JP2002160852A - Device for detecting corner fold of printing paper in folding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a corner fold of a printing paper in a folding stage by a folding machine. SOLUTION: Photo sensors from SN1 to SN4 are disposed adjacent to a first fold starting part in the rear part of a printing paper carrier part 52 of the folding machine. The sensors confirm the moving state of the printing paper P and detect the corner fold generated in the four corners of the printing paper P. When detecting the corner fold of the printing paper P, a valve V of a suction path of a paper feed rotor 50 is closed to temporarily interrupt the feed of the printing paper P by the paper feed rotor 50 and an alarm means 3 is actuated to notify the generation of the corner fold. Meanwhile, the folding machine itself is driven so that the corner fold is generated in a section going out from the last folding process or a section of one before. After removing the section with the corner fold, a reset part 2 is actuated and the valve V is opened so that the feed of the printing P by the paper feed rotor 50 is restarted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting a fold at four corners of a sheet to be folded in a folding step which is one of bookbinding steps.

[0002]

2. Description of the Related Art As one of bookbinding processes, a sheet (hereinafter referred to as "printing paper") in which a plurality of pages are printed on both sides is folded a predetermined number of times to form a signature, which is a booklet of continuous pages. There is a folding process.

The above-mentioned folding step will be described with reference to FIG. 6 and FIG. 1 showing an embodiment of the present invention. The folding operation of the printing paper is performed by first folding the printing paper in two and then further folding the two-fold. , Eight-fold, sixteen-fold, etc., sequentially, to form a signature in which the pages pre-printed on the printing paper are continuous. This folding step is automatically performed by a large folding machine as shown in the figure.

That is, for example, a large number of printing papers P of about 10,000 sheets
Are placed one on top of the other. The uppermost printing paper out of the printing paper P is taken out by the paper feed rotor 50, and the rotation of the paper feed rotor 50 moves the transfer section including the transfer means such as the belt conveyor 51 in the direction of the arrow. here,
A large number of suction holes are formed in the circumferential surface of the sheet feed rotor 50, and the uppermost printing paper P is sucked by sucking the air A from the suction holes, and the printing paper P is rotated by itself. It is sent to the transfer section 52.

When the leading end of the printing paper P moving in the transfer section 52 enters the guide section 55 due to the rotation of the guide roller 53 and the paper folding roller 54 and the leading end hits a preset stopper 59, the printing paper P is printed. P (denoted by P1) is bent by the movement of the rear part of the printing paper fed by the guide roller 53 and the paper folding roller 54, and this bent part is bent by the rotation of the paper folding rollers 54 and 56, and the bent part is placed at the top. Then, the paper folding roller 56 and the guide roller 57 rotate to move to the next four-folding step. This first-stage half-folding step includes the sheet feeding rotor 50
The time required from the suction of the printing paper P to the completion of folding in two is about 1 second, and the folding is performed at a considerably high speed.

When a valve (electromagnetic valve, etc.) V is intermittently opened and closed by the control device 1, the paper feed rotor 50 intermittently sucks the printing paper P and feeds it to the transfer section 52. Reference numeral P2 denotes a printing sheet subsequent to the printing sheet P1.
By adjusting the suction timing, the supply speed of the printing paper P can be adjusted.

[0007]

In the above-mentioned folding process, a fold may be found in a folded signature. The folding is caused by the progress of the folding process in a state where some of the four corners of the printing paper having a rectangular or square plane are folded inward. It should be noted that the folding of a part of the four corners inside the printing paper in this manner is hereinafter referred to as “corner folding”.

[0008] Since the corner breaks rarely occur continuously, and occur randomly, for example, one in thousands or ten thousand thousands of signatures, corner breaks are found at the folding stage. That is virtually impossible. That is, in reality, it is almost always discovered for the first time in a cutting process of cutting out each side of each signature after aligning the respective signatures and binding them in the form of one book. In this way, since it is discovered for the first time near the final step of bookbinding, it takes a lot of trouble such as cutting the corner bent part by pulling out this corner bent part and shaping the cut surface with sandpaper. become.

For example, if it is assumed that corner bending occurs at a rate of one for every 10,000 signatures, and 50,000 books are to be bound into one book with 50 signatures, then the signature of The number is 2.5 million, which is 50,000 books multiplied by 50 signatures. In this state, if it is assumed that corner bending occurs at the above ratio, corner bending occurs in 250 sheets, which is 1/1000 of the total 2.5 million signatures. Considering that corner breaks occur randomly, the number of books having corner breaks is close to this 250 books. Therefore, it is necessary to first find about 250 books having the above-mentioned corner breaks from 50,000 books, and to repair the found corner breaks individually and manually, and these operations require a great deal of labor. Becomes

Conventionally, however, it is unavoidable that corner breaks occur to some extent, and no special consideration has been given to finding corner breaks in each step, and attention has been paid exclusively to repairing corner breaks that have occurred. That was the fact.

In view of the above points, the present inventors have conducted various studies on the causes of corner breaks in the folding process.
From the relationship between the folded signatures and the respective pages, it was found that most of the signatures were at one of the two corners ahead of the four corners of the printing paper before being folded in the moving direction. However, as will be described later, the rear two corners of the printing paper are also notably broken, but these rear corners are not generated in the folding process. It can be seen that this occurred in the previous printing paper cutting process and the printing paper printing process.

That is, in the folding process, the printed surface appears when the printed surface is folded because the printed surface is folded. On the other hand, the corner fold generated in the printing process or the like is printed at the corner fold, and when the corner fold is developed, a portion corresponding to the corner fold on the printing surface is not printed. As a result, it is almost clear at which stage the corner break occurred.

Next, as described above, most of the corner breaks generated in the folding step are either of the two corners in the front of the moving direction among the four corners of the printing paper before being folded in half.
The inventors consider that natural causes such as static electricity, humidity, and the like are caused as well as flattening to improve the separation of a large number of flat stacked printing papers P when the paper feeding rotor 50 sucks the printing papers. Various causes, such as bending of the printing paper caused by air blown to both sides of the front upper portion of the printing paper P (portion indicated by reference numeral a in the drawing), act in combination,
The printing paper P is transported by the paper feed rotor 50 to the transfer section 52.
It is presumed that this occurs at the stage where the tip enters the. Based on this presumption, a system for detecting whether or not the corner of the printing paper P was bent before entering the folding step as in the present invention described later was found, and almost all of the signatures having corner breaks were found. From this, it was found from the effect of the present invention that the estimation of the position where the corner break occurred was correct.

[0014]

SUMMARY OF THE INVENTION The present invention relates to a corner break detecting device constructed on the basis of the knowledge obtained by the inventors as described above, and at least detects a corner break occurring at the folding stage. Further, the present invention is characterized in that it is a corner break detecting device capable of detecting a corner break occurring before a folding step such as a printing step.

That is, in the first configuration of the present invention, a plurality of photosensors (hereinafter simply referred to as “sensors”) for monitoring at least two front corners in the printing paper movement direction among the four corners of the printing paper P being moved. ) Is positioned with respect to the printing paper moving surface before the two-folding process, and the presence or absence of a corner break is detected based on the operation sequence of the printing paper detection by the respective sensors for each corner of the moving printing paper. This is a device for detecting corner breaks in a printed paper, which is configured to shut off the air suction path of the paper feed rotor and temporarily interrupt the supply of the subsequent printed paper to the folding machine in the case of finding a fold.

A second configuration of the present invention is an apparatus configured to monitor at least two corners behind the printing paper in the printing paper moving direction by using at least the plurality of sensors.

Further, in order to enhance the detection accuracy of the corner break, in addition to the sensor for directly detecting the corner break, a front center sensor for detecting the presence or absence of printing paper is provided in front of the position where the corner break detection sensor is disposed. This is a corner detection device for a printed paper which is configured to increase the detection accuracy of the sensor by providing a rear center sensor for detecting the presence / absence of a printed paper behind the position where the corner bent detection sensor is disposed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With respect to a printing paper that has been advanced toward a two-folding part through a transfer section of a folding machine, sensors are arranged at substantially both ends in the width direction of the printing paper. A broken corner of the paper is detected. In this case, in addition to the sensor for directly detecting the corner break, a sensor for detecting the actual position of the printing paper is provided at the approximate center of the two sensors and for the sensor for directly detecting the corner break. Used as a sensor to prevent malfunction of the discovery operation.

When detecting a corner break in front of the printing paper,
The point at which the center sensor detects the printed sheet is defined as the timing of detecting a bent corner, and the presence / absence of a bent corner is detected based on the presence / absence of an operation of detecting the printed sheet by both corner bent sensors.

When detecting a corner break behind the printing paper,
If at least one of the corner break sensors changes from the printing paper detection state to the non-detection state, and the rear central sensor detects the printing paper, it is determined that there is a corner break.

If a corner break is found in any part of the printing paper by the above method, the printing paper is supplied to the transfer section of the folding machine by means such as closing the solenoid valve at the same time as this finding. Cut off the air suction path of the paper feed rotor. As a result, the supply of the printing paper by the paper feed rotor is interrupted. On the other hand, a folded paper sheet proceeds through the folding process to the final process.
However, since the supply of the subsequent printing paper is interrupted, the signature leading to the final folding step has already entered the transfer section when the signature having corner folds or the air suction path of the sheet feed rotor is cut off. Since only the signature of the subsequent normal printing paper has been used, the signature with corner folds can be easily eliminated only by checking the signature that has come out of the final step of folding. Also, if you remove the signature with a broken corner,
The folding operation is restarted by opening the air suction path of the sheet feeding rotor.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 2 shows a first embodiment of the present invention. Sign S
N1, SN2, SN3 and SN4 denote photosensors for detecting the printing paper P moving in the transporting section 52 (see FIG. 1) of the folding machine. Among them, SN2 and SN3 directly detect corner breaks of the printing paper P. (Hereinafter referred to as “corner break detection sensor”). SN1 is a sensor (hereinafter referred to as "front center sensor") which is disposed in front of the corner folding detecting sensors SN2 and SN3 and detects the presence or absence of the printing paper P. Similarly, SN4 is the corner breaking detecting sensor. Sensor S
A sensor (hereinafter referred to as a “rear central sensor”) that is disposed behind the arrangement portion of N2 and SN3 and detects the presence or absence of the printing paper P.

The sensors SN1 to SN4 are:
The following describes an example of a sensor that performs an ON operation when the printing paper P is detected and an OFF operation when the printing paper P is not detected. The detection speed of each sensor is at least 500
What has performance of 1/100 second, preferably about 1/1000 second is good. Further, each of the sensors SN1 to SN4 is shown in FIG.
As shown in (1), the printing paper P (P1) is arranged in a positional relationship described later at a position before the two-folding step, which is the first folding step. In FIG. 1, reference numeral 1 denotes a control device, 2 denotes a reset unit, and 3 denotes an alarm unit.

FIG. 2 shows the moving direction of the printing paper P (indicated by an arrow).
Shows a configuration for finding a corner bend of two front corners. When finding a front bend, the rear center sensor SN4 is basically not used. The corner break detecting sensors SN2 and SN3 are respectively arranged at positions near both side edges of the printing paper P in the width direction of the printing paper P. On the other hand, the front center sensor SN1 is provided with each corner break detection sensor SN2 and S
With respect to the position where N3 is arranged (indicated by the broken line L), it is arranged ahead by the distance D1 in the printing paper traveling direction. In this state, the sensors SN1, SN2, and SN3 detect the printing paper P.

Here, the moving speed of the printing paper P in the moving section 52 of the folding machine is quite high, and usually moves at about 2000 mm / sec. That is, the printing paper P in one thousandth of a second
Will move about 2 mm. The distance D1 is set based on the moving speed of the printing paper P. This distance D
1 is set to 4 mm, for example, and the moving speed of the printing paper P is as described above. When the front center sensor SN1 detects the front end of the moving printing paper P and turns ON, each corner break detection sensor For SN2 and SN3, the printed paper should be located two thousandths of a second before. In this way, the actual position of the printing paper P is detected by the front center sensor SN1 (because it is almost impossible for the central part of the printing paper P to be bent), and each corner bending detection sensor SN2 and SN
3 sets a state in which the printing paper P can be completely detected.

The detection of the presence or absence of the two corners in front of the printing paper P in the above state will be described with reference to the flowchart shown in FIG. In the folding operation, the sheet feeding rotor 5 shown in FIG.
The controller 1 intermittently opens and closes (Sa1) the valve (electromagnetic valve) V of the air suction system of No. 0, and sequentially sucks the uppermost printing paper P among the printing papers P on the lifting table 58 (Sa).
2) The sucked printing paper P moves through the transfer unit 52 at the above speed (Sa3). When the leading end of the moving printing paper P is detected by the front center sensor SN1 (Sa4)
Is the detection timing of the presence or absence of a corner break.

When the front center sensor SN1 is ON,
That is, when the leading edge of the printing paper P is detected, each corner break detection sensor SN located behind the front center sensor SN1 is detected.
2 and SN3 must of course be ON. Therefore, at the detection timing when the center sensor SN1 is turned on, the operation state of the detection sensors SN2 and SN3 is detected (Sa5). If at least one of the corner break detection sensors SN2 and SN3 is not turned on, the valve V is turned on. Close and stop suction (Sa7, Sa8).
Stop supplying. In the case of the drawing, in order to clearly show the work order, it is displayed in chronological order as a flow chart,
By incorporating the ON / OFF signal of each sensor into the opening / closing circuit of the valve V, steps Sa4 to Sa6 proceed almost simultaneously (for example, about 1/0000 second to 2/1000 second), and are printed almost simultaneously with the detection of a corner break. The supply of the paper P is stopped. On the other hand, when both corner break detecting sensors SN2 and SN3 are ON in step Sa5, the folding operation is continued.

In step Sa5, when there is a corner bend, the control device 1 closes the valve V as described above. Notifies the operator of the occurrence of corner breaks, such as blinking of. In the example of FIG. 2, the front right corner of the printing paper P is bent (indicated by a symbol Pp1). At this time, the corner broken detection sensor SN2 is ON, but the corner broken detection sensor SN3 is turned on. Is still O
This means that the FF state is maintained.

Even in such a state where corner breaks occur,
The folding machine itself is operating as it is, and only the supply of the printing paper P is interrupted. Therefore, in addition to the printing paper P in which the corner fold has occurred, in some cases, in addition to the printing paper in which the corner fold has occurred, the subsequent printing paper supplied to the moving section 52 before the corner fold is detected is the final fold. Proceed to the process. In other words, since the last printed paper from which the supply of the printing paper P has been interrupted or the signature made by the immediately preceding printing paper has been bent, the corner is easily bent at this folding stage. Can be found reliably.

It should be noted that although corner breaks are found depending on the state of corner breaks, it has been confirmed that corner breaks can be found with a high probability even if the width W of the break (see FIG. 2) is 10 mm or less. Further, since corner breaks are hardly found after bookbinding by the test using the apparatus of the present invention, almost all corner breaks, including those generated in the printing process, may occur before the first fold. It could be confirmed.

As described above, in this embodiment, the ON operation of the front center sensor SN1 is used as the timing of detecting a corner break. However, this front center sensor SN1 is eliminated, and the time when each of the corner break detection sensors SN2 and SN3 is turned ON. It is theoretically possible to find a corner bend by judging the simultaneity. In this case, it is necessary to pay attention to the influence of a slight difference between the operations of the corner break detection sensors SN2 and SN3 on the detection accuracy and the setting of the detection timing. Therefore, as in the present embodiment, the front center sensor SN
ON of sensors SN2 and SN3 at the time of 1 ON,
The method of detecting a corner break by detecting the OFF state is the most reliable method at the time of filing the present application. However, if the response speed of the sensor can be further increased and the processing speed of the sensor signal can be further increased, a method without using the front center sensor SN1 is also practical.

FIG. 4 shows an arrangement for finding a broken corner of two rear corners in the direction of movement of the printing paper P. It should be noted that, as described above, the corner breaks at the two corners at the rear end of the printing paper P do not occur almost 100% in the folding process, and have already occurred on the printing paper P before the folding process, such as the printing stage. It is confirmed by the printing condition of the printing paper.

In order to find the corner break, the rear center sensor SN
4 and corner break detection sensors SN2 and SN3. As shown in FIG. 2, the rear center sensor SN4
1 is a distance D in the traveling direction of the printing paper P with respect to the position where each of the corner break detection sensors SN1 and SN3 is disposed.
It is located two behind. The distance D2 may be set to the same value as the distance D1 between the front center sensor SN1 and the broken line L1.

The detection of the presence or absence of the two bent corners behind the printing paper P in the above state will be described with reference to the flowchart shown in FIG. As for the discovery of the corner break of the printing paper P, as described above, the presence or absence of the corner bending at both the top corners with respect to the traveling direction of the printing paper is detected according to the progress of the printing paper P.
The two corner breaks at the rear end side are detected. That is, the control device 1 intermittently opens and closes (Sb1) the valve (electromagnetic valve) V of the air suction system of the paper feed rotor 50 in common with the flow shown in FIG. Among them, the uppermost printing paper P is sucked (Sb2), and the sucked printing paper P moves through the transfer unit 52 at the above speed (Sb3).

With the movement of the printing paper P, the rear center sensor SN
Reference numeral 4 detects the printing paper P, changes from OFF to ON, and keeps the ON state while the printing paper P is moving (Sb4). At this time, both corner break detecting sensors SN2 and SN3 have also detected the printing paper P and are turned ON. Next, the rear center sensor SN
When at least one of the corner break detection sensors SN2 and SN3 is turned from ON to OFF in the ON state (S
b5) The valve V is immediately closed (Sa7), and the suction of the succeeding printing paper P is stopped in the same manner as in the case of the detection of the corner break at the front of the printing paper (Sb8).

That is, since the rear center sensor SN4 can detect the actual position of the printing paper P, the fact that the rear center sensor SN4 is ON means that the printing paper P is at the detection position of the rear center sensor SN4. It means that it still exists. At this time, the corner break detection sensors SN2 and SN3
That at least one of them changes from ON to OFF,
This means that although the printing paper P is actually at the position detected by each of the sensors SN2, SN3, and SN4, it is not detected, that is, there is a corner break.

Incidentally, in the case of FIG. 4, this step Sb5
In this case, the supply of the printing paper P is stopped by turning the corner break detection sensor SN2 from ON to OFF. Thereafter, as in the case described above, the corners of the signature discharged from the final process are checked. On the other hand, corner break detection sensors SN2 and SN3 are O
If the rear center sensor SN4 is in the OFF state (Sb6) in the N state, no corner bending has occurred, and the folding operation is continued.

In the meantime, also in the case of detecting the corner break at the rear end of the printing paper, the corner break is found by a method of omitting the rear center sensor SN4 and judging the simultaneity of the time when the corner break detection sensors SN2 and SN3 are turned off. Such a configuration is theoretically possible.

In mounting the sensors SN1 to SN4, a special member may be inserted into the transfer unit, and the individual sensors may be mounted on the special member. Alternatively, the sensors SN1 to SN4 may be mounted on an existing member of the folding machine. . For example, in FIG. 6, a positioning member called a ruler (not shown) is arranged on the left side of the printing paper transport section 52 in the folding machine, and the left side edge of the printing paper P in the traveling direction corresponds to this ruler. It is configured to proceed in contact. By moving the ruler in the width direction of the transfer unit 52 in accordance with the size of the printing paper, the printing paper always moves in the center of the folding machine regardless of the size of the printing paper.

On the other hand, a holding member for regulating the right side of the printing paper P is provided, and the position of the holding member is also adjusted in accordance with the adjustment of the ruler. That is, if the ruler and the holding member are provided with the corner break detecting sensors SN2 and SN3, respectively, even if the size of the printing paper P is changed, the ruler and the holding member are automatically set in accordance with the new setting of the ruler and the holding member. The position setting of the corner break detection sensors SN2 and SN3 is performed. Further, the front center sensor SN1 and the rear center sensor SN
Reference numeral 4 indicates that if the printing paper P is always fixedly attached to the center of a bar or the like which is extended over the two-folded portion, the printing paper P always moves in the center of the transfer unit 52 by the above-mentioned adjustment regardless of its size. SN1, rear center sensor SN4
It is not necessary to reset the position of.

[0041]

As described above, the present invention has been specifically described.
It is now possible to find corner breaks in the folding process, which was almost impossible in the past, and the finding rate is extremely high, so it is possible to repair books due to corner breaks found in the final stage of the bookbinding process,
Alternatively, it is possible to eliminate almost all labor or waste such as disposal.

Further, since the supply of the subsequent printing paper to the folding machine is temporarily interrupted upon the detection of the corner fold, the signature having the corner fold is the last signature discharged from the final folding process or this signature. Since it is known as the signature in front of the signature, there is no need to search for a signature with a broken corner at all.

Further, even when a corner is found to be folded, the folding machine itself continues to operate, and when the signature with the corner is removed, the printing paper can be supplied immediately to start the folding operation. The interruption of work is very short,
It is possible to find and eliminate corner breaks without substantially affecting the entire folding operation.

[Brief description of the drawings]

FIG. 1 is a schematic view of a folding machine provided with an apparatus according to the present invention.

FIG. 2 is a diagram showing a position state of each sensor for detecting a front corner break of a printing paper.

FIG. 3 is a flowchart showing a process for finding a front corner break of a printing sheet.

FIG. 4 is a diagram showing a position state of each sensor for detecting a rear corner break of a printing paper.

FIG. 5 is a flow chart showing a process for finding a rear corner break of the printing paper.

FIG. 6 is a partial perspective view of a folding machine to which the apparatus of the present invention is attached.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Control device 2 Reset part 3 Alarm means 50 Feeding rotor 52 Transfer part P (P1, P2) Printing paper Pp1 Corner break SN1 Front center sensor SN2 Corner break detection sensor SN3 Corner break detection sensor SN4 Rear center sensor

Claims (10)

[Claims] An apparatus provided in a folding device for sequentially transferring a large number of printing papers to a folding step by a paper feeding means such as a paper feeding rotor and folding the printing papers a predetermined number of times. Corner break detection sensors for detecting the presence or absence of printing paper are provided in the vicinity of both ends in the orthogonal printing paper width direction, and signals of these corner break detection sensors are input to the control unit. The paper feeding device is stopped when the ON / OFF operation is performed in a state in which the corner is bent in a predetermined state, and the supply of the printing paper to the folding process is stopped. A device that detects breaks. 2. In addition to the corner break detection sensors, a position substantially at the center of the arrangement position of each of the corner break detection sensors and in front of the installation position of these corner break detection sensors with respect to the printing paper moving direction. Is provided with a front center sensor for detecting the presence or absence of the printing paper.When the front center sensor detects the printing paper, the presence or absence of a detection operation of the printing paper by the corner break detection sensor in the direction of the printing paper movement. Printing paper front 2
2. The apparatus according to claim 1, wherein the apparatus is configured to detect a corner bend at a location. 3. In addition to the corner fold detection sensors, at a position substantially at the center of the arrangement position of each of the corner fold detection sensors, at a position behind the installation position of the corner fold detection sensors with respect to the printing paper movement direction. When a rear central sensor for detecting the presence or absence of printing paper is provided, and when the rear central sensor continues to operate with printing paper, at least one of the corner break detection sensors performs operation without printing paper. The apparatus for detecting a corner break of a printing paper in the folding apparatus according to claim 1, wherein the corner break is present. 4. When each of the sensors is turned on when a printed sheet is detected, when at least one of the two corner break detecting sensors is in an OFF state at the time when the front center sensor is turned on, a corner is detected. 3. The folding device according to claim 2, wherein the folding device detects the corner of the printing paper. 5. Each of the sensors is turned on when detecting a printed sheet, and when at least one of the corner break detection sensors is turned off while the rear center sensor continues to be turned on. 4. The apparatus according to claim 3, wherein the corner is broken. 6. A means for supplying the printing paper to a transfer unit,
A paper feed rotor that sucks the printing paper by suctioning air,
6. The folding device according to claim 1, wherein a valve is provided in a suction air path for the sheet feeding rotor, and the control device controls supply of the printing paper by opening and closing the valve. A device that detects corner breaks in printing paper. 7. The control device according to claim 1, wherein alarm means is connected to the control device, and an alarm is issued in response to the detection of a corner break and the stoppage of the supply of printing paper. A device that detects corners of printed paper in a folding device. 8. The control device is provided with a resetting means, and after removing a signature with a corner bend, the resetting means activates a paper feeding means to supply a printing paper to the operating folding machine. The apparatus for detecting a corner break of a printing paper in the folding apparatus according to any one of claims 1 to 7, wherein the apparatus is configured to restart. 9. A corner-break detecting sensor is disposed on each of the printing-paper-position adjusting members of the folder, and the corner-break detecting sensors themselves are adjusted by adjusting the printing-paper-position adjusting members in accordance with the size of the printing paper. 10. A folding device according to claim 1, wherein the presence or absence of the printing paper is always detected at an appropriate position without changing the setting. apparatus. 10. The folding device according to claim 1, wherein each of the front center sensor, the rear center sensor, and each corner fold detection sensor is a photo sensor. The device to discover.