US2694347A - Suction press roll arrangement - Google Patents

Description

Nov. 16, 1954 L. HORNBOSTEL 2,694,347

SUCTION PRESS ROLL ARRANGEMENT Filed Aug. 31, 1950 s Sheets-Sheet 1 fzu enfar HZZL E Nov. 16, 1954 L. HORNBOSTEL 2,694,347

SUCTION PRESS ROLL ARRANGEMENT Filed Aug. 31. 1950 3 Sheets-Sheet 2 Nov. 16, 1954 L. HORNBOSTEL 2,694,347

SUCTION PRESS ROLL ARRANGEMENT Filed Aug. 31. 1950 s Sheets-Sheet 3 @iiij) L 203a ffqivzbosfei United States Patent Office 2,694,347 Patented Nov. 16, 1954 2,694,347 SUCTION PRESS noun ARRANGEMENT.-

Lloyd Hornbostel, Beloit, Wis., assignpr toB eloit Iron Works, B eloit, Wis., 'afcorporatioii of Wisconsin Application August 31, 1950,; Serial No, 182,579

9 Claims. cit; 92 -49 The present invention relatesto a suction press for a paper making machine and more. particularly t'o a paper machine suction press wherein ,thesuetion applied at the press nip is exerted aganistanuncovered press felt to facilitate drying of the felt by 'the passage of fluid therethrough.

In the paper making art it,-is conventional practicetto pass a moist paperweb supported upon a, press felt through one or more suction presses, whereby moisture is removed from the web byme'chanical nip, pressure of a pair of cooperating press rolls, togetherwith suction exerted at the press nip. Generally, Fourdrinier-type paper makingmachines are designed to sufficiently d'ry the web by suction while still on theforrning wire, sothat suction alone in a later press section is not elfective to r r eri q Web. cco dingly, these tim chanical pressure eitheralone or intco'njunc'tion with suction is necessary for further vveb dewaterin'g, "Press felts are generallyutilized to convey; th Wb from the termingwire to the paper machine' dri er part,"'the felt also serving to absorb moisture from' thej web: in surfacekon; tact therewith. This water absorption by the felt is par' ticularly effective when the felt and'web are subjected simultaneously to mechanical pressurasuch asa' press nip.

The presentinvention now Iproyides'a noyel forrnof, suction 4 press wherein one roll: of, apir of pressure, nip, defining rolls has an interior suction'gland defining ani arcuate suction area extending to both the oncoming and off-running sidesof the pressurel nip, A,pre'ss',fel't" passes through the nip andis lapped about theone rollto cover the, entire suction areath'ereof, The web to belf dewatered, however, is guided through the r-lip tocon'tactQ only a part of the suctiori area, coyeringfelt portion, erablyonlyat the nip prope'r. The felt i covered for most of. itslrunl oyerth'e su I, before and after the nip prop er, and sucti'o'n-tis elfective to dewaterthe felt. I Such: deyvatering is par'ticula'rly ef feetive on the-uncovered felt since itis:openpfor the passage 7 of atmospheric air therlethro'ugh into the suction afreaof the roll. This passage of atmospheric "airinto.

datethe drainage of moistureitherethrough.

lt lalsoperm its full air flowthrough; the ho les of-the suction roll shell causingthe Water squee'z'edsintoathese' holes to be drawn into tl re SLlQtiQn glandl a resullt; the water cannot be thrown back into the fel't and webs Further, as the web and the feltlexp aildrfrorn "their: ompress d state. n, he ip ir l e vl v. i b' el fill hs.. i e t t whe o d in he ett aiedyby the web filled with water thrown from .the suctionlrollj holes. i

In any press roll assembly, ahigh pressurearea is created I at the, incoming side, of th e nip sd lQ; 0,,convergencelofthe, rotating rolls and av low. pressure, area .is created fat' the 1 qlgoingrside ofthe nip fdue to the. divergencesbf the. rotating rolls, The resulting pressures dilferen'tialibetween j the two sides of the nip tends to draw water throughfthefl nip, Since, inthe present-invention, the felt is open' an'd' uncovered by'the web, on theotfgoingvside ofltheniip, the, educ d. nip load on the felt is relieved and, the -rtend,e ncy to, carry water throughthe nip willjbe nullified; Heretofore, any. extension of the suction area beyond the nip had the "dis; advantage of further decreasing the reduced pressure on, the-ofF-going siderof-the nip creaitjed bythe divergence; of the rolls sineethe-felt wascoveredby the'web aiid couldznot I quickly ventthesreduced pressure afea'therejof the suction area "opens the pores of the; felt" to accommof pressurearea in the felt ,is' relieved as sooin a's the,

to -the atmosphere.v Asa result the extendedsuction-area the nip.

On the.oncoming side oflthe, nip, the passagc of air through the felt isfeifectiveltti remove; water; squeezed from the webinto the felt by mechanical nip pressure. On the off-going sideof, the nip, the passage qf air through the felt removesrsidu'al moisture presen'tin the felt after the subjection of ,thefelt .'to mechanical nip pressure, and also the pores of the, felt are, openedand freed from web fibers, free lignins and other substances squeezed from; the Web at the nip, Thesopeningtof thefelt pores after passage of they feltthrough' the Pressure nip also promotes freer airflow throjughthe, felt, together with consequent improved air drying characteristics of thefelt as it is trained ahout itsguide, 'rollspriorf to re-passage through the su'ctiodpress.

Prior to this time; thosefskilled in the. art, in analyzing the most effective utilization of suction'inconjun'c tion with mechanicalnip pressure in a; su ctionl pressfassembly, have 'concludedthat"rapid.drying of the web could best be promoted by extended w,eb -f elt contact in the suction area, thereby increasing thedrainage of moisture through the web, and the fe'lt' under differential air pressure conditions, Applicant has discovered :the unobvious advantages hereinbe'foreirecit'e'd residing in the Icon-s tact of the felt with theweb' only' at the point of mechanical nip pressure, with the felt 'alone being directe'd about the suctionv area both on the' .on-coming and off-running sides of the point of mechanical'nip" prcssure. By promoting felt drying and by opening up the feltpores, applicant has greatly increasedfthe possibilityiof water absorptiomby the, felt without decre'asing suction removal of water from the web at'the'press nip..'

It is, therefore, an; important object of,the.present ini vention to provide an improved 'suction press for a paper making machine includinga press rolhhaving an arcuate suction area andanuncovered-porous press felt lapping said suction area for promoting drying ofthe felt and;

opening of the felt pores.

Another important object ofthe present invention is to provide an improved'method of dewatering a moist paper web by the passage' of' the" web and a pressfelt'throu'gh the pressure nip of a suctiompress and subjecting the felt alone to suction both on the t n-coming" and off-running sides of the .press nip to open'the pores of the felt," thereby increasing thewater absorption capacity of the felt.

Still it i's-a further-important objectof thepresentinvention to provide an improved-'suct ion press including a suction press roll qcooperatingwithan additionalrolltodefine a pressuren-iptherebetwee'n, means lapping-a press felt about the entire suctionareaof the press-roll both onthe on -com ingr'and olf-running-sidesofthepress' nip and means directingralmoistenedpaper web to-contactwiththel-tpress felt only at the-press -nip, the press felt pores being opened by flow of air thcrethroughas the same passes. about the'suction area to-increase the water absorpt'ionelfieiency ofsthe-vfelt atvthe' pressure nip.

Still anothersimportant object of the; present invention is to provideamethod=ofsincreasing.thev water removal efiiciency of a. suctionlpres's, by providing a suction press havinga mechanical pressure nip, subjecting a-PIeS$Lf6lf to vacuum on both theflon-coming andzotfirunmngsides of the pressure nip, and guidingtalpaper. web in contact with the felt only at the press nip," whereby thewater absorption -efiiciency of :the felt is increased bythe opening of'the pores of :thefeltand-the drying; of the same under vacuumiwiththe web out of contact.

Yetranother important object of the present-inventionis to provide arpaper machine press inwh-ich-sucttonus applied to a press felt both in advance of-and'immediately after passage of thefelt through a mechanical pressure nip and in which a moist paper webis guided into contact with the press felt only-at the pressure nip,

whereby the water'absorptionefliciency of the felt is increased without interfering-With the-efiiciency of'water removalfrom the web by the concurrent application of mechanical pressure and vacuum at the'pressur'e nip.

Other and'further important objects of this invention will be apparent from the disclosures in the specification and the accompanying drawings.

On the drawings:

Figure 1 is a diagrammatic representation of the present invention as embodied in a straight through suction press;

Figure 2 is an enlarged vertical cross-sectional view, with parts shown in elevation, illustrating in detail the operation of the suction press of Figure 1;

Figure 3 is a diagrammatic representation of the present invention as utilized in a straight through reverse press;

Figure 4 is a diagrammatic representation of the present invention as applied to a reverse suction press;

Figure 5 is a diagrammatic representation of the present invention as applied to a horizontal dual suction press;

Figure 5A is a diagrammatic representation of the present invention as applied to a suction press and drum combination for a cylinder type paper machine.

Figure 6 is a diagrammatic representation of the present invention as applied to a double suction press;

Figure 7 is a diagrammatic representation of the present invention as used in conjunction with a Yankee dryer; and

Figure 8 is a diagrammatic representation of the present invention as utilized within a conventional paper machine drier section.

As shown on the drawings:

In Figure 1, reference numeral 10 refers generally to a foraminous Fourdrinier-type forming wire wrapped about a suction couch roll 11. formed on the wire and substantially freed of surface water while thereon, is removed from the wire and trained beneath a guide roll 12 in spaced relation to a press felt 13 trained about a guide roll 14. The felt is passed through a suction press nip 15 defined by a plain upper press roll 16 and a lower suction roll 17 partially surrounded by a conventional arcuate save-all pan 17a. The suction roll 17 is provided with an arcuate suction area 18 defined by a suction gland G disposed within the interior of a perforated rotating shell and defined by a front gland wall 19 and a rear gland wall 20. The suction area 18 and walls 19 and 20 are displaced peripherally of the roll 17 on the on-coming and off-running sides, respectively, of the nip 15 so that suction is applied at the roll periphery both immediately in advance of and immediately in the rear of the area 21 at which the mechanical nip pressure is applied.

The web W contacts the felt 13 only at the nip pressure area 21, and the web W is partially lapped about the upper press roll 16 by means of a guide roll 22 positioned above the felt and adjacent the upper plain roll 16 of the felt in advance of the nip 15. A second guide roll 22 is positioned adjacent the upper roll 16 immediately after the nip 15 to aid in stripping the web W from the upper roll 16. As is apparent the nip 15 lies in a plane generally tangential to both the rolls 16 and 17, and the guide rolls 22, 22 are positioned above said plane or on the (top) side thereof opposite the suction roll 17.

On the other hand, the felt 13 is lapped about the lower suction roll 17 to contact that portion of the roll periphery overlying the interior suction area 18. In this manner, the sole suction effect of the roll gland G is applied to the felt. The moist paper web W contacts the felt 13 only at the nip pressure area 21 so that the web is subjected to the suction effect of the roll 17 only at the exact point of mechanical pressure.

It will be appreciated that water will be forced from the moist felt W by the nip pressure at the point 21 and that the water thus removed from the web will be drawn through the felt 13 into the suction area 18 of the roll 17, as is well known in the art. However, the suction effect of the roll 17 at the remainder of the suction area 18 will be exerted solely upon the press felt and the suction thus exerted will serve to draw atmospheric air through the felt to open the felt pores and to remove residual moisture therefrom. Further on the on-coming side of the immediate nip area 21, the suction area 18 will serve to remove moisture squeezed from the web and the felt. Such moisture generally collects upon the surface of the web and the felt immediately in advance of the nip, and the suction area will be effective to remove this surface moisture.

On the off-going side of the felt, namely, between the area 21 and the rear suction gland wall 20, the Suction The web W, initially will effectively remove the residual moisture from the felt and open the pores of the felt to increase circumambient atmospheric drying of the felt as it IS guided upon its return path to the nip 15 about the guide rolls 14. After passage through the mechanical pressure nip, the felt is squeezed and compacted so that its density is materially increased and the fiow of air and moisture through the felt is hindered. The drawing of atmospheric air through the felt will serve to open the felt pores, thereby materially increasing the drying of the felt.

In the embodiment shown in Figure 3, the reference numeral 10 again refers to a Fourdrinier-type forming wire with the web W being removed therefrom and lapped again about roll 12 into contact with a press felt 13. Felt 13 is passed through a conventional first suction press including a plain upper press roll 23 and a lower press roll 24 defining a press nip 25 therebetween. The suction press roll 24 is provided with an interior suction area 26 which is lapped by the press felt 13 and the web W. A conventional arcuate save-all pan 27 is provided to receive water centrifugally thrown from the surface perforations of the press roll 24.

Following the passage of the web W through the press nip 25, the web is stripped from the felt 13 and is passed about a web guide roll 28 through the nip 29 of a reverse press assembly defined by a lower plain press roll 30 and an upper suction press roll 31. The end of the press roll 31 is provided with an arcuate suction area 32 lapped by a press felt 33 trained about the roll 31 and through the press nip 29. The save-all pan 34 is provided adjacent the suction roll 31 within the loop of the press felt 33 toreceive water thrown down the apertured periphery of the roll 31.

Here, again, it will be noted that the felt 33 is guided by a pair of guide rolls 35 into contact with the entire arcuate suction area 32, while the web W overlies the suction area 32 only at the exact point of nip pressure, that is, at the point where the rolls 30 and 31 define the nip 29. Thus, the suction effect of the arcuate area 32 is exerted mainly upon the felt to dry the felt on both the on-coming and out-going sides of the nip.

In Figure 3, the felt W is retained upon a felt trained through the nip 41 of a conventional suction press including an upper plain press roll 42 and a lower sueti pln press roll 43 having a suction area 44 at the mp Following passage of the web W on the felt 40 through the nip 41, the web is removed from the felt 40 by means of a web guide roll 45 and the web W is trained into contact with a press felt 46 lapped about a press guide roll 47. The web W is subsequently removed from the felt 46 by means of a web guide roll 48 positioned adjacent an upper plain press roll 49 of a reverse press assembly. The roll 48 is effective to guide the web W into surface contact with the roll 49 for passage thereabout and subsequent stripping therefrom by means of a web guide roll 50. The lower roll of the reverse suction press assembly takes the form of a suction press roll 51 having an arcuate interior suction area extending toward the on-coming and off-running sides of a reverse suction press nip 53 defined by the rolls 49 and 51. The felt 46 is lapped about the entire arcuate suction area 52, while the web W, having been stripped from the felt 46, overlies the suction area 52 only at the pressure nip of the rolls 49 and 51.

In this manner, as hereinbefore explained, the suction area effectively operates upon the felt 46 to remove moisture therefrom on both the on-coming and the olfgoing sides of the nip, so that the felt is dried and a drier felt surface is presented to the web at the nip 53. Also, the opening of the felt pores by the passage of air into the suction area 52 on the out-going side of the nip promotes the air drying of the felt as it is passed abriulthe guide rolls 54 in its return path to the guide rol As illustrated in Figure 5 of the drawings, the invention may also be applied to a horizontal dual suction press. In this figure of the drawings, the forming wire 10 is again lapped about a suction couch roll 11, and the web W is removed by means of a guide roll 12 for conveying the web into contact with a first press felt 56. The press felt 56 is guided by a felt guide roll 57 to a first suction press roll 58. A plain press roll is aligned with the first suction roll 58 and a second suction press roll 59 positioned in a diametrically opposed relation to thetroll fioandin horiaontal a rial alignment with'the press rolls. 58.;aiid 603.,

The suction roll 58 is "provided withtarcua te suction area 6 1;about.which. the .felt 56 ';is"lappe,d and with an arcuate save-all pan :62 positionedlwithin"theloop of the..felt 56 The'felt 56,,passes" about the: peripheryof the' roll'58, while the'web 'W. isremovedfrom the felt.

56. for 'passageabout a web guide .rollI 63. pbsitioned above the suction roll 58. The. w'eb.W..passes about the guide roll 63. and is in contact with thecentral plain press roll 60 for conveyance .by the roll to a first suction tendency for the webW toadhe're tolthesurface of the plain roll.60, particularly after. going throughthe first.

nip 6.4, onlythe guide 'roll.6 3. (positioned-on the. plain roll side of the plane of 'thefirst nip 6,4) is reqli iredtto obtainthe desired web, travel; andw'felt guide 'rollss'uch as the roll .57 within the loop of .the'felt5'6 provide guide means for separating 'the'web Wand the felt 56 at the outgoing side .of the nip. l64. This latter feature of s'e'p arating the web W. from theffel't atthe'outgoing side of.

the nip when the web is permitted to adhere to vthe plain roll surface is shown more .clearly in Fig. {through the use of .the, guide. rolls 54. for. the web i4 6..(wh ereb'y' guide means 54 positioned on the suction .roll side of the plane ofthe nip. 53 accomplish this purpose). 'Theroll 5911s} lapped by a second press'felt 66 which is lapped about felt. guide rolls 67 and 68inc'on'tact with the entire suction area 69 ofthe roll 59. Roll 59 is also providedwith an. arcuatesa've-all pan.70. Following thepassag'e of.- the web W.thr'ough nips. 64 and-65, the web is removed sequent air drying of the felts onth'e. retiirn passageof the felts about their respective. guide. rolls to the suction nips.

In the embodiment shown in Figure 5A, theforrning wire is on a cylinder mold M rotatably mounted in a vat V of a cylinder type paper" makingrnachine and the web W is couched off of 'the moldwire ltl onto the bottom face of a conventional piekmp felt P. U.- by. the couch roll ,C of 1 the machine.

horizontal suction nip 73. A. suction area; 72c defined .by a'fgland in the suction roll 72b. extends throughand bg yond both sides of the'nip.73. A cover felt C. F. is lapped around the suctionarea 720 of the roll 72b but contacts the web W only in'the nip. 73ts o thatthe suction area portions extendingbeyond both sides of the nip area are covered by-thecoverfelt C. B. only. A

guide roll G1 receiving the, felt (I. F. thereove'rata level.

below the suction roll 72b directs the feltinto lapping relation with the top portion of the suctionroll 72bahead of the nip .73 while a guide roll G2, on the other side .of the nip receives the felt:C. E. thereunderto lap. the felt around the off-going side of-the suction area of roll 72b. The felt C. F. extends upwardly.fromthev roll'GZ to a roll GSspaced in front of asuction drum press 74 consisting ofa-plain top roll ;74r t..an d.a suction drum roll 741; with a wide-mounted suction gland;de-. fining an extended suction area 740 around theascending side and top of the drurn'roll.

The pick-up feltP. U. with the web W on the underface thereof, afterpassing through; nip 73, is lapped around the underside of'a guide I'OILYG471IQ be directed:

onto the ascending side of thedrum roll 74b for covering the suction area 740. The cover felt C.- thencon: tacts the web W' as the web enters into the. suction nip of the drum press 74 on the pick-up felt after boththe web and pick-up felt have .been treated by. suction from the portion of the suction area 746 in. advanceof the suction nip. After passage through the nip of;the drun1 v press, the cover felt is trained back to. the-guidefrolLGi while the pick-up felt is trained backto the couch roll.

C. The cover felt has runs of appreciable length betweencontacts with the web.

In the embodiment of Figure 5A, the freshly forrned' W r t b m. e l n r m shin nys sl 1 11 111 s-p1ic r r f l a ies the web straight through a suctionpress 72 rhaving a plain top roll 72a and a bottom suction roll;72b defining a tion both. before, and after; Contact; wt the ;web

=6 zqnt llvi he a sxs si. Q j tq shi ri 'r ts i t i ere by.,a c er -felt'in thenipt covenfelt'js g aroundjthe suction roll ofithe press tqpefieatedb isle t i ht.

e I 1h nipso that .air willbe phlle d througli the felt as show by'th'e arrows. The felt will be opened'up and de'izvate ,d'. for betterabsorptionof water fromthe web. Thejweb and, ,pck-up. felt, after treatmentjirijthe, horizontal nip, of thesuctiongprelsQ are th9n[.-lapped;aropnd the suction area ofthe drurnpre'ss." Thecoverffelt, after suction. treatmenton thefofi fgoing side. fthe horizontal nip/of the suction press, thenlr'eco ts the. weblaltthejsuction nip of the drum press to ag n .cover the; web as .itp'ass'es through a suction nip; A s ing'le, cpy'enfelt.thereforecontacts the web at several nips,

only. after being t'reated alone by suction ad acent one the trips. This arrange;

ment greatly increases the drying c'agizicitv of the tlnlrn press and suction press "cornbinat on;

In that forrn of the invention show. in. Fi ure. 6; there is illustrated a doubletsuction press assembly; including an upper suction roll 75 and a 'ldwen su'c t'ionfroll 76 defining a double suction press-nip 77. The upperpres's roll 7 5 .is positionedwithin theflooppf a pick-up. felt,

still carried=by the"feltj8 3,,1s tralned abouta gu de roll;

100 about, the roll; 96 to lap= theentire arcu ate suction its guide rolls for su'hseggient re further processing.

roll 75 The lovvel suctiq i.1 s rtl,76. isipliovidedwitli' an. arcuate suction area.'80.,which.incompletely/lapped tionon both theon-comingand offgoing .sides of ,the.

nip 77.. The suet exert nen .fth felt 'inadvance of; the nip 7?; drawsl'airi into; the suction: area. 80. through; the felt 81, thereby removing" moisture 'squeezedfrorn. e. web. n thw pg fdtflt t i n n nvr'e's urt 9 mqistur t omt e. .ZW. h ti s 'tiq itor the suction area, 8t);e tfect yfi onftheioif-gding; sidebffthl nip 7-7 opens ,,the pores (if th e bdttern felhSl-j'to efieetuatef the removalofresi ual Imc'hs re; fro'rn theifeltf'and,to promote latenair drying of th felt .as it' istraiued about sasejth fl h;.' h.: r?- 77. Thus, the, present invent efi eetive, t'qidry Ithe. wer pr ss. felt, en hqushi the is qnfi 'df etw n: lp i f t '& .'a idl. as itmass hr gh the .7 i it.

In another form. of the invention shown .in Figure 7, f rence. m r 0. ain. e rs o o i ns onrdr icr ypel o web o m n s r ace wr ppe a o a suction couch roll 11, The web, W..'is.remoyed-;from, the wire 1t) bymeansjof',a piclg-up felt sltlapped about. a stiq .pi kr p ro l snt qt m 5 W5 smQv the sarne from the wire 10,. Felt 83. thengpass'es {through a ip fi a conve t n-s :P a i' r s l bl d fined L by 7 an upper press roll 86.; and ;a' .lowerjpressroll v87, the te oll ein'a ppe y.,a.p. s. elt .8 Z

After passing fth-mllg. the,.P Ze,ss nip 85; the. web. W,

89 to a suction press r'ollfltl, defining a press .nip91 with a heated Ya keef drier drurn 92 'Thefp'ress' roll .is provided w ith 'a suction area 913 cooperatingwith the Trier drum 92 to-provid e a suction pressat the nip 91. of which the web is transferred to the surface of the drum 92: The. web W is carried by the d rurn' 92 for removaltherefrom by meansof'a doctorblade 94, after which the web is passed'abo ut'a web guide roll 95 for A secondsuctio'n press roll 96=ispositioned adjacent. the-drivedrurn 92tbeyond-Jthe press ro1l.'90. The roll 9618 provided twith-an arcuate .suction area-9fl positioned at.th.e.nip, 9&tdefined-byHthe-roll 96.;and;the drier drurnv 92; A felt 9-9 is guided by a plurality. of guide rolls,

area-.9fl thereof. lt will be seenjthat the felt 99 contac ts" the 'fvvbwwi hly sfit jis supported the surfaeelfof' thdrier drum '92. and that 'the only actual contact between the weband thel felt. 99 ,'occursfat the'pr cssure nip t' i l s bs' 'b re iafdg bkit hafial 2. in l pped aboutthee ntire suctiqn a apr of;the roll 96, is dried by the passage of'air into th e suction area 97. urtherdr i ot hewslawfl n dsii safiq. hatt rv effect exerted by the relatively "dry felt 99 and the suction area 97, is accomplished by the pre-heating of the web at the surface of the drum 92. At the time the felt 99 contacts the web W, the web W has been preheated on the drum 92, so that a freer web W is presented to the drum, thereby causing improved water removal. I

The application of the concept of the present invention to the drying of a web passing through a paper machine drying section is shown in Figure 8 in WhlCh the web W is, conveyed through a conventional drier section 110 by upper and lower felts 111 and 112, respectively, partially lapped about upper and lower rows of drier drums 113-114, respectively. In this form of the invention, the lower felt 112 islapped about a pair of guide rolls 115 to remove the felt 112 from contact with one of the lower drier drums 114. The one lower drier drum 114 conveying the web thereabout cooperates with a suction press roll 118 having a press felt 116 trained thereabout by a plurality of felt guide rolls 117. The superimposed rolls 114 and 118 thus define a suction press nip 120.

Here, again, the press felt 116 laps the entire arcuate suction area 119 of the roll 118, while the web W contacts the felt 116 only at the point of pressure contact between the roll 118 and the associated drum 114. Thus, the felt is dried by the passage of air therethrough into the suction gland at both' the on-coming and offgoing sides of the nip 120, so that the felt is again dried to improve the water removal characteristics thereof.

It will thus be seen that the present invention provides means for improving the desired drying characteristics of the paper machine press felt. This improvement in the drying characteristics is accomplished by increasing the moisture absorption potential of the felt, rather than as previously attempted by increasing either the suction exerted upon the sheet or the mechanical pressure exerted thereon.

In accordance with the principles of the present invention, a press felt and a paper web are each guided through a suction press nip. However, the felt and the web are separately guided through the nip so that contact of the web with the felt occurs only at the actual pressure nip of the press. The press felt is'lapped about the entire suction area which extends on both the on-coming and off-running sides of the press nip. On the on-coming and off-running sides of the nip, the felt is not covered with the web, so that the suction area is effective to draw air through the felt into the suction area. v

This passage of air through the felt into the suction area accomplishes several immediate results which increase the drying efficiency of the felt. First, on the on-coming side of the nip, water squeezed from the web and the felt of the pressure nip accumulates ahead of the nip, and suction through the felt removes this water by passage under differential air pressure into the interior of the suction area. Also, the felt itself is subjected to a final drying action so that it is substantially free of water prior to its contacting the web at the pressure nip. Further, the felt pores are open immediately prior to the contacting of the felt with the web at the nip so that a freer felt is presented to the web at the pressure nip.

On the off-going side of the pressure nip, the felt is again subjected to suction drawing atmospheric air through the felt into the suction area of the suction press roll. This suction effect again serves to remove residual moisture from the felt and to remove free lignin and pulp particles from the felt pores. In addition, the felt pores are again opened which serves an important purpose inasmuch as the felt is normally compacted and the pores clogged by passage of the felt through the pressure nip. This opening of the felt pores increases surface drying of the felt upon exposure to the circumambient atmosphere during its passage about the associated felt guide rolls to its next pass through the pressure nip.

The effect of the subjection of the felt alone to suction both in advance of and immediately in rear of the pres-' sure nip results in an increase in the moisture absorption efiiciency of the felt. This increase in absorption efficiency facilitates the more ready removal of moisture from the felt, the presentation of a dryer felt to the web, and the more efficient air drying of the felt after its passage through the pressure nip.

It will be understood that modifications and variations a suction area straddling said nip, an endless felt trained' through the nip of said press and completely lapping the suction area of said suction roll, and guide rolls positioned on the side of said plane opposite said suction roll and adjacent the other of said press rolls for guiding a moist paper web through said nip and said guide rolls being positioned sufficiently far on the side of said plane opposite said suction roll to maintain the felt uncovered by the web for most of its run over the suction area on both the on-coming and off-going sides of said nip, said web contacting said felt only at said nip intermediate that portion of said felt lapping the suction area of said one roll, whereby said felt is dried by said suction area both immediately before and immediately after contacting said felt with said web.

2. A paper machine suction press assembly comprising a central plain press roll, a pair of suction press rolls on diametrically opposed sides of said plain central press roll cooperatively defining successive pressure nips therewith each lying in a plane generally tangential to the two rolls defining such nip, each of said suction press rolls having a suction area straddling its respective pressure nip, a press felt trained about each of said suction press rolls for completely lapping the suction area thereof, and guide means positioned on the plain roll side of both said planes for guiding a moist paper web into contact with said plain central roll for conveyance thereby through said successive pressure nips, said guide means being positioned sufiiciently far on the plain roll side of both said planes to maintain the felt uncovered by the web for most of its run over each suction area on both the oncoming and off-going sides of each nip, said web contacting said press felt only at said nips and said press felt being dried by said suction areas both before and after contact with said web at the nips.

3. A paper machine suction press assembly comprising a pair of suction press rolls cooperatively defining a press nip therebetween lying in a plane generally tangential to both of said rolls, a suction area in each of said rolls, each straddling the press nip, press felts lapping each of said suction areas, a moist paper web carried by one of said felts for passage through said nip, guide means positioned on one side of said plane associated with the felt carrying the paper web for effecting separation of the felt carrying the web from the other felt before and after passage of said felts through said nip, the other of said felts contacting said web only at said nip and being dried by the associated suction area before and after contact with said web, said guide means being positioned sufiiciently far on said one side of said plane to maintain said other of said felts uncovered by the web for most of its run over the suction area on both the on-coming and offgoing sides of said nip.

4. In a paper machine drier section, a heated drier drum having a paper web lapped thereabout, a suction press roll cooperating with said heated drier drum to define a press nip therebetween lying in a plane generally tangential to said drum and said roll and having a suction area extending on both the on-coming and off-going sides of said press nip, guide means on the drier drum side of said plane guiding the paper web travel to effect the lapping thereof about said drier drum and a press felt trained about said press roll and completely lapping the suction area thereof for passage through said nip, said press felt contacting said web at said nip only and the felt alone being subjected to suction by said suction area on both the on-coming and the off-going sides of said nip for drying said felt, said guide means being positioned sufiiciently far on the drier drum side of said plane to maintain said press felt uncovered by the web for most of its run over the suction area on both the on-coming and off-going sides of said nip.

5. A straight through reverse suction press assembly for a paper making machine which comprises a first press including a plain top roll and a bottom suction roll together defining a substantially horizontal nip, a first press felt having a substantially horizontal top run trained through said substantially horizontal nip of the first press for conveying a wet web of paper through the press in contact with the plain press roll thereof, means for stripping said wet web from said first press felt beyond said first press, a second suction press including a plain bottom roll and a suction top roll together defining a substantially horizontal nip therebetween, said suction roll of said second press having a suction gland defining a suction area extending continuously from a point in advance of the oncoming side of the nip to a point beyond the offgoing side of the nip for providing a continuous suction nip with suction zones both in advance of and beyond the nip, a second press felt on said top suction roll of the second press lapping the entire suction area of said second suction press and compressively loaded in said nip by said bottom plain roll of said second suction press, means for lapping the paper web stripped from said first press felt on the plain roll to pass through the nip of the second press on the plain roll of the second press from a point in advance of the nip to a point beyond the nip thereof, said means holding the web in spaced relation from said suction zones to contact the second felt only in said nip of the second press and to leave the felt uncovered along said suction zones, said means being positioned sufficiently far beneath a horizontal plane through the nip of said second suction press to maintain the felt uncovered by the web for most of its run over the suction area of the top suction roll of said second suction press on both the on-coming and off-going sides of the nip, and an exhaust outlet for evacuating the suction area of the top suction roll of said second press to evacuate the nip and pull air from the atmosphere through the uncovered second felt along said suction zones.

6. An upside down suction press which comprises a lower plain roll, an upper suction roll, said upper suction roll having a perforated cylindrical shell in pressure nip defining relation with the periphery of the plain roll, a suction gland in said shell defining a suction area opening downwardly and extending along the lower portion of the shell from a point in advance of the oncoming side of the nip through the nip to a point beyond the offgoing side of the nip for providing a continuous suction nip with suction zones on the shell both in advance of and beyond the nip, a press felt on the shell lapping the entire suction area and compressively loaded in said nip by said plain roll, means for lapping a paper web on the plain roll to pass through the nip on the plain roll from a point in advance of the nip to a point beyond the nip, said means holding the web in spaced relation from said suction zones to contact the felt only in said nip and leave the felt uncovered along said suction zones, said means being positioned sufiiciently far beneath a plane through said nip and generally tangential to both said rolls to maintain the felt uncovered by the web for most of its run over the suction zones on both the oncoming and off-going sides of said nip, and an exhaust outlet for evacuating said suction gland to evacuate the nip and pull air from the atmosphere upwardly through the uncovered felt along said suction zones for creating an air lift for water squeezed from the web.

7. A paper machine suction press assembly comprising a pair of adjacent press rolls cooperatively defining a pressure nip therebetween lying in a plane generally tangential to both said rolls, one of said rolls being a plain roll and the other of said rolls being a perforated suction roll having a suction area straddling and extending beyond both sides of the nip and extending through said nip, 2. press felt lapping the entire suction area of said suction roll and compressively loaded in said pressure nip, guide means positioned on the side of said plane opposite said area straddling both sides of the press nip guiding a moist paper web into contact with said plain roll in advance of the nip for conveyance thereon through said nip and beyond the nip for contact with said felt in the nip only at the point of pressure 10 loading exerted by said rolls, said guide means being positioned sufliciently far on the side of said plane opposite said area to maintain the felt uncovered by web for most of its run over the suction area on both the on-coming and off-going sides of said nip, and means for pulling air from the atmosphere directly through the felt immediately adjacent both sides of the loaded portion of the nip to minimize the pressure differential between the oncoming and offgoing sides of the nip and thereby reduce the flow of Water through the nip while simultaneously drying the felt and draining the perforated suction roll.

8. A paper machine suction press comprising a pair of adjacent press rolls cooperatively defining therebetween a pressure nip lying in a plane generally tangential to both said rolls, one of said rolls being a suction roll with a suction gland disposed therein and defining a suction area extending through and beyond the pressure nip on both the on-coming and off-going sides of said nip, a porous press felt lapping said suction roll and overlying the entire suction area thereof, and means positioned on the side of the plane opposite said suction roll holding a moist paper web against the other of said rolls both before and after the nip for passage through said nip on said other roll and for contact with said felt only at said nip, said means being positioned sufficiently far on the side of the plane opposite said suction roll to maintain the felt uncovered by the web for most of its run over the suction area on both the on-coming and off-going sides of said nip, whereby the suction effect of said suction area is exerted solely on said felt on both the oncoming and off-going sides of said nip to pull the air directly from the atmosphere through the felt into the suction gland of said suction roll.

9. In a paper machine suction press, including an upper plain press roll and a lower suction press roll cooperatively defining therebetween a pressure nip lying in a generally horizontal plane, a suction area in said suction roll extending on both the oncoming and offgoing sides of said pressure ni a press felt lapped about the suction area of said suction roll, first guide means positioned below said plane at the oifgoing side of said pressure nip for directingsaid press felt away from a moist paper web at the oifgoing side of said pressure nip, and second guide means positioned sufiiciently far above said horizontal plane to maintain the felt uncovered by the web for most of its run over the suction area on both the oncoming and ofr'going sides of said nip, said second guide means being positioned above said horizontal plane for directing the moist paper web into contact with said plane press roll for conveyance thereby through said nip, said web contacting said felt only at said nip, and said suction area subjecting said felt alone to suction on both the oncoming and offgoing sides of said nip to dry the felt before and after its contact with the web.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,163,253 Millspaugh Dec. 7, 1915 1,600,509 Millspaugh Sept. 21, 1926 1,905,911 Kellett Apr. 25, 1933 1,981,049 Kellett Nov. 20, 1934 2,083,818 Berry June 15, 1937 2,083,819 Berry June 15, 1937 2,111,834 Berry Mar. 22, 1938 2,144,770 Millspaugh Jan. 24, 1939 2,204,426 Millspaugh June 11, 1940 2,209,758 Berry July 30, 1940 2,209,761 Berry July 30, 1940 2,386,584 Berry Oct. 9, 1945 2,415,350 Hornbostel et al Feb. 4, 1947

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