A known sorting/distributing system has a central carousel containing a plurality of load carrying trays and a plurality of discharge stations each representative of a particular destination. The carousel has a control system which serves to discharge a load on a tray at the appropriate discharge station. As the tray carrying the load passes the discharge station, the tray is tilted and the load is deposited via a steel chute onto a short length of belt conveyor which is designed to slow the load down and to stop it if required. The load is then transferred from the short conveyor belt onto a main discharge conveyor belt which is inclined downwardly at an angle of approximately 15°, terminating in a picking station from which the loads are removed manually by a picker.

The sequence of operations with this known apparatus is that when a load is discharged onto the short conveyor belt, the load is first slowed and then, if the main conveyor is holding a load at its input end in a first section, stopped at the end of the short belt conveyor. If there is a load on the first section of the inclined main discharge belt conveyor the load on the short section cannot be transferred onto the discharge conveyor. In these circumstances, a signal is sent to the carousel to stop any further loads for that station from being discharged from the carousel. In normal operation, the inclined conveyor is stopped from rotating when a load is present at the discharge end. If there is no load in this station, the conveyor is able to move incrementally every time a load is placed on the input end of the conveyor. Thus, when a load is sensed at the top of the conveyor but no load is sensed at the bottom, the conveyor is rotated by an increment which is just sufficient to enable another load to be placed on the input end. Thus, the conveyor is run incrementally as succeeding loads are placed on the conveyor until a load reaches the discharge station. Thereupon, the conveyor stops until the picker removes the load from the discharge station. This arrangement has the disadvantage that the picker cannot begin to unload the conveyor until it is fully loaded with a load in every section. This means that the picker is frequently left waiting for sufficient loads for that destination to be off-loaded from the central carousel to fill the conveyor to enable the first load to reach the discharge station. To overcome this disadvantage, the conveyor is provided with an override switch operable by the packer to enable him to bring a load down to the discharge station. Again, there is a delay in achieving this. A consequence of using the manual override is that it is possible to have a load at the discharge station and a load at the input end with nothing in between. The load at the input end effectively prevents any more loads being transferred to that destination conveyor. In practice, it has been found that this greatly reduces the throughput of loads and often loads pass round the central carousel several times before space is made available for them at the selected destination. The known system therefore has the two disadvantages that throughput of the loads through the system is slower than desirable and the efficiency of the picker is also much reduced by the delays in waiting for the loads to be transported along the discharge conveyor. The present invention seeks to provide an improved form of belt conveyor and control system to improve the speed and efficiency of throughput when used in this particular application.

According to a first aspect of the present invention there is provided a belt conveyor having a plurality of endless elongate drive belts mounted in parallel about at least two spaced rollers, one at least of which comprises a drive roller, and brake means including a brake surface located so as to be movable between a non- operable position below a load supporting surface of the drive belts and an operable position above said load supporting surfaces to lift a load thereon clear of the drive belts to thereby brake the load.

According to a second aspect of the invention there is provided a sorting/distribution system for sorting and distributing loads, including a supply conveying means having a plurality of discharge stations each representative of a criteria such as a destination or load type, each station having a belt conveyor according to the first aspect of the invention to transport loads from an input end to which loads are transferred from the supply conveying means, to a discharge position.

The invention also provides a method of operating a discharge conveyor of a sorting distribution system the conveyor being adapted to support a plurality of loads in respective ones of a plurality of zones, one form of the method comprising moving the loads to a discharge zone and stopping the load by lifting it clear of the rotating conveyor belt, moving succeeding loads along the conveyor towards the discharge zone and lifting a load clear of the conveyor when it is in a zone where there is a load already present in the zone immediately downstream.

In a typical installation, the discharge conveyor in the sorting/distribution system will consist of three separate belt conveyors each having four brake means spaced along the length of each conveyor, each brake means being operable to lift a load in its zone out of contact with the conveyor belt when there is a load in the zone immediately downstream. Thus, a nine metre length of discharge conveyor, made up of three three metre lengths, can support a total of twelve loads.

A preferred embodiment of the present invention will now be described by way of example with reference to the accompanying drawings in which:- Figure 1 shows a plan view of a belt conveyor, Figure 2 shows a sectional side view of the conveyor of Figure 1, Figure 3 shows a view of the conveyor of Figure 1 incorporating brake devices and, Figure 4 shows a longitudinal section through Figure 3.

Referring now to Figure 1, there is shown a plan view of a belt conveyor consisting of a plurality of endless, elongate drive belts 2 mounted in parallel so as to be rotatable about two rollers 3 and 4. The roller 4 constitutes a drive roller being driven by an electric motor 5 through a short drive belt 6 as shown in Figure 2. The upper belt runs of the belts 2 form a load supporting surface 7. In this example there are eleven such belts but this number may be varied depending upon the application of the conveyor and the loads to be transported.

As can be seen in Figure 2, the lower run of the belts 2 is supported and guided by idler rollers 8. The system also includes a tensioning roller 9 located below the idler rollers 8. The position of the tensioning roller 9 is adjustable towards and away from the idler rollers 8 to enable the correct belt tension to be maintained. Each of the upper runs of the belts 2 is located in a shallow channel 10 which serves to support the belt throughout the length of the conveyor and also to constrain it against lateral movement. The upper edges of the side walls of the channel lie below the load supporting surface of the belt.

Referring now to Figures 3 and 4, Figure 3 shows an plan view of the belt conveyor of Figure 1 when fitted with brake devices and Figure 4 shows a sectional view corresponding to Figure 2 showing the brake devices in more detail. As can be seen particularly in Figure 4, the conveyor is divided into four zones each having a plurality of brake shoes 11 spaced across the width on the conveyor. Each brake shoe 11 consists of an elongate member located between adjacent belts 2. In this embodiment, a brake shoe 11 is located between each belt and the next although it is envisaged that brake shoes may be provided only between every other space between the belts. The brake shoe 11 extends substantially throughout the length of its zone as can be seen in Figure 4, and has on its upper face a braking surface of a relatively high friction material. The brake shoe 11 is movable by air cylinders shown schematically as reference 12 between a non-operable position in which the brake surface is located about lOmm below the load supporting surface of the belts 2 and an operable, braking position in which the brake shoe surface is approximately 5mm above the conveyor load supporting surface. The leading and trailing edges of each shoe 13 and 14 are inclined slightly downwardly to reduce the risk of a load catching on the end of the brake shoe and damaging either the load or the brake shoe. The control system for raising and lowering the brake shoes extends across all the brake shoes of each zone so that all the brake shoes of that zone are raised and lowered simultaneously. In this embodiment the brakes are raised by air cylinders controlled by electrically operable solenoids, the brake shoes of each zone may be mounted together on a parallelogram framework in which the brake shoes are mounted on arms inclined at an angle to the vertical, in parallel, which are pivotally mounted on the conveyor framework and on each of the brake shoes. The whole framework can be pivoted by a single solenoid, pneumatic cylinder or other means. When the solenoid is energised, the inclined pivot arms are moved towards the vertical position, thus causing the brake shoes to rise above the load supporting surface of the belts. Such a system is shown in outline only on one of the zones at reference 15, the control solenoid and air cylinder being indicated by reference 16. Thus, the same parallelogram linkage could control all the brake shoes in this zone by means of one air cylinder device controlled by a single solenoid.

In one preferred application in a sorting/distribution system, three conveyors of the type illustrated in Figures 1 to 4 are combined to form a total belt conveyor nine metres long giving a total of twelve zones in which the brakes of each zone can be controlled selectively. The conveyors are inclined at an angle of 15° to the horizontal although this will depend on the particular application. Loads to be distributed are placed on a main carousel at a loading station for distribution to a selected one of a plurality of discharge stations. Each discharge location represents a particular destination for the products. In one installation, for example, there are forty such discharge stations each representative of a particular supermarket. The destination of each load is either input when the load is placed on the carousel or is read automatically by means of, for example, a bar code on the load. The carousel consists of an endless belt of individual load carrying trays which are tiltable between a transport position and a discharge position. As the load approaches its desired destination, the tray is tilted to discharge the load onto a chute from where it passes onto an input end of the belt conveyor 1. The belt conveyor is normally kept rotating continuously. The presence or absence of a load in each zone of the conveyor is detected by photoelectric cells and when the load reaches the last unoccupied zone, its presence there is detected, the brake means is energised and the brake shoe 11 is raised to lift the load off the load supporting surface 2 of the conveyor belt to thereby brake the load to a standstill. Initially, the first load on the belt will be transported directly to the discharge station where it is immediately available for picking by the picker.

Even if the load is not picked straight away, since the belt continues to rotate, succeeding loads may be transferred along the conveyor to the first unoccupied zone.

When a succeeding load reaches the next unoccupied zone, the presence of a load in the zone downstream is detected and this causes the brake shoes in the second zone to be raised to lift the load there clear of the rotating belt surfaces. This process can be repeated until all twelve zones are occupied, at which point a control signal is sent to the carousel to tell it not to deliver any more loads to that discharge station.

When a load is picked from the discharge station by the picker, the brakes in all of the zones carrying a load are moved to the inoperable position to enable all the loads to be moved towards the discharge station. In this way, the zone at the input end is kept as empty as possible to reduce to a minimum the number of times when a load cannot be discharged at that station. This reduces bottle necks on the main carousel and enables the throughput of the system to be greatly improved.

Although described with reference to the particular application of a sorting distribution system for supermarkets, it will be appreciated that the invention is not limited to this application. It is particularly applicable to this application because the use of the narrow belts containing a plurality of braking shoes in each zone, copes with the wide variety of size, shape, weight and rigidity of loads being sorted.

In an alternative solution to the disadvantages of the prior art described earlier, it would be possible to provide twelve short belt conveyors, each belt conveyor being the equivalent of one of the zones in the embodiment described above. In such an arrangement, the braking would take place by stopping the belt in that zone instead of lifting the load clear of the continually rotating belt. In another embodiment, a roller conveyor system is used having an accumulation mode in which short sections of the rollers form the zones, the rollers in each zone being selectively stopped, as required.

In order to reduce the risk of loads falling through the conveyor, the rollers, which may be formed by a plurality of co-axial wheels, are positioned very closely together.

These embodiments would still enable the method of the present invention to be carried out.