CA2130224A1 - Apparatus for a paper/board machine and use of the same - Google Patents

Abstract

(57) Abstract:
An apparatus for a paper or board machine, said apparatus including a pressure-tight chamber. The chamber is adapted cross-directionally to the travel of a wire, felt or similar fabric so as to essentially extend over said fabric. The invention is characterized by having the pressure-tight chamber adapted to include a roll (1) with an at least partially permeable shell. The roll shell surface is advantageously formed by a fabric, furthermore, the roll is appropriately free-rotating mounted in bearings at both ends of roll shaft. The invention is further characterized by having the pressure-tight chamber operated with an over- or underpressure relative to the ambient pressure about the chamber.
(Figure 1)

Description

213022~

A~paratu~ ~or a ~a~erJbo~rd ~achi~ ~nd ~co ~ tha ~

~he present ir.~-ent.on relates t~ an apparatus in accordance ~ith the preambie ~. claim 1 fG_ u~e in ~ ~aper/board machine.

~on~ention~ily, w~er remov~' -n the wire sectio~ has taken place bY means o~ gra~ity, table ~-olls, hydrofoils, vacuu~
$?il boxes, flat suc~ior. b~xes, ce~tri~ugal force and 0 ~ovins vacuum rubber belts. As ~ rule, all paper/boar~
machires em~loy a co~bination o, the a~ove-mentioned water removal metnods.

The func~ions o~ tk.~ ire sect- erl have been charact~ri~ed lS by the concomitant increase of ~ne wire secti~n frictional load ~ith the increase of ~he r.a~hine sveed as ~igh~r vaculm is required ~ue ~o the ..eed for :~eepin~ the solids at a constant i~vei. However, ~l~is r~sul~s i~ ~unnin~
problems and intermittent stops or the ~ire section.
~o A major po-tion of the ~ric~ior.al wire load occurs in the regior~ o~ t:~ w0e suction DOX, wnere the wi~e i~ ~uck~d agAinst .ne suction box surf~ce hith ~ :~igh force that is exerted over ~ large area.

~he flat suction box ha~ a limi~e~ water r~moval capabili-ty . I ts ef f ect can be in~r~as~d by usin~ a higher vacuu~, whereby e.lao th~ ~ri~tion ~etween tne box cov~r surf~c~ and the wir~ t ncr~ses. which resu_ts in gr~ater wire wear a~d short~r ii~e. The friction sets _he limit to the maximum ~s~ble v~cuum in the box. If the vacuum ~ above a c~rtain limit, the wire s~ops f~o~ moving. In paper mac~ines ~orming the sheet from pulp co~air.ing car~onate fillar, th~ elevated friction causes rapid wire wear.
Moving v~cuum b~lt~ made ~rom ru~ber (e.~., Rotabelt, FLO-VAC) are ca~abie of eli.~inati~g the friction caused by :; :
the ~ac~m, but the high vacuum e~loyed results in sheet ~ ~

,:~; . . .

-- .. : : ~ , . . : : .

` 2~ 3~2~'1 ~nar3ci~g by the slot pattern o~ ~he b~ u~ber bel ~s are ex~rem~l~r costli and di ~ -icult to service. ~oreo-~rer, they are p . o}; lem3.tic to drive .

5 Felt quct or~ box is a t~picai _e' ~ cor.di~ ~ oner . Tts opera-.,ion _equires ~ vac~ n of 5~ ~20. whic~ rn~st b~ ac~om-plished using suction pumps. The felt s~ction box cau~s rather he~vy felt -.Jear on the s de suppoXting the web and resl~lts in ~nr~ecessar~l-y premat~e 'elt changes. The ~mount of air flo~ through _~e su~tion box is c~ucial to the con-citio~inS result. I~ -.ew ~el_s -he air ~s freely sucked th~ough tne felt, b~t wi~h the ~radual plugging o~ the f~lt, the ,~mount o. a~ passing through the felt is reduced. Then, t:~e water ~emovai capabili~y Of the felt lp co~ditioner is im~aired a~; the a,..ou~t of ~ir sucked through the feit is r.o longer sufficie~ 'o remove all wa~e- fr~m ~he ~e't.

~o ~verco~e the 2~0ve-describea ~roblem~, a no-~el wa~er-~emOvA' ...etnod has bee~ develooea c:ap~bie of I;lini~izir~g the ~rictiohal effest of suot' on anG ~~o~idin~ sufficient wor~ing time 'or ~he suction. ~h9 characte~izing prope~ties o th~ appara~u~ a~co-ding ~o .-e .r.ven~ion ,'or use in a :~
papert~oard ~acnine are aisclosea ir the a~pended c~aims.
~n the embodiment acco-ding to ~:~e in~er~ion, a p~rMeable jacket roll, most advanta~eousl~ ~ f~bri~-jack~t~a~ roll, ~s adapted i~ a pr~as~ure-t g~t oh~er, advanta~ously a suction box. The 'aDric-jacketea -oll supports the runnin~
wire d~ring the suction and prov_de~ ~ working ~ime for the suctl~n acting on tho sheet bet.~ n the DOX seallng strips that is sevexal times lon~er ana lninterru~ted with regard~ :
to a perforated suctio~ box. The rotary suction box with the fabric-jacketed roll b~comes _he mor~ ef~ective the 35 larger ~he fabric: roll diamete~, ,,hat is, the working time of the suction. H~wever, che s~c~.' on cap~city must be herein i~crea~ed appropriately. -h~ benefi~ of che fabric ' " - ":,.. ~ ' ' ' . ~ ''. ' ~.. `' " ' '" ' ,, ,. ... . ' : .

213~2~

-oll over a con~-erltion~1 suCt~ion roll ls its 'reedom from causir~g w~b mar~i~g, ~hich facili~ates the use o~ the ~resent arrarlgement -~ith extremely fine ~rades of paper ~d board. The apparatis accorair.~ ~o che in~ention, wnich advanra~eously ~s a rotar~ ric--oll su~tion box, said appara~us incorporating a pressu~e-tigh~ chamber such as a vacuum or a pressure box, and in conjunction With said pressure-tisht chamber is ada~lec a p~rme~bl~ ~acket roll, advantageous'y a fabric-jack~tea roll, i.s superior o~er the prior art wi~h ~he benefits de~cribed below. A flatbox, or a suCtion box, ~:astes a poreion ~~ _he vacuum energy a~
rriction which at - t5 worst ha~ers che drivin~ of t~e wire (~aking the wire sli~?. ~he r~ar,v fa~ric-roll suction box accordin~ to the inve~tion r~si s ~he running of the wire cnly b-~ the amount OL the frict_on occurring in its bearings. he 'ric~ on of a æu~t ~n box c~uses the -~ire ~o we~r fro~ its urders_de. This eL_ece ~ay cause prebiem~ -particuiari~ in papor machir~es ~s ng filler-containing stock. Obviously, ~ ar '~ fast~, the hi~her the vacuum ~n ~he ~ox, 3~ contrast, nv sliding Lriction occurs be~ween the rot~ry f~b~ic-~^oii ~uction bo~. and ~he wire, ~-conse~u~n~ly ca~sin~ ~o wire wear due to friction.

Cor.ventionally, a suc~ion box '~ operated at the maximum 25 vacuum still permitt~r.g the runnl~g o~ the wire ~n~ nqt yet causin~ exc~ssive economi~a; ~roblems from wire wear. ~y contraæt, a rotary 'abric-roll suction box c~n be operat~d :.
wi~h a ~rAcuum aeterIr.in~ by the.:ocal situation or neod.
The limit of hi~h ~-acu~m is dictar~d by th~ structural strength of the roll. ~ moderate va~uum can be u~ed i~ the rotary fabxic-roll suction box still achieving good suction result ~o~ing to the lon~ worki~g time of the vacu~, and ~he cont~nt ~ f r.e. solids i~ the sheet c~n be kept hi~her than with ~h~ use of a sl1ct-o~ box. The ~uum reserve of a suction box is availabl~ at the a~stance of the ceram~c box cover from t~e sheec. By contras.. the rotary ~abric-roll suction box puts the ~cuum reserve at the sheet ~ur~ce by ' '~',~ " ' ' . ' ~ , , ' ` ' .', ~' ' ' ~ ' ' .

" - 2130224 virtue of the ~en structure of the roll ~nd the ~i_e.
Corlsequently, the efficiençy of '~e suc.lon provid~d by the f~bric roll ~s ~etter ~han ~nat Oc the suction box.

The suc~ion wo.kirl~ time provid~a ~y the rotary ~abri~-roll suction ~ox is ~everal ~i~es (depending on the ~abric roll di~meter and box seom~t-y) that achie~able by th~ use of sucti~r. box. ~r~ a suc-ion bvx the ~-acuum is cut off ~tex each h~le of tne perforation. In o~ner wo~ds, a portion of 0 the ~racuum energy is used a~ each hoie for restarting ~he ~ucti~n wo~k. 3y con~rast, in a rotary ~aor'c-roll ~uc~ion box the vacuum pre~a-;s over the e~tire machine-~rectional -~id~h of the suct' on ~cx op~nin~ hereby energy is lcse only o~ce for starti~ the suction work.
The uni t p~ice of cke rot~ry Labric-roil suction ~ox ls i~
~he same or~er ~ith -uction 'ooxes ~t ~epiaces. The vacuum arrange~ment s si~.p1er th.An that of a suction bo:c, regui~-ing less expe~diture _n ~he ere~tion o r new i~tal'ations.
20 ~u~ ~-o ~h~ io-~-er en~r5y losses o~ the ~otary fabric-roli suction box, 'he ope~2~ ng costs are r~duced.

A suction -o' l of tne paper ~achine can norlr.ally be oper-ated with .he m~xi~U~ acuum permit~c hy the shee~ qu~1ity and physi~al l~w9 (temperature). AnalogGusly to the suct~on ~oll, t~.e us~bl~ ;nax_mum v~cuum in t;he rot~zy ~bric-roll suction ~ox _s limi~ed by the ro ~ 1 construction or sheet tem~erAtUre . ~:

l:ue to ~he pcrm~ble structure of the roll surface. th~
rotary fabric-rol1 ~uction box system is free ~om the sh~ot m~rking tendency. By contrast, ~h~ proportion of suction holes drilled on a suction roll shell is norm~lly ~nly approX. 50 ~ o~ 1he suction roll surf~ce, ~hero~y the arillin~ pattern of t~e suction roil easily marks the sheet if the solids content of ~h~ sheet i5 too low when reachin~
th~ suction roll.

: s . ': ~

213~224 The rotary fabrtc-rell suc~ion box system achieves a signifLcar.tly longer vacuum ~one alo~g the ~ch~ne-direc~ion~l ~ravel c. the sheet as the vacuum prevails in the bcx encl~s-~y -he f~oric roll~ Q~ a suc~ion roll. the 5 vacuu~, sone e~tk LS limi~ed by the arc covered by suction box adapted to the ins. de of he suction roll. ln practice, the vacuum zone of a suc~ion roll in the machine direction covers ~pprox. 1~O m~, while in a rotary f~oric-roll system the vacuum zor.e can have a length ir excess of 2~0 mm.

ln ~ suctior. roll ~he vacuum rQ~erVe is ~isplaced at a distance ~approx. /0-~0 .~m) Oc tne roll shell thickness _ro~ the poinLi 3f suction. In a roeary 'abric-~oll sy~tem the ~-acuum reserv~ i~ located immedia~ely under the ~lre.
~his is ~caus~ all -i~w-choking con~e_ictions are eliminat~d fr~.~ the system.
.
A ~UCtiO.I rol; is exD~nsive due to special materials And m~nufacturin~ ~etr.ods re~uired. The fab~ic-j~cketcd roll h~s simpier ~-~stru~t'on and is ~ccordinglY cheaper to man~iacture.

A suction ro;; - aif~icult to clean due to its clos~d structure. Owing ~o its operLs structuxe, th~ fabric ~s ~ollisuction 20x syscem is easy to cl~n.

All se~vicing poin~s of a suction roll are located to the interior of .;~e roll .~ith the exception of the bearing~.
re~uirin~ the removai o~ ~he roll from the .~achine an~
dismantli~y thereof for s~heduied mair.tenance. By conr.rast, all essentiai service-r~quirin~ compo~.ent of the rotary fabric-roll system ~re located on the outer surface of the a~paratus, where ~hey can be ser~iced or replaced during a shut-dowr. wi~hout ~he nead for remo~al o~ the ~pparatus 36 rom tho paper machi~e. The only exception 1.~ the Çabric j~c~et o~ ~h~ _oll ~a wir~ ~acket).

`i, 3'`

;,.. ,;~ . : ., :: , ..

- `" 2~3~2~

The fab~ic roll ca7~lses a small bump on ~he wire travel, but ~limina~es almost enti~ely the sliding friction. ~ence, ~he only resist~ce to the ~ire ~r~vel _s comprised by the friction ~f t~e s-~pport ~trips anc tne rotational ~ricti~n cf -he beari~gs. T~.e rot~ry fabric-~oil suc~ion b~x ~ at~s ~he use of demar.d-controlled pi-ess~re gradient for wate~ ~emc~al a~ ~he outgoing end of the wire section, -~hich in m-~l~ t -piy sheet form~t . on -L~pro-~res boDdin6 ~tween the plie-~, ana in 2l1 sheet lormation elevates the solids 0 con~en~ erms o' s~eci~ic suc~ion enersy consumptio~, he ~ota~y fabric-_o1l suction box provides higher econom~
than ~ s~t of suction bo~es with A corr~sponding effective ~rea of suction openi~gs. ~he ro~ary faDric-roli suction box is capab l e of -ep1acing 3-5 suc~ion boxes of e~al 15 size. ~ne c~st of the rotar~ fab-ic-roil suction ~ox is onl~ a f~ac~;on of _he cos~ o~ a suction roil ana ~ movi~g sio~~ed--u~r vacuu~ belt. _~ ~ s quie~er and can b~ :
ope-ated wi~h smalie- ~ressure gradier._ due to its longer suc~io~ ~ rking tir~e. Accordin~ , .he vac~um can be proaucea usi~ ~ suction fan whic:~ needs less energy than iiquid-r r~ pump. ~educed wear ~i~o means ~ ~99 wire woAX
and exte~aea wire i-_e. Success ui suction action with ~
~ed~ced ~ress~re graGient h~lps ~eepi~.g ~.e f ne solid~ in ~he shee~, ~-nereby ~:~e final p~oduct s~oothness is impreved. l'he ~o~a~y -abri~-ro'~l sucti~r box sys'em is easier to kee~ cl~ Ahan a ~uction roii and a suction box as tne ~ixture of sucion air and orai~d water passe~
~h~ough ~e fabric ~ol' .rom ~oll inside radially ou~ward on th~ c~osite side t~ that ~aclng the wire thu~ re~ovin~
30 ~art.ic~i~te matter adhering to ehe roll surface.

The ~acuu~ ~ox into ~hicAh tke fabric roll is a~ap~d ~ust be rigid enou~h to support the ~acuum without dimensior.al changes. CorA-espoAIdingly, t;~e fabric roll mus~ take the forces imposed by the vacuum prevailinq ir. the vacuum box withou~ any bending o dimension~l ~han~es. If tAhe roll shaft is designed to extend through th~ entire lengtA~A of 213~2 ~

the roil, ~he :Eree space fox~ned between the shaft and the sheil of Zhe rol. must b~ at leas~ half the width of the suction open_ng _:1 order to a-~oid c:~oking of the suction 'lo~ in ths s~ctlo~ ~o~king areA du~ to o~structiorS in the s roll con~uction.

The proportion o_ suc~ion openings on the roll shell ~ust b~ as r.i~h ~s ~ossible to achieve aR ho~ogeneous vacuum at each poi~t of ~-ne shell surface as ~ossible.

?he roli sn~i; is jac:~eted by a shrinkable rabric with a ~esh o. 'our yarns ~er centimeter, ~or instnnce. Such a permeable fabric ~er-v-es for optim~l~y equ~lizing the ~uum over -he ~ntir~ are~ of the suc~ion o~e~ing by slightl~
di.splacirlg the run~ing wir~ fro~. t~e roll shell surf~ce.

~urther app ications of ~e app~ratus according to tho in~ention for a ~ap~r~30a~d machine ca~ b~ found as, e.g., 2 fel. conditioner. a ~ressure-gradient Qryer on the pres~
sectio~ and ah applicatio~ ir. a twin-wire machine. Herein, -ela~ed ;o ~per an~ board ~achir.es designed fox runnin~
~he shoeL between t~o ~ires, a pressure oox fed with he~ted com~ressed air ls adapted at the rotary fabric-roli suction box. 3y -virtue of the overpressure prevailing in the 26 ~ressure box, ~he wate~ containea in the sn~et i5 expell~d to tr.e ~-orking r2~g~ of the suction box vacuum. Usi~g the rotary fa~ic-~oil suc~ion box ~ccording to the in~ention, a wire section can be ~onstructed by ta~ing the wires of a twin-wire section in e zig-z~ fashior. for wat~r removal so ~.at a first r~tary ~abr_c-roll suction box is adapted to blow, a secon~ is ~d~ted to suc~ from the oppo~ite side, and a third is again adap~ed ~o blow from ~he same side as ~he first rotary fabri~-roll suctio~ box. ~ence, the water ~emoval always oc~urs in the same dir~ction, whereby the best effic~e~ey in water re~ov~l is achieved . Under the blowin~ fabri~-~oll boxes is adapted a vacuu~ box similar .o th~ blo-~ing boxes, whereby air passa~e thro~gh the wire -- 2~224 is a~rgmenteQ enhancing the drying result. ~orein, the ~ACU~ level .may not be ad~ust~d so high tnat the ~acuum-riAe ~lre is detach~d from tne sheet.

s The invention .s ~urthe- related to th~ ~se of ~he ~ppA-ratus fcr a pa~er/bo~d ~chine a~ant~geouYly ~c A w~ter re~o~-al ~nit, ~ressure-gradient dryer o~ fele conditio~er.

~he ir~vention i~ rex~ ex~min~d in greateX detail ~ith ¦ 10 refe-ence to ~xe.~.piifying embodiments i;iustrated in the a~penaed d~wings, in wni~h -igure ' is a.~ end v ie~,- of .he ~paratus according to eha i~v~ntion for ~ paperJboard ~achine;

ri~re ~ ~s a ~hree-dimensional p~ojection~l view of ~he apparatUs illustra~ea in Fig. 1:

~lg~lre 3 '9 a d-agra~matic iayout vie-~ of ar applic~tion z~ ol -;ee a~para.us accord~g ~o ~he _nvention ~s a ~ressure-gradient dry~r on the p-ess section;

~igure 4 is c di~gra.~matic layouc v~ie-~r of an appllcation o ;~e a~paratus accord~n~ t~ the i~.venti~ on a C~in-wire ~ection; and ~igure 5 is a diagr~matic layouc vie~ of ~n applicntion of .:.e apparatus accordina to the invention ~9 felt eondit1o~er.
~o r~ th ~e~eren~ ~o Figs. 1 and 2. a pe~eab1e ~acket roll 1, advan~a~eously a fabric-j~cke~ed roll, is ad~pted to the in~ide Or a ~_~ssure-~igh~ chamber 2, adva~tageously ~
VACUU~ bcx. ~he ~pper ~rface of ~ne roll 1 remains over the top surface of the box 2. The pressure gradient, ~dv~n-ta~ously a vac~um. ~rovided b~ the box is exerc~d via the roll ' and the ~ire 5 to a sheet 6 running cn the wire. As ` -` 2 ~ 2 ~ ~

the sheet 5 reStS o~ the wi~e ~, th~ vacu~ sucks t~e wire ~ against the fab~ic ~ur~ac~ of tho roll 7, whereby the roll 1 s~art~ ~o rotate at ths speed of ~he wire 5. uring 'r.~ rotalion of the r~ll 1, the sheet 6 r~nnin~ on th~ wire ; 5 is subjected to suc~ion wnich prevai's ~ith a const~nt ~_essurz ~radien' all ~he way .rom ~he -nco~.ing side sealing str7~ 3 .o the outgoing side sealing stri~ ~ of the box ~ . ~ke long work~r~ time of _he suc~io~ makes th~ water remova a~tio~ highiy efficient, and t..e fa~ric jacket 7 0 equali2es the sucti~n in a markir.g-free ~anner o-~er the ~7ntirQ area of ~he suc_ion ope~ing.
-~ith reference to Figs. 3 and 4, such a~lica~ions of ~he a~paratus accord ng to the invention are shown i- whi~h the press~l-e-ti~t ~hamber 2 is ~s~d as a Dressure box. The ~ressure box is advantageous in sit~ations rleedlng detach-ment of tre sheet 5 C-~m t~e wire 5, c~ alternatively, -~ater re~.7.oval fro~ the sneet 6 in a directlor. opposite to the box. Norr.ai'y, suc'- ~n appl~catlon usin~ t~e pres~ure zo box pr~umes a t-~-in~ ire secti~n. rhen, the pressure box ~a~ he opposed ~y a vacuum b~x, ~herebv th0 -~acuum may not, ~owever, be adj~lsted so high as to detach the vacuu~-$i~e wire Erom the sr.eet.

~,~ith reference to Fig . 5, an applicatio~ of the apparatus according to the .nv~ntion for use as a felt condi~ioner il s~ow~ rei~, ~h~ press~re-.ight chamber 2 ineluded in the a~aratus is u~ed as a ~re~suro box. Re~lacing the felt guide roll, the apparatus is ~vantageousl~ ~laced ~t location where the felt is maxi~ally deflected. To ~he other side o~ the felt ~s aaapted a vacuum box for d~inage o~ the waeer removed f-om the felt So much ~eAted air is ~assed to t~e pressure ~ox 2 including the ~oll 1 th~t a continuo~9 overpressure is e~tablished nside th~ roll 1.

3~ The overpressure expels water co~t~ine~ in the felt, which ~tion is furthe~ a~gm~nted by the centzi~ugal fGrce gonerated by the elt -ravel about th~ perimeter of the `

--` 21~2~

rotati~ he ^~acuum trough plac~d on the opposite side o t~le îelt _s connected to a suction ~an Ouited to ; produce a moderate vacuum to ~aid o~pos~ te side of th~
; felt.
~ 5 3 ~he apparatus described herein is aiso ~el_ suited for use ~s a conditioner ~or A wee wir~ ~nd i~ dryin~ wire.

~en equipped ~ a pressure ~ox, the aDp~ratuS accordin~
~o t:~e invention s ~n xcell~n~ replacem~nt for a ~ire ' ~uide s;~o~. Comp r~enting ~he centrifug~; a~tion, ~he pressure yradien. pr~vided by the a~paratus enh~nces water remo~al. Mo~eover. ~he -~-earin~ action imposed by the guide shoe on rhe wire is eliminated resulclna in l~nger -~Jlre life, l~o one s~ d i~ the srt it ls obvious ~h~t _hc invention is lnoc .. i~ited '~y ~ exe~.p~irying e~bcdimer~s des~rib~d :~
a~ove, ~ut ratke~, c~n ~e varied wit~in -hre3 scop~ and 2~ s~irit ~ ~he i~nncxed claims.

::i: , . ; . ~ . , .;., . ... .~ : ".. :: ,:, ~ . : i : :

~: .
.. . . .

Claims (13)

1. An apparatus for a paper board machine, said apparatus including a pressure-tight chamber (2) and said chamber being adapted cross-directionally to the travel of a wire, felt or similar fabric (5) so as to essentially extend over said fabric (5), c h a r a c t e r i z e d in that to the pressure-tight chamber (2) is adapted a roll (1) having an at least partially permeable shell.

2. An apparatus as defined in claim 1, c h a r a c -t e r i z e d in that to said pressure-tight chamber (2) is adapted at least one sealing strip (3, 4), nozzle or similar element and a roll (1) with an essentially permeable shell, said roll (1) being mounted preferably free-rotating in bearings adapted to the ends of the roll shaft (12).

3. An apparatus as defined in any foregoing claim, c h a r a c t e r i z e d in that said roll (1) comprises an essentially cylindrical and permeable shell, a shaft (12) and at least one support element joining the shell to the shaft such as a support plate (8), support strip (9) or support wire (10).

4. An apparatus as defined in any foregoing claim, c h a r a c t e r i z e d in that the total area of openings on the shell of the roll (1) is at least 50 %, advantageously 60 - 80 %, of the shell total area.

5. An apparatus as defined in any foregoing claim, c h a r a c t e r i z e d in that the shell of the roll (1) is advantageously formed by a fabric jacket.

6. An apparatus as defined in any foregoing claim, c h a r a c t e r i z e d in that the shell of the roll (1) is coated with a jacket such as a shrinkable wire or similar material (11).

7. An apparatus as defined in any foregoing claim, c h a r a c t e r i z e d in that the free space formed between the shaft and the shell of the roll is at least 50 %, advantageously 60 - 80 %, of the width of the suction opening.

8. An apparatus as defined in any foregoing claim, c h a r a c t e r i z e d in that said roll (1) is adapted in conjunction with at least one pressure-tight chamber (2).

9. An apparatus as defined in any foregoing claim, c h a r a c t e r i z e d in that said pressure-tight chamber (2) is operated with an over- or underpressure relative to the ambient pressure said chamber.

10. An apparatus as defined in any foregoing claim, c h a r a c t e r i z e d in that said pressure-tight chamber (2) is operated with an overpressure in the range of 0 - 0.25 bar, or correspondingly, with an underpressure in the range of 0 - 0.5 bar.

11. An apparatus as defined in any foregoing claim, c h a r a c t e r i z e d in that the overpressure or underpressure, respectively, prevailing in said pressure-tight chamber (2) acts radially essentially through the entire roll (1).

12. Use of a roll (1) in a paper/board machine, said roll having an at least partially permeable jacket and said roll being adapted to a pressure-tight chamber (2).

13. Use as defined in claim 12 advantageously as a water removal unit, pressure-gradient dryer or felt conditioner.