore, it takes a long time to perform both-side printing work and cannot meet the demand for double-sided high-speed printing from the user.

(3) Like the double-sided printing machine of FIG. 8, in addition to the paper feed tray 106 and the final paper tray 107, an intermediate paper tray 108 is provided, and the intermediate paper tray 108 is configured to be movable up and down. The entire printing press becomes complicated and large. In addition, since the double-sided printing machine of FIG. 8 includes the switching mechanism 110 that switches the conveyance path between single-side printing and other-side printing, the structure of the reverse conveyance path becomes complicated and also causes a paper jam. Become.

(4) In the double-sided printing machine shown in FIG. 8, sheets that are reversed after single-sided printing are sequentially stacked on the paper tray 108, and after completion of single-side printing, the paper tray 108 is raised and re-feeded from above. Therefore, the first sheet printed on one side is fed last when printing on the other side. In the case of a stencil printing machine, when the number of printed sheets increases, the stencil sheet wound around the plate cylinder may gradually stretch and the printed image may also stretch in the printing direction. When the printed paper is fed last when printing on the other side, the printed image on one side is not stretched but the other side is stretched. The double-sided printed image.

(5) When double-sided printing is performed by the double-sided printing machine of FIG. 10, the paper printed on one side by the first printing unit 301 is immediately supplied to the second printing unit 302 without staying in the middle, and the other side is Since printing is performed, it is very difficult to mutually adjust the paper feed timing between the printing units 301 and 302 and the conveyance speed of the reverse conveyance device 311, and the print positions on the front and back sides of the paper are likely to be shifted.

  An object of the present invention is to make it possible to prevent the conveyance member and paper from being stained due to ink transfer and retransfer while maintaining the compactness and work efficiency of the duplex printing machine. Another object is to ensure the necessary ink drying time while meeting the demand for high-speed printing on both sides.

In order to solve the above-mentioned problem, the invention described in claim 1 includes a paper feeding device that feeds paper, a first printing unit that prints one side of the fed paper, and a downward direction from the first printing unit. A reversing conveying device that forms a curved reversing conveying path, a paper stacking table on which single-sided printed paper is stacked, and an intermediate paper feeding device with a suction mechanism that sucks and feeds the sheets on the paper stacking table in the order they are stacked An intermediate conveyance device that conveys the sheet fed from the intermediate sheet feeding device, a second printing unit that prints the other side of the single-side printed paper that is conveyed from the intermediate conveyance device, and a second printing unit The paper discharge device that discharges the double-side printed paper printed in step 1 and stacks it on the paper tray, the paper stack detection means for detecting the paper stack on the paper stack base, and the paper stack detection means are loaded first. The number of detections is measured from the time when the loading of the paper to be detected is detected. Number, when it reaches the arbitrary settable predetermined number, and a, and a control means for starting the driving of the intermediate sheet feeder.

According to a second aspect of the present invention, a paper feeding device that feeds paper, a first printing unit that prints one side of the fed paper, and a reverse conveyance path that curves downward from the first printing unit are formed. A reversing transport device, a paper stacking table on which single-sided printed paper is stacked, an intermediate paper feeding device with a suction mechanism that sucks and feeds the paper on the paper stacking base in the order of stacking, and an intermediate paper feeding device An intermediate conveyance device that conveys the fed paper, a second printing unit that prints the other side of the single-side printed paper that is conveyed from the intermediate conveyance device, and a duplex printing that is printed by the second printing unit A paper discharge device that discharges the paper and stacks it on the paper tray, and a paper stack detection means for detecting the paper stack on the paper stack base, and the paper stack detection means detects the loading of the first loaded paper The elapsed time is measured from the time it was taken, and the measured elapsed time is set arbitrarily Upon reaching a capacity of a predetermined time, and a, and a control means for starting the driving of the intermediate sheet feeder.

According to a third aspect of the present invention, in the double-sided printing machine according to the first or second aspect, a blower is provided to send air to the paper from the front in the paper feeding direction of the intermediate paper feeding device.

According to a fourth aspect of the present invention, in the double-sided printing machine according to the first or second aspect of the present invention, the double-sided printing machine includes a blower that sends air to a sheet from a direction opposite to a sheet feeding direction of the intermediate sheet feeding device. A guide member for guiding the upper sheet is disposed on the upper part of the sheet stacking table.

According to a fifth aspect of the present invention, in the double-sided printing machine according to the second aspect, the predetermined time is determined based on the size or thickness of the paper.

According to a sixth aspect of the present invention, in the double-sided printing machine according to the second aspect, the predetermined time is determined based on a print image amount of paper.

(1) The non-printed surface of the single-side printed paper discharged from the printing unit is sucked by a reverse conveyance member such as a reverse conveyance belt, and reversely conveyed so as to go around to the paper stacking table below the printing unit. In this case, only the unprinted surface is sucked and brought into contact with the reversal conveying member, and the printed surface on which the ink is not dried can be prevented from being disturbed by rubbing with the roller or the like. Can be prevented from being transferred and retransferred to the next sheet from a roller or the like, and the printing quality can be maintained.

(2) If the paper after single-sided printing is stacked on a paper stacking base located below the printing unit and stayed, the space below the printing unit can be used effectively in a double-sided printing machine, and the compactness of the printing machine It can contribute to the conversion.

(3) If a guide member for guiding the reversely conveyed single-sided printed paper is arranged on the upper part of the paper stacking table, the guide surface comes into contact with the non-printed surface of the paper. Single-sided printed sheets can be stacked in an orderly manner without being stained.

(4) If air is sent from the front of the sheet feeding direction of the intermediate sheet feeding device to the sheets by the blower, the front end of the stacked sheets is separated and the sheets are fed one by one in the stacking order. Thus, it is possible to reliably perform the discharging operation, and it is possible to promote drying of the ink on the printing surface.

(6) If air is sent from the rear in the paper feeding direction on the intermediate paper stacking base, the work of feeding the paper one by one from the bottom, for example, from the bottom is more reliably and quickly performed. In addition, drying of the ink on the printing surface can be further promoted. In particular, the wind from the rear is effective in the case of a large sheet (A3 or the like). As described above, the separation of the front end of the sheet by the wind from the front and the separation of the rear end of the sheet by the wind from the rear. In addition, the feeding operation can be performed and the feeding efficiency is improved.

(7) In the double-sided printing machine, when the single-sided printed paper printed by the first printing unit is temporarily stacked on an intermediate paper stacking base below the first printing unit and retained, Ink drying time can be ensured, and in the process of transporting from the intermediate sheet stacking plate to the second printing unit for printing on the other side, the printing surface is disturbed by the transport roller or transferred to the transport roller or the like. Thus, the problem of retransfer to the next sheet can be prevented.

(8) In the double-sided printing machine, the single-side printed paper printed by the first printing unit is temporarily stacked on an intermediate paper stacking base below the first printing unit, and is retained. If the paper is re-fed to the printing unit, the feeding timing to the image forming part of the second printing unit by, for example, the timing roller is harmonized only with the feeding timing from the intermediate paper stacking base. All you have to do is adjust it so that Therefore, it is not necessary to coordinate the timing with the first printing unit, and the timing setting operation in the double-sided printing operation is simplified with respect to the change of the paper size and the like.

(9) In a double-sided printing machine, when single-sided printed paper stacked on an intermediate paper stacking table is fed out in the stacking order and re-fed to the second printing unit, the single-sided printing order In this way, it is supplied to the second printing section. That is, a first-in first-out state is established, and the ink is re-feeded in the order of drying, so that the dry state of each sheet sent to the second printing unit can be made substantially uniform.

“First Embodiment”
[Overall structure of stencil duplex printing machine]
FIG. 1 is a schematic front view schematically showing a stencil double-sided printing machine to which the present invention is applied. For convenience of explanation, as shown in FIG. The “rear side” and the arrangement side of the paper discharge device 3 will be referred to as “front side” and will be described below.

  The printer body 1 is provided with an image reading device 4 on the upper side, an operation panel 5 and a control device (control means) 6 on the front side, together with the paper discharge device 3 and the paper supply device 2 on the front and rear sides.

  A first printing unit 11 is provided in the latter half of the printer main body 1, and a second printing unit 12 is provided in the first half in parallel with the first printing unit 11. Are provided with a first and second plate making section 13 and a first and second plate discharging section 14, respectively. The first and second plate making sections 13 and the first and second plate discharging sections 14 can be shared by the printing sections 11 and 12 by providing one each as a movable type in the front-rear direction. .

  On the front side of the first printing unit 11, a carry-out belt 28 is provided for carrying the single-side printed paper N printed and discharged by the first printing unit 11 forward.

  Below the first printing unit 11, an intermediate sheet stacking table 30 inclined in a front-up manner is disposed, and a reverse conveying device is provided between the front end of the sheet stacking table 30 and the front end of the carry-out belt 28. 36 is provided. A belt-type intermediate sheet feeding device 31 with a suction mechanism that is inclined at substantially the same angle as the sheet loading table 30 is disposed at the front end of the sheet loading table 30. An extended intermediate conveyance device 33 is disposed, and the intermediate conveyance device 33 reaches the timing roller 35 of the second printing unit 12.

[Paper Feeder]
The sheet feeding device 2 includes a sheet feeding table 18, a sheet feeding roller 20, a timing roller 21, a guide roller 22 that is pressed against the timing roller 21, and the like. The paper feed roller 20 feeds the paper one by one from the top and feeds it to the timing roller 21. The timing roller 21 rotates at an appropriate timing in synchronism with the driving of the first printing unit 11, and feeds the printing paper N to the first printing unit 11 in cooperation with the guide roller 22.

[Paper delivery device]
The paper discharge device 3 includes a paper discharge belt 25 having a suction mechanism 26 such as a suction fan, and a paper tray 27 on which double-side printed paper is stacked. The paper discharge belt 25 has a number of through holes. The sheet N on the paper discharge belt 25 is attracted to the paper discharge belt 25 by the suction mechanism 26 disposed below.

[First and second printing sections]
FIG. 2 is a front view of the inside of the printing machine main body 1. The first printing unit 11 includes a plate cylinder 39 in which an ink roller 41 is inscribed and rotationally driven in the direction of arrow R, and a lower side of the plate cylinder 39. The pressure roller 40 and the like are opposed to each other so as to be capable of being pressed against each other. A large number of holes are formed in the peripheral wall of the plate cylinder 39, and a stencil sheet which has been made is mounted. An ink supply unit including a squeegee 42 is provided on the outer peripheral surface of the ink roller 41, and ink from an ink tank (not shown) is supplied to the ink supply unit from an ink supply pipe 43. The second printing unit 12 has the same structure as that of the first printing unit 11, and the corresponding parts are denoted by the same reference numerals and description thereof is omitted.

[Reverse conveying device]
The reverse conveying device 36 includes a belt guide tube 45 that also serves as a suction duct, a rubber reverse conveying belt (reverse conveying member) 46, and the like. The belt guide tube 45 is formed, for example, in a cylindrical box shape using a stainless steel plate, and its upper end is positioned at substantially the same height as the carry-out belt 28 of the first printing unit 11, and the upper half of the front wall surface is a semicircle. It protrudes forward in shape, and its lower half extends linearly downward and rearward at substantially the same inclination angle as the intermediate paper stacking base 30. Rotating rollers 48 and 49 are disposed in the vicinity of the upper and lower ends of the rear wall of the belt guide tube 45, and a tension roller 50 is disposed between the rotating rollers 48 and 49. The rollers 48, 49 and 50 and the belt guide The reverse conveying belt 46 is wound around the front wall surface of the tube 45.

  The reverse conveyance path M is formed along the outer periphery of the reverse conveyance belt 46. That is, the reverse conveyance path M protrudes forward from the vicinity of the front end portion (exit end portion) of the carry-out belt 28, wraps around the rear lower side, extends rearward and lower, and extends near the upper front end portion of the intermediate sheet stacking base 30. Is formed. The belt guide cylinder 45 is connected to a suction port of a suction fan (suction mechanism) 52, and the suction fan 52 generates a negative pressure in the belt guide cylinder 45.

  The reversing and conveying device 36 is provided with a reversing and conveying guide 47, which is arranged at a predetermined interval with respect to the front wall of the belt guide tube 45 and along the reversing and conveying path M. Is formed.

  3 is a plan view of a range III portion of FIG. 2. The reverse conveying belt 46 has a large number of suction holes 53 and is divided into, for example, three sheets at intervals in the left-right direction. A plurality of suction ports 54 are formed on the peripheral wall at positions corresponding to the reversal conveyance belts 46, and the paper on the reversal conveyance belt 46 is sucked from the suction ports 54. The suction port 54 is formed in a strip shape along the reverse conveyance path.

  The reverse conveying guy 47 is made of, for example, a thin rod-shaped member made of stainless steel, and a total of three reversal conveying guys 47 are arranged for each reverse conveying belt 46.

  FIG. 4 is an enlarged front view of the reverse conveying device 36. At least one of the rotating rollers 48 and 49 is linked to the output shaft of the drive motor 56 via the belt transmission mechanism 55, and the reverse conveying belt 46 is moved in the direction of arrow D. It is supposed to make it go around.

[Intermediate paper loading platform]
In FIG. 2, the paper stacking base 30 includes a bottom plate 58, a rear plate 59 erected on the upper surface of the bottom plate 58 so that the front and rear positions can be adjusted, and a pair of left and right side plates 60 erected so that the left and right positions can be adjusted. It is configured. A guide plate 61 made of a flexible resin band plate is disposed above the paper stacking table 30, and the front upper end portion of the guide plate 61 is fixed to the upper part of the exit of the reverse conveyance path M, As it goes rearward, it inclines so as to approach the bottom plate 58 of the paper stacking table 30, and the rear end portion can contact the bottom plate 58 at a position near the rear plate 59.

  In FIG. 5 showing a plan view, one guide plate 61 is arranged, for example, at a substantially central portion of the left-right width of the loading table 20.

[Intermediate paper feeder and blower]
In FIG. 4, the intermediate sheet feeding device 31 includes a pair of front and rear rollers 65, a feeding belt 66 wound around the rollers 65, and a suction duct / belt guide cylinder 67. The drive motor 88 is linked and connected.

  In FIG. 5 showing a plan view, the feeding belt 66 is divided and arranged in seven rows with an interval in the left-right direction as an example. The belt guide cylinder 67 communicates with the suction fan 69 and has suction ports 68 formed at positions corresponding to the left and right sides of each feeding belt 66 so that the sheet can be adsorbed to the feeding belt 66. Each suction port 68 is formed in a rectangular shape that is long in the front-rear direction.

  A blower 71 is disposed on the front side of the intermediate sheet feeding device 31 in order to separate the lowermost sheet and the second or more sheets and to dry them at the time of sheet feeding. The blower device 71 includes a duct 72 communicating with the blower fan 73, and a blower guide plate 74 that opens rearward from the rear surface of the duct 72. As shown in FIG. It blows as shown by an arrow E toward the lower end of the edge.

  Further, above the intermediate sheet feeding device 31, a separating plate 76 that hangs from above at a right angle to the bottom plate 58 of the stacking table 30 is disposed.

  As shown in FIG. 2, an auxiliary air blower (blower fan) 64 is also arranged behind the paper stacking base 30, and is attached to the rear end of the stacked paper N on the stacking base 30 through a hole formed in the rear plate 59. It is designed to send the wind.

[Intermediate transfer device]
In FIG. 2, the intermediate transport device 33 is composed of a plurality of transport guide plates 81 and a plurality of pairs of transport rollers 80 and the like that are disposed to face each other so as to sandwich the transport guide plate 81. The conveyance guide plate 81 is divided into a plurality of parts from the front end of the intermediate sheet feeding device 31 to the timing roller 35 of the second printing unit 12, and each pair of conveyance rollers 80 is arranged at intervals in the conveyance path. Has been.

  In FIG. 3 showing a plan view, the conveyance guide plates 81 are made of resin band plates, and are arranged in, for example, seven rows at intervals in the left-right direction. The conveyance roller 80 is formed in a portion between the conveyance guide plates 81 of the roller shaft 80a.

[Paper loading detection sensor and control device]
In FIG. 2, at the exit end of the reverse conveyance path M, a paper stack detection sensor (paper stack detection means) 87 such as an optical sensor that detects the passage of the paper discharged from the reverse conveyance path M onto the paper stacking base 30. Is arranged, and is connected to the input unit of the control device 6.

  FIG. 6 is a block diagram related to control, and the control device 6 includes a CPU 90 and a storage unit 91, as in a general control device, and in the CPU 90, a control unit 92, an arithmetic processing unit 93, and the like. In addition, a timer 94 and a counter 95 are also incorporated. The storage unit 91 includes a ROM 96, a RAM 97, and the like. The input / output unit of the CPU 90 is connected to the sheet stacking detection sensor 87 and the driving unit of each device of the duplex printing machine. That is, the paper feeding device 2, the paper discharge device 3, the image reading device 4, the input unit and display unit of the operation panel 5, the first printing unit 11, the second printing unit 12, and the first and second plate making units. 13, the plate discharging unit 14, the reverse conveying device 36 (the driving unit of the driving motor 56 and the suction fan 52), the intermediate conveying device 33, and the blower devices 71 and 64 from the front and rear of the intermediate paper feeding device 31 are connected.

  Various programs for executing operations according to the present invention are written in the storage means (for example, ROM) 96 of the CPU 90. That is, with respect to the control of the intermediate paper feeding device 31 and the like, the timer 94 is set when the paper discharge detection sensor 87 detects the paper discharged to the paper stacking base 30 for the first time after the paper passage detection sensor 87 has not detected the passage of the paper for a certain period of time. A program for operating the drive motor 88 of the intermediate sheet feeding device 31 and starting the intermediate sheet feeding device 31 when a predetermined time elapses after the operation and detection of the first passing sheet is written.

  In addition, the intermediate conveyance device 33, the second printing unit 12, and the like are also programmed to start with the start of the intermediate paper feeding device 31.

  That is, when a large number of sheets are continuously printed, sheets that are first-side printed by the first printing unit 11 and loaded on the intermediate sheet stacking board 30 have a predetermined time set by the timer 94. It is programmed so that it stays on the intermediate sheet stacking table 30 and then is fed out by the intermediate sheet feeding device 31. As a result, the ink drying time after one-side printing (substantially the time for the ink to soak into the paper) can be secured.

  The predetermined time set by the timer 94 is basically the time for the ink on the paper printed on one side to dry, and is set according to the size or thickness of the paper and according to the print image amount of the paper. The For example, when the amount of print images is large, the predetermined time is set longer, and when the size and thickness of the paper are large, the predetermined time is set longer. It is also adjusted by the quality of the paper. In short, when the condition that requires a long ink drying time is used, the predetermined time is adjusted to be long.

  In addition, if the predetermined time is set long as described above, the ink drying time can be sufficiently secured. However, if the predetermined time is set too long, the number of sheets staying on the paper stacking board 30 becomes too large, and the lowest sheet in the stacking order. It may be difficult to feed paper from the beginning. For this reason, it is appropriate to set the number of sheets of paper staying on the sheet stacking table 30 in the range of 5 to 40 in general. It is preferable to set the number of sheets to about one.

  Regarding the control of the blower 71 that blows air from the front of the intermediate paper feeder 31, the paper stacking detection sensor 87 does not detect the passage of paper for a certain period of time or completes the paper feed for the set number of prints. The first blower 71 is programmed to detect the first passing paper after being set and start the first one-side printed paper on the intermediate paper stacking base 30. This promotes initial drying.

  On the other hand, regarding the control of the blower 64 that blows air from behind the intermediate paper feeder 31, the size of the single-side printed paper that is initially stacked on the intermediate paper stacking base 30 is larger than a predetermined size (for example, A3). If the amount of printed images is large even if the paper is not large, it is programmed to start almost simultaneously with the loading of the first paper on the paper stacking table 30 together with the front blower 71.

[Printing process]
(1) In FIG. 1, the image reading device 4 reads the front and back surfaces of the document, respectively, makes the plates by the first and second plate making sections 13, and makes the stencil sheet (master) after the plate making each plate cylinder. Attach to 39.

(2) At least the required number of unprinted sheets are stacked on the sheet feed stand 18 and the print start button on the operation panel 5 is pressed, whereby the sheet feed device 2, the carry-out belt 28, and the reverse conveyance device 36 are driven. The intermediate paper feeding device 31, the intermediate transport device 33, the second printing unit 12, and the paper discharge device 3 are in a stopped state.

(3) When printing is started, the printing paper on the paper feed tray 18 is continuously fed out one by one by the paper feed roller 20, and is synchronized with the rotation of the plate cylinder 39 of the first printing unit 11 by the timing roller 21. Then, it is fed into the lower end image forming portion of the plate cylinder 39, and one side (upper surface) of the paper is printed.

(4) In FIG. 2, the sheet on which one side is printed by the first printing unit 11 is sent to the reverse conveying device 36 via the carry-out belt 28, and due to the negative pressure in the belt guide cylinder 45 that also serves as a suction duct, The unprinted surface (lower surface) is attracted to the outer peripheral surface of the reverse conveying belt 46. Then, in the adsorbed state, the sheet is conveyed in the curved reversal conveyance path M and discharged from the rear lower end exit of the reversal conveyance path M onto the paper stacking table 30.

(5) In the conveyance process in the reverse conveyance path M, for example, when the paper is inserted from the carry-out belt 28 and then turns forward, the front edge of the paper may be separated from the reverse conveyance belt 46 and jump forward due to inertia applied to the paper. In this case, the reversing conveyance guide 47 is contacted and guided into the conveyance path M. Note that even if the sheet comes into contact with the reverse conveyance guide 47 as described above, since it is almost only the front end portion of the sheet, the printing surface of the single-sided printing sheet does not get dirty or the ink is not transferred to the reverse conveyance guide 47.

(6) When the first single-side printed paper is discharged to the paper stacking base 30, when the paper stack detection sensor 87 detects it, the timer 94 of the control device 6 is activated. Simultaneously with the operation of the timer 94, the blower 71 in front of the intermediate sheet feeder 31 is also started. Further, in the case of a large sheet or a large print image amount, the rear blower 64 is also started to start initial drying. Even if the paper stack sensor 87 detects the second and subsequent single-side printed sheets, the timer 94 does not operate repeatedly since a predetermined time has not passed since the preceding single-side printed sheet was detected.

(7) When the paper is discharged to the paper stacking base 30, it is guided from above by the guide plate 61, so that the paper is stacked on the paper stacking base 30 in a neatly arranged state. Further, when the sheet is discharged to the sheet stacking base 30, the upper unprinted surface of the sheet that has been printed on one side is pressed by the guide plate 61, so that the stacked sheet can be maintained in a stable state and the guide plate 61 becomes dirty. There is nothing.

(8) On the paper stacking board 30, the single-side printed paper is sequentially released and stacked in a reversed state. The single-sided printed paper that is stacked stays on the intermediate paper stacking base 30 for a certain period of time until the timer 94 finishes counting, whereby the ink on the printing surface is dried.

(9) When the timer 94 finishes counting, the intermediate paper feeding device 31, the intermediate transport device 33, the second printing unit 12, and the paper discharge device 3 are started.

(10) In the refeeding by the intermediate sheet feeding device 31, the front end portion of the sheet at the lowest position of the sheet stacking table 30 is adsorbed by the feeding belt 66 of the intermediate sheet feeding device 31, and at the same time from the front blowing device 71. The second or more sheets are lifted by the wind, and are separated from the lowermost sheet for easy feeding. Furthermore, the separation action between sheets is accelerated | stimulated by sending a wind from the back air blower 64 to the rear end of a sheet.

  As described above, even after the operation of feeding out the lowermost sheet of the sheet stacking base 30 is started, sheets that are printed on one side by the first printing unit 11 pass through the reversing and conveying device 36 and are successively printed. It is loaded on the loading table 30. That is, on the loading table 30, the paper feeding operation (paper refeeding operation) and the paper stacking operation are in progress at the same time, thereby improving the efficiency of the duplex printing operation.

(11) The single-side printed paper fed out by the intermediate paper feeding device 31 is transported on the guide plate 81 by the rotation of the transport roller 80 and reaches the timing roller 35 of the second printing unit 12.

(12) In the second printing unit 12, the timing roller 35 is sent to the lower end image forming portion of the plate cylinder 39 in synchronization with the rotation of the plate cylinder 39 of the second printing unit 12, and the other side of the sheet is printed. Is done. In this case, the feeding timing of the timing roller 35 is adjusted between the feeding timing of the intermediate sheet feeding device 31 and is not restricted by the feeding timing by the timing roller 21 of the first printing unit 11.

(13) The paper on which the other surface of the second printing unit 12 is printed is in a double-sided printing state, and is discharged to the paper tray 27 via the discharge belt 25 with the suction mechanism 26. At this time, the printing surface immediately after printing by the second printing unit 12 is located on the upper side, and the lower surface side where the ink has already dried is adsorbed to the carry-out belt 25, so that the ink is transferred to the discharge belt 25. There is nothing.

“Other Embodiments of the Invention”
(1) In the embodiment described above, the timer 94 in FIG. 6 is used as a control parameter to control the residence time on the intermediate paper stacking table 30. Instead of the timer 94, the number of sheets is measured. It is also possible to use the counter 95 to be used. Also in this case, as in the case of using the timer, after the first sheet of a large number of continuously fed sheets has been printed on one side, the time when the sheet is stacked on the intermediate sheet stacking base 30 is detected. , The number of stacked sheets is counted, and after the predetermined number of sheets is counted, the program is performed so as to start the feeding operation (refeeding operation) of the single-sided printing paper on the paper stacking board 30.

  FIG. 7 shows a flow chart of control in counting the number of stacked sheets. In step S1, it is determined whether or not the first single-side printed sheet is stacked on the sheet stacking board 30, and if NO, it is again. Returning to step S1, if YES, the process proceeds to step S2, starting counting the number of detected sheets, and simultaneously starting the front blowing device 71 (or the rear blowing device 64) of the intermediate sheet feeding device 31 at the same time.

  After starting the counting of the number of discharged sheets, the process proceeds to step S3, where it is determined whether or not the counted number has reached a predetermined number. If NO, the process returns to step S3 again. If YES, it is determined that the predetermined number of sheets has been counted, and the process proceeds to step S4, where the intermediate sheet feeding device 31 is driven, the sheets on the sheet stacking table 30 are fed out in the stacking order, and re-feeded to the second printing unit 12. To do.

  In step S5, it is determined whether or not the number of sheets detected by the paper stack detection sensor 87 has reached the required total number of prints. If NO, the process returns to step S5. If YES, the process proceeds to step S6. The paper feeding device 31 is stopped.

(2) In the above embodiment, the conveying belt 46 is used as the reverse conveying member of the reverse conveying device 36, but it is also possible to use a roller conveyor composed of a large number of rotating rollers.

(3) The paper stacking detection sensor can be arranged in the paper feeding device 2.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic front view showing a stencil duplex printing machine to which the present invention is applied, seeing through the inside. It is an enlarged front view which shows the structure of the principal part in the stencil duplex printing machine of FIG. FIG. 3 is a plan view corresponding to the range III-III in FIG. 2. It is an enlarged front view of a reverse conveying apparatus. It is a top view of a paper stacking table. It is a block diagram of a control system applied to the present invention. It is a flowchart which shows an example of printing control. It is a schematic front view of a prior art example. It is a schematic front view of another prior art example. It is a schematic front view of another prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer body 2 Paper feeder 3 Paper discharge device 6 Control device (controller)
11 First printing unit 12 Second printing unit 21 Timing roller 30 of first printing unit Intermediate sheet stacking base 31 Intermediate sheet feeding device 33 Intermediate conveying device 35 Timing roller 36 of second printing unit Reverse conveying device 45 Belt guide tube 46 Reverse conveying belt (reverse conveying member)
47 Reverse conveyance guide 52 Suction fan (suction mechanism) for reverse conveyance device
61 Guide plate (guide member)
64 Air blower 71 from the rear Air blower 73 from the front Air blower fan 80 Carrying roller 81 Carrying guide plate 87 Paper stacking detection sensor (paper stacking detection means)
88 Drive motor 94 Timer 95 Counter

Claims (6)

A paper feeder for feeding paper,
A first printing unit that prints one side of the fed paper;
A reversing and conveying apparatus that forms a reversing and conveying path that curves downward from the first printing unit;
A paper stacking table for loading single-sided printed paper;
An intermediate sheet feeding device with a suction mechanism for feeding sheets while sucking the sheets on the sheet loading table in the order of loading;
An intermediate transport device for transporting paper fed from the intermediate paper feed device;
A second printing unit for printing the other side of the single-side printed paper conveyed from the intermediate conveyance device;
A paper discharge device for discharging the double-side printed paper printed by the second printing unit and stacking the paper on a paper tray;
A paper stack detection means for detecting the paper stack on the paper stack;
The number of times of detection is measured from when the paper stacking detection unit first detects the loading of the loaded paper. When the number of times of detection reaches a predetermined number that can be set, the intermediate paper feeding device is driven. A double-sided printing machine, comprising: A paper feeder for feeding paper,
A first printing unit that prints one side of the fed paper;
A reversing and conveying apparatus that forms a reversing and conveying path that curves downward from the first printing unit;
A paper stacking table for loading single-sided printed paper;
An intermediate sheet feeding device with a suction mechanism for feeding sheets while sucking the sheets on the sheet loading table in the order of loading;
An intermediate transport device for transporting paper fed from the intermediate paper feed device;
A second printing unit for printing the other side of the single-side printed paper conveyed from the intermediate conveyance device;
A paper discharge device for discharging the double-side printed paper printed by the second printing unit and stacking the paper on a paper tray;
A paper stack detection means for detecting the paper stack on the paper stack;
The elapsed time is measured from the time when the paper stack detection means detects the first paper stack, and the intermediate paper feeding device is driven when the measured elapsed time reaches a predetermined time that can be arbitrarily set. A double-sided printing machine, comprising: The double-sided printing machine according to claim 1 or 2,
A double-sided printing machine comprising: a blower that sends air to the sheet from the front in the sheet feeding direction of the intermediate sheet feeder. The double-sided printing machine according to claim 1 or 2,
A blower that sends air to the paper from a direction opposite to the paper feeding direction of the intermediate paper feeder;
A double-sided printing machine, characterized in that a guide member for guiding the paper on the paper stacking board is disposed above the paper stacking board. The double-sided printing machine according to claim 2,
The double-sided printing machine, wherein the predetermined time is determined based on a size or thickness of a sheet. The double-sided printing machine according to claim 2,
The double-sided printing machine , wherein the predetermined time is determined based on a print image amount of paper .

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