US2736246A - Papermaking machine - Google Patents

Description

Feb. 28, 1956 A. .1. cRl'rTl-:NDEN ET AL 2,736,246

PAPERMAKING MACHINE Filed May 29, 1951 5 Sheets-Sheet 1 T0 VACUUM PUMP Feb. 28, 1956. A, J, CR|TTENDEN ETAL 2,736,246

PAPERMAKING MACHINE ,5. m /MM wm M y@ Filed May 29. 1951 Feb. 28, 1956 A. J. CRITTENDEN E-rAL 2,736,246

PAPERMAKING MACHINE 5 Sheets-Sheet 3 Filed May 29. 1951 Q/.u .m/

HH n a, wy /f JW ww...

Tw) Pszrsssune Anz INLET ,4 1- H w l H H Q fw E l M l 5 M w Feb. 28, 1956 A. J. cRlTTENDL-:N ETAL '2,736,246

PAPERMAKING MACHINE STOCK :2E-wand i f Z l W5.

PAPERMAKING MACHINE Filed May 29, 1951 5 Sheets-Sheet 5 TO WHITE WATER SYSTEM United States Patent- PAPERMAKING MACHINE Adam Jay Crittenden, Sylacanga, Ala., and Charles A. Lee, Neenah, Wis., assignors, by mesne assignments, to Kimberly-Clark Corporation, a corporation of Delaware f Application May 29,1951, serial No, 228,934

19 claims. (ci. 92-44y The present invention relates to papermaking machinery, and especially to the construction and operation of papermaking headbox and inlet mechanisms wherein the stock is maintained at a predetermined pressure or level, or both. ln this connection, the term stock as used herein will be understood to refer to the dilute, aqueous suspension of papermaking fiber, with or without additional papermaking materials, which is delivered as a liowing stream of fluid to the web-forming region of a papermaking machine by way of the headbox, inlet or other stock delivery mechanism.

In the manufacture of a given weight paper on a particular machine, it will usually be found that there is an optimum depth for the owing stream of stock which is contained within-a headbox or other inlet mechanism, and this depth is, in general, independent of the speed of operation of the machine.V At the same time, in order to attain satisfactory machine operation, it is necessary to supply the stock to the web-forming region of the machine at a pressure which is capable of producing a spouting velocity at the slice, or equivalent means deiining the downstream edge of the web-forming region,

approximately equalto the velocity of the forming wire.-

The two requirements are inherently conicting and are incapable of correlation except at some one range of operating speeds, which is usually at very low wire speed. As a result, the operation of most papermaking machines, and especially headbox type machines, has been conducted under compromise conditions. Specifically, in order to obtain suliicient head to produce a spouting velocity at the slice that is adequate for satisfactory operation, it has been necessary to utilize headbox constructions wherein the stock has been vmaintained at a depth far greater than that which would produce the optimum results insokfar as the quality of the paper is concerned.

in an-effort to avoid some of these diiculties, it has been proposedrto use what is sometimes spoken of as a pressurized headbox construction. In arrangements of this type, the stock is supplied to an enclosed ponding or headbox chamber, from which it is discharged onto the wire. The upper portion of the ponding chamber is connected to a source of pressure air, and during operation, a body or pad of air, under pressure, is maintained in the upper portion of the ponding chamber. This has the effect of reducing the level of the stock within the ponding chamber, while maintaining sufficient pressure to Secure adequate spouting velocity at the slice. However, the apparatus does not include any means for maintaining the level of the stock in the ponding chamber at any particular value, and because of this and certain other inherent features, the apparatus tends to be instable in operation and Vis subject to certain other difficulties.

Subsequent to this initial arrangement, pressurized headbox apparatus was developed which included a vent in the side wall of the headbox, arranged to maintain automatically the level of the stock within the headbox or inlet chamber at a predetermined value. This arrangement has also proved subject to certain important opera- 2,736,246 Patented Feb. 28, 14956 "ice connection with papermaking machinery wherein it is desired to maintain the level of the stock within the headbox or equivalent chamber at a value less than about 1.8 inches. ln-such instances, the wall vent level regulating mechanism produces conditions of instability in the .region of the slice, which conditions are evidenced, in part, V-by the formation at the slice of irregularities in the Yilow pattern having the general shape of fishtails. YThesel irregularities of flow have proven almost impossible to control, and since they lower materially the quality of the paper produced, their avoidance is greatly to be desired. i

Thus, while the present invention is directed to the same general yproblem as these earlier structures, that is, the provision of a headbox or equivalent type papermaking machine wherein the liquid level in the headbox chamber can be controlled independently of the pressure maintained within that chamber, the principal object of the present invention is the elimination of the transient instabilities and other operational diliiculties which are inherent in the previously known pressurized headbox constructions.y

In the attainment of this object, the level regulating means of the invention provides for introducing air, or an equivalent gas, which may be under pressure, into a headbox chamber and for removing air and stock from that chamber under such conditions that no surface or sub-surface disturbances are set up in the stock contained within the headbox chamber. As will appear, the invention thereby makes possible the maintaining of the stock at a predetermined depth within the headbox chamber, independently of the pressure conditions within that chamber, while at the same time eliminating the difficulties inherent in the previously known arrangements.

The invention iinds its most important immediate use in connection with headbox type Fourdrinier papermaking machines, and will be described in conjunction with such a machine. It will be understood, however, that the principles of the invention are applicable to other types of apparatus.

In the drawings, wherein certain representative embodiments of the invention are illustrated:

Y' wet end of a headbox type,.Fourdrinier papermaking machine;

Figure 2 ,is a sectional View of one of the air inlet and air outlet tubes, constituting a part of the apparatus illusytrated in Figure 1;

Figure 3 is a fragmentary, sectional view illustrating a portion of a seal mechanism embodied in the apparatus illustrated in Figure l;

Figures 4 and 5 are, respectively, lisometric and schematic views, showing the general arrangement of the level and pressure control mechanism embodied in the structure shown in Figure l; and

Figures 6 to 9 are schematic views, similar to Figure 5, illustrating other stock level and pressure control mechanisms Vin accordance with the principles of the present invention.

As previously pointed out, the pressure and level-regulating mechanism of the present inventionis operable to maintain within a headbox or equivalent stock delivery mechanism, a predetermined level of stock, which level is maintained independently of the total pressure head (or spouting velocity) of the stock. Further, this level is maintained independently of the total volume ofpstock which is passing through the headbox chamber, and the control is accomplished under such conditions and in such manner rthat there Ais substantially no disturbance at the surface or below the surface of the body of stock -drawings are intended especially for use in conjunction with Fourdrinier type machines, and in Figure l a breast roll an a Fourdrinier wire of conventional design are illustrated at lil and i3. It will be understood that the machine will also include the usual stock supply system, white water system, deckles for confining the stock on the Wire, suction boxes, presses, felts, driers, and the other additional apparatus which is required in the manufacture of paper, the apparatus shown in Kellett Patent No. 2,134,408 being illustrative of such arrangements. The breast roll 13 will desirably be supported in such manner that its position relative to the headbox can be accurately adjusted. This may be accomplished by the use of an automatically operable, adjustable roll support of a hydraulic or other type, these mechanisms being commercially available.

The defining walls of the headbox structure are fabricated of suitable angle, beam and plate sections, conveniently by welding, and the entire headbox is supported in cooperative relation tothe wire, breast roll and other machine elements by means of suitable steel and concrete pillars, as illustrated at l and l7. Essentially, the headbox comprises two, rigid, vertically extending side elements 19, commonly designated pond sides, which are fastened to each other by a suitable bottom section 2l and an end wall 23, which extends across the stock inflow end of the headbox.

To further strengthen the structure, the upper end of the pond sides 2 9 are connected by a stiifening member 2.5 which is circular in cross-section. Stock is delivered to the headbox at a predetermined pressure by means of a conduit 27 which leads to a suitable source of stock at a predetermined pressure, for example, the discharge end of a series of screens or a suitable constant pressure pump, not shown. The discharge end 29 of the stock delivery conduit 27 in the illustrated structure is rectangular in outline and is adapted to connect with the inflow end 3l of a flow spreading conduit 33 which is adapted to widen the relatively narrow stream of stock delivered by the stock supply means to the full width of the machine.

The upstream vertical surface of the ow spreading conduit 33 is defined by a plate member 35 which extends transversely across the machine. The downstream surface of the llow spreading conduit 33 is defined by one surface of a vertically adjustable, throttling slice 37. The throttling slice 37 is a hollow, completely enclosed, fabricated, box-like structure which extends across the full width of the machine and is supported for limited vertical movement relative to the pond sides 19 by means of suitable guide members 39, which engage guide slots 41 formed in those sides.

The lower surface 43 of the throttling slice 37 cooperates with the adjacent surface 45 of the headbox bottom 2l to define a generally wedge-shaped passageway 47 of uniform cross-sectional outline and of uniformly increasing cross-sectional area in the downstream direction, across the entire width of the machine. The passageway 47 serves to conduct the stock, which is delivered to the headbox at predetermined pressure, into the ponding chamber 49 within the headbox proper.

The defining Walls of the ponding chamber 49, which receives and holds momentarily the stock ilowuig into and through the headbox, are defined by the sides 19 and bottom 2l of the headbox, the downstream surface 51 of the throttling slice 37, a top or cover unit 53, and the upstream surface of the discharge or wire slice 57. The

wire slice 57, similar to the thrcttling slice 37, constitutes a hollow, fabricated, box-like structure which is supported for limited vertical movement within the headbox by means of suitable projecting guides S9 which engage guide slots 69 inthe pond sides 19.

The cover unit 53 is likewise of fabricated construction, and extends between-the two pond sides 19 in the position shown in the drawings. In order that the throttling and Wire slices 37 and 57 may be adjusted during operation of the machine, it is desirable that the mechanism include yieldable sealing means 61 between the foreand-aft edges of the cover unit, and the adjacent slice surfaces S and S5. This sealing means may conveniently comprise an O-ring type seal, constituting, as shown in Figure 3, a resilient sealing tube 63, which is disposed within an under-cut slot 65. The tube 63 may or may not be under internal pressure.

To provide for convenient adjustment of the slice mechanisms, a pair of spaced-apart, power-operated lift units 67 are connected to each of the slice structures 37 and 57. The units 67 are supported upon suitable transversely-extending beam sections 69, and the two units operating each of the slices are desirably interconnected, as by the shaft indicated at 71, in order to assure simultaneous operation of the lift units associated with each slice.

One or more power driven, rotatable distributor rolls, as illustrated at 73, may be provided within the ponding chamber 49, and it is desirable that all such rolls shall be adjustably supported, in order that the position of the rolls within the ponding chamber 49 can be adjusted to produce optimum operating conditions. The headbox structure also includes suitable seals at either side of the ponding chamber 49 for engaging the surface of the wire in the region of the wire slice 57,

The cover unit 53 for the ponding chamber, which unit co-acts with the other elements of the headbox structure to completely enclose that chamber, except for the stock inflow opening 47 and the stock outow opening provided beneath the lower edge of the wire slice 57 and the adjacent surface of the wire 11, may be provided with one or more covered access openings, as indicated generally at 76. The cover unit 53 also serves as the support for certain of the elements of the air .inow and air outflow mechanisms constituting a part of the depth and pressure control mechanism embodied in the apparatus.

The complete control mechanism is illustrated in Figures 4 and 5, and as there shown, it includes a horizontally extending air inflow tube 77 and a horizontally extending air outflow tube 79. In order to minimize air disturbance within the ponding chamber 49 during operation of the control mechanism, the air iniiow tube 77 and the air outflow tube 79 both comprise a closed conduit having a plurality of spaced orifices in the upper surface thereof, as indicated at Si, and the tubes are arranged in close proximity to each other in the upper portion of the pending chamber. The tubes 77 and 79 thus accomplish an air diffusion function, and this, in combination with the close spacing and positioning of the tubes effectively prevents any disturbance of the surface of the stock within the ponding chamber as a result of the flow of air into and out of that chamber.

The air inflow and air outil- ow tubes 77 and 79 are supported upon the cover unit 53 of the ponding chamber' by means of suitable flanged connections 83 (Fig. l) which engage vertically extending pipes 85 and S7, one of Which is connected to the central portion of one of thc tubes, as shown. The pipe 35 connected to the air inflow tube 77 is, in turn, connected by additional piping to a source of pressure air. The source of pressure air i's desirably of a constant pressure type or the iine 89 may include an adjustable pressure regulating unit, as indicated at 9i?. The support pipe 37 for the air outflow tube 79 is connected by other piping 9i to the upper end of a cylindricaliy shaped, auxiliary tank or receiver 93, which is supported adjacent one of the pond sides 19 with the bottom of the tank adjacent the bottom of the pending chamber 49.

The auxiliary tank or receiver 93 should have a vertical dimension which is greater than the depth of liquid Aceiver 93 is a combination air and liquid discharge line 103 vwhich is also adapted to empty into the stock return "97, and which may also be provided with a shut-off valve, "as'fshown at 105. The discharge line 103 passes into the receiver 93'by way of a sliding gland connection 10T/,which includes a screw-on gland iitting 109, and by Vrriea'ns lof which it is possible to raise or lower the discharge tube relative to the receiver. The inlet end 111 of Y -thedischarge line 103 is desirably cut at an angle in order `to facilitate the simultaneous discharge of air and liquid therethrough, as will be hereinafter described.

'.The apparatus illustrated in Figures 1 and 4, and the diagrammatic view, Figure 5, is operable to maintain the stock within the ponding chamber 49 at a predetermined level which is independent of the pressure at which the stock is maintained. It mayalso be used to maintain the stock at a predetermined pressure as well as a predetermined level, although under normal operation, the stock pressure will be determined by the pressure at which the stoel; is delivered to the ponding chamber 49.

,The stock pressure may, therefore, ybe regulated to any predeterminedvalue by adjustment of the stock supply pressure in the stock delivery conduit 27 and, to a lesser extent, by adjustment of thek throttlng slice 37. More specically, the operation of the apparatus is as follows:

lithelevel vofthe .s folswifhn .theredigsrlnnibsf `49 draps below the level `attivi/bleh tobentaintained, the stock level withinthe" receiver v93 will" als drop.

` This will'result in an increase in 'the area of the opening 'at' the inletend 4of ,the discharge line 1 03 throughwliich air can be vented from the 'receivenand airlwillfbe discharge'datlan increasing rate ,through ther` discharge vline discharged "will rdecrasl" The increased discharge of air will result in av lowering ofthe sure withinzthe ponding 'chamber' 49, thatfvvill'be accompanied a rise in the rlevel of tlemstoclevvithin thatlA c :h ainb e1" .v As the stock level rises, it `will progressively lose-oli the opening into the discharge 103,' and in;- a very short interval, a'balan'cewill be reached, at which timesorne air landY some stoclcfwill againfbe "dischargedsimultaneously through they discharge rcnduit i If the stock level 'rises' above`v the selected value, the

operation will be substantially f reversed. 'Ifhe 'rising stock'will reduce or completelyfshutloi the normal Yliow of pressureair out'ofthereceiveri93t rlhat will cause (the pressure within the ponding chamber to increasewith vresulting lowering ofthestock level yto the` determined operating level.

The apparatus is operable to maintain the level of stock 'within very"close"limits, lAtk the same time, by virtue of kStock reaches the interior of the ponding chamber 49 via the iiow spreading conduit 33 and the passageway, 4 7 at a predetermined pressure. T he level at which the stock is maintained within the ponding chamber 47 is controlled bythe positionof the inflow end 111 of the stock and air discharge line 103, `and by virtue of the adjustable support for that line, provided by the gland.4- connection 107, the stock level can be adjusted to any predetermined value within the dimensional ylimits ofthe receiver chamber. Air is supplied to theV enclosed ponding chamber 49, through the air inow pipe 39 yand the air vinflow tube 77, at a pressure which shouldbe at leastsomewhat greater than thepressure at which the A stock is del ivered to the ponding chamber. isfree to flow outwardly from the vair inow tube 77 .into the interior of the ponding chamber 49. By virtue This air of the use of the spaced-apart air discharge openings 81 ber 49. is at the predetermined height, a condition of balance will exist. Suflicient pressure air will ow into Ythe ponding chamber 49 to balance leakage and to provide at leasta small excess which is discharged through the air outflow tube 79. There will also be some ow of stock from the ponding chamber into the receiver via the conduit 95, since under balance conditions, there is desirably a small `continuous discharge of both stock a andair from within the receiver93 via the discharge line 103,

the manner in whichl the air pressure isintroduced in to the ponding chamber yand the-manner inr which stock and air are discharged froml that chamber, there is substantially no tendency for surface or sub-surface disturbance of the bo'dy of stock which is vcontained within the pondingchamber. The mechanisrnis and entirelyvfoplproof in its operationjandit cprnpletely elimnatesthe diiiiculties which are inherent in the prior pressure and level regulating mechanisms. As previously stated; the invention maybe carried out by the use of a number of diierent types of apparatus, and various other control arrangementsjn accordance with the invention are illustrated in Figures 6 through 9 inclusive. In all of these arrangements, however, provision is madefor maintaining control of the pressure and level within the ponding or other liow chamber without disturbing the surface of the body of stock within that chamber, and without setting-up undesirable sub-surface iiow currents therein. t

It is generally impractical to effect/the complete sealing of a headbox structure, and accordingly, itzis possible t0 in the inilow tube 77, whichy openings are arranged tol discharge upwardly against the cover element 53 for"the ponding chamber, the air inowinto that chamber will ,be we ll diused and will not produce ilow disturbances at the Vsurface of the stock iiowing through the ponding operate mechanisms in accordance withthe invention without providing a specific air discharge mechanism. In lother words, the leakage within`a headbox structure is relied upon to furnish an adequate air discharge means. An arrangement ,operating in this manner is shownin -the diagrammatic view of Figure 6.` In that view, a headbox or equivalent stock delivery mechanism is illustratedat 113. .The headbox structure denes the walls of a ponding chamber 115, which is Vclosed except for stock inlet and stock outlet openings, and the usual leakage openings. Y

An air inow diffuser tube 117,v similar to the air inlet tube 77 of the `apparatus illustrated in Figures 1.5 is shown in position to discharge air. upwardly through spaced discharge orifices 119 into the upper portion of the ponding chamber 11s. The dinuse'r tube 117 is, in fu'm,

connected toa source ofpressure air, such as the linev 121, by way of an air-operated throttlng valve 123 and suitable piping 125. vAn auxiliary controlvv tank or receiver 127 is connected at its lower end to the ponding chamber 115, below the level of the Lstock contained therein, by a conduit 129. The upper end of the receiver 127 is connectedl to the ponding chamber 115, above the level of the stock contained therein by a similar conduit 131. Disposed within the receiver is a tloat 133, which is arranged to operate an adjustable pilot valve 135, supported on the defining walls of the receiver. The pilot valve 135, in turn, is operable to controlV the 151 in the upper surface thereof.

reame Y delivery efairltofthe Vair-operated throttling valve 123 by way of pressure, lines 137 and 138.

The pilot valve 135 is capable of being adjusted with reference to the throttling valve 123 so that the amount of pressure .air being delivered to the pending chamber 115 through the inflow diffuser 117 will be controlled in response to the level of the stock in the receiver or auxiliary control ychamber 127, which level is responsive to the level in the pending chamber115.` It is possible, by this arrangement, to admit just suflicient air to balance the amount of leakage within the pending chamber 115, and thereby to maintain thev stock yat a predetermined level while under a pressure head which is independent of the actual depth `of the stock. The pressure head is necesi sarily determined primarily by the pressure at which the stock is delivered te the pending chamber 115, but this is readily capable of adjustment to any required value by control of the stock delivery pump or other mechanism.

, In the operation of apparatus of this type, it is generally advantageous to deliver air to the throttling valve structure at a pressure which is not greatly in excess of the maximum pressure which is to be maintained within the headbox pending chamber. However, the use of a suitably designed .throttling Valve makes possible satisfactory operation, even in instances where the pressure is substantially different or where the supply pressure may vary during the operating cycle.

In all instances, however, the operation will follow essentially the same pattern. After adjustment of the pilot and throttling valves 135 and 123 to effect admission of pressure air to the pending chamber 115 at a suitable, predetermined pressure, the float 133 is adjusted to effect operation of the pilot valve when the stock level goes above or below the level at which the stock is to be maintained within the pending chamber.

Under stable operation, the amount of air admitted tovthe pending rchamber will exactly balance leakage l losses, andthe liquid levelwill remain constant. .stoclcdelivery pressure should decrease, because the malf the chine is being slowed downror for any other reason, the stock level will drop. The pilot and throttling valves will then operate to restrict thedelivery of pressure air to the i pending chamber, and after a short interval, leakage from the headbox will restore the proper pressure relationships and the stock level will return to the proper operating value. Similarly, if the stock level rises, pressure air will be admitted te the pending chamber at an increased rate until the stock level drops to the proper value and equilibrium isagain reached.

lt is also possible to accomplish control of the liquid level by controllingy the rate at which pressure air is discharged from the headbox and this arrangement, an example of which `is yshown in Figure 7, is sometimes preferable to the arrangement shown in Figure 6. The structure illustrated in Figure 7 includes a headbox 139, which defines the walls of a pending chamber 1411 that is closed except for stock inflow and stock outflow openings. As in the previously described structures, an air inow diffuser conduit 143 is disposed within the pending chamber 141 adjacent the upper wall thereof, and this conduit ,isy connected to` a source of supply of pressure air by suitable piping 14.5.Y As in the Figure arrangement, the line 145 may include an adjustable pressure regulator'7 indicated at 146, to assure the delivery of air at a constant pressure. The difuserconduit 1153 includes spaced oriice openings 147, whereby air is admitted to the interior of the headbox pending chamber under such conditions that disturbance of the surface of the stock contained within that chamber is avoided.

The apparatus also includes air outlet means, consisting of a tube or conduit 149 disposed above the air inflow 143 and provided with spaced openings or perforatiens l An auxiliary control chamber or receiver 153, similar to the auxiliary control receivers 93 and 127. in the previously described structure,

is connected at its lower end to the pending chamber 141, below the level of the stock contained within that chamber by a conduit The upper end ofthe receiver 153 is connected directly tothe air outllow pipe 151 in the upper portion of the pending chamber by a line 157. Within the receiver 153, there is provided a float operated throttling valve 159 which is connected into an air discharge line 161 extending through the upper defining wall of the receiver.

in the operation of this mechanism, the rate at which is vented to the atmosphere from the auxiliary con` trol chamber provided within the receiver 153 isdetermined by operation of the float controlled throttling valve 159. As in the other structures, the pressure at which the stock is maintained within the pending chamber 141 is determined primarily by the pressure at which the stock is delivered to that chamber, and the stock level is determined by adjustment of the operating position of the float valve 159. The pressure air should be supplied at a pressure which is above the pressure to be maintained within the pending chamber, and at a rate which is in excess of the normal rate of leakage.

During normal operation, the adjustment of the throt tling valve 159 will be such that the rate ef air discharge through the line 161, when the stock level is at the predetermined value, willjust balance therate at which the excess air reaches the receiver through the line 157. The pressure within the headbox will then be equal to the stock pressure and equilibrium conditions will exist. In the event that the level of the .stock within theponding chamber drops below the predetermined value, the throttling valve 15,E will open to increase the rate of discharge of air through the discharge line. This will llower the pressure of the air pad within the pending chamber 141, whereupon the liquid level will rise. If the stock level within the pending chamber 141 rises above the preselected value, the iieat valve will then operate to reduce the rate of air discharge. Increased pressure will be produced within the pending chamber, the liquid levelwill drop, and balance will be restored.

In the arrangements heretofore described, the pressure air which has been admitted to the interior of the pending chamber has been supplied through aline which is separate from the connections vte the auxiliary or control chamber. lt is possible to operate equipment in accordance with the invention by the use of only two connectiensto the interior of the pending chamber, one above and one below the stock level, and an arrangement of this type is shown in Figure 8. In the Figure 8 structure, the walls of the headbox are indicated at 163 and the pending chamber within the headbox at 165. The headbox 163 similar to the headbox of the Figure 1 structure, includes stock inow and stock outiiow openings located below the stock level and is otherwise closed. An auxiliary control chamber is illustrated at 167, andas shown, the upper end of that chamber is connectedvby a conduit 169 directly to a diffusion type air inow conduit, which consists of a pipe 171 provided with spaced openings 173 in the upper surface thereof, and which is disposed in the upper portion of the headbox pending chamber 165. The lower end of the auxiliary chamber 167 is connected to the pending chamber 165 below the stock level therein by a second conduit 175.

Pressure air in excess is supplied to the free space in the upper portion of the auxiliary chamber 167 by means of a conduit 177, which may include a pressure regulating unit 179, and the discharge of air and stock from the auxiliary chamber 167 is effected through a U-shaped discharge conduit 181. The conduit 181 is desirably mounted so that it may be moved upwardly and downwardly relative to the auxiliary chamber 167 in order'that the liquid level within that chamber and within the ponding chamber can be adjusted to the selected value. The outflow end of the conduit 181 is arranged to discharge the, Figure structure.

:value which is above atmospheric.

.r below atmospheric pressure. operate in this manner is illustrated in Figure 9..

*The Figure 9 structure includes a headbox 187, withinwhich there is provided a ponding chamber 189, and an A.auxiliary chamber 191, the lower end of which is conafnam ...into an airseparator. and stock return unit183 which convvnects with the white water system. t', -,..Ingeneral, the operation of this mechanism is similar :to the other embodiments of the invention, and especially Pressure air, conveniently at a controlled, uniform pressure, is supplied through the con- V. duitf 177, the ow control chamber 167 andthe conduit v16,910 the diffuser tube 171. vStock is supplied tothe ponding chamber 165 by way of the stock inilow opening, and normally the stock will be supplied at a uniform, predeterminedpressure. The discharge conduit 181 will-be vlocated in such a position that when the stock level is at the desired, predetermined height, the amount of air adthereby besupplied to the interiorof. the headbox, and

.-indueY course, the stock level will return to the normal .;operating value.

If the stock level drops below the pre- Vgdeterminedvalue, more air will be vented from the chamvber 167 through the conduit 181 and this will eifect a-re-v r-duction 4in the pressure within the ponding chamber.

Suchvreduction will cause the stock level to rise and equilibrium conditions will again be restored. As in the :.:arrangements of Figures. 4 and 5, it is intended that there will be some discharge of both air and stock during nor- AAmal operation ofthe apparatus. .-The various embodiments of the invention described inthe-foregoing are intended to operate under conditions where the pressure maintained above the stock is zt a It may be desirable, under certain conditions, to operate with the stock in the fponding orother ilow control chamber ata value which is One apparatus arranged to nected by a conduit 193 to the ponding chamber-189, at a point below the level of the stock normally contained e therein. The upper end of the auxiliary chamber is con-1, nected by another conduit 195 to the ponding chamber at a,region above the normal level of the stock contained therein, and to minimize disturbance of the air within the vponding chamber, the conduit 195 terminates in an air inflow diiuser pipe 197, as shown.

,l j- Since this apparatus is especially intended to operate junder reduced pressure, the auxiliary chamber 191 is L connected to a second auxiliary chamber 199 by means of a vertically-adjustable discharge conduit 201.

The lower end of the second auxiliary chamber 199 is connected to a stock reservoir 203 by means of a barometric column 205, and the upper end of the second auxiliary 'chamber 199 is connected to a vacuum pump 207, as illustrated.

During normal operation, the vacuum pump 207 is .operable to maintain a predetermined reduced pressure within the second auxiliary chamber 199. This reduced pressure is communicated to the ponding chamber 189 within the headbox 187 by way of the vertically adjustable discharge conduit 201, the rst auxiliary chamber 191, the conduit 195 and the diffuser tube 197 located the conduit 201, the chamber 199 and the pumpv 207,

Vwill justbalance theleaka'ge into Athe .ponding chamber.

,At thisv lsame time, there will also be somecontinuous Ydischarge of stock by way of the conduit 193, the chamber 195, the chamber 199, and the barometric column 2.05.

If thestock levelwithin the ponding chamber rises, the lamount of air being vented to the second auxiliary chamber 199 will be reduced, due to a reduction or a shuttingoi of the opening through which air iiows intothe inflow endof the discharge eonduit.201. This will .result in an increase in the pressure within the ponding chamber 189 and a simultaneous increase in the .rate Yat which stock is discharged into the chamber 199 and the barometric column 205. The stock level will' thereby be lowered until stability is restored to the system atthe preselected stock level.

A lowering of the stock level from the selected operating level will have substantially the opposite effect. More air and less stockwillbe dischargedfromthe Iauxiliary .chamber until the stock level again rises to the operating level. v Y Stock which ows into the bar ometric column 205 and thence into the reservoir 203 at the bottom of that column may be returned to the white water system by a suitable pump, as illustrated at I209. The

primary vfunction of the second auxiliary chamber 199 and the barometric column 205 is to effect separation of Vther air andvstockdischarged from the conduit 201, and

other structural arrangements capable of accomplishing this function can obviously be substituted therefor. It will be understood that an arrangement such as that shown in Figure 9 may include an air inflow conduit lsuch ing chamber during normal operation.

,as the perforated pipe dilusion unit illustrated at 77 in Figures l and 4. When suchv a unit is used, it should be throttled to reduce substantially the amount of air admitted to the headbox ponding chamber. The use of a con- -trollable airinilowwill, however, facilitate somewhat the control ofthe pressure and stock level being maintained within theponding chamber. As in the previously described structures, an excess of air is supplied to the pond- It will also be understood that apparatus in accordance with the invention can be used to accomplish stock. level lcontrol inother portionstof the stock delivery system of apapermaking machine. For example, stock delivery conduits such as the conduit illustrated at 27 in Figure l,

. sometimes -include an enlarged cross-sectional area por- .-tion,-as,illustrated at 211, which may be used to accomplish a deaeration or other function. To that end, it is usualto maintain a-reduced pressure above the stock as turbances often carry through to the web-forming region,

. and to maintain .the stock level at a preselected value, in-

dependently of the actual pressure maintained above the stock, the apparatus may desirably include a level regulating means in accordance with the invention, as for example. the apparatus illustrated in Figure 9.

. The variousarrangements described in the foregoing constitute convenient and reliable means for maintaining a body or a flowing stream of stock within a headbox or other flow control chamber at a predetermined level which is independent of the total pressure or head which exists within that body or flowing stream of stock, and which is also independent of change in the rate of iloW of the stock. The described mechanisms and procedures accomplish the desired result, under such conditions that there is substantially no disturbance of the surface of the body of stock within the headbox chamber, and without the creation of any surges or other undesirable Ilow conditions i within the stock body.

v While the invention has particular utility in connection with the operation ofV pressurized headbox equipment aada@ 'wherein .the stock` is maintainedy under a positive pressure and at a depth which is lower vthan about eighteen inches,

this by no means defines its useful limits. The arrange ment can be used to control stock level under conditions of reduced pressure and to control headbox operation in accordance with lfactors other than stock level. For example, the invention'lends itself to use in instances l where it is desired to effect control of the total pressure head at the slice, or elsewhere, without necessarily maintaining a fixed stock level. It can alsolbe used in instances where control in response to stock turbulence is being accomplished. l a v Certain of the embodiments of the invention embody no moving parts, and all of the disclosed arrangements` are structurally simple and completely reliable in operation. Various of the features of the invention believed to be new are set forth in the appended claims.

We claim: l. In apparatus of the class described, means defining the walls of an enclosed chamber which is adapted to receive a body of stock, said chamber having a stock inflow opening and a stock outfiow opening located below ,the normal leve; of the body of stock which is contained ,of said auxiliary chamber connecting with said stock chamber at a point which is a substantial distance below the normal level of the stock` contained within said stock chamber, the upper end of said auxiliary chamber connecting with said stock chamber at a point which is spaced a substantial distance above the normal level of fthe stock contained in that chamber, means operable to deliver air which is at a pressure greater than the pressure normally existing within said stock chamber to the interior of said stock chamber, said air delivery means including a source of pressure air, an air conduit which terminates in an air diffusing discharge unit disposed within said stock chamber a substantial distance above the normal level of the stock contained in that chamber, and means responsive to the level of the stock contained within said auxiliary chamber for controlling the pressure of the air within said` stock chamber, thereby to regulate the level of the stock within that chamber.

2. In apparatus of the class described, means defining the walls of an enclosedchamber which is adapted to contain a body of stock, said chamber having spacedapart stock inflow and stock outflow openings located below the normal level of the stock which is contained therein, means for delivering stock to said stock chamber through said stock inflow opening, said apparatus being adapted to discharge stock through. said outflow opening,

` means defining the walls of an auxiliary enclosed chamber,

the vertical dimension and position of said auxiliary chamber being such that its upper and lower ends are respectively located substantially above and substantially below the normal level of the stock contained ywithin said stock chamber7 a stock conduit which connects the lower end of said auxiliary chamber to said stock chamber at a point which is a substantial distance below the normal level of the stock contained within said stock chamber, air conduit means which terminates in the upper portion of said stock chamber, connecting the upper end of said auxiliary chamber to said stock chamber at a point which is spaced a substantial distance above the normal level of the stock contained within said stock chamber, means operable to produce a continuous fiow of air which is at a pressure greater than the pressure existing within the said stock chamber into the interiory of said stock chamber, said flow producing means including al source of pressure air and any air conduit which terminates in an air diffusing discharge unit disposed within said stock chamber a substantial distance above the normal level of the stock contained in that chamber, and means responsive to the level of the stock contained within said auxiliary chamber for controling the rate of ow of pressure air into said stock chamber, thereby to regulate the level of the stock within that chamber.

3. In apparatus of the class described, means defining the walls of an enclosed chamber which is adapted to contain a body of stock, said chamber having spaced-apart stock inflow and stock outfiow openings located below the normal level of the stock which is contained therein, means for delivering a flowing stream of stock, which is under pressure, to said stock chamber through said stock inflow opening, said apparatus being adapted to discharge stock through said outflow opening, means defining the walls of an auxiliary enclosed chamber, the vertical dimension and position of said auxiliary chamber being such that its upper and lower endsare respectively located substantially above and substantially below the normal level of the stock contained within said stock chamber, a stock conduit which connects the lower end of said auxiliary chamber to said stock chamber at a point which is below the normal level' of the stock contained within said stock chamber, air conduit means, which terminates in the upper portion 'of said stock chamber, connecting the upper end of said auxiliary chamber to said stock chamber at a point which is spaced above the normal level of the stock contained within said stock chamber, a normally open vent line which terminates within said auxiliary chamber, means including a source of air which is at a pressure greater than that normally maintained within said stock chamber, for producing a iiow of air into the upper portion of said stock chamber, and means operablein response to the level of the stock contained within -said auxiliary chamber to effect at least an intermittent, controlled fiow of pressure air through said air conduit means from said stock chamber into said auxiliary chamber and thence out of said auxiliary chamber via said vent line, thereby to regulate the level of the stock within said stock chamber.

4. Apparatus in accordance with claim 3, wherein the vent line which extends into said auxiliary chamber` terminates in an air vent opening having a substantial vertical dimension, whereby the area of said air vent opening is automatically varied in response to the level of the stock contained within said auxiliary chamber.

5. In apparatus of the class described, means defining the walls of an enclosed chamber which is adapted to contain a body of stock, said chamber having spacedapart stock infiow and stock outflow openings located below the normal level of the stock which is contained therein, means for delivering stock to said chamber through said stock infiow opening, said apparatus being adapted to discharge stock through said outow opening, means defining the walls of an auxiliary enclosed chamber, the vertical dimension and position of said auxiliary chamber being such that its upper and lower ends are respectively located substantially aboveand substantially below the normal level of the stock contained within said stock chamber, the lower end of said auxiliary chamber connecting with said stock chamber at a point which is below the normal level of the stock contained within said stock chamber, the upper end of said auxiliary chamber connecting with said stock chamber at a point which is spaced a substantial distance above the normal level of the stock contained in that chamber, means for producing at least an intermittent fiow of air which is at a pressure greater than the pressure existing within said stock chamber into the interior of said stock chamber, and means including a combination air and stock discharge conduit which extendsi'into said auxiliary chamber and which is operable, depending upon the stock level in said auxiliary chamber, to discharge air, stock or mixtures thereof from said auxiliary chamber, thereby maintaining a predetermined stock level Within said stock chamber.

6. In apparatus of the class described, means defining the walls of an enclosed chamberwhich is adapted to l contain a body of stock, said chamber having spacednormal level of the stock contained within said stock chamber, a stock conduit which connects the lower end of said auxiliary chamber to said stock chamber at a point which is a substantial distance below the normal level of the stock contained within said stock chamber, and air conduit connecting the upper end of said auxiliary chamber to said stock chamber at a point which is spaced a substantial distance above the normal level of the stock contained in that chamber, means including a source of pressure air and a conduit which terminates in an air diffusing unit located within said stock chamber, for producing at least an intermittent flow of air which is at ya pressure greater than the pressure existing within said stock chamber into that chamber, and means including 'a combination air and stock discharge conduit which extends into said auxiliary chamber and which is operable, depending on the stock level in said auxiliary chamber,

g-to discharge air, stock or mixtures thereof from said .auxiliary chamber, thereby maintaining a predetermined stock level within said stock chamber.

7. A stock feed device for a papermaking machine comprising a closed headbox having stock inlet and stock outlet openings in spaced relation to each other and an ienclosed ponding chamber therebetween, means for delivering stock, under pressure, to said ponding chamber via said stock inlet opening, means defining the walls "of an auxiliary enclosed chamber, the vertical dimension and position of said auxiliary chamber being suchthat its upper and lower ends are respectively located substantially above and substantially below the normal level of the stock contained within said ponding chamber, stock conduit means connecting the lower end of said f auxiliary chamber to said ponding chamber at a point which is below the normal level of the stock within that chamber, air conduit means connecting the other end f of said auxiliary chamber to said ponding chamber at a point which is spaced above the normal level of the stock contained in said ponding chamber, a source of pressure air, means including an air diffusion unit located VWithin said headbox for discharging air from said pressure source into said ponding chamber under such conditions that disturbance of the surface of the stock con- 'tained within said ponding chamber is substantially V-avoided, and means responsive to the level of liquid VWithin said auxiliary chamber for controlling the delivery of pressure air to said ponding chamber, thereby to regulate the level of the stock within said ponding chamber. 8. A stock feed device for a papermaking machine I comprising means defining the walls of a closed headbox having stock inflow and stock outflow openings in spaced relation to each other and an enclosed ponding chamber therebetween, said infiow and outflow openings being located below the normal level of the stock which is'contained within said ponding chamber, means for delivering stock under pressure to said ponding f ,chamber through said stock inflow opening, said device ,beingadapted to discharge stock continuously through 14 said outflow opening, and means for maintaining the body of stock which is contained within said ponding chamber at a predetermined level during the operation of said' apparatus, including means defining the walls of an auxiliary enclosed chamber, the vertical dimension and position of said auxiliary chamber being such that its upper and lower ends are respectively located -substantially above and substantially below the normal level of the stock contained within said ponding chamber, a stock conduit which connects the lower end of `said auxiliary chamber to said ponding chamber at a point which is below the normal level of the stock contained within said ponding chamber, an air conduit kmeans, which terminates in the upper portion of said ponding chamber, connecting the other end of said 'auxiliary chamber to Vsaid ponding chamber, meansincluding a conduit which terminates in an air diffusion mechanism located in the upper portion of said ponding chamber for continuously admitting air at a pressure which is greater than the pressure existing within said ponding chamber to the interior of said ponding chamber, and means including a discharge conduit which extends into said auxiliary chamber and which is adapted to discharge pressure air from said ponding chamber by way of said auxiliary chamber at a variable rate responsive to the level of the stock within said stock chamber.

9. A stock feed device for a papermaking machine comprising means defining the walls of a closed headbox having spaced-apart stock iniiow and stock outflow openings in spaced relation to each other and an enclosed ponding chamber therebetween, means for delivering stock under pressure to said ponding chamber through said stock inflow opening, said device being adapted to discharge stock continuously through said outflow opening, and means for maintaining the body of stock which is contained within said ponding chamber at'a predetermined level during the operation of said apparatus, -said level maintaining means including means defining the Walls of an auxiliary enclosed chamber, the vertical dimension and position of said auxiliary chamber being such that its upper and lower ends are respectively located substantially above and substantially below the normal level of the stock contained within said ponding chamber, a stock conduit which connects the lower end of said auxiliary chamber'to said ponding chamber at a point which is below the normal level of the stock contained within said ponding chamber, means connecting theother end of said auxiliary chamber to said ponding chamber at a point which is spaced above the normal level of the stock contained in said ponding chamber, means including an air conduit which terminates in an air diffusion mechanism located in the upper portion of said ponding chamber for admitting pressure air intoy said ponding chamber without disturbing the surface of the stock contained within that chamber, and means including a float valve responsive to the level of the stock within said auxiliary chamber for controlling-the rate at which pressure air is admitted to said ponding chamber. l0. A stock feed device for a papermaking machine, comprising a closed headbox having stock inlet and stock outlet openings in spaced relation to each other and an enclosed ponding chamber therebetween, means for delivering stock, under pressure, to said ponding chamber via said stock inlet opening, said device being adapted to discharge stock continuously through said outflow opening, means defining the walls of an auxiliary enclosed chamber, the vertical dimension and position of said auxiliary chamber being such that its upper and lower ends are respectively located substantially above and substantially below the normal level of the stock contained within said ponding chamber, stock conduit means connecting the lower end of said auxiliary chamber to said ponding chamber at a point which is below the normal level of the stock within that chamber, air conduit kmeans which terminates in the upper portion of -v enclosed ponding chamber delivering stock under pressure to said pending chamber jsaidponding chamber connecting the upper end of said aturiliary chamber to said ponding chamber, a source of pressure air, means including a conduit which terminates in an air diffusing mechanism located at the upper portion of said stock chamber for discharging air from said pressure source into the upper portieri of said ponding chamber, said air being discharged into said pending chamber at-a pressur which is greater than the pressure normally existing within said pending chamber, and means including an adjustable vent line which extends into said auxiliary chamber and which is operable, depending-upon the stock level in said pending chamber, to idischarge air, stock or mixtures thereof from said auxiliary chamber, thereby maintaining a predetermined stock level within said stock chamber.

ll. A stock feed device for a papermaking machine comprising a closed headbox having stock inlet and stock-Outlet openings in snaced relation to each other 1' and an enclosed pending chamber therebetween, means for delivcrinfr .ook under ressure to said ondin chamber via said stock inlet opening, said device being adapted to discharge stock continuously through said outflow opening, means defining the walls of an auxiliary enclosed chamber, the vertical dimension and position of said auxiliary chamber being such that its upper and lower ends are respectively located substantially above and substantially below the normal level of the stock contained within said pending chamber, stock conduit means connecting the lower end of said auxiliary chamber to said ponding chamber at a point which is below the normal level of the stock within that chamber, means chamber, means including a source of pressure air and a second conduit connected to the upper end of said auxiliary chamber for admitting pressure air into that chamber, at a pressure which is greater than the pressure normally existing within said pending chamber, and m'eansincluding a combination air and stock discharge conduit which extends into said auxiliary chamber and which is operable to discharge air, stock or mixtures thereof'from said auxiliary chamber, thereby to control the delivery of pressure air to said ponding chamber and to maintain a predetermined stock level within said ponding chamber.

Vl2. A stock feed device for a papermalting machine v comprising a closed headbox having stock inlet and stock outlet openings in spaced relation to each other and an therebetween, means for via said stock inlet opening, said device being adapted to discharge stock continuously through said outflow opening, means defining the walls of an auxiliary enclosed chamber, the vertical dimension and position of said auxiliary chamber being such that its upper and lower ends are respectively located substantially above and substantially below the normal level of the stock contained within said ponding chamber, stock conduit means connecting the lower end of said auxiliary chamber to said ponding chamber at a point which is below the normal level of the stockv within that chamber, means comprising a conduit which terminates in an air collecting'mechanism located within said stock chamber for connecting the upper end of said auxiliary chamber to said ponding chamber at a point which is spaced above the normal level of the stock contained in said ponding chamber, a combination air and stock discharge conduit which extends into said auxiliary chamber and which is operable, depending upon the stoel; level in said auxiliary Vvchamber, to discharge air, stock or mixtures thereof from I-vsaid auxiliary chamber, thereby maintaining a predetermined stock level within said stock chamber, means deiining the walls of second auxiliary chamber connected to the outlet end of said air and stock' discharge conduit and means associated with said second auxiliary chamber for maintaining a predetermined pressure therein.

13. The method of operating a pressurized headbox which comprises delivering stock to the headboxA at a predetermined pressure, simultaneously maintaining the level of the stoel: at a predetermined value, which is independent of the pressure of the stock, by admitting air to the interior of the headbox at a pressure which is greater than the pressure normally maintained within said headbox, and, at the same time, discharging, in response to the level of stock in the headbox, air, stoclt, or mixtures thereof from the headbox at levels which are'different from the level of the stock in the headbox, and under such conditions that there is substantially no disturbance at or beneath the surface of the stool; within the headbox.

i4. The method oi operating a pressurized headbox which comprises delivering a flowing stream of stock to the headbox at a predetermined pressure, and simultaneously maintaining the level of the stoel( at a predetermined value, which is independent of the pressure of the stock, by diffus-:diy admitting air to the interior of the headbox at a pressure which is greater than the pressure normally maintained within said headbox, and at the same time discharging, in response to the level of stock in the headbox, air, stock, or mixtures thereof from the headbox at individually variable rates, at levels which are ditlerent from the level of the stock in the headbox, and under such conditions that such discharge produces substantially no disturbance at or beneath the surface of the stock within the headbox.

l5. Apparatus in accordance with claim 8 wherein the discharge conduit which extends into said auxiliary chamber terminates in an air vent opening having a substantial vertical dimension, whereby the area of said air vent opening is automatically varied in response to the level of the stock contained within said :auxiliary chamber. i

16. A stock feed device for a papermaking'machine comprising a closed headbox having stock inlet and stock outlet openings in spaced relation to each other, and-an enclosed ponding chamber therebetween, means `for delivering stock under pressure to said ponding'chamber via said stock inlet opening, means defining the walls of an auxiliary enclosed chamber, the vertical dimension and position of said auxiliary chamber being such that its upper and lower ends are respectively located substantially above and substantially below the normal level of the stock contained within said ponding chamber, stock conduit means connecting the lower end of said auxiliary chamber to said ponding chamber at apoint which is a substantial distance below the normal level of the stock contained within that chamber, air conduit means connecting the other end of said auxiliary chamber to said ponding chamber, said air conduit means terminating within said headbox in a perforated tube disposed a substantial distance above the normal level of the stoclf` contained in said pending chamber, means for producing at least an intermittent llow of air which is at a pressure greater than the pressure existing within said stock chamber into the interior of said stock chamber, and means responsive to the level of the stock contained within said auxiliary chamber for controlling the pressure of the air within said stoel; chamber, thereby to regulate the level of the stock within said chamber.

l7. The method of operating a pressurized stock feed device having an enclosed stock chamber through which the stock flows, which comprises delivering stock to the stock chamber at a predetermined pressure, and simultaneously maintaining the level of the stock within said chamber at a predetermined value, which is independent of the pressure at which the stock is delivered to said chamber by diffusing air into the interior of the stock chamber at a pressure which is greater than the pressure normally maintained within said headbox, and at a rate which is in excess of normal leakage from said chamber, and at the same time, discharging, from said chamber, in response to the level of stock therein, air, stock, or mixtures thereof, thereby to control the pressure of the air within said stock chamber and to regulate the level of the stock Within that chamber.

18. In apparatus of the class described, means defining the walls of an enclosed chamber which is adapted to receive a body of stock, said chamber having a stock inliow and a stock outflow opening located below the normal level of the body of stock which is contained therein, means for delivering stock continuously to said chamber through said stock inow opening, said apparatus being operable to discharge stock continuously through said outow opening, means operable to deliver air which s at a pressure greater than the pressure normally existing within said stock chamber to the interior of said stock chamber, said air delivery means including a source of pressure air and an air conduit which terminates in an air diffusing discharge unit disposed within said stock chamber a substantial distance above the normal level of the stock contained in that chamber, and means responsive to the level of the stock within said chamber for controlling the delivery of air into said chamber, thereby to regulate the level of the stock within said chamber.

19. Apparatus as defined in claim 18 wherein said means for controlling the delivery of air into said chamber comprises means operable in response to the level of the stock in said stock chamber to discharge air, stock or mixtures thereof from said stock chamber.

References Cited in the tile of this patent UNITED STATES PATENTS 645,925 Whitney et al Mar. 20, 1900 1,461,683 Sears et al. July 10, 1923 1,590,321 Sartakol June 29, 1926 2,381,286 Hornbostel Aug. 7, 1945 2,509,822 Hornbostel May 30, 1950 2,566,449 Hornbostel Sept. 4, 1951 2,566,450 Hornbostel Sept. 4, 1951 2,677,991 Goumeniouk May 11, 1954 FOREIGN PATENTS 254,873 Germany Dec. 17, 1912 682,846 Germany Oct. 25, 1939 423,646 Great Britain Feb. 5, 1935

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