US2299459A - Paper manufacture - Google Patents

Description

Oct 2 1942'. H. G. CHATAIN PAPER MANUFACTURE Filed March 15, 1940 4 SheetsQ-Sheet 1 INVENTOR Henri G'.Chazin B $6M, ATTORNEY Oct. 20, 1942. H. a. CHATAIN PAPER MANUFACTURE Filed March 15, 1940 4 Sheets-Sheet 2 RN 8% @Sv Qsw a ATTORNEY Oct. 20, 1942. H. G. CHATAIN PAPER MANUFACTURE 4 Sheets-Shea} 3 b 'em'z' GiC/ratairz BY 8.0M

. ATTORNEY Filed March 15, 1940 Oct. 20, 1942. H. s. CHATAIN PAPER MANUFACTURE Filed March 15,1940

4 Sheets-Sheet 4 INVENTOR Henri 6 hatai'n. BY

ATTORNEY Patented Oct. 20, 1942 arcane mean Henri G. Chatain, Erie, lla... or to Hasnmlll Paper Company, Erie, Pa, a aeration oi Pennsyl Application ch 15, 1940, No. SZQJMH 1s Claims.

This invention relates A30 the manufacture of paper and is more particularly concerned with preventing objectionable shrinking of paper dun ing its passage through the dryer section of a paper machine. In the customary operations, the paper emerging from the dryer rolls usually has rough edges, or, in other words, the edges are grainy or corrugated, sometimes for a dis .tance of sixinches or so into the'width of the sheet. The portions of the sheet involving the grainy edges are not salable as a first-class prod not and must be trimmed from the sheet, with substantial manufacturing loss. Also the sheet after passage through the dryers is frequently prone to curl.

I have found that these difilculties can be overcome by preventing or diminishing the admission of air to the central zone of the dryer section, i. e., the zone between the upper and lower sets of dryer rolls, so that the air in that section will be saturated, or nearly so, thus preventing water from escaping to said air from the portions of the sheet which are passing through the spaces between the dryer rolls. As a result the paper is subjected to a drying action practically entirely on the dryer rolls, where it is held from sing, and the production of rough edges" is. avoided.

Furthermore, the air with its water vapor in' the aforementioned central zone becomes thoroughly difiused to thereby cause evenness of such small amount of drying as may occur in said zone, with consequent elimination of strains set up in the paper as it is being dried, thus obviating the conditions which cause curling, and resulting in a sheet of paper which will lie flat.

The invention further achieves these. results without sacrifices of the desired extent of drying in elevation, illustrating an embodiment of my invention.

Fig. 2 is a horizontal sectional view taken approximately on line 2'-2 of Fig. 1.

Fig. 3 is a fragmentary elevation of a detail.

Fig. 4 is a transverse vertical section, taken approximately on lined-4, of Fig. 1.

(on. Si)

Fig.5 is a diagmatic view in side elevation illustrating provisions for supplying *heated and conditioned air to the housings 29 and it, for the upper and lower zones of the drier section.

5 Fig. 6 is a diagrammatic end view of the arrangement illustrated in Fig. 5'. i Refs to the drawings, there is shown a dryer section oi a paper machine, said dryer section including the usual upper and lower sets of w dryer'rolls. The numerals l, 3, 5, l, and 9 desigpate dryer rolls in the upper set, while numerals 2', 3, e, d, and theater to dryer rolls in the lower set. Said rolls may be supplied with steam in the customary way through pipes i and may be is driven through gears 2 in any suitable or conventional manner to advance the web of paper H through the dryer section in the direction in dicated by the arrow M. Overlying the paper in its passage over the upper rollers is'the usual 2o, endless felt band i2 which passes over suitable rollers, such as are indicated at is and the lower course of which travels in the same direction as the-paper and presses the latter firmly against said upper dryer rolls. Conventional tension reg- 25 ulating apparatus for the felt band 92 is indicated at M.

- it an endless felt band 65 passes over the usual rollers it and tension regulating means i! in the lower part of the dryer section, the

'upper course of which band travels in the same direction as the paper and maintains the latter pressed firmly against the lower drying-rolls.

The various rolls may be mounted in suitable main side frames A and B (Fig. 4), each of 35 which side frames may comprise a series of lower pedestals, such as indicated at Isa, 69b, I90, use

and lSe. which pedestals are connected by beam 20. The lower dryer rolls may be journaled in bearings M on the beams 2t. Supported on each of said beams is a series of upwardly extending pedestals, such as 22a..22d, carrying bearings 23 at their upper ends, in which bearings the upper dryer rolls are journaled. .The pedestals, such as nor-22d of ,each series, may be interconnected 45 by, frame elements,- as indicated at Mat-25c,

which frame elements are joined at their upper ends by beam sections such as shown at 26a-26e. The last. mentioned beam sections are suitably joined together and may carry bearings 21 and pedestals or supports 25 and 28' for various other ions later to be described. It will be understood that the various pedestals and beams may be secured together in any suitable way, as by bolts or welding.

, A housing 29 oi sheet metal .or other material is mounted, through inwardly projecting extensions 29', on flanges of the beams 2It28e, as shown in Fig. ,4, and serves to enclose the top portion of the dryer section. At the front and rear sides of the lower portion of said dryer section there are provided suitable plates or frames 36 and 3|, respectively, each having a flange 30',

I 3i projecting into engagement with a flange. of

the adjacent beam 26), said frames extending to the bottom of said section. The flanged portion SI of frame 3| may be pocketed as shown at 3!" in Fig. 4 to accommodate the gears for driving the respective lower dryer rolls. Similarly, the flanged rear portion of houslngfifi may be pocketed, as indicated at as", to accommodate the gears for driving the respective upper dryer rolls.

As above noted, my invention provides for maintaining the air in the central zone of the dryer section (i. e., the zone wherein the paper passes between the upper and lower drying rolls) in sufficiently humid condition to prevent any substantial drying of the paper in said zone. To this end I provide for isolating the air in said zone from the air exterior to the dryer section, as well as from the air in the upper ahd lower portions of said section.

At the rear side of the machine the entrance of exterior air to said central zone may be. ex?- cluded by a frame or plate 32 extending along said. rear'side and suitably secured at its top to the housing 29 and at its bottom to the plate At the front, the exterior air may be ex-' 3i. cluded in any desired manner, but I prefer-to provide a series of curtains, such as illustrated at 33, 34, and 85 (Figures 3 and 4) which may tie-mounted on rollers 38 journaled in suitable brackets 86'.

As illustrated .in Figures 3 and 4,, each curtain may be mounted between adjacent beam elements 31, of T-shaped cross section, which elements extend from top to bottom of the machine, and to which elements said brackets 38' are welded or otherwise suitably secured. Said beam elements 37 also serve as reinforcing members, in-which connectionit will be noted that the frame or plate 30 may consist of sections 30a secured to said beam elements, as by bolts or through welding, and exten therebetween. Similarly the front wall of the housing 29 may comprise sections 29a extending between said beam elements 31 and suitably fastened thereto.

Each curtain may contain a window 38 of flexible, transparent material so that the operator may look into the interior of the dryer section without raising the curtain. In Fig. 3. the

curtain 38 is shown in slightly raised position,

ply to show more clearly its relation to oertain associated parts. In normal operation, all of the curtains will be in their lowermost posigigms, as illustrated in conjunction with curtain It has been previously noted that the lower course of the felt band I: travels in the same direction as the paper through the dryer section, i. e., in the direction of the arrow ii, and presses the paper firmly against the upper dryer rolls.' As shown in Figures -1 and 2, said, felt passes around the upper half of the circumference of each of said rolls and also passes .under guide rolls 39 positioned between said dryer rolls. Said felt also is of such width as extend over substantially the entire length of eac of the aforesaid rolls.

30 each of the beam sections 25w- -26e may be the respective side frames A and B, I provide means in the form of shields ill, 4!, for blocking substantially any interchange of air between the aforementioned central and upper zones around the ends of said rolls. Sincesaid shields t0 and SI may be substantial duplicates, a description of shield 40 will sufilce.

Said shield Mi may be of metal and, as shown, ma be curved to conform with the curvature of the dryer rolls. Said shield may conveniently be formed in sections dim-Me each of whic may be formed integrally with a correspondin one of the beam sections Mia- 26e, and also with a corresponding one of the frame elements Between adjacent dryer rolls, each' of the shield sections comprises a portion 40 ado-Me.

shown in Figures 1 and 4. Each of the frame sections rat-24 mayhave a flange t4 projecting from thebottom web 24' thereof and merging with the associatedbearing portion 42 to impart additional rigidity thereto. Each of the shield sections may be also provided with a web at extending upwardly from the aforementioned portion 40' and merging with the Between the ends of the upper dryer rolls and lower flange d4 of the corresponding one of the frame elements him-24c, and also merging with the aforesaid bearing portion d2. If desired,

cast integrally with its associated frame element ado-Ede, and the corresponding shield section may be cast integrally with said beam section and associated frame element, or the corresponding sections and elements may be formed separately and welded or otherwise secured; together.

It will be seen that the above mentioned shield sections follow substantially the course of the lower run of the felt I 2 and extend be-.

tween the adjacent edge of said felt and the frame A. As above noted, the shield between the opposite edge of the felt and the frame B may be constructed of sections arranged in the same manner as described in connection with the shield to. In the drawings, the sections of shield 4| are designated did-die, respectively. Since the air in the above mentioned central zone cannot pass upwardly through the dryer and guide rolls aforementioned, or through the felt I! which extends over substantially the entire lengths of said rolls and passes betweenthe dryer rolls, and since said air also cannot pass upwardly through the shields 40, and M interposed between said rolls and the side frames, it will be apparent that the air in said central zone is substantially isolated from that in the upper portion of the machine. a

The upper course of the felt I5, as previously observed, runs in the same direction as that in which the paper travels through the machine and presses the paper firmly against the lower dryer rolls. Said felt passes around the lower half of the circumference of each of said lower dryer rolls'and also over guide rolls 46 jour- 'naled m the pedestals arc-22a of the side Shields 1 and l8,

tion, as well as from the outside air. when the machine is set into operation, said air tral and lower zones around the ends of said rolls.

Referring to Figures 1 and 4, it will be seen that the shield-4! may be formed in sections cast integrally with or otherwise united to the side frame A. As shown, said shield comprises sections E'ia, 41b, 41c, 41d, and "a, united to the beam 20 and to the respective pedestals Hit-498, as well as to reinforcing webs l9 integral with said beams and pedestals. Said shield also comprises intermediate sections llf, 37g, 47h, and 47f, cast integrally with or otherwise secured to the respective pedestals 22a-22d. The shield 88 may be formed in like manner.

The guide rollers 46 for the upper run of the felt band l5 may be ioumalled for rotation in the pedestals 2211-2211 as previously noted; and the shields 41, 48 are arranged as shown, to follow the course of the felt'and to pass above said rollers. The air in the central zone aforesaid cannot pass downwardly through the lower dryer same manner as the upper and lower sets of dryer rolls for the paper. Said dryer rolls 59 may, as shown, be mounted in bearings 21 on the beam sections m, 281), etc. The aforementioned rollers 39, as well as other guide rollers 5i, may be provided to guide the felt in its passage to and; from the rolls 50. Thus, as shown in Fig. l, the-felt, after passing over the paper on the dryer roll l, passes around the adjacent guide roller 5H,, thence over the felt dryer roll 50, then around a guide roller 39, and then over the paper on the succeeding dryer roll 3. The

guide rolls El may be mounted in various ones and, guide rollers or through the felt into the lower zone of the machine, nor can it pass through the shields into said lower zone. I

It will thus be evident that I have provided for substantially isolating the air in'the central zone of the dryer section of a paper machine from the air in the upper and lower zones of said sec- As a result,

in the central zone will speedily become saturated with moisture to such extent as to be unable to absorb any substantial amount of moisture from the paper passing between the upper and lower sets of drying rolls, and drying of the paperwill be substantially prevented-in said central zone. Thus, the drying of the paper will'be practically entirely restricted to 'the dryer rolls, on which I the paper is held from shrinking or curling, and

the conditions which give rise to curling and shrinking are obviated.

While a slight interchange of air may take place between said central zone and the zones above and below the same, since a small space exists between'the edges of the shields and the ends of the dryer rolls, no more than a small interchange of air can take place between said zones, so that the central zone is substantially isolated from said upper and lower zones. I prefer not to obtain a complete elimination of drying ;in said central zone, because some small shrinkage is desirable to prevent slack of the paper from manifesting itself at some point. My in-- vention enables the prevention of drying in said central zone to the extent desired and without preventing some slight drying therein sufficient for preventing the occurrence of slack. The space between said shields and the ends of the drier rolls may be so chosen as to achieve the desired extent of prevention of drying in the central zone. I prefer to eliminate all drying in that zone except for the very small amount desirable for preventing slack.

of the frame elements 24a, 24b, etc.

The housing 29 for the upper zone of the dryer section above noted, is preferably connected at the dry end to a system of ducts and pressure fans such as to receive a measured supply of heated air under a slight pressure. The capacity of the zone is such as to contain a sufficient amount of air for drying purposes so that the said air will under all conditions be exhaus d at the opposite or wet end of the zone with he saturation desired. The air travels through said zone, counter-current to the travel of the paper 'and felt, toward the wet end of the drier section.

Fans 52, mounted at convenient points in said housing, may be provided to direct currents of air back and forth across the machine and over exposed surfaces of the felt l2 to assist in removing water vapor therefrom. Thus the air in said housing not only travels counter-current toward the wet end of the machine but is furthermore circulatedback and forth across the machine by the fans 52, asthe result of which the air becomes progressively wetter until, at the wet end of the machine it becomes saturatedto a desired extent, preferably to such extent as to be no longer suitable for drying purposes. The wet air may then be exhausted to atmosphere or conducted to a suitable heat reclamation system. In addition to being heated, the air supplied to said housing 28 may be conditioned in any suitable manner to lower its moisture content to a housing.

In starting the machine, or in case of a break,

the operator may raise one or more .of the curtains 33, 34, or 35; to obtain greater accessibility. The above noted prevention of curling and shrinking of the paper is furthermore accom-' plished without impairment of the speed of .p-

eration of the machine despite the fact tha no substantial drying of the paper takes place in the aforementioned central zone. To this end, the felt may pass over any desired number, of steamheated drying rolls in the upper and lower portions of the dryer'section, which are open at op- Likewise, in the lower zoneof the dryer section there are provided steam-heated dryer rolls for the felt band 1-5, one of which dryer rolls is indicated at 53; mountedin bearings on pedestals N. The previously mentioned guide rollers 46, as well as other guide rollers 56, guide the felt band ii to and from the respective dryer rolls 53.

Thus, for example, the felt passing from the paper on the roll 2 passes around the adjacent guide roller 56, thence around the associated dryer roll 53, and then around a guide roll 46 from which it passes 'on to the paper on ,the

. succeeding paper dryer roll 4. Guide rollers 56 end to a system of ducts and pressure fans forreceiving a measur quantity of heated and humidity-conditioned a. under slight pressune,

v dryer cylinders.

and fans 51 may be provided in said lower zone to direct currents of said air back and forth across the machine and over exposed portions of the felt l5 to promote the drying thereof. In

the lower, as in the upper, housing the air travelscounter-current to the paper. and felt, and becomes p rogressively wetter, emerging at the wet end either to atmosphere or to a heat reclamation system.

As. shown in Figures 5 and 6, the housings 29 and 30 for the respective upper and lower zones above mentioned may, for example, be connected by ducts 6i, S2, respectively, to an air supply fan 63, which draws air through a suitable air conditioner 64 and heater 55, and passes said air into said upper and lower zones in a direction counter-current to the travel of the paper.

It may be observed that while the central zone of the dryer section is, of course, open at opposite ends, exterior air cannot enter said central zone from either end to any substantial extent, since the web of paper passes across said central zone between the upper and lower sets of paper dryer rolls, and said web is of such width as to extend over substantially the entire lengths of said rolls.

The aforementioned provisions for drying. the felt bands I2 and I5 also, of course, facilitate the drying of the paper in contact with the felt. As many dryer rolls 5!! and 53 may be provided as desired.

In the upperand lower zones above referred to, there may also be included supplemental paper drying rolls 5 8-, of the type illustrated in the Any desired number of said supplemental paper dryer rolls may be provided. The rolls 58 in the upper portion of said section may be mounted in bearings on suitable pedestals or supports 28, 28' on various ones of the beam sections 28a-26e, while those in the lower portion may be mounted in supports SI, SI mounted on various ones of the pedestals ISa-Nd and on the associated reinforcing webs l9.

When the paper first comes into the dryer section it is quite cool and wet, and paper making technique demands that the sheet temperature be raised gradually to minimize tendencies to cockle. Evaporation at this stage is quite limited with the conventional arrangement of felts and preferably located in the region adjacent the forward or wet end of the dryer section, in which region the dryer felts are capable of. blotting up considerable moisture from the damp paper sheet. This moisture is immediately driven out of the felt by means of the felt dryer rolls, whereby the subsequent paper drying rolls may be used for the sole purpose of drying the paper without the necessity of also having to dry the felt. It ispreferred that the felt dryer rolls be maintained at a temperature considerably higher than that of the first few paper dryer rolls, to

expedite the driving ofmoisture from the felts.

The felt dryer rolls 50, 53 are tion above described can be employed to good advantage. At the end of the felt-drying region the paper sheet has-been brought up to its nor,-'

mal drying temperature, and it is in the succeeding region that the aforementioned supple-j mental drying rolls 58 are preferably located.

The air directed onto the paper from said supplemental rolls subjects the paper to a uniform drying action across the full width of its surface.

While, when said supplemental dryer rolls 58 are provided, the paper opposite said rolls is not engaged by thefelt, said paper is held against shrinkage by its adhesion to the main dryer When said supplemental dryer rolls are the paper surface has become dried to such extent that the influence of air currents across said surface has no substantial effect on the drying rate. Furthermore, the discontinuance of said supplemental rolls at that pointis desirable since when thatstage of drying is reached the ability of the paper sheet to cling to the surface of the main dryer rolls has been'materially'lessened. From that point on to the end of the dryer section the drying is primarily a question of the rate at which moisture in the interior of the sheet can be driven to the surface. The agent best suited for this purpose is heat. Hence, in the portion of the dryer section following said supplemental rolls 58 the drying can be effectively accomplished by the main dryer rolls against.

which the paper is firmly pressed by the felts. In the drawings, only a portion of the dryer section is shown, for purposes of illustration, but it will be understood that the rolls 58, when employed, are preferably not provided beyond the point above indicated, and that from said point on to the dry-or rearward end of the dryer section the sheet is held on the main dryer rolls by the felts, and is dried by said rolls in the customary manner.

My invention, in substantially eliminating drying of the paper in the spaces between the main dryer rolls and in restricting'the drying practically entirely to the portions of the paper on said dryer rolls, not only results in the production of a paper having superior characteristics and in overcoming the objectionable rough edges and curling tendencies heretofore encountered, but furthermore enables increased production rates to be obtained. Inprevious prac tice the speed at which particular grades of paper were run through the machine were frequently held down in endeavors to curtail the severity of rough edges. Through my invention it is unnecessary to sacrific speed of operation, and rough edges are at the same time effectively prevented. In addition, a sheetof paper which is dried substantially entirely on the dryer rolls, as in my invention, is found to result in a superior product having minimum 'reactivity to humidity changes and a strikingly reduced tendency tocurl, aswell as 'a paper which beables-a substantial increase in available produc- The supplemental drying rolls 58 are preferdryers. 1

tion to be achieved since the full deckle-width is available at all times, and thedifferen'ce between reel width and finished roll width is markedly reduced owing to pronounced decrease in crosswise shrinkage of the sheet throughout the between said sets ofrolls to thereby prevent The invention furthermore decreasesthe'oost of manufacture because the machine will make less broke, thereby saving considerable time as well as effecting substantial saving of steam heretofore required to dry the broke, which has to be remanutactured.

The particular arrangement of felt dryers and supplemental dryer rolls above described is not claimed herein, since such arrangement is the joint invention of H. G. Chatain and H. L. Dyer,

and is claimed in the above mentioned appli= comprising preventing substantial escape of air from the zone intermediate said sets of rolls to thereby maintain in contact with the paper besubstantial drying of said paper in said zone, said means comprising shielding means between the ends of said rolls and the side frames and extending along-substantially the courses of said bands in engagement with said rolls 'for substantially preventing air in said zone from passing into zones above and below the first-mentioned zone.

6. Paper drying apparatus comprising a set oiuppcr drying rolls and a set of lower drying rolls around which a web of paper passes, side frames in which said rolls are mounted, an upper endless flexible band the lower course of which s over the rolls of the-upper set and engages portions of the paper thereon, a lower endless fiexible band the upper course of which passes over the rolls, of the lower set'and engages portions oi the paper thereon, shielding means between the ends of the upper rolls and said side frames for substantially preventing air in the zone between said sets of rolls from passing into the zone thereabove, shielding means between the ends of the lower rolls and said side frames for substantially preventing air from said first-mentioned zone from passing into the zone therebelow, means substantially preventing estween said sets of rolls a substantially isolated I mass of humid air to prevent substantial drying of the paper in said zone. 2. The method of controlling the drying of paper passing through upper and lower sets of a dryer rolls in the dryer section of a paper machine, said method comprising excluding substantial entrance of air from the exterior of the machine and from the upper and lower portions of said section into the zone between said sets of dryer rolls andpreventing substantial escape of vapor from the last mentioned zone to thereby prevent substantial drying of said paper in 40 said zone.

3. Paper drying apparatus comprising a set of upper drying rolls and a 'set of lower drying rolls around which a web of paper passes, side frames in which said sets of rolls are mounted, a pair of endless flexible bands engaging the paper on the respective upper and lower sets of drying rolls, means at the sides of said apparatusfor preventing entrance of exterior air into the zone between said sets of drying rolls, and means between said flexible bands and said side frames for'substantially preventing air from zones above and below the first-mentioned zone from entering said first-mentioned zone.

4. Paper drying apparatus comprising a set of upper drying rolls and a set of lower drying rolls around. which a web of paper passes,

side frames in which said rolls are mounted.

and means for preventing substantial escape of air from the zone wherein said paper passes between said sets of rolls to thereby prevent substantial drying of said paper in and zone, said means comprising shielding means between said side frames and the ends of the rolls of said sets for substantially preventing air in said zone from passing into zones above and below the first-mentioned zone. a

5. Paper drying apparatus comprising a set of upper drying rolls-and a set of lower drying rolls around which a web of paper passes, side frames in which said rolls are mounted, flexible bands passing around the rolls of the re pective sets and engaging portions of the paper thereon, and means for preventing substantial escape of cape of air laterally from said inst-mentioned zone, each of saidside frames comprising a plurality of contacting sections secured together, and each of said shielding means comprising a plurality 'of contacting sections joined with corresponding side frame sections.

7. Paper drying apparatus comprising a set of upper drying rolls and a set of lower drying rolls around which a' web of paper passes, side irames in which said rolls are mounted, an upper endless flexible band the lower course of which passes over the rolls of the upper set and engages portions of the paper thereon, a lower'endless flexible band the upper course .0! which passes over the rolls of the lower set and engages portions of the paper thereon, shielding means between the ends of the upper rolls and said side frames for substantially preventing air in the zone between said sets of rolls from passing into the zone thereabove, shielding means between the ends of the lower rolls and said side frames for substantially preventing air from said flrst-mentioned zone from passing into the zone therebelow, means substantially preventing escapetof air laterally from said first-mentioned zone, guide rollers, for said flexible bands between the dryer air from the zone wherein said paper passes 7 rolls-of the respective sets, and bearing means on the respective shielding means for, supporting" said guide rollers.

8. Paper drying apparatus comprising a set of upper drying rolls and a set of lower drying rolls around which a web of paper passes, flexible bands enga ing portions of the paper on the respective sets of rolls and means for preventing substantial escape of air from the zone between said bands to thereby maintain in contact with the paper in said zone a substantially isolated mass of humid air to prevent substantial drying oi the paper in said zone.

9. Paper drying apparatus comprising a set of upper drying rolls and a set of lower drying rolls around. which 'a web of paper passes, flexible bands engaging portions of the paper on the respective sets of rolls, means for preventing substantial escape of air from. the zone between said bands to thereby maintain in contact with the paper in said zone a substantially isolated mass of humid air to prevent substantial drying of the paper in said zone, and means supplemental to said rolls of one of said sets and engaging a portion of the corresponding flexible band in its passage from one of said rolls to the next for accelerating the drying of the paper.

10. Paper drying apparatus comprising a set of upper drying rolls and a set of lower drying rolls around which a web. of paper passes, means for substantially confining the air in the zone wherein the paper passes between said sets to prevent substantial drying of the paper in said zone, said means including a curtain at one side of said apparatus together with means at the opposite side substantially preventing lateral escape of air from. said zone. i

11. The method of controlling the drying of paper passing through upper, and lower sets of dryer rolls in a paper machine and pressed against said rolls by moisture absorbing felts, said method comprising preventing substantial exchange of air between the zone intermediate said sets of rolls and the zones above and below said rolls, causing air to flow through the last mentioned zones counter-current to the direction of travel of the paper through said machine in contact with said felts, and simultaneously directing currents of said air back and forth across saidfelts in contact therewith;

12. The method of controlling the drying of paper passing'through upper and lower sets of dryer rolls in a paper machine and pressed against said rolls by moisture absorbing felts, said method comprising passing air streams in contact with said felts in a direction countercurrent to the travel of the paper through said machine and simultaneously directing currents of I I said air streams back and forth transversely of said felts in contact therewith.

13. Paper drying apparatus comprising a set of upper drying rolls and a set of lower drying rolls around which a web of paper passes, side frames in which said rolls are mounted, means between said side frames and the ends of the rolls of said sets for substantially preventing air in the zone wherein the paper is out of contact with said rolls from passing into zones above and below the first-mentioned zone, means substantially preventing escape of air laterally from said first mentioned zone, andrhousin'gs for the zones above and below said first-mentioned zone, said housings being open at their ends for the passage. of air streams therethrough.

14. Paper drying apparatus comprising a set of upper drying rolls and a set of lower drying rolls around which a web of paper passes, side frames in which said rolls are mounted, means between said side frames and the ends of the rolls of said sets for. substantially preventing air in the zone wherein the paper is out of contact with said rolls from passing into zones above and below the first-mentioned zone, means substantially preventing escape of air laterally from said first mentioned zone, housings for the zones above and below said first-mentioned zone, said housings being open at their ends for the passage of air streams therethrough, and means in said houslugs for directing air currents back and forth across said housings.

HENRI G.- CHATAIN.

Images