GB2100691A - A mail Discriminator - Google Patents

Abstract

A mail discriminator for sorting a mixed stream of postal items into categories of parcels, packets and letters comprises a one drum segregator (2) having wide gauging slots (4) between its slats (3) which, in use, separates parcels (7) from letters (5) and packets (6), and another drum segregator (8) having narrow gauging slots (4) between its slats (3) the other drum segregator (8) being arranged downstream of the one drum segregator (2) to receive letters (5) and packets (6) from the one drum segregator (2) and, in use, to separate the packets (6) from the letters (5). The one drum segregator (2) may be located wholly within the other drum segregator (8) or, alternatively, the two drum segregators (2 and 8) may be remote from one another in which case, means are provided to collect the packets (6) and letters (5) from beneath the one drum segregator (2) and transfer these to the inside of the other drum segregator (8). <IMAGE>

Description

SPECIFICATION A mail discriminator Postal items sent through the mail can be broadly classified into three different categories; large, relatively bulky items having a substantial size in all three dimensions, smal ler thick flat packages such as padded bags and thick letters in general having a thickness greater than 6 mm, and thin flexible substantially flat letters usually having a thickness less than 6 mm and which are capable of being handled by automatic letter handling machinery. Subsequently, these three different types will be referred to as parcels, packets and letters respectively.

Mail comprising a mixture of postal items enters a postal sorting office and the first step that it is subjected to is to sort the mail into these three categories and particularly to sort out the letters that are capable of being handled by automatic letter handling machinery from the parcels and packets that are handled manually. Various attempts have been made to mechanise this initial sorting operation since it is relatively time consuming and since most of the remaining steps in the sorting of postal items have been successfully mechanised.

The first proposal that was made by the British Post Office as long ago as 1 959 was to use a drum segregator to sort the letters from the remainer of the postal items. A drum segregator is generally cylindrical in configuration having its side wall formed by a number of overlapping slats which are inclined to the tangential direction of the drum with the edge of each slat which leads on rotation of the drum closer to the centre of the drum than the trailing edge to leave a series of gauging slots between the edges of adjacent slats. The axis of the rotation of the segretator drum is inclined to the horizontal and the postal items are introduced into the inside of the drum at its highest end and the drum rotated slowly.

The parcels and packets tumble about inside the drum describing a generally helical path over the inside of the drum until they leave the dowmstream, lowermost end of the drum from where they are taken to a manual sorting system. The intention is that the letters fall through the gauging slots between adjacent slats and are then collected beneath the drum and taken to an automatic sorting apparatus.

Most drum type segregators have also been arranged to increase the width of the gauging slots at some portions during the rotation of the drum to ensure that any packets stuck in the gauging slots are released and returned to the middle of the drum.

The drum segregator has not lived up to its expected performance in practice because not all the letters are separated by the drum segregator and so some are discharged together with the parcels and packets. This causes an embarrassment in the parcel and packet sorting area and as a result of this various attempts have been made to improve on the initial proposal of a drum segregator. It appears that the letters get trapped and held by the parcels and larger packets and are so prevented from escaping through the gauging slots between adjacent slats. This trapping of the letters is particularly severe when a large amount of mail is introduced into the drum segregator and is also particularly severe when the majority of mail inside the segregator is composed of packets and/or parcels.

Thus, if the letters fail to escape shortly after being introduced into the drum segregator then, with an increasing predominance of packets and parcels present in the segregator as the mail moves to downwards through its length the letters become less likely to escape since they only form a minor proportion of the total mail inside the segregator in these regions and they are continually trapped by the parcels.

One early attempt that was made to overcome this problem was to increase the width of the gauging slots towards the downstream end of the drum segregator but this proposal merely resulted in some of the packets escaping through the wider gauging slots towards the downstream end of the drum together with the letters and this resulting mixture still had to be sorted between those that could be handled by automatic sorting machinery and those that could not.

To overcome the problems with segregators a brush and belt system has been proposed and is used in many countries. In this system the postal items are fed to a wide flat belt conveyor having a continuously moving brush mounted transversely a preset distance above the the surface of the belt conveyor. The brush sweeps across the conveyor and so sweeps the packets sideways off the edge of the belt conveyor whilst allowing the letters to pass beneath the brush. Normally there are two or three stages one beneath the other to try and reduce the quantity of letters that are swept off together with the packets and parcels, but even when three separate stages are included there are still a number of machine handleable letters which are carried off the conveyor with other packets.Furthermore, such a segregator experiences considerable difficulty in handling parcels and these are usually culled manually to prevent them jamming and interfering with the operation of the segregator.

Attempts have even been made to return to an entirely manual sorting system in which the items of mail are fed through a slowly moving flat belt conveyor from which the parcels and packets are removed manually leaving simply the letters that are capable of being handled by an automatic sorting ma chine to proceed along the conveyor to the automatic sorting machine.Such systems are principally intended to be used as a manual aid for smaller sorting offices but it has been found that because the segregation is wholly manual it is very subjective and, as a result of this and as a result of the wrong subjective judgement being exercised by the operators a number of letters that are not suitable for machine handling are not removed so leading to jamming of the automatic sorting apparatus and equally, some of the items that are re moved could, in fact, have been handled by the automatic sorting apparatus. Human operators are not good at making fine judgements particularly with regard to size, thickness and stiffness when a postal item is on the margins of its being capable of being handled by a machine.

A further attempt that has been made is to reduce the loading in the drum segregator by providing two or more drum segregators arranged in parallel so that the incoming stream of mail is divided between the two or more segregators so that the loading of each segregator is relatively low. Whilst the performance of a drum segregator under these conditions can be improved it is still not satisfactory and, in addition to this, the cost of the equipment needed to subdivide the flow of mail has to be added to the increased cost of the drum segregators.

According to this invention a mail discriminator for sorting a mixed stream of postal items into different categories comprises one drum segregator having wide gauging slots between its slats which, in use, separates parcels from letters and packets, and another drum segregator having narrow gauging slots between its slats, the other drum segregator being arranged downstream of the one drum segregator to receive letters and packets from the one drum segregator and, in use, to separate the packets from the letters.

This tandem arrangement of two drum segregators one after the other solves the problems that were present when using a single drum segregator and solves the problems inherent with each of the various other proposals that have been put forward. With the arrangement in accordance with this invention what, in fact, is being done is that the one drum segregator is used to extract the parcels from a mixed stream of postal items and then the other discriminator used to separate the packets from the letters. This is in contrast to the earlier systems in which what was attempting to be done was to separate the letters from a mixed stream of postal items and this has proved not to be practical.A drum segregator can be used to make a fine separation of thickness between the packets and the letters provided that, its action is not interefered with by the presence of parcels and consequently by removing the parcels the final drum segregator is then enabled to make a perfectly satisfactory separation between the packets and the letters.

It is also possible for the mail discriminator in accordance with this invention to include a conventional initial stage in which some of the letters are removed. In this case an initial conventional drum segregator is located upstream of the one drum segregator, the initial drum segregator having narrow gauging slots between its slats equal in width to those of the other drum segregator. When the mail discriminator in accordance with this invention includes a conventional initial stage the slats of the one drum are preferably arranged so that at their upstream ends the gap between them is narrow and then towards their downstream ends the width of the gaps between adjacent slats increases.

The one drum may be located wholly within the other drum and, in this case, the mixed stream of postal items are fed into the side of the one drum and then, the letters and packets pass out through the wide slots between the slats of the one drum whilst the parcels proceed throughout the entire length of the one drum and emerge from the end. The letters and packets leaving through the gauging slots of the drist drum then fall into the inside of the other drum segregator and, in the other drum segregator the separation between the packets and the letters occurs with the letters passing out through the relatively narrow gauging slots between adjacent slats whilt the packets are carried down through the entire length of the other drum.Alternatively, the two drums may be remote from one another and, in this case, means are provided to collect the packets and letters from beneath the one drum and transfer these to the inside of the other drum.

Preferably the width of the gap between adjacent slats in the one drum is in a range 1 5 mm to 50 mm more particularly between 1 5 mm and 30 mm. It is preferred that the gap is of the order of 25 mm. The width of the gauging slots in the second drum is preferably substantially 6mm. The overall length of the one drum may be considerably shorter than that of the other drum and typically the overall length of the one drum is 2 metres whereas the typical length for the other drum is 4 metres.

A particular example of a mail discriminator in accordance with this invention will now be described with reference to the accompanying drawings; in which: Figure 1 is a diagram of the discriminator; and, Figure 2 is a diagrammatic cross-section through the first drum.

A stream 1 of mixed postal items are fed to a first drum segregator 2 having a length of 2 metres. The drum segregator 2 is generally cylindrical and has its side wall formed by number of slats 3, typically eight, which overlap and which are inclined to the tangential direction of the drum with the edge of each slat which on rotation of the drum leads, being closer to the centre of the drum than the trailing edge of each slat to leave a number of gauging slots 4 between the edges of adjacent slats. The rotational axis of the drum is inclined downwardly to the horizontal so that postal items fed into the uppermost inlet end of the drum gradually describe a generally helical path around the inside of the drum before being discharged at the lowermost downstream end.The width of the gauging slots 4 of the first drum segregator 2 is 25 mm and the letters 5 and packets 6 pass through these gauging slots 4 whilst the parcels 7 pass along the drum segregator 2 and emerge from the lowermost or downstream end.

The letters 5 and the packets 6 are collected from beneath the drum segregator 2 and conveyed to the inlet of a second drum segregator 8. The drum segregator 8 is constructed in a similar fashion to the drum segregator 2 except that it has an overall length of 4 metres. Also, the width of the gauging slots 4 in the second drum segregator 8 is substantially 6 mm. The mixed stream of letters 5 and packets 6 entering the second drum segregator 8 is separated by the second drum segregator 8 into letters 5 which have a thickness less than 6 mm and which are capable of being handled by an automatic sorting machine and so pass through the slots 4 in the second segregator drum 8, and packets 6 which describe a generally helical path along the second drum segregator 8 before emerging at its lowermost downstream end.

Claims (9)

1. A mail discriminator for sorting a mixed stream of postal items into different categories comprising one drum segregator having wide gauging slots between its slats which, in use, separates parcels from letters and packets, and another drum segregator having narrow gauging slots between its slats the other drum segregator being arranged downstream of the one drum segregator to receive letters and packets from the first drum segregator and, in use, to separate the packets from the letters.

2. A mail discriminator accoing to claim 1, in which the one drum segregator is located wholly within the other drum segregator.

3. A mail discriminator according to claim 1, in which the two drum segregators are remote from one another and which also include means to collect the packets and letters from beneath the one drum segregator and transfer these to the inside of the other drum segregator.

4. A mail discriminator according to any one of the preceding claims, in which the width of the gauging slot between adjacent slats in the one drum is in a range from 1 5 mm to 30 mm over at least part of its length.

5. A mail discriminator according to claim 4, in which the width of the gauging slot is substantially 25 mm over at least part of its length.

6. A mail discriminator according to any one of the preceding claims, in which the width of the gauging slots in the other drum is preferably substantially 6 mm.

7 A mail discriminator according to any one of the preceding claims, in which the overall length of the one drum is shorter than that of the other drum.

8. A mail discriminator according to claim 7, in which the overall length of the one drum is substantially 2 metres and the length of the other drum is substantially 4 metres.

9. A mail discriminator according to claim 1, constructed substantially as described with reference to the accompanying drawings.