Drive device and method for transporting at least one wagon along a conveyor track

Abstract

Drive device for conveying at least one carriage along a conveyor track, comprising at least one carriage movable along a linearly extending conveyor track, characterized by at least two conveying elements extending parallel to each other along the conveyor track and capable of being driven to relative displacements in opposite directions along the conveyor track, each conveying element comprising a number of coupling elements for coupling to the carriage, arranged at intervals from each other along the respective conveying element, whereby the carriage can be selectively coupled to a first or a second of the two conveying elements.

Description

[0001] The present invention relates to a drive device for conveying at least one carriage along a conveyor track, according to the preamble of claim 1, and to a method for operating such a drive device.

[0002] Drive devices of this type are used, for example, in industrial production to move large machines or machine parts from one production or processing station to the next. The parts to be moved are arranged on trolleys, which are usually moved on floor rails along a conveyor track. Such trolleys are also known as floor conveyors. They are low-profile and have a platform on top to support the load.

[0003] The cars do not have their own drives, but are moved by drive systems that are embedded, for example, between the rails in the hall floor.

[0004] Carriage transport should be carried out as uninterruptedly as possible. One problem is how to transport the car continuously over long distances using a stationary drive. Usually, recoupling from one drive unit to another is necessary. An example of such an arrangement is shown in DE 10 2016 125 132 A1. The drive device disclosed therein comprises drive units that are offset from one another in the conveying direction and overlap one another, so that recoupling from one drive unit to another is possible in the overlapping sections of the conveying path. This coupling change can be performed as a continuous transfer from one drive unit to the next while the car is traveling.

[0005] The drive device presented here has the disadvantage of being comparatively complex in design due to the sheer number of overlapping conveyor sections with individual coupling elements. Therefore, there is a need for a simplified drive device that enables uninterrupted recoupling and thus continuous carriage travel, yet features a simplified design. Furthermore, the individual conveyor sections dictate a drive timing that is fixed by design and cannot be individually adapted to the prevailing conditions.

[0006] DE 10 2016 125 835 A1 discloses a drive device for conveying at least one carriage along a conveyor track, comprising a drive unit for conveying the carriage along a conveyor path. This drive unit comprises at least one coupling element for releasably coupling to the carriage, which coupling element is movable along the conveyor path of the drive unit. The drive unit comprises at least one carriage movable along the conveyor path and an arm attached thereto, which projects from the carriage in or against the conveying direction and to which the coupling element is attached.

[0007] DE 10 2016 125 832 A1 describes a drive device for transporting carriages along a conveyor track, comprising a plurality of operating units for transporting a carriage along a conveyor line. The drive units each comprise at least one coupling element for releasably coupling to a coupling position of the carriage, which coupling element is movable along the conveyor line of the respective drive unit. The conveyor lines of the drive units are offset from one another laterally and in the conveying direction and overlap one another. When traveling over the overlapping sections of the conveyor lines, their coupling elements can be selectively coupled to coupling positions arranged accordingly on the carriage.

[0008] DE 10 2011 007 233 A1 comprises a transport device for a section-by-section transport of molds of a confectionery production plant along a transport path, comprising a driven driver for each of the transport sections of the transport path.

[0009] It is therefore an object of the present invention to provide a drive device for conveying at least one carriage along a conveyor track, which enables continuous carriage transport over a longer distance with individual adjustment of the conveying cycle, but is constructed in a comparatively simple and cost-effective manner.

[0010] This object is achieved according to the invention by the drive device having the features of claim 1 and by a method for operating this drive device having the features of claim 17. Preferred embodiments of this device and this method are specified in the subclaims.

[0011] The drive device according to the invention comprises at least a first and a second conveyor element, which extend parallel to one another along the conveyor track and can be driven for relative displacement in opposite directions along the conveyor track. Each of these conveyor elements comprises a number of coupling members for coupling to the carriage, which are arranged at intervals along the respective conveyor element. This allows the carriage to be selectively coupled to the first or second conveyor element.

[0012] The parallel conveyor elements are movable in opposite directions such that one of the conveyor elements, which is coupled to the carriage, can move a predetermined distance in the conveying direction, thereby carrying the carriage, while the second conveyor element is moved in the opposite direction. Eventually, the carriage reaches a position where a coupling change can take place, in which the second conveyor element takes over conveying the carriage. This is then moved in the conveying direction together with the carriage, while the first conveyor element, now no longer coupled to the carriage, is pushed in a feed direction opposite the conveying direction. This movement pattern can be repeated continuously.

[0013] The carriage is thus moved alternately by the two conveyor elements and can be coupled alternately to the coupling elements of the two conveyor elements. It is important to note that changing the coupling does not necessarily require an interruption of carriage transport; rather, the carriage can be transferred seamlessly from one conveyor element to the other during travel by synchronizing the drive(s).

[0014] One advantage of the drive device according to the invention is that, under certain circumstances, it is sufficient to use only two conveyor elements, each equipped with its own drive. Under certain circumstances, it is also possible to drive both conveyor elements with a common drive. Within the scope of the invention, it is also possible to provide more than two conveyor elements.

[0015] According to a preferred embodiment of the present invention, the conveyor elements can be driven to move in opposite directions for cyclically conveying the carriage, wherein in a first movement cycle the first conveyor element is coupled to the carriage and driven to move in the conveying direction, while the second conveyor element is detached from the carriage and driven to move in an opposite feed direction, and in a subsequent second movement cycle the second conveyor element is coupled to the carriage and driven to move in the conveying direction and the first conveyor element is detached from the carriage and driven to move in the feed direction. The conveying distances covered by the carriage during the first and / or second movement cycle (conveying cycle) can be adjusted by appropriately controlling the drive(s) of the conveyor elements.This allows for more individual and flexible timing than is the case with the current state of the art.

[0016] The coupling elements are preferably designed as drivers, which are intended to engage a corresponding coupling element of the carriage during a conveying movement of the conveying element to which the respective driver is attached, in the conveying direction. These drivers can operate without their own motor drive. In a simple embodiment, these can be cams that protrude from the conveying elements and engage a corresponding engagement position of the carriage.

[0017] Further preferably, the drivers are designed to be able to slide over the corresponding coupling element of the carriage without engaging it during a feed movement of the respective conveyor element relative to the carriage that is opposite to the conveying movement of the carriage. Thus, the driver of a conveyor element can pass the coupling element with virtually no resistance, contrary to the conveying direction.

[0018] According to a further preferred embodiment, the drivers are designed such that they can yield during sliding over a coupling element and evade the coupling element. For example, it is conceivable that a driver configured as a cam is spring-loaded upwards and slides downwards against the spring tension during the sliding movement over the coupling element, thus offering no resistance.

[0019] According to a further preferred embodiment, the coupling element(s) are designed to yield while a carrier slides over the coupling element and to be able to avoid the carrier. In this case, the coupling elements of the carriage can yield while the carriers remain stationary.

[0020] Preferably, the conveying elements comprise pull rods or push rods.

[0021] According to a further preferred embodiment, the drive device according to the invention comprises at least one drive for the conveying elements, which comprises at least one spindle drive and at least one motor. The torque generated by the motor is then converted into a linear movement of the conveying elements via the spindle drive.

[0022] Further preferably, an individual drive is provided for each conveyor element, comprising a spindle drive and a motor for moving the spindle drive. Each of the motors thus drives a conveyor element. The use of servo motors, for example, is conceivable here. Furthermore, it is possible to control the existing drive motors, and thus the movements of the conveyor elements, via a common control system.

[0023] According to a preferred embodiment of the present invention, the coupling members of each conveyor element are arranged at equal spacing intervals thereon.

[0024] Furthermore, the spacing intervals of the coupling elements on both conveying elements are preferably the same.

[0025] According to a further preferred embodiment, the carriage runs on rails, and at least the conveying elements are arranged between the rails.

[0026] Preferably, in this case, the rails are floor rails, and the conveyor elements are embedded in the floor between the rails and extend under the carriage.

[0027] According to a further preferred embodiment, the drive device according to the invention comprises a brake for holding the carriage in its position along the conveyor track in the non-driven state. This can be one or more friction brakes that resiliently press toward a guide rail of the carriage.

[0028] Preferably, the brake is designed to continuously exert a braking effect during the carriage's movement along the conveyor track. The aforementioned friction brake can thus be in continuous contact with the guide rail. The braking effect is sufficient to hold the carriage in its position, but does not impede its conveying movement.

[0029] According to a further embodiment, the brake is designed to exert a braking effect only at predetermined points along the conveyor track. In this case, it does not engage continuously, but rather, for example, runs up to predetermined braking points on or next to the rail, while otherwise having no contact with the rail.

[0030] The present invention further relates to a method for operating a drive device of the type according to the invention, in which the conveyor elements are driven to move in opposite directions for cyclically conveying the carriage, wherein in a first movement cycle the first conveyor element is coupled to the carriage and driven to move in the conveying direction, while the second conveyor element is detached from the carriage and driven to move in an opposite feed direction, and in a subsequent second movement cycle the second conveyor element is coupled to the carriage and driven to move in the conveying direction and the first conveyor element is detached from the carriage and driven to move in the feed direction.

[0031] In each of the movement cycles, the carriage is conveyed by one of the conveying elements, while the other conveying element is moved in the opposite direction to the conveying direction, while in a subsequent movement cycle the other conveying element conveys the carriage.

[0032] In the following, a preferred embodiment of the present invention is explained in more detail with reference to the accompanying drawings. Fig. 1A, Fig. 1B and Fig. 1C show an embodiment of the drive device according to the invention for transporting at least one carriage along a conveyor track, Fig. 2A and Fig. 2B show detailed views of a second embodiment of this drive device, Fig. 3A and Fig. 3B show detailed views of a third embodiment of this drive device, and Fig. 4A and Fig. 4B show detailed views of a fourth embodiment of this drive device.

[0033] According to the Fig. 1A, Fig. 1B and Fig. 1C, the drive device 10 according to the invention comprises two parallel rails 12a, 12b on which a carriage 14 can be moved. For this purpose, the carriage is equipped with four wheel sets 16a, 16b, 16c, and 16d, which are arranged in pairs on the rails, so that two wheel sets 16a and 16b run on the rail 12a arranged at the top in the figures, and the two remaining wheel sets 16c and 16d run on the lower rail 12b.

[0034] The rails 12a, 12b extend linearly and together form a conveyor track along which the carriage 14 is movable. In the movement sequence described below, the carriage 14 moves along the rails 12a, 12b from the right side of the drawing to the left. This direction is referred to here as conveying direction A.

[0035] The rails 12a, 12b are floor rails embedded in the subsurface, for example, the floor of a production hall. Carriage 14 is a floor conveyor for transporting workpieces.

[0036] In the present embodiment, the carriage is driven by two conveyor elements 18a, 18b, which extend parallel to each other centrally between the rails 12a, 12b along the conveyor track. The conveyor elements 18a, 18b are embedded in the floor between the rails 12a, 12b and extend beneath the carriage 14. Both conveyor elements 18a, 18b are of the same length.

[0037] In this case, the conveyor elements 18a, 18b are pull rods. They can be moved relative to each other in opposite directions along the conveyor track. They are essentially identical in design and each have a number of coupling elements for coupling to the carriage 14, which are arranged at intervals along the respective conveyor element 18a, 18b.

[0038] The upper conveyor element 18a in the drawings will hereinafter be referred to as the first conveyor element. Eight coupling elements 18a.1, 18a.2, 18a.3, 18a.4, 18a.5, 18a.6, 18a.7, and 18a.8 (hereinafter: first coupling elements 18a.1 to 18a.8) are arranged at equal spacing intervals along the first conveyor element 18a, in the order mentioned, starting from the free (right-hand end in the figures) end 20 of the first conveyor element 18a in the direction of a drive of the first conveyor element 18a, which will be described in more detail below. Similarly, the second conveying element 18b comprises eight coupling members 18b.1, 18b.2, 18b.3, 18b.4, 18b.5, 18b.6, 18b.7 and 18b.8 (hereinafter: second coupling members 18b.1 to 18b.8), which are arranged in this order from the free end 22 of the conveying element in the direction of its drive at equal spacing intervals.

[0039] The spacing intervals between the coupling elements 18b.1 to 18b.8 are the same as the spacing intervals between the coupling elements 18a.1 to 18a.8 of the first conveying element 18a.

[0040] A coupling device 24 is provided on the carriage 14, which is designed to interact with the first coupling members 18a.1 to 18a.8 and the second coupling members 18b.1 to 18b.8. For this purpose, the coupling device 24 comprises coupling elements designed to engage the coupling members 18a.1 to 18a.8 and 18b.1 to 18b.8, so that the carriage 14 is selectively coupled to the first conveyor element 18a or the second conveyor element 18b, and the carriage 14 is carried along in the coupled state by the respective conveyor element 18a or 18b. For this purpose, the coupling elements 18a.1 to 18a.8 and 18b.1 to 18b.8 are designed as drivers, which are cams that protrude from the respective conveying elements 18a and 18b.

[0041] The interaction between the coupling elements 18a.1 to 18a.8, 18b.1 to 18b.8 and the coupling device 24 will be explained in more detail with reference to the Fig. 2A and Fig. 2B will be explained.

[0042] In the Fig. 2A and Fig. Figure 2B shows the first conveyor element 18a as an example. Its free end 20 is located on the left in the figure, while the conveying direction A points to the right. An embodiment of the rail carriage 14 is also shown, with the coupling device 24 located on its left side.

[0043] By way of example, two coupling members 18a.1 and 18a.2 are also shown on the coupling element 18a. These are projecting drivers, namely cams, that protrude from the upper side of the conveying element 18a.

[0044] The coupling members 18a.1, 18a.2 are designed to engage a coupling element 24a of the coupling device 24 of the carriage 14 during a movement of the conveying element 18a relative to the carriage 14 in the conveying direction A. This situation is in Fig. 2A. For example, the coupling element 18a.1 engages the coupling element 24a and thus pulls the carriage 14 in the conveying direction A on the rails not shown in detail.

[0045] However, if according to Fig. 2B, the conveyor element 18a is moved in the opposite direction to the left, i.e., pushed forward under the carriage 14, the coupling element 18a.1 can slide under the coupling element 24a. The coupling element 24a is designed to yield during this sliding movement of the coupling element 18a.1 over the coupling element 24a during the feed movement and to avoid the driver 18a.1. For this purpose, the coupling element 24a is designed as a pivotable element, which is pivoted by the coupling element 18a.1 during its feed movement ( Fig. 2B) can be pushed upwards in the opposite direction during a movement in conveying direction A ( Fig. 2A) but remains rigid against the car 14 and cannot avoid it.

[0046] In this way, it is possible to advance the conveying element 18a under the carriage 14 against the conveying direction A until the coupling member 18a.1 has passed the coupling element 24a, and then to reverse this movement so that the conveying element 18a is pulled in the conveying direction A and engages with the coupling member 18a.1 on the coupling device 24 of the carriage 14 and takes it along.

[0047] In the present case, the carriage 14 is also equipped with a brake 40, which is designed to hold the carriage 14 along the conveyor track in the non-driven state. This prevents the carriage 14 from rolling away in the non-driven state. In the embodiment in the Fig. 2A and Fig. 2B, the brake 40 is designed to continuously exert a braking effect during the movement of the carriage along the conveyor track. For this purpose, the brake 40 is designed as a friction brake, which permanently presses a brake shoe against the respective rail 12a, 12b by spring pressure. In the example shown, the brake shoe is pressed onto the respective rail 12a, 12b. In other variants, the brake shoe can be pressed laterally against a respective rail 12a or 12b, for example, from between the rails 12a, 12b or from outside (in Fig. 1A, i.e., above the rail 12a or below the rail 12b). Accordingly, the brake 40 can be arranged above the respective rail 12a, 12b or at another position, e.g., between the rails 12a, 12b or laterally outside the respective rail 12a, 12b.

[0048] The Fig. 3A and Fig. 3B show an alternative embodiment of the brake 42, which is designed to exert the braking effect only at predetermined points along the conveyor track. At these points, brake cams 46 are provided next to one of the rails 12a, 12b. If the carriage 14 has braked via the brake shoe 44 at such a braking point according to Fig. 3B contact with the brake cam 46, it does not leave its position on the rail when not driven. The brake cams 46 can be arranged at a position, for example, between the rails 12a, 12b or laterally outside the respective rail 12a, 12b.

[0049] The design of the fixed coupling elements 18a.1, 18a.2 on the conveying element 18a and the coupling element 24a which is flexible in one direction is the same as in the Fig. 2A and Fig. 2B.

[0050] The Fig. 4A and Fig. 4B show a further embodiment of the drive device according to the invention, in which the coupling elements 24a are fixed, but the coupling members 18a.1, 18a.2 are designed to be flexible. The coupling members 18a.1, 18a.2 are pressed upwards by spring pressure. If the conveyor element 18a is pulled in the conveying direction A relative to the carriage 14 ( Fig. 4A), the coupling element 18a.1 engages the coupling element 24a and guides the carriage 14 during the further movement. If the conveyor element 18a is moved in the opposite direction ( Fig. 4B), the coupling element 18a.1 is pressed downward by the coupling element 24a, so that the coupling element 24a can slide over the coupling element 18a.1 and pass through it. The conveyor element 18a can thus slide under the carriage 14 with virtually no resistance.

[0051] In the embodiment in the Fig. 4A and Fig. 4B is also a constantly active friction brake 40 according to the Fig. 2A and Fig. 2B.

[0052] According to Fig. 1A, Fig. 1B and Fig. 1C, each of the first and second conveyor elements 18a, 18b is driven by an individual drive. This drive comprises a motor 26a, 26b that drives a spindle 28a, 28b to rotate. The spindle 28a, 28b is in turn coupled to the respective conveyor element 18a, 18b via a carriage 30a, 30b running thereon, such that the rotation of the spindle 28a, 28b causes the carriage 30a, 30b to move linearly and, during this movement, displaces the conveyor element 18a, 18b. The two spindles 28a, 28b are arranged parallel to each other beneath the conveyor elements 18a, 18b, and the motors 26a, 26b are arranged at opposite ends of this spindle pair, with each motor 26a, 26b driving one of the spindles 28a, 28b for rotation. The motors 26a, 26b are controlled by a common controller.

[0053] These drives allow the two conveyor elements 18a, 18b to be driven in opposite directions, in or against the conveying direction A, so that they move in opposite directions along the conveyor track. This allows the carriage 14 to be transported in cycles by the two conveyor elements 18a, 18b.

[0054] In the situation in Fig. 1A, the conveying elements 18a, 18b are displaced relative to one another in such a way that the first conveying element 18a is displaced further against the conveying direction A than the second conveying element 18b by a distance interval between the two coupling members 18a.1 and 18a.2. The carriage 14 is coupled to the conveying element 18a via its coupling device 24 and the coupling member 18a.2 in such a way that it can be moved in the conveying direction A by driving the conveying element 18a. The coupling between the carriage 14 and the conveying element 18a takes place as above in connection with Fig. 2A, Fig. 3A or Fig. 4A.

[0055] During this movement of the first conveyor element 18a, the second conveyor element 18b is simultaneously moved in the opposite direction, i.e. against the conveying direction A, by two distance intervals until the situation in Fig. 1B is reached. During this movement, the coupling members 18b.2 and 18b.3 slide under the coupling element 24a of the coupling device 24, so that the coupling member 18b.3 can engage the coupling element 24a during a reversal of movement of the conveyor elements 18a, 18b and carries the carriage 14 further in the conveying direction A by a distance interval, while the first conveyor element 18a advances against the conveying direction A until the situation in Fig. 1C is reached.

[0056] The movement of Fig. 1A to Fig. 1B corresponds to a first movement cycle in which the first conveyor element 18a is coupled to the carriage 14 and driven to move in the conveying direction A, while the second conveyor element 18b is detached from the carriage and driven to move in an opposite feed direction B. In contrast, the movement of Fig. 1B to Fig. 1C a second movement cycle in which the second conveyor element 18b is coupled to the carriage 14 and driven to move in the conveying direction A and the first conveyor element 18a is detached from the carriage 14 and driven to move in the feed direction B.

[0057] In the present embodiment, the coupling elements are when changing the coupling from the first conveyor element 18a to the second conveyor element 18b and vice versa, i.e. approximately in the situation in Fig. 1B, aligned with each other with respect to the conveying direction A. Here, the coupling of the carriage 14 is released from the first conveyor element 18a and picked up by the conveyor element 18b via the coupling member 18b.3, which continues to guide the carriage 14. This coupling change can be accomplished by appropriately synchronizing the motors 26a, 26b without interrupting the movement of the carriage 14.

[0058] The arrangement of the coupling members 18a.1 to 18a.8 and 18b.1 to 18b.8 on the conveyor elements 18a, 18b is shown in the present embodiment in the Fig. 1A, Fig. 1B and Fig. 1C is merely an example. The coupling elements can also be arranged at irregular intervals and do not have to be arranged at equal distances on both conveyor elements 18a, 18b. Additional conveyor elements can also be arranged between the rails 12a, 12b, allowing for a more detailed implementation of the carriage's movement cycle.

[0059] It is also by no means necessary to move the carriage 14 by exactly one distance interval between the coupling elements during a movement cycle; rather, a displacement can also be performed by different distances, i.e., even across other coupling elements of the counter-rotating conveyor element, before the coupling change and the reversal of movement take place. Finally, the carriage 14 does not have to cover the same conveying distances in every movement cycle; rather, these distances can be individually controlled. The spindle stroke of the spindle drive of a motor 26a, 26b can also be dimensioned larger than that required to move the carriage 14 within the conveying direction A during a movement cycle.

[0060] Finally, it is possible to convey the carriage 14 further in the conveying direction A by at least one of the conveying elements 18a, 18b at its end, i.e., for example, to transfer it to a further section of a track not shown in detail, a turning station or the like. List of reference symbols 10 Drive device 12a,12b rails 14 cars 16a, 16b, 16c, 16d wheelsets 18a first conveyor element (first pull rod) 18b second conveyor element (second pull rod) 18a.1 to 18a.8 Coupling elements (drivers) of the first conveyor element 18b.1 to 18b.8 Coupling elements (drivers) of the second conveyor element 20 free end of the first conveyor element 22 free end of the second conveyor element 24 Coupling device 24a Coupling element 26a, 26b engines 28a, 28b spindles 30a, 30b sledge 40, 42 brakes 44 brake shoe 46 brake cams A conveying direction B Feed direction

Claims

[1] Drive device (10) for conveying at least one carriage (14) along a conveyor track, comprising at least one carriage (14) which is movable along a linearly extending conveyor track, characterized by at least a first and a second conveyor element (18a, 18b) which extend parallel to one another along the conveyor track and can be driven for relative displacements in opposite directions along the conveyor track, and of which each conveyor element (18a, 18b) comprises a number of coupling members (18a.1 to 18a.8, 18b.1 to 18b.8) for coupling to the carriage (14), which coupling members are arranged at intervals from one another along the respective conveyor element (18a, 18b), whereby the carriage (14) can be coupled selectively to the first or the second conveyor element (18a, 18b). [2] Drive device (10) according to claim 1, characterized bythat the conveying elements (18a, 18b) can be driven to move in opposite directions for the cyclical conveyance of the carriage (14), wherein in a first movement cycle, the first conveyor element (18a) is coupled to the carriage (14) and driven to move in the conveying direction (A), while the second conveyor element (18b) is detached from the carriage (14) and driven to move in an opposite feed direction (B), and in a subsequent second movement cycle, the second conveyor element (18b) is coupled to the carriage (14) and driven to move in the conveying direction (A) and the first conveyor element (18a) is detached from the carriage (14) and driven to move in the feed direction (B). [3] Drive device (10) according to claim 1 or 2, characterized bythat the coupling members (18a.1 to 18a.8, 18b.1 to 18b.8) are designed as drivers which are intended to engage a corresponding coupling element (24a) of the carriage (14) in the conveying direction (A) during a conveying movement of the conveying element (18a, 18b) to which the respective driver is attached. [4] Drive device (10) according to claim 3, characterized by that the drivers are designed to be able to slide over a coupling element (24a) of the carriage (14) during a feed movement of the respective conveyor element (18a, 18b) relative to the carriage (14) opposite to the conveying direction (A), without engaging therewith. [5] Drive device (10) according to claim 4, characterized by that the drivers are designed in such a way that they can yield during sliding over a coupling element and can avoid the coupling element (24a). [6] Drive device (10) according to claim 4, characterized bythat the coupling elements (24a) are designed to give way during the sliding of a driver over the respective coupling element (24a) and to be able to avoid the driver. [7] Drive device (10) according to one of the preceding claims, characterized by that the conveying elements (18a, 18b) comprise pull rods or push rods. [8] Drive device (10) according to one of the preceding claims, characterized by at least one drive for the conveying elements (18a, 18b), which comprises at least one spindle drive (28a, 28b) and at least one motor (26a, 26b). [9] Drive device (10) according to claim 8, characterized by that an individual drive is provided for each conveying element (18a, 18b), comprising a spindle drive (28a, 28b) and a motor (26a, 26b) for moving the spindle drive (28a, 28b). [10] Drive device (10) according to one of the preceding claims, characterized bythat the coupling members (18a.1 to 18a.8, 18b.1 to 18b.8) of each conveying element (18a, 18b) are arranged at equal spacing intervals thereon. [11] Drive device (10) according to one of the preceding claims, characterized by that the spacing intervals of the coupling elements (18a.1 to 18a.8, 18b.1 to 18b.8) on both conveying elements (18a, 18b) are the same. [12] Drive device (10) according to one of the preceding claims, characterized by that the carriage (14) runs on rails (12a, 12b) and at least the conveying elements (18a, 18b) are arranged between the rails (12a, 12b). [13] Drive device (10) according to claim 12, characterized by that the rails (12a, 12b) are floor rails and the conveyor elements (18a, 18b) are embedded in the floor between the rails (12a, 12b) and extend under the carriage (14). [14] Drive device (10) according to one of the preceding claims, characterized by a brake (40, 42) for holding the carriage (14) in its position along the conveyor track in the non-driven state. [15] Drive device (10) according to claim 14, characterized by that the brake (40) is designed to continuously exert a braking effect during the movement of the carriage (14) along the conveyor track. [16] Drive device (10) according to claim 14, characterized by that the brake (42) is designed to exert a braking effect only at predetermined points along the conveyor track. [17] Method for operating a drive device (10) according to one of the preceding claims, characterized by that the conveying elements are driven to a counter-rotating movement for the cyclical conveyance of the carriage (14), wherein in a first movement cycle, the first conveyor element (18a) is coupled to the carriage (14) and driven to move in the conveying direction (A), while the second conveyor element (18b) is detached from the carriage (14) and driven to move in an opposite feed direction (B), and in a subsequent second movement cycle, the second conveyor element (18b) is coupled to the carriage (14) and driven to move in the conveying direction (A) and the first conveyor element (18a) is detached from the carriage (14) and driven to move in the feed direction (B).

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