WO2000021351A2

WO2000021351A2 - A conveyor system with multiple conveyor units guided by rails

Info

Publication number: WO2000021351A2
Application number: PCT/DK1999/000526
Authority: WO
Inventors: Ralph Kofoed; Per Nielsen
Original assignee: Crisplant A/S
Priority date: 1998-10-05
Filing date: 1999-10-05
Publication date: 2000-04-13
Also published as: WO2000021351A3; AU5851199A

Abstract

A conveyor system for conveying and/or sorting items, wherein the conveyor system comprises a plurality of conveyor units (52) which are coupled together to form a chain of conveyor units. The chain of conveyor units is adapted to run along a conveyor path, and wherein at least some of the conveyor units comprise pick-up means (55) for picking up current from a power conducting rail (53) that extends along at least part of the conveyor path. Power transmitting means (57) are provided between two successive conveyor units (52). The power conducting rail (53) comprises a guiding rail (56) for guiding the pick-up means (55) into the power conducting rail (53). A holding member (58) for connecting the pick-up means (55) to the conveyor unit (52) is provided.

Description

A CONVEYOR SYSTEM

Technical field

The present invention relates to a conveyor system for conveying and/or sorting items, such as piece goods, postal items, packages etc., and comprising a power conducting rail and power pick-up means for transmitting power from the rail to power consuming parts, such as, e.g., cross belt units, provided on conveyor units or carts of the conveyor system. The invention further relates to a power supply system for a conveyor system.

Background of the invention

From the prior art, a number of systems for transmitting electrical power to conveyors are known. Such systems may comprise generator means wherein, e.g., every conveyor unit or cart of a conveyor system comprises a generator with a rotating runner engaging a stationary part of the conveyor system, e.g., a side portion of a track.

Further systems for transmitting electrical power to conveyors may comprise a power conducting rail extending along tracks of the conveyor systems, whereby the conveyor units or carts may be provided with pick-up shoes which pick up current through sliding contact with the rail. Non-contact power transmission systems wherein power is transmitted through magnetic induction are also known.

US 5,701 ,992 discloses a sorting equipment comprising a plurality of running trucks which are coupled with one another along a travelling route comprising a pair of rails. Each truck comprises a cross-belt for loading and discharging objects in a direction perpendicular to the travelling direction of the trucks. The trucks are driven by linear induction motors. A pick-up coil is mounted on each of the trucks, the pick-up coil being adapted to pick up current from a pair of induction lines producing a magnetic flux that generates an electromotive force in the pick-up coil, so as to provide power to a motor for driving the cross-belts. Accordingly, power is transmitted from the induction lines to the pick-up coil without physical contact between the pick-up coil and the induction lines. An earthling conductor interconnecting the trucks is provided. DE 41 22 425 discloses a device for supplying electrical energy to conveyor units of a conveyor, wherein the conveyor units are electrically interconnected by means of a flexible cable. In one embodiment, generators for generating power are provided on some of the conveyor units, the generators being adapted to transmit power to the flexible cable and through the flexible cable to other conveyor units. In another embodiment, power is picked up from a current rail by sliding contacts provided on some of the conveyor units, the picked-up power being transmitted to the flexible cable and therethrough to the other conveyor units.

In systems wherein power is consumed in order to activate loading or discharging of items, e.g., by means of cross-belts, activation of loading/discharging may be performed at parts of the conveyor system next to which a power conducting rail extends. Thus, power transmission from the power conducting rail to a conveyor unit may be activated when loading/discharging of an item is to be performed, and power transmission may be switched off when the action of loading/discharging is to be ended. Such activation and deactivation of power transmission may be controlled, e.g., by means of one or more relays controlled by a control system of the conveyor system.

In case the power pick-up means comprise pick-up shoes which are adapted to pick up power from the power conducting rail through sliding contacts, such pick-up shoes have to be regularly maintained in order to ensure proper electrical contact between the shoes and the rail. Normally, such maintenance comprises replacement of the pick-up shoes at regular intervals, such as, e.g., every 20-40 days.

Description of the invention

It has been realised that a problem in known power transmission systems of conveyor systems is the poor connection between the power conducting rail and the pick-up shoes of the conveyor system due to abrupt changes of potential on a current receiving part, e.g., a current pick-up shoe. It is thus an object of the present invention to provide a system which solves that problem.

An object of the present invention is to provide a conveyor system wherein electrical power may be transmitted from a power conduction rail to a plurality of conveyor units, wherein the position and/or the extend of the power conducting rail is substantially independent of the overall layout of the conveyor system. A further object of the invention is to provide a system which is flexible with respect to curves and/or level changes provided along which the conveyor may move. A further object of the invention is to provide a conveyor system wherein the position and/or the extent of the power conducting rail is not restricted to the location of loading and/or discharge stations. A further object of the invention is to provide a conveyor system, wherein the power conducting rail does not necessarily have to extent along the entire length of the conveyor path. Another object of the invention is to provide a conveyor system, wherein the wear between power pick-up means and the power conducting rail is reduced in order to reduce maintenance labour and costs. A further object of the invention is to provide a system which may be adapted to cross belt conveyors and/or sorters and which allows for improved efficiency of cross belt units comprised in such a conveyor and/or sorter. A further object of the invention is to provide a system which meets at least some the above-mentioned requirements or needs while being cheap to manufacture and install.

Thus, the present invention provides a conveyor system for conveying and/or sorting items and comprising:

a plurality of conveyor units which are coupled together to form a chain of conveyor units adapted to run along a conveyor path, at least some of the conveyor units comprising one or more power consuming parts,

at least one power conducting rail for conducting electrical current, the power conducting rail extending along at least part the conveyor path,

wherein at least a selected one of the conveyor units comprises pick-up means for picking up current from the power conducting rail.

Preferably, the selected conveyor unit is electrically coupled to at least one further conveyor unit, so as to transmit power being picked up by the pick up means of the selected conveyor unit to the at least one further conveyor unit. If the conveyor units are not electrically coupled together, each conveyor units preferably comprises a pick-up means. The conveyor system according to the invention is particularly advantageous in relation to prior art systems due to the serial interconnection of at least some of the conveyor units. The connection of the conveyor units in series of, e.g., 2 units contributes to reduced wear on the pick-up means and the power conducting rail as the accumulated distance travelled by the pick-up means along the rail is shorter, e.g., 2 times shorter than the distance travelled by the pick-up means along the rail if each conveyor unit were provided with its own pick-up means. A further advantage is that maintenance costs are reduced since less pick-up shoes have to be maintained, and since time intervals between maintenance operations may be increased. In a typical application, the distance travelled by the pick-up means is approximately 10-15% of the total length of the conveyor path. Additionally, installation and manufacturing costs of the conveyor system are reduced. In systems, wherein the power conducting rail does not extend along the entire length of the conveyor path, wear is reduced due to the reduced length of the power conducting rail.

The conveyor system may comprise driving means for driving the conveyor units along the conveyor path. Such mean may, e.g., comprise a chain drive or a linear motor drive. Alternatively, the conveyor units may be self-propelled, in which case the power needed for the conveyor units may be supplied from the power conducting rail.

The power conducting rail may be an alternating current rail or a direct current rail. When appropriate, both an alternating current rail and a direct rail may be provided. In case the pick-up means comprise one or more pick-up shoes through which current may be picked up through sliding contact with the rail, the power conducting rail may be either an alternating or a direct current rail. In case the power conducting rail induces a magnetic field around a primary part and the pick-up means comprise a secondary part which is adapted to induce a current around a coil, the power conducting rail is preferably an alternating current rail. In the configuration wherein the power conducting rail induces a magnetic field around a primary part and the pick-up means comprise a secondary part which is adapted to induce a current around a coil, power may be transmitted without any mechanical contact between the rail and the pick-up means.

If the power conducting rail is an alternating current rail, at least some of the conveyor units may comprise an AC to DC converter, so as to supply direct current to the one or more power consuming parts or to one or more accumulators optionally provided on one or more of the conveyor units. The AC to DC converter preferably converts alternating current to direct current at typically 12 V, 24 V, 48 V, or 70 V. However, the converter may be adapted to provide direct current at any other appropriate voltage. The above- mentioned levels of voltage may be applied if the power conducting rail is a direct current rail.

The power conducting rail may comprise a first and a second sub-rail with a potential difference therebetween. Thus, the first sub-rail may conduct current at a first voltage, and the second sub-rail may conduct current at a second voltage which is lower than the first voltage. The potential difference may be, e.g., 12 V, 24 V, 48 V or 70 V or any other appropriate potential difference. The pick-up means may comprise a first and a second pick-up shoe, which shoes are adapted to pick up current through sliding contact with the first and second sub-rails, respectively. Furthermore, an earthling rail or cable may be provided. Preferably, the electrical system of the conveyor system or at least parts of the electrical system is/are in correspondence with the DIN EN 60-204 norm.

A particular feature of the present invention is that the pick-up shoes may be made from pure graphite which contributes significantly to the life time of the shoes and the power conducting rail as compared to known pick-up shoes made from a composition of graphite and copper. This further implies that oxidation of the rail is avoided.

The conveyor unit or units may be adapted to utilise at least part of the power being picked up for driving the chain of conveyor units. As mentioned above, this may be the case if the conveyor units are self-propelled, or if at least one of the conveyor units is self- propelled and mechanically coupled in series to the conveyor units of the conveyor system. Another possibility is that the power which is being picked up by the pick-up means is fed to a central power supply unit adapted to supply power to, e.g., a chain drive or one or more linear motors for driving the chain of conveyor units.

The power which is picked up may be used for feeding the power consuming parts. Such power consuming parts may comprise means for receiving and/or discharging items, such as, e.g., cross belt units. A cross belt unit of a conveyor unit may comprise a belt which is adapted to move an item which is being carried by the conveyor unit in a direction which is substantially perpendicular to the travelling direction of the conveyor unit, so as to load and/or discharge the item. The belt is typically driven by an electromotor. It has been found that a conveyor system according to the invention comprising cross belt units has considerably reduced power losses and therethorugh considerably improved electromechanical efficiency as compared to systems wherein power is supplied via one or more generators having a rotating runner which runs along, e.g., the tracks of the conveyor system.

The means for receiving and/or loading items may comprise other means, such as tilting devices for tilting a surface which is adapted to carry an item or different kinds of actuators for discharging and/or receiving items. Electrical discharge actuators mounted on each or some of the conveyor units allow for minimisation of the mechanical contact between moving and stationary parts of the conveyor system, thus minimising wear, tear and noise generation originating from mechanical contact between moving and stationary parts. Moreover, electrical discharge actuators allow for a dynamic control of the discharge operation of an item, the discharge operation being, e.g., dependent of the position of an item on the conveyor unit, the weight of the item and/or other parameters. The power consuming parts may comprise other means, such as loaders or dispensers, electronic control means for controlling, e.g., discharging and loading of items, light emitters for use, e.g., in a photoelectric system for identifying a conveyor unit. For example, in a PLC-controlled conveyor/sorter system, scanners, photo eyes or other equipment can be mounted on the conveyor units. The power consuming parts may comprise processor means which may constitute part of the control system of the conveyor system. Other examples of power consuming parts are elevator means for moving an items in an upward and a downward direction, so as to allow the conveyor units to cooperate with other means such as other conveyors, discharge or loading stations etc., which is in particularly useful in case each conveyor unit carries more than one item. The power consuming parts may further comprise means for moving one or more receptacles provided in or on the conveyor units in relation to each other. Telescopic receptacles can be provided, so as to allow for variable geometry and size of the receptacles. Devices for moving an item in relation to the receptacle of a conveyor unit may be provided in order to adjust the position of the item while being conveyed by the conveyor unit. Means for keeping the receptacle(s) of a conveyor unit in a horizontal position in level changes may be provided or for tilting the receptacle(s) in curves, so as to compensate for centrifugal forces. In order to establish a mechanical coupling between the receptacles of two consecutive conveyor units, e.g., for safer transport of items occupying two receptacles, electrically coupling means may be provided. Flexible operation of one or more of a number of power consuming parts comprised in the conveyor units, cf. the above description, relies on the provision of power on board each or some of the conveyor units of the conveyor system. Thus, at least some of the conveyor units may each comprise one or more accumulators for accumulating power. The accumulators may be batteries, capacitors, hydraulic and/or mechanical power storage means. In the case of hydraulic and/or mechanical storage means being provided, power conversion means may be applied for converting electrical power to mechanical power.

Such accumulators provide the particular advantage that power may be picked at one location along the conveyor path and consumed at another location along the conveyor path. Thus, the power conducting rail may be located at any location along the conveyor path. This is beneficial because the power is often needed by the power consuming parts at loading or discharge stations arranged along the conveyor path, at which stations mounting of the power conducting rail can be troublesome because the space available next to the conveyor path is occupied by item induction and/or discharge installations, chutes and/or other equipment.

In addition to providing accumulators on the conveyor units or as an alternative to accumulators, the conveyor units may be electrically interconnected in such a way that power may be picked up at one location along the conveyor path and substantially immediately transmitted to another location where the power is needed. Whereas the accumulators comprised in the conveyor units may convey accumulated power along the conveyor path at the travelling speed of the conveyor units, an electrical interconnection between the conveyor units allows power to be conveyed from one location to another without any measurable delay. By ensuring that power is always being picked up at at least one location along the conveyor path and providing an electrical interconnection between the conveyor units, power may be supplied to any power consuming part at any location along the conveyor path.

The selected conveyor unit which comprises the pick-up means may be electrically coupled in series to a number of further conveyor units. The number of conveyor units being coupled together in series may be at least 2, such as at least 3, at least 4, preferably at least 5, such as at least 6 or 7, such as at least 8, or 9 or more, such as 10- 30, such as 11 , 12, 13, 14, 15, 16, 18, 20, 22, 24, 26, 28 or more, such as 31-50, 51-100, 100-200, 200-400, 401-500, 501-1000, 1000-2000, such as 2000-5000 or even more. For some applications, the selected conveyor unit and a number of further conveyor units may electrically be coupled together in series, so that all the conveyor units of a conveyor system are coupled together. The total number of conveyor units in the conveyor system may be between 50 and 5000.

All the conveyor units of the conveyor system may be electrically coupled together, so as to form a closed loop. Alternatively, the conveyor units may be electrically coupled together in sections, wherein each section comprises a plurality of conveyor units, and wherein no electrical coupling is provided between conveyor units of different sections. In the latter case, improved securing of the conveyor units and their electrical parts is provided in the case of an electrical shortcut occurring in the system. For example, in a conveyor system comprising 600 conveyor units, 4 sections of 150 conveyor units may be provided.

In preferred embodiments of the invention, only the selected conveyor unit comprises pick-up means, whereas each of the conveyor units comprises an accumulator. In relation to systems wherein each one of the conveyor units comprises pick-up means, the conveyor system according to the invention has the particular advantage that only a fraction of the number of conveyor units have to be provided with pick-up means.

A plurality of power conducting rails may be arranged along the conveyor path. Each power conducting rail preferably extends along a part of the conveyor path only, and preferably the total length of all power conducting rails provided in the conveyor system is less than the length of the conveyor system. Thereby, in case the pick-up means comprise pick-up shoes for picking up power through sliding contact with the rail, wear on the pick-up means and the rail may be reduced in comparison to systems wherein the rail extends along the entire length of the conveyor path. Thus, the ratio between the total length of all power conducting rails and the total length of the conveyor path is preferably less than 1 and in most cases greater than 0.001 , such as less than 0.8, such as less than 0.6 or less than 0.5, such as less than 0.4, usually less than 0,3, such as less than 0.25 or less than 0.2, such as less than 0J8, less than 0J5 or less than 0J3, such as less than 0.12, less than 0.11 or less than 0J , such as less than 0.08 or less than 0.05, such as less than 0.01 or even lower. In case each power conducting rail comprises one or more sub-rails, the total length of all power conducting rails is not the total length of all sub-rails but the mere length of the power conducting rail itself.

In case the pick-up means comprise one or more pick-up shoes through which current may be picked up through sliding contact with the rail, the relatively short length of the rail in comparison to the total length of the conveyor path reduces the need for maintenance considerably. The total distance travelled by a conveyor unit during operation is typically 7 km per hour, i.e. 168 km per day in the case of 24 hour operation. The total life time of a pick-up shoe is typically equivalent to an accumulated travelling distance in sliding contact with the rail of 3000 - 20000 km, i.e. in systems wherein the power conducting rail extends along the entire length of the conveying path, the total life time is approximately between 18 and 120 days. Therefore, it is a particular advantage that the total length of the power conducting rail or rails is shorter than the length of the conveyor path. In a typical application, the total length of the rail is approximately 10-15% of the total length of the conveyor path and 1 out of 10 conveyor units is a selected conveyor units being provided with pick-up shoes. Thus, maintenance intervals may be approximately 1/0J5 - 1/0J , i.e., 6.7 - 10 times longer than if the rail would extend over the entire length of the conveyor path. As only 1 out of 10 conveyor units is provided with a pick-up shoe, the costs of replacing pick-up shoes or parts thereof are reduced by a factor between 10 x 6.7 and 10 x 10, i.e., a factor between 67 and 100. If fewer conveyor units are provided with pick-up shoes, then maintenance costs are even lower.

Maintenance costs may alternatively and/or additionally be reduced by operating the conveyor system in such a way that a plasma of ionized air exists between the pick-up shoe and the power conducting rail. Thereby wear on the pick-up shoes and the rail is considerably reduced. This may be obtained by operating the conveyor system, such that the magnitude of the current conducted by the power conducting rail is between 0.5 and 5 A during idle run, such as between 1 and 2 A, and between 10 A and 200 A during power loaded operation, such as between 20 and 150 A, such as 30, 50, 70, 90, 110, 130 A, while keeping the voltage constant at, e.g., 48 V or 70 V.

Preferably, the length of each power conducting rail is greater than the distance between two consecutive pick-up means of two conveyor units, so that at least one power pick-up means always engages the power conducting rail during operation of the conveyor system. This prevents sparks from being generated when a pick-up shoe is brought into contact with the rail because no abrupt potential change on a current receiving part, e.g., a current pick-up shoe, occurs.

In case the pick-up means comprise pick-up shoes, a guiding mechanism for guiding each of the pick-up shoes into engagement with the power conducting rails is preferably provided at the upstream end of each power conducting rail. Each pick-up shoe or a group of pick-up shoes is preferably biased towards a power conducting rail when engaging the rail. Each pick-up shoe or a group of pick-up shoes may be mounted on an arm extending from the conveyor unit. The arm may be pivotally connected to the conveyor unit and spring-biased, so as to bias the pick-up shoe or shoes towards the power conducting rail.

Diagnose means for surveying functioning of the pick-up means may be provided. The diagnose means may comprise a power receiving rail adapted to receive power from the at least one pick-up shoe, and a power measuring device adapted to determine whether power is being transmitted from the pick-up shoe to the power receiving rail. Furthermore, a control means for generating a control signal if no power being transmitted from the pick-up shoe to the power receiving rail is preferably provided. The power receiving rail is preferably positioned immediately upstream of the power conducting rail and is preferably electrically disconnected therefrom. When the pick-up shoes are moved along power receiving rail, it is determined whether power is transmitted from the pick-up shoe to the power receiving rail. Preferably, this is done by measuring the voltage over the power receiving rail. In case it is determined that the pick-up shoes do not function properly, i.e. in case a proper amount of power is not being transmitted to the power receiving rail, or that for other reasons no power is transmitted to the power receiving rail, discharge actions which are already initiated but not terminated may be completed by utilising/consuming power being picked-up by another pick-up shoe than the defect one.

A guiding rail for guiding the pick-up shoes into and/or out of engagement with the power conducting rail may be provided at an inlet and/or an outlet, respectively, of each power conducting rail. The guiding rail may have a curved shape, so that the path travelled by the pick-up shoes is substantially continuous.

Impurity-removing means for disposing/removing impurities from the pick-up shoes may be provided, e.g., at the inlet of the power conducting rail or at the inlet of the guiding rail. Thus, means for brushing or sweeping impurities away from the pick-up shoes may be provided.

The invention further relates to a power supply system for supplying power to a conveyor system, the conveyor system comprising a plurality of conveyor units which are coupled together to form a chain of conveyor units adapted to run along a conveyor path, at least some of the conveyor units comprising one or more power consuming parts, the power supply system comprising:

- at least one power conducting rail for conducting electrical current and being adapted to extend along at least part of the conveyor path,

pick-up means adapted to be mounted on at least a selected one of the conveyor units and being adapted to pick-up current from the power conducting rail.

Coupling means for electrically coupling the selected conveyor unit to at least one further conveyor unit may be provided, so as to allow power being picked up by the pick-up means to be transmitted from the selected conveyor unit to the at least one further conveyor unit.

The power supply system according to the invention may be easily installed in an existing conveyor system, whereby that existing conveyor system is given the advantages outlined above in connection with the conveyor system according to the invention.

The features and characteristics of the power conducting rail and the pick-up means described above in connection with the conveyor system according to the invention also apply to the power conducting rail and the pick-up means comprised in the power supply system. The power supply system may comprise one or more AC to DC converters to be mounted on one or more of the conveyor units. One or more accumulators for mounting on one or more of the conveyor units may be comprised in the power supply system.

The invention further relates to a method for conveying and/or sorting items in a conveyor system, the conveyor system comprising: a plurality of conveyor units which are coupled together to form a chain of conveyor units adapted to run along a conveyor path, at least some of the conveyor units comprising one or more power consuming parts,

- at least one power conducting rail for conducting electrical current, the power conducting rail extending along at least part of the conveyor path,

at least a selected one of the conveyor units comprising pick-up means for picking up current from the power conducting rail,.

the method comprising:

moving the pick-up means into electrical and/or magnetic contact with the power conducting rail at an inlet thereof,

moving the pick-up means along the power rail, so as to collect power from the power conducting rail,

moving the pick-up means out of contact with the power conducting rail at an outlet end thereof.

The method may further comprise:

determining whether power is being transmitted from the pick-up means to a power receiving rail provided at an upstream end of the power conducting rail,

generating, in a control system of the conveyor system, a control signal if no power is being transmitted from the pick-up shoe to the power receiving rail.

The method may further comprise any steps carried out or made possible by any of the features defined above in connection with the conveyor system and the power supply system according to the invention. Brief description of the drawings

A preferred embodiment of the invention will now be described with reference to the appended drawings, in which:

Fig. 1 is a perspective illustration of a conveyor system according to the invention,

Fig. 2 is a perspective illustration of a detail of a conveyor system according to the invention,

Fig. 3 is a perspective illustration of a guiding rail for guiding current pick-up shoe assemblies into engagement with a power conducting rail,

Fig. 4 is a top view of the guiding rail of Fig. 3,

Fig. 5 is a perspective view of the current pick-up shoe assemblies shown in Figs. 3 and 4.

Detailed description of the drawings

Fig. 1 shows an overall illustration of a conveyor system 51 having a closed loop conveyor path and comprising a plurality of conveyor units 52, the conveyor units 52 being provided with cross belt units. A power conducting rail 53 extends along part of the length of the conveyor path. Each one of a number of selected conveyor units 54 is provided with a pick-up shoe assembly 55 for engaging into sliding contact with the rail 53. At the upstream and downstream end of the rail 53 there is provided a guiding rail 56 for guiding the pick-up shoe assemblies 55 into sliding contact with the rail 53. Power transmitting means in the form of electrical conductors/cables 57 are provided between two successive conveyor units 52.

As shown in Fig. 2 which shows a detail of Fig. 1 , each pick-up shoe assembly is rigidly connected to the remaining parts of the conveyor unit by a holding member 58. Figs. 3 and 4 show the guiding rail 56, the pick-up shoe assembly 55 and the rail 53. The rail 53 is divided into a first and a second sub-rail 53a and 53b, respectively, over which a potential difference exists. The guiding rail 56 is divided into a first and second guiding sub-rail 56a and 56b. No current is conducted by the guiding rail or by its sub-rails. First pick-up shoes 59a are adapted to be brought into sliding contact with the first sub-rail 53a, whereas second pick-up shoes 59b are adapted to be brought into sliding contact with the second sub-rail 53b. The first and second pick-up shoes 59a and 59b, respectively, are mounted on shoe holding members 60 which are connected to arms 61 , the shoe holding members 60 being pivotally mounted around a common pivot 62. The arms 61 are mounted on the holding member 58.

Fig. 5 shows that each of the first and second pick-up shoes 59a and 59b, respectively, comprises a conducting part 63 which is adapted to be brought into sliding contact with one of the sub-rails 53a, 53b of the rail 53. Each conducting part 63 is mounted on a holding part 64 which is connected to or integrated in a pick-up shoe. Current is lead to one or more power consuming parts or accumulators through electrical conductors (not shown).

Claims

1. A conveyor system for conveying and/or sorting items and comprising:

- a plurality of conveyor units which are coupled together to form a chain of conveyor units adapted to run along a conveyor path, at least some of the conveyor units comprising one or more power consuming parts,

at least one power conducting rail for conducting electrical current, the power conducting rail extending along at least part of the conveyor path,

2. A conveyor system according to claim 1 , wherein said selected conveyor unit is electrically coupled to at least one further conveyor unit, so as to transmit power being picked up by the pick up means of the selected conveyor unit to the at least one further conveyor unit.

3. A conveyor system according to claim 1 , wherein the power conducting rail is an alternating current rail.

4. A conveyor system according to claim 3, wherein the pick-up means comprise at least one pick-up shoe which is adapted to pick up current through sliding contact with the power conducting rail.

5. A conveyor system according to claim 3, wherein the power conducting rail is adapted to induce a magnetic field around a primary part, and wherein the pick-up means comprise a secondary part which is adapted to induce current in a coil, whereby power can be transmitted from the power conducting rail to the pick-up means without any contact therebetween.

6. A conveyor system according to any of claims 3-5, wherein at least some of the conveyor units comprise an AC to DC converter, so as to supply direct current to the one or more power consuming parts.

7. A conveyor system according to claim 1 , wherein the power conducting rail is an alternating or a direct current rail comprising a first and a second sub-rail, the first sub-rail conducting current at a relatively high voltage, the second sub-rail conducting current at a relatively low voltage, the pick-up means comprising at least a first and a second pick-up shoe which shoes are adapted to pick up current through sliding contact with the first and second sub-rails, respectively.

8. A conveyor system according to claim 7, wherein the power conducting rail comprises more than two sub-rails, each of which conducts current at different voltages.

9. A conveyor system according to claim 7 or 8, wherein the length of each power conducting rail is greater than the distance between two consecutive pick-up means of two conveyor units, so that at least one power pick-up means always engages the power conducting rail during operation of the conveyor system.

10. A conveyor system according to any of claims 4-9 and being adapted to be operated in such a way that a plasma of ionized air exists between the pick-up shoe and the power conducting rail.

11. A conveyor system according to any of the preceding claims, wherein the conveyor unit or units is/are adapted to utilise at least part of the power being picked up for driving the chain of conveyor units.

12. A conveyor system according to any of the preceding claims, wherein the conveyor unit or units is/are adapted to utilise at least part of the power being picked up for feeding the power consuming parts.

13. A conveyor system according to any of the preceding claims, wherein the power consuming parts comprise means for receiving and/or loading items.

14. A conveyor system according to any of the preceding claims, wherein the means for receiving and/or loading items comprise a cross-belt unit comprising a cross-belt and an electromotor for driving the cross-belt.

15. A conveyor system according to any of claims 1-13, wherein the means for receiving and/or loading items comprise a tilt-tray unit comprising a tray and an electrical actuator for tilting the tray.

5 16. A conveyor system according to any of the preceding claims, wherein at least some of the conveyor units each comprise one or more accumulators for accumulating power.

17. A conveyor system according to any of the preceding claims, wherein the selected conveyor unit and a number of further conveyor units are electrically coupled together in

10 series, the number of conveyor units being coupled together in series being at least 2, such as at least 3, at least 4, preferably at least 5, such as at least 6 or 7, such as at least 8, or 9 or more, such as 10-30, such as 11 , 12, 13, 14, 15, 16, 18, 20, 22, 24, 26, 28 or more, such as 31-50, 51-100, 100-200, 200-400, 401-500, 501-1000, 1000-2000, such as 2000-5000 or even more.

15

18. A conveyor system according to any of the preceding claims, wherein the selected conveyor unit and a number of further conveyor units are electrically coupled together in series, so that all the conveyor units of a conveyor system are coupled together.

20 19. A conveyor system according to any of the preceding claims, wherein the total number of conveyor units in the conveyor system is in the between 50 and 5000.

20. A conveyor system according to any of the preceding claims and comprising a plurality of selected conveyor units, each comprising pick-up means.

25

21. A conveyor system according to any of claims 17-20, wherein one conveyor unit in a series of conveyor units is provided with pick-up means.

22. A conveyor system according to any of the preceding claims, wherein each of the one 30 or more power conducting rails extends along a part of the conveyor path only.

23. A conveyor system according to claim 22 and comprising a plurality of power conducting rails.

24. A conveyor system according to claim 22 or 23, wherein the length of each power conducting rail is greater than the distance between two consecutive pick-up means of two conveyor units, so that at least one power pick-up means always engages the power conducting rail during operation of the conveyor system.

25. A conveyor system according to any of claims 22-24, wherein the ratio between the total length of all power conducting rails and the total length of the conveyor path is less than or equal to 1 and greater than 0.001 , such as less than 0.8, such as less than 0.6 or less than 0.5, such as less than 0.4, usually less than 0,3, such as less than 0.25 or less than 0.2, such as less than 0J8, less than 0J5 or less than 0J3, such as less than 0J2, less than 0.11 or less than 0.1 , such as less than 0.08 or less than 0.05, such as less than 0.01 or even lower.

26. A conveyor system according to any of claims 4-25, wherein a guiding mechanism for guiding each of the pick-up shoes into engagement with the power conducting rail is provided at the upstream end of each power conducting rail.

27. A conveyor system according to claim 26, wherein each pick-up shoe or a group of pick-up shoes is biased towards a power conducting rail when engaging the rail.

28. A conveyor system according to claim 27, wherein each pick-up shoe or a group of pick-up shoes is pivotally mounted on an arm extending from the conveyor unit, the arm being pivotally connected to the conveyor unit and being spring-biased, so as to bias the pick-up shoe or shoes towards the power conducting rail.

29. A conveyor system according to any of the preceding claims, further comprising diagnose means for surveying functioning of the pick-up means.

30. A conveyor system according to claims 4 and 29, wherein the diagnose means comprise:

a power receiving rail adapted to receive power from the at least one pick-up shoe, a power measuring device adapted to determine whether power is being transmitted from the pick-up shoe to the power receiving rail, a control means for generating a control signal if no power being transmitted from the pick-up shoe to the power receiving rail.

31. A conveyor system according to any of claims 4-30, wherein a guiding rail for guiding 5 the pick-up shoes into and/or out of engagement with the power conducting rail is provided at an inlet and/or an outlet, respectively, of each power conducting rail.

32. A conveyor system according to claim 31 , wherein the guiding rail has a curved shape, so that the path travelled by the. pick-up shoes is substantially continuous.

10

33. A conveyor system according to claim 31 or 32, wherein impurity-removing means for the pick-up shoes are provided at the inlet of the guiding rail, so as to dispose impurities from the pick-up shoes.

15 34. A conveyor system according to claim 33, wherein the impurity-removing means comprise means for brushing or sweeping impurities away from the pick-up shoes.

35. A power supply system for supplying power to a conveyor system, the conveyor system comprising a plurality of conveyor units which are coupled together to form a chain 20 of conveyor units adapted to run along a conveyor path, at least some of the conveyor units comprising one or more power consuming parts, the power supply system comprising:

at least one power conducting rail for conducting electrical current and being 25 adapted to extend along at least part of the conveyor path,

30 36. A power supply system according to claim 35 further comprising coupling means for electrically coupling the selected conveyor unit to at least one further conveyor unit, so as to allow power being picked up by the pick-up means to be transmitted from the selected conveyor unit to the at least one further conveyor unit.

37. A method for conveying and/or sorting items in a conveyor system, the conveyor system comprising:

10 at least a selected one of the conveyor units comprising pick-up means for picking up current from the power conducting rail,

said method comprising: 15 moving the pick-up means into electrical and/or magnetic contact with the power conducting rail at an inlet thereof,

moving the pick-up means along the power rail, so as to collect power from the 20 power conducting rail,

25 38. A method according to claim 37 further comprising:

30 - generating, in a control system of the conveyor system, a control signal if no power is being transmitted from the pick-up shoe to the power receiving rail.