WO1997005967A1

WO1997005967A1 - Method of controlling a letter-sorting system

Info

Publication number: WO1997005967A1
Application number: PCT/EP1996/003457
Authority: WO
Inventors: Boris Lohmann; Hauke LÜBBEN
Original assignee: Siemens Aktiengesellschaft
Priority date: 1995-08-05
Filing date: 1996-08-05
Publication date: 1997-02-20
Also published as: EP0785827A1; DE59606043D1; EP0785827B1; JPH11502769A; DE19528828C1

Abstract

The invention concerns a method of controlling a letter-sorting system with a controllable feed device, a conveyor on which the letters are individually transported and an overlap facility with a first and a second transport path. The invention calls for a letter to be fed in when measurement of the gap L between it and the previous letter shows that L > Smin and L < S1 or L > Sstack (Smin, S1 and Sstack being predefined gap values) and, when L has a different value, for no letters to be fed in until L > Sstack.

Description

description

Method for controlling a mail distribution system

The present invention relates to a method for controlling a mail distribution system according to the preamble of claim 1.

In automatic mail distribution systems, letters and similar flat mail items are individually fed to a conveyor line, transported on it, and assigned to a plurality of stacking compartments according to predetermined sorting criteria and stacked in them, with information about the sorting being recorded by the letters at a suitable point on the conveyor line .

In order to achieve the highest possible throughput, the letters run on the conveyor line with the highest possible speed and the smallest possible gaps between the individual letters. One problem with this is that letters that are to be routed into one and the same compartment must have a minimum distance sg- ^ gp _g i in order to achieve good stack quality. Otherwise there is a risk that congestion is caused by the leading edge of a subsequent consignment running onto the trailing edge of the preceding consignment. The minimum distance for safe stacking is far above the absolute minimum distance s _m j _n required for the other conveying process. Since the target compartment of a letter is not yet known at the time of delivery to the conveyor line, ie at the start of the transport, but is only determined during the transport in the machine, the required distance between the mail items cannot be increased in advance by enlarging the gaps in question the delivery of the shipments to the conveyor line can be ensured. On the other hand, a general increase of all distances to s _s t _a p _e | solve the stacking problem, but lead to a significant reduction in throughput.

A stacking device is already known from DE 37 23 259, in which two successive mail items which are to be routed into the same compartment are deliberately overlapped. For this purpose, the rear shipment is routed on two consecutive shipments over a secondary conveyor line and over one

ORIGINAL DOCUMENTS Unification point introduced back into the main conveyor line, the length and speed of transport of the secondary conveyor line are dimensioned such that after the unification point, the second consignment, after the previous letter, is transported in an overlapping manner. In the overlapped form, the pair of letters can be removed from the letter flow like a single item and stacked with good stack quality. At the same time, there is a sufficient distance from the next letter. In the known device, two branch lines are provided so that three different cases can be mastered:

Case 1: the second broadcast is close to the first. The front shipment takes route 1 and the rear one takes route 2, the required overlap occurs.

Case 2: the second shipment is at a greater distance from the first than in case 1, but still too small a distance to be steered safely into the same compartment without overlap. Therefore, the front mail is routed via route 1 and the rear via the considerably shorter route 3, the necessary overlap occurs.

Case 3: The following program has a distance from the first which is greater than sstapei ^'st -' ⁿ this case, both transmissions are routed over the path 1, an orderly stacking is possible without overlapping.

A disadvantage of this two-way system known from the prior art is the high construction effort and an increased space requirement.

The invention has for its object to control a mail distribution system with a controllable feed device and an overlapping device with a first and a second conveying path such that letters that are assigned to the same stacking compartment can be safely stacked.

This object is achieved by the features of claim 1. The invention is based on the idea of controlling the feed device and the overlap device no longer in isolation, as before, but together. This enables the overlap device to be simplified considerably without impairing the performance of the overall system.

Advantageous embodiments of the invention can be found in the subclaims and the description.

The invention is described in more detail below with reference to drawings. It shows

FIG. 1 shows a schematic illustration of an overlap device known from the prior art with three conveying paths

FIG. 2 shows a schematic illustration of a mail distribution system with an overlap device

FIG. 3 shows a schematic illustration of an overlap device with only two paths

FIG. 4 shows a diagrammatic representation of the mail gap areas known from the prior art

FIG. 1 schematically shows an overlap device known from the prior art with three conveying paths 1, 2, and 3 as well as switches 4. FIG. 2 schematically shows an overall view of a letter distribution system with a feed device 10, to which mail items are fed a transport route 20 on which the letters or Programs with constant speed V are promoted. Information for sorting the mail items is picked up by the mail items by a reading device 30, usually 30 is an automatic address reader. The sorting information is supplied to the machine controller 40. The machine controller 40 controls the switches, the overlap direction 50, gives control signals for controlling the feed device £ 0 "and controls the sorting area 70 in which the Shipments are placed in stacking compartments. In principle, the conveying speed of the mail items in the transport route 20 is not variable; only the frequency of the delivery of mail items by the feed device 10 can be set.

Two control strategies are preferably provided in a system according to FIG. 2:

The delivery of a shipment is requested by the higher-level machine control 40. Under certain circumstances, depending on the reading results of the device 30, the case may arise that the delivery of several letters is requested.

According to the second control strategy, a fixed feed rate of the mail items in mail items / second is specified by the higher-level machine control. In this case, the feed device separates the letters at associated constant time intervals.

FIG. 4 shows diagrammatically the mail gap areas that occur during operation of the mail distribution system, wherein s _m j _n denotes the absolute minimum gap required overall by the conveying mechanism and s _s tapel denotes the minimum gap required for orderly stacking in a stacking compartment. Si denotes the maximum gap that can be overlapped between two consecutive mail items when using the conveyor path 2. In the mailing of the stacking device known from the prior art, a mailing of an overlap becomes larger than S- | , ie a consignment whose distance from the previous consignment falls into area B, are transported via the conveyor path 3.

FIG. 3 schematically shows an overlap device with two conveying paths 100, 200 into which the mail items can be controlled by the switch 400. If a consignment with a gap smaller than S _] compared to the preceding consignment is routed via the conveyor path 200, then an overlap with the preceding consignment routed via the conveyor path 100 is possible. According to the method according to the invention, a consignment is fed by the feed device to the conveyor 20, provided that the gap to the preceding consignment is greater than the absolute minimum gap ^s min and smaller than the maximum gap si, which can just be overlapped with the preceding consignment if it is is transported via the conveyor path 200 or if the gap to the previous shipment is so large that an overlap is not necessary. If neither of the two conditions is met, the delivery of the item is waited until the gap to the previous item is greater than s _s t _a n _e | has become.

The situation can be described as follows with reference to FIG. 4. In the case of two consecutive mail items in a short distance, the distance between the two items is in the range between s _m j _n and sj. In this case, the second consignment is routed via the conveyor path 200 and then overlaps with the preceding consignment routed via the conveyor path 100. In successive transmissions with a very large distance greater than sstapei not ^{'st e'} ^ne overlap required. On the other hand, the area of the shipment spacing, which is larger than si but smaller than sstapei, is prohibited. This area is avoided by the control method according to the invention.

In the event that the shipments are supplied on request by the higher-level machine control 40, a shipment is thus delivered as soon as it is requested and the gap to the preceding shipment is not in the prohibited range between s- | and sstapei lies. If several letters are requested in this case, the first will be sent as described. The other items are delivered with the absolute minimum distance s _m j _n . Every consignment supplied is immediately reported back to the machine control 40. After 1, 2 or x consignments have been fed, the machine control can stop the feed device again.

The procedure for specifying a fixed feed rate in shipments / per second is similar. A counter is incremented according to the specified feed rate. The status of this counter is still a number consignments to be fed and the consignment is supplied, provided that the distance to the previous consignment is not in the prohibited area between s- | and sstapei '' ^e 9t- The counter is decremented with each shipment.

When controlling the mail distribution system according to the method according to the invention, there are no longer any gaps which would make a conveying path 3 from FIG. 1 necessary, since there are no gaps between the prohibited area between si and sstapei between the mail items.

The throughput of the mail distribution system that can be achieved with the method according to the invention is not reduced in comparison with formation with three conveying paths. There are three different cases:

Case 1: If high numbers of consignments or throughputs are required, the consignments are fed with a minimum distance or almost minimum distance to the conveying device and, if necessary, overlapped by the overlapping device.

Case 2: In the case of lower shipment numbers or throughput numbers, shipments are alternately fed with a small and a large distance apart, but never with impermissible intervals that cannot be processed by the overlap. When viewed over a longer period of time, the number of consignments and throughputs is converted exactly into the consignments that are being delivered.

Case 3: The number of consignments or throughputs is so low that only distances between the consignments larger than sstapei would occur.

Claims

Process for controlling a mail distribution system

1 . Method for controlling a letter distribution system with a controllable feed device, a conveyor line on which the letters are transported individually and an overlap device with a first and a second conveyor path, characterized in that a letter is fed when a measurement of the gap L to the previous one takes place Letter shows that L> S _m j _n and L <Sj or L> Sstapei ^is t, where S _m j _n , S- \ and Sstapei are predetermined gap values, and that with other values of L a supply is not made until L> Sstapei ' ^st -

2. The method according to claim 1, characterized in that the letter is fed on request by a higher-level machine control.

3. The method according to claim 2, characterized in that when requesting several letters by the machine control, after the supply of the first letter, further requested letters are supplied with the distance S _m j _n .

4. The method according to claim 1, characterized in that a fixed feed rate of programs / second is predetermined.