US3171775A - Distributor system for a paper machine headbox - Google Patents

Description

March 2, 1965 5. L. CALEHUFF DISTRIBUTQR SYSTEM FOR A PAPER MACHINE HEADBOX 2 Sheets-Sheet 1 Filed May 18, 1962 March 1965 e. L. CALEHUFF DISTRIBUTOR SYSTEM FOR A PAPER MACHINE HEADBOX Filed May 18, 1962 2 Sheets-Sheet 2 INVENTOR. GlRARD L. CALEHUF? wiaw AGE NT United States Patent t e-A ,7 3,171,775 DISTRIBUTOR SYSTEM FOR A PAZER MACHINE HEADBOX Girard L. Calehutl, Covington, Va., assignor to West Virginia Pulp and Paper (Iompany, New York, N.Y.,

a corporation of Delaware Filed May 18, 1962, Ser. No. 195,815 Claims. ((31. 162216) This invention relates to new and useful improvements in apparatus for and methods of distributing a dilute paper stock uniformly across the width of the paper machine headbox.

It is well known in the art of papermaking that flow irregularities remaining in the dilute paper stock at the slice, such as non-uniform velocity profiles, unstable velocity profiles, and non-parallel flow conditions, cause undesirable deviations in the physical properties of the finished paper; e.g., varying basis weight profiles and sheet strength due primarily to poor fiber distribution. Poor formation of the sheet because of slice flow irregularities is a common cause of rejection by prospective buyers. Economically, the papermaker cannot afford rejections of this sort, and has made many attempts to eliminate the slice flow irregularities.

In a typical paper machine, the slice is formed from the downstream portion of a substantial rectangular chamber commonly referred to as a headbox. The upstream portion of the headbox is terminated by some form of distributor system.

The function of a distributor system is to convert the flow of dilute paper stock from flow in a round pipe as is the condition of the How approaching the distributor system to a flow in a rectangular passage extending the width of the headbox as is the condition of the flow leaving the distributor system. The velocity and direction of flow of the dilute paper stock must be carefully controlled during the conversion by the distributor system so that the fluid speed leaving the system is essentially uniform and so that the direction of the fluid flow leaving is everywhere parallel (no cross flows). An ideal distributor system would convert the flow so efficiently that further flow evening would not be necessary and the dilute paper stock would flow from the distributor system directly through a slice onto the paper web former. To date, no distributor system has been designed that has overcome the need for additional tlow evening in the headbox. However, regardless of the headbox construction, the distributor system must bring about an eflicient conversion of the flow of dilute paper stock. Even in headboxes having complex systems of flow eveners and flow rectification means, such as numerous rectifier rolls, larger scale velocity differentials not dissipated in the distributor system will travel through the headbox to the slice and result in unequal slice jet velocities.

The velocity profile must be controlled by the distributor system so that fluctuations or surges developed in the flow prior to the distributor system, and fluctuations developed in the flow during the conversion by the distributor system are inefliective to the flow leaving the distributor system. These fiow irregularities can be traced to a plurality of effects.

The foremost flow irregularity occurring before the conversion is that of pressure surging which is either an inherent part of or a possible threat to every system supplying dilute paper stock to a distribtuor system. Pres sure surges, as the name implies, are cyclic changes in the pressure of the dilute paper stock that reach high and low absolute values which can be related to time intervals. It is to be understood that the pressure surges, in all probability, are complex combinations of many sep- 3,171,775 Patented Mar. a, less arate cyclic pressure surges, such as those caused by the cyclic beating action of the impellers of pumps supplying the dilute paper stock that have been combined to form the surges at the distributor system.

Flow irregularities developed during the conversion can be attributed to inherent characteristics of the distributor system, and to the characteristics of the dilute paper stock.

The dilute paper stock passing through the distributor system is a liquid (mostly water) containing a forced suspension of solids (fibers). The fibers settle or flock together in relatively tranquil regions. A distributor system must be designed to prevent settling of the fibers by constantly mixing and agitating the dilute paper stock, and prevent collecting by eliminating stagnation regions.

Various distributor systems have been set forth in the past in an attempt to obtain the flow conversion. The majority of the distributor systems begin conversion by introducing the dilute paper stock into a separate chamber extending across the width of the headbox. The chambers, or manifolds, are varied in shape, size, and performance. Some manifolds have in-lets in both ends and are referred to as cross flow manifolds. Others have an inlet in one end, and usually are tapered with the inlet located at the Wider end. The function of the various manifolds is to convert the flow of dilute paper stock from circular flow in a single pipe to a series of flow streams that extend across the Width of the paper machine.

In the majority of manifolds, the series of flow streams flow in a direction parallel with the flow through the slice, and perpendicular to the inlet flow direction, requiring a turning of the dilute paper stock into a direction substantially perpendicular to the original flow. The exact method of turning the flow has received careful attention from the industry which has long realized the detrimental effects that evolve from poor turning, such as cross flows, secondary eddies, and stock floccing. Development of a suitable manifold that will distribute the stock across the Width of the headbox and turn the stock into a direction parallel with the flow through the slice has led to a tapered manifold using a row of relatively short pipes extending from a Wall of the manifold to a portion of the headbox. However, such a manifold has not overcome pressure surging, and, as used in the past, has created flow irregularities in the following portions of the distributor system.

The row of relatively short pipes distributing the dilute paper stock across the Width of the headbox are separated streams that must be blended or mixed into a single rectangular stream. Mixing is an important phase of the distributor system and in the past has been a troublesome feature that developed fiow irregularities during conversion of the flow. A great many of the distributor systems attempted to mix the individual flows from the pipes by using various combinations of redirection, impinging and expanding methods on the dilute paper stock issuing from the pipes. Redirection and impingement mixing systems have proven to set up troublesome secondary flows, create unequal flow velocities and create unstable mixing conditions that set up unequal flow velocities. The unequal flow velocities are perhaps most disadvantageous of all in that the occurrence cannot be determined from prior experience with the paper machine but varies in a somewhat random manner.

Systems that obtain uniform flow distribution by expanding the dilute paper stock suspensions are sensitive to flow rate changes, and may, in certain flow rate conditions, operate in an overexpanded condition. This promotes separation of the fiow from the Walls of the fluid a) expanding chamber and the fluid diffuses in an unpredictable manner. This operating condition not only presents a poorly distributed flow to the headbox, but also creates secondary eddies that tend to separate or classify the stock through centrifugal action.

A distributor system that fulfills the converting is the subject of my copending application, Serial Number 159,396, filed December 14, 1961. The present distributor system, although based upon the same operating concepts as my copending application, nevertheless is materially different in apparatus. One difference between this invention and that covered by my copending application is the simplification and redesign of the construction of the chamber performing the mixing including a reduction in the number of pipes extending from the manifold to the chamber performing the mixing.

The present invention, like my copending application, overcomes the effects of pressure surging and mixes the streams of dilute paper stock leaving the manifold without uncontrollable impinging and unpredictable stock expansion.

Therefore, the principal purpose of this invention is to provide an even and stable velocity flow of dilute paper stock to the headbox regardless of the flow conditions of the feed pipes and to redirect the flow in such a manner that the flow is parallel.

In addition, this invention simplifies the construction of a distributor system and thereby is adapted to be used as an improvement modification on existing paper machine headboxes.

It has'removed flocculation problems resulting from relatively tranquil regions and eliminates large scale secondary flows and the attendant stock separation.

It contains novel means for reducing the pressure variations inherent in the infeed system.

The distributor system is constructed to subject the dilute paper stock to continual and controlled agitation which prevents floccing of stock and aids in the breaking up of stock flocs formed prior to the distributor system.

The distributor system is applicable to a wide range of machine speeds and stock furnishes.

Further advantages of this invention will hereinafter appear in connection with a detailed description of the drawings in which:

FIG. 1 is a sectional elevational view of the distributor system according to a preferred embodiment of this invention.

FIG. 2 is a partial elevational view taken along the line 22 of FIG. 1.

FIG. 3 is a fragmentary view taken along the line 3-3 of FIG. 2.

FIG. 4 is an enlarged fragmentary view of the embodiment of the distributor shown in FIG. 1.

FIG. 5 is an enlarged fragmentary view of another embodiment of the distributor system shown in FIG. 1.

FIG. 6 is an enlarged fragmentary view of a portion of the embodiment of the distributor system shown in FIG. 5.

FIG. 7 is an enlarged fragmentary view of still another embodiment of the distributor shown in FIG. 1.

FIG. 8 is an enlarged fragmentary view of the embodiment taken along the line 88 of FIG. 7.

Referring to FIG. 1 of the drawings, the headbox is indicated by the reference 10 and is shown for the purposes of illustration as being a pressurized type containing two flow evener rolls 11 for aiding in the deflocculation of the stock and preventing the buildup of minor flow irregularities as the stock travels through the headbox to the slice 12 that feeds the dilute paper stock onto the forming wire 13 at the breast roll 14. The preferred embodiment of the distributor system 15 is angled to the upstream wall 16 of the headbox 1t) and extends across the width of the headbox. The distributor system 15 is connected to the headbox by the flanges 17 and, in the particular embodiment shown, consists of a tapered manifold 18, a row of pipes 19, a headbox inlet chamber 20, and a perforated mixing roll 21. The combination of the components provide a distributor system that not only overcomes the disadvantages of the prior art systems but also carries out the function of a distributor system in an economical and efficient manner.

Referring to FIG. 2 of the drawings, the dilute paper stock flows from a suitable supply (not shown) into the wider end of the tapered manifold 18 as indicated by the reference letter P. The tapered manifold 18 in this particular embodiment is circular in cross section. A rectangular manifold would operate equally Well. The dilute paper stock is subjected to a flow division in the manifold 18 wherein a portion flows through a row of pipes 19 as the dilute paper stock travels from the larger end toward the smaller end. The internal area is reduced to compensate for the flow leaving through pipes 19 so that the flow through the manifold will retain a relatively constant pressure.

Referring generally to FIGS. 1 and 4, and particularly to FIG. 4, the row of pipes 19 have outlet ends received by a transition wall 22. The pipes are joined to the transition wall 22 in a non-perpendicular fashion with each pipe outlet terminating in the center of the transition wall 22 thus forming a single row of outlets extending across the width of the paper machine. As best shown in FIG. 3, alternate pipes 19 contain portions 23 extending at an angle upwardly away from the transition wall 22 while the remaining pipes 19 contain portions 24 extending at an angle downwardly away from the transition wall 22.

Distributor systems in which the single row of pipes are attached perpendicularly to the transition Wall create unpredictable mixing conditions. The jets of dilute paper stock issuing from the pipes attach themselves to one of the diverging inlet chamber walls in an unpredictable manner, depending upon flow conditions and errors in physical geometry of the pipes and the diverging inlet chamber walls. As a result, a number of adjacent jets of dilute paper stock may attach themselves to one of the diverging inlet chamber walls which will establish a relatively tranquil flow zone along the other diverging inlet chamber wall. Floccing, stock classifying, and poor blending will be the undesirable result. By attaching the pipes 19 to the transition wall 22 as described, the alternate jets of dilute paper stock attach themselves to one of the diverging inlet chamber walls and the remaining jets of dilute paper stock attach themselves to the other diverging inlet chamber wall. It should become obvious in light of the previous discussion that the formation of relatively tranquil regions and therefore the associated floccing and stock classifying are prevented by attaching the alternate jets of dilute paper stock to one of the diverging inlet chamber walls, and the remaining jets of diltlrlte paper stock to the other diverging inlet chamber wa The pipes 19a forming the end of the row of pipes 19 are preferably spaced from the end walls 25 and 26 approximately /2 the distance between the pipes 19.

Referring to FIGS. 3 and 4, the sum of the area of the outlets of the pipes 19 can be seen to equal a substantial part of the internal cross sectional area of the portion of the headbox inlet chamber 20 that is joined to the transition wall 22 by the flange 27. The headbox inlet chamber 20 is defined by the area enclosed by the diverging inlet chamber walls 28 and 29, the end walls 25 and 26, the pipe outlets, and the parallel inlet chamber walls 30 and 31. The diverging inlet chamber walls 28 and 29 extend from the transition wall 22 in an angle approximately equal to the angle that the pipes 19 approach the transition wall 22. The angle of divergence (angle A of FIG. 4) should be less than approximately 30. The dilute paper stock flows through the headbox inlet chamber 20 in the diverging directions indicated by the arrows referenced by the letter P. The diverging inlet chamber walls 28 and 29 diverge in the direction of the stock flow and extend to the parallel inlet chamber walls 30 and 31, respectively. The parallel inlet chainber walls 39 and 31 extend to the fiange 17. The internal cross sectional area of the headbox inlet chamber 20 is constant from the flange 17 to the upstream termination of the parallel inlet chamber walls 36 and 31, and as a result, no additional stock expansion occurs within the headbox inlet chamber after the mixing roll 21.

All pipes 19 have equal diameters and equal lengths. The pipe length is considerable as compared with the pipe diameter. The jets of dilute paper stock issuing from the pipes 19 are initially separate streams of high energy and must be blended into a single, uniform and equal velocity stream extending throughout the cross sectional area of the headbox inlet chamber 20. Once formed, the blended stream will remain uniform throughout the headbox to the slice 12. Mixing of the separate jets of dilute paper stock occurs in the mixing portion of the headbox inlet chamber which is defined by the area enclosed within the headbox inlet end walls 25 and 26, the diverging inlet chamber walls 28 and 29, the transition Wall 22, and the upstream or impinging surface of the perforated mixing roll 21. The dilute paper stock is required to expand only in the mixing portion where expansion is carefully controlled by the deployment of the components defining the mixing portion.

Referring to FIGS. 1 and 4, the pipes are angled relative to the transition wall 22 so that the jets of dilute paper stock issuing therefrom attach themselves to one of the diverging inlet chamber walls 28 and 29, and impinge upon fixed impingement plates 32 and the upstream surface of the mixing roll 21. The upstream surfaces 33 of the fixed impingement plates 32 redirect the jets of dilute paper stock to the impinging surface of the mixing roll 21, and are curvilinear in this particular embodiment. The redirection of the jets of dilute paper stock to the surface of the mixing roll 21 by the fixed imp ngement lates 32 prevents secondary eddies and completely blends the individual jets of dilute paper stock resulting in a uniform flow of dilute paper stock that extends throughout the cross sectional area of the headbox inlet chamber extending downstream from the mixing roll 21. By alternately changing the emergence direction of the jets of dilute paper stock to fulfill the previously explained conditions, the jet mixing occurs in the complete absence of any large scale, stationary standing eddies extending across the width of the mixing chamber. High shear fields caused by the interaction of the jets from adjacent pipes which are caused to fiow across the upstream surface of the mix ing roll 21 by the combined effect of the emergence direction of the jets of dilute paper stock, the divergence of the diverging inlet chamber walls 23 and 29, and the fixed impingement plates 32. The internal area of the mixing portion of the headbox inlet chamber is everywhere purged by high energy jets thus preventing the formation of stock iiocs and standing eddies. Further, standing eddies are prevented from forming near the end walls 25 and 26 by being pur ed by high energy jets that flow from the outlets of the terminating pipes 19a which are located relatively close thereto. The purging action also prevents fiber buildup on the end walls 25 and 26. Optimum mixing conditions are realized when the pipes are separated by approximately one to two times the internal diameter. The pipes should not be separated by a distance greater than approximately 5 times the pipe diameter. The impingement of the jets of dilute paper stock on the upstream surface 33 of the fixed impingement plates 32 and on the upstream surface of the mixing roll 21 when interrelated with the spacing of the pipes 19, the emergence direction of the jets of dilute paper stock from the pipes 19, and the diverging inlet chamber walls 28 and 29 completely mixes and blends the streams into a rectangular flow of substantially equal velocity.

Optimum mixing conditions are rea ized when the mixing roll has a ratio of open to closed area in the range of 20-50%. A ratio of approximately will perform quite satisfactorily. Experimental results indicate the velocity of the jets when leaving the outlet ends of the pipes should be in the range of 530 ft. per second with optimum controlled mixing occurring in a range of 10-20 ft. per second. Omission of the mixing roll 21 and the fixed impingement plates 32 results in substantial pressure variations, large scale secondary flows and uncontrollable turbulence in the headbox inlet chamber. If the mixing roll is improperly positioned, the jets no longer interact and blend, but become separated jets of high energy that have a tendency to set up large scale eddies and uneven flow patterns (non-parallel flow).

The fixed impingement plates 32 are flow deflectors having several purposes. The jets of dilute paper stock are prevented from passing through the space between the surface of the mixing roll 21 and the parallel inlet chamber Walls 30 and 31. Dilute paper stock passing through this space would not be properly blended, and would have a higher velocity than the dilute paper stock passing through the mixing roll 21. In addition, the fixed impingement plates 32 deflect the diverging jets of dilute paper stock into converging directions toward the mixing roll 21 which is necessary to the blending.

Referring to FIG. 2 the perforated mixing roll 21 has a shaft 34 supported by bearings 35 in spaced parallel arrangement with the transition wall 22. The mixing roll 21 is driven by any suitable means which is indicated by the sprocket 36 and the chain drive 37. A standard roll used in the industry to even velocity differentials within the headbox performs quite satisfactorily as a mixing roll if the ratio of closed to open area is in the range previously discussed. By rotating the mixing roll 6-10 rpm. there is no possibility of fiber buildup on the surface.

Referring to FIG. 5 which is illustrative of another embodiment of the mixing portion of the headbox inlet chamberftwo rows of pipes '19 are connected substantially perpendicular to the transition wall 33. In FIG. 5, the diverging inlet chamber walls 39 and 40 are separated at the upstream termination by a distance appreciably greater than the diameter of the pipes 19, while in FIG. 4 the diverging inlet chamber walls 28 and 29 are separated at their upstream terminations by a distance substantially equal to the pipe diameter. In FIG. 5, the distance separating the pipes 19 from the diverging inlet chamber walls 39 and 40 is approximately half the distance separating the pipes 19. Thejets of dilute paper stock issuing from the pipes 19 attach themselves to the nearest diverging inlet chamber wall. Alternate pipes are spaced closer to one of the diverging inlet chamber Walls and the remaining pipes are spaced closer to the other diverging inlet chamber wall thus setting up optimum mixing conditions as explained in connection with the embodiment of FIGS. 1, 2, and 3 The embodiment of FIG. 5 like the embodiment previously discussed, contains a mixing roll 41 and fixed impingement plates 42 upon which the jets of dilute paper stock issuing from the pipes 19 impinges. The fixed impingement plates 42 contain an upstream surface 43 that directs the jets of dilute paper stock into and through the mixing roll 41 much in the manner described in the previous embodiment. The diverging inlet chamber walls 39 and 40 terminate in the parallel inlet chamber walls 44 and 45, respectively, which like the previous embodiment prevents stock expansion after the mixing portion of the headbox inlet chamber 29. I

In FIG. 6, a fillet 46 has been incorporated into the embodiment shown in FIG. 5. The fillet 46 is formed from transition wall 38 which otherwise allows the formation of standing eddies, and the associated fioccing and stock separating.

Referring to FIG. 7 which is illustrative of yet another embodiment of the mixing portion of the headbox inlet chamber, one row of pipes 19 are connected substantially perpendicular to the transition wall 47. In FIG. 7, the diverging inlet chamber walls 48 and 49 are separated at the upstream termination by a distance substantially equal to the pipe diameter 19, similar to the embodiment shown in FIG. 4. In FIG. 7, the jets of dilute paper stock issuing from alternate pipes 19 are attached to the diverging inlet wall 48 by the deflectors 50, while the jets of dilute paper stock issuing from the remaining pipes 19 are attached to the diverging inlet chamber Wall 49 by the deflectors 51. Referring to FIGS. 7 and 8, the deflectors 50 and 51 contain an impinging surface 52 that extends into the jets of dilute paper stock issuing from the pipes and deflects the jets toward the diverging inlet chamber walls 48 and 49. This deflection should be readily apparent from an inspection of the drawings and is indicated by the arrows referenced by the letter P in FIGS. 7 and 8. The space behind the impinging surface 52 of the deflectors 50 and 51 is preferably blocked ofl by a filler 53 to prevent the formation of standing eddies and the associated fioccing and stock separating. This embodiment, like the previous embodiments, employs a mixing roll 54, and fixed impingement plates 55 that contain an upstream surface 56 for directing the jets of dilute paper into and through the mixing roll 54. The mixing or blending action is as described in the previous embodiment and is not repeated in connection with this embodiment. The diverging inlet chamber walls 48 and 49 terminate in parallel inlet chamber walls 57 and 58, respectively, and prevent stock expansion after the mixing portion of the headbox inlet chamber 20.

The tapered manifold 18 used with the distributor systems described herein is preferably designed to have a substantially constant internal pressure. However, the tapered manifold when used as a part of distributor systems designed according to the invention can contain pressure variations without creating detrimental velocity differentials in the slice. Even in the absence of a complex flow evening headbox, as will become evident in the following discussion, the manifold is no longer critical when employed in the distributor system. The underlying reasons for the non-criticality of the heretofore critical internal shape of the tapered manifold will become obvious after the discussion of further important and novel features of the distributor system.

By utilizing a region of high energy loss, the distributor systems have incorporated a novel means for removing the velocity differentials that would normally appear in the headbox and at the slice as a result of the pressure deviation developed by the manifold and of pressure purges developed by upstream disturbances. Those skilled in the art of hydrodynamics can reason that the ability of upstream pressure deviations to affect downstream velocities in a fluid can be substantially removed by passing the fluid through a region of high energy loss. In applying this theory, the present invention employs one or two rows of long pipes 19 having a predetermined energy loss in the form of friction looses to overcome the ability of the pressure deviations developed in the manifolds that result from the usage of non-tapered manifolds, or from poorly designed manifolds to produce downstream velocity diflferentials in the headbox and at the slice. As a result, the dilute paper stock leaving each pipe is substantially uniform and equal in velocity.

The pipes overcome another pressure variation, pressure surging. Fluctuations or surges in the pressure of the dilute paper stock delivered to the tapered manifold caused by apparatus located upstream from the manifold, such as a pump, develop velocity differentials within the headbox and at the slice that vary directly with the square root of the pressure fluctuation or surge. Pipes having relatively small diameters and having considerable lengths as compared with the diameters, effectively block the ability of the pressure surges to develop the associated velocity diflerentials within the headbox and at the slice. In addition, the efficiency of the pipes in blocking the velocity differentials that are developed by pressure surges is increased within limits proportionately with an increase in velocity of the dilute paper stock within the pipes. A velocity of approximately. 5-30 ft./ sec. will effectively dampen most of the pressure surges developed before the tapered manifold 18, thus overcoming the tendency of the pressure surges to develop velocity differentials within the headbox and at the slice. When the pipes are long enough to substantially reduce the effect of pressure deviations and pressure surges, the flow of dilute paper stock is completely redirected and the turning difliculties associated with some of the prior manifold systems are overcome.

In the distributor systems, the pipe length is varied within limits directly with the amplitude of the pressure surges developed upstream from the manifold; i.e., the pipe length necessary to remove the velocity differentials within the headbox increases with the amplitude of the pressure surge for constant values of velocity through the pipes. In a similar manner, the pipe is varied directly within limits with the pressure deviations in the manifold; i.e., the pipe length necessary to remove the velocity dififerentials within the headbox increases with increases in the pressure deviation. Both effects can usually be rendered ineffective in ability to produce velocity differentials at the slice by employing pipes having a length of about 310 ft. and a diameter of about /2 to 3 inches. The controlling factor is not the exact physical dimensions of the pipes but the energy loss through the pipes. The range of physical dimensions given will develop an energy loss in the range of approximately 3 to 10 ft. of water.

Yet another important design consideration for the proper design of a distributor system according to the invention is the treatment of the dilute paper stock to prevent fioccing or settling of the fibers and to break up the flocced fibers (fiber bundles). Continual agitation is necessary to prevent fioccing and to break up flocs formed upstream of the distributor system. Both actions are dependent upon the flow conditions in the distributor system.

Flow of dilute paper stock can be broken down into three relatively distinct flow regimes which for round pipes seem to be characterized by:

(1) Reynolds number=DV/v where D is pipe diameter, V is average velocity, and v is kinematic viscosity; the kinematic viscosity v being an expression of the ratio of viscosity of density.

(2) Pipe diameter.

(3) Fiber characteristics, such as flexibility, length stock consistency, etc.

In the first regime, the fibers form a coherent network (plug flow) in the center of the pipe so that all the change in fluid velocity from average velocity to zero at the pipe wall takes place in an annulus adjacent to the pipe wall. The annulus is usually of very low stock consistency. The so-called plug flow does not allow fiber flocs to break up, and hence should be avoided in paper machine distributor systems.

The second regime is obtained by increasing the velocity (V) above that required in the first regime. In this type of flow, the annulus becomes turbulent and begins to destroy the center plug flow and is often referred to as mixed flow because it consists partly of plug flow in the center of the pipe and a turbulent annulus. The presence of the plug flow infers poor mixing and no defioccing both of which are undesirable.

The third regime consists of a fully turbulent flow and hence has the best mixing and defioccing action. Present experience indicates that for the usual paper-making consistencies and for pipes having relatively small diameters, the turbulent flow regime occurs for Reynolds numbers above approximately 10 The flow through the pipes should be such that the turbulent regime is obtained. The minimum Velocity required should not be unquestionably defined by a Reynolds number of 10 because of the influence of other variables, such as consistency and fiber properties. However, if precise data is not available to determine experimentally the Reynolds number for turbulent flow, DV/v of can be used to size the distributor system pipes 19.

Experience has indicated that the functions of the pipes can be carried out with pipes having diameters in the range of approximately /2 to 3 inches. Pipe diameters below approximately /2 an inch have tendencies to become clogged with the fibers carried by the dilute paper stock. As explained above, the pipes will overcome the pressure deviations more eificiently as the length is increased, therefore no maximum pipe length can be given based on desirable operation. Space limitations, available pump head, and economic considerations decide practical maximum pipe lengths. Keeping these facts in mind, the pipes will ordinarily have a length of less than approximately feet, and will perform in the range of 310 feet, which under normal conditions, if the velocity of the dilute paper stock through each pipe is in the range of approximately 5-30 ft./sec., will have suliicient pressure drop (energy loss) to overcome pressure surges and steady state pressure deviations. Equal diameter pipes having an equal length are preferred which results in an equal pressure drop (energy loss) and velocity through each pipe.

The mixing roll 21, 41, or 54 (depending upon the embodiment) has three important functions. First, the mixing roll provides a surface which forces the jets of dilute paper stock to blend in a controlled, uniform manner preventing the establishment of an uneven tiow pattern. Second, the blending is obtained without subjecting the dilute paper stock to drastic redirectional flow paths removing the possibility of forming uncontrollable turbulence that is a possible threat in systems containing redirecting blending chambers. Third, the mixing roll subjects the stock to an additional velocity evening zone which is contained within the internal area of the mixing roll thus further equalizing the velocity profiles of the dilute paper stock while in the distributor system. Referring to FIG. 1 of the drawings, the How of dilute paper stock in the distributor system is subjected to one extreme turning condition (90 or more) which occurs at the inlet ends of the pipes. The flow of dilute paper stock is thereafter substantially straight and is contained Within the headbox inlet chamber which after the blending is preferably constant in cross sectional area. As a result, the distributor system has completely removed the possibility of any uncontrollable or unpredictable turbulence, secondary eddies, or velocity ditferentials that are present in distributor systems subjecting the flow to multiple turning conditions of 90 or more. The mixing roll should be separated from the outlets of the pipes 19 by approximately five inches and not more than approximately 20 inches. Approximately 12 inches can be expected to Work in most cases.

A distributor system of the type described herein is necessarily complex to design because of the number of factors that must be taken into account, all of which are decidedly important but some of which are necessarily dependent upon more controlling factors. The following discussion deals with a design procedure which is felt to be desirable. The design procedure can be affected by conditions that vary from one paper machine to another. As an example, adding the distributor system to existing paper machines sometimes develops space limitations, and available pumping head.

Under ordinary conditions the design can be determined by beginning with the fiow at which the paper machine will be running the majority of the time. The width of the paper machine is related to the total flow of dilute paper stock to determine the shape of the manifold in any manner commonly followed in the industry. A flow velocity and a pipe diameter for each pipe is chosen so that the flow through each pipe is fully turbulent. The

flow condition "in the pipes is then effective against pressure surges, flocculation, and steady state pressure deviations. Pipe diameter and velocity are divided into the total diow to determine the number of pipes necessary. The number of pipes are physically deployed as explained previously to obtain proper mixing and to prevent overexpansion. The length of the pipes is determined based on the principle that the ability of pressure deviations to cause velocity differentials is inversely proportional to the pipe length. An energy loss of 310 ft. of water in the pipes will usually overcome the pressure deviations. Finally, the position of the mixing roll is determined. The mixing roll should have an outside diameter just slightly less than the width of the mixing portion of the headbox inlet chamber. Provisions should be incorporated till the design so that the mixing roll can be rotated to prevent buildup of fibers carried in the dilute paper stock on the roll surfaces. impingement plates are designed and placed within the distributor system. The construction of the headbox is not a part of the invention and can be one of several general types. Care should be exercised to employ a headbox that will not create flow disturbances or 'fioccin'g problems.

The distributor system when designed accordingly will effectively block upstream disturbances including manifold inaccuracies resulting in stable and uniform flows of dilute paper stock throughout the headbox. It should be realized that many modifications and variations are possible that are still within the scope of this invention.

1 claim:

1. A distributor system for a paper machine headbox comprising:

.(a) A headbox inlet chamber opening into the upstream portion of the headbox,

('b) said headbox inlet chamber having opposing diverging walls extending across the width of the headbox and diverging toward the headbox,

(c) means for introducing a multiplicity of separated streams of dilute paper stock into the headbox inlet chamber between the diverging walls, and

(d) means for directing alternate streams primarily along one of said diverging Walls While directing the remaining streams primarily along the other of said diverging walls.

2. The apparatus of claim 1 further including:

(a) Means for redirecting said alternate streams and said remaining streams into converging directions, said convergence causing a blending of said streams into a single stream of uniform velocity extending across the width of the headbox.

3. The apparatus of claim 2 wherein:

(a) Said re-directing means includes a pair of impingement plates extending across the width of the headbox in spaced, parallel relationship to each other, and

(12) each of said plates is attached to an inside surface of an associated diverging wall extending inwardly away therefrom.

4. The apparatus of claim 1 wherein:

(a) Said introducing means comprises a multiplicity of pipes of equal diameters having considerable length as compared with diameter,

(b) said pipes being arranged in at least two groups in which all of the pipes in each group are parallel to each other,

(0) said pipes having outlet ends received between said diverging walls,

(a!) alternate pipes forming one group having portions extending angularly upstream away from said outlet ends in one direction, and

(e) the remaining pipes forming the second group having portions extending angularly upstream away from said outlet ends in another direction.

5. The apparatus of claim 1 wherein:

(a) Said introducing means comprises a multiplicity l. "i of pipes of equal diameter having considerable length as compared with diameter,

(b), said pipes being arranged in two rows,

(c) said pipes in both rows having outlet ends received between said diverging walls,

(d) the outlet ends of the pipes of one of said rows being disposed adjacent one of said diverging walls, and

(e) the outlet ends of the pipes of the other of said rows being disposed adjacent the other of said diverging walls.

6. The apparatus of claim 1 wherein:

(a) Said introducing means comprising a multiplicity of pipes of equal diameters having considerable length as compared with diameter,

(b) said pipes having outlet ends received between said diverging walls,

() two rows of deflectors etxending angularly across said outlet ends and forming deflecting surfaces for directing jets of dilute paper stock issuing from said pipes along said diverging Walls,

(d) alternate deflectors forming one row extending angularly across the associated pipe outlet ends in one direction and directing the associated jets of dilute paper stock along one of said diverging walls, and

(e) remaining deflectors forming the second row and extending angularly across the associated pipe outlets in another direction and directing the associated jets along the other of said diverging walls.

7. A distributor system for a paper machine headbox comprising:

(a) A headbox inlet chamber opening into the headbox and extending the width thereof,

(b) said headbox inlet chamber having a mixing portion formed by opposing diverging walls,

(0) mixing means forming a discontinuous surface between said opening and said mixing portion of the headbox inlet chamber,

(d) two rows of pipes of equal diameters having considerable length as compared with the diameter,

(e) said rows of pipes having outlet ends received by said mixing portion oppositely to said discontinuous surface and between said diverging walls,

(1) a pair of impingement plates extending across the width of the headbox in parallel spaced relationship,

(g) each of said plates being attached to the inside surface of an associated diverging wall adjacent the downstream extremity thereof and extending inward- 1y away therefrom, and

(h) means for introducing dilute paper stock of relatively constant static pressure to the inlet ends of the pipes.

8. In a paper machine headbox having an inlet chamber including a pair of opposite walls diverging in a downstream direction, the method of distributing dilute paper stock uniformly across the width of the headbox which comprises the steps of:

(a) Dividing a single stream of dilute paper stock into a row of smaller and equally sized parallel streams of dilute paper stock,

(b) directing adjacent streams of dilute paper stock from the row of streams of dilute paper stock in diverging directions parallel to said diverging walls whereby the total flow along each of said walls is substantially equal, and

(c) re-directing the diverging streams of dilute paper 12 stock into one stream of uniform velocity extending across the width of the headbox.

9. In a paper machine headbox having an inlet chamber including a pair of opposing walls diverging in a downstream direction, the method of distributing dilute paper stock uniformly across the width of the headbox which comprises the steps of:

(a) Dividing a stream of dilute paper stock into a multiplicity of smaller and equally sized parallel streams of dilute paper stock extending across the width of the headbox,

(b) directing alternate streams primarily in one diverging direction substantially parallel to one of said diverging walls,

(6) directing remaining streams primarily in another diverging direction substantially parallel to the other of said diverging walls,

(d) blending said alternate streams and said remaining streams into a single stream extending across the width of the headbox by redirecting said alternate streams and said remaining streams into converging directions, and

(e) restraining the flow of the said single stream to a substantially undeviating constant cross section after blending.

10. In a paper machine headbox having an inlet chamber including a pair of opposing walls diverging in a downstream direction, the method of distributing dilute paper stock uniformly across the width of the headbox which comprises the steps of:

(a) Dividing a stream of dilute paper stock into two rows of smaller and equally sized streams of dilute paper stock extending across the width of the head- "box whereby the total flow in each of the two rows of streams is substantially equal,

(b) directing the streams of dilute paper stock in each row angularly away from the streams of dilute paper stock in the other of said rows with each of said streams being substantially parallel to one of said diverging walls,

(c) blending said angularly directed streams of dilute paper stock into a single stream extending across the width of the headbox by re-directing the angularly directed streams into converging directions with streams from one row impinging upon streams of another row, and

(d) restraining the flow of said single stream to a substantially undeviating constant cross section after blending.

References Cited by the Examiner UNITED STATES PATENTS 2,677,991 5/54 Goumeniouk 162338 2,747,471 5/56 Corbin Vet al 162342 2,894,581 7/59 Goumeniouk 162339 2,973,034 *2/61 White 162--339 2,993,538 7/61 Mustonen 162-347 3,055,421 9/62 Cirrito 162--340 3,065,788 11/62 Beachler 162-636 3,076,502 2/63 Robinson l62339 FOREIGN PATENTS 636,101 2/62 Canada.

DONALL H. SYLVESTER, Primary Examiner,

MORRIS O. WOLK, Examiner,

Claims (2)

1. A DISTRIBUTOR SYSTEM FOR A PAPER MACHINE HEADBOX COMPRISING: (A) A HEADBOX INLET CHAMBER OPENING INTO THE UPSTREAM PORTION OF THE HEADBOX, (B) SAID HEADBOX INLET CHAMBER HAVING OPPOSING DIVERGING WALLS EXTENDING ACROSS THE WIDTH OF THE HEADBOX AND DIVERGING TOWARD THE HEADBOX, (C) MEANS FOR INTRODUCING A MULTIPLICITY OF SEPARATED STREAMS OF DILUTE PAPER STOCK INTO THE HEADBOX INLET CHAMBER BETWEEN THE DIVERGING WALLS, AND (D) MEANS FOR DIRECTING ALTERNATE STREAMS PRIMARILY ALONG ONE OF SAID DIVERGING WALLS WHILE DIRECTING THE REMAINING STREAMS PRIMARILY ALONG THE OTHER OF SAID DIVERGING WALS.

8. IN A PAPER MACHINE HEADBOX HAVING AN INLET CHAMBER INCLUDING A PAIR OF OPPOSITE WALLS DIVERGING IN A DOWNSTREAM DIRECTION, THE METHOD OF DISTRIBUTING DILUTE PAPER STOCK UNIFORMLY ACROSS THE WIDTH OF THE HEADBOX WHICH COMPRISES THE STEPS OF: (A) DIVIDING A SINGLE STREAM OF DILUTE PAPER STOCK INTO A ROW OF SMALLER AND EQUALLY SIZED PARALLEL STREAMS OF DILUTE PAPER STOCK, (B) DIRECTING ADJACENT STREAMS OF DILUTE PAPER STOCK FROM THE ROW OF STREAMS OF DILUTE PAPER STOCK IN DIVERGING DIRECTIONS PARALLEL TO SAID DIVERGING WALLS WHEREBY THE TOTAL FLOW ALONG EACH OF SAID WALLS IS SUBSTANTIALLY EQUAL, AND (C) RE-DIRECTING THE DIVERGING STREAMS OF DILUTE PAPER STOCK INTO ONE STREAM OF UNIFORM VELOCITY EXTENDING ACROSS THE WIDTH OF THE HEADBOX.

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