Roller device for treating flat material, in particular for smoothing foils or plates, smoothing device, and method for producing flat material, in particular foils or plates

1. A roller device for treating a sheet-form material (F), comprising a first roller unit and a second roller unit, wherein each roller unit comprises:

at least one drive motor with a motor moment of inertia J M ,

a roller with a roller moment of inertia J W , and

at least one gear for the kinematic coupling of the roller to the at least one drive motor with a transmission ratio i MW between the at least one drive motor and the roller,

wherein the roller of the second roller unit is rotatable in the opposite direction to the roller of the first roller unit, and wherein there is formed between the roller of the first roller unit and the roller of the second roller unit a first roller gap through which the sheet-form material (F) is guided,

characterised in that

in at least one of the first and second roller units, the moment of inertia/speed ratio between the at least one drive motor and the roller M MW is ≦6 and the transmission ratio 5<i MW ≦40 is chosen,

wherein

M

MW

=

J

M

J

W

·

i

MW

2

where

i

MW

=

(

n

M

n

W

)

where n M : speed of the drive motor and n W : speed of the roller.

2. The roller device according to claim 1 ,

characterised in that

in the first and second roller units the speed ratio between the at least one drive motor and the roller M MW is ≦6 and the transmission ratio 5<i MW ≦40 is chosen.

3. The roller device according to claim 1 ,

characterised in that

the at least one drive motor of at least one of the first and second roller units is speed-controlled.

4. The roller device according to claim 1 ,

characterised in that

the at least one drive motor of at least one of the first and second roller units is a three-phase electric motor with frequency conversion.

5. The roller device according to claim 4 ,

characterised in that

the at least one drive motor of at least one of the first and second roller units is a synchronous motor.

6. The roller device according to claim 5 ,

characterised in that

the synchronous motor is in multipolar form.

7. The roller device according to claim 4 ,

characterised in that

the at least one drive motor of at least one of the first and second roller units comprises a compensation unit for compensating for the cogging torques.

8. The roller device according to claim 1 ,

characterised in that

the at least one drive motor of at least one of the first and second roller units and/or the roller of at least one of the first and second roller units is coupled by way of a rigid coupling to the at least one gear.

9. The roller device according to claim 1 ,

characterised in that

the at least one gear of at least one of the first and second roller units is in the form of a planetary gear.

10. The roller device according to claim 1 ,

characterised in that

the roller device comprises a control unit for controlling the at least one drive motor of the first roller unit and the at least one drive motor of the second roller unit, wherein the control unit is so configured that the torque and/or the peripheral speed of the roller of the first roller unit and of the roller of the second roller unit are each so controlled that one roller is coupled to the other roller by means of the sheet-form material (F) guided through the roller gap.

11. The roller device according to claim 1 ,

characterised in that

the roller device comprises a third roller unit comprising a roller, wherein there is formed between the roller of the first roller unit and the roller of the third roller unit a second roller gap through which the sheet-form material (F) is further guided after leaving the first roller gap.

12. The roller device according to claim 11 ,

characterised in that

the axes of the roller of the first roller unit, of the roller of the second roller unit and of the roller of the third roller unit are arranged substantially in a plane, wherein the sheet-form material (F), after leaving the first roller gap, is guided to the second roller gap on the peripheral surface of the roller of the first roller unit.

13. A smoothing device for smoothing films or sheets having a roller device according to claim 1 .

14. A process for the production of sheet-form material, comprising:

producing a melt film of the sheet-form material (F),

smoothing of the melt film in a first roller gap between a roller of a first roller unit with a roller moment of inertia J W1 and a roller of a second roller unit with a roller moment of inertia J W2 ,

wherein the roller of the first roller unit and the roller of the second roller unit are each coupled by way of at least one gear to at least one drive motor with a motor moment of inertia J M1,M2 ,

characterised in that

in the case of the roller of at least one roller unit, the moment of inertia/speed ratio between the drive motor and the roller M MW is ≦6 and the transmission ratio is 5<i MW ≦40,

wherein

M

MW

=

J

M

J

W

·

i

MW

2

where

i

MW

=

(

n

M

n

W

)

where n M : speed of the drive motor and n W : speed of the roller.

15. The roller device according to claim 1 , wherein there is chosen as the transmission ratio 10≦i MW ≦40.

16. The roller device according to claim 1 , wherein there is chosen as the transmission ratio 20≦i MW ≦40.

17. The roller device according to claim 6 , wherein the synchronous motor is in 10-polar form.

18. The roller device according to claim 9 , wherein the at least one gear of at least one of the first and second roller units is in the form of a planetary gear that is not free from play.

19. The process according to claim 14 , wherein the melt film of the sheet-form material is produced by extrusion.