JPH08127119A - Paper exhaustion detector of printing press - Google Patents

Abstract

PURPOSE: To instantly detect paper exhaustion by connecting an incremental encoder to the touch roller of a pair of backup rollers nipping a web from both surfaces thereof and rotated by the running of the web and electrically detecting paper exhaustion when the touch roller is reversed by the cutting of the web. CONSTITUTION: A touch roller 26 nipping the web 12 running from a printing unit 10 to a drying unit 20 along with a backup roller 24 is provided. A pulse generator 34 is provided to the touch roller 26 through a shaft and, when the web 12 is cut during operation, the tensile force of the web 12 is instantly lost and the web is wound around a blanket cylinder 14 to be allowed to run in a reverse direction. Therefore, the input shaft of the pulse generator 34 is reversed to output a pulse signal as a paper exhaustion signal. As a result, the paper exhaust signal can be generated rapidly and the detection reliability of paper exhaustion is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper breakage detecting device for a printing press, which detects cutting of a running web (continuous paper) in an offset rotary press or the like.

[0002]

2. Description of the Related Art Generally, in a printing machine such as an offset rotary press, a web is unwound from a web mounted in a paper feeding unit, and a printing unit, a drying unit and a cooling unit arranged in sequence are run and introduced into a folding machine. It is then folded and becomes a printed product. In the printing unit, the web travels between the nips of a pair of rotating cylinders, at least one of which is a printing cylinder, to perform printing. When the web is cut (broken) inside the drying unit during the operation of such a printing machine, the pulling force against the web pulled out from the printing cylinder disappears and the ink stickiness is added to the nip of the printing cylinder to print the web. It causes a big accident that the blanket of the wrapping printing cylinder is damaged by being pulled back to the cylinder and that the printing cylinder needs to be deformed and replaced when a large amount of wrapping occurs. For this purpose, a paper cut device for appropriately arranging a sensor for detecting paper breakage in a passage of the web such as the entrance and exit of the drying unit and activating the cutter by this sensor signal to cut the web pulled back to the printing cylinder near the printing cylinder. And a protective device for preventing the web from wrapping around the printing cylinder.

[0003]

However, the conventional paper break detection sensor uses a reflection type or transmission type photoelectric switch or an air blow type switch which optically detects the presence or absence of the web at the arranged position. ,
In reality, paper breakage often occurs at a location separate from the location where the photoelectric switch is placed, and one of the cut-out edges runs through to the upstream side, or the other is pulled back toward the printing cylinder. Only when the web disappears from the place where the photoelectric switch is arranged, the paper break will be detected. Therefore, the sensor signal is output by detecting the paper break at a timing delayed from the actual occurrence of the paper break, and there is a problem that the wrapping of the web around the printing cylinder cannot be minimized. Especially when the photoelectric switch is arranged at the entrance of the drying unit which has a long furnace length and is likely to run out of paper inside the drying unit,
It is difficult to detect the paper break instantly, and the delay of the paper break detection is noticeable. In order to reduce the delay of paper break detection, it is proposed to increase the number of locations where photoelectric switches are arranged and to arrange a special switch inside the drying furnace that can withstand the high temperature in the furnace, but the number of paper break detection sensors If it is increased, it becomes a factor that induces various malfunctions.
There is a problem in that an extra accident such as cutting the web or stopping the operation is accidentally performed by activating the paper cutting device due to a malfunction even though it is unnecessary.

Also, when a touch lever or a touch roll is kept in contact with the running web and the web loses tension when the paper is cut and loosens, the touch lever or the touch roll swings to actuate a micro switch which is abutted. There is also a device that detects the paper out. However, since the breakage of the web detects a paper break, the reliability is poor and the malfunction described above occurs.

In view of the above, the present invention solves the above-mentioned problems, and by minimizing the delay of paper break detection, it is possible to suppress the winding of the web around the printing cylinder to the minimum level that does not cause an accident. Even if there is no need to minimize the cause of malfunction, the paper cut device is activated to eliminate unnecessary accidents such as cutting the web or stopping the operation, and the reliability of paper break detection is improved. The purpose is to provide a device.

[0006]

SUMMARY OF THE INVENTION To achieve the above object, a paper breakage detecting device in a printing machine according to the present invention comprises a pair of backup rollers and a touch roller which nip the web from both sides and are rotated by the traveling of the web. When the web is pulled back toward the printing cylinder and travels in the opposite direction due to the cutting of the web, the touch roller is electrically rotated in the opposite direction. It is characterized by comprising a detection means for detecting and emitting a signal.

In this case, it is preferable that the detecting means is an incremental encoder or is composed of a rotary generator and a comparator.

[0008]

When the web is cut (paper out) at the downstream side (for example, inside the drying unit) from the nip position of the backup roller and the touch roller during operation of the printing machine,
For the web from the exit side of the printing cylinder to the cut position, the pulling force to run toward the downstream side disappears instantly, the ink stickiness is added to the nip force of the printing cylinder, and the web begins to wind around the printing cylinder, As it is pulled back toward the printing cylinder, the resulting cut web will run in the opposite direction, and the touch roller that nips the web with the backup roller will rotate in the opposite direction to detect The means is driven in the reverse rotation, and the electric signal that detects the reverse rotation is immediately output as the paper break detection signal.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a main part of an offset rotary press, in which a plurality of printing units 10 are inserted through a web 12 which is unwound from a paper roll mounted in a paper feed unit (not shown) and runs substantially horizontally.
And the drying units 20 are arranged linearly. The printing unit 10 is provided with a pair of printing cylinders, a blanket cylinder 14 and a plate cylinder 16 above and below a web 12 that crosses substantially the center, and the ink of the printing plate wound on the plate cylinder 16 is transferred to the blanket cylinder 14. Double-sided printing is performed on the passing web 12. The drying unit 20
The ink printed on the web 12 sent from the printing unit 10 is heated and dried, and then sent to a cooling unit and a folding machine (not shown) that follow.

Here, the paper break detection device 22 according to the present invention is provided on the web path extending from the most downstream printing unit 10 to the drying unit 20. That is, as shown in FIG. 2, the paper break detection device 22 is provided with a pair of rollers including a backup roller 24 and a touch roller 26 facing each other at a position where the traveling web 12 is nipped from both sides. At least one of the pair of rollers can be pressed against and released from the web 12. In the illustrated embodiment, the touch roller 26 side is connected to the air cylinder 28 and moves vertically. ing. In this case, the structure for attachment / detachment is not limited to that shown in the drawing, and attachment / detachment via a swing arm is also adopted. The pair of rollers may be rotated by the traveling of the web 12 that is pressed and nipped, and may be formed to have a small diameter and a narrow width that can receive this rotational force. It is desirable to wind. Further, the position in the width direction at which the pair of rollers nips the web 12 has a structure that is movable in the width direction of the web 12 so that a blank portion which is not printed can be selected. In the illustrated embodiment, , Backup roller 2
Numeral 4 movably fits the bearings to a support shaft 30 installed in the width direction of the unit, and touch roller 26 movably inserts a clevis pin hole of an air cylinder 28 suspending the bearings to a support shaft 32. It is designed to be set at a predetermined opposing position.

Further, an incremental encoder (pulse generator) 34 is axially attached to the touch roller 26 as a means for electrically detecting the reverse rotation, and the incremental encoder 34 is the touch roller 26 according to the traveling of the web 12 described above. The input shaft is driven according to the rotation of. The incremental encoder 34 has a public characteristic for identifying the rotation direction of the input shaft. That is, FIG.
As shown in, a square wave that repeats one revolution of the input shaft by dividing it into a predetermined number of pulses emits A-phase and B-phase pulse signals that are shifted by half a pitch, and rotates in the direction of arrow F in FIG. A
If the rotation in the direction in which the B-phase square-wave rising signal is shifted by a half pitch from the phase-square-wave rising signal is forward rotation, the rotation is in the direction of arrow R, and the B-phase square wave The rotation of the A-phase square wave deviated by a half pitch from the rising signal is identified as the rotation in the direction in which the rising signal is output, and the output signal is obtained.

Next, the operation of the paper break detecting device 22 having the above-described structure will be described. In the offset rotary press shown in FIG. 1, the touch roller 26 provided so as to nip the web 12 running from the most downstream printing unit 10 to the drying unit 20 between the backup roller 24 and the normal running web 12. The input shaft of the incremental encoder 34 is driven according to the rotation of the touch roller 26, and a pulse signal for forward rotation is output. Therefore, when the web 12 is cut (paper out) on the downstream side of the nip position of the touch roller 26 (for example, inside the drying unit 20) during operation, the web 12 is cut from a position fed from the blanket cylinder 14 of the printing unit 10. With respect to the web 12 up to the point, the pulling force for running in the positive direction toward the downstream side is instantly lost, the ink stickiness is added to the nip force of the blanket cylinder 14, and the web 12 begins to wind around the blanket cylinder 14. Since it is pulled back to the blanket cylinder 14 side, as a result, the cut web 12 travels in the opposite direction, and the web 12 is backed up.
4, the touch roller 26 nipping with 4 is rotated in the opposite direction, so that the input shaft of the incremental encoder 34 is driven in the reverse rotation, and a pulse signal that identifies this reverse rotation is immediately output as a paper break detection signal. To be done. Then, the output signal is used to activate or stop the paper cutting device equipped as a protection device.

As another embodiment, instead of using the above-mentioned incremental encoder, a rotary generator known by the abbreviation of tachogenerator may be connected to the touch roller 26. The output characteristic of the rotary generator when the input shaft of the rotary generator changes from the normal rotation during operation to the reverse rotation due to the cutting of the web 12 described above is as shown in FIG. The generated voltage is, for example, from positive (plus) to negative (minus)
It is possible to take out the part that changes to as an output signal. In this case, there is the trouble of requiring a comparator, but in the course of changing from the forward rotation to the reverse rotation (for example, voltage 0
The advantage of being able to output the paper break detection signal quickly is that.

[0014]

As described above, according to the present invention, a backup roller and a touch roller, which are nipped from both sides of a running web and rotated, are provided, and an incremental encoder that is driven by being connected to the touch roller is provided. When the cutting of the web occurs, the web is pulled back toward the printing cylinder, travels in the opposite direction, and the reverse rotation of the touch roller is electrically detected by the incremental encoder to generate a signal. Therefore, the wrapping of the web around the printing cylinder can be minimized without causing an accident, and the delay in paper break detection can be minimized.
Even if there is no need to minimize the cause of malfunction, the paper cut device is activated to eliminate unnecessary accidents such as cutting the web or stopping the operation, and the reliability of paper break detection is improved. A device can be provided.

[Brief description of drawings]

FIG. 1 is a schematic side view showing a main part of an offset rotary press provided with a paper break detection device in a printing machine according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing the paper break detection device of FIG. 1 in an enlarged manner in the direction of arrow XX.

FIG. 3 is a characteristic diagram showing an output of a pulse signal of an incremental encoder.

FIG. 4 is a characteristic diagram showing an output voltage of the rotary generator.

[Explanation of symbols]

 10 Printing Unit 12 Web 14 Blanket Cylinder 16 Plate Cylinder 20 Drying Unit 22 Paper Out Detection Device 24 Backup Roller 26 Touch Roller 28 Air Cylinder 30 Spindle 32 Spindle 34 Incremental Encoder (Pulse Generator)

Claims (3)

[Claims] 1. A pair of backup rollers and a touch roller which are nipped from both sides of the web and are rotated by the running of the web, and a web which is driven by being connected to the rotated touch roller and is cut by cutting the web. A paper breakage detection device in a printing press, comprising: a detection unit that electrically detects that the touch roller has been reversely rotated when the print roller is pulled back toward the printing cylinder and travels in the reverse direction, and outputs a signal. 2. The paper break detection device for a printing press according to claim 1, wherein the detection unit is an incremental encoder. 3. The paper break detection device for a printing press according to claim 1, wherein the detection means includes a rotary generator and a comparator.