US3445331A - Fiber suspension distribution system - Google Patents

Description

C. A. LEE ET FIBER SUSPENSION DISTRIBUTION SYSTEM May 20, 1969 Sheet Filed Aug. 16, 1965 /4/t E4/ r015 l'lAfLf dun (Arc J4 s ,4, lfvrmr Br W, M, ya, a

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FIBER SUSPENSION DISTRIBUTION SYSTEM Filed Aug. 16, 1965 Sheet 3 014 'I I II 1| 1 l- I I I I II to QrL May 20, 196% Q; LEE ETAL 3,445,331

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United States Patent Office 3,445,331 Patented May 20, 1969 FIBER SUSPENSION DISTRIBUTION SYSTEM Charles Allen Lee, Knoxville, Tenn., and James A. Murphy, Toronto, Ontario, Canada, assignors, by direct and mesne assignments, to Canadian International Paper Company, Montreal, Quebec, Canada, a body corporated and politic Filed Aug. 16, 1965, Ser. No. 479,797 Int. Cl. D21f 1/06 U.S. Cl. 162-338 7 Claims ABSTRACT OF THE DISCLOSURE A movable distribution system for a paper making machine including a mixing chamber with a plurality of orifices distributed over its area. The total cross-sectional area of flow at the inlet end of the mixing chamber is intermediate the cross-sectional area of the mixing chamber and the total cross-sectional area of said orifices.

This invention relates to a distribution system for supplying a suspension of papermaking fibers to the headbox of a papermaking machine, and more particularly to a distribution system in which the suspension is introduced through a plate having a plurality of orifices into a headbox having a plurality of tubes at its inlet end.

In making paper, it is ordinarily desirable that the paper be made uniform. This requires that the papermaking fibers be laid down uniformly upon the papermaking wire on which the paper is formed. In order to lay the fibers down uniformly, it is generally necessary that a homogeneous suspension of fibers be evenly distributed across the wire from a headbox. In order that the flow from the headbox be uniform across the width of the wire, it is helpful if the inlet into the headbox provides for uniform distribtuion of the fibers and that the fibers be uniformly distributed in the incoming fluid.

The present invention is directed to a distribution system for delivering a substantially homogeneous mixture of paper fibers in an aqueous suspension projected into the headbox substantially uniformly across its inlet, most particularly when the headbox is of the type having a plurality of parallel tubes at its inlet end, through which the incoming suspension flows.

In headboxes of the prior art, it is known to utilize a bank of substantially parallel tubes uniformly distributed in the inlet of the headbox to stabilize the flow of turbulent fluid. One such headbox is shown in Bennett Canadian Patent No. 503,957, which describes the operation of the headbox to establish the condition of frozen fiow. In such headboxes, the suspension was introduced into each tube through an orifice in a plate closing the inlet end of each tube.

In earlier distribution systems, it has been the practice, as shown in the aforesaid Bennett patent, to supply the fiber suspension to the orifices through a number of inlet tubes. The tubes were relatively few in number, for example six, and the flow from the inlet tubes was in separate streams each flowing directly against a particular section of the plate. The orifices directly in the path of the streams readily passed the suspension at a relatively high rate whereas the orifices not in the direct path of any stream passed the suspension only after a devious route and loss of energy and consequently at a relatively lower rate. This resulted in a non-uniform distribution of flow through the respective tubes. This in turn resulted in a non-uniform flow of fluid from the headbox and hence non-uniform distribution of fibers on the wire.

A further difficulty with the distribution system previously used for headboxes of the type having a bank of tubes in its inlet end was the great difiiculty in keeping the tubes clean. More particularly, on shut down fibers often collected in the pockets created by the plates closing the ends of the tubes. Fibers also collected at other places in the distribution system, as in the inlet tubes to the mixing; chamber of the system. Such collections of fibers were released from time to time into the flow, hence producing non uniformity.Non-uniformity was also produced when the fiber suspension was changed. For example, on most papermaking machines it is on occasion necessary or desirable to change the type or color of the stock. In the case of color changes or when producing changes of type, it is often intolerable to have fibers of the wrong color or type mixed in with the proper fibers, and it therefore may be necessary that the headbox be cleaned when changing from one color or type of paper to another. Under such circumstances, the cleaning of the distribution systems of the prior art has encountered difficulties and delays.

To overcome the non-uniformities occasioned by nonuniform distribution of flow through the orifices, the suspended fibers may be introduced into a mixing chamber substantially uniformly across the chamber with a relatively negligible component of flow in the cross direction of the chamber. The suspension is mixed by deflecting the entering suspension, and then forcing the mixed fibers through a plurality of small holes in a distribution plate, the holes being substantially uniformly distributed across the entire width of the headbox. These small streams pass into the inlet of the headbox. The total cross-sectional area of the inlet to the mixing chamber is less than the cross-sectional area of the mixing chamber but greater than the total cross-sectional area of the orifices. Under these conditions of changing direction of flow and changing cross section of flow, the fiber suspension is substantially uniformly mixed within the mixing chamber and is discharged through the orifices under substantially uniform conditions of turbulence at substantially uniform rates of flow through the respective orifices.

In the case of the headbox having a bank of tubes in its inlet end, there is a single orifice disposed centrally of each tube in the headbox. The distribution system of this invention thus provides the same flow of fiber suspension through each tube in the inlet of the headbox.

For the purpose of cleaning the headbox and particularly the tubes in the inlet thereof, the distribution plate is made readily removable. Further, the plate in its op erating position is not disposed against the ends of the headbox tubes but rather is disposed a short distance away, this distance being such that the jet of fluid through each orifice passes centrally into a respective tube while producing backward flowing vortex rings or eddy currents outside the jet to clean the inlet ends of the respective tubes. This distance should be larger than about inch in order that the fiber suspension is free to move between the ends of the tubes and the distribution plate rather than being trapped and caught in a pocket; however, this distance should not be so great as to permit the jet to strike the ends of the tubes.

Not only is the distribution plate made easily removable, but the entire mixing chamber is made readily removable in order that the inlet into the chamber can be cleaned.

It is therefore a primary object of this invention to provide a distribution system for supplying a turbulent homogeneous suspension of papermaking fibers uniformly across the inlet of the headbox of a papermaking machine. Another object of the invention is to provide such a distribution system in which the fluid is supplied through a plurality of orifices in a perforated distribution plate with the flow from each orifice being directed into a respective tube in the inlet of the headbox.

Still another object of the invention is to provide such a distribution system in which the distribution plate is placed such a distance from the inlet ends of the tubes that the jets of fiber suspension through the distribution plate cleanses the tubes rather than permitting fibers to collect at their inlet ends.

Still another object of the invention is to provide a mixing chamber and distribution plate readily removable from the inlet end of the headbox to facilitate cleaning of the headbox and the distribution system, including the inlet thereto, and to permit quick and simple changing of the orifice size merely by changing the distribution late. p Other objects and advantages of the invention will become apparent from consideration of the following detailed description, particularly when taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a side elevation, partly in section, of a headbox for a papermaking machine, showing its association with a preferred form of a stock distribution system according to the present invention;

FIGURE 2 is an enlarged view, partly in section, of the distribution system shown in FIGURE 1 as secured to the headbox, and showing in dashed lines the position of the mixing chamber of the distribution system when retracted from the headbox;

FIGURE 3 is an elevation of the other side of the machine showing the manner in which the mixing chamber is moved;

FIGURE 4 is an end elevation view, partly in section, taken along the section 4-4 of FIGURE 2, showing the distribution system;

FIGURE 5 is a sectional view, taken along the section 5-5 of FIGURE 4, showing the mixing chamber, with a distribution plate affixed thereto, mounted in place on the headbox;

FIGURE 6 is a sectional view showing the same apparatus as FIGURE 5, but with the mixing chamber and distribution plate slightly retracted from the headbox;

FIGURE 7 is an end elevation of a number of the tubes in the inlet of the headbox shown in FIGURE 1, showing by dashed lines the relationship of the orifices in the distribution plate; and

FIGURE '8 is a sectional view, taken along section 88 of FIGURE 7, showing the relationship between the distribution plate and the tubes in the headbox.

In FIGURE 1 is shown a papermaking machine including a distribution system 8 of the present invention. The distribution system is at the inlet end of a head-box 9. The headbox 9 comprises an upwardly slanting rectangular channel portion 10. The interior of the channel portion 10 contains a plurality of relatively small, straight tubes 11 disposed parallel to the longitudinal axis of the channel 10. As shown best in FIGURE 7, the tubes may be hexagonal in cross section so as to fill the channel portion 10 in honeycomb fashion. Other cross sections, such as round or square, may be used. The channel 10 and, indeed, the entire headbox 9 is of substantially the same width as wire 12 upon which the stock suspension 13 is deposited to form the paper web. The inlet ends of the tubes are disposed substantially in a plane. At the upper or outlet end of the tubes the tubes may be of varying lengths, as illustrated, with the lowermost tier being the longest and the uppermost tier being the shortest. The length of the tubes relative to their diameter is such as to provide the condition of the suspension 13 necessary to produce the stabilization of flow.

The upper or discharge end of the channel 10 joins a relatively long, horizontally disposed channel portion 15 formed from metal plates having a smooth inner surface and provided at its discharge end with an adjustable slice assembly diagrammatically indicated at 16. The slice assembly 16 itself may be of any suitable construction and may include a slice lip and an apron between which the suspension 13 flows out of the headbox 9 onto the wire 12.

While the mechanical details per se of the slice mechanism form no part of the present invention, it will be appreciated that its construction may be of such a nature that the assembly which has generally been indicated at 16 includes stationary mounting elements 19 which slidea'bly support slice lip carrying elements 20 adapted to be adjustably positioned in any desired operating location as by adjusting screw and hand wheel assemblies generally indicated at 21.

In the illustrated embodiment of the invention, the headbox is shown as it would be fabricated to operate as a pressure headbox in which the depth of flow of the fiber suspension in the horizontal channel 15 is less than the overall depth of the channel. When such a design is employed, means are provided for maintaining air pressure in that portion of the channel 15 above the flowing fiber suspension and in the present instance comprises an inlet pipe 22 opening into the channel 15 and connected with a suitable source (not shown) of compressed air. In order that proper control may be effected on the stock flowing under air pressure through the channel 15, including control of the depth of flow and the corresponding velocity of the stock in the channel, a bleeder pipe 23 of relatively small diameter is afiixed to one wall of and opens into the channel 15 at a height substantially equal to the designed depth of flow of the stock suspension. An adjustable valve 24 generally will be provided so as to restrict the leakage of compressed air, and the discharge side of the valve 24 may be connected to the wire pit of the paper machine. If an open headbox is used, the fluid level in the headbox is of course greater.

In many papermaking machines the suspension 13 is deposited upon the wire 12 in a turbulent condition. The turbulence tends to keep the fibers from floccing together by the shearing action of eddy currents. Although the turbulence prevents excessive fioc formation, the turbulent flow out of the slice orifice disturbs the uniform formation of the paper web. It is for this reason that frozen flow from the slice is sometimes desired. Frozen or plug flow is characterized by a thin shear zone adjacent to any surface of the channel contacted by the stock in which the fibers tend to roll or shear past one another, while all the rest of the cross section of the flowing suspension appears to be frozen into a solid plug, moving parallel to the axis of the channel and with uniform velocity throughout its cross section. With little or no movement of the fibers in relation to one another within a frozen flow, the gathering together of the fibers into flocs takes place very slowly or not at all.

Under some operating conditions, some flocculation of the fibers may occur, resulting in a floc pattern which may be retained through the slice orifice and in the paper. In the event that this floc pattern contains flocs of objectionably large size, there may be provided desirably a rotatable cage-type defloccing roll 25 transversely positioned within the horizontal channel 15 at either of the positions shown and driven by suitable power connections (not shown).

The headbox just described is well known. The improvement of the present invention lies in the distribution system 8 which supplies the fiber suspension to the headbox and in the manner in which the distribution system is coupled to the headbox. The distribution system 8 is shown in greater detail in FIGURES 2 and 4. The distribution system includes a manifold 26 into which the fiber suspension is pumped at the large end. The pressure in the manifold drives the fluid upwardly through a number of inlet tubes 28 into a mixing chamher 30, whence it passes through a perforated distribution plate 32 into the headbox 9. The distribution plate covers the outlet end of the mixing chamber.

In order that the distribution system and the headbox can be cleaned easily, the mixing chamber is made removable. To this end the walls 33 defining the chamber are mounted on rollers or wheels 34 for movement along tracks 36. As shown best in FIGURE 3, the walls defining the mixing chamber are moved along the track by operation of a hand operated wheel 38 operating through gears to drive a chain 40 to turn a gear 42 which in turn is coupled to gears 44 which mesh with racks 46 to drive the mixing chamber along the tracks 36. A shaft 48 couples the gears 44 together. The tracks are preferably horizontal in order that the apparatus can be easily moved without having to overcome the force of gravity.

The removable mounting of the mixing chamber is best observed by comparing FIGURES and 6. The mixing chamber 30 is shown mounted in operating position in FIGURE 5, while in FIGURE 6 it is shown slightly retracted. When in place, the walls 33 form an enclosed housing closed in part by the stationary base member 52. The mixing chamber 30 is closed at its ends by end plates 54 and is sealed by seals 56. The seals 56 may be hydraulically operated so that the mixing chamber housing 50 and end plates 54 may be secured in place by bolts 58 and 60 before the tight seal is made.

When the mixing chamber is in operating condition as shown in FIGURE 5, the fiber suspension passes upwardly through the inlet tubes 28 into the mixing chamber 30 and thence through orifices 62 in the distribution plate 32. Each orifice is disposed centrally of a respective tube 11, as indicated more specifically in FIGURES 7 and 8. When in operating position, the distribution plate 32 is mounted a short distance from the inlet ends of the tubes 11, the ends of the tubes 11 lying substantially in a plane parallel to the distribution plate and with the tubes 11 extending perpendicular to this plane. For the sake of adjustment and support, a plurality of spacer screws 64 are mounted in the distribution plate 32 and protrude therefrom toward the inlet tubes 11 by a predetermined amount. These spacer screws serve to determine the amount by which the distribution plate 32 is spaced from the tubes 11. Additionally, these spacer screws 64 also serve to hold the distribution plate 32 away from the tubes 11 during operation, for when the fiber suspension is forced into the mixing chamber 30, the pressure on the distribution plate 32 bows it toward the tubes 11.

For optimum performance, the relative sizes of the various components and their relative disposition are somewhat critical. The size and shape of the manifold 26 is such as to maintain substantially the same pressure at the inlet of each of the inlet tubes 28. The fiber suspension is introduced at the large end of the manifold 26. This end may be 24 inches in diameter. The diameter of the manifold 26 decreases toward the narrow end at such rate as to compensate for the decrease in the horizontal fluid flow occasioned by the extraction of fluid through the earlier inlet tubes 28. By this means the linear rate of flow is maintained constant to prevent the increase in pressure that would otherwise be occasioned by the slowing down of the fluid in the manifold 26. The flow of fluid from the small end of the manifold 26 may be controlled to aid in the balancing of pressures at the inlet ends of the inlet tubes 28 to provide for equal flow through each tube.

Relatively large numbers of inlet tubes pass from the manifold 26 to the mixing chamber 30. As shown, twentyfive inlet tubes have proved satisfactory, each of a diameter of about 2 /2 inches. In the prior art, it has been known to use six inlet tubes of larger diameter. However, the larger number of inlet tubes provides for greater homogeneity in the mixing chamber. That is, with the relatively large number of inlet tubes 28 the fiber suspension is introduced into the mixing chamber substantially uniformly across its inlet end. There is a sufiicient number of inlet tubes sufliciently close together that the jets emitted from the tops of the inlet tubes 28 promptly merge by the turbulence created by the jets. These inlet tubes 28 are preferably relatively long to reduce any cross flow pattern within the individual tubes, so that the flow is substantially entirely lengthwise of the tubes. The tubes 28 are preferably straight and are substantially parallel at their entrance into the mixing chamber 30 in order that there be substantially no component of flow in the cross direction of the chamber 30.

Proper flow into the mixing chamber may be achieved by use of alternative inlets. For example, a flow spreader may be interposed between the single large round pipe at the inlet to the manifold 26 and the mixing chamber. This flow spreader could convert the flow from a single concentrated stream to a single flat stream evenly distributed across the entire inlet side of the mixing chamber and all flowing in the machine direction with substantially no component of flow in the cross direction of the chamber.

In the prior art, the output from the inlet tubes moved in jets toward the tubes 11 thus driving more of the suspension into some of the tubes than others. To avoid this the incoming jets from the tubes 28 do not move directly toward the orifices 62 but rather are forced to make a substantial change in direction and to mix with the fluid previously in the chamber 30 before leaving through the orifices 62. The fluid may be directed, as shown, generally toward the top of the housing and deflected by the wall 33 and the fluid previously in the mixing chamber 30. The mixing chamber 30 thus produces turbulence in the suspension and provides substantially uniform distribution of the fibers in the fluid. It is in this state that the fluid moves through the distribution plate 32.

In the preferred form of the invention, the total crosssectional area of all of the orifices 62 in the distribution plate 32 is less than the total cross-sectional area of the inlet tubes 28, which in turn is smaller than the crosssectional area of the flow through the mixing chamber between the inlet tubes 28 and the outlet orifices 62. This aids in the production of the desired amount of turbulence.

The desired size of the orifices 62 depends on a number of factors including the number and size of the tubes 11. With tubes of about 2 /2 inches in diameter, orifices of about inch have proven suitable. Similarly, the desired spacing between the distribution plate and the inlet ends of the tubes 11 depends upon several factors. With inch orifices and 2 /2 inch tubes about inch spacing has proven satisfactory. It is desirable that the distribution plate 32 be fiat and have the orifices 62 substantially perpendicularly therethrough in order that the jets 66 produced by the flow of fluid through the orifices 62 be in the direction of the tubes 11. Preferably the inlet ends of the orifices have rounded edges so as not to wear excessively.

As previously mentioned, it is important that fibers not collect in the inlet end of the tube.- If fluid flowed against the inlet edges 68 of the tubes 11, they would tend to staple or wrap around the edges and accumulate fibers. By spacing the distribution plate 32 at the proper distance from these edges 68, the jets of fiber suspension 66 actually wash away any fibers that happen to collect. That is, the entering jets 66 drive the fluid suspension into the centers of the tubes 11, and these forward moving streams do not strike the walls of the tubes 11 until some distance from the inlet ends 68. In the intervening region the jets create turbulence in the nature of vortex rings or eddy currents 70 which provide a reverse flow along the insides of the tubes toward their inlet end, thus washing away any fibers tending to collect on the edges 68. Typically, the spacing between the distribution plate 32 and the edges 68 of the tubes 11 should be larger than about /1 inch in order that the fibers may pass freely through this space and not be trapped. At the same time the spacing must be short enough that the edges 68 are in the region of reverse flow or vortex rings 70. A spacing of about two orifice diameters has proven suitable.

Although the tubes 11 are thus self-cleansing with the distribution system of the present invention, the distribution system is additionally made particularly suitable for cleaning by reason of being easily removable from the headbox. The mixing chamber 30 may be readily moved upon the tracks 36 by operation of the wheel 38 after the bolts 58 and 60 have been released. This exposes the inlet ends of the tubes 11 in the tube bank for swabbing. It also exposes the vertical inlet tubes 28 for sWabbing. The distribution plate 32 is itself demountable from the walls 33 for cleaning on both sides and also permitting the cleaning of the interior of the walls 33. As noted earlier, such cleaning of the distribution system and headbox is often necessary when changing the type or color of the fiber suspension. In practice, it has been found that the system of the present invention can be cleaned in less than 20 percent of the time needed to clean the distribution system and headbox of the prior art devices where the headbox tubes were individually covered by permanently installed plates Further, the distribution plate may be changed for one having orifices of different diameter, as may be desirable for operating at different speeds. This provides greater flexibility to the overall operation of the papermaking machine.

A patent is solicited for any and all herein disclosed patentable subject matter invented by applicants.

The embodiment particularly disclosed herein may be changed or modified in various ways without departing from the scope of the invention.

Various features now believed to be new and patentable are set forth in the appended claims.

What is claimed is:

1. A distribution system for supplying a fiber suspension to the inlet end of a headbox of a papermaking machine, said distribution system comprising wall means defining a mixing chamber of substantially the same width as said inlet end of said headbox and having an outlet end and an inlet end of substantially said same width, a perforated distribution plate mounted on said wall means to cover said outlet end of said mixing chamber and having a multiplicity of orifices of substantially the same size substantially uniformly distributed over the area of said plate and extending in the same direction through said plate for admitting said fiber suspension from said mixing chamber into said headbox in a plurality of jets moving in the same direction, a multiplicity of substantially parallel inlet tubes of substantially equal diameter coupled to said inlet end of said mixing chamber, and manifold means for supplying said fiber suspension at substantially equal rates to each of said inlet tubes, said inlet tubes being substantially uniformly spaced across said inlet end of said mixing chamber sufiiciently close together that said fiber suspension is introduced into said mixing chamber substantially uniformly across its inlet end, said inlet tubes being sufficiently long and extending in such direction that said fiber suspension issues therefrom into said mixing chamber in the same direction which same direction differs substantially from the direction of flow of said fiber suspension through said orifices and with a relatively negligible component of flow in the cross direction of said mixing chamber, and the total cross-sectional area of said inlet tubes being intermediate the cross-sectional area of said mixing chamber and the total cross-sectional area of said orifices, whereby said fiber suspension is substantially uniformly mixed within said mixing chamber and is discharged in substantially uniform turbulent conditions at substantially uniform rates through the respective orifices into said headbox.

2. A distribution system for supplying a fiber suspension to the inlet end of a headbox of a papermaking machine, said distribution system comprising wall means defining a mixing chamber of substantially the same width as said inlet end of said headbox and having an outlet end and an inlet end, said Wall means being mounted upon a movable carriage, a perforated distribution plate removably mounted on said wall means to cover said outlet end of said mixing chamber and having a multiplicity of orifices of substantially the same size substantially uniformly distributed over the area of said plate and extending in the same direction through said plate for admitting said fiber suspension from said mixing chamber into said headbox in a plurality of jets moving in the same direction, means coupled to said carriage for moving said carriage with said Wall means and distribution plate mounted thereon from a first position remote from said inlet end of said headbox to a second position wherein said distribution plate is disposed at said inlet end of said headbox, and inlet means for coupling to said inlet end of said mixing chamber to introduce said fiber suspension into said inlet end of said mixing chamber, the total cross-sectional area of said inlet means being intermediate the cross-sectional area of said mixing chamber and the total cross-sectional area of said orifices, whereby said fiber suspension is substantially uniformly mixed within said mixing chamber and is discharged in substantially uniform turbulent conditions at substantially uniform rates through the respective orifices into said headbox.

3. A distribution system for supplying a fiber suspension to the inlet end of a headbox of a papermaking machine, said distribution system comprising wall means defining a mixing chamber of substantially the same Width as said inlet end of said headbox and having an outlet end and an inlet end of substantially said same width, said wall means being mounted upon a movable carriage, a perforated flat distribution plate removably mounted on said wall means to cover said outlet end of said mixing chamber and having a multiplicity of round orifices of substantially equal diameter substantially uniformly distributed over the area of said plate and extending normally through said plate for admitting said fiber suspension from said mixing chamber into said headbox in a plurality of jets moving in the same direction, a multiplicity of substantially parallel inlet tubes of substantially equal cross section for coupling to said inlet end of said mixing chamber, means coupled to said carriage for moving said carriage horizontally with said wall means and distribution plate mounted thereon from a first position remote from said inlet end of said headbox to a second position wherein said distribution plate is disposed at said inlet end of said headbox and substantially perpendicular to the direction of flow in said inlet end of said headbox, and wherein said inlet tubes are coupled to said inlet end of said mixing chamber, and manifold means for supplying said fiber suspension at substantially equal rates to each of said inlet tubes, said inlet tubes being substantially uniformly spaced across said inlet end of said mixing chamber sutficiently close together that said fiber suspension is introduced into said mixing chamber substantially uniformly across its inlet end, said inlet tubes being sufiiciently long and extending in such direction that said fiber suspension issues therefrom into said mixing chamber in the same direction which same direction differs substantially from the direction of flow of said fiber suspension through said orifices and with a relatively negligible component of flow in the cross direction of said mixing chamber, and the total cross-sectional area of said inlet tubes being intermediate the cross-sectional area of said mixing chamber and the total cross-sectional area of said orifices, whereby said fiber suspension is substantially uniformly mixed within said mixing chamber and is discharged in substantially uniform turbulent conditions at substantially uniform rates through the respective orifices into said headbox.

4. A distribution system for supplying a fiber suspension to the inlet end of a headbox of a papermaking machine, said inlet end of said headbox having a multiplicity of substantially straight and parallel headbox tubes substantially uniformly distributed over said inlet end of said headbox for stabilizing the flow within said headbox, said distribution system comprising -wal1 means defining a mixing chamber of substantially the same Width as said inlet end of said headbox and having an outlet end and an inlet end, said wall means being mounted upon a movable carriage, a perforated distribution plate removably mounted on said wall means to cover said outlet end of said mixing chamber and having a multiplicity of orifices of substantially the same size each corresponding to one of said headbox tubes to admit said fiber suspension from said mixing chamber into said corresponding one of said headbox tubes, the cross section of each orifice being small relative to the cross section of each of said headbox tubes, means coupled to said carriage for moving said carriage with said wall means and distribution plate mounted thereon from a first position remote from said inlet end of said headbox to a second position wherein said distribution plate is disposed substantially perpendicular to said headbox tubes and spaced therefrom by a distance permitting said fiber suspension to move freely between the ends of said headbox tubes and said distribution plate with said orifices disposed substantially centrally of said corresponding headbox tubes and with the inlet end of each headbox tube within the region of reverse flow occasioned by the jet of fluid through a respective orifice, and inlet means for supplying said fiber suspension to said inlet end of said mixing chamber, and the total cross-sectional area of said inlet means being intermediate the cross-sectional area of said mixing chamber and the total cross-sectional area of said orifices, whereby said fiber suspension is discharged in substantially uniform turbulent conditions at substantially uniform rates through the respective orifices into the center of corresponding ones of said headbox tubes.

5. A distribution system for supplying a fiber suspension to the inlet end of a headbox of a papermaking machine, said inlet end of said headbox having a multiplicity of substantially straight and parallel headbox tubes substantially uniformly distributed over said inlet end of said headbox for stabilizing the flow within said headbox, said distribution system comprising wall means definng a mixing chamber of substantially the same width as said inlet end of said headbox and having an outlet end and an inlet end, a perforated distribution plate mounted on said wall means to cover said outlet end of said mixing chamber and having a multiplicity of orifices of substantially the same size extending through said plate in a direction parallel to said headbox tubes and each disposed substantially centrally of a corresponding one of said headbox tubes to admit said fiber suspension from said mixing chamber into said corresponding one of said headbox tubes, the cross section of each orifice being small relative to the cross section of each of said headbox tubes, said distribution plate being spaced from said headbox tubes by a distance permitting said fiber suspension to move freely between the ends of said headbox tubes and said distribution plate with the inlet end of each headbox tube within the region of reverse flow occasioned by the jet of fluid through a respective orifice, and inlet means for supplying said fiber suspension to said inlet end of each mixing chamber, the total cross-sectional area of said inlet means being intermediate the cross-sectional area of said mixing chamber and the total cross-sectional area of said orifices, whereby said fiber suspension is discharged in substantially uniform turbulent conditions at a substantially uniform rates through the respective orifices into the center of corresponding ones of said headbox tubes.

6. A distribution system for supplying a fiber suspension to the inlet end of a headbox of a papermaking machine, said inlet end of said headbox having a multiplicity of substantially straight and parallel headbox tubes substantially uniformly distributed over said inlet end of said headbox for stabilizing the flow within said headbox, said distribution system comprising wall means defining a mixing chamber of substantially the same width as said inlet end of said headbox and having an outlet end and an inlet end of substantially said same width, a perforated flat distribution plate mounted on said wall means to cover said outlet end of said mixing chamber and having a multiplicity of round orifices of substantially equal diameter extending through said plate in a direction parallel to said headbox tubes and each disposed substantially centrally of a corresponding one of said headbox tubes to admit said fiber suspension from said mixing chamber into said corresponding one of said headbox tubes, the cross section of each orifice being small relative to the cross section of each of said headbox tubes, said distribution plate being disposed substantially perpendicular to said headbox tubes and spaced therefrom by a distance permitting said fiber suspension to move freely between the ends of said headbox tubes and said distribution plate with the inlet end of each headbox tube within the region of reverse flow occasioned by the jet of fluid through a respective orifice, a multiplicity of substantially parallel inlet tubes of substantially equal cross section coupled to said inlet end of said mixing chamber, and manifold means for supplying said fiber suspension at substantially equal rates to each of said inlet tubes, said inlet tubes being substantially uniformly spaced across said inlet end of said mixing chamber sufiiciently close together that said fiber suspension is introduced into said mixing chamber substantially uniformly across its inlet end, said inlet tubes being sufliciently long and extending in such direction that said fiber suspension issues therefrom into said mixing chamber in the same direction which same direction differs substantially from the direction of flow of said fiber suspension through said orifices and with a relatively negligible component of flow in the cross direction of said mixing chamber, and the total cross-sectional area of said inlet tubes being intermediate the crosssectional area of said mixing chamber and the total crosssectional area of said orifices, whereby said fiber suspension is substantially uniformly mixed within said mixing chamber and is discharged in substantially uniform turbulent conditions at substantially uniform rates through the respective orifices into the center of corresponding ones of said headbox tubes.

7. A distribution system for supplying a fiber suspension to the inlet end of a headbox of a papermaking machine, said inlet end of said headbox having a multiplicity of substantially straight and parallel headbox tubes substantially uniformly distributed over said inlet end of said headbox for stabilizing the flow within said head box, said distribution system comprising wall means defining a mixing chamber of substantially the same width as said inlet end of said headbox and having an outlet end and an inlet end of substantially said same width, said Wall means being mounted upon a movable carriage, a perforated fiat distribution plate removably mounted on. said wall mearns to cover said outlet end of said mixing chamber and having a multiplicity of round orifices of substantially equal diameter each corresponding toone of said headbox tubes to admit said fiber suspension from said mixing chamber into said corresponding one of said headbox tubes, each orifice having a cross section small relative to the cross section of each of said headbox tubes and extending normally through said plate, a multiplicity of substantially straight and parallel inlet tubes of substantially equal cross section for coupling to said inlet end of said mixing chamber, means coupled to said carriage for moving said carriage horizontally with said wall means and distribution plate mounted thereon from a first position remote from said inlet end of said headbox to a second position wherein said distribution plate is disposed substantially perpendicular to said headbox tubes and spaced therefrom by a distance permitting said fiber suspension to move freely between the ends of said headbox tubes and said distribution plate with said orifices disposed substantially centrally of said corresponding headbox tubes and with the inlet end of each headbox tube within the region of reverse flow occasioned by the jet of fluid through a respective orifice and wherein said inlet tubes are coupled to said inlet end of said mixing chamber, and manifold means for supplying said fiber suspension at substantially equal rates to each of said inlet tubes, said inlet tubes being substantially uniformly spaced across said inlet end of said mixing chamber sufficiently close together that said fiber suspension is introduced into said mixing chamber substantially uniformly across its inlet end, said inlet tubes being sufficiently long and extending in such direction that said fiber suspension issues therefrom into said mixing chamber in the same direction which same direction differs substantially from the direction of flow of said fiber suspension through said orifices and with a relatively negligible component of flow in the cross direction of said mixing chamber, and the total cross-sectional area of said inlet tubes being intermediate the cross sectional area of said mixing chamber References Cited UNITED STATES PATENTS 3,098,787 7/ 1963 Sieber 162343 X DONALL H. SYLVESTER, Primary Examiner.

A. C. HODGSON, Assistant Examiner.

US. Cl. X.R. 162336, 343

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