Abstract:
A sheet supply control apparatus for a printing press includes a sucker, a memory, a sheet detector, a counter, and a CPU. The sucker supplies sheets to a printing unit one by one with a predetermined supply interval. A count of sheets to be supplied to the printing unit is set in the memory. The sheet detector detects the sheets supplied from the sucker. The counter counts sheets supplied from the sucker after the sheet detector detects a first sheet. The CPU controls supply operation of the sucker, on the basis of the count preset in the memory and the count of the counter, such that the count of sheets supplied from the sucker coincides with the count preset in the memory. A sheet supply control method for a printing press is also disclosed.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a sheet supply control apparatus and method for a printing press which supply sheet-like printing products to a printing unit one by one. 
     FIG. 6 shows the main part of an ink supply unit in the printing unit of a web offset printing press. 
     Referring to FIG. 6, an ink fountain  1  stores an ink  2 . An ink fountain roller  3  supplies the ink  2  in the ink fountain  1  to an ink roller group  6 . A plurality of ink fountain keys  4  are aligned in the axial direction of the ink fountain roller  3 . An ink ductor roller  5  is arranged between the ink fountain roller  3  and ink roller group  6 . A printing plate  7  is mounted on a plate cylinder  20 . 
     In this ink supply unit, the ink  2  in the ink fountain  1  is supplied to the ink fountain roller  3  by adjusting the aperture ratios of the ink fountain keys  4 . The ink  2  supplied to the ink fountain roller  3  is supplied to the printing plate  7  through the ink roller group  6  which is rotated in accordance with the feed operation of the ink ductor roller  5  in the operation of the printing press. 
     In the web offset printing press, when the printing plate is changed to a new printing plate  7 , the aperture ratios of the ink fountain keys  4  and the rotation ratio of the ink fountain roller  3  are preset as preset data to values corresponding to the image of the printing plate  7 . More specifically, the aperture ratios of the ink fountain keys  4  and the rotation ratio of the ink fountain roller  3  are set to values corresponding to the image of the new printing plate  7 , and the ink  2  in the ink fountain  1  is supplied to the printing plate  7  through the ink roller group  6 . In this case, test printing is performed before final printing to adjust the ink supply amount, thereby obtaining a satisfactory color tone. With this operation, a desired ink film thickness distribution (gradient of thickness of the ink film) is formed on the ink roller group  6 . 
     In the conventional ink supply unit, however, when the printing plate is changed to the new printing plate  7  from the previous one, the ink film thickness distribution corresponding to the image on the previous printing plate remains on the ink roller group  6 . For this reason, the ink film thickness distribution for the previous printing plate must be gradually changed to the ink film thickness distribution for the new printing plate  7 . This operation excessively requires adjustment of the ink supply amount and test printing until a satisfactory color tone is obtained, resulting in various problems including an increase in preparation time for printing, an increase in work load, waste of printing materials, a decrease in production efficiency, and an increase in cost. 
     In order to decrease the numbers of operation times of adjustment of the ink supply amount and test printing that must be done until a satisfactory color tone is obtained, the present applicant/assignee proposed “Ink Film Thickness Control Method for Ink Supply Apparatus” in U.S. Pat. Nos. 5,884,562 and 5,921,184. According to this ink film thickness control method, when the previous printing plate is to be exchanged to a new printing plate  7 , an ink removing (deletion of ink history) operation is performed first. 
     In the ink removing operation, first, printing on a predetermined count of blank sheets is performed with the previous printing plate being mounted on the plate cylinder. In this case, after printing with the previous printing plate is completed, the blank sheet printing count is set, and the ink removing mode is selected on the operation panel. While the feed operation of an ink ductor roller  5  is stopped, the printing press is operated at a predetermined operation speed, and printing is performed for the preset blank sheet printing count. 
     At this time, on an ink roller group  6 , a second ink film thickness distribution Mb (see FIG. 7B) corresponding to the image of the previous printing plate is superposed on a minimum first ink film thickness distribution Ma (see FIG. 7A) the thickness of which decreases from the upstream side to the downstream side and which is required during printing. When the feed operation of the ink ductor roller  5  is turned off and the printing press is operated with the previous printing plate being mounted, the ink on the ink roller group  6  is consumed, and its film thickness decreases gradually. In this case, the ink is consumed much on a zone having many images, and is consumed less on a zone having few images. After printing is performed for the preset blank sheet printing count, the first ink film thickness distribution Ma is left on the ink roller group  6 . 
     In this case, the blank sheet printing count which is preset for ink removing can be obtained from preset data for final data of the previous printing plate. More specifically, an ink supply amount is obtained from the preset data for final printing, and the second ink film thickness distribution Mb left on the ink roller group  6  is obtained from the obtained ink supply amount. The relationship between the second ink film thickness distribution Mb and the blank sheet printing count is obtained through tests in advance in the form of a table. Therefore, when the table data is looked up with reference to the obtained second ink film thickness distribution Mb, the blank sheet printing count necessary for leaving the first ink film thickness distribution Ma can be obtained. The obtained blank sheet printing count can be freely set or changed by the operator through a ten-key pad and the like. 
     In this manner, ink removing is ended with the first ink film thickness distribution Ma left on the ink roller group  6 . After ink removing, the operator cleans the blanket, and changes the previous printing plate to the new printing plate  7 . 
     In the web offset printing plate described above, sheets are supplied to the printing unit for ink removing as shown in FIG.  8 . Referring to FIG. 8, a sheet detector  9  is set at a terminal end (front lay)  8   a  of a feeder board  8  to detect sheets  11  attracted by a sucker  10  and supplied onto the feeder board  8  one by one. In this case, after the first sheet  11  is detected, every time the sheet  11  is supplied, a pulse (timing pulse of the printing press) generated by a pulse generator (rotary encoder) is counted. When the number of pulses becomes equal to the preset blank sheet printing count, the sheet supply operation of the sucker  10  is stopped, and the operation of the printing press is stopped. 
     Therefore, in the conventional case, after printing for the preset blank sheet count is performed, a sheet  11  remains on the feeder board  8  between the sucker  10  and sheet detector  9 . This sheet  11  must be removed, posing a load to the operator. The removed sheet  11  is discarded, which is a waste. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a sheet supply control apparatus and method for a printing press, in which, after printing for a preset printing count is performed, an operation of removing a sheet on a supply path to a printing unit need not be performed. 
     In order to achieve the above object, according to the present invention, there is provided a sheet supply control apparatus for a printing press, comprising sheet supply means for supplying sheet-like objects to a printing unit one by one with a predetermined supply interval, setting means in which a count of sheet-like objects to be supplied to the printing unit is set, detection means for detecting the sheet-like objects supplied from the sheet supply means, count means for counting sheet-like objects supplied from the sheet supply means after the detection means detects a first sheet-like object, and sheet supply control means for controlling supply operation of the sheet supply means, on the basis of the count preset in the setting means and the count of the count means, such that the count of sheet-like objects supplied from the sheet supply means coincides with the count preset in the setting means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of a sheet supply control apparatus for a printing press according to the first embodiment of the present invention; 
     FIG. 2 is a flow chart showing ink removing operation performed by the sheet supply control apparatus of FIG. 1; 
     FIG. 3 is a view showing a position where the sheet detector shown in FIG. 4 is set; 
     FIG. 4 is a block diagram of a sheet supply control apparatus for a printing press according to the second embodiment of the present invention; 
     FIG. 5 is a flow chart showing ink removing operation performed by the sheet supply control apparatus of FIG. 4; 
     FIG. 6 is a view schematically showing an ink supply unit in the printing unit of a web offset printing press; 
     FIGS. 7A and 7B are views showing ink film thickness distributions Ma and Mb, respectively, formed on an ink roller group; and 
     FIG. 8 is a view showing a position where a sheet detector is set in the prior art and in the first embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will be described in detail with reference to the accompanying drawings. 
     [First Embodiment] 
     According to the first embodiment, in the same manner as in FIG. 8, a sheet detector  9  is set at a terminal end (front lay)  8   a  of a feeder board  8 . Paper sheets  11  as sheet-like objects supplied onto the feeder board  8  with a predetermined supply interval by a sucker  10  are detected by the sheet detector  9 . After the first sheet  11  is detected by the sheet detector  9 , the subsequently supplied sheets  11  are sequentially counted. When the supply count (count) of the sheets  11  after initial detection becomes equal to the difference between a preset blank sheet printing count (the number of sheets  11  that should be supplied to the printing unit) N and a stored sheet supply count M (to be described later), the sheet supply operation of the sucker  10  is stopped. 
     The number of sheets  11  fed onto the feeder board  8  by the sucker  10  since the sucker  10  starts sheet supply operation until the sheet detector  9  detects the first sheet  11  is known. This known count is stored in a memory in advance as the count M of sheets supplied to the sheet detector  9  (this will be referred to as the sheet supply count M hereinafter). 
     FIG. 1 shows a sheet supply control apparatus for a printing press according to this embodiment. 
     Referring to FIG. 1, the sheet supply control apparatus has a CPU (Central Processing Unit)  12 , a ROM (Read-Only Memory)  13 , a RAM (Random Access Memory)  14 , a touch panel display  17 , a printing press control unit  18 , a feed control unit  19 , a fountain roller rotation ratio control unit  20 , an ink fountain key aperture ratio control unit  21 , a floppy disk drive unit  22 , a pulse generator  23 , memories  24  and  25 , and a counter  26 . The feed control unit  19  turns on/off a feed mechanism. The pulse generator  23  is comprised of a rotary encoder which generates a pulse every time one sheet  11  is supplied. The memory  24  stores the sheet supply count M described above. The memory  25  stores the blank sheet printing count N set on the display  17 . 
     The sheet detector  9 , printing press control  18 , feed control unit  19 , rotation ratio control unit  20 , aperture ratio control unit  21 , drive unit  22 , and pulse generator  23  are connected to an I/O interface  16 , and the display  17  is connected to an I/O interface  15 . The ROM  13 , RAM  14 , I/O interfaces  15  and  16 , memories  24  and  25 , and counter  26  are connected to the CPU  12  through a bus  30 . 
     Upon reception of various types of input information supplied through the I/O interfaces  15  and  16 , the CPU  12  performs various types of processing operations in accordance with a program stored in the ROM  13  while accessing the RAM  14 . The various types of input information in the CPU  12  are output to the display  17 , printing press control unit  18 , feed control unit  19 , rotation ratio control unit  20 , aperture ratio control unit  21 , and drive unit  22  through the I/O interfaces  15  and  16 . 
     Ink removing operation performed before the printing plate is changed will be described with reference to FIG.  2 . 
     When printing with the previous plate is ended, a blank sheet printing count N is set, and the ink removing mode is selected on the display  17 . The preset blank sheet printing count N is stored in the memory  25 . When the ink removing mode is started, the CPU  12  sends an instruction to the feed control unit  19  to stop the feed operation of an ink ductor roller  5  (step S 301 ). 
     Subsequently, the CPU  12  reads out the blank sheet printing count N from the memory  25  (step S 302 ), and the sheet supply count M from the memory  24  (step S 303 ). Then, the CPU  12  calculates a difference Z between the readout blank sheet printing count N and sheet supply count M (Z=N−M) (step S 304 ), and checks whether Z≦0 (step S 305 ). 
     Assume that the blank sheet printing count N is set at 10 and that the sheet supply count M is set at 4. In this case, since the difference Z between the blank sheet printing count N and sheet supply count M is 6, Z=6 is set as a count CA in the counter  26  in step S 307 . The CPU  12  then operates the printing press at a predetermined operation speed (step S 308 ) to start sheet supply operation with the sucker  10  (step S 309 ). 
     Hence, the sheets  11  are sequentially sent onto a feeder board  8  (FIG.  8 ), and conveyance of the sheets  11  to the printing unit is started. At this time, when a sheet detector  9  detects that the first sheet  11  is supplied (step S 310 ), the CPU  12  starts counting pulses sent from the pulse generator  23 . 
     More specifically, the CPU  12  checks whether the count CA of the counter  26  is 0 (step S 311 ). Since the count CA is set at 6, when the pulse generator  23  generates a pulse, 1 is subtracted from the count CA (steps S 312 , S 313 ). The CPU  12  then checks whether the count CA is 0 (step S 314 ). The processes of steps S 312 , S 313 , and S 314  are repeated until the count CA becomes 0. 
     The pulse generator  23  generates a pulse every time one sheet  11  is supplied. After the sheet detector  9  detects the first sheet  11 , when sheets  11  in a count that renders Z=6 are supplied by the sucker  10  onto the feeder board  8 , the count CA becomes 0. In step S 314 , if CA=0, i.e., if the count C of the counter  26  becomes equal to the difference between the blank sheet printing count N and the count M of sheets supplied to the sheet detector  9  (C=N−M), the CPU  12  stops the sheet supply operation of the sucker  10  (step S 315 ). 
     After 4 (=M) sheets  11  are supplied onto the feeder board  8  in this manner, when 6 (=C) sheets  11  are supplied, the operation of supplying the sheets  11  by the sucker  10  is stopped. As a result, a total of  10  (=M+C) sheets have been supplied onto the feeder board  8 . Therefore, when the operation of the printing press is continued even after the sheet supply operation of the sucker  10  is stopped, printing for the preset N blank sheets can be performed without leaving any sheet  11  on the feeder board  8 . 
     After the sheet supply operation by the sucker  10  is stopped, at least all the blank sheets  11  left on the feeder board  8  are printed, and after that the operation of the printing press is stopped (step S 316 ). 
     In step S 305 , if Z≦0, the flow advances to step S 306  to set Z=0. More specifically, if the blank sheet printing count N is equal the sheet supply count M or less, Z=0 is set in step S 306 . For example, when the count M of sheets supplied to the sheet detector  9  is 6 and the blank sheet printing count N is 2, since N −M=−4, Z=0 is set. The count CA of the counter  26  is set at 0 (step S 307 ), and the operation of a printing press and sheet supply operation by the sucker  10  are started (steps S 308  and S 309 ). 
     When the sheet detector  9  detects the first sheet  11  in step S 310 , the sheet supply operation of the sucker  10  and the operation of the printing press are immediately stopped in step S 317 . Note that in this case, 4 sheets  11  are left on the feeder board  8 . 
     In the first embodiment, the sheet detector  9  is provided to the terminal end  8   a  of the feeder board  8 . However, the position of the sheet detector  9  is not limited to that on the feeder board  8 . For example, a missing sheet sensor may be provided downstream of a feeder board  8  and be used as a sheet detector  9 . A missing sheet sensor is a sensor for constantly detecting a sheet gripped by a gripper unit and conveyed from a transfer cylinder to an impression cylinder. When the missing sheet sensor cannot detect a sheet, it is determined that a sheet is dropped from the gripper unit. 
     More specifically, the sheet detector  9  may be arranged at a position downstream or upstream of the position shown in FIG. 1 as far as the distance from the sucker  10  to the sheet detector  9  is longer than the supply interval of the sheets  11 . 
     [Second Embodiment] 
     In the first embodiment, when the blank sheet printing count N is less than the sheet supply count M, the sheet  11  is left on the feeder board  8 . Therefore, when the blank sheet printing count N is less than the sheet supply count M, the sheets must be supplied in the desired count N by the manual operation of the operator, thus performing ink removing operation. 
     The blank sheet printing count N for ink removing changes depending on various types of printing conditions (the material, the preset condition of the printing press, the printing density reference, and the like), and is thus sometimes equal to the sheet supply count M or less. 
     In the second embodiment, even when the blank sheet printing count N is less than the sheet supply count, printing of preset N blank sheets can be performed without leaving any sheet  11  on the feeder board  8 . In order to realize this, as shown in FIG. 3, a sheet detector  9  is provided to the most upstream portion, close to a sucker  10 , of the feeder board  8 . When the first sheet  11  is started to be fed to the feeder board  8  by the sucker  10 , the sheet detector  9  detects it immediately. 
     In FIG. 1, the sheet detector  9  is arranged at the most upstream portion of the feeder board  8 . It suffices if the sheet detector  9  is arranged at such a position that it can detect the first sheet  11  since the first sheet  11  is started to be fed to the feeder board  8  and before the next sheet  11  is started to be fed there. More specifically, the sheet detector  9  may be arranged downstream or upstream of the position shown in FIG. 3 as far as the distance from the sucker  10  to the sheet detector  9  is shorter than the supply interval of the sheets  11 . 
     FIG. 4 shows a sheet supply control apparatus for a printing press according to the second embodiment. In FIG. 4, portions that are identical to those in FIG. 1 are denoted by the same reference numerals as in FIG. 1, and a detailed description thereof will be omitted. FIG. 4 is different from FIG. 1 in that the memory  24  shown in FIG. 1 for setting the sheet supply count is omitted. 
     Ink removing operation performed before the printing plate is changed will be described with reference to FIG.  5 . 
     When printing with the previous plate is ended, a blank sheet printing count N is set in the same manner as in the first embodiment, and the ink removing mode is selected on a display  17 . The preset blank sheet printing count N is stored in a memory  25 . A CPU  12  sends an instruction to a feed control unit  19  to stop the feed operation of an ink ductor roller  5  (step S 501 ). 
     The CPU  12  then resets a count CA of a counter  26  to 0 (step S 502 ), and reads out the blank sheet printing count N from the memory  25  (step S 503 ). After that, the CPU  12  operates the printing press at a predetermined operation speed (step S 504 ), to start sheet supply operation with the sucker  10  (step S 505 ). 
     When the sheet detector  9  detects the first sheet  11  (step S 506 ), the CPU  12  starts counting pulses sent from a pulse generator  23 . More specifically, every time the pulse generator  23  generates a pulse, the CPU  12  increments the count CA of the counter  26  by one (steps S 507  and S 508 ), and checks whether N=CA (step S 509 ). After that, the process operations of steps S 507 , S 508 , and S 509  are repeated until N=CA is obtained in step S 509 . 
     The pulse generator  23  generates a pulse every time one sheet  11  is supplied. After the sheet detector  9  detects the first sheet  11 , when N sheets  11  are supplied onto the feeder board  8 , N=CA is obtained in step S 509 . When N=CA is obtained in step S 509 , that is, when a count C of the counter  26  becomes equal to the blank sheet printing count N (C=N), the CPU  12  stops the sheet supply operation of the sucker  10  (step S 510 ). 
     Hence, when N sheets  11  are supplied to the feeder board  8 , the operation of supplying the sheets  11  with the sucker  10  is stopped. Therefore, when the operation of the printing press is continued even after the sheet supply operation of the sucker  10  is stopped, printing for the preset N blank sheets can be performed without leaving any sheet  11  on the feeder board  8 . 
     After the sheet supply operation by the sucker  10  is stopped, all the blank sheets  11  left on the feeder board  8  are printed. Then, the operation of the printing press is stopped (step S 511 ). 
     In the second embodiment, even if the blank sheet printing count N is 1, printing for the preset N count can be performed without leaving any sheet  11  on the feeder board  8 . Also, a complicated ink removing process as in the first embodiment is not required, so that the load on the CPU  12  is reduced. 
     In place of the sheet detector  9  which directly detects the sheet  11 , a pressure sensor may be provided to the pipe path of the suction port air of the sucker  10 . The pressure sensor detects a pressure drop occurring when the sheet  11  is attracted, and this timing is used as a sheet supply start timing. 
     According to the embodiments described above, the sheet detector  9  is arranged at the most upstream portion of the feeder board  8 , or the pressure sensor is provided to the pipe path of the suction port air of the sucker  10 . When compared to a case wherein the ON timing of the air valve of the sucker  10  is detected as a sheet supply start timing, the sheet supply start timing can be detected reliably. 
     In the embodiments described above, the printing product is a paper sheet. However, the printing product is not limited to a paper sheet but can be of any type as far as it is a sheet-like printing product. 
     As has been described above, according to the present invention, printing for the preset count N can be performed without leaving any printing product on the sheet supply path. This can reduce the load to the operator and eliminate waste paper. 
     Even if the blank sheet printing count is 1, ink removing operation can be performed without requiring a complicated process.