Position correcting method and apparatus for ink fountain key in printing press

Abstract

In a method of correcting a position of each ink fountain key, a position of an ink fountain key is set as a present position with reference to a home position by using print data including an image area ratio of a reference plate having a predetermined image. A printing product is printed by using the reference plate with the ink fountain key being set at the present position. A density of each of respective areas, corresponding to the ink fountain keys, of the obtained printing product is measured. One of the home position and the present position of the ink fountain key is corrected on the basis of a difference between the measured density of the corresponding area and a reference density stored in advance. A position correcting apparatus is also disclosed.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a position correcting method and apparatus for an ink fountain key that correct the home position/present position of an ink fountain key in a printing press when adjusting the opening amount (position) of the ink fountain key.

FIG. 19 shows the schematic arrangement of an ink supply unit in each printing unit of a rotary printing press. Referring to FIG. 19 , the ink supply unit has an ink fountain 1 , an ink 2 stored in the ink fountain 1 , an ink fountain roller 3 , a plurality of ink fountain keys 4 aligned in the axial direction of the ink fountain roller 3 , an ink ductor roller 5 , an ink roller group 6 , a plate 7 , and a plate cylinder 8 .

FIG. 20 shows the outline of a general four-color rotary printing press. Referring to FIG. 20 , printing units 9 - 1 to 9 - 4 perform printing in units of colors. The ink supply unit shown in FIG. 19 is separately provided in each of the printing units 9 - 1 to 9 - 4 .

In the printing press having the above arrangement, the ink 2 in the ink fountain 1 is supplied to the ink fountain roller 3 by adjusting the opening amount of the ink fountain keys 4 . The ink supplied to the ink fountain roller 3 is supplied to the plate 7 through the ink roller group 6 by the ducting operation of the ink ductor roller 5 . A print sheet supplied from a feeder is printed with the ink supplied to the plate 7 .

The opening amount (present position) of the ink fountain keys 4 with respect to the ink fountain roller 3 is set by using print data created in accordance with the image area ratio or the like of each of areas, corresponding to the ink fountain keys 4 , of the plate 7 with reference to the home position (fully open or fully closed position) of the ink fountain keys 4 stored in advance. In this case, if printing is performed over a long period of time, the home position of the ink fountain keys 4 changes due to various reasons.

When the home position of the ink fountain keys 4 changes, the actual opening amount of the ink fountain keys 4 also changes, and a correct ink amount cannot be supplied to the plate 7 . Then, the color tone of the printing product becomes largely different from a desired one, making it very difficult to obtain a printing product having a desired color tone.

Conventionally, the home position and present position of the ink fountain keys 4 are adjusted by the operator by measuring the ink thickness on the ink fountain roller 3 with a measurement unit or confirming the ink color.

In this adjusting method, the home position and present position of the ink fountain keys 4 are adjusted while measuring the ink thickness or visually confirming the ink color. This adjusting method is accordingly very difficult and takes a long period of time.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a position correcting method and apparatus for an ink fountain key, which can adjust the home position/present position of the ink fountain key easily within a short period of time.

In order to achieve the above object, according to the present invention, there is provided a method of correcting a position of an ink fountain key in a printing press, in which an amount of ink to be supplied is adjusted by adjusting a position of each of a plurality of ink fountain keys with reference to a home position, comprising the steps of setting a position of the ink fountain key as a present position with reference to the home position by using print data including an image area ratio of a reference plate having a predetermined image, printing a printing product by using the reference plate with the ink fountain key being set at the present position, measuring a density of each of respective areas, corresponding to the ink fountain keys, of the obtained printing product and correcting one of the home position and the present position of the ink fountain key on the basis of a difference between the measured density of a corresponding area and a reference density stored in advance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart explaining the correcting operation of the home position correcting apparatus shown in FIG. 2 ;

FIG. 2 is a block diagram of the home position correcting apparatus for ink fountain keys according to the first embodiment of the present invention;

FIG. 3 is a plan view of a testing plate used in the home position correcting apparatus shown in FIG. 2 ;

FIG. 4 is a block diagram of a home position correcting apparatus for ink fountain keys according to the second embodiment of the present invention;

FIG. 5 is a flow chart explaining the correcting operation of the home position correcting apparatus shown in FIG. 4 ;

FIG. 6 is a block diagram of a home position correcting apparatus for ink fountain keys according to the third embodiment of the present invention;

FIG. 7 is a flow chart explaining the correcting operation of the home position correcting apparatus shown in FIG. 6 ;

FIG. 8 is a block diagram of a home position correcting apparatus for ink fountain keys according to the fourth embodiment of the present invention;

FIG. 9 is a flow chart explaining the correcting operation of the home position correcting apparatus shown in FIG. 8 ;

FIG. 10 is a block diagram of a present position correcting apparatus for ink fountain keys according to the fifth embodiment of the present invention;

FIG. 11 is a flow chart explaining the correcting operation of the present position correcting apparatus shown in FIG. 10 ;

FIG. 12 is a block diagram of a present position correcting apparatus for ink fountain keys according to the sixth embodiment of the present invention;

FIG. 13 is a flow chart explaining the correcting operation of the present position correcting apparatus shown in FIG. 12 ;

FIG. 14 is a plan view showing another example of a testing plate;

FIG. 15 is a block diagram of a home position correcting apparatus for ink fountain keys according to the seventh embodiment of the present invention;

FIG. 16 is a flow chart explaining the correcting operation of the home position correcting apparatus shown in FIG. 15 ;

FIG. 17 is a block diagram of a home position correcting apparatus for ink fountain keys according to the eighth embodiment of the present invention;

FIG. 18 is a flow chart for explaining the correcting operation of the home position correcting apparatus shown in FIG. 17 ;

FIG. 19 is a diagram showing the schematic arrangement of an ink supply unit in each printing unit of a rotary printing press;

FIG. 20 is a side view showing the schematic arrangement of a four-color sheet-fed rotary printing press;

FIG. 21 is a view showing the functional block of the CPU shown in FIG. 2 ;

FIG. 22 is a view showing the functional block of the CPU shown in FIG. 6 ; and

FIG. 23 is a view showing the functional block of the CPU shown in FIG. 12 .

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described in detail with reference to the accompanying drawings.

First Embodiment

The first embodiment is described here with reference to FIGS. 2 and 19 . FIG. 2 shows the home position correcting apparatus for ink fountain keys according to the first embodiment of the present invention. Referring to FIG. 2 , this apparatus includes a CPU (Central Processing Unit) 10 A, a ROM (Read Only Memory) 11 , a RAM (Random Access Memory) 12 , a switch group 13 , a display 14 , a drive 15 such as a floppy disk drive or magnetic card drive, a densitometer 16 , an A/D (Analog to Digital) converter 17 , input/output (I/O) interfaces 18 and 19 , a reference density memory 20 , a preset position memory 21 , a home position memory 22 , and a plurality of ink fountain key drivers 23 . The switch group 13 includes a home position setting switch 13 - 1 . The drive 15 drives a storage medium such as a floppy disk or magnetic card. The reference density memory 20 stores a reference density based on a testing plate in advance. The preset position memory 21 stores the target position of the ink fountain keys 4 , i.e., the present position of the ink fountain key with reference to the home position. The home position memory 22 stores the home position of the ink fountain keys 4 . The ink fountain key drivers 23 drive the ink fountain keys 4 (FIG. 19 ).

The plurality of ink fountain key drivers 23 are provided in units of the ink fountain keys 4 to separately adjust the opening amounts of the respective ink fountain keys 4 with respect to an ink fountain roller 3 . Each ink fountain key driver 23 is comprised of an input/output (I/O) interface 23 A, a D/A converter 23 B, a fountain key motor driver 23 C, a fountain key motor 23 D, a potentiometer 23 E provided to the fountain key motor 23 D, and an A/D converter 23 F.

In the home position adjusting apparatus descried above, a testing plate 7 A is mounted on the outer surface of a plate cylinder 8 . As shown in FIG. 3 , the testing plate 7 A is formed with a color patch portion 7 A 1 and a home position adjusting image portion 7 A 2 in a direction perpendicular to the sheet convey direction (axial direction of the plate cylinder 8 ). The color patch portion 7 A 1 is a known belt-like image portion used for printing quality measurement. In the color patch portion 7 A 1 , a plurality of patches p are formed within respective areas E corresponding to the ink fountain keys 4 , at predetermined gaps from each other in the axial direction of the plate cylinder 8 . The patches p of the color patch portion 7 A 1 are used to measure the density of the printing sample.

The home position adjusting image portion 7 A 2 is provided parallel to the color patch portion 7 A 1 to have a belt-like shape. The image area ratios in the respective areas E corresponding to the ink fountain keys 4 are set to be equal to those of the color patch portion 7 A 1 . The image area ratios in the home position adjusting image portion 7 A 2 are measured in units of areas E, and the measured image area ratios are used when setting the ink fountain keys 4 . The patches p of the color patch portion 7 A 1 are provided to correspond to the areas E of the home position adjusting image portion 7 A 2 .

The density of each patch p of the color patch portion 7 A 1 having the same image area ratio as that of the testing plate 7 A is set in the reference density memory 20 as the reference density. The home position adjusting image portion 7 A 2 is set to have an image area ratio of a certain degree. This is because if the opening amounts of the ink fountain keys 4 are zero, no ink is supplied to the ink supply unit, and normal printing cannot be performed.

The correcting operation of the home position correcting apparatus having the above arrangement as shown in FIG. 2 will be described further with reference to the flow chart shown in FIG. 1 along with features described in FIGS. 3 and 19 .

To correct the home positions of the ink fountain keys 4 , the operator measures the image area ratio of the home position adjusting image portion 7 A 2 of the testing plate 7 A with a plate area ratio meter to obtain print data. More specifically, the operator measures the image area ratios of the respective areas E, corresponding to the ink fountain keys 4 , of the home position adjusting image portion 7 A 2 , and creates print data corresponding to the ink fountain keys 4 on the basis of the measured image area ratios.

The operator then inputs the created print data to the home position correcting apparatus to set the opening amount (present position) of each ink fountain key 4 (step S 101 ). More specifically, the CPU 10 A reads out the home position (present home position) of the ink fountain key 4 stored in the home position memory 22 in advance. The opening amount of the ink fountain key 4 is set by using the print data with reference to the read home position. The CPU 10 A also stores the preset opening amount of the ink fountain key 4 in the preset position memory 21 as the target position of the ink fountain key 4 .

With the testing plate 7 A being set on the plate cylinder 8 , the operator performs printing to acquire printing samples (step S 102 ). The density of the printing sample acquired from each patch p of the color patch portion 7 A 1 is measured by using the densitometer 16 (step S 103 ), and is supplied to the CPU 10 A through the A/D converter 17 and I/O interface 18 . On the basis of the data supplied from the densitometer 16 , the CPU 10 A checks whether the density (measured density) of the patch p for each ink fountain key 4 coincides with the corresponding reference density stored in advance in the reference density memory 20 (step S 104 ).

If the measured density and the reference density do not coincide with each other, i.e., if the difference between the measured density and the reference density is not zero or does not fall within a predetermined range, the CPU 10 A determines that an error has occurred in the home position of the ink fountain key 4 corresponding to the patch p of the color patch portion 7 A 1 . A description will be made on an assumption that the measured density and the reference density do not coincide with each other in all the patches p of the color patch portion 7 A 1 .

The CPU 10 A sequentially performs fine adjustment of all the ink fountain keys 4 (step S 105 ). More specifically, the opening amount of each ink fountain key 4 is adjusted by the corresponding ink fountain key driver 23 so that the measured density and the reference density coincide with each other.

After that, the operator performs printing again with the testing plate 7 A being set on the plate cylinder 8 , and acquires a printing sample from each patch p of the color patch portion 7 A 1 (step S 106 ). The CPU 10 A measures the density of the obtained printing sample in the same manner as in step S 103 (step S 107 ) to check whether the measured density of the patch p for the corresponding ink fountain key 4 coincides with the reference density (step S 108 ).

Steps S 105 to S 108 are repeated until the measured density coincides with the reference density in all the patches p corresponding to the ink fountain keys 4 . When the measured density coincides with the reference density in all the patches p, the operator turns on the home position setting switch 13 - 1 (step S 109 ). The CPU 10 A accordingly reads out the target position (the preset position with reference to the home position) of the ink fountain key stored in the preset position memory 21 (step S 110 ), and successively reads out the present position of the ink fountain key 4 fine-adjusted in step S 105 (step S 111 ). The CPU 10 A then calculates the difference between the target position and the present position of the ink fountain key 4 (step S 112 ).

The CPU 10 A reads out the present home position of the ink fountain key 4 from the home position memory 22 (step S 113 ). The CPU 10 A then corrects the present home position of the ink fountain key 4 obtained in step S 113 by an amount corresponding to the difference between the target position and the present position of the ink fountain key 4 obtained in step S 112 (step S 114 ).

More specifically, the home position of the ink fountain key 4 is corrected using as the correction value the difference between the target position and the present position of the ink fountain key 4 obtained in step S 112 . The CPU 10 A writes the corrected home position in the home position memory 22 as the present home position of the ink fountain key 4 (step S 115 ). The CPU 10 A successively writes the corrected home position of the ink fountain key 4 in a storage medium through the drive 15 to save it in an external unit (step S 116 ).

If the measured density and the reference density coincide with each other in step S 104 , the flow advances to step S 116 without performing correction.

According to this embodiment, after the correction, the target position of the ink fountain key 4 is set with reference to the corrected home position. Therefore, a printing product having a desired color tone can be obtained reliably.

Second Embodiment

FIG. 4 shows a home position correcting apparatus according to the second embodiment of the present invention. In FIG. 4 , the same reference numerals as in FIGS. 2 and 19 denote the same or equivalent constituent elements, and a detailed description thereof will be omitted. In the home position correcting apparatus of this embodiment, in addition to the arrangement of FIG. 2 , a position difference memory 25 for storing the position difference (to be described later) of each ink fountain key 4 is provided. A switch group 13 has, in addition to a home position setting switch 13 - 1 , a home position correction value calculating switch 13 - 2 and a home position reset switch 13 - 3 .

The correcting operation of the home position correcting apparatus having the above arrangement will be described with reference to the flow chart shown in FIG. 5 . In this home position correcting apparatus as well, a testing plate 7 A identical to that shown in FIG. 3 is used as a plate to be mounted on a plate cylinder 8 . The image area ratios of respective areas E, corresponding to the ink fountain keys 4 , of the testing plate 7 A are measured in the same manner as in the first embodiment, and print data for the ink fountain keys 4 is created on the basis of the measured image area ratios.

First, in steps S 501 to S 508 , a CPU 10 B performs the same operations as in steps S 101 to S 108 in FIG. 1 . When all the measured densities coincide with the corresponding reference densities in step S 508 , the operator turns on the home position correction value calculating switch 13 - 2 (step S 509 ). Accordingly, the CPU 10 B reads out the target position of each ink fountain key 4 stored in a preset position memory 21 (step S 510 ), and successively reads the present position of the ink fountain key 4 (step S 511 ).

Next, a difference between positions where ink fountain keys 4 -l to 4 -n are to be and the present position is calculated (S 512 ). The CPU 10 B then writes the difference between the target position of the ink fountain key 4 obtained in step S 510 and the present position of the same obtained in step S 511 in the position difference memory 25 (step S 513 ). The CPU 10 B writes the difference between the target position and the present position of the ink fountain key 4 obtained in step S 512 in a storage medium through a drive 15 (step S 514 ).

After that, to perform actual printing, the operator turns on the home position setting switch 13 - 1 (step S 515 ). Accordingly, the CPU 10 B reads out the present home position of the ink fountain key 4 from a home position memory 22 (step S 516 ), and successively reads out the difference between the target position and the present position of the ink fountain key 4 from the position difference memory 25 (step S 517 ).

The CPU 10 B corrects the present home position of the ink fountain key 4 obtained in step S 516 by an amount corresponding to the position difference of the ink fountain keys 4 obtained in step S 517 (step S 518 ). More specifically, the home position of the ink fountain keys 4 is corrected by the position difference of the ink fountain key 4 obtained in step S 517 as a correction value. The CPU 10 B then writes the corrected home position in the home position memory 22 as the present home position (step S 519 ). In this case, the CPU 10 B keeps the home position before correction in the home position memory 22 as the original home position.

According to this embodiment, when the home position setting switch 13 - 1 is turned on in step S 515 , the opening amount of the ink fountain key 4 is controlled with reference to the home position corrected in step S 518 .

Although not shown in the flow chart of FIG. 5 , when the operator wishes to restore the ink fountain key 4 to the original home position, he turns on the home position reset switch 13 - 3 . Then, the present home position (corrected home position) in the home position memory 22 is updated to the original home position (home position before correction), and the opening amount of the ink fountain key 4 can be controlled with reference to the original home position.

Third Embodiment

FIG. 6 shows a home position correcting apparatus for ink fountain keys according to the third embodiment of the present invention. In FIG. 6 , the same reference numerals as in FIG. 2 denote the same or equivalent constituent elements, and a detailed description thereof will be omitted. In the home position correcting apparatus of this embodiment, in place of the preset position memory 21 of FIG. 2 , a density difference-correction amount conversion table 26 is arranged.

The correcting operation of the home position correcting apparatus having the above arrangement will be described with reference to the flow chart shown in FIG. 7 . In this home position correcting apparatus as well, a testing plate 7 A identical to that shown in FIG. 3 is used as a plate to be mounted on a plate cylinder 8 . The image area ratios of respective areas E, corresponding to ink fountain keys 4 , of the testing plate 7 A are measured in the same manner as in the first embodiment, and print data for the ink fountain keys 4 is created on the basis of the measured image area ratios.

First, in steps S 701 to S 703 , a CPU 10 C performs the same operations as in steps S 101 to S 103 of FIG. 1 . The operator then turns on a home position setting switch 13 - 1 (step S 704 ). When the home position setting switch 13 - 1 is turned on, the CPU 10 C calculates the difference (density difference) between the density (measured density) of the patch p for each ink fountain key 4 and a corresponding reference density stored in a reference density memory 20 in advance (step S 705 ). The home position correction amount of the ink fountain key 4 corresponding to the density difference is obtained by looking up the density difference-correction amount conversion table 26 (step S 706 ).

The CPU 10 C then reads out the present home position of the ink fountain key 4 from a home position memory 22 (step S 707 ) and corrects the read present home position of the ink fountain key 4 by an amount corresponding to the home position correction amount obtained in step S 706 (step S 708 ). More specifically, the home position of the ink fountain key 4 is correct by the home position correction amount obtained in step S 706 as the correction amount. Successively, the CPU 10 C writes the corrected home position in the home position memory 22 as the present home position (step S 709 ).

Fourth Embodiment

FIG. 8 shows a home position correcting apparatus for ink fountain keys according to the fourth embodiment of the present invention. In FIG. 8 , the same reference numerals as in FIG. 4 denote the same or equivalent constituent elements, and a detailed description thereof will be omitted. In the home position correcting apparatus of this embodiment, a density difference-correction amount conversion table 26 and a correction amount memory 27 for storing the correction amount of each ink fountain key are provided in place of the preset position memory 21 and position difference memory 25 shown in FIG. 4 .

The correcting operation of the home position correcting apparatus having the above arrangement will be described with reference to the flow chart shown in FIG. 9 . In this home position correcting apparatus as well, a testing plate 7 A identical to that shown in FIG. 3 is used as a plate to be mounted on a plate cylinder 8 . The image area ratios of respective areas E, corresponding to ink fountain keys 4 , of the testing plate 7 A are measured in the same manner as in the first embodiment, and print data for the ink fountain keys 4 is created on the basis of the measured image area ratios.

First, in steps S 901 to S 903 , a CPU 10 D performs the same operations as in steps S 101 to S 103 of FIG. 1 . The operator then turns on a home position correction value calculating switch 13 - 2 (step S 904 ). When the home position correction value calculating switch 13 - 2 is turned on, the CPU 10 D calculates the difference (density difference) between the density (measured density) of the patch p for each ink fountain key 4 and a corresponding reference density stored in a reference density memory 20 in advance (step S 905 ). The CPU 10 D then calculates the home position correction amount of the ink fountain key 4 corresponding to the density difference by looking up the density difference-correction amount conversion table 26 (step S 906 ). The CPU 10 D writes the calculated home position correction amount of the ink fountain key 4 in the correction amount memory 27 (step S 907 ).

After that, to perform actual printing, the operator turns on a home position setting switch 13 - 1 (step S 908 ). Accordingly, the CPU 10 D reads out the present home position of the ink fountain key 4 from a home position memory 22 (step S 909 ) and successively the home position correction amount of the ink fountain key 4 from the correction amount memory 27 (step S 910 ).

The CPU 10 D corrects the present home position of the ink fountain key 4 obtained in step S 909 by the home position correction amount of the ink fountain keys 4 obtained in step S 910 (step 901 ). More specifically, the home positions of the ink fountain keys 4 are corrected by the home position correction amounts of ink fountain keys 4 -l to 4 -n obtained in step S 910 as the correction values (step S 911 ). The CPU 10 D then writes the corrected home position in the home position memory 22 as the present home position (step S 912 ). In this case, the CPU 10 D keeps the home position before correction in the home position memory 22 as the original home position.

According to this embodiment, when the home position setting switch 13 - 1 is turned on in step S 908 , the opening amount of the ink fountain key 4 is controlled with reference to the home position corrected in step S 911 .

Although not shown in the flow chart of FIG. 9 , when the operator wishes to restore the home position to the original home position, he turns on the home position reset switch 13 - 3 . Then, the present home position (corrected home position) in the home position memory 22 is updated to the original home position (home position before correction), and the opening amount of the ink fountain key 4 can be controlled with reference to the original home position.

Fifth Embodiment

FIG. 10 shows a present position correcting apparatus for ink fountain keys according to the fifth embodiment of the present invention. In FIG. 10 , the same reference numerals as in FIG. 2 denote the same or equivalent constituent elements, and a detailed description thereof will be omitted. In the present position correcting apparatus of this embodiment, a present position memory 24 for storing the present positions of ink fountain keys 4 is arranged in place of the home position memory 22 shown in FIG. 2 .

The correcting operation of the present position correcting apparatus having the above arrangement will be described with reference to the flow chart shown in FIG. 11 . In this present position correcting apparatus as well, a testing plate 7 A identical to that shown in FIG. 3 is used as a plate to be mounted on a plate cylinder 8 . The image area ratios of respective areas E, corresponding to ink fountain keys 4 , of the testing plate 7 A are measured in the same manner as in the first embodiment, and print data for the ink fountain keys 4 is created on the basis of the measured image area ratio.

First, in steps S 1101 to S 1111 , a CPU 10 E performs the same operations as in steps S 101 to S 111 of FIG. 1 . Step S 1110 may be omitted. The CPU 10 E then writes the present position of each ink fountain key 4 obtained in step S 1111 in a preset position memory 21 as the target position of the ink fountain key 4 (step S 1112 ).

More specifically, the target position of the ink fountain key 4 stored in the preset position memory 21 is updated by the present position of the ink fountain key 4 obtained in step S 1111 . After that, the opening amount of the ink fountain key 4 is controlled with reference to the target position of the ink fountain key 4 updated in step S 1112 .

Sixth Embodiment

FIG. 12 shows a present position correcting apparatus for ink fountain keys according to the sixth embodiment of the present invention. In FIG. 12 , the same reference numerals as in FIG. 6 denote the same or equivalent constituent elements, and a detailed description thereof will be omitted. In the present position correcting apparatus of this embodiment, a present position memory 24 for storing the present positions of the ink fountain keys 4 is arranged in place of the home position memory 22 shown in FIG. 6 .

The correcting operation of the present position correcting apparatus having the above arrangement will be described with reference to the flow chart shown in FIG. 13 . In this present position correcting apparatus as well, a testing plate 7 A identical to that shown in FIG. 3 is used as a plate to be mounted on a plate cylinder 8 . The image area ratios of respective areas E, corresponding to ink fountain keys 4 , of the testing plate 7 A are measured in the same manner as in the first embodiment, and print data for the ink fountain keys 4 is created on the basis of the measured image area ratio.

First, in steps S 1301 to S 1303 , a CPU 10 F performs the same operations as in steps S 101 to S 103 of FIG. 1 . The operator then turns on a home position setting switch 13 - 1 (step S 1304 ). When the home position setting switch 13 - 1 is turned on, the CPU 10 F calculates the difference (density difference) between the density (measured density) of the patch p for each ink fountain key 4 and a corresponding reference density stored in a reference density memory 20 in advance (step S 1305 ). The home position correction amount of the ink fountain key 4 corresponding to the density difference is obtained by looking up a density difference-correction amount conversion table 26 (step S 1306 ).

The CPU 10 F then reads out the present position (present opening amount) of the ink fountain key 4 from the present position memory 24 , and corrects the read present opening amount of the ink fountain key 4 by the home position correction amount obtained in step S 1306 (step S 1307 ). More specifically, the present opening amount of the ink fountain key 4 is corrected by the home position correction amount obtained in step S 1306 as the correction value. The CPU 10 F then writes the corrected present opening amount in the present position memory 24 (step S 1308 ). After that, the opening amount of the ink fountain key 4 is controlled with reference to the present opening amount of the ink fountain key 4 updated in step S 1308 .

In the first to sixth embodiments described above, the testing plate 7 A having the color patch portion 7 A 1 and home position adjusting image portion 7 A 2 is used. However, the present invention is not limited to this. For example, a plate used in ordinary printing, which has images of almost the same areas in the right-to-left direction of the paper may be used in the same manner as the testing plate 7 A. Alternatively, a plate for a printing product, the reference density of which is known in advance because printing is performed previously by using it, may be used.

In this case, when the testing plate 7 A is to be used, printing must be performed by using the testing plate 7 A. In contrast to this, when the plate for ordinary printing is to be used, a printing sample obtained by ordinary printing can be used, and the printing material and time may be economized.

Seventh Embodiment

In the first to sixth embodiments described above, the testing plate 7 A having the color patch portion 7 A 1 and home position adjusting image portion 7 A 2 is used. Alternatively, a testing plate 7 B ( FIG. 14 ) having only a color patch portion 7 A 1 may be used.

FIG. 15 shows a home position correcting apparatus for ink fountain keys according to the seventh embodiment of the present invention. In FIG. 15 , the same reference numerals as in FIG. 2 denote the same or equivalent constituent elements, and a detailed description thereof will be omitted. In the home position correcting apparatus of this embodiment, the preset position memory 21 shown in FIG. 2 is omitted.

The correcting operation of the home position correcting apparatus having the above arrangement will be described with reference to the flow chart shown in FIG. 16. A testing plate 7 B having only a color patch portion 7 A 1 is used in place of a testing plate 7 A.

First, in steps S 1601 to S 1609 , a CPU 10 G performs the same operations as in steps S 101 to S 109 of FIG. 1 . In step S 1601 , the CPU 10 G measures the image area ratios of respective areas E of the testing plate 7 B corresponding to ink fountain keys 4 , and creates print data for the ink fountain keys 4 on the basis of the measured image area ratio. In steps S 1602 and S 1606 , a printing sample J printed by using the testing plate 7 B is acquired. In steps S 1603 and S 1607 , the densities of patches p of the color patch portion 7 A 1 are measured by using the testing plate 7 B.

The CPU 10 G then turns on a home position setting switch 13 - 1 to read the opening amount of each ink fountain key 4 , which is obtained when the measured density and the reference density coincide with each other (step S 1601 ), and writes the read opening amount in a home position memory 22 as the home position of the ink fountain key 4 (step S 1611 ). Finally, the CPU 10 G writes the corrected home position in a storage medium (step S 1612 ).

The present position of the ink fountain key 4 is written in the home position memory 22 as the home position because the position of the ink fountain key 4 set by using the testing plate 7 B substantially having no image is the home position.

Eighth Embodiment

FIG. 17 shows a home position correcting apparatus for ink fountain keys according to the eighth embodiment of the present invention. In FIG. 17 , the same reference numerals as in FIGS. 2 and 19 denote the same or equivalent constituent elements, and a detailed description thereof will be omitted. In the home position correcting apparatus of this embodiment, a density difference-correction amount conversion table 26 is arranged in place of the preset position memory 21 shown in FIG. 2 .

The correcting operation of the home position correcting apparatus having the above arrangement will be described with reference to the flow chart shown in FIG. 18. A testing plate 7 B having only a color patch portion 7 A 1 is used in place of a testing plate 7 A.

In steps S 1801 to S 1809 , a CPU 10 H performs the same operations as in steps S 701 to S 709 of FIG. 7 . In step S 1801 , the CPU 10 H measures the image area ratios of respective areas E, corresponding to ink fountain keys 4 , of the testing plate 7 B, and creates print data for the ink fountain keys 4 on the basis of the measured image area ratio. In steps S 1802 and S 1806 , a printing sample J printed by using the testing plate 7 B is acquired. In steps S 1803 and S 1807 , the density of each patch p of the color patch portion 7 A 1 is measured by using the testing plate 7 B.

FIG. 21 shows the functional block of the CPU 10 A shown in FIG. 2 . Referring to FIG. 21 , a present position setting portion 101 performs step S 101 of FIG. 1 . Of a position correcting portion 102 , a present position adjusting portion 102 A, a calculating portion 102 B, and a home position correcting portion 102 C perform steps S 105 to S 108 , step S 112 , and step S 114 , respectively. The CPU 10 B shown in FIG. 4 has the same functional block as this.

FIG. 22 shows the functional block of the CPU 10 C shown in FIG. 6 . Referring to FIG. 22 , a present position setting portion 201 performs step S 701 of FIG. 7 . Of a position correcting portion 202 , a density difference calculating portion 202 A, a home position correction amount calculating portion 202 B, and a home position correcting portion 202 C perform step S 705 , step S 706 , and step S 708 , respectively. The CPU 10 D shown in FIG. 8 has the same functional block as this.

FIG. 23 shows the functional block of the CPU 10 F shown in FIG. 12 . Referring to FIG. 23 , a present position setting portion 301 performs step S 1301 of FIG. 13 . Of a position correcting portion 302 , a density difference calculating portion 302 A, a home position correction amount calculating portion 302 B, and a home position correcting portion 302 C perform step S 1305 , step S 1306 , and step S 1307 , respectively.

As has been described above, according to the present invention, a printing product is obtained by using a plate having a predetermined image. The densities of the respective patches p of the obtained printing product corresponding to the respective ink fountain keys are measured. The home position and present position of each ink fountain key are corrected on the basis of the difference between the measured density of the corresponding patch p and the corresponding reference density stored in advance. The thickness of the ink on the ink fountain roller need not be measured by a measurement unit, or need not be adjusted by checking the color. As a result, the home positions and present positions of the ink fountain keys can be adjusted easily within a short period of time.

Claims

1. A method of correcting a position of an ink fountain key in a printing press, in which an amount of ink to be supplied is adjusted by adjusting a position of each of a plurality of ink fountain keys with reference to a home position, comprising the steps of:setting a position of said ink fountain key as a present position with reference to a home position by using print data including an image area ratio of a reference plate having a predetermined image before actual printing; printing a printing product by using said reference plate with said ink fountain key being set at the present position; measuring a density of each of respective areas, corresponding to said ink fountain keys, of the obtained printing product; correcting one of the home position and the present position of said ink fountain key on the basis of a difference between the measured density of a corresponding area and a reference density; and controlling an operating amount of said ink fountain key based on one of the corrected home position and the corrected present position of said ink fountain key which is stored in a memory when the actual printing is performed.

2. A method according to claim 1, wherein the correcting step comprises the step of adjusting the present position of said ink fountain key such that the difference between the measured density of said area and the reference density stored in advance falls within a predetermined range.

3. A method according to claim 2, further comprising the step of storing the present position of said ink fountain key with reference to the home position as a preset position.

4. A method according to claim 3, wherein the correcting step further comprises the steps ofcalculating the difference between the adjusted present position of said ink fountain key and the stored preset position of said ink fountain key, and correcting the home position of said ink fountain key in accordance with a calculation result obtained from the present position and the preset position of said ink fountain key.

5. A method according to claim 4, further comprising the step of updating and storing the corrected home position of said ink fountain key as the stored home position of said ink fountain key.

6. A method according to claim 2, wherein the correcting step further comprises the step ofupdating and storing the adjusted present position of said ink fountain key as the preset position of said ink fountain key.

7. A method according to claim 1, wherein the correcting step further comprises the steps ofcalculating a difference between the measured density of each area and the reference density stored in advance, calculating a correction amount for the home position of said ink fountain key from the calculated density difference, and correcting the home position of said ink fountain key on the basis of the calculated home position correction amount.

8. A method according to claim 1, wherein the correcting step further comprises the steps ofcalculating a density difference between the measured density of said area and the reference density stored in advance, calculating a correction amount for the home position of said ink fountain key from the calculated density difference, and calculating a corrected present position for said ink fountain key calculated by adding the calculated home position correction amount to the present position of said ink fountain keys.

9. A method according to claim 8, further comprising the step of updating and storing the stored home position of said ink fountain key by the corrected home position of said ink fountain key.

10. The method of claim 1 wherein said setting further comprises setting a position of an ink fountain key as the present position with reference to an original home position.

11. A position correcting apparatus for ink fountain keys in a printing press, in which an amount of ink to be supplied is adjusted by adjusting a position of each said ink fountain key of a plurality of ink fountain keys, comprising:setting means for setting a position of said ink fountain key as a present position with reference to a home position by using print data including an image area ratio of a reference plate having a predetermined image before actual printing; density measuring means for measuring a density of each of respective areas, corresponding to said ink fountain keys, of the obtained printing product by using a printing product printed by using said reference plate with each of said ink fountain keys being set at the present position; position correcting means for correcting one of the home position and the present position of said ink fountain key on the basis of a difference between the measured density of a corresponding area measured by said density measuring means and a reference density; and controlling means for controlling an operating amount of said ink fountain key, based on one of the corrected home position and the corrected present position of said ink fountain key which is stored in a memory when the actual printing is performed.

12. An apparatus according to claim 11, wherein said position correcting means further comprises position adjusting means for adjusting the present position of said ink fountain key such that the difference between the measured density of said area and the reference density stored in advance falls within a predetermined range.

13. An apparatus according to claim 12, further comprising first storage means for storing the present position of said ink fountain key with reference to the home position as a preset position.

14. An apparatus according to claim 13, wherein said position correcting means further comprisescalculating means for calculating the difference between the present position of said ink fountain key sent from said position adjusting means and the preset position of said ink fountain key stored in said first storage means, and correcting means for correcting the home position of said ink fountain key in accordance with a calculation result obtained from said calculating means.

15. An apparatus according to claim 14, further comprising second storage means for storing the home position of said ink fountain key and updating and storing the corrected home position of said ink fountain key as the home position of said ink fountain key.

16. An apparatus according to claim 12, further comprising first storage means for updating and storing the present position of said ink fountain key sent from said position adjusting means as the preset position of said ink fountain key.

17. An apparatus according to claim 11, wherein said position correcting means further comprisesfirst calculating means for calculating a difference between the density of each area sent from said density measuring means and the reference density stored in advance, second calculating means for calculating a correction amount for the home position of said ink fountain key from the density difference calculated by said first calculating means, and home position correcting means for correcting the home position of said ink fountain key by using the correction amount calculated by said second calculating means.

18. An apparatus according to claim 11, wherein said position correcting means further comprisesfirst calculating means for calculating a density difference between the measured density of each area and the reference density stored in advance, second calculating means for calculating a correction amount for the home position of said ink fountain key from the density difference calculated by said first calculating means, and third calculating means for calculating a present position for said ink fountain key corrected by adding the home position correction amount calculated by said second calculating means to the present position of said ink fountain key.

19. An apparatus according to claim 18, further comprising second storage means for storing the home position of said ink fountain key and updating and storing the corrected home position of said ink fountain key as the home position of said ink fountain key.

20. A method of correcting a home position of an ink fountain key comprising:mounting a reference plate having a predetermined image on a printing press that includes said ink fountain key; setting the present position of said ink fountain key with reference to the home position of the ink fountain key corresponding to an image area ratio of said reference plate, said setting of said present position in absence of actual printing on the reference plate; printing a print product by using said reference plate with said ink fountain key set at the present position; measuring a density of the print product associated with said ink fountain key; and correcting the home position of said ink fountain key based on a difference between the measured density of the print product associated with said ink fountain key and a reference density.

21. A method of correcting an ink fountain key position of an ink fountain key of a printing press, said method comprising:setting a present position of said ink fountain key corresponding to a first print density value of a reference plate of said printing press, said setting of said present position corresponding with said key in absence of actual printing on the reference plate; printing a printing product with said reference plate, said printing product having a second print density value corresponding with said key; and revising said present position to a corrected present position based on a difference between said first print density value and said second print density value to correct said ink fountain key position.