JPS61162459A - Paper roll feeding device for electronic photoengraving machine - Google Patents

Abstract

PURPOSE:To prevent an adverse influence from being exercised on printing finish even if a sensitized paper is nipped for a long time, by a method wherein, after cutters are actuated, nip rollers are reversed to return the forward end of the sensitized paper by a distance shorter than a distance between the nip roller and the cutter. CONSTITUTION:After a sensitized paper 30 is fed by a given length through conveyance rollers 35 and 36 and a charging device 37 through forward rotation of nip rollers 31 and 32, the paper is cut through the working of cutters 33 and 34, and is exposed on a suction box 40 by an optical axis 10 from a photographing lense 6. Meanwhile, right after the cutters 33 and 34 are actuated, the nip rollers 35 and 36 and reversed, and the cut end of the sensitized paper 30 is returned to a position in the vicinity of the nip roller 31. Thus, even if the sensitized paper 30 is left in a nipped condition between the nip rollers 31 and 32 for a long time, printing contamination and unevenness of a picture, occurring due to the nipping state for a long time, are gathered to the side end of the sensitized paper, and in case the paper is set to an offset printer, it can be pressed by a press metal, and this prevents an adverse influence from being exercised on printing finish.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic engraving machine for creating 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 photosensitive paper used for this offset master has a backing layer, a subbing layer, and a photoconductive layer layered one after another on a support, and the photoconductive layer is given photosensitivity by being charged. I can do it. In conventional electrophotographic engraving machines, a roll of photosensitive paper is used, and a pair of nip rollers pull out the photosensitive paper, and the paper is transferred to a conveying means to be conveyed to an exposure position. A cutter is disposed between the nip roller and the conveyance means, and is activated to cut the photosensitive sheet when the photosensitive paper 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 areas 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 rollers are designed to stop after the cutter is activated, so the leading edge of the photosensitive paper remains at the cutter position 1 until the next plate-making starts, and the photosensitive paper is tightly gripped by the nip rollers. It has become. If left in this state, nip pressure will be concentrated on the area nipped 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. This printing stain is
It has been found that the longer the standing time and the greater the nip pressure, the more likely it is to occur. 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 appears as white spots in the print, causing "image unevenness". It may happen. It is known that the higher the humidity, the more likely this white spot will occur.

Conventionally, as a countermeasure against printing smudges or image unevenness, 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 removed from 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 printing stains and image unevenness caused by nip rollers and does not affect the print finish. be.

[Means for solving problems]

In order to achieve the above object, the present invention includes a two roller reversing means, and after cutting the photosensitive paper with a cutter disposed between the nip roller and the conveying means, the nip roller is reversed and stopped at the cutter position. The leading edge of the photosensitive paper is returned to the nip roller.

By returning the leading edge of the photosensitive paper to a position where it does not come off the nip roller, printing stains and image unevenness that occur when the photosensitive paper is nipped with the nip roller for a long time are reduced compared to when the photosensitive paper is not returned. Occurs near the edge of the paper. In an offset printing machine, the printing drum is equipped with a presser 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. . In this way, no ink will be deposited on these areas, so no problems will occur in the print finish.

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

〔Example〕

In Figure 1 showing a camera-type electrophotographic engraving machine, original 1
A mirror 3 is placed above the stage 2 on which the lamp is placed, and on both sides of the mirror 3 are placed illumination arms 5 to which rod-shaped light sources 4 are attached.

The reflected light from the original 1 illuminated by the light source 4 is reflected diagonally backward by the mirror 3, passes through the photographic 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 the photographic lens 6 is equipped with a lens shutter 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 is disposed that fits into a part of the mirror holder 8, and when the feed screw shaft 12 is rotated by a stepping motor 13, the mirror holder 8 moves forward or backward depending on the direction of rotation. A feed screw shaft 14 that fits into a part of the lens holder 9 is provided, and the lens holder 9 moves back and forth when the stepping motor 15 rotates. 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 by a function of the image point distance, the stepping motor 13 is driven so as to obtain this distance.

Only the photographic light that passes through the photographic lens 6 is blocked by a light shielding plate)
A bellows 18 is connected to the lens holder 9 and the plate 17 in order to allow the lens to pass through the opening 17a of the lens holder 9 and the plate 17.

Note that numerals 20 to 25 are bearings.

Photosensitive paper 30 is wound in a roll around a core 29, and is pulled out and sent toward a cutting position by normal rotation of a pair of nip rollers 31 and 32. At this cutting position, a well-known cutter consisting of a rotary type 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. The photosensitive paper 30 that has passed the cutting position is transferred to a pair of conveyance rollers 35.
, 36 and transported toward a charger 37. In front of the charger 37, a reflective first sensor 38 consisting of a light projecting section and a light receiving section is arranged, and detects passage of the leading edge of the photosensitive paper 30.

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. The suction box 40 is connected to a suction blower 45 via a hose 44.

A toothed pulley 47 is attached coaxially with the roller 42, and a toothed belt 50 is hung between the toothed pulley 49 attached to the output shaft of the stepping motor 48. Also, roller 41, nip roller 31. l
Toothed pulleys 51 to 53 are attached coaxially with the lt feed roller 35, and a toothed belt 54 is wrapped around these pulleys. In addition, the nip roller 31 and the toothed pulley 5
An electromagnetic clutch is disposed between the cutter 2 and the nip roller 31, 32 to stop the rotation of the nip rollers 31 and 32 after the cutter is activated.

After the photosensitive sheet 30a is exposed at the exposure position, it is sent toward the development processing section 57 by the forward rotation of the suction belt 39. When sending out this photosensitive sheet 30a,
A second sensor 55 using a reflective photosensor detects the rear end of the photosensitive sheet 30a. This second sensor 5
When 5 detects the rear end of the photosensitive paper 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 the nip roller 3.
1. Return to a position close to 32.

The exposed photosensitive sheet 30a that has entered the development processing section 57 via the guide 56 is subjected to development processing here. This development processing section 57 includes a pair of development entrance rollers 58 and 59,
An upper electrode plate 60 and a lower electrode plate 61 arranged opposite to each other, a developer supply nozzle 62, and a pair of squeeze rollers 63, 6
4 and a developer tank 65.

The developed photosensitive sheet t-30a is transferred to the fixing processing section 68.
The film is then sent to the printer, where it undergoes heat fixing. This fixing processing section 6
Reference numeral 8 denotes a pair of fixing inlet rollers 69 and 70, a pair of fixing outlet rollers 71 and 72, a guide plate 73 disposed between these, a heater 74 disposed above the guide plate 73, and a reflector. The photosensitive sheet 7, which has undergone the fixing process, is sent out to a tray 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 1-302 is exposed. It is designed to stop when a sensor detects that the end has passed the fixing exit rollers 71 and 72, or when the time required for development and fixing processing has elapsed.

FIG. 2 shows a control device for a stepping motor. The keyboard 80 includes a start key 80a and a function key 80 for specifying work contents such as magnification conversion.
bl! It consists of a numeric keypad 80C for specifying magnification values, etc., and by pressing each key, specified information can be sent to the sequence controller 81. This sequence controller 81 operates the motor control unit 82 . Counter 83. driver 84
control the operation of etc. The part surrounded by the dotted line is the CP
It is U85.

The motor control unit 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 unit 87 to control the rotation. A number of drive pulses are generated according to the amount. This driver 86 inputs a rotation direction signal and a drive pulse to drive the stepping motor 4.
Controls the rotation of 8.

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

The counter 83 is also reset when the second sensor 55 detects the rear end of the exposed photosensitive sheet 30a, and counts the driving pulses while the stepping motor 48 is in reverse rotation, and calculates the return position of the leading end of the photosensitive sheet 30. Detect. 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 return amount is too large, the leading edge of the photosensitive paper 30 will come off the nip rollers 31, 32, so for the next plate making, the leading edge of the photosensitive paper 30 must be pulled out to a predetermined position before being placed on the nip rollers 31, 32. You'll have to let it bite. - Therefore, the amount of return of the photosensitive paper 30 needs to be set 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 embodiment described above 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 motor 13.
15 rotates to move the mirror 3 and photographic lens 6 to a predetermined image magnification position. After the original 1 is set on the stage 2, when the start key 80a is turned on, the sequence controller 8 connects the electromagnetic clutch 88. Then, after the time T required for the electromagnetic clutch 88 to be completely connected has elapsed, the sequence controller 81 sends a rotation command to the motor IIJ 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. This suction belt 39
The forward rotation of the nip roller 31 is performed via the toothed belt 54.
and is transmitted to the conveyance rollers 35, causing them to rotate normally.

When the nip roller 31 rotates normally, it nips the photosensitive paper 30 with another nip roller 32 and feeds it toward the conveying rollers 35 and 36. This conveyance roller 3
The photosensitive paper 30 held by the first sensor 38
After passing through a charger 37 and a charger 37, it reaches a succinic belt 39. When the first sensor 37 detects the leading edge of the photosensitive paper 30, the counter 83 is reset, so that the counter 83 counts the driving pulses sent to the driver 86 thereafter. Further, the charger 37 charges the photosensitive paper 30 passing therethrough and imparts 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 and 32 are stopped. Separated photosensitive sheet 30
A is attracted and held by the Succicon belt 39 and sent toward the exposure position. In addition, this suction belt 3
9 is provided with suction force 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 normal 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 transfer the exposed photosensitive sheet 30a to the development processing section 5.
Transport towards 7. 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.

When the rear end of the photosensitive sheet 30a is detected by the second sensor 55 after the leading end of the photosensitive sheet 30a enters the development processing section 57, 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 connects the electromagnetic clutch 88 again, and then rotates the stepping motor 48 in the reverse direction.

When the stepping motor 48 is reversed, the nip rollers 31.32 are reversed, so that the leading edge of the photosensitive paper 30 is returned from the cutting position toward the nip rollers 31.32.

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 brought into a closed state. .

The exposed photosensitive sheet 30 sent to the development processing section 57
A is developed here. In this development processing section 57, while an electric field is applied between the upper and lower electrode plates 60, 61,
The developer discharged from the developer supply nozzle 62 is applied. The developed photosensitive sheet 30a is transferred to the fixing processing section 6.
8, where it is heated by a heater 74 to perform thermal fixing, and finally the receiver is discharged onto a table 76. In the heat-fixed photosensitive sheet 1-30a, 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. If the photosensitive paper 30 is nipped with the nip rollers 31 and 32 and left for a long time, ring streaks P will occur, which will cause print stains. (A) shows the printing stains that occur when the present invention is practiced, 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, the printing stain P occurs at a position closer to the edge by a distance 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 represented by a code. In the present invention, the photosensitive paper is shifted by the distance and nipped, so the generated print stain P falls within this range, which affects the printing. It has no effect. On the other hand, in the case of nipping as shown in (B), the ring streak P protrudes from the above range, 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. Conveyance roller 35.
Although the sucsigin belt 39 is 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 activated to return the photosensitive paper 30. Alternatively, the second sensor 55 may be omitted, and instead, when the stepping motor 48 is rotating forward to send the exposed photosensitive sheet 30a to the development processing section 57, the contents of the counter 83 may be checked, or the timer may be used. By checking the time from the start of normal rotation of the stepping motor 48 using
You can know the timing of the start of the reverse rotation of 8.

〔Effect of the invention〕

In the present invention having the above configuration, after cutting the photosensitive paper, the nip rollers are reversed and the leading edge of the photosensitive paper is returned to the nip roller. Even if stains or uneven images occur, these will occur at positions near the edges of the photosensitive paper depending on the amount of return of the photosensitive paper, and the edges of the photosensitive paper will be attached to the presser foot when installed in an offset printing machine. Since it is a part that is held down by metal fittings, it will not have any negative 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 control device for a stepping motor. FIG. 3 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 31.32... Nip roller 33.34... Cutter 35.36... Conveyance roller 37... Charger 38...First sensor 39...
Saxicon belt 48...Stepping motor 55...Second sensor 57...Development processing section 68...Fixing processing section P...Ring stripe L...Return amount.

Claims (5)

[Claims] (1) A roll of photosensitive paper is pulled out by a pair of nip rollers and then conveyed toward the exposure position by a conveying means, and a cutter placed between the nip roller and the conveying means cuts the photosensitive paper into a photosensitive sheet of a predetermined length. In a roll feeding device of an electrophotographic engraving machine configured to cut the photosensitive paper, a reversing means for reversing the nip roller is provided, and after the cutter is activated, the nip roller is reversed to feed the photosensitive paper by a distance shorter than the distance between the nip roller and the cutter. A roll feeding device characterized in that the leading edge of the paper is returned. (2) The nip roller reversing means operates after the exposed photosensitive sheet is conveyed to the developing/fixing processing section by the conveying means to return the leading edge of the photosensitive paper. Roll paper feeding device as described in section. (3) The nip roller includes a clutch mechanism disposed between the conveyance means and the nip roller, and the nip roller rotates in conjunction with the conveyance means via the clutch mechanism. Roll paper feeding device as described in section. (4) The conveyance means includes a pair of conveyance rollers that sandwich and feed the photosensitive sheet that has passed through the cutter position, and a suction belt that suctions and holds the photosensitive sheet 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 photosensitive sheet when it is transported by the suction belt to the developing/fixing processing section, and the stepping motor is reversed based on a signal from this sensor. A roll paper feeding device according to claim 4 characterized by: