US1949998A - Dewatering apparatus - Google Patents

Description

March 6, 1934. w FRENCH 1,949,998

DEWATERING APPARATUS Filed Sept. 16, 1931 2 Sheets-Sheet l Q INVENTOR in BY ATTORNEY March 6, 1934. w FRENCH 1,949,998 I DEWATERING APPARATUS Filed Sept. 16. 1931 2 Sheets-Sheet 2 FA'ITORNEY INVENTOR Patented Mir. 6, 1934 UNITED STATE PATENT Fries 8 Claims.

This invention relates to improvements in apparatus of the type employed for the purpose of removing water from pulp or the like. At certain stages in the manufacture of paper it is necessary to remove a large quantity of water from pulp of low concentration so as to thicken it sufficiently to permit it to be formed into continuous sheets .or webs. Various types of apparatus have been employed to effect this removal of water. Among these are included what is commonly termed a decker machine which comprises a rotating, screen-covered drum known as a cylinder mold and a presser or couch roll above the mold adapted to assist in squeezing water from the layer of pulp deposited on the surface of the mold. Heretofore these molds have commonly been formed by arranging a series of rods circumferentially around a number of spaced supporting plates or spiders and wrapping one or two wire cloths around the periphery to form backing wires for supporting the final face wire which forms the exterior surface of the cylinder. The arrangement of the rods and backing wires is such as to greatly reduce the effective drainage area of the cylinder. This necessitates a relatively slow operation of the mold so as to insure proper removal of a desired portion of the water content of the pulp.

One of the objects of the present invention has been to provide an improved form of cylinder mold for dewatering machines which will have a relatively large effective drainage surface thus permitting more rapid and efficient operation of the mold than has heretofore been possible. This has been accomplished by the formation of the mold from a metallic cylindrical shell supported by a series of suitably spaced discs. the shell being provided with suitable,

drainage apertures over its entire periphery and being adapted to support the outer facing wire. A more sturdy and rigid structure results from this construction. This is an important consideration inasmuch as there is a great tendency to distort the cylinder molds from their true cylindrical peripheries by virtue of the action of the presser or couch roll or of the doctor blade employed in the removal of the stock from the mold. When the mold loses its true cylindrical form there is not only a lack of uniformity in its action but there is a tendency to produce wrinkles and cracks in the outer face wire. These difiiculties are obviated by the present invention through the provision of a sturdymold' which is capable of retaining its true cylindrical form in spite of the action of the presser roll or doctor blade.

Another feature of the invention is the provision of an improved form of presser or couchroll. In lieu of providing this roll with a soft flexible covering of felt, wool, rubber or the like, as has been the common practice in the past, it is proposed to form it entirely of metal and provide it with a smooth outer surface adapted to contact the upper surface of the sheet of pulp. This is made possible by the mounting of the roll in such a way that it is spaced at all times from the surface of the cylinder mold and never comes in direct contact therewith. Heretofore it has been customary to permit the couch roll to rest directly upon the mold whenever the two were not separated by the passage of pulp between them. Furthermore the couch roll has been driven simply by frictional engagement with the mold or the intervening pulp. According to' the present invention a separate drive is provided for the couch roll and the construction is such that the roll and mold may be driven from the same source even though their relation may vary. Special provisions are included for regulating the position of the couch roll. Its supporting shaft may be either raised or lowered, as desired, by means of a lever which may be shifted and held by a suitable stop. Considerable wear on the face wire of the mold and breakage of this wire is avoided by maintaining the mold and roll constantly out of engagement.

Another feature of the invention is the provision of an agitator at the bottom of the tank which surrounds the cylinder mold. This agitator may, if desired, be continuously driven although it is particularly useful when the apparatus is first put into operation after a period of idleness. It is important that the pulp should be stirred up sufficiently to maintain a substantially uniform consistency throughout the tank. After the apparatus has been in operation for some time this is accomplished by the rotation of the mold itself but at the beginning of an operation it is quite desirable to supplement the action of the mold by an agitator. Special provisions for this purpose are included in the present invention.

Other features and advantages of the invention will appear from a detailed. description of an illustrative form of the same which will now be given in conjunction with the accompanying drawings in which:

Figure 1 is a front elevational view, partly broken away and partly in section, illustrating a a series of perforations.

decker machine embodying the features of the invention.

Figure 2 is a side elevation, partly broken away, of the apparatus of Figure 1.

Figure 3 is a horizontal sectional view through certain drive mechanism of the machine, and

Figure 4 is a view taken along the line 44 of Figure 1 showing the end of the cylinder mold.

Referring now to the drawings the apparatus may include a vat or tank 10 formed of or lined with some suitable non-corrosive material and adapted to retain a desired quantity of pulp in solution or suspension in water. The vat, which is preferably provided with a semi-cylindrical bottom, may be supported from any convenient form of retaining structure, such as foundation blocks or walls, by means of projections 11 secured to the vat. A main or pipe 12 extending longitudinally of the vat and connected at one or bothends to a suitable source or to' a plurality of sources of pulp to be dewatered may be provided with a series of branches 13 through which the pulp may be introduced into the vat at various spaced points. The pulp is introduced preferably at a point above the center of the vat. At each end of the vat there is provided a discharge opening 14 beneath the central axis of the vat and spaced slightly from the bottom. Each of these openings leads into a header or collector 15 at the end of the vat connected with adischarge pipe 16 which may be connected to any suitable disposal system. As will appear more fully hereinafter the openings 14 and discharge pipes 16 are for the removal from the vat of the clear or white water which is taken from the pulp in the course of operation of the machine. A washout drain 17 is provided at the bottom of the vat to permit complete removal of the contents and washing of the interior at intermittent periods.

A shaft 18 which extends longitudinally of the vat along its central axis is supported by bearings 19 at its ends, these being carried by suitable brackets 20 attached to the end walls of the vat. Where the shaft 18 is passed through the walls of the vat it may be provided with stufiing boxes or similar means, not shown, for preventing the escape of the liquid from the interior. Within the vat there may be mounted on the shaft, for rotation therewith, a sleeve 21 forming a part of a cylinder mold. At spaced intervals along the sleeve there may be secured a series of plates or discs 22 formed preferably of a corrosive-resistant metal such as Monel metal. stainless steel or the like and advantageously stamped from such metal. Each disc may be formed with a hub portion 23 adapted to closely surround the sleeve 21 and connected therewith. A series of openings 24 may be provided at spaced intervals around the 505 adjacent their peripheries, four being preferably provided as in the disc shown in Figure 4. The outer edges of the discs are cupped slightly to provide a flange 25 adapted to support a metal shell 26 wrapped around the discs and secured thereto in any suitable way, as by welding. The shell26 is preferably also formed of, or lined, or coated with, a suitable corrosive-resistant metal. A large number of perforations 27 are formed through the shell, these being preferably elongated and arranged at an acute angle to the longitudinal axis of the cylinder. This, as best shown in Figure 1, leaves no complete band around the cylinder which is not provided with Any plane perpendicular to the axis of the cylinder will pass through a series of perforations which are so closely spaced as to leave a large percentage of the surface of the cylinder open. Preferably the arrangement should be such as to leave substantially 50% of the cylinder area open. It has been found advantageous to form the perforations by punching or stamping them from the sheet which is later rolled into cylindrical shape. The punching, furthermore, should preferably take place from the outer surface toward the inner surface of the sheet and a slight deformation of the material-around the perforation may be permitted. This will provide a smooth,

perforation on the side which faces outwardly so that the liquid withdrawn from the pulp in the operation of the machine will be permitted to flow rather freely toward the interior of the cylinder. At the same time the tendency to cut the face wire, which is applied in the manner to be explained, adjacent the edges of the perforations will be reduced to a minimum. The ends of the sheet, rolled to form the shell 28 maybe joined and held together in any appropriate way, as by butt-welding. If desired the sheet 26 may be formed of several sections each extending only part way around the circumference and all preferably welded together at their joints.

On the outer surface of the mold there is provided a fine mesh screen 28 which constitutes the face wire adapted to pick up and carry a layer of pulp in-the usual way. The resulting cylinder mold construction is lighter than that normally employed, is more efficient due to the larger percentage of open area permitted, and

is less expensive to maintain because of the fact that it retains its true circular shape and does not have as great a tendency to wrinkle or crack the face wire.

Above the mold there is mounted a presser or couch roll 29 carried by trunnions, formed as extensions of a hollow shaft or sleeve 30, joumaled in anti-friction bearings 31. In order to provide for adjustment of the bearings so as to permit variation in the distance between the couch roll and mold, the bearings are mounted eccentrically in discs 32. These discs are mounted in straps 33 and it will be apparent that rotation of the discs will serve to vary the height of the bearings 31 and hence the distance between the centers of the roll and-mold. Any suitable means may be provided for turning the discs 32 to effect the desired adjustment of the bearings. For example the disc at the right end of the roll (Figure 1) may have connected with it a face plate 341 and a handle or lever 34 by which it may be rotated. A coordinated movement of the disc at the opposite end may be produced by connecting it with a shaft 35 which extends through the hollow shaft 30. Shaft 35 at its right end is connected with the handle 34 so as to be rotated therewith. A set-screw 36 passed through the strap 33 and cooperating with the periphery of the disc 32 mayserve to hold the latter in any adjusted position.

The couch roll is preferably formed of sheets of metal resistant to corrosion and erosion caused by the water and acids in the pulp or similar material being handled. These sheets are rolled or pressed into cylindrical form and are welded together. The roll so formed is then turned and polished to present a smooth, absolutely cylindrical surface. In lieu of forming the roll entirely of non-corrosive material as mentioned above it may be cast or drawn from material which will slightly beveled or depressed edge around thecorrode and then covered by a thin shell of noncorrosive material or the latter may be deposited on the outer surface'of the roll by electrolysis.

By the arrangement described it will be apparent that a smooth, hard surface, not subject to attack by the liquid carried by'the pulp, is presented at any predetermined desired distances from the surface of the mold. The surface of the roll need not at any time come into direct contact with the mold but the roll, when adjusted, will remain at a definite distance from the mold. This again tends to preserve the face wire on the mold.

The eccentric straps 33 at each end may be carried by brackets 37 secured to the end walls of the vat. A doctor blade 38, carried by supports 39 also mounted on the end walls of the vat, may extend across the width of the couch roll for the purpose of removing the layer of pulp carried around on the surface of this roll.

Means are provided for driving both the cylinder mold and the couch roll. The shaft 18 whichsupports the cylinderzmold may be connected through any suitable form of reduction gearing with a motor or other source of power, not shown. A gear 40 secured to this shaft meshes with a pinion 41- carried by a stub shaft 42 mounted in a pivoted frame 43. The latter is pivotally supported by the shaft 18. A sprocket wheel 44, also, carried by the shaft 42 is connected by a chain 45 with a sprocket wheel &6 secured to the shaft 30. In this way the couch roll is driven in synchronism with the cylinder mold and at the same-peripheral speed. The gear ratio between the gear 40 and pinion 41 should be such as to account for the difference in diameter between the roll and mold. The direction of drive should be such that the mold will rotate clockwise, Figure 2, and the couch roll anti-clockwise. It will be noted that the transmission of power between the gear 40 and pinion 4:1 is such as to cause a downward pressure on the frame 43 about its pivotal support. This, in addition to the action oi gravity on the frame, will provide an automatic chain-tightening action. The construction is such, furthermore, that adjustment of the couch roll may be made in the manner explained without interference with the drive.

At the bottom of the vat there is preferably provided an agitator 47 of any suitable construction adapted to maintain the pulp and water in more or less continuous agitation so that the pulp will remain in solution or in suspension. The agitator may be driven by extending its shaft 48 beyond the vat and connecting a sprocket 49 thereon by means of a chain 50 with a sprocket 51 secured to the shaft 18. Since the rotation of the mold tends to maintain the pulp in agitation when the machine is in operation the agitatorneed only be driven at the beginning of the operation, if desired. For this purpose the sprocket 51 may be connected with the shaft 18 through a clutch. not shown, if desired or it may be driven by a separate motor in lieu of the connections shown.

It is believed that the operation of the dewatering machine will be apparent from the foregoing. A mixture of pulp and water to be thickened is introduced into the vat 10 at various points through the pipe 12. The mixture is agitated by the rotation ofrthe mold and, if desired, also by the agitator. As the mold rotates pulp is deposited on the face wire and due to a slight pressure differential created by the the vat may be cleaned.

operation of the machine, water is drained through the face wire and through the apertures 2'7 into the interior of the mold. As the pulp is carried upwardly itis passed beneath the couch roll and is squeezed between the roll and mold to force more of the water into the interior of the mold. Thepulp which has been dewatered to a desirable degree is carried around on the smooth surface of the couch roll and is removed therefrom by the doctor blade 38. The water which is forced into the interior of the mold flows toward the ends of the latter through the openings 24 in the discs 22." From the outermost discs at the ends of the mold the white water is discharged into the headers mcollectors 15 at the ends of the vat and is passed by the pipes 16 to any suitable point of disposal. At the end of an operation the contents of the vat may be withdrawn through the pipe 17 and While an illustrative form of the invention has been disclosed herein in considerable detail it will be understood that various changes may be made in the construction and arrangement of the several parts without departing from the general 309 spirit and scope of the invention as defined by the claims. I

i. In apparatus'of the class described 9. cylinder mold comprising a supporting spindle, a

plurality of spaced, perforated discs carried by said spindle, a cylindrical shell carried by said discs, said shell having a series of elongated periorationseach inclined at an acute angle to the axis of the shell, said perforations constituting substantially fill-per cent of the area of mg :28 shell, and a face wire wrapped around said ell. 2. In apparatus of the class described a cylinder mold comprising a supporting spindle, a plurality of spaced, perforated discs carried by said 335 spindle, acylindrical shell carried by said discs, said shell having a series of elongated perforations each inclined at an acute angle to the axis of the shell, said perforations being so arranged that a series of them will be intersected by any plane perpendicular to the axis of the mold and constituting substantiallyco per cent of the area of the shell, and a face wire wrapped around said shell.

. 3. In apparatus of the class described a cylinder mold comprising a supporting spindle, a plurality of spaced, perforated discs carried by said spindle, a cylindrical shell carried by said discs. said shell having a series of elongated perforations each inclined at an acute angle to the axis 30 of the shell, said'perforatlons being punched from the material of the shell in a direction from the outer surface to the inner surface thereof and having smooth depressed edges around their peripherles, shell.

4. In apparatus of the class described a cylinder mold comprising a supporting spindle, a plurality of spaced, perforated discs carried by -said spindle, a. cylindrical shell carried said discs and shell being formed of material resistant to corrosion by the acids contained in a pulp mixture, said shell having a seriesof elongated perforations each inclined at "an acute. an-

gle to the axis of the shell,'said perforations constituting substantially 50 per cent of the area 01f1 the shell, and a face wire wrapped around said s ell.

5. In apparatus of the class described a vat. a cylinder mold rotatably mounted therein, a

and a face wire wrapped around said 135' by said discs, 14o

couch roll supported above said mold and spaced 2. definite distance therefrom, means. for varying the distance between said roll and mold, and means for driving both said mold and roll.

6. In apparatus of the class descried a vat,

a cylinder mold rotatablv mounted therein, a

couch roll above said mold, and means including a pair of eccentrics for supporting -said roll spaced from said mold, said means permi mold.

I. In apparatus adjustment of the distance the roll of the class described "a;

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