US2981328A - Method and apparatus for reducing power required by moving suction box cover - Google Patents

Description

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Aprll 25, 1961 E. J. JUSTUS 2,981,328

METHOD AND APPARATUS FOR REDUCING POWER REQUIRED BY MOVING SUCTION BOX COVER Filed Jan. 14, 1958 2 Sheets-Sheet l 7 O A H be EZUT Edgar (j c/wizzs b H/AZZ/M/MMVW flrr s- April 25, 1961 E. J. JUS 8 2,981,328

METHOD AND APPARATUS F REDUCING POWER REQUIRED BY MOVING SUCTION BOX COVER Filed Jan. 14, 1958 2 Sheets-Sheet 2 Zia 22.1fm?

' Edgar cf c/uszus METHOD AND APPARATUS FOR REDUCING POWER REQUIRED BY MOVING SUCTIUN BOX COVER Edgar J. Justus, Beloit, Wis., assignor to Beloit Iron Works, Beloit, Wis, a corporation of Wisconsin Filed Jan. 14, 1958, SerflNo. 708,878

Claims. (Cl. 162-367) The instant invention relates to paper machines, and more particularly, to an improved suction box structure for paper machines.

As is well known, the conventional Fourdrinier type paper machine comprises a looped traveling forming wire presenting a forming reach extending from a breast roll (whereat stock is flowed onto the wire) to a suction couch roll (at approximately the location at which the formed Web is removed from the wire). Various dewatering devices are mounted beneath this reach of forming wire and one of the more common dewatering devices is known as the suction box, which presents a flat perforate top to the bottom side of the wire. The interior of the suction box is exhausted so as to assist in drawing Water from the web through the wire and through the perforations in the flat top of the suction box. The pressure differential thus created tends to hold the traveling wire down against the stationary flat tops of the suction box so as to increase wear on the wire.

Various devices have been suggested for the purpose of avoiding this wear on the wire caused by drawing the moving wire over the fixed suction boxes; and one of the most well known of these devices is often referred to as the Evans Roto Belt, which is described and claimed in US. Patent No; 2,039,308 issued to William P. Evans on May 5, 1936. In the Evans structure a perforated moving belt with solid edges is installed between the traveling Fourdrinier wire and the suction box covers in an attempt to reduce wire wear and also suction box cover wear. A difficulty with this device has been the very large power requirement in order to drive the ap paratus at practical paper machine speeds. The pressure differential in the suction box, of course, causes the belt to be urged against the suction box covers by relatively great forces and a substantial amount of power is required to drag thebelt over the suction box covers. The power must be supplied either through the wire itself or by means of an independent drive, but in either case substantial difficulties are encountered in operating at the high machine speeds currently employed. In addition, great difficulty has been found in guiding the belt properly across the suction box covers, also because of the frictional drag created by attempting to move the belt across the suction box covers.

The instant invention resides in a novel, simple and particularly effective arrangement for overcoming these difiiculties. The instant invention is based upon the discovery that probably the greatest source of difliculty is the tendency for the rubber belt to wipe land areas of the suction box cover dry, thus removing water which is one of the better fluid lubricants for rubber. These land areas between the suction box perforations or drainage holes coincide with land areas in the belt between drainage holes in the belt and the movement of the rubber belt over the suction box cover wipes the land areas in the cover dry and creates very great frictional drag. In accordance with the teachings of the instant invention,

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grooves are mounted in the land areas of the suction box cover and a fluid lubricant, e.g., a liquid, preferably water, is forced under slight pressure into such grooves so as to continuously lubricate the inner faces between land areas on the suction box cover and on the bottom of the belt. The force with which these land areas are urged together at the inner face is such that a controlled but slight amount of water may flow from the grooves into the drainage holes in the suction box cover, thus effecting no appreciable increase in the load of water that must be drawn off through the suction-boxes, while greatly reducing the power requirement for driving the belt.

It is, therefore, an important object of the instant invention to provide an improved paper machine, and more particularly, to provide an improved suction box structure.

It is a further object of the instant invention to provide an improved suction box structure for dewatering a web on a traveling wire, comprising a suction box having a generally flat top with perforations therein and land areas intermediate the perforations, an endless flexible perforate belt covering the suction box top and adapted to support and engage the bottom side of the wire, means defining shallow grooves in the land areas of said suction box top, and means connected to a source of liquid under pressure communicating with the grooves for flowing liquid between the bottom side of the belt and the suction box top to lubricate the same.

Other and further objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed description thereof and the drawings attached hereto and made a part hereof.

On the drawings:

Figure 1 is an essentially diagrammatic elevational view of a paper machine having a suction box structure embodying the instant invention;

Figure 2 is an enlarged view of the suction box structure shown in Figure 1;

Figure 3 is an enlarged sectional fragmentary detail view taken substantially along the line IIIIII of Figure 2, with parts shown diagrammatically;

Figure 4 is a sectional elevational fragmentary view taken substantially along the line IV-IV of Figure 3; and

Figure 5 is a fragmentary detail top plan view of a suction box cover embodying the instant invention.

As shown on the drawings:

In Figures 1 and 2 there is shown a paper machine indicated generally by the reference numeral 10 comprising a looped forming Wire 11 trained over a breast roll 12, table rolls 13, suction boxes 14, a couch roll 15, a turning roll 16, and return rolls 17. Stock is deposited on the upper wire run 11a from a head box 18 in the region of the breast roll 12 and the stock is dewatered during its travel on the upper wire run 11a to form a web W which is removed from the wire 11 by a pickup felt 19 urged against the web W by a suction pickup roll 20. A rotary belt 21 mounted on rolls 22, 23 and 24 is interposed between the suction boXes 14 and the wire run 11a.

As best shown in Figure 2, the wire run 11a travels in the direction indicated by the arrow with the Web W thereon. The traveling endless belt 21 engages the bottom side of the Wire and is mounted for traveling on a roll 22 closely spaced from the oncoming side of the suction boxes 14, 14 and a roll 23 closely spaced from the off-running side of the suction boxes 14, 14 (with a third guide roll 24). The rolls 22 or 23, or both, are driven. As here shown, the roll 23 is driven by suitable drive means 25 (shown diagrammatically). The wire run 11a may also be used to drive the belt 21.

Each of the suction boxes 14, 14, 14 is equipped with a generally flat top 14a having perforations 14b therein which open into the interior 14c. Exhaust means in the form of a pump 26 (shown diagrammatically) connect to drop legs 14d of each of the suction boxes 14 for purposes of exhausting the interiors 14c, 14c, 14c to effect dewatering of the web W through the perforations 14b.

As indicated in Figure 2 the perforations 14b in the suction box top 14a are spaced longitudinally in the direction of wire travel. As shown in Figure 3, the perforations 14b in the suction box top or cover 14:: are also spaced laterally and there are land areas Me on the generally flat upper face of the cover 14a. Such land areas 144 are intermediate the perforations 14b and actually provide the supporting surface for the cover 14a that supports the traveling belt 21 moving thereover. In the practice of the instant invention, it will be seen that the land areas 14c are provided shallow grooves 14 which face the belt 21 traveling thereover. These shallow grooves 14 are closed off from the interior 14c of the suction box 14.

As here shown the land areas 142 mounting the grooves 14f and the grooves ldfthemselves extend longitudinally of the direction of wire travel. The machine direction is indicated in Figures 4 and 5 by arrows. The grooves 14 extend from near the off-running edge 14g (Figure 4) of the suction box covers 1411 to near the oncoming edge (not shown).

As indicated diagranunatically in Figure 3, means conneoted to a source of liquid under pressure communicate with the grooves 14f for flowing liquid between the bottom side of the belt 21 and the suction box top 14a to lubricate the same. Such means indicated generally at 39 in Figure 3 are shown diagrammatically and they in clude a pump 31, a pressure control valve 32 (for maintaining a predetermined pressure in the water header 33), and conduits extending from the header 33 to the grooves 14- which conduits are indicated generally at 34. Referring to Figure 4, it will be noted that water under pressure flows from the header 33 through the conduit 34 into the groove 14 As indicated by the arrows in light lines in Figure 5, the water flows from the grooves 14f along the land areas 14c and ultimately to the perforations 14b in the cover 7140. This flow indicated in Figure 5 is very slight and is controlled by the pressure of the belt 21 against the land areas 142, but the flow is suflicient to lubricate the rubber belt 21 and to prevent the dragging of the rubber belt 21 over dry land areas 14:2.

The belt 21 is, of course, provided with perforations or drainage holes, indicated at 21a in Figures 3 and 4. The drainage holes 21a are so mounted in the traveling belt 21 that they do not align themselves with the grooves 14f in the suction box cover 14a. In this way water is not forced back up through the drainage holes 21a. Instead, the drainage holes 21a periodically align themselves with the perforations 14b in the suction box cover 14a. The bottom side of the belt 21 has, of course, a number of openings therein formed by the drainage holes 21a. Intermediate the drainage holes 21a there are land areas 21b on the bottom side of the belt 21. These land areas normally cover the grooves 14 in the land areas 14e on the top side of the suction box cover 14a. These belt land areas 21b are urged downwardly against the suction box land areas 14c by the pressure difierential created by the suction box 14. For this reason water is urged into the grooves 14 under slight pressure to efliect continuous seepage of water between the faces of the land areas He and 21b. Water seepage at this interface 14a, 21b is necessary to prevent the rubber belt 21 from wiping the land areas 142 dry and thereby increasing the frictional drag. Preferably the seepage of water is very slight, so as not to overload the water removal system for the suction box 14.

The top side of the belt 21 is preferably provided with a plurality of longitudinally spaced laterally extending grooves or channels 210. Each such groove 210 is provided with one or more drainage holes 21a, and as here shown the groove 210 (of Figure 3) is provided With a plurality of drainage holes 21a. The same structure is employed for each of the other grooves 21c shown in cross-section in Figure 4.

Processwise, the instant invention involves a method of dewatering a paper web W traveling upon a wire 11a passing over a stationary suction box cover 14a, that comprises passing a perforate elastomer belt 21 between the wire 11a and the suction box cover 1411, exhausting the suction box 14 to urge the belt 21 and the box cover 14a toward surface to surface contact, and forcing fluid lubricant, e.g., a liquid between the belt 21 and the cover 14a to maintain a lubricating film therebetween. It will be appreciated, of course, that the instant system com-prises an improved distribution system for the fluid lubricant, i.e. means for distributing the fluid lubricant between the land area 142 (Figs. 4- and 5) and the belt 21, said means comprising passages 34, 34 extending through the land area and spaced within said lands to maintain said lubricant between said belt 21 and said land areas (along the regions generally indicated by the dashed-line arrows on the lands 14c, of Fig. 5).

It will be understood that modifications and variations may be effected without departing from the spirit and scope of the novel concepts of the present invention.

I claim as my invention:

1. An improved suction box structure for dewatering a web on a traveling wire, comprising a suction box having a generally flat top with drain perforations therein and land areas intermediate the perforations of substantially greater total area than the total area of said perforations, an endless flexible perforate belt covering the suction box top and adapted to support and engage the bottom side of the wire, means for distributing a fluid lubricant between the land area and said belt, said means comprising passages extending through the land area and spaced within said lands to maintain said lubricant between said belt and said land areas, and means connected to a source of fluid lubricant under pressure communicating with the passages for flowing fluid film in opposite transverse directions across the land areas and toward the drain perforations between the bottom side of the belt and the suction box top to lubricate the same.

2. An improved suction box structure for dewatering a web on a traveling wire, comprising a suction box having a generally flat top with drain perforations therein opening into an interior portion of the box and land areas intermediate the perforations, the total area defined by said perforations being substantially less than the total area of said land areas, an endless flexible perforate belt covering the suction box top and adapted to support and engage the bottom side of the wire, means defining a plurality of generally parallel shallow grooves in the land areas of said suction box top closed otf from said interior portion and extending continuously in a longitudinal direction from adjacent the oncoming edge to adjacent the off-running edge of said box top, means exhausting said interior portion to effect dewatering through perforations in the box top and the belt, and means connected to a source of liquid under pressure communicating with the grooves for flowing a liquid film in opposite transverse directions across the land areas and toward the drain perforations between the bottom side of the belt and the suction box top to lubricate the same, the area defined by said grooves being essentially coextensive with the interior portion of the suction box.

3. In a paper machine, a traveling forming wire carrying a paper web thereon, a traveling endless belt engag ing the'bottom side of the wire, means defining laterally extending grooves with drainage holes and with closed selvedges in said belt, a suction box having a generally flat top with a plurality of transversely spaced rows of longitudinally aligned spaced drain perforations therein and land areas intermediate the perforations of substantially greater total area than the total area of said perforations, means defining shallow grooves in the land areas of said suction box top and said land areas and said grooves extending longitudinally in the direction of wire travel, and means connected to a source of liquid under pressure communicating with the grooves for flowing a liquid film in opposite transverse directions across the land areas and toward the drain perforations between the bottom side of the belt and the suction box top to lubricate the same.

4. In a paper machine, a traveling forming wire carrying a paper web thereon, a traveling endless belt engaging the bottom side of the wire, means defining laterally extending grooves with drainage holes and with closed selvedges in said belt, a suction box having a generally fiattop with a plurality of transversely spaced rows of longitudinally aligned spaced drain perforations therein opening into an interior portion of the box and land areas intermediate the perforations of substantially greater total area than the total area of said perforations, means defining a plurality of generally parallel, continuous and longitudinally extending shallow grooves in the land areas of said suction box top closed off from said interior portion, means exhausting said interior portion to efiect dewatering through perforations in the box top and the belt, and means connected to a source of liquid under pressure communicating with the grooves for flowing a liquid film in opposite transverse directions across the land areas and toward the drain perforations between the bottom side of the belt and the suction box top to lubricate the same, the area defined by the perforations in the suction box top being substantially coextensive with the area defined by the grooves in said top;

5. In a paper machine, a traveling forming wire carrying a paper web thereon, a traveling endless belt having its top engaging the bottom side of the wire, means defining laterally extending grooves with drainage holes connecting therewith and with closed selvedges in said belt on its top side and land areas intermediate the drainage holes on the bottom side of the belt, a suction box having a generally fiat top with perforations therein and land areas intermediate the perforations, the total area defined by said perforations being substantially less than the total area of said land areas, means defining longitudinally extending shallow grooves in the land areas of said we tion box top, said grooves being normally covered by the land areas on the bottom side of the belt, and means connected to a source of liquid under pressure communicating with the grooves for flowing liquid at a pressure in excess of static pressure between the bottom side of the belt and the suction box top to lubricate the same with a relatively thin liquid film flowing in opposite transverse directions across the land areas and toward the perforations.

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