EP1425113B1 - Method for sorting in a distribution order - Google Patents

Description

Distribution order sorting of shipments is the process of bringing into line the shipments to be distributed that correspond to the order of the distribution stops, e.g. according to house numbers / mailboxes, corresponds. These distribution stops are systematically started or approached by the distributor in its delivery area. A distribution stop is not an absolute sorting destination but a relative position in the distribution order.

This sorting is manually very expensive. By means of a sorting machine, this sorting can be carried out with considerably less time, the sorting being based on a sorting plan. This sorting plan is a list which makes the assignment of addresses to the defined delivery points, that is, describes the order. In the machine, it is the relation between a machine-readable address code and the sequence number. Since the number of delivery stops is normally greater than the number of sorting machines, the sorting of sorting of the items to be sorted takes place in several sorting runs. In this case, the items are returned to the sorting machine sorted in the previous run.

The following example demonstrates how to sort in two passes. Let's assume that a certain number of shipments should be distributed to 20 delivery points. It is sufficient to have 4 sorting bins in the first sorting pass and 5 sorting bins in the second sorting pass, since 4 x 5 = 20. Delivery code (postal code) ursprüngl. Distribution order number mod. Distribution order number Sorting bin sorting 1 Sorting bin sorting 2 78453: 332/025 1 1A 1 (A) 1 78453: 332/027 2 1B 2 B) 1 78453: 332/029 3 1C 3 (C) 1 78453: 335/102 4 1D 4 (D) 1 78453: 335/104 5 2A 1 (A) 2 ... ... ... ... ... ... ... ... 78453: 347/045 19 5C 3 (C) 5 78453: 347/047 20 5D 4 (D) 5

In the first sorting pass, the broadcasts are divided into 4 bins, that is, the first bin receives all shipments containing an "A", the second bin receives all shipments containing a "B", etc. The bins are cleared and the bins empty Shipments are reentered in the cloth input, starting with the mailings of the first bin ("A"), then those of the second bin ("B"), etc. During the second sorting pass, the mailpieces are distributed into 5 bins according to the number, ie the first bin receives all shipments that contain a "1" and so on. Since, after the first sorting pass, the shipments containing an "A" are already in front of the shipments containing a "B", bin 1 now gets first, the programs containing "1A", then "1B", etc. The same applies analogously to all other subjects, so that the distribution order sorting is finished after the second sorting pass. According to the prior art, it is necessary to create an assignment table the so-called sorting plan, which has a unique relation between the delivery code thus determines the postcode and the sorting bin within a run. A variant of this method merely establishes a relation between the delivery code and the distribution order number. The sort bin assignment is made during sorting. Assuming the distribution order number of a recognized delivery code is known - it is provided by the sorting plan, it must now be translated into a bin number. The distribution sequence number itself can be regarded as a combination of specialist assignment rules, which has the following features, for example:
The machine has 10 compartments (accordingly, the distribution order number is a decimal number), the trays are designated 0 ... 9, the number of passes is equal to the number of decimal places in the distribution order sequence number. Example: The distribution sequence number 528 is sorted in 3 passes, in the 1st sort run in bin 8, in the 2nd sort bin in bin 2, in the 3rd sort bin in bin 5. In another machine with 64 available bins in the first sort bin and 30 in the second Sorting run, the same distribution order number (528) would be distributed as follows: in the first sorting pass in bin 16, in the second sorting bin in bin 8. Generally, the number of digits corresponds to the number of passes required, the numerical base of each digit corresponds to the number of the respective sorting pass available subjects.
This consideration initially ignores the number of shipments sorted by distribution order number. Assuming that there is an almost uniform distribution of the shipment quantities, eg an average of 3 shipments per distribution sequence number, it is possible to exploit optimally, taking into account the total shipment quantity, the number of sorting bins and their size, a sorting machine without the bin full situation occurring. Sporadically occurring sorting overflows can be intercepted by the use of overflow compartments.

In this prior art sorting, bins may be overflowing or even filled with only a very small number of mailings. Because of the possible overflow, overflow fans are provided. However, this reservation of overflow compartments means a reduction of the sorting capacity of the sorting machine with regard to the possible distribution stopping points.

A gradual optimization of the sorting plan can reduce, but not replace, the number of overflow slots required, since the composition and size of the mailings remain unknown. When emptying the sorting machine and merging the contents of sorting and overflow compartments, operator errors may occur which may change the order so much that a repetition of the sorting becomes necessary.

On the other hand, the use of overflow compartments does not guarantee that no further compartment full situations can occur. In a method for avoiding overflows according to US Pat. No. 5,363,971, the ZIP codes are read and assigned to distribution stops. Thereafter, the assignment of the ZIP codes to the distribution breakpoints is modified by a microprocessor to optimize the distribution of the broadcasts in the bins. This is done by not all possible distribution breakpoints are used, but reserve holding points are provided. By allocating the ZIP codes to the distribution breakpoints and placing the reserve breakpoints between the associated distribution breakpoints, it is possible to distribute the shipments in an improved manner to minimize the likelihood of technical overflows. As a result, only the remaining amount remaining is sorted into the original compartment combination, resulting in unintentional non-uniform compartment filling. With only low levels of the sorting compartments, time losses occur, since the time required for emptying a low-filled Faches is not or only insignificantly different from the emptying of a full subject.

In DE 196 25 007 A1, a method for distribution order sorting is described in which the shipments of each original distribution stop point are so divided to avoid distribution full situations by iterative search steps in a simulation of the sorting process before the sorting performed by the sorting machine on modified distribution breakpoints in that the bins can pick up the items without overflow.

This iterative simulation is very time consuming, so that in a certain period of time only a limited difference in quantity between the distribution stops can be compensated.

In DE 196 47 973 C1 is described in the generation of sorting plans volume statistics of the daily consignment history of the past and in DE 43 02 231 A1 set out to use the sorting plan statistical averages for the postal goods for certain destinations. How the sorting plans with this information are optimally designed, but is not specified.

The invention is therefore based on the object to significantly increase the range of permissible differences in the shipment volume for different distribution stops at the same time frame for the assignment of the sorting compartments to the distribution stops, without causing overflows of sorting compartments.

According to the invention the object is achieved by the features of claim 1.

The delivery quantities statistically determined for the individual real distribution order items of a certain distribution order are divided among the largest possible number of virtual distribution order items, which is formed by the product of the numbers of the sorting bins in the sorting runs, for the sorting runs before the last sorting run, so that the expected items are as far as possible evenly distributed to the virtual distribution order points. This is followed by carrying out the sorting runs upstream of the last sorting pass, in which the actual shipments are distributed as evenly as possible over the determined virtual distribution order points. The last sort pass is then performed so that the mailings of a dispatching order are sorted into adjacent sort bins.
It is believed that because of the number of sorting bins available, a sorting machine for the dispatching order can handle significantly more routing order points within a sorting process than is necessary for the sorting of one or more real distribution orders. Thus, real distribution order points with large shipment quantities can be divided into many virtual distribution order points with the smallest possible shipment quantities. Before sorting, therefore, no time-consuming iterative simulation is necessary anymore, but the distribution of the shipments takes place on the basis of statistically determined frequency distributions.

Advantageous embodiments of the invention are shown in the subclaims.

• Ermittlung der minimalen Anzahl der Sortierfächer im letzten/p-ten Sortierlauf NSTnmin für eine bestimmte Verteilreihenfolge, ausgehend von der Anzahl der Sendungen und der Verteilreihenfolgepunkte,
• Ermittlung der Anzahl der möglichen virtuellen Verteilreihenfolgepunkte Vdpn, die für die Verteilreihenfolge bereitgestellt werden können, mittels der Beziehung $$\mathit{Vdpn}=\mathit{NSTp}\times \mathit{\Pi NST}$$
  
  $$\mathit{\Pi NST}=\mathit{NST}1\times \mathit{NST}2\times \mathrm{...}\mathit{NST}(p-1),$$
  
  
  NSTi = Anzahl der Sortierfächer der Maschine im i-ten Sortierlauf,
  NSTp = Anzahl der Sortierfächer der Maschine im letzten Sortierlauf,
• Ermittlung der statistisch zu erwartenden Anzahl der Sendungen Erg, die jeder virtuelle Verteilreihenfolgepunkt bei gleichmäßiger Verteilung aufnehmen kann, durch die Beziehung Erg = NITEM/Vdpn.
  mit NITEM = statistisch zu erwartende Anzahl der Sendungen der Verteilreihenfolge
• Ermittlung der Anzahl der virtuellen Verteilreihenfolgepunkte Vdpn (Erg) für jeden realen Verteilreihenfolgepunkt auf der Basis statistisch ermittelter Sendungsstückzahlen für den jeweiligen Verteilreihenfolgepunkt, indem die statistisch ermittelte Anzahl der Sendungen für diesen Verteilreihenfolgepunkt durch die Anzahl der Sendungen Erg, die jeder Verteilreihenfolgepunkt bei gleichmäßiger Verteilung aufnehmen kann, dividiert wird, wobei bei gebrochenzahligen Werten von Vdpn (Erg) mit größeren und kleineren ganzzahligen Werten eine Aufteilung auf virtuelle Verteilreihenfolgepunkte so erfolgt, dass die Summe der virtuellen Verteilreihenfolgepunkte aller physikalischen Verteilreihenfolgepunkte Σ Vdpn (Erg), der Anzahl der möglichen virtuellen Verteilreihenfolgespunkte Vdpn entspricht.

Thus, the distribution of the shipments to the virtual distribution order points before the first sorting run is advantageously carried out by the following steps:

• Determine the minimum number of bins in the last / pth sort run NSTnmin for a particular distribution order, based on the number of shipments and the distribution order points.
• Determine the number of possible virtual distribution order points Vdpn that can be provided for the distribution order by means of the relationship $$\mathit{order\; points\; Vdpn}=\mathit{NSTp}\times \mathit{\Pi NST}$$
  
  $$\mathit{\Pi NST}=\mathit{<figure-callout\; id="1"\; label="NST"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">NST</figure-callout>}1\times \mathit{<figure-callout\; id="2"\; label="NST"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">NST</figure-callout>}2\times \mathrm{...}\mathit{NST}(p-1).$$
  
  
  NCTS = number of sorting compartments of the machine in the i th sorting pass,
  NSTp = number of bins of the machine in the last sort run,
• Determine the statistically expected number of transmissions Erg that each virtual distribution order point can receive with even distribution by the relationship Erg = NITEM / Vdpn.
  with NITEM = statistically expected number of programs of the distribution order
• Determine the number of virtual dispatching order points Vdpn ( Erg ) for each real distribution order point based on statistically determined shipment numbers for the respective distribution order point by dividing the statistically determined number of shipments for this distribution order point by the number of shipments Erg that each distribution order point can receive with equal distribution is divided, and for fractional values of Vdpn ( Erg ) with larger and smaller integer values, distribution to virtual distribution order points is such that the sum of virtual distribution order points of all physical distribution order points Σ Vdpn ( Erg ) corresponds to the number of possible virtual distribution order points Vdpn ,

mit NSTCAP = Aufnahmekapazität eines Sortierfaches
und die Anzahl der Sortierfächer NSTdpn zur Bearbeitung der Verteilreihenfolgepunkte im letzten/p-ten Sortierlauf mittels der Beziehung $$\mathit{NSTdpn}=\mathit{NDPN}/\mathit{\Pi NST}$$

mit NDPN = Anzahl der Verteilreihenfolgepunkte
ermittelt wird und der nächst größere ganzzahlige Wert des größeren Wertes von NSTitem und NSTdpn die minimale Anzahl der Sortierfächer im letzten/p-ten Sortierlauf NSTnmin ergibt.It is advantageous in this context, if for determining the minimum number of bins in the last / p- th sorting run, the number of bins NSTitem for receiving all shipments in the last / p- th sorting run by means of the relationship $$\mathit{NSTitem}=\mathit{NITEM}/\mathit{NSTCAP}$$

with NSTCAP = capacity of a bin
and the number of bins NSTdpn for processing the distribution order points in the last / p- th sorting run by means of the relationship $$\mathit{NSTdpn}=\mathit{NDPN}/\mathit{\Pi NST}$$

with NDPN = number of distribution order points
is determined and the next larger integer value of the larger value of NSTitem and NSTdpn results in the minimum number of bins in the last / pth sort run NSTnmin .

It is useful if the sorting compartments for the virtual distribution order points of a real distribution order point are arranged side by side.
For the economic use of sorting capacities, it is favorable to sort several distribution orders on the basis of a sufficiently large number of sorting bins and their size simultaneously on a mail sorting machine, with no further distribution orders being sorted upon reaching a fixed filling limit of the sorting bins.
The sorting of the mailings for the sorting runs before the last sorting run is preferably carried out in Verteilreihenfolgeschichten over all sorting compartments. In the last sorting run, the shipments for the various distribution orders are then separated by sorting by distribution order into adjacent bins.
If, after the first distribution of the real distribution order points into virtual distribution order points, sorting compartments are still unoccupied, then the distribution is as even as possible the programs advantageous to assign the virtual Verteilreihenpunktepunkte in a further step while maintaining the sequence integrity by means of random algorithm to the sorting compartments.

Subsequently, the invention will be explained in an embodiment with reference to the drawings.

FIG 1

die Planung der Verteilreihenfolgesortierung;

FIG 2

Datenflüsse und Module eines Systems und markiert die Stellen, an denen die Erfindung zum Einsatz kommt (Verteilalgorithmus);

FIG 3

eine mögliche Verteilung von Sendungsmengen auf Verteilreihenfolgepunkte innerhalb einer bestimmten Verteilreihenfolge, wie sie in der Realität vorkommen kann;

FIG 4

eine mögliche Anordnung der Sendungen von zwei unterschiedlichen Verteilreihenfolgen im ersten Sortierlauf ohne Anwendung des erfindungsgemäßen Verfahrens;

FIG 5

die Anordnung von zwei Verteilreihenfolgen im ersten Sortierlauf bei Aufteilung auf virtuelle Verteilreihenfolgepunkte;

FIG 6

das Einfügen von Sortierfächern im zweiten Sortierlauf bei unerwartet hohen Sendungsmengen im zweiten Sortierlauf.

Show

FIG. 1

the planning of the distribution order sorting;

FIG. 2

Data flows and modules of a system and marks the places where the invention is used (distribution algorithm);

FIG. 3

a possible distribution of shipment quantities to distribution order points within a certain distribution order, as may occur in reality;

FIG. 4

a possible arrangement of the shipments of two different distribution orders in the first sorting run without application of the method according to the invention;

FIG. 5

the arrangement of two distribution orders in the first sorting run when distributed to virtual distribution order points;

FIG. 6

the insertion of sorting bins in the second sorting run with unexpectedly high shipment quantities in the second sorting run.

1 shows the starting situation of a complex sorting system. From a database-based system, the distribution order Definitions 1 - hereinafter referred to as distribution order - are derived, which contain the assignment of the destination code information to distribution order points and the expected shipment quantities per distribution order point. In the distribution order sorting plan 2, the predefined distribution orders become available Sorting machines distributed. This planning is carried out on the one hand according to the logistical criteria of the operator and on the other hand according to utilization criteria of the machines. In practice, this means that the planner tries to map the logistical criteria of the operator to the existing machinery and therefore requires a tool that can constantly check during planning whether the capacity limits of one or more machines have already been reached or not. The result of the planning are the distribution order sorting schedules 4 for the machines (note: the sorting device for separating the shipments to be sorted into assignments for each machine - the separation sorting plan 3 - will not be considered in this context).

2 shows the arrangement of the elements reduced to a single machine. The distribution order definitions 1 are examined in the distribution order sorting schedule with the sorting plan management 5, which as a result determines the capacity load of the sorting machine 6 by each of the distribution orders selected for that machine. For this purpose, the distribution algorithm, which will be described in more detail, is used, which later controls the actual sorting in the real sorting machine 6. By means of this method, it can already be ensured during the planning that the composition of the distribution sequences on a sorting machine 6 does not exceed their sorting capacity. The sorting plan 4 generated for a machine contains the distribution orders with the assignments of the destination code information to the distribution order points. This sorting plan 4 is loaded into the machine 6 and the same distribution algorithm, which has enabled the distribution to be determined even in the planning phase, controls the real sorting in the machine.

3 shows an example of the distribution of 1800 transmissions to 180 distribution order points within a single Distribution order. The aim of the method according to the invention is to arrange this uneven distribution on the machine so that the lowest possible capacity load of the machine occurs.

NST

- Anzahl der Sortierfächer (210);

NSTCAP

- Anzahl der Sendungen, die ein Sortierfach aufnehmen kann (600);

P

- Anzahl der Sortierläufe (2).

Die Kennwerte der Verteilreihenfolge sind:

NITEM

- erwartete Gesamtmenge an Sendungen (1800);

NDPN

- Anzahl der Verteilreihenfolgepunkte (180).

Unter der Annahme, dass die Sendungen der Verteilreihenfolge im zweiten Sortierlauf in einer möglichst geringen Anzahl von Sortierfächern zusammengefasst werden soll, lassen sich aus diesen Kennwerten die Minimalanforderungen zur Sortierung dieser Verteilreihenfolge ableiten: NSTitem = NITEM / NSTCAP 1800/600 = 3 Anzahl der Sortierfächer zur Aufnahme aller Sendungen im zweiten Sortierlauf NSTdpn = NDPN / NST 180 / 210 = 1 Anzahl der Sortierfächer zur Bearbeitung der Verteilreihenfolgenummern im zweiten Sortierlauf
Der größere der Werte NSTitem und NSTdpn wird als Anzahl der Sortierfächer im zweiten Sortierlauf festgelegt.
Dann läßt sich die Minimalanzahl der notwendigen Sortierfächer für den ersten Sortierlauf bestimmen. NST1 = NDPN / NST2 180 / 3 = 60 Anzahl der Sortierfächer zur Bearbeitung der Verteilreihenfolgenummern im zweiten Sortierlauf The characteristic values of a machine are with 2 sorting runs:

NST

- number of bins (210);

NSTCAP

- Number of shipments a bin can receive (600);

P

- Number of sorting runs (2).

The characteristics of the distribution order are:

NITEM

- expected total amount of shipments (1800);

NDPN

- Number of distribution order points (180).

Assuming that the shipments of the distribution order in the second sorting run are to be combined in as small a number of sorting bins as possible, the minimum requirements for sorting this distribution sequence can be derived from these characteristic values: NSTitem = NITEM / NSTCAP 1800/600 = 3 Number of bins to hold all shipments in the second sorting pass NSTdpn = NDPN / NST 180/210 = 1 Number of bins for processing distribution order numbers in the second sorting pass
The larger of the values NSTitem and NSTdpn is set as the number of bins in the second sort.
Then, the minimum number of necessary sorting compartments for the first sorting run can be determined. NST1 = NDPN / NST2 180/3 = 60 Number of bins for processing distribution order numbers in the second sorting pass

Because the machine can handle more than one distribution order due to its size, and the distribution order separation occurs automatically at the transition from the first to the second sort (each distribution order has its own sort group in the second sort), a separate virtual machine can be described for each distribution order.

Table 1 below shows some calculation examples for distribution orders and the calculated virtual machines: Table 1 Distribution order Characteristics necessary sorting bins in the second sorting pass (calculation) virtual machine No. NITEM NDPN NSTitem NSTdpn NST2 NST1 1 1800 30 2.99 0.14 3 10 2 1800 180 2.99 0.86 3 60 3 600 180 1.00 0.86 1 180 4 1200 180 1.99 0.86 2 90 5 1500 700 2.49 3.33 4 175 6 600 600 1.00 2.86 3 200 7 1800 630 2.99 3.00 3 210 8th 2400 600 3.99 3.00 4 150 9 2400 850 3.99 4.05 5 170

FIG. 4 and Table 1 show that the example distribution sequences occupy the machine very differently in the first sorting pass, if only the minimum conditions are actually met. It can also be seen that this type of distribution is very sensitive to changes in shipment volumes relative to the utilization of the sorting compartments, especially if the actual shipment quantities deviate significantly from the expected shipment quantities.

FIG. 5 illustrates the distribution of the shipment quantities when the actual distribution order points of the distribution order 1 are mapped to virtual distribution order points. This process does not disturb the order, but results in a more even distribution of the shipments on the machine. For distribution order 1, 30 real distribution order points 1 with 60 items each are split into 180 virtual distribution order items with 10 items each. That is, each real distribution order point now contains 6 virtual distribution order points. During the sort operation, distributed distributions are counted when distributing to the virtual distribution order points because the virtual distribution order points are not a distribution characteristic on the shipments, but only exist during the distribution process. Shipments that exceed the expected shipment amount for a dispatching order point are evenly distributed to their associated virtual dispatching order points.
While in the preceding example, the conditions are easily understood, the method for a real distribution order, as shown in FIG 3, must be refined. The calculation of the sizes of virtual distribution order points and the determination of the resulting distribution on the machine is the central part of the method according to the invention and is performed separately for each distribution order. The respective result is mapped in a virtual machine (a software machine), which sums up the expected fill levels of the bins. The Sorting Management System only accepts additional distribution orders for a particular machine during the planning process, as long as the specified maximum quantities for the shipment quantity per bin are not exceeded.

The distribution of a single distribution order is calculated in 4 steps.

Step 1: Calculation of the characteristic values and minimum requirements of a distribution sequence NSTitem = NITEM / NSTCAP Number of bins to hold all expected shipments in p- th (p = 2) sort run (last sort run) NSTdpn = NDPN / NST1 Number of bins for processing distribution order numbers in p- th sorting run NSTp = (ceil) max ( NSTitem, NSTdpn ) Number of bins in p- th (p = 2) sort run (greater value of NSTitem and NSTdpn ) Vdpn = NSTp * NST Number of possible virtual distribution order points that can be provided for the distribution order Erg = (float) NITEM / Vdpn Number of shipments each virtual distribution order point of a distribution order should receive based on the total number of shipments. Erg_h = (ceil) erg Virtual Distribution Order Point Size (High Value) Erg_l = Erg_h - 1 Virtual Distribution Order Point Size (Low Value) With:
NST1 - Number of bins in the machine (in the first sort pass)
NSTCAP - Capacity of a bin
NITEM - Expected number of shipments in the distribution order
NDPN - Number of distribution order numbers of a distribution order
(ceil): next larger integer value
(float): floating point value

The number of shipments per virtual dispatching order point must be increased from the exact value Erg to the integer value Erg_h. As this results in the sum of all shipments (Vdpn * Erg_h) being greater than the actual shipment amount, the lower integer value Erg_l is additionally introduced by 1.

Step 2: Compute the number of virtual distribution order points for each real distribution order point, dividing this fractional value in the ratio Erg to the integer values Erg_h and Erg_l.

Step 3: The overhang of (actually non-existing) shipments resulting from the distribution of the shipment quantities to the virtual distribution order points of the quantities Erg_h and Erg_l is corrected by elements from Erg_l by replacing elements which have arisen from Erg_h.

Step 4: Distribution of shipment quantities to virtual distribution order points of sizes Erg_h and Erg_l may have the effect of requiring more virtual distribution order points than are available (NST2 * NST1). This is corrected by introducing a third virtual dispatch order size variable Erg_spec, which can accommodate either a multiple of Erg_h or a multiple of Erg_l on broadcasts.

In the calculation, cases occur where, despite the smallest possible size 1 of virtual distribution order points, not all available virtual distribution order points are assigned, the occupied virtual distribution order points can be distributed randomly over the available sorting compartments. This avoids that an accumulation of such virtual distribution order points can occur in one and the same bin.
During the sorting, a statistic about the occurrence of the expected distribution order points is kept. After the end of the first sorting pass, the actual composition or distribution of the shipment quantities to the respective distribution order points is known. During the first sorting run, the occurrence of sorting bin full of situations can be avoided by the uniform distribution of the virtual distribution order points over all available sorting bins, then in the second sorting run, due to the concentration of the distribution sequences on the minimum number of bins, overflow situations can occur, if the actual shipment quantities significantly exceed the expected shipment quantities. In the run-up to the actual sorting, the planning can take this circumstance into account and preemptively reserve bins and report this to the machine in a suitable manner, usually as part of the sorting plan. These reserved bins are initially assigned to any distribution order. Since the machine does not get notified as a sorting plan a destination code for sorting assignment, but with the help of the method according to the invention determines this assignment itself, it is also able to make changes to the sorting assignment independently if necessary.

6 shows the basic sequence. The planning has reserved a sorting compartment at the "end" of the machine or, with the aid of the calculation carried out by the method according to the invention, takes less account of a sorting compartment than is actually available in the machine. After the end of the first sorting pass, the machine checks on the basis of the Statistics, the expected sorting bin fillings for the second sorting run and notes that the second bin of the distribution sequence 1 is to receive more shipments than has been specified for the bin. The machine therefore shifts all sorting compartment allocations above the sorting bin 2 considered by one position and now allocates the excess mailings of the sorting bin 2 to the sorting bin 3 that has become free. Thus, the sorting can be continued without a delay in the process through a bin full situation occurs.

List of used symbols

NST Number of bins of a machine NCTS Number of bins of the machine in the i-th sorting pass P Number of sorting runs of a sorting device NDPN Number of actual distribution order points of a given distribution order order points Vdpn Number of possible virtual distribution order points that can be provided for a distribution order NITEM Expected number of shipments of a distribution order NSTCAP Capacity of a bin NSTitem Number of bins to hold all expected shipments in pth (last) sort run NSTdpn Number of bins for processing distribution order numbers in the pth (last) sort run. NSTp Number of sorting locations (compartments) for sorting in the pth (last) sorting pass = larger value of NSTitem and NSTdpn. I inst Product of the number of bins in the sort runs without the last sort run. erg Number of shipments each virtual distribution order point of a distribution order should receive based on the total number of shipments. Erg_h Size of a Virtual Distribution Point (High Value) Erg_l Size of a Virtual Distribution Point (Low Value) Erg_spec Size of a Virtual Distribution Point, SPECIAL value, multiple of Erg_h or Erg_l.

Claims (7)

1. Method for distribution order sorting on a mail sorting machine, in which each item of mail is classified in a distribution order in accordance with its read and recognized address coding, the sorting being carried out in a number of passes depending on the number and size of the existing sorting compartments and the number of distribution stopping points describing the distribution order, comprising the following method steps, given a knowledge of the complete address coding of all the items of mail:

   - subdividing the quantities of items of mail determined statistically for the individual real distribution order points of a specific distribution order to the largest possible number of virtual distribution order points, predefined by the product of the numbers of the sorting compartments in the sorting passes, for the sorting passes before the last/pth sorting pass, in such a way that the expected items of mail are distributed as uniformly as possible to the virtual distribution order points,

   - carrying out the sorting passes before the last sorting pass, in which the actual items of mail are distributed as uniformly as possible to the virtual distribution order points determined in the first method step,

   - carrying out the last/pth sorting pass in such a way that the items of mail from a distribution order are sorted into sorting compartments located beside one another.
2. Method according to Claim 1, characterized by the following steps for subdividing the items of mail to the virtual distribution order points before the first sorting pass:

   - determining the minimum number of sorting compartments in the last/pth sorting pass NSTp for a specific distribution order, starting from the number of items of mail and the distribution order points,

   - determining the number of possible virtual distribution order points Vdpn which can be provided for the distribution order, by means of the relationship $$\mathit{Vdpn}\mathit{=}\mathit{NSTp}\mathit{\times }\mathit{\Pi NST}$$

   

   $$\mathit{\Pi NST}\mathit{=}\mathit{NST}\mathit{1}\mathit{\times }\mathit{NST}\mathit{2}\mathit{\times }\mathit{...}\mathit{NST}(p-1),$$

   

   
   NSTi = number of sorting compartments in the machine in the ith sorting pass,
   NSTp = number of sorting compartments in the machine in the last sorting pass,

   - determining the number of items of mail Erg which each virtual distribution order point can accommodate given a uniform distribution, by means of the relationship $$\mathit{Erg}\mathit{=}\mathit{NITEM}\mathit{/}\mathit{Vdpn}$$

   

   
   where NITEM = number of items of mail from the distribution order to be expected statistically,

   - determining the number of virtual distribution order points Vdpn (Erg) for each real distribution order point on the basis of statistically determined numbers of items of mail for the respective distribution order point, by the statistically determined number of items of mail for this distribution order point being divided by the number of items of mail Erg which each distribution order point can accommodate given uniform distribution, in the case of fractional values of Vdpn (Erg) with larger and smaller integer values, the subdivision to virtual distribution order points being carried out in such a way that the sum of the virtual distribution order points of all the physical distribution order points Σ Vdpn (Erg) corresponds to the number of possible virtual distribution order points Vdpn.
3. Method according to Claim 2, characterized in that the number of sorting compartments NSTitem to accommodate all the items of mail in the last/pth sorting pass is determined by means of the relationship $$\mathit{NSTitem}\mathit{=}\mathit{NITEM}\mathit{/}\mathit{NSTCAP}$$

   

   
   where NSTCAP = holding capacity of a sorting compartment
   and the number of sorting compartments NSTdpn for processing the distribution order points in the last/pth sorting pass is determined by means of the relationship $$\mathit{NSTdpn}\mathit{=}\mathit{NDPN}\mathit{/}\mathit{\Pi NST}$$

   

   
   where NDPN = number of distribution order points of the distribution order
   and the next largest integer value of the larger value of NSTitem and NSTdpn gives the minimum number of sorting compartments in the last/pth sorting pass NST _p .
4. Method according to Claim 1 or 2, characterized in that the sorting compartments for the virtual distribution order points of a real distribution order point are arranged beside one another.
5. Method according to one of Claims 1-4, characterized in that, on the basis of a sufficiently large number of sorting compartments and their size, the items of mail from a plurality of distribution orders are sorted simultaneously on one mail sorting machine, no more items of mail from a further distribution order being sorted in when a defined filling limit of the sorting compartments is reached.
6. Method according to Claim 5, characterized in that sorting in the items of mail for the sorting passes before the last sorting pass is carried out in distribution order layers over all the sorting compartments and, in the last/pth sorting pass, the items of mail for the various distribution orders are separated, by being sorted distribution order by distribution order into compartments located beside one another.
7. Method according to one of Claims 1-4, characterized in that if, following the first subdivision of the real distribution order points into virtual distribution order points, sorting compartments are still unoccupied, the virtual distribution order points are assigned to the sorting compartments by means of a random algorithm in a further step, while preserving the integrity of the sequence.

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