US3013605A - Trailing edge seal for moving suction belt apparatus - Google Patents

Description

E. J. JUSTUS Dec. 19, 1961 TRAILING EDGE SEAL FORiMOVING SUCTION BELT APPARATUS Filed July 13, 1959 fnyenzar 06149 J JU57'l/5 United States Patent 055cc 3,013,605 Patented Dec. 19, 1961 3,013,605 TRAILING EDGE SEAL FOR MOVING SUCTEON BELT APl ARATUS Edgar J. Justus, Beioit, Wis, assiguor to Beioit Iron Works, Beloit, Wis., a corporation of Wisconsin Filed July 13, 1959, Ser. No. 826,642 6 Claims. (Cl. 162349) The present invention relates broadly to paper machines, and is more particularly concerned with novel means having especial utility in eliminating wet streaks in the paper sheet or web during travel from moving belt suction apparatus to the couch roll of paper machines.

It is now known in the art that a Fourdriner type paper machine generally embodies dewatering devices beneath the forming reach presented by the looped traveling forming wire which extends from the breast to the suction couch rolls. One form of dewatering device performing well in commercial practice is known as a suction box which presents a flat perforate top to the bottom side of the wire and has its interior exhausted to draw water from the web through the wire and through the perforations in the suction box top. However, in this arrangement substantial wire wear results during movement of the forming wire in hugging contact with the flat stationary top of the suction box, and a solution to this problem is to provide relatively shallow grooves in the land areas of the suction box top and intermediate the perforations therein, and to mount an endless, flexible and driven belt between the bottom surface of the forming wire and flat top surface of the suction box. A liquid is then flowed under pressure to the shallow grooves in the suction box top to provide effective lubrication and thereby substantially reducing the power requirements to drag the belt across the suction box top.

While the structure described is a great step forward in the paper machine art, it has recently been found that wet streaks appear in the web as the forming wire with web thereon leaves the perforate endless belt and moves toward the couch roll, at which point the web is removed from the wire. An examination of the web indicates that the wet streaks therein correspond in location to the perforations in the flexible belt, and it is now believed that a cause of the Wet streaks is the admission of air into the perforations of the belt from below before the belt and the Wire are separated. During the passage of the belt perforations over the suction area, water and air are drawn into and through these perforations from (and through) the web overlying the wire. As the perforations travel otf the suction area the web offers suflicient resistance to the flow of water and air to function as a seal, and a partial vacuum persists in the said perforations. If then the inner ends of the perforations are opened to atmosphere, while the outer ends remain in effect sealed by the web carried on the wire, the abrupt expansion and the air inrush tend to drive the residual water out of the condition described.

It is, therefore, an important aim of the present invention to provide an improved paper machine incorporating means at the off-running end of the suction box to essentially entirely eliminate wet streaks in the Web.

Another object of this invention lies in the provision of seal means located at the downstream side of suction box structure and which provides an effective barrier against air flow into perforations from within theloop of the endless flexible belt, extending sufficiently down-- stream to at least the point at which the forming wire and flexible belt separate.

A further object of the instant invention is to provide a suction box for paper machines featuring a curved trailing surface forming an extension of the end wall of the suction box and generally coextensive therewith to seal the perforated belt against upward air flow therethrough until the forming wire supporting the web is spaced from the flexible belt.

Other objects and advantages of the invention will become more apparent during the course ofthe following description, particularly when taken in connection with the accompanying drawings.

In the drawings, wherein like numerals designate like parts throughout the same: I

FIGURE 1 is an, essentially diagrammatic elevational' view of a paper machine having suction box structure constructed in accordance with the principles of this invention; FIGURE 2 is an enlarged view of the suction box structure of FIGURE 1;

FIGURE 3 is an enlarged sectional fragmentary detail view taken substantially along the line Hi -III of FIGURE 2, and with parts therein shown diagrammati-' cally; and v 1 1 FIGURE 4 is an enlarged fragmentary view of another form of suction box structure embodying the concepts of this invention.

Referring now tothe drawings, there is shown in FIG-' URE l a paper machine indicated generally by the reference numeral 10, and comprising a looped forming wire 11 trained over abreast 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. or lower surface of the wire and is mounted for traveling on a roll 22 closely spaced from the on coming side of the suction boxes 14, and on a roll 23' closely spaced from seal means 25 (to be later described in detail) on the downstream or otf-running side of the suction boxes 14. Either or both ofthe rolls 22 and 23 may be driven, and as illustrated, the roll 23 is driven by suitable drive means 26, shown somewhat diagrammatically;

As will be noted later, the wire run 11a may also be used 1 to drive the belt 21.

The present invention is directed particularly to the seal means 25 of FlGURES land 2 and seal means of FIGURE 4 in association with a suction box and flexible belt movable thereover in a Fourdriner type paper machine. The structural detail of the traveling belt and the suction boxes, except where they intimately cooperate with the seal means or 50, form no part of this invention, and the illustrative suction box and movable belt structure are shown in some detail only to facilitate a more complete understanding of the present invention. Accordingly, it will be appreciated that other suction boxes and movable belts may be substituted in lieu of the structure shown, although the illustrated constructions have proven in practice to have substantial advantages over the earlier arrangements.

Briefly, each suction box 14 is provided with a generally fiat top 14a having perforations 14b therein which open into the interior 14c. Exhaust means in the form of a pump 27 (shown diagrammatically) connect to drop legs 14a of the suction boxes 14 for the purpose of exhausting the interiors 140 to effect the watering of the web W through the perforations 14b. If desired, the perforations may be countersunk at their upper ends.

As is shown, the perforations 14b in the suction box tops 14a are spaced longitudinally in the direction of wire travel and also laterally or transversely across the machine width. Land areas He are provided intermediate the perforations 14b in the box tops or covers 14a, and these land areas constitute the supporting surface for the traveling belt 21 moving thereover. The land areas He are provided with relatively shallow grooves 14] (FIG- URE 3) which face the belt 21 traveling thereover and which are closed off from the interior 140 of each suction box 14. The land areas 14:: and the grooves 14 extend longitudinally of the direction of wire travel indicated by arrow in FIGURE 2, and these grooves extend from near the off-running edge of each suction box cover 14a to near the oncoming edge thereof. While not shown, the grooves 14f may communicate with relatively shallow longitudinally spaced and laterally extending grooves to provide a substantially increased lubricated area whereby resistance to belt movement is even further reduced.

As indicated diagrammatically in FIGURE 3, means connected to a source of liquid under pressure communicate with the grooves 14 for flowing liquid between the bottom side of the belt 21 and the suction box tops 14a to lubricate the same. Such means, generally indicated at 28, may comprise a pump 29, a pressure control valve 30 for maintaining a predetermined pressure in water header 3-1, and conduits 32 extending from the header 31 to the grooves 14 As is now apparent, water flows from the grooves 14 along the land areas 14e and ultimately to the perforations 14b in the covers 14a. This flow is very slight and is controlled in accordance with the pressure of the belt 21 against the land areas 14a. However, the flow is sufficient to lubricate the rubber belt 21 and to prevent its dragging over the dry land areas Me. As is further appreciated, other grooving arrangements may be employed.

The belt 21 is constructed with perforations or drainage holes 21a which are so arranged that they do not align themselves with the grooves 14f in the suction box covers 14a to force water back up through the drainage holes 21a. Rather, the drainage holes 21a periodically align themselves with the perforations 14b in the box covers or tops 14a. The grooves 141 in the land areas 14c on the top side of the suction box'covers 14a are covered by land areas 21b on the bottom side of the belt 21 and intermediate the drainage holes 21a therein. The belt land areas are urged downwardly against the suction box land areas 142 by the pressure differential created by the suction boxes 14, and accordingly, water is urged into the grooves 14f under slight pressure to effect continuous seepage of water between the faces of the land areas 142 and 21b. The seepage is necessary to prevent the rubber belt 21 from wiping the land areas 14e dry, and thereby increasing frictional drag. However, the

water seepage is preferably very slight so as not to over load the water removal system for the suction boxes 14.

On the top side of the belt 21 there is preferably provided a plurality of longitudinally spaced and laterally extending g ooves or channels 21c, one of which is shown in FIGURE 3. Each such groove 21c is provided with one or more of the drainage holes 21a, which as earlier noted, periodically communicate with the perforations 14b in the suction box covers 14a. And was also earlier noted, the specific described structure of suction boxes and moving belt is illustrative only, and other arrangements may be employed in connection with the seal means 25 and 50 which are the essence of the invention herein disclosed.

As appears in FIGURE 2, the seal means 25 is in the form of a curved trailing surface on the off-running side of the downstream suction box 14, although of course the illustrative arrangement of three suction boxes is exemplary only and one continuous suction box may be provided between the rolls 22 and 23. The seal means 25 may be of either solid or hollow metal construction, and is provided with a top surface 25a which is generally in horizontal alignment with the upper surface of the suction box cover 14a, although the seal means top surface 25a may be inclined slightly downwardly to facilitate separation of the belt 21 and wire run 11a. The seal means 25 further has an upstream end wall 25b which abuts against the downstream end wall of the suction box 14 and which may provide the mode of attachment thereto. Of course, there is no vacuum drawn in the seal means 25.

The seal means 25 may have a lower surface 250 forming a continuation of the bottom surface of the suction box 14, and the top surface 25a and bottom lie of the seal means 25 are connected by an arcuate downstream or off-running front wall or surface 25d. It is important to note in this connection that the arcuate face 25d of the seal means has a degree of curvature closely corresponding to that of the roll 23, and further, the surface 25d is of sufiicient length in a downstream direction so that the farthest point downstream on the surface 25d is beyond the point of separation of the belt 21 and the wire run 11a. Specifically, it is to be seen in FIGURE 2 that the surface 25d terminates at a point designated at "x," whereas the point of separation of the belt 21 and wire run 11a is substantial distance upstream therefrom as designated by the legend y.

It is therefore to be now seen that a barrier or seal is provided from the point y to the point x representing the distance required to effect the desired amount of separation of the wire run from the belt so that the vacuum persisting in the perforations thereof is relieved by air entering the wire and the top of the belt and prevented from entering the inner ends of the perforations thus preventing the air inrush and expansion from driving water from the perforations back into the web. Furthermore, this permits obtaining a separation of the wire from the belt so that any normal air flow between the seal means surface 25d and the circumference of the roll 23 can have no harmful effects upon the web W. In other words, the length of the top surface 251: and the arcuate length of the surface 25d are calculated to dimensions so that no air penetration can take place through the belt perforations 21a until the wire run 11a with web W thereon is at a sufficient elevation above the belt that any residual water in the perforations cannot have sufficient force under actions described to create wet streaks in the web. In FIGURE 2 the numeral 33 has been applied to the arrow indicating the general direction of upward air flow between the surface 25d of the seal means 25 and the circumference of the roll 23. It may be seen therefrom that the air flow has an arcuate path conforming to the confining surfaces and that the air is directed thereby in a generally downstream direction, so that if any water should remain in the belt perforations 21a, such water would have to travel through a substantial air space between the belt upper surface and the wire run lower surface, through the wire run itself, and then into the forming web. Experience has demonstrated that a distance of this degree is sufficient to dissipate to a nonharmful condition the impingement efiects of any residual water.

In addition to elfectively sealing the perforations in the flexible belt 21 until the forming wire and web are separated therefrom, the trailing edge surface 25 has the following further effects. By provision of the air block or barrier described, an air flow path having a generally upstream direction and substantially tangential to the roll 23 is created by the air required to restore the perfora tions in the belt to atmospheric pressure. This is indicated in FIGURE 2 by arrows to which the numeral 34 is applied, and it may be noted that this path of air flow follows generally the periphery of the flexible belt 21 during passage over the roll 23 and additionally has no harmful effects upon the web W since separation of the forming wire 11a from the belt 21 has occurred.

The seal means 50 of FIGURE 4 is representative of another form which the trailing edge surface may take. In this view, with the exception of the seal means 50 all parts therein are preferably identical to those shown in the preceding figures, and accordingly, like numerals have been applied to like parts. The seal means 50 may therefore be seen to be in substitution for the roll 23 and trailing edge surface 25, and the belt 21 may be driven by the forming wire W. This view further illustrates a single suction box 14- extending along the forming reach, and of course, a plurality of suction boxes as in FIGURES 1 and 2 may be substituted therefor.

The seal means 59 is provided by a water lubricated belt supporting member or shoe having a generally arcuate body portion 50:; integral with an end portionStib abutting against off-running end wall 142 of the suction box 114. The seal means 50 may be attached to either the paper machine or the suction box 14 in any suitable manner, and it may be seen in the FIGURE 4 that the end portion Silb of the seal means may have an inclined upper surface 59c receiving the belt 21 and lowering the same away from the wire run 11a to effect the desired separation therebetween in the manner earlier described. It may further be observed from FIGURE 4 that the seal means 50 has generally flat oncoming and off-running ends Stld and 5%, respectively, as well as generally fiat and parallel inner and outer faces Eli) and 59g, respectively. Preferably, the outer belt contacting surface 56g is smooth and polished to minimize frictional losses.

The seal means 51 is coextensive with the belt 21, and

spaced downstream from the oncoming end 50d of the seal means is groove or open passage 5% extending transversely of the shoe. The groove 59h is formed along the contacting face 50g of the seal means and is generally U shaped in cross-section. A particular configuration of groove 5011 which works well includes a generally rounded groove bottom opening to an outwardly flared rounded discharge lip. However, in substitution for the groove 5th: the shoe or seal means 58 may be passaged throughout with a plurality of relatively small spaced holes extending therethrough, and which has the advantage of reduced fabrication costs and avoiding the possibility of lubrication losses in the event the single groove 5011 should become plugged. With this arrangement the seal means is most conveniently constructed with inner and outer walls Siih and 58g adapted to contain lubricating water, in lieu of the manifold 52. A suitable arrangement for supplying lubricant, which may be water, to the groove 50h may comprise a plurality of pipe lines or stems 51 connecting with a header 52 and leading to a suitable pump 53.

It may now be seen that the seal means 50 provides a complete barrier against entry of deleterious air flow into or through the belt 21 and into the web W on the wire run 11a. The seal means 50 by being coextensive with the belt 21 and by abutting against the suction box 14 thereby shields the web W until sufiicient separation elimination of one of the rolls 23 a possible out-of-balance.

condition is removed, and by having the seal means lubricated, frictional losses are reduced to a minimum.

There has been described herein two exemplary forms of seal means, and it is of course appreciated that their particular configurations can readily be varied. In addition, other changes and modifications will become apparent to those versed in the art, and such variations as come within the spirit and scope. of the novel concept of the present invention are intended to be covered hereby.

I claim as my invention:

1. In a paper machine which include a suction box, a traveling wire and an endless perforate belt movable over said box with the wire thereon, the improvement which comprises a curved trailing imperforate surface abutting the off-running end of the suction box and having a length sufficient in a downstream direction to firmly support the belt until said belt and wire separate, so that the belt and wireare sealed against the entry of air upwardly thereinto until said belt and wire separation takes place.

2. In a paper machine which includes a suction box, a traveling wire and an endless perforate belt movable over said box with the wire thereon, the improvement which comprises seal means having an arcuate surface extending'downstream from the off-running end of the suction box in the direction of the belt travel to at least the point of belt and Wire separation and preventing air flow upwardly into the belt and wire until said belt and wire part one from the other.

3. In a paper machine which includes a suction box, a traveling wire and an endless perforate belt movable over said box with the wire thereon, the improvement which comprises seal means having a surface forming a continuation of the suction box upper surface extending downstream therefrom to at least the point of belt and wire separation and receiving the perforate belt to support and seal the same against the entry of upwardly directed air streams therethrough and prevent any residual liquid in the belt perforations from impinging against the paper web to cause wet streaks therein.

4. In a paper machine which includes a suction box, a traveling wire and an endless perforate belt movable over said box with the wire thereon, the improvement which comprises a body impassable to air having an upstream end wall abutting the suction box, a top wall receiving the belt from the suction box, and a downstream wall converinging with the top wall at a point substantially downstream from the point at which the traveling wire and endless belt separate, whereby generally upwardly directed air streams pass through the belt perforations only beyond the point at which Wire and belt separation occur and wet streaks in the paper web are thereby prevented,

5. In a paper machine which includes a suction box, a traveling wire and an endless perforate belt trained about a pair of rolls and movable over said box with the wire thereon, the improvement which comprises an imperforate body having an upstream end wall abutting the suction box, a top wall receiving the belt from the suction box, and a downstream wall of arcuate shape conforming to the curvature of the downstream roll and closely spaced thereto, said arcuate wall converging with the top wall at a point substantially downstream from the point at which the traveling wire and endless belt separate upstream of the roll, whereby generally upwardly directed air streams follow the arcuate downstream wall and roll circumference and pass through the belt perforations beyond the point at which Wire and belt separation occurs and wet streaks in the paper web are thereby prevented.

6. A paper machine, comprising a suction box, a traveling wire, an endless perforate belt movable over said box with the wire thereon, a roll at the upstream end of the box training said belt, and a relatively slender stationary seal member of arcuate shape abutting the downstream end of the suction box and supporting the belt during travel from said downstream end, the seal member having an inner wall impassable to air which extends a substantial distance downstream from the point at which the References Cited in the file of this patent UNITED STATES PATENTS 762,431 McGrath June 14, 1904 FOREIGN PATENTS 3,572 Great Britain of 1880

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