EP2602217B1 - Sheet feeder with two suction wheels - Google Patents

Description

The invention relates to a sheet feeder for separating sheets with the preamble features of claim 1.

State of the art

From a standing pocket folding machines are known. The construction of a Taschenfalzmaschine with a variety of Taschenfalzwerken goes out of the DE 10 2004 041 471 A1 out. A respective pocket folder consists of a folding pocket and three folding rollers, which are arranged in two pairs of folding rollers. Further sword folding machines are known. From the DE 29 40 360 A1 is a single sword folding machine for folding of printed and pre-folded sheet known. Combination folding machines combine pocket folders and knife folders. Here are folded in a first folding station in Taschenfalzwerken parallel breaks and in a subsequent folding station in Schwertfalzwerken cross breaks. The DE 10 2006 055 301 A1 shows Kombifalzmaschinen with a plurality of Taschenfalzwerken and nachranging arranged Schwertfalzwerken.

Sheet feeders known from the prior art for sheet-fed printing machines as well as so-called stackers for sheet-folding machines have a suction head with combined lifting / pulling suckers for separating and accelerating separated sheets. A disadvantage of such alternating systems is that the Schleppsauger performs a forward and backward movement, and only during the forward movement of an arc can be transported. During the backward movement as a return movement of the Schleppsaugers no bow can be transported, which thus represents a dead time. If the number of cycles of the sheet feeder to be increased, ie the performance of the sheet feeder are increased and more sheets are applied per unit time, the speed of the drag sucker unit must be increased in their forward and backward movement. The increase in the speed of Drag sucker unit is mechanically limited by the translational, alternating motion sequence.

In order to increase the output of folding machines, ie their productivity, the speed of passage of the sheets is usually increased by the folding machine. By increasing the speed, however, a respective folded sheet undergoes deformations and damage, which leads to conveyor errors and thus to significant loss of quality of the end products.

In the DE 10 2008 048 287 A1 a sheet feeder of a folding machine is described, which has in the region of the trailing edge of a sheet pile lifting and separating suction and in the front region of the stack a suction wheel. By adjusting the Saugradposition is thereby made possible to change the Unterschuppungsgrad the transported over a subsequent transport table to a subsequent Bogenfalzmaschine sheet. The shingled seaming enables higher folding rates without having to increase the bow speed accordingly, so that the quality of the signatures is not affected.

WO 2006/024295 A1 discloses a sheet feeder according to the preamble of claim 1. Objective The object of the present invention is to provide a sheet feeder which provides an increase in reliability regardless of the quality of the sheet material to be processed and an increase in performance (ie applied sheets per unit time) low cost means and low energy consumption allows. Another task is to allow a submerged installation of bow. This object is achieved by a sheet feeder with the features of claim 1. The sheet feeder according to the invention is used to separate sheets of paper, cardboard, plastic and the like from a stack and feeding the sheet in a sheet transport direction in a sheet transport plane to a subsequent, bow-processing Machine, for example a folding machine. Advantageously the sheet feeder - seen in the direction of sheet transport - first suction and a - seen in the sheet transport direction - second suction wheel, the first Saugrad above the stack and the second Saugrad - seen in the sheet transport direction - downstream of the stack and above or preferably below the sheet transport plane. The arrangement below the sheet transport plane is preferred, as well as a submerged system of sheets is made possible. The suction wheels are used for sucking and transporting the bow. Reset movements with dead times are not required. By using the suction wheels, which can be operated rotationally continuously, thus the performance of the sheet feeder, ie the working stroke of the sheet feeder, can be substantially increased.

In this application, a suction wheel is also understood to mean a suction wheel with a belt that circulates around a device for removing sheets from a stack, as shown in FIG DE 196 32 657 C1 and the DE 196 48 742 A1 is described.

The sheet feeder according to the invention has in the region of the trailing edge of the stack a separating device for lifting a respective uppermost sheet from the stack at the sheet trailing edge. The separation device may be a lifting suction device that is generally known to the person skilled in the art or particularly effective blower air nozzles.

According to the invention, the distance A of a rotation axis of the first suction wheel from the trailing edge of the stack is greater than the distance B or at least equal to the distance B of a rotation axis of the second suction wheel from the front edge of the stack, wherein the distances A, B are measured in each case in the horizontal. This ensures that a respective arc can be gripped by the second suction wheel in the region of the leading edge of the sheet before the first suction wheel releases the sheet in the region of its trailing edge. A respective arc can thus be transferred in a defined manner from the first suction wheel to the second suction wheel and thus transported safely.

According to the invention, at least one suction and conveying path is provided on the periphery of the first suction wheel, wherein the distance between the axis of rotation of the first suction wheel and the rear edge of the stack is approximately equal to the length of the at least one suction conveyor. and conveyor line corresponds. The suction and conveying section occupies only a part of the circumference, ie it does not extend over the entire circumference. Rather, a release path is provided in the remaining part of the circumference, which is not carried out suction and allows a transfer of the sheet to the second suction wheel. This ensures that the first suction wheel transported as far as the top sheet by the action of the suction and conveying path until the sheet leaves with its trailing edge the effective range of the suction and conveying path and the first suction a next, lying below the newly conveyed sheet Can suck in bow.

In a particularly advantageous and therefore preferred development of the sheet feeder according to the invention, during operation of the sheet feeder, the mean rotational speed of the second suction wheel is greater than the average rotational speed of the first suction wheel and the instantaneous rotational speed of the second suction wheel is always greater than the instantaneous rotational speed of the first suction wheel. This configuration advantageously makes it possible for a respective sheet to be reliably gripped and separated from the first suction wheel at a reduced speed and then subsequently accelerated by the second suction wheel to the speed of the sheet following the sheet feeder. In the limit case, the rotational speeds are at least the same size. For this example, a first drive for the first suction and a second drive for the second suction can be provided, either both drives are formed by servomotors, or wherein an electric motor and arranged between the electric motor and the respective suction gear can be provided.

In a first embodiment of the sheet feeder according to the invention this has a connected at least to the first Saugrad via lines vacuum generator for permanently applying the first Saugrads with a suction air in the operation of the sheet feeder.

In a second embodiment variant, the sheet feeder has a negative pressure generator connected at least to the first suction wheel via lines for clocking the first suction wheel with a suction air. It is particularly advantageous if at least the following three cycles are provided: sheet suction - sheet holding and transporting - sheet release or transfer. For this purpose, either a control valve connected via data lines to a machine control or a valve coupled to the rotational movement of the first suction wheel can be provided. In the former case, corresponding control rules are stored in the machine control.

In a further development of this variant, the sheet feeder has a machine control and a data line connected to the machine control servo motor for driving the first Saugrads, wherein the servo motor is so controlled and is controlled that this imprints the suction wheel only during the cycle "sheet holding" a rotational movement. In other words, during the cycle "sheet suction" and the clock "sheet release" performs the first suction through no rotational movement, so that there can be no relative movements between the first suction and arc when gripping and releasing the sheet and thus avoid marks on the sheet become.

In a further development of the embodiment of the sheet feeder with permanently sucking suction wheel, the sheet feeder has a drive connected to the first suction wheel for rotating the first suction wheel at a constant rotational speed. The control effort for this embodiment is significantly lower, so that this variant represents a particularly robust and stable solution.

In an advantageous development of a sheet feeder described above, this has in the region of the side edges of the stack arranged side edge blower for venting the stack with blown air, wherein a respective side edge blower has a rotatably mounted on an axis nozzle body having a plurality of multi-directionally aligned nozzles and an air duct connected to the nozzle body , In this context, multidirectionally oriented nozzles are understood to be nozzles whose blast air jets act in different and different directions. This ensures in an advantageous manner that at least one blown air jet in one approximately right angles to the side edge of the sheet pile meets, so unfolds effect, and thus contributes to the formation of an air cushion between the bow.

The invention also relates to a method for operating a sheet feeder as described above.

The described invention and the described advantageous developments of the invention are also in any combination with each other advantageous developments of the invention.

With regard to further advantages and constructive and functional aspects of advantageous embodiments of the invention, reference is made to the dependent claims and the description of embodiments with reference to the accompanying drawings.

embodiment

Fig. 1

einen erfindungsgemäßen Bogenanleger mit nachfolgender Falzmaschine

Fig. 2

eine Draufsicht auf den Bogenanleger

Fig. 3

einer Ansicht des Bogenanlegers

Fig. 4

den Seitenkantenbläser des Bogenanlegers in einer Detaildarstellung

Fig. 5

einen alternativen Bogenanleger

The invention will be explained in more detail with reference to preferred embodiments. It show in a schematic representation

Fig. 1

a sheet feeder according to the invention with subsequent folding machine

Fig. 2

a plan view of the sheet feeder

Fig. 3

a view of the sheet feeder

Fig. 4

the side edge blower of the sheet feeder in a detailed view

Fig. 5

an alternative sheet feeder

Corresponding elements and components are provided in the figures with the same reference numerals.

Fig. 1 shows a sheet feeder 10 according to the invention for separating sheets 1000 from a sheet stack 100 and feeding the separated sheets 1000 via a feed table 11 to a sheet-processing machine 12, which is shown here as Taschenfalzstation a sheet folding machine. The sheet feeder 10 has a first Saugrad 1 and a second Saugrad 2. The first Saugrad 1 is disposed above the sheet pile 100, while the second Saugrad 2 below the sheet transport plane E and - seen in the sheet transport direction T - downstream of the stack 100 is arranged. The axis of rotation of the first Saugrads 1 has a distance A to the stack trailing edge 100.1 of the sheet stack 100. The second Saugrad 2 is arranged at a distance B in front of the stack leading edge 100.2 of the sheet stack 100. The distance A is greater than or at least equal to the distance B. This ensures that a top sheet 1000 of the sheet stack 100 caught by the first suction wheel 1 is reliably transferred to the second suction wheel 2 before a next succeeding sheet 1000 of the first Suction wheel 1 is sucked in and also transported. The sheet feeder 10 has two height sensors 4.1 and 4.2, which serve on the one stacking of the stack 100, as well as the height adjustment of the unit from the first Saugrad 1 and lifting unit or separation unit 3. The lifting unit or separation unit 3 is in the region of the trailing edge 100.1 of Arranged sheet stack 100 and is used to lift a respective top sheet 1000 from the sheet stack 100, whereby this top sheet is separated from the sheet stack. Downstream of the second suction wheel 2 there is a sensor 5, by means of which double sheets or multiple sheets as well as the distance between individual sheets or the degree of subflooring of the sheets can be detected. If an error is detected by the sensor 5, the corresponding sheet 1000 can still be discharged at this point or its position can be corrected in the arc current.

As indicated by rotation arrows, the first suction wheel 1 is rotated at a rotational speed v1 and the second suction wheel 2 at a rotational speed v2. The rotation speed v1 is always smaller than or at least equal to the rotation speed v2. In other words, while the first suction wheel 1 sucks and transports a sheet 1000 with a lower rotation speed v1 and thus higher accuracy and less risk of damage to the sheet 1000, the sheet 1000 is greatly accelerated by the much larger rotation speed v2 of the second suction wheel 2. It is particularly advantageous if the sheet 1000 is accelerated by the second suction wheel 2 to the production speed of the folding station 12. By choosing the speed difference of v2 and v1, the arc distance between individually conveyed sheet 1000 and the degree of subshing of scalloped conveyed sheet can be adjusted.

In Fig. 2 the sheet feeder 10 according to the invention is shown in a plan view. It can be seen here that the sheet feeder 10 has 100 additional side edge blowers 7 in the area of the stack side edges 100. 3 of the sheet pile 100. These side edge blowers 7 are used to aerate the sheet stack 100 and especially the construction of an air cushion between the top sheet 1000 and the underlying sheet and thus are crucial for a secure separation of the sheet 1000. One possible embodiment of such a side edge blower 7 will be described below with reference to FIGS Fig. 4 described in more detail.

In Fig. 3 the sheet feeder 10 is shown in a detailed representation. A vacuum generator 8 supplies the first suction wheel 1 with a suction air. Also, the second Saugrad 2 is supplied with a suction air, in which case also the vacuum generator 8 can serve as Saugluftquelle (where the connection to the vacuum generator 8 is not shown). If the suction wheel 1 is not permanently exposed to a suction air, then a control valve 6 may be provided in the suction air supply line between vacuum generator 8 and the first suction wheel 1. This allows to apply the suction wheel 1 only to certain work cycles with suction. The control valve 6 is connected to a machine control 9. The suction wheel 1 further has an electromotive drive 1.1, which may for example be designed as a servomotor. This drive 1.1. is also connected to the machine control 9.

Depending on whether, during a rotation of the first suction wheel 1, a sheet 1000 or during a rotation successively several sheets 1000 to be sucked and transported, the first suction has a corresponding number of suction and conveyor lines 1.2. If, for example, the first suction wheel 1 has two suction and conveying sections 1.2, two sheets are sequentially separated and removed during one revolution of the suction wheel 1.

In Fig. 4 a possible embodiment of a side edge blower 7 is shown. This has a nozzle body 71 which is rotatable about a rotation axis 74. In this Body 71 is a plurality of multi-directionally aligned nozzles 72 are provided. Through these nozzles 72, a blast air 73 is discharged. The blast air 73 is directed to the stack side edge 100.3 and serves to ventilate the sheet stack 100. Connected to the nozzle body 71 is an air baffle 75. This air baffle 75 can perform together with the nozzle body 71 said rotation about the rotation axis 74. In this case, the air guide plate 75 serves to guide the blowing air 73 emerging from the blowing nozzles 72 in the direction of the sheet stack 100. As can be seen, the blown air streams 73 emerging from the nozzles 72 are directed in different directions. It is thereby achieved that, despite the rotation of the nozzle body 71, at least one blast air jet 73 strikes the stack side edge 100.3 in such a way that the blast air 73 can penetrate between the respective sheets 1000 and an air cushion can form between the sheets 1000.

In Fig. 5 an alternative sheet feeder 10 is shown. In contrast to the execution according to Fig. 1 the second suction wheel 2 was placed above the sheet transport plane E.

The sucking, separating and conveying of sheets takes place by means of an overhead first suction wheel 1 which is arranged above the sheet to be conveyed. A lifting unit 3 is arranged at the top between the sheet trailing edge and the suction wheel. A lower second Saugrad 2 is placed at a dependent distance B in front of the sheet leading edge below the sheet to be conveyed. The distance B is less than or equal to the distance A, wherein the distance A is determined as a function of the conveying distance (area of the circumference) of the first suction wheel 1.
The shape of the first Saugrades above can be designed round or even round and have a plurality of delivery areas over the circumference. The rotation of the first Saugrades and thus the promotion itself can be performed both timed and run permanently or clocked.
The necessary for the sheet transfer from the first Saugrad above to the second Saugrad below suction-free transfer zones (Saugrad above gives bow and the Saugrad below takes over the sheet transport) can be realized by means of a separate Saugtaktventils or by clearly defined suction-free zones in the suction wheel itself.
The first Saugrad above rotates at a uniform speed V1, but can also be clocked by means of servo drive, so with a non-uniform speed defined travel paths.
Here, the overhead suction wheel takes over the functionality of the drag sucker. Hoover and conveyor are not coupled with each other.
The suction wheel down rotates at a uniform velocity v2 where v2 is always greater than or equal to v1. Via a speed difference of v1 to v2 and as a function of the arc length a constant arc distance or a desired degree of desquamation can be set.
Furthermore, can be realized by the independently controllable speeds "Suction up - Suction wheel down", ie by not existing coupling of the speeds of feeder and subsequent sheet processing machine, a set-up operation at a defined machine speed, eg folder speed.
In other words, the sheet feeding speed is decoupled from the speed of the subsequent processing unit.
The deduction of the sheets from the feeder can be approached adapted to the starting conditions at low speed. The folding machine with speed V2 can run at production speed without speed adjustments, independent of the beginning, and thus produce in production quality. The gradual increase in the sheet feed is realized only by increasing the speed of the upper Saugrad.
So-called fold corrections, ie changes in the folding process by increasing the feeder speed are no longer necessary.

• Mit Start des Anlegers 10 wird zuerst eine definierte Vereinzelungs- und
• Vorbelüftungsphase eingeleitet.

Hierbei wird kein Bogen gefördert.
Die Haftreibung zwischen den zu fördernden Bogen 1000 des Bogenstapels 100 wird mittels Seiten-, Hinterkanten- und Trennbläsern reduziert.
Hierzu ist der Bogenstapel seitlich von einer Kombination aus Bogenführungselementen und Blasluftdüsen eingerahmt.
Diese seitlichen Elemente zentrieren die zu fördernden Bogen sowohl seitlich als auch in der Höhe und verhindern ein seitliches Verschieben und ein Aufsteigen der aufgefächerten oberen Stapelebene.
Die seitlichen Elemente können je nach Formatlänge und Formatbreite entsprechend auf die Seitenkanten positioniert werden.
Hierzu werden Teilbereiche der Seiten- und Höhenanschläge aus der Arbeitsebene herausgefahren.
Die in den Seiten- und Höhenanschlägen integrierten Fächerdüsen werden durch diesen Prozess automatisch deaktiviert.
Die Fächerluftdüsen 7 passen sich, durch verändern des Blasluftwinkel, der jeweiligen Stapelform an. Dieses geschieht über das Luftleitblech welches vom zu fördernden Bogen angehoben wird.
Die Fächerluft wird in Abhängigkeit vom Förderzustand geregelt und kann sowohl getaktet als auch permanent anliegen.
Vorzugsweise wird der zu fördernde Bogen vor dem Förderbeginn mittels Fächerluft von der oberen Stapelebene getrennt, so dass der Bogen ohne Haftreibungswiderstand gefördert werden kann. Hierzu blasen die seitlichen Fächerdüsen mit hohem Druck und kurzer Dauer seitlich in die obere Stapelebene. Auf diese Weise kann der Fächerluftstrahl tief in die Stapelmitte eindringen und den Bogen vom Bogenstapel separieren. Die geringe Luftmenge verhindert hierbei, dass der Stapel sich übermäßig aufbläht und es zu Förderstörungen kommt.
Anschließend wird die Hubeinheit aktiviert. Vakuum baut sich auf und der zu fördernde Bogen wird an der Hinterkante angehoben und zeitlich definiert gehalten.
Zwischen dem angehobenen Bogen und dem Bogenstapel wird in definierter Weise Trennluft geblasen. Der obere Bogen wird vom Bogenstapel getrennt und mittels Trennluft an das oben liegende Saugrad angehoben.
Der so zur Förderung vorbereitete Bogen kann nun von der Saugzone des ersten Saugrades erfasst und gefördert werden. Bei einem gesteuerten Saugradantrieb kann der Ansaugprozess während der Ruhephase, d.h. im Stillstand des Saugrades erfolgen.
Die Bogenförderung beginnt erst nach Abschluss des Ansaugprozesses wenn der Bogen am ersten Saugrad anliegt.
Durch die Drehbewegung des Saugrad oben wird die Saugzone wirksam und der Bogen am Saugrad angesaugt, gehalten und transportiert. Alternativ kann eine Saugluftsteuerung diese Funktion aktivieren.
Zeitgleich wird an der Hubeinheit das Vakuum der Hubsauger durch Blasluft (Störluft) abgebaut und der Bogen zur Förderung freigegeben. Die Hubsauger verweilen hierbei in oberer Position. Erst wenn der Bogen den Hubsaugerbereich verlassen hat fahren die Hubsauger in die untere Position.
Kurz vor dem unteren Totpunkt der Hubsauger werden die Bogen des Stapels mittels Fächerdüsen voneinander getrennt. Dieser Trennvorgang wird erst nach Beginn der Aufwärtsbewegung deaktiviert. Nach Erreichen der oberen Hubsaugerposition werden die Trennluftdüsen aktiviert und der zu fördernde Bogen vom Stapel mittels Luft getrennt. Hierbei hebt der oberste Bogen vom Bogenstapel ab und liegt am ersten Saugrad an.
Das Saugrad selber fördert den vorhergehenden Bogen und übergibt diesen am Ende der zu fördernden Stecke an das unten liegende Saugrad welches den Bogen übernimmt und auf eine Geschwindigkeit v2 beschleunigt.
In der Übergabephase wird durch die Drehbewegung des oben liegenden Saugrades die Vakuumzufuhr unterbrochen - der Bogen kann ohne Krafteinflüsse vom unteren Saugrad auf v2 beschleunigt werden. Nach Ablauf dieser Übergabe wird die Vakuumzufuhr durch die Rotation des oberen Saugrades wieder wirksam. Alternativ kann eine Saugluftsteuerung diese Funktion aktivieren, z.B. mittels steuerbaren Ventilen.
Parallel zu diesem Vorgang wird der Bogen von den Hubsaugern abgeblasen (Störluft) und der Bogen wird vom oberen Saugrad gefördert.
Der Prozess beginnt nachfolgend wieder von vorne.
Nachfolgend sei eine zusätzliche Komponente des Bogenanlegers 10 näher betrachtet:

• In Förderrichtung hinter dem Saugrad unten ist ein Sensor angeordnet. Der Sensor 5 selber kann Bogen, Mehrfachbogen und Bogenlücken erkennen. Abweichungen vom normalen Bogenlaufbild können über diesen Sensor erfasst werden. Auf die Weise können Fehler wie Doppelbogen, Frühbogen oder verspätete Bogen erkannt werden. Je nach Überwachungsfunktion und Fehlerbild können verschiedene Prozesse aktiviert werden.

Fehlerbogen können durch Stoppen vom Zuführsystem vor der Zuführung ins Falzwerk gestoppt werden. Alternativ können Fehlerbogen durch Anpassung der Geschwindigkeit prozesssicher ausgeschleuste werden.The procedure for separating and feeding sheets is described below:

• With the start of the investor 10 is first a defined separation and
• Pre-venting initiated.

Here, no bow is promoted.
The static friction between the sheet 1000 to be conveyed of the sheet stack 100 is reduced by means of side, trailing edge and Trennbläsern.
For this purpose, the sheet stack is framed laterally by a combination of sheet guiding elements and Blasluftdüsen.
These lateral elements center the sheets to be conveyed both laterally and in height and prevent lateral shifting and rising of the fanned-out upper stack level.
Depending on the format length and format width, the lateral elements can be positioned on the side edges accordingly.
For this purpose, partial areas of the side and height stops are moved out of the working plane.
The fan nozzles integrated in the side and height stops are automatically deactivated by this process.
The fan air nozzles 7 adjust, by changing the Blasluftwinkel, the respective stack shape. This is done via the air baffle which is raised by the sheet to be conveyed.
The fan air is regulated as a function of the delivery status and can be both clocked and permanently applied.
Preferably, the sheet to be conveyed is separated by fan air from the upper stack level before the start of delivery, so that the sheet can be promoted without static friction. For this purpose, the lateral fan nozzles blow with high pressure and short duration laterally into the upper stack level. In this way, the fan air jet can penetrate deep into the stack center and separate the sheet from the sheet stack. The small amount of air prevents the pile from over-inflating and causing delivery problems.
Then the lifting unit is activated. Vacuum builds up and the sheet to be conveyed is raised at the trailing edge and kept in time.
Between the raised sheet and the sheet stack separation air is blown in a defined manner. The upper sheet is separated from the sheet stack and raised by means of separating air to the overhead suction wheel.
The sheet thus prepared for conveying can now be detected and conveyed by the suction zone of the first suction wheel. In a controlled Saugradantrieb the suction process during the rest phase, ie take place at a standstill of the suction wheel.
The sheet conveying begins only after completion of the suction when the sheet is applied to the first suction.
By the rotational movement of the Saugrad above the suction zone is effective and sucked the bow on the suction, held and transported. Alternatively, a suction air control can activate this function.
At the same time the vacuum of the lifting sucker is reduced by blowing air (interfering air) at the lifting unit and released the sheet for promotion. The lifting suckers stay in the upper position. Only when the bow has left the Hubsaugerbereich drive the Hubsauger in the lower position.
Shortly before the bottom dead center of the Hubsauger the sheets of the stack are separated by fan nozzles from each other. This separation process is deactivated only after the beginning of the upward movement. After reaching the upper Hubsaugerposition the separating air nozzles are activated and the sheet to be conveyed separated from the stack by means of air. Here, the topmost bow lifts off the pile of sheets and rests against the first suction wheel.
The suction wheel itself promotes the previous sheet and passes this at the end of the conveyed plug to the suction wheel below which takes over the sheet and accelerates to a speed v2.
In the transfer phase, the vacuum supply is interrupted by the rotational movement of the overhead suction wheel - the sheet can be accelerated from the lower suction wheel to v2 without any force. After expiration of this transfer, the vacuum supply by the rotation of the upper Saugrades again effective. Alternatively, a suction air control can activate this function, eg by means of controllable valves.
Parallel to this process, the arc is blown off by the Hubsaugern (interfering air) and the sheet is supported by the upper Saugrad.
The process starts again from the beginning.
In the following, an additional component of the sheet feeder 10 is considered in more detail:

• In the conveying direction behind the Saugrad below a sensor is arranged. The sensor 5 itself can recognize sheets, multiple sheets and sheet gaps. Deviations from the normal sheet running image can be detected by this sensor. In this way, errors such as double sheets, early sheets or late sheets can be detected. Depending on the monitoring function and error image, different processes can be activated.

Errors can be made by stopping the feeding system before feeding it to the folder being stopped. Alternatively, error arcs can be reliably removed by adjusting the speed.

In a sheet feeder clocked with suction impinged suction wheel 1 and controlled rotational movement of the Saugrads the suction process can be carried out at standstill (rest phase) of the suction wheel. Taking into account the maximum intake time, the delivery start point suction wheel arc can be determined in such a way that the sheet rests on the suction wheel with a force fit before the start of the rotation. As a result, tolerances of the sheet suction (tolerances distance arc - suction wheel, tolerances vacuum build-up, tolerances slip) are avoided.
Because the suction wheel rotates only when bow can be promoted it will not come to rub marks of the sheet to be conveyed.
Next, the arc can be positioned with a clocked Saugradantrieb in a kind of readiness.
Erroneously sucked sheets (missing sheets) can be transported by changing the direction of rotation of the suction wheel against the conveying direction and thus allow a discharge or loose shaking with subsequently controlled acceleration.

LIST OF REFERENCE NUMBERS

1

First suction wheel

1.1

Drive suction wheel

1.2

Suction and conveyor line

2

Second suction wheel

3

Lifting unit / separation unit

4.1

height sensor

4.2

height sensor

5

sensor

6

control valve

7

Side edge blowers

8th

Vacuum generator

9

machine control

10

sheet feeder

11

feed

12

Folding station (sheet processing machine)

71

nozzle body

72

jet

73

blowing air

74

axis of rotation

75

Air baffle

100

sheet pile

100.1

Stack trailing edge

100.2

Stack front edge

100.3

Pile side edge

1000

bow

A

Distance 1. Suction wheel

B

Distance 2. Suction wheel

e

Sheet transport plane

T

Sheet transport direction

v1

Rotation speed 1. Suction wheel

v2

Rotation speed 2. Suction wheel

Claims (7)

1. Sheet feeder (10) for separating sheets (1000) of paper, cardboard, plastic, and the like from a stack (100) and for feeding the sheets (1000) in a direction of sheet travel (T) in a plane (E) of sheet travel to a downstream machine (12) processing sheets,
   the sheet feeder (10) comprising a first suction wheel (1) as viewed in the direction of sheet travel (T) and a second suction wheel (2) as viewed in the direction of sheet travel (T),
   wherein the first suction wheel (1) is arranged above the stack (100) and the second suction wheel (2) is arranged downstream of the stack (100) and above or below the plane (E) of sheet travel,
   characterized in
   that the sheet feeder (10) comprises a separation device (3) arranged in the region of the rear edge (100.1) of the stack (100) for lifting a respective uppermost sheet (1000) off of the stack (100),
   and that the distance (A) between an axis of rotation of the first suction wheel (1) and the rear edge (100.1) of the stack (100) is greater than or equal to the distance (B) between an axis of rotation of the second suction wheel (2) and the front edge (100.2) of the stack (100)
   and that at least one suction and conveying path (1.2) is provided on the circumference of the first suction wheel (1), wherein the distance (A) between the axis of rotation of the first suction wheel (1) and the rear edge (100.1) of the stack (100) approximately corresponds to the length of the at least one suction and conveying path (1.2).
2. Sheet feeder according to Claim 1,
   characterized in
   that the average rotational speed (v2) of the second suction wheel (2) is higher than or equal to the average rotational speed (v1) of the first suction wheel (1), and that the current rotational speed (v2) of the second suction wheel (2) is always higher than or equal to the current rotational speed (v1) of the first suction wheel (1).
3. Sheet feeder according to any one of the preceding claims,
   characterized in
   that the sheet feeder (10) includes a vacuum source (8) connected at least to the first suction wheel (1) for continuously supplying suction air to the first suction wheel (1).
4. Sheet feeder according to any one of the preceding claims,
   characterized in
   that the sheet feeder (10) includes a drive (1.1) connected to the first suction wheel (1) for rotating the first suction wheel (1) at a constant rotational speed (v1).
5. Sheet feeder according to any one of Claims 1-2,
   characterized in
   that the sheet feeder (10) includes a vacuum source (8) connected to the first suction wheel (1) and that suction air is cyclically suppliable to the first suction wheel (1).
6. Sheet feeder according to Claim 5,
   characterized in
   that three cycles are provided: attracting the sheet by suction, holding the sheet, releasing the sheet.
7. Sheet feeder according to Claims 5 and 6,
   characterized in
   that the sheet feeder (10) includes a machine control unit (9) and a servomotor (1.1) for driving the first suction wheel (1), the servomotor (1.1) being connected to the machine control unit (9) by a data exchange connection, in particular data lines, wherein the servomotor (1.1) is actuatable in such a way that it imparts a rotary movement (v1) to the suction wheel (1) exclusively during the "holding the sheet" cycle.

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