CA1085128A - Method for production of fibrous sheet material and apparatus for carrying out the same - Google Patents

Abstract

Abstract of the Disclosure A method for production of fibrous sheet material com-prising dispersing fibres in a gas stream to obtain a gas--fibre stream, supplying the gas-fibre stream onto a flat screen, removing gas from the gas-fibre stream through said screen to form a fibrous sheet layer thereon, and its subsequent treating to obtain a fibrous sheet material, a part of gas being removed from the gas-fibre stream prior to supplying it onto the flat screen, so as to bring the fibre concentra-tion up to 20-500 g/m3. The concentration is chosen in accor-dance with the kind and properties of fibres. Simultaneously transversal pulsations induced in the gas-fibre stream in the course of its movement are damped. An apparatus for carrying out this method comprises a slot nozzle having side walls which are normal to converging frontal walls, its inlet ope-ning being connected with a means for dispersing fibres in a gas stream, while its outlet opening is connected with a chamber, a flat screen adapted to form a fibrous layer thereon, mounted under said chamber, and a suction box arranged under-neath the flat screen, wherein the side walls of the slot nozzle are in parallel relationship with respect to each other, a means for removing a part of gas from the gas-fibre stream is arranged in the chamber under the outlet opening of the slot nozzle, and the chamber is provided with branch pipes for gas exhaust, mounted substantially in the upper portion of the chamber.

Description

1~35~28 ~ield o~ the Invention q'he present invention relates to the proces~ g of ~ibres, and more paIlticularl~ 9 to methods for productioll o~ ~ibrous sheet matexials and apparatu~ for carxin~ out the same~
T'he present i~ve~tion can mo5t advarltageously be used in ..
pulp-a~d-paper9 textile a~d constructlon--material industries for pxoducing various kinds o~ papar, board, non-woven fabric, felt~ construction boardæ~
Back~rou~d of the Invention To produce a ~ibrous sheet material it i5 esse~tial to ob tai~ a uni~orm distribu-tio~ o~ ~ibrous material i~ a ~as stream ~ith a predetermined dispersity value o~ the air-fibre stream a~d to maintai~ the initial dispersit~ value of bhe air-~ibr~ ~txeam along the e~tire path of the ~low.
q'he air-fibre stream mu~t possess a speci~ic ~luidity e~abling t~le shape of the stream to be tra~s~ormed to a flat one 9 as well as the i~ternal structure o~ the aix-fibre stream to be trans~oxmed i~ order to obtain a homoge~eous ~ibre distribution throughout the stream~
The dispersity value of the air-~ibre stream is aæsumed to be a ratio o.~ a volume of discr~te fibres or small ~ibrous aggregabes to a volume of a~ indi~id~al fibre of mode-length9 i~eO the ~ength which predominates i~ the fibre le~gth dist-tributio~

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~L~38531 28 The ho:~o~eneous f.ibre distributio~ i.n the ai.:~ stream assumes the fibre concentration i~ each i.ndividua:L stream volume to have little or no fluctuations.
The dispersity value of th~ air~fib.re stream a~d the homo~eneous ~ibr~ dis-tribution throughout the stream decides the degree o~ uniformity of the structuxal homoge~eity o~ the obtained fibre sheet material, while the degree of tha ~ibre co~ce~tratio~ in the air stream determines the amou~t o~ gas to be remo~ed from the air-~ibre mixture to ~orm a la~er o~
fibrous material on a flat screen, 0~ one hand, the dispersity value of the air-fibre sus-pension is reduced due to high autoadhesion of fibrcs 7 i.e.
grouping of ~eparate fibres takcs place. ~o decrease the probability of fibre collision causing the adhesion and grouping d~e to turbule~t forces induced in the moving air~
~ ibre stream9 the fibre concentration must be low. Generall~, fib~e conce~tration is to be in the ra~ge ~rom 5 to 30 g/m3 depending ~po~ the properties of the material to be produced and upo~ the kind o~ ~ib.re.
Moreover, a high fibre conce~tration of the air-fibre stream decreases fluidity of bhe stream9 said ~luidit~ being an obligatoxy prexequisite ~or trans~orming the outer shape of the air-fibre stream~ e.g. a cylindrical shape into a flat one 7 as well as for changi:~g the internal structure of the ~ 4 .--'.; ' ., . ; .. . , . -.... .
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air-fibre stream to attain a uniform distribution o~ the ve-locity field in the stream cros~~s~ction, this being nec~ssary for forming a u~i~orm layex of f1brous ma~erial on a flat screen.
'Thus 9 ~ low ~ibre concentration of the gas fibre stream is a ~ecessa~y prerequisite for ~orming a fib~ous sheet material~ Therefor0~ if a layer o~ fibrous material is being formed with a high velocity, e~g. on the ~lat screen txave~
ling at a velocity ra~ging ~rom 180 -to 900 m/min9 a conside~
rable amount of gas is to be removad from the gas~ibre mixtuxe.
The flat screen with fibres settled thereon to ~orm a layer o~ fibrous material has a high xesistance coe~icien~
valued fxom 20 to 500, depending on the kind of fibr0 and on the fibro~ layer thic~ness. ~herefore, the removal o~ great amount of gas per unit of time, required in a high-speed ma~u~acturing o~ the ~iborus layer 9 leads to an increasad electric power cons~nptio~0 The power expended in defeating the resistance can be redu-ced with adequate increase in an acti~e a~ea o~ the flat scree~.
~his leads, however, to objectio~able irlcIe~se in the size of the equipme~t and9 as a result, to a~ increased metal input.
0~ the other hand, the power consumped in defeating th~
resistance developed o~ the screen duri~g a layer ~o~ming process when gas is being removed through the screen and ~ 5 : : ,: ~ ~ ,.

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L2~3 fibrous layer precipitated the~eon~ ca~ be reduced by increasin~
the co~ce~tration of fibres i.rl the gas-~i.bre stream. In this case the gas-~ibre stream must be ex~a~ded before it is supplied onto the scree~ in ordex to achieve a u~iform dis-tribution of the velocity ~ield, a homogeneous distributio~
o~ fibres over a~ e~tire ~tream volume, and an increase i~
dispersity value of the gas~fibre stream, all this making it.possible to obtai~ a layer of fibrous material of homoge-neous structure, iOe. the material u~iform by it~ mechanical -ancl physical charact~risticsO
Known in the art is a method ~or productio~ of ~ibrous sheet material (cf. US Patent ~o 2~689.985). ~ccordi~g to this method th~ fibrous material is fi~aly divided and is delivered into the expanding ~as ~tream to be transformed therein by mechanical intermixi~g, whereby the uni~orm distri- :
bution o~ the velocity ~ield i~ achieved and a æeparation of large aggregates i~o small fibLous ~olids takes place.
~he~ the gas-fibre mixture is precipitated on the screen to form a fibrous layer thereon.
A device for carrying out this method ~or productio~ of fibrous sheet material comprises a disc mill to i~dividuali~
æe the fibres, said mill being co~nected through a dischar-gillg pipe to a di~f~ser having divergirlg side and fror~tal walls, a;~d a ro~ati~g roller axra;nged thereirl, the latter comprising teeth0 '~he gas-fibre stream is trans~ormed ~vith .
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mecha~ical agitation cau~ed by the rotatin~ roller9 thus resulting in homogeneous fibre distribution throughout ~ho entixe volume o~ the gas-fibra stream~ 'rhe gas-fibre stream is supplied from the diffusex o~to a ~lat screen.
PDou~ted ~der the screen i5 a suction box for removing gas from the gas-~ibre stream supplied onto the scree~ during the layer ~orming process, The disadvantage o~ the abovementioned method and appa-ratus ~or carryi~g out the same consists in that~ because of local fibre ~locculation caused by mechanical agitatiQn~
it enables the gas-~ibre stream having fibxe conce~tra~ion as low as 5-10 g/m3 to be trans~ormad~ When a gas-fibre stream o~ higher concentration is used9 homogeneous distribution o~ fibres throughout the entire volume of the stream is disturbed.
Furthermore, the gas-fibre stream supplied onto the ~lat scxeen has a low ~ibre concentration. This leads to an inc-reased electric po~er consumption e~pended i~ defeati g the resistance developed on the flat screen during ~he fibrous layer ~orming process when a great amount of gas is being removed through the screen and fibxous layer settled thexeo~.
A gas-fibre stream o~ higher fibre concentratio~ ca~ be supplied onto the screen i~ the tra~sforma-tio~ of the stream befo~e it is supplied o~to the flat scree~, is attained with mu~tiple dispersion o~ fibres in the gas streamO

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: ' ' , ~ 8 K~o~vn in t~e art i5 a method for producbion of fibrous sheet ma~erial~ In thls l)rocess the fibrous material is grou~d and is fed into the e~pallding gas stream. rThe obt~ined ~as--fibxe stream is subjected to multiple dispersio~ and the~
is supplied o~to the fla-t screexl to form a ~ibrous layer thereon, An apparatus ~or carrying out this proce~s comprises a diffuser havi~g diverging side wallsS with iks inlet ope~i~g communicati~g with a ~as-~ibre stream su~plyi~g pipe li~e, while its outlet ope~ing is co~ected with a rectarlgular upright chamber~ Several faixed airfoil-fo~m bodies are arra~-~ed in the chamber with their pla~es parallel to the chamber side walls, the upper portion of each body disposed inside the di~user9 When the gas-fibre stream is impacted agaiLsk the ~aired- :
-~o~m bodi.ss~ a multiple dispersio~ effect occurs due to the resilie~t repelling of the~ibres agai~ the co~vex surfaces of the faired-form bodies, ulhereby the gas-fibre stream is distributed u~iîo~m~;y edgewise over the recta~;ular chamber, a~d the u~iIor~ distributiorl of the velociliy field is a-ktai:lledO
q'he abovementioned method for production o~ ;~ibrous sheet material and the apparatus fox car~ying out the same, however~ ~ail to transform a gas ~ibre stream having fibre - :
conce~trat;ion higher tha:~ 5 to 15 g/m~ the gas-Iibre stream o~ highex fibre conce~ration is îe~l to îaired-:from ' s . . ; , ~ , . :

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35~2~3 bodies, the power o~ th~ ditstribution fields is .i~su~ficie~t for transfo.rmin~ the gas-~ibre stream, i.e. forc~s developed in the proces~ axe insufficie~t for inte]r,mixing the ~a~--fibre stream containing a great ~uantity of ~ibxes per unit o~ its volum~. ~s a xesult, a unifo~ ~elocity ~isld distribu~io~ is not achieved i~ the tra~f`ormed gas ~ibre stream.
Moreover, the ~ibre co~c0ntratio~ of the stream supplied onto the ~lat scxeen conti~ue to be lowg this leadi~g to an increased exp~nditure of curre~t, consumed in de~eating the resi~tance deve~oped on the f'lat screen duri~g the ~ibrous layer forming process, since a gxeat amou~t o~ gas is to be removed through the screen and f'ibrous layer precipitat~d thereon.
q'he gas fibre stream can be transform0d, simultaneously using ~he mulGiple fibre dispersio~ effect and transYersal pulsations induced in the gas-fibre stream.
Kno~n in the art is a method for production o~ fi~rous ~heet material. I~ this process fibres are dispersed i~ a gas stream to obtai~ a gas-fibre stream~ the gas-fibre stream being then distributed i~ a ~latte~ ~orm. ~he obtained ~lat-ten ou~ gas-Pibre stream is txansformed b~ supplying it to a cylind~x elem~nt~
The intera~tio~ of the flatten-~orm ga~-fibre stream with the cyli~der causes multiple ~ibre dispersio~ e~ect .
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resul-ti~ from the resilie~t repelli~g o~ ~ibrous solids a~ai~lst the cylinder sur~aceO Thu~ ~ibre sol.id sh~edding, i.e.
increasing o~ the dispersion value, take~ place.
~ 'he cylinder~ scheduled in th~ appa~atu~, prov~de~ f'or tra~sversal pulsations in the ~as-fibxe stream flowing over the cyli~der, thus resulting in the uniform distributio~ of the stream velocity field~ The traIIsformed gas-~ibre stream is the~ supplied onto the flat screen to form a ~ibrous layer thereonO l`he fibrous layer is subjected to a subsequent ; treatment to obtai~ fi~ished sheet materialO ~:
A device ~or car~ing out the abo~emen-tioned process for productio~ of ~ibrous sheet material co~prises a~ elongated slot nozzle having mutually perpendicular diverging side walls and convergi~g ~rontal walls~ the inlet opening o~ said nozzle being i~ co~nunicatio~ wi-th a means ~or dispersing ~ibres in a gas stxeam to obtai~ a gas ~ibre mi~ture, while its ou~let opening is con~cted witk a chamberP ;~
Arxanged underneath the elo~gated nozzle7 along its enti~ -rQ length, is a cylinder ~ixed with its ends to the side walls o~ ~he chamber~ A special lattice f'or eli~inati~g stream turbulence is placed downstream ~rom the cylinder a~d spa~s the chamber cross-sectio~.
The layer ~ormi~g process takes place on a ~lat scree~
with the help o~ a suctio~ bo~ disposed u~der the chamber~

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~ hs disadva~tages of the described method for production o~ fibrous sheet mat~rial and o~ the apparatus for carl~ing out said method co~sist in9 that this apparatus pe~mit~ to txansform ~hc gas-~ib.re stream having fibxe concentrutiorl onl~
of 10 to 30 g/m3. When the gas~f`ibre s~ream is delivered.
onto the cylinder, the transversal pulsations in the gas fibre stream ~lowing past the c~ dex, are generated, power of said pulsatio~s gradually decreasing as the stream mo~e~
away ~rom the cylinder. There~ore, in case the gas-~ibre stream of higher fibre concentration is ~ed to the cylinder, the power of distribution fields and that o~ transve.rsal pulsations are i~su~icient for trans~orming the stream and for obtaining the sheet ~aterial homogeneous in structure, No one o~ the stream transformi~g apparatus can pro~icle ~or the desired degree o~ transforming o~ the stream having high ~ibre concentratio~.
: Consequently, only a gas fibre stream having low ~ibre concent~atio~ can be supplied on the flat scxeen i~ order to pxoduce sheet material homoge~eous in structure. ~his re-: sults in an increa~ed power cor~sumption9 since a great amoun~
o~ gas is to be removed per unit of time during the layer ~orming process O
Summar~ of the Inventio~
It is an object of the pxesent inventio~ to provide a me- ~ :
thod fo~ p~oduc~io~ o~ fibrous sheet material a~d a~ appara 11 ~

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~ 5~ 8 tus fo.r car~ying out the same, such as to trans~orm a gas-~ibre stream in order to obtain o~ a ~lat screen a ~iblous layer homogeneous .i~ stllucture, the gas-fibre s-tream bein~
of high fibre co~centrationO
Another object of the present invention is to provide a process for production o~ f`ibrous sheet materlal homogeneous i~ structure~ which process is characterized by an increased production output, Still another object of the present inve~tio~ is to redu~
ce ~xpe~diture of current by virtue o~ reductio~ o~ amou~t of ~as to be removed per u~it of time durin~ the fibrous layer forming processO
Yet another object of the present invention is to decrease size~ and metal consumption needed ~or the appara-GUS made therefrom.
With these a~d other objects in view there is provided a method for production o~ ~ibrous sheet material~ comprising dispersing of fibres i~ a gas stream ~o obbain a gas-fibre s~ream9 supplyi~g the gas-fib~e stream onto a ~lat scree~, removing gas from the gas-fibre stream thIough said screen ~:
to form a ~ibrous layer thereon9 a~d its subseque~t treati~g : .
to obtain a ~ibrous sheet material~ wherei~9 accordi~g to ~ .
the i~ventio~, a part of gas is removed ~rom the gas-~ibre s~xeam p~ior to 5uppl~i~g it onto the ~lat screen so as to bri~g ~ibre co~ce~tratio~ in the gae-fibre stream up to :: .

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20 to 500 g/m3 t said concentration bei~g chosen il~. accordance with the kind a~d proper~ies of fibres9 a~d trans~ersal pul-sation~ induced in the gas-fibre stream in -ths course of moving, are dampedO
l`he gas-fibre stream i~ trans~ormed ~lccording to the pro-posed methocl so that its ~ibre co~centrat:Lon increa~es ~rorn 5,o-50 g/m3 to 20-500 g~m3. ~`his occur~ due -to the existence o~ motion of fibres with respect to gas, whereby the fibres approach each othex in a regular manner9 this resulting in increase in local fibre concentrationO Owin~ to that 9 a part of gas which is purged of fibres ma~ be removed independently of the part o~ gas saturated wi.th fibresO
Vu~ to the provision o~ dampi~g of transver~al pulsa-tions induced in the gas-fibre stream in the course o~ moving~
sheet material of homogeneous structure is obt~ined, this bei~g a~ieved by elimi~ation of local flocculation taki~g place in the gas-~ibre stream as its fibre concentration increases O
It is advisable to ~eep the amount o~ gas being removed f'rom the gas-fibre stream prior to supply it onto the flat screen wi.thin the limits ra~gri~g from 20 to 90 percentO
It is also desirable to damp the transversal pulsatio~s by contracti~g the gas-fibre stream i~ the direction normal to the path of the stream movement~
The contracting of the gas ~ibre ~tream in the directio~
~ormal to ths path of the stream provides ~or con~used ~low .
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o~ the streai~ with uniform distribution o~ the velocity Pield profile. ~his co~tributes to u~iform re~ular fibre thicke~ing and to reductio~ o~ the cross-stream cornpone~t ol~ th~ stream turbul~rlce .
With these a~d other obaects in view~ there is also provided a~ apparatus for carryi~g out the method for produc-tion of ~ibrous sheet material9 comprising a slot ~oæzle having ~ide walls ~ormal to converging ~rontal walls, an inlet ope~ing o~ said ~o~le bein~ con~ected with a means for dis- :
per~i~g o~ fibres in a gas stream~ while its outlet opening is communicated with a chamber, a flat screen adapted to foxm a ~ibrous layer thereo~S mou~ted under said chamber, a~d a suction box arranged under the ~lat scree~, wherei~9 accox-di~g to the invention, the side walls of the slot nozzle are i~ parallel relationship wiGh respect to each other, a means for removing a part of gas from the gas-fibxe stream is arranged within the chamber under the outlet opening o~ :
the slot ~ozzle, and the chamber is provided with bra~ch pipes for gas exhau~t, mou~ted substantiall~ in the upper portio~ of the chamber. ~ .
The parallel arrangement o~ the side wall~ of ~he slot ~ozzle eliminate~ a~y considerable elongation o~ the velocity ~ield pro~ile, i.e. provides ~or uni~orm di~tributio~ o~ the ~eloci~y field pro~ileO
Owing to the provision o~ the means ~or removing a par~
of ga~ from the gas-~ibre streamJ disposed u~der the outlet 14 _ ".. " . ~ ~, .. . ~ .. - , . . . .. ... .. . . ..
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ope~i~g of the slot nozzle 9 gas xemoving through the bra~ch pipes arranged iIl the upper portion o~ the chambe:r is achie-ved~ whereby fibre concentratio~ of th~ stream increases, ~vhile expe~diture o~ current consul~ed in dividing the media during the ~ibxous layer fol~ing process i~ reduc~d~
~ According to one embodiment o:E the i~ntion~ the mea~
for xemoving a part o~ gas from the gas-~ibre ~tr~am i~ em-bodied as a plurality o~ guidi~g bodies arxar~ed in parallel one u~der the other and spaced 3 to 20 mm apart, so as to form a vextical row disposed u~der one of the fxontal walls of the siot nozæle a~d inclined at 3,5 to 11 rela-tive to the axis o~ the slot nozzle, each of the guidi~g bodies being inclined ~ith respect to the a~is o~ the slok ~ozz:Le at a.n angle ranging between 10 and 35 ln the directio~ of gas fibre stream movemerltO
l'he mea~s ~or removi~g a part of gas from the gas fibre stream made as a plurality of guidi~g bodies arra~ged in parallel o~e under the other to ~orm a vertical ro~ disposed unde~ one of the fro~-tal walls of the slot nozzle, i~clined at a particular arlgle with the respect to the axis of the slot ~ozzle~ developes resistar~ce to the gas-~ibre stream lea~ing the outlet opening of the slot nozzle~ whereby a part o~ gas charlges its initial direction arld is gradually removed whe~
passing through gaps between the guidi~g bodies as the gas-~i bre stream îlows along the row o~ guidirlg bodi es .

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Z~3 ~ u~ to the provision of gradual removal of gas tbu~ough the gaps between the gu:iding bodies, ~ibre conce~txation of the strec~m increases, this contributi~g to u~iform di~tribu-tion o~ the velocity field pro~ile of the gas-fibre streamO
O~ving to thc inclination o~ the row of the guidinO bo-dies with respect to the axis o~ the slot ~o~le, the ga~--fibre stream is co~tracted as it flows along the guidi~g bodies~ thus i~creasing homoge~eity of the gas-fibre stream6 According to another embodiment of the invention~ the means for remo~ing a part of gas from the gas-fibre ~tream : :
is made as a plurality o~ guiding bodies arra~ged in para-llel o~e under the other and spaced 3 to 20 mm apart so as to form two vertical rows~ each disposed under o~e frontal wall of the slot nozzle a~d incli~ed at ~,5 to 11 with xespect to the a~is of the slot no~zle 9 each of said guiding bodies bei~O inclined relative to the axis of the slot ~ozæle at an angle xangi~g between 10 and 35 in the di~
rection of the gas-fibre stream movement? while the guidi~g bodies of one row are in a mirrorimage position with respect ~ :
to the guidi~g bodies o~ the other rOW4 Such a design of the means îor removing a part of gas from the gas~f`ibr~ stream, incorporatiIlg guiding bodie~;
arra~ged i~ parallel o~e u~der the other so as to ~orm two vertical rows 9 each o~ the rows being disposed u~der one ~'J

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: ~ , , ' : . ', '' : "' ` ' ~5~8 frontal wall of the slot noz~l~, enables the len~;th o~ an active zone throu~h which gas is removedp to be doubled, thus pe~littillg to reduce sizes of the u~it, while maintai~i~g the pxoduction outpu-t at the same level.
Due to the converged position of the guiding bodles~
contl;acting of the gas-fibre stream is effected in the direc tio~ ~ormal to the direction of its movement~ whereby tra~s-versal pulsations are partially damped.
It is advisable to make the guiding bodies in the form of blades~
Owi~g to the blade form o~ the guidin6 bodies, the gas~
-~ibre stream is ~revented from ~ibre loss when a part of gas is being removed.
It is advisable to arra~ge the guiding bodies o~ each row ~o as to ~o~m at least two groupes of blades and -to provide e~ual gaps between the guidi~g bodies in each group, the gaps between the guiding bodie~ of the upstream group being gxeatex tha~ the gaps betwee~ the guiding bodies o~
the doY~nstream group.
Due to the provision of ~wo groups of guiding bodies in each row~ said guiding bodies in each group being equally -~
spaced to each other a~d -the gaps betwee~ the guidixlg bodies of tho upstream group being greater than the gaps betwee~ ~, the guiding bodies o~ the downstream group~ removal of a par~ o~ gas without ~ibre loss i~ ensured as the g~s-~ibre stream flo~s alo~g the row of guiding bodie~ , 17 - !

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'l'he gap between the guiding bodies of the upstrea~ ~rou~
should not exceed 20 mlrlp ~hile the ~;ap between the guiding bodies o~ the downstream group should not be und~r 3 mm.
Other objects, advantages and fea~ures of the inve~tlon will become appare~t ~rom the ~ollowi~g detailed description of the inve~tion and the accompanying drawi~gs, i~ which:
~ IG. 1 is a flow dia~ram illustrati~g a method f3r productio~ of ~ibrous sheet material, according to the prese~t i~ve~tion;
FIG. 2 is a diagrammatic vie~ of an apparatus ~vhi.ch u-tilizes the m~thod ~or production of fibrous sheet material;
accordi~g to the i~vention, general view;
~IG. ~ is the same as shown in ~IG.~, longitudi~al ~:
sectio~; .
FIG. L~ iS an enlaxged vi.ew of the assembly A sho~ in FIG 9 2;
~ IG. 5 is an enlarged view of the assembly B shown i~ FIG. 2;
FIG. ~ is a view of an alternative fo~m o~ an appaxatus for carrying out the method for production of ~ibrous sheet :
material t according to the inventio~;
~ IG, 7 is the same as show~ in ~IG. 6, perspective ~iew;
FIG. 8 shows a~other embodiment of an apparatus for car-x~ing out the method of the present inventio~ ~or pro~uction o~ fibrous shee-t material;

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FIGo 9 i~ the same as shown in ~IG. 8 9 lo~gi.tudi~al section;
FIG, 10 shorls still another embodime~t of arl apparatus for carryi.ng out the method o~ the prese:nt inven~ion ~or pr-oduction of fibrous sheet material~
A method ~or production of ~ibrous sheet material is illustrated b~ a flo~v diagram show~ i~ F:LG. 10 ~ ibrous material a~d gas are ~upplied to a mea~s 1 ~or dispersi~g fibres i~ a gas stream~ whereby a gas-fibre stream 2 is obtai~edO The obtai~ed gas-fibre stream 2 is delivered thr~ugh a slot ~ozzle 3 i~to a chamber 4. Within the chamber 4 the ~as-fibre stream 2 is co~tracted9 and due to inertia ~orces, relative motion of gas a~d fibres is deve-loped. When the gas-fibre stream is contracted, the gas and fibres move in different directions due to the ~act that the density of fibrou~ material is 800 times more than that o~ gas. ~he Xibres travel alo~g the path coincidi~g with the initial path of the gas-~lbxe stream 2, while a par~ of gas, free of fibres, start~ to move i~ a direction opposite to the i~itial direc-tion of the gas-fibre stream 2. A part of gas removed, fibre concentratio~ of the stream i~creases~
Flow path of that part of gas, which has changed its directio~ of movement is show~ by the arrows "a".
~ he gas~fibre stream 2 is contracted i~ the direc~ion normal to the direction of its mo~ement, whereby the trans~

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versal pulsations i~lduced i~ the gas-fibre stream are gradual-ly damped. ~'hus a u~iformity of a velocit~ field profile of fibrou.~ material in the g~s-ibre strea~, as well as a small-scale tu~bulent structure~ are achi.eved. 'l'his, in turn~
ensure~ high ~ib.re co~ce~txatio~ and, at the same time, homo~eneous structure of the gas~fibre ~tream having passed through the chamber 4D
~ he gas-fibre stream 2 is ~urther d~livered from the chamber 4 onto a ~lat screen 5, the remaini~g paxt of gas being removed therefrom by a suctio~ box 6 mounted u~der the ~ ;
flat scr~h 5.
~ he direction of the paxt of ga~ removed from the gas-fi-bre stream 2 when it is bei~ laid on the flat screen 5 is indicated by the arrows "c". A flbrous layer ~ettled on the flat screen 5 is then subiected to a special treatme~t to obtain a ~inished fibrous sheet matexial~
The part of gas removed from the gas-~ibre stream 2 i~ -the chamber 4, and that removed from the fl~t screen 5 may be reused by supplying them i~to the means 1 for dis-persi~g fibres without any additional cleaning of fibres from gas, ~ince the fibr~ co~te~t in gas is o~ 0.02 to 0~5 g/m3.
X'hese ~ibxes may be reused a~ well.
q'hus the problem of the environ~~ment protection is ef~icie~tly solved~
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A part of gas being removed ~rom the gas-fibre stream 2 i~ the chamber 4 is valued ~ 20 to 90 percent.
~ 'he amount o~ gas to be removed from the gas~fibre strcam 2 is chosen in ac~orda~ce with a desired mass o~ 1 s~uare meter of the finished material arld with the length o~ ~ibre~
fcd into the dispersi~g means ~.
The amount of gas valued as 20 to 40 perce~t i~ to be removed in order to provide for mobility o~ ~ibres having len~th from 0~5 to 38 mm when fibrous sheet material with high degree of structural homoge~eity, having mass o~ 12 to 40 g/m , is to be obtai~ed~
~ rom 40 to 60 percent o~ gas is to be removed ~rom the gas~fibre stream ~ i~ case a lower mobility of fibres having length from 0.5 to 38 mm is allowable when homoge~eous fi-brous sheet material havi~g mass of 40 to 100 g/m2 is to be formed, ~ rom 60 to 90 percent oP ga~ is to be removed ~rom the gas-fibre stream 2 is case of still lower mobility of ~ibres in the gas-fibre stream 27 ~his being permissible i~ produci~g homogeneous ~ibrous ~heet mate~ial whose mass per square~me-ter is more tha~ 100 g.
I~ the amoun-t of gas being removed is u~der 20 percent~
the proces~ doe~ not ju~tify the e~pe~diture o~ cu~rent9 the latter dr~tically increa~i~g because of co~siderable vo~
ll~e o~ gas to be removed per unit of` timeO
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It is next to impossible to remove mor~ tha~ 90 percent of gas ~rom the gas-fibre stream 2.
An apparatus for carrying out the method for production ~ ~
of flbrous sheet material comprises a pi,pe 8 (FIG. 2) inter- ,;
connectillg the mealls 1 for dispersing fi'bres in a gas stream and an inlet openin~ o~ the slot noz~le 30 q'he ~lot ~ozæle 3 has parallel side walls 9, 10 (FIG. 3) w:hich are normal to converging frontal walls 11, 12. An outlet opening of the slot nozzle 3 co~municates with the chamber 4.
I~stalled within the chamber 4 under the fro~tal wall 11 of the slot nozzle 3 are guiding boides rspresen~ing 'blades 13 ;~
(~IG. '1). ~he blades are disposed in a ~paced parallel rela-tio~ship o~e under the other, a gap 14 therebetween ,ranging from 20 to 3 mm~
he gap 1~ between the blades 13 is chosen in acco~dance wlth the length of fibres used in a layer forming process. I~
the ~ibre length is ~ mm a~d under, the gap 14 is chosen from 10 to 3 mm, ~or the ~ibre le~gth equal to 20~35 mm the gap 14 is i~ the range between 10 and 20 mmO ~he blades 13 are i~clined at an acute angle c~ with respect to the axis of the slot noz~le 3 in the directio~ of the stream movementO
qlhe a~gle CX~ is chose~ in accordance with the masæ of fibrous material and with the elasticity o~ fibres~ In case the fibres posses adequate elasticity a~d the ~ibrous material mass is suf~icient, considerable inertia forces are generated ~' in the gas fibre ætream 2 as it mo~es alo~g the blades 13~ ~

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To prev~t the gas-~ibre stream 2 from ~ibre 108s occurri~g thxough the gaps 14 between the blasde~ 13, the ar~gle ~ is set close to 35 0 Owing to this~ the fibres are repelled against the blade surfaces toward the axis of the chamber 4 J
Moreover, such an angle pro~ides a~ additio~al resistance of~ered by the blades 13 to the gas~ibre strea~ ~9 this r~sulti~g in i~te~if~i~g the process o~ removing a part of gas from the gas-~ibre stream 2.
I~ case the fibres possess low elasticity and their mass is small~ whereby reduced inertia ~orces are developed in the gas-fibre stream 2 as it moves along the blades 1~, the angle ~ is set close to 10 in order to provide a smooth movement o~ fibres not possessing an adequate elastici~
t~ to be repelled ~rom the blade surfaces, along the blades 13, Moreover, such an a~gle ~ offers a negligible ad~itional resistance of the blades to the gas-~ibre stream 2~ this eliminati~ fibre loss whe~ the gas i~ being removedO
~ he blades 13 are fixed with their e~d faces to the side wall~ 9, 10 (~IG. ~) o~ the chamber 4, the length o~ each blade being equal to the distance between the side walls 9, 10 o~ -the chamber 49 ~ he blades 13 form a vertical roYv inclined with respect to the axis of the slot nozzle 3 at an angle ~ G~ 5) chose~l within the limits ra~ging from 3.5 to 114 ~ he most angle ~ is set i~ a steep build-up of blade resisJGance to the gas-~ibre stream 2 is to be cxeate~ i~ order ~;

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5~8 to intensi~y the removal of ~as. I~igh inkensit~ ~sas removal from the gas~ribra stream 2 may be effected o~ly in case th~
mass o~ every elementa~ fibre is significa~tg e,g. when fibres having co~siderable length ox density (as~es-tos ~ibres) are used. In this case inertia forces acti~g upon the fibres in the gas-~ibre stream 2 are great, whereby the fibre loss with the gas being removed is ne~ligible, Setting the row o~ blades at an angle ~ greater than 11 con-tributes to an u~duly intensive removal of gas resulting i~ appreciable fibre loss accompanying removal o~ gas, I~ the ~lbres are shor~ or possess low density, e~g~ hol-low fibres, inertia forces acti~g ~hereo~9 ~re insignificant.
In this case an intensive gas removal is impermissible, sin ce a great amount of fibrous material will be lost~ ~here-foxe, gas xemoving p~ocess is to be per~ormed with a lower i~tensity9 i.e. a low resistal~ce to the gas-fibre strea~ 2 is to be ~chieved. The need for satisfying these reguirements dictates the a~gle ~ be close to 3~5.
Con~ected to the upper portiou o~ tha chamber ~ (FIG. 2) is a bra~ch pipe 15~ ~'he flat screen 5 is found under the chamber 4. ~he suct*on box 6 is dispo~ed under~eath the ~lat scree~ 5. A ~ibrous layer ~ormed on the ~lat ~creen 5 is the~ .~ed to a mea~s 7 where it is subjected to a~ter treat-ment to obtain a fi~ished sheet materialO
= ~IGS 69 7 sho~ ahother embodiment of a~ apparatus ~or productio~ o~ ~ib~ous sheet material~ wherei~ a means ~or '~
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~ 2~ -removin~ a part of gas from the ga~-fibre str~am 2 i~ made as a plulalit~ of blad.es 13 disposed so as to fo:r~ two ver-tical rows~ each row being located undex o~e of the fro~tal walls 11, 12 o~ the slot nozzle 3 a~d inclined xelative to the axis o~ the slot nozzle 3 at an a~gle xa~giLg from 3.5 to 11.
The blades 1~ ~orming a row disposed under the ~rontal wall 11 are positioned in a mirror-image wc~y with respect to the blades 13 ~orming a row disposed under the fxontal wall 12 of the slot nozzle 3 . ~he blades 13 in each row are mounted in parallel o~e under the other and are spaced 3 to 20 mm apart9 each blade 1~ being inclined relative to the axis o~ the slot noz~le 3 at an angle 10-35 in the clirec-tion of the stream movement.
~ IGS 8, 9 show still another embodiment of an apparatus for production o~ fibrous sheet material, wherei~ each ro~
. o~ the blades 13 is divided into two sections I a~d II. ~he section I is po~itioned above the section II. ~he gap 1~
between the blades 13 of the section I is set from 20 to 10 mm9 while the gap 14 betwee~ the blades 13 of the section II is set ~rom 10 to 3 mm.
FIGo 10 illustrates a still further embodime~t o~ a~
apparatus ~or production o~ ~ibrous sheet material, wherein .
each row o~ the blades 13 is divided into ~our sections III, ~:~
IV9 V, Vl~ ~he gap 14 between th~ blades 13 over ~he sectio~

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III i~ set withi~ 20 to 17 mm, the ~ap 14 ~e-tweel~ the blades 13 over the section IV i~ set ~rom 16 to 12 mrn, the gap 1 betiweon ~he blados ~3 ovex the section V is set ~rom 11 to 6 mm~ and ti}le same gap over the sectio~ VI is set from 6 to 3 mmO
'l~he followiIlg considerations where taken i~to account when settin~ the ~ap distance betwee~ the blad~s in each section~ When the ~as~ibre stream 2 ent~rs the zo~e of sec tion I (FIG. 3), fibre concentra-tiion in the gas-~ibre stream is lo~ and the resistance e~erted ~y fibrous material o~to the transverqal ~low of gas during its removal is also low~ ~ -Moreover9 due to high mobility o~ fibrcs re~ulting ~rom low fibra conce~tration over the section I, the inertia of each fibre particle shows itsel~ up more clearly than over the subse~uent secbions~ Owing to that, more intensive remo~al of gas is ~sured in the zone o~ section I, a~d a large gap dista~ce between the blades 13 may be provided practically without any ~ibre loss. ~he fibre concentrati.on of the ~as--fibre stream 2 increases as it p~sses through the zone o~
the section I and enters tho zone o~ the section IIo .-The resistance to the tra~sversal gas ~low raises over the sec~ion II because o~ an increased ~ibre concentrationO
The same is responsible for the low mobility o~ fibres, æaid mobility occurring under the action o~ inertia forces.
Thus, the probab.ilit;y oY .eibre loss ~sith ga~ being removed~
incxeases ., ~ ~ 5~ Z~

The gap distance be-twee~ the blades 13 over the secblon II, however, i ~ ,small, whereby the 6as removal ~Hlocity ~ becomes lower and the fibre loss is reduced~
- Thus; varyin~ the gap c~ista~ce between the blade~ 13 over each ~ectio~, gas bleeding is controlled over the entire leng~h of the row o~ blades 13~
The proposed apparatus for pxoduction o~ ~ibrous sheet material operates a~ followsO The ~ibres are supplied to the means 1 (FIGo 6) ~or dispersi~g fibres in a gas stream. f~he obtained gas-fibre stream 2 is fed thxough the pipe 8 to the inlet opening of the slot nozzle ~. Due to the provision o~
converging ~ro~tal walls 119 12 and parallel side walls 9~
10 (FIG. 7), the cros,s sectional area of the slot nozzle 3 i6 reduced9 whereby the velocity of the gas~fibre stream 2 increases as it leaves the slot ~ozzle 3. At the same time the gas-~ibre stream 2 is contracted, this resulti~ in u~i~'o~ distributio~ of its velocity field. ~ `-Upon ~eavin~ the slot nozzle 3 (FIG. 6) the gas-~ibre stream 2 e~counters the resistance exhibited by convergi~g rows o~ blades 13. As a result, a considerable part of gas changes the direction o~ its moveme~t a~d, being directed into the gaps 14 betwee~ the blades ~3, enters the chamber 4 a~d then is removed ~rom the apparatus through the pipe branches 150 The de~sity of ~ibres being much greater tha~ that o~
the air~ the ~ibres under the action o~ inertia ~orces con ~ 27 ~

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tinue their rectilinear move~lent between the conv~rging rows of the blades 13. Q pal~t of ~ibres which make~ co~tact with the blade surfaces impacts against these surfaces and, bei~g repelled theref'rom due to blade orientation at a curtain angle xela~ive to the axis o~ the slot nozzle 3~ move~
towaxds the central part of th~ cavity ~ormed by t~Jo co~-verging rows o~ the blades 13~
As the gas is bei~g gradually removed through the gaps ~4 betwee~ the blades 13, the ~ibre conce~tration o~ the gas~ibre stxeam ~ increases.
~ he converged position of the rows o~ the blades 13, providing for contracting the gas~Pibre stream 2, contribu-tes to increase i~ degree o~ homoge~eity oX the stream.
A high ~ibre conce~tration of the gas fibxe stream causes decrease in fibre mobilityD
Upo~ passing betwee~ the rows of the blades 137 the gas-fibxe stxeam 2 is transformed to meet the requirements imposed there upon to ob-tain fibrous sheet material of homo-ge~eous structule, a~d is supplied onto the movi~g screen 50 As the gas-fibre stream 2 comes into co~tact with the flat screen 5, -the remaining part of gas is removed by means oX the suction box 6, whereby the ~i.bres are precipitated on ~he flat screen 5 to ~orm a ~ibrous layer homoge~eous i~
struc~ure. '~he obtained layer is then ~ed to the mean~ 7 where it is subjected to a t~eatme~t to produce ~ ho~oge~eous ~ibrous sheet material~

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,: . . , l~B5il28 Example 1 Sb.eet ma-terial having a mass of 1~5 g/m2 is to be produced from ~sbestos fibres of 2.5 mm mode-lengt;h.
a) fib.re conce~tration in the gas~fi.bre stream 0O.. ~,.. ~.... ~..... ,.... ~.. ~........................................ ..50 g/m3 b) Yelocity of the gas fibre stre~m ..... 0 10 m/s c) cross-stream compo~ent of gas-~ibre stream turbulence inte~sity ..,...~ 20%
d) air is ~sed as a gas medium e) an amount of gas to be removed ranges ~rom 8~o ~0 9~o, since a ~ibrous material o~ 105 g/m2 is to obtained from sho.rt fibxes.
~ 'he means for removing a part of gas ~'rom the gas fibre strea~ is embodied as a plurali~y of blades formiDg two vertical rows, each row being disposed u~der one fro~tal wall of the 510t nozzle. Each blade is inclined relati~e to the axis of the slot ~ozzle at 10, and each row o~
blades is incli~ed relative to the axis of the slot nozzle at 11o 'r`he abovementio~ed minimum angle of blade inclination a~d maximum angle of row incli~ation with respect oto the -slot nozzle axis are chose~ i~ order to provide an inte~sive xemoval of gas ~rom the gas-fibre stream as the latter is movi~g between the rows o~ bladesO
Each row of blades is divided in four sec~ions. The fi~st three sectionsg as view~d from the nozzle~ are of the same 29 :
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2~ -length~ ~he length o~ the f`ourth section is e~ual to 1.2 timesthe le~th oX the first sectio~. ~'he Lap between the blade~
over the first section is equal to 12 mm, kh0 gap between the blades over the second section is equal to 8 mm, tha gap between the blades over the third ~ect:ion is e~ual to 6 mm9 and the gap between the blades over t;he fourth section is equal to 3 mm.
Due to the provisio~ o~ ~our sections, each havi~g a differe~t gap distance between the blade~ ? a smooth removing o~ gas ~rom the gas-fibre stream is ensured. ~he loss o:E as- .
bestos fibres including a considerable amou~t o~ small-siæed fraction, is insigni~icantO 'l'hough the length o~ ~ibres is ~mall, ~he mass o~ the asbes tOS fibres i~ great, therefore, the gap dista~ce between the blades over the first section ma~ be set much greater than the fibre le~gthO In this case considerable inertia forces are developed in the gas-fibres stream as i-t moves alo~g the bla~es of the first section, these forces preventing ~ibre loss~
~ 'he gas-fibre stream is supplied to the slot ~ozzle at a velocity of 10 m/sO Upon leaving the slot nOYJZ1e ~ its velocity increases up to 15 m/s due to the provisio~ o~ converging frontal walls. As the gas-fibre stream travels between the rows o~ bladesg the gas is being partially removed there~rom 9 50 percent of ga~ bei~g removed over the ~irst sectio~ 30 per-cent9 over the seco~d section9 15 percent9 over the -third -- ~0 --, -:
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section, a~d 5 percent, over the fourth section~ '~he total amount of gas partially removed from the gas-fibre stl~am is taken as 100 pexcent~ The gas removed from the gas-,~ibre stream is delivered from the chamber thlough bra~ch pipe~ to the means ~or dispersi~g fibres i~ a gas stream. r~he total fi.bre 105s does not exceed 10 percent~
As a result o~ removing from 80 to 90 .percent of ~as, ~ibre co~ce~tra~ion in the gas fibr~ stream is brough~ up tO 250-500 g/m3, ~Ihile the transv~rsal pul~ations charactexi~
æed by the c~o~s-st~eam component of gas-fibre stream turbu-lence intensity, fall to 5-8 percent, this enabling a gas fibre stream homoge~eous structure to be obtained.
~ he gas-fibre stream moving with a velocity o~ 15 m/s is ~urcher supplied onto the flat screen traveliing at the same velocity. 'llhe remaining part of gas ra~ging betwee~ 10 a~d 20 perc~nt is removed by means o~ a suction box, thus foxmi~g on the flat scree~ a ~ibrous la~ex having c~ ass of 70 g/m2.
The ~ibrous la~er is then subjected to impregnatio~,with

3% silico~ emulsion to ob~ai~ a material having a mass o~
105 g/m2, rolli~g and dr~i~g to achieve the humidity o~ 2 per-cent. A finished sheet material possesses high -thermal a~a electrical lnsulation proper-ties and ca~ be advarltageousl~ ~
used in electrical engineeri~gO
Example 2 ~ heet material ha~i~g a mass of 110 g/m2 is to be produced fxom sulfate bleached cellulose~ fibxe mode~length bein~
of 175 F~ o , - 31 -.

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a) fibre concenGra-tion i~ the gas-fibr~ stream ~. 50 g/m3;
b) as a gas medium ai.r is used, contai~ing 10 perce~t carbQne dioxide additio~ to prevent e~plosion o~
gas-~ibre mixture under the actio~ of static elect-ric charges;
c) velocity o~ the gas-~ibre stream ~ 300~ 8 m/s;
d) crosswstream compone~t of gas-fibre stream turbulence intensity .~ .-0. J ~ 0 25Yo The amou~t of gas to be preremoved ra.~ges between 60 a~d 80 percent 9 since the material havi~g a ma~ o~ 110 g/m2 is to be obtai~ed.
The means ~or removi~g a part of gas from the gas-fibre stream is embodied as a plurality o~ blades ~oxmin~ two verti- .
cal rows, each ro~ being ~isposed under one ~ro~tal wall of the slot nozzle. Each blade is i~cli~ed with respect to the axis of the slot nozzle at 10, and each row of blades is i~clined with respect to the axis o~ the slot nozzle at 305. ~ .
The abovementioned mi~imum a~gles of incli~atio~ of each blade a~d of the row of blades relative to the axis of the slot ~ozzle are chosen in order to provide an inte~siv~
removal o~ gas from the gas-~ibre stream as the latter moves between the rows of blades~
~ ach row o~ blades is divided i~ three sections of the same le~gth~ ~he gap distance bet~een the blades over the first section lS equal to 1~ mm9 the gap distance between ~ 32 -- . .- , ::

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the blades ove.r -the second section is equal to 9 mm~ and the gap dis~ance be-tween th~ blades of the third section is e~ual to 4 m~.
Cellulosic fibres have a~ amoun-t of small-sized fractio~
less tha~ the asbestos fibres have~ hence i.t is su~ficient to di~id~ tha ro~s o~ blades only into three sections and to car.ry out the removal of gas with less smooth~ess.
Blade~to~blade gap distances over each sectio~ ensure a~ -inte~sive removal of gas without co~siderable fibxe loss.
~ he gas-fibre stream i~ supplied to the slot nozzle at a velocity of 8 m/s. Upon leaving the slot nozzle, its velo-city increases up to 10 m/sO As the gas-fib.re stream travels bet~leen the rows of blades, the gas is being partially remo- -ved thexefrom, 55 percent of ~as bein~ removed over the first sectio~ 30 perce~t of gas being remoYed over the seco~d section, a~d 7 percent of gas beinO removed over the thixd section. '~he total amount o~ gas bei~g partially removed ~rom the gas-fibre stxeam is taken as 100 percent.
~ s a xesult of removing o~ 60 to 80 perce~t of gas, fibre concentration i~ the gas-fibre stream is brought up to 125-250 g/m3, while the tra~sversal pulsatio~s o~ the gas-~ibre stream ~all to 4-6 percent, this enabli.ng a gas-fibre stxeam of homoge~eous structure to be obtained The gas fibre stream moving with a speed o~ 10 m/s is further swpplied o~to the ~lat ~cree~ trave~ling with the . .

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same speed. The remaining part of gas rangirlg from 20 to 40 per-cont is removed by means of a suctio~ bo~ thus ~ormin~ on the flat screen ~ layer of cellulosic fibres, having a mass of 90 g/m . The fibrous layer is impregnated with 3% solution of modif`ied mai~e starch to increase the mass of the material up to 110 g/m2 7 and then is subjected to rolling and drying, ~vhereby a wrappin~ paper is obtained.
Example 3 Sheet material having a mass o~ 40 g/m2 is to be produced from ~iscose fibres, fibre mode length bei~g of 8 mm.
a) fibre concen~ration in the gas fibre stream ~ -O---O~ --------O~ 25 gfm3 b) air is used as a gas medium c) velocity o~ the gas-fibre stream 0.Ol....... 6 m/s d) cross-stream compone~t of gas-fibre stream turbulence intensity ...... 0....... O~.... O 3&~o ~`he amount of ga~ to bs prexemo~ed ranges between 50 and 60 percent, since viscose ~ibres are lo~g a~d since the material of L~0 g/m is to be obtai~edO
The means for removing a part o~ ~as from the gas--~ibre strea~ is embodied as a plurality of blades forming two vertical rows, each row being disposed und~r one of the fron tal walls of th~ slot nozzle. ~ach blade .i5 inclined relative to the axis o~ the slot ~ozzle at 15~ each row o~ blades being inclined relative to the ~xis of the slot ~ozzle at 7O

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~085~28 Si~ce the ~iscos0 fibres do ~ot posse9s adequate resilien-ce7 an i~clinatio~ of t~le blades with respect to the axis of th~ slot noæzle at 15 provides ~or smooth slip~i~g of fibres ~long~ the blades 9 while a~ incli~ation of the row o~ blades relative to the axis o~ the slot ~ozzl~ at 7 ensures modera-te i~tensity o~ gas removal f`rom the gas-~ibre strGam~
Each ro~J of blades is divided i~to two sectio~s of the same length ~lade-to blade gap distance over the first sec-tio~ is equal to 10 mm9 the gap dista~ce betwe~n the blades o~er the seco~d section is equal to 5 mmO ~ -The gas~ibre str0am is supplied to tha ~lot ~ozzle ata velocit~ increases up to 8 mJs As the gas-~ibre stream passes between the rows of blades~ the gas is partially re-moved therefrom? 60 percent o~ gas being removed over the first sectio~, and 30 perce~t o~ gas being removed over : . the.second section. The total amount of gas preremoved from the gas-fibre stream is taken as 100 percent.
As a result o~ removing ~rom 50 to 60 percent of ga~
fibre conce~tratio~ i~ the gas-~ibre stream i~creases ~rom ~.
25 g/m3 to 50 - 64 g/m3, while the tra~sversal pulsatio~s of the gas~ibre stream fall., due to contracting of the stream, to 7 percent, thus providi~g for homogeneous structure of the gas fibre stream.
~ he gas~fib~e stream moving with the speed of 8 m/s is supplied onto the ~lat scree~ travelli~g with the same speedO

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'' . ~,. , ., ' . . . ' ,', : , ~ ~ 5~ ~ 8 The xemai.rlin~ part of ~as, xan~ing ~ro~ 40 to 50 percentg i~
removed by means of a suc~ion box, thus ~ormi~ o~ a ~lat screen a layer of vi~cous fibres, having mass o~ 30 g/m2, which i~ then i~pr0~rnated with 15% water~polyvinyl acetate disper~
sion to i~crease the mass of the ~i~ished ~aterial up to 40 gjm2. ~he ma~erial is subjected to rolling and drying to produce a no~woven oil filtering material for large-scale diesel engines. ~.

~J~a~pl e L~
Sheet material having a mass o~ 20 g/m2 is to be pro-duced Prom polyester man-made ~.ibres of 28 mm mode-length.
a) fibre concentration in the gas-fibre stream ..0 8 g/m3;
b) ionized air stream is used as a ga~ medium;
c) velocity of the gas-fibre stream .. ,~.......... Ø.. ...7 m/s;
d) cross-stream component of gas-~ibre stream turbulence i~tensity ...... 0.~.......... ~O... ~. 35%~ The amount of gas to be preremoved ranges ~rom 20 to 25 percent, ~i~ce a fibrous sheet mate~ial having a mass o~
20 ~/m is to be produced.
The means ~ox removi~g a part of gas ~rom the gas-~ibre stream is made as a plurality of blades forming one ~ertical row disposed under one of the ~xontal walls o~ the slot ~ozzl~0 Blade~toblade gap distance is equal to 20 mm. Each blade is inGlined relative to the axis of -the slot nozzle at 35~ while .

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the row of blades i5 inclined relative to the axis o~ the slot nozzle at 3-5O
'rhe abovementio~ed angles o~ inclirlatio~ of each blade and o~ the row of blades with respect to the axi.s o~ the slo~
nozzle are chosen to ensure a removal o~ small amount of gas essentiall~ without fibre loss.
~ he gas-fibre stream is supplied to the slot ~ozzle at a velocity of 7 m/s. ~pon leavi~g the slot nozzle, its veloci-ty is as high as 10 m/s. ~s the gas-fibre stream travels along the blades, 20 percent of gas is removed theref`rom. ~5 a result o~ remo~,ing of 20 perce~t o~ gas, fibre conce~tratio~ i~ tho gas-fibre stream raises from 16 g/m3 to 21 g/m30 ~he cxoss-streRm component of the turbulence inte~sity falls, due to gas-fibre streRm contracting, to 12 percentO
'rhe gas~fibre s~ream moving with a speed of 15 m/s is supplied onto the flat screen moving with the same speed. ~he remaining paxt o~ gas~ namely 80 pexcent o~ gas, i~ rjemoved ~rom the gas-~ibra stream by means of a suctio~ box, thus forming a layex of man-made fibres, having a mass of 15 g/m2O
1'he layer is impregnated with 5% solution of poly~i~yl alcohol to obtain a material havi~g ~ ~ass of 20 g/m2~ which is then subjected to rolling and drying. ~`he finished material is a long grai~ paper practicable in electxlcal e~gineering.
~ xample 5 Sheet ~aterial ha~ing-a ~ass of 50 g/m2 is to be prod~lced ~from defi~red wood ~ibrous particles.

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a) fibre co~centra-tion of th~ ga~fibre stream ~ 50 g/m~;
b) veloci-ty of the ~as-~ibre stream ..~0O.,O..,... 8 m/s;
c~ cross~stream compo~ent of the turbulence in-tensity .~0.,..,...,O~O..OOO...OO..~...O.~..u 32%
d) air is used as a ~as medium;
e) an amount oP gas to be removed ranges from 85 to 90 percent, since a ~ibrous material h~ing a mass o~er 100 g/m? is to be produced.
The means ~or removi~g a part o~ gas from the gas-~ibre stream is embodied as a plurality of blad0s arranged so as to form two vertical rows, earh disposed ~mder o~e of the frontal walls of the slot ~ozzle, each blade being inclined relative to the axis of the slot nozæle at 30, while each row of blades is i~clined relative to the axis o~ the slot ~ozæle at ~1o The aboveme~tioned maximu~ angles of i~clination of each blade a~d o~ each row relative to the a~i.s o~ the slot nozzle are chosen i~ order to provide an intensive ~emoval of gas ~xom the gas-~ibre stream as it flows betwee~ the rov~s of blades.
Wood ~ibrous particles used in the proceæs posse~s great mass and considexable resilience 9 there~ore inertia force~
acti~g upon ~ib~ous material are significa~t.
For the same reason blade~to bl~de gap distances have the same dimensio~s e~ual to 6 mm. ~he gas-~ibre s~xeam iq - ~8 -,. : . , . ~:
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is fed to ~he slot noæY~le at a velocity of 8 m/s. ~po~ lea~ing the 510t nozzle the velocity o~ the gas-fibre ~ream increa-ses up to 10 m/s~
As the stream o~ gas a~d wood fibrous particles flows be tween the rows o~ blades, a part o~ gas accou~ting ~or 85-90 p~rcent is removed. As a result~ the concentration of wood fibrous particles is brought up to 334-500 g/m30 Th0 cross~stream compone~t fof the turbulence inte~sit~ fall,s~
due to co~tracting of' the stream of gas a~d wood fibrous particles, to 7-10 percent.
~he stream is ~urther supplied onto the flat screen i~ a direction normal to its pla~e. s ~`he flat screen travels at a velocity o~ 0.8 m/s. The remaining part o~ gas accounti~g ~or 10-15 percent~ is removed ~rom the gas-~ibre stream by means o~ a suction bo~, thus ~orming a la~er of~wood fibrous particles, havi~g mass o~
400 g/m3. The obtained layer is impregnated with a solutio~
o~ a phenolic resi~ so as to bri~g the mass o~ the fi~ished - -' material up to 500 g/m3~ ~he material is the~ cut into sheets havi~g dimensions 3~3 m and subjected to pressure o~ 60 kg/cm during 20 min. at 180C.
'l'ho finish~d mat~rial is a fibrous cohstruction board practic~ble in co~structio~ ma-terial industry.
Example 6 " ~ .
Woole~ ~elt having a ma~s o~` 400 O/m' is to be produced ~rom ~ibres o~ 10-35 m~ mode~le~th.

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a) fibre ooncentration in the gas-fibre stxeam .~ ........ D ~ O ~ 40 ~/m3t b) velocity o~ the gas-fibre stream ~,.,....0 6 m/s;
c) cross-stream component o~ the turbule~ce intensity ~0%;
d) air is used as a gas medium;
e) the amount of gas to be removed ~,.,O~....~ 90V/o.
~ '~he means ~or removing a part o~ gas is embodied a~ two rows o~ blades, each row bei~ disposed under one o~ ~he fron-tal walls of the slot nozzle. q~he blades in each row are in-clined at 18, each ro~ being inclined at 11~
The abovementioned angles of inclination of the elemen~s are chosen with xegard to the mass of eleme~tary ~:ibres and their resilience~ ~ince the fibres are long and posses~ a considerable mass, an intensiYe removal of gas i~ allowable.
1'he resilience of the fibres is ve~y hi~h, there.~ore the angle of inclination of the blade is set 18.
Gap distances betwee~ the blades are the same and equal to 10 mm, since the mass of each ~ibre is su~ficient to ensureS un,der the actio~ o~ inertia $orces, a high velocity transversal flow of gas being ~emovedO
The stream of gas and woolen ~ibres is ~ed to the slo~
~ozzle with a speed o~ ? m/s. Upon leaving the slot ~ozzle the stream moves at a speed o~ B.5 m/s and is channelled between to rows o~ blades~ ~s the stream flows between two ~ ~

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row~ of blades, a~ amount o~ gas accou~tin~ for 88-90 pex-cent is being removed. 'l'he co~ce~tration of fi.bres in the gas-f`.ibre ~tream is brought up to 410-500 g/m3. A paxt of gas removed, the ~as-fibre stream is supp:lied onto the flat screen with a velocity of 8.5 m/s at 120 with re~pect to its planeO q'he flat screen moves at a velocity of 1.35 m/s9 the remaini~g part of gas is removed by mea~ of a suction boxO
As a result, a layer of fibrous material havi~ a mass of ~0O g/m2 i~ formed o~ the screen.
The obtained layer is subJected to rolli~.
The finished material is a Pelt u~ed in te~tile and construction material industries.
While particular embodiments o~ the inventio~ have been shown a~d described in detail, various modificatio~s thereo~
will be appare~t to those skilled in the art and there- -fore it is not i~te~ded that the inve~tio~ be limit~d to the disclosed embodiments or ~o the details the~eof a~a the de partures may be made therefrom withi~ the splrit and scope o~ the i~ventio~ as defi~ed in the claims.
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Claims (14)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for production of fibrous sheet material, comprising the following steps:
dispersing of fibres in a gas stream to obtain a gas-fi-bre stream;
removing of a part of gas from the gas-fibre stream to bring the fibre concentration in the gas-fibre stream up to 20 to 500 g/m3 said concentration being chosen within said limits in accordance with the kind and properties of the fibres;
damping of transversal pulsations induced in the gas-fibre stream in the course of moving;
supplying the gas-fibre stream, a part of gas remo-ved therefrom, onto a flat screen;
removing of the remaining part of gas from the gas-fibre stream through said flat screen to form a fibrous layer the reon;
treating of the obtained fibrous layer to produce a fi-nished material;
whereby fibrous concentration in the gas-fibre stream increases and hence the amount of gas to be removed through the flat screen during the fibrous layer forming process is reduced, this resulting in decrease in the expenditure of current.

2. A method for production of fibrous sheet material, ac-cording, to Claim 1, wherein the amount of gas being removed from the gas-fibre stream prior to supply it onto the flat screen is kept in the range between 20 and 90 percent.

3. A method for production of fibrous sheet material, according to Claim 1, wherein the transversal pulsations are damped by contracting the gas-fibre stream in the direc-tion normal to the path of the stream.

4. An apparatus for carrying out the method for produc-tion of fibrous sheet material, comprising:
a means for dispersing fibres in a gas stream to obtain a gas-fibre stream;
a slot nozzle having an inlet opening to receive the gas fibre stream fed from said means for dispersing fibres in a gas stream, and an outlet opening;
said slot nozzle having parallel side walls normal to converging frontal walls;
a chamber having an inlet opening communicated with the outlet opening of said slot nozzle, and an outlet opening;
a means for removing a part of gas from the gas-fibre stream, arranged in said chamber under the outlet opening of said slot nozzle;
branch pipes to remove a part of gas from said chamber, said branch pipes being arranged substantially in the upper portion of said chamber;

a flat screen to form a fibrous layer thereon, dispo-sed underneath said chamber substantially in a zone where the gas-fibre stream escapes from the outlet opening of said chamber;
a suction box to remove the remaining part of gas from the gas fibre stream supplied onto said flat screen, said suction box being arranged under said flat screen;
a means for treating the fibrous layer being fed the-reto from said flat screen to obtain a finished sheet material.

5. An apparatus according to Claim 4, wherein, the means for removing a part of gas from the gas-fibre stream is embodied as a plurality of guiding bodies arranged in para-llel one under the other and spaced 3 to 20 mm apart so as to form a vertical row disposed under one of the frontal walls of the slot nozzle and inclined at an an angle ranging between 3.5° and 11° relative to the axis of the slot nozzle, each of the guiding bodies being inclined relative to the axis of the slot nozzle at an angle ranging between 10° and 35° in the direction of gas-fibre stream movement.

6. An apparatus according to Claim 4, wherein the means for removing a part of gas from the gas-fibre stream is embo-died as a plurality of guiding bodies arranged in parallel one under the other and spaced 3 to 20 mm apart so as to form two vertical rows, each disposed under one of the frontal walls of the slot nozzle and inclined at an angle ranging between 3.5° and 11° relative to the axis of the slot nozzle, each of said guiding bodies being inclined relative to the axis of the slot nozzle at an angle ranging between 10°
and 35° in the direction of gas-fibre stream movement, while the guiding bodies of one row are in a mirror-image position with respect to the guding bodies of the other row.

7. An apparatus according to Claim 5, Wherein the guiding bodies are made in the form of blades.

8. An apparatus according to Claim 6, wherein the gui-ding bodies are made in the form of blades.

9. An apparatus according to Claim 5, wherein said gui-ding bodies of said row are arranged so as to form at least two sections and to provide equal gaps between the guding bodies of each section, the gap between the guiding bodies of the upstream section being greater than the gap between the guiding bodies of the downstream section.

10. An apparatus according to Claim 6, wherein said guid-ing bodies of each of said rows are arranged so as to form at least two sections and to provide equal gaps between the guiding bodies of each section, the gap between the guiding bodies of the upstream section being greater than the gap between the guiding bodies of the downstream section.

11. An apparatus according to Claim 9, wherein the gap between the guiding bodies of the upstream section does not exceed 20 mm.

12. An apparatus according to Claim 9, wherein the gap between the guiding bodies of the downstream section is not under 3 mm.

13. An apparatus according to Claim 10, wherein the gap between the guiding bodies of the upstream section does not exceed 20 mm.

14. An apparatus according to Claim 10, wherein the gap between the guiding bodies of the downstream section is not under 3 mm.