Abstract:
According to the invention, in the transport path between the input device and the output device, at least one intermediate buffer is arranged that serves as input device and as output device. The input device, the output device and the intermediate buffer are positioned adjacent to the conveyor belt and operated by the control device in such a way, that sheets forwarded from the input device or sheets stocked in the intermediate buffer are coupleable pneumatically to the lower side of the conveyor belt, and that sheets pneumatically attached to the lower side of the conveyor belt are selectively decoupleable at the intermediate buffer or at the output device.

Description:
FIELD OF THE INVENTION 
     The invention claimed and disclosed herein pertains to a device and a method for transporting sheet-like material, particularly sheets of media, such as paper, cardboard or plastic foils from at least one source to at least one destination. The invention further pertains to a conveyor system comprising at least one printing line. 
     BACKGROUND OF THE INVENTION 
     In the printing industry, printing lines with a plurality of workstations are used, with which sheet-like material can be processed. Processing steps include for example printing, coating, coupling, creasing, perforating and/or folding. A printing line with a plurality of workstations is disclosed for example in [1], JP4327996. Typically, printing lines of this kind are adapted to precisely defined processes that subsequently cannot be altered without changing the structure of the printing line. Often, all sheets are transported and processed by the printing line in the same manner. Devices installed in such a printing line are adapted to a specific task or function required at a given point within the printing line. 
     A printing line can also be integrated into a unitary processing unit such as the sheet stacking apparatus and image forming apparatus disclosed in [2], US2008157466A1. The modules of this apparatus are adapted to individual tasks and are firmly integrated in the apparatus. 
     From [3], US2007120934A1, a mixed output printing system is known that comprises a first and a second printing unit that deliver paper sheets to a merging module, that comprises a sheet rotor which can turn the sheets by 90°. Further, an input buffer, from which sheets can be taken, and an output buffer, on which sheets can be stacked, are provided. This system allows transferring sheets from a first printing line to a second printing line aligned perpendicularly thereto. The merging module comprises controllable deflectors and at least one merging path, along which the sheets can be merged, and at least one path, along which sheets can be transported directly from a first workstation to a second workstation. For obtaining several transport paths within the system a plurality of roller pairs is provided, which guide the sheets along the selected paths. Hence, conveying devices of this kind exhibit a high mechanical complexity and, in spite of additional functions such as a by-pass function, a relatively small flexibility. 
     Besides the complex mechanical system and the costs related thereto, large rooms are required for this conveyor technology. 
     [4], U.S. Pat. No. 5,979,890A, discloses a sheet transfer system that uses a conveyor belt which attracts the back side of the sheet under vacuum along a conveyance passage including a bent portion. With the conveyor belt, sheets can selectively be transported to a first or to a second sheet sorter. A first conveyor belt is used to transport sheets vertically down at a related sorter. A second conveyor belt is used for transporting a sheet past the first sorter to the second sorter. Along this transport path the sheets are transported on top of the second conveyor belt, which is arranged between the sheets and the first sorter that is by-passed. Hence, this system requires various conveyor belts for transporting sheets to different destinations. 
     Further, also in this system sheets are transported from first to second processing units that are adapted to a specific function. 
     Further for directing the sheets to the related destinations various air blowers are provided that can direct an air flow against the upper surface of the conveyor belt at a bent portion of a conveyance passage so that the sheet can be bent along the surface of the conveyor belt and can either be transported along the first conveyor belt down the first sorter or along the second conveyor belt past the first sorter. The system therefore requires space for the rather voluminous air blowers which allow forcing a sheet into a desired direction. Further, the air flows generated by various air blowers within a device may cause interferences and related disturbances. Further, such air blowers which act from a distance require considerable energy, when generating the required air flows. 
     Modules for transporting sheets with conveyor belts that allow the application of air suction are known from [5], DE102007024916A1. 
     The present invention is therefore based on the object of providing an improved device and an improved method for conveying sheet-like material. Further, an improved conveyor system with at least one processing line shall be created. 
     In particular a device for conveying sheet-like material shall be defined, which allows creating two or more transport paths and conveying functions in a simple manner and with reduced volume so that it can be installed in small rooms. 
     The inventive conveyor device shall allow implementing two or more process functions, such as functions for picking up, delivering, merging, sorting, deflecting and distributing sheets in a simple and efficient manner. 
     The transported sheets shall be treated smoothly so that damages are avoided. Further the transported sheets shall be sensed optically in order to optimally control the conveying process. 
     It shall be possible to create conveying systems with at least one printing line or with a plurality of printing lines that cross one another with reduced efforts and reduced space requirements. 
     It shall be possible to use inventive conveying devices advantageously in one or more positions within a printing line, in order to locally implement one or more of the above-mentioned process functions. Thereby, an adaptation to different process functions shall be implementable by a simple change of the operation mode with the installed software. Hence, with inventive conveyor devices, it shall be possible to construct and change printing lines with reduced effort. 
     SUMMARY OF THE INVENTION 
     The defined objects are reached with a conveyor device according to claim  1 , a conveyor system according to claim  9  and a method according to claim  11 . Preferred embodiments of the invention are defined in further claims 
     The inventive device, which serves for conveying sheet-like material, such as sheets of paper, cardboard or plastic, along a transport path, comprises a control device for controlling a conveyor process, at least one conveyor belt provided with air channels and at least one pneumatic device that is connected to the control device and to the air channels of the conveyor belt, so that sheets forwarded from an input device can be coupled pneumatically to the conveyor belt and can be decoupled from the conveyor belt at an output device. 
     According to the invention, in the transport path between the input device and the output device, at least one intermediate buffer is arranged that serves as input device and as output device. The input device, the output device and the intermediate buffer are positioned adjacent to the conveyor belt and operated by the control device in such a way, that sheets forwarded from the input device or sheets stocked in the intermediate buffer are coupleable pneumatically to the lower side of the conveyor belt, and that sheets pneumatically attached to the lower side of the conveyor belt are selectively decoupleable at the intermediate buffer or at the output device. 
     Hence, the inventive conveyor device allows advantageous transportation of the sheets that can selectively be picked up from different sources at different positions, that, coupled to the lower side of the conveyor belt, can be transported, and can selectively be decoupled from the lower side of the conveyor belt at different positions and can be forwarded further. 
     Typically, endless conveyor belts are used that have an inner and an outer side. A sheet pneumatically attached to the outer side of a conveyor belt is travelling from the upper side of the conveyor belt to the lower side of the conveyor belt and back to the upper side with one with each round of the conveyor belt. The conveyor belts are driven by a drive device. A conveyor belt, the drive device and optionally a pneumatic unit form a conveyor unit. Below reference is made typically directly to the conveyor belts. 
     The inventive conveyor device can be installed at the input side of a workstation and can pick up sheets from a staple or a sheet buffer and can forward sheets to the workstation. 
     The same conveyor device can be installed at the output side of the workstation and can receive, transport and selectively place processed sheets on a staple or transport processed sheets via an output device further, e.g. to a second workstation. 
     The inventive conveyor device allows selectively picking up sheets from one or a plurality of sources, particularly from sheet buffers, and to transport sheets to one or a plurality of destinations, particularly sheet buffers and workstations. 
     Further, sheets can be exchanged between a plurality of sources, particularly sheet buffers, in order to sort sheets. Thereby an intelligent sorting can be implemented advantageously, that involves identifying sheets taken from a sheet buffer and for transporting the sheets depending on the determined identity, e.g. to a defined workstation or to a defined sheet buffer. This advantageously allows sorting of sheets. E.g., identical sheets can be forwarded to the same sheet buffer. Alternatively, sheets taken from different sheet buffers can be stored in a desired sequence in a further sheet buffer. The order of a sheet sequence can also be inverted without additional effort. Further, a sheet delivered by a workstation, e.g. a printer, can also bypass one or a plurality of sheet buffers and can be delivered directly to the next or a further workstation downstream. 
     The inventive conveyor device can therefore be used for providing various process functions, such as functions for picking up, delivering, merging, sorting, turning, deflecting and distributing sheets. Furthermore the inventive device allows bi-directional transportation of the processed sheets without additional effort. 
     The inventive conveyor device can universally and advantageously be installed at several points within a processing line particularly a printing line or within a conveyor system that encompasses a plurality of printing lines. Particularly advantageous is the installation of an inventive conveyor device at the crossing points of printing lines. The conveyor device can selectively act as a so-called feeder, i.e. as a device that draws sheets from a staple, or as a so-called stacker, i.e. as a device that forwards sheets to a staple. Due to the universal applicability of the inventive conveyor device, the traditional designations for the inventive conveyor device are individually selected according the present application. In the event that the inventive conveyor device is installed at the input of a printer, the technical term “feeder” is appropriate. In the event that the same conveyor device is installed at the output of the printer, the technical term “stacker” is appropriate. In the event that a mixed operation between two workstations is implemented, then the technical term “feeder-stacker” is appropriate. The conveyor device can also execute both functions, i.e. forwarding sheets to a staple or drawing sheets from the same staple. Further, the inventive conveyor device can incorporate and operate one or a plurality of sheet buffers, which can selectively be used or bypassed. Hence, sheets can also bypass the sheet buffers and can be delivered to different destinations, so that besides the feeder-function and stacker-function also a by-pass-function can be implemented. Hence, in a preferred embodiment a single inventive conveyor device is installed between two workstations, which serves for the first workstation as stacker and for the second workstation as feeder, or selectively as transfer unit or by-pass-unit. 
     Further, with the inventive conveyor device, sheets held at the lower side of the conveyor belt can be transported bi-directionally, in one direction and in the opposite direction. In preferred embodiments, sheets held at the lower side of the conveyor belt can be forwarded to the upper side of the conveyor belt and thus can be turned by 180°. There, the sheets can be decoupled and can be moved vertically or laterally. In preferred embodiments the sheets are forwarded to the upper side of the conveyor belt and are then moved downwards, e.g. towards a sheet buffer. This can be performed in a simple manner, by using two separate pneumatic conveyor belts that are aligned in a mutual distance that allows moving a sheet that has been forwarded to the upper side of the conveyor belts downwards between the two conveyor belts. 
     Sheets can be released from the conveyor belt by interrupting or inverting the air flow that is supplied to the conveyor belt. Thereby, the sheets are not only decoupled from the conveyor belt, but also conveyed downwards or upwards. In order to move the sheets quickly to the destination, preferably an additional transfer blower is used that emits an air flow, which delivers the sheets for example to a sheet buffer. 
     Decoupling the sheets from the conveyor belt or picking up sheets from a sheet buffer can further be supported by mechanical devices such as a lever arm that can grasp, lift and lower a sheet. For lifting sheets, preferably lever arms are used that comprise suction elements. Alternatively, for picking up and delivering sheets the sheet buffer is lifted or the conveyor belt or the parallel conveyor belts are lowered. 
     In a preferred embodiment, a duct is arranged above the sheet buffers, into which sheets can be dropped. After a sheet has been transported by the conveyor belt, i.e. the conveyor device to the duct entrance, the air flow in the air channels of the conveyor belt is inverted and the pneumatically held sheets are decoupled and blown into the duct. 
     In a further preferred embodiment, a plurality of conveyor belts is provided that are arranged serially behind one another, so that these conveyor belts can at the same time perform different functions. Preferably, the conveyor belts are designed and arranged in such a way, e.g. supported vertically movable, that they can selectively pick up and put down sheets. Conveyor belts are preferably adapted to the maximum sheet-length and surveyed by means of optical sensors. As soon as the completed delivery of a sheet to a conveyor belt has been signalled, the conveyor belt can be lowered to a sheet buffer and the sheet can be decoupled and discharged. 
     In a preferred embodiment the conveyor device comprises a rotor unit, which can grasp delivered sheets and can turn a grasped sheet by a desired angle, preferably by +/−90° or 180°. Rotated sheets can then be processed within the same printing line or can be transferred to another printing line. 
     Thereby, the rotor unit can be arranged serially with a further conveyor belt. For this purpose, a rotor unit is provided preferably with rotatably supported pneumatic conveyor belts. The conveyor device with the rotor unit can advantageously be arranged at the crossing point of two processing or printing lines and is embedded selectively into the one or the other transport path. 
     Alternatively, the rotor unit can interact with a conveyor belt and can receive sheets decoupled from the lower side of a conveyor belt, can turn the sheets and can deliver the sheets back to the lower side of the conveyor belt. Sheets guided along the first printing line and rotated sheets can advantageously be stored in a sheet buffer located at the crossing point of the first printing line and a second printing line and can be picked up again from the sheet buffer and can be transported further along the first or the second printing line. 
     In a further preferred embodiment the at least one conveyor belt, which is provided with air channels, is held by two shafts, of which at least one is designed as a pneumatic shaft that comprises a hollow with one or a plurality of air channels. The pneumatic shaft is connected to the pneumatic device in such a way, that air is transferable selectively into the one or the other direction through the pneumatic shaft, in order to pull or push sheets onto or off the conveyor belt. In this manner, further options result for advantageously handling and conveying the sheets. 
     In a preferred embodiment a pneumatic shaft is provided at least on the output side of the conveyor belt, i.e. the conveyor unit and forms a deflector, with which the transfer of the sheets is controllable by the control unit and the pneumatic unit in such a way,
     a) that, by emission of air, the sheets are pressed downwards and are released from the conveyor belt; or   b) that, by intake of air, the sheets are travelling around the pneumatic shaft and are deflected, or, if selected, returned along the upper side of the conveyor belt; or   c) that, without or with reduced emission of air, the sheets are released from the conveyor belt and are transported further in a straight line.   

     Hence, sheets can be released from the conveyor belt in such a way that they by an air flow can guided to a sheet buffer, by air suction can be deflected or returned back, or by interruption of the air flow can be forwarded along a straight line e.g. to a further conveyor belt or to the next workstation. By deflection elements or by the appropriate dosage of the air flow, the deflection function can be optimised in all three variations and can be adapted to the date of the sheets. 
     Hence, with the inventive conveyor device a conveyor system with one or a plurality of printing lines can be built in a simple manner and with a compact setup. Inventive conveyor devices can be installed between workstations and can be adapted to these workstations. Preferably, an interface is provided, which allows the inventive conveyor device to communicate and to exchange data with the neighbouring workstations. By means of these data, the conveyor can automatically be configured. Further, based on these data the working processes can be controlled. The conveyor system preferably comprises a higher-level control device, which observes and controls all routines and processes and the related local control units. Thereby it is possible to run sub-processes within the conveyor system. The user can load and unload individual inventive conveyor devices or their sheet buffers and operate processes with selectable functions and workstations upstream and downstream. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The invention is described below with reference to the drawings. Thereby show: 
         FIG. 1  a conveyor system  1000  with two printing lines  100 A,  100 B, that are crossing one another and that are equipped with inventive conveyor devices  1 A, . . . ,  1 F, with which sheets  9  can selectively be transported between sheet buffers B and workstations W 1 , . . . , W 8 ; 
         FIG. 2  the first inventive conveyor device  1 A of  FIG. 1 , which connects the first and the second workstation W 1 , W 2  with one another and which comprises a conveyor unit  10  as well as two sheet buffers B A1 , B E2 , that are arranged serially behind one another; 
         FIG. 3  the conveyor unit  10  of the conveyor device  1  of  FIG. 2  in a preferred embodiment; 
         FIG. 4  a printing line  100  with the two workstations W 1 , W 2  of  FIG. 2 , that are arranged between three identical inventive conveyor devices  1 A,  1 B,  1 C, that each comprise one sheet buffer B E1 , B A1  or B E2 , B A2 , only; 
         FIG. 5  the second workstation W 2  of  FIG. 2 , with three inventive conveyor devices  1 A,  1 B,  1 C installed upstream in series and with an inventive conveyor device  1 D installed downstream; 
         FIG. 6  an inventive conveyor device  1  in a preferred embodiment, with which sheets  9  can be rotated as desired and turned over and can be released at any side of the conveyor device  1 ; 
         FIG. 7   a ,  7   b  two different views of a preferred conveyor unit  10  with a pneumatic device  3 A with a pneumatic unit  30  that is connected or can be connected to the pneumatic conveyor belt  2 A and also to two pneumatic shafts  21 A P ,  22 A P  with which the conveyor belt  2 A is held; and 
         FIG. 8  a conveyor belt  2 A with two parts  2 A 1 ,  2 A 2 , that can be shifted towards one another. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a conveyor system  1000  with two processing lines or printing lines  100 A,  100 B that are crossing one another. The first printing line  100 A is equipped with four workstations W 1 , W 2 , W 3 , W 4 , four inventive conveyor devices  1 A,  1 B,  1 C,  1 D and with sheet buffers B E1 , B A1 , B E2 , B A2 , B A6 , B E3 , B E4 , and B A4  that are preferably all integrated in related conveyor devices  1 A,  1 B,  1 C,  1 D. The second printing line  100 B is equipped with four workstations W 5 , W 6 , W 7 , W 8 , three inventive conveyor devices  1 E,  1 B,  1 F and with sheet buffers B E5 , B A6 , B A2  and B E8  that are preferably all integrated in related conveyor devices  1 E,  1 B, and  1 F. 
     One of the conveyor devices  1 B with two sheet buffers B A2 , B A6  integrated therein is located at the crossing point of the two printing lines  100 A,  100 B. Both sheet buffers B A2 , B A6  can selectively be integrated into the processes or sub-processes of the two printing lines  100 A,  100 B. Hence, by means of the available sub-processes the user can selectively define production processes, with which sheets  9  can be processed. 
       FIG. 1  shows an example of three production processes P 1 , P 2 , P 3 . With the first production process P 1 , sheets  9  are transported in the first printing line  100 A from sheet buffer B E1  to the first workstation W 1 , e.g. a printing device. At the output of the first workstation W 1  printed sheets  9  are gripped by the first conveyor device  1 A and are routed by means of the bypass-function past the sheet buffers B A1 , B E2  to the second workstation W 2 . Sheets  9  processed and delivered by the second workstation W 2  are gripped by a second inventive conveyor device  1 B, which is located at the crossing point of the first and the second printing line  100 A,  100 B, and are delivered to a sheet buffer B A2 . In the second sheet buffer B A2 , sheets  9  are stored, which for example are either kept ready for further processing in the first or second printing line  100 A,  100 B, or which have been examined and are not transported further due to a recognised deficiency. Hence, the sheet buffer B A2  can be used as “stacker” for the second workstation W 2  and as “feeder” for the subsequent workstation W 7  in the second printing line  100 B, as the illustrated production process P 2  shows. The second conveyor device  1 B comprises means with which the alignment of the sheets  9  can be changed as required, preferably in steps of 90°. In this way, sheets  9  can be delivered properly aligned to workstation W 7 . 
     With the third production process P 3  sheets  9  are selectively taken from the first workstation W 1  or one of the two sheet buffers B A1 , B E2  and delivered to the second workstation W 2 . From the second workstation W 2 , sheets  9  are guided to the second conveyor device  1 B, which forwards the sheets  9  to conveyor device  1 E, which is arranged within the second printing line  100 B. Sheets  9  are guided from the second conveyor device  1 B to a fifth workstation W 5  and further to a subsequent sixth workstation W 6  and then to the second conveyor device  1 B. Hence, two inventive conveyor devices  1 B,  1 E can also be connected with one another directly by a conveyor belt, in order to bridge one or a plurality of workstations W 5 , W 6  or another distance along a printing line. 
       FIG. 6  shows the second conveyor device  1 B with a roller pair  12 D, through which sheets  9 D can be delivered upwards to a conveyor belt  2 T, which preferably is part of an inventive conveyor device  1 T. Sheets  9  can be transferred via conveyor device  1 T from the second conveyor device  1 B to conveyor device  1 E. Production process P 3  further transports the sheets  9  to the workstations W 3  and W 4  as well as to the further inventive conveyor devices  1 C and  1 D. 
       FIG. 2  shows the first inventive conveyor device  1 A of  FIG. 1 , which connects the first workstation W 1 , e.g. a printing device, and the second workstation W 2 , e.g. a coating device or a folding device, with one another. 
     In this embodiment the conveyor device  1 A comprises two conveyor units  10 A,  10 B shown in  FIG. 3 , which comprise conveyor belts  2 A,  2 B that are serially aligned behind one another and with which sheets  9  can be transported from the first to the second workstation W 1 , W 2  or can selectively be placed in one of two sheet buffers B A1 , B E2 . Alternatively, sheets  9  can selectively be picked up from one of the two sheet buffer B A1 , B E2  and can be transported to the second workstation W 2 . 
     The conveyor belts  2 A,  23  are provided with air channels  200  and are held each by a set of two shafts  21 A,  22 A or  21 B,  22 B respectively. Further, pneumatic devices  3 A,  3 B are provided, that are connected to a pneumatic unit  30  which serves for the supply of air. The pneumatic unit  30  is connected with pneumatic lines  31 ,  32 , through which air having excess pressure or underpressure can be guided to control units  51 , . . . ,  56  that are actuated by means of a control device  7 . With the control units  51 , . . . ,  56 , that comprise actuators and valves, one of the pneumatic lines  31 ,  32  can be connected to a related output line  33 . The output line  33  of the control units  52  and  55  are connected to the pneumatic devices  3 A,  3 B, which suck air or blow air through the air channels  200  provided in the conveyor belt  2 A and  2 B. The control units  51 , . . . ,  56  can be integrated in one assembly  50  (see  FIG. 6 ). 
     The control units  51  and  53  as well as  54  and  56  are connected to pneumatic output lines  33  that are guided to pneumatic shafts  21 A,  22 A and  21 B,  22 B, which hold the two conveyor belts  2 A,  2 B. Hence, with the control units  51 , . . . ,  56 , which are controlled by the control device  71  via control lines  71 , air can selectively be sucked or blown through the pneumatic shafts  21 A,  22 A and  21 B,  22 B and through the conveyor belts  2 A,  2 B. In this way, sheets  9  can selectively be coupled to or decoupled from the conveyor belts  2 A,  2 B and coupled to or decoupled from the pneumatic shafts  21 A,  22 A and  21 B,  22 B. These procedures are executed depending on the position of the transported sheets  9 , wherefore sensors  41 ,  42  are provided, with which the position of the sheets  9  can be determined preferably optically. Measurement signals are forwarded from the sensors  41 ,  42  via measuring line  72  to the control device  7 . Typically the appearance of the front edge or the rear edge of the sheet  9  is detected, in order to take appropriate action. 
     According to the invention, a sheet  9  delivered by the first workstation W 1  or outputted by a corresponding output roller pair  81  of the workstation W 1  this forwarded to the lower side of the first conveyor belt  2 A and can there be grasped by the conveyor belt  2 A, or even before by the pneumatic shaft  21 A and can be transported further. In the same manner, the sheet  9  transported by the first conveyor belt  2 A can be transferred to the lower side of the second conveyor belt  2 B. For decoupling the sheet  9  the air flow guided through the conveyor belt  2 A or  23  or through the pneumatic shafts  22 A,  22 B can be inverted. 
     In order to enable picking up and putting down the sheets  9  from and to the sheet buffers B A1 , B E2 , the sheet buffers B A1 , B E2  are provided each with a table that serves for receiving a staple, which can be lifted or lowered with a drive device  16 A,  16 B that is schematically shown. With this arrangement the staple with sheets  9  held by the sheet buffers B A1 , B E2 , can be lifted upwards towards the first or second conveyor belt  2 A,  2 B, in order to pick up a sheet  9 , and then be lowered again, in order to move the staple with sheets  9  away from the conveyor belt  2 A,  2 B. Sensors  43  are provided for measuring the distance between the conveyor belts  2 A,  2 B and the upper edge of the stapled sheets  9 . When the optimal distance of the stapled sheets  9  relative to the conveyor belts  2 A,  2 B is reached, then the sensors  43  are sending corresponding signals to the control device  7 . 
     In order to uniformly staple the sheets  9 , an active or passive guiding element  18  is provided that lies adjacent to the staple or that can be guided against the staple, so that the sheets  9  are aligned on the front side and/or laterally. 
     Subsequently, stapled sheets  9  can be taken from the sheet buffers B A1 , B E2  and can be guided with the conveyor device  2 B via an output conveyor part  12 , for example via an input roller pair  82  to the next workstation W 2 . Further, a sheet  9  delivered by the first workstation W 1  can also be guided further directly to the second workstation W 2 . 
       FIG. 4  shows a printing line  100  with the two workstations W 1 , W 2  of  FIG. 2  that are arranged between three identical inventive conveyor devices  1 A,  1 B,  1 C, which comprise each only one sheet buffer B E1 , B A1  or B E2 , B A2 , and only one conveyor unit  10 A,  10 B or  10 C. 
       FIG. 4  illustrates, that inventive conveyor devices  1 A,  1 B,  1 C can be employed as desired. Each of the conveyor devices  1 A,  1 B,  1 C is equipped with one conveyor unit  10 A,  10 B,  10 C that each comprises a conveyor belt  2 A,  2 B,  2 C and a pneumatic device  3 A,  3 B,  3 C. The first conveyor device  1 A serves as feeder for the first workstation W 1 . The second conveyor device  1 B serves as stacker for the first workstation W 1  and simultaneously as feeder for the second workstation W 2 . The third conveyor device  1 C serves as stacker for the second workstation W 2 . The sheet buffers B E1 , B A1  or B or B E2 , B A2  of the three conveyor devices  1 A,  1 B, and  1 C fulfil the corresponding functions. 
       FIG. 4  shows further that the conveyor devices  1 A,  1 B,  1 C and the workstations W 1 , W 2  comprise each a local control unit P 1A , P 1B , P 1C  or P W1 , P W2 . In preferred embodiments, the local control units P 1A , P 1B , P 1C  or P W1 , P W2  of neighbouring entities  1 A, W 1 ; W 1 ,  1 B;  1 B, W 2  of the printing line  100  are directly connected with one another via communication means, such as a data bus. In this preferred embodiment the local control units P 1A , P 1B , P 1C  or P W1 , P W2  are connected in addition via a data bus with a central control unit  1100 . Hence, the local control units P 1A , P 1B , P 1C  of the conveyor devices  1 A,  1 B, and  1 C can retrieve data from neighbouring units, such as neighbouring workstations W 1 , W 2  or neighbouring inventive conveyor devices  1  directly or indirectly and can configure themselves accordingly. Preferably wireless communication takes place, e.g. by means of the protocols of a mobile communication system, such as Bluetooth-systems. After establishing contact, the conveyor devices  1 A,  1 B,  1 C and the workstations W 1 , W 2  can form an (Ad hoc) network or can communicate wireless with the central control unit. 
     Thereby, it is possible that corresponding protocols, particularly control protocols, are loaded. Further, adjustments or adaptation of the hardware, i.e. of the conveyor unit  10 , is performed automatically. E.g., the conveyor device  1  recognises the settings of the workstations W 1 , W 2  or the formats of the sheets  9  used and performs automatically the required adjustments. E.g., the distance between the conveyor belts  2   A1  and  2   A2  of the conveyor shown in  FIG. 8  is automatically set. 
       FIG. 5  shows the second workstation W 2  of  FIG. 2  with three inventive conveyor devices  1 A,  1 B,  1 C installed upstream in serious and an inventive conveyor device  1 D installed downstream. Each of the conveyor devices  1 A,  1 B,  1 C,  1 D is equipped with one conveyor unit  10 A,  10 B,  10 C,  10 D that each comprise a conveyor belt  2 A,  2 B,  2 C,  2 D and a pneumatic device  3 A,  3 B,  3 C,  3 D. The conveyor devices  1 A,  1 B,  1 C, which serve as feeders for the workstation W 2 , allow sorting of sheets  9  before they are supplied to the workstation W 2 . E.g., sheets  9  are alternatingly taken from the first two conveyor devices  1 A,  1 B and are forwarded to the third conveyor device  1 C. In the conveyor device  1 D installed downstream of the workstation W 2  the sheets  9  are stapled. It is illustrated that this task can easily be performed with a duct  8 , into which the supplied sheets  9  can be dropped. This process can be supported with the pneumatic device  3 A that blows air into the duct  8  or that sucks air out of the duct  8 , in order to generate a vacuum. Preferably, at least the side walls of the duct are movable, in order to align the sheets  9  on the staple laterally or on the front side. 
       FIG. 6  shows an extended embodiment of the second inventive conveyor device  1 B of  FIG. 1  that comprises several conveyor units  10 A,  10 B,  10 C,  10 T,  10 R that each comprise a conveyor belt  2 A,  2 B,  2 C,  2 T,  2 R and a pneumatic device  3 A,  3 B,  3 C,  3 T,  3 R. 
     In this embodiment of the conveyor device  1 B, sheets  9  can be rotated and turned over as desired and can be released at any side of the conveyor device  1 B. The conveyor device  1 B comprises a first central conveyor belt  2 A that can deliver sheets  9  that are received via the input conveyor part  11  or picked up from a sheet buffer B, directly or via further conveyor belts  2 B,  2 C, to four different output roller pairs  12 A,  12 B,  12 C,  12 D. Via the output roller pairs  12 A and  12 C, the sheets  9 A and  9 C are outputted on the front side. Via the output roller pair  12 C the sheets  9 B are outputted laterally. Via the output roller pair  12 D the sheets  9 D are outputted upwards to a further conveyor device  1 T or a conveyor belt  2 T, which can transport sheets  9 D to any desired point of the conveyor system  1000  and which has a corresponding length. 
     It is shown that the first conveyor belt  2 A comprises a pneumatic shaft  22 A P  at the output side, which is connected via pneumatic lines  31 ,  32  and  33  and an assembly  50 , that comprises pneumatic control units  51 ,  52 ,  53 , . . . , with the pneumatic unit  30 . Air flow can be guided through the pneumatic shaft  22 A P  into one and an inverse direction in order to suck sheets  9  towards the pneumatic shaft  22 A P  or blew sheets  9  away from the pneumatic shaft  22 A P . If no air is guided through the pneumatic shaft  22 A P , then the sheets  9  are conveyed in a straight line without changing the direction. Hence, the pneumatic shaft  22 A P  forms a deflector, with which the sheets  9  can be guided downwards to the sheet buffer B, straight on to the second conveyor belt  2 B or upwards to the third conveyor belt  2 C or to the output roller pair  12 D. It is shown that on the front side of the third conveyor belt  2 C an input conveyor part, i.e. a pneumatic shaft  11 P is provided, with which sheets  9  can be sucked towards the lower side of the conveyor belt  2 C or with which sheets can also be pushed away so that they are guided to the output roller pair  12 D. It is further shown that sheets  9 E can also be guided and turned around the pneumatic shaft  22 A P  by 180° and an can be transported back on the upper side of the first conveyor belt  2 A and can be released again at the input side. Alternatively the sheets  9 E that have been turned over and that are guided on the upper side of a pair of conveyor belts  2 A 1 ,  2 A 2  can also be conveyed downwards onto a sheet buffer B.  FIG. 8  shows that between the conveyor belts  2 A 1 ,  2 A 2  an air flow can be introduced, in order to push the sheets  9 E between the conveyor belts  2 A 1 ,  2 A 2  downwards. In this way, sheets  9 E are turned and can be placed upside down onto the sheet buffer B. 
     Hence, the pneumatic shafts  22 A P  and  11 P can advantageously be combined with the conveyor belts  2 A,  2 B and  2 C of the inventive conveyor devices  1 ,  1 B, in order to selectively control the coupling and decoupling of sheets  9  and to establish a desired transport path. Thereby, the air flows through the conveyor belt  2 A and the pneumatic shaft  22 A P  can be combined as desired. While the conveyor belt  2 A can attract a sheet  9 , the pneumatic shaft  22 A P  can push off the same sheet  9 . Further, the air flows guided through the conveyor belt  2 A and through the pneumatic shaft  22 A P  can be synchronised. Further, an air flow can also be guided through the conveyor belt  2 A or through the pneumatic shaft  22 A P  only, in a desired direction. Further, pneumatic shafts can be used as auxiliary shafts separated from the conveyor belts in order to direct sheets  9  in a presently selected direction. 
     The conveyor device  1 B of  FIG. 6  further comprises a rotor unit R that allows alignment of a sheet  9  in a plane as desired. E.g., in order to transfer the sheets  9  travelling along the first printing line  100 A into the second printing line  100 B, the sheets  9  are turned typically by +/−90°. 
     Thereby, a rotor unit R can be equipped with a conveyor belt  2 R that receives sheets  9  delivered by a first conveyor belt  2 X, rotates sheets  9  by a desired angle and delivers the sheets  9  to a second conveyor belt  2 X. A rotor unit R of this embodiment can be installed at the crossing point of the two printing lines  100 A,  100 B shown in  FIG. 1 . Hence, an inventive conveyor device  1  can be equipped with one conveyor belt  2 R or with a plurality of conveyor belts  2 A,  2 B,  2 C,  2 R, of which e.g. one can be rotatable. In the conveyor device  1 B of  FIG. 6  the conveyor belt  2 A or the related conveyor unit can be replaced by the conveyor belt  2 R or the related conveyor unit  10 . 
     However, in the embodiment shown, the conveyor belt  2 R is arranged below the conveyor belt  2 A and can receive sheets  9  from the lower side of the conveyor belt  2 A, and can turn and deliver the sheets back to the conveyor belt  2 A. For this purpose, a turntable  152  can be used, with which sheets  9  are attracted, turned, stored and/or supplied. The rotor unit R comprises a rotor  151  that is driven by a motor  150 . The handover of sheets  9  is controlled by the control device  7 , which is connected to sensors  40  that indicate the position of the sheets  9 . For the handover of the sheets  9 , the conveyor belt  2 A is preferably briefly stopped and the air flow through the conveyor belt  2 A is inverted, so that a sheet  9  can be forwarded to the rotor unit R. 
       FIGS. 7   a  and  7   b  show two illustrations of a preferred conveyor unit  10 , which comprises a pneumatic unit  30  that is equipped with two pneumatic shafts  21 A P ,  22 A P  and that is connected to a pneumatic device  3 A, that sucks air through the part of the conveyor belt  2 A, which lies adjacent to the lower sides of the pneumatic shafts  21 A P ,  22 A P . 
       FIG. 7   a  shows the supply of air pressure (excess pressure or underpressure) to the pneumatic shaft  21 A P , that comprises an axial bore  221 , into which a pressure line  33 , e.g. a tube, is inserted. The air can exit through the openings  212 , which are provided radially at the pneumatic shaft  21 A P , which is driven by a motor  25 . Arrows symbolise, that air is sucked in or blown out through the pneumatic shafts  21 A P ,  22 A P  and through the conveyor belt  2 A radially towards the outside or radially towards the inside. 
     In the embodiment shown, the conveyor unit  10  further comprises a drive motor  250  that turns a jackscrew  255 , with which the conveyor belt  2 A can be moved vertically downwards and upwards, in order to pick up or release sheets  9 .  FIG. 7   b  shows the pneumatic unit  30 , which is driven by a motor  35 . 
       FIG. 8  shows a conveyor device  1 A with two conveyor units  10 A 1 ,  10 A 2  with conveyor belts  2 A 1 ,  2 A 2  that are aligned in parallel towards one another and that can be moved by means of a drive device  26  towards one another. Each of the conveyor belts  2 A 1 ,  2 A 2  is provided with air channels and surrounds a pneumatic device  3 A 1 ,  3 A 2 , which can suck in or blow out air. Hence, a sheet  9  can be coupled to or decoupled from the lower side or the upper side of the conveyor belts  2 A 1 ,  2 A 2 . 
     Further, a guide unit  18  with a holding device  180  is shown that holds control members  181 ,  182  laterally and on the front side. Preferably a guide unit  18  is connected to each of the parts  2 A 1 ,  2 A 2 , that with shifting of the two parts  2 A 1 ,  2 A 2  is automatically adapted to the width of the sheets  9 . 
     REFERENCED DOCUMENTS 
     
         
         [1] JP4327996 
         [2] US2008157466A1 
         [3] US2007120934A1 
         [4] U.S. Pat. No. 5,979,890A 
         [5] DE102007024916A1 
       
    
     LIST OF REFERENCES 
     
         
         B sheet buffer 
         R rotor unit 
         P local control units 
         W workstation 
           1  conveyor 
           10  conveyor unit 
           100  printing line 
           1000  conveyor system 
           1100  central control unit 
           11  input device 
           12  output device 
           150  motor 
           151  rotor 
           152  turntable 
           16 A,  16 B buffer drives 
           18  guide unit 
           180  holding device 
           181  lateral control member 
           182  front sided control member 
           2 A,  2 B, . . . conveyor belt 
           2 R turntable with conveyor belt 
           200  air channels 
           21 ,  22  shafts 
           21 A P ,  22 A P  pneumatic shafts 
           211 ,  212  air channels in den pneumatic shafts  21 A P ,  22 A P    
           25  motor for driving the conveyor belt  2 A 
           250  motor for driving the jackscrew 
           255  jackscrew 
           26  motor for the adjustment of the conveyor belt  2 A 
           281 ,  282  translatory axes 
           3 A,  3 B, . . . pneumatic devices 
           30  pneumatic unit 
           300  transfer blower 
           31 ,  32 ,  33  pneumatic lines 
           35  drive motor for the pneumatic unit  3 A 
           40 ,  41 ,  42  sensors 
           50  control assembly 
           51 , . . . ,  56  control units, actuators and valves 
           7  control device 
           71  control line 
           72  measuring line 
           8  duct 
           81  output roller pair 
           82  input roller pair 
           9  sheets