JPH11188962A - Screen printing density control method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screen printing density control method and apparatus capable of widely and finely changing printing density at various printing speeds. SOLUTION: In a printing density control method of screen printing wherein perforated screen printing base paper is wound around the outer peripheral surface of a plate cylinder receiving the supply of ink on its inner peripheral surface and the plate cylinder is rotated and printing paper is brought into contact with the outer peripheral surface of the stencil paper under pressure to transfer ink to the paper through perforations, the value of D is selected within a range capable of taking the value of the formula D=√ (F/f) (wherein F is the pressure contact farce of paper to the plate cylinder and f is the rotational speed of the plate cylinder) to control an increase and decrease in the transfer amt. of ink to the paper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stencil printing density control method and apparatus capable of easily controlling printing density.

[0002]

2. Description of the Related Art A perforated stencil sheet is wound around an outer peripheral surface of a cylindrical plate cylinder supplied with ink on an inner peripheral surface, and the plate cylinder is rotated, and printing paper is wrapped around the outer peripheral surface of the stencil sheet. A stencil printing machine for transferring ink to the paper through the perforations by pressing the stencil is well known.

In the stencil printing apparatus as described above, the pressing force of the printing paper against the plate cylinder is variably set in accordance with print density information set by print density information setting means provided by a print density setting key provided on an operation panel. A method of variably setting the print density of an image to be printed on printing paper by doing so has already been proposed in Japanese Patent Application Laid-Open No. Sho 62-127276.

Further, since the printing density of stencil printing varies depending on the printing speed, the printing paper for the plate cylinder is set in accordance with printing speed information set by printing speed information setting means such as a printing speed setting key provided on an operation panel. JP-A-6-155880 has already proposed that stencil printing of a desired density can be performed irrespective of a change in printing speed by variably setting the pressing force of the stencil.

[0005]

In recent years, with the diversification of paper quality and originals of printing paper, there has been a demand for a stencil printing apparatus capable of finely adjusting the printing density more widely. However, because the index for controlling print density was not clear,
In order to meet such demands, it is necessary to collect enormous data on the relationship between the rotation speed of the plate cylinder corresponding to various printing densities and the pressing force of the printing paper against this, and this data is installed in a stencil printing machine. Thus, controlling the print density was a practically impossible task.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a stencil printing density control method and apparatus capable of widely and finely changing the printing density at various printing speeds.

[0007]

The inventor of the present invention has conducted intensive studies on the above-mentioned object, and as a result, the transfer amount of the ink was Δ (F / f).
(Where F is the pressing force of the sheet against the plate cylinder, and f is the rotational speed of the plate cylinder), and in particular, it has been found that it is approximately proportional to the value of √ (F / f). This means that even when the rotation speeds of the plate cylinders are different, printing density can be matched by printing in combination with the pressing force showing the same value of √ (F / f).

Conventionally, it was based on experience only as to how much pressure force required to compensate for a change in printing speed to obtain the same printing density. However, according to the present invention, an index of printing density was used. By simply selecting the value of √ (F / f), the printing speed and the pressing force can be easily determined. Therefore, whether the test printing is performed at a low speed or the final printing is performed at a high speed, or when the printing speed is changed during printing. However, it is possible to control the printing machine so as to always provide a print at a constant print density regardless of the print speed.

Thus, according to the present invention, a perforated stencil sheet is wound around the outer peripheral surface of the plate cylinder to which ink has been supplied to the inner peripheral surface, and the plate cylinder is rotated and the outer peripheral surface of the base paper is rotated. A printing density control method for stencil printing in which a printing sheet is pressed against a surface and ink is transferred to said sheet through said perforations, wherein D = √ (F / f) (wherein F is Stencil printing density control method characterized by controlling the increase or decrease of the amount of ink transferred to the paper by selecting the value of D within a range in which the value of the pressure contact force of the paper (f is the rotation speed of the plate cylinder) can be taken. Is provided.

The stencil printing density control method of the present invention is characterized in that
A first step of selecting a value of D from the range of values of D to set a desired print density; calculating a range of possible values of f with the selected value of D; A second step of setting a desired printing speed by selecting a value of f within the range, and a third step of calculating the value of F from the selected value of D and the value of f to set the pressing force. It may consist of Here, the second step is a step of calculating and displaying a range of possible values of f with the selected value of D, and selecting the value of f within the range of the displayed value of f. And setting a desired printing speed.

Further, the stencil printing density control method of the present invention comprises:
a first step of selecting a value of f to set a desired printing speed; calculating a range of possible values of D for the selected value of f; And a second step of setting the desired print density by selecting
And a third step of calculating the value of F from the value of D and the value of D to set the pressing force. Here, the second step is a step of calculating and displaying a range of possible values of D with the selected value of f, and selecting the value of D within the range of the displayed value of D. And setting a desired print density.

According to another aspect of the present invention, a perforated stencil sheet is wound around an outer peripheral surface of a plate cylinder having ink supplied to an inner peripheral surface thereof, and the plate cylinder is rotated. A printing density control method of stencil printing in which printing paper is pressed against the outer peripheral surface of the base paper to transfer ink to the paper via the perforations, wherein D = √ (F / f) (where F is the aforementioned The value of the pressing force of the paper against the plate cylinder, f is the rotation speed of the plate cylinder), and the fluctuation of the value of D is ± 0.05.
(Kg · f / rpm) The stencil printing density control method is characterized by controlling the values of F and f so as to keep the printing density constant. Here, the value of F was monitored, and the fluctuation of the value of D was ± 0.05.
(Kg · f / rpm) or less, the rotation speed of the plate cylinder can be controlled by calculating the value of f according to the increase or decrease of the value of F. Conversely, the value of f is monitored, Variation of D value ±
It is also possible to control the pressing force by calculating the value of F according to the increase or decrease of the value of f so as to keep it at 0.05 (kg · f / rpm) or less.

Further, according to another aspect of the present invention, a perforated stencil sheet is wound around an outer peripheral surface of a plate cylinder having ink supplied to an inner peripheral surface thereof, and the plate cylinder is rotated. A printing density control device for stencil printing in which printing paper is pressed against the outer peripheral surface of the base paper and ink is transferred to the paper via the perforations, wherein D = √ (F / f) (where F is the aforementioned Means for increasing or decreasing the amount of ink transferred to the sheet by selecting the value of D within a range in which the value of the pressure contact force of the sheet against the plate cylinder, f is the rotation speed of the plate cylinder) can be taken. A stencil printing density control device is provided.

The stencil printing density control device according to the present invention comprises a printing density setting means for selecting a value of D from the range of D values, and calculating a range of f values possible with the selected D value. Printing speed setting means for selecting the value of f within the range of the value of f, and pressing force control means for calculating the value of F from the selected value of D and the value of f to set the pressing force May be provided. Here, the printing speed setting means calculates and displays a range of f values possible with the selected D value, and displays the f value displayed on the display means.
And a speed setting means for selecting a value of f within the range of the value and setting a desired printing speed.

Further, the stencil printing density control device of the present invention includes a printing speed setting means for selecting a value of f and setting a desired printing speed, and a printing speed setting means for setting a desired printing speed. A print density setting means for calculating a range and selecting a value of D within the range of the value of D to set a desired print density; and calculating a value of F from the selected value of f and the value of D. And a pressing force control means for controlling the pressing force. Here, the print density setting means calculates and displays a range of possible values of D with the selected value of f, and displays D within the range of the value of D displayed on the display means. And a density setting means for setting a desired print density by selecting the value of the above.

According to another aspect of the present invention, a perforated stencil sheet is wound around an outer peripheral surface of a plate cylinder supplied with ink on an inner peripheral surface, and the plate cylinder is rotated. A recording medium on which a printing density control program for stencil printing in which printing paper is pressed against the outer peripheral surface of the base paper to transfer ink to the paper via the perforations is recorded, D = √ (F / f) (formula Where F is the pressing force of the sheet against the plate cylinder, and f is the value of F selected based on the value of D selected within the range of values of the rotation speed of the plate cylinder. And a recording medium on which a stencil printing density control program is recorded.

The control program stores the selected value of D, calculates a range of possible values of f with the stored value of D, displays the value as necessary, and displays the range of the value of f. The value of f selected in the above is stored, and the value of F is calculated from the selected value of D and the value of f to set the pressing force.

Further, the control program stores the selected value of f, calculates a range of possible values of D based on the stored value of f, and selects the range of values of D within the range of D. The pressure contact force may be set by storing the value of D and calculating the value of F from the selected value of f and the value of D.

In the present invention, D = √ (F / f)
Is synonymous with D ² = (F / f), selecting D is the same as selecting D ² , and D ′ =
It is also possible to derive an expression such as a√ (F / f) + b (a and b are arbitrary constants). In such a derivation expression, selecting D ′ means selecting D. It goes without saying that they are the same.

In the present invention, the rotational speed f of the plate cylinder
(Rpm) is usually synonymous with the number of times a given fixed point in the printable surface of the plate cylinder is pressed against in one minute. Therefore,
In a normal printing machine in which one sheet is passed during one rotation of the plate cylinder, this corresponds to the number of prints finished in one minute. However, when a plurality of sheets are passed during one rotation of the plate cylinder, or when one sheet is passed during a plurality of rotations,
The rotation speed of the plate cylinder and the printing speed do not always match. Further, when the rotation of the plate cylinder is uneven (for example, when the plate cylinder is accelerated / decelerated or stopped during the rotation), the value obtained by converting the surface speed of the plate cylinder at the fixed point into a rotation speed f (rpm) is obtained. Rotation speed f (rpm) of the plate cylinder used in the present invention
It is.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples.

FIG. 1 shows a stencil printing apparatus having a stencil making function as one embodiment of the stencil printing apparatus according to the present invention. The stencil printing apparatus includes a document reading unit 11 and a stencil making unit 1.
3 and a printing unit 15.

The document reading unit 11 is an image scanner, and includes a line image sensor 17 for reading an image of a document conveyed in the sub-scanning direction, and a document feed roller 1.
9.

The plate making section 13 includes a base paper roll section 21, a thermal head 23 composed of a plurality of point heating elements arranged in a horizontal line, base paper feed rollers 25 and 27, and base paper guide rollers 29 and 31. , 33, and a stencil cutter 35, and a plurality of dot heating elements of the thermal head 23 selectively and individually generate heat, thereby forming a heat-sensitive stencil sheet M on the heat-sensitive stencil sheet M in a dot matrix manner. Then, the stencil sheet M after stencil making is cut by the cutter 35.

The printing unit 15 includes a porous plate-shaped ink-permeable cylindrical plate cylinder 37 made of an ink-permeable material such as a perforated metal plate and a mesh structure, and a squeegee disposed inside the plate cylinder 37. An ink supply device 39 including a roller 38 and a doctor roller 40, and a press roller 41;
A stencil sheet M after stencil making is wound and mounted on the outer periphery of the plate cylinder 37.

On one side of the printing unit 15, a paper feeding unit 43 is provided.
On the other side of the printing unit 15, a paper discharging unit 45 is provided.

The paper supply unit 43 includes a paper supply table 47 on which the print papers P are stacked and stacked, a pickup roller 49 for taking out the print papers P one by one from the paper supply table 47, and a print cylinder P with the plate cylinder 37. It has a paper feed timing roller 51 that feeds between it and the press roller 41.

The paper discharging section 45 has a stripping claw 53 for peeling the printing paper from the plate cylinder 37, a paper discharging feeding belt section 55, and a paper discharging table 57 on which the printed printing paper P is stacked. .

On one side of the printing unit 15, the used stencil sheet M is peeled off from the plate cylinder 37 and the stencil sheet M is removed.
A plate discharge section 63 including a plate discharge roller 61 that feeds into the inside 9 is provided.

In this stencil printing machine, a predetermined color of printing ink is supplied to the inside of the plate cylinder 37 by an ink supply device 39, and the plate cylinder 37 is rotated around its own central axis by rotation driving means (not shown). As shown in the drawing, the print paper P is driven to rotate counterclockwise, and is moved from the left to the right in the figure by the paper feed timing roller 51 at a predetermined timing in synchronization with the rotation of the plate cylinder 37. The printing paper P is supplied between the printing drum 37 and the press roller 41, and the printing paper P is pressed against the stencil sheet M wound around the outer peripheral surface of the printing drum 37 by the pressing roller 41, so that the printing paper P Stencil printing with a printing ink of a predetermined color is performed.

FIG. 2 shows a driving device for the press roller 41. The press roller 41 extends in the axial direction of the plate cylinder 37 and is rotatably supported by a bracket 65 around its own central axis. The bracket 65 is rotatably supported by a frame (not shown) that is a fixed side member. Is fixedly mounted on the pressed shaft 69. As a result, the press roller 41 can be pivotally displaced in a substantially vertical direction about the press shaft 69, and a retracted position separated from the outer peripheral surface of the plate cylinder 37 and a press contact position pressed against the outer peripheral surface of the plate cylinder 37. It is movable between and.

A press drive lever 71 is fixedly mounted on the press shaft 69, and the press shaft 69 rotatably supports a press drive plate 73.

A hook member 77 is rotatably attached to the press drive plate 73 by a pivot 75. The hook member 77 is mounted on the solenoid 7 mounted on the press drive plate 73.
9, and is selectively engaged with the press drive lever 71 to drive-connect the press drive lever 71 and the press drive plate 73 to each other.

One end of a first link member 83 is pivotally connected to an end of the press driving plate 73 by a pivot 81. Elongated holes 85 are formed in the first link member 83 at two locations, each extending in the same direction, and a pin 89 of the second link member 87 is engaged with each of the elongated holes 85. As a result, the first link member 83 and the second link member 87 are connected to each other so as to be displaceable in the link length direction within the range of the elongated hole 85, that is, substantially vertically in FIG.

At the lower end of the first link member 83, a bent flange piece 91 is provided.
The adjusting screw 93 is penetrated so as to be movable in the reciprocating direction of the first link member 83. The adjusting screw 93 is screwed with a spur gear-shaped nut member 99 having external teeth 97 for receiving a thrust through a collar 95 at a position below the bent flange piece 91 via a collar 95. A tension coil spring 101 is provided at the upper end of 93.
Is locked at one end.

The adjusting screw 93 is prevented from rotating by locking one end of the tension coil spring 101 to the adjusting screw 93, and moves in the axial direction with respect to the first link member 83 by the rotation of the nut member 99.

The tension coil spring 101 has a pin 8 at the other end.
9, the first link member 83 is connected to the second link member 8
7, in other words, the press drive plate 73 is applied around the press shaft 69 in the counterclockwise direction in FIG. I'm going.

The second link member 87 has a pivot 10 at its upper end.
3, it is pivotally connected to the distal end of the cam lever 105. The cam lever 105 is rotatably supported by a frame (not shown) by a support shaft 107, and rotatably supports a cam follower roller 109 by a pivot shaft 103 at a distal end portion. The cam follower roller 109 has a main shaft 111
And is engaged with the press cam 113 attached to the second cam. The main shaft 111 is rotatably supported by a frame (not shown).

The press cam 113 rotates in synchronism with the rotation of the plate cylinder 37, and a stencil clamp (not shown) provided on the outer periphery of the plate cylinder 37 is located at a rotation position corresponding to the press roller 41. Occasionally, in order to avoid interference between the press roller 41 and the stencil sheet clamp portion, the cam profile for positioning the press roller 41 at the retracted position is provided.

A motor 1302 for adjusting the pressing force is attached to the bent flange piece 91, and a drive gear 119 is fixedly mounted on the output shaft 117 of the motor 1302 for adjusting the pressing force. The drive gear 119 meshes with the external teeth 97 of the nut member 99, and transmits the rotation of the output shaft of the press-contact force adjusting motor 1302 to the nut member 99.

In this press roller driving device, the rotation of the plate cylinder 37 causes the press cam 113 to rotate clockwise in FIG. 2, and the rotation causes the second link member 87 to reciprocate substantially up and down. Movement is tension coil spring 1
01 to the first link member 83. The reciprocating motion of the first link member 83 causes the press driving plate 73 to reciprocate around the press shaft 69, and at this time, the solenoid 7
9, the hook member 77 is moved to the engagement position and is engaged with the press drive lever 71, whereby the reciprocating rotation of the press drive plate 73 is transmitted to the press shaft 69, and the reciprocal rotation of the press shaft 69 is performed. As a result, the press roller 41 swings and displaces in a substantially vertical direction about the press shaft 69, and the press roller 41 is retracted from the outer peripheral surface of the plate cylinder 37 and is pressed against the outer peripheral surface of the plate cylinder 37. And move between.

At this time, the movement of the press roller 41 to the press contact position is performed by raising the second link member 87 and transmitting this movement to the first link member 83 while applying a tensile force to the tension coil spring 101, and the press drive is performed. The plate 73 is a press shaft 69
2, the press roller 41 is pressed against the outer peripheral surface of the plate cylinder 37 with the print paper P interposed therebetween, and the press drive plate 7 is rotated.
The rotation in the counterclockwise direction about the press shaft 69 of FIG. 3 in FIG. 2 is restricted, and the second link member 87 is still pulled up from this state, so that the second link member 8
7 is displaced with respect to the first link member 83, and the tension coil spring 101 expands. As a result, the press roller 41 is pressed by the spring force of the extension of the tension coil spring 101.
Is pressed against the outer peripheral surface of the plate cylinder 37 across the printing paper P. Therefore, the pressing force is determined by the spring force.

In adjusting the pressing force, the driving gear 119 is rotated by driving the pressing force adjusting motor 1302.
The rotation of the drive gear 119 is transmitted to the nut member 99, and the rotation of the nut member 99 causes the adjusting screw 93 to move in the axial direction with respect to the first link member 83, so that the adjusting screw 93 moves in the axial direction with respect to the first link member 83. The position changes. As a result, the locking portion between the tension coil spring 101 and the adjusting screw 93 becomes the first link member 8.
3, the axial length of the tension coil spring 101 changes due to the displacement, and the mounting load changes. Due to the change in the mounting load of the tension coil spring 101, the force for pressing the press roller 41 against the outer peripheral surface of the plate cylinder 37 under the above-described action, that is, the pressure contact force changes. It is apparent that other means such as a solenoid, an air cylinder, a hydraulic pressure, and a hydraulic pressure may be used as the means for generating the pressing force.

The plate cylinder 37 used in this embodiment
As described in JP-B-62-28757, an ink bottle containing printing ink, an ink supply pump that sucks out printing ink from the ink bottle and sends it to the ink supply device 39, together with a motor for driving the ink supply pump. The unit is supported on a movable plate cylinder support frame provided so as to be able to be drawn out and moved from the stencil printing apparatus main body, and the entire unit is replaceable with respect to the stencil printing apparatus main body in a drawer type.

FIG. 3 shows a control device for generally controlling the operation of the stencil printing apparatus including the operation control of the pressing force adjusting motor 1302, and relates to the stencil printing apparatus according to the present invention for simplifying the explanation. Only the part is excerpted and shown.

The control device shown in FIG. 3 stores a CPU 1201 composed of a microprocessor or the like, a ROM 1202 storing a program for controlling each mechanism in the device, and the results of operation of the microprocessor and various input information as needed. And a RAM 1203.

The stencil printing apparatus has an operation panel 1100 having ten keys 1101, a print speed setting key 1102, a print density setting key 1103, a print start key 1104, and a display 1105 for setting the number of prints and the like. Number-of-prints setting information set by the numeric keypad 1101, printing speed information set by the printing speed setting key 1102, ie, information on the rotation speed of the plate cylinder, and relative printing density information set by the printing density setting key 1103, ie, √ ( Information about the value of F / f), information for instructing the start of printing set by the print start key 1104, and the like are captured. CPU1
Reference numeral 201 denotes a plate cylinder drive motor 13 via a plate cylinder drive motor drive circuit 1311 in accordance with the acquired printing speed information.
12 and a rotation speed sensor 131 for the plate cylinder.
3 receives feedback of the actual rotation speed information of the plate cylinder.

The CPU 1201 calculates the pressing force for printing based on the set value of √ (F / f) and the rotation speed of the plate cylinder, or obtains it by referring to a table in which the calculation result is stored in advance. Also, an adjusting motor 1302 for obtaining a target pressure contact force.
Is determined and the operation amount signal is output to the motor drive circuit 1301.
Output to Further, when the rotation speed of the plate cylinder is accelerated or decelerated during printing, the already set √ (F /
The pressing force adjusting motor 1302 is controlled so as to increase or decrease the pressing force so as to keep the value of f) constant.

FIGS. 4 and 5 show a control flow of the print density adjusting operation of the stencil printing apparatus according to the present invention. In this control flow, first, either the print mode of the density priority mode or the speed priority mode is selected (step 100).

In the case of the density priority mode, the operation panel 110
From 0, the print density is set using the print density setting key 1103. The print density can be set using the numeric keypad or the like.
A method of directly inputting the value of f) may be used, but in order to allow the user to easily set the value, the value is selected by a key or volume corresponding to several steps of display such as "dark" and "light". Is also good.

As an example of a method of not directly inputting the value of √ (F / f), the value of √ (F / f) is set indirectly by inputting or selecting a number from 1 to 20 using a key or a volume. How to do it. A printing press capable of changing and controlling the pressing force between 10 and 20 kgf and the rotation speed of the plate cylinder between 30 and 120 rpm has a value of Δ (F / f) of 0.289-0.8.
Variable and controllable in 16 ranges. That is, √ (F /
The print density printed under the print condition in which the value of f) is 0.289 is the lightest print density, and the value of √ (F / f) is 0.816.
The print density is variable and controllable within a range where the print density printed under the print condition of is the highest print density.

When a density index n having an arbitrary numerical value from 1 to 20 is defined, the density index n can be converted into a value of √ (F / f) according to Expression 1 for this printing press.

[0053]

(Equation 1)

Note that 1 ≦ n ≦ 20.

According to this method, when indicating the condition for printing lightest, 1 is set as the density index on the operation panel 110.
If it is input from 0, it will be processed and calculated as the value of √ (F / f).
289 is set. If you want to print darkly, you need to enter a larger numerical value. To print the darkest, a numerical value 20 may be input.

In this specific example, the settable print density range is the entire controllable value of √ (F / f). However, only the frequently used portion may be set. Further, the change amount of √ (F / f) between the density indices may be made constant as shown in Expression 1, but it is also possible to partially narrow or widen it.

Also, factors such as the use environment of the printing press such as the environmental temperature, the use situation such as the non-use period, and the type of ink used fluctuate, and the range of the √ (F / f) value frequently used. Is changed, a sensor for sensing the change of the factor is provided, and the form of the function for converting the concentration index into the value of √ (F / f) is changed according to the change, or a coefficient or a constant is added. In addition, the user can easily select the print density.

Print density setting key 1 on operation panel 1100
At 103, a density index is input. The concentration index entered here and n _c (step 110). CPU1201 is converted by referring to the table was the value in the calculation or previously stored calculation results of √ a concentration index n _c (F / f) according to the following equation, it is stored in RAM 1203. The value of √ (F / f) calculated as in Expression 2 is defined as C (step 12).
0).

[0059]

(Equation 2)

[0060] CPU1201 calls the maximum value f _max and the minimum value f _min of the rotational speed of the maximum value F _max and a minimum value F _min and a controllable plate cylinder of a controllable contact pressure printing press from ROM 1202. Next, f _a and f _b are calculated according to Equation 3, or are determined by referring to a table in which the calculation results are stored in advance.

[0061]

(Equation 3)

If f _a ≤f _{min as a} result of the operation, f
_min is set to the minimum value of the plate cylinder rotational speed at which f _a can be set when f _a ≧ f _min . Similarly, if a f _b ≧ f _max to f _max, if a f _b ≦ f _max is the maximum value of the rotational speed of the settable printing drum and f _b. Then, the maximum value and the minimum value are displayed on the operation panel 1100 (step 1).
30).

The user inputs rotation speed information of the plate cylinder from the displayed range of the rotation speed of the plate cylinder by using the printing speed setting key 1102 and stores the information in the RAM 1203. The rotational speed of the plate cylinder set here and f _c (step 140).

In the case of the speed priority mode, first, the operation panel 1
From 100, the rotation speed of the plate cylinder is set by the print speed setting key 1102, and the rotation speed information of the plate cylinder is stored in the RAM 1203. The rotational speed of the plate cylinder set here and f _d (step 300).

[0065] CPU1201 calls the maximum value F _max and a minimum value F _min of the controllable contact pressure printing press from the ROM 1202, also calls the rotational speed f _d of the plate cylinder from the RAM 1203, selectable concentration index according to equation 4 Maximum value n _max
And the minimum value n _min are determined with reference to a calculation or a table in which the calculation result is stored in advance.

[0066]

(Equation 4)

The operation panel 1100 displays n _min as the lightest density index of the selectable print density and n _max as the lightest density index of the selectable print density (step 310).

A density index is selected from the range of the density index displayed on the operation panel 1100 using the print density setting key 1103 and input. The concentration index set here and n _d (step 320).

The CPU 1201 calculates √ (F /
The value of f) is calculated or determined with reference to a table in which the calculation result is stored in advance, and stored in the RAM 1203. The value of √ (F / f) calculated here is set to D (step 33).
0).

[0070]

(Equation 5)

Next, the numeric keypad 110 on the operation panel 1100
1, the number of prints is set, and the print number information is stored in the RAM 120.
3 (step 150).

It is monitored whether the print start key on the operation panel 1100 has been pressed in, that is, whether printing has started (step 160). When printing is started, the plate cylinder starts to be driven.However, even when the stopped plate cylinder is accelerated to the set rotation speed or when the speed is changed during printing, a sharp shift is preferable. It is desired that the gears be shifted slowly. On the other hand, since the print density depends on the rotation speed of the plate cylinder, it is necessary to compensate the print density by a pressing force when performing a shift. In this specific example, as described below with reference to FIG. 5, a method of monitoring the rotational speed of the plate cylinder and subordinately determining a press-contact force to appropriately compensate is adopted. However, a method of compensating for the rotational speed of the plate cylinder while monitoring the pressing force may be used as a compensation method.

As shown in FIG. 5, first, the CPU 1201
Collects rotational speed information of the plate cylinder from a rotational speed sensor such as a rotary encoder attached to the plate cylinder or a motor for driving the plate cylinder (step 170). The rotational speed of the rotational speed f _t1, the set plate cylinder to RAM1203 the observed plate cylinder and f _e. The CPU 1201 compares f _t1 and f _e , and if the difference is 30 rpm or more, outputs a control signal to the plate cylinder drive motor drive circuit to perform acceleration / deceleration of 30 rpm,
If it is less than 30 rpm, a control signal is output to the plate cylinder driving motor drive circuit so that f _t1 and f _e coincide (step 180).

After shifting the gears according to the control signal, the CPU 1201 reads the rotational speed information of the plate cylinder again (step 190). Observed plate cylinder rotation speed is f _t2 , RAM1
The value of the density information √ (F / f) set in 203 is E
In the case of, the CPU 1201 determines an appropriate pressing force by referring to a table in which a calculation or a calculation result is stored in advance according to Equation 6 (Step 200).

[0075]

(Equation 6)

The CPU 1201 outputs an operation amount signal to the pressing force adjusting motor drive circuit 1301 so as to realize the calculated proper pressing force. As a result, the pressing force adjusting motor 1302 is driven, the nut member 99 is rotated so that the pressing force becomes an appropriate value, and the mounting load of the tension coil spring 101 is set to an appropriate value (step 210).

Each time the printing process is executed on one print sheet, 1 is added to the numerical value N of the counter and stored again (step 2).
20). The set number of prints P is compared with the numerical value N of the counter, and if N is greater than or equal to P, printing is terminated (step 230). If N is less than P, it is checked whether the printing speed has been reset during the printing operation (step 240). Assuming that the reset rotation speed of the plate cylinder is f _g , the rotation speed of the plate cylinder stored in the RAM 1203 is rewritten from f _e to f _g (step 250). Further, it is checked whether or not the print density has been reset during the printing operation (step 260). Let the concentration index being reset be n
_h , the value is converted into a corresponding value of √ (F / f) (step 270), and the value of √ (F / f) stored in the RAM 1203 is stored.
The value of f) is rewritten from E to H (step 280). Information on the resetting of the plate cylinder rotation speed and print density is reflected in steps 180 and 200, and the plate cylinder rotation speed or pressing force is adjusted.

[0078]

EXAMPLE In the rotary stencil printing machine shown in FIG. 1 controlled by the above control method, printing was performed under printing conditions showing different values of √ (F / f). Using a gray chart with an image rate of 11%, in which a slight change in print density can be sensed sensitively, as a manuscript, a stencil master (GR76W, manufactured by Riso Kagaku Kogyo Co., Ltd.) under the same conditions is used for plate making and printing. Commercially available stencil printing inks (GR Ink Black, manufactured by Riso Kagaku Corporation) as inks,
Printing was performed using high-quality paper (ideal paper thinner A3 manufactured by Riso Kagaku Kogyo Co., Ltd.) as printing paper.

The rotation speed of the plate cylinder was measured with a rotary encoder in units of rpm. The pressing force of the press roller was measured by a load cell in units of kg · f using a load cell while the pressing roller was performing a pressing operation by a driving device. The density of the printed image was evaluated using a reflection densitometer (RD920, manufactured by Macbeth). The evaluation results are shown in Tables 1 and 2.

[0080]

[Table 1]

[0081]

[Table 2]

From Tables 1 and 2, it was found that √ (F / f) and the print density were in a roughly proportional relationship, and the print density could be freely controlled using the value of √ (F / f). It was also found that even if the rotation speed of the plate cylinder changes, printing density can be stabilized by selecting and pressing the pressing force so that √ (F / f) becomes the same. Further, it was found that if the variation of the value of √ (F / f) was ± 0.05 or less, the difference in the print density could not be visually discriminated.

The data in Tables 1 and 2 were obtained using a 0.31 m long press roller. Further, printing was performed in the same manner as described above, except that press rollers having different lengths were used. Table 3 shows the results.

[0084]

[Table 3]

From Table 3, it was confirmed that the value of √ (F / f) was also effective for controlling the print density of press rollers having different lengths. Also, from Tables 1 to 3, the print density is calculated by the formula D = 0.128 ° regardless of the length of the press roller.
As shown by (F / (fW)) + 0.087,
It was confirmed that the value was proportional to the value of √ (F / (f · W)).

[0086]

According to the present invention, √ (F / f) or √
By controlling the print density using the value of (F / (f · W)) as an index, an experiment on an enormous number of combinations of an enormous number of rotation speeds of the plate cylinder and a pressing force of the printing paper against the plate cylinder is required. Without this, it is possible to determine the rotational speed and the pressing force of the plate cylinder that gives a constant print density. Thus, the print density can be adjusted over a wide range and finely while making the most of the performance of the stencil printing apparatus.

[Brief description of the drawings]

FIG. 1 is a side sectional view schematically showing an internal structure of a specific example of a stencil printing apparatus according to the present invention.

FIG. 2 is a side view showing a driving device of a press roller of the apparatus of FIG.

FIG. 3 is a block diagram showing a specific example of a control device in the stencil printing apparatus of the present invention.

FIG. 4 is a flowchart showing a control operation of the control device of FIG. 3 up to the start of printing.

FIG. 5 is a flowchart showing a control operation of the control device of FIG. 3 during printing.

[Explanation of symbols]

11: original reading section, 13: plate making section, 15: printing section,
37: plate cylinder, 39: ink supply device, 41: press roller, 93: adjusting screw, 99: nut member, 1
01 ... Tension coil spring, 1302 ... Pressing force adjusting motor

Claims (18)

[Claims] 1. A perforated stencil sheet is wound around an outer peripheral surface of a plate cylinder to which ink is supplied on an inner peripheral surface, and the printing drum is pressed against the outer peripheral surface of the stencil while rotating the plate cylinder. Wherein the ink is transferred to the paper through the perforation in a stencil printing density control method, wherein D = √ (F / f) (where F is the pressing force of the paper against the plate cylinder, f Stencil printing density control method, wherein the value of D is selected within a range in which the value of the rotation of the plate cylinder can be taken, thereby controlling the increase or decrease of the amount of ink transferred to the paper. 2. A first step of selecting a value of D from the range of values of D to set a desired print density, and calculating a range of values of f possible with the selected value of D. And a second step of selecting a value of f within the range of the value of f to set a desired printing speed, and calculating a value of F from the selected value of D and the value of f to determine the pressing force. 3. The control method according to claim 1, comprising a third step of setting. 3. The step of calculating and displaying a range of possible values of f for the selected value of D, and the step of calculating the value of f within the displayed range of values of f. 3. The control method according to claim 2, further comprising the step of: selecting a desired print speed by selecting a print speed. 4. A first step of selecting a value of f to set a desired printing speed, calculating a range of possible values of D for the selected value of f, and setting a range of the value of D. A second step of setting a desired print density by selecting a value of D within the range, and a third step of calculating the value of F from the selected value of f and the value of D to set the pressing force. The control method according to claim 1, comprising: 5. The step of calculating and displaying a range of possible values of D for the selected value of f, and the step of calculating the value of D within the displayed range of D values. 5. The control method according to claim 4, further comprising the step of selecting a desired print density by selecting. 6. A perforated stencil sheet is wound around an outer peripheral surface of a plate cylinder to which ink is supplied on an inner peripheral surface, and the plate cylinder is rotated and a printing paper is pressed against the outer peripheral surface of the stencil sheet. Wherein the ink is transferred to the paper through the perforation in a stencil printing density control method, wherein D = √ (F / f) (where F is the pressing force of the paper against the plate cylinder, f Is the rotation speed of the plate cylinder), and the fluctuation of the value of D is ± 0.05.
A stencil printing density control method, characterized in that the printing density is controlled to be constant by controlling the values of F and f so as to keep them at or below (kg · f / rpm). 7. The method according to claim 7, wherein the value of F is monitored and a change in the value of D is ±
7. The stencil printing density control method according to claim 6, wherein the value of f is calculated according to the increase or decrease of the value of F so as to maintain the value at 0.05 (kg · f / rpm) or less, and the rotation speed of the plate cylinder is controlled. 8. Monitoring the value of f and detecting a change in the value of D by ±
7. The pressure contact force is controlled by calculating the value of F according to the increase or decrease of the value of f so as to keep it at 0.05 (kg · f / rpm) or less.
3. A stencil printing density control method according to item 1. 9. A perforated stencil sheet is wound around an outer peripheral surface of a plate cylinder to which ink is supplied to an inner peripheral surface, and the printing drum is pressed against the outer peripheral surface of the stencil while rotating the plate cylinder. A stencil printing density control device for transferring ink to the paper via the perforations, wherein D = √ (F / f) (where F is the pressing force of the paper on the plate cylinder, f Stencil printing density control device, characterized by comprising means for increasing or decreasing the amount of ink transferred to the paper by selecting the value of D within a range in which the value of (rotational speed of the plate cylinder) can be taken. 10. A print density setting means for selecting a value of D from the range of the value of D;
Is calculated, and within the range of f, f
10. The printing speed setting means according to claim 9, further comprising: a printing speed setting means for selecting the value of (f); and a pressing force control means for calculating the value of F from the selected value of D and f value to set the pressing force. Stencil printing density control device. 11. The printing speed setting unit calculates and displays a range of f values possible with the selected D value, and displays the range of f values displayed on the display unit. And f
11. The stencil printing density control device according to claim 10, further comprising speed setting means for setting a desired printing speed by selecting the value of (1). 12. A printing speed setting means for selecting a value of f to set a desired printing speed, calculating a range of possible values of D by the selected value of f, and setting a range of the value of D Print density setting means for setting a desired print density by selecting the value of D within the range, and pressing force control means for controlling the pressing force by calculating the value of F from the selected value of f and the value of D The stencil printing density control device according to claim 9, comprising: 13. The print density setting means calculates and displays a range of possible values of D with the selected value of f, and displays the range of D values displayed on the display means. In D
13. A stencil printing density control device according to claim 12, further comprising a density setting means for setting a desired printing density by selecting the value of (1). 14. A perforated stencil sheet is wound around an outer peripheral surface of a plate cylinder to which ink is supplied to an inner peripheral surface, and the printing drum is pressed against the outer peripheral surface of the stencil paper while rotating the plate cylinder. A recording medium for recording a stencil printing density control program for transferring ink to the paper through the perforations, wherein D = √ (F / f) (where F is the paper with respect to the plate cylinder) The stencil printing density control program is characterized in that the value of F and the value of f are calculated based on the value of D selected in the range where the value of the pressure contact force (f is the rotation speed of the plate cylinder) can be taken. Recording medium. 15. The control program according to claim 1, wherein the selected D
Is calculated, a range of possible values of f is calculated based on the stored value of D, a value of f selected within the range of the value of f is stored, and the selected value of D is stored. The recording medium according to claim 14, wherein the pressing force is set by calculating a value of F from the values of f and f. 16. The control program according to claim 1, wherein the selected D
Is stored, the range of f values possible with the stored D value is calculated and displayed, and the value of f selected within the displayed range of f values is stored. Selected D value and f
The recording medium according to claim 15, wherein the pressing force is set by calculating a value of F from the value of. 17. The control program according to claim 1, wherein the selected f
Is calculated, a range of possible values of D is calculated based on the stored value of f, a value of D selected within the range of the value of D is stored, and the selected value of f is stored. 15. The recording medium according to claim 14, wherein the pressing force is set by calculating the value of F from the values of D and D. 18. The control program according to claim 1, wherein the selected f
Is stored, the range of possible D values is calculated and displayed based on the stored value of f, and the value of D selected within the displayed range of D values is stored. Selected value of f and D
The recording medium according to claim 17, wherein the pressing force is set by calculating a value of F from the value of.