US1674848A - Method and apparatus for finishing paper - Google Patents

Description

June 26, 1928.

S. W. WEBB ET Al.

METHOD AND APPARATUS FOR FINISHING PAPER Filed March 22, 1926 2 Sheets-Sheet l l.Hume 26, 15928.'

s. W. WEBB ET AL METHOD AND APPARATUS PoP PINISHING PAPER Filed Maron 22, 1926 2 sneetssheet 2 Vr l JI 'Parenteel im@ ze, reale.

STUART W. WEBB, OF BROOiKLINE, AND JOHN G. CALLN, OF CBRIIJGE, MASSACHU- ASll'llTS, AND ALBERT ALLEN, OF BANGOR, MAINE, ASSIGNORS TO EASTERN MANU- FACTURING COMPANY, OFiBO'STON, vMASSCHUSE'JE'IS, A CORPORATION OF MASSA- cHUsErTs.

i umrrionl AND APPARATUS rola FINIsHrNe PAPER. i

Application led March v22, 1926. Serial No. 96,507.

'paper is passed-between two endless fabricl belts through the nip between presser rolls and is intended to be used in connection with a machine for this purpose in which one of the rolls is relatively hard and the other relatively soft asset forth in Patent No. 1.277,714 granted September 3, 1.918, to` Eastern Manufacturing Company as assignee of Henry J. Guild `for method and mea-ns for .finishing paper.

The purpose of the present invention is the production of linen marked orv other fabric marked paper of surface more exactly simulating orduplcating that of paper finished by the' Well known. processof plating or even eXcelling it in those qualities recognized in the trade as defining a plated paper vof the highest gra-de.

In order to understand the nature and operation of the improvement-s herein described, it is necessary to know something of the character of the fabric-like marking that distinguishes platedA paper Vfrom other fabrie marked paper, such, for example, as embossed paper, or as weve paper which still shows the. wire mark.

For antithesis the two last named examples of fabricmarkfng that are not Vplating will be descr.' bed first. The wire mark i on pape-r is dueto thelwet paper stock de` positing on the wire gauze of the Fourdrinier wire or the cylinder mold as the case may` be,:like snow over slightly irregular ground,

leaving more' stock in the hollows and less onlthe elevations, so'that not only the thickness, Vbut the amount of paper material varies minutely from point to point of the lsheet due to this cause. In the case of an embossed sheet one of the .embossing rolls `that produces the effect has engraved upon it av likeness of a fabric sheet in cameo,

and the othera' conjugate likeness of the same sheet in intaglio so that the paper is slightly raised on one side at the same point, and in the same degree, that it is de- Y, pressed on the other. Thus there is a right and a wrong side, one side bemg the inverse of the other. .The embossing Vprocess does not change'the thlckness of the sheet .from vpoint to point, but only its surface conformation. Because of this, the pattern is not defined in lines of varying tran-slucency visible on looking through, as described next Yin the case of plated paper.

All plated papers have certain characteristics in common, and good plated papers are vdifferentiated fromfpoor ones by the degree and. relation of these characteristics. ln all cases the plated paper 'is marked by being heavily compressed between marking members madec up in one or another way of fabric-commonly of linen. rlhere is no right or wrong side. The paper is unevenly compressed in a fabric-like pattern by the woven fabrics on its two sides; where fa thread on one side registers with a thread on the other, the compression is maximum, and conversely, where al space on one slde registers with a space on the other it is minimum. `Heavy threads and particularly the varying compressiondueto random registratiop of threads and spaces give-a desired irregularity. llhe paper is not merely embossed, but actually varies in thickness and inversely in density from point to point, but so far as the result of plating action -is concerned, the amount of stock should remain the same at all points.

ln the standard` and well known plating l process, where the linens used are of single ply and sheets of znc are interposed between theV linen-paper-linen units, a maximum of d'efiniteness ofimpression results and the,

paper is called lawn.. A blurred eect used on regular linen finish may be secured by piling, say, eight sheets of paper alternating with nine sheets of linen--commonly two-ply-into a pack before interposing the next metal sheet. An ideal-lawn paper hasv a surface of somewhat more than an eggshell gloss, but not shiny, this gloss being imparted by the slight repeated slip of paper on linen inthe pack. rlhe surface relief is appreciable, but appears to be much greater than yit actually is, for the reason that the traces lvof threads that chance to register with thread 4traces on the op oste side are rendered darker to reflected ight, and. converselyY more translucent, by Acompression ofthe fibers into contact and partial optical continuity, the optical eHect being the same whereby white opaque snow may be compressed into a dark,translucent .cable only tothe cheaper grades.

ice-like mass. This irregular weave inter-A the fabric pattern is seen to be clearly though irregularly ydelineated by these line-s of varying translucency, which do not reproduce the weave of a single linen, but rather the thread superposition'of the two. lff two ply linens are substituted for single ply, the back linens have an effect, but a much Iless sharp one thanl do those in direct contact with the paper on each side.

Up to the time of the present invention the various processes for fabric marking a continuous paper web have produced papers that lack in various degrees the distinguishing characteristics of high grade plated paper, and they have thereforebeen appli- Some of the di'erences between best current continuous process finishes and best plater finishes,

y are noticeable onlv to one reasonably skilled in judging linen nish papers, but in the aggregate they determine a difference in selling price' amounting to many thousand'y dollars annually in the product of each machine; Our apparatus and process when constructed and operated as hereinafter described produces a finish quite indistinguishable from that of the highest grade of plated -v nary conditions, and in commercial practice paper for such machines has been prepared -for. finishing by ino-istening as by sprays mechanically or compressedair actuated or applied b-y'means of brushes. In all of the methods comlnercially attempted the`paper was given, or was allowed to retain, a percentage of moisture usually between 7 .5 and 8.5 of dry weight uniformly distributed through the. whole of the paper substance. Where sprays were used, and there was some "unavoidable initial streakiness, the paper was rolled up and allowed to stand long enough to insure absorption and 'equalization from pointi to point in the sheet and through the thickness thereof.

4Paper carrying some such degree of moisi ture has sufficient plasticity so that it receives on the belt machine a strong surface impression, and shows on looking through a clear fabric-like pattern, but in comparison with a first rateA plater lawn the finishI of even'the best of these papers made upon a continuous finishing machine bashed an ln the machine to which our improve-v ments directly apply, one of the nip rollsv which forcethe marking fabric into contact with the paper is of some such material as compressed cotton or paper, and the maximum specific pressure that can be applied to any point of the paper to be nmarked is limited by that which. can be continuously supported by this soft roll, and is for this reason considerably less than the maximum available in plating by the ordinary process; it is in fact not enough to give a sufficient mark on paper even of the soft linen grades containing so little as, say, 5% moisture; this weakness is considerably morev apparent if the paper has been previously calendered. ,Even if the total loading on the nip be greatly increased, the soft roll compreses, and widens the concave area supporting this pressure, so that the specific pressure at any point is not increased proportionately. Further, the total pressure cannot be carried up beyond a certain point, variable from roll to roll, without causing rapid'deterioration of the cotton, paper or other filling of the soft roll.

Paper moistened throughout its thickness by any of the procedures enumerated above to a point where it marks well` is thereby rendered somewhat limp, plastic and susceptible of a` sort of molding process under pressure. Such paper, when run through the unimproved continuous finishing machin-e, acquires a look through not very much different from that of plater lawn except that there is less of the slight general transluceney that is imparted to the look-through of lawn by repeated extremelyl heavy pressure on paper that is resilient rather 4than soggy. The surface, however, is much less satisfactory; the imprint of the fabric is in the nature of an exact molded replica of the surface of the ladjacent linen rather than an interference or coincidence pattern recording the weave registration of the linens on the two sides. rlhis lack of diversity or4 character in the marking is the main reason that has led to the characterization ofy such paper as mechanical, monotonous or dead in appearance. A very large amount of work was done and many samples and comparisons made before it became apparent that the difference was due to the fact that the plater lawn was marked primarily with a pinched-in interference pattern of the marking fabrics on the two sides of the sheet, with only a slight and occasionalfsurface molding sketchily reproducing the adjacent fabric surface, while the reverse was true of the belt-finished or continuous inish linen marked paper which showed on each side a faithful mold of the -sure in the continuous machine as compared tlf) with the plater, and the single pass in the former against usually two or four'in the latteread to less actual polish on the continuous finish paper, even from hard and soft roll machines which give some slip during the passage through the nip. lSecond, the close network of lines on thesurface of the continuous finish paper compared with the relatively sparsely marked surface of the plated paper gives the former an appearance of lesser polish even when, the actual ratio of specular to diduse redection as determined by polarized light test is the same in the two cases.

lli/lith paper moistened throughout to 8% or 9% the pleasing diversiiied pinch or weave interference pattern on the surface, even with the best possible belt construction, was found to be obscured by the monotonously regular; plastic reproduction of the surface weave of the adjacent linen. `With paper of 5% or 6% moisture, well absorbed, there is notable improvement in that the paper doesnot so fully hold the plastic surface mark, but the interference pattern also is less marked and with still drier paper there is no sufficient mark of f an kind, `though what there is consists of t e high points of an interference pattern.

'llhe best of this paper heretofore pro duced has had a good surface mark, but not a sucient polish for high grade llinen paper. lf supercalendering was resorted to, to increase the polish, paper suciently wet to receive the linen finish was found liable to blacken due to becoming compacted to translucency. While some remarkably good ysamples have been produced by thisl coinbinatlon of moisture and supercalendering it has been found commercially impossible to hold with reasonable consistency the distributed moisture content suciently uniform, low enough to avoid blackenin `in.

. the supercalender and yet high enoug to get a good pinchm-ark with the fabric after l being hardened in the supercalen;

Frther experiments have shown that moisture may be held in paper in various ways andthe-t the behavior of the paper is `much adected thereby. rlhe cookmg and A beaters. Paper that is'taken from the paper machine with a high moisture content seems to have a. part at least of its moisture in this state of close attachment or pseudo com- -binat-ionwith the fibers and the ibersvare rendered limp and plastic thereby. Conversely, paper that has been dried and is moistenedagain does not for a considerablen time at least, incorporate the water into the fibers in so intimate a relation and the amount of limpness and plasticity due to a given moisture content is less. Finally, our experiments ,indicate that ,for a few moments after water is deposited on d specimen of paper,rit resides upon the surface and'in the interstices between the fibers without at once adecting the resiliency or other properties of the fibers themselves, unless it is forced into them by great pressure. We have found, therefore, that if the paper on the per machine is dried to a low moisture content such as 4% to 5%, is thensupercalendered and afterwards the necessary additional moisture -is applied just' before the paper enters the finishing machine, it is possible to produce consistently and continuously a linen iinish equa-l to the best grades of plater lawn and having a similar market value. y 4

liu order to derive the maximum benefit from the procedure of the present invention, however, itis important that the ply of fabric directly contacting the paper shall be so formed that the individual threads are stid and hard while the interstices between them are unobstructed, since this brings the specie pressure of thread coincident lines higher for a given total pressure.

A satisfactory method of adding the i moisture content is by the use of a. steam box through which the paper asses 1mmediately before it reaches the mp between the finishing rolls, the amount` of steam being so adjusted as to supply sucient quan- Vtity of moisture so that the weave interference pattern prevails over the plastic surface mark in'about the same degree as 1n high grade plater lawn, and that the sur face is free enough from deeply marked re- '25' linen inish machine for getting pinch mark,

i (3) promotes plastic surface mark, so that in paper wlth excess of such` moisture the surface mark catches up with and obscures the pinch or interference mark, and reticu- .lates o-r c uts up the surface and obscures the polish. For No.2 linen, 4% is low, and 5.5% high.

Calendering makes the paper glossy, hard to mark, and indisposed to plastic surface marking. vdupercalenders differ so much that it is sutlicient to direct a skillful operator tocalender rather lightly, trying first with no weights other than the rolls.

Steaming develops susceptibility to pinch mark, without corresponding retention ofplast-ic surface mark. We believe that the supercially deposited water is squeezed in to suchv intimate relation with the fibers along the heavily compressed pinch lines as `to materially help development of optical continuity and translucency, but that the pressure elsewhere is not enough to bring about this effect in such degree as to determine much perm-anent molding of the surface. Whether or'not this explanation is correct, the results are as stated, that is,

steaming as'directed herein promotesk pinchv mark `more than it'doessurface mark.

For a more complete understanding of lthis invention, reference may be had to the accompanying drawings in which A Figure 1 is a side elevation of a paperd finishing machine embodying this invencated a stand in which is journaled in superposed relation three rolls 2` 3 and Il. Through the nip between the rolls2 and 3, which are pressed together with heavy pressure, 1s passed a pairof. fabric belts 5 and 6, one of these rolls, as 3, being relatively soft and the other being relatively hard. The belt 5 is shown as'passed about the roll2 past abelt? steering mechanism 8 and overl a head roll 9, the tension lof the belt being maintalned by j mounting the -roll 9- on a slidable carriage 10 l 'urged away from the stand lby means such as a weight 11 attached to al cable 12 passing,

about a pulley 13 and xed to the slide 10. .The belt t passesfpartially'about the rela?.

noreste tively soft roll 3 about an idlero15, a steerin device 16 and a head roll17 'llhis head rol 17 is mounted on a slide 18 which is urged away from the roller stand as by means of a wei ht 19 similarly to the upper slide 10.

'l e paper to be finished is shown as in a. roll` 20 and is led from this roll about a guide roll21, vertically through a steam box indicated generally at 22,y about a roll 23. and from thence is guided tothe nip between the rolls 2 and 3 between the confronting stretches of the belts 5 and 6. lt will thus be seen that the paper passes through the steam box on its way to the nips between the rolls 2 and 3and these rolls travel at a sufficiently high rate so that the time elapsing between the emergence of the paper from the steam box and4 its passage through the nip is very short preferably not over two or three seconds.

"lhe steam box itself comprises an outer casin proc ed wood, andwithin this casin ,tand spaced therefrom lengthwise thereo is a metal inner lining. This lining is shown as composed of a pair of plates 31 having their I lower ends bowed upwardly as at 32, as best shown in Figure, and their upper ends 33 converging toward the'outletopening for the paper. These plates 31 terminate somewhat within end plates 3 5 of the steamer, as shown best in Figure 5, so that steam admitted between them in the manner present-ly to be described ,may escape about their ends and pass between them and the casing by which means they are maintained hot so that after the first few minutes of operation the moisture from the steam is not condensed thereon. The outer casing 30 is provided witha slot 36' for the passa e of the sheet of paper into the steamer ang strips 37 along opposite edges thereof form supports to re- 30 which may be made of waterceive, the lower rounded faces of the plates 33. Extending wit-hin the plates above these faces and within the looped lower portions thereof are positioned the steam distributor pipes 40. Each of these pipes is provided with a longitudinallyv extending slot t1-open lIID ing into thespace defined by the lower curved portion of the corresponding plate 33, these pipes being positionedl substantially concen-` trically 'of these spaces. Positioned onl these pipes beyond the extremities of the .slot 41 lare collars 42 between whichl the end plates 35 are clamped. y

Arranged concentrically within the distributor ipes 40 are the steam mains 46.

.These-mams extend forwardly from one end only of the distributorI .pipes and are perforated at intervals as at 4:7 to permitl the steam Ato escape therefrom into the annular s ace between them and the inner faces of the distributor pipes from which the -stealn escapes throu h the slots 41 int the steamer with@ lill@ l) a@ 33. lt desired the du lation as may be determined by experiment.-

temete tributr pipes 40 may be so mounted as to The pipes 46 as shown lead to a main steam supply pipe 50. I l

In order that there maybe no drip of condensed steam which shall reach the lweb of paper passing up through the steamer,

,the entrance and exit openings for the paper ,are-1, partially closed off by heated members 'fetch asiashown in dean in Figure a. nach "'ofthese members 'comprises a main pipe 51 to which is fixed spaced 'E' ttings 52 which join through elbows 53 with a pipe 54`extending parallel to and spaced from pipe 51. 'llhe ends of the'plates 31 are preferably bent over to partially engage about the pipes 51 and 54: and the plane of the central axes of these pipes is arranged at such an angle to the passage of the paper that the paper passestherebetween and together therewith substantially seals the entrance and exit openings through which the paper passes. These pipes are connected'through pipe connections 55 and 56 with the main steam lines, and for the purpose of removing condensation therefrom, the opposite ends of the pipes 51 are shown as connected to the pipes 57 and lead to a suitable exhaust or condensation vdevice (not shown). Thus'the A paper passes between members which act to substantially seal olf the interior of the steamer but which are maintained heated so that there is no tendency for steam to be condensed thereon and to drip. onto the paper, the paper as itl passes through the steamer being supported by the Wooden rolls 21 and 23 and maintained in a substantially vertical .plane through the steamer. .Pref

erably the pipe 54 1s so connected to the pipe 51 as'to permit the angularityof the planes of the axes of these two pipes to be adjusted to suit the paper passing therethrough, the"v pipes on the o posite side of the web being relatively o set lengthwise thereof, permitting as closera sealing contactKA as may be necessary without actually causin contact to be madeA therebetween. At

6() is shown the steam exhaust which comture from the steam thereon which remains` on or substantiall .near the surface of the a er on both si es until such time as lthe nishing has vbeen accomplished. The amount of moisture distributedon the paper depends on the proportion of steam to air -the'air adjacent to the surface to be freed` from its moisturel which thereupon acts as `a heat insulator and prevents further condensation thereon. The supply ofvsteam is so adjusted by suitable valves asfto suiiciently moisten both sides of the paper equally, which is shown b absence of any tendency forit to curl. s soon'as it has passed through this steamer the paper passes to and through the' nip between the rela-- tively hard and soft rolls and between the fabric impression belts so that the desired fabric finish is nimparted thereto.

In order that the initial threading y of the paper through the steamer maybe readily eifected, means for drawing the paper through the steamer may be provided. -As

shown in Figures 2, 3, 5 and '8 this meansI may comprise an endless belt which passes through the steam space within the steamer and returns outside of the casing. rlhis belt is preferably formed of two layers of material as at liti, 67 which are stitched together at intervals at 68 to form loop portions which may be separated to permit the this invention, it should be evident to those` skilled in the art that various changes-and modifications may be made therein without departing from its spirit or scope as de.

fined by the appended claims.

We claim:

1. The method of yfinishingpaper which comprises surface moistening thev comparative y llc dry paper, and immediately thereafter subjecting it to heavy pressure between I finishing surfaces. i i

' 2. The method of finishing paper which comprises scalendering the paper while itv is relatively dry, surface moistening the paper,

and immediatelv thereafter subjectingit to heavy pressure etween finishing surfaces.

3. The method of applying fabric finish to paper which comprises supercalendering the comparatively dry paper2 subjectin the surface of the paper to moisture, an immediately thereafter passing the paper interposed between fabric surfaces through the nipbetween relatively hard and soft lsurfaced rolls.

ff. 'lihe method of imparting a fabric finish to paper, which comprises superficially moistening the paper, and immediately thereafter passing the paper between fabric plies through the nip between a relatively hard and a relatively soft roll pressed together under heavy pressure.

5. rThe method of imparting a fabric finish to paper, which comprises imparting a slight gloss to .the surface of relatively dry paper, superficially moistening the paper, and immediately thereafter passing the paper between fabricplies through the nip between a relatively hard and a relatively'soft roll pressed together under heavy pressure.

6. The method of imparting a fabric finish to paper which comprises lightly calenderinfr paper having a low moisture content, supercially moistening the paper, and 1mme'diately thereafter passing said paper be-` tween plies of fabric through the nip between a'relatively hard and a relatively soft roll pressed together under heavy pressure.

7. The method of continuously finishing paper with a fabric'finish, which comprises supercalendering the. relatively dry paper, progressively'moistening the lsurface of the paper, and immediately thereafter progressively subjecting the paper t0 heavy pressure between fabric surfaces.

8. rThe method of continuously finishing paper, which comprises progressively supercalendering the paper, progressively subv]ecting the paper to steam for a period of sufficient length to moisten the surface only, and immediately 'thereafter subjecting the moistened paper to heavy pressure between fabric surfaces.

9. The method of continuously finishing paper, whlch comprises progressively superremata calendering the paper, progressively subjecting the paper to steam for a perlod of sufficient length to moisten the surface only,

and immediately thereafter passing the paper between fabric plies through the nip between rolls of different hardness pressed together under heavy pressure.

l0. An apparatus of the class described,

comprising a. pair of rotary pressure rolls, a`

pair of fabric surface belts passed through the nip between said rolls, means for prethe nip between said rolls, means for presenting paper to be finished lbetween said belts to pass through the nip therewith and a steam box through which the paper passes on its way to said nip, means for directing steam into said box into contact -with the paer vand means for moisteninff the' surface of the paper before it reaches said nip.

12. In combination with a paper finishing machine comprising a-pair of rotary pressure rolls, one of said rolls being softer than the other a pair of endless finishing belts passed together through the nip between said rolls, and means to direct paper to be finished through the nip between said rolls between said belts, of an enclosure through which the paper passes on its way'to said nip, and means for directing steam into said enclosure into contact with both faces of the paper. g p

ln testimony whereof we lhave affixed our

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