Abstract:
An item sorting system includes at least three modules for processing items requiring sorting, a conveyor line to transport the items in a first transport path from the first to the second and to the third module, and a bypass to transport items requiring sorting in a second transport path from the first to the third module thereby bypassing the second module. A control unit sets a spacing between the items in the conveyor line upstream of the bypass as a function of an activation of the bypass. The bypass is to mitigate stresses to which items are exposed when the item sorting system is used in a plurality of passes with different functions.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to an item sorting system comprising at least three modules for processing shipping items requiring sorting and a conveyor line for transporting the items in a first transport path from the first, to the second and to the third module. 
     Different systems, each of which performs different functions, are known for processing items to be shipped. Thus, for example, there are systems which perform only the process of positioning the items and canceling the postage stamp, or the process of reading the address and coding, or the fine sorting process. As a result of ergonomic requirements and process requirements, however, there is an increasing demand for systems which can perform a plurality of processes. In this case the corresponding process devices are connected one after the other in series, with the shipping items passing through the entire system. If a process device is not required for a specific function, it is deactivated. 
     SUMMARY OF THE INVENTION 
     It is the object of the present invention to specify an item sorting system which handles shipping items with care. 
     This object is achieved by an item sorting system of the type cited in the introduction which inventively provides a bypass for transporting items requiring sorting in a second transport path from the first to the third module thereby circumventing the second module. The effect of bypassing the second module is that fewer structures are present on which mechanical stresses, in particular damage, can occur. As a result the shipping items are subjected to a lower mechanical load. In addition it is possible, by means of the bypass which circumvents the unused second module, to shorten the second transport path relative to the first transport path, as a result of which the mechanical load on the items can additionally be reduced due to the shorter transport path. It is also conceivable that although the second transport path is just as long or longer, items are still handled with greater care if the second module is bypassed, so a more gentle treatment of the items is achieved nonetheless. 
     The invention is based on the further idea that different sorting processes can be performed in separate passes on one item sorting system. For example, a system for reading addresses and coding the items is used in a first pass for reading, coding and presorting into collecting containers, and in a second pass the system is used as a fine sorting machine which sorts the coded and presorted items once again into collecting containers, albeit according to finer criteria. The modules for reading and coding can be circumvented in the second pass by means of the bypass, as a result of which the items are handled with greater care. 
     The shipping item sorting system can be a postal item sorting system, in particular a letter item sorting system. A module in this context can be understood to denote a means for modifying the item, for example in terms of its position—apart from a pure, destination-oriented transport—or in terms of its components, e.g., by printing. A module can be a means for positive or negative acceleration, for sorting, aligning, rotating, printing, labeling, delaying, e.g., a queuing section, separating (“singling”), collecting or the like, and can be in particular a means which puts the items under greater stress than a spatially destination-oriented transport. 
     The conveyor line also comprises the bypass which circumvents a conveyor sub-line of the conveyor line. The bypass itself comprises a conveyor sub-line which is expediently shorter than the conveyor sub-line circumvented by the bypass. The bypass is advantageously free of a module which is the same as the second module or similar thereto. A sorting by the item sorting system is also understood to signify a processing of the shipping items in the form of a preparation for sorting, for example by applying a sorting code such as an identity code, a destination code or the like. A subdividing of the items into at least two containers is also understood as sorting. The item sorting system advantageously comprises a control unit for activating the bypass and steering the items through the bypass. By this means a decision as to whether an item stream is to run through the bypass can be automated and in particular linked with protection functions. 
     In an advantageous embodiment of the invention the item sorting system comprises a control unit which permits a routing of an item stream from a plurality of items arranged one immediately after another into the bypass and blocks a routing of only individual items from the item stream into the bypass—with other items of the item stream being routed past the bypass. In this way a collision of items downstream of the bypass can be easily avoided. 
     A collision of items can likewise be easily avoided if the item sorting system comprises a control unit for controlling different system operating modes and for activating the bypass as a function of the system operating mode. The item sorting system can be easily operated without items flowing both via the bypass and past the bypass. Consequently, the items cannot collide downstream of the bypass. The items can be routed by the control unit via the bypass in one system operating mode and past the bypass in the other system operating mode. A changeover between the operating modes is expediently only controlled when both the bypass and the conveyor sub-line circumvented by it are free of items, in particular only during an idle phase of the conveyor line or before or after a transportation of items by means of the conveyor line. 
     In a further advantageous development of the invention the item sorting system comprises a control unit for setting a spacing between the items in the conveyor line as a function of an activation of the bypass. By this means a small spacing between the items can be set when the bypass is activated and consequently a high item throughput rate through the item sorting system can be achieved. This embodiment is based on the idea that as a result of the bypassing of the second module and the consequently achievable lower loading during the transport, the items are displaced to a lesser extent relative to one another. Because of the smaller displacement the spacings of the items from one another, e.g., during feeding into the conveyor line, can be reduced. With the bypass activated, the spacing is therefore less than with a deactivated bypass. By reducing the spacings an increase in the throughput of items through the item sorting system can be achieved at the same transport speed. The spacing is expediently set in a feeder of the item sorting system which individually separates (“singles”) the items. 
     It is also proposed that the item sorting system comprises a control unit for deactivating a conveyor sub-line circumvented by the bypass as a function of an activation of the bypass. The wear and tear to which the switched-off conveyor sub-line is exposed can be kept low and noise emissions can be reduced. With the conveyor sub-line deactivated, the item sorting system also requires less energy. A simple deactivation of the conveyor sub-line can be achieved if the item sorting system comprises two drives for driving the conveyor line which can be operated independently of each other, with the control unit for deactivating the conveyor sub-line circumvented by the bypass being provided by a deactivation of one of the drives. In addition or alternatively, with the bypass activated, the second module circumvented by the bypass can be switched off, as a result of which the wear and tear on the second module and its energy consumption can be reduced. 
     The modules of the item sorting system can have different functions. Thus, for example, the first module may be a feeder for separating loads into single items and feeding them to the conveyor line, the second module may be a printer for printing an identity code or destination code on the items, and the third module may be a subdividing device for allocating the items to different collecting containers. The maximum speed at which the items can be transported through the system can in this case be determined by the second module, for example the printer, which specifies the upper speed limit of the transport on the basis of its print speed. In a circumventing of the second module by means of the bypass it can happen that this upper speed limit is no longer relevant, but instead another module specifies a higher upper speed limit, thus enabling the speed of the items through the system to be increased. In order to set the expediently optimal transport speed of the items, the item sorting system advantageously comprises a control unit for setting a transport speed of the items in the conveyor line as a function of an activation of the bypass. Depending on the properties of the bypassed module or the bypassed modules, a maximum transport speed can be set automatically and an optimal throughput of the system achieved. 
     Images of handwritten addresses are usually output online to an employee who reads the address and enters it into a computer so that the corresponding item can be coded according to the input. For this purpose a small time interval is required in which the item is transported in a transport section for generating a time delay between the read module and the coding module. A transport section of this kind can be 40 m or more in length and have a plurality of curves. If the second module is a transport section for generating a time delay, by bypassing this module it is possible to reduce the exposure of the items to stresses to a substantial degree. In this case the processing function of the module is the time delay and expediently not primarily a transport to a destination, since the transport section in particular is longer than a technically expedient transport path between modules which it links. The transport section can be embodied as a single part or divided into multiple parts, i.e., interrupted by further modules. 
     The vast majority of supplied items are typically already presorted and require no further alignment into a common orientation. In order to sort these items, a second module which has an aligning means for aligning the items into a common orientation can advantageously be circumvented by means of the bypass. 
     In a further refinement of the invention the second module has a labeling means for labeling the items. Said module can expediently be bypassed in a second pass in which no further coding has to be performed. The labeling means can be a postage stamp canceling device or an identification printer, e.g., a barcode printer. 
     If the second module has a recording means for recording an image of the items, in a second pass in which addresses are already present in machine-readable form, said recording means can advantageously be circumvented by means of the bypass. 
     As described above, item sorting systems can be used with a plurality of modules in a plurality of passes for different functions or sorting methods. For this purpose the item sorting system advantageously comprises a control unit for controlling at least two different sorting methods and for activating the bypass as a function of the sorting method that is to be performed. Depending on sorting method, for example first the sorting method of reading the addresses and coding and then the sorting method of fine sorting, one or more bypasses can be easily, in particular automatically, activated, thereby exposing the items to less stress. 
     In order to avoid a complicated and error-prone merging of items from two transport sub-lines into a common conveyor sub-line, the item sorting system advantageously comprises a control unit which blocks a switchover from the first to the second transport path when items are contained in a conveyor sub-line circumvented by the bypass. For example, a switchover between the transport paths may be allowed only at the beginning of a sorting operation, or a switchover can only be performed after a waiting time which is long enough to ensure that within this time all the items from the conveyor sub-line to be bypassed have been conveyed out of said conveyor sub-line. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The invention is explained in more detail with reference to an exemplary embodiment which is shown in a drawing with a single FIGURE, which shows in a schematic representation an item sorting system comprising a number of modules for processing items. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The figure shows in a schematic representation an item sorting system  2  comprising a number of modules  4 ,  6 ,  8 ,  10 ,  12 ,  14 ,  16 ,  18 ,  20 ,  22  for processing items  24  requiring sorting at a conveyor line  26  for transporting the items  24 . The module  4  is a presorting device into which the items  24  are input by the bagful and which separates out too large, too small, too thick or too inflexible items  24  and only allows standard letters to pass through. Said letters are brought to the module  6  which comprises a singling device, also referred to as a feeder, which individually separates the items  26  and between them sets a spacing specified by a control unit  28 . The control unit  28  is connected for control purposes to all the modules  4 ,  6 ,  8 ,  10 ,  12 ,  14 ,  16 ,  18 ,  20 ,  22  as well as to further components of the item sorting system  2 . 
     The items thus separated into single items are pinched between two elastic belts by the conveyor line  26  and transported to the module  10  which is implemented as an aligning unit and aligns the items  24  by their lower edge as they pass. The items  24  are then guided by the conveyor line  26  without interruption past a reader device  30 , for example a barcode reader and address reader which reads a barcode possibly present on items  24  or an address printed onto the items  24 . Since the items  24  coming from the module  6  usually bear no barcode and certain items  24  have handwritten addresses which cannot be recognized by the reader device  30 , the items  24  are guided along by the conveyor line  26  past an image recording device  32  which records images of both sides of the items  24  in a bitmap format and supplies them to the control unit  28 . The control unit  28  sends images of those items  24  whose address is not machine-readable online to a reading center (not shown) in which the images are output on screens and read by staff who enter at least parts of the address via a keyboard. This data is forwarded online to the control unit  28 . 
     In the further course of the sorting method the items  24  are fed to the module  12  embodied as an aligning means which brings the items  24  into a uniform orientation, for example so that the address on all the items  24  is head up and the stamp is aligned in the transport direction. The authenticity of the stamp is then verified in the module  14  and the stamp is canceled. 
     All the items  24  are now supplied to the module  16  which is embodied as an approximately 50 m long transport section for generating a time delay of about 14 seconds. As a result of this delay the reading staff has several seconds in order to input the read address via the keyboard before the items  24  reach the module  18  embodied as a labeling means which prints a barcode onto the non-machine-readable items  24 . Said barcode indicates at least a part of the address of the respective item  24 , which address is consequently machine-readable. In a module  20  likewise implemented as a labeling means, a forwarding label is attached to items  24  for whose address a forwarding order is present, said forwarding label subsequently being printed with the forwarding address. Finally the items  24  are conveyed by the conveyor line  26  to the module  22  which is a subdividing device and roughly distributes the items  24  into a plurality of containers according to their address, for example 100 zip codes per container in each case. Also conceivable as a module  22  for processing the items  24  is a subdividing device for splitting into only two collection points or an item collecting means for feeding to a further sorting process. 
     The item sorting system  2  also comprises with the module  8  a second feeder for individually separating (“singling”) items  24  which are supplied already prepared by companies. Said items are already uniformly aligned and provided with a postage paid stamp, so they no longer require processing by the modules  12  and  14 . In a further system operating mode the item sorting system  2  can therefore be fed by the module  8  in which the control unit  28  activates a corresponding switch  34  which guides the items  24  into a bypass  36  and hence past the modules  12  and  14 . The bypass  36  comprises a conveyor sub-line  38  which is driven by a separate drive  40 , with the result that when the bypass  36  is activated the control unit  28  can set the conveyor sub-line  38  in motion and when the bypass  36  is deactivated the control unit  28  can bring the conveyor sub-line  38  to rest. A conveyor sub-line  42  which supplies the modules  12 ,  14  is likewise assigned a separate drive  44  which—depending on the status of the bypass  36 —can be switched on or switched off. 
     The bypass  36  can be activated by the control unit  28  if the item sorting system  2  is loaded with correspondingly uniformly oriented and canceled items  24 , not by the module  6 , but solely by the module  8 . In this case the system operating mode is switched over and the modules  12 ,  14  and the drive  44  are switched off by the control unit  28 . However, there is also the possibility that the module  8  loads the item sorting system  2  automatically if the module  6  has large loading gaps, for example if the presorting device is currently operating at no load. In this case the control unit  28  waits until there are no more items in the conveyor sub-line  42  and then activates the new system operating mode and hence the module  8  and the bypass  36 . As long as the conveyor sub-line  42  is not free of items  24  the control unit  28  blocks the bypass  36 . With such a brief activation of the bypass  36 , the modules  12 ,  14  remain in operation and the drive  44  remains in motion. If the module  6  reports a new loading requirement, for example after a manual filling, the control unit  28  switches over the system operating modes once again. 
     In a second pass controlled by the control unit  28 , the item sorting system  2  can be used in a further system operating mode for fine sorting, e.g., for fine sorting of the items  24  presorted previously in the first pass as described above. The containers filled with items  24  are then taken from the module  22  and the items  24  contained therein passed into the feeder of the module  8  which once again individually separates (“singles”) the items  24  and feeds them to the conveyor line  26 . These items  24  are all uniformly oriented, canceled and provided with a machine-readable address or an identity code which is read by the reader device  30 . Consequently the modules  12 ,  14 ,  16 ,  18  and  20  are not required for further fine sorting. A switch  46  is therefore set by the control unit  28  such that a second bypass  48  is activated which comprises a conveyor sub-line  50 . The latter is driven by a separate drive  52  and can therefore be driven or, as the case may be, shut down independently of the other parts of the conveyor line  26 . If the items are guided in the transport path via the bypass  48  in a second pass, the modules  12 ,  14 ,  16 ,  18 ,  20 , the drives  40 ,  44  and a further drive  54  are switched off, with the result that the corresponding part of the item sorting system  2  is in an idle state and the item sorting system  2  runs quietly and at a low level of wear and tear. 
     A spacing between the items  24  is also set in the feeder of the module  8 , said spacing being smaller than a spacing between items  24  which pass through the modules  16 ,  18  and  20 . The typical throughput of the item sorting system  2  is calculated according to the following equation: 
     
       
         
           
             
               
                 
                   Throughput 
                   = 
                   
                     transport 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       speed 
                       / 
                       
                         ( 
                         
                           
                             item 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             length 
                           
                           + 
                           spacing 
                         
                         ) 
                       
                     
                   
                 
               
             
             
               
                 
                   = 
                   
                     3.5 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       
                         m/s 
                       
                       / 
                       
                         ( 
                         
                           
                             200 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             mm 
                           
                           + 
                           
                             80 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             mm 
                           
                         
                         ) 
                       
                     
                   
                 
               
             
             
               
                 
                   = 
                   
                     45 
                     , 
                     000 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       items 
                       / 
                       
                         hour 
                         . 
                       
                     
                   
                 
               
             
           
         
       
     
     Owing to the approximately 3 m long bypass  48 , more than 50 m of transport section and a pass through the modules  16 ,  18 ,  20  are avoided, as a result of which the spacing can be set 20 mm less. This yields a throughput of 
                   Throughput   =     3.5   ⁢           ⁢       m/s     /     (       200   ⁢           ⁢   mm     +     60   ⁢           ⁢   mm       )                     =     48   ,   461   ⁢           ⁢     items   /   hour                   
and hence an increase of 3,461 items per hour, which is equivalent to about 8%.
 
     During full operation of the item sorting system  2 , the maximum transport speed is determined by the printer of the module  20 . If the modules  18 ,  20  are deactivated when the bypass  48  is active, the control unit  28  sets the transport speed of the items  24  faster in accordance with other conditions, as a result of which the throughput of the item sorting system  2  can additionally be increased.