Method and apparatus for collating postal items

Abstract

For collating postal items into sets, the actual relative positions of the collated first and second postal items ( 6 - 9 ) is measured and a tolerance between nominal relative positions of the first and second postal items ( 6 - 9 ) and the actual relative positions of the collated first and second postal items ( 6 - 9 ) is determined. For at least one later set to be collated, the feeding of the second postal item ( 7, 9, 52 - 55; 102 ) is controlled for bringing the leading or trailing edge ( 27, 29; 57 - 60; 104 ) of the second postal item ( 7, 9, 52 - 55; 102 ) into a nominal off-set relative to the leading or, respectively, the trailing edge ( 26, 28; 56; 103 ) of the first postal item ( 6, 8; 61; 101 ), which nominal off-set is larger than or equal to the determined tolerance. An apparatus for carrying out such a method is also described.

1 . A method for collating postal items into sets, comprising:
 a) for each of the sets:   transporting a first postal item in a transport direction along a transport track, the first postal item being transported having a leading edge and a trailing edge in the transport track and perpendicular to the transport direction;   detecting a leading or trailing edge of the first postal item in the transport track; and   in response to said detection of the leading or trailing edge of the first postal item, transporting a second postal item in a feeding direction, with a leading edge and a trailing edge in a feeding track and perpendicular to the feeding direction, along the feeding track into a position collated with the first postal item in the transport track and retaining the second postal item in said position relative to the first postal item;   b) measuring the actual relative positions of the collated first and second postal items; and   c) determining a tolerance between nominal relative positions of the first and second postal items and the actual relative positions of the collated first and second postal items of each of said first plurality of said sets;   d) wherein, for at least one of said sets after said first plurality of said sets, the feeding of the second postal item is controlled for bringing the leading or trailing edge of the second postal item into a nominal off-set relative to the leading or, respectively, the trailing edge of the first postal item said nominal off-set being larger than or equal to said determined tolerance.   
   
   
       2 . A method according to  claim 1 , wherein the actual relative positions of the collated first and second postal items of a first plurality of said sets of collated postal items is measured by measuring the length of each of said first plurality of said sets of collated postal items. 
   
   
       3 . A method according to  claim 1 , further comprising determining a bias between nominal relative positions of the first and second postal items and the measured actual relative positions of the collated postal items of said first plurality of said sets. 
   
   
       4 . A method according to  claim 2 , further comprising determining a bias between nominal relative positions of the first and second postal items and the measured actual relative positions of the collated postal items of said first plurality of said sets, wherein, for each of a first plurality of said sets of collated postal items, the feeding of the second postal item is controlled for bringing the leading or trailing edge of the second postal item into a nominal off-set relative to the leading or, respectively, the trailing edge of the first postal item, said nominal off-set being larger than the largest expectable tolerance between the nominal relative positions of the first and second postal items and the actual relative positions of the collated postal items. 
   
   
       5 . A method according to  claim 1 , wherein said sets of said first plurality of said sets of collated postal items are collated during a setting phase and wherein said at least one of said sets after said first plurality of said sets are collated during a production phase and processed into mail pieces. 
   
   
       6 . A method according to  claim 1 , wherein, for at least one of said sets after said first plurality of said sets, either the nominal off-set of the trailing edge of the second postal item relative to the trailing edge of the first postal item is in transport direction or the nominal off-set of the leading edge of the second postal item relative to the leading edge of the first postal item is in a direction opposite to the transport direction. 
   
   
       7 . A method according to  claim 1 , wherein at least one of said sets after said first plurality of said sets is folded after collating, the second postal items each have a length measured from the leading edge to the trailing edge that is shorter than the length of each of the first postal items from the leading edge to the trailing edge thereof and shorter than or equal to the length measured from the leading or trailing edge to the envisaged position of a fold to be made in the first postal item, and wherein, for at least one of said sets after said first plurality of said sets, either the nominal off-set of the trailing edge of the second postal item relative to the trailing edge of the first postal item is in a direction opposite to the transport direction or the nominal off-set of the leading edge of the second postal item relative to the leading edge of the first postal item is in the transport direction. 
   
   
       8 . A method according to  claim 1 , wherein said nominal offset is equal to the sum of said determined tolerance and a safety margin. 
   
   
       9 . An apparatus for collating postal items into sets comprising:
 a transport track for transporting postal items in a transport direction with a leading edge and a trailing edge in the transport track and oriented perpendicular to the transport direction and for retaining collated postal items in the transport track fixedly positioned relative to each other;   a detector along the transport track for detecting a leading or trailing edge of each first postal item in the transport track;   a feeding track for feeding second postal items in a feeding direction, the second postal items each having a leading edge and a trailing edge in the feeding track and oriented perpendicular to the feeding direction, the feeding track merging with the transport track downstream of the detector, for collating each of the second postal items with one of the first postal items transported in the transport track;   a sensor structure for measuring the actual relative positions of the collated first and second postal items of said sets of collated postal items;   a control system for each time causing the feeding of one of the second postal items in the feeding direction along the feeding track in response to said detection of the leading or trailing edge of the first postal item by the detector, into a position collated with one of the first postal items in the transport track;   wherein the control system is arranged for:   determining a tolerance between nominal relative positions of the first and second postal items and the actual relative positions of the collated first and second postal items of each of said first plurality of said sets; and   for at least one of said sets after said first plurality of said sets, controlling the transport of the second postal item for bringing the leading or trailing edge of the second postal item into a nominal off-set relative to the leading or, respectively, the trailing edge of the first postal item, said nominal off-set being larger than or equal to said determined tolerance.