Patent Publication Number: US-7588237-B2

Title: Apparatus and method for collecting sheets into sets

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority from Dutch Patent Application No. NL 1029387, filed on Jun. 30, 2005. 
   FIELD AND BACKGROUND OF THE INVENTION 
   The invention relates to an apparatus and a method for collecting sheets into sets. 
   In particular, in the context of machine assembly of mail items, it is known to use an apparatus having:
         a main supply station equipped with a sheet holder for storing a stack of sheets, a separation system for separating sheets piece by piece from the sheet holder, and a sheet supply track for conveying separated sheets to the conveyor track; and   at least two insert supply stations, each equipped with a sheet holder for storing a stack of sheets, a separation system for separating sheets piece by piece from the sheet holder, and a sheet supply track for conveying separated sheets to the conveyor track.       

   A first one of the insert supply stations is then equipped for supplying sheets to a first position on the conveyor track downstream of the main supply station and a second one of the attachment supply stations is arranged for supplying sheets to a second position on the conveyor track downstream of the first position on the conveyor track. 
   The sheets can be, for instance, address carriers, letters, brochures, reply cards, prepaid envelopes, carriers with a plastic card, etc. 
   In practice, it frequently happens that in assembling very large numbers of sets, for the purpose of supplying inserts to main documents coming from the main supply station, a switch is made from one of the insert supply stations to another one of the insert supply stations, both insert supply stations being initially loaded with inserts of the same type. 
   In order to prevent loss of production, it is desirable that this can be done automatically and without stopping the apparatus, in response to (imminent) emptiness of the insert supply station from which inserts are being added. A problem here is that if the insert supply station that is to take over the supply of documents from an emptied insert station is situated upstream of the emptied insert station, there is at least one main document or at least one set of main documents to which no insert document can be added without stopping the machine and executing such addition manually. This is disadvantageous in particular if the main documents, as is often the case, are each unique documents destined for a particular recipient. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention, in the processing of sheets into mail items, to provide a solution which makes it possible, during the processing of main documents with sets of inserts into mail items, without stopping, to switch from the supply of sets of inserts from one of the insert supply stations to the feeding of sets of inserts from another one of the insert supply stations, also when the latter is situated upstream of the emptied one of the insert supply stations. 
   According to the present invention, this object is achieved by providing an apparatus for collecting sheets into sets, equipped with a conveyor track, a main supply station having a sheet holder for storing a stack of sheets, a separation system for separating sheets piece by piece from the sheet holder, and a sheet supply track for conveying separated sheets to the conveyor track, and at least two insert supply stations, each having a sheet holder for storing a stack of sheets, a separation system for separating sheets piece by piece from the sheet holder, and a sheet supply track for conveying separated sheets to the conveyor track. 
   A first one of the insert supply stations is arranged for supplying sheets to a first position on the conveyor track downstream of the main supply station and a second one of the insert supply stations is arranged for supplying sheets to a second position on the conveyor track downstream of the first position on the conveyor track. 
   The sheet supply tracks of the insert supply stations each have a stacking position arranged for collecting sheets received piece by piece into a stacked set and for feeding the set. 
   The sheet supply tracks of the insert supply stations are each arranged for adding to a sheet or to a set of sheets coming from the main supply station at least one set of sheets. 
   At least the sheet supply track of the second insert supply station has a waiting position which is arranged for receiving a set coming from the stacking position and holding the received set in readiness while in the stacking position a next set is being collected. 
   A control is arranged for, in response to lack of a complete, feedable set in the stacking position of the second insert supply station, causing a set to be added from the first insert supply station to a main document. 
   The invention can also be embodied in a method which can be carried out with such apparatus, for collecting sheets into sets, utilizing: a conveyor track; a main supply station having a sheet holder for storing a stack of sheets, a separation system for separating sheets piece by piece from the sheet holder, and a sheet supply track for conveying separated sheets to the conveyor track; and at least two insert supply stations, each having a sheet holder for storing a stack of sheets, a separation system for separating sheets piece by piece from the sheet holder, and a sheet supply track for conveying separated sheets to the conveyor track. 
   Each time, a first one of the insert supply stations supplies sheets to a first position on the conveyor track downstream of the main supply station and a second one of the insert supply stations supplies sheets to a second position on the conveyor track downstream of the first position on the conveyor track. 
   The sheet supply tracks of the insert supply stations each in a stacking position collect sheets, received piece by piece, into a stacked set and feed it. 
   The sheet supply tracks of the insert supply stations add to a sheet or to a set of sheets coming from the main supply station at least one set of sheets. 
   In a waiting position in the sheet supply track of the second insert supply station, a set of sheets coming from the stacking position is received and held in readiness while in the stacking position a next set of sheets is collected. 
   In response to lack of a complete, feedable set in the stacking position of the second insert supply station, from the first insert supply station a set of sheets is added to a main document. 
   As at least the sheet supply track of the second insert supply station comprises a waiting position, which is arranged for receiving a set coming from the stacking position and holding the received set in readiness while in the stacking position a next set is being collected, and the apparatus is arranged for, in response to the lack of a complete feedable set in the stacking position of the second insert supply station, adding to a main document a set from the first insert supply station, there is, at the moment when it is detected that no complete set is available in the stacking position, still a set available in the waiting position which can still be added to a main document which has already been conveyed too far to receive a set of inserts from the first one of the insert supply stations. It is noted that the designations ‘first’ and ‘second’ for the insert supply stations are not intended to indicate that there can be only two insert supply stations or that they should specifically be the first and second insert supply stations if there are more than two insert supply stations. The point is merely to distinguish the insert supply stations from each other as regards their relative positions, while more insert supply stations may be present in the apparatus. 
   Particular elaborations of the invention are set forth in the dependent claims. 
   These and further features as well as effects and details of the invention will be described hereinbelow and elucidated with reference to an exemplary embodiment represented in the Figures. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic representation of an example of an apparatus according to the invention; 
       FIG. 2  is a schematic representation of a portion of the apparatus according to  FIG. 1 ; and 
       FIGS. 3A-3C  are highly schematic representations of three consecutive operating conditions of the apparatus according to the example represented in  FIGS. 1 and 2 . 
   

   DETAILED DESCRIPTION 
   The apparatus for assembling mail items according to the example represented in  FIGS. 1 and 2  is equipped with a supply station  16  for supplying main documents, insert supply stations  17 - 20  for supplying inserts, a folding station  21  and an inserter station  22 . A transport track  5  extends from the supply station  16  for supplying main documents to the inserter station  22 . The control structure  9  comprises a main control unit  24  with a memory  8  and a connecting structure  23  which operatively connects the main control unit  24  with the stations  16 - 22 , as is schematically represented in  FIG. 1 . The stations are equipped with distributed control units  25 - 31  for processing instructions coming from the main control unit  24  and for delivering signals representing the status of the respective station  16 - 22 . According to this example, the supply stations  16 - 20  are each suitable for feeding multiple sheets to each set. 
   The sheets  1 ,  2  to be processed can for instance be of a different size. 
   The sheet  1  can for instance be of A4 size and a set of sheets  2  can for instance be 12 cm long, measured in conveying direction  4 . 
   The sheets  1 ,  2  are conveyed in conveying directions  3  and  4 , respectively, along the conveyor track  5  and a supply track  6 . 
   Next, at least the sheet  1  or the set of sheets  2  is stopped, until the relative positions of the sheets  1 ,  2  are suitable for combining the sheets  1 ,  2  is to a stacked set in the conveyor track  5  and then the sheets  1 ,  2  are simultaneously conveyed further and combined to a stacked set 
   According to this example, in the folding station  21 , the stacked set is folded twice to form a zigzag structure. 
   The sheets  1 ,  2  of the set  7  are then, from the combining until the folding of the set  7 , mutually fixed. In folding, a first fold  14  is provided in all sheets  1 ,  2  of the set  7  and a second fold  15  is provided only in the sheet  1 . 
     FIG. 2  shows the insert supply station  19  of the apparatus according to  FIG. 1  in more detail. The conveyor track  5  for conveying sheets  1  is designed with pairs of opposite sets of conveyor belts  33 ,  34 :  35 ,  36 . The conveyor belts are each tensioned around end rollers  36 - 44 . Tension rollers  44 ,  45  serve for tensioning the upper conveyor belts  33 ,  35 . The opposite sets of conveyor belts  33 ,  34 ,  35 ,  36  operatively ensure that sheets of sets being conveyed between them are mutually fixed in a reliable manner. 
   The supply track  6  converging with the conveyor track  5  is determined by a collecting platform  46  with an end stop  47  whose position is adjustable, a movable stop  48  and a pair of conveyor rollers  58  located downstream thereof. 
   For collecting a set of sheets  2  on the collecting platform  46 , means are provided for piece by piece supplying sheets  2  from a stock. For this, many possible solutions are known from the state of the art. According to this example, the means for piece by piece supplying sheets from a stock comprise a sheet holder  49 , a supply roller  50  for supplying sheets, a conveyor roller  51  and a separation roller  52  for conveying and, if necessary, separating sheets  2  supplied by the supply roller  50 , two sets of conveyor rollers  53 ,  54 ,  55 ,  56  for conveying separated sheets, whether or not at increasing speeds v 1 , v 2 , v 3 , and a diagrammatically represented system of guides  57 . 
   In cooperation with a passage between the upstream one  33  and the downstream one  35  of the upper conveyor belts  33 ,  35 , the nip between the pair of conveyor rollers  58  downstream of the collecting platform forms the connection of the sheet supply track, formed by the supply track  6 , the rollers  53 - 56  and the guide  57 , to the conveyor track  5  for combining sheets  1 ,  2 , supplied via conveyor track  5  and supply track  6 , to a stacked set  7 . 
   For controlling the transport of the sheets  2 , the means for supplying sheets  2  to the sheet platform  46  comprise a first insert detector  59  for detecting the presence of a sheet  2  directly downstream of the nip between the conveyor roller pair  53 . A coupling  60  operates the drive of the conveyor rollers  50 ,  51  and  53  upstream of the detector  60  by coupling or uncoupling the conveyor rollers  50 ,  51  and  53  upstream of the detector  60  with or from a motor/pulse disc assembly  61 , while the local control unit  28  is arranged for controlling the coupling for stopping sheets in a waiting position with a leading edge shortly beyond the first insert detector  59  and for driving the conveyor rollers  50 ,  51  and  53  upstream of the detector  60 , until the detector has detected and signaled the presence of a leading edge of a next sheet  2 . 
   The central control unit  24  is arranged for determining the folding length or folding lengths α of the set  7  to be folded and for storing data representing the size of the sheets  2  of the second, smaller size in the memory  8 . Further, the central control unit  24  is arranged for, in response to a difference between the folding length or folding lengths α and the size of the second sheet that is within a predetermined range, signaling to the respective distributed control units  26 - 29  of the insert supply stations  17 - 20  that, in combining sheets  1  and  2  supplied via tracks  5 ,  6  into the set  7 , leading edges of the sheets  1 ,  2  are to be positioned at a mutual distance in the conveying direction  3  and trailing edges of the sheets  1 ,  2  are to be positioned at a mutual distance in the conveying direction  3 . In response to what range the central control unit  24  does not position the sheets  2  of the second, smaller size with leading or trailing edges in alignment on the leading and trailing edges, respectively, of the sheets  1  of the first, larger size, depends on the specific properties of the folding station  21  with which the sets  7  are folded. 
   For controlled positioning of the sheets  2  of the second, smaller size with respect to the sheets  1  of the first, larger size in a position with both leading and trailing edges mutually staggered over (directly or indirectly) predetermined distances in conveying direction, the apparatus according to the example shown is designed as follows. 
   For driving the conveyor track  5  in the area of the insert supply station  19 , a drive structure is provided, of which an electric motor  62  and a pulse disc  63  are parts. Operating means for starting and stopping the first drive structure are formed by the local control unit  28 . For this purpose, the latter is provided with a motor control, which can also be part of the drive structure. For detecting at least a leading or trailing edge of a sheet  1  in the conveyor track  5 , a track monitoring detector  64  has been placed upstream of the area where the supply track  6  connects to the conveyor track  5 . 
   A second drive structure for driving the supply track  6  is formed by the motor/pulse disc assembly  61  and a second coupling  65  with which the conveyor roller pair  58  downstream of the collecting platform can be coupled with and uncoupled from the motor/pulse disc assembly  61 . The local control unit  28  is further arranged for operating the movable stop  48  between a stacking position as represented and a pass position at a slight distance above the supply track  6 . The movement to the pass position is executed by moving the stop initially in conveying direction  4  and then rotating it away from the supply track  6 . The supply track  6  is thereby cleared for conveying a set of sheets collected on the platform  46 . The local control unit  28  is further arranged for starting and stopping the second drive structure, and in particular the conveyor roller pair  58  downstream of the collecting platform  46 , by operating the second coupling  65 . In this way, the transport of the set of sheets  2  collected on the collecting platform  46  to a waiting position can be controlled. Sets of sheets  2  received in the waiting position can be held in readiness there while on the platform  46  a next set is being collected. According to this example, this is enabled in that the movable stop  48 , each time after it has moved to the pass position and the stack of sheets has passed, is moved to the stacking position again while a trailing portion of the set of sheets in the waiting position is still on the collecting platform  46 . Thus, in the station  19 , simultaneously, two collected sets or sheets can be present, while allowing a compact construction in that a next set of sheets can be collected in a position overlapping the set of sheets in the waiting position. 
     FIGS. 3A-3C  illustrate how, owing to at least the sheet supply track of the second insert supply station  18  including a waiting position, which is arranged for receiving a set coming from the stacking position and holding the received set in readiness while in the stacking position a next set is being collected, and owing to the apparatus being arranged for, in response to the lack of a complete, feedable set in the stacking position of the second insert supply station  18 , adding to a main document a set Sri from the first attachment supply station  17  at the moment when it is detected that no complete set is available in the stacking position in the second insert supply station  18 , still a set SB is available in the waiting position which can still be added to a main document LAB which has already been conveyed too far to receive a set of inserts from the first one of the insert supply stations  17 . The same principle is also applicable by feeding an insert set from the second insert supply station  18  in response to the lack of an insert set in the stacking position in the third insert supply station  19 . 
   A second insert detector  66  ( FIG. 2 ) for detecting at least one leading or trailing edge of a set of sheets  2  or a single sheet in the supply track  6  is located just downstream of the conveyor roller pair  58  downstream of the collecting platform  46 . 
   The local control unit  28  is arranged for clearing the supply track  6  and for controlling the second coupling  65  for starting the drive of the supply track  6  by coupling and for starting the motor  62  for driving the conveyor track  5 . As a result, sheets  1  and  2  are supplied along the tracks  6 ,  6 . The local control unit  28  is further arranged for then, in response to detection of a leading or trailing edge of a set of sheets  2  in the supply track  6 , controlling the second coupling  65  for interrupting the drive of the supply track  6  by uncoupling. As a result, the set of sheets  2  in the supply track  6  is stopped in the waiting position. The local control unit  28  is further arranged for then, in response to detection of a leading or trailing edge of a sheet by the detector  64  along the conveyor track  5 , controlling the second coupling  65  for restarting the drive of the supply track  6  by recoupling. Because the distances from the detector  64  along the conveyor track  5  and the distance from the second insert detector  66  along the supply track  3  and from the stop  47  to the place where the supply track  6  meets the conveyor track  5  are known, it is possible, by carrying out the restart of the drive of the supply track  6  at a suitable time, to position the set of sheets  2  accurately at any desired position on the first sheet  1 . 
   Downstream of the supply track  6 , along the conveyor track  5 , a downstream detector  67  is located for detecting the trailing edge  12  of a set  7  collected in the insert supply station  19 . The local control unit  28  is arranged for stopping the motor  62  which drives the conveyor track  5  in response to a signal from the detector  67  which indicates the passage of such a trailing edge  12 . 
   In the following table, in successive lines, successive detections and the actions carried out in response thereto are shown: 
   
     
       
         
             
             
           
             
               TABLE 1 
             
             
                 
             
             
               Detection 
               Action 
             
             
                 
             
           
          
             
               ready signal (for instance 
               coupling 65 IN, motor 62 ON 
             
             
               coming from downstream 
             
             
               station 20) 
             
             
               leading edge of sheet 2 at 
               coupling 65 FREE 
             
             
               detector second insert 
             
             
               detector 66 
             
             
               trailing edge at detector 64 
               start pulse counting pulse disc 3 
             
             
               pulse counting has reached 
               coupling 65 IN 
             
             
               predetermined value trailing 
               coupling 65 FREE, motor 62 OFF 
             
             
               edge at detector 67 
               stop 48 from stacking position via pass 
             
             
                 
               position back to stacking position 
             
             
                 
             
          
         
       
     
   
   The pulse disc  63  thus forms a movement indicator coupled with the local control unit  28  of the control structure  9  for detecting movement in conveying direction by the conveyor track  5 . The local control unit  28  is here arranged for restarting the supply track  6  in response to a particular movement signaled by the movement indicator  63 , which movement has been chosen such that the sheet  2  of the second size is positioned in the intended position in conveying direction on the sheet  1  of the first size. Although, in view of the greater movements along the conveyor track  5  along which according to this example the sheet  1  which is longer in conveying direction is conveyed, it is preferred to stop or at least decelerate the conveyor track until the intended relative positioning of the sheets  1 ,  2  has been obtained, it is also possible to stop or decelerate the conveyor track for obtaining the intended relative positions. Also, in principle, it is possible, depending on the conditions, to decelerate or accelerate the conveyor track and/or the supply track for obtaining the intended relative positions of the collected sheets. Further, the insert supply stations may also feed single sheets instead of stacks of sheets.