US3028298A

US3028298A - Flow control apparatus

Info

Publication number: US3028298A
Application number: US796098A
Authority: US
Inventors: Charles A Lee
Original assignee: Kimberly Clark Corp
Current assignee: Kimberly Clark Corp
Priority date: 1959-02-27
Filing date: 1959-02-27
Publication date: 1962-04-03
Anticipated expiration: 1979-04-03

Description

April 3, 1962 c. A. LEE

FLOW CONTROL APPARATUS 5 Sheets-Sheet 1 Original Filed April 1-7, 1956 fiver:

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3,628,298 FLUW CONTRGL APPARATUS Charles A. Lee, Newtown, Conn, assignor to Kimberly- Clark Corporation, Neenah, Wis, a corporation of Delaware Continuation of application Ser. No. 578,618, Apr. 17, 1956. This application Feb. 27, 1959, Ser. No. 796,098

16 Claims. (Cl. 162214) The present invention relates to the manufacture of felted web and sheet products from suspensions of fibrous materials, and has particular relation to the manufacture of paper on Fourdrinier papermaking machines of the inlet or pressure-forming type.

This application is a continuation of my oopending application Serial No. 578,618, filed April 17, 1956, for Flow Control Apparatus, now abandoned.

In the ope-ration of inlet or pressure-forming type papermaking machines, an aqueous suspension of fiber and such other papermaking materials as may be used, which suspension is commonly designated as stock, is supplied to a web-forming region through which the F-ourdrinier wire is moved. The stock reaches the wire as a relatively high energy, flowing stream which is usually under substantial hydraulic pressure. Examples of these machines are shown in United States Patents Nos. 2,060,808; 2,134,408; 2,225,435, and 2,308,370.

Prior to the developments of the inlet or pressure-forming type papermaking machine it was the general practice in the operation of Fourdrinie-r papermaking machines to form the matte of fibers of which the paper web is composed by applying to the upper surface of the Fourdrinier wire, as by flowing or spouting thereon, a layer of stock which was then caused or permitted to drain through the wire. The stock so applied to the wire contained the required amount of fiber in an amount of water which was sufficient to produce the proper distribution of the fibers in the web, and sufiicient drainage of water was effected during the period of time that the formed web remained on the wire to produce a coherent sheet, capable of being couched off at the downstream end of the wire.

Various mechanisms, including suction boxes, table rolls, and water doctors were disposed beneath the wire for increasing the rate of drainage therethrough, and since there was no substantial pressure differential across the wire in the web-forming region along the Wire, the speed of operation of these machines was determined primarily by the capacity and effectiveness of the drainage means.

in contrast with this arrangement, in the inlet or pressure-forming machines, the stock, while contained within an enclosed flow conduit, is applied to a restricted area section of the Fourdn'nier wire as the wire is moved across the discharge end of that conduit. During the web-forming operation, the stock constitutes a confined, relatively high energy, flowing stream, which is under substantial hydraulic pressure, i.e., the pressure energy component of the stream of stock applied to the wire is usually quite large in relation to the velocity energy component. A large portion of the water in the stock mixure is thereby forced through the wire in the web-forming region at a relatively high rate, the flow through the Wire occurring primarily as a result of the substantial pressure ditferential existing across the forming wire in the web-forming region. The usual pressure-forming machine is capable of being operated at a much higher speed than the earlier type of Fourdrinier papermaking machines, and these machines have been quite widely used in the paperrnaking industry, epescially in the manufacture of sheets having a basis weight up to about 15 to 20 pounds per standard team of 500 sheets 24 x 36 inches.

However, such pressure-forming type machines possess certain inherent operational limitations or deficiencies.

Patent When such machines are at speeds in excess of from about 1500 to 2000 feet per minute, intermittent conditions of flow instability tend to occur. In addition to these operational difficulties, product deficiencies also result as the operating speeds of pressure-forming machines are increased.

In my prior applications, Serial Nos. 121,525 (now Patent No. 2,756,651); 196,893 (now Patent No. 2,756,- 650); 242,519 (now Patent No. 2,756,649); and 323,966 (now Patent No. 2,75 6,648), which were filed on October 14, 1949; November 21, 1950; August 18, 1951, and December 4, 1952, respectively, certain of these conditions and difliculties are discussed. Also, these prior applications disclose arrangements overcoming various of the flow instabilities previously referred to, and set forth, in some detail, certain operational principles applicable generally to pressure-forming and other machines. The applications further disclose and teach how these principles may be embodied in pressure-forming machines and other apparatus operable to accomplish the manufacture of fibrous webs from fluid suspensions, to permit much higher speeds of operation and much better control of the character and arrangement of the constituent fibers of the web than has heretofore been possible.

The present invention is directed to the same general problem as my prior applications, i.e., the provision of improved apparatus and methods for the manufacture of felted fibrous webs from fluid suspensions of fibrous materials, and especially the provision of improved paperrnaking apparatus of the pressure-forming type.

The present invention also includes the discovery of additional procedures, methods, and apparatus, the use of which results in good web formation, i.e., very uniform fiber distribution in the web and also provides for effective control of the machine direction to cross-machine direction strength ratio in the web. Of particular importance in this regard is the discovery that effective control of the machine direction to cross-machine direction strength ratio can be effected by control and adjustment of a flow control member which is located upstream of and in vertically spaced relationship to the web-forming region and which is capable of controlling the relative relation of the velocity and pressure energy components of the flowing stream of stock within the web-forming region.

These and other features of the invention will be made more apparent from the following description and accompanying drawings as applied particularly to pressureforming or inlet type Fourdrinier papermaking machines.-

In the drawings:

FIGURE 1 is a schematic view partially in vertical section and partially in side elevation of the Wet end of a Fourdrinier pressure-inlet type papermaking machine embodying certain of the features of the invention and certain accessory equipment;

FIGURE 2 is an enlarged vertical cross-sectional view of a portion of the machine illustrated in FIGURE 1, this view showing certain of the details and features of the Web-forming and flow control mechanisms in accordance with the invention, which is embodied in that machine;

FIGURE 3 is an enlarged fragmentary sectional view of the web-forming section of the machine illustrated in FIGURES 1 and 2;

FIGURE 4 is an enlarged fragmentary sectional View taken along the line 44 of FIGURE 3; and

FIGURE 5 is a typical graph showing how the machine direction strength to cross-machine direction strength ratio of a Web formed on apparatus such as is illustrated in FIGURES 1 to 3 is related to the velocity of the forming roll and the velocity of the forming wire.

It will be appreciated that certain of the principles and arrangements of the present invention are readily applicable to the older types of existing pressure-forming machines, and when so applied make possible substantial improvement in the characteristics of the product being made, and substantial increase in the possible operating speeds of the machines, both under operating conditions which are substantially more flexible and readily controlled than any arrangement heretofore developed.

The diagrammatic view, FIGURE 1, illustrates the structure and arrangement of a pressure-forming or inlet type Fourdrinier papermaking machine of the general character to which the present application has particular application. As there shown, the Fourdrinier wire 11 is supported upon a breast roll 13 and a couch roll 15 and is adapted to pass over a plurailty of spaced table rolls 17 and suction boxes 1?. The wire 11 is tensioned by additional guide or tensioning means as illustrated at 21. The wire 11 is driven by suitable drive means which, in the illustrated structure, includes a main drive and a helper drive. The main drive connects with the couch roll 15 and supplies a major portion of the energy necessary for driving the wire 11. The main drive includes a motor 18, sprockets 20, and a chain drive 22. The

helper drive connects with the breast roll 13 and supplies a portion of the energy for driving this roll. The helper drive includes a motor 23, sprockets 25, and a chain drive 27. The main drive and the helper drive are suitably interconnected or synchronized so that the periphery of the breast roll 13 moves at the linear velocity of the wire 11.

A tray 29, which is adapted to collect the white water, i.e., the liquid which drains through the wire during the web-forming operation, is disposed within the upper and lower reaches of the wire 11, as illustrated, and this tray is arranged to discharge into a mixing tank 31, which is normally maintained about three-fourths filled. Fresh water for make-up purposes may be added to the mixing tank through the pipe 33, and additional stock, as is necessary to maintain the proper consistency of fiber concentration in the fluid suspension or stock being delivered to the web-forming region, is added through a second inlet pipe 35.

The bottom of the mixing tank 31 is inclined, as shown, and a main flow line 37 connects to the tank at the lower end thereof. The main flow line includes a branch extension 39 having a valve 41 therein for use in draining the mixing tank 31, and the main flow line also connects with the inflow side of a stock or fan pump 43, which is the principal means relied upon to deliver stock to the web-forming region of the machine.

The outlet of the fan pump 43 is connected to the inlet structure of the machine by suitable piping, indicated generally at 45. Included in this piping is an automati cally operable pressure-regulating valve 47, a transition section 49, which converts the circular cross-sectional stream delivered by the fan pump and piping to a stream of rectangular outline, and a flow spreader 51. The flow spreader 51 accomplishes the function of converting the uniformly dimensioned stream delivered by the transition section 49 into a relatively shallow stream of rectangular cross section which desirably has a transverse width substantially equal to the cross-machine width of the Webforming region of the machine.

The outlet end of the flow spreader 51 is connected to the web-forming region of the machine by a conduit 53 which is provided in the upstream end of a flow control unit 55 which embodies various of the features of the present invention. The conduit 53 is rectangular in cross section and of the same dimensions as the outlet end of the flow spreader 51. The piping 45 also includes a by-pass line 57 which connects the outlet side of the fan pump 43 upstream of the pressure-regulating valve 47, with the mixing tank 31, as shown. The by-pass line 57 includes a shut-01f valve 59. Suitable showers or sprays, indicated generally at 61, are provided for effecting continuous cleaning of the rolls and wire, in accordance with usual papermaking practices.

The particular breast roll 13 constituting a part of the apparatus illustrated in FIGURES l and 2 is of the opensurfaced type and is illustrated in some detail in FIG-

URES

2, 3, and 4. As there shown, the breast roil 13 comprises a cylindrical inner shell 63 Which'may be of bronze or other corrosion resistant material, and which is supported for rotation by means of a pair of shaft sections 65, each of which is mechanically connected to one end of the shell by a suitable annular header 67. As shown in FIGURE 4, each of the headers 67 is welded or otherwise attached at its periphery to one end of the shell 63 and the hub of each of the annular headers is welded to the inner end portion of one of the two shaft sections 65. The outer ends of the shaft sections 65 extend into suitable supporting bearings (not shown). At least one of the shaft sections extends outwardly beyond its associated bearing and supports a sprocket 25 which connects with the chain drive 27.

At spaced intervals along the shell 63, the roll 13 is provided with a plurality of outwardly-projecting ring units 69. The rings 69* are integrally attached to the shell 63 and are provided with spaced, radially extending notches 71 (FIGURE 3) which support a plurality of elongated bar or vane members 73. These vane members are inclined in the direction of rotation of the roll 13, as shown particularly in FIGURE 3, and extend longitudinally of the roll surface with the longitudinal axes thereof substantially parallel to the axis of rotation of the roll.

The spaced vane members 73 are used to receive and to hold temporarily the liquid Which is forced through the wire and the adjacent underlying surface of the roll 13 during the web-forming operation. Each of the vanes 73, as shown particularly in FIGURE 3, includes a base or root portion which is rectangular in cross section, and which is adapted to fit within the radiallyextending vane-supporting notches 71 in the ring units 69. The upper portion of each vane is disposed at an angle of about to the root portion of the vane.

The outer edge portion of each of the vane units 73 is also notched, as shown particularly at 75 in FIGURE 4, and during the manufacture of the roll 13, an edgewise disposed ribbon 77 of Monel or other corrosion resistant material is wound into these slots 75 so as to provide a helical coil of closely spaced turns which extend along the periphery of the roll 13 This is shown particularly in FIGURE 4, and it will be noted that the helical ribbon projects above the outer edges of the vanes. This arrangement permits free circulation of liquid between the cells or cavities formed in the roll periphery by the spaced vanes 73, and it also minimizes vane shadows in the formed web.

In roll constructions of the general type illustrated, the vanes 73 are preferably spaced within the range of from about to inch along the roll periphery, and the turns of the edgewise-wound wire ribbon 77 which defines the outer surface of the breast roll 13 should be spaced sufliciently close together to prevent appreciable deformation of the forming wire during the operation of the machine. In a practical embodiment of the invention, where the breast roll 13 had an overali diameter of approximately 36 inches, the helical ribbon winding was wound at a pitch of 10 turns to the inch, and constituted a strip of monel ribbon having a thickness of .023 inch, and a cross-sectional dimension of .210 inch. In this same construction, the edges of the vanes 73 were about .0625 inch below the outer peripheral edge of the ribbon 77. A coarse mesh woven wire covering, such as a 12-14 mesh screen (not shown), may be applied over the ribbon winding, if desired.

As shown in FIGURE 4, each end of the breast roll 13 includes a pair of outer, interengaged protective end rings 79 and 81 which are held in position by means of cap screws 83. Each of the outer end rings 81 extends beyond the outer periphery of the cylindrical shell 63 to approximately the outer peripheral edge of the ribbon 77, and includes a laterally extending flange portion 85 which overlies a portion of the outer peripheral surface of the adjacent annular header 67. The innermost ends of the flange portions 85 extend vertically downwardly into contact with the outer surface of the cylindrical shell 63 and engage notches in the end sections of the vanes 73, thereby locking the vanes in position. The particular arrangement of the vane elements 73 and the ribbon support 77 for the forming wire present a minimum of resistance to the flow of fluid through the wire into the breast roll. At the same time, the vanes 73 are operable to retain the liquid which is received therein during the period in which the forming wire moves out of the web-forming region.

Referring to FIGURE 2, it will be seen that the flow control unit 55 includes a lower or stationary section 87 and a pair of hingedly interconnected, generally horizontally aligned upper sections 89 and 91, the section 89 being supported directly on the stationary section 87. The lower section 87 includes suitable plate and structural elements which define a frame portion having a flat upper surface 98, a pair of upwardly-extending sides 92, and the walls of the closed conduit 53 through which the stock is conducted to other elements of the flow control means.

The upper sections 89 and 91 of the flow control unit are likewise of fabricated construction and each includes oppositely arranged

side walls

93 and 95, respectively, which are connected together by suitable transversely extending structural members to define a pair of generally horizontally disposed box structures. The box-like sections 89 and 91 are generally horizontally aligned with the section 91 located forwardly of the section 89. The upper section 89 is supported upon the flat upper surface 90 of the frame portion of the stationary section 87 in a manner so as to be movable longitudinally of the apparatus, thus permitting the sections 89 and 91 to move towards and away from the vertical center line of the breast roll 13.

To facilitate the accomplishing of this movement, the side walls 92 of the stationary section 87 are provided with guideways 97 adapted to receive and coact with suitable guide members 99 constituting an integral part of the side walls 93 of the adjustable upper section 89. The coacting guideways 97 and guide members 99 serve the additional function of preventing the hydraulic pressure which is developed within the flow passageways of the flow control unit 55 from displacing the adjustable section 89 relative to the lower stationary section 87. To further aid in accomplishing this, it is desirable that the guides and guideways shall be constructed to very close tolerances. It may also be found desirable to include seals such as for example the O-ring type seal illustrated at 101 between the engaging surfaces of the upper and lower sections 87 and 89 to minimize the possibility of fluid leakage in the operation of the system. Locking screws as illustrated at 103 may be used to aid in holding the sections in proper adjustment.

In order to adjust the horizontal position of the upper sections 89 and 91 relative to the center line of the breast roll 13, suitable drive means such as a motor 105 which is supported on the upper surface 90 of the stationary section 87 is suitably connected through suitable gear means (not shown) to one or more longitudinally extending, threaded shafts 107 which engage internally threaded passageways 109 within a rear, transversely extending structural member 111 of the section 89. The threaded shafts 107 are arranged for simultaneous rotation by the drive means. In this manner, it is possible to move the adjustable upper sections 89 and 91 of the flow control unit 55 towards and away from the center line of the breast roll 13 and thereby vary the 6 dimensions and relative location of the web-forming region on the wire 11. The plane of separation between the upper and lower sections 89 and 87, which plane is coincident with the surface 90, normally extends substantially parallel to the surface of the horizontal position of the forming wire 11.

The flow conduit 55 through which the stock is conducted from the discharge end of the flow spreader 51 is rectangular in cross section and may have the same crosssectional area and dimensions as that end of the flow spreader. In the structure illustrated in FIGURES 2 and 3, the lower surface of the flow conduit 53 extends in a horizontal direction adjacent and beyond the forward end of the rearward adjustable section 89. This lower surface approaches in a horizontal direction the upper section of the lower, rearward quadrant of a transversely extending, cylindrical flow control member 113 which forms a portion of the forward adjustable section 91 and then curves smoothly to a downward arcuate path which is spaced below and which extends approximately parallel the adjacent surface of the roll 113. The end of the lower surface of the conduit 53 in the region adjacent the webforming region is defined by a downwardly extending apron plate 115 which extends transversely the full Width of the machine. The lower surface of the outer or lip portion 117 of the apron plate is cut away, as shown, and desirably this surface is curved so as to provide with the adjacent surface of the wire 11 which is supported on the breast roll 13, a passageway 119 which is of increasing cross-sectional area in the direction opposite to the direction of movement of the wire 11. The apron plate 115 extends within suitable guide means 121 provided in the adjacent portion of the stationary section 87 and is fixedly positioned therein by means such as screws 123. The apron plate is provided with a suitable slot 125 which permits adjustment of the outer tip of the apron plate 115 relative to the forming wire 11. Normally, the apparatus is adjusted so that the tip of the apron plate 115 is spaced approximately 1% to 2 inches rearwardly of the center line of the breast roll 13.

The lower adjacent ends of the sections 89 and 91 are pivotally interconnected through hinge members 127 and 129, respectively, which extend outwardly from the lower edges of these sections. These pivotal hinge members 127 and 129 extend transversely the full width of the machine and have lower surfaces which form continuations of the lower walls of these sections, thus permitting stock to flow smoothly between these lower surfaces. A suitable seal such as the O-ring type seal illustrated at 131 may be provided between the engaging surfaces of the hinge members to minimize the possibility of fluid leakage in the operation of the apparatus.

The hinge members 127 and 129 are maintained in contact with each other by biasing means which includes suitable nut and bolt assemblies 133 which extend through enlarged openings 135 and 137 in the transverse supporting walls of the sections 89 and 91 adjacent the hinge members 127 and 129 and springs 139 which extend around the outer ends of the bolts and bear against the inner faces of these transverse supporting walls. The two upper sections 89 and 91 are also interconnected through an upwardly and forwardly extending overhead arm which is connected at its lower end to the upper forward end of the section 89, an intermediate arm or link 132 which is pivotally connected at its upper end to the outer end of the overhead arm 130, and a member 134 which is pivotally connected at its upper end through an eccentric connection to the arm 132 and which is connected at its lower end to the upper end of the section 91. The vertical position of the outer end of the section 91 may be adjusted by rotating the shaft 136 of the eccentric connection.

The upper forward section 91 of the flow control unit 55 includes transversely extending structural elements 141 integrally attached to the side walls which define the walls of a generally cylindrical flow control chamber 143, and the cylindrical flow control member 113 which is disposed within the flow control chamber in generally symmetrical relation thereto. The unit also includes an adjustable member indicated generally at 145 which is positioned at the inflow side of the flow control chamber, and a slice 147. As may be seen in FIGURE 3, the slice 147 is wedge-shaped with its apex or leading edge located upstream adjacent the surface of the cylindrical flow control member 113. The upper surface of the slice 147 extends upwardly along an arcuate path and forms a portion of the wall of the cylindrical chamber 143 and the lower surface of the slice 147 extends downwardly in a direction generally parallel to the upper surface of the apron plate 115 and terminates adjacent the wire 11. The lower edge of the slice 147 defines the downstream edge of the pressure-forming zone on the wire 11.

'In the particular apparatus illustrated in FIGURES 2 and 3, the flow control member 113 comprises a closed cylinder or roll whose surface is provided with transversely extending, saw-toothed roughness elements 149, as shown, and is supported for rotation within the cylindrical chamber 143 by suitable supporting shaft sections 144 which extend into bearings, not shown. The peripheral diameter of the flow control member should be almost as large as the diameter of the flow control chamber 143. In general, the diameter of the flow control member 113 should be within /a inch, and preferably within between 7 and /8 inch of the diameter of the flow control chamber 143.

The flow control member 113 is connected to a drive means in order that it may be driven at predetermined speeds during the operation of the apparatus. The roll drive means, which may include a motor 151, sprockets 153, and a drive chain 155, should be capable of driving the roll at relatively high speed. For example, in a structure using a flow control roll approximately 16 inches in diameter, and having an operational or wire speed of about 2000 feet per minute, the drive means should be capable of driving this roll at a speed within the range of 100 to 800 r.p.m. during normal operating conditions of the machine.

The adjusting member 145 embodied in the illustrated apparatus is not necessary for the purposes of the present invention and may be replaced by a fixed wall section which curves downwardly so as to direct the upper portion of the moving stream of stock from a horizontal direction to a direction approximately tangential to the surface of the flow control roll 113. The adjustable mechanism 145 is provided in order to permit the mechine to be converted to other types of operation (not shown) where a throttling mechanism at the inflow end of the flow control chamber is desirable. The adjustable mechanism 145 includes a bar or vane member 157 which extends completely across the width of the machine and which is supported for limited movement towards and away from the adjacent lower surface of the conduit 53 by means of suitable guide means 159 which are integrally attached to the transversely extending structure of the flow control section 91.

Movement of the vane member 157 and accurate positioning of that member is accomplished by means of a plurality of spaced rods 1.61, each of which is connected at one end to the member 157 and provided with a threaded end portion 163 at its other end. The threaded end portions 163 engage suitable internally threaded gear wheels 165 which are supported on the frame of the upper section 91 of the flow control unit. These gear units are rotated in unison by coacting worm units 167 supported upon and keyed to a suitable actuating shaft 169. This arrangement permits the member 157 to be moved so as to vary and adjust the vertical height of the lower end of that member. The lower surface of the member 157 and the guide means 159 are suitably cut away, as shown, to direct the flowing stream tangentially into the flow control chamber 143 and to conform generally to the outline of the stream lines existing in the flow pattern within the apparatus during operation.

To prevent leakage along the sides of the vane member 157, it is desirable to include sealing means, such as the resilient O-ring seals 171 located intermediate the member 157 on the sides of the guide support 159 therefor.

It is desirable that the breast roll 13 be supported in such manner that its position relative to the flow control unit 55 can be accurately adjusted; this in conjunction with the adjustable apron plate 115 and the permissive fore and aft adjustment of the upper sections 89 and 91 of the flow control unit making possible very close control and adjustment of the dimensions of the webforming region and the flow passageways adjacent that region. Adjustment of the position of the breast roll 13 is most easily accomplished by the use of an automatically operable adjustable roll support of an hydraulic or other type. Such mechanisms are commercially available and will not be described in detail.

The wedge-shaped slice or discharge lip structure 147 forms an important part of the present apparatus. In the disclosed structure, the slice 147 is formed of two mating sections 173 and 175, the upstream ends of which abut against a member 177 which is affixed to the transverse structure of the section 91 by means of screws 179 or the like. The slice structure 147 which includes both slice sections 173 and 175 is fixedly secured to the member 177 by means of tongue and

groove connections

181 and 183 and bolts 185 which extend through the member 177 and are threadably received in the slice section 173.

The leading edge of the slice 147 is located upstream of the center line of the cylindrical roll 113. It should also be as close as possible to the surface of the roll 113 and preferably should be spaced approximately 4 inch therefrom. The wedge-shaped slice structure 147 presents a narrow leading edge to the flowing stream which directs the upper portion of the moving stream of stock in the direction of the forming region, i.e., it tends to peel the high velocity fluid which is moving in an arcuate path around the surface of the roll 113 and to direct this fluid downwardly toward the forming region. The slice section 175 has a lower surface which is inclined at a somewhat steeper angle than the lower surface of the slice section 173. This increased slope provides additional clearance between the wire and under-surface of the slice immediately upstream of the outer edge of the slice. The member 175 is removable in order to provide easy replacement thereof due to the wearing away of its lower edge during use. The downstream surface of the slice structure 147 provides with the adjacent surface of the wire 11 a flow passageway of substantial length and constantly decreasing in cross-sectional area in the direction of movement of the wire 11, and the formed web. This arrangement in combination with the available adjustment of the downstream edge or lip of the slice plate 115 makes possible accurate control of the amount of stock which is discharged from the flow control unit 55 on top of the formed web and is of important value in assuring satisfactory operation of the mechanism.

The two sides of the flow control chamber 143 are enclosed by the end walls of the flow control section 91 and suitable sealing units 187 which are adapted to ride on the wire 11 during machine operation. These sealing units 137 may be similar to the sealing unit shown in FIGURE 4, comprising L-shaped sections 189 of rubber or other resilient material which is backed by a rigid metal angle 191, the entire structure being adjustably held in position by a support 193, which is bolted to the side of the flow control unit by suitable bolts 195.

In the operation of apparatus of the type illustrated in FIGURES 1 through 3, the stock is delivered to the inlet to the flow control chamber 143 as a high energy flowing stream having substantial velocity and pressure energy components. This is accomplished by delivering the stock from the fan pump 43 at a relatively high head and by throttling the stock adjacent the inlet to the flow control chamber 143. As previously pointed out, the stock which is delivered to the wire 11 downwardly in a generally curved path around the lower upstream quadrant of the cylindrical roll 11?: to the leading edge of the outlet slice 173 and thence in a path which is generally tangential to the roll surface and extending to the wire 11. Since the leading edge of the slice is upstream of the center line of the roll 113, the axis of the stream of stock is oblique to the plane of the wire 11 in the webforming region.

Within the flow control chamber 143, the stream of stock which is generally rectangular in cross-sectional outline, flows into contact with the outer periphery of a second stream of stock which is flowing in a generally vorticular path around the rotating cylindrical roll 113. The velocity of this vorticularly flowing stream is generally considerably greater than the velocity of the stock entering the flow control chamber 143. Since the pressure within the vorticular stream is considerably less than the pressure of the stream entering the forming chamber 143, the upper layers of the stream of stock entering the flow control chamber adjacent the surface of the dew control roll 113 are caused to increase in velocity to a somewhat greater extent than the lower layers of the stream of stock which are spaced from the roll surface. As the stream of stock moves within the flow control chamber 143 below the lower upstream quadrant of the rotating roll 113, there is a partial intermixing of the vorticular stream with the stream which is delivered from the fan pump 43, causing an increase in the average velocity of the stream moving towards the forming wire 11. This intermixing action is accompanied by a conversion of the velocity energy component of a portion of the stream into pressure energy, together with the creation of a fine-scale turbulence condition. At a point upstream of the vertical center line of the rotating roll, the stream comes into contact with the leading edge of the wedge-shaped slice 147. The leading edge of the slice 147 closely approaches the surface of the rotating roll 113 so as to peel off as large an amount of the faster moving upper portion of the stream as possible and to direct the stream towards the forming wire 11. As the higher velocity stream portion flows adjacent the lower surface of the slice member, it slows down due to its contact with both the stationary slice wall and the underlying, slower moving portion of the stream. The slowing down of this faster moving fluid helps to maintain the velocity of the underlying fluid so that the horizontal component of the velocity of the fluid passing through the forming wire does not appreciably vary throughout the web-forming region.

The high velocity vorticular flow which is used to effect an increase of velocity of the fluid moving towards the web-forming region as well as to maintain the horizontal component of the velocity of the fluid passing through the forming wire approximately constant is produced by the recirculation of a quantity of the stock around the rotating roll 113 within the flow control chamber 143. The velocity of the recirculating vorticular stream is controlled and determined by the speed of rotation of the cylindrical roll 113 within the flow control chamber 143.

It will be appreciated that means other than the throttling of the fluid can be employed in the production of the high energy stream entering the flow control chamber 143, for example, a flow channel of suitable dimensions might be employed, although this arrangement has the disadvantage of introducing rather serious head and energy losses within the flowing stream, especially if the channel should be of substantial length.

One of the important discoveries constituting part of the present invention is the discovery that the flow instabilities which are normally incident to the rotation of a smooth cylindrical roll within an enclosed cylindrical chamber may be effectively controlled by reducing the spacing between the roll surface and the outer chamber to a value of less than 7 inch and adding roughness elements to the outer surface of the roll which increases the friction between the roll surface and the flowing stream. The actual roughness pattern may be varied considerably. The important considerations in this regard are the height of the roughness elements and the spacing index of the roughness, that is, the ratio of the spacing between the roughened elements circumferentially around the roll to the depth of the roughness elements on the surface of the roll. The height of the roughness elements should be between and inch and the spacing index should be between 4 and 12 and preferably about 8 for maximum eifectiveness in controlling flow disturbances in the flowing stream between the roll surface and the wall of the flow control chamber.

Another of the important discoveries constituting a part of the present invention is the discovery that the ratio of the machine direction strength to the cross-machine direction strength of the formed web can be varied by adjustment and control of either the speed of the flow control roll 113 or the speed of the forming wire 11 during the operation of the apparatus.

More particularly, it has been discovered that with the use of apparatus of the type illustrated in FIGURES 1 through 3, the ratio of the machine direction strength to the cross-machine direction strength in the formed web is related to the linear velocity of the forming roll 113 and to the velocity of the forming wire 11 by the following generalized empirical equation:

MD V, CD w where: M is a constant which is related to the geometry of the slice: k is a constant which is related to the carding action of the wire; V is the tangential velocity of the forming roll; and V is the tangential velocity of the wire. A typical graph of machine direction strength to crossmachine direction strength ratio versus for apparatus of the type described is shown in FIG- URE 5.

In one typical installation used in the manufacture of tissue having a basis weight of up to 8 or 9 pounds per standard ream from a furnish consisting of 25 percent bleached sulphite and 75 percent bleached sulphate with a consistency of about .20 percent, the wire 11 was set to run at a constant speed of 2,500 feet per minute and the fan pump 43 delivered approximately 12,000 gallons of stock per minute at a head of approximately 120 inches of water measured at the inlet of the flow control unit. The vertical height of the approach conduit to the inlet of the flow control chamber 143 was 3 inches and the vertical height of the flow passageway to the forming wire 11 within the flow control unit was inch. The rotating cylindrical roll 113 was 18 inches in diameter and the spacing, between the cylindrical roll 113 and the wall of the flow control chamber 143 was approximately A; inch except at the leading edge of the slice 147 where the spacing was about inch. The leading edge of the slice 147 was located approximately 3 inches behind the center line of the breast roll 13 and approximately inch behind the center line of the cylindrical roll 113, and the tip of the outer lip portion 117 of the apron plate was located 1 /2 inches behind the center line of the breast roll 13. The slice tip was set .015 inch from the surface of the wire 11, which distance was just sufficient to lubricate the web as it passed beneath the slice tip. By adjusting the tangential velocity of the roll 113 in this installation within the range of 500 to 3,800 feet per minute, one could control the machine direction to cross-machine direction strength 11 ratio of the formed web Within the range of 1 to about 4.5.

When the horizontal velocity component of the stream passing through the wire 11 is less than the velocity of the forming wire, it is necessary to accelerate the fluid which enters the breast roll. This is accomplished in the disclosed apparatus by providing the breast roll 13 with a helper drive which may supply as much as 75 percent of the force necessary to turn the breast roll, the wire 11 providing the remaining 25 percent. Sufficient force must be supplied by the main drive to pull the wire 11 under the slice 147 and across the various table rolls 17 and suction boxes 19. It is, of course, necessary to interconnect or synchronize the main wire drive and the helper drive so that the periphery of the breast roll 13 moves at the linear velocity of the forming member 11.

With an approach conduit 3 inches in depth, it has been found that the dimension A, the depth of the stream passing through the flow control chamber 143 towards the web-forming region, may vary from inch to 2 /2 inches, openings of from inch to 1% inches being found especially useful.

In general, the upstream edge of the slice 147 may be located from about 2 /2 to 3 inches behind the center line of the breast roll 113 and the tip of the outer lip 117 of the apron plate 115 may be located from about 1% to 2 inches behind the center line of the breast roll Under most operating conditions, it has been found that the pressure dififerential across the wire 11 in the web-forming region should be at a minimum in the upstream portion of the web-forming region and should increase in the direction of movement of the forming wire. This condition is achieved in the present apparatus by virtue of the slowing down of the faster moving upper layer of the stream flowing above the forming wire due to frictional contact with the surface of the slice 147 and with the underlying slower moving fluid and by the shape of the slice which because of the drainage of stock through the forming wire coacts with the wire 11 to form a conduit section wherein the stream is decelerated with accompanying increasing pressure.

As previously indicated, the upper boundary layer portion of the fluid which passes through the lower part of the flow control chamber 143 is recirculated within the flow control chamber and therefore does not reach the web forming region. In this connection, as much as 30 percent of the flow may be recirculated around the dome. In addition, a predetermined part of the lower portion of the stream moving towards the web-forming region will, under most conditions, be conducted out of the flow control chamber backwardly along the wire. When so operated, the arrangement results in the delivery to the web-forming region of only the central portion of the flowing stream which passes through the lower portion of the forming chamber upstream of the slice.

In eifect, the main stream of stock passing into the flow control unit, which stream, as previously stated, is of generally rectangular cross-sectional outline, is joined by the vorticularly rotating fluid passing around the dome which forms the upper part of the flow control chamber 143, and the resultant stream may be considered as constituting at least three divisions or layers. Each division constitutes a portion of the stream having the same width transversely of the stream as the main stream, and the three divisions are thus disposed layerwise in side-by-side relationship in the direction of movement of the forming member. The central division passes directly through the fiow control unit, first downwardly around the lower upstream quadrant of the forming roll 113 and then through the passageway formed by the apron plate 115 and slice 147 into contact with the wire 11 or other web-forming member. The lower division is caused to flow backwardly along the wire 11 or other forming member as that member moves into the webforming region and the third or upper division flows between the upstream tip of the slice member 147 and the flow control roll 113 and is caused to be recirculated around the dome which forms the upper portion of the forming chamber.

It will be evident that this mode of operation results in the continuous carrying away of the upper and lower boundary or surface layers of the stream of stock passing through the lower portion of the forming chamber 14-3. In other words, the upper boundary layer which is in frictional contact with the forming roll 113 and the lower boundary layer which is in frictional contact with the apron plate 115, which layers are affected by the frictional contact with those surfaces, are continuously removed from the web-forming region with resultant important improvement in the hydraulic characteristics of the stream division which passes through the forming member.

In the control and adjustment of the operating conditions of papermaking machines of the general type illustrated in FIGURES 1 through 3, the most important operating controls are the pressure at which the stock is delivered to the inlet side of the flow control unit, the speed of the forming wire, the speed of rotation of the forming roll and the length of the web-forming region.

Under normal conditions of operation, the member is adjusted so as to direct the upper portion of the stream of fluid into the flow control chamber 143 in a direction approximately tangentially of the roll 113. It therefore acts merely as a transition section for smoothing the flow of stock into the forming chamber 143. As previously indicated, for the purposes of the present invention, one could substitute a stationary member of proper shape and dimensions for the member 145. This has not been done in the illustrated embodiment to permit the conversion of this apparatus to other types of operation (not shown).

Control of the velocity of the recirculating vorticular flow is accomplished by the control of the speed of rotation of the flow control member 113. Since the velocity of the vorticularly moving fluid affects the velocity of the stream section which enters the web-forming region, a change in speed of rotation of the roll 113 will produce a change in the horizontal velocity component of that portion of the stream which passes through the forming member. The speed of rotation of the roll 113 will also aflect, to a certain extent, the pressure in the stream of stock immediately above the forming member; however, a change in the roll speed will alter the magnitude but not the basic character of the increasing pressure pattern within the stream of stock above the forming member in the direction of movement of the forming member.

The physical dimensions of the forming region, specifically its length in the direction of wire movement, can be adjusted by changing the longitudinal position of the upper section 91 of the flow control unit and to a slight extent by adjustment of the position of the apron plate 115.

In accomplishing most satsifactory web formation and overall stability of operation under certain operating conditions, and especially during very high speed operation, it is desirable, as above noted, that a portion of the flowing stream of stock delivered to the web-forming region flow backwardly along the moving wire 11 through the passageway existing between the under-surface of the apron plate lip 117 and the forming wire 11. When the stock velocity within the flow control unit is high, i.e., 1,500 to 2,000 feet per minute or higher, the instability conditions which are inherent in pressure-forming type machines tend to appear, and these instabilities can be avoided by the creation of a stable, backwardly flowing stream of stock at the upstream end of the web-forming region. This backwardly flowing stream stabilizes the flow at the upstream portion of the Web-forming region and effects the creation of a line of stagnation points transversely across the machine in the region above and rearward of the apron lip 117.

When operating under conditions which involve relatively low wire speeds and low stock velocities, this tendency to instability is substantailly reduced and under such conditions, it may not be necessary to provide the backwardly flowing stream of stock. The provision of the backwardly flowing stream of stock at the upstream end of the web-forming region has, however, an important advantage over and above instability control in that its removes from the web-forming region the lower boundary layer of the stream which is flowing through the flow control chamber towards the web-forming region. Since there is some slowing down of the lower stream layers as they move along the lower wall of the flow control chamber, the removal of that layer accomplishes the very desirable result of assuring that only the central and upper portion of the flowing stream flows into the web-forming region. This materially facilitates the adjustment of the flow velocity in the web-forming region.

In most flow control units of the type described, it will rarely be found necessary to institute back-flow in excess of about 10 percent of the total flow into the flow control unit, and generally, back-flow in the amount of 2 to 5 percent will usually be adequate.

The amount of stock which is recirculated within the flow control chamber 143 will vary depending upon the relative dimensions of the cylindrical roll 113, and the flow control chamber 143, and the speed of rotation of the roll 1113. In the manufacture of tissue web sheets at wire speeds within the range of 500 to 3,000 feet per minute by the use of machines of the type illustrated in FIGURES 1 through 3, and with stock having a consistency within the range of .08 to .25 percent, the amount of recirculating fluid will generally be within the range of from 20 to 40 percent of the fluid approaching the slice member 147.

The amount of stock which flows out of the flow control unit 5'5 on top of the formed web is controlled by the positioning of the slice lip or other means defining the downstream edge of the pressure-forming region. Under all conditions of operation, it is advisable to so position the slice lip that there will be a suflicient amount of water on the wire as it passes beneath the slice lip to efiect lubrication of the web and prevent its derangement. Generally, a discharge with the formed web of an amount of Water equal to from about 5 to 8 percent of the total amount delivered to the flow control unit to effect formation of the web will accomplish satisfactory lubrication of the formed web.

As indicated above, the slice mechanism 147 accomplishes the important function of conducting the formed web out of the web-forming region without disturbing or deranging the web fibers. This involves the accomplishment of a transition action during which the pressure existing in the formed web must be reduced from the pressure existing in the web-forming region within the flow control unit to atmospheric pressure.

For the purposes of this application, the web-forming region may be defined as that region wherein the concentration and deposition of those fibers which ultimately constitute the formed web is actually taking place. Alternatively, the web-forming region may be defined as that region wherein there is substantial flow through the web-forming member of the white water or other fluid carrier for the fibers. In the described apparatus where the amount of water discharged beneath the slice lip is merely suficient to lubricate the web, almost all of the fiber deposition and flow of white water through the Wire will occur in the region included within radial lines drawn from the center of the breast roll to the downstream edge of the apron plate lip and to the slice lip, which region might also be described as the region of pressure at the start-up.

forming. There may be some deposition of fibers on the wire from the backwardly flowing stream of stock which is discharged through the passageway 119, although this is usually of a very small magnitude.

When papermaking apparatus of the type illustrated in FIGURES 1 through 3 is to be placed into operation, the speed of the Wire 11, the fore and aft positioning of the upper section M of the flow control unit 55, the pressure at which stock is delivered to the flow control unit 55, the positioning of the apron plate 11$, the vertical position of the slice structure 147, and the speed of rotation of the cylindrical roll 113 are usually based upon approximate calculations. If an adjustable throttling member such as the member is used, one would initially adjust that member so that it directs the upper section or layer of the flowing stream into the flow control chamber in a direction generally tangential to the surface of the cylindrical roll 113. The major adjustment and usually the initial adjustment aside from the member 145 will probably be that of the speed of rotation of the cylindrical roll 113. This adjustment may conveniently be based upon examination of the sheet being manufactured. Adjustment of the vertical position of the slice 147 is made to assure that the formed web is passing out of the web-forming region without derangement. Some fore and aft adjustment of the flow control unit 55 and even some minor adjustment of the relative position of the breast roll 13 may also be found desirable, particularly Inspection of the formed web may be relied upon to a considerable degree for determining the optimum position of the various control elements.

In the foregoing, I have disclosed a new form of pressure-forming apparatus and various principles of operation which are determinative of the relationship between machine direction and cross-machine direction strength in webs which are manufactured on such appara tus. The use of these principles to attain any desired relationship between the machine direction and crossmachine direction strength ratio and in the attainment of other formation properties have been set forth at some length.

In addition, I have disclosed novel means for accomplishing the desired velocity and pressure control within the web-forming region, and also ways in which this control can be used to change or affect the physical properties of the formed sheet.

The structural arrangements disclosed are applicable for use in connection with existing equipment with only relatively minor modifications of that equipment. Moreover, important benefits can be accomplished by the use of only part of the arrangements and procedures disclosed.

Certain of the features of the invention believed to be new are set forth in the appended claims.

What is claimed is:

1. In the manufacture of continuous fibrous webs under pressure-forming conditions by the use of a confined flowing stream of a fluid suspension of fibrous material which is caused to How obliquely into contact with a moving, fluid-permeable forming member in a web-formin g region, the improvement which consists in controlling the pressure and velocity distribution within the flowing stream adjacent the forming member by directing the upper portion of the flowing stream at a point upstream of the webforrning region into a vortex wherein the fluid has a greater velocity than the average velocity of the fluid within said flowing stream, causing a portion of said vorticularly moving fluid to tangentially engage and partially interrnix with the upper layers of said flowing stream, and maintaining said vortex by the controlled addition thereof of substantial amounts of energy, said energy addition being effected by a driving means which is'located at the center of the vortex.

2. In the manufacture of continuous fibrous webs under pressure-forming conditions by the use of a confined flowing stream of a fluid suspension of fibrous material which is caused to flow obliquely into contact with a moving, fluid-permeable forming member in a web-forming region, the improvement which consists in selectively increasing the velocity within various layers of said flowing stream upstream of said web-forming region by directing the upper portion of the flowing stream upstream of said webforming region into a vortex wherein the fluid has a predetermined velocity greater than the average velocity of said flowing stream, and causing a portion of said vorticularly moving fluid to tangentially engage and partially intermix with the upper layers of said flowing stream, maintaining said vortex by the controlled addition thereto of substantial amounts of energy, said energy addition being effected by a driving means which is located at the center of the vortex, and directing said flowing stream from the region of said vortex obliquely into the webforming region through a suitable conduit to effect a predetermined pressure and velocity distribution within the flowing stream adjacent the forming member.

3. In the manufacture of continuous fibrous webs under pressure-forming conditions by the use of a confined flowing stream of a fluid suspension of fibrous material which is of generally rectangular cross-sectional outline having a web-forming portion and at least one other portion wln'ch constitutes an upper boundary layer of said flowing stream, said web-forming portion being caused to flow into contact with a moving, fluid-permeable forming member in a web-forming region in such manner that the longitudinal component of the velocity of the webforming portion extends in a direction generally parallel to the direction of movement of said forming member as said forming member passes through the web-forming region, the improvement which comprises selectively controlling the velocity of the various layers of said flowing stream upstream of the web-forming region by the addition of fluid of velocity greater than the average velocity of said flowing stream into the upper layers of said stream, conducting away the upper boundary layer of said flowing stream upstream of said web-forming region and then directing the web-forming portions of said flowing stream obliquely to the web-forming region through a suitable conduit to effect a predetermined pressure and velocity distribution within the flowing stream adjacent the forming member.

4. In the manufacture of continuous fibrous webs under pressure-forming conditions by the use of a combined flowing stream of a fluid suspension of fibrous material Which is of generally rectangular cross-sectional outline having a web-forming portion and at least two other portions which constitute upper and lower boundary layers of said flowing stream, said web-forming portion being caused to flow obliquely into contact with a moving, fluidpermeable forming member in a Web-forming region in such manner that the longitudinal component of the velocity of the web-forming portion extends in a direction generally parallel to the direction of movement of said forming member as said forming member passes through the web-forming region, the improvement which comprises selectively controlling the velocity of the various layers of said flowing stream upstream of the webforming region by adding fluid of predetermined velocity greater than the average velocity of said flowing stream into the upper layers of said stream, conducting away the upper boundary layer of said flowing stream downstream of said fluid addition and upstream of said forming region, and then directing the web-forming portion and lower boundary layer of said flowing stream to the web-forming region through a suitable conduit to effect a predetermined pressure and velocity distribution within the flowing stream adjacent the forming member, and conducting away the lower boundary layer of said flowing stream at the upstream end of the web-forming region and causing said lower boundary layer to flow backwardly along said forming member.

5. In web-forming apparatus of the pressure-forming type, a continuous web-forming member, means for supporting said member and for moving said member through the web-forming region of said apparatus, a source of supply of a fluid suspension of fibrous material, a flow control unit having an inflow opening connected to said source of supply and having an outflow opening through which a flowing stream of said fluid is discharged onto said forming member under pressure-forming conditions as that member is moved through said web-forming region, said web-forming region being located at the outflow opening of said flow control unit, said flow control unit including a generally cylindrical chamber through which the fluid delivered to said web-forming region is caused to flow, a cylindrical rotor located within said chamber and means for rotating said rotor within said chamber, the spacing between the rotor surface and the inner wall of said cylindrical chamber being less than inch over a major portion of the surface area of said rotor and the surface of said rotor having roughness elements thereon whereby the flow instabilities which are normally incident to the rotation of a cylindrical roll within an enclosed cylindrical chamber are effectively controlled.

6. In web-forming apparatus of the pressure-forming type, a continuous web-forming member, means for supporting said member and for moving said member through the web-forming region of said apparatus, a source of supply of a fluid suspension of fibrous material, a flow control unit having an inflow opening connected to said source of supply and having an outflow opening through which a flowing stream of said fluid is discharged onto said forming member under pressure-forming conditions as that member is moved through said web-forming region, said web-forming region being located at the outflow opening of said flow control unit, said flow control unit including a generally cylindrical chamber through which the fluid delivered to said web-forming region is caused to flow, a cylindrical rotor located within said chamber and means for rotating said rotor within said chamber, the spacing between the rotor surface and the inner wall of the cylindrical chamber being less than A inch over a major portion of the surface area of said rotor, the surface of said rotor including a plurality of spaced roughness elements, said roughness elements being between and inch in height, and the ratio of the spacing between the roughness elements circumferentially around the roll to the depth of the roughness elements being between 4 and 12 whereby the flow instabilities which are normally incident to the rotation of a cylindrical roll within an enclosed cylindrical chamber are effectively controlled.

7. In web-forming apparatus of the pressure-forming type, a continuous web-forming member, a breast roll for supporting said member for movement into and "through the web-forming region of said apparatus, a source of supply of a fluid suspension of a fibrous material, and a flow control unit having an inflow opening connected to said source of supply and having an outflow opening through which a confined flowing stream of said fluid is discharged onto said forming member under pressure-forming conditions as that member is moved through said web-forming region, said web-forming region being located at the outflow opening of said flow control unit, said flow control unit including an upper and a lower section, portions of which define the walls of a generally cylindrical flow control chamber which is closed except for a pair of circumferentially spaced openings through which the fluid delivered to said web-forming region is caused to flow, a transversely extending flow control member forming a portion of said upper section disposed within said chamber so as to provide a re-entrant passageway within said chamber within which the uppermost surface layer of the flowing stream of fluid is continuously circulated during operation of said apparatus, the upper section of said flow control unit being pivotally connected at its lower upstream end within said appara- 17 ins and adjustable means for rotating said upper section about said pivotal connection, thereby permitting an adjustment of the position of said flow control unit relative to said forming member.

8. In web-forming apparatus of the pressure-forming type, a continuous web-forming member, a breast roll for supporting said member for movement into and through the web-forming region of said apparatus, a source of supply of a fluid suspension of a fibrous material, and a flow control unit having an inflow opening connected to said source of supply and having an outflow opening through which a confined flowing stream of said fluid is discharged onto said forming member under pressureforming conditions as that member is moved through said web-forming region, said web-forming region being located at the outflow opening of said flow control unit, said flow control unit including an upper and a lower section, portions of which define the walls of a generally cylindrical flow control chamber with the major axis thereof extending transversely to the direction of movement of the webforming member and a forwardly extending, downwardly directed conduit, said cylindrical chamber being closed except for a pair of axially extending, circumferentially spaced openings through which the fluid delivered to said web-forming region is caused to flow, one of said openings forming said inflow opening andthe other of said openings forming an inlet opening into said conduit, the other end of said conduit forming said outflow opening, a transversely extending, cylindrical rotor forming a portion of said upper section disposed within said chamber so as to provide a re-entrant passageway within said chamber, within which the uppermost surface layer of the flowing stream of fluid is continuously circulated during operation of said apparatus, the circulatory flow of fluid through said chamber intermixing with the main stream of fluid upstream of said web-forming region to thereby establish a predetermined velocity of the flowing stream in the webforming region in the direction of movement of the forming member in response to the rotation of said rotor, adjustable drive means for controlling the rotation of said rotor, the upper section of said flow control unit being pivotally connected at its lower upstream end within said apparatus and adjustable means for varying the position of said upper section about said pivotal axis, thereby permitting an adjustment ofthe position of said flow control unit relative to said forming member.

9. In web-forming apparatus of the pressure-forming type, a continuous web-forming member, a breast roll for supporting said member for movement into and through the web-forming region of said apparatus, a source of supply of a fluid suspension of a fibrous material, and a flow control unit having an inflow openingconnected to said source of supply and having an outflow opening through which a confined flowing stream of said fluid is discharged onto said forming member under pressureforming conditions as that member is moved through said web-forming region, said web-forming region being located at the outflow opening of said flow control unit, said flow control unit including means defining the walls of a generally cylindrical flow control chamber with the major axis thereof extending transversely to the direction of movement of the forming member and a forwardly extending, downwardly directed conduit, said cylindrical chamber being closed except for a pair of axially extending, circumferentially spaced openings through which the fluid delivered to said web-forming region is caused to flow, one of said openings forming said inflow opening and the other of said openings forming an inlet opening into said conduit, the other end of said conduit forming said outflow opening, a transversely extending, cylindrical rotor disposed within said chamber so as to provide a re-entrant passageway within said chamber within which the uppermost surface layer of the flowing stream of fluid is continuously circulated during operation of said apparatus, the circulatory flow of fluid through said chamher intermixing with the main stream of fluid upstream of said web-forming region to thereby establish a predetermined velocity of the flowing stream in the web-forming region in the direction of movement of the forming member in response to the rotation of said rotor, adjustable drive means for controlling the rotation of said rotor, said cylindrical rotor being of a diameter such that the spacing between the rotor surface and the inner wall of the chamber is less than A inch over a major portion of the surface area of said rotor, the surface of said rotor including a plurality of roughness elements, said spacing and roughness elements eflectively controlling the flow instabilities which are normally incident to the rotation of a rotor within a cylindrical chamber, the upper wall of said conduit forming a slice member, the upstream edge of said slice member being spaced approximately inch from the surface of said rotor so as to peel off as large an amount of fluid from adjacent the rotor as possible and to direct said fluid towards the forming member, and the forward edge of said slice being positioned adjacent the forming member and defining the downstream edge of the web-forming region, said upstream edge of said slice member being located between about 2 /2 to 3 inches behind the center line of the breast roll and the lip of said apron plate being located from about 1 /2 to 2 inches behind the center line of the breast roll.

10. In web-forming apparatus of the pressure-forming type, a continuous web-forming member, a breast roll for supporting said member for movement into and through the web-forming region of said apparatus, a source of supply of a [fluid suspension of a fibrous material, and a flow control unit having an inflow opening connected to said source of supply and having an outflow opening through which a confined flowing stream of said fluid is discharged onto said forming member under pressureformi-ng conditions as that member is moved through said web-forming region, said web-forming region being located at the outflow opening of said flow control unit, said flow control unit including means defining the walls of a generally cylindrical flow control chamber with the major axis thereof extending transversely to the direction of movement of the web-forming member and a forwardly extending, downwardly directed conduit, said cylindrical chamber being closed except for a pair of axially extending, circumferentially spaced openings through which the fluid delivered to said web-forming region is caused to flow, one of said openings forming said inflow opening and the other of said openings forming an inlet opening into said conduit, the other end of said conduit forming said outflow opening, a transversely extending, cylindrical rotor disposed within said chamber so as to provide a re-entrant passageway within said chamber, within which the uppermost surface layer of the flowing stream of fluid is continuously circulated during operation of said apparatus, the circulatory flow of fluid through said chamber intermixing with the main stream of fluid upstream of said web-forming region to thereby establish a predetermined velocity of the flowing stream in the web-forming region in the direction of movement of the forming member in response to the rotation of said rotor, adjustable drive means for controlling the rotation of said rotor, said cylindrical rotor being of a diameter such that the spacing between the rotor surface and the inner wall of the chamber is less than inch over a major portion of the surface area of said rotor, the surface of said rotor including a plurality of roughness elements, said spacing and roughness elements eflectively controlling the flow instabilities which are normally incident to the rotation of a rotor within a cylindrical chamber, the lower wall of said conduit forming an apron plate having a lip on its forward edge which is so positioned relative to said forming member and breast roll that a portion of the flowing stream of fluid which is delivered to the web-forming region will flow under stable flow conditions, between said lip and the forming member in a direction opposite to the direction of movement of said forming member during operation of said apparatus, the upper wall of said conduit forming a slice member, the upstream edge of said slice member being spaced approximately /16 inch from the surface of said rotor so as to peel off as large an amount of fluid from adjacent the rotor as possible and to direct said fluid towards the forming member, and the forward edge of said slice being positioned adjacent the forming member and defining the downstream edge of the web forming region, said upstream edge of said slice member being located between about 2 /2 to 3 inches behind the center line of the breast roll and the lip of said apron plate being located from about 1 /2 to 2 inches behind the center line of the breast roll.

11. In web-forming apparatus of the pressure-forming type, a continuous web-forming member, a breast roll for supporting said member for movement into and through the web-forming region of said apparatus, a source of supply of a fluid suspension of a fibrous material, and a flow control unit having an inflow opening connected to said source of supply and having an outflow opening through which a confined flowing stream of said fluid is discharged onto said forming member under pressure-forming conditions as that member is moved through said web-forming region, said web-forming region being located at the outflow opening of said flow control unit, said flow control unit including means defining the walls of a generally cylindrical flow control chamber with the major axis thereof extending transversely to the direction of movement of the web-forming member and a forwardly extending, downwardly directed conduit, said cylindrical chamber being closed except for a pair of axially extending, circumferentially spaced openings through which the fluid delivered to said web-forming region is caused to flow, one of said openings forming said inflow opening and the other of said openings form ing an inlet opening into said conduit, the other end of said conduit forming said outflow opening, a transversely extending, cylindrical rotor forming a portion of said upper section disposed within said chamber so as to provide a re-entrant passageway within said chamber within which the uppermost surface layer of the flowing stream of fluid is continuously circulated during operation of said apparatus, the circulatory flow of fluid through said chamber intermixing with the main stream of fluid upstream of said web-forming region to thereby establish a predetermined velocity of the flowing stream in the web-forming region in the direction of movement of the forming member in response to the rotation of said rotor, adjustable drive means for controlling the rotation of said rotor, said cylindrical rotor being of a diameter such that the spacing between the rotor surface and the inner wall of the chamber is less than 3 inch over a major portion of the surface area of said rotor, the surface of said rotor including a plurality of roughness elements, said roughness elements being between A and inch in height and the ratio of the spacing between said roughness elements circumferentially around the rotor surface to the depth of the roughness elements being between 4 and 12, said spacing and roughness elements effectively controlling the flow instabilities which are normally incident -to the rotation of a rotor within a cylindrical chamher, the lower wall of said conduit forming an apron plate having a lip on its forward edge which is so positioned relative to said forming member and breast roll that a portion of the flowing stream of fluid which is delivered to the web-forming region will flow under stable flow conditions, between said lip and the forming member in a direction opposite to the direction of movement of said forming member during operation of said apparatus, the upper wall of said conduit forming a slice member, the upstream edge of said slice member being spaced approximately inch from the surface of said rotor so as to peel off as large an amount of fluid from adjacent the rotor as possible and to direct said fluid towards the forming member, and the forward edge of said lice being positioned adjacent the forming member and defining the downstream edge of the web-forming region, said upstream edge of said slice member being located between about 2 /2 to 3 inches behind the center line of the breast roll and the lip of said apron plate being located from about 1 /2 to 2 inches behind the center line of the breast roll.

12. In web-forming apparatus of the pressure-forming type, a continuous web-forming member, a breast roll having an open cellular periphery for supporting said member for movement into and through the web-forming region of said apparatus, a drive means connected with said breast roll for providing a portion of the energy necessary for turning said breast roll, a source of supply of a fluid suspension of a fibrous material, and a flow control unit having an inflow opening connected to said source of supply and having an outflow opening through which a confined flowing stream of said fluid is discharged onto said forming member under pressure-forming conditions as that member is moved through said web-forming region, said web-forming region being located at the outflow opening of said flow control unit, said flow control unit including an upper and a lower section, portions of which define the walls of a generally cylindrical flow control chamber with the major axis thereof extending transversely to the direction of movement of the web-forming member and a forwardly extending, downwardly directed conduit, said cylindrical chamber being closed except for a pair of axially extending, circumferentially spaced openings through which the fluid delivered to said web-forming region is caused to flow, one of said openings forming said inflow opening and the other of said openings forming an inlet opening into said conduit, the other end of said conduit forming said outflow opening, a transversely extending, cylindrical rotor forming a portion of said uppersection disposed within said chamber so as to provide a reentrant passageway within said chamber within which the uppermost surface layer of the flowing stream of fluid is continuously circulated during operation of said apparatus, the circulatory flow of fluid through said chamber intermixing with the main stream of fluid upstream of said Web-forming region to thereby establish a predetermined velocity of the flowing stream in the web-forming region in the direction of movement of the forming member in response to the rotation of said rotor, adjustable drive means for controlling the rotation of said rotor, said cylindrical rotor being of a diameter such that the spacing between the rotor surface and the inner wall of the chamber is less than inch over a major portion of v the surface area of said rotor, the surface of said rotor including a plurality of roughness elements, said spacing and roughness elements effectively controlling the flow instabilities which are normally incident to the rotation of a rotor within a cylindrical chamber, the lower wall of said conduit forming an apron plate having a lip on its forward edge which is so positioned relative to said forming member and breast roll that a portion of the flowing stream of fluid which is delivered to the web-forming region will flow under stable flow conditions, between said lip and the forming member in a direction opposite to the direction of movement of said forming member during operation of said apparatus, the upper wall of said conduit forming a slice member, the upstream edge of said slice member being spaced approximately inch from the surface of said rotor so as to peel off as large an amount of fluid from adjacent the rotor as possible and to direct said fluid towards the forming member, and the forward edge of said slice being positioned adjacent the forming member and defining the downstream edge of the web-forming region, said upstream edge of said slice member being located between about 2 /2 to 3 inches behind the center line of the breast roll and the lip of said apron plate being located from about 1 /2 to 2 inches behind the center line of the breast roll, the upper section of said flow control unit being pivotally connected at its lower upstream end within said apparatus and adjustable means for rotating said upper section about said pivotal connection, thereby permitting an adjustment of the position of said slice member relative to said forming member.

13. In web forming apparatus of the pressure forming type, a continuous web forming member, means for supporting and driving said member, a source of supply of a fluid suspension of fibrous material, a flow control unit defining an inflow opening connected to said source of supply and defining an outflow opening through which a stream of said fluid suspension is discharged on to said forming member under pressure forming conditions as said member is driven, a cylindrical rotor within said flow control unit and having an imperforate outer surface and disposed within said flow control unit and providing a fluid suspension passage along a relatively short are of the rotor and between the rotor and an opposite Wall of the unit and connecting said inflow and outflow openings, and means for driving said rotor, said rotor being encased within and in substantially uniform close proximity to the walls of a cylindrical chamber within said flow control unit except for said passage forming arc so as to form a bypass passage around the periphery of the rotor which is of less cross sectional thickness than said first named passage so that part of the fluid suspension flowing in said first named passage flows between the rotor and the adjacent walls of the cylindrical chamber for changing the velocity of the fluid suspension as it flows through said outflow opening, said flow control unit including a wedge shaped slice having its tip in close proximity to said rotor and having surfaces defining both said bypass passage and also said outflow opening.

14. In web forming apparatus of the pressure forming type, a continuous web forming member, means for supporting and driving said member, a source of supply of a fluid suspension of fibrous material, a flow control unit defining an inflow opening connected to said source of supply and defining an outflow opening through which a stream of said fluid suspension is discharged on to said forming member under pressure forming conditions as said member is driven, a cylindrical imperforate rotor within said flow control unit and providing a fluid suspension passage along a relatively short are of the rotor and between the rotor and an opposite wall of the unit and connecting said inflow and outflow openings, and means for driving said rotor, said rotor being encased within and in substantially uniformly close proximity to the walls of a cylindrical chamber within said flow control unit except for said passage forming arc so as to provide a bypass passage around the periphery of the rotor to receive fluid suspension from and return it to said first named passage for changing the velocity of the fluid suspension as it flows through said outflow opening, said rotor being serrated on its exterior for increasing the energy supplied by the rotor to said fluid suspension and said outflow opening extending obliquely with respect to said web forming member so as to project the fluid suspension flowing through the opening on to the forming member in the direction of movement of the forming member.

15. In web forming apparatus of the pressure forming type, a continuous web forming member, means for supporting and driving said member, a source of supply of a fluid suspension of fibrous material, a flow control unit defining an inflow opening connected to said source of supply and defining an-voutflow opening through which a stream of said fluid suspension is discharged on to said forming member under pressure forming conditions as said member is driven, a cylindrical imperforate rotor within said flow control unit and providing a fluid suspension passage along a relatively short are of the rotor and between the rotor and an opposite wall of the unit and connecting said inflow and outflow openings, said rotor being encased within and in substantially uniform close proximity to the walls of a cylindrical chamber within said flow control unit so as to provide a bypass passage of relatively small sectional area compared to that of said first named passage and receiving fluid suspension from and returning it to said first named passage, and means for driving said rotor, said flow control unit including a Wedge shaped slice having a surface defining one end of said second named passage and defining one wall of said outflow opening so that the outflow opening extends obliquely with respect to said Web forming member to discharge fluid suspension on said web forming member in the direction of movement of the web forming member and so that the slice peels oil a layer of stock suspension adjacent said rotor in said first named passage with rotation of the rotor and directs it around the rotor in said bypass passage.

16. In web forming apparatus of the pressure forming type, a continuous web forming member, means for supporting and driving said member, a source of supply of a fluid suspension of fibrous material, a flow control unit defining an inflow opening connected to said source of supply and defining an outflow opening through which a stream of said fluid suspension is discharged on to said forming member under pressure forming conditions as said member is driven, a cylindrical rotor within said flow control unit and providing a fluid suspension passage along a relatively short are of the rotor and between the rotor and an opposite Wall of said unit and connecting said inflow and outflow openings, and means for driving said rotor, said rotor being encased within and substantially uniformly spaced with respect to the walls of a cylindrical chamber within said lfiOW control unit except for said passage forming arc for forming a bypass passage connected with said first named passage so that part of the fluid suspension flowing in said first named passage flows through said bypass passage from and back into said first named passage to have energy added to the fluid suspension by said rotor, said outflow opening being defined by two opposite plane walls so as to extend obliquely with respect to said web forming member to direct fluid suspension on the web forming member in the direction of movement of the web forming member.

References Cited in the file of this patent UNITED STATES PATENTS 2,756,648 Lee July 31, 1956 FOREIGN PATENTS 881,631 France Jan. 29, 1943 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,028,298 April 3, 1962 Charles A. Lee

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 14, for "plurailty" read plurality column 13, line 7, for Fsubstantailly" read substantially line 13, for "its" read it. column l5, line 40, for "portions" read portion line 16 for "combined" read confined Signed and sealed thi'saBlst day of July 1962.

(SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents

Claims

1. IN THE MANUFACTURE OF CONTINUOUS FIBROUS WEBS UNDER PRESSURE-FORMING CONDITIONS BY THE USE OF A CONFINED FLOWING STREAM OF A FLUID SUSPENSION OF FIBROUS MATERIAL WHICH IS CAUSED TO FLOW OBLIQUELY INTO CONTACT WITH A MOVING, FLUID-PERMEABLE FORMING MEMBER IN A WEB-FORMING REGION, THE IMPROVEMENT WHICH CONSISTS IN CONTROLLING THE PRESSURE AND VELOCITY DISTRIBUTION WITHIN THE FLOWING STREAM ADJACENT THE FORMING MEMBER BY DIRECTING THE UPPER PORTION OF THE FLOWING STREAM AT A POINT UPSTREAM OF THE WEBFORMING REGION INTO A VORTEX WHEREIN THE FLUID HAS A GREATER VELOCITY THAN THE AVERAGE VELOCITY OF THE FLUID WITHIN SAID FLOWING STREAM, CAUSING A PORTION OF SAID VORTICULARLY MOVING FLUID TO TANGENTIALLY ENGAGE AND PARTIALLY INTERMIX WITH THE UPPER LAYERS OF SAID FLOWING STREAM, AND MAINTAINING SAID VORTEX BY THE CONTROLLED ADDITION THEREOF OF SUBSTANTIAL AMOUNTS OF ENERGY, SAID ENERGY ADDITION BEING EFFECTED BY A DRIVING MEANS WHICH IS LOCATED AT THE CENTER OF THE VORTEX.