JPH0248110B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an exposure device for a plate-making machine that makes an original plate for offset printing, and is particularly suitable for use when printing multiple sides of the same original on a master paper (original plate). This relates to an exposure device.

[Prior art]

Conventionally, when printing multiple copies of the same original on master paper, the first image is taken by placing black paper 1 on the area where the original will be placed for the second time, as shown in Figure 1a, and exposed; As shown in b, make sure that the latent image 2 formed in the first exposure is not exposed to light.
I try to place black paper 1 on the original part for the first time. In addition, in the figure, 3 is a manuscript table, 4 is a manuscript, 5,
6 is a lens and mirror constituting the optical system, 7 is a master paper, 8 is an exposed area, 9 is an unexposed area,
10 is a latent image formed by the second exposure.

However, in such a light shielding method using black paper, it is necessary to move the original 4 during the first and second imaging, which is a cumbersome task.
It is difficult to achieve positional accuracy, and it takes time to position with high accuracy. Also,
Even if black paper 1 is placed on the document table 3 side to block light, black paper 1
Since it cannot completely absorb light, the potential of the part 9 that is blocked from light during the first imaging and is imaged the second time decreases, and if it takes time to replace the document 4, the potential also decreases due to dark decay. There were drawbacks such as a significant image difference between the first and second imaging.

[Summary of the invention]

The present invention has been made in view of the above-mentioned points, and includes first and second light-shielding curtains wound in the form of a roll, and the first light-shielding curtain is pulled out at the time of the first image capture, and the second light-shielding curtain is removed from the master paper. The extremely simple structure of shielding the exposed area during imaging, and pulling out the second light-shielding curtain during the second imaging to shield the latent image from the first imaging, makes it easy to operate without requiring the document to be moved, and is very expensive. The present invention provides an exposure device for a plate-making machine that can obtain image position accuracy and reduce the image difference between the first and second imaging.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

〔Example〕

FIG. 2 is a partially cutaway perspective view showing an embodiment of the exposure apparatus according to the present invention, and FIG. 2 is a side view showing the schematic structure of the apparatus. In these figures, an exposure apparatus 20 is equipped with a suction box 21 arranged substantially perpendicularly within the projection field of an optical system consisting of a lens 5 and a mirror 6. As shown in FIG. suction box 21
, a suction plate 21A in which a large number of small holes 22 are formed, and a pair of side plates 21B, 21.
C. One side plate 21 is formed into a vertically long thin box shape by a back plate (not shown), an upper plate, a lower plate, etc.
A blower 23 is disposed at B, and a total of four rollers A to D are disposed in pairs on the upper and lower surfaces of the box 21, and each of these rollers A to D has a large number of small holes 25. A plurality of endless conveyor belts 24 are stretched to form a suction box 2.
It surrounds the outer circumference of 1. The conveyor belt 24 is rotated from top to bottom in the exposure process of the suction box 21 by transmitting the rotation of the driving pulse motor 26 disposed at the lower part of the side plate 21B through the drive chain 27 and the like. The paper feed unit 28 feeds the charging unit 2.
It is configured to hold the master paper 7 sent through 9, and to transport it to a predetermined exposure position and stop it there. At this time, master paper 7
The blower 23 passes through the small hole 25 of the conveyor belt 24 and the small hole 22 of the suction plate 21A.
By being absorbed by, it is held in close contact with the conveyor belt 24. Further, a stop sensor 30 for detecting the leading edge of the master paper 7 is disposed at the center of the suction plate 21A.

Above and below the exposure surface of the suction box 21, first and second light shielding curtains 40 and 60, which characterize the present invention, are wound into a roll. As shown in FIG. 4, the first light-shielding curtain 40 is rotatably disposed on the outer periphery of the drum shaft 41 via a bush 42 and a boss 43, and has a rotational behavior in the unwinding direction by a winding spring 44. One end is fixed to the outer periphery of the provided light-shielding curtain drum 45, and the other end is fixed to the bar 46. Usually, it is wound around the outer periphery of the drum 45 by the force of the winding spring 44. It is configured to be pulled out downward when taking an image. The drum shaft 41 is supported between the upper ends of the side plates 21B and 21C so as to be prevented from rotating. The winding spring 44 is housed in the light-shielding drum 45, and in a twisted state, both ends are fixed to a pair of left and right bosses 43 (however, one boss is fixed to the drum shaft 41). Therefore, when the light-shielding curtain 40 is pulled out in the direction of the arrow in FIG. 4 from this set state, the light-shielding curtain drum 45 is rotated clockwise, so that the wound spring 44 is further twisted and stores energy. Guide rollers 47 are rotatably disposed at both ends of the bar 46, and wires 49 and 50 are fixed thereto. The guide roller 47 is connected to each side plate 21B,
It is configured to roll along a longitudinally long rail 48 formed by bending the edge on the exposure surface side of 21C. Of the wires 49, 50, the wire 49 on the right side is connected to a first light-shielding curtain drive motor 55, which is comprised of pulleys 51, 52, 53 and a pulse motor, which are respectively disposed on the side plate 21C.
The drive pulley 54 is directly connected to the drive pulley 54. Similarly, the wire 50 on the left side is stretched around three pulleys disposed on the side plate 21B and another drive pulley (none of which is shown) that is directly connected to the drive motor 55.
In this case, the drive shaft 56 of the drive motor 55 is pivotally supported by the left and right side plates 21B and 21C, and its tip protrudes outside the side plate 21B, and the other drive pulley described above is attached to the protruding end. It is assumed that Therefore, when the first light shielding curtain driving motor 55 is driven to move the wires 49 and 50 in the direction of arrow 58 in FIG.
is pulled out against the winding spring 44 and stopped at that position when the motor 55 is braked by DC application, and is wound back by the force of the winding spring 44 when the brake is released.

The second light-shielding curtain 60 is configured exactly the same as the first light-shielding curtain 40 described above, so the explanation thereof will be omitted, but since it is arranged upside down from the first light-shielding curtain 40, The wires 62 and 63 are driven by a second light shielding curtain drive motor 61 consisting of a pulse motor.
It is constructed so that it can be pulled upward when it is moved in the direction of arrow 64 in FIG. In addition, 65,
66 and 67 are pulleys to which the wire 62 is stretched;
68 is a drive pulley directly connected to the second light shielding curtain drive motor 61, and 69 and 70 are pulleys for the wire 63.

Next, a two-time exposure operation in the exposure apparatus having such a configuration will be explained.

Set the master paper 7 in the paper feed section 28,
When the print button on the operation panel is operated, the master paper 7 is sucked and held by the vacuum suction device 80, charged by the charging section 29, and then sent to the exposure device 20. And master paper 7
is closely fixed to the conveyor belt 24, and after passing through a stop sensor 30 (see FIG. 3), it is sent by the amount of pulses based on the input data and stopped at the first imaging position. Further, the first light-shielding curtain 40 is pulled out downward as the first light-shielding curtain driving motor 55 is driven based on the input data, and by braking the motor 55, the first light-shielding curtain 40 is pulled out downwardly.
It is set at a position that covers the area to be imaged for the second time. FIGS. 2 and 3 show this state, and by operating the exposure button, an image of the original 4 on the original platen 3 is captured on the master paper 7.

When the first image capturing is completed, the brake of the first light-shielding curtain drive motor 55 is released, so that the first light-shielding curtain 40 is rolled up to its original state by the force of the winding spring 44. At the same time, the drive motor 26 drives the conveyor belt 24 by a pulse amount based on the input data, so that the master paper 7 is transported downward by a predetermined amount and stopped at the second imaging position. Further, the second light-shielding curtain 60
As shown in the figure, the second light-shielding curtain drive motor 61 is driven based on input data, and the curtain is set at a position covering the latent image portion 2 formed by the first imaging.
When the second image capturing is completed, the brake of the second light-shielding curtain drive motor 61 is released, so the second light-shielding curtain 60 is lowered and wound up by the force of the winding spring, and the master paper 7 is transferred to the conveyor belt 24. is sent to the developing section.

〔Effect of the invention〕

As described above, the exposure device of the plate-making machine according to the present invention is provided with the first and second light-shielding curtains, and the first light-shielding curtain is pulled out during the first imaging to expose the exposed portion of the master paper during the second imaging. Since the second light-shielding curtain is pulled out during the second image capture to cover the latent image area from the first image capture, there is no need to move the document on the document table, and multiple exposures can be performed with a single document set. It is simple, easy and can be done in a short time. Also, since the original is not moved,
The plate-making work is efficient, the plate-making speed is fast, the image position accuracy is good, and the image difference between the first and second images is small, and a high-quality original plate can be manufactured. Furthermore, unlike the method of placing black paper on the original surface, the exposed surface of the master paper is directly shielded from light with a light-shielding curtain, so the second exposure is not affected by the first exposure. The effect is very large.

[Brief explanation of drawings]

Figures 1a and b are diagrams showing a conventional light shielding method using black paper, Figure 2 is a partially cutaway perspective view showing an embodiment of the exposure apparatus according to the present invention, and Figure 3 is the first photograph of the same apparatus. FIG. 4 is a partially cutaway perspective view showing the structure of a light-shielding curtain, and FIG. 5 is a side view showing the general structure at the time of second photographing. 3...Original table, 4...Original, 5...Lens, 6
...Mirror, 7...Master paper, 20...
Exposure device, 21... Suction box, 22...
...Small hole, 24...Transport belt, 25...Small hole, 2
6...Motor, 40...First light-shielding curtain, 44...
Winding spring, 45...Shading curtain drum, 55...
...First light-shielding curtain drive motor, 60... Second light-shielding curtain, 61... Second light-shielding curtain drive motor.

Claims (1)

[Claims] 1. A suction box having a large number of small holes on its surface and disposed within the projection field of the optical system, the inside of which is evacuated; and a master paper having a large number of small holes and arranged so as to surround the suction box. a conveyor belt that moves and stops the conveyor belt at a predetermined exposure position, a motor that drives the conveyor belt, and first and second light-shielding curtains that are wound in rolls and disposed at both ends of the suction box, respectively. , said first
and first and second light-shielding curtain drive motors that selectively pull out the second light-shielding curtain, and the first light-shielding curtain drive motor is driven to pull out the first light-shielding curtain at the time of first imaging. paper 2
The exposure area during the second image capturing is shielded from light, and during the second image capturing, the master paper is moved and stopped at the second image capturing position by driving the motor, and the second light shielding curtain drive motor is driven to remove the second light shielding curtain. An exposure device for a plate-making machine, characterized in that a latent image formed in the first imaging of a master paper is shielded from light by drawing out the latent image.