US1515614A - Method and machine for drying paper - Google Patents

Description

T. Ily'f. FINDER METHOD AND MACHINE FOR DRYING EAPER Nov. 1.851924 Frned Feb. z, 1922 2 Sheets-Sheet 2 l l l l ENToR T FzncZer ATTORNEYS 1 homogeneous thickness of the web. The

Patented Nov. 18, 19h24.

UNITED STATES PATENT oFFiCE.

THoMAs F. PINDER, or AnDMoRE, rENNsYLvAnIA, Assreno 'ro CHARLES c. oncU'rT, oF NEW YORK, N. Y.

METHOD .ANP MACHINE FOR DRYIN'G PAPER.

' To all 'w/om it may concern:

Be it known that I,` THOMAS F FINDER, a citizen of the United States, residing -at Ardmore, in theV county of Montgomery, State of Pennsylvania, have.. inventedcertain new and useful Improvements in Methods and f-Machines for'Drying Paper; and I do, hereby declare the followingtoxbe a full, ,clear,'and' ,exact description of the invention, suchas will enable others skilled in the art to which it appertainsfto make and usethesamej.:

My'invention is an improvement in methods and machines 'for' drying paper, and relates Iparticularly to -methods and machines for drying the heavier grades of paper". FIn present methods of 'paper making,.evapora tion is relied upon to' remove the `excess moisture. Obviously suchmoisture cannot be removed except at the surface of the .paper web and it must travel to the surface by way of the pores of the web. Inl some grades of paper, namely those which are relatively thick, such for instance; as paper a plurlity board, the web is composed of' of layers, and the pulp fibers of each layer are interlaced and intermeshed with each other. The fibers of adjacent layers are not, however, so intimately interlaced and intermeshed. In making @such paper, suc--4 cessive layers of pulp, more or less compact, are superposed, and the iibers ofthe several layers are in effect distinct from those of l A Aiin. Figures 1 and '2, I providea casing 1 .of sheet metal, of considerable thickness,

adjacent layers, merely lyi-n alongsidesuch fibers, without being inter aced or intermeshed therewith. In paper so made, the fibrous structure of the web is not of a character throughout the continuity; of

the pores, that is of the cellular structure of the web, is interru ted between the layers,

and the travel of t e moisture to the faces of the web is checked and hindered-atfthe abutting faces of the adjacent layers. Hence,

a'- large amount of heat 'is necessary to dry the paper, and th finished product is not so uniform in texture and moisture content as is desired. Cempessionf'of the web to express the moisture can' be carried only to a certain degree, and only a relatively small amount of moisture can be expressed at any one operation.. `As soon as the pressure is relaxed, the web becauseof its`natural resiliency expandsyand a large amount of the expressed moisture is reabsorbed.

In the presentI invention, I provide a method of drying, wherein compression and evaporation are alternated, the paper web .being subjected to recurring compressions,

whereby to express only such quantity of moisture' as may be quickly and completely evaporated before/any considerable quantity thereof is reabsorbed, and before the web is again compressed. I subject the paper .-web, to what is,-.in effect, a kneading opera-,

tion, therebytowork the moisture fromjthe 'center of the paper toward the surfaces where .it may be easily evaporated, and I so 'treat theweb prior to compression, that -the contained moisturefis of a temperature such that when expressed it will quickly" evaporate, and may be expeditiously removedwithout the necessity'for reheating,

showing another `embodimentlof the invenv tion. In the embodiment of the invention shown and preferably of a size to enclose the pit 2 in which the usual construction of dryer is arranged. Within this" casing, which` is closed at its top, but open atrfits bottom, I arrange a series of dryer units 3, three in the present instance, eachin the'form of` a casing rectangular4 in. cross-section. The units are supported one xabove the other, in spaced relation, and each has openings 4: at its ends .through which the paper web indicated at 5, may pass, to traverse the casing. An endless belt or 'apron g6 is`so mounted with respect tothe casing, that the-upper 'run thereof will pass thrqugh the casing,

the lower 'run' being below .the casing. The

,endless apron is supported at its ends by rollers 7, and intermediate ts ends by series` ing, and below the casing, respectively. The rollers 8 support thupper'run'of the apro/n,

and the rollers 9 sup ort the lower run, and the belt is preferab y of Iforaminous material,`as for instance, wire mesh. Abovepairs of either series, it will be held parallel with the upper runs of the endless aprons. In the present instance two series of coinpression rolls 10 are provided, so that the paper web is supported in-ive horizontal runs, three ofwhich pass through the .casings, and two above the casings. A suction .box 11 is arranged at each end of each cas-l ing 3. Each of the said boxes is pf usual construction, having a slot in its top extending transversely of the 'direction vof travel of the web, and having suitable exhaust mechanism connected with the bo`x. The paper 5 enters the casing 1 by way of andopening 13 from the press rollers 12 of the paper making machine. An endless belt 11*L of perforate material is mounted in such manner that its -up er run asses over the slot in the suction ox, in t e-direction of travelof the paper, the belt being supported b rollers 11", and being driven by any suitable mechanism connected with one of the said rollers.. Preferably the'belt is geared totravel a little faster than the movement of the paper. AAfter leaving the last casing,

the paper passes between compression rollers l10 of the lower series, eventuall7 leaving .the

casing 1 through an opening '14. Suitable heating means is arranged within each of the casings 3, the-said means being indicated at 15, and the heating. means is arranged above and below the web, so that it will simultaneously heat both faces of the same. The tem rature in the casings is in the neighbor ood of 600'o F., and in its passagethrough the successive casings, the web is thoroughly heated, but in a saturated atmosphere, thus bringing the contained moisture to the temperature of evaporation, .while at the Sametime preventingsurface drying of the web. Because of t-he obstructedvcapillary movement of the moisture inthick webs there is great liability to surface drying. After the web leaves the last casing 3, it 'is subjected to the action of dry heated air, which is circulated. in close proximity to the rfac/es of theweb, and while it is so subjected t0 the action of the warm dry air, it is gompressed at'frequent intervals to, express a' quantity of moisture such as may be readily T evaporated before the webais againcompressed. 'Thus the )moisture is removed by alternate compression and evaporation.

' Means is provided, for circulating dry heated airthrough the entirecasing 1, the said means com rising an inlet header 16, having branches 1 communicatingwith thel casing 1 at the level of the series of pairs of rolls 10. The moisture laden air is withdrawn the casing 1, and at the opposite side Jfrom 10 the header 16. The circulation of air is transverse to the web, and the branch pipes 17 are so arranged that the circulation will be about the same at both faces of the web. The rolls l0 are driven from a line shaft, indicated at 19, through belts 20. These belts connect pulleys ony the line shaft, with pulleys on the rolls. Each pair of rolls is driven independently of the other from the line shaft, and there is suicient slip in the belt to prevent puckering or wrinkling ofthe web between the pairs of rolls. Doors 2 1 are provided in the rear wall of the casing 1, for permitting access to the web above the dryer'u'nits, and these doors are preferably spring held in closed position. The air which is circulated through the casing 1 need not be highly heated, a temperature of approximately 140 being sufficient. The operation of the device is as follows The paper passing from the press rolls enters the casing 1, and passes in succession through the dryer casings 3. Gradually the Itemperature is elevated to a high degree, but

in an atmosphere saturated with moisture, so that there is but slight evaporation. As the web leaves the casing of the last dryer, andas it passes from casing to casing, it is subjected to the action of the dry air circulating through the casing 1, and this air is in the best possible condition to absorb moisture. l

In Figure 4, an embodiment of the invention is shown wherein the heating 'is done on the usual dryer indicated at 22 and composed of a plurality of drying cylinders. These cylinders are arranged in the usual pit 23 and the casing 24, which corresponds to the casing l1, is mounted over the pit. Within the casing 2li-a plurality of series of pairs of compression rolls 25 is arranged, in a similar manner to the arrangement of Figure 1, and b tween the series the web is guided by press rolls 26. The casing 24 is similar in all respects to the casing 1, having the circulation pipes for circulating dry heated air oyer the paper.

In the loperation ofthis embodiment, the paper web 27 passes from the press rbllers 28 of the paper making machine, through the dryer 22, where the web is heated in a' saturated atmosphere. The atmosphere it the dryingcylinders 22 is always saturated with moisture,`because of the evaporation from the paperon` the cylinders. Fronrthe dryer, the paper passes between the pairs of compression rolls, where it is subjected to recurring compression in (the presence of dry heated air, circulating in close proximity to y i that the top of the belts 11a ture.

scription, that the paper web is subjected to what is, in effect, a kneading operation, the web being alternately compressed and relaxed,-thereby to Work the moisture towardl the Asurfaces of the paper.

As rapidly as the moisture reaches the surface it is evaporated, and the kneading operation eventually eliminates all of the excess mois- The process comprises essentially, lirst raising the temperature of the web and its contained moisture to a relatively' high degree, in a saturated atmosphere and afterwards subjecting the heated web to an active circulation of dry heated air, while' kneading' the paper to work the moisture to the surfaces, where it may be readily taken up by the Warm dry air.

It will be noticed that when, in the present method, the paper web'is subjected t`o compression, such compression is equal on both faces, and there is no bending ofthe paper such as would tend tofseparate the fibers andiweaken the web. In the usual other than 1s necessary to change the direction -of vits travel, when the reached a condition of dryness su vstresses will be set up.

The compression squeeze rollers 10 lare just suiiiciently heavy to gently massage and knead the web, squeezing .and working the moisture from the center to the surfaces, to insure equal drying .throfhout the entire web, without crushing the l bers on .the two surfaces. The provision of the suction boxes and the tension rollers maintains thepaper at all times free from strain due age, the paper being held just sufficiently taut to prevent wrinkles. It will be noticed are arranged at a lower -level than the plane of the paper run, so that the paper moves downward onto the beltsof the suctionl boxes. rollers 11 paper has c that such arranged outside of the suction boxes constrain thepaper to move in this manner, and prevent release of the web from the suction boxes. -A gentle vaction is the suction boxes tending to move it in the direction of its travel, but therey is no tension strain as would be the casev were the web nipped by rollers. It will be obvious that instead of a plurality of independent casings, the web.

be run through'a single casing, in

The guide a plurality of runs, all of the heating in the saturated atmosphere in such case being done in one casing.

I claim:

1. The method of drying paper and the like, which comprises heating the paper to a highV temperature in a saturated atmosphere t0 prevent surface drying, and after- War s removing the moisture from the paper by currents of dry heated air at a lower temperature.

2. The method of drying paper and the like, which comprises heating the paper to a high temperature in a saturated atmosphere to prevent surface drying, and afterwards removing the moisture by currents of dry heated air, and subjecting the paper'to recurring compression during the circulation of the air.

- 3. The method of drying paper and the like, which com-prises heating the paper to a high temperature in a saturated atmosphere, removing t-he paper from the atmosphere and then circulating dry heated air in proximity to the faces of the paper, while subjecting the paper to,`recurring compression.

4. The method of drying paper and the like, which comprises heating the paper to a' high temperature in a saturated atmosphere, and afterwards .subjecting vthe Vpaper to successive compressions sufficient to express moisture therefrom at a relatively low temperature and with active circulation of'- the heating medium.

5. The method of drying paper and the like, which comprises heating the paper to a high temperature by means of a heating medium with restricted 'circulation and afterwards subjecting the paper t0 successive compressions at a relatively low temperature and with active circulation of the heating medium.

6. Apparatus for drying paperand the like, which comprises means for heating the paper to a relatively high temperature in a saturated atmosphere, and means for afterwards'subjecting the paper to' recurring compression in a dry atmosphere.

7. Apparatus for drying paper and the like, comprising means for heating the paper, t0 a relatively high temperature in a saturated atmosphere, means for afterwards circulating air over the surfacesv of the paper, and means for subjecting the paper to recurrin ture towar the surface.

8. Apparatus for drying paper andthe like, comprisin means for heating the paper to a re atively high temperature,

compression to Work the moismeans for restricting the circulation of air while the paper is being so heated to provide a saturated atmosphere, means for afterwards subjectinv the paper' torecurring compressions ereby -to work the moisture to the surface, and means for circulating dry air over the paper while itis being compressed.

9. Apparatus for drying paper and the like, comprising a closed casing through which the paper is passed, means for heating the casing, and a plurality of series of pairs of press rolls outside the casing through which the paper is passed, to subl ject the paper to recurring compression.

10. Apparatus for drying paper and the like, comprising a closed casing through which the paper is passed, means for. heating the casing, a plurality of series of pairs of press rolls outside the casing through which the paperis passed, to sub'ect the paper to recurring compression, an means` comprises heating the paper to raise the temperature of the contained moisture LwWell above the boiling point, and afterwards drying the paper in air having a lower reg-r ulatedtemperature. p 1

12. A method of drying (paper, which comprises heating the paper`in a saturated atmosphere to a temperature well above the boiling point of Water, and afterwards dry- 1 ing the paper in air having a lower temperature.

In testimony whereof I aflix my signature.

THOMAS F. FINDER.

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