TECHNICAL FIELD

The present invention refers to a method of producing printed products by means of digital printing and subsequent binding and an interface between a digital printer and a binding unit able to implement this method.

BACKGROUND ART

Digital printing is becoming increasingly widespread in the publishing world. Thanks to the ease of production, transmission and filing of text and images in electronic format and to the absence of minimum run limits, digital printing enables the demands of an ever-growing public, both professional and lay, to be satisfied.

With regard to the lay public, the use of digital printing services oyer the Internet for printing photographs, photograph albums, calendars and even actual books, is now quite common; in the professional sphere, digital printing enables the printing of books on demand, avoiding the costs connected with storing copies of low-demand books and various types of printed products such as brochures, booklets, etc.

In general, a printed product is made by digitally printing a plurality of sheets and subsequently binding these sheets by various binding techniques (e.g., bookbinding, booklet stapling, etc . ) .

The jobs produced by the printers are collected and transported by hand to the binding machine. The handling of the jobs is therefore entrusted to the precision and reliability of personnel and is subject to inevitable errors. Even just accidentally dropping a job can change the order of the pages and crease or dirty one or more pages. It should be noted that in the case of digital printing, each print job is "unique". Unlike high-run printing techniques, where the individual pages or signatures are repeatedly printed and therefore a certain reject percentage is permitted, in the case of digital printing each job is composed by an ordered succession of pages and therefore any error results in rejection of the entire job.

Up to now, the problem of creating an "industrial" type of interface between one or more digital printers and the binding machines has not been resolved.

Spiral band storage devices for printed products are known in the art. An example of a device of this type is described in United States Patent 4,684,118 and consists of a band wound in a spiral on a drum in a manner such that the printed products can be restrained between two successive spires of the band. Rotation of the drum causes the winding or unwinding of the band on the drum itself and, in consequence, the storage or release of the printed products.

Devices of the above-mentioned type are normally used as accumulation "reservoirs" for rotary presses, to compensate the different production rates of two successive process units on a production line. These devices are therefore typically used for temporarily storing pages or signatures that are all the same, and are not able to handle the variety of printed products associated with digital printers.

DISCLOSURE OF INVENTION

The object of the present invention is to create a method of producing printed products by means of digital printing and subsequent binding that resolves the above-described problems related to the known art.

The aforementioned object is achieved by a method according to claim 1.

A further object of the present invention is to create an interface unit between a digital printer and a binding device for embodying said method.

This object is achieved by a unit according to claim 6. BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, a preferred embodiment will now described by way of non-limited example and with reference to the attached drawings, where: Figure 1 is a schematic side view of an input unit of a storage device of an interface unit according to a first embodiment of present invention, where the input unit is associated with a digital printer;

Figure 2 is a schematic top view of the input unit and storage device in Figure 1;

Figure 3 is a schematic side view of the storage device and an output unit of the interface unit of the present invention; Figure 4 is a schematic top view of the storage device and the output unit in Figure 3;

Figure 5 and Figure 6 are similar views to those in Figures 1 and 2 respectively, where a different embodiment of the input unit is shown;

Figures 7 and 8 are similar views to those in Figures 3 and 4 respectively, of an interface unit comprising a different embodiment of the output unit;

Figures 9 and 10 are similar views to those in Figures 3 and 4 respectively, of an interface unit using two storage devices in parallel; and

Figures 11 and 12 are similar views to those in Figures 9 and 10 respectively, of an interface unit with two storage devices in parallel and an output unit similar to that in Figures 7 and 8. BEST MODE FOR CARRYING OUT THE INVENTION

With reference to Figures 1 to 4, reference numeral 1 indicates, as a whole, an interface unit for handling jobs between a digital printer 2 and a binding line 3 (partially shown) for the production of printed products. The binding line 3 can be more or less complex, and possibly consist of a single machine.

The unit 1 basically comprises an input unit 4 (Figures 1 and 2) suitable for being connected to an output of the digital printer 2, an output unit 5 (Figures 3 and 4) suitable for being connected to an input of the binding line 3 and a mobile storage device 6 suitable for temporarily storing the printout produced by the digital printer 2 and being selectively connected to the input unit 4 and to the output unit 5.

The digital printer 2, of a conventional type, is controlled by a computer, not shown, which is preferable connected to a network. The printer 2 is able to receive print commands from the computer for print job production. Each job is composed of a plurality of sheets 7, which can be printed on individual pages just on one side or front and back for the production of books, or multiple page or signature sheets for the production of booklets. The sheets are output by the digital printer 2 in a discrete succession, one after the other, in the conventional manner (Figures 1 and 2) .

The input unit 4, described in greater detail below, is able to arrange the sheets 7 in output from the printer in a "shingled" succession, where each sheet 7 is partially overlaid by the previous one. The input unit 4 comprises a gripper conveyor 8 basically composed of a pair of motorized gripper belts 8a and 8b, arranged side by side for taking the sheets 7 in output from the digital printer 2. The sheets 7 are kept in contact with the gripper belts 8a, 8b by conventional pinch rollers 9.

An optional processing unit is placed downstream of the gripper conveyor 8, for example, a creasing unit 10 able to perform creasing operations on the sheets 7 to facilitate possible subsequent folding operations.

An optical detector 11 is arranged above the gripper conveyor 8 that can comprise a camera for printout quality control, an optical code reader (bar-code or other type of code visible in white light or in the presence of radiation in a predetermined frequency outside the visible spectrum) for controlling or storing the sequence of sheets in arrival, and/or a photocell for detecting the arrival of sheets and activating the creasing unit 10. All of the aforesaid functions can be incorporated in a single video camera.

A sequencing unit 12 is placed after the creasing unit 10 with the purpose of transforming the discrete succession of sheets in output from the digital printer 2 into a shingled formation 13.

The sequencing unit 12 comprises a pair of motorized belts 14, placed side by side and arranged downstream of the creasing unit 10 so as to take the sheets 7 from the latter, and a pair of pinch rollers 15 able to keep the sheets 7 in contact with the belts 14. The belts 14 are operated at a lower speed than belts 8a and 8b so as to reduce the pitch between the sheets themselves and produce the shingled formation 13. Lastly, the input unit 4 comprises an output conveyor 16 comprising a pair of output belts 17, arranged in series with belts 14 and operated at the same speeds, preferably by a common motor 18.

The output belts 17 are carried on a horizontally pivoted support structure 19 and are wrapped on a drive roller 20 with its axis A adjacent to the sequencing unit 12 and on an idle roller 21 arranged on a portion 22 of the output conveyor 16 projecting from the structure of the input unit 4. The support structure 19 is hinged to the structure 23 of the input unit 4 such that it can turn around the axis A of the drive roller 20. A linear actuator 24 acts on the support structure 19 to vary the inclination of the structure itself by turning it around axis A, as shall be described more in detail further on.

The input unit 4 comprises a programmable control unit El, which is connected to the optical detector 11, the creasing unit 10, the motors of the gripper conveyor 8 and the sequencing unit 12, and to the linear actuator 24.

The control unit El can operate in a network or independently via autonomous data acquisition. In the first case, the control unit El acquires data regarding the job to be handled from a central computer, not shown, or from the printer 2, by means of a network connection. The passage of each sheet, the print quality and the correct sequence is checked by means of the optical detector 11.

In the second case, the control unit El acquires the data identifying the job from printing codes present on the sheets by means of the optical detector 11. The combination of the printing code and the number of sheets detected permits identification of the job. A combination of processing cycles previously stored in a memory unit is associated with each job.

The control unit El is able to control the processing unit based on the job to be performed and to control its execution.

The control unit El is also able to dialogue with the storage device 6 as shall be described in greater detail further on.

The storage device 6 comprises a substantially closed casing 25, except for a side opening 26 for loading/unloading, expediently mounted on wheels 27 to facilitate manoeuvring. An idler drum 28, rotating around a horizontal axis B and on which a band 29 is wrapped in a spiral, is mounted inside the casing 25. An end portion 30 of the band 29 is unwound from the drum 28, forming an open pocket 32 with the wrapped portion 31 of the band 29 in a direction substantially tangential to and facing the side opening 26, and is constrained to a roller 34 arranged beneath the drum 28 and driven by a motor 35.

The storage device 6 is equipped with its own control unit E2 dedicated to controlling the motor 35.

When the storage device 6 is connected to the input unit 4, the portion 22 projecting from the output conveyor 16 of the input unit 4 is housed in the opening 26. The linear actuator 24 acts on the support structure 19 so as to keep the output belts 17 substantially tangential to the wrapped portion 31 of the band 29, at the sides of the unwound portion 30. Therefore, when the input unit 4 feeds the sheets 7, they reach the pocket 32 and can be collected by the storage device 6 by rotation of the drum 28, driven in rotation in the anticlockwise direction with reference to Figure 1. The motorized roller 34 is made to turn in the opposite direction by the motor 35, which is controlled so as to keep the band 29 in tension. In this way, the band 29 unwinds from the roller 34 and winds onto the drum 28, and the sheets 7 are collected between two successive spires of the band 29.

Lastly, the storage device 6 is equipped with a memory 36 able to record the data regarding the jobs accumulated within it.

The memory 36 is able to receive identification data of said jobs from the control unit El of the input unit 4 when the storage device 6 is connected to it. This data can be transferred by means of a physical connection or by any wireless system, for example, via radio using RFID.

Figures 3 and 4 show the output unit 5, associated with a binding line 3, of which only an input station is shown.

The output unit 5 is structurally similar to the input unit 4, but has reverse functions and consequently has an inverted arrangement of the main units. Put very succinctly, the output unit 5 comprises, in cascade, an input conveyor 40 similar to output conveyor 16, an intermediate conveyor 41 similar to the sequencing unit 12 and an output conveyor similar to input conveyor 8.

More in detail, the input conveyor 40 comprises a pair of input belts 43 carried by a horizontally pivoted support structure 44, which are wound around a drive roller 45 with its axis C adjacent to the stop gate unit 41 and a driven roller 46 arranged on a portion 47 of the input conveyor 40 projecting beyond the structure 48 of the output unit 5 so that it can be inserted in the opening 26 of the storage device 6.

The support structure 44 is hinged to the structure 48 of the output unit 5 such that it can turn around the C axis of the drive roller 45. A linear actuator 49 acts on the support structure 44 to vary the inclination of the structure itself by turning it around axis C, in order to keep the input belts 43 in a substantially tangential position with respect to the wrapped portion 31 of the band 29 of the storage device 6, at the sides of the band 29.

The release of the sheets 7 from the storage device 6 to the input conveyor 40 takes place by operating the latter so that the drum 28 is rotated in the opposite direction to that of loading (but still in the anticlockwise direction with reference to Figure 3, as the storage device 6 is seen from the opposite side with respect to Figure 1) ; the roller 34 is turned in an opposite direction to that previously described (in clockwise direction with reference to Figure 3) so as to progressively unwind the band 29 from the drum 28, keeping it in tension.

The intermediate conveyor 41 comprises a pair of motorized belts 50, arranged side by side and downstream of the input conveyor 40 so as to take the sheets 7 from the latter, and a pair of pinch rollers 51 able to keep the sheets 7 in contact with the belts 50. The belts 50 are driven at the same lower speed as the belts 43 of the input conveyor so as to transport the sheets 7 whilst leaving the shingled formation unchanged. The output conveyor 42 comprises a pair of motorized output belts 54, arranged side by side, for taking the sheets 7 from the belts 50 of the intermediate conveyor 41. The feed speed of output belts 54 is opportunely greater than that of belts 50, so that the sheets 7 are separated, i.e. transformed from a shingled formation 13 to a succession of discrete sheets. The sheets 7 are kept in contact with output belts 50 by conventional pinch rollers 55.

An optical detector 56 is arranged above the output conveyor 42, for example an optical code reader (bar-code or other type of code visible in white light or in the presence of radiation in a predetermined frequency outside the visible spectrum) for controlling the sequence of the sheets in arrival and handling the subsequent operations. The output unit 5 comprises a control unit E3 connected to the optical detector 56, to the respective electric motors 52 and 53 of the intermediate conveyor 41 and the output conveyor 42 and to the linear actuator 49. The control unit E3 is also capable of dialoguing with the memory 36 of the storage device 6, once it is connected to the output unit 5, by means of a physical connection or by any wireless system, for example, via radio using RFID.

If the system works in a network, the control unit E3 acquires the data regarding the job to be handled from the central memory via a network connection. This data is compared with that received from the memory 36 of the storage device and with that received from the optical detector 56 during the passage of the sheets 7. It is then possible to check both the correct sequence of the jobs and the correct sequence of the pages within each job. The control unit E3 is also able to dialogue with the binding line 3 associated with the output unit 5, to which it can transmit data for adjusting process parameters. The same data can be sent to the central computer so that the latter can check consistency between the jobs stored in the storage device 6 and the machine or binding line, and generate permission signals for unloading jobs from the storage device 6 and the execution of subsequent operations .

Instead, if the control unit E3 operates independently, it acquires the identification data of the jobs present in the storage device 6 from the memory 36 of the storage device 6 and compares it with the data acquired in succession from the optical detector 56 on the passage of the sheets. In this case as well, the control unit E3 could be capable of interacting with the binding machine or line to adjust the processing parameters according to the specific job. The output unit 5 could include accessory modules. In the embodiment shown in Figures 3 and 4, the sheets 7 in output from the output conveyor 42 reach a lateral transfer table 57, having a platform of inclined rollers 58 and a lateral register square 59, and then a storage unit 60, forming part of the binding line 3 and constituting the input module of the line itself.

The storage unit 60 could comprise a programmable-translation belt conveyor 61 for forming piles 62 of sheets 7. The functioning of the interface unit 1, already partially evident from the foregoing, is as follows.

The storage device 6 is first connected to the input unit 5 associated with the digital printer 2.

The sheets 7 in output from the printer are arranged in a shingled formation 13 by the input unit 5 and fed in this way to the storage device 6, where they are loaded. This device therefore houses inside itself an ordered succession of print jobs.

Data regarding the content of the storage device 6 is stored in the memory 36 of the device itself as described above. Once the loading of the print jobs inside the storage device 6 is completed, the storage device 6 is removed from the input unit 4 and interfaced with the binding line 3 by means of the output unit 5. Before unloading the print jobs, it is possible to implement a control step where compatibility between the print jobs contained in the storage device 6, identified by reading the stored data, and the binding line 3 can be checked.

In the case where the storage device has been connected to a wrong binding line, the unloading of the print jobs can be inhibited.

Instead, if the binding line 3 is compatible with the print jobs contained in the storage device 6, they can be unloaded and, in the example shown, conveyed in the storage unit 60, from which they can be taken and processed in the binding unit 3 to make the finished printed products.

If all of the print jobs contained in the storage device 6 can be processed in the same unit 3, the device 6 will be completely unloaded and ready to acquire new jobs from the printer 2. Otherwise, the storage device 6 can be removed from the binding unit 3 and interfaced with another binding unit suitable for handling the remaining jobs.

In short, the interface unit 1 enables implementing a method of producing printed products comprising the steps of:

printing a plurality of jobs by means of at least one digital printer, each job corresponding to a printed product and being formed by one or more printed sheets;

arranging the jobs being output from the printer in a shingled formation of sheets;

loading the formation of printed sheets in a spiral band storage device;

- transferring the storage device containing the jobs to a binding unit;

unloading the jobs from the storage device; and

binding the jobs to form the respective printed products. Figures 5 and 6 show a second embodiment of the input unit 4 of the interface unit 1, which is only described regarding the differences from that shown in Figures 1 and 2 and previously described.

The input unit 4 in Figures 5 and 6 comprises a rotation device 65 able to turn the sheets 7 in input by a preset angle, for example 90°. The rotation device 65 comprises a stop 66 arranged at the side of one of the gripper belts 8a and able to interact with front edge of the sheets in input, in proximity to a corner of the sheets. The stop 66 is controlled by a linear actuator 67 with vertical travel that is mobile between a raised rest position and a lowered operative position. A ball pressure unit 68 keeps the sheet 7 in contact with the gripper belt 8a adjacent to the stop 66 to ensure feed and consequently rotation around the stop 66. For the rest, the input unit 4 is similar to that previously described.

Figures 7 and 8 show an output unit 5 equipped with an accessory folding module 70.

The module 70, arranged at the output of the lateral transfer table 57, has a folding saddle 71 defined by two slopes 72 converging in an upper edge 73 extending in the direction of transport of the sheets. A creasing wheel 74, equipped with a V groove complementary to the edge 73, cooperates with the latter to create a longitudinal fold 75 in the sheets 7 along a longitudinal median line. The fold in the sheets is made by means of a pair of shaped folding rods 76. The folded sheets 7 are laid on top of the saddle 71 and accumulate in a predetermined number. A step conveyor 77, equipped with a series of equidistant hooks 78 positioned close to one of the slopes 72, takes each set of sheets and makes it advance to the binding unit (not shown) , which can be a stapling station (for making magazines) or a stitching station (for making books) . Figures 9 and 10 show a multiple output unit 5, a double one in this specific case, or rather composed of a number (two in this specific case) of units 5a and 5b in parallel converging on a common table 57. The two groups 5a and 5b are fed by respective storage devices 6a and 6b, respectively containing sheets printed in black and white 7a and sheets printed in colour 7b arriving from respective digital printers. These sheets, extracted from the respective storage devices 6a and 6b according to a predetermined sequence, are combined and are laid on top of each other in a storage unit 60 similar to that described with reference to Figures 3 and 4.

Using two different printers for colour and for black and white it is possible to exploit the productivity of each printer to the maximum and compensate the different production rates (black and white printers are normally faster than colour ones) by means of the storage devices 6a and 6b.

The embodiment in Figures 11 and 12 comprises a double output unit 5, like that in Figures 9 and 10, and a folding module 70 as described with reference to Figures 7 and 8.

From examination of the characteristics of the interface units 1 described, the advantages that can be achieved with the present invention are evident.

First of all, the printed sheets in output from the printer are loaded in a storage device that ensures correct handling between the printer and the binding unit, avoiding possible errors and problems connected with manual handling.

The use of a storage device equipped with a memory able to store content data also enables checks and control able to be carried out to ensure that the jobs are sent to the correct binding unit. Accessory functions, such as the creasing or folding of the sheets, can be easily integrated into the input and output units of the interface unit.

Lastly, the "reservoir" function created by the storage device allows the different production rates of the printer and the binding line to be compensated, enabling maximum productivity to be achieved.

Finally, it is understood that changes or modifications may be made to the interface units described and illustrated herein without departing from the scope of protection defined by the claims .

For example, accessory operations (creasing, punching or cutting) can be carried out in the output unit 5 instead of in the input unit 4. This is particularly useful in the case where multiple printers 2 or binding lines 3 are used.