US2460042A - Method of making cockle paper - Google Patents

Description

Jan. 25, 1949.

s. B. STAFFORD METHOD OF MAKING COCKLE PAPER Filed Jan. 13, 1945 5%}: Han BSTQHQWL Gttomeg Patented Jan. 25, 1949 ice B rton-Cnrnq tim, pr e ie r Mass, a ..eormnafibnofMass ts ApplicationfJanuarir-13, 1945, Serial No. 572,711 teams. (01. iii-+11) .1 inventio r la e t atmethcrl oi m kin wels -Pa erer eo lsl a e ha been-"m denb aak plume eo kle b izi asi mg4 9 a panel" Web ifed eentinuous y from a su ly T011": and-there fte 19% thi W bpmere s dr hrou a dry n her-wherein the paper is hung-in festoons on erosshars or so-called stiekswhieh are meved for- V wa d me hani ll afte th nap h bee un ethereen -'l?he-wet pa e -han wi h the $1111 Meightpie eh loo sus e d dfro -th a i n where ere s biee edl t di p q thepa e e d b ut-out'ans carde :Ehi e uire -tu pa e i t i a e heet and ns in h m and csgrting I out. the defe tive mark ereafter the rejeetedsheets-are a ga asrnaller size and inspected and sorted-once'more. involves not only' a hi h labor charge but particularly aver-y largewaste of paper.

It has also been attempted to dry that sized paper passing itback and forth over 'a-series elf-positively driven'rolls, but, these rolls-put tension Orr-the :paper whichtend'to pull out the eoekle-efiect and thus-to smoothcut the paper. The cockleappearanee is caused. inv part by the uneven, shrinkage of the paper pulp fibres whereinn they tend to curl andmove somewhat durin 'the-.;drying operation, endthis is neateriallzs"v aided by he sizing Which-in shrinkage-tends to distort thepaperinto a bumpy and locally wrinkled apggearance It is found that any attemptatmaking eeekl ap -b -method twhicn pu te sie nthe paper st in inwet st e t nds to.:. royh. eeek esl-izeee ii n an thu defea th pr m ry ab Ml ee 1m s hi inrentiqe-i iem ke re b i en een' ln t eape w th a suitable sizing and then drying the paper under sueh eonditions that, it isnot subjectedto amate- Fia ee d e sio an t ee teq -withsupth dryin (aera on ml i i d o d-:0ck1e;- fie a;-P dwitho A a aa Eurthe p le swfl e ap arm-inthe ellew ee s e nr @3 to-the draw n ,a arethe illus, tsetse-"e reie re mnstru tion ape leof-earryla eutmr me eda h e Fig; 3 iss-ravverticalgtransverse;sectiontakens-ubst t ll-y-en the ine .3.--,3 of Fi In accordancewith my preferred method,=a web of paper is, treated with a suitable animal or vegetable sizing material, sueh-as;g1ue,- st arch,

a, oonvertedystaromsoy bean- Vflour, casein, .a syn-' thetic resin, various: cellulose; derivatives ormixtures ofthese, or other suitable adhesive coating materials inaan aqueous or other suitable evaporable. medium. This sizing-may be incorporated in, or applied tothe, paper in various ways, such asby sprayin or flowing an aqueous-suspension or solution of the. sizing on the surface of the paper. But I; prefer to impregnate the paper -by feeding a vveb ofpaper lllprogressively from ya I supplyroll-ll or other-suitable sou-rcethrough a sizing bath lz of anaqueous'solution of starch and gluein-eny;desiredproportions held in a vat Band thenbetween massive pressurerolls l4 arrangedabove the vatwhioh remove the excess'of sizing: and Squeeze the rest into the paper. These rolls serve also to draw the paper forward- .from the supply roll at auniform rate andxthus present it "progressively for the drying step. The paper strip isheld beneath thesurface: of the sizing by a-roll l5.

In, the drylng-zonethepaper is dried in a horizontal position by suitably applied heat, and" is movedforwardunder a controlled light tension. It may he moved by a suitable-conveyor, such as the ladder type endless belt conveyor I6 which may-vslipzrelative to the paper as it frietionally ,=;rips the. under surface thereof and thus not mark the papenmaterially. In the preferredarrangement the paper issubjected to a heated air cur rentwh lethusmovins; nd th air-maybe reetedvagainstgthe under side of the paper to give a-huoya-nt eitect that materially reduces'the stick marleing and thepressure: 01: contact of the paper on heeonveyon ;The:.-buoyantair current,-which ngayesuchgaste-float the paperstrip partially or.suhstantially fully, is derived from aniair duct [8 arran ed: below onerunofthe conveyor; The .PQ DQI'aPQSSess through the drying zone in a substantialy'flateand' horizontal :position and under aminimumtension. It. then travels .over a-set of guide rolls l9 ands-20 which provide enough tenSiDn-inthe-idrypaper so it may be satisfacte fll Wound A on "ya! suitably driven winding spool ;,g1oi,1i' nthisswlet condition through the drying gzpne. an exaessiveten-sion would tend to break This space is formed by the upper perforated wall 30 of the duct l8 and the lowerp'e'rforated wall 32 of a further hot air duct 33. An impervious top wall 34 and suitable connecting side walls complete the upper duct 33. Thelowefduct I 8 has a solid wall 35 for its bottom, and suitableconnecting side walls. The lower run of thecconveyor l6 passesbetween the wall 35 and a lower horizontal wall 36 spaced therefrom. Side walls s1 and end walls 38 provide a substantially closed chamber for the dryer. The paper enters and leavesrthe drying chamber through theopenings 39 in theendwalls.

Heated air is conveyed to the upperand lower ducts" l8 and 33 above and below the run of the paper l0 by means of ducts 4B throughwhichair is blown by means of a-su itable driven fan 42 arranged to draw air through a heating zone, such as over a set of steam heated pipes 43. Although the air may be recirculated, it is'shown as coming from the outside atmosphere through an opening 44 in the wall of the heating compartment. The side ducts 40 receive heated air from a common duct 45 connecting with' the fan chamber, and they project laterally and then upwardly on each side of the drying'chamber where.

they communicate through lateral ducts 46 and 41 respectivelywith the lower and upper spaces I8 and 33 for delivering the heated air to the paper. 3 These various passages and compartments are suitably arranged so that the heated air is forced to travel only through the openings inthe perforated walls'3flan'd' 32 into contact withthe paper 10. The heated air may be exliausted to the outside atmosphere through ducts In order to adjust the relative amounts oi heated air passing into the upper'and lower ducts above and below the paper, I provide a pivoted flap damper 50 at the junction point between the smaller ducts 46 and 41, and this is controlled by an outside handle 5| or other suitable means.

Figr3, the damper may be moved to a position where the major portion of the air goes into and through the lower duct [8 'andthus against the underside of the paper. 'In the latter case, the pressure of the air beneath the paper tends to iioat the paper above the conveyor l1, and the air issuing through the top wall 32 does not provide. enough pressure to force the paper downwardly to a material extent.

I The paper may be conveyed through the drying zone under a minimum" of tension'by the construction illustrated, in which the conveyor 16 is I formed of cross bars or sticks 54 shaped ashollow metal tubes. A shaft 56 fits into each'end of the metal tube and the outerend of each shaft is a bearing support for a roller 51. Each roller 5'! at :.theupper run of the conveyor rides on the rail 58 4 suitably carried by the walls of the drying apparatus. A further rail 55 supports the lower run of the conveyor. Chain links 68 connect the shafts 56 at each side of the rollers and thus form an endless jointed ladder type of conveyor as will be apparent. This endless conveyor is driven by any suitable construction, suchas the two pairs of gear shaped wheels 5| mounted on cross shafts 62 that are suitably driven, as by means of a pulley and belt drivefiii connected with a source of power. The drive gears 6i have teeth so spaced as to engage the rolls 5'? which. carry the cross bars 54. V

I may also provide a supplemental carrier for the. paper at the exit end of the drying zone which may either cooperate with or replace the endless carrier above described. This supplei .ental carrier may comprise an endless belt made of felt or canvas or other suitable material mounted on and moved by two rollers 63 suitably driven by power mechanism. In the construction illustrated in Fig. 1, the paper ill is shown as passing in a loop beneath that belt and not conveyed by it. But the paper may be fed across this endless belt 65, and because of the frictional grip of the belt surface, the paper will be gently pulled along. The belt 65 servesprimarily when the paper is fully supported on the air currents derived from'the air duct l8. In that case, the paper is movedthrough the drying zone without an unnecessarily high tension which would serve to break or injure the paper or to pull out the cockle thereof, since the only tension required is that slight amount required to hold the ends of the paper against'the force ofthe supporting air current and to. move it along. Thisfrictionless support and conveyance of the paper can be delicately controlled so that very thin paper may be safely transported and dried. V

In its mechanical operation, the construction as thus described, serves to draw the dry paper from the supply roll I! through the sizing bath 5? and thence between the power driven pressure rolls M which press the sizing material into the fibres and pores of the paper and squeeze off any surplus that does not impregnatethe paper. Then the paper is drawn gently forward byrneans of the frictional grip of the cross sticks or bars 5 of the endless conveyor It as it is subjected, to the. hot air currentsirom ducts l8 and 23 arranged above and below the paper. In order that variations in speed of the supplemental winding apparatus may not place any tension on the paper, the paper passes in a long self-supporting loop from the exit end of the drying apparatus to the ro1lsfl9. As soon as the paper is fully dry, it may be wound on thespool' 22 without destroying the cookie, and the tight roll will keep out moisture'and insure that, the cockle will remain until the paper canbe cut into sheets andthen Wrapped in required sizes. V

A substantial portion of theweight of thepaper is supported on the air currents issuing from the lower air duct I8, but the paper remains in sufficient contact with the top run of the endless conveyor I6 so that the cross bars a will have sufiicient frictional grip on the paper to draw it gentlyforward through the drying zone. The endless conveyor is driven at a speed materially greater than that at which the paperis to go through the drying zone, and the cross bars 54 will therefo're'slip frictionally against the paper and so leave no visible stick marks The contact between stick and paper is so light that no marks are left even if the paper is wafted'on theheated einmneumntezemrsut .srscontaetmsthsthezernss we constructinm ff wijdniy tissue;

the dryer ibejvaried smore-eor-ilesS'; in dil'maysbelfoot the-weight f emer waterricontamed nyi-t:andrithertypeeoficoclrlesde shied. may

of the paper will stay at the wet: bulb-temper tuteofi somewhere z-between 1360 and-- 120 P :F ant :a'veragevcase. TREK-"3G8" reachsthatemperatureior:2 or sari-steam midi-1 80i is not :i-zrim'ed he dryi g process: ems qthesrate-of-gdryingq annual may be ndtedithat although, "the ;air ateenpenatuseimayiheiafiof rettthestemperature their-ate a. which. thepapempassesthmugh the-dryerqqr:byanakingthe diiterent hwn-idities: and; ztempenaturesg nay .be

.proavided bmprovldipg tween more; s jparate' sets-er inlet. ducts. and 4,1 and, it desired. separate sources ot heatedzaino selectedtemperatureswhich serveto: .introduce.a g ofdesired 'characteristicssat .differ-tent sipoints'. along. a=thee'xtent of .the drying chamber. Suitable instruments be -e p qycdrtormeasurezthe dryness of the paper and thus to indicate a proper control of the humidity. It will also berneten =thata uritheaecnstruction illustrated, the paper is subjected -.to a. "radually incrasedte'xnperatureas"it approach ducts l6 and 41 and thereafter toa temperature. menswear tem. 1 be controlled byfans to regulate the'ILhum-i'dity as. well. asstemperature of the air ithrou'ghollteithe drying zone. 1

When the paper goes to the drying one from the sizing'bath, it may contain about; 42% of moisture, but this is only a very slight amount of water due to the thinness of thej 'paper, and it is readily evaporated. It is desirable to dry out the water between the paper fibres but to leave the fibres with a normal moisturecontent.

g-iye-=a;,desiredlcontrolled drying curveteammatee "high; de o coc sle to :th ;.mne dry-inesta e; hen e the: ond oner: dryin the leaner whileitissubstantially g and; while it :isunder; only a, sli h 1510 1 3 litothe product of-a supe ior p oduct alsoice observed that the proportions of: Elna bath as well-as the nature f the in-.

gredientseuScdvmay-be varied widely within the knowled e zthoseslr d n t artlihe ross :bars 54 do not impart material-1 tepsipmfio the Wet paper; since the paper is-supe ported-t. .asubstantialextentby the air currents from the sta gered: holes in the lowerwall as the paperapartially floats or waves abovev conveyor; Oriits pressure thereon is reduced, th rossbarsanove-alongrelative thereto as they; draw. thepaper jforward and this sliding; move ment FdQfiSrliOt leave detrimental marks. The bars move only;;slightly faster than the paper so:

. thepcross, sticks-slide only a slight distance, suchas a little morethan the spacingbetween two sticks,- pd-thus give a uniform appearance t as isproduced' by the slight 51 310- tie al. sliding contact. The operator of the machine: may vary the float, condition of the. pa er by moving the-damper 50. In fact, the :may rest.. lig;htlyall of the time on the Qro s-. l1ars,iliut{because of;-the very lightfrictional {engagement with the paper, the 'bars will linrelative thereto; andany marks causedby til ores barswillbemade substantially uniform atqliigrtheszlength; oi the paper. Hence it will-not be. v.Hecessawt cut out. the stick marks W 1 have -.herelio;-;cr.eated such a loss in the total am. nto the final-product.

fi neepthe paper is held substantially fiat and; horizontalaas; itpas'ses. through the drying zone the tension onthe paper is only'that which is. reguired: to. pull it; along in :a horizontal position. dlsohthefl paper is-not. supported on the cross. bars to six-chair extent that it will sag between them so-fermiestoons or loops. Any such would prevent slippage of the cross sticks, EA-and. se-would ave marks where h paper f;v

the-parseandy t mpa t.sufi i t fr io l r n thereo 439 38. that. the paper will move along.

The total dryness of the paper is preferably about 3%, and it will ordinarily be in the {neighborhood of 2% to 5% by weight of totalfinoisture, which represents a dry condition lsuificient to hold the cockle in the paper. This a dition of dryness of the paper is 'to be emphasized, since the paper must be substantially dry or in such a condition when it leaves the dryin game that the cookie will not be pulled out materially when the paper is thereafter subjected to tension, such as is involved in a winding operation, or in cutting the paper by knives and while under pressure. Some of'the cookie is lost or -.converted to a more subtle appearance during thesetnsioning and pressure stages, but such" hahge does not aifect the. utility and market y of the paper. However, because of this su sure or tension stage, it is all the;

through the drying zone. =is omitted, then the paper will pass over the belt 65, and because of frictional drag on the If the conveyor l6.

very dry paper at this point, the belt will not injure or mark the paper but will give a desired tension to move the paper forward While it is entirely supported on the lower air currents derived from the duct [8. Because of this method of fully or partially floating the paper while it is drying, I may dry it at a far greater speed than heretoforefeasible. It will also be understood that the ratesof movement of the feed and pressure rolls l4 and of the wind-up drum 22 and the associated rolls are suitably coordinated to insure that the paper is held loosely after it leaves the drying zone and so does not tend to impose undesired tension upon the drying paper. The wind-up roll may be run at a slightly slower rate than that of rolls I4 so as to compensate for shrinkage in thelength of the paper.

It will now be appreciated that my method comprises impregnating a paper strip of desired weight and texture with a suitable aqueous sizing and then drying that paperin a substantially horizontal and fiat condition to dry the paper and associated sizing under such controlled temperature and humidity conditions as to procurrents from beneath andpreferably also from above, and these air currents may be so proportioned as to providea buoyant effect that tends to support some of the weight of the paper, and this buoyancy'may be such as to insure that the paper floatssubstantially fully during at least the first part of the drying stage Where the paper is wet and weak in structure. Since'the paper is held in this horizontal position, only a sniall degree of longitudinal tension is required'to move it lengthwise through the drying zone. This forcerequired to move the paper may be dis-- tributed throughout the length of the drying zone as is the case where the paper is moved forward bythe cross sticks of an endless laddertype conveyor. Where that conveyor is employed, the paper tends to lag behind the sticks and' thus the sticks slip along the under side of the paper and do not leave noticeable marks. If the paper, is fully floated on the heated air current, then it is dragged forward by a suitable device engaging the paper after it has been fully dried so that this propelling mechanism will not destroy-the cookie. 'It is desirable that the paper be dried to a total water content of not over by weight and preferably less so thatthe cockle condition will not be materially destroyed during subsequent operations, such as slipping the paper into narrower strips or winding it in a roll, but wide variations may be made in temperature control depending on the requirements of the papermaker. The heat for drying the paper may be obtained from any suitable source of conductive, convective or radiant heat, such as" infra red electric light bulbs or other heating devices located above and below the straight run of the paper in the drying zone, or such devices may be installed in the heating chamber where the steam pipes are located, or as desired-.'

Various modifications in this process will now 8; '1.Tne method of making cockled paper comprising the steps of providing a strip of paper which isimpregnated with waterand a oockle stabilizing sizing, progressivelymoving the strip forward through a drying zone in:a substantially ilatand horizontal position with the under side of the paperstri'p located above aseriesof cross sticks moving longitudinally forward in a. paper supporting position,blowing against, the underside ofthe paper and upwardly directedbuoyant currentof 'air' which prevents the paper from adhering locally to and looping between the cross sticks, while controlling the rate of paper movement at bothsides of the drying zone and maintainingthe paper under only suicient tension to move it forward without destroying the cockle, and evaporating the water progressively and shrinking the paper and causing the sizing to stabilize the cockle. l

2. The method of making cockled paper comprising the step'sof providingawet strip of paper impregnated with water and a cockl'e'stabili'zing sizing, progressively feeding the paper strip forward into, through'andoutof a' drying zone in a substantially horizontal and flat condition with theaid of traveling cross sticks there beneath 'moving'longitudinallyforward faster than the strip and which frictionally engage and slip relative to the underside of the paper strip, while supporting a part of the wet weight of the strip on a buoyant current of heated :air' projected upwardly between the sticks and against theunder side of the strip and subjecting the-strip to onl that light surface frictional contact with the sticks and a longitudinal tensionwhich is sufli cient to move the partially floated paper horizontally without destroying thecockled eiiect, and evaporating the water and shrinking the paper and thus causingstabilization of the cookie by the sizing remaining therein.

' STEPHEN B. STAFFORD.

REFERENCES The following references are of record in the me of this patent:

V UNITED STATES PATENTS Number Name Date 1,951,004 Willis Mar. 13, 19.34:

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