EP1857390B1 - Collecting device - Google Patents

Description

The present invention relates to a collecting device according to the preamble of claim 1.

Collection devices which fix a plurality of supplied sheets successively on a rotating rotary body and thereby form a sheet stack, for example, from EP-A 1 471 022 , of the US-A 2002/0074716 , of the DE 763 627 or the DE 620 892 known. All collecting devices are intended to fix the sheets on the one hand and align them register-accurate on the other hand. The known collection devices have to holding and stop elements, which are arranged on the outer surface of the rotary body. The stop elements form a radially outwardly projecting from the outer surface mechanical stop on which the leading edge of a newly arriving bow is aligned. The holding elements fix the sheet (s) mechanically by clamping. In the collecting device according to DE 763 627 or DE 620 892 There are two types of grippers that perform the stop / hold function. EP-A 1 471 022 uses only one type of gripper. The identical grippers are divided into two groups, which functionally alternate as stop or holding elements.

A disadvantage of the known devices are the predetermined by the mechanical stop and holding elements receiving positions for the sheets on the circumference of the rotary body. By these defined receiving positions, on the one hand, the setup of the collecting device is complicated, because a sheet must be fed so that its leading edge meets the stop. Furthermore, these collection devices are inflexible because they only have a fixed picking position. The recording of multiple sheets at different recording positions and thus the simultaneous formation of multiple sheet stacks with shorter formats (multiple uses), switching from single to multiple use or staggered recording of sheets is not possible.

It is known to hold together already finished paper stacks or already superimposed paper webs by electrostatic charging in order to be able to process them more easily, see, for example CH 659 035 , Furthermore, it is known to stack the latter by utilizing the electrostatic forces of electrostatically charged flat workpieces ( DE-A-28 40 915 ).

A generic collecting device with the features of the preamble of claim 1 is in the EP-A-1 464 603 described.

The invention has for its object to provide a collecting device available that allows the collection of sheets at previously unspecified recording positions and thus the flexible processing of different formats.

This object is achieved by a collecting device with the features of claim 1. The method for operating the collecting device according to the invention is characterized by the features of claim 5. Advantageous developments of the invention will become apparent from the dependent claims, the description and the drawings.

The collecting device according to the invention comprises, in a manner known per se, a supply device for sheets, a rotary body rotatably mounted about an axis, a drive with which the rotary body is set in rotation, and a device for generating a holding force for fixing at least two sheets in the form of a Sheet pile on the outer surface of the rotating body, and a control device. In contrast to the prior art, the device for generating a holding force is not arranged on the rotary body, but comprises an electrode arrangement which has at least one electrode arranged at a distance from the rotary body and radially outside the outer surface of the rotary body. It generates waiving with the rotary body co-moving mechanical holding means a sheet stack on the rotary body fixing holding force. The rotary body and the feeding device are driven synchronized so that the sheets are recorded in register or with a predetermined offset. For this purpose, the control device is able to change the rotation of the rotating body and / or the feed speed of the feed device such that the incoming sheet is fixed flush with or omitted at a predetermined distance to optionally already fixed sheets waiving with the rotating body mitbewegte mechanical stop means. In this way, one or more sheet stacks can be formed on the outer surface of the rotary body, which sheets may comprise in any arrangement relative to each other. Also, two or more partially overlapping sheets are referred to as "sheet stacks" below.

The above-mentioned device for generating a holding force is not moved in contrast to the prior art and is located outside of the rotating body. In addition to the rotary body, which may be involved in the generation of the holding force, only radially spaced from the outer surface device parts are present. The holding force is not only punctually and temporally clocked by acting on the front edge holding elements, but preferably temporally continuous and exercised over part or all of the surface of the sheet. The holding force acting on a sheet is thus substantially independent of the rotational position of the rotating body despite stationary arranged device for their generation. As a result, there are no predetermined receiving positions along the outer surface of the rotating body.

• Der Umfang des Drehkörpers kann flexibel zur Aufnahme von Bögen genutzt werden. Wenn die Formatlänge beispielsweise weniger als die Hälfte des Umfangs beträgt, können mehrere Bogenstapel zeitgleich gebildet werden. Die Umstellung von Einfach- auf Mehrfachnutzen ist ohne mechanischen Eingriff möglich. Hierzu muss lediglich die Steuerung angepasst werden.
• Die Aufnahme von Bögen unterschiedlichen Formats und ihre Ausrichtung in flexibler Weise relativ zueinander ist möglich, z.B. Ausrichtung eines Bogens an der vorderkante und des nächsten Bogens an der Hinterkante eines bereits abgelegten ersten Bogens.
• Indem sich die Haltekraft über einen Teil oder den gesamten Bogen verteilt, wird der Bogen punktuell weniger belastet.
• Kompliziertes zeitlich getaktetes Ansteuern von Haltemitteln entfällt.

The following advantages are associated with this construction:

• The circumference of the rotating body can be flexibly used to accommodate bows. For example, if the format length is less than half the circumference, multiple sets of sheets may be formed at the same time. The conversion from single to multiple benefits is possible without mechanical intervention. For this purpose, only the controller needs to be adjusted.
• The recording of sheets of different format and their orientation in a flexible manner relative to each other is possible, for example, alignment of a sheet on the leading edge and the next sheet at the trailing edge of a first bow already stored.
• By distributing the holding force over part or all of the arc, the arc is selectively less stressed.
• Complex timed actuation of holding means is eliminated.

The holding force for fixing the sheets or the sheet pile is based on electrostatic charging of the incoming sheets. In electrostatic charging, the two surfaces of the arc will be understood to have opposite polarity charges. By attracting these charges, the arcs are fixed to each other and to the outer surface of the rotating body. This is particularly suitable for paper sheets or sheets of another electrically insulating material. The charging can be effected by a pair of electrodes arranged above and below the sheet plane in the region of the feed device. However, a particularly good holding effect results when the rotary body, which is electrically conductive thereto at least on the outer surface, as a counter electrode to the outside of the rotary body arranged electrode, e.g. a tip electrode is used, in particular grounded.

The drive of the feeder and the drive of the rotary body are preferably in a master-slave relationship to each other. The rotating body rotates continuously and unregulated at a predetermined speed until a first sheet is picked up. The feeding of a sheet by means of the feed device is communicated to the control device by means of a preferably optical detection device, for example a light barrier. This detects the leading or trailing edge of a sheet or arranged on the sheet register mark and transmits the controller a corresponding control signal. The control device, preferably the rotational position of the rotary body continuously can detect the rotational position at the time of arrival of the control signal. From this and from the known rotational speed, the position of the first sheet is determined on its recording on the rotary body, for example, the rotational position upon arrival of the leading edge on the outer surface of the rotating body. An appropriate size is stored as a target rotational position, which must be taken again on arrival of another sheet. Upon detection of another sheet by the detection device, the rotational position of the rotary body is also registered and a correction variable determined, by means of which the rotational speed is adjusted so that the rotational position when receiving the other sheet, for example, on arrival of the leading edge on the outer surface of the target rotational position equivalent.

The roles of the two drives can be reversed in principle, i. the rotary body (master) can be driven at a predefined speed and the feeder (slave) readjusted.

Instead of a detection device generating a control signal, which notifies the control device of the arrival of an arc, a trigger signal of an upstream unit, e.g. a printer or a cutting device. If there is a fixed relationship between the time of this trigger signal and the time of recording on the rotary body, the target rotational position can also be determined from such a trigger signal.

The collection device according to the invention can be particularly advantageous in connection with the production of digital newspapers "on demand", ie in Insert small pads. Here, the belonging to a newspaper sheets are printed in series with a digital press. A first newspaper with a first format is often followed by a second newspaper of a different format. The newspapers may also contain "have" bows or supplements in another format. The collecting device allows a quasi-instantaneous, purely control-technical switching between different format lengths from one newspaper to the next or within the same newspaper.

Fig. 1

eine Sammelvorrichtung und eine vorgelagerte Querschneidevorrichtung beim Sammeln von einem Bogenstapel am Umfang des Drehkörpers;

Fig. 2

die Sammelvorrichtung aus Fig. 1 beim Sammeln von jeweils zwei Bogenstapeln am Umfang des Drehkörpers.

An example of a collecting device according to the invention is shown in the drawings and described below. It shows purely schematically:

Fig. 1

a collecting device and an upstream cross-cutting device when collecting a stack of sheets on the circumference of the rotary body;

Fig. 2

the collection device Fig. 1 when collecting two sheet stacks on the circumference of the rotating body.

The collecting device 10 according to the invention comprises a feed device 12 and a rotary body 14 rotatable about an axis A in the form of a cylinder or a drum. In Fig. 1 For example, the formation of a sheet stack 34 from individual sheets 30 is shown (single use) while FIG Fig. 2 the simultaneous formation of two sheet stacks 34, 35 of sheets 30, 31 shows (multiple benefits). The collecting device 10 is the same in both cases, in Fig. 2 However, for reasons of clarity, individual elements are omitted.

The structure of the collector 10 will be described below.

In the present case, the feed device 12 comprises a plurality of conveyor roller pairs 13, which are moved by a drive 22 in order to move an incoming sheet 30, 31 with a feed speed v _z to the rotary body 14 in a horizontal feed plane E in the conveying direction F. The Zuförderebene E runs here tangentially to the cylinder jacket or to the outer surface 16 of the rotary body 14, but also a curved feed is conceivable. As the receiving area 46 of that region is referred to, in which the Zuförderebene E strikes the outer surface 16 of the rotating body 14 and minimally approaches, here the area around the uppermost point of the rotating body fourteenth

Another drive 18 is provided to enable the rotary body 14 in rotation. The peripheral speed v _u on the outer surface 16 of the rotary body 14 is present in the limits of the control range approximately equal to the feed rate v _z .

The outer surface 16 of the rotary body 14 according to the invention has no radially outwardly projecting mechanical elements. Thus, there is no mechanical element arranged on the rotary body 14 within that spatial region 42 which is swept by a sheet 30, 31 or sheet stack 34, 35 resting against the outer surface 16 during rotation of the rotary body 14. This space area 42 has the shape of a cylinder with an annular base. The outer surface 16 is understood to be that surface to which the sheet 30, 31 or sheet stack 34, 35 applies during operation. It can also be broken, for example consist of several segments.

In the present case, a device for generating a holding force 23 comprises an electrode or electrode arrangement 24, which is arranged radially outside the rotary body 14. It is located at a distance d above the rotary body 14. Between the rotary body 14 and the electrode 24, a conveying gap 44 is formed. The distance d is approximately between 20 and 40 mm.

The electrode 24 is constantly connected to a high voltage source 25, while the rotary body 14 is grounded and acts as a counter electrode. There is a DC voltage of about 10 to 30 kV. Preferably, a tip electrode device is used, which has a plurality of sharp-pointed expiring individual electrodes, which are arranged transversely to the feed direction F.

In the feed direction F in front of the rotary body 14 is a detecting means 28 for scanning the leading edge 32 of a sheet or other sheet features, e.g. of printed register marks. The detection means is preferably an optical sensor, e.g. a photocell.

For discharging a sheet stack 34, 35, a mechanical switch 27 is provided, which can be retracted from the outside into the space area 42 described above, to peel the sheet stack 34, 35 from the outer surface 16 of the rotary body 14. The inactive position of the switch 27 is represented here by solid lines, the active position by dashed lines. For conveying away the sheet stack 34, 35 is a Wegfördereinrichtung 26, which is designed, for example, analogous to the feed device with driven conveyor roller pairs 26 '. As an alternative, the switch can also within the Outer surface 16 preferably be arranged stationary so that they can enter from inside into the space area 42 and the sheet stack 34, 35 can lift off, whereupon this is taken over by the Wegfördereinrichtung 26.

A control device 20 controls the drives 18, 22 of the rotary body 14 or the feed device 12 and receives signals S1, S2 from the detection device 28 or from the drive 18 of the rotary body 14.

The collecting device 10 is preceded by a preceding module 40, by means of which the sheets 30, 31 or the still undivided material web are conveyed to the feed device 12 at a speed v _p . It is also a drive 41 is provided. The predecessor module 40 is here a cross-cutting device which separates a continuous material web into individual sheets 30, 31.

The collector 10 works as follows:

The sheets 30, 31 are conveyed in the feeder 12 at a feed speed v _z . The control device 20 outputs to a corresponding control signal to the drive 22. Likewise, the control device 20, the peripheral speed v _{u of} the rotary body 14 by a corresponding control signal to the drive 18 before. The peripheral speed v _u corresponds to the feed speed v _z .

In order to produce a gap 38 between the sheets 30, 31 conveyed without gaps or even as a continuous web in the predecessor module 40, the feed rate v _z is greater than the speed v _p in the preceding module 40 by the ratio gap length 1 to arc length L. The gap length becomes 1 adapted to the bow length L chosen that arc length L plus gap length 1 corresponds to the circumference of the rotary body 14 ( Fig. 1 ). When collecting multiple benefits ( Fig. 2 ), the sum of n arcs plus n gaps corresponds to the circumference of the rotary body. The speed ratio v _z to v _p calculated in this way is set electronically via the control device 20, the predecessor module 40 specifying the speed v _p . A corresponding feed signal is forwarded digitally to the control device 20. The drive 41 of the predecessor module 40 and the drive 22 of the feed device 12 are therefore coupled together via an electronic transmission, so that the transmission ratio is variable. If sheets of different length L are to be collected in a common stack 34, 35, the feed rate v _z and thus also the peripheral speed v _{u is changed} during collection. Thus, for example, after a bend 30, 31 with a shorter arc length L, a larger gap 38 must be created by increasing v _z and v _u , so that the leading edge 32 of a following signature comes to rest on the stack 34, 35 in register. The control device 20 evaluates trigger signals from the predecessor module 40, with which the sheet length L or the cutting operations are displayed.

The rotary body 14 is continuously driven, unregulated until receiving a first sheet 30. As soon as the leading edge 32 of a first sheet 30 conveyed by the feed device 12 is detected by the detection device 28, the detection device 28 transmits a signal S1 to the control device 20. The sheet 30 is meanwhile conveyed further and strikes the rotary body 14 in the receiving region 46 Area is present Also, the electrode 24. With the electrode, first the leading edge 32 and the further rotation of the rotary body 14 of the entire sheet 30 is electrostatically charged and thus fixed to the rotary body 14. The rotational position when picking up a first sheet 30 is arbitrary, since there are no predetermined by mechanical elements recording positions. For synchronization of subsequent sheets 30, the control device 20 is able to determine the rotational position when recording a first sheet or a proportional size to save as a target rotational position and the drives 18 and 22 to influence such that the target rotational position even on arrival another sheet 30 is taken again. The control device 20 therefore acts as a position controller for the rotary body 14.

The control device 20 receives to continuously or on request signals S2 from the drive 18 of the rotary body 14, from which the current rotational position with respect to a predetermined reference position can be closed. From the signal S2, which was transmitted or interrogated at the time of the input of the signal S1, the control unit 20 can determine the rotational position of the rotary body 14 upon impact of the leading edge 32 on the rotary body 14 or arrival of the leading edge 32 in the receiving area 46. This is possible since the peripheral speed v _u or rotational frequency of the rotary body 14, the feed speed v _z and the distance b of the detection device 28 from the receiving area 46 are known.

The rotational position determined in this way when a first sheet strikes or a signal directly linked thereto is stored as a desired rotational position by the control device.

When scanning the leading edge 32 of another sheet 30, a signal S1 is also transmitted to the control device 20 by the detection device 28 and the current rotational position is determined by the drive 18 by signal S2. From this, the uncorrected rotational position can be determined on the expected rotational moment of the front edge 32 on the rotary body 14 (actual rotational position). By comparing the actual rotational position with the target rotational position, a correction variable K is determined and transmitted to the drive. This correction variable K indicates the amount by which the circumferential or angular velocity of the rotary body 14 must be changed so that the position error is corrected until the leading edge 32 has reached the receiving region 46. Thus, the leading edge 32 of the sheet 30 is placed flush with the leading edge 36 of the stack 34.

For producing a sheet stack 34 according to Fig. 1 For example, the first sheet 30 is electrostatically fixed to the rotary body 14 and the following sheets 30 are respectively fixed to the preceding sheet 30. Since the rotary body 14 acts as a counter electrode, the electrostatic charge is refreshed with each revolution. It has been shown that at field strengths of 0.7 to 6.0 kV / m in the receiving area 46 sheet stacks 34, 35 can be easily fixed from 2 to 24 paper sheets (with a maximum of 40-65 g / m ² ).

The complete stack 34 is peeled off by means of the switch 27 connected to the gap from the rotary body 14 and fed to a successor module 26. This is the last Supplied sheet 30 of the stack 34 and immediately transported away with the completed stack 34.

For multiple benefits according to Fig. 2 Shorter sheets 30, 31 are generated, which are alternately assigned to one of the two stacks 34, 35. The control device 20 determines a plurality (here two) of the desired rotational positions and corrects the movement of the rotary body 14 accordingly so that the sheets 30, 31 are received flush with the leading edge 36, 37 of the stack 34, 35.

Furthermore, it is possible that the nominal rotational position is mathematically adjusted from sheet to sheet, e.g. to variably synchronize an additional sheet to the trailing edge or the center of an already recorded sheet.

Claims (6)

1. A gathering device (10) for collating sheets (30, 31), especially printed paper sheets, to form a sheet stack (34, 35), with

   - a revolving body (14) mounted and able to turn on an axis (A),

   - a drive unit (18) by which the revolving body (14) can be displaced in rotation,

   - a feed device (12) for feeding sheets (30, 31) to the revolving body (14),

   - a device (23) for generating a holding force to secure sheet stacks (34, 35) consisting of at least two sheets (30, 31) on the outer surface (16) of the revolving body (14), and

   - a control device (20), that is able to alter the rotation of the revolving body (14) and/or the feeding speed (v_z) of the feed device (12) so that the arriving sheet (30) is secured flush with or at a predetermined distance from sheets (30) which may already be secured,

   characterized in that

   - the gathering device comprises a detection device (28) connected to the control device, which detecting device (28) detects a leading or trailing edge (32) of a sheet (30) to be received and/or a register mark arranged on the sheet (30) and relays a corresponding signal (S1) to the control device (20),

   - the device (23) for generating a holding force comprises as well an arrangement of electrodes (24) having at least one electrode, arranged stationary at a distance (d) from the revolving body (14) and radially outside the outer surface (16) of the revolving body (14), as a voltage source (25) connected to the arrangement of electrodes (24), by means of which voltage source (25) an arriving sheet (30) is electrostatically charged to generate the holding force for securing the sheet stack (34, 35) at the revolving body (14), and

   the control device (20), continuously detecting the rotary position of the revolving body (14), determines, in dependence on a first signal (S1) of the detection device (28) concerning a first arriving sheet and a second signal (S2) corresponding to the instantaneous rotary position of the revolving body (14), a NOMINAL rotary position of the revolving body (14), and also determines, in dependence on a third signal of the detection device (28) concerning an additional arriving sheet (30), the simultaneously detected second signal (S2) and the previously determined NOMINAL rotary position, a correction quantity (K) and, by means of the correction quantity (K), acts on the drive unit (18) of the revolving body (14) and/or the feed device (12) in such a way that the revolving body (14) takes up the NOMINAL rotary position when receiving the additional sheet (30).
2. The gathering device as claimed in claim 1, characterized in that the revolving body (14) has an outer surface (16) in the form of a closed or interrupted cylinder envelope with no elements projecting radially outward from it.
3. The gathering device as claimed in claim 1, characterized in that the revolving body (14) acts as a counterelectrode, with preferably at least the outer surface (16) of the revolving body (14) being electrically conductive and the revolving body (14) being preferably grounded.
4. The gathering device as claimed in claim 3, characterized in that the electric field strength at the outer surface (16) of the revolving body (14) in the region of the arrangement of electrodes (24) is at least 0.6 V/m, preferably between 0.6 and 7.0 kV/m.
5. A method for operating a gathering device as claimed in one of the claims 1 to 4, characterized in that

   - the device (23) for generating a holding force is operated continuously;

   - the revolving body (14) and the feed device (12) are driven continuously;

   - the control device (20) actuates the drive unit (18) of the revolving body (14) and the feed device (12) in a coordinated manner, so that an arriving sheet (30) is secured flush with or at a predetermined distance from sheets (30) which may already be secured.
6. The method as claimed in claim 5, characterized in that the feed device (12) is driven at a given speed (v_z) and the revolving body (14) at a speed (v_u) adapted to that, but able to vary within certain ranges.

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