US1550695A - Apparatus for drying paper - Google Patents

Description

Aug. 25, 1925.

H. H. HANSON ET AL APPARATUS PQR DRYING PAPER 1 l l l I I I l l l l I 1 l ll 7 t A ,M w/ 7 v w Ll M @Nw A A 4 w n v .JW m m5, 6. 9W w3 KS NQ R m J m S Am AQ @f h fil r E -,:utwa .9,--- @5-0i A@ 1.9. 11.0.-- VNU@ MQ a QS A O C f. 0 C\f.\ O o O C o e @IOIQNAH -zmwmw WQJX \x,\\ \|w\ IPL .Il 1 :gw Q Nl .RS bm) l ,in m w .lm \w\ m w n H. H. HANSON ET AL APPARATUS FOR DRYING PAPER Filed Jan. 26. 1.921. 4 Sheets-Sheet 2 Aug. 25, T925.

1,550,695 H H HANsoN ET Al.

APPARATUS FOR DRYING PAPER Filed Jan, ze, 1921 4 sheets-sheet s w m @N QS kw Aug. 25, 1925.

H. H. HANSON ET AL APPARATU-S FOR DRYING PAPER Flled Jan. 26. 1921 4 Sheets-Sheet 4 Patented Aug. 25, 1925.

UNITED STATES HUGO H. HANSON, CF BOSTON, MASSACHUSETTS, AND WILFRED A. WYLDE, OF BAN'-y s 1,550,695 PATENT oFFlcE. f

GOB, MAINE, ASSIGNORS TO EASTERN MANUFACTURING COMPANY, OF BOSTON, MASSACHUSETTS, A CORPORATION F MASSACHUSETTS. i

nAPPARATUS FOR DRYI-NG PAPER.

Application iled January t26, 1921. Serial No. 440,173.

To all 'whom t may concern:

Be it known that We, HUGO H. HANsoN and 'WILFRED A. WYLDE, both citizens of the United States, and residents of Boston, in

the count of Suffolk, State of Massachusetts, andY of Bangor, in the county of Penobscot and State of Maine, have invented new and useful Improvements in Apparatus for Drying Paper, of which the fol-x 10 lowing is a specification.

This invention has for its object to produce a high grade Writing aper having the characteristics of "loft-dried) paper but with greater strength, by a continuous process.y

l5 Loft-dried paper is characterized by a eertain fcockle, due to the manner in Which the paper is dried.- It comprises the three papers known usually as bond, ledger and linen finished papers. Ledger paper and linen finished paper, the first because of the character of the calendering which is ernployed in its manufaeture,.and the second ecause of the plating operation to which it is submitted, do not possess the cockle to the same extent as bond paper, but all three have to a certain extent that cockle which is characteristic of loft-dried paper.

In the loft-drying of paper, as usually carried out, the dry web from the dry end 0f the paper machine is carried through a` tubsiZingbatli, then slit and cut into sheets and arranged in Vpiles or packets. yEach packet is then hung over a pole in a loft or -drying chamber, and subjected to a tem- 5 perature of approximately -120o F. until dried. The period required ,for the drying operation varies froih fifteen to eighteen hours, andthe total `time for hanging, 'drying and pulling a. paper so loft-dried 4 vtakes from thirty to thirty-four hours. The

process is, therefore, not continuous, andy apart as they would be if the drying took' place under restraint, and consequently the paper, possesses greater strength than one Which is dried under constraint as in the usual drying machine having the characteristic drying rolls and felts. Second, because the paper feels firmer 'to the touch and has what is called a better tone As stated, such papers, and artieularly bond papers which are not hig ly calendered in finishing, retain a cockled surface, due to the shrinkage of the fibers, which is highly desired bythe trade and is regarded as the characteristic of a high grade Writing paper.

Due to the fact that the drying of paper by the loft process is expensive, various attempts have been made tovduplicate loftdried paper, especially bond paper, hy coutinuous processes, but, so far as we know, t-hese attempts have been unsuccessful` producing only air-dried paper which lacked the appearance of loft-dried paper and has less commercial value,-this being particularly true in heavier paper on which a cockled surface is difficult to obtain.

In accordance With our process the paper is dried continuously in the web, after having been subjected to the tub-sizing operation, and after being dried may be cut into sheets of the desired length. Bearingin mind that the paper must be free from constraint during the drying operation so as to permit the fibers to shrink to the desired extent and give the paper the highl \v desirable cockled appearance, We carry ,on the process in such manner that the paper is at no time required to sustain its own weight. except for short lengths in which its weight is insufficient to have any tendency to pull the fibers apart. That is toisay, instead of festooning the paper or in causing it to pass up and down alternately over and under rolls which are arranged in different. horizontal planes, we make provision for the paper to travel for considerable distances in a horizontal plane, during which time it is supported looselyon rolls upon which it may rest, and which, if desired, may he rotated so as to prevent the surface of the paper from being dragged thereover and to assist in causing the longitudinal travel of the paper. It is possible, of course. to have the drying operation carried on while the paper is traveling continuously in a horizontal direction so that entering the drying and is then dried as herein described to a' point where it contains not over 5 to 6% of moisture, the resulting paper will not only possess the highly desired cockled appearance and tone, but will possessa marked increase in strength over paper which has been dried to a bone-dry condition before it is subjected to the sizing operation.

We have further found that itis possible to expedite the drying operation by -heating the drying atmosphere to a temperature of approximately 240 F. It has heretofore been regarded as dangerous for the paper, to employ a drying atmosphere heated to the temperature mentioned and, of course, it will be readily understood that if paper were in fact held at to suth a temperature for any considerable length of time, its fibers would be injured and the paper would be brittle and undesirable. Such a condition does not exist for the reason that the rapid evaporization of moisture from the paper keeps the temperature of the paper itself very much below that of the surrounding air: for example, paper containing 12% moisture showed a temperature under 120 F. in an atmosphere well 'above 200 F. Thus the time during which the paper is at a high temperature is exceedinglyshort.

In an yapparatus for carrying out the proccss as hereiiroutlined, during which the paper is dried as it is traveling without constraint in a horizontal direction, provision must be made for effecting a differential rotation of the rolls by which it is supported in order to compensate for the shrinkage of the web during the drying operation, and therefore we provide means b which the various supporting rolls may e so driven that their peripheral speed is e ual to or greater than the desired speed o travel of the web, and yetby which they are driven at differential, speeds at different .points in the travel of the web. Thus, as the drying of the paper progresses and the web shrinks, the successive rolls are driven at a decreased surfacespeed, as a result of which tension on the' web is eliminated.

In the accompanying drawings we have illustrated more or less diagrammatically and conventionally an apparatus embodying our invention by which our process may be practiced in connection with sized paper, but lit will be understood, of course, that many changes may be made in the yapparatus as illustrated without departing from the spirit and scope of our invention.

Referring to said drawings:

Figures 1 and 1A represent the dryin apparatus in side elevation, there being illustrated at the left of Figure l a portion of the dry end of a paper machine, certain winding reels and a tub sizing apparatus, all illustrated conventionally.

Figure 2 represents a plan view of the air supply chamber of the loft on a smaller scale, being more or less diagrammatic for the purpose of illustrating the circulation of the drying atmosphere.

y'Figure 3 represents an end elevation of the apparatus.

Figure 4 represents diagrammaticall the first tier ofhorizontal rolls over Whic the web passes after entering the loft and illustrates more or less conventionally the mechanism for drying the web on said rolls.

yFigure 5 is a similar view illustrating the second or intermediate tier of rolls.

Figure 6 is a similar view'7 illustrating the lowest or bottom tier of rolls.

Figure 7 illustrates the transmitting mechanism for transmitting power from the main drive shaft to a series of rolls in each of the threel tiers.

Figure 8 represents the end of .the web which is formed with a tail reparatory to its being carried through the oft by an initial paper feeding apparatus with which theloft is equipped.

On the drawings, reference being hadiat yuntil it has a very low moisture content, it

is so weakened that when subjected to the further sizing and drying operation it does not possess what we regard as a desirable strength. We should not regard it as a departure from our invention, however, if the paper were dried to a greater extent, so far as other features of our process are concerned.

At B we have indicated conventionally a reeling apparatus by which the web delivered from the paper machine may be coiled or wound into rolls, and removed for storage or otherwise. At C is indicated a supplemental reel stand, on which the rolls may be' located if it be desired to pass the Lament 8 web therefrom through the drying apparatus or continuous lloft described. If desired, neither of these reel stands is employed, but the paperA is transferred directly from the dry end of the paper machine to the sizing tub which is indicated at D. This sizing tub is illustrated conventionally, beng provided With a vat d in which the bath of sizing'compound isl contained, and in which it is maintained at the desired temperature by the usual means. 1t is also provided with the usual squeeze rolls e and b for removing the excess sizing compound from the paper. g indicates a guide roll over which the web passes on its Way to the loft.

The loft which may be utilized in carrying out our process, consists, as stated, of a plurality of rolls arranged with their axes approximately in a horizontal plane, though, of course, it is not essential that the plane of the axes should be strictly horizontal, as the plane might be inclined, if desired. The point is that the paper is not caused to travel up and down, over and under alternate rolls disposed in different horizontal planes, but is caused to travel over a series of rolls arranged in approximately the same plane, during which time it is without constraint so that the paper is permitted to shrink and dry. The drier is, therefore, comparable With a loft, but without the disadvantages due to hanging packets of paper over rods or poles by which a curvature is set in each sheet.

le could, as previously indicated, employ a single long tier of yrolls so that the paper would travel practically without deviation during the entire period of drying, but for mechanical purposes we prefer to arrange the rolls in horizontal tiers, one over the other, thereby decreasing the length of the drying chamber. In its sim lest aspect `the loft comprises an oblong cas ng formed of any suitable material which is approximately air-tight, and in which the rolls of the several tiers maybe journaled, andwith y means for circulating a highly heated atmosphere through the casing.

In Figure 1, in which the loft or drier vis more or less conventionally illustrated, a

' thesizing tub through a narrow slot` or opening in one end wallof the chamber, and, passing over the top tier of rolls, descende, travels in the opposite direction over the intermediate tier ofrolls, descends again and travels forwardly on the lower tier of rolls and is finallyl delivered through a narrow slot or throat in the other end wall of the chamber and i's'then Wound into rolls, as Will 'be described. During the time' that it travels over the rolls of the sevferal tiers, it is subjected to a highly heated atmosphere which is kept continuousl in circulation so that the web of paper is ried to the `desired extent. The mechanism by which the` heated atmosphere is supplied and maintained in circulation will subsequently be described. y 'p As we have previously stated, it is desir'- able and, in fact, necessaryv that the rolls in the several tiers should` be driven at different speeds in order to compensate for the shrinkage of the paper web, this being particularly true of the end roll in. each tier over which the web passes previous to its being delivered to the next, succeeding tier of rolls. These end rolls should, of course, be rotated so thatl their peripheral speed is` equal to thespeed of travel of the web, but the other rolls of the tier may be driven at a peripheral speed somewhat higher than the speed of travel of the web so as toassist in feeding it throu h the drier.

Any suitable di erential driving mechanism may be utilized for imparting power to the several rolls in the different tiers. We have illustrated conventionally a main driving shaft' 14 (see Figures 4, 5 and 6) Awhich is located outside of the main drying chamber or loft and which extends longitudinally' thereof. This shaft is,'of course, mounted in suitable bearings and it is drivenfrom any suitable source of power by variablespeed power-transmitting mechanism. For this purpose, we may employ, if desired, an initial driving shaft 15 receiving its power from a motor or a counter-shaft, and for. this purpose being equipped with a' driving pulley 16. The shaft 15 is illustrated as being provided with a cone pulley 17, which, by the medium of a belt 18, drives a parallel cone pulley 19 on a shaft\20, which, by al belt'21 and pulleys 22, .23, drives the shaft 14. Bymoving the belt 18 lengthwise ofthe pulleys 17 and 19, the shaft 14 may be driven at any desired speed, notwithstanding the initial power shaft may be driven at constant speed.

1n Figure 4, we have illustrated the rolls of the first tier. Y These` rolls comprise the two end rolls l24, 25, and intervening groups of rolls which are indicated at 26, 27 and 28.

The'end roll 24 is theone over which the",y

web initially passes as it, enters the drier, and the roll 25 is the one over which the web passes on its-way to the second tier of rolls. This last-mentioned roll 25 is of large diameter, say, preferably, 24 to 30 inches, so that by its use we are able toavoid the 'fortively small' diameter.

mation oflongitudinal wrinkles in the web, for we have found that, where a roll of smaller diameter is employed, there is a constant tendency for the damp web to form longitudinal wrinkles Orpleats.

The rolls 26, 27 and 28 may all be of rela- The rolls 26 of the first series are illustrated asydriven from a shaft 29 which, in turn, is driven by a belt 30 and pulleys '31, 32, from the main variable speed-driving shaft 14. We have illustrated the shaftsof the rolls 26 as being provided with bevel gears 33 intermeshing with and driven 'by complemental gears 34 von the shaft 29. For driving the firstl roll 24, aV

short supple-mental shaft 35, driven by bevel gears 36, 37 (tl'ielatter` being on -the shaft 29), is employed and power istransmitted therefrom to the roll 24 by pulleys 38, 39 and a vbelt 40. The roll 24 is driven at a peripheral speed `somewhat higher thanthe speed at which the sized web is. delive1ed` from the sizing tub, in order to pull it away from the size press, it being understood that the arc of contact between the paper and the roll is very small and the tension is not sufficient to injure the paper. The roll 25, however, is driven'at a somewhat slower speed so as to compensate for the shrinkage of the web during its initial drive.- As its. speed must be varied from time to time according tothe caliper or character ofthe paper, we,

preferably, employ a separate variable-speed power-'transmitting mechanism for driving the roll 25 from Vthe variable-speed drivmg l shaft 14,

-To vthis end the shaft of roll 25 is pro.- vided with af'lcone pulley 41 driven by a belt'42 from a cone ulley 43 on a shaft 44 which, through beve gears 45, 46, receives its power from the shaft- 14." The rolls 28 ofthe third series of thefirst ,tier aredriven at somewhat'higher speed vthan the" roll 2 5, but at a slower speed than the rolls 26 but still'at .a higher peripheral' s eed than the travel of the web. Any suitalile means may be utilized for drivingthe .rolls'28. We have illustrated them, conventionally, as being driven by a pulley 47 `on' the shaft of the end roll 25. A belt 48 passes from the pulley 47 to the pulley 49 of the roll 28, which is' farthest from the roll 25,

and is ressed into engagement with the pulleys oythe intervening rolls Iby intervening belt-tightening pulleys 50.

All of the rolls- 28, as' stated, may be driven at the same speed, since, as a practical matter, it is not essential that all of the rolls of the. series from end to end of the tier -should be driven at successively slower speeds. il?.l p. y The series of rolls 27, located between those at`26 and 28, are driven at a surface vspeed higher than the travel of the paper,

but ata speed intermediate 'the speed of the rolls 26 and the rolls 28. For this purpose, the shaft 51 of one of the rolls 27 is provided with al pulley 52 driven by a belt 53 from a pulley 54 `on a shaft 55 driven by bevel gears 56, 57 from the variable-speed maindriving shaft 14. A belt 58 is engaged with pulleys 59 on the shafts of the rolls 27 by idler belt-tightening rolls 60, s0 that all of these rolls 27 are drlven in unison.

After leaving the end roll 25 of the first tier of-rolls, the web of paper passes downwardly to the second tier (indicated as a whole at 12) and it then travels in the direction of the arrows in Figure 5 ,While resting on said rolls. The second tier of'rolls comprises three groups indicated at 61, .62 and 63. The last roll of the group 63 has a large-roll 64. The rolls 61 are all driven by the same belt 48 from the shaft of roll 25, by which the rolls 28 are driven. The rolls 62 are driven from the shaft 55 by a pulley 65, a belt 66 and a ulley 67 Von the shaft of one of the rolls/6g. driven by a common belt 68 from the shaft 69.y The rolls 63 and 64 are all driven from a shaft 70 by bevel gears 71, 72. The shaft 70is driven from the main drivin shaft 14 by variable-speed power-transmitting mechanism, including the two cone ulleys 73, 74 with their belt 75, the cone pullley 73 being driven by pulleys 76, 77 and a belt 78 from the shaft 14, and the shaft 70 being driven from the cone pulley` 74 by pulleys..79, 80 and belt 81. The three groups of rolls in the second tier are drivenat progressively decreasin peripheral speeds.

The ro ls of the lowermost or third tier I are illustrated in Figure 6 and they are illustrated as comprising thethree groups indicated at 82, 83 ,and 84. As the web passes around the last large roll 64 of the second tier,'it drops a short distance and is then.

carried in the direction of the arrows by the rolls of the third or lowermost tier and 011e of the rolls 83, the shaft 93 itself being driven by a pulley 94 on the shaft 55, a belt 95 and a pulley 96 on said shaft 93. The last group of rolls 82 are driven by a common belt 97 from a pulley 98 on the last roll 82 of the group. In passing over the third tier, where the paper is nearly dry, some slight tension may be exerted to keep the web from travelling sidewise, but this would not be suiicient to injure the paper.

The shaft' 198 may be driven from any suitable source of ower, but we have illustrated it as being riven from a shaft 99 of The rolls 62 are all we will subsequently describe in detail. It

is sufficient for present purposes to state that the shaft 99 is provided with a pulley 100, from which,`b a crossed 'belt 101 and a pulley 102 on the ast roll 8,2, the pulley 98 1s rotated. The shaft 99 is illustrated as providedwith a gear 103 to which power is transmitted from the"-variablesp'eed driving shaft 14 by variable speed power transmitting mechanism.` This mechanism is illustrated as comprising a bevel gear'104 on the shaft 14 intermeshing with and driving` r a complemental gear 105 on a shaft 106.

This last-mentioned shaft is provided'with a cone pulley 107 which transmits power to a complemental cone pulley 108 by a beltv 109. The last-mentioned cone pulley 108 is on a shaft 110 having a pinion 111 intermeshing with the gear 103.

It is desirable, or necessary, that the web of dried paper should be removed from the drier'so as not to exert' tension on the web as it is being carried through the loft`and we, therefore, provide a supplementaldelivering or draught mechanism whichreceives the web as it emerges from the loft and feeds it to a roll-forming mechanism at such speed that' the'web is under no longitudinal constraint'at any point between its entrance into the loft and its emergence therefrom.

Any suitable draught mechanism may be' utilized, but in any event it should be capable of being driven at variable speeds under proper control. We have illustrated in Figs. 1^ and'4.- a draught mechanism which is suitable for the purpose and which will now be described.

This mechanism comprises two rolls 112, 113, one located above the other but spaced lapart so that the web is not' gripped thereby. These. two rolls are geared together so as to rotatesynchronously, one of the gears being illustrated in Figure 6 at 114. The shaft 99 (previouslyreferred to) is' provided with a gear which intermeshes with that upon shaft 14, but which is not illustrated. Co-acting with the two rolls 112, 113 are two endless bands 115, 116 formed of ordinary cotton duck. felt, or other equivalent material. Each of these bands passes around a series of idler rolls, those for the band 115 being indicated at 117, 118, and those for the band 116 being indicated'at 119, 120. These idler rolls' for each band are so located that the band engages its associated large` roll through an arc of slightly less than 180. The `web emerging from the loft passes under an idler roll 121, then over one-of the rolls 118 and passes, with the band 115, down under the draught roll 112, thence between the rolls 112, 113 and around the latter roll and out under one of the rolls 120 to a reeling mechanism which is indicated as a whole at E. The web is gripped against the two rolls 112, 113 by the associated endless bands 115,1116, which prevent any slippage of the paper relatively to the rolls and ensures that the web will pass around the rolls without pleating or wrinkling.

The two traction or draught rolls are driven by the variable 'speed mechanism from .the shaft 14, which we have previously I described and which includes the shaft 106, the shaft 99 and the intervening cone pulle s. Assuming that the squeeze rolls'e, f o the` sizing tub are driven at constant speed, so that the web of paper travels at a redetermi'ned speed `as it enters thel loft, 1t is possible for the attendant so to vary the s eed of the various rolls of the several tiers 1n the loft and the speed of the draught rolls 112, 113, that the'paper will be carried. through the'loft in such manner as to l`release it from mechanical constraint, which would prevent the. fibers -from shrinking freely during the drying o eration, and permit the paper to assume t at cockled appearance which is characteristic of high grade ,writing paper.

'We desire to -empha'sizethe fact that the web travels to all intents and purposes'in substantially a single plane, notwithstanding the fact that as it passes from one tier of rolls to the other, it must necessarily deviate from that plane. tween the tiers ofrolls is so short that no length of the web is called upon to with- The distance betially tangential to these rolls, both in passing to and leaving them. Again, while in the particular embodiment of the invention we have illustrated the paper, in traveling over the several tiers of rolls, as passing along paths which are substantially parallel, this is merely for the purpose of reducing the necessary height of the loft, since each of the tiers of rolls could be. at an inclination.

After the paper has left the draught or traction delivery rolls 112, 113, it may be subjected to tension in reeling it onthe reeling mechanism without injury to the paper, since the web is gripped frictionally agalnst said rolls by the endless bands, and the tension exerted on the web between the draught or traction rolls and the reeling mechanism is lrliot transmitted back beyond the traction ro s.

'As previously indicated we find that, by means of an apparatus substantially as herein described. it is possible to carry the paper through the loft at high speed without exerting a tension thereon or subjecting it to longitudinal constraint. Conselquently, we are able to maintain the drying-atmosphere of the loft at a high tem-v perature without danger of injuring xthe web, for we have found it practical to heat thedryingatmosphere to a temperature of 240 F.

.- Any suitable means may be employed for 'heating the air in the loft and for delivering heated air thereto.

)Ve have -illustrated means which may be employed for this purpose. Above the casing which constitutes the loft or'drying-chamber (and which, by the way, is of sufficient width to -receive the widest web of -paperproduced in the mill) we rovide a second chamber which is practica y double the-width I of the loft. This second chamber is indicated in Figure 2 at 121 and comprises end and side walls and a suitable cover-or top wall. Thechamber is separated from the loft by a Hoor or par- 2o tition. -Heatedfffresh air is supplied to one side of this chmbenintermediate its ends, a trunk or conduit 123 which may be 4provided with a manually controlled damper 124. Communicating with this conduit 'there is '-a fan 125, the inlet to which communicates with an inlet chamberv 126 provided with any suitable heating means by Awhich the air'entering the same may be fend of the loft.

In the air chamber 121 we have illustrated three separate air heating units indicated at 130, 131 and 132, through which the air is circulated and by which it may be heated to a high temperature.' In lieu of three separate units, which overlap as shownin-Figure 2, we might, of course, employ a single heating unit extending across the air chamber 121 and provided with the proper number of steam coils or pipes to supply the necessary radiating surface. These heating units are located relatively near the right hand end of the airchamber, and to the' right of v the mouth of the trunk or air duct 123.

It is desirable that the air should be delivered in proximity' to the three tiers of rolls, so that currents of air will travel lengthwise ofthe paper passing over the rolls and thence back up into theair chamber 121. For this purpose we provide three air conduits indicated at 133. 134 and 135, all of which communicate with an upright trunk or manifold 136 which is arranged at the left hand end of the machine and which extends-downwardly to one side of the loft. At the inlets of these three ducts' are placed fans 137,` Avcrhiclij the'heated .air may be forced therethrough into theA up.

right manifold or duct,.136. From the vertical manifold 136- there are horizontal trunks `140, 141 through which. the-heated air issues into the loft a-t the left handend thereof. The duct 140 is located between the top and the intermediate tiers of rolls, and the duct 141 lies between the intermediate and the lowest tiers -of lrolls. These ducts have open mouths or delivery noz'zles 142, 143, respectively, wh'ich direct the-air towards the right hand end' of the'l machine under those portions of the web which are traveling on the upper and intermediate tiers of rolls.

For supplying heated air to the loft above the level of the paper on the upper tier of rolls, we employ a 4conduit 144 which leads from' the trunk 133, as is best shown in Figures 1` and 2. This'last mentioned duct 144 has a vmouth or nozzle 145 Ywhich delivers the air into the loft above the upper tier of rolls, so that a current of air will pass along the web thereon to the right hand end of the loft. From the space in the loft ordrying chamber above the upper tier of rolls the air may pass to the'air chamber 121 through an opening 146. For conducting the air back into the chamber 121 from levels between the first and secondand second and third tiers of rolls, we provide outlets 147', 148 in the side wall of the loft or ldrying'- chamber which communicate with a large duct or trunk 149 (see Figure 3) 'Which opens into thev floor of the chamber 122 through the large opening 150 (see Figure 2). The exhaust fan 128 has its inlet communicatin with the air chamber 122 through t e right hand end wall thereof, above the openlng 146, as shown in Figure 1^, taken in connection with Figure 3.

The drawings illustrating the mechanisms described are more or less diagrammatic and conventional and, of course, the larrangement as we have describedit-maybe modilied or changed in many particulars. The

ros

point is that the'appa'ratus, as a whole,.com

prises a large chamber, separated from the drying chamber or loft, in whichthe air5 may be heated by suitable heatin elements and from which it may be cause to circulate at relatively high seed in currents directed longitudinally o the travel of the web against both faces thereof. In. addition to these instrumentalities, we employ a fan for su plying continually a certain amount of resh highly heated air to the air cham-ber, -and a fan for exhausting from the chamber approximately as much air as is delivered thereto by the inlet fan. By constantly supplying fresh air and exhaust ing a portion of the used air, which contains a relatively high moisture content, and by utilizing, in addition, the internal fans Ithrough the loft and were v. not circulated 'again and again therethrough a greater amount o f heat would be necessary initially to heat the entire volume of air to the proper temperature. Vhile, of course, we prefer i to re-heat a portion ofthe air which has already been utilized in drying a web, and using it again, we would not consider it a ldeparture from the spirit and scope of-our invention if the air were passed only once through the loft or drying chamber.

In an apparatus such as herein described, in which the internal heating elements are utilized forheating the re-circulated air, we regard it as desirable to have the hea-ted fresh air delivered to the air chamber for admixture with the air after it has been .heated by the internal heating elements and it is for this purpose that the outlet of the duct 123, at lts point of entrance into the air chambergis located between the re-heating velements and the fans or blowers which deliver the air to the loft or drying chamappearance as ber. yPreferably the air passing through this Vduct 123 is'heated to a temperature of approximately 240 F., and the -heating ele- 130, 131, -132 are kept at said temperaments ture, so tained at a F. In operating our apparatus, care should be taken to prevent the atmosphere at any point in the whole apparatus from reaching that the re-circulated air is maina temperature lower than the dew point in` order that condensation of moisture may be eliminated, for reasons which will be readily understood by those skilled in the art.

Recapitulating what has been explained in this specification, it may be stated thatthe web of paper as delivered from the dry end of the initial'pa-per making machine preferably has a moisture -content of 10% when delivered to the sizing tub. In passing through the loft or drying chamber the web,

being under no mechanical constraint and not having to support its own weight, the fibers are permitted to dry and shrink in substantially the same way that they are when the paper is hung over poles in the usual loft, so that it has the same coekled the best loft dried paper, but has a firmer tone and greater strength. The speed of travel of the paper through the drier and th'e temperature of the drying atmosphere may be so related that the web` on leaving the drier` has a moisture content. of approximately 5 to 6%, although. if desired, the drying may be proceeded with to such au extent that the web has a much lower moisture content. vWe, however, do not regard this as so desirable when the paper is to be subsequently finished.

. We have provided in connection 'with the vtion of their travel.

temperature approximately 240?V drier a novel mechanism for automatically feeding or threading the end of a web of paper throu h the loft. This feeding mechanism comprises two tapes 151, 152 which are narrow in width and by which a tail 153 on the end of a web 154'(see-Figure 8) may be gripped and carried, over the various tiers of rolls. These two tapes have confronting vfaces throughout the greater por- At the receiving en of the machine they are separated by a bar 155. as .s'hown in Figure 1,so' that when the tail 153 is formed into a wad by the machine l attendant, it can be insertedfbetween the two ta'pes and carried by them as they travel through the drier. These two tapes are passed over the upper tier of rolls, thence downwardly around the large roll 25,`at the right, end thereof, thence back over the secondor intermediate tier ofvrolls, thence down under the large roll 64' to 'the lower tier ofn rolls, whence they pass around a supplemental roll 156 below the delivery slot in the end wall of the loft and back to a roll 157. Iassing upwardly from the roll 157, the tapes are lseparated by the bar 155 and then meet as they pass over the first roll 24 of the first tier. The tapes which are thus in facial contact throughout practically all of their travel track over the rolls with which they engage at one extreme end thereof, where they are out of the normal path of travel of the paper web as it passes through the loft or drier.

-lVhen the tail wad is inserted between the two tapes. the tapes carry it and the succeeding length of the web along the first tier of rolls, thence back over the second lier of rolls and forwardlvover the third tier of a rolls until the 'wad is delivered at the delivery slot in the end wall of the dryingv chamber. where it is caught b v the attendant, and pulled out from the tapes and thence passed to the-traction or draught instrumentalities. rl`lier. .fo1e, the web of paper. which has been 'traveling slightly diagonally. is `caused to pursue a rectilinear path through the drying chamber.

Having thus explained the nature. of our said invention and described a way of malt'- ing and using tli'e same, although without attempting to set forth all of the forms in which' it may be made or4 all of the modes of its use. what we claim is:

1. A paper drying apparatus comprising 1 chamber, a plurality of groups of Vrolls urranged in a continuous series therein over which a web of wet paper may be passed in a plane tangential thereto, and means for rotating said groups of rolls at different speeds.

3. A paper drier comprising adryin chamber-a plurality of vertically. spaced horizontal tiers of rolls therein, on which al continuous web of paper may travel in suc .cession without the formation of dependent loops between adjacent rolls, the last endY a continuous web of paper may travelin succession without the formation of de- 5. A paper drier comprising a dryingchamber, a plurality of vertically spaced horizontal tiers ofrolls therein whereon the web of paper mayt'r'avel over the rolls from each tier to the next succeeding tier without the formation of dependent loops between adjacent rolls, the rolls over which the paper travels from one tier to the neat succeeding tier being of larger diameter than the remaining rolls, means for rotating said large 'rolls to impart thereto a peripheral speed equal to the desired speed of travel of the web, and means for rotating the relatively smaller rolls to impart thereto a peripheral speed greater than the desired speed of travel of the web. l

6. In combination, a casing, means for positively feeding a web of moist paper into said casing to be dried therein, means for positively feeding the dried web out of said casing at a speed sufficiently lower than the feeding in speed to compensate for the shrinkage of the paper during the drying operation and impart notens'ion to. the web within said casing, and means forsupporting and carrying forward the web in said casing without substantial restraint in any direction while it is being dried.

7. In combination, a casing, means for positively feeding a web of moist paperinto saidcasing to be dried therein,.means for positively feeding the dried web out of said casing at a speed sufficiently lower than the feeding in speed to compensate for the shrinkage of the paper during the drying operation and impart no tension to the web within said casing, means for supporting and carrying forward the web in said caspaper drier -comprising a drying without substantial restraint in any difor positively feeding the dried web out of said casing at a speed sufficiently lower than the feeding in 'speed' to compensate for the shrinkage of the paper during la drying operation and impartl no tension to the web within saidv casing, means for supporting -and carrying forward the web in'said casing comprising rolls on which the web rests, and rolls over substantial arcs of which the web engages, means for driving said first mentioned rolls with a'surface velocity greater than. the velocity ofthe web resting thereon, and means for driving said last mentioned rolls with surface velocities equal to that of the webengaging thereover.

9. In combination with a casing, of means forpositively feeding a web of moist paper into said casing to be dried therein, means for positively feeding the dried web out of said casing at a speed suieiently lower'than the feeding in speed to compensate for the shrinkage of the' paper during a drying operation and impart no tension to the web within said casing, means for supporting and carrying forward the web in said casing' comprising rolls on which the web rests, and y rolls over substantial arcs of which the web engages, means for driving said first mentioned rolls with 'a surface velocity greater than the velocity of the web resting'thereon,

and means for driving said last mentioned rolls with surface velocities equal to that of the web engaging thereover, said last mentioned rolls being positioned at int-ervallls' between groups of said first mentioned ro s.

10. In combination,a casing, means for positively feeding a web of moist paper into said casing to be dried therein, means for positively feeding the dried web out of said casing at a speed sufficiently lower than the feeding in speed tol compensate for the shrin tage of the paper during the drying operation and impart no tension to the web within said casing, means for supporting and carrying forward the web in said casing comprising 'superposed tiers of' rolls on which the web rests and rolls at the ends of said tiers over substantial ares of which the web engages in passing from one tier tov the next, means for driving said first mentioned rolls at a surface velocity greater than that of the web'resting thereon, and means --for driving said second mentioned rolls with surface velocities equal to those of the web engaging thereover.

11. In combination, a drier casing, means for positively feeding a web of moist paper into said casing to be dried therein, means for positively feeding the dried Web out of said casing at a speed suficiently lower than the feeding in speed to compensate for the shrinkage of the paper. during the drying operation and impart nontensio'n thereto Within said casing, and feeding mechanism in said casing closely engaging the Web and moving at a speed intermediate the speeds of the feeding in and feeding out means.

l2. In combination, a drier casing, means for positively feeding a web of moist paper into said casing to be dried therein, means for positively feeding the dried Web out of said casing at a speed sufliciently lower than the feeding in speed to compensate for the shrinkage of the paper during the drying operation and impart no tension thereto Within said casing, feeding mechanism in said casing closely engaging the web and moving at a speed intermediate the speeds of the feeding in and feeding out means, and feeding means in said casing with which the web loosely engages, movable at a higher speed than said mechanism. v

In testimony whereof We have afiixed our signatures.

HUGO H. HAN SON. WILFRED A. WYLDE.

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