US3351522A

US3351522A - Approach flow system for papermaking machine

Info

Publication number: US3351522A
Application number: US387133A
Authority: US
Inventors: Lopas Kasimir
Original assignee: Time Inc
Current assignee: TI Gotham Inc
Priority date: 1964-08-03
Filing date: 1964-08-03
Publication date: 1967-11-07
Anticipated expiration: 1984-11-07

Description

Nov. 7, 1967 o s 3,351

APPROACH FLOW SYSTEM FOR PAPER MAKING MACHINE Filed Aug. 5, 1964 4 Sheets-Sheet l KA'SIMIR LOPAS A TTOR/VE rs Nov. 7, 1967 K. LOFAS APPROACH FLOW SYSTEM FOR PAPER-MAKING MACHINE 4 Sheets-Sheet 2 Filed Aug. 5, 1964 INVENTOR. KASIMIR LOPAS his A TTOfi/VEYS K. LOPAS 3,351,522

APPROACH FLOW SYSTEM FOR PAPER-MAKING MACHINE Nov. 7, 1967 Filed Aug. 5, 1964 4 Sheets-Sheet 5 m l hv INVENTOR. KASiMIR LOPAS Em, J Wfl ATTORNEYS his K. LOPAS 3,351,522 APPROACH FLOW SYSTEM FOR PAPER-MAKING MACHINE Nov. 7, 1967 4 Sheets-Sheet 4 Filed Aug. 5, 1964 INVENTOR.

KASI MIR LOPAS W- PM @W k gww his A TTORNEYS United States Patent 3,351,522 APPROACH FLOW SYSTEM FUR PAPER- MAKING MACHINE Kasimir Lopas, Stamford, Conn., assignor to THEME,

Incorporated, New York, N.Y., a corporatron of New York Filed Aug. 3, 1964, Ser. No. 387,133 11 Claims. (Cl. 162-637) This invention relates to paper-making methods and apparatus and, more particularly, to novel and highly effective methods of and apparatus for delivering to a paper-making machine a paper stock under conditions of uniform consistency and velocity.

It is of the utmost importance that the paper stock delivered to a paper-making machine be of uniform consistency and velocity at the slice. Variations in the consistency or velocity of a paper stock at the slice result in variations from point to point in the characteristics of the paper produced. Such uneven characteristics con stitute a serious imperfection in the paper, particularly when the paper is intended for use in a process such as the printing of magazines and books.

The maintenance of uniformity of stock consistency and velocity at the slice is extremely difficult. The stock supplied from a vat or other storage means to the flow system may not be perfectly homogeneous. Moreover, turns or bends in the ductwork forming typical stockflow systems result in non-uniform velocity of the stock as it leaves the turns. For these and other reasons, the stock as it exits from the slice and onto the foraminous belt of the paper-making apparatus is never of completely uniform consistency or velocity, either spatially i.e., across the face of the slice-or temporallyi.e., from one moment to the next.

An object of the present invention is to remedy the difliculties referred to above. In particular, an object of the present invention is to provide a stock-flow system which provides a flow of stock of substantially uniform consistency and having a substantially uniform velocity at all points of a given cross-sectional area of the flow system, such as the cross-sectional flow area at the slice, and from moment to moment. Another object of the invention is to provide means for changing the direction of flow of a stream of stock so that the stock emerges from the change of direction having a uniform velocity at all points across a cross-section of the stock.

These and other objects are attained in accordance with a representative embodiment of the invention by a recirculating loop and a tapered-flow header which may be used separately or in combination. The recirculating loop delivers stock from a source to the paper-forming apparatus over a plurality of paths of unequal length. The tapered-flow header has a cross-sectional flow area which decreases in a first direction of flow from a maximum value to a minimum value, the maximum and minimum values being so related to each other and to energy losses due to friction that the horizontal components of the pressure gradient in the paper stock normal to the second direction at the origin of movement of the stock in the second direction substantially vanish and the components of the pressure gradient in the paper stock in the second direction at the origin of movement of the stock in the second direction are of substantially equal magnitude. Specially-designed stock-flow guide vanes may be mounted in the tapered-flow header to facilitate turning of the paper stock from flow in the second direction at substantially uniform velocity across a cross section of the flow in the second direction to flow in a third direction at substantially uniform velocity across a cross-section of the flow in the third direction.

An understanding of further aspects of the invention 3,351,522 Patented Nov. 7, 1967 may be gained from a consideration of the following detailed description of several representative embodiments thereof in conjunction with the accompanying figures in the drawings, of which:

FIG. 1 is an end elevational view, partly in phantom, of apparatus constructed in accordance with the invention;

FIG. 2 is a sectional vew taken substantially along the line 2-2 of FIG. 1 and looking in the direction of the arrows;

FIG. 2A is a side sectional view similar to FIG. 2 but showing a modification in accordance with the invention of a portion of the apparatus of FIG. 2;

FIG. 3 is a plan view of one form of tapered-flow header constructed in accordance with the invention;

FIG. 4 is a view taken substantially along the line 44 of FIG. 3;

FIG. 5 is a plan view of a combination in accordance with the invention of a recirculating loop and the taperedfiow header shown on a larger scale in FIG. 3;

FIG. 6 is a fragmentary view of a portion of FIG. 5;

FIG. 7 is a plan view of another combination of tapered-flow header and recirculating loop constructed in accordance with the invention;

FIG. 8 is an enlarged view taken substantially along the line 88 of FIG. 7 and looking in the direction of the arrows; and

FIG. 9 is a view taken substantially along the line 9-9 of FIG. 8 and looking in the direction of the arrows.

Throughout the present disclosure, the word paper is used in a generic sense to include paper, paperboard, and similar products.

FIGS. 1 and 2 show an exemplary embodiment of apparatus constructed in accordance with the invention. Those figures show lower and

upper breast rolls

10, 12 about which are trained lower and upper Fourdrinier

wires

14, 16 or other permeable belts adapted to transport a web of paper stock and effect removal of water therefrom to form a web of paper. The lower breast roll 10 is rotatably mounted on a shaft 13, and the upper breast roll 12 is also rotatably mounted on a shaft (not shown). The

breast rolls

10, 12 may be foraminous or solid and may be mounted in various positions with respect to each other.

Paper stock is delivered by a flow system designated generally by the numeral 20 through a slice 22 which ejects the stock between the

wires

14, 116 as a wide flat layer lying in a plane normal to the plane of the figure. The breast rolls 10, 11 rotate in the directions indicated by the arrows at speeds which are typically substantially equal to the speed with which the stock is ejected from the slice 22. Water is expressed from the stock through the

wires

14, 16 to form a web of paper.

The present invention relates not to the paper-making apparatus downstream of the slice 22 but to the flow system 20. In accordance with the invention, a source of paper stock such as a supply-flow channel 24 (FIG. 1) forms a fluid-conducting connection 26 with a recirculating loop designated generally by the reference numeral 27. The stock enters the recirculating loop 27 in the direction indicated by the arrows and travels therein in a clockwise direction (FIG. 1). A delivery-flow channel 30 forms a fluid-conducting connection 31 with the recirculating loop 27, and a portion of the stock in the recirculating loop 27 is bled from the loop and into the delivery-flow channel 30, the remaining portion of the stock in the loop being recirculated.

Stock-flow-amount-varying means such as a valve 32 is mounted in the recirculating loop 27 at a location having its co-ordinate, measured in the direction of circulation of the stock, between the connection 31 between the recirculating loop 27 and the delivery-flow channel 30 and the connection 26 between the recirculating loo 27 and the supply-flow channel 24. In accordance with the invention, portions of the stock having maximum consistency are recirculated in the loop and mixed with other portions of the stock having lower consistency. In like manner, portions of the stock having minimum consistency are recirculated and mixed with other portions of the stock having higher consistency. The valve means 32 can be adjusted so that varying proportions of the stock are recirculated.

As FIG. shows, the stock-flow-amount-varying means need not be a valve but may be variable impeller means such as a screw propeller 4-4 with constant or variable pitch rotatably mounted on a propeller shaft 46 and powered at constant or variable angular velocity by motive means such as an electric motor 48. Thus, almost any proportion, say 50% or more, of the stock may be recirculated, so that a given portion of the stock is likely to make several trips through the recirculating loop 49 before finding its way to the delivery-flow channel 50. Hence, the stock is thoroughly mixed and of uniform consistency.

Moreover, the stock in the loop is made to travel at a velocity suflicient to assist defiocculation and prevent reflocculation and dewatering. At the same time, no harmful eddies are created. Conventional apparatus, in contrast, typically permits flocculation and dewatering or generates harmful eddies. Dewatering of a stock results from collection of water adjacent to surfaces defining the interior of a tank or pipe where stock flow is slow. This collected water breaks away from the surfaces and into the body of the stock from time to time and causes a lack of homogeneity. The mixer typically employed to maintain sufficient stock velocity to prevent dewatering and flocculation generates harmful eddies which are evidenced by non-uniform web formation.

Flow-stabilizing means such as vanes 44, conveniently four in number, are mounted downstream of the propeller 44 is closely-spaced-apart relation thereto to prevent the propellers imparting a helical movement to the stock. The vanes are attached along their longitudinal axes to the wall of a portion of the loop 49 and have inner edges 44a tapering in the direction of stock flow from the Wall toward the center of that portion of the loop. Their downstream ends 4411 are normal to the direction of stock flow. The angle of the taper of the edges 44a is about 15 for relatively low stock velocities (which velocities, however, should and, in accordance with the invention, can be maintained sufliciently high to prevent flocculation and dewatering) and may be as great as 45 for high stock velocities. The vanes may be straight and extend parallel to the direction of stock flow or may be given a slight helical twist in a sense opposite to the helical movement the propeller 44 would impart to the stock in the absence of the vanes 44'.

All of the recirculating loops constructed in accordance with the invention are adapted to deliver paper stock to paper-forming apparatus over a plurality of paths of unequal length. Moreover, the recirculating loop may itself be divided into a plurality of branches of unequal length, unequal capacity, or unequal length and unequal capacity. FIG. 5 shows a recirculating loop 49 having first and second branches 52 and 54, the supplyfiow channel 56 intersecting the branch 52 prior to its reunion with the branch 54. This division of the recirculating loop 49 into a plurality of paths at least along a portion of the length of the loop further facilitates intimate mixing of the stock and the provision of a stock of uniform consistency at the slice. In particular, it permits the simultaneous smoothing out of variations in consistency generated at a plurality of frequencies.

The suppdy-flow channel 56 and the branch 52 meet in a base portion 57 of expanding cross-sectional area so that the capacity of the reciruclating loop 49 at various points along its length in the vicinity of the base portion 57 is substantially a linear function of the volume of stock to be transported thereby at such points per unit time. Similarly, at other convergent junctions in recirculating loops constructed in accordance with the invention and at divergent junctions (see, for example, FIG. 6) therein, the cross-sectional flow areas of the various stem and branch portions of the junctions expand and contract as necessary to maintain the capacity of the loop at various points along its length substantially a linear function of the volume of stock to be transported by the loop at such points per unit time. Thus, stock flow through the loop is at substantially uniform velocity for a given input of stock from the supply-flow channel 56.

The impeller means 44 may be mounted in any of several locations but is preferably coupled with the recirculating loop 49 at a location having its co-ordinate, measured in the direction of circulation of the stock, between the connection 53 between the recirculating loop 49 and the delivery-flow channel 50 and the connection 59 between the recirculating loop 49 and the supply-flow channel 56.

FIG. 6, which is a fragmentary representation of the recirculating loop 49 and the supply-flow channel 50 in the region where the two meet, shows a Y-branch pipe 69. The Y-branch pipe 60 comprises three portions: a base or stem portion 62 and two branch portions. One of the branch portions 64 is a continuation of the stem portion 62 and forms with the stem portion 62 a first stock-flow path, and the other of the branch portions 66 penetrates the first stock-flow path, forming with the stem portion 62 a second stock-flow path in part coextensive with and in part divergent from the first stock-flow path, and having an end 68 positioned within the stern portion 62. The end 68 and, adjacent to the end 68, the stern portion 62 extend substantially in the same direction, and the end 68 has a blunt-lipped mouth 70 whose surface is formed of a substance having a low coefficient of friction. A blunt leading ring formed of polytetrafluoroethylene, a material sold by the E. I. du Pont de Nemours and Co. under the trademark Teflon, may be mounted on the end 68 to assure the desired low coefficient of friction.

The construction of FIG. '6 maintains stock flow at substantially uniform speed and permits division of the stock flow into a plurality of separate streams while inhibiting hang-up of the stock.

FIGS. 1 and 7 show embodiments in which the delivery-flow channels 30, '73 are connected to the recirculating loops 27, 74 with which they are respectively associated along a considerable fraction of the length of the loops, and guide

vanes

100, 101 to be described hereinafter are mounted relatively close to the associated recirculating loops. In FIG. 1, especially, the delivery-flow channel 30 is connected to the recirculating loop 27 along a considerable fraction of the length of the loop. In FIG. 5, on the other hand, the delivery-flow channel 50 is connected to the recirculating loop 49 along a relatively small fraction of the length of the loop, and the stock-flow guide vanes 99 are located relatively remotely from the recirculating loop.

FIG. 2A shows a flow system 20 similar to the flow system 20 disclosed in FIG. 2, the principal difference being that, in the embodiment of FIG. 2A, the bend in the delivery-flow channel 30' of the flow system 20 between the loop 27 and the slice 22 is substantially eliminated, while the advantages of a horizontal or substantially horizontal slice and of an inclined delivery-flow system facilitating elimination of air bubbles in the stock are retained. It is to be noted that the loop 27' is in a substantially horizontal plane, that the flow system 20 between the loop 27' and the slice 22' is inclined at a small angle, say 5 to 15, to the horizontal, and that the wall portion 94 is continuous with the upper wall portion to which certain of the vanes 100' are attached.

This construction facilitates passage of air bubbles, which naturally migrate upwardly in the stock, out of the loop 27', through the remainder of the flow system 20, and out the slice 22', and hence discourages stock hang-up.

A turning-flow channel constructed in accordance with the invention for changing the direction of movement of the paper stock from a first direction in a first portion of the turning-flow channel to a second direction in a second portion of the turning-flow channel, the first and second directions being different, may lie in the recirculating loop as in FIGS. 1 and 7 or may be separate therefrom as in FIGS. 3 and 5.

FIG. 3 shows a turning-flow channel 75 for changing the direction of movement of the paper stock from a first direction indicated by the arrows 76 in a first portion '77 of the turning fiow channel 75 to a second direction indicated by the arrows 78 in a second portion 89 of the turning-flow channel 75. The first portion 77 has a cross-sectional flow area which decreases in the direction of the arrows 76 from a maximum value in an area A to a minimum value in an area B, the maximum and minimum values being so related to each other and to energy losses due to friction that the horizontal components of the pressure gradient in the paper stock normal to the arrows 78 at the second portion 80i.e., at the origin of movement of the stock in the direction of the arrows 78substantially vanish. Further, the components of the pressure gradient in the paper stock in the direction of the arrows 78 at the origin of movement of the stock in the direction of the arrows 78 are of substantially equal magnitude.

More particularly, the minimum value (which is measured at area B) of the crosssectional flow area of the stock in the direction of the arrows 76 is 8% to 20% of the maximum value (which is measured at area A) and preferably 8% to 15%. In tests of an eighteen-inchwide fiow system constructed in accordance with the invention, the minimum value was 9.55% of the maximum value, and it was found that this relationship exactly compensated for losses due to friction, so that the hori- Zontal components of the pressure gradient in the paper stock normal to the arrows 78 at the origin of movement of the stock in the direction of the arrows 78 substantially vanished and the components of the pressure gradient in the paper stock in the direction of the arrows 78 at the origin of movement of the stock in the direction of the arrows 78 were of substantially equal magnitude. Because of these characteristics of the pressure gradient, the velocity of the paper stock in the direction of the arrows 78 was substantially uniform as to both to magnitude and direction across the turning-flow channel 75 at the origin of movement of the stock in the direction of the arrows 78.

In the embodiments of FIGS. 1 and 7, the minimum value tends to be greater in comparison to the maximum value than in the case of the embodiment of FIGS. 3 and 5. That is because, in the embodiments of FIGS. 1 and 7, the downstream end of the turning-flow channel is open to permit recirculation of the stock.

In the embodiments of the turning-flow channels shown in the drawings, the decrease in the cross-sectional flow area in the first direction (in FIG. 3, the direction of the arrows 76) is linear between the maximum and minimum values. (In flow systems larger than the eighteem inch-wide flow system referred to above, the decrease may but need not be linear.) A cross-sectional flow area is of course proportionate to the product of two dimensions normal to the direction of flow. The turning-flow channel tapers in two dimensions (see FIG. 2, which shows that not only the wall but also the walls 92, .94 taper), and the wall 90 and, in FIGS. 3 and 5, the wall must be curved rather than straight in order to maintain the desired linear relationship. At the downstream end of the header, the wall 95 (FIG. 3) curves smoothly about a radius R into the wall 96 to avoid a discontinuity.

The invention also comprises a stock-flow guide vane for mounting in a paper stock flow system to facilitate turning of a paper stock from flow in one direction (which may be the second directionthe direction of the arrows 78 in FIG. 3-referred to above in connection with the tapered-flow header) at substantially uniform velocity across a cross section of the fiow in the One direction to flow in another direction at substantially uniform velocity across a cross section of the flow in the other direction.

FIG. 1 shows a plurality of stock-flow guide vanes 100 constructed in accordance with the invention. Each vane has a nose portion 102 extending parallel to the second direction referred to above and a tail portion 104 extending parallel to the third direction and is adapted for mounting with the nose portion 102 upstream of the tail portion 104 in the flow system.

Each vane 100 is elongated along a first axis extending from the nose portion 162 to the tail portion 104 and narrow along a second axis normal to the first axis and to the plane of FIG. 1. The narrow dimension of the vanes is presented to view in FIG. 2. Each vane is substantially flat along a third axis normal to the first and second axes. The smallest surfaces of the vanes are presented to view in FIG. 1. Each vane has a pair of oppositely disposed sides 108, generally parallel to the first and second axes and is curved in a plane normal to the second axis-i.e., in the plane of FIG. l-to impart a convexity to one of the sides-the side 108 in FIG. 1- and a concavity to the other of the sides-the side 110 in FIG. 1. The tail portion 104 of each vane is tapered to a sharp terminus 112, as shown in FIG. 2.

In the embodiment shown in FIG. 2, the terminus is a pair of

edges

114, 116 each forming an acute angle with the first axis and tapering to a common point 118. This construction evens flow by providing a drag near the center of the channel to match the drag produced by the walls 126, 128 of the channel. In the embodiment of the stock-flow guide vanes 101 shown .in FIGS. 7-9, the terminus is an edge 120 normal to the first axis.

In the embodiment of the stock-flow guide vanes shown in FIGS. 79, the nose portion is covered with a substance 122 to discourage hang-up of the paper stock. The substance 122 may be polytetrafluoroethylene.

In the embodiment of the stock-flow guide vanes shown in FIGS. 3 and 4, the flow system comprises a flow channel having first and second wall portions 126, 128 opposed to each other and spaced apart from each other a distance substantially less than their width in a direction transverse of the direction of stock flow therebetween, the stock therefore having a cross-sectional flow area of a width substantially exceeding its depth as it passes between the first and second wall portions 126, 128. The stock-flow guide vanes are mounted in

slots

129, 130 in the channel across the width thereof alternately on the first and second wall portions 126, 128. The nose portion of each vane terminates in an edge 124 forming an acute angle with the first axis and tapering towards the tail portion, and, in the same sense, away from the one of the first and second wall portions 126, 128 on which the vane is mounted to a point 125 removed from both of the first and second wall portions 126, 128. This construction facilitates turning of the stock while inhibiting hang-up thereof. Long stock fibers, which might have a tendency to staple over the edge 124, slide to the point 125 and thence. along the space between the vane and the wall 126 (or 125, as the case may be).

The stock-flow guide vanes 101 shown in FIGS. 7-9 are thicker than the vanes 100 but are nevertheless substantially flat, as FIGS. 7 and 9 show. A certain thickness is given the vanes 101, however, near their upstream ends and middle portions so that a section of a vane 101 in a plane normal to the second vane axis referred to above has generally the form of a longitudinal section of a raindrop (see. FIG. 9). .Thethickness is sufficient to permit the passing of securing means 131 through the vanes 101 to facilitate the securing of the Walls 132, 133 together without heavy and expensive external bracing.

Thus there is provided in accordance with the invention novel and highly effective methods of and apparatus for delivering paper stock to paper-making apparatus, the stock being delivered at substantially uniform consistency and velocity. Many modifications in form and detail of the representative embodiments of the invention disclosed herein will readily occur to those skilled in the art. Accordingly, the invention is to be construed as including all of the modifications thereof within the scope of the appended claims.

I claim:

1. In a flow system for delivering a paper stock to paper-forming apparatus, a Y-branch pipe comprising a stem portion and two branch portions, one of said branch portions being a continuation of said stem portion and forming with said stem portion a first stock-flow path and the other of said branch portions penetrating said first stock-flow path, forming with said stem portion a second stock-flow path in part coextensive with and in part divergent from said first stock-flow path, and having an end positioned within said stem portion, said end and said stem portion adjacent to said end having axes extending substantially in the same direction and said end having a blunt-lipped mouth having a surface formed of a substance having a low-coetficient of friction.

2. A flow system for delivering a paper stock to paperforming apparatus, the flow system comprising a flow channel having first and second wall portions opposed to each other and spaced apart from each other a given distance substantially less than their width in a direction transverse of the direction of stock flow therebetween, the stock therefore having a cross-sectional flow area of a width substantially exceeding its depth as it passes between said first and second wall portions, and a plurality of stock-flow guide vanes mounted in said channel across the width thereof alternately on said first and second wall portions, each vane (11) having a nose portion and a tail portion, (b) being (1) mountable with said nose portion upstream of said tail portion in said flow system, (2) elongated along a first axis extending from said nose portion to said tail portion, (3) narrow along a second axis normal to said first axis, and (4) substantially fiat along a third axis normal to said first and second axes, having a pair of oppositely disposed sides extending parallel to said second axis, and (d) being curved in a plane normal to said second axis to impart a convexity to one of said sides and a concavity to the other of said sides, said tail portion of each vane being formed with a pair of edges each forming an acute angle with said first axis and tapering to a common point and said nose portion of each vane terminating in an edge forming an acute angle with said first axis and tapering (a) toward said tail portion and, in the same sense, (b) from the one of said first and second wall portions on which said vane is mounted to a point (1) removed from both of said first and second wall portions, and (2) spaced apart from said common point a distance substantially greater than said given distance.

3. A paper-stock pressure-flow system comprising a source of paper stock, a delivery-flow channel, a recircu1 lating loop having an entrance for coupling to said source in fluid-conducting relation and an exit for coupling to said delivery-flow channel in fluid-conducting relation, means connecting the recirculating loop and said source, said delivery-flow channel comprising a turning flow channel for changing the direction of movement of the paper stock from a first direction in a first portion of said turning-flow channel to a second direction in a second portion of said turning-flow channel, said first and second directions being different, said first portion having a cross-sectional flow area which decreases in said first direction from a maximum value to a minimum value, said maxi n o mum and minimum values being so related to each other and to energy losses due to friction that the horizontal components of the pressure gradient in the paper stock normal to said second direction at the origin of movement of said stock in said second direction substantially vanish and the components of the pressure gradient in the paper stock in said second direction at the origin of movement of said stock in said second direction are of substantially equal magnitude, and a plurality of stock-flow guide vanes mounted in said second portion to facilitate turning of the paper stock from flow in said second direction at substantially uniform velocity across a cross section of said flow in said second direction to flow in a third direction at substantially uniform velocity across a cross section of said flow in said third direction, each of said vanes (a) having a nose portion extending parallel to said second direction and a tail portion extending parallel to said third direction, (b) being (I) mounted with said nose portion upstream of said tail portion in said fiow system, (2) elongated along a first axis extending from said nose portion to said tail portion, (3) narrow along a second axis normal to said first axis, and (4) substantially flat along a third axis normal to said first and second axes, (0) having a pair of oppositely-disposed sides extending parallel to said second axis, and (0!) being curved in a plane normal to said second axis to impart a convexity to one of said sides and a concavity to the other of said sides, and said tail portion being tapered to a sharp terminus.

4. A flow system for delivering a paper stock to paperforming apparatus, the flow system comprising a supplyfioW channel for transporting the paper stock, a recirculating loop, said recirculating loop and said supply-flow channel having a fluid-conducting connection with each other, a delivery-flow channel, said recirculating loop and said delivery-flow channel having a fluid-conducting connection with each other, a screw propeller coupled with said recirculating loop for varying the amount of the stock which is recirculated, and flow-stabilizing means mounted in said loop for preventing the acquisition by said stock of a helical motion due to the action of said propeller.

5. A stock-flow guide vane for mounting in a paperstock flow system to facilitate turning of a paper stock from flow in one direction at substantially uniform velocity across a cross section of said flow in said one direction to flow in another direction at substantially uniform velocity across a cross section of said flow in said other direction, the vane (at) having a nose portion covered with a substance to discourage hang-up of said paper stock and a tail portion tapering to a sharp terminus, (b) being (1) mountable with said nose portion upstream of said tail portion in said flow system, (2) elongated along a first axis extending from said nose portion to said tail portion, (3) narrow along a second axis normal to said first axis, and (4) substantially flat along a third axis normal to said first and second axes, (0) having a pair of oppositely disposed sides extending parallel to said second axis, and (d) being curved in a plane normal to said second axis to impart a convexity to one of said sides and a concavity to the other of said sides, a section of said vane in a plane normal to said second axis having generally the form of a longitudinal section of a raindrop.

6. A stock-flow guide vane as defined in claim 5 in which said substance is polytetrafiuoroethylene.

7. In apparatus for facilitating turning of a paper stock from flow in one direction at substantially uniform velocity across a cross section of said flow in said one direction to flow in another direction at substantially uniform velocity across a cross section of said flow in said other direction, the improvement comprising a plurality of vanes mounted in parallel relation, each vane (a) having a tail portlon tapering to a sharp terminus and a nose portion, (b) being (I) mounted with said nose portion upstream of said tail portion in said flow system, (2) elongated along a first axis extending from said nose portion to said t l E Z iQ 3) narrow along a second axis normal to" 9 said first axis, and (4) substantially flat along a third axis normal to said first and second axes, (0) having a pair of oppositely disposed sides extending parallel to said second axis, and (d) being curved in a plane normal to said second axis to impart a convexity to one of said sides and a concavity to the other of said sides.

8. A stock-flow guide vane as defined in claim 7 in which said terminus is an edge normal to said first axis.

9. A stock-flow guide vane as defined in claim 7 in which said terminus is a pair of edges each forming an acute angle with said first axis and tapering to a common point.

10. A stock-flow guide vane as defined in claim 7 in which a section of said vane in a plane normal to said second axis has generally the form of a longitudinal section of a raindrop.

11. A stock-flow guide vane as defined in claim 7 in which said nose portion terminates in an edge forming an acute angle with said first axis.

References Cited OTHER REFERENCES Gavelin: Fourdrinier Papermaking, Lockwood Trade Journal Co. Inc., New York (1963), pp. 43-45, copy in Group 170.

Keller: The Manifold Problem, Journal of Applied Mechanics, March 1949, pp. 77-85.

S. LEON BASHORE, Primary Examiner. J. H. NEWSOME, Assistant Examiner.

Claims

4. A FLOW SYSTEM FOR DELIVERING A PAPER STOCK TO PAPERFORMING APPARATUS, THE FLOW SYSTEM COMPRISING A SUPPLYFLOW CHANNEL FOR TRANSPORTING THE PAPER STOCK, A RECIRCULATING LOOP, SAID RECIRCULATING LOOP AND SAID SUPPLY-FLOW CHANNEL HAVING A FLUID-CONDUCTING CONNECTION WITH EACH OTHER, A DELIVERY-FLOW CHANNEL, SAID RECIRCULATING LOOP AND SAID DELIVERY-FLOW CHANNEL HAVING A FLUID-CONDUCTING CONNECTION WITH EACH OTHER, A SCREW PROPELLER COUPLED WITH SAID RECIRCULATING LOOP FOR VARYING THE AMOUNT OF THE STOCK WHICH IS RECIRCULATED, AND FLOW-STABILIZING MEANS MOUNTED IN SAID LOOP FOR PREVENTING THE ACQUISITION BY SAID STOCK OF A HELICAL MOTION DUE TO THE ACTION OF SAID PROPELLER.
7. IN APPARATUS FOR FACILITATING TURNING OF A PAPER STOCK FROM FLOW IN ONE DIRECTION AT SUBSTANTIALLY UNIFORM VELOCITY ACROSS A CROSS SECTION OF SAID FLOW IN SAID ONE DIRECTION TO FLOW IN ANOTHER DIRECTION AT SUBSTANTIALLY UNIFORM VELOCITY ACROSS A CROSS SECTION OF SAID FLOW IN SAID OTHER DIRECTION, THE IMPROVEMENT COMPRISING A PLURALITY OF VANES MOUNTED IN PARALLEL RELATION, EACH VANE (A) HAVING A TAIL PORTION TAPERING TO A SHARP TERMINUS AND A NOSE PORTION, (B) BEING (1) MOUNTED WITH SAID NOSE PORTION UPSTREAM