AU2019245717A1

AU2019245717A1 - Support-roll stand comprising a pivoting frame for a belt conveyor system

Info

Publication number: AU2019245717A1
Application number: AU2019245717A
Authority: AU
Inventors: Holger Gropp; Uwe Motzkau; Rolf Schwandtke
Original assignee: Artur Kuepper & Co KG GmbH; Schaeffler Technologies AG and Co KG
Current assignee: Artur Kuepper & Co KG GmbH; Schaeffler Technologies AG and Co KG
Priority date: 2018-03-26
Filing date: 2019-03-07
Publication date: 2020-10-08
Anticipated expiration: 2039-03-07
Also published as: PE20210529A1; DE102018107127B4; CL2020002072A1; BR112020016428A2; EP3774602A1; DE102018107127A1; CN111741912A; CN111741912B; EP3774602B1; WO2019185322A1; AU2019245717B2

Abstract

A support-roll stand for a belt conveyor system, comprising a pivoting frame (6), on which at least two support rolls (20, 21) are mounted, at least one of the support rolls (20, 21) mounted on the pivoting frame (6) being directly and gearlessly electrically driven.

Description

Support-roller stand with pivoting frame for a conveyor belt system

The invention relates to a support-roller stand according to the preamble of claim 1, which has a pivoting frame and is suitable for a conveyor belt system.

A support-roller stand of this type is known from WO 2017/068055 Al. Located on the pivoting frame of the known support-roller stand are two support rollers which can be electrically driven. In particular, the support rollers may have a dedicated electric drive.

A long conveyor belt system typically comprises a plurality of support-roller stands which are arranged one behind the other. For example, three or four support rollers, which are arranged relative to one another in a trough-like manner, are rotatably mounted in each individual support-roller stand. If one support roller is driven, this is therefore an intermediate drive of the conveyor belt system.

One possible construction of a support-roller drive for a conveyor belt system is disclosed in DE 10 2014 216 733 Al. In said support-roller drive, a support roller which acts as a drive roller is coupled to an electric motor via a coupling.

DE 2 146 218 C discloses a troughed conveyor belt system, in which a conveyor belt is guided with the aid of a plurality of so-called garlands. In this case, each garland has at least one central support roller and two lateral roller pairs. The support rollers may be driven by slip-on motors or may be designed as drum motors.

A possible drive for a roller provided for driving a conveyor track is described in EP 0 300 127 Bl. In this case, an electric motor assembly and a gear assembly are arranged in the interior of a drive roller.

Another drive unit for a transport roller is disclosed in EP 3 034 437 Al. In this case, an electric drive either may be designed as a gearless external rotor motor or may interact with a gear mechanism, depending on the design of the drive unit.

A method for operating a conveyor belt system having support rollers which are driven in a distributed manner is described in DE 10 2014 107 591 Al. In the context of said method, driven support rollers are operated by means of decentralized controllers, which are linked to one another by means of a hierarchically constructed control structure.

A belt conveyor described in CH 440 123 comprises a drive belt and also an endless conveyor belt which surrounds the drive belt and is driven by the latter.

A long-distance conveyor comprising a conveyor belt and a plurality of carrier belts, that is to say drive belts, is described in DE 1 178 359 B.

Another intermediate drive for belts of endless belt conveyors is described in DE 26 43 559 Al. In this case, too, a plurality of endless drive belts are located between the upper run and lower run of a belt of a belt conveyor.

DE 203 05 351 Ul discloses a drive belt/support belt drive, in which a plurality of drive drums are each coupled to a drive motor via straight bevel gear pairs.

The problem addressed by the invention is that of specifying a support-roller stand which has been further developed in comparison to the prior art, said support-roller stand having at least one driven roller and being characterized by a particularly high degree of robustness while at the same time having a compact, easy-to-assemble structure.

This problem is solved according to the invention by a support roller stand having the features of claim 1. In a basic concept known per se, the support-roller stand has a pivoting frame on which at least two support rollers, in particular exactly two support rollers, are mounted, at least one of said support rollers having a dedicated electric drive. Optionally, the support-roller stand additionally has two non-driven lateral support rollers which flank the pivoting frame and are arranged in an inclined manner relative to the pivoting frame. The lateral support rollers form a trough shape together with the support rollers mounted on the pivoting frame.

According to the invention, the dedicated electric drive of the support roller is designed as a gearless drive, that is to say as an electric direct drive. An electric direct drive will be understood to mean a drive in which the driven part, in the present case a support roller, is connected to the rotor of the electric motor for co-rotation therewith or is designed directly as the rotor of the electric motor.

To differentiate the term direct drive from other, indirect drives, reference is made to DE 202 05 428 Ul. In said document, a compact drive unit in the form of a geared motor is proposed for driving a conveyor belt. Such a drive unit is said to enable direct driving of a belt. However, since a geared motor by definition comprises a gear mechanism, this is not an electric direct drive in the sense of the present invention, but rather an indirect drive.

In the case of the support-roller stand according to the invention, the gearless drive, that is to say the direct drive, is preferably designed in the form of an external rotor motor having a hollow rotor which is connected to the shell of the support roller for co-rotation therewith, the associated stator being located in the interior of the support roller. By way of example, the gearless drive is a permanent-magnet-excited direct drive motor. Such a direct drive motor offers good possibilities for speed control and is characterized by a good balance between the space that is taken up and the torque that can be achieved. In addition, no power supply to rotating parts is necessary.

Regardless of the type of electric motor, the omission of a gear mechanism provides good conditions for driving a support roller with particularly high efficiency.

According to one possible embodiment, the support rollers attached to the pivoting frame are each mounted on arms which are pivotably articulated on side parts of the pivoting frame. This geometric design corresponds in principle to the design known from WO 2017/068055 Al (see Fig. 2 therein). Stating that the arms are pivotably attached to the side parts of the pivoting frame does not necessarily imply that the arms, on which the support rollers are mounted, are mounted directly on the side parts. Rather, constructions in which the arms are pivotably mounted on other parts, for example on crossmembers which connect the side parts to one another, can also be implemented with the same function.

Instead of mounting the support rollers on pivotable arms, it is also possible to mount the support rollers on an inherently rigid or on an adjustable pivoting frame, for example a rectangular frame with an adjustable side length. Regardless of the way in which the support rollers are attached, the two support rollers mounted in the pivoting frame can each be electrically directly driven and electronically synchronized with one another. In this case, the conveyor belt to be driven can rest directly on the support rollers. An electrical synchronization of the support rollers means that the support rollers are controlled separately, the controls being dependent on one another. In this way, slippage during operation of the conveyor belt system is avoided. Each driven support roller, which is integrated in the synchronization by a linked controller, has a built-in sensor system with regard to the angle position and/or change in angle of the support roller in question.

In one preferred embodiment, the support rollers mounted in the pivoting frame have a drive belt wrapped therearound. In this case, the conveyor belt to be driven rests on the drive belt.

The drive belt can already be driven by a single driven support roller. Alternatively, both support rollers can also be driven in this case, the drives of the individual support rollers being synchronized in the manner described.

Due to the drive belt placed around the support rollers, the area in contact with the conveyor belt to be driven is greatly increased in comparison to a support-roller stand which has driven support rollers on which the conveyor belt rests directly, and this enables a particularly high power input into the conveyor belt. In addition, the large wrap angle around the support roller, that is to say the extended area of contact between the support roller and the drive belt, promotes a high power input into the conveyor belt.

In various operating states, the enlarged force transmission area has enormous advantages over drive devices involving direct contact between the support roller and the conveyor belt. By way of example, when the belt starts up, particularly if there is little or no load on the conveyor belt from goods to be conveyed, slippage is avoided with a high degree of reliability. Even under unfavorable ambient conditions, such as extremely low temperatures which significantly reduce the flexibility of the conveyor belt, a sufficient force transmission capability between the drive belt and the conveyor belt is maintained.

The support-roller stand, which transmits force to the conveyor belt over a large area, namely via a drive belt, is also particularly well suited for braking the conveyor belt, for example in the event of emergency braking. Even in the event of emergency braking, it is possible to brake the entire conveyor belt in a decentralized manner by way of the support rollers. Compared to conventional conveyor belt systems, only moderate quality requirements have to be met by the conveyor belt due to this decentralized braking function. During the braking process, energy can be recovered by the direct drive motors.

During normal operation of the conveyor belt system, the drive belt has the effect of reducing wear on the conveyor belt due to the fact that there is little or no slippage. In addition, the drive belt itself and also the directly driven support rollers, which transmit drive power to the drive belt, are only exposed to a small degree of wear. This applies even when subjected to the stresses that are typical during operation, which can be caused by abrasive material such as sand or dust. Overall, the service lives of both the conveyor belt and the support-roller shell are significantly increased compared to conventional solutions. In particular, the low surface pressures between the drive belt and the conveyor belt and also the reduced surface pressures between the support roller and the drive belt due to the large wrap angle have a positive effect compared to surface pressures that occur between a conveyor belt and a support roller driving the latter directly. The large-area contact between the drive belt and the conveyor belt also ensures that the conveyor belt is only slightly deformed in the area of support and drive by the support-roller stand, which means only a small amount of flexing both in the conveyed goods and also in the conveyor belt and in the drive belt.

In principle, it is possible to coat the surface of the directly driven support roller. The parameters of such a coating are to be determined as a function of the contact between the support roller and the drive belt. Since, as explained, the stresses at this location are lower than when there is contact between the support roller and the conveyor belt, there are correspondingly reduced requirements for the coating, which is to the benefit of both efficient production and a long service life. Materials suitable for coating the support roller are, for example, polyurethane, rubber, and ceramic.

Regardless of the presence of a coating on the support roller, the surface thereof must be designed as a function of the stresses that occur in the individual case, which includes both mechanical stresses and environmental influences, for example due to moisture. The surface of the support roller, possibly formed by a coating, may for example be smooth, rough, or structured in a defined manner, for example provided with bumps. The basic set-up of the electric direct drive of the support roller is in principle independent of this.

In order to guide the drive belt in the axial direction of the driven support rollers, that is to say transversely to the conveying direction of the conveyor belt, the outer surfaces of the support rollers may be crowned, which results in a self centering effect. In addition to or instead of such a self centering, guidance by additional guide rollers is possible. Lateral guidance of the drive belt by shaped elements, for example abutment shoulders, on the support-roller shell is also possible.

The drive belt placed around the support rollers can be tensioned by means of various mechanisms:

By way of example, the effective side length of the pivoting frame is adjustable in order to keep the drive belt under tension. If arms, on which the support rollers are mounted, are articulated on the side parts of the pivoting frame, the effective length of said arms may for example be adjustable. Equally, an adjustment device may be integrated directly in an open receiving end of a rigid side part, into which a support roller is to be inserted, the axis of rotation of the support roller being fixable in a freely selectable position.

Devices which are provided to keep the drive belt under tension are generally referred to as belt-tensioning devices. These include both devices with automatic retensioning and devices which require the user to change the setting. Simple automatic retensioning may be achieved for example by means of a spring mounting of rollers, in extreme cases even a single roller. In particular, a support roller may be spring-mounted within the support-roller stand, a spring force acting on the support roller being oriented in the conveying direction of the conveyor belt system.

In various embodiments, inter alia in constructions in which the axes of rotation of the support rollers are in a fixed position relative to the pivoting frame, a setting of the tension of the drive belt can be changed for example by at least one tensioning roller. The tensioning roller is thus part of the belt tensioning device. The mechanism which changes the position of the tensioning roller in relation to non-adjustable parts of the support-roller stand in order to vary the tension of the drive belt is generally referred to as a roller-tensioning device. Thus, by definition, any type of roller-tensioning device is part of a belt-tensioning device. Conversely, however, a belt tensioning device does not necessarily include a roller tensioning device since, as mentioned, belt-tensioning devices can also be constructed without the use of separate tensioning rollers. A roller-tensioning device can be designed as a manually adjustable or automatic tensioning device.

In one particularly preferred embodiment, two tensioning rollers are arranged as components of a belt-tensioning device in each case next to the pivot axis of the pivoting frame, in particular as a mirror image in relation to the pivot axis of the pivoting frame, the positioning of each tensioning roller being variable. The individual tensioning rollers may for example be spring loaded and/or fixable in a locking manner. A guiding of the drive belt is optionally aided by guide disks on the tensioning rollers.

Both in embodiments with a drive belt and in embodiments without a drive belt, the entire pivoting frame may be height adjustable, in particular in the form of an automatic height adjustment, whereby the required contact pressure on the conveyor belt to be driven can be established or adjusted. In this case, the pivoting frame is mounted for example on helical springs which are attached to a crossbar. This crossbar may be suspended for example in an upper-run stand of a conveyor belt system. Equally, a height adjustment of only the support rollers may be provided. This may take place either by way of an active adjustment mechanism, for example using an electric motor, or by way of a passive mechanism, in particular a spring mechanism which comprises for example torsion bar springs or leg springs.

If the support-roller stand comprises further, lateral support rollers in addition to the support rollers mounted on the pivoting frame, the axes of rotation of the total of four support rollers, namely two horizontal support rollers arranged one behind the other and two lateral, inclined support rollers, can be positioned relative to one another in an adjustable or fixed manner in various ways:

On the one hand, constructions can be implemented in which the horizontal support rollers mounted on the pivoting frame, at least one of which is electrically directly driven, are tiltable together with the pivoting frame in relation to a stand in which the inclined support rollers are mounted, which is also referred to as a base frame. The pivoting frame is in this case suspended either centrally or off-center. In the latter case, the support rollers which are mounted on the pivoting frame are not arranged as a mirror image in relation to the pivot axis. The same can apply to the tensioning rollers. Such an asymmetrical design makes it possible to compensate at least in part for effects that result from the direction of movement of the conveyor belt.

On the other hand, four or more support rollers may be coupled to one another in the manner of a so-called garland. With regard to the technical background, reference is made in this connection to document DE 20 2013 011 823 Ul. Designing the support-roller stand in the manner of a garland makes it possible to vary the angle between the lateral, flanking support rollers and the central, substantially horizontal support rollers in such a way that the trough angle changes. In this type of construction, for example, helical springs may be fastened to the edge of the frame, that is to say the garland, next to the lateral support rollers in order to lift the entire garland in a flexible manner. Due to the fact that the garland is suspended in a spring-loaded manner, sufficient contact is made with the conveyor belt for the transmission of drive power or braking power under all load conditions, even when there is little or no loading by conveyed goods.

Seals of a type known in principle may be used between rotating and non-rotating parts of a support roller with an electric direct drive. The same applies to support rollers without a drive. In this connection, reference is made for example to document DE 10 2015 115 831 Al, which discloses a support roller with labyrinth seals and additional frictional ring seals. By means of such seals, particularly long service lives of all the mechanical components, including driven components, of the support-roller stand can be achieved.

Compared to conventional, non-driven support rollers, the electric direct drive has no effect on the width and diameter of the directly driven support rollers accommodated in the support-roller stand. The cooling of the direct drive motor can be implemented as passive cooling. An extensive sensor system for controlling and monitoring the direct drive motor and also the bearings, in particular roller bearings, which may include a speed, temperature and force measurement, can be integrated within the support roller and thus is both accommodated in a space-saving manner and protected from environmental influences.

The support-roller stand can be used for example in extensive conveyor belt systems in opencast or underground mining. Central drive stations of conveyor belt systems can be supplemented with or replaced by a plurality of support-roller stands, each having at least one driven support roller. In the case of existing systems, modifications which significantly increase the conveying capacity can be made by retrofitting pivoting frames with driven support rollers in the sense of a system retrofit.

Support-roller stands with directly driven support rollers are preferably integrated in a conveyor belt system with such power and number that there is redundancy of the drive, that is to say that the functionality of the system is maintained even in the event of failure of the drive or drives of an individual support roller stand.

Due to the fact that power is supplied in a decentralized manner by means of directly driven support rollers, which are integrated in support-roller stands with pivoting frames and do not impair the tiltability of the pivoting frame in any way, a high degree of variability of a conveyor belt system is achieved, in particular with regard to moving or extending the system, whereby overall - including restructuring phases - a very high degree of availability of the conveyor belt system is achieved.

The fact that a conveyor belt system with a constant conveyor belt cross-section and unchanged conveyor belt quality can be subsequently extended is of particular advantage. The conveyor belt cross-section, which is small in relation to the extension of the conveyor belt system, is accompanied by a low conveyor belt tension, which enables small radii of curvature within the conveyor belt system.

Several exemplary embodiments of the invention will be explained in greater detail below with reference to a drawing. In the drawing, partially in simplified form:

Fig. 1 shows a first exemplary embodiment of a support-roller stand in a perspective view,

Fig. 2 shows a further support-roller stand in a view analogous to Fig. 1,

Fig. 3 shows a detail of the support-roller stand shown in Fig. 2,

Fig. 4 shows a support-roller stand with a tensioning device for a drive belt,

Fig. 5 schematically shows components of a support-roller drive.

Unless otherwise stated, the following explanations relate to all the exemplary embodiments. Parts which correspond to one another or which in principle have the same effect are denoted by the same reference signs in all figures.

A support-roller stand, denoted as a whole by reference sign 1, is provided for driving a conveyor belt which is denoted by 35 and which is illustrated only in Fig. 2. With regard to the basic function of the support-roller stand 1, reference is made to the prior art cited in the introduction, in particular the document W02017/068055 Al originating from the applicant. The support-roller stand 1, which is also referred to as a pivoting frame unit, can replace a conventional support roller arranged in the upper run.

A baseplate 2, together with mounting plates 3, 4 and other parts fixedly connected to the baseplate 2, forms a base frame , in which a pivoting frame 6 is mounted in a tiltable manner. The corresponding pivot axis is denoted by SW. In principle, any type of stand present in a conveyor belt system can be equipped with the pivoting frame 6.

The pivoting frame 6 has a rectangular basic shape and has two side parts 7, 8, which in the exemplary embodiments are designed as U-shaped profiles. The side parts 7, 8 are connected to one another by crosspieces 9, 10, 11, the central axis of the crosspiece 10 coinciding with the pivot axis SW. At the ends of the side parts 7, 8, said side parts are coupled to arms 12 in an articulated manner in the variants shown in Figs. 1, 2, 3 and , the corresponding pivot axes, about which the arms 12 are pivotable, being referred to as adjustment axes EA. A torque is exerted on the arms 12 for example by springs (not shown). Alternatively, rigid connections between the arms 12 and the side parts 7, 8 are possible.

The ends of the arms 12 are designed as fork mounts 14, which are also referred to as retaining slots. An axle end 13 of a support roller 20, 21, which directly or indirectly supports the conveyor belt 35, is received in each retaining slot 14. The axle ends 13 represent the hubs of the support rollers 20, 21 or are fixedly connected to the hub of the respective support roller 20, 21. The support rollers 20, 21 are thus mounted on the pivoting frame 6. Lateral support rollers 22, 23 are mounted on the base frame 5 in a corresponding manner. Overall, therefore, a trough shape of the conveyor belt 35 is aided by the support-roller stand 1.

The support-roller stand 1 is designed not only to guide but also to drive the conveyor belt 35. For this purpose, at least one of the support rollers 20, 21 is electrically driven. Details of this drive, which is suitable for all the exemplary embodiments shown in Figs. 1 to 4, are illustrated in Fig. 5.

The axle end 13 and thus the entire axle of the support roller , 21 is fixedly connected to a stator 16 of an electric motor. In the case shown schematically in Fig. 5, the stator 16 is secured against rotation by a width across flats at the axle end 13 and the correspondingly contoured retaining slot 14. In the exemplary embodiment, the rotor 19 is equipped with permanent magnets 18. The adjustment axis EA visible in Fig. 5 is present only as an option.

The rotor 19 and the support-roller shell, denoted by 15, of the support roller 20 are connected for co-rotation, so that the support-roller shell 15 is electrically directly driven, that is to say in a gearless manner. Since the rotor 19 is designed as an external rotor equipped with permanent magnets, no power supply to the rotor 19 is required. The support-roller shell 15 is mounted by means of bearings (not shown), in particular roller bearings. No separate bearing of the rotor 19 is provided.

In the exemplary embodiment shown in Fig. 1, both support rollers 20, 21 mounted on the pivoting frame 6 are electrically directly driven. The conveyor belt 35 (not shown in Fig. 1) rests directly on the support rollers 20, 21.

In contrast to this, in the embodiments shown in Figs. 2 to 4, a drive belt 31 is placed around the support rollers 20, 21. In Fig. 2, cables 28 and electrical connection elements 29, 30 can also be seen, which enable the energy supply to the driven support rollers 20, 21 and also a signal transmission.

The drive belt 31 may be guided in the form of a slight belt trough, thereby establishing an enlarged area of contact with the conveyor belt 35, which is accompanied by the ability to transmit greater forces. Compared to the construction shown in Fig. 2, the distance between the support rollers 20, 21 can be increased in order to provide an extended run-in and run-out length and thus to enable a low-tension deformation of the drive belt 31 and also a large-area bearing of the conveyor belt 35 against the drive belt 31.

A first possibility for tensioning the drive belt 31 is illustrated in Fig. 3. In this case, a holder 26 designed as a sheet-metal profile is located on the arm 12. A threaded rod 24 is fixed in the holder 26 by means of adjusting nuts 25. A ring shaped socket 27, which is coupled to the hub 13, is adjustable by means of the threaded rod 24 such that the distance between the adjustment axis EA and the support-roller axis, denoted by TA, can be varied. A belt-tensioning device, denoted by 36, is thus provided, by which the tension of the drive belt 31 can be varied. In a manner not shown, the distance between the axes EA, TA can be varied by means of a spring mechanism as an alternative or in addition to a fixing mechanism.

A cable 28, which serves to transmit energy and signals, is guided centrally through the hub 13 and is connected to the direct drive motor (not shown in detail in Fig. 3) of the support roller 20, said direct drive motor comprising the stator 16 and the rotor 19. The electrical connection of the support rollers , 21 can also be implemented in the same way in the all other constructions of the support-roller stand 1.

In contrast to the design shown in Fig. 3, in the variant shown in Fig. 4 the distance between the two support-roller axes TA is not adjustable. In this case, there are instead tensioning rollers 32, by which the drive belt 31 can be tensioned. The tensioning rollers 32 are components of a roller-tensioning device, denoted by 37, which can be assigned to the belt tensioning device 36.

Locking contours 33, which are illustrated in Fig. 4 and are also referred to as a hole pattern, enable the tensioning rollers 32 to be fixed in place and in the exemplary embodiment shown in Fig. 4 are located on side plates 34 which are fixedly connected to the side parts 7, 8 of the pivoting frame 6. The adjustment range of the tensioning rollers 32 is limited such that the drive belt 31 is guided in all adjustments at a sufficient distance above the baseplate 2, that is to say the transverse strut of the support-roller stand 1. In addition, the tensioning rollers 32 have the effect of enlarging the areas of contact between the support rollers 20, 21 and the drive belt 31, this effect being all the greater the more the tensioning rollers 32 are raised and thus the drive belt 31 is tensioned. Thanks to the tensioning rollers 32, the wrap angle between the support rollers 20, 21 and the drive belt 31 is more than 1800. The drive belt 31 can not only be driven by the support rollers , 21 but also can be braked when required, for example for the purpose of an emergency stop of the conveyor belt 35. For this purpose, on the one hand a braking torque can be generated by the electric direct drive 16, 19 and on the other hand a braking torque that acts on the support roller 20, 21 can be generated by means of an optional mechanical brake (not shown).

List of reference signs

1 support-roller stand 2 baseplate, transverse strut 3 mounting plate 4 mounting plate base frame 6 pivoting frame 7 side part 8 side part 9 crosspiece crosspiece 11 crosspiece 12 arm 13 hub, axle end 14 retaining slot, fork mount support-roller shell 16 stator 17 winding 18 permanent magnet 19 rotor, hollow rotor support roller 21 support roller 22 lateral support roller 23 lateral support roller 24 threaded rod adjusting nut 26 holder, sheet-metal profile 27 socket, ring-shaped 28 cable 29 connection element connection element 31 drive belt 32 tensioning roller 33 locking contour 34 side plate conveyor belt 36 belt-tensioning device

37 roller-tensioning device

EA adjustment axis, pivot axis of the arm 12 SW pivot axis of the pivoting frame 6 TA support-roller axis, axis of rotation of the support roller 20,21

Claims

1. A support-roller stand of a conveyor belt system, having a pivoting frame (6) on which at least two support rollers (20, 21) are mounted, at least one of said support rollers (20, 21) having a dedicated electric drive, characterized in that the dedicated electric drive is designed as a gearless drive (16, 19).

2. The support-roller stand as claimed in claim 1, characterized in that the gearless drive (16, 19) is designed as an external rotor motor having an internal stator (16) and a hollow rotor (19) which is connected to the shell of the support roller (20, 21) for co-rotation therewith.

3. The support-roller stand as claimed in claim 2, characterized in that the gearless drive (16, 19) is designed as a permanent-magnet-excited direct drive motor.

4. The support-roller stand as claimed in one of claims 1 to 3, characterized in that the support rollers (20, 21) mounted on the pivoting frame (6) are each mounted on arms (12) which are pivotably articulated on side parts (7, 8) of the pivoting frame (6).

5. The support-roller stand as claimed in one of claims 1 to 4, characterized in that two support rollers (20, 21) mounted on the pivoting frame (6) are electrically directly driven and electronically synchronized.

6. The support-roller stand as claimed in one of claims 1 to , characterized in that two support rollers (20, 21) mounted on the pivoting frame (6), at least one of which is electrically directly driven, have a drive belt (31) wrapped therearound.

7. The support-roller stand as claimed in claim 6, characterized in that only one of the support rollers (20, 21) mounted on the pivoting frame (6) is electrically directly driven.

8. The support-roller stand as claimed in claim 6 or 7, characterized in that the distance of the axis of rotation (TA) of a support roller (20, 21) from the pivot axis (EA) of the associated arms (12) is adjustable.

9. The support-roller stand as claimed in one of claims 6 to 8, characterized in that the tension of the drive belt (31) is variable by means of a belt-tensioning device (36).

10. The support-roller stand as claimed in claim 9, characterized in that the belt-tensioning device (36) comprises at least one tensioning roller (32).

11. The support-roller stand as claimed in claim 10, characterized in that two tensioning rollers (32) are arranged next to the pivot axis (SW) of the pivoting frame (6), the positioning of each tensioning roller (32) being variable by means of a roller-tensioning device (37), in particular an automatic tensioning device.

12. The support-roller stand as claimed in claim 10, characterized in that the roller-tensioning device (37) comprises two tensioning levers (33) articulated on the pivoting frame (6).

13. The support-roller stand as claimed in one of claims 1 to 12, characterized by two non-driven lateral support rollers (22, 23) which flank the pivoting frame (6) and are arranged in an inclined manner relative to the pivoting frame (6).

14. The support-roller stand as claimed in one of claims 1 to 13, characterized in that the pivoting frame (6) is height adjustable, in particular automatically height-adjustable, in relation to a base frame (5) which supports it in a tiltable manner.