[1]Utlited States Patetit Office 3@1359652 P a t e n t e d J u n e 2 , 1 9 6 4 3 135,652 -LIQUID LEVEL CONTROL FOR A PREASSURIZE4D HEADBOX OF A PAPER-MAKING MACBINE Robert E. Smith, Hradson Fafls N.Y., assignor to The Sandy Hill Iron & Brass Wo@lks, Hudson FlaRs, N.Y., 5 a corporation Filed Aiig. 17, 1962, Ser. No. 217,729 1 CIaim. (C]. 162-259) This concerns a pressurized headbox of a papermaking 1 0 machine and means for employing same in either high or low speed operations under predetermined and controlled stock level or head conditions selectively in a pressurized air or vacuum system, according to the dictates of practical operating speed capabilities of the marhine in fo@m 15 ing a specific sheet type from the dilute aqueous suspension of paperrnaking fibers delivered to the webforniing region froni the headbox. In Mgh speed operation, a pressure witwn the headbox of atmospheric or above, allowing a certain con- 20 trolled headbox head, niay be a desideratum for the attainment of optimum sheet-forming conditions. Contrariwise, in low speed operation, a pressure below atmospheric, altbwing a controlled headbox head less than or below said certain level, may be a desideratum and for 25 the identical reason. The maintenance of such head as to maintain the rectifying means in a continuously submerged condition below the stork level is a primary consideration, as a rotative roll not thusly covered exhibits a capacitv to splash stock 30 onto the headbox walls allowing stock lumping, with the lumps,rollin.- back into the stock and passing out into the web-forming region with objectionable results. In the manufacture of a given weight paper, there is normajly an optimum depth for the headbox stock gen- 35 erally independent of the macl-,Line operating speed, although to acbieve best macbine operating conditions, it is necessary to supply the stock at a pressure or under a vacuum capable of producing a spouting velocity at the slice substantially equal to the formin.- wire velocity. 40 To obtain such a presstire by prior conventional means, it has been necessary to provide a relatively high headbox head, but in such case, the stock velocity in the headbox may be so slow that the fibers settle, leadin.- to poor paper formation. The two requirements being inherently 4 5 conflicting, a conipromise means for obtaining optimum results is requisite. Pressurized head boxes have been used where part of the liquid head is replaced by a pressurized air pad in the upper portion of the ponding chamber to maintain the 50 reqiiired head, baving the effect of reducing the stock level to allow an increase in liquid velocity within the headbox and thus prevent settling, while maintaining sufficient pressure to allow adequate spouting velocity, but same have been deficient in adequate head control 55 means. I offer means for accurately controlling the head level to maintain a constant stock v@-locity where air pressure or vacuum and head are directly interrelated to allow control of the latter as a function of the former, with 60 the consequent elimination of the transient instabilities and operational difficulties of previ(>usly known; constrlictions as presented by the inherent necessity for maintaining a head bigher than practical for a specific spouting velocity due to the omnipresent roll submeraence problem. 65 NVhereas, in high speed operation, a higher head is needed than in low speed operations and a pressurized lieadbox best accommodates the needs, in low speed operations, a vacuum within the lieadbox best serves. The system hereof advantageously allows the use of a single 70 headbox and cooperant instrunientation alternately for high speed and/or low speed operations, and adnlirably 2 accomniodates both operating conditions while insurinaccurate stock level control Illustrative of the desira'bility of en-Lploying a condition of vacuum in preference to one of pressurized air, assuine that a 20" head is requisite to keep the rectifying roll fully submerged, but assume further that a run of 500 feet per minute is desired, with known optimum spouting veloc-ity at the slice bein.- obtained with no greater than an 8" head. The two conflicting factors, one of a cerlain stock level requisite for adequate roll covering and the other of a different stock level requisite for allowing optimum spoliting velocity, are herein compensated for by means allowing an artificial or synthetic elevated head reaching to a mean datum line at the 20" level to preclude rectifier exposure and a rell head su@h as to ensure proper spouting velocity, 12" of the head thus being artificial and ineffective, and 8" thereof thus being real and effective as to spouting velocity. This control system, pneumatically, or hydraulically operated, relites the air pressure or vacuum in the headbox, as the case may be, to the head, whereby the head can be acellrately controlled within narrow liniits at a predetermined optinium level, the control means being rapidly and atitomatically responsive to stoc-k level changes to effectuate the requisite adjustments to bring the level back to the predetermined optimum mean. I provide, witwn a closed headbox receiving a predetermined constant stock gallonage, a co ition, elt 0 air of a desired presstire or of vacuum, w by, in either case, a throttling is effected by means of a ragmoperated control valve sensed by a liquid level control means to effectuate the appropriate opening or closing of valve means and resultant rnaintenance of the predetermined head. In one instance, pressurized air is introduced into the headbox; in the other instance, air is evacuated from the headbox. Through the same instrumentation, the liquid level control means servcs, in ei@ther instance, the identical purpose of s-.nsing the liquid level change, with the intelligence being reflected in automatic valve opeiiing or closing functions. In the drawings: FIG. I is a fragmentary and broken side elevational view of a headbox embodying th@ invention; FIG. 2 is a broken top pla.1 view of the headbox shown in FIG. 1; and FIG. 3 is a schematic diagram for illustrating the principles of the invention. In the drawings, 2 represents one of a pair of transYerselyspaced headbox side walls or pond sides joined by transverselyextending forward, rearward, top and bottom walls 4, 6, 8, and 10 respectively to provide a closed receptacle of comparatively small vertical dimension, supported in cooperative relation to the other machine elements. An inlet 12 of appropriate configuration is cornected to a stock source (not shown) wherevrith stock is forced to the headbox by a suitable pump (not shown) and at a predeterrnined constant gallonage. Bottom wall 10 has a forwardly-projecting extension to provide an apron 13 disposed vertically below and spaced from a verticallyadjustable throttling lip 14, comprising the lower portion of forward wall 4, to form a slice or discharge opening 16 therebetween through which stock flows onlo a web forming wire 18 entrained around a breast roll 20. Lip 14 may be adjusted in conventional manner to vary the crosssectional slice dimension as by a plurality of tran sversely-spaced rods 22 pivoted to brackets 24 secured to the lip and having upper ends coupled as by interc6nnecting links 26 and 28 to pistons 30 of hydraulic or pneumatic cylinders 32 and supported relative to the lip as by a transversely-extending beam 34.
[2]3 IVindows 36 may allow observatio@i of the headbox interior. One or Tnore power driven rotatable d-Istributor rolls 38 may be provided within the ponding chamber a-.id may be adjustable. An air inlet 40, s,,iitably valved at 42, is conne,,',Cd at its outboard terminus to a pressure source and at its inboard term;nl-is to and throu.-h a headbox wall. An outlet pipe 50 exlends from the headbox aiid is suitably valved by a diaphragm operated control valve 52 on the inboard side of a T coupling 54 and an air eyhaust valve 56 on the outboard side thereof, the outer Lree extremity of the pipe leading to atmosphere. Spaced from a headbox s-@de wall exteriorly of the headbox so as not to be adversely affected by conditions or turbulence therewiciain, a vertic-,tlly-exter@d;ilg liqu-id level controller 60, of commercially available type, si-ich as Mason-Neilan 1:@quid level co.itro'Jer (produced by Mason-Neilan Divisioi, Worthir@gton Corporation, I"Torwood, Massachusetts, U.S.A.) or eq7aiva'@erit, is statio@iarily secured and is o' such design as to be opera:bl@, by displacement accordin-.1y as the s'@ock level increases or decreases, and to control or operate cooperant means for effectuating the retention of air within or discharge of air from the headbox. Control valve 52 is opera' ed by and is under the control of the sensing niechaiiisni iticorporated within controller 60, it being responsive in its movements direcily proportiong to the outp-at signal generated by the sensi mechanism which in turn is directly proport;onal to the hev,d under control. A connecting pipe 70 is connected to coiiplin(., 54 and has a spring-loajed vacuum relief valve 72 provided therealong adjacent couplin-, 54 and a valve 74 provided therealong adjacent a couplin.- 76 at its opposite terminus. An air entering pipe '.20 has a valve 82 provided therealong at one side of i's :@nterconnection with coupli-@l-g 76 op,oosite from a vacutim pump 90 also, provided therealong. Vacuum pump 90 is also provided with a pipe 100 having a c6upling 102 provided therealong and a valve 104 provided therealong out,@vardly of couplin-, 102. A pipe 110 is coupled to coupling 102 at orie terminus and to a coupling 112 at its opposite terminus connecting it to pip.- 40 with a valve 114 provided along its lengch. Valve me-.nbers 42, 56, 74, 82, 104 and 114 @niay tal@e any practical form desir-,d. . In the case of presslre application, stocl, is supplied to inlet 12 at a predeterm@ined constant gallona-,e and simultaneously therewith air, under predetermined pressure and at a conslant rate of low, is supplied the headbox through pipe 80, valve 82 in open position, vacuum pump 90, p:@Pes 100 and 110, valve 114, and pipe 40, v;:Ith valves 74 and 104 and 42 beina set in closed position. Slice lip 14 is adji,-sted to restrict the stocl,, flow orylo the wire, and thereby, the stock level ;s lowered with an increase of pressure within the box, rp.3ultilig in an increasing spouting velocity. As the head attains the prede'Lermir@ed optimum level, and under the predetermined air pressure condition, the hydraulic pressure at that moment will be such as to cause a sufficient signal to be com-ii-iunicated to diaphragm operated control valve 52 to effecluate its closing wherefor normal operation ensues. if the stock level were to rise above or drop from th@predetermined optimum level, the resultant increase or decrease in hydraulic pressure would be transmitted to control means 60 causin@ a decreased or increased signal to be communicated to control valve 52, whi,@'n valve in turn partially opens or closes accordin. y, thus prectudiiig or allowing the bleeding of air from withiii the headbox resultin- in a raising of the headbox air pressure to allow the stock level to drop to 'the predeter@nined ortimum level or a lowering of the h-.adbox air pressure tO allow th-- stock level to rise to the predeterm,.ned optimum level. In the case of vact,.um applicat;on, stof-k is supplied to inlet 12 at a predetermined conslart gallonage. Simulr) taneously th,-rew,.th, a vacuum is created by vacuum pump 90 Nvhich ca@dses air to be drawn from the headbox through pipe 50, coi@rol valve 52, pipe 70, relief v,,ilve 72, valve 74, ppe 80, pump 90, pir,-- 100, atid valve 104 to atmosphere, with valves ,2, 56, 82 ard 114 being sct 10 in closed position, valve 114 being clos-.d. The lip of the slice is, adjusted and gradually closed to restrict the flow of stock from 'Lhe outlel and onto th-,. wire so that the s,ock level in the headbox ris-.s w:lth an increase of vacuum wi'thin the box and resul,-s in i-@icreas15 ing velocity of stock from the outic@,. As the stock a,tains 'the pred-@'Lerm@@ed level, liqu:@d level con,roiler GO assumes a closing pos;tion to catise air pressure to ac'@ivafe th@- diap-hr-@g@-ii of control valve 52 to throl@tle tb-e discliarge of air in p;p-- 50 from the 2,0 headbox, and to result in aii increase oi air pressilre v,,ilhin the headbox. Air pressure in ti7ie headbox do@,s not activa'e the d,'@aphra.-m valve, thp, mill air compressor system bein.- used for this ptirpos-.. As the sensing valve of co-@itroller 60 moves from a 25 posii-iO-.i, and in closing direction, it causes valve 52 to restrict the fow of pressure froni the beadbox in pipe 50. As the level of stock in the headbox derreases, the sensing valve op.-rates the a;r dis-.har.- c mechani@.m so that pressure with:@n the headbox is reduced. 30 1
