Conveying device for automatically discharging battery units

Abstract

The invention relates to a conveying device (10) comprising at least one conveying track (11), which extends along a conveying path (12), and at least one workpiece carrier (20), which can be frictionally driven along the conveying path (12) by drive means (15) of the conveying track (11). According to the invention, a positive and a negative workpiece carrier contact (32; 33) are arranged on the bottom side (22) of the workpiece carrier (20), battery units (40) to be discharged being connected between the positive and the negative workpiece carrier contact, wherein an associated pair (36) of a positive and a negative conveying track contact (34; 35), which pair is arranged on the conveying track (11), is connected to a discharge device (50) in order to discharge the battery units (40).

Description

[0001] Conveyor device for automatic unloading of battery units

[0002] The invention relates to a conveying device according to the preamble of claim 1.

[0003] EP 2 189 399 B1 discloses a conveyor device in the form of a roller conveyor. The conveyor track is formed by a plurality of parallel conveyor rollers, with groups of conveyor rollers being driven by an associated electric motor so that they can frictionally engage a plate-like workpiece carrier. The corresponding conveyor path comprises straight sections, each aligned perpendicular to the conveyor rollers. Two or more straight sections of the conveyor path can be connected to one another by means of lifting / transverse units, switches, or curves, so that conveyor paths of any complexity are possible. The present invention is preferably used in conjunction with such a roller conveyor, although other types of conveyor devices can also be used, for example, chain conveyors or double-belt conveyors.

[0004] A device for discharging battery units is known from the German patent application with the file number DE102022204047.3. The battery units are transported on carrier units or workpiece carriers of a conveyor system. For discharging, the battery units are connected via flexible cable connections.

[0005] GB 1 011 008 A discloses a conveying device in the form of an overhead conveyor. The conveyor track is provided with continuous contact rails, with brushes arranged on the workpiece carrier that can be brought into electrical contact with an associated contact rail. This allows workpieces on the workpiece carrier to be electrically tested during transport. An advantage of the present invention is that the workpiece carrier can be easily and quickly loaded and unloaded with battery units by the personnel operating the conveying device, with the electrical discharging process of the battery units also being able to take place automatically. With the conveying device, a large number of battery units can be electrically discharged simultaneously, making the discharging process particularly time-efficient and cost-effective.

[0006] According to claim 1, it is proposed that an upper side of the workpiece carrier, which faces away from the conveyor track, comprises a receiving means for the releasable fastening of at least one battery unit, wherein for each battery unit, a positive and a negative battery contact is arranged on the workpiece carrier in such a way that an electrical contact with the respective battery unit exists when the battery unit is fastened in the associated receiving means, wherein a cover, which is optionally present on the workpiece carrier, is closed, wherein a positive and a negative workpiece carrier contact are arranged on an underside of the workpiece carrier, which faces the conveyor track, wherein the positive workpiece carrier contact is permanently or switchably electrically connected to at least one positive battery contact, wherein the negative workpiece carrier contact is permanently or switchably electrically connected to at least one negative battery contact,wherein at least one pair of a positive and a negative conveyor track contact is arranged on the conveyor track such that, in a position of the workpiece carrier assigned to said pair, there is electrical contact between the positive workpiece carrier contact and the positive conveyor track contact, wherein there is also electrical contact between the negative workpiece carrier contact and the negative conveyor track contact, wherein said electrical contact is canceled when the workpiece carrier moves away from said position, wherein all pairs of conveyor track contacts are connected to a discharge device with which said at least one battery unit can be electrically discharged.

[0007] When closed, the lid covers the battery units, in particular the relevant battery contacts, preferably in such a way that they can no longer be touched by operating personnel. Said battery contacts can be arranged on the lid or on the remaining workpiece carrier. Said lid is preferably designed such that, when closed, it holds the battery units in the associated receiving means, with the battery contacts resting against the associated battery unit under pretension. If the conveyor device is designed as a roller conveyor, the positive and negative conveyor track contacts are arranged along the conveyor path, preferably between the conveyor rollers. Said position of the workpiece carrier can preferably be detected by means of a position sensor, which is most preferably designed as an inductive proximity switch.

[0008] Advantageous further developments and improvements of the invention are specified in the dependent claims.

[0009] It can be provided that all positive conveyor track contacts and all negative conveyor track contacts are aligned along the conveyor path, with the positive workpiece carrier contact and the negative workpiece carrier contact of a workpiece carrier being aligned along the conveyor path, with the corresponding contact spacings being selected to be large enough that, in any position of the workpiece carrier, there is no short circuit between the positive workpiece carrier contact and the negative workpiece carrier contact, which is mediated via a positive or a negative conveyor track contact. It is obvious to use two separate tracks for the positive and negative poles so that a short circuit cannot occur from the outset.However, the preferred roller conveyor requires too much space for this solution because many other components, such as separators or sensors, may be located on the underside of the workpiece carrier, each of which takes up part of the width of the workpiece carrier. With the proposed arrangement, only a small portion of the width of the workpiece carrier is required for contacting, while still reliably preventing a short circuit.

[0010] It can be provided that the receiving means of the at least one

[0011] The workpiece carrier is designed in such a way that a plurality of battery units can be accommodated, the corresponding positive and negative battery contacts being electrically connected together in such a way that, at least when the cover is closed, the electrical voltage of the series connection and / or the parallel connection of all battery units accommodated in the holding means is present between the positive and negative workpiece carrier contacts. It is conceivable that groups of parallel-connected battery units are connected in series, with all groups comprising the same number of battery units. This allows all battery units on the workpiece carrier to be discharged simultaneously using a single discharge device. Preferably, all battery units on a workpiece carrier are connected in series.

[0012] It can be provided that at least one pair of positive and negative battery contacts assigned to a battery unit is short-circuited when said battery unit is not accommodated in the receiving means. This allows the discharging process to take place even if not all positions of the receiving means are occupied by battery units. This embodiment is preferably used when all battery units on the workpiece carrier are connected in series. The short circuit is preferably implemented for all pairs of positive and negative battery contacts.

[0013] It can be provided that the positive workpiece carrier contact and / or the negative workpiece carrier contact is each designed in the form of a metal plate, wherein the metal plate is elongated along the conveyor path and is firmly connected to the workpiece carrier. In this way, a large contact area and therefore a low contact resistance can be achieved, whereby only a small part of the width of the workpiece carrier is required for contacting. The said metal plate is preferably a flat plate with a constant thickness. It is preferably made of copper. The metal plate is preferably assigned an insertion bevel for the contact element explained below, which can be arranged either on the metal plate itself or on the surrounding workpiece carrier. It can be provided that the positive conveyor track contact and / or the negative conveyor track contact each comprise a spring which is under pretension when the positive or negative contact is connected.The negative workpiece carrier contact rests on the associated positive or negative conveyor track contact, with the remaining weight of the workpiece carrier being supported by the conveyor track. This ensures low-resistance electrical contact. If the conveyor device is designed as a roller conveyor, the remaining weight of the workpiece carrier is preferably supported by the conveyor rollers.

[0014] It can be provided that the positive and / or negative conveyor track contact each comprises a contact element made of graphite, whereby the contact element can directly contact the respective associated positive or negative workpiece carrier contact. This ensures a low-resistance electrical contact.

[0015] It can be provided that switching means are provided on the conveyor track, by means of which several pairs of plus and minus conveyor track contacts can be electrically connected together in order to simultaneously discharge the battery units accommodated on the associated workpiece carriers by means of the discharge device.

[0016] It can be provided that at least one sensor is arranged on the workpiece carrier, wherein the sensor is permanently assigned to at least one battery unit, wherein the sensor can measure a voltage and / or a temperature of the respective battery unit(s). The discharge process, in particular the discharge current, is preferably controlled or regulated using the measured values ​​determined by the said sensors.

[0017] It can be provided that the workpiece carrier comprises a separate cover and a cover switching device, wherein the said switchable connection at the plus and / or minus workpiece carrier contact is closed by means of the cover switching device when the cover is closed, and is otherwise open, wherein the cover switching device can be actuated from the cover.

[0018] This protects the operating personnel from the dangers posed by the electrical voltages applied to the battery units.

[0019] The conveyor device can be designed as a roller conveyor, the conveyor path comprising at least one straight section in which a plurality of parallel conveyor rollers are distributed along the straight conveyor path, with all pairs of positive and negative conveyor track contacts being arranged in a straight section of the conveyor path. The corresponding conveyor device is particularly cost-effective. The aforementioned conveyor track contacts are preferably arranged along the straight conveyor path between two respectively assigned conveyor rollers.

[0020] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0021] The invention is explained in more detail below with reference to the accompanying drawings. They show:

[0022] Fig. 1 is a roughly schematic representation of a conveying device according to the invention with a workpiece carrier and an unloading device;

[0023] Fig. 2 is a perspective view of a conveying device according to the invention with a workpiece carrier;

[0024] Fig. 3 is a perspective view of the workpiece carrier from Fig. 2 from the underside; and Fig. 4 is a roughly schematic representation of an interconnection of several battery units on a workpiece carrier.

[0025] Fig. 1 shows a roughly schematic representation of a conveying device 10 according to the invention with a workpiece carrier 20 and an unloading device 50. The conveying device 10 is designed as a roller conveyor, with Fig. 1 showing a short section of the straight conveying path 13. There, a plurality of rotatable conveyor rollers 14 are arranged distributed along the conveying path 12, with their axes of rotation each aligned perpendicular to the conveying path 12. The conveyor rollers 14 are designed to be identical to one another in such a way that they form a common conveying plane on which the underside 22 of the workpiece carrier 20 runs. In the present case, the conveyor rollers 14 are driven by a drive means 15 in the form of an electric motor by means of a main shaft 16. This drive is preferably designed according to EP 2 163 497 B1, the entire content of which is incorporated by reference and made part of the present application.

[0026] The workpiece carrier 20 is designed in the form of a box 28 with a pivotable lid 24. The lid 24 can be designed in the form of a continuous wall. However, it can also be designed as a grid structure. In the present case, two battery units 40 are accommodated inside the box 28, with one workpiece carrier 20 preferably carrying more battery units 40. The inner bottom of the box 28 is designed as a receiving means 23 for the battery units 40. If the battery units 40 are cuboid-shaped, as shown here, a cuboid-shaped recess can be provided on the bottom for each battery unit 40, which recess is adapted to the battery unit 40 with slight play. It is understood that the battery unit 40 can have any shape commonly available on the market, with the receiving means 23 being adapted to the shape of the respective battery unit 40.

[0027] Each battery unit 40 is assigned a positive and a negative battery contact 30; 31 on the bottom of the box 28, which makes electrical contact with the battery unit 40 when it is inserted into the receiving means 23. The battery contacts 30; 31 can be formed by metal plates, in particular copper plates.

[0028] The pivotable cover 24 is designed such that, when the cover 24 is closed, the battery units 40 are pressed into the receiving means 23 by the cover 24, so that the battery units 40 bear forcefully against the associated battery contacts 30; 31. For this purpose, an elastic pressure piece 25 is provided on the cover 24 for each battery unit 40, which is slightly compressed when the cover is closed. The cover 24 preferably engages in the closed position so that the locking mechanism can absorb the resulting clamping force. The locking mechanism is preferably unlockable so that the cover 24 can be opened.

[0029] When the lid 24 is closed, the second pressure pin 42 in the box 28 is pressed downward, so that the associated electrical closer 44 is closed when the lid 24 is closed, and is open when the lid 24 is open. Furthermore, each battery unit 40 is assigned a first pressure pin 41, which is pressed downward when the battery unit 40 is inserted, so that it opens the associated electrical opener 43. The opener 43 is closed when the respective battery unit 40 is not inserted into the receiving means 23.

[0030] When battery units 40 are inserted, the electrical current can flow from the positive workpiece carrier contact 32 via the directly connected positive battery contact 30 on the left in Fig. 1, then via the respective battery unit 40, then via the associated negative battery contact 31, then to the directly connected positive battery contact 30 on the right in Fig. 1, then via the associated battery unit 40, then via the associated negative battery contact 31, then via the closed normally open contact 44, then to the negative workpiece carrier contact 33. The two battery units 40 are therefore electrically connected in series between the positive workpiece carrier contact 32 and the negative workpiece carrier contact 33, so that their electrical voltages are added together. The current path explained above is interrupted by the normally open contact 44 when the cover 24 is opened. This is intended to minimize any danger to the operating personnel of the conveyor device 10.The two battery contacts 30; 31 of a battery unit 40 are electrically short-circuited by the opener 43 when the corresponding battery unit 40 is not inserted. This allows current flow even if some positions of the workpiece carrier 40 are not occupied by battery units 40. When the battery unit 40 is inserted, the aforementioned short circuit is eliminated.

[0031] Further attention should be drawn to the sensors 63, which are accommodated in the workpiece carrier 20. In this case, the sensors 63 measure the electrical voltage of the respectively assigned battery unit 40, with the corresponding measured value being transmitted, for example, wirelessly, to a control device 55, which controls the discharging process based on the measured values. Additionally or alternatively, temperature sensors (not shown) can be provided, which measure the temperature of a respectively assigned battery unit 40, with this measured value also being transmitted, for example, wirelessly, to the control device 55. The control device 55 preferably controls the discharging process in such a way that no battery unit 40 overheats during discharging.

[0032] The underside 22 of the workpiece carrier 20 is flat so that it can rest on several conveyor rollers 14 to support the weight of the workpiece carrier 20 and so that the workpiece carrier 20 can be frictionally carried by the conveyor rollers 14. Pairs 36 of a positive and a negative conveyor contact 34; 35 are arranged on the conveyor track 11. A conveyor contact 34; 35 is preferably arranged along the conveyor path 12 between two conveyor rollers 14 so that it can touch or contact the underside 22 of the workpiece carrier 20 at the respectively assigned workpiece carrier contact 32; 33.

[0033] Contrary to the illustration in Fig. 1, preferably several pairs 36 of conveyor track contacts 34; 35 are provided, so that several workpiece carriers 20 can be connected to the unloading device 50 simultaneously. Consequently, many battery units 40 can be discharged in a short time. The corresponding interconnection is preferably switchable such that, depending on the measured values ​​of the sensors 63, different workpiece carriers 20 can be interconnected in such a way that an optimally fast unloading process results.

[0034] The workpiece carrier contacts 32; 33 are preferably each designed in the form of a metal plate, in particular a copper plate, which is fixedly, in particular immovably, arranged on the underside 22 of the workpiece carrier 20. In contrast, the conveyor track contacts 34; 35 preferably have a contact element 62 that is movable perpendicular to the conveying plane and is preferably designed as a graphite brush. This contact element is preferably pressed against the respectively assigned workpiece carrier contact 32; 33 by a preloaded spring 61, thus ensuring an optimally low contact resistance.

[0035] As explained above, the conveyor track contacts 34; 35 are connected to the discharging device 50, specifically to its DC / DC converter 51. It is conceivable for the discharging device 40 to comprise a separate DC / DC converter 51 for each workpiece carrier 20 to be discharged, with all DC / DC converters 51 being connected in parallel to the DC intermediate circuit 52. This allows the different voltages at the different workpiece carriers 20 to be discharged to be adapted to the uniform voltage of the common DC intermediate circuit 52. The discharging of the individual workpiece carrier 20 can be controlled so that it occurs at an optimal speed, while reliably preventing damage to the battery units, in particular their catching on fire.

[0036] The DC voltage of the DC intermediate circuit 52 is adapted to the AC voltage of the public AC voltage network 54 by a DC / AC converter 53. The electrical energy generated during the discharge can thus be used beneficially elsewhere and does not have to be converted into heat. Also noteworthy is the position sensor 27 on the conveyor track 11, which is preferably designed as an inductive proximity switch. A metal insert 26 is fixedly arranged on the underside 22 of the workpiece carrier 20, the presence of which can be detected by the position sensor 27. The metal insert 26 is designed to be so small and arranged that the position sensor 27 only responds when the workpiece carrier contacts 32; 33 make electrical contact with the associated pair 36 of conveyor track contacts 34; 35.

[0037] It should also be noted that the conveyor device 10 is preferably designed as a multi-branched roller conveyor, wherein the branching points are implemented, for example, with lifting / transverse units. A supply branch of the conveyor device serves to supply and / or store the workpiece carriers loaded with battery units. Workpiece carriers can be quickly removed from the system via an emergency outlet branch if problems arise during unloading. In the supply branch and the emergency outlet branch, which are, for example, directly adjacent to one another, no conveyor track contacts are provided, since no unloading is intended to take place there. Instead, the conveyor track contacts are provided in one or more parallel unloading branches, which branch off, for example, at right angles from the emergency outlet branch. Only there does the battery unit unload.

[0038] The emergency discharge branch can subsequently also be used to fill the unloading branches with workpiece carriers. To minimize disruption to its emergency function, a discharge branch is only loaded with workpiece carriers when there are enough workpiece carriers on the supply branch. These are then transported from the supply branch to the desired unloading branch as quickly as possible, for example, via the emergency discharge branch.

[0039] Fig. 2 shows a perspective view of a conveyor device 10 according to the invention with a workpiece carrier 20. The box with the lid explained above is not shown here, although it is preferably used. In this case, the workpiece carrier 20 accommodates twelve battery units 40 for unloading them together. Furthermore, Fig. 2 shows that the conveyor rollers 14 are carried by two parallel support profiles 17, each formed as an extruded aluminum profile. The straight support profiles 17 are aligned parallel to the straight conveyor path 12. In this case, only a straight section 13 of the conveyor path 12 is shown.

[0040] Fig. 3 shows a perspective view of the workpiece carrier 20 from Fig. 2 from the underside 22. The plate-like workpiece carrier known from EP 2 189 399 B1 is attached to the underside 22, but equipped with the battery contacts 32; 33. The entire content of EP 2 189 399 B1 is incorporated by reference and incorporated into the present application.

[0041] The two workpiece carrier contacts 32; 33 are aligned in the direction of the straight conveyor path 12. They are each designed in the form of a preferably cuboid-shaped metal plate, which is made in particular of copper. The aforementioned metal plate is recessed into the workpiece carrier 20 so that its flat contact surface is flush with the remaining flat surface of the workpiece carrier. In the direction of the conveyor path 12, in front of and behind the two workpiece carrier contacts 32; 33, a groove 65 is provided in the workpiece carrier 20, which runs parallel to the straight conveyor path 12. This groove is somewhat wider than the conveyor track contacts 34; 35, so that their spring (No. 61 in Fig. 1) is largely relieved in the area of ​​the groove 65. The groove 65 merges into the aforementioned metal plate via a lead-in slope 66, which is arranged on the plate-like workpiece carrier 20.The said groove is preferably not present between the two workpiece carrier contacts 32; 33, so that no springback of the conveyor track contacts 34; 35 occurs there.

[0042] Fig. 4 shows a roughly schematic representation of an interconnection of several battery units 40 on a workpiece carrier 20. The twelve battery units 40 are arranged on the workpiece carrier 20, as shown in Fig. 2, i.e. in two synchronous rows of six battery units 40 each. The electrical connecting lines 69 preferably run in a zigzag pattern over the workpiece carrier 20 in order to implement the series connection of the battery units 40 explained above. The number 67 indicates the voltage measuring points at which an electrical potential of the electrical voltage to be measured can be tapped. Preferably, all voltage measuring points 67 are connected to a multiplexer, via which two voltage measuring points directly adjacent along the current path can be connected to a single voltage measuring device.This allows for individual voltage measurement for each battery unit 40 in a simple and cost-effective manner. The voltage measuring points 67 are arranged largely in close proximity to one another, so that the corresponding cabling effort is minimal.

[0043] Furthermore, Fig. 4 shows the temperature measuring points 68 at which temperature sensors can be arranged. The temperature measuring points 68 are each arranged such that they are located in the corner area of ​​four assigned battery units 40. The temperature measurement value is essentially determined by the highest temperature of the four assigned battery units 40. This allows a small number of temperature sensors to reliably detect when an individual battery unit 40 is overheating, since in most cases, two assigned temperature sensors are triggered. This is particularly the case for the battery units 40 inside the workpiece carrier, which are critical with regard to overheating.

[0044] Reference symbol

[0045] 10 Conveyor device

[0046] 11 Conveyor track

[0047] 12 Conveyor path

[0048] 13 straight section of the conveyor path

[0049] 14 conveyor roller

[0050] 15 Propulsion means

[0051] 16 vertical shaft

[0052] 17 Support profile

[0053] 20 workpiece carriers

[0054] 21 Top

[0055] 22 Bottom

[0056] 23 recording media

[0057] 24 lids

[0058] 25 pressure piece

[0059] 26 metal insert

[0060] 27 Position sensor

[0061] 28 boxes

[0062] 30 Plus battery contact

[0063] 31 Negative battery contact

[0064] 32 Plus workpiece carrier contact

[0065] 33 Minus workpiece carrier contact

[0066] 34 Plus conveyor contact

[0067] 35 Minus conveyor contact

[0068] 36 Pair of conveyor contacts 40 Battery unit

[0069] 41 first pressure pin (on the battery unit)

[0070] 42 second pressure pin (on the lid)

[0071] 43 openers

[0072] 44 closers

[0073] 50 Discharge device

[0074] 51 DC / DC converters

[0075] 52 DC link

[0076] 53 DC / AC converters

[0077] 54 AC voltage network

[0078] 55 Control device

[0079] 60 Metal plate of a workpiece carrier contact

[0080] 61 Spring of a conveyor track contact

[0081] 62 contact element

[0082] 63 Sensor

[0083] 64 Cover - Switching device

[0084] 65 Groove on the workpiece carrier

[0085] 66 Inlet slope

[0086] 67 Voltage measuring point

[0087] 68 temperature measuring point

[0088] 69 connecting line

Claims

Claims 1. Conveying device (10) comprising at least one conveyor track (11) extending along a conveyor path (12) and at least one workpiece carrier (20) which can be driven frictionally along the conveyor path (12) by drive means (15) of the conveyor track (11), characterized in that an upper side (21) of the workpiece carrier (20), which faces away from the conveyor track (11), comprises a receiving means (23) for the releasable fastening of at least one battery unit (40), wherein for each battery unit (40) there is in each case a positive and a negative battery contact (30;31) is arranged on the workpiece carrier (20) in such a way that there is electrical contact with the relevant battery unit (40) when the battery unit (40) is fastened in the associated receiving means (23), wherein a cover (24) which is optionally present on the workpiece carrier (20) is closed, wherein a positive and a negative workpiece carrier contact (32; 33) are arranged on an underside (22) of the workpiece carrier (20), which faces the conveyor track (11), wherein the positive workpiece carrier contact (32) is permanently or switchably electrically connected to at least one positive battery contact (30), wherein the negative workpiece carrier contact (33) is permanently or switchably electrically connected to at least one negative battery contact (31), wherein at least one pair (36) of a positive and a negative conveyor track contact (34;35) is arranged such that, in a position of the workpiece carrier (40) associated with said pair (36), there is electrical contact between the positive workpiece carrier contact (32) and the positive conveyor track contact (34), wherein there is also electrical contact between the negative workpiece carrier contact (33) and the negative conveyor track contact (35), wherein said electrical contact is canceled when the workpiece carrier (20) moves away from said position, wherein all pairs (36) of conveyor track contacts are connected to a discharge device (50) with which said at least one battery unit (40) can be electrically discharged.

2. Conveyor device (10) according to claim 1, wherein all positive conveyor track contacts (34) and all negative conveyor track contacts (35) along the conveyor path (12) are arranged in alignment, wherein the positive workpiece carrier contact (32) and the negative workpiece carrier contact (33) of a workpiece carrier (20) are arranged in alignment along the conveyor path (12), wherein the corresponding contact distances are selected to be large enough that in no position of the workpiece carrier (20) is there a short circuit between the positive workpiece carrier contact (32) and the negative workpiece carrier contact (33), which is mediated via a positive or a negative conveyor track contact (35; 36).

3. Conveying device (10) according to one of the preceding claims, wherein the receiving means (23) of the at least one workpiece carrier (20) is designed such that a plurality of battery units (40) can be received, wherein the corresponding plus and minus battery contacts (30; 31) are electrically connected together such that, at least when the cover (24) is closed, the electrical voltage of the series connection and / or the parallel connection of all battery units (40) received in the receiving means (23) is present between the plus and minus workpiece carrier contacts (32; 33).

4. Conveyor device (10) according to claim 3, wherein at least one pair of a plus and a minus battery contact (30; 31) associated with a battery unit (40) is short-circuited when said battery unit (40) is not received in the receiving means (23).

5. Conveying device (10) according to one of the preceding claims, wherein the plus workpiece carrier contact (32) and / or the minus workpiece carrier contact (33) are each in the form of a metal plate (60) is formed, wherein the metal plate (60) is elongated along the conveying path (12), wherein it is firmly connected to the workpiece carrier (20).

6. Conveying device (10) according to one of the preceding claims, wherein the plus conveyor track contact (34) and / or the minus conveyor track contact (35) each comprise a spring (61) which is prestressed when the plus or minus workpiece carrier contact (32; 33) rests on the associated plus or minus conveyor track contact (34; 35), wherein a weight of the workpiece carrier (20) is otherwise supported by the conveyor track (11).

7. Conveying device (10) according to one of the preceding claims, wherein the positive and / or negative conveyor track contact (34; 35) each comprises a contact element (62) made of graphite, wherein the contact element can directly contact the respectively associated positive or negative workpiece carrier contact (32; 33).

8. Conveyor device (10) according to one of the preceding claims, wherein switching means are provided on the conveyor track (11), by means of which switching means several pairs of plus and minus conveyor track contacts (33; 34) can be electrically connected together in order to simultaneously discharge the battery units (40) accommodated on the associated workpiece carriers (20) by means of the discharge device (50).

9. Conveying device (10) according to one of the preceding claims, wherein at least one sensor (63) is arranged on the workpiece carrier (20), wherein the sensor (63) is permanently assigned to at least one battery unit (40), wherein a voltage and / or a temperature of the respective battery unit (40) or the respective battery units (40) can be measured with the sensor (63).

10. Conveying device (10) according to one of the preceding claims, wherein the workpiece carrier (20) comprises a separate cover (24) and a cover switching device (64), wherein said switchable connection at the plus and / or minus workpiece carrier contact (32; 33) is closed by means of the cover switching device (64) when the cover (24) is closed, and is otherwise open, wherein the cover switching device (64) is actuatable from the cover (24).

11. Conveyor device (10) according to one of the preceding claims, wherein the conveyor device (10) is designed as a roller conveyor, wherein the conveyor path (12) thereof comprises at least one straight section (13) in which a plurality of parallel conveyor rollers (14) are arranged distributed along the straight conveyor path (12), wherein all pairs of a plus and a minus conveyor path contact (35; 36) are arranged in a straight section of the conveyor path (13).

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