US1562763A

US1562763A - Drying apparatus

Info

Publication number: US1562763A
Application number: US580416A
Authority: US
Inventors: Harris Gordon Don
Original assignee: IND DRYER CORP
Current assignee: IND DRYER CORP; INDUSTRIAL DRYER Corp
Priority date: 1922-08-08
Filing date: 1922-08-08
Publication date: 1925-11-24
Anticipated expiration: 1942-11-24

Description

Nov. 24, 1925. 1,562,763

G. D. HARRIS DRYING APPARATUS Filed Aug. 8, 1922 4 Sheets-Sheet 1 INVENTOR ATTORNEY Nov. 24, 1925. 4 1,562,763

G. D. HARRIS DRYING APPARATUS Filed Aug. 8, 1922 4 Sheets-Sheet 2 INVENTO ATTORNEY Nov. 24, 1925. 1,562,763

G. D. HARRIS DRYING APPARATUS Filed Aug. 8. 1922 4 Sheets-Sheet 5 R E w a one IN VISA/70R Q Mg Q N owzm W V ATTORNEY Nov. 24, 1925- 1,562,763

G. D. HARRIS DRYING APPARATUS m/enfo/ 'l atented News 'tl-ORDUN' non HARRIS, 9E ISLIL, NEW YORK, ASSIG-NOR, BY MESNE ASSIGNMENTS,

Tl THE TIFDUidlFETflrL DRYEH CQRPORJQTION, Q1? STAMFGRD, CONNECTICUT, A COR- DRYING APPARATUS.

Application filed August 8, 192%. Serial No. 580,416

To aZZ whom may concern:

Be it known that l, Gounon Don lllmius, a citizen of the United States, residing at Tslip, county of Suffolk, and State of New York, have invented a certain new and useful Drying Apparatus, of which the following is a specification,

This invention is an apparatus for the evaporation of moisture from materialsuto which movement is imparted at the same time that a drying atmosphere is circulated into contact with. said materials, for the purposes of drying or oxidising the same.

The invention is useful in connection with the drying of textile materials in web form, in which example of said invention the welo material is placed. under tension and is moved through and withina succession of drying" chambers by means known ordinarily in the textile art as a tentering mechanism; but it is to he understood that the apparatus is equally well adapted for drying; materials other than textiles, for which other materials carriers are employed and which. carriers are operable for transporting the materials under treatment within a succession of chambers The object is to evaporate moisture from materials while movement is imparted to such materials with a view to effecting the rapid and economical drying of such materials,

In the drying of textiles in web form, the

operations are conducted in a manner to eliminate a certain percentage of the moisture present in said material, with a view to conditioning such material by retaining a low moisture content, and further, the tex tile is retained. in a taut or stretched condition during the final stages at the drying op-- -eration.

According to this invention, the material under treatment is conducted within a succession of flow channels through which is circulated a drying atmosphere, the direc tionof flow of such atmosphere lacing trans versely to the path of movement of such material owing to the interposition of the mate rial itself or of the material carriers in the line of how of the drying atmosphere, the sheet of which. is to direct the flow of the drying atmosphere over and into contact with the material so that said drying at mosphere is controlled to flow downwardly rial is moved within the how channel,

whence the atmosphere flows downwardly at the respective sides of the material. The

drying atmosphere is circulated in the described path, and into contact with different layers or runs of the same material undergoing movement within the succession of flow channels, and during its circulation in this manner, said atmosphere is boosted by 2 succession of reheaters, following which op eration the drying atmosphere, in a more or less humid condition, flows away from or out of the presence of the material.

For economy of operation, and particular-- ly to reduce the expense of boosting the atmosphere to the desired temperature, the atmosphere flowing out of the presence of the material is recirculated within vthe flow channels, and prior to the return of the atmosphere to the flow channels, it is mixedwithlreshair and such mixture of moist air with the fresh air is reheated to a desired temperature p Tn one embodiment of my invention, T have associated a drier with a textile machine of the character known in the art as a tentering machine, the latter operating to place tension upon the web while said weh ishexposed to the-efi'ect of a drying atmosp ere.

in the specified adaptation of the invention, there is associated with the tentering machine a drying mechanism which encases said tentering machine soas to result in a unitary structure adapted to occupy substantially the floor space originally taken up .by the tentcring machine, said drying mech anism being installed. without disturbing the tenterino machine at least to an a reciable C extent, and the resulting structure being adapted for the economical handling of; the textile material in a manner to eliminate moisture therefrom while such material is in a stretched or taut condition,

The drier associated with the tentering' lid machine includes means for channeling the flow of a drying atmosphere, means for directing a continuous web of material within said channeling means, means for recirculating a drying atmosphere by exhausting the same from the presence of the tentering machine and blowing said atmosphere within the channeling means, and means for boosting or reheating the. drying atmos phere during the recirculation thereof.

The flow of a drying atmosphere, usually air, into contact with the moist material effects theexchange of heat for moisture, with the result that said atmosphere as it flows away from the material carries an increased moisture content and its temperature is appreciably decreased. According to this invention, the condition of the drying atmosphere during the period of its recirculation is modified with respect to its moisture content and to its temperature. Such conditioning of said atmosphere is brought about, first, by the admixture of fresh atmospheric air with the warm humid atmosphere subsequent to the exhausting of said humid atmosphere from the presence of the web, and, second, by boosting or reheating the mixed atmosphere prior to its return to the channeling means.

The specified procedure whereby the drying atmosphere is conditioned both as to its moisture content and its temperature is desirable in the treatment of textile materials, "for the reason that the atmosphere flowing into contact with the web of textile material may be modified or controlled in such manner as to retain in, or impart to, the web of material a desired moisture content.

The drying means is co-extensive with the tentering machine. Owing to the length of the combined structure, it is preferable to employ an exhauster intermediate the ends of the apparatus, which exhauster operates to .dischargeinto the surrounding air some of the humid atmosphere drawn from the apparatus, and moreover, it is desirable to employ recirculating devices in multiple, each recirculating device constituting a unit of the recirculating means, and which recirculating units are spaced at appropriate intervals in the len th of the combined apparatus.

Other functions and advantages of the invention will appear from the following description taken in connection with the drawings, wherein- Figure 1 is a vertical cross section through my drier associated with a tentering ma chine, the plane of the section being indicated by the dotted line 1-]l of Figure 2..

Figure 1 is a diagrammatic view in side elevation, with arts broken away and 1n section, illustrating the exhauster and the units of the recirculating means.

Figure 2 is a horizontal sectional View with certain parts in plan, taken the plane indicated by the irregular line 22 of Figure 1.

Figure 3 is a vertical sectional elevation taken in the plane of thedotted line 3-3 of Figure 2.

- Figure 4 is a longitudinal section through another embodiment of the invention wherein a plurality of conveyers are employed for transporting material within a succession of .flow channels.

' Figure 5 is a vertical cross section of the apparatus shown in Figure 4:.

Figureb is a vertical longitudinal section through another form of apparatus wherein a continuous carrier is supported and operated within the flow channels, and

Figure 7 is a cross section through the apparatus of Figure 6.

I will first proceed to describe the embodiment of the invention shown in Figures 1, 2 and 3, wherein the drier is associated with a tentering machine whereby the web of textile material is dried at the same time it is stretched and moved at a desired speed. Said tentering mechanism may be of any construction known in the art, but in order that others may understand the relation of "my drier to said tentering mechanism, I have indicated the carrier chains diagrammatically at A in Figure 1 and at B inthe same figure that part of the web material which is engaged by said chains A, illustration of other parts of said tentering machine being omitted, for the reason, mainly, that they arewell known and do not re quire further illustration nor explanation.

A housing 0 is erected around the tentering mechanism, said housing being co-extensive to said tentering machine and encasing the latter. The housing is divided interiorly to produce means for channeling the flow of a drying medium and to provide for directing multiple lengths of the web material, as well as for the accommodation of multiple boosters, and the reception of multiple recirculating devices. A vertical wall a extends lengthwise within the housing parallel to one of the side walls a thereof, and between said internal wall a and side wall a (see Figures 1 and 2). are positioned transverse vertical walls 1), resulting in a plurality of booster chambers D D D extending vertically within the housing adjacent one side thereof. 7

Within the housing are the channel forming battles c, d, e, positioned horizontally between the internal wall; a and the .opposite side wall a? of the housing, said' battles being parallel to each other and spaced at appropriate intervals to produce a succession of flow channels E E E a chamber F (see Figure 3) being at the ports 9 extending in series lengthwise of said batlle 0, whereby the drying medium flowing into the top channel E is directed downwardly upon a length of Web material. In battles d, e, are provided ports h, c', respectively, the ports of each series 9, h, i, being substantially central of said battles.

The end wall a of the housing is provided with an exit j in the plane of the web supported and operated by the tentering machine, whereas the other end wall a of said housing is provided with a plurality of inlets la, Z, m, in horizontal planes below the bodies 0, d, 6, respectively, see Figure 3.

Means are provided within the tlow channels E E for directing therein lengths of the web material, the latter being continuous and being conducted in straight runs within the flow channels E E and chamber b so as to be exposed in a fiat condition to the drying atmosphere which is circulated within said channels and chamber. The web directing means may be of any approved character, but in the drawings the same are shown as a plurality of horizontal series of rollers G: G, although running tapes may be employed as a carrier for the web material, see Figures 6 and 7. Said rollers are mounted for free rotation in suitable bearings provided in the walls a a of the housing, and they are'positioned within the flow channels E l substantially in the horizontal planes of inlets k Z.

The web material B is continuous so as to run in straight lengths within flow channels E E and chamber Rone'length being supported by the rollers G and driven by rollers l-l within channel ll another len h,

being supported by rollers Gr and driven by rollers H within channel E and a third length being engaged by chains A of the tentering mechanism so as to run within chamber The web material from a suitable source runs over a sheave or roller H. and enters at it, is loo ed around an inside drum or driven roll l passes opening Z to and around an outside drum H thence through slot at to the tentering chains, and emerges through exit The upper, middle and bottom lengths of the continuous web are supported by rollers G G and chains A below the ports g, h, z, res ectively, so that the drying atmosphere is delivered downwardly upon the flat runs of the web, substantially centrally thereof, whereby the atmosphere is directed to flow laterally over and into contact with the web, whence the atmosphere is diverted by the web to flow in opposite directions'lrom the ports in a path parallel to the surface or the web and at right angles to the direction in which the web is moved within the flow channels, whence the atmosphere flows downwardly around and at "the opposite sides of the web.

The drying atmosphere flowing into contact with the web material exchanges heat for moisture, resulting in a drop in temperature of said drying atmosphere, but to restore the heat units of which the drying atmosphere is deprived, provision is made for boosting said atmosphere as it flows from one run to the middle part of the next run below it, to attain which object boosters or reheaters l l are provided within the flow channels, each booster being shown as a steam coil positioned horizontally in the spaces intervening a run of the web material supported on one series of rollers Gr or G and the adjacent battles, d or c, see Figures 1 and 2.

in the circulation of the drying atmos phere it :ilows from one run of the web to the run nest below it, and during its flow into contact with each run the atmosphere is fed centrally of the web oft material, flows across and into contact with the. run and downwardly over and around the op posite side edges of the web, the transverse flow of theatmosphere in contact with the web being in a direction at a right angle to the movement of the web within the ilow channel. i

The atmosphere is supplied centrally to the web and downwardly upon it by row cl ports extending in series for practically the full length of the dew channel and the web moving within said tlow channel, and

although the atmosphere is directed down.

wardly upon the web, centrally thereof, the direction of llow is changed or diverted from a downward flow into a flow in a horizontal path, oven and in contact with the web.

The atmowhere flows out of the presence of the material on the tentering machine, but instead of discharging the atmosphere in more or less humid condition, said atmosphere, or substantial portion thereof, is recirculated within the The recirculatin means for said drying atmosphere is in multiple, a plurality of recirculating devices being provided at desired intervals in the length oitthe apparatus, and each of said devices constituting; a unit of a; multiple recirculating means. The several units include a plurality of blowers J J, see igure 1, with which are associated intalre mains K K 7 each closed at one end by head 0 and connected by a branch p with the intake of the proper blower. The several intalre mains ot the recirculating units are positioned within the chamber F, substantially centrally thereof, and directly below the web-carrying chains A of the tentering machine, said intake mains extending for certain distances and longitudinally of the apparatus. Said intake mains are provided with inlet ports 57, shown as positioned in the top surface thereof, and extending in longitudinal series with respect to the-mains, whereby the rotation of the blower fan operates to draw air through the ports and into said mains, the ell'ect of which is to exhaust is drawn into the chamber by the blower, and

such air becomes mixed with the humid drying atmosphere within the chamber F.

As shown in Figure 1", the intake mains K K for blowers J J extend from the opposite ends of housing C for suitable distances toward the middle portion of said housing, and similarly the intake main K for the blower J extends from a point adjacent head 0 of main K for a suitable distance lengthwise of chamber F but this main K for blower J is separatedby a head a from a relatively short intake main 0 of an exhauster J adapted to draw moist air from chamber F intermediate the ends of the drier, said exhauster; J discharging a given quantity of the moisture laden air into a stack or uptake J by which the humid air s discharged into the outer air without flowmg through the drying room or loft. The

arrangement of the intake mains K K K centrally within the chamber F, and. directly below the web ofmaterial, and for practically the length of the drying apparatus, enables the humid atmosphere to be drawn at numerous places away from the presence of the material, and to be carried away from that length of said web which is undergoing the final stage in the drying operation; but for economy in the operation, not all of the humid atmosphere is discharged, for the reason, first, the exhauster J blows out through stack J only a definite portion of such atmosphere, whereas the remainder of thewarm humid air is recirculated by the blowers J J" J and, second, such recirculated air is conditioned with respect to its moisture content by the admixture of fresh air supplied through ports 1', the latter being damper controlled as usual or desired,

The blowers of the recirculating units are shown in Figure 1 as having outlets 8 ex-.

tending into the chambers D D D each of said chambers containing a booster or reheater Laround which the more or less humid atmosphere, exhausted from the res ence of the web and mixed with fresh air, is blown by the action of the blowers, the effect of which reheating is to restore to the drying atmosphere the required heat units, and to utilize such atmosphere as the carrier for tentering machine, the motion of which chains imparts the required movement to the web. The blowers having been set into action, and steam supplied to the boosters, some of the humid atmosphere is discharged by exhauster J whereas the remainder of the humid atmosphere is recirculated by the blowers J J J the drying atmosphere being conditioned by admixture with fresh air supplied by ports '1'. The course of the recirculated air is indicated by the arrows, flowing downwardly within chamber F, entering the ports mains K K K blowers J J J, thence flowing upwardly through chambers D D D and into contact with boosters L, thence flowing over the battle 0 and through ports 9 into contact with the middle portion of the top run of the. web within flow channel E, thence flowing laterally and over the web and dbwnwardly around the side edges of said top run and into contact with booster I, thence flowing through ports h in baflie d downwardly upon the middle portion of the intermediate run. of the web within flow channel E and passing laterally over the intermediate run of the web, and downwardly around the side edges thereof, and into contact with booster I, thence flowing through ports i of bafile e and into central contact with that run of the web which is engaged by the chains A of the tentering machine, the drying atmosphere flowing laterally over the web and downwardly at the side edges into the chamber F, whence said atmosphere is exhausted through ports Q in the intake mains, and is thence recirculated by the blowers.

The drying atmosphere is directed in .a definite path across and into contact with the web moving within the flow channels, whereas the moving web is conducted in a Hat sheet like condition within said flow channels by the action of the rollers and the chains of the tentering machine, the direction of flow of the atmosphere in the presence of -the web being across the line or path of movement of the web material within said flow channels, The web f material while exposed to the drying atmosphere is so related to the bafies 0 (5 e and to the ports 9 k t that the atmosphere flows downwardly upon said web", centrally thereof, and is deflected by the web itself to flow over the top of each run of said web and downwardly varound the side edges thereof, thus exposing all portions of the web and each run thereof to the action of said drying atmosphere, securing efficiency in the drying operation while said web is undertension for that length thereof which is under the influence of the tentering machine. The drying atmosphere flows into contact alternately with the moistmaterial and with the boosters I I, the latter acting to restore to the atmosphere the heat units lost by the exchange of heat for moisture at each pass of said drying atmosphere into contact with the web, and while the atmosphere is ex? hausted from the presence of the web within the tentering machine, such atmosphere is recirculated by blowers acting to force the humid and conditioned. atmosphere through boosters L L prior to the return of the atmosphere to the circulatory path constituted by the flow channels.

Although I have illustrated my invention in Figures 1, 2 and 3 as associated with a textile tentering mechanism, it is to be understood that said invention is not limited in its application to textile fabrics, for the reason, among others, that the invention maybe, and is, useful in the drying of other materials, such as loose or bulk materials. Thus in Figures and 5 I have illustrated a drier wherein a plurality of carriers are employed for. imparting movement to a material within a succession of flow channels, to which a drying atmosphere is supplied downwardly upon the material and substantially centrally thereof so as to be directed by the carriers or the material itself into a path over and into contact with the material, the line of flow of the atmosphere in contact with the material being transversely of the direction of movement of the material itself.

The housing C is divided interiorly thereof by horizontal baifles c, d, e, and

by a vertical wall a to )roduce a succession of flow channels E, E E together with the bottom chamber F and the divided booster chamber D at one side of the houssaid horizontal bafiies c, d, 6, being In prb vided with ports 9, h, i, said ports in each baflie extending in a' longitudinal 1 other that the delivery end of one conveyer is over the loading end of the conveyer next below it, so that the material is discharged from one conveyer to the next, and the mathereof. Within the bottom chamber F is positioned the exhaust main K with an inlet port 9 and a connection p with a blower J Fresh air is supplied to chamber F by an inlet 1', and the moist air is drawn from the presence of the material by the action of the blower, the outflow of the moist air through the main K inducing the inflow of fresh air through inlet 9, thus mixing fresh air with the moist air, and the blower acting to blow the mixed air through chamber D around, reheater L, and to recirculate the mixed reheated air back to the flow channel E.

The apparatus of Figures 1, 2, and 3 employs drums or sheaves for supporting and moving the web of material,. certain of which drums or sheaves H H are positioned exteriorly of the housing C. In lieu. of drums or sheaves, I may use rotary spiders I, and locate the same within the housing as shown in Figures 6 and 7. Again, the material in web form may be supported within and moved along the flow channels by bands or tapes Q, as shown; but-as otherwise mentioned, the drier of Figures 6 and 7 is constructed and operated as shown in Figures 1,2 and 3, or in Figures 6 and 7.

, Having thus fully described the invention, what I claim as'new and desire to secure by Letters Patent is:

1'. In an apparatus of the *class described,

a housing provided with means for channeling the flow of a dryingatmosphere, means for moving material within a succession of flow channels, and means for feeding a drying atmosphere downwardly upon the moving material, substantially centrally thereof, the drying atmosphere flowing crosswise of thedirection of movement of said material and into contact therewith.

2. In an apparatus of the class described,

a housing provided with a succession of flow channels, means whereby material is moved within the flow channels lengthwise thereof, means for feeding a drying atmosphere downwardl upon the material substantially centrally thereof, said drying atmosphere flowing in the presence of the material in a direction crosswise of the path of movement of the material within said flow channels, and means for reheating the drying atmosphere during its circulation within the succession of flow channels.

3. In an apparatus of the class described, a housing containing a succession of flow channels, means whereby material is moved within the flow channels lengthw se thereof,

means for feeding a drying atmosphere downwardly upon the material within each flow channel and substantially centrally thereof, and reheaters in the line of flow of the drying atmosphere, said means for the material being so related to the housing and to the atmosphere-feeding means that said atmosphere is directed to flow crosswise of the material, into contact therewith, and in a direction transversely to the path of movement of said material within the fiow channels.

4. In an apparatus of the class described, a succession of flow channels, means whereby material is moved within said flow channels lengthwise thereof, means positioned substantially centrally of each flow channel for feeding a drying atmosphere downwardly upon the material adapted for movement within each flow channel, and

means whereby the drying atmosphere is directed to fiow around the opposlte edge portions of the material, into contact therewith and in a direction crosswise of the direction of movement of said material within each flow channel.

5. In an apparatus of the class described, the combination with tentering mechanism operable for placing tension upon a web of material, of means for channeling the flow of a drying atmosphere in definite paths with respect to a succession of lengths of said web, and means for directing said .web of material in a flat straight condition within each length of said flow channel.

6. In an apparatus of the class described, the combination with tentering mechanism operable for placing tension upon a web 0 material and im arting movement thereto, of means for cliannelmg the flow of a drying atmosphere in a definite path relatively to the path of movement of said web, means operable for directin said web material in a fiat straight condition within a succession of said flow channels, and means. for feeding the drying atmosphere substantially centrally u on the web material moving within the ow channels.

7 In an apparatus of the class described, the combination with tentering mechanism operable for placing tension upon a web 0 material "and imparting movement thereto, of means for channeling the flow of i a drying atmosphere in a. definite path relatively to the web of material, means operable for directing said web material in a flatstraight condition within a sucheating the same.

cessi'on of said flow channels, and boosters positioned within the flow channels and in the path of the drying atmosphere for re- 8. In an apparatus of the class described, the combination with tentering mechanism operable for placing tension upon .a web flow of a drying atmosphere in a definite path relatively to said, web, means for directingtsaid web material in a flat condition within said flow channels, means for feed- 1 ing a drying atmosphere downwardly upon the web substantially centrally thereof, and

means for recirculating the drying atmos phere by exhausting. the same from the presence of the web material, and returning suci atmosphere to the flow channels.

10. In an apparatus of the class de scribed, the combination with tentering mechanism operable for placing tension upon a web ofmaterial, of means for channeling the flow of a drying atmosphere in a definite path relativelyto the web of material, means for directing said web material in a flat condition within said flow channels, means for feeding the drying atmosphere downwardly upon the web substantially centrally thereof, means for recirculating the drying atmosphere by exhausting the same from the presence of theweb material and returning such atmosphere'to the flow channels, and means for reheating said drying atmosphere during the recirculation thereof; v

11. In an apparatus ofthe class described, the combination with tentering mechanism 0 erable' for placing tension upona web 0 material, of means for channeling the flow of a drying atmosphere in a definite path relatively to theweb of material, means for directing said web ma terial, in aflat condition within said fiow channels, means for feeding the drying atmosphere downwardly upon the web substantially centrally thereof boosters po-. sitioned within said flow ch for recirculating a definite volume of the drying atmosphere by exhausting the same from'the presence of the web an returning the same to the flow channels, and other boosters in the line of flow of the drying atmosphere for reheatin the atmosphere durin the recirculation t ereof.

12. 11 an apparatus of the class described,

annels, means the combination with tentering mechanism the flow channels, means for recirculating the drying atmosphere by exhausting the same from the presence'of the web material and returning said atmosphere to the flow channels, means for conditioning said atmosphere with respect to its moisture content by the admixture of fresh atmospheric air therewith, and means for boosting the drying atmosphere.

13. In an apparatus of thevclass described, the combination with tentering mechanism operable for placing tension upon a web of material, of a housing encasing said tentering mechanism, baflies within said housing for producing therein a succession of flow channels, means for directing web material in a flat condition within the flow channels,

means for feeding a drying atmosphere downwardly upon the web material substantially centrally thereof, and boosters within the How channels.

14. In an apparatus of the class described, the combination with tentering mechanism operable for placing tension upon a web of material, of a housing encasing said tentering mechanism, baffles within said housing for producing therein a succession of flow channels, means for directing web material in a fiatcondition within the flow channels, means for feeding a drying atmosphere downwardly upon the web material substantially centrally thereof, means for recirculating the drying atmosphere by exhausting the same from the presence of the web material and returnin such atmosphere to the flow channels, and boosters in the line of flow of the drying atmosphere.

15. In an apparatus of the class described, the combination with tentering mechanism operable for placing tension upon a Web of material, of a housing encasing said tentering mechanism, means for channeling the fl'ow of a drying atmosphere in a plane above the tentering mechanism, means for directing web material in a fiat condition within said flow channels, and a plurality of recirculating units spaced relatively to each other and operable for exhausting the drying atmosphere from the presence of the.

web material and returning such atmosphere to the flow channels.

16. In an apparatus of the class described, the combination with tentering mechanism operable for placing tension upon a web of material, of a housing encasing said tentering mechanism, means for channeling the flow of a drying atmosphere in a plane above the tentering mechanism, means for directing web material in a flat condition within said flow channels, and a plurality of recirculating units each including a blower and an intake main positioned in a definite relation to the tentering mechanism for exhausting the drying atmosphere fromthe presence of the web material and for returning such atmosphere to the flow channels.

17. In an apparatus of the class described, the combination with tentering mechanism operable for placing tension upon a web of material, of a housing encasing said tentering mechanism, means for channeling the flow of a drying atmosphere in a plane above said tentering mechanism, means for directing web material in a flat condition within said flow channels, and a plurality of recirculating devices for exhausting the drying atmosphere from the presence of the web material and returning the same to the ,flow channels, each recirculating device ineluding a blower and an intake main extending for a definite distance below the tenterflow of a drying atmosphererelatively to GORDON non HARRIS.