Abstract:
A method and an installation for sorting flat articles, in particular flat items of mail, discharges each article to be sorted, in dependence on a respectively measured feature value, into an output device. A resulting stack is moved onto a transporting configuration with planes of the articles of the stack perpendicular to a first transporting direction. The transporting configuration transports the stack toward a processing device. The transporting configuration transports the stack initially in the first transporting direction. Following transportation in the first transporting direction, the transporting configuration rotates the stack around a curve from the first transporting direction into a second transporting direction. The transporting configuration then transports the stack toward the processing device in the second transporting direction.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the priority, under 35 U.S.C. §119, of German Patent Application DE 10 2009 016 559.2, filed Apr. 6, 2009; the prior application is herewith incorporated by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    The invention relates to a method and an installation for sorting flat articles, in particular flat items of mail. 
         [0003]    European Patent EP 0 634 957 B1, corresponding to U.S. Pat. No. 5,421,464, discloses method for sorting flat articles each extending over an article plane. The method includes providing a sorting installation having a processing device and a plurality of output devices, measuring, with the sorting installation, a value assumed by a predetermined feature for each article to be sorted, and discharging each article, with the sorting installation, in dependence on the respectively measured feature value, into an output device of the sorting installation, to create a stack of flat articles in at least one output device having been discharged into that output device, moving at least one stack onto a transporting configuration to cause the planes of the articles of the stack to be located perpendicularly to a first transporting direction, transporting the stack, with the transporting configuration, toward a processing device, transporting the stack, with the transporting configuration, toward the processing device initially in the first transporting direction and then in a second transporting direction, and processing the stack with the processing device. 
         [0004]    European Patent EP 0 634 957 B1, corresponding to U.S. Pat. No. 5,421,464, also discloses a sorting installation for sorting flat articles each extending over an article plane. The sorting installation includes a measuring device, a discharging device, a transporting configuration having a first transporting device and a second transporting device, a plurality of output devices, and a processing device. The measuring device is configured to measure a value assumed by a predetermined feature for each article to be sorted. The discharging device is configured to discharge each article, in dependence on the respectively measured feature value, into one of the output devices to create a stack of flat articles, in at least one of the output devices, having been discharged into the at least one output device. The first transporting device is configured to move a stack of flat articles out of one of the output devices onto the first transporting device with all of the planes of the articles of the stack located perpendicularly to a first transporting direction, and the first transporting device is configured to transport a stack toward the processing device in the first transporting direction, with the planes of the articles of the stack located perpendicularly to the first transporting direction. The second transporting device is configured to transport the stack toward the processing device in a second transporting direction, and the processing device is configured to process the stack. 
         [0005]    European Patent EP 0 634 957 B1, corresponding to U.S. Pat. No. 5,421,464, describes a method of sorting flat items of mail and a sorting installation. The items of mail which are to be sorted are sorted in a number of successive sorting sequences (sequencing). The sorting installation used for that purpose has an input module 5 with a separator, a discharging device and at least one row 1 of output devices (stacking compartments a, b, c, etc.). A feeding conveying belt 2 is disposed in relation to the row 1 in such a way that the row 1 and the feeding conveying belt 2 form two legs of a U. 
         [0006]    The separator of the sorting installation of European Patent EP 0 634 957 B1, corresponding to U.S. Pat. No. 5,421,464, separates the items of mail and generates a stream of spaced-apart items of mail. The discharging device divides those items of mail between the output devices a, b, c, etc., and therefore a respective stack of upright flat items of mail is formed in each output device. A respective stack of items of mail is removed from an output device a, b, c, etc. and moved onto the feeding conveying belt for a subsequent sorting sequence. In one configuration, a transfer bridge 6 is used for that purpose. During transfer from the output device onto the feeding conveying belt, the stack is removed from the output device, in the first instance, by a linear movement, then is rotated through 90° away from the separator and then is transported linearly toward the separator. The items of mail of the stack then run through the sorting installation again. 
         [0007]    U.S. Pat. No. 5,857,830 describes an article handling system 10 with a discharging device (sorter 15), and also describes a configuration (array 19) with a number of rows of output devices (output compartment 20) located one above the other. A container (cartridge switch) with flat articles can be moved into each output device. A handling machine (XY cartridge transfer and handling robot 30) has a bearing surface 35 for containers and is able to displace containers vertically and horizontally. Containers can also be stored on an interim basis in an interim storage device (buffer shell 40). The handling machine 30 is able to transfer containers back and forth between the configuration 19 and the interim storage device 40 and is located between the configuration 19 and the interim storage device 40. The sorting installation also has a feeding device (auto feeder 50) with a separator (feeding station 70). The handling machine 30 is able to move filled containers towards feeding devices 50, optionally from an output device 20 of the configuration 19 or from the interim storage device 40, and to rotate the container through 90° in the process. 
         [0008]    U.S. Pat. No. 7,467,792 B2 describes a sorting installation with a plurality of conveying belts. Such a conveying belt transports a container, which is filled with items of mail, in a first transporting direction, around a curve and in a second transporting direction, as is seen in FIGS. 10a to 10d. 
       SUMMARY OF THE INVENTION 
       [0009]    It is accordingly an object of the invention to provide a method and an installation for sorting flat articles, which overcome the hereinafore-mentioned disadvantages of the heretofore-known methods and installations of this general type and which avoid the need for a processing device to be disposed in such a way that a transporting configuration transports a stack to the processing device by way of a linear movement in a first transporting direction. 
         [0010]    With the foregoing and other objects in view there is provided, in accordance with the invention, a method for sorting flat articles each extending over an article plane. The method comprises providing a sorting installation having a processing device and a plurality of output devices, measuring, with the sorting installation, a value assumed by a predetermined feature for each article to be sorted, and discharging each article, with the sorting installation, in dependence on the respectively measured feature value, into an output device of the sorting installation, to create a stack of flat articles in at least one output device having been discharged into that output device, moving at least one stack onto a transporting configuration to cause the planes of the articles of the stack to be located perpendicularly to a first transporting direction, transporting the stack, with the transporting configuration, toward a processing device, transporting the stack, with the transporting configuration, toward the processing device initially in the first transporting direction and then in a second transporting direction, processing the stack with the processing device, providing a curved transporting device of the transporting configuration, and rotating the stack, with the curved transporting device, following transportation in the first transporting direction, around a curve from the first transporting direction into the second transporting direction, causing the stack to fan out upon rotation through the curve. 
         [0011]    With the objects of the invention in view, there is also provided a sorting installation for sorting flat articles each extending over an article plane. The sorting installation comprises a measuring device, a discharging device, a transporting configuration having a first transporting device, a second transporting device and a curved transporting device, a plurality of output devices, and a processing device. The measuring device is configured to measure a value assumed by a predetermined feature for each article to be sorted. The discharging device is configured to discharge each article, in dependence on the respectively measured feature value, into one of the output devices to create a stack of flat articles, in at least one of the output devices, having been discharged into the at least one output device. The first transporting device is configured to move a stack of flat articles out of one of the output devices onto the first transporting device with all of the planes of the articles of the stack located perpendicularly to a first transporting direction, and the first transporting device is configured to transport a stack toward the processing device in the first transporting direction, with the planes of the articles of the stack located perpendicularly to the first transporting direction. The second transporting device is configured to transport the stack toward the processing device in a second transporting direction. The processing device is configured to process the stack and the curved transporting device is configured to rotate a stack around a curve from the first transporting direction into the second transporting direction to cause the stack to fan out upon rotation through the curve. 
         [0012]    As mentioned above, the invention specifies a method and an installation for sorting flat articles. Each flat article which is to be sorted extends over an article plane. 
         [0013]    The sorting installation according to the invention includes a processing device and a plurality of output devices. The method according to the invention is implemented by using such a sorting installation, having a processing device and output devices. 
         [0014]    A measurable feature is predetermined. The sorting installation measures, for each article which is to be sorted, the value assumed by the predetermined feature for this article. 
         [0015]    The sorting installation discharges each article which is to be sorted, in dependence on the respectively measured feature value, into an output device of the sorting installation. This creates, in at least one output device, a stack of flat articles which have been discharged into this output device. 
         [0016]    The at least one stack is moved onto a transporting configuration in such a way that the planes of the articles of the stack are located perpendicularly to a first transporting direction. 
         [0017]    The transporting configuration transports the stack toward a processing device. The transporting configuration in this case transports the stack in the first instance in the first transporting direction. Following transportation in the first transporting direction, the transporting configuration rotates the stack around a curve from the first transporting direction into a second transporting direction. The transporting configuration then transports the stack toward the processing device in the second transporting direction. 
         [0018]    The method according to the invention and the apparatus according to the invention do away with the need to rotate the at least one stack, e.g. manually or through the use of a handling machine, once the stack has been moved onto the transporting configuration. Rather, the transporting configuration rotates the stack automatically in the respectively desired direction. 
         [0019]    The invention makes it possible to transport the stack from the output device toward the processing device around the sorting installation. The processing device can thus be positioned in a manner which is expedient for further processing. 
         [0020]    The transporting path over which the stack is transported can be made up of a straight section of freely selectable length, of a curved segment with a freely selectable radius and angle of curvature and of a very straight section of freely selectable length. It is possible to add further curved segments and straight sections. This makes it possible for the processing device to be placed in any desired position relative to the output device, even when the positions of further constituent parts of the sorting installation around which the stack has to be transported are already fixed. 
         [0021]    The processing device is preferably configured as a separator. The method according to the invention and the installation according to the invention can be used in order to sort articles in two sorting sequences. In the first sorting sequence, the sorting installation discharges the articles into the output device and divides them up between the output devices. In the process, a stack is formed in at least one output device. This stack is moved onto the transporting configuration. The transporting configuration transports the stack to the separator. This separator separators the articles, and the separated articles run through the sorting installation again, this time in a second sorting sequence. 
         [0022]    The curved transporting device may include a turntable which rotates about a vertical axis of rotation. This configuration allows a mechanically straightforward construction of the curved transporting device without a conveying belt or any other elastic parts which may render ongoing maintenance necessary. It is possible for this turntable to be constructed in one piece (in an integrally formed manner) or to be made up of lamellae. 
         [0023]    The curved transporting device may also include an endless conveying belt which is guided around the curve. This configuration saves space in relation to a turntable because the conveying belts need only cover the angle of curvature which is actually required rather than a full circle of 360 degrees. 
         [0024]    Other features which are considered as characteristic for the invention are set forth in the appended claims. 
         [0025]    Although the invention is illustrated and described herein as embodied in a method and an installation for sorting flat articles, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
         [0026]    The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0027]      FIG. 1  is a diagrammatic, top-plan view of a sorting installation of an exemplary embodiment of the invention; 
           [0028]      FIG. 2  is a top-plan view of four output devices and a transporting configuration of the sorting installation of  FIG. 1 , with a stack in one output device; 
           [0029]      FIG. 3  is a fragmentary, top-plan view of a configuration of a curved transporting device of  FIG. 1  with two rails; 
           [0030]      FIG. 4  is a top-plan view of a configuration of the curved transporting device of  FIG. 1  with an endless conveying belt which is produced from a circular ring; 
           [0031]      FIG. 5  is a fragmentary, side-elevational view of a turntable and two endless conveying belts; and 
           [0032]      FIG. 6  is a fragmentary, cross-sectional view of two output devices without side walls. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0033]    In the exemplary embodiment, the sorting installation is used in order to sort flat items of mail, in particular standard letters, large letters, postcards and/or catalogs. Each item of mail extends over an article plane and has a front side and a rear side. One side of each item of mail bears information relating to a delivery address to which the item of mail has to be transported. This information is in a form which can be read by a person or is in the form of a bar code or of a matrix code or of some other coding. 
         [0034]    Referring now to the figures of the drawings in detail and first, particularly, to  FIG. 1  thereof, there is seen a diagrammatic, top-plan view of a sorting installation of an exemplary embodiment of the invention. This sorting installation includes the following constituent parts:
       a feeding device (feeder) with a separator (singulator)  20 ,   a transporting device  21 ,   a reader  22 ,   a discharging device  23 ,   a configuration having a multiplicity of output device  2 . 1 ,  2 . 2 , etc.,   a first transporting device  1 ,   a second transporting device  28 ,   a curved transporting device  29 ,   a positioning device  30 , and   a machine controller  24 .       
 
         [0045]    The first transporting device  1 , the second transporting device  28  and the curved transporting device  29  together form a transporting configuration. 
         [0046]    In the exemplary embodiment, an endless conveying belt  26  belongs both to the feeding device and to the second transporting device  28 . The conveying belt  26  transports stacks of items of mail in a second transporting direction T 2 . 
         [0047]    A stack of items of mail, which are to be sorted, is fed to the feeding device. The items of mail stand upright during the feeding operation. The conveying belt  26  of the feeding device transports the items of mail to the separator  20 . This separator  20  separates the stack of the items of mail by successively withdrawing a respective item of mail from the stack in a withdrawal direction AR. The separator  20  thus creates a series of upright items of mail which are spaced apart from one another. 
         [0048]    The transporting device  21  transports the sequence of spaced-apart, upright items of mail through the sorting installation. The transporting device  21  preferably includes a system of a plurality of vertically disposed endless conveying belts, of which two clamp an item of mail temporarily between them in each case. It is possible for an item of mail to be turned by the conveying belts of the transporting device  21 , e.g. in order for it to be possible to read the delivery address. 
         [0049]    During transportation, the items of mail pass the reader  22 . The reader  22  generates a respective digital image of that side of an item of mail on which the information relating to the delivery address can be found. The reader  22  evaluates this image and attempts, in a first instance, to decode the delivery address automatically, e.g. by Optical Character Recognition (OCR) or by bar code reading. If this is unsuccessful, then the image is displayed on a screen of a video coding station. An operator reads the delivery address and enters it into a keyboard or the like. 
         [0050]    The machine controller  24  evaluates a computer-available sorting plan SP which is stored in a data memory. This sorting plan SP assigns a respective output device  2 . 1 ,  2 . 2 , etc. to each possible delivery address of an item of mail. The sorting plan SP thus establishes which items of mail with which delivery addresses should be discharged into which output device. 
         [0051]    In the exemplary embodiment, there are considerably more possible delivery addresses than output devices, and therefore the sorting plan SP usually assigns a number of delivery addresses to one output device  2 . 1 ,  2 . 2 , etc. It is possible for the sorting plan SP to reserve individual output device for just a single delivery address in each case because a large number of items of mail are directed to this delivery address. 
         [0052]    The transporting device  21  transports the items of mail further to the discharging device  23 . This discharging device  23  preferably includes a series of diverters, namely in each case at least one diverter per output device  2 . 1 ,  2 . 2 , etc. In each diverter, a discharging path branches off from the transporting path to the associated output device. A respective discharging path connects the transporting path to the output device. The diverter is activated by the machine controller  24  and optionally deflects an item of mail into the discharging path or leaves the item of mail in the transporting path. 
         [0053]    The actual transporting speed of each transporting path is measured. The machine controller  24  thus “knows” at which point in time each item of mail is located at which location in the transporting device  21 . Moreover, the machine controller  24  “knows” the respective delivery address of each item of mail once the reader  22  has decoded the delivery address. The machine controller  24  activates that diverter which connects the transporting path to that discharging path which leads to that output device  2 . 1 ,  2 . 2 , etc. into which the item of mail is to be discharged in accordance with the read delivery address and the sorting plan SP. The item of mail is discharged from the transporting path through the use of the diverter and is transported on the discharging path to the output device and stacked there. 
         [0054]    The multiplicity of output devices  2 . 1 ,  2 . 2 , etc. of the configuration are disposed one behind the other, as seen in a longitudinal direction L. In the exemplary embodiment, the longitudinal direction L is oriented away from the feeding device with the separator  20 . It is possible for the output device  2 . 1 , etc. to be provided in a number of rows and for the rows to be disposed vertically or obliquely one above the other. Each row extends along the longitudinal direction L. 
         [0055]      FIG. 2  shows four output devices  2 . 1 ,  2 . 2 ,  2 . 3  and  2 . 4  and the first transporting device  1  from the discussion above. It is also the case that the first transporting device  1  extends along the longitudinal direction L. In addition, a stack St is shown in the output device  2 . 3 . 
         [0056]    The items of mail stand on a conveying belt  11  of the first transporting device  1  while the conveying belt  11  transports the transversely located stack or stacks. The first transporting device  1  transports each stack in a first transporting direction T 1 . In the exemplary embodiment, this first transporting direction T 1  runs counter to the longitudinal direction L. A stacking direction SR is located perpendicularly to the first transporting direction T 1 . 
         [0057]    In one configuration, the items of mail are guided by a lateral guide device  10  during transportation in the first transporting direction T 1 . The endless conveying belt  11  is located between this guide device  10  and the rows of output devices  2 . 1 ,  2 . 2 , etc. The guide device  10  is, for example, in the form of a guard rail. 
         [0058]    In another configuration, there is no guide device  10  provided, and it is therefore possible for a transported stack to include items of mail of any desired width. 
         [0059]    In one configuration, the stack is supported, and pushed, by a respective supporting device. This supporting device is positioned behind the stack, as seen in the transporting directions T 1  and T 2 . A respective supporting surface of the supporting device extends in a supporting plane parallel to the article planes and perpendicularly to the stacking direction SR. A connecting member connects the supporting surface to a guide device. The connecting member and thus also the supporting surface SF, are displaced in the transporting directions and around a curve and push the stack in front of them.  FIG. 1  shows, by way of example, a supporting surface SF behind the stack ST from the output device  2 . 3 . 
         [0060]    The curved transporting device  29  transfers each stack automatically from the first transporting device  1  onto the second transporting device  28 . 
         [0061]    The transition from the first transporting device  1  to the curved transporting device  29  preferably forms a step, through which a transported stack slides downward. The vertical extent of the step is significantly smaller than the height of each item of mail, e.g. 20 mm to 30 mm. Such a step is preferably also incorporated between the curved transporting device  29  and the second transporting device  28 . 
         [0062]    For example, the first transporting device includes an endless conveying belt  11  which has a small vertical dimension because it is guided around a thin roller. This roller and one end of the endless conveying belt  11  are located above the curved transporting device  29 . This end of the endless conveying belt  11  forms the step. 
         [0063]    While the curved transporting device  29  transports a stack through the curve, the stack fans out. The distance between two items of mail of the stack is greater on the outside of the curve than on the inside. The curved transporting device  29  transports at a predetermined maximum speed in order to ensure that the centrifugal force does not destroy the stack. The radius is greater than or equal to a minimum radius. 
         [0064]    It is possible for both the first transporting device  1  and the curved transporting device  29  to each include an endless conveying belt. These two conveying belts are provided on the same level. A slit is located between them. The conveying belts are narrower than the items of mail, and therefore the items of mail project beyond the conveying belt at least on one side. At least one supporting unit alongside the conveying belts bears the items of mail in addition and prevents an item of mail from falling through the slit between the two conveying belts. 
         [0065]    The following items of mail push an item of mail over the slit from the first transporting device  1  onto the curved transporting device  29 . It is also possible for the transition between the curved transporting device  29  and the second transporting device  28  to be configured in this way. The support is preferably in the form of two rails S 1 , S 2 , between which the conveying belts  11 ,  31 ,  26  run. 
         [0066]      FIG. 3  shows this configuration with a supporting device in the form of two rails S 1 , S 2 . The figure illustrates two rails S 1  and S 2 , on which the items of mail are transported first of all in the first transporting direction T 1 , then through the curve and then in the second transporting direction T 2 . The figure also illustrates the endless conveying belt  11  of the first transporting device  1 , an endless conveying belt  31  of the curved transporting device  29  and the endless conveying belt  26  of the second transporting device  28 . The endless conveying belt  31  of the curved transporting device  29  is guided around two rollers R 1 , R 2 . One roller, preferably the downstream roller R 2 , is driven, the other roller is not. The rails S 1 , S 2  run through the curve. 
         [0067]    In one configuration, the curved transporting device  29  includes an endless conveying belt  31 . This conveying belt is produced from a segment of a circle or of a circular ring (torus).  FIG. 4  shows, by way of example, a segment of such a circular ring. In order to ensure that the curved transporting device  29  is able to convey a stack through a curve of α [degrees], use is made of a segment with an angle of at least 2*α. In the example of  FIG. 4 , α is 90 degrees. This circular ring is folded about an axis As, and the two sections are connected to one another at straight ends E 1 , E 2  of the circular ring. This creates an endless conveying belt  31 . 
         [0068]    In another configuration, which  FIG. 5  shows, the curved transporting device  29  includes a horizontal turntable  32  which is mounted rotatably about a vertical axis of rotation D and is rotated about this axis. The stack stands on this turntable  32  while the rotating turntable  32  transports the stack through the curve. It is also the case in this configuration that the items of mail are transported over two steps, stages or intervals. There is one step between the first transporting device  1  and the turntable  32 , and a further step between the turntable  32  and the second transporting device  28 .  FIG. 5  shows a configuration in which the first transporting device  1  has an endless conveying belt  11  and the second transporting device  28  has an endless conveying belt  26 . The second transporting direction T 2  is located perpendicularly to the plane of the drawing in  FIG. 5 . 
         [0069]    The conveying belt  11  is guided around a roller R 11 . The roller R 11  is seated on a driven shaft W 11 . The shaft W 11  rotates, and rotates the roller R 11  along with it. This makes the conveying belt  11  rotate. Accordingly, the conveying belt  26  is guided around a roller R 26 , and the roller  26  is seated on a shaft W 26 . 
         [0070]    In the embodiment which  FIGS. 1 and 3  show, the curve is 90 degrees, i.e. there is an angle of 90 degrees between the first transporting direction T 1  and the second transporting direction T 2 . It is also possible for the curve to have some other angle of curvature. 
         [0071]    The endless conveying belt  26  of the second transporting device  28  transports each stack in a second transporting direction T 2 . In the exemplary embodiment, the second transporting direction T 2  is located perpendicularly to the first transporting direction T 1 . Generally, the angle between the two transporting directions T 1  and T 2  is equal to the angle of curvature a of the curved transporting device  29 . The direction SR of each stack runs parallel to the second transporting direction T 2  while the second transporting device  28  transports the stack in the second transporting direction T 2 . 
         [0072]    The endless conveying belt  26  of the second transporting device  28  transports each stack to the separator  20  in the second transporting direction T 2 . Throughout transportation from the respective output device to the separator  20 , the stack is not rotated relative to the transporting configuration  1 ,  28 ,  29 . Rather, the stacking direction SR remains unchanged relative to the transporting configuration  1 ,  28 ,  29 , and thus changes only in the curved transporting device  29  together with the transporting direction. 
         [0073]    It is also possible for the second transporting device  28  to transport the stack St not to a separator  20 , but to some other processing device, e.g. to a stack storage device in which the stacks are stored on a temporary basis. 
         [0074]    Each output device  2 . 1 ,  2 . 2 , etc. includes a base. In one embodiment, two adjacent output device  2 . 1 ,  2 . 2 , etc. are separated from one another by a respective side wall. 
         [0075]    In another embodiment, the bases of the output devices  2 . 1 ,  2 . 2 , etc. are inclined in relation to the horizontal, and there is an edge between two adjacent output devices. 
         [0076]    In a preferred development of this embodiment, the base of each output device  2 . 1 ,  2 . 2 , etc. has a region in which the surface is covered with imbricated scales. The scales are disposed in such a way that they make it more difficult for a stack St of flat items of mail to be displaced in the longitudinal direction L or counter to the longitudinal direction L. The example of  FIG. 2  shows four regions  3 . 1 ,  3 . 2 ,  3 . 3  and  3 . 4  with scale-covered surfaces. These regions  3 . 1 ,  3 . 2 , etc. belong to the bases of the output device  2 . 1 ,  2 . 2 , etc. 
         [0077]    It can be seen in the figures that each base, as seen in the stacking direction SR, in the first instance has a respective scale-covered region  3 . 1 ,  3 . 2 ,  3 . 3  and  3 . 4 , which is adjoined in each case by a non-scaled region  4 . 1 ,  4 . 2 ,  4 . 3 ,  4 . 4 . A non-scaled region  4 . 1 ,  4 . 2 ,  4 . 3 ,  4 . 4  is thus located between the scale-covered region  3 . 1 ,  3 . 2 ,  3 . 3 ,  3 . 4  and the first transporting device  1  with the conveying belt  11 . 
         [0078]    As a result of this configuration, the scales make it difficult for an item of mail to be displaced while the item of mail is being discharged. In contrast, once the item of mail has come into contact with the stack St, even the friction between the items of mail of the stack St makes it more difficult for an individual item of mail to be displaced, and therefore the surface of the base beneath the stack need no longer be covered with scales. 
         [0079]    As already explained, a number of flat items of mail are usually discharged into the same output device, that is to say all of the items of mail with delivery addresses which the sorting plan SP assigns to this output device. Those flat items of mail which have been discharged into this output device  2 . 3  form a stack St. The direction SR of this stack St is located perpendicularly to the planes of the items of mail and, in the exemplary embodiment, also perpendicularly to the longitudinal direction L. 
         [0080]    In the example of  FIG. 2 , a number of items of mail are discharged into the output device  2 . 3  and form a stack St there. 
         [0081]    Each output device  2 . 1 ,  2 . 2 , etc., moreover, has a respective output-device-supporting component. This supporting component includes a supporting surface, a connecting member and a guide rail. The support surface and the connecting member, together, are in the form of a paddle. The guide rail runs parallel to the stacking direction SR. The connecting member is fixed to the supporting surface and is able to slide back and forth in the guide rail. 
         [0082]    In  FIG. 2 , four paddles  5 . 1 ,  5 . 2 ,  5 . 3  and  5 . 4  of the four output devices  2 . 1 ,  2 . 2 ,  2 . 3  and  2 . 4  can be seen from above, as can four guide rails  7 . 1 ,  7 . 2 ,  7 . 3  and  7 . 4 . The stack St of items of mail in the output device  2 . 3  has displaced the paddle  5 . 3  toward the first transporting device  1 . 
         [0083]    The output-device-supporting component  5 . 1 ,  5 . 2 , etc. prevents tipping over of the stack of items of mail in the output device. The items of mail are discharged into the output device, in the stacking direction SR, against the paddle. The growing stack St displaces the paddle, in the stacking direction SR, away from the diverter and thus, perpendicularly to the longitudinal direction L, toward the first transporting device  1 . In the example of  FIG. 2 , the paddle  5 . 3  is displaced by the stack St in the output device  2 . 3 . 
         [0084]    The connecting member is connected to a restoring component, preferably to a spring. The growing stack St displaces the paddle  5 . 3  counter to the force of the restoring component. The paddle  5 . 3  thus pushes the stack St toward the diverter again, counter to the stacking direction SR. This prevents the stack St from falling over. 
         [0085]    In the exemplary embodiment, the first transporting device  1  with the conveying belt  11  is adjacent the row or the rows of output devices  2 . 1 ,  2 . 2 , etc. in such a way that the distance between the output devices  2 . 1 ,  2 . 2 , etc. and the first transporting device  1  is small, e.g. less than 10 cm. The distance is small enough for it to be possible for a stack of items of mail to be transferred easily from the row of output devices onto the first transporting device  1 . 
         [0086]    It is also possible for the distance between the output devices  2 . 1 ,  2 . 2 , etc. and the first transporting device  1  to be significantly greater. For example, a transfer bridge may transfer the stack. Such a transfer bridge is described, for example, in European Patent EP 0 634 957 B1, corresponding to U.S. Pat. No. 5,421,464, and in German Patent DE 42 36 507 C1, corresponding to U.S. Pat. No. 5,353,903. 
         [0087]      FIG. 6  shows the two output devices  2 . 1  and  2 . 2  in cross section. The conveying belt  11  of the first transporting device  1  is located behind the two output devices  2 . 2  and  2 . 3 , as seen in the viewing direction of  FIG. 6 . The scales on the bases of the two output devices  2 . 2  and  2 . 3 , inter alia two sets of scales  8 . 2  and  8 . 3 , are illustrated. Also evident is an edge  9 . 2  between the adjacent output devices  2 . 1  and  2 . 2  and an edge  9 . 3  between the adjacent output device  2 . 2  and  2 . 3 . 
         [0088]    The aforementioned supporting component  5 . 3  in the form of a paddle is moved toward the discharging device, counter to the stacking direction SR, by a restoring component. The supporting component  5 . 3  thus supports a stack St in the output device  2 . 3 . The stack St is located in front of the supporting component  5 . 3  of the output device  2 . 3 , as seen in the viewing direction of  FIG. 6 . 
         [0089]    The stacking direction SR is located perpendicularly to the plane of the drawing in  FIG. 6 , and the stack St pushes the supporting component  5 . 3  toward the conveying belt  11  and away from anyone viewing  FIG. 6 . 
         [0090]    In the embodiment which is shown in  FIG. 6 , the base of each output device forms a planar surface which is covered with scales in one region. In a development of this configuration, the base of each output surface is subdivided into two regions which are located one behind the other as seen in the direction of ascent A, that is to say one beside the other as seen in the stacking direction SR: a relatively steep region and a shallower region. The edge between the output device and the adjacent output device is adjoined, as seen in the direction of ascent A, in the first instance by a region which is inclined to a relatively pronounced extent in relation to the horizontal and then by a region which is inclined to a less pronounced extent or is even horizontal.