Abstract
A dewatering box cover including a main body having a leading edge, a trailing edge opposite the leading edge, a first side edge, a second side edge opposite the first side edge, a top surface, and a bottom surface and a plurality of sets of holes formed within the main body. The holes within each set are aligned with one another along an imaginary line that is angled from 30° to 70° relative to horizontal and the holes extend downwards from the top surface of the main body towards the bottom surface of the main body at an angle of 20° to 45° relative to vertical.
Claims
1. A dewatering box cover comprising: a main body having a leading edge, a trailing edge opposite the leading edge, a first side edge, a second side edge opposite the first side edge, a top surface, and a bottom surface; and a plurality of sets of holes formed within the main body, wherein the holes within each set are aligned with one another along an imaginary line that is angled from 30° to 70° relative to horizontal and the holes extend downwards from the top surface of the main body towards the bottom surface of the main body at an angle of 20° to 45° relative to vertical.
2. The dewatering box cover of claim 1, wherein the holes within each set are aligned with one another along an imaginary line that is angled 39° relative to horizontal.
3. The dewatering box cover of claim 1, wherein the main body has a length measured from the first side edge to the second side edge that is 1.0 meter to 8 meter.
4. The dewatering box cover of claim 1, wherein the main body has a width measured from the leading edge to the trailing edge that is 130 mm to 170 mm.
5. The dewatering box cover of claim 1, wherein the holes provide the dewatering box cover with a total open area of 15,000 mm.sup.2 to 500,000 mm.sup.2.
6. The dewatering box cover of claim 1, wherein the holes provide the dewatering box cover with a total open area of 160,000 mm.sup.2.
7. The dewatering box cover of claim 1, wherein the cover is configured for attachment to a dewatering box to which vacuum is applied.
8. The dewatering box cover of claim 1, wherein the plurality of sets of holes comprise at least five sets of holes.
9. The dewatering box of cover of claim 1, wherein the plurality of sets of holes comprise of at least fifteen sets of holes.
10. A method of dewatering a fabric used in a papermaking process, comprising the steps of: passing the fabric traveling in a machine direction over a dewatering box, wherein the dewatering box comprises a dewatering box cover, and the dewatering box cover comprises: a main body having a leading edge, a trailing edge opposite the leading edge, a first side edge, a second side edge opposite the first side edge, a top surface, and a bottom surface; and a plurality of sets of holes formed within the main body, wherein the holes within each set are aligned with one another along an imaginary line that is angled from 30° to 70° relative to horizontal and the holes extend downwards from the top surface of the main body towards the bottom surface of the main body at an angle of 20° to 45° relative to vertical, and wherein the dewatering box cover is positioned so that the leading edge of the dewatering box cover is upstream in the machine direction relative to the trailing edge.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] The present invention will be better understood when read in conjunction with the appended drawings. It should be understood, however, that the invention is not limited to the precise arrangements shown. In the drawings:
[0040] FIG. 1 is a top view of a dewatering box cover according to an exemplary embodiment of the invention;
[0041] FIG. 2 is a perspective view of the dewatering box cover of FIG. 1;
[0042] FIG. 3 is a side view of the dewatering box cover of FIG. 1;
[0043] FIG. 4 is a cross-section view along line A-A of FIG. 3;
[0044] FIG. 5 is a representational diagram showing angles of a cut made through a vacuum box cover so as to form a slot in the cover in accordance with an exemplary embodiment of the present invention.
[0045] FIG. 6 is a perspective view of a dewatering box cover according to an exemplary embodiment of the present invention;
[0046] FIG. 7 is a top view of the dewatering box cover of FIG. 6;
[0047] FIG. 8 is a side view of the dewatering box cover of FIG. 6;
[0048] FIG. 9 is a cross-section view along line A-A of FIG. 8; and
[0049] FIG. 10 is a cross-section view showing a hole that partially extends through the thickness of the cover at 30° relative to vertical, then transitions to 90° through the remainder of the cover.
DETAILED DESCRIPTION
[0050] Referring to FIG. 1, a vacuum dewatering box cover, generally designated by reference number 10, in accordance with an exemplary embodiment of the present invention is shown. The cover 10 may be used on a vacuum dewatering box used to remove moisture from a papermaking fabric or felt. Such vacuum dewatering boxes may be used as a suction box in the forming section of the papermaking machine, or may be used as a Uhle box in the press section, through air drier (“TAD”) section or under fabric cleaning showers. Vacuum dewatering boxes can also be used in connection with other types of dewatering or moisture removing operations, and is not limited solely to the preferred use in a papermaking machine.
[0051] The cover 10 includes a main body 12 having a leading edge 14, a trailing edge 16, a first side edge 18 and a second side edge 20. The leading and trailing edges 14 and 16 extend along the length of the cover 10 and the first and second side edges 18 and 20 extend along the width of the cover 10. In exemplary embodiments, the length of the main body 12 may be in the range of 3 m to 8 m and the width of the main body may be in the range of 120 mm to 160 mm. In a specific exemplary embodiment, the length is 5.6 m and the width is 140 mm.
[0052] A “v” shaped center slot 2 is formed at or near the center of the top surface of the cover 10 (e.g., at or near a center line of the main body 12 that extends perpendicular to the length of the main body 12). Additional slots 1 are formed in the cover 10 adjacent to the center slot at both sides of the center slot 2. In exemplary embodiments, the center slot 2 and the additional slots 1 are formed by cutting into the material used to form the cover 10. In this regard, FIG. 5 is a representational diagram showing the angles of the Cut C, including an angle A relative to the horizontal plane X-Y and an angle B relative to the vertical plane X-Z. The angle A may be referred to as the angle relative to horizontal and the angle B may be referred to as the angle relative to vertical. The arms of the center slot 2 and the slots 1 are arranged so that the angle A (i.e., the angle relative to horizontal) is 41°, yielding a 39° projected angle on the top surface. This angle may vary based on the overall size of the vacuum opening. For example, the angle A may be 36.95° instead of 41°, or some other suitable value. As depicted by reference number 5 in FIG. 4, the slots extend through the thickness of the cover 10 (e.g., from the top surface to a bottom surface of the cover 10) so that the angle B (i.e., the angle relative to vertical) is 30°. It should be appreciated that the orientations of the slots 1 and 2 are not limited to the angles mentioned herein, and in other exemplary embodiments the angle A may be greater or less than 39° (e.g., 45°) and/or the angle B may be greater or less than 30°.
[0053] Without being bound by theory, it is believed that as a fabric passes over the top surface of the cover 10, the angled arrangement of the slots 1, 2 results in forces within the plane of the fabric that stretch the fabric, which in turn results in opening of the pores in the fabric. This mechanism provides for easier and more efficient removal of water from the fabric.
[0054] In exemplary embodiments, the slots 1, 2 may be angled all in one direction or may be angled in differing directions (e.g., bi-directional). The slots 1, 2 may be any shape including, but not limited to, elliptical, rectangular, trapezoidal, and the like.
[0055] In exemplary embodiments, holes 3 may be drilled through the cover 10 to accommodate screws that attach the cover to the dewatering box. As shown in FIGS. 2 and 4, the bottom surface of the vacuum dewatering box cover 10 may have an arcuate shape 6 to accommodate the vacuum box to which it is attached.
[0056] A fabric travels in direction 7 from the leading edge 14 to the trailing edge 16 of the dewatering box cover 10 such that the underside of the papermaking fabric is drawn downwardly against the top surface of the cover 10 by the vacuum force acting through the slots 1, 2 in the cover 10. In this regard, the vacuum dewatering box 10 generally extends in the cross direction and the papermaking fabric travels in the machine direction.
[0057] The cover 10 is preferably formed of a wear resistant surface material or coating. The wear-resistant material may be, for example, metal such as stainless steel or the like, a plastic such as high-density polyethylene or high-density polypropylene, or a ceramic material such as silicon nitride or aluminum oxide, or combinations thereof, to name a few. It should be appreciated that the material used to form the cover 10 is not limited to the examples provided herein, and other materials may be utilized which have a high wear resistance and smooth surface characteristics. The dewatering box cover 10 may be mounted to the vacuum box using an adhesive or potting compound, drilled holes and screws, or other mechanical methods such as a T bar or dovetail joint.
[0058] As shown in FIG. 1, in accordance with an exemplary embodiment, at least one generally longitudinally oriented slot 1 or hole is cut or drilled with an angle B of 30° into the cover 10. The shape and size of the at least one slot is determined by the desired open area for the permeability of the fabric and the amount of vacuum used. The permeability of a conventional fabric typically ranges from 200 to 700 cubic feet per minute. The cover 10 may have a rectangular shape, with the slots arranged equally spaced apart. In exemplary embodiments, the spacing, size and/or shapes of the slots may vary. For example, and without limitation, the slots may be 45 mm long and 17 mm wide. The minimum number of slots required may be a function of the amount of vacuum needed (open area) and the cover geometry. The angle A of the slots and their size may be optimized to assure acceptable open area and an outward driving force to spread the fabric. The vertical angle B of the slots may be optimized to utilize centrifugal force from the water being released from a moving fabric. In this way, the leading edge of every slot acts as a foil to remove water
[0059] The following Example illustrates advantages of the present invention. The dimensions, process parameters and other values set forth in the Example are not intended to be limiting to the present invention.
[0060] Moisture Content Test Method
[0061] The moisture test was conducted with an L&W Moisture Tester with microwave sensor, available from ABB Ltd., Zurich, Switzerland. The procedure is to press the moisture meter against the fabric after the dewatering box in direction of the fabric travel and depress the test button on the handle and depress it again to stop and record the reading in gsm.
Example 1
[0062] A dewatering box cover of FIG. 1 was made from high density polyethylene. The dewatering box cover had the same configuration as shown in FIGS. 1-4. This box cover was used on a pilot scale papermaking machine and was named the “FQT V-max” cover. The desired open area was calculated to be 15,000 mm.sup.2. The length of the cover was 1.2 m. The width of the cover was 140 mm (fabric contact width being 107.35 mm). The length of each slot was 45 mm. The width of each slot was 17 mm. All slots were formed with 30° angle cuts relative to vertical. The cover had a V-shaped slot in the center of the cover, with both arms of the V at 45° relative to one another on the 30° plane relative to horizontal projected through the cover. Seven slots were formed in the cover, each adjacent the next with the slots aligned to the left of the V. An addition, seven slots, each adjacent to the next were aligned to the right of the V. The slots had an angle relative to horizontal of 39°. The cover was attached to a dewatering box of a through air dried fabric cleaning station. The box had vacuum applied to assist in water removal. Water was removed through the box and drained to a save all. As a fabric with water passed over the dewatering box cover from leading edge to trailing edge, the combination of vacuum and the design of the box cover stretched out the fabric, thereby increasing the pore size in the fabric and facilitating water removal at lower cost. The moisture content in the fabric after the dewatering box was 8% to 12% lower with the FQT V-Max cover than the two slotted box cover and the dispersed holes cover which had equal open areas to the FQT V-Max cover. The two slotted box cover and the dispersed holes cover can be purchased from IBS Of America Corp., 3732 Profit Way, Chesapeake, Va., USA 23323. The commercial names for these covers are “Two-Slotted Dewatering Box Cover” and “Press Master Dewatering Box Cover”, respectively. With the same fabric on the paper machine (composite laminated belt at 30×7 mesh and count, with 350 cfm, and a vacuum of 25 kpa at the dewatering box), the FQT V-Max resulted in a drier exiting moisture content of 90 grams per square meter (gsm) as compared to 98 gsm for the dispersed holes box and 102 gsm for the two slotted box cover.
[0063] It should be appreciated that the dewatering box cover in accordance with exemplary embodiments of the present invention is not limited to the specific configuration previously described with reference to FIGS. 1-5. For example, the dewatering box cover may be made from several different materials including high density polyethylene, ceramics and glass reinforced plastic, and combinations thereof, to name a few. In a specific exemplary embodiment, the dewatering box cover may have the following properties: an open area of approximately 129,363 mm.sup.2; a length of 5.74 m; a width of 161.12 mm (fabric contact width being 155.12 mm); length of each slot is 61.71 mm; width of each slot is 13.76 mm; slots formed with 30° angle cuts relative to vertical; a V-shaped slot in the center, with both arms of the V at 73.9 degrees relative to one another on the 30° plane relative to horizontal projected through the cover; seventy nine slots formed in the cover, each adjacent to the next and aligned to the left of the V; seventy nine additional slots formed in the cover, each adjacent to the next and aligned to the right of the V; and slots formed with 36.95° angle cuts relative to horizontal.
[0064] The size of the box cover, number of slots, spacing between the slots, open area and size and angle of the slots may all vary on a larger, commercial scale papermaking machine. The number of slots, size of slots, etc. can be extrapolated from the teaching above with a directional limitation. In other words, slots to one side of the central V can be extrapolated based on overall size of the cover and box. Slots on the other side of the V would be extrapolated separately.
[0065] It should also be appreciated that the open area may be varied using deckle inserts, which are non-permeable plastic pieces that can be manually moved inward from the front or tending side of the machine or the back or drive side of the machine. The positions of the deckle inserts can be adjusted to close down the cross-direction width of the open area of the dewatering box to a width marginally wider than the sheet width. For example, with a sheet width of 5.33 m, the deckle inserts would be moved in to reduce the dewatering box width from full width of 5.60 m to a width of 5.38 m, which is 0.05 m wider than the sheet width, or 0.025 m wider on the front side and 0.025 m wider on the back side.
[0066] FIGS. 6-9 show a vacuum dewatering box cover, generally designated by reference number 100, according to another exemplary embodiment of the present invention. The cover 100 includes a main body 120 having a leading edge 140, a trailing edge 160, a first side edge 180 and a second side edge 200. The leading and trailing edges 140 and 160 extend along the length of the cover 100 and the first and second side edges 180 and 200 extend along the width of the cover 100. In exemplary embodiments, the length of the main body 120 may be in the range of 3 m to 8 m and the width of the main body may be in the range of 120 mm to 160 mm. In a specific exemplary embodiment, the length is 5.6 m and the width is 140 mm.
[0067] In embodiments, fifteen sets of holes 110 with three holes 110 in each set are formed in the cover 100. In exemplary embodiments, the holes 110 are formed by cutting into the material used to form the cover 10. Within each set, the holes 110 are aligned at a 39° angle relative to an imaginary line that is perpendicular to the side edge of the cover 100 (i.e., the angle relative to horizontal). As depicted by reference number 50 in FIG. 9, the holes 110 extend through the thickness of the cover 100 at an angle of 30° relative to vertical. It should be appreciated that the orientations of the holes 110 are not limited to the angles mentioned herein, and in other exemplary embodiments the angle relative to horizontal may greater or less than 39° (e.g., 45°) and/or the angle relative to vertical may be greater or less than 30°. Further, the number and alignment of the holes within each set is not limited to that described herein.
Example 2
[0068] A dewatering box cover having the same configuration as that shown in FIG. 6-9 was made from high density polyethylene. This box cover was made for use on a pilot scale papermaking machine. The cover was attached to a dewatering box of a through air dried fabric cleaning station. The box had vacuum applied to assist in water removal. Water was removed through the box and drained to a save all. As a fabric with water passed over the dewatering box cover from leading edge to trailing edge, vacuum applied removed the water through the numerous holes in the cover. The design of holes in the cover was such that the fabric remained primarily above the plane of the box cover due to the support areas between the holes, thereby decreasing the drag on the fabric drive and reducing wear on the fabric yarns. This dispersed hole cover had the same open area as and performed equally to a double slotted box cover in terms of dewatering capability on a pilot scale. It is expected that in a commercial setting the dispersed hole cover will equal the double slotted cover in terms of dewatering but result in less wear on the TAD fabric and lower electrical energy costs related to lower drive drag. The two slotted box cover and the dispersed holes cover can be purchased from IBS Of America Corp., 3732 Profit Way, Chesapeake, Va., USA 23323. The commercial names for these covers are “Two-Slotted Dewatering Box Cover” and “Press Master Dewatering Box Cover”, respectively. With the same fabric on the paper machine (composite laminated belt at 30×7 mesh and count, with 350 cfm, and a vacuum of 25 kpa at the dewatering box), the dispersed hole box cover performed equally to the double slotted cover.
[0069] In exemplary embodiments, the slots or holes may extend partially through the thickness of the cover at an angle of 30° relative to an imaginary line that extends through the lateral center of the cover and then transition to perpendicular to the horizontal axis. For example, FIG. 10 illustrates a box cover 200 with slots or holes 210 that extend 30° relative to vertical, then transitions to 90° relative to the horizontal axis through the remainder of the cover 30. In exemplary embodiments, the slots or holes 210 may extend from about 5 percent to about 80 percent or from about 10 to about 30 percent through the thickness of the cover at 30° relative to vertical, then transition to 90° relative to the horizontal axis through the remainder of the cover. Without being bound by theory, it is believed that this configuration may extend the life and improve the performance of the cover. It should be appreciated that the angles and dimensions shown in FIG. 10 are not intended to be limiting.
[0070] In exemplary embodiments, the cover may have a multi-layer construction. In this regard, the cover may include an upper layer and a lower layer. The upper layer may be made of ceramic and the lower layer may be made of high-density polyethylene. The slots or holes may extend from about 5 percent to about 30 percent or about 10 percent through the thickness of the ceramic upper layer at 30° relative to vertical, then transition to 90° relative to horizontal through the high-density polyethylene cover lower layer. As shown in FIG. 10, the angled slot or hole may transition into a larger pre-vacuum box area 220 in the high-density polyethylene layer. In embodiments, the pre-vacuum box area has a higher volume than the angled slots and is oriented vertically relative to and has the same width of a corresponding vacuum box slot. The ceramic upper layer may be attached to the high-density polyethylene lower layer with a heat set adhesive.
[0071] Now that embodiments of the present invention have been shown and described in detail, various modifications and improvements thereon can become readily apparent to those skilled in the art. Accordingly, the exemplary embodiments of the present invention, as set forth above, are intended to be illustrative, not limiting. The spirit and scope of the present invention is to be construed broadly.
