GB2032578A

GB2032578A - Pressing or reversing roller for example for a double screen belt dewatering machine

Info

Publication number: GB2032578A
Application number: GB7933943A
Authority: GB
Original assignee: Andritz AG
Current assignee: Andritz AG
Priority date: 1979-10-01
Filing date: 1979-10-01
Publication date: 1980-05-08
Also published as: GB2032578B

Abstract

A pressing or reversing roller (4) for a dewatering machine has a pair of spaced screen belts (6, 6) enclosing a web (7) of material being dewatered. The roller is in two parts (4a, 4b) supported at each end by bearings (5, 5) and at the centre of its length, between the adjacent ends of the two parts (4a, 4b) by a bearing (3) which has a stationary sliding shoe or cover member (2) whose outer radius is the same as that of the roller, to provide a continuous rolling surface for the screen belts and the web. <IMAGE>

Description

SPECIFICATION Pressing or reversing roller for example for a double screen belt dewatering machine This invention relates to a pressing or reversing roller for a double screen belt dewatering machine for removing water from a suspension, in particular a pressing roller which is partly looped around by screen webs with a web of material between them, and which is constructed in several pieces over the width of the screen web, a supporting bearing being disposed at the point of contact between any two adjacent rollers.

Pressing or reversing rollers in a double screen belt dewatering machines express liquid from the suspension which is carried between two screen webs and which is gradually exposed to higher pressure.

It is known to provide pressing or reversing rollers whose length is the same as the width of the screen web, to achieve a seamless filter cake.

The same also applies to removal of water from webs of paper, since in this case the primary requirement is to establish a web of paper without noticeable joints or other impressed irregularities.

The requirement for increased web speed and improved machine efficiency calls for constant increase of the roller pressures and thus also larger roller diameters so that they can withstand the high pressures. However, since the specific pressure is in proportion to the radius, it is advantageous to keep the diameter of the rollers small in order to be able to achieve a high pressure. However, this requirement cannot be satisfied since, in the case of a wide machine, the rollers are of such length that they could sag in the middle and no longer be useable for removing water.

An arrangement of rollers is known (U.S. Patent No. 1 764 456) in which a roller is in two parts across the width of the screen web. This provides an opportunity for accommodating an additional bearing in the centre of the roller, and also for staggering the rollers in the direction of web movement. A disadvantage of this arrangement is that removal of water is no longer possible in the centre of the roller and therefore the filter cake has excessive residuai moisture content.

It is also known to dispose a plurality of individual rollers across the width of the screen web, the individual rollers being of relatively small diameter and being supported on a carrier through a plurality of bearings. For removal of water from the total width of the web in stepless fashion, the individual rollers are mounted so that they interengage. The result is a smooth web of material which is evenly freed from water in all its zones. However, this arrangement is only suitable for plane webs of material.

The invention is based on the problem of providing a pressing roller of small diameter for a wide dewatering machine, and which can be used both as a supporting roller for a plane material web and also as a reversing roller, the roller having multipie mountings and nevertheless providing stepless elimination of water from the web.

According to this invention, there is provided a pressing or reversing roller for a dewatering machine, for example a pressure roller around which screen belts with a web of material between them are partially looped, the roller being constructed in a plurality of parts over its length, at least one support bearing being disposed between two adjacent roller parts, which bearing includes a bearing member over which is a fixed cover whose outer contour is of the same radius as that of the roller parts, at least in the region of the roller around which a belt is lopped, and which constitutes a sliding shoe. Such a divided pressing roller provides for stepless removal of water from screen webs with a web of material interposed between them, over the entire width. The roller can be used not only for plane screen webs, but as a pressing roller at places where the belts are diverted.

The invention will now be explained by way of example with reference to the drawing, in which: Fig. 1 is an elevation of a pressing or reversing roller with a central mounting; and Fig. 2 shows the construction of a sliding shoe.

Fig. 1 shows a supported pressing roller 4, which is not in one piece but has roller parts 4a, 4b and is, as usual, mounted at its ends in outer bearings 5,5. It also has a central bearing comprising a bearing block 1, a bearing member 3, and a sliding shoe 2. The sliding shoe 2 has the same radius as the radius of the roller 4 and extends at least over the area around which screen belts 6 (Fig. 2) are looped. The bearing member 3 with bearings 3a is so located that it is in part incorporated into the side walls of the roller parts 4a, 4b of the roller 4. At this location for instance ball bearings are accommodated. The outer bearings 5 are connected to the frame of the machine. The upper and lower screen belts 6 with the sludge or filter cake 7 between them are passed over the pressing roller 4.

Fig. 2 shows a section through the roller 4 at the central bearing location, and illustrates that the looping angle may be as much as 180". For this angular range, the sliding shoe 2 must have the same radius as the pressing roller 4.

This construction of the pressing roller 4 permits the roller diameter to be of smaller diameter for the required high contact pressure, because there is an intermediate bearing, in this case at the centre of the roller. It is also possible to provide more than one such bearing. The sliding shoe should fill the gap between two adjacent end faces of the roller parts to achieve a stepless filter cake.

1. A pressing or reversing roller for a dewatering machine, for example a pressing roller around which screen belts with a web of material between them are partially looped, the roller being constructed in a plurality of parts over its length, at least one support bearing being disposed

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Pressing or reversing roller for example for a double screen belt dewatering machine This invention relates to a pressing or reversing roller for a double screen belt dewatering machine for removing water from a suspension, in particular a pressing roller which is partly looped around by screen webs with a web of material between them, and which is constructed in several pieces over the width of the screen web, a supporting bearing being disposed at the point of contact between any two adjacent rollers. Pressing or reversing rollers in a double screen belt dewatering machines express liquid from the suspension which is carried between two screen webs and which is gradually exposed to higher pressure. It is known to provide pressing or reversing rollers whose length is the same as the width of the screen web, to achieve a seamless filter cake. The same also applies to removal of water from webs of paper, since in this case the primary requirement is to establish a web of paper without noticeable joints or other impressed irregularities. The requirement for increased web speed and improved machine efficiency calls for constant increase of the roller pressures and thus also larger roller diameters so that they can withstand the high pressures. However, since the specific pressure is in proportion to the radius, it is advantageous to keep the diameter of the rollers small in order to be able to achieve a high pressure. However, this requirement cannot be satisfied since, in the case of a wide machine, the rollers are of such length that they could sag in the middle and no longer be useable for removing water. An arrangement of rollers is known (U.S. Patent No. 1 764 456) in which a roller is in two parts across the width of the screen web. This provides an opportunity for accommodating an additional bearing in the centre of the roller, and also for staggering the rollers in the direction of web movement. A disadvantage of this arrangement is that removal of water is no longer possible in the centre of the roller and therefore the filter cake has excessive residuai moisture content. It is also known to dispose a plurality of individual rollers across the width of the screen web, the individual rollers being of relatively small diameter and being supported on a carrier through a plurality of bearings. For removal of water from the total width of the web in stepless fashion, the individual rollers are mounted so that they interengage. The result is a smooth web of material which is evenly freed from water in all its zones. However, this arrangement is only suitable for plane webs of material. The invention is based on the problem of providing a pressing roller of small diameter for a wide dewatering machine, and which can be used both as a supporting roller for a plane material web and also as a reversing roller, the roller having multipie mountings and nevertheless providing stepless elimination of water from the web. According to this invention, there is provided a pressing or reversing roller for a dewatering machine, for example a pressure roller around which screen belts with a web of material between them are partially looped, the roller being constructed in a plurality of parts over its length, at least one support bearing being disposed between two adjacent roller parts, which bearing includes a bearing member over which is a fixed cover whose outer contour is of the same radius as that of the roller parts, at least in the region of the roller around which a belt is lopped, and which constitutes a sliding shoe. Such a divided pressing roller provides for stepless removal of water from screen webs with a web of material interposed between them, over the entire width. The roller can be used not only for plane screen webs, but as a pressing roller at places where the belts are diverted. The invention will now be explained by way of example with reference to the drawing, in which: Fig. 1 is an elevation of a pressing or reversing roller with a central mounting; and Fig. 2 shows the construction of a sliding shoe. Fig. 1 shows a supported pressing roller 4, which is not in one piece but has roller parts 4a, 4b and is, as usual, mounted at its ends in outer bearings 5,5. It also has a central bearing comprising a bearing block 1, a bearing member 3, and a sliding shoe 2. The sliding shoe 2 has the same radius as the radius of the roller 4 and extends at least over the area around which screen belts 6 (Fig. 2) are looped. The bearing member 3 with bearings 3a is so located that it is in part incorporated into the side walls of the roller parts 4a, 4b of the roller 4. At this location for instance ball bearings are accommodated. The outer bearings 5 are connected to the frame of the machine. The upper and lower screen belts 6 with the sludge or filter cake 7 between them are passed over the pressing roller 4. Fig. 2 shows a section through the roller 4 at the central bearing location, and illustrates that the looping angle may be as much as 180". For this angular range, the sliding shoe 2 must have the same radius as the pressing roller 4. This construction of the pressing roller 4 permits the roller diameter to be of smaller diameter for the required high contact pressure, because there is an intermediate bearing, in this case at the centre of the roller. It is also possible to provide more than one such bearing. The sliding shoe should fill the gap between two adjacent end faces of the roller parts to achieve a stepless filter cake. CLAIMS

1. A pressing or reversing roller for a dewatering machine, for example a pressing roller around which screen belts with a web of material between them are partially looped, the roller being constructed in a plurality of parts over its length, at least one support bearing being disposed between two adjacent roller parts, which bearing includes a bearing member over which is a fixed cover whose outer contour is of the same radius as that of the roller parts, at least in the region of the roller around which a belt is looped, and which constitutes a sliding shoe.

2. A roller according to claim 1 wherein the bearing is disposed centrally of the length of the roller.

3. A roller according to claim 1 having a plurality of bearings each disposed between adjacent ends of roller parts.

4. A pressing or reversing roller constructed and arranged substantially as herein described and shown in the drawing.

5. A dewatering machine having a roller according to any preceding claim.