JPH0471827B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic engraving machine that creates an original plate (offset master) for offset printing.
Alternatively, the present invention relates to a roll feeding device that is improved so as to prevent the occurrence of image unevenness due to missing white spots, thereby not affecting the finish of printing.

[Prior art]

Electrophotographic engraving machines create offset masters by electrophotography, and because they are easy to handle, they have become quite popular in the printing industry. The printing plate used for this offset master (hereinafter referred to as photosensitive paper) has a backing layer, a subbing layer, and a photoconductive layer layered one after another on a support. can be imparted with photosensitivity. In a conventional electrophotographic engraving machine, a roll of photosensitive paper is used, and a pair of nip rollers pulls out the photosensitive paper, transfers it to a conveyance means, and conveys it to an exposure position. A cutter is arranged between this nip roller and the conveyance means,
It is activated to cut the photosensitive sheet when it is pulled out by a predetermined length. When this photosensitive sheet is sent to an exposure position, it passes through a charger and is imparted with photosensitivity. The photosensitive sheet set at the exposure position is exposed to light from the original, and as a result of this exposure, charge escapes from the portions hit by the light, so that a latent image due to static electricity is recorded on the photosensitive sheet. The photosensitive sheet on which the latent image has been recorded is sent by a conveying means to a developing/fixing processing section, where it is subjected to developing/fixing processing. Toner does not adhere to exposed areas that are exposed to light, and toner adheres to unexposed areas that are not exposed to light, thereby forming an image. The photosensitive sheet on which this image is recorded is treated with an etcher to make the areas to which toner does not adhere hydrophilic, and the areas to which toner adheres to become lipophilic, thereby forming an offset master. This offset master is wrapped around the drum of a printing press, coated with oil-based ink, and used for printing.

The nip roller is designed to stop after the cutter is activated, so the leading edge of the photosensitive paper remains at the cutter position until the next plate-making starts.
The photosensitive paper was then strongly bitten by the Nitz roller. If left in this state, the nip pressure will be concentrated on the area held by the nip rollers, resulting in insufficient desensitization during etching, and this area will appear as black streaks after printing. This may cause print smudges. It has been found that this printing stain is more likely to occur the longer the exposure time and the greater the nip pressure. Also,
In some cases, there may be a difference in the amount of charge between the part nipped by the nip roller and the part that is not nipped, and this may appear as white spots in the print, causing "image unevenness". There is. It is known that the higher the humidity, the more likely this white spot is to occur.

Conventionally, as a countermeasure against printing smudges or uneven images, conventional methods have been to separate a pair of nip rollers or pull out the photosensitive paper from between the nip rollers, but these methods are cumbersome, and the photosensitive paper cannot be pulled out from between the nip rollers. When resetting the photosensitive paper, the leading edge of the photosensitive paper tends to be misaligned, which causes a problem in that the length of the photosensitive sheet obtained by cutting with a cutter varies.

[Problem that the invention seeks to solve]

SUMMARY OF THE INVENTION An object of the present invention is to provide a roll feeding device for an electrophotographic engraving machine that prevents print smudges and image unevenness caused by the nip roller and does not affect the print finish. be.

[Means for solving problems]

In order to achieve the above object, the present invention provides a nip roller reversing means to cut an electrophotographic printing plate in a roll form into sheets of a predetermined length with a cutter disposed between the nip roller and the conveying means. After that, the nip roller is reversed to return the tip of the printing plate, which is in the form of a roll and is stopped at the cutter position, toward the nip roller.

By returning the printing plate to a position where it does not come off the nip roller, printing stains and image unevenness that occur when the printing plate is nipped with the nip roller for a long time can be reduced compared to when the printing plate is not returned. Occurs near the edge of In an offset printing machine, the printing drum is equipped with a metal fitting that presses the edge of the offset master, so by shifting the position of printing stains and uneven images to the edge of the offset master, it can be placed inside the presser metal fitting. can. In this way, no ink will be deposited on these areas, so there will be no problems with the print finish.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

〔Example〕

In FIG. 1 showing a camera-type electrophotographic engraving machine, a mirror 3 is arranged above a stage 2 on which a document 1 is placed, and an illumination arm with a rod-shaped light source 4 attached to both sides of the mirror 3. 5 is placed. The reflected light from the original 1 illuminated by the light source 4 is reflected obliquely backward by the mirror 3, passes through the photographing lens 6, reaches the exposure position, and forms an image of the original 1 on the photosensitive sheet set at this exposure position. Form an image.
Note that a lens shutter is attached to the photographing lens 6 as is well known.

The mirror 3 and photographing lens 6 are held by a mirror holder 8 and a lens holder 9, respectively. These mirror holder 8 and lens holder 9 are fitted into a guide rod 11 arranged parallel to the optical axis 10 of the photographic lens 6, and move along this guide rod 11 during magnification conversion. In order to move the mirror holder 8, a feed screw shaft 12 that fits into a part of the mirror holder 8 is arranged, and when this feed screw shaft 12 is rotated by a stepping motor 13, the rotation direction The mirror holder 8 moves forward or backward. Similarly, a feed screw shaft 14 that fits into a part of the lens holder 9 is provided, and when the stepping motor 15 rotates, the lens holder 9 moves back and forth. Since the image point distance is uniquely determined by specifying the magnification based on the lens formula and the magnification formula, the stepping motor 15 is rotated to position the photographing lens 6 so that this image point distance is achieved. At the same time, since the object point distance is determined as a function of the image point distance, the stepping motor 13 is driven so as to obtain this distance.

A bellows 18 is attached to the lens holder 9 and the plate 17 so that only the photographing light that has passed through the photographic lens 6 passes through the opening 17a of the light shielding plate 17.
are connected. Note that numerals 20 to 25 are bearings.

A photosensitive paper 30 used as an electrophotographic printing plate is wound around a core 29 in the form of a roll, and is pulled out by normal rotation of a pair of nip rollers 31 and 32 and sent toward a cutting position. At this cutting position, a well-known cutter consisting of a rotary movable blade 33 and a fixed blade 34 is arranged, and the photosensitive paper 30 is fed by a predetermined length determined according to the size of the drum of the printing machine. The photosensitive paper 30 is activated to cut the photosensitive paper 30 into a photosensitive sheet 30a. After passing through the cutting position, the photosensitive paper 30 is transferred to a pair of transport rollers 35, 3.
6 and transported toward the charger 37. In front of this charger 37, a reflective first sensor 38 consisting of a light emitting part and a light receiving part is arranged.
The passage of the leading edge of the photosensitive paper 30 is detected. The photosensitive paper 30, which has been charged and made photosensitive by the charger 37, reaches a suction belt 39 in which a large number of suction holes are formed, is attracted and held by the suction belt 39, and is conveyed to an exposure position. A plurality of suction belts 39 are arranged in parallel and are hung on rollers 41 and 42 attached to a suction box 40, respectively, and a punch board 43 is arranged between them to maintain the flatness of the suction belts 39. There is. The suction box 40 is connected to a suction blower 4 via a hose 44.
5.

A toothed pulley 47 is attached coaxially with the roller 42, and a toothed belt 50 is hung between it and a toothed pulley 49 attached to the output shaft of a stepping motor 48. Also, roller 4
1. Toothed pulleys 51 to 53 are attached coaxially with the nip roller 31 and the conveyance roller 35, and a toothed belt 54 is hung around these pulleys. In addition, the Nitsu roller 31 and the toothed pulley 52
An electromagnetic clutch is disposed between the two and stops the rotation of the nipper rollers 31 and 32 when the cutter is in operation.

After the photosensitive sheet 30a is exposed at the exposure position, the suction belt 39 rotates in the normal direction and the photosensitive sheet 30a is sent toward the development processing section 57. When the photosensitive sheet 30a is fed out, the second sensor 55 using a reflective photo sensor detects the rear end of the photosensitive sheet 30a. When the second sensor 55 detects the rear end of the photosensitive sheet 30a, the stepping motor 48 reverses, rotates the nip rollers 31 and 32, and moves the leading edge of the photosensitive paper 30 from the cutting position to a position close to the nip rollers 31 and 32. return.

The exposed photosensitive sheet 30a that has entered the development processing section 57 via the guide 56 is subjected to development processing here. The development processing section 57 includes a pair of development inlet rollers 58 and 59, an upper electrode plate 60 and a lower electrode plate 61 arranged opposite to each other, and a developer supply nozzle 62.
, a pair of squeeze rollers 63 and 64, and a developer tank 65.

The developed photosensitive sheet 30a is sent to a fixing processing section 68, where heat fixing is performed. This fixing processing section 68 includes a pair of fixing entrance rollers 69,
70, a pair of fixing exit rollers 71 and 72, a guide plate 73 disposed between these, a heater 74 disposed above the guide plate 73, and a reflecting plate 75. The processed photosensitive sheet 7 is delivered to a receiving table 76. The various rollers provided in the development processing section 57 and the fixing processing section 68 are connected to a motor (not shown) and rotate after the photosensitive sheet 30a is exposed. Fixing exit rollers 71, 72
It is designed to stop when a sensor detects that the image has passed through, or when the time required for development and fixing processing has elapsed.

FIG. 2 shows a stepping motor control device. The keyboard 80 has a start key 8
0a, a function key 80b for specifying work contents such as magnification conversion, and a numeric keypad 80c for specifying image magnification values, etc. By pressing each key, specified information can be sent to the sequence controller 81. can. This sequence controller 81 controls the operations of the motor control section 82, counter 83, driver 84, etc. according to a preprogrammed procedure. Note that the portion surrounded by a dotted line is the CPU 85.

The motor control section 82 is for controlling the rotation direction and rotation amount of the stepping motor 48, and sends a signal specifying the rotation direction to the driver 86, and also controls the operation of the drive pulse generation section 87. Generate a number of drive pulses according to the amount of rotation. This driver 86 controls the rotation of the stepping motor 48 by inputting a rotation direction signal and a drive pulse.

The counter 83 is reset when the first sensor 38 detects the leading edge of the photosensitive paper 30, counts the number of drive pulses sent to the driver 86, and detects the position of the leading edge of the photosensitive paper 30 from the count. The sequence controller 81 operates the cutter by taking in the contents of the counter 83, and also determines the timing for disengaging the electromagnetic clutch 88 via the driver 84 to stop the nip rollers 31 and 32, and for controlling the timing of the stepping motor 48. Stop the rotation and remove the photosensitive sheet 3.
The timing for positioning 0a at the exposure position is determined.

Further, the counter 83 is connected to the second sensor 55.
It is also reset when the rear end of the exposed photosensitive sheet 30a is detected, and the driving pulses are counted while the stepping motor 48 is rotating in reverse, and the return position of the leading end of the photosensitive paper 30 is detected. The sequence controller 81 reads the contents of the counter 83 while the stepping motor 48 is rotating in reverse, and stops the stepping motor 48 when it detects that the photosensitive paper 30 has been returned to a predetermined position. The larger the amount of return of the photosensitive paper 30 is, the more desirable it is because the position where printing stains and image unevenness occur can be shifted. However, if the amount of return is too large, the tip of the photosensitive paper 30 will be
1 and 32, so that the leading edge of the photosensitive paper 30 must be pulled out to a predetermined position before being held by the nip rollers 31 and 32 for the next plate making. Therefore, it is necessary to set the amount of return of the photosensitive paper 30 to be smaller than the distance between the cutter and the nip roller 31, taking into consideration the pressing distance by the presser fitting of the offset printing machine.

Next, the operation of the above embodiment will be explained with reference to the timing chart of FIG. First, the user operates the function key 80b and numeric keypad 80c to specify the image magnification. When this image magnification is specified, the stepping motors 13 and 15 rotate,
The mirror 3 and photographic lens 6 are moved to a predetermined image magnification position. After setting the original 1 on the stage 2, if the start key 80a is turned on, the sequence controller 81 brings the electromagnetic clutch 88 into the connected state. Then, after the time T required for the electromagnetic clutch 88 to become completely connected has elapsed, the sequence controller 81 sends a rotation command to the motor control section 82.

Upon receiving the rotation command, the motor control section 82 sends a rotation direction signal to the driver 86 and operates the drive pulse generation section 87 . The drive pulse generator 87 generates drive pulses and sends them to the driver 86 to rotate the stepping motor 48 in the normal direction. When the stepping motor 48 rotates normally, the suction belt 39 connected to the stepping motor 48 via the toothed belt 50 rotates in the direction of the arrow. The normal rotation of the suction belt 39 is transmitted to the nip roller 31 and the conveyance roller 35 via the toothed belt 54, and these are rotated in the normal direction.

When the nip roller 31 rotates normally, it nips the photosensitive paper 30 between it and another nip roller 32 and feeds it toward the transport rollers 35 and 36. The photosensitive paper 30 held by the transport rollers 35 and 36 passes through a first sensor 38 and a charger 37, and then reaches a suction belt 39. When the first sensor 37 detects the leading edge of the photosensitive paper 30, the counter 83 is reset.
It counts as 3. Further, the charger 37 is
The photosensitive paper 30 passing through this is charged to impart photosensitivity to it.

When the sequence controller 81 detects from the contents of the counter 83 that the photosensitive paper 30 has passed the cutting position by a predetermined length, it operates a cutter to cut the photosensitive paper 30 into photosensitive sheets 30a. At the same time, since the electromagnetic clutch 88 is disengaged, the nip rollers 31, 32
stops. The separated photosensitive sheet 30a is
It is sucked and held by the suction belt 39 and sent toward the exposure position. Note that suction force is applied to this suction belt 39 by a suction blower 45 that operates simultaneously with the normal rotation of the stepping motor 48. When it is detected from the contents of the counter 83 that the photosensitive sheet 30a is set at the exposure position, the forward rotation of the stepping motor 48 is stopped.

The sequence controller 81 stops the stepping motor 48, turns on the light source 4, and immediately thereafter operates the shutter to form an image of the original 1 on the photosensitive sheet 30a. After this exposure, the stepping motor 48 rotates normally again to convey the exposed photosensitive sheet 30a toward the development processing section 57. The leading end of the photosensitive sheet 30a enters the developing processing section 57 via the guide 56, and is caught by the developing entrance rollers 58 and 59.

The leading end of the photosensitive sheet 30a is in the development processing section 57.
After entering the photosensitive sheet 30a, the rear end of the photosensitive sheet 30a
When detected by the sensor 55, the sequence controller 81 stops the suction blower 45 and the stepping motor 48, and also resets the counter 83. At the same time, the sequence controller 81 reconnects the electromagnetic clutch 88 and then reverses the stepping motor 48. When this stepping motor 48 reverses,
Since the nip rollers 31 and 32 rotate in reverse, the leading edge of the photosensitive paper 30 moves from the cutting position to the nip rollers 31 and 3.
Returned to 2. The amount of return of the photosensitive paper 30 is detected from the contents of the counter 83, and when the photosensitive paper 30 has returned by a predetermined amount, the stepping motor 48 stops rotating in reverse, and at the same time, the electromagnetic clutch 88 is disengaged. Ru.

The exposed photosensitive sheet 30a sent to the development processing section 57 is developed there. In this development processing section 57, a developer discharged from a developer supply nozzle 62 is applied while an electric field is applied between the upper and lower electrode plates 60, 61. The developed photosensitive sheet 30a is sent to the fixing processing section 68,
Here, it is heated by a heater 74 to perform thermal fixing.
Finally, it is discharged onto a receiving tray 76. In the heat-fixed photosensitive sheet 30a, no toner is attached to the exposed portions, and toner is attached to the unexposed portions.

FIG. 4 shows a comparison of the positions where printing stains occur between the present invention and the conventional example. Nitsu Prora 3
If the photosensitive paper 30 is nipped in steps 1 and 32 and left for a long time, black streaks P will occur, which will cause print stains. (A) shows the printing stains that occur when the present invention is implemented, and (B) shows the printing stains that occur when the photosensitive paper is nipped as it is without returning it from the cutting position. In the present invention, since the photosensitive paper is returned, printing stains P occur at a position that is closer to the edge by a distance L corresponding to the amount of return. In an offset printing press, when an offset master is wound around a printing drum, its ends are held down with a presser metal fitting. The range that can be held down by this presser metal fitting is denoted by the symbol D. In the present invention, since the photosensitive paper is shifted by a distance L and nipped, the generated print stain P falls within this range D, which affects the printing. It has no effect. On the other hand, in the case of a nip as shown in (B), the black stripe P protrudes from the range D, which causes printing stains.

The above comparison has been made regarding printing stains, but image unevenness due to white streaks can also be explained in the same way.

In the embodiment described above, the nip roller 31, the conveyance roller 35, and the suction belt 39 are driven by the same stepping motor 48.
Another stepping motor may be used to drive the nip roller 31. In this case, in addition to returning the photosensitive paper 30 after exposure as described above, the stepping motor can be reversed immediately after the cutter is operated to return the photosensitive paper 30. Alternatively, the second sensor 55 may be omitted, and instead, when the stepping motor 48 is rotating in the forward direction to send the exposed photosensitive sheet 30a to the development processing section 57, the contents of the counter 83 may be checked; By checking the time from when the stepping motor 48 starts rotating in the normal direction using a timer, it is possible to know the timing at which the stepping motor 48 starts rotating in the reverse direction.

[Effects of the Invention] As explained above, according to the present invention, after cutting a roll-shaped printing plate for creating an offset master into sheets of a predetermined length, the nip roller is reversed to cut the printing plate after cutting. The leading edge of the printing plate was returned to the nip roller so that the nipping position by the nipping roller was brought closer to the leading edge of the printing plate.Then, the printing plate was left nipped with the nipping roller for a long time, and the offset master was removed from the printing plate. Even if printing stains or image unevenness occur in the nip marks when they are created, these places will be located near the edges of the offset master. Therefore, when this offset master is installed in an offset printing machine, the defective portion is hidden by the presser metal fitting and does not have any adverse effect on the print finish.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a camera-type electrophotographic engraving machine embodying the present invention. FIG. 2 is a block diagram showing a stepping motor control device. Third
The figure is a timing chart of FIG. 2. FIG. 4 is an explanatory diagram showing a comparison of the positions of printing stains that occur when the photosensitive paper is returned and when it is not returned. 1...Original, 3...Mirror, 6...Photographing lens, 30...Photosensitive paper, 30a...Photosensitive sheet, 3
1, 32...Nip roller, 33, 34...Cutter, 35, 36...Transport roller, 37...Charger, 38...First sensor, 39...Suction belt, 48...Stepping motor, 55 ……
Second sensor, 57... Development processing section, 68... Fixing processing section, P... Black stripe, L... Return amount.

Claims (1)

[Scope of Claims] 1. After performing charging, exposure, development, and fixing, a roll-shaped electrophotographic printing plate, which becomes an offset printing original plate through hydrophilic treatment, is pulled out and charged, and a predetermined length is After cutting the sheet into sheets and transporting it to the exposure position, the sheet is exposed to light to form a latent image due to static electricity, followed by development and fixing processing to create an offset master. In the paper device, a pair of nip rollers that pull out the printing plate in a roll form, a transport means for transporting the printing plate sent by the nip rollers toward the exposure position, and a pair of nip rollers disposed between the transport means and the nip rollers. , a cutter for cutting the printing plate conveyed by the conveyance means into sheets of the predetermined length; and after the operation of the cutter, the nip roller is reversed, and the tip of the printing plate is cut from the distance between the nip roller and the cutter. and a reversing means for pulling the printing plate back toward the nip roller by a short fixed distance and stopping the leading edge of the printing plate at a position close to the nip position of the nip roller. A roll feeding device for an electrophotographic engraving machine, characterized in that nip marks are brought closer to the edge of an offset master. 2. The nip roller reversing means operates after the exposed sheet is transported to the development/fixing processing section by the transporting means to return the leading edge of the printing plate. The roll feeding device according to item 1. 3. The nip roller is provided with a clutch mechanism disposed between the conveyance means and the nip roller, and the nip roller is rotated in conjunction with the conveyance means via the clutch mechanism. The roll feeding device according to item 2 of the scope of the invention. 4. The conveyance means includes a pair of conveyance rollers that sandwich and feed the printing plate that has passed through the cutter position, and a suction belt that sucks and holds the plate fed by the conveyance rollers and sets it at the exposure position. , and a stepping motor that drives the conveyance roller and the suction belt. 5. A sensor is provided to detect the trailing edge of the exposed sheet when it is conveyed to the processing/fixing processing section by the suction belt, and the stepping motor is reversed by a signal from this sensor. Claim 4 characterized by
Roll paper feeding device as described in section.