US 2488700 A
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Nov. 22, 1949 G. L. BIDWELL APPARATUS FOR PAPER MANUFAGTURE 3 Sheets-Sheet 1 Filed May 17, 1945 u. me.. .W m M l 4W ZJ. L E r ,5M i .0. MM M 7 6 7 ...MH u w/ H m .m rw 7 3 7 j t.. El i? Q \w\\\ n u Y 4 U n fr H ML\ u." 1V H M. Z//
ATTORNEYS Nov. 22, 1949 G. L.. BgDwELL APPARATUS FOR PAPER 4MANIJFAG'IUE 3 She'ets-Sheet 2 Filed May 17, 1945 INVENTOR 650865 L BIDIYELL PM@ nam.; WM
ATTORN EYS Nov. 22, 1949 G. l.. BlDwELL 2,488,700
APPARATUS FOR PAPER MANUFACTURE Filed May 17, 1945 Y 3 sheets-sheet 3 ATTORNEYS Patented Nov. 22, 1949 UNITED STATES PATENT OFFICE g 2,488,100 APPARATUS Fon raras MaNUrAc'rUnr-J George L. Bidwell, ltlegelsville, Pa., assignor to Riegel Paper Corporation, New York, N. Y., a corporation of New Jersey Application May 17, 1945, Serial No.594,21
2 Claims. l
This invention relates to improvements in apparatus for paper manufacture.
Paper has heretofore been made by three primary methods and three primary kinds of equipment, the papers made being handmade paper. cylinder made paper and Fourdrinier made paper. Handmade paper is made with a sheet mold dipped into and lifted out of a vat containing diluted pulp. In using this method instant formation is obtained as the mold is lifted from the vat, that is, the mold has a wire screen which rises through the pond of pulp, draining water quickly. Cylinder paper is made by revolving a screen cylinder in a vat containing diluted pulp. Fourdrinier paper is made by flowing diluted pulp onto a long, endless wire screen. In the Fourdrinier process water is removed a little at a time, being aided iirst by capillary attraction of the tube rolls that support the wire screen and later bysuction boxes usually placed toward the end of this wire screen, these boxes by pulling air through the sheet into a vacuum removing more water. This wire screen in modern machines varies in length from 40 feet to 120 feet. During the travel of the stock on the wire the latter is usually subjected to a shaking motion to cross the bers so as to approach the .manufacture of paper that will tear equally as well across the grair as with the grain. The wire screen in the Fourdrinler usually travels on a level or is slightly lower at the breast roll end of the wire or very much higher at the breast roll end of the wire.
The present invention provides an improved apparatus and equipment for paper manufacture which is less elaborate and complicated than that found in the standard cylinder and Fourdrinier paper machines and enables paper to be produced at a lower cost of initial investment and future maintenance. The apparatus enablesl an improved process of paper making to be carried out and a new and distinctive sheet of paper to be produced.
Thepaper product which is made with the newV apparatus has characteristics similar to the characteristics in all of the three common types of paper, i. e., handmade, cylinder and Fourdrinier, but is of a distinctive composite character, with layers of fibers cross-grained in opposite directions, the crossing of the fibers resulting in a paper having practically a square tear and with a tensile test having a good ratio in the machine direction compared with the cross machine direction.
The new apparatus for making paper gives a paper which more nearly approaches handmade paper than the paper made by the other two methods and apparatus, i. e., cylinder and Fourdrinier, but a composite and distinctive paper which is distinguished from handmade paper as well as from cylinder made and Fourdrinier made paper.
According to the present invention I make use of a short, endless wire screen travelling upward- 1y at an angle and malntain a pond of diluted fiber of progressively decreasing depth above the upwardly travelling screen and subject the screen below the pond to suction to draw water therethrough and also air during the later stages of the upward travel so that an endless sheet of paper. is formed immediately and continuously on the endless screen as it passes upwardly beneath the pond of pulp and is subjected to suction on` the lower side. The short, endless wire Vscreen travels over rolls arranged in a form which I designate as a triangle. The improved apparatus may be considered as a triangular Fourdrinier, although it is an essentially different apparatus from the ordinary Fourdrinier. As contrasted with the radically greater length of the wire screen in modern Fourdrinier machines the new triangular Fourdriniers may have an overall length of e. g., around S feet. inclined travelling portion of the screen forms one side of the triangle and the screen is returned over rolls which may be considered to form the other two sides of the triangle.
The angle at which the short, endless wire screen travels between the pond of diluted fiber and the suction box is advantageously an angle of around 15 but this angle can be varied somewhat and a'somewhat greater or smaller angle used according to the texture required in the finished sheet.
The apparatus generally considered includes a breast roll, a couch roll, and other rolls over which the short, endless wire screen travels, with the breast roll located at the lower end of the upwardly inclined side of the screen, a wide suction box which pulls water and air through the wire as the wire rises from the breast roll and a pond of diluted ber of progressively decreasing depth above the wire screen and above the wide suction box so that a sheet of paper is formed immediately on the wire screen as it passes from the breast roll between the pond of pulp and the suction box. The sheet of paper is formed continuously as an endless sheet and travels to the couch roll where it is lifted oi by a felt travelling around said couch and is eventually delivered to the main press from which point it is taken through other presses, etc. for completing the paper making operation, such as the usual batteries of dryers and -calenders, onto a reel, Winder or sheet cutter. The apparatus is also advantageously provided with a further suction box for further removal of water from the sheet before it reaches the couch roll.
The flow box by which the diluted ber is supplied has an extension thereof arranged above The upwardly the inclined screen and wide suction box to provide and maintain a pond of dilute stock of decreasing depth extending over the area oi' the suction box.
The wide suction box used in producing the new and distinctive sheet of paper is divided into two longitudinal sections arranged transversely of the screen and the surface of these two sections oi' the suction box have narrow strips of wood. micarta or metal standing on edge and set at an angle, e. g.. oi.' 45, so that these narrow strips come in contact with the wire screen as it passes over the suction box. The strips in one section of the suction box are arranged at an angle o1 e. g., 45 in one direction and the strips of the other section of the suction box are arranged at an angle of e. g., 45 in the other direction. These strips are placed moderately wide apart and act as cross-graining devices. As the wire screen passes over and in contact with the top of the suction box and these narrow strips, the water striving to pass through the wire mesh into the vacuum of the suction box causes the ilbers to be deposited on the screen in an angular manner determined by the angle of the guiding strips; and with the two sets of strips in the two sections of the suction box with their angles acting first in one direction and then in a crosswise direction an excellent crossing of the fibers is produced in the nature of a composite or lamig nated arrangement with a layer of fibers rst laid down being arranged at an angle in one direction followed by a layer in a crosswise direction, thus giving a paper characterized by a tear which may be practically a square tear and with the tensile tests lengthwise and crosswise having a good ratio to each other.
After the sheet is thus formed by the Wide suction box on the screen it passes over one or more suction boxes similar to the standard suction boxes used on the regular Fourdrinier machine to eiIect further removal of water therefrom before the sheet reaches the couch roll and is removed therefrom.
The improved apparatus of the present invention is Well adapted for making thin sheets as well as thicker sheets. Paper as light in weight as 5 pounds to 480 sheets (24 x 36 inch size) can thus readily be made; as well as thicker sheets. In making single sheets of paper or single-ply paper the sheet formed on the short, endless wire, screen may be removed therefrom for subsequent handling in various ways. The sheet may thus be transferred from the couch roll to the first felt by using a top couch and a pick-up felt or by using a suction bottom couch.
The apparatus of the present invention is advantageously used in making multi-ply paper by arranging a series of the triangular Fourdriniers with their short, endless wire screens on which the individual sheets are made so that the sheets made by different triangular Fourdriniers may be combined as they leave the short, endless screens to form a multi-ply paper. The sheets thus made on the diiferent triangular Fourdriniers may be couched oil the wire following the regular cylinder machine practice or by supporting the sheets between two felts after couching, the two felts preventing any tendency of the sheets from dropping o' the felt by their own weight when several plies of paper are made.
I'he wire screen used .in the short endless screen of the present apparatus may vary in mesh to suit the quality and thickness of paper desired,
4 e. g., a mesh from 50 wires per inch to 90 wires per inch.
The diluted stock used in making the paper can be varied in its composition and the extent of dilution depending on the characteristics desired in the thin sheet of paper. 'I'he flow oi' diluted Pulp to the screen is up an incline, e. g., oi' approximately 15 where the screen is inclined at an angle of 15 in its passage under the pond of diluted pulp and over the wide suction box.
In order to create the vacuum in the suction boxes a positive displacement pump is advantageously used capable of handling a large volume of water. The water is discharged from this pump in a manner which allows it to deaerate before it is used again to mix with the pulp in the further carrying out of the process. This suction box water is commonly referred to as white water and is used over and over again to dilute the pulp to form the diluted pulp which ilows on to the endless wire screen.
Where multi-ply paper is made with the use of two or more of the triangular Fourdriniers each of these machines will have its own supply of pulp and will in eiect act as a separate machine in the initial forming of the sheet of paper. The stock used in the different machines may vary and multi-ply papers made with the plies diiTering from each other depending on the stock used in the different machines. Because of the relatively short length of the individual machines a series of machines can be arranged in a relatively short space with the distance between centers of the different machines of e. g., around 8 feet so that the entire plant for making multiply paper may occupy a radically reduced floor space as compared with the ordinary Fourdrinier machine. Such a series of machines forming a multi-ply triangular Fourdrinier may be driven by diierent driving mechanism to maintain a uniform or synchronized speed of the individual machines. Power may thus be furnished by direct connected motors to the intake shaft of each couch roll if the paper machine proper is equipped with sectional electric drive or by power furnished by a D. C. generator driven from the intake shaft of the main press, or if a mechanical drive is used then powermay be applied to the intake shaft of each couch roll by means of counter shafts driven from the intake shaft of the main press.
When multi-ply paper is made by the use of a series of the triangular Fourdriniers and by combining the individual sheets therefrom to make the composite sheet, the multi-ply sheet thus produced will also be of a distinctive character. Each ply of the multi-ply sheet will have the composite character above described with the fibers of each ply made up, so to speak, of layers arranged crosswise first at an angle in one direction and then at an angle in the other direction and the composite plies of sheets of crossed fibers will then be combined into a multi-ply sheet. Thus where the wide suction boxes of the successive triangular Fourdriniers have the narrow nection with the accompanying drawings which illustrate in a somewhat conventional and diagrammatic manner apparatus embodying the invention, but it is intended andwill be understood that the invention is illustrated lthereby but is not limited thereto.
' In the accompanying drawings:
Figure 1 shows in elevation and with parte in section one form of the triangular Fourdrinier for making single-ply paper; Y
Fig. 2 is a plan view of one form of vacuum box with a section of the wire screen and of the rubber apron of the flow box;
Fig. 3 is a section of the iiow box oi' Fig. 2 taken on the lines 3-3 of Fig. 2;
Fig. 4 is a transverse section of the vacuum box taken on the line 4-4 of Fig. 2;
Fig. 5 shows a modiiled arrangement of the apparatus for making single-ply paper with the use of a suction couch. to dry the paper sufiiciently to permit it to pass to the ilrst press felt;
Fig. 6 is a somewhat enlarged view oi one form of the triangular Fourdrinier;
Fig. 7 shows an arrangement of apparatus for making multi-ply paper;
Fig. 8 is a diagrammatic arrangement of means for driving the triangular Fourdriniers of Fig. 7; and
Fig. 9 shows an alternative or modified `ar rangement of the triangular Fourdriniers for making multi-ply paper.
In the diierent figures the same or corresponding parts are indicated by the same reference numerals, in some cases with letters appended thereto.
In Fig. 1, which shows one form of the triangular Fourdrinier for making single ply Paper, the short endless wire screen I passes over the breast roll 2, the wire supporting roll 4, the guide roll 5, the couch roll 3, and the stretch roll 6. Immediately in front of the breast roll 2 is a wide suction box V'I which pulls water and air through the wire as the wire rises from the breast roll. An additional suction box 8 is provided for further drying the paper.
A specially constructed ilow box I0 is provided with ilow evener il and with an extension Il which extends over the suction box 1 so that the pond of diluted stock in the ow box comes directly in contact with the screen I above the y suction box 1.
The construction and arrangement of the flow box and its relation to the large suction box are illustrated in the enlarged view shown in Fig. 6 and in connection with the large suction box 1 in Figs. 2, 3 and 4. The extension I I of the ilow box has a metal apron I3 forming part of the bottom of this extension, and also a rubber apron I4 on the metal apron and extending over the traveling screen to the front edge of the suction box at I5, and with strips of the rubber apron extending along the sides of the screen above the ends of the iiow box to the point I6 as indicated in Figs. 2 and 3. Attached to the sides of the extension II of the iiow box are separate rubber strips or aprons IIA secured to the sides by metal clamps IIB and turned in at the bottom as illustrated in Fig. 3. The arrangement is such that a tight joint is maintained by the side aprons carried by the side walls, and the strips of apron that lie on the screen above the ends of the suction box. This makes a tight joint so that there is no leakage of pulp out of the sides of the pond in the extension of the flow box.
The area of the screen in contact with the dilute pulp and on which the sheet of paper is formed extends from the end of the rubber apron at I5 on one side of the suction box to the point I6 at the other side of the suction box and between the side strips of the apron on the screen at the ends of the suction box.
The ilow box has a partition which is adjustable in height by taking out or putting in the strips I2 that form the dam that feeds the pond of pulp in the extension of the flow box. This pond of pulp, as shown in Fig. 6, extends over the screen I and above the suction box, being in contact with the screen from the end of the rubber apron at I5 at one side oi.' the suction box 1 to the point I6 at the end of the iiow box, where the influence of the vacuum ends, and from the two rubber strips extending along the sides of the extension above the screen at the ends of the suction box.
The flow box and ilow evener provide a uniform head of dilute pulp in the extension of the flow box above the traveling screen but it will be noted from Flg.'6 that the pond of dilute pulp above the screen and vacuum box, between the points I5 and I6, is of progressively decreasing depth and decreases near the point I6 so that the ber will settle down on the wire before it passes the point I6 so that air will be drawn through the sheet and the sheet will be dried to some extent thereby before it passes the point I6.
In practice, the dilute stock will be supplied and regulated so that it extends over the entire area of the screen above the suction box 1 and can be varied with the speed at which the machine is being operated and also with the weight of the sheet of paper being formed and with control of the amount of vacuum. Thus where only a thin layer of stock is presen't near the point I6 where the influence of suction ends the vacuum and other factors will be regulated so that water will be removed to the extent that air will also be drawn through the layer of paper formed before the sheet travels past the point I6.
Accordingly, as the endless screen passes upwardly at an angle from the breast roll 2 over the suction box "I, the pond of dilute pulp above the screen in the extension II of the iiow box will come under the iniiuence of the vacuum in the suction box. This action begins as the sgreen passes the end of the rubber apron at I5 and continues as the screen passes in its travel upwardly to the point I6 with the result that there is an instant and continuous formation of paper.
One advantageous form of vacuum box is shown in Figs. 2, 3 and 4. As shown, the suction box 'l has a central vertical partition 30 dividing the box lengthwise into two transverse compartments arrangedin tandem in. the direction of travel of the screen. Horizontal partitions 3| are shown extending inwardly from each end to near the center of the box and leaving an opening between them, and four outlet pipes 32 are shown leading to a header or headers 33, shown in Fig. 6 and connected to a suction pump (not shown) which will be adequate tol handle a relatively large volume of water and to create the necessary vacuum in the suction box. The amount of vacuum can be controlled and will depend to some extent on the speed that the machine is being operated at and also on the basis weight of the paper.
The two transverse sections of the suction box 'I are shown as having thin strips. e. g. of v*wood or metal, standing on edge at an angle of 45 Thus, the thin strips 36 of the section of the suc-- tion box adjacent the rubber apron I4 are set at an angle o f 45 in one direction. and the narrow strips 35 of the other section are set at an angle of 45 in the opposite direction. These strips as shown are spaced moderately wide apart and are thin strips which extend to the top i' the suction box 1 so that the wire screen comes in contact with them as it passes over the top of the suction box. These angularly arranged narrow strips serve as cross-graining devices. As the screen moves upwardly over the two sections of the suction box, the layer of paper ilist laid down will have the bers tending to arrange themselves in one direction as the screen passes over the first section of the suction box, and then in the other direction as it passes over the other section of the suction box. This results in the instant and continuous formation of paper having fibers crossed in two layers, one pointing at an angle toward one side of the paper, and the other at an angle toward the other side of the paper, giving a composite paper with the two layers imparting to the paper square tear properties.
Referring again to Fig. 1, the composite sheet of paper thus laid down on the screen in its continuous upward passage at an angle over the large suction box 1 passes with the screen over the wire supporting roll 4, and over a further standard suction box 8 for further drying the paper as it passes over this suction box. The screen and paper then pass over the guide roll 5 to the couch roll 3 Where the sheet of paper is removed, after which the screen passes round the couch roll 3 and over the stretch roll 6 to the breast roll 2.
The single ply sheet 28 thus formed comes in contact with the felt I8 as it passes between the lower couch roll 3 and the upper rubber-covered couch roll I1. The felt I8, which in this case is the top felt, passes around the upper couch roll I1, the upper press roll 22, the felt carrying rolls I9, the stretch roll 2|, and between squeeze rolls 20. Water shower devices are shown at 24 and a felt whipper at 23. A felt suction box is shown at 25. I
A bottom lfelt 26 is shown vas passing around the lower bottom suction press roll 21, the felt carrying rolls 29, and the stretch roll 2 I.
'I'he sheet of paper 28 continuously formed on .the triangular Fourdrinier is couched 01T the wire screen by the upper pick-up felt I8 as the wire screen and paper pass between the lower and upper couch rolls 3 and I1, and is carried by the :telt to the rst press rolls 22 and 21. The sheet 2l is taken from the lower felt 25 to the paper machine for standard paper machine operations.
In the Operation of the apparatus shown in Fig. 1, diluted stock is forced into the ow evener and iiow box and a pond is formed in the extension of the ow box. As the short, endless wire screen passes in an upwardly inclined direction rfrom the couch roll over the large suction box, the sheet of paper is laid down on the wire screen and is f-urther dried by passing over the suction box 8, then is removed from the screen by the upper felt I8 and upper couch roll I1 and delivered to the suction press rolls 22 and 21, from which it passes to the paper machine for further drying, etc.
The apparatus of Fig. 5 shows a somewhat modified arrangement in which the couch roll IA is a suction couch roll, .this being used in- 8 stead of the top and bottom couch rolls and pickup device shown in Fig. 1. In this case the sheet of paper 28 may .be dried sutilciently to pass directly to the telt 28 and to the first press rolls 22 and 21 without the intermediate use of an uprper felt and yupper couch roll, as shown in 'FILL' In Fis. 6, a somewhat different arrangement oi.' the short endless screen is shown with the screen passing from the breast roll 2 over the large special suction box 1 and then over a standard suction box l to the couch roll I. In this case, Ithe couch roll l serves as an upper couch roll and the sheet is removed by a telt IIA carried by a lower couch roll I'IA.
Fig. 7 shows a series of triangular Fourdriniers similar to that of Fig. 6. arranged in tandem. 'Ihe felt IUC passes between the three pairs of couch rolls 3 and I1C. and picks up successive plies oi' paper from the three triangular Fourdriniers and takes them as a multi-ply layer or sheet to the extractor rolls 40 and 4I, which serve to remove water from the multi-ply paper before it passes with the felt IIC to the main suction press rolls (not shown) In such a tandem arrangement various types oi driving mechanism may be used, including a sectional electric drive or a D. C. generator driven -trom the intake shaft of the main press furnishing .power for individual D. C. motors or by a mechanical drive connected to drive the diderent Fourdriniers at a uniform speed. One form ci' driving mechanism is illustrated conventionally in Fig. 8, the lower extractor noli 4I being driven and being connected, e. g. by sprockets 42 and chain lbelts 43 with the lower couch roll of each of the three triangular Fourdriniers.
'I'he arrangement of Fig. 7 illustrates the advantage oi' the new triangular Fourdriniers, each with its short, endless wire screen traveling over rolls and arranged for forming individual sheets of paper. I'hese individual machines can be arranged on centers as close as eight feet, which is somewhat less than the room occupied by cylinder molds and vats used in the multiple cylinder type of paper machine.
With such an arrangement of a plurality of triangular Fourdriniers, the single ply sheets made on the different machines may be made oi' the same or dinerent stock, so that each machine has its own auxiliary equipment and functions as a separate machine until the plies oi' paper meet and are combined to form the multiply paper.
An alternative arrangement of the triangular Fourdrinier for making multi-ply paper is illustrated in Fig. 9. The individual triangular Fourdriniers are similar to those shown in Fig. 1. In this arrangement, each ply of paper is picked oi! the bottom of the couch roll I by means of a top cylinder wet felt ISD with the aid of a couch roll I'ID. which is adjusted in contact with .the wire traveling around the couch roll 2 by means of a lever and Weight 44. As the last ply is picked up, the felt IBD .passes around the last couch roll I1D and meets the bottom felt 26D, supported by squeeze roll 45 and felt carrying rolls 29. The multi-ply lpaper 28D is supported between the bottom and top Ielts 26D and I8D until it reaches the suction press roll 21D and passes between this lower .press roll and the upper weighted press roll 22D, from which point the multi-ply paper is taken over to the paper machine for further drying, etc.
The means for applying pressure to the couch rolls I1D, the squeeze rolls 45 and the top :press roll 22D, is shown conventionally in Fig. 9 and iS omitted from the other gures. It will be vunderstood that pressure may be applied in various ways, by means of counter' balances with single or compound leverage, or by other pressure devices.
In practice, provision will be made for a quick release of the contact of the coucher with the wire screen, and for raising or lowering the coucher when desired, but such devices are well known in the art and are not shown in the drawing.
The construction of the couch rolls and other rolls can also be varied, in a manner which will be readily understood. In making single ply paper, the couch roll on the triangular Fourdrinier may either have a plain or grooved surface, and is made e. g. of gun metal. The other couch roll will usually be a soft rubber couch roll, carrying the pick-up felt that removes the sheet of paper from the wire screen. The paper may be removed from either the top or bottom of the couch roll as illustrated in the diierent gures of the drawing.
In the drawings, somewhat dierent arrangements of the short, endless wire screen have been shown with different combinations and arrangements of rolls over which the endless wire screen travels. In all cases there is an upwardly inclined travel of the screen under the pond of diluted stock in the ow box and over the special formation suction box, this upwardly inclined travel of the screen forming one side of the triangle, the other sides being formed by the travel of the screen over the other rolls in its return to the breast roll.
The detailed construction and arrangement of the special formation suction box can also be varied, as well as the angle of inclination of the screen as it passes over the suction box with the pond of diluted stock of progressively decreasing depth in the direction of travel of the screen. The arrangement of the guide strips 35 and 36 can also be somewhat varied from the exact arrangement oi' 45 in opposite directions. Thus.' where it is desired to produce a paper with a greater tear strength lengthwise of the continuous sheet as compared with the tensile strength crosswise of the sheet, this can readily be accomplished by a different arrangement of the guide strips, or by omitting them entirely. But by a proper arrangement of the guide strips in crosswise directions, as hereinbeiore illustrated and described, it is possibleto make a composite sheet of paper with two more or less distinct but interblending layers, with a rst layer laid down with the grain or general arrangement of the fibers in one direction, and the-next layer in the other, giving crossed bers which impart'a desirable strength crosswise of the paper, properly regulated or correlated with the strength lengthwise oi' the paper. A composite sheet of paper can thus be prepared in a continuous manner, having properties similar in some respects to hand-made n paper and combining advantages of hand-made an upwardly inclined direction, a flow box for supplying diluted ber to said screen during a portion of said upward travel and for forming a pond of such diluted fiber of progressively de 'creasingfdepth in the direction of travel of the screen, a suction box arranged below the screen and below the pond of diluted ber above the screen, said suction box being divided into two transverse sections arranged in tandem in the direction of travel of the screen, one section having a series of guiding vanes arranged at an angle for causing transverse ow in one direction and the other section having a series of guiding vanes arranged at an angle in a cross-wise direction for causing transverse ow in a cross-wise direction as the screen passes upwardly thereover below the pond of diluted ber, and means for removing the resulting sheet of paper from the screen as it passes over the couch roll.
2. A paper machine having a short endless wire screen passing over breast and couch rolls, a portion of the screen being arranged to travel upwardly at an angle ot about 15 from said breast roll, a special suction box located beneath said upwardly inclined portion of the screen adjacent the breast roll and having two transverse sections arranged in tandem in the direction of travel of the screen, the guiding vanes of one section being arranged at an angle for causing transverse ow in one direction and the guiding vanes of the other section being arranged at an angle in a cross-wise direction for causing ow in a cross-wise direction as the screen passes upwardly thereover below the pond of diluted ber, a ow box arranged to maintain a pond of diluted ber in contact with the endless wire screen above said suction box of progressively decreasing depth in the direction of travel of the screen, another suction box located between said special suction box and the couch roll for drying a sheet formed on said screen as it passes thereover, and means for removing the sheet from said screen at the couch roll.
, GEORGE L. BIDWEIL.
REFERENCES CITED The following references are of record in the le of this patent:
UNITED STATES PA TENTS Number Name Date 708,219 Gilbert Sept. 2, 1902 840,223 Milne Jan. 1, 1907 920,100 Whisner Apr. 29, 1909 1,152,747 Metcalf Sept. 7, 1915 1,385,341 Wagner July 19, 1921 1,599,378 Charleson Sept. 7, 1926 1,599,385 Pryor Sept. 7, 1926 1,655,511 Russell Jan. 10, 1928 1,799,350 Barnes Apr. 7, 1931 1,829,660 Knopp Oct. 27, 1981 1,917,098 Coti-in July 4, 1933 1,927,378 Street Sept. 19, 1933 1,974,103 Corcoran Sept. 18, 1934 2,073,654 Smiley Mar. 16, 1937 2,394,509 Boettinger Feb. 5. 1946 2,396,696 Berry Mar. 19, 1946 FOREIGN PATENTS Number Oountry Date 11,894 Great Britain ot 1848 165,877 A Germany Dec. 9, 1906 860.674 Germany Nov. 24, 1922 my, m -.--nlnln--umi 15