Abstract:
The invention is related to a transport system for sheet material including a conveyor belt charged with a vacuum. The transport system includes a vacuum chamber providing the vacuum to charge the conveyor belt while moving along the vacuum chamber in a transport direction, wherein the conveyor belt is permeable to air by recesses having specified distances from each other, and air nozzles arranged at a deflection position inside the vacuum chamber. The specified distances from each other correlate with the distances of the recesses in the conveyor belt to allow pressurized air charged to the air nozzles to pass through the recesses in the conveyor belt.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention is related to a transport system for sheet material comprising a conveyor belt charged with a vacuum. 
       BACKGROUND OF THE INVENTION 
       [0002]    Transport systems for sheet material comprising a conveyor belt charged with a vacuum are known form the state of the art. These transport systems are built up by a vacuum chamber and a conveyor belt moving along the vacuum chamber. The vacuum chamber is coupled to a vacuum pump which evacuates the chamber to produce a vacuum or low pressure inside the chamber. The conveyor belt covers one or more openings in the vacuum chamber which charge the belt with the vacuum. Via bores or other recesses in the belt the vacuum or low pressure inside the chamber produces suction forces which adhere the sheet material to the conveyor belt for transport. 
         [0003]    The transport systems for sheet material comprising a conveyor belt charged with a vacuum known form the state of the art suffer form the drawback that they are complex and expensive because of the fact that vacuum pumps are used. The known transport systems are in addition inflexible with respect to allowing changes in the direction of transport or changes of the orientation of the sheet material being transported. 
       SUMMARY OF THE INVENTION 
       [0004]    Therefore one aspect of the invention is to provide a transport system for sheet material comprising a conveyor belt charged with a vacuum which allows changing the direction of transport or the orientation of the sheet material being transported or both a change of transport direction and orientation. It is preferred that the invention can be used for high speed transport of sheet material. 
         [0005]    It is another aspect of the invention to provide a transport for sheet material comprising a conveyor belt charged with a vacuum which allows an inexpensive and not complex realization which in particular can be used for changing the direction of transport or the orientation of the sheet material or both a change of transport direction and orientation. 
         [0006]    In one embodiment of the invention there is provided a transport system for sheet material comprising a conveyor belt charged with a vacuum, and a vacuum chamber providing the vacuum to charge the conveyor belt while moving along the vacuum chamber in a transport direction, wherein the conveyor belt is permeable to air by recesses having specified distances to each other, and air nozzles arranged at a deflection position inside the vacuum chamber, wherein the air nozzles are arranged to have specified distances to each other correlating with the distances of the recesses in the conveyor belt, to allow pressurized air charged to the air nozzles to pass through the recesses in the conveyor belt. 
         [0007]    The transport system allows changing the direction of transport or the orientation of the sheet material being transported or both a change of transport direction and orientation at the defection position at high transport speeds. 
         [0008]    As the change of transport direction and/or orientation of the sheet material are effected without mechanical means, no wear of the sheet material is caused in the transport system. As a second positive aspect of not using mechanical means for changing the direction of transport and/or the orientation of the sheet material transported, the occurrence of jammed sheet material is reduced considerably. In summery the transport system allows a more careful and more rapid transportation and easy change of transport direction and/or orientation of sheet material. This is caused by deflecting the sheet material by pressurized air producing a force which is applied to the whole surface or a considerable part of the surface of the sheet material, as compared to mechanical systems for deflection of sheet material which only apply a deflection force to the front edge of the sheet material seen in the direction of transport. 
         [0009]    In another embodiment of the invention there is provided a transport system for sheet material, comprising a conveyor belt charged with a vacuum, and a vacuum chamber providing the vacuum to charge the conveyor belt while moving along the vacuum chamber in a transport direction, wherein at least one fan is attached to a housing forming the vacuum chamber to produce the vacuum. 
         [0010]    The transport system allows an inexpensive and not complex realization of a transport system for sheet material comprising a conveyor belt charged with a vacuum, by using inexpensive fans instead of vacuum pumps to produce a vacuum or low pressure within the vacuum chamber for charging the conveyor belt. 
         [0011]    Additional advantages result from the dependent claims and from the following description and figures. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0012]    The figures show 
           [0013]      FIG. 1  a transport system for sheet material comprising a conveyor belt charged with a vacuum, in a first operating state, 
           [0014]      FIG. 2  the transport system for sheet material as shown in  FIG. 1 , in a second operating state, 
           [0015]      FIG. 3  the transport system for sheet material as shown in  FIG. 1 , in a three dimensional representation, and 
           [0016]      FIG. 4  an embodiment of air nozzles as used in the transport system for sheet material. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]      FIG. 1  shows a transport system for sheet material comprising a conveyor belt charged with a vacuum. 
         [0018]    The transport system comprises a first conveyor  10  with a conveyor belt  14 , which is permeable to air, e. g. by means of bores or recesses  14 ′, and rollers  11  and  12 , of which at least one is propelled by a drive  13 . Between the two rollers  11  and  12  a vacuum chamber  16  is located. The chamber  16  can be formed a housing made of sheet metal  15 . To create a vacuum or low pressure inside the chamber  16  one or more fans  17  can be used to exhaust air E form the chamber  16 . The conveyor belt  14  is moving over one surface of the chamber  16  and seals one or more openings in the surface of the chamber  16 . The conveyor belt  14  is charged with the vacuum inside the chamber  16  through the openings. Via the bores  14 ′ the vacuum or low pressure in the chamber  16  produces suction forces S which adhere sheet material BN, BN′ to the conveyor belt  14  for transport. The single sheet material BN, BN′ is transported in parallel to its long edges in a direction of transport T and delivered to other parts  18  of the transport system. 
         [0019]    As can be seen better from  FIG. 3 , a second conveyor  20  is intersecting the first conveyor  10 . First and second conveyor  10  and  20  are arranged to have a small distance from each other, e. g. less than 2 cm. The second conveyor  20  is constructed in the same way as the first conveyor  10 , having rollers  21 ,  22 , of which at least one is propelled by a drive (not shown), a conveyor belt  24  which is permeable to air, e. g. by means of bores or recesses  24 ′, a chamber  26  which can be a housing made of sheet metal  25 , and at least one fan  27 , which exhausts air E form the chamber  26  to create a vacuum or low pressure inside the chamber  26 . 
         [0020]    In operation, as shown in  FIG. 1 , the sheet material BN is adhered to the conveyor belt  14  of the first conveyor  10  by the suction forces S produced by the fans  17 . When sheet material BN′ is passing the intersection with the second conveyor  20  the sheet material BN′ will stay on the first conveyor  10 , because in first and second conveyors  10  and  20  a vacuum of approximately the same strength is produced by the fans  16  and  26  and because of the two conveyors  10  and  20  are separated by the small distance mentioned above. If a change in the direction of movement or the orientation of the sheet material transported or both is required, the sheet material has to be handed over to another conveyor. 
         [0021]      FIG. 2  shows the handing over of a piece of sheet material BN′ to the second conveyor  20 , whereby a change in the direction of movement and the orientation of the sheet material BN′ is caused. 
         [0022]    The first conveyor  10  comprises air nozzles  34  which are located inside the chamber  16 . The air nozzles  34  are arranged with distances to each other matching the distances of the bores  14 ′ of the conveyor belt  14 . As can be seen from  FIG. 2 , there may be one air nozzle for each bore  14 ′, but it is also possible to provide less air nozzles. The air nozzles  34  are arranged at the intersection of the first conveyor  10  and the second conveyor  20 . The air nozzles  34  may occupy the whole area defined by the intersecting conveyors  10 ,  20  respectively their conveyor belts  14 ,  24 . The area occupied by the air nozzles  34  should at least be equal to an area defined by the biggest piece of sheet material transported or a substantial part of it. By means of a valve  32 , e. g. an electromagnetic or solenoid valve, pressurized air  33  can be charged to the air nozzles  34 . To charge the pressurized air  33  at definite points in time to the air nozzles  34  a control means  30 , e. g. a microcomputer, is used to control the valve  32 . 
         [0023]    Connected to the control means  30  are a detector  31  and a position encoder  19 . The detector  31  can be a camera, e. g. a CCD-camera, or a simple photo sensor which detects the presence of a piece of sheet material BN being transported by the position of the detector  31 , forming a means for position detection with the control means  30 . The position encoder  19  may be a separate part as depicted or may also be part of the drive  13  or of one of the rollers  11 ,  12  of the first conveyor  10 . With the help of the signal of the position encoder  19  the control means  30  can calculate the position of the bores  14 ′ of the conveyor belt  14  while the conveyor belt  14  is moved, forming a means for alignment of the air nozzles  34  with the moving bores  14 ′ of the conveyor belt  14 . 
         [0024]    Additionally a control line  35  is connected to the control means  30 . The control line  35  can be used to input a command to the control means  30  to deflect a particular piece of sheet material BN′ in order to change its direction of movement and/or its orientation. The command may be produced by a sheet material processing machine making use of the transport system, e. g. a banknote processing machine like a banknote sorter. 
         [0025]    After the command to deflect a particular piece of sheet material BN′ has been input to the control means  30  via control line  35  the control means  30  calculates the point in time the particular piece of sheet material BN′ reaches the deflection position at the intersection of the first conveyor  10  and the second conveyor  20  by analyzing the signal of the detector  31 . In addition the control means  30  calculates from the signal of the position encoder  19  when the air nozzles  34  are in alignment with the bores  14 ′ of the conveyor belt  14 . For the calculated point in time when the particular piece of sheet material BN′ reaches the deflection position at the intersection of the conveyors  10 ,  20  and the alignment of bores  14 ′ and air nozzles  34 , the valve  32  is actuated by the control means  30  to charge the air nozzles  34  with the pressurized air  33 . The air nozzles  34  are charged for a short time only, e. g. for 5 ms or less, because the movement of the conveyor belt  14  causes misalignment of the air nozzles  34  and the bores  14 ′. After the nozzles  34  and the bores  14 ′ are aligned again, the air nozzles  34  can be charged again with pressurized air. 
         [0026]    It is also possible to charge the air nozzles  34  with pressurized air  33  during the whole time the sheet material BN′ to be deflected is present in the intersecting area of the first and second conveyors  10 ,  20 . 
         [0027]    As another alternative the nozzles  34  can be moved in synchronism with the bores  14 ′ in the conveyor belt  14  while being charged with pressurized air  33 . 
         [0028]    An embodiment for moving air nozzles is shown in  FIG. 4 . As can be seen form  FIG. 4 , the air nozzles  34  are formed by a belt  40  having recesses or bores  40 ′ being spaced form each other as the bores  14 ′ in conveyor belt  14 . The belt  40  is built in a housing  43 , e. g. made from sheet metal, which is attached to the pressurized air  33 . The housing  43  of the air nozzles  34  is placed inside the vacuum chamber  16  of the first conveyor  10 , as described above. The belt  40  is moved by rollers  41 ,  42  of which at least one is propelled by a drive (not shown). The belt  40  moves in a direction and speed Tn equal to the direction and speed T of the conveyor belt  14 . This can be achieved by a using a drive comprising a position encoder to propel belt  40 , comparable to the drive  13  and position encoder  19 , as described above in conjunction with the first conveyor belt  14 . It is also possible to use a synchronous gear to couple belt  40  to drive  13  of the first conveyor  10  to achieve the synchronous movement of belt  40  and first conveyor belt  14  and there-with the synchronous movement of bores  14 ′ and  40 ′. 
         [0029]    Through the air nozzles  34  and the aligned bores  14 ′ of the conveyor belt  14  the pressurized air  34  is causing a force P against the sheet material BN′. Because of the pressurized air  34  form the air nozzles  34  the vacuum or low pressure inside the chamber  16  no longer can adhere the sheet material BN′ to the conveyor belt  14  of the first conveyor  10 . The force P of the pressurized air  34  moves the sheet material BN′ in a direction toward the second conveyor  20  and the sheet material BN′ is adhered to the conveyor belt  24  of the second conveyor  20  by the suction force S produced by vacuum or low pressure in chamber  26  of the second conveyor  20 . The sheet material BN′ is then transported by the second conveyor  20  in a transport direction T′ different for the transport direction T of the first conveyor  10 . In addition the orientation of the sheet material BN′ is changed as the second conveyor  20  transports the sheet material BN′ in parallel to its short edges. 
         [0030]    In addition to the detector  31  or instead of using the detector  31  the point in time for charging the air nozzles  32  can also be calculated by the control means  30  by determining the position of the sheet material BN′ on the first conveyor  10  from the known speed of transport. In addition or alternatively the signals of the position encoder  19  can be used to calculate the position of the sheet material BN′ while being transported by the first conveyor  10 . 
         [0031]    The conveyors  10 ,  20  as described herein by example can also have a modular vacuum chamber  16 ,  26  design, i. e. the vacuum chamber can be separated into several sub chambers (modules). Each module having a separate housing  15 ′ (see  FIG. 1 ), e. g. made from sheet metal, having at least one fan. The modular design allows the built up of conveyors being flexible in length by concatenating an appropriate number of modules. 
         [0032]    All fans  17 ,  27  of the vacuum chamber  16 ,  26  can operate permanently to produce a vacuum or low pressure. In addition it is also possible to only operate a particular fan if a vacuum is needed, i. e. if a piece of sheet material BN, BN′ is at the position of the particular fan or in the vicinity of the particular fan. To only operate particular fans is especially advantageous if using the modular built up of the vacuum chamber as described above. 
         [0033]    The conveyors  10 ,  20  as described herein by example can also be used as a switch for a change in the direction of movement of the sheet material, without changing the orientation of the sheet material. 
         [0034]    The conveyor as described herein and its use for changing the direction of movement and/or orientation of sheet material can be used for banknotes being processed in banknote processing machines, e. g. banknote sorters, especially in banknote processing machines operating at high speeds of 20, 40, 50 or even more banknotes per second.