US3853695A

US3853695A - Entraining a liquid into a fiber slurry to accelerate it prior to discharge from a flow path onto a forming wire

Info

Publication number: US3853695A
Application number: US00437112A
Authority: US
Inventors: I Reba; D Wilhoit; S Back
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-10-12
Filing date: 1974-01-28
Publication date: 1974-12-10
Anticipated expiration: 1991-12-10

Abstract

A slurry mixture of fibrous material and fluid is introduced into a predetermined flow path which leads to an exit aperture. A restricted opening preferably in the form of a slit is provided which communicates with the flow path at a predetermined location upstream from said exit aperture. An entraining fluid, such as clear or white water, is introduced through the slit and into the flow path whereupon the entraining fluid, due to a ''''Coanda effect,'''' attaches itself to a convexly-curved flow attachment surface positioned adjacent to said slit whereby said entraining fluid flows along said flow path in a direction toward said exit aperture at a velocity substantially greater than the flow velocity of the slurry upstream from the slit. The entraining fluid accelerates the slurry and causes same to exit from the exit aperture at a high rate of speed to the forming surface of a web-forming machine positioned adjacent to the exit aperture.

Description

United States tt- 1191 Back et a1.

[ ENTRAINING A LIQUID INTO A FIBER I SLURRY TO ACCELERATE 1'11 PRIOR TO DISCHARGE FROM A FLOW PATH ONTU A FORMING WIRE [22] Filed: Jan. 28, 19741 [21] Appl. No.: 437,112

Related US. Application Data [63] Continuation of'Ser. No. 297,094, Oct. 12,1972,

abandoned.

52 U.S. c1 162/216, 162/104, 162/129, 162 336, 162/338, 162/343, 162/344,

51 1m. (:1 ..D21i1/02,D21fl/06 [58} Field of Search 162/216, 104, 129, 336,

[56] References Cited UNITED STATES PATENTS 2,017,339 10/1935 Bryant et a1. 162/104 2,052,869 9/1936 Coanda... 28/114 X 2,615,374 10/1952 Malkin 162/347 2,904,461 9/1959 Washburn et a1 162/344 X- 1451 Dec. 1111, 197 4 Primary ExaminerS. Leon Bashore Assistant Examiner-Richard H. Tushin Attorney, Agent, or Firm'Thomas R. Lampe [57] ABSTRACT A slurry mixture of fibrous material and fluid is introduced into a predetermined flow path which leads to I an exit aperture. A restricted opening preferably in the form of a slit is provided which communicates with the flow path at a predetermined location. upstream from said exit aperture. An entraining fluid, such as clear or white water, is introduced through the slit and into the flow path whereupon the entraining fluid, due to a Coanda effect, attaches itself to a convexly-curved -flow attachment surface positioned adjacent to said slit whereby said entraining fluid flows along said flow path in a directiontoward said exit aperture at a velocity substantially greater than the flow velocity of the slurry upstream from the slit. The entrainingfluid accelerates the slurry and causes same to exit from the exit aperture at a high rate of speed to the forming surface of a web-forming machine posi tioned adjacent to the exit aperture.

24 Claims, 10 Drawing Figures PATENTEL k 3 853.59?)

NEW 18? 5 PMENIEL SEE I 0 I974 SHEET 4 0F 5 1 ENTRAINING A LIQUIDINTO A FIBER SLURRY TO ACCELERATE IT PRIOR TO DISCHARGE FROM A FLOW PATH ONTO A FORMING WIRE This is a continuation of application Ser. No. 297,094 filed Oct. 12, 1972, now abandoned.

BACKGROUND OF THE INVENTION.

The present invention relates to an apparatus'and method for delivering a fiber slurry to the forming surface of a web-forming machine, such as the wire of a Fourdrinier-type papermaking machine.

In a typical web-forming machine, such as a papermaking machine, the fiber slurry, which is disposed in a headbox, is ejected from the exit slit of the headbox onto a Fourdrinier wire or other suitable web-forming device by having energy transmitted directly to the fiber suspension or slurry itself. This is conventionally accomplished in existing equipment by feeding the entire stream of fibrous slurry through a pump which exerts sufficient energy to expel the fibrous slurry at the desired velocity through the discharge orifice of the headbox. Alternatively, the head of the slurry itself is utilized to force the slurry out of the headbox discharge orifice. Such an approach obviously requires a headbox of great depth to maintain the exit speed of the slurry at a sufficiently high velocity to provide for proper delivery of the slurry as it exits from they headbox discharge orifice. Sometimes, the energy used to accelerate the fiber slurry is at least partially derived from a pressurized air cap above the slurry in the headbox.

headboxes is the-nonuniform distribution of the energy applied to the system across the span of the discharge jet. Nonuniforrn distribution of energy ismanifested in several ways such as cross-machine velocity gradients, locally high or low velocities, transient disturbances, wakes, cross-flows and nonuniform turbulence scale. In turn, these phenomena appear in the finished, dried, fibrous web as undesirable thick spots, thin areas, patterns or blemishes.

In addition to the nonuniform distribution of energy, the typical headbox also creates a situation of nonuniform distribution of fibers. Fibers in suspension tend to form flocs, clods, or agglomerations which, if not broken up in some manner, will likewise cause the finished, fibrous web to have undesirable local irregularities. In the case of existing web-forming machines, it has been necessary to employ rectifier rolls, baffles, tubes, converging plates or other physical means of controling or acting upon the mass and energy distributions of the entire fibrous slurry in attempts to obtain uniform distribution of energy and fibers.

According to the present invention, many of these typical flow problems are overcome so that the fiber suspension may be accelerated to the desired uniform velocity and dispersion of fibers immediately 'prior to discharge to the forming wire or other forming surface of a web-forming machine. This is accomplished by utilizing a phenomenon'known as the-Coanda effect to indirectly accelerate the slurry. The Coanda effect has been known for many years, as exemplified by US. Pat.

No. 2,052,869, issued ,to Henri Coanda'. Briefly, this phenomenon can be described as the tendency'of a fluid, which emerges from a slit under pressure, to attach itself or cling to and follow a surface in the form of an extended lip of the slit, which recedes from the One major problem inherent in these typical existing 2 flow axis of the fluid as itemerges from the slit. This creates a zone of reduced pressure in the area of the slit so that any entrainable material which is in the zone will become entrained and flow with the fluid which has attached itself to the extended lip.

SUMMARY According to the present invention, the Coanda effect has been utilized as a direct means for introducing a high percentage of all energy required to accelerate slurry fibers through a discharge orifice to a foaming surface. Specifically, energy is introduced into the slurry stream by forcing a fluid under pressure through a narrow slit communicating with. the slurry flow path and causing said fluid to attach itself to a convexlycurved fluid flow attachment surface adjacent tosaid slit whereby the entraining fluid, by virtue of the Coanda effect, rapidly proceeds toward an exit aperture for the'slurry. Rapid flow of the entraining fluid after expulsion from the slit, induces flow of the slurry, causing same to be entrained and accelerated, and the combined flows then mix and proceed toward the exit aperture. In other words, in contrast to conventional headbox arrangements wherein the slurry stream is pushed through the exit aperture, in apparatus con-- structed in accordance with the present invention the slurry stream is ,pulled through the exit aperture. Consequently, handling of long, fibrous materials is facilitated, without tangling and matting problems customarily associated with such materials. During-the interval from the slit to the exit aperture, the high, initial velocity and concentration gradients between the two streams tend to level out resulting in a relatively uniform vertical slurry concentration and energy distributions at the point of discharge.

In practice, clear or white water under pressure may be utilized in the system of this invention as the entraining fluid. Because theentraining fluid is a clear liquid, its energy content may be easily controled and modulated, and many of the problems that usually attend attempts to modulate and control velocity (or energy), such as nonuniformities in pulp slurry, are eliminated. Simple, inexpensive screens, and/or small diameter tubes whch are commonly used to smooth and control velocity and turbulence in clear fluids, may freely be used to achieve dessired desired characteristics of entraining fluid expelled through the slit. In this way, the problems of shedding, plugging, etc., which are encountered when control of the entire process slurry stream is attempted, may be avoided.

Furthermore, the necessity of utilizing rectifier rolls is eliminated due to the shear conditions imposed on 'the incoming, entrained fiber slurry. The velocity ratio between the entraining fluid andthe entrained fiber slurry stream is in the order of at least ten in the region of initial mutual contact therebe'tween. The resultant highshear with combined dilution breaks the flocs and creates a condition of uniform fiber dispersion as the entraining fluid and slurry mixture exit together onto a web-forming surface.

The method and apparatus according to the present cessity for any pressure cap and/or direct pumping of the slurry. It also permits the use of a low profile construction, and offers the ability to control basis weight of the web with minimum time delay. The invention has as its further aspect the provision of an improved method and apparatus for delivering a fibrous slurry to a forming machine which is readily adapted to a wide variety of slurry types and consistencies.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the present invention are illustrated in the accompanying drawings in which:

FIG. 1 is a generally diagrammatic side view and partial section of apparatus constructed in accordance with the principles of the present invention;

FIG. 2 is an enlarged cross-sectional view illustrating certain operational details of the apparatus of FIG. 1.

FIG. 3 is a view taken along line 3- -3 of FIG, 1;

FIG. 4 is a view taken along line 44 of FIG. 1;

FIG. 5 is a vertical cross-sectional schematic view of a fragmentary portion of an alternative embodiment of a machine constructed in accordance with the teachings of the present invention;

FIG. 6 is an enlarged, vertical, cross-sectional schematic view of a fragmentary portion of still another type of machine incorporating the present invention;

FIGS. 7, 8 and 9 are side elevational, sectional views showing selected components of still another alternative embodiment of a machine constructed in accordance with the present invention, said components being illustrated in three separate, selected, operational GENERAL DESCRIPTION Reffering now to FIGS. 1, 3 and 4, the apparatus constructed in accordance with the teachings of the present invention is indicated generally by means of reference numeral 10'. Apparatus 10 includes a bottom wall 12, end walls 14 and 16, and

side walls

18 and 20. The walls may be constructed of any suitable material such as reinforced plastic or stainless steel and are secured together in any desired manner to provide a generally box-like configuration. Disposed within the walls are three segmented

separate baffles

21, 23 and 36. Lower baffle 21 has a top contour defined by the surface 22. Baffle 23 has a flow surface 24 and is pinned and capable of rotation about its mounting pin -25 to permit minor adjustments of the flow channel defined between

surfaces

22 and 24. Baffle 36, having a flow surface 34, operatessimilarly to 23, and can be selectively moved about its mounting pin 27 to adjust the clearance between surfaces 34 and 22.

Pins

25 and 27 extend between side walls 18 and and are mounted thereon in any suitable manner. Baffles 21, 23 and 36 may be constructed of any suitable material such as plastic. With particular reference to FIG. 3, aplurality of divider panels 28 extend lengthwise between the confines of

side walls

18 and 20, thereby dividing the apparatus 10 are adapted to maintain a constant head in reservoir 50 walls are separate segments or slices of

baffles

21, 23

and 36, the respective contoured surfaces 22 24 and 34 of which form in each chamber 30 a flow passage 100 (FIG. 1 The segments of

baffles

21, 23 and 36 are of a size to fit snugly against panels 28, thereby permitting easy adjustment of these baffles to vary the configuration of the flow passage. If desired, the baffles may be mounted for total removal from the rest of the apparatus.

A plurality of flexible slurry-supply conduits communicate with the interior of each chamber 30 through apertures formed in end wall 16. The slurry-supply conduits 40 are attached to the end wall 16 by suitable coupling elements 42. The other ends of slurry-supply conduits 40 are connected through valves 46 to the interior of head control box or reservoir 50. Reservoir 50 may be selectively moved up or down through a suitable mechanism (not shown) with respect to its supporting wall 52. Reservoir 50 is adapted to supply fiber slurry to apparatus 10 in a manner that will be described in greater detail below. A plurality of supply tubes 54 lead to the interior of reservoir 50 as shown. The other ends of the supply tubes are connected to a main fiber slurry stock reservoir (not shown) whereby reservoir 50 is continuously supplied from the main stock reservoir. One or more overflow lines 56 may be provided which and allow the overflow to return to the main stock reservoir. The rate of discharge from head control box or reservoir 50 may be controled by adjustment of valves 46 and/or by raising or lowering same with respect to its supportingwall 52. v

Referring now to FIGS. 1, 2 and 4, apparatus 10 includes at the forward or downstreamend thereof (the left-hand side of the apparatusas viewed in FIGS. 1 and 2) a mechanism utilizing the Coanda effect which induces flow in the fiber slurry introduced in apparatus 10 and causes same to exit onto a web-forming surface such as a Fourdn'nier wire 58 which is conventionally joumaled on a breast roll 60 to receive the fiber slurry exiting from apparatus 10 in a manner to be described.

Depending from the downstream end of bottom wall spect thereto. A hydraulic or electrically operable ram device 70, or other suitable mechanism, is employed to move the upper end of first slit-defining member 6810 the desired predetermined location. A number of such rams are distributed span-wise along member 68 so that the local span-wise position ofmember 68 may be precisely controled.

- an entraining fluid flow path 74 is defined by the first into a plurality of substantially equi-dimensioned chambers 30. Sandwiched between adjacent divider panels 28 and between the endmost panels and side and second slit-defining

members

68 and 72 and side plates 76 and 78 (FIG. 4) which extend upwardly from support frame 64 and are attached to

side walls

18 and 20 in any desired fluid-tight manner. A pressure gauge 80 is preferably attached to second slit-defining memher 72 so that the pressure of the fluid flowing through entraining fluid flow path 74 may bemonitored. The upper end of second slit-defining member 72 has formed thereon a convexly-curved fluid-flow attachment surface or foil 82. Fluid-flow attachment surface 82 leads from a slit 84 formed between the upper end of first slit-defining member 68 and the second slitdefining member 72. The curved fluid-flow attachment surface 82 is in the form of an extended lip which recedes from the flow axis of fluid as it emerges from the slit to provide a flow attachment surface for the fluid so that it operates in accordance with the aforementioned Coanda effect.

Leading to the entraining fluidflow path 74 through apertures provided in support frame 64 are a plurality of entraining fluid conduits 86. The other ends of the conduits are connected to a manifold 88. The interior of manifold 88 is connected to a suitable source of pressurized entraining fluid through valve 90. The manifold and plurality of conduits operate to introduce entraining fluid into entraining fluid-flow path 74 in a uniform manner across the width of the fluid-flow path.

Cooperating with second slit-defining member 72 to form an exit aperture from the interior of apparatus is an articulated upper lip comprised of a first lip element 92 pivotally attached to pin 25 so that it overhangs slit 84 and a second lip element 94 pivotally atto one another and relative to thecurved fluidflow attachment surface 82 controls such characteristics as entrainment ratios, angle of the discharged jet, turbulence and jet stability.

Curved surfaces

22, 24 and 34 and the divider panels 28 serve to smooth out the flow of the slurry as it progresses through apparatus lift. in addition, such elements discourage coagulation, eliminate back flow, eddies and vortices, which will cause air entrainment. Also, flow path 10% is designed to develop a uniform flow velocity for the slurry as it approaches the vicinity of slit 84.

tached to lip element 92 at the outermost extent 7 thereof.

Lip elements

92 and 94 are adapted for relative rotation with respect to wall 14 and with respect to each other by means of prime movers, which, in the present embodiment, are in the form of

hydraulic rams

96a and 96b.

The operation of the aforedescribedembodiment of the present invention is as follows: For purposes of H lustration, the apparatus and method according to the present invention will be described as being utilized in the papermaking art, with the fiber slurry being a conventional pulp slurry and the entraining fluid being water. It will be appreciated, however, that the apparatus and method may be utilized to advantage with a wide variety of slurry and entraining fluid materials.

Valve 90, controling the entraining fluid, which, in i this case, is clear or white water, is opened allowing the water to enter into manifold 88. The water moves along entraining fluidflow path 74 and thence'through the slit 84 at which point it attaches itself to curved fluid-flow attachment surface 82 by virtue of the Coanda effect and flows in the direction of the arrow towardthe exit aperture of apparatus 10 formed between the fluid-flow attachment surface $2 and

elements

92 and 94.

At the same time, the desired. pulp slurry head is established in reservoir or head control box'50, and

The combined flows progress from'the region of the slit to the exit aperture and then on to the forming surface of the web former, which in this case is Fourdrinier wire 5%. Thorough mixing of the water and pulp slurry occurs in the region between slit 84 and the exit aperture. Adjustment of

lip elements

92 and 94 with respect The velocity ratio of the entraining fluid to the entrained slurry is one way to define the conditions for proper operation of the present apparatus. F or efficient operation of the apparatus, the velocity ratio between the entraining fluid and the slurry immediately upstream from the slit 84 shouldpreferably be at least equal to the value of ten and, typically, may have a value of twenty or more. The high velocity differentials existing between these two streams result in another important advantage for this system. The extreme shears generated will disperse the fiber flocs or agglomerates, and the simultaneous dilution by the entraining fluid will prevent flocs from reforming. Dispersion is thus effected fluid-dynamically eliminating the need of troublesome mechanical devices such as the rectifier roll.

Another way of defining the'operating conditions for this method and apparatus is to note the ratio of the kinetic energy level of the entraining fluid to that of the entrained slurry stream immediately upstream from the slit. Kinetic energy content at the given point of interest is defined as mass flow rate times velocity squared divided by two times g (the conversion factor) mv /2g Units derived from this expression are footpounds/seconds. The ratios for efficient operation of the apparatus and method according to this invention are preferably greater than 5% and may run as high as 400, or more.

Operation of the structure thus far described can best be understood by referring to F lGS. l and 2 in connection with the following description. A device, as illustrated in FIGS. l and 2, was constructed having a width of twelveinches. Apparatus Ml wasleft open to the air and a stock head of only eleven inches, i.e., approxi mately 0.4 psi, was maintained. The slurry utilized was a pulp slurry and the entraining fluid was clear or white water. During operation of this unit, the width of slitd tl was selectively varied between 0.01 inch and 0.07 inch. With the velocity ratio between the entraining fluid and the slurry immediately upstream from the slit (approximately one inch from the slit in the illustrative device) being maintained at a value of 10 or more, approximately 90 percent or more of the energy neededto accelerate the fiber slurry was supplied by the entraining fluid. Since the entraining fluid itself contained no fibers, it was able to pass through small valves, small diameter tubes and orifices without plugging or shedding,

I problems which typically attend flow of a fiber slurry between these two streams resulted in extreme shears through such apparatus. in this way, the energy required to drive the system was thoroughly controled before it performed the ultimate. task of accelerating the fiber slurry. The high velocity differentials existing which dispersed the fiber flocs or agglomerates.

In general, it has been found that discharge velocity of the material from the apparatus desscribed varies in accordaznce with changes made in the width of the slit and the pressure of the entraining fluid, the higher the pressure and/or the wider the slit, the higher the discharge velocity. Likewise, the exit aperture or slice dimension A and the throat dimension B, shown in FIG. 2, are important variables for regulating the discharge velocity of the jet. In general, minimizing throat and slice will yield higher discharge velocites.

An important interrelationshp having a bearing on proper operation of apparatus constructed in accordance with the teachings of the present invention exists between R, the radius of curvature of the fluid-flow attachment surface at the location of the slit 84, and the width (hereinafter,S) of the slit. Experimental data suggests that the apparatus will operate efficiently when the ratio of R to S, i.e., R/S, lies in the range of from 2.5 to 150.

The entrainment ratio, which is defined as the mass or volumetric ratio of the slurry stock to the entraining fluid flow, depends upon the width of the slit and, also, upon the width of the exit aperture. Furthermore, the ratio between exit aperture or slice dimension A and the throat dimension B has a critical effect on entrainment ratios. In general, the slice-to-throat ratio increases, the entrainment ratio also increases; however, when slice-to-throat ratio exceeds unity, the resulting divergence of the jet may limit the practical value of slice-to-throat ratios greater than one. Entrainment ratio also depends on pressure of the entraining fluid to a lesser degree, with the entrainment ratio increasing gradually as the pressure decreases. I

It is felt that the ability to handle a wide range-of pulp consistencies, especially those of a high consistency, is one of the important advantage of the present invention as compared to the prior art. Experimentation has shown that apparatus constructed in accordance with the teachings of the present invention is capable of handling pulp slurries in the high consistency range of from 1 to 4 percent or above, as well as those slurries in the low consistency pulp range of between 0.2 and 1.0 percent. Virtually any slurry which can be delivered to theapparatus may successfully be delivered from its exit aperture at high speeds. It should be understood that the dilution of the entrained fiber slurry by the entraining stream is one of the necessary aspects of operation for the apparatus. For example, if the entrained slurry is supplied at 4 percent consistency and the entrained slurry flows in a rate twice that of the entraining fluid (i.e. entrainment ratio equals 2), then the discharge consistency will have been diluted to 2.67 percent. Corresponding dilution of the incoming fiber will occur according to the entrainment ratio resulting from specific operating conditions.

shapes of the slurry-flowpath defining means may be varied, as, for example, in the manner illustrated in' FIG. 5. In that figure, the Coanda effect is actually utilized in a plurality of locations in the illustrated apparatus. In this embodiment, two or more fiber slurries may be mixed just prior to their ejection on to an appropriate web-forming surface. In unitary chamber H0 of the illustrated alternative embodiment, for example, may be disposed a synthetic fiber slurry H2 which is kept continually mixed by means of a mixed impeller H4 driven by a suitable prime mover such as electric motor I 16. Flowing through conduits U8 into a flow path defined by

curved baffle members

120 and 122 is a second type of slurry, for example, a conventional wood pulp slurry. Alternatively, one of conduits 118 may be a source of a chemical or, for that matter, plain water. Simultaneously, any desired fluid such as water may be introduced through conduit 124 into a flowpath defined by bent wall 126 of chamber 110 and a plate 128 extending downwardly from a convexly-curved fluidflow attachment surface 130 formed on baffle member 122. Since a'slit is formed between the uppermost extent of bent wall 126 and the plate I28 at the location where the plate joins baffle 122, the Coanda effect will operate to direct flow of the fluid passing through conduit 124 about convexly-curved fluid-flow attachment surface 130. This fluid flow will serve to entrain and induceflow of synthetic fiber slurry 112 as shown by the arrows.

A convexly-curved fluid-flow attachment surface 132 is also formed on baffle member 120 in the vicinity of a slit 134 formed by the outermost extremity of baffle member 122 and baffle member 126. This arrangement again utilizes the Coanda effect to induce additional flow of synthetic fiber slurry I 12 and cause same to mix with the material exiting from conduits 118.

The final application of the Coanda effect in the FIG. 5 embodiment is at the downstream end of the apparatus wherein a fluid such as water is injected through manifold 136 and conduits 1138 into passageway M0. The fluid exits from the passageway through a slit in the vicinity of a convexly curved surface formed on a lower rotatable jaw member 142 which defines, along with upper jaw member 143, the exit aperture from the apparatus. The material, such as water, which flows through passageway H40 attaches itself to the curved surface of the lower jaw member and thus entrains and mixes with the material flowing into engagement therewith, the purpose of the final slit being to accelerate the incoming mixture to the final desired velocity.

The arrangement illustrated in FIG. 5 has great versatility in that it can be used to form a wide variety of webs through the admixture of various types of slurries and fluids. For example, soluble chemicals, such as wet strength aids, drainage aids or flocking agents, which may hamper operation of upstream screens or media. equipment, might successfully be introduced in one of the entraining mecia. Chemical reactants f one introduced on the fibers (such as polyvinyl alcohol) and the other introduced as a soluble salt in the entraining stream (such as borax) might be utilized in the manufacture of paper products. Similarly, dispersions of foamed fibers for functional webs can be introduced to the system and accelerated to high speeds. If desired, a reinforcing scrim of nylon or other suitable material may be fed into the system, as shown schematically and identified by means of reference numeral 146. Because the system utilizes induced flow and a high velocity anism, the scrim may be placed on a freely rotating roll and will be self-fed therefrom by virtue of its entrainment in theflow path stream. The slurry fibers will adhere to the scrim upon its exit from the apparatus and reinforcement means is thus provided for the finished web.

Referring now to FIG. 6,'still another alternative embodiment of apparatus constructed according to the teachings of the present invention is illustrated. A'fiow path for the slurry being delivered from a suitable reservoir is defined by

curved walls

150 and 152. The walls converge and gradually flatten out with the terminal portions thereof cooperating with

jaw members

154 and 156, respectively, to provide narrow slits l58'and 160, as shown.

Jaw members

154 and 156 are provided with convexly-curved fluid-flow attachment surfaces 162 and 166 leading in a downstream direction from

slits

158 and 160, respectively. The size of

slits

158 and 160 may be varied by the operator through the manipulation of

cantilever members

166 and 168 as by means of

hydraulic ram members

170 and 172. Fluid flow paths are defined by the jaw members and the cantilever members so that a desired fluid may be introduced through the slits into the slurry flow path, as indicated by the arrows, so that the slurry is entrained at both the top and bottom thereof prior to its exit from the aperture formed by the jaw members. In other words, entraining fluidsare introduced at two locations in the system and the Coanda effect is utilized at both locations. Introduction of entraining fluid at both locations enhances the jet discharge velocity through the exit aperture as compared to the single slit apparatus of FIGS.

1-4. The same type of entraining fluid may be used at both locations or, alternatively, two different types of while the other may be a source of clear water. The ap paratus shown in FIG. 6 may be used, if desired, to

form a multilayered web.- To produce a two-layered web, two slurries I51 and 153 are introduced thereinto from two separate sources of slurry (not shown). A thin, flexible plastic or metal strip 149, anchored at a location upstream of entry points for slurries 151 and 153, and fixedly secured to the side walls of the unit, maintains separation between the two entrained slurry streams I51 and 153, as they flow simultaneously toward the exit aperture. One potential application for such an arrangement may, for example, be in the manti facture of linerboard having a good print surface on its exterior and an inexpensive fibrous body. This construction could be made by introducing board stock as slurry I53 and the print-grade fiber as slurry 1511. Other potential applications will become-readily apparent to those skilled in the art of sheet-and web-forming. If desired, the separation strip may beadjustably mounted in any suitable mannerrelative-to the side walls of the unit so that the relative thicknesses of the slurry layers may be selectively varied.

Still another alternative embodiment of apparatus constructed in accordancewith the teachings of the present invention is shown in FIGS. 7, 8 and 9 of the drawing. This embodiment incorporates features which render it particularly effective for use with a wide variety of slurry materials and other changing operating conditions.

Large scale turbulence is an undesirable property of the jet discharged from the apparatus as it leads to nonuniformities in the finished wet web product. Through the utilization of the form of apparatus shown in FIGS. '7, 8 and 9, reduction in the scale of turbulence and consequent minimization of local irregular flow pat terns in the discharge stream may readily be effected. It has been found that the location of the slit through which the entraining fluid exits into the main flow path of the apparatus relative to its associated flow attachment surface has a marked influence on the formation and location of eddies, back flow systems and vortices in the area of mixing of the entraining fluid and the entrained slurry. This area is located between the slit and the exit aperture. The eddies and vortices which form in this mixing zone, in turn, control discharge jet stability and turbulence level. With the form of apparatus shown in FIGS. '7, 8 and 9, the location of the slit relative to the flow attachment or foil surface may be adjusted in accordance with changed materials or conditions encountered, such as changes in entraining fluid or. slurry consistency or pressure, changes in the dimension of the exit'aperture, throat opening and slit width, contour and length of lips, etc. Additional influence on turbulence and efficiency of the discharge jet from the apparatus may be effected through the utilization of lips of various lengths, contour and flexibility.

In the form of apparatus shown in FIGS. '7, h and 9,

two lips 174i and 1176 are employed to define at the extremities thereof an exit aperture or slice A and a throat opening B. Upper lip I74 is connected at the up a span-wise beam element 192. The outer or down-.

stream terminal end of lower lip ll76 also cooperates with a similar beam element 196. The clearance between lips IM and 176 (which in turn influences discharge jet turbulence and stability) can be adjusted overall and/or locally by appropriate motion of rams 1M and T89, a number of which are disposed lengthwise in operative association with their

respective beam elements

182 and 186. It is also by virtue of adjustment .of rams 1184- and M9 and attached beam elements 162 and 1196, that the thickness and velocity of the dis- 'convexly-curved fluid-flow attachment or foil surface 266 formed on member 193. Mounted in any suitable manner for rotatable ,rnovemen't relative to member 1193, is a rotatable member 196 which may be selectively positioned relative to member 193 through the action of a cooperating geared driving pinion T94,

which, in turn, is driven by a suitable prime mover (not shown).

Rotatable member 190 has formed therein a fluid flow path 196 for entraining fluid which is introduced therein through conduit 198. The upper right-hand side of the flow path 196 is, as may be clearly seen with reference to the figures, defined by a cantilever member 200 which is fixedly attached at the lower end thereof to rotatable member 190. Attached to the upper terminal end of cantilever member 200 is a flexible, fluidflow-path defining plate 202 which has the other end thereof rigidly secured to a fixed fluid-flow-path defining member 204. Thecantilever member 200 cooperates with the curved fluid-flow attachment surface 206 formed on fixed member 193 to form a narrow slit 208 through which the entraining fluid exits. A cam member 210 is mounted on a bracket affixed to rotatable member 190 to selectively vary the size of the slit 208, as desired, by its interaction with cantilever 200.

Through the rotation of

members

190 and 200 relative'to member 193 by pinion 194, the location of the slit 208 relative lto flow attachment surface 206 may be selectively varied to control turbulence and efficiency of the apparatus for a wide range of conditions, including changes in the entrained slurry consistency, speed of discharge jet, slice opening, basis weight of desired product. For optimum operation of the induced flow system according to this invention, a balance is established among entrainment efficiency, discharge velocity and turbulence of the discharge jet. To compensate for changes in the width of slit 208, the height of the exit aperture A, throat opening B, and pressure of the entraining fluid, angular orientation of the slit may be changed by rotating rotatable member 190 as shown in FIGS. 8 and 9, which illustrate the extreme positions which may be assumed by this member. It should be noted that rotation of member 190 also has the effect of changing the angular disposition of the-slit discharge axis relative to the axis of the flow path. To illustrate the operation of the embodiment FIGS. 7, 8 and 9 more clearly, it will be assumed that the slurry mixture is a pulp slurry and the entraining fluid is water. After introduction of water under pressure through conduit 198, the flow is through fluid flow path 196 and then outwardly through slit 208. The size of the slit may be adjusted by rotation of the cam member 210 against the cantilever member 200. As has been described with rspect'to the otherembodiments of this invention, the entraining fluid issuing from the slit accelerates the entrained slurry stream which is introduced into the channel formed by curved plate 178 and flexible plate 202 from whence it progresses through lips 1'74 and 176 and discharges onto a webety of physical characteristics. For example, either or both of the lips may be rigid or flexible. Also, the lips. may be curved or straight, have varying lengths, or be constructed of different, suitable materials. For example, in FIGS. 7, 8 and 9, lip 174 is illustrated as being straight and constructed of relatively thin, flexible plastic material while lower lip 176 is illustrated as being curved and constructed of stainless steel which is thick enough to prevent deformation of lip 176. Lip 174, on the other hand, is flexible enough to deform under the pressures exerted by the slurry flow. It has been found that at least under certain conditions the use of at least one flexible lip results in minimizing turbulence and increasing entrainment efficiency due to the ability of the flexible lip to respond to changes in pressures exerted thereon by the slurry flow. If desired, the lips may be selectively releasably secured to the rest of the apparatus by means of clamps or other releasable attachment means so that different types of lips may be interchanged, as desired by the operator.

Although the apparatus according to the present invention has thus far been illustrated as being utilized to deliver slurry streams in a generally horizontal direction onto a horizontally disposed web-forming surface, the principles of the invention may be employed on apparatus adapted to deliver a slurry in other than a horizontal direction and onto a web-forming surface that is disposed other than horizontally; for example, the present system may be utilized in combination with a generally vertically disposed twin wire paper former, such as the Verti-Former former manufactured by the Black Clawson Company and the Bel Baie former manufactured by Beloit Corporation.

An embodiment of the present invention that may be employed in connection with generally vertically disposed forrners is illustrated in FIG. 10. This apparatus incorporates several features already discussed, such as the dual entraining fluid system and dual fluid attachmerit surfaces which permit operation at speeds-and slice openings greater than those obtainable with the single foil surface arrangement. Also, the apparatus of FIG. 10 incorporates an arrangement whereby the posi- 1 tion or discharge angle of the entraining fluid slits may be varied with respect to the direction of slice discharge, thus providing a high degree of adjustability to the system. Furthermore, the system can be fed with two or more separate entrained flow slurries or with a single slurry, as desired.

The entraining flow is supplied under pressure through flexible supply conduits 198a and 19812 and attaches to the fluid-flow attachment surfaces 206a and 206!) formed on members 103a and 193i).

The slit openings can be adjusted by operating cams 210a and 210b, while slit location with respect to the fluid-flow attachment surfaces 206a and 206b can be appropriately adjusted by rotation of pinions 194a and 1194b which, in turn, will rotate members a and b and other integrally attached elements in the manner previously disclosed relative to the apparatus lid of FIGS. ,7, 8 and 9. Dimension B, which is the throat or distance between the foil surfaces 206a and 206b, is not adjustable in the arrangement here illustrated; however, suitable means for providing such adjustment could be readily devised and utilized where appropriate.

The entrained slurry is supplied from one or more head control boxes similar in design and concept to that shown in FIG. 1, but not illustrated in FIG. 10. Slurry flow from the head control box (or boxes) then proceeds via flexible tubes 212a and 2ll2b through side walls 214a and 2141b into a passageway defined by lower baffle member 220 and curved upper plates 222a and 2221) which are attached to the side walls. The

walls

214a and 214b, the

plates

222a and 222b and the lower baffle member 220 may be constructed of any suitable material, such as plastic or stainless steel.

Plates

222a and 22% are curved upwardly, as shown, to provide a centrally disposed orifice in communication with'throat opening B. The uppermost portions of the plates 222a and 22212 are in fluid-tight, slideable engagement with cantilever members 200a and 200b, respectively. Member 220 is shaped to insure that the slurry passageway gradually converges as it approaches the throat opening. Two or more-types of slurry material may be introduced into the system merely by placing conduits 212a and 21212 in communication with separate sources of different slurries. Slurry material will then enter the system from both the right and left sides, as viewed in FIG. 10. If, however, the operator wishes to draw slurry from only one side of the unit, a baffle plate, such as baffle plate 240 (illustrated by dashed lines), may be mounted in any suitable manner within the system to cut off flow from one side or other of the system.

By virtue of the Coanda effect previously described, slurry flowing into the passage defined by

plates

222a, 222b and baffle member 220 is drawn into the throat opening and through the passage formed by the slice lips 176a and T7619 which are suitably positioned by prime movers 186a and 18617. The combined flows then proceed toward the exit aperture where the discharge is intercepted between the converging

continuous twin wires

216a and 216b which, together, comprise the web former section of a generally vertically disposed twin wire former of the type described above. For purposes of simplicity, only this portion of the former is shown since the operation of such devices is well knovim.

We claim:

1. Apparatus for delivering a fiber slurry to the forming surface of asheetor web-forming machine, includmeans defining a flow path for saidslurry and leading to an elongate exit aperture; means defining at least one elongate,

communicating with said flow path and-extending narrow slit lid substantially parallel to said exit aperture closely adjacent thereto;

means for introducing an entraining fluid through said slit and into said flow path at a velocity substantially greater than the flow velocity of said slurry immediately upstream from said slit; and

a convex, generally curved fluid-flow attachment surface leading from said slit toward said exit aperture to which the entraining fluid attaches itself due to the Coanda effect and exerts a substantial pulling force on said slurry to entrain and accelerate said slurry toward said exit aperture while mixing with said slurry, and provide a high percentage of all energy required to accelerate said slurry.

2. The apparatus according to claim ll wherein said slit is disposed substantially perpendicularly to said 3. The apparatus according to claim ll including means for selectively varying the location of said slit relative to said flow attachment surface.

4. The apparatus according to claim ll including means for selectively varying the angular disposition of said slit relative to said slurry flow path.

5. The apparatus according to claim ll wherein said flow-path defining means includes a pair of spacedapart lips for directing said entraining fluid and the en trained slurry to said forming surface.

6. The apparatus according to claim 5 wherein said fluid-flow attachment surface is formed on at least one of said lips.

7. The apparatus according to claim 5 additionally including means for adjustably moving said lips relative to one another.

8. The apparatus according to claim 5 wherein at least oneof said lips is constructed of a flexible material.

9. The apparatus according to claim 5 wherein one of said lips extends inwardly from said exit aperture a sufficient distance such that a portion thereof is juxtaposed relative to said slit.

10. The apparatus according to claim ll wherein said entraining fluid introduction means is adapted to introduce said entraining fluid into said flow path at a flow velocity equal to at least ten times the flow velocity of the slurry immediately upstream from said slit.

111. The apparatus according to claim E wherein said entraining fluid introduction means is adapted to introduce said entraining fluid into said flow path at a kinetic energy level of at least fifty times the magnitude of the kinetic energy level of the slurry immediately up tached thereto in a downstream direction.

M. The apparatus according to claim 13 additionally including separator means disposed in said flow path between at least some of said fluid-flow attachment surfaces.

15. The apparatus according to claim 1 wherein said means defining a flow path for said slurry includes a headbox chamber.

16. The apparatus according to claim wherein baffle means is disposed in said headbox chamber for the purpose of smoothing the flow of said slurry along said flow path.

'17. The apparatus according to claim 1 wherein the ratio of the radius of curvature of said surface at the slit location to the width of said slit in the range from 2.5 to 150.

18. A method for delivering a fiber slurry to the forming surface of a sheetor web-forming machine, comprising the steps of:

introducing a slurry mixture into a predetermined injecting a fluid under pressure through an elongated slit disposed substantially perpendicular to said flow path into said flow path at a predetermined location upstream of said forming surface and at a velocity substantially greater than the velocity of the slurry mixture immediately upstream from said location; attaching the injected fluid due to the Coanda effect to a convex, generally curved fluid-flow attachmentsurface leading in a downstream direction from said predetermined injection location whereby the injected fluid exerts a substantial pulling force on said slurry and entrains and accelerates the flow of the slurry along said predetermined flow path, and provides a high percentage of all energy required to accelerate said slurry; mixing the injected fluid and the slurry; and directing the mixed fluid and entrained slurry onto the forming surface. 19.The method according to claim 18 wherein the step of entraining said slurry is accomplished by creating a zone of reduced pressure in said flow path in the vicinity of said fluid-flow attachment surface.

20. The method according to claim 18 wherein said injected fluid is water.

21. The method according to claim 18 wherein said fluid is injected into said predetermined flow path at a flow velocity equal to at least ten times the flow velocity of the slurry immediately upstream of said predetermined location.

22. The method according to claim 18 wherein said fluid is injected into said predetermined flow path at a kinetic energy level ofat least fifty times the magnitude of the kinetic energy level of the slurry immediately. upstream from said slit. 23. A method for delivering a slurry to the forming surface of a sheetor web-forming machine, comprising the steps of:

introducing a slurry mixture into a predetermined flow path leading toward an exit aperture disposed adjacent to said forming surface; introducing an entraining fluid into said flow path under pressure in the form of a thin, elongated stream; and directing the flow of said fluid toward said exit aperture by attaching said thin, elongated stream of fluid due to the Coanda effect toa convex, generally curved fluid-flow attachment surface leading from the location of introduction of said slurry toward said exit aperture whereby said slurry is pulled toward said exit aperture by a substantial pulling force exerted by said fluid to provide a high percentage of all energy required to accelerate said slurry. 24. In combination: means defining a forming surface; and means for delivering a slurry to said forming surface comprising: a. means defining a predetermined flow path for said slurry leading to an elongate exit aperture through which said slurry is adapted to discharge into engagement with said forming surface; b. means defining at least one elongate restricted opening communicating with said flow path closely adjacent to said exit aperture and in substantially parallel relationship thereto;

c. a convex, generally curved fluid-flow attachment surface leading from said restricted opening toward said exit aperture; and

d. means for introducingan entraining fluid under pressure into said flow path through said restricted opening whereby said fluid attaches itself to said fluid-flow attachment surface due to the Coanda effect to exert a substantial pulling force on said slurry and direct said slurry toward said exit aperture and provide a high percentage of all energy required to accelerate said slurry.

*aaaa Dated December 10,, 197

Patent No.

Inventofls) Sangho E. Back et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the Title Page, the following; should be added:

--- [75} Assignees: Cromi Zellerbech Corporation, San

Francisco Calif Signed and sealed this 15th day of July 1.975.,

(SEAL) Attest 5 Ce MARSHALL DANN RUTH C, MASON Commissioner of Patents Arresting Officer and Trademarks USCOMM'DC 60376-P69 u.s. GOVIRNMENT Pmmme OFFICE: 8 930

Claims

1. Apparatus for delivering a fiber slurry to the forming surface of a sheet- or web-forming machine, including: means defining a flow path for said slurry and leading to an elongate exit aperture; means defining at least one elongate, narrow slit communicating with said flow path and extending substantially parallel to said exit aperture closely adjacent thereto; means for introducing an entraining fluid through said slit and into said flow path at a velocity substantially greater than the flow velocity of said slurry immediately upstream from said slit; and a convex, generally curved fluid-flow attachment surface leading from said slit toward said exit aperture to which the entraining fluid attaches iTself due to the Coanda effect and exerts a substantial pulling force on said slurry to entrain and accelerate said slurry toward said exit aperture while mixing with said slurry, and provide a high percentage of all energy required to accelerate said slurry.

2. The apparatus according to claim 1 wherein said slit is disposed substantially perpendicularly to said slurry flow path.

3. The apparatus according to claim 1 including means for selectively varying the location of said slit relative to said flow attachment surface.

4. The apparatus according to claim 1 including means for selectively varying the angular disposition of said slit relative to said slurry flow path.

5. The apparatus according to claim 1 wherein said flow-path defining means includes a pair of spaced-apart lips for directing said entraining fluid and the entrained slurry to said forming surface.

8. The apparatus according to claim 5 wherein at least one of said lips is constructed of a flexible material.

10. The apparatus according to claim 1 wherein said entraining fluid introduction means is adapted to introduce said entraining fluid into said flow path at a flow velocity equal to at least ten times the flow velocity of the slurry immediately upstream from said slit.

11. The apparatus according to claim 1 wherein said entraining fluid introduction means is adapted to introduce said entraining fluid into said flow path at a kinetic energy level of at least fifty times the magnitude of the kinetic energy level of the slurry immediately upstream from said slit.

12. The apparatus according to claim 1 additionally including means for adjusting the size of said slit.

13. The apparatus according to claim 1 wherein a plurality of slits communicate with said flow path and said means for introducing said entraining fluid into said flow path includes means for forcing entraining fluid through each slit and a fluid-flow attachment surface leading from each slit, each said fluid-flow attachment surface being positioned to direct the fluid attached thereto in a downstream direction.

14. The apparatus according to claim 13 additionally including separator means disposed in said flow path between at least some of said fluid-flow attachment surfaces.

16. The apparatus according to claim 15 wherein baffle means is disposed in said headbox chamber for the purpose of smoothing the flow of said slurry along said flow path.

17. The apparatus according to claim 1 wherein the ratio of the radius of curvature of said surface at the slit location to the width of said slit in the range from 2.5 to 150.

18. A method for delivering a fiber slurry to the forming surface of a sheet- or web-forming machine, comprising the steps of: introducing a slurry mixture into a predetermined flow path; injecting a fluid under pressure through an elongated slit disposed substantially perpendicular to said flow path into said flow path at a predetermined location upstream of said forming surface and at a velocity substantially greater than the velocity of the slurry mixture immediately upstream from said location; attaching the injected fluid due to the Coanda effect to a convex, generally curved fluid-flow attachment surface leading in a downstream direction from said predetermined injection location whereby the injected fluid exerts a substantial pulling force on said slurry and entrains and accelerates tHe flow of the slurry along said predetermined flow path, and provides a high percentage of all energy required to accelerate said slurry; mixing the injected fluid and the slurry; and directing the mixed fluid and entrained slurry onto the forming surface.

19. The method according to claim 18 wherein the step of entraining said slurry is accomplished by creating a zone of reduced pressure in said flow path in the vicinity of said fluid-flow attachment surface.

20. The method according to claim 18 wherein said injected fluid is water.

22. The method according to claim 18 wherein said fluid is injected into said predetermined flow path at a kinetic energy level of at least fifty times the magnitude of the kinetic energy level of the slurry immediately upstream from said slit.

24. In combination: means defining a forming surface; and means for delivering a slurry to said forming surface comprising: a. means defining a predetermined flow path for said slurry leading to an elongate exit aperture through which said slurry is adapted to discharge into engagement with said forming surface; b. means defining at least one elongate restricted opening communicating with said flow path closely adjacent to said exit aperture and in substantially parallel relationship thereto; c. a convex, generally curved fluid-flow attachment surface leading from said restricted opening toward said exit aperture; and d. means for introducing an entraining fluid under pressure into said flow path through said restricted opening whereby said fluid attaches itself to said fluid-flow attachment surface due to the Coanda effect to exert a substantial pulling force on said slurry and direct said slurry toward said exit aperture and provide a high percentage of all energy required to accelerate said slurry.

32. A METHOD FOR DELIVERING A SLURRY TO THE FORMING SURFACE OF A SHEET- OR WEB-FORMING MACHINE, COMPRISING THE STEPS OF: INTRODUCTING A SLURRY MIXTURE INTO A PREDETERMINED FLOW PATH LEADING TOWARD EXIT APERTURE DISPOSED ADJACENT TO SAID FORMING SURFACE; INTRODUCING AN ENTRAINING FLUID INTO SAID FLOW PATH UNDER PRESSURE IN THE FORM OF A THIN, ELONGATED STREAM; AND DURECTING THE FLOW OF SAID FLUID TOWARD SAID EXIT APERTURE BY ATTACHING SAID THIN, ELONGATED STREAM OF FLUID DUE TO THE COANDA EFFECT TO A CONVEX, GENERALLY CURVED FLUID-FLOW ATTACHMENT SURFACE LEADING FROM THE LOCATION OF INTRODUCTION OF SAID SLURRY TOWARD SAID EXIT APERTURE WHEREBY SAID SLURRY IS PULLED TOWARD SAID EXIT APERTURE BY A SUBSTANTIAL PULLING FORCE EXERTED BY SAID FLUID TO RPOVIDE A HIGH PERCENTAGE OF ALL ENERGY REQUIRED TO ACCELERATE SAID SLURRY.