CONVEYOR SYSTEM

Abstract: A conveyor system comprising a plurality of modular conveyor units, adapted to be assembled together in a desired layout, and a control system for controlling the operation of the conveyor units. The control system has a main control device (12) and control means (14-20) on at least some of the conveyor units, each control means (14-20) being adapted to control the operation of its associated conveyor unit or units in a predetermined sequence determinated by the main control device (12), the sequence operating as predetermined until fresh control signals are sent from the main control device (12).

Description: Conveyor System This invention relates to a conveyor system and to a control system for such a system. Conveyor systems having a plurality of paths for objects being conveyed by the system are known particularly, but not exclusively, in warehouse systems for the transportation, sorting, storage and delivery of loads and other packaged items. Such conveyor systems typically utilise roller conveyors and/or belt conveyors and a variety of controllable sorting/ merging elements for directing particular packages along a desired path to a desired destination. This necessitates the use of units designed to enable the packages being transported, for example, to be diverted on to other tracks, to be weighed, and to have labels such as addresses and postage franking, automatically placed on the load in accordance with predetermined requirements. In general terms, such elements as diverters and sorters are well known. Typically, such large scale systems are designed and built on an individual basis depending on the design requirements. Control of such systems is typically achieved from a central computerised location to which each operating part of the conveyor system is connected to enable control signals to be sent to that part. Power to drive electric motors etc. is also achieved by wiring the whole conveyor system on an individual, bespoke manner. Such systems have two prime disadvantages. Firstly, since they are designed for a single installation on a one-off basis, the design, manufacture assembly and installation costs are high and not easily predictable. Particularly, a skilled workforce is required to install and set up the system and its control circuitry, which requires the use of skills in several disciplines. Such systems also lack flexibility if subsequent changes are required to the functioning and/or layout of the system. Furthermore, the use of a centralised computerised control system has practical limits in the amount of signals which can be given to each unit and the more units there are and the more signals that are required to be processed, the slower the control system can function. In a typical installation, each unit where options for the functioning of the unit are possible, has detector means to detect the presence or absence of a package and frequently to send a signal to the central control identifying the package. The central computer then has to work out what should happen to the package and should then send the appropriate signals to the controls on the unit concerned. Testing out all these aspects of a bespoke system which has been designed and built as a one-off is very expensive. It is also necessary to spend a great deal of time and effort on commissioning and testing all aspects of the system. The present invention seeks to provide a conveyor system which alleviates die problems of the known apparatus. According to the present invention there is provided a conveyor system comprising a plurality of modular conveyor units, adapted to be assembled together in a desired layout, and a control system for controlling the operation of the conveyor units, the control system having a main control device and control means on at least some of the conveyor units, each control means being adapted to control the operation of its associated conveyor unit in a predetermined sequence determined by the main input, the sequence operating as predetermined until fresh control signals are sent from the main control device. Preferably, at least some of the conveyor units include power means adapted to control the functioning of that unit in accordance with control signals from the control means on the unit. Preferably, the control means of each unit includes cabling such as electrical or optical cables and, optionally, a power cable to power the power means, the cabling of adjacent conveyor units being adapted to be connected together, preferably by standardised plug couplings. In this way, the conveyor system according to the present invention provides a plurality of standardised conveyor units which may be easily assembled into a required configuration by using the necessary selection from a plurality of standardised units. Preferred embodiments of die present invention will now be described by way of example with reference to the accompanying drawings in which :- Figure 1 shows, in block diagram form, the layout of a known system, Figure 2 shows a schematic diagram of a control system in accordance with the present invention, Figure 3A shows a side view of a straight roller conveyor section driven by an electric motor, Figure 3B shows schematically, a braking arrangement for incorporation in the unit of Figure 3A, Figure 4A shows a powered curved conveyor unit, Figure 4B shows a cross-section through the unit shown in Figure 4A, Figure 4C shows a detail of the drive arrangement of the embodiment of Figure 4A, Figures 5A to 5H show a selection of modular conveyor units and, Figures 6 A to 61 show further examples of modular conveyor units. Referring now to Figure 1 , there is shown, in schematic form, a known type of control arrangement for a conveyor system. The system has a centralised management control 1, which supplies control signals to a centralised control computer 2, known as a router, a hub 3 connected to the router 2 and a plurality of control means 4 connected to the hub each designed to control a particular part of the conveyor system. The system has three further stations connected to the router 2, namely a label printing station 5, a weighing station 6 and a user interface station 7, which may be, for example, a dispatch station. Each of these stations has associated with it a bar code reader, respectively 5', 6' and 7' designed to detect the presence of and identify a package in the appropriate station. This information is sent to the router which then computes the appropriate signal for the stations 5, 6 and 7 and/or, receives information from these stations which is used to calculate, for example, the type of label to be placed on the package, postage rates for franking and destination. It can be seen that this known system requires the central computer in the router 2 to perform a large number of calculations. The more calculations that the router has to make, the slower it operates, which is a disadvantage of the known system. Turning now to Figure 2, there is shown in schematic form, the concept of the present invention. As in the known arrangement, the system has a main control input 11 and a main computer 12. The computer 12 is connected to a bus 13. The control system is intended to control the operation of a conveyor system consisting of a plurality of individual modular units. Distributed among these units are a number of control means 14 to 20 comprising a programmable embedded electronic controller connected to the bus 13. The control means on each modular unit can include a bar code reader (BCR) which is designed to read a bar code on packages passing along the modular unit. This signal is sent to the embedded electronic controller which is pre-programmed by the main computer 12 to initiate the appropriate functioning for the unit. For example, in the embedded electronic controller 16 the package at a weighing station in the associated conveyor unit has its weight determined. This information in conjunction with the information derived from the bar code reader is processed by the embedded electronic controller 16 to, for example, send all packages below a certain weight along a first path and packages above that weight along a second path utilising, for example, a diverter to do so. Examples of such diverters are described hereinafter. This predetermined functioning of the conveyor unit containing the embedded electronic controller 16 remains unchanged until the embedded electronic controller is reprogrammed by control signals from the main computer 12. In this way, the operation of the conveyor unit controlled by the embedded electronic controller 16 is controlled on the unit itself so that there is no need for control signals to be sent to and from the main computer 12. In this way, the functioning of the computer 12 is not slowed down or impaired in any way and the conveyor unit is controlled much more quickly and accurately, without the possibility of interference, by the localised control exerted by the embedded electronic controller. Although described as utilising bar code readers to detect and identify packages, it will be appreciated that in certain circumstances the mere presence of a package may be all the control information required, in which case a simple presence detector would provide the input to the embedded electronic controller. Turning now to Figure 3 A, there is shown a sectional side view of a conveyor unit 21 consisting of a plurality of rollers 22 driven via a belt 23 by an electric motor 24. The electric motor 24 drives a belt drive wheel 25, the drive belt 23 being guided by guide rollers 26 so that it passes round at least half the circumference of the drive wheel 25. The drive belt 23 is an endless belt and extends over d e length of the conveyor unit, being supported by idler rollers 27 spaced at intervals along its length below the bottom run of the belt and idler rollers 28 which support the top run of the belt in a predetermined plane. The rollers 22 are provided at their two ends wid through axles 22A by which the rollers 22 are freely rotatably mounted in die frame of the conveyor unit. The through axles rest in slots open at their top edge so that the conveyor rollers 22 can simply be dropped into die slots as appropriate. The rollers 22 rest on the top run of the drive belt 23 widi their stub axles clear of the bottom of the slots in which they are located. This arrangement not only has the advantage of rapid assembly of the conveyor but also if a foreign body falls between the rollers 22 and die drive belt 23, die rollers 22 are just lifted up in the slots. In this way, the risk of damage to die conveyor unit or the drive mechanism by such foreign bodies is substantially reduced. The drive force on the rollers 22 on the belt 23 is derived simply from the weight of the rollers 22. When a load is resting on the rollers 22, they are urged with a much greater force onto the drive belt 23 to enable a sufficientiy powerful driving force to be transmitted to the rollers 22 as the frictional driving force is, to a large extent, weight-dependent. This has die further advantage diat when a load is not being driven by die rollers 22 only a very low stress is applied to die drive belt 23 as diis is generated solely by die weight of the roller 22. Figure 3B shows a braking arrangement which is incorporated in the conveyor unit illustrated in Figure 3A. Four brake units 29, 30, 31 and 32 are illustrated. As die brakes are identical, only one will be described. The brakes extend along the length of the conveyor unit and are each designed to brake approximately a quarter of the length of the conveyor unit, selectively, in dependence upon detection apparatus (not shown), which detects die presence or absence of a load in the section of conveyor controlled by the respective braking unit. The brakes 29 to 32 each comprise a flat brake plate 33, which, when the brakes are not operable, lies adjacent die drive belt 23 immediately below die lowermost part of the rollers 22. The braking plate 33 is raised by two pneumatic air cylinders 34 to lift the rollers 22 clear of the drive belt 23. In tiris way the rollers 22 are brought to a standstill together with any load resting on them. The action of the braking plate 33 lifts the rollers and die load on die rollers up so that die rollers are clear of the moving drive belt 23. The upper most surface of die braking plate 33 is of a high friction material, such as rubber. The braking force imparted on the rollers by this friction material is dependent (as widi anydiing with a constant coefficient of friction) upon die load applied. The load applied is die weight of the load to be decelerated and hence die braking force applied to a load is largely proportional to its weight. This results in very consistent stopping distances between light and heavy packages. This represents a significant advantage over alternative and known methods of braking which apply a constant force to retard die conveying rollers 22. These systems give varying stopping distances between packages of different weights and can consequentiy cause boxes to overshoot sensors and/or cause commissioning problems. The control system of the conveyor unit 21 includes sensors to detect die presence or absence of a load in each of die four zones determined by d e braking units 29 to 32. Thus, if a load is detected in the zone controlled by die unit 29, the brake 30 is operated to stop die rollers in its zone to stop a load in this zone hitting die load in die zone 29. Although, as shown, the braking surfaces are lifted into die braking position by pneumatic cylinders, it will be understood that otiier forms of lifting the brakes may be used. The control system of the braking can, again, be controlled locally on the individual conveyor unit. Turning now to Figures 4A, 4B and 4C, tiiere is shown a curved track section of roller conveyor on a module 35, tire rollers being driven by an electric motor 36. The conveyor unit 35 is a self-contained module which includes its own electric motor in a similar way to the straight section of roller conveyor described widi reference to Figure 3. The unit 35 consists of a plurality of taper rollers 38 which are rotatably mounted in side frames 37A and 37B. The rollers 38 are driven by die electric motor 36 through a drive belt 39, shown more clearly in Figure 4C. The electric motor 36 powers a drive pulley 40 around which the drive belt 39 is guided by two guide wheels 41 and 42 so that the drive belt extends over more tiian 180 of the circumference of the drive wheel 40. At die ends of die conveyor unit, die drive belt passes round idler wheels 43 and 44. In order to maintain the arcuate path of die drive belt 39, which is of circular cross-section, and to ensure tirat die drive belt is in firm driving engagement which the taper rollers 38, the drive belt is guided and supported by a plurality of pressure rollers 45, shown in Figures 4B and 4C in addition to Figure 4A. The drive belt supporting surface on the pressure rollers 45 is substantially arcuate, the surface of the arc being substantially radial at the outermost part of the surface and extending axially at the innermost part of the arc. In this way, the pressure rollers accommodate die curve of the belt around the curve of the side frame 37A. The arc also serves to bias d e drive belt 39 into driving contact with die taper rollers 38. Figures 5A to 5E show different configurations of conveyor unit which may be incorporated in a conveyor system of the present invention. Figure 5a shows a conveyor having a number of narrow parallel belts. Figure 5B shows the conveyor in 5A with a means of lifting die load off the moving belts in four separate zones along its length. Figure 5C represents a similar conveyor fitted widi powered roller transfers. These are mechanically raised to above die level of die narrow belts to transfer load perpendicular to its former direction of travel. These transfers can be bi-directional as indicated. Figure 5D shows a variant of figure 5A configured to merge with another conveyor at an angle. Figure 5E shows a spur drive in which conveyor sections at approximately 30 ° to the axis of a straight section of conveyor are provided to enable items to be fed on to die straight section. Figure 5F shows a module known as a plough merge where two parallel conveyors 46 and 47 (roller or belt conveyors) each carry loads and tiiese are then merged into one row 48. The movement of die loads into die single line is done so by controlling each of the two feeding conveyors 46 & 47. The intelligence for this operation would be provided by a locally mounted embedded electronic controller. Figure 5G shows a gate 50 with sensors 51 which are again designed to control the operation of die gate utilising control signals generated on a purely local basis. Figure 5H shows a lane cross-over unit in which loads are fransported from three parallel input belts 52 on to appropriate ones of three output belts 53 by control means which are controlled by control means located on die module itself. Figures 6A to 61 show further designs of module. Figures 6 A and 6C show straightforward straight sections of belt conveyor. Figures 6B shows a powered curved section. Figure 6E shows an arrangement in which a 90 ° transfer, in either direction, is possible. Again, this unit incorporates the necessary sensors and local control to detect die presence of a load and to determine its intended destination. The drive direction of the transfer unit is then determined locally by die control system on the unit itself. Figure 6F shows a module comprising a diverter unit to divert loads from a longitudinal path off at 30 to one or both sides of die straight section of conveyor, in accordance widi locally generated control signals. Figure 6G shows a similar arrangement to that illustrated in Figure 6E. Figure 6H shows an arrangement similar to Figure 6F but incorporating a bar code reader. Figure 61 shows a module comprising a picking lane transfer. In this module, loads entering from a conveyor section 55 are detected and identified by a bar code reader 56 and in accordance widi tiύs data, the local control system moves the load to a selected one of two output conveyors 56 and 57. It is envisaged, tiiat the control and power wiring and cabling on each module will be designed to be incorporated as an integral part of the module and will terminate in standardised plug couplings. In tiiis way, a conveyor system can be assembled by selecting appropriate modules from a catalogue so that the modules, in effect, constitute building blocks to enable the complete system to be assembled in any desired configuration. This system has great advantages since each individual module will be able to be built, and tested, in d e suppliers' factory before being transported to site for assembly. Once on site, die individual modules can be readily positioned, secured and connected to adjacent modules widi the wiring simply being plugged togetiier. The main computer could tiien be simply plugged in at an appropriate part of the system. Thus, assembly and set-up on site are gready speeded up and simplified and do not need such skilled labour. Minor imperfections of the premises, such as floor levels, in which the system is to be installed, are easily accommodated by die flexibility provided by a number of relatively small units being connected togetiier on site. In contrast, in the traditional bespoke systems long lengths of conveyor are constructed on- site and any minor undulations in the floor surface of the premises can cause difficulties in maintaining the correct alignment of the roller conveyor surface and frequentiy necessitate very time consuming packing of supports and realignment of the whole conveyor section. The module concept of die present invention gready facilitates the subsequent rearrangement of die conveyor system if requirements should change. The use of the local embedded electronic controllers also gready speeds die functioning of die apparatus. For a given type of conveying, sorting and merging operation, once each individual module has been set up widi its requirements from the main computer all control signals are generated and acted upon locally within that module so tiiat the main computer is not overloaded and slowed down by having to process many control signals. If the requirements of die conveyor system are changed, for example, by changing destinations of die load or changes in the weight requirement labelling etc., it is merely necessary for the individual embedded electronic controllers to be reprogrammed from the main computer on an individual basis. Thus, only tiiose requiring change are processed. This leads to gready increased speed of control and adaptability for d e whole apparatus. It would be appreciated tiiat many modifications may be made to die apparatus without departing from the overall concept of the invention of using a modular system in which each module has its own drive and each module or group of modules has its own localised controller which once set in accordance widi an electronic instruction does not need control signals from the main computer.

Claims: Claims 1. A conveyor system comprising a plurality of modular conveyor units, adapted to be assembled togetiier in a desired layout, and a control system for controlling the operation of die conveyor units, characterised in that die control system has a main control device (12) and control means (14-20) on at least some of die conveyor units, each control means (14-20) being adapted to control die operation of its associated conveyor unit or units in a predetermined sequence determined by die main control device (12), the sequence operating as predetermined until fresh control signals are sent from the main control device (12). 2. A conveyor system according to Claim 1, wherein at least some of the conveyor units include power means adapted to control die functioning of tiiat unit in accordance widi control signals from the respective control means. 3. A conveyor system according to Claim 1 or Claim 2, wherein the control means of each unit includes cabling such as electrical or optical cables, die cabling of adjacent conveyor units being adapted to be connected togetiier, 4. A conveyor system according to Claim 3, wherein adjacent conveyor units are connectable together by standardised plug couplings. 5. A conveyor system according to Claim 3 or Claim 4, wherein the cabling includes a power cable to power die power means. 6. A brake for use in a conveyor system according to any one of claims 1 to 5, wherein die conveyor unit comprises a plurality of rollers (22) forming a load bearing surface, which rollers (22) are driven via a belt (23) characterised in that the rollers (22) are displaceable in a plane perpendicular to die load bearing surface and in tiiat a braking plate (33) is provided, which braking plate (33) is actuatable to displace die rollers (22) such that d e belt (23) no longer imparts a driving force to the rollers (22), diereby providing a braking force. 7. A brake according to Claim 6, wherein a surface of the braking plate (23) adapted to engage die rollers (22) is provided with a friction material, so that the braking force applied to die rollers (22) is load-dependent. 8. A brake according to Claim 6 or Claim 7, wherein die braking plate (33) is actuated by means of one or more pneumatic air cylinders (34). 9. A brake according to any one of Claims 6 to 8, wherein the actuation of the brake is controllable by means of a confrol system associated with each conveyor unit of a modular conveyor system. 10. A conveyor unit for use in a conveyor system according to any one of claims 1 to 5, comprising a plurality of rollers (22) forming a load bearing surface driven by a drive belt (23), characterised in tiiat die rollers (22) are mounted in slots in a frame of die conveyor unit such tiiat die rollers are displaceable in a direction perpendicular to die load bearing surface, wherein in die driving position die rollers (22) rest on the drive belt (23), said drive belt imparting the driving force to rotate said rollers. 11. A conveyor unit according to Claim 10, wherein die slots are open at their top edge. 12. A conveyor unit according to Claim 10 or Claim 11 , wherein in the unloaded position die rollers rest on the drive belt clear of the bottom of the slot, so that die frictional driving force imparted by the belt to die rollers (22) is at least in part load dependent. 13. A conveyor unit for use in a conveyor system according to Claims 1 to 5, comprising a plurality of rollers forming a load bearing surface driven by a drive belt (39), characterised in tiiat die rollers are taper rollers (38) adapted to form a curved section of conveyor track, the belt (39) having an arcuate path, the belt (39) being supported and guided by a plurality of pressure rollers (45) such that die belt (39) remains in driving contact with die rollers (38). 14. A conveyor unit according to Claim 13, wherein the drive belt (39) has a substantially arcuate support surface, die surface of the arc being substantially radial at die outermost part of the surface and extending substantially axially at the innermost part of the arc. 15. A conveyor unit according to Claim 13 or Claim 14, wherein the belt is driven via a drive pulley 40 and is guided by two guide wheels 41 and 42 so tiiat die drive belt (39) extends over more 180° ( rad) of die circumference of the drive wheel (40).

Inventors: WARRILOW JONATHAN, WHITTLES PAUL, WARRILOW, JONATHAN, WHITTLES, PAUL
Applicants: DEXION GROUP LIMITED, WARRILOW JONATHAN, WHITTLES PAUL, WARRILOW, JONATHAN, WHITTLES, PAUL
Application year: 1998
Main classification: B65G43
IPC codes: B65G43