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

Abstract

The present invention relates to a roller device for treating sheet-form material, in particular for smoothing films (F*) or sheets, comprising a first roller unit 1 and a second roller unit 2, wherein each roller unit (1, 2) comprises: at least one drive motor with a motor moment of inertia J.sub.M, a roller (10, 20) with a roller moment of inertia J.sub.W, and at least one gear for the kinematic coupling of the roller (10, 20) to the at least one drive motor with a transmission ratio i.sub.MW between the at least one drive motor and the roller (10, 20),
wherein the roller (20) of the second roller unit (2) is rotatable in the opposite direction to the roller (10) of the first roller unit (1), and wherein there is formed between the roller (10) of the first roller unit (1) and the roller (20) of the second roller unit (2) a first roller gap (40) through which the sheet-form material (F) is guided. According to the invention, the roller device is characterized in that in at least one of the first and second roller units (1, 2), the moment of inertia/speed ratio between the at least one drive motor and the roller (10, 20) M.sub.MW is 6 and the transmission ratio 1<i.sub.MW40 is chosen,
wherein $M_{\mathrm{MW}}=\frac{J_M}{J_W}.Math.i_{\mathrm{MW}}^2$
where $i_{\mathrm{MW}}=\left(\frac{n_M}{n_W}\right)$
where n.sub.M: speed of the drive motor and n.sub.W: speed of the roller (10, 20). The invention relates further to a smoothing device for smoothing films or sheets, and to a process for the production of sheet-form material, in particular of films or sheets.

Claims

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.sub.M, a roller with a roller moment of inertia J.sub.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.sub.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.sub.MW is 6 and the transmission ratio 5<i.sub.MW40 is chosen, wherein $M_{\mathrm{MW}}=\frac{J_M}{J_W}.Math.i_{\mathrm{MW}}^2$ where $i_{\mathrm{MW}}=\left(\frac{n_M}{n_W}\right)$ where n.sub.M: speed of the drive motor and n.sub.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.sub.MW is 6 and the transmission ratio 5<i.sub.MW40 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.sub.W1 and a roller of a second roller unit with a roller moment of inertia J.sub.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.sub.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.sub.MW is 6 and the transmission ratio is 5<i.sub.MW40, wherein $M_{\mathrm{MW}}=\frac{J_M}{J_W}.Math.i_{\mathrm{MW}}^2$ where $i_{\mathrm{MW}}=\left(\frac{n_M}{n_W}\right)$ where n.sub.M: speed of the drive motor and n.sub.W: speed of the roller.

15. The roller device according to claim 1, wherein there is chosen as the transmission ratio 10i.sub.MW40.

16. The roller device according to claim 1, wherein there is chosen as the transmission ratio 20i.sub.MW40.

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.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The invention is explained in greater detail below by means of a drawing showing an exemplary embodiment. In the drawing:

(2) FIG. 1 shows a smoothing device for smoothing films or sheets, in particular melt films extruded immediately beforehand.

(3) The smoothing device of FIG. 1, which is shown in a highly diagrammatic sectional drawing, comprises a total of three roller units 1, 2, 3, each of which comprises a drive motor with a motor moment of inertia J.sub.M1,M2,M3, a tempered roller 10, 20, 30 with a roller moment of inertia J.sub.W1,W2,W3 and a gear for the kinematic coupling of the roller 10, 20, 30 to the associated drive motor with a transmission ratio i.sub.MW1,MW2,MW3 between the drive motor and the roller 10, 20, 30. The roller 20 of the second roller unit 2 is rotatable in the opposite direction to the roller 10 of the first roller unit 1. Likewise, the roller 30 of the third roller unit 3 is rotatable in the opposite direction to the roller 10 of the first roller unit. Between the roller 10 of the first roller unit 1 and the roller 20 of the second roller unit 2 there is formed a first roller gap 40. Furthermore, between the roller 10 of the first roller unit 1 and the roller 30 of the third roller unit 3 there is formed a second roller gap 50, the melt film to be smoothed passing first through the first roller gap and then through the second roller gap, as is explained in detail below.

(4) In the present case, in the case of the three roller units, the moment of inertia/speed ratio between the at least one drive motor and the roller M.sub.MWi is chosen to be 6 and the transmission ratio is chosen to be 1<i.sub.MWi40, wherein

(5) $M_{\mathrm{MW}}=\begin{array}{c}{J}_M\\ J_W\end{array}.Math.i_{\mathrm{MW}}^2$
where

(6) $i_{\mathrm{MW}}=\left(\frac{n_M}{n_W}\right)$
where n.sub.M: speed of the drive motor and n.sub.W: speed of the roller and roller index i=1, 2, 3.

(7) For the transmission ratio i.sub.MW, a range of preferably 5i.sub.MW40, especially 10i.sub.MW40 and particularly preferably 20i.sub.MW40 is chosen.

(8) By the choice of these parameters, a particularly high degree of synchronism of the rollers is achieved, as a result of which the surface quality of the smoothed film is improved significantly. In particular, the visibility of chatter marks can be reduced very considerably or even eliminated altogether.

(9) The indicated drawing of the smoothing device shows the three rollers 10, 20, 30 of the three roller units 1, 2, 3 in a sectional view. Accordingly, the gear, which in the present case is coupled in a known manner directly to a shaft journal, and the drive motor, which in turn is coupled to the gear input shaft, are not shown. It is possible to couple a gear and a drive motor to the two shaft journals of each roller. In the present case, each drive motor is coupled to its associated gear by way of a rigid coupling. Likewise, each gear is coupled to the shaft of its associated roller 10, 20, 30 by way of a rigid coupling. The gears are in each case in the form of planetary gears which are not free from play.

(10) In the present case, the electric motors driving the rollers 10, 20, 30 are in the form of three-phase electric motors with frequency conversion, especially in the form of synchronous motors. Precise adjustment and control of the motor speed with optimal synchronism properties is thereby possible. In order further to increase the synchronism of such a synchronous motor, it is further provided that the motors are in multipolar, in particular 10-polar, form. A common control unit (not shown) allows the drive motors to be controlled and adjusted jointly. Furthermore, each of the drive motors of the roller units 1, 2, 3 comprises a compensation unit for compensating for the cogging torques, which compensation units in the present case are each in the form of a software module in the control unit of the drive motors.

(11) The mode of operation of the smoothing device is as follows:

(12) In an extrusion unit (not shown), a melt of polycarbonate, for example, is produced in a distributor tool 60 (die) with a thickness of typically from 500 to 1200 m and is passed in the form of a melt film F in the direction towards the rollers 10, 20, 30, which are arranged beneath the distributor tool in a horizontal plane, where it is smoothed. The melt film F there enters the roller gap 40 formed between the roller 10 of the first roller unit 1 and the roller 20 of the second roller unit 2. As is shown, the rollers 1, 2 rotate in opposite directions and thereby draw the melt film F into the roller gap 40. After leaving the roller gap 40, the film sheet F* is guided on the underside of the arrangement of the rollers 1, 2, 3 around the roller 1 through an angle of about 180 and enters from below the second roller gap 50, which is formed between the roller 1 and the roller 3 rotating in the opposite direction to the roller 1, where it is smoothed further. After leaving the second roller gap 50, the smoothed film sheet F* is guided around the roller 3 through an angle of about 90, for example, and is then taken off in the form of a finished, smoothed film sheet F**.

(13) In order to optimise the smoothing of the film sheet and eliminate the formation of chatter marks as completely as possible, the control unit the drive motors of the rollers 1, 2, 3 is so configured in the present case that the torque and/or the peripheral speed of the rollers 1, 2, 3 are each controlled in such a manner that one roller drags the other roller by means of the sheet-form material guided through the roller gap. In the present case, the roller 1 serves as the guide roller in respect of the torque and the peripheral speed.

EXAMPLE

(14) In a smoothing device of the type operated above for smoothing polycarbonate films, three roller units were operated with the following parameters:

(15) TABLE-US-00001 Motor power: 4.49 kW Motor torque: 23.6 Nm Motor speed: 2000 min.sup.1 Motor moment of inertia J.sub.M: 65 kgcm.sup.2 Transmission ratio i.sub.MW: 35.34 Roller torque: 834.02 Nm Roller speed: 56.59 min.sup.1 Moment of inertia/speed ratio M.sub.MW: 4.91

(16) With these settings, no more chatter marks were visible on the finished, smoothed polycarbonate film.

COMPARISON EXAMPLE

(17) In a smoothing device of the type operated above for smoothing polycarbonate films, three roller units were operated with the following parameters:

(18) TABLE-US-00002 Motor power: 1.48 kW Motor torque: 2.35 Nm Motor speed: 6000 min.sup.1 Motor moment of inertia J.sub.M: 1.5 kgcm.sup.2 Transmission ratio i.sub.MW: 125.6 Roller torque: 443.37 Nm Roller speed: 47.77 min.sup.1 Moment of inertia/speed ratio M.sub.MW: 16.83

(19) Here, clear chatter marks were visible on the surface of the finished, smoothed polycarbonate surface.