EP3597430B1 - Device and method for selectively cross folding of sequentially printed sheets - Google Patents

Description

The invention relates to a device and a method for the optional cross-folding of successive, sequentially printed printed sheets. Optional cross-folding means that the printed sheets to be processed one after the other are either cross-folded or not cross-folded. The device has a first transport path on which printed sheets transported one after the other in a guide plane can each be provided in a folding position. In addition, the device has at least two folding rollers arranged on a first side of the guide plane, each having an axis of rotation and a folding gap between them for the first printing sheets to be folded transversely, whose axes of rotation are both essentially parallel to one another and essentially parallel to the guide plane. Furthermore, the device is equipped with a compressed air device which is aligned essentially parallel to the axes of rotation of the folding rollers, is arranged on a second side of the guide plane opposite the first side of the guide plane and in the region of the fold gap. The latter is connected to a compressed air source and to a control unit and has at least one outlet opening for compressed air directed towards the folding gap. Finally, the device has a second transport path for folded first printed sheets and a third transport path for unfolded second printed sheets. The first, second and third transport routes have a common, first route point at which the first transport route ends and both the second and the third transport route begin. The common, first route point lies on a line of intersection of the guide plane and a fold plane running through the fold gap and the at least one outlet opening of the compressed air device.

In the method, at least a first and a second printed sheet are conveyed one after the other in a guide plane of a first transport path and in provided a folding position. The first printed sheet provided is folded on a first side of the guide plane in a folding gap between at least two rotating folding rollers, each having an axis of rotation, at a folding line provided. Before the transverse folding, from a second side of the guide plane opposite the first side, a compressed air jet directed in the region of the folding gap onto the first printed sheet provided in the folding position is triggered from at least one outlet opening of a compressed air device connected to a compressed air source and a control unit, and the first provided The printed sheet is transported from the management level on a second transport path to the rotating folding rollers under the action of the compressed air blast and, after the transverse folding, is transported further on this second transport path. In addition, a blast of compressed air is suppressed on the second printed sheet provided in the folding position and the second printed sheet, which is thus unfolded, is introduced into a third transport path.

The sequentially printed printed sheets can be unfolded and / or longitudinally folded printed sheets which are fed inline, that is to say directly or indirectly following a digital printing machine. Alternatively, the supply is also possible offline, i.e. starting from an intermediately stored, sequentially printed material web, from which printed sheets are then separated and then if necessary longitudinally folded or from an intermediate store with unfolded and / or longitudinally folded printed sheets.

With digital printing, the print image is transferred directly from a computer to the printing machine without the use of static printing forms. The material web can be printed in the specified sequence of the finished printed product, ie sequentially, depending on the intended folding scheme. In this way, relatively small numbers up to a single printed product can be realized. In contrast to conventional printing processes, such as offset printing, there are very often successive printed sheets with different properties, such as the imprint itself, the number of printed pages per printed sheet and its respective format.

After all, digital printing machines nowadays print ever larger quantities of printing material per unit of time. Regardless of whether it is digital printing machines that process material webs or individual print sheets, these large quantities of printing material must then be processed further. Due to the large throughput of material, there are high transport speeds, which make it difficult to process the printed sheets carefully. Depending on the devices used for further processing, gaps must be formed between the printed sheets, which additionally increases the transport speed. In addition, because of the technical possibilities of digital printing, blank pages in a printed product are less and less accepted today.

From the EP2727868 A1 and the EP2727869 A1 a device and a method for longitudinal or transverse folding by means of a digital printing machine sequentially printed printed sheets are known. The device has a compressed air device connected to a compressed air source and a control unit with at least one outlet opening for compressed air. In this way, a compressed air blast of the compressed air device conveying the printed sheet from a feed plane between the folding rollers can be dosed simply and quickly according to the properties of a printed sheet currently to be folded, so that both good folding quality and high folding performance can be achieved over the entire spectrum of printed sheets to be folded. If the printed sheet does not meet the quality requirements, the compressed air blast can optionally be suppressed. This print sheet is then not fed to the folding rollers, and is therefore not folded and discharged on a separate conveyor path.

With such a device, the transport speed of a print sheet that has been separated from the material web in the meantime or also a print sheet that has been individually printed in the digital printing machine can be reduced by one or more transverse folds. For this purpose, the gap that arises between successive printed sheets during cross-folding can be reduced. The gap is also enlarged by ejecting faulty printed sheets.

This device thus only allows the production of a product stream of folded printed sheets. On the one hand, the cross-folding facilitates careful further processing of the printed sheets, but with the same number of folds, it potentially leads to an undesirable, larger number of blank pages. In contrast, it is known to reduce the number of blank pages in a printed product by integrating unfolded printed sheets. However, neither the known device nor the known method are able to integrate unfolded printed sheets into the product flow. In addition, the use of unfolded printed sheets increases the number of cycles, which, depending on the further processing devices used, results in a high transport speed and, in turn, makes gentle further processing more difficult and can lead to quality problems.

With the EP2818331 A2 a device and a method for further processing a paper web sequentially printed by a digital printing machine are known. The printed paper web first passes through a perforating and cutting station. The printed sheets separated there are individually folded once or several times with cross and longitudinal folding devices. After folding, the printed sheets that will later form a common partial book block are brought together like scales in a collating device before they are stacked and glued to form a partial book block in an adjoining stacking device. The partial book blocks are then transported for further processing. To reduce the number of blank pages, the folded print sheets can also be merged with an unfolded print sheet. However, this unfolded printed sheet must always be supplied at the end of a printed product to be formed, ie after the folded printed sheet. The pocket folding unit usually used for this requires a gap between a folded and an unfolded printed sheet to operate a mechanical flap that deflects a single printed sheet, unfolded, through the folding rollers instead of being folded into the folding pocket. Switching this flap requires a certain amount of time, ie depending on the transport speed a corresponding gap. Such a gap can be created, for example, by a stop and go operation. This gap is greater, the greater the transport speed and the smaller the section length of the printed sheet and consequently the higher the number of cycles. The time required to switch the flap can be minimized by using the latest drive technology, but it cannot be eliminated.

With such a solution, a certain reduction in the number of blank pages can be achieved on the basis of the optimization of folding patterns that takes place automatically in the machine control in accordance with the respective production orders, depending on the number of uses. However, the costs, the space requirements and the control and regulation effort are relatively high due to the number of processing stations. Depending on the mode of operation, the transport speed of the printed sheets to be transported through the device initially individually and at a very short distance one after the other after separation is also relatively high, so that quality problems can arise during their further processing. In addition, the paper web is briefly stopped in the cross cutter upstream of a pocket folder used for cross folding, which leads to discontinuous operation and the use of a relatively complex, upstream storage section. Finally, the transport path is only cleared again when the preceding printed sheet has been conveyed out of the pocket folder again after folding.

Alternatively, a gap can also be formed by increasing the transport speed of the preceding printed sheets or the subsequent units or by slowing down the web of material to be fed. However, increasing the transport speeds of the subsequent processes to form the gap has physical limitations in the known folding machines with pocket folding units, which have a negative effect on the output, so that such folding machines are rather unsuitable for processing large quantities. In general, accelerating or decelerating compared to a constant speed can lead to problems with the print quality.

From the DE102016203043 A1 a folding machine is known to which the printed sheets are fed in shingled form in order to increase the output, whereby a reduction in the transport speed or an increase in the number of printed sheets can be achieved at the same transport speed. This also results in a more flexible solution, which, however, is ultimately very limited when processing large quantities per unit of time. Due to the above-mentioned dependency, this method is also not suitable for dynamically processing individual printed sheets. In addition, the different folding roller spacing required depending on the feed of individual printed sheets or an imbricated flow would have to be changed over with high dynamics, which further complicates process control.

The object of the invention was therefore to create a flexible device and a corresponding method which enable the production of a printed product consisting of cross-folded first and unfolded second printed sheets. The device and the method should allow a simple and inexpensive adaptation to changed properties of successive printed sheets with high folding quality and folding performance and should therefore also be suitable for further processing of printed sheets sequentially printed by means of digital printing machines. In addition, a potential reduction in the number of blank pages in the finished printed product should be achieved.

This object is achieved in a device according to the invention for the optional cross-folding of successive, sequentially printed printed sheets in that the compressed air device has a first control element connected to the control unit for optionally triggering or suppressing a compressed air blast from the at least one outlet opening of the compressed air device, so that in each case starting from the folding position a first printed sheet can be introduced into the second transport path for cross-folding or a second printed sheet can be introduced into the third transport path to bypass the cross-fold. The third transport path ends downstream of the folding rollers at a common, second route point in the second transport path. Furthermore, a fourth transport route connects downstream of the common, second route point. In addition, is the third transport path is longer than the second transport path or can be operated more slowly than the second transport path, such that a first sequence of the printed sheets following one another on the first transport path is equal to a second sequence of the printed sheets following one another on the fourth transport path.

In the method according to the invention, this object is achieved in that the unfolded second printed sheet introduced into the third transport path is conveyed longer on the third transport path than the folded first printed sheet conveyed on the second transport path and the unfolded second printed sheet after the folded first printed sheet a fourth transport path following the second transport path is initiated so that the sequence of the printed sheets following one another on the first transport path is restored.

In such a device and with the corresponding method, digital printing machines can be used to process sequentially printed sheets either cross-folded or unfolded, so that the production of a printed product consisting of cross-folded first and unfolded second printed sheets and thus also a reduction in the number of blank pages in the finished printed product becomes. The unfolded second printed sheet can be inserted into the gap created by avoiding the cross-folding after the cross-folded first printed sheet and at a distance from it while maintaining or restoring the original sequence. In addition to triggering or suppressing a blast of compressed air, the first control element can also be used to change the duration of the application of compressed air to a printed sheet provided in a folding position. Since the printed sheets can be fed to the device with almost no gaps, no or almost no increase in the transport speed is advantageously necessary.

According to one embodiment of the device according to the invention, the third transport path is made substantially longer than the second transport path by half a sheet length of a first printed sheet to be folded transversely.

The unfolded second printed sheet can thus be introduced at a defined position after the folded first printed sheet and thus advantageously also centrally between two cross-folded first printed sheets. There are no abrupt or substantial changes in the speed of the printed sheets, so that influences on the printed sheets that impair process stability and / or reduce quality can be avoided.

According to a further embodiment of the device according to the invention, a device for its length adjustment is arranged in the area of the third transport path. According to a corresponding embodiment of the method according to the invention, the third transport path has a length which is changed accordingly in a subsequent work order with printed sheets that have at least a different format compared to the previous work order. Both the device and the method can thus advantageously be adapted to different lengths of the printed sheets of successive work orders.

In a next embodiment of the device according to the invention, a light barrier and / or an image-capturing device for detecting a leading edge of a printed sheet transported on the first transport path is arranged in the area of the first transport path and is connected to the control unit. According to a corresponding embodiment of the method according to the invention, a leading edge of a printed sheet transported on the first transport path is automatically detected. Based on this, corresponding information is forwarded to the control unit. The control unit generates a corresponding pulse at the time of the optional triggering or suppression of a compressed air blast from the at least one outlet opening of the compressed air device onto the printed sheet that has meanwhile been provided in the folding position and forwards this pulse to a first control element connected to the compressed air source and the compressed air device. Due to the arrangement of the light barrier and / or the image capturing device in the area of the first transport path and thus shortly in front of the compressed air device, the time at which the compressed air blast is triggered or suppressed can be advantageous can be controlled very precisely. The decision as to whether such a burst of compressed air is triggered or suppressed depends on the work orders stored in the control unit. If, in addition to or as an alternative to the at least one light barrier, an image-capturing device is arranged, the printed sheets can advantageously be clearly identified with the aid of corresponding identification features directly in front of the cross-folding device.

According to a further embodiment of the device according to the invention, a first discharge switch is arranged in the second transport path and a first receptacle for first printed sheets is arranged downstream of the first discharge switch. According to a corresponding embodiment of the method according to the invention, the first printed sheet is removed from the second transport path for control purposes. The operator can therefore remove a folded first printed sheet located on the second transport path at any time for control purposes.

According to a next embodiment of the device according to the invention, the folding rollers are arranged above and the compressed air device below the guide plane. Therefore, the removal of a first printed sheet located on the second transport path by the machine operator for control purposes can take place at an ergonomically favorable working height.

According to a further embodiment of the device according to the invention, a second discharge switch is arranged in the fourth transport path and a second receptacle for printed sheets is arranged downstream of the second discharge switch. According to a corresponding embodiment of the method according to the invention, defective first and / or second printed sheets are discharged from the fourth transport path. In this way, unprinted printed sheets produced at the beginning or at the end of a work order can also be discharged.

According to a next embodiment of the device according to the invention, the first, second, third and fourth transport sections have a common drive which is connected to the control unit. As a result, there is no additional regulation and / or control effort with corresponding sensors and monitoring, which is why this solution is inexpensive. Due to the common drive, there are no additional accelerations and decelerations of the printed sheets, so that corresponding quality-reducing effects can be avoided.

According to a further embodiment of the device according to the invention, a fifth transport path begins downstream of the fourth transport path and at a distance from it, which has a separate drive connected to the control unit, with which the fifth transport path runs at a different speed than the fourth transport path and, in particular, slower than the fourth transport path is operable. According to a corresponding embodiment of the method according to the invention, the printed sheets are transferred downstream of the fourth transport path to a fifth transport path that is driven separately from this and is arranged at a distance from this, on which the printed sheets are transferred at a different speed than on the fourth transport path and in particular more slowly than on the fourth Transport route are promoted. Because the speed of the fifth transport path differs from the speed of the fourth transport path, the latter can advantageously be adapted to the needs of the subsequent further processing. If the fifth transport path is operated more slowly than the fourth transport path, the gaps that arise in the device between successive printed sheets can be minimized to a desired level.

In a next embodiment of the device according to the invention, the fourth transport path and / or the fifth transport path has an adjusting element for adjusting a distance between these two transport paths. According to a corresponding embodiment of the method according to the invention, in a subsequent work order in which at least one print sheet has a different format than the print sheet of the previous one Has work order, a distance between the fourth transport route and the fifth transport route changed accordingly. With a device designed in this way or the corresponding method, an adaptation to successive work orders with printed sheets of different lengths can take place, so that in a subsequent work order a printed sheet with a larger format located at the transition from the fourth to the fifth transport route is not clamped and simultaneously on both transport routes is compressed, wrinkled or even destroyed in the process. On the other hand, a printed sheet with a smaller format located at the transition from the fourth to the fifth transport path should also be able to be safely taken over by the fifth transport path in the case of a subsequent work order.

According to a further embodiment of the device according to the invention, it has at least one further control element connected to the compressed air source and the control unit for changing a cross-sectional area of the at least one outlet opening of the compressed air device and / or for changing a pressure of the compressed air that can be fed to this outlet opening. By appropriately applying at least one of the two further control elements, the compressed air blast of the compressed air device can be dosed simply and quickly according to the properties of a first printed sheet that is currently provided in the folding position and currently to be folded across and across the entire spectrum of first printed sheet to be folded across the entire range of both a good folding quality and a high folding performance can be achieved.

According to a next embodiment of the method according to the invention, a first partial gap is generated in the second transport path when an unfolded second printed sheet is forwarded into the third transport path, upstream of a folded first printed sheet. During the folding process of a further first printed sheet belonging to the same work order, a second partial gap is produced downstream of this further first printed sheet and adjacent to the first partial gap. Both partial gaps together form an infeed gap into which the unfolded second printed sheet conveyed on the third transport path is introduced again in the area of the fourth transport path between the folded first printed sheet and the further, folded first printed sheet. This creates an infeed gap in the second transport path in a simple manner and this is used in the area of the fourth transport path to insert the unfolded second printed sheet bypassing the folding rollers and conveyed on the third transport path between the two folded first printed sheets belonging to the same work order.

According to a further embodiment of the method according to the invention, a first printed sheet with a first sheet length, a second printed sheet with a second sheet length and a further first printed sheet with a first sheet length are provided in the folding position one after the other, with the first sheet length being essentially double for printed sheets of the same work order as large as the second arc length. This ensures that the first printed sheet after folding has essentially the same sheet length as the associated, unfolded second printed sheet, so that the latter can be easily inserted into the entry gap between two consecutive first printed sheets in the area of the fourth transport path.

Fig. 1

Eine schematische Seitenansicht einer erfindungsgemässen Vorrichtung zum wahlweisen Querfalzen aufeinander folgender, sequenziell bedruckter Druckbogen, in einem ersten Ausführungsbeispiel.

Fig. 2

Eine vergrösserte schematische Darstellung einer Querfalzeinrichtung der erfindungsgemässen Vorrichtung, dargestellt zu einem etwas früheren Zeitpunkt als bei der Fig. 1.

Fig. 3

Eine schematische Draufsicht auf die Querfalzeinrichtung nach Fig. 1 und 2, wobei sich in der Querfalzeinrichtung, d.h. zwischen deren Falzwalzen und der Drucklufteinrichtung, ein erster Druckbogen in einer Falzposition befindet.

Fig. 4

Eine schematische Seitenansicht der Vorrichtung nach Fig. 1, wobei jedoch sämtliche Druckbogen gefalzt worden sind bzw. gefalzt werden.

Fig. 5

Eine erste Momentaufnahme der Vorrichtung nach Fig. 1, wobei sämtliche zur Weiterverarbeitung, d.h. beispielsweise zur späteren Bildung von Teilbuchblocks vorgesehenen Druckbogen die Falzwalzen umgehen und somit nicht gefalzt werden.

Fig. 6

Eine zweite, gegenüber der Fig. 5 spätere Momentaufnahme der Vorrichtung nach Fig. 1.

Fig. 7

Eine vergrösserte schematische Darstellung des in Fig. 1 dargestellten stromabwärtigen Bereichs der Vorrichtung, in einem zweiten Ausführungsbeispiel mit einer zusätzlichen, fünften Transportstrecke.

Fig. 8

Eine Darstellung wie in Fig. 7, jedoch zu einem etwas späteren Verfahrenszeitpunkt.

The invention is described in more detail below on the basis of exemplary embodiments. Show:

Fig. 1

A schematic side view of a device according to the invention for the optional cross-folding of successive, sequentially printed printed sheets, in a first exemplary embodiment.

Fig. 2

An enlarged schematic illustration of a transverse folding device of the device according to the invention, shown at a somewhat earlier point in time than in FIG Fig. 1 .

Fig. 3

A schematic plan view of the cross folder according to Fig. 1 and 2 , wherein in the transverse folding device, ie between its folding rollers and the compressed air device, a first printed sheet is in a folding position.

Fig. 4

A schematic side view of the device according to Fig. 1 , in which however, all print sheets have been or are being folded.

Fig. 5

A first snapshot of the device after Fig. 1 , with all of the printed sheets provided for further processing, ie for example for the later formation of partial book blocks, bypassing the folding rollers and thus not being folded.

Fig. 6

A second, across from the Fig. 5 later snapshot of the device Fig. 1 .

Fig. 7

An enlarged schematic representation of the in Fig. 1 shown downstream area of the device, in a second embodiment with an additional, fifth transport path.

Fig. 8

A representation like in Fig. 7 , but at a somewhat later point in the proceedings.

Fig. 1 shows in a first embodiment a schematic side view of a device 1 according to the invention for the optional cross-folding of printed sheets 2, 3, ie here the illustrated printed sheets 3a, 2a "; 2b ', 3b, 2b"; 2c ', 3c, 2c ", 2d', which have previously been printed sequentially by a digital printing machine (not shown) and which, downstream of the device 1, each form a sub-book block 4a, 4b, 4c, 4d, etc., indicated in different figures by means of curly brackets. According to the illustration, first printed sheets 2a ", 2b ', 2b", 2c' have already been folded in the device 1, while a next first printed sheet 2c "is being folded and a further first printed sheet 2d 'is in a next process step is to be folded. Second printed sheets 3, here for example the printed sheets 3a, 3b, 3c, are transported through the device 1 without being folded. The print sheets 3a, 2a "and a leading, not shown print sheet 2a 'are for the later production of the first partial book block 4a, the print sheets 2b', 3b, 2b" for the later production of the second partial book block 4b and the print sheets 2c ', 3c, 2c " for a third, in Fig. 7 and in Fig. 8 also provided later partial book block 4c indicated by curly brackets. Furthermore, printed sheets 2, 3 that have already been ejected from the device 1, used for control purposes or faulty, ie here the printed sheets 2x, 3y and 2z, are shown. Although in this representation If three printed sheets are provided to form a partial book block, such a block can of course also be formed by a different number of printed sheets. In addition, instead of ejecting a single printed sheet 2, 3, a whole number of printed sheets can also be ejected one after the other.

A cutting and perforating unit, also not shown, is arranged upstream of the device 1 according to the invention. The cutting and perforating unit is followed by a first transport path 5 belonging to the device 1, which is connected to a transverse folding device 6 of the device 1. In the area of the first transport path 5 and directly in front of the transverse folding device 6, at least one light barrier 7 and / or an image capturing device 8 is arranged.

The Fig. 2 shows an enlarged schematic representation of the transverse folding device 6 of the device 1 according to the invention, in which, in contrast to FIG Fig. 1 however, the folding of the first printed sheet 2c ″ has only just begun. The first transport path 5 has a guide plane 9, in which a next printed sheet 2, 3, here the next first printed sheet 2d 'to be folded across, is fed and ends in of the cross-folding device 6 at a first route point 10, from which the first printed sheet 2c ″ has currently been forwarded for cross-folding.

The guide plane 9 shown here running horizontally can of course also be arranged vertically or at any desired angle in space, which, depending on the specific application conditions, enables a variety of structural options. Although only a single print sheet 2, 3 has been described and shown in the figures so far and also below, for reasons of simplicity, it is in each case at least one print sheet 2, 3, i.e. either actually around a single print sheet or around several superimposed print sheets 2, 3.

On a first side 11 of the transverse folding device 6 located above the guide plane 9, two folding rollers 12 are arranged. These each have one Axis of rotation 13 and form a folding gap 14 between them for the on a prepared folding line 15 ( Fig. 3 ) or on an unprepared fold line to be folded transversely first printed sheet 2. The axes of rotation 13 of the folding rollers 12 are aligned both essentially parallel to one another and essentially parallel to the guide plane 9. Based on previously known order data or from currently recorded data, the folding gap 14 can be adjusted manually or advantageously also by motor, depending on the material thickness and the number of first printed sheets 2 to be folded transversely. The diameters of the two folding rollers 12 can be the same but also different. For example, in order to prevent the printed sheet from touching the downstream folding roller 12 and thus preventing the printing sheet from being braked, the diameter of the downstream folding roller 12 can be made smaller than the diameter of the upstream folding roller 12.

On a second side 16 of the transverse folding device 6 opposite the first side 11 of the guide plane 9 and thus below the guide plane 9, a compressed air device 17 of the transverse folding device 6 is arranged in the region of the folding gap 14. The compressed air device 17, which is aligned essentially parallel to the axes of rotation 13 of the folding rollers 12, has at least one, but preferably several outlet openings 18 directed towards the folding gap 14 ( Fig. 2 , Fig. 3 ) for compressed air 19 and is connected via a compressed air line 20 to a compressed air source 21 and this in turn is connected to a control unit 23 of the device 1 via a control line 22. In addition, the compressed air device 17 has a first control element 24, which is designed, for example, as a solenoid valve, for applying an in an in Fig. 3 First printed sheet 2 shown, here the first printed sheet 2c ", with compressed air 19, in which folding position 25 the first printed sheet 2 lies stretched out flat between the folding rollers 12 and the compressed air device 17, or to change the duration of the application of the at least one Outlet opening 18 with compressed air 19.

In Fig. 3 the printed sheets 2d ', 3d, 2d "belonging to a partial book block 4d which can be produced downstream of the device 1 are also shown, which, like the other first printed sheets 2, each have a first sheet length 2" or like the other second printed sheets 3 each have a second sheet length 3 ". The sheet lengths 2", 3 "of associated printed sheets 2, 3 differ such that the first sheet length 2" is essentially twice as large as the second sheet length 3 ". Although except in Fig. 3 also in the Figures 1 , 2 , 7th and 8th it is shown that an unfolded second printed sheet 3 is inserted between two transversely folded first printed sheets 2 or is intended for insertion there, the device 1 can of course in principle be used to generate any sequence of transversely folded first printed sheets 2 and unfolded second printed sheets 3.

Furthermore, the compressed air device 17 can have a second control element 26, designed here, for example, as a slide, for changing a cross-sectional area, not shown, of the at least one outlet opening 18, and a third control element 27, designed for example as a pressure reducing valve, arranged in the compressed air line 20, for changing a pressure of the at least one Outlet opening 18 have feedable compressed air 19 ( Fig. 2 ). In this case, the second control element 26 can be connected, for example, to a diaphragm which is also not shown, is displaceable and has at least one recess. By moving this diaphragm accordingly, the at least one outlet opening 18 is partially or completely exposed or else completely covered, ie its cross-sectional area is changed. Of course, this cross-sectional area can also be changed by other suitable means. The control elements 24, 26, 27 are each connected to the control unit 23 via a control line 22.

A second transport route 28 for transversely folded first printed sheets 2 begins in the first route point 10 and leads between the folding rollers 12 of the transverse folding device 6 through to a second route point 29. A first ejection switch 30 is arranged along the second transport route 28, with which a transversely folded first printed sheet 2x can be fed to a first receptacle 31 designed, for example, to take samples ( Fig. 1 ).

A third transport path 32 for unfolded second printed sheets 3, which likewise begins at the first route point 10, connects to the first transport path 5. The first route point 10 is thus a common route point of the first transport route 5 ending there and the second and third transport routes 28 and 32 beginning there. The third transport route 32 meets the second transport route 28 at the second route point 29 and ends there. It has a length which is greater than the length of the second transport path 28. In addition, the third transport path 32 has a device 33 for length adjustment, which as in FIG Fig. 1 shown, for example, has a sliding cylinder 33a with a cylinder rod 33b and a roller 33c attached to it and interacting with the third transport path 32. Of course, another suitable device can also be used to adjust the length of the third transport path 32. The first route point 10 lies on a line of intersection 34 of the guide plane 9 and a fold plane 35 running through the folding gap 14 and the at least one outlet opening 18 of the compressed air device 17 ( Fig. 2 , Fig. 3 ).

A fourth transport route 36 connects to the second and third transport route 28, 32 at the second route point 29 ( Fig. 1 ). The second route point 29 is thus a common route point of the second, third and fourth transport routes 28, 32, and 36. With a second diverting switch 37 arranged along the fourth transport route 36, both transversely folded first printed sheets 2 and unfolded second printed sheets 3, here the Printed sheets 2z and 3y, but also waste, can be removed and fed to a second receptacle 38. A further light barrier 7 ′ can be arranged in front of the first and second discharge switch 30, 37 in order to be able to switch the respective discharge switch 30, 37 precisely.

As shown in Fig. 1 a first printed sheet 2 to be folded transversely, followed by a second printed sheet 3 not to be folded and this in turn followed by a further first printed sheet 2 to be folded transversely, have been fed to the device 1 on the first transport path 5 several times in succession. In the downstream area of the fourth transport path 36 of the device 1, these are the unfolded second printed sheet 3a and the cross-folded first printed sheet 2a ″, which are provided for the first partial book block 4a together with a leading, not shown, cross-folded first printed sheet 2a '. For this purpose, the printed sheets 2a', 3a, 2a "first in this order one after the other on the first transport path 5 up to the folding position 25 ( Fig. 3 ) promoted, in which they were stretched out flat between the folding rollers 12 and the compressed air device 17. Starting from this folding position 25, the first printed sheets 2a ', 2a "to be folded transversely, as in FIG Fig. 2 for the first printed sheet 2c ", each acted upon by a compressed air blast 19 'from the at least one outlet opening 18 of the compressed air device 17. Due to this compressed air blast 19', the first printed sheets 2a ', 2a" to be folded transversely are in their middle area between the folding rollers 12 pressed, thereby diverted to the second transport path 28 and then folded transversely by means of the folding rollers 12. The compressed air blast 19 ′ has been triggered by forwarding a corresponding control signal from the control unit 23 via the control line 22 to the first control element 24, and compressed air 19 has been provided from the compressed air source 21. In contrast, such a blast of compressed air 19 'on the second printed sheet 3a, which is meanwhile also in the folding position 25 and not to be folded, was suppressed, so that it was immediately forwarded to the folding rollers 12 on the third transport path 32. The decision as to whether such a compressed air blast 19 ′ is triggered or suppressed depends on the work orders stored in the control unit 23. Since the control unit 23 also knows the number and the sequence of the first printed sheets 2 to be folded transversely and the second printed sheets 3 not to be folded provided for the respective partial book blocks 4a, 4b, 4c, 4d, etc., by means of the the transverse folding device 6 arranged at least one light barrier 7 and / or image capturing device 8 determines the exact time for a pulse for triggering or suppressing the compressed air blast 19 '. If an image-capturing device 8 is arranged in addition or as an alternative to the at least one light barrier 7, the printed sheets 2, 3 can advantageously be clearly identified directly in front of the cross-folding device 6 using corresponding identification features.

By forwarding the unfolded second printed sheet 3a to the third transport path 32, a first partial gap 39a is created in the second transport path 28, upstream of the first printed sheet 2a ', which in FIG Fig. 1 is shown in an analogous manner upstream of the first printed sheet 2c 'with a curly bracket. This first partial gap 39a was followed by a second partial gap 39b created downstream of the first printing sheet 2a ″ by its folding process, which is shown in FIG Fig. 1 is also shown in an analogous manner downstream of the first printed sheet 2c "with curly brackets. The second partial gap 39b arises in each case because the first printed sheet 2 to be folded transversely before reaching the folding rollers 12 initially with its leading edge 2 '( Fig. 2 , Fig. 3 ) and penetrate the third transport path 32 almost to the middle of the sheet before they are finally deflected into the folding rollers 12 by the action of the compressed air blast 19 'on the middle of the sheet and their original sheet length 2 "is thus halved. The two partial gaps 39a, 39b formed a common entry gap 39 between the two successive first printed sheets 2a ', 2a ", as shown in FIG Fig. 1 is shown by the corresponding entry gap 39, also shown by means of curly brackets, between the first printed sheet 2c 'located in the second transport path 28 and the following first printed sheet 2c "which is currently in the folding process. After its transport on the third transport path 32, the unfolded second printed sheet 3a was inserted in the region of the second route point 29 exactly into this entry gap 39 between the transversely folded first printed sheet 2a ', 2a ". The sequence described above is also carried out analogously with the printed sheets 2b ', 3b, 3b "provided for the second partial book block 4b, the Fig. 1 shows exactly the situation in which the unfolded second printed sheet 3b has been introduced into the previously existing entry gap 39 between the two transversely folded first printed sheets 2b 'and 2b ". If, in a subsequent work order, printed sheets 2, 3 with at least one compared to the previous work order different formats are processed, the third transport path 32 can be lengthened or shortened with the device 33 for length adjustment in such a way that the unfolded second printed sheet 3 conveyed on this transport path 32 is advantageously also centered in the infeed gap 39 between the associated, transversely folded first printed sheet 2 is insertable.

The print sheets 2, 3 are transported on all transport routes 5, 28, 32, 36 with in Fig. 3 conveying elements 40, 40 'shown, arranged on both sides of the printed sheets 2, 3, for example as conveyor belts or conveyor belts. Due to the representation of the Fig. 3 Transport paths 5, 32, which are only shown running horizontally, the conveying elements 40, 40 'are arranged there both below and above the printed sheets 2, 3 to be transported. In the case of vertical or inclined transport routes, as is the case, for example, in the upstream area of the second transport route 28 and in the downstream area of the third transport route 32, the conveyor elements 40, 40 ′ can be arranged laterally. In Fig. 3 For the sake of simplicity, the lower conveying elements 40 ′ were only shown in the third transport path 32. Similar conveyor elements 40, 40 'are also shown in FIG Fig. 7 and in Fig. 8 and partly in Fig. 2 shown. The conveyor elements 40, 40 'of the transport routes 5, 28, 32, 36 are driven at the same speed v _1-4 and have an in Fig. 7 and 8th common drive 41 shown. Of course, the transport routes 5, 28, 32, 36 can also have their own drives. In the Fig. 1 and in the Figures 4 to 6 In the third transport path 32, several deflection and / or tensioning rollers 42 are shown for their conveying elements 40, 40 ', which are not shown in detail in these figures. Similar deflection and / or tensioning rollers for the conveyor elements can of course also be arranged in the second transport path 28.

According to Fig. 4 the device 1 can also be operated in such a way that only first printed sheets 2 to be folded crosswise are used. Therefore, there is no discharge of unfolded second printed sheets 3 via the third transport path 32, that is to say it remains inactive. Based on an exemplary order with a sequence of partial book blocks with two, three and a first printed sheet 2 to be folded crosswise, FIG Fig. 4 from left to right the already transversely folded first printed sheets 2a ', 2a ", 2b', 2b", 2b "', a first printed sheet 2c' which has just been raised from the folding position in the direction of the folding rollers 12 by means of a compressed air blast 19 'in the middle of the sheet, and a further according to a subsequent order across folding first printed sheet 2d 'shown. In this operating mode of the device 1, whenever a first printed sheet 2 is in the folding position 25, a compressed air blast 19 'is triggered. As a result of the folding process, a first ejection gap 43, shown with a curly bracket, also arises between the cross-folded first printed sheets 2, which allows the two ejector switches 30, 37 to be switched on without problems, so that cross-folded first printed sheets 2 can be used for trial purposes or incorrect ones if necessary Specimens like the one in Fig. 4 shown, cross-folded first printed sheet 2x, 2z, can be ejected. The first printed sheets 2 that have not been ejected can in turn be further processed downstream of the device 1, for example into partial book blocks (not shown here).

Corresponding Fig. 5 This results in a further operating mode of the device in which all of the second printed sheets 3 provided for further processing, ie for example for the later formation of partial book blocks, also not shown here, ie the printed sheets 3a ', 3a ", 3b', 3b", 3b '"shown. , 3c ', 3d', 3d ", 3e ', 3e", bypass the folding rollers 12 and are therefore not folded. For this purpose, on the second printed sheet 3 located in the folding position 25, as with the illustrated second printed sheet 3e', the compressed air blast 19 'is suppressed, so that the second printed sheets 3 are thus conveyed through the third transport path 32. In this case, the second printed sheets 3 are transported virtually without gaps through the entire device 1. If necessary, however, e.g. be ejected, as has already happened in the case of the second printed sheet 3z located in the second receiving container 38. For example, by another, still on the third To remove the second printed sheet 3z located in the transport path 32 via the second discharge gate 37, a first printed sheet in front of this second printed sheet 3z and located in the folding position 25 was deflected twice by means of a compressed air blast 19 'in the direction of the folding rollers 12 and thus to the second transport path 28. In this way there is in the third transport path 32 and between the leading second printed sheet 3d ″ and the further second printed sheet to be ejected later into the second receiving container 38 3z a second discharge gap 44 has been formed. In Fig. 5 a first snapshot is shown, according to which this second discharge gap 44 in the third transport path 32 has already moved somewhat in the direction of the second route point 29. In Fig. 6 on the other hand, a later snapshot of the beginning of the ejection of the further, ejected second printed sheet 3z is shown after this has been previously detected at the further light barrier 7 'and the second ejection switch 37 has been switched accordingly. The second discharge gap 44 previously used to switch the second discharge switch 37 is already largely downstream of the second discharge switch 37 during this snapshot. The further second printed sheets 3e ', 3e ", 3e"', 3f ', 3f ", 3g follow upstream 'and 3g ".

According to Fig. 5 The first printed sheet 2x located on the second transport path 28 and used to enable the second discharge switch 37 to be switched and thus to discharge the further second printed sheet 3z was previously folded transversely between the folding rollers 12. However, since this first printed sheet 2x will not become part of the later partial book blocks and is therefore intended to be discharged into the first receiving container 31, it can be folded transversely at any point. The switching of the first ejection switch 30 after the first printed sheet 2x has been detected by the further light barrier 7 'also proves to be unproblematic, because no further first printed sheet 2 immediately precedes the first printed sheet 2x. Fig. 6 shows the ejected first printed sheet 2x already located in the first receiving container 31. By triggering the compressed air blast 19 'on the first printed sheet 2x earlier, ie before it reaches its folding position 25, this first printed sheet 2x can also be deflected towards the folding rollers 12 in such a way that it passes through these unfolded and can advantageously be used again later. When starting up or switching off the device 1 or a digital printing press upstream of it, such a first printed sheet 2x belongs to waste anyway and is thus disposed of from the first receptacle 31.

In a second embodiment ( Fig. 7 , Fig. 8 ) of the device 1 closes downstream of the fourth transport path 36, a fifth transport path 45 at a distance from this, on which the printed sheets 2, 3 are fed to a downstream device (not shown) for further processing, for example a device for forming partial book blocks 4a, 4b, 4c, 4d etc. As in Fig. 7 shown, the printed sheets 2a ″ and 2b 'are currently being conveyed on the fifth transport path 45. The fifth transport path 45 also has conveyor elements 40, 40', which, however, compared to the common drive 41 of the transport paths 5, 28, 32, 36 via a separate Drive 46. Due to this separate drive 46, the fifth transport path 45 can be operated at a speed v ₅ , which differs from the speed v _{1-4 of} the other four transport paths 5, 28, 32, 36.

For example, the speed v _{5 is selected to} be lower than the speed v _1-4 if there are partial gaps, such as the one in Fig. 7 The partial gap 39b shown between the two successive transversely folded first printed sheets 2b "and 2c 'should be minimized. This also applies to the minimization of residual gaps of the previous partial gaps 39a, 39b. A first residual gap 39a' is, for example, downstream of the straight ahead generated gap 39 between the transversely folded first printed sheet 2c 'and 2c "introduced, unfolded second printed sheet 3c and such a forming second residual gap 39b' can be seen downstream of the transversely folded first printed sheet 2c". A further second residual gap 39b 'is located in the downstream Area of the fourth transport path 36. Of course, depending on the further processing taking place downstream of the device 1, the speed v ₅ can also be greater than the speed v _1-4 , for example when in the device 1 according to FIG Fig. 5 and Fig. 6 only unfolded second printed sheets 3 are guided over the third transport path 32, and if corresponding gaps between the second printed sheets 3 are required for further processing.

When transferring a printed sheet 2, 3 from the fourth transport path 36 to the fifth transport path 45, as in FIG Fig. 7 of the unfolded second printed sheet 3b, it is initially transported by the conveyor elements 40, 40 'of the fourth transport path 36 until it no longer passes through at its rear edge this conveyor elements 40, 40 'is clamped. Fig. 7 shows exactly the subsequent moment in which the front edge 3 'of the unfolded second printed sheet 3b is clamped for the first time by the conveyor elements 40, 40' of the fifth transport path 45 and its transport is taken over by the fifth transport path 45. The fifth transport path 45 thus begins at a third route point 47 spaced from the fourth transport path 36, at which a printed sheet 2, 3 first receives a conveying pulse from the fifth transport path 45. Since the respective printed sheet 2, 3 is always only between the Conveying elements 40, 40 'one of the two transport routes 36, 45 is clamped, compression, creasing or even destruction of this printed sheet 2, 3 can be effectively avoided.

Because the size of a distance 48 existing between the two transport routes 36, 45 is therefore decisive for the correct transfer of the respective printed sheet 2, 3 and because, depending on the production order, printed sheets 2, 3 of different formats can be processed, at least one of the two transport routes 36, 45, but both are advantageously provided with an adjusting element 49 for changing this distance 48. The adjusting element or elements 49 can be operated manually or advantageously by a motor.

Fig. 8 shows one opposite the Fig. 7 somewhat later snapshot, in which now the transversely folded first printed sheet 2b "following the unfolded second printed sheet 3b" has just been released by the conveyor elements 40, 40 'of the fourth transport path 36 and at its leading edge at the third point 47 on the route with the conveyor elements 40, 40' the fifth transport path 45 has been clamped. The first transversely folded printed sheet 2b ″ is now transferred to the fifth transport path 45 and the further transport takes place with its conveyor elements 40, 40 '.

Due to the lower speed v _{5 of} the fifth transport path 45 compared to the speed v _{1-4 of} the transport lines 5, 28, 32, 36, the speed in FIG Fig. 7 between the signature 3b and 2b "in the downstream area of the fourth Transport path 36 still existing second remaining gap 39b 'in Fig. 8 already been minimized. Since the speed v _{5 of} the first printed sheet 2b "now conveyed on the fifth transport path is also lower than the speed of the subsequent printed sheet 2c ', which is still conveyed on the fourth transport path 36, the second partial gap, which has meanwhile been transported into the downstream area of the fourth transport path 36 39b between these first printed sheets 2b ", 2c 'will soon be minimized. This later also applies analogously to the two remaining gaps 39a ', 39b' and to all subsequent gaps between the printed sheets.

Triggered by the control device 23, the separate drive 46 can be operated at different speeds, so that successively different speeds v _{5 of} the fifth transport path 45 can be realized. In this way, the remaining gaps between the printed sheets 2, 3 conveyed on the fifth transport path 45 can be given a uniform length if necessary.

Of course, the connection of the control unit 23 of the device 1 with the control elements 24, 26, 27 of the transverse folding device 6, with the light barriers 7, 7 ', with the image capturing device 8, with the two Diverters 30, 37 and also with the drives 41, 46 of the transport routes 5, 28, 32, 36, 45 can also be wireless. Of course, further sensors, drives or devices, such as the device 33 for length adjustment, can also be connected to the control unit 23, as shown in FIG Fig. 1 is shown with a dashed line.

Claims (20)

1. Apparatus for selectively cross-folding sequentially printed sheets (2, 3) following one another, comprising

   • a first transport segment (5), on which printed sheets (2, 3) transported one after another in a guide plane (9) are providable in a folding position (25),

   • at least two folding rolls (12), which are arranged on a first side (11) of the guide plane (9), each have an axis of rotation (13) and form between them a folding gap (14) for first printed sheets (2) to be cross-folded, and the axes of rotation (13) of which are aligned both substantially parallel to each other and also substantially parallel to the guide plane (9),

   • a compressed air device (17) which is oriented substantially parallel to the axes of rotation (13) of the folding rolls (12), is arranged on a second side (16) of the guide plane (9), opposite the first side (11) of the guide plane (9), and is arranged in the region of the folding gap (14), which is connected to a compressed air source (21) and to a control unit (23) and has at least one outlet opening (18) for compressed air (19) that is directed at the folding gap (14),

   • a second transport segment (28) for cross-folded first printed sheets (2) and a third transport segment (32) for unfolded second printed sheets (3), wherein the first, second and third transport segments (5, 28, 32) have a common first segment point (10), at which the first transport segment (5) ends and both the second transport segment (28) and the third transport segment (32) begin, and wherein the common first segment point (10) is located on a line of intersection (34) of the guide plane (9) and a folding plane (35) extending through the folding gap (14) and the at least one outlet opening (18) of the compressed air device (17),
   wherein

   • the compressed air device (17) has a first control element (24) connected to the control unit (23) for selectively triggering or suppressing a compressed air blast (19') from the at least one outlet opening (18) of the compressed air device (17) in such a way that, in each case starting from the folding position (25), a first printed sheet (2) is introductable into the second transport segment (28) to be folded or a second printed sheet (3) is introductable into the third transport segment (32) to bypass the folding, characterized in that

   • the third transport segment (32) opens into the second transport segment (28) downstream of the folding rolls (12) at a common second segment point (29),

   • a fourth transport segment (36) follows downstream of the common second segment point (29), and

   • the third transport segment (32) is longer than the second transport segment (28) or is operable more slowly than the second transport segment (28) in such a way that a first sequence of the printed sheets (2, 3) following one another on the first transport segment (5) is the same as a second sequence of the printed sheets (2, 3) following one another on the fourth transport segment (36).
2. Apparatus according to Claim 1, characterized in that the third transport segment (32) is substantially longer than the second transport segment (28) by half a sheet length (2") of a first printed sheet (2) to be cross-folded.
3. Apparatus according to Claim 1 or 2, characterized in that a device (33) for adjusting the length of the third transport segment (32) is arranged in the region of the third transport segment (32).
4. Apparatus according to one of Claims 1 to 3, characterized in that a light barrier (7) and/or an image-acquiring device (8) for detecting a leading edge (2', 3') of a printed sheet (2, 3) transported on the first transport segment (5) is arranged in the region of the first transport segment (5) and is connected to the control unit (23).
5. Apparatus according to one of Claims 1 to 4, characterized in that a first diverter (30) is arranged in the second transport segment (28), and a first receiving container (31) for first printed sheets (2) is arranged downstream of the first diverter (30).
6. Apparatus according to one of Claims 1 to 5, characterized in that the folding rolls (12) are arranged above and the compressed air device (17) below the guide plane (9).
7. Apparatus according to one of Claims 1 to 6, characterized in that a second diverter (37) is arranged in the fourth transport segment (36), and a second receiving container (38) for printed sheets (2, 3) is arranged downstream of the second diverter (37).
8. Apparatus according to one of Claims 1 to 7, characterized in that the first, second, third and fourth transport segments (5, 28, 32, 36) have a common drive (41), which is connected to the control unit (23).
9. Apparatus according to one of Claims 1 to 8, characterized in that a fifth transport segment (45) begins downstream of the fourth transport segment (36) and at a distance from the latter, and has a separate drive (46) which is connected to the control unit (23) and with which the fifth transport segment (45) is operable at a different speed from the fourth transport segment (36) and in particular more slowly than the fourth transport segment (36).
10. Apparatus according to Claim 9, characterized in that the fourth transport segment (36) and/or the fifth transport segment (45) has an actuating element (49) for adjusting a distance (48) between these two transport segments (36, 45).
11. Apparatus according to Claim 1 to 9, characterized in that it has at least one further control element (26, 27), connected to the compressed air source (21) and the control unit (23), for changing a cross-sectional area of the at least one outlet opening (18) of the compressed air device (17) and/or for changing a pressure of the compressed air (19) that can be supplied to this outlet opening (18).
12. Method for selectively cross folding sequentially printed sheets (2, 3) following one another, in which

    • at least a first printed sheet (2) and a second printed sheet (3) are conveyed one after the other in a guide plane (9) on a first transport segment (5) and are made available in a folding position (25),

    • the first printed sheet (2) that is made available is cross-folded on a folding line (15) on a first side (11) of the guide plane (9) in a folding gap (14) between at least two rotating folding rolls (12) each having an axis of rotation (13),

    • before the folding, starting from a second side (16) of the guide plane (9), opposite the first side (11), a compressed air blast (19') from at least one outlet opening (18) of a compressed air device (17) connected to a compressed air source (21) and to a control unit (23), directed at the first printed sheet (2) that is made available in the folding position (25), is triggered and the first printed sheet (2) that is made available is transported out of the guide plane (9) on a second transport segment (28) to the rotating folding rolls (12) under the action of the compressed air blast (19') and, after the folding, is transported onward on this second transport segment (28),

    • a compressed air blast (19') onto the second printed sheet (3) that is made available in the folding position (25) is suppressed, and the therefore unfolded second printed sheet (3) is introduced into a third transport segment (32),
    characterized in that

    • the unfolded second printed sheet (3) introduced into the third transport segment (32) is conveyed for a longer time on the third transport segment (32) than the cross-folded first printed sheet (2) conveyed on the second transport segment (28), and

    • the unfolded second printed sheet (3) is introduced into a fourth transport segment (36) following the second transport segment (28) after the cross-folded first printed sheet (2) in such a way that the sequence of the printed sheets (2, 3) following one another on the first transport segment (5) is re-established.
13. Method according to Claim 12, characterized in that the third transport segment (32) has a length which is changed appropriately in the event of a following working job having printed sheets (2, 3) which have at least a different format as compared with the preceding working job.
14. Method according to either of Claims 12 and 13, characterized in that a leading edge (2', 3') of a printed sheet (2, 3) transported on the first transport segment (5) is detected automatically, on the basis thereof, appropriate information is forwarded to the control unit (23), the control unit (23) generates a corresponding pulse at the time of the selective triggering or suppression of a compressed air blast (19') from the at least one outlet opening (18) of the compressed air device (17) onto the printed sheet (2, 3) temporarily made available in the folding position (25), and forwards this pulse to a first control element (24) connected to the compressed air source (21) and the compressed air device (17).
15. Method according to one of Claims 12 to 14, characterized in that first printed sheets (2) are removed from the second transport segment (28) for control purposes.
16. Method according to one of Claims 12 to 15, characterized in that defective first and/or second printed sheets (2, 3) are removed from the fourth transport segment (36).
17. Method according to one of Claims 12 to 16, characterized in that downstream of the fourth transport segment (36), the printed sheets (2, 3) are transferred to a fifth transport segment (45) driven separately and arranged at a distance from the fourth transport segment (36), on which the printed sheets (2, 3) are conveyed at a different speed from that on the fourth transport segment (36) and in particular more slowly than on the fourth transport segment (36).
18. Method according to Claim 17, characterized in that in the event of a following working job in which at least one printed sheet (2, 3) has a different format as compared with the preceding working job, a distance (48) between the fourth transport segment (36) and the fifth transport segment (45) is changed accordingly.
19. Method according to one of Claims 12 to 18, characterized in that in the second transport segment (28), when forwarding an unfolded second printed sheet (3) into the third transport segment (32), a first partial gap (39a) is produced upstream of a folded first printed sheet (2), in that during the folding operation of a further first printed sheet (2) belonging to the same working job, a second partial gap (39b) is produced downstream of this further first printed sheet (2) and adjacent to the first partial gap (39a), in that the two partial gaps (39a, 39b) jointly form an insertion gap (39), in which the unfolded second printed sheet (3) conveyed on the third transport segment (32) is introduced between the folded first printed sheet (2) and the further folded first printed sheet (2) again in the region of the fourth transport segment (36).
20. Method according to Claim 19, characterized in that a first printed sheet (2) having a first sheet length (2"), a second printed sheet (3) having a second sheet length (3") and a further first printed sheet (2) having a first sheet length (2") are made available one after another in the folding position (25), and in that in the case of printed sheets (2, 3) of the same working job, the first sheet length (2") is substantially twice as large as the second sheet length (3").

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