EP2041509A2

EP2041509A2 - Drum device and flexible belts

Info

Publication number: EP2041509A2
Application number: EP07803799A
Authority: EP
Inventors: Jean-Michel Dubus
Original assignee: Rieter Perfojet SAS
Current assignee: Andritz Perfojet SAS
Priority date: 2006-07-11
Filing date: 2007-06-28
Publication date: 2009-04-01
Also published as: WO2008006954A2; WO2008006954A3; US20090320323A1

Abstract

This device comprises a drum having a lateral surface through which fluid can pass and two flexible belts (2) passing over the lateral surface of the drum (1) at a distance from each other and each over its own idle guide roller (3). Each roller (3) pivots on a vertical axis (8). Applicable to driers.

Description

DRUM DEVICE AND SOFT BANDS

The present invention relates to drum and flexible belt devices. The invention relates to a device for adjusting the effective width of a permeable surface cylinder. It relates in particular to the field of drying non-woven fabrics (or textile or paper) by a dryer said air dryer through with air blowing through the product to be dried. But it can also relate to the field of filtration or any other field in which one seeks to pass a fluid through the surface of a cylinder.

In the case of a through-air dryer, the product is usually encumbered around one or more permeable drums. Hot air is blown by a hood around the drum or drums. A depression is made inside the drum or drums to suck this air that passes through the product. By passing through the product, the air exchanges energy and causes the evaporation of water. The water vapor is then entrained with the airflow. Part of the air is then vented to the outside, the larger part is reheated and re-circulated.

In this technology, it is important for the efficiency of the dryer that the permeable width of the drum corresponds to the width of the web to be dried. Indeed, if the product is wider than the permeable zone of the drum, the ends of the product to be dried will not be traversed by the air flow and will therefore be poorly dried.

Otherwise, if the product is narrower than the permeable zone of the furnace, the air flow will tend to pass preferentially through the areas not covered by the product. This results in a general decrease in the efficiency of the dryer and a heterogeneity of the drying of the veil: the edges of the veil located near the zones of leakage remain wetter than the parts farther away from the leaks.

To avoid this phenomenon, it is therefore desirable to have a system for adjusting the suction width of the drum to the product width to be dried. The principle is to close by means adequate both ends of the permeable zone of the drum. Such systems exist (fixed bands around the drum, adjustable baffle devices located inside the drum). ^'These systems are effective but have the disadvantages of either having to stop the machine to make the adjustment (for fixed bands) or to be relatively expensive.

There is a device having two flexible strips arranged around the drum, outside, and each tensioned by a return roller. The return roller is mounted on a carriage which slides vertically to ensure the tension of the belt (the weight of the carriage is adapted to the necessary tension). The guide of the band is ensured by the use of a convex roller with convex or biconical profile. Adjusting the position of the two bands defines the suction width of the drum.

This device has, however, limitations.

There is a very large difference in diameter between the main drum of the dryer (generally between 1 m and 3 m in diameter) and the return roller (generally 100 to 200 mm in diameter). On the other hand, the free strands of the band (length elements during which the band is not in contact with the main drum or with the return roller) are very short. This configuration results in: A slight defect in the geometry of the main drum, the band or a very slight defect of parallelism between the main drum and the deflection roller creates at each turn a significant deflection of the band which naturally tends to follow the trajectory imposed by the drum. .

The reduced length of the soft strands of the belt between the main drum and the return roller does not allow the belt to compensate for this deflection by simple deformation and also does not allow the curved or biconical profile of the return roller to maintain the belt. in the central part of the return roller.

As a result, the band tends to move towards one or the other of the return roller, until it bears on the fixed parts of the device. This results in damage to the strip which reduces its life and a risk of polluting the nonwoven by foreign particles from the strip.

When the operator tries to correct this displacement by changing the setting of the carriage, it usually happens to obtain a setting that causes the band to move in the other direction. But the point of balance, where the band is perfectly centered, is extremely sensitive and almost impossible to obtain.

An additional constraint is the operating temperature of the device, which causes deformation of the elements and modifies the geometry of the assembly. Thus, a setting giving correct behavior at a certain temperature will no longer be stable when the temperature changes due to different production conditions.

Finally, it should be noted that the adjustment of the position of the two strips on the drum, which must allow the width to be precisely defined. suction, is impossible at production speed. This setting requires the drum to rotate at a reduced speed allowing operators to work safely. This results in a loss of productivity of the line and an additional difficulty because the width of the nonwoven on the main drum is also sensitive to the speed of production of the line and an optimized working width at low speed will no longer be at the normal production speed.

The invention overcomes these disadvantages.

The subject of the invention is a device comprising

a drum having an axis of rotation and a lateral surface through which fluid can pass and

two flexible strips passing on the lateral surface of the drum, at a distance from each other, and each on a guide roller which is its own. A drum of this kind is revealed by the DE 44

36,745 Al.

The invention is characterized in that each roller is pivotally mounted about an axis perpendicular to the axis of rotation of the roller and which lies in the median plane perpendicular to the axis of the roller.

When the axis of rotation of the drum is horizontal and when the guide rollers also have horizontal axes of rotation and are below the drum, each roller is pivotally mounted about a vertical axis or inclined to the vertical less 30 ° upstream with respect to the running direction of the web. Preferably, the vertical axis of pivoting of the roll is offset from the upstream side, with respect to the direction of travel of the strip, of the axis of roll rotation of less than 15 °.

The invention provides the deflection roller with a degree of orientation which enables it to compensate, on the one hand, for misalignment between the components and, on the other hand, the geometry defects of the components (roller, drum or bandaged) . The geometry of the device defined by the invention also allows the orientation of the roller is caused by the band itself when it deviates from its ideal central position without help from an external device. Thus, once the position of the guide carriage has been defined, the system no longer requires external intervention and maintains perfect guidance of the belt, even if the conditions change due to temperature or other external parameters. Preferably, each roller is slidably mounted parallel to the axis of the drum and is mounted so as to slide vertically. A convenient way to realize the invention is to mount each roller on a carriage adjusting its position. Each roller can be rotatably mounted about its axis in a cradle connected to the carriage provided with two lateral rollers rotatably mounted about an axis perpendicular to the strip, the rollers being disposed on either side of the roller.

A device which, while being particularly simple, makes it possible to combine in a single function the movements of vertical sliding and orientation in the horizontal plane of each roller, is that in which each roller can be mounted rotating about its axis in a cradle rigidly fixed to a cylindrical axis guided by cylindrical rings.

When the axis of rotation of the drum is horizontal and when the guide rollers also have horizontal axes of rotation and are below the drum, each roller is pivotally mounted around a vertical axis or inclined vertically less than 30 ° upstream with respect to the direction of travel of the strip. Preferably, the vertical axis of pivoting of the roll is offset from the upstream side, with respect to the running direction of the strip, of the axis of rotation of the roll by less than 15 °.

The invention provides the deflection roller with a degree of orientation which enables it to compensate, on the one hand, for misalignment between the components and, on the other hand, the geometry defects of the components (roller, drum or bandaged) . The geometry of the device defined by the invention also allows the orientation of the roller is caused by the band itself when it deviates from its ideal central position without help from an external device. Thus, once the position of the guide carriage has been defined, the system no longer requires external intervention and maintains perfect guidance of the belt, even if the conditions change due to temperature or other external parameters, each roller is slidably mounted parallel to the axis of the drum and is also mounted vertically sliding. A convenient way to realize the invention is to mount each roller on a carriage adjusting its position. Each roller can be rotatably mounted about its axis in a cradle connected to the carriage provided with two lateral rollers rotatably mounted about an axis perpendicular to the strip, the rollers being disposed on either side of the roller.

The pivot axis of the roller may pass through the middle of the axis of rotation of the roller but, preferably, it is offset from the upstream side with respect to the running direction of the web of the axis of rotation of the roller.

The invention also relates to a dryer comprising a blower hood and a device according to the invention disposed in the hood. It is planned ways to do pass a web to dry or another web product to dry on the drum between the two strips.

In the drawings, given by way of example only: Figure 1 is a schematic side view of a through air oven, Figure 2 is a schematic sectional view of the through air oven of Figure 1; is a perspective view of a drum and two rollers on which bands are passed according to the invention, Figure 4 is a partial perspective view of the device according to the invention, Figure 5 is a partial sectional view, parallel 6 is a partial sectional view perpendicular to the axis of the drum of the device according to the invention, FIG. 7 is a schematic view illustrating a variant, FIG. is a schematic explanatory view corresponding to the variant of Figure 7, Figure 9 is a schematic view illustrating another variant, Figure 4 is a partial perspective view of a variant of the device according to the invention, Figure 5 is a V a partial section perpendicular to the axis of the drum of a variant of the device according to the invention.

The through air oven shown in Figures

1 and 2 comprises a blowing hood H surrounding a drum 1 whose side surface is perforated. Hot air is blown from the hood inside the drum where there is a depression. Some of the air is evacuated to the outside via a fan V and an evacuation E, while another part is heated and returned to the hood H. The arrows in Figures 1 and 2 illustrate the passage of air .

As shown in Figure 3, the drum has an axis xx 'of horizontal rotation and a perforated side surface through which fluid can pass. Two strips 2 pass on the lateral surface of the drum 1, being at a distance from each other. Each passes on a roller 3, mounted crazy, guide. The roll is preferably of domed or biconical profile. The position of the two strips 2 setting defines the suction width of the drum 1. As shown in Figures 4 to 6, the device according to the invention comprises: a drum ^'one permeable surface of diameter generally comprised between 1.0 and 3.0 m in diameter, but the invention may also be suitable for diameters smaller or larger than these values.

A set of flexible strips 2, usually two, arranged around the drum. These strips bear against the surface of the drum in order to seal the permeable surface of the drum on an area defined by the width of the band and the winding angle of the band around the drum. By adjusting the distance between the two bands, it is thus possible to change the suction width of the drum.

Each band is associated with a tensioning and guiding device comprising: a conveying roll 3 with a cylindrical, curved or biconic profile. This roller is mounted on a cylindrical axis 4 by means of two bearings 5 to ensure the free rotation of the roller. The roller is positioned inside the loop formed by the band, to ensure the tension of the latter.

The assembly is mounted in a cradle 6 connected to a carriage 9. The connection between the cradle and the carriage is carried out via an axis 8 and two bearings or thrust bearings 7 allowing the free rotation of the cradle around of a vertical axis while blocking the other degrees of freedom between these two elements. The cradle is also equipped with two pebbles

10 lateral whose axis of rotation is perpendicular to the band. These rollers serve as a stop for the band when it tends to move laterally on the return roller. A frame 11 equipped with vertical rails 12 receives the carriage 7 and allows it to slide in a vertical direction. This vertical movement, caused by the weight of the carriage, allows to give the band the necessary tension. The frame 11 is mounted on a fixed frame 13 via a guide assembly allowing the frame to move in a horizontal direction parallel to the axis of rotation of the permeable drum. The guide assembly may consist of a set of rings 14 sliding on a fixed shaft. A device consisting of an endless screw 15 makes it possible to actuate the movement either by a hand-held steering wheel 16 or by an electric motor driven remotely. Other guide devices and motorization to ensure this translational movement can also be used.

As shown in FIGS. 4 'and 5', a preferred variant of the device according to the invention comprises: a drum 1 of permeable surface, of diameter generally between 1.0 and 3.0 m in diameter, but the invention may also be suitable for diameters smaller or larger than these values.

Each band is associated with a tensioning and guiding device comprising a roll 3 for conveying cylindrical profile, convex or biconical. This roller is mounted on a cylindrical axis 4 by means of two bearings 5 to ensure the free rotation of the roller. The roll is positioned inside the loop formed by the band, to ensure the tension of the latter. The assembly is mounted in a cradle 6 'fixed rigidly to a cylindrical axis 9' guided by cylindrical rings 12 '. It is thus possible to combine in a single function the vertical sliding movements and orientation in the horizontal plane of the roller 3. A frame 11 equipped with cylindrical rings 12 'receives the axis 9' and allows its sliding in a vertical direction . This vertical movement, caused by the weight of the carriage, allows to give the band the necessary tension. The frame 11 is mounted on a fixed frame 13 via a guide assembly allowing the frame to move in a horizontal direction parallel to the axis of rotation of the permeable drum. The guide assembly may consist of a set of rings 14 sliding on a fixed shaft. A device constituted by an endless screw 15 makes it possible to actuate the movement either by a manually controlled steering wheel 16 or by an electric motor driven remotely. Other guide devices and motorization to ensure this translational movement can also be used.

Two principles are taken into account in the operation of the invention and are both related to the behavior of a band when it is wound on a rotating drum.

The first principle is related to the fact that the adhesion of the band on the drum requires the band to follow, during its contact around the drum, the trajectory of the point of contact. Thus, if the strip comes into contact with a cylinder which is not perfectly perpendicular to the direction of arrival of the strip, the strip will, for the duration of the contact with the drum, follow a different direction perpendicular to the rotation axis of the drum. When it leaves the drum again, it has therefore undergone a more or less pronounced lateral displacement depending on the deflection angle and the length of the contact strip / cylinder.

The second principle that is taken into account in the operation of the invention is the behavior of a strip when it is wound flat on a non-cylindrical surface, for example a cone.

In this case, a band that is perpendicular to the axis of the cone goes in order to wind flat on the surface of the cone, follow a spiral path and thus move towards the large diameter of the cone.

Finally, for the understanding of the invention, it is necessary to consider the forces that are applied by the return roller on the strip and therefore, by reaction, the tape on the return roller.

The band 2, wrapped around the return roller 3, is a kind of V whose two walls are constituted by the strands of the band. These two strands undergo a tension force T, proportional to the weight P suspended under the return roller. As a result, throughout the area of contact of the web on the idler roll, the web exerts on the idler roll a pressure pr which applies perpendicularly to the surface of the idler roll. By adding all the pressure forces applied to each element of the contact surface, the overall force applied by the strip on the return roller is obtained.

This force is directed along the bisector of the angle created by the two strands of the strip and is directed perpendicular to the surface of the return roller.

This force can be decomposed into a force Fv parallel to the direction of the axis of rotation of the pivot 8 and a force Fh perpendicular to the direction of the axis of rotation of the pivot 8.

Thus, according to the relative position of the two strands of the band and the position and the angle of the axis of the pivot, this force can create a torque that tends to change the orientation of the roller around the axis of the axis. pivot.

This orientation will tend to move the band laterally.

By judiciously choosing the geometry of the device, it is thus possible to obtain perfect guiding of the strip, as well with a cylindrical return roller with a biconical or curved profile return roller.

As a last resort, if the stresses generated by the tape are too small to cause a rotation of the return roller sufficient to return the tape to the center of the return roller, it will come to rest on the side rollers. This bearing force will create a torque that adds to the torque described above and increase the orientation of the return roller.

In the variant shown in Figure 7, the pivot axis of the roll has been moved to the web 2a upstream in the running direction of the web, the downstream web bearing the reference number 2b. The torque bringing the band in position 2 is thus increased and the device reacts more stably and more effectively.

The same is true in the variant shown in FIG. 9, in which the tilting axis 7 makes an angle of 7 ° with the vertical, being inclined upwards in the direction of the upstream strand 2a of the strip.

Claims

1. Device comprising:

a drum (1) having an axis (xx ¹ ) of rotation and a lateral surface through which fluid can pass, and

- two flexible strips (2) passing on the lateral surface of the drum (1) at a distance from each other and each on a roller (3) fou guiding of its own, characterized in that each roller (3 ) is pivotally mounted about an axis perpendicular to the axis (4) of rotation of the roller (3) and which lies in the median plane perpendicular to the axis (4) of the roller (3).

2. Device according to claim 1, characterized in that the axis (x-x ') of the drum (1) is horizontal and the rollers (3) are below the drum

(1), the axis (7) of tilting of the roller being vertical or being inclined vertically less than 30 ° upstream with respect to the running direction of the strip (2).

3. Device according to one of the preceding claims, characterized in that each roller (3) is slidably mounted parallel to the axis (xx ¹ ) of the drum

(D •

4. Device according to one of the preceding claims, characterized in that each roller (3) is mounted vertically sliding.

5. Device according to one of the preceding claims, characterized in that each roller (3) is mounted on a carriage (9) for adjusting its position.

6. Device according to one of the preceding claims, characterized in that each roller (3) is rotatably mounted about its axis in a cradle (6) connected to the carriage (9) provided with two side rollers (10) rotatably mounted about an axis perpendicular to the band (2), the rollers (10) being arranged on either side of the roll (3).

7. Device according to one of the preceding claims, characterized in that the axis (7) of pivoting of the roller (2) passes through the middle of the axis (4) of rotation of the roller.

8. Device according to one of the preceding claims, characterized in that the vertical axis (7) of pivoting of the roller (2) is offset, the upstream side relative to the direction of movement of the strip (2), the axis (4) of rotation of the roller.

9. Device according to one of the preceding claims, characterized in that each roller (3) is pivotally mounted about an axis inclined to the vertical of less than 30 ° upstream with respect to the running direction of the strip .

10. Device according to one of claims 1 to 5, characterized in that each roller (3) is pivotally mounted about an axis perpendicular to the axis (4) of rotation of the roller (3) and which is in the median plane perpendicular to the axis (4) of the roller (3) each roller being rotatably mounted about its axis in a cradle (β ¹ ) fixed rigidly to a cylindrical axis (9 ') guided by rings (H') cylindrical.

11. Dryer comprising a hood (H) blowing, characterized in that a device according to one of the preceding claims is disposed in the hood (H), and there is provided means for passing a web to dry on the drum (1) between the two strips (2).