Method and apparatus for adjusting ink supply amount for printing press

In an ink supply amount adjusting method for this printing machine, reference opening amounts of ink fountain keys are obtained in accordance with image area ratios of respective areas, corresponding to the ink fountain keys, of a plate by following a preset relationship between an image area ratio and opening amounts of the ink fountain keys. The obtained reference opening amounts are uniformly corrected with preset correction values, thereby obtaining set values of the opening amounts of the ink fountain keys. An ink supply amount adjusting apparatus is also disclosed.

BACKGROUND OF THE INVENTION

The present invention relates to a method and apparatus for adjusting an ink supply amount for a printing press, which adjust the amount of ink to be supplied to a plate by adjusting setting of the opening amount of an ink fountain key and the feed rate (rotation amount) of an ink fountain roller.

A four-color rotary printing press shown inFIG. 16has printing units9-1to9-4provided for four ink colors. An ink supply unit shown inFIG. 15is provided in each of the printing units9-1to9-4.

The ink supply unit shown inFIG. 15has an ink fountain1, an ink2stored in the ink fountain1, an ink fountain roller3, a plurality of ink fountain keys4(4-1to4-n) aligned in the axial direction of the ink fountain roller3, an ink ductor roller5, an ink roller group6, a plate7, and a plate cylinder8.

In the printing press having the above arrangement, the amount of ink to be supplied from the ink fountain1to the ink fountain roller3is adjusted by adjusting the opening amounts of the ink fountain keys4. The amount of ink to be supplied from the ink fountain roller3to the plate7through the ink roller group6is adjusted by adjusting the feed rate (rotation amount) of the ink fountain roller3. A print sheet is printed with the ink finally supplied to the plate7.

The opening amount of each ink fountain key4is set in accordance with the image area ratio of each of areas, corresponding to the ink fountain keys4, of the plate7by following the “conversion curve of the image area ratio to the opening amount of the ink fountain key” stored in advance. The feed rate of the ink fountain roller3is set in accordance with a predetermined reference ink feed rate. The opening amounts of the ink fountain keys4and the feed rate of the ink fountain roller3(ink feed rate) are set in units of printing units9-1to9-4. More specifically, the “conversion curve of the image area ratio to the opening amount of the ink fountain key” and the reference ink feed rate are determined in units of ink colors.

Conventionally, since the “conversion curve of the image area ratio to the opening amount of the ink fountain key” and the reference ink feed rate are uniquely determined by the printing machine manufacturer, differences in standard density among the printing companies and differences depending on the environment are not considered. For this reason, the operator of each printing company actually checks the color of the printed printing product after the opening amounts of the respective ink fountain keys4and the feed rate of the ink fountain roller3are set by using the standard characteristics in units of printing units9-1to9-4.

In accordance with the result of color checking, the operator finely adjusts the opening amounts of the ink fountain keys4separately, or the feed rate of the ink fountain roller3, thereby dealing with the differences in standard density and the differences depending on the environment. This fine adjustment of the amount of ink to be supplied requires a very advanced technique and can be performed only by a skilled operator. The fine adjustment takes a very long period of time, leading to a delay in printing operation.

Also, conventionally, the “conversion curve of the image area ratio to the opening amount of the ink fountain key” and the reference ink feed rate must be stored in units of ink colors, and a very large memory capacity is accordingly necessary.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method and apparatus for adjusting an ink supply amount for a printing press, which can perform color matching for actual printing and set and adjust the amount of ink to be supplied easily and within a short period of time.

It is another object of the present invention to provide a method and apparatus for adjusting an ink supply amount for a printing press, which do not require a very large memory capacity.

In order to achieve the above objects, according to the present invention, there is provided an ink supply amount adjusting method for a printing press having an ink fountain for storing an ink, an ink fountain roller to which the ink is supplied from the ink fountain, a plurality of ink fountain keys aligned in an axial direction of the ink fountain roller to adjust an amount of ink to be supplied from the ink fountain to the ink fountain roller, and an ink roller group for supplying the ink to a plate in an amount adjusted in accordance with a feed rate of the ink fountain roller, comprising the steps ofobtaining reference opening amounts of the ink fountain keys in accordance with image area ratios of respective areas, corresponding to the ink fountain keys, of the plate by following a preset relationship between an image area ratio and opening amounts of the ink fountain keys, anduniformly correcting the obtained reference opening amounts of the ink fountain keys with preset correction values, thereby obtaining set values of the opening amounts of the ink fountain keys.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described in detail with reference to the accompanying drawings. In the following description,FIGS. 15 and 16are also referred to.

First Embodiment

FIG. 1shows an ink supply amount adjusting apparatus for a printing press according to the first embodiment of the present invention. Referring toFIG. 1, the ink supply amount adjusting apparatus is comprised of a CPU (Central Processing Unit)10, a ROM (Read Only Memory)11, a RAM (Random Access Memory)12, a switch group13, a display14, a drive15for a floppy disk or magnetic card, a printer16, a densitometer17, a measurement unit18for measuring the plate image area ratio of a testing plate, A/D (Analog-to-Digital) converters19and20, input/output (I/O) interfaces21to23, a reference density memory24, a conversion curve memory25, an ink feed rate memory26, a correction amount memory27, an ink fountain key drive unit28, and an ink fountain roller drive unit29.

The CPU10obtains various kinds of input information supplied through the input/output interfaces21to23and performs various processing operations in accordance with programs stored in the ROM11while accessing the RAM12.

The standard densities in units of respective ink colors unique to the printing company (in units of printing units) are stored in the reference density memory24if necessary. Usually, when the printing press is shipped from the manufacturer, standard densities in units of ink colors are stored in the memory24. The “conversion curve of the image area ratio to the opening amount of the ink fountain key” for each ink color is stored in the conversion curve memory25. When the printing press is shipped from the manufacturer, the one and only standard characteristic for each ink color is stored in the memory25.

The ink feed rates in units of ink colors are stored in the ink feed rate memory26. When the printing press is shipped from the manufacturer, the reference ink feed rates in units of ink colors are stored in the memory26as the standard values. The correction amounts (increments/decrements) of the opening amounts of the ink fountain keys in units of ink colors are stored in the correction amount memory27as the uniform values for the respective ink fountain keys4. More specifically, correction amounts common to all the ink fountain keys4(FIG. 15) are set as the correction amounts of the opening amounts of the ink fountain keys in units of ink colors. When the printing press is shipped from the manufacturer, the correction amounts of the opening amounts of the ink fountain keys are set to 0 for each ink color.

The ink fountain key drive unit28is separately provided to correspond to each ink fountain key4of each of the printing units9-1to9-4. More specifically, in each of the printing units9-1to9-4, n (n is a positive integer of 2 or more) ink fountain key drive units28are provided to correspond to the n ink fountain keys4. In this case, the opening amounts of the n ink fountain keys4with respect to the ink fountain roller3are separately adjusted by the n ink fountain key drive units28having the same arrangement.

The ink fountain key drive unit28has an input/output interface28A, a D/A converter28B, a fountain key motor driver28C, a fountain key motor28D, a potentiometer28E added to the fountain key motor28D, and an A/D converter28F.

The ink fountain roller drive unit29is separately provided to correspond to each ink fountain roller3of each of the printing units9-1to9-4. More specifically, in the four-color printing press, four ink fountain roller drive units29are provided to correspond to the four printing units9-1to9-4. In this case, the feed rates of the ink fountain rollers3of the respective printing units9-1to9-4are separately adjusted by the four ink fountain roller drive units29having the same arrangement.

The ink fountain roller drive unit29has an input/output interface29A, a D/A converter29B, a fountain roller driving motor driver29C, a fountain roller driving motor29D, a rotary encoder29E added to the fountain roller driving motor29D, an F/V converter29F, and an A/D converter29G.

[How to Adjust Correction Amount of Opening Amount of Ink Fountain Key and Ink Feed Rate in Adjustment Before Actual Printing (FIG. 2)]

Prior to the start of printing, the correction amounts of the opening amounts of the ink fountain keys in units of ink colors stored in the correction amount memory27and the ink feed rates in units of ink colors stored in the ink feed rate memory26are adjusted. In this adjustment, testing plates7A having the same image as shown inFIG. 4are used in units of ink colors. A color patch portion7A1and ink supply amount adjusting image portion7A2are formed on each testing plate7A.

The color patch portion7A1is a known image portion used for measuring printing quality, and is constituted by a plurality of patches (not shown) which are printed in the respective areas corresponding to the ink fountain keys4to be continuous in the direction of array of the ink fountain keys4. The ink supply amount adjusting image portion7A2has a right-angled triangular shape, and the image area ratios within the respective areas corresponding to the ink fountain keys4gradually change in the direction along which the ink fountain keys4are aligned.

To adjust the correction amounts of the opening amounts of the ink fountain keys4and the ink feed rate, the operator measures the image area ratios of the testing plate7A with the measurement unit18and supplies them to the CPU10(step S101). More specifically, the operator measures the image area ratios, corresponding to the ink fountain keys4, of the respective areas of the testing plate7A, and supplies them to the CPU10through the A/D converter20and input/output interface22.

The CPU10calculates the reference opening amounts of the ink fountain keys4of the respective ink colors in accordance with the image area ratios, corresponding to the ink fountain keys4, of the respective areas of the testing plate7A by following the “conversion curve (standard characteristics) of the image area ratio to the opening amount of the ink fountain key” for each ink color (step S102) and stored in the conversion curve memory25in advance.

The (reference) ink feed rates in units of ink colors are read out from the ink feed rate memory26(step S103), and the readout ink feed rates of the respective ink colors are set in the ink fountain rollers3of the printing units9-1to9-4through the ink fountain roller drive unit29. The reference opening amounts of the ink fountain keys4of the respective ink colors obtained in step S102are also set through the ink fountain key drive unit28(step S104).

With the four testing plates7A being set on the plate cylinders8of the respective ink colors, the operator performs printing to acquire a printing sample (step S105). The density of each ink color of the acquired printing sample is measured with the densitometer17(step S106), and is supplied to the CPU10through the A/D converter19and input/output interface21. On the basis of data supplied from the densitometer17, the CPU10checks whether the density (measured density) of each area, corresponding to the ink fountain key4, of each ink color of the printing sample coincides with the corresponding reference density (the reference density unique to the printing company) of each ink color stored in the reference density memory24in advance (step S107).

If the measured density and the reference density do not coincide with each other, i.e., if the difference between the measured density and reference density is not zero or does not fall within a predetermined range, the CPU10determines that the density must be adjusted. For the sake of descriptive convenience, assume that the measured density and the reference density do not coincide with each other in all areas of the respective ink colors.

When the density need be adjusted, the operator adjusts the correction amounts of the opening amounts of the ink fountain keys in units of ink colors stored in the correction amount memory27and the ink feed rates of the respective ink colors stored in the ink feed rate memory26(step S108). More specifically, the operator increases or decreases the current correction amounts of the opening amounts of the ink fountain keys of the respective ink colors and the current ink feed rates in units of ink colors while monitoring them displayed on the display14. The adjusted correction amounts of the opening amounts of the ink fountain keys and the adjusted ink feed rates, of the respective ink colors are overwritten in the correction amount memory27and ink feed rate memory26.

The CPU10reads out the adjusted correction amounts of the opening amounts of the ink fountain keys of the respective ink colors from the correction amount memory27(step S109). The CPU10then adds the readout correction amounts of the opening amounts of the ink fountain keys of the respective ink colors to the reference opening amounts of the ink fountain keys4of the respective ink colors obtained in step S102, thereby correcting the opening amounts of the ink fountain keys4of the respective ink colors (step S110). More specifically, if the correction amounts are positive values, they are uniformly added to the opening amounts of the ink fountain keys4; if they are negative values, they are uniformly subtracted from the opening amounts of the ink fountain keys4.

The CPU10then reads out the adjusted ink feed rates of the respective ink colors from the ink feed rate memory26(step S111). The readout ink feed rates of the respective ink colors, and the opening amounts of the ink fountain keys4of the respective ink colors corrected in step S110, are set in the CPU10through the ink fountain roller drive unit29and ink fountain key drive unit28(step S112).

In each ink color, if the measured density obtained in step S107is a constant value A, as indicated by a characteristic curve I shown inFIG. 5A, regardless of the image area ratio, this characteristic curve is changed by adjusting the ink feed rate in step S112. For example, when the ink feed rate is increased, the density increases, as indicated by a characteristic curve II. The density does not increase sharply at a portion with a low image area ratio, but increases gradually as the image area ratio increases, and stays at a substantially constant value when the image area ratio reaches a certain value.

In each ink color, if the measured density obtained in step S107is a constant value A, as indicated by a characteristic curve I shown inFIG. 5B, regardless of the image area ratio, this characteristic curve is changed by adjusting the opening amounts of the respective ink fountain keys4in step S112. For example, when the opening amounts of the ink fountain keys4are uniformly increased, the density increases, as indicated by a characteristic curve III. The density increases largely at a portion with a low image area ratio, but decreases gradually as the image area ratio increases, and stays at substantially a constant value when the image area ratio reaches a certain value.

In step S112, since both the ink feed rates and the opening amounts of the ink fountain keys are adjusted, the characteristic curves II and III are combined to provide a characteristic curve IV, as shown inFIG. 5C. The printing density of each ink color can be adjusted to a desired density (reference density) B by translation without changing the “conversion curve of the image area ratio to the opening amount of the ink fountain key” for each ink color and stored in the conversion curve memory25.

After this adjustment, the operator performs printing again with the testing plate7A being set on the plate cylinder8of each ink color, and acquires a printing sample (step S113). The operator then measures the density of each ink color of the acquired printing sample (step S114). The CPU10checks whether the measured density of each area, corresponding to the ink fountain key4, of the corresponding ink color of the acquired printing sample coincides with the reference density in the same manner as in the previous step S107(step S115).

The CPU10repeats the steps S108to S115until the measured densities of all areas of the respective ink colors coincide with the reference densities. When the measured densities of all areas of the respective ink colors coincide with the reference densities, the CPU10ends adjustment of the correction amounts of the opening amounts of the ink fountain keys and the ink feed rates performed before the start of printing.

[How to Set Ink Supply Amount at Start of Actual Printing (FIG. 3)]

Prior to the start of printing with the plate7of each ink color being mounted, the operator separately measures the image area ratio of the plate7of each ink color with the plate image area ratio measurement unit18, and supplies the obtained ratio to the CPU10(step S201). More specifically, the operator measures the image area ratios, corresponding to the ink fountain keys4, of the respective areas of the plates7of the respective ink colors, and supplies the measured image area ratios to the CPU10through the A/D converter20and input/output interface22.

The CPU10obtains the reference opening amounts of the ink fountain keys4of the respective ink colors in accordance with the image area ratios of the respective areas, corresponding to the ink fountain keys4, of the plate7of the respective ink colors by following the “conversion curve of the image area ratio to the opening amount of the ink fountain key” for each ink color (step S202) and stored in the conversion curve memory25in advance. The operator then reads out the correction amounts of the opening amounts of the ink fountain keys of the respective ink colors from the correction amount memory27(step S203). The CPU10then adds the readout correction amounts of the opening amounts of the ink fountain keys of the respective ink colors to the reference opening amounts of the ink fountain keys4of the respective ink colors obtained in step S202, thereby obtaining preset values of the opening amounts of the ink fountain keys4for the respective ink colors (step S204). More specifically, if the correction amounts are positive amounts, they are uniformly added to the opening amounts of the ink fountain keys4; if they are negative values, they are uniformly subtracted from the opening amounts of the ink fountain keys4.

The CPU10then reads out the ink feed rates of the respective ink colors from the ink feed rate memory26(step S205). The readout ink feed rates of the respective ink colors, and the opening amounts of the ink fountain keys4of the respective ink colors obtained in step S204, are set in the CPU10through the ink fountain roller drive unit29and ink fountain key drive unit28(step S206). Printing is then started (step S207).

In this case, the ink feed rates of the respective ink colors in the ink feed rate memory26and the correction amounts of the opening amounts of the ink fountain keys of the respective ink colors in the correction amount memory27are adjusted such that the reference densities of the respective ink colors unique to the printing company are obtained by repeating steps S108to S115before the start of printing regardless of the image area ratios. Therefore, appropriate ink supply amounts can be obtained from the beginning.

More specifically, conventionally, the opening amounts of the ink fountain keys4and the ink feed rates, of the respective ink colors are set in accordance with the reference densities unique to the printing company to be employed and the printing environmental conditions, and after that the operator adjusts the opening amounts of the ink fountain keys and the ink feed rates of the respective ink colors without regularity while repeating printing test of the printing products with the plates7, such that appropriate amounts of inks are supplied. According to this embodiment, such ink supply amount adjustment with the plates7being mounted is not necessary. Appropriate amounts of inks can be obtained immediately after the plates7are mounted.

According to this embodiment, since the correction amounts of the opening amounts of the ink fountain keys of the respective ink colors are uniform, the correction amounts and ink feed rates can be adjusted before the start of printing easily within a short period of time when compared to a method of setting separate correction amounts in units of ink fountain keys. The basic “conversion curve of the image area ratio to the opening amount of the ink fountain key” determined by the printing machine manufacturer in units of ink colors need not be changed, and the adjusting operation can be simplified.

According to this embodiment, both the correction amounts of the opening amounts of the ink fountain keys and the ink feed rates, of the respective ink colors are adjusted. In some cases, only either the correction amounts of the opening amounts of the ink fountain keys or the ink feed rates, of the respective ink colors need be adjusted. For example, inFIG. 5B, within an image area ratio range where the characteristic curve III of the density translates, a desired density B can be obtained only by adjusting the correction amounts of the opening amounts of the ink fountain keys of the respective ink colors. InFIG. 5A, within an image area ratio range where the characteristic curve II of the density translates, a desired density B can be obtained only by adjusting the ink feed rates of the respective ink colors.

When the density obtained by printing with the conditions set by the printing machine manufacturer exhibits a characteristic curve III as shown inFIG. 5B, the desired density B can be obtained only by adjusting the ink feed rates. When the density obtained by printing exhibits a characteristic curve II shown inFIG. 5A, the desired density B can be obtained only by adjusting the correction amounts of the opening amounts of the ink fountain keys.

Second Embodiment

FIG. 6shows an ink supply amount adjusting apparatus for a printing press according to the second embodiment of the present invention. Referring toFIG. 6, the same reference numerals as inFIG. 1denote the same or equivalent constituent elements, and a detailed description thereof will be omitted.

The ink supply amount adjusting apparatus according to this embodiment has, in addition to the arrangement shown inFIG. 1, a coefficient memory30for storing the coefficients of ink feed rates in units of ink colors. The coefficients of the ink feed rates in units of ink colors (in units of printing units) are set to “1” when the printing machine is shipped from the manufacturer.

[How to Adjust Correction Amount of Opening Amount of Ink Fountain Key and Coefficient of Ink Feed Rate in Adjustment Before Actual Printing (FIG. 7)]

Prior to the start of printing, the correction amounts of the opening amounts of the ink fountain keys in units of ink colors stored in a correction amount memory27and the coefficients of the ink feed rates in units of ink colors stored in a coefficient memory30are adjusted. In this adjustment as well, testing plates7A identical to that shown inFIG. 4are used.

The processes of steps S301to S307and S314to S316inFIG. 7are the same as those of steps S101to S107and S113to S115inFIG. 2, and a description thereof will accordingly be omitted.

When it is determined in step S307that the density need be adjusted, the operator adjusts the correction amounts of the opening amounts of the ink fountain keys of the respective ink colors stored in the correction amount memory27and the coefficients of the ink feed rates of the respective ink colors stored in the coefficient memory30(step S308). More specifically, the operator increases or decreases the current correction amounts of the opening amounts of the ink fountain keys and the current coefficients of the ink feed rates, of the respective ink colors while monitoring them displayed on a display14. The adjusted correction amounts of the opening amounts of the ink fountain keys and the adjusted coefficients of the ink feed rates, of the respective ink colors are overwritten in the correction amount memory27and coefficient memory30, respectively.

The CPU10reads out the adjusted correction amounts of the opening amounts of the ink fountain keys of the respective ink colors from the correction amount memory27(step S309). The CPU10then adds the readout correction amounts (increments/decrements) of the opening amounts of the ink fountain keys of the respective ink colors to the reference opening amounts of the ink fountain keys4of the respective ink colors obtained in step S302, thereby correcting the opening amounts of ink fountain keys4of the respective ink colors (step S310). More specifically, if the correction amounts are positive values, they are uniformly added to the opening amounts of the ink fountain keys4; if they are negative values, they are uniformly subtracted from the opening amounts of the ink fountain keys4.

The CPU10then reads out the adjusted coefficients of the ink feed rates of the respective ink colors from the coefficient memory30(step S311). The CPU10multiplies the reference ink feed rate for each ink color, read by the step S303, by the readout coefficients of the ink feed rates of the respective ink colors, thereby correcting the ink feed rates of the respective ink colors (step S312). Subsequently, the CPU10sets the opening amounts of the ink fountain keys4of the respective ink colors obtained in step S310and the ink feed rates of the respective ink colors obtained in step S312through an ink fountain key drive unit28and ink fountain roller drive unit29(step S313). When the setting operation is ended, the flow advances to step S315.

[How to Set Ink Supply Amount at Start of Actual Printing (FIG. 8)]

Processes of steps S401to S404inFIG. 8are the same as those of steps S201to S204inFIG. 3, and a description thereof will accordingly be omitted.

The CPU10reads out the reference ink feed rate for each ink color from the ink feed rate memory26in step S405, and reads the coefficients of the ink feed rates of the respective ink colors from the coefficient memory30(step S406). The CPU10then multiplies the reference ink feed rate for each ink color, read in step S405, by the readout coefficients of the ink feed rates of the respective ink colors, thereby obtaining preset values of the ink feed rates of the respective ink colors (step S407).

The CPU10sets the opening amounts of the ink fountain keys4of the respective ink colors obtained in step S404, and the ink feed rates of the respective ink colors obtained in step S407through the ink fountain key drive unit28and ink fountain roller drive unit29(step S408). Printing is then started (step S409).

In this embodiment, the ink feed rates of the respective ink colors are corrected by multiplying them by the coefficients. Alternatively, if correction values are obtained and added to the reference ink feed rate, in the same manner as that performed when adjusting the opening amounts of the ink fountain keys, the same effect can be obtained.

Third Embodiment

FIG. 9shows an ink supply amount adjusting apparatus for a printing press according to the third embodiment of the present invention. Referring toFIG. 9, the same reference numerals as inFIG. 1denote the same or equivalent constituent elements, and a detailed description thereof will be omitted.

The ink supply amount adjusting apparatus according to this embodiment has, in addition to the arrangement shown inFIG. 1, a zero position memory31for storing the zero positions (origin positions) of the opening amounts of the ink fountain keys in units of ink colors.

[How to Adjust Correction Amount of Opening Amount of Ink Fountain Key and Ink Feed Rate in Adjustment Before Actual Printing (FIG. 10)]

Prior to the start of printing, the correction amounts of the opening amounts of the ink fountain keys in units of ink colors stored in a correction amount memory27and the ink feed rates in units of ink colors stored in an ink feed rate memory26are adjusted. In this adjustment as well, testing plates7A identical to that shown inFIG. 4are used. The processes of steps S501to S515inFIG. 10are the same as those of steps S101to S115inFIG. 2, and a description thereof will be omitted.

[How to Set Ink Supply Amount at Start of Actual Printing (FIG. 11)]

The operator measures the image area ratio of the testing plate7A with a measurement unit18and supplies it to a CPU10(step S601). The CPU10reads out the zero positions of the opening amounts of the ink fountain keys of the respective ink colors stored in the zero position memory31(step S602), and the correction amounts of the opening amounts of the ink fountain keys of the respective ink colors stored in the correction amount memory27(step S603). Subsequently, the CPU10adds the correction amounts (increments/decrements) of the opening amounts of the ink fountain keys of the respective ink colors to the readout zero positions of the opening amounts of the ink fountain keys of the respective ink colors, thereby correcting the zero positions of the opening amounts of the ink fountain keys of the respective ink colors (step S604). More specifically, if the correction amounts are positive values, they are uniformly added to the zero positions of the opening amounts of the ink fountain keys; if they are negative values, they are uniformly subtracted from the zero positions of the opening amounts of the ink fountain keys.

The CPU10obtains the reference opening amounts of the ink fountain keys4of the respective ink colors in accordance with the image area ratios of the respective areas, corresponding to the ink fountain keys4, of the plates7of the respective ink colors by following the “conversion curve of the image area ratio to the opening amount of the ink fountain key” for each ink color (step S605) and stored in a conversion curve memory25in advance. The operator then obtains the opening amounts of the ink fountain keys of the respective ink colors from the corrected zero positions of the opening amounts of the ink fountain keys of the respective ink colors obtained in step S604and the reference opening amounts of the ink fountain keys of the respective ink colors obtained in step S605(step S606).

The CPU10reads out the ink feed rates of the respective ink colors from the ink feed rate memory26(step S607). The CPU10then sets the readout ink feed rates of the respective ink colors and the opening amounts of ink fountain keys4of the respective ink colors obtained in step S606through an ink fountain roller drive unit29and ink fountain key drive unit28(step S608). After that, printing is started (step S609).

In this case, the opening amounts of the ink fountain keys4of the respective ink colors are set with reference to the corrected zero positions of the opening amounts of the ink fountain keys of the respective ink colors. More specifically, the opening amounts of the ink fountain keys4of the respective ink colors are set with reference to the zero positions that are adjusted such that the reference densities of the respective ink colors unique to the printing company can be obtained regardless of the image area ratio. Therefore, when the setting operation of the opening amounts is combined with the setting operation of the ink feed rates of the respective ink colors read from the ink feed rate memory26, appropriate ink supply amounts can be obtained from the beginning.

Fourth Embodiment

FIG. 12shows an ink supply amount adjusting mechanism for a printing press according to the fourth embodiment of the present invention. Referring toFIG. 12, the same reference numerals as inFIG. 6denote the same or equivalent constituent elements, and a detailed description thereof will be omitted.

The ink supply amount adjusting mechanism according to this embodiment has, in addition to the arrangement shown inFIG. 6, a memory31for storing the zero positions (origin positions) of the opening amounts of the ink fountain keys in units of ink colors.

[How to Adjust Correction Amount of Opening Amount of Ink Fountain Key and Coefficient of Ink Feed Rate in Adjustment Before Actual Printing (FIG. 13)]

Prior to the start of printing, the correction amounts of the opening amounts of the ink fountain keys in units of ink colors stored in a correction amount memory27and the coefficients of the ink feed rates in units of ink colors stored in a memory30are adjusted. In this adjustment as well, testing plates7A identical to that shown inFIG. 4are used. The processes of steps S701to S716inFIG. 13are the same as those of steps S301to S316inFIG. 7, and a description thereof will be omitted.

[How to Set Ink Supply Amount at Start of Actual Printing (FIG. 14)]

The operator measures the image area ratio of the testing plate7A with a measurement unit18and supplies it to a CPU10(step S801). The CPU10reads out the zero positions of the opening amounts of the ink fountain keys of the respective ink colors stored in the zero position memory31(step S802), and the correction amounts of the opening amounts of the ink fountain keys of the respective ink colors stored in the correction amount memory27(step S803). Subsequently, the CPU10adds the correction amounts (increments/decrements) of the opening amounts of the ink fountain keys of the respective ink colors to the readout zero positions of the opening amounts of the ink fountain keys of the respective ink colors, thereby correcting the zero positions of the opening amounts of the ink fountain keys of the respective ink colors (step S804). More specifically, if the correction amounts are positive values, they are uniformly added to the zero positions of the opening amounts of the ink fountain keys; if they are negative values, they are uniformly subtracted from the zero positions of the opening amounts of the ink fountain keys.

The CPU10obtains the reference opening amounts of the ink fountain keys4of the respective ink colors in accordance with the image area ratios of the respective areas, corresponding to ink fountain keys, of the plate7of the respective ink colors4by following the “conversion curve of the image area ratio to the opening amount of the ink fountain key” for each ink color (step S805) stored in a conversion curve memory25in advance. The CPU10then obtains the opening amounts of the ink fountain keys of the respective ink colors from the corrected zero positions of the opening amounts of the ink fountain keys of the respective ink colors obtained in step S804and the reference opening amounts of the ink fountain keys of the respective ink colors obtained in step S805(step S806).

The CPU10reads out the reference ink feed rate common to the ink colors from an ink feed rate memory26(step S807), and the coefficients of the ink feed rates of the respective ink colors from the coefficient memory30(step S808). The CPU10then multiplies the reference ink feed rate for each ink color read in step S807by the readout coefficients of the ink feed rates of the respective ink colors, thereby obtaining preset values of the ink feed rates of the respective ink colors (step S809).

The CPU10sets the opening amounts of the ink fountain keys4of the respective ink colors obtained in step S806and the ink feed rates of the respective ink colors obtained in step S809through an ink fountain key drive unit28and ink fountain roller drive unit29. After that, printing is started (step S811).

In this case, the opening amounts of the ink fountain keys4of the respective ink colors are set with reference to the corrected zero positions of the opening amounts of the ink fountain keys of the respective ink colors. More specifically, the opening amounts of the ink fountain keys4of the respective ink colors are set with reference to the zero positions that are adjusted such that the reference densities of the respective ink colors unique to the printing company can be obtained regardless of the image area ratio. Therefore, when the setting operation of the opening amounts is combined with the setting operation of the ink feed rates of the respective ink colors obtained in step S809, appropriate ink supply amounts can be obtained from the beginning.

In this embodiment, the ink feed rates of the respective ink colors are corrected by multiplying them by the coefficients. Alternatively, if correction values are obtained and added to the reference ink feed rates, in the same manner as that performed when adjusting the opening amounts of the ink fountain keys, the same effect can be obtained.

FIGS. 17A,17B, and17C show the relationships between the function blocks of the CPUs10ofFIGS. 1,9, and12and their processing steps. In the CPU10ofFIG. 1shown inFIG. 17A, a first reference opening amount calculating portion101performs the process of step S102ofFIG. 2, and an opening amount correction value calculating portion102performs the processes of steps S108to S115ofFIG. 2. A second reference opening amount calculating portion103performs the process of step S202ofFIG. 3, and an opening amount preset value calculating portion104performs the process of step S206ofFIG. 3. The same applies to the CPU10shown inFIG. 6.

In the CPU10ofFIG. 9shown inFIG. 17B, a first reference opening amount calculating portion201performs the process of step S502ofFIG. 10, and an opening amount correction value calculating portion202performs the processes of steps S508to S515ofFIG. 10. An origin position correcting portion203performs the process of step S604ofFIG. 11, and an opening amount preset value calculating portion204performs the process of step S606ofFIG. 11.

In the CPU10ofFIG. 12shown inFIG. 17C, an overwriting portion301performs the processes of steps S708to S716ofFIG. 13, a feed rate correction value setting portion302performs the process of step S808ofFIG. 14, and a feed rate preset value calculating portion303performs the process of step S809ofFIG. 14. A CPU10ofFIG. 12can also have at least one functional block of the CPUs10ofFIGS. 1 and 9.

As has been described above, according to the present invention, in particular, color matching in actual printing can be more effectively facilitated within a short period of time. In particular, when at least one of the correction amounts/origin positions of the opening amounts of the ink fountain keys of the respective ink colors and the correction values of the ink feed rates of the respective ink colors is adjusted such that the reference densities of the respective ink colors unique to the printing company can be obtained regardless of the image area ratio before the start of printing, a higher effect can be obtained. As the relationship between the image area ratio and the opening amounts of the ink fountain keys, it suffices if only one reference value is set to be common to the respective ink colors. Therefore, a large memory capacity is not needed, and the image capacity can be reduced greatly.

According to the present invention, the correction amounts of the opening amounts of the ink fountain keys and the correction amounts of the ink feed rates, of the ink colors can be overwritten. Therefore, the amount of ink to be supplied, which varies depending on the printing companies and the differences in the environment, can be adjusted easily within a short period of time by adjusting the correction values (increments/decrements) of the opening amounts of the ink fountain keys and the correction amounts of the ink feed rates, of the ink colors before the start of printing.