US 3326745 A
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June 20, 1967 J. B. GRAHAM 3,326,745
APPARATUS FOR FORMING PAPER BETWEEN A FORMING WIRE AND FELT Fild Dec. 4. 1964 2 Sheets-Sheet June 20, 1967 J. B. GRAHAM 3,326,745
APPARATUS FOR FORMING PAPER BETWEEN A FORMING WIRE AND FELT Filed Dec. 4. 1964 z Sheets-Sheet 2 United States Patent 3,326,745 APPARATUS FOR FORMING PAPER BETWEEN A FORMING WIRE AND FELT John B. Graham, Neenah, Wis., assignor to Kimberly- Clark Corporation, Neenah, Wis., a corporation of Delaware Filed Dec. 4, 1964, Ser. No. 416,078 3 Claims. (Cl. 162-313) ABSTRACT OF THE DISCLOSURE Paper forming apparatus including a movable endless felt and a movable endless foraminous forming wire so disposed that the wire and felt provide a tapering cavity between them into which paper stock is discharged, with a supporting shoe being provided for the portion of the felt forming one side of the tapering cavity to prevent undue flexing of the felt. The supporting shoe may be either in the form of a fiat backing plate or a plate having a convex external surface of gradually decreasing radius.
i The present invention relates generally to papermaking machines and more particularly to stock inlet arrangements for such machines.
It has previously been proposed that formation of a paper web may take place between a foraminous forming fabric and a felt, with the forming fabric and felt being carried by two adjacent turning rolls, the arrangement being such that the forming fabric and felt are brought substantially into contact along web formation areas thereof lying along one or both of these rolls. After dewatering in the formation areas, the formed web follows and is carried by the felt, and subsequent dewatering and transference to steam heated driers occurs as the web travels with the felt. Such arrangements are disclosed in the co-pending application of C. A. Lee and C. A. Lamb, Ser. No. 161,058, filed Dec. 21, 1961, now Patent No. 3,224,928.
It is an object of the present invention to provide an improved form of this general type of arrangement which is particularly adapted for forming heavyweight sheets at increased speed of production and has increased web dewatering capabilities for such sheets.
Briefly stated, the present invention includes an inlet arrangement for a papermaking machine which provides a tapering forming section between a forming fabric or wire and a felt for preliminary dewatering action on the web being formed prior to the passage of the forming fabric and felt around a curved section, such as a turning roll, on which centrifugal force and a pressure between forming fabric and felt due to the curvature are exerted for intensive web dewatering action.
The invention consists of the novel constructions, arrangements and devices to be hereinafter described and claimed for carrying out the above stated objects, and such other objects, as will be apparent from the following description of preferred forms of the invention, illustrated with reference to the accompanying drawings, wherein:
FIG. 1 is a schematic fragmentary illustration of the wet end of a papermaking machine including the improved stock inlet construction of the invention;
FIG. 1A is a fragmentary illustration on an enlarged scale of the stock inlet construction of the invention; and
FIGS. 2 and 3 are fragmentary illustrations of modified stock inlet constructions of the invention.
Like characters of reference designate like parts in the several views.
Referring now to FIG. 1 of the drawings, the embodiment of the invention therein illustrated may be seen. to comprise a loop of web forming fabric or wire which is disposed about rolls 11, 12, 13, 14, 15, 16, 17 and 18.
The fabric 10 is a conventional paper web forming fabric for use in Fourdrinier machines made up of interwoven warp and shute strands for providing drainage openings there'between through which water may drain from dilute paper stock applied on the fabric. The strands may be either metal or may be of synthetic material in accordance with well known practice. The roll 12 may be termed a couch roll, since it is at this point that the paper web formed in the machine is removed from the fabric 10 as will hereafter appear; and the rolls 11, 13, 16, 17 and 18 are simple turning rolls. The roll 13 may be used as a stretch roll with suitable conventional mechanism (not shown) for simultaneously adjustably moving both ends of the roll for maintaining the fabric 10 taut about the rolls. The roll is a conventional guide roll having one end fixed and the other movable, and any suitable conventional apparatus (not shown) may be connected with the movable end of the roll 15 so that the roll functions to maintain the fabric loop traveling in substantially the same path about the rolls supporting the fabric. One or more of the fabric supporting rolls, such as, for example,
the roll 11, may be driven for the purpose of driving the fabric 10 so that it travels in the direction indicated by the arrow A.
An upper loop of fabric 19 is disposed about rolls 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, and 33, in addition to the roll 11. The fabric 19 is one that absorbs water to a greater extent than does the usual water draining paper web forming fabric. The fabric 19 may, for example, be a conventional papermakers top felt.
The rolls 27 and 29 are pressure rolls each of which has a pressure nip with a steam heated Yankee drier drum 34. The roll 29 may, for example, have a perforate periphery, and a suction gland 35 may be disposed within the roll 29 adjacent to its nip with the drum 34. All of a the other rolls supporting the loop of fabric 19 may have imperforate outer surfaces. The roll 22 is a conventional guide roll having one end fixed and the other end movable under the control of any suitable control mechanism (not shown) for maintaining the fabric 19 traveling in a predetermined path about the rolls supporting the fabric. The roll 24 is a conventional stretch roll having both ends simultaneously adjustably movable by suitable adjusting mechanism (not shown) for maintaining the fabric 19 taut about the supporting rolls. The roll 32 may constitute one roll of a main press 36 which also includes another roll 37 having a pressure nip with the roll 32. The roll 37 has a perforate outer surface, and a suction gland 38 is disposed within the roll 37 adjacent to the nip of the rolls 32 and 37. The roll 33 is located adjacent to the roll 12 to have a'slight pressure nip with the roll 12 so that the paper web transfers from the fabric 10 on to the fabric 19 as the fabric 19 leaves the couch roll 12.
An endless bottom felt 39 also passes between rolls 32 and 37. The felt 39 is held in looped form by means of supporting rolls 4t), 41, 42, 43, 44, 45 and 46. The roll 46 constitutes on roll of wringer 47 which includes also a roll 48 having a pressure nip with the roll 46. The roll 41 is a conventional stretch roll having both ends simultaneously adjustably movable by suitable adjusting mechanism (not shown) for maintaining the bottom felt 39 taut about its supporting rolls. The roll 44 is a conventional guide roll having one end fixed and the other end movable under the control of any suitable control mechanism (not shown) for maintaining the felt 39 traveling in a predetermined path about the rolls supporting the fabric. The others of the rolls 40 to 46 are simple turning rolls.
It will be observed that the rolls 11 and 18 are positioned with respect to each other so as to provide a stretch 102 of the fabric 10 which is substantially vertical. The roll 20 is so positioned with respect to the roll 11 as to provide a stretch 19z of the fabric 19 which lies slightly off vertical so that a tapered cavity 49 is formed between the fabric stretches 191 and 192. A flat backing plate 50 is disposed between the rolls 11 and 20 behind the fabric stretch 191, as illustrated. A stock inlet 51 is provided for directing paper stock into the cavity 49, and this inlet may comprise simply a pair of parallel plates 52 and 53 terminating within the cavity 49. The plates 52 and 53 may be positioned inch to inch apart and may be 12 inches to 20 inches in length, for example. More details of a stock inlet of this type which provides fine scale turbulence in the stock may be obtained from the co-pending application of David W. Appel et al., Ser. No. 278,521, filed May 2, 1963 (now abandoned).
In operation, the forming fabric or wire 10, the top felt 19 and the bottom felt 39 are respectively driven in the directions indicated by the arrows A, B and C by any suitable ones of the supporting rolls. Paper stock flows through the inlet 51 and between the parallel plates 52 and 53 into the cavity 49; and dewatering of the stock begins within the cavity 49, the water moving outwardly through the interstices in the fabric 10. Dewatering continues as the stock moves downwardly in the cavity 49 along with the fabrics and 19 and also continues as the fabrics travel around the roll 11.
The pressure between the fabric 10 and felt 19 is increased as the fabric and felt travel around the roll 11, and this pressure increases the dewatering action of the stock which by the time it reaches the roll 11 from the ends of the plates 52 and 53, is dewatered to some extent. The magnitude of this pressure varies with both the tension on the wire 10 and also the radius of curvature of the roll 11, the pressure increasing with increased wire tension and decreased roll radius. The centrifugal force on the water within the stock also is effective in dewatering the stock as it passes around the roll 11, as will be understood.
The paper web passes from the roll 11 to the rolls 12 and 33, and at this point it leaves the forming fabric 10 and travels on the under side of the felt 19 to the main press 36. The main press together with the bottom felt 39 further dewater the web, and the web travels along with the felt to the pressure roll 29 and transfers at this point to the Yankee drier 34 for drying and subsequent reeling.
The backing plate 51 is preferably provided behind the felt 19 in View of the fact that the felt 19 is general ly more elastic than the forming wire 10 and also in view of the fact that a less tension of 10 to pounds per lineal inch, for example, is maintained on the felt, as compared to the tension on the wire 10 of to 35 pounds per lineal inch, for example. The backing plate thus prevents bowing of the felt 19.
The provision of the tapered cavity 49 prior to the roll 11 provides preliminary dewatering of the stock prior to the high pressures and centrifugal forces effective as the fabric 10 and felt 19 pass around the roll 11. The illustrated arrangement thus is particularly suitable for heavy basis weight webs. The rate of closure of the forming fabric 10 with respect to the felt 19 in the vicinity of the cavity 49 can, incidentally, be controlled by ad justing the position of the roll 18 to provide optimum operating conditions for various basis weight webs. It will be obvious also that the length of the cavity 49 can be increased by moving the roll 18 and inlet 51 away from the roll 11 to thereby increase the drainage length of the cavity 49 prior to the roll 11 for heavier basis Weight sheets. Obviously, if it is desired to increase the pressure of the wire 10 on the felt 19 and the centrifugal force on the web as it passes around the roll 11 for increased dewatering action, the roll 11 may be decreased in radius.
Advantageously, the tapered cavity 49 provides a gradual closure between the wire 10 and the felt 19, before the wire and felt completely close around the roll 11, and allows dewatering and drainage from the web to take place without rejection of the stock, particularly the high consistency stocks for heavy basis weight webs, out from the nip of the wire and felt on the roll 11. The 21"- rangement provides a long, gradually closing forming area defined by the fabric 10 and felt 19 on the sides of the cavity 49 obviating the necessity for a large diameter forming roll 11.
The paper machine inlet arrangement illustrated in FIG. 2 is basically similar to that shown in FIGS. 1 and 1A, except that a rigid plate 54 has been substituted for the backing plate 50 and turning roll 11. The plate 54 iS flat from one end 54a to a mid-line 54b and is curved on a radius R from the mid-line 54b to the other end 540. Rolls 55 and 56 respectively support the wire 10a and felt 19a so as to provide the tapered cavity 49a extending from the rolls 55 and 56 to the mid-line 541) at which the felt and wire come together, and a supporting roll 57 is provided adjacent the end 54c of the plate 54 and between the plate 54 and rolls 12a and 33a that correspond with rolls 12 and 33. It will be understood that other rolls, such as rolls corresponding to rolls 13 to 17 and rolls 21 to 32 support the forming fabric 10a and felt 19a in looped form as in the first described embodiment. Dewatering of the sheet takes place within the tapered cavity 49a, and increased pressure between the fabric 10a and felt 19a and centrifugal force on the web for additional dewatering take place as the felt and fabric pass around the rounded part of the plate 54, similarly to the dewatering effect in the tapered cavity 49 and around the roll 11 in the first described embodiment.
The papermaking machine inlet arrangement illustrated in FIG. 3 is substantially the same as that shown in FIG. 2, except that a differently shaped plate 58 has been substituted for the plate 54. The forming fabric 10b is supported by the roll 55b and travels around the plate 58 and roll 57b to the rolls 12b and 33b corresponding to the rolls 12 and 33 and the rolls 12a and 33a. The felt 19b travels around the roll 56b and around the plate 58 also to the rolls 57b, 33b and 12b. The inlet 51b, which is similar to the inlets 51 and 51a, discharges stock into a tapered cavity 49b provided between the forming fabric 10b and felt 19b.
The plate 58 has a plane portion between one end 58a and a center line 58b extending longitudinally of the plate 58 which corresponds to the portion of the plate 54 between the end 54a and line 54b, and the fabric 10b and felt 19b come together substantially along the line 58b. The fabric 10b and felt 19b provide the tapering cavity 49b between the plate end 58a and the line 58b, and the initial dewatering of the stock occurs in this cavity. The plate 58, however, differs from the plate 54 in that, between the lines 58b and the end 58c, the plate 58 is provided with a changing curvature. The curvature of the plate 58 close to the line 58b is relatively slight; however, the radius of curvature of the plate 58 as it approaches the roll 57b becomes less and less. The radius of curvature along the longitudinal line 58a, for example, is much greater than is the radius of curvature along the longitudinal line 58:: on the plate 58.
The plate 58 with this gradually decreasing radius of curvature provides a greater and greater pressure between the forming fabric 10b and felt 19b as the fabric and felt approach the roll 57b and also provides more and more centrifugal force on the moisture in the web being formed between the fabric 10b and felt 19b as the web approaches the roll 57b. This increased pressure is in view of the relation mentioned above, namely, that the pressure between wire and felt increases with decreased radius of curvature. The arrangement illustrated in FIG. 3 is particularly suitable for very heavy basis weight webs and is such that rejection of stock back toward the inlet is less likely to occur with very heavy basis weight webs in view of the fact that, as a sheet is dewatered to a greater and greater extent, it is more able to withstand increased pressure between forming fabric and felt and increased centrifugal forces. Also, utilizing the arrangement of FIG. 3, greater forming speed and a drier sheet may be expected with such heavy basis weight webs than if a constant radius is utilized, such as, for example, the radius R of the plate 54b in FIG. 2.
I wish it to be understood that the invention is not to be limited to the specific constructions, arrangements and devices shown and described, except only insofar as the claims may be so limited, as it will be understood to those skilled in the art that changes may be made without departing from the principles of the invention.
What is claimed is:
1. In a paper web forming machine, an endless felt, means for moving and supporting said felt and including a roll about which the felt moves, and endless paper web forming fabric having interstices therethrough for draining paper stock deposited thereon, means for moving and supporting said fabric so that the fabric also extends around said roll on top of the felt, said supporting means for said fabric and felt including a pair of rolls one of which supports the fabric and the other of which supports the felt and which are so spaced and positioned that the fabric and felt form a tapering cavity between them extending from these rolls to said first named roll, a paper stock inlet for discharging stock into said tapering cavity, and a flat backing plate disposed within said felt and backing the portion of the felt that extends from said first named roll to one of said pair of rolls for preventing substantial bowing of the felt under the action of the paper stock discharged into said cavity.
2. In a paper web forming machine, an endless felt, means for moving and supporting said felt and including a plate having a convex external surface about which the felt moves, and endless paper web forming fabric having interstices therethrough for draining paper stock disposed thereon, means for moving and supporting said fabric so that the fabric also extends around said convex surface on top of the felt, said supporting means for said fabric and felt being so arranged that the fabric and felt form a tapering cavity between them which extends to said convex surface, and a paper stock inlet for discharging stock into said tapering cavity, said convex surface gradually decreasing in radius of curvature in the direction of movement of said fabric and felt about said surface.
3. In a paper web forming machine, an endless felt, means for moving and supporting said felt and including a plate having a plane external surface joining a convex curved external surface and positioned so that the felt moves on said plane surface and from thence around said convex surface, an endless paper web forming fabric having interstices for draining paper stock deposited thereon, means for moving and supporting said fabric so that the fabric also extends around said convex surface on top of the felt and travels with the felt and forms a tapering cavity between it and the portion of the felt on said plane surface, and a paper stock inlet for discharging stock into said tapering cavity.
References Cited UNITED STATES PATENTS 1,927,360 9/1933 Edge 162317 X 2,977,277 3/1961 Kelly 162-403 3,132,990 5/1964 Trufitt 162317 3,224,928 12/1965 Lee et al. 162-203 X FOREIGN PATENTS 4,182 1881 Great Britain.
S. LEON BASHORE, Primary Examiner.
DONALL H. SYLVESTER, Examiner.
J. NEWSOME, Assistant Examiner.