FI92738C - Belt - Google Patents

Description

92738 ΗΙΗΝΑ

The invention relates to a belt as defined in the preamble of claim 1.

The invention relates to a mechanism for removing water from a web of material and more particularly from a fibrous web from which a paper product is made in a paper machine. In particular, the invention provides a tight belt designed for use with a paper machine long nip press.

In the papermaking process, a fibrous web is formed on a forming wire by placing it on a fibrous pulp. A large amount of water is removed from the pulp in this process, after which the newly formed web 15 continues into the press section. The press section includes a series of press nips in which pressing forces are applied to the fibrous web by removing water therefrom. Eventually, the web continues to a drying section that includes heated drying drums around which the web is guided. Lam-20 measurable dryers reduce the water content of the web to the desired level by evaporation.

Increased energy costs have made it increasingly desirable to remove as much water from the web as possible before it enters the drying section. Drying drums are often heated internally by steam and the cost can be significant, especially when large amounts of water need to be removed from the web.

Traditionally, press sections consist of a series of nips formed by adjacent press rolls of cylinders. Recently, the use of extended press nips has been found to be advantageous over nips consisting of pairs of adjacent rollers. The longer the web is subjected to compression in the nip, the more water can be removed therefrom and further less water remains in the web to be removed by evaporation in the drying section.

The present invention relates to a shoe-type longitudinal ---- ___________ 92738 2 cam nip press. In this type of long nip press, the nip is formed between a cylindrical press roll and a curved press shoe. The latter has a cylindrical concave surface with a radius of curvature close to the radius of curvature of the cylindrical press roll.

When the roll and the shoe are brought into close contact, a nip is formed, which may be five to ten times longer in the machine direction than the nip formed between the two press rolls. This increases the residence time of the fibrous web 10 in the extended nip, maintaining the same compression level per unit area as in the twin roll press. As a result of this new long nip technology, there has been a significant increase in the dewatering of the fibrous web in the long nip compared to traditional nips in paper machines.

A shoe-type long nip press requires a special belt, such as that described in Canadian Patent 1,188,556. Such a belt is to be made into a flat impermeable surface which passes or slides over a fixed shoe over a lubricating film 25 or oil. The belt moves through the nip at approximately the same speed as the press fabric, so that the press fabric is subjected to as little abrasion against the solid components as possible.

The normal design of a long nip press involves the use of two press fabrics. The components of the nip can be listed in the following order: a grooved cylindrical press roll, a first press fabric, a fibrous web or a forming paper web, a second press fabric, a special belt, a lubricating film, and a curved press shoe.

All long nip presses currently in commercial use have the structure described above.

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However, this so-called two-felt long nip press is limited to certain types of paper grades.

When extending the use of the long nip press to fine-grained paper grades and newsprint, it is necessary to develop a single-felt long nip press.

In a single-felt long nip press, the components of the nip can be listed in the following order: a flat cylindrical press roll, a fibrous web or a resulting paper web, a press fabric, a special belt, a lubricating film, and a curved press shoe.

In a two-felt long nip press, water compressed from the fibrous web can enter either of the press fabrics as well as the grooves of the cylindrical press roll. In a single-felt long nip press-15, two of these water constraints have been removed. It has only one felt, and since the fibrous web directly contacts the cylindrical press roll, the roll must have a smooth surface. Of course, the removal of this temporary water reservoir must be compensated if the single-felt long nip press 20 is ever to be used extensively. It is absolutely essential that the nip of the press has grooves so that the water to be pressed from the paper web into the single-felt long nip press has space.

25 Two approaches have been used to achieve a satisfactory solution to this problem. Canadian Patent 1,190,779 discloses a long nip press belt with grooves on the belt side. These grooves are formed by the fabric of the base fabric and the unsaturated part of the felt side of the belt 30 and form a place where liquid can pass through the press fabric of the fibrous web and the special felt as it passes through the nip.

Another approach is disclosed in U.S. Patents 4,559,258 and 4,643,916. These discloses a long nip press belt with grooves on the felt side for storing water compressed from a fibrous web.

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When these two approaches are mainly aimed at achieving a solution to the dewatering problems in a single-felt long nip press, it has been found that the use of both women's felts in a double-felt long nip press results in increased re-wetting.

In practice, however, it has been found that satisfactorily grooved long nip press belts cannot be made for commercial use. All attempts to make such a structure have resulted in a failed product due to groove delamination and / or groove breakage. The invention relates to a special belt in a long nip press which is not prone to delamination.

Despite the above-mentioned problems, special long nip press belts with grooves in a polyurethane coated surface represent good dewatering properties when used in long nip presses. The invention is a belt for a long nip press which is not prone to these problems due to its physical structure and can be considered as an improvement on the belt disclosed in Canadian Patent 1,190,779. The belt according to the invention is characterized by what is stated in claim 1.

Tate's invention is a belt for use in a long * nip press on a paper machine to remove water from a fibrous web from which some kind of paper product is made. The strap includes an endless loop-shaped underlay with an inner surface and an outer surface. The inner surface 30 is coated with a polymeric resin which partially impregnates the substrate; i.e., the coating does not completely penetrate the structure of the underlay. The coating makes the base fabric impermeable to liquids, it is even and of constant thickness. The coated side of the belt is in contact with the curved press shoe when using the long nipple crosser. More specifically, it slides on the surface of the curved press shoe against the film or lubricating oil.

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The outer surface or half of the felt of the belt is different from that of Canadian Patent 1,190,779. It is characterized by a plurality of flat monofilament yarns suitably attached to the base fabric. The flat monofilament yarns 5 form channels between them to receive water compressed from the fibrous web. The channels formed in this way are not crushed by nip compression, as is the case with prior art belts. Likewise, delamination of the grooves is not a problem because the flat monofilament-10 yarns are woven into the structure of the base fabric.

The invention will now be described in detail with reference to the accompanying drawings, in which Figure 1 is a side sectional view of a long nip on which a belt according to the invention is designed, Figure 2 is a partially sectioned side view of the nip of Figure 1, Figure 3 is a plan view of a belt according to the invention. Figure 4 is a sectional view of the belt according to the invention of Figure 3 taken along line 4-4 and Figure 5 is a sectional view of the belt according to the invention of Figure 3 taken along line 5-5.

Figures 1 and 2 show a single felt long nip press for removing water from a fibrous web from which a paper product is made in a paper machine. The nip 10 of the press-25 is formed by a flat cylindrical press roller 12, a curved press shoe 14 and a belt 16 according to the invention arranged so as to rest against the cylindrical press roll 12. The radius of curvature of the curved press shoe 14 is approximately equal to that of the cylindrical press roll 12. The distance between the cylindrical press roll and the curved press shoe 14 can be controlled by means of conventional tank devices 18, not shown. 18 can also be used to provide the desired compression to the curved press shoe 14.

It should be noted that the cylindrical press roll 12 and the curved press shoe 14 described above and shown in Figures 1 and 2 92738 6 are conventional prior art.

Figures 1 and 2 also show a press fabric 15 of a paper machine 5 and a fibrous web 17 from which a paper web is made. The movements of the belt 16, the press fabric 15, the fibrous web 17 and the cylindrical press roll 12 are shown in Figure 1 by arrows.

Figure 3 shows a plan view of a belt 16 according to the invention 10. It has an outer surface 19 and an inner surface 20. The belt 16 comprises an endless loop-shaped underlay. The base fabric can be made or woven in pMåtto-mass form or it can be made in planar form, e.g. as flat weave, and joined to the endless form by a seam.

The endless sealing is preferably performed before the inner surface of the belt 16 is coated with a polymeric resin.

An embodiment of the belt 16 is shown in Figure 4, which is a sectional view of Figure 3 taken along line 20 4-4. Here the cut is in the machine direction, i.e. around the 16 loops of the belt. The outer surface 19 and the inner surface 20 are generally marked. The belt 16 includes a multilayer underlay 22 woven from machine direction yarns 24 and transverse yarns 26 impregnated 25 with an inner resin 20 of a polymeric resin, such as polyurethane, to keep it impermeable to liquids, including lubricating oil. The inner surface 20 is on the so-called shoe side of the belt 16.

The backing fabric 22 is sufficiently open to allow saturation to eliminate the possibility of the formation of unwanted cracks in the belt 16 on the shoe side, with the inner surface 20 against the curved press shoe 14. The slits are highly undesirable because they would allow the passage of lubricating oil used between the belt 16 and the curved press-35 tincture 14 through the belt 16 to contaminate the press felt and the fibrous web.

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After polymer impregnation and coating, the inside 20 of the belt 16 can be ground evenly and given a uniform thickness to the belt in lubricated sliding contact with the curved press shoe 14 in the press nip 10.

The outer side 19 of the belt 16 is characterized by machine-running flat monofilament yarns 28. These are attached to the base fabric 22 by random transverse yarns 30. It will be appreciated that the representations of Figures 4 and 5 are somewhat exaggerated on the scale of the invention.

The purpose of the flat monofilament yarns 28 can be more clearly explained with reference to Figure 5, which is a sectional view of Figure 3 taken along line 5-5. Thus, it is a cross-section of the machine, i.e. across the belt loop. The components of component 15 have the same reference numeral as in Figure 4. The flat monofilament yarns 28 are shown in cross-sections and are attached to the base fabric 22 by occasional weaving together with the cross-machine direction yarns 30. 20 channels 32 are formed between the flat monofilament yarns 28 to remove water compressed from the fibrous web in the nip 10. Preferably, the flat monofilament yarns 28 are arranged to form three to four channels at 32 centimeters. Channels 32 with a width of 0.6 mm and a depth of 2.5 mm have been found to give good results.

When Figures 4 and 5 show machine direction flat monofilaments 28, which is a preferred alternative, they can also be transverse with good results.

As shown in Figures 4 and 5, the flat single fiber yarns 28 are preferably arranged to have long strands due to occasional interweaving with the transverse yarns 30 to form channels or slots between the flat monofilament yarns 28 into which water can flow. The same 35 may occur in the case where the flat monofilament yarns 28 are transverse.

In general, the belt 16 8 92738 of the invention can be dewatered outside the nip 10 much more easily than the belt disclosed in Canadian Patent 1,190,779. TMsså the felt side of the web tends to pidåttamåån wets, does not occur in the belt of the keksinndn 5 16 32 channels.

It will be readily apparent to those skilled in the art that various applications will be apparent within the scope of the appended claims.

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Claims (9)

92738 A belt (16) for use in a flat nip press to remove water from a cultured nip (17), the long nip press having a cylindrical nozzle roll (12) and a curved press shoe (14) which together form a nipple (s) 10 through the nip (10) together with the press felt (15) between the press felt (15) and the curved press-10 tongue (14) for supporting and conveying the fibrous web (17) to be dried, and the belt (16) comprises - a ribless loop shape a base fabric (22) having an inner surface (20) and an outer surface (19), the longitudinal direction of which is around the end loop and the transverse direction is in the transverse direction of the end loop, - a polymeric resin coating (40) on the inner surface (20) of the base fabric (22), the coating (40) being partially absorbed and penetrating the substrate (22) and rendering the substrate (22) liquid impermeable, the coating (40) being smooth and of a belt (16) of uniform thickness, characterized in that a plurality of flat monofilament yarns (28) are arranged on the outer surface (19) of the base fabric (22), the flat monofilament yarns 25 (28) forming channels (32) in their molds, and that the means (30) are arranged ) attaching a plurality of flat monofilament yarns (28) to the outer surface (19) of the base fabric (22). Belt according to Claim 1, characterized in that the polymeric resin is polyurethane. Belt according to Claim 1, characterized in that the outer surface (19) has three to four channels (32) per centimeter. Belt according to Claim 1, characterized in that the channels (32) are 0.6 mm wide and 2.5 mm deep. A belt according to claim 1, 92738, characterized in that the flat monofilament yarns (28) slide in the base fabric (22) in the longitudinal direction and form the channels (32) in the longitudinal direction. A belt according to claim 1, characterized in that the flat monofilament yarns (28) are located in the base fabric (22) in the transverse direction and form the channels (32) in the transverse direction. A belt according to claim 1, characterized in that the base fabric (22) is woven from 10 longitudinal (24) and transverse (26) yarns, and said means (30) for fastening a plurality of flat monofilament yarns (28) consist of at least one longitudinal yarn. interweaving the yarn (24) with the transverse yarns (26) 15. Belt according to Claim 7, characterized in that the base fabric (22) is made of a multilayer fabric. A belt according to claim 7, characterized in that the means (30) for fastening the plurality of flat monofilament yarns (28) comprise long runs so that water compressed from the fibrous web can flow along the channels (32). II 92738