CA1121197A - Procedure and means for treating a fibre web - Google Patents
Procedure and means for treating a fibre webInfo
- Publication number
- CA1121197A CA1121197A CA000343290A CA343290A CA1121197A CA 1121197 A CA1121197 A CA 1121197A CA 000343290 A CA000343290 A CA 000343290A CA 343290 A CA343290 A CA 343290A CA 1121197 A CA1121197 A CA 1121197A
- Authority
- CA
- Canada
- Prior art keywords
- roll
- felt
- press
- web
- suction
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F3/00—Press section of machines for making continuous webs of paper
- D21F3/02—Wet presses
- D21F3/04—Arrangements thereof
Abstract
ABSTRACT OF THE DISCLOSURE:
A procedure and means for efficient transfer of the web from the forming wire onto the transfer felt in the press section, utilizing the kinetic energy of the web itself while at the same time making efficient use of centrifugal force towards detaching the web from the wire and towards it attaching to the transfer felt of the press section, while at the same time the concumption of suction energy is minimized, as well as the noise arising from the operation of suction rolls.
A procedure and means for efficient transfer of the web from the forming wire onto the transfer felt in the press section, utilizing the kinetic energy of the web itself while at the same time making efficient use of centrifugal force towards detaching the web from the wire and towards it attaching to the transfer felt of the press section, while at the same time the concumption of suction energy is minimized, as well as the noise arising from the operation of suction rolls.
Description
~l'hl~{3~7 The present invention concerns a procedure for treating a fibre web between the forming fabric section and the drying section of a paper machine, utilizing so-called clo~ed conduction, such procedure comprisin~ as a combinatlon the following steps: detaching of the web from the forminy fabric at the point of detachment and substantially simultaneous affixing thereof on the surface of a transfer felt; transport of the web carried by the transfer felt's surface from the point of detachment to a first press nip; conduction of the lower felt of the press section into the first press nip defined by a recessed surface lower roll and a dewatering upper roll con-nected to a suction system; pressing of the web between the transfer felt and the lower felt and simultaneous dewatering of the web in two directions in the first press nip; conduction of the web on the surface of the transfer felt of the press section to a second press nip defined by said upper roll and a solid smooth-surface central roll of the press section;
dewatering of the web in the second press nip with water flow passing into the transfer felt.
In addition, the present invention concerns a means applying the procedure of the invention.
It is well known that in paper machines running at high speeds or used to manufacture low strength paper brands one is compelled to employ so-called close transfer systems without any free draws, so that the web will be continuously supported with the aid of a felt as it passes from the wire over to the press section. These systems operace in the manner that the transfer felt of the press section is conducted into contiguity with the web on the wire. The transfer felt may be urged against the web on the wire the aid of a rotating roll so that the web is made adheren-t to the felt and comes ofE the wire and that it continues its travel affi~ed to the felt surface, this felt l~Z1~7 carrying the web subsequently to the Eirst press nip in the press section.
Generally speaking there are two main t~pes oE clo~d transfer system. 5implest is the so-called :Lick-up trans~er, which is based on the ability of a wet so-called lick-up felt to bind the paper web to its surface. Another type is the vacuum pick-up system in which suction has been arranged to act at the point of transfer, and which renders`possible a positive transfer of the web from the wire to the transfer felt. The vacuum pick-up system offers greater possibilities, particularly regarding selection o-f felt, compared with the lick-off system.
In order to affix the web Eirmly to the felt during its travel between the point of detachment and the Elrst press nip, it has been a commonly known method to use a comparatively wet felt to promote the web adhesion. But if the transfer felt also operates as press felt, the wetness of the felt naturally detracts form the web dewatering capacity in the Eirst press nip. It would therefore be desirable, with a view to highest possible dewatering capacity, to keep the felt as dry as possible As a rule, the pick-up system of the paper machine and - its press section contain a plurality of press felts, which serve partly as web-supporting means and partly aid the dewater-ing action in the press nips. There is usually one felt per web treating point. In some instances one felt may serve the web treatment at six different points. The pick-up press section, which has one pick-up nip and three dewatering nips, may comprise four felts or fabrics. For each of these a great number of felt guide rolls and tensioning and guiding means are required for guiding the running of the felt. Also felt reconditioning means are required for each such felt, for the continuous washing of the felt during operation.
? ~ L9~
Owing to the multitude of such e~uipment, the press section has become unwieldy, space-consuming and expensive.
The numerous, or fre~uently necessary, felt chanyes or replace-ments are hiyhly inconvenient. Therefc~e, it would be de~ir~
able to provide in the press section the minimurn number of felts and different felt types which is ~easible.
The most important aim of the present invention is to provide a simple paper machine press section and procedure which for its operation implies a minimum of operative components.
By the expression "operative components" are meant: press rolls, suction rolls in particular, press felts, felt guide rolls, felt guiding and tensioning means, and felt conditioning means.
Another object of the present invention is to provide a procedure and means for efficient transfer of the web from the forming wire onto the transfer felt in the press section, utilizing the kinetic ener~gy of the web itself while at the same time making efficient use of centrifugal force towards detaching the web from the wire and towards it attaching to the transfer felt of the press section, while at the same time the consumption of suction energy is minimized, as well as the noise arising from the operation of suction rolls. The detri-ments of suction rolls as sources of objectionable noise and as energy consumers have been discussed e.g. in the same applicant's Canadian pate~t No. 1,059~356 of July 31, 1979.
In order to attain the aims stated, and others which will become evident later on, the procedure of the invention is mainly characterized in that the transEer felt participates in the treatment of the fibre web still in the third dewater-ing nip, in that in association with the aforementioned steps the transfer felt is detached from the web after the second press nip and conducted to a first felt conditioning means for the reconditioning of the felt, that the fibre web is transferred, adherent to the surface o:~ the central roll, ~o a third press nip defined by the smooth central roll and the second, recessed surface, roll of the press section, the transEer felt bei.ng conducted from the first felt conditionil-g means t~ said third press nip, where the web is pressed between the smoo~h roll surface and the felt so as to express water from the web towards the recessed surface roll, whereupon the felt is detached from the web and conducted throuyh a second felt conditioner back to be adjacen.t to the return roll within the forming fabric loop, at which roll detachment of the fibre web from the forming fabric takes place, and that the fibre web is transferred after the third press nip on the surface of the smooth roll to the point where the web is detached from the roll surface to be con-ducted to the drying section.
The means of the invention, again, is characterized in that the means comprises in combination the following mutually associated components:
- a forming fabric;
- a fabric return roll within the forming fabric loop;
- a press suction roll connected to a suction system;
- a first recessed surface press roll, defining with said suc-tion roll a first dewate~in~ ~ip;
- a smooth-surfaced press roll, defining with said suction roll a second dewatering nip;
- a second recessed surface press roll, defining with the smooth-surfaced press roll a third dewatering nip;
- in total ~wo press felt fabrics, whereof the felt fabric belonging to the top part structure of the press section serves as transport felt conveying the fibre web from the point of detachment to the first and second dewatering nips and which within its loop encloses the suction roll and the second recess-ed surface press roll, covering of the suction rollsubstantially ,~ ' ' ~h'l ~
at least that sector on which the suction oE the s~ction rol1 is active, ancl whereof the ~elt fabric belonging to the bottom part structure of the press section wi~hin its Lcop enc:Loses ~h~
first recessed surfAce press roll and serves as water-receiviny lower Eelt in the first press nip;
- a first transfer felt conditioning means on the Eelt run between the second and first dewatering nips;
- a second transfer felt conditioning means`on the felt run follow-ing after the third dewatering nip;
- a third felt conditioning means for the lower felt.
Thus, as taught by the invention, the wet fibre web is conducted with the aid of the Eorming wire onto the return roll at the point of detachment, to which point the suitably reconditioned and comparatively dry transfer felt is also conveyed. At thepoint of detachment the web is detached from the wire and transferred onto the transfer felt without using any separate pick-up suction roll. Instead, one may use a detaching suction box or, in an alternative favourable design, the suction roll of the press section, which operates as pick-up roll. The transfer felt also serves as press felt in three nips of the press section. At the detachment of the web from the wire, and in its transferring onto the felt, the adhesion forces of the felt and the centrifugal force acting on the web are utilized, as the web is lapping the wire return roll on a sector in excess of 90 degrees. After the web has thus become adherent to the surface of the transfer felt, the felt proceeds to the ~irst press nip of the press sec~ion, this first nip being double-felted, the transfer -felt itself being the upper felt in the double~felted press nip.
~fter the first press nip, the web is acted upon by the suction of the press suction roll, this serving to make sure that the web remains adherent to the transfer felt, which together with the web runs through the first press nip to the second press nip of the press section, this second press nip being defined by said suction roll and the smooth-surfaced roll in the press section.
The present invention is in particular applicable in press sections o~ the type disclosed in the same applicant's Canadian pa-tent application No. 971,790 of July 29l 1975~
It is a remarkable feature of the invention that not more than two press felts are indispensable for the operation of this press section: the upper felt and the lower felt. The path of the upper felt has been so arranged that it serves at one and the same time four purposes or functions, that is:
constituting a pick-up transfer felt and at the same time also working in three consecutive dewatering press nips. The lower felt only serves the first nip, which is double-felted. The minimum number or felts implies that it is possible massively to reduce the number of felt guide rolls, felt guiding means and tensioning means, compared with a pick-up part comprising three dewatering nips in which it may be necessary to use four felts.
In one embodiment of the invention, the suction roll of the press is of a design incorporating an external suction chamber. In this case the expensive foraminous suction roll is not absolutely necessary and it may be replaced with a solid-shell recessed surface roll at which the suction exerts ~-- its effect through passages encircling the roll periphery.
This design contributes to great savings of suction energy.
In the following, the invention shall be described in detail with reference being made to certain embodiment examples of the invention.
In Fig. l is shown, schematically, the first embodiment of the invention.
~ - . _~_ Fig. 2 displays, in equivalent manner, a second embodim~nt of the invention, Fig. 3 presents ~n example o~ the surEace st~ucture o~
the press suction roll emplo~ed in ~'ig. 2, in partial axial section~
The web forming section depicted in Fig. 1 comprises a pair oE endless wire loops 10 and 20, which have a common ascending run, thereby constituting a -twin wire former. The running oE the wire 10 is guided by the aid of the rolls 12 and also by means of the guiding roll 13 disposed halfway on the joint run of the wires. Moreover, this wire 10 laps the breast roll 11 so that it forms a single-wire section, on-to which the headbox 14 supplies pulp stock. The twin wire former also comprises a lower forming roll 21 and a wire board 15, which is disposed to lie on the single-wire run extending from the breast roll 11 to the lower forming roll 21. The wire board 15 has a solid or perforated cover, or one with slot openings, adjacent to the wire 10. The ~ower forming roll 21, located within the wire loop 20, has a suction zone 21a, in the region
dewatering of the web in the second press nip with water flow passing into the transfer felt.
In addition, the present invention concerns a means applying the procedure of the invention.
It is well known that in paper machines running at high speeds or used to manufacture low strength paper brands one is compelled to employ so-called close transfer systems without any free draws, so that the web will be continuously supported with the aid of a felt as it passes from the wire over to the press section. These systems operace in the manner that the transfer felt of the press section is conducted into contiguity with the web on the wire. The transfer felt may be urged against the web on the wire the aid of a rotating roll so that the web is made adheren-t to the felt and comes ofE the wire and that it continues its travel affi~ed to the felt surface, this felt l~Z1~7 carrying the web subsequently to the Eirst press nip in the press section.
Generally speaking there are two main t~pes oE clo~d transfer system. 5implest is the so-called :Lick-up trans~er, which is based on the ability of a wet so-called lick-up felt to bind the paper web to its surface. Another type is the vacuum pick-up system in which suction has been arranged to act at the point of transfer, and which renders`possible a positive transfer of the web from the wire to the transfer felt. The vacuum pick-up system offers greater possibilities, particularly regarding selection o-f felt, compared with the lick-off system.
In order to affix the web Eirmly to the felt during its travel between the point of detachment and the Elrst press nip, it has been a commonly known method to use a comparatively wet felt to promote the web adhesion. But if the transfer felt also operates as press felt, the wetness of the felt naturally detracts form the web dewatering capacity in the Eirst press nip. It would therefore be desirable, with a view to highest possible dewatering capacity, to keep the felt as dry as possible As a rule, the pick-up system of the paper machine and - its press section contain a plurality of press felts, which serve partly as web-supporting means and partly aid the dewater-ing action in the press nips. There is usually one felt per web treating point. In some instances one felt may serve the web treatment at six different points. The pick-up press section, which has one pick-up nip and three dewatering nips, may comprise four felts or fabrics. For each of these a great number of felt guide rolls and tensioning and guiding means are required for guiding the running of the felt. Also felt reconditioning means are required for each such felt, for the continuous washing of the felt during operation.
? ~ L9~
Owing to the multitude of such e~uipment, the press section has become unwieldy, space-consuming and expensive.
The numerous, or fre~uently necessary, felt chanyes or replace-ments are hiyhly inconvenient. Therefc~e, it would be de~ir~
able to provide in the press section the minimurn number of felts and different felt types which is ~easible.
The most important aim of the present invention is to provide a simple paper machine press section and procedure which for its operation implies a minimum of operative components.
By the expression "operative components" are meant: press rolls, suction rolls in particular, press felts, felt guide rolls, felt guiding and tensioning means, and felt conditioning means.
Another object of the present invention is to provide a procedure and means for efficient transfer of the web from the forming wire onto the transfer felt in the press section, utilizing the kinetic ener~gy of the web itself while at the same time making efficient use of centrifugal force towards detaching the web from the wire and towards it attaching to the transfer felt of the press section, while at the same time the consumption of suction energy is minimized, as well as the noise arising from the operation of suction rolls. The detri-ments of suction rolls as sources of objectionable noise and as energy consumers have been discussed e.g. in the same applicant's Canadian pate~t No. 1,059~356 of July 31, 1979.
In order to attain the aims stated, and others which will become evident later on, the procedure of the invention is mainly characterized in that the transEer felt participates in the treatment of the fibre web still in the third dewater-ing nip, in that in association with the aforementioned steps the transfer felt is detached from the web after the second press nip and conducted to a first felt conditioning means for the reconditioning of the felt, that the fibre web is transferred, adherent to the surface o:~ the central roll, ~o a third press nip defined by the smooth central roll and the second, recessed surface, roll of the press section, the transEer felt bei.ng conducted from the first felt conditionil-g means t~ said third press nip, where the web is pressed between the smoo~h roll surface and the felt so as to express water from the web towards the recessed surface roll, whereupon the felt is detached from the web and conducted throuyh a second felt conditioner back to be adjacen.t to the return roll within the forming fabric loop, at which roll detachment of the fibre web from the forming fabric takes place, and that the fibre web is transferred after the third press nip on the surface of the smooth roll to the point where the web is detached from the roll surface to be con-ducted to the drying section.
The means of the invention, again, is characterized in that the means comprises in combination the following mutually associated components:
- a forming fabric;
- a fabric return roll within the forming fabric loop;
- a press suction roll connected to a suction system;
- a first recessed surface press roll, defining with said suc-tion roll a first dewate~in~ ~ip;
- a smooth-surfaced press roll, defining with said suction roll a second dewatering nip;
- a second recessed surface press roll, defining with the smooth-surfaced press roll a third dewatering nip;
- in total ~wo press felt fabrics, whereof the felt fabric belonging to the top part structure of the press section serves as transport felt conveying the fibre web from the point of detachment to the first and second dewatering nips and which within its loop encloses the suction roll and the second recess-ed surface press roll, covering of the suction rollsubstantially ,~ ' ' ~h'l ~
at least that sector on which the suction oE the s~ction rol1 is active, ancl whereof the ~elt fabric belonging to the bottom part structure of the press section wi~hin its Lcop enc:Loses ~h~
first recessed surfAce press roll and serves as water-receiviny lower Eelt in the first press nip;
- a first transfer felt conditioning means on the Eelt run between the second and first dewatering nips;
- a second transfer felt conditioning means`on the felt run follow-ing after the third dewatering nip;
- a third felt conditioning means for the lower felt.
Thus, as taught by the invention, the wet fibre web is conducted with the aid of the Eorming wire onto the return roll at the point of detachment, to which point the suitably reconditioned and comparatively dry transfer felt is also conveyed. At thepoint of detachment the web is detached from the wire and transferred onto the transfer felt without using any separate pick-up suction roll. Instead, one may use a detaching suction box or, in an alternative favourable design, the suction roll of the press section, which operates as pick-up roll. The transfer felt also serves as press felt in three nips of the press section. At the detachment of the web from the wire, and in its transferring onto the felt, the adhesion forces of the felt and the centrifugal force acting on the web are utilized, as the web is lapping the wire return roll on a sector in excess of 90 degrees. After the web has thus become adherent to the surface of the transfer felt, the felt proceeds to the ~irst press nip of the press sec~ion, this first nip being double-felted, the transfer -felt itself being the upper felt in the double~felted press nip.
~fter the first press nip, the web is acted upon by the suction of the press suction roll, this serving to make sure that the web remains adherent to the transfer felt, which together with the web runs through the first press nip to the second press nip of the press section, this second press nip being defined by said suction roll and the smooth-surfaced roll in the press section.
The present invention is in particular applicable in press sections o~ the type disclosed in the same applicant's Canadian pa-tent application No. 971,790 of July 29l 1975~
It is a remarkable feature of the invention that not more than two press felts are indispensable for the operation of this press section: the upper felt and the lower felt. The path of the upper felt has been so arranged that it serves at one and the same time four purposes or functions, that is:
constituting a pick-up transfer felt and at the same time also working in three consecutive dewatering press nips. The lower felt only serves the first nip, which is double-felted. The minimum number or felts implies that it is possible massively to reduce the number of felt guide rolls, felt guiding means and tensioning means, compared with a pick-up part comprising three dewatering nips in which it may be necessary to use four felts.
In one embodiment of the invention, the suction roll of the press is of a design incorporating an external suction chamber. In this case the expensive foraminous suction roll is not absolutely necessary and it may be replaced with a solid-shell recessed surface roll at which the suction exerts ~-- its effect through passages encircling the roll periphery.
This design contributes to great savings of suction energy.
In the following, the invention shall be described in detail with reference being made to certain embodiment examples of the invention.
In Fig. l is shown, schematically, the first embodiment of the invention.
~ - . _~_ Fig. 2 displays, in equivalent manner, a second embodim~nt of the invention, Fig. 3 presents ~n example o~ the surEace st~ucture o~
the press suction roll emplo~ed in ~'ig. 2, in partial axial section~
The web forming section depicted in Fig. 1 comprises a pair oE endless wire loops 10 and 20, which have a common ascending run, thereby constituting a -twin wire former. The running oE the wire 10 is guided by the aid of the rolls 12 and also by means of the guiding roll 13 disposed halfway on the joint run of the wires. Moreover, this wire 10 laps the breast roll 11 so that it forms a single-wire section, on-to which the headbox 14 supplies pulp stock. The twin wire former also comprises a lower forming roll 21 and a wire board 15, which is disposed to lie on the single-wire run extending from the breast roll 11 to the lower forming roll 21. The wire board 15 has a solid or perforated cover, or one with slot openings, adjacent to the wire 10. The ~ower forming roll 21, located within the wire loop 20, has a suction zone 21a, in the region
2~ of whlch the dewatering takes place. This dewatering is simultaneous in both directions, namely, away from the roll 21 by effect of centrifugal force and inward in the direction of the suction zone 21a. The wires 10 and 20 pass along the point run upward over the lower forming roll 21, the inter-,. .
mediate roll 13 guiding them onto the upper forming roll orcouch roll 22, which features a suction zone 22a, this zone ensuring that the web W that has been formed will after the twin wire forming section continue, carried by the wire 20, toward the right past the upper forming roll 22, as shown in Fig. 1 The wire 20 is guided by ~he aid of appropriate guide rolls 23.
The detachlng of the formed web W from the carrying ~ire 20 takes place on the wire return roll 25. ~s shown in Fig. 1, the wlre 20 covers the return roll 25 on an angle slightly in excess oE 90 degrees, and the transEer felt 30 is likewise conducted to cover ~his rol~ 2S on a sectc)r thu~ i~a~
been markecl ~. In the region of the sector ~, the web is detached from the wire 20 and becomes adherent to the ~elt 30.
At the point where the transfer Eelt 30 and the web W residing thereupn separate from the wire 20 there ha~s been placed a suction box 24, connected to the suction system of the paper machine, within the loop of the transfer felt 30, to ensure the detaching of the web W. The more detailed design of the suction box 24 is described in the same applicant's U.S. Patent No. 4,113,557. It should be noted that in actual fact the web W starts to become detached from the wire 20 already before it reaches the centre point of the sector ~, this being the result of the centrifugal force acting on the web W in that area where the direction of the web-carrying wire 20 first begins to change. However, the suction box is not indispensable in every case.
The course of the transfer felt 30, before it comes into contact with the return roll 25 of the wire 20, is guided with the aid of the guide rolls 32. As has been schematically shown in Figs 1 and 2, one special guiding roll 32a is so adjustable that the transfer felt 30 can be guided into contiguity with the return roll 25 in such manner that the size of that sector on which the felt 30 covers the wire 20 and the web W resid-in~ thereupon can be adjusted. It is possible in this way to enhance the affixing of the web W to the transfer felt 30 by increasing the extension of the sector ~ and thereby increasing the time of contact between the felt 30 and the web W.
- As shown in Fig. 1, the press section comprises four .
press rolls and which define three press nips. the Eirs-t nip N1 is defined between press rolls 31 and 4:L, whereof the upper roll 31 is a conventional suction roll, whi:Le the lower ro~l 41 is a water-receiviny roll having a recessed surface, for instance a grooved or blind drilled surEace. The upper roll 31 is provlded with a suction sector having two compartmen-ts 34a and 34b, The first suction compartment 34a extends ahead of the press nlp Nl to such extent that the~detachment of the web W from the ~elt 30 ~by centrifugal effect for instance) is prevented. The purpose of the suction compartment 34b is on one hand to keep the web attached to the felt 30 while travelling between the nips Nl and N2 and, on the other hand, to prevent rewetting of the web, by maintaining the water in the mesh of the felt. The suction roll may as well be of the type describ-ed later on in connection with Fig. 2.
The press section furthermore comprises a smooth-surfaced central roll 61, for instance a stone roll, which together with the upper suction roll 31 deEines the second press nip N2.
This roll 61 cooperates also with the press roll 71, defining the third press nip N3. The roll 71 has a water-receiving recessed surface. On the free sector on the underside of the smooth-surface press roll 61 a doctor blade 62 has been provid-ed to keep its surface clean, The web is detached from the roll 61 in a well-known manner and it is conducted by -the aid of the roll 74 to the drying section of the machine.
As shown in Fig. 1, in the press section only two press felts 30 and ~0 are used to aid the dewatering in the press nips and the transport of the web through the press section, these being the transfer felt 30, which transports the web from the forming wire 20 to the first nip Nl and which at the same time serves as upper felt of the whole press section, participating in the pressing process also in the second nip N2 and in the third nip N3; and the press felt 40 of the lower press roll ~1, this Eelt operating in the pressing event in one nip only: in the Eirst nip Nl as the lower ~elt thereof, under guidance by the ~lide rolls ~2. qlhe Eel~ ~0 has been provided with reconditioning means ~3, whi~h ma~ be of any conventional and expedient design, As already mentioned, the course of the upper felt 30 has been arranged with the aid of the guide~rolls 32. It is necessary in order to gaarantee a successful pressing event, to clean, wash and press the felt 30 in all nips during opera-tion. To this end, after the nip N2, the felt 30 is conducted into the felt reconditioner 33, whereafter the felt 30 is further conducted to the third press nip N3, whereafter the felt 30 is once again conducted to another felt reconditioner, this being a washing press and comprising two press rolls 34a and 34b. Such felt reconditioning means and their connection with the water supply and vacuum systems are well understood by persons skilled in the art and need therefore no detailed explanation. After passing the washing press, the felt 30 is conducted back to the wire section and to the point of detachment of the web W on the roll 25.
The main part of the guide rolls 32 of felt 30, and the felt drying means, have been accommodated on a supporting beam structure 35, shown by a schematic dotted line above the press roll part.
In Fig. 2, another embodiment of the invention is depic~-ed, comprising a wire section and a press section, both of which are in the main similar as shown in Fig. 1. However, in the design shown in Fig. 2, the wire return roll 25 has been disposed substantially on the same horizontal level as the press roll 31' of the press section so that the wire return roll 25 and the roll 31' of the press section are side by side and 9~7 define a transfer nip NO, in which the web W is detached from the forming wire 20 and becomes adherent to the felt 30.
The transfer oE the web W Erom wire 20 ko Eel~ 30 i~
facilitated, in part at least, b~ effect of centrifuc~al force, this Eorce being created on the wire return roll 25' owing to the change of direction of the wire 20, similarly as in the embodiment example of Fig. 1. However, in the design shown in Fig. 2, the transfer of the web W to the felt 30 is greatly promoted by the aid of suction from the suction roll 31' of the press. The wire return roll 25' may simply comprise a solid shell (either smooth or grooved), but a foraminous shell may also be employed, as has been disclosed in the same applicant's Canadian patent No. l~0~?/~l7r o~ rch 10r 1981, accor*in~ to which within the shell of the corresponding roll particular blowing means have been provided. Moreover, the detaching of the web W and its trans~er from the wire 20 to the felt 30 may be facilitated by an appropriate selection of the line pressure in the transfer nip NO.
The suction roll 31' is of such type wherein the suction chamber 36 is located on the outside of the roll and has been provided with seal'ing strips abutting on the outer surface of the rol~ shell and/or acting against the felt 3~. A design of this kind, and is advantages, have been extensively covered in ~ the same applicant's Finnish patent application No. 7.721.129.
As shown in Figs 2 and 3, theshell of the roll 31' has a recessed surface structure, comprising for instance grooves 37 or passages extending peripherally around the surface of the roll 31'. The suction chamber 36, extending over the whole breadth of the machine, is connected to the vacuum system of the paper machine, which is in itself known in the art. The suction chamber 36 covers the surface of the roll,31' on a sector ~. The subatmospheric pressure which is caused in the ~ -11 grooves 37 of the sur~clce of the roll 31 on the sector ~ becomes effective also in the grooves 37 of the roll 31' on the sector ~which is opposite to the sector ~ The sec-tor ~is substantial-ly equivalent to the sector NO-N1-N2. rrhereby, thc suba~ osphe~ic pressure prevailing in -the groovecl surface conigura~ion of the sec~or ~ has the same effect and task as has the suctlon in the compartments 3~a and 34b in Fig. ]..
The roll 31' may, although it is pro~ided with an external suction chamber 36, alternatively have a foraminous shell of the kind employed in conventional suction rolls. Such a design presents the advantage that it is possible to place an additional suction box within the shell in the region of the transfer nip NO. This suction box (not depicted) may have a narrow suction area in order to create a comparatively high vacuum in the nip NO to ensure the detachment of the web from the forming wire 20. The subatmospheric pres~sure produced by the suction chamber 36 in the foraminous shell and therein acts on the web W through the felt 30 and this suffices to keep the web adherent to the felt between the nips NO and Nl and the nips Nl and N2.
The apparatus depicted in Figs 1 and 2 operates as follows The headboxl4 supplies pulp stock onto the wire 10 of - - the twin wire former so that water escapes ~o some extent at the foraminous wire board 15 before the forming roll 21, although the dewatering mainly takes place on the forming roll 21. Dewatering continues in a lesser degree at the guide roll 13, and some dewatering is also effected at the couch roll 22.
~he suction sector 22a of the roll 22 effects the adherence of the web W to the wire 20, which transports the web to the wire return roll 25 (or 25' in Fig. 2). In the latter area the transfer felt 30, which also constitutes the upper felt of the press section, is conducted into contiguity with the web W so that the web is detached Erom ~he wire 20 and become~ a~herent to the felt 30 as has been presented beEore.
The web W, which is attached to the felt 30, goes along with the felt 30 to the first dewateriny press nip Nl. The first press nip Nl is defined between the upper suction roll 31 (or 31' in Fig. 2) within the upper felt loop and the lower press roll 41, this latter being a water-receiving roll and having a recessed surface, e.g. onethat has been sui~ably grooved.
This roll 41 naturally has its own felt 40. After the first press nip, the web W remains adherent to the felt 30 thanks to the subatmospheric pressure present on the suction roll 31, and the web is thus transferred with the aid of the felt 30 to the second press nip N2.
In the second press nip N2, defined between the roll 31 (or 31' in Fig. 2) and the smooth-surfaced roll 61, which is the central roll of the press section, additional pressing of the web W takes place for water removal, but in this nip the web W is detached from the felt 30 and becomes adherent to the smooth surface of the roll 61 and goes together with the roll 61 into the third press nip N3. The felt 30 is now conducted into a felt reconditioner 33, where the felt 30 is washed and water is remove~ therefrom. This is an important step because in the nips Nl and N2 the felt takes up from the weh ~ a large quantity of water and, along therewith also a considerable amount of fines and fillers. After being reconditioned, the felt 30 proceeds to the third nip N3.
The third press nip N3 has been accomplished by placing in cooperation with the roll ~I, a water-receiving roll 71, which also operates within the felt loop 30 as hasbeen shown in the foregoing~ This roll 71, too, is a foraminous surface roll, for instance a water-receiving grooved roll, and in the third press nip N3 the web is Eurther dewatered so that lts dry matter content lncreases. After the third press nip M3r the web has been shown to be de~achecl ~rorn t~e ro~ 1 in aonven~
tional manner, and it then goes to the drying section o~ the paper machine, which is known in itsel-f in the a~t. After the press, the felt 30 is conducted back again to the wire return roll at the point of detachment.
Xn the foregoing the most important ~feature of the present invention has been described: that the transfer felt 30 operates as press felt throughout the press section, and expressly it serves as the upper felt thereof. This upper felt contributes to the treatment of the web W and to the pressing process in four steps: to begin with, in the detach-ing of the web W form the forming wire - or in the pick-up process - and later at the pressing of the web W in the three subsequent press nips.
The system of the present invention numerous advantages over a conventional paper machine having separate felts at least for the pick-up nip and with it Eor the first press nip, for the second nip and for the third nip. The system here . . .
presented implies in structural respect that the course of the felt may be arranged in a very simple manner so that it com-prises virtually all felt guide rolls and felt reconditioning means disposed to be carried by one single supporting beam construction. This design implies that felt change is easy to carry out, because the number of felt tensioning and guiding members has been minimized.
Another conse~uence of the ~urnishing of the press section with one single upper felt and one lower felt is that shut-downs necessitated by the changing of a worn-out felt will occur considerably less than in the case in which the press section has four felts with different changing intervals.
One advantages oE the system presented here is: that the web W may be ~etachecl Erom the forming wire withou~ any separate pick-up roll. As has been described, -the detachment is effected by utili~in~ th~ centrieu~al ~rce ac~inc~ on the w~h and ~hl~
combined with the adhesive force of the transEer felt, and furthermore applying suction if required. In the alterna~ive design, the pick-up roll has been replaced with the suction press roll of the press section, said press~roll defining, simultaneously, three operative nips.
The felt 30 is required to meet certain conditions so that it might operate as intended in this system. The most modern felt manufacturing technology, which uses new materials and new weaving techniques, affords new, improved felt brands and structures, which are appropriate in the application of the present invention.
The design outlined in Fig. 2, in particular, implies no exceptional felt adhesion properties with regard to the web W. No water film is necessary on the surface of -the felt in transport of the web from the transfer nip NO to the first nip Nl, and the structure of the felt 30 may be wholly selected considering its water absorption properties. The felt 30 may be as dry as possible when it is being conducted into the nip NO. Sufficient dryness of the felt can be achieved by the aid of appropriate felt conditioners and a felt press 34a/34b.
Therefore, the principles of operation of the present invention and the consequential advantages may be briefly stated as follows. The number of press felts needed in the - press section is only two, with the result of a simple and comparatively inexpensive design featuring rather few guide rolls. The changing of felts is easy owing to the simple design. The felt change intervals and the need to change felts is reduced, particularly in comparison with the four-felt system. In the whole system only one suction roll is needed, and this roll may operate with an external suction chamber, a solution which economizes the suckion power and lessens' the noise detriment.
It is undes-tood that the speci~ic desiyn of the p~ess section and oE the components participating in the web trans-fer which precede it may be modified from the design shown in the figure. In the case of the embodiment presented in Fig.
2, for instance, it is possible within the scope of the present invention to furnish the suction roll 31' with a foraminous shell and with a conventional suction compartment therewithin, to further facilitate the transfer of the web to the felt and to enhance the dewatering in the nips Nl and N2. The seals of the suction box 36 may be designed in numerous different ways.
As regards the design of the suction roll 31' and its external suction box 36, reference is made to the same applicant's Canadian patent No. ik05913'56 of July 31,-1979.
It is also obvious that the invention is not confined to the twin wire former apparatus types depicted in ~igs 1 and 2. It may be applied e.g. in connection with a conven-tion-al Fourdrinier wire machine. In the a~ea between nips Nl and .. ~ . . ~
N2 a steam supply may be provided in order to enhance the dewatèring action, so as to achieve sufficient dryness of the web in and after the nip N2. At this point, reference is made to the same applicant's Canadian patent ~o. 1,076,861.
As regards the felt reconditioning apparatus, many alternatives ' and combinations are passible by which the desired result is attained.
Theinvention is in no way confined to the designs disclosed in the foregoing and which have been described in detail above and illustrated in the drawings: instead, the details in the carrying out of the invention may vary within the scope of the inventive idea defined by the set of claims following below.
mediate roll 13 guiding them onto the upper forming roll orcouch roll 22, which features a suction zone 22a, this zone ensuring that the web W that has been formed will after the twin wire forming section continue, carried by the wire 20, toward the right past the upper forming roll 22, as shown in Fig. 1 The wire 20 is guided by ~he aid of appropriate guide rolls 23.
The detachlng of the formed web W from the carrying ~ire 20 takes place on the wire return roll 25. ~s shown in Fig. 1, the wlre 20 covers the return roll 25 on an angle slightly in excess oE 90 degrees, and the transEer felt 30 is likewise conducted to cover ~his rol~ 2S on a sectc)r thu~ i~a~
been markecl ~. In the region of the sector ~, the web is detached from the wire 20 and becomes adherent to the ~elt 30.
At the point where the transfer Eelt 30 and the web W residing thereupn separate from the wire 20 there ha~s been placed a suction box 24, connected to the suction system of the paper machine, within the loop of the transfer felt 30, to ensure the detaching of the web W. The more detailed design of the suction box 24 is described in the same applicant's U.S. Patent No. 4,113,557. It should be noted that in actual fact the web W starts to become detached from the wire 20 already before it reaches the centre point of the sector ~, this being the result of the centrifugal force acting on the web W in that area where the direction of the web-carrying wire 20 first begins to change. However, the suction box is not indispensable in every case.
The course of the transfer felt 30, before it comes into contact with the return roll 25 of the wire 20, is guided with the aid of the guide rolls 32. As has been schematically shown in Figs 1 and 2, one special guiding roll 32a is so adjustable that the transfer felt 30 can be guided into contiguity with the return roll 25 in such manner that the size of that sector on which the felt 30 covers the wire 20 and the web W resid-in~ thereupon can be adjusted. It is possible in this way to enhance the affixing of the web W to the transfer felt 30 by increasing the extension of the sector ~ and thereby increasing the time of contact between the felt 30 and the web W.
- As shown in Fig. 1, the press section comprises four .
press rolls and which define three press nips. the Eirs-t nip N1 is defined between press rolls 31 and 4:L, whereof the upper roll 31 is a conventional suction roll, whi:Le the lower ro~l 41 is a water-receiviny roll having a recessed surface, for instance a grooved or blind drilled surEace. The upper roll 31 is provlded with a suction sector having two compartmen-ts 34a and 34b, The first suction compartment 34a extends ahead of the press nlp Nl to such extent that the~detachment of the web W from the ~elt 30 ~by centrifugal effect for instance) is prevented. The purpose of the suction compartment 34b is on one hand to keep the web attached to the felt 30 while travelling between the nips Nl and N2 and, on the other hand, to prevent rewetting of the web, by maintaining the water in the mesh of the felt. The suction roll may as well be of the type describ-ed later on in connection with Fig. 2.
The press section furthermore comprises a smooth-surfaced central roll 61, for instance a stone roll, which together with the upper suction roll 31 deEines the second press nip N2.
This roll 61 cooperates also with the press roll 71, defining the third press nip N3. The roll 71 has a water-receiving recessed surface. On the free sector on the underside of the smooth-surface press roll 61 a doctor blade 62 has been provid-ed to keep its surface clean, The web is detached from the roll 61 in a well-known manner and it is conducted by -the aid of the roll 74 to the drying section of the machine.
As shown in Fig. 1, in the press section only two press felts 30 and ~0 are used to aid the dewatering in the press nips and the transport of the web through the press section, these being the transfer felt 30, which transports the web from the forming wire 20 to the first nip Nl and which at the same time serves as upper felt of the whole press section, participating in the pressing process also in the second nip N2 and in the third nip N3; and the press felt 40 of the lower press roll ~1, this Eelt operating in the pressing event in one nip only: in the Eirst nip Nl as the lower ~elt thereof, under guidance by the ~lide rolls ~2. qlhe Eel~ ~0 has been provided with reconditioning means ~3, whi~h ma~ be of any conventional and expedient design, As already mentioned, the course of the upper felt 30 has been arranged with the aid of the guide~rolls 32. It is necessary in order to gaarantee a successful pressing event, to clean, wash and press the felt 30 in all nips during opera-tion. To this end, after the nip N2, the felt 30 is conducted into the felt reconditioner 33, whereafter the felt 30 is further conducted to the third press nip N3, whereafter the felt 30 is once again conducted to another felt reconditioner, this being a washing press and comprising two press rolls 34a and 34b. Such felt reconditioning means and their connection with the water supply and vacuum systems are well understood by persons skilled in the art and need therefore no detailed explanation. After passing the washing press, the felt 30 is conducted back to the wire section and to the point of detachment of the web W on the roll 25.
The main part of the guide rolls 32 of felt 30, and the felt drying means, have been accommodated on a supporting beam structure 35, shown by a schematic dotted line above the press roll part.
In Fig. 2, another embodiment of the invention is depic~-ed, comprising a wire section and a press section, both of which are in the main similar as shown in Fig. 1. However, in the design shown in Fig. 2, the wire return roll 25 has been disposed substantially on the same horizontal level as the press roll 31' of the press section so that the wire return roll 25 and the roll 31' of the press section are side by side and 9~7 define a transfer nip NO, in which the web W is detached from the forming wire 20 and becomes adherent to the felt 30.
The transfer oE the web W Erom wire 20 ko Eel~ 30 i~
facilitated, in part at least, b~ effect of centrifuc~al force, this Eorce being created on the wire return roll 25' owing to the change of direction of the wire 20, similarly as in the embodiment example of Fig. 1. However, in the design shown in Fig. 2, the transfer of the web W to the felt 30 is greatly promoted by the aid of suction from the suction roll 31' of the press. The wire return roll 25' may simply comprise a solid shell (either smooth or grooved), but a foraminous shell may also be employed, as has been disclosed in the same applicant's Canadian patent No. l~0~?/~l7r o~ rch 10r 1981, accor*in~ to which within the shell of the corresponding roll particular blowing means have been provided. Moreover, the detaching of the web W and its trans~er from the wire 20 to the felt 30 may be facilitated by an appropriate selection of the line pressure in the transfer nip NO.
The suction roll 31' is of such type wherein the suction chamber 36 is located on the outside of the roll and has been provided with seal'ing strips abutting on the outer surface of the rol~ shell and/or acting against the felt 3~. A design of this kind, and is advantages, have been extensively covered in ~ the same applicant's Finnish patent application No. 7.721.129.
As shown in Figs 2 and 3, theshell of the roll 31' has a recessed surface structure, comprising for instance grooves 37 or passages extending peripherally around the surface of the roll 31'. The suction chamber 36, extending over the whole breadth of the machine, is connected to the vacuum system of the paper machine, which is in itself known in the art. The suction chamber 36 covers the surface of the roll,31' on a sector ~. The subatmospheric pressure which is caused in the ~ -11 grooves 37 of the sur~clce of the roll 31 on the sector ~ becomes effective also in the grooves 37 of the roll 31' on the sector ~which is opposite to the sector ~ The sec-tor ~is substantial-ly equivalent to the sector NO-N1-N2. rrhereby, thc suba~ osphe~ic pressure prevailing in -the groovecl surface conigura~ion of the sec~or ~ has the same effect and task as has the suctlon in the compartments 3~a and 34b in Fig. ]..
The roll 31' may, although it is pro~ided with an external suction chamber 36, alternatively have a foraminous shell of the kind employed in conventional suction rolls. Such a design presents the advantage that it is possible to place an additional suction box within the shell in the region of the transfer nip NO. This suction box (not depicted) may have a narrow suction area in order to create a comparatively high vacuum in the nip NO to ensure the detachment of the web from the forming wire 20. The subatmospheric pres~sure produced by the suction chamber 36 in the foraminous shell and therein acts on the web W through the felt 30 and this suffices to keep the web adherent to the felt between the nips NO and Nl and the nips Nl and N2.
The apparatus depicted in Figs 1 and 2 operates as follows The headboxl4 supplies pulp stock onto the wire 10 of - - the twin wire former so that water escapes ~o some extent at the foraminous wire board 15 before the forming roll 21, although the dewatering mainly takes place on the forming roll 21. Dewatering continues in a lesser degree at the guide roll 13, and some dewatering is also effected at the couch roll 22.
~he suction sector 22a of the roll 22 effects the adherence of the web W to the wire 20, which transports the web to the wire return roll 25 (or 25' in Fig. 2). In the latter area the transfer felt 30, which also constitutes the upper felt of the press section, is conducted into contiguity with the web W so that the web is detached Erom ~he wire 20 and become~ a~herent to the felt 30 as has been presented beEore.
The web W, which is attached to the felt 30, goes along with the felt 30 to the first dewateriny press nip Nl. The first press nip Nl is defined between the upper suction roll 31 (or 31' in Fig. 2) within the upper felt loop and the lower press roll 41, this latter being a water-receiving roll and having a recessed surface, e.g. onethat has been sui~ably grooved.
This roll 41 naturally has its own felt 40. After the first press nip, the web W remains adherent to the felt 30 thanks to the subatmospheric pressure present on the suction roll 31, and the web is thus transferred with the aid of the felt 30 to the second press nip N2.
In the second press nip N2, defined between the roll 31 (or 31' in Fig. 2) and the smooth-surfaced roll 61, which is the central roll of the press section, additional pressing of the web W takes place for water removal, but in this nip the web W is detached from the felt 30 and becomes adherent to the smooth surface of the roll 61 and goes together with the roll 61 into the third press nip N3. The felt 30 is now conducted into a felt reconditioner 33, where the felt 30 is washed and water is remove~ therefrom. This is an important step because in the nips Nl and N2 the felt takes up from the weh ~ a large quantity of water and, along therewith also a considerable amount of fines and fillers. After being reconditioned, the felt 30 proceeds to the third nip N3.
The third press nip N3 has been accomplished by placing in cooperation with the roll ~I, a water-receiving roll 71, which also operates within the felt loop 30 as hasbeen shown in the foregoing~ This roll 71, too, is a foraminous surface roll, for instance a water-receiving grooved roll, and in the third press nip N3 the web is Eurther dewatered so that lts dry matter content lncreases. After the third press nip M3r the web has been shown to be de~achecl ~rorn t~e ro~ 1 in aonven~
tional manner, and it then goes to the drying section o~ the paper machine, which is known in itsel-f in the a~t. After the press, the felt 30 is conducted back again to the wire return roll at the point of detachment.
Xn the foregoing the most important ~feature of the present invention has been described: that the transfer felt 30 operates as press felt throughout the press section, and expressly it serves as the upper felt thereof. This upper felt contributes to the treatment of the web W and to the pressing process in four steps: to begin with, in the detach-ing of the web W form the forming wire - or in the pick-up process - and later at the pressing of the web W in the three subsequent press nips.
The system of the present invention numerous advantages over a conventional paper machine having separate felts at least for the pick-up nip and with it Eor the first press nip, for the second nip and for the third nip. The system here . . .
presented implies in structural respect that the course of the felt may be arranged in a very simple manner so that it com-prises virtually all felt guide rolls and felt reconditioning means disposed to be carried by one single supporting beam construction. This design implies that felt change is easy to carry out, because the number of felt tensioning and guiding members has been minimized.
Another conse~uence of the ~urnishing of the press section with one single upper felt and one lower felt is that shut-downs necessitated by the changing of a worn-out felt will occur considerably less than in the case in which the press section has four felts with different changing intervals.
One advantages oE the system presented here is: that the web W may be ~etachecl Erom the forming wire withou~ any separate pick-up roll. As has been described, -the detachment is effected by utili~in~ th~ centrieu~al ~rce ac~inc~ on the w~h and ~hl~
combined with the adhesive force of the transEer felt, and furthermore applying suction if required. In the alterna~ive design, the pick-up roll has been replaced with the suction press roll of the press section, said press~roll defining, simultaneously, three operative nips.
The felt 30 is required to meet certain conditions so that it might operate as intended in this system. The most modern felt manufacturing technology, which uses new materials and new weaving techniques, affords new, improved felt brands and structures, which are appropriate in the application of the present invention.
The design outlined in Fig. 2, in particular, implies no exceptional felt adhesion properties with regard to the web W. No water film is necessary on the surface of -the felt in transport of the web from the transfer nip NO to the first nip Nl, and the structure of the felt 30 may be wholly selected considering its water absorption properties. The felt 30 may be as dry as possible when it is being conducted into the nip NO. Sufficient dryness of the felt can be achieved by the aid of appropriate felt conditioners and a felt press 34a/34b.
Therefore, the principles of operation of the present invention and the consequential advantages may be briefly stated as follows. The number of press felts needed in the - press section is only two, with the result of a simple and comparatively inexpensive design featuring rather few guide rolls. The changing of felts is easy owing to the simple design. The felt change intervals and the need to change felts is reduced, particularly in comparison with the four-felt system. In the whole system only one suction roll is needed, and this roll may operate with an external suction chamber, a solution which economizes the suckion power and lessens' the noise detriment.
It is undes-tood that the speci~ic desiyn of the p~ess section and oE the components participating in the web trans-fer which precede it may be modified from the design shown in the figure. In the case of the embodiment presented in Fig.
2, for instance, it is possible within the scope of the present invention to furnish the suction roll 31' with a foraminous shell and with a conventional suction compartment therewithin, to further facilitate the transfer of the web to the felt and to enhance the dewatering in the nips Nl and N2. The seals of the suction box 36 may be designed in numerous different ways.
As regards the design of the suction roll 31' and its external suction box 36, reference is made to the same applicant's Canadian patent No. ik05913'56 of July 31,-1979.
It is also obvious that the invention is not confined to the twin wire former apparatus types depicted in ~igs 1 and 2. It may be applied e.g. in connection with a conven-tion-al Fourdrinier wire machine. In the a~ea between nips Nl and .. ~ . . ~
N2 a steam supply may be provided in order to enhance the dewatèring action, so as to achieve sufficient dryness of the web in and after the nip N2. At this point, reference is made to the same applicant's Canadian patent ~o. 1,076,861.
As regards the felt reconditioning apparatus, many alternatives ' and combinations are passible by which the desired result is attained.
Theinvention is in no way confined to the designs disclosed in the foregoing and which have been described in detail above and illustrated in the drawings: instead, the details in the carrying out of the invention may vary within the scope of the inventive idea defined by the set of claims following below.
Claims (9)
1. Procedure for treating a fibre web between the forming fabric section and the drying section of a paper machine, utilizing so-called closed conduction, such procedure comprising as a combination the following steps: detaching of the web from the forming fabric at the point of detachment and substantially simultaneous affixing thereof on the surface of a transfer felt;
transport of the web carried by the transfer felt's surface from the point of detachment to a first press nip; conduction of the lower felt of the press section into the first press nip defined by a recessed surface lower roll and a dewatering upper roll connected to a suction system; pressing of the web between the transfer felt and the lower felt and simultaneous dewatering of the web in two directions in the first press nip; conduction of the web on the surface of the transfer felt of the press section to a press nip defined by said upper roll and a solid smooth-surface central roll of the press section; dewatering of the web in the second press nip with water flow passing into the transfer felt, characterized in that the transfer felt participates in the treatment of the fibre web still in the third dewatering nip, in that in association with the afore-mentioned steps the transfer felt is detached from the web after the second press nip and conducted to a first felt conditioning means for the reconditioning of the felt, that the fibre web is transferred, adherent to the surface of the central roll, to a third press nip defined by the smooth central roll and the second, recessed, surface, roll of the press section, the transfer felt being conducted from the first felt conditioning means to said third press nip, where the web is pressed between the smooth roll surface and the felt so as to express water from the web into the felt toward the recessed surface roll, whereupon the felt is detached from the web and conducted back through a second felt conditioner to be adjacent to the return roll within the forming fabric loop, at which roll detachment of the fibre web from the forming fabric takes place, and that the fibre web is transferred after the third press nip on the surface of the smooth roll to the point where the web is detached from the surface of the roll to be conducted to the drying section.
transport of the web carried by the transfer felt's surface from the point of detachment to a first press nip; conduction of the lower felt of the press section into the first press nip defined by a recessed surface lower roll and a dewatering upper roll connected to a suction system; pressing of the web between the transfer felt and the lower felt and simultaneous dewatering of the web in two directions in the first press nip; conduction of the web on the surface of the transfer felt of the press section to a press nip defined by said upper roll and a solid smooth-surface central roll of the press section; dewatering of the web in the second press nip with water flow passing into the transfer felt, characterized in that the transfer felt participates in the treatment of the fibre web still in the third dewatering nip, in that in association with the afore-mentioned steps the transfer felt is detached from the web after the second press nip and conducted to a first felt conditioning means for the reconditioning of the felt, that the fibre web is transferred, adherent to the surface of the central roll, to a third press nip defined by the smooth central roll and the second, recessed, surface, roll of the press section, the transfer felt being conducted from the first felt conditioning means to said third press nip, where the web is pressed between the smooth roll surface and the felt so as to express water from the web into the felt toward the recessed surface roll, whereupon the felt is detached from the web and conducted back through a second felt conditioner to be adjacent to the return roll within the forming fabric loop, at which roll detachment of the fibre web from the forming fabric takes place, and that the fibre web is transferred after the third press nip on the surface of the smooth roll to the point where the web is detached from the surface of the roll to be conducted to the drying section.
2. Means in the wire and press sections of a paper machine for treating a fibre web between forming section and drying section of the paper machine,characterized in that the means com-prises in combination the following mutually associated components:
- a forming fabric;
- a fabric return roll within the forming fabric loop;
- a press suction roll connected to a suction system;
- a first recessed surface press roll, defining with said suction roll a first dewatering nip;
- a smooth-surfaced press roll, defining with said suction roll a second dewatering nip;
- a second recessed surface press roll, defining with the smooth-surfaced press roll a third dewatering nip;
- in total two press felt fabrics, whereof the felt fabric belonging to the top part structure of the press section serves as transport felt conveying the fibre web from the point of detachment to the first and second dewatering nips and which within its loop encloses the suction roll and the second recessed surface press roll, covering of the suction roll substantially at least that sector on which the suction of the suction roll is active, and whereof the felt fabric belonging to the bottom part structure of the press section within its loop encloses the first recessed surface press roll and serves as water-receiving lower felt in the first press nip;
- a first transfer felt conditioning means on the felt run between the second and first dewatering nips;
- a second transfer felt conditioning means on the felt run following after the third dewatering nip;
- a third felt conditioning means for the lower felt.
- a forming fabric;
- a fabric return roll within the forming fabric loop;
- a press suction roll connected to a suction system;
- a first recessed surface press roll, defining with said suction roll a first dewatering nip;
- a smooth-surfaced press roll, defining with said suction roll a second dewatering nip;
- a second recessed surface press roll, defining with the smooth-surfaced press roll a third dewatering nip;
- in total two press felt fabrics, whereof the felt fabric belonging to the top part structure of the press section serves as transport felt conveying the fibre web from the point of detachment to the first and second dewatering nips and which within its loop encloses the suction roll and the second recessed surface press roll, covering of the suction roll substantially at least that sector on which the suction of the suction roll is active, and whereof the felt fabric belonging to the bottom part structure of the press section within its loop encloses the first recessed surface press roll and serves as water-receiving lower felt in the first press nip;
- a first transfer felt conditioning means on the felt run between the second and first dewatering nips;
- a second transfer felt conditioning means on the felt run following after the third dewatering nip;
- a third felt conditioning means for the lower felt.
3. Means according to claim 2, characterized in that the suction roll of the press section defines a transfer nip with the return roll of the forming fabric, said return roll having been disposed on substantially equal horizontal level with said suction roll.
4. Means according to claim 2, characterized in that the return roll of the forming fabric has been disposed at a substantially higher elevation than the suction roll of the press section and that the transfer felt loop has been conducted onto a sector of said return roll.
5. Means according to claim 2, characterized in that within the transfer felt loop adjacent to said return roll has been disposed a detaching suction box, which contributes to helping the web to transfer from the forming fabric onto the outer surface of the transfer felt loop.
6. Means according to claim 3, or 4, characterized in that the suction roll is a foraminous shell roll.
7. Means according to claim 3, characterized in that the connecting of the suction roll to the vacuum system has been accomplished using an external suction chamber.
8. Means according to claim 7, characterized in that the suction roll has a non-perforated shell, the surface of this shell having been provided witn one or several groove passages encircling the periphery.
9. Means according to claim 7, characterized in that the suction roll has been provided with at least one suction chamber internal within its shell.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI790105 | 1979-01-12 | ||
| FI790105A FI790105A (en) | 1979-01-12 | 1979-01-12 | FOERFARANDE OCH ANORDNING FOER BEHANDLING AV FIBERBANA |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1121197A true CA1121197A (en) | 1982-04-06 |
Family
ID=8512299
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000343290A Expired CA1121197A (en) | 1979-01-12 | 1980-01-09 | Procedure and means for treating a fibre web |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS5598993A (en) |
| BR (1) | BR8000121A (en) |
| CA (1) | CA1121197A (en) |
| DE (1) | DE3000100A1 (en) |
| FI (1) | FI790105A (en) |
| FR (1) | FR2446356A1 (en) |
| GB (1) | GB2039308A (en) |
| IT (1) | IT1130358B (en) |
| SE (1) | SE8000225L (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2025447C (en) * | 1989-11-07 | 1995-01-17 | David V. Lange | Method and apparatus for reducing vibration in the press section of a papermaking machine |
| AT395184B (en) * | 1990-07-04 | 1992-10-12 | Andritz Ag Maschf | DEVICE FOR TREATING CELLULOSE AND OR OR MULTIPLE MIXTURES OR SUSPENSIONS |
| US5393383A (en) * | 1991-12-19 | 1995-02-28 | Valmet Paper Machinery Inc. | Compact press section with closed draw of the web in a paper machine |
| DE19835063A1 (en) * | 1998-08-04 | 2000-02-10 | Voith Sulzer Papiertech Patent | Press section in a papermaking machine has an initial press stage with conditioning of the press blanket between the initial and main press stages |
| DE10309050A1 (en) * | 2003-03-01 | 2004-09-23 | Voith Paper Patent Gmbh | Device for producing a fibrous web |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3258530A (en) * | 1962-06-07 | 1966-06-28 | Dick Co Ab | Facsimile scanning machine |
| US4106061A (en) * | 1977-03-03 | 1978-08-08 | The Mead Corporation | Density control for ink jet copier |
-
1979
- 1979-01-12 FI FI790105A patent/FI790105A/en unknown
-
1980
- 1980-01-02 GB GB8000051A patent/GB2039308A/en not_active Withdrawn
- 1980-01-03 DE DE19803000100 patent/DE3000100A1/en not_active Withdrawn
- 1980-01-09 CA CA000343290A patent/CA1121197A/en not_active Expired
- 1980-01-09 BR BR8000121A patent/BR8000121A/en unknown
- 1980-01-11 FR FR8000650A patent/FR2446356A1/en active Granted
- 1980-01-11 IT IT19171/80A patent/IT1130358B/en active
- 1980-01-11 JP JP197680A patent/JPS5598993A/en active Pending
- 1980-01-11 SE SE8000225A patent/SE8000225L/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| IT8019171A0 (en) | 1980-01-11 |
| FR2446356A1 (en) | 1980-08-08 |
| GB2039308A (en) | 1980-08-06 |
| FR2446356B3 (en) | 1981-11-20 |
| IT1130358B (en) | 1986-06-11 |
| SE8000225L (en) | 1980-07-13 |
| BR8000121A (en) | 1980-10-29 |
| JPS5598993A (en) | 1980-07-28 |
| FI790105A (en) | 1980-07-13 |
| DE3000100A1 (en) | 1980-07-24 |
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| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |