Mail Sorting System

Abstract

In a mail sorting system in which mail items are routed from a number of distributing stations to appropriate, essentially parallel conveying channels, the stations being spaced along the channels and each item being fed to a selected channel on the basis of its destination address, overloading of a channel is indicated by providing an electrical simulation of the distribution at each moment of items along each channel, the simulation being in response to routing signals from the stations, and by producing an alarm signal when the simulation shows that more than a predetermined number of items are present in a selected length of any one channel upstream of its junction with at least the last station, taken in the direction of conveyance along the channels.

Description

BACKGROUND OF THE INVENTION

The present invention relates to mail sorting systems, particularly those of the automatic or semi-automatic type in which individual mail items are delivered from several distributing stations to selected distributing channels on the basis of their intended destination.

It is known to mechanically process mail shipments in distributing systems including a plurality of distributing stations disposed along a collecting conveying path which consists of a plurality of distributing channels. These channels are generally upright conveyor paths. In addition, outlet conveying paths are arranged transversely across the collecting conveying path and can be selectively connected with each one of the distributing channels by means of switches. A distributing system of this type is described, for example, in German Pat. No. 1,172,885.

At each one of the distributing stations of such a system the items are presented individually to an operator from a storage container which is filled, manually or from a common feed path. The operator then uses a keyboard to apply a target, or destination, identification to the items, which information is derived from the address on the item. This could likewise be done by a reading device if the address can be read by machine. An associating device, or collator, forms a setting signal from the target information to set that switch which leads to the distributing channel assigned to the particular target information.

Such a distributing system with, for example, 10 distributing channels usually serves only to effect a rough, or coarse, distribution of the items and this is followed immediately or at a later time by a fine distribution in distributors able to handle a large number of distributing directions. Only part of the distributing channels of the above-mentioned collecting conveyor path leads directly to the final stackers. For purposes of the fine distribution, a printing mechanism then prints a coded guide imprint onto each item which imprint is also formed in a collator from the above-mentioned target information. Such distributing stations are called coding stations. In the following discussion distributing stations are considered to include coding stations as well as such distributing stations where no guide imprint is made on the items.

Since the individual distributing channels receive the items at a large numer of input points and at randomly varying times, the item flow density, the average of which increases from one distributing station to the next distributing station in the flow direction, is also subject to random variations. The items arrive partly individually and partly with irregular overlapping and accumulation. In order to be able to stack the items without malfunctions at the end of the distributing channel, even if they arrive with overlaps and in large numbers, be it in final stackers or in intermediate stackers for further transfer to fine distributing machines, it is advisable to include passthrough separators or pass-through overlappers in the system. These serve the purpose of producing a conveying stream of substantially uniform density and, if required, uniform direction of overlap from the items arriving in irregular quantities and with irregular overlapping.

A pass-through separator or overlapper, however, can also handle only a limited flow density -- measured in items per unit time or, with a given conveying speed, in items per unit of length. If this flow density is exceeded annoying stoppages or other malfunctions will occur.

Such distributing systems are thus dimensioned or operated, with respect to the number of coding stations and distributing paths and their association with certain target information, so that approximately the same average flow density will result for the individual distributing channels. This is done on the basis of long term statistics about the quantity and structure of the arriving mail. Because of the above-mentioned random fluctuations occurring within the distributing system itself, the permissible average flow density must not be based on the limit value which the processing devices following the distributing channels can handle. Rather a safety factor must be provided to allow for flow densities which temporarily substantially exceed the average value. The closer the assumed average value of the flow density comes to the stated limit value in the interest of maximum utilization of the system, the greater becomes the probability of the occurrence of temporary flow densities which exceed this limit value. High operational dependability must thus be paid for with a reduced degree of utilization.

The above considerations do not take into account that the frequency of occurrence of individual addresses will correspond to the set average distribution pattern only over relatively long periods of time. Temporarily there may occur deviations from this frequency distribution which result in a considerable shift in the flow density values in the individual distributing channels. If this fact is also considered in the determination of the average flow density for the individual distributing channels a further reduction in the degree of utilization of the distributing system will result.

However, in many cases it would be uneconomical to design a mail distribution system to achieve complete dependability with respect to overloads due to deviation from the average distribution pattern.

It may happen that in bulk shipments all items will have the same destination so that after a while all coding stations direct their items into one and the same distributing channel while the other distributing channels remain empty. If such a composition of the items to be distributed is not noted and the coding stations are not provided in time with items to be distributed which have a different composition, the occurrence of grave interruptions in operation would be unavoidable in prior art systems, particularly those employing a large number of coding stations.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to overcome the above-described difficulties and drawbacks in a mail distribution, or sorting, system of the above-mentioned type.

A more specific object of the invention is to provide an automatic signal when there exists the danger of the occurence of malfunctions due to the fact that the permissible flow density is locally exceeded.

A further object of the invention is to overcome the drawback that there is presently no useful device which would make it possible to directly measure the flow density occurring at certain points in a distributing channel.

The sorting system to which the present invention relates is of the type which includes a plurality of distributing stations arranged along a collecting conveying path composed of a plurality of distributing channels. The distributing stations have outlet conveying paths arranged transversely across the collecting conveying path, and switches disposed to connect any outlet path to any distributing channel. At the exit ends of the distributing channels, processing devices having a limited flow capacity are provided. Each distributing station is associated with a keyboard via which is fed in routing or destination information derived from the address on each mail item, and a collator which forms from this information a setting signal for the switch associated with the distributing channel which corresponds to the address of each item.

The objects of the invention are achieved by associating such a system with, for each distributing channel 1: an electrical simulation circuit which presents an electrical representation of the distribution of items supplied to its associated distributing channel; an input unit connected to the circuit for supplying thereto simulation signals in a manner to cause the circuit to contain an indication of the time of delivery of each item to the channel and the location along the channel of each such delivery; a control device associated with the circuit for causing the circuit to continuously indicate the location of each such item as it travels along the distributing channel, a monitoring circuit associated with at least the last station, in the direction of conveyance of items along the path, and connected to the circuit for deriving a representation of the number of such items indicated by the circuit to be present in a selected length of the channel upstream, relative to the direction of item conveyance, of the junction between the channel and the switch connecting the channel and the last station; and a comparator connected to the monitoring circuit for emitting an alarm signal when the monitoring circuit derives a representation corresponding to more than a predetermined number of items.

The alarm signal provided by the present invention can serve, in the simplest case, to actuate suitable indicating devices and thus permit the operators to initiate the proper reorganizing or operative countermeasures.

Further embodiments of the present invention relate to the goal of providing a distributing system of the above-mentioned type in which the occurrence of operating malfunctions of the described type is automatically prevented without any action by the operating personnel. It is clear that such a distributing system can be designed, without interfering with operational dependability, so that high utilization of its conveying devices results.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of part of a data processing device according to the invention and the mechanical portion of a mail distributing system with coding stations which are fed by a common input path.

FIG. 2 is a schematic block diagram of the data processing system of FIG. 1 providing electrical simulation of one of the distribution channels.

FIG. 3 is a block diagram of an embodiment of the evaluator circuits which are illustrated generally in FIG. 2.

FIG. 4 is a diagram illustrating the actuation of the indicator device shown also in FIG. 1.

FIG. 5 is a schematic circuit diagram of control circuitry of the mail distributing system shown in FIGS. 1 and 2.

FIG. 6 is a schematic circuit diagram of a further embodiment of the circuitry shown in FIG. 5.

FIG. 7 is a diagram illustrating the actuation of a modified indicator device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The mail distributing system schematically illustrated in FIG. 1 includes seven coding stations 11, 12, 13, 14, 15, 16 and 17 arranged along a collecting conveying path 50. The collecting conveying path includes five distributing channels 100, 200, 300, 400 and 500 and a return channel 600. The outlet conveying paths 21, 22, 23, 24, 25, 26 and 27 of the coding stations are arranged transversely -- in the embodiment used in practice they are oblique -- above the collecting conveying path and can be selectively connected with any one of the distributing channels via switches 111-117, 211-217 . . . 511-517. The reference numerals for the switches are selected so that the hundreds digit indicates the distributing channel into which the switch opens and the tens and ones digits coincide with the reference numeral of the coding station in whose outlet conveying path the switch is disposed. For reasons of a clearer illustration the number of coding stations and distributing channels in the embodiment was selected to be smaller than would generally be the case in practice.

Behind the point where the switches 117 . . . 517 of the last coding station 17 open into the respective distributing channels 100 . . . 500, processing devices are included which can handle only a limited flow density, i.e. number of items per unit time. In the illustrated embodiment these are pass-through separators 51 which serve to render the conveying flow uniform so that the items can be stacked in subsequent stackers or intermediate stackers without malfunctions.

Storage containers 52 for coding stations 11 . . . 17, which containers are designed as intermediate stackers, are automatically supplied with the items to be distributed from an input point 55 via switches 53 in a common input conveying path 54. For this purpose the input station is provided with two storage units 56 and 57 which are subdivided into sections and from which groups of overlapping items are selectively removed. An arrangement for automatically feeding the coding stations is known and one embodiment is disclosed in detail, for example, in German Pat. No. 1,431,001.

An operator is stationed in the area of the input station 55 to fill the units 56 and 57 and to observe the operation of the system.

At the coding stations, e.g., coding station 17, the items are brought singly from the storage containers 52 to a reading field 58. An operator at the station derives destination information from the address on the item and feeds this information into a keyboard 59 from where it travels via the appropriate conductor 37 to the data processing device 60 of the system. Stations 11-16 are similarly provided with keyboards and respective conductors 31-36.

Device 60 is of a known type and includes a collector which forms, from the destination information, a setting signal for that switch which leads to the particular distributing channel indicated by the destination information for the particular item. The setting signal is delivered via a suitable actuating line. For the sake of clarity FIG. 1 shows completely only those actuating lines 221, 222, 223 . . . 227 between the data processing device 60 and the switches 211 . . . 217 which feed the second distributing channel 200. The other corresponding actuating lines, e.g. lines 125, 325, 425 and 525 for switches 115, 315, 415 and 515 of outlet conveying path 25 for coding station 15, are only indicated by dashed lines.

At each coding station 11 . . . 17 there also is provided, in the conveying path between the reading field 58 and the outlet conveying path 21 . . . 27, a printer of a known type which is not shown in FIG. 1 and which would be located approximately below the storage container 52. It serves to permit a coded guide indication on each item.

The basic arrangement of the part of the conveying path in the vicinity of the printer is shown schematically, for example, in FIGS. 5 and 6 which show different embodiments of control circuitry, to be discussed below.

After the destination information has been fed in, the item 64 is removed from the reading field 58, travels in the direction of arrow 61 between the printer 62 and a supporting plate 63, and is stopped at abutment 65 in the position shown in FIG. 6. This abutment is fastened at the end of one arm of a two-armed lever 67 which pivots about an axis 66. The lever is held in the first position shown in FIG. 6 by a tension spring 68 where the conveying path is blocked by the abutment. By exciting a pulling magnet 69 the lever 67 can be moved, in a latter phase of the operation, to a second position as shown in FIG. 5 where the conveying path is unblocked. At the same time the item 64 is accelerated in the direction of arrow 70 when a pressure roller 71 mounted on lever 67 comes into engagement with the item and presses it against a continuously driven conveying roller 72.

In addition to the already mentioned setting signal, the collator produces printing information from the destination information fed into the data processing device 60 through the appropriate one of lines 31 . . . 37, which printing information is applied via line 73 to effect a selection of the printing dies required for the guide indication. As soon as the item which has entered the area of the printer 62 has arrived at abutment 65 in the position shown in FIG. 6, a line 74 also coming from data processing device 60 conducts the printing order. Upon completion of the printing process which has thus been initiated -- for the sake of clarity in the illustrated embodiment by the printer 62 itself -- the pulling magnet 69 at the coding station is excited by a signal applied via a line 75'. Thus lever 67 moves to its second position, shown in FIG. 5. The item 64, which now has been provided with a guide indication, is transferred in the above-described manner to the associated outlet conveying path, moving in the direction of arrow 70, and reaches the corresponding distributing channel 100 . . . 500 via the switch which has been actuated by the setting signal.

The above-described arrangements and procedures are already known in the art and are described, for instance, in the article "Eine neue Grossanlage zur automatischen Briefverteilung" (A new large-scale installation for automatic letter sorting) which has been published in the periodical "TECHNISCHE MITTEILUNGEN AEG-TELEFUNKEN" 1968, pages 1 to 7.

In accordance with the present invention, the data processing device 60 of the distributing system has one electrical equivalent, i.e. a so-called analogon, for each one of the distributing channels 100 . . . 500 of the collecting conveying path 50. FIG. 2 shows, in the region 260 which is outlined in dot-dash lines, that portion of the data processing device which contains the simulation, and further elements cooperating therewith, for the distributing channels 200. The corresponding parts for the other distributing channels are identically constructed.

Electrical simulations of conveying paths are known in sorting systems and in the mail distribution art. The simulations made in the prior art constitute sorting conveying paths with an input and a plurality of outputs which branch off therefrom by way of switches, each containing only separated items. The purpose of the known simulations is to shift the setting signals for the switches associated with the items and to make them effective when the item is disposed in front of the respective switch.

In the practice of the present invention, however, the simulation is for the collecting conveying path whose individual channels have a plurality of inputs distributed over their length. The items do not move individually but rather in irregular distributions or accumulations. The purpose of the simulation is to detect in a novel manner the instantaneous values of the flow density existing in these channels. Thus the configuration of these simulations and of the further elements cooperating therewith differs from those of the known arrangements.

In the simulation circuit shown in FIG. 2, the switch for chanel 200 for each of the coding stations except for the last coding station 17 has its own shift register 231, 232, 233, 234, 235, or 236 associated to it. The number of bit locations differs between shift registers to correspond with the different spacings between the point at which each switch 211 . . . 216 of the respective coding station 11 . . . 16 opens into distribution channel 200 and the point at which switch 217 of coding station 17 opens into that distributing channel. Thus it is accomplished that the signals representing the items are written into the simulation circuit at locations corresponding to the positions of the entrances of the transferring switches along the distributing channel 200.

Also the time of writing in of a signal into the simulation circuit must correspond to the time of transfer of the respective item into the distribution channel, or at least it must have a defined spacing therefrom. The write-in signal could, for example, be generated by a photoelectric cell disposed in front of the respective switch or entrance point to be actuated by the item.

Another advantageous feature of the illustrated embodiment is that the writing-in of the signals corresponding to the items is effected by the setting signal for the respective switch leading to the associated distributing channel, in this case channel 200. FIG. 2 shows that the write-in lines 241, 242, 243, 244, 245 and 246 are each connected directly with the respective one of actuating lines 221, 222, 223, 224, 225 and 226 leading to switches 211 . . . 216 of distributing channel 200. In the circuit region of coding stations 11 to 14, the lines 241-244 are also connected directly with the lines 251 . . . 254, respectively, coming from the collator and carrying the setting signals, while in the region of coding stations 15, 16 and 17 an AND circuit 76 is connected between the lines 245, 225; 246, 226; and 227 and the lines 255, 256 and 257, respectively, coming from the collator, for reasons which will be explained below.

The clock pulses for shifting the signal bits stored in the distribution channel simulations can be generated by a mechanical-optical deivce, as shown in FIG. 2. This device includes a perforated disc 77 having a shaft 78 coupled to the conveying members of the distribution channels 100 . . . 500 in a manner such that the time for one revolution of the perforated disc is equal to the travel time of an item along any channel from one switch entrance to the next. The number of perforations 79 is equal to the number of bit locations in each shift register which corresponds to the spacing between adjacent entrances, i.e. for the illustration in FIG. 2 this is equal to 4. The perforations permit passage of the beam of a light barrier 80/81 in a manner to apply pulses to an amplifier 82 which feeds a line 83 leading to the shift inputs of the shift registers of the five channel simulations.

It should be mentioned also that in the illustration of the shift registers in FIG. 2 the travel time of the items from the coding station to the output side of the respective switch, i.e. the entry into the conveying channel, was not considered for the sake of clarity. It is understood, however, that any shift register can be correspondingly extended at its input side to account for this.

The flow density cannot reach any dangerous values in the regions of the first coding stations, i.e., stations 11-14. It must be monitored only over the portion of the collecting conveying path in the region of subsequent further coding stations, depending on the basic dimensions of the distribution system. In the illustrated embodiment the flow density is monitored and considered in the region of the coding stations 15, 16 and 17.

The flow density is determined with the aid of the simulated distribution channels in accordance with the present invention in that each simulation has associated with it means for forming sum indications which represent the instantaneous sum of all signals simultaneously disposed in certain locations of the simulation. That is, for the special purpose of achieving the results of the invention sum indications are produced for locations of a channel simulation which correspond to certain lengths of that distribution channel which lie before, or upstream from, the entrance of the switches of the respective coding stations.

Depending on the operating characteristics of the simulation circuitry, the above-mentioned means for forming the sum information may be additional circuit elements which perform addition; or they may be components of the simulation circuits themselves. The first case is shown for the embodiment of FIG. 2 whose individual shift registers can receive at each location only a signal which maximally corresponds to one item, i.e. one bit. The second case would apply, for example, for simulation circuits whose individual locations are constituted by counters or, for example, for simulation circuits whose locations are able to store analog values.

In this embodiment the shift registers 231 . . . 236 in the region of the coding stations 15, 16 and 17 are associated with evaluator circuits 265, 266 and 267, respectively, which for space saving reasons were only shown as boxes in FIG. 2. They are shown in greater detail in FIG. 3.

To form sum information from the contents of shift registers 231 . . . 234, the evaluator circuit 265 is provided with an adder 84 which is connected, via a number of reading lines 275 represented by a single line, with the locations of these shift registers which correspond to a short conveying section of distribution channel 200 located directly before, or upstream from, the entrance of switch 215. At the output of adder 84 there thus appears a value which indicates the present number of items in the respective conveying section -- corresponding to the value for the flow density in question.

A corresponding task is performed by the adders 85 and 86 in evaluator circuits 266 and 267, respectively. These are connected via reading line groups 276 and 277, respectively, with those locations of shift registers 231 . . . 235 and 231 . . . 236, respectively, which correspond to short conveying sections of the distribution channel 200 directly before the opening, or entrance, of switches 216 and 217, respectively. At the outputs of adders 85 and 86 there thus appear values which indicate the respective number of items disposed before these openings in distribution channel 200.

The output values of adders 84, 85 and 86 are fed, in each of the evaluator circuits 265, 266 and 267, to the input of a comparator 87 at whose output a signal appears when the sum formed by the adders exceeds a given value which corresponds to a given number of items in the above-mentioned respective short conveying sections of distribution channel 200. In the illustrated embodiment the given value is assumed to be three to correspond to the other dimensions which serve to provide the simplified illustration.

These output signals of the three comparators 87, which in the evaluator circuit 265 are fed directly and in the evaluator circuit 266 and 267 are fed via an OR circuit 88 to an alarm line 285, 286 or 287, respectively, serve as alarm signals.

As stated above, the adders 84, 85 and 86 serve to determine the flow density in the short conveying sections directly before the switches 215, 216 and 217, respectively. Thus temporary peak values are in particular detected. However, in such a distribution system the instantaneous value of the average flow density existing in a longer conveying section may also be of interest. Such is the case for the illustrated embodiment of the evaluation circuits 266 and 267 to be described below.

In order to determine the momentary sum of the items disposed in the distribution channel 200 directly behind the entrance of switch 215, an item fed in via this switch is also considered in the result produced by this embodiment. For this purpose, the evaluator circuit 266 contains a further adder 89 whose first input is connected with the output of the adder 84 and whose second input is connected via a reading line 296 with the first location of the shift register 235. The momentary sum of the items disposed directly before the entrance of switch 216 is given by the output value of adder 85. The outputs of adders 89 and 85 are fed to the respective ones of accumulators or counting memories 90 and 91 which are also connected with the clock pulse line 83. Each of memories 90 and 91 is designed to add the count value at its input after each shift pulse to the previous total sum value present in the memory. The output values of counting memories 90 and 91 thus correspond to the total sum of the items which have passed through the distribution channel 200 in the short sections behind the entrance of switch 215 and before the entrance of switch 216, respectively.

In a further stage 92 the difference between these two total sums is formed so that the output value of stage 92 provides in an advantageous manner an indication of the number of all items presently, or instantaneously, disposed in the long conveying section between the two switches 215 and 216.

In a corresponding manner an output value is formed in evaluator circuit 267 by means of a reading line 297 connected to the first location of register 236, an adder 89, two counting memories 90 and 91 and a difference-forming stage 92; the output value corresponds to the number of all items then present in the long conveying section between the two switches 216 and 217.

In each one of the evaluator circuits 266 and 267 the output values from stage 92 are fed to a further comparator 87' which emits an output signal when a further given value is exceeded which corresponds, for example, to seven items in the above-mentioned section. These output signals are also applied, via an OR circuit 88, to a respective one of alarm lines 286 and 287 as alarm signals.

The alarm signals made available in alarm lines 285, 286 or 287 by the above-described circuit arrangements can serve to actuate a visible and/or audible indicator, or warning, device. FIG. 4 is a schematic representation of an advantageous embodiment of an optical indicator device 93, also represented in FIG. 1, in which each conveying section of distribution channels 100 . . . 500 which is disposed before the switches associated with coding stations 15, 16 and 17, has its own indicator element 93', for example, a colored light bulb, associated with it. The indicator elements are arranged in rows and columns to correspond to the path of the distribution channels and the locations of the coding stations so that it can be ascertained at a glance in which one of the distribution channels and ahead of which coding station there exists the danger of exceeding the permissible flow density.

The individual indicator elements 93' could be connected directly to the alarm lines coming from comparators 87 or OR circuits 88, respectively, of the circuit of FIG. 3 of the corresponding part 260, for example, of the data processing device 60, such as alarm lines 285, 286 and 287. Alternately, it may be advantageous, as shown in FIG. 4, to include an extension stage 94 connected in the line leading to each indicator element, for example a monostable multivibrator, which maintains the indication for a given period of time even after the alarm signal disappears.

FIG. 7 is illustrating a simplification of the arrangement described in connection with FIG. 4, wherein the alarm lines coming from the individual comparators of a simulation circuit, e.g. the alarm lines 285, 286 and 287, are combined via an OR circuit 94' to actuate, within the indicator device 93'", common indicator element 93' associated with one of the distributing channels, e.g. the channel 200.

If, as in the embodiment shown in FIG. 1, the storage receptacles 52 at the coding stations are fed with the items to be distributed from an input point through a common fed line 54, it is also advantageous to dispose the indicator device 93 in the direct visual region of the input point 55. The operator employed at this location can then immediately recognize the danger of exceeding the permissible flow density at a certain point in the collecting conveying path and can counteract it by appropriate measures. For example, the operator can simply stop supplying to the coding stations items having unfavorably frequently occuring addresses, or the coding stations in question can be temporarily stopped or switched to a slower operating speed when continued normal operation would lead to malfunctions.

Measures provided in further advantageous embodiments of the present invention will now be described which automatically prevent the occurrence of malfunctions due to exceeding a given flow density without any action by the operating personnel.

As mentioned above, in the circuit range of coding stations 11 . . . 14 the lines 251 . . . 254 carrying the setting signals for channel 200 are directly connected with the actuating lines 221 . . . 224 for the switches 211 . . . 214, while in the region of coding stations 15, 16 and 17 an AND circuit 76 is included between the lines 255, 256 and 257 coming from the collator and the actuating lines 225, 226 and 227 of switches 215, 216 and 217, respectively. The inverted, or negated, version of the signal on the alarm line 285, 286 or 287, respectively, is connected to the second input of the AND circuit.

Thus, for stations 15, 16 and 17, during the duration of an alarm signal a setting signal is prevented from becoming effective if this setting signal is intended for the switch which connects to the distributing channel in question; i.e. for the switch which follows that section of the distributing channel in question for which the associated comparator of the corresponding simulation circuit emits an alarm signal.

In this embodiment, the item is transferred to the outlet conveying path of the coding station even if, due to the occurrence of an alarm signal, as described above, no switch setting signal has become effective. The item is then fed into the return channel 600 which leads to a store 95 disposed in the vicinity of the input point 55. As shown by broken lines, a further pass-through separator 51 could be included in the conveying path defined by the return channel. For operating reasons which bear no relation to this invention, the outlet conveying paths of the coding stations 11 . . . 14 in which no items are discharged due to the occurence of an alarm signal could also be connected to the return channel 600.

Since in the present embodiment the coding stations are provided with printers, the items which have been discharged into the outlet conveying path without a switch setting signal must be prevented from being previously provided with a guide indication. The arrangement shown in FIG. 5 is provided for this purpose.

FIG. 5 relates by way of example to coding station 15. The lines 155, 255, 355, 455 and 555 carrying the setting signals for switches 115, 215, 315, 415 and 515, respectively, and the alarm lines 185, 285, 385, 485 and 585 are conjunctively linked in pairs by way of AND circuits 96. The outputs of these five AND circuits are disjunctively linked by means of an OR circuit 97. At the output of the OR circuit 97 a signal appears only when a setting signal is prevented, i.e., only when there simultaneously appear a setting signal and an alarm signal, for one of the five switches associated with coding station 15 due to the above-described overload conditions.

The line 74 which carries the printing signal is not connected directly with the printer 62 but is rather connected via an AND circuit 98 whose other input receives the inverted, or negated, version of the output signal from the OR circuit 97. The output of a second AND circuit 98' is connected directly with the line 75' which comes from printer 62 and serves to actuate the pulling magnet 69, the inputs of this AND circuit also being connected to line 74 and directly to the output of OR circuit 97. This results in the following mode of operation:

If no alarm signal is present for coding station 15, there is no output signal from OR circuit 97, so that the printer 62 and abutment 65 operate in the usual manner as explained earlier with reference to FIG. 6. Upon the arrival of the printing signal via line 74, the printer prints the guide indication on the item and then the pulling magnet 69 is excited by a signal applied via line 75' so that lever 67 moves into the position shown in FIG. 5 and the item 64 is discharged to the outlet conveying path 25.

If, however, an alarm signal is present in one of the alarm lines 185 . . . 585 and a setting signal appears simultaneously on the corresponding one of lines 155 . . . 555 which leads to the same AND circuit 96, and thus a signal is emitted from the output of OR circuit 97 to the AND circuits 98 and 98', the arrangement changes its mode operation. The printing signal in line 74 cannot become effective at printer 62 and no imprint is made. Instead this signal directly actuates, via AND circuit 98' the pulling magnet 69 so that the item is discharged as desired to the outlet conveying path 25 without imprint.

FIG. 6 illustrates another embodiment where it is again assumed that the illustrated printer 62 is associated with coding station 15. The arrangement of FIG. 6 contains the same logic circuits 96, 97 as the arrangement of FIG. 5. However, the output signal from OR circuit 97 is employed in a different manner.

As can be seen in the drawing, line 74 for the printing instruction is connected in the usual manner with the printer 62. However, an AND circuit 99 is inserted in the line 75 between the printer and the pulling magnet 69, and line 75' is eliminated, and the inverted version of the output signal from OR circuit 97 is applied to the second input of this AND circuit 99. The arrangement thus operates as follows:

If the output line from OR circuit 97 contains no signal, the connecting line 75 between the printer 62 and the pulling magnet 69 is completed via AND circuit 99. The arrangement then operates in the usual, above-described, manner as if line 75' were present. If however, the OR circuit 97 carries a signal for the reasons described above in connection with FIG. 5, then the above-mentioned connection between line 75 and magnet 69 is interrupted. The printing process does take place, but the item 64 remains in the printer. It is subsequently transferred to the outlet conveying path 25, and, via the appropriate switch, to the intended distribution channel, only upon termination of the alarm signal which had prevented the setting signal associated with the item from becoming effective. The alarm signal terminates when there is a suitable change in the flow density. In this embodiment a return channel 600 is thus not required, at least not in connection with the formation and evaluation of alarm signals.

It has also already been stated that various possibilities exist for the engineering design of the simulation circuitry employed in connection with the distribution system according to the present invention. The only significant factor is that the simulation circuitry must perform the essential functions outlined above in the SUMMARY OF THE INVENTION. It is therefore also possible, within the scope of the present invention, to realize the functions of the simulation circuit in an appropriately programmed digital computer. A particularly advantageous embodiment of the invention results if a process computer is employed in the distribution system for other purposes, among others, for example, to constitute the collator for the formation of the setting signals and the printing information and for controlling the various process sequences. This process computer can then also take over, in addition to the functions of the simulation circuits, the functions of the summing, or monitoring, devices and of the comparators. A mail sorting system which makes use of an appropriate process computer is described in the article "Informationsverarbeitung fur eine moderne Briefverteilanlage" (Information handling for a modern mail sorting installation), published in the periodical "Zeitschrift fur das Post- und Fernmeldewesen" 1971, pages 523 to 527.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

Claims

We claim:

1. In a mail sorting system composed of: a collecting conveying path constituted by a plurality of distributing channels; a plurality of distributing stations disposed along the collecting conveying path and having outlet conveying paths arranged transversely across the collecting conveying path; switches disposed to connect each outlet path to any distributing channel; each station including a keyboard for supplying destination information derived from the address on each mail item supplied to that station, and a collator for forming from such information a setting signal for the switch associated with the channel which corresponds to the address on each item, the improvement comprising, for each said distributing channel:

electrical simulation circuit means for providing an electrical representation of the distribution of items supplied to its associated distributing channel;

input means connected to said circuit means for supplying thereto simulation signals in a manner to cause said circuit means to contain an indication of the time of delivery of each item to said channel and the location along said channel of each such delivery;

control means associated with said circuit means for causing said circuit means to continuously indicate the location of each such item as it travels along said distributing channel;

monitoring means associated with at least the last of said stations, in the direction of conveyance of items along said path, and connected to said circuit means for deriving a representation of the number of such items indicated by said circuit means to be present in a selected length of said channel upstream, relative to the direction of item conveyance, of the junction between said channel and the switch connecting said channel and said last of said stations; and

comparator means connected to said monitoring means for emitting an alarm signal when said monitoring means derives a representation corresponding to more than a predetermined number of items.

2. An arrangement as defined in claim 1 further comprising an indicator device connected to be actuated by such alarm signal.

3. An arrangement as defined in claim 2 further comprising a prolongation device connected in the alarm signal path between said comparator means and said indicator device for prolonging the actuation thereof for a given period of time after the alarm signal has disappeared.

4. An arrangement as defined in claim 2 further comprising mail storage containers at an input location, and means delivering mail therefrom to said distributing stations, and wherein said indicator device is disposed in the region of such input location.

5. An arrangement as defined in claim 2 wherein there are monitoring means comparator means associated with a plurality of said stations and said indicator device includes an indicator element connected to receive the alarm signals from all comparators associated with one distributing channel.

6. An arrangement as defined in claim 2 wherein there are monitoring means and comparator means associated with a plurality of said stations and said indicator devices comprises a plurality of indicator elements each associated with a respective channel and station, said indicator elements being arranged in rows and columns corresponding to the disposition of the distributing channels and the locations of said distributing stations.

7. An arrangement as defined in claim 1 further comprising a blocking circuit connected to said comparator means for receiving alarm signals for blocking, during the duration of such an alarm signal, delivery of a setting signal to the switch disposed between the respective distributing channel and said station.

8. An arrangement as defined in claim 7 further comprising means for delivering to a separate collecting point those items prevented from reaching said distributing channel by the action of said blocking circuit.

9. An arrangement as defined in claim 8 wherein each said distributing station comprises a printer for printing a coded guide indication on each item corresponding to printing information which is also formed in said collator from the destination information therefor; and a logic circuit connected to provide an output signal which effects the discharge of an item to the outlet conveying path of said station without actuation of the printer whenever delivery of the setting signal has been blocked due to the presence of an alarm signal.

10. An arrangement as defined in claim 1 wherein said station comprises a logic circuit connected to said comparator means for preventing the transfer of an item to the outlet conveying path of said station during emission of an alarm signal by said comparator means.

11. An arrangement as defined in claim 1 wherein said input means are connected to supply to said circuit means signals derived from the setting signals formed by said collator.

12. An arrangement as defined in claim 1 wherein said simulation circuit means comprises a plurality of shift registers each associated with a respective one of said stations disposed ahead of said last station with respect to the direction of conveyance along said path, with the number of bit locations of each said register being proportional to the distance, along said path, between its associated station and said last station.

13. An arrangement as defined in claim 1 wherein, for all of said channels, said simulation circuits, said monitoring means, and said comparator means are constituted by a programmed process computer.

14. An arrangement as defined in claim 13 wherein said process computer also constitutes said collator.