DE102010024137A1 - Apparatus for clamping transport strap of sheet turning unit, has roller which is rotatable around locally stationary rotation axis, where another roller is rotatable around another locally stationary rotation axis - Google Patents

Abstract

The apparatus (17) has a roller (3) which is rotatable around a locally stationary rotation axis. Another roller (5) is rotatable around another locally stationary rotation axis. A third roller is located between the former and the latter roller, and is rotatable around a third rotational axis. A lever member is rotatably mounted around a fourth axis of rotation, and has a free end. An independent claim is also included for a sheet turning unit.

Description

The present invention relates to a device for tensioning a conveyor belt of a sheet turning unit, in particular for substrate sheets in a printing press with transport belts, which are guided over a plurality of deflection rollers.

Such sheet turning units are known in particular for the handling of substrate sheets, which are processed in printing presses. The conveyor belts are rotated together by 180 °, and the substrate sheets are turned by such a sheet turning unit for printing on both sides. However, the clamping device described here can also be used in other machines for processing a sheet, for example in the further processing of the substrate sheets after printing.

Turnover units with conveyor belts rotated against one another are for example out DE 10059913 A1 and from DE 10023151 A1 known. In these two publications suitable pulleys, transport belt assemblies and the general function of such a sheet turning unit are described.

In these sheet turning units, it has been customary to use an elastic transport belt without reinforcement, which is made of polyurethane (PU). Such a conveyor belt is usually not tensioned by tension rollers with a belt tensioner, since the tension rollers would have to travel a long way when clamping and would have to be provided in the machine much installation space. Rather, fixed deflection pulleys are used, on which the conveyor belts are placed elastically biased. The tension of the conveyor belt is therefore defined by the spring rate and the preload when placing the conveyor belt.

In order to meet the required accuracy of transport of a sheet with respect to angle of rotation (skew) and lateral offset (Xtrack offset) relative to the central axis of the transport direction and the position of the sheet in the transport direction (timing), the spring rate and unstrained length for both conveyor belts must be precisely equal for elastic conveyor belts be. Such similar characteristics can only be achieved by special manufacturing processes and precise quality management for each batch of conveyor belts produced. Another problem is a strong clamping force, which must be applied manually during the assembly of a conveyor belt. Since printing machines offer very little installation space, it is hardly possible for many operators to apply the required clamping force. Another disadvantage is that the material properties of a PU transport belt change after a longer storage time. The PU gets harder, shrinks and the belt tension increases. As a result, in some cases, even the maximum starting torque of the belt drive can be exceeded, so that the conveyor belt can not start. Furthermore, during operation of the elastic conveyor belts, changes in the tension also occur, for example due to elongation of the conveyor belt. As a result, the transport accuracy of the sheets decreases with increasing transit time of the conveyor belt so far that with long running time of the belt, the number of caused by no longer correctable transport errors machine malfunction increases sharply. These characteristics and problems described above mean that such an elastic conveyor belt can be used for only a limited number (for example, about 600,000) DIN A4 sheets and then must be replaced.

A solution to some of the problems described above is provided by a polyester fiber reinforced transport belt which eliminates the longitudinal elasticity of the belt. However, an additional belt tensioner must be provided within the limited installation space of the printing press in these reinforced conveyor belt. The additional belt tensioner ensures a constant tension of the conveyor belt independent of a spring rate or length of the conveyor belt. An advantage over the above-mentioned elastic transport belts is that the reinforced transport belt does not require any special quality control of the spring rate and the unstressed length. Likewise, the installation of the reinforced transport belt is simpler, since only the belt tensioner has to be loosened and the transport belt can be guided without tension over the deflection rollers. The belt tensioner provides a constant tension of the conveyor belt over the service life. Although the base material of the reinforced transport belt also hardens, this does not result in a change in the belt tension because the belt tensioner generates the tensioning force. Thus, the transport performance of the reinforced conveyor belt remains constant over the entire service life. A permanent elongation of the conveyor belt reinforced with polyester fibers is only slight. Such a reinforced transport belt achieves an approximately 5 × longer service life than an elastic transport belt (for example, about 3 million DIN A4 sheets).

A well-known belt tensioner has a linearly movable tension pulley, which is tensioned by a compression or tension spring. This construction usually requires relatively expensive milled parts. Furthermore, such brings Execution of the belt tensioner experience shows the risk of sheet jams, for example, by tilting the belt tensioner and thus decreasing belt tension, and excessive wear with it.

The object of the present invention is to provide a device for tensioning a conveyor belt, which ensures a constant tension and long service life of the conveyor belt.

The object of the present invention is achieved by a device according to the invention for tensioning a conveyor belt of a sheet turning unit according to claim 1 and by a sheet turning unit according to claim 6.

The device for tensioning a conveyor belt has a first roller, which is rotatable about a locally stationary first axis of rotation, further a second roller, which is rotatable about a locally stationary second axis of rotation, and a third roller, which is rotatable about a third axis of rotation and lies between the first and second rolls. A lever member rotatably supported about a fourth rotation axis has a free end and supports the third rotation axis of the third roller at a position offset from the fourth rotation axis of the lever member so that the position of the third rotation axis is changeable with respect to the first and second rotation axes , A tension member is provided which engages the free end of the lever member and biases it in a first direction, wherein the transport belt can be guided around the rollers such that movement of the lever member and thus the third roller in the first direction one way Extended belt around the rollers and thus strained the belt. By this tensioning device, the tension of a conveyor belt can be kept constant within narrow limits, even if the properties of the conveyor belt change over time or if different conveyor belts are used.

Preferably, the clamping element is arranged so that increases its leverage on the lever member in its movement in the first direction. In this way, the torque about the fourth axis of rotation, which is generated by the action of the clamping element, be kept approximately constant.

The first axis of rotation of the first roller and the fourth axis of rotation of the lever element preferably coincide. As a result, space and costs can be saved.

In one embodiment, the lever member has a stop which cooperates with a stationary stop to limit the movement of the lever member. Thus, a wear limit for the conveyor belt can be set and / or a fixation of the lever element for the installation and removal of the conveyor belt can be created.

In a further embodiment of the tensioning device, the first and third rollers are arranged such that a transport belt guided around the first and third rollers describes an S-curve. This results in a simple and symmetrical design with good mechanical behavior.

Turning unit with two conveyor belts, which are arranged so twisted to each other that an interposed sheet is turned by a predetermined angle, may have an embodiment of the invention described above tensioning device for at least one of the conveyor belt. Such a sheet turning unit allows safe and reliable operation over a large number of processed sheets even with changing mechanical and elastic properties of the tensioned conveyor belt.

The invention as well as further details and advantages thereof will be explained below with reference to preferred embodiments with reference to the figures. Show it:

1 a schematic representation of a sheet turning unit of the prior art;

2 a perspective view of a sheet turning unit, which has a device according to the invention for tensioning a conveyor belt;

3 a perspective view of the device for tensioning a conveyor belt 2 ;

4 an exploded perspective view of parts of 2 and 3 shown device for tensioning a conveyor belt;

5 a side view of the in the 2 . 3 and 4 shown device for tensioning a conveyor belt and a part of the sheet turning unit;

6 a schematic view of a printing press, in which the device for tensioning a conveyor belt can be used.

It should be noted that in the following description, the terms top, bottom, right, left front and rear and as well as similar references to the orientations and arrangements shown in the figures and perspective representations and serve only to describe the embodiments. However, these terms are not to be understood in a limiting sense.

1 schematically shows a sheet turning unit 1 in the side view. A substrate sheet 2 , in the following arc 2 , For example, a paper sheet is conveyed in a conveying direction (arrow F) from left to right. The sheet turning unit 1 has four cooperating pulleys 3 . 4 such as 5 . 6 on. A first transport belt 7 is around the two pulleys 3 and 4 guided, and a second conveyor belt 8th is around the two pulleys 5 and 6 guided. Between the bottom of the pulley 3 and the top of the pulley 4 runs a belt part or leading strand 7 ' of the conveyor belt 7 , and from the bottom of the pulley 4 to the top of the pulley 3 runs a returning strand 7 '' , Accordingly, runs from the lower pulley 5 at the top to the upper pulley 6 below a belt part or leading strand 8th' of the conveyor belt 8th , and from the top of the pulley 6 to the bottom of the pulley 5 leads a back leading trick 8th'' of the conveyor belt 8th , Between the transport rollers 3 . 4 . 5 and 6 there is a swivel area 10 in which the two transport belts 7 and 8th are twisted against each other.

The transport and the turn of the sheet are made by means of the two transport belts 7 . 8th , which are arranged to each other so that the two strands 7 ' and 8th' extend in the conveying direction F. Here are the transport belts 7 and 8th so twisted or swung that in front of the swivel range 10 the leading way 7 ' above and the leading strand 8th' located below, and that continues after the Schränkungsbereich 10 the strand 8th' located above and the strand 7 ' located below. Through this limitation of the transport belt 7 and 8th will be between the runs 7 ' and 8th' held bow 2 turned by 180 °.

The return trips 7 ' . 8th' and 7 '' . 8th'' touch each other at the belt intersection in the swivel area 10 lightly and rub against each other, hence the leading strands 7 ' and 8th' there by the resulting pressure force the vertical arc 2 can hold safely. Otherwise, particularly short, wide, heavy bends could slip down and cause machine malfunctions. For example, for this purpose, the pulleys 3 . 4 such as 5 . 6 be slightly inclined. Furthermore, not shown for this purpose holding rollers can be used. Because the bow 2 must be held securely during a turning process and during the turning process parallel to the transport direction 9 must be aligned, are leadership roles 11 . 12 . 13 and 14 in contact with the leading strand 7 ' . 8th' the transport belt 7 . 8th intended. The leadership roles 11 . 12 . 13 and 14 are alternately on the runs 7 ' and 8th' arranged so that they are the straps 7 and 8th deflecting to a small extent from the linear direction, so that the driving force of these strands 7 ' and 8th' on the bow 2 is increased.

2 shows in perspective view a sheet turning unit 1 which is a device according to the invention 17 for tensioning a conveyor belt 7 . 8th having. The 2 shows except for the additionally provided device 17 for tensioning a conveyor belt, the same components of the sheet turning unit 1 that already related to 1 have been described. In 2 is shown as several consecutively transported bows 2 are turned and arranged in different phases of the turning process. A bow delivered from the left 2 has a rear, outer edge 16 ' and a front edge 16 on (in the perspective view of 2 ).

Furthermore, in the 2 delineators 19 . 20 and 21 the sheet turning unit 1 shown, which serve to assist the turning process. A guide 19 in the form of a twisted linkage is the leadership of the rear, outer edge 16 ' of the bow 2 , The guide 19 starts at the back 15 where the outer edge is 16 ' of the bow 2 moved upwards. The guide 19 then extends forward in the direction of the end of the sheet turning unit 1 that the outer edge 16 ' up to the position of the bow 2 at the right end of the sheet turning unit 1 to be led. It is only the course of the twisted linkage of the guide 19 in 2 shown, with its attachment has been omitted for simplicity. It should be noted that the guide 19 on the side 15 extends as far back and is attached to the frame of a printing press such that the attachment of the turning operation of the bow 2 not disabled.

Another guide 20 serves to make the front outer edge 16 standing in front of the cabinet area 10 moved down and after the Schränkungsbereich 10 moved up, guided, until the bow 2 has reached the end position on the right side. The edge slides 16 or the part of the bow 2 near the edge 16 on the guide 20 until the bow 2 is aligned horizontally in a plane.

The third guide 21 is parallel to the second guide 20 on the opposite side of the pulley 4 and serves to boil the edge 16 ' Towards the end of the turning process, so that the edge 16 ' 'can not hang down. In this case, the guide extends 21 so far out, that they are to the edge 16 ' of the bow 2 enough. The guide 21 is in 2 shown cut off to still part of the pulley 4 to show in the perspective view. It should be noted that the guide 21 has the same extent as the guide 20 ,

The turning process in the direction of the arrows W in 2 runs as follows. A bow 2 , which in the conveying direction, ie in the direction of the arrow F through the sheet turning unit 1 is conveyed, moves from left to right through the sheet turning unit 1 , During the turning process, the edge at the beginning of the turning process moves outwards 16 ' of the bow 2 to the top, ie to the zenith, and the front outer edge 16 of the bow 2 moves in the racking area 10 downward. After the Schränkungsbereich 10 moves the upper outer edge 16 ' forward and down, and the lower outer edge 16 moves back and up. At the end of the turning process, and thus on the right side of the sheet turning unit 1 lies the former rear outer edge 16 ' now in front, and the formerly outer front edge 16 is behind.

In 3 is a perspective view of the clamping device 17 to see. The device for tensioning a conveyor belt has a deflection roller 23 on which on a frame 24 the sheet turning unit 1 is fixed, and about a locally stationary axis of rotation 25 is rotatable. Furthermore, the device 17 for tensioning a transport belt on a second role, namely the deflection roller 5 , which also on the frame 24 the sheet turning unit 1 is fixed and about a locally stationary second axis of rotation 26 is rotatable. The device 17 also has a third pulley 27 on that around a third axis of rotation 28 is rotatable and between the first guide roller 23 and the second pulley 5 lies. The third pulley 27 is from a lever element 30 worn, which is best in the exploded perspective view of 4 is shown and described in more detail below. Between a point of attachment 31 at the free end of the lever element 30 and a point of attachment 32 at the frame 24 the sheet turning unit 1 runs a clamping element 33 which applies a tensile force.

The lever 30 For example, is made of sheet metal and has a flat L-shaped body 34 which is generally perpendicular to the axes of rotation 25 . 26 . 28 the pulleys 5 . 23 . 27 extends. The L-shaped body 34 has a first leg 35 which extends generally horizontally and a second leg 36 which extends generally vertically. The first leg 35 and the second leg 36 meet in a middle area 37 through which a hole 38 runs, where the axis of rotation 28 the pulley 27 is attached. At the other end of the first thigh 35 there is a hole 39 through which the axis 25 the pulley 23 runs. An approach 40 extends from the outer end of the first leg 35 above the hole 39 up to a bend 41 , After the bend 41 extends an approach 42 generally at an angle of 90 ° to the frame 24 the sheet turning unit 1 out. The stop 42 works in the assembled state with part of the frame 24 together, a pivoting movement of the lever element 30 to limit.

Another approach 43 is at the outer end of the second leg 36 arranged. The approach 43 is essentially at an angle of 90 ° opposite to the stop 42 arranged. The approach 43 extends from the L-shaped body 34 in the opposite direction as the stop 42 and leads to the attachment point 31 for fastening the clamping element 33 , The attachment points 31 and 32 For example, they can be designed as hooks, holes or axles.

The lever element 30 is by means of a bearing sleeve 45 on the axis of rotation 25 the pulley 23 stored. In the assembled state ( 3 ) engages the stop 42 of the lever element 30 in a slot 46 of the frame 24 the sheet turning unit 1 one. Depending on the length and position of the slot is thus a limited pivotal movement of the lever element 30 around the axis of rotation 25 possible.

The tensioning element 33 may be, for example, a gas spring or a spiral tension spring. The clamping element has a flat spring constant, ie, that of the clamping element 33 applied spring force changes only slightly depending on the change in length.

How best in the 3 and 5 to see, the conveyor belt runs 8th around the pulley 5 , d. h the second role of the device 17 , continue around the pulley 27 ie the third roll of the device 17 , and then around the pulley 23 ie the first roll of the device 17 , This describes the transport belt 8th an S-shaped path. The transport belt 8th is laterally by a side guide roller 48 guided on the frame 24 is rotatably mounted. The side guide roller 48 has an axis of rotation that is substantially perpendicular to the axes of rotation, 25 . 26 and 28 is aligned.

How best in 5 can be seen, exercises the clamping element 33 a tensile force between the frame 24 , the turn-round unit 1 and the end 31 of the lever element 30 out. The clamping force FS acts at a distance, ie a radius RS, to the axis of rotation 25 the pulley 23 and generates a moment MS of FS × RS. The moment MS acts d. going to make it the lever element 30 counterclockwise in 5 tried to turn. The clamping element thus engages the free end of the lever element and biases the lever element 30 in a first direction, ie counterclockwise. This will cause the transport belt 8th curious; excited. On the transport belt 8th a belt force FR acting throughout the belt acts 8th acts and whose elasticity is.

The belt force FR, which acts in the belt part, which between the pulley 27 and the pulley 23 is equal to the belt force FR, in the belt part of the conveyor belt 8th acts, between the pulley 27 and the pulley 5 runs. The two belt forces FR meet at an intersection 50 who is their point of action. Starting from this intersection 50 let the belt forces FR disassemble into a fraction FR1, that of the point of intersection 50 out in the direction of the axis of rotation 28 the pulley 27 directed, and in a proportion FR2, which at an angle of 90 ° to the direction of action of the force FR1 in the direction of the axis of rotation 25 the pulley 23 acts. The portions FR1 of both belt forces FR together generate an overall belt force in the direction of the rotation axis 25 of 2 times FR1 = 2FR1, which at a distance or a radius RR to the axis of rotation 25 the pulley 23 acts. The effective direction of the total belt force 2FR1 runs from the point of intersection 50 in the direction of the axis of rotation 28 , The force 2FR1 generates with the radius RR a moment MR = 2FR1 × RR, which counteracts the moment MS and has the same magnitude. The moment MR tends to the pulley 27 and the lever element 30 to turn clockwise.

In operation, it may happen that the transport belt 8th lengthens or contracts due to aging. It will now be the operation of the device 17 for tensioning the conveyor belt 8th described in the case when the conveyor belt is elongated. In this case, the lever element would 30 with the pulley rotatably mounted thereon 27 by the tensile force of the tensioning element 33 turn counterclockwise. The axis of rotation around which the lever element 33 and the pulley 27 turn, is the rotation axis 25 the pulley 23 , An elongation of the conveyor belt 8th causes the end 31 of the lever element 33 moved down on a circular path. Because the attachment point 32 of the clamping element 33 at the frame 24 is stationary, the line of action of the force FS of the clamping element moves away 33 from the axis of rotation 25 the pulley 23 , that is, the radius RS becomes larger, and thus the torque MS = RS × FS becomes larger. It should be remembered that the tensioning element 33 applied force changes only slightly with the path. If the transport role 27 with the lever element 30 Moving downwards on a circular path, the looping of the conveyor belt also increases 8th around the pulley 27 , The wrap of the conveyor belt 8th around the pulley 23 gets larger, and the wrap of the conveyor belt 8th around the pulley 5 gets smaller. When the transport role 27 in relation to the in 5 However, the proportion FRR of the force FR is greater, that of the intersection 50 in the direction of the axis of rotation 28 the pulley 27 acts. The radius RR remains the same. The torque MR, which counteracts the increased moment MS, thus also increases, since with a constant radius MR, but a larger radial portion FR1 of the force FR, the moment MR = 2FR1 × RR becomes greater.

The arrangement of the attachment points 31 and 32 relative to the axis of rotation 25 the pulley 23 and the lever element 30 and the arrangement of the axis of rotation 28 relative to the axis of rotation 25 are chosen such that the increase of the torque MS counterclockwise by an increase in the radius RS an approximately equal increase in the clockwise torque MR by an increase in the force FRR. It should be noted that this ratio should be approximately present only over a small range of rotation to the advantageous effect of the device according to the invention 17 to reach for tensioning the conveyor belt. The elongation or shortening of the conveyor belt 7 or 8th causes only a relatively small change in position of the pivotally suspended pulley 27 ,

At a shortening of the conveyor belt 8th the guide roller moves 27 together with the lever element 30 in a clockwise direction in a pivoting movement about the axis of rotation 25 , That through the clamping element 33 generated torque MS is lower because the line of action of the force FS closer to the axis of rotation 25 moves and thus reduces the radius RS. However, the torque MR counteracting the torque MR is also lower, since the looping of the conveyor belt 8th around the pulley 27 decreases and the proportion FRR of the belt acting in the conveyor belt FR decreases. The torque MR in the clockwise direction thus also becomes smaller, since the torque-generating force 2FRR becomes smaller for the same radius RR.

In summary, it can be said that the device 17 for tensioning both transport belts 7 and 8th can be used, even if they are here only for the transport belt 8th has been described. The device 17 moves the pulley 27 , which acts as a tension roller, on a circular path. The bearing sleeve 45 of the lever element 30 is designed so that they are at full tension of the transport belt 7 . 8th works with low friction, For example, with a plain bearing (the in 4 shown bearing sleeve 45 ) or a ball bearing (not shown). This results in a low mechanical hysteresis to even small voltage changes during operation of the conveyor belt 7 . 8th to compensate.

In experiments it has been proven that the device 17 for tensioning a conveyor belt during operation a voltage of 55 N +/- 5 N over the entire operating range, ie pivoting range of the lever element 30 can maintain. This is a clamping force required for the operation of the transport belt 7 . 8th ideal. In this area of the clamping force, the turning unit has namely the highest transport accuracy.

It should be noted that the axis of rotation of the lever element 30 with the rotation axis 25 the pulley 23 may coincide, as described in this embodiment. However, it is also possible in other embodiments, a separate axis of rotation for the lever element 30 provided, for example, if a different force distribution is desired. It is important that the lever element is mounted such that the position of the axis of rotation of the deflection roller 27 with regard to the position of the axes of rotation 25 and 26 the pulleys 23 and 5 is changeable.

As mentioned earlier, the apparatus for tensioning a conveyor belt can be used for a variety of transport belts. In this example, however, the apparatus becomes for tensioning a conveyor belt of the sheet turning unit 1 used. In 6 is a printing press 60 with a sheet turning unit 1 shown. The printing press 60 has an image transfer area 62 on, in the means of several printing modules 63 . 64 . 65 . 66 Part color images on the bows 2 be transmitted. The bows 2 come for example from a feeder 68 from an unillustrated reservoir for bows 2 , This will be the bows 2 from a paper path 70 guided. After the image transfer area 62 is in the paper path 70 a switch 72 to the bows 2 to a boom 74 to redirect them or to reprint the image transfer area 62 feed again. This leads to a paper path 70 from the switch 72 back to the image transfer area 62 , In this returning paper path 28 is a turnaround unit 1 arranged, which ensures that the sheets are turned, which then the back of the sheets 2 and the printing modules 63 . 64 . 65 . 66 facing, and can be printed.

The invention has been described with reference to preferred embodiments, wherein the individual features of the described embodiments can be combined freely with each other and / or replaced, if they are compatible. Likewise, individual features of the described embodiments may be omitted, unless they are absolutely necessary. Numerous modifications and embodiments are possible and obvious to those skilled in the art without departing from the inventive concept.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10059913 A1 [0003]
• DE 10023151 A1 [0003]

Claims (6)

Contraption ( 17 ) for tensioning a conveyor belt ( 7 . 8th ) a sheet turning unit ( 1 ), the device ( 17 ) comprises: a first roll ( 23 ) around a locally stationary first axis of rotation ( 25 ) is rotatable; a second roll ( 5 ) around a locally stationary second axis of rotation ( 26 ) is rotatable; a third role ( 27 ) around a third axis of rotation ( 28 ) is rotatable and between the first and second rollers ( 23 . 5 ) lies; a lever element ( 30 ) around a fourth axis of rotation ( 25 ) is rotatably mounted, which has a free end ( 36 . 43 . 31 ) and that the third axis of rotation ( 28 ) of the third roller at a position offset from the fourth axis of rotation ( 25 ) of the lever element ( 30 ), so that the position of the third axis of rotation ( 28 ) with respect to the first and second axes of rotation ( 25 . 26 ) is changeable; and a tensioning element ( 33 ), which at the free end ( 36 . 43 . 31 ) of the lever element ( 30 ) and biases this in a first direction, wherein the transport belt ( 7 . 8th ) around the roles ( 23 . 5 . 27 ) can be guided around such that a movement of the lever element ( 30 ) and thus the third role ( 27 ) in the first direction a path of the conveyor belt ( 7 . 8th ) around the roles ( 23 . 5 . 27 ) and thus the transport belt ( 7 . 8th ) tense. Contraption ( 17 ) according to claim 1, characterized in that the tensioning element ( 33 ) is arranged so that its leverage on the lever element ( 30 ) increases in its movement in the first direction. Contraption ( 17 ) according to one of the preceding claims, characterized in that the first axis of rotation ( 25 ) of the first roll ( 23 ) and the fourth axis of rotation ( 25 ) of the lever element ( 30 ) coincide. Contraption ( 17 ) according to one of the preceding claims, characterized in that the lever element ( 30 ) a stop ( 42 ) which cooperates with a stationary stop to the movement of the lever element ( 30 ) to limit. Contraption ( 17 ) according to one of the preceding claims, characterized in that the first and third rollers ( 23 . 5 ) are arranged so that one around the first and third roles ( 23 . 5 ) guided transport belt ( 7 . 8th ) describes an S-curve. Turning unit ( 1 ) with two transport belts ( 7 . 8th ) which are arranged in such a twisted relationship to one another that an arc ( 2 ) is turned by a predetermined angle, characterized by a device ( 17 ) according to one of the preceding claims for at least one of the transport belts ( 7 . 8th ).

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