US20040200592A1

US20040200592A1 - Method and device for installing a belt onto a long nip press or shoe calender

Info

Publication number: US20040200592A1
Application number: US10/413,007
Authority: US
Inventors: Bo-Christer Aberg
Original assignee: Albany International Corp
Current assignee: Albany International Corp
Priority date: 2003-04-14
Filing date: 2003-04-14
Publication date: 2004-10-14

Abstract

A method and device for installing a belt onto a long nip press or calender of the shoe type. The belt to be installed has a number of opposing flaps on each edge for securing the belt to the press. The flaps are inserted and passed through corresponding slots spaced around the rotating head ends of the press. Positioning wedge devices are slid into position on each flap and locking pins are inserted into holes in the flaps. The wedge devices effectively lock the flaps in place by securing the locking pins. The devices precisely align and tension the flaps on the press, thereby ensuring a proper installation of the belt. Once the flaps are secured to the press, the positioning devices and locking pins are removed.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the papermaking arts. More specifically, the present invention relates to a method and device for installing a belt onto a long nip press or calender of the shoe type.

2. Description of the Prior Art

During the papermaking process, a cellulosic fibrous web is formed by depositing a fibrous slurry, that is, an aqueous dispersion of cellulose fibers, onto a moving forming fabric in the forming section of a paper machine. A large amount of water is drained from the slurry through the forming fabric, leaving the cellulosic fibrous web on the surface of the forming fabric.

The newly formed cellulosic fibrous web proceeds from the forming section to a press section, which includes a series of press nips. The cellulosic fibrous web passes through the press nips supported by a press fabric, or, as is often the case, between two such press fabrics. In the press nips, the cellulosic fibrous web is subjected to compressive forces which squeeze water therefrom, and which adhere the cellulosic fibers in the web to one another to turn the cellulosic fibrous web into a paper sheet. The water is accepted by the press fabric or fabrics and, ideally, does not return to the paper sheet.

The paper sheet finally proceeds to a dryer section, which includes at least one series of rotatable dryer drums or cylinders, which are internally heated by steam. The newly formed paper sheet is directed in a serpentine path sequentially around each in the series of drums by a dryer fabric, which holds the paper sheet closely against the surfaces of the drums. The heated drums reduce the water content of the paper sheet to a desirable level through evaporation.

It should be appreciated that the forming, press and dryer fabrics all take the form of endless loops on the paper machine and function in the manner of conveyors. It should further be appreciated that paper manufacture is a continuous process which proceeds at considerable speeds. That is to say, the fibrous slurry is continuously deposited onto the forming fabric in the forming section, while a newly manufactured paper sheet is continuously wound onto rolls after it exits from the dryer section.

Traditionally, press sections have included a series of nips formed by pairs of adjacent cylindrical press rolls. In recent years, the use of long nip presses has been found to be advantageous over the use of nips formed by pairs of adjacent press rolls. This is because the longer the time a cellulosic fibrous web can be subjected to pressure in the nip, the more water can be removed there, and, consequently, the less water will remain behind in the web for removal through evaporation in the dryer section.

The present invention relates to long nip presses of the shoe type. In this variety of long nip press, the nip is formed between a cylindrical press roll and an arcuate pressure shoe. The latter has a cylindrically concave surface having a radius of curvature close to that of the cylindrical press roll. When the roll and shoe are brought into close physical proximity to one another, a nip, which can be five to ten times longer in the machine direction than one formed between two press rolls, is formed. This increases the so-called dwell time of the cellulosic fibrous web in the long nip while maintaining an adequate level of pressure per square inch of pressing force. The result of this long nip technology has been a dramatic increase in dewatering of the cellulosic fibrous web in the long nip when compared to conventional press nips on paper machines.

A long nip press of the shoe type requires a special belt, such as that taught in commonly assigned U.S. Pat. No. 6,465,074 to Fitzpatrick. This belt is designed to protect the press fabric supporting, carrying and dewatering the cellulosic fibrous web from the accelerated wear that would result from direct, sliding contact over the stationary pressure shoe. Such a belt must be provided with a smooth, impervious surface that rides, or slides, over the stationary shoe on a lubricating film of oil. The belt moves through the nip at roughly the same speed as the press fabric, thereby subjecting the press fabric to minimal amounts of rubbing against the surface of the belt.

Belts of the variety shown in U.S. Pat. No. 6,465,074 are made by impregnating a woven base fabric, which takes the form of an endless loop, with a synthetic polymeric resin. Preferably, the resin forms a coating of some predetermined thickness at least on the inner surface of the belt, so that the yarns from which the base fabric is woven may be protected from direct contact with the arcuate pressure shoe component of the long nip press. It is specifically this coating which must have a smooth, impervious surface to slide readily over the lubricated shoe and to prevent any of the lubricating oil from penetrating the structure of the belt to contaminate the press fabric, or fabrics, and cellulosic fibrous web.

In addition to being useful in a long nip press, the present invention also relates to other papermaking and paper-processing applications, such as calendering. As part of the later or last manufacturing steps, the surface of the paper may be smoothed by calendering, i.e. a belt roll calender or a shoe nip calender. The calendering process smoothes or glazes the paper or cloth by pressing it between two rolls or pressing it through a roll and a shoe to smooth, glaze or thin into a sheet. An arrangement similar to the long nip press may be employed in calendering the fibrous web. The paper to be calendered is placed under tension and is compressed or calendered to obtain the desired thickness and gloss characteristics.

The calender typically comprises at least one smooth roll that can be heated and a belt for preventing the fibrous web from contacting the shoe; to prevent lubricating oil from escaping from the shoe press; and in some cases, to support the fibrous web. The heated roll or rolls are at a temperature in a range from room temperature to 300° C., the exact temperature to be used being governed by the polymeric resin material making up the yarns of the fabric, applied compressive load, and desired paper properties. The belt comprises an endless, impervious, flexible material with lateral edges. The belt may be made of any suitable material known in the art, such as, for example, a polymer such as polyurethane or some types of nitrile rubber.

In both the long nip shoe press and shoe calender processes, the belts are subject to wear and fatigue, and must be replaced over time.

Proper installation of these belts is crucial to the runnability of the belt. A proper installation results in a balanced belt that is equally tensioned across its surface. An imperfect installation, wherein the belt is “out of round,” results in reduced belt life, increased sheet breaks, and uneven sheet dewatering or thickness profile. Often an improperly installed belt must be reworked (reinstalled) to reduce vibration and improve runnability.

Despite these drawbacks, few belts are installed in accordance with the exact manufacturer's specifications. This may be due to inexperienced personnel or simply due to a lack of time since a typical installation is time consuming. Moreover, some shoe presses are not provided with ideal installation tooling to assure a proper belt installation. Therefore, a need exists for a method and device for installing belts on shoe type presses that ensures a proper installation.

SUMMARY OF THE INVENTION

The present invention is method and device for installing belts on shoe type presses. The method provides a solution to the problem of improper belt installation. For this discussion, “press” will be used to define the shoe nip whether it is located in a press section press or in a shoe calendar.

It is therefore an object of the invention to overcome the above mentioned problems when installing a belt on shoe type presses.

The present invention is a method of installing a belt onto a long nip press in the situation where the belt has a plurality of opposing flaps on each outside edge for securing the belt to the press and the press has a corresponding plurality of slots spaced around the rotating head ends of the press. The method herein passes the flaps of the belt through the corresponding slots on the rotating head ends of the press, slides positioning wedge devices over the flaps, and inserts a locking pin through a hole in each flap. The positioning wedge devices lock into position on the locking pins and precisely align and tension the belt flaps on the press, thereby ensuring even installation of the belt.

The method may further comprise the steps of securing the flaps to the press and removing the positioning wedge devices and locking pins from the flaps after the belt is secured in position by the head rings. In the present method, the positioning wedge device has a wedge shaped body having a device flap slot which allows the device to slide over the flap. The wedge device also has a concave recess in an angled top surface for securing the locking pin inserted into each flap.

The present invention also covers a device for installing a belt onto a long nip press in the situation where the belt has a plurality of opposing flaps on each edge for securing the belt to the press and the press has a corresponding plurality of slots spaced around the rotating head ends of the press. The flaps are passed through the corresponding slots and a locking pin is inserted through a hole in each flap. The present device is a wedge shaped body having an angled top surface, a flat bottom surface, a point end, a vertical end surface, and wedge shaped front and back surfaces. The angled top surface connects with the flat bottom surface at the point end. A device flap slot extends from the angled top surface through to the flat bottom surface and extends from the point end into the wedge shaped body for a distance at least equal to the width of the flaps. A concave recess in the angled top surface secures the locking pin inserted into each flap. This concave recess is located a predetermined distance from the flat bottom surface.

The present device is slid over the flap such that the flap passes through the device flap slot and the inserted locking pin is secured in the concave recess of the angled top surface. In this manner, the secured locking pin is positioned at the predetermined distance from the rotating head ends of the press so that the flap and consequently the belt is properly tensioned for installation. A plurality of the devices are used corresponding to the plurality of flaps. The device is removed once the belt is finally secured to the press and is reusable.

Other aspects of the present invention include that the long nip press herein may be a shoe calender. The belt may have any number of flaps, but preferably has twelve (12) opposing flaps on each edge. The hole in each flap preferably has a grommet.

The present invention will now be described in more complete detail with frequent reference being made to the drawing figures, which are identified below.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the invention, reference is made to the following description and accompanying drawings, in which: [0025]
FIG. 1 is a side cross-sectional view of a long nip press; [0026]
FIG. 2 is a side cross-sectional diagram showing an exemplary layout for flap slots on the end of a long nip press; [0027]
FIG. 3 is a side cross-sectional close-up view of an exemplary slot on the rotating head segment of a long nip press; [0028]
FIG. 4 is a side cross-sectional close-up view of the exemplary slot of FIG. 3 having a belt flap inserted therethrough and annotated to illustrate insertion of a locking pin through a hole in the inserted flap; [0029]
FIG. 5 is a diagram illustrating use of a positioning device for tensioning an inserted belt flap in accordance with the present invention; [0030]
FIG. 6 is a side view of a positioning device in accordance with the present invention; [0031]
FIG. 7 is a side cross-sectional close-up view showing the positioning device of FIG. 6 being applied to a flap; [0032]
FIG. 8 is an off-angle view of the present device as shown in FIG. 7; [0033]
FIG. 9 is a side view of a positioning device in accordance with the present invention in a locked position on a belt flap; and [0034]
FIG. 10 is an angled top view of the positioning device shown in FIG. 9 in a locked position on a belt flap.[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to a method and device for installing a belt onto a long nip press or calender of the shoe type. FIG. 1 is a side cross-sectional view of an exemplary long nip press which is applicable to the present invention. Such a press may be used to press excess water during processing of a paper product on a paper machine. The press nip [0036] 10 is defined by a smooth cylindrical press roll 12 and an arcuate pressure shoe 14. The arcuate pressure shoe 14 has about the same radius of curvature as the cylindrical press roll 12. The distance between the cylindrical press roll 12 and the arcuate pressure shoe 14 may be adjusted by hydraulic means operatively attached to arcuate pressure shoe 14 to control the loading of the nip 10. Smooth cylindrical press roll 12 may be a controlled crown roll matched to the arcuate pressure shoe 14 to obtain a level cross-machine nip profile.
Long nip [0037] press belt 16 extends in a closed loop through nip 10, separating cylindrical press roll 12 from arcuate pressure shoe 14. A press fabric 18 and a cellulosic fibrous web 20 being processed into a paper sheet pass together through nip 10 as indicated by the arrows in FIG. 1. Cellulosic fibrous web 20 is supported by press fabric 18 and comes into direct contact with smooth cylindrical press roll 12 in nip 10. Cellulosic fibrous web 20 and press fabric 18 proceed through the nip 10 as indicated by the arrows. Long nip press belt 16, also moving through press nip 10 as indicated by the arrows, that is, counterclockwise as depicted in FIG. 1, prevents press fabric 18 from directly sliding against arcuate pressure shoe 14, and slides thereover on a lubricating film of oil. Long nip press belt 16, accordingly, must be impermeable to oil, so that press fabric 18 and cellulosic fibrous web 20 will not be contaminated thereby.
Long nip press belts, for the closed loop press types, depending on the size requirements of the long nip presses on which they are installed, have lengths from roughly 10 to 20 feet (approximately 3 to 6 meters), measured longitudinally around their endless-loop forms, and widths from roughly 100 to 450 inches (approximately 250 to 1125 centimeters), measured transversely across those forms. [0038]
The long nip press belts include a base support structure generally taking the form of an endless loop having an inner surface, an outer surface, a longitudinal direction and a transverse direction. The base support structure is formed from a plurality of elements coated with a first polymeric resin material, which may be, for example, a polyurethane resin material. When the elements are yarns, the yarns may be coated by any of the methods so used by those of ordinary skill in the art, such as dip coating and crosshead extrusion. The coated yarns may also be given their coating after the base support structure has been assembled by weaving, knitting, braiding or the like. [0039]
The yarns themselves, coated and uncoated, may be of any of the yarn varieties used by those of ordinary skill in the art to produce paper machine clothing. Monofilament yarns are preferred, although plied monofilament, multifilament, plied multifilament, knitted and braided yarns may also be used. The yarns may be of any of the polymeric resins from which yarns for paper machine clothing are commonly extruded or produced, such as polyamide, polyester, polyetheretherketone (PEEK), polyaramid (for example, KEVLAR® and NOMEX®) and polyolefin resins. [0040]
The base fabric of the belt may also include a staple fiber batt needled or otherwise entangled into the woven structure thereof. Such a staple fiber batt may comprise fibers of a polymeric resin material, such as polyamide or polyester, or of any of the other materials commonly used for this purpose by those in the paper machine clothing industry. The fibers may, in addition, be coated with the same first polymeric resin material coating the yarns, or may themselves be made of the first polymeric resin material, to improve the bond to be formed with the impregnating material. [0041]
The present method requires the belt to be installed to have a plurality of opposing flaps on each edge for securing the belt to the press. Currently, belts have been custom manufactured with flaps which are suitable for use in the present invention. The flaps are preferably manufactured as integral elements of the belt; i.e. the flaps and belt are produced as one piece. These flaps are preferably manufactured with a grommeted hole for insertion of a positioning/locking pin. [0042]
Further, the press must also have at least a corresponding number of slots through the rotating head ends of the press to pass these flaps through the head. Preferably, the flaps and slots are evenly spaced to ensure an even distribution of force during installation. [0043]
An exemplary embodiment of the present invention calls for the use of 12 flaps (or tabs) on each belt edge and then using one positioning device on each flap to secure that the edge of the belt body is in contact with the inside of the clamping segments. However, the present method may be used with any number of flaps, although obviously the more flaps used, the more even the belt installation will be. (Note that 12 flaps corresponds to the number of slots on the rotating head of the long nip press machine shown in the following figures.) [0044]
FIG. 2 is a side cross-sectional diagram showing the exemplary layout for flap slots on the end of a long nip press in accordance with the present invention. Each rotating [0045] head end 200 of the press has a number of preferably equally spaced slots 210 passing through the head. The belt 220 is typically installed as a cylindrical roll cover on the press and fastened on each end to the rotating head. (Only a portion of the belt is shown in FIG. 2).
In the present invention, the belt has a number of [0046] flaps 230 on each end which correspond to the slots 210 in the head. FIG. 3 is a side cross-sectional close-up view of an exemplary slot on the rotating head segment of a long nip press.
In this example, the 12 flaps (tabs) in each side of the belt are fit into the corresponding 12 slots already manufactured into each rotating shoe press head. [0047]
FIG. 4 is a side cross-sectional close-up view of the exemplary slot of FIG. 3 having a belt flap inserted therethrough and annotated to illustrate insertion of a positioning (or fastening/locking) [0048] pin 300 into a hole in the inserted flap. In this manner, the flaps are passed through the slots and secured.
In other words, the flaps ensure the total width of the belt is equally supported around the circumference of the rotating head. This is especially relevant when a belt is larger than the size of the head. [0049]
Even with the use of these flaps, care must be taken that the flaps are properly positioned and tensioned within the slots to ensure a proper installation. As discussed previously, proper installation of these belts is crucial to the runnability of the belt. A proper installation results in a trued and balanced belt that is equally tensioned across its surface. An imperfect installation, wherein the belt is “out of round,” results in reduced belt life, increased sheet breaks, and uneven sheet dewatering. Often an improperly installed belt must be reworked to reduce vibration and improve runnability. [0050]
Accordingly, the present invention uses a positioning device (or tool) to properly position and tension the flaps within the slots before the belt is secured to the head. The use of this device, as described below, ensures an equal cross-machine direction (CD) load when the rotating head pressure (CD tensioning device) tensions the belt. [0051]
FIG. 5 is a diagram illustrating use of this positioning device or [0052] tool 500 for tensioning an inserted belt flap in accordance with the present invention. In FIG. 5, a flap 230 of the belt 220 has been inserted through a slot 210 in the rotating press head 200. The present device 500 is a wedge shaped block having a slot 510 extending through the block. FIG. 6 is a side view of the positioning device. Along the angled side of the wedge there is a concave recess 520 which is sized to mate with the pin 300. The device 500 is slid into position with the flap extending through the slot and a pin 300 has been inserted into a hole in the flap. FIG. 7 is a side cross-sectional close-up view showing the positioning device of FIG. 6 being applied to a flap. FIG. 8 is an off-angle view of the present device as shown in FIG. 7. The pin in the flap slides up the angled side of the wedge, thereby tensioning the flap and belt, until it slips securely in place in the concave recess. FIG. 9 is a side view of the device in position on a flap with the pin secured in position by the concave recess. FIG. 10 is an angled top view of the positioning device shown in FIG. 9. The concave recess is precisely positioned along the angle so that the pin ends up a precise distance from the surface of the press head. This precise distance is calculated to result in a predetermined tension on the flap.
In this exemplary embodiment, a total of 24 positioning devices would be needed; one for each flap. Once all the flaps have been properly tensioned using the present devices, the belt is secured by any of the commonly used clamping means for securing the belt to the press. The positioning devices and locking pins are then removed from the flaps and the installation is complete. These devices can be easily fabricated from any suitably rigid material and are reusable. [0053]
Installation with the present device/tool is significantly easier and faster for the installer and the rotational shape of the belt is improved for all shoe press/shoe calender applications regardless of the number of flaps/tabs. [0054]
Advantages of the present invention include improved belt shape (roundness in use), improved runnability, reduced vibration, and fewer reworked belt installations. The present invention also eases the tolerancing requirements for variation in the machine direction (MD) size of the belts in order to properly fit the belt without wobble. [0055]
The present method is also advantageous for use when a belt to be installed has a circumference which does not match the circumference of the press. If a belt is larger than the press, the excess portion of the belt may become bunched at one or more locations around the press. The present method solves this problem by allowing for even distribution of the excess around the circumference of the belt. The present method also allows for even installation when a belt is slightly smaller than the press, which commonly occurs from shrinkage in the belt after manufacture. Currently such belts are very difficult to install and must essentially be forced into position on the press. This often results in irregularly stressed and sometimes damaged belts. Accordingly, the flaps and device of the present method can be used as a force leveling mechanism to evenly stretch the belt onto the press to ensure proper installation. [0056]
Furthermore, the teachings of the present invention are equally applicable to the installation of calender belts for a shoe calender. The calendering process is typically used to modify characteristics of paper including the permeability, caliper, and smoothness. Although calenders typically involve at least two smooth rolls (at least one of which can be heated), the calender may use a shoe arrangement, such as a shoe nip calender, as in the long nip press, such that a roll presses the fibrous paper web against the belt over the shoe. [0057]
Modifications to the above would be obvious to those of ordinary skill in the art, but would not bring the invention so modified beyond the scope of the present invention. The claims to follow should be construed to cover such situations. [0058]

Claims

What is claimed is:

1. A method of installing a belt onto a long nip press; the belt having a plurality of opposing flaps on each edge for securing the belt to the press; the press having a corresponding plurality of slots spaced around rotating head ends of the press; comprising the steps of:

passing the flaps of the belt through the corresponding slots on the rotating head ends of the press;

sliding positioning wedge devices over the flaps; and

inserting a locking pin through a hole in each flap; the positioning wedge devices locking into position on the locking pins and precisely aligning and tensioning the flaps on the press, thereby ensuring even installation of the belt.

2. The method of claim 1, further comprising the steps of:

securing the flaps to the press; and

removing the positioning wedge devices and locking pins from the flaps.

3. The method of claim 1, wherein the positioning wedge device has a wedge shaped body having a device flap slot which allows the device to slide over the flap such that the flap passes through the device flap slot; the wedge device having a concave recess in an angled top surface for securing the locking pin inserted into each flap.

4. The method of claim 1, wherein the long nip press is a shoe press or a shoe calender.

5. The method of claim 1, wherein the belt has twelve (12) opposing flaps on each edge.

6. The method of claim 1, wherein the hole in each flap has a grommet.

7. A device for installing a belt onto a long nip press, comprising:

a wedge shaped body having an angled top surface, a flat bottom surface, a point end, a vertical end surface, and wedge shaped front and back surfaces; the angled top surface connecting with the flat bottom surface at the point end;

a device flap slot extending from the angled top surface through to the flat bottom surface and extending from the point end into the wedge shaped body for a distance at least equal to a width of each of a plurality of opposing flaps on each edge of the belt; and

a concave recess in the angled top surface for securing a locking pin inserted into each flap; the concave recess located a predetermined distance from the flat bottom surface.

8. The device of claim 7, whereby the device is slid over the flap such that the flap passes through the device flap slot and the inserted locking pin is secured in the concave recess of the angled top surface.

9. The device of claim 8, whereby the secured locking pin is positioned at the predetermined distance from the rotating head ends of the press so that the flap is properly tensioned for installation.

10. The device of claim 7, wherein a plurality of the devices are used corresponding to said plurality of flaps.

11. The device of claim 7, wherein the device is removed once the flap is secured to the press; the device being reusable.

12. The device of claim 7, wherein the long nip press is a shoe calender.

13. The device of claim 7, wherein the belt has twelve (12) opposing flaps on each edge.

14. The device of claim 7, wherein the hole in each flap has a grommet.