JPH05286221A - Stencil printer - Google Patents

Abstract

PURPOSE:To provide a stencil printer which can obtain a large number of sheets of favorable images. CONSTITUTION:The title printer is provided with a printing drum 1 wherein at least a part of a circumferential side where it is necessary from a view point of formation of an image is perforated, an ink roller whose axis of rotation is parallel with that of the printing drum 1 on the inside of the printing drum 1 and press rollers 2, 3 which press on the rear of printing paper at the time of only printing and has the axis of rotation which is parallel with that of the printing drum 1 on the outside of the printing drum. The press rollers 2, 3 are comprised of at least two rollers whose hardness and/or diameters are different with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stencil printing machine, and more particularly to a single-cylinder type stencil printing machine which can obtain a high quality image by supplying an appropriate amount of ink.

[0002]

2. Description of the Related Art Conventional stencil printing machines have the drawback that the image density of printed matter changes when the printing speed changes. In addition, there is also a drawback in that, at a low speed, the amount of ink deposited increases and set-off occurs. In order to solve this problem, a method has been proposed in which the force (pressing pressure) for pressing the press roller against the plate cylinder is changed according to the printing speed to control the amount of ink ejected (JP-A-2-245371). JP-A-2-151473 and the like).

By the way, generally, the ink adhesion amount is given by the following equation. p; printing pressure t; pressurization time A; constant Therefore, when the printing pressure is constant, when the printing speed doubles, the pressurization time becomes 0.5 times, and the ink adhesion amount becomes approximately 0.7 times. turn into. That is, in the device that attempts to control the ink ejection amount by changing the proposed printing pressure, the printing pressure must be doubled in order to make the ink adhesion amount the same. There is an inconvenience that the applied force becomes large and the printing durability is impaired. In addition, there is a concern that noise generated by increasing the printing pressure also increases. In addition to this, the structure of the stencil printing machine adopting the method of controlling the ink extrusion amount is extremely complicated, and the printed matter is inevitably expensive.

[0004]

The inventors of the present invention have solved the above-mentioned inconveniences and drawbacks, performed desired printing, and obtained a large number of high-quality printed matter (especially, "single-body type stencil printing apparatus". It is advantageous to a "printing device").

[0005]

SUMMARY OF THE INVENTION According to the present invention, a printing drum is provided with a hole in at least a portion necessary for image formation on a peripheral side surface, and a rotation shaft is provided inside the printing drum and a rotation shaft of the printing drum. A stencil printing machine comprising: parallel ink rollers; and a press roller that presses the outside of the printing drum from the back surface of the printing paper only when printing and the rotation axis is parallel to the rotation axis of the printing drum. The roller is composed of two or more rollers having different hardness, and the press roller is selected according to the printing speed. When the press roller is in the print standby state, the outer circumference of the printing drum and the outer circumference of the selected press roller are Is characterized in that the intervals of are equal and constant no matter which press roller is selected,
(2) The press roller is composed of two or more press rollers having different diameters, an appropriate press roller is selected according to the printing speed, and when the press roller is in a print standby state, the press roller and the outer circumference of the print drum are Is it characterized in that the distance from the outer circumference of the selected press roller is equal and constant no matter which press roller is selected, (3) the press roller has both the above (1) and (2). (4) The press roller is composed of two or more rollers having different hardnesses, an appropriate press roller is selected according to the printing speed, and the press roller is in a print standby state, Whether the distance between the outer circumference of the printing drum and the outer circumference of the selected press roller is different regardless of which press roller is selected, and the state is maintained, (5) The less roller is composed of two or more press rollers having different diameters, and an appropriate press roller is selected according to the printing speed. When the press roller is in a print standby state, the outer circumference of the print drum and the selected press roller are selected. Is different from the distance between the outer circumferences of the press rollers regardless of which press roller is selected, or (6) the press roller has the characteristics of both (4) and (5). It is something that

The present inventors have studied stencil printing methods and devices from various angles in order to solve the disadvantages and defects of the prior art. As a result, the stencil printing devices are equipped with press rollers having different hardness and / or diameter. It was confirmed that the above-mentioned problems can be achieved by mounting two or more and using them according to the printing speed. That is, when the printing speed is slow, a press roller having a low hardness or a press roller having a small diameter is used, and when the printing speed is fast, a press roller having a high hardness or a press roller having a large diameter is used. Further, a press roller having a combination of hardness and diameter can be used. The present invention has been made based on these findings.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIGS. 1A and 1B show the positional relationship between the printing drum 1 and the press rollers 2 and 3. As mentioned above, the number of press rollers is not limited to two as shown in the drawing, and may be three or more.

Now, according to information from an operation unit (not shown), the press roller rotation drive unit 5 rotates the press roller rotation support unit 4 to select the press roller 2 according to the information.
Fix it. When printing is started, the press roller pressing support portion 6 is released by a cam (not shown) and is pressed against the printing drum 1 by a pressing spring (not shown). Further, the set position of the press roller 1 or 2 may be the same or different depending on the mounting position of the press roller rotation support center 7.

Although the press rollers 1 or 2 according to the present invention are drawn to have different diameters in the drawings, they may have different diameters and may have the same hardness or different hardness, or may have the same diameter. It doesn't matter if the hardness is different. The hardness and the diameter of two or more press rollers are not unconditionally determined, but may be appropriately determined according to the purpose.

When the apparatus of the present invention is actually operated, the press roller contacting the back surface of the printing paper is changed depending on the difference in printing speed.

[0011]

EXAMPLES Next, examples and comparative examples will be shown.

Example 1 A press roller having an outer diameter of 30 mm and a hardness of 35 and a press roller having the same outer diameter and a hardness of 15 were used, and the printing speed was 90 cpm.
In the following, the Ricoh stencil printing machine was remodeled so that the latter press roller was set at a predetermined position and the former press roller was set at the same position at 90 cpm or more.

Example 2 A press roller having a hardness of 25 and an outer diameter of 25 mm and a press roller having an outer diameter of 35 mm and a printing speed of 90 mm were used.
If it is less than cpm, the former press roller is set to a predetermined position, and if it is more than 90 cpm, the latter press roller has the same distance as the former press roller and the plate cylinder (actually a stencil printing plate). The stencil printer manufactured by Ricoh was modified after being set.

Example 3 A press roller having an outer diameter of 25 mm and a hardness of 15 and an outer diameter of 35
with a press roller having a hardness of 35 mm and a printing speed of 90
At less than cpm, the former press roller was set at a predetermined position, and at greater than 90 cpm, the latter press roller was set to be the same as the distance between the latter press roller and the plate cylinder made by Ricoh.

Example 4 A press roller having an outer diameter of 30 mm and a hardness of 35 and a press roller having the same outer diameter and a hardness of 15 were used, and the printing speed was 90 cpm.
In the following, the latter press roller is set in a predetermined position, and in the case of 90 cpm or more, the former press roller is set at a position apart from the distance between the latter press roller and the plate cylinder to modify the Ricoh stencil printing machine. .

Example 5 A press roller having a hardness of 25 and an outer diameter of 25 mm and a press roller having the same hardness and an outer diameter of 35 mm were used, and a printing speed of 90
If it is less than cpm, the former press roller is set at a predetermined position, and if it is more than 90 cpm, the latter press roller is set at a position farther than the distance between the former press roller and the plate cylinder. did.

Example 6 A press roller having an outer diameter of 25 mm and a hardness of 15 and an outer diameter of 35
with a press roller having a hardness of 35 mm and a printing speed of 90
At less than cpm, the former press roller was set at a predetermined position, and at greater than 90 cpm, the latter press roller was set at a position separated from the distance between the latter press roller and the plate cylinder to remodel the stencil printer manufactured by Ricoh.

Comparative Example 1 A press roller having an outer diameter of 30 mm and a hardness of 30 was used in a stencil printer Preport VT-3300 manufactured by Ricoh Company.

Comparative Example 2 Ricoh stencil printer Preport VT-3300 had an outer diameter of 3
Printing was performed by using a press roller having a hardness of 30 at 0 mm and changing the printing pressure in proportion to the speed based on the third speed of Comparative Example 1.

Under the conditions of these Examples 1 to 6 and Comparative Examples 1 and 2, printing was carried out in an environment of 24 ° C. and 65 RH, and images were evaluated. The results are summarized in Table 1.

[0021]

[Table 1]

[0022]

By using the stencil printing machine of the present invention, it is possible to obtain a stable printed matter with little change in image density even when the printing speed is changed, and with little set-off even at a low speed.

[Brief description of drawings]

FIG. 1 (a) is a front view for explaining the outline of the device of the present invention, and FIG. 1 (b) is a side view thereof.

[Explanation of symbols]

 1 Printing Drum 2 Press Roller 1 3 Press Roller 2 4 Press Roller Rotation Support Section 5 Press Roller Rotation Drive Section 6 Press Roller Press Support Section 7 Press Roller Rotation Support Section Center

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Hiroshi Tateishi 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72) Naoto Shimoda 1-3-3 Nakamagome, Ota-ku, Tokyo Shares Company Ricoh

Claims (6)

[Claims] 1. A printing drum having a hole formed in at least a portion necessary for image formation on a peripheral side surface, an ink roller having a rotation axis parallel to the rotation axis of the printing drum inside the printing drum, and the printing. In a stencil printing machine provided with a press roller which is pressed from the back surface of the printing paper only on the outside of the drum during printing and has a rotation axis parallel to the rotation axis of the printing drum, the press roller is composed of two or more rollers having different hardness. Then, an appropriate press roller is selected according to the printing speed, and when the press roller is in a print standby state, which press roller is selected as the distance between the outer circumference of the printing drum and the outer circumference of the selected press roller. A stencil printing machine characterized in that it is equally constant even in some cases. 2. A printing drum having a hole formed in at least a portion necessary for image formation on the peripheral side surface, an ink roller having a rotation axis parallel to the rotation axis of the printing drum inside the printing drum, and the printing. In a stencil printing machine equipped with a press roller which is pressed from the back surface of the printing paper only on the outside of the drum during printing and has a rotation axis parallel to the rotation axis of the printing drum, the press rollers are two or more press rollers having different diameters. Consists of
When an appropriate press roller is selected according to the printing speed, and the press roller is in a print standby state, which press roller is selected when the distance between the outer circumference of the printing drum and the outer circumference of the selected press roller is selected. A stencil printing machine characterized in that it is equally constant even if it exists. 3. The stencil printing machine according to claim 1, wherein the press roller comprises two or more rollers having different hardness and diameter. 4. A printing drum having a hole formed in at least a portion necessary for image formation on the peripheral side surface, an ink roller having a rotation axis parallel to the rotation axis of the printing drum inside the printing drum, and the printing. In a stencil printing machine equipped with a press roller that pressurizes from the back surface of the printing paper only on the outside of the drum when printing and has a rotation axis parallel to the rotation axis of the printing drum, the press rollers are two or more press rollers having different hardnesses. The appropriate press roller is selected according to the printing speed.
When the press roller is in a print standby state, the distance between the outer periphery of the printing drum and the outer periphery of the selected press roller is different regardless of which press roller is selected, and the state is maintained. Stencil printer. 5. A printing drum having a hole formed in at least a portion necessary for image formation on the peripheral side surface, an ink roller having a rotation axis parallel to the rotation axis of the printing drum inside the printing drum, and the printing. In a stencil printing machine equipped with a press roller which is pressed from the back surface of the printing paper only on the outside of the drum during printing and has a rotation axis parallel to the rotation axis of the printing drum, the press rollers are two or more press rollers having different diameters. Consists of
An appropriate press roller is selected according to the printing speed, and when the press roller is in a print standby state, whichever press roller is selected as the distance between the outer circumference of the printing drum and the outer circumference of the selected press roller. Differently, the stencil printing machine is characterized in that the state is maintained. 6. The stencil printing machine according to claim 4, wherein the press roller comprises two or more press rollers having different hardness and diameter.