Method for removing water from a press roll sleeve or belt on a paper making machine

Abstract

A blade (20) for wiping water from a grooved sleeve (26) mounted on a press roll (14) in a paper making machine is adjustably mounted on the machine for movement toward and away from the sleeve (26). The wiper blade (20) is positionable against the surface of the sleeve (26) to wipe water therefrom adjacent and upstream from the nip between the sleeve (26) and a mating press roll (12).

Description

FIELD OF THE INVENTION

[0001] The present invention relates to paper making machines and, more particularly, to press rolls employed in paper making machines and, most particularly, to an apparatus for removing water from the shoe press sleeve or belt in the press section of a paper making machine.

BACKGROUND OF THE INVENTION

[0002] Paper, linerboard, and other sheet products produced from cellulose fibers are produced in a paper making machine by depositing an aqueous slurry of cellulose fiber containing various additives from a head box on a fabric screen to form a cellulose mat. Water is extracted from the slurry via vacuum boxes positioned below the fabric leaving a mat or sheet of cellulose fibers on the fabric. The mat is then transferred to a continuous press felt. The felt and mat are then run to a first pair of nip rolls, commonly referred to as a top press roll and a bottom press roll. Additional water is extracted from the mat as it passes between the top and bottom press rolls. A polyethylene sleeve or belt is mounted on one of the press rolls, typically the top press roll. Circumferential grooves are provided in the sleeve to allow the water being squeezed from the mat to travel laterally and thus extract it from the mat. Some of this water is removed from the grooves by the centrifugal force created by the spinning top press roll.

[0003] However, it has been observed that water may still puddle ahead of the nip between the press rolls. The presence of this water detracts from the performance of the press rolls. It is therefore desirable to reduce or eliminate the puddling that occurs ahead of the nip between the press rolls. Heretofore, however, the origin of the water that puddles ahead of the nip and how to remove that water have not been fully understood.

SUMMARY OF THE INVENTION

[0004] It has now been recognized that despite removal of water from the top press roll by centrifugal force, much water still remains on the surface of the rolls and particularly in the circumferential grooves in the sleeve. The present invention removes this water from the surface and the grooves by providing a means for wiping the surface of the grooved sleeve. This is accomplished with a top press roll wiper blade mounted in a bracket, which in turn is mounted on the paper making machine framework. The wiper blade has an edge that is positioned in contact with the surface of the sleeve upstream from the nip between the top and bottom press rolls. As the top press roll spins in the direction of the wiper blade and the nip, the wiper blade removes water from the surface of the sleeve and, moreover, removes water from the circumferential grooves in the sleeve. In a preferred form of the invention, the wiper blade is mounted for movement toward and away from the sleeve so as to allow for varying the pressure of the wiper blade on the sleeve and for retracting it from contact with the sleeve when it is not needed, or for repair or replacement.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

[0006] FIG. 1 is a schematic view of top and bottom press rolls in a paper making machine along with a preferred form of the wiper blades constructed in accordance with the present invention;

[0007] FIG. 2 is an enlarged side view of the wiper blade shown in FIG. 1;

[0008] FIG. 3 is a top view of a segment of the wiper blade and mounting mechanism shown in FIG. 2; and

[0009] FIG. 4 is an illustration of a top press roll, a wiper blade, and a trough constructed in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0010] Referring first to FIG. 1, the first set of press rolls 10 of a press section of a conventional paper making machine is shown in phantom. The press section of a conventional paper making machine may have more than one set of press rolls. The bottom press roll 12 is usually mounted on the paper making machine framework for rotation in a counterclockwise direction. The top press roll 14 is mounted for rotation in a clockwise direction. The top press roll is conventionally mounted so that it can be moved up and down, that is, toward and away, from the bottom press roll 12. A felt 18 forming part of the press carries a mat of cellulose fibers between the nip 16 of the top and bottom press rolls. In this view, the paper mat is omitted for purposes of simplicity. The top press roll 14 normally carries a sleeve (shown in FIG. 2 as 26) that carries a plurality of circumferential grooves that assist in extracting water from the mat of cellulose fibers being run through the nip 16 between the rolls 12 and 14. A wiper blade 20 constructed in accordance with the present invention is mounted on a blade mounting assembly 22, in turn mounted on framework 24 of the paper making machine.

[0011] Referring now to FIGS. 2 and 3, the blade 20 is positioned against the grooved sleeve 26 forming part of the top press roll 14. The blade 20 itself is an elongated member that is at least the length of the sleeve 26. A cross-sectional profile shows the blade coming to a sharp edge at the instance where it contacts the sleeve 26. The opposite edge of the blade is fixed to the mounting assembly 22 as described further below. Although the blade is shown as a straight edge, in other embodiments the blade edge may be profiled to match the groove profile in the sleeve. For grooved sleeves, the blade edge would then be provided with protrusions to match the profile of the grooves. Groove profiles may be trapezoidal, square, U-shaped, or any other profile. It is also to be appreciated that other surface patterns besides grooves may be machined on the sleeve. For example, a drilled pattern sleeve can be used in place of a grooved sleeve.

[0012] The blade assembly 22 has a first section 30 that is pivotally attached to a second section 32. Opposing flanges 34 and 36 extend from the first and second sections 30 and 32, respectively, and are coupled together by a pivot pin 38. The axis of the pivot pin 38 is substantially parallel to the rotational axis of the top press roll 14. The blade 20 is secured in the first section 30 of the bracket by conventional fasteners, such as bolts 40. The second section 32 of the blade mounting assembly is affixed to an L-shaped bracket 42 by a conventional fastener 44 such as a bolt. The L-shaped bracket 42 has an upright arm 42b and a generally horizontal arm 42a, which rests on a horizontal surface 46 forming part of the main framework 24 of the paper making machine. The L-shaped bracket 42 is mounted for movement toward and away from the press roll 14 in the direction of arrows 48. A jack screw assembly 50 is employed to adjust the position of the L-shaped bracket relative to the top press roll 14. The screw 50a is rotatably mounted in flange 52 attached to framework 24. A threaded nut 50b is affixed to bracket 42. A lock nut 53 is employed to lock the screw 50a to the nut 52b. The jack screw mechanism provides a gross positioning of the blade mounting assembly 22 relative to the press roll 14.

[0013] The entire blade assembly and captive blade extend the entire length of the top press roll 14. Only one end portion of the blade 20 and mounting assembly 22 is shown in FIG. 3. Several of the jack screw mechanisms 50 are placed at intervals along the length of the blade mounting assembly. In a preferred installation, it is preferred that the blade 20 be mounted less than about 90 degrees from the nip 16 of the top press roll 14.

[0014] The blade mounting assembly 22 also has a pair of bladders 54 and 56 mounted between the first and second sections 30 and 32 and above and below the pivot pin 38. The bladders are coextensive in length with the blade mounting assembly 22. Selective inflation of the bladders 54 and 56 allows the first section 30 to be pivoted to and fro so that the blade 20 can be moved toward and away from contact with the surface of the sleeve 26 and so that variable pressure can be applied by the leading edge blade of the wiper blade 20 against the surface of the sleeve 26. In other embodiments, the bladders 54 and 56 can be replaced with other equally suitable biasing devices, including leaf or coil springs. In a preferred embodiment, the blade mounting assembly is constructed so as to allow movement of the blade toward and away from the surface of the sleeve 26 of the top press roll 14 from one to two inches. The blade load may be adjusted so that loads on the order of 0.2 pounds per linear inch (PLI) (36 grams per cm) can be applied by the blade against the surface of the press roll sleeve 26.

[0015] In a preferred embodiment, the sleeve 26 of the top press roll is preferably comprised of polyethylene. The grooves in the sleeve 26 are conventionally machined into the surface of the polyethylene. It is also preferred that the blade 20 also be made of polyethylene. Thus, when the blade is brought into contact with the press roll sleeve 26, a minimum of frictional wear is created. Without the wiper blade of the present invention, the sleeve appears to be free of water. However, when the blade is positioned against the sleeve, substantial amounts of water are removed. Measurements have shown that on the order of an additional 66 gallons of water per minute are removed from a sleeve in the press section of a paper making machine running at an overall output of 58 tons per hour of paper. This results in substantial overall energy savings in the paper making process because the amount of water that is removed from the sleeve is not required to be evaporated from the fiber mat at a later stage.

[0016] Referring now to FIG. 4, one embodiment of the present invention is illustrated, whereby a trough 50 is located below the blade 20. The trough has a lower base 56 surrounded by peripheral walls 58, thus forming a collection basin for water that may run off from the outboard side of the blade 20. The water is indicated by arrows 52. The trough 50 has sufficient width to also collect water that may run off from the inboard side of the blade 20, said water run off being indicated by arrow 54. Lengthwise, the trough 50 is at least as long as the blade 20. The trough 50 has sufficient volume to contain the expected water collection from the sleeve surface 26 and the sleeve grooves 26a. The trough 50 is inclined, meaning that one end of the trough is at a higher relative position than its opposite and lower end. At the lower end, a pipe 60, or other suitable conduit, may be connected to channel away the collected water from the roll. The trough 50 may be positioned at any location below the blade 20. However, in one embodiment, the trough is located below the machine framework 24. In this manner, any water that is collected from the sleeve 26 and the sleeve grooves 26a may be captured and discarded from the process.

[0017] The invention may be incorporated into any paper making process that produces paperboard, linerboard, and/or any other sheet products produced from cellulose fibers that are formed into a fiber mat. The process includes depositing an aqueous slurry of cellulose fiber containing various additives from a head box onto a fabric screen to form a cellulose fiber mat. Water is extracted from the slurry via vacuum boxes positioned below the fabric screen leaving a fiber mat or fiber sheet of cellulose fibers on the fabric. Paper making machines having a press roll system often include more than one pair of nip rolls. After forming, the fiber mat or sheet is then transferred to a continuous press felt. The felt and the mat are run through the press roll system to a first pair of nip rolls. The nip rolls are also referred to as a top press roll and a bottom press roll. As mentioned previously, the press roll system can include a plurality of pairs of nip rolls. Water is further extracted from the fiber mat or sheet as it passes between the pairs of top and bottom press rolls. The present invention can be incorporated into any one top or bottom press roll or both and in one or more pairs of press rolls in the press roll system. Any roll that is provided with a surface patterned sleeve can be modified to incorporate the wiper blade in accordance with the present invention. The water is removed from the fiber mat or sheet by the wiper blade assembly in accordance with the invention, thus producing a fiber mat of reduced water content before further processing, meaning less water than would ordinarily be expected will need to be evaporated from the fiber mat or sheet.

[0018] While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention. For example, one of ordinary skill will recognize that, alternatively or in addition, a grooved sleeve can be mounted on the bottom press roll. A wiper blade constructed in accordance with the present invention can be positioned to contact such a sleeve upstream from the nip and remove water from the sleeve so positioned.

Claims

1. A method for removing water from a sleeve mounted on a press roll in a paper making machine comprising:

positioning a blade in intimate contact with the surface of said sleeve as it rotates; and

collecting the water in a trough positioned below said blade.

2. The method of claim 1 wherein the blade is positioned upstream from the nip between the sleeve and a mating press roll.

3. The method of claim 1 wherein said blade and said sleeve are comprised of the same material.

4. The method of claim 3 wherein said material comprises polyethylene.

5. The method of claim 1 further comprising:

selectively moving said blade toward and away from the surface of said sleeve.

6. A method of reducing water content in a fiber mat, comprising:

forming a fiber mat from an aqueous slurry;

passing the fiber mat through at least one press roll;

collecting water on a patterned surface of the roll; and

removing the water from the patterned surface of the roll with a blade aligned with the roll; and,

collecting the removed water and transporting the removed water away from the press roll.

7. The method of claim 6 wherein said patterned surface includes at least one of a grooves and pattern holes.

8. The method of claim 6 wherein the distance between said blade and roll is varied.

9. The method of claim 6 wherein said blade is in contact with said roll.

10. The method of claim 10 wherein the pressure made by contact between said blade and said roll is varied.

11. The method of claim 6 wherein said fiber mat passes between at least one pair of nip rolls.